linux-kernel - Re: [PATCH v4 11/13] xen/pvcalls: implement poll command

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Message-ID: <alpine.DEB.2.10.1710061638320.3073@sstabellini-ThinkPad-X260>
Date:   Fri, 6 Oct 2017 16:39:42 -0700 (PDT)
From:   Stefano Stabellini <sstabellini@...nel.org>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>
cc:     Stefano Stabellini <sstabellini@...nel.org>,
        xen-devel@...ts.xen.org, linux-kernel@...r.kernel.org,
        jgross@...e.com, Stefano Stabellini <stefano@...reto.com>
Subject: Re: [PATCH v4 11/13] xen/pvcalls: implement poll command

On Fri, 22 Sep 2017, Boris Ostrovsky wrote:
> > +static unsigned int pvcalls_front_poll_passive(struct file *file,
> > +					       struct pvcalls_bedata *bedata,
> > +					       struct sock_mapping *map,
> > +					       poll_table *wait)
> > +{
> > +	int notify, req_id, ret;
> > +	struct xen_pvcalls_request *req;
> > +
> > +	if (test_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
> > +		     (void *)&map->passive.flags)) {
> > +		uint32_t req_id = READ_ONCE(map->passive.inflight_req_id);
> > +
> > +		if (req_id != PVCALLS_INVALID_ID &&
> > +		    READ_ONCE(bedata->rsp[req_id].req_id) == req_id)
> > +			return POLLIN | POLLRDNORM;
> 
> 
> Do we need to clear PVCALLS_FLAG_ACCEPT_INFLIGHT? Or do we expect a
> (subsequent?) accept() to do that?

No need to clear, here we only need to say whether there is data to read
or not. Subsequent accept calls will clear PVCALLS_FLAG_ACCEPT_INFLIGHT.

 
> > +
> > +		poll_wait(file, &map->passive.inflight_accept_req, wait);
> > +		return 0;
> > +	}
> > +
>