blob: de54755f8924cd64d7c9181b809ae32d9cb9de18 [file] [log] [blame]
// Copyright (c) 2012 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 "ipc/ipc_sync_channel.h"
#include <stddef.h>
#include <stdint.h>
#include <utility>
#include "base/bind.h"
#include "base/lazy_instance.h"
#include "base/location.h"
#include "base/logging.h"
#include "base/memory/ptr_util.h"
#include "base/synchronization/waitable_event.h"
#include "base/synchronization/waitable_event_watcher.h"
#include "base/threading/thread_local.h"
#include "base/threading/thread_task_runner_handle.h"
#include "base/trace_event/trace_event.h"
#include "ipc/ipc_channel_factory.h"
#include "ipc/ipc_logging.h"
#include "ipc/ipc_message_macros.h"
#include "ipc/ipc_sync_message.h"
using base::TimeDelta;
using base::TimeTicks;
using base::WaitableEvent;
namespace IPC {
// When we're blocked in a Send(), we need to process incoming synchronous
// messages right away because it could be blocking our reply (either
// directly from the same object we're calling, or indirectly through one or
// more other channels). That means that in SyncContext's OnMessageReceived,
// we need to process sync message right away if we're blocked. However a
// simple check isn't sufficient, because the listener thread can be in the
// process of calling Send.
// To work around this, when SyncChannel filters a sync message, it sets
// an event that the listener thread waits on during its Send() call. This
// allows us to dispatch incoming sync messages when blocked. The race
// condition is handled because if Send is in the process of being called, it
// will check the event. In case the listener thread isn't sending a message,
// we queue a task on the listener thread to dispatch the received messages.
// The messages are stored in this queue object that's shared among all
// SyncChannel objects on the same thread (since one object can receive a
// sync message while another one is blocked).
class SyncChannel::ReceivedSyncMsgQueue :
public base::RefCountedThreadSafe<ReceivedSyncMsgQueue> {
public:
// Returns the ReceivedSyncMsgQueue instance for this thread, creating one
// if necessary. Call RemoveContext on the same thread when done.
static ReceivedSyncMsgQueue* AddContext() {
// We want one ReceivedSyncMsgQueue per listener thread (i.e. since multiple
// SyncChannel objects can block the same thread).
ReceivedSyncMsgQueue* rv = lazy_tls_ptr_.Pointer()->Get();
if (!rv) {
rv = new ReceivedSyncMsgQueue();
ReceivedSyncMsgQueue::lazy_tls_ptr_.Pointer()->Set(rv);
}
rv->listener_count_++;
return rv;
}
// Called on IPC thread when a synchronous message or reply arrives.
void QueueMessage(const Message& msg, SyncChannel::SyncContext* context) {
bool was_task_pending;
{
base::AutoLock auto_lock(message_lock_);
was_task_pending = task_pending_;
task_pending_ = true;
// We set the event in case the listener thread is blocked (or is about
// to). In case it's not, the PostTask dispatches the messages.
message_queue_.push_back(QueuedMessage(new Message(msg), context));
message_queue_version_++;
}
dispatch_event_.Signal();
if (!was_task_pending) {
listener_task_runner_->PostTask(
FROM_HERE, base::Bind(&ReceivedSyncMsgQueue::DispatchMessagesTask,
this, base::RetainedRef(context)));
}
}
void QueueReply(const Message &msg, SyncChannel::SyncContext* context) {
received_replies_.push_back(QueuedMessage(new Message(msg), context));
}
// Called on the listener's thread to process any queues synchronous
// messages.
void DispatchMessagesTask(SyncContext* context) {
{
base::AutoLock auto_lock(message_lock_);
task_pending_ = false;
}
context->DispatchMessages();
}
void DispatchMessages(SyncContext* dispatching_context) {
bool first_time = true;
uint32_t expected_version = 0;
SyncMessageQueue::iterator it;
while (true) {
Message* message = NULL;
scoped_refptr<SyncChannel::SyncContext> context;
{
base::AutoLock auto_lock(message_lock_);
if (first_time || message_queue_version_ != expected_version) {
it = message_queue_.begin();
first_time = false;
}
for (; it != message_queue_.end(); it++) {
int message_group = it->context->restrict_dispatch_group();
if (message_group == kRestrictDispatchGroup_None ||
message_group == dispatching_context->restrict_dispatch_group()) {
message = it->message;
context = it->context;
it = message_queue_.erase(it);
message_queue_version_++;
expected_version = message_queue_version_;
break;
}
}
}
if (message == NULL)
break;
context->OnDispatchMessage(*message);
delete message;
}
}
// SyncChannel calls this in its destructor.
void RemoveContext(SyncContext* context) {
base::AutoLock auto_lock(message_lock_);
SyncMessageQueue::iterator iter = message_queue_.begin();
while (iter != message_queue_.end()) {
if (iter->context.get() == context) {
delete iter->message;
iter = message_queue_.erase(iter);
message_queue_version_++;
} else {
iter++;
}
}
if (--listener_count_ == 0) {
DCHECK(lazy_tls_ptr_.Pointer()->Get());
lazy_tls_ptr_.Pointer()->Set(NULL);
}
}
WaitableEvent* dispatch_event() { return &dispatch_event_; }
base::SingleThreadTaskRunner* listener_task_runner() {
return listener_task_runner_.get();
}
// Holds a pointer to the per-thread ReceivedSyncMsgQueue object.
static base::LazyInstance<base::ThreadLocalPointer<ReceivedSyncMsgQueue> >
lazy_tls_ptr_;
// Called on the ipc thread to check if we can unblock any current Send()
// calls based on a queued reply.
void DispatchReplies() {
for (size_t i = 0; i < received_replies_.size(); ++i) {
Message* message = received_replies_[i].message;
if (received_replies_[i].context->TryToUnblockListener(message)) {
delete message;
received_replies_.erase(received_replies_.begin() + i);
return;
}
}
}
base::WaitableEventWatcher* top_send_done_watcher() {
return top_send_done_watcher_;
}
void set_top_send_done_watcher(base::WaitableEventWatcher* watcher) {
top_send_done_watcher_ = watcher;
}
private:
friend class base::RefCountedThreadSafe<ReceivedSyncMsgQueue>;
// See the comment in SyncChannel::SyncChannel for why this event is created
// as manual reset.
ReceivedSyncMsgQueue() :
message_queue_version_(0),
dispatch_event_(true, false),
listener_task_runner_(base::ThreadTaskRunnerHandle::Get()),
task_pending_(false),
listener_count_(0),
top_send_done_watcher_(NULL) {
}
~ReceivedSyncMsgQueue() {}
// Holds information about a queued synchronous message or reply.
struct QueuedMessage {
QueuedMessage(Message* m, SyncContext* c) : message(m), context(c) { }
Message* message;
scoped_refptr<SyncChannel::SyncContext> context;
};
typedef std::list<QueuedMessage> SyncMessageQueue;
SyncMessageQueue message_queue_;
uint32_t message_queue_version_; // Used to signal DispatchMessages to rescan
std::vector<QueuedMessage> received_replies_;
// Set when we got a synchronous message that we must respond to as the
// sender needs its reply before it can reply to our original synchronous
// message.
WaitableEvent dispatch_event_;
scoped_refptr<base::SingleThreadTaskRunner> listener_task_runner_;
base::Lock message_lock_;
bool task_pending_;
int listener_count_;
// The current send done event watcher for this thread. Used to maintain
// a local global stack of send done watchers to ensure that nested sync
// message loops complete correctly.
base::WaitableEventWatcher* top_send_done_watcher_;
};
base::LazyInstance<base::ThreadLocalPointer<SyncChannel::ReceivedSyncMsgQueue> >
SyncChannel::ReceivedSyncMsgQueue::lazy_tls_ptr_ =
LAZY_INSTANCE_INITIALIZER;
SyncChannel::SyncContext::SyncContext(
Listener* listener,
const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner,
WaitableEvent* shutdown_event)
: ChannelProxy::Context(listener, ipc_task_runner),
received_sync_msgs_(ReceivedSyncMsgQueue::AddContext()),
shutdown_event_(shutdown_event),
restrict_dispatch_group_(kRestrictDispatchGroup_None) {
}
SyncChannel::SyncContext::~SyncContext() {
while (!deserializers_.empty())
Pop();
}
// Adds information about an outgoing sync message to the context so that
// we know how to deserialize the reply. Returns a handle that's set when
// the reply has arrived.
void SyncChannel::SyncContext::Push(SyncMessage* sync_msg) {
// Create the tracking information for this message. This object is stored
// by value since all members are pointers that are cheap to copy. These
// pointers are cleaned up in the Pop() function.
//
// The event is created as manual reset because in between Signal and
// OnObjectSignalled, another Send can happen which would stop the watcher
// from being called. The event would get watched later, when the nested
// Send completes, so the event will need to remain set.
PendingSyncMsg pending(SyncMessage::GetMessageId(*sync_msg),
sync_msg->GetReplyDeserializer(),
new WaitableEvent(true, false));
base::AutoLock auto_lock(deserializers_lock_);
deserializers_.push_back(pending);
}
bool SyncChannel::SyncContext::Pop() {
bool result;
{
base::AutoLock auto_lock(deserializers_lock_);
PendingSyncMsg msg = deserializers_.back();
delete msg.deserializer;
delete msg.done_event;
msg.done_event = NULL;
deserializers_.pop_back();
result = msg.send_result;
}
// We got a reply to a synchronous Send() call that's blocking the listener
// thread. However, further down the call stack there could be another
// blocking Send() call, whose reply we received after we made this last
// Send() call. So check if we have any queued replies available that
// can now unblock the listener thread.
ipc_task_runner()->PostTask(
FROM_HERE, base::Bind(&ReceivedSyncMsgQueue::DispatchReplies,
received_sync_msgs_.get()));
return result;
}
WaitableEvent* SyncChannel::SyncContext::GetSendDoneEvent() {
base::AutoLock auto_lock(deserializers_lock_);
return deserializers_.back().done_event;
}
WaitableEvent* SyncChannel::SyncContext::GetDispatchEvent() {
return received_sync_msgs_->dispatch_event();
}
void SyncChannel::SyncContext::DispatchMessages() {
received_sync_msgs_->DispatchMessages(this);
}
bool SyncChannel::SyncContext::TryToUnblockListener(const Message* msg) {
base::AutoLock auto_lock(deserializers_lock_);
if (deserializers_.empty() ||
!SyncMessage::IsMessageReplyTo(*msg, deserializers_.back().id)) {
return false;
}
if (!msg->is_reply_error()) {
bool send_result = deserializers_.back().deserializer->
SerializeOutputParameters(*msg);
deserializers_.back().send_result = send_result;
DVLOG_IF(1, !send_result) << "Couldn't deserialize reply message";
} else {
DVLOG(1) << "Received error reply";
}
base::WaitableEvent* done_event = deserializers_.back().done_event;
TRACE_EVENT_FLOW_BEGIN0(
TRACE_DISABLED_BY_DEFAULT("ipc.flow"),
"SyncChannel::SyncContext::TryToUnblockListener", done_event);
done_event->Signal();
return true;
}
void SyncChannel::SyncContext::Clear() {
CancelPendingSends();
received_sync_msgs_->RemoveContext(this);
Context::Clear();
}
bool SyncChannel::SyncContext::OnMessageReceived(const Message& msg) {
// Give the filters a chance at processing this message.
if (TryFilters(msg))
return true;
if (TryToUnblockListener(&msg))
return true;
if (msg.is_reply()) {
received_sync_msgs_->QueueReply(msg, this);
return true;
}
if (msg.should_unblock()) {
received_sync_msgs_->QueueMessage(msg, this);
return true;
}
return Context::OnMessageReceivedNoFilter(msg);
}
void SyncChannel::SyncContext::OnChannelError() {
CancelPendingSends();
shutdown_watcher_.StopWatching();
Context::OnChannelError();
}
void SyncChannel::SyncContext::OnChannelOpened() {
shutdown_watcher_.StartWatching(
shutdown_event_,
base::Bind(&SyncChannel::SyncContext::OnWaitableEventSignaled,
base::Unretained(this)));
Context::OnChannelOpened();
}
void SyncChannel::SyncContext::OnChannelClosed() {
CancelPendingSends();
shutdown_watcher_.StopWatching();
Context::OnChannelClosed();
}
void SyncChannel::SyncContext::CancelPendingSends() {
base::AutoLock auto_lock(deserializers_lock_);
PendingSyncMessageQueue::iterator iter;
DVLOG(1) << "Canceling pending sends";
for (iter = deserializers_.begin(); iter != deserializers_.end(); iter++) {
TRACE_EVENT_FLOW_BEGIN0(TRACE_DISABLED_BY_DEFAULT("ipc.flow"),
"SyncChannel::SyncContext::CancelPendingSends",
iter->done_event);
iter->done_event->Signal();
}
}
void SyncChannel::SyncContext::OnWaitableEventSignaled(WaitableEvent* event) {
if (event == shutdown_event_) {
// Process shut down before we can get a reply to a synchronous message.
