/*
* 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