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Commit a1835615 authored by Srivatsa Vaddagiri's avatar Srivatsa Vaddagiri Committed by Ingo Molnar
Browse files

sched: introduce a mutex and corresponding API to serialize access to doms_curarray 



doms_cur[] array represents various scheduling domains which are
mutually exclusive. Currently cpusets code can modify this array (by
calling partition_sched_domains()) as a result of user modifying
sched_load_balance flag for various cpusets.

This patch introduces a mutex and corresponding API (only when
CONFIG_FAIR_GROUP_SCHED is defined) which allows a reader to safely read
the doms_cur[] array w/o worrying abt concurrent modifications to the
array.

The fair group scheduler code (introduced in next patch of this series)
makes use of this mutex to walk thr' doms_cur[] array while rebalancing
shares of task groups across cpus.

Signed-off-by: default avatarSrivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 58e2d4ca

kernel/sched.c

+19 −0
Original line number Diff line number Diff line
@@ -185,6 +185,9 @@ static struct cfs_rq *init_cfs_rq_p[NR_CPUS]; 
 */

static DEFINE_MUTEX(task_group_mutex);



/* doms_cur_mutex serializes access to doms_cur[] array */

static DEFINE_MUTEX(doms_cur_mutex);



/* Default task group.

 *	Every task in system belong to this group at bootup.

 */
@@ -234,11 +237,23 @@ static inline void unlock_task_group_list(void) 
	mutex_unlock(&task_group_mutex);

}



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_cfs_rq(struct task_struct *p, unsigned int cpu) { }

static inline void lock_task_group_list(void) { }

static inline void unlock_task_group_list(void) { }

static inline void lock_doms_cur(void) { }

static inline void unlock_doms_cur(void) { }



#endif	/* CONFIG_FAIR_GROUP_SCHED */
@@ -6543,6 +6558,8 @@ void partition_sched_domains(int ndoms_new, cpumask_t *doms_new) 
{

	int i, j;



	lock_doms_cur();



	/* always unregister in case we don't destroy any domains */

	unregister_sched_domain_sysctl();
@@ -6583,6 +6600,8 @@ match2: 
	ndoms_cur = ndoms_new;



	register_sched_domain_sysctl();



	unlock_doms_cur();

}



#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)