Bug 1894045

Questions from QE:
1. Since the chance to reproduce it is rare, is there any other way to reproduce it instead of the eventtest?
2. This fix is a workaround for the glib before glib-2.63.6(commit https://gitlab.gnome.org/GNOME/glib/-/merge_requests/1353). Will it work on the glib>=2.63.6? Will it be reverted when the minimal required version >= glib-2.63.6?

(In reply to Han Han from comment #5)
ad 1. I don't know about any.  The glib issue itself mentions it only being reported couple of times, so I don't expect it to be very reproducible.  

ad 2. It looks like it is scheduled for 2.64.0 and will be backported to 2.62.x as well, but since the fix is not a workaround, just a more safe way of handling things, I do not see a reason for that to be reverted.

I am fine with this going in without much testing (basically unless anything else breaks it's fine), but I do not know if there is a process for it.  Some way to tag this BZ maybe?

Can we get this out as async as soon as it is verified?

Get a reproducer here by run unittest:
1. Install the src rpm of libvirt-6.6.0-7
# rpm -i LIVBRIT_6_6_SRCRPM_URL

2. Compile the libvirt-6.6
# rpmbuild -bc -v rpmbuild/SPECS/libvirt.spec
(you may need to disable rbd storage in libvirt.spec and recompile if error happens on rbd)

3. Run eventtest
# cd /root/rpmbuild/BUILD/libvirt-6.6.0/x86_64-redhat-linux-gnu

Run eventtest until it hit an error:
# while true;do ./tests/eventtest; if [ $? -ne 0 ];then break;fi;done


(process:2738769): GLib-CRITICAL **: 20:57:16.306: source_remove_from_context: assertion 'source_list != NULL' failed

# coredumpctl -1                                                     
TIME                            PID   UID   GID SIG COREFILE  EXE
Tue 2021-01-12 20:57:16 EST  2738769     0     0  11 present   /root/rpmbuild/BUILD/libvirt-6.6.0/x86_64-redhat-

Backtrace:
(gdb) bt fu
#0  0x00007f9ca01348b8 in g_source_unref_internal (source=0x55881d6a5090, context=0x55881d6a7af0, have_lock=1)
    at gmain.c:2127
        old_cb_data = 0x55881d6a4910
        old_cb_funcs = 0x55881d664010
        __func__ = "g_source_unref_internal"
#1  0x00007f9ca0134a0e in g_source_iter_next
    (iter=iter@entry=0x7f9c9932a930, source=source@entry=0x7f9c9932a928) at gmain.c:980
        next_source = <optimized out>
#2  0x00007f9ca01373df in g_main_context_check
    (context=context@entry=0x55881d6a7af0, max_priority=200, fds=fds@entry=0x7f9c940024a0, n_fds=n_fds@entry=26)
    at gmain.c:3715
        source = 0x55881d6a5090
        iter = 
          {context = 0x55881d6a7af0, may_modify = 1, current_list = 0x55881d6a4660 = {0x55881d6a4640}, source = 0x55881d6a5090}
        pollrec = <optimized out>
        n_ready = 0
        i = <optimized out>
#3  0x00007f9ca0137a60 in g_main_context_iterate
    (context=context@entry=0x55881d6a7af0, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>)
    at gmain.c:3899
        max_priority = 200
        timeout = 0
        some_ready = <optimized out>
        nfds = 26
        allocated_nfds = 32
        fds = 0x7f9c940024a0
#4  0x00007f9ca0137be0 in g_main_context_iteration (context=0x55881d6a7af0, 
    context@entry=0x0, may_block=may_block@entry=1) at gmain.c:3963
        retval = <optimized out>
#5  0x00007f9ca370e3a4 in virEventGLibRunOnce () at ../../src/util/vireventglib.c:496
#6  0x000055881c416b65 in eventThreadLoop (data=<optimized out>) at ../../tests/eventtest.c:176
#7  0x00007f9c9fcce14a in start_thread (arg=<optimized out>) at pthread_create.c:479
        ret = <optimized out>
        pd = <optimized out>
        unwind_buf = 
              {cancel_jmp_buf = {{jmp_buf = {140310561863424, 8770522698823025210, 140727661230654, 140727661230655, 0, 140310561860352, -8751033350172917190, -8751030135613111750}, mask_was_saved = 0}}, priv = {pad = {0x0, 0x0, 0x0, 0x0}, data = {prev = 0x0, cleanup = 0x0, canceltype = 0}}}
        not_first_call = <optimized out>
#8  0x00007f9c9f5e4763 in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

Test as comment19 for thousands of loops on libvirt-6.6.0-8.module+el8.3.1+8648+130818f2. No reproduced.

Covered by unit test

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (virt:8.3 bug fix and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2021:0639