fdb6bb0b33561af759e24d8806776dfc0823867c
[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 *pick_next_task_stop(struct rq *rq)
27 {
28         struct task_struct *stop = rq->stop;
29
30         if (stop && stop->on_rq) {
31                 stop->se.exec_start = rq_clock_task(rq);
32                 return stop;
33         }
34
35         return NULL;
36 }
37
38 static void
39 enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags)
40 {
41         inc_nr_running(rq);
42 }
43
44 static void
45 dequeue_task_stop(struct rq *rq, struct task_struct *p, int flags)
46 {
47         dec_nr_running(rq);
48 }
49
50 static void yield_task_stop(struct rq *rq)
51 {
52         BUG(); /* the stop task should never yield, its pointless. */
53 }
54
55 static void put_prev_task_stop(struct rq *rq, struct task_struct *prev)
56 {
57         struct task_struct *curr = rq->curr;
58         u64 delta_exec;
59
60         delta_exec = rq_clock_task(rq) - curr->se.exec_start;
61         if (unlikely((s64)delta_exec < 0))
62                 delta_exec = 0;
63
64         schedstat_set(curr->se.statistics.exec_max,
65                         max(curr->se.statistics.exec_max, delta_exec));
66
67         curr->se.sum_exec_runtime += delta_exec;
68         account_group_exec_runtime(curr, delta_exec);
69
70         curr->se.exec_start = rq_clock_task(rq);
71         cpuacct_charge(curr, delta_exec);
72 }
73
74 static void task_tick_stop(struct rq *rq, struct task_struct *curr, int queued)
75 {
76 }
77
78 static void set_curr_task_stop(struct rq *rq)
79 {
80         struct task_struct *stop = rq->stop;
81
82         stop->se.exec_start = rq_clock_task(rq);
83 }
84
85 static void switched_to_stop(struct rq *rq, struct task_struct *p)
86 {
87         BUG(); /* its impossible to change to this class */
88 }
89
90 static void
91 prio_changed_stop(struct rq *rq, struct task_struct *p, int oldprio)
92 {
93         BUG(); /* how!?, what priority? */
94 }
95
96 static unsigned int
97 get_rr_interval_stop(struct rq *rq, struct task_struct *task)
98 {
99         return 0;
100 }
101
102 /*
103  * Simple, special scheduling class for the per-CPU stop tasks:
104  */
105 const struct sched_class stop_sched_class = {
106         .next                   = &dl_sched_class,
107
108         .enqueue_task           = enqueue_task_stop,
109         .dequeue_task           = dequeue_task_stop,
110         .yield_task             = yield_task_stop,
111
112         .check_preempt_curr     = check_preempt_curr_stop,
113
114         .pick_next_task         = pick_next_task_stop,
115         .put_prev_task          = put_prev_task_stop,
116
117 #ifdef CONFIG_SMP
118         .select_task_rq         = select_task_rq_stop,
119 #endif
120
121         .set_curr_task          = set_curr_task_stop,
122         .task_tick              = task_tick_stop,
123
124         .get_rr_interval        = get_rr_interval_stop,
125
126         .prio_changed           = prio_changed_stop,
127         .switched_to            = switched_to_stop,
128 };