Move some misc thread-related stuff from base to base/thread and into the bas...

base/worker_pool_posix.h

-// Copyright (c) 2009 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-//
-// The thread pool used in the POSIX implementation of WorkerPool dynamically
-// adds threads as necessary to handle all tasks.  It keeps old threads around
-// for a period of time to allow them to be reused.  After this waiting period,
-// the threads exit.  This thread pool uses non-joinable threads, therefore
-// worker threads are not joined during process shutdown.  This means that
-// potentially long running tasks (such as DNS lookup) do not block process
-// shutdown, but also means that process shutdown may "leak" objects.  Note that
-// although PosixDynamicThreadPool spawns the worker threads and manages the
-// task queue, it does not own the worker threads.  The worker threads ask the
-// PosixDynamicThreadPool for work and eventually clean themselves up.  The
-// worker threads all maintain scoped_refptrs to the PosixDynamicThreadPool
-// instance, which prevents PosixDynamicThreadPool from disappearing before all
-// worker threads exit.  The owner of PosixDynamicThreadPool should likewise
-// maintain a scoped_refptr to the PosixDynamicThreadPool instance.
-//
-// NOTE: The classes defined in this file are only meant for use by the POSIX
-// implementation of WorkerPool.  No one else should be using these classes.
-// These symbols are exported in a header purely for testing purposes.
-
-#ifndef BASE_WORKER_POOL_POSIX_H_
-#define BASE_WORKER_POOL_POSIX_H_
-#pragma once
-
-#include <queue>
-#include <string>
-
-#include "base/basictypes.h"
-#include "base/condition_variable.h"
-#include "base/lock.h"
-#include "base/platform_thread.h"
-#include "base/ref_counted.h"
-#include "base/scoped_ptr.h"
-
-class Task;
-
-namespace base {
-
-class PosixDynamicThreadPool
-    : public RefCountedThreadSafe<PosixDynamicThreadPool> {
- public:
-  class PosixDynamicThreadPoolPeer;
-
-  // All worker threads will share the same |name_prefix|.  They will exit after
-  // |idle_seconds_before_exit|.
-  PosixDynamicThreadPool(const std::string& name_prefix,
-                         int idle_seconds_before_exit);
-  ~PosixDynamicThreadPool();
-
-  // Indicates that the thread pool is going away.  Stops handing out tasks to
-  // worker threads.  Wakes up all the idle threads to let them exit.
-  void Terminate();
-
-  // Adds |task| to the thread pool.  PosixDynamicThreadPool assumes ownership
-  // of |task|.
-  void PostTask(Task* task);
-
-  // Worker thread method to wait for up to |idle_seconds_before_exit| for more
-  // work from the thread pool.  Returns NULL if no work is available.
-  Task* WaitForTask();
-
- private:
-  friend class PosixDynamicThreadPoolPeer;
-
-  const std::string name_prefix_;
-  const int idle_seconds_before_exit_;
-
-  Lock lock_;  // Protects all the variables below.
-
-  // Signal()s worker threads to let them know more tasks are available.
-  // Also used for Broadcast()'ing to worker threads to let them know the pool
-  // is being deleted and they can exit.
-  ConditionVariable tasks_available_cv_;
-  int num_idle_threads_;
-  std::queue<Task*> tasks_;
-  bool terminated_;
-  // Only used for tests to ensure correct thread ordering.  It will always be
-  // NULL in non-test code.
-  scoped_ptr<ConditionVariable> num_idle_threads_cv_;
-
-  DISALLOW_COPY_AND_ASSIGN(PosixDynamicThreadPool);
-};
-
-}  // namespace base
-
-#endif  // BASE_WORKER_POOL_POSIX_H_