From mboxrd@z Thu Jan  1 00:00:00 1970
From: "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH] bitops: add _local bitops
Date: Wed, 09 May 2012 09:45:57 -0700
Message-ID: <4FAA9F45.1080608@zytor.com>
References: <20120509134528.GA18044@redhat.com> <4FAA7939.6040706@zytor.com> <20120509154734.GB20867@redhat.com> <4FAA9A49.8080900@zytor.com> <20120509163641.GA21344@redhat.com>
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Cc: Rob Landley <rob@landley.net>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, x86@kernel.org,
	Arnd Bergmann <arnd@arndb.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	David Howells <dhowells@redhat.com>,
	Akinobu Mita <akinobu.mita@gmail.com>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	Herbert Xu <herbert@gondor.hengli.com.au>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-arch@vger.kernel.org, Gleb Natapov <gleb@redhat.com>,
	Paolo Bonzini <pbonzini@redhat.com>, kvm@vger.kernel.org,
	Avi Kivity <avi@redhat.com>,
	Marcelo Tosatti <mtosatti@redhat.com>,
	Linus Torvalds <torvalds@linux-foundation.org>
To: "Michael S. Tsirkin" <mst@redhat.com>
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On 05/09/2012 09:36 AM, Michael S. Tsirkin wrote:
> 
> Well it talks about a memory barrier, not an
> optimization barrier.
> 

Same thing.

> If compiler reorders code, changes will appear in
> the wrong order on the current processor,
> not just on other processors, no?

Yes.

For your _local I would just copy the atomic bitops but remote the locks
in most cases.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.