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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_H_
#define ART_RUNTIME_BASE_MUTEX_H_
#include <pthread.h>
#include <stdint.h>
#include <iosfwd>
#include <string>
#include "atomic.h"
#include "base/logging.h"
#include "base/macros.h"
#include "globals.h"
#if defined(__APPLE__)
#define ART_USE_FUTEXES 0
#else
#define ART_USE_FUTEXES 1
#endif
// Currently Darwin doesn't support locks with timeouts.
#if !defined(__APPLE__)
#define HAVE_TIMED_RWLOCK 1
#else
#define HAVE_TIMED_RWLOCK 0
#endif
namespace art {
class LOCKABLE ReaderWriterMutex;
class ScopedContentionRecorder;
class Thread;
// LockLevel is used to impose a lock hierarchy [1] where acquisition of a Mutex at a higher or
// equal level to a lock a thread holds is invalid. The lock hierarchy achieves a cycle free
// partial ordering and thereby cause deadlock situations to fail checks.
//
// [1] http://www.drdobbs.com/parallel/use-lock-hierarchies-to-avoid-deadlock/204801163
enum LockLevel {
kLoggingLock = 0,
kMemMapsLock,
kSwapMutexesLock,
kUnexpectedSignalLock,
kThreadSuspendCountLock,
kAbortLock,
kJdwpSocketLock,
kReferenceQueueSoftReferencesLock,
kReferenceQueuePhantomReferencesLock,
kReferenceQueueFinalizerReferencesLock,
kReferenceQueueWeakReferencesLock,
kReferenceQueueClearedReferencesLock,
kReferenceProcessorLock,
kRosAllocGlobalLock,
kRosAllocBracketLock,
kRosAllocBulkFreeLock,
kAllocSpaceLock,
kDexFileMethodInlinerLock,
kDexFileToMethodInlinerMapLock,
kMarkSweepMarkStackLock,
kTransactionLogLock,
kInternTableLock,
kOatFileSecondaryLookupLock,
kDefaultMutexLevel,
kMarkSweepLargeObjectLock,
kPinTableLock,
kLoadLibraryLock,
kJdwpObjectRegistryLock,
kModifyLdtLock,
kAllocatedThreadIdsLock,
kMonitorPoolLock,
kClassLinkerClassesLock,
kBreakpointLock,
kMonitorLock,
kMonitorListLock,
kThreadListLock,
kBreakpointInvokeLock,
kAllocTrackerLock,
kDeoptimizationLock,
kTraceLock,
kProfilerLock,
kJdwpEventListLock,
kJdwpAttachLock,
kJdwpStartLock,
kRuntimeShutdownLock,
kHeapBitmapLock,
kMutatorLock,
kThreadListSuspendThreadLock,
kZygoteCreationLock,
kLockLevelCount // Must come last.
};
std::ostream& operator<<(std::ostream& os, const LockLevel& rhs);
const bool kDebugLocking = kIsDebugBuild;
// Record Log contention information, dumpable via SIGQUIT.
#ifdef ART_USE_FUTEXES
// To enable lock contention logging, set this to true.
const bool kLogLockContentions = false;
#else
// Keep this false as lock contention logging is supported only with
// futex.
const bool kLogLockContentions = false;
#endif
const size_t kContentionLogSize = 4;
const size_t kContentionLogDataSize = kLogLockContentions ? 1 : 0;
const size_t kAllMutexDataSize = kLogLockContentions ? 1 : 0;
// Base class for all Mutex implementations
class BaseMutex {
public:
const char* GetName() const {
return name_;
}
virtual bool IsMutex() const { return false; }
virtual bool IsReaderWriterMutex() const { return false; }
virtual void Dump(std::ostream& os) const = 0;
static void DumpAll(std::ostream& os);
protected:
friend class ConditionVariable;
BaseMutex(const char* name, LockLevel level);
virtual ~BaseMutex();
void RegisterAsLocked(Thread* self);
void RegisterAsUnlocked(Thread* self);
void CheckSafeToWait(Thread* self);
friend class ScopedContentionRecorder;
void RecordContention(uint64_t blocked_tid, uint64_t owner_tid, uint64_t nano_time_blocked);
void DumpContention(std::ostream& os) const;
const LockLevel level_; // Support for lock hierarchy.
const char* const name_;
// A log entry that records contention but makes no guarantee that either tid will be held live.
struct ContentionLogEntry {
ContentionLogEntry() : blocked_tid(0), owner_tid(0) {}
uint64_t blocked_tid;
uint64_t owner_tid;
AtomicInteger count;
};
struct ContentionLogData {
ContentionLogEntry contention_log[kContentionLogSize];
// The next entry in the contention log to be updated. Value ranges from 0 to
// kContentionLogSize - 1.
