1 files changed, 166 insertions, 82 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 1d7f5941bcdc..a7af49b3a337 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -163,7 +163,10 @@ static inline int __task_prio(const struct task_struct *p)
 	if (p->sched_class == &stop_sched_class) /* trumps deadline */
 		return -2;
 
-	if (rt_prio(p->prio)) /* includes deadline */
+	if (p->dl_server)
+		return -1; /* deadline */
+
+	if (rt_or_dl_prio(p->prio))
 		return p->prio; /* [-1, 99] */
 
 	if (p->sched_class == &idle_sched_class)
@@ -192,8 +195,24 @@ static inline bool prio_less(const struct task_struct *a,
 	if (-pb < -pa)
 		return false;
 
-	if (pa == -1) /* dl_prio() doesn't work because of stop_class above */
-		return !dl_time_before(a->dl.deadline, b->dl.deadline);
+	if (pa == -1) { /* dl_prio() doesn't work because of stop_class above */
+		const struct sched_dl_entity *a_dl, *b_dl;
+
+		a_dl = &a->dl;
+		/*
+		 * Since,'a' and 'b' can be CFS tasks served by DL server,
+		 * __task_prio() can return -1 (for DL) even for those. In that
+		 * case, get to the dl_server's DL entity.
+		 */
+		if (a->dl_server)
+			a_dl = a->dl_server;
+
+		b_dl = &b->dl;
+		if (b->dl_server)
+			b_dl = b->dl_server;
+
+		return !dl_time_before(a_dl->deadline, b_dl->deadline);
+	}
 
 	if (pa == MAX_RT_PRIO + MAX_NICE)	/* fair */
 		return cfs_prio_less(a, b, in_fi);
@@ -240,6 +259,9 @@ static inline int rb_sched_core_cmp(const void *key, const struct rb_node *node)
 
 void sched_core_enqueue(struct rq *rq, struct task_struct *p)
 {
+	if (p->se.sched_delayed)
+		return;
+
 	rq->core->core_task_seq++;
 
 	if (!p->core_cookie)
@@ -250,6 +272,9 @@ void sched_core_enqueue(struct rq *rq, struct task_struct *p)
 
 void sched_core_dequeue(struct rq *rq, struct task_struct *p, int flags)
 {
+	if (p->se.sched_delayed)
+		return;
+
 	rq->core->core_task_seq++;
 
 	if (sched_core_enqueued(p)) {
@@ -1269,7 +1294,7 @@ bool sched_can_stop_tick(struct rq *rq)
 	 * dequeued by migrating while the constrained task continues to run.
 	 * E.g. going from 2->1 without going through pick_next_task().
 	 */
-	if (sched_feat(HZ_BW) && __need_bw_check(rq, rq->curr)) {
+	if (__need_bw_check(rq, rq->curr)) {
 		if (cfs_task_bw_constrained(rq->curr))
 			return false;
 	}
@@ -1672,6 +1697,9 @@ static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p)
 	if (unlikely(!p->sched_class->uclamp_enabled))
 		return;
 
+	if (p->se.sched_delayed)
+		return;
+
 	for_each_clamp_id(clamp_id)
 		uclamp_rq_inc_id(rq, p, clamp_id);
 
@@ -1696,6 +1724,9 @@ static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p)
 	if (unlikely(!p->sched_class->uclamp_enabled))
 		return;
 
+	if (p->se.sched_delayed)
+		return;
+
 	for_each_clamp_id(clamp_id)
 		uclamp_rq_dec_id(rq, p, clamp_id);
 }
@@ -1975,14 +2006,21 @@ void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
 		psi_enqueue(p, (flags & ENQUEUE_WAKEUP) && !(flags & ENQUEUE_MIGRATED));
 	}
 
