Subject: Re: [BUG] Variable stopmachine_state should be volatile
From: Arjan van de Ven <arjan@infradead.org>
To: "Zhang, Yanmin" <yanmin.zhang@intel.com>
Cc: linux-kernel@vger.kernel.org,
       "Pallipadi, Venkatesh" <venkatesh.pallipadi@intel.com>,
       "Shah, Rajesh" <rajesh.shah@intel.com>
In-Reply-To: <8126E4F969BA254AB43EA03C59F44E84040B3069@pdsmsx404>
References: <8126E4F969BA254AB43EA03C59F44E84040B3069@pdsmsx404>
Content-Type: text/plain
Date: Fri, 02 Dec 2005 09:04:26 +0100
Message-Id: <1133510666.16520.3.camel@laptopd505.fenrus.org>
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On Wed, 2005-11-30 at 10:04 +0800, Zhang, Yanmin wrote:
> The model to access variable stopmachine_state is that a main thread
> writes it and other threads read it. Its declaration has no sign
> volatile. In the while loop in function stopmachine, this variable is
> read, and compiler might optimize it by reading it once before the loop
> and not reading it again in the loop, so the thread might enter dead
> loop.

cpu_relax() includes a compiler barier..... so... what's wrong with the
compiler that it ignores such barriers?


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