[sheepdog] [PATCH 1/2] sheep: use work queue for asynchronous local request

[MORITA Kazutaka]

At Fri, 17 Jan 2014 16:32:51 +0800,
Liu Yuan wrote:
> 
> On Fri, Jan 17, 2014 at 12:35:31PM +0900, MORITA Kazutaka wrote:
> > From: MORITA Kazutaka <morita.kazutaka at lab.ntt.co.jp>
> > 
> > We can use our work queue framework for handling asynchrouns requests.
> > There is no need to create short living events.
> > 
> > Signed-off-by: MORITA Kazutaka <morita.kazutaka at lab.ntt.co.jp>
> > ---
> >  sheep/request.c    | 73 +++++++++++++++++++++++++++++-------------------------
> >  sheep/sheep.c      |  4 ++-
> >  sheep/sheep_priv.h |  2 +-
> >  3 files changed, 43 insertions(+), 36 deletions(-)
> > 
> > diff --git a/sheep/request.c b/sheep/request.c
> > index 161b7db..a15fd8c 100644
> > --- a/sheep/request.c
> > +++ b/sheep/request.c
> > @@ -575,31 +575,11 @@ out:
> >  	return ret;
> >  }
> >  
> > -static void local_req_async_handler(int fd, int events, void *data)
> > -{
> > -	struct request *req = data;
> > -	struct request_iocb *iocb = req->iocb;
> > -
> > -	if (events & EPOLLERR)
> > -		sd_err("request handler error");
> > -	eventfd_xread(fd);
> > -
> > -	if (unlikely(req->rp.result != SD_RES_SUCCESS))
> > -		iocb->result = req->rp.result;
> > -
> > -	if (uatomic_sub_return(&iocb->count, 1) == 0)
> > -		eventfd_xwrite(iocb->efd, 1);
> > -
> > -	unregister_event(req->local_req_efd);
> > -	close(req->local_req_efd);
> > -	free_local_request(req);
> > -}
> > -
> >  worker_fn struct request_iocb *local_req_init(void)
> >  {
> >  	struct request_iocb *iocb = xzalloc(sizeof(*iocb));
> >  
> > -	iocb->efd = eventfd(0, 0);
> > +	iocb->efd = eventfd(0, EFD_SEMAPHORE);
> >  	if (iocb->efd < 0) {
> >  		sd_err("eventfd failed, %m");
> >  		free(iocb);
> > @@ -613,7 +593,8 @@ worker_fn int local_req_wait(struct request_iocb *iocb)
> >  {
> >  	int ret;
> >  
> > -	eventfd_xread(iocb->efd);
> > +	for (int i = 0; i < iocb->count; i++)
> 
> i should be uint32_t to avoid overflow
> 
> > +		eventfd_xread(iocb->efd);
> 
> Does this work for following case:
> 
> 3 threads call eventfd_xwrite(efd), after that we call eventfd_xread(efd) here,
> so we will only return once, not 3 times, no?

No, EFD_SEMAPHORE is already used in this patch.

Thanks,

Kazutaka