-	uclamp_rq_inc(rq, p);
 	p->sched_class->enqueue_task(rq, p, flags);
+	/*
+	 * Must be after ->enqueue_task() because ENQUEUE_DELAYED can clear
+	 * ->sched_delayed.
+	 */
+	uclamp_rq_inc(rq, p);
 
 	if (sched_core_enabled(rq))
 		sched_core_enqueue(rq, p);
 }
 
-void dequeue_task(struct rq *rq, struct task_struct *p, int flags)
+/*
+ * Must only return false when DEQUEUE_SLEEP.
+ */
+inline bool dequeue_task(struct rq *rq, struct task_struct *p, int flags)
 {
 	if (sched_core_enabled(rq))
 		sched_core_dequeue(rq, p, flags);
@@ -1995,8 +2033,12 @@ void dequeue_task(struct rq *rq, struct task_struct *p, int flags)
 		psi_dequeue(p, flags & DEQUEUE_SLEEP);
 	}
 
+	/*
+	 * Must be before ->dequeue_task() because ->dequeue_task() can 'fail'
+	 * and mark the task ->sched_delayed.
+	 */
 	uclamp_rq_dec(rq, p);
-	p->sched_class->dequeue_task(rq, p, flags);
+	return p->sched_class->dequeue_task(rq, p, flags);
 }
 
 void activate_task(struct rq *rq, struct task_struct *p, int flags)
@@ -2014,12 +2056,25 @@ void activate_task(struct rq *rq, struct task_struct *p, int flags)
 
 void deactivate_task(struct rq *rq, struct task_struct *p, int flags)
 {
-	WRITE_ONCE(p->on_rq, (flags & DEQUEUE_SLEEP) ? 0 : TASK_ON_RQ_MIGRATING);
+	SCHED_WARN_ON(flags & DEQUEUE_SLEEP);
+
+	WRITE_ONCE(p->on_rq, TASK_ON_RQ_MIGRATING);
 	ASSERT_EXCLUSIVE_WRITER(p->on_rq);
 
+	/*
+	 * Code explicitly relies on TASK_ON_RQ_MIGRATING begin set *before*
+	 * dequeue_task() and cleared *after* enqueue_task().
+	 */
+
 	dequeue_task(rq, p, flags);
 }
 
+static void block_task(struct rq *rq, struct task_struct *p, int flags)
+{
+	if (dequeue_task(rq, p, DEQUEUE_SLEEP | flags))
+		__block_task(rq, p);
+}
+
 /**
  * task_curr - is this task currently executing on a CPU?
  * @p: the task in question.
@@ -2233,6 +2288,12 @@ void migrate_disable(void)
 	struct task_struct *p = current;
 
 	if (p->migration_disabled) {
+#ifdef CONFIG_DEBUG_PREEMPT
+		/*
+		 *Warn about overflow half-way through the range.
+		 */
+		WARN_ON_ONCE((s16)p->migration_disabled < 0);
+#endif
 		p->migration_disabled++;
 		return;
 	}
@@ -2251,14 +2312,20 @@ void migrate_enable(void)
 		.flags     = SCA_MIGRATE_ENABLE,
 	};
 
+#ifdef CONFIG_DEBUG_PREEMPT
+	/*
+	 * Check both overflow from migrate_disable() and superfluous
+	 * migrate_enable().
+	 */
+	if (WARN_ON_ONCE((s16)p->migration_disabled <= 0))
+		return;
+#endif
+
 	if (p->migration_disabled > 1) {
 		p->migration_disabled--;
 		return;
 	}
 
-	if (WARN_ON_ONCE(!p->migration_disabled))
-		return;
-
 	/*
 	 * Ensure stop_task runs either before or after this, and that
 	 * __set_cpus_allowed_ptr(SCA_MIGRATE_ENABLE) doesn't schedule().
@@ -3607,8 +3674,6 @@ ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags,
 		rq->idle_stamp = 0;
 	}
 #endif
-
-	p->dl_server = NULL;
 }
 
