runtime/thread_list.cc - platform/art - Git at Google

 /*
  * 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"

 #include <dirent.h>
 #include <sys/types.h>
 #include <unistd.h>

 #include "base/mutex.h"
 #include "base/timing_logger.h"
 #include "debugger.h"
 #include "thread.h"
 #include "utils.h"

 namespace art {

 ThreadList::ThreadList()
     : allocated_ids_lock_("allocated thread ids lock"),
       suspend_all_count_(0), debug_suspend_all_count_(0),
       thread_exit_cond_("thread exit condition variable", *Locks::thread_list_lock_) {
 }

 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.
   if (Contains(Thread::Current())) {
     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->tid_ == tid) {
       return true;
     }
   }
   return false;
 }

 pid_t ThreadList::GetLockOwner() {
   return Locks::thread_list_lock_->GetExclusiveOwnerTid();
 }

 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: ", false);
   }
   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(Thread* self) NO_THREAD_SAFETY_ANALYSIS {
   Runtime* runtime = Runtime::Current();
   std::ostringstream ss;
   ss << "Thread suspend timeout\n";
   runtime->DumpLockHolders(ss);
   ss << "\n";
   runtime->GetThreadList()->DumpLocked(ss);
   LOG(FATAL) << ss.str();
 }
 #endif

 size_t ThreadList::RunCheckpoint(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);
   }

   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_);
     for (const auto& thread : list_) {
       if (thread != self) {
         for (;;) {
           if (thread->RequestCheckpoint(checkpoint_function)) {
             // This thread will run it's checkpoint some time in the near future.
             count++;
             break;
           } else {
             // We are probably suspended, try to make sure that we stay suspended.
             MutexLock mu2(self, *Locks::thread_suspend_count_lock_);
             // The thread switched back to runnable.
             if (thread->GetState() == kRunnable) {
               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.
       uint64_t start = NanoTime();
       do {
         // Sleep for 100us.
         usleep(100);
       } while (!thread->IsSuspended());
       uint64_t end = NanoTime();
       // Shouldn't need to wait for longer than 1 millisecond.
       const uint64_t threshold = 1;
       if (NsToMs(end - start) > threshold) {
         LOG(INFO) << "Warning: waited longer than " << threshold
                   << " ms for thread suspend\n";
       }
     }
     // We know for sure that the thread is suspended at this point.
     thread->RunCheckpointFunction();
     {
       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;
 }

 void ThreadList::SuspendAll() {
   Thread* self = Thread::Current();

   VLOG(threads) << *self << " SuspendAll starting...";

   if (kIsDebugBuild) {
     Locks::mutator_lock_->AssertNotHeld(self);
     Locks::thread_list_lock_->AssertNotHeld(self);
     Locks::thread_suspend_count_lock_->AssertNotHeld(self);
     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 (UNLIKELY(!Locks::mutator_lock_->ExclusiveLockWithTimeout(self, 30 * 1000, 0))) {
     UnsafeLogFatalForThreadSuspendAllTimeout(self);
   }
 #else
   Locks::mutator_lock_->ExclusiveLock(self);
 #endif

   // Debug check that all threads are suspended.
   AssertThreadsAreSuspended(self, self);

   VLOG(threads) << *self << " SuspendAll complete";
 }

 void ThreadList::ResumeAll() {
   Thread* self = Thread::Current();

   VLOG(threads) << *self << " ResumeAll starting";

   // 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.
     VLOG(threads) << *self << " ResumeAll waking others";
     Thread::resume_cond_->Broadcast(self);
   }
   VLOG(threads) << *self << " ResumeAll complete";
 }

 void ThreadList::Resume(Thread* thread, bool for_debugger) {
   Thread* self = Thread::Current();
   DCHECK_NE(thread, self);
   VLOG(threads) << "Resume(" << *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)) {
       return;
     }
     thread->ModifySuspendCount(self, -1, for_debugger);
   }

   {
     VLOG(threads) << "Resume(" << *thread << ") waking others";
     MutexLock mu(self, *Locks::thread_suspend_count_lock_);
     Thread::resume_cond_->Broadcast(self);
   }

   VLOG(threads) << "Resume(" << *thread << ") complete";
 }

 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(self);
   } 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 << " SuspendAll 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->suspend_count_, 0);
   }

   VLOG(threads) << *self << " self-suspending (debugger)";

   // 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->suspend_count_ != 0) {
       Thread::resume_cond_->Wait(self);
       if (self->suspend_count_ != 0) {
         // The condition was signaled but we're still suspended. This
         // can 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).
         LOG(DEBUG) << *self << " still suspended after undo "
                    << "(suspend count=" << self->suspend_count_ << ")";
       }
     }
     CHECK_EQ(self->suspend_count_, 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->debug_suspend_count_ == 0) {
         continue;
       }
       thread->ModifySuspendCount(self, -thread->debug_suspend_count_, 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()->IsShuttingDown());
       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;
   }

   // 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_);
   self->suspend_count_ = suspend_all_count_;
   self->debug_suspend_count_ = debug_suspend_all_count_;
   if (self->suspend_count_ > 0) {
     self->AtomicSetFlag(kSuspendRequest);
   }
   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->thin_lock_id_;
   self->thin_lock_id_ = 0;
   ReleaseThreadId(self, thin_lock_id);
   while (self != NULL) {
     // 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);
     CHECK(Contains(self));
     // 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 = NULL;
     }
     Locks::thread_list_lock_->ExclusiveUnlock(self);
   }

   // 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(RootVisitor* visitor, void* arg) const {
   MutexLock mu(Thread::Current(), *Locks::thread_list_lock_);
   for (const auto& thread : list_) {
     thread->VisitRoots(visitor, arg);
   }
 }

 void ThreadList::VerifyRoots(VerifyRootVisitor* visitor, void* arg) const {
   MutexLock mu(Thread::Current(), *Locks::thread_list_lock_);
   for (const auto& thread : list_) {
     thread->VerifyRoots(visitor, arg);
   }
 }

 uint32_t ThreadList::AllocThreadId(Thread* self) {
   MutexLock mu(self, allocated_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, allocated_ids_lock_);
   --id;  // Zero is reserved to mean "invalid".
   DCHECK(allocated_ids_[id]) << id;
   allocated_ids_.reset(id);
 }

 Thread* ThreadList::FindThreadByThinLockId(uint32_t thin_lock_id) {
   MutexLock mu(Thread::Current(), *Locks::thread_list_lock_);
   for (const auto& thread : list_) {
     if (thread->GetThinLockId() == thin_lock_id) {
       return thread;
     }
   }
   return NULL;
 }

 }  // namespace art
	/*
	* 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"

	#include <dirent.h>
	#include <sys/types.h>
	#include <unistd.h>

	#include "base/mutex.h"
	#include "base/timing_logger.h"
	#include "debugger.h"
	#include "thread.h"
	#include "utils.h"

	namespace art {

	ThreadList::ThreadList()
	: allocated_ids_lock_("allocated thread ids lock"),
	suspend_all_count_(0), debug_suspend_all_count_(0),
	thread_exit_cond_("thread exit condition variable", *Locks::thread_list_lock_) {
	}

	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.
	if (Contains(Thread::Current())) {
	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->tid_ == tid) {
	return true;
	}
	}
	return false;
	}

	pid_t ThreadList::GetLockOwner() {
	return Locks::thread_list_lock_->GetExclusiveOwnerTid();
	}

	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: ", false);
	}
	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(Thread* self) NO_THREAD_SAFETY_ANALYSIS {
	Runtime* runtime = Runtime::Current();
	std::ostringstream ss;
	ss << "Thread suspend timeout\n";
	runtime->DumpLockHolders(ss);
	ss << "\n";
	runtime->GetThreadList()->DumpLocked(ss);
	LOG(FATAL) << ss.str();
	}
	#endif

	size_t ThreadList::RunCheckpoint(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);
	}

	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_);
	for (const auto& thread : list_) {
	if (thread != self) {
	for (;;) {
	if (thread->RequestCheckpoint(checkpoint_function)) {
	// This thread will run it's checkpoint some time in the near future.
	count++;
	break;
	} else {
	// We are probably suspended, try to make sure that we stay suspended.
	MutexLock mu2(self, *Locks::thread_suspend_count_lock_);
	// The thread switched back to runnable.
	if (thread->GetState() == kRunnable) {
	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.
	uint64_t start = NanoTime();
	do {
	// Sleep for 100us.
	usleep(100);
	} while (!thread->IsSuspended());
	uint64_t end = NanoTime();
	// Shouldn't need to wait for longer than 1 millisecond.
	const uint64_t threshold = 1;
	if (NsToMs(end - start) > threshold) {
	LOG(INFO) << "Warning: waited longer than " << threshold
	<< " ms for thread suspend\n";
	}
	}
	// We know for sure that the thread is suspended at this point.
	thread->RunCheckpointFunction();
	{
	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;
	}

	void ThreadList::SuspendAll() {
	Thread* self = Thread::Current();

	VLOG(threads) << *self << " SuspendAll starting...";

	if (kIsDebugBuild) {
	Locks::mutator_lock_->AssertNotHeld(self);
	Locks::thread_list_lock_->AssertNotHeld(self);
	Locks::thread_suspend_count_lock_->AssertNotHeld(self);
	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 (UNLIKELY(!Locks::mutator_lock_->ExclusiveLockWithTimeout(self, 30 * 1000, 0))) {
	UnsafeLogFatalForThreadSuspendAllTimeout(self);
	}
	#else
	Locks::mutator_lock_->ExclusiveLock(self);
	#endif

	// Debug check that all threads are suspended.
	AssertThreadsAreSuspended(self, self);

	VLOG(threads) << *self << " SuspendAll complete";
	}

	void ThreadList::ResumeAll() {
	Thread* self = Thread::Current();

	VLOG(threads) << *self << " ResumeAll starting";

	// 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.
	VLOG(threads) << *self << " ResumeAll waking others";
	Thread::resume_cond_->Broadcast(self);
	}
	VLOG(threads) << *self << " ResumeAll complete";
	}

	void ThreadList::Resume(Thread* thread, bool for_debugger) {
	Thread* self = Thread::Current();
	DCHECK_NE(thread, self);
	VLOG(threads) << "Resume(" << *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)) {
	return;
	}
	thread->ModifySuspendCount(self, -1, for_debugger);
	}

	{
	VLOG(threads) << "Resume(" << *thread << ") waking others";
	MutexLock mu(self, *Locks::thread_suspend_count_lock_);
	Thread::resume_cond_->Broadcast(self);
	}

	VLOG(threads) << "Resume(" << *thread << ") complete";
	}

	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(self);
	} 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 << " SuspendAll 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->suspend_count_, 0);
	}

	VLOG(threads) << *self << " self-suspending (debugger)";

	// 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->suspend_count_ != 0) {
	Thread::resume_cond_->Wait(self);
	if (self->suspend_count_ != 0) {
	// The condition was signaled but we're still suspended. This
	// can 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).
	LOG(DEBUG) << *self << " still suspended after undo "
	<< "(suspend count=" << self->suspend_count_ << ")";
	}
	}
	CHECK_EQ(self->suspend_count_, 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->debug_suspend_count_ == 0) {
	continue;
	}
	thread->ModifySuspendCount(self, -thread->debug_suspend_count_, 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()->IsShuttingDown());
	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;
	}

	// 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_);
	self->suspend_count_ = suspend_all_count_;
	self->debug_suspend_count_ = debug_suspend_all_count_;
	if (self->suspend_count_ > 0) {
	self->AtomicSetFlag(kSuspendRequest);
	}
	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->thin_lock_id_;
	self->thin_lock_id_ = 0;
	ReleaseThreadId(self, thin_lock_id);
	while (self != NULL) {
	// 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);
	CHECK(Contains(self));
	// 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 = NULL;
	}
	Locks::thread_list_lock_->ExclusiveUnlock(self);
	}

	// 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(RootVisitor* visitor, void* arg) const {
	MutexLock mu(Thread::Current(), *Locks::thread_list_lock_);
	for (const auto& thread : list_) {
	thread->VisitRoots(visitor, arg);
	}
	}

	void ThreadList::VerifyRoots(VerifyRootVisitor* visitor, void* arg) const {
	MutexLock mu(Thread::Current(), *Locks::thread_list_lock_);
	for (const auto& thread : list_) {
	thread->VerifyRoots(visitor, arg);
	}
	}

	uint32_t ThreadList::AllocThreadId(Thread* self) {
	MutexLock mu(self, allocated_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, allocated_ids_lock_);
	--id; // Zero is reserved to mean "invalid".
	DCHECK(allocated_ids_[id]) << id;
	allocated_ids_.reset(id);
	}

	Thread* ThreadList::FindThreadByThinLockId(uint32_t thin_lock_id) {
	MutexLock mu(Thread::Current(), *Locks::thread_list_lock_);
	for (const auto& thread : list_) {
	if (thread->GetThinLockId() == thin_lock_id) {
	return thread;
	}
	}
	return NULL;
	}

	} // namespace art