| /* |
| * Copyright (C) 2008 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #include "monitor.h" |
| |
| #include <vector> |
| |
| #include "base/mutex.h" |
| #include "base/stl_util.h" |
| #include "class_linker.h" |
| #include "dex_file-inl.h" |
| #include "dex_instruction.h" |
| #include "mirror/abstract_method-inl.h" |
| #include "mirror/class-inl.h" |
| #include "mirror/object-inl.h" |
| #include "mirror/object_array-inl.h" |
| #include "object_utils.h" |
| #include "scoped_thread_state_change.h" |
| #include "thread.h" |
| #include "thread_list.h" |
| #include "verifier/method_verifier.h" |
| #include "well_known_classes.h" |
| |
| namespace art { |
| |
| /* |
| * Every Object has a monitor associated with it, but not every Object is |
| * actually locked. Even the ones that are locked do not need a |
| * full-fledged monitor until a) there is actual contention or b) wait() |
| * is called on the Object. |
| * |
| * For Android, we have implemented a scheme similar to the one described |
| * in Bacon et al.'s "Thin locks: featherweight synchronization for Java" |
| * (ACM 1998). Things are even easier for us, though, because we have |
| * a full 32 bits to work with. |
| * |
| * The two states of an Object's lock are referred to as "thin" and |
| * "fat". A lock may transition from the "thin" state to the "fat" |
| * state and this transition is referred to as inflation. Once a lock |
| * has been inflated it remains in the "fat" state indefinitely. |
| * |
| * The lock value itself is stored in Object.lock. The LSB of the |
| * lock encodes its state. When cleared, the lock is in the "thin" |
| * state and its bits are formatted as follows: |
| * |
| * [31 ---- 19] [18 ---- 3] [2 ---- 1] [0] |
| * lock count thread id hash state 0 |
| * |
| * When set, the lock is in the "fat" state and its bits are formatted |
| * as follows: |
| * |
| * [31 ---- 3] [2 ---- 1] [0] |
| * pointer hash state 1 |
| * |
| * For an in-depth description of the mechanics of thin-vs-fat locking, |
| * read the paper referred to above. |
| * |
| * Monitors provide: |
| * - mutually exclusive access to resources |
| * - a way for multiple threads to wait for notification |
| * |
| * In effect, they fill the role of both mutexes and condition variables. |
| * |
| * Only one thread can own the monitor at any time. There may be several |
| * threads waiting on it (the wait call unlocks it). One or more waiting |
| * threads may be getting interrupted or notified at any given time. |
| * |
| * TODO: the various members of monitor are not SMP-safe. |
| */ |
| |
| // The shape is the bottom bit; either LW_SHAPE_THIN or LW_SHAPE_FAT. |
| #define LW_SHAPE_MASK 0x1 |
| #define LW_SHAPE(x) static_cast<int>((x) & LW_SHAPE_MASK) |
| |
| /* |
| * Monitor accessor. Extracts a monitor structure pointer from a fat |
| * lock. Performs no error checking. |
| */ |
| #define LW_MONITOR(x) \ |
| (reinterpret_cast<Monitor*>((x) & ~((LW_HASH_STATE_MASK << LW_HASH_STATE_SHIFT) | LW_SHAPE_MASK))) |
| |
| /* |
| * Lock recursion count field. Contains a count of the number of times |
| * a lock has been recursively acquired. |
| */ |
| #define LW_LOCK_COUNT_MASK 0x1fff |
| #define LW_LOCK_COUNT_SHIFT 19 |
| #define LW_LOCK_COUNT(x) (((x) >> LW_LOCK_COUNT_SHIFT) & LW_LOCK_COUNT_MASK) |
| |
| bool (*Monitor::is_sensitive_thread_hook_)() = NULL; |
| uint32_t Monitor::lock_profiling_threshold_ = 0; |
| |
| bool Monitor::IsSensitiveThread() { |
| if (is_sensitive_thread_hook_ != NULL) { |
| return (*is_sensitive_thread_hook_)(); |
| } |
| return false; |
| } |
| |
| void Monitor::Init(uint32_t lock_profiling_threshold, bool (*is_sensitive_thread_hook)()) { |
| lock_profiling_threshold_ = lock_profiling_threshold; |
| is_sensitive_thread_hook_ = is_sensitive_thread_hook; |
| } |
| |
| Monitor::Monitor(Thread* owner, mirror::Object* obj) |
| : monitor_lock_("a monitor lock", kMonitorLock), |
| owner_(owner), |
| lock_count_(0), |
| obj_(obj), |
| wait_set_(NULL), |
| locking_method_(NULL), |
| locking_dex_pc_(0) { |
| monitor_lock_.Lock(owner); |
| // Propagate the lock state. |
| uint32_t thin = *obj->GetRawLockWordAddress(); |
| lock_count_ = LW_LOCK_COUNT(thin); |
| thin &= LW_HASH_STATE_MASK << LW_HASH_STATE_SHIFT; |
| thin |= reinterpret_cast<uint32_t>(this) | LW_SHAPE_FAT; |
| // Publish the updated lock word. |
| android_atomic_release_store(thin, obj->GetRawLockWordAddress()); |
| // Lock profiling. |
| if (lock_profiling_threshold_ != 0) { |
| locking_method_ = owner->GetCurrentMethod(&locking_dex_pc_); |
| } |
| } |
| |
| Monitor::~Monitor() { |
| DCHECK(obj_ != NULL); |
| DCHECK_EQ(LW_SHAPE(*obj_->GetRawLockWordAddress()), LW_SHAPE_FAT); |
| } |
| |
| /* |
| * Links a thread into a monitor's wait set. The monitor lock must be |
| * held by the caller of this routine. |
| */ |
| void Monitor::AppendToWaitSet(Thread* thread) { |
| DCHECK(owner_ == Thread::Current()); |
| DCHECK(thread != NULL); |
| DCHECK(thread->wait_next_ == NULL) << thread->wait_next_; |
| if (wait_set_ == NULL) { |
| wait_set_ = thread; |
| return; |
| } |
| |
| // push_back. |
| Thread* t = wait_set_; |
| while (t->wait_next_ != NULL) { |
| t = t->wait_next_; |
| } |
| t->wait_next_ = thread; |
| } |
| |
| /* |
| * Unlinks a thread from a monitor's wait set. The monitor lock must |
| * be held by the caller of this routine. |
| */ |
| void Monitor::RemoveFromWaitSet(Thread *thread) { |
| DCHECK(owner_ == Thread::Current()); |
| DCHECK(thread != NULL); |
| if (wait_set_ == NULL) { |
| return; |
| } |
| if (wait_set_ == thread) { |
| wait_set_ = thread->wait_next_; |
| thread->wait_next_ = NULL; |
| return; |
| } |
| |
| Thread* t = wait_set_; |
| while (t->wait_next_ != NULL) { |
| if (t->wait_next_ == thread) { |
| t->wait_next_ = thread->wait_next_; |
| thread->wait_next_ = NULL; |
| return; |
| } |
| t = t->wait_next_; |
| } |
| } |
| |
| mirror::Object* Monitor::GetObject() { |
| return obj_; |
| } |
| |
| void Monitor::Lock(Thread* self) { |
| if (owner_ == self) { |
| lock_count_++; |
| return; |
| } |
| |
| if (!monitor_lock_.TryLock(self)) { |
| uint64_t waitStart = 0; |
| uint64_t waitEnd = 0; |
| uint32_t wait_threshold = lock_profiling_threshold_; |
| const mirror::AbstractMethod* current_locking_method = NULL; |
| uint32_t current_locking_dex_pc = 0; |
| { |
| ScopedThreadStateChange tsc(self, kBlocked); |
| if (wait_threshold != 0) { |
| waitStart = NanoTime() / 1000; |
| } |
| current_locking_method = locking_method_; |
| current_locking_dex_pc = locking_dex_pc_; |
| |
| monitor_lock_.Lock(self); |
| if (wait_threshold != 0) { |
| waitEnd = NanoTime() / 1000; |
| } |
| } |
| |
| if (wait_threshold != 0) { |
| uint64_t wait_ms = (waitEnd - waitStart) / 1000; |
| uint32_t sample_percent; |
| if (wait_ms >= wait_threshold) { |
| sample_percent = 100; |
| } else { |
| sample_percent = 100 * wait_ms / wait_threshold; |
| } |
| if (sample_percent != 0 && (static_cast<uint32_t>(rand() % 100) < sample_percent)) { |
| const char* current_locking_filename; |
| uint32_t current_locking_line_number; |
| TranslateLocation(current_locking_method, current_locking_dex_pc, |
| current_locking_filename, current_locking_line_number); |
| LogContentionEvent(self, wait_ms, sample_percent, current_locking_filename, current_locking_line_number); |
| } |
| } |
| } |
| owner_ = self; |
| DCHECK_EQ(lock_count_, 0); |
| |
| // When debugging, save the current monitor holder for future |
| // acquisition failures to use in sampled logging. |
| if (lock_profiling_threshold_ != 0) { |
| locking_method_ = self->GetCurrentMethod(&locking_dex_pc_); |
| } |
| } |
| |
| static void ThrowIllegalMonitorStateExceptionF(const char* fmt, ...) |
| __attribute__((format(printf, 1, 2))); |
| |
| static void ThrowIllegalMonitorStateExceptionF(const char* fmt, ...) |
| SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) { |
| va_list args; |
| va_start(args, fmt); |
| Thread* self = Thread::Current(); |
| ThrowLocation throw_location = self->GetCurrentLocationForThrow(); |
| self->ThrowNewExceptionV(throw_location, "Ljava/lang/IllegalMonitorStateException;", fmt, args); |
| if (!Runtime::Current()->IsStarted()) { |
| std::ostringstream ss; |
| self->Dump(ss); |
| std::string str(ss.str()); |
| LOG(ERROR) << "IllegalMonitorStateException: " << str; |
| } |
| va_end(args); |
| } |
| |
| static std::string ThreadToString(Thread* thread) { |
| if (thread == NULL) { |
| return "NULL"; |
| } |
| std::ostringstream oss; |
| // TODO: alternatively, we could just return the thread's name. |
| oss << *thread; |
| return oss.str(); |
| } |
| |
| void Monitor::FailedUnlock(mirror::Object* o, Thread* expected_owner, Thread* found_owner, |
| Monitor* monitor) { |
| Thread* current_owner = NULL; |
| std::string current_owner_string; |
| std::string expected_owner_string; |
| std::string found_owner_string; |
| { |
| // TODO: isn't this too late to prevent threads from disappearing? |
| // Acquire thread list lock so threads won't disappear from under us. |
| MutexLock mu(Thread::Current(), *Locks::thread_list_lock_); |
| // Re-read owner now that we hold lock. |
| current_owner = (monitor != NULL) ? monitor->owner_ : NULL; |
| // Get short descriptions of the threads involved. |
| current_owner_string = ThreadToString(current_owner); |
| expected_owner_string = ThreadToString(expected_owner); |
| found_owner_string = ThreadToString(found_owner); |
| } |
| if (current_owner == NULL) { |
| if (found_owner == NULL) { |
| ThrowIllegalMonitorStateExceptionF("unlock of unowned monitor on object of type '%s'" |
| " on thread '%s'", |
| PrettyTypeOf(o).c_str(), |
| expected_owner_string.c_str()); |
| } else { |
| // Race: the original read found an owner but now there is none |
| ThrowIllegalMonitorStateExceptionF("unlock of monitor owned by '%s' on object of type '%s'" |
| " (where now the monitor appears unowned) on thread '%s'", |
| found_owner_string.c_str(), |
| PrettyTypeOf(o).c_str(), |
| expected_owner_string.c_str()); |
| } |
| } else { |
| if (found_owner == NULL) { |
| // Race: originally there was no owner, there is now |
| ThrowIllegalMonitorStateExceptionF("unlock of monitor owned by '%s' on object of type '%s'" |
| " (originally believed to be unowned) on thread '%s'", |
| current_owner_string.c_str(), |
| PrettyTypeOf(o).c_str(), |
| expected_owner_string.c_str()); |
| } else { |
| if (found_owner != current_owner) { |
| // Race: originally found and current owner have changed |
| ThrowIllegalMonitorStateExceptionF("unlock of monitor originally owned by '%s' (now" |
| " owned by '%s') on object of type '%s' on thread '%s'", |
| found_owner_string.c_str(), |
| current_owner_string.c_str(), |
| PrettyTypeOf(o).c_str(), |
| expected_owner_string.c_str()); |
| } else { |
| ThrowIllegalMonitorStateExceptionF("unlock of monitor owned by '%s' on object of type '%s'" |
| " on thread '%s", |
| current_owner_string.c_str(), |
| PrettyTypeOf(o).c_str(), |
| expected_owner_string.c_str()); |
| } |
| } |
| } |
| } |
| |
| bool Monitor::Unlock(Thread* self, bool for_wait) { |
| DCHECK(self != NULL); |
| Thread* owner = owner_; |
| if (owner == self) { |
| // We own the monitor, so nobody else can be in here. |
| if (lock_count_ == 0) { |
| owner_ = NULL; |
| locking_method_ = NULL; |
| locking_dex_pc_ = 0; |
| monitor_lock_.Unlock(self); |
| } else { |
| --lock_count_; |
| } |
| } else if (for_wait) { |
| // Wait should have already cleared the fields. |
| DCHECK_EQ(lock_count_, 0); |
| DCHECK(owner == NULL); |
| DCHECK(locking_method_ == NULL); |
| DCHECK_EQ(locking_dex_pc_, 0u); |
| monitor_lock_.Unlock(self); |
| } else { |
| // We don't own this, so we're not allowed to unlock it. |
| // The JNI spec says that we should throw IllegalMonitorStateException |
| // in this case. |
| FailedUnlock(obj_, self, owner, this); |
| return false; |
| } |
| return true; |
| } |
| |
| /* |
| * Wait on a monitor until timeout, interrupt, or notification. Used for |
| * Object.wait() and (somewhat indirectly) Thread.sleep() and Thread.join(). |
| * |
| * If another thread calls Thread.interrupt(), we throw InterruptedException |
| * and return immediately if one of the following are true: |
| * - blocked in wait(), wait(long), or wait(long, int) methods of Object |
| * - blocked in join(), join(long), or join(long, int) methods of Thread |
| * - blocked in sleep(long), or sleep(long, int) methods of Thread |
| * Otherwise, we set the "interrupted" flag. |
| * |
| * Checks to make sure that "ns" is in the range 0-999999 |
| * (i.e. fractions of a millisecond) and throws the appropriate |
| * exception if it isn't. |
| * |
| * The spec allows "spurious wakeups", and recommends that all code using |
| * Object.wait() do so in a loop. This appears to derive from concerns |
| * about pthread_cond_wait() on multiprocessor systems. Some commentary |
| * on the web casts doubt on whether these can/should occur. |
| * |
| * Since we're allowed to wake up "early", we clamp extremely long durations |
| * to return at the end of the 32-bit time epoch. |
| */ |
