Re: [Qemu-block] [PATCH RFC v2 05/22] block/pcache: add aio requests into cache

[Pavel Butsykin]

On 06.09.2016 20:07, Kevin Wolf wrote:
> Am 06.09.2016 um 18:54 hat Pavel Butsykin geschrieben:
> > > > +        *out_node = found;
> > > > +        return false;
> > > > +    }
> > > > +    atomic_add(&s->pcache.curr_size, new_node->cm.nb_sectors);
> > >
> > > atomic_add() implies that you have concurrent threads. I don't see any.
> > Yeah, but what about iothread? Doesn't presence of iothread lead to
> > parallel handling of requests in multiple threads?
>
> No, it doesn't. We're running under the AioContext lock.

Yes, you're right. For some reason I thought that there is such a
possibility :)

> If we were actually running in parallel threads, your locks might also
> be needed, but then they would have to be real thread locks instead of
> coroutine locks. But it doesn't happen today, so I think it's best to
> ignore.

I agree, use coroutine locks to protect the data was a bad idea.

> Kevin