// Cancel pending Send calls, which will end up setting the send done event.
CancelPendingSends();
} else {
// We got the reply, timed out or the process shutdown.
DCHECK_EQ(GetSendDoneEvent(), event);
base::MessageLoop::current()->QuitNow();
}
}
base::WaitableEventWatcher::EventCallback
SyncChannel::SyncContext::MakeWaitableEventCallback() {
return base::Bind(&SyncChannel::SyncContext::OnWaitableEventSignaled, this);
}
// static
std::unique_ptr<SyncChannel> SyncChannel::Create(
const IPC::ChannelHandle& channel_handle,
Channel::Mode mode,
Listener* listener,
const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner,
bool create_pipe_now,
base::WaitableEvent* shutdown_event) {
std::unique_ptr<SyncChannel> channel =
Create(listener, ipc_task_runner, shutdown_event);
channel->Init(channel_handle, mode, create_pipe_now);
return channel;
}
// static
std::unique_ptr<SyncChannel> SyncChannel::Create(
std::unique_ptr<ChannelFactory> factory,
Listener* listener,
const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner,
bool create_pipe_now,
base::WaitableEvent* shutdown_event) {
std::unique_ptr<SyncChannel> channel =
Create(listener, ipc_task_runner, shutdown_event);
channel->Init(std::move(factory), create_pipe_now);
return channel;
}
// static
std::unique_ptr<SyncChannel> SyncChannel::Create(
Listener* listener,
const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner,
WaitableEvent* shutdown_event) {
return base::WrapUnique(
new SyncChannel(listener, ipc_task_runner, shutdown_event));
}
SyncChannel::SyncChannel(
Listener* listener,
const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner,
WaitableEvent* shutdown_event)
: ChannelProxy(new SyncContext(listener, ipc_task_runner, shutdown_event)) {
// The current (listener) thread must be distinct from the IPC thread, or else
// sending synchronous messages will deadlock.
DCHECK_NE(ipc_task_runner.get(), base::ThreadTaskRunnerHandle::Get().get());
StartWatching();
}
SyncChannel::~SyncChannel() {
}
void SyncChannel::SetRestrictDispatchChannelGroup(int group) {
sync_context()->set_restrict_dispatch_group(group);
}
scoped_refptr<SyncMessageFilter> SyncChannel::CreateSyncMessageFilter() {
scoped_refptr<SyncMessageFilter> filter = new SyncMessageFilter(
sync_context()->shutdown_event(),
sync_context()->IsChannelSendThreadSafe());
AddFilter(filter.get());
if (!did_init())
pre_init_sync_message_filters_.push_back(filter);
return filter;
}
bool SyncChannel::Send(Message* message) {
#ifdef IPC_MESSAGE_LOG_ENABLED
std::string name;
Logging::GetInstance()->GetMessageText(message->type(), &name, message, NULL);
TRACE_EVENT1("ipc", "SyncChannel::Send", "name", name);
#else
TRACE_EVENT2("ipc", "SyncChannel::Send",
"class", IPC_MESSAGE_ID_CLASS(message->type()),
"line", IPC_MESSAGE_ID_LINE(message->type()));
#endif
if (!message->is_sync()) {
ChannelProxy::Send(message);
return true;
}
// *this* might get deleted in WaitForReply.
scoped_refptr<SyncContext> context(sync_context());
if (context->shutdown_event()->IsSignaled()) {
DVLOG(1) << "shutdown event is signaled";
delete message;
return false;
}
SyncMessage* sync_msg = static_cast<SyncMessage*>(message);
context->Push(sync_msg);
WaitableEvent* pump_messages_event = sync_msg->pump_messages_event();
ChannelProxy::Send(message);
// Wait for reply, or for any other incoming synchronous messages.
