From: Christian Borntraeger <kernel@borntraeger.net>
To: joe.korty@ccur.com, dhowells@redhat.com, akpm@osdl.org
Subject: Re: [PATCH] volatile may be needed in rwsem
Date: Tue, 27 Jan 2004 21:20:42 +0100
User-Agent: KMail/1.5.4
Cc: linux-kernel@vger.kernel.org
References: <20040127191155.GA12128@tsunami.ccur.com>
In-Reply-To: <20040127191155.GA12128@tsunami.ccur.com>
MIME-Version: 1.0
Content-Type: text/plain;
  charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
Message-Id: <200401272120.42675.kernel@borntraeger.net>
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 592
Lines: 19

Joe Korty wrote:
> 'flags' should be declared volatile as rwsem_down_failed_common() spins
> waiting for this to change.  Untested.


You should use barrier() to prevent the compiler from optimizing reads away, 
not volatile. 
Here the compiler hopefully considers schedule() as a memory barrier. So 
everything should be fine.

cheers

Christian

-
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/