From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753508AbZAEJGJ (ORCPT ); Mon, 5 Jan 2009 04:06:09 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751845AbZAEJFz (ORCPT ); Mon, 5 Jan 2009 04:05:55 -0500 Received: from cn.fujitsu.com ([222.73.24.84]:57377 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751735AbZAEJFy (ORCPT ); Mon, 5 Jan 2009 04:05:54 -0500 Message-ID: <4961CD36.7070507@cn.fujitsu.com> Date: Mon, 05 Jan 2009 17:04:54 +0800 From: Li Zefan User-Agent: Thunderbird 2.0.0.9 (X11/20071115) MIME-Version: 1.0 To: Andrew Morton CC: Ingo Molnar , Rusty Russell , Mike Travis , Paul Menage , LKML Subject: Re: [PATCH 3/6] cpuset: convert cpuset_attach() to use cpumask_var_t 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> In-Reply-To: <20090105010147.bc42b655.akpm@linux-foundation.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.