1 // Copyright 2013 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.
5 #include "mojo/system/core.h"
9 #include "base/logging.h"
10 #include "base/time/time.h"
11 #include "mojo/embedder/platform_shared_buffer.h"
12 #include "mojo/embedder/platform_support.h"
13 #include "mojo/public/c/system/macros.h"
14 #include "mojo/system/constants.h"
15 #include "mojo/system/data_pipe.h"
16 #include "mojo/system/data_pipe_consumer_dispatcher.h"
17 #include "mojo/system/data_pipe_producer_dispatcher.h"
18 #include "mojo/system/dispatcher.h"
19 #include "mojo/system/handle_signals_state.h"
20 #include "mojo/system/local_data_pipe.h"
21 #include "mojo/system/memory.h"
22 #include "mojo/system/message_pipe.h"
23 #include "mojo/system/message_pipe_dispatcher.h"
24 #include "mojo/system/shared_buffer_dispatcher.h"
25 #include "mojo/system/waiter.h"
30 // Implementation notes
32 // Mojo primitives are implemented by the singleton |Core| object. Most calls
33 // are for a "primary" handle (the first argument). |Core::GetDispatcher()| is
34 // used to look up a |Dispatcher| object for a given handle. That object
35 // implements most primitives for that object. The wait primitives are not
36 // attached to objects and are implemented by |Core| itself.
38 // Some objects have multiple handles associated to them, e.g., message pipes
39 // (which have two). In such a case, there is still a |Dispatcher| (e.g.,
40 // |MessagePipeDispatcher|) for each handle, with each handle having a strong
41 // reference to the common "secondary" object (e.g., |MessagePipe|). This
42 // secondary object does NOT have any references to the |Dispatcher|s (even if
43 // it did, it wouldn't be able to do anything with them due to lock order
44 // requirements -- see below).
46 // Waiting is implemented by having the thread that wants to wait call the
47 // |Dispatcher|s for the handles that it wants to wait on with a |Waiter|
48 // object; this |Waiter| object may be created on the stack of that thread or be
49 // kept in thread local storage for that thread (TODO(vtl): future improvement).
50 // The |Dispatcher| then adds the |Waiter| to a |WaiterList| that's either owned
51 // by that |Dispatcher| (see |SimpleDispatcher|) or by a secondary object (e.g.,
52 // |MessagePipe|). To signal/wake a |Waiter|, the object in question -- either a
53 // |SimpleDispatcher| or a secondary object -- talks to its |WaiterList|.
55 // Thread-safety notes
57 // Mojo primitives calls are thread-safe. We achieve this with relatively
58 // fine-grained locking. There is a global handle table lock. This lock should
59 // be held as briefly as possible (TODO(vtl): a future improvement would be to
60 // switch it to a reader-writer lock). Each |Dispatcher| object then has a lock
61 // (which subclasses can use to protect their data).
63 // The lock ordering is as follows:
64 // 1. global handle table lock, global mapping table lock
65 // 2. |Dispatcher| locks
66 // 3. secondary object locks
68 // INF. |Waiter| locks
71 // - While holding a |Dispatcher| lock, you may not unconditionally attempt
72 // to take another |Dispatcher| lock. (This has consequences on the
73 // concurrency semantics of |MojoWriteMessage()| when passing handles.)
74 // Doing so would lead to deadlock.
75 // - Locks at the "INF" level may not have any locks taken while they are
78 // TODO(vtl): This should take a |scoped_ptr<PlatformSupport>| as a parameter.
79 Core::Core(scoped_ptr<embedder::PlatformSupport> platform_support)
80 : platform_support_(platform_support.Pass()) {
86 MojoHandle Core::AddDispatcher(const scoped_refptr<Dispatcher>& dispatcher) {
87 base::AutoLock locker(handle_table_lock_);
88 return handle_table_.AddDispatcher(dispatcher);
91 scoped_refptr<Dispatcher> Core::GetDispatcher(MojoHandle handle) {
92 if (handle == MOJO_HANDLE_INVALID)
95 base::AutoLock locker(handle_table_lock_);
96 return handle_table_.GetDispatcher(handle);
99 MojoTimeTicks Core::GetTimeTicksNow() {
100 return base::TimeTicks::Now().ToInternalValue();
103 MojoResult Core::Close(MojoHandle handle) {
104 if (handle == MOJO_HANDLE_INVALID)
105 return MOJO_RESULT_INVALID_ARGUMENT;
107 scoped_refptr<Dispatcher> dispatcher;
109 base::AutoLock locker(handle_table_lock_);
111 handle_table_.GetAndRemoveDispatcher(handle, &dispatcher);
112 if (result != MOJO_RESULT_OK)
116 // The dispatcher doesn't have a say in being closed, but gets notified of it.
117 // Note: This is done outside of |handle_table_lock_|. As a result, there's a
118 // race condition that the dispatcher must handle; see the comment in
119 // |Dispatcher| in dispatcher.h.
120 return dispatcher->Close();
123 MojoResult Core::Wait(MojoHandle handle,
124 MojoHandleSignals signals,
125 MojoDeadline deadline,
126 UserPointer<MojoHandleSignalsState> signals_state) {
127 uint32_t unused = static_cast<uint32_t>(-1);
128 HandleSignalsState hss;
129 MojoResult rv = WaitManyInternal(&handle,
134 signals_state.IsNull() ? nullptr : &hss);
135 if (rv != MOJO_RESULT_INVALID_ARGUMENT && !signals_state.IsNull())
136 signals_state.Put(hss);
140 MojoResult Core::WaitMany(UserPointer<const MojoHandle> handles,
141 UserPointer<const MojoHandleSignals> signals,
142 uint32_t num_handles,
143 MojoDeadline deadline,
144 UserPointer<uint32_t> result_index,
145 UserPointer<MojoHandleSignalsState> signals_states) {
147 return MOJO_RESULT_INVALID_ARGUMENT;
148 if (num_handles > kMaxWaitManyNumHandles)
149 return MOJO_RESULT_RESOURCE_EXHAUSTED;
151 UserPointer<const MojoHandle>::Reader handles_reader(handles, num_handles);
152 UserPointer<const MojoHandleSignals>::Reader signals_reader(signals,
154 uint32_t index = static_cast<uint32_t>(-1);
156 if (signals_states.IsNull()) {
157 rv = WaitManyInternal(handles_reader.GetPointer(),
158 signals_reader.GetPointer(),
164 UserPointer<MojoHandleSignalsState>::Writer signals_states_writer(
165 signals_states, num_handles);
166 // Note: The |reinterpret_cast| is safe, since |HandleSignalsState| is a
167 // subclass of |MojoHandleSignalsState| that doesn't add any data members.
168 rv = WaitManyInternal(handles_reader.GetPointer(),
169 signals_reader.GetPointer(),
173 reinterpret_cast<HandleSignalsState*>(
174 signals_states_writer.GetPointer()));
175 if (rv != MOJO_RESULT_INVALID_ARGUMENT)
176 signals_states_writer.Commit();
178 if (index != static_cast<uint32_t>(-1) && !result_index.IsNull())
179 result_index.Put(index);
183 MojoResult Core::CreateMessagePipe(
184 UserPointer<const MojoCreateMessagePipeOptions> options,
185 UserPointer<MojoHandle> message_pipe_handle0,
186 UserPointer<MojoHandle> message_pipe_handle1) {
187 MojoCreateMessagePipeOptions validated_options = {};
189 MessagePipeDispatcher::ValidateCreateOptions(options, &validated_options);
190 if (result != MOJO_RESULT_OK)
193 scoped_refptr<MessagePipeDispatcher> dispatcher0(
194 new MessagePipeDispatcher(validated_options));
195 scoped_refptr<MessagePipeDispatcher> dispatcher1(
196 new MessagePipeDispatcher(validated_options));
198 std::pair<MojoHandle, MojoHandle> handle_pair;
200 base::AutoLock locker(handle_table_lock_);
201 handle_pair = handle_table_.AddDispatcherPair(dispatcher0, dispatcher1);
203 if (handle_pair.first == MOJO_HANDLE_INVALID) {
204 DCHECK_EQ(handle_pair.second, MOJO_HANDLE_INVALID);
205 LOG(ERROR) << "Handle table full";
206 dispatcher0->Close();
207 dispatcher1->Close();
208 return MOJO_RESULT_RESOURCE_EXHAUSTED;
211 scoped_refptr<MessagePipe> message_pipe(MessagePipe::CreateLocalLocal());
212 dispatcher0->Init(message_pipe, 0);
213 dispatcher1->Init(message_pipe, 1);
215 message_pipe_handle0.Put(handle_pair.first);
216 message_pipe_handle1.Put(handle_pair.second);
217 return MOJO_RESULT_OK;
220 // Implementation note: To properly cancel waiters and avoid other races, this
221 // does not transfer dispatchers from one handle to another, even when sending a
222 // message in-process. Instead, it must transfer the "contents" of the
223 // dispatcher to a new dispatcher, and then close the old dispatcher. If this
224 // isn't done, in the in-process case, calls on the old handle may complete
225 // after the the message has been received and a new handle created (and
226 // possibly even after calls have been made on the new handle).
227 MojoResult Core::WriteMessage(MojoHandle message_pipe_handle,
228 UserPointer<const void> bytes,
230 UserPointer<const MojoHandle> handles,
231 uint32_t num_handles,
232 MojoWriteMessageFlags flags) {
233 scoped_refptr<Dispatcher> dispatcher(GetDispatcher(message_pipe_handle));
234 if (!dispatcher.get())
235 return MOJO_RESULT_INVALID_ARGUMENT;
237 // Easy case: not sending any handles.
238 if (num_handles == 0)
239 return dispatcher->WriteMessage(bytes, num_bytes, nullptr, flags);
241 // We have to handle |handles| here, since we have to mark them busy in the
242 // global handle table. We can't delegate this to the dispatcher, since the
243 // handle table lock must be acquired before the dispatcher lock.
245 // (This leads to an oddity: |handles|/|num_handles| are always verified for
246 // validity, even for dispatchers that don't support |WriteMessage()| and will
247 // simply return failure unconditionally. It also breaks the usual
248 // left-to-right verification order of arguments.)
249 if (num_handles > kMaxMessageNumHandles)
250 return MOJO_RESULT_RESOURCE_EXHAUSTED;
252 UserPointer<const MojoHandle>::Reader handles_reader(handles, num_handles);
254 // We'll need to hold on to the dispatchers so that we can pass them on to
255 // |WriteMessage()| and also so that we can unlock their locks afterwards
256 // without accessing the handle table. These can be dumb pointers, since their
257 // entries in the handle table won't get removed (since they'll be marked as
259 std::vector<DispatcherTransport> transports(num_handles);
261 // When we pass handles, we have to try to take all their dispatchers' locks
262 // and mark the handles as busy. If the call succeeds, we then remove the
263 // handles from the handle table.
265 base::AutoLock locker(handle_table_lock_);
267 handle_table_.MarkBusyAndStartTransport(message_pipe_handle,
268 handles_reader.GetPointer(),
271 if (result != MOJO_RESULT_OK)
276 dispatcher->WriteMessage(bytes, num_bytes, &transports, flags);
278 // We need to release the dispatcher locks before we take the handle table
280 for (uint32_t i = 0; i < num_handles; i++)
284 base::AutoLock locker(handle_table_lock_);
285 if (rv == MOJO_RESULT_OK) {
286 handle_table_.RemoveBusyHandles(handles_reader.GetPointer(), num_handles);
288 handle_table_.RestoreBusyHandles(handles_reader.GetPointer(),
296 MojoResult Core::ReadMessage(MojoHandle message_pipe_handle,
297 UserPointer<void> bytes,
298 UserPointer<uint32_t> num_bytes,
299 UserPointer<MojoHandle> handles,
300 UserPointer<uint32_t> num_handles,
301 MojoReadMessageFlags flags) {
302 scoped_refptr<Dispatcher> dispatcher(GetDispatcher(message_pipe_handle));
303 if (!dispatcher.get())
304 return MOJO_RESULT_INVALID_ARGUMENT;
306 uint32_t num_handles_value = num_handles.IsNull() ? 0 : num_handles.Get();
309 if (num_handles_value == 0) {
310 // Easy case: won't receive any handles.
311 rv = dispatcher->ReadMessage(
312 bytes, num_bytes, nullptr, &num_handles_value, flags);
314 DispatcherVector dispatchers;
315 rv = dispatcher->ReadMessage(
316 bytes, num_bytes, &dispatchers, &num_handles_value, flags);
317 if (!dispatchers.empty()) {
318 DCHECK_EQ(rv, MOJO_RESULT_OK);
319 DCHECK(!num_handles.IsNull());
320 DCHECK_LE(dispatchers.size(), static_cast<size_t>(num_handles_value));
323 UserPointer<MojoHandle>::Writer handles_writer(handles,
326 base::AutoLock locker(handle_table_lock_);
327 success = handle_table_.AddDispatcherVector(
328 dispatchers, handles_writer.GetPointer());
331 handles_writer.Commit();
333 LOG(ERROR) << "Received message with " << dispatchers.size()
334 << " handles, but handle table full";
335 // Close dispatchers (outside the lock).
336 for (size_t i = 0; i < dispatchers.size(); i++) {
337 if (dispatchers[i].get())
338 dispatchers[i]->Close();
340 if (rv == MOJO_RESULT_OK)
341 rv = MOJO_RESULT_RESOURCE_EXHAUSTED;
346 if (!num_handles.IsNull())
347 num_handles.Put(num_handles_value);
351 MojoResult Core::CreateDataPipe(
352 UserPointer<const MojoCreateDataPipeOptions> options,
353 UserPointer<MojoHandle> data_pipe_producer_handle,
354 UserPointer<MojoHandle> data_pipe_consumer_handle) {
355 MojoCreateDataPipeOptions validated_options = {};
357 DataPipe::ValidateCreateOptions(options, &validated_options);
358 if (result != MOJO_RESULT_OK)
361 scoped_refptr<DataPipeProducerDispatcher> producer_dispatcher(
362 new DataPipeProducerDispatcher());
363 scoped_refptr<DataPipeConsumerDispatcher> consumer_dispatcher(
364 new DataPipeConsumerDispatcher());
366 std::pair<MojoHandle, MojoHandle> handle_pair;
368 base::AutoLock locker(handle_table_lock_);
369 handle_pair = handle_table_.AddDispatcherPair(producer_dispatcher,
370 consumer_dispatcher);
372 if (handle_pair.first == MOJO_HANDLE_INVALID) {
373 DCHECK_EQ(handle_pair.second, MOJO_HANDLE_INVALID);
374 LOG(ERROR) << "Handle table full";
375 producer_dispatcher->Close();
376 consumer_dispatcher->Close();
377 return MOJO_RESULT_RESOURCE_EXHAUSTED;
379 DCHECK_NE(handle_pair.second, MOJO_HANDLE_INVALID);
381 scoped_refptr<DataPipe> data_pipe(new LocalDataPipe(validated_options));
382 producer_dispatcher->Init(data_pipe);
383 consumer_dispatcher->Init(data_pipe);
385 data_pipe_producer_handle.Put(handle_pair.first);
386 data_pipe_consumer_handle.Put(handle_pair.second);
387 return MOJO_RESULT_OK;
390 MojoResult Core::WriteData(MojoHandle data_pipe_producer_handle,
391 UserPointer<const void> elements,
392 UserPointer<uint32_t> num_bytes,
393 MojoWriteDataFlags flags) {
394 scoped_refptr<Dispatcher> dispatcher(
395 GetDispatcher(data_pipe_producer_handle));
396 if (!dispatcher.get())
397 return MOJO_RESULT_INVALID_ARGUMENT;
399 return dispatcher->WriteData(elements, num_bytes, flags);
402 MojoResult Core::BeginWriteData(MojoHandle data_pipe_producer_handle,
403 UserPointer<void*> buffer,
404 UserPointer<uint32_t> buffer_num_bytes,
405 MojoWriteDataFlags flags) {
406 scoped_refptr<Dispatcher> dispatcher(
407 GetDispatcher(data_pipe_producer_handle));
408 if (!dispatcher.get())
409 return MOJO_RESULT_INVALID_ARGUMENT;
411 return dispatcher->BeginWriteData(buffer, buffer_num_bytes, flags);
414 MojoResult Core::EndWriteData(MojoHandle data_pipe_producer_handle,
415 uint32_t num_bytes_written) {
416 scoped_refptr<Dispatcher> dispatcher(
417 GetDispatcher(data_pipe_producer_handle));
418 if (!dispatcher.get())
419 return MOJO_RESULT_INVALID_ARGUMENT;
421 return dispatcher->EndWriteData(num_bytes_written);
424 MojoResult Core::ReadData(MojoHandle data_pipe_consumer_handle,
425 UserPointer<void> elements,
426 UserPointer<uint32_t> num_bytes,
427 MojoReadDataFlags flags) {
428 scoped_refptr<Dispatcher> dispatcher(
429 GetDispatcher(data_pipe_consumer_handle));
430 if (!dispatcher.get())
431 return MOJO_RESULT_INVALID_ARGUMENT;
433 return dispatcher->ReadData(elements, num_bytes, flags);
436 MojoResult Core::BeginReadData(MojoHandle data_pipe_consumer_handle,
437 UserPointer<const void*> buffer,
438 UserPointer<uint32_t> buffer_num_bytes,
439 MojoReadDataFlags flags) {
440 scoped_refptr<Dispatcher> dispatcher(
441 GetDispatcher(data_pipe_consumer_handle));
442 if (!dispatcher.get())
443 return MOJO_RESULT_INVALID_ARGUMENT;
445 return dispatcher->BeginReadData(buffer, buffer_num_bytes, flags);
448 MojoResult Core::EndReadData(MojoHandle data_pipe_consumer_handle,
449 uint32_t num_bytes_read) {
450 scoped_refptr<Dispatcher> dispatcher(
451 GetDispatcher(data_pipe_consumer_handle));
452 if (!dispatcher.get())
453 return MOJO_RESULT_INVALID_ARGUMENT;
455 return dispatcher->EndReadData(num_bytes_read);
458 MojoResult Core::CreateSharedBuffer(
459 UserPointer<const MojoCreateSharedBufferOptions> options,
461 UserPointer<MojoHandle> shared_buffer_handle) {
462 MojoCreateSharedBufferOptions validated_options = {};
463 MojoResult result = SharedBufferDispatcher::ValidateCreateOptions(
464 options, &validated_options);
465 if (result != MOJO_RESULT_OK)
468 scoped_refptr<SharedBufferDispatcher> dispatcher;
469 result = SharedBufferDispatcher::Create(
470 platform_support(), validated_options, num_bytes, &dispatcher);
471 if (result != MOJO_RESULT_OK) {
472 DCHECK(!dispatcher.get());
476 MojoHandle h = AddDispatcher(dispatcher);
477 if (h == MOJO_HANDLE_INVALID) {
478 LOG(ERROR) << "Handle table full";
480 return MOJO_RESULT_RESOURCE_EXHAUSTED;
483 shared_buffer_handle.Put(h);
484 return MOJO_RESULT_OK;
487 MojoResult Core::DuplicateBufferHandle(
488 MojoHandle buffer_handle,
489 UserPointer<const MojoDuplicateBufferHandleOptions> options,
490 UserPointer<MojoHandle> new_buffer_handle) {
491 scoped_refptr<Dispatcher> dispatcher(GetDispatcher(buffer_handle));
492 if (!dispatcher.get())
493 return MOJO_RESULT_INVALID_ARGUMENT;
495 // Don't verify |options| here; that's the dispatcher's job.
