On Mon, Apr 09, 2018 at 04:39:56PM +0800, Peter Xu wrote: > Free the AIO context earlier than the GMainContext (if we have) to > workaround a glib2 bug that GSource context pointer is not cleared even > if the context has already been destroyed (while it should). > > The patch itself only changed the order to destroy the objects, no > functional change at all. Without this workaround, we can encounter > qmp-test hang with oob (and possibly any other use case when iothread is > used with GMainContexts): > > #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 > > The glib2 bug is fixed in commit 26056558b ("gmain: allow > g_source_get_context() on destroyed sources", 2012-07-30), the first > good version is glib2 2.33.10. So this error will be encountered before > any glib version older than 2.33.10 (not including). Since we are still > supporting even older glib versions, we may want this workaround. > > Let's make sure we destroy the GSources first before its owner context > until we drop support for glibs older than 2.33.10. > > Signed-off-by: Peter Xu <pet...@redhat.com> > --- > v2: > - verified the root cause of the bug, and enhance commit message and > comments correspondingly > --- > iothread.c | 18 ++++++++++++++---- > 1 file changed, 14 insertions(+), 4 deletions(-)
Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com>
signature.asc
Description: PGP signature