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// Copyright (c) 2006-2008 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/message_loop.h"
#include "base/string_util.h"
#include "base/waitable_event.h"
// 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);
}
};
Thread::Thread(const char *name)
: message_loop_(NULL),
startup_event_(NULL),
name_(name),
thread_created_(false) {
}
Thread::~Thread() {
Stop();
}
// 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.
// Note that if we start doing complex stuff in other static initializers
// this could cause problems.
// TODO(evanm): this shouldn't rely on static initialization.
TLSSlot Thread::tls_index_;
void Thread::SetThreadWasQuitProperly(bool flag) {
#ifndef NDEBUG
tls_index_.Set(reinterpret_cast<void*>(flag));
#endif
}
bool Thread::GetThreadWasQuitProperly() {
bool quit_properly = true;
#ifndef NDEBUG
quit_properly = (tls_index_.Get() != 0);
#endif
return quit_properly;
}
bool Thread::Start() {
return StartWithStackSize(0);
}
bool Thread::StartWithStackSize(size_t stack_size) {
DCHECK(!message_loop_);
SetThreadWasQuitProperly(false);
base::WaitableEvent event(false, false);
startup_event_ = &event;
if (!PlatformThread::Create(stack_size, this, &thread_)) {
DLOG(ERROR) << "failed to create thread";
return false;
}
// Wait for the thread to start and initialize message_loop_
startup_event_->Wait();
startup_event_ = NULL;
DCHECK(message_loop_);
return true;
}
void Thread::Stop() {
if (!thread_created_)
return;
DCHECK_NE(thread_id_, PlatformThread::CurrentId()) <<
"Can't call Stop() on the currently executing thread";
// If StopSoon was called, then we won't have a message loop anymore, but
// more importantly, we won't need to tell the thread to stop.
if (message_loop_)
message_loop_->PostTask(FROM_HERE, new ThreadQuitTask());
// Wait for the thread to exit. It should already have terminated but make
// sure this assumption is valid.
PlatformThread::Join(thread_);
// The thread can't receive messages anymore.
message_loop_ = NULL;
// The thread no longer needs to be joined.
thread_created_ = false;
}
void Thread::StopSoon() {
if (!message_loop_)
return;
DCHECK_NE(thread_id_, PlatformThread::CurrentId()) <<
"Can't call StopSoon() on the currently executing thread";
// We had better have a message loop at this point! If we do not, then it
// most likely means that the thread terminated unexpectedly, probably due
// to someone calling Quit() on our message loop directly.
DCHECK(message_loop_);
message_loop_->PostTask(FROM_HERE, new ThreadQuitTask());
// The thread can't receive messages anymore.
message_loop_ = NULL;
}
void Thread::ThreadMain() {
// The message loop for this thread.
MessageLoop message_loop;
// Complete the initialization of our Thread object.
thread_id_ = PlatformThread::CurrentId();
PlatformThread::SetName(thread_id_, name_.c_str());
message_loop.set_thread_name(name_);
message_loop_ = &message_loop;
thread_created_ = true;
startup_event_->Signal();
// startup_event_ can't be touched anymore since the starting thread is now
// unlocked.
// Let the thread do extra initialization.
Init();
message_loop.Run();
// 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;
}
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