496 scoped_refptr<Dispatcher> new_dispatcher;
498 dispatcher->DuplicateBufferHandle(options, &new_dispatcher);
499 if (result != MOJO_RESULT_OK)
502 MojoHandle new_handle = AddDispatcher(new_dispatcher);
503 if (new_handle == MOJO_HANDLE_INVALID) {
504 LOG(ERROR) << "Handle table full";
506 return MOJO_RESULT_RESOURCE_EXHAUSTED;
509 new_buffer_handle.Put(new_handle);
510 return MOJO_RESULT_OK;
513 MojoResult Core::MapBuffer(MojoHandle buffer_handle,
516 UserPointer<void*> buffer,
517 MojoMapBufferFlags flags) {
518 scoped_refptr<Dispatcher> dispatcher(GetDispatcher(buffer_handle));
519 if (!dispatcher.get())
520 return MOJO_RESULT_INVALID_ARGUMENT;
522 scoped_ptr<embedder::PlatformSharedBufferMapping> mapping;
523 MojoResult result = dispatcher->MapBuffer(offset, num_bytes, flags, &mapping);
524 if (result != MOJO_RESULT_OK)
528 void* address = mapping->GetBase();
530 base::AutoLock locker(mapping_table_lock_);
531 result = mapping_table_.AddMapping(mapping.Pass());
533 if (result != MOJO_RESULT_OK)
537 return MOJO_RESULT_OK;
540 MojoResult Core::UnmapBuffer(UserPointer<void> buffer) {
541 base::AutoLock locker(mapping_table_lock_);
542 return mapping_table_.RemoveMapping(buffer.GetPointerValue());
545 // Note: We allow |handles| to repeat the same handle multiple times, since
546 // different flags may be specified.
547 // TODO(vtl): This incurs a performance cost in |RemoveWaiter()|. Analyze this
548 // more carefully and address it if necessary.
549 MojoResult Core::WaitManyInternal(const MojoHandle* handles,
550 const MojoHandleSignals* signals,
551 uint32_t num_handles,
552 MojoDeadline deadline,
553 uint32_t* result_index,
554 HandleSignalsState* signals_states) {
555 DCHECK_GT(num_handles, 0u);
556 DCHECK_EQ(*result_index, static_cast<uint32_t>(-1));
558 DispatcherVector dispatchers;
559 dispatchers.reserve(num_handles);
560 for (uint32_t i = 0; i < num_handles; i++) {
561 scoped_refptr<Dispatcher> dispatcher = GetDispatcher(handles[i]);
562 if (!dispatcher.get()) {
564 return MOJO_RESULT_INVALID_ARGUMENT;
566 dispatchers.push_back(dispatcher);
569 // TODO(vtl): Should make the waiter live (permanently) in TLS.
574 MojoResult rv = MOJO_RESULT_OK;
575 for (i = 0; i < num_handles; i++) {
576 rv = dispatchers[i]->AddWaiter(
577 &waiter, signals[i], i, signals_states ? &signals_states[i] : nullptr);
578 if (rv != MOJO_RESULT_OK) {
583 uint32_t num_added = i;
585 if (rv == MOJO_RESULT_ALREADY_EXISTS)
586 rv = MOJO_RESULT_OK; // The i-th one is already "triggered".
587 else if (rv == MOJO_RESULT_OK)
588 rv = waiter.Wait(deadline, result_index);
590 // Make sure no other dispatchers try to wake |waiter| for the current
591 // |Wait()|/|WaitMany()| call. (Only after doing this can |waiter| be
592 // destroyed, but this would still be required if the waiter were in TLS.)
593 for (i = 0; i < num_added; i++) {
594 dispatchers[i]->RemoveWaiter(&waiter,
595 signals_states ? &signals_states[i] : nullptr);
597 if (signals_states) {
598 for (; i < num_handles; i++)
599 signals_states[i] = dispatchers[i]->GetHandleSignalsState();
605 } // namespace system