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linux_old1/kernel/sched/deadline.c

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// SPDX-License-Identifier: GPL-2.0
/*
* Deadline Scheduling Class (SCHED_DEADLINE)
*
* Earliest Deadline First (EDF) + Constant Bandwidth Server (CBS).
*
* Tasks that periodically executes their instances for less than their
* runtime won't miss any of their deadlines.
* Tasks that are not periodic or sporadic or that tries to execute more
* than their reserved bandwidth will be slowed down (and may potentially
* miss some of their deadlines), and won't affect any other task.
*
* Copyright (C) 2012 Dario Faggioli <raistlin@linux.it>,
* Juri Lelli <juri.lelli@gmail.com>,
* Michael Trimarchi <michael@amarulasolutions.com>,
* Fabio Checconi <fchecconi@gmail.com>
*/
/*
* Default limits for DL period; on the top end we guard against small util
* tasks still getting ridiculously long effective runtimes, on the bottom end we
* guard against timer DoS.
*/
static unsigned int sysctl_sched_dl_period_max = 1 << 22; /* ~4 seconds */
static unsigned int sysctl_sched_dl_period_min = 100; /* 100 us */
#ifdef CONFIG_SYSCTL
static struct ctl_table sched_dl_sysctls[] = {
{
.procname = "sched_deadline_period_max_us",
.data = &sysctl_sched_dl_period_max,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec,
},
{
.procname = "sched_deadline_period_min_us",
.data = &sysctl_sched_dl_period_min,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec,
},
{}
};
static int __init sched_dl_sysctl_init(void)
{
register_sysctl_init("kernel", sched_dl_sysctls);
return 0;
}
late_initcall(sched_dl_sysctl_init);
#endif
static inline struct task_struct *dl_task_of(struct sched_dl_entity *dl_se)
{
return container_of(dl_se, struct task_struct, dl);
}
static inline struct rq *rq_of_dl_rq(struct dl_rq *dl_rq)
{
return container_of(dl_rq, struct rq, dl);
}
static inline struct dl_rq *dl_rq_of_se(struct sched_dl_entity *dl_se)
{
struct task_struct *p = dl_task_of(dl_se);
struct rq *rq = task_rq(p);
return &rq->dl;
}
static inline int on_dl_rq(struct sched_dl_entity *dl_se)
{
return !RB_EMPTY_NODE(&dl_se->rb_node);
}
#ifdef CONFIG_RT_MUTEXES
static inline struct sched_dl_entity *pi_of(struct sched_dl_entity *dl_se)
{
return dl_se->pi_se;
}
static inline bool is_dl_boosted(struct sched_dl_entity *dl_se)
{
return pi_of(dl_se) != dl_se;
}
#else
static inline struct sched_dl_entity *pi_of(struct sched_dl_entity *dl_se)
{
return dl_se;
}
static inline bool is_dl_boosted(struct sched_dl_entity *dl_se)
{
return false;
}
#endif
#ifdef CONFIG_SMP
static inline struct dl_bw *dl_bw_of(int i)
{
RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(),
"sched RCU must be held");
return &cpu_rq(i)->rd->dl_bw;
}
static inline int dl_bw_cpus(int i)
{
struct root_domain *rd = cpu_rq(i)->rd;
int cpus;
RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(),
"sched RCU must be held");
if (cpumask_subset(rd->span, cpu_active_mask))
return cpumask_weight(rd->span);
cpus = 0;
for_each_cpu_and(i, rd->span, cpu_active_mask)
cpus++;
return cpus;
}
static inline unsigned long __dl_bw_capacity(int i)
{
struct root_domain *rd = cpu_rq(i)->rd;
unsigned long cap = 0;
RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(),
"sched RCU must be held");
for_each_cpu_and(i, rd->span, cpu_active_mask)
cap += capacity_orig_of(i);
return cap;
}
/*
* XXX Fix: If 'rq->rd == def_root_domain' perform AC against capacity
* of the CPU the task is running on rather rd's \Sum CPU capacity.
*/
static inline unsigned long dl_bw_capacity(int i)
{
if (!static_branch_unlikely(&sched_asym_cpucapacity) &&
capacity_orig_of(i) == SCHED_CAPACITY_SCALE) {
return dl_bw_cpus(i) << SCHED_CAPACITY_SHIFT;
} else {
return __dl_bw_capacity(i);
}
}
static inline bool dl_bw_visited(int cpu, u64 gen)
{
struct root_domain *rd = cpu_rq(cpu)->rd;
if (rd->visit_gen == gen)
return true;
rd->visit_gen = gen;
return false;
}
static inline
void __dl_update(struct dl_bw *dl_b, s64 bw)
{
struct root_domain *rd = container_of(dl_b, struct root_domain, dl_bw);
int i;
RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(),
"sched RCU must be held");
for_each_cpu_and(i, rd->span, cpu_active_mask) {
struct rq *rq = cpu_rq(i);
rq->dl.extra_bw += bw;
}
}
#else
static inline struct dl_bw *dl_bw_of(int i)
{
return &cpu_rq(i)->dl.dl_bw;
}
static inline int dl_bw_cpus(int i)
{
return 1;
}
static inline unsigned long dl_bw_capacity(int i)
{
return SCHED_CAPACITY_SCALE;
}
static inline bool dl_bw_visited(int cpu, u64 gen)
{
return false;
}
static inline
void __dl_update(struct dl_bw *dl_b, s64 bw)
{
struct dl_rq *dl = container_of(dl_b, struct dl_rq, dl_bw);
dl->extra_bw += bw;
}
#endif
static inline
void __dl_sub(struct dl_bw *dl_b, u64 tsk_bw, int cpus)
{
dl_b->total_bw -= tsk_bw;
__dl_update(dl_b, (s32)tsk_bw / cpus);
}
static inline
void __dl_add(struct dl_bw *dl_b, u64 tsk_bw, int cpus)
{
dl_b->total_bw += tsk_bw;
__dl_update(dl_b, -((s32)tsk_bw / cpus));
}
static inline bool
__dl_overflow(struct dl_bw *dl_b, unsigned long cap, u64 old_bw, u64 new_bw)
{
return dl_b->bw != -1 &&
cap_scale(dl_b->bw, cap) < dl_b->total_bw - old_bw + new_bw;
}
static inline
void __add_running_bw(u64 dl_bw, struct dl_rq *dl_rq)
{
u64 old = dl_rq->running_bw;
lockdep_assert_rq_held(rq_of_dl_rq(dl_rq));
dl_rq->running_bw += dl_bw;
SCHED_WARN_ON(dl_rq->running_bw < old); /* overflow */
SCHED_WARN_ON(dl_rq->running_bw > dl_rq->this_bw);
/* kick cpufreq (see the comment in kernel/sched/sched.h). */
cpufreq_update_util(rq_of_dl_rq(dl_rq), 0);
}
static inline
void __sub_running_bw(u64 dl_bw, struct dl_rq *dl_rq)
{
u64 old = dl_rq->running_bw;
lockdep_assert_rq_held(rq_of_dl_rq(dl_rq));
dl_rq->running_bw -= dl_bw;
SCHED_WARN_ON(dl_rq->running_bw > old); /* underflow */
if (dl_rq->running_bw > old)
dl_rq->running_bw = 0;
/* kick cpufreq (see the comment in kernel/sched/sched.h). */
cpufreq_update_util(rq_of_dl_rq(dl_rq), 0);
}
static inline
void __add_rq_bw(u64 dl_bw, struct dl_rq *dl_rq)
{
u64 old = dl_rq->this_bw;
lockdep_assert_rq_held(rq_of_dl_rq(dl_rq));
dl_rq->this_bw += dl_bw;
SCHED_WARN_ON(dl_rq->this_bw < old); /* overflow */
}
static inline
void __sub_rq_bw(u64 dl_bw, struct dl_rq *dl_rq)
{
u64 old = dl_rq->this_bw;
lockdep_assert_rq_held(rq_of_dl_rq(dl_rq));
dl_rq->this_bw -= dl_bw;
SCHED_WARN_ON(dl_rq->this_bw > old); /* underflow */
if (dl_rq->this_bw > old)
dl_rq->this_bw = 0;
SCHED_WARN_ON(dl_rq->running_bw > dl_rq->this_bw);
}
static inline
void add_rq_bw(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
{
if (!dl_entity_is_special(dl_se))
__add_rq_bw(dl_se->dl_bw, dl_rq);
}
static inline
void sub_rq_bw(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
{
if (!dl_entity_is_special(dl_se))
__sub_rq_bw(dl_se->dl_bw, dl_rq);
}
static inline
void add_running_bw(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
{
if (!dl_entity_is_special(dl_se))
__add_running_bw(dl_se->dl_bw, dl_rq);
}
static inline
void sub_running_bw(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
{
if (!dl_entity_is_special(dl_se))
__sub_running_bw(dl_se->dl_bw, dl_rq);
}
static void dl_change_utilization(struct task_struct *p, u64 new_bw)
{
struct rq *rq;
BUG_ON(p->dl.flags & SCHED_FLAG_SUGOV);
if (task_on_rq_queued(p))
return;
rq = task_rq(p);
if (p->dl.dl_non_contending) {
sub_running_bw(&p->dl, &rq->dl);
p->dl.dl_non_contending = 0;
/*
* If the timer handler is currently running and the
* timer cannot be canceled, inactive_task_timer()
* will see that dl_not_contending is not set, and
* will not touch the rq's active utilization,
* so we are still safe.
*/
if (hrtimer_try_to_cancel(&p->dl.inactive_timer) == 1)
put_task_struct(p);
}
__sub_rq_bw(p->dl.dl_bw, &rq->dl);
__add_rq_bw(new_bw, &rq->dl);
}
/*
* The utilization of a task cannot be immediately removed from
* the rq active utilization (running_bw) when the task blocks.
* Instead, we have to wait for the so called "0-lag time".
*
* If a task blocks before the "0-lag time", a timer (the inactive
* timer) is armed, and running_bw is decreased when the timer
* fires.
*
* If the task wakes up again before the inactive timer fires,
* the timer is canceled, whereas if the task wakes up after the
* inactive timer fired (and running_bw has been decreased) the
* task's utilization has to be added to running_bw again.
* A flag in the deadline scheduling entity (dl_non_contending)
* is used to avoid race conditions between the inactive timer handler
* and task wakeups.
*
* The following diagram shows how running_bw is updated. A task is
* "ACTIVE" when its utilization contributes to running_bw; an
* "ACTIVE contending" task is in the TASK_RUNNING state, while an
* "ACTIVE non contending" task is a blocked task for which the "0-lag time"
* has not passed yet. An "INACTIVE" task is a task for which the "0-lag"
* time already passed, which does not contribute to running_bw anymore.
* +------------------+
* wakeup | ACTIVE |
* +------------------>+ contending |
* | add_running_bw | |
* | +----+------+------+
* | | ^
* | dequeue | |
* +--------+-------+ | |
* | | t >= 0-lag | | wakeup
* | INACTIVE |<---------------+ |
* | | sub_running_bw | |
* +--------+-------+ | |
* ^ | |
* | t < 0-lag | |
* | | |
* | V |
* | +----+------+------+
* | sub_running_bw | ACTIVE |
* +-------------------+ |
* inactive timer | non contending |
* fired +------------------+
*
* The task_non_contending() function is invoked when a task
* blocks, and checks if the 0-lag time already passed or
* not (in the first case, it directly updates running_bw;
* in the second case, it arms the inactive timer).
*
* The task_contending() function is invoked when a task wakes
* up, and checks if the task is still in the "ACTIVE non contending"
* state or not (in the second case, it updates running_bw).
*/
static void task_non_contending(struct task_struct *p)
{
struct sched_dl_entity *dl_se = &p->dl;
struct hrtimer *timer = &dl_se->inactive_timer;
struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
struct rq *rq = rq_of_dl_rq(dl_rq);
s64 zerolag_time;
/*
* If this is a non-deadline task that has been boosted,
* do nothing
*/
if (dl_se->dl_runtime == 0)
return;
if (dl_entity_is_special(dl_se))
return;
WARN_ON(dl_se->dl_non_contending);
zerolag_time = dl_se->deadline -
div64_long((dl_se->runtime * dl_se->dl_period),
dl_se->dl_runtime);
/*
* Using relative times instead of the absolute "0-lag time"
* allows to simplify the code
*/
zerolag_time -= rq_clock(rq);
/*
* If the "0-lag time" already passed, decrease the active
* utilization now, instead of starting a timer
*/
if ((zerolag_time < 0) || hrtimer_active(&dl_se->inactive_timer)) {
if (dl_task(p))
sub_running_bw(dl_se, dl_rq);
if (!dl_task(p) || READ_ONCE(p->__state) == TASK_DEAD) {
struct dl_bw *dl_b = dl_bw_of(task_cpu(p));
if (READ_ONCE(p->__state) == TASK_DEAD)
sub_rq_bw(&p->dl, &rq->dl);
raw_spin_lock(&dl_b->lock);
__dl_sub(dl_b, p->dl.dl_bw, dl_bw_cpus(task_cpu(p)));
__dl_clear_params(p);
raw_spin_unlock(&dl_b->lock);
}
return;
}
dl_se->dl_non_contending = 1;
get_task_struct(p);
hrtimer_start(timer, ns_to_ktime(zerolag_time), HRTIMER_MODE_REL_HARD);
}
static void task_contending(struct sched_dl_entity *dl_se, int flags)
{
struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
/*
* If this is a non-deadline task that has been boosted,
* do nothing
*/
if (dl_se->dl_runtime == 0)
return;
if (flags & ENQUEUE_MIGRATED)
add_rq_bw(dl_se, dl_rq);
if (dl_se->dl_non_contending) {
dl_se->dl_non_contending = 0;
/*
* If the timer handler is currently running and the
* timer cannot be canceled, inactive_task_timer()
* will see that dl_not_contending is not set, and
* will not touch the rq's active utilization,
* so we are still safe.
*/
if (hrtimer_try_to_cancel(&dl_se->inactive_timer) == 1)
put_task_struct(dl_task_of(dl_se));
} else {
/*
* Since "dl_non_contending" is not set, the
* task's utilization has already been removed from
* active utilization (either when the task blocked,
* when the "inactive timer" fired).
* So, add it back.
*/
add_running_bw(dl_se, dl_rq);
}
}
static inline int is_leftmost(struct task_struct *p, struct dl_rq *dl_rq)
{
struct sched_dl_entity *dl_se = &p->dl;
return rb_first_cached(&dl_rq->root) == &dl_se->rb_node;
}
static void init_dl_rq_bw_ratio(struct dl_rq *dl_rq);
void init_dl_bandwidth(struct dl_bandwidth *dl_b, u64 period, u64 runtime)
{
raw_spin_lock_init(&dl_b->dl_runtime_lock);
dl_b->dl_period = period;
dl_b->dl_runtime = runtime;
}
void init_dl_bw(struct dl_bw *dl_b)
{
raw_spin_lock_init(&dl_b->lock);
if (global_rt_runtime() == RUNTIME_INF)
dl_b->bw = -1;
else
dl_b->bw = to_ratio(global_rt_period(), global_rt_runtime());
dl_b->total_bw = 0;
}
void init_dl_rq(struct dl_rq *dl_rq)
{
dl_rq->root = RB_ROOT_CACHED;
#ifdef CONFIG_SMP
/* zero means no -deadline tasks */
dl_rq->earliest_dl.curr = dl_rq->earliest_dl.next = 0;
dl_rq->dl_nr_migratory = 0;
dl_rq->overloaded = 0;
dl_rq->pushable_dl_tasks_root = RB_ROOT_CACHED;
#else
init_dl_bw(&dl_rq->dl_bw);
#endif
dl_rq->running_bw = 0;
dl_rq->this_bw = 0;
init_dl_rq_bw_ratio(dl_rq);
}
#ifdef CONFIG_SMP
static inline int dl_overloaded(struct rq *rq)
{
return atomic_read(&rq->rd->dlo_count);
}
static inline void dl_set_overload(struct rq *rq)
{
if (!rq->online)
return;
cpumask_set_cpu(rq->cpu, rq->rd->dlo_mask);
/*
* Must be visible before the overload count is
* set (as in sched_rt.c).
*
* Matched by the barrier in pull_dl_task().
*/
smp_wmb();
atomic_inc(&rq->rd->dlo_count);
}
static inline void dl_clear_overload(struct rq *rq)
{
if (!rq->online)
return;
atomic_dec(&rq->rd->dlo_count);
cpumask_clear_cpu(rq->cpu, rq->rd->dlo_mask);
}
static void update_dl_migration(struct dl_rq *dl_rq)
{
if (dl_rq->dl_nr_migratory && dl_rq->dl_nr_running > 1) {
if (!dl_rq->overloaded) {
dl_set_overload(rq_of_dl_rq(dl_rq));
dl_rq->overloaded = 1;
}
} else if (dl_rq->overloaded) {
dl_clear_overload(rq_of_dl_rq(dl_rq));
dl_rq->overloaded = 0;
}
}
static void inc_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
{
struct task_struct *p = dl_task_of(dl_se);
if (p->nr_cpus_allowed > 1)
dl_rq->dl_nr_migratory++;
update_dl_migration(dl_rq);
}
static void dec_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
{
struct task_struct *p = dl_task_of(dl_se);
if (p->nr_cpus_allowed > 1)
dl_rq->dl_nr_migratory--;
update_dl_migration(dl_rq);
}
#define __node_2_pdl(node) \
rb_entry((node), struct task_struct, pushable_dl_tasks)
static inline bool __pushable_less(struct rb_node *a, const struct rb_node *b)
{
return dl_entity_preempt(&__node_2_pdl(a)->dl, &__node_2_pdl(b)->dl);
}
/*
* The list of pushable -deadline task is not a plist, like in
* sched_rt.c, it is an rb-tree with tasks ordered by deadline.
*/
static void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p)
{
struct rb_node *leftmost;
BUG_ON(!RB_EMPTY_NODE(&p->pushable_dl_tasks));
leftmost = rb_add_cached(&p->pushable_dl_tasks,
&rq->dl.pushable_dl_tasks_root,
__pushable_less);
if (leftmost)
rq->dl.earliest_dl.next = p->dl.deadline;
}
static void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)
{
struct dl_rq *dl_rq = &rq->dl;
struct rb_root_cached *root = &dl_rq->pushable_dl_tasks_root;
struct rb_node *leftmost;
if (RB_EMPTY_NODE(&p->pushable_dl_tasks))
return;
leftmost = rb_erase_cached(&p->pushable_dl_tasks, root);
if (leftmost)
dl_rq->earliest_dl.next = __node_2_pdl(leftmost)->dl.deadline;
RB_CLEAR_NODE(&p->pushable_dl_tasks);
}
static inline int has_pushable_dl_tasks(struct rq *rq)
{
return !RB_EMPTY_ROOT(&rq->dl.pushable_dl_tasks_root.rb_root);
}
static int push_dl_task(struct rq *rq);
static inline bool need_pull_dl_task(struct rq *rq, struct task_struct *prev)
{
return rq->online && dl_task(prev);
}
static DEFINE_PER_CPU(struct callback_head, dl_push_head);
static DEFINE_PER_CPU(struct callback_head, dl_pull_head);
static void push_dl_tasks(struct rq *);
static void pull_dl_task(struct rq *);
static inline void deadline_queue_push_tasks(struct rq *rq)
{
if (!has_pushable_dl_tasks(rq))
return;
queue_balance_callback(rq, &per_cpu(dl_push_head, rq->cpu), push_dl_tasks);
}
static inline void deadline_queue_pull_task(struct rq *rq)
{
queue_balance_callback(rq, &per_cpu(dl_pull_head, rq->cpu), pull_dl_task);
}
static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq);
static struct rq *dl_task_offline_migration(struct rq *rq, struct task_struct *p)
{
struct rq *later_rq = NULL;
struct dl_bw *dl_b;
later_rq = find_lock_later_rq(p, rq);
if (!later_rq) {
int cpu;
/*
* If we cannot preempt any rq, fall back to pick any
* online CPU:
*/
cpu = cpumask_any_and(cpu_active_mask, p->cpus_ptr);
if (cpu >= nr_cpu_ids) {
/*
* Failed to find any suitable CPU.
* The task will never come back!
*/
BUG_ON(dl_bandwidth_enabled());
/*
* If admission control is disabled we
* try a little harder to let the task
* run.
*/
cpu = cpumask_any(cpu_active_mask);
}
later_rq = cpu_rq(cpu);
double_lock_balance(rq, later_rq);
}
if (p->dl.dl_non_contending || p->dl.dl_throttled) {
/*
* Inactive timer is armed (or callback is running, but
* waiting for us to release rq locks). In any case, when it
* will fire (or continue), it will see running_bw of this
* task migrated to later_rq (and correctly handle it).
*/
sub_running_bw(&p->dl, &rq->dl);
sub_rq_bw(&p->dl, &rq->dl);
add_rq_bw(&p->dl, &later_rq->dl);
add_running_bw(&p->dl, &later_rq->dl);
} else {
sub_rq_bw(&p->dl, &rq->dl);
add_rq_bw(&p->dl, &later_rq->dl);
}
/*
* And we finally need to fixup root_domain(s) bandwidth accounting,
* since p is still hanging out in the old (now moved to default) root
* domain.
*/
dl_b = &rq->rd->dl_bw;
raw_spin_lock(&dl_b->lock);
__dl_sub(dl_b, p->dl.dl_bw, cpumask_weight(rq->rd->span));
raw_spin_unlock(&dl_b->lock);
dl_b = &later_rq->rd->dl_bw;
raw_spin_lock(&dl_b->lock);
__dl_add(dl_b, p->dl.dl_bw, cpumask_weight(later_rq->rd->span));
raw_spin_unlock(&dl_b->lock);
set_task_cpu(p, later_rq->cpu);
double_unlock_balance(later_rq, rq);
return later_rq;
}
#else
static inline
void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p)
{
}
static inline
void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)
{
}
static inline
void inc_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
{
}
static inline
void dec_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
{
}
static inline void deadline_queue_push_tasks(struct rq *rq)
{
}
static inline void deadline_queue_pull_task(struct rq *rq)
{
}
#endif /* CONFIG_SMP */
static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags);
static void __dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags);
static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p, int flags);
/*
* We are being explicitly informed that a new instance is starting,
* and this means that:
* - the absolute deadline of the entity has to be placed at
* current time + relative deadline;
* - the runtime of the entity has to be set to the maximum value.
*
* The capability of specifying such event is useful whenever a -deadline
* entity wants to (try to!) synchronize its behaviour with the scheduler's
* one, and to (try to!) reconcile itself with its own scheduling
* parameters.
*/
static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se)
{
struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
struct rq *rq = rq_of_dl_rq(dl_rq);
WARN_ON(is_dl_boosted(dl_se));
WARN_ON(dl_time_before(rq_clock(rq), dl_se->deadline));
/*
* We are racing with the deadline timer. So, do nothing because
* the deadline timer handler will take care of properly recharging
* the runtime and postponing the deadline
*/
if (dl_se->dl_throttled)
return;
/*
* We use the regular wall clock time to set deadlines in the
* future; in fact, we must consider execution overheads (time
* spent on hardirq context, etc.).
*/
dl_se->deadline = rq_clock(rq) + dl_se->dl_deadline;
dl_se->runtime = dl_se->dl_runtime;
}
/*
* Pure Earliest Deadline First (EDF) scheduling does not deal with the
* possibility of a entity lasting more than what it declared, and thus
* exhausting its runtime.
*
* Here we are interested in making runtime overrun possible, but we do
* not want a entity which is misbehaving to affect the scheduling of all
* other entities.
* Therefore, a budgeting strategy called Constant Bandwidth Server (CBS)
* is used, in order to confine each entity within its own bandwidth.
*
* This function deals exactly with that, and ensures that when the runtime
* of a entity is replenished, its deadline is also postponed. That ensures
* the overrunning entity can't interfere with other entity in the system and
* can't make them miss their deadlines. Reasons why this kind of overruns
* could happen are, typically, a entity voluntarily trying to overcome its
* runtime, or it just underestimated it during sched_setattr().
*/
static void replenish_dl_entity(struct sched_dl_entity *dl_se)
{
struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
struct rq *rq = rq_of_dl_rq(dl_rq);
BUG_ON(pi_of(dl_se)->dl_runtime <= 0);
/*
* This could be the case for a !-dl task that is boosted.
* Just go with full inherited parameters.
*/
if (dl_se->dl_deadline == 0) {
dl_se->deadline = rq_clock(rq) + pi_of(dl_se)->dl_deadline;
dl_se->runtime = pi_of(dl_se)->dl_runtime;
}
if (dl_se->dl_yielded && dl_se->runtime > 0)
dl_se->runtime = 0;
/*
* We keep moving the deadline away until we get some
* available runtime for the entity. This ensures correct
* handling of situations where the runtime overrun is
* arbitrary large.
*/
while (dl_se->runtime <= 0) {
dl_se->deadline += pi_of(dl_se)->dl_period;
dl_se->runtime += pi_of(dl_se)->dl_runtime;
}
/*
* At this point, the deadline really should be "in
* the future" with respect to rq->clock. If it's
* not, we are, for some reason, lagging too much!
* Anyway, after having warn userspace abut that,
* we still try to keep the things running by
* resetting the deadline and the budget of the
* entity.
*/
if (dl_time_before(dl_se->deadline, rq_clock(rq))) {
printk_deferred_once("sched: DL replenish lagged too much\n");
dl_se->deadline = rq_clock(rq) + pi_of(dl_se)->dl_deadline;
dl_se->runtime = pi_of(dl_se)->dl_runtime;
}
if (dl_se->dl_yielded)
dl_se->dl_yielded = 0;
if (dl_se->dl_throttled)
dl_se->dl_throttled = 0;
}
/*
* Here we check if --at time t-- an entity (which is probably being
* [re]activated or, in general, enqueued) can use its remaining runtime
* and its current deadline _without_ exceeding the bandwidth it is
* assigned (function returns true if it can't). We are in fact applying
* one of the CBS rules: when a task wakes up, if the residual runtime
* over residual deadline fits within the allocated bandwidth, then we
* can keep the current (absolute) deadline and residual budget without
* disrupting the schedulability of the system. Otherwise, we should
* refill the runtime and set the deadline a period in the future,
* because keeping the current (absolute) deadline of the task would
* result in breaking guarantees promised to other tasks (refer to
* Documentation/scheduler/sched-deadline.rst for more information).
*
* This function returns true if:
*
* runtime / (deadline - t) > dl_runtime / dl_deadline ,
*
* IOW we can't recycle current parameters.
*
* Notice that the bandwidth check is done against the deadline. For
* 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, 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_of(dl_se)->dl_deadline >> DL_SCALE) * (dl_se->runtime >> DL_SCALE);
right = ((dl_se->deadline - t) >> DL_SCALE) *
(pi_of(dl_se)->dl_runtime >> DL_SCALE);
return dl_time_before(right, left);
}
/*
* Revised wakeup rule [1]: For self-suspending tasks, rather then
* re-initializing task's runtime and deadline, the revised wakeup
* rule adjusts the task's runtime to avoid the task to overrun its
* density.
*
* Reasoning: a task may overrun the density if:
* runtime / (deadline - t) > dl_runtime / dl_deadline
*
* Therefore, runtime can be adjusted to:
* runtime = (dl_runtime / dl_deadline) * (deadline - t)
*
* In such way that runtime will be equal to the maximum density
* the task can use without breaking any rule.
*
* [1] Luca Abeni, Giuseppe Lipari, and Juri Lelli. 2015. Constant
* bandwidth server revisited. SIGBED Rev. 11, 4 (January 2015), 19-24.
*/
static void
update_dl_revised_wakeup(struct sched_dl_entity *dl_se, struct rq *rq)
{
u64 laxity = dl_se->deadline - rq_clock(rq);
/*
* If the task has deadline < period, and the deadline is in the past,
* it should already be throttled before this check.
*
* See update_dl_entity() comments for further details.
*/
WARN_ON(dl_time_before(dl_se->deadline, rq_clock(rq)));
dl_se->runtime = (dl_se->dl_density * laxity) >> BW_SHIFT;
}
/*
* Regarding the deadline, a task with implicit deadline has a relative
* deadline == relative period. A task with constrained deadline has a
* relative deadline <= relative period.
*
* We support constrained deadline tasks. However, there are some restrictions
* applied only for tasks which do not have an implicit deadline. See
* update_dl_entity() to know more about such restrictions.
*
* The dl_is_implicit() returns true if the task has an implicit deadline.
*/
static inline bool dl_is_implicit(struct sched_dl_entity *dl_se)
{
return dl_se->dl_deadline == dl_se->dl_period;
}
/*
* When a deadline entity is placed in the runqueue, its runtime and deadline
* might need to be updated. This is done by a CBS wake up rule. There are two
* different rules: 1) the original CBS; and 2) the Revisited CBS.
*
* When the task is starting a new period, the Original CBS is used. In this
* case, the runtime is replenished and a new absolute deadline is set.
*
* When a task is queued before the begin of the next period, using the
* remaining runtime and deadline could make the entity to overflow, see
* dl_entity_overflow() to find more about runtime overflow. When such case
* is detected, the runtime and deadline need to be updated.
*
* If the task has an implicit deadline, i.e., deadline == period, the Original
* CBS is applied. the runtime is replenished and a new absolute deadline is
* set, as in the previous cases.
*
* However, the Original CBS does not work properly for tasks with
* deadline < period, which are said to have a constrained deadline. By
* applying the Original CBS, a constrained deadline task would be able to run
* runtime/deadline in a period. With deadline < period, the task would
* overrun the runtime/period allowed bandwidth, breaking the admission test.
*
* In order to prevent this misbehave, the Revisited CBS is used for
* constrained deadline tasks when a runtime overflow is detected. In the
* Revisited CBS, rather than replenishing & setting a new absolute deadline,
* the remaining runtime of the task is reduced to avoid runtime overflow.
* Please refer to the comments update_dl_revised_wakeup() function to find
* more about the Revised CBS rule.
*/
static void update_dl_entity(struct sched_dl_entity *dl_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, rq_clock(rq))) {
if (unlikely(!dl_is_implicit(dl_se) &&
!dl_time_before(dl_se->deadline, rq_clock(rq)) &&
!is_dl_boosted(dl_se))) {
update_dl_revised_wakeup(dl_se, rq);
return;
}
dl_se->deadline = rq_clock(rq) + pi_of(dl_se)->dl_deadline;
dl_se->runtime = pi_of(dl_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_rq_held(rq);
/*
* 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_HARD);
}
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))
goto unlock;
/*
* The task might have been boosted by someone else and might be in the
* boosting/deboosting path, its not throttled.
*/
if (is_dl_boosted(dl_se))
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);
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_lockp(rq), rf.cookie);
rq = dl_task_offline_migration(rq, p);
rf.cookie = lockdep_pin_lock(__rq_lockp(rq));
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_HARD);
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 (deadline < 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(is_dl_boosted(dl_se) || !start_dl_timer(p)))
return;
dl_se->dl_throttled = 1;
if (dl_se->runtime > 0)
dl_se->runtime = 0;
}
}
static
int dl_runtime_exceeded(struct sched_dl_entity *dl_se)
{
return (dl_se->runtime <= 0);
}
/*
* This function implements the GRUB accounting rule:
* according to the GRUB reclaiming algorithm, the runtime is
* not decreased as "dq = -dt", but as
* "dq = -max{u / Umax, (1 - Uinact - Uextra)} dt",
* where u is the utilization of the task, Umax is the maximum reclaimable
* utilization, Uinact is the (per-runqueue) inactive utilization, computed
* as the difference between the "total runqueue utilization" and the
* runqueue active utilization, and Uextra is the (per runqueue) extra
* reclaimable utilization.
* Since rq->dl.running_bw and rq->dl.this_bw contain utilizations
* multiplied by 2^BW_SHIFT, the result has to be shifted right by
* BW_SHIFT.
