- 根目录:
- kernel
- sched
- deadline.c
/*
* 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>
*/
#include "sched.h"
#include <linux/slab.h>
struct dl_bandwidth def_dl_bandwidth;
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);
}
static inline int is_leftmost(struct task_struct *p, struct dl_rq *dl_rq)
{
struct sched_dl_entity *dl_se = &p->dl;
return dl_rq->rb_leftmost == &dl_se->rb_node;
}
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;
}
extern unsigned long to_ratio(u64 period, u64 runtime);
void init_dl_bw(struct dl_bw *dl_b)
{
raw_spin_lock_init(&dl_b->lock);
raw_spin_lock(&def_dl_bandwidth.dl_runtime_lock);
if (global_rt_runtime() == RUNTIME_INF)
dl_b->bw = -1;
else
dl_b->bw = to_ratio(global_rt_period(), global_rt_runtime());
raw_spin_unlock(&def_dl_bandwidth.dl_runtime_lock);
dl_b->total_bw = 0;
}
void init_dl_rq(struct dl_rq *dl_rq, struct rq *rq)
{
dl_rq->rb_root = RB_ROOT;
#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;
#else
init_dl_bw(&dl_rq->dl_bw);
#endif
}
#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);
}
/*
* 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 dl_rq *dl_rq = &rq->dl;
struct rb_node **link = &dl_rq->pushable_dl_tasks_root.rb_node;
struct rb_node *parent = NULL;
struct task_struct *entry;
int leftmost = 1;
BUG_ON(!RB_EMPTY_NODE(&p->pushable_dl_tasks));
while (*link) {
parent = *link;
entry = rb_entry(parent, struct task_struct,
pushable_dl_tasks);
if (dl_entity_preempt(&p->dl, &entry->dl))
link = &parent->rb_left;
else {
link = &parent->rb_right;
leftmost = 0;
}
}
if (leftmost)
dl_rq->pushable_dl_tasks_leftmost = &p->pushable_dl_tasks;
rb_link_node(&p->pushable_dl_tasks, parent, link);
rb_insert_color(&p->pushable_dl_tasks, &dl_rq->pushable_dl_tasks_root);
}
static void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)
{
struct dl_rq *dl_rq = &rq->dl;
if (RB_EMPTY_NODE(&p->pushable_dl_tasks))
return;
if (dl_rq->pushable_dl_tasks_leftmost == &p->pushable_dl_tasks) {
struct rb_node *next_node;
next_node = rb_next(&p->pushable_dl_tasks);
dl_rq->pushable_dl_tasks_leftmost = next_node;
}
rb_erase(&p->pushable_dl_tasks, &dl_rq->pushable_dl_tasks_root);
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);
}
static int push_dl_task(struct rq *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)
{
}
#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 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);
WARN_ON(!dl_se->dl_new || dl_se->dl_throttled);
/*
* 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) + pi_se->dl_deadline;
dl_se->runtime = pi_se->dl_runtime;
dl_se->dl_new = 0;
}
/*
* 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_setscheduler_ex().
*/
static void replenish_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);
BUG_ON(pi_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_se->dl_deadline;
dl_se->runtime = pi_se->dl_runtime;
}
/*
* 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_se->dl_period;
dl_se->runtime += pi_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))) {
static bool lag_once = false;
if (!lag_once) {
lag_once = true;
printk_sched("sched: DL replenish lagged to much\n");
}
dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
dl_se->runtime = pi_se->dl_runtime;
}
}
/*
* 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.txt for more informations).
*
* This function returns true if:
*
* runtime / (deadline - t) > dl_runtime / dl_period ,
*
* IOW we can't recycle current parameters.
*
* Notice that the bandwidth check is done against the period. For
* task with deadline equal to period this is the same of using
* dl_deadline instead of dl_period 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_period >> 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);
/*
* The arrival of a new instance needs special treatment, i.e.,
* the actual scheduling parameters have to be "renewed".
