/* * Copyright (C) 2008 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_MONITOR_H_ #define ART_RUNTIME_MONITOR_H_ #include #include #include #include #include #include #include "base/allocator.h" #include "base/atomic.h" #include "base/mutex.h" #include "gc_root.h" #include "lock_word.h" #include "obj_ptr.h" #include "read_barrier_option.h" #include "runtime_callbacks.h" #include "thread_state.h" namespace art { class ArtMethod; class IsMarkedVisitor; class LockWord; template class Handle; class StackVisitor; class Thread; typedef uint32_t MonitorId; namespace mirror { class Object; } // namespace mirror enum class LockReason { kForWait, kForLock, }; class Monitor { public: // The default number of spins that are done before thread suspension is used to forcibly inflate // a lock word. See Runtime::max_spins_before_thin_lock_inflation_. constexpr static size_t kDefaultMaxSpinsBeforeThinLockInflation = 50; ~Monitor(); static void Init(uint32_t lock_profiling_threshold, uint32_t stack_dump_lock_profiling_threshold); // Return the thread id of the lock owner or 0 when there is no owner. static uint32_t GetLockOwnerThreadId(ObjPtr obj) NO_THREAD_SAFETY_ANALYSIS; // TODO: Reading lock owner without holding lock is racy. // NO_THREAD_SAFETY_ANALYSIS for mon->Lock. static ObjPtr MonitorEnter(Thread* thread, ObjPtr obj, bool trylock) EXCLUSIVE_LOCK_FUNCTION(obj.Ptr()) NO_THREAD_SAFETY_ANALYSIS REQUIRES(!Roles::uninterruptible_) REQUIRES_SHARED(Locks::mutator_lock_); // NO_THREAD_SAFETY_ANALYSIS for mon->Unlock. static bool MonitorExit(Thread* thread, ObjPtr obj) NO_THREAD_SAFETY_ANALYSIS REQUIRES(!Roles::uninterruptible_) REQUIRES_SHARED(Locks::mutator_lock_) UNLOCK_FUNCTION(obj.Ptr()); static void Notify(Thread* self, ObjPtr obj) REQUIRES_SHARED(Locks::mutator_lock_) { DoNotify(self, obj, false); } static void NotifyAll(Thread* self, ObjPtr obj) REQUIRES_SHARED(Locks::mutator_lock_) { DoNotify(self, obj, true); } // Object.wait(). Also called for class init. // NO_THREAD_SAFETY_ANALYSIS for mon->Wait. static void Wait(Thread* self, ObjPtr obj, int64_t ms, int32_t ns, bool interruptShouldThrow, ThreadState why) REQUIRES_SHARED(Locks::mutator_lock_) NO_THREAD_SAFETY_ANALYSIS; static ThreadState FetchState(const Thread* thread, /* out */ ObjPtr* monitor_object, /* out */ uint32_t* lock_owner_tid) REQUIRES(!Locks::thread_suspend_count_lock_) REQUIRES_SHARED(Locks::mutator_lock_); // Used to implement JDWP's ThreadReference.CurrentContendedMonitor. static ObjPtr GetContendedMonitor(Thread* thread) REQUIRES_SHARED(Locks::mutator_lock_); // Calls 'callback' once for each lock held in the single stack frame represented by // the current state of 'stack_visitor'. // The abort_on_failure flag allows to not die when the state of the runtime is unorderly. This // is necessary when we have already aborted but want to dump the stack as much as we can. static void VisitLocks(StackVisitor* stack_visitor, void (*callback)(ObjPtr, void*), void* callback_context, bool abort_on_failure = true) REQUIRES_SHARED(Locks::mutator_lock_); static bool IsValidLockWord(LockWord lock_word); template ObjPtr GetObject() REQUIRES_SHARED(Locks::mutator_lock_); void SetObject(ObjPtr object); Thread* GetOwner() const NO_THREAD_SAFETY_ANALYSIS { return owner_; } int32_t GetHashCode(); bool IsLocked() REQUIRES_SHARED(Locks::mutator_lock_) REQUIRES(!monitor_lock_); bool HasHashCode() const { return hash_code_.load(std::memory_order_relaxed) != 0; } MonitorId GetMonitorId() const { return monitor_id_; } // Inflate the lock on obj. May fail to inflate for spurious reasons, always re-check. static void InflateThinLocked(Thread* self, Handle obj, LockWord lock_word, uint32_t hash_code) REQUIRES_SHARED(Locks::mutator_lock_); // Not exclusive because ImageWriter calls this during a Heap::VisitObjects() that // does not allow a thread suspension in the middle. TODO: maybe make this exclusive. // NO_THREAD_SAFETY_ANALYSIS for monitor->monitor_lock_. static bool Deflate(Thread* self, ObjPtr obj) REQUIRES_SHARED(Locks::mutator_lock_) NO_THREAD_SAFETY_ANALYSIS; #ifndef __LP64__ void* operator new(size_t size) { // Align Monitor* as per the monitor ID field size in the lock word. void* result; int error = posix_memalign(&result, LockWord::kMonitorIdAlignment, size); CHECK_EQ(error, 0) << strerror(error); return result; } void operator delete(void* ptr) { free(ptr); } #endif private: Monitor(Thread* self, Thread* owner, ObjPtr obj, int32_t hash_code) REQUIRES_SHARED(Locks::mutator_lock_); Monitor(Thread* self, Thread* owner, ObjPtr obj, int32_t hash_code, MonitorId id) REQUIRES_SHARED(Locks::mutator_lock_); // Install the monitor into its object, may fail if another thread installs a different monitor // first. bool Install(Thread* self) REQUIRES(!monitor_lock_) REQUIRES_SHARED(Locks::mutator_lock_); // Links a thread into a monitor's wait set. The monitor lock must be held by the caller of this // routine. void AppendToWaitSet(Thread* thread) REQUIRES(monitor_lock_); // Unlinks a thread from a monitor's wait set. The monitor lock must be held by the caller of // this routine. void RemoveFromWaitSet(Thread* thread) REQUIRES(monitor_lock_); void SignalContendersAndReleaseMonitorLock(Thread* self) RELEASE(monitor_lock_); // Changes the shape of a monitor from thin to fat, preserving the internal lock state. The // calling thread must own the lock or the owner must be suspended. There's a race with other // threads inflating the lock, installing hash codes and spurious failures. The caller should // re-read the lock word following the call. static void Inflate(Thread* self, Thread* owner, ObjPtr obj, int32_t hash_code) REQUIRES_SHARED(Locks::mutator_lock_) NO_THREAD_SAFETY_ANALYSIS; // For m->Install(self) void LogContentionEvent(Thread* self, uint32_t wait_ms, uint32_t sample_percent, ArtMethod* owner_method, uint32_t owner_dex_pc) REQUIRES_SHARED(Locks::mutator_lock_); static void FailedUnlock(ObjPtr obj, uint32_t expected_owner_thread_id, uint32_t found_owner_thread_id, Monitor* mon) REQUIRES(!Locks::thread_list_lock_, !monitor_lock_) REQUIRES_SHARED(Locks::mutator_lock_); // Try to lock without blocking, returns true if we acquired the lock. bool TryLock(Thread* self) REQUIRES(!monitor_lock_) REQUIRES_SHARED(Locks::mutator_lock_); // Variant for already holding the monitor lock. bool TryLockLocked(Thread* self) REQUIRES(monitor_lock_) REQUIRES_SHARED(Locks::mutator_lock_); template void Lock(Thread* self) REQUIRES(!monitor_lock_) REQUIRES_SHARED(Locks::mutator_lock_); bool Unlock(Thread* thread) REQUIRES(!monitor_lock_) REQUIRES_SHARED(Locks::mutator_lock_); static void DoNotify(Thread* self, ObjPtr obj, bool notify_all) REQUIRES_SHARED(Locks::mutator_lock_) NO_THREAD_SAFETY_ANALYSIS; // For mon->Notify. void Notify(Thread* self) REQUIRES(!monitor_lock_) REQUIRES_SHARED(Locks::mutator_lock_); void NotifyAll(Thread* self) REQUIRES(!monitor_lock_) REQUIRES_SHARED(Locks::mutator_lock_); static std::string PrettyContentionInfo(const std::string& owner_name, pid_t owner_tid, ArtMethod* owners_method, uint32_t owners_dex_pc, size_t num_waiters) REQUIRES_SHARED(Locks::mutator_lock_); // Wait on a monitor until timeout, interrupt, or notification. Used for Object.wait() and // (somewhat indirectly) Thread.sleep() and Thread.join(). // // If another thread calls Thread.interrupt(), we throw InterruptedException and return // immediately if one of the following are true: // - blocked in wait(), wait(long), or wait(long, int) methods of Object // - blocked in join(), join(long), or join(long, int) methods of Thread // - blocked in sleep(long), or sleep(long, int) methods of Thread // Otherwise, we set the "interrupted" flag. // // Checks to make sure that "ns" is in the range 0-999999 (i.e. fractions of a millisecond) and // throws the appropriate exception if it isn't. // // The spec allows "spurious wakeups", and recommends that all code using Object.wait() do so in // a loop. This appears to derive from concerns about pthread_cond_wait() on multiprocessor // systems. Some commentary on the web casts doubt on whether these can/should occur. // // Since we're allowed to wake up "early", we clamp extremely long durations to return at the end // of the 32-bit time epoch. void Wait(Thread* self, int64_t msec, int32_t nsec, bool interruptShouldThrow, ThreadState