blob: 725a7084130dcf53fd78d3fe01e72166a114fe7f [file] [log] [blame]
/*
* Copyright (C) 2011 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 "thread_list.h"
#define ATRACE_TAG ATRACE_TAG_DALVIK
#include <cutils/trace.h>
#include <dirent.h>
#include <ScopedLocalRef.h>
#include <ScopedUtfChars.h>
#include <sys/types.h>
#include <unistd.h>
#include "base/mutex.h"
#include "base/mutex-inl.h"
#include "base/timing_logger.h"
#include "debugger.h"
#include "jni_internal.h"
#include "lock_word.h"
#include "monitor.h"
#include "scoped_thread_state_change.h"
#include "thread.h"
#include "utils.h"
#include "well_known_classes.h"
namespace art {
static constexpr uint64_t kLongThreadSuspendThreshold = MsToNs(5);
ThreadList::ThreadList()
: suspend_all_count_(0), debug_suspend_all_count_(0),
thread_exit_cond_("thread exit condition variable", *Locks::thread_list_lock_) {
CHECK(Monitor::IsValidLockWord(LockWord::FromThinLockId(kMaxThreadId, 1)));
}
ThreadList::~ThreadList() {
// Detach the current thread if necessary. If we failed to start, there might not be any threads.
// We need to detach the current thread here in case there's another thread waiting to join with
// us.
bool contains = false;
{
Thread* self = Thread::Current();
MutexLock mu(self, *Locks::thread_list_lock_);
contains = Contains(self);
}
if (contains) {
Runtime::Current()->DetachCurrentThread();
}
WaitForOtherNonDaemonThreadsToExit();
// TODO: there's an unaddressed race here where a thread may attach during shutdown, see
// Thread::Init.
SuspendAllDaemonThreads();
}
bool ThreadList::Contains(Thread* thread) {
return find(list_.begin(), list_.end(), thread) != list_.end();
}
bool ThreadList::Contains(pid_t tid) {
for (const auto& thread : list_) {
if (thread->GetTid() == tid) {
return true;
}
}
return false;
}
pid_t ThreadList::GetLockOwner() {
return Locks::thread_list_lock_->GetExclusiveOwnerTid();
}
void ThreadList::DumpNativeStacks(std::ostream& os) {
MutexLock mu(Thread::Current(), *Locks::thread_list_lock_);
for (const auto& thread : list_) {
os << "DUMPING THREAD " << thread->GetTid() << "\n";
DumpNativeStack(os, thread->GetTid(), "\t");
os << "\n";
}
}
void ThreadList::DumpForSigQuit(std::ostream& os) {
{
MutexLock mu(Thread::Current(), *Locks::thread_list_lock_);
DumpLocked(os);
}
DumpUnattachedThreads(os);
}
static void DumpUnattachedThread(std::ostream& os, pid_t tid) NO_THREAD_SAFETY_ANALYSIS {
// TODO: No thread safety analysis as DumpState with a NULL thread won't access fields, should
// refactor DumpState to avoid skipping analysis.
Thread::DumpState(os, NULL, tid);
DumpKernelStack(os, tid, " kernel: ", false);
// TODO: Reenable this when the native code in system_server can handle it.
// Currently "adb shell kill -3 `pid system_server`" will cause it to exit.
if (false) {
DumpNativeStack(os, tid, " native: ");
}
os << "\n";
}
void ThreadList::DumpUnattachedThreads(std::ostream& os) {
DIR* d = opendir("/proc/self/task");
if (!d) {
return;
}
Thread* self = Thread::Current();
dirent* e;
while ((e = readdir(d)) != NULL) {
char* end;
pid_t tid = strtol(e->d_name, &end, 10);
if (!*end) {
bool contains;
{
MutexLock mu(self, *Locks::thread_list_lock_);
contains = Contains(tid);
}
if (!contains) {
DumpUnattachedThread(os, tid);
}
}
}
closedir(d);
}
void ThreadList::DumpLocked(std::ostream& os) {
os << "DALVIK THREADS (" << list_.size() << "):\n";
for (const auto& thread : list_) {
thread->Dump(os);
os << "\n";
}
}
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 != ignore1 && thread != ignore2) {
CHECK(thread->IsSuspended())
<< "\nUnsuspended thread: <<" << *thread << "\n"
<< "self: <<" << *Thread::Current();
}
}
}
#if HAVE_TIMED_RWLOCK
// Attempt to rectify locks so that we dump thread list with required locks before exiting.
