linux-kernel - Re: [PATCH v3 15/18] xen/pvcalls: implement the ioworker functions

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Date:   Tue, 13 Jun 2017 17:56:29 -0700 (PDT)
From:   Stefano Stabellini <sstabellini@...nel.org>
To:     Juergen Gross <jgross@...e.com>
cc:     Stefano Stabellini <sstabellini@...nel.org>,
        xen-devel@...ts.xen.org, linux-kernel@...r.kernel.org,
        boris.ostrovsky@...cle.com,
        Stefano Stabellini <stefano@...reto.com>
Subject: Re: [PATCH v3 15/18] xen/pvcalls: implement the ioworker functions

On Tue, 13 Jun 2017, Juergen Gross wrote:
> On 02/06/17 21:31, Stefano Stabellini wrote:
> > We have one ioworker per socket. Each ioworker goes through the list of
> > outstanding read/write requests. Once all requests have been dealt with,
> > it returns.
> > 
> > We use one atomic counter per socket for "read" operations and one
> > for "write" operations to keep track of the reads/writes to do.
> > 
> > We also use one atomic counter ("io") per ioworker to keep track of how
> > many outstanding requests we have in total assigned to the ioworker. The
> > ioworker finishes when there are none.
> > 
> > Signed-off-by: Stefano Stabellini <stefano@...reto.com>
> > CC: boris.ostrovsky@...cle.com
> > CC: jgross@...e.com
> > ---
> >  drivers/xen/pvcalls-back.c | 27 +++++++++++++++++++++++++++
> >  1 file changed, 27 insertions(+)
> > 
> > diff --git a/drivers/xen/pvcalls-back.c b/drivers/xen/pvcalls-back.c
> > index 6afe7a0..0283d49 100644
> > --- a/drivers/xen/pvcalls-back.c
> > +++ b/drivers/xen/pvcalls-back.c
> > @@ -99,8 +99,35 @@ static int pvcalls_back_release_active(struct xenbus_device *dev,
> >  				       struct pvcalls_fedata *priv,
> >  				       struct sock_mapping *map);
> >  
> > +static void pvcalls_conn_back_read(unsigned long opaque)
> 
> Why not void *opaque? You could drop the cast below then.

Good idea

 
> > +{
> > +}
> > +
> > +static int pvcalls_conn_back_write(struct sock_mapping *map)
> > +{
> > +	return 0;
> > +}
> > +
> >  static void pvcalls_back_ioworker(struct work_struct *work)
> >  {
> > +	struct pvcalls_ioworker *ioworker = container_of(work,
> > +		struct pvcalls_ioworker, register_work);
> > +	struct sock_mapping *map = container_of(ioworker, struct sock_mapping,
> > +		ioworker);
> > +
> > +	while (atomic_read(&map->io) > 0) {
> > +		if (atomic_read(&map->release) > 0) {
> > +			atomic_set(&map->release, 0);
> > +			return;
> > +		}
> > +
> > +		if (atomic_read(&map->read) > 0)
> > +			pvcalls_conn_back_read((unsigned long)map);
> > +		if (atomic_read(&map->write) > 0)
> > +			pvcalls_conn_back_write(map);
> > +
> > +		atomic_dec(&map->io);
> > +	}
> >  }
> >  
> >  static int pvcalls_back_socket(struct xenbus_device *dev,
> > 
>