| void Monitor::Wait(Thread* self, int64_t ms, int32_t ns, |
| bool interruptShouldThrow, ThreadState why) { |
| DCHECK(self != NULL); |
| DCHECK(why == kTimedWaiting || why == kWaiting || why == kSleeping); |
| |
| // Make sure that we hold the lock. |
| if (owner_ != self) { |
| ThrowIllegalMonitorStateExceptionF("object not locked by thread before wait()"); |
| return; |
| } |
| monitor_lock_.AssertHeld(self); |
| |
| // We need to turn a zero-length timed wait into a regular wait because |
| // Object.wait(0, 0) is defined as Object.wait(0), which is defined as Object.wait(). |
| if (why == kTimedWaiting && (ms == 0 && ns == 0)) { |
| why = kWaiting; |
| } |
| |
| WaitWithLock(self, ms, ns, interruptShouldThrow, why); |
| } |
| |
| void Monitor::WaitWithLock(Thread* self, int64_t ms, int32_t ns, |
| bool interruptShouldThrow, ThreadState why) { |
| // Enforce the timeout range. |
| if (ms < 0 || ns < 0 || ns > 999999) { |
| ThrowLocation throw_location = self->GetCurrentLocationForThrow(); |
| self->ThrowNewExceptionF(throw_location, "Ljava/lang/IllegalArgumentException;", |
| "timeout arguments out of range: ms=%lld ns=%d", ms, ns); |
| return; |
| } |
| |
| /* |
| * Add ourselves to the set of threads waiting on this monitor, and |
| * release our hold. We need to let it go even if we're a few levels |
| * deep in a recursive lock, and we need to restore that later. |
| * |
| * We append to the wait set ahead of clearing the count and owner |
| * fields so the subroutine can check that the calling thread owns |
| * the monitor. Aside from that, the order of member updates is |
| * not order sensitive as we hold the pthread mutex. |
| */ |
| AppendToWaitSet(self); |
| int prev_lock_count = lock_count_; |
| lock_count_ = 0; |
| owner_ = NULL; |
| const mirror::AbstractMethod* saved_method = locking_method_; |
| locking_method_ = NULL; |
| uintptr_t saved_dex_pc = locking_dex_pc_; |
| locking_dex_pc_ = 0; |
| |
| /* |
| * Update thread state. If the GC wakes up, it'll ignore us, knowing |
| * that we won't touch any references in this state, and we'll check |
| * our suspend mode before we transition out. |
| */ |
| self->TransitionFromRunnableToSuspended(why); |
| |
| bool was_interrupted = false; |
| { |
| // Pseudo-atomically wait on self's wait_cond_ and release the monitor lock. |
| MutexLock mu(self, *self->wait_mutex_); |
| |
| // Set wait_monitor_ to the monitor object we will be waiting on. When wait_monitor_ is |
| // non-NULL a notifying or interrupting thread must signal the thread's wait_cond_ to wake it |
| // up. |
| DCHECK(self->wait_monitor_ == NULL); |
| self->wait_monitor_ = this; |
| |
| // Release the monitor lock. |
| Unlock(self, true); |
| |
| // Handle the case where the thread was interrupted before we called wait(). |
| if (self->interrupted_) { |
| was_interrupted = true; |
| } else { |
| // Wait for a notification or a timeout to occur. |
| if (why == kWaiting) { |
| self->wait_cond_->Wait(self); |
| } else { |
| DCHECK(why == kTimedWaiting || why == kSleeping) << why; |
| self->wait_cond_->TimedWait(self, ms, ns); |
| } |
| if (self->interrupted_) { |
| was_interrupted = true; |
| } |
| self->interrupted_ = false; |
| } |
| } |
| |
| // Set self->status back to kRunnable, and self-suspend if needed. |
| self->TransitionFromSuspendedToRunnable(); |
| |
| { |
| // We reset the thread's wait_monitor_ field after transitioning back to runnable so |
| // that a thread in a waiting/sleeping state has a non-null wait_monitor_ for debugging |
| // and diagnostic purposes. (If you reset this earlier, stack dumps will claim that threads |
| // are waiting on "null".) |
| MutexLock mu(self, *self->wait_mutex_); |
| DCHECK(self->wait_monitor_ != NULL); |
| self->wait_monitor_ = NULL; |
| } |
| |
| // Re-acquire the monitor lock. |
| Lock(self); |
| |
| self->wait_mutex_->AssertNotHeld(self); |
| |
| /* |
| * We remove our thread from wait set after restoring the count |
| * and owner fields so the subroutine can check that the calling |
| * thread owns the monitor. Aside from that, the order of member |
| * updates is not order sensitive as we hold the pthread mutex. |
| */ |
| owner_ = self; |
| lock_count_ = prev_lock_count; |
| locking_method_ = saved_method; |
| locking_dex_pc_ = saved_dex_pc; |
| RemoveFromWaitSet(self); |
| |
| if (was_interrupted) { |
| /* |
| * We were interrupted while waiting, or somebody interrupted an |
| * un-interruptible thread earlier and we're bailing out immediately. |
| * |
| * The doc sayeth: "The interrupted status of the current thread is |
| * cleared when this exception is thrown." |
| */ |
| { |
| MutexLock mu(self, *self->wait_mutex_); |
| self->interrupted_ = false; |
| } |
| if (interruptShouldThrow) { |
| ThrowLocation throw_location = self->GetCurrentLocationForThrow(); |
| self->ThrowNewException(throw_location, "Ljava/lang/InterruptedException;", NULL); |
| } |
| } |
| } |
| |
| void Monitor::Notify(Thread* self) { |
| DCHECK(self != NULL); |
| // Make sure that we hold the lock. |
| if (owner_ != self) { |
| ThrowIllegalMonitorStateExceptionF("object not locked by thread before notify()"); |
| return; |
| } |
| monitor_lock_.AssertHeld(self); |
| NotifyWithLock(self); |
| } |
| |
| void Monitor::NotifyWithLock(Thread* self) { |
| // Signal the first waiting thread in the wait set. |
| while (wait_set_ != NULL) { |
| Thread* thread = wait_set_; |
| wait_set_ = thread->wait_next_; |
| thread->wait_next_ = NULL; |
| |
| // Check to see if the thread is still waiting. |
| MutexLock mu(self, *thread->wait_mutex_); |
| if (thread->wait_monitor_ != NULL) { |
| thread->wait_cond_->Signal(self); |
| return; |
| } |
| } |
| } |
| |
| void Monitor::NotifyAll(Thread* self) { |
| DCHECK(self != NULL); |
| // Make sure that we hold the lock. |
| if (owner_ != self) { |
| ThrowIllegalMonitorStateExceptionF("object not locked by thread before notifyAll()"); |
| return; |
| } |
| monitor_lock_.AssertHeld(self); |
| NotifyAllWithLock(); |
| } |
| |
| void Monitor::NotifyAllWithLock() { |
| // Signal all threads in the wait set. |
| while (wait_set_ != NULL) { |
| Thread* thread = wait_set_; |
| wait_set_ = thread->wait_next_; |
| thread->wait_next_ = NULL; |
| thread->Notify(); |
| } |
| } |
| |
| /* |
| * Changes the shape of a monitor from thin to fat, preserving the |
| * internal lock state. The calling thread must own the lock. |
| */ |
| void Monitor::Inflate(Thread* self, mirror::Object* obj) { |
| DCHECK(self != NULL); |
| DCHECK(obj != NULL); |
| DCHECK_EQ(LW_SHAPE(*obj->GetRawLockWordAddress()), LW_SHAPE_THIN); |
| DCHECK_EQ(LW_LOCK_OWNER(*obj->GetRawLockWordAddress()), static_cast<int32_t>(self->GetThinLockId())); |
| |
| // Allocate and acquire a new monitor. |
| Monitor* m = new Monitor(self, obj); |
| VLOG(monitor) << "monitor: thread " << self->GetThinLockId() |
| << " created monitor " << m << " for object " << obj; |
| Runtime::Current()->GetMonitorList()->Add(m); |
| } |
| |
| void Monitor::MonitorEnter(Thread* self, mirror::Object* obj) { |
| volatile int32_t* thinp = obj->GetRawLockWordAddress(); |
| uint32_t sleepDelayNs; |
| uint32_t minSleepDelayNs = 1000000; /* 1 millisecond */ |
| uint32_t maxSleepDelayNs = 1000000000; /* 1 second */ |
| uint32_t thin, newThin; |
| |
| DCHECK(self != NULL); |
| DCHECK(obj != NULL); |
| uint32_t threadId = self->GetThinLockId(); |
| retry: |
| thin = *thinp; |
| if (LW_SHAPE(thin) == LW_SHAPE_THIN) { |
| /* |
| * The lock is a thin lock. The owner field is used to |
| * determine the acquire method, ordered by cost. |
| */ |
| if (LW_LOCK_OWNER(thin) == threadId) { |
| /* |
| * The calling thread owns the lock. Increment the |
| * value of the recursion count field. |
| */ |
| *thinp += 1 << LW_LOCK_COUNT_SHIFT; |
| if (LW_LOCK_COUNT(*thinp) == LW_LOCK_COUNT_MASK) { |
| /* |
| * The reacquisition limit has been reached. Inflate |
| * the lock so the next acquire will not overflow the |
| * recursion count field. |
| */ |
| Inflate(self, obj); |
| } |
| } else if (LW_LOCK_OWNER(thin) == 0) { |
| // The lock is unowned. Install the thread id of the calling thread into the owner field. |
| // This is the common case: compiled code will have tried this before calling back into |
| // the runtime. |
| newThin = thin | (threadId << LW_LOCK_OWNER_SHIFT); |
| if (android_atomic_acquire_cas(thin, newThin, thinp) != 0) { |
| // The acquire failed. Try again. |
| goto retry; |
| } |
| } else { |
| VLOG(monitor) << StringPrintf("monitor: thread %d spin on lock %p (a %s) owned by %d", |
| threadId, thinp, PrettyTypeOf(obj).c_str(), LW_LOCK_OWNER(thin)); |
| // The lock is owned by another thread. Notify the runtime that we are about to wait. |
| self->monitor_enter_object_ = obj; |
