| // Copyright 2013 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/edk/system/core.h" |
| |
| #include <vector> |
| |
| #include "base/logging.h" |
| #include "base/time/time.h" |
| #include "mojo/edk/embedder/platform_shared_buffer.h" |
| #include "mojo/edk/embedder/platform_support.h" |
| #include "mojo/edk/system/async_waiter.h" |
| #include "mojo/edk/system/configuration.h" |
| #include "mojo/edk/system/data_pipe.h" |
| #include "mojo/edk/system/data_pipe_consumer_dispatcher.h" |
| #include "mojo/edk/system/data_pipe_producer_dispatcher.h" |
| #include "mojo/edk/system/dispatcher.h" |
| #include "mojo/edk/system/handle_signals_state.h" |
| #include "mojo/edk/system/memory.h" |
| #include "mojo/edk/system/message_pipe.h" |
| #include "mojo/edk/system/message_pipe_dispatcher.h" |
| #include "mojo/edk/system/shared_buffer_dispatcher.h" |
| #include "mojo/edk/system/waiter.h" |
| #include "mojo/public/c/system/macros.h" |
| #include "mojo/public/cpp/system/macros.h" |
| |
| namespace mojo { |
| namespace system { |
| |
| // Implementation notes |
| // |
| // Mojo primitives are implemented by the singleton |Core| object. Most calls |
| // are for a "primary" handle (the first argument). |Core::GetDispatcher()| is |
| // used to look up a |Dispatcher| object for a given handle. That object |
| // implements most primitives for that object. The wait primitives are not |
| // attached to objects and are implemented by |Core| itself. |
| // |
| // Some objects have multiple handles associated to them, e.g., message pipes |
| // (which have two). In such a case, there is still a |Dispatcher| (e.g., |
| // |MessagePipeDispatcher|) for each handle, with each handle having a strong |
| // reference to the common "secondary" object (e.g., |MessagePipe|). This |
| // secondary object does NOT have any references to the |Dispatcher|s (even if |
| // it did, it wouldn't be able to do anything with them due to lock order |
| // requirements -- see below). |
| // |
| // Waiting is implemented by having the thread that wants to wait call the |
| // |Dispatcher|s for the handles that it wants to wait on with a |Waiter| |
| // object; this |Waiter| object may be created on the stack of that thread or be |
| // kept in thread local storage for that thread (TODO(vtl): future improvement). |
| // The |Dispatcher| then adds the |Waiter| to an |AwakableList| that's either |
| // owned by that |Dispatcher| (see |SimpleDispatcher|) or by a secondary object |
| // (e.g., |MessagePipe|). To signal/wake a |Waiter|, the object in question -- |
| // either a |SimpleDispatcher| or a secondary object -- talks to its |
| // |AwakableList|. |
| |
| // Thread-safety notes |
| // |
| // Mojo primitives calls are thread-safe. We achieve this with relatively |
| // fine-grained locking. There is a global handle table lock. This lock should |
| // be held as briefly as possible (TODO(vtl): a future improvement would be to |
| // switch it to a reader-writer lock). Each |Dispatcher| object then has a lock |
| // (which subclasses can use to protect their data). |
| // |
| // The lock ordering is as follows: |
| // 1. global handle table lock, global mapping table lock |
| // 2. |Dispatcher| locks |
| // 3. secondary object locks |
| // ... |
