ipc/chromium/src/base/object_watcher.cc@6474c204b198 (annotated)
ipc/chromium/src/base/object_watcher.cc
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) 2006-2008 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 | #include "base/object_watcher.h" |
| michael@0 | 6 | |
| michael@0 | 7 | #include "base/logging.h" |
| michael@0 | 8 | |
| michael@0 | 9 | namespace base { |
| michael@0 | 10 | |
| michael@0 | 11 | //----------------------------------------------------------------------------- |
| michael@0 | 12 | |
| michael@0 | 13 | struct ObjectWatcher::Watch : public Task { |
| michael@0 | 14 | ObjectWatcher* watcher; // The associated ObjectWatcher instance |
| michael@0 | 15 | HANDLE object; // The object being watched |
| michael@0 | 16 | HANDLE wait_object; // Returned by RegisterWaitForSingleObject |
| michael@0 | 17 | MessageLoop* origin_loop; // Used to get back to the origin thread |
| michael@0 | 18 | Delegate* delegate; // Delegate to notify when signaled |
| michael@0 | 19 | bool did_signal; // DoneWaiting was called |
| michael@0 | 20 | |
| michael@0 | 21 | virtual void Run() { |
| michael@0 | 22 | // The watcher may have already been torn down, in which case we need to |
| michael@0 | 23 | // just get out of dodge. |
| michael@0 | 24 | if (!watcher) |
| michael@0 | 25 | return; |
| michael@0 | 26 | |
| michael@0 | 27 | DCHECK(did_signal); |
| michael@0 | 28 | watcher->StopWatching(); |
| michael@0 | 29 | |
| michael@0 | 30 | delegate->OnObjectSignaled(object); |
| michael@0 | 31 | } |
| michael@0 | 32 | }; |
| michael@0 | 33 | |
| michael@0 | 34 | //----------------------------------------------------------------------------- |
| michael@0 | 35 | |
| michael@0 | 36 | ObjectWatcher::ObjectWatcher() : watch_(NULL) { |
| michael@0 | 37 | } |
| michael@0 | 38 | |
| michael@0 | 39 | ObjectWatcher::~ObjectWatcher() { |
| michael@0 | 40 | StopWatching(); |
| michael@0 | 41 | } |
| michael@0 | 42 | |
| michael@0 | 43 | bool ObjectWatcher::StartWatching(HANDLE object, Delegate* delegate) { |
| michael@0 | 44 | if (watch_) { |
| michael@0 | 45 | NOTREACHED() << "Already watching an object"; |
| michael@0 | 46 | return false; |
| michael@0 | 47 | } |
| michael@0 | 48 | |
| michael@0 | 49 | Watch* watch = new Watch; |
| michael@0 | 50 | watch->watcher = this; |
| michael@0 | 51 | watch->object = object; |
| michael@0 | 52 | watch->origin_loop = MessageLoop::current(); |
| michael@0 | 53 | watch->delegate = delegate; |
| michael@0 | 54 | watch->did_signal = false; |
| michael@0 | 55 | |
| michael@0 | 56 | // Since our job is to just notice when an object is signaled and report the |
| michael@0 | 57 | // result back to this thread, we can just run on a Windows wait thread. |
| michael@0 | 58 | DWORD wait_flags = WT_EXECUTEDEFAULT | WT_EXECUTEONLYONCE; |
| michael@0 | 59 | |
| michael@0 | 60 | if (!RegisterWaitForSingleObject(&watch->wait_object, object, DoneWaiting, |
| michael@0 | 61 | watch, INFINITE, wait_flags)) { |
| michael@0 | 62 | NOTREACHED() << "RegisterWaitForSingleObject failed: " << GetLastError(); |
| michael@0 | 63 | delete watch; |
| michael@0 | 64 | return false; |
| michael@0 | 65 | } |
| michael@0 | 66 | |
| michael@0 | 67 | watch_ = watch; |
| michael@0 | 68 | |
| michael@0 | 69 | // We need to know if the current message loop is going away so we can |
| michael@0 | 70 | // prevent the wait thread from trying to access a dead message loop. |
