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![Steven Rostedt (VMware)](/assets/img/avatar_default.png)
I was testing Daniel's changes with his test case, and tweaked it a little. Instead of having the runtime equal to the deadline, I increased the deadline ten fold. Daniel's test case had: attr.sched_runtime = 2 * 1000 * 1000; /* 2 ms */ attr.sched_deadline = 2 * 1000 * 1000; /* 2 ms */ attr.sched_period = 2 * 1000 * 1000 * 1000; /* 2 s */ To make it more interesting, I changed it to: attr.sched_runtime = 2 * 1000 * 1000; /* 2 ms */ attr.sched_deadline = 20 * 1000 * 1000; /* 20 ms */ attr.sched_period = 2 * 1000 * 1000 * 1000; /* 2 s */ The results were rather surprising. The behavior that Daniel's patch was fixing came back. The task started using much more than .1% of the CPU. More like 20%. Looking into this I found that it was due to the dl_entity_overflow() constantly returning true. That's because it uses the relative period against relative runtime vs the absolute deadline against absolute runtime. runtime / (deadline - t) > dl_runtime / dl_period There's even a comment mentioning this, and saying that when relative deadline equals relative period, that the equation is the same as using deadline instead of period. That comment is backwards! What we really want is: runtime / (deadline - t) > dl_runtime / dl_deadline We care about if the runtime can make its deadline, not its period. And then we can say "when the deadline equals the period, the equation is the same as using dl_period instead of dl_deadline". After correcting this, now when the task gets enqueued, it can throttle correctly, and Daniel's fix to the throttling of sleeping deadline tasks works even when the runtime and deadline are not the same. Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com> Cc: Juri Lelli <juri.lelli@arm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Luca Abeni <luca.abeni@santannapisa.it> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Romulo Silva de Oliveira <romulo.deoliveira@ufsc.br> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tommaso Cucinotta <tommaso.cucinotta@sssup.it> Link: http://lkml.kernel.org/r/02135a27f1ae3fe5fd032568a5a2f370e190e8d7.1488392936.git.bristot@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
1864 lines
48 KiB
C
1864 lines
48 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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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)
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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_running > 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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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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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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dl_rq->earliest_dl.next = p->dl.deadline;
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}
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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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if (next_node) {
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dl_rq->earliest_dl.next = rb_entry(next_node,
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struct task_struct, pushable_dl_tasks)->dl.deadline;
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}
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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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static inline bool need_pull_dl_task(struct rq *rq, struct task_struct *prev)
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{
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return dl_task(prev);
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}
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static DEFINE_PER_CPU(struct callback_head, dl_push_head);
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static DEFINE_PER_CPU(struct callback_head, dl_pull_head);
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static void push_dl_tasks(struct rq *);
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static void pull_dl_task(struct rq *);
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static inline void queue_push_tasks(struct rq *rq)
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{
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if (!has_pushable_dl_tasks(rq))
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return;
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queue_balance_callback(rq, &per_cpu(dl_push_head, rq->cpu), push_dl_tasks);
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}
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static inline void queue_pull_task(struct rq *rq)
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{
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queue_balance_callback(rq, &per_cpu(dl_pull_head, rq->cpu), pull_dl_task);
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}
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static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq);
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static struct rq *dl_task_offline_migration(struct rq *rq, struct task_struct *p)
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{
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struct rq *later_rq = NULL;
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later_rq = find_lock_later_rq(p, rq);
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if (!later_rq) {
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int cpu;
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/*
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* If we cannot preempt any rq, fall back to pick any
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* online cpu.
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*/
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cpu = cpumask_any_and(cpu_active_mask, &p->cpus_allowed);
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if (cpu >= nr_cpu_ids) {
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/*
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* Fail to find any suitable cpu.
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* The task will never come back!
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*/
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BUG_ON(dl_bandwidth_enabled());
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/*
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* If admission control is disabled we
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* try a little harder to let the task
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* run.
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*/
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cpu = cpumask_any(cpu_active_mask);
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}
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later_rq = cpu_rq(cpu);
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double_lock_balance(rq, later_rq);
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}
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set_task_cpu(p, later_rq->cpu);
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double_unlock_balance(later_rq, rq);
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return later_rq;
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}
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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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static inline bool need_pull_dl_task(struct rq *rq, struct task_struct *prev)
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{
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return false;
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}
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static inline void pull_dl_task(struct rq *rq)
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{
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}
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static inline void queue_push_tasks(struct rq *rq)
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{
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}
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static inline void queue_pull_task(struct rq *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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{
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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_boosted);
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WARN_ON(dl_time_before(rq_clock(rq), dl_se->deadline));
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/*
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* We are racing with the deadline timer. So, do nothing because
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* the deadline timer handler will take care of properly recharging
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* the runtime and postponing the deadline
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*/
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if (dl_se->dl_throttled)
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return;
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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) + dl_se->dl_deadline;
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dl_se->runtime = dl_se->dl_runtime;
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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_setattr().
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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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if (dl_se->dl_yielded && dl_se->runtime > 0)
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dl_se->runtime = 0;
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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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printk_deferred_once("sched: DL replenish lagged too much\n");
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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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if (dl_se->dl_yielded)
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dl_se->dl_yielded = 0;
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if (dl_se->dl_throttled)
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dl_se->dl_throttled = 0;
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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_deadline ,
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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 deadline. For
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* task with deadline equal to period this is the same of using
|
|
* dl_period instead of dl_deadline in the equation above.
|
|
*/
|
|
static bool dl_entity_overflow(struct sched_dl_entity *dl_se,
|
|
struct sched_dl_entity *pi_se, u64 t)
|
|
{
|
|
u64 left, right;
|
|
|
|
/*
|
|
* left and right are the two sides of the equation above,
|
|
* after a bit of shuffling to use multiplications instead
|
|
* of divisions.
|
|
*
|
|
* Note that none of the time values involved in the two
|
|
* multiplications are absolute: dl_deadline and dl_runtime
|
|
* are the relative deadline and the maximum runtime of each
|
|
* instance, runtime is the runtime left for the last instance
|
|
* and (deadline - t), since t is rq->clock, is the time left
|
|
* to the (absolute) deadline. Even if overflowing the u64 type
|
|
* is very unlikely to occur in both cases, here we scale down
|
|
* as we want to avoid that risk at all. Scaling down by 10
|
|
* means that we reduce granularity to 1us. We are fine with it,
|
|
* since this is only a true/false check and, anyway, thinking
|
|
* of anything below microseconds resolution is actually fiction
|
|
* (but still we want to give the user that illusion >;).
|
|
*/
|
|
left = (pi_se->dl_deadline >> DL_SCALE) * (dl_se->runtime >> DL_SCALE);
|
|
right = ((dl_se->deadline - t) >> DL_SCALE) *
|
|
(pi_se->dl_runtime >> DL_SCALE);
|
|
|
|
return dl_time_before(right, left);
|
|
}
|
|
|
|
/*
|
|
* When a -deadline entity is queued back on the runqueue, its runtime and
|
|
* deadline might need updating.
|
|
*
|
|
* The policy here is that we update the deadline of the entity only if:
|
|
* - the current deadline is in the past,
|
|
* - using the remaining runtime with the current deadline would make
|
|
* the entity exceed its bandwidth.
|
|
*/
|
|
static void update_dl_entity(struct sched_dl_entity *dl_se,
|
|
struct sched_dl_entity *pi_se)
|
|
{
|
|
struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
|
|
struct rq *rq = rq_of_dl_rq(dl_rq);
|
|
|
|
if (dl_time_before(dl_se->deadline, rq_clock(rq)) ||
|
|
dl_entity_overflow(dl_se, pi_se, rq_clock(rq))) {
|
|
dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
|
|
dl_se->runtime = pi_se->dl_runtime;
|
|
}
|
|
}
|
|
|
|
static inline u64 dl_next_period(struct sched_dl_entity *dl_se)
|
|
{
|
|
return dl_se->deadline - dl_se->dl_deadline + dl_se->dl_period;
|
|
}
|
|
|
|
/*
|
|
* If the entity depleted all its runtime, and if we want it to sleep
|
|
* while waiting for some new execution time to become available, we
|
|
* set the bandwidth replenishment timer to the replenishment instant
|
|
* and try to activate it.