| // INF. |Waiter| locks |
| // |
| // Notes: |
| // - While holding a |Dispatcher| lock, you may not unconditionally attempt |
| // to take another |Dispatcher| lock. (This has consequences on the |
| // concurrency semantics of |MojoWriteMessage()| when passing handles.) |
| // Doing so would lead to deadlock. |
| // - Locks at the "INF" level may not have any locks taken while they are |
| // held. |
| |
| // TODO(vtl): This should take a |scoped_ptr<PlatformSupport>| as a parameter. |
| Core::Core(embedder::PlatformSupport* platform_support) |
| : platform_support_(platform_support) { |
| } |
| |
| Core::~Core() { |
| } |
| |
| MojoHandle Core::AddDispatcher(const scoped_refptr<Dispatcher>& dispatcher) { |
| MutexLocker locker(&handle_table_mutex_); |
| return handle_table_.AddDispatcher(dispatcher); |
| } |
| |
| scoped_refptr<Dispatcher> Core::GetDispatcher(MojoHandle handle) { |
| if (handle == MOJO_HANDLE_INVALID) |
| return nullptr; |
| |
| MutexLocker locker(&handle_table_mutex_); |
| return handle_table_.GetDispatcher(handle); |
| } |
| |
| MojoResult Core::GetAndRemoveDispatcher(MojoHandle handle, |
| scoped_refptr<Dispatcher>* dispatcher) { |
| if (handle == MOJO_HANDLE_INVALID) |
| return MOJO_RESULT_INVALID_ARGUMENT; |
| |
| MutexLocker locker(&handle_table_mutex_); |
| return handle_table_.GetAndRemoveDispatcher(handle, dispatcher); |
| } |
| |
| MojoResult Core::AsyncWait(MojoHandle handle, |
| MojoHandleSignals signals, |
| const base::Callback<void(MojoResult)>& callback) { |
| scoped_refptr<Dispatcher> dispatcher = GetDispatcher(handle); |
| DCHECK(dispatcher); |
| |
| scoped_ptr<AsyncWaiter> waiter = make_scoped_ptr(new AsyncWaiter(callback)); |
| MojoResult rv = dispatcher->AddAwakable(waiter.get(), signals, 0, nullptr); |
| if (rv == MOJO_RESULT_OK) |
| ignore_result(waiter.release()); |
| return rv; |
| } |
| |
| MojoTimeTicks Core::GetTimeTicksNow() { |
| return base::TimeTicks::Now().ToInternalValue(); |
| } |
| |
| MojoResult Core::Close(MojoHandle handle) { |
| if (handle == MOJO_HANDLE_INVALID) |
| return MOJO_RESULT_INVALID_ARGUMENT; |
| |
| scoped_refptr<Dispatcher> dispatcher; |
| { |
| MutexLocker locker(&handle_table_mutex_); |
| MojoResult result = |
| handle_table_.GetAndRemoveDispatcher(handle, &dispatcher); |
| if (result != MOJO_RESULT_OK) |
| return result; |
| } |
| |
| // The dispatcher doesn't have a say in being closed, but gets notified of it. |
| // Note: This is done outside of |handle_table_mutex_|. As a result, there's a |
| // race condition that the dispatcher must handle; see the comment in |
| // |Dispatcher| in dispatcher.h. |
| return dispatcher->Close(); |
| } |
| |
| MojoResult Core::Wait(MojoHandle handle, |
| MojoHandleSignals signals, |
| MojoDeadline deadline, |
| UserPointer<MojoHandleSignalsState> signals_state) { |
| uint32_t unused = static_cast<uint32_t>(-1); |
| HandleSignalsState hss; |
| MojoResult rv = WaitManyInternal(&handle, &signals, 1, deadline, &unused, |
| signals_state.IsNull() ? nullptr : &hss); |
| if (rv != MOJO_RESULT_INVALID_ARGUMENT && !signals_state.IsNull()) |
| signals_state.Put(hss); |
| return rv; |
| } |
| |
| MojoResult Core::WaitMany(UserPointer<const MojoHandle> handles, |
| UserPointer<const MojoHandleSignals> signals, |
| uint32_t num_handles, |
| MojoDeadline deadline, |
| UserPointer<uint32_t> result_index, |
| UserPointer<MojoHandleSignalsState> signals_states) { |
| if (num_handles < 1) |
| return MOJO_RESULT_INVALID_ARGUMENT; |
| if (num_handles > GetConfiguration().max_wait_many_num_handles) |
| return MOJO_RESULT_RESOURCE_EXHAUSTED; |
| |
| UserPointer<const MojoHandle>::Reader handles_reader(handles, num_handles); |
| UserPointer<const MojoHandleSignals>::Reader signals_reader(signals, |
| num_handles); |
| uint32_t index = static_cast<uint32_t>(-1); |
| MojoResult rv; |
| if (signals_states.IsNull()) { |
| rv = WaitManyInternal(handles_reader.GetPointer(), |
| signals_reader.GetPointer(), num_handles, deadline, |
| &index, nullptr); |
| } else { |
| UserPointer<MojoHandleSignalsState>::Writer signals_states_writer( |
| signals_states, num_handles); |
| // Note: The |reinterpret_cast| is safe, since |HandleSignalsState| is a |
| // subclass of |MojoHandleSignalsState| that doesn't add any data members. |
| rv = WaitManyInternal(handles_reader.GetPointer(), |
| signals_reader.GetPointer(), num_handles, deadline, |
| &index, reinterpret_cast<HandleSignalsState*>( |
| signals_states_writer.GetPointer())); |
| if (rv != MOJO_RESULT_INVALID_ARGUMENT) |
| signals_states_writer.Commit(); |
| } |
| if (index != static_cast<uint32_t>(-1) && !result_index.IsNull()) |
| result_index.Put(index); |
| return rv; |
| } |
| |
| MojoResult Core::CreateMessagePipe( |
| UserPointer<const MojoCreateMessagePipeOptions> options, |
| UserPointer<MojoHandle> message_pipe_handle0, |
| UserPointer<MojoHandle> message_pipe_handle1) { |
| MojoCreateMessagePipeOptions validated_options = {}; |
| MojoResult result = |
| MessagePipeDispatcher::ValidateCreateOptions(options, &validated_options); |
| if (result != MOJO_RESULT_OK) |
| return result; |
| |
| scoped_refptr<MessagePipeDispatcher> dispatcher0 = |
| MessagePipeDispatcher::Create(validated_options); |
| scoped_refptr<MessagePipeDispatcher> dispatcher1 = |
| MessagePipeDispatcher::Create(validated_options); |
| |
| std::pair<MojoHandle, MojoHandle> handle_pair; |
| { |
| MutexLocker locker(&handle_table_mutex_); |
| handle_pair = handle_table_.AddDispatcherPair(dispatcher0, dispatcher1); |
| } |
| if (handle_pair.first == MOJO_HANDLE_INVALID) { |
| DCHECK_EQ(handle_pair.second, MOJO_HANDLE_INVALID); |
| LOG(ERROR) << "Handle table full"; |
| dispatcher0->Close(); |
| dispatcher1->Close(); |
| return MOJO_RESULT_RESOURCE_EXHAUSTED; |
| } |
| |
| scoped_refptr<MessagePipe> message_pipe(MessagePipe::CreateLocalLocal()); |
| dispatcher0->Init(message_pipe, 0); |
| dispatcher1->Init(message_pipe, 1); |
| |
| message_pipe_handle0.Put(handle_pair.first); |
| message_pipe_handle1.Put(handle_pair.second); |
| return MOJO_RESULT_OK; |
| } |
| |
| // Implementation note: To properly cancel waiters and avoid other races, this |
| // does not transfer dispatchers from one handle to another, even when sending a |
| // message in-process. Instead, it must transfer the "contents" of the |
| // dispatcher to a new dispatcher, and then close the old dispatcher. If this |
| // isn't done, in the in-process case, calls on the old handle may complete |
| // after the the message has been received and a new handle created (and |
