mythbackend crashed with SIGSEGV in QSemaphore::release()

[Stephen Worthington]

Mythbackend seems to do this crash sometimes at the start of a recording when several recordings start at the same time and at least on other recording is already running. I think I have had it at least three times now since I upgraded from MythTV 0.24. I am not sure if it happened in 0.25 (I was running that for only a couple of weeks before I upgraded to 0.26). Mythbackend restarts automatically, and starts all the recordings (new and existing) correctly. Of course this creates two files for any recording that was running at the time, and there is a short gap in recording while mythbackend is restarting.

In MythTV 0.24 in the same circumstances, I used to sometimes get a deadlock happening that prevented any more recordings from starting, but allowed existing recordings to continue. The frequency of those deadlocks occurring was the same as the frequency of this problem. So I suspect that the fix for the deadlock problem might possibly be the trigger for this one.

ProblemType: Crash
DistroRelease: Ubuntu 12.04
Package: mythtv-backend 2:0.26.0+fixes.20121125.10479af-0ubuntu0mythbuntu2 [origin: LP-PPA-mythbuntu-0.26]
ProcVersionSignature: Ubuntu 3.2.0-33.52-generic 3.2.31
Uname: Linux 3.2.0-33-generic x86_64
NonfreeKernelModules: tbs5922fe nvidia
.var.log.mythtv.mythavtest.log:

.var.log.mythtv.mythccextractor.log:

.var.log.mythtv.mythfilldatabase.log:

.var.log.mythtv.mythjobqueue.log:

.var.log.mythtv.mythlcdserver.log:

.var.log.mythtv.mythmediaserver.log:

.var.log.mythtv.mythshutdown.log:

.var.log.mythtv.mythtranscode.log:

.var.log.mythtv.mythutil.log:

.var.log.mythtv.mythwelcome.log:

ApportVersion: 2.0.1-0ubuntu13
Architecture: amd64
CrashCounter: 1
CrashDB: mythbuntu
Date: Mon Nov 26 20:29:05 2012
ExecutablePath: /usr/bin/mythbackend
InstallationMedia: Mythbuntu 12.04 "Precise Pangolin" - Release amd64 (20120425)
Installed_mythtv_dbg: 0.0
ProcCmdline: /usr/bin/mythbackend --syslog local7 --user mythtv
ProcEnviron:
 TERM=linux
 PATH=(custom, no user)
 LANG=en_NZ.UTF-8
SegvAnalysis:
 Segfault happened at: 0x7fc0770383d6 <_ZN10QSemaphore7releaseEi+22>: mov (%rdi),%rbp
 PC (0x7fc0770383d6) ok
 source "(%rdi)" (0x00000020) not located in a known VMA region (needed readable region)!
 destination "%rbp" ok
 Stack memory exhausted (SP below stack segment)
SegvReason: reading NULL VMA
Signal: 11
SourcePackage: mythtv
StacktraceTop:
 QSemaphore::release(int) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
 ?? () from /usr/lib/libmythbase-0.26.so.0
 ?? () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
 ?? () from /usr/lib/nvidia-current-updates/libGL.so.1
 start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
Title: mythbackend crashed with SIGSEGV in QSemaphore::release()
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: audio cdrom dialout video

[Thomas Mashos (tgm4883)]

We really do appreciate you opening this ticket to help improve Mythbuntu, but it needs to be closed for a number of reasons. The biggest one is that upstream has moved on to a new version and believes this to be fixed. Could you please verify if this issue still exists in the latest version?

Please do not let the closing of this ticket dissuade you from opening a new ticket if this (or any other) problem occurs with the newer versions.