// *this* might get deleted, so only call static functions at this point.
WaitForReply(context.get(), pump_messages_event);
TRACE_EVENT_FLOW_END0(TRACE_DISABLED_BY_DEFAULT("ipc.flow"),
"SyncChannel::Send", context->GetSendDoneEvent());
return context->Pop();
}
void SyncChannel::WaitForReply(
SyncContext* context, WaitableEvent* pump_messages_event) {
context->DispatchMessages();
while (true) {
WaitableEvent* objects[] = {
context->GetDispatchEvent(),
context->GetSendDoneEvent(),
pump_messages_event
};
unsigned count = pump_messages_event ? 3: 2;
size_t result = WaitableEvent::WaitMany(objects, count);
if (result == 0 /* dispatch event */) {
// We're waiting for a reply, but we received a blocking synchronous
// call. We must process it or otherwise a deadlock might occur.
context->GetDispatchEvent()->Reset();
context->DispatchMessages();
continue;
}
if (result == 2 /* pump_messages_event */)
WaitForReplyWithNestedMessageLoop(context); // Run a nested message loop.
break;
}
}
void SyncChannel::WaitForReplyWithNestedMessageLoop(SyncContext* context) {
base::WaitableEventWatcher send_done_watcher;
ReceivedSyncMsgQueue* sync_msg_queue = context->received_sync_msgs();
DCHECK(sync_msg_queue != NULL);
base::WaitableEventWatcher* old_send_done_event_watcher =
sync_msg_queue->top_send_done_watcher();
base::WaitableEventWatcher::EventCallback old_callback;
base::WaitableEvent* old_event = NULL;
// Maintain a local global stack of send done delegates to ensure that
// nested sync calls complete in the correct sequence, i.e. the
// outermost call completes first, etc.
if (old_send_done_event_watcher) {
old_callback = old_send_done_event_watcher->callback();
old_event = old_send_done_event_watcher->GetWatchedEvent();
old_send_done_event_watcher->StopWatching();
}
sync_msg_queue->set_top_send_done_watcher(&send_done_watcher);
send_done_watcher.StartWatching(context->GetSendDoneEvent(),
context->MakeWaitableEventCallback());
{
base::MessageLoop::ScopedNestableTaskAllower allow(
base::MessageLoop::current());
base::MessageLoop::current()->Run();
}
sync_msg_queue->set_top_send_done_watcher(old_send_done_event_watcher);
if (old_send_done_event_watcher && old_event) {
old_send_done_event_watcher->StartWatching(old_event, old_callback);
}
}
void SyncChannel::OnWaitableEventSignaled(WaitableEvent* event) {
DCHECK(event == sync_context()->GetDispatchEvent());
// The call to DispatchMessages might delete this object, so reregister
// the object watcher first.
event->Reset();
dispatch_watcher_.StartWatching(event, dispatch_watcher_callback_);
sync_context()->DispatchMessages();
}
void SyncChannel::StartWatching() {
// Ideally we only want to watch this object when running a nested message
// loop. However, we don't know when it exits if there's another nested
// message loop running under it or not, so we wouldn't know whether to
// stop or keep watching. So we always watch it, and create the event as
// manual reset since the object watcher might otherwise reset the event
// when we're doing a WaitMany.
dispatch_watcher_callback_ =
base::Bind(&SyncChannel::OnWaitableEventSignaled,
base::Unretained(this));
dispatch_watcher_.StartWatching(sync_context()->GetDispatchEvent(),
dispatch_watcher_callback_);
}
void SyncChannel::OnChannelInit() {
for (const auto& filter : pre_init_sync_message_filters_) {
filter->set_is_channel_send_thread_safe(
context()->IsChannelSendThreadSafe());
}
pre_init_sync_message_filters_.clear();
}
} // namespace IPC