Commit 2d3d891d authored by Dario Faggioli's avatar Dario Faggioli Committed by Ingo Molnar

sched/deadline: Add SCHED_DEADLINE inheritance logic

Some method to deal with rt-mutexes and make sched_dl interact with
the current PI-coded is needed, raising all but trivial issues, that
needs (according to us) to be solved with some restructuring of
the pi-code (i.e., going toward a proxy execution-ish implementation).

This is under development, in the meanwhile, as a temporary solution,
what this commits does is:

 - ensure a pi-lock owner with waiters is never throttled down. Instead,
   when it runs out of runtime, it immediately gets replenished and it's
   deadline is postponed;

 - the scheduling parameters (relative deadline and default runtime)
   used for that replenishments --during the whole period it holds the
   pi-lock-- are the ones of the waiting task with earliest deadline.

Acting this way, we provide some kind of boosting to the lock-owner,
still by using the existing (actually, slightly modified by the previous
commit) pi-architecture.

We would stress the fact that this is only a surely needed, all but
clean solution to the problem. In the end it's only a way to re-start
discussion within the community. So, as always, comments, ideas, rants,
etc.. are welcome! :-)
Signed-off-by: default avatarDario Faggioli <raistlin@linux.it>
Signed-off-by: default avatarJuri Lelli <juri.lelli@gmail.com>
[ Added !RT_MUTEXES build fix. ]
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1383831828-15501-11-git-send-email-juri.lelli@gmail.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent fb00aca4
......@@ -1124,8 +1124,12 @@ struct sched_dl_entity {
* @dl_new tells if a new instance arrived. If so we must
* start executing it with full runtime and reset its absolute
* deadline;
*
* @dl_boosted tells if we are boosted due to DI. If so we are
* outside bandwidth enforcement mechanism (but only until we
* exit the critical section).
*/
int dl_throttled, dl_new;
int dl_throttled, dl_new, dl_boosted;
/*
* Bandwidth enforcement timer. Each -deadline task has its
......@@ -1359,6 +1363,8 @@ struct task_struct {
struct rb_node *pi_waiters_leftmost;
/* Deadlock detection and priority inheritance handling */
struct rt_mutex_waiter *pi_blocked_on;
/* Top pi_waiters task */
struct task_struct *pi_top_task;
#endif
#ifdef CONFIG_DEBUG_MUTEXES
......
......@@ -35,6 +35,7 @@ static inline int rt_task(struct task_struct *p)
#ifdef CONFIG_RT_MUTEXES
extern int rt_mutex_getprio(struct task_struct *p);
extern void rt_mutex_setprio(struct task_struct *p, int prio);
extern struct task_struct *rt_mutex_get_top_task(struct task_struct *task);
extern void rt_mutex_adjust_pi(struct task_struct *p);
static inline bool tsk_is_pi_blocked(struct task_struct *tsk)
{
......@@ -45,6 +46,10 @@ static inline int rt_mutex_getprio(struct task_struct *p)
{
return p->normal_prio;
}
static inline struct task_struct *rt_mutex_get_top_task(struct task_struct *task)
{
return NULL;
}
# define rt_mutex_adjust_pi(p) do { } while (0)
static inline bool tsk_is_pi_blocked(struct task_struct *tsk)
{
......
......@@ -1090,6 +1090,7 @@ static void rt_mutex_init_task(struct task_struct *p)
p->pi_waiters = RB_ROOT;
p->pi_waiters_leftmost = NULL;
p->pi_blocked_on = NULL;
p->pi_top_task = NULL;
#endif
}
......
......@@ -96,13 +96,16 @@ static inline int
rt_mutex_waiter_less(struct rt_mutex_waiter *left,
struct rt_mutex_waiter *right)
{
if (left->task->prio < right->task->prio)
if (left->prio < right->prio)
