1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/ipc/chromium/src/base/worker_pool_linux.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,88 @@
1.4 +// Copyright (c) 2009 The Chromium Authors. All rights reserved.
1.5 +// Use of this source code is governed by a BSD-style license that can be
1.6 +// found in the LICENSE file.
1.7 +//
1.8 +// The thread pool used in the Linux implementation of WorkerPool dynamically
1.9 +// adds threads as necessary to handle all tasks. It keeps old threads around
1.10 +// for a period of time to allow them to be reused. After this waiting period,
1.11 +// the threads exit. This thread pool uses non-joinable threads, therefore
1.12 +// worker threads are not joined during process shutdown. This means that
1.13 +// potentially long running tasks (such as DNS lookup) do not block process
1.14 +// shutdown, but also means that process shutdown may "leak" objects. Note that
1.15 +// although LinuxDynamicThreadPool spawns the worker threads and manages the
1.16 +// task queue, it does not own the worker threads. The worker threads ask the
1.17 +// LinuxDynamicThreadPool for work and eventually clean themselves up. The
1.18 +// worker threads all maintain scoped_refptrs to the LinuxDynamicThreadPool
1.19 +// instance, which prevents LinuxDynamicThreadPool from disappearing before all
1.20 +// worker threads exit. The owner of LinuxDynamicThreadPool should likewise
1.21 +// maintain a scoped_refptr to the LinuxDynamicThreadPool instance.
1.22 +//
1.23 +// NOTE: The classes defined in this file are only meant for use by the Linux
1.24 +// implementation of WorkerPool. No one else should be using these classes.
1.25 +// These symbols are exported in a header purely for testing purposes.
1.26 +
1.27 +#ifndef BASE_WORKER_POOL_LINUX_H_
1.28 +#define BASE_WORKER_POOL_LINUX_H_
1.29 +
1.30 +#include <queue>
1.31 +#include <string>
1.32 +
1.33 +#include "base/basictypes.h"
1.34 +#include "base/condition_variable.h"
1.35 +#include "base/lock.h"
1.36 +#include "base/platform_thread.h"
1.37 +#include "base/ref_counted.h"
1.38 +#include "base/scoped_ptr.h"
1.39 +
1.40 +class Task;
1.41 +
1.42 +namespace base {
1.43 +
1.44 +class LinuxDynamicThreadPool
1.45 + : public RefCountedThreadSafe<LinuxDynamicThreadPool> {
1.46 + public:
1.47 + class LinuxDynamicThreadPoolPeer;
1.48 +
1.49 + // All worker threads will share the same |name_prefix|. They will exit after
1.50 + // |idle_seconds_before_exit|.
1.51 + LinuxDynamicThreadPool(const std::string& name_prefix,
1.52 + int idle_seconds_before_exit);
1.53 + ~LinuxDynamicThreadPool();
1.54 +
1.55 + // Indicates that the thread pool is going away. Stops handing out tasks to
1.56 + // worker threads. Wakes up all the idle threads to let them exit.
1.57 + void Terminate();
1.58 +
1.59 + // Adds |task| to the thread pool. LinuxDynamicThreadPool assumes ownership
1.60 + // of |task|.
1.61 + void PostTask(Task* task);
1.62 +
1.63 + // Worker thread method to wait for up to |idle_seconds_before_exit| for more
1.64 + // work from the thread pool. Returns NULL if no work is available.
1.65 + Task* WaitForTask();
1.66 +
1.67 + private:
1.68 + friend class LinuxDynamicThreadPoolPeer;
1.69 +
1.70 + const std::string name_prefix_;
1.71 + const int idle_seconds_before_exit_;
1.72 +
1.73 + Lock lock_; // Protects all the variables below.
1.74 +
1.75 + // Signal()s worker threads to let them know more tasks are available.
1.76 + // Also used for Broadcast()'ing to worker threads to let them know the pool
1.77 + // is being deleted and they can exit.
1.78 + ConditionVariable tasks_available_cv_;
1.79 + int num_idle_threads_;
1.80 + std::queue<Task*> tasks_;
1.81 + bool terminated_;
1.82 + // Only used for tests to ensure correct thread ordering. It will always be
1.83 + // NULL in non-test code.
1.84 + scoped_ptr<ConditionVariable> num_idle_threads_cv_;
1.85 +
1.86 + DISALLOW_COPY_AND_ASSIGN(LinuxDynamicThreadPool);
1.87 +};
1.88 +
1.89 +} // namespace base
1.90 +
1.91 +#endif // BASE_WORKER_POOL_LINUX_H_
