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- // SPDX-License-Identifier: GPL-2.0
- /*
- * 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 flags)
- {
- return task_cpu(p); /* stop tasks as never migrate */
- }
- static int
- balance_stop(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
- {
- return sched_stop_runnable(rq);
- }
- #endif /* CONFIG_SMP */
- static void
- check_preempt_curr_stop(struct rq *rq, struct task_struct *p, int flags)
- {
- /* we're never preempted */
- }
- static void set_next_task_stop(struct rq *rq, struct task_struct *stop, bool first)
- {
- stop->se.exec_start = rq_clock_task(rq);
- }
- static struct task_struct *pick_task_stop(struct rq *rq)
- {
- if (!sched_stop_runnable(rq))
- return NULL;
- return rq->stop;
- }
- static struct task_struct *pick_next_task_stop(struct rq *rq)
- {
- struct task_struct *p = pick_task_stop(rq);
- if (p)
- set_next_task_stop(rq, p, true);
- return p;
- }
- 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 now, delta_exec;
- now = rq_clock_task(rq);
- delta_exec = now - curr->se.exec_start;
- if (unlikely((s64)delta_exec < 0))
- delta_exec = 0;
- schedstat_set(curr->stats.exec_max,
- max(curr->stats.exec_max, delta_exec));
- update_current_exec_runtime(curr, now, delta_exec);
- }
- /*
- * scheduler tick hitting a task of our scheduling class.
- *
- * NOTE: This function can be called remotely by the tick offload that
- * goes along full dynticks. Therefore no local assumption can be made
- * and everything must be accessed through the @rq and @curr passed in
- * parameters.
- */
- static void task_tick_stop(struct rq *rq, struct task_struct *curr, int queued)
- {
- }
- 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 void update_curr_stop(struct rq *rq)
- {
- }
- /*
- * Simple, special scheduling class for the per-CPU stop tasks:
- */
- DEFINE_SCHED_CLASS(stop) = {
- .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,
- .set_next_task = set_next_task_stop,
- #ifdef CONFIG_SMP
- .balance = balance_stop,
- .pick_task = pick_task_stop,
- .select_task_rq = select_task_rq_stop,
- .set_cpus_allowed = set_cpus_allowed_common,
- #endif
- .task_tick = task_tick_stop,
- .prio_changed = prio_changed_stop,
- .switched_to = switched_to_stop,
- .update_curr = update_curr_stop,
- };
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