return 1;
/*
* If both tasks are dl_task(), we check their deadlines.
* If both waiters have dl_prio(), we check the deadlines of the
* associated tasks.
* If left waiter has a dl_prio(), and we didn't return 1 above,
* then right waiter has a dl_prio() too.
*/
if (dl_prio(left->task->prio) && dl_prio(right->task->prio))
if (dl_prio(left->prio))
return (left->task->dl.deadline < right->task->dl.deadline);
return 0;
......@@ -197,10 +200,18 @@ int rt_mutex_getprio(struct task_struct *task)
if (likely(!task_has_pi_waiters(task)))
return task->normal_prio;
return min(task_top_pi_waiter(task)->task->prio,
return min(task_top_pi_waiter(task)->prio,
task->normal_prio);
}
struct task_struct *rt_mutex_get_top_task(struct task_struct *task)
{
if (likely(!task_has_pi_waiters(task)))
return NULL;
return task_top_pi_waiter(task)->task;
}
/*
* Adjust the priority of a task, after its pi_waiters got modified.
*
......@@ -210,7 +221,7 @@ static void __rt_mutex_adjust_prio(struct task_struct *task)
{
int prio = rt_mutex_getprio(task);
if (task->prio != prio)
if (task->prio != prio || dl_prio(prio))
rt_mutex_setprio(task, prio);
}
......@@ -328,7 +339,7 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task,
* When deadlock detection is off then we check, if further
* priority adjustment is necessary.
*/
if (!detect_deadlock && waiter->task->prio == task->prio)
if (!detect_deadlock && waiter->prio == task->prio)
goto out_unlock_pi;
lock = waiter->lock;
......@@ -350,7 +361,7 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task,
/* Requeue the waiter */
rt_mutex_dequeue(lock, waiter);
waiter->task->prio = task->prio;
waiter->prio = task->prio;
rt_mutex_enqueue(lock, waiter);
/* Release the task */
......@@ -448,7 +459,7 @@ static int try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task,
* 3) it is top waiter
*/
if (rt_mutex_has_waiters(lock)) {
if (task->prio >= rt_mutex_top_waiter(lock)->task->prio) {
if (task->prio >= rt_mutex_top_waiter(lock)->prio) {
if (!waiter || waiter != rt_mutex_top_waiter(lock))
return 0;
}
......@@ -508,6 +519,7 @@ static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
__rt_mutex_adjust_prio(task);
waiter->task = task;
waiter->lock = lock;
waiter->prio = task->prio;
/* Get the top priority waiter on the lock */
if (rt_mutex_has_waiters(lock))
......@@ -653,7 +665,8 @@ void rt_mutex_adjust_pi(struct task_struct *task)
raw_spin_lock_irqsave(&task->pi_lock, flags);
waiter = task->pi_blocked_on;
if (!waiter || waiter->task->prio == task->prio) {
if (!waiter || (waiter->prio == task->prio &&
!dl_prio(task->prio))) {
raw_spin_unlock_irqrestore(&task->pi_lock, flags);
return;
}
......
......@@ -54,6 +54,7 @@ struct rt_mutex_waiter {
struct pid *deadlock_task_pid;
struct rt_mutex *deadlock_lock;
#endif
int prio;
};
/*
......
......@@ -947,7 +947,7 @@ static inline void check_class_changed(struct rq *rq, struct task_struct *p,
if (prev_class->switched_from)
prev_class->switched_from(rq, p);
p->sched_class->switched_to(rq, p);
} else if (oldprio != p->prio)
} else if (oldprio != p->prio || dl_task(p))
p->sched_class->prio_changed(rq, p, oldprio);
}
......@@ -2781,7 +2781,7 @@ EXPORT_SYMBOL(sleep_on_timeout);
*/
void rt_mutex_setprio(struct task_struct *p, int prio)
{
int oldprio, on_rq, running;
int oldprio, on_rq, running, enqueue_flag = 0;
struct rq *rq;
const struct sched_class *prev_class;
......@@ -2808,6 +2808,7 @@ void rt_mutex_setprio(struct task_struct *p, int prio)
}
trace_sched_pi_setprio(p, prio);
p->pi_top_task = rt_mutex_get_top_task(p);
