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comparison: ipc/chromium/src/base/worker_pool_linux.h
ipc/chromium/src/base/worker_pool_linux.h
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| 1 // Copyright (c) 2009 The Chromium Authors. All rights reserved. | |
| 2 // Use of this source code is governed by a BSD-style license that can be | |
| 3 // found in the LICENSE file. | |
| 4 // | |
| 5 // The thread pool used in the Linux implementation of WorkerPool dynamically | |
| 6 // adds threads as necessary to handle all tasks. It keeps old threads around | |
| 7 // for a period of time to allow them to be reused. After this waiting period, | |
| 8 // the threads exit. This thread pool uses non-joinable threads, therefore | |
| 9 // worker threads are not joined during process shutdown. This means that | |
| 10 // potentially long running tasks (such as DNS lookup) do not block process | |
| 11 // shutdown, but also means that process shutdown may "leak" objects. Note that | |
| 12 // although LinuxDynamicThreadPool spawns the worker threads and manages the | |
| 13 // task queue, it does not own the worker threads. The worker threads ask the | |
| 14 // LinuxDynamicThreadPool for work and eventually clean themselves up. The | |
| 15 // worker threads all maintain scoped_refptrs to the LinuxDynamicThreadPool | |
| 16 // instance, which prevents LinuxDynamicThreadPool from disappearing before all | |
| 17 // worker threads exit. The owner of LinuxDynamicThreadPool should likewise | |
| 18 // maintain a scoped_refptr to the LinuxDynamicThreadPool instance. | |
| 19 // | |
| 20 // NOTE: The classes defined in this file are only meant for use by the Linux | |
| 21 // implementation of WorkerPool. No one else should be using these classes. | |
| 22 // These symbols are exported in a header purely for testing purposes. | |
| 23 | |
| 24 #ifndef BASE_WORKER_POOL_LINUX_H_ | |
| 25 #define BASE_WORKER_POOL_LINUX_H_ | |
| 26 | |
| 27 #include <queue> | |
| 28 #include <string> | |
| 29 | |
| 30 #include "base/basictypes.h" | |
| 31 #include "base/condition_variable.h" | |
| 32 #include "base/lock.h" | |
| 33 #include "base/platform_thread.h" | |
| 34 #include "base/ref_counted.h" | |
| 35 #include "base/scoped_ptr.h" | |
| 36 | |
| 37 class Task; | |
| 38 | |
| 39 namespace base { | |
| 40 | |
| 41 class LinuxDynamicThreadPool | |
| 42 : public RefCountedThreadSafe<LinuxDynamicThreadPool> { | |
| 43 public: | |
| 44 class LinuxDynamicThreadPoolPeer; | |
| 45 | |
| 46 // All worker threads will share the same |name_prefix|. They will exit after | |
| 47 // |idle_seconds_before_exit|. | |
| 48 LinuxDynamicThreadPool(const std::string& name_prefix, | |
| 49 int idle_seconds_before_exit); | |
| 50 ~LinuxDynamicThreadPool(); | |
| 51 | |
| 52 // Indicates that the thread pool is going away. Stops handing out tasks to | |
| 53 // worker threads. Wakes up all the idle threads to let them exit. | |
| 54 void Terminate(); | |
| 55 | |
| 56 // Adds |task| to the thread pool. LinuxDynamicThreadPool assumes ownership | |
| 57 // of |task|. | |
| 58 void PostTask(Task* task); | |
| 59 | |
| 60 // Worker thread method to wait for up to |idle_seconds_before_exit| for more | |
| 61 // work from the thread pool. Returns NULL if no work is available. | |
| 62 Task* WaitForTask(); | |
| 63 | |
| 64 private: | |
| 65 friend class LinuxDynamicThreadPoolPeer; | |
| 66 | |
| 67 const std::string name_prefix_; | |
| 68 const int idle_seconds_before_exit_; | |
| 69 | |
| 70 Lock lock_; // Protects all the variables below. | |
| 71 | |
| 72 // Signal()s worker threads to let them know more tasks are available. | |
| 73 // Also used for Broadcast()'ing to worker threads to let them know the pool | |
| 74 // is being deleted and they can exit. | |
| 75 ConditionVariable tasks_available_cv_; | |
| 76 int num_idle_threads_; | |
| 77 std::queue<Task*> tasks_; | |
| 78 bool terminated_; | |
| 79 // Only used for tests to ensure correct thread ordering. It will always be | |
| 80 // NULL in non-test code. | |
| 81 scoped_ptr<ConditionVariable> num_idle_threads_cv_; | |
| 82 | |
| 83 DISALLOW_COPY_AND_ASSIGN(LinuxDynamicThreadPool); | |
| 84 }; | |
| 85 | |
| 86 } // namespace base | |
| 87 | |
| 88 #endif // BASE_WORKER_POOL_LINUX_H_ |
