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| 1 // Copyright (c) 2011 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 #include "base/threading/post_task_and_reply_impl.h" | |
| 6 | |
| 7 #include "base/bind.h" | |
| 8 #include "base/location.h" | |
| 9 #include "base/single_thread_task_runner.h" | |
| 10 #include "base/thread_task_runner_handle.h" | |
| 11 | |
| 12 namespace base { | |
| 13 | |
| 14 namespace { | |
| 15 | |
| 16 // This relay class remembers the MessageLoop that it was created on, and | |
| 17 // ensures that both the |task| and |reply| Closures are deleted on this same | |
| 18 // thread. Also, |task| is guaranteed to be deleted before |reply| is run or | |
| 19 // deleted. | |
| 20 // | |
| 21 // If this is not possible because the originating MessageLoop is no longer | |
| 22 // available, the the |task| and |reply| Closures are leaked. Leaking is | |
| 23 // considered preferable to having a thread-safetey violations caused by | |
| 24 // invoking the Closure destructor on the wrong thread. | |
| 25 class PostTaskAndReplyRelay { | |
| 26 public: | |
| 27 PostTaskAndReplyRelay(const tracked_objects::Location& from_here, | |
| 28 const Closure& task, | |
| 29 const Closure& reply) | |
| 30 : from_here_(from_here), | |
| 31 origin_task_runner_(ThreadTaskRunnerHandle::Get()) { | |
| 32 task_ = task; | |
| 33 reply_ = reply; | |
| 34 } | |
| 35 | |
| 36 ~PostTaskAndReplyRelay() { | |
| 37 DCHECK(origin_task_runner_->BelongsToCurrentThread()); | |
| 38 task_.Reset(); | |
| 39 reply_.Reset(); | |
| 40 } | |
| 41 | |
| 42 void Run() { | |
| 43 task_.Run(); | |
| 44 origin_task_runner_->PostTask( | |
| 45 from_here_, Bind(&PostTaskAndReplyRelay::RunReplyAndSelfDestruct, | |
| 46 base::Unretained(this))); | |
| 47 } | |
| 48 | |
| 49 private: | |
| 50 void RunReplyAndSelfDestruct() { | |
| 51 DCHECK(origin_task_runner_->BelongsToCurrentThread()); | |
| 52 | |
| 53 // Force |task_| to be released before |reply_| is to ensure that no one | |
| 54 // accidentally depends on |task_| keeping one of its arguments alive while | |
| 55 // |reply_| is executing. | |
| 56 task_.Reset(); | |
| 57 | |
| 58 reply_.Run(); | |
| 59 | |
| 60 // Cue mission impossible theme. | |
| 61 delete this; | |
| 62 } | |
| 63 | |
| 64 tracked_objects::Location from_here_; | |
| 65 scoped_refptr<SingleThreadTaskRunner> origin_task_runner_; | |
| 66 Closure reply_; | |
| 67 Closure task_; | |
| 68 }; | |
| 69 | |
| 70 } // namespace | |
| 71 | |
| 72 namespace internal { | |
| 73 | |
| 74 bool PostTaskAndReplyImpl::PostTaskAndReply( | |
| 75 const tracked_objects::Location& from_here, | |
| 76 const Closure& task, | |
| 77 const Closure& reply) { | |
| 78 PostTaskAndReplyRelay* relay = | |
| 79 new PostTaskAndReplyRelay(from_here, task, reply); | |
| 80 if (!PostTask(from_here, Bind(&PostTaskAndReplyRelay::Run, | |
| 81 Unretained(relay)))) { | |
| 82 delete relay; | |
| 83 return false; | |
| 84 } | |
| 85 | |
| 86 return true; | |
| 87 } | |
| 88 | |
| 89 } // namespace internal | |
| 90 | |
| 91 } // namespace base | |
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