fix: synchronize CustomAudioSource's sinks_ against AddSink/RemoveSink - #285
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sinks_ was mutated and iterated with no synchronization at all: the CritScope locks in AddSink/RemoveSink/PushAudioData, and the mutex itself, were commented out. AddSink/RemoveSink are called by WebRTC's own thread as a track attaches to or detaches from a peer connection, while PushAudioData runs on whatever thread the application pushes audio from, so this was a genuine data race on the sinks_ vector (iterator invalidation, potential crash), not something fixable by synchronizing on the application side. Restores the lock using webrtc::Mutex/MutexLock (the CriticalSection API this used before is gone from current WebRTC), also covering SetAudioCaptureDelay's write to audio_capture_delay_us_ for the same reason. Fixes #213
devopvoid
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Summary
CustomAudioSource'ssinks_vector was mutated/iterated with no synchronization at all — theCritScopelocks inAddSink/RemoveSink/PushAudioData, and the mutex itself, were commented out.AddSink/RemoveSinkare called by WebRTC's own thread as a track attaches to or detaches from a peer connection, whilePushAudioDataruns on whatever thread the application pushes audio from — a genuine data race onsinks_(iterator invalidation, potential crash), not something fixable from the application side.webrtc::Mutex/webrtc::MutexLock(theCriticalSectionAPI this used before is gone from current WebRTC), also coveringSetAudioCaptureDelay's write toaudio_capture_delay_us_for the same reason.concurrentAddRemoveSinkDoesNotCrash) that exercisesaddSink/removeSinkfrom one thread while pushing audio from another.Fixes #213
Test plan
mvn -pl webrtc-jni package -DskipTests— native build succeeds and linksmvn -pl webrtc test -Dtest=CustomAudioSourceTest— 8/8 pass, including the new regression testmvn -pl webrtc test(full module suite) — 149/149 pass