1516 lines
57 KiB
C++
1516 lines
57 KiB
C++
/*
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* Copyright (C) 2008 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "monitor.h"
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#include <vector>
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#include "android-base/stringprintf.h"
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#include "art_method-inl.h"
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#include "base/mutex.h"
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#include "base/stl_util.h"
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#include "base/systrace.h"
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#include "base/time_utils.h"
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#include "class_linker.h"
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#include "dex_file-inl.h"
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#include "dex_instruction-inl.h"
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#include "lock_word-inl.h"
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#include "mirror/class-inl.h"
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#include "mirror/object-inl.h"
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#include "object_callbacks.h"
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#include "scoped_thread_state_change-inl.h"
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#include "stack.h"
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#include "thread.h"
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#include "thread_list.h"
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#include "verifier/method_verifier.h"
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#include "well_known_classes.h"
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namespace art {
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using android::base::StringPrintf;
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static constexpr uint64_t kLongWaitMs = 100;
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/*
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* Every Object has a monitor associated with it, but not every Object is actually locked. Even
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* the ones that are locked do not need a full-fledged monitor until a) there is actual contention
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* or b) wait() is called on the Object.
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*
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* For Android, we have implemented a scheme similar to the one described in Bacon et al.'s
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* "Thin locks: featherweight synchronization for Java" (ACM 1998). Things are even easier for us,
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* though, because we have a full 32 bits to work with.
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*
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* The two states of an Object's lock are referred to as "thin" and "fat". A lock may transition
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* from the "thin" state to the "fat" state and this transition is referred to as inflation. Once
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* a lock has been inflated it remains in the "fat" state indefinitely.
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*
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* The lock value itself is stored in mirror::Object::monitor_ and the representation is described
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* in the LockWord value type.
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*
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* Monitors provide:
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* - mutually exclusive access to resources
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* - a way for multiple threads to wait for notification
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*
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* In effect, they fill the role of both mutexes and condition variables.
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*
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* Only one thread can own the monitor at any time. There may be several threads waiting on it
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* (the wait call unlocks it). One or more waiting threads may be getting interrupted or notified
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* at any given time.
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*/
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uint32_t Monitor::lock_profiling_threshold_ = 0;
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uint32_t Monitor::stack_dump_lock_profiling_threshold_ = 0;
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void Monitor::Init(uint32_t lock_profiling_threshold,
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uint32_t stack_dump_lock_profiling_threshold) {
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lock_profiling_threshold_ = lock_profiling_threshold;
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stack_dump_lock_profiling_threshold_ = stack_dump_lock_profiling_threshold;
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}
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Monitor::Monitor(Thread* self, Thread* owner, mirror::Object* obj, int32_t hash_code)
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: monitor_lock_("a monitor lock", kMonitorLock),
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monitor_contenders_("monitor contenders", monitor_lock_),
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num_waiters_(0),
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owner_(owner),
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lock_count_(0),
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obj_(GcRoot<mirror::Object>(obj)),
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wait_set_(nullptr),
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hash_code_(hash_code),
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locking_method_(nullptr),
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locking_dex_pc_(0),
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monitor_id_(MonitorPool::ComputeMonitorId(this, self)) {
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#ifdef __LP64__
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DCHECK(false) << "Should not be reached in 64b";
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next_free_ = nullptr;
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#endif
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// We should only inflate a lock if the owner is ourselves or suspended. This avoids a race
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// with the owner unlocking the thin-lock.
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CHECK(owner == nullptr || owner == self || owner->IsSuspended());
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// The identity hash code is set for the life time of the monitor.
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}
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Monitor::Monitor(Thread* self, Thread* owner, mirror::Object* obj, int32_t hash_code,
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MonitorId id)
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: monitor_lock_("a monitor lock", kMonitorLock),
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monitor_contenders_("monitor contenders", monitor_lock_),
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num_waiters_(0),
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owner_(owner),
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lock_count_(0),
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obj_(GcRoot<mirror::Object>(obj)),
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wait_set_(nullptr),
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hash_code_(hash_code),
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locking_method_(nullptr),
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locking_dex_pc_(0),
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monitor_id_(id) {
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#ifdef __LP64__
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next_free_ = nullptr;
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#endif
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// We should only inflate a lock if the owner is ourselves or suspended. This avoids a race
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// with the owner unlocking the thin-lock.
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CHECK(owner == nullptr || owner == self || owner->IsSuspended());
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// The identity hash code is set for the life time of the monitor.
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}
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int32_t Monitor::GetHashCode() {
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while (!HasHashCode()) {
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if (hash_code_.CompareExchangeWeakRelaxed(0, mirror::Object::GenerateIdentityHashCode())) {
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break;
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}
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}
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DCHECK(HasHashCode());
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return hash_code_.LoadRelaxed();
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}
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bool Monitor::Install(Thread* self) {
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MutexLock mu(self, monitor_lock_); // Uncontended mutex acquisition as monitor isn't yet public.
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CHECK(owner_ == nullptr || owner_ == self || owner_->IsSuspended());
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// Propagate the lock state.
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LockWord lw(GetObject()->GetLockWord(false));
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switch (lw.GetState()) {
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case LockWord::kThinLocked: {
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CHECK_EQ(owner_->GetThreadId(), lw.ThinLockOwner());
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lock_count_ = lw.ThinLockCount();
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break;
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}
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case LockWord::kHashCode: {
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CHECK_EQ(hash_code_.LoadRelaxed(), static_cast<int32_t>(lw.GetHashCode()));
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break;
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}
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case LockWord::kFatLocked: {
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// The owner_ is suspended but another thread beat us to install a monitor.
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return false;
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}
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case LockWord::kUnlocked: {
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LOG(FATAL) << "Inflating unlocked lock word";
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break;
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}
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default: {
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LOG(FATAL) << "Invalid monitor state " << lw.GetState();
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return false;
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}
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}
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LockWord fat(this, lw.GCState());
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// Publish the updated lock word, which may race with other threads.
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bool success = GetObject()->CasLockWordWeakRelease(lw, fat);
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// Lock profiling.
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if (success && owner_ != nullptr && lock_profiling_threshold_ != 0) {
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// Do not abort on dex pc errors. This can easily happen when we want to dump a stack trace on
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// abort.
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locking_method_ = owner_->GetCurrentMethod(&locking_dex_pc_, false);
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}
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return success;
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}
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Monitor::~Monitor() {
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// Deflated monitors have a null object.
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}
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void Monitor::AppendToWaitSet(Thread* thread) {
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DCHECK(owner_ == Thread::Current());
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DCHECK(thread != nullptr);
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DCHECK(thread->GetWaitNext() == nullptr) << thread->GetWaitNext();
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if (wait_set_ == nullptr) {
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wait_set_ = thread;
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return;
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}
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// push_back.
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Thread* t = wait_set_;
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while (t->GetWaitNext() != nullptr) {
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t = t->GetWaitNext();
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}
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t->SetWaitNext(thread);
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}
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void Monitor::RemoveFromWaitSet(Thread *thread) {
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DCHECK(owner_ == Thread::Current());
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DCHECK(thread != nullptr);
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if (wait_set_ == nullptr) {
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return;
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}
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if (wait_set_ == thread) {
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wait_set_ = thread->GetWaitNext();
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thread->SetWaitNext(nullptr);
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return;
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}
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Thread* t = wait_set_;
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while (t->GetWaitNext() != nullptr) {
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if (t->GetWaitNext() == thread) {
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t->SetWaitNext(thread->GetWaitNext());
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thread->SetWaitNext(nullptr);
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return;
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}
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t = t->GetWaitNext();
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}
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}
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void Monitor::SetObject(mirror::Object* object) {
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obj_ = GcRoot<mirror::Object>(object);
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}
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// Note: Adapted from CurrentMethodVisitor in thread.cc. We must not resolve here.
