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Date: Mon, 25 Sep 2006 14:22:13 -0700
From: Jeremy Fitzhardinge <jeremy@goop.org>
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To: Mathieu Desnoyers <compudj@krystal.dyndns.org>
CC: Martin Bligh <mbligh@google.com>, "Frank Ch. Eigler" <fche@redhat.com>,
       Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>, prasanna@in.ibm.com,
       Andrew Morton <akpm@osdl.org>, Ingo Molnar <mingo@elte.hu>,
       Paul Mundt <lethal@linux-sh.org>,
       linux-kernel <linux-kernel@vger.kernel.org>, Jes Sorensen <jes@sgi.com>,
       Tom Zanussi <zanussi@us.ibm.com>,
       Richard J Moore <richardj_moore@uk.ibm.com>,
       Michel Dagenais <michel.dagenais@polymtl.ca>,
       Christoph Hellwig <hch@infradead.org>,
       Greg Kroah-Hartman <gregkh@suse.de>,
       Thomas Gleixner <tglx@linutronix.de>, William Cohen <wcohen@redhat.com>,
       ltt-dev@shafik.org, systemtap@sources.redhat.com,
       Alan Cox <alan@lxorguk.ukuu.org.uk>, Karim Yaghmour <karim@opersys.com>,
       Pavel Machek <pavel@suse.cz>, Joe Perches <joe@perches.com>,
       "Randy.Dunlap" <rdunlap@xenotime.net>,
       "Jose R. Santos" <jrs@us.ibm.com>
Subject: Re: [PATCH] Linux Kernel Markers 0.11 for 2.6.17
References: <20060925151028.GA14695@Krystal> <45181CE9.1080204@goop.org> <20060925201036.GB13049@Krystal> <45183B20.2080907@goop.org> <20060925203502.GA3770@Krystal> <20060925204701.GB3770@Krystal>
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Mathieu Desnoyers wrote:
> Better idea : we could put a read/write dependency on a memory location.
>   

Yes, that works well.  And it needn't even exist:

	extern int __marker_sequencer;		/* doesn't exist, never referenced */

	asm volatile("first asm" : "+m" (__marker_sequencer));

	asm volatile("second asm" : "+m" (__marker_sequencer));

This keeps the asms ordered with respect to each other (and prevents to 
independent markers from being intermingled), but it doesn't prevent 
them from being re-ordered with respect to other code.

    J
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