[mythtv-commits] Ticket #13571: Crash of backend on delete of program being recorded

[MythTV]

#13571: Crash of backend on delete of program being recorded
------------------------------------+--------------------------
     Reporter:  Klaas de Waal       |      Owner:  (none)
         Type:  Bug Report - Crash  |     Status:  new
     Priority:  minor               |  Milestone:  needs_triage
    Component:  MythTV - General    |    Version:  Master Head
     Severity:  medium              |   Keywords:
Ticket locked:  0                   |
------------------------------------+--------------------------
 Over the last two weeks I have now experienced three times a segfault of
 the mythbackend when deleting a program that is still being recorded. The
 program is deleted from the frontend on a separate machine.
 This happens on my "production" living room system and it does happen only
 incidentally but it is happening only since I am running master in the
 living room. This is a master of a few weeks old.
 All three segfaults are in the same piece of code.

 Backend identification:
 {{{
 2020-01-26 10:09:44.408326 C [23981/23981] thread_unknown
 mythcommandlineparser.cpp:2602 (ConfigureLogging) - mythbackend version:
 master [v31-Pre-1811-g0d3bb87db7] www.mythtv.org
 2020-01-26 10:09:44.408371 C [23981/23981] thread_unknown
 mythcommandlineparser.cpp:2606 (ConfigureLogging) - Qt version: compile:
 5.12.5, runtime: 5.12.5
 2020-01-26 10:09:44.408411 I [23981/23981] thread_unknown
 mythcommandlineparser.cpp:2608 (ConfigureLogging) - Fedora 31 (Workstation
 Edition) (x86_64)
 2020-01-26 10:09:44.408415 N [23981/23981] thread_unknown
 mythcommandlineparser.cpp:2610 (ConfigureLogging) - Enabled verbose msgs:
 general channel record
 2020-01-26 10:09:44.408524 N [23981/23981] thread_unknown logging.cpp:724
 (logStart) - Setting Log Level to LOG_INFO
 }}}

 Last few lines of the backend log:
 {{{
 2020-02-02 21:16:47.721784 I [23981/24016] TVRecEvent tv_rec.cpp:4433
 (ClearFlags) - TVRec[19]: ClearFlags(PENDINGACTIONS,) ->
 RunMainLoop,RingBufferReady, @ tv_rec.cpp:3640
 2020-02-02 21:16:47.721844 I [23981/87786] ProcessRequest tv_rec.cpp:4433
 (ClearFlags) - TVRec[19]: ClearFlags(CancelNextRecording,KillRec,) ->
 RunMainLoop,RingBufferReady, @ tv_rec.cpp:721
 2020-02-02 21:16:47.723057 I [23981/87786] ProcessRequest tv_rec.cpp:692
 (SetRecordingStatus) - TVRec[19]: SetRecordingStatus(Opname->Onbekend) on
 line 723
 2020-02-02 21:16:47.775262 C [23981/23981] CoreContext
 signalhandling.cpp:299 (handleSignal) - Received Segmentation fault: Code
 1, PID 40, UID 0, Value 0x00000000
 2020-02-02 21:16:47.841684 I [23981/24025] Scheduler scheduler.cpp:2425
 (HandleReschedule) - Scheduled 91 items in 0.1 = 0.00 match + 0.00 check +
 0.06 place
 }}}


 This is the backtrace of the latest crash:
 {{{
 (gdb) bt
 #0  0x0000000000449be2 in EncoderLink::IsLocal() const (this=0x0) at
 encoderlink.h:51
 #1  0x000000000048c11f in
 MainServer::DoHandleStopRecording(RecordingInfo&, PlaybackSock*)
 (this=0x1b26620, recinfo=..., pbs=0x0) at mainserver.cpp:2914
 #2  0x000000000048cc55 in
 MainServer::DoHandleDeleteRecording(RecordingInfo&, PlaybackSock*, bool,
 bool, bool)
     (this=0x1b26620, recinfo=..., pbs=0x7f4f74042490,
 forceMetadataDelete=false, lexpirer=false, forgetHistory=false) at
 mainserver.cpp:3018
 #3  0x000000000048c553 in MainServer::HandleDeleteRecording(QString&,
 QString&, PlaybackSock*, bool, bool)
     (this=0x1b26620, chanid=..., starttime=..., pbs=0x7f4f74042490,
 forceMetadataDelete=false, forgetHistory=false) at mainserver.cpp:2967
 #4  0x0000000000473e43 in MainServer::ProcessRequestWork(MythSocket*)
 (this=0x1b26620, sock=0x7f50702e4ce0) at mainserver.cpp:641
 #5  0x0000000000472a90 in MainServer::ProcessRequest(MythSocket*)
 (this=0x1b26620, sock=0x7f50702e4ce0) at mainserver.cpp:456
 #6  0x00000000004c9d04 in ProcessRequestRunnable::run()
 (this=0x7f500001f840) at mainserver.cpp:160
 #7  0x00007f5087d0c8d7 in MPoolThread::run() (this=0x7f4f74010a30) at
 mthreadpool.cpp:140
 #8  0x00007f5087d09258 in MThreadInternal::run() (this=0x7f4f7044ae10) at
 mthread.cpp:79
 #9  0x00007f5084e8e4e6 in QThreadPrivate::start(void*)
 (arg=0x7f4f7044ae10) at thread/qthread_unix.cpp:361
 #10 0x00007f50863d34e2 in start_thread (arg=<optimized out>) at
 pthread_create.c:479
 #11 0x00007f50849ad693 in clone () at
 ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

 }}}

 The crash is now in mainserver.cpp line 2914 but the previous two crashes
 were in line 2910.

 {{{
 (gdb) l
 2909        TVRec::s_inputsLock.lockForRead();
 2910        for (auto iter = m_encoderList->begin(); iter !=
 m_encoderList->end(); ++iter)
 2911        {
 2912            EncoderLink *elink = *iter;
 2913
 2914            if (elink->IsLocal() && elink->MatchesRecording(&recinfo))
 2915            {
 2916                recnum = iter.key();
 2917
 2918                elink->StopRecording();
 (gdb) p iter
 $1 = {i = 0x7f502c024d20}
 (gdb) p elink
 $2 = (EncoderLink *) 0x0
 (gdb)

 }}}

 It looks to me that m_encoderList is corrupt but I have not been able to
 find the cause of this. hence this ticket.

-- 
Ticket URL: <https://code.mythtv.org/trac/ticket/13571>
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