Revert "Revert^8 "Thread suspension cleanup and deadlock fix""
This reverts commit 221b6c5fcd66d4b6f2626c311d03bde2fb1589f9.
Reason for revert: Preemptive revert. Earlier versions have had a tendency to cause subtle breakage.
Please do not submit unless something breaks.
Change-Id: Iad2a7f920756f365789c422948632f5db5a28fd5
diff --git a/openjdkjvmti/ti_stack.cc b/openjdkjvmti/ti_stack.cc
index 71c9767..c3aab4c 100644
--- a/openjdkjvmti/ti_stack.cc
+++ b/openjdkjvmti/ti_stack.cc
@@ -365,13 +365,7 @@
REQUIRES_SHARED(art::Locks::mutator_lock_) {
// Note: requires the mutator lock as the checkpoint requires the mutator lock.
GetAllStackTracesVectorClosure<Data> closure(max_frame_count, data);
- // TODO(b/253671779): Replace this use of RunCheckpointUnchecked() with RunCheckpoint(). This is
- // currently not possible, since the following undesirable call chain (abbreviated here) is then
- // possible and exercised by current tests: (jvmti) GetAllStackTraces -> <this function> ->
- // RunCheckpoint -> GetStackTraceVisitor -> EncodeMethodId -> Class::EnsureMethodIds ->
- // Class::Alloc -> AllocObjectWithAllocator -> potentially suspends, or runs GC, etc. -> CHECK
- // failure.
- size_t barrier_count = art::Runtime::Current()->GetThreadList()->RunCheckpointUnchecked(&closure);
+ size_t barrier_count = art::Runtime::Current()->GetThreadList()->RunCheckpoint(&closure, nullptr);
if (barrier_count == 0) {
return;
}
diff --git a/openjdkjvmti/ti_thread.cc b/openjdkjvmti/ti_thread.cc
index 34e8c36..b5bc35e 100644
--- a/openjdkjvmti/ti_thread.cc
+++ b/openjdkjvmti/ti_thread.cc
@@ -900,13 +900,16 @@
}
}
}
+ bool timeout = true;
art::Thread* ret_target = art::Runtime::Current()->GetThreadList()->SuspendThreadByPeer(
- target_jthread, art::SuspendReason::kForUserCode);
- if (ret_target == nullptr) {
+ target_jthread,
+ art::SuspendReason::kForUserCode,
+ &timeout);
+ if (ret_target == nullptr && !timeout) {
// TODO It would be good to get more information about why exactly the thread failed to
// suspend.
return ERR(INTERNAL);
- } else {
+ } else if (!timeout) {
// we didn't time out and got a result.
return OK;
}
@@ -924,7 +927,11 @@
// This can only happen if we race with another thread to suspend 'self' and we lose.
return ERR(THREAD_SUSPENDED);
}
- self->IncrementSuspendCount(self, nullptr, nullptr, art::SuspendReason::kForUserCode);
+ // We shouldn't be able to fail this.
+ if (!self->ModifySuspendCount(self, +1, nullptr, art::SuspendReason::kForUserCode)) {
+ // TODO More specific error would be nice.
+ return ERR(INTERNAL);
+ }
}
// Once we have requested the suspend we actually go to sleep. We need to do this after releasing
// the suspend_lock to make sure we can be woken up. This call gains the mutator lock causing us
diff --git a/runtime/base/locks.h b/runtime/base/locks.h
index e8c83fe..c15e5de 100644
--- a/runtime/base/locks.h
+++ b/runtime/base/locks.h
@@ -108,6 +108,10 @@
kClassLinkerClassesLock, // TODO rename.
kSubtypeCheckLock,
kBreakpointLock,
+ // This is a generic lock level for a lock meant to be gained after having a
+ // monitor lock.
+ kPostMonitorLock,
+ kMonitorLock,
kMonitorListLock,
kThreadListLock,
kAllocTrackerLock,
@@ -121,10 +125,7 @@
kRuntimeShutdownLock,
kTraceLock,
kHeapBitmapLock,
- // This is a generic lock level for a lock meant to be gained after having a
- // monitor lock.
- kPostMonitorLock,
- kMonitorLock,
+
// This is a generic lock level for a top-level lock meant to be gained after having the
// mutator_lock_.
kPostMutatorTopLockLevel,
@@ -137,7 +138,7 @@
kUserCodeSuspensionLock,
kZygoteCreationLock,
- // The highest valid lock level. Use this for locks that should only be acquired with no
+ // The highest valid lock level. Use this if there is code that should only be called with no
// other locks held. Since this is the highest lock level we also allow it to be held even if the
// runtime or current thread is not fully set-up yet (for example during thread attach). Note that
// this lock also has special behavior around the mutator_lock_. Since the mutator_lock_ is not
diff --git a/runtime/base/mutex-inl.h b/runtime/base/mutex-inl.h
index 712b61d..dba1e12 100644
--- a/runtime/base/mutex-inl.h
+++ b/runtime/base/mutex-inl.h
@@ -60,44 +60,43 @@
// The check below enumerates the cases where we expect not to be able to check the validity of
// locks on a thread. Lock checking is disabled to avoid deadlock when checking shutdown lock.
// TODO: tighten this check.
- CHECK(!Locks::IsSafeToCallAbortRacy() ||
- // Used during thread creation to avoid races with runtime shutdown. Thread::Current not
- // yet established.
- level == kRuntimeShutdownLock ||
- // Thread Ids are allocated/released before threads are established.
- level == kAllocatedThreadIdsLock ||
- // Thread LDT's are initialized without Thread::Current established.
- level == kModifyLdtLock ||
- // Threads are unregistered while holding the thread list lock, during this process they
- // no longer exist and so we expect an unlock with no self.
- level == kThreadListLock ||
- // Ignore logging which may or may not have set up thread data structures.
- level == kLoggingLock ||
- // When transitioning from suspended to runnable, a daemon thread might be in
- // a situation where the runtime is shutting down. To not crash our debug locking
- // mechanism we just pass null Thread* to the MutexLock during that transition
- // (see Thread::TransitionFromSuspendedToRunnable).
- level == kThreadSuspendCountLock ||
- // Avoid recursive death.
- level == kAbortLock ||
- // Locks at the absolute top of the stack can be locked at any time.
- level == kTopLockLevel ||
- // The unexpected signal handler may be catching signals from any thread.
- level == kUnexpectedSignalLock)
- << level;
-}
-
-inline void BaseMutex::RegisterAsLocked(Thread* self, bool check) {
- if (UNLIKELY(self == nullptr)) {
- if (check) {
- CheckUnattachedThread(level_);
- }
- } else {
- RegisterAsLockedImpl(self, level_, check);
+ if (kDebugLocking) {
+ CHECK(!Locks::IsSafeToCallAbortRacy() ||
+ // Used during thread creation to avoid races with runtime shutdown. Thread::Current not
+ // yet established.
+ level == kRuntimeShutdownLock ||
+ // Thread Ids are allocated/released before threads are established.
+ level == kAllocatedThreadIdsLock ||
+ // Thread LDT's are initialized without Thread::Current established.
+ level == kModifyLdtLock ||
+ // Threads are unregistered while holding the thread list lock, during this process they
+ // no longer exist and so we expect an unlock with no self.
+ level == kThreadListLock ||
+ // Ignore logging which may or may not have set up thread data structures.
+ level == kLoggingLock ||
+ // When transitioning from suspended to runnable, a daemon thread might be in
+ // a situation where the runtime is shutting down. To not crash our debug locking
+ // mechanism we just pass null Thread* to the MutexLock during that transition
+ // (see Thread::TransitionFromSuspendedToRunnable).
+ level == kThreadSuspendCountLock ||
+ // Avoid recursive death.
+ level == kAbortLock ||
+ // Locks at the absolute top of the stack can be locked at any time.
+ level == kTopLockLevel ||
+ // The unexpected signal handler may be catching signals from any thread.
+ level == kUnexpectedSignalLock) << level;
}
}
-inline void BaseMutex::RegisterAsLockedImpl(Thread* self, LockLevel level, bool check) {
+inline void BaseMutex::RegisterAsLocked(Thread* self) {
+ if (UNLIKELY(self == nullptr)) {
+ CheckUnattachedThread(level_);
+ return;
+ }
+ RegisterAsLockedImpl(self, level_);
+}
+
+inline void BaseMutex::RegisterAsLockedImpl(Thread* self, LockLevel level) {
DCHECK(self != nullptr);
DCHECK_EQ(level_, level);
// It would be nice to avoid this condition checking in the non-debug case,
@@ -108,7 +107,7 @@
if (UNLIKELY(level == kThreadWaitLock) && self->GetHeldMutex(kThreadWaitLock) != nullptr) {
level = kThreadWaitWakeLock;
}
- if (check) {
+ if (kDebugLocking) {
// Check if a bad Mutex of this level or lower is held.
bool bad_mutexes_held = false;
// Specifically allow a kTopLockLevel lock to be gained when the current thread holds the
@@ -162,12 +161,10 @@
inline void BaseMutex::RegisterAsUnlocked(Thread* self) {
if (UNLIKELY(self == nullptr)) {
- if (kDebugLocking) {
- CheckUnattachedThread(level_);
- }
- } else {
- RegisterAsUnlockedImpl(self, level_);
+ CheckUnattachedThread(level_);
+ return;
}
+ RegisterAsUnlockedImpl(self , level_);
}
inline void BaseMutex::RegisterAsUnlockedImpl(Thread* self, LockLevel level) {
@@ -309,7 +306,7 @@
}
inline void MutatorMutex::TransitionFromSuspendedToRunnable(Thread* self) {
- RegisterAsLockedImpl(self, kMutatorLock, kDebugLocking);
+ RegisterAsLockedImpl(self, kMutatorLock);
AssertSharedHeld(self);
}
diff --git a/runtime/base/mutex.cc b/runtime/base/mutex.cc
index 542e91b..728dc84 100644
--- a/runtime/base/mutex.cc
+++ b/runtime/base/mutex.cc
@@ -246,12 +246,11 @@
}
void BaseMutex::CheckSafeToWait(Thread* self) {
- if (!kDebugLocking) {
- return;
- }
if (self == nullptr) {
CheckUnattachedThread(level_);
- } else {
+ return;
+ }
+ if (kDebugLocking) {
CHECK(self->GetHeldMutex(level_) == this || level_ == kMonitorLock)
<< "Waiting on unacquired mutex: " << name_;
bool bad_mutexes_held = false;
@@ -571,7 +570,6 @@
}
}
-template <bool kCheck>
bool Mutex::ExclusiveTryLock(Thread* self) {
DCHECK(self == nullptr || self == Thread::Current());
if (kDebugLocking && !recursive_) {
@@ -602,7 +600,7 @@
#endif
DCHECK_EQ(GetExclusiveOwnerTid(), 0);
exclusive_owner_.store(SafeGetTid(self), std::memory_order_relaxed);
- RegisterAsLocked(self, kCheck);
+ RegisterAsLocked(self);
}
recursion_count_++;
if (kDebugLocking) {
@@ -613,9 +611,6 @@
return true;
}
-template bool Mutex::ExclusiveTryLock<false>(Thread* self);
-template bool Mutex::ExclusiveTryLock<true>(Thread* self);
-
bool Mutex::ExclusiveTryLockWithSpinning(Thread* self) {
// Spin a small number of times, since this affects our ability to respond to suspension
// requests. We spin repeatedly only if the mutex repeatedly becomes available and unavailable
diff --git a/runtime/base/mutex.h b/runtime/base/mutex.h
index 30d720c..87e9525 100644
--- a/runtime/base/mutex.h
+++ b/runtime/base/mutex.h
@@ -103,11 +103,10 @@
BaseMutex(const char* name, LockLevel level);
virtual ~BaseMutex();
- // Add this mutex to those owned by self, and optionally perform lock order checking. Caller
- // may wish to disable checking for trylock calls that cannot result in deadlock. For this call
- // only, self may also be another suspended thread.
- void RegisterAsLocked(Thread* self, bool check = kDebugLocking);
- void RegisterAsLockedImpl(Thread* self, LockLevel level, bool check);
+ // Add this mutex to those owned by self, and perform appropriate checking.
+ // For this call only, self may also be another suspended thread.
+ void RegisterAsLocked(Thread* self);
+ void RegisterAsLockedImpl(Thread* self, LockLevel level);
void RegisterAsUnlocked(Thread* self);
void RegisterAsUnlockedImpl(Thread* self, LockLevel level);
@@ -184,10 +183,7 @@
void ExclusiveLock(Thread* self) ACQUIRE();
void Lock(Thread* self) ACQUIRE() { ExclusiveLock(self); }
- // Returns true if acquires exclusive access, false otherwise. The `check` argument specifies
- // whether lock level checking should be performed. Should be defaulted unless we are using
- // TryLock instead of Lock for deadlock avoidance.
- template <bool kCheck = kDebugLocking>
+ // Returns true if acquires exclusive access, false otherwise.
bool ExclusiveTryLock(Thread* self) TRY_ACQUIRE(true);
bool TryLock(Thread* self) TRY_ACQUIRE(true) { return ExclusiveTryLock(self); }
// Equivalent to ExclusiveTryLock, but retry for a short period before giving up.
diff --git a/runtime/cha.cc b/runtime/cha.cc
index 2a45f2f..a40afb4 100644
--- a/runtime/cha.cc
+++ b/runtime/cha.cc
@@ -237,10 +237,11 @@
: barrier_(0),
method_headers_(method_headers) {}
- void Run(Thread* thread) override REQUIRES_SHARED(Locks::mutator_lock_) {
+ void Run(Thread* thread) override {
// Note thread and self may not be equal if thread was already suspended at
// the point of the request.
Thread* self = Thread::Current();
+ ScopedObjectAccess soa(self);
CHAStackVisitor visitor(thread, nullptr, method_headers_);
visitor.WalkStack();
barrier_.Pass(self);
diff --git a/runtime/debugger.cc b/runtime/debugger.cc
index 3c8e6e6..a7b818e 100644
--- a/runtime/debugger.cc
+++ b/runtime/debugger.cc
@@ -340,11 +340,7 @@
Dbg::DdmSendThreadNotification(thread, CHUNK_TYPE("THCR"));
finish_barrier.Pass(cls_self);
});
- // TODO(b/253671779): The above eventually results in calls to EventHandler::DispatchEvent,
- // which does a ScopedThreadStateChange, which amounts to a thread state change inside the
- // checkpoint run method. Hence the normal check would fail, and thus we specify Unchecked
- // here.
- size_t checkpoints = Runtime::Current()->GetThreadList()->RunCheckpointUnchecked(&fc);
+ size_t checkpoints = Runtime::Current()->GetThreadList()->RunCheckpoint(&fc);
ScopedThreadSuspension sts(self, ThreadState::kWaitingForCheckPointsToRun);
finish_barrier.Increment(self, checkpoints);
}
diff --git a/runtime/entrypoints_order_test.cc b/runtime/entrypoints_order_test.cc
index 91dc6a0..be1c58d 100644
--- a/runtime/entrypoints_order_test.cc
+++ b/runtime/entrypoints_order_test.cc
@@ -70,6 +70,7 @@
EXPECT_OFFSET_DIFFP(Thread, tls32_, daemon, throwing_OutOfMemoryError, 4);
EXPECT_OFFSET_DIFFP(Thread, tls32_, throwing_OutOfMemoryError, no_thread_suspension, 4);
EXPECT_OFFSET_DIFFP(Thread, tls32_, no_thread_suspension, thread_exit_check_count, 4);
+ EXPECT_OFFSET_DIFFP(Thread, tls32_, thread_exit_check_count, is_transitioning_to_runnable, 4);
// TODO: Better connection. Take alignment into account.
EXPECT_OFFSET_DIFF_GT3(Thread, tls32_.thread_exit_check_count, tls64_.trace_clock_base, 4,
@@ -107,14 +108,13 @@
EXPECT_OFFSET_DIFFP(Thread, tlsPtr_, name, pthread_self, sizeof(void*));
EXPECT_OFFSET_DIFFP(Thread, tlsPtr_, pthread_self, last_no_thread_suspension_cause,
sizeof(void*));
- EXPECT_OFFSET_DIFFP(Thread, tlsPtr_, last_no_thread_suspension_cause,
- active_suspendall_barrier, sizeof(void*));
- EXPECT_OFFSET_DIFFP(
- Thread, tlsPtr_, active_suspendall_barrier, active_suspend1_barriers, sizeof(void*));
- EXPECT_OFFSET_DIFFP(Thread, tlsPtr_, active_suspend1_barriers, thread_local_pos, sizeof(void*));
+ EXPECT_OFFSET_DIFFP(Thread, tlsPtr_, last_no_thread_suspension_cause, active_suspend_barriers,
+ sizeof(void*));
+ EXPECT_OFFSET_DIFFP(Thread, tlsPtr_, active_suspend_barriers, thread_local_start,
+ sizeof(Thread::tls_ptr_sized_values::active_suspend_barriers));
+ EXPECT_OFFSET_DIFFP(Thread, tlsPtr_, thread_local_start, thread_local_pos, sizeof(void*));
EXPECT_OFFSET_DIFFP(Thread, tlsPtr_, thread_local_pos, thread_local_end, sizeof(void*));
- EXPECT_OFFSET_DIFFP(Thread, tlsPtr_, thread_local_end, thread_local_start, sizeof(void*));
- EXPECT_OFFSET_DIFFP(Thread, tlsPtr_, thread_local_start, thread_local_limit, sizeof(void*));
+ EXPECT_OFFSET_DIFFP(Thread, tlsPtr_, thread_local_end, thread_local_limit, sizeof(void*));
EXPECT_OFFSET_DIFFP(Thread, tlsPtr_, thread_local_limit, thread_local_objects, sizeof(void*));
EXPECT_OFFSET_DIFFP(Thread, tlsPtr_, thread_local_objects, checkpoint_function, sizeof(size_t));
EXPECT_OFFSET_DIFFP(Thread, tlsPtr_, checkpoint_function, jni_entrypoints,
@@ -138,12 +138,11 @@
Thread, tlsPtr_, top_reflective_handle_scope, method_trace_buffer, sizeof(void*));
EXPECT_OFFSET_DIFFP(
Thread, tlsPtr_, method_trace_buffer, method_trace_buffer_index, sizeof(void*));
- EXPECT_OFFSET_DIFFP(
- Thread, tlsPtr_, method_trace_buffer_index, thread_exit_flags, sizeof(void*));
// The first field after tlsPtr_ is forced to a 16 byte alignment so it might have some space.
auto offset_tlsptr_end = OFFSETOF_MEMBER(Thread, tlsPtr_) +
sizeof(decltype(reinterpret_cast<Thread*>(16)->tlsPtr_));
- CHECKED(offset_tlsptr_end - OFFSETOF_MEMBER(Thread, tlsPtr_.thread_exit_flags) == sizeof(void*),
+ CHECKED(offset_tlsptr_end - OFFSETOF_MEMBER(Thread, tlsPtr_.method_trace_buffer_index) ==
+ sizeof(void*),
"async_exception last field");
}
diff --git a/runtime/gc/collector/concurrent_copying.cc b/runtime/gc/collector/concurrent_copying.cc
index 0f4676e..5118523 100644
--- a/runtime/gc/collector/concurrent_copying.cc
+++ b/runtime/gc/collector/concurrent_copying.cc
@@ -476,10 +476,11 @@
}
void Run(Thread* thread) override REQUIRES_SHARED(Locks::mutator_lock_) {
- // We are either running this in the target thread, or the target thread will wait for us
- // before switching back to runnable.
+ // Note: self is not necessarily equal to thread since thread may be suspended.
Thread* self = Thread::Current();
- DCHECK(thread == self || thread->GetState() != ThreadState::kRunnable)
+ CHECK(thread == self ||
+ thread->IsSuspended() ||
+ thread->GetState() == ThreadState::kWaitingPerformingGc)
<< thread->GetState() << " thread " << thread << " self " << self;
thread->SetIsGcMarkingAndUpdateEntrypoints(true);
if (use_tlab_ && thread->HasTlab()) {
@@ -503,6 +504,7 @@
// We can use the non-CAS VisitRoots functions below because we update thread-local GC roots
// only.
thread->VisitRoots(this, kVisitRootFlagAllRoots);
+ concurrent_copying_->GetBarrier().Pass(self);
}
void VisitRoots(mirror::Object*** roots,
@@ -772,12 +774,17 @@
}
Thread* self = Thread::Current();
Locks::mutator_lock_->AssertNotHeld(self);
+ gc_barrier_->Init(self, 0);
ThreadFlipVisitor thread_flip_visitor(this, heap_->use_tlab_);
FlipCallback flip_callback(this);
- Runtime::Current()->GetThreadList()->FlipThreadRoots(
+ size_t barrier_count = Runtime::Current()->GetThreadList()->FlipThreadRoots(
&thread_flip_visitor, &flip_callback, this, GetHeap()->GetGcPauseListener());
+ {
+ ScopedThreadStateChange tsc(self, ThreadState::kWaitingForCheckPointsToRun);
+ gc_barrier_->Increment(self, barrier_count);
+ }
is_asserting_to_space_invariant_ = true;
QuasiAtomic::ThreadFenceForConstructor();
if (kVerboseMode) {
diff --git a/runtime/gc/collector/mark_compact.cc b/runtime/gc/collector/mark_compact.cc
index 8f7c6d3..3c2606a 100644
--- a/runtime/gc/collector/mark_compact.cc
+++ b/runtime/gc/collector/mark_compact.cc
@@ -614,6 +614,7 @@
CHECK(collector_->compacting_);
thread->SweepInterpreterCache(collector_);
thread->AdjustTlab(collector_->black_objs_slide_diff_);
+ collector_->GetBarrier().Pass(self);
}
private:
@@ -665,10 +666,15 @@
{
// Compaction pause
+ gc_barrier_.Init(self, 0);
ThreadFlipVisitor visitor(this);
FlipCallback callback(this);
- runtime->GetThreadList()->FlipThreadRoots(
+ size_t barrier_count = runtime->GetThreadList()->FlipThreadRoots(
&visitor, &callback, this, GetHeap()->GetGcPauseListener());
+ {
+ ScopedThreadStateChange tsc(self, ThreadState::kWaitingForCheckPointsToRun);
+ gc_barrier_.Increment(self, barrier_count);
+ }
}
if (IsValidFd(uffd_)) {
diff --git a/runtime/gc/heap.cc b/runtime/gc/heap.cc
index 056ae06..3b7f0e8 100644
--- a/runtime/gc/heap.cc
+++ b/runtime/gc/heap.cc
@@ -2715,122 +2715,113 @@
}
ScopedThreadStateChange tsc(self, ThreadState::kWaitingPerformingGc);
Locks::mutator_lock_->AssertNotHeld(self);
- SelfDeletingTask* clear; // Unconditionally set below.
+ if (self->IsHandlingStackOverflow()) {
+ // If we are throwing a stack overflow error we probably don't have enough remaining stack
+ // space to run the GC.
+ // Count this as a GC in case someone is waiting for it to complete.
+ gcs_completed_.fetch_add(1, std::memory_order_release);
+ return collector::kGcTypeNone;
+ }
+ bool compacting_gc;
{
- // We should not ever become runnable and re-suspend while executing a GC.
- // This would likely cause a deadlock if we acted on a suspension request.
- // TODO: We really want to assert that we don't transition to kRunnable.
- ScopedAssertNoThreadSuspension("Performing GC");
- if (self->IsHandlingStackOverflow()) {
- // If we are throwing a stack overflow error we probably don't have enough remaining stack
- // space to run the GC.
- // Count this as a GC in case someone is waiting for it to complete.
+ gc_complete_lock_->AssertNotHeld(self);
+ ScopedThreadStateChange tsc2(self, ThreadState::kWaitingForGcToComplete);
+ MutexLock mu(self, *gc_complete_lock_);
+ // Ensure there is only one GC at a time.
+ WaitForGcToCompleteLocked(gc_cause, self);
+ if (requested_gc_num != GC_NUM_ANY && !GCNumberLt(GetCurrentGcNum(), requested_gc_num)) {
+ // The appropriate GC was already triggered elsewhere.
+ return collector::kGcTypeNone;
+ }
+ compacting_gc = IsMovingGc(collector_type_);
+ // GC can be disabled if someone has a used GetPrimitiveArrayCritical.
+ if (compacting_gc && disable_moving_gc_count_ != 0) {
+ LOG(WARNING) << "Skipping GC due to disable moving GC count " << disable_moving_gc_count_;
+ // Again count this as a GC.
gcs_completed_.fetch_add(1, std::memory_order_release);
return collector::kGcTypeNone;
}
- bool compacting_gc;
- {
- gc_complete_lock_->AssertNotHeld(self);
- ScopedThreadStateChange tsc2(self, ThreadState::kWaitingForGcToComplete);
- MutexLock mu(self, *gc_complete_lock_);
- // Ensure there is only one GC at a time.
- WaitForGcToCompleteLocked(gc_cause, self);
- if (requested_gc_num != GC_NUM_ANY && !GCNumberLt(GetCurrentGcNum(), requested_gc_num)) {
- // The appropriate GC was already triggered elsewhere.
- return collector::kGcTypeNone;
- }
- compacting_gc = IsMovingGc(collector_type_);
- // GC can be disabled if someone has a used GetPrimitiveArrayCritical.
- if (compacting_gc && disable_moving_gc_count_ != 0) {
- LOG(WARNING) << "Skipping GC due to disable moving GC count " << disable_moving_gc_count_;
- // Again count this as a GC.
- gcs_completed_.fetch_add(1, std::memory_order_release);
- return collector::kGcTypeNone;
- }
- if (gc_disabled_for_shutdown_) {
- gcs_completed_.fetch_add(1, std::memory_order_release);
- return collector::kGcTypeNone;
- }
- collector_type_running_ = collector_type_;
- last_gc_cause_ = gc_cause;
+ if (gc_disabled_for_shutdown_) {
+ gcs_completed_.fetch_add(1, std::memory_order_release);
+ return collector::kGcTypeNone;
}
- if (gc_cause == kGcCauseForAlloc && runtime->HasStatsEnabled()) {
- ++runtime->GetStats()->gc_for_alloc_count;
- ++self->GetStats()->gc_for_alloc_count;
- }
- const size_t bytes_allocated_before_gc = GetBytesAllocated();
-
- DCHECK_LT(gc_type, collector::kGcTypeMax);
- DCHECK_NE(gc_type, collector::kGcTypeNone);
-
- collector::GarbageCollector* collector = nullptr;
- // TODO: Clean this up.
- if (compacting_gc) {
- DCHECK(current_allocator_ == kAllocatorTypeBumpPointer ||
- current_allocator_ == kAllocatorTypeTLAB ||
- current_allocator_ == kAllocatorTypeRegion ||
- current_allocator_ == kAllocatorTypeRegionTLAB);
- switch (collector_type_) {
- case kCollectorTypeSS:
- semi_space_collector_->SetFromSpace(bump_pointer_space_);
- semi_space_collector_->SetToSpace(temp_space_);
- semi_space_collector_->SetSwapSemiSpaces(true);
- collector = semi_space_collector_;
- break;
- case kCollectorTypeCMC:
- collector = mark_compact_;
- break;
- case kCollectorTypeCC:
- collector::ConcurrentCopying* active_cc_collector;
- if (use_generational_cc_) {
- // TODO: Other threads must do the flip checkpoint before they start poking at
- // active_concurrent_copying_collector_. So we should not concurrency here.
- active_cc_collector = (gc_type == collector::kGcTypeSticky) ?
- young_concurrent_copying_collector_ :
- concurrent_copying_collector_;
- active_concurrent_copying_collector_.store(active_cc_collector,
- std::memory_order_relaxed);
- DCHECK(active_cc_collector->RegionSpace() == region_space_);
- collector = active_cc_collector;
- } else {
- collector = active_concurrent_copying_collector_.load(std::memory_order_relaxed);
- }
- break;
- default:
- LOG(FATAL) << "Invalid collector type " << static_cast<size_t>(collector_type_);
- }
- // temp_space_ will be null for kCollectorTypeCMC.
- if (temp_space_ != nullptr &&
- collector != active_concurrent_copying_collector_.load(std::memory_order_relaxed)) {
- temp_space_->GetMemMap()->Protect(PROT_READ | PROT_WRITE);
- if (kIsDebugBuild) {
- // Try to read each page of the memory map in case mprotect didn't work properly
- // b/19894268.
- temp_space_->GetMemMap()->TryReadable();
- }
- CHECK(temp_space_->IsEmpty());
- }
- } else if (current_allocator_ == kAllocatorTypeRosAlloc ||
- current_allocator_ == kAllocatorTypeDlMalloc) {
- collector = FindCollectorByGcType(gc_type);
- } else {
- LOG(FATAL) << "Invalid current allocator " << current_allocator_;
- }
-
- CHECK(collector != nullptr) << "Could not find garbage collector with collector_type="
- << static_cast<size_t>(collector_type_)
- << " and gc_type=" << gc_type;
- collector->Run(gc_cause, clear_soft_references || runtime->IsZygote());
- IncrementFreedEver();
- RequestTrim(self);
- // Collect cleared references.
- clear = reference_processor_->CollectClearedReferences(self);
- // Grow the heap so that we know when to perform the next GC.
- GrowForUtilization(collector, bytes_allocated_before_gc);
- old_native_bytes_allocated_.store(GetNativeBytes());
- LogGC(gc_cause, collector);
- FinishGC(self, gc_type);
+ collector_type_running_ = collector_type_;
+ last_gc_cause_ = gc_cause;
}
+ if (gc_cause == kGcCauseForAlloc && runtime->HasStatsEnabled()) {
+ ++runtime->GetStats()->gc_for_alloc_count;
+ ++self->GetStats()->gc_for_alloc_count;
+ }
+ const size_t bytes_allocated_before_gc = GetBytesAllocated();
+
+ DCHECK_LT(gc_type, collector::kGcTypeMax);
+ DCHECK_NE(gc_type, collector::kGcTypeNone);
+
+ collector::GarbageCollector* collector = nullptr;
+ // TODO: Clean this up.
+ if (compacting_gc) {
+ DCHECK(current_allocator_ == kAllocatorTypeBumpPointer ||
+ current_allocator_ == kAllocatorTypeTLAB ||
+ current_allocator_ == kAllocatorTypeRegion ||
+ current_allocator_ == kAllocatorTypeRegionTLAB);
+ switch (collector_type_) {
+ case kCollectorTypeSS:
+ semi_space_collector_->SetFromSpace(bump_pointer_space_);
+ semi_space_collector_->SetToSpace(temp_space_);
+ semi_space_collector_->SetSwapSemiSpaces(true);
+ collector = semi_space_collector_;
+ break;
+ case kCollectorTypeCMC:
+ collector = mark_compact_;
+ break;
+ case kCollectorTypeCC:
+ collector::ConcurrentCopying* active_cc_collector;
+ if (use_generational_cc_) {
+ // TODO: Other threads must do the flip checkpoint before they start poking at
+ // active_concurrent_copying_collector_. So we should not concurrency here.
+ active_cc_collector = (gc_type == collector::kGcTypeSticky) ?
+ young_concurrent_copying_collector_ : concurrent_copying_collector_;
+ active_concurrent_copying_collector_.store(active_cc_collector,
+ std::memory_order_relaxed);
+ DCHECK(active_cc_collector->RegionSpace() == region_space_);
+ collector = active_cc_collector;
+ } else {
+ collector = active_concurrent_copying_collector_.load(std::memory_order_relaxed);
+ }
+ break;
+ default:
+ LOG(FATAL) << "Invalid collector type " << static_cast<size_t>(collector_type_);
+ }
+ // temp_space_ will be null for kCollectorTypeCMC.
+ if (temp_space_ != nullptr
+ && collector != active_concurrent_copying_collector_.load(std::memory_order_relaxed)) {
+ temp_space_->GetMemMap()->Protect(PROT_READ | PROT_WRITE);
+ if (kIsDebugBuild) {
+ // Try to read each page of the memory map in case mprotect didn't work properly b/19894268.
+ temp_space_->GetMemMap()->TryReadable();
+ }
+ CHECK(temp_space_->IsEmpty());
+ }
+ } else if (current_allocator_ == kAllocatorTypeRosAlloc ||
+ current_allocator_ == kAllocatorTypeDlMalloc) {
+ collector = FindCollectorByGcType(gc_type);
+ } else {
+ LOG(FATAL) << "Invalid current allocator " << current_allocator_;
+ }
+
+ CHECK(collector != nullptr)
+ << "Could not find garbage collector with collector_type="
+ << static_cast<size_t>(collector_type_) << " and gc_type=" << gc_type;
+ collector->Run(gc_cause, clear_soft_references || runtime->IsZygote());
+ IncrementFreedEver();
+ RequestTrim(self);
+ // Collect cleared references.
+ SelfDeletingTask* clear = reference_processor_->CollectClearedReferences(self);
+ // Grow the heap so that we know when to perform the next GC.
+ GrowForUtilization(collector, bytes_allocated_before_gc);
+ old_native_bytes_allocated_.store(GetNativeBytes());
+ LogGC(gc_cause, collector);
+ FinishGC(self, gc_type);
// Actually enqueue all cleared references. Do this after the GC has officially finished since
// otherwise we can deadlock.
clear->Run(self);
diff --git a/runtime/mirror/object.cc b/runtime/mirror/object.cc
index f1e177a..5016c20 100644
--- a/runtime/mirror/object.cc
+++ b/runtime/mirror/object.cc
@@ -185,8 +185,7 @@
hash_code_seed.store(new_seed, std::memory_order_relaxed);
}
-template <bool kAllowInflation>
-int32_t Object::IdentityHashCodeHelper() {
+int32_t Object::IdentityHashCode() {
ObjPtr<Object> current_this = this; // The this pointer may get invalidated by thread suspension.
while (true) {
LockWord lw = current_this->GetLockWord(false);
@@ -204,9 +203,6 @@
break;
}
case LockWord::kThinLocked: {
- if (!kAllowInflation) {
- return 0;
- }
// Inflate the thin lock to a monitor and stick the hash code inside of the monitor. May
// fail spuriously.
Thread* self = Thread::Current();
@@ -234,12 +230,6 @@
}
}
-int32_t Object::IdentityHashCode() { return IdentityHashCodeHelper</* kAllowInflation= */ true>(); }
-
-int32_t Object::IdentityHashCodeNoInflation() {
- return IdentityHashCodeHelper</* kAllowInflation= */ false>();
-}
-
void Object::CheckFieldAssignmentImpl(MemberOffset field_offset, ObjPtr<Object> new_value) {
ObjPtr<Class> c = GetClass();
Runtime* runtime = Runtime::Current();
diff --git a/runtime/mirror/object.h b/runtime/mirror/object.h
index 5e770f4..95b9f86 100644
--- a/runtime/mirror/object.h
+++ b/runtime/mirror/object.h
@@ -137,16 +137,11 @@
REQUIRES_SHARED(Locks::mutator_lock_)
REQUIRES(!Roles::uninterruptible_);
- // Returns a nonzero value that fits into lockword slot.
int32_t IdentityHashCode()
REQUIRES_SHARED(Locks::mutator_lock_)
REQUIRES(!Locks::thread_list_lock_,
!Locks::thread_suspend_count_lock_);
- // Identical to the above, but returns 0 if monitor inflation would otherwise be needed.
- int32_t IdentityHashCodeNoInflation() REQUIRES_SHARED(Locks::mutator_lock_)
- REQUIRES(!Locks::thread_list_lock_, !Locks::thread_suspend_count_lock_);
-
static constexpr MemberOffset MonitorOffset() {
return OFFSET_OF_OBJECT_MEMBER(Object, monitor_);
}
@@ -731,10 +726,6 @@
REQUIRES_SHARED(Locks::mutator_lock_);
private:
- template <bool kAllowInflation>
- int32_t IdentityHashCodeHelper() REQUIRES_SHARED(Locks::mutator_lock_)
- REQUIRES(!Locks::thread_list_lock_, !Locks::thread_suspend_count_lock_);
-
// Get a field with acquire semantics.
template<typename kSize>
ALWAYS_INLINE kSize GetFieldAcquire(MemberOffset field_offset)
diff --git a/runtime/monitor.cc b/runtime/monitor.cc
index 4e9e4d9..3fed8d4 100644
--- a/runtime/monitor.cc
+++ b/runtime/monitor.cc
@@ -1005,7 +1005,7 @@
if (monitor->num_waiters_.load(std::memory_order_relaxed) > 0) {
return false;
}
- if (!monitor->monitor_lock_.ExclusiveTryLock</* check= */ false>(self)) {
+ if (!monitor->monitor_lock_.ExclusiveTryLock(self)) {
// We cannot deflate a monitor that's currently held. It's unclear whether we should if
// we could.
return false;
@@ -1065,10 +1065,13 @@
ThreadList* thread_list = Runtime::Current()->GetThreadList();
// Suspend the owner, inflate. First change to blocked and give up mutator_lock_.
self->SetMonitorEnterObject(obj.Get());
+ bool timed_out;
Thread* owner;
{
ScopedThreadSuspension sts(self, ThreadState::kWaitingForLockInflation);
- owner = thread_list->SuspendThreadByThreadId(owner_thread_id, SuspendReason::kInternal);
+ owner = thread_list->SuspendThreadByThreadId(owner_thread_id,
+ SuspendReason::kInternal,
+ &timed_out);
}
if (owner != nullptr) {
// We succeeded in suspending the thread, check the lock's status didn't change.
diff --git a/runtime/mutator_gc_coord.md b/runtime/mutator_gc_coord.md
index ca83d5a..b3635c5 100644
--- a/runtime/mutator_gc_coord.md
+++ b/runtime/mutator_gc_coord.md
@@ -100,11 +100,7 @@
Logically the mutator lock is held in shared/reader mode if ***either*** the
underlying reader-writer lock is held in shared mode, ***or*** if a mutator is in
-runnable state. These two ways of holding the mutator mutex are ***not***
-equivalent: In particular, we rely on the garbage collector never actually
-entering a "runnable" state while active (see below). However, it often runs with
-the explicit mutator mutex in shared mode, thus blocking others from acquiring it
-in exclusive mode.
+runnable state.
Suspension and checkpoint API
-----------------------------
@@ -221,92 +217,6 @@
checkpoints do not preclude client threads from being in the middle of an
operation that involves a weak reference access, while nonempty checkpoints do.
-**Suspending the GC**
-Under unusual conditions, the GC can run on any thread. This means that when
-thread *A* suspends thread *B* for some other reason, Thread *B* might be
-running the garbage collector and conceivably thus cause it to block. This
-would be very deadlock prone. If Thread *A* allocates while Thread *B* is
-suspended in the GC, and the allocation requires the GC's help to complete, we
-deadlock.
-
-Thus we ensure that the GC, together with anything else that can block GCs,
-cannot be blocked for thread suspension requests. This is accomplished by
-ensuring that it always appears to be in a suspended thread state. Since we
-only check for suspend requests when entering the runnable state, suspend
-requests go unnoticed until the GC completes. It may physically acquire and
-release the actual `mutator_lock_` in either shared or exclusive mode.
-
-Thread Suspension Mechanics
----------------------------
-
-Thread suspension is initiated by a registered thread, except that, for testing
-purposes, `SuspendAll` may be invoked with `self == nullptr`. We never suspend
-the initiating thread, explicitly exclusing it from `SuspendAll()`, and failing
-`SuspendThreadBy...()` requests to that effect.
-
-The suspend calls invoke `IncrementSuspendCount()` to increment the thread
-suspend count for each thread. That adds a "suspend barrier" (atomic counter) to
-the per-thread list of such counters to decrement. It normally sets the
-`kSuspendRequest` ("should enter safepoint handler") and `kActiveSuspendBarrier`
-("need to notify us when suspended") flags.
-
-After setting these two flags, we check whether the thread is suspended and
-`kSuspendRequest` is still set. Since the thread is already suspended, it cannot
-be expected to respond to "pass the suspend barrier" (decrement the atomic
-counter) in a timely fashion. Hence we do so on its behalf. This decrements
-the "barrier" and removes it from the thread's list of barriers to decrement,
-and clears `kActiveSuspendBarrier`. `kSuspendRequest` remains to ensure the
-thread doesn't prematurely return to runnable state.
-
-If `SuspendAllInternal()` does not immediately see a suspended state, then it is up
-to the target thread to decrement the suspend barrier.
-`TransitionFromRunnableToSuspended()` calls
-`TransitionToSuspendedAndRunCheckpoints()`, which changes the thread state, and
-then calls `CheckActiveSuspendBarriers()` to check for the
-`kActiveSuspendBarrier` flag and decrement the suspend barrier if set.
-
-The `suspend_count_lock_` is not consistently held in the target thread
-during this process. Thus correctness in resolving the race between a
-suspension-requesting thread and a target thread voluntarily suspending relies
-on the following: If the requesting thread sets the flags with
-`kActiveSuspendBarrier` before the target's state is changed to suspended, then
-the target thread will see `kActiveSuspendBarrier` set, and will attempt to
-handle the barrier. If, on the other hand, the target thread changes the thread
-state first, then the requesting thread will see the suspended state, and handle
-the barrier itself. Since the actual update of suspend counts and suspend
-barrier data structures is done under the `suspend_count_lock_`, we always
-ensure that either the requestor removes/clears the barrier for a given target,
-or the target thread(s) decrement the barrier, but not both. This also ensures
-that the barrier cannot be decremented after the stack frame holding the barrier
-goes away.
-
-This relies on the fact that the two stores in the two threads to the state and
-kActiveSuspendBarrier flag are ordered with respect to the later loads. That's
-guaranteed, since they are all stored in a single `atomic<>`. Thus even relaxed
-accesses are OK.
-
-The actual suspend barrier representation still varies between `SuspendAll()`
-and `SuspendThreadBy...()`. The former relies on the fact that only one such
-barrier can be in use at a time, while the latter maintains a linked list of
-active suspend barriers for each target thread, relying on the fact that each
-one can appear on the list of only one thread, and we can thus use list nodes
-allocated in the stack frames of requesting threads.
-
-**Avoiding suspension cycles**
-
-Any thread can issue a `SuspendThreadByPeer()` or `SuspendAll()` request. But if
-Thread A increments Thread B's suspend count while Thread B increments Thread
-A's suspend count, and they then both suspend during a subsequent thread
-transition, we're deadlocked.
-
-For `SuspendAll()`, we enforce a requirement that at most one `SuspendAll()`
-request is running at one time. In addition, in all cases, we refuse to initiate
-a suspend request from a registered thread that is also being asked to suspend
-(i.e. the suspend count is nonzero). Instead the requestor waits for that
-condition to change. This means that we cannot create a cycle in which each
-thread has asked to suspend the next one, and thus no thread can progress. The
-required atomicity of the requestor suspend count check with setting the suspend
-count of the target(s) target is ensured by holding `suspend_count_lock_`.
[^1]: Some comments in the code refer to a not-yet-really-implemented scheme in
which the compiler-generated code would load through the address at
diff --git a/runtime/native/dalvik_system_VMStack.cc b/runtime/native/dalvik_system_VMStack.cc
index bf441b4..71078c9 100644
--- a/runtime/native/dalvik_system_VMStack.cc
+++ b/runtime/native/dalvik_system_VMStack.cc
@@ -48,29 +48,19 @@
} else {
// Never allow suspending the heap task thread since it may deadlock if allocations are
// required for the stack trace.
- Thread* heap_task_thread = nullptr;
- for (int i = 0; i < 20; ++i) {
- heap_task_thread = Runtime::Current()->GetHeap()->GetTaskProcessor()->GetRunningThread();
- if (heap_task_thread != nullptr) {
- break;
- }
- // heap_task_thread could be null if the daemons aren't fully running yet. But it can appear
- // in enumerations, and thus we could try to get its stack even before that. Try to wait
- // for a non-null value so we can avoid suspending it.
- static constexpr int kHeapTaskDaemonSleepMicros = 5000;
- usleep(kHeapTaskDaemonSleepMicros);
- }
- if (heap_task_thread == nullptr) {
- LOG(ERROR) << "No HeapTaskDaemon; refusing to get thread stack.";
- return nullptr;
- }
- if (decoded_peer == heap_task_thread->GetPeerFromOtherThread()) {
+ Thread* heap_task_thread =
+ Runtime::Current()->GetHeap()->GetTaskProcessor()->GetRunningThread();
+ // heap_task_thread could be null if the daemons aren't yet started.
+ if (heap_task_thread != nullptr && decoded_peer == heap_task_thread->GetPeerFromOtherThread()) {
return nullptr;
}
// Suspend thread to build stack trace.
