Re: [Qemu-devel] [PATCH v12 14/21] migration: Multifd channels always wait on the sem

[Dr. David Alan Gilbert]

* Juan Quintela (address@hidden) wrote:
> Either for quit, sync or packet, we first wake them.
> 
> Signed-off-by: Juan Quintela <address@hidden>
> ---
>  migration/ram.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/migration/ram.c b/migration/ram.c
> index 0f1340b4e3..21b448c4ed 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -754,6 +754,7 @@ static void *multifd_send_thread(void *opaque)
>      p->num_packets = 1;
>  
>      while (true) {
> +        qemu_sem_wait(&p->sem);
>          qemu_mutex_lock(&p->mutex);
>          multifd_send_fill_packet(p);
>          if (p->quit) {
> @@ -761,7 +762,9 @@ static void *multifd_send_thread(void *opaque)
>              break;
>          }
>          qemu_mutex_unlock(&p->mutex);
> -        qemu_sem_wait(&p->sem);
> +        /* this is impossible */
> +        error_setg(&local_err, "multifd_send_thread: Unknown command");
> +        break;

This error disappears in a later patch saying that you can have spurious
wakeups.

>      }
>  
>  out:
> @@ -905,6 +908,7 @@ static void *multifd_recv_thread(void *opaque)
>      trace_multifd_recv_thread_start(p->id);
>  
>      while (true) {
> +        qemu_sem_wait(&p->sem);
>          qemu_mutex_lock(&p->mutex);

All this stuff seems to change again in later patches.

Is there stuff here that can be flattened into the other patches?

Dave

>          if (false)  {
>              /* ToDo: Packet reception goes here */
> @@ -919,9 +923,14 @@ static void *multifd_recv_thread(void *opaque)
>              break;
>          }
>          qemu_mutex_unlock(&p->mutex);
> -        qemu_sem_wait(&p->sem);
> +        /* this is impossible */
> +        error_setg(&local_err, "multifd_recv_thread: Unknown command");
> +        break;
>      }
>  
> +    if (local_err) {
> +        multifd_recv_terminate_threads(local_err);
> +    }
>      qemu_mutex_lock(&p->mutex);
>      p->running = false;
>      qemu_mutex_unlock(&p->mutex);
> -- 
> 2.17.0
> 
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK