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

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Pull scheduler fixes from Ingo Molnar:
 "Three CPU hotplug related fixes and a debugging improvement"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/debug: Add debugfs knob for "sched_debug"
  sched/core: WARN() when migrating to an offline CPU
  sched/fair: Plug hole between hotplug and active_load_balance()
  sched/fair: Avoid newidle balance for !active CPUs
This commit is contained in:
Linus Torvalds 2017-09-13 12:22:32 -07:00
commit ec846ecd63
5 changed files with 25 additions and 3 deletions
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4
kernel/sched/core.c
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@ -1173,6 +1173,10 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&p->pi_lock) ||
lockdep_is_held(&task_rq(p)->lock)));
#endif
/*
* Clearly, migrating tasks to offline CPUs is a fairly daft thing.
*/
WARN_ON_ONCE(!cpu_online(new_cpu));
#endif
trace_sched_migrate_task(p, new_cpu);

5
kernel/sched/debug.c
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@ -181,11 +181,16 @@ static const struct file_operations sched_feat_fops = {
.release = single_release,
};
__read_mostly bool sched_debug_enabled;
static __init int sched_init_debug(void)
{
debugfs_create_file("sched_features", 0644, NULL, NULL,
&sched_feat_fops);
debugfs_create_bool("sched_debug", 0644, NULL,
&sched_debug_enabled);
return 0;
}
late_initcall(sched_init_debug);

13
kernel/sched/fair.c
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@ -8436,6 +8436,12 @@ static int idle_balance(struct rq *this_rq, struct rq_flags *rf)
*/
this_rq->idle_stamp = rq_clock(this_rq);
/*
* Do not pull tasks towards !active CPUs...
*/
if (!cpu_active(this_cpu))
return 0;
/*
* This is OK, because current is on_cpu, which avoids it being picked
* for load-balance and preemption/IRQs are still disabled avoiding
@ -8543,6 +8549,13 @@ static int active_load_balance_cpu_stop(void *data)
struct rq_flags rf;
rq_lock_irq(busiest_rq, &rf);
/*
* Between queueing the stop-work and running it is a hole in which
* CPUs can become inactive. We should not move tasks from or to
* inactive CPUs.
*/
if (!cpu_active(busiest_cpu) || !cpu_active(target_cpu))
goto out_unlock;
/* make sure the requested cpu hasn't gone down in the meantime */
if (unlikely(busiest_cpu != smp_processor_id() ||

2
kernel/sched/sched.h
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@ -1951,6 +1951,8 @@ extern struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq);
extern struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq);
#ifdef CONFIG_SCHED_DEBUG
extern bool sched_debug_enabled;
extern void print_cfs_stats(struct seq_file *m, int cpu);
extern void print_rt_stats(struct seq_file *m, int cpu);
extern void print_dl_stats(struct seq_file *m, int cpu);

4
kernel/sched/topology.c
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@ -14,11 +14,9 @@ cpumask_var_t sched_domains_tmpmask2;
#ifdef CONFIG_SCHED_DEBUG
static __read_mostly int sched_debug_enabled;
static int __init sched_debug_setup(char *str)
{
sched_debug_enabled = 1;
sched_debug_enabled = true;
return 0;
}