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struct NthCallerWithDexPcVisitor FINAL : public StackVisitor {
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explicit NthCallerWithDexPcVisitor(Thread* thread, size_t frame)
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REQUIRES_SHARED(Locks::mutator_lock_)
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: StackVisitor(thread, nullptr, StackVisitor::StackWalkKind::kIncludeInlinedFrames),
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method_(nullptr),
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dex_pc_(0),
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current_frame_number_(0),
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wanted_frame_number_(frame) {}
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bool VisitFrame() OVERRIDE REQUIRES_SHARED(Locks::mutator_lock_) {
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ArtMethod* m = GetMethod();
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if (m == nullptr || m->IsRuntimeMethod()) {
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// Runtime method, upcall, or resolution issue. Skip.
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return true;
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}
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// Is this the requested frame?
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if (current_frame_number_ == wanted_frame_number_) {
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method_ = m;
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dex_pc_ = GetDexPc(false /* abort_on_error*/);
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return false;
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}
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// Look for more.
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current_frame_number_++;
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return true;
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}
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ArtMethod* method_;
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uint32_t dex_pc_;
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private:
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size_t current_frame_number_;
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const size_t wanted_frame_number_;
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};
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// This function is inlined and just helps to not have the VLOG and ATRACE check at all the
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// potential tracing points.
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void Monitor::AtraceMonitorLock(Thread* self, mirror::Object* obj, bool is_wait) {
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if (UNLIKELY(VLOG_IS_ON(systrace_lock_logging) && ATRACE_ENABLED())) {
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AtraceMonitorLockImpl(self, obj, is_wait);
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}
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}
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void Monitor::AtraceMonitorLockImpl(Thread* self, mirror::Object* obj, bool is_wait) {
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// Wait() requires a deeper call stack to be useful. Otherwise you'll see "Waiting at
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// Object.java". Assume that we'll wait a nontrivial amount, so it's OK to do a longer
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// stack walk than if !is_wait.
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NthCallerWithDexPcVisitor visitor(self, is_wait ? 1U : 0U);
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visitor.WalkStack(false);
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const char* prefix = is_wait ? "Waiting on " : "Locking ";
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const char* filename;
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int32_t line_number;
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TranslateLocation(visitor.method_, visitor.dex_pc_, &filename, &line_number);
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// It would be nice to have a stable "ID" for the object here. However, the only stable thing
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// would be the identity hashcode. But we cannot use IdentityHashcode here: For one, there are
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// times when it is unsafe to make that call (see stack dumping for an explanation). More
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// importantly, we would have to give up on thin-locking when adding systrace locks, as the
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// identity hashcode is stored in the lockword normally (so can't be used with thin-locks).
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//
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// Because of thin-locks we also cannot use the monitor id (as there is no monitor). Monitor ids
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// also do not have to be stable, as the monitor may be deflated.
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std::string tmp = StringPrintf("%s %d at %s:%d",
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prefix,
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(obj == nullptr ? -1 : static_cast<int32_t>(reinterpret_cast<uintptr_t>(obj))),
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(filename != nullptr ? filename : "null"),
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line_number);
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ATRACE_BEGIN(tmp.c_str());
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}
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void Monitor::AtraceMonitorUnlock() {
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if (UNLIKELY(VLOG_IS_ON(systrace_lock_logging))) {
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ATRACE_END();
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}
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}
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std::string Monitor::PrettyContentionInfo(const std::string& owner_name,
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pid_t owner_tid,
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ArtMethod* owners_method,
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uint32_t owners_dex_pc,
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size_t num_waiters) {
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Locks::mutator_lock_->AssertSharedHeld(Thread::Current());
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const char* owners_filename;
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int32_t owners_line_number = 0;
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if (owners_method != nullptr) {
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TranslateLocation(owners_method, owners_dex_pc, &owners_filename, &owners_line_number);
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}
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std::ostringstream oss;
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oss << "monitor contention with owner " << owner_name << " (" << owner_tid << ")";
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if (owners_method != nullptr) {
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oss << " at " << owners_method->PrettyMethod();
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oss << "(" << owners_filename << ":" << owners_line_number << ")";
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}
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oss << " waiters=" << num_waiters;
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return oss.str();
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}
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bool Monitor::TryLockLocked(Thread* self) {
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if (owner_ == nullptr) { // Unowned.
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owner_ = self;
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CHECK_EQ(lock_count_, 0);
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// When debugging, save the current monitor holder for future
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// acquisition failures to use in sampled logging.
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if (lock_profiling_threshold_ != 0) {
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locking_method_ = self->GetCurrentMethod(&locking_dex_pc_);
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}
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} else if (owner_ == self) { // Recursive.
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lock_count_++;
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} else {
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return false;
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}
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AtraceMonitorLock(self, GetObject(), false /* is_wait */);
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return true;
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}
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bool Monitor::TryLock(Thread* self) {
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MutexLock mu(self, monitor_lock_);
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return TryLockLocked(self);
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}
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void Monitor::Lock(Thread* self) {
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MutexLock mu(self, monitor_lock_);
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while (true) {
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if (TryLockLocked(self)) {
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return;
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}
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// Contended.
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const bool log_contention = (lock_profiling_threshold_ != 0);
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uint64_t wait_start_ms = log_contention ? MilliTime() : 0;
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ArtMethod* owners_method = locking_method_;
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uint32_t owners_dex_pc = locking_dex_pc_;
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// Do this before releasing the lock so that we don't get deflated.
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size_t num_waiters = num_waiters_;
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++num_waiters_;
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// If systrace logging is enabled, first look at the lock owner. Acquiring the monitor's
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// lock and then re-acquiring the mutator lock can deadlock.
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bool started_trace = false;
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if (ATRACE_ENABLED()) {
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if (owner_ != nullptr) { // Did the owner_ give the lock up?
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std::ostringstream oss;
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std::string name;
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owner_->GetThreadName(name);
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oss << PrettyContentionInfo(name,
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owner_->GetTid(),
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owners_method,
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owners_dex_pc,
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num_waiters);
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// Add info for contending thread.
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uint32_t pc;
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ArtMethod* m = self->GetCurrentMethod(&pc);
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const char* filename;
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int32_t line_number;
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TranslateLocation(m, pc, &filename, &line_number);
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oss << " blocking from "
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<< ArtMethod::PrettyMethod(m) << "(" << (filename != nullptr ? filename : "null")
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<< ":" << line_number << ")";
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ATRACE_BEGIN(oss.str().c_str());
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started_trace = true;
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}
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}
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monitor_lock_.Unlock(self); // Let go of locks in order.
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self->SetMonitorEnterObject(GetObject());
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{
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ScopedThreadSuspension tsc(self, kBlocked); // Change to blocked and give up mutator_lock_.
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uint32_t original_owner_thread_id = 0u;
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{
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// Reacquire monitor_lock_ without mutator_lock_ for Wait.
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MutexLock mu2(self, monitor_lock_);
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if (owner_ != nullptr) { // Did the owner_ give the lock up?
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original_owner_thread_id = owner_->GetThreadId();
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monitor_contenders_.Wait(self); // Still contended so wait.
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}
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}
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if (original_owner_thread_id != 0u) {
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// Woken from contention.
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if (log_contention) {
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uint64_t wait_ms = MilliTime() - wait_start_ms;
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uint32_t sample_percent;
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if (wait_ms >= lock_profiling_threshold_) {
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sample_percent = 100;
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} else {
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sample_percent = 100 * wait_ms / lock_profiling_threshold_;
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}
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if (sample_percent != 0 && (static_cast<uint32_t>(rand() % 100) < sample_percent)) {
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// Reacquire mutator_lock_ for logging.
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ScopedObjectAccess soa(self);
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bool owner_alive = false;
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pid_t original_owner_tid = 0;
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std::string original_owner_name;
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const bool should_dump_stacks = stack_dump_lock_profiling_threshold_ > 0 &&
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wait_ms > stack_dump_lock_profiling_threshold_;
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std::string owner_stack_dump;
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// Acquire thread-list lock to find thread and keep it from dying until we've got all
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// the info we need.
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{
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MutexLock mu2(Thread::Current(), *Locks::thread_list_lock_);
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// Re-find the owner in case the thread got killed.
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Thread* original_owner = Runtime::Current()->GetThreadList()->FindThreadByThreadId(
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original_owner_thread_id);
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if (original_owner != nullptr) {
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owner_alive = true;
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original_owner_tid = original_owner->GetTid();
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original_owner->GetThreadName(original_owner_name);
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if (should_dump_stacks) {
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// Very long contention. Dump stacks.
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struct CollectStackTrace : public Closure {
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void Run(art::Thread* thread) OVERRIDE
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REQUIRES_SHARED(art::Locks::mutator_lock_) {
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thread->DumpJavaStack(oss);
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}
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std::ostringstream oss;
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};
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CollectStackTrace owner_trace;
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original_owner->RequestSynchronousCheckpoint(&owner_trace);
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owner_stack_dump = owner_trace.oss.str();
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}
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}
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// This is all the data we need. Now drop the thread-list lock, it's OK for the
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// owner to go away now.
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}
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// If we found the owner (and thus have owner data), go and log now.
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if (owner_alive) {
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// Give the detailed traces for really long contention.
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if (should_dump_stacks) {
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// This must be here (and not above) because we cannot hold the thread-list lock
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// while running the checkpoint.
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std::ostringstream self_trace_oss;
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self->DumpJavaStack(self_trace_oss);
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uint32_t pc;
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ArtMethod* m = self->GetCurrentMethod(&pc);
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LOG(WARNING) << "Long "
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<< PrettyContentionInfo(original_owner_name,
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original_owner_tid,
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owners_method,
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owners_dex_pc,
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num_waiters)
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<< " in " << ArtMethod::PrettyMethod(m) << " for "
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<< PrettyDuration(MsToNs(wait_ms)) << "\n"
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<< "Current owner stack:\n" << owner_stack_dump
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<< "Contender stack:\n" << self_trace_oss.str();
|
|
} else if (wait_ms > kLongWaitMs && owners_method != nullptr) {
|
|
uint32_t pc;
|
|
ArtMethod* m = self->GetCurrentMethod(&pc);
|
|
// TODO: We should maybe check that original_owner is still a live thread.
|
|
LOG(WARNING) << "Long "
|
|
<< PrettyContentionInfo(original_owner_name,
|
|
original_owner_tid,
|
|
owners_method,
|
|
owners_dex_pc,
|
|
num_waiters)
|
|
<< " in " << ArtMethod::PrettyMethod(m) << " for "
|
|
<< PrettyDuration(MsToNs(wait_ms));
|
|
}
|
|
LogContentionEvent(self,
|
|
wait_ms,
|
|
sample_percent,
|
|
owners_method,
|
|
owners_dex_pc);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
if (started_trace) {
|
|
ATRACE_END();
|
|
}
|
|
self->SetMonitorEnterObject(nullptr);
|
|
monitor_lock_.Lock(self); // Reacquire locks in order.
|
|
--num_waiters_;
|
|
}
|
|
}
|
|
|
|
static void ThrowIllegalMonitorStateExceptionF(const char* fmt, ...)
|
|
__attribute__((format(printf, 1, 2)));
|
|
|
|
static void ThrowIllegalMonitorStateExceptionF(const char* fmt, ...)
|
|
REQUIRES_SHARED(Locks::mutator_lock_) {
|
|
va_list args;
|
|
va_start(args, fmt);
|
|
Thread* self = Thread::Current();
|
|
self->ThrowNewExceptionV("Ljava/lang/IllegalMonitorStateException;", fmt, args);
|
|
if (!Runtime::Current()->IsStarted() || VLOG_IS_ON(monitor)) {
|
|
std::ostringstream ss;
|
|
self->Dump(ss);
|
|
LOG(Runtime::Current()->IsStarted() ? ::android::base::INFO : ::android::base::ERROR)
|
|
<< self->GetException()->Dump() << "\n" << ss.str();
|
|
}
|
|
va_end(args);
|
|
}
|
|
|
|
static std::string ThreadToString(Thread* thread) {
|
|
if (thread == nullptr) {
|
|
return "nullptr";
|
|
}
|
|
std::ostringstream oss;
|
|
// TODO: alternatively, we could just return the thread's name.
|
|
oss << *thread;
|
|
return oss.str();
|
|
}
|
|
|
|
void Monitor::FailedUnlock(mirror::Object* o,
|
|
uint32_t expected_owner_thread_id,
|
|
uint32_t found_owner_thread_id,
|
|
Monitor* monitor) {
|
|
// Acquire thread list lock so threads won't disappear from under us.
|
|
std::string current_owner_string;
|
|
std::string expected_owner_string;
|
|
std::string found_owner_string;
|
|
uint32_t current_owner_thread_id = 0u;
|
|
{
|
|
MutexLock mu(Thread::Current(), *Locks::thread_list_lock_);
|
|
ThreadList* const thread_list = Runtime::Current()->GetThreadList();
|
|
Thread* expected_owner = thread_list->FindThreadByThreadId(expected_owner_thread_id);
|
|
Thread* found_owner = thread_list->FindThreadByThreadId(found_owner_thread_id);
|
|
|
|
// Re-read owner now that we hold lock.
|
|
Thread* current_owner = (monitor != nullptr) ? monitor->GetOwner() : nullptr;
|
|
if (current_owner != nullptr) {
|
|
current_owner_thread_id = current_owner->GetThreadId();
|
|
}
|
|
// Get short descriptions of the threads involved.
|
|
current_owner_string = ThreadToString(current_owner);
|
|
expected_owner_string = expected_owner != nullptr ? ThreadToString(expected_owner) : "unnamed";
|
|
found_owner_string = found_owner != nullptr ? ThreadToString(found_owner) : "unnamed";
|
|
}
|
|
|
|
if (current_owner_thread_id == 0u) {
|
|
if (found_owner_thread_id == 0u) {
|
|
ThrowIllegalMonitorStateExceptionF("unlock of unowned monitor on object of type '%s'"
|
|
" on thread '%s'",
|
|
mirror::Object::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(),
|
|
mirror::Object::PrettyTypeOf(o).c_str(),
|
|
expected_owner_string.c_str());
|
|
}
|
|
} else {
|
|
if (found_owner_thread_id == 0u) {
|
|
// 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(),
|
|
mirror::Object::PrettyTypeOf(o).c_str(),
|
|
expected_owner_string.c_str());
|
|
} else {
|
|
if (found_owner_thread_id != current_owner_thread_id) {
|
|
// 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(),
|
|
mirror::Object::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(),
|
|
mirror::Object::PrettyTypeOf(o).c_str(),
|
|
expected_owner_string.c_str());
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
bool Monitor::Unlock(Thread* self) {
|
|
DCHECK(self != nullptr);
|
|
uint32_t owner_thread_id = 0u;
|
|
{
|
|
MutexLock mu(self, monitor_lock_);
|
|
Thread* owner = owner_;
|
|
if (owner != nullptr) {
|
|
owner_thread_id = owner->GetThreadId();
|
|
}
|
|
if (owner == self) {
|
|
// We own the monitor, so nobody else can be in here.
|
|
AtraceMonitorUnlock();
|
|
if (lock_count_ == 0) {
|
|
owner_ = nullptr;
|
|
locking_method_ = nullptr;
|
|
locking_dex_pc_ = 0;
|
|
// Wake a contender.
|
|
monitor_contenders_.Signal(self);
|
|
} else {
|
|
--lock_count_;
|
|
}
|
|
return true;
|
|
}
|
|
}
|
|
// 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(GetObject(), self->GetThreadId(), owner_thread_id, this);
|
|
return false;
|
|
}
|
|
|
|
void Monitor::Wait(Thread* self, int64_t ms, int32_t ns,
|
|
bool interruptShouldThrow, ThreadState why) {
|
|
DCHECK(self != nullptr);
|
|
DCHECK(why == kTimedWaiting || why == kWaiting || why == kSleeping);
|
|
|
|
monitor_lock_.Lock(self);
|
|
|
|
// Make sure that we hold the lock.
|
|
if (owner_ != self) {
|
|
monitor_lock_.Unlock(self);
|
|
ThrowIllegalMonitorStateExceptionF("object not locked by thread before wait()");
|
|
return;
|
|
}
|
|
|
|
// 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;
|
|
}
|
|
|
|
// Enforce the timeout range.
|
|
if (ms < 0 || ns < 0 || ns > 999999) {
|
|
monitor_lock_.Unlock(self);
|
|
self->ThrowNewExceptionF("Ljava/lang/IllegalArgumentException;",
|
|
"timeout arguments out of range: ms=%" PRId64 " 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);
|
|
++num_waiters_;
|
|
int prev_lock_count = lock_count_;
|
|
lock_count_ = 0;
|
|
owner_ = nullptr;
|
|
ArtMethod* saved_method = locking_method_;
|
|
locking_method_ = nullptr;
|
|
uintptr_t saved_dex_pc = locking_dex_pc_;
|
|
locking_dex_pc_ = 0;
|
|
|
|
AtraceMonitorUnlock(); // For the implict Unlock() just above. This will only end the deepest
|
|
// nesting, but that is enough for the visualization, and corresponds to
|
|
// the single Lock() we do afterwards.
|
|
AtraceMonitorLock(self, GetObject(), true /* is_wait */);
|
|
|
|
bool was_interrupted = false;
|
|
{
|
|
// 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.
|
|
ScopedThreadSuspension sts(self, why);
|
|
|
|
// Pseudo-atomically wait on self's wait_cond_ and release the monitor lock.
|
|
MutexLock mu(self, *self->GetWaitMutex());
|
|
|
|
// 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->GetWaitMonitor() == nullptr);
|
|
self->SetWaitMonitor(this);
|
|
|
|
// Release the monitor lock.
|
|
monitor_contenders_.Signal(self);
|
|
monitor_lock_.Unlock(self);
|
|
|
|
// Handle the case where the thread was interrupted before we called wait().
|
|
if (self->IsInterrupted()) {
|
|
was_interrupted = true;
|
|
} else {
|
|
// Wait for a notification or a timeout to occur.
|
|
if (why == kWaiting) {
|
|
self->GetWaitConditionVariable()->Wait(self);
|
|
} else {
|
|
DCHECK(why == kTimedWaiting || why == kSleeping) << why;
|
|
self->GetWaitConditionVariable()->TimedWait(self, ms, ns);
|
|
}
|
|
was_interrupted = self->IsInterrupted();
|
|
}
|
|
}
|
|
|
|
{
|
|
// 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->GetWaitMutex());
|
|
DCHECK(self->GetWaitMonitor() != nullptr);
|
|
self->SetWaitMonitor(nullptr);
|
|
}
|
|
|
|
// Allocate the interrupted exception not holding the monitor lock since it may cause a GC.
|
|
// If the GC requires acquiring the monitor for enqueuing cleared references, this would
|
|
// cause a deadlock if the monitor is held.
|
|
if (was_interrupted && interruptShouldThrow) {
|
|
/*
|
|
* 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."
|
|
*/
|
|
self->SetInterrupted(false);
|
|
self->ThrowNewException("Ljava/lang/InterruptedException;", nullptr);
|
|
}
|
|
|
|
AtraceMonitorUnlock(); // End Wait().
|
|
|
|
// Re-acquire the monitor and lock.
|
|
Lock(self);
|
|
monitor_lock_.Lock(self);
|
|
self->GetWaitMutex()->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;
|
|
--num_waiters_;
|
|
RemoveFromWaitSet(self);
|
|
|
|
monitor_lock_.Unlock(self);
|
|
}
|
|
|
|
void Monitor::Notify(Thread* self) {
|
|
DCHECK(self != nullptr);
|
|
MutexLock mu(self, monitor_lock_);
|
|
// Make sure that we hold the lock.
|
|
if (owner_ != self) {
|
|
ThrowIllegalMonitorStateExceptionF("object not locked by thread before notify()");
|
|
return;
|
|
}
|
|
// Signal the first waiting thread in the wait set.
|
|
while (wait_set_ != nullptr) {
|
|
Thread* thread = wait_set_;
|
|
wait_set_ = thread->GetWaitNext();
|
|
thread->SetWaitNext(nullptr);
|
|
|
|
// Check to see if the thread is still waiting.
|
|
MutexLock wait_mu(self, *thread->GetWaitMutex());
|
|
if (thread->GetWaitMonitor() != nullptr) {
|
|
thread->GetWaitConditionVariable()->Signal(self);
|
|
return;
|
|
}
|
|
}
|
|
}
|
|
|
|
void Monitor::NotifyAll(Thread* self) {
|
|
DCHECK(self != nullptr);
|
|
MutexLock mu(self, monitor_lock_);
|
|
// Make sure that we hold the lock.
|
|
if (owner_ != self) {
|
|
ThrowIllegalMonitorStateExceptionF("object not locked by thread before notifyAll()");
|
|
return;
|
|
}
|
|
// Signal all threads in the wait set.
|
|
while (wait_set_ != nullptr) {
|
|
Thread* thread = wait_set_;
|
|
wait_set_ = thread->GetWaitNext();
|
|
thread->SetWaitNext(nullptr);
|
|
thread->Notify();
|
|
}
|
|
}
|
|
|
|
bool Monitor::Deflate(Thread* self, mirror::Object* obj) {
|
|
DCHECK(obj != nullptr);
|
|
// Don't need volatile since we only deflate with mutators suspended.
|
|
LockWord lw(obj->GetLockWord(false));
|
|
// If the lock isn't an inflated monitor, then we don't need to deflate anything.
|
|
if (lw.GetState() == LockWord::kFatLocked) {
|
|
Monitor* monitor = lw.FatLockMonitor();
|
|
DCHECK(monitor != nullptr);
|
|
MutexLock mu(self, monitor->monitor_lock_);
|
|
// Can't deflate if we have anybody waiting on the CV.
|
|
if (monitor->num_waiters_ > 0) {
|
|
return false;
|
|
}
|
|
Thread* owner = monitor->owner_;
|
|
if (owner != nullptr) {
|
|
// Can't deflate if we are locked and have a hash code.
|
|
if (monitor->HasHashCode()) {
|
|
return false;
|
|
}
|
|
// Can't deflate if our lock count is too high.
|
|
if (static_cast<uint32_t>(monitor->lock_count_) > LockWord::kThinLockMaxCount) {
|
|
return false;
|
|
}
|
|
// Deflate to a thin lock.
|
|
LockWord new_lw = LockWord::FromThinLockId(owner->GetThreadId(),
|
|
monitor->lock_count_,
|
|
lw.GCState());
|
|
// Assume no concurrent read barrier state changes as mutators are suspended.
|
|
obj->SetLockWord(new_lw, false);
|
|
VLOG(monitor) << "Deflated " << obj << " to thin lock " << owner->GetTid() << " / "
|
|
<< monitor->lock_count_;
|
|
} else if (monitor->HasHashCode()) {
|
|
LockWord new_lw = LockWord::FromHashCode(monitor->GetHashCode(), lw.GCState());
|
|
// Assume no concurrent read barrier state changes as mutators are suspended.
