Commit 712555ee authored by Heiko Carstens's avatar Heiko Carstens Committed by Ingo Molnar
Browse files

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: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 690229a0

kernel/sched.c

+12 −17
Original line number Diff line number Diff line
@@ -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);

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