Date: Wed, 30 Nov 2005 23:19:31 +0100
From: Pavel Machek <pavel@ucw.cz>
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>
Subject: Re: [BUG] Variable stopmachine_state should be volatile
Message-ID: <20051130221931.GB2056@elf.ucw.cz>
References: <8126E4F969BA254AB43EA03C59F44E84040B3069@pdsmsx404>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <8126E4F969BA254AB43EA03C59F44E84040B3069@pdsmsx404>
User-Agent: Mutt/1.5.9i
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 757
Lines: 19

Hi!

> 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.

No. volatile may look like a solution, but it usually is not. You may
need some barriers, atomic_t or locking.
								Pavel
-- 
Thanks, Sharp!
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/