Re: [libvirt] [PATCH 2/5] qemu: Avoid using stale data in virDomainGetBlockInfo

On Tue, Dec 24, 2013 at 07:22:38 -0700, Eric Blake wrote: > On 12/20/2013 02:36 PM, Jiri Denemark wrote: >> Generally, every API that is going to begin a job should do that before >> fetching data from vm->def. However, qemuDomainGetBlockInfo does not >> know whether it will have to start a job or not before checking vm->def. >> To avoid using disk alias that might have been freed while we were >> waiting for a job, we use its copy. In case the disk was removed in the >> meantime, we will fail with "cannot find statistics for device '...'" >> error message. >> >> Signed-off-by: Jiri Denemark <jdenemar(a)redhat.com&gt; >> --- >> src/qemu/qemu_driver.c | 17 ++++++++++++----- >> 1 file changed, 12 insertions(+), 5 deletions(-) > > This fixes the potential for a crash, but isn't this related to the same > problem that John has been working on? That is, when one thread is > migrating a domain and the other is getting block info, we have a race > where qemu will quit before we get a chance to probe for the block info. > https://www.redhat.com/archives/libvir-list/2013-December/msg00984.html > > Would changing when we grab the job (and grabbing it unconditionally, > even if we end up not needing to query) help solve both issues? I might help with what John was trying to do but I don't think this patch alone would solve the issue. May I consider this patch ACKed? :-)