why) REQUIRES(!monitor_lock_) REQUIRES_SHARED(Locks::mutator_lock_); // Translates the provided method and pc into its declaring class' source file and line number. static void TranslateLocation(ArtMethod* method, uint32_t pc, const char** source_file, int32_t* line_number) REQUIRES_SHARED(Locks::mutator_lock_); uint32_t GetOwnerThreadId() REQUIRES(!monitor_lock_); // Support for systrace output of monitor operations. ALWAYS_INLINE static void AtraceMonitorLock(Thread* self, ObjPtr obj, bool is_wait) REQUIRES_SHARED(Locks::mutator_lock_); static void AtraceMonitorLockImpl(Thread* self, ObjPtr obj, bool is_wait) REQUIRES_SHARED(Locks::mutator_lock_); ALWAYS_INLINE static void AtraceMonitorUnlock(); static uint32_t lock_profiling_threshold_; static uint32_t stack_dump_lock_profiling_threshold_; Mutex monitor_lock_ DEFAULT_MUTEX_ACQUIRED_AFTER; ConditionVariable monitor_contenders_ GUARDED_BY(monitor_lock_); // Number of people waiting on the condition. size_t num_waiters_ GUARDED_BY(monitor_lock_); // Which thread currently owns the lock? Thread* volatile owner_ GUARDED_BY(monitor_lock_); // Owner's recursive lock depth. int lock_count_ GUARDED_BY(monitor_lock_); // What object are we part of. This is a weak root. Do not access // this directly, use GetObject() to read it so it will be guarded // by a read barrier. GcRoot obj_; // Threads currently waiting on this monitor. Thread* wait_set_ GUARDED_BY(monitor_lock_); // Threads that were waiting on this monitor, but are now contending on it. Thread* wake_set_ GUARDED_BY(monitor_lock_); // Stored object hash code, generated lazily by GetHashCode. AtomicInteger hash_code_; // Method and dex pc where the lock owner acquired the lock, used when lock // sampling is enabled. locking_method_ may be null if the lock is currently // unlocked, or if the lock is acquired by the system when the stack is empty. ArtMethod* locking_method_ GUARDED_BY(monitor_lock_); uint32_t locking_dex_pc_ GUARDED_BY(monitor_lock_); // The denser encoded version of this monitor as stored in the lock word. MonitorId monitor_id_; #ifdef __LP64__ // Free list for monitor pool. Monitor* next_free_ GUARDED_BY(Locks::allocated_monitor_ids_lock_); #endif friend class MonitorInfo; friend class MonitorList; friend class MonitorPool; friend class mirror::Object; DISALLOW_COPY_AND_ASSIGN(Monitor); }; class MonitorList { public: MonitorList(); ~MonitorList(); void Add(Monitor* m) REQUIRES_SHARED(Locks::mutator_lock_) REQUIRES(!monitor_list_lock_); void SweepMonitorList(IsMarkedVisitor* visitor) REQUIRES(!monitor_list_lock_) REQUIRES_SHARED(Locks::mutator_lock_); void DisallowNewMonitors() REQUIRES(!monitor_list_lock_); void AllowNewMonitors() REQUIRES(!monitor_list_lock_); void BroadcastForNewMonitors() REQUIRES(!monitor_list_lock_); // Returns how many monitors were deflated. size_t DeflateMonitors() REQUIRES(!monitor_list_lock_) REQUIRES(Locks::mutator_lock_); size_t Size() REQUIRES(!monitor_list_lock_); typedef std::list> Monitors; private: // During sweeping we may free an object and on a separate thread have an object created using // the newly freed memory. That object may then have its lock-word inflated and a monitor created. // If we allow new monitor registration during sweeping this monitor may be incorrectly freed as // the object wasn't marked when sweeping began. bool allow_new_monitors_ GUARDED_BY(monitor_list_lock_); Mutex monitor_list_lock_ DEFAULT_MUTEX_ACQUIRED_AFTER; ConditionVariable monitor_add_condition_ GUARDED_BY(monitor_list_lock_); Monitors list_ GUARDED_BY(monitor_list_lock_); friend class Monitor; DISALLOW_COPY_AND_ASSIGN(MonitorList); }; // Collects information about the current state of an object's monitor. // This is very unsafe, and must only be called when all threads are suspended. // For use only by the JDWP implementation. class MonitorInfo { public: MonitorInfo() : owner_(nullptr), entry_count_(0) {} MonitorInfo(const MonitorInfo&) = default; MonitorInfo& operator=(const MonitorInfo&) = default; explicit MonitorInfo(ObjPtr o) REQUIRES(Locks::mutator_lock_); Thread* owner_; size_t entry_count_; std::vector waiters_; }; } // namespace art #endif // ART_RUNTIME_MONITOR_H_