Re: [Qemu-devel] [PATCH RFC 0/3] iothread: release iothread around aio_poll

[Paolo Bonzini]

On 20/02/2015 17:26, Paolo Bonzini wrote:
> Right now, iothreads are relying on a "contention callback" to release
> the AioContext (e.g. for block device operations or to do bdrv_drain_all).
> This is necessary because aio_poll needs to be called within an
> aio_context_acquire.
> 
> This series drops this requirement for aio_poll, with two effects:
> 
> 1) it makes it possible to remove the "contention callback" in RFifoLock
> (and possibly to convert it to a normal GRecMutex, which is why I am not
> including a patch to remove callbacks from RFifoLock).
> 
> 2) it makes it possible to start work around making critical sections
> for the block layer fine-grained.
> 
> In order to do this, some data is moved from AioContext to local storage.
> Stack allocation has size limitations, so thread-local storage is used
> instead.  There are no reentrancy problems because the data is only live
> throughout a small part of aio_poll, and in particular not during the
> invocation of callbacks.
> 
> Comments?

Stefan, can you put this on track for 2.4 or do you need a repost?

Paolo