commit 3ea3e0c345936911ad7c1ff706355dc95e2132bc
author Ilya Nikolaevskiy <ilnik@webrtc.org> Wed Jul 29 16:20:13 2020
committer Commit Bot <commit-bot@chromium.org> Wed Jul 29 17:26:07 2020
tree 725d13a7233e56133c844f751ac9d33d5dc4fa59
parent 81d2bbf96eb1251bacf03f0beeb19a1f8feb6f12

Fix potential deadlock in VideoAnalyzer

Bug: webrtc:11809
Change-Id: I9b037f7bc06ff8e5b5b6abf3467d7a3825c212e8
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/180520
Commit-Queue: Björn Terelius <terelius@webrtc.org>
Reviewed-by: Björn Terelius <terelius@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31807}

video/video_analyzer.cc

diff --git a/video/video_analyzer.cc b/video/video_analyzer.cc
index 365a089..a1174b5 100644
--- a/video/video_analyzer.cc
+++ b/video/video_analyzer.cc
@@ -456,9 +456,15 @@
 }
 
 void VideoAnalyzer::PollStats() {
+  // Do not grab |comparison_lock_|, before |GetStats()| completes.
+  // Otherwise a deadlock may occur:
+  // 1) |comparison_lock_| is acquired after |lock_|
+  // 2) |lock_| is acquired after internal pacer lock in SendRtp()
+  // 3) internal pacer lock is acquired by GetStats().
+  Call::Stats call_stats = call_->GetStats();
+
   MutexLock lock(&comparison_lock_);
 
-  Call::Stats call_stats = call_->GetStats();
   send_bandwidth_bps_.AddSample(call_stats.send_bandwidth_bps);
 
   VideoSendStream::Stats send_stats = send_stream_->GetStats();