70 lines
2.4 KiB
C++
70 lines
2.4 KiB
C++
// Copyright 2019 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_MESSAGE_LOOP_WORK_ID_PROVIDER_H_
|
|
#define BASE_MESSAGE_LOOP_WORK_ID_PROVIDER_H_
|
|
|
|
#include <atomic>
|
|
|
|
#include "base/base_export.h"
|
|
#include "base/threading/thread_checker.h"
|
|
|
|
namespace base {
|
|
namespace sequence_manager {
|
|
namespace internal {
|
|
class ThreadControllerWithMessagePumpImpl;
|
|
}
|
|
} // namespace sequence_manager
|
|
|
|
// WorkIdProvider associates with the current thread (via TLS) an id state
|
|
// reflecting the current work item being executed by the message loop. The item
|
|
// is accessed lock-free from other threads to provide a snapshot of the
|
|
// currently-executing work item.
|
|
//
|
|
// The expected user is the ThreadProfiler which samples the id along with the
|
|
// thread's stack to identify cases where the same task spans multiple
|
|
// samples. The state is stored in TLS rather than on the MessageLoop or the
|
|
// ThreadProfiler because the lifetime relationship between the two classes
|
|
// varies depending on which thread is being profiled, plus the fact that
|
|
// MessageLoop doesn't have a well-defined creation point/owner on some threads.
|
|
class BASE_EXPORT WorkIdProvider {
|
|
public:
|
|
// Returns the WorkIdProvider for the current thread. Allocates a
|
|
// WorkIdProvider in TLS if not already present.
|
|
static WorkIdProvider* GetForCurrentThread();
|
|
|
|
// Returns the work id for the thread to which this WorkIdProvider
|
|
// belongs. The work id is 0 before calls to IncrementWorkId() and always
|
|
// non-zero after that point. The implementation supports being invoked while
|
|
// other threads are suspended, and thus is guaranteed to take no locks,
|
|
// directly or indirectly. May be called from any thread, as long as the
|
|
// owning thread hasn't been destroyed.
|
|
unsigned int GetWorkId();
|
|
|
|
// Public to support unique_ptr<WorkIdProvider>.
|
|
~WorkIdProvider();
|
|
|
|
void SetCurrentWorkIdForTesting(unsigned int id);
|
|
void IncrementWorkIdForTesting();
|
|
|
|
WorkIdProvider(const WorkIdProvider&) = delete;
|
|
WorkIdProvider& operator=(const WorkIdProvider&) = delete;
|
|
|
|
private:
|
|
// Friended to allow use of IncrementWorkId().
|
|
friend class sequence_manager::internal::ThreadControllerWithMessagePumpImpl;
|
|
|
|
WorkIdProvider();
|
|
|
|
void IncrementWorkId();
|
|
|
|
std::atomic_uint work_id_;
|
|
|
|
THREAD_CHECKER(thread_checker_);
|
|
};
|
|
|
|
} // namespace base
|
|
|
|
#endif // BASE_MESSAGE_LOOP_WORK_ID_PROVIDER_H_
|