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1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. | 1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 #ifndef BASE_THREADING_SEQUENCED_WORKER_POOL_H_ | 5 #ifndef BASE_THREADING_SEQUENCED_WORKER_POOL_H_ |
6 #define BASE_THREADING_SEQUENCED_WORKER_POOL_H_ | 6 #define BASE_THREADING_SEQUENCED_WORKER_POOL_H_ |
7 | 7 |
8 #include <cstddef> | 8 #include <cstddef> |
9 #include <string> | 9 #include <string> |
10 | 10 |
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38 // | 38 // |
39 // - No two tasks with the same token will run at the same time. | 39 // - No two tasks with the same token will run at the same time. |
40 // | 40 // |
41 // - Given two tasks T1 and T2 with the same token such that T2 will | 41 // - Given two tasks T1 and T2 with the same token such that T2 will |
42 // run after T1, then T2 will start after T1 is destroyed. | 42 // run after T1, then T2 will start after T1 is destroyed. |
43 // | 43 // |
44 // - If T2 will run after T1, then all memory changes in T1 and T1's | 44 // - If T2 will run after T1, then all memory changes in T1 and T1's |
45 // destruction will be visible to T2. | 45 // destruction will be visible to T2. |
46 // | 46 // |
47 // Example: | 47 // Example: |
48 // SequencedWorkerPool::SequenceToken token = pool.GetSequenceToken(); | 48 // SequencedWorkerPool::SequenceToken token = |
| 49 // SequencedWorkerPool::GetSequenceToken(); |
49 // pool.PostSequencedWorkerTask(token, SequencedWorkerPool::SKIP_ON_SHUTDOWN, | 50 // pool.PostSequencedWorkerTask(token, SequencedWorkerPool::SKIP_ON_SHUTDOWN, |
50 // FROM_HERE, base::Bind(...)); | 51 // FROM_HERE, base::Bind(...)); |
51 // pool.PostSequencedWorkerTask(token, SequencedWorkerPool::SKIP_ON_SHUTDOWN, | 52 // pool.PostSequencedWorkerTask(token, SequencedWorkerPool::SKIP_ON_SHUTDOWN, |
52 // FROM_HERE, base::Bind(...)); | 53 // FROM_HERE, base::Bind(...)); |
53 // | 54 // |
54 // You can make named sequence tokens to make it easier to share a token | 55 // You can make named sequence tokens to make it easier to share a token |
55 // across different components. | 56 // across different components. |
56 // | 57 // |
57 // You can also post tasks to the pool without ordering using PostWorkerTask. | 58 // You can also post tasks to the pool without ordering using PostWorkerTask. |
58 // These will be executed in an unspecified order. The order of execution | 59 // These will be executed in an unspecified order. The order of execution |
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154 virtual void OnHasWork() = 0; | 155 virtual void OnHasWork() = 0; |
155 virtual void WillWaitForShutdown() = 0; | 156 virtual void WillWaitForShutdown() = 0; |
156 virtual void OnDestruct() = 0; | 157 virtual void OnDestruct() = 0; |
157 }; | 158 }; |
158 | 159 |
159 // Gets the SequencedToken of the current thread. | 160 // Gets the SequencedToken of the current thread. |
160 // If current thread is not a SequencedWorkerPool worker thread or is running | 161 // If current thread is not a SequencedWorkerPool worker thread or is running |
161 // an unsequenced task, returns an invalid SequenceToken. | 162 // an unsequenced task, returns an invalid SequenceToken. |
162 static SequenceToken GetSequenceTokenForCurrentThread(); | 163 static SequenceToken GetSequenceTokenForCurrentThread(); |
163 | 164 |
164 // Returns the SequencedWorkerPool that owns this thread, or null if the | 165 // Gets a SequencedTaskRunner for the current thread. If the current thread is |
165 // current thread is not a SequencedWorkerPool worker thread. | 166 // running an unsequenced task, a new SequenceToken will be generated and set, |
166 static scoped_refptr<SequencedWorkerPool> GetWorkerPoolForCurrentThread(); | 167 // so that the returned SequencedTaskRunner is guaranteed to run tasks after |
| 168 // the current task has finished running. |
