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

Pull scheduler updates from Ingo Molnar:
 "The main scheduler changes in this cycle were:

   - various sched/deadline fixes and enhancements

   - rescheduling latency fixes/cleanups

   - rework the rq->clock code to be more consistent and more robust.

   - minor micro-optimizations

   - ->avg.decay_count fixes

   - add a stack overflow check to might_sleep()

   - idle-poll handler fix, possibly resulting in power savings

   - misc smaller updates and fixes"

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/Documentation: Remove unneeded word
  sched/wait: Introduce wait_on_bit_timeout()
  sched: Pull resched loop to __schedule() callers
  sched/deadline: Remove cpu_active_mask from cpudl_find()
  sched: Fix hrtick_start() on UP
  sched/deadline: Avoid pointless __setscheduler()
  sched/deadline: Fix stale yield state
  sched/deadline: Fix hrtick for a non-leftmost task
  sched/deadline: Modify cpudl::free_cpus to reflect rd->online
  sched/idle: Add missing checks to the exit condition of cpu_idle_poll()
  sched: Fix missing preemption opportunity
  sched/rt: Reduce rq lock contention by eliminating locking of non-feasible target
  sched/debug: Print rq->clock_task
  sched/core: Rework rq->clock update skips
  sched/core: Validate rq_clock*() serialization
  sched/core: Remove check of p->sched_class
  sched/fair: Fix sched_entity::avg::decay_count initialization
  sched/debug: Fix potential call to __ffs(0) in sched_show_task()
  sched/debug: Check for stack overflow in ___might_sleep()
  sched/fair: Fix the dealing with decay_count in __synchronize_entity_decay()

1 files changed, 69 insertions, 38 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 1612578a5b7a..1f37fe7f77a4 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -119,7 +119,9 @@ void update_rq_clock(struct rq *rq)
 {
 	s64 delta;
 
-	if (rq->skip_clock_update > 0)
+	lockdep_assert_held(&rq->lock);
+
+	if (rq->clock_skip_update & RQCF_ACT_SKIP)
 		return;
 
 	delta = sched_clock_cpu(cpu_of(rq)) - rq->clock;
@@ -490,6 +492,11 @@ static __init void init_hrtick(void)
  */
 void hrtick_start(struct rq *rq, u64 delay)
 {
+	/*
+	 * Don't schedule slices shorter than 10000ns, that just
+	 * doesn't make sense. Rely on vruntime for fairness.
+	 */
+	delay = max_t(u64, delay, 10000LL);
 	__hrtimer_start_range_ns(&rq->hrtick_timer, ns_to_ktime(delay), 0,
 			HRTIMER_MODE_REL_PINNED, 0);
 }
@@ -1046,7 +1053,7 @@ void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
 	 * this case, we can save a useless back to back clock update.
 	 */
 	if (task_on_rq_queued(rq->curr) && test_tsk_need_resched(rq->curr))
-		rq->skip_clock_update = 1;
+		rq_clock_skip_update(rq, true);
 }
 
 #ifdef CONFIG_SMP
@@ -1836,6 +1843,9 @@ static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
 	p->se.prev_sum_exec_runtime	= 0;
 	p->se.nr_migrations		= 0;
 	p->se.vruntime			= 0;
+#ifdef CONFIG_SMP
+	p->se.avg.decay_count		= 0;
+#endif
 	INIT_LIST_HEAD(&p->se.group_node);
 
 #ifdef CONFIG_SCHEDSTATS
@@ -2755,6 +2765,10 @@ again:
  *          - explicit schedule() call
  *          - return from syscall or exception to user-space
  *          - return from interrupt-handler to user-space
+ *
+ * WARNING: all callers must re-check need_resched() afterward and reschedule
+ * accordingly in case an event triggered the need for rescheduling (such as
+ * an interrupt waking up a task) while preemption was disabled in __schedule().
  */
 static void __sched __schedule(void)
 {
@@ -2763,7 +2777,6 @@ static void __sched __schedule(void)
 	struct rq *rq;
 	int cpu;
 
-need_resched:
 	preempt_disable();
 	cpu = smp_processor_id();
 	rq = cpu_rq(cpu);
@@ -2783,6 +2796,8 @@ need_resched:
 	smp_mb__before_spinlock();
 	raw_spin_lock_irq(&rq->lock);
 
+	rq->clock_skip_update <<= 1; /* promote REQ to ACT */
+
 	switch_count = &prev->nivcsw;
 	if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {
 		if (unlikely(signal_pending_state(prev->state, prev))) {
@@ -2807,13 +2822,13 @@ need_resched:
 		switch_count = &prev->nvcsw;
 	}
 
-	if (task_on_rq_queued(prev) || rq->skip_clock_update < 0)
+	if (task_on_rq_queued(prev))
 		update_rq_clock(rq);
 
 	next = pick_next_task(rq, prev);
 	clear_tsk_need_resched(prev);
 	clear_preempt_need_resched();
-	rq->skip_clock_update = 0;
+	rq->clock_skip_update = 0;
 
 	if (likely(prev != next)) {
 		rq->nr_switches++;
@@ -2828,8 +2843,6 @@ need_resched:
 	post_schedule(rq);
 
 	sched_preempt_enable_no_resched();
-	if (need_resched())
-		goto need_resched;
 }
 
 static inline void sched_submit_work(struct task_struct *tsk)
@@ -2849,7 +2862,9 @@ asmlinkage __visible void __sched schedule(void)
 	struct task_struct *tsk = current;
 
 	sched_submit_work(tsk);
-	__schedule();
+	do {
+		__schedule();
+	} while (need_resched());
 }
 EXPORT_SYMBOL(schedule);
 
@@ -2884,6 +2899,21 @@ void __sched schedule_preempt_disabled(void)
 	preempt_disable();
 }
 
+static void preempt_schedule_common(void)
+{
+	do {
+		__preempt_count_add(PREEMPT_ACTIVE);
+		__schedule();
+		__preempt_count_sub(PREEMPT_ACTIVE);
+
+		/*
+		 * Check again in case we missed a preemption opportunity
+		 * between schedule and now.
+		 */
+		barrier();
+	} while (need_resched());
+}
+
 #ifdef CONFIG_PREEMPT
 /*
  * this is the entry point to schedule() from in-kernel preemption
@@ -2899,17 +2929,7 @@ asmlinkage __visible void __sched notrace preempt_schedule(void)
 	if (likely(!preemptible()))
 		return;
 
-	do {
-		__preempt_count_add(PREEMPT_ACTIVE);
-		__schedule();
-		__preempt_count_sub(PREEMPT_ACTIVE);
-
-		/*
-		 * Check again in case we missed a preemption opportunity
-		 * between schedule and now.
-		 */
-		barrier();
-	} while (need_resched());
+	preempt_schedule_common();
 }
 NOKPROBE_SYMBOL(preempt_schedule);
 EXPORT_SYMBOL(preempt_schedule);
@@ -3405,6 +3425,20 @@ static bool check_same_owner(struct task_struct *p)
 	return match;
 }
 
+static bool dl_param_changed(struct task_struct *p,
+		const struct sched_attr *attr)
+{
+	struct sched_dl_entity *dl_se = &p->dl;
+
+	if (dl_se->dl_runtime != attr->sched_runtime ||
+		dl_se->dl_deadline != attr->sched_deadline ||
+		dl_se->dl_period != attr->sched_period ||
+		dl_se->flags != attr->sched_flags)
+		return true;
+
+	return false;
+}
+
 static int __sched_setscheduler(struct task_struct *p,
 				const struct sched_attr *attr,
 				bool user)
@@ -3533,7 +3567,7 @@ recheck:
 			goto change;
 		if (rt_policy(policy) && attr->sched_priority != p->rt_priority)
 			goto change;
-		if (dl_policy(policy))
+		if (dl_policy(policy) && dl_param_changed(p, attr))
 			goto change;
 
 		p->sched_reset_on_fork = reset_on_fork;
@@ -4225,17 +4259,10 @@ SYSCALL_DEFINE0(sched_yield)
 	return 0;
 }
 
-static void __cond_resched(void)
-{
-	__preempt_count_add(PREEMPT_ACTIVE);
-	__schedule();
-	__preempt_count_sub(PREEMPT_ACTIVE);
-}
-
 int __sched _cond_resched(void)
 {
 	if (should_resched()) {
-		__cond_resched();
+		preempt_schedule_common();
 		return 1;
 	}
 	return 0;
@@ -4260,7 +4287,7 @@ int __cond_resched_lock(spinlock_t *lock)
 	if (spin_needbreak(lock) || resched) {
 		spin_unlock(lock);
 		if (resched)
-			__cond_resched();
+			preempt_schedule_common();
 		else
 			cpu_relax();
 		ret = 1;
@@ -4276,7 +4303,7 @@ int __sched __cond_resched_softirq(void)
 
 	if (should_resched()) {
 		local_bh_enable();
-		__cond_resched();
+		preempt_schedule_common();
 		local_bh_disable();
 		return 1;
 	}
@@ -4531,9 +4558,10 @@ void sched_show_task(struct task_struct *p)
 {
 	unsigned long free = 0;
 	int ppid;
-	unsigned state;
+	unsigned long state = p->state;
 
-	state = p->state ? __ffs(p->state) + 1 : 0;
+	if (state)
+		state = __ffs(state) + 1;
 	printk(KERN_INFO "%-15.15s %c", p->comm,
 		state < sizeof(stat_nam) - 1 ? stat_nam[state] : '?');
 #if BITS_PER_LONG == 32
@@ -4766,7 +4794,7 @@ static struct rq *move_queued_task(struct task_struct *p, int new_cpu)
 
 void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
 {
-	if (p->sched_class && p->sched_class->set_cpus_allowed)
+	if (p->sched_class->set_cpus_allowed)
 		p->sched_class->set_cpus_allowed(p, new_mask);
 
 	cpumask_copy(&p->cpus_allowed, new_mask);
@@ -7276,6 +7304,11 @@ void __init sched_init(void)
 	enter_lazy_tlb(&init_mm, current);
 
 	/*
+	 * During early bootup we pretend to be a normal task:
+	 */
+	current->sched_class = &fair_sched_class;
+
+	/*
 	 * Make us the idle thread. Technically, schedule() should not be
 	 * called from this thread, however somewhere below it might be,
 	 * but because we are the idle thread, we just pick up running again
@@ -7285,11 +7318,6 @@ void __init sched_init(void)
 
 	calc_load_update = jiffies + LOAD_FREQ;
 
-	/*
-	 * During early bootup we pretend to be a normal task:
-	 */
-	current->sched_class = &fair_sched_class;
-
 #ifdef CONFIG_SMP
 	zalloc_cpumask_var(&sched_domains_tmpmask, GFP_NOWAIT);
 	/* May be allocated at isolcpus cmdline parse time */
@@ -7350,6 +7378,9 @@ void ___might_sleep(const char *file, int line, int preempt_offset)
 			in_atomic(), irqs_disabled(),
 			current->pid, current->comm);
 
+	if (task_stack_end_corrupted(current))
+		printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
+
 	debug_show_held_locks(current);
 	if (irqs_disabled())
 		print_irqtrace_events(current);