ScopedThreadSuspension sts(soa.Self(), ThreadState::kNative);
ThreadList* thread_list = Runtime::Current()->GetThreadList();
- Thread* thread = thread_list->SuspendThreadByPeer(peer, SuspendReason::kInternal);
+ bool timed_out;
+ Thread* thread = thread_list->SuspendThreadByPeer(peer,
+ SuspendReason::kInternal,
+ &timed_out);
if (thread != nullptr) {
// Must be runnable to create returned array.
{
@@ -80,6 +70,9 @@
// Restart suspended thread.
bool resumed = thread_list->Resume(thread, SuspendReason::kInternal);
DCHECK(resumed);
+ } else if (timed_out) {
+ LOG(ERROR) << "Trying to get thread's stack failed as the thread failed to suspend within a "
+ "generous timeout.";
}
}
return trace;
diff --git a/runtime/native/java_lang_Thread.cc b/runtime/native/java_lang_Thread.cc
index fd67a0a..570c554 100644
--- a/runtime/native/java_lang_Thread.cc
+++ b/runtime/native/java_lang_Thread.cc
@@ -147,8 +147,11 @@
// thread list lock to avoid this, as setting the thread name causes mutator to lock/unlock
// in the DDMS send code.
ThreadList* thread_list = Runtime::Current()->GetThreadList();
+ bool timed_out;
// Take suspend thread lock to avoid races with threads trying to suspend this one.
- Thread* thread = thread_list->SuspendThreadByPeer(peer, SuspendReason::kInternal);
+ Thread* thread = thread_list->SuspendThreadByPeer(peer,
+ SuspendReason::kInternal,
+ &timed_out);
if (thread != nullptr) {
{
ScopedObjectAccess soa(env);
@@ -156,6 +159,9 @@
}
bool resumed = thread_list->Resume(thread, SuspendReason::kInternal);
DCHECK(resumed);
+ } else if (timed_out) {
+ LOG(ERROR) << "Trying to set thread name to '" << name.c_str() << "' failed as the thread "
+ "failed to suspend within a generous timeout.";
}
}
diff --git a/runtime/native/org_apache_harmony_dalvik_ddmc_DdmVmInternal.cc b/runtime/native/org_apache_harmony_dalvik_ddmc_DdmVmInternal.cc
index f20cd28..081ec20 100644
--- a/runtime/native/org_apache_harmony_dalvik_ddmc_DdmVmInternal.cc
+++ b/runtime/native/org_apache_harmony_dalvik_ddmc_DdmVmInternal.cc
@@ -59,6 +59,7 @@
trace = Thread::InternalStackTraceToStackTraceElementArray(soa, internal_trace);
} else {
ThreadList* thread_list = Runtime::Current()->GetThreadList();
+ bool timed_out;
// Check for valid thread
if (thin_lock_id == ThreadList::kInvalidThreadId) {
@@ -66,7 +67,9 @@
}
// Suspend thread to build stack trace.
- Thread* thread = thread_list->SuspendThreadByThreadId(thin_lock_id, SuspendReason::kInternal);
+ Thread* thread = thread_list->SuspendThreadByThreadId(thin_lock_id,
+ SuspendReason::kInternal,
+ &timed_out);
if (thread != nullptr) {
{
ScopedObjectAccess soa(env);
@@ -76,6 +79,11 @@
// Restart suspended thread.
bool resumed = thread_list->Resume(thread, SuspendReason::kInternal);
DCHECK(resumed);
+ } else {
+ if (timed_out) {
+ LOG(ERROR) << "Trying to get thread's stack by id failed as the thread failed to suspend "
+ "within a generous timeout.";
+ }
}
}
return trace;
diff --git a/runtime/oat.h b/runtime/oat.h
index 4be2cb9..e062baa 100644
--- a/runtime/oat.h
+++ b/runtime/oat.h
@@ -44,8 +44,8 @@
class PACKED(4) OatHeader {
public:
static constexpr std::array<uint8_t, 4> kOatMagic { { 'o', 'a', 't', '\n' } };
- // Last oat version changed reason: Change suspend barrier data structure.
- static constexpr std::array<uint8_t, 4> kOatVersion{{'2', '3', '1', '\0'}};
+ // Last oat version changed reason: ARM64: Enable implicit suspend checks; compiled code check.
+ static constexpr std::array<uint8_t, 4> kOatVersion { { '2', '3', '0', '\0' } };
static constexpr const char* kDex2OatCmdLineKey = "dex2oat-cmdline";
static constexpr const char* kDebuggableKey = "debuggable";
diff --git a/runtime/stack.cc b/runtime/stack.cc
index bf844b4..d7d5851 100644
--- a/runtime/stack.cc
+++ b/runtime/stack.cc
@@ -77,7 +77,7 @@
context_(context),
check_suspended_(check_suspended) {
if (check_suspended_) {
- DCHECK(thread == Thread::Current() || thread->GetState() != ThreadState::kRunnable) << *thread;
+ DCHECK(thread == Thread::Current() || thread->IsSuspended()) << *thread;
}
}
@@ -801,7 +801,7 @@
template <StackVisitor::CountTransitions kCount>
void StackVisitor::WalkStack(bool include_transitions) {
if (check_suspended_) {
- DCHECK(thread_ == Thread::Current() || thread_->GetState() != ThreadState::kRunnable);
+ DCHECK(thread_ == Thread::Current() || thread_->IsSuspended());
}
CHECK_EQ(cur_depth_, 0U);
diff --git a/runtime/thread-inl.h b/runtime/thread-inl.h
index a03d616..f99b435 100644
--- a/runtime/thread-inl.h
+++ b/runtime/thread-inl.h
@@ -17,6 +17,8 @@
#ifndef ART_RUNTIME_THREAD_INL_H_
#define ART_RUNTIME_THREAD_INL_H_
+#include "thread.h"
+
#include "arch/instruction_set.h"
#include "base/aborting.h"
#include "base/casts.h"
@@ -25,8 +27,8 @@
#include "jni/jni_env_ext.h"
#include "managed_stack-inl.h"
#include "obj_ptr.h"
+#include "suspend_reason.h"
#include "thread-current-inl.h"
-#include "thread.h"
#include "thread_pool.h"
namespace art {
@@ -220,7 +222,7 @@
}
}
-inline void Thread::CheckActiveSuspendBarriers() {
+inline void Thread::PassActiveSuspendBarriers() {
while (true) {
StateAndFlags state_and_flags = GetStateAndFlags(std::memory_order_relaxed);
if (LIKELY(!state_and_flags.IsFlagSet(ThreadFlag::kCheckpointRequest) &&
@@ -228,7 +230,7 @@
!state_and_flags.IsFlagSet(ThreadFlag::kActiveSuspendBarrier))) {
break;
} else if (state_and_flags.IsFlagSet(ThreadFlag::kActiveSuspendBarrier)) {
- PassActiveSuspendBarriers();
+ PassActiveSuspendBarriers(this);
} else {
// Impossible
LOG(FATAL) << "Fatal, thread transitioned into suspended without running the checkpoint";
@@ -236,20 +238,6 @@
}
}
-inline void Thread::AddSuspend1Barrier(WrappedSuspend1Barrier* suspend1_barrier) {
- suspend1_barrier->next_ = tlsPtr_.active_suspend1_barriers;
- tlsPtr_.active_suspend1_barriers = suspend1_barrier;
-}
-
-inline void Thread::RemoveFirstSuspend1Barrier() {
- tlsPtr_.active_suspend1_barriers = tlsPtr_.active_suspend1_barriers->next_;
-}
-
-inline bool Thread::HasActiveSuspendBarrier() {
- return tlsPtr_.active_suspend1_barriers != nullptr ||
- tlsPtr_.active_suspendall_barrier != nullptr;
-}
-
inline void Thread::TransitionFromRunnableToSuspended(ThreadState new_state) {
// Note: JNI stubs inline a fast path of this method that transitions to suspended if
// there are no flags set and then clears the `held_mutexes[kMutatorLock]` (this comes
@@ -265,7 +253,7 @@
// Mark the release of the share of the mutator lock.
GetMutatorLock()->TransitionFromRunnableToSuspended(this);
// Once suspended - check the active suspend barrier flag
- CheckActiveSuspendBarriers();
+ PassActiveSuspendBarriers();
}
inline ThreadState Thread::TransitionFromSuspendedToRunnable() {
@@ -275,7 +263,6 @@
// inlined from the `GetMutatorLock()->TransitionFromSuspendedToRunnable(this)` below).
// Therefore any code added here (other than debug build assertions) should be gated
// on some flag being set, so that the JNI stub can take the slow path to get here.
- DCHECK(this == Current());
StateAndFlags old_state_and_flags = GetStateAndFlags(std::memory_order_relaxed);
ThreadState old_state = old_state_and_flags.GetState();
DCHECK_NE(old_state, ThreadState::kRunnable);
@@ -297,7 +284,7 @@
break;
}
} else if (old_state_and_flags.IsFlagSet(ThreadFlag::kActiveSuspendBarrier)) {
- PassActiveSuspendBarriers();
+ PassActiveSuspendBarriers(this);
} else if (UNLIKELY(old_state_and_flags.IsFlagSet(ThreadFlag::kCheckpointRequest) ||
old_state_and_flags.IsFlagSet(ThreadFlag::kEmptyCheckpointRequest))) {
// Checkpoint flags should not be set while in suspended state.
@@ -319,6 +306,7 @@
thread_to_pass = this;
}
MutexLock mu(thread_to_pass, *Locks::thread_suspend_count_lock_);
+ ScopedTransitioningToRunnable scoped_transitioning_to_runnable(this);
// Reload state and flags after locking the mutex.
old_state_and_flags = GetStateAndFlags(std::memory_order_relaxed);
DCHECK_EQ(old_state, old_state_and_flags.GetState());
@@ -330,15 +318,27 @@
DCHECK_EQ(old_state, old_state_and_flags.GetState());
}
DCHECK_EQ(GetSuspendCount(), 0);
- } else if (UNLIKELY(old_state_and_flags.IsFlagSet(ThreadFlag::kRunningFlipFunction))) {
- DCHECK(!old_state_and_flags.IsFlagSet(ThreadFlag::kPendingFlipFunction));
- // Do this before transitioning to runnable, both because we're waiting, and so that the
- // thread running the flip function can DCHECK we're not runnable.
- WaitForFlipFunction(this);
- } else if (old_state_and_flags.IsFlagSet(ThreadFlag::kPendingFlipFunction)) {
- // Logically acquire mutator lock in shared mode.
- DCHECK(!old_state_and_flags.IsFlagSet(ThreadFlag::kRunningFlipFunction));
- if (EnsureFlipFunctionStarted(this, /*become_runnable=*/true)) {
+ } else if (UNLIKELY(old_state_and_flags.IsFlagSet(ThreadFlag::kRunningFlipFunction)) ||
+ UNLIKELY(old_state_and_flags.IsFlagSet(ThreadFlag::kWaitingForFlipFunction))) {
+ // The thread should be suspended while another thread is running the flip function.
+ static_assert(static_cast<std::underlying_type_t<ThreadState>>(ThreadState::kRunnable) == 0u);
+ LOG(FATAL) << "Transitioning to Runnable while another thread is running the flip function,"
+ // Note: Keeping unused flags. If they are set, it points to memory corruption.
+ << " flags=" << old_state_and_flags.WithState(ThreadState::kRunnable).GetValue()
+ << " state=" << old_state_and_flags.GetState();
+ } else {
+ DCHECK(old_state_and_flags.IsFlagSet(ThreadFlag::kPendingFlipFunction));
+ // CAS the value with a memory barrier.
+ // Do not set `ThreadFlag::kRunningFlipFunction` as no other thread can run
+ // the flip function for a thread that is not suspended.
+ StateAndFlags new_state_and_flags = old_state_and_flags.WithState(ThreadState::kRunnable)
+ .WithoutFlag(ThreadFlag::kPendingFlipFunction);
+ if (LIKELY(tls32_.state_and_flags.CompareAndSetWeakAcquire(old_state_and_flags.GetValue(),
+ new_state_and_flags.GetValue()))) {
+ // Mark the acquisition of a share of the mutator lock.
+ GetMutatorLock()->TransitionFromSuspendedToRunnable(this);
+ // Run the flip function.
+ RunFlipFunction(this, /*notify=*/ false);
break;
}
}
@@ -346,7 +346,6 @@
old_state_and_flags = GetStateAndFlags(std::memory_order_relaxed);
DCHECK_EQ(old_state, old_state_and_flags.GetState());
}
- DCHECK_EQ(this->GetState(), ThreadState::kRunnable);
return static_cast<ThreadState>(old_state);
}
@@ -412,7 +411,7 @@
if (kIsDebugBuild) {
// Note: self is not necessarily equal to this thread since thread may be suspended.
Thread* self = Thread::Current();
- DCHECK(this == self || GetState() != ThreadState::kRunnable)
+ DCHECK(this == self || IsSuspended() || GetState() == ThreadState::kWaitingPerformingGc)
<< GetState() << " thread " << this << " self " << self;
}
tlsPtr_.thread_local_alloc_stack_end = nullptr;
@@ -425,70 +424,35 @@
}
}
-inline void Thread::IncrementSuspendCount(Thread* self,
- AtomicInteger* suspendall_barrier,
- WrappedSuspend1Barrier* suspend1_barrier,
- SuspendReason reason) {
- if (kIsDebugBuild) {
- Locks::thread_suspend_count_lock_->AssertHeld(self);
- if (this != self && !IsSuspended()) {
- Locks::thread_list_lock_->AssertHeld(self);
+inline bool Thread::ModifySuspendCount(Thread* self,
+ int delta,
+ AtomicInteger* suspend_barrier,
+ SuspendReason reason) {
+ if (delta > 0 &&
+ (((gUseUserfaultfd || gUseReadBarrier) && this != self) || suspend_barrier != nullptr)) {
+ // When delta > 0 (requesting a suspend), ModifySuspendCountInternal() may fail either if
+ // active_suspend_barriers is full or we are in the middle of a thread flip. Retry in a loop.
+ while (true) {
+ if (LIKELY(ModifySuspendCountInternal(self, delta, suspend_barrier, reason))) {
+ return true;
+ } else {
+ // Failure means the list of active_suspend_barriers is full or we are in the middle of a
+ // thread flip, we should release the thread_suspend_count_lock_ (to avoid deadlock) and
+ // wait till the target thread has executed or Thread::PassActiveSuspendBarriers() or the
+ // flip function. Note that we could not simply wait for the thread to change to a suspended
+ // state, because it might need to run checkpoint function before the state change or
+ // resumes from the resume_cond_, which also needs thread_suspend_count_lock_.
+ //
+ // The list of active_suspend_barriers is very unlikely to be full since more than
+ // kMaxSuspendBarriers threads need to execute SuspendAllInternal() simultaneously, and
+ // target thread stays in kRunnable in the mean time.
+ Locks::thread_suspend_count_lock_->ExclusiveUnlock(self);
+ NanoSleep(100000);
+ Locks::thread_suspend_count_lock_->ExclusiveLock(self);
+ }
}
- }
- if (UNLIKELY(reason == SuspendReason::kForUserCode)) {
- Locks::user_code_suspension_lock_->AssertHeld(self);
- }
-
- uint32_t flags = enum_cast<uint32_t>(ThreadFlag::kSuspendRequest);
- if (suspendall_barrier != nullptr) {
- DCHECK(suspend1_barrier == nullptr);
- DCHECK(tlsPtr_.active_suspendall_barrier == nullptr);
- tlsPtr_.active_suspendall_barrier = suspendall_barrier;
- flags |= enum_cast<uint32_t>(ThreadFlag::kActiveSuspendBarrier);
- } else if (suspend1_barrier != nullptr) {
- AddSuspend1Barrier(suspend1_barrier);
- flags |= enum_cast<uint32_t>(ThreadFlag::kActiveSuspendBarrier);
- }
-
- ++tls32_.suspend_count;
- if (reason == SuspendReason::kForUserCode) {
- ++tls32_.user_code_suspend_count;
- }
-
- // Two bits might be set simultaneously.
- tls32_.state_and_flags.fetch_or(flags, std::memory_order_seq_cst);
- TriggerSuspend();
-}
-
-inline void Thread::IncrementSuspendCount(Thread* self) {
- IncrementSuspendCount(self, nullptr, nullptr, SuspendReason::kInternal);
-}
-
-inline void Thread::DecrementSuspendCount(Thread* self, bool for_user_code) {
- if (kIsDebugBuild) {
- Locks::thread_suspend_count_lock_->AssertHeld(self);
- if (this != self && !IsSuspended()) {
- Locks::thread_list_lock_->AssertHeld(self);
- }
- }
- if (UNLIKELY(tls32_.suspend_count <= 0)) {
- UnsafeLogFatalForSuspendCount(self, this);
- UNREACHABLE();
- }
- if (for_user_code) {
- Locks::user_code_suspension_lock_->AssertHeld(self);
- if (UNLIKELY(tls32_.user_code_suspend_count <= 0)) {
- LOG(ERROR) << "user_code_suspend_count incorrect";
- UnsafeLogFatalForSuspendCount(self, this);
- UNREACHABLE();
- }
- --tls32_.user_code_suspend_count;
- }
-
- --tls32_.suspend_count;
-
- if (tls32_.suspend_count == 0) {
- AtomicClearFlag(ThreadFlag::kSuspendRequest);
+ } else {
+ return ModifySuspendCountInternal(self, delta, suspend_barrier, reason);
}
}
@@ -521,34 +485,6 @@
tlsPtr_.stack_end = tlsPtr_.stack_begin + GetStackOverflowReservedBytes(kRuntimeISA);
}
-inline void Thread::NotifyOnThreadExit(ThreadExitFlag* tef) {
- tef->next_ = tlsPtr_.thread_exit_flags;
- if (tef->next_ == nullptr) {
- tlsPtr_.thread_exit_flags = tef;
- } else {
- DCHECK(!tef->next_->HasExited());
- tef->next_->prev_ = tef;
- }
- tef->prev_ = nullptr;
-}
-
-inline void Thread::UnregisterThreadExitFlag(ThreadExitFlag* tef) {
- if (tef->HasExited()) {
- // List is no longer used; each client will deallocate its own ThreadExitFlag.
- return;
- }
- // Remove tef from the list.
- if (tef->next_ != nullptr) {
- tef->next_->prev_ = tef->prev_;
- }
- if (tef->prev_ == nullptr) {
- DCHECK_EQ(tlsPtr_.thread_exit_flags, tef);
- tlsPtr_.thread_exit_flags = tef->next_;
- } else {
- tef->prev_->next_ = tef->next_;
- }
-}
-
} // namespace art
#endif // ART_RUNTIME_THREAD_INL_H_
diff --git a/runtime/thread.cc b/runtime/thread.cc
index 1589b8a..77f53cf 100644
--- a/runtime/thread.cc
+++ b/runtime/thread.cc
@@ -1453,7 +1453,7 @@
}
// Attempt to rectify locks so that we dump thread list with required locks before exiting.
-void Thread::UnsafeLogFatalForSuspendCount(Thread* self, Thread* thread) NO_THREAD_SAFETY_ANALYSIS {
+static void UnsafeLogFatalForSuspendCount(Thread* self, Thread* thread) NO_THREAD_SAFETY_ANALYSIS {
LOG(ERROR) << *thread << " suspend count already zero.";
Locks::thread_suspend_count_lock_->Unlock(self);
if (!Locks::mutator_lock_->IsSharedHeld(self)) {
@@ -1471,52 +1471,141 @@
std::ostringstream ss;
Runtime::Current()->GetThreadList()->Dump(ss);
LOG(FATAL) << ss.str();
- UNREACHABLE();
}
-bool Thread::PassActiveSuspendBarriers() {
- DCHECK_EQ(this, Thread::Current());
- // Grab the suspend_count lock and copy the current set of barriers. Then clear the list and the
- // flag. The IncrementSuspendCount function requires the lock so we prevent a race between setting
- // the kActiveSuspendBarrier flag and clearing it.
- std::vector<AtomicInteger*> pass_barriers{};
- {
- MutexLock mu(this, *Locks::thread_suspend_count_lock_);
- if (!ReadFlag(ThreadFlag::kActiveSuspendBarrier)) {
- // quick exit test: the barriers have already been claimed - this is possible as there may
- // be a race to claim and it doesn't matter who wins.
- // All of the callers of this function (except the SuspendAllInternal) will first test the
- // kActiveSuspendBarrier flag without lock. Here double-check whether the barrier has been
- // passed with the suspend_count lock.
+bool Thread::ModifySuspendCountInternal(Thread* self,
+ int delta,
+ AtomicInteger* suspend_barrier,
+ SuspendReason reason) {
+ if (kIsDebugBuild) {
+ DCHECK(delta == -1 || delta == +1)
+ << reason << " " << delta << " " << this;
+ Locks::thread_suspend_count_lock_->AssertHeld(self);
+ if (this != self && !IsSuspended()) {
+ Locks::thread_list_lock_->AssertHeld(self);
+ }
+ }
+ // User code suspensions need to be checked more closely since they originate from code outside of
+ // the runtime's control.
+ if (UNLIKELY(reason == SuspendReason::kForUserCode)) {
+ Locks::user_code_suspension_lock_->AssertHeld(self);
+ if (UNLIKELY(delta + tls32_.user_code_suspend_count < 0)) {
+ LOG(ERROR) << "attempting to modify suspend count in an illegal way.";
return false;
}
- if (tlsPtr_.active_suspendall_barrier != nullptr) {
- // We have at most one active active_suspendall_barrier. See thread.h comment.
- pass_barriers.push_back(tlsPtr_.active_suspendall_barrier);
- tlsPtr_.active_suspendall_barrier = nullptr;
+ }
+ if (UNLIKELY(delta < 0 && tls32_.suspend_count <= 0)) {
+ UnsafeLogFatalForSuspendCount(self, this);
+ return false;
+ }
+
+ if (delta > 0 && this != self && tlsPtr_.flip_function != nullptr) {
+ // Force retry of a suspend request if it's in the middle of a thread flip to avoid a
+ // deadlock. b/31683379.
+ return false;
+ }
+
+ uint32_t flags = enum_cast<uint32_t>(ThreadFlag::kSuspendRequest);
+ if (delta > 0 && suspend_barrier != nullptr) {
+ uint32_t available_barrier = kMaxSuspendBarriers;
+ for (uint32_t i = 0; i < kMaxSuspendBarriers; ++i) {
+ if (tlsPtr_.active_suspend_barriers[i] == nullptr) {
+ available_barrier = i;
+ break;
+ }
}
- for (WrappedSuspend1Barrier* w = tlsPtr_.active_suspend1_barriers; w != nullptr; w = w->next_) {
- pass_barriers.push_back(&(w->barrier_));
+ if (available_barrier == kMaxSuspendBarriers) {
+ // No barrier spaces available, we can't add another.
+ return false;
}
- tlsPtr_.active_suspend1_barriers = nullptr;
+ tlsPtr_.active_suspend_barriers[available_barrier] = suspend_barrier;
+ flags |= enum_cast<uint32_t>(ThreadFlag::kActiveSuspendBarrier);
+ }
+
+ tls32_.suspend_count += delta;
+ switch (reason) {
+ case SuspendReason::kForUserCode:
+ tls32_.user_code_suspend_count += delta;
+ break;
+ case SuspendReason::kInternal:
+ break;
+ }
+
+ if (tls32_.suspend_count == 0) {
+ AtomicClearFlag(ThreadFlag::kSuspendRequest);
+ } else {
+ // Two bits might be set simultaneously.
+ tls32_.state_and_flags.fetch_or(flags, std::memory_order_seq_cst);
+ TriggerSuspend();
+ }
+ return true;
+}
+
+bool Thread::PassActiveSuspendBarriers(Thread* self) {
+ // Grab the suspend_count lock and copy the current set of
+ // barriers. Then clear the list and the flag. The ModifySuspendCount
+ // function requires the lock so we prevent a race between setting
+ // the kActiveSuspendBarrier flag and clearing it.
+ AtomicInteger* pass_barriers[kMaxSuspendBarriers];
+ {
+ MutexLock mu(self, *Locks::thread_suspend_count_lock_);
+ if (!ReadFlag(ThreadFlag::kActiveSuspendBarrier)) {
+ // quick exit test: the barriers have already been claimed - this is
+ // possible as there may be a race to claim and it doesn't matter
+ // who wins.
+ // All of the callers of this function (except the SuspendAllInternal)
+ // will first test the kActiveSuspendBarrier flag without lock. Here
+ // double-check whether the barrier has been passed with the
+ // suspend_count lock.
+ return false;
+ }
+
+ for (uint32_t i = 0; i < kMaxSuspendBarriers; ++i) {
+ pass_barriers[i] = tlsPtr_.active_suspend_barriers[i];
+ tlsPtr_.active_suspend_barriers[i] = nullptr;
+ }
AtomicClearFlag(ThreadFlag::kActiveSuspendBarrier);
}
uint32_t barrier_count = 0;
- for (AtomicInteger* barrier : pass_barriers) {
- ++barrier_count;
- int32_t old_val = barrier->fetch_sub(1, std::memory_order_release);
- CHECK_GT(old_val, 0) << "Unexpected value for PassActiveSuspendBarriers(): " << old_val;
+ for (uint32_t i = 0; i < kMaxSuspendBarriers; i++) {
+ AtomicInteger* pending_threads = pass_barriers[i];
+ if (pending_threads != nullptr) {
+ bool done = false;
+ do {
+ int32_t cur_val = pending_threads->load(std::memory_order_relaxed);
+ CHECK_GT(cur_val, 0) << "Unexpected value for PassActiveSuspendBarriers(): " << cur_val;
+ // Reduce value by 1.
+ done = pending_threads->CompareAndSetWeakRelaxed(cur_val, cur_val - 1);
#if ART_USE_FUTEXES
- if (old_val == 1) {
- futex(barrier->Address(), FUTEX_WAKE_PRIVATE, INT_MAX, nullptr, nullptr, 0);
- }
+ if (done && (cur_val - 1) == 0) { // Weak CAS may fail spuriously.
+ futex(pending_threads->Address(), FUTEX_WAKE_PRIVATE, INT_MAX, nullptr, nullptr, 0);
+ }
#endif
+ } while (!done);
+ ++barrier_count;
+ }
}
CHECK_GT(barrier_count, 0U);
return true;
}
+void Thread::ClearSuspendBarrier(AtomicInteger* target) {
+ CHECK(ReadFlag(ThreadFlag::kActiveSuspendBarrier));
+ bool clear_flag = true;
+ for (uint32_t i = 0; i < kMaxSuspendBarriers; ++i) {
+ AtomicInteger* ptr = tlsPtr_.active_suspend_barriers[i];
+ if (ptr == target) {
+ tlsPtr_.active_suspend_barriers[i] = nullptr;
+ } else if (ptr != nullptr) {
+ clear_flag = false;
+ }
+ }
+ if (LIKELY(clear_flag)) {
+ AtomicClearFlag(ThreadFlag::kActiveSuspendBarrier);
+ }
+}
+
void Thread::RunCheckpointFunction() {
// If this thread is suspended and another thread is running the checkpoint on its behalf,
// we may have a pending flip function that we need to run for the sake of those checkpoints
@@ -1568,25 +1657,28 @@
}
bool Thread::RequestCheckpoint(Closure* function) {
- StateAndFlags old_state_and_flags(0 /* unused */), new_state_and_flags(0 /* unused */);
- do {
- old_state_and_flags = GetStateAndFlags(std::memory_order_relaxed);
- if (old_state_and_flags.GetState() != ThreadState::kRunnable) {
- return false; // Fail, thread is suspended and so can't run a checkpoint.
- }
- new_state_and_flags = old_state_and_flags;
- new_state_and_flags.SetFlag(ThreadFlag::kCheckpointRequest);
- } while (!tls32_.state_and_flags.CompareAndSetWeakSequentiallyConsistent(
- old_state_and_flags.GetValue(), new_state_and_flags.GetValue()));
- // Succeeded setting checkpoint flag, now insert the actual checkpoint.
- if (tlsPtr_.checkpoint_function == nullptr) {
- tlsPtr_.checkpoint_function = function;
- } else {
- checkpoint_overflow_.push_back(function);
+ StateAndFlags old_state_and_flags = GetStateAndFlags(std::memory_order_relaxed);
+ if (old_state_and_flags.GetState() != ThreadState::kRunnable) {
+ return false; // Fail, thread is suspended and so can't run a checkpoint.
}
- DCHECK(ReadFlag(ThreadFlag::kCheckpointRequest));
- TriggerSuspend();
- return true;
+
+ // We must be runnable to request a checkpoint.
+ DCHECK_EQ(old_state_and_flags.GetState(), ThreadState::kRunnable);
+ StateAndFlags new_state_and_flags = old_state_and_flags;
+ new_state_and_flags.SetFlag(ThreadFlag::kCheckpointRequest);
+ bool success = tls32_.state_and_flags.CompareAndSetStrongSequentiallyConsistent(
+ old_state_and_flags.GetValue(), new_state_and_flags.GetValue());
+ if (success) {
+ // Succeeded setting checkpoint flag, now insert the actual checkpoint.
+ if (tlsPtr_.checkpoint_function == nullptr) {
+ tlsPtr_.checkpoint_function = function;
+ } else {
+ checkpoint_overflow_.push_back(function);
+ }
+ CHECK(ReadFlag(ThreadFlag::kCheckpointRequest));
+ TriggerSuspend();
+ }
+ return success;
}
bool Thread::RequestEmptyCheckpoint() {
@@ -1618,8 +1710,8 @@
barrier_.Pass(self);
}
- void Wait(Thread* self, ThreadState wait_state) {
- if (wait_state != ThreadState::kRunnable) {
+ void Wait(Thread* self, ThreadState suspend_state) {
+ if (suspend_state != ThreadState::kRunnable) {
barrier_.Increment<Barrier::kDisallowHoldingLocks>(self, 1);
} else {
barrier_.Increment<Barrier::kAllowHoldingLocks>(self, 1);
@@ -1632,9 +1724,9 @@
};
// RequestSynchronousCheckpoint releases the thread_list_lock_ as a part of its execution.
-bool Thread::RequestSynchronousCheckpoint(Closure* function, ThreadState wait_state) {
+bool Thread::RequestSynchronousCheckpoint(Closure* function, ThreadState suspend_state) {
Thread* self = Thread::Current();
- if (this == self) {
+ if (this == Thread::Current()) {
Locks::thread_list_lock_->AssertExclusiveHeld(self);
// Unlock the tll before running so that the state is the same regardless of thread.
Locks::thread_list_lock_->ExclusiveUnlock(self);
@@ -1646,196 +1738,158 @@
// The current thread is not this thread.
if (GetState() == ThreadState::kTerminated) {
- Locks::thread_list_lock_->Unlock(self);
+ Locks::thread_list_lock_->ExclusiveUnlock(self);
return false;
}
- Locks::thread_list_lock_->AssertExclusiveHeld(self);
- // If target "this" thread is runnable, try to schedule a checkpoint. Do some gymnastics to not
- // hold the suspend-count lock for too long.
- if (GetState() == ThreadState::kRunnable) {
- BarrierClosure barrier_closure(function);
- bool installed = false;
- {
- MutexLock mu(self, *Locks::thread_suspend_count_lock_);
- installed = RequestCheckpoint(&barrier_closure);
+ struct ScopedThreadListLockUnlock {
+ explicit ScopedThreadListLockUnlock(Thread* self_in) RELEASE(*Locks::thread_list_lock_)
+ : self_thread(self_in) {
+ Locks::thread_list_lock_->AssertHeld(self_thread);
+ Locks::thread_list_lock_->Unlock(self_thread);
}
- if (installed) {
- // Relinquish the thread-list lock. We should not wait holding any locks. We cannot
- // reacquire it since we don't know if 'this' hasn't been deleted yet.
- Locks::thread_list_lock_->ExclusiveUnlock(self);
- ScopedThreadStateChange sts(self, wait_state);
- // Wait state can be kRunnable, in which case, for lock ordering purposes, it's as if we ran
- // the closure ourselves. This means that the target thread should not acquire a pre-mutator
- // lock without running the checkpoint, and the closure should not acquire a pre-mutator
- // lock or suspend.
- barrier_closure.Wait(self, wait_state);
- return true;
+
+ ~ScopedThreadListLockUnlock() ACQUIRE(*Locks::thread_list_lock_) {
+ Locks::thread_list_lock_->AssertNotHeld(self_thread);
+ Locks::thread_list_lock_->Lock(self_thread);
}
- // No longer runnable. Fall-through.
- }
- // Target "this" thread was not runnable. Suspend it, hopefully redundantly,
- // but it might have become runnable in the meantime.
- // Although this is a thread suspension, the target thread only blocks while we run the
- // checkpoint, which is presumed to terminate quickly even if other threads are blocked.
- // Note: IncrementSuspendCount also expects the thread_list_lock to be held in
- // certain situations.
- {
- bool is_suspended = false;
- WrappedSuspend1Barrier wrapped_barrier{};
+ Thread* self_thread;
+ };
- {
- MutexLock suspend_count_mu(self, *Locks::thread_suspend_count_lock_);
- // If wait_state is kRunnable, function may not suspend. We thus never block because
- // we ourselves are being asked to suspend.
- if (UNLIKELY(wait_state != ThreadState::kRunnable && self->GetSuspendCount() != 0)) {
- // We are being asked to suspend while we are suspending another thread that may be
- // responsible for our suspension. This is likely to result in deadlock if we each
- // block on the suspension request. Instead we wait for the situation to change.
- ThreadExitFlag target_status;
- NotifyOnThreadExit(&target_status);
- for (int iter_count = 1; self->GetSuspendCount() != 0; ++iter_count) {
- Locks::thread_suspend_count_lock_->Unlock(self);
- Locks::thread_list_lock_->Unlock(self);
- {
- ScopedThreadStateChange sts(self, wait_state);
- usleep(ThreadList::kThreadSuspendSleepUs);
- }
- CHECK_LT(iter_count, ThreadList::kMaxSuspendRetries);
- Locks::thread_list_lock_->Lock(self);
- if (target_status.HasExited()) {
- Locks::thread_list_lock_->Unlock(self);
- return false;
- }
- Locks::thread_suspend_count_lock_->Lock(self);
- }
- UnregisterThreadExitFlag(&target_status);
+ for (;;) {
+ Locks::thread_list_lock_->AssertExclusiveHeld(self);
+ // If this thread is runnable, try to schedule a checkpoint. Do some gymnastics to not hold the
+ // suspend-count lock for too long.
+ if (GetState() == ThreadState::kRunnable) {
+ BarrierClosure barrier_closure(function);
+ bool installed = false;
+ {
+ MutexLock mu(self, *Locks::thread_suspend_count_lock_);
+ installed = RequestCheckpoint(&barrier_closure);
}
- IncrementSuspendCount(self, nullptr, &wrapped_barrier, SuspendReason::kInternal);
- DCHECK_GT(GetSuspendCount(), 0);
- DCHECK_EQ(self->GetSuspendCount(), 0);
- // Since we've incremented the suspend count, "this" thread can no longer disappear.
- Locks::thread_list_lock_->ExclusiveUnlock(self);
- if (IsSuspended()) {
- // See the discussion in mutator_gc_coord.md for the race here.
- RemoveFirstSuspend1Barrier();
- if (!HasActiveSuspendBarrier()) {
- AtomicClearFlag(ThreadFlag::kActiveSuspendBarrier);
- }
- is_suspended = true;
+ if (installed) {
+ // Relinquish the thread-list lock. We should not wait holding any locks. We cannot
+ // reacquire it since we don't know if 'this' hasn't been deleted yet.
+ Locks::thread_list_lock_->ExclusiveUnlock(self);
+ ScopedThreadStateChange sts(self, suspend_state);
+ barrier_closure.Wait(self, suspend_state);
+ return true;
+ }
+ // Fall-through.
+ }
+
+ // This thread is not runnable, make sure we stay suspended, then run the checkpoint.
+ // Note: ModifySuspendCountInternal also expects the thread_list_lock to be held in
+ // certain situations.
+ {
+ MutexLock mu2(self, *Locks::thread_suspend_count_lock_);
+
+ if (!ModifySuspendCount(self, +1, nullptr, SuspendReason::kInternal)) {
+ // Just retry the loop.
+ sched_yield();
+ continue;
}
}
- if (!is_suspended) {
- bool success =
- Runtime::Current()->GetThreadList()->WaitForSuspendBarrier(&wrapped_barrier.barrier_);
- CHECK(success);
+
+ {
+ // Release for the wait. The suspension will keep us from being deleted. Reacquire after so
+ // that we can call ModifySuspendCount without racing against ThreadList::Unregister.
+ ScopedThreadListLockUnlock stllu(self);
+ {
+ ScopedThreadStateChange sts(self, suspend_state);
+ while (GetState() == ThreadState::kRunnable) {
+ // We became runnable again. Wait till the suspend triggered in ModifySuspendCount
+ // moves us to suspended.
+ sched_yield();
+ }
+ }
+
+ function->Run(this);
}
- function->Run(this);
- }
+ {
+ MutexLock mu2(self, *Locks::thread_suspend_count_lock_);
- {
- MutexLock mu2(self, *Locks::thread_suspend_count_lock_);
- DCHECK_NE(GetState(), ThreadState::kRunnable);
- DCHECK_GT(GetSuspendCount(), 0);
- DecrementSuspendCount(self);
- resume_cond_->Broadcast(self);
- }
+ DCHECK_NE(GetState(), ThreadState::kRunnable);
+ bool updated = ModifySuspendCount(self, -1, nullptr, SuspendReason::kInternal);
+ DCHECK(updated);
+ }
- return true;
+ {
+ // Imitate ResumeAll, the thread may be waiting on Thread::resume_cond_ since we raised its
+ // suspend count. Now the suspend_count_ is lowered so we must do the broadcast.
+ MutexLock mu2(self, *Locks::thread_suspend_count_lock_);
+ Thread::resume_cond_->Broadcast(self);
+ }
+
+ // Release the thread_list_lock_ to be consistent with the barrier-closure path.
+ Locks::thread_list_lock_->ExclusiveUnlock(self);
+
+ return true; // We're done, break out of the loop.
+ }
}
void Thread::SetFlipFunction(Closure* function) {
// This is called with all threads suspended, except for the calling thread.
DCHECK(IsSuspended() || Thread::Current() == this);
DCHECK(function != nullptr);
- DCHECK(GetFlipFunction() == nullptr);
- tlsPtr_.flip_function.store(function, std::memory_order_relaxed);
+ DCHECK(tlsPtr_.flip_function == nullptr);
+ tlsPtr_.flip_function = function;
DCHECK(!GetStateAndFlags(std::memory_order_relaxed).IsAnyOfFlagsSet(FlipFunctionFlags()));
AtomicSetFlag(ThreadFlag::kPendingFlipFunction, std::memory_order_release);
}
-bool Thread::EnsureFlipFunctionStarted(Thread* self,
- bool become_runnable,
- ThreadExitFlag* tef,
- bool* finished) {
- bool check_exited = (tef != nullptr);
- auto maybe_release = [=]() NO_THREAD_SAFETY_ANALYSIS /* conditionally unlocks */ {
- if (check_exited) {
- Locks::thread_list_lock_->Unlock(self);
- }
- };
- auto set_finished = [=](bool value) {
- if (finished != nullptr) {
- *finished = value;
- }
- };
-
- if (check_exited) {
- Locks::thread_list_lock_->Lock(self);
- if (tef->HasExited()) {
- Locks::thread_list_lock_->Unlock(self);
- set_finished(true);
- return false;
- }
- }
+void Thread::EnsureFlipFunctionStarted(Thread* self) {
while (true) {
- StateAndFlags old_state_and_flags = GetStateAndFlags(std::memory_order_acquire);
+ StateAndFlags old_state_and_flags = GetStateAndFlags(std::memory_order_relaxed);
if (!old_state_and_flags.IsFlagSet(ThreadFlag::kPendingFlipFunction)) {
- maybe_release();
- set_finished(!old_state_and_flags.IsFlagSet(ThreadFlag::kRunningFlipFunction));
- return false;
+ return;
}
DCHECK(!old_state_and_flags.IsFlagSet(ThreadFlag::kRunningFlipFunction));
StateAndFlags new_state_and_flags =
old_state_and_flags.WithFlag(ThreadFlag::kRunningFlipFunction)
.WithoutFlag(ThreadFlag::kPendingFlipFunction);
- if (become_runnable) {
- DCHECK_EQ(self, this);
- DCHECK_NE(self->GetState(), ThreadState::kRunnable);
- new_state_and_flags = new_state_and_flags.WithState(ThreadState::kRunnable);
- }
if (tls32_.state_and_flags.CompareAndSetWeakAcquire(old_state_and_flags.GetValue(),
new_state_and_flags.GetValue())) {
- if (become_runnable) {
- GetMutatorLock()->TransitionFromSuspendedToRunnable(this);
- }
- art::Locks::mutator_lock_->AssertSharedHeld(self);
- maybe_release();
- // Thread will not go away while kRunningFlipFunction is set.
- RunFlipFunction(self);
+ RunFlipFunction(self, /*notify=*/ true);
DCHECK(!GetStateAndFlags(std::memory_order_relaxed).IsAnyOfFlagsSet(FlipFunctionFlags()));
- set_finished(true);
- return become_runnable;
+ return;
}
}
- // Unreachable.
}
-void Thread::RunFlipFunction(Thread* self) {
- // This function is called either by the thread running `ThreadList::FlipThreadRoots()` or when
- // a thread becomes runnable, after we've successfully set the kRunningFlipFunction ThreadFlag.
- DCHECK(ReadFlag(ThreadFlag::kRunningFlipFunction));
+void Thread::RunFlipFunction(Thread* self, bool notify) {
+ // This function is called for suspended threads and by the thread running
+ // `ThreadList::FlipThreadRoots()` after we've successfully set the flag
+ // `ThreadFlag::kRunningFlipFunction`. This flag is not set if the thread is
+ // running the flip function right after transitioning to Runnable as
+ // no other thread may run checkpoints on a thread that's actually Runnable.
+ DCHECK_EQ(notify, ReadFlag(ThreadFlag::kRunningFlipFunction));
- Closure* flip_function = GetFlipFunction();
- tlsPtr_.flip_function.store(nullptr, std::memory_order_relaxed);
+ Closure* flip_function = tlsPtr_.flip_function;
+ tlsPtr_.flip_function = nullptr;
DCHECK(flip_function != nullptr);
flip_function->Run(this);
- // The following also serves as a very approximate check for a deallocated thread.
- DCHECK_NE(GetState(), ThreadState::kTerminated);
- DCHECK(!ReadFlag(ThreadFlag::kPendingFlipFunction));
- AtomicClearFlag(ThreadFlag::kRunningFlipFunction, std::memory_order_release);
- // From here on this thread may go away, and it is no longer safe to access.
- // Notify all threads that are waiting for completion.
- // TODO: Should we create a separate mutex and condition variable instead
- // of piggy-backing on the `thread_suspend_count_lock_` and `resume_cond_`?
- MutexLock mu(self, *Locks::thread_suspend_count_lock_);
- resume_cond_->Broadcast(self);
+ if (notify) {
+ // Clear the `ThreadFlag::kRunningFlipFunction` and `ThreadFlag::kWaitingForFlipFunction`.
+ // Check if the latter was actually set, indicating that there is at least one waiting thread.
+ constexpr uint32_t kFlagsToClear = enum_cast<uint32_t>(ThreadFlag::kRunningFlipFunction) |
+ enum_cast<uint32_t>(ThreadFlag::kWaitingForFlipFunction);
+ StateAndFlags old_state_and_flags(
+ tls32_.state_and_flags.fetch_and(~kFlagsToClear, std::memory_order_release));
+ if (old_state_and_flags.IsFlagSet(ThreadFlag::kWaitingForFlipFunction)) {
+ // Notify all threads that are waiting for completion (at least one).
+ // TODO: Should we create a separate mutex and condition variable instead
+ // of piggy-backing on the `thread_suspend_count_lock_` and `resume_cond_`?
+ MutexLock mu(self, *Locks::thread_suspend_count_lock_);
+ resume_cond_->Broadcast(self);
+ }
+ }
}
-void Thread::WaitForFlipFunction(Thread* self) const {
+void Thread::WaitForFlipFunction(Thread* self) {
// Another thread is running the flip function. Wait for it to complete.
// Check the flag while holding the mutex so that we do not miss the broadcast.
// Repeat the check after waiting to guard against spurious wakeups (and because
@@ -1845,39 +1899,19 @@
StateAndFlags old_state_and_flags = GetStateAndFlags(std::memory_order_acquire);
DCHECK(!old_state_and_flags.IsFlagSet(ThreadFlag::kPendingFlipFunction));
if (!old_state_and_flags.IsFlagSet(ThreadFlag::kRunningFlipFunction)) {
- return;
+ DCHECK(!old_state_and_flags.IsAnyOfFlagsSet(FlipFunctionFlags()));
+ break;
}
- // We sometimes hold mutator lock here. OK since the flip function must complete quickly.
- resume_cond_->WaitHoldingLocks(self);
- }
-}
-
-void Thread::WaitForFlipFunctionTestingExited(Thread* self, ThreadExitFlag* tef) {
- Locks::thread_list_lock_->Lock(self);
- if (tef->HasExited()) {
- Locks::thread_list_lock_->Unlock(self);
- return;
- }
- // We need to hold suspend_count_lock_ to avoid missed wakeups when the flip function finishes.
- // We need to hold thread_list_lock_ because the tef test result is only valid while we hold the
- // lock, and once kRunningFlipFunction is no longer set, "this" may be deallocated. Hence the
- // complicated locking dance.
- MutexLock mu(self, *Locks::thread_suspend_count_lock_);
- while (true) {
- StateAndFlags old_state_and_flags = GetStateAndFlags(std::memory_order_acquire);
- DCHECK(!old_state_and_flags.IsFlagSet(ThreadFlag::kPendingFlipFunction));
- Locks::thread_list_lock_->Unlock(self); // So we can wait or return.
- if (!old_state_and_flags.IsFlagSet(ThreadFlag::kRunningFlipFunction)) {
- return;
+ if (!old_state_and_flags.IsFlagSet(ThreadFlag::kWaitingForFlipFunction)) {
+ // Mark that there is a waiting thread.
+ StateAndFlags new_state_and_flags =
+ old_state_and_flags.WithFlag(ThreadFlag::kWaitingForFlipFunction);
+ if (!tls32_.state_and_flags.CompareAndSetWeakRelaxed(old_state_and_flags.GetValue(),
+ new_state_and_flags.GetValue())) {
+ continue; // Retry.
+ }
}
- resume_cond_->WaitHoldingLocks(self);
- Locks::thread_suspend_count_lock_->Unlock(self); // To re-lock thread_list_lock.
- Locks::thread_list_lock_->Lock(self);
- Locks::thread_suspend_count_lock_->Lock(self);
- if (tef->HasExited()) {
- Locks::thread_list_lock_->Unlock(self);
- return;
- }
+ resume_cond_->Wait(self);
}
}
@@ -2199,27 +2233,19 @@
if (obj == nullptr) {
os << msg << "an unknown object";
} else {
- const std::string pretty_type(obj->PrettyTypeOf());
- // It's often unsafe to allow lock inflation here. We may be the only runnable thread, or
- // this may be called from a checkpoint. We get the hashcode on a best effort basis.
- static constexpr int kNumRetries = 3;
- static constexpr int kSleepMicros = 10;
- int32_t hash_code;
- for (int i = 0;; ++i) {
- hash_code = obj->IdentityHashCodeNoInflation();
- if (hash_code != 0 || i == kNumRetries) {
- break;
- }
- usleep(kSleepMicros);
- }
- if (hash_code == 0) {
- os << msg
- << StringPrintf("<@addr=0x%" PRIxPTR "> (a %s)",
- reinterpret_cast<intptr_t>(obj.Ptr()),
- pretty_type.c_str());
+ if ((obj->GetLockWord(true).GetState() == LockWord::kThinLocked) &&
+ Locks::mutator_lock_->IsExclusiveHeld(Thread::Current())) {
+ // Getting the identity hashcode here would result in lock inflation and suspension of the
+ // current thread, which isn't safe if this is the only runnable thread.
+ os << msg << StringPrintf("<@addr=0x%" PRIxPTR "> (a %s)",
+ reinterpret_cast<intptr_t>(obj.Ptr()),
+ obj->PrettyTypeOf().c_str());
} else {
- // - waiting on <0x608c468> (a java.lang.Class<java.lang.ref.ReferenceQueue>)
- os << msg << StringPrintf("<0x%08x> (a %s)", hash_code, pretty_type.c_str());
+ // - waiting on <0x6008c468> (a java.lang.Class<java.lang.ref.ReferenceQueue>)
+ // Call PrettyTypeOf before IdentityHashCode since IdentityHashCode can cause thread
+ // suspension and move pretty_object.
+ const std::string pretty_type(obj->PrettyTypeOf());
+ os << msg << StringPrintf("<0x%08x> (a %s)", obj->IdentityHashCode(), pretty_type.c_str());
}
}
if (owner_tid != ThreadList::kInvalidThreadId) {
@@ -2417,13 +2443,6 @@
soa.Self(), thread_group_object, thread_object);
}
-void Thread::SignalExitFlags() {
- for (ThreadExitFlag* tef = tlsPtr_.thread_exit_flags; tef != nullptr; tef = tef->next_) {
- tef->exited_ = true;
- }
- tlsPtr_.thread_exit_flags = nullptr; // Now unused.
-}
-
Thread::Thread(bool daemon)
: tls32_(daemon),
wait_monitor_(nullptr),
@@ -2448,10 +2467,12 @@
tlsPtr_.rosalloc_runs + kNumRosAllocThreadLocalSizeBracketsInThread,
gc::allocator::RosAlloc::GetDedicatedFullRun());
tlsPtr_.checkpoint_function = nullptr;
- tlsPtr_.active_suspendall_barrier = nullptr;
- tlsPtr_.active_suspend1_barriers = nullptr;
- tlsPtr_.flip_function.store(nullptr, std::memory_order_relaxed);
+ for (uint32_t i = 0; i < kMaxSuspendBarriers; ++i) {
+ tlsPtr_.active_suspend_barriers[i] = nullptr;
+ }
+ tlsPtr_.flip_function = nullptr;
tlsPtr_.thread_local_mark_stack = nullptr;
+ tls32_.is_transitioning_to_runnable = false;
ResetTlab();
}
@@ -2594,8 +2615,8 @@
CHECK(!ReadFlag(ThreadFlag::kEmptyCheckpointRequest));
CHECK(tlsPtr_.checkpoint_function == nullptr);
CHECK_EQ(checkpoint_overflow_.size(), 0u);
- // A pending flip function request is OK. FlipThreadRoots will have been notified that we
- // exited, and nobody will attempt to process the request.
+ CHECK(tlsPtr_.flip_function == nullptr);
+ CHECK_EQ(tls32_.is_transitioning_to_runnable, false);
// Make sure we processed all deoptimization requests.
CHECK(tlsPtr_.deoptimization_context_stack == nullptr) << "Missed deoptimization";
@@ -4697,17 +4718,15 @@
return Runtime::Current()->IsAotCompiler();
}
-mirror::Object* Thread::GetPeerFromOtherThread() {
+mirror::Object* Thread::GetPeerFromOtherThread() const {
DCHECK(tlsPtr_.jpeer == nullptr);
- // Ensure that opeer is not obsolete.
- while (ReadFlag(ThreadFlag::kPendingFlipFunction)) {
- Thread* self = Thread::Current();
- EnsureFlipFunctionStarted(self);
- if (ReadFlag(ThreadFlag::kRunningFlipFunction)) {
- WaitForFlipFunction(self);
- }
- }
mirror::Object* peer = tlsPtr_.opeer;
+ if (gUseReadBarrier && Current()->GetIsGcMarking()) {
+ // We may call Thread::Dump() in the middle of the CC thread flip and this thread's stack
+ // may have not been flipped yet and peer may be a from-space (stale) ref. So explicitly
+ // mark/forward it here.
+ peer = art::ReadBarrier::Mark(peer);
+ }
return peer;
}
diff --git a/runtime/thread.h b/runtime/thread.h
index caa09e8..1362f9f 100644
--- a/runtime/thread.h
+++ b/runtime/thread.h
@@ -47,7 +47,6 @@
#include "reflective_handle_scope.h"
#include "runtime_globals.h"
#include "runtime_stats.h"
-#include "suspend_reason.h"
#include "thread_state.h"
namespace unwindstack {
@@ -103,6 +102,7 @@
class ScopedObjectAccessAlreadyRunnable;
class ShadowFrame;
class StackedShadowFrameRecord;
+enum class SuspendReason : char;
class Thread;
class ThreadList;
enum VisitRootFlags : uint8_t;
@@ -134,25 +134,29 @@
kEmptyCheckpointRequest = 1u << 2,
// Register that at least 1 suspend barrier needs to be passed.
- // Changes to this flag are guarded by suspend_count_lock_ .
kActiveSuspendBarrier = 1u << 3,
// Marks that a "flip function" needs to be executed on this thread.
- // Set only while holding thread_list_lock_.
kPendingFlipFunction = 1u << 4,
// Marks that the "flip function" is being executed by another thread.
//
- // This is used to guard against multiple threads trying to run the
+ // This is used to guards against multiple threads trying to run the
// "flip function" for the same thread while the thread is suspended.
//
- // Set either by the thread itself or while holding thread_list_lock, Prevents a thread from
- // exiting.
+ // This is not needed when the thread is running the flip function
+ // on its own after transitioning to Runnable.
kRunningFlipFunction = 1u << 5,
+ // Marks that a thread is wating for "flip function" to complete.
+ //
+ // This is used to check if we need to broadcast the completion of the
+ // "flip function" to other threads. See also `kRunningFlipFunction`.
+ kWaitingForFlipFunction = 1u << 6,
+
// Request that compiled JNI stubs do not transition to Native or Runnable with
// inlined code, but take a slow path for monitoring method entry and exit events.
- kMonitorJniEntryExit = 1u << 6,
+ kMonitorJniEntryExit = 1u << 7,
// Indicates the last flag. Used for checking that the flags do not overlap thread state.
kLastFlag = kMonitorJniEntryExit
@@ -184,28 +188,6 @@
kDisabled
};
-// See Thread.tlsPtr_.active_suspend1_barriers below for explanation.
-struct WrappedSuspend1Barrier {
- WrappedSuspend1Barrier() : barrier_(1), next_(nullptr) {}
- AtomicInteger barrier_;
- struct WrappedSuspend1Barrier* next_ GUARDED_BY(Locks::thread_suspend_count_lock_);
-};
-
-// Mostly opaque structure allocated by the client of NotifyOnThreadExit. Allows a client to
-// check whether the thread still exists after temporarily releasing thread_list_lock_, usually
-// because we need to wait for something.
-class ThreadExitFlag {
- public:
- ThreadExitFlag() : exited_(false) {}
- bool HasExited() REQUIRES(Locks::thread_list_lock_) { return exited_; }
-
- private:
- ThreadExitFlag* next_ GUARDED_BY(Locks::thread_list_lock_);
- ThreadExitFlag* prev_ GUARDED_BY(Locks::thread_list_lock_);
- bool exited_ GUARDED_BY(*Locks::thread_list_lock_);
- friend class Thread;
-};
-
// This should match RosAlloc::kNumThreadLocalSizeBrackets.
static constexpr size_t kNumRosAllocThreadLocalSizeBracketsInThread = 16;
@@ -339,10 +321,7 @@
}
bool IsSuspended() const {
- // We need to ensure that once we return true, all prior accesses to the Java data by "this"
- // thread are complete. Hence we need "acquire" ordering here, and "release" when the flags
- // are set.
- StateAndFlags state_and_flags = GetStateAndFlags(std::memory_order_acquire);
+ StateAndFlags state_and_flags = GetStateAndFlags(std::memory_order_relaxed);
return state_and_flags.GetState() != ThreadState::kRunnable &&
state_and_flags.IsFlagSet(ThreadFlag::kSuspendRequest);
}
@@ -358,30 +337,20 @@
return tls32_.define_class_counter;
}
- // Increment suspend count and optionally install at most one suspend barrier.
+ // If delta > 0 and (this != self or suspend_barrier is not null), this function may temporarily
+ // release thread_suspend_count_lock_ internally.
ALWAYS_INLINE
- void IncrementSuspendCount(Thread* self,
- AtomicInteger* suspendall_barrier,
- WrappedSuspend1Barrier* suspend1_barrier,
- SuspendReason reason) REQUIRES(Locks::thread_suspend_count_lock_);
-
- // The same, but default reason to kInternal, and barriers to nullptr.
- ALWAYS_INLINE void IncrementSuspendCount(Thread* self)
+ bool ModifySuspendCount(Thread* self,
+ int delta,
+ AtomicInteger* suspend_barrier,
+ SuspendReason reason)
+ WARN_UNUSED
REQUIRES(Locks::thread_suspend_count_lock_);
- // Follows one of the above calls. For_user_code indicates if SuspendReason was kForUserCode.
- ALWAYS_INLINE void DecrementSuspendCount(Thread* self, bool for_user_code = false)
- REQUIRES(Locks::thread_suspend_count_lock_);
-
- private:
- NO_RETURN static void UnsafeLogFatalForSuspendCount(Thread* self, Thread* thread);
-
- public:
// Requests a checkpoint closure to run on another thread. The closure will be run when the
// thread notices the request, either in an explicit runtime CheckSuspend() call, or in a call
// originating from a compiler generated suspend point check. This returns true if the closure
- // was added and will (eventually) be executed. It returns false if this was impossible
- // because the thread was suspended, and we thus did nothing.
+ // was added and will (eventually) be executed. It returns false otherwise.
//
// Since multiple closures can be queued and some closures can delay other threads from running,
// no closure should attempt to suspend another thread while running.
@@ -395,55 +364,34 @@
// RequestSynchronousCheckpoint releases the thread_list_lock_ as a part of its execution. This is
// due to the fact that Thread::Current() needs to go to sleep to allow the targeted thread to
- // execute the checkpoint for us if it is Runnable. The wait_state is the state that the thread
+ // execute the checkpoint for us if it is Runnable. The suspend_state is the state that the thread
// will go into while it is awaiting the checkpoint to be run.
- // The closure may be run on Thread::Current() on behalf of "this" thread.
- // Thus for lock ordering purposes, the closure should be runnable by the caller. This also
- // sometimes makes it reasonable to pass ThreadState::kRunnable as wait_state: We may wait on
- // a condition variable for the "this" thread to act, but for lock ordering purposes, this is
- // exactly as though Thread::Current() had run the closure.
+ // NB Passing ThreadState::kRunnable may cause the current thread to wait in a condition variable
+ // while holding the mutator_lock_. Callers should ensure that this will not cause any problems
+ // for the closure or the rest of the system.
// NB Since multiple closures can be queued and some closures can delay other threads from running
// no closure should attempt to suspend another thread while running.
bool RequestSynchronousCheckpoint(Closure* function,
- ThreadState wait_state = ThreadState::kWaiting)
- REQUIRES_SHARED(Locks::mutator_lock_) RELEASE(Locks::thread_list_lock_)
- REQUIRES(!Locks::thread_suspend_count_lock_);
+ ThreadState suspend_state = ThreadState::kWaiting)
+ REQUIRES_SHARED(Locks::mutator_lock_)
+ RELEASE(Locks::thread_list_lock_)
+ REQUIRES(!Locks::thread_suspend_count_lock_);
bool RequestEmptyCheckpoint()
REQUIRES(Locks::thread_suspend_count_lock_);
- Closure* GetFlipFunction() { return tlsPtr_.flip_function.load(std::memory_order_relaxed); }
-
// Set the flip function. This is done with all threads suspended, except for the calling thread.
- void SetFlipFunction(Closure* function) REQUIRES(Locks::thread_suspend_count_lock_)
- REQUIRES(Locks::thread_list_lock_);
+ void SetFlipFunction(Closure* function);
- // Ensure that thread flip function started running. If no other thread is executing it, the
- // calling thread shall run the flip function and then notify other threads that have tried to
- // do that concurrently. After this function returns, the `ThreadFlag::kPendingFlipFunction` is
- // cleared but another thread may still run the flip function as indicated by the
- // `ThreadFlag::kRunningFlipFunction`. Optional arguments:
- // - If become_runnable is true, we logically acquire the mutator lock if we win the race to
- // run the flip function. If it's false we assume we already hold the mutator lock. Returns
- // true if this call acquired the muator lock.
- // - If tef is non-null, we ensure that the thread has not yet exited, as indicated by tef. In
- // that case, we acquire thread_list_lock_ as needed.
- // - If finished is non-null, we assign to *finished to indicate whether the flip was known to
- // be completed when we returned.
- bool EnsureFlipFunctionStarted(Thread* self,
- bool become_runnable = false,
- ThreadExitFlag* tef = nullptr,
- /*out*/ bool* finished = nullptr)
- TRY_ACQUIRE_SHARED(true, Locks::mutator_lock_);
+ // Ensure that thread flip function started running. If no other thread is executing
+ // it, the calling thread shall run the flip function and then notify other threads
+ // that have tried to do that concurrently. After this function returns, the
+ // `ThreadFlag::kPendingFlipFunction` is cleared but another thread may still
+ // run the flip function as indicated by the `ThreadFlag::kRunningFlipFunction`.
+ void EnsureFlipFunctionStarted(Thread* self) REQUIRES_SHARED(Locks::mutator_lock_);
- // Wait for the flip function to complete if still running on another thread. Assumes the "this"
- // thread remains live.
- void WaitForFlipFunction(Thread* self) const REQUIRES(!Locks::thread_suspend_count_lock_);
-
- // An enhanced version of the above that uses tef to safely return if the thread exited in the
- // meantime.
- void WaitForFlipFunctionTestingExited(Thread* self, ThreadExitFlag* tef)
- REQUIRES(!Locks::thread_suspend_count_lock_, !Locks::thread_list_lock_);
+ // Wait for the flip function to complete if still running on another thread.
+ void WaitForFlipFunction(Thread* self) REQUIRES_SHARED(Locks::mutator_lock_);
gc::accounting::AtomicStack<mirror::Object>* GetThreadLocalMarkStack() {
CHECK(gUseReadBarrier);
@@ -576,12 +524,10 @@
CHECK(tlsPtr_.jpeer == nullptr);
return tlsPtr_.opeer;
}
- // GetPeer is not safe if called on another thread in the middle of the thread flip and
+ // GetPeer is not safe if called on another thread in the middle of the CC thread flip and
// the thread's stack may have not been flipped yet and peer may be a from-space (stale) ref.
- // This function will force a flip for the other thread if necessary.
- // Since we hold a shared mutator lock, a new flip function cannot be concurrently
- // installed.
- mirror::Object* GetPeerFromOtherThread() REQUIRES_SHARED(Locks::mutator_lock_);
+ // This function will explicitly mark/forward it.
+ mirror::Object* GetPeerFromOtherThread() const REQUIRES_SHARED(Locks::mutator_lock_);
bool HasPeer() const {
return tlsPtr_.jpeer != nullptr || tlsPtr_.opeer != nullptr;
@@ -704,19 +650,6 @@
void NotifyThreadGroup(ScopedObjectAccessAlreadyRunnable& soa, jobject thread_group = nullptr)
REQUIRES_SHARED(Locks::mutator_lock_);
- // Request notification when this thread is unregistered or exits. The caller must allocate a
- // ThreadExitFlag, and pass it in. The caller is responsible for either waiting until the
- // thread has exited, or uregistering the ThreadExitFlag, and then, and only then, deallocating
- // the ThreadExitFlag. (This scheme avoids an allocation and questions about what to do if the
- // allocation fails. Allows detection of thread exit after temporary release of
- // thread_list_lock_)
- void NotifyOnThreadExit(ThreadExitFlag* tef) REQUIRES(Locks::thread_list_lock_);
- void UnregisterThreadExitFlag(ThreadExitFlag* tef) REQUIRES(Locks::thread_list_lock_);
-
- // Called when thread is unregistered. May be called repeatedly, in which case only newly
- // registered clients are processed.
- void SignalExitFlags() REQUIRES(Locks::thread_list_lock_);
-
// JNI methods
JNIEnvExt* GetJniEnv() const {
return tlsPtr_.jni_env;
@@ -1298,27 +1231,8 @@
tlsPtr_.held_mutexes[level] = mutex;
}
- // Possibly check that no mutexes at level kMonitorLock or above are subsequently acquired.
- // Only invoked by the thread itself.
- void DisallowPreMonitorMutexes() {
- if (kIsDebugBuild) {
- CHECK(this == Thread::Current());
- CHECK(GetHeldMutex(kMonitorLock) == nullptr);
- // Pretend we hold a kMonitorLock level mutex to detect disallowed mutex
- // acquisitions by checkpoint Run() methods. We don't normally register or thus check
- // kMonitorLock level mutexes, but this is an exception.
- static Mutex dummy_mutex("checkpoint dummy mutex", kMonitorLock);
- SetHeldMutex(kMonitorLock, &dummy_mutex);
- }
- }
-
- // Undo the effect of the previous call. Again only invoked by the thread itself.
- void AllowPreMonitorMutexes() {
- if (kIsDebugBuild) {
- CHECK(GetHeldMutex(kMonitorLock) != nullptr);
- SetHeldMutex(kMonitorLock, nullptr);
- }
- }
+ void ClearSuspendBarrier(AtomicInteger* target)
+ REQUIRES(Locks::thread_suspend_count_lock_);
bool ReadFlag(ThreadFlag flag) const {
return GetStateAndFlags(std::memory_order_relaxed).IsFlagSet(flag);
@@ -1421,6 +1335,14 @@
bool ProtectStack(bool fatal_on_error = true);
bool UnprotectStack();
+ bool IsTransitioningToRunnable() const {
+ return tls32_.is_transitioning_to_runnable;
+ }
+
+ void SetIsTransitioningToRunnable(bool value) {
+ tls32_.is_transitioning_to_runnable = value;
+ }
+
uint32_t DecrementForceInterpreterCount() REQUIRES(Locks::thread_list_lock_) {
return --tls32_.force_interpreter_count;
}
@@ -1534,7 +1456,8 @@
static constexpr uint32_t FlipFunctionFlags() {
return enum_cast<uint32_t>(ThreadFlag::kPendingFlipFunction) |
- enum_cast<uint32_t>(ThreadFlag::kRunningFlipFunction);
+ enum_cast<uint32_t>(ThreadFlag::kRunningFlipFunction) |
+ enum_cast<uint32_t>(ThreadFlag::kWaitingForFlipFunction);
}
static constexpr uint32_t StoredThreadStateValue(ThreadState state) {
@@ -1556,7 +1479,6 @@
private:
explicit Thread(bool daemon);
- // A runnable thread should only be deleted from the thread itself.
~Thread() REQUIRES(!Locks::mutator_lock_, !Locks::thread_suspend_count_lock_);
void Destroy(bool should_run_callbacks);
@@ -1584,8 +1506,7 @@
// Avoid use, callers should use SetState.
// Used only by `Thread` destructor and stack trace collection in semi-space GC (currently
- // disabled by `kStoreStackTraces = false`). May not be called on a runnable thread other
- // than Thread::Current().
+ // disabled by `kStoreStackTraces = false`).
// NO_THREAD_SAFETY_ANALYSIS: This function is "Unsafe" and can be called in
// different states, so clang cannot perform the thread safety analysis.
ThreadState SetStateUnsafe(ThreadState new_state) NO_THREAD_SAFETY_ANALYSIS {
@@ -1594,13 +1515,12 @@
if (old_state == new_state) {
// Nothing to do.
} else if (old_state == ThreadState::kRunnable) {
- DCHECK_EQ(this, Thread::Current());
// Need to run pending checkpoint and suspend barriers. Run checkpoints in runnable state in
// case they need to use a ScopedObjectAccess. If we are holding the mutator lock and a SOA
// attempts to TransitionFromSuspendedToRunnable, it results in a deadlock.
TransitionToSuspendedAndRunCheckpoints(new_state);
// Since we transitioned to a suspended state, check the pass barrier requests.
- CheckActiveSuspendBarriers();
+ PassActiveSuspendBarriers();
} else {
while (true) {
StateAndFlags new_state_and_flags = old_state_and_flags;
@@ -1674,24 +1594,9 @@
REQUIRES(!Locks::thread_suspend_count_lock_, !Roles::uninterruptible_)
REQUIRES_SHARED(Locks::mutator_lock_);
- // Call PassActiveSuspendBarriers() if there are active barriers. Only called on current thread.
- ALWAYS_INLINE void CheckActiveSuspendBarriers()
+ ALWAYS_INLINE void PassActiveSuspendBarriers()
REQUIRES(!Locks::thread_suspend_count_lock_, !Roles::uninterruptible_);
- // Decrement all "suspend barriers" for the current thread, notifying threads that requested our
- // suspension. Only called on current thread.
- bool PassActiveSuspendBarriers() REQUIRES(!Locks::thread_suspend_count_lock_);
-
- // Add an entry to active_suspend1_barriers.
- ALWAYS_INLINE void AddSuspend1Barrier(WrappedSuspend1Barrier* suspend1_barrier)
- REQUIRES(Locks::thread_suspend_count_lock_);
-
- // Remove last-added entry from active_suspend1_barriers.
- // Only makes sense if we're still holding thread_suspend_count_lock_ since insertion.
- ALWAYS_INLINE void RemoveFirstSuspend1Barrier() REQUIRES(Locks::thread_suspend_count_lock_);
-
- ALWAYS_INLINE bool HasActiveSuspendBarrier() REQUIRES(Locks::thread_suspend_count_lock_);
-
// Registers the current thread as the jit sensitive thread. Should be called just once.
static void SetJitSensitiveThread() {
if (jit_sensitive_thread_ == nullptr) {
@@ -1706,6 +1611,13 @@
is_sensitive_thread_hook_ = is_sensitive_thread_hook;
}
+ bool ModifySuspendCountInternal(Thread* self,
+ int delta,
+ AtomicInteger* suspend_barrier,
+ SuspendReason reason)
+ WARN_UNUSED
+ REQUIRES(Locks::thread_suspend_count_lock_);
+
// Runs a single checkpoint function. If there are no more pending checkpoint functions it will
// clear the kCheckpointRequest flag. The caller is responsible for calling this in a loop until
// the kCheckpointRequest flag is cleared.
@@ -1714,6 +1626,9 @@
REQUIRES_SHARED(Locks::mutator_lock_);
void RunEmptyCheckpoint();
+ bool PassActiveSuspendBarriers(Thread* self)
+ REQUIRES(!Locks::thread_suspend_count_lock_);
+
// Install the protected region for implicit stack checks.
void InstallImplicitProtection();
@@ -1817,9 +1732,9 @@
// Format state and flags as a hex string. For diagnostic output.
std::string StateAndFlagsAsHexString() const;
- // Run the flip function and notify other threads that may have tried
+ // Run the flip function and, if requested, notify other threads that may have tried
// to do that concurrently.
- void RunFlipFunction(Thread* self) REQUIRES_SHARED(Locks::mutator_lock_);
+ void RunFlipFunction(Thread* self, bool notify) REQUIRES_SHARED(Locks::mutator_lock_);
static void ThreadExitCallback(void* arg);
@@ -1864,6 +1779,7 @@
throwing_OutOfMemoryError(false),
no_thread_suspension(0),
thread_exit_check_count(0),
+ is_transitioning_to_runnable(false),
is_gc_marking(false),
is_deopt_check_required(false),
weak_ref_access_enabled(WeakRefAccessState::kVisiblyEnabled),
@@ -1873,7 +1789,8 @@
make_visibly_initialized_counter(0),
define_class_counter(0),
num_name_readers(0),
- shared_method_hotness(kSharedMethodHotnessThreshold) {}
+ shared_method_hotness(kSharedMethodHotnessThreshold)
+ {}
// The state and flags field must be changed atomically so that flag values aren't lost.
// See `StateAndFlags` for bit assignments of `ThreadFlag` and `ThreadState` values.
@@ -1909,6 +1826,11 @@
// How many times has our pthread key's destructor been called?
uint32_t thread_exit_check_count;
+ // True if the thread is in TransitionFromSuspendedToRunnable(). This is used to distinguish the
+ // non-runnable threads (eg. kNative, kWaiting) that are about to transition to runnable from
+ // the rest of them.
+ bool32_t is_transitioning_to_runnable;
+
// True if the GC is in the marking phase. This is used for the CC collector only. This is
// thread local so that we can simplify the logic to check for the fast path of read barriers of
// GC roots.
@@ -2013,11 +1935,9 @@
name(nullptr),
pthread_self(0),
last_no_thread_suspension_cause(nullptr),
- active_suspendall_barrier(nullptr),
- active_suspend1_barriers(nullptr),
+ thread_local_start(nullptr),
thread_local_pos(nullptr),
thread_local_end(nullptr),
- thread_local_start(nullptr),
thread_local_limit(nullptr),
thread_local_objects(0),
checkpoint_function(nullptr),
@@ -2030,8 +1950,7 @@
async_exception(nullptr),
top_reflective_handle_scope(nullptr),
method_trace_buffer(nullptr),
- method_trace_buffer_index(0),
- thread_exit_flags(nullptr) {
+ method_trace_buffer_index(0) {
std::fill(held_mutexes, held_mutexes + kLockLevelCount, nullptr);
}
@@ -2129,37 +2048,27 @@
// If no_thread_suspension_ is > 0, what is causing that assertion.
const char* last_no_thread_suspension_cause;
- // After a thread observes a suspend request and enters a suspended state,
- // it notifies the requestor by arriving at a "suspend barrier". This consists of decrementing
- // the atomic integer representing the barrier. (This implementation was introduced in 2015 to
- // minimize cost. There may be other options.) These atomic integer barriers are always
- // stored on the requesting thread's stack. They are referenced from the target thread's
- // data structure in one of two ways; in either case the data structure referring to these
- // barriers is guarded by suspend_count_lock:
- // 1. A SuspendAll barrier is directly referenced from the target thread. Only one of these
- // can be active at a time:
- AtomicInteger* active_suspendall_barrier GUARDED_BY(Locks::thread_suspend_count_lock_);
- // 2. For individual thread suspensions, active barriers are embedded in a struct that is used
- // to link together all suspend requests for this thread. Unlike the SuspendAll case, each
- // barrier is referenced by a single target thread, and thus can appear only on a single list.
- // The struct as a whole is still stored on the requesting thread's stack.
- WrappedSuspend1Barrier* active_suspend1_barriers GUARDED_BY(Locks::thread_suspend_count_lock_);
+ // Pending barriers that require passing or NULL if non-pending. Installation guarding by
+ // Locks::thread_suspend_count_lock_.
+ // They work effectively as art::Barrier, but implemented directly using AtomicInteger and futex
+ // to avoid additional cost of a mutex and a condition variable, as used in art::Barrier.
+ AtomicInteger* active_suspend_barriers[kMaxSuspendBarriers];
+
+ // Thread-local allocation pointer. Moved here to force alignment for thread_local_pos on ARM.
+ uint8_t* thread_local_start;
// thread_local_pos and thread_local_end must be consecutive for ldrd and are 8 byte aligned for
// potentially better performance.
uint8_t* thread_local_pos;
uint8_t* thread_local_end;
- // Thread-local allocation pointer. Can be moved above the preceding two to correct alignment.
- uint8_t* thread_local_start;
-
// Thread local limit is how much we can expand the thread local buffer to, it is greater or
// equal to thread_local_end.
uint8_t* thread_local_limit;
size_t thread_local_objects;
- // Pending checkpoint function or null if non-pending. If this checkpoint is set and someone
+ // Pending checkpoint function or null if non-pending. If this checkpoint is set and someone\
// requests another checkpoint, it goes to the checkpoint overflow list.
Closure* checkpoint_function GUARDED_BY(Locks::thread_suspend_count_lock_);
@@ -2182,9 +2091,8 @@
// Support for Mutex lock hierarchy bug detection.
BaseMutex* held_mutexes[kLockLevelCount];
- // The function used for thread flip. Set while holding Locks::thread_suspend_count_lock_ and
- // with all other threads suspended. May be cleared while being read.
- std::atomic<Closure*> flip_function;
+ // The function used for thread flip.
+ Closure* flip_function;
// Current method verifier, used for root marking.
verifier::MethodVerifier* method_verifier;
@@ -2207,9 +2115,6 @@
// The index of the next free entry in method_trace_buffer.
size_t method_trace_buffer_index;
-
- // Pointer to the first node of an intrusively doubly-linked list of ThreadExitFlags.
- ThreadExitFlag* thread_exit_flags;
} tlsPtr_;
// Small thread-local cache to be used from the interpreter.
@@ -2358,6 +2263,20 @@
Thread* const self_;
};
+class ScopedTransitioningToRunnable : public ValueObject {
+ public:
+ explicit ScopedTransitioningToRunnable(Thread* self)
+ : self_(self) {
+ DCHECK_EQ(self, Thread::Current());
+ self_->SetIsTransitioningToRunnable(true);
+ }
+
+ ~ScopedTransitioningToRunnable() { self_->SetIsTransitioningToRunnable(false); }
+
+ private:
+ Thread* const self_;
+};
+
class ThreadLifecycleCallback {
public:
virtual ~ThreadLifecycleCallback() {}
diff --git a/runtime/thread_list.cc b/runtime/thread_list.cc
index b986e51..d98415f 100644
--- a/runtime/thread_list.cc
+++ b/runtime/thread_list.cc
@@ -67,10 +67,10 @@
using android::base::StringPrintf;
static constexpr uint64_t kLongThreadSuspendThreshold = MsToNs(5);
-// Track the number of times SuspendAll loops for various reasons.
-// TODO(hboehm): Consider changing this back to kIsDebugBuild. However this has been known to only
-// fail in non-debug builds.
-static constexpr bool kTrackLoopReasons = true;
+// Use 0 since we want to yield to prevent blocking for an unpredictable amount of time.
+static constexpr useconds_t kThreadSuspendInitialSleepUs = 0;
+static constexpr useconds_t kThreadSuspendMaxYieldUs = 3000;
+static constexpr useconds_t kThreadSuspendMaxSleepUs = 5000;
// Whether we should try to dump the native stack of unattached threads. See commit ed8b723 for
// some history.
@@ -79,7 +79,7 @@
ThreadList::ThreadList(uint64_t thread_suspend_timeout_ns)
: suspend_all_count_(0),
unregistering_count_(0),
- suspend_all_histogram_("suspend all histogram", 16, 64),
+ suspend_all_historam_("suspend all histogram", 16, 64),
long_suspend_(false),
shut_down_(false),
thread_suspend_timeout_ns_(thread_suspend_timeout_ns),
@@ -140,10 +140,10 @@
{
ScopedObjectAccess soa(Thread::Current());
// Only print if we have samples.
- if (suspend_all_histogram_.SampleSize() > 0) {
+ if (suspend_all_historam_.SampleSize() > 0) {
Histogram<uint64_t>::CumulativeData data;
- suspend_all_histogram_.CreateHistogram(&data);
- suspend_all_histogram_.PrintConfidenceIntervals(os, 0.99, data); // Dump time to suspend.
+ suspend_all_historam_.CreateHistogram(&data);
+ suspend_all_historam_.PrintConfidenceIntervals(os, 0.99, data); // Dump time to suspend.
}
}
bool dump_native_stack = Runtime::Current()->GetDumpNativeStackOnSigQuit();
@@ -279,11 +279,11 @@
}
}
-void ThreadList::AssertOtherThreadsAreSuspended(Thread* self) {
+void ThreadList::AssertThreadsAreSuspended(Thread* self, Thread* ignore1, Thread* ignore2) {
MutexLock mu(self, *Locks::thread_list_lock_);
MutexLock mu2(self, *Locks::thread_suspend_count_lock_);
for (const auto& thread : list_) {
- if (thread != self) {
+ if (thread != ignore1 && thread != ignore2) {
CHECK(thread->IsSuspended())
<< "\nUnsuspended thread: <<" << *thread << "\n"
<< "self: <<" << *Thread::Current();
@@ -310,9 +310,20 @@
}
#endif
-size_t ThreadList::RunCheckpoint(Closure* checkpoint_function,
- Closure* callback,
- bool allow_lock_checking) {
+// Unlike suspending all threads where we can wait to acquire the mutator_lock_, suspending an
+// individual thread requires polling. delay_us is the requested sleep wait. If delay_us is 0 then
+// we use sched_yield instead of calling usleep.
+// Although there is the possibility, here and elsewhere, that usleep could return -1 and
+// errno = EINTR, there should be no problem if interrupted, so we do not check.
+static void ThreadSuspendSleep(useconds_t delay_us) {
+ if (delay_us == 0) {
+ sched_yield();
+ } else {
+ usleep(delay_us);
+ }
+}
+
+size_t ThreadList::RunCheckpoint(Closure* checkpoint_function, Closure* callback) {
Thread* self = Thread::Current();
Locks::mutator_lock_->AssertNotExclusiveHeld(self);
Locks::thread_list_lock_->AssertNotHeld(self);
@@ -321,12 +332,9 @@
std::vector<Thread*> suspended_count_modified_threads;
size_t count = 0;
{
- // Call a checkpoint function for each thread. We directly invoke the function on behalf of
- // suspended threads.
+ // Call a checkpoint function for each thread, threads which are suspended get their checkpoint
+ // manually called.
MutexLock mu(self, *Locks::thread_list_lock_);
- if (kIsDebugBuild && allow_lock_checking) {
- self->DisallowPreMonitorMutexes();
- }
MutexLock mu2(self, *Locks::thread_suspend_count_lock_);
count = list_.size();
for (const auto& thread : list_) {
@@ -337,21 +345,31 @@
// This thread will run its checkpoint some time in the near future.
if (requested_suspend) {
// The suspend request is now unnecessary.
- thread->DecrementSuspendCount(self);
+ bool updated =
+ thread->ModifySuspendCount(self, -1, nullptr, SuspendReason::kInternal);
+ DCHECK(updated);
requested_suspend = false;
}
break;
} else {
- // The thread is probably suspended.
- if (!requested_suspend) {
- // This does not risk suspension cycles: We may have a pending suspension request,
- // but it cannot block us: Checkpoint Run() functions may not suspend, thus we cannot
- // be blocked from decrementing the count again.
- thread->IncrementSuspendCount(self);
- requested_suspend = true;
+ // The thread is probably suspended, try to make sure that it stays suspended.
+ if (thread->GetState() == ThreadState::kRunnable) {
+ // Spurious fail, try again.
+ continue;
}
- if (thread->IsSuspended()) {
- // We saw it suspended after incrementing suspend count, so it will stay that way.
+ if (!requested_suspend) {
+ bool updated =
+ thread->ModifySuspendCount(self, +1, nullptr, SuspendReason::kInternal);
+ DCHECK(updated);
+ requested_suspend = true;
+ if (thread->IsSuspended()) {
+ break;
+ }
+ // The thread raced us to become Runnable. Try to RequestCheckpoint() again.
+ } else {
+ // The thread previously raced our suspend request to become Runnable but
+ // since it is suspended again, it must honor that suspend request now.
+ DCHECK(thread->IsSuspended());
break;
}
}
@@ -360,8 +378,6 @@
suspended_count_modified_threads.push_back(thread);
}
}
- // Thread either has honored or will honor the checkpoint, or it has been added to
- // suspended_count_modified_threads.
}
// Run the callback to be called inside this critical section.
if (callback != nullptr) {
@@ -379,7 +395,8 @@
checkpoint_function->Run(thread);
{
MutexLock mu2(self, *Locks::thread_suspend_count_lock_);
- thread->DecrementSuspendCount(self);
+ bool updated = thread->ModifySuspendCount(self, -1, nullptr, SuspendReason::kInternal);
+ DCHECK(updated);
}
}
@@ -390,9 +407,6 @@
Thread::resume_cond_->Broadcast(self);
}
- if (kIsDebugBuild && allow_lock_checking) {
- self->AllowPreMonitorMutexes();
- }
return count;
}
@@ -505,125 +519,109 @@
// from-space to to-space refs. Used to synchronize threads at a point
// to mark the initiation of marking while maintaining the to-space
// invariant.
-void ThreadList::FlipThreadRoots(Closure* thread_flip_visitor,
- Closure* flip_callback,
- gc::collector::GarbageCollector* collector,
- gc::GcPauseListener* pause_listener) {
+size_t ThreadList::FlipThreadRoots(Closure* thread_flip_visitor,
+ Closure* flip_callback,
+ gc::collector::GarbageCollector* collector,
+ gc::GcPauseListener* pause_listener) {
TimingLogger::ScopedTiming split("ThreadListFlip", collector->GetTimings());
Thread* self = Thread::Current();
Locks::mutator_lock_->AssertNotHeld(self);
Locks::thread_list_lock_->AssertNotHeld(self);
Locks::thread_suspend_count_lock_->AssertNotHeld(self);
CHECK_NE(self->GetState(), ThreadState::kRunnable);
+ size_t runnable_thread_count = 0;
+ std::vector<Thread*> other_threads;
collector->GetHeap()->ThreadFlipBegin(self); // Sync with JNI critical calls.
// ThreadFlipBegin happens before we suspend all the threads, so it does not
// count towards the pause.
const uint64_t suspend_start_time = NanoTime();
- VLOG(threads) << "Suspending all for thread flip";
- SuspendAllInternal(self);
+ SuspendAllInternal(self, self, nullptr);
if (pause_listener != nullptr) {
pause_listener->StartPause();
}
// Run the flip callback for the collector.
Locks::mutator_lock_->ExclusiveLock(self);
- suspend_all_histogram_.AdjustAndAddValue(NanoTime() - suspend_start_time);
+ suspend_all_historam_.AdjustAndAddValue(NanoTime() - suspend_start_time);
flip_callback->Run(self);
+ // Releasing mutator-lock *before* setting up flip function in the threads
+ // leaves a gap for another thread trying to suspend all threads. That thread
+ // gets to run with mutator-lock, thereby accessing the heap, without running
+ // its flip function. It's not a problem with CC as the gc-thread hasn't
+ // started marking yet and the from-space is accessible. By delaying releasing
+ // mutator-lock until after the flip function are running on all threads we
+ // fix that without increasing pause time, except for any thread that might be
+ // trying to suspend all. Even though the change works irrespective of the GC,
+ // it has been limited to userfaultfd GC to keep the change behind the flag.
+ //
+ // TODO: It's a temporary change as aosp/2377951 is going to clean-up at a
+ // broad scale, including not allowing concurrent suspend-all.
- std::vector<Thread*> flipping_threads; // All suspended threads. Includes us.
- int thread_count;
- // Flipping threads might exit between the time we resume them and try to run the flip function.
- // Track that in a parallel vector.
- std::unique_ptr<ThreadExitFlag[]> exit_flags;
+ // Resume runnable threads.
{
TimingLogger::ScopedTiming split2("ResumeRunnableThreads", collector->GetTimings());
MutexLock mu(self, *Locks::thread_list_lock_);
MutexLock mu2(self, *Locks::thread_suspend_count_lock_);
- thread_count = list_.size();
- exit_flags.reset(new ThreadExitFlag[thread_count]);
- flipping_threads.resize(thread_count, nullptr);
- int i = 1;
+ --suspend_all_count_;
for (Thread* thread : list_) {
// Set the flip function for all threads because once we start resuming any threads,
// they may need to run the flip function on behalf of other threads, even this one.
- DCHECK(thread == self || thread->IsSuspended());
thread->SetFlipFunction(thread_flip_visitor);
- // Put ourselves first, so other threads are more likely to have finished before we get
- // there.
- int thread_index = thread == self ? 0 : i++;
- flipping_threads[thread_index] = thread;
- thread->NotifyOnThreadExit(&exit_flags[thread_index]);
+ if (thread == self) {
+ continue;
+ }
+ // Resume early the threads that were runnable but are suspended just for this thread flip or
+ // about to transition from non-runnable (eg. kNative at the SOA entry in a JNI function) to
+ // runnable (both cases waiting inside Thread::TransitionFromSuspendedToRunnable), or waiting
+ // for the thread flip to end at the JNI critical section entry (kWaitingForGcThreadFlip),
+ ThreadState state = thread->GetState();
+ if ((state == ThreadState::kWaitingForGcThreadFlip || thread->IsTransitioningToRunnable()) &&
+ thread->GetSuspendCount() == 1) {
+ // The thread will resume right after the broadcast.
+ bool updated = thread->ModifySuspendCount(self, -1, nullptr, SuspendReason::kInternal);
+ DCHECK(updated);
+ ++runnable_thread_count;
+ } else {
+ other_threads.push_back(thread);
+ }
}
- DCHECK(i == thread_count);
+ Thread::resume_cond_->Broadcast(self);
}
+ collector->RegisterPause(NanoTime() - suspend_start_time);
if (pause_listener != nullptr) {
pause_listener->EndPause();
}
- // Any new threads created after this will be created by threads that already ran their flip
- // functions. In the normal GC use case in which the flip function converts all local references
- // to to-space references, these newly created threads will also see only to-space references.
- ResumeAll();
- collector->RegisterPause(NanoTime() - suspend_start_time);
- // Since all threads were suspended, they will attempt to run the flip function before
- // reentering a runnable state. We will also attempt to run the flip functions ourselves. Any
- // intervening checkpoint request will do the same. Exactly one of those attempts will succeed,
- // and the target thread will not be able to reenter a runnable state until one of them does.
-
collector->GetHeap()->ThreadFlipEnd(self);
// Try to run the closure on the other threads.
{
- TimingLogger::ScopedTiming split3("RunningThreadFlips", collector->GetTimings());
- ReaderMutexLock mu(self, *Locks::mutator_lock_);
- for (int i = 0; i < thread_count; ++i) {
- bool finished;
- flipping_threads[i]->EnsureFlipFunctionStarted(self,
- /*become_runnable=*/false,
- &exit_flags[i],
- &finished);
- if (finished) {
- MutexLock mu2(self, *Locks::thread_list_lock_);
- flipping_threads[i]->UnregisterThreadExitFlag(&exit_flags[i]);
- flipping_threads[i] = nullptr;
- }
+ TimingLogger::ScopedTiming split3("FlipOtherThreads", collector->GetTimings());
+ for (Thread* thread : other_threads) {
+ thread->EnsureFlipFunctionStarted(self);
+ DCHECK(!thread->ReadFlag(ThreadFlag::kPendingFlipFunction));
}
- // Make sure all flips complete before we return.
- for (int i = 0; i < thread_count; ++i) {
- if (UNLIKELY(flipping_threads[i] != nullptr)) {
- flipping_threads[i]->WaitForFlipFunctionTestingExited(self, &exit_flags[i]);
- MutexLock mu2(self, *Locks::thread_list_lock_);
- flipping_threads[i]->UnregisterThreadExitFlag(&exit_flags[i]);
- }
- }
+ // Try to run the flip function for self.
+ self->EnsureFlipFunctionStarted(self);
+ DCHECK(!self->ReadFlag(ThreadFlag::kPendingFlipFunction));
}
-}
-bool ThreadList::WaitForSuspendBarrier(AtomicInteger* barrier) {
-#if ART_USE_FUTEXES
- timespec wait_timeout;
- InitTimeSpec(false, CLOCK_MONOTONIC, NsToMs(thread_suspend_timeout_ns_), 0, &wait_timeout);
-#endif
- while (true) {
- int32_t cur_val = barrier->load(std::memory_order_acquire);
- if (cur_val <= 0) {
- CHECK_EQ(cur_val, 0);
- return true;
+ Locks::mutator_lock_->ExclusiveUnlock(self);
+
+ // Resume other threads.
+ {
+ TimingLogger::ScopedTiming split4("ResumeOtherThreads", collector->GetTimings());
+ MutexLock mu2(self, *Locks::thread_suspend_count_lock_);
+ for (const auto& thread : other_threads) {
+ bool updated = thread->ModifySuspendCount(self, -1, nullptr, SuspendReason::kInternal);
+ DCHECK(updated);
}
-#if ART_USE_FUTEXES
- if (futex(barrier->Address(), FUTEX_WAIT_PRIVATE, cur_val, &wait_timeout, nullptr, 0) != 0) {
- if (errno == ETIMEDOUT) {
- return false;
- } else if (errno != EAGAIN && errno != EINTR) {
- PLOG(FATAL) << "futex wait for suspend barrier failed";
- }
- }
-#endif
- // Else spin wait. This is likely to be slow, but ART_USE_FUTEXES is set on Linux,
- // including all targets.
+ Thread::resume_cond_->Broadcast(self);
}
+
+ return runnable_thread_count + other_threads.size() + 1; // +1 for self.
}
void ThreadList::SuspendAll(const char* cause, bool long_suspend) {
@@ -638,7 +636,7 @@
ScopedTrace trace("Suspending mutator threads");
const uint64_t start_time = NanoTime();
- SuspendAllInternal(self);
+ SuspendAllInternal(self, self);
// All threads are known to have suspended (but a thread may still own the mutator lock)
// Make sure this thread grabs exclusive access to the mutator lock and its protected data.
#if HAVE_TIMED_RWLOCK
@@ -662,26 +660,16 @@
const uint64_t end_time = NanoTime();
const uint64_t suspend_time = end_time - start_time;
- suspend_all_histogram_.AdjustAndAddValue(suspend_time);
+ suspend_all_historam_.AdjustAndAddValue(suspend_time);
if (suspend_time > kLongThreadSuspendThreshold) {
LOG(WARNING) << "Suspending all threads took: " << PrettyDuration(suspend_time);
}
if (kDebugLocking) {
// Debug check that all threads are suspended.
- AssertOtherThreadsAreSuspended(self);
+ AssertThreadsAreSuspended(self, self);
}
}
-
- // This logically acquires the mutator lock in exclusive mode, which makes us logically runnable
- // and capable of accessing the Java heap. Ensure that we do not have a pending flip function.
- // Note that a flip function can be installed ony while another thread is inside a SuspendAll,
- // and that's impossible here, because we only allow one at a time.
- if (self->ReadFlag(ThreadFlag::kPendingFlipFunction)) {
- self->EnsureFlipFunctionStarted(self);
- DCHECK(!self->ReadFlag(ThreadFlag::kRunningFlipFunction));
- }
-
ATraceBegin((std::string("Mutator threads suspended for ") + cause).c_str());
if (self != nullptr) {
@@ -691,32 +679,11 @@
}
}
-// Only used for kIsDebugBuild statistics.
-struct DelayInfo {
- DelayInfo() : suspend_all_(0), self_susp_(0) {}
- int suspend_all_;
- int self_susp_;
-};
-
-static inline std::ostream& operator<<(std::ostream& os, DelayInfo di) {
- if (kTrackLoopReasons) {
- return os << "suspend_all = " << di.suspend_all_ << " self_suspend = " << di.self_susp_;
- } else {
- return os << "(no delay info)";
- }
-}
-
-static inline bool TrackIfFalse(bool cond, int* field) {
- if (kTrackLoopReasons && !cond) {
- ++*field;
- }
- return cond;
-}
-
// Ensures all threads running Java suspend and that those not running Java don't start.
-void ThreadList::SuspendAllInternal(Thread* self, SuspendReason reason) {
- // self can be nullptr if this is an unregistered thread.
- const uint64_t start_time = NanoTime();
+void ThreadList::SuspendAllInternal(Thread* self,
+ Thread* ignore1,
+ Thread* ignore2,
+ SuspendReason reason) {
Locks::mutator_lock_->AssertNotExclusiveHeld(self);
Locks::thread_list_lock_->AssertNotHeld(self);
Locks::thread_suspend_count_lock_->AssertNotHeld(self);
@@ -734,80 +701,85 @@
// The atomic counter for number of threads that need to pass the barrier.
AtomicInteger pending_threads;
-
- DelayInfo di;
- for (int iter_count = 1;; ++iter_count) {
- {
- MutexLock mu(self, *Locks::thread_list_lock_);
- MutexLock mu2(self, *Locks::thread_suspend_count_lock_);
- if (LIKELY(TrackIfFalse(suspend_all_count_ == 0, &di.suspend_all_) &&
- TrackIfFalse(self == nullptr || self->GetSuspendCount() == 0, &di.self_susp_))) {
- // The above condition remains valid while we hold thread_suspend_count_lock_ .
- bool found_myself = false;
- // Update global suspend all state for attaching threads.
- ++suspend_all_count_;
- pending_threads.store(list_.size() - (self == nullptr ? 0 : 1), std::memory_order_relaxed);
- // Increment everybody else's suspend count.
- for (const auto& thread : list_) {
- if (thread == self) {
- found_myself = true;
- } else {
- VLOG(threads) << "requesting thread suspend: " << *thread;
- DCHECK_EQ(suspend_all_count_, 1);
- thread->IncrementSuspendCount(self, &pending_threads, nullptr, reason);
-
- // Must install the pending_threads counter first, then check thread->IsSuspended()
- // and clear the counter. Otherwise there's a race with
- // Thread::TransitionFromRunnableToSuspended() that can lead a thread to miss a call
- // to PassActiveSuspendBarriers().
- if (thread->IsSuspended()) {
- // Effectively pass the barrier on behalf of the already suspended thread.
- DCHECK_EQ(thread->tlsPtr_.active_suspendall_barrier, &pending_threads);
- pending_threads.fetch_sub(1, std::memory_order_seq_cst);
- thread->tlsPtr_.active_suspendall_barrier = nullptr;
- if (!thread->HasActiveSuspendBarrier()) {
- thread->AtomicClearFlag(ThreadFlag::kActiveSuspendBarrier);
- }
- }
- }
- }
- DCHECK(self == nullptr || found_myself);
- break;
- }
- }
- // The if (LIKELY ...) condition above didn't hold. This is a bad time to initiate a suspend.
- // Either the suspendall_barrier is already in use, or proceeding at this time risks deadlock.
- // Note that in the event of a competing Suspend or SuspendAll, we are about to be "suspended"
- // anyway, but this wouldn't stop us from continuing to loop. We hold no locks, so it's safe
- // to sleep and retry.
- if (iter_count >= kMaxSuspendRetries) {
- LOG(FATAL) << "Too many SuspendAll retries: " << di;
- }
- {
- MutexLock mu2(self, *Locks::thread_suspend_count_lock_);
- DCHECK_LE(suspend_all_count_, 1);
- if (suspend_all_count_ != 0) {
- // This may take a while, and we're not runnable, and thus would otherwise not block.
- Thread::resume_cond_->WaitHoldingLocks(self);
- continue;
- }
- }
- usleep(kThreadSuspendSleepUs);
- // We're already not runnable, so an attempt to suspend us should succeed.
+ uint32_t num_ignored = 0;
+ if (ignore1 != nullptr) {
+ ++num_ignored;
}
-
- if (!WaitForSuspendBarrier(&pending_threads)) {
- const uint64_t wait_time = NanoTime() - start_time;
+ if (ignore2 != nullptr && ignore1 != ignore2) {
+ ++num_ignored;
+ }
+ {
MutexLock mu(self, *Locks::thread_list_lock_);
MutexLock mu2(self, *Locks::thread_suspend_count_lock_);
- std::ostringstream oss;
+ // Update global suspend all state for attaching threads.
+ ++suspend_all_count_;
+ pending_threads.store(list_.size() - num_ignored, std::memory_order_relaxed);
+ // Increment everybody's suspend count (except those that should be ignored).
for (const auto& thread : list_) {
- if (thread != self && !thread->IsSuspended()) {
- oss << std::endl << "Thread not suspended: " << *thread;
+ if (thread == ignore1 || thread == ignore2) {
+ continue;
+ }
+ VLOG(threads) << "requesting thread suspend: " << *thread;
+ bool updated = thread->ModifySuspendCount(self, +1, &pending_threads, reason);
+ DCHECK(updated);
+
+ // Must install the pending_threads counter first, then check thread->IsSuspend() and clear
+ // the counter. Otherwise there's a race with Thread::TransitionFromRunnableToSuspended()
+ // that can lead a thread to miss a call to PassActiveSuspendBarriers().
+ if (thread->IsSuspended()) {
+ // Only clear the counter for the current thread.
+ thread->ClearSuspendBarrier(&pending_threads);
+ pending_threads.fetch_sub(1, std::memory_order_seq_cst);
}
}
- LOG(::android::base::FATAL) << "Timed out waiting for threads to suspend, waited for "
- << PrettyDuration(wait_time) << oss.str();
+ }
+
+ // Wait for the barrier to be passed by all runnable threads. This wait
+ // is done with a timeout so that we can detect problems.
+#if ART_USE_FUTEXES
+ timespec wait_timeout;
+ InitTimeSpec(false, CLOCK_MONOTONIC, NsToMs(thread_suspend_timeout_ns_), 0, &wait_timeout);
+#endif
+ const uint64_t start_time = NanoTime();
+ while (true) {
+ int32_t cur_val = pending_threads.load(std::memory_order_relaxed);
+ if (LIKELY(cur_val > 0)) {
+#if ART_USE_FUTEXES
+ if (futex(pending_threads.Address(), FUTEX_WAIT_PRIVATE, cur_val, &wait_timeout, nullptr, 0)
+ != 0) {
+ if ((errno == EAGAIN) || (errno == EINTR)) {
+ // EAGAIN and EINTR both indicate a spurious failure, try again from the beginning.
+ continue;
+ }
+ if (errno == ETIMEDOUT) {
+ const uint64_t wait_time = NanoTime() - start_time;
+ MutexLock mu(self, *Locks::thread_list_lock_);
+ MutexLock mu2(self, *Locks::thread_suspend_count_lock_);
+ std::ostringstream oss;
+ for (const auto& thread : list_) {
+ if (thread == ignore1 || thread == ignore2) {
+ continue;
+ }
+ if (!thread->IsSuspended()) {
+ oss << std::endl << "Thread not suspended: " << *thread;
+ }
+ }
+ LOG(kIsDebugBuild ? ::android::base::FATAL : ::android::base::ERROR)
+ << "Timed out waiting for threads to suspend, waited for "
+ << PrettyDuration(wait_time)
+ << oss.str();
+ } else {
+ PLOG(FATAL) << "futex wait failed for SuspendAllInternal()";
+ }
+ } // else re-check pending_threads in the next iteration (this may be a spurious wake-up).
+#else
+ // Spin wait. This is likely to be slow, but on most architecture ART_USE_FUTEXES is set.
+ UNUSED(start_time);
+#endif
+ } else {
+ CHECK_EQ(cur_val, 0);
+ break;
+ }
}
}
@@ -826,7 +798,7 @@
if (kDebugLocking) {
// Debug check that all threads are suspended.
- AssertOtherThreadsAreSuspended(self);
+ AssertThreadsAreSuspended(self, self);
}
long_suspend_ = false;
@@ -839,9 +811,11 @@
--suspend_all_count_;
// Decrement the suspend counts for all threads.
for (const auto& thread : list_) {
- if (thread != self) {
- thread->DecrementSuspendCount(self);
+ if (thread == self) {
+ continue;
}
+ bool updated = thread->ModifySuspendCount(self, -1, nullptr, SuspendReason::kInternal);
+ DCHECK(updated);
}
// Broadcast a notification to all suspended threads, some or all of
@@ -886,7 +860,11 @@
<< ") thread not within thread list";
return false;
}
- thread->DecrementSuspendCount(self, /*for_user_code=*/(reason == SuspendReason::kForUserCode));
+ if (UNLIKELY(!thread->ModifySuspendCount(self, -1, nullptr, reason))) {
+ LOG(ERROR) << "Resume(" << reinterpret_cast<void*>(thread)
+ << ") could not modify suspend count.";
+ return false;
+ }
}
{
@@ -912,19 +890,40 @@
}
}
-Thread* ThreadList::SuspendThreadByPeer(jobject peer, SuspendReason reason) {
- bool is_suspended = false;
+Thread* ThreadList::SuspendThreadByPeer(jobject peer,
+ SuspendReason reason,
+ bool* timed_out) {
+ bool request_suspension = true;
+ const uint64_t start_time = NanoTime();
+ int self_suspend_count = 0;
+ useconds_t sleep_us = kThreadSuspendInitialSleepUs;
+ *timed_out = false;
Thread* const self = Thread::Current();
+ Thread* suspended_thread = nullptr;
VLOG(threads) << "SuspendThreadByPeer starting";
- Thread* thread;
- WrappedSuspend1Barrier wrapped_barrier{};
- for (int iter_count = 1;; ++iter_count) {
+ while (true) {
+ Thread* thread;
{
- // Note: this will transition to runnable and potentially suspend.
+ // Note: this will transition to runnable and potentially suspend. We ensure only one thread
+ // is requesting another suspend, to avoid deadlock, by requiring this function be called
+ // holding Locks::thread_list_suspend_thread_lock_. Its important this thread suspend rather
+ // than request thread suspension, to avoid potential cycles in threads requesting each other
+ // suspend.
ScopedObjectAccess soa(self);
MutexLock thread_list_mu(self, *Locks::thread_list_lock_);
thread = Thread::FromManagedThread(soa, peer);
if (thread == nullptr) {
+ if (suspended_thread != nullptr) {
+ MutexLock suspend_count_mu(self, *Locks::thread_suspend_count_lock_);
+ // If we incremented the suspend count but the thread reset its peer, we need to
+ // re-decrement it since it is shutting down and may deadlock the runtime in
+ // ThreadList::WaitForOtherNonDaemonThreadsToExit.
+ bool updated = suspended_thread->ModifySuspendCount(soa.Self(),
+ -1,
+ nullptr,
+ reason);
+ DCHECK(updated);
+ }
ThreadSuspendByPeerWarning(soa,
::android::base::WARNING,
"No such thread for suspend",
@@ -932,63 +931,84 @@
return nullptr;
}
if (!Contains(thread)) {
+ CHECK(suspended_thread == nullptr);
VLOG(threads) << "SuspendThreadByPeer failed for unattached thread: "
<< reinterpret_cast<void*>(thread);
return nullptr;
}
- // IsSuspended on the current thread will fail as the current thread is changed into
- // Runnable above. As the suspend count is now raised if this is the current thread
- // it will self suspend on transition to Runnable, making it hard to work with. It's simpler
- // to just explicitly handle the current thread in the callers to this code.
- CHECK_NE(thread, self) << "Attempt to suspend the current thread for the debugger";
VLOG(threads) << "SuspendThreadByPeer found thread: " << *thread;
{
MutexLock suspend_count_mu(self, *Locks::thread_suspend_count_lock_);
- if (LIKELY(self->GetSuspendCount() == 0)) {
- thread->IncrementSuspendCount(self, nullptr, &wrapped_barrier, reason);
- if (thread->IsSuspended()) {
- // See the discussion in mutator_gc_coord.md for the race here.
- thread->RemoveFirstSuspend1Barrier();
- if (!thread->HasActiveSuspendBarrier()) {
- thread->AtomicClearFlag(ThreadFlag::kActiveSuspendBarrier);
- }
- is_suspended = true;
+ if (request_suspension) {
+ if (self->GetSuspendCount() > 0) {
+ // We hold the suspend count lock but another thread is trying to suspend us. Its not
+ // safe to try to suspend another thread in case we get a cycle. Start the loop again
+ // which will allow this thread to be suspended.
+ ++self_suspend_count;
+ continue;
}
- DCHECK_GT(thread->GetSuspendCount(), 0);
- break;
+ CHECK(suspended_thread == nullptr);
+ suspended_thread = thread;
+ bool updated = suspended_thread->ModifySuspendCount(self, +1, nullptr, reason);
+ DCHECK(updated);
+ request_suspension = false;
+ } else {
+ // If the caller isn't requesting suspension, a suspension should have already occurred.
+ CHECK_GT(thread->GetSuspendCount(), 0);
}
- // Else we either hold the suspend count lock but another thread is trying to suspend us,
- // making it unsafe to try to suspend another thread in case we get a cycle. In either
- // case, start the loop again, which will allow this thread to be suspended.
+ // IsSuspended on the current thread will fail as the current thread is changed into
+ // Runnable above. As the suspend count is now raised if this is the current thread
+ // it will self suspend on transition to Runnable, making it hard to work with. It's simpler
+ // to just explicitly handle the current thread in the callers to this code.
+ CHECK_NE(thread, self) << "Attempt to suspend the current thread for the debugger";
+ // If thread is suspended (perhaps it was already not Runnable but didn't have a suspend
+ // count, or else we've waited and it has self suspended) or is the current thread, we're
+ // done.
+ if (thread->IsSuspended()) {
+ VLOG(threads) << "SuspendThreadByPeer thread suspended: " << *thread;
+ if (ATraceEnabled()) {
+ std::string name;
+ thread->GetThreadName(name);
+ ATraceBegin(StringPrintf("SuspendThreadByPeer suspended %s for peer=%p", name.c_str(),
+ peer).c_str());
+ }
+ return thread;
+ }
+ const uint64_t total_delay = NanoTime() - start_time;
+ if (total_delay >= thread_suspend_timeout_ns_) {
+ if (suspended_thread == nullptr) {
+ ThreadSuspendByPeerWarning(soa,
+ ::android::base::FATAL,
+ "Failed to issue suspend request",
+ peer);
+ } else {
+ CHECK_EQ(suspended_thread, thread);
+ LOG(WARNING) << "Suspended thread state_and_flags: "
+ << suspended_thread->StateAndFlagsAsHexString()
+ << ", self_suspend_count = " << self_suspend_count;
+ // Explicitly release thread_suspend_count_lock_; we haven't held it for long, so
+ // seeing threads blocked on it is not informative.
+ Locks::thread_suspend_count_lock_->Unlock(self);
+ ThreadSuspendByPeerWarning(soa,
+ ::android::base::FATAL,
+ "Thread suspension timed out",
+ peer);
+ }
+ UNREACHABLE();
+ } else if (sleep_us == 0 &&
+ total_delay > static_cast<uint64_t>(kThreadSuspendMaxYieldUs) * 1000) {
+ // We have spun for kThreadSuspendMaxYieldUs time, switch to sleeps to prevent
+ // excessive CPU usage.
+ sleep_us = kThreadSuspendMaxYieldUs / 2;
+ }
}
+ // Release locks and come out of runnable state.
}
- // All locks are released, and we should quickly exit the suspend-unfriendly state. Retry.
- if (iter_count >= kMaxSuspendRetries) {
- LOG(FATAL) << "Too many suspend retries";
- }
- usleep(kThreadSuspendSleepUs);
- }
- // Now wait for target to decrement suspend barrier.
- if (is_suspended || WaitForSuspendBarrier(&wrapped_barrier.barrier_)) {
- // wrapped_barrier.barrier_ has been decremented and will no longer be accessed.
- VLOG(threads) << "SuspendThreadByPeer thread suspended: " << *thread;
- if (ATraceEnabled()) {
- std::string name;
- thread->GetThreadName(name);
- ATraceBegin(
- StringPrintf("SuspendThreadByPeer suspended %s for peer=%p", name.c_str(), peer).c_str());
- }
- return thread;
- } else {
- LOG(WARNING) << "Suspended thread state_and_flags: " << thread->StateAndFlagsAsHexString();
- // thread still has a pointer to wrapped_barrier. Returning and continuing would be unsafe
- // without additional cleanup.