static void UnsafeLogFatalForThreadSuspendAllTimeout() NO_THREAD_SAFETY_ANALYSIS __attribute__((noreturn));
static void UnsafeLogFatalForThreadSuspendAllTimeout() {
Runtime* runtime = Runtime::Current();
std::ostringstream ss;
ss << "Thread suspend timeout\n";
Locks::mutator_lock_->Dump(ss);
ss << "\n";
runtime->GetThreadList()->DumpLocked(ss);
LOG(FATAL) << ss.str();
exit(0);
}
#endif
// 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 and total_delay_us
// accumulates the total time spent sleeping for timeouts. The first sleep is just a yield,
// subsequently sleeps increase delay_us from 1ms to 500ms by doubling.
static void ThreadSuspendSleep(Thread* self, useconds_t* delay_us, useconds_t* total_delay_us) {
useconds_t new_delay_us = (*delay_us) * 2;
CHECK_GE(new_delay_us, *delay_us);
if (new_delay_us < 500000) { // Don't allow sleeping to be more than 0.5s.
*delay_us = new_delay_us;
}
if (*delay_us == 0) {
sched_yield();
// Default to 1 milliseconds (note that this gets multiplied by 2 before the first sleep).
*delay_us = 500;
} else {
usleep(*delay_us);
*total_delay_us += *delay_us;
}
}
size_t ThreadList::RunCheckpoint(Closure* checkpoint_function) {
Thread* self = Thread::Current();
Locks::mutator_lock_->AssertNotExclusiveHeld(self);
Locks::thread_list_lock_->AssertNotHeld(self);
Locks::thread_suspend_count_lock_->AssertNotHeld(self);
if (kDebugLocking) {
CHECK_NE(self->GetState(), kRunnable);
}
std::vector<Thread*> suspended_count_modified_threads;
size_t count = 0;
{
// Call a checkpoint function for each thread, threads which are suspend get their checkpoint
// manually called.
MutexLock mu(self, *Locks::thread_list_lock_);
MutexLock mu2(self, *Locks::thread_suspend_count_lock_);
for (const auto& thread : list_) {
if (thread != self) {
while (true) {
if (thread->RequestCheckpoint(checkpoint_function)) {
// This thread will run its checkpoint some time in the near future.
count++;
break;
} else {
// We are probably suspended, try to make sure that we stay suspended.
// The thread switched back to runnable.
if (thread->GetState() == kRunnable) {
// Spurious fail, try again.
continue;
}
thread->ModifySuspendCount(self, +1, false);
suspended_count_modified_threads.push_back(thread);
break;
}
}
}
}
}
// Run the checkpoint on ourself while we wait for threads to suspend.
checkpoint_function->Run(self);
// Run the checkpoint on the suspended threads.
for (const auto& thread : suspended_count_modified_threads) {
if (!thread->IsSuspended()) {
// Wait until the thread is suspended.
useconds_t total_delay_us = 0;
do {
useconds_t delay_us = 100;
ThreadSuspendSleep(self, &delay_us, &total_delay_us);
} while (!thread->IsSuspended());
// Shouldn't need to wait for longer than 1000 microseconds.
constexpr useconds_t kLongWaitThresholdUS = 1000;
if (UNLIKELY(total_delay_us > kLongWaitThresholdUS)) {
LOG(WARNING) << "Waited " << total_delay_us << " us for thread suspend!";
}
}
// We know for sure that the thread is suspended at this point.
checkpoint_function->Run(thread);
{
MutexLock mu2(self, *Locks::thread_suspend_count_lock_);
thread->ModifySuspendCount(self, -1, false);
}
}
{
// Imitate ResumeAll, threads may be waiting on Thread::resume_cond_ since we raised their
// 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);
}
// Add one for self.
return count + suspended_count_modified_threads.size() + 1;
}
// Request that a checkpoint function be run on all active (non-suspended)
// threads. Returns the number of successful requests.
size_t ThreadList::RunCheckpointOnRunnableThreads(Closure* checkpoint_function) {
Thread* self = Thread::Current();
if (kIsDebugBuild) {
Locks::mutator_lock_->AssertNotExclusiveHeld(self);
Locks::thread_list_lock_->AssertNotHeld(self);
Locks::thread_suspend_count_lock_->AssertNotHeld(self);
CHECK_NE(self->GetState(), kRunnable);
}
size_t count = 0;
{
// Call a checkpoint function for each non-suspended thread.
