From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751267AbVKEGjB (ORCPT ); Sat, 5 Nov 2005 01:39:01 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751266AbVKEGjB (ORCPT ); Sat, 5 Nov 2005 01:39:01 -0500 Received: from smtp.osdl.org ([65.172.181.4]:53930 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S1751267AbVKEGjA (ORCPT ); Sat, 5 Nov 2005 01:39:00 -0500 Date: Fri, 4 Nov 2005 22:38:10 -0800 From: Andrew Morton To: Paul Jackson Cc: Simon.Derr@bull.net, ak@suse.de, pj@sgi.com, linux-kernel@vger.kernel.org, clameter@sgi.com Subject: Re: [PATCH 6/5] cpuset: rebind numa vma mempolicy fix Message-Id: <20051104223810.31355dce.akpm@osdl.org> In-Reply-To: <20051104082833.8786.5266.sendpatchset@jackhammer.engr.sgi.com> References: <20051104082833.8786.5266.sendpatchset@jackhammer.engr.sgi.com> X-Mailer: Sylpheed version 1.0.4 (GTK+ 1.2.10; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Paul Jackson wrote: > > It's ok to not complete the refresh_mems() operation > if we notice we are already holding mmap_sem. We > will try again, next time we allocate memory. What's the call path? alloc_pages_current() and alloc_page_vma()? > > --- 2.6.14-rc5-mm1-cpuset-patches.orig/kernel/cpuset.c 2005-11-03 21:18:26.783391082 -0800 > +++ 2.6.14-rc5-mm1-cpuset-patches/kernel/cpuset.c 2005-11-03 23:11:15.480042373 -0800 > @@ -656,7 +656,12 @@ static void refresh_mems(void) > if (current->cpuset_mems_generation != my_cpusets_mem_gen) { > struct cpuset *cs; > nodemask_t oldmem = current->mems_allowed; > + struct mm_struct *mm = current->mm; > > + /* numa_policy_rebind() needs mmap_sem - don't nest */ > + if (!mm || !down_write_trylock(&mm->mmap_sem)) > + return; > + up_write(&mm->mmap_sem); What happens if the task is doing _all_ its allocation under down_read(mmap_sem)? Like, memset(malloc(lots))? Does all that memory end up in the wrong place, or what? Something less hacky^W^W more deterministic would be nice.