oldprio = p->prio;
prev_class = p->sched_class;
on_rq = p->on_rq;
......@@ -2817,19 +2818,42 @@ void rt_mutex_setprio(struct task_struct *p, int prio)
if (running)
p->sched_class->put_prev_task(rq, p);
if (dl_prio(prio))
/*
* Boosting condition are:
* 1. -rt task is running and holds mutex A
* --> -dl task blocks on mutex A
*
* 2. -dl task is running and holds mutex A
* --> -dl task blocks on mutex A and could preempt the
* running task
*/
if (dl_prio(prio)) {
if (!dl_prio(p->normal_prio) || (p->pi_top_task &&
dl_entity_preempt(&p->pi_top_task->dl, &p->dl))) {
p->dl.dl_boosted = 1;
p->dl.dl_throttled = 0;
enqueue_flag = ENQUEUE_REPLENISH;
} else
p->dl.dl_boosted = 0;
p->sched_class = &dl_sched_class;
else if (rt_prio(prio))
} else if (rt_prio(prio)) {
if (dl_prio(oldprio))
p->dl.dl_boosted = 0;
if (oldprio < prio)
enqueue_flag = ENQUEUE_HEAD;
p->sched_class = &rt_sched_class;
else
} else {
if (dl_prio(oldprio))
p->dl.dl_boosted = 0;
p->sched_class = &fair_sched_class;
}
p->prio = prio;
if (running)
p->sched_class->set_curr_task(rq);
if (on_rq)
enqueue_task(rq, p, oldprio < prio ? ENQUEUE_HEAD : 0);
enqueue_task(rq, p, enqueue_flag);
check_class_changed(rq, p, prev_class, oldprio);
out_unlock:
......
......@@ -16,20 +16,6 @@
*/
#include "sched.h"
static inline int dl_time_before(u64 a, u64 b)
{
return (s64)(a - b) < 0;
}
/*
* Tells if entity @a should preempt entity @b.
*/
static inline
int dl_entity_preempt(struct sched_dl_entity *a, struct sched_dl_entity *b)
{
return dl_time_before(a->deadline, b->deadline);
}
static inline struct task_struct *dl_task_of(struct sched_dl_entity *dl_se)
{
return container_of(dl_se, struct task_struct, dl);
......@@ -242,7 +228,8 @@ static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
* 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)
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);
......@@ -254,8 +241,8 @@ static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se)
* 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;
dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
dl_se->runtime = pi_se->dl_runtime;
dl_se->dl_new = 0;
}
......@@ -277,11 +264,23 @@ static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se)
* 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)
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
......@@ -289,8 +288,8 @@ static void replenish_dl_entity(struct sched_dl_entity *dl_se)
* arbitrary large.
*/
while (dl_se->runtime <= 0) {
dl_se->deadline += dl_se->dl_period;
dl_se->runtime += dl_se->dl_runtime;
dl_se->deadline += pi_se->dl_period;
dl_se->runtime += pi_se->dl_runtime;
}
/*
......@@ -309,8 +308,8 @@ static void replenish_dl_entity(struct sched_dl_entity *dl_se)
lag_once = true;
printk_sched("sched: DL replenish lagged to much\n");
}
dl_se->deadline = rq_clock(rq) + dl_se->dl_deadline;
dl_se->runtime = dl_se->dl_runtime;
dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
dl_se->runtime = pi_se->dl_runtime;
}
}
......@@ -337,7 +336,8 @@ static void replenish_dl_entity(struct sched_dl_entity *dl_se)
* 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, u64 t)
static bool dl_entity_overflow(struct sched_dl_entity *dl_se,
struct sched_dl_entity *pi_se, u64 t)
{
u64 left, right;
......@@ -359,8 +359,8 @@ static bool dl_entity_overflow(struct sched_dl_entity *dl_se, u64 t)
* of anything below microseconds resolution is actually fiction
* (but still we want to give the user that illusion >;).
*/
left = (dl_se->dl_period >> 10) * (dl_se->runtime >> 10);
right = ((dl_se->deadline - t) >> 10) * (dl_se->dl_runtime >> 10);
left = (pi_se->dl_period >> 10) * (dl_se->runtime >> 10);
right = ((dl_se->deadline - t) >> 10) * (pi_se->dl_runtime >> 10);
return dl_time_before(right, left);
}
......@@ -374,7 +374,8 @@ static bool dl_entity_overflow(struct sched_dl_entity *dl_se, u64 t)
* - 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)
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);
......@@ -384,14 +385,14 @@ static void update_dl_entity(struct sched_dl_entity *dl_se)
* the actual scheduling parameters have to be "renewed".
*/
if (dl_se->dl_new) {
setup_new_dl_entity(dl_se);
setup_new_dl_entity(dl_se, pi_se);
return;
}
if (dl_time_before(dl_se->deadline, rq_clock(rq)) ||
dl_entity_overflow(dl_se, rq_clock(rq))) {
dl_se->deadline = rq_clock(rq) + dl_se->dl_deadline;
dl_se->runtime = dl_se->dl_runtime;
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;
}
}
......@@ -405,7 +406,7 @@ static void update_dl_entity(struct sched_dl_entity *dl_se)
* 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)
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);
......@@ -414,6 +415,8 @@ static int start_dl_timer(struct sched_dl_entity *dl_se)
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
......@@ -573,7 +576,7 @@ static void update_curr_dl(struct rq *rq)
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)))
if (likely(start_dl_timer(dl_se, curr->dl.dl_boosted)))
dl_se->dl_throttled = 1;
else
enqueue_task_dl(rq, curr, ENQUEUE_REPLENISH);
......@@ -728,7 +731,8 @@ static void __dequeue_dl_entity(struct sched_dl_entity *dl_se)
}
static void
enqueue_dl_entity(struct sched_dl_entity *dl_se, int flags)
enqueue_dl_entity(struct sched_dl_entity *dl_se,
struct sched_dl_entity *pi_se, int flags)
{
BUG_ON(on_dl_rq(dl_se));
......@@ -738,9 +742,9 @@ enqueue_dl_entity(struct sched_dl_entity *dl_se, int flags)
* we want a replenishment of its runtime.
*/
if (!dl_se->dl_new && flags & ENQUEUE_REPLENISH)
replenish_dl_entity(dl_se);
replenish_dl_entity(dl_se, pi_se);
else
update_dl_entity(dl_se);
update_dl_entity(dl_se, pi_se);
__enqueue_dl_entity(dl_se);
}
......@@ -752,6 +756,18 @@ static void dequeue_dl_entity(struct sched_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
......@@ -761,7 +777,7 @@ static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags)
if (p->dl.dl_throttled)
return;
enqueue_dl_entity(&p->dl, flags);
enqueue_dl_entity(&p->dl, pi_se, flags);
if (!task_current(rq, p) && p->nr_cpus_allowed > 1)
enqueue_pushable_dl_task(rq, p);
......@@ -985,8 +1001,7 @@ static void task_dead_dl(struct task_struct *p)
{
struct hrtimer *timer = &p->dl.dl_timer;
if (hrtimer_active(timer))
hrtimer_try_to_cancel(timer);
hrtimer_cancel(timer);
}
static void set_curr_task_dl(struct rq *rq)
......
......@@ -107,6 +107,20 @@ static inline int task_has_dl_policy(struct task_struct *p)
return dl_policy(p->policy);
}
static inline int dl_time_before(u64 a, u64 b)
{
return (s64)(a - b) < 0;
}
/*
* Tells if entity @a should preempt entity @b.
*/
static inline
int dl_entity_preempt(struct sched_dl_entity *a, struct sched_dl_entity *b)
{
return dl_time_before(a->deadline, b->deadline);
}
/*
* This is the priority-queue data structure of the RT scheduling class:
*/
......
......@@ -16,6 +16,7 @@
#include <linux/uaccess.h>
#include <linux/ftrace.h>
#include <linux/sched/rt.h>
#include <linux/sched/deadline.h>
#include <trace/events/sched.h>
#include "trace.h"
......
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