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- /*
- * Copyright 2019 The WebRTC project authors. All Rights Reserved.
- *
- * Use of this source code is governed by a BSD-style license
- * that can be found in the LICENSE file in the root of the source
- * tree. An additional intellectual property rights grant can be found
- * in the file PATENTS. All contributing project authors may
- * be found in the AUTHORS file in the root of the source tree.
- */
- #ifndef RTC_BASE_SYNCHRONIZATION_SEQUENCE_CHECKER_H_
- #define RTC_BASE_SYNCHRONIZATION_SEQUENCE_CHECKER_H_
- #include <type_traits>
- #include "api/task_queue/task_queue_base.h"
- #include "rtc_base/platform_thread_types.h"
- #include "rtc_base/synchronization/mutex.h"
- #include "rtc_base/system/rtc_export.h"
- #include "rtc_base/thread_annotations.h"
- namespace webrtc {
- // Real implementation of SequenceChecker, for use in debug mode, or
- // for temporary use in release mode (e.g. to RTC_CHECK on a threading issue
- // seen only in the wild).
- //
- // Note: You should almost always use the SequenceChecker class to get the
- // right version for your build configuration.
- class RTC_EXPORT SequenceCheckerImpl {
- public:
- SequenceCheckerImpl();
- ~SequenceCheckerImpl();
- bool IsCurrent() const;
- // Changes the task queue or thread that is checked for in IsCurrent. This can
- // be useful when an object may be created on one task queue / thread and then
- // used exclusively on another thread.
- void Detach();
- // Returns a string that is formatted to match with the error string printed
- // by RTC_CHECK() when a condition is not met.
- // This is used in conjunction with the RTC_DCHECK_RUN_ON() macro.
- std::string ExpectationToString() const;
- private:
- mutable Mutex lock_;
- // These are mutable so that IsCurrent can set them.
- mutable bool attached_ RTC_GUARDED_BY(lock_);
- mutable rtc::PlatformThreadRef valid_thread_ RTC_GUARDED_BY(lock_);
- mutable const TaskQueueBase* valid_queue_ RTC_GUARDED_BY(lock_);
- mutable const void* valid_system_queue_ RTC_GUARDED_BY(lock_);
- };
- // Do nothing implementation, for use in release mode.
- //
- // Note: You should almost always use the SequenceChecker class to get the
- // right version for your build configuration.
- class SequenceCheckerDoNothing {
- public:
- bool IsCurrent() const { return true; }
- void Detach() {}
- };
- // SequenceChecker is a helper class used to help verify that some methods
- // of a class are called on the same task queue or thread. A
- // SequenceChecker is bound to a a task queue if the object is
- // created on a task queue, or a thread otherwise.
- //
- //
- // Example:
- // class MyClass {
- // public:
- // void Foo() {
- // RTC_DCHECK_RUN_ON(sequence_checker_);
- // ... (do stuff) ...
- // }
- //
- // private:
- // SequenceChecker sequence_checker_;
- // }
- //
- // In Release mode, IsCurrent will always return true.
- #if RTC_DCHECK_IS_ON
- class RTC_LOCKABLE SequenceChecker : public SequenceCheckerImpl {};
- #else
- class RTC_LOCKABLE SequenceChecker : public SequenceCheckerDoNothing {};
- #endif // RTC_ENABLE_THREAD_CHECKER
- namespace webrtc_seq_check_impl {
- // Helper class used by RTC_DCHECK_RUN_ON (see example usage below).
- class RTC_SCOPED_LOCKABLE SequenceCheckerScope {
- public:
- template <typename ThreadLikeObject>
- explicit SequenceCheckerScope(const ThreadLikeObject* thread_like_object)
- RTC_EXCLUSIVE_LOCK_FUNCTION(thread_like_object) {}
- SequenceCheckerScope(const SequenceCheckerScope&) = delete;
- SequenceCheckerScope& operator=(const SequenceCheckerScope&) = delete;
- ~SequenceCheckerScope() RTC_UNLOCK_FUNCTION() {}
- template <typename ThreadLikeObject>
- static bool IsCurrent(const ThreadLikeObject* thread_like_object) {
- return thread_like_object->IsCurrent();
- }
- };
- } // namespace webrtc_seq_check_impl
- } // namespace webrtc
- // RTC_RUN_ON/RTC_GUARDED_BY/RTC_DCHECK_RUN_ON macros allows to annotate
- // variables are accessed from same thread/task queue.
- // Using tools designed to check mutexes, it checks at compile time everywhere
- // variable is access, there is a run-time dcheck thread/task queue is correct.
- //
- // class ThreadExample {
- // public:
- // void NeedVar1() {
- // RTC_DCHECK_RUN_ON(network_thread_);
- // transport_->Send();
- // }
- //
- // private:
- // rtc::Thread* network_thread_;
- // int transport_ RTC_GUARDED_BY(network_thread_);
- // };
- //
- // class SequenceCheckerExample {
- // public:
- // int CalledFromPacer() RTC_RUN_ON(pacer_sequence_checker_) {
- // return var2_;
- // }
- //
- // void CallMeFromPacer() {
- // RTC_DCHECK_RUN_ON(&pacer_sequence_checker_)
- // << "Should be called from pacer";
- // CalledFromPacer();
- // }
- //
- // private:
- // int pacer_var_ RTC_GUARDED_BY(pacer_sequence_checker_);
- // SequenceChecker pacer_sequence_checker_;
- // };
- //
- // class TaskQueueExample {
- // public:
- // class Encoder {
- // public:
- // rtc::TaskQueue* Queue() { return encoder_queue_; }
- // void Encode() {
- // RTC_DCHECK_RUN_ON(encoder_queue_);
- // DoSomething(var_);
- // }
- //
- // private:
- // rtc::TaskQueue* const encoder_queue_;
- // Frame var_ RTC_GUARDED_BY(encoder_queue_);
- // };
- //
- // void Encode() {
- // // Will fail at runtime when DCHECK is enabled:
- // // encoder_->Encode();
- // // Will work:
- // rtc::scoped_refptr<Encoder> encoder = encoder_;
- // encoder_->Queue()->PostTask([encoder] { encoder->Encode(); });
- // }
- //
- // private:
- // rtc::scoped_refptr<Encoder> encoder_;
- // }
- // Document if a function expected to be called from same thread/task queue.
- #define RTC_RUN_ON(x) \
- RTC_THREAD_ANNOTATION_ATTRIBUTE__(exclusive_locks_required(x))
- namespace webrtc {
- std::string ExpectationToString(const webrtc::SequenceChecker* checker);
- // Catch-all implementation for types other than explicitly supported above.
- template <typename ThreadLikeObject>
- std::string ExpectationToString(const ThreadLikeObject*) {
- return std::string();
- }
- } // namespace webrtc
- #define RTC_DCHECK_RUN_ON(x) \
- webrtc::webrtc_seq_check_impl::SequenceCheckerScope seq_check_scope(x); \
- RTC_DCHECK((x)->IsCurrent()) << webrtc::ExpectationToString(x)
- #endif // RTC_BASE_SYNCHRONIZATION_SEQUENCE_CHECKER_H_
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