Bug 212693

Summary: Read MediaPlayerPrivateMediaStreamAVFObjC::m_canEnqueueDisplayLayer after the lock
Product: WebKit Reporter: youenn fablet <youennf>
Component: WebRTCAssignee: youenn fablet <youennf>
Status: RESOLVED FIXED    
Severity: Normal CC: eric.carlson, ews-watchlist, glenn, jer.noble, philipj, sergio, webkit-bug-importer, youennf
Priority: P2 Keywords: InRadar
Version: WebKit Nightly Build   
Hardware: Unspecified   
OS: Unspecified   
Attachments:
Description Flags
Patch none

Description youenn fablet 2020-06-03 06:46:21 PDT 
Read MediaPlayerPrivateMediaStreamAVFObjC::m_canEnqueueDisplayLayer after the lock.
As spotted by Eric, there might be an edge case where m_canEnqueueDisplayLayer check would be bypassed:
- enqueueVideoSample is called in a background thread, checks m_canEnqueueDisplayLayer which is true and pauses just after the check.
- destroyLayers is called, which sets m_canEnqueueDisplayLayer to false.
- ensureLayers recreates the display layer which is then not yet initialized
- enqueueVideoSample continues and will try to enqueue the sample while m_canEnqueueDisplayLayer is false.
Comment 1 youenn fablet 2020-06-03 06:49:40 PDT 
Created attachment 400915 [details]
Patch
Comment 2 EWS 2020-06-04 06:01:40 PDT 
Committed r262532: <https://trac.webkit.org/changeset/262532>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 400915 [details].
Comment 3 Radar WebKit Bug Importer 2020-06-04 06:02:17 PDT 
<rdar://problem/63975063>