From owner-freebsd-arch@FreeBSD.ORG  Tue Sep 18 20:17:07 2012
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To: Jeff Roberson <jroberson@jroberson.net>
From: "Poul-Henning Kamp" <phk@phk.freebsd.dk>
In-Reply-To: Your message of "Tue, 18 Sep 2012 09:00:38 -1000."
	<alpine.BSF.2.00.1209180858190.47770@desktop>
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Date: Tue, 18 Sep 2012 20:17:06 +0000
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Cc: Konstantin Belousov <kostikbel@gmail.com>, attilio@freebsd.org,
	freebsd-arch@freebsd.org, arch@freebsd.org
Subject: Re: Aliasing issue with TAILQ on ppc64 ?
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In message <alpine.BSF.2.00.1209180858190.47770@desktop>, Jeff Roberson writes:

>If you compile at low optimization levels I assume it goes away?

I don't have access to the machine at this time, and in general
I'm not particular focused on PPC64, since this is a general
problem on any architecture, as I understand the C-language rules.

>Can you place asm volatile ("" ::: "memory"); between the two tailq macros 
>with the same optimization level?

I tried earlier to put a printf("FOO") there, and that fixed it, which
I why I diagnosed it as an aliasing issue in the first place.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.