linux-kernel - Re: [PATCH 6/8] i386: bitops: Don't mark memory as clobbered unnecessarily

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Message-ID: <46A6CD3D.8010507@yahoo.com.au>
Date:	Wed, 25 Jul 2007 14:10:37 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
CC:	Trond Myklebust <trond.myklebust@....uio.no>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Satyam Sharma <ssatyam@....iitk.ac.in>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	David Howells <dhowells@...hat.com>, Andi Kleen <ak@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 6/8] i386: bitops: Don't mark memory as clobbered	unnecessarily

Benjamin Herrenschmidt wrote:
> On Tue, 2007-07-24 at 17:55 -0400, Trond Myklebust wrote:
> 
>>If you want to use bitops as spinlocks you should rather be using
>><linux/bit_spinlock.h>. That also does the right thing w.r.t.
>>pre-emption and sparse locking annotations.
> 
> 
> Heh, I didn't know about those... A bit annoying that I can't override
> them in the arch, I might be able to save a barrier or two here. Our

I guess the test_and_set_bit_lock / clear_bit_unlock will allow you to
override them in a way.

The big performance problem I see on my powerpc system is not the bit
spinlocks (open-coded or not), but the bit sleep locks.

Anyway, I'll finally send out the lock bitops patches again today...

-- 
SUSE Labs, Novell Inc.
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