On Fri, Nov 6, 2015 at 2:09 PM, Denis V. Lunev <d...@openvz.org> wrote: > On 11/06/2015 04:35 PM, Stefan Hajnoczi wrote: >> >> On Wed, Nov 04, 2015 at 08:27:22PM +0300, Denis V. Lunev wrote: >>> >>> It is required for bdrv_drain. >> >> What bug does this patch fix? >> >> Existing blk_set_aio_context() callers acquire the AioContext or are >> sure it's already acquired by their caller, so I don't see where the bug >> is. >> >> No function in block/block-backend.c acquires AioContext internally. >> The same reasoning I mentioned in another email thread about consistent >> locking strategy applies here. Either all blk_*() functions should take >> the AioContext internally (which I disagree with) or none of them should >> take it. > > > #5 0x00005555559b31bf in bdrv_drain (bs=0x5555564274a0) at block/io.c:258 > #6 0x0000555555963321 in bdrv_set_aio_context (bs=0x5555564274a0, > new_context=0x55555640c100) at block.c:3764 > #7 0x00005555559a8b67 in blk_set_aio_context (blk=0x555556425d20, > new_context=0x55555640c100) at block/block-backend.c:1068 > #8 0x00005555556a4c52 in virtio_scsi_hotplug (hotplug_dev=0x5555579f22b0, > dev=0x555557bc8470, errp=0x7fffffffd9e0) > at /home/den/src/qemu/hw/scsi/virtio-scsi.c:773 > #9 0x00005555557eb3e2 in hotplug_handler_plug (plug_handler=0x5555579f22b0, > plugged_dev=0x555557bc8470, errp=0x7fffffffd9e0) at hw/core/hotplug.c:22 > #10 0x00005555557e7794 in device_set_realized (obj=0x555557bc8470, > value=true, > errp=0x7fffffffdb90) at hw/core/qdev.c:1066 > #11 0x000055555595580b in property_set_bool (obj=0x555557bc8470, > v=0x555557b51bc0, opaque=0x555557bc8740, name=0x555555a43841 "realized", > errp=0x7fffffffdb90) at qom/object.c:1708 > #12 0x0000555555953e2a in object_property_set (obj=0x555557bc8470, > v=0x555557b51bc0, name=0x555555a43841 "realized", errp=0x7fffffffdb90) > at qom/object.c:965 > #13 0x00005555559566c7 in object_property_set_qobject (obj=0x555557bc8470, > value=0x555557bc8370, name=0x555555a43841 "realized", > errp=0x7fffffffdb90) > ---Type <return> to continue, or q <return> to quit--- > at qom/qom-qobject.c:24 > #14 0x00005555559540cd in object_property_set_bool (obj=0x555557bc8470, > value=true, name=0x555555a43841 "realized", errp=0x7fffffffdb90) > at qom/object.c:1034 > #15 0x0000555555760e47 in qdev_device_add (opts=0x5555563f90f0, > errp=0x7fffffffdc18) at qdev-monitor.c:589 > #16 0x0000555555772501 in device_init_func (opaque=0x0, opts=0x5555563f90f0, > errp=0x0) at vl.c:2305 > #17 0x0000555555a198cb in qemu_opts_foreach ( > list=0x555555e96a60 <qemu_device_opts>, > func=0x5555557724c3 <device_init_func>, opaque=0x0, errp=0x0) > at util/qemu-option.c:1114 > #18 0x0000555555777b20 in main (argc=83, argv=0x7fffffffe058, > envp=0x7fffffffe2f8) at vl.c:4523 > > You want the lock to be taken by the function. It would be > quite natural to add assert(aio_context_is_owner(ctx)) in that > case.
This stack trace is fine since hw/scsi/virtio-scsi.c:virtio_scsi_hotplug(): aio_context_acquire(s->ctx); blk_set_aio_context(sd->conf.blk, s->ctx); aio_context_release(s->ctx); What bug does this patch fix? I still don't see the problem.
