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 (as in SF_BWRECL_DL reclaiming policy); - 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. Signed-off-by: Dario Faggioli --- include/linux/sched.h | 3 ++ kernel/fork.c | 1 + kernel/rtmutex.c | 13 ++++++++- kernel/sched.c | 3 +- kernel/sched_dl.c | 65 +++++++++++++++++++++++++++++++------------------ 5 files changed, 58 insertions(+), 27 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index c3d1f17b..7cf78e2 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1535,6 +1535,8 @@ struct task_struct { struct rb_node *pi_waiters_leftmost; /* Deadlock detection and priority inheritance handling */ struct rt_mutex_waiter *pi_blocked_on; + /* */ + struct task_struct *pi_top_task; #endif #ifdef CONFIG_DEBUG_MUTEXES @@ -2118,6 +2120,7 @@ extern unsigned int sysctl_sched_compat_yield; #ifdef CONFIG_RT_MUTEXES extern int rt_mutex_getprio(struct task_struct *p); +extern struct task_struct *rt_mutex_get_top_task(struct task_struct *task); extern void rt_mutex_setprio(struct task_struct *p, int prio); extern void rt_mutex_adjust_pi(struct task_struct *p); #else diff --git a/kernel/fork.c b/kernel/fork.c index aceb248..c8f2555 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -938,6 +938,7 @@ 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 2e9c0dc..84ea165 100644 --- a/kernel/rtmutex.c +++ b/kernel/rtmutex.c @@ -196,6 +196,14 @@ 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. * @@ -205,7 +213,7 @@ 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); } @@ -671,7 +679,8 @@ 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.c b/kernel/sched.c index 853473a..97db370 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -4611,10 +4611,11 @@ void rt_mutex_setprio(struct task_struct *p, int prio) unsigned long flags; struct rq *rq; - BUG_ON(prio < 0 || prio > MAX_PRIO); + BUG_ON(prio > MAX_PRIO); rq = task_rq_lock(p, &flags); trace_sched_pi_setprio(p, prio); + p->pi_top_task = rt_mutex_get_top_task(p); __setprio(rq, p, prio); task_rq_unlock(rq, &flags); } diff --git a/kernel/sched_dl.c b/kernel/sched_dl.c index 4d24109..991a4f2 100644 --- a/kernel/sched_dl.c +++ b/kernel/sched_dl.c @@ -223,15 +223,16 @@ static int push_dl_task(struct rq *rq); * 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); WARN_ON(!dl_se->dl_new || dl_se->dl_throttled); - dl_se->deadline = rq->clock + dl_se->dl_deadline; - dl_se->runtime = dl_se->dl_runtime; + dl_se->deadline = rq->clock + pi_se->dl_deadline; + dl_se->runtime = pi_se->dl_runtime; dl_se->dl_new = 0; #ifdef CONFIG_SCHEDSTATS trace_sched_stat_new_dl(dl_task_of(dl_se), rq->clock, dl_se->flags); @@ -256,7 +257,8 @@ static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se) * could happen are, typically, a entity voluntarily trying to overcume 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); @@ -269,8 +271,8 @@ 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; } /* @@ -284,8 +286,8 @@ static void replenish_dl_entity(struct sched_dl_entity *dl_se) */ if (dl_time_before(dl_se->deadline, rq->clock)) { WARN_ON_ONCE(1); - dl_se->deadline = rq->clock + dl_se->dl_deadline; - dl_se->runtime = dl_se->dl_runtime; + dl_se->deadline = rq->clock + pi_se->dl_deadline; + dl_se->runtime = pi_se->dl_runtime; reset = 1; } #ifdef CONFIG_SCHEDSTATS @@ -306,7 +308,8 @@ 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; @@ -323,8 +326,8 @@ static bool dl_entity_overflow(struct sched_dl_entity *dl_se, u64 t) * to the (absolute) deadline. Therefore, overflowing the u64 * type is very unlikely to occur in both cases. */ - left = dl_se->dl_deadline * dl_se->runtime; - right = (dl_se->deadline - t) * dl_se->dl_runtime; + left = pi_se->dl_deadline * dl_se->runtime; + right = (dl_se->deadline - t) * pi_se->dl_runtime; return dl_time_before(right, left); } @@ -338,7 +341,8 @@ 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); @@ -349,14 +353,14 @@ 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) || - dl_entity_overflow(dl_se, rq->clock)) { - dl_se->deadline = rq->clock + dl_se->dl_deadline; - dl_se->runtime = dl_se->dl_runtime; + dl_entity_overflow(dl_se, pi_se, rq->clock)) { + dl_se->deadline = rq->clock + pi_se->dl_deadline; + dl_se->runtime = pi_se->dl_runtime; overflow = 1; } #ifdef CONFIG_SCHEDSTATS @@ -374,7 +378,7 @@ 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); @@ -391,7 +395,7 @@ static int start_dl_timer(struct sched_dl_entity *dl_se) * This won't affect the other -deadline tasks, but if we are * a CPU-hog, lower scheduling classes will starve! */ - if (dl_se->flags & SF_BWRECL_DL) + if (boosted || dl_se->flags & SF_BWRECL_DL) return 0; /* @@ -595,7 +599,7 @@ 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->pi_top_task))) throttle_curr_dl(rq, curr); else enqueue_task_dl(rq, curr, ENQUEUE_REPLENISH); @@ -749,7 +753,8 @@ 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)); @@ -759,9 +764,9 @@ 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); } @@ -773,6 +778,18 @@ 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 && dl_entity_preempt(&pi_task->dl, &p->dl)) + 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 @@ -782,7 +799,7 @@ 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->dl.nr_cpus_allowed > 1) enqueue_pushable_dl_task(rq, p); @@ -847,7 +864,7 @@ static long wait_interval_dl(struct task_struct *p, struct timespec *rqtp, */ wakeup = timespec_to_ns(rqtp); if (dl_time_before(wakeup, dl_se->deadline) && - !dl_entity_overflow(dl_se, wakeup)) { + !dl_entity_overflow(dl_se, dl_se, wakeup)) { u64 ibw = (u64)dl_se->runtime * dl_se->dl_period; ibw = div_u64(ibw, dl_se->dl_runtime); -- 1.7.2.3 -- <> (Raistlin Majere) ---------------------------------------------------------------------- Dario Faggioli, ReTiS Lab, Scuola Superiore Sant'Anna, Pisa (Italy) http://blog.linux.it/raistlin / raistlin@ekiga.net / dario.faggioli@jabber.org