Re: [Xen-devel] [PATCH Linux-2.6.18] scsifront: avoid aquiring same lock twice if ring is full

[Juergen Gross <jgross@xxxxxxxx>]

On 01/13/2015 07:53 PM, Pasi Kärkkäinen wrote:
> Hi,
>
> On Tue, Jan 13, 2015 at 05:22:58PM +0100, Juergen Gross wrote:
> > The locking in scsifront_dev_reset_handler() is obviously wrong. In
> > case of a full ring the host lock is aquired twice.
> >
> > Fixing this issue enables to get rid of the endless fo loop with an
> > explicit break statement.
> Is this patch needed in upstream Linux kernel aswell, now that Xen PVSCSI 
> drivers are in upstream Linux ?
No, especially this part of the code was reorganized and doesn't
have that issue.

Juergen

> Thanks,
>
> -- Pasi
>
>
> > Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> > ---
> >
> > diff -r 078f1bb69ea5 drivers/xen/scsifront/scsifront.c
> > --- a/drivers/xen/scsifront/scsifront.c Wed Dec 10 10:22:39 2014 +0100
> > +++ b/drivers/xen/scsifront/scsifront.c Tue Jan 13 14:32:33 2015 +0100
> > @@ -447,12 +447,10 @@ static int scsifront_dev_reset_handler(s
> >         uint16_t rqid;
> >         int err = 0;
> >
> > -       for (;;) {
> >   #if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,12)
> > -               spin_lock_irq(host->host_lock);
> > +       spin_lock_irq(host->host_lock);
> >   #endif
> > -               if (!RING_FULL(&info->ring))
> > -                       break;
> > +       while (RING_FULL(&info->ring)) {
> >                 if (err) {
> >   #if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,12)
> >                         spin_unlock_irq(host->host_lock);
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxx
> > http://lists.xen.org/xen-devel

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