#include "sched.h" /* * stop-task scheduling class. * * The stop task is the highest priority task in the system, it preempts * everything and will be preempted by nothing. * * See kernel/stop_machine.c */ #ifdef CONFIG_SMP static int select_task_rq_stop(struct task_struct *p, int cpu, int sd_flag, int flags) { return task_cpu(p); /* stop tasks as never migrate */ } #endif /* CONFIG_SMP */ static void check_preempt_curr_stop(struct rq *rq, struct task_struct *p, int flags) { /* we're never preempted */ } static struct task_struct * pick_next_task_stop(struct rq *rq, struct task_struct *prev, struct pin_cookie cookie) { struct task_struct *stop = rq->stop; if (!stop || !task_on_rq_queued(stop)) return NULL; put_prev_task(rq, prev); stop->se.exec_start = rq_clock_task(rq); return stop; } static void enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags) { add_nr_running(rq, 1); } static void dequeue_task_stop(struct rq *rq, struct task_struct *p, int flags) { sub_nr_running(rq, 1); } static void yield_task_stop(struct rq *rq) { BUG(); /* the stop task should never yield, its pointless. */ } static void put_prev_task_stop(struct rq *rq, struct task_struct *prev) { struct task_struct *curr = rq->curr; u64 delta_exec; delta_exec = rq_clock_task(rq) - curr->se.exec_start; if (unlikely((s64)delta_exec < 0)) delta_exec = 0; schedstat_set(curr->se.statistics.exec_max, max(curr->se.statistics.exec_max, delta_exec)); curr->se.sum_exec_runtime += delta_exec; account_group_exec_runtime(curr, delta_exec); curr->se.exec_start = rq_clock_task(rq); cpuacct_charge(curr, delta_exec); } static void task_tick_stop(struct rq *rq, struct task_struct *curr, int queued) { } static void set_curr_task_stop(struct rq *rq) { struct task_struct *stop = rq->stop; stop->se.exec_start = rq_clock_task(rq); } static void switched_to_stop(struct rq *rq, struct task_struct *p) { BUG(); /* its impossible to change to this class */ } static void prio_changed_stop(struct rq *rq, struct task_struct *p, int oldprio) { BUG(); /* how!?, what priority? */ } static unsigned int get_rr_interval_stop(struct rq *rq, struct task_struct *task) { return 0; } static void update_curr_stop(struct rq *rq) { } /* * Simple, special scheduling class for the per-CPU stop tasks: */ const struct sched_class stop_sched_class = { .next = &dl_sched_class, .enqueue_task = enqueue_task_stop, .dequeue_task = dequeue_task_stop, .yield_task = yield_task_stop, .check_preempt_curr = check_preempt_curr_stop, .pick_next_task = pick_next_task_stop, .put_prev_task = put_prev_task_stop, #ifdef CONFIG_SMP .select_task_rq = select_task_rq_stop, .set_cpus_allowed = set_cpus_allowed_common, #endif .set_curr_task = set_curr_task_stop, .task_tick = task_tick_stop, .get_rr_interval = get_rr_interval_stop, .prio_changed = prio_changed_stop, .switched_to = switched_to_stop, .update_curr = update_curr_stop, }; c

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