Re: [PATCH 4/4] migration: fix migrate_cancel multifd migration leads destination hung forever

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

* Juan Quintela (quintela@redhat.com) wrote:
> From: Ivan Ren <renyime@gmail.com>
> 
> When migrate_cancel a multifd migration, if run sequence like this:
> 
>         [source]                              [destination]
> 
> multifd_send_sync_main[finish]
>                                     multifd_recv_thread wait &p->sem_sync
> shutdown to_dst_file
>                                     detect error from_src_file
> send  RAM_SAVE_FLAG_EOS[fail]       [no chance to run multifd_recv_sync_main]
>                                     multifd_load_cleanup
>                                     join multifd receive thread forever
> 
> will lead destination qemu hung at following stack:
> 
> pthread_join
> qemu_thread_join
> multifd_load_cleanup
> process_incoming_migration_co
> coroutine_trampoline
> 
> Signed-off-by: Ivan Ren <ivanren@tencent.com>
> Reviewed-by: Juan Quintela <quintela@redhat.com>
> Message-Id: <1561468699-9819-4-git-send-email-ivanren@tencent.com>
> Signed-off-by: Juan Quintela <quintela@redhat.com>

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
>  migration/ram.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/migration/ram.c b/migration/ram.c
> index eb6716710e..889148dd84 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -1292,6 +1292,11 @@ int multifd_load_cleanup(Error **errp)
>  
>          if (p->running) {
>              p->quit = true;
> +            /*
> +             * multifd_recv_thread may hung at MULTIFD_FLAG_SYNC handle code,
> +             * however try to wakeup it without harm in cleanup phase.
> +             */
> +            qemu_sem_post(&p->sem_sync);
>              qemu_thread_join(&p->thread);
>          }
>          object_unref(OBJECT(p->c));
> -- 
> 2.21.0
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK