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#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, struct rq_flags *rf)
 28{
 29	struct task_struct *stop = rq->stop;
 
 30
 31	if (!stop || !task_on_rq_queued(stop))
 
 
 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	add_nr_running(rq, 1);
 45}
 46
 47static void
 48dequeue_task_stop(struct rq *rq, struct task_struct *p, int flags)
 49{
 50	sub_nr_running(rq, 1);
 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	cgroup_account_cputime(curr, delta_exec);
 75}
 76
 77/*
 78 * scheduler tick hitting a task of our scheduling class.
 79 *
 80 * NOTE: This function can be called remotely by the tick offload that
 81 * goes along full dynticks. Therefore no local assumption can be made
 82 * and everything must be accessed through the @rq and @curr passed in
 83 * parameters.
 84 */
 85static void task_tick_stop(struct rq *rq, struct task_struct *curr, int queued)
 86{
 87}
 88
 89static void set_curr_task_stop(struct rq *rq)
 90{
 91	struct task_struct *stop = rq->stop;
 92
 93	stop->se.exec_start = rq_clock_task(rq);
 94}
 95
 96static void switched_to_stop(struct rq *rq, struct task_struct *p)
 97{
 98	BUG(); /* its impossible to change to this class */
 99}
100
101static void
102prio_changed_stop(struct rq *rq, struct task_struct *p, int oldprio)
103{
104	BUG(); /* how!?, what priority? */
105}
106
107static unsigned int
108get_rr_interval_stop(struct rq *rq, struct task_struct *task)
109{
110	return 0;
111}
112
113static void update_curr_stop(struct rq *rq)
114{
115}
116
117/*
118 * Simple, special scheduling class for the per-CPU stop tasks:
119 */
120const struct sched_class stop_sched_class = {
121	.next			= &dl_sched_class,
122
123	.enqueue_task		= enqueue_task_stop,
124	.dequeue_task		= dequeue_task_stop,
125	.yield_task		= yield_task_stop,
126
127	.check_preempt_curr	= check_preempt_curr_stop,
128
129	.pick_next_task		= pick_next_task_stop,
130	.put_prev_task		= put_prev_task_stop,
 
131
132#ifdef CONFIG_SMP
 
133	.select_task_rq		= select_task_rq_stop,
134	.set_cpus_allowed	= set_cpus_allowed_common,
135#endif
136
137	.set_curr_task          = set_curr_task_stop,
138	.task_tick		= task_tick_stop,
139
140	.get_rr_interval	= get_rr_interval_stop,
141
142	.prio_changed		= prio_changed_stop,
143	.switched_to		= switched_to_stop,
144	.update_curr		= update_curr_stop,
145};

  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, bool first)
 
 33{
 34	stop->se.exec_start = rq_clock_task(rq);
 35}
 36
 37static struct task_struct *pick_next_task_stop(struct rq *rq)
 38{
 39	if (!sched_stop_runnable(rq))
 40		return NULL;
 41
 42	set_next_task_stop(rq, rq->stop, true);
 43	return rq->stop;
 
 
 
 44}
 45
 46static void
 47enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags)
 48{
 49	add_nr_running(rq, 1);
 50}
 51
 52static void
 53dequeue_task_stop(struct rq *rq, struct task_struct *p, int flags)
 54{
 55	sub_nr_running(rq, 1);
 56}
 57
 58static void yield_task_stop(struct rq *rq)
 59{
 60	BUG(); /* the stop task should never yield, its pointless. */
 61}
 62
 63static void put_prev_task_stop(struct rq *rq, struct task_struct *prev)
 64{
 65	struct task_struct *curr = rq->curr;
 66	u64 delta_exec;
 67
 68	delta_exec = rq_clock_task(rq) - curr->se.exec_start;
 69	if (unlikely((s64)delta_exec < 0))
 70		delta_exec = 0;
 71
 72	schedstat_set(curr->se.statistics.exec_max,
 73			max(curr->se.statistics.exec_max, delta_exec));
 74
 75	curr->se.sum_exec_runtime += delta_exec;
 76	account_group_exec_runtime(curr, delta_exec);
 77
 78	curr->se.exec_start = rq_clock_task(rq);
 79	cgroup_account_cputime(curr, delta_exec);
 80}
 81
 82/*
 83 * scheduler tick hitting a task of our scheduling class.
 84 *
 85 * NOTE: This function can be called remotely by the tick offload that
 86 * goes along full dynticks. Therefore no local assumption can be made
 87 * and everything must be accessed through the @rq and @curr passed in
 88 * parameters.
 89 */
 90static void task_tick_stop(struct rq *rq, struct task_struct *curr, int queued)
 91{
 92}
 93
 
 
 
 
 
 
 
 94static void switched_to_stop(struct rq *rq, struct task_struct *p)
 95{
 96	BUG(); /* its impossible to change to this class */
 97}
 98
 99static void
100prio_changed_stop(struct rq *rq, struct task_struct *p, int oldprio)
101{
102	BUG(); /* how!?, what priority? */
103}
104
 
 
 
 
 
 
105static void update_curr_stop(struct rq *rq)
106{
107}
108
109/*
110 * Simple, special scheduling class for the per-CPU stop tasks:
111 */
112const struct sched_class stop_sched_class
113	__attribute__((section("__stop_sched_class"))) = {
114
115	.enqueue_task		= enqueue_task_stop,
116	.dequeue_task		= dequeue_task_stop,
117	.yield_task		= yield_task_stop,
118
119	.check_preempt_curr	= check_preempt_curr_stop,
120
121	.pick_next_task		= pick_next_task_stop,
122	.put_prev_task		= put_prev_task_stop,
123	.set_next_task          = set_next_task_stop,
124
125#ifdef CONFIG_SMP
126	.balance		= balance_stop,
127	.select_task_rq		= select_task_rq_stop,
128	.set_cpus_allowed	= set_cpus_allowed_common,
129#endif
130
 
131	.task_tick		= task_tick_stop,
 
 
132
133	.prio_changed		= prio_changed_stop,
134	.switched_to		= switched_to_stop,
135	.update_curr		= update_curr_stop,
136};