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// Copyright (c) 2006-2009 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 "base/thread.h"
#include "base/lazy_instance.h"
#include "base/string_util.h"
#include "base/thread_local.h"
#include "base/waitable_event.h"
namespace base {
// This task is used to trigger the message loop to exit.
class ThreadQuitTask : public Task {
public:
virtual void Run() {
MessageLoop::current()->Quit();
Thread::SetThreadWasQuitProperly(true);
}
};
// Used to pass data to ThreadMain. This structure is allocated on the stack
// from within StartWithOptions.
struct Thread::StartupData {
// We get away with a const reference here because of how we are allocated.
const Thread::Options& options;
// Used to synchronize thread startup.
WaitableEvent event;
explicit StartupData(const Options& opt)
: options(opt),
event(false, false) {}
};
Thread::Thread(const char *name)
: stopping_(false),
startup_data_(NULL),
thread_(0),
message_loop_(NULL),
thread_id_(0),
name_(name) {
}
Thread::~Thread() {
Stop();
}
namespace {
// We use this thread-local variable to record whether or not a thread exited
// because its Stop method was called. This allows us to catch cases where
// MessageLoop::Quit() is called directly, which is unexpected when using a
// Thread to setup and run a MessageLoop.
base::LazyInstance<base::ThreadLocalBoolean> lazy_tls_bool(
base::LINKER_INITIALIZED);
} // namespace
void Thread::SetThreadWasQuitProperly(bool flag) {
lazy_tls_bool.Pointer()->Set(flag);
}
bool Thread::GetThreadWasQuitProperly() {
bool quit_properly = true;
#ifndef NDEBUG
quit_properly = lazy_tls_bool.Pointer()->Get();
#endif
return quit_properly;
}
bool Thread::Start() {
return StartWithOptions(Options());
}
bool Thread::StartWithOptions(const Options& options) {
DCHECK(!message_loop_);
SetThreadWasQuitProperly(false);
StartupData startup_data(options);
startup_data_ = &startup_data;
if (!PlatformThread::Create(options.stack_size, this, &thread_)) {
DLOG(ERROR) << "failed to create thread";
startup_data_ = NULL; // Record that we failed to start.
return false;
}
// Wait for the thread to start and initialize message_loop_
startup_data.event.Wait();
DCHECK(message_loop_);
return true;
}
void Thread::Stop() {
if (!thread_was_started())
return;
StopSoon();
// Wait for the thread to exit.
//
// TODO(darin): Unfortunately, we need to keep message_loop_ around until
// the thread exits. Some consumers are abusing the API. Make them stop.
//
PlatformThread::Join(thread_);
// The thread should NULL message_loop_ on exit.
DCHECK(!message_loop_);
// The thread no longer needs to be joined.
startup_data_ = NULL;
stopping_ = false;
}
void Thread::StopSoon() {
// We should only be called on the same thread that started us.
DCHECK_NE(thread_id_, PlatformThread::CurrentId());
if (stopping_ || !message_loop_)
return;
stopping_ = true;
message_loop_->PostTask(FROM_HERE, new ThreadQuitTask());
}
void Thread::Run(MessageLoop* message_loop) {
message_loop->Run();
}
void Thread::ThreadMain() {
// The message loop for this thread.
MessageLoop message_loop(startup_data_->options.message_loop_type);
// Complete the initialization of our Thread object.
thread_id_ = PlatformThread::CurrentId();
PlatformThread::SetName(name_.c_str());
message_loop.set_thread_name(name_);
message_loop_ = &message_loop;
// Let the thread do extra initialization.
// Let's do this before signaling we are started.
Init();
startup_data_->event.Signal();
// startup_data_ can't be touched anymore since the starting thread is now
// unlocked.
Run(message_loop_);
// Let the thread do extra cleanup.
CleanUp();
// Assert that MessageLoop::Quit was called by ThreadQuitTask.
DCHECK(GetThreadWasQuitProperly());
// We can't receive messages anymore.
message_loop_ = NULL;
thread_id_ = 0;
}
} // namespace base
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