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// 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/system/core.h"
#include <vector>
#include "base/logging.h"
#include "base/time/time.h"
#include "mojo/public/c/system/macros.h"
#include "mojo/system/constants.h"
#include "mojo/system/data_pipe.h"
#include "mojo/system/data_pipe_consumer_dispatcher.h"
#include "mojo/system/data_pipe_producer_dispatcher.h"
#include "mojo/system/dispatcher.h"
#include "mojo/system/local_data_pipe.h"
#include "mojo/system/memory.h"
#include "mojo/system/message_pipe.h"
#include "mojo/system/message_pipe_dispatcher.h"
#include "mojo/system/raw_shared_buffer.h"
#include "mojo/system/shared_buffer_dispatcher.h"
#include "mojo/system/waiter.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 a |WaiterList| 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 |WaiterList|.
// 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.
Core::Core() {
}
Core::~Core() {
}
MojoHandle Core::AddDispatcher(
const scoped_refptr<Dispatcher>& dispatcher) {
base::AutoLock locker(handle_table_lock_);
return handle_table_.AddDispatcher(dispatcher);
}
scoped_refptr<Dispatcher> Core::GetDispatcher(MojoHandle handle) {
if (handle == MOJO_HANDLE_INVALID)
return NULL;
base::AutoLock locker(handle_table_lock_);
return handle_table_.GetDispatcher(handle);
}
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;
{
base::AutoLock locker(handle_table_lock_);
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_lock_|. 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) {
return WaitManyInternal(&handle, &signals, 1, deadline);
}
MojoResult Core::WaitMany(const MojoHandle* handles,
const MojoHandleSignals* signals,
uint32_t num_handles,
MojoDeadline deadline) {
if (!VerifyUserPointerWithCount<MojoHandle>(handles, num_handles))
return MOJO_RESULT_INVALID_ARGUMENT;
if (!VerifyUserPointerWithCount<MojoHandleSignals>(signals, num_handles))
return MOJO_RESULT_INVALID_ARGUMENT;
if (num_handles < 1)
return MOJO_RESULT_INVALID_ARGUMENT;
if (num_handles > kMaxWaitManyNumHandles)
return MOJO_RESULT_RESOURCE_EXHAUSTED;
return WaitManyInternal(handles, signals, num_handles, deadline);
}
MojoResult Core::CreateMessagePipe(const MojoCreateMessagePipeOptions* options,
MojoHandle* message_pipe_handle0,
MojoHandle* message_pipe_handle1) {
MojoCreateMessagePipeOptions validated_options = {};
// This will verify the |options| pointer.
MojoResult result = MessagePipeDispatcher::ValidateCreateOptions(
options, &validated_options);
if (result != MOJO_RESULT_OK)
return result;
if (!VerifyUserPointer<MojoHandle>(message_pipe_handle0))
return MOJO_RESULT_INVALID_ARGUMENT;
if (!VerifyUserPointer<MojoHandle>(message_pipe_handle1))
return MOJO_RESULT_INVALID_ARGUMENT;
scoped_refptr<MessagePipeDispatcher> dispatcher0(
new MessagePipeDispatcher(validated_options));
scoped_refptr<MessagePipeDispatcher> dispatcher1(
new MessagePipeDispatcher(validated_options));
std::pair<MojoHandle, MojoHandle> handle_pair;
{
base::AutoLock locker(handle_table_lock_);
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(new MessagePipe());
dispatcher0->Init(message_pipe, 0);
dispatcher1->Init(message_pipe, 1);
*message_pipe_handle0 = handle_pair.first;
*message_pipe_handle1 = 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,
const void* bytes,
uint32_t num_bytes,
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, NULL, 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 (!VerifyUserPointerWithCount<MojoHandle>(handles, num_handles))
return MOJO_RESULT_INVALID_ARGUMENT;
if (num_handles > kMaxMessageNumHandles)
return MOJO_RESULT_RESOURCE_EXHAUSTED;
// 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.
{
base::AutoLock locker(handle_table_lock_);
MojoResult result = handle_table_.MarkBusyAndStartTransport(
message_pipe_handle, handles, 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();
{
base::AutoLock locker(handle_table_lock_);
if (rv == MOJO_RESULT_OK)
handle_table_.RemoveBusyHandles(handles, num_handles);
else
handle_table_.RestoreBusyHandles(handles, num_handles);
}
return rv;
}
MojoResult Core::ReadMessage(MojoHandle message_pipe_handle,
void* bytes,
uint32_t* num_bytes,
MojoHandle* handles,
uint32_t* num_handles,
MojoReadMessageFlags flags) {
scoped_refptr<Dispatcher> dispatcher(GetDispatcher(message_pipe_handle));
if (!dispatcher)
return MOJO_RESULT_INVALID_ARGUMENT;
if (num_handles) {
if (!VerifyUserPointer<uint32_t>(num_handles))
return MOJO_RESULT_INVALID_ARGUMENT;
if (!VerifyUserPointerWithCount<MojoHandle>(handles, *num_handles))
return MOJO_RESULT_INVALID_ARGUMENT;
}
// Easy case: won't receive any handles.
if (!num_handles || *num_handles == 0)
return dispatcher->ReadMessage(bytes, num_bytes, NULL, num_handles, flags);
DispatcherVector dispatchers;
MojoResult rv = dispatcher->ReadMessage(bytes, num_bytes,
&dispatchers, num_handles,
flags);
if (!dispatchers.empty()) {
DCHECK_EQ(rv, MOJO_RESULT_OK);
DCHECK(num_handles);
DCHECK_LE(dispatchers.size(), static_cast<size_t>(*num_handles));
bool success;
{
base::AutoLock locker(handle_table_lock_);
success = handle_table_.AddDispatcherVector(dispatchers, handles);
}
if (!success) {
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();
}
}
}
return rv;
}
MojoResult Core::CreateDataPipe(const MojoCreateDataPipeOptions* options,
MojoHandle* data_pipe_producer_handle,
MojoHandle* data_pipe_consumer_handle) {
MojoCreateDataPipeOptions validated_options = {};
// This will verify the |options| pointer.