| // possibly even after calls have been made on the new handle). |
| MojoResult Core::WriteMessage(MojoHandle message_pipe_handle, |
| UserPointer<const void> bytes, |
| uint32_t num_bytes, |
| UserPointer<const MojoHandle> handles, |
| uint32_t num_handles, |
| MojoWriteMessageFlags flags) { |
| scoped_refptr<Dispatcher> dispatcher(GetDispatcher(message_pipe_handle)); |
| if (!dispatcher) |
| return MOJO_RESULT_INVALID_ARGUMENT; |
| |
| // Easy case: not sending any handles. |
| if (num_handles == 0) |
| return dispatcher->WriteMessage(bytes, num_bytes, nullptr, flags); |
| |
| // We have to handle |handles| here, since we have to mark them busy in the |
| // global handle table. We can't delegate this to the dispatcher, since the |
| // handle table lock must be acquired before the dispatcher lock. |
| // |
| // (This leads to an oddity: |handles|/|num_handles| are always verified for |
| // validity, even for dispatchers that don't support |WriteMessage()| and will |
| // simply return failure unconditionally. It also breaks the usual |
| // left-to-right verification order of arguments.) |
| if (num_handles > GetConfiguration().max_message_num_handles) |
| return MOJO_RESULT_RESOURCE_EXHAUSTED; |
| |
| UserPointer<const MojoHandle>::Reader handles_reader(handles, num_handles); |
| |
| // We'll need to hold on to the dispatchers so that we can pass them on to |
| // |WriteMessage()| and also so that we can unlock their locks afterwards |
| // without accessing the handle table. These can be dumb pointers, since their |
| // entries in the handle table won't get removed (since they'll be marked as |
| // busy). |
| std::vector<DispatcherTransport> transports(num_handles); |
| |
| // When we pass handles, we have to try to take all their dispatchers' locks |
| // and mark the handles as busy. If the call succeeds, we then remove the |
| // handles from the handle table. |
| { |
| MutexLocker locker(&handle_table_mutex_); |
| MojoResult result = handle_table_.MarkBusyAndStartTransport( |
| message_pipe_handle, handles_reader.GetPointer(), num_handles, |
| &transports); |
| if (result != MOJO_RESULT_OK) |
| return result; |
| } |
| |
| MojoResult rv = |
| dispatcher->WriteMessage(bytes, num_bytes, &transports, flags); |
| |
| // We need to release the dispatcher locks before we take the handle table |
| // lock. |
| for (uint32_t i = 0; i < num_handles; i++) |
| transports[i].End(); |
| |
| { |
| MutexLocker locker(&handle_table_mutex_); |
| if (rv == MOJO_RESULT_OK) { |
| handle_table_.RemoveBusyHandles(handles_reader.GetPointer(), num_handles); |
| } else { |
| handle_table_.RestoreBusyHandles(handles_reader.GetPointer(), |
| num_handles); |
| } |
| } |
| |
| return rv; |
| } |
| |
| MojoResult Core::ReadMessage(MojoHandle message_pipe_handle, |
| UserPointer<void> bytes, |
| UserPointer<uint32_t> num_bytes, |
| UserPointer<MojoHandle> handles, |
| UserPointer<uint32_t> num_handles, |
| MojoReadMessageFlags flags) { |
| scoped_refptr<Dispatcher> dispatcher(GetDispatcher(message_pipe_handle)); |
| if (!dispatcher) |
| return MOJO_RESULT_INVALID_ARGUMENT; |
| |
| uint32_t num_handles_value = num_handles.IsNull() ? 0 : num_handles.Get(); |
| |
| MojoResult rv; |
| if (num_handles_value == 0) { |
| // Easy case: won't receive any handles. |
