[mythtv] Need help catching a segfault in mythbackend?

Mitko Haralanov voidtrance at comcast.net
Tue May 22 19:14:31 UTC 2007

On Tue, 22 May 2007 11:19:21 -0500
"Carl Fongheiser" <carlfongheiser at gmail.com> wrote:

> Well, you have several options.  One is to set your system up so that it
> will generate core dumps.  Another is to use gdb to attach to the running
> mythbackend process.  Yet another is to not use /etc/init.d/mythbackend
> (temporarily), and run mythbackend directly from gdb.  None of this requires
> you to be there when it happens; you just need to start it up in a virtual
> terminal (using xterm, or screen, or the like.)  It'll be there waiting for
> you when you return.

OK, as it turns out the changes that I made to enable core dumps did
work and I just did not look at the correct place to find the dump.
Now, that I found it, I can post a backtrace:

(gdb) bt
#0  0x0000003b55ffdcd0 in QMutex::lock () from /usr/lib64/qt-3.3/lib/libqt-mt.so.3 
#1  0x00000034bfc30f5e in MythSocket::UpRef () from /usr/lib64 libmyth-0.20.so.0 
#2 0x0000000000468ca9 in QMap<QString, QString>::end () 
#3 0x0000003b55d60456 in QObject::event () from /usr/lib64/qt-3.3/lib/libqt-mt.so.3 
#4  0x0000003b55d00105 in QApplication::internalNotify () from /usr/lib64/qt-3.3/lib/libqt-mt.so.3 
#5  0x0000003b55d015c4 in QApplication::notify () from /usr/lib64/qt-3.3/lib/libqt-mt.so.3 
#6 0x0000003b55d010f9 in QApplication::sendPostedEvents () from /usr/lib64/qt-3.3/lib/libqt-mt.so.3 
#7  0x0000003b55caeddc in QEventLoop::processEvents () from /usr/lib64/qt-3.3/lib/libqt-mt.so.3
#8  0x0000003b55d178c1 in QEventLoop::enterLoop ()
from /usr/lib64/qt-3.3/lib/libqt-mt.so.3 
#9  0x0000003b55d17792 in QEventLoop::exec () from /usr/lib64/qt-3.3/lib/libqt-mt.so.3 
#10 0x0000000000448041 in HttpServerExtension::HttpServerExtension$base ()
#11 0x0000003b4f61da44 in __libc_start_main () from /lib64/libc.so.6
#12 0x000000000041ab79 in QGList::~QGList$delete () 
#13 0x00007fffdfa84748 in ?? () 
#14 0x0000000000000000 in ?? ()

Unfortunately, 'bt full' does not display any more information.

Below is the corresponding message from syslog:
May 21 20:00:02 mythtv kernel: mythbackend[2909]: segfault at
00000000000000b8 rip 0000003b55ffdcd0 rsp 00007fffdfa82948 error 4

Mitko Haralanov
voidtrance at comcast dot net

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