Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935554AbZAPOKx (ORCPT ); Fri, 16 Jan 2009 09:10:53 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S934969AbZAPOKT (ORCPT ); Fri, 16 Jan 2009 09:10:19 -0500 Received: from rtr.ca ([76.10.145.34]:35185 "EHLO mail.rtr.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934477AbZAPOKR (ORCPT ); Fri, 16 Jan 2009 09:10:17 -0500 Message-ID: <49709547.7060001@rtr.ca> Date: Fri, 16 Jan 2009 09:10:15 -0500 From: Mark Lord Organization: Real-Time Remedies Inc. User-Agent: Thunderbird 2.0.0.19 (X11/20090105) MIME-Version: 1.0 To: Andrew Morton Cc: Ingo Molnar , Tejun Heo , "H. Peter Anvin" , Brian Gerst , ebiederm@xmission.com, cl@linux-foundation.org, rusty@rustcorp.com.au, travis@sgi.com, linux-kernel@vger.kernel.org, steiner@sgi.com, hugh@veritas.com Subject: Re: [PATCH] percpu: add optimized generic percpu accessors References: <496D8CEB.5060402@zytor.com> <20090114093834.GA19799@elte.hu> <496F0F50.6070200@kernel.org> <20090115113045.GG22850@elte.hu> <496F2032.5080502@kernel.org> <20090115122611.GJ22850@elte.hu> <496F346B.6020804@kernel.org> <20090115130740.GE21839@elte.hu> <496F38C7.5000403@kernel.org> <20090115093007.4215b4b4.akpm@linux-foundation.org> <20090115180259.GJ22472@elte.hu> <20090115103406.a85968f0.akpm@linux-foundation.org> In-Reply-To: <20090115103406.a85968f0.akpm@linux-foundation.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 848 Lines: 25 Andrew Morton wrote: > On Thu, 15 Jan 2009 19:02:59 +0100 Ingo Molnar wrote: > >> * Andrew Morton wrote: .. >>> I wonder if the preempt_disable()/preempt_enable() in here actually >>> does anything useful on any architecture. >> Provides "this is IRQ safe" > > ? > >> and "this is preempt safe" semantics. > > Of course. But do any architectures actually _need_ that for a single read? .. If the target is unaligned, then RISC architectures will need protection there. If we can guarantee correct memory alignment of the target, then no / none. Cheers -- 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/