On 11/09/2017 02:43 PM, Max Reitz wrote: > Draining a BDS may lead to graph modifications, which in turn may result > in it and other BDS being stripped of their current references. If > bdrv_drain_all_begin() and bdrv_drain_all_end() do not keep strong > references themselves, the BDS they are trying to drain (or undrain) may > disappear right under their feet -- or, more specifically, under the > feet of BDRV_POLL_WHILE() in bdrv_drain_recurse(). > > This fixes an occasional hang of iotest 194. > > Signed-off-by: Max Reitz <mre...@redhat.com> > --- > block/io.c | 47 ++++++++++++++++++++++++++++++++++++++++++++--- > 1 file changed, 44 insertions(+), 3 deletions(-)
> +
> + /* Keep a strong reference to all root BDS and copy them into
> + * an own list because draining them may lead to graph
'an own' sounds awkward; maybe 'copy them into a local list'
> + * modifications. */
> + bdrv_ref(bs);
> + bs_list = g_slist_prepend(bs_list, bs);
> }
> void bdrv_drain_all_end(void)
> {
> BlockDriverState *bs;
> BdrvNextIterator it;
> + GSList *bs_list = NULL, *bs_list_entry;
> +
> + /* Must be called from the main loop */
> + assert(qemu_get_current_aio_context() == qemu_get_aio_context());
>
> + /* Keep a strong reference to all root BDS and copy them into an
> + * own list because draining them may lead to graph modifications.
And again.
With that tweak,
Reviewed-by: Eric Blake <ebl...@redhat.com>
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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