From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757653Ab0IRTpt (ORCPT ); Sat, 18 Sep 2010 15:45:49 -0400 Received: from kroah.org ([198.145.64.141]:51598 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754474Ab0IRTB7 (ORCPT ); Sat, 18 Sep 2010 15:01:59 -0400 X-Mailbox-Line: From gregkh@clark.site Sat Sep 18 11:59:59 2010 Message-Id: <20100918185959.142903861@clark.site> User-Agent: quilt/0.48-11.2 Date: Sat, 18 Sep 2010 11:58:38 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Ingo Molnar , Peter Zijlstra , Greg KH , Thomas Gleixner , Peter Zijlstra , Mike Galbraith Subject: [074/123] sched: Use rcu in sched_get/set_affinity() References: <20100918185724.290702750@clark.site> Content-Disposition: inline; filename=sched-use-rcu-in-sched_get-set_affinity.patch In-Reply-To: <20100918190024.GA14388@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Thomas Gleixner commit 23f5d142519621b16cf2b378cf8adf4dcf01a616 upstream tasklist_lock is held read locked to protect the find_task_by_vpid() call and to prevent the task going away. sched_setaffinity acquires a task struct ref and drops tasklist lock right away. The access to the cpus_allowed mask is protected by rq->lock. rcu_read_lock() provides the same protection here. Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra LKML-Reference: <20091209100706.789059966@linutronix.de> Signed-off-by: Ingo Molnar Signed-off-by: Mike Galbraith Signed-off-by: Greg Kroah-Hartman --- kernel/sched.c | 16 ++++++---------- 1 file changed, 6 insertions(+), 10 deletions(-) --- a/kernel/sched.c +++ b/kernel/sched.c @@ -6563,22 +6563,18 @@ long sched_setaffinity(pid_t pid, const int retval; get_online_cpus(); - read_lock(&tasklist_lock); + rcu_read_lock(); p = find_process_by_pid(pid); if (!p) { - read_unlock(&tasklist_lock); + rcu_read_unlock(); put_online_cpus(); return -ESRCH; } - /* - * It is not safe to call set_cpus_allowed with the - * tasklist_lock held. We will bump the task_struct's - * usage count and then drop tasklist_lock. - */ + /* Prevent p going away */ get_task_struct(p); - read_unlock(&tasklist_lock); + rcu_read_unlock(); if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) { retval = -ENOMEM; @@ -6664,7 +6660,7 @@ long sched_getaffinity(pid_t pid, struct int retval; get_online_cpus(); - read_lock(&tasklist_lock); + rcu_read_lock(); retval = -ESRCH; p = find_process_by_pid(pid); @@ -6680,7 +6676,7 @@ long sched_getaffinity(pid_t pid, struct task_rq_unlock(rq, &flags); out_unlock: - read_unlock(&tasklist_lock); + rcu_read_unlock(); put_online_cpus(); return retval;