From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761305AbYD0VMi (ORCPT ); Sun, 27 Apr 2008 17:12:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751058AbYD0VM1 (ORCPT ); Sun, 27 Apr 2008 17:12:27 -0400 Received: from mtagate8.de.ibm.com ([195.212.29.157]:58438 "EHLO mtagate8.de.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751042AbYD0VM1 (ORCPT ); Sun, 27 Apr 2008 17:12:27 -0400 Date: Sun, 27 Apr 2008 23:12:24 +0200 From: Heiko Carstens To: Andrew Morton Cc: Gautham R Shenoy , Ingo Molnar , Paul Jackson , linux-kernel@vger.kernel.org Subject: [PATCH] sched: missing locking in sched_domains code Message-ID: <20080427211224.GA21830@osiris.boeblingen.de.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Heiko Carstens Concurrent calls to detach_destroy_domains and arch_init_sched_domains were prevented by the old scheduler subsystem cpu hotplug mutex. When this got converted to get_online_cpus() the locking got broken. Unlike before now several processes can concurrently enter the critical sections that were protected by the old lock. So add a new sched_domains_mutex which protects these sections again. Cc: Gautham R Shenoy Cc: Ingo Molnar Cc: Paul Jackson Signed-off-by: Heiko Carstens --- include/linux/sched.h | 2 ++ kernel/cpuset.c | 2 ++ kernel/sched.c | 11 +++++++++++ 3 files changed, 15 insertions(+) Index: linux-2.6/kernel/sched.c =================================================================== --- linux-2.6.orig/kernel/sched.c +++ linux-2.6/kernel/sched.c @@ -7807,14 +7807,23 @@ match2: unlock_doms_cur(); } +/* + * Protects against concurrent calls to detach_destroy_domains + * and arch_init_sched_domains. + */ +DEFINE_MUTEX(sched_domains_mutex); + #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT) int arch_reinit_sched_domains(void) { + static DEFINE_MUTEX(arch_reinit_sched_domains_mutex); int err; get_online_cpus(); + mutex_lock(&sched_domains_mutex); detach_destroy_domains(&cpu_online_map); err = arch_init_sched_domains(&cpu_online_map); + mutex_unlock(&sched_domains_mutex); put_online_cpus(); return err; @@ -7932,10 +7941,12 @@ void __init sched_init_smp(void) BUG_ON(sched_group_nodes_bycpu == NULL); #endif get_online_cpus(); + mutex_lock(&sched_domains_mutex); arch_init_sched_domains(&cpu_online_map); cpus_andnot(non_isolated_cpus, cpu_possible_map, cpu_isolated_map); if (cpus_empty(non_isolated_cpus)) cpu_set(smp_processor_id(), non_isolated_cpus); + mutex_unlock(&sched_domains_mutex); put_online_cpus(); /* XXX: Theoretical race here - CPU may be hotplugged now */ hotcpu_notifier(update_sched_domains, 0); Index: linux-2.6/include/linux/sched.h =================================================================== --- linux-2.6.orig/include/linux/sched.h +++ linux-2.6/include/linux/sched.h @@ -809,6 +809,8 @@ struct sched_domain { #endif }; +extern struct mutex sched_domains_mutex; + extern void partition_sched_domains(int ndoms_new, cpumask_t *doms_new, struct sched_domain_attr *dattr_new); extern int arch_reinit_sched_domains(void); Index: linux-2.6/kernel/cpuset.c =================================================================== --- linux-2.6.orig/kernel/cpuset.c +++ linux-2.6/kernel/cpuset.c @@ -684,7 +684,9 @@ restart: rebuild: /* Have scheduler rebuild sched domains */ get_online_cpus(); + mutex_lock(&sched_domains_mutex); partition_sched_domains(ndoms, doms, dattr); + mutex_unlock(&sched_domains_mutex); put_online_cpus(); done: