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| 1 // Copyright 2017 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 "mojo/public/cpp/system/simple_watcher.h" | |
| 6 | |
| 7 #include "base/bind.h" | |
| 8 #include "base/macros.h" | |
| 9 #include "base/memory/ptr_util.h" | |
| 10 #include "base/single_thread_task_runner.h" | |
| 11 #include "base/synchronization/lock.h" | |
| 12 #include "base/trace_event/heap_profiler.h" | |
| 13 #include "mojo/public/c/system/watcher.h" | |
| 14 | |
| 15 namespace mojo { | |
| 16 | |
| 17 // Thread-safe Context object used to dispatch watch notifications from a | |
| 18 // arbitrary threads. | |
| 19 class SimpleWatcher::Context : public base::RefCountedThreadSafe<Context> { | |
| 20 public: | |
| 21 // Creates a |Context| instance for a new watch on |watcher|, to watch | |
| 22 // |handle| for |signals|. | |
| 23 static scoped_refptr<Context> Create( | |
| 24 base::WeakPtr<SimpleWatcher> watcher, | |
| 25 scoped_refptr<base::SingleThreadTaskRunner> task_runner, | |
| 26 WatcherHandle watcher_handle, | |
| 27 Handle handle, | |
| 28 MojoHandleSignals signals, | |
| 29 MojoResult* watch_result) { | |
| 30 scoped_refptr<Context> context = new Context(watcher, task_runner); | |
| 31 | |
| 32 // If MojoWatch succeeds, it assumes ownership of a reference to |context|. | |
| 33 // In that case, this reference is balanced in CallNotify() when |result| is | |
| 34 // |MOJO_RESULT_CANCELLED|. | |
| 35 context->AddRef(); | |
| 36 | |
| 37 *watch_result = MojoWatch(watcher_handle.value(), handle.value(), signals, | |
| 38 context->value()); | |
| 39 if (*watch_result != MOJO_RESULT_OK) { | |
| 40 // Balanced by the AddRef() above since watching failed. | |
| 41 context->Release(); | |
| 42 return nullptr; | |
| 43 } | |
| 44 | |
| 45 return context; | |
| 46 } | |
| 47 | |
| 48 static void CallNotify(uintptr_t context_value, | |
| 49 MojoResult result, | |
| 50 MojoHandleSignalsState signals_state, | |
| 51 MojoWatcherNotificationFlags flags) { | |
| 52 auto* context = reinterpret_cast<Context*>(context_value); | |
| 53 context->Notify(result, signals_state, flags); | |
| 54 | |
| 55 // That was the last notification for the context. We can release the ref | |
| 56 // owned by the watch, which may in turn delete the Context. | |
| 57 if (result == MOJO_RESULT_CANCELLED) | |
| 58 context->Release(); | |
| 59 } | |
| 60 | |
| 61 uintptr_t value() const { return reinterpret_cast<uintptr_t>(this); } | |
| 62 | |
| 63 void DisableCancellationNotifications() { | |
| 64 base::AutoLock lock(lock_); | |
| 65 enable_cancellation_notifications_ = false; | |
| 66 } | |
| 67 | |
| 68 private: | |
| 69 friend class base::RefCountedThreadSafe<Context>; | |
| 70 | |
| 71 Context(base::WeakPtr<SimpleWatcher> weak_watcher, | |
| 72 scoped_refptr<base::SingleThreadTaskRunner> task_runner) | |
| 73 : weak_watcher_(weak_watcher), task_runner_(task_runner) {} | |
| 74 ~Context() {} | |
| 75 | |
| 76 void Notify(MojoResult result, | |
| 77 MojoHandleSignalsState signals_state, | |
| 78 MojoWatcherNotificationFlags flags) { | |
| 79 if (result == MOJO_RESULT_CANCELLED) { | |
| 80 // The SimpleWatcher may have explicitly cancelled this watch, so we don't | |
| 81 // bother dispatching the notification - it would be ignored anyway. | |
| 82 // | |
| 83 // TODO(rockot): This shouldn't really be necessary, but there are already | |
| 84 // instances today where bindings object may be bound and subsequently | |
| 85 // closed due to pipe error, all before the thread's TaskRunner has been | |
| 86 // properly initialized. | |
| 87 base::AutoLock lock(lock_); | |
| 88 if (!enable_cancellation_notifications_) | |
| 89 return; | |
| 90 } | |
| 91 | |
| 92 if ((flags & MOJO_WATCHER_NOTIFICATION_FLAG_FROM_SYSTEM) && | |
| 93 task_runner_->RunsTasksOnCurrentThread() && weak_watcher_ && | |
| 94 weak_watcher_->is_default_task_runner_) { | |
| 95 // System notifications will trigger from the task runner passed to | |
| 96 // mojo::edk::InitIPCSupport(). In Chrome this happens to always be the | |
| 97 // default task runner for the IO thread. | |
| 98 weak_watcher_->OnHandleReady(make_scoped_refptr(this), result); | |
| 99 } else { | |
| 100 task_runner_->PostTask( | |
| 101 FROM_HERE, base::Bind(&SimpleWatcher::OnHandleReady, weak_watcher_, | |
| 102 make_scoped_refptr(this), result)); | |
| 103 } | |
| 104 } | |
| 105 | |
| 106 const base::WeakPtr<SimpleWatcher> weak_watcher_; | |
| 107 const scoped_refptr<base::SingleThreadTaskRunner> task_runner_; | |
| 108 | |
| 109 base::Lock lock_; | |
| 110 bool enable_cancellation_notifications_ = true; | |
| 111 | |
| 112 DISALLOW_COPY_AND_ASSIGN(Context); | |
| 113 }; | |
| 114 | |
| 115 SimpleWatcher::SimpleWatcher(const tracked_objects::Location& from_here, | |
| 116 ArmingPolicy arming_policy, | |
| 117 scoped_refptr<base::SingleThreadTaskRunner> runner) | |
| 118 : arming_policy_(arming_policy), | |
| 119 task_runner_(std::move(runner)), | |
| 120 is_default_task_runner_(task_runner_ == | |
| 121 base::ThreadTaskRunnerHandle::Get()), | |
| 122 heap_profiler_tag_(from_here.file_name()), | |
| 123 weak_factory_(this) { | |
| 124 MojoResult rv = CreateWatcher(&Context::CallNotify, &watcher_handle_); | |
| 125 DCHECK_EQ(MOJO_RESULT_OK, rv); | |
| 126 DCHECK(task_runner_->BelongsToCurrentThread()); | |
| 127 } | |
| 128 | |
| 129 SimpleWatcher::~SimpleWatcher() { | |
| 130 if (IsWatching()) | |
| 131 Cancel(); | |
| 132 } | |
| 133 | |
| 134 bool SimpleWatcher::IsWatching() const { | |
| 135 DCHECK(thread_checker_.CalledOnValidThread()); | |
| 136 return context_ != nullptr; | |
| 137 } | |
| 138 | |
| 139 MojoResult SimpleWatcher::Watch(Handle handle, | |
| 140 MojoHandleSignals signals, | |
| 141 const ReadyCallback& callback) { | |
| 142 DCHECK(thread_checker_.CalledOnValidThread()); | |
| 143 DCHECK(!IsWatching()); | |
| 144 DCHECK(!callback.is_null()); | |
| 145 | |
| 146 callback_ = callback; | |
| 147 handle_ = handle; | |
| 148 | |
| 149 MojoResult watch_result = MOJO_RESULT_UNKNOWN; | |
| 150 context_ = | |
| 151 Context::Create(weak_factory_.GetWeakPtr(), task_runner_, | |
| 152 watcher_handle_.get(), handle_, signals, &watch_result); | |
| 153 if (!context_) { | |
| 154 handle_.set_value(kInvalidHandleValue); | |
| 155 callback_.Reset(); | |
| 156 DCHECK_EQ(MOJO_RESULT_INVALID_ARGUMENT, watch_result); | |
| 157 return watch_result; | |
| 158 } | |
| 159 | |
| 160 if (arming_policy_ == ArmingPolicy::AUTOMATIC) | |
| 161 ArmOrNotify(); | |
| 162 | |
| 163 return MOJO_RESULT_OK; | |
| 164 } | |
| 165 | |
| 166 void SimpleWatcher::Cancel() { | |
| 167 DCHECK(thread_checker_.CalledOnValidThread()); | |
| 168 | |
| 169 // The watcher may have already been cancelled if the handle was closed. | |
| 170 if (!context_) | |
| 171 return; | |
| 172 | |
| 173 // Prevent the cancellation notification from being dispatched to | |
| 174 // OnHandleReady() when cancellation is explicit. See the note in the | |
| 175 // implementation of DisableCancellationNotifications() above. | |
| 176 context_->DisableCancellationNotifications(); | |
| 177 | |
| 178 handle_.set_value(kInvalidHandleValue); | |
| 179 callback_.Reset(); | |
| 180 | |
| 181 // Ensure |context_| is unset by the time we call MojoCancelWatch, as may | |
| 182 // re-enter the notification callback and we want to ensure |context_| is | |
| 183 // unset by then. | |
| 184 scoped_refptr<Context> context; | |
| 185 std::swap(context, context_); | |
| 186 MojoResult rv = | |
| 187 MojoCancelWatch(watcher_handle_.get().value(), context->value()); | |
| 188 | |
| 189 // It's possible this cancellation could race with a handle closure | |
| 190 // notification, in which case the watch may have already been implicitly | |
| 191 // cancelled. | |
| 192 DCHECK(rv == MOJO_RESULT_OK || rv == MOJO_RESULT_NOT_FOUND); | |
| 193 } | |
| 194 | |
| 195 MojoResult SimpleWatcher::Arm(MojoResult* ready_result) { | |
| 196 DCHECK(thread_checker_.CalledOnValidThread()); | |
| 197 uint32_t num_ready_contexts = 1; | |
| 198 uintptr_t ready_context; | |
| 199 MojoResult local_ready_result; | |
| 200 MojoHandleSignalsState ready_state; | |
| 201 MojoResult rv = | |
| 202 MojoArmWatcher(watcher_handle_.get().value(), &num_ready_contexts, | |
| 203 &ready_context, &local_ready_result, &ready_state); | |
| 204 if (rv == MOJO_RESULT_FAILED_PRECONDITION) { | |
| 205 DCHECK(context_); | |
| 206 DCHECK_EQ(1u, num_ready_contexts); | |
| 207 DCHECK_EQ(context_->value(), ready_context); | |
| 208 if (ready_result) | |
| 209 *ready_result = local_ready_result; | |
| 210 } | |
| 211 | |
| 212 return rv; | |
| 213 } | |
| 214 | |
| 215 void SimpleWatcher::ArmOrNotify() { | |
| 216 DCHECK(thread_checker_.CalledOnValidThread()); | |
| 217 | |
| 218 // Already cancelled, nothing to do. | |
| 219 if (!IsWatching()) | |
| 220 return; | |
| 221 | |
| 222 MojoResult ready_result; | |
| 223 MojoResult rv = Arm(&ready_result); | |
| 224 if (rv == MOJO_RESULT_OK) | |
| 225 return; | |
| 226 | |
| 227 DCHECK_EQ(MOJO_RESULT_FAILED_PRECONDITION, rv); | |
| 228 task_runner_->PostTask(FROM_HERE, base::Bind(&SimpleWatcher::OnHandleReady, | |
| 229 weak_factory_.GetWeakPtr(), | |
| 230 context_, ready_result)); | |
| 231 } | |
| 232 | |
| 233 void SimpleWatcher::OnHandleReady(scoped_refptr<const Context> context, | |
| 234 MojoResult result) { | |
| 235 DCHECK(thread_checker_.CalledOnValidThread()); | |
| 236 | |
| 237 // This notification may be for a previously watched context, in which case | |
| 238 // we just ignore it. | |
| 239 if (context != context_) | |
| 240 return; | |
| 241 | |
| 242 ReadyCallback callback = callback_; | |
| 243 if (result == MOJO_RESULT_CANCELLED) { | |
| 244 // Implicit cancellation due to someone closing the watched handle. We clear | |
| 245 // the SimppleWatcher's state before dispatching this. | |
| 246 context_ = nullptr; | |
| 247 handle_.set_value(kInvalidHandleValue); | |
| 248 callback_.Reset(); | |
| 249 } | |
| 250 | |
| 251 // NOTE: It's legal for |callback| to delete |this|. | |
| 252 if (!callback.is_null()) { | |
| 253 TRACE_HEAP_PROFILER_API_SCOPED_TASK_EXECUTION event(heap_profiler_tag_); | |
| 254 | |
| 255 base::WeakPtr<SimpleWatcher> weak_self = weak_factory_.GetWeakPtr(); | |
| 256 callback.Run(result); | |
| 257 if (!weak_self) | |
| 258 return; | |
| 259 | |
| 260 if (unsatisfiable_) | |
| 261 return; | |
| 262 | |
| 263 // Prevent |MOJO_RESULT_FAILED_PRECONDITION| task spam by only notifying | |
| 264 // at most once in AUTOMATIC arming mode. | |
| 265 if (result == MOJO_RESULT_FAILED_PRECONDITION) | |
| 266 unsatisfiable_ = true; | |
| 267 | |
| 268 if (arming_policy_ == ArmingPolicy::AUTOMATIC && IsWatching()) | |
| 269 ArmOrNotify(); | |
| 270 } | |
| 271 } | |
| 272 | |
| 273 } // namespace mojo | |
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Chromium Code Reviews
Issue 2750373002:
Revert of Mojo: Armed Watchers (Closed)
