Date: Fri, 3 Jul 2009 20:18:15 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Arjan van de Ven <arjan@infradead.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>,
       Linus Torvalds <torvalds@linux-foundation.org>, mingo@redhat.com,
       linux-kernel@vger.kernel.org
Subject: Re: [PATCH -tip] x86: atomic64: inline atomic64_read()
Message-ID: <20090703181815.GC3405@elte.hu>
References: <alpine.LFD.2.01.0907021653030.3210@localhost.localdomain> <tip-9103cab145a93cef13378632b332a824758a2f6f@git.kernel.org> <4A4E1AA2.30002@gmail.com> <20090703180450.GB3405@elte.hu> <20090703111033.6e9627de@infradead.org>
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* Arjan van de Ven <arjan@infradead.org> wrote:

> On Fri, 3 Jul 2009 20:04:50 +0200
> Ingo Molnar <mingo@elte.hu> wrote:
> 
> > > +static inline u64 atomic64_read(atomic64_t *ptr)
> > > +{
> > > +	u64 res;
> > > +
> > > +	asm volatile(
> > > +		"mov %%ebx, %%eax\n\t"
> > > +		"mov %%ecx, %%edx\n\t"
> > > +		LOCK_PREFIX "cmpxchg8b %1\n"
> 
> also afaik cmpxchg implies the lock prefix, so no need to make an
> explicit one... it just adds code size and alternatives-work

good point!

Is the same true of XADD as well? If yes then we can remove the lock 
prefix from those as well - there's a few uses of that on 32-bit and 
64-bit as well.

	Ingo
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