On Wed, 04/04 14:53, Peter Xu wrote:
> Free the AIO context earlier than the GMainContext (if we have) to
> workaround a possible Glib bug. No functional change at all.
>
> We encountered a qmp-test hang with oob:
>
> #0 0x00007f35ffe45334 in __lll_lock_wait () from /lib64/libpthread.so.0
> #1 0x00007f35ffe405d8 in _L_lock_854 () from /lib64/libpthread.so.0
> #2 0x00007f35ffe404a7 in pthread_mutex_lock () from /lib64/libpthread.so.0
> #3 0x00007f35fc5b9c9d in g_source_unref_internal (source=0x24f0600,
> context=0x7f35f0000960, have_lock=0) at gmain.c:1685
> #4 0x0000000000aa6672 in aio_context_unref (ctx=0x24f0600) at
> /root/qemu/util/async.c:497
> #5 0x000000000065851c in iothread_instance_finalize (obj=0x24f0380) at
> /root/qemu/iothread.c:129
> #6 0x0000000000962d79 in object_deinit (obj=0x24f0380, type=0x242e960) at
> /root/qemu/qom/object.c:462
> #7 0x0000000000962e0d in object_finalize (data=0x24f0380) at
> /root/qemu/qom/object.c:476
> #8 0x0000000000964146 in object_unref (obj=0x24f0380) at
> /root/qemu/qom/object.c:924
> #9 0x0000000000965880 in object_finalize_child_property (obj=0x24ec640,
> name=0x24efca0 "mon_iothread", opaque=0x24f0380) at
> /root/qemu/qom/object.c:1436
> #10 0x0000000000962c33 in object_property_del_child (obj=0x24ec640,
> child=0x24f0380, errp=0x0) at /root/qemu/qom/object.c:436
> #11 0x0000000000962d26 in object_unparent (obj=0x24f0380) at
> /root/qemu/qom/object.c:455
> #12 0x0000000000658f00 in iothread_destroy (iothread=0x24f0380) at
> /root/qemu/iothread.c:365
> #13 0x00000000004c67a8 in monitor_cleanup () at /root/qemu/monitor.c:4663
> #14 0x0000000000669e27 in main (argc=16, argv=0x7ffc8b1ae2f8,
> envp=0x7ffc8b1ae380) at /root/qemu/vl.c:4749
>
> With glib version 2.28.8-9 (current default version on centos6) we might
> encounter above with the old code. It is verified that glib version
> 2.50.3-3 won't trigger that bug again, but since we are still supporting
> glib 2.28.8-9, we may want this workaround.
>
> Signed-off-by: Peter Xu <pet...@redhat.com>
> ---
> iothread.c | 18 ++++++++++++++----
> 1 file changed, 14 insertions(+), 4 deletions(-)
>
> diff --git a/iothread.c b/iothread.c
> index e675c38442..d41d661cdf 100644
> --- a/iothread.c
> +++ b/iothread.c
> @@ -117,16 +117,26 @@ static void iothread_instance_finalize(Object *obj)
> IOThread *iothread = IOTHREAD(obj);
>
> iothread_stop(iothread);
> + /*
> + * With glib version 2.28.8-9 (current default version on centos6)
> + * we might encounter problem of qmp-test OOB hang if we unref the
> + * AIO context later than the GMainContext below. Let's free the
> + * AIO context earlier to bypass that possible glib bug.
> + *
> + * It is verified that glib version 2.50.3-3 (or even earlier)
> + * won't trigger that bug again, but since we are still supporting
> + * glib 2.28.8-9, we need this workaround.
> + */
> + if (iothread->ctx) {
> + aio_context_unref(iothread->ctx);
> + iothread->ctx = NULL;
> + }
> if (iothread->worker_context) {
> g_main_context_unref(iothread->worker_context);
> iothread->worker_context = NULL;
> }
> qemu_cond_destroy(&iothread->init_done_cond);
> qemu_mutex_destroy(&iothread->init_done_lock);
> - if (!iothread->ctx) {
> - return;
> - }
> - aio_context_unref(iothread->ctx);
> }
>
> static void iothread_complete(UserCreatable *obj, Error **errp)
> --
> 2.14.3
>
Reviewed-by: Fam Zheng <f...@redhat.com>