|
|
obj->SetLockWord(new_lw, false);
|
|
VLOG(monitor) << "Deflated " << obj << " to hash monitor " << monitor->GetHashCode();
|
|
} else {
|
|
// No lock and no hash, just put an empty lock word inside the object.
|
|
LockWord new_lw = LockWord::FromDefault(lw.GCState());
|
|
// Assume no concurrent read barrier state changes as mutators are suspended.
|
|
obj->SetLockWord(new_lw, false);
|
|
VLOG(monitor) << "Deflated" << obj << " to empty lock word";
|
|
}
|
|
// The monitor is deflated, mark the object as null so that we know to delete it during the
|
|
// next GC.
|
|
monitor->obj_ = GcRoot<mirror::Object>(nullptr);
|
|
}
|
|
return true;
|
|
}
|
|
|
|
void Monitor::Inflate(Thread* self, Thread* owner, mirror::Object* obj, int32_t hash_code) {
|
|
DCHECK(self != nullptr);
|
|
DCHECK(obj != nullptr);
|
|
// Allocate and acquire a new monitor.
|
|
Monitor* m = MonitorPool::CreateMonitor(self, owner, obj, hash_code);
|
|
DCHECK(m != nullptr);
|
|
if (m->Install(self)) {
|
|
if (owner != nullptr) {
|
|
VLOG(monitor) << "monitor: thread" << owner->GetThreadId()
|
|
<< " created monitor " << m << " for object " << obj;
|
|
} else {
|
|
VLOG(monitor) << "monitor: Inflate with hashcode " << hash_code
|
|
<< " created monitor " << m << " for object " << obj;
|
|
}
|
|
Runtime::Current()->GetMonitorList()->Add(m);
|
|
CHECK_EQ(obj->GetLockWord(true).GetState(), LockWord::kFatLocked);
|
|
} else {
|
|
MonitorPool::ReleaseMonitor(self, m);
|
|
}
|
|
}
|
|
|
|
void Monitor::InflateThinLocked(Thread* self, Handle<mirror::Object> obj, LockWord lock_word,
|
|
uint32_t hash_code) {
|
|
DCHECK_EQ(lock_word.GetState(), LockWord::kThinLocked);
|
|
uint32_t owner_thread_id = lock_word.ThinLockOwner();
|
|
if (owner_thread_id == self->GetThreadId()) {
|
|
// We own the monitor, we can easily inflate it.
|
|
Inflate(self, self, obj.Get(), hash_code);
|
|
} else {
|
|
ThreadList* thread_list = Runtime::Current()->GetThreadList();
|
|
// Suspend the owner, inflate. First change to blocked and give up mutator_lock_.
|
|
self->SetMonitorEnterObject(obj.Get());
|
|
bool timed_out;
|
|
Thread* owner;
|
|
{
|
|
ScopedThreadSuspension sts(self, kBlocked);
|
|
owner = thread_list->SuspendThreadByThreadId(owner_thread_id,
|
|
SuspendReason::kInternal,
|
|
&timed_out);
|
|
}
|
|
if (owner != nullptr) {
|
|
// We succeeded in suspending the thread, check the lock's status didn't change.
|
|
lock_word = obj->GetLockWord(true);
|
|
if (lock_word.GetState() == LockWord::kThinLocked &&
|
|
lock_word.ThinLockOwner() == owner_thread_id) {
|
|
// Go ahead and inflate the lock.
|
|
Inflate(self, owner, obj.Get(), hash_code);
|
|
}
|
|
bool resumed = thread_list->Resume(owner, SuspendReason::kInternal);
|
|
DCHECK(resumed);
|
|
}
|
|
self->SetMonitorEnterObject(nullptr);
|
|
}
|
|
}
|
|
|
|
// Fool annotalysis into thinking that the lock on obj is acquired.
|
|
static mirror::Object* FakeLock(mirror::Object* obj)
|
|
EXCLUSIVE_LOCK_FUNCTION(obj) NO_THREAD_SAFETY_ANALYSIS {
|
|
return obj;
|
|
}
|
|
|
|
// Fool annotalysis into thinking that the lock on obj is release.
|
|
static mirror::Object* FakeUnlock(mirror::Object* obj)
|
|
UNLOCK_FUNCTION(obj) NO_THREAD_SAFETY_ANALYSIS {
|
|
return obj;
|
|
}
|
|
|
|
mirror::Object* Monitor::MonitorEnter(Thread* self, mirror::Object* obj, bool trylock) {
|
|
DCHECK(self != nullptr);
|
|
DCHECK(obj != nullptr);
|
|
self->AssertThreadSuspensionIsAllowable();
|
|
obj = FakeLock(obj);
|
|
uint32_t thread_id = self->GetThreadId();
|
|
size_t contention_count = 0;
|
|
StackHandleScope<1> hs(self);
|
|
Handle<mirror::Object> h_obj(hs.NewHandle(obj));
|
|
while (true) {
|
|
// We initially read the lockword with ordinary Java/relaxed semantics. When stronger
|
|
// semantics are needed, we address it below. Since GetLockWord bottoms out to a relaxed load,
|
|
// we can fix it later, in an infrequently executed case, with a fence.
|
|
LockWord lock_word = h_obj->GetLockWord(false);
|
|
switch (lock_word.GetState()) {
|
|
case LockWord::kUnlocked: {
|
|
// No ordering required for preceding lockword read, since we retest.
|
|
LockWord thin_locked(LockWord::FromThinLockId(thread_id, 0, lock_word.GCState()));
|
|
if (h_obj->CasLockWordWeakAcquire(lock_word, thin_locked)) {
|
|
AtraceMonitorLock(self, h_obj.Get(), false /* is_wait */);
|
|
return h_obj.Get(); // Success!
|
|
}
|
|
continue; // Go again.
|
|
}
|
|
case LockWord::kThinLocked: {
|
|
uint32_t owner_thread_id = lock_word.ThinLockOwner();
|
|
if (owner_thread_id == thread_id) {
|
|
// No ordering required for initial lockword read.
|
|
// We own the lock, increase the recursion count.
|
|
uint32_t new_count = lock_word.ThinLockCount() + 1;
|
|
if (LIKELY(new_count <= LockWord::kThinLockMaxCount)) {
|
|
LockWord thin_locked(LockWord::FromThinLockId(thread_id,
|
|
new_count,
|
|
lock_word.GCState()));
|
|
// Only this thread pays attention to the count. Thus there is no need for stronger
|
|
// than relaxed memory ordering.
|
|
if (!kUseReadBarrier) {
|
|
h_obj->SetLockWord(thin_locked, false /* volatile */);
|
|
AtraceMonitorLock(self, h_obj.Get(), false /* is_wait */);
|
|
return h_obj.Get(); // Success!
|
|
} else {
|
|
// Use CAS to preserve the read barrier state.
|
|
if (h_obj->CasLockWordWeakRelaxed(lock_word, thin_locked)) {
|
|
AtraceMonitorLock(self, h_obj.Get(), false /* is_wait */);
|
|
return h_obj.Get(); // Success!
|
|
}
|
|
}
|
|
continue; // Go again.
|
|
} else {
|
|
// We'd overflow the recursion count, so inflate the monitor.
|
|
InflateThinLocked(self, h_obj, lock_word, 0);
|
|
}
|
|
} else {
|
|
if (trylock) {
|
|
return nullptr;
|
|
}
|
|
// Contention.
|
|
contention_count++;
|
|
Runtime* runtime = Runtime::Current();
|
|
if (contention_count <= runtime->GetMaxSpinsBeforeThinLockInflation()) {
|
|
// TODO: Consider switching the thread state to kBlocked when we are yielding.
|
|
// Use sched_yield instead of NanoSleep since NanoSleep can wait much longer than the
|
|
// parameter you pass in. This can cause thread suspension to take excessively long
|
|
// and make long pauses. See b/16307460.
