Re: [RFC PATCH 0/5] Removal of AioContext lock, bs->parents and ->children: proof of concept

[Paolo Bonzini]

On 4/4/22 11:51, Emanuele Giuseppe Esposito wrote:
>>
>> I agree that it doesn't. This new lock is only protecting ->parents and
>> ->children. 
> Side note: it will also be used to protect other fields, like
> .aio_context I think. I haven't checked if there is something else we
> might want to protect that is currently protected by AioContext lock.
> 
> At least, I think we are going to use the same lock, right?

I have no idea honestly.  It can make sense for anything that is changed
very rarely and read during requests.

.aio_context has the .detach/.attach callbacks and I wonder if there
should be any reason to access it outside the callbacks.  A lot of uses
of .aio_context (for example for aio_bh_new or
aio_bh_schedule_oneshot/replay_bh_schedule_oneshot_event) can, and
perhaps should, be changed to just qemu_get_current_aio_context().  For
multiqueue we probably want the same BlockDriverState to use the
AioContext corresponding to a virtio queue, rather than always the same one.

Paolo