Re: [Qemu-devel] [PATCH 4/5] migration: fix qemu carsh when RDMA live migration

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* 858585 jemmy (jemmy858585@gmail.com) wrote:
> On Thu, Apr 12, 2018 at 12:43 AM, Dr. David Alan Gilbert
> <dgilbert@redhat.com> wrote:
> > * Lidong Chen (jemmy858585@gmail.com) wrote:
> >> After postcopy, the destination qemu work in the dedicated
> >> thread, so only invoke yield_until_fd_readable before postcopy
> >> migration.
> >
> > The subject line needs to be more discriptive:
> >    migration: Stop rdma yielding during incoming postcopy
> >
> > I think.
> > (Also please check the subject spellings)
> >
> >> Signed-off-by: Lidong Chen <lidongchen@tencent.com>
> >> ---
> >>  migration/rdma.c | 4 +++-
> >>  1 file changed, 3 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/migration/rdma.c b/migration/rdma.c
> >> index 53773c7..81be482 100644
> >> --- a/migration/rdma.c
> >> +++ b/migration/rdma.c
> >> @@ -1489,11 +1489,13 @@ static int qemu_rdma_wait_comp_channel(RDMAContext *rdma)
> >>       * Coroutine doesn't start until migration_fd_process_incoming()
> >>       * so don't yield unless we know we're running inside of a coroutine.
> >>       */
> >> -    if (rdma->migration_started_on_destination) {
> >> +    if (rdma->migration_started_on_destination &&
> >> +        migration_incoming_get_current()->state == MIGRATION_STATUS_ACTIVE) {
> >
> > OK, that's a bit delicate; watch if it ever gets called in a failure
> > case or similar - and also wathc out if we make more use of the status
> > on the destination, but otherwise, and with a fix for the subject;
> 
> How about use migration_incoming_get_current()->have_listen_thread?

That's supposed to be pretty internal to the postcopy code, so I prefer
the status check.

Dave

>     if (rdma->migration_started_on_destination &&
>         migration_incoming_get_current()->have_listen_thread == false) {
>         yield_until_fd_readable(rdma->comp_channel->fd);
>     }
> 
> >
> >
> > Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> >
> >>          yield_until_fd_readable(rdma->comp_channel->fd);
> >>      } else {
> >>          /* This is the source side, we're in a separate thread
> >>           * or destination prior to migration_fd_process_incoming()
> >> +         * after postcopy, the destination also in a seprate thread.
> >>           * we can't yield; so we have to poll the fd.
> >>           * But we need to be able to handle 'cancel' or an error
> >>           * without hanging forever.
> >> --
> >> 1.8.3.1
> >>
> > --
> > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK