1// SPDX-License-Identifier: GPL-2.0
 
  2/*
  3 * stop-task scheduling class.
  4 *
  5 * The stop task is the highest priority task in the system, it preempts
  6 * everything and will be preempted by nothing.
  7 *
  8 * See kernel/stop_machine.c
  9 */
 10#include "sched.h"
 11
 12#ifdef CONFIG_SMP
 13static int
 14select_task_rq_stop(struct task_struct *p, int cpu, int sd_flag, int flags)
 15{
 16	return task_cpu(p); /* stop tasks as never migrate */
 17}
 18
 19static int
 20balance_stop(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
 21{
 22	return sched_stop_runnable(rq);
 23}
 24#endif /* CONFIG_SMP */
 25
 26static void
 27check_preempt_curr_stop(struct rq *rq, struct task_struct *p, int flags)
 28{
 29	/* we're never preempted */
 30}
 31
 32static void set_next_task_stop(struct rq *rq, struct task_struct *stop)
 33{
 34	stop->se.exec_start = rq_clock_task(rq);
 35}
 36
 37static struct task_struct *
 38pick_next_task_stop(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
 39{
 40	WARN_ON_ONCE(prev || rf);
 41
 42	if (!sched_stop_runnable(rq))
 43		return NULL;
 44
 45	set_next_task_stop(rq, rq->stop);
 46	return rq->stop;
 
 
 
 47}
 48
 49static void
 50enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags)
 51{
 52	add_nr_running(rq, 1);
 53}
 54
 55static void
 56dequeue_task_stop(struct rq *rq, struct task_struct *p, int flags)
 57{
 58	sub_nr_running(rq, 1);
 59}
 60
 61static void yield_task_stop(struct rq *rq)
 62{
 63	BUG(); /* the stop task should never yield, its pointless. */
 64}
 65
 66static void put_prev_task_stop(struct rq *rq, struct task_struct *prev)
 67{
 68	struct task_struct *curr = rq->curr;
 69	u64 delta_exec;
 70
 71	delta_exec = rq_clock_task(rq) - curr->se.exec_start;
 72	if (unlikely((s64)delta_exec < 0))
 73		delta_exec = 0;
 74
 75	schedstat_set(curr->se.statistics.exec_max,
 76			max(curr->se.statistics.exec_max, delta_exec));
 77
 78	curr->se.sum_exec_runtime += delta_exec;
 79	account_group_exec_runtime(curr, delta_exec);
 80
 81	curr->se.exec_start = rq_clock_task(rq);
 82	cgroup_account_cputime(curr, delta_exec);
 83}
 84
 85/*
 86 * scheduler tick hitting a task of our scheduling class.
 87 *
 88 * NOTE: This function can be called remotely by the tick offload that
 89 * goes along full dynticks. Therefore no local assumption can be made
 90 * and everything must be accessed through the @rq and @curr passed in
 91 * parameters.
 92 */
 93static void task_tick_stop(struct rq *rq, struct task_struct *curr, int queued)
 94{
 95}
 96
 
 
 
 
 
 
 
 97static void switched_to_stop(struct rq *rq, struct task_struct *p)
 98{
 99	BUG(); /* its impossible to change to this class */
100}
101
102static void
103prio_changed_stop(struct rq *rq, struct task_struct *p, int oldprio)
104{
105	BUG(); /* how!?, what priority? */
106}
107
108static unsigned int
109get_rr_interval_stop(struct rq *rq, struct task_struct *task)
110{
111	return 0;
112}
113
114static void update_curr_stop(struct rq *rq)
115{
116}
117
118/*
119 * Simple, special scheduling class for the per-CPU stop tasks:
120 */
121const struct sched_class stop_sched_class = {
122	.next			= &dl_sched_class,
123
124	.enqueue_task		= enqueue_task_stop,
125	.dequeue_task		= dequeue_task_stop,
126	.yield_task		= yield_task_stop,
127
128	.check_preempt_curr	= check_preempt_curr_stop,
129
130	.pick_next_task		= pick_next_task_stop,
131	.put_prev_task		= put_prev_task_stop,
132	.set_next_task          = set_next_task_stop,
133
134#ifdef CONFIG_SMP
135	.balance		= balance_stop,
136	.select_task_rq		= select_task_rq_stop,
137	.set_cpus_allowed	= set_cpus_allowed_common,
138#endif
139
 