|
|
*
|
|
* Notice that it is important for the caller to know if the timer
|
|
* actually started or not (i.e., the replenishment instant is in
|
|
* the future or in the past).
|
|
*/
|
|
static int start_dl_timer(struct task_struct *p)
|
|
{
|
|
struct sched_dl_entity *dl_se = &p->dl;
|
|
struct hrtimer *timer = &dl_se->dl_timer;
|
|
struct rq *rq = task_rq(p);
|
|
ktime_t now, act;
|
|
s64 delta;
|
|
|
|
lockdep_assert_held(&rq->lock);
|
|
|
|
/*
|
|
* We want the timer to fire at the deadline, but considering
|
|
* that it is actually coming from rq->clock and not from
|
|
* hrtimer's time base reading.
|
|
*/
|
|
act = ns_to_ktime(dl_next_period(dl_se));
|
|
now = hrtimer_cb_get_time(timer);
|
|
delta = ktime_to_ns(now) - rq_clock(rq);
|
|
act = ktime_add_ns(act, delta);
|
|
|
|
/*
|
|
* If the expiry time already passed, e.g., because the value
|
|
* chosen as the deadline is too small, don't even try to
|
|
* start the timer in the past!
|
|
*/
|
|
if (ktime_us_delta(act, now) < 0)
|
|
return 0;
|
|
|
|
/*
|
|
* !enqueued will guarantee another callback; even if one is already in
|
|
* progress. This ensures a balanced {get,put}_task_struct().
|
|
*
|
|
* The race against __run_timer() clearing the enqueued state is
|
|
* harmless because we're holding task_rq()->lock, therefore the timer
|
|
* expiring after we've done the check will wait on its task_rq_lock()
|
|
* and observe our state.
|
|
*/
|
|
if (!hrtimer_is_queued(timer)) {
|
|
get_task_struct(p);
|
|
hrtimer_start(timer, act, HRTIMER_MODE_ABS);
|
|
}
|
|
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* 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_flags rf;
|
|
struct rq *rq;
|
|
|
|
rq = task_rq_lock(p, &rf);
|
|
|
|
/*
|
|
* The task might have changed its scheduling policy to something
|
|
* different than SCHED_DEADLINE (through switched_from_dl()).
|
|
*/
|
|
if (!dl_task(p)) {
|
|
__dl_clear_params(p);
|
|
goto unlock;
|
|
}
|
|
|
|
/*
|
|
* The task might have been boosted by someone else and might be in the
|
|
* boosting/deboosting path, its not throttled.
|
|
*/
|
|
if (dl_se->dl_boosted)
|
|
goto unlock;
|
|
|
|
/*
|
|
* Spurious timer due to start_dl_timer() race; or we already received
|
|
* a replenishment from rt_mutex_setprio().
|
|
*/
|
|
if (!dl_se->dl_throttled)
|
|
goto unlock;
|
|
|
|
sched_clock_tick();
|
|
update_rq_clock(rq);
|
|
|
|
/*
|
|
* If the throttle happened during sched-out; like:
|
|
*
|
|
* schedule()
|
|
* deactivate_task()
|
|
* dequeue_task_dl()
|
|
* update_curr_dl()
|
|
* start_dl_timer()
|
|
* __dequeue_task_dl()
|
|
* prev->on_rq = 0;
|
|
*
|
|
* We can be both throttled and !queued. Replenish the counter
|
|
* but do not enqueue -- wait for our wakeup to do that.
|
|
*/
|
|
if (!task_on_rq_queued(p)) {
|
|
replenish_dl_entity(dl_se, dl_se);
|
|
goto unlock;
|
|
}
|
|
|
|
#ifdef CONFIG_SMP
|
|
if (unlikely(!rq->online)) {
|
|
/*
|
|
* If the runqueue is no longer available, migrate the
|
|
* task elsewhere. This necessarily changes rq.