 /*
@@ -3644,12 +3709,14 @@ static int ttwu_runnable(struct task_struct *p, int wake_flags)
 
 	rq = __task_rq_lock(p, &rf);
 	if (task_on_rq_queued(p)) {
+		update_rq_clock(rq);
+		if (p->se.sched_delayed)
+			enqueue_task(rq, p, ENQUEUE_NOCLOCK | ENQUEUE_DELAYED);
 		if (!task_on_cpu(rq, p)) {
 			/*
 			 * When on_rq && !on_cpu the task is preempted, see if
 			 * it should preempt the task that is current now.
 			 */
-			update_rq_clock(rq);
 			wakeup_preempt(rq, p, wake_flags);
 		}
 		ttwu_do_wakeup(p);
@@ -4029,11 +4096,16 @@ int try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
 		 * case the whole 'p->on_rq && ttwu_runnable()' case below
 		 * without taking any locks.
 		 *
+		 * Specifically, given current runs ttwu() we must be before
+		 * schedule()'s block_task(), as such this must not observe
+		 * sched_delayed.
+		 *
 		 * In particular:
 		 *  - we rely on Program-Order guarantees for all the ordering,
 		 *  - we're serialized against set_special_state() by virtue of
 		 *    it disabling IRQs (this allows not taking ->pi_lock).
 		 */
+		SCHED_WARN_ON(p->se.sched_delayed);
 		if (!ttwu_state_match(p, state, &success))
 			goto out;
 
@@ -4322,9 +4394,11 @@ static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
 	p->se.nr_migrations		= 0;
 	p->se.vruntime			= 0;
 	p->se.vlag			= 0;
-	p->se.slice			= sysctl_sched_base_slice;
 	INIT_LIST_HEAD(&p->se.group_node);
 
+	/* A delayed task cannot be in clone(). */
+	SCHED_WARN_ON(p->se.sched_delayed);
+
 #ifdef CONFIG_FAIR_GROUP_SCHED
 	p->se.cfs_rq			= NULL;
 #endif
@@ -4572,6 +4646,8 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p)
 
 		p->prio = p->normal_prio = p->static_prio;
 		set_load_weight(p, false);
+		p->se.custom_slice = 0;
+		p->se.slice = sysctl_sched_base_slice;
 
 		/*
 		 * We don't need the reset flag anymore after the fork. It has
@@ -4686,7 +4762,7 @@ void wake_up_new_task(struct task_struct *p)
 	update_rq_clock(rq);
 	post_init_entity_util_avg(p);
 
-	activate_task(rq, p, ENQUEUE_NOCLOCK);
+	activate_task(rq, p, ENQUEUE_NOCLOCK | ENQUEUE_INITIAL);
 	trace_sched_wakeup_new(p);
 	wakeup_preempt(rq, p, WF_FORK);
 #ifdef CONFIG_SMP
@@ -5769,8 +5845,8 @@ static inline void schedule_debug(struct task_struct *prev, bool preempt)
 	schedstat_inc(this_rq()->sched_count);
 }
 
-static void put_prev_task_balance(struct rq *rq, struct task_struct *prev,
-				  struct rq_flags *rf)
+static void prev_balance(struct rq *rq, struct task_struct *prev,
+			 struct rq_flags *rf)
 {
 #ifdef CONFIG_SMP
 	const struct sched_class *class;
@@ -5787,8 +5863,6 @@ static void put_prev_task_balance(struct rq *rq, struct task_struct *prev,
 			break;
 	}
 #endif
-
-	put_prev_task(rq, prev);
 }
 
 /*
@@ -5800,6 +5874,8 @@ __pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
 	const struct sched_class *class;
 	struct task_struct *p;
 
+	rq->dl_server = NULL;
+
 	/*
 	 * Optimization: we know that if all tasks are in the fair class we can
 	 * call that function directly, but only if the @prev task wasn't of a
@@ -5815,35 +5891,28 @@ __pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
 
 		/* Assume the next prioritized class is idle_sched_class */
 		if (!p) {
-			put_prev_task(rq, prev);
-			p = pick_next_task_idle(rq);
+			p = pick_task_idle(rq);
+			put_prev_set_next_task(rq, prev, p);
 		}
 
-		/*
-		 * This is the fast path; it cannot be a DL server pick;
-		 * therefore even if @p == @prev, ->dl_server must be NULL.
-		 */
-		if (p->dl_server)
-			p->dl_server = NULL;
-
 		return p;
 	}
 
 restart:
-	put_prev_task_balance(rq, prev, rf);
-
-	/*
-	 * We've updated @prev and no longer need the server link, clear it.
-	 * Must be done before ->pick_next_task() because that can (re)set
-	 * ->dl_server.
-	 */
-	if (prev->dl_server)
-		prev->dl_server = NULL;
+	prev_balance(rq, prev, rf);
 
 	for_each_class(class) {
-		p = class->pick_next_task(rq);
-		if (p)
-			return p;
+		if (class->pick_next_task) {
+			p = class->pick_next_task(rq, prev);
+			if (p)
+				return p;
+		} else {
+			p = class->pick_task(rq);
+			if (p) {
+				put_prev_set_next_task(rq, prev, p);
+				return p;
+			}
+		}
 	}
 
 	BUG(); /* The idle class should always have a runnable task. */
@@ -5873,6 +5942,8 @@ static inline struct task_struct *pick_task(struct rq *rq)
 	const struct sched_class *class;
 	struct task_struct *p;
 
+	rq->dl_server = NULL;
+
 	for_each_class(class) {
 		p = class->pick_task(rq);
 		if (p)
@@ -5911,6 +5982,7 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
 		 * another cpu during offline.
 		 */
 		rq->core_pick = NULL;
+		rq->core_dl_server = NULL;
 		return __pick_next_task(rq, prev, rf);
 	}
 
@@ -5929,16 +6001,13 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
 		WRITE_ONCE(rq->core_sched_seq, rq->core->core_pick_seq);
 
 		next = rq->core_pick;
-		if (next != prev) {
-			put_prev_task(rq, prev);
-			set_next_task(rq, next);
-		}
-
+		rq->dl_server = rq->core_dl_server;
 		rq->core_pick = NULL;
-		goto out;
+		rq->core_dl_server = NULL;
+		goto out_set_next;
 	}
 
-	put_prev_task_balance(rq, prev, rf);
+	prev_balance(rq, prev, rf);
 
 	smt_mask = cpu_smt_mask(cpu);
 	need_sync = !!rq->core->core_cookie;
@@ -5979,6 +6048,7 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
 		next = pick_task(rq);
 		if (!next->core_cookie) {
 			rq->core_pick = NULL;
+			rq->core_dl_server = NULL;
 			/*
 			 * For robustness, update the min_vruntime_fi for
 			 * unconstrained picks as well.
@@ -6006,7 +6076,9 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
 		if (i != cpu && (rq_i != rq->core || !core_clock_updated))
 			update_rq_clock(rq_i);
 
-		p = rq_i->core_pick = pick_task(rq_i);
+		rq_i->core_pick = p = pick_task(rq_i);
+		rq_i->core_dl_server = rq_i->dl_server;
+
 		if (!max || prio_less(max, p, fi_before))
 			max = p;
 	}
@@ -6030,6 +6102,7 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
 		}
 
 		rq_i->core_pick = p;
+		rq_i->core_dl_server = NULL;
 
 		if (p == rq_i->idle) {
 			if (rq_i->nr_running) {
@@ -6090,6 +6163,7 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
 
 		if (i == cpu) {
 			rq_i->core_pick = NULL;
+			rq_i->core_dl_server = NULL;
 			continue;
 		}
 
@@ -6098,6 +6172,7 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
 
 		if (rq_i->curr == rq_i->core_pick) {
 			rq_i->core_pick = NULL;
+			rq_i->core_dl_server = NULL;
 			continue;
 		}
 
@@ -6105,8 +6180,7 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
 	}
 
 out_set_next:
-	set_next_task(rq, next);
-out:
+	put_prev_set_next_task(rq, prev, next);
 	if (rq->core->core_forceidle_count && next == rq->idle)
 		queue_core_balance(rq);
 
