From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753368AbZAEJPp (ORCPT ); Mon, 5 Jan 2009 04:15:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753846AbZAEJPT (ORCPT ); Mon, 5 Jan 2009 04:15:19 -0500 Received: from smtp1.linux-foundation.org ([140.211.169.13]:44677 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753792AbZAEJPQ (ORCPT ); Mon, 5 Jan 2009 04:15:16 -0500 Date: Mon, 5 Jan 2009 01:14:14 -0800 From: Andrew Morton To: Li Zefan Cc: Ingo Molnar , Rusty Russell , Mike Travis , Paul Menage , LKML Subject: Re: [PATCH 3/6] cpuset: convert cpuset_attach() to use cpumask_var_t Message-Id: <20090105011414.176a5ee3.akpm@linux-foundation.org> In-Reply-To: <4961CD36.7070507@cn.fujitsu.com> References: <495B2EA6.7010808@cn.fujitsu.com> <495B2EC2.9090305@cn.fujitsu.com> <495B2EE7.4040406@cn.fujitsu.com> <495B2EFB.302@cn.fujitsu.com> <20090104233856.8c72eb58.akpm@linux-foundation.org> <4961C919.6040404@cn.fujitsu.com> <20090105010147.bc42b655.akpm@linux-foundation.org> <4961CD36.7070507@cn.fujitsu.com> X-Mailer: Sylpheed 2.4.8 (GTK+ 2.12.5; x86_64-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 List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 05 Jan 2009 17:04:54 +0800 Li Zefan wrote: > Andrew Morton wrote: > > On Mon, 05 Jan 2009 16:47:21 +0800 Li Zefan wrote: > > > >> Allocate a global cpumask_var_t at boot, and use it in cpuset_attach(), so > >> we won't fail cpuset_attach(). > >> > >> Signed-off-by: Li Zefan > >> Acked-by: Mike Travis > >> --- > >> kernel/cpuset.c | 14 +++++++++----- > >> 1 files changed, 9 insertions(+), 5 deletions(-) > >> > >> diff --git a/kernel/cpuset.c b/kernel/cpuset.c > >> index afa29cf..1e32e6b 100644 > >> --- a/kernel/cpuset.c > >> +++ b/kernel/cpuset.c > >> @@ -1306,6 +1306,9 @@ static int fmeter_getrate(struct fmeter *fmp) > >> return val; > >> } > >> > >> +/* Protected by cgroup_lock */ > >> +static cpumask_var_t cpus_attach; > >> + > >> /* Called by cgroups to determine if a cpuset is usable; cgroup_mutex held */ > >> static int cpuset_can_attach(struct cgroup_subsys *ss, > >> struct cgroup *cont, struct task_struct *tsk) > >> @@ -1330,7 +1333,6 @@ static void cpuset_attach(struct cgroup_subsys *ss, > >> struct cgroup *cont, struct cgroup *oldcont, > >> struct task_struct *tsk) > >> { > >> - cpumask_t cpus; > >> nodemask_t from, to; > >> struct mm_struct *mm; > >> struct cpuset *cs = cgroup_cs(cont); > >> @@ -1338,13 +1340,13 @@ static void cpuset_attach(struct cgroup_subsys *ss, > >> int err; > >> > >> if (cs == &top_cpuset) { > >> - cpus = cpu_possible_map; > >> + cpumask_copy(cpus_attach, cpu_possible_mask); > >> } else { > >> mutex_lock(&callback_mutex); > >> - guarantee_online_cpus(cs, &cpus); > >> + guarantee_online_cpus(cs, cpus_attach); > >> mutex_unlock(&callback_mutex); > >> } > >> - err = set_cpus_allowed_ptr(tsk, &cpus); > >> + err = set_cpus_allowed_ptr(tsk, cpus_attach); > >> if (err) > >> return; > >> > >> @@ -1357,7 +1359,6 @@ static void cpuset_attach(struct cgroup_subsys *ss, > >> cpuset_migrate_mm(mm, &from, &to); > >> mmput(mm); > >> } > >> - > >> } > >> > >> /* The various types of files and directories in a cpuset file system */ > >> @@ -1838,6 +1839,9 @@ int __init cpuset_init(void) > >> if (err < 0) > >> return err; > >> > >> + if (!alloc_cpumask_var(&cpus_attach, GFP_KERNEL)) > >> + BUG(); > >> + > >> number_of_cpusets = 1; > >> return 0; > >> } > > > > OK, that works. > > > > Do we need to dynamically allocate cpus_attach? Can we just do > > > > static cpumask_t cpus_attach; > > > > ? > > > > Yes, it's used by cpuset_attach() only, and cpuset_attach() is called with > cgroup_lock() held, so it won't happen that 2 threads access cpus_attach > concurrently. You misunderstand my question. I think. Can we allocate cpus_attach at compile time? Completely, not partially. By doing static cpumask_t cpus_attach; instead of static cpumask_var_t cpus_attach; ... alloc_cpumask_var(&cpus_attach, GFP_KERNEL); ?