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// Copyright 2011 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_THREADING_THREAD_CHECKER_IMPL_H_
#define BASE_THREADING_THREAD_CHECKER_IMPL_H_
#include <memory>
#include "base/base_export.h"
#include "base/sequence_token.h"
#include "base/synchronization/lock.h"
#include "base/thread_annotations.h"
#include "base/threading/platform_thread_ref.h"
namespace base {
namespace debug {
class StackTrace;
}
// Real implementation of ThreadChecker, for use in debug mode, or for temporary
// use in release mode (e.g. to CHECK on a threading issue seen only in the
// wild).
//
// Note: You should almost always use the ThreadChecker class to get the right
// version for your build configuration.
// Note: This is only a check, not a "lock". It is marked "LOCKABLE" only in
// order to support thread_annotations.h.
class LOCKABLE BASE_EXPORT ThreadCheckerImpl {
public:
static void EnableStackLogging();
ThreadCheckerImpl();
~ThreadCheckerImpl();
// Allow move construct/assign. This must be called on |other|'s associated
// thread and assignment can only be made into a ThreadCheckerImpl which is
// detached or already associated with the current thread. This isn't
// thread-safe (|this| and |other| shouldn't be in use while this move is
// performed). If the assignment was legal, the resulting ThreadCheckerImpl
// will be bound to the current thread and |other| will be detached.
ThreadCheckerImpl(ThreadCheckerImpl&& other);
ThreadCheckerImpl& operator=(ThreadCheckerImpl&& other);
// On returning false, if logging is enabled with EnableStackLogging() and
// `out_bound_at` is not null, this method allocates a StackTrace and returns
// it in the out-parameter, storing inside it the stack from where the failing
// ThreadChecker was bound to its thread.
[[nodiscard]] bool CalledOnValidThread(
std::unique_ptr<debug::StackTrace>* out_bound_at = nullptr) const;
// Changes the thread that is checked for in CalledOnValidThread. This may
// be useful when an object may be created on one thread and then used
// exclusively on another thread.
void DetachFromThread();
// Returns ownership of a pointer to StackTrace where the ThreadCheckerImpl
// was bound for debug logs, or nullptr if such logging was not enabled at
// the time.
std::unique_ptr<debug::StackTrace> GetBoundAt() const;
private:
void EnsureAssignedLockRequired() const EXCLUSIVE_LOCKS_REQUIRED(lock_);
// Members are mutable so that CalledOnValidThread() can set them.
// Synchronizes access to all members.
mutable base::Lock lock_;
// The location where the ThreadChecker was bound to the current
// thread/task/sequence. Default-initialized with 0 frames until bound.
mutable std::unique_ptr<debug::StackTrace> bound_at_ GUARDED_BY(lock_);
// Thread on which CalledOnValidThread() may return true.
mutable PlatformThreadRef thread_id_ GUARDED_BY(lock_);
// TaskToken for which CalledOnValidThread() always returns true. This allows
// CalledOnValidThread() to return true when called multiple times from the
// same task, even if it's not running in a single-threaded context itself
// (allowing usage of ThreadChecker objects on the stack in the scope of one-
// off tasks). Note: CalledOnValidThread() may return true even if the current
// TaskToken is not equal to this.
mutable TaskToken task_token_ GUARDED_BY(lock_);
// SequenceToken for which CalledOnValidThread() may return true. Used to
// ensure that CalledOnValidThread() doesn't return true for ThreadPool
// tasks that happen to run on the same thread but weren't posted to the same
// SingleThreadTaskRunner.
mutable SequenceToken sequence_token_ GUARDED_BY(lock_);
};
} // namespace base
#endif // BASE_THREADING_THREAD_CHECKER_IMPL_H_
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