From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759024AbZHRP6Y (ORCPT ); Tue, 18 Aug 2009 11:58:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751435AbZHRP6Y (ORCPT ); Tue, 18 Aug 2009 11:58:24 -0400 Received: from fgwmail7.fujitsu.co.jp ([192.51.44.37]:58337 "EHLO fgwmail7.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751393AbZHRP6X (ORCPT ); Tue, 18 Aug 2009 11:58:23 -0400 Date: Wed, 19 Aug 2009 00:57:54 +0900 (JST) X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 From: KOSAKI Motohiro To: linux-mm , LKML , Andrew Morton Subject: [PATCH for mmotm] oom: remove unnecessary task->sighand->siglock grabbing. Cc: kosaki.motohiro@jp.fujitsu.com, Oleg Nesterov Message-Id: <20090819005301.A650.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Becky! ver. 2.50.07 [ja] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Subject: [PATCH] oom: remove unnecessary task->sighand->siglock grabbing. Oleg Nesterov get_oom_adj() doesn't need grab task->sighand->siglock. tasklist_lock already prevent any race. This patch remove its unnecessary lock. Reported-by: Oleg Nesterov Signed-off-by: KOSAKI Motohiro --- mm/oom_kill.c | 29 +++++++---------------------- 1 file changed, 7 insertions(+), 22 deletions(-) Index: b/mm/oom_kill.c =================================================================== --- a/mm/oom_kill.c 2009-08-19 00:25:28.000000000 +0900 +++ b/mm/oom_kill.c 2009-08-19 00:43:31.000000000 +0900 @@ -34,17 +34,13 @@ int sysctl_oom_dump_tasks; static DEFINE_SPINLOCK(zone_scan_lock); /* #define DEBUG */ -int get_oom_adj(struct task_struct *tsk) +static int get_oom_adj(struct task_struct *tsk) { - unsigned long flags; - int oom_adj = OOM_DISABLE; - - if (tsk->mm && lock_task_sighand(tsk, &flags)) { - oom_adj = tsk->signal->oom_adj; - unlock_task_sighand(tsk, &flags); - } + /* OOM Killer can't kill kernel thread */ + if (!tsk->mm) + return OOM_DISABLE; - return oom_adj; + return tsk->signal->oom_adj; } void set_oom_adj(struct task_struct *tsk, int oom_adj) @@ -97,7 +93,6 @@ unsigned long badness(struct task_struct struct task_struct *child; int oom_adj; struct task_cputime task_time; - unsigned long flags; unsigned long utime; unsigned long stime; @@ -105,10 +100,7 @@ unsigned long badness(struct task_struct if (oom_adj == OOM_DISABLE) return 0; - if (!lock_task_sighand(p, &flags)) - return 0; thread_group_cputime(p, &task_time); - unlock_task_sighand(p, &flags); task_lock(p); mm = p->mm; @@ -329,8 +321,6 @@ static struct task_struct *select_bad_pr static void dump_tasks(const struct mem_cgroup *mem) { struct task_struct *g, *p; - unsigned long flags; - int oom_adj; printk(KERN_INFO "[ pid ] uid tgid total_vm rss cpu oom_adj " "name\n"); @@ -342,12 +332,6 @@ static void dump_tasks(const struct mem_ if (!thread_group_leader(p)) continue; - if (!lock_task_sighand(p, &flags)) - continue; - - oom_adj = p->signal->oom_adj; - unlock_task_sighand(p, &flags); - task_lock(p); mm = p->mm; if (!mm) { @@ -361,7 +345,8 @@ static void dump_tasks(const struct mem_ } printk(KERN_INFO "[%5d] %5d %5d %8lu %8lu %3d %3d %s\n", p->pid, __task_cred(p)->uid, p->tgid, mm->total_vm, - get_mm_rss(mm), (int)task_cpu(p), oom_adj, p->comm); + get_mm_rss(mm), (int)task_cpu(p), get_oom_adj(p), + p->comm); task_unlock(p); } while_each_thread(g, p); }