sched: introduce a mutex and corresponding API to serialize access to doms_curarray (a1835615) · Commits · 戴 / test

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>

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)

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