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->RequestCheckpoint(checkpoint_function)) {
// This thread will run its checkpoint some time in the near future.
count++;
}
}
}
}
// Return the number of threads that will run the checkpoint function.
return count;
}
void ThreadList::SuspendAll() {
Thread* self = Thread::Current();
if (self != nullptr) {
VLOG(threads) << *self << " SuspendAll starting...";
} else {
VLOG(threads) << "Thread[null] SuspendAll starting...";
}
ATRACE_BEGIN("Suspending mutator threads");
uint64_t start_time = NanoTime();
Locks::mutator_lock_->AssertNotHeld(self);
Locks::thread_list_lock_->AssertNotHeld(self);
Locks::thread_suspend_count_lock_->AssertNotHeld(self);
if (kDebugLocking && self != nullptr) {
CHECK_NE(self->GetState(), kRunnable);
}
{
MutexLock mu(self, *Locks::thread_list_lock_);
MutexLock mu2(self, *Locks::thread_suspend_count_lock_);
// Update global suspend all state for attaching threads.
++suspend_all_count_;
// Increment everybody's suspend count (except our own).
for (const auto& thread : list_) {
if (thread == self) {
continue;
}
VLOG(threads) << "requesting thread suspend: " << *thread;
thread->ModifySuspendCount(self, +1, false);
}
}
// Block on the mutator lock until all Runnable threads release their share of access.
#if HAVE_TIMED_RWLOCK
// Timeout if we wait more than 30 seconds.
if (!Locks::mutator_lock_->ExclusiveLockWithTimeout(self, 30 * 1000, 0)) {
UnsafeLogFatalForThreadSuspendAllTimeout();
}
#else
Locks::mutator_lock_->ExclusiveLock(self);
#endif
uint64_t end_time = NanoTime();
if (end_time - start_time > kLongThreadSuspendThreshold) {
LOG(WARNING) << "Suspending all threads took: " << PrettyDuration(end_time - start_time);
}
if (kDebugLocking) {
// Debug check that all threads are suspended.
AssertThreadsAreSuspended(self, self);
}
ATRACE_END();
ATRACE_BEGIN("Mutator threads suspended");
if (self != nullptr) {
VLOG(threads) << *self << " SuspendAll complete";
} else {
VLOG(threads) << "Thread[null] SuspendAll complete";
}
}
void ThreadList::ResumeAll() {
Thread* self = Thread::Current();
if (self != nullptr) {
VLOG(threads) << *self << " ResumeAll starting";
} else {
VLOG(threads) << "Thread[null] ResumeAll starting";
}
ATRACE_END();
ATRACE_BEGIN("Resuming mutator threads");
if (kDebugLocking) {
// Debug check that all threads are suspended.
AssertThreadsAreSuspended(self, self);
}
Locks::mutator_lock_->ExclusiveUnlock(self);
{
MutexLock mu(self, *Locks::thread_list_lock_);
MutexLock mu2(self, *Locks::thread_suspend_count_lock_);
// Update global suspend all state for attaching threads.
--suspend_all_count_;
// Decrement the suspend counts for all threads.
for (const auto& thread : list_) {
if (thread == self) {
continue;
}
thread->ModifySuspendCount(self, -1, false);
}
// Broadcast a notification to all suspended threads, some or all of
// which may choose to wake up. No need to wait for them.
if (self != nullptr) {
VLOG(threads) << *self << " ResumeAll waking others";
} else {
VLOG(threads) << "Thread[null] ResumeAll waking others";
}
Thread::resume_cond_->Broadcast(self);
}
ATRACE_END();
if (self != nullptr) {
VLOG(threads) << *self << " ResumeAll complete";
} else {
VLOG(threads) << "Thread[null] ResumeAll complete";
}
}
void ThreadList::Resume(Thread* thread, bool for_debugger) {
Thread* self = Thread::Current();
DCHECK_NE(thread, self);
VLOG(threads) << "Resume(" << reinterpret_cast<void*>(thread) << ") starting..."
<< (for_debugger ? " (debugger)" : "");
{
// To check Contains.
