Commit 103b0870 authored by Waiman Long's avatar Waiman Long Committed by Tejun Heo
Browse files

cgroup/cpuset: Fail if isolated and nohz_full don't leave any housekeeping 



Currently the user can set up isolated cpus via cpuset and nohz_full in
such a way that leaves no housekeeping CPU (i.e. no CPU that is neither
domain isolated nor nohz full). This can be a problem for other
subsystems (e.g. the timer wheel imgration).

Prevent this configuration by blocking any assignation that would cause
the union of domain isolated cpus and nohz_full to covers all CPUs.

[longman: Remove isolated_cpus_should_update() and rewrite the checking
 in update_prstate() and update_parent_effective_cpumask()]

Originally-by: default avatarGabriele Monaco <gmonaco@redhat.com>
Signed-off-by: default avatarWaiman Long <longman@redhat.com>
Reviewed-by: default avatarChen Ridong <chenridong@huawei.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 55939cf2

kernel/cgroup/cpuset.c

+73 −1
Original line number Diff line number Diff line
@@ -1393,6 +1393,45 @@ static bool partition_xcpus_del(int old_prs, struct cpuset *parent, 
	return isolcpus_updated;

}



/*

 * isolated_cpus_can_update - check for isolated & nohz_full conflicts

 * @add_cpus: cpu mask for cpus that are going to be isolated

 * @del_cpus: cpu mask for cpus that are no longer isolated, can be NULL

 * Return: false if there is conflict, true otherwise

 *

 * If nohz_full is enabled and we have isolated CPUs, their combination must

 * still leave housekeeping CPUs.

 *

 * TBD: Should consider merging this function into

 *      prstate_housekeeping_conflict().

 */

static bool isolated_cpus_can_update(struct cpumask *add_cpus,

				     struct cpumask *del_cpus)

{

	cpumask_var_t full_hk_cpus;

	int res = true;



	if (!housekeeping_enabled(HK_TYPE_KERNEL_NOISE))

		return true;



	if (del_cpus && cpumask_weight_and(del_cpus,

			housekeeping_cpumask(HK_TYPE_KERNEL_NOISE)))

		return true;



	if (!alloc_cpumask_var(&full_hk_cpus, GFP_KERNEL))

		return false;



	cpumask_and(full_hk_cpus, housekeeping_cpumask(HK_TYPE_KERNEL_NOISE),

		    housekeeping_cpumask(HK_TYPE_DOMAIN));

	cpumask_andnot(full_hk_cpus, full_hk_cpus, isolated_cpus);

	cpumask_and(full_hk_cpus, full_hk_cpus, cpu_active_mask);

	if (!cpumask_weight_andnot(full_hk_cpus, add_cpus))

		res = false;



	free_cpumask_var(full_hk_cpus);

	return res;

}



static void update_isolation_cpumasks(bool isolcpus_updated)

{

	int ret;
@@ -1551,6 +1590,9 @@ static int remote_partition_enable(struct cpuset *cs, int new_prs, 
	if (!cpumask_intersects(tmp->new_cpus, cpu_active_mask) ||

	    cpumask_subset(top_cpuset.effective_cpus, tmp->new_cpus))

		return PERR_INVCPUS;

	if ((new_prs == PRS_ISOLATED) &&

	    !isolated_cpus_can_update(tmp->new_cpus, NULL))

		return PERR_HKEEPING;



	spin_lock_irq(&callback_lock);

	isolcpus_updated = partition_xcpus_add(new_prs, NULL, tmp->new_cpus);
@@ -1650,6 +1692,9 @@ static void remote_cpus_update(struct cpuset *cs, struct cpumask *xcpus, 
		else if (cpumask_intersects(tmp->addmask, subpartitions_cpus) ||

			 cpumask_subset(top_cpuset.effective_cpus, tmp->addmask))

			cs->prs_err = PERR_NOCPUS;

		else if ((prs == PRS_ISOLATED) &&

			 !isolated_cpus_can_update(tmp->addmask, tmp->delmask))

			cs->prs_err = PERR_HKEEPING;

		if (cs->prs_err)

			goto invalidate;

	}
@@ -1750,6 +1795,7 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd, 
	int part_error = PERR_NONE;	/* Partition error? */

	int isolcpus_updated = 0;

	struct cpumask *xcpus = user_xcpus(cs);

	int parent_prs = parent->partition_root_state;

	bool nocpu;



	lockdep_assert_held(&cpuset_mutex);
@@ -1813,6 +1859,10 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd, 
		if (prstate_housekeeping_conflict(new_prs, xcpus))

			return PERR_HKEEPING;



		if ((new_prs == PRS_ISOLATED) && (new_prs != parent_prs) &&

		    !isolated_cpus_can_update(xcpus, NULL))

			return PERR_HKEEPING;



		if (tasks_nocpu_error(parent, cs, xcpus))

			return PERR_NOCPUS;
@@ -1866,6 +1916,7 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd, 
		 *

		 * For invalid partition:

		 *   delmask = newmask & parent->effective_xcpus

		 *   The partition may become valid soon.

		 */

		if (is_partition_invalid(cs)) {

			adding = false;
@@ -1880,6 +1931,23 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd, 
			deleting = cpumask_and(tmp->delmask, tmp->delmask,

					       parent->effective_xcpus);

		}



		/*

		 * TBD: Invalidate a currently valid child root partition may

		 * still break isolated_cpus_can_update() rule if parent is an

		 * isolated partition.

		 */

		if (is_partition_valid(cs) && (old_prs != parent_prs)) {

			if ((parent_prs == PRS_ROOT) &&

			    /* Adding to parent means removing isolated CPUs */

			    !isolated_cpus_can_update(tmp->delmask, tmp->addmask))

				part_error = PERR_HKEEPING;

			if ((parent_prs == PRS_ISOLATED) &&

			    /* Adding to parent means adding isolated CPUs */

			    !isolated_cpus_can_update(tmp->addmask, tmp->delmask))

				part_error = PERR_HKEEPING;

		}



		/*

		 * The new CPUs to be removed from parent's effective CPUs

		 * must be present.
@@ -2994,6 +3062,10 @@ static int update_prstate(struct cpuset *cs, int new_prs) 
		 * A change in load balance state only, no change in cpumasks.

		 * Need to update isolated_cpus.

		 */

		if ((new_prs == PRS_ISOLATED) &&

		    !isolated_cpus_can_update(cs->effective_xcpus, NULL))

			err = PERR_HKEEPING;

		else

			isolcpus_updated = true;

	} else {

		/*