From d3a3e9ef36a821789142a0e702ba78997932dc61 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Niels=20M=C3=B6ller?= <nisse@webrtc.org>
Date: Wed, 28 Oct 2020 15:15:55 +0100
Subject: [PATCH] Delete internal locking in TimestampExtrapolator class.

Only use, in VCMTiming, protects it with its own mutex.

Bug: webrtc:12102
Change-Id: I9c09976f9d938565b3e2908eca6cfee0c4063f6f
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/190721
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Reviewed-by: Tommi <tommi@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#32529}
---
 modules/video_coding/timing.h           |  6 ++++--
 rtc_base/time/timestamp_extrapolator.cc | 14 +-------------
 rtc_base/time/timestamp_extrapolator.h  |  5 +----
 3 files changed, 6 insertions(+), 19 deletions(-)

diff --git a/modules/video_coding/timing.h b/modules/video_coding/timing.h
index 5c7cfbc8b4..69352de93a 100644
--- a/modules/video_coding/timing.h
+++ b/modules/video_coding/timing.h
@@ -118,8 +118,10 @@ class VCMTiming {
   mutable Mutex mutex_;
   Clock* const clock_;
   bool master_ RTC_GUARDED_BY(mutex_);
-  TimestampExtrapolator* ts_extrapolator_ RTC_GUARDED_BY(mutex_);
-  std::unique_ptr<VCMCodecTimer> codec_timer_ RTC_GUARDED_BY(mutex_);
+  TimestampExtrapolator* ts_extrapolator_ RTC_GUARDED_BY(mutex_)
+      RTC_PT_GUARDED_BY(mutex_);
+  std::unique_ptr<VCMCodecTimer> codec_timer_ RTC_GUARDED_BY(mutex_)
+      RTC_PT_GUARDED_BY(mutex_);
   int render_delay_ms_ RTC_GUARDED_BY(mutex_);
   // Best-effort playout delay range for frames from capture to render.
   // The receiver tries to keep the delay between |min_playout_delay_ms_|
diff --git a/rtc_base/time/timestamp_extrapolator.cc b/rtc_base/time/timestamp_extrapolator.cc
index bf9f726c42..99445284dc 100644
--- a/rtc_base/time/timestamp_extrapolator.cc
+++ b/rtc_base/time/timestamp_extrapolator.cc
@@ -15,8 +15,7 @@
 namespace webrtc {
 
 TimestampExtrapolator::TimestampExtrapolator(int64_t start_ms)
-    : _rwLock(RWLockWrapper::CreateRWLock()),
-      _startMs(0),
+    : _startMs(0),
       _firstTimestamp(0),
       _wrapArounds(0),
       _prevUnwrappedTimestamp(-1),
@@ -34,12 +33,7 @@ TimestampExtrapolator::TimestampExtrapolator(int64_t start_ms)
   Reset(start_ms);
 }
 
-TimestampExtrapolator::~TimestampExtrapolator() {
-  delete _rwLock;
-}
-
 void TimestampExtrapolator::Reset(int64_t start_ms) {
-  WriteLockScoped wl(*_rwLock);
   _startMs = start_ms;
   _prevMs = _startMs;
   _firstTimestamp = 0;
@@ -58,13 +52,10 @@ void TimestampExtrapolator::Reset(int64_t start_ms) {
 }
 
 void TimestampExtrapolator::Update(int64_t tMs, uint32_t ts90khz) {
-  _rwLock->AcquireLockExclusive();
   if (tMs - _prevMs > 10e3) {
     // Ten seconds without a complete frame.
     // Reset the extrapolator
-    _rwLock->ReleaseLockExclusive();
     Reset(tMs);
-    _rwLock->AcquireLockExclusive();
   } else {
     _prevMs = tMs;
   }
@@ -100,7 +91,6 @@ void TimestampExtrapolator::Update(int64_t tMs, uint32_t ts90khz) {
   if (_prevUnwrappedTimestamp >= 0 &&
       unwrapped_ts90khz < _prevUnwrappedTimestamp) {
     // Drop reordered frames.
-    _rwLock->ReleaseLockExclusive();
     return;
   }
 
@@ -131,11 +121,9 @@ void TimestampExtrapolator::Update(int64_t tMs, uint32_t ts90khz) {
   if (_packetCount < _startUpFilterDelayInPackets) {
     _packetCount++;
   }
-  _rwLock->ReleaseLockExclusive();
 }
 
 int64_t TimestampExtrapolator::ExtrapolateLocalTime(uint32_t timestamp90khz) {
-  ReadLockScoped rl(*_rwLock);
   int64_t localTimeMs = 0;
   CheckForWrapArounds(timestamp90khz);
   double unwrapped_ts90khz =
diff --git a/rtc_base/time/timestamp_extrapolator.h b/rtc_base/time/timestamp_extrapolator.h
index 63af57b227..b325d2cbaa 100644
--- a/rtc_base/time/timestamp_extrapolator.h
+++ b/rtc_base/time/timestamp_extrapolator.h
@@ -13,14 +13,12 @@
 
 #include <stdint.h>
 
-#include "rtc_base/synchronization/rw_lock_wrapper.h"
-
 namespace webrtc {
 
+// Not thread safe.
 class TimestampExtrapolator {
  public:
   explicit TimestampExtrapolator(int64_t start_ms);
-  ~TimestampExtrapolator();
   void Update(int64_t tMs, uint32_t ts90khz);
   int64_t ExtrapolateLocalTime(uint32_t timestamp90khz);
   void Reset(int64_t start_ms);
@@ -28,7 +26,6 @@ class TimestampExtrapolator {
  private:
   void CheckForWrapArounds(uint32_t ts90khz);
   bool DelayChangeDetection(double error);
-  RWLockWrapper* _rwLock;
   double _w[2];
   double _pP[2][2];
   int64_t _startMs;