Subject: Re: [PATCH 0/7] ppc: remove cli()/sti() from arch/ppc/*

From: Christoph Hellwig <[email-masked]>
Date: Wed, 5 Jan 2005 10:26:59 +0100

On Tue, Jan 04, 2005 at 09:44:06PM -0500, Jim Nelson wrote:
> Brian Gerst wrote:
> 
> >James Nelson wrote:
> >
> >>This series of patches is to remove the last cli()/sti() function 
> >>calls in arch/ppc.
> >>
> >>These are the only instances in active code that grep could find.
> >
> >
> >Are you sure none of these need real spinlocks instead of just 
> >disabling interrupts?
> >
> >-- 
> >                Brian Gerst
> >
> These are for single-processor systems, mostly evaluation boards and 
> embedded processors.  I coudn't find any reference to multiprocessor 
> setups for the processors in question after a peruse of the code or a 
> quick google on the boards in question.

think CONFIG_PREEMPT.  In either case a spinlock becomes
lock_irq_disable in the !SMP, !PREEMPT case but it documents the
intention a whole lot better.

Also you're locking only in a single plpace which is a ***BIG*** warning
sign.  At least look at the other users of the data structure, it's
extremly likely they'll need locking aswell.