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Ingo Molnarfa72e9e2007-07-09 18:51:58 +02001/*
2 * idle-task scheduling class.
3 *
4 * (NOTE: these are not related to SCHED_IDLE tasks which are
5 * handled in sched_fair.c)
6 */
7
Gregory Haskinse7693a32008-01-25 21:08:09 +01008#ifdef CONFIG_SMP
Peter Zijlstra0017d732010-03-24 18:34:10 +01009static int
10select_task_rq_idle(struct rq *rq, struct task_struct *p, int sd_flag, int flags)
Gregory Haskinse7693a32008-01-25 21:08:09 +010011{
12 return task_cpu(p); /* IDLE tasks as never migrated */
13}
14#endif /* CONFIG_SMP */
Ingo Molnarfa72e9e2007-07-09 18:51:58 +020015/*
16 * Idle tasks are unconditionally rescheduled:
17 */
Peter Zijlstra7d478722009-09-14 19:55:44 +020018static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int flags)
Ingo Molnarfa72e9e2007-07-09 18:51:58 +020019{
20 resched_task(rq->idle);
21}
22
Ingo Molnarfb8d4722007-08-09 11:16:48 +020023static struct task_struct *pick_next_task_idle(struct rq *rq)
Ingo Molnarfa72e9e2007-07-09 18:51:58 +020024{
25 schedstat_inc(rq, sched_goidle);
Peter Zijlstra74f51872010-04-22 21:50:19 +020026 calc_load_account_idle(rq);
Ingo Molnarfa72e9e2007-07-09 18:51:58 +020027 return rq->idle;
28}
29
30/*
31 * It is not legal to sleep in the idle task - print a warning
32 * message if some code attempts to do it:
33 */
34static void
Peter Zijlstra371fd7e2010-03-24 16:38:48 +010035dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags)
Ingo Molnarfa72e9e2007-07-09 18:51:58 +020036{
Thomas Gleixner05fa7852009-11-17 14:28:38 +010037 raw_spin_unlock_irq(&rq->lock);
Peter Zijlstra3df0fc52009-12-20 14:23:57 +010038 printk(KERN_ERR "bad: scheduling from the idle thread!\n");
Ingo Molnarfa72e9e2007-07-09 18:51:58 +020039 dump_stack();
Thomas Gleixner05fa7852009-11-17 14:28:38 +010040 raw_spin_lock_irq(&rq->lock);
Ingo Molnarfa72e9e2007-07-09 18:51:58 +020041}
42
Ingo Molnar31ee5292007-08-09 11:16:49 +020043static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
Ingo Molnarfa72e9e2007-07-09 18:51:58 +020044{
45}
46
Peter Zijlstra8f4d37e2008-01-25 21:08:29 +010047static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
Ingo Molnarfa72e9e2007-07-09 18:51:58 +020048{
49}
50
Srivatsa Vaddagiri83b699e2007-10-15 17:00:08 +020051static void set_curr_task_idle(struct rq *rq)
52{
53}
54
Steven Rostedtcb469842008-01-25 21:08:22 +010055static void switched_to_idle(struct rq *rq, struct task_struct *p,
56 int running)
57{
58 /* Can this actually happen?? */
59 if (running)
60 resched_task(rq->curr);
61 else
Peter Zijlstra15afe092008-09-20 23:38:02 +020062 check_preempt_curr(rq, p, 0);
Steven Rostedtcb469842008-01-25 21:08:22 +010063}
64
65static void prio_changed_idle(struct rq *rq, struct task_struct *p,
66 int oldprio, int running)
67{
68 /* This can happen for hot plug CPUS */
69
70 /*
71 * Reschedule if we are currently running on this runqueue and
72 * our priority decreased, or if we are not currently running on
73 * this runqueue and our priority is higher than the current's
74 */
75 if (running) {
76 if (p->prio > oldprio)
77 resched_task(rq->curr);
78 } else
Peter Zijlstra15afe092008-09-20 23:38:02 +020079 check_preempt_curr(rq, p, 0);
Steven Rostedtcb469842008-01-25 21:08:22 +010080}
81
H Hartley Sweeten6d686f42010-01-13 20:21:52 -070082static unsigned int get_rr_interval_idle(struct rq *rq, struct task_struct *task)
Peter Williams0d721ce2009-09-21 01:31:53 +000083{
84 return 0;
85}
86
Ingo Molnarfa72e9e2007-07-09 18:51:58 +020087/*
88 * Simple, special scheduling class for the per-CPU idle tasks:
89 */
Harvey Harrison2abdad02008-04-25 10:53:13 -070090static const struct sched_class idle_sched_class = {
Ingo Molnar5522d5d2007-10-15 17:00:12 +020091 /* .next is NULL */
Ingo Molnarfa72e9e2007-07-09 18:51:58 +020092 /* no enqueue/yield_task for idle tasks */
93
94 /* dequeue is not valid, we print a debug message there: */
95 .dequeue_task = dequeue_task_idle,
96
97 .check_preempt_curr = check_preempt_curr_idle,
98
99 .pick_next_task = pick_next_task_idle,
100 .put_prev_task = put_prev_task_idle,
101
Peter Williams681f3e62007-10-24 18:23:51 +0200102#ifdef CONFIG_SMP
Li Zefan4ce72a22008-10-22 15:25:26 +0800103 .select_task_rq = select_task_rq_idle,
Peter Williams681f3e62007-10-24 18:23:51 +0200104#endif
Ingo Molnarfa72e9e2007-07-09 18:51:58 +0200105
Srivatsa Vaddagiri83b699e2007-10-15 17:00:08 +0200106 .set_curr_task = set_curr_task_idle,
Ingo Molnarfa72e9e2007-07-09 18:51:58 +0200107 .task_tick = task_tick_idle,
Steven Rostedtcb469842008-01-25 21:08:22 +0100108
Peter Williams0d721ce2009-09-21 01:31:53 +0000109 .get_rr_interval = get_rr_interval_idle,
110
Steven Rostedtcb469842008-01-25 21:08:22 +0100111 .prio_changed = prio_changed_idle,
112 .switched_to = switched_to_idle,
113
Ingo Molnarfa72e9e2007-07-09 18:51:58 +0200114 /* no .task_new for idle tasks */
115};