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Re: [libvirt] libvirtd segfault



On 01/02/2013 09:45 AM, Scott Sullivan wrote:
On 12/29/2012 04:09 AM, Michal Privoznik wrote:
On 28.12.2012 20:23, Scott Sullivan wrote:
<snip/>
I have just now received another SIGSEGV, with your patch applied.

Here's the info from the GDB session:

Detaching after fork from child process 11266.
2012-12-28 18:56:53.261+0000: 29943: error : qemuMonitorIO:614 :
internal error End of file from monitor

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fffec0cd700 (LWP 29955)]
qemuDomainObjBeginJobInternal (driver=0x7fffe4013520,
driver_locked=true, obj=0x7fff7801fc80, job=QEMU_JOB_DESTROY,
asyncJob=QEMU_ASYNC_JOB_NONE) at qemu/qemu_domain.c:780
780         priv->jobs_queued++;
(gdb) bt
#0 qemuDomainObjBeginJobInternal (driver=0x7fffe4013520, driver_locked=true, obj=0x7fff7801fc80, job=QEMU_JOB_DESTROY, asyncJob=QEMU_ASYNC_JOB_NONE) at qemu/qemu_domain.c:780 #1 0x00007fffea599f46 in qemuDomainDestroyFlags (dom=<value optimized out>, flags=<value optimized out>) at qemu/qemu_driver.c:2189 #2 0x00007ffff7a83587 in virDomainDestroy (domain=0x7fffe414a510) at libvirt.c:2215 #3 0x00000000004296e2 in remoteDispatchDomainDestroy (server=<value optimized out>, client=<value optimized out>, msg=<value optimized out>, rerr=0x7fffec0ccbc0, args=<value optimized out>, ret=<value optimized out>) at remote_dispatch.h:1277 #4 remoteDispatchDomainDestroyHelper (server=<value optimized out>, client=<value optimized out>, msg=<value optimized out>, rerr=0x7fffec0ccbc0, args=<value optimized out>, ret=<value optimized out>) at remote_dispatch.h:1255 #5 0x00007ffff7ad0d02 in virNetServerProgramDispatchCall (prog=0x6814d0, server=0x678df0, client=0x693a80, msg=0x6986d0) at rpc/virnetserverprogram.c:431 #6 virNetServerProgramDispatch (prog=0x6814d0, server=0x678df0, client=0x693a80, msg=0x6986d0) at rpc/virnetserverprogram.c:304 #7 0x00007ffff7aceaa6 in virNetServerProcessMsg (srv=<value optimized out>, client=0x693a80, prog=<value optimized out>, msg=0x6986d0) at rpc/virnetserver.c:173 #8 0x00007ffff7acf5e3 in virNetServerHandleJob (jobOpaque=<value optimized out>, opaque=0x678df0) at rpc/virnetserver.c:194 #9 0x00007ffff79e8fdc in virThreadPoolWorker (opaque=<value optimized out>) at util/threadpool.c:144 #10 0x00007ffff79e88c9 in virThreadHelper (data=<value optimized out>) at util/threads-pthread.c:161
#11 0x000000300a2077f1 in start_thread () from /lib64/libpthread.so.0
#12 0x0000003009ae570d in clone () from /lib64/libc.so.6
(gdb)
This means, even though we successfully incremented reference counter on
virDomainObjPtr object, somebody free()d it anyway (well, the
privateData at least). Looks like a locking/concurrent access issue to
me then. Unfortunately, I don't have any suggestions yet, as the domain
object is supposed to be locked when entering the
qemuDomainObjBeginJobInternal() function so it shouldn't get free()d
meanwhile.

Michal
Michal,

I have a faster way to reproduce the crash (~10 minutes). Continue to read for new (easier) steps. This test was done with the standard v1.0.0 libvirtd code source, with no other patches applied.

<snip>


Not sure how much this helps, but in my testing I have found this issue was introduced with v0.9.12.

I cannot reproduce this issue under v0.9.11.X or older. Comparing src/qemu/qemu_domain.c between v0.9.11.X and v0.9.12 I see numerous changes to the code related to locking/concurrency. For instance, the introduction of qemuDomainTrackJob as one large difference I see.



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