linux-kernel - Re: [PATCH 1/1] Misc: phantom, move to unlocked

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Date:	Fri, 18 May 2007 23:25:52 +0200
From:	"Jiri Slaby" <jirislaby@...il.com>
To:	"Andrew Morton" <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] Misc: phantom, move to unlocked_ioctl

On 5/18/07, Andrew Morton <akpm@...ux-foundation.org> wrote:
> On Fri, 18 May 2007 22:34:53 +0200 (CEST)
> Jiri Slaby <jirislaby@...il.com> wrote:
>
> > @@ -118,7 +125,9 @@ static int phantom_ioctl(struct inode *inode, struct file *file, u_int cmd,
> >               if (r.reg > 7)
> >                       return -EINVAL;
> >
> > +             spin_lock(&dev->ioctl_lock);
> >               r.value = ioread32(dev->iaddr + r.reg);
> > +             spin_unlock(&dev->ioctl_lock);
>
> What is that locking protecting in here?

Well, what led me to do it is that I didn't know how much atomic are
ioread and iowrite. If concurrent process writes something to the
place in that space while the other one is reading it, doesn't matter,
correct?

thanks,
-- 
http://www.fi.muni.cz/~xslaby/            Jiri Slaby
faculty of informatics, masaryk university, brno, cz
e-mail: jirislaby gmail com, gpg pubkey fingerprint:
B674 9967 0407 CE62 ACC8  22A0 32CC 55C3 39D4 7A7E
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