i did the debugging as you said. Kindly refer the following logs:

(gdb) c
Continuing.
thread apply all bt
[New Thread 0x7fc337c6b700 (LWP 29520)]

Program received signal SIGSEGV, Segmentation fault.
0x0000000000000000 in ?? ()
(gdb) thread apply all bt

Thread 12 (Thread 0x7fc337c6b700 (LWP 29520)):
#0  0x00007fc33509f18d in read () from /lib/x86_64-linux-gnu/libpthread.so.0
#1  0x00007fc32b1555c4 in read_all (fd=26, data=0x7fc3380e0a70, data@entry=0x20, len=len@entry=16, nonblocking=nonblocking@entry=0) at xs.c:365
#2  0x00007fc32b1556d8 in read_message (h=h@entry=0x7fc324013ee0, nonblocking=nonblocking@entry=0) at xs.c:1071
#3  0x00007fc32b156005 in read_thread (arg=0x7fc324013ee0) at xs.c:1137
#4  0x00007fc335097b50 in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#5  0x00007fc3349daa3d in clone () from /lib/x86_64-linux-gnu/libc.so.6
#6  0x0000000000000000 in ?? ()

Thread 11 (Thread 0x7fc330e7f700 (LWP 29170)):
#0  0x00007fc33509c2d4 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/x86_64-linux-gnu/libpthread.so.0
#1  0x00007fc3371ae9ea in virCondWait (c=c@entry=0x7fc3380dbd80, m=m@entry=0x7fc3380dbd58) at util/virthreadpthread.c:117
#2  0x00007fc3371af0cb in virThreadPoolWorker (opaque=opaque@entry=0x7fc3380db870) at util/virthreadpool.c:103
#3  0x00007fc3371ae686 in virThreadHelper (data=<optimized out>) at util/virthreadpthread.c:161
#4  0x00007fc335097b50 in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#5  0x00007fc3349daa3d in clone () from /lib/x86_64-linux-gnu/libc.so.6
#6  0x0000000000000000 in ?? ()

Thread 10 (Thread 0x7fc33067e700 (LWP 29171)):
#0  0x00007fc33509c2d4 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/x86_64-linux-gnu/libpthread.so.0
#1  0x00007fc3371ae9ea in virCondWait (c=c@entry=0x7fc3380dbd80, m=m@entry=0x7fc3380dbd58) at util/virthreadpthread.c:117
#2  0x00007fc3371af0cb in virThreadPoolWorker (opaque=opaque@entry=0x7fc3380db640) at util/virthreadpool.c:103
#3  0x00007fc3371ae686 in virThreadHelper (data=<optimized out>) at util/virthreadpthread.c:161
#4  0x00007fc335097b50 in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#5  0x00007fc3349daa3d in clone () from /lib/x86_64-linux-gnu/libc.so.6
#6  0x0000000000000000 in ?? ()

Thread 9 (Thread 0x7fc32fe7d700 (LWP 29172)):
#0  0x00007fc33509c2d4 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/x86_64-linux-gnu/libpthread.so.0
#1  0x00007fc3371ae9ea in virCondWait (c=c@entry=0x7fc3380dbd80, m=m@entry=0x7fc3380dbd58) at util/virthreadpthread.c:117
#2  0x00007fc3371af0cb in virThreadPoolWorker (opaque=opaque@entry=0x7fc3380db870) at util/virthreadpool.c:103
#3  0x00007fc3371ae686 in virThreadHelper (data=<optimized out>) at util/virthreadpthread.c:161
#4  0x00007fc335097b50 in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#5  0x00007fc3349daa3d in clone () from /lib/x86_64-linux-gnu/libc.so.6
#6  0x0000000000000000 in ?? ()

Thread 8 (Thread 0x7fc32f67c700 (LWP 29173)):
#0  0x00007fc33497cb9f in realloc () from /lib/x86_64-linux-gnu/libc.so.6
#1  0x00007fc3349eec85 in __vasprintf_chk () from /lib/x86_64-linux-gnu/libc.so.6
---Type <return> to continue, or q <return> to quit---
#2  0x00007fc3371aac0a in vasprintf (__ap=0x7fc32f67b6d0, __fmt=0x7fc337391017 "%llu: %s : %s:%d : %s\n", __ptr=0x7fc32f67b830)
    at /usr/include/x86_64-linux-gnu/bits/stdio2.h:199
#3  virVasprintfInternal (report=report@entry=false, domcode=0, filename=0x0, funcname=0x0, linenr=0, strp=0x7fc32f67b830, 
    fmt=fmt@entry=0x7fc337391017 "%llu: %s : %s:%d : %s\n", list=list@entry=0x7fc32f67b6d0) at util/virstring.c:337
#4  0x00007fc3371aad1b in virAsprintfInternal (report=report@entry=false, domcode=domcode@entry=0, filename=filename@entry=0x0, funcname=funcname@entry=0x0, 
    linenr=linenr@entry=0, strp=strp@entry=0x7fc32f67b830, fmt=fmt@entry=0x7fc337391017 "%llu: %s : %s:%d : %s\n") at util/virstring.c:358
#5  0x00007fc33718cb59 in virLogFormatString (str=<optimized out>, priority=VIR_LOG_DEBUG, funcname=0x7fc337394734 "virObjectRef", linenr=293, msg=0x7fc32f67b830)
    at util/virlog.c:719
#6  virLogVMessage (source=VIR_LOG_FROM_TRACE, priority=VIR_LOG_DEBUG, filename=0x7fc337394597 "util/virobject.c", linenr=293, funcname=0x7fc337394734 "virObjectRef", 
    metadata=0x0, fmt=fmt@entry=0x7fc3373945f1 "OBJECT_REF: obj=%p", vargs=vargs@entry=0x7fc32f67b8c0) at util/virlog.c:846
#7  0x00007fc33718cfc7 in virLogMessage (source=source@entry=VIR_LOG_FROM_TRACE, priority=priority@entry=VIR_LOG_DEBUG, 
    filename=filename@entry=0x7fc337394597 "util/virobject.c", linenr=linenr@entry=293, funcname=funcname@entry=0x7fc337394734 "virObjectRef", 
    metadata=metadata@entry=0x0, fmt=fmt@entry=0x7fc3373945f1 "OBJECT_REF: obj=%p") at util/virlog.c:778
#8  0x00007fc33719c3d7 in virObjectRef (anyobj=0x7fc338102720) at util/virobject.c:293
#9  0x00007fc32af1824f in libxlDriverConfigGet (driver=driver@entry=0x7fc338108930) at libxl/libxl_conf.c:1124
#10 0x00007fc32af1a50e in libxlVmCleanup (driver=driver@entry=0x7fc338108930, vm=vm@entry=0x7fc32400f530, reason=reason@entry=VIR_DOMAIN_SHUTOFF_DESTROYED)
    at libxl/libxl_driver.c:264
#11 0x00007fc32af20274 in libxlVmReap (driver=0x7fc338108930, vm=0x7fc32400f530, reason=VIR_DOMAIN_SHUTOFF_DESTROYED) at libxl/libxl_driver.c:338
#12 0x00007fc32af207de in libxlDomainDestroyFlags (dom=0x7fc3380e3770, flags=<optimized out>) at libxl/libxl_driver.c:1507
#13 0x00007fc33723cd37 in virDomainDestroy (domain=domain@entry=0x7fc3380e3770) at libvirt.c:2342
#14 0x00007fc337cb9ba4 in remoteDispatchDomainDestroy (args=<optimized out>, rerr=0x7fc32f67bcd0, client=0x7fc32400ee60, server=<optimized out>, msg=<optimized out>)
    at remote_dispatch.h:3165
#15 remoteDispatchDomainDestroyHelper (server=<optimized out>, client=0x7fc32400ee60, msg=<optimized out>, rerr=0x7fc32f67bcd0, args=<optimized out>, 
    ret=<optimized out>) at remote_dispatch.h:3143
#16 0x00007fc3372b4d79 in virNetServerProgramDispatchCall (msg=0x7fc324014070, client=0x7fc32400ee60, server=0x7fc3380dbba0, prog=0x7fc324007750)
    at rpc/virnetserverprogram.c:435
#17 virNetServerProgramDispatch (prog=0x7fc324007750, server=server@entry=0x7fc3380dbba0, client=0x7fc32400ee60, msg=0x7fc324014070) at rpc/virnetserverprogram.c:305
#18 0x00007fc3372aea78 in virNetServerProcessMsg (msg=<optimized out>, prog=<optimized out>, client=<optimized out>, srv=0x7fc3380dbba0) at rpc/virnetserver.c:165
#19 virNetServerHandleJob (jobOpaque=<optimized out>, opaque=0x7fc3380dbba0) at rpc/virnetserver.c:186
#20 0x00007fc3371af02e in virThreadPoolWorker (opaque=opaque@entry=0x7fc3380db640) at util/virthreadpool.c:144
#21 0x00007fc3371ae686 in virThreadHelper (data=<optimized out>) at util/virthreadpthread.c:161
#22 0x00007fc335097b50 in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#23 0x00007fc3349daa3d in clone () from /lib/x86_64-linux-gnu/libc.so.6
#24 0x0000000000000000 in ?? ()

Thread 7 (Thread 0x7fc32ee7b700 (LWP 29174)):
#0  0x00007fc33509c2d4 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/x86_64-linux-gnu/libpthread.so.0
#1  0x00007fc3371ae9ea in virCondWait (c=c@entry=0x7fc3380dbd80, m=m@entry=0x7fc3380dbd58) at util/virthreadpthread.c:117
#2  0x00007fc3371af0cb in virThreadPoolWorker (opaque=opaque@entry=0x7fc3380db870) at util/virthreadpool.c:103
#3  0x00007fc3371ae686 in virThreadHelper (data=<optimized out>) at util/virthreadpthread.c:161
---Type <return> to continue, or q <return> to quit---
#4  0x00007fc335097b50 in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#5  0x00007fc3349daa3d in clone () from /lib/x86_64-linux-gnu/libc.so.6
#6  0x0000000000000000 in ?? ()

Thread 6 (Thread 0x7fc32e67a700 (LWP 29175)):
#0  0x00007fc33509c2d4 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/x86_64-linux-gnu/libpthread.so.0
#1  0x00007fc3371ae9ea in virCondWait (c=c@entry=0x7fc3380dbe18, m=m@entry=0x7fc3380dbd58) at util/virthreadpthread.c:117
#2  0x00007fc3371af0eb in virThreadPoolWorker (opaque=opaque@entry=0x7fc3380db640) at util/virthreadpool.c:103
#3  0x00007fc3371ae686 in virThreadHelper (data=<optimized out>) at util/virthreadpthread.c:161
#4  0x00007fc335097b50 in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#5  0x00007fc3349daa3d in clone () from /lib/x86_64-linux-gnu/libc.so.6
#6  0x0000000000000000 in ?? ()

Thread 5 (Thread 0x7fc32de79700 (LWP 29176)):
#0  0x00007fc33509c2d4 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/x86_64-linux-gnu/libpthread.so.0
#1  0x00007fc3371ae9ea in virCondWait (c=c@entry=0x7fc3380dbe18, m=m@entry=0x7fc3380dbd58) at util/virthreadpthread.c:117
#2  0x00007fc3371af0eb in virThreadPoolWorker (opaque=opaque@entry=0x7fc3380db870) at util/virthreadpool.c:103
#3  0x00007fc3371ae686 in virThreadHelper (data=<optimized out>) at util/virthreadpthread.c:161
#4  0x00007fc335097b50 in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#5  0x00007fc3349daa3d in clone () from /lib/x86_64-linux-gnu/libc.so.6
#6  0x0000000000000000 in ?? ()

Thread 4 (Thread 0x7fc32d678700 (LWP 29177)):
#0  0x00007fc33509c2d4 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/x86_64-linux-gnu/libpthread.so.0
#1  0x00007fc3371ae9ea in virCondWait (c=c@entry=0x7fc3380dbe18, m=m@entry=0x7fc3380dbd58) at util/virthreadpthread.c:117
#2  0x00007fc3371af0eb in virThreadPoolWorker (opaque=opaque@entry=0x7fc3380db640) at util/virthreadpool.c:103
#3  0x00007fc3371ae686 in virThreadHelper (data=<optimized out>) at util/virthreadpthread.c:161
#4  0x00007fc335097b50 in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#5  0x00007fc3349daa3d in clone () from /lib/x86_64-linux-gnu/libc.so.6
#6  0x0000000000000000 in ?? ()

Thread 3 (Thread 0x7fc32ce77700 (LWP 29178)):
#0  0x00007fc33509c2d4 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/x86_64-linux-gnu/libpthread.so.0
#1  0x00007fc3371ae9ea in virCondWait (c=c@entry=0x7fc3380dbe18, m=m@entry=0x7fc3380dbd58) at util/virthreadpthread.c:117
#2  0x00007fc3371af0eb in virThreadPoolWorker (opaque=opaque@entry=0x7fc3380db870) at util/virthreadpool.c:103
#3  0x00007fc3371ae686 in virThreadHelper (data=<optimized out>) at util/virthreadpthread.c:161
#4  0x00007fc335097b50 in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#5  0x00007fc3349daa3d in clone () from /lib/x86_64-linux-gnu/libc.so.6
#6  0x0000000000000000 in ?? ()

---Type <return> to continue, or q <return> to quit---
Thread 2 (Thread 0x7fc32c676700 (LWP 29179)):
#0  0x00007fc33509c2d4 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/x86_64-linux-gnu/libpthread.so.0
#1  0x00007fc3371ae9ea in virCondWait (c=c@entry=0x7fc3380dbe18, m=m@entry=0x7fc3380dbd58) at util/virthreadpthread.c:117
#2  0x00007fc3371af0eb in virThreadPoolWorker (opaque=opaque@entry=0x7fc3380db640) at util/virthreadpool.c:103
#3  0x00007fc3371ae686 in virThreadHelper (data=<optimized out>) at util/virthreadpthread.c:161
#4  0x00007fc335097b50 in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#5  0x00007fc3349daa3d in clone () from /lib/x86_64-linux-gnu/libc.so.6
#6  0x0000000000000000 in ?? ()

Thread 1 (Thread 0x7fc337c4d7c0 (LWP 29169)):
#0  0x0000000000000000 in ?? ()
#1  0x00007fc32ace881e in libxl_osevent_occurred_timeout (ctx=<optimized out>, for_libxl=0x7fc3380edf38) at libxl_event.c:1039
#2  0x00007fc32af199c7 in libxlDomainObjTimerCallback (timer=<optimized out>, timer_info=0x7fc3380e3310) at libxl/libxl_domain.c:216
#3  0x00007fc33717cf7d in virEventPollDispatchTimeouts () at util/vireventpoll.c:451
#4  virEventPollRunOnce () at util/vireventpoll.c:644
#5  0x00007fc33717b70b in virEventRunDefaultImpl () at util/virevent.c:274
#6  0x00007fc3372b0065 in virNetServerRun (srv=0x7fc3380dbba0) at rpc/virnetserver.c:1112
#7  0x00007fc337c9851c in main (argc=<optimized out>, argv=<optimized out>) at libvirtd.c:1513
(gdb) 
(gdb) 

****

regards,
cooldharma06.


On Thu, Dec 19, 2013 at 3:30 PM, Daniel P. Berrange <berrange@redhat.com> wrote:
On Thu, Dec 19, 2013 at 03:09:14PM +0530, cool dharma06 wrote:
> I am newbie to this gdb debugging. now i did the bt in the debugging. In my
> side still it showing the error. Following are the stacktrace which i got.
> Kindly refer the following logs for full information:
>
> ****
> [New Thread 0x7f8503695700 (LWP 20012)]
>
> Program received signal SIGSEGV, Segmentation fault.
> 0x0000000000000000 in ?? ()
> (gdb) bt
> #0  0x0000000000000000 in ?? ()
> #1  0x00007f84f671281e in libxl_osevent_occurred_timeout (ctx=<optimized
> out>, for_libxl=0x7f8503bbbc38) at libxl_event.c:1039
> #2  0x00007f84f69439c7 in libxlDomainObjTimerCallback (timer=<optimized
> out>, timer_info=0x7f8503bb5930) at libxl/libxl_domain.c:216
> #3  0x00007f8502ba6f7d in virEventPollDispatchTimeouts () at
> util/vireventpoll.c:451
> #4  virEventPollRunOnce () at util/vireventpoll.c:644
> #5  0x00007f8502ba570b in virEventRunDefaultImpl () at util/virevent.c:274
> #6  0x00007f8502cda065 in virNetServerRun (srv=0x7f8503ba6ba0) at
> rpc/virnetserver.c:1112
> #7  0x00007f85036c251c in main (argc=<optimized out>, argv=<optimized out>)
> at libvirtd.c:1513
> (gdb)

In this case, that stack trace looks like it ought to be sufficient
to identify the problem - a clear NULL pointer reference. In general
though you want to capture a stack trace of all threads in a program

eg instead of 'bt', do 'thread apply all bt' next time.

Regards,
Daniel
--
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