| rv = dispatcher->ReadMessage(bytes, num_bytes, nullptr, &num_handles_value, |
| flags); |
| } else { |
| DispatcherVector dispatchers; |
| rv = dispatcher->ReadMessage(bytes, num_bytes, &dispatchers, |
| &num_handles_value, flags); |
| if (!dispatchers.empty()) { |
| DCHECK_EQ(rv, MOJO_RESULT_OK); |
| DCHECK(!num_handles.IsNull()); |
| DCHECK_LE(dispatchers.size(), static_cast<size_t>(num_handles_value)); |
| |
| bool success; |
| UserPointer<MojoHandle>::Writer handles_writer(handles, |
| dispatchers.size()); |
| { |
| MutexLocker locker(&handle_table_mutex_); |
| success = handle_table_.AddDispatcherVector( |
| dispatchers, handles_writer.GetPointer()); |
| } |
| if (success) { |
| handles_writer.Commit(); |
| } else { |
| LOG(ERROR) << "Received message with " << dispatchers.size() |
| << " handles, but handle table full"; |
| // Close dispatchers (outside the lock). |
| for (size_t i = 0; i < dispatchers.size(); i++) { |
| if (dispatchers[i]) |
| dispatchers[i]->Close(); |
| } |
| if (rv == MOJO_RESULT_OK) |
| rv = MOJO_RESULT_RESOURCE_EXHAUSTED; |
| } |
| } |
| } |
| |
| if (!num_handles.IsNull()) |
| num_handles.Put(num_handles_value); |
| return rv; |
| } |
| |
| MojoResult Core::CreateDataPipe( |
| UserPointer<const MojoCreateDataPipeOptions> options, |
| UserPointer<MojoHandle> data_pipe_producer_handle, |
| UserPointer<MojoHandle> data_pipe_consumer_handle) { |
| MojoCreateDataPipeOptions validated_options = {}; |
| MojoResult result = |
| DataPipe::ValidateCreateOptions(options, &validated_options); |
| if (result != MOJO_RESULT_OK) |
| return result; |
| |
| scoped_refptr<DataPipeProducerDispatcher> producer_dispatcher = |
| DataPipeProducerDispatcher::Create(); |
| scoped_refptr<DataPipeConsumerDispatcher> consumer_dispatcher = |
| DataPipeConsumerDispatcher::Create(); |
| |
| std::pair<MojoHandle, MojoHandle> handle_pair; |
| { |
| MutexLocker locker(&handle_table_mutex_); |
| handle_pair = handle_table_.AddDispatcherPair(producer_dispatcher, |
| consumer_dispatcher); |
| } |
| if (handle_pair.first == MOJO_HANDLE_INVALID) { |
| DCHECK_EQ(handle_pair.second, MOJO_HANDLE_INVALID); |
| LOG(ERROR) << "Handle table full"; |
| producer_dispatcher->Close(); |
| consumer_dispatcher->Close(); |
| return MOJO_RESULT_RESOURCE_EXHAUSTED; |
| } |
| DCHECK_NE(handle_pair.second, MOJO_HANDLE_INVALID); |
| |
| scoped_refptr<DataPipe> data_pipe(DataPipe::CreateLocal(validated_options)); |
| producer_dispatcher->Init(data_pipe); |
| consumer_dispatcher->Init(data_pipe); |
| |
| data_pipe_producer_handle.Put(handle_pair.first); |
| data_pipe_consumer_handle.Put(handle_pair.second); |
| return MOJO_RESULT_OK; |
| } |
| |
| MojoResult Core::WriteData(MojoHandle data_pipe_producer_handle, |
| UserPointer<const void> elements, |
| UserPointer<uint32_t> num_bytes, |
| MojoWriteDataFlags flags) { |
| scoped_refptr<Dispatcher> dispatcher( |
| GetDispatcher(data_pipe_producer_handle)); |
| if (!dispatcher) |
| return MOJO_RESULT_INVALID_ARGUMENT; |
| |
| return dispatcher->WriteData(elements, num_bytes, flags); |
| } |
| |
| MojoResult Core::BeginWriteData(MojoHandle data_pipe_producer_handle, |
| UserPointer<void*> buffer, |
| UserPointer<uint32_t> buffer_num_bytes, |
| MojoWriteDataFlags flags) { |
| scoped_refptr<Dispatcher> dispatcher( |
