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Introduces rtc_base/synchronization/mutex.h.

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This change introduces a new non-reentrant mutex to WebRTC. It
enables eventual migration to Abseil's mutex.

The mutex types supportable by webrtc::Mutex are

- absl::Mutex
- CriticalSection (Windows only)
- pthread_mutex (POSIX only)

In addition to introducing the mutexes, the CL also changes
PacketBuffer to use the new mutex instead of rtc::CriticalSection.

The method of yielding from critical_section.cc was given a
mini-cleanup and YieldCurrentThread() was added to
rtc_base/synchronization/yield.h/cc.

Additionally, google_benchmark benchmarks for the mutexes were added
(test courtesy of danilchap@), and some results from a pthread/Abseil
shootout were added showing Abseil has the advantage in higher
contention.

Bug: webrtc:11567, webrtc:11634
Change-Id: Iaec324ccb32ec3851bf6db3fd290f5ea5dee4c81
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/176230
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Tommi <tommi@webrtc.org>
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31443}
This commit is contained in:
Markus Handell
2020-06-04 00:41:20 +02:00
committed by Commit Bot
parent e917379c5b
commit f70fbc8411
24 changed files with 779 additions and 44 deletions
Download Patch File Download Diff File Expand all files Collapse all files

46
modules/video_coding/packet_buffer.h
View File

@ -22,8 +22,8 @@
#include "modules/rtp_rtcp/source/rtp_packet_received.h"
#include "modules/rtp_rtcp/source/rtp_video_header.h"
#include "rtc_base/copy_on_write_buffer.h"
#include "rtc_base/critical_section.h"
#include "rtc_base/numerics/sequence_number_util.h"
#include "rtc_base/synchronization/mutex.h"
#include "rtc_base/thread_annotations.h"
#include "system_wrappers/include/clock.h"
@ -83,67 +83,67 @@ class PacketBuffer {
~PacketBuffer();
InsertResult InsertPacket(std::unique_ptr<Packet> packet) ABSL_MUST_USE_RESULT
RTC_LOCKS_EXCLUDED(crit_);
RTC_LOCKS_EXCLUDED(mutex_);
InsertResult InsertPadding(uint16_t seq_num) ABSL_MUST_USE_RESULT
RTC_LOCKS_EXCLUDED(crit_);
void ClearTo(uint16_t seq_num) RTC_LOCKS_EXCLUDED(crit_);
void Clear() RTC_LOCKS_EXCLUDED(crit_);
RTC_LOCKS_EXCLUDED(mutex_);
void ClearTo(uint16_t seq_num) RTC_LOCKS_EXCLUDED(mutex_);
void Clear() RTC_LOCKS_EXCLUDED(mutex_);
// Timestamp (not RTP timestamp) of the last received packet/keyframe packet.
absl::optional<int64_t> LastReceivedPacketMs() const
RTC_LOCKS_EXCLUDED(crit_);
RTC_LOCKS_EXCLUDED(mutex_);
absl::optional<int64_t> LastReceivedKeyframePacketMs() const
RTC_LOCKS_EXCLUDED(crit_);
RTC_LOCKS_EXCLUDED(mutex_);
private:
Clock* const clock_;
// Clears with |crit_| taken.
void ClearInternal() RTC_EXCLUSIVE_LOCKS_REQUIRED(crit_);
// Clears with |mutex_| taken.
void ClearInternal() RTC_EXCLUSIVE_LOCKS_REQUIRED(mutex_);
// Tries to expand the buffer.
bool ExpandBufferSize() RTC_EXCLUSIVE_LOCKS_REQUIRED(crit_);
bool ExpandBufferSize() RTC_EXCLUSIVE_LOCKS_REQUIRED(mutex_);
// Test if all previous packets has arrived for the given sequence number.
bool PotentialNewFrame(uint16_t seq_num) const
RTC_EXCLUSIVE_LOCKS_REQUIRED(crit_);
RTC_EXCLUSIVE_LOCKS_REQUIRED(mutex_);
// Test if all packets of a frame has arrived, and if so, returns packets to
// create frames.
std::vector<std::unique_ptr<Packet>> FindFrames(uint16_t seq_num)
RTC_EXCLUSIVE_LOCKS_REQUIRED(crit_);
RTC_EXCLUSIVE_LOCKS_REQUIRED(mutex_);
void UpdateMissingPackets(uint16_t seq_num)
RTC_EXCLUSIVE_LOCKS_REQUIRED(crit_);
RTC_EXCLUSIVE_LOCKS_REQUIRED(mutex_);
rtc::CriticalSection crit_;
mutable Mutex mutex_;
// buffer_.size() and max_size_ must always be a power of two.
const size_t max_size_;
// The fist sequence number currently in the buffer.
uint16_t first_seq_num_ RTC_GUARDED_BY(crit_);
uint16_t first_seq_num_ RTC_GUARDED_BY(mutex_);
// If the packet buffer has received its first packet.
bool first_packet_received_ RTC_GUARDED_BY(crit_);
bool first_packet_received_ RTC_GUARDED_BY(mutex_);
// If the buffer is cleared to |first_seq_num_|.
bool is_cleared_to_first_seq_num_ RTC_GUARDED_BY(crit_);
bool is_cleared_to_first_seq_num_ RTC_GUARDED_BY(mutex_);
// Buffer that holds the the inserted packets and information needed to
// determine continuity between them.
std::vector<std::unique_ptr<Packet>> buffer_ RTC_GUARDED_BY(crit_);
std::vector<std::unique_ptr<Packet>> buffer_ RTC_GUARDED_BY(mutex_);
// Timestamp of the last received packet/keyframe packet.
absl::optional<int64_t> last_received_packet_ms_ RTC_GUARDED_BY(crit_);
absl::optional<int64_t> last_received_packet_ms_ RTC_GUARDED_BY(mutex_);
absl::optional<int64_t> last_received_keyframe_packet_ms_
RTC_GUARDED_BY(crit_);
RTC_GUARDED_BY(mutex_);
absl::optional<uint32_t> last_received_keyframe_rtp_timestamp_
RTC_GUARDED_BY(crit_);
RTC_GUARDED_BY(mutex_);
absl::optional<uint16_t> newest_inserted_seq_num_ RTC_GUARDED_BY(crit_);
absl::optional<uint16_t> newest_inserted_seq_num_ RTC_GUARDED_BY(mutex_);
std::set<uint16_t, DescendingSeqNumComp<uint16_t>> missing_packets_
RTC_GUARDED_BY(crit_);
RTC_GUARDED_BY(mutex_);
// Indicates if we should require SPS, PPS, and IDR for a particular
// RTP timestamp to treat the corresponding frame as a keyframe.