Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S938719AbXHIN5h (ORCPT ); Thu, 9 Aug 2007 09:57:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S937115AbXHIN5A (ORCPT ); Thu, 9 Aug 2007 09:57:00 -0400 Received: from mx1.redhat.com ([66.187.233.31]:48303 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S939641AbXHIN45 (ORCPT ); Thu, 9 Aug 2007 09:56:57 -0400 Date: Thu, 9 Aug 2007 09:56:23 -0400 From: Chris Snook To: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, torvalds@linux-foundation.org Cc: netdev@vger.kernel.org, akpm@linux-foundation.org, ak@suse.de, heiko.carstens@de.ibm.com, davem@davemloft.net, schwidefsky@de.ibm.com, wensong@linux-vs.org, horms@verge.net.au, wjiang@resilience.com, cfriesen@nortel.com, zlynx@acm.org, rpjday@mindspring.com, jesper.juhl@gmail.com Subject: [PATCH 11/24] make atomic_read() behave consistently on m68knommu Message-ID: <20070809135623.GA16554@shell.boston.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1137 Lines: 28 From: Chris Snook Make atomic_read() volatile on m68knommu. This ensures that busy-waiting for an interrupt handler to change an atomic_t won't get compiled to an infinite loop, consistent with SMP architectures. Signed-off-by: Chris Snook --- linux-2.6.23-rc2-orig/include/asm-m68knommu/atomic.h 2007-07-08 19:32:17.000000000 -0400 +++ linux-2.6.23-rc2/include/asm-m68knommu/atomic.h 2007-08-09 07:00:24.000000000 -0400 @@ -15,7 +15,11 @@ typedef struct { int counter; } atomic_t; #define ATOMIC_INIT(i) { (i) } -#define atomic_read(v) ((v)->counter) +/* + * Casting to volatile here minimizes the need for barriers, + * without having to declare the type itself as volatile. + */ +#define atomic_read(v) (*(volatile int *)&(v)->counter) #define atomic_set(v, i) (((v)->counter) = i) static __inline__ void atomic_add(int i, atomic_t *v) - 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/