*/
if (dl_se->dl_new) {
setup_new_dl_entity(dl_se, pi_se);
return;
}
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;
}
}
/*
* 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 enforcement 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 sched_dl_entity *dl_se, bool boosted)
{
struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
struct rq *rq = rq_of_dl_rq(dl_rq);
ktime_t now, act;
ktime_t soft, hard;
unsigned long range;
s64 delta;
if (boosted)
return 0;
/*
* 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_se->deadline);
now = hrtimer_cb_get_time(&dl_se->dl_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;
hrtimer_set_expires(&dl_se->dl_timer, act);
soft = hrtimer_get_softexpires(&dl_se->dl_timer);
hard = hrtimer_get_expires(&dl_se->dl_timer);
range = ktime_to_ns(ktime_sub(hard, soft));
__hrtimer_start_range_ns(&dl_se->dl_timer, soft,
range, HRTIMER_MODE_ABS, 0);
return hrtimer_active(&dl_se->dl_timer);
}
/*
* This is the bandwidth enforcement timer callback. If here, we know
* a task is not on its dl_rq, since the fact that the timer was running
* means the task is throttled and needs a runtime replenishment.
*
* However, what we actually do depends on the fact the task is active,
* (it is on its rq) or has been removed from there by a call to
* dequeue_task_dl(). In the former case we must issue the runtime
* replenishment and add the task back to the dl_rq; in the latter, we just
* do nothing but clearing dl_throttled, so that runtime and deadline
* updating (and the queueing back to dl_rq) will be done by the
* next call to enqueue_task_dl().
*/
static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
{
struct sched_dl_entity *dl_se = container_of(timer,
struct sched_dl_entity,
dl_timer);
struct task_struct *p = dl_task_of(dl_se);
struct rq *rq = task_rq(p);
raw_spin_lock(&rq->lock);
/*
* We need to take care of a possible races here. In fact, the
* task might have changed its scheduling policy to something
* different from SCHED_DEADLINE or changed its reservation
* parameters (through sched_setscheduler()).
*/
if (!dl_task(p) || dl_se->dl_new)
goto unlock;
sched_clock_tick();
update_rq_clock(rq);
dl_se->dl_throttled = 0;
if (p->on_rq) {
enqueue_task_dl(rq, p, ENQUEUE_REPLENISH);
if (task_has_dl_policy(rq->curr))
check_preempt_curr_dl(rq, p, 0);
else
resched_task(rq->curr);
#ifdef CONFIG_SMP
/*
* Queueing this task back might have overloaded rq,
* check if we need to kick someone away.
*/
if (has_pushable_dl_tasks(rq))
push_dl_task(rq);
#endif
}
unlock:
raw_spin_unlock(&rq->lock);
return HRTIMER_NORESTART;
}
void init_dl_task_timer(struct sched_dl_entity *dl_se)
{
struct hrtimer *timer = &dl_se->dl_timer;
if (hrtimer_active(timer)) {
hrtimer_try_to_cancel(timer);
return;
}
hrtimer_init(timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
timer->function = dl_task_timer;
}
static
int dl_runtime_exceeded(struct rq *rq, struct sched_dl_entity *dl_se)
{
int dmiss = dl_time_before(dl_se->deadline, rq_clock(rq));
int rorun = dl_se->runtime <= 0;
if (!rorun && !dmiss)
return 0;
/*
* If we are beyond our current deadline and we are still
* executing, then we have already used some of the runtime of
* the next instance. Thus, if we do not account that, we are
* stealing bandwidth from the system at each deadline miss!
*/
if (dmiss) {
dl_se->runtime = rorun ? dl_se->runtime : 0;
dl_se->runtime -= rq_clock(rq) - dl_se->deadline;
}
return 1;
}
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))
delta_exec = 0;
schedstat_set(curr->se.statistics.exec_max,
max(curr->se.statistics.exec_max, delta_exec));
curr->se.sum_exec_runtime += delta_exec;
account_group_exec_runtime(curr, delta_exec);
curr->se.exec_start = rq_clock_task(rq);
cpuacct_charge(curr, delta_exec);
sched_rt_avg_update(rq, delta_exec);
dl_se->runtime -= delta_exec;
if (dl_runtime_exceeded(rq, dl_se)) {
__dequeue_task_dl(rq, curr, 0);
if (likely(start_dl_timer(dl_se, curr->dl.dl_boosted)))
dl_se->dl_throttled = 1;
else
enqueue_task_dl(rq, curr, ENQUEUE_REPLENISH);
if (!is_leftmost(curr, &rq->dl))
resched_task(curr);
}
/*
* Because -- for now -- we share the rt bandwidth, we need to
* account our runtime there too, otherwise actual rt tasks
* would be able to exceed the shared quota.
*
* Account to the root rt group for now.
*
* The solution we're working towards is having the RT groups scheduled
* using deadline servers -- however there's a few nasties to figure
* out before that can happen.
*/
if (rt_bandwidth_enabled()) {
struct rt_rq *rt_rq = &rq->rt;
raw_spin_lock(&rt_rq->rt_runtime_lock);
/*
* 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 struct task_struct *pick_next_earliest_dl_task(struct rq *rq, int cpu);
static inline u64 next_deadline(struct rq *rq)
{
struct task_struct *next = pick_next_earliest_dl_task(rq, rq->cpu);
if (next && dl_prio(next->prio))
return next->dl.deadline;
else
return 0;
}
static void inc_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
{
struct rq *rq = rq_of_dl_rq(dl_rq);
if (dl_rq->earliest_dl.curr == 0 ||
dl_time_before(deadline, dl_rq->earliest_dl.curr)) {
/*
* If the dl_rq had no -deadline tasks, or if the new task
* has shorter deadline than the current one on dl_rq, we
* know that the previous earliest becomes our next earliest,
* as the new task becomes the earliest itself.
*/
dl_rq->earliest_dl.next = dl_rq->earliest_dl.curr;
dl_rq->earliest_dl.curr = deadline;
cpudl_set(&rq->rd->cpudl, rq->cpu, deadline, 1);
} else if (dl_rq->earliest_dl.next == 0 ||
dl_time_before(deadline, dl_rq->earliest_dl.next)) {
/*
* On the other hand, if the new -deadline task has a
* a later deadline than the earliest one on dl_rq, but
* it is earlier than the next (if any), we must
* recompute the next-earliest.
*/
dl_rq->earliest_dl.next = next_deadline(rq);
}
}
static void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
{
struct rq *rq = rq_of_dl_rq(dl_rq);
/*
* Since we may have removed our earliest (and/or next earliest)
* task we must recompute them.
*/
if (!dl_rq->dl_nr_running) {
dl_rq->earliest_dl.curr = 0;
dl_rq->earliest_dl.next = 0;
cpudl_set(&rq->rd->cpudl, rq->cpu, 0, 0);
} else {
struct rb_node *leftmost = dl_rq->rb_leftmost;
struct sched_dl_entity *entry;
entry = rb_entry(leftmost, struct sched_dl_entity, rb_node);
dl_rq->earliest_dl.curr = entry->deadline;
dl_rq->earliest_dl.next = next_deadline(rq);
cpudl_set(&rq->rd->cpudl, rq->cpu, entry->deadline, 1);
}
}
#else
static inline void inc_dl_deadline(struct dl_rq *dl_rq, u64 deadline) {}
static inline void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline) {}
#endif /* CONFIG_SMP */
static inline
void inc_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
{
int prio = dl_task_of(dl_se)->prio;
u64 deadline = dl_se->deadline;
WARN_ON(!dl_prio(prio));
dl_rq->dl_nr_running++;
inc_nr_running(rq_of_dl_rq(dl_rq));
inc_dl_deadline(dl_rq, deadline);
inc_dl_migration(dl_se, dl_rq);
}
static inline
void dec_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
{
int prio = dl_task_of(dl_se)->prio;
WARN_ON(!dl_prio(prio));
WARN_ON(!dl_rq->dl_nr_running);
dl_rq->dl_nr_running--;
dec_nr_running(rq_of_dl_rq(dl_rq));
dec_dl_deadline(dl_rq, dl_se->deadline);
dec_dl_migration(dl_se, dl_rq);
}
static void __enqueue_dl_entity(struct sched_dl_entity *dl_se)
{
struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
struct rb_node **link = &dl_rq->rb_root.rb_node;
struct rb_node *parent = NULL;
struct sched_dl_entity *entry;
int leftmost = 1;
BUG_ON(!RB_EMPTY_NODE(&dl_se->rb_node));
while (*link) {
parent = *link;
entry = rb_entry(parent, struct sched_dl_entity, rb_node);
if (dl_time_before(dl_se->deadline, entry->deadline))
link = &parent->rb_left;
else {
link = &parent->rb_right;
leftmost = 0;
}
}
if (leftmost)
dl_rq->rb_leftmost = &dl_se->rb_node;
rb_link_node(&dl_se->rb_node, parent, link);
rb_insert_color(&dl_se->rb_node, &dl_rq->rb_root);
inc_dl_tasks(dl_se, dl_rq);
}
static void __dequeue_dl_entity(struct sched_dl_entity *dl_se)
{
struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
if (RB_EMPTY_NODE(&dl_se->rb_node))
return;
if (dl_rq->rb_leftmost == &dl_se->rb_node) {
struct rb_node *next_node;
next_node = rb_next(&dl_se->rb_node);
dl_rq->rb_leftmost = next_node;
}
rb_erase(&dl_se->rb_node, &dl_rq->rb_root);
RB_CLEAR_NODE(&dl_se->rb_node);
dec_dl_tasks(dl_se, dl_rq);
}
static void
enqueue_dl_entity(struct sched_dl_entity *dl_se,
struct sched_dl_entity *pi_se, int flags)
{
BUG_ON(on_dl_rq(dl_se));
/*
* If this is a wakeup or a new instance, the scheduling
* parameters of the task might need updating. Otherwise,
* we want a replenishment of its runtime.
*/
if (!dl_se->dl_new && flags & ENQUEUE_REPLENISH)
replenish_dl_entity(dl_se, pi_se);
else
update_dl_entity(dl_se, pi_se);
__enqueue_dl_entity(dl_se);
}
static void dequeue_dl_entity(struct sched_dl_entity *dl_se)
{
__dequeue_dl_entity(dl_se);
}
static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags)
{
struct task_struct *pi_task = rt_mutex_get_top_task(p);
struct sched_dl_entity *pi_se = &p->dl;
/*
* Use the scheduling parameters of the top pi-waiter
* task if we have one and its (relative) deadline is
* smaller than our one... OTW we keep our runtime and
* deadline.
*/
if (pi_task && p->dl.dl_boosted && dl_prio(pi_task->normal_prio))
pi_se = &pi_task->dl;
/*
* If p is throttled, we do nothing. In fact, if it exhausted
* its budget it needs a replenishment and, since it now is on
* its rq, the bandwidth timer callback (which clearly has not
* run yet) will take care of this.
*/
if (p->dl.dl_throttled)
return;
enqueue_dl_entity(&p->dl, pi_se, flags);
if (!task_current(rq, p) && p->nr_cpus_allowed > 1)
enqueue_pushable_dl_task(rq, p);
}
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)
{
struct task_struct *p = rq->curr;
/*
* We make the task go to sleep until its current deadline by
* forcing its runtime to zero. This way, update_curr_dl() stops
* it and the bandwidth timer will wake it up and will give it
* new scheduling parameters (thanks to dl_new=1).
*/
if (p->dl.runtime > 0) {
rq->curr->dl.dl_new = 1;
p->dl.runtime = 0;
}
update_curr_dl(rq);
}
#ifdef CONFIG_SMP
static int find_later_rq(struct task_struct *task);
static int
select_task_rq_dl(struct task_struct *p, int cpu, int sd_flag, int flags)
{
struct task_struct *curr;
struct rq *rq;
if (sd_flag != SD_BALANCE_WAKE && sd_flag != SD_BALANCE_FORK)
goto out;
rq = cpu_rq(cpu);
rcu_read_lock();
curr = ACCESS_ONCE(rq->curr); /* unlocked access */
/*
* If we are dealing with a -deadline task, we must
* decide where to wake it up.
* If it has a later deadline and the current task
* on this rq can't move (provided the waking task
* can!) we prefer to send it somewhere else. On the
* other hand, if it has a shorter deadline, we
* try to make it stay here, it might be important.
*/
if (unlikely(dl_task(curr)) &&
(curr->nr_cpus_allowed < 2 ||
!dl_entity_preempt(&p->dl, &curr->dl)) &&
(p->nr_cpus_allowed > 1)) {
int target = find_later_rq(p);
if (target != -1)
cpu = target;
}
rcu_read_unlock();
out:
return cpu;
}
static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
{
/*
* Current can't be migrated, useless to reschedule,
* let's hope p can move out.
*/
if (rq->curr->nr_cpus_allowed == 1 ||
cpudl_find(&rq->rd->cpudl, rq->curr, NULL) == -1)
return;
/*
* p is migratable, so let's not schedule it and
* see if it is pushed or pulled somewhere else.
*/
if (p->nr_cpus_allowed != 1 &&
cpudl_find(&rq->rd->cpudl, p, NULL) != -1)
return;
resched_task(rq->curr);
}
#endif /* CONFIG_SMP */
/*
* Only called when both the current and waking task are -deadline
* tasks.
*/
static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
int flags)
{
if (dl_entity_preempt(&p->dl, &rq->curr->dl)) {
resched_task(rq->curr);
return;
}
#ifdef CONFIG_SMP
/*
* In the unlikely case current and p have the same deadline
* let us try to decide what's the best thing to do...
*/
if ((p->dl.deadline == rq->curr->dl.deadline) &&
!test_tsk_need_resched(rq->curr))
check_preempt_equal_dl(rq, p);
#endif /* CONFIG_SMP */
}
#ifdef CONFIG_SCHED_HRTICK
static void start_hrtick_dl(struct rq *rq, struct task_struct *p)
{
s64 delta = p->dl.dl_runtime - p->dl.runtime;
if (delta > 10000)
hrtick_start(rq, p->dl.runtime);
}
#endif
static struct sched_dl_entity *pick_next_dl_entity(struct rq *rq,
struct dl_rq *dl_rq)
{
struct rb_node *left = dl_rq->rb_leftmost;
if (!left)
return NULL;
return rb_entry(left, struct sched_dl_entity, rb_node);
}
struct task_struct *pick_next_task_dl(struct rq *rq)
{
struct sched_dl_entity *dl_se;
struct task_struct *p;
struct dl_rq *dl_rq;
dl_rq = &rq->dl;
if (unlikely(!dl_rq->dl_nr_running))
return NULL;
dl_se = pick_next_dl_entity(rq, dl_rq);
BUG_ON(!dl_se);
p = dl_task_of(dl_se);
p->se.exec_start = rq_clock_task(rq);
/* Running task will never be pushed. */
dequeue_pushable_dl_task(rq, p);
#ifdef CONFIG_SCHED_HRTICK
if (hrtick_enabled(rq))
start_hrtick_dl(rq, p);
#endif
#ifdef CONFIG_SMP
rq->post_schedule = has_pushable_dl_tasks(rq);
#endif /* CONFIG_SMP */
return p;
}
static void put_prev_task_dl(struct rq *rq, struct task_struct *p)
{
update_curr_dl(rq);
if (on_dl_rq(&p->dl) && p->nr_cpus_allowed > 1)
enqueue_pushable_dl_task(rq, p);
}
static void task_tick_dl(struct rq *rq, struct task_struct *p, int queued)
{
update_curr_dl(rq);
#ifdef CONFIG_SCHED_HRTICK
if (hrtick_enabled(rq) && queued && p->dl.runtime > 0)
start_hrtick_dl(rq, p);
#endif
}
static void task_fork_dl(struct task_struct *p)
{
/*
* SCHED_DEADLINE tasks cannot fork and this is achieved through
* sched_fork()
*/
}
static void task_dead_dl(struct task_struct *p)
{
struct hrtimer *timer = &p->dl.dl_timer;
struct dl_bw *dl_b = dl_bw_of(task_cpu(p));
/*
* Since we are TASK_DEAD we won't slip out of the domain!
*/
raw_spin_lock_irq(&dl_b->lock);
dl_b->total_bw -= p->dl.dl_bw;
raw_spin_unlock_irq(&dl_b->lock);
hrtimer_cancel(timer);
}
static void set_curr_task_dl(struct rq *rq)
{
struct task_struct *p = rq->curr;
p->se.exec_start = rq_clock_task(rq);
/* You can't push away the running task */
dequeue_pushable_dl_task(rq, p);
}
#ifdef CONFIG_SMP
/* Only try algorithms three times */
#define DL_MAX_TRIES 3
static int pick_dl_task(struct rq *rq, struct task_struct *p, int cpu)
{
if (!task_running(rq, p) &&
(cpu < 0 || cpumask_test_cpu(cpu, &p->cpus_allowed)) &&
(p->nr_cpus_allowed > 1))
return 1;
return 0;
}
/* Returns the second earliest -deadline task, NULL otherwise */
static struct task_struct *pick_next_earliest_dl_task(struct rq *rq, int cpu)
{
struct rb_node *next_node = rq->dl.rb_leftmost;
struct sched_dl_entity *dl_se;
struct task_struct *p = NULL;
next_node:
next_node = rb_next(next_node);
if (next_node) {
dl_se = rb_entry(next_node, struct sched_dl_entity, rb_node);
p = dl_task_of(dl_se);
if (pick_dl_task(rq, p, cpu))
return p;
goto next_node;
}
return NULL;
}
static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl);
static int find_later_rq(struct task_struct *task)
{
struct sched_domain *sd;
struct cpumask *later_mask = __get_cpu_var(local_cpu_mask_dl);
int this_cpu = smp_processor_id();
int best_cpu, cpu = task_cpu(task);
/* Make sure the mask is initialized first */
if (unlikely(!later_mask))
return -1;
if (task->nr_cpus_allowed == 1)
return -1;
best_cpu = cpudl_find(&task_rq(task)->rd->cpudl,
task, later_mask);
if (best_cpu == -1)
return -1;
/*
* If we are here, some target has been found,
* the most suitable of which is cached in best_cpu.
* This is, among the runqueues where the current tasks
* have later deadlines than the task's one, the rq
* with the latest possible one.
*
* Now we check how well this matches with task's
* affinity and system topology.
*
* The last cpu where the task run is our first
* guess, since it is most likely cache-hot there.
*/
if (cpumask_test_cpu(cpu, later_mask))
return cpu;
/*
* Check if this_cpu is to be skipped (i.e., it is
* not in the mask) or not.
*/
if (!cpumask_test_cpu(this_cpu, later_mask))
this_cpu = -1;
rcu_read_lock();
for_each_domain(cpu, sd) {
if (sd->flags & SD_WAKE_AFFINE) {
/*
* If possible, preempting this_cpu is
* cheaper than migrating.
*/
if (this_cpu != -1 &&
cpumask_test_cpu(this_cpu, sched_domain_span(sd))) {
rcu_read_unlock();
return this_cpu;
}
/*
* Last chance: if best_cpu is valid and is
* in the mask, that becomes our choice.
*/
if (best_cpu < nr_cpu_ids &&
cpumask_test_cpu(best_cpu, sched_domain_span(sd))) {
rcu_read_unlock();
return best_cpu;
}
}
}
rcu_read_unlock();
/*
* At this point, all our guesses failed, we just return
* 'something', and let the caller sort the things out.
*/
if (this_cpu != -1)
return this_cpu;
cpu = cpumask_any(later_mask);
if (cpu < nr_cpu_ids)
return cpu;
return -1;
}
/* Locks the rq it finds */
static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq)
{
struct rq *later_rq = NULL;
int tries;
int cpu;
for (tries = 0; tries < DL_MAX_TRIES; tries++) {
cpu = find_later_rq(task);
if ((cpu == -1) || (cpu == rq->cpu))
break;
later_rq = cpu_rq(cpu);
/* Retry if something changed. */
if (double_lock_balance(rq, later_rq)) {
if (unlikely(task_rq(task) != rq ||
!cpumask_test_cpu(later_rq->cpu,
&task->cpus_allowed) ||
task_running(rq, task) || !task->on_rq)) {
double_unlock_balance(rq, later_rq);
later_rq = NULL;
break;
}
}
/*
* If the rq we found has no -deadline task, or
* its earliest one has a later deadline than our
* task, the rq is a good one.
*/
if (!later_rq->dl.dl_nr_running ||
dl_time_before(task->dl.deadline,
later_rq->dl.earliest_dl.curr))
break;
/* Otherwise we try again. */
double_unlock_balance(rq, later_rq);
later_rq = NULL;
}
return later_rq;
}
static struct task_struct *pick_next_pushable_dl_task(struct rq *rq)
{
struct task_struct *p;
if (!has_pushable_dl_tasks(rq))
return NULL;
p = rb_entry(rq->dl.pushable_dl_tasks_leftmost,
struct task_struct, pushable_dl_tasks);
BUG_ON(rq->cpu != task_cpu(p));
BUG_ON(task_current(rq, p));
BUG_ON(p->nr_cpus_allowed <= 1);
BUG_ON(!p->on_rq);
BUG_ON(!dl_task(p));
return p;
}
/*
* See if the non running -deadline tasks on this rq
* can be sent to some other CPU where they can preempt
* and start executing.
*/
static int push_dl_task(struct rq *rq)
{
struct task_struct *next_task;
struct rq *later_rq;
if (!rq->dl.overloaded)
return 0;
next_task = pick_next_pushable_dl_task(rq);
if (!next_task)
return 0;
retry:
if (unlikely(next_task == rq->curr)) {
WARN_ON(1);
return 0;
}
/*
* If next_task preempts rq->curr, and rq->curr
* can move away, it makes sense to just reschedule
* without going further in pushing next_task.
*/
if (dl_task(rq->curr) &&
dl_time_before(next_task->dl.deadline, rq->curr->dl.deadline) &&
rq->curr->nr_cpus_allowed > 1) {
resched_task(rq->curr);
return 0;
}
/* We might release rq lock */
get_task_struct(next_task);
/* Will lock the rq it'll find */
later_rq = find_lock_later_rq(next_task, rq);
if (!later_rq) {
struct task_struct *task;
/*
* We must check all this again, since
* find_lock_later_rq releases rq->lock and it is
* then possible that next_task has migrated.
*/
task = pick_next_pushable_dl_task(rq);
if (task_cpu(next_task) == rq->cpu && task == next_task) {
/*
* The task is still there. We don't try
* again, some other cpu will pull it when ready.
*/
dequeue_pushable_dl_task(rq, next_task);
goto out;
}
if (!task)
/* No more tasks */
goto out;
put_task_struct(next_task);
next_task = task;
goto retry;
}
deactivate_task(rq, next_task, 0);
set_task_cpu(next_task, later_rq->cpu);
activate_task(later_rq, next_task, 0);
resched_task(later_rq->curr);
double_unlock_balance(rq, later_rq);
out:
put_task_struct(next_task);
return 1;
}
static void push_dl_tasks(struct rq *rq)
{
/* Terminates as it moves a -deadline task */
while (push_dl_task(rq))
;
}
static int pull_dl_task(struct rq *this_rq)
{
int this_cpu = this_rq->cpu, ret = 0, cpu;
struct task_struct *p;
struct rq *src_rq;
u64 dmin = LONG_MAX;
if (likely(!dl_overloaded(this_rq)))
return 0;
/*
* Match the barrier from dl_set_overloaded; this guarantees that if we
* see overloaded we must also see the dlo_mask bit.
*/
smp_rmb();
for_each_cpu(cpu, this_rq->rd->dlo_mask) {
if (this_cpu == cpu)
continue;
src_rq = cpu_rq(cpu);
/*
* It looks racy, abd it is! However, as in sched_rt.c,
* we are fine with this.
*/
if (this_rq->dl.dl_nr_running &&
dl_time_before(this_rq->dl.earliest_dl.curr,
src_rq->dl.earliest_dl.next))
continue;
/* Might drop this_rq->lock */
double_lock_balance(this_rq, src_rq);
/*
* If there are no more pullable tasks on the
* rq, we're done with it.
*/
if (src_rq->dl.dl_nr_running <= 1)
goto skip;
p = pick_next_earliest_dl_task(src_rq, this_cpu);
/*
* We found a task to be pulled if:
* - it preempts our current (if there's one),
* - it will preempt the last one we pulled (if any).
*/
if (p && dl_time_before(p->dl.deadline, dmin) &&
(!this_rq->dl.dl_nr_running ||
dl_time_before(p->dl.deadline,
this_rq->dl.earliest_dl.curr))) {
WARN_ON(p == src_rq->curr);
WARN_ON(!p->on_rq);
/*
* Then we pull iff p has actually an earlier
* deadline than the current task of its runqueue.
*/
if (dl_time_before(p->dl.deadline,
src_rq->curr->dl.deadline))
goto skip;
ret = 1;
deactivate_task(src_rq, p, 0);
set_task_cpu(p, this_cpu);
activate_task(this_rq, p, 0);
dmin = p->dl.deadline;
/* Is there any other task even earlier? */
}
skip:
double_unlock_balance(this_rq, src_rq);
}
return ret;
}
static void pre_schedule_dl(struct rq *rq, struct task_struct *prev)
{
/* Try to pull other tasks here */
if (dl_task(prev))
pull_dl_task(rq);
}
static void post_schedule_dl(struct rq *rq)
{
push_dl_tasks(rq);
}
/*
* Since the task is not running and a reschedule is not going to happen
* anytime soon on its runqueue, we try pushing it away now.
*/
static void task_woken_dl(struct rq *rq, struct task_struct *p)
{
if (!task_running(rq, p) &&
!test_tsk_need_resched(rq->curr) &&
has_pushable_dl_tasks(rq) &&
p->nr_cpus_allowed > 1 &&
dl_task(rq->curr) &&
(rq->curr->nr_cpus_allowed < 2 ||
dl_entity_preempt(&rq->curr->dl, &p->dl))) {
push_dl_tasks(rq);
}
}
static void set_cpus_allowed_dl(struct task_struct *p,
const struct cpumask *new_mask)
{
struct rq *rq;
int weight;
BUG_ON(!dl_task(p));
/*
* Update only if the task is actually running (i.e.,
* it is on the rq AND it is not throttled).
*/
if (!on_dl_rq(&p->dl))
return;
weight = cpumask_weight(new_mask);
/*
* Only update if the process changes its state from whether it
* can migrate or not.
*/
if ((p->nr_cpus_allowed > 1) == (weight > 1))
return;
rq = task_rq(p);
/*
* The process used to be able to migrate OR it can now migrate
*/
if (weight <= 1) {
if (!task_current(rq, p))
dequeue_pushable_dl_task(rq, p);
BUG_ON(!rq->dl.dl_nr_migratory);
rq->dl.dl_nr_migratory--;
} else {
if (!task_current(rq, p))
enqueue_pushable_dl_task(rq, p);
rq->dl.dl_nr_migratory++;
}
update_dl_migration(&rq->dl);
}
/* Assumes rq->lock is held */
static void rq_online_dl(struct rq *rq)
{
if (rq->dl.overloaded)
dl_set_overload(rq);
if (rq->dl.dl_nr_running > 0)
cpudl_set(&rq->rd->cpudl, rq->cpu, rq->dl.earliest_dl.curr, 1);
}
/* Assumes rq->lock is held */
static void rq_offline_dl(struct rq *rq)
{
if (rq->dl.overloaded)
dl_clear_overload(rq);
cpudl_set(&rq->rd->cpudl, rq->cpu, 0, 0);
}
void init_sched_dl_class(void)
{
unsigned int i;
for_each_possible_cpu(i)
zalloc_cpumask_var_node(&per_cpu(local_cpu_mask_dl, i),
GFP_KERNEL, cpu_to_node(i));
}
#endif /* CONFIG_SMP */
static void switched_from_dl(struct rq *rq, struct task_struct *p)
{
if (hrtimer_active(&p->dl.dl_timer) && !dl_policy(p->policy))
hrtimer_try_to_cancel(&p->dl.dl_timer);
#ifdef CONFIG_SMP
/*
* 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 (!rq->dl.dl_nr_running)
pull_dl_task(rq);
#endif
}
/*
* 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)
{
int check_resched = 1;
/*
* If p is throttled, don't consider the possibility
* of preempting rq->curr, the check will be done right
* after its runtime will get replenished.
*/
if (unlikely(p->dl.dl_throttled))
return;
if (p->on_rq || rq->curr != p) {
#ifdef CONFIG_SMP
if (rq->dl.overloaded && push_dl_task(rq) && rq != task_rq(p))
/* Only reschedule if pushing failed */
check_resched = 0;
#endif /* CONFIG_SMP */
if (check_resched && task_has_dl_policy(rq->curr))
check_preempt_curr_dl(rq, p, 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 (p->on_rq || 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)
pull_dl_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) &&
rq->curr == p)
resched_task(p);
#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_task(p);
#endif /* CONFIG_SMP */
} else
switched_to_dl(rq, p);
}
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,
.pre_schedule = pre_schedule_dl,
.post_schedule = post_schedule_dl,
.task_woken = task_woken_dl,
#endif
.set_curr_task = set_curr_task_dl,
.task_tick = task_tick_dl,
.task_fork = task_fork_dl,
.task_dead = task_dead_dl,
.prio_changed = prio_changed_dl,
.switched_from = switched_from_dl,
.switched_to = switched_to_dl,
};