AtomicInteger cur_content_log_entry;
// Number of times the Mutex has been contended.
AtomicInteger contention_count;
// Sum of time waited by all contenders in ns.
Atomic<uint64_t> wait_time;
void AddToWaitTime(uint64_t value);
ContentionLogData() : wait_time(0) {}
};
ContentionLogData contention_log_data_[kContentionLogDataSize];
public:
bool HasEverContended() const {
if (kLogLockContentions) {
return contention_log_data_->contention_count.LoadSequentiallyConsistent() > 0;
}
return false;
}
};
// A Mutex is used to achieve mutual exclusion between threads. A Mutex can be used to gain
// exclusive access to what it guards. A Mutex can be in one of two states:
// - Free - not owned by any thread,
// - Exclusive - owned by a single thread.
//
// The effect of locking and unlocking operations on the state is:
// State | ExclusiveLock | ExclusiveUnlock
// -------------------------------------------
// Free | Exclusive | error
// Exclusive | Block* | Free
// * Mutex is not reentrant and so an attempt to ExclusiveLock on the same thread will result in
// an error. Being non-reentrant simplifies Waiting on ConditionVariables.
std::ostream& operator<<(std::ostream& os, const Mutex& mu);
class LOCKABLE Mutex : public BaseMutex {
public:
explicit Mutex(const char* name, LockLevel level = kDefaultMutexLevel, bool recursive = false);
~Mutex();
virtual bool IsMutex() const { return true; }
// Block until mutex is free then acquire exclusive access.
void ExclusiveLock(Thread* self) EXCLUSIVE_LOCK_FUNCTION();
void Lock(Thread* self) EXCLUSIVE_LOCK_FUNCTION() { ExclusiveLock(self); }
// Returns true if acquires exclusive access, false otherwise.
bool ExclusiveTryLock(Thread* self) EXCLUSIVE_TRYLOCK_FUNCTION(true);
bool TryLock(Thread* self) EXCLUSIVE_TRYLOCK_FUNCTION(true) { return ExclusiveTryLock(self); }
// Release exclusive access.
void ExclusiveUnlock(Thread* self) UNLOCK_FUNCTION();
void Unlock(Thread* self) UNLOCK_FUNCTION() { ExclusiveUnlock(self); }
// Is the current thread the exclusive holder of the Mutex.
bool IsExclusiveHeld(const Thread* self) const;
// Assert that the Mutex is exclusively held by the current thread.
void AssertExclusiveHeld(const Thread* self) {
if (kDebugLocking && (gAborting == 0)) {
CHECK(IsExclusiveHeld(self)) << *this;
}
}
void AssertHeld(const Thread* self) { AssertExclusiveHeld(self); }
// Assert that the Mutex is not held by the current thread.
void AssertNotHeldExclusive(const Thread* self) {
if (kDebugLocking && (gAborting == 0)) {
CHECK(!IsExclusiveHeld(self)) << *this;
}
}
void AssertNotHeld(const Thread* self) { AssertNotHeldExclusive(self); }
// Id associated with exclusive owner. No memory ordering semantics if called from a thread other
// than the owner.
uint64_t GetExclusiveOwnerTid() const;
// Returns how many times this Mutex has been locked, it is better to use AssertHeld/NotHeld.
unsigned int GetDepth() const {
return recursion_count_;
}
virtual void Dump(std::ostream& os) const;
private:
#if ART_USE_FUTEXES
// 0 is unheld, 1 is held.
AtomicInteger state_;
// Exclusive owner.
volatile uint64_t exclusive_owner_;
// Number of waiting contenders.
AtomicInteger num_contenders_;
#else
pthread_mutex_t mutex_;
volatile uint64_t exclusive_owner_; // Guarded by mutex_.
#endif
const bool recursive_; // Can the lock be recursively held?
unsigned int recursion_count_;
friend class ConditionVariable;
DISALLOW_COPY_AND_ASSIGN(Mutex);
};
// A ReaderWriterMutex is used to achieve mutual exclusion between threads, similar to a Mutex.
// Unlike a Mutex a ReaderWriterMutex can be used to gain exclusive (writer) or shared (reader)
// access to what it guards. A flaw in relation to a Mutex is that it cannot be used with a
// condition variable. A ReaderWriterMutex can be in one of three states:
// - Free - not owned by any thread,
// - Exclusive - owned by a single thread,
// - Shared(n) - shared amongst n threads.
//
// The effect of locking and unlocking operations on the state is:
//
// State | ExclusiveLock | ExclusiveUnlock | SharedLock | SharedUnlock
// ----------------------------------------------------------------------------
// Free | Exclusive | error | SharedLock(1) | error
// Exclusive | Block | Free | Block | error
// Shared(n) | Block | error | SharedLock(n+1)* | Shared(n-1) or Free
// * for large values of n the SharedLock may block.
std::ostream& operator<<(std::ostream& os, const ReaderWriterMutex& mu);
class LOCKABLE ReaderWriterMutex : public BaseMutex {
public:
explicit ReaderWriterMutex(const char* name, LockLevel level = kDefaultMutexLevel);
~ReaderWriterMutex();
virtual bool IsReaderWriterMutex() const { return true; }
// Block until ReaderWriterMutex is free then acquire exclusive access.
void ExclusiveLock(Thread* self) EXCLUSIVE_LOCK_FUNCTION();
void WriterLock(Thread* self) EXCLUSIVE_LOCK_FUNCTION() { ExclusiveLock(self); }
// Release exclusive access.
void ExclusiveUnlock(Thread* self) UNLOCK_FUNCTION();
void WriterUnlock(Thread* self) UNLOCK_FUNCTION() { ExclusiveUnlock(self); }
// Block until ReaderWriterMutex is free and acquire exclusive access. Returns true on success
// or false if timeout is reached.
#if HAVE_TIMED_RWLOCK
bool ExclusiveLockWithTimeout(Thread* self, int64_t ms, int32_t ns)
EXCLUSIVE_TRYLOCK_FUNCTION(true);
#endif
// Block until ReaderWriterMutex is shared or free then acquire a share on the access.
void SharedLock(Thread* self) SHARED_LOCK_FUNCTION() ALWAYS_INLINE;
void ReaderLock(Thread* self) SHARED_LOCK_FUNCTION() { SharedLock(self); }
// Try to acquire share of ReaderWriterMutex.
bool SharedTryLock(Thread* self) EXCLUSIVE_TRYLOCK_FUNCTION(true);
// Release a share of the access.
void SharedUnlock(Thread* self) UNLOCK_FUNCTION() ALWAYS_INLINE;
void ReaderUnlock(Thread* self) UNLOCK_FUNCTION() { SharedUnlock(self); }
// Is the current thread the exclusive holder of the ReaderWriterMutex.
bool IsExclusiveHeld(const Thread* self) const;
// Assert the current thread has exclusive access to the ReaderWriterMutex.
void AssertExclusiveHeld(const Thread* self) {
if (kDebugLocking && (gAborting == 0)) {
CHECK(IsExclusiveHeld(self)) << *this;
}
}
void AssertWriterHeld(const Thread* self) { AssertExclusiveHeld(self); }
// Assert the current thread doesn't have exclusive access to the ReaderWriterMutex.
void AssertNotExclusiveHeld(const Thread* self) {
if (kDebugLocking && (gAborting == 0)) {
CHECK(!IsExclusiveHeld(self)) << *this;
}
}
void AssertNotWriterHeld(const Thread* self) { AssertNotExclusiveHeld(self); }
// Is the current thread a shared holder of the ReaderWriterMutex.
bool IsSharedHeld(const Thread* self) const;
// Assert the current thread has shared access to the ReaderWriterMutex.
void AssertSharedHeld(const Thread* self) {
if (kDebugLocking && (gAborting == 0)) {
// TODO: we can only assert this well when self != NULL.
CHECK(IsSharedHeld(self) || self == NULL) << *this;
}
}
void AssertReaderHeld(const Thread* self) { AssertSharedHeld(self); }
// Assert the current thread doesn't hold this ReaderWriterMutex either in shared or exclusive
// mode.
void AssertNotHeld(const Thread* self) {
if (kDebugLocking && (gAborting == 0)) {
CHECK(!IsSharedHeld(self)) << *this;
}
}
// Id associated with exclusive owner. No memory ordering semantics if called from a thread other
// than the owner.
uint64_t GetExclusiveOwnerTid() const;
virtual void Dump(std::ostream& os) const;
private:
#if ART_USE_FUTEXES
// -1 implies held exclusive, +ve shared held by state_ many owners.
AtomicInteger state_;
// Exclusive owner. Modification guarded by this mutex.
volatile uint64_t exclusive_owner_;
// Number of contenders waiting for a reader share.
AtomicInteger num_pending_readers_;
// Number of contenders waiting to be the writer.
AtomicInteger num_pending_writers_;
#else
pthread_rwlock_t rwlock_;
volatile uint64_t exclusive_owner_; // Guarded by rwlock_.
#endif
DISALLOW_COPY_AND_ASSIGN(ReaderWriterMutex);
};
// ConditionVariables allow threads to queue and sleep. Threads may then be resumed individually
// (Signal) or all at once (Broadcast).
class ConditionVariable {
public:
explicit ConditionVariable(const char* name, Mutex& mutex);
~ConditionVariable();
void Broadcast(Thread* self);
void Signal(Thread* self);
// TODO: No thread safety analysis on Wait and TimedWait as they call mutex operations via their
// pointer copy, thereby defeating annotalysis.
void Wait(Thread* self) NO_THREAD_SAFETY_ANALYSIS;
void TimedWait(Thread* self, int64_t ms, int32_t ns) NO_THREAD_SAFETY_ANALYSIS;
// Variant of Wait that should be used with caution. Doesn't validate that no mutexes are held
// when waiting.
// TODO: remove this.
void WaitHoldingLocks(Thread* self) NO_THREAD_SAFETY_ANALYSIS;
private:
const char* const name_;
// The Mutex being used by waiters. It is an error to mix condition variables between different
// Mutexes.
Mutex& guard_;
#if ART_USE_FUTEXES
// A counter that is modified by signals and broadcasts. This ensures that when a waiter gives up
// their Mutex and another thread takes it and signals, the waiting thread observes that sequence_
// changed and doesn't enter the wait. Modified while holding guard_, but is read by futex wait
// without guard_ held.
AtomicInteger sequence_;
// Number of threads that have come into to wait, not the length of the waiters on the futex as
// waiters may have been requeued onto guard_. Guarded by guard_.
volatile int32_t num_waiters_;
#else
pthread_cond_t cond_;
#endif
DISALLOW_COPY_AND_ASSIGN(ConditionVariable);
};
// Scoped locker/unlocker for a regular Mutex that acquires mu upon construction and releases it
// upon destruction.
class SCOPED_LOCKABLE MutexLock {
public:
explicit MutexLock(Thread* self, Mutex& mu) EXCLUSIVE_LOCK_FUNCTION(mu) : self_(self), mu_(mu) {
mu_.ExclusiveLock(self_);
}
~MutexLock() UNLOCK_FUNCTION() {
mu_.ExclusiveUnlock(self_);
}
private:
Thread* const self_;
Mutex& mu_;
DISALLOW_COPY_AND_ASSIGN(MutexLock);
};
// Catch bug where variable name is omitted. "MutexLock (lock);" instead of "MutexLock mu(lock)".
#define MutexLock(x) COMPILE_ASSERT(0, mutex_lock_declaration_missing_variable_name)
// Scoped locker/unlocker for a ReaderWriterMutex that acquires read access to mu upon
// construction and releases it upon destruction.
class SCOPED_LOCKABLE ReaderMutexLock {
public:
explicit ReaderMutexLock(Thread* self, ReaderWriterMutex& mu) EXCLUSIVE_LOCK_FUNCTION(mu) :
self_(self), mu_(mu) {
mu_.SharedLock(self_);
}
~ReaderMutexLock() UNLOCK_FUNCTION() {
mu_.SharedUnlock(self_);
}
private:
Thread* const self_;
ReaderWriterMutex& mu_;
DISALLOW_COPY_AND_ASSIGN(ReaderMutexLock);
};
// Catch bug where variable name is omitted. "ReaderMutexLock (lock);" instead of
// "ReaderMutexLock mu(lock)".
#define ReaderMutexLock(x) COMPILE_ASSERT(0, reader_mutex_lock_declaration_missing_variable_name)
// Scoped locker/unlocker for a ReaderWriterMutex that acquires write access to mu upon
// construction and releases it upon destruction.
class SCOPED_LOCKABLE WriterMutexLock {
public:
explicit WriterMutexLock(Thread* self, ReaderWriterMutex& mu) EXCLUSIVE_LOCK_FUNCTION(mu) :
self_(self), mu_(mu) {
mu_.ExclusiveLock(self_);
}
~WriterMutexLock() UNLOCK_FUNCTION() {
mu_.ExclusiveUnlock(self_);
}
private:
Thread* const self_;
ReaderWriterMutex& mu_;
DISALLOW_COPY_AND_ASSIGN(WriterMutexLock);
};
// Catch bug where variable name is omitted. "WriterMutexLock (lock);" instead of
// "WriterMutexLock mu(lock)".
#define WriterMutexLock(x) COMPILE_ASSERT(0, writer_mutex_lock_declaration_missing_variable_name)
// Global mutexes corresponding to the levels above.
class Locks {
public:
static void Init();
// There's a potential race for two threads to try to suspend each other and for both of them
// to succeed and get blocked becoming runnable. This lock ensures that only one thread is
// requesting suspension of another at any time. As the the thread list suspend thread logic
// transitions to runnable, if the current thread were tried to be suspended then this thread
// would block holding this lock until it could safely request thread suspension of the other
// thread without that thread having a suspension request against this thread. This avoids a
// potential deadlock cycle.
static Mutex* thread_list_suspend_thread_lock_;
// The mutator_lock_ is used to allow mutators to execute in a shared (reader) mode or to block
// mutators by having an exclusive (writer) owner. In normal execution each mutator thread holds
// a share on the mutator_lock_. The garbage collector may also execute with shared access but
// at times requires exclusive access to the heap (not to be confused with the heap meta-data
// guarded by the heap_lock_ below). When the garbage collector requires exclusive access it asks
// the mutators to suspend themselves which also involves usage of the thread_suspend_count_lock_
// to cover weaknesses in using ReaderWriterMutexes with ConditionVariables. We use a condition
// variable to wait upon in the suspension logic as releasing and then re-acquiring a share on
// the mutator lock doesn't necessarily allow the exclusive user (e.g the garbage collector)
// chance to acquire the lock.
//
// Thread suspension:
// Shared users | Exclusive user
// (holding mutator lock and in kRunnable state) | .. running ..
// .. running .. | Request thread suspension by:
// .. running .. | - acquiring thread_suspend_count_lock_
// .. running .. | - incrementing Thread::suspend_count_ on
// .. running .. | all mutator threads
// .. running .. | - releasing thread_suspend_count_lock_
// .. running .. | Block trying to acquire exclusive mutator lock
// Poll Thread::suspend_count_ and enter full | .. blocked ..
// suspend code. | .. blocked ..
// Change state to kSuspended | .. blocked ..
// x: Release share on mutator_lock_ | Carry out exclusive access
// Acquire thread_suspend_count_lock_ | .. exclusive ..
// while Thread::suspend_count_ > 0 | .. exclusive ..
// - wait on Thread::resume_cond_ | .. exclusive ..
// (releases thread_suspend_count_lock_) | .. exclusive ..
// .. waiting .. | Release mutator_lock_
// .. waiting .. | Request thread resumption by:
// .. waiting .. | - acquiring thread_suspend_count_lock_
// .. waiting .. | - decrementing Thread::suspend_count_ on
// .. waiting .. | all mutator threads
// .. waiting .. | - notifying on Thread::resume_cond_
// - re-acquire thread_suspend_count_lock_ | - releasing thread_suspend_count_lock_
// Release thread_suspend_count_lock_ | .. running ..
// Acquire share on mutator_lock_ | .. running ..
// - This could block but the thread still | .. running ..
// has a state of kSuspended and so this | .. running ..
// isn't an issue. | .. running ..
// Acquire thread_suspend_count_lock_ | .. running ..
// - we poll here as we're transitioning into | .. running ..
// kRunnable and an individual thread suspend | .. running ..
// request (e.g for debugging) won't try | .. running ..
// to acquire the mutator lock (which would | .. running ..
// block as we hold the mutator lock). This | .. running ..
// poll ensures that if the suspender thought | .. running ..
// we were suspended by incrementing our | .. running ..
// Thread::suspend_count_ and then reading | .. running ..
// our state we go back to waiting on | .. running ..
// Thread::resume_cond_. | .. running ..
// can_go_runnable = Thread::suspend_count_ == 0 | .. running ..
// Release thread_suspend_count_lock_ | .. running ..
// if can_go_runnable | .. running ..
// Change state to kRunnable | .. running ..
