From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755135AbZLIKPr (ORCPT ); Wed, 9 Dec 2009 05:15:47 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753687AbZLIKPd (ORCPT ); Wed, 9 Dec 2009 05:15:33 -0500 Received: from www.tglx.de ([62.245.132.106]:40019 "EHLO www.tglx.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755080AbZLIKPb (ORCPT ); Wed, 9 Dec 2009 05:15:31 -0500 Message-Id: <20091209100706.862897167@linutronix.de> User-Agent: quilt/0.47-1 Date: Wed, 09 Dec 2009 10:15:11 -0000 From: Thomas Gleixner To: LKML Cc: Ingo Molnar , Peter Zijlstra Subject: [patch 4/4] sched: Use rcu in sched_get_rr_param References: <20091209100540.511353305@linutronix.de> Content-Disposition: inline; filename=sched-use-rcu-in-sched-get-rr-param.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org read_lock(&tasklist_lock) does not protect sys_sched_get_rr_param() against a concurrent update of the policy or scheduler parameters as do_sched_scheduler() does not take the tasklist_lock. The access to task->sched_class->get_rr_interval is protected by task_rq_lock(task). Use rcu_read_lock() to protect find_task_by_vpid() and prevent the task struct from going away. Signed-off-by: Thomas Gleixner --- kernel/sched.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) Index: linux-2.6-tip/kernel/sched.c =================================================================== --- linux-2.6-tip.orig/kernel/sched.c +++ linux-2.6-tip/kernel/sched.c @@ -6892,7 +6892,7 @@ SYSCALL_DEFINE2(sched_rr_get_interval, p return -EINVAL; retval = -ESRCH; - read_lock(&tasklist_lock); + rcu_read_lock(); p = find_process_by_pid(pid); if (!p) goto out_unlock; @@ -6905,13 +6905,13 @@ SYSCALL_DEFINE2(sched_rr_get_interval, p time_slice = p->sched_class->get_rr_interval(rq, p); task_rq_unlock(rq, &flags); - read_unlock(&tasklist_lock); + rcu_read_unlock(); jiffies_to_timespec(time_slice, &t); retval = copy_to_user(interval, &t, sizeof(t)) ? -EFAULT : 0; return retval; out_unlock: - read_unlock(&tasklist_lock); + rcu_read_unlock(); return retval; }