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// Copyright 2015 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/mojo/async_handle_waiter.h"
#include "base/atomic_ref_count.h"
#include "base/bind.h"
#include "base/bind_helpers.h"
#include "base/location.h"
#include "base/logging.h"
#include "base/macros.h"
#include "mojo/edk/embedder/embedder.h"
namespace IPC {
namespace internal {
class AsyncHandleWaiterContextTraits {
public:
static void Destruct(const AsyncHandleWaiter::Context* context);
};
// The thread-safe part of |AsyncHandleWaiter|.
// As |AsyncWait()| invokes the given callback from an arbitrary thread,
// |HandleIsReady()| and the bound |this| have to be thread-safe.
class AsyncHandleWaiter::Context
: public base::RefCountedThreadSafe<AsyncHandleWaiter::Context,
AsyncHandleWaiterContextTraits>,
public base::MessageLoopForIO::IOObserver {
public:
Context(base::WeakPtr<AsyncHandleWaiter> waiter)
: io_runner_(base::MessageLoopForIO::current()->task_runner()),
waiter_(waiter),
last_result_(MOJO_RESULT_INTERNAL),
io_loop_level_(0),
should_invoke_callback_(false) {
base::MessageLoopForIO::current()->AddIOObserver(this);
}
void HandleIsReady(MojoResult result) {
last_result_ = result;
// If the signaling happens in the IO handler, use |IOObserver| callback
// to invoke the callback.
if (IsCalledFromIOHandler()) {
should_invoke_callback_ = true;
return;
}
io_runner_->PostTask(FROM_HERE,
base::Bind(&Context::InvokeWaiterCallback, this));
}
private:
friend void base::DeletePointer<const Context>(const Context* self);
friend class AsyncHandleWaiterContextTraits;
friend class base::RefCountedThreadSafe<Context>;
~Context() override {
DCHECK(base::MessageLoopForIO::current()->task_runner() == io_runner_);
base::MessageLoopForIO::current()->RemoveIOObserver(this);
}
bool IsCalledFromIOHandler() const {
base::MessageLoop* loop = base::MessageLoop::current();
if (!loop)
return false;
if (loop->task_runner() != io_runner_)
return false;
return io_loop_level_ > 0;
}
// Called from |io_runner_| thus safe to touch |waiter_|.
void InvokeWaiterCallback() {
MojoResult result = last_result_;
last_result_ = MOJO_RESULT_INTERNAL;
if (waiter_)
waiter_->InvokeCallback(result);
}
// IOObserver implementation:
void WillProcessIOEvent() override {
DCHECK(io_loop_level_ != 0 || !should_invoke_callback_);
DCHECK_GE(io_loop_level_, 0);
io_loop_level_++;
}
void DidProcessIOEvent() override {
// This object could have been constructed in another's class's
// DidProcessIOEvent.
if (io_loop_level_== 0)
return;
DCHECK_GE(io_loop_level_, 1);
// Leaving a nested loop.
if (io_loop_level_ > 1) {
io_loop_level_--;
return;
}
// The zero |waiter_| indicates that |this| have lost the owner and can be
// under destruction. So we cannot wrap it with a |scoped_refptr| anymore.
if (!waiter_) {
should_invoke_callback_ = false;
io_loop_level_--;
return;
}
// We have to protect |this| because |AsyncHandleWaiter| can be
// deleted during the callback.
scoped_refptr<Context> protect(this);
while (should_invoke_callback_) {
should_invoke_callback_ = false;
InvokeWaiterCallback();
}
io_loop_level_--;
}
// Only |io_runner_| is accessed from arbitrary threads. Others are touched
// only from the IO thread.
const scoped_refptr<base::TaskRunner> io_runner_;
const base::WeakPtr<AsyncHandleWaiter> waiter_;
MojoResult last_result_;
int io_loop_level_;
bool should_invoke_callback_;
DISALLOW_COPY_AND_ASSIGN(Context);
};
AsyncHandleWaiter::AsyncHandleWaiter(base::Callback<void(MojoResult)> callback)
: callback_(callback),
weak_factory_(this) {
context_ = new Context(weak_factory_.GetWeakPtr());
}
AsyncHandleWaiter::~AsyncHandleWaiter() {
}
MojoResult AsyncHandleWaiter::Wait(MojoHandle handle,
MojoHandleSignals signals) {
return mojo::edk::AsyncWait(handle, signals,
base::Bind(&Context::HandleIsReady, context_));
}
void AsyncHandleWaiter::InvokeCallback(MojoResult result) {
callback_.Run(result);
}
base::MessageLoopForIO::IOObserver* AsyncHandleWaiter::GetIOObserverForTest() {
return context_.get();
}
base::Callback<void(MojoResult)> AsyncHandleWaiter::GetWaitCallbackForTest() {
return base::Bind(&Context::HandleIsReady, context_);
}
// static
void AsyncHandleWaiterContextTraits::Destruct(
const AsyncHandleWaiter::Context* context) {
context->io_runner_->PostTask(
FROM_HERE,
base::Bind(&base::DeletePointer<const AsyncHandleWaiter::Context>,
base::Unretained(context)));
}
} // namespace internal
} // namespace IPC
|