@@ -6342,19 +6416,12 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
  * Constants for the sched_mode argument of __schedule().
  *
  * The mode argument allows RT enabled kernels to differentiate a
- * preemption from blocking on an 'sleeping' spin/rwlock. Note that
- * SM_MASK_PREEMPT for !RT has all bits set, which allows the compiler to
- * optimize the AND operation out and just check for zero.
+ * preemption from blocking on an 'sleeping' spin/rwlock.
  */
-#define SM_NONE			0x0
-#define SM_PREEMPT		0x1
-#define SM_RTLOCK_WAIT		0x2
-
-#ifndef CONFIG_PREEMPT_RT
-# define SM_MASK_PREEMPT	(~0U)
-#else
-# define SM_MASK_PREEMPT	SM_PREEMPT
-#endif
+#define SM_IDLE			(-1)
+#define SM_NONE			0
+#define SM_PREEMPT		1
+#define SM_RTLOCK_WAIT		2
 
 /*
  * __schedule() is the main scheduler function.
@@ -6395,9 +6462,14 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
  *
  * WARNING: must be called with preemption disabled!
  */
-static void __sched notrace __schedule(unsigned int sched_mode)
+static void __sched notrace __schedule(int sched_mode)
 {
 	struct task_struct *prev, *next;
+	/*
+	 * On PREEMPT_RT kernel, SM_RTLOCK_WAIT is noted
+	 * as a preemption by schedule_debug() and RCU.
+	 */
+	bool preempt = sched_mode > SM_NONE;
 	unsigned long *switch_count;
 	unsigned long prev_state;
 	struct rq_flags rf;
@@ -6408,13 +6480,13 @@ static void __sched notrace __schedule(unsigned int sched_mode)
 	rq = cpu_rq(cpu);
 	prev = rq->curr;
 
-	schedule_debug(prev, !!sched_mode);
+	schedule_debug(prev, preempt);
 
 	if (sched_feat(HRTICK) || sched_feat(HRTICK_DL))
 		hrtick_clear(rq);
 
 	local_irq_disable();
-	rcu_note_context_switch(!!sched_mode);
+	rcu_note_context_switch(preempt);
 
 	/*
 	 * Make sure that signal_pending_state()->signal_pending() below
@@ -6443,22 +6515,32 @@ static void __sched notrace __schedule(unsigned int sched_mode)
 
 	switch_count = &prev->nivcsw;
 
+	/* Task state changes only considers SM_PREEMPT as preemption */
+	preempt = sched_mode == SM_PREEMPT;
+
 	/*
 	 * We must load prev->state once (task_struct::state is volatile), such
 	 * that we form a control dependency vs deactivate_task() below.
 	 */
 	prev_state = READ_ONCE(prev->__state);
-	if (!(sched_mode & SM_MASK_PREEMPT) && prev_state) {
+	if (sched_mode == SM_IDLE) {
+		if (!rq->nr_running) {
+			next = prev;
+			goto picked;
+		}
+	} else if (!preempt && prev_state) {
 		if (signal_pending_state(prev_state, prev)) {
 			WRITE_ONCE(prev->__state, TASK_RUNNING);
 		} else {
+			int flags = DEQUEUE_NOCLOCK;
+
 			prev->sched_contributes_to_load =
 				(prev_state & TASK_UNINTERRUPTIBLE) &&
 				!(prev_state & TASK_NOLOAD) &&
 				!(prev_state & TASK_FROZEN);
 
-			if (prev->sched_contributes_to_load)
-				rq->nr_uninterruptible++;
+			if (unlikely(is_special_task_state(prev_state)))
+				flags |= DEQUEUE_SPECIAL;
 
