[mythtv-commits] Ticket #13488: IPTV fix for deadlock, handle redirects

MythTV noreply at mythtv.org
Mon Oct 7 09:07:02 UTC 2019

#13488: IPTV fix for deadlock, handle redirects
 Reporter:  ijc                      |          Owner:  paul-h
     Type:  Patch - Bug Fix          |         Status:  accepted
 Priority:  minor                    |      Milestone:  31.0
Component:  MythTV - HTTP Streaming  |        Version:  Master Head
 Severity:  medium                   |     Resolution:
 Keywords:                           |  Ticket locked:  0

Comment (by Ian Campbell <ijc@…>):

 In [changeset:"783e0dfd6971d8f10165bf810f4c9dd4e9819da5/mythtv"
 #!CommitTicketReference repository="mythtv"
 HLSReader: fix deadlock in HLSReader cancellation.

 The thread running HLSReader::Cancel calls HLSPlaylistWorker::Cancel with
 stream lock held, which blocks waiting for the thread to exit.

 The HLSPlaylistWorker::run thread however can be at the point between the
 m_cancel check and the call to HLSReader::PlaylistRetrying. Since
 PlaylistRetrying also takes the stream lock we are therefore deadlocked.

 To address this introduce a separate worker lock covering the
 and m_streamworker fields. This means that HLSReader::Cancel only needs to
 this new lock and therefore cannot deadlock against the use of the stream
 in HLSReader::PlaylistRetrying.

 When they need to be held together the new lock is consistently nested
 the old. Refs #13488

 Signed-off-by: Paul Harrison <pharrison at mythtv.org>
 (cherry picked from commit 946efc5c303fd651276437294c6afaa10bb95e72)

Ticket URL: <https://code.mythtv.org/trac/ticket/13488#comment:7>
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