Re: [Qemu-devel] [PATCH v2 11/11] block: Only poll block layer fds in bdrv_aio_poll

[Paolo Bonzini]

On 29/07/2015 12:57, Fam Zheng wrote:
> On Wed, 07/29 09:37, Paolo Bonzini wrote:
>>
>>
>> On 29/07/2015 06:42, Fam Zheng wrote:
>>> @@ -2613,6 +2613,8 @@ bool bdrv_aio_poll(AioContext *ctx, bool blocking)
>>>  {
>>>      bool ret;
>>>  
>>> +    aio_disable_clients(ctx, AIO_CLIENT_DATAPLANE | AIO_CLIENT_NBD_SERVER);
>>>      ret = aio_poll(ctx, blocking);
>>> +    aio_enable_clients(ctx, AIO_CLIENT_DATAPLANE | AIO_CLIENT_NBD_SERVER);
>>>      return ret;
>>
>> This is not enough, because another thread's aio_poll can sneak in
>> between calls to bdrv_aio_poll if the AioContext lock is released, and
>> they will use the full set of clients.
>>
>> Similar to your v1, it works with the large critical sections we
>> currently have, but it has the same problem in the longer term.
> 
> Can we add more disable/enable pairs around bdrv_drain on top?

Yes, though I think you'd end up reverting patches 10 and 11 in the end.

All 11 patches are okay, though it would be great if you could post the
full series before this is applied.

Paolo