140	.task_tick		= task_tick_stop,
141
142	.get_rr_interval	= get_rr_interval_stop,
143
144	.prio_changed		= prio_changed_stop,
145	.switched_to		= switched_to_stop,
146	.update_curr		= update_curr_stop,
147};

  1#include "sched.h"
  2
  3/*
  4 * stop-task scheduling class.
  5 *
  6 * The stop task is the highest priority task in the system, it preempts
  7 * everything and will be preempted by nothing.
  8 *
  9 * See kernel/stop_machine.c
 10 */
 
 11
 12#ifdef CONFIG_SMP
 13static int
 14select_task_rq_stop(struct task_struct *p, int cpu, int sd_flag, int flags)
 15{
 16	return task_cpu(p); /* stop tasks as never migrate */
 17}
 
 
 
 
 
 
 18#endif /* CONFIG_SMP */
 19
 20static void
 21check_preempt_curr_stop(struct rq *rq, struct task_struct *p, int flags)
 22{
 23	/* we're never preempted */
 24}
 25
 
 
 
 
 
 26static struct task_struct *
 27pick_next_task_stop(struct rq *rq, struct task_struct *prev)
 28{
 29	struct task_struct *stop = rq->stop;
 30
 31	if (!stop || !stop->on_rq)
 32		return NULL;
 33
 34	put_prev_task(rq, prev);
 35
 36	stop->se.exec_start = rq_clock_task(rq);
 37
 38	return stop;
 39}
 40
 41static void
 42enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags)
 43{
 44	inc_nr_running(rq);
 45}
 46
 47static void
 48dequeue_task_stop(struct rq *rq, struct task_struct *p, int flags)
 49{
 50	dec_nr_running(rq);
 51}
 52
 53static void yield_task_stop(struct rq *rq)
 54{
 55	BUG(); /* the stop task should never yield, its pointless. */
 56}
 57
 58static void put_prev_task_stop(struct rq *rq, struct task_struct *prev)
 59{
 60	struct task_struct *curr = rq->curr;
 61	u64 delta_exec;
 62
 63	delta_exec = rq_clock_task(rq) - curr->se.exec_start;
 64	if (unlikely((s64)delta_exec < 0))
 65		delta_exec = 0;
 66
 67	schedstat_set(curr->se.statistics.exec_max,
 68			max(curr->se.statistics.exec_max, delta_exec));
 69
 70	curr->se.sum_exec_runtime += delta_exec;
 71	account_group_exec_runtime(curr, delta_exec);
 72
 73	curr->se.exec_start = rq_clock_task(rq);
 74	cpuacct_charge(curr, delta_exec);
 75}
 76
 
 
 
 
 
 
 
 
 77static void task_tick_stop(struct rq *rq, struct task_struct *curr, int queued)
 78{
 79}
 80
 81static void set_curr_task_stop(struct rq *rq)
 82{
 83	struct task_struct *stop = rq->stop;
 84
 85	stop->se.exec_start = rq_clock_task(rq);
 86}
 87
 88static void switched_to_stop(struct rq *rq, struct task_struct *p)
 89{
 90	BUG(); /* its impossible to change to this class */
 91}
 92
 93static void
 94prio_changed_stop(struct rq *rq, struct task_struct *p, int oldprio)
 95{
 96	BUG(); /* how!?, what priority? */
 97}
 98
 99static unsigned int
100get_rr_interval_stop(struct rq *rq, struct task_struct *task)
101{
102	return 0;
103}
104
 
 
 
 
105/*
106 * Simple, special scheduling class for the per-CPU stop tasks:
107 */
108const struct sched_class stop_sched_class = {
109	.next			= &dl_sched_class,
110
111	.enqueue_task		= enqueue_task_stop,
112	.dequeue_task		= dequeue_task_stop,
113	.yield_task		= yield_task_stop,
114
115	.check_preempt_curr	= check_preempt_curr_stop,
116
117	.pick_next_task		= pick_next_task_stop,
118	.put_prev_task		= put_prev_task_stop,
 
119
120#ifdef CONFIG_SMP
 
121	.select_task_rq		= select_task_rq_stop,
 
122#endif
123
124	.set_curr_task          = set_curr_task_stop,
125	.task_tick		= task_tick_stop,
126
127	.get_rr_interval	= get_rr_interval_stop,
128
129	.prio_changed		= prio_changed_stop,
130	.switched_to		= switched_to_stop,
 
131};