Merge tag 'v3.16' into p/abusse/merge_upgrade
[projects/modsched/linux.git] / kernel / sched / cfs / stop_task.c
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
13 static int
14 select_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
20 static void
21 check_preempt_curr_stop(struct rq *rq, struct task_struct *p, int flags)
22 {
23         /* we're never preempted */
24 }
25
26 static struct task_struct *
27 pick_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
41 static void
42 enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags)
43 {
44         add_nr_running(rq, 1);
45 }
46
47 static void
48 dequeue_task_stop(struct rq *rq, struct task_struct *p, int flags)
49 {
50         sub_nr_running(rq, 1);
51 }
52
53 static void yield_task_stop(struct rq *rq)
54 {
55         BUG(); /* the stop task should never yield, its pointless. */
56 }
57
58 static 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
77 static void task_tick_stop(struct rq *rq, struct task_struct *curr, int queued)
78 {
79 }
80
81 static 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
88 static void switched_to_stop(struct rq *rq, struct task_struct *p)
89 {
90         BUG(); /* its impossible to change to this class */
91 }
92
93 static void
94 prio_changed_stop(struct rq *rq, struct task_struct *p, int oldprio)
95 {
96         BUG(); /* how!?, what priority? */
97 }
98
99 static unsigned int
100 get_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  */
108 const 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 };