| 169 static scoped_refptr<SequencedTaskRunner> |
| 170 GetSequencedTaskRunnerForCurrentThread(); |
| 171 |
| 172 // Returns a unique token that can be used to sequence tasks posted to |
| 173 // PostSequencedWorkerTask(). Valid tokens are always nonzero. |
| 174 // TODO(bauerb): Rename this to better differentiate from |
| 175 // GetSequenceTokenForCurrentThread(). |
| 176 static SequenceToken GetSequenceToken(); |
167 | 177 |
168 // When constructing a SequencedWorkerPool, there must be a | 178 // When constructing a SequencedWorkerPool, there must be a |
169 // ThreadTaskRunnerHandle on the current thread unless you plan to | 179 // ThreadTaskRunnerHandle on the current thread unless you plan to |
170 // deliberately leak it. | 180 // deliberately leak it. |
171 | 181 |
172 // Pass the maximum number of threads (they will be lazily created as needed) | 182 // Pass the maximum number of threads (they will be lazily created as needed) |
173 // and a prefix for the thread name to aid in debugging. | 183 // and a prefix for the thread name to aid in debugging. |
174 SequencedWorkerPool(size_t max_threads, | 184 SequencedWorkerPool(size_t max_threads, |
175 const std::string& thread_name_prefix); | 185 const std::string& thread_name_prefix); |
176 | 186 |
177 // Like above, but with |observer| for testing. Does not take ownership of | 187 // Like above, but with |observer| for testing. Does not take ownership of |
178 // |observer|. | 188 // |observer|. |
179 SequencedWorkerPool(size_t max_threads, | 189 SequencedWorkerPool(size_t max_threads, |
180 const std::string& thread_name_prefix, | 190 const std::string& thread_name_prefix, |
181 TestingObserver* observer); | 191 TestingObserver* observer); |
182 | 192 |
183 // Returns a unique token that can be used to sequence tasks posted to | |
184 // PostSequencedWorkerTask(). Valid tokens are always nonzero. | |
185 SequenceToken GetSequenceToken(); | |
186 | |
187 // Returns the sequence token associated with the given name. Calling this | 193 // Returns the sequence token associated with the given name. Calling this |
188 // function multiple times with the same string will always produce the | 194 // function multiple times with the same string will always produce the |
189 // same sequence token. If the name has not been used before, a new token | 195 // same sequence token. If the name has not been used before, a new token |
190 // will be created. | 196 // will be created. |
191 SequenceToken GetNamedSequenceToken(const std::string& name); | 197 SequenceToken GetNamedSequenceToken(const std::string& name); |
192 | 198 |
193 // Returns a SequencedTaskRunner wrapper which posts to this | 199 // Returns a SequencedTaskRunner wrapper which posts to this |
194 // SequencedWorkerPool using the given sequence token. Tasks with nonzero | 200 // SequencedWorkerPool using the given sequence token. Tasks with nonzero |
195 // delay are posted with SKIP_ON_SHUTDOWN behavior and tasks with zero delay | 201 // delay are posted with SKIP_ON_SHUTDOWN behavior and tasks with zero delay |
196 // are posted with BLOCK_SHUTDOWN behavior. | 202 // are posted with BLOCK_SHUTDOWN behavior. |
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359 // Avoid pulling in too many headers by putting (almost) everything | 365 // Avoid pulling in too many headers by putting (almost) everything |
360 // into |inner_|. | 366 // into |inner_|. |
361 const scoped_ptr<Inner> inner_; | 367 const scoped_ptr<Inner> inner_; |
362 | 368 |
363 DISALLOW_COPY_AND_ASSIGN(SequencedWorkerPool); | 369 DISALLOW_COPY_AND_ASSIGN(SequencedWorkerPool); |
364 }; | 370 }; |
365 | 371 |
366 } // namespace base | 372 } // namespace base |
367 | 373 |
368 #endif // BASE_THREADING_SEQUENCED_WORKER_POOL_H_ | 374 #endif // BASE_THREADING_SEQUENCED_WORKER_POOL_H_ |
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