Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754751Ab0BVWGi (ORCPT ); Mon, 22 Feb 2010 17:06:38 -0500 Received: from smtp-out.google.com ([216.239.33.17]:38604 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754701Ab0BVWGc (ORCPT ); Mon, 22 Feb 2010 17:06:32 -0500 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=date:from:x-x-sender:to:cc:subject:in-reply-to:message-id: references:user-agent:mime-version:content-type:x-system-of-record; b=fhmuzjAw3vbGSH2LHBQSHKgJIGU/f7aenbTZ4hsWiax3YLX4qJubwTHwzqLBOirYj SaHBBH4pGsXDtfO6jQwfg== Date: Mon, 22 Feb 2010 14:06:25 -0800 (PST) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Miao Xie cc: Nick Piggin , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Lee Schermerhorn Subject: Re: [regression] cpuset,mm: update tasks' mems_allowed in time (58568d2) In-Reply-To: <4B827043.3060305@cn.fujitsu.com> Message-ID: References: <20100218134921.GF9738@laptop> <20100219033126.GI9738@laptop> <4B827043.3060305@cn.fujitsu.com> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3438 Lines: 110 On Mon, 22 Feb 2010, Miao Xie wrote: > >>> guarantee_online_cpus() truly does require callback_mutex, the > >>> cgroup_scan_tasks() iterator locking can protect changes in the cgroup > >>> hierarchy but it doesn't protect a store to cs->cpus_allowed or for > >>> hotplug. > >> > >> Right, but the callback_mutex was being removed by this patch. > >> > > > > I was making the case for it to be readded :) > > But cgroup_mutex is held when someone changes cs->cpus_allowed or doing hotplug, > so I think callback_mutex is not necessary in this case. > Then why is it taken in update_cpumask()? > I think this patch can't fix this bug, because mems_allowed of tasks in the > top group is set to node_possible_map by default, not when the task is > attached. > Ok, I thought that all tasks get their ->attach() function called whenever their cgroup is mounted. > I made a new patch at the end of this email to fix it, but I have no machine > to test it now. who can test it for me. > > --- > diff --git a/init/main.c b/init/main.c > index 4cb47a1..512ba15 100644 > --- a/init/main.c > +++ b/init/main.c > @@ -846,7 +846,7 @@ static int __init kernel_init(void * unused) > /* > * init can allocate pages on any node > */ > - set_mems_allowed(node_possible_map); > + set_mems_allowed(node_states[N_HIGH_MEMORY]); > /* > * init can run on any cpu. > */ > diff --git a/kernel/cpuset.c b/kernel/cpuset.c > index ba401fa..e29b440 100644 > --- a/kernel/cpuset.c > +++ b/kernel/cpuset.c > @@ -935,10 +935,12 @@ static void cpuset_migrate_mm(struct mm_struct *mm, const nodemask_t *from, > struct task_struct *tsk = current; > > tsk->mems_allowed = *to; > + wmb(); > > do_migrate_pages(mm, from, to, MPOL_MF_MOVE_ALL); > > guarantee_online_mems(task_cs(tsk),&tsk->mems_allowed); > + wmb(); > } > > /* > @@ -1391,11 +1393,10 @@ static void cpuset_attach(struct cgroup_subsys *ss, struct cgroup *cont, > > if (cs == &top_cpuset) { > cpumask_copy(cpus_attach, cpu_possible_mask); > - to = node_possible_map; > } else { > guarantee_online_cpus(cs, cpus_attach); > - guarantee_online_mems(cs, &to); > } > + guarantee_online_mems(cs, &to); > > /* do per-task migration stuff possibly for each in the threadgroup */ > cpuset_attach_task(tsk, &to, cs); Do we need to set cpus_attach to cpu_possible_mask? Why won't cpu_active_mask suffice? > @@ -2090,15 +2091,19 @@ static int cpuset_track_online_cpus(struct notifier_block *unused_nb, > static int cpuset_track_online_nodes(struct notifier_block *self, > unsigned long action, void *arg) > { > + nodemask_t oldmems; Is it possible to use NODEMASK_ALLOC() instead? > + > cgroup_lock(); > switch (action) { > case MEM_ONLINE: > - case MEM_OFFLINE: > + oldmems = top_cpuset.mems_allowed; > mutex_lock(&callback_mutex); > top_cpuset.mems_allowed = node_states[N_HIGH_MEMORY]; > mutex_unlock(&callback_mutex); > - if (action == MEM_OFFLINE) > - scan_for_empty_cpusets(&top_cpuset); > + update_tasks_nodemask(&top_cpuset, &oldmems, NULL); > + break; > + case MEM_OFFLINE: > + scan_for_empty_cpusets(&top_cpuset); > break; > default: > break; Looks good. -- 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/