blob: 3c68eec3235ab01a936676d3c51e4f089dbfc24a [file] [log] [blame]
// Copyright 2018 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/memory/ref_counted.h"
#include "base/optional.h"
#include "base/synchronization/lock.h"
#include "base/task/sequence_manager/moveable_auto_lock.h"
#include "base/task/sequence_manager/task_queue.h"
#include "base/task/sequence_manager/tasks.h"
namespace base {
namespace sequence_manager {
namespace internal {
struct AssociatedThreadId;
class TaskQueueImpl;
// Task runners are ref-counted and unaccountable, so we need a safe way
// to delete a task queue while associated task runners might be still around.
// When TaskQueueImpl goes away, this proxy becomes a stub and later on gets
// ref-count-destructed once no TaskQueueTaskRunner remains.
// NOTE: Instances must be constructed or detached only by TaskQueueImpl,
// unless |task_queue_impl| is null (which is useful for stub task runners).
class TaskQueueProxy : public RefCountedThreadSafe<TaskQueueProxy> {
TaskQueueProxy(TaskQueueImpl* task_queue_impl,
scoped_refptr<AssociatedThreadId> associated_thread);
// May be called on any thread.
bool PostTask(PostedTask task) const;
bool RunsTasksInCurrentSequence() const;
// PostTask will reject any task after this call.
// Must be called on main thread only.
void DetachFromTaskQueueImpl();
friend class RefCountedThreadSafe<TaskQueueProxy>;
// Doesn't acquire lock on main thread.
Optional<MoveableAutoLock> AcquireLockIfNeeded() const;
mutable Lock lock_;
TaskQueueImpl* task_queue_impl_; // Not owned.
const scoped_refptr<AssociatedThreadId> associated_thread_;
} // namespace internal
} // namespace sequence_manager
} // namespace base