MojoResult result = DataPipe::ValidateCreateOptions(options,
&validated_options);
if (result != MOJO_RESULT_OK)
return result;
if (!VerifyUserPointer<MojoHandle>(data_pipe_producer_handle))
return MOJO_RESULT_INVALID_ARGUMENT;
if (!VerifyUserPointer<MojoHandle>(data_pipe_consumer_handle))
return MOJO_RESULT_INVALID_ARGUMENT;
scoped_refptr<DataPipeProducerDispatcher> producer_dispatcher(
new DataPipeProducerDispatcher());
scoped_refptr<DataPipeConsumerDispatcher> consumer_dispatcher(
new DataPipeConsumerDispatcher());
std::pair<MojoHandle, MojoHandle> handle_pair;
{
base::AutoLock locker(handle_table_lock_);
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(new LocalDataPipe(validated_options));
producer_dispatcher->Init(data_pipe);
consumer_dispatcher->Init(data_pipe);
*data_pipe_producer_handle = handle_pair.first;
*data_pipe_consumer_handle = handle_pair.second;
return MOJO_RESULT_OK;
}
MojoResult Core::WriteData(MojoHandle data_pipe_producer_handle,
const void* elements,
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,
void** buffer,
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,
void* elements,
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,
const void** buffer,
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(
const MojoCreateSharedBufferOptions* options,
uint64_t num_bytes,
MojoHandle* shared_buffer_handle) {
MojoCreateSharedBufferOptions validated_options = {};
// This will verify the |options| pointer.
MojoResult result =
SharedBufferDispatcher::ValidateCreateOptions(options,
&validated_options);
if (result != MOJO_RESULT_OK)
return result;
if (!VerifyUserPointer<MojoHandle>(shared_buffer_handle))
return MOJO_RESULT_INVALID_ARGUMENT;
scoped_refptr<SharedBufferDispatcher> dispatcher;
result = SharedBufferDispatcher::Create(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 = h;
return MOJO_RESULT_OK;
}
MojoResult Core::DuplicateBufferHandle(
MojoHandle buffer_handle,
const MojoDuplicateBufferHandleOptions* options,
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.
if (!VerifyUserPointer<MojoHandle>(new_buffer_handle))
return MOJO_RESULT_INVALID_ARGUMENT;
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 = new_handle;
return MOJO_RESULT_OK;
}
MojoResult Core::MapBuffer(MojoHandle buffer_handle,
uint64_t offset,
uint64_t num_bytes,
void** buffer,
MojoMapBufferFlags flags) {
scoped_refptr<Dispatcher> dispatcher(GetDispatcher(buffer_handle));
if (!dispatcher)
return MOJO_RESULT_INVALID_ARGUMENT;
if (!VerifyUserPointerWithCount<void*>(buffer, 1))
return MOJO_RESULT_INVALID_ARGUMENT;
scoped_ptr<RawSharedBufferMapping> mapping;
MojoResult result = dispatcher->MapBuffer(offset, num_bytes, flags, &mapping);
if (result != MOJO_RESULT_OK)
return result;
DCHECK(mapping);
void* address = mapping->base();
{
base::AutoLock locker(mapping_table_lock_);
result = mapping_table_.AddMapping(mapping.Pass());
}
if (result != MOJO_RESULT_OK)
return result;
*buffer = address;
return MOJO_RESULT_OK;
}
MojoResult Core::UnmapBuffer(void* buffer) {
base::AutoLock locker(mapping_table_lock_);
return mapping_table_.RemoveMapping(buffer);
}
// 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 |RemoveWaiter()|. Analyze this
// more carefully and address it if necessary.
MojoResult Core::WaitManyInternal(const MojoHandle* handles,
const MojoHandleSignals* signals,
uint32_t num_handles,
MojoDeadline deadline) {
DCHECK_GT(num_handles, 0u);
DispatcherVector dispatchers;
dispatchers.reserve(num_handles);
for (uint32_t i = 0; i < num_handles; i++) {
scoped_refptr<Dispatcher> dispatcher = GetDispatcher(handles[i]);
if (!dispatcher)
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]->AddWaiter(&waiter, signals[i], i);
if (rv != MOJO_RESULT_OK)
break;
}
uint32_t num_added = i;
if (rv == MOJO_RESULT_ALREADY_EXISTS) {
rv = static_cast<MojoResult>(i); // The i-th one is already "triggered".
} else if (rv == MOJO_RESULT_OK) {
uint32_t context = static_cast<uint32_t>(-1);
rv = waiter.Wait(deadline, &context);
if (rv == MOJO_RESULT_OK)
rv = static_cast<MojoResult>(context);
}
// 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]->RemoveWaiter(&waiter);
return rv;
}
} // namespace system
} // namespace mojo