8:29 a.m.
2010/1/10 <pspreadborough(a)comcast.net>:
----- "Matthias Bolte" <matthias.bolte(a)googlemail.com> wrote:
> 2010/1/10 <pspreadborough(a)comcast.net>:
> >
> > Hello,
> >
> > I have been trying to use the domain event C code example but
> > unfortunately it segfaults (signal 11) every time I run it:
> >
> > [root@Spring events-c]# ./event-test
> > myEventAddHandleFunc:221: Add handle 5 1 0xf081a0 0x8f727f8
> > myEventAddHandleFunc:221: Add handle 7 1 0xf09990 0x8f727f8
> > myEventAddHandleFunc:221: Add handle 8 1 0xed7940 0x8f727f8
> > myEventAddTimeoutFunc:251: Adding Timeout -1 0xedefa0 0x8f727f8
> > myEventAddHandleFunc:221: Add handle 11 1 0xed7940 0x8f727f8
> > myEventAddTimeoutFunc:251: Adding Timeout -1 0xedefa0 0x8f727f8
> > main:322 :: Registering domain event cbs
> > Segmentation fault (core dumped)
> >
> > Core was generated by
> >
> `/root/libvirt-0.7.5/examples/domain-events/events-c/.libs/lt-event-test'.
> > Program terminated with signal 11, Segmentation fault.
> > [New process 21806]
> > [New process 21822]
> > #0 remoteDomainEventQueueFlush (timer=-1, opaque=0x8f727f8) at
> > remote/remote_driver.c:8720
> > 8720 tempQueue.count = priv->domainEvents->count;
> > (gdb) bt
> > #0 remoteDomainEventQueueFlush (timer=-1, opaque=0x8f727f8) at
> > remote/remote_driver.c:8720
> > #1 0x080490d3 in main (argc=Cannot access memory at address 0x1
> > ) at event-test.c:347
> >
> > The stack looks corrupted so I'm doubtful that this trace if of much
> value.
> > I have built
> > and installed libvirt-0.7.5 and it and it's tools seem to be
> operating
> > correctly.
>
> I tried the event-test with libvirt-0.7.5 and QEMU/Xen and both are
> working as expected. No segfaults.
>
> Could you inspect the values of priv and priv->domainEvents in GDB
> using 'p priv' to see if they are NULL and try to dereference them in
> GDB using 'p *priv' to see if they point to valid memory areas?
>
> Yes the backtrace looks corrupted. If there is stack/heap corruption
> involved valgrind may reveal it, so try to run the event-test in
> valgrind and see if that gives any hints.
>
> You can also try the GIT version of libvirt. There was a invalid free
> call (resulting in heap corruption) in the node device code fixed
> after the 0.7.5 release. But that should have no effect on the
> event-test.
>
> Matthias
Matthias,
priv->domainEvents is NULL, here's the gdb output:
This explains the segfault. The next question is, why is it NULL?
(gdb) p *priv
$1 = {lock = {lock = {__data = {__lock = 1, __count = 0, __owner = 21806, __kind = 0,
__nusers = 1, {__spins = 0, __list = {
__next = 0x0}}}, __size =
"\001\000\000\000\000\000\000\000.U\000\000\000\000\000\000\001\000\000\000\000\000\000",
__align = 1}}, sock = 150469168, watch = 3, pid = 4, uses_tls = 1982791681,
is_secure = 1815048801, session = 0x782f6269,
Seeing uses_tls and is_secure being large numbers and knowing that
both are used as boolean values in the code and should have values of
0 or 1 make me think that priv points to already freed memory here.
type = 0x2f646e65 <Address 0x2f646e65 out of bounds>, counter
= 1684956536, localUses = 1668248365,
hostname = 0x74656b <Address 0x74656b out of bounds>, debugLog = 0x0, saslconn =
0x0, saslDecoded = 0x0, saslDecodedLength = 0,
type and hostname are char pointers, but the seem to point into
nowhere, confirms that this is either freed memory or priv itself got
overwritten due to heap corruption.
saslDecodedOffset = 0, saslEncoded = 0x0, saslEncodedLength = 0,
saslEncodedOffset = 0,
buffer = '\0' <repeats 68 times>,
"n\000\000\000\001\000\000\000\000\000\000\000\001\000\000\000\000\000\000\000\001\000\000\000\001\000\000\000\000\000\000\000\001\000\000\000\bQ�\b����\030\034�\b\000\000\000\000�\033�\b\001\000\000\000\002\000\000\000�\033�\b\000\000\000\000\025|�\000\a",
'\0' <repeats 11 times>, "X\000�\b", '\0' <repeats 12
times>, "\021\000\000\000\002\000\000\000P��\b\000\000\000\000\021",
'\0' <repeats 15 times>,
"\021\000\000\0008\036�\b\f\000\000\000\020\000\000\000\021\000\000\000\a\000\000\000\b\000\000\000\t\000\000\000\021\000\000\000\002\000\000\000\230\034�\b\000\000\000\000A\000\000\000\003\000\000\000\001\000\000\000\001\000"...,
bufferLength = 0,
bufferOffset = 0, callbackList = 0x0, domainEvents = 0x0, eventFlushTimer = 0,
domainEventDispatching = 1, wakeupSendFD = 0,
wakeupReadFD = 0, waitDispatch = 0x0, streams = 0x0}
I'll try a run with valgrind and post the results.
Pete
Could you test the Python version of this example found in
examples/domain-events/events-python/event-test.py? Does this work?
Otherwise lets see if valgrind gives any hints.
Matthias