* Since rq->dl.bw_ratio contains 1 / Umax multiplied by 2^RATIO_SHIFT,
* dl_bw is multiped by rq->dl.bw_ratio and shifted right by RATIO_SHIFT.
* Since delta is a 64 bit variable, to have an overflow its value
* should be larger than 2^(64 - 20 - 8), which is more than 64 seconds.
* So, overflow is not an issue here.
*/
static u64 grub_reclaim(u64 delta, struct rq *rq, struct sched_dl_entity *dl_se)
{
u64 u_inact = rq->dl.this_bw - rq->dl.running_bw; /* Utot - Uact */
u64 u_act;
u64 u_act_min = (dl_se->dl_bw * rq->dl.bw_ratio) >> RATIO_SHIFT;
/*
* Instead of computing max{u * bw_ratio, (1 - u_inact - u_extra)},
* we compare u_inact + rq->dl.extra_bw with
* 1 - (u * rq->dl.bw_ratio >> RATIO_SHIFT), because
* u_inact + rq->dl.extra_bw can be larger than
* 1 * (so, 1 - u_inact - rq->dl.extra_bw would be negative
* leading to wrong results)
*/
if (u_inact + rq->dl.extra_bw > BW_UNIT - u_act_min)
u_act = u_act_min;
else
u_act = BW_UNIT - u_inact - rq->dl.extra_bw;
return (delta * u_act) >> BW_SHIFT;
}
/*
* 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, scaled_delta_exec;
int cpu = cpu_of(rq);
u64 now;
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.
*/
now = rq_clock_task(rq);
delta_exec = now - curr->se.exec_start;
if (unlikely((s64)delta_exec <= 0)) {
if (unlikely(dl_se->dl_yielded))
goto throttle;
return;
}
schedstat_set(curr->stats.exec_max,
max(curr->stats.exec_max, delta_exec));
trace_sched_stat_runtime(curr, delta_exec, 0);
curr->se.sum_exec_runtime += delta_exec;
account_group_exec_runtime(curr, delta_exec);
curr->se.exec_start = now;
cgroup_account_cputime(curr, delta_exec);
if (dl_entity_is_special(dl_se))
return;
/*
* For tasks that participate in GRUB, we implement GRUB-PA: the
* spare reclaimed bandwidth is used to clock down frequency.
*
* For the others, we still need to scale reservation parameters
* according to current frequency and CPU maximum capacity.
*/
if (unlikely(dl_se->flags & SCHED_FLAG_RECLAIM)) {
scaled_delta_exec = grub_reclaim(delta_exec,
rq,
&curr->dl);
} else {
unsigned long scale_freq = arch_scale_freq_capacity(cpu);
unsigned long scale_cpu = arch_scale_cpu_capacity(cpu);
scaled_delta_exec = cap_scale(delta_exec, scale_freq);
scaled_delta_exec = cap_scale(scaled_delta_exec, scale_cpu);
}
dl_se->runtime -= scaled_delta_exec;
throttle:
if (dl_runtime_exceeded(dl_se) || dl_se->dl_yielded) {
dl_se->dl_throttled = 1;
/* If requested, inform the user about runtime overruns. */
if (dl_runtime_exceeded(dl_se) &&
(dl_se->flags & SCHED_FLAG_DL_OVERRUN))
dl_se->dl_overrun = 1;
__dequeue_task_dl(rq, curr, 0);
if (unlikely(is_dl_boosted(dl_se) || !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);
}
}
static enum hrtimer_restart inactive_task_timer(struct hrtimer *timer)
{
struct sched_dl_entity *dl_se = container_of(timer,
struct sched_dl_entity,
inactive_timer);
struct task_struct *p = dl_task_of(dl_se);
struct rq_flags rf;
struct rq *rq;
rq = task_rq_lock(p, &rf);
sched_clock_tick();
update_rq_clock(rq);
if (!dl_task(p) || READ_ONCE(p->__state) == TASK_DEAD) {
struct dl_bw *dl_b = dl_bw_of(task_cpu(p));
if (READ_ONCE(p->__state) == TASK_DEAD && dl_se->dl_non_contending) {
sub_running_bw(&p->dl, dl_rq_of_se(&p->dl));
sub_rq_bw(&p->dl, dl_rq_of_se(&p->dl));
dl_se->dl_non_contending = 0;
}
raw_spin_lock(&dl_b->lock);
__dl_sub(dl_b, p->dl.dl_bw, dl_bw_cpus(task_cpu(p)));
raw_spin_unlock(&dl_b->lock);
__dl_clear_params(p);
goto unlock;
}
if (dl_se->dl_non_contending == 0)
goto unlock;
sub_running_bw(dl_se, &rq->dl);
dl_se->dl_non_contending = 0;
unlock:
task_rq_unlock(rq, p, &rf);
put_task_struct(p);
return HRTIMER_NORESTART;
}
void init_dl_inactive_task_timer(struct sched_dl_entity *dl_se)
{
struct hrtimer *timer = &dl_se->inactive_timer;
hrtimer_init(timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
timer->function = inactive_task_timer;
}
#define __node_2_dle(node) \
rb_entry((node), struct sched_dl_entity, rb_node)
#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)) {
if (dl_rq->earliest_dl.curr == 0)
cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_HIGHER);
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);
cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio.curr);
} else {
struct rb_node *leftmost = rb_first_cached(&dl_rq->root);
struct sched_dl_entity *entry = __node_2_dle(leftmost);
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 inline bool __dl_less(struct rb_node *a, const struct rb_node *b)
{
return dl_time_before(__node_2_dle(a)->deadline, __node_2_dle(b)->deadline);
}
static inline struct sched_statistics *
__schedstats_from_dl_se(struct sched_dl_entity *dl_se)
{
return &dl_task_of(dl_se)->stats;
}
static inline void
update_stats_wait_start_dl(struct dl_rq *dl_rq, struct sched_dl_entity *dl_se)
{
struct sched_statistics *stats;
if (!schedstat_enabled())
return;
stats = __schedstats_from_dl_se(dl_se);
__update_stats_wait_start(rq_of_dl_rq(dl_rq), dl_task_of(dl_se), stats);
}
static inline void
update_stats_wait_end_dl(struct dl_rq *dl_rq, struct sched_dl_entity *dl_se)
{
struct sched_statistics *stats;
if (!schedstat_enabled())
return;
stats = __schedstats_from_dl_se(dl_se);
__update_stats_wait_end(rq_of_dl_rq(dl_rq), dl_task_of(dl_se), stats);
}
static inline void
update_stats_enqueue_sleeper_dl(struct dl_rq *dl_rq, struct sched_dl_entity *dl_se)
{
struct sched_statistics *stats;
if (!schedstat_enabled())
return;
stats = __schedstats_from_dl_se(dl_se);
__update_stats_enqueue_sleeper(rq_of_dl_rq(dl_rq), dl_task_of(dl_se), stats);
}
static inline void
update_stats_enqueue_dl(struct dl_rq *dl_rq, struct sched_dl_entity *dl_se,
int flags)
{
if (!schedstat_enabled())
return;
if (flags & ENQUEUE_WAKEUP)
update_stats_enqueue_sleeper_dl(dl_rq, dl_se);
}
static inline void
update_stats_dequeue_dl(struct dl_rq *dl_rq, struct sched_dl_entity *dl_se,
int flags)
{
struct task_struct *p = dl_task_of(dl_se);
if (!schedstat_enabled())
return;
if ((flags & DEQUEUE_SLEEP)) {
unsigned int state;
state = READ_ONCE(p->__state);
if (state & TASK_INTERRUPTIBLE)
__schedstat_set(p->stats.sleep_start,
rq_clock(rq_of_dl_rq(dl_rq)));
if (state & TASK_UNINTERRUPTIBLE)
__schedstat_set(p->stats.block_start,
rq_clock(rq_of_dl_rq(dl_rq)));
}
}
static void __enqueue_dl_entity(struct sched_dl_entity *dl_se)
{
struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
BUG_ON(!RB_EMPTY_NODE(&dl_se->rb_node));
rb_add_cached(&dl_se->rb_node, &dl_rq->root, __dl_less);
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;
rb_erase_cached(&dl_se->rb_node, &dl_rq->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, int flags)
{
BUG_ON(on_dl_rq(dl_se));
update_stats_enqueue_dl(dl_rq_of_se(dl_se), dl_se, flags);
/*
* 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) {
task_contending(dl_se, flags);
update_dl_entity(dl_se);
} else if (flags & ENQUEUE_REPLENISH) {
replenish_dl_entity(dl_se);
} else if ((flags & ENQUEUE_RESTORE) &&
dl_time_before(dl_se->deadline,
rq_clock(rq_of_dl_rq(dl_rq_of_se(dl_se))))) {
setup_new_dl_entity(dl_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)
{
if (is_dl_boosted(&p->dl)) {
/*
* Because of delays in the detection of the overrun of a
* thread's runtime, it might be the case that a thread
* goes to sleep in a rt mutex with negative runtime. As
* a consequence, the thread will be throttled.
*
* While waiting for the mutex, this thread can also be
* boosted via PI, resulting in a thread that is throttled
* and boosted at the same time.
*
* In this case, the boost overrides the throttle.
*/
if (p->dl.dl_throttled) {
/*
* The replenish timer needs to be canceled. No
* problem if it fires concurrently: boosted threads
* are ignored in dl_task_timer().
*/
hrtimer_try_to_cancel(&p->dl.dl_timer);
p->dl.dl_throttled = 0;
}
} else if (!dl_prio(p->normal_prio)) {
/*
* Special case in which we have a !SCHED_DEADLINE task that is going
* to be deboosted, but exceeds its runtime while doing so. No point in
* replenishing it, as it's going to return back to its original
* scheduling class after this. If it has been throttled, we need to
* clear the flag, otherwise the task may wake up as throttled after
* being boosted again with no means to replenish the runtime and clear
* the throttle.
*/
p->dl.dl_throttled = 0;
BUG_ON(!is_dl_boosted(&p->dl) || 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_implicit(&p->dl))
dl_check_constrained_dl(&p->dl);
if (p->on_rq == TASK_ON_RQ_MIGRATING || flags & ENQUEUE_RESTORE) {
add_rq_bw(&p->dl, &rq->dl);
add_running_bw(&p->dl, &rq->dl);
}
/*
* If p is throttled, we do not enqueue it. 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.
* However, the active utilization does not depend on the fact
* that the task is on the runqueue or not (but depends on the
* task's state - in GRUB parlance, "inactive" vs "active contending").
* In other words, even if a task is throttled its utilization must
* be counted in the active utilization; hence, we need to call
* add_running_bw().
*/
if (p->dl.dl_throttled && !(flags & ENQUEUE_REPLENISH)) {
if (flags & ENQUEUE_WAKEUP)
task_contending(&p->dl, flags);
return;
}
check_schedstat_required();
update_stats_wait_start_dl(dl_rq_of_se(&p->dl), &p->dl);
enqueue_dl_entity(&p->dl, 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)
{
update_stats_dequeue_dl(&rq->dl, &p->dl, 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);
if (p->on_rq == TASK_ON_RQ_MIGRATING || flags & DEQUEUE_SAVE) {
sub_running_bw(&p->dl, &rq->dl);
sub_rq_bw(&p->dl, &rq->dl);
}
/*
* This check allows to start the inactive timer (or to immediately
* decrease the active utilization, if needed) in two cases:
* when the task blocks and when it is terminating
* (p->state == TASK_DEAD). We can handle the two cases in the same
* way, because from GRUB's point of view the same thing is happening
* (the task moves from "active contending" to "active non contending"
* or "inactive")
*/
if (flags & DEQUEUE_SLEEP)
task_non_contending(p);
}
/*
* 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);
}
#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 flags)
{
struct task_struct *curr;
bool select_rq;
struct rq *rq;
if (!(flags & WF_TTWU))
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.
*/
select_rq = unlikely(dl_task(curr)) &&
(curr->nr_cpus_allowed < 2 ||
!dl_entity_preempt(&p->dl, &curr->dl)) &&
p->nr_cpus_allowed > 1;
/*
* Take the capacity of the CPU into account to
* ensure it fits the requirement of the task.
*/
if (static_branch_unlikely(&sched_asym_cpucapacity))
select_rq |= !dl_task_fits_capacity(p, cpu);
if (select_rq) {
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 migrate_task_rq_dl(struct task_struct *p, int new_cpu __maybe_unused)
{
struct rq_flags rf;
struct rq *rq;
if (READ_ONCE(p->__state) != TASK_WAKING)
return;
rq = task_rq(p);
/*
* Since p->state == TASK_WAKING, set_task_cpu() has been called
* from try_to_wake_up(). Hence, p->pi_lock is locked, but
* rq->lock is not... So, lock it
*/
rq_lock(rq, &rf);
if (p->dl.dl_non_contending) {
update_rq_clock(rq);
sub_running_bw(&p->dl, &rq->dl);
p->dl.dl_non_contending = 0;
/*
* If the timer handler is currently running and the
* timer cannot be canceled, inactive_task_timer()
* will see that dl_not_contending is not set, and
* will not touch the rq's active utilization,
* so we are still safe.
*/
if (hrtimer_try_to_cancel(&p->dl.inactive_timer) == 1)
put_task_struct(p);
}
sub_rq_bw(&p->dl, &rq->dl);
rq_unlock(rq, &rf);
}
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))
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))
return;
resched_curr(rq);
}
static int balance_dl(struct rq *rq, struct task_struct *p, struct rq_flags *rf)
{
if (!on_dl_rq(&p->dl) && need_pull_dl_task(rq, p)) {
/*
* 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've
* not yet started the picking loop.
*/
rq_unpin_lock(rq, rf);
pull_dl_task(rq);
rq_repin_lock(rq, rf);
}
return sched_stop_runnable(rq) || sched_dl_runnable(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 void set_next_task_dl(struct rq *rq, struct task_struct *p, bool first)
{
struct sched_dl_entity *dl_se = &p->dl;
struct dl_rq *dl_rq = &rq->dl;
p->se.exec_start = rq_clock_task(rq);
if (on_dl_rq(&p->dl))
update_stats_wait_end_dl(dl_rq, dl_se);
/* You can't push away the running task */
dequeue_pushable_dl_task(rq, p);
if (!first)
return;
if (hrtick_enabled_dl(rq))
start_hrtick_dl(rq, p);
if (rq->curr->sched_class != &dl_sched_class)
update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 0);
deadline_queue_push_tasks(rq);
}
static struct sched_dl_entity *pick_next_dl_entity(struct dl_rq *dl_rq)
{
struct rb_node *left = rb_first_cached(&dl_rq->root);
if (!left)
return NULL;
return __node_2_dle(left);
}
static struct task_struct *pick_task_dl(struct rq *rq)
{
struct sched_dl_entity *dl_se;
struct dl_rq *dl_rq = &rq->dl;
struct task_struct *p;
if (!sched_dl_runnable(rq))
return NULL;
dl_se = pick_next_dl_entity(dl_rq);
BUG_ON(!dl_se);
p = dl_task_of(dl_se);
return p;
}
static struct task_struct *pick_next_task_dl(struct rq *rq)
{
struct task_struct *p;
p = pick_task_dl(rq);
if (p)
set_next_task_dl(rq, p, true);
return p;
}
static void put_prev_task_dl(struct rq *rq, struct task_struct *p)
{
struct sched_dl_entity *dl_se = &p->dl;
struct dl_rq *dl_rq = &rq->dl;
if (on_dl_rq(&p->dl))
update_stats_wait_start_dl(dl_rq, dl_se);
update_curr_dl(rq);
update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 1);
if (on_dl_rq(&p->dl) && p->nr_cpus_allowed > 1)
enqueue_pushable_dl_task(rq, p);
}
/*
* scheduler tick hitting a task of our scheduling class.
*
* NOTE: This function can be called remotely by the tick offload that
* goes along full dynticks. Therefore no local assumption can be made
* and everything must be accessed through the @rq and @curr passed in
* parameters.