|
|
*/
|
|
lockdep_unpin_lock(&rq->lock, rf.cookie);
|
|
rq = dl_task_offline_migration(rq, p);
|
|
rf.cookie = lockdep_pin_lock(&rq->lock);
|
|
update_rq_clock(rq);
|
|
|
|
/*
|
|
* Now that the task has been migrated to the new RQ and we
|
|
* have that locked, proceed as normal and enqueue the task
|
|
* there.
|
|
*/
|
|
}
|
|
#endif
|
|
|
|
enqueue_task_dl(rq, p, ENQUEUE_REPLENISH);
|
|
if (dl_task(rq->curr))
|
|
check_preempt_curr_dl(rq, p, 0);
|
|
else
|
|
resched_curr(rq);
|
|
|
|
#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)) {
|
|
/*
|
|
* Nothing relies on rq->lock after this, so its safe to drop
|
|
* rq->lock.
|
|
*/
|
|
rq_unpin_lock(rq, &rf);
|
|
push_dl_task(rq);
|
|
rq_repin_lock(rq, &rf);
|
|
}
|
|
#endif
|
|
|
|
unlock:
|
|
task_rq_unlock(rq, p, &rf);
|
|
|
|
/*
|
|
* This can free the task_struct, including this hrtimer, do not touch
|
|
* anything related to that after this.
|
|
*/
|
|
put_task_struct(p);
|
|
|
|
return HRTIMER_NORESTART;
|
|
}
|
|
|
|
void init_dl_task_timer(struct sched_dl_entity *dl_se)
|
|
{
|
|
struct hrtimer *timer = &dl_se->dl_timer;
|
|
|
|
hrtimer_init(timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
|
|
timer->function = dl_task_timer;
|
|
}
|
|
|
|
/*
|
|
* During the activation, CBS checks if it can reuse the current task's
|
|
* runtime and period. If the deadline of the task is in the past, CBS
|
|
* cannot use the runtime, and so it replenishes the task. This rule
|
|
* works fine for implicit deadline tasks (deadline == period), and the
|
|
* CBS was designed for implicit deadline tasks. However, a task with
|
|
* constrained deadline (deadine < period) might be awakened after the
|
|
* deadline, but before the next period. In this case, replenishing the
|
|
* task would allow it to run for runtime / deadline. As in this case
|
|
* deadline < period, CBS enables a task to run for more than the
|
|
* runtime / period. In a very loaded system, this can cause a domino
|
|
* effect, making other tasks miss their deadlines.
|
|
*
|
|
* To avoid this problem, in the activation of a constrained deadline
|
|
* task after the deadline but before the next period, throttle the
|
|
* task and set the replenishing timer to the begin of the next period,
|
|
* unless it is boosted.
|
|
*/
|
|
static inline void dl_check_constrained_dl(struct sched_dl_entity *dl_se)
|
|
{
|
|
struct task_struct *p = dl_task_of(dl_se);
|
|
struct rq *rq = rq_of_dl_rq(dl_rq_of_se(dl_se));
|
|
|
|
if (dl_time_before(dl_se->deadline, rq_clock(rq)) &&
|
|
dl_time_before(rq_clock(rq), dl_next_period(dl_se))) {
|
|
if (unlikely(dl_se->dl_boosted || !start_dl_timer(p)))
|
|
return;
|
|
dl_se->dl_throttled = 1;
|
|
}
|
|
}
|
|
|
|
static
|
|
int dl_runtime_exceeded(struct sched_dl_entity *dl_se)
|
|
{
|
|
return (dl_se->runtime <= 0);
|
|
}
|
|
|
|
extern bool sched_rt_bandwidth_account(struct rt_rq *rt_rq);
|
|
|
|
/*
|
|
* 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)) {
|
|
if (unlikely(dl_se->dl_yielded))
|
|
goto throttle;
|
|
return;
|
|
}
|
|
|
|
/* kick cpufreq (see the comment in kernel/sched/sched.h). */
|
|
cpufreq_update_this_cpu(rq, SCHED_CPUFREQ_DL);
|
|
|
|
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;
|
|
|
|
throttle:
|
|
if (dl_runtime_exceeded(dl_se) || dl_se->dl_yielded) {
|
|
dl_se->dl_throttled = 1;
|
|
__dequeue_task_dl(rq, curr, 0);
|
|
if (unlikely(dl_se->dl_boosted || !start_dl_timer(curr)))
|
|
enqueue_task_dl(rq, curr, ENQUEUE_REPLENISH);
|
|
|
|
if (!is_leftmost(curr, &rq->dl))
|
|
resched_curr(rq);
|
|
}
|
|
|
|
/*
|
|
* 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);
|
|
/*
|
|
* We'll let actual RT tasks worry about the overflow here, we
|
|
* have our own CBS to keep us inline; only account when RT
|
|
* bandwidth is relevant.
|
|
*/
|
|
if (sched_rt_bandwidth_account(rt_rq))
|
|
rt_rq->rt_time += delta_exec;
|
|
raw_spin_unlock(&rt_rq->rt_runtime_lock);
|
|
}
|
|
}
|
|
|
|
#ifdef CONFIG_SMP
|
|
|
|
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)) {
|
|
dl_rq->earliest_dl.curr = deadline;
|
|
cpudl_set(&rq->rd->cpudl, rq->cpu, deadline);
|
|
}
|
|
}
|
|
|
|
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_clear(&rq->rd->cpudl, rq->cpu);
|
|
} 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;
|
|
cpudl_set(&rq->rd->cpudl, rq->cpu, entry->deadline);
|
|
}
|
|
}
|
|
|
|
#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++;
|
|
add_nr_running(rq_of_dl_rq(dl_rq), 1);
|
|
|
|
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--;
|
|
sub_nr_running(rq_of_dl_rq(dl_rq), 1);
|
|
|
|
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 (flags & ENQUEUE_WAKEUP)
|
|
update_dl_entity(dl_se, pi_se);
|
|
else if (flags & ENQUEUE_REPLENISH)
|
|
replenish_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 inline bool dl_is_constrained(struct sched_dl_entity *dl_se)
|
|
{
|
|
return dl_se->dl_deadline < dl_se->dl_period;
|
|
}
|
|
|
|
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 (absolute) 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;
|
|
} else if (!dl_prio(p->normal_prio)) {
|
|
/*
|
|
* Special case in which we have a !SCHED_DEADLINE task
|
|
* that is going to be deboosted, but exceedes its
|
|
* runtime while doing so. No point in replenishing
|
|
* it, as it's going to return back to its original
|
|
* scheduling class after this.
|
|
*/
|
|
BUG_ON(!p->dl.dl_boosted || flags != ENQUEUE_REPLENISH);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Check if a constrained deadline task was activated
|
|
* after the deadline but before the next period.
|
|
* If that is the case, the task will be throttled and
|
|
* the replenishment timer will be set to the next period.
|
|
*/
|
|
if (!p->dl.dl_throttled && dl_is_constrained(&p->dl))
|
|
dl_check_constrained_dl(&p->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 && !(flags & ENQUEUE_REPLENISH))
|
|
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);
|
|
}
|
|
|
|
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);
|
|
}
|
|
|
|
/*
|
|
* 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)
|
|
{
|
|
/*
|
|
* 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_yielded=1).
|
|
*/
|
|
rq->curr->dl.dl_yielded = 1;
|
|
|
|
update_rq_clock(rq);
|
|
update_curr_dl(rq);
|
|
/*
|
|
* Tell update_rq_clock() that we've just updated,
|
|
* so we don't do microscopic update in schedule()
|
|
* and double the fastpath cost.
|
|
*/
|
|
rq_clock_skip_update(rq, true);
|
|
}
|
|
|
|
#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)
|
|
goto out;
|
|
|
|
rq = cpu_rq(cpu);
|
|
|
|
rcu_read_lock();
|
|
curr = READ_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 &&
|
|
(dl_time_before(p->dl.deadline,
|
|
cpu_rq(target)->dl.earliest_dl.curr) ||
|
|
(cpu_rq(target)->dl.dl_nr_running == 0)))
|
|
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_curr(rq);
|
|
}
|
|
|
|
#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_curr(rq);
|
|
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)
|
|
{
|
|
hrtick_start(rq, p->dl.runtime);
|
|
}
|
|
#else /* !CONFIG_SCHED_HRTICK */
|
|
static void start_hrtick_dl(struct rq *rq, struct task_struct *p)
|
|
{
|
|
}
|
|
#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 task_struct *prev, struct rq_flags *rf)
|
|
{
|
|
struct sched_dl_entity *dl_se;
|
|
struct task_struct *p;
|
|
struct dl_rq *dl_rq;
|
|
|
|
dl_rq = &rq->dl;
|
|
|
|
if (need_pull_dl_task(rq, prev)) {
|
|
/*
|
|
* This is OK, because current is on_cpu, which avoids it being
|
|
* picked for load-balance and preemption/IRQs are still
|
|
* disabled avoiding further scheduler activity on it and we're
|
|
* being very careful to re-start the picking loop.
|
|
*/
|
|
rq_unpin_lock(rq, rf);
|
|
pull_dl_task(rq);
|
|
rq_repin_lock(rq, rf);
|
|
/*
|
|
* pull_dl_task() can drop (and re-acquire) rq->lock; this
|
|
* means a stop task can slip in, in which case we need to
|
|
* re-start task selection.
|
|
*/
|
|
if (rq->stop && task_on_rq_queued(rq->stop))
|
|
return RETRY_TASK;
|
|
}
|
|
|
|
/*
|
|
* When prev is DL, we may throttle it in put_prev_task().
|
|
* So, we update time before we check for dl_nr_running.
|
|
*/
|
|
if (prev->sched_class == &dl_sched_class)
|
|
update_curr_dl(rq);
|
|
|
|
if (unlikely(!dl_rq->dl_nr_running))
|
|
return NULL;
|
|
|
|
put_prev_task(rq, prev);
|
|
|
|
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);
|
|
|
|
if (hrtick_enabled(rq))
|
|
start_hrtick_dl(rq, p);
|
|
|
|
queue_push_tasks(rq);
|
|
|
|
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);
|
|
|
|
/*
|
|
* Even when we have runtime, update_curr_dl() might have resulted in us
|
|
* not being the leftmost task anymore. In that case NEED_RESCHED will
|
|
* be set and schedule() will start a new hrtick for the next task.
|
|
*/
|
|
if (hrtick_enabled(rq) && queued && p->dl.runtime > 0 &&
|
|
is_leftmost(p, &rq->dl))
|
|
start_hrtick_dl(rq, p);
|
|
}
|
|
|
|
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 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);
|
|
/* XXX we should retain the bw until 0-lag */
|
|
dl_b->total_bw -= p->dl.dl_bw;
|
|
raw_spin_unlock_irq(&dl_b->lock);
|
|
}
|
|
|
|
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) &&
|
|
cpumask_test_cpu(cpu, &p->cpus_allowed))
|
|
return 1;
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Return the earliest pushable rq's task, which is suitable to be executed
|
|
* on the CPU, NULL otherwise:
|
|
*/
|
|
static struct task_struct *pick_earliest_pushable_dl_task(struct rq *rq, int cpu)
|
|
{
|
|
struct rb_node *next_node = rq->dl.pushable_dl_tasks_leftmost;
|
|
struct task_struct *p = NULL;
|
|
|
|
if (!has_pushable_dl_tasks(rq))
|
|
return NULL;
|
|
|
|
next_node:
|
|
if (next_node) {
|
|
p = rb_entry(next_node, struct task_struct, pushable_dl_tasks);
|
|
|
|
if (pick_dl_task(rq, p, cpu))
|
|
return p;
|
|
|
|
next_node = rb_next(next_node);
|
|
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 = this_cpu_cpumask_var_ptr(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;
|
|
|
|
/*
|
|
* We have to consider system topology and task affinity
|
|
* first, then we can look for a suitable cpu.
|
|
*/
|
|
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);
|
|
|
|
if (later_rq->dl.dl_nr_running &&
|
|
!dl_time_before(task->dl.deadline,
|
|
later_rq->dl.earliest_dl.curr)) {
|
|
/*
|
|
* Target rq has tasks of equal or earlier deadline,
|
|
* retrying does not release any lock and is unlikely
|
|
* to yield a different result.
|
|
*/
|
|
later_rq = NULL;
|
|
break;
|
|
}
|
|
|
|
/* 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) ||
|
|
!dl_task(task) ||
|
|
!task_on_rq_queued(task))) {
|
|
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(!task_on_rq_queued(p));
|
|
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;
|
|
int ret = 0;
|
|
|
|
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_curr(rq);
|
|
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.
|
|
*/
|
|
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);
|
|
ret = 1;
|
|
|
|
resched_curr(later_rq);
|
|
|
|
double_unlock_balance(rq, later_rq);
|
|
|
|
out:
|
|
put_task_struct(next_task);
|
|
|
|
return ret;
|
|
}
|
|
|
|
static void push_dl_tasks(struct rq *rq)
|
|
{
|
|
/* push_dl_task() will return true if it moved a -deadline task */
|
|
while (push_dl_task(rq))
|
|
;
|
|
}
|
|
|
|
static void pull_dl_task(struct rq *this_rq)
|
|
{
|
|
int this_cpu = this_rq->cpu, cpu;
|
|
struct task_struct *p;
|
|
bool resched = false;
|
|
struct rq *src_rq;
|
|
u64 dmin = LONG_MAX;
|
|
|
|
if (likely(!dl_overloaded(this_rq)))
|
|
return;
|
|
|
|
/*
|
|
* 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_earliest_pushable_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(!task_on_rq_queued(p));
|
|
|
|
/*
|
|
* 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;
|
|
|
|
resched = true;
|
|
|
|
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);
|
|
}
|
|
|
|
if (resched)
|
|
resched_curr(this_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) &&
|
|
p->nr_cpus_allowed > 1 &&
|
|
dl_task(rq->curr) &&
|
|
(rq->curr->nr_cpus_allowed < 2 ||
|
|
!dl_entity_preempt(&p->dl, &rq->curr->dl))) {
|
|
push_dl_tasks(rq);
|
|
}
|
|
}
|
|
|
|
static void set_cpus_allowed_dl(struct task_struct *p,
|
|
const struct cpumask *new_mask)
|
|
{
|
|
struct root_domain *src_rd;
|
|
struct rq *rq;
|
|
|
|
BUG_ON(!dl_task(p));
|
|
|
|
rq = task_rq(p);
|
|
src_rd = rq->rd;
|
|
/*
|
|
* Migrating a SCHED_DEADLINE task between exclusive
|
|
* cpusets (different root_domains) entails a bandwidth
|
|
* update. We already made space for us in the destination
|
|
* domain (see cpuset_can_attach()).
|
|
*/
|
|
if (!cpumask_intersects(src_rd->span, new_mask)) {
|
|
struct dl_bw *src_dl_b;
|
|
|
|
src_dl_b = dl_bw_of(cpu_of(rq));
|
|
/*
|
|
* We now free resources of the root_domain we are migrating
|
|
* off. In the worst case, sched_setattr() may temporary fail
|
|
* until we complete the update.
|
|
*/
|
|
raw_spin_lock(&src_dl_b->lock);
|
|
__dl_clear(src_dl_b, p->dl.dl_bw);
|
|
raw_spin_unlock(&src_dl_b->lock);
|
|
}
|
|
|
|
set_cpus_allowed_common(p, new_mask);
|
|
}
|
|
|
|
/* Assumes rq->lock is held */
|
|
static void rq_online_dl(struct rq *rq)
|
|
{
|
|
if (rq->dl.overloaded)
|
|
dl_set_overload(rq);
|
|
|
|
cpudl_set_freecpu(&rq->rd->cpudl, rq->cpu);
|
|
if (rq->dl.dl_nr_running > 0)
|
|
cpudl_set(&rq->rd->cpudl, rq->cpu, rq->dl.earliest_dl.curr);
|
|
}
|
|
|
|
/* Assumes rq->lock is held */
|
|
static void rq_offline_dl(struct rq *rq)
|
|
{
|
|
if (rq->dl.overloaded)
|
|
dl_clear_overload(rq);
|
|
|
|
cpudl_clear(&rq->rd->cpudl, rq->cpu);
|
|
cpudl_clear_freecpu(&rq->rd->cpudl, rq->cpu);
|
|
}
|
|
|
|
void __init 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)
|
|
{
|
|
/*
|
|
* Start the deadline timer; if we switch back to dl before this we'll
|
|
* continue consuming our current CBS slice. If we stay outside of
|
|
* SCHED_DEADLINE until the deadline passes, the timer will reset the
|
|
* task.
|
|
*/
|
|
if (!start_dl_timer(p))
|
|
__dl_clear_params(p);
|
|
|
|
/*
|
|
* Since this might be the only -deadline task on the rq,
|
|
* this is the right place to try to pull some other one
|
|
* from an overloaded cpu, if any.
|
|
*/
|
|
if (!task_on_rq_queued(p) || rq->dl.dl_nr_running)
|
|
return;
|
|
|
|
queue_pull_task(rq);
|
|
}
|
|
|
|
/*
|
|
* When switching to -deadline, we may overload the rq, then
|
|
* we try to push someone off, if possible.
|
|
*/
|
|
static void switched_to_dl(struct rq *rq, struct task_struct *p)
|
|
{
|
|
|
|
/* If p is not queued we will update its parameters at next wakeup. */
|
|
if (!task_on_rq_queued(p))
|
|
return;
|
|
|
|
/*
|
|
* If p is boosted we already updated its params in
|
|
* rt_mutex_setprio()->enqueue_task(..., ENQUEUE_REPLENISH),
|
|
* p's deadline being now already after rq_clock(rq).
|
|
*/
|
|
if (dl_time_before(p->dl.deadline, rq_clock(rq)))
|
|
setup_new_dl_entity(&p->dl);
|
|
|
|
if (rq->curr != p) {
|
|
#ifdef CONFIG_SMP
|
|
if (p->nr_cpus_allowed > 1 && rq->dl.overloaded)
|
|
queue_push_tasks(rq);
|
|
#endif
|
|
if (dl_task(rq->curr))
|
|
check_preempt_curr_dl(rq, p, 0);
|
|
else
|
|
resched_curr(rq);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* If the scheduling parameters of a -deadline task changed,
|
|
* a push or pull operation might be needed.
|
|
*/
|
|
static void prio_changed_dl(struct rq *rq, struct task_struct *p,
|
|
int oldprio)
|
|
{
|
|
if (task_on_rq_queued(p) || rq->curr == p) {
|
|
#ifdef CONFIG_SMP
|
|
/*
|
|
* 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
|
|
* or lowering its prio, so...
|
|
*/
|
|
if (!rq->dl.overloaded)
|
|
queue_pull_task(rq);
|
|
|
|
/*
|
|
* If we now have a earlier deadline task than p,
|
|
* then reschedule, provided p is still on this
|
|
* runqueue.
|
|
*/
|
|
if (dl_time_before(rq->dl.earliest_dl.curr, p->dl.deadline))
|
|
resched_curr(rq);
|
|
#else
|
|
/*
|
|
* Again, we don't know if p has a earlier
|
|
* or later deadline, so let's blindly set a
|
|
* (maybe not needed) rescheduling point.
|
|
*/
|
|
resched_curr(rq);
|
|
#endif /* CONFIG_SMP */
|
|
}
|
|
}
|
|
|
|
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,
|
|
|
|
.check_preempt_curr = check_preempt_curr_dl,
|
|
|
|
.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,
|
|
.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,
|
|
|
|
.update_curr = update_curr_dl,
|
|
};
|
|
|
|
#ifdef CONFIG_SCHED_DEBUG
|
|
extern void print_dl_rq(struct seq_file *m, int cpu, struct dl_rq *dl_rq);
|
|
|
|
void print_dl_stats(struct seq_file *m, int cpu)
|
|
{
|
|
print_dl_rq(m, cpu, &cpu_rq(cpu)->dl);
|
|
}
|
|
#endif /* CONFIG_SCHED_DEBUG */
|