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From: Denis Vlasenko <vda@port.imtp.ilyichevsk.odessa.ua>
Reply-To: vda@port.imtp.ilyichevsk.odessa.ua
To: Francois Romieu <romieu@cogenit.fr>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] cli()/sti() fix for drivers/net/depca.c
Date: Thu, 3 Oct 2002 00:26:53 -0200
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On 2 October 2002 18:40, Francois Romieu wrote:
> Denis Vlasenko <vda@port.imtp.ilyichevsk.odessa.ua> :
> > diff -u --recursive linux-2.5.38orig/drivers/net/depca.c
> > linux-2.5.38/drivers/net/depca.c ---
> > linux-2.5.38orig/drivers/net/depca.c	Sun Sep 22 04:25:10 2002 +++
> > linux-2.5.38/drivers/net/depca.c	Wed Oct  2 01:16:57 2002
>
> [...]
>
> > @@ -1999,18 +2000,19 @@
> >      break;
> >
> >    case DEPCA_GET_STATS:              /* Get the driver statistics */
> > -    cli();
> > +
> > +    spin_lock_irqsave(&lp->lock, flags);
> >      ioc->len = sizeof(lp->pktStats);
> >      if (copy_to_user(ioc->data, &lp->pktStats, ioc->len))
> >        status = -EFAULT;
> > -    sti();
> > +    spin_unlock_irqrestore(&lp->lock, flags);

Did I say it's my first network patch? :-)

> - copy_to_user() may sleep. Sleeping with spinlock held hurts badly.

Ho to do it properly? Make a copy on stack under lock, release lock,
proceed with copy_to_user? That's 88 bytes at least...

> - on SMP, pktStat can be updated while the copy progresses, see depca_rx().

Should I place these pktStat updates under lp->lock?
--
vda
-
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