From: "Dmitry Adamushko" - Make TASK_PREEMPTS_CURR(task, rq) return "true" only if the task's prio is higher than the current's one and the task is in the "active" array. This ensures we don't make redundant resched_task() calls when the task is in the "expired" array (as may happen now in set_user_prio(), rt_mutex_setprio() and pull_task() ) ; - generalise conditions for a call to resched_task() in set_user_nice(), rt_mutex_setprio() and sched_setscheduler() Signed-off-by: Dmitry Adamushko Cc: Con Kolivas Cc: Ingo Molnar Signed-off-by: Andrew Morton --- kernel/sched.c | 31 +++++++++++++------------------ 1 file changed, 13 insertions(+), 18 deletions(-) diff -puN kernel/sched.c~sched-redundant-reschedule-when-set_user_nice-boosts-a-prio-of-a-task-from-the-expired-array kernel/sched.c --- a/kernel/sched.c~sched-redundant-reschedule-when-set_user_nice-boosts-a-prio-of-a-task-from-the-expired-array +++ a/kernel/sched.c @@ -169,7 +169,7 @@ unsigned long long __attribute__((weak)) (MAX_BONUS / 2 + DELTA((p)) + 1) / MAX_BONUS - 1)) #define TASK_PREEMPTS_CURR(p, rq) \ - ((p)->prio < (rq)->curr->prio) + (((p)->prio < (rq)->curr->prio) && ((p)->array == (rq)->active)) #define SCALE_PRIO(x, prio) \ max(x * (MAX_PRIO - prio) / (MAX_USER_PRIO / 2), MIN_TIMESLICE) @@ -4077,13 +4077,13 @@ void rt_mutex_setprio(struct task_struct struct prio_array *array; unsigned long flags; struct rq *rq; - int oldprio; + int delta; BUG_ON(prio < 0 || prio > MAX_PRIO); rq = task_rq_lock(p, &flags); - oldprio = p->prio; + delta = prio - p->prio; array = p->array; if (array) dequeue_task(p, array); @@ -4099,13 +4099,10 @@ void rt_mutex_setprio(struct task_struct enqueue_task(p, array); /* * Reschedule if we are currently running on this runqueue and - * our priority decreased, or if we are not currently running on - * this runqueue and our priority is higher than the current's + * our priority decreased, or if our priority became higher + * than the current's. */ - if (task_running(rq, p)) { - if (p->prio > oldprio) - resched_task(rq->curr); - } else if (TASK_PREEMPTS_CURR(p, rq)) + if (TASK_PREEMPTS_CURR(p, rq) || (delta > 0 && task_running(rq, p))) resched_task(rq->curr); } task_rq_unlock(rq, &flags); @@ -4153,10 +4150,11 @@ void set_user_nice(struct task_struct *p enqueue_task(p, array); inc_raw_weighted_load(rq, p); /* - * If the task increased its priority or is running and - * lowered its priority, then reschedule its CPU: + * Reschedule if we are currently running on this runqueue and + * our priority decreased, or if our priority became higher + * than the current's. */ - if (delta < 0 || (delta > 0 && task_running(rq, p))) + if (TASK_PREEMPTS_CURR(p, rq) || (delta > 0 && task_running(rq, p))) resched_task(rq->curr); } out_unlock: @@ -4383,13 +4381,10 @@ recheck: __activate_task(p, rq); /* * Reschedule if we are currently running on this runqueue and - * our priority decreased, or if we are not currently running on - * this runqueue and our priority is higher than the current's + * our priority decreased, or our priority became higher + * than the current's. */ - if (task_running(rq, p)) { - if (p->prio > oldprio) - resched_task(rq->curr); - } else if (TASK_PREEMPTS_CURR(p, rq)) + if (TASK_PREEMPTS_CURR(p, rq) || (task_running(rq, p) && p->prio > oldprio)) resched_task(rq->curr); } __task_rq_unlock(rq); _