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Date: Wed, 25 Jul 2007 14:10:37 +1000
From: Nick Piggin <nickpiggin@yahoo.com.au>
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To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
CC: Trond Myklebust <trond.myklebust@fys.uio.no>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Satyam Sharma <ssatyam@cse.iitk.ac.in>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       David Howells <dhowells@redhat.com>, Andi Kleen <ak@suse.de>,
       Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 6/8] i386: bitops: Don't mark memory as clobbered	unnecessarily
References: <20070723160528.22137.84144.sendpatchset@cselinux1.cse.iitk.ac.in>	 <20070723160558.22137.71943.sendpatchset@cselinux1.cse.iitk.ac.in>	 <alpine.LFD.0.999.0707231054290.3607@woody.linux-foundation.org>	 <1185270756.5439.256.camel@localhost.localdomain>	 <alpine.LFD.0.999.0707241021210.3607@woody.linux-foundation.org>	 <1185298932.6586.22.camel@localhost>	 <alpine.LFD.0.999.0707241108360.3607@woody.linux-foundation.org>	 <1185313061.5439.283.camel@localhost.localdomain>	 <1185314112.6586.93.camel@localhost> <1185316368.5439.293.camel@localhost.localdomain>
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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.