| // Copyright 2017 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "mojo/public/cpp/system/wait.h" |
| |
| #include <memory> |
| #include <vector> |
| |
| #include "base/memory/ptr_util.h" |
| #include "base/memory/ref_counted.h" |
| #include "base/synchronization/waitable_event.h" |
| #include "mojo/public/c/system/watcher.h" |
| #include "mojo/public/cpp/system/watcher.h" |
| |
| namespace mojo { |
| namespace { |
| |
| class WatchContext : public base::RefCountedThreadSafe<WatchContext> { |
| public: |
| WatchContext() |
| : event_(base::WaitableEvent::ResetPolicy::AUTOMATIC, |
| base::WaitableEvent::InitialState::NOT_SIGNALED) {} |
| |
| base::WaitableEvent& event() { return event_; } |
| MojoResult wait_result() const { return wait_result_; } |
| MojoHandleSignalsState wait_state() const { return wait_state_; } |
| uintptr_t context_value() const { return reinterpret_cast<uintptr_t>(this); } |
| |
| static void OnNotification(uintptr_t context_value, |
| MojoResult result, |
| MojoHandleSignalsState state, |
| MojoWatcherNotificationFlags flags) { |
| auto* context = reinterpret_cast<WatchContext*>(context_value); |
| context->Notify(result, state); |
| if (result == MOJO_RESULT_CANCELLED) { |
| // Balanced in Wait() or WaitMany(). |
| context->Release(); |
| } |
| } |
| |
| private: |
| friend class base::RefCountedThreadSafe<WatchContext>; |
| |
| ~WatchContext() {} |
| |
| void Notify(MojoResult result, MojoHandleSignalsState state) { |
| if (wait_result_ == MOJO_RESULT_UNKNOWN) { |
| wait_result_ = result; |
| wait_state_ = state; |
| } |
| event_.Signal(); |
| } |
| |
| base::WaitableEvent event_; |
| |
| // NOTE: Although these are modified in Notify() which may be called from any |
| // sequence, Notify() is guaranteed to never run concurrently with itself. |
| // Furthermore, they are only modified once, before |event_| signals; so there |
| // is no need for a WatchContext user to synchronize access to these fields |
| // apart from waiting on |event()|. |
| MojoResult wait_result_ = MOJO_RESULT_UNKNOWN; |
| MojoHandleSignalsState wait_state_ = {0, 0}; |
| |
| DISALLOW_COPY_AND_ASSIGN(WatchContext); |
| }; |
| |
| } // namespace |
| |
| MojoResult Wait(Handle handle, |
| MojoHandleSignals signals, |
| MojoWatchCondition condition, |
| MojoHandleSignalsState* signals_state) { |
| ScopedWatcherHandle watcher; |
| MojoResult rv = CreateWatcher(&WatchContext::OnNotification, &watcher); |
| DCHECK_EQ(MOJO_RESULT_OK, rv); |
| |
| scoped_refptr<WatchContext> context = new WatchContext; |
| |
| // Balanced in WatchContext::OnNotification if MojoWatch() is successful. |
| // Otherwise balanced immediately below. |
| context->AddRef(); |
| |
| rv = MojoWatch(watcher.get().value(), handle.value(), signals, condition, |
| context->context_value()); |
| if (rv == MOJO_RESULT_INVALID_ARGUMENT) { |
| // Balanced above. |
| context->Release(); |
| return rv; |
| } |
| DCHECK_EQ(MOJO_RESULT_OK, rv); |
| |
| uint32_t num_ready_contexts = 1; |
| uintptr_t ready_context; |
| MojoResult ready_result; |
| MojoHandleSignalsState ready_state; |
| rv = MojoArmWatcher(watcher.get().value(), &num_ready_contexts, |
| &ready_context, &ready_result, &ready_state); |
| if (rv == MOJO_RESULT_FAILED_PRECONDITION) { |
| DCHECK_EQ(1u, num_ready_contexts); |
| if (signals_state) |
| *signals_state = ready_state; |
| return ready_result; |
| } |
| |
| // Wait for the first notification only. |
| context->event().Wait(); |
| |
| ready_result = context->wait_result(); |
| DCHECK_NE(MOJO_RESULT_UNKNOWN, ready_result); |
| |
| if (signals_state) |
| *signals_state = context->wait_state(); |
| |
| return ready_result; |
| } |
| |
| MojoResult WaitMany(const Handle* handles, |
| const MojoHandleSignals* signals, |
| size_t num_handles, |
| size_t* result_index, |
| MojoHandleSignalsState* signals_states) { |
| if (!handles || !signals) |
| return MOJO_RESULT_INVALID_ARGUMENT; |
| |
| ScopedWatcherHandle watcher; |
| MojoResult rv = CreateWatcher(&WatchContext::OnNotification, &watcher); |
| DCHECK_EQ(MOJO_RESULT_OK, rv); |
| |
| std::vector<scoped_refptr<WatchContext>> contexts(num_handles); |
| std::vector<base::WaitableEvent*> events(num_handles); |
| for (size_t i = 0; i < num_handles; ++i) { |
| contexts[i] = new WatchContext(); |
| |
| // Balanced in WatchContext::OnNotification if MojoWatch() is successful. |
| // Otherwise balanced immediately below. |
| contexts[i]->AddRef(); |
| |
| MojoResult rv = |
| MojoWatch(watcher.get().value(), handles[i].value(), signals[i], |
| MOJO_WATCH_CONDITION_SATISFIED, contexts[i]->context_value()); |
| if (rv == MOJO_RESULT_INVALID_ARGUMENT) { |
| if (result_index) |
| *result_index = i; |
| |
| // Balanced above. |
| contexts[i]->Release(); |
| |
| return MOJO_RESULT_INVALID_ARGUMENT; |
| } |
| |
| events[i] = &contexts[i]->event(); |
| } |
| |
| uint32_t num_ready_contexts = 1; |
| uintptr_t ready_context = 0; |
| MojoResult ready_result = MOJO_RESULT_UNKNOWN; |
| MojoHandleSignalsState ready_state{0, 0}; |
| rv = MojoArmWatcher(watcher.get().value(), &num_ready_contexts, |
| &ready_context, &ready_result, &ready_state); |
| |
| size_t index = num_handles; |
| if (rv == MOJO_RESULT_FAILED_PRECONDITION) { |
| DCHECK_EQ(1u, num_ready_contexts); |
| |
| // Most commonly we only watch a small number of handles. Just scan for |
| // the right index. |
| for (size_t i = 0; i < num_handles; ++i) { |
| if (contexts[i]->context_value() == ready_context) { |
| index = i; |
| break; |
| } |
| } |
| } else { |
| DCHECK_EQ(MOJO_RESULT_OK, rv); |
| |
| // Wait for one of the contexts to signal. First one wins. |
| index = base::WaitableEvent::WaitMany(events.data(), events.size()); |
| ready_result = contexts[index]->wait_result(); |
| ready_state = contexts[index]->wait_state(); |
| } |
| |
| DCHECK_NE(MOJO_RESULT_UNKNOWN, ready_result); |
| DCHECK_LT(index, num_handles); |
| |
| if (result_index) |
| *result_index = index; |
| |
| if (signals_states) { |
| for (size_t i = 0; i < num_handles; ++i) { |
| if (i == index) { |
| signals_states[i] = ready_state; |
| } else { |
| signals_states[i] = handles[i].QuerySignalsState(); |
| } |
| } |
| } |
| |
| return ready_result; |
| } |
| |
| } // namespace mojo |