Commit ff0ce721 authored by Waiman Long's avatar Waiman Long Committed by Tejun Heo
Browse files

cgroup/cpuset: Eliminate unncessary sched domains rebuilds in hotplug 



It was found that some hotplug operations may cause multiple
rebuild_sched_domains_locked() calls. Some of those intermediate calls
may use cpuset states not in the final correct form leading to incorrect
sched domain setting.

Fix this problem by using the existing force_rebuild flag to inhibit
immediate rebuild_sched_domains_locked() calls if set and only doing
one final call at the end. Also renaming the force_rebuild flag to
force_sd_rebuild to make its meaning for clear.

Signed-off-by: default avatarWaiman Long <longman@redhat.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 311a1bdc

kernel/cgroup/cpuset.c

+17 −16
Original line number Diff line number Diff line
@@ -232,6 +232,13 @@ static cpumask_var_t isolated_cpus; 
/* List of remote partition root children */

static struct list_head remote_children;



/*

 * A flag to force sched domain rebuild at the end of an operation while

 * inhibiting it in the intermediate stages when set. Currently it is only

 * set in hotplug code.

 */

static bool force_sd_rebuild;



/*

 * Partition root states:

 *
@@ -1475,7 +1482,7 @@ static void update_partition_sd_lb(struct cpuset *cs, int old_prs) 
			clear_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);

	}



	if (rebuild_domains)

	if (rebuild_domains && !force_sd_rebuild)

		rebuild_sched_domains_locked();

}
@@ -1833,7 +1840,7 @@ static void remote_partition_check(struct cpuset *cs, struct cpumask *newmask, 
			remote_partition_disable(child, tmp);

			disable_cnt++;

		}

	if (disable_cnt)

	if (disable_cnt && !force_sd_rebuild)

		rebuild_sched_domains_locked();

}
@@ -2442,7 +2449,8 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp, 
	}

	rcu_read_unlock();



	if (need_rebuild_sched_domains && !(flags & HIER_NO_SD_REBUILD))

	if (need_rebuild_sched_domains && !(flags & HIER_NO_SD_REBUILD) &&

	    !force_sd_rebuild)

		rebuild_sched_domains_locked();

}
@@ -3104,7 +3112,8 @@ static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs, 
	cs->flags = trialcs->flags;

	spin_unlock_irq(&callback_lock);



	if (!cpumask_empty(trialcs->cpus_allowed) && balance_flag_changed)

	if (!cpumask_empty(trialcs->cpus_allowed) && balance_flag_changed &&

	    !force_sd_rebuild)

		rebuild_sched_domains_locked();



	if (spread_flag_changed)
@@ -4501,11 +4510,9 @@ hotplug_update_tasks(struct cpuset *cs, 
		update_tasks_nodemask(cs);

}



static bool force_rebuild;



void cpuset_force_rebuild(void)

{

	force_rebuild = true;

	force_sd_rebuild = true;

}



/**
@@ -4653,15 +4660,9 @@ static void cpuset_handle_hotplug(void) 
		       !cpumask_empty(subpartitions_cpus);

	mems_updated = !nodes_equal(top_cpuset.effective_mems, new_mems);



	/*

	 * In the rare case that hotplug removes all the cpus in

	 * subpartitions_cpus, we assumed that cpus are updated.

	 */

	if (!cpus_updated && !cpumask_empty(subpartitions_cpus))

		cpus_updated = true;



	/* For v1, synchronize cpus_allowed to cpu_active_mask */

	if (cpus_updated) {

		cpuset_force_rebuild();

		spin_lock_irq(&callback_lock);

		if (!on_dfl)

			cpumask_copy(top_cpuset.cpus_allowed, &new_cpus);
@@ -4717,8 +4718,8 @@ static void cpuset_handle_hotplug(void) 
	}



	/* rebuild sched domains if cpus_allowed has changed */

	if (cpus_updated || force_rebuild) {

		force_rebuild = false;

	if (force_sd_rebuild) {

		force_sd_rebuild = false;

		rebuild_sched_domains_cpuslocked();

	}