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/*
* 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.
*/
#ifndef ART_RUNTIME_BASE_MUTEX_INL_H_
#define ART_RUNTIME_BASE_MUTEX_INL_H_
#include "mutex.h"
#include "cutils/atomic-inline.h"
#include "runtime.h"
#include "thread.h"
namespace art {
#define CHECK_MUTEX_CALL(call, args) CHECK_PTHREAD_CALL(call, args, name_)
#if ART_USE_FUTEXES
#include "linux/futex.h"
#include "sys/syscall.h"
#ifndef SYS_futex
#define SYS_futex __NR_futex
#endif
static inline int futex(volatile int *uaddr, int op, int val, const struct timespec *timeout, volatile int *uaddr2, int val3) {
return syscall(SYS_futex, uaddr, op, val, timeout, uaddr2, val3);
}
#endif // ART_USE_FUTEXES
class ScopedContentionRecorder {
public:
ScopedContentionRecorder(BaseMutex* mutex, uint64_t blocked_tid, uint64_t owner_tid)
: mutex_(kLogLockContentions ? mutex : NULL),
blocked_tid_(kLogLockContentions ? blocked_tid : 0),
owner_tid_(kLogLockContentions ? owner_tid : 0),
start_nano_time_(kLogLockContentions ? NanoTime() : 0) {
}
~ScopedContentionRecorder() {
if (kLogLockContentions) {
uint64_t end_nano_time = NanoTime();
mutex_->RecordContention(blocked_tid_, owner_tid_, end_nano_time - start_nano_time_);
}
}
private:
BaseMutex* const mutex_;
const uint64_t blocked_tid_;
const uint64_t owner_tid_;
const uint64_t start_nano_time_;
};
static inline uint64_t SafeGetTid(const Thread* self) {
if (self != NULL) {
return static_cast<uint64_t>(self->GetTid());
} else {
return static_cast<uint64_t>(GetTid());
}
}
static inline void CheckUnattachedThread(LockLevel level) NO_THREAD_SAFETY_ANALYSIS {
// The check below enumerates the cases where we expect not to be able to sanity check locks
// on a thread. Lock checking is disabled to avoid deadlock when checking shutdown lock.
// TODO: tighten this check.
if (kDebugLocking) {
Runtime* runtime = Runtime::Current();
CHECK(runtime == NULL || !runtime->IsStarted() || runtime->IsShuttingDown() ||
level == kDefaultMutexLevel || level == kRuntimeShutdownLock ||
level == kThreadListLock || level == kLoggingLock || level == kAbortLock);
}
}
inline void BaseMutex::RegisterAsLocked(Thread* self) {
if (UNLIKELY(self == NULL)) {
CheckUnattachedThread(level_);
return;
}
if (kDebugLocking) {
// Check if a bad Mutex of this level or lower is held.
bool bad_mutexes_held = false;
for (int i = level_; i >= 0; --i) {
BaseMutex* held_mutex = self->GetHeldMutex(static_cast<LockLevel>(i));
if (UNLIKELY(held_mutex != NULL)) {
LOG(ERROR) << "Lock level violation: holding \"" << held_mutex->name_ << "\" "
<< "(level " << LockLevel(i) << " - " << i
<< ") while locking \"" << name_ << "\" "
<< "(level " << level_ << " - " << static_cast<int>(level_) << ")";
if (i > kAbortLock) {
// Only abort in the check below if this is more than abort level lock.
bad_mutexes_held = true;
}
}
}
CHECK(!bad_mutexes_held);
}
// Don't record monitors as they are outside the scope of analysis. They may be inspected off of
// the monitor list.
if (level_ != kMonitorLock) {
self->SetHeldMutex(level_, this);
}
}
inline void BaseMutex::RegisterAsUnlocked(Thread* self) {
if (UNLIKELY(self == NULL)) {
CheckUnattachedThread(level_);
return;
}
if (level_ != kMonitorLock) {
if (kDebugLocking && !gAborting) {
CHECK(self->GetHeldMutex(level_) == this) << "Unlocking on unacquired mutex: " << name_;
}
self->SetHeldMutex(level_, NULL);
}
}
inline void ReaderWriterMutex::SharedLock(Thread* self) {
DCHECK(self == NULL || self == Thread::Current());
#if ART_USE_FUTEXES
bool done = false;
do {
int32_t cur_state = state_;
if (LIKELY(cur_state >= 0)) {
// Add as an extra reader.
done = android_atomic_acquire_cas(cur_state, cur_state + 1, &state_) == 0;
} else {
// Owner holds it exclusively, hang up.
ScopedContentionRecorder scr(this, GetExclusiveOwnerTid(), SafeGetTid(self));
android_atomic_inc(&num_pending_readers_);
if (futex(&state_, FUTEX_WAIT, cur_state, NULL, NULL, 0) != 0) {
if (errno != EAGAIN) {
PLOG(FATAL) << "futex wait failed for " << name_;
}
}
android_atomic_dec(&num_pending_readers_);
}
} while (!done);
#else
CHECK_MUTEX_CALL(pthread_rwlock_rdlock, (&rwlock_));
#endif
RegisterAsLocked(self);
AssertSharedHeld(self);
}
inline void ReaderWriterMutex::SharedUnlock(Thread* self) {
DCHECK(self == NULL || self == Thread::Current());
AssertSharedHeld(self);
RegisterAsUnlocked(self);
#if ART_USE_FUTEXES
bool done = false;
do {
int32_t cur_state = state_;
if (LIKELY(cur_state > 0)) {
// Reduce state by 1.
done = android_atomic_release_cas(cur_state, cur_state - 1, &state_) == 0;
if (done && (cur_state - 1) == 0) { // cas may fail due to noise?
if (num_pending_writers_ > 0 || num_pending_readers_ > 0) {
// Wake any exclusive waiters as there are now no readers.
futex(&state_, FUTEX_WAKE, -1, NULL, NULL, 0);
}
}
} else {
LOG(FATAL) << "Unexpected state_:" << cur_state << " for " << name_;
}
} while (!done);
#else
CHECK_MUTEX_CALL(pthread_rwlock_unlock, (&rwlock_));
#endif
}
} // namespace art
#endif // ART_RUNTIME_BASE_MUTEX_INL_H_
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