*/
static void task_tick_dl(struct rq *rq, struct task_struct *p, int queued)
{
update_curr_dl(rq);
update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 1);
/*
* 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_dl(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()
*/
}
#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_mask))
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 task_struct *p = NULL;
struct rb_node *next_node;
if (!has_pushable_dl_tasks(rq))
return NULL;
next_node = rb_first_cached(&rq->dl.pushable_dl_tasks_root);
next_node:
if (next_node) {
p = __node_2_pdl(next_node);
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 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.
*/
if (!cpudl_find(&task_rq(task)->rd->cpudl, task, later_mask))
return -1;
/*
* If we are here, some targets have been found, including
* the most suitable which 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) {
int best_cpu;
/*
* 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;
}
best_cpu = cpumask_any_and_distribute(later_mask,
sched_domain_span(sd));
/*
* Last chance: if a CPU being in both later_mask
* and current sd span is valid, that becomes our
* choice. Of course, the latest possible CPU is
* already under consideration through later_mask.
*/
if (best_cpu < nr_cpu_ids) {
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_distribute(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_mask) ||
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 = __node_2_pdl(rb_first_cached(&rq->dl.pushable_dl_tasks_root));
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 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;
}
if (is_migration_disabled(next_task))
return 0;
if (WARN_ON(next_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 == 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, *push_task;
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 */
push_task = NULL;
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;
if (is_migration_disabled(p)) {
push_task = get_push_task(src_rq);
} else {
deactivate_task(src_rq, p, 0);
set_task_cpu(p, this_cpu);
activate_task(this_rq, p, 0);
dmin = p->dl.deadline;
resched = true;
}
/* Is there any other task even earlier? */
}
skip:
double_unlock_balance(this_rq, src_rq);
if (push_task) {
raw_spin_rq_unlock(this_rq);
stop_one_cpu_nowait(src_rq->cpu, push_cpu_stop,
push_task, &src_rq->push_work);
raw_spin_rq_lock(this_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,
u32 flags)
{
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_sub(src_dl_b, p->dl.dl_bw, dl_bw_cpus(task_cpu(p)));
raw_spin_unlock(&src_dl_b->lock);
}
set_cpus_allowed_common(p, new_mask, flags);
}
/* 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));
}
void dl_add_task_root_domain(struct task_struct *p)
{
struct rq_flags rf;
struct rq *rq;
struct dl_bw *dl_b;
raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
if (!dl_task(p)) {
raw_spin_unlock_irqrestore(&p->pi_lock, rf.flags);
return;
}
rq = __task_rq_lock(p, &rf);
dl_b = &rq->rd->dl_bw;
raw_spin_lock(&dl_b->lock);
__dl_add(dl_b, p->dl.dl_bw, cpumask_weight(rq->rd->span));
raw_spin_unlock(&dl_b->lock);
task_rq_unlock(rq, p, &rf);
}
void dl_clear_root_domain(struct root_domain *rd)
{
unsigned long flags;
raw_spin_lock_irqsave(&rd->dl_bw.lock, flags);
rd->dl_bw.total_bw = 0;
raw_spin_unlock_irqrestore(&rd->dl_bw.lock, flags);
}
#endif /* CONFIG_SMP */
static void switched_from_dl(struct rq *rq, struct task_struct *p)
{
/*
* task_non_contending() can start the "inactive timer" (if the 0-lag
* time is in the future). If the task switches back to dl before
* the "inactive timer" fires, it can continue to consume its current
* runtime using its current deadline. If it stays outside of
* SCHED_DEADLINE until the 0-lag time passes, inactive_task_timer()
* will reset the task parameters.
*/
if (task_on_rq_queued(p) && p->dl.dl_runtime)
task_non_contending(p);
if (!task_on_rq_queued(p)) {
/*
* Inactive timer is armed. However, p is leaving DEADLINE and
* might migrate away from this rq while continuing to run on
* some other class. We need to remove its contribution from
* this rq running_bw now, or sub_rq_bw (below) will complain.
*/
if (p->dl.dl_non_contending)
sub_running_bw(&p->dl, &rq->dl);
sub_rq_bw(&p->dl, &rq->dl);
}
/*
* We cannot use inactive_task_timer() to invoke sub_running_bw()
* at the 0-lag time, because the task could have been migrated
* while SCHED_OTHER in the meanwhile.
*/
if (p->dl.dl_non_contending)
p->dl.dl_non_contending = 0;
/*
* 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;
deadline_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 (hrtimer_try_to_cancel(&p->dl.inactive_timer) == 1)
put_task_struct(p);
/* If p is not queued we will update its parameters at next wakeup. */
if (!task_on_rq_queued(p)) {
add_rq_bw(&p->dl, &rq->dl);
return;
}
if (rq->curr != p) {
#ifdef CONFIG_SMP
if (p->nr_cpus_allowed > 1 && rq->dl.overloaded)
deadline_queue_push_tasks(rq);
#endif
if (dl_task(rq->curr))
check_preempt_curr_dl(rq, p, 0);
else
resched_curr(rq);
} else {
update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 0);
}
}
/*
* 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) || task_current(rq, 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)
deadline_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 */
}
}
DEFINE_SCHED_CLASS(dl) = {
.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,
.set_next_task = set_next_task_dl,
#ifdef CONFIG_SMP
.balance = balance_dl,
.pick_task = pick_task_dl,
.select_task_rq = select_task_rq_dl,
.migrate_task_rq = migrate_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,
.find_lock_rq = find_lock_later_rq,
#endif
.task_tick = task_tick_dl,
.task_fork = task_fork_dl,
.prio_changed = prio_changed_dl,
.switched_from = switched_from_dl,
.switched_to = switched_to_dl,
.update_curr = update_curr_dl,
};
/* Used for dl_bw check and update, used under sched_rt_handler()::mutex */
static u64 dl_generation;
int sched_dl_global_validate(void)
{
u64 runtime = global_rt_runtime();
u64 period = global_rt_period();
u64 new_bw = to_ratio(period, runtime);
u64 gen = ++dl_generation;
struct dl_bw *dl_b;
int cpu, cpus, ret = 0;
unsigned long flags;
/*
* Here we want to check the bandwidth not being set to some
* value smaller than the currently allocated bandwidth in
* any of the root_domains.
*/
for_each_possible_cpu(cpu) {
rcu_read_lock_sched();
if (dl_bw_visited(cpu, gen))
goto next;
dl_b = dl_bw_of(cpu);
cpus = dl_bw_cpus(cpu);
raw_spin_lock_irqsave(&dl_b->lock, flags);
if (new_bw * cpus < dl_b->total_bw)
ret = -EBUSY;
raw_spin_unlock_irqrestore(&dl_b->lock, flags);
next:
rcu_read_unlock_sched();
if (ret)
break;
}
return ret;
}
static void init_dl_rq_bw_ratio(struct dl_rq *dl_rq)
{
if (global_rt_runtime() == RUNTIME_INF) {
dl_rq->bw_ratio = 1 << RATIO_SHIFT;
dl_rq->extra_bw = 1 << BW_SHIFT;
} else {
dl_rq->bw_ratio = to_ratio(global_rt_runtime(),
global_rt_period()) >> (BW_SHIFT - RATIO_SHIFT);
dl_rq->extra_bw = to_ratio(global_rt_period(),
global_rt_runtime());
}
}
void sched_dl_do_global(void)
{
u64 new_bw = -1;
u64 gen = ++dl_generation;
struct dl_bw *dl_b;
int cpu;
unsigned long flags;
if (global_rt_runtime() != RUNTIME_INF)
new_bw = to_ratio(global_rt_period(), global_rt_runtime());
for_each_possible_cpu(cpu) {
rcu_read_lock_sched();
if (dl_bw_visited(cpu, gen)) {
rcu_read_unlock_sched();
continue;
}
dl_b = dl_bw_of(cpu);
raw_spin_lock_irqsave(&dl_b->lock, flags);
dl_b->bw = new_bw;
raw_spin_unlock_irqrestore(&dl_b->lock, flags);
rcu_read_unlock_sched();
init_dl_rq_bw_ratio(&cpu_rq(cpu)->dl);
}
}
/*
* We must be sure that accepting a new task (or allowing changing the
* parameters of an existing one) is consistent with the bandwidth
* constraints. If yes, this function also accordingly updates the currently
* allocated bandwidth to reflect the new situation.
