Re: [PATCH 2/2] vhost: Avoid that vhost_work_flush() returns early

[Bart Van Assche <bvanassche@acm.org>]

On 08/14/13 13:46, Michael S. Tsirkin wrote:
> I'm confused by this explanation.
> done_seq is set here:
>                  if (work) {
>                          work->done_seq = seq;
>                          if (work->flushing)
>                                  wake_up_all(&work->done);
>                  }
>
> and work is set here:
>
>                  if (!list_empty(&dev->work_list)) {
>                          work = list_first_entry(&dev->work_list,
>                                                  struct vhost_work, node);
>                          list_del_init(&work->node);
>                          seq = work->queue_seq;
>                  }
>
> this work is processed on the next line:
>
>                  if (work) {
>                          __set_current_state(TASK_RUNNING);
>                          work->fn(work);
>                          if (need_resched())
>                                  schedule();
>                  }
>
> so how do we end up with a sequence of a work item
> that isn't processed?

I was wondering what would happen if a work item got requeued before 
done_seq is set. I think you are right and this should work fine.

Bart.