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Add in Documentation/scheduler/ some hints about the design choices, the usage and the future possible developments of the sched_dl scheduling class and of the SCHED_DEADLINE policy. Reviewed-by: Henrik Austad <henrik@austad.us> Signed-off-by: Dario Faggioli <raistlin@linux.it> Signed-off-by: Juri Lelli <juri.lelli@gmail.com> [ Re-wrote sections 2 and 3. ] Signed-off-by: Luca Abeni <luca.abeni@unitn.it> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1390821615-23247-1-git-send-email-juri.lelli@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
1642 lines
42 KiB
C
1642 lines
42 KiB
C
/*
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* Deadline Scheduling Class (SCHED_DEADLINE)
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*
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* Earliest Deadline First (EDF) + Constant Bandwidth Server (CBS).
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*
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* Tasks that periodically executes their instances for less than their
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* runtime won't miss any of their deadlines.
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* Tasks that are not periodic or sporadic or that tries to execute more
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* than their reserved bandwidth will be slowed down (and may potentially
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* miss some of their deadlines), and won't affect any other task.
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*
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* Copyright (C) 2012 Dario Faggioli <raistlin@linux.it>,
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* Juri Lelli <juri.lelli@gmail.com>,
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* Michael Trimarchi <michael@amarulasolutions.com>,
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* Fabio Checconi <fchecconi@gmail.com>
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*/
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#include "sched.h"
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#include <linux/slab.h>
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struct dl_bandwidth def_dl_bandwidth;
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static inline struct task_struct *dl_task_of(struct sched_dl_entity *dl_se)
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{
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return container_of(dl_se, struct task_struct, dl);
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}
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static inline struct rq *rq_of_dl_rq(struct dl_rq *dl_rq)
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{
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return container_of(dl_rq, struct rq, dl);
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}
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static inline struct dl_rq *dl_rq_of_se(struct sched_dl_entity *dl_se)
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{
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struct task_struct *p = dl_task_of(dl_se);
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struct rq *rq = task_rq(p);
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return &rq->dl;
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}
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static inline int on_dl_rq(struct sched_dl_entity *dl_se)
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{
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return !RB_EMPTY_NODE(&dl_se->rb_node);
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}
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static inline int is_leftmost(struct task_struct *p, struct dl_rq *dl_rq)
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{
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struct sched_dl_entity *dl_se = &p->dl;
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return dl_rq->rb_leftmost == &dl_se->rb_node;
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}
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void init_dl_bandwidth(struct dl_bandwidth *dl_b, u64 period, u64 runtime)
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{
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raw_spin_lock_init(&dl_b->dl_runtime_lock);
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dl_b->dl_period = period;
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dl_b->dl_runtime = runtime;
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}
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extern unsigned long to_ratio(u64 period, u64 runtime);
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void init_dl_bw(struct dl_bw *dl_b)
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{
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raw_spin_lock_init(&dl_b->lock);
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raw_spin_lock(&def_dl_bandwidth.dl_runtime_lock);
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if (global_rt_runtime() == RUNTIME_INF)
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dl_b->bw = -1;
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else
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dl_b->bw = to_ratio(global_rt_period(), global_rt_runtime());
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raw_spin_unlock(&def_dl_bandwidth.dl_runtime_lock);
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dl_b->total_bw = 0;
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}
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void init_dl_rq(struct dl_rq *dl_rq, struct rq *rq)
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{
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dl_rq->rb_root = RB_ROOT;
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#ifdef CONFIG_SMP
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/* zero means no -deadline tasks */
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dl_rq->earliest_dl.curr = dl_rq->earliest_dl.next = 0;
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dl_rq->dl_nr_migratory = 0;
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dl_rq->overloaded = 0;
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dl_rq->pushable_dl_tasks_root = RB_ROOT;
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#else
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init_dl_bw(&dl_rq->dl_bw);
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#endif
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}
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#ifdef CONFIG_SMP
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static inline int dl_overloaded(struct rq *rq)
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{
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return atomic_read(&rq->rd->dlo_count);
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}
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static inline void dl_set_overload(struct rq *rq)
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{
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if (!rq->online)
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return;
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cpumask_set_cpu(rq->cpu, rq->rd->dlo_mask);
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/*
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* Must be visible before the overload count is
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* set (as in sched_rt.c).
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*
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* Matched by the barrier in pull_dl_task().
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*/
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smp_wmb();
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atomic_inc(&rq->rd->dlo_count);
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}
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static inline void dl_clear_overload(struct rq *rq)
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{
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if (!rq->online)
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return;
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atomic_dec(&rq->rd->dlo_count);
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cpumask_clear_cpu(rq->cpu, rq->rd->dlo_mask);
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}
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static void update_dl_migration(struct dl_rq *dl_rq)
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{
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if (dl_rq->dl_nr_migratory && dl_rq->dl_nr_total > 1) {
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if (!dl_rq->overloaded) {
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dl_set_overload(rq_of_dl_rq(dl_rq));
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dl_rq->overloaded = 1;
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}
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} else if (dl_rq->overloaded) {
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dl_clear_overload(rq_of_dl_rq(dl_rq));
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dl_rq->overloaded = 0;
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}
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}
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static void inc_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
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{
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struct task_struct *p = dl_task_of(dl_se);
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dl_rq = &rq_of_dl_rq(dl_rq)->dl;
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dl_rq->dl_nr_total++;
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if (p->nr_cpus_allowed > 1)
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dl_rq->dl_nr_migratory++;
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update_dl_migration(dl_rq);
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}
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static void dec_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
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{
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struct task_struct *p = dl_task_of(dl_se);
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dl_rq = &rq_of_dl_rq(dl_rq)->dl;
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dl_rq->dl_nr_total--;
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if (p->nr_cpus_allowed > 1)
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dl_rq->dl_nr_migratory--;
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update_dl_migration(dl_rq);
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}
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/*
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* The list of pushable -deadline task is not a plist, like in
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* sched_rt.c, it is an rb-tree with tasks ordered by deadline.
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*/
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static void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p)
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{
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struct dl_rq *dl_rq = &rq->dl;
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struct rb_node **link = &dl_rq->pushable_dl_tasks_root.rb_node;
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struct rb_node *parent = NULL;
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struct task_struct *entry;
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int leftmost = 1;
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BUG_ON(!RB_EMPTY_NODE(&p->pushable_dl_tasks));
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while (*link) {
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parent = *link;
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entry = rb_entry(parent, struct task_struct,
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pushable_dl_tasks);
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if (dl_entity_preempt(&p->dl, &entry->dl))
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link = &parent->rb_left;
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else {
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link = &parent->rb_right;
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leftmost = 0;
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}
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}
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if (leftmost)
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dl_rq->pushable_dl_tasks_leftmost = &p->pushable_dl_tasks;
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rb_link_node(&p->pushable_dl_tasks, parent, link);
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rb_insert_color(&p->pushable_dl_tasks, &dl_rq->pushable_dl_tasks_root);
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}
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static void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)
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{
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struct dl_rq *dl_rq = &rq->dl;
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if (RB_EMPTY_NODE(&p->pushable_dl_tasks))
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return;
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if (dl_rq->pushable_dl_tasks_leftmost == &p->pushable_dl_tasks) {
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struct rb_node *next_node;
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next_node = rb_next(&p->pushable_dl_tasks);
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dl_rq->pushable_dl_tasks_leftmost = next_node;
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}
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rb_erase(&p->pushable_dl_tasks, &dl_rq->pushable_dl_tasks_root);
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RB_CLEAR_NODE(&p->pushable_dl_tasks);
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}
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static inline int has_pushable_dl_tasks(struct rq *rq)
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{
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return !RB_EMPTY_ROOT(&rq->dl.pushable_dl_tasks_root);
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}
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static int push_dl_task(struct rq *rq);
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#else
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static inline
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void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p)
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{
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}
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static inline
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void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)
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{
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}
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static inline
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void inc_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
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{
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}
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static inline
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void dec_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
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{
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}
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#endif /* CONFIG_SMP */
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static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags);
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static void __dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags);
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static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
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int flags);
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/*
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* We are being explicitly informed that a new instance is starting,
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* and this means that:
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* - the absolute deadline of the entity has to be placed at
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* current time + relative deadline;
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* - the runtime of the entity has to be set to the maximum value.
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*
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* The capability of specifying such event is useful whenever a -deadline
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* entity wants to (try to!) synchronize its behaviour with the scheduler's
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* one, and to (try to!) reconcile itself with its own scheduling
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* parameters.
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*/
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static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se,
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struct sched_dl_entity *pi_se)
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{
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struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
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struct rq *rq = rq_of_dl_rq(dl_rq);
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WARN_ON(!dl_se->dl_new || dl_se->dl_throttled);
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/*
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* We use the regular wall clock time to set deadlines in the
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* future; in fact, we must consider execution overheads (time
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* spent on hardirq context, etc.).
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*/
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dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
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dl_se->runtime = pi_se->dl_runtime;
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dl_se->dl_new = 0;
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}
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/*
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* Pure Earliest Deadline First (EDF) scheduling does not deal with the
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* possibility of a entity lasting more than what it declared, and thus
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* exhausting its runtime.
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*
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* Here we are interested in making runtime overrun possible, but we do
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* not want a entity which is misbehaving to affect the scheduling of all
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* other entities.
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* Therefore, a budgeting strategy called Constant Bandwidth Server (CBS)
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* is used, in order to confine each entity within its own bandwidth.
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*
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* This function deals exactly with that, and ensures that when the runtime
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* of a entity is replenished, its deadline is also postponed. That ensures
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* the overrunning entity can't interfere with other entity in the system and
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* can't make them miss their deadlines. Reasons why this kind of overruns
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* could happen are, typically, a entity voluntarily trying to overcome its
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* runtime, or it just underestimated it during sched_setscheduler_ex().
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*/
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static void replenish_dl_entity(struct sched_dl_entity *dl_se,
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struct sched_dl_entity *pi_se)
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{
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struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
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struct rq *rq = rq_of_dl_rq(dl_rq);
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BUG_ON(pi_se->dl_runtime <= 0);
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/*
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* This could be the case for a !-dl task that is boosted.
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* Just go with full inherited parameters.
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*/
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if (dl_se->dl_deadline == 0) {
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dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
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dl_se->runtime = pi_se->dl_runtime;
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}
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/*
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* We keep moving the deadline away until we get some
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* available runtime for the entity. This ensures correct
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* handling of situations where the runtime overrun is
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* arbitrary large.
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*/
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while (dl_se->runtime <= 0) {
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dl_se->deadline += pi_se->dl_period;
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dl_se->runtime += pi_se->dl_runtime;
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}
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/*
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* At this point, the deadline really should be "in
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* the future" with respect to rq->clock. If it's
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* not, we are, for some reason, lagging too much!
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* Anyway, after having warn userspace abut that,
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* we still try to keep the things running by
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* resetting the deadline and the budget of the
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* entity.
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*/
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if (dl_time_before(dl_se->deadline, rq_clock(rq))) {
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static bool lag_once = false;
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if (!lag_once) {
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lag_once = true;
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printk_sched("sched: DL replenish lagged to much\n");
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}
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dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
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dl_se->runtime = pi_se->dl_runtime;
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}
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}
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/*
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* Here we check if --at time t-- an entity (which is probably being
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* [re]activated or, in general, enqueued) can use its remaining runtime
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* and its current deadline _without_ exceeding the bandwidth it is
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* assigned (function returns true if it can't). We are in fact applying
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* one of the CBS rules: when a task wakes up, if the residual runtime
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* over residual deadline fits within the allocated bandwidth, then we
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* can keep the current (absolute) deadline and residual budget without
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* disrupting the schedulability of the system. Otherwise, we should
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* refill the runtime and set the deadline a period in the future,
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* because keeping the current (absolute) deadline of the task would
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* result in breaking guarantees promised to other tasks (refer to
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* Documentation/scheduler/sched-deadline.txt for more informations).
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*
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* This function returns true if:
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*
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* runtime / (deadline - t) > dl_runtime / dl_period ,
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*
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* IOW we can't recycle current parameters.
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*
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* Notice that the bandwidth check is done against the period. For
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* task with deadline equal to period this is the same of using
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* dl_deadline instead of dl_period in the equation above.
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*/
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static bool dl_entity_overflow(struct sched_dl_entity *dl_se,
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struct sched_dl_entity *pi_se, u64 t)
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{
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u64 left, right;
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/*
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* left and right are the two sides of the equation above,
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* after a bit of shuffling to use multiplications instead
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* of divisions.
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*
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* Note that none of the time values involved in the two
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* multiplications are absolute: dl_deadline and dl_runtime
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* are the relative deadline and the maximum runtime of each
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* instance, runtime is the runtime left for the last instance
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* and (deadline - t), since t is rq->clock, is the time left
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* to the (absolute) deadline. Even if overflowing the u64 type
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* is very unlikely to occur in both cases, here we scale down
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* as we want to avoid that risk at all. Scaling down by 10
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* means that we reduce granularity to 1us. We are fine with it,
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* since this is only a true/false check and, anyway, thinking
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* of anything below microseconds resolution is actually fiction
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* (but still we want to give the user that illusion >;).
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*/
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left = (pi_se->dl_period >> DL_SCALE) * (dl_se->runtime >> DL_SCALE);
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right = ((dl_se->deadline - t) >> DL_SCALE) *
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(pi_se->dl_runtime >> DL_SCALE);
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return dl_time_before(right, left);
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}
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/*
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* When a -deadline entity is queued back on the runqueue, its runtime and
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* deadline might need updating.
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*
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* The policy here is that we update the deadline of the entity only if:
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* - the current deadline is in the past,
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* - using the remaining runtime with the current deadline would make
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* the entity exceed its bandwidth.
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*/
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static void update_dl_entity(struct sched_dl_entity *dl_se,
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struct sched_dl_entity *pi_se)
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{
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struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
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struct rq *rq = rq_of_dl_rq(dl_rq);
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/*
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* The arrival of a new instance needs special treatment, i.e.,
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* the actual scheduling parameters have to be "renewed".
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*/
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if (dl_se->dl_new) {
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setup_new_dl_entity(dl_se, pi_se);
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return;
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}
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if (dl_time_before(dl_se->deadline, rq_clock(rq)) ||
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dl_entity_overflow(dl_se, pi_se, rq_clock(rq))) {
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dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
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dl_se->runtime = pi_se->dl_runtime;
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}
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}
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/*
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* If the entity depleted all its runtime, and if we want it to sleep
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* while waiting for some new execution time to become available, we
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* set the bandwidth enforcement timer to the replenishment instant
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* and try to activate it.
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*
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* Notice that it is important for the caller to know if the timer
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* actually started or not (i.e., the replenishment instant is in
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* the future or in the past).
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*/
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static int start_dl_timer(struct sched_dl_entity *dl_se, bool boosted)
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{
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struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
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struct rq *rq = rq_of_dl_rq(dl_rq);
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ktime_t now, act;
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ktime_t soft, hard;
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unsigned long range;
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s64 delta;
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if (boosted)
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return 0;
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/*
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* We want the timer to fire at the deadline, but considering
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* that it is actually coming from rq->clock and not from
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* hrtimer's time base reading.
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*/
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act = ns_to_ktime(dl_se->deadline);
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now = hrtimer_cb_get_time(&dl_se->dl_timer);
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delta = ktime_to_ns(now) - rq_clock(rq);
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act = ktime_add_ns(act, delta);
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/*
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* If the expiry time already passed, e.g., because the value
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* chosen as the deadline is too small, don't even try to
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* start the timer in the past!
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*/
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if (ktime_us_delta(act, now) < 0)
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return 0;
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hrtimer_set_expires(&dl_se->dl_timer, act);
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soft = hrtimer_get_softexpires(&dl_se->dl_timer);
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hard = hrtimer_get_expires(&dl_se->dl_timer);
|
|
range = ktime_to_ns(ktime_sub(hard, soft));
|
|
__hrtimer_start_range_ns(&dl_se->dl_timer, soft,
|
|
range, HRTIMER_MODE_ABS, 0);
|
|
|
|
return hrtimer_active(&dl_se->dl_timer);
|
|
}
|
|
|
|
/*
|
|
* This is the bandwidth enforcement timer callback. If here, we know
|
|
* a task is not on its dl_rq, since the fact that the timer was running
|
|
* means the task is throttled and needs a runtime replenishment.
|
|
*
|
|
* However, what we actually do depends on the fact the task is active,
|
|
* (it is on its rq) or has been removed from there by a call to
|
|
* dequeue_task_dl(). In the former case we must issue the runtime
|
|
* replenishment and add the task back to the dl_rq; in the latter, we just
|
|
* do nothing but clearing dl_throttled, so that runtime and deadline
|
|
* updating (and the queueing back to dl_rq) will be done by the
|
|
* next call to enqueue_task_dl().
|
|
*/
|
|
static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
|
|
{
|
|
struct sched_dl_entity *dl_se = container_of(timer,
|
|
struct sched_dl_entity,
|
|
dl_timer);
|
|
struct task_struct *p = dl_task_of(dl_se);
|
|
struct rq *rq = task_rq(p);
|
|
raw_spin_lock(&rq->lock);
|
|
|
|
/*
|
|
* We need to take care of a possible races here. In fact, the
|
|
* task might have changed its scheduling policy to something
|
|
* different from SCHED_DEADLINE or changed its reservation
|
|
* parameters (through sched_setscheduler()).
|
|
*/
|
|
if (!dl_task(p) || dl_se->dl_new)
|
|
goto unlock;
|
|
|
|
sched_clock_tick();
|
|
update_rq_clock(rq);
|
|
dl_se->dl_throttled = 0;
|
|
if (p->on_rq) {
|
|
enqueue_task_dl(rq, p, ENQUEUE_REPLENISH);
|
|
if (task_has_dl_policy(rq->curr))
|
|
check_preempt_curr_dl(rq, p, 0);
|
|
else
|
|
resched_task(rq->curr);
|
|
#ifdef CONFIG_SMP
|
|
/*
|
|
* Queueing this task back might have overloaded rq,
|
|
* check if we need to kick someone away.
|
|
*/
|
|
if (has_pushable_dl_tasks(rq))
|
|
push_dl_task(rq);
|
|
#endif
|
|
}
|
|
unlock:
|
|
raw_spin_unlock(&rq->lock);
|
|
|
|
return HRTIMER_NORESTART;
|
|
}
|
|
|
|
void init_dl_task_timer(struct sched_dl_entity *dl_se)
|
|
{
|
|
struct hrtimer *timer = &dl_se->dl_timer;
|
|
|
|
if (hrtimer_active(timer)) {
|
|
hrtimer_try_to_cancel(timer);
|
|
return;
|
|
}
|
|
|
|
hrtimer_init(timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
|
|
timer->function = dl_task_timer;
|
|
}
|
|
|
|
static
|
|
int dl_runtime_exceeded(struct rq *rq, struct sched_dl_entity *dl_se)
|
|
{
|
|
int dmiss = dl_time_before(dl_se->deadline, rq_clock(rq));
|
|
int rorun = dl_se->runtime <= 0;
|
|
|
|
if (!rorun && !dmiss)
|
|
return 0;
|
|
|
|
/*
|
|
* If we are beyond our current deadline and we are still
|
|
* executing, then we have already used some of the runtime of
|
|
* the next instance. Thus, if we do not account that, we are
|
|
* stealing bandwidth from the system at each deadline miss!
|
|
*/
|
|
if (dmiss) {
|
|
dl_se->runtime = rorun ? dl_se->runtime : 0;
|
|
dl_se->runtime -= rq_clock(rq) - dl_se->deadline;
|
|
}
|
|
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* Update the current task's runtime statistics (provided it is still
|
|
* a -deadline task and has not been removed from the dl_rq).
|
|
*/
|
|
static void update_curr_dl(struct rq *rq)
|
|
{
|
|
struct task_struct *curr = rq->curr;
|
|
struct sched_dl_entity *dl_se = &curr->dl;
|
|
u64 delta_exec;
|
|
|
|
if (!dl_task(curr) || !on_dl_rq(dl_se))
|
|
return;
|
|
|
|
/*
|
|
* Consumed budget is computed considering the time as
|
|
* observed by schedulable tasks (excluding time spent
|
|
* in hardirq context, etc.). Deadlines are instead
|
|
* computed using hard walltime. This seems to be the more
|
|
* natural solution, but the full ramifications of this
|
|
* approach need further study.
|
|
*/
|
|
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);
|
|
|
|
sched_rt_avg_update(rq, delta_exec);
|
|
|
|
dl_se->runtime -= delta_exec;
|
|
if (dl_runtime_exceeded(rq, dl_se)) {
|
|
__dequeue_task_dl(rq, curr, 0);
|
|
if (likely(start_dl_timer(dl_se, curr->dl.dl_boosted)))
|
|
dl_se->dl_throttled = 1;
|
|
else
|
|
enqueue_task_dl(rq, curr, ENQUEUE_REPLENISH);
|
|
|
|
if (!is_leftmost(curr, &rq->dl))
|
|
resched_task(curr);
|
|
}
|
|
|
|
/*
|
|
* Because -- for now -- we share the rt bandwidth, we need to
|
|
* account our runtime there too, otherwise actual rt tasks
|
|
* would be able to exceed the shared quota.
|
|
*
|
|
* Account to the root rt group for now.
|
|
*
|
|
* The solution we're working towards is having the RT groups scheduled
|
|
* using deadline servers -- however there's a few nasties to figure
|
|
* out before that can happen.
|
|
*/
|
|
if (rt_bandwidth_enabled()) {
|
|
struct rt_rq *rt_rq = &rq->rt;
|
|
|
|
raw_spin_lock(&rt_rq->rt_runtime_lock);
|
|
rt_rq->rt_time += delta_exec;
|
|
/*
|
|
* We'll let actual RT tasks worry about the overflow here, we
|
|
* have our own CBS to keep us inline -- see above.
|
|
*/
|
|
raw_spin_unlock(&rt_rq->rt_runtime_lock);
|
|
}
|
|
}
|
|
|
|
#ifdef CONFIG_SMP
|
|
|
|
static struct task_struct *pick_next_earliest_dl_task(struct rq *rq, int cpu);
|
|
|
|
static inline u64 next_deadline(struct rq *rq)
|
|
{
|
|
struct task_struct *next = pick_next_earliest_dl_task(rq, rq->cpu);
|
|
|
|
if (next && dl_prio(next->prio))
|
|
return next->dl.deadline;
|
|
else
|
|
return 0;
|
|
}
|
|
|
|
static void inc_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
|
|
{
|
|
struct rq *rq = rq_of_dl_rq(dl_rq);
|
|
|
|
if (dl_rq->earliest_dl.curr == 0 ||
|
|
dl_time_before(deadline, dl_rq->earliest_dl.curr)) {
|
|
/*
|
|
* If the dl_rq had no -deadline tasks, or if the new task
|
|
* has shorter deadline than the current one on dl_rq, we
|
|
* know that the previous earliest becomes our next earliest,
|
|
* as the new task becomes the earliest itself.
|
|
*/
|
|
dl_rq->earliest_dl.next = dl_rq->earliest_dl.curr;
|
|
dl_rq->earliest_dl.curr = deadline;
|
|
cpudl_set(&rq->rd->cpudl, rq->cpu, deadline, 1);
|
|
} else if (dl_rq->earliest_dl.next == 0 ||
|
|
dl_time_before(deadline, dl_rq->earliest_dl.next)) {
|
|
/*
|
|
* On the other hand, if the new -deadline task has a
|
|
* a later deadline than the earliest one on dl_rq, but
|
|
* it is earlier than the next (if any), we must
|
|
* recompute the next-earliest.
|
|
*/
|
|
dl_rq->earliest_dl.next = next_deadline(rq);
|
|
}
|
|
}
|
|
|
|
static void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
|
|
{
|
|
struct rq *rq = rq_of_dl_rq(dl_rq);
|
|
|
|
/*
|
|
* Since we may have removed our earliest (and/or next earliest)
|
|
* task we must recompute them.
|
|
*/
|
|
if (!dl_rq->dl_nr_running) {
|
|
dl_rq->earliest_dl.curr = 0;
|
|
dl_rq->earliest_dl.next = 0;
|
|
cpudl_set(&rq->rd->cpudl, rq->cpu, 0, 0);
|
|
} else {
|
|
struct rb_node *leftmost = dl_rq->rb_leftmost;
|
|
struct sched_dl_entity *entry;
|
|
|
|
entry = rb_entry(leftmost, struct sched_dl_entity, rb_node);
|
|
dl_rq->earliest_dl.curr = entry->deadline;
|
|
dl_rq->earliest_dl.next = next_deadline(rq);
|
|
cpudl_set(&rq->rd->cpudl, rq->cpu, entry->deadline, 1);
|
|
}
|
|
}
|
|
|
|
#else
|
|
|
|
static inline void inc_dl_deadline(struct dl_rq *dl_rq, u64 deadline) {}
|
|
static inline void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline) {}
|
|
|
|
#endif /* CONFIG_SMP */
|
|
|
|
static inline
|
|
void inc_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
|
|
{
|
|
int prio = dl_task_of(dl_se)->prio;
|
|
u64 deadline = dl_se->deadline;
|
|
|
|
WARN_ON(!dl_prio(prio));
|
|
dl_rq->dl_nr_running++;
|
|
|
|
inc_dl_deadline(dl_rq, deadline);
|
|
inc_dl_migration(dl_se, dl_rq);
|
|
}
|
|
|
|
static inline
|
|
void dec_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
|
|
{
|
|
int prio = dl_task_of(dl_se)->prio;
|
|
|
|
WARN_ON(!dl_prio(prio));
|
|
WARN_ON(!dl_rq->dl_nr_running);
|
|
dl_rq->dl_nr_running--;
|
|
|
|
dec_dl_deadline(dl_rq, dl_se->deadline);
|
|
dec_dl_migration(dl_se, dl_rq);
|
|
}
|
|
|
|
static void __enqueue_dl_entity(struct sched_dl_entity *dl_se)
|
|
{
|
|
struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
|
|
struct rb_node **link = &dl_rq->rb_root.rb_node;
|
|
struct rb_node *parent = NULL;
|
|
struct sched_dl_entity *entry;
|
|
int leftmost = 1;
|
|
|
|
BUG_ON(!RB_EMPTY_NODE(&dl_se->rb_node));
|
|
|
|
while (*link) {
|
|
parent = *link;
|
|
entry = rb_entry(parent, struct sched_dl_entity, rb_node);
|
|
if (dl_time_before(dl_se->deadline, entry->deadline))
|
|
link = &parent->rb_left;
|
|
else {
|
|
link = &parent->rb_right;
|
|
leftmost = 0;
|
|
}
|
|
}
|
|
|
|
if (leftmost)
|
|
dl_rq->rb_leftmost = &dl_se->rb_node;
|
|
|
|
rb_link_node(&dl_se->rb_node, parent, link);
|
|
rb_insert_color(&dl_se->rb_node, &dl_rq->rb_root);
|
|
|
|
inc_dl_tasks(dl_se, dl_rq);
|
|
}
|
|
|
|
static void __dequeue_dl_entity(struct sched_dl_entity *dl_se)
|
|
{
|
|
struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
|
|
|
|
if (RB_EMPTY_NODE(&dl_se->rb_node))
|
|
return;
|
|
|
|
if (dl_rq->rb_leftmost == &dl_se->rb_node) {
|
|
struct rb_node *next_node;
|
|
|
|
next_node = rb_next(&dl_se->rb_node);
|
|
dl_rq->rb_leftmost = next_node;
|
|
}
|
|
|
|
rb_erase(&dl_se->rb_node, &dl_rq->rb_root);
|
|
RB_CLEAR_NODE(&dl_se->rb_node);
|
|
|
|
dec_dl_tasks(dl_se, dl_rq);
|
|
}
|
|
|
|
static void
|
|
enqueue_dl_entity(struct sched_dl_entity *dl_se,
|
|
struct sched_dl_entity *pi_se, int flags)
|
|
{
|
|
BUG_ON(on_dl_rq(dl_se));
|
|
|
|
/*
|
|
* If this is a wakeup or a new instance, the scheduling
|
|
* parameters of the task might need updating. Otherwise,
|
|
* we want a replenishment of its runtime.
|
|
*/
|
|
if (!dl_se->dl_new && flags & ENQUEUE_REPLENISH)
|
|
replenish_dl_entity(dl_se, pi_se);
|
|
else
|
|
update_dl_entity(dl_se, pi_se);
|
|
|
|
__enqueue_dl_entity(dl_se);
|
|
}
|
|
|
|
static void dequeue_dl_entity(struct sched_dl_entity *dl_se)
|
|
{
|
|
__dequeue_dl_entity(dl_se);
|
|
}
|
|
|
|
static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags)
|
|
{
|
|
struct task_struct *pi_task = rt_mutex_get_top_task(p);
|
|
struct sched_dl_entity *pi_se = &p->dl;
|
|
|
|
/*
|
|
* Use the scheduling parameters of the top pi-waiter
|
|
* task if we have one and its (relative) deadline is
|
|
* smaller than our one... OTW we keep our runtime and
|
|
* deadline.
|
|
*/
|
|
if (pi_task && p->dl.dl_boosted && dl_prio(pi_task->normal_prio))
|
|
pi_se = &pi_task->dl;
|
|
|
|
/*
|
|
* If p is throttled, we do nothing. In fact, if it exhausted
|
|
* its budget it needs a replenishment and, since it now is on
|
|
* its rq, the bandwidth timer callback (which clearly has not
|
|
* run yet) will take care of this.
|
|
*/
|
|
if (p->dl.dl_throttled)
|
|
return;
|
|
|
|
enqueue_dl_entity(&p->dl, pi_se, flags);
|
|
|
|
if (!task_current(rq, p) && p->nr_cpus_allowed > 1)
|
|
enqueue_pushable_dl_task(rq, p);
|
|
|
|
inc_nr_running(rq);
|
|
}
|
|
|
|
static void __dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
|
|
{
|
|
dequeue_dl_entity(&p->dl);
|
|
dequeue_pushable_dl_task(rq, p);
|
|
}
|
|
|
|
static void dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
|
|
{
|
|
update_curr_dl(rq);
|
|
__dequeue_task_dl(rq, p, flags);
|
|
|
|
dec_nr_running(rq);
|
|
}
|
|
|
|
/*
|
|
* Yield task semantic for -deadline tasks is:
|
|
*
|
|
* get off from the CPU until our next instance, with
|
|
* a new runtime. This is of little use now, since we
|
|
* don't have a bandwidth reclaiming mechanism. Anyway,
|
|
* bandwidth reclaiming is planned for the future, and
|
|
* yield_task_dl will indicate that some spare budget
|
|
* is available for other task instances to use it.
|
|
*/
|
|
static void yield_task_dl(struct rq *rq)
|
|
{
|
|
struct task_struct *p = rq->curr;
|
|
|
|
/*
|
|
* We make the task go to sleep until its current deadline by
|
|
* forcing its runtime to zero. This way, update_curr_dl() stops
|
|
* it and the bandwidth timer will wake it up and will give it
|
|
* new scheduling parameters (thanks to dl_new=1).
|
|
*/
|
|
if (p->dl.runtime > 0) {
|
|
rq->curr->dl.dl_new = 1;
|
|
p->dl.runtime = 0;
|
|
}
|
|
update_curr_dl(rq);
|
|
}
|
|
|
|
#ifdef CONFIG_SMP
|
|
|
|
static int find_later_rq(struct task_struct *task);
|
|
|
|
static int
|
|
select_task_rq_dl(struct task_struct *p, int cpu, int sd_flag, int flags)
|
|
{
|
|
struct task_struct *curr;
|
|
struct rq *rq;
|
|
|
|
if (sd_flag != SD_BALANCE_WAKE && sd_flag != SD_BALANCE_FORK)
|
|
goto out;
|
|
|
|
rq = cpu_rq(cpu);
|
|
|
|
rcu_read_lock();
|
|
curr = ACCESS_ONCE(rq->curr); /* unlocked access */
|
|
|
|
/*
|
|
* If we are dealing with a -deadline task, we must
|
|
* decide where to wake it up.
|
|
* If it has a later deadline and the current task
|
|
* on this rq can't move (provided the waking task
|
|
* can!) we prefer to send it somewhere else. On the
|
|
* other hand, if it has a shorter deadline, we
|
|
* try to make it stay here, it might be important.
|
|
*/
|
|
if (unlikely(dl_task(curr)) &&
|
|
(curr->nr_cpus_allowed < 2 ||
|
|
!dl_entity_preempt(&p->dl, &curr->dl)) &&
|
|
(p->nr_cpus_allowed > 1)) {
|
|
int target = find_later_rq(p);
|
|
|
|
if (target != -1)
|
|
cpu = target;
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
out:
|
|
return cpu;
|
|
}
|
|
|
|
static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
|
|
{
|
|
/*
|
|
* Current can't be migrated, useless to reschedule,
|
|
* let's hope p can move out.
|
|
*/
|
|
if (rq->curr->nr_cpus_allowed == 1 ||
|
|
cpudl_find(&rq->rd->cpudl, rq->curr, NULL) == -1)
|
|
return;
|
|
|
|
/*
|
|
* p is migratable, so let's not schedule it and
|
|
* see if it is pushed or pulled somewhere else.
|
|
*/
|
|
if (p->nr_cpus_allowed != 1 &&
|
|
cpudl_find(&rq->rd->cpudl, p, NULL) != -1)
|
|
return;
|
|
|
|
resched_task(rq->curr);
|
|
}
|
|
|
|
#endif /* CONFIG_SMP */
|
|
|
|
/*
|
|
* Only called when both the current and waking task are -deadline
|
|
* tasks.
|
|
*/
|
|
static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
|
|
int flags)
|
|
{
|
|
if (dl_entity_preempt(&p->dl, &rq->curr->dl)) {
|
|
resched_task(rq->curr);
|
|
return;
|
|
}
|
|
|
|
#ifdef CONFIG_SMP
|
|
/*
|
|
* In the unlikely case current and p have the same deadline
|
|
* let us try to decide what's the best thing to do...
|
|
*/
|
|
if ((p->dl.deadline == rq->curr->dl.deadline) &&
|
|
!test_tsk_need_resched(rq->curr))
|
|
check_preempt_equal_dl(rq, p);
|
|
#endif /* CONFIG_SMP */
|
|
}
|
|
|
|
#ifdef CONFIG_SCHED_HRTICK
|
|
static void start_hrtick_dl(struct rq *rq, struct task_struct *p)
|
|
{
|
|
s64 delta = p->dl.dl_runtime - p->dl.runtime;
|
|
|
|
if (delta > 10000)
|
|
hrtick_start(rq, p->dl.runtime);
|
|
}
|
|
#endif
|
|
|
|
static struct sched_dl_entity *pick_next_dl_entity(struct rq *rq,
|
|
struct dl_rq *dl_rq)
|
|
{
|
|
struct rb_node *left = dl_rq->rb_leftmost;
|
|
|
|
if (!left)
|
|
return NULL;
|
|
|
|
return rb_entry(left, struct sched_dl_entity, rb_node);
|
|
}
|
|
|
|
struct task_struct *pick_next_task_dl(struct rq *rq)
|
|
{
|
|
struct sched_dl_entity *dl_se;
|
|
struct task_struct *p;
|
|
struct dl_rq *dl_rq;
|
|
|
|
dl_rq = &rq->dl;
|
|
|
|
if (unlikely(!dl_rq->dl_nr_running))
|
|
return NULL;
|
|
|
|
dl_se = pick_next_dl_entity(rq, dl_rq);
|
|
BUG_ON(!dl_se);
|
|
|
|
p = dl_task_of(dl_se);
|
|
p->se.exec_start = rq_clock_task(rq);
|
|
|
|
/* Running task will never be pushed. */
|
|
dequeue_pushable_dl_task(rq, p);
|
|
|
|
#ifdef CONFIG_SCHED_HRTICK
|
|
if (hrtick_enabled(rq))
|
|
start_hrtick_dl(rq, p);
|
|
#endif
|
|
|
|
#ifdef CONFIG_SMP
|
|
rq->post_schedule = has_pushable_dl_tasks(rq);
|
|
#endif /* CONFIG_SMP */
|
|
|
|
return p;
|
|
}
|
|
|
|
static void put_prev_task_dl(struct rq *rq, struct task_struct *p)
|
|
{
|
|
update_curr_dl(rq);
|
|
|
|
if (on_dl_rq(&p->dl) && p->nr_cpus_allowed > 1)
|
|
enqueue_pushable_dl_task(rq, p);
|
|
}
|
|
|
|
static void task_tick_dl(struct rq *rq, struct task_struct *p, int queued)
|
|
{
|
|
update_curr_dl(rq);
|
|
|
|
#ifdef CONFIG_SCHED_HRTICK
|
|
if (hrtick_enabled(rq) && queued && p->dl.runtime > 0)
|
|
start_hrtick_dl(rq, p);
|
|
#endif
|
|
}
|
|
|
|
static void task_fork_dl(struct task_struct *p)
|
|
{
|
|
/*
|
|
* SCHED_DEADLINE tasks cannot fork and this is achieved through
|
|
* sched_fork()
|
|
*/
|
|
}
|
|
|
|
static void task_dead_dl(struct task_struct *p)
|
|
{
|
|
struct hrtimer *timer = &p->dl.dl_timer;
|
|
struct dl_bw *dl_b = dl_bw_of(task_cpu(p));
|
|
|
|
/*
|
|
* Since we are TASK_DEAD we won't slip out of the domain!
|
|
*/
|
|
raw_spin_lock_irq(&dl_b->lock);
|
|
dl_b->total_bw -= p->dl.dl_bw;
|
|
raw_spin_unlock_irq(&dl_b->lock);
|
|
|
|
hrtimer_cancel(timer);
|
|
}
|
|
|
|
static void set_curr_task_dl(struct rq *rq)
|
|
{
|
|
struct task_struct *p = rq->curr;
|
|
|
|
p->se.exec_start = rq_clock_task(rq);
|
|
|
|
/* You can't push away the running task */
|
|
dequeue_pushable_dl_task(rq, p);
|
|
}
|
|
|
|
#ifdef CONFIG_SMP
|
|
|
|
/* Only try algorithms three times */
|
|
#define DL_MAX_TRIES 3
|
|
|
|
static int pick_dl_task(struct rq *rq, struct task_struct *p, int cpu)
|
|
{
|
|
if (!task_running(rq, p) &&
|
|
(cpu < 0 || cpumask_test_cpu(cpu, &p->cpus_allowed)) &&
|
|
(p->nr_cpus_allowed > 1))
|
|
return 1;
|
|
|
|
return 0;
|
|
}
|
|
|
|
/* Returns the second earliest -deadline task, NULL otherwise */
|
|
static struct task_struct *pick_next_earliest_dl_task(struct rq *rq, int cpu)
|
|
{
|
|
struct rb_node *next_node = rq->dl.rb_leftmost;
|
|
struct sched_dl_entity *dl_se;
|
|
struct task_struct *p = NULL;
|
|
|
|
next_node:
|
|
next_node = rb_next(next_node);
|
|
if (next_node) {
|
|
dl_se = rb_entry(next_node, struct sched_dl_entity, rb_node);
|
|
p = dl_task_of(dl_se);
|
|
|
|
if (pick_dl_task(rq, p, cpu))
|
|
return p;
|
|
|
|
goto next_node;
|
|
}
|
|
|
|
return NULL;
|
|
}
|
|
|
|
static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl);
|
|
|
|
static int find_later_rq(struct task_struct *task)
|
|
{
|
|
struct sched_domain *sd;
|
|
struct cpumask *later_mask = __get_cpu_var(local_cpu_mask_dl);
|
|
int this_cpu = smp_processor_id();
|
|
int best_cpu, cpu = task_cpu(task);
|
|
|
|
/* Make sure the mask is initialized first */
|
|
if (unlikely(!later_mask))
|
|
return -1;
|
|
|
|
if (task->nr_cpus_allowed == 1)
|
|
return -1;
|
|
|
|
best_cpu = cpudl_find(&task_rq(task)->rd->cpudl,
|
|
task, later_mask);
|
|
if (best_cpu == -1)
|
|
return -1;
|
|
|
|
/*
|
|
* If we are here, some target has been found,
|
|
* the most suitable of which is cached in best_cpu.
|
|
* This is, among the runqueues where the current tasks
|
|
* have later deadlines than the task's one, the rq
|
|
* with the latest possible one.
|
|
*
|
|
* Now we check how well this matches with task's
|
|
* affinity and system topology.
|
|
*
|
|
* The last cpu where the task run is our first
|
|
* guess, since it is most likely cache-hot there.
|
|
*/
|
|
if (cpumask_test_cpu(cpu, later_mask))
|
|
return cpu;
|
|
/*
|
|
* Check if this_cpu is to be skipped (i.e., it is
|
|
* not in the mask) or not.
|
|
*/
|
|
if (!cpumask_test_cpu(this_cpu, later_mask))
|
|
this_cpu = -1;
|
|
|
|
rcu_read_lock();
|
|
for_each_domain(cpu, sd) {
|
|
if (sd->flags & SD_WAKE_AFFINE) {
|
|
|
|
/*
|
|
* If possible, preempting this_cpu is
|
|
* cheaper than migrating.
|
|
*/
|
|
if (this_cpu != -1 &&
|
|
cpumask_test_cpu(this_cpu, sched_domain_span(sd))) {
|
|
rcu_read_unlock();
|
|
return this_cpu;
|
|
}
|
|
|
|
/*
|
|
* Last chance: if best_cpu is valid and is
|
|
* in the mask, that becomes our choice.
|
|
*/
|
|
if (best_cpu < nr_cpu_ids &&
|
|
cpumask_test_cpu(best_cpu, sched_domain_span(sd))) {
|
|
rcu_read_unlock();
|
|
return best_cpu;
|
|
}
|
|
}
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
/*
|
|
* At this point, all our guesses failed, we just return
|
|
* 'something', and let the caller sort the things out.
|
|
*/
|
|
if (this_cpu != -1)
|
|
return this_cpu;
|
|
|
|
cpu = cpumask_any(later_mask);
|
|
if (cpu < nr_cpu_ids)
|
|
return cpu;
|
|
|
|
return -1;
|
|
}
|
|
|
|
/* Locks the rq it finds */
|
|
static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq)
|
|
{
|
|
struct rq *later_rq = NULL;
|
|
int tries;
|
|
int cpu;
|
|
|
|
for (tries = 0; tries < DL_MAX_TRIES; tries++) {
|
|
cpu = find_later_rq(task);
|
|
|
|
if ((cpu == -1) || (cpu == rq->cpu))
|
|
break;
|
|
|
|
later_rq = cpu_rq(cpu);
|
|
|
|
/* Retry if something changed. */
|
|
if (double_lock_balance(rq, later_rq)) {
|
|
if (unlikely(task_rq(task) != rq ||
|
|
!cpumask_test_cpu(later_rq->cpu,
|
|
&task->cpus_allowed) ||
|
|
task_running(rq, task) || !task->on_rq)) {
|
|
double_unlock_balance(rq, later_rq);
|
|
later_rq = NULL;
|
|
break;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* If the rq we found has no -deadline task, or
|
|
* its earliest one has a later deadline than our
|
|
* task, the rq is a good one.
|
|
*/
|
|
if (!later_rq->dl.dl_nr_running ||
|
|
dl_time_before(task->dl.deadline,
|
|
later_rq->dl.earliest_dl.curr))
|
|
break;
|
|
|
|
/* Otherwise we try again. */
|
|
double_unlock_balance(rq, later_rq);
|
|
later_rq = NULL;
|
|
}
|
|
|
|
return later_rq;
|
|
}
|
|
|
|
static struct task_struct *pick_next_pushable_dl_task(struct rq *rq)
|
|
{
|
|
struct task_struct *p;
|
|
|
|
if (!has_pushable_dl_tasks(rq))
|
|
return NULL;
|
|
|
|
p = rb_entry(rq->dl.pushable_dl_tasks_leftmost,
|
|
struct task_struct, pushable_dl_tasks);
|
|
|
|
BUG_ON(rq->cpu != task_cpu(p));
|
|
BUG_ON(task_current(rq, p));
|
|
BUG_ON(p->nr_cpus_allowed <= 1);
|
|
|
|
BUG_ON(!p->on_rq);
|
|
BUG_ON(!dl_task(p));
|
|
|
|
return p;
|
|
}
|
|
|
|
/*
|
|
* See if the non running -deadline tasks on this rq
|
|
* can be sent to some other CPU where they can preempt
|
|
* and start executing.
|
|
*/
|
|
static int push_dl_task(struct rq *rq)
|
|
{
|
|
struct task_struct *next_task;
|
|
struct rq *later_rq;
|
|
|
|
if (!rq->dl.overloaded)
|
|
return 0;
|
|
|
|
next_task = pick_next_pushable_dl_task(rq);
|
|
if (!next_task)
|
|
return 0;
|
|
|
|
retry:
|
|
if (unlikely(next_task == rq->curr)) {
|
|
WARN_ON(1);
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* If next_task preempts rq->curr, and rq->curr
|
|
* can move away, it makes sense to just reschedule
|
|
* without going further in pushing next_task.
|
|
*/
|
|
if (dl_task(rq->curr) &&
|
|
dl_time_before(next_task->dl.deadline, rq->curr->dl.deadline) &&
|
|
rq->curr->nr_cpus_allowed > 1) {
|
|
resched_task(rq->curr);
|
|
return 0;
|
|
}
|
|
|
|
/* We might release rq lock */
|
|
get_task_struct(next_task);
|
|
|
|
/* Will lock the rq it'll find */
|
|
later_rq = find_lock_later_rq(next_task, rq);
|
|
if (!later_rq) {
|
|
struct task_struct *task;
|
|
|
|
/*
|
|
* We must check all this again, since
|
|
* find_lock_later_rq releases rq->lock and it is
|
|
* then possible that next_task has migrated.
|
|
*/
|
|
task = pick_next_pushable_dl_task(rq);
|
|
if (task_cpu(next_task) == rq->cpu && task == next_task) {
|
|
/*
|
|
* The task is still there. We don't try
|
|
* again, some other cpu will pull it when ready.
|
|
*/
|
|
dequeue_pushable_dl_task(rq, next_task);
|
|
goto out;
|
|
}
|
|
|
|
if (!task)
|
|
/* No more tasks */
|
|
goto out;
|
|
|
|
put_task_struct(next_task);
|
|
next_task = task;
|
|
goto retry;
|
|
}
|
|
|
|
deactivate_task(rq, next_task, 0);
|
|
set_task_cpu(next_task, later_rq->cpu);
|
|
activate_task(later_rq, next_task, 0);
|
|
|
|
resched_task(later_rq->curr);
|
|
|
|
double_unlock_balance(rq, later_rq);
|
|
|
|
out:
|
|
put_task_struct(next_task);
|
|
|
|
return 1;
|
|
}
|
|
|
|
static void push_dl_tasks(struct rq *rq)
|
|
{
|
|
/* Terminates as it moves a -deadline task */
|
|
while (push_dl_task(rq))
|
|
;
|
|
}
|
|
|
|
static int pull_dl_task(struct rq *this_rq)
|
|
{
|
|
int this_cpu = this_rq->cpu, ret = 0, cpu;
|
|
struct task_struct *p;
|
|
struct rq *src_rq;
|
|
u64 dmin = LONG_MAX;
|
|
|
|
if (likely(!dl_overloaded(this_rq)))
|
|
return 0;
|
|
|
|
/*
|
|
* Match the barrier from dl_set_overloaded; this guarantees that if we
|
|
* see overloaded we must also see the dlo_mask bit.
|
|
*/
|
|
smp_rmb();
|
|
|
|
for_each_cpu(cpu, this_rq->rd->dlo_mask) {
|
|
if (this_cpu == cpu)
|
|
continue;
|
|
|
|
src_rq = cpu_rq(cpu);
|
|
|
|
/*
|
|
* It looks racy, abd it is! However, as in sched_rt.c,
|
|
* we are fine with this.
|
|
*/
|
|
if (this_rq->dl.dl_nr_running &&
|
|
dl_time_before(this_rq->dl.earliest_dl.curr,
|
|
src_rq->dl.earliest_dl.next))
|
|
continue;
|
|
|
|
/* Might drop this_rq->lock */
|
|
double_lock_balance(this_rq, src_rq);
|
|
|
|
/*
|
|
* If there are no more pullable tasks on the
|
|
* rq, we're done with it.
|
|
*/
|
|
if (src_rq->dl.dl_nr_running <= 1)
|
|
goto skip;
|
|
|
|
p = pick_next_earliest_dl_task(src_rq, this_cpu);
|
|
|
|
/*
|
|
* We found a task to be pulled if:
|
|
* - it preempts our current (if there's one),
|
|
* - it will preempt the last one we pulled (if any).
|
|
*/
|
|
if (p && dl_time_before(p->dl.deadline, dmin) &&
|
|
(!this_rq->dl.dl_nr_running ||
|
|
dl_time_before(p->dl.deadline,
|
|
this_rq->dl.earliest_dl.curr))) {
|
|
WARN_ON(p == src_rq->curr);
|
|
WARN_ON(!p->on_rq);
|
|
|
|
/*
|
|
* Then we pull iff p has actually an earlier
|
|
* deadline than the current task of its runqueue.
|
|
*/
|
|
if (dl_time_before(p->dl.deadline,
|
|
src_rq->curr->dl.deadline))
|
|
goto skip;
|
|
|
|
ret = 1;
|
|
|
|
deactivate_task(src_rq, p, 0);
|
|
set_task_cpu(p, this_cpu);
|
|
activate_task(this_rq, p, 0);
|
|
dmin = p->dl.deadline;
|
|
|
|
/* Is there any other task even earlier? */
|
|
}
|
|
skip:
|
|
double_unlock_balance(this_rq, src_rq);
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
|
|
static void pre_schedule_dl(struct rq *rq, struct task_struct *prev)
|
|
{
|
|
/* Try to pull other tasks here */
|
|
if (dl_task(prev))
|
|
pull_dl_task(rq);
|
|
}
|
|
|
|
static void post_schedule_dl(struct rq *rq)
|
|
{
|
|
push_dl_tasks(rq);
|
|
}
|
|
|
|
/*
|
|
* Since the task is not running and a reschedule is not going to happen
|
|
* anytime soon on its runqueue, we try pushing it away now.
|
|
*/
|
|
static void task_woken_dl(struct rq *rq, struct task_struct *p)
|
|
{
|
|
if (!task_running(rq, p) &&
|
|
!test_tsk_need_resched(rq->curr) &&
|
|
has_pushable_dl_tasks(rq) &&
|
|
p->nr_cpus_allowed > 1 &&
|
|
dl_task(rq->curr) &&
|
|
(rq->curr->nr_cpus_allowed < 2 ||
|
|
dl_entity_preempt(&rq->curr->dl, &p->dl))) {
|
|
push_dl_tasks(rq);
|
|
}
|
|
}
|
|
|
|
static void set_cpus_allowed_dl(struct task_struct *p,
|
|
const struct cpumask *new_mask)
|
|
{
|
|
struct rq *rq;
|
|
int weight;
|
|
|
|
BUG_ON(!dl_task(p));
|
|
|
|
/*
|
|
* Update only if the task is actually running (i.e.,
|
|
* it is on the rq AND it is not throttled).
|
|
*/
|
|
if (!on_dl_rq(&p->dl))
|
|
return;
|
|
|
|
weight = cpumask_weight(new_mask);
|
|
|
|
/*
|
|
* Only update if the process changes its state from whether it
|
|
* can migrate or not.
|
|
*/
|
|
if ((p->nr_cpus_allowed > 1) == (weight > 1))
|
|
return;
|
|
|
|
rq = task_rq(p);
|
|
|
|
/*
|
|
* The process used to be able to migrate OR it can now migrate
|
|
*/
|
|
if (weight <= 1) {
|
|
if (!task_current(rq, p))
|
|
dequeue_pushable_dl_task(rq, p);
|
|
BUG_ON(!rq->dl.dl_nr_migratory);
|
|
rq->dl.dl_nr_migratory--;
|
|
} else {
|
|
if (!task_current(rq, p))
|
|
enqueue_pushable_dl_task(rq, p);
|
|
rq->dl.dl_nr_migratory++;
|
|
}
|
|
|
|
update_dl_migration(&rq->dl);
|
|
}
|
|
|
|
/* Assumes rq->lock is held */
|
|
static void rq_online_dl(struct rq *rq)
|
|
{
|
|
if (rq->dl.overloaded)
|
|
dl_set_overload(rq);
|
|
|
|
if (rq->dl.dl_nr_running > 0)
|
|
cpudl_set(&rq->rd->cpudl, rq->cpu, rq->dl.earliest_dl.curr, 1);
|
|
}
|
|
|
|
/* Assumes rq->lock is held */
|
|
static void rq_offline_dl(struct rq *rq)
|
|
{
|
|
if (rq->dl.overloaded)
|
|
dl_clear_overload(rq);
|
|
|
|
cpudl_set(&rq->rd->cpudl, rq->cpu, 0, 0);
|
|
}
|
|
|
|
void init_sched_dl_class(void)
|
|
{
|
|
unsigned int i;
|
|
|
|
for_each_possible_cpu(i)
|
|
zalloc_cpumask_var_node(&per_cpu(local_cpu_mask_dl, i),
|
|
GFP_KERNEL, cpu_to_node(i));
|
|
}
|
|
|
|
#endif /* CONFIG_SMP */
|
|
|
|
static void switched_from_dl(struct rq *rq, struct task_struct *p)
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{
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if (hrtimer_active(&p->dl.dl_timer) && !dl_policy(p->policy))
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hrtimer_try_to_cancel(&p->dl.dl_timer);
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#ifdef CONFIG_SMP
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/*
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* Since this might be the only -deadline task on the rq,
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* this is the right place to try to pull some other one
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* from an overloaded cpu, if any.
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*/
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if (!rq->dl.dl_nr_running)
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pull_dl_task(rq);
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#endif
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}
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/*
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* When switching to -deadline, we may overload the rq, then
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* we try to push someone off, if possible.
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*/
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static void switched_to_dl(struct rq *rq, struct task_struct *p)
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{
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int check_resched = 1;
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/*
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* If p is throttled, don't consider the possibility
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* of preempting rq->curr, the check will be done right
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* after its runtime will get replenished.
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*/
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if (unlikely(p->dl.dl_throttled))
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return;
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if (p->on_rq || rq->curr != p) {
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#ifdef CONFIG_SMP
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if (rq->dl.overloaded && push_dl_task(rq) && rq != task_rq(p))
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/* Only reschedule if pushing failed */
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check_resched = 0;
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#endif /* CONFIG_SMP */
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if (check_resched && task_has_dl_policy(rq->curr))
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check_preempt_curr_dl(rq, p, 0);
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}
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}
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/*
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* If the scheduling parameters of a -deadline task changed,
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* a push or pull operation might be needed.
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*/
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static void prio_changed_dl(struct rq *rq, struct task_struct *p,
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int oldprio)
|
|
{
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if (p->on_rq || rq->curr == p) {
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#ifdef CONFIG_SMP
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|
/*
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|
* This might be too much, but unfortunately
|
|
* we don't have the old deadline value, and
|
|
* we can't argue if the task is increasing
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* or lowering its prio, so...
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|
*/
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if (!rq->dl.overloaded)
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pull_dl_task(rq);
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|
|
|
/*
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* If we now have a earlier deadline task than p,
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|
* then reschedule, provided p is still on this
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|
* runqueue.
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|
*/
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if (dl_time_before(rq->dl.earliest_dl.curr, p->dl.deadline) &&
|
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rq->curr == p)
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|
resched_task(p);
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#else
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|
/*
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|
* Again, we don't know if p has a earlier
|
|
* or later deadline, so let's blindly set a
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|
* (maybe not needed) rescheduling point.
|
|
*/
|
|
resched_task(p);
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|
#endif /* CONFIG_SMP */
|
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} else
|
|
switched_to_dl(rq, p);
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|
}
|
|
|
|
const struct sched_class dl_sched_class = {
|
|
.next = &rt_sched_class,
|
|
.enqueue_task = enqueue_task_dl,
|
|
.dequeue_task = dequeue_task_dl,
|
|
.yield_task = yield_task_dl,
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|
|
|
.check_preempt_curr = check_preempt_curr_dl,
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|
|
|
.pick_next_task = pick_next_task_dl,
|
|
.put_prev_task = put_prev_task_dl,
|
|
|
|
#ifdef CONFIG_SMP
|
|
.select_task_rq = select_task_rq_dl,
|
|
.set_cpus_allowed = set_cpus_allowed_dl,
|
|
.rq_online = rq_online_dl,
|
|
.rq_offline = rq_offline_dl,
|
|
.pre_schedule = pre_schedule_dl,
|
|
.post_schedule = post_schedule_dl,
|
|
.task_woken = task_woken_dl,
|
|
#endif
|
|
|
|
.set_curr_task = set_curr_task_dl,
|
|
.task_tick = task_tick_dl,
|
|
.task_fork = task_fork_dl,
|
|
.task_dead = task_dead_dl,
|
|
|
|
.prio_changed = prio_changed_dl,
|
|
.switched_from = switched_from_dl,
|
|
.switched_to = switched_to_dl,
|
|
};
|