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* Copyright (C) 2012 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
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#include <deque>
#include <functional>
#include <vector>
#include "barrier.h"
#include "base/mem_map.h"
#include "base/mutex.h"
namespace art {
class ThreadPool;
class Closure {
virtual ~Closure() { }
virtual void Run(Thread* self) = 0;
class Task : public Closure {
// Called after Closure::Run has been called.
virtual void Finalize() { }
class SelfDeletingTask : public Task {
virtual ~SelfDeletingTask() { }
virtual void Finalize() {
delete this;
class FunctionTask : public SelfDeletingTask {
explicit FunctionTask(std::function<void(Thread*)>&& func) : func_(std::move(func)) {}
void Run(Thread* self) override {
std::function<void(Thread*)> func_;
class ThreadPoolWorker {
static const size_t kDefaultStackSize = 1 * MB;
size_t GetStackSize() const {
return stack_.Size();
virtual ~ThreadPoolWorker();
// Set the "nice" priorty for this worker.
void SetPthreadPriority(int priority);
Thread* GetThread() const { return thread_; }
ThreadPoolWorker(ThreadPool* thread_pool, const std::string& name, size_t stack_size);
static void* Callback(void* arg) REQUIRES(!Locks::mutator_lock_);
virtual void Run();
ThreadPool* const thread_pool_;
const std::string name_;
MemMap stack_;
pthread_t pthread_;
Thread* thread_;
friend class ThreadPool;
// Note that thread pool workers will set Thread#setCanCallIntoJava to false.
class ThreadPool {
// Returns the number of threads in the thread pool.
size_t GetThreadCount() const {
return threads_.size();
const std::vector<ThreadPoolWorker*>& GetWorkers();
// Broadcast to the workers and tell them to empty out the work queue.
void StartWorkers(Thread* self) REQUIRES(!task_queue_lock_);
// Do not allow workers to grab any new tasks.
void StopWorkers(Thread* self) REQUIRES(!task_queue_lock_);
// Add a new task, the first available started worker will process it. Does not delete the task
// after running it, it is the caller's responsibility.
void AddTask(Thread* self, Task* task) REQUIRES(!task_queue_lock_);
// Remove all tasks in the queue.
void RemoveAllTasks(Thread* self) REQUIRES(!task_queue_lock_);
// Create a named thread pool with the given number of threads.
// If create_peers is true, all worker threads will have a Java peer object. Note that if the
// pool is asked to do work on the current thread (see Wait), a peer may not be available. Wait
// will conservatively abort if create_peers and do_work are true.
ThreadPool(const char* name,
size_t num_threads,
bool create_peers = false,
size_t worker_stack_size = ThreadPoolWorker::kDefaultStackSize);
virtual ~ThreadPool();
// Create the threads of this pool.
void CreateThreads();
// Stops and deletes all threads in this pool.
void DeleteThreads();
// Wait for all tasks currently on queue to get completed. If the pool has been stopped, only
// wait till all already running tasks are done.
// When the pool was created with peers for workers, do_work must not be true (see ThreadPool()).
void Wait(Thread* self, bool do_work, bool may_hold_locks) REQUIRES(!task_queue_lock_);
size_t GetTaskCount(Thread* self) REQUIRES(!task_queue_lock_);
// Returns the total amount of workers waited for tasks.
uint64_t GetWaitTime() const {
return total_wait_time_;
// Provides a way to bound the maximum number of worker threads, threads must be less the the
// thread count of the thread pool.
void SetMaxActiveWorkers(size_t threads) REQUIRES(!task_queue_lock_);
// Set the "nice" priorty for threads in the pool.
void SetPthreadPriority(int priority);
// Wait for workers to be created.
void WaitForWorkersToBeCreated();
// get a task to run, blocks if there are no tasks left
virtual Task* GetTask(Thread* self) REQUIRES(!task_queue_lock_);
// Try to get a task, returning null if there is none available.
Task* TryGetTask(Thread* self) REQUIRES(!task_queue_lock_);
Task* TryGetTaskLocked() REQUIRES(task_queue_lock_);
// Are we shutting down?
bool IsShuttingDown() const REQUIRES(task_queue_lock_) {
return shutting_down_;
bool HasOutstandingTasks() const REQUIRES(task_queue_lock_) {
return started_ && !tasks_.empty();
const std::string name_;
Mutex task_queue_lock_;
ConditionVariable task_queue_condition_ GUARDED_BY(task_queue_lock_);
ConditionVariable completion_condition_ GUARDED_BY(task_queue_lock_);
volatile bool started_ GUARDED_BY(task_queue_lock_);
volatile bool shutting_down_ GUARDED_BY(task_queue_lock_);
// How many worker threads are waiting on the condition.
volatile size_t waiting_count_ GUARDED_BY(task_queue_lock_);
std::deque<Task*> tasks_ GUARDED_BY(task_queue_lock_);
std::vector<ThreadPoolWorker*> threads_;
// Work balance detection.
uint64_t start_time_ GUARDED_BY(task_queue_lock_);
uint64_t total_wait_time_;
Barrier creation_barier_;
size_t max_active_workers_ GUARDED_BY(task_queue_lock_);
const bool create_peers_;
const size_t worker_stack_size_;
friend class ThreadPoolWorker;
friend class WorkStealingWorker;
} // namespace art