Messages in this thread Patch in this message | | | Date | Sun, 27 Apr 2008 23:12:24 +0200 | From | Heiko Carstens <> | Subject | [PATCH] sched: missing locking in sched_domains code |
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From: Heiko Carstens <heiko.carstens@de.ibm.com>
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 <ego@in.ibm.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Paul Jackson <pj@sgi.com> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> --- 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:
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