From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754067AbZJQVVe (ORCPT ); Sat, 17 Oct 2009 17:21:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753869AbZJQVVc (ORCPT ); Sat, 17 Oct 2009 17:21:32 -0400 Received: from server1.wserver.cz ([82.113.45.157]:60879 "EHLO server1.wserver.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753974AbZJQVV1 (ORCPT ); Sat, 17 Oct 2009 17:21:27 -0400 From: Jiri Slaby To: akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org, Jiri Slaby , Oleg Nesterov Subject: [PATCH -repost 7/8] core: optimize setrlimit for current task Date: Sat, 17 Oct 2009 23:21:21 +0200 Message-Id: <1255814482-13994-7-git-send-email-jirislaby@gmail.com> X-Mailer: git-send-email 1.6.4.2 In-Reply-To: <1255814482-13994-1-git-send-email-jirislaby@gmail.com> References: <1255814482-13994-1-git-send-email-jirislaby@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Don't take tasklist lock for 'current'. It's not needed, since current->sighand/signal can't disappear. This improves serlimit called especially via sys_setrlimit. Signed-off-by: Jiri Slaby Cc: Oleg Nesterov --- kernel/sys.c | 16 ++++++++++------ 1 files changed, 10 insertions(+), 6 deletions(-) diff --git a/kernel/sys.c b/kernel/sys.c index 5bb80d6..6886f7d 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -1250,11 +1250,14 @@ int setrlimit(struct task_struct *tsk, unsigned int resource, if (resource == RLIMIT_NOFILE && new_rlim->rlim_max > sysctl_nr_open) return -EPERM; - /* protect tsk->signal and tsk->sighand from disappearing */ - read_lock(&tasklist_lock); - if (!tsk->sighand) { - retval = -ESRCH; - goto out; + /* optimization: 'current' doesn't need locking, e.g. setrlimit */ + if (tsk != current) { + /* protect tsk->signal and tsk->sighand from disappearing */ + read_lock(&tasklist_lock); + if (!tsk->sighand) { + retval = -ESRCH; + goto out; + } } retval = security_task_setrlimit(tsk, resource, new_rlim); @@ -1294,7 +1297,8 @@ int setrlimit(struct task_struct *tsk, unsigned int resource, update_rlimit_cpu(tsk, new_rlim->rlim_cur); out: - read_unlock(&tasklist_lock); + if (tsk != current) + read_unlock(&tasklist_lock); return retval; } -- 1.6.4.2