sched/numa: Cure update_numa_stats() vs. hotplug (5eca82a9) · Commits · 戴 / test

Because we're completely unserialized against hotplug its well possible to try and generate numa stats for an offlined node. Bail out early (and avoid a /0) in this case. The resulting stats are all 0 which should result in an undesirable balance target -- not to mention that actually trying to migrate to an offline CPU will fail. Reported-by:

Prarit Bhargava <prarit@redhat.com> Signed-off-by:

Peter Zijlstra <peterz@infradead.org> Cc: Mel Gorman <mgorman@suse.de> Link: http://lkml.kernel.org/n/tip-orja0qylcvyhxfsuebcyL5sI@git.kernel.org Signed-off-by:

Ingo Molnar <mingo@kernel.org>

kernel/sched/fair.c

+14 −1

Original line number	Diff line number	Diff line
		@@ -1000,7 +1000,7 @@ struct numa_stats {
		*/
		static void update_numa_stats(struct numa_stats *ns, int nid)
		{
		int cpu;
		int cpu, cpus = 0;

		memset(ns, 0, sizeof(*ns));
		for_each_cpu(cpu, cpumask_of_node(nid)) {
		@@ -1009,8 +1009,21 @@ static void update_numa_stats(struct numa_stats *ns, int nid)
		ns->nr_running += rq->nr_running;
		ns->load += weighted_cpuload(cpu);
		ns->power += power_of(cpu);

		cpus++;
		}

		/*
		* If we raced with hotplug and there are no CPUs left in our mask
		* the @ns structure is NULL'ed and task_numa_compare() will
		* not find this node attractive.
		*
		* We'll either bail at !has_capacity, or we'll detect a huge imbalance
		* and bail there.
		*/
		if (!cpus)
		return;

		ns->load = (ns->load * SCHED_POWER_SCALE) / ns->power;
		ns->capacity = DIV_ROUND_CLOSEST(ns->power, SCHED_POWER_SCALE);
		ns->has_capacity = (ns->nr_running < ns->capacity);

Admin message