|
|
// TODO: We should literally spin first, without sched_yield. Sched_yield either does
|
|
// nothing (at significant expense), or guarantees that we wait at least microseconds.
|
|
// If the owner is running, I would expect the median lock hold time to be hundreds
|
|
// of nanoseconds or less.
|
|
sched_yield();
|
|
} else {
|
|
contention_count = 0;
|
|
// No ordering required for initial lockword read. Install rereads it anyway.
|
|
InflateThinLocked(self, h_obj, lock_word, 0);
|
|
}
|
|
}
|
|
continue; // Start from the beginning.
|
|
}
|
|
case LockWord::kFatLocked: {
|
|
// We should have done an acquire read of the lockword initially, to ensure
|
|
// visibility of the monitor data structure. Use an explicit fence instead.
|
|
QuasiAtomic::ThreadFenceAcquire();
|
|
Monitor* mon = lock_word.FatLockMonitor();
|
|
if (trylock) {
|
|
return mon->TryLock(self) ? h_obj.Get() : nullptr;
|
|
} else {
|
|
mon->Lock(self);
|
|
return h_obj.Get(); // Success!
|
|
}
|
|
}
|
|
case LockWord::kHashCode:
|
|
// Inflate with the existing hashcode.
|
|
// Again no ordering required for initial lockword read, since we don't rely
|
|
// on the visibility of any prior computation.
|
|
Inflate(self, nullptr, h_obj.Get(), lock_word.GetHashCode());
|
|
continue; // Start from the beginning.
|
|
default: {
|
|
LOG(FATAL) << "Invalid monitor state " << lock_word.GetState();
|
|
UNREACHABLE();
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
bool Monitor::MonitorExit(Thread* self, mirror::Object* obj) {
|
|
DCHECK(self != nullptr);
|
|
DCHECK(obj != nullptr);
|
|
self->AssertThreadSuspensionIsAllowable();
|
|
obj = FakeUnlock(obj);
|
|
StackHandleScope<1> hs(self);
|
|
Handle<mirror::Object> h_obj(hs.NewHandle(obj));
|
|
while (true) {
|
|
LockWord lock_word = obj->GetLockWord(true);
|
|
switch (lock_word.GetState()) {
|
|
case LockWord::kHashCode:
|
|
// Fall-through.
|
|
case LockWord::kUnlocked:
|
|
FailedUnlock(h_obj.Get(), self->GetThreadId(), 0u, nullptr);
|
|
return false; // Failure.
|
|
case LockWord::kThinLocked: {
|
|
uint32_t thread_id = self->GetThreadId();
|
|
uint32_t owner_thread_id = lock_word.ThinLockOwner();
|
|
if (owner_thread_id != thread_id) {
|
|
FailedUnlock(h_obj.Get(), thread_id, owner_thread_id, nullptr);
|
|
return false; // Failure.
|
|
} else {
|
|
// We own the lock, decrease the recursion count.
|
|
LockWord new_lw = LockWord::Default();
|
|
if (lock_word.ThinLockCount() != 0) {
|
|
uint32_t new_count = lock_word.ThinLockCount() - 1;
|
|
new_lw = LockWord::FromThinLockId(thread_id, new_count, lock_word.GCState());
|
|
} else {
|
|
new_lw = LockWord::FromDefault(lock_word.GCState());
|
|
}
|
|
if (!kUseReadBarrier) {
|
|
DCHECK_EQ(new_lw.ReadBarrierState(), 0U);
|
|
// TODO: This really only needs memory_order_release, but we currently have
|
|
// no way to specify that. In fact there seem to be no legitimate uses of SetLockWord
|
|
// with a final argument of true. This slows down x86 and ARMv7, but probably not v8.
|
|
h_obj->SetLockWord(new_lw, true);
|
|
AtraceMonitorUnlock();
|
|
// Success!
|
|
return true;
|
|
} else {
|
|
// Use CAS to preserve the read barrier state.
|
|
if (h_obj->CasLockWordWeakRelease(lock_word, new_lw)) {
|
|
AtraceMonitorUnlock();
|
|
// Success!
|
|
return true;
|
|
}
|
|
}
|
|
continue; // Go again.
|
|
}
|
|
}
|
|
case LockWord::kFatLocked: {
|
|
Monitor* mon = lock_word.FatLockMonitor();
|
|
return mon->Unlock(self);
|
|
}
|
|
default: {
|
|
LOG(FATAL) << "Invalid monitor state " << lock_word.GetState();
|
|
return false;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
void Monitor::Wait(Thread* self, mirror::Object *obj, int64_t ms, int32_t ns,
|
|
bool interruptShouldThrow, ThreadState why) {
|
|
DCHECK(self != nullptr);
|
|
DCHECK(obj != nullptr);
|
|
LockWord lock_word = obj->GetLockWord(true);
|
|
while (lock_word.GetState() != LockWord::kFatLocked) {
|
|
switch (lock_word.GetState()) {
|
|
case LockWord::kHashCode:
|
|
// Fall-through.
|
|
case LockWord::kUnlocked:
|
|
ThrowIllegalMonitorStateExceptionF("object not locked by thread before wait()");
|
|
return; // Failure.
|
|
case LockWord::kThinLocked: {
|
|
uint32_t thread_id = self->GetThreadId();
|
|
uint32_t owner_thread_id = lock_word.ThinLockOwner();
|
|
if (owner_thread_id != thread_id) {
|
|
ThrowIllegalMonitorStateExceptionF("object not locked by thread before wait()");
|
|
return; // Failure.
|
|
} else {
|
|
// We own the lock, inflate to enqueue ourself on the Monitor. May fail spuriously so
|
|
// re-load.
|
|
Inflate(self, self, obj, 0);
|
|
lock_word = obj->GetLockWord(true);
|
|
}
|
|
break;
|
|
}
|
|
case LockWord::kFatLocked: // Unreachable given the loop condition above. Fall-through.
|
|
default: {
|
|
LOG(FATAL) << "Invalid monitor state " << lock_word.GetState();
|
|
return;
|
|
}
|
|
}
|
|
}
|
|
Monitor* mon = lock_word.FatLockMonitor();
|
|
mon->Wait(self, ms, ns, interruptShouldThrow, why);
|
|
}
|
|
|
|
void Monitor::DoNotify(Thread* self, mirror::Object* obj, bool notify_all) {
|
|
DCHECK(self != nullptr);
|
|
DCHECK(obj != nullptr);
|
|
LockWord lock_word = obj->GetLockWord(true);
|
|
switch (lock_word.GetState()) {
|
|
case LockWord::kHashCode:
|
|
// Fall-through.
|
|
case LockWord::kUnlocked:
|
|
ThrowIllegalMonitorStateExceptionF("object not locked by thread before notify()");
|
|
return; // Failure.
|
|
case LockWord::kThinLocked: {
|
|
uint32_t thread_id = self->GetThreadId();
|
|
uint32_t owner_thread_id = lock_word.ThinLockOwner();
|
|
if (owner_thread_id != thread_id) {
|
|
ThrowIllegalMonitorStateExceptionF("object not locked by thread before notify()");
|
|
return; // Failure.
|
|
} else {
|
|
// We own the lock but there's no Monitor and therefore no waiters.
|
|
return; // Success.
|
|
}
|
|
}
|
|
case LockWord::kFatLocked: {
|
|
Monitor* mon = lock_word.FatLockMonitor();
|
|
if (notify_all) {
|
|
mon->NotifyAll(self);
|
|
} else {
|
|
mon->Notify(self);
|
|
}
|
|
return; // Success.
|
|
}
|
|
default: {
|
|
LOG(FATAL) << "Invalid monitor state " << lock_word.GetState();
|
|
return;
|
|
}
|
|
}
|
|
}
|
|
|
|
uint32_t Monitor::GetLockOwnerThreadId(mirror::Object* obj) {
|
|
DCHECK(obj != nullptr);
|
|
LockWord lock_word = obj->GetLockWord(true);
|
|
switch (lock_word.GetState()) {
|
|
case LockWord::kHashCode:
|
|
// Fall-through.
