kernel/sched/stop_task.c

   1 #include "sched.h"
   2 #ifdef CONFIG_HMP_TRACER
   3 #include <trace/events/sched.h>
   4 #endif
   5
   6 /*
   7  * stop-task scheduling class.
   8  *
   9  * The stop task is the highest priority task in the system, it preempts
  10  * everything and will be preempted by nothing.
  11  *
  12  * See kernel/stop_machine.c
  13  */
  14
  15 #ifdef CONFIG_SMP
  16 static int
  17 select_task_rq_stop(struct task_struct *p, int sd_flag, int flags)
  18 {
  19         return task_cpu(p); /* stop tasks as never migrate */
  20 }
  21 #endif /* CONFIG_SMP */
  22
  23 static void
  24 check_preempt_curr_stop(struct rq *rq, struct task_struct *p, int flags)
  25 {
  26         /* we're never preempted */
  27 }
  28
  29 static struct task_struct *pick_next_task_stop(struct rq *rq)
  30 {
  31         struct task_struct *stop = rq->stop;
  32
  33         if (stop && stop->on_rq) {
  34                 stop->se.exec_start = rq->clock_task;
  35                 return stop;
  36         }
  37
  38         return NULL;
  39 }
  40
  41 static void
  42 enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags)
  43 {
  44         inc_nr_running(rq);
  45 #ifdef CONFIG_HMP_TRACER
  46         trace_sched_runqueue_length(rq->cpu,rq->nr_running);
  47 #endif
  48         #ifdef CONFIG_MET_SCHED_HMP
  49         RqLen(smp_processor_id(),rq->nr_running);
  50         #endif
  51 }
  52
  53 static void
  54 dequeue_task_stop(struct rq *rq, struct task_struct *p, int flags)
  55 {
  56         dec_nr_running(rq);
  57 #ifdef CONFIG_HMP_TRACER
  58         trace_sched_runqueue_length(rq->cpu,rq->nr_running);
  59 #endif
  60         #ifdef CONFIG_MET_SCHED_HMP
  61         RqLen(smp_processor_id(),rq->nr_running);
  62         #endif
  63 }
  64
  65 static void yield_task_stop(struct rq *rq)
  66 {
  67         BUG(); /* the stop task should never yield, its pointless. */
  68 }
  69
  70 static void put_prev_task_stop(struct rq *rq, struct task_struct *prev)
  71 {
  72         struct task_struct *curr = rq->curr;
  73         u64 delta_exec;
  74
  75         delta_exec = rq->clock_task - curr->se.exec_start;
  76         if (unlikely((s64)delta_exec < 0))
  77                 delta_exec = 0;
  78
  79         schedstat_set(curr->se.statistics.exec_max,
  80                         max(curr->se.statistics.exec_max, delta_exec));
  81
  82         curr->se.sum_exec_runtime += delta_exec;
  83         account_group_exec_runtime(curr, delta_exec);
  84
  85         curr->se.exec_start = rq->clock_task;
  86         cpuacct_charge(curr, delta_exec);
  87 }
  88
  89 static void task_tick_stop(struct rq *rq, struct task_struct *curr, int queued)
  90 {
  91 }
  92
  93 static void set_curr_task_stop(struct rq *rq)
  94 {
  95         struct task_struct *stop = rq->stop;
  96
  97         stop->se.exec_start = rq->clock_task;
  98 }
  99
 100 static void switched_to_stop(struct rq *rq, struct task_struct *p)
 101 {
 102         BUG(); /* its impossible to change to this class */
 103 }
 104
 105 static void
 106 prio_changed_stop(struct rq *rq, struct task_struct *p, int oldprio)
 107 {
 108         BUG(); /* how!?, what priority? */
 109 }
 110
 111 static unsigned int
 112 get_rr_interval_stop(struct rq *rq, struct task_struct *task)
 113 {
 114         return 0;
 115 }
 116
 117 /*
 118  * Simple, special scheduling class for the per-CPU stop tasks:
 119  */
 120 const struct sched_class stop_sched_class = {
 121         .next                   = &rt_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 #endif
 135
 136         .set_curr_task          = set_curr_task_stop,
 137         .task_tick              = task_tick_stop,
 138
 139         .get_rr_interval        = get_rr_interval_stop,
 140
 141         .prio_changed           = prio_changed_stop,
 142         .switched_to            = switched_to_stop,
 143 };