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sched: fix missing locking in sched_domains code 

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 use the already present doms_cur_mutex to protect these sections again.

Cc: Gautham R Shenoy <ego@in.ibm.com>
Cc: Paul Jackson <pj@sgi.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Heiko Carstens 2008-04-28 11:33:07 +02:00 committed by Ingo Molnar
parent 690229a091
commit 712555ee4f
1 changed files with 12 additions and 17 deletions
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29
kernel/sched.c
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@ -242,6 +242,12 @@ static void destroy_rt_bandwidth(struct rt_bandwidth *rt_b)
}
#endif
/*
* sched_domains_mutex serializes calls to arch_init_sched_domains,
* detach_destroy_domains and partition_sched_domains.
*/
static DEFINE_MUTEX(sched_domains_mutex);
#ifdef CONFIG_GROUP_SCHED
#include <linux/cgroup.h>
@ -308,9 +314,6 @@ static DEFINE_PER_CPU(struct rt_rq, init_rt_rq) ____cacheline_aligned_in_smp;
*/
static DEFINE_SPINLOCK(task_group_lock);
/* doms_cur_mutex serializes access to doms_cur[] array */
static DEFINE_MUTEX(doms_cur_mutex);
#ifdef CONFIG_FAIR_GROUP_SCHED
#ifdef CONFIG_USER_SCHED
# define INIT_TASK_GROUP_LOAD (2*NICE_0_LOAD)
@ -358,21 +361,9 @@ static inline void set_task_rq(struct task_struct *p, unsigned int cpu)
#endif
}
static inline void lock_doms_cur(void)
{
mutex_lock(&doms_cur_mutex);
}
static inline void unlock_doms_cur(void)
{
mutex_unlock(&doms_cur_mutex);
}
#else
static inline void set_task_rq(struct task_struct *p, unsigned int cpu) { }
static inline void lock_doms_cur(void) { }
static inline void unlock_doms_cur(void) { }
#endif /* CONFIG_GROUP_SCHED */
@ -7822,7 +7813,7 @@ void partition_sched_domains(int ndoms_new, cpumask_t *doms_new,
{
int i, j;
lock_doms_cur();
mutex_lock(&sched_domains_mutex);
/* always unregister in case we don't destroy any domains */
unregister_sched_domain_sysctl();
@ -7871,7 +7862,7 @@ match2:
register_sched_domain_sysctl();
unlock_doms_cur();
mutex_unlock(&sched_domains_mutex);
}
#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
@ -7880,8 +7871,10 @@ int arch_reinit_sched_domains(void)
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;
@ -7999,10 +7992,12 @@ 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);