MutexLock mu(self, *Locks::thread_list_lock_);
// To check IsSuspended.
MutexLock mu2(self, *Locks::thread_suspend_count_lock_);
DCHECK(thread->IsSuspended());
if (!Contains(thread)) {
// We only expect threads within the thread-list to have been suspended otherwise we can't
// stop such threads from delete-ing themselves.
LOG(ERROR) << "Resume(" << reinterpret_cast<void*>(thread)
<< ") thread not within thread list";
return;
}
thread->ModifySuspendCount(self, -1, for_debugger);
}
{
VLOG(threads) << "Resume(" << reinterpret_cast<void*>(thread) << ") waking others";
MutexLock mu(self, *Locks::thread_suspend_count_lock_);
Thread::resume_cond_->Broadcast(self);
}
VLOG(threads) << "Resume(" << reinterpret_cast<void*>(thread) << ") complete";
}
static void ThreadSuspendByPeerWarning(Thread* self, int level, const char* message, jobject peer) {
JNIEnvExt* env = self->GetJniEnv();
ScopedLocalRef<jstring>
scoped_name_string(env, (jstring)env->GetObjectField(peer,
WellKnownClasses::java_lang_Thread_name));
ScopedUtfChars scoped_name_chars(env, scoped_name_string.get());
if (scoped_name_chars.c_str() == NULL) {
LOG(level) << message << ": " << peer;
env->ExceptionClear();
} else {
LOG(level) << message << ": " << peer << ":" << scoped_name_chars.c_str();
}
}
Thread* ThreadList::SuspendThreadByPeer(jobject peer, bool request_suspension,
bool debug_suspension, bool* timed_out) {
static const useconds_t kTimeoutUs = 30 * 1000000; // 30s.
useconds_t total_delay_us = 0;
useconds_t delay_us = 0;
bool did_suspend_request = false;
*timed_out = false;
Thread* self = Thread::Current();
VLOG(threads) << "SuspendThreadByPeer starting";
while (true) {
Thread* thread;
{
// 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 mu(self, *Locks::thread_list_lock_);
thread = Thread::FromManagedThread(soa, peer);
if (thread == nullptr) {
ThreadSuspendByPeerWarning(self, WARNING, "No such thread for suspend", peer);
return nullptr;
}
if (!Contains(thread)) {
VLOG(threads) << "SuspendThreadByPeer failed for unattached thread: "
<< reinterpret_cast<void*>(thread);
return nullptr;
}
VLOG(threads) << "SuspendThreadByPeer found thread: " << *thread;
{
MutexLock mu(self, *Locks::thread_suspend_count_lock_);
if (request_suspension) {
thread->ModifySuspendCount(self, +1, debug_suspension);
request_suspension = false;
did_suspend_request = true;
} else {
// If the caller isn't requesting suspension, a suspension should have already occurred.
CHECK_GT(thread->GetSuspendCount(), 0);
}
// 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;
return thread;
}
if (total_delay_us >= kTimeoutUs) {
ThreadSuspendByPeerWarning(self, FATAL, "Thread suspension timed out", peer);
if (did_suspend_request) {
thread->ModifySuspendCount(soa.Self(), -1, debug_suspension);
}
*timed_out = true;
return nullptr;
}
}
// Release locks and come out of runnable state.
}
VLOG(threads) << "SuspendThreadByPeer sleeping to allow thread chance to suspend";
ThreadSuspendSleep(self, &delay_us, &total_delay_us);
}
}
static void ThreadSuspendByThreadIdWarning(int level, const char* message, uint32_t thread_id) {
LOG(level) << StringPrintf("%s: %d", message, thread_id);
}
Thread* ThreadList::SuspendThreadByThreadId(uint32_t thread_id, bool debug_suspension,
bool* timed_out) {
static const useconds_t kTimeoutUs = 30 * 1000000; // 30s.
useconds_t total_delay_us = 0;
useconds_t delay_us = 0;
*timed_out = false;
Thread* suspended_thread = nullptr;
Thread* self = Thread::Current();
CHECK_NE(thread_id, kInvalidThreadId);
VLOG(threads) << "SuspendThreadByThreadId starting";
while (true) {
{
// 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 mu(self, *Locks::thread_list_lock_);
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(WARNING, "No such thread id for suspend", thread_id);
return nullptr;
}
VLOG(threads) << "SuspendThreadByThreadId found thread: " << *thread;
DCHECK(Contains(thread));
{
MutexLock mu(self, *Locks::thread_suspend_count_lock_);
if (suspended_thread == nullptr) {
thread->ModifySuspendCount(self, +1, debug_suspension);
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);
}
// 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) << "SuspendThreadByThreadId thread suspended: " << *thread;
return thread;
}
if (total_delay_us >= kTimeoutUs) {
ThreadSuspendByThreadIdWarning(WARNING, "Thread suspension timed out", thread_id);
if (suspended_thread != nullptr) {
thread->ModifySuspendCount(soa.Self(), -1, debug_suspension);
}
*timed_out = true;
return nullptr;
}
}
// Release locks and come out of runnable state.
}
VLOG(threads) << "SuspendThreadByThreadId sleeping to allow thread chance to suspend";
ThreadSuspendSleep(self, &delay_us, &total_delay_us);
}
}
Thread* ThreadList::FindThreadByThreadId(uint32_t thin_lock_id) {
Thread* self = Thread::Current();
MutexLock mu(self, *Locks::thread_list_lock_);
for (const auto& thread : list_) {
if (thread->GetThreadId() == thin_lock_id) {
CHECK(thread == self || thread->IsSuspended());
return thread;
}
}
return NULL;
}
void ThreadList::SuspendAllForDebugger() {
Thread* self = Thread::Current();
Thread* debug_thread = Dbg::GetDebugThread();
VLOG(threads) << *self << " SuspendAllForDebugger starting...";
{
MutexLock mu(self, *Locks::thread_list_lock_);
{
MutexLock mu(self, *Locks::thread_suspend_count_lock_);
// Update global suspend all state for attaching threads.
++suspend_all_count_;
++debug_suspend_all_count_;
// Increment everybody's suspend count (except our own).
for (const auto& thread : list_) {
if (thread == self || thread == debug_thread) {
continue;
}
VLOG(threads) << "requesting thread suspend: " << *thread;
thread->ModifySuspendCount(self, +1, true);
}
}
}
// Block on the mutator lock until all Runnable threads release their share of access then
// immediately unlock again.
#if HAVE_TIMED_RWLOCK
// Timeout if we wait more than 30 seconds.
if (!Locks::mutator_lock_->ExclusiveLockWithTimeout(self, 30 * 1000, 0)) {
UnsafeLogFatalForThreadSuspendAllTimeout();
} else {
Locks::mutator_lock_->ExclusiveUnlock(self);
}
#else
Locks::mutator_lock_->ExclusiveLock(self);
Locks::mutator_lock_->ExclusiveUnlock(self);
#endif
AssertThreadsAreSuspended(self, self, debug_thread);
VLOG(threads) << *self << " SuspendAllForDebugger complete";
}
void ThreadList::SuspendSelfForDebugger() {
Thread* self = Thread::Current();
// The debugger thread must not suspend itself due to debugger activity!
Thread* debug_thread = Dbg::GetDebugThread();
CHECK(debug_thread != NULL);
CHECK(self != debug_thread);
CHECK_NE(self->GetState(), kRunnable);
Locks::mutator_lock_->AssertNotHeld(self);
{
// Collisions with other suspends aren't really interesting. We want
// to ensure that we're the only one fiddling with the suspend count
// though.
MutexLock mu(self, *Locks::thread_suspend_count_lock_);
self->ModifySuspendCount(self, +1, true);
CHECK_GT(self->GetSuspendCount(), 0);
}
VLOG(threads) << *self << " self-suspending (debugger)";
// Tell JDWP we've completed invocation and are ready to suspend.
DebugInvokeReq* pReq = self->GetInvokeReq();
DCHECK(pReq != NULL);
if (pReq->invoke_needed) {
// Clear this before signaling.
pReq->Clear();
VLOG(jdwp) << "invoke complete, signaling";
MutexLock mu(self, pReq->lock);
pReq->cond.Signal(self);
}
// Tell JDWP that we've completed suspension. The JDWP thread can't
// tell us to resume before we're fully asleep because we hold the
// suspend count lock.
Dbg::ClearWaitForEventThread();
{
MutexLock mu(self, *Locks::thread_suspend_count_lock_);
while (self->GetSuspendCount() != 0) {
Thread::resume_cond_->Wait(self);
if (self->GetSuspendCount() != 0) {
// The condition was signaled but we're still suspended. This
// can happen when we suspend then resume all threads to
// update instrumentation or compute monitor info. This can
// also happen if the debugger lets go while a SIGQUIT thread
// dump event is pending (assuming SignalCatcher was resumed for
// just long enough to try to grab the thread-suspend lock).
VLOG(jdwp) << *self << " still suspended after undo "
<< "(suspend count=" << self->GetSuspendCount() << ", "
<< "debug suspend count=" << self->GetDebugSuspendCount() << ")";
}
}
CHECK_EQ(self->GetSuspendCount(), 0);
}
VLOG(threads) << *self << " self-reviving (debugger)";
}
void ThreadList::UndoDebuggerSuspensions() {
Thread* self = Thread::Current();
VLOG(threads) << *self << " UndoDebuggerSuspensions starting";
{
MutexLock mu(self, *Locks::thread_list_lock_);
MutexLock mu2(self, *Locks::thread_suspend_count_lock_);
// Update global suspend all state for attaching threads.
suspend_all_count_ -= debug_suspend_all_count_;
debug_suspend_all_count_ = 0;
// Update running threads.
for (const auto& thread : list_) {
if (thread == self || thread->GetDebugSuspendCount() == 0) {
continue;
}
thread->ModifySuspendCount(self, -thread->GetDebugSuspendCount(), true);
}
}
{
MutexLock mu(self, *Locks::thread_suspend_count_lock_);
Thread::resume_cond_->Broadcast(self);
}
VLOG(threads) << "UndoDebuggerSuspensions(" << *self << ") complete";
}
void ThreadList::WaitForOtherNonDaemonThreadsToExit() {
Thread* self = Thread::Current();
Locks::mutator_lock_->AssertNotHeld(self);
bool all_threads_are_daemons;
do {
{
// No more threads can be born after we start to shutdown.
MutexLock mu(self, *Locks::runtime_shutdown_lock_);
CHECK(Runtime::Current()->IsShuttingDownLocked());
CHECK_EQ(Runtime::Current()->NumberOfThreadsBeingBorn(), 0U);
}
all_threads_are_daemons = true;
MutexLock mu(self, *Locks::thread_list_lock_);
for (const auto& thread : list_) {
if (thread != self && !thread->IsDaemon()) {
all_threads_are_daemons = false;
break;
}
}
if (!all_threads_are_daemons) {
// Wait for another thread to exit before re-checking.
thread_exit_cond_.Wait(self);
}
} while (!all_threads_are_daemons);
}
void ThreadList::SuspendAllDaemonThreads() {
Thread* self = Thread::Current();
MutexLock mu(self, *Locks::thread_list_lock_);
{ // Tell all the daemons it's time to suspend.
MutexLock mu2(self, *Locks::thread_suspend_count_lock_);
for (const auto& thread : list_) {
// This is only run after all non-daemon threads have exited, so the remainder should all be
// daemons.
CHECK(thread->IsDaemon()) << *thread;
if (thread != self) {
thread->ModifySuspendCount(self, +1, false);
}
}
}
// Give the threads a chance to suspend, complaining if they're slow.
bool have_complained = false;
for (int i = 0; i < 10; ++i) {
usleep(200 * 1000);
bool all_suspended = true;
for (const auto& thread : list_) {
if (thread != self && thread->GetState() == kRunnable) {
if (!have_complained) {
LOG(WARNING) << "daemon thread not yet suspended: " << *thread;
have_complained = true;
}
all_suspended = false;
}
}
if (all_suspended) {
return;
}
}
LOG(ERROR) << "suspend all daemons failed";
}
void ThreadList::Register(Thread* self) {
DCHECK_EQ(self, Thread::Current());
if (VLOG_IS_ON(threads)) {
std::ostringstream oss;
self->ShortDump(oss); // We don't hold the mutator_lock_ yet and so cannot call Dump.
LOG(INFO) << "ThreadList::Register() " << *self << "\n" << oss.str();
}
// Atomically add self to the thread list and make its thread_suspend_count_ reflect ongoing
// SuspendAll requests.