// else | .. running ..
// Goto x | .. running ..
// .. running .. | .. running ..
static ReaderWriterMutex* mutator_lock_ ACQUIRED_AFTER(thread_list_suspend_thread_lock_);
// Allow reader-writer mutual exclusion on the mark and live bitmaps of the heap.
static ReaderWriterMutex* heap_bitmap_lock_ ACQUIRED_AFTER(mutator_lock_);
// Guards shutdown of the runtime.
static Mutex* runtime_shutdown_lock_ ACQUIRED_AFTER(heap_bitmap_lock_);
// Guards background profiler global state.
static Mutex* profiler_lock_ ACQUIRED_AFTER(runtime_shutdown_lock_);
// Guards trace (ie traceview) requests.
static Mutex* trace_lock_ ACQUIRED_AFTER(profiler_lock_);
// Guards debugger recent allocation records.
static Mutex* alloc_tracker_lock_ ACQUIRED_AFTER(trace_lock_);
// Guards updates to instrumentation to ensure mutual exclusion of
// events like deoptimization requests.
// TODO: improve name, perhaps instrumentation_update_lock_.
static Mutex* deoptimization_lock_ ACQUIRED_AFTER(alloc_tracker_lock_);
// The thread_list_lock_ guards ThreadList::list_. It is also commonly held to stop threads
// attaching and detaching.
static Mutex* thread_list_lock_ ACQUIRED_AFTER(deoptimization_lock_);
// Guards breakpoints.
static ReaderWriterMutex* breakpoint_lock_ ACQUIRED_AFTER(trace_lock_);
// Guards lists of classes within the class linker.
static ReaderWriterMutex* classlinker_classes_lock_ ACQUIRED_AFTER(breakpoint_lock_);
// When declaring any Mutex add DEFAULT_MUTEX_ACQUIRED_AFTER to use annotalysis to check the code
// doesn't try to hold a higher level Mutex.
#define DEFAULT_MUTEX_ACQUIRED_AFTER ACQUIRED_AFTER(Locks::classlinker_classes_lock_)
static Mutex* allocated_monitor_ids_lock_ ACQUIRED_AFTER(classlinker_classes_lock_);
// Guard the allocation/deallocation of thread ids.
static Mutex* allocated_thread_ids_lock_ ACQUIRED_AFTER(allocated_monitor_ids_lock_);
// Guards modification of the LDT on x86.
static Mutex* modify_ldt_lock_ ACQUIRED_AFTER(allocated_thread_ids_lock_);
// Guards intern table.
static Mutex* intern_table_lock_ ACQUIRED_AFTER(modify_ldt_lock_);
// Guards reference processor.
static Mutex* reference_processor_lock_ ACQUIRED_AFTER(intern_table_lock_);
// Guards cleared references queue.
static Mutex* reference_queue_cleared_references_lock_ ACQUIRED_AFTER(reference_processor_lock_);
// Guards weak references queue.
static Mutex* reference_queue_weak_references_lock_ ACQUIRED_AFTER(reference_queue_cleared_references_lock_);
// Guards finalizer references queue.
static Mutex* reference_queue_finalizer_references_lock_ ACQUIRED_AFTER(reference_queue_weak_references_lock_);
// Guards phantom references queue.
static Mutex* reference_queue_phantom_references_lock_ ACQUIRED_AFTER(reference_queue_finalizer_references_lock_);
// Guards soft references queue.
static Mutex* reference_queue_soft_references_lock_ ACQUIRED_AFTER(reference_queue_phantom_references_lock_);
// Have an exclusive aborting thread.
static Mutex* abort_lock_ ACQUIRED_AFTER(reference_queue_soft_references_lock_);
// Allow mutual exclusion when manipulating Thread::suspend_count_.
// TODO: Does the trade-off of a per-thread lock make sense?
static Mutex* thread_suspend_count_lock_ ACQUIRED_AFTER(abort_lock_);
// One unexpected signal at a time lock.
static Mutex* unexpected_signal_lock_ ACQUIRED_AFTER(thread_suspend_count_lock_);
// Guards the maps in mem_map.
static Mutex* mem_maps_lock_ ACQUIRED_AFTER(unexpected_signal_lock_);
// Have an exclusive logging thread.
static Mutex* logging_lock_ ACQUIRED_AFTER(unexpected_signal_lock_);
};
} // namespace art
#endif // ART_RUNTIME_BASE_MUTEX_H_