| 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 || !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 | |
| 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 | static void update_curr_stop(struct rq *rq) |
| 106 | { |
| 107 | } |
| 108 | |
| 109 | /* |
| 110 | * Simple, special scheduling class for the per-CPU stop tasks: |
| 111 | */ |
| 112 | const struct sched_class stop_sched_class = { |
| 113 | .next = &dl_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 | |
| 124 | #ifdef CONFIG_SMP |
| 125 | .select_task_rq = select_task_rq_stop, |
| 126 | .set_cpus_allowed = set_cpus_allowed_common, |
| 127 | #endif |
| 128 | |
| 129 | .set_curr_task = set_curr_task_stop, |
| 130 | .task_tick = task_tick_stop, |
| 131 | |
| 132 | .get_rr_interval = get_rr_interval_stop, |
| 133 | |
| 134 | .prio_changed = prio_changed_stop, |
| 135 | .switched_to = switched_to_stop, |
| 136 | .update_curr = update_curr_stop, |
| 137 | }; |