MutexLock mu(self, *Locks::thread_list_lock_);
MutexLock mu2(self, *Locks::thread_suspend_count_lock_);
CHECK_GE(suspend_all_count_, debug_suspend_all_count_);
// 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 = debug_suspend_all_count_; delta > 0; delta--) {
self->ModifySuspendCount(self, +1, true);
}
for (int delta = suspend_all_count_ - debug_suspend_all_count_; delta > 0; delta--) {
self->ModifySuspendCount(self, +1, false);
}
CHECK(!Contains(self));
list_.push_back(self);
}
void ThreadList::Unregister(Thread* self) {
DCHECK_EQ(self, Thread::Current());
VLOG(threads) << "ThreadList::Unregister() " << *self;
// Any time-consuming destruction, plus anything that can call back into managed code or
// suspend and so on, must happen at this point, and not in ~Thread.
self->Destroy();
uint32_t thin_lock_id = self->GetThreadId();
while (self != nullptr) {
// Remove and delete the Thread* while holding the thread_list_lock_ and
// thread_suspend_count_lock_ so that the unregistering thread cannot be suspended.
// Note: deliberately not using MutexLock that could hold a stale self pointer.
Locks::thread_list_lock_->ExclusiveLock(self);
if (!Contains(self)) {
std::ostringstream os;
DumpNativeStack(os, GetTid(), " native: ", nullptr);
LOG(ERROR) << "Request to unregister unattached thread\n" << os.str();
self = nullptr;
} else {
// Note: we don't take the thread_suspend_count_lock_ here as to be suspending a thread other
// than yourself you need to hold the thread_list_lock_ (see Thread::ModifySuspendCount).
if (!self->IsSuspended()) {
list_.remove(self);
delete self;
self = nullptr;
}
}
Locks::thread_list_lock_->ExclusiveUnlock(self);
}
// Release the thread ID after the thread is finished and deleted to avoid cases where we can
// temporarily have multiple threads with the same thread id. When this occurs, it causes
// problems in FindThreadByThreadId / SuspendThreadByThreadId.
ReleaseThreadId(nullptr, thin_lock_id);
// Clear the TLS data, so that the underlying native thread is recognizably detached.
// (It may wish to reattach later.)
CHECK_PTHREAD_CALL(pthread_setspecific, (Thread::pthread_key_self_, NULL), "detach self");
// Signal that a thread just detached.
MutexLock mu(NULL, *Locks::thread_list_lock_);
thread_exit_cond_.Signal(NULL);
}
void ThreadList::ForEach(void (*callback)(Thread*, void*), void* context) {
for (const auto& thread : list_) {
callback(thread, context);
}
}
void ThreadList::VisitRoots(RootCallback* callback, void* arg) const {
MutexLock mu(Thread::Current(), *Locks::thread_list_lock_);
for (const auto& thread : list_) {
thread->VisitRoots(callback, arg);
}
}
class VerifyRootWrapperArg {
public:
VerifyRootWrapperArg(VerifyRootCallback* callback, void* arg) : callback_(callback), arg_(arg) {
}
VerifyRootCallback* const callback_;
void* const arg_;
};
static void VerifyRootWrapperCallback(mirror::Object** root, void* arg, uint32_t /*thread_id*/,
RootType root_type) {
VerifyRootWrapperArg* wrapperArg = reinterpret_cast<VerifyRootWrapperArg*>(arg);
wrapperArg->callback_(*root, wrapperArg->arg_, 0, NULL, root_type);
}
void ThreadList::VerifyRoots(VerifyRootCallback* callback, void* arg) const {
VerifyRootWrapperArg wrapper(callback, arg);
MutexLock mu(Thread::Current(), *Locks::thread_list_lock_);
for (const auto& thread : list_) {
thread->VisitRoots(VerifyRootWrapperCallback, &wrapper);
}
}
uint32_t ThreadList::AllocThreadId(Thread* self) {
MutexLock mu(self, *Locks::allocated_thread_ids_lock_);
for (size_t i = 0; i < allocated_ids_.size(); ++i) {
if (!allocated_ids_[i]) {
allocated_ids_.set(i);
return i + 1; // Zero is reserved to mean "invalid".
}
}
LOG(FATAL) << "Out of internal thread ids";
return 0;
}
void ThreadList::ReleaseThreadId(Thread* self, uint32_t id) {
MutexLock mu(self, *Locks::allocated_thread_ids_lock_);
--id; // Zero is reserved to mean "invalid".
DCHECK(allocated_ids_[id]) << id;
allocated_ids_.reset(id);
}
} // namespace art