From: Dario Faggioli <[email protected]> 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: Dario Faggioli <[email protected]> Signed-off-by: Juri Lelli <[email protected]> --- include/linux/sched.h | 8 +++- include/linux/sched/rt.h | 1 + kernel/fork.c | 1 + kernel/rtmutex.c | 14 +++++- kernel/sched/core.c | 36 ++++++++++++--- kernel/sched/deadline.c | 91 +++++++++++++++++++++---------------- kernel/sched/sched.h | 14 ++++++ kernel/trace/trace_sched_wakeup.c | 1 + 8 files changed, 119 insertions(+), 47 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index f95bafd..9dad4f3 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1099,8 +1099,12 @@ 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 @@ -1345,6 +1349,8 @@ 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 diff --git a/include/linux/sched/rt.h b/include/linux/sched/rt.h index a157797..1fa88a2c 100644 --- a/include/linux/sched/rt.h +++ b/include/linux/sched/rt.h @@ -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) { diff --git a/kernel/fork.c b/kernel/fork.c index aa6e18d..7247105 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1092,6 +1092,7 @@ 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 } diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c index 4ea7eaa..f7f667e 100644 --- a/kernel/rtmutex.c +++ b/kernel/rtmutex.c @@ -14,6 +14,7 @@ #include <linux/export.h> #include <linux/sched.h> #include <linux/sched/rt.h> +#include <linux/sched/deadline.h> #include <linux/timer.h> #include "rtmutex_common.h" @@ -200,6 +201,14 @@ int rt_mutex_getprio(struct task_struct *task) 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. * @@ -209,7 +218,7 @@ 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); } @@ -652,7 +661,8 @@ 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->task->prio == task->prio && + !dl_prio(task->prio))) { raw_spin_unlock_irqrestore(&task->pi_lock, flags); return; } diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 6a3ab87..d9dca90 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -951,7 +951,7 @@ 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); } @@ -3042,7 +3042,7 @@ 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; @@ -3069,6 +3069,7 @@ 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; @@ -3078,19 +3079,42 @@ 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: diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index a4b86b0..3b251b0 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -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 @@ -593,7 +596,7 @@ 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); @@ -748,7 +751,8 @@ 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)); @@ -758,9 +762,9 @@ 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); } @@ -772,6 +776,18 @@ 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 = p->pi_top_task; + 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 @@ -781,7 +797,7 @@ 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); @@ -1020,8 +1036,7 @@ 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) diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index b04aeed..4da50db 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -105,6 +105,20 @@ 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: */ diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c index 1457fb1..b5a9f02 100644 --- a/kernel/trace/trace_sched_wakeup.c +++ b/kernel/trace/trace_sched_wakeup.c @@ -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" -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
