From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756531AbZBWUJw (ORCPT ); Mon, 23 Feb 2009 15:09:52 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753480AbZBWUJn (ORCPT ); Mon, 23 Feb 2009 15:09:43 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:53392 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753211AbZBWUJn (ORCPT ); Mon, 23 Feb 2009 15:09:43 -0500 Date: Mon, 23 Feb 2009 21:09:25 +0100 From: Ingo Molnar To: Andrew Morton Cc: paulmck@linux.vnet.ibm.com, nickpiggin@yahoo.com.au, vegard.nossum@gmail.com, stable@kernel.org, npiggin@suse.de, penberg@cs.helsinki.fi, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: fix lazy vmap purging (use-after-free error) Message-ID: <20090223200925.GA25994@elte.hu> References: <20090220140157.GA12799@elte.hu> <20090222030030.GD6860@linux.vnet.ibm.com> <20090223051709.GA5990@linux.vnet.ibm.com> <200902240029.37815.nickpiggin@yahoo.com.au> <20090223161726.GD6751@linux.vnet.ibm.com> <20090223111009.d48ff81d.akpm@linux-foundation.org> <20090223193351.GA11921@elte.hu> <20090223120401.b1354133.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090223120401.b1354133.akpm@linux-foundation.org> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Andrew Morton wrote: > On Mon, 23 Feb 2009 20:33:51 +0100 > Ingo Molnar wrote: > > > > > > Nice work all (btw. if this patch goes in rather than using system_state, > > > > > then please make the variable __read_mostly). > > > > > > > > Hmmm... I misread this and made system_state be __read_mostly. Let > > > > me know if this is bad, easy to fix if needed. > > > > > > Please don't use system_state. The whole thing is just bad > > > design. It's a global variable, breaks encapsulation, creates > > > interactions etc. CS-101 stuff. > > > > ok, i've removed the patch > > Thanks. > > > - Paul, would you mind to re-send your original flag > > solution, with it marked __read_mostly and with the extern > > declarations put into a suitable header file? > > It would still make sense to mark system_state __read_mostly. > > (That's assuming that __read_mostly makes sense. I still > wanna rename it to > __pack_all_write_often_variables_into_the_same_cacheline and > see what happens then) the write often variables should be on separate cachelines. Putting them on the same cacheline as a read-mostly variable is not helpful. Ingo