ipc/chromium/src/base/worker_pool_linux.h@6474c204b198 (annotated)
ipc/chromium/src/base/worker_pool_linux.h
Wed, 31 Dec 2014 06:09:35 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Wed, 31 Dec 2014 06:09:35 +0100
- changeset 0
- 6474c204b198
- permissions
- -rw-r--r--
Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.
| michael@0 | 1 | // Copyright (c) 2009 The Chromium Authors. All rights reserved. |
| michael@0 | 2 | // Use of this source code is governed by a BSD-style license that can be |
| michael@0 | 3 | // found in the LICENSE file. |
| michael@0 | 4 | // |
| michael@0 | 5 | // The thread pool used in the Linux implementation of WorkerPool dynamically |
| michael@0 | 6 | // adds threads as necessary to handle all tasks. It keeps old threads around |
| michael@0 | 7 | // for a period of time to allow them to be reused. After this waiting period, |
| michael@0 | 8 | // the threads exit. This thread pool uses non-joinable threads, therefore |
| michael@0 | 9 | // worker threads are not joined during process shutdown. This means that |
| michael@0 | 10 | // potentially long running tasks (such as DNS lookup) do not block process |
| michael@0 | 11 | // shutdown, but also means that process shutdown may "leak" objects. Note that |
| michael@0 | 12 | // although LinuxDynamicThreadPool spawns the worker threads and manages the |
| michael@0 | 13 | // task queue, it does not own the worker threads. The worker threads ask the |
| michael@0 | 14 | // LinuxDynamicThreadPool for work and eventually clean themselves up. The |
| michael@0 | 15 | // worker threads all maintain scoped_refptrs to the LinuxDynamicThreadPool |
| michael@0 | 16 | // instance, which prevents LinuxDynamicThreadPool from disappearing before all |
| michael@0 | 17 | // worker threads exit. The owner of LinuxDynamicThreadPool should likewise |
| michael@0 | 18 | // maintain a scoped_refptr to the LinuxDynamicThreadPool instance. |
| michael@0 | 19 | // |
| michael@0 | 20 | // NOTE: The classes defined in this file are only meant for use by the Linux |
| michael@0 | 21 | // implementation of WorkerPool. No one else should be using these classes. |
| michael@0 | 22 | // These symbols are exported in a header purely for testing purposes. |
| michael@0 | 23 | |
| michael@0 | 24 | #ifndef BASE_WORKER_POOL_LINUX_H_ |
| michael@0 | 25 | #define BASE_WORKER_POOL_LINUX_H_ |
| michael@0 | 26 | |
| michael@0 | 27 | #include <queue> |
| michael@0 | 28 | #include <string> |
| michael@0 | 29 | |
| michael@0 | 30 | #include "base/basictypes.h" |
| michael@0 | 31 | #include "base/condition_variable.h" |
| michael@0 | 32 | #include "base/lock.h" |
| michael@0 | 33 | #include "base/platform_thread.h" |
| michael@0 | 34 | #include "base/ref_counted.h" |
| michael@0 | 35 | #include "base/scoped_ptr.h" |
| michael@0 | 36 | |
| michael@0 | 37 | class Task; |
| michael@0 | 38 | |
| michael@0 | 39 | namespace base { |
| michael@0 | 40 | |
| michael@0 | 41 | class LinuxDynamicThreadPool |
| michael@0 | 42 | : public RefCountedThreadSafe<LinuxDynamicThreadPool> { |
| michael@0 | 43 | public: |
| michael@0 | 44 | class LinuxDynamicThreadPoolPeer; |
| michael@0 | 45 | |
| michael@0 | 46 | // All worker threads will share the same |name_prefix|. They will exit after |
| michael@0 | 47 | // |idle_seconds_before_exit|. |
| michael@0 | 48 | LinuxDynamicThreadPool(const std::string& name_prefix, |
| michael@0 | 49 | int idle_seconds_before_exit); |
| michael@0 | 50 | ~LinuxDynamicThreadPool(); |
| michael@0 | 51 | |
| michael@0 | 52 | // Indicates that the thread pool is going away. Stops handing out tasks to |
| michael@0 | 53 | // worker threads. Wakes up all the idle threads to let them exit. |
| michael@0 | 54 | void Terminate(); |
| michael@0 | 55 | |
| michael@0 | 56 | // Adds |task| to the thread pool. LinuxDynamicThreadPool assumes ownership |
| michael@0 | 57 | // of |task|. |
| michael@0 | 58 | void PostTask(Task* task); |
| michael@0 | 59 | |
| michael@0 | 60 | // Worker thread method to wait for up to |idle_seconds_before_exit| for more |
| michael@0 | 61 | // work from the thread pool. Returns NULL if no work is available. |
| michael@0 | 62 | Task* WaitForTask(); |
| michael@0 | 63 | |
| michael@0 | 64 | private: |
| michael@0 | 65 | friend class LinuxDynamicThreadPoolPeer; |
| michael@0 | 66 | |
| michael@0 | 67 | const std::string name_prefix_; |
| michael@0 | 68 | const int idle_seconds_before_exit_; |
| michael@0 | 69 | |
| michael@0 | 70 | Lock lock_; // Protects all the variables below. |
| michael@0 | 71 | |
| michael@0 | 72 | // Signal()s worker threads to let them know more tasks are available. |
| michael@0 | 73 | // Also used for Broadcast()'ing to worker threads to let them know the pool |
| michael@0 | 74 | // is being deleted and they can exit. |
| michael@0 | 75 | ConditionVariable tasks_available_cv_; |
| michael@0 | 76 | int num_idle_threads_; |
| michael@0 | 77 | std::queue<Task*> tasks_; |
| michael@0 | 78 | bool terminated_; |
| michael@0 | 79 | // Only used for tests to ensure correct thread ordering. It will always be |
| michael@0 | 80 | // NULL in non-test code. |
| michael@0 | 81 | scoped_ptr<ConditionVariable> num_idle_threads_cv_; |
| michael@0 | 82 | |
| michael@0 | 83 | DISALLOW_COPY_AND_ASSIGN(LinuxDynamicThreadPool); |
| michael@0 | 84 | }; |
| michael@0 | 85 | |
| michael@0 | 86 | } // namespace base |
| michael@0 | 87 | |
| michael@0 | 88 | #endif // BASE_WORKER_POOL_LINUX_H_ |
