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| -rw-r--r-- | third_party/libwebrtc/api/sequence_checker.h | 126 |
1 files changed, 126 insertions, 0 deletions
diff --git a/third_party/libwebrtc/api/sequence_checker.h b/third_party/libwebrtc/api/sequence_checker.h new file mode 100644 index 0000000000..33e0f3c074 --- /dev/null +++ b/third_party/libwebrtc/api/sequence_checker.h @@ -0,0 +1,126 @@ +/* + * 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 API_SEQUENCE_CHECKER_H_ +#define API_SEQUENCE_CHECKER_H_ + +#include "rtc_base/checks.h" +#include "rtc_base/synchronization/sequence_checker_internal.h" +#include "rtc_base/thread_annotations.h" + +namespace webrtc { + +// 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. +class RTC_LOCKABLE SequenceChecker +#if RTC_DCHECK_IS_ON + : public webrtc_sequence_checker_internal::SequenceCheckerImpl { + using Impl = webrtc_sequence_checker_internal::SequenceCheckerImpl; +#else + : public webrtc_sequence_checker_internal::SequenceCheckerDoNothing { + using Impl = webrtc_sequence_checker_internal::SequenceCheckerDoNothing; +#endif + public: + enum InitialState : bool { kDetached = false, kAttached = true }; + + explicit SequenceChecker(InitialState initial_state = kAttached) + : Impl(initial_state) {} + + // Returns true if sequence checker is attached to the current sequence. + bool IsCurrent() const { return Impl::IsCurrent(); } + // Detaches checker from sequence to which it is attached. Next attempt + // to do a check with this checker will result in attaching this checker + // to the sequence on which check was performed. + void Detach() { Impl::Detach(); } +}; + +} // 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 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::TaskQueueBase& Queue() { return encoder_queue_; } +// void Encode() { +// RTC_DCHECK_RUN_ON(&encoder_queue_); +// DoSomething(var_); +// } +// +// private: +// rtc::TaskQueueBase& 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)) + +// Checks current code is running on the desired sequence. +// +// First statement validates it is running on the sequence `x`. +// Second statement annotates for the thread safety analyzer the check was done. +// Such annotation has to be attached to a function, and that function has to be +// called. Thus current implementation creates a noop lambda and calls it. +#define RTC_DCHECK_RUN_ON(x) \ + RTC_DCHECK((x)->IsCurrent()) \ + << webrtc::webrtc_sequence_checker_internal::ExpectationToString(x); \ + []() RTC_ASSERT_EXCLUSIVE_LOCK(x) {}() + +#endif // API_SEQUENCE_CHECKER_H_ |