Commit-ID: 5eca82a9ac2c961cfbd26a4b6f43e6e3747a71dd Gitweb: http://git.kernel.org/tip/5eca82a9ac2c961cfbd26a4b6f43e6e3747a71dd Author: Peter Zijlstra <pet...@infradead.org> AuthorDate: Wed, 6 Nov 2013 18:47:57 +0100 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Wed, 13 Nov 2013 13:33:52 +0100
sched/numa: Cure update_numa_stats() vs. hotplug 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 <pra...@redhat.com> Signed-off-by: Peter Zijlstra <pet...@infradead.org> Cc: Mel Gorman <mgor...@suse.de> Link: http://lkml.kernel.org/n/tip-orja0qylcvyhxfsuebcyl...@git.kernel.org Signed-off-by: Ingo Molnar <mi...@kernel.org> --- kernel/sched/fair.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index c11e36f..201be78 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -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); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