|
|
case LockWord::kUnlocked:
|
|
return ThreadList::kInvalidThreadId;
|
|
case LockWord::kThinLocked:
|
|
return lock_word.ThinLockOwner();
|
|
case LockWord::kFatLocked: {
|
|
Monitor* mon = lock_word.FatLockMonitor();
|
|
return mon->GetOwnerThreadId();
|
|
}
|
|
default: {
|
|
LOG(FATAL) << "Unreachable";
|
|
UNREACHABLE();
|
|
}
|
|
}
|
|
}
|
|
|
|
void Monitor::DescribeWait(std::ostream& os, const Thread* thread) {
|
|
// Determine the wait message and object we're waiting or blocked upon.
|
|
mirror::Object* pretty_object = nullptr;
|
|
const char* wait_message = nullptr;
|
|
uint32_t lock_owner = ThreadList::kInvalidThreadId;
|
|
ThreadState state = thread->GetState();
|
|
if (state == kWaiting || state == kTimedWaiting || state == kSleeping) {
|
|
wait_message = (state == kSleeping) ? " - sleeping on " : " - waiting on ";
|
|
Thread* self = Thread::Current();
|
|
MutexLock mu(self, *thread->GetWaitMutex());
|
|
Monitor* monitor = thread->GetWaitMonitor();
|
|
if (monitor != nullptr) {
|
|
pretty_object = monitor->GetObject();
|
|
}
|
|
} else if (state == kBlocked) {
|
|
wait_message = " - waiting to lock ";
|
|
pretty_object = thread->GetMonitorEnterObject();
|
|
if (pretty_object != nullptr) {
|
|
if (kUseReadBarrier && Thread::Current()->GetIsGcMarking()) {
|
|
// We may call Thread::Dump() in the middle of the CC thread flip and this thread's stack
|
|
// may have not been flipped yet and "pretty_object" may be a from-space (stale) ref, in
|
|
// which case the GetLockOwnerThreadId() call below will crash. So explicitly mark/forward
|
|
// it here.
|
|
pretty_object = ReadBarrier::Mark(pretty_object);
|
|
}
|
|
lock_owner = pretty_object->GetLockOwnerThreadId();
|
|
}
|
|
}
|
|
|
|
if (wait_message != nullptr) {
|
|
if (pretty_object == nullptr) {
|
|
os << wait_message << "an unknown object";
|
|
} else {
|
|
if ((pretty_object->GetLockWord(true).GetState() == LockWord::kThinLocked) &&
|
|
Locks::mutator_lock_->IsExclusiveHeld(Thread::Current())) {
|
|
// Getting the identity hashcode here would result in lock inflation and suspension of the
|
|
// current thread, which isn't safe if this is the only runnable thread.
|
|
os << wait_message << StringPrintf("<@addr=0x%" PRIxPTR "> (a %s)",
|
|
reinterpret_cast<intptr_t>(pretty_object),
|
|
pretty_object->PrettyTypeOf().c_str());
|
|
} else {
|
|
// - waiting on <0x6008c468> (a java.lang.Class<java.lang.ref.ReferenceQueue>)
|
|
// Call PrettyTypeOf before IdentityHashCode since IdentityHashCode can cause thread
|
|
// suspension and move pretty_object.
|
|
const std::string pretty_type(pretty_object->PrettyTypeOf());
|
|
os << wait_message << StringPrintf("<0x%08x> (a %s)", pretty_object->IdentityHashCode(),
|
|
pretty_type.c_str());
|
|
}
|
|
}
|
|
// - waiting to lock <0x613f83d8> (a java.lang.Object) held by thread 5
|
|
if (lock_owner != ThreadList::kInvalidThreadId) {
|
|
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->GetMonitorEnterObject();
|
|
if (result == nullptr) {
|
|
// ...but also a monitor that the thread is waiting on.
|
|
MutexLock mu(Thread::Current(), *thread->GetWaitMutex());
|
|
Monitor* monitor = thread->GetWaitMonitor();
|
|
if (monitor != nullptr) {
|
|
result = monitor->GetObject();
|
|
}
|
|
}
|
|
return result;
|
|
}
|
|
|
|
void Monitor::VisitLocks(StackVisitor* stack_visitor, void (*callback)(mirror::Object*, void*),
|
|
void* callback_context, bool abort_on_failure) {
|
|
ArtMethod* m = stack_visitor->GetMethod();
|
|
CHECK(m != nullptr);
|
|
|
|
// 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->GetCurrentHandleScope(sizeof(void*))->GetReference(0);
|
|
callback(jni_this, callback_context);
|
|
}
|
|
return;
|
|
}
|
|
|
|
// Proxy methods should not be synchronized.
|
|
if (m->IsProxyMethod()) {
|
|
CHECK(!m->IsSynchronized());
|
|
return;
|
|
}
|
|
|
|
// Is there any reason to believe there's any synchronization in this method?
|
|
const DexFile::CodeItem* code_item = m->GetCodeItem();
|
|
CHECK(code_item != nullptr) << m->PrettyMethod();
|
|
if (code_item->tries_size_ == 0) {
|
|
return; // No "tries" implies no synchronization, so no held locks to report.
|
|
}
|
|
|
|
// Get the dex pc. If abort_on_failure is false, GetDexPc will not abort in the case it cannot
|
|
// find the dex pc, and instead return kDexNoIndex. Then bail out, as it indicates we have an
|
|
// inconsistent stack anyways.
|
|
uint32_t dex_pc = stack_visitor->GetDexPc(abort_on_failure);
|
|
if (!abort_on_failure && dex_pc == DexFile::kDexNoIndex) {
|
|
LOG(ERROR) << "Could not find dex_pc for " << m->PrettyMethod();
|
|
return;
|
|
}
|
|
|
|
// 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, dex_pc, &monitor_enter_dex_pcs);
|
|
for (uint32_t monitor_dex_pc : monitor_enter_dex_pcs) {
|
|
// 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).
|
|
const Instruction* monitor_enter_instruction =
|
|
Instruction::At(&code_item->insns_[monitor_dex_pc]);
|
|
|
|
// Quick sanity check.
|
|
CHECK_EQ(monitor_enter_instruction->Opcode(), Instruction::MONITOR_ENTER)
|
|
<< "expected monitor-enter @" << monitor_dex_pc << "; was "
|
|
<< reinterpret_cast<const void*>(monitor_enter_instruction);
|
|
|
|
uint16_t monitor_register = monitor_enter_instruction->VRegA();
|
|
uint32_t value;
|
|
bool success = stack_visitor->GetVReg(m, monitor_register, kReferenceVReg, &value);
|
|
CHECK(success) << "Failed to read v" << monitor_register << " of kind "
|
|
<< kReferenceVReg << " in method " << m->PrettyMethod();
|
|
mirror::Object* o = reinterpret_cast<mirror::Object*>(value);
|
|
callback(o, callback_context);
|
|
}
|
|
}
|
|
|
|
bool Monitor::IsValidLockWord(LockWord lock_word) {
|
|
switch (lock_word.GetState()) {
|
|
case LockWord::kUnlocked:
|
|
// Nothing to check.
|
|
return true;
|
|
case LockWord::kThinLocked:
|
|
// Basic sanity check of owner.
|
|
return lock_word.ThinLockOwner() != ThreadList::kInvalidThreadId;
|
|
case LockWord::kFatLocked: {
|
|
// Check the monitor appears in the monitor list.
|
|
Monitor* mon = lock_word.FatLockMonitor();
|
|
MonitorList* list = Runtime::Current()->GetMonitorList();
|
|
MutexLock mu(Thread::Current(), list->monitor_list_lock_);
|
|
for (Monitor* list_mon : list->list_) {
|
|
if (mon == list_mon) {
|
|
return true; // Found our monitor.
|
|
}
|
|
}
|
|
return false; // Fail - unowned monitor in an object.
|
|
}
|
|
case LockWord::kHashCode:
|
|
return true;
|
|
default:
|
|
LOG(FATAL) << "Unreachable";
|
|
UNREACHABLE();
|
|
}
|
|
}
|
|
|
|
bool Monitor::IsLocked() REQUIRES_SHARED(Locks::mutator_lock_) {
|
|
MutexLock mu(Thread::Current(), monitor_lock_);
|
|
return owner_ != nullptr;
|
|
}
|
|
|
|
void Monitor::TranslateLocation(ArtMethod* method,
|
|
uint32_t dex_pc,
|
|
const char** source_file,
|
|
int32_t* line_number) {
|
|
// If method is null, location is unknown
|
|
if (method == nullptr) {
|
|
*source_file = "";
|
|
*line_number = 0;
|
|
return;
|
|
}
|
|
*source_file = method->GetDeclaringClassSourceFile();
|
|
if (*source_file == nullptr) {
|
|
*source_file = "";
|
|
}
|
|
*line_number = method->GetLineNumFromDexPC(dex_pc);
|
|
}
|
|
|
|
uint32_t Monitor::GetOwnerThreadId() {
|
|
MutexLock mu(Thread::Current(), monitor_lock_);
|
|
Thread* owner = owner_;
|
|
if (owner != nullptr) {
|
|
return owner->GetThreadId();
|
|
} else {
|
|
return ThreadList::kInvalidThreadId;
|
|
}
|
|
}
|
|
|
|
MonitorList::MonitorList()
|
|
: allow_new_monitors_(true), monitor_list_lock_("MonitorList lock", kMonitorListLock),
|
|
monitor_add_condition_("MonitorList disallow condition", monitor_list_lock_) {
|
|
}
|
|
|
|
MonitorList::~MonitorList() {
|
|
Thread* self = Thread::Current();
|
|
MutexLock mu(self, monitor_list_lock_);
|
|
// Release all monitors to the pool.
|
|
// TODO: Is it an invariant that *all* open monitors are in the list? Then we could
|
|
// clear faster in the pool.
|
|
MonitorPool::ReleaseMonitors(self, &list_);
|
|
}
|
|
|
|
void MonitorList::DisallowNewMonitors() {
|
|
CHECK(!kUseReadBarrier);
|
|
MutexLock mu(Thread::Current(), monitor_list_lock_);
|
|
allow_new_monitors_ = false;
|
|
}
|
|
|
|
void MonitorList::AllowNewMonitors() {
|
|
CHECK(!kUseReadBarrier);
|
|
Thread* self = Thread::Current();
|
|
MutexLock mu(self, monitor_list_lock_);
|
|
allow_new_monitors_ = true;
|
|
monitor_add_condition_.Broadcast(self);
|
|
}
|
|
|
|
void MonitorList::BroadcastForNewMonitors() {
|
|
Thread* self = Thread::Current();
|
|
MutexLock mu(self, monitor_list_lock_);
|
|
monitor_add_condition_.Broadcast(self);
|
|
}
|
|
|
|
void MonitorList::Add(Monitor* m) {
|
|
Thread* self = Thread::Current();
|
|
MutexLock mu(self, monitor_list_lock_);
|
|
// CMS needs this to block for concurrent reference processing because an object allocated during
|
|
// the GC won't be marked and concurrent reference processing would incorrectly clear the JNI weak
|
|
// ref. But CC (kUseReadBarrier == true) doesn't because of the to-space invariant.
|
|
while (!kUseReadBarrier && UNLIKELY(!allow_new_monitors_)) {
|
|
// Check and run the empty checkpoint before blocking so the empty checkpoint will work in the
|
|
// presence of threads blocking for weak ref access.
|
|
self->CheckEmptyCheckpointFromWeakRefAccess(&monitor_list_lock_);
|
|
monitor_add_condition_.WaitHoldingLocks(self);
|
|
}
|
|
list_.push_front(m);
|
|
}
|
|
|
|
void MonitorList::SweepMonitorList(IsMarkedVisitor* visitor) {
|
|
Thread* self = Thread::Current();
|
|
MutexLock mu(self, monitor_list_lock_);
|
|
for (auto it = list_.begin(); it != list_.end(); ) {
|
|
Monitor* m = *it;
|
|
// Disable the read barrier in GetObject() as this is called by GC.
|
|
mirror::Object* obj = m->GetObject<kWithoutReadBarrier>();
|
|
// The object of a monitor can be null if we have deflated it.
|
|
mirror::Object* new_obj = obj != nullptr ? visitor->IsMarked(obj) : nullptr;
|
|
if (new_obj == nullptr) {
|
|
VLOG(monitor) << "freeing monitor " << m << " belonging to unmarked object "
|
|
<< obj;
|
|
MonitorPool::ReleaseMonitor(self, m);
|
|
it = list_.erase(it);
|
|
} else {
|
|
m->SetObject(new_obj);
|
|
++it;
|
|
}
|
|
}
|
|
}
|
|
|
|
size_t MonitorList::Size() {
|
|
Thread* self = Thread::Current();
|
|
MutexLock mu(self, monitor_list_lock_);
|
|
return list_.size();
|
|
}
|
|
|
|
class MonitorDeflateVisitor : public IsMarkedVisitor {
|
|
public:
|
|
MonitorDeflateVisitor() : self_(Thread::Current()), deflate_count_(0) {}
|
|
|
|
virtual mirror::Object* IsMarked(mirror::Object* object) OVERRIDE
|
|
REQUIRES_SHARED(Locks::mutator_lock_) {
|
|
if (Monitor::Deflate(self_, object)) {
|
|
DCHECK_NE(object->GetLockWord(true).GetState(), LockWord::kFatLocked);
|
|
++deflate_count_;
|
|
// If we deflated, return null so that the monitor gets removed from the array.
|
|
return nullptr;
|
|
}
|
|
return object; // Monitor was not deflated.
|
|
}
|
|
|
|
Thread* const self_;
|
|
size_t deflate_count_;
|
|
};
|
|
|
|
size_t MonitorList::DeflateMonitors() {
|
|
MonitorDeflateVisitor visitor;
|
|
Locks::mutator_lock_->AssertExclusiveHeld(visitor.self_);
|
|
SweepMonitorList(&visitor);
|
|
return visitor.deflate_count_;
|
|
}
|
|
|
|
MonitorInfo::MonitorInfo(mirror::Object* obj) : owner_(nullptr), entry_count_(0) {
|
|
DCHECK(obj != nullptr);
|
|
LockWord lock_word = obj->GetLockWord(true);
|
|
switch (lock_word.GetState()) {
|
|
case LockWord::kUnlocked:
|
|
// Fall-through.
|
|
case LockWord::kForwardingAddress:
|
|
// Fall-through.
|
|
case LockWord::kHashCode:
|
|
break;
|
|
case LockWord::kThinLocked:
|
|
owner_ = Runtime::Current()->GetThreadList()->FindThreadByThreadId(lock_word.ThinLockOwner());
|
|
entry_count_ = 1 + lock_word.ThinLockCount();
|
|
// Thin locks have no waiters.
|
|
break;
|
|
case LockWord::kFatLocked: {
|
|
Monitor* mon = lock_word.FatLockMonitor();
|
|
owner_ = mon->owner_;
|
|
entry_count_ = 1 + mon->lock_count_;
|
|
for (Thread* waiter = mon->wait_set_; waiter != nullptr; waiter = waiter->GetWaitNext()) {
|
|
waiters_.push_back(waiter);
|
|
}
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
} // namespace art
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