| michael@0 | 71 | MessageLoop::current()->AddDestructionObserver(this); |
| michael@0 | 72 | return true; |
| michael@0 | 73 | } |
| michael@0 | 74 | |
| michael@0 | 75 | bool ObjectWatcher::StopWatching() { |
| michael@0 | 76 | if (!watch_) |
| michael@0 | 77 | return false; |
| michael@0 | 78 | |
| michael@0 | 79 | // Make sure ObjectWatcher is used in a single-threaded fashion. |
| michael@0 | 80 | DCHECK(watch_->origin_loop == MessageLoop::current()); |
| michael@0 | 81 | |
| michael@0 | 82 | // If DoneWaiting is in progress, we wait for it to finish. We know whether |
| michael@0 | 83 | // DoneWaiting happened or not by inspecting the did_signal flag. |
| michael@0 | 84 | if (!UnregisterWaitEx(watch_->wait_object, INVALID_HANDLE_VALUE)) { |
| michael@0 | 85 | NOTREACHED() << "UnregisterWaitEx failed: " << GetLastError(); |
| michael@0 | 86 | return false; |
| michael@0 | 87 | } |
| michael@0 | 88 | |
| michael@0 | 89 | // Make sure that we see any mutation to did_signal. This should be a no-op |
| michael@0 | 90 | // since we expect that UnregisterWaitEx resulted in a memory barrier, but |
| michael@0 | 91 | // just to be sure, we're going to be explicit. |
| michael@0 | 92 | MemoryBarrier(); |
| michael@0 | 93 | |
| michael@0 | 94 | // If the watch has been posted, then we need to make sure it knows not to do |
| michael@0 | 95 | // anything once it is run. |
| michael@0 | 96 | watch_->watcher = NULL; |
| michael@0 | 97 | |
| michael@0 | 98 | // If DoneWaiting was called, then the watch would have been posted as a |
| michael@0 | 99 | // task, and will therefore be deleted by the MessageLoop. Otherwise, we |
| michael@0 | 100 | // need to take care to delete it here. |
| michael@0 | 101 | if (!watch_->did_signal) |
| michael@0 | 102 | delete watch_; |
| michael@0 | 103 | |
| michael@0 | 104 | watch_ = NULL; |
| michael@0 | 105 | |
| michael@0 | 106 | MessageLoop::current()->RemoveDestructionObserver(this); |
| michael@0 | 107 | return true; |
| michael@0 | 108 | } |
| michael@0 | 109 | |
| michael@0 | 110 | HANDLE ObjectWatcher::GetWatchedObject() { |
| michael@0 | 111 | if (!watch_) |
| michael@0 | 112 | return NULL; |
| michael@0 | 113 | |
| michael@0 | 114 | return watch_->object; |
| michael@0 | 115 | } |
| michael@0 | 116 | |
| michael@0 | 117 | // static |
| michael@0 | 118 | void CALLBACK ObjectWatcher::DoneWaiting(void* param, BOOLEAN timed_out) { |
| michael@0 | 119 | DCHECK(!timed_out); |
| michael@0 | 120 | |
| michael@0 | 121 | Watch* watch = static_cast<Watch*>(param); |
| michael@0 | 122 | |
| michael@0 | 123 | // Record that we ran this function. |
| michael@0 | 124 | watch->did_signal = true; |
| michael@0 | 125 | |
| michael@0 | 126 | // We rely on the locking in PostTask() to ensure that a memory barrier is |
| michael@0 | 127 | // provided, which in turn ensures our change to did_signal can be observed |
| michael@0 | 128 | // on the target thread. |
| michael@0 | 129 | watch->origin_loop->PostTask(FROM_HERE, watch); |
| michael@0 | 130 | } |
| michael@0 | 131 | |
| michael@0 | 132 | void ObjectWatcher::WillDestroyCurrentMessageLoop() { |
| michael@0 | 133 | // Need to shutdown the watch so that we don't try to access the MessageLoop |
| michael@0 | 134 | // after this point. |
| michael@0 | 135 | StopWatching(); |
| michael@0 | 136 | } |
| michael@0 | 137 | |
| michael@0 | 138 | } // namespace base |
