linux-kernel - Re: fs hang in 2.6.27.y | Fwd: [Bug 15658] New: [PATCH] x86 constant_test_bit() prone to misoptimization with gcc-4.4

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Message-ID: <20100926115354.GA30247@osdn.org.ua>
Date:	Sun, 26 Sep 2010 14:53:54 +0300
From:	Michael Shigorin <mike@...n.org.ua>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Volodymyr G. Lukiianyk" <volodymyrgl@...il.com>,
	Alexander Chumachenko <ledest@...il.com>,
	Glauber de Oliveira Costa <gcosta@...hat.com>
Subject: Re: fs hang in 2.6.27.y | Fwd: [Bug 15658] New: [PATCH] x86 constant_test_bit() prone to misoptimization with gcc-4.4

On Thu, Sep 23, 2010 at 04:50:22PM -0700, Andrew Morton wrote:
> Working around a gcc-4.4 bug is a good thing, and the patch cleans the
> code up anyway - is there a reason for casting away the `volatile const'?

It turned out that I translated the original assumption of _gcc_
fault (from our bugzilla) when the latter conclusion was that it
was correctly optimizing the code given that addr wasn't marked
as volatile.  My fault, sorry; fixed the commit comment this time.

> I changed the patch cosmetics a bit, see below.
> We don't have a Signed-off-by: for this patch - it would be
> good to have one, please.  We should at least have yours, as
> you sent the patch.

The simplicity of adding that somewhat went over my head --
please find attached the corrected original patch against HEAD
with Signed-off-by: for both of us.  led@ didn't change cosmetics
-- thanks for providing it anyways.

> Also, we prefer to have real names in kernel commits.
> Does "Led" refer to Alexander Chumachenko?

(just in case) Yes.

-- 
 ---- WBR, Michael Shigorin <mike@...linux.ru>
  ------ Linux.Kiev http://www.linux.kiev.ua/

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