Re: [Qemu-devel] [PATCH] ceph/rbd block driver for qemu-kvm (v4)

[Yehuda Sadeh Weinraub]

On Thu, Oct 7, 2010 at 12:51 PM, Anthony Liguori <address@hidden> wrote:
> On 10/07/2010 01:41 PM, Yehuda Sadeh Weinraub wrote:
>>
>> On Thu, Oct 7, 2010 at 11:38 AM, Anthony Liguori<address@hidden>
>>  wrote:
>>
>>>
>>> On 10/07/2010 01:08 PM, Yehuda Sadeh Weinraub wrote:
>>>
>>>> On Thu, Oct 7, 2010 at 7:12 AM, Anthony Liguori<address@hidden>
>>>
...
>>> There's no fd at all?   How do you get notifications about an
>>> asynchronous
>>> event completion?
>>>
>>> Regards,
>>>
>>> Anthony Liguori
>>>
>>>
>>
>> (resending to list, sorry)
>>
>> The fd is hidden deep under in librados. We get callback notifications
>> for events completion.
>>
>
> How is that possible?  Are the callbacks delivered in the context of a
> different thread?  If so, don't you need locking?

Not sure I'm completely following you. The callbacks are delivered in
the context of a different thread, but won't run concurrently. Do you
see any specific concurrency issue? We can add some mutex protection
around at the aio callback, so that if librados turns multithreaded at
this point we're covered.


Thanks,
Yehuda