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Commit fe8a45df authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull scheduler fixes from Ingo Molnar:
 "Four bugfixes and one performance fix"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/fair: Avoid integer overflow
  sched: Optimize task_sched_runtime()
  sched/numa: Cure update_numa_stats() vs. hotplug
  sched/numa: Fix NULL pointer dereference in task_numa_migrate()
  sched: Fix endless sync_sched/rcu() loop inside _cpu_down()
parents 5e30025a 85b088e9

kernel/cpu.c

+4 −1
Original line number Diff line number Diff line
@@ -306,7 +306,6 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen) 
				__func__, cpu);

		goto out_release;

	}

	smpboot_park_threads(cpu);



	/*

	 * By now we've cleared cpu_active_mask, wait for all preempt-disabled
@@ -315,12 +314,16 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen) 
	 *

	 * For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu() might

	 * not imply sync_sched(), so explicitly call both.

	 *

	 * Do sync before park smpboot threads to take care the rcu boost case.

	 */

#ifdef CONFIG_PREEMPT

	synchronize_sched();

#endif

	synchronize_rcu();



	smpboot_park_threads(cpu);



	/*

	 * So now all preempt/rcu users must observe !cpu_active().

	 */

kernel/sched/core.c

+14 −0
Original line number Diff line number Diff line
@@ -2253,6 +2253,20 @@ unsigned long long task_sched_runtime(struct task_struct *p) 
	struct rq *rq;

	u64 ns = 0;



#if defined(CONFIG_64BIT) && defined(CONFIG_SMP)

	/*

	 * 64-bit doesn't need locks to atomically read a 64bit value.

	 * So we have a optimization chance when the task's delta_exec is 0.

	 * Reading ->on_cpu is racy, but this is ok.

	 *

	 * If we race with it leaving cpu, we'll take a lock. So we're correct.

	 * If we race with it entering cpu, unaccounted time is 0. This is

	 * indistinguishable from the read occurring a few cycles earlier.

	 */

	if (!p->on_cpu)

		return p->se.sum_exec_runtime;

#endif



	rq = task_rq_lock(p, &flags);

	ns = p->se.sum_exec_runtime + do_task_delta_exec(p, rq);

	task_rq_unlock(rq, p, &flags);

kernel/sched/fair.c

+28 −3
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);
@@ -1201,9 +1214,21 @@ static int task_numa_migrate(struct task_struct *p) 
	 */

	rcu_read_lock();

	sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));

	if (sd)

		env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;

	rcu_read_unlock();



	/*

	 * Cpusets can break the scheduler domain tree into smaller

	 * balance domains, some of which do not cross NUMA boundaries.

	 * Tasks that are "trapped" in such domains cannot be migrated

	 * elsewhere, so there is no point in (re)trying.

	 */

	if (unlikely(!sd)) {

		p->numa_preferred_nid = cpu_to_node(task_cpu(p));

		return -EINVAL;

	}



	taskweight = task_weight(p, env.src_nid);

	groupweight = group_weight(p, env.src_nid);

	update_numa_stats(&env.src_stats, env.src_nid);
@@ -2153,7 +2178,7 @@ static inline void __update_tg_runnable_avg(struct sched_avg *sa, 
	long contrib;



	/* The fraction of a cpu used by this cfs_rq */

	contrib = div_u64(sa->runnable_avg_sum << NICE_0_SHIFT,

	contrib = div_u64((u64)sa->runnable_avg_sum << NICE_0_SHIFT,

			  sa->runnable_avg_period + 1);

	contrib -= cfs_rq->tg_runnable_contrib;