| GetDispatcher(data_pipe_producer_handle)); |
| if (!dispatcher) |
| return MOJO_RESULT_INVALID_ARGUMENT; |
| |
| return dispatcher->BeginWriteData(buffer, buffer_num_bytes, flags); |
| } |
| |
| MojoResult Core::EndWriteData(MojoHandle data_pipe_producer_handle, |
| uint32_t num_bytes_written) { |
| scoped_refptr<Dispatcher> dispatcher( |
| GetDispatcher(data_pipe_producer_handle)); |
| if (!dispatcher) |
| return MOJO_RESULT_INVALID_ARGUMENT; |
| |
| return dispatcher->EndWriteData(num_bytes_written); |
| } |
| |
| MojoResult Core::ReadData(MojoHandle data_pipe_consumer_handle, |
| UserPointer<void> elements, |
| UserPointer<uint32_t> num_bytes, |
| MojoReadDataFlags flags) { |
| scoped_refptr<Dispatcher> dispatcher( |
| GetDispatcher(data_pipe_consumer_handle)); |
| if (!dispatcher) |
| return MOJO_RESULT_INVALID_ARGUMENT; |
| |
| return dispatcher->ReadData(elements, num_bytes, flags); |
| } |
| |
| MojoResult Core::BeginReadData(MojoHandle data_pipe_consumer_handle, |
| UserPointer<const void*> buffer, |
| UserPointer<uint32_t> buffer_num_bytes, |
| MojoReadDataFlags flags) { |
| scoped_refptr<Dispatcher> dispatcher( |
| GetDispatcher(data_pipe_consumer_handle)); |
| if (!dispatcher) |
| return MOJO_RESULT_INVALID_ARGUMENT; |
| |
| return dispatcher->BeginReadData(buffer, buffer_num_bytes, flags); |
| } |
| |
| MojoResult Core::EndReadData(MojoHandle data_pipe_consumer_handle, |
| uint32_t num_bytes_read) { |
| scoped_refptr<Dispatcher> dispatcher( |
| GetDispatcher(data_pipe_consumer_handle)); |
| if (!dispatcher) |
| return MOJO_RESULT_INVALID_ARGUMENT; |
| |
| return dispatcher->EndReadData(num_bytes_read); |
| } |
| |
| MojoResult Core::CreateSharedBuffer( |
| UserPointer<const MojoCreateSharedBufferOptions> options, |
| uint64_t num_bytes, |
| UserPointer<MojoHandle> shared_buffer_handle) { |
| MojoCreateSharedBufferOptions validated_options = {}; |
| MojoResult result = SharedBufferDispatcher::ValidateCreateOptions( |
| options, &validated_options); |
| if (result != MOJO_RESULT_OK) |
| return result; |
| |
| scoped_refptr<SharedBufferDispatcher> dispatcher; |
| result = SharedBufferDispatcher::Create(platform_support_, validated_options, |
| num_bytes, &dispatcher); |
| if (result != MOJO_RESULT_OK) { |
| DCHECK(!dispatcher); |
| return result; |
| } |
| |
| MojoHandle h = AddDispatcher(dispatcher); |
| if (h == MOJO_HANDLE_INVALID) { |
| LOG(ERROR) << "Handle table full"; |
| dispatcher->Close(); |
| return MOJO_RESULT_RESOURCE_EXHAUSTED; |
| } |
| |
| shared_buffer_handle.Put(h); |
| return MOJO_RESULT_OK; |
| } |
| |
| MojoResult Core::DuplicateBufferHandle( |
| MojoHandle buffer_handle, |
| UserPointer<const MojoDuplicateBufferHandleOptions> options, |
| UserPointer<MojoHandle> new_buffer_handle) { |
| scoped_refptr<Dispatcher> dispatcher(GetDispatcher(buffer_handle)); |
| if (!dispatcher) |
| return MOJO_RESULT_INVALID_ARGUMENT; |
| |
| // Don't verify |options| here; that's the dispatcher's job. |
| scoped_refptr<Dispatcher> new_dispatcher; |
| MojoResult result = |
| dispatcher->DuplicateBufferHandle(options, &new_dispatcher); |
| if (result != MOJO_RESULT_OK) |
| return result; |
| |
| MojoHandle new_handle = AddDispatcher(new_dispatcher); |
| if (new_handle == MOJO_HANDLE_INVALID) { |