*
* This function is called while holding p's rq->lock.
*/
int sched_dl_overflow(struct task_struct *p, int policy,
const struct sched_attr *attr)
{
u64 period = attr->sched_period ?: attr->sched_deadline;
u64 runtime = attr->sched_runtime;
u64 new_bw = dl_policy(policy) ? to_ratio(period, runtime) : 0;
int cpus, err = -1, cpu = task_cpu(p);
struct dl_bw *dl_b = dl_bw_of(cpu);
unsigned long cap;
if (attr->sched_flags & SCHED_FLAG_SUGOV)
return 0;
/* !deadline task may carry old deadline bandwidth */
if (new_bw == p->dl.dl_bw && task_has_dl_policy(p))
return 0;
/*
* Either if a task, enters, leave, or stays -deadline but changes
* its parameters, we may need to update accordingly the total
* allocated bandwidth of the container.
*/
raw_spin_lock(&dl_b->lock);
cpus = dl_bw_cpus(cpu);
cap = dl_bw_capacity(cpu);
if (dl_policy(policy) && !task_has_dl_policy(p) &&
!__dl_overflow(dl_b, cap, 0, new_bw)) {
if (hrtimer_active(&p->dl.inactive_timer))
__dl_sub(dl_b, p->dl.dl_bw, cpus);
__dl_add(dl_b, new_bw, cpus);
err = 0;
} else if (dl_policy(policy) && task_has_dl_policy(p) &&
!__dl_overflow(dl_b, cap, p->dl.dl_bw, new_bw)) {
/*
* XXX this is slightly incorrect: when the task
* utilization decreases, we should delay the total
* utilization change until the task's 0-lag point.
* But this would require to set the task's "inactive
* timer" when the task is not inactive.
*/
__dl_sub(dl_b, p->dl.dl_bw, cpus);
__dl_add(dl_b, new_bw, cpus);
dl_change_utilization(p, new_bw);
err = 0;
} else if (!dl_policy(policy) && task_has_dl_policy(p)) {
/*
* Do not decrease the total deadline utilization here,
* switched_from_dl() will take care to do it at the correct
* (0-lag) time.
*/
err = 0;
}
raw_spin_unlock(&dl_b->lock);
return err;
}
/*
* This function initializes the sched_dl_entity of a newly becoming
* SCHED_DEADLINE task.
*
* Only the static values are considered here, the actual runtime and the
* absolute deadline will be properly calculated when the task is enqueued
* for the first time with its new policy.
*/
void __setparam_dl(struct task_struct *p, const struct sched_attr *attr)
{
struct sched_dl_entity *dl_se = &p->dl;
dl_se->dl_runtime = attr->sched_runtime;
dl_se->dl_deadline = attr->sched_deadline;
dl_se->dl_period = attr->sched_period ?: dl_se->dl_deadline;
dl_se->flags = attr->sched_flags & SCHED_DL_FLAGS;
dl_se->dl_bw = to_ratio(dl_se->dl_period, dl_se->dl_runtime);
dl_se->dl_density = to_ratio(dl_se->dl_deadline, dl_se->dl_runtime);
}
void __getparam_dl(struct task_struct *p, struct sched_attr *attr)
{
struct sched_dl_entity *dl_se = &p->dl;
attr->sched_priority = p->rt_priority;
attr->sched_runtime = dl_se->dl_runtime;
attr->sched_deadline = dl_se->dl_deadline;
attr->sched_period = dl_se->dl_period;
attr->sched_flags &= ~SCHED_DL_FLAGS;
attr->sched_flags |= dl_se->flags;
}
/*
* This function validates the new parameters of a -deadline task.
* We ask for the deadline not being zero, and greater or equal
* than the runtime, as well as the period of being zero or
* greater than deadline. Furthermore, we have to be sure that
* user parameters are above the internal resolution of 1us (we
* check sched_runtime only since it is always the smaller one) and
* below 2^63 ns (we have to check both sched_deadline and
* sched_period, as the latter can be zero).
*/
bool __checkparam_dl(const struct sched_attr *attr)
{
u64 period, max, min;
/* special dl tasks don't actually use any parameter */
if (attr->sched_flags & SCHED_FLAG_SUGOV)
return true;
/* deadline != 0 */
if (attr->sched_deadline == 0)
return false;
/*
* Since we truncate DL_SCALE bits, make sure we're at least
* that big.
*/
if (attr->sched_runtime < (1ULL << DL_SCALE))
return false;
/*
* Since we use the MSB for wrap-around and sign issues, make
* sure it's not set (mind that period can be equal to zero).
*/
if (attr->sched_deadline & (1ULL << 63) ||
attr->sched_period & (1ULL << 63))
return false;
period = attr->sched_period;
if (!period)
period = attr->sched_deadline;
/* runtime <= deadline <= period (if period != 0) */
if (period < attr->sched_deadline ||
attr->sched_deadline < attr->sched_runtime)
return false;
max = (u64)READ_ONCE(sysctl_sched_dl_period_max) * NSEC_PER_USEC;
min = (u64)READ_ONCE(sysctl_sched_dl_period_min) * NSEC_PER_USEC;
if (period < min || period > max)
return false;
return true;
}
/*
* This function clears the sched_dl_entity static params.
*/
void __dl_clear_params(struct task_struct *p)
{
struct sched_dl_entity *dl_se = &p->dl;
dl_se->dl_runtime = 0;
dl_se->dl_deadline = 0;
dl_se->dl_period = 0;
dl_se->flags = 0;
dl_se->dl_bw = 0;
dl_se->dl_density = 0;
dl_se->dl_throttled = 0;
dl_se->dl_yielded = 0;
dl_se->dl_non_contending = 0;
dl_se->dl_overrun = 0;
#ifdef CONFIG_RT_MUTEXES
dl_se->pi_se = dl_se;
#endif
}
bool dl_param_changed(struct task_struct *p, const struct sched_attr *attr)
{
struct sched_dl_entity *dl_se = &p->dl;
if (dl_se->dl_runtime != attr->sched_runtime ||
dl_se->dl_deadline != attr->sched_deadline ||
dl_se->dl_period != attr->sched_period ||
dl_se->flags != (attr->sched_flags & SCHED_DL_FLAGS))
return true;
return false;
}
#ifdef CONFIG_SMP
int dl_cpuset_cpumask_can_shrink(const struct cpumask *cur,
const struct cpumask *trial)
{
int ret = 1, trial_cpus;
struct dl_bw *cur_dl_b;
unsigned long flags;
rcu_read_lock_sched();
cur_dl_b = dl_bw_of(cpumask_any(cur));
trial_cpus = cpumask_weight(trial);
raw_spin_lock_irqsave(&cur_dl_b->lock, flags);
if (cur_dl_b->bw != -1 &&
cur_dl_b->bw * trial_cpus < cur_dl_b->total_bw)
ret = 0;
raw_spin_unlock_irqrestore(&cur_dl_b->lock, flags);
rcu_read_unlock_sched();
return ret;
}
int dl_cpu_busy(int cpu, struct task_struct *p)
{
unsigned long flags, cap;
struct dl_bw *dl_b;
bool overflow;
rcu_read_lock_sched();
dl_b = dl_bw_of(cpu);
raw_spin_lock_irqsave(&dl_b->lock, flags);
cap = dl_bw_capacity(cpu);
overflow = __dl_overflow(dl_b, cap, 0, p ? p->dl.dl_bw : 0);
if (!overflow && p) {
/*
* We reserve space for this task in the destination
* root_domain, as we can't fail after this point.
* We will free resources in the source root_domain
* later on (see set_cpus_allowed_dl()).
*/
__dl_add(dl_b, p->dl.dl_bw, dl_bw_cpus(cpu));
}
raw_spin_unlock_irqrestore(&dl_b->lock, flags);
rcu_read_unlock_sched();
return overflow ? -EBUSY : 0;
}
#endif
#ifdef CONFIG_SCHED_DEBUG
void print_dl_stats(struct seq_file *m, int cpu)
{
print_dl_rq(m, cpu, &cpu_rq(cpu)->dl);
}
#endif /* CONFIG_SCHED_DEBUG */
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