- {
- ScopedObjectAccess soa(self);
- ThreadSuspendByPeerWarning(
- soa, ::android::base::FATAL, "SuspendThreadByPeer timed out", peer);
- }
- UNREACHABLE();
+ VLOG(threads) << "SuspendThreadByPeer waiting to allow thread chance to suspend";
+ ThreadSuspendSleep(sleep_us);
+ // This may stay at 0 if sleep_us == 0, but this is WAI since we want to avoid using usleep at
+ // all if possible. This shouldn't be an issue since time to suspend should always be small.
+ sleep_us = std::min(sleep_us * 2, kThreadSuspendMaxSleepUs);
}
}
@@ -998,73 +1018,101 @@
LOG(severity) << StringPrintf("%s: %d", message, thread_id);
}
-Thread* ThreadList::SuspendThreadByThreadId(uint32_t thread_id, SuspendReason reason) {
- bool is_suspended = false;
+Thread* ThreadList::SuspendThreadByThreadId(uint32_t thread_id,
+ SuspendReason reason,
+ bool* timed_out) {
+ const uint64_t start_time = NanoTime();
+ useconds_t sleep_us = kThreadSuspendInitialSleepUs;
+ *timed_out = false;
+ Thread* suspended_thread = nullptr;
Thread* const self = Thread::Current();
CHECK_NE(thread_id, kInvalidThreadId);
VLOG(threads) << "SuspendThreadByThreadId starting";
- Thread* thread;
- WrappedSuspend1Barrier wrapped_barrier{};
- for (int iter_count = 1;; ++iter_count) {
+ while (true) {
{
- // Note: this will transition to runnable and potentially suspend.
+ // Note: this will transition to runnable and potentially suspend. We ensure only one thread
+ // is requesting another suspend, to avoid deadlock, by requiring this function be called
+ // holding Locks::thread_list_suspend_thread_lock_. Its important this thread suspend rather
+ // than request thread suspension, to avoid potential cycles in threads requesting each other
+ // suspend.
ScopedObjectAccess soa(self);
MutexLock thread_list_mu(self, *Locks::thread_list_lock_);
- thread = FindThreadByThreadId(thread_id);
+ Thread* thread = nullptr;
+ for (const auto& it : list_) {
+ if (it->GetThreadId() == thread_id) {
+ thread = it;
+ break;
+ }
+ }
if (thread == nullptr) {
+ CHECK(suspended_thread == nullptr) << "Suspended thread " << suspended_thread
+ << " no longer in thread list";
// There's a race in inflating a lock and the owner giving up ownership and then dying.
ThreadSuspendByThreadIdWarning(::android::base::WARNING,
"No such thread id for suspend",
thread_id);
return nullptr;
}
- DCHECK(Contains(thread));
- CHECK_NE(thread, self) << "Attempt to suspend the current thread for the debugger";
VLOG(threads) << "SuspendThreadByThreadId found thread: " << *thread;
+ DCHECK(Contains(thread));
{
MutexLock suspend_count_mu(self, *Locks::thread_suspend_count_lock_);
- if (LIKELY(self->GetSuspendCount() == 0)) {
- thread->IncrementSuspendCount(self, nullptr, &wrapped_barrier, reason);
- if (thread->IsSuspended()) {
- // See the discussion in mutator_gc_coord.md for the race here.
- thread->RemoveFirstSuspend1Barrier();
- if (!thread->HasActiveSuspendBarrier()) {
- thread->AtomicClearFlag(ThreadFlag::kActiveSuspendBarrier);
- }
- is_suspended = true;
+ if (suspended_thread == nullptr) {
+ if (self->GetSuspendCount() > 0) {
+ // We hold the suspend count lock but another thread is trying to suspend us. Its not
+ // safe to try to suspend another thread in case we get a cycle. Start the loop again
+ // which will allow this thread to be suspended.
+ continue;
}
- DCHECK_GT(thread->GetSuspendCount(), 0);
- break;
+ bool updated = thread->ModifySuspendCount(self, +1, nullptr, reason);
+ DCHECK(updated);
+ suspended_thread = thread;
+ } else {
+ CHECK_EQ(suspended_thread, thread);
+ // If the caller isn't requesting suspension, a suspension should have already occurred.
+ CHECK_GT(thread->GetSuspendCount(), 0);
}
- // Else we either hold the suspend count lock but another thread is trying to suspend us,
- // making it unsafe to try to suspend another thread in case we get a cycle. In either
- // case, start the loop again, which will allow this thread to be suspended.
+ // IsSuspended on the current thread will fail as the current thread is changed into
+ // Runnable above. As the suspend count is now raised if this is the current thread
+ // it will self suspend on transition to Runnable, making it hard to work with. It's simpler
+ // to just explicitly handle the current thread in the callers to this code.
+ CHECK_NE(thread, self) << "Attempt to suspend the current thread for the debugger";
+ // If thread is suspended (perhaps it was already not Runnable but didn't have a suspend
+ // count, or else we've waited and it has self suspended) or is the current thread, we're
+ // done.
+ if (thread->IsSuspended()) {
+ if (ATraceEnabled()) {
+ std::string name;
+ thread->GetThreadName(name);
+ ATraceBegin(StringPrintf("SuspendThreadByThreadId suspended %s id=%d",
+ name.c_str(), thread_id).c_str());
+ }
+ VLOG(threads) << "SuspendThreadByThreadId thread suspended: " << *thread;
+ return thread;
+ }
+ const uint64_t total_delay = NanoTime() - start_time;
+ if (total_delay >= thread_suspend_timeout_ns_) {
+ ThreadSuspendByThreadIdWarning(::android::base::WARNING,
+ "Thread suspension timed out",
+ thread_id);
+ if (suspended_thread != nullptr) {
+ bool updated = thread->ModifySuspendCount(soa.Self(), -1, nullptr, reason);
+ DCHECK(updated);
+ }
+ *timed_out = true;
+ return nullptr;
+ } else if (sleep_us == 0 &&
+ total_delay > static_cast<uint64_t>(kThreadSuspendMaxYieldUs) * 1000) {
+ // We have spun for kThreadSuspendMaxYieldUs time, switch to sleeps to prevent
+ // excessive CPU usage.
+ sleep_us = kThreadSuspendMaxYieldUs / 2;
+ }
}
+ // Release locks and come out of runnable state.
}
- // All locks are released, and we should quickly exit the suspend-unfriendly state. Retry.
- if (iter_count >= kMaxSuspendRetries) {
- LOG(FATAL) << "Too many suspend retries";
- }
- usleep(kThreadSuspendSleepUs);
- }
- // Now wait for target to decrement suspend barrier.
- if (is_suspended || WaitForSuspendBarrier(&wrapped_barrier.barrier_)) {
- // wrapped_barrier.barrier_ has been decremented and will no longer be accessed.
- VLOG(threads) << "SuspendThreadByThreadId thread suspended: " << *thread;
- if (ATraceEnabled()) {
- std::string name;
- thread->GetThreadName(name);
- ATraceBegin(
- StringPrintf("SuspendThreadByPeer suspended %s for id=%d", name.c_str(), thread_id)
- .c_str());
- }
- return thread;
- } else {
- // thread still has a pointer to wrapped_barrier. Returning and continuing would be unsafe
- // without additional cleanup.
- ThreadSuspendByThreadIdWarning(
- ::android::base::FATAL, "SuspendThreadByThreadId timed out", thread_id);
- UNREACHABLE();
+ VLOG(threads) << "SuspendThreadByThreadId waiting to allow thread chance to suspend";
+ ThreadSuspendSleep(sleep_us);
+ sleep_us = std::min(sleep_us * 2, kThreadSuspendMaxSleepUs);
}
}
@@ -1140,7 +1188,8 @@
// daemons.
CHECK(thread->IsDaemon()) << *thread;
if (thread != self) {
- thread->IncrementSuspendCount(self);
+ bool updated = thread->ModifySuspendCount(self, +1, nullptr, SuspendReason::kInternal);
+ DCHECK(updated);
++daemons_left;
}
// We are shutting down the runtime, set the JNI functions of all the JNIEnvs to be
@@ -1240,10 +1289,11 @@
// SuspendAll requests.
MutexLock mu(self, *Locks::thread_list_lock_);
MutexLock mu2(self, *Locks::thread_suspend_count_lock_);
- if (suspend_all_count_ == 1) {
- self->IncrementSuspendCount(self);
- } else {
- DCHECK_EQ(suspend_all_count_, 0);
+ // Modify suspend count in increments of 1 to maintain invariants in ModifySuspendCount. While
+ // this isn't particularly efficient the suspend counts are most commonly 0 or 1.
+ for (int delta = suspend_all_count_; delta > 0; delta--) {
+ bool updated = self->ModifySuspendCount(self, +1, nullptr, SuspendReason::kInternal);
+ DCHECK(updated);
}
CHECK(!Contains(self));
list_.push_back(self);
@@ -1292,7 +1342,6 @@
// Note: deliberately not using MutexLock that could hold a stale self pointer.
{
MutexLock mu(self, *Locks::thread_list_lock_);
- self->SignalExitFlags();
if (!Contains(self)) {
std::string thread_name;
self->GetThreadName(thread_name);
@@ -1302,19 +1351,16 @@
break;
} else {
MutexLock mu2(self, *Locks::thread_suspend_count_lock_);
- if (!self->IsSuspended() && !self->ReadFlag(ThreadFlag::kRunningFlipFunction)) {
- Thread::StateAndFlags state_and_flags = self->GetStateAndFlags(std::memory_order_acquire);
- if (!state_and_flags.IsFlagSet(ThreadFlag::kRunningFlipFunction)) {
- list_.remove(self);
- break;
- }
+ if (!self->IsSuspended()) {
+ list_.remove(self);
+ break;
}
}
}
// In the case where we are not suspended yet, sleep to leave other threads time to execute.
// This is important if there are realtime threads. b/111277984
usleep(1);
- // We failed to remove the thread due to a suspend request or the like, loop and try again.
+ // We failed to remove the thread due to a suspend request, loop and try again.
}
delete self;
@@ -1353,11 +1399,13 @@
MutexLock mu(self, *Locks::thread_list_lock_);
MutexLock mu2(self, *Locks::thread_suspend_count_lock_);
for (Thread* thread : list_) {
- thread->IncrementSuspendCount(self);
+ bool suspended = thread->ModifySuspendCount(self, +1, nullptr, SuspendReason::kInternal);
+ DCHECK(suspended);
if (thread == self || thread->IsSuspended()) {
threads_to_visit.push_back(thread);
} else {
- thread->DecrementSuspendCount(self);
+ bool resumed = thread->ModifySuspendCount(self, -1, nullptr, SuspendReason::kInternal);
+ DCHECK(resumed);
}
}
}
@@ -1372,7 +1420,8 @@
{
MutexLock mu2(self, *Locks::thread_suspend_count_lock_);
for (Thread* thread : threads_to_visit) {
- thread->DecrementSuspendCount(self);
+ bool updated = thread->ModifySuspendCount(self, -1, nullptr, SuspendReason::kInternal);
+ DCHECK(updated);
}
}
}
diff --git a/runtime/thread_list.h b/runtime/thread_list.h
index 3649dd6..51fac4a 100644
--- a/runtime/thread_list.h
+++ b/runtime/thread_list.h
@@ -49,11 +49,7 @@
static constexpr uint32_t kInvalidThreadId = 0;
static constexpr uint32_t kMainThreadId = 1;
static constexpr uint64_t kDefaultThreadSuspendTimeout =
- kIsDebugBuild ? 2'000'000'000ull : 4'000'000'000ull;
- // We fail more aggressively in debug builds to catch potential issues early.
- // The number of times we may retry when we find ourselves in a suspend-unfriendly state.
- static constexpr int kMaxSuspendRetries = kIsDebugBuild ? 500 : 5000;
- static constexpr useconds_t kThreadSuspendSleepUs = 100;
+ kIsDebugBuild ? 50'000'000'000ull : 10'000'000'000ull;
explicit ThreadList(uint64_t thread_suspend_timeout_ns);
~ThreadList();
@@ -74,7 +70,7 @@
bool Resume(Thread* thread, SuspendReason reason = SuspendReason::kInternal)
REQUIRES(!Locks::thread_suspend_count_lock_) WARN_UNUSED;
- // Suspends all other threads and gets exclusive access to the mutator lock.
+ // Suspends all threads and gets exclusive access to the mutator lock.
// If long_suspend is true, then other threads who try to suspend will never timeout.
// long_suspend is currenly used for hprof since large heaps take a long time.
void SuspendAll(const char* cause, bool long_suspend = false)
@@ -85,7 +81,10 @@
// Suspend a thread using a peer, typically used by the debugger. Returns the thread on success,
// else null. The peer is used to identify the thread to avoid races with the thread terminating.
- Thread* SuspendThreadByPeer(jobject peer, SuspendReason reason)
+ // If the suspension times out then *timeout is set to true.
+ Thread* SuspendThreadByPeer(jobject peer,
+ SuspendReason reason,
+ bool* timed_out)
REQUIRES(!Locks::mutator_lock_,
!Locks::thread_list_lock_,
!Locks::thread_suspend_count_lock_);
@@ -93,8 +92,8 @@
// Suspend a thread using its thread id, typically used by lock/monitor inflation. Returns the
// thread on success else null. The thread id is used to identify the thread to avoid races with
// the thread terminating. Note that as thread ids are recycled this may not suspend the expected
- // thread, that may be terminating.
- Thread* SuspendThreadByThreadId(uint32_t thread_id, SuspendReason reason)
+ // thread, that may be terminating. If the suspension times out then *timeout is set to true.
+ Thread* SuspendThreadByThreadId(uint32_t thread_id, SuspendReason reason, bool* timed_out)
REQUIRES(!Locks::mutator_lock_,
!Locks::thread_list_lock_,
!Locks::thread_suspend_count_lock_);
@@ -114,21 +113,11 @@
// Running threads are not suspended but run the checkpoint inside of the suspend check. The
// return value includes already suspended threads for b/24191051. Runs or requests the
// callback, if non-null, inside the thread_list_lock critical section after determining the
- // runnable/suspended states of the threads. Does not wait for completion of the checkpoint
- // function in running threads. If the caller holds the mutator lock, then all instances of the
- // checkpoint function are run with the mutator lock.
- size_t RunCheckpoint(Closure* checkpoint_function,
- Closure* callback = nullptr,
- bool allow_lock_checking = true)
+ // runnable/suspended states of the threads. Does not wait for completion of the callbacks in
+ // running threads.
+ size_t RunCheckpoint(Closure* checkpoint_function, Closure* callback = nullptr)
REQUIRES(!Locks::thread_list_lock_, !Locks::thread_suspend_count_lock_);
- // Convenience version of the above to disable lock checking inside Run function. Hopefully this
- // and the third parameter above will eventually disappear.
- size_t RunCheckpointUnchecked(Closure* checkpoint_function, Closure* callback = nullptr)
- REQUIRES(!Locks::thread_list_lock_, !Locks::thread_suspend_count_lock_) {
- return RunCheckpoint(checkpoint_function, callback, false);
- }
-
// Run an empty checkpoint on threads. Wait until threads pass the next suspend point or are
// suspended. This is used to ensure that the threads finish or aren't in the middle of an
// in-flight mutator heap access (eg. a read barrier.) Runnable threads will respond by
@@ -139,10 +128,10 @@
// Flip thread roots from from-space refs to to-space refs. Used by
// the concurrent moving collectors.
- void FlipThreadRoots(Closure* thread_flip_visitor,
- Closure* flip_callback,
- gc::collector::GarbageCollector* collector,
- gc::GcPauseListener* pause_listener)
+ size_t FlipThreadRoots(Closure* thread_flip_visitor,
+ Closure* flip_callback,
+ gc::collector::GarbageCollector* collector,
+ gc::GcPauseListener* pause_listener)
REQUIRES(!Locks::mutator_lock_,
!Locks::thread_list_lock_,
!Locks::thread_suspend_count_lock_);
@@ -197,25 +186,26 @@
REQUIRES(!Locks::thread_list_lock_, !Locks::thread_suspend_count_lock_,
!Locks::mutator_lock_);
- // Wait for suspend barrier to reach zero. Return false on timeout.
- bool WaitForSuspendBarrier(AtomicInteger* barrier);
-
private:
uint32_t AllocThreadId(Thread* self);
void ReleaseThreadId(Thread* self, uint32_t id) REQUIRES(!Locks::allocated_thread_ids_lock_);
+ size_t RunCheckpoint(Closure* checkpoint_function, bool includeSuspended)
+ REQUIRES(!Locks::thread_list_lock_, !Locks::thread_suspend_count_lock_);
+
void DumpUnattachedThreads(std::ostream& os, bool dump_native_stack)
REQUIRES(!Locks::thread_list_lock_);
void SuspendAllDaemonThreadsForShutdown()
REQUIRES(!Locks::thread_list_lock_, !Locks::thread_suspend_count_lock_);
- void SuspendAllInternal(Thread* self, SuspendReason reason = SuspendReason::kInternal)
- REQUIRES(!Locks::thread_list_lock_,
- !Locks::thread_suspend_count_lock_,
- !Locks::mutator_lock_);
+ void SuspendAllInternal(Thread* self,
+ Thread* ignore1,
+ Thread* ignore2 = nullptr,
+ SuspendReason reason = SuspendReason::kInternal)
+ REQUIRES(!Locks::thread_list_lock_, !Locks::thread_suspend_count_lock_);
- void AssertOtherThreadsAreSuspended(Thread* self)
+ void AssertThreadsAreSuspended(Thread* self, Thread* ignore1, Thread* ignore2 = nullptr)
REQUIRES(!Locks::thread_list_lock_, !Locks::thread_suspend_count_lock_);
std::bitset<kMaxThreadId> allocated_ids_ GUARDED_BY(Locks::allocated_thread_ids_lock_);
@@ -223,9 +213,7 @@
// The actual list of all threads.
std::list<Thread*> list_ GUARDED_BY(Locks::thread_list_lock_);
- // Ongoing suspend all requests, used to ensure threads added to list_ respect SuspendAll. The
- // value is always either 0 or 1. TODO: Can we make the exclusive mutator lock acquisition ensure
- // this instead? There seem to be tricky ordering issues.
+ // Ongoing suspend all requests, used to ensure threads added to list_ respect SuspendAll.
int suspend_all_count_ GUARDED_BY(Locks::thread_suspend_count_lock_);
// Number of threads unregistering, ~ThreadList blocks until this hits 0.
@@ -233,7 +221,7 @@
// Thread suspend time histogram. Only modified when all the threads are suspended, so guarding
// by mutator lock ensures no thread can read when another thread is modifying it.
- Histogram<uint64_t> suspend_all_histogram_ GUARDED_BY(Locks::mutator_lock_);
+ Histogram<uint64_t> suspend_all_historam_ GUARDED_BY(Locks::mutator_lock_);
// Whether or not the current thread suspension is long.
bool long_suspend_;
diff --git a/test/129-ThreadGetId/expected-stdout.txt b/test/129-ThreadGetId/expected-stdout.txt
index 4455320..aadf90d 100644
--- a/test/129-ThreadGetId/expected-stdout.txt
+++ b/test/129-ThreadGetId/expected-stdout.txt
@@ -1,8 +1,2 @@
-Thread finished
-Thread finished
-Thread finished
-Thread finished
-Thread finished
-All joined
HeapTaskDaemon depth 0
Finishing
diff --git a/test/129-ThreadGetId/src/Main.java b/test/129-ThreadGetId/src/Main.java
index d46bb25..50e8c09 100644
--- a/test/129-ThreadGetId/src/Main.java
+++ b/test/129-ThreadGetId/src/Main.java
@@ -20,42 +20,19 @@
public class Main implements Runnable {
static final int NUMBER_OF_THREADS = 5;
static final int TOTAL_OPERATIONS = 900;
- static int[] progress = new int[NUMBER_OF_THREADS];
- int index;
-
- Main(int i) {
- index = i;
- }
public static void main(String[] args) throws Exception {
final Thread[] threads = new Thread[NUMBER_OF_THREADS];
- Thread watchdog = new Thread() {
- public void run() {
- try {
- Thread.sleep(50_000);
- System.out.print("Watchdog timed out: ");
- for (int i = 0; i < NUMBER_OF_THREADS; ++i) {
- System.out.print(progress[i] + ", ");
- }
- System.out.println("");
- System.err.println("Watchdog thread timed out");
- System.exit(1);
- } catch (InterruptedException e) {}
- }
- };
- watchdog.start();
for (int t = 0; t < threads.length; t++) {
- threads[t] = new Thread(new Main(t));
+ threads[t] = new Thread(new Main());
threads[t].start();
}
for (Thread t : threads) {
t.join();
}
- System.out.println("All joined");
// Do this test after the other part to leave some time for the heap task daemon to start
// up.
test_getStackTraces();
- watchdog.interrupt();
System.out.println("Finishing");
}
@@ -110,10 +87,8 @@
}
public void run() {
- for (int i = 1; i <= TOTAL_OPERATIONS; ++i) {
+ for (int i = 0; i < TOTAL_OPERATIONS; ++i) {
test_getId();
- progress[index] = i;
}
- System.out.println("Thread finished");
}
}
diff --git a/test/2011-stack-walk-concurrent-instrument/stack_walk_concurrent.cc b/test/2011-stack-walk-concurrent-instrument/stack_walk_concurrent.cc
index 493f1d4..78bb772 100644
--- a/test/2011-stack-walk-concurrent-instrument/stack_walk_concurrent.cc
+++ b/test/2011-stack-walk-concurrent-instrument/stack_walk_concurrent.cc
@@ -81,8 +81,10 @@
jobject target) {
while (!instrument_waiting) {
}
+ bool timed_out = false;
Thread* other = Runtime::Current()->GetThreadList()->SuspendThreadByPeer(
- target, SuspendReason::kInternal);
+ target, SuspendReason::kInternal, &timed_out);
+ CHECK(!timed_out);
CHECK(other != nullptr);
ScopedSuspendAll ssa(__FUNCTION__);
Runtime::Current()->GetInstrumentation()->InstrumentThreadStack(other,