| LOG(ERROR) << "Handle table full"; |
| dispatcher->Close(); |
| return MOJO_RESULT_RESOURCE_EXHAUSTED; |
| } |
| |
| new_buffer_handle.Put(new_handle); |
| return MOJO_RESULT_OK; |
| } |
| |
| MojoResult Core::MapBuffer(MojoHandle buffer_handle, |
| uint64_t offset, |
| uint64_t num_bytes, |
| UserPointer<void*> buffer, |
| MojoMapBufferFlags flags) { |
| scoped_refptr<Dispatcher> dispatcher(GetDispatcher(buffer_handle)); |
| if (!dispatcher) |
| return MOJO_RESULT_INVALID_ARGUMENT; |
| |
| scoped_ptr<embedder::PlatformSharedBufferMapping> mapping; |
| MojoResult result = dispatcher->MapBuffer(offset, num_bytes, flags, &mapping); |
| if (result != MOJO_RESULT_OK) |
| return result; |
| |
| DCHECK(mapping); |
| void* address = mapping->GetBase(); |
| { |
| MutexLocker locker(&mapping_table_mutex_); |
| result = mapping_table_.AddMapping(mapping.Pass()); |
| } |
| if (result != MOJO_RESULT_OK) |
| return result; |
| |
| buffer.Put(address); |
| return MOJO_RESULT_OK; |
| } |
| |
| MojoResult Core::UnmapBuffer(UserPointer<void> buffer) { |
| MutexLocker locker(&mapping_table_mutex_); |
| return mapping_table_.RemoveMapping(buffer.GetPointerValue()); |
| } |
| |
| // Note: We allow |handles| to repeat the same handle multiple times, since |
| // different flags may be specified. |
| // TODO(vtl): This incurs a performance cost in |Remove()|. Analyze this |
| // more carefully and address it if necessary. |
| MojoResult Core::WaitManyInternal(const MojoHandle* handles, |
| const MojoHandleSignals* signals, |
| uint32_t num_handles, |
| MojoDeadline deadline, |
| uint32_t* result_index, |
| HandleSignalsState* signals_states) { |
| DCHECK_GT(num_handles, 0u); |
| DCHECK_EQ(*result_index, static_cast<uint32_t>(-1)); |
| |
| DispatcherVector dispatchers; |
| dispatchers.reserve(num_handles); |
| for (uint32_t i = 0; i < num_handles; i++) { |
| scoped_refptr<Dispatcher> dispatcher = GetDispatcher(handles[i]); |
| if (!dispatcher) { |
| *result_index = i; |
| return MOJO_RESULT_INVALID_ARGUMENT; |
| } |
| dispatchers.push_back(dispatcher); |
| } |
| |
| // TODO(vtl): Should make the waiter live (permanently) in TLS. |
| Waiter waiter; |
| waiter.Init(); |
| |
| uint32_t i; |
| MojoResult rv = MOJO_RESULT_OK; |
| for (i = 0; i < num_handles; i++) { |
| rv = dispatchers[i]->AddAwakable( |
| &waiter, signals[i], i, signals_states ? &signals_states[i] : nullptr); |
| if (rv != MOJO_RESULT_OK) { |
| *result_index = i; |
| break; |
| } |
| } |
| uint32_t num_added = i; |
| |
| if (rv == MOJO_RESULT_ALREADY_EXISTS) |
| rv = MOJO_RESULT_OK; // The i-th one is already "triggered". |
| else if (rv == MOJO_RESULT_OK) |
| rv = waiter.Wait(deadline, result_index); |
| |
| // Make sure no other dispatchers try to wake |waiter| for the current |
| // |Wait()|/|WaitMany()| call. (Only after doing this can |waiter| be |
| // destroyed, but this would still be required if the waiter were in TLS.) |
| for (i = 0; i < num_added; i++) { |
| dispatchers[i]->RemoveAwakable( |
| &waiter, signals_states ? &signals_states[i] : nullptr); |
| } |
| if (signals_states) { |
| for (; i < num_handles; i++) |
| signals_states[i] = dispatchers[i]->GetHandleSignalsState(); |
| } |
| |
| return rv; |
| } |
| |
| } // namespace system |
| } // namespace mojo |
