Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753678Ab0H0FvM (ORCPT ); Fri, 27 Aug 2010 01:51:12 -0400 Received: from ipmail06.adl2.internode.on.net ([150.101.137.129]:12401 "EHLO ipmail06.adl2.internode.on.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753094Ab0H0FvK (ORCPT ); Fri, 27 Aug 2010 01:51:10 -0400 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AvsEAMrsdkx5Ld90/2dsb2JhbACgU3K8aIU3BA Date: Fri, 27 Aug 2010 15:51:05 +1000 From: Nick Piggin To: Peter Zijlstra Cc: Nick Piggin , Tejun Heo , Linus Torvalds , Jonathan Corbet , Rusty Russell , Al Viro , LKML Subject: Re: [PATCH] lglock: make lg_lock_global() actually lock globally Message-ID: <20100827055105.GA3857@amd> References: <20100825132815.108d8217@bike.lwn.net> <4C762BF9.5010305@kernel.org> <20100826094613.GA6411@amd> <4C7638B7.9060306@kernel.org> <1282817329.1975.486.camel@laptop> <20100826113858.GA6856@amd> <1282823139.1975.689.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1282823139.1975.689.camel@laptop> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1138 Lines: 29 On Thu, Aug 26, 2010 at 01:45:39PM +0200, Peter Zijlstra wrote: > On Thu, 2010-08-26 at 21:38 +1000, Nick Piggin wrote: > > I think for CPU plug, stop_machine is reasonable (especially > > considering it is required in unload, which means any frequent > > amount of cpu plug activity already will require stop_machine to > > run anyway). > > How is it required? Well, as is implemented. > Its currently implemented as such, and its sure a lot easier to do that > way, but I could imagine that unplugging a CPU could be done without it. I would much prefer the rules to be simpler and easier for all other kernel code, and keep complexity and overheads in cpu plug/unplug. I don't see what is so nice about stop_machine()less cpu plug/unplug or module unload. Module load definitely is nice because you can have a lot of modules and on demand loading from non-privileged operations. -- 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/