Re: [Qemu-devel] [PATCH v6 1/3] linux-aio: fix submit aio as a batch

[Ming Lei <ming.lei@canonical.com>]

On Tue, Nov 25, 2014 at 9:08 PM, Stefan Hajnoczi <stefanha@redhat.com> wrote:
> On Tue, Nov 25, 2014 at 03:23:11PM +0800, Ming Lei wrote:
>> @@ -296,12 +370,14 @@ void laio_detach_aio_context(void *s_, AioContext *old_context)
>>
>>      aio_set_event_notifier(old_context, &s->e, NULL);
>>      qemu_bh_delete(s->completion_bh);
>> +    qemu_bh_delete(s->io_q.abort_bh);
>>  }
>>
>>  void laio_attach_aio_context(void *s_, AioContext *new_context)
>>  {
>>      struct qemu_laio_state *s = s_;
>>
>> +    s->io_q.abort_bh = aio_bh_new(new_context, ioq_abort_bh, s);
>>      s->completion_bh = aio_bh_new(new_context, qemu_laio_completion_bh, s);
>>      aio_set_event_notifier(new_context, &s->e, qemu_laio_completion_cb);
>>  }
>
> These functions are incomplete when ->aborting == true.  I can't think

Could you explain in a bit when ->aborting is true during attach callback?

> of a reason why we are guaranteed never to hit that state, and fixing it
> is easy.  Just add the following to the end of
> laio_attach_aio_context():
>
> if (s->aborting) {
>     qemu_bh_schedule(s->io_q.abort_bh);
> }

You mean the abort BH may not have chance to run before its deletion
in the detach callback?

If so, bdrv_drain_all() from bdrv_set_aio_context() should have
handled the pending BH, right?


Thanks,
Ming Lei