Created attachment 1186985 [details]
Minimal example of program crashing

Description of problem:

It seems that if I close a connection while a domain event callback is
in progress, I can easily have a crash. Here is a backtrace:

#v+
#0  virFree (ptrptr=0x0) at ../../../src/util/viralloc.c:582
        save_errno = <optimized out>
#1  0x00007fc8328a4ad2 in virObjectEventCallbackListPurgeMarked (cbList=0xadfc30) at ../../../src/conf/object_event.c:282
        freecb = <optimized out>
        n = 0
#2  virObjectEventStateFlush (state=0xaf5380) at ../../../src/conf/object_event.c:819
        tempQueue = {
          count = 0,
          events = 0x0
        }
#3  virObjectEventTimer (timer=<optimized out>, opaque=0xaf5380) at ../../../src/conf/object_event.c:560
        state = 0xaf5380
#4  0x00007fc83280b7aa in virEventPollDispatchTimeouts () at ../../../src/util/vireventpoll.c:457
        cb = 0x7fc8328a48d0 <virObjectEventTimer>
        timer = 1
        opaque = 0xaf5380
        now = 1470212691501
        i = 0
        ntimeouts = 1
#5  virEventPollRunOnce () at ../../../src/util/vireventpoll.c:653
        fds = 0x7fc824000920
        ret = <optimized out>
        timeout = <optimized out>
        nfds = 1
        __func__ = "virEventPollRunOnce"
        __FUNCTION__ = "virEventPollRunOnce"
#6  0x00007fc83280a141 in virEventRunDefaultImpl () at ../../../src/util/virevent.c:314
        __func__ = "virEventRunDefaultImpl"
#7  0x0000000000400b37 in loop (arg=0x0) at crash.c:8
        __PRETTY_FUNCTION__ = "loop"
#v-

And the state of cbList:

#v+
>>> print *cbList
$2 = {
  nextID = 11419456,
  count = 1,
  callbacks = 0x0
}
#v-

I have another thread, but it is just sleeping when the crash happens.

Source code to trigger the problem is provided as an attachment. Running the program in loop triggers the bug in less than a second.


Version-Release number of selected component (if applicable):

2.0.0 (from Debian)

How reproducible:

Always

Steps to Reproduce:
1. compile the attached program with "gcc -Wall crash.c -lvirt -lpthread -o crash"
2. while ./crash; do echo -n "." ; done


Actual results:

Crashes after a few seconds. Usually after displaying "leak...".

Expected results:

Should not crash, despite the "leak..." message.