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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: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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1 changed files with 19 additions and 0 deletions
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@ -185,6 +185,9 @@ static struct cfs_rq *init_cfs_rq_p[NR_CPUS];
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*/
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static DEFINE_MUTEX(task_group_mutex);
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/* doms_cur_mutex serializes access to doms_cur[] array */
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static DEFINE_MUTEX(doms_cur_mutex);
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/* Default task group.
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* Every task in system belong to this group at bootup.
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*/
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@ -234,11 +237,23 @@ static inline void unlock_task_group_list(void)
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mutex_unlock(&task_group_mutex);
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}
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static inline void lock_doms_cur(void)
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{
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mutex_lock(&doms_cur_mutex);
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}
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static inline void unlock_doms_cur(void)
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{
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mutex_unlock(&doms_cur_mutex);
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}
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#else
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static inline void set_task_cfs_rq(struct task_struct *p, unsigned int cpu) { }
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static inline void lock_task_group_list(void) { }
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static inline void unlock_task_group_list(void) { }
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static inline void lock_doms_cur(void) { }
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static inline void unlock_doms_cur(void) { }
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#endif /* CONFIG_FAIR_GROUP_SCHED */
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@ -6543,6 +6558,8 @@ void partition_sched_domains(int ndoms_new, cpumask_t *doms_new)
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{
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int i, j;
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lock_doms_cur();
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/* always unregister in case we don't destroy any domains */
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unregister_sched_domain_sysctl();
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@ -6583,6 +6600,8 @@ void partition_sched_domains(int ndoms_new, cpumask_t *doms_new)
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ndoms_cur = ndoms_new;
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register_sched_domain_sysctl();
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unlock_doms_cur();
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}
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#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
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