 			/*
 			 * __schedule()			ttwu()
@@ -6471,17 +6553,13 @@ static void __sched notrace __schedule(unsigned int sched_mode)
 			 *
 			 * After this, schedule() must not care about p->state any more.
 			 */
-			deactivate_task(rq, prev, DEQUEUE_SLEEP | DEQUEUE_NOCLOCK);
-
-			if (prev->in_iowait) {
-				atomic_inc(&rq->nr_iowait);
-				delayacct_blkio_start();
-			}
+			block_task(rq, prev, flags);
 		}
 		switch_count = &prev->nvcsw;
 	}
 
 	next = pick_next_task(rq, prev, &rf);
+picked:
 	clear_tsk_need_resched(prev);
 	clear_preempt_need_resched();
 #ifdef CONFIG_SCHED_DEBUG
@@ -6523,7 +6601,7 @@ static void __sched notrace __schedule(unsigned int sched_mode)
 		psi_account_irqtime(rq, prev, next);
 		psi_sched_switch(prev, next, !task_on_rq_queued(prev));
 
-		trace_sched_switch(sched_mode & SM_MASK_PREEMPT, prev, next, prev_state);
+		trace_sched_switch(preempt, prev, next, prev_state);
 
 		/* Also unlocks the rq: */
 		rq = context_switch(rq, prev, next, &rf);
@@ -6599,7 +6677,7 @@ static void sched_update_worker(struct task_struct *tsk)
 	}
 }
 
-static __always_inline void __schedule_loop(unsigned int sched_mode)
+static __always_inline void __schedule_loop(int sched_mode)
 {
 	do {
 		preempt_disable();
@@ -6644,7 +6722,7 @@ void __sched schedule_idle(void)
 	 */
 	WARN_ON_ONCE(current->__state);
 	do {
-		__schedule(SM_NONE);
+		__schedule(SM_IDLE);
 	} while (need_resched());
 }
 
@@ -8228,8 +8306,6 @@ void __init sched_init(void)
 #endif /* CONFIG_RT_GROUP_SCHED */
 	}
 
-	init_rt_bandwidth(&def_rt_bandwidth, global_rt_period(), global_rt_runtime());
-
 #ifdef CONFIG_SMP
 	init_defrootdomain();
 #endif
@@ -8284,8 +8360,13 @@ void __init sched_init(void)
 		init_tg_cfs_entry(&root_task_group, &rq->cfs, NULL, i, NULL);
 #endif /* CONFIG_FAIR_GROUP_SCHED */
 
-		rq->rt.rt_runtime = def_rt_bandwidth.rt_runtime;
 #ifdef CONFIG_RT_GROUP_SCHED
+		/*
+		 * This is required for init cpu because rt.c:__enable_runtime()
+		 * starts working after scheduler_running, which is not the case
+		 * yet.
+		 */
+		rq->rt.rt_runtime = global_rt_runtime();
 		init_tg_rt_entry(&root_task_group, &rq->rt, NULL, i, NULL);
 #endif
 #ifdef CONFIG_SMP
@@ -8317,10 +8398,12 @@ void __init sched_init(void)
 #endif /* CONFIG_SMP */
 		hrtick_rq_init(rq);
 		atomic_set(&rq->nr_iowait, 0);
+		fair_server_init(rq);
 
 #ifdef CONFIG_SCHED_CORE
 		rq->core = rq;
 		rq->core_pick = NULL;
+		rq->core_dl_server = NULL;
 		rq->core_enabled = 0;
 		rq->core_tree = RB_ROOT;
 		rq->core_forceidle_count = 0;
@@ -8333,6 +8416,7 @@ void __init sched_init(void)
 	}
 
 	set_load_weight(&init_task, false);
+	init_task.se.slice = sysctl_sched_base_slice,
 
 	/*
 	 * The boot idle thread does lazy MMU switching as well:
@@ -8548,7 +8632,7 @@ void normalize_rt_tasks(void)
 		schedstat_set(p->stats.sleep_start, 0);
 		schedstat_set(p->stats.block_start, 0);
 
-		if (!dl_task(p) && !rt_task(p)) {
+		if (!rt_or_dl_task(p)) {
 			/*
 			 * Renice negative nice level userspace
 			 * tasks back to 0: