From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756427AbZICUJe (ORCPT ); Thu, 3 Sep 2009 16:09:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756414AbZICUJb (ORCPT ); Thu, 3 Sep 2009 16:09:31 -0400 Received: from server1.wserver.cz ([82.113.45.157]:51035 "EHLO server1.wserver.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756324AbZICUIk (ORCPT ); Thu, 3 Sep 2009 16:08:40 -0400 From: Jiri Slaby To: oleg@redhat.com Cc: akpm@linux-foundation.org, mingo@redhat.com, linux-kernel@vger.kernel.org, Jiri Slaby Subject: [PATCH v2 7/8] core: optimize setrlimit for current task Date: Thu, 3 Sep 2009 22:08:43 +0200 Message-Id: <1252008524-5376-7-git-send-email-jirislaby@gmail.com> X-Mailer: git-send-email 1.6.3.3 In-Reply-To: <20090903174106.GC27161@redhat.com> References: <20090903174106.GC27161@redhat.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 791b5c5..feca9d6 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -1247,11 +1247,14 @@ 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); @@ -1291,7 +1294,8 @@ 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; } -- 1.6.3.3