[mythtv] mythweb crashes mythbackend

Joel David Elkins jde at elkins.cx
Sun Feb 20 05:29:55 UTC 2005 

Hi, I'm barely two weeks into my myth addiction, but an annoying bug has
already caused me to join -dev :)

I've been having quite a lot of backend segfaults ever since I installed
myth. (I've been using cvs versions since the start). The pattern is, I
make a schedule change using mythweb and sometimes, certainly not
always, mythweb reports that the backend has isn't running. Then, I know
that the backend has segfaulted. After restarting, invariably the
schedule change DID in fact happen. The crashes "seem" to be more
frequent when the backend is recording.

For what it's worth, my setup is basically the following. All of the
myth components (mythweb, backend, etc) are from CVS as of evening of
2/17/05.

backend/frontend:
PVR-250 & PVR-350
kernel: vanilla 2.6.10 SMP
backend runs under dedicated non privildged account
CPU: P4 3.06 HT
(system is gentoo, but not the gentoo kernel)

mythweb:
runs apache2, mysql (this box also hosts the myth database)
kernel: vanilla 2.6.10 SMP
CPUs: dual Celeron 350's
(system is gentoo, but not the gentoo kernel)

Backtrace follows. To my amateur eyes, it looks like a race condition on
the RefSocket reference count, causing RefSocket::DownRef() to try to
delete a an already deleted socket. Would one of you have a look through
this part of the code? A more experienced myth hacker could surely root
out this bug faster than I could.

Sorry for the long post and thanks in advance!

Regards,
Joel

Thread 15 (Thread 213006 (LWP 17060)):
#0  0x44b3e07b in read () from /lib/libpthread.so.0
No symbol table info available.
#1  0xb7f37b58 in ?? () from /usr/lib/libmythtv-0.17.so.0
No symbol table info available.

Thread 14 (Thread 196621 (LWP 17059)):
#0  0x44996a96 in nanosleep () from /lib/libc.so.6
No symbol table info available.

Thread 13 (Thread 180236 (LWP 17057)):
#0  0x44b3aae3 in __pthread_sigsuspend () from /lib/libpthread.so.0
No symbol table info available.
#1  0x44b3a5e8 in __pthread_wait_for_restart_signal ()
from /lib/libpthread.so.0
No symbol table info available.
#2  0x00000020 in ?? ()
No symbol table info available.
#3  0xbe3ff968 in ?? ()
No symbol table info available.
#4  0xffffffff in ?? ()
No symbol table info available.

Thread 12 (Thread 163851 (LWP 17056)):
#0  0x44b3aae3 in __pthread_sigsuspend () from /lib/libpthread.so.0
No symbol table info available.
#1  0x44b3a5e8 in __pthread_wait_for_restart_signal ()
from /lib/libpthread.so.0
No symbol table info available.
#2  0x00000020 in ?? ()
No symbol table info available.
#3  0xbe5ff968 in ?? ()
No symbol table info available.
#4  0xffffffff in ?? ()
No symbol table info available.

Thread 11 (Thread 147466 (LWP 17055)):
#0  0x44b3aae3 in __pthread_sigsuspend () from /lib/libpthread.so.0
No symbol table info available.
#1  0x44b3a5e8 in __pthread_wait_for_restart_signal ()
from /lib/libpthread.so.0
No symbol table info available.
#2  0x00000020 in ?? ()
No symbol table info available.
#3  0xbe7ff968 in ?? ()
No symbol table info available.
#4  0xffffffff in ?? ()
No symbol table info available.

Thread 10 (Thread 131081 (LWP 17054)):
#0  0x44b3aae3 in __pthread_sigsuspend () from /lib/libpthread.so.0
No symbol table info available.
#1  0x44b3a5e8 in __pthread_wait_for_restart_signal ()
from /lib/libpthread.so.0
No symbol table info available.
#2  0x00000020 in ?? ()
No symbol table info available.
#3  0xbe9ff968 in ?? ()
No symbol table info available.
#4  0xbe9ff990 in ?? ()
No symbol table info available.

Thread 9 (Thread 114696 (LWP 17053)):
#0  0x44b3aae3 in __pthread_sigsuspend () from /lib/libpthread.so.0
No symbol table info available.
#1  0x44b3a5e8 in __pthread_wait_for_restart_signal ()
from /lib/libpthread.so.0
No symbol table info available.
#2  0x00000020 in ?? ()
No symbol table info available.
#3  0xbebff968 in ?? ()
No symbol table info available.
#4  0xffffffff in ?? ()
No symbol table info available.

Thread 8 (Thread 98311 (LWP 17052)):
#0  0x44996a96 in nanosleep () from /lib/libc.so.6
No symbol table info available.

Thread 7 (Thread 81926 (LWP 17051)):
#0  0x44996a96 in nanosleep () from /lib/libc.so.6
No symbol table info available.

Thread 6 (Thread 65541 (LWP 17050)):
#0  0x44996a96 in nanosleep () from /lib/libc.so.6
No symbol table info available.

Thread 5 (Thread 49156 (LWP 17049)):
#0  0x44b3ea16 in nanosleep () from /lib/libpthread.so.0
No symbol table info available.
#1  0x00000001 in ?? ()
No symbol table info available.
#2  0x44b3a9ea in __pthread_timedsuspend_new ()
from /lib/libpthread.so.0
No symbol table info available.

Thread 4 (Thread 32771 (LWP 17048)):
#0  0x44996a96 in nanosleep () from /lib/libc.so.6
No symbol table info available.

Thread 3 (Thread 16386 (LWP 17046)):
#0  0x44996a96 in nanosleep () from /lib/libc.so.6
No symbol table info available.

Thread 2 (Thread 32769 (LWP 17045)):
#0  0x449be181 in fts_children () from /lib/libc.so.6
No symbol table info available.
#1  0x449be24c in poll () from /lib/libc.so.6
No symbol table info available.
#2  0x44b37d10 in __pthread_manager () from /lib/libpthread.so.0
No symbol table info available.
#3  0x44b37f37 in __pthread_manager_event () from /lib/libpthread.so.0
No symbol table info available.
#4  0x449c74da in clone () from /lib/libc.so.6
No symbol table info available.

Thread 1 (Thread 16384 (LWP 17041)):
#0  0x0069006c in ?? ()
No symbol table info available.
#1  0x08087c05 in RefSocket::DownRef() (this=0xb5e0d240) at server.h:14
No locals.
#2  0x080682a6 in MainServer::customEvent(QCustomEvent*)
(this=0xb5e00620, e=0x819f608) at mainserver.cpp:529
        pbs = (PlaybackSock *) 0xb5e0dcd8
        sock = (RefSocket *) 0xb5e0d240
        sendGlobal = false
        sentSet = { = {<> = {}, firstNode = 0x817b798, lastNode =
0x817b798, curNode = 0x817b798, curIndex = 0, 
    numNodes = 1, iterators = 0x0}, }
        iter = {> = {}, 
  _M_current = 0x80fcb08}
        broadcast = {> = {sh = 0x81414e8}, }
        sendstuff = true
#3  0xb6e068bc in QObject::event(QEvent*) ()
from /usr/qt/3/lib/libqt-mt.so.3
No symbol table info available.
#4  0xb6dacc6f in QApplication::internalNotify(QObject*, QEvent*) ()
from /usr/qt/3/lib/libqt-mt.so.3
No symbol table info available.
#5  0xb6dac02e in QApplication::notify(QObject*, QEvent*) ()
from /usr/qt/3/lib/libqt-mt.so.3
No symbol table info available.
#6  0xb6dada66 in QApplication::sendPostedEvents(QObject*, int) ()
from /usr/qt/3/lib/libqt-mt.so.3
No symbol table info available.
#7  0xb6dad8e6 in QApplication::sendPostedEvents() ()
from /usr/qt/3/lib/libqt-mt.so.3
No symbol table info available.

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