| self->TransitionFromRunnableToSuspended(kBlocked); |
| // Spin until the thin lock is released or inflated. |
| sleepDelayNs = 0; |
| for (;;) { |
| thin = *thinp; |
| // Check the shape of the lock word. Another thread |
| // may have inflated the lock while we were waiting. |
| if (LW_SHAPE(thin) == LW_SHAPE_THIN) { |
| if (LW_LOCK_OWNER(thin) == 0) { |
| // The lock has been released. Install the thread id of the |
| // calling thread into the owner field. |
| newThin = thin | (threadId << LW_LOCK_OWNER_SHIFT); |
| if (android_atomic_acquire_cas(thin, newThin, thinp) == 0) { |
| // The acquire succeed. Break out of the loop and proceed to inflate the lock. |
| break; |
| } |
| } else { |
| // The lock has not been released. Yield so the owning thread can run. |
| if (sleepDelayNs == 0) { |
| sched_yield(); |
| sleepDelayNs = minSleepDelayNs; |
| } else { |
| NanoSleep(sleepDelayNs); |
| // Prepare the next delay value. Wrap to avoid once a second polls for eternity. |
| if (sleepDelayNs < maxSleepDelayNs / 2) { |
| sleepDelayNs *= 2; |
| } else { |
| sleepDelayNs = minSleepDelayNs; |
| } |
| } |
| } |
| } else { |
| // The thin lock was inflated by another thread. Let the runtime know we are no longer |
| // waiting and try again. |
| VLOG(monitor) << StringPrintf("monitor: thread %d found lock %p surprise-fattened by another thread", threadId, thinp); |
| self->monitor_enter_object_ = NULL; |
| self->TransitionFromSuspendedToRunnable(); |
| goto retry; |
| } |
| } |
| VLOG(monitor) << StringPrintf("monitor: thread %d spin on lock %p done", threadId, thinp); |
| // We have acquired the thin lock. Let the runtime know that we are no longer waiting. |
| self->monitor_enter_object_ = NULL; |
| self->TransitionFromSuspendedToRunnable(); |
| // Fatten the lock. |
| Inflate(self, obj); |
| VLOG(monitor) << StringPrintf("monitor: thread %d fattened lock %p", threadId, thinp); |
| } |
| } else { |
| // The lock is a fat lock. |
| VLOG(monitor) << StringPrintf("monitor: thread %d locking fat lock %p (%p) %p on a %s", |
| threadId, thinp, LW_MONITOR(*thinp), |
| reinterpret_cast<void*>(*thinp), PrettyTypeOf(obj).c_str()); |
| DCHECK(LW_MONITOR(*thinp) != NULL); |
| LW_MONITOR(*thinp)->Lock(self); |
| } |
| } |
| |
| bool Monitor::MonitorExit(Thread* self, mirror::Object* obj) { |
| volatile int32_t* thinp = obj->GetRawLockWordAddress(); |
| |
| DCHECK(self != NULL); |
| //DCHECK_EQ(self->GetState(), kRunnable); |
| DCHECK(obj != NULL); |
| |
| /* |
| * Cache the lock word as its value can change while we are |
| * examining its state. |
| */ |
| uint32_t thin = *thinp; |
| if (LW_SHAPE(thin) == LW_SHAPE_THIN) { |
| /* |
| * The lock is thin. We must ensure that the lock is owned |
| * by the given thread before unlocking it. |
| */ |
| if (LW_LOCK_OWNER(thin) == self->GetThinLockId()) { |
| /* |
| * We are the lock owner. It is safe to update the lock |
| * without CAS as lock ownership guards the lock itself. |
| */ |
| if (LW_LOCK_COUNT(thin) == 0) { |
| /* |
| * The lock was not recursively acquired, the common |
| * case. Unlock by clearing all bits except for the |
| * hash state. |
| */ |
| thin &= (LW_HASH_STATE_MASK << LW_HASH_STATE_SHIFT); |
| android_atomic_release_store(thin, thinp); |
| } else { |
| /* |
| * The object was recursively acquired. Decrement the |
| * lock recursion count field. |
| */ |
| *thinp -= 1 << LW_LOCK_COUNT_SHIFT; |
| } |
| } else { |
| /* |
| * We do not own the lock. The JVM spec requires that we |
| * throw an exception in this case. |
| */ |
| FailedUnlock(obj, self, NULL, NULL); |
| return false; |
| } |
| } else { |
| /* |
| * The lock is fat. We must check to see if Unlock has |
| * raised any exceptions before continuing. |
| */ |
| DCHECK(LW_MONITOR(*thinp) != NULL); |
| if (!LW_MONITOR(*thinp)->Unlock(self, false)) { |
| // An exception has been raised. Do not fall through. |
| return false; |
| } |
| } |
| return true; |
| } |
| |
| /* |
| * Object.wait(). Also called for class init. |
| */ |
| void Monitor::Wait(Thread* self, mirror::Object *obj, int64_t ms, int32_t ns, |
| bool interruptShouldThrow, ThreadState why) { |
| volatile int32_t* thinp = obj->GetRawLockWordAddress(); |
| |
| // If the lock is still thin, we need to fatten it. |
| uint32_t thin = *thinp; |
| if (LW_SHAPE(thin) == LW_SHAPE_THIN) { |
| // Make sure that 'self' holds the lock. |
| if (LW_LOCK_OWNER(thin) != self->GetThinLockId()) { |
| ThrowIllegalMonitorStateExceptionF("object not locked by thread before wait()"); |
| return; |
| } |
| |
| /* This thread holds the lock. We need to fatten the lock |
| * so 'self' can block on it. Don't update the object lock |
| * field yet, because 'self' needs to acquire the lock before |
| * any other thread gets a chance. |
| */ |
| Inflate(self, obj); |
| VLOG(monitor) << StringPrintf("monitor: thread %d fattened lock %p by wait()", self->GetThinLockId(), thinp); |
| } |
| LW_MONITOR(*thinp)->Wait(self, ms, ns, interruptShouldThrow, why); |
| } |
| |
| void Monitor::Notify(Thread* self, mirror::Object *obj) { |
| uint32_t thin = *obj->GetRawLockWordAddress(); |
| |
| // If the lock is still thin, there aren't any waiters; |
| // waiting on an object forces lock fattening. |
| if (LW_SHAPE(thin) == LW_SHAPE_THIN) { |
| // Make sure that 'self' holds the lock. |
| if (LW_LOCK_OWNER(thin) != self->GetThinLockId()) { |
| ThrowIllegalMonitorStateExceptionF("object not locked by thread before notify()"); |
| return; |
| } |
| // no-op; there are no waiters to notify. |
| Inflate(self, obj); |
| } else { |
| // It's a fat lock. |
| LW_MONITOR(thin)->Notify(self); |
| } |
| } |
| |
| void Monitor::NotifyAll(Thread* self, mirror::Object *obj) { |
| uint32_t thin = *obj->GetRawLockWordAddress(); |
| |
| // If the lock is still thin, there aren't any waiters; |
| // waiting on an object forces lock fattening. |
| if (LW_SHAPE(thin) == LW_SHAPE_THIN) { |
| // Make sure that 'self' holds the lock. |
| if (LW_LOCK_OWNER(thin) != self->GetThinLockId()) { |
| ThrowIllegalMonitorStateExceptionF("object not locked by thread before notifyAll()"); |
| return; |
| } |
| // no-op; there are no waiters to notify. |
| Inflate(self, obj); |
| } else { |
| // It's a fat lock. |
| LW_MONITOR(thin)->NotifyAll(self); |
| } |
| } |
| |
| uint32_t Monitor::GetThinLockId(uint32_t raw_lock_word) { |
| if (LW_SHAPE(raw_lock_word) == LW_SHAPE_THIN) { |
| return LW_LOCK_OWNER(raw_lock_word); |
| } else { |
| Thread* owner = LW_MONITOR(raw_lock_word)->owner_; |
| return owner ? owner->GetThinLockId() : 0; |
| } |
| } |
| |
| void Monitor::DescribeWait(std::ostream& os, const Thread* thread) { |
| ThreadState state = thread->GetState(); |
| |
| mirror::Object* object = NULL; |
| uint32_t lock_owner = ThreadList::kInvalidId; |
| if (state == kWaiting || state == kTimedWaiting || state == kSleeping) { |
| if (state == kSleeping) { |
| os << " - sleeping on "; |
| } else { |
| os << " - waiting on "; |
| } |
| { |
| Thread* self = Thread::Current(); |
| MutexLock mu(self, *thread->wait_mutex_); |
| Monitor* monitor = thread->wait_monitor_; |
| if (monitor != NULL) { |
| object = monitor->obj_; |
| } |
| } |
| } else if (state == kBlocked) { |
| os << " - waiting to lock "; |
| object = thread->monitor_enter_object_; |
| if (object != NULL) { |
| lock_owner = object->GetThinLockId(); |
| } |
| } else { |
| // We're not waiting on anything. |
| return; |
| } |
| |
| // - waiting on <0x6008c468> (a java.lang.Class<java.lang.ref.ReferenceQueue>) |
| os << "<" << object << "> (a " << PrettyTypeOf(object) << ")"; |
| |
| // - waiting to lock <0x613f83d8> (a java.lang.Object) held by thread 5 |
| if (lock_owner != ThreadList::kInvalidId) { |
| os << " held by thread " << lock_owner; |
| } |
| |
| os << "\n"; |
| } |
| |
| mirror::Object* Monitor::GetContendedMonitor(Thread* thread) { |
| // This is used to implement JDWP's ThreadReference.CurrentContendedMonitor, and has a bizarre |
| // definition of contended that includes a monitor a thread is trying to enter... |
| mirror::Object* result = thread->monitor_enter_object_; |
| if (result != NULL) { |
| return result; |
| } |
| // ...but also a monitor that the thread is waiting on. |
| { |
| MutexLock mu(Thread::Current(), *thread->wait_mutex_); |
| Monitor* monitor = thread->wait_monitor_; |
| if (monitor != NULL) { |
| return monitor->obj_; |
| } |
| } |
| return NULL; |
| } |
| |
| void Monitor::VisitLocks(StackVisitor* stack_visitor, void (*callback)(mirror::Object*, void*), |
| void* callback_context) { |
| mirror::AbstractMethod* m = stack_visitor->GetMethod(); |
| CHECK(m != NULL); |
| |
| // Native methods are an easy special case. |
| // TODO: use the JNI implementation's table of explicit MonitorEnter calls and dump those too. |
| if (m->IsNative()) { |
| if (m->IsSynchronized()) { |
| mirror::Object* jni_this = stack_visitor->GetCurrentSirt()->GetReference(0); |
| callback(jni_this, callback_context); |
| } |
| return; |
| } |
| |
| // Proxy methods should not be synchronized. |
| if (m->IsProxyMethod()) { |
| CHECK(!m->IsSynchronized()); |
| return; |
| } |
| |
| // <clinit> is another special case. The runtime holds the class lock while calling <clinit>. |
| MethodHelper mh(m); |
| if (mh.IsClassInitializer()) { |
| callback(m->GetDeclaringClass(), callback_context); |
| // Fall through because there might be synchronization in the user code too. |
| } |
| |
| // Is there any reason to believe there's any synchronization in this method? |
| const DexFile::CodeItem* code_item = mh.GetCodeItem(); |
| CHECK(code_item != NULL) << PrettyMethod(m); |
| if (code_item->tries_size_ == 0) { |
| return; // No "tries" implies no synchronization, so no held locks to report. |
| } |
| |
| // Ask the verifier for the dex pcs of all the monitor-enter instructions corresponding to |
| // the locks held in this stack frame. |
| std::vector<uint32_t> monitor_enter_dex_pcs; |
| verifier::MethodVerifier::FindLocksAtDexPc(m, stack_visitor->GetDexPc(), monitor_enter_dex_pcs); |
| if (monitor_enter_dex_pcs.empty()) { |
| return; |
| } |
| |
| for (size_t i = 0; i < monitor_enter_dex_pcs.size(); ++i) { |
| // The verifier works in terms of the dex pcs of the monitor-enter instructions. |
| // We want the registers used by those instructions (so we can read the values out of them). |
| uint32_t dex_pc = monitor_enter_dex_pcs[i]; |
| uint16_t monitor_enter_instruction = code_item->insns_[dex_pc]; |
| |
| // Quick sanity check. |
| if ((monitor_enter_instruction & 0xff) != Instruction::MONITOR_ENTER) { |
| LOG(FATAL) << "expected monitor-enter @" << dex_pc << "; was " |
| << reinterpret_cast<void*>(monitor_enter_instruction); |
| } |
| |
| uint16_t monitor_register = ((monitor_enter_instruction >> 8) & 0xff); |
| mirror::Object* o = reinterpret_cast<mirror::Object*>(stack_visitor->GetVReg(m, monitor_register, |
| kReferenceVReg)); |
| callback(o, callback_context); |
| } |
| } |
| |
| void Monitor::TranslateLocation(const mirror::AbstractMethod* method, uint32_t dex_pc, |
| const char*& source_file, uint32_t& line_number) const { |
| // If method is null, location is unknown |
| if (method == NULL) { |
| source_file = ""; |
| line_number = 0; |
| return; |
| } |
| MethodHelper mh(method); |
| source_file = mh.GetDeclaringClassSourceFile(); |
| if (source_file == NULL) { |
| source_file = ""; |
| } |
| line_number = mh.GetLineNumFromDexPC(dex_pc); |
| } |
| |
| MonitorList::MonitorList() : monitor_list_lock_("MonitorList lock") { |
| } |
| |
| MonitorList::~MonitorList() { |
| MutexLock mu(Thread::Current(), monitor_list_lock_); |
| STLDeleteElements(&list_); |
| } |
| |
| void MonitorList::Add(Monitor* m) { |
| MutexLock mu(Thread::Current(), monitor_list_lock_); |
| list_.push_front(m); |
| } |
| |
| void MonitorList::SweepMonitorList(IsMarkedTester is_marked, void* arg) { |
| MutexLock mu(Thread::Current(), monitor_list_lock_); |
| typedef std::list<Monitor*>::iterator It; // TODO: C++0x auto |
| It it = list_.begin(); |
| while (it != list_.end()) { |
| Monitor* m = *it; |
| if (!is_marked(m->GetObject(), arg)) { |
| VLOG(monitor) << "freeing monitor " << m << " belonging to unmarked object " << m->GetObject(); |
| delete m; |
| it = list_.erase(it); |
| } else { |
| ++it; |
| } |
| } |
| } |
| |
| MonitorInfo::MonitorInfo(mirror::Object* o) : owner(NULL), entry_count(0) { |
| uint32_t lock_word = *o->GetRawLockWordAddress(); |
| if (LW_SHAPE(lock_word) == LW_SHAPE_THIN) { |
| uint32_t owner_thin_lock_id = LW_LOCK_OWNER(lock_word); |
| if (owner_thin_lock_id != 0) { |
| owner = Runtime::Current()->GetThreadList()->FindThreadByThinLockId(owner_thin_lock_id); |
| entry_count = 1 + LW_LOCK_COUNT(lock_word); |
| } |
| // Thin locks have no waiters. |
| } else { |
| CHECK_EQ(LW_SHAPE(lock_word), LW_SHAPE_FAT); |
| Monitor* monitor = LW_MONITOR(lock_word); |
| owner = monitor->owner_; |
| entry_count = 1 + monitor->lock_count_; |
| for (Thread* waiter = monitor->wait_set_; waiter != NULL; waiter = waiter->wait_next_) { |
| waiters.push_back(waiter); |
| } |
| } |
| } |
| |
| } // namespace art |
