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

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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: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Srivatsa Vaddagiri 2008-01-25 21:08:00 +01:00 committed by Ingo Molnar
parent 58e2d4ca58
commit a183561567
1 changed files with 19 additions and 0 deletions
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19
kernel/sched.c
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@ -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)