Messages in this thread Patch in this message |  | | Subject | [RFC][PATCH] fix SCHED_FIFO spec violation | From | Peter Zijlstra <> | Date | Mon, 16 Jun 2008 22:22:25 +0200 |
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Hi Guys,
It came to my attention that we violate the SCHED_FIFO spec when un-boosting tasks in that we should move them to the head of the lower priority queue instead of to the tail.
[1] http://www.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_08.html#tag_02_08_04_01 [2] http://www.opengroup.org/onlinepubs/009695399/functions/pthread_mutexattr_setprotocol.html
Also, while doing this patch, I noticed that the rt-group code further violates the spec by re-ordering the upper level entries. Any bright ideas? - if not I'll probably attempt the brute force method.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> --- diff --git a/include/linux/sched.h b/include/linux/sched.h index c5d3f84..0db49d5 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -888,11 +888,16 @@ struct uts_namespace; struct rq; struct sched_domain; +#define ENQUEUE_WAKEUP 0x01 +#define ENQUEUE_HEAD 0x02 + +#define DEQUEUE_SLEEP 0x01 + struct sched_class { const struct sched_class *next; - void (*enqueue_task) (struct rq *rq, struct task_struct *p, int wakeup); - void (*dequeue_task) (struct rq *rq, struct task_struct *p, int sleep); + void (*enqueue_task) (struct rq *rq, struct task_struct *p, int flags); + void (*dequeue_task) (struct rq *rq, struct task_struct *p, int flags); void (*yield_task) (struct rq *rq); int (*select_task_rq)(struct task_struct *p, int sync); diff --git a/kernel/sched.c b/kernel/sched.c index eaf6751..f594f17 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -1432,7 +1432,7 @@ static const u32 prio_to_wmult[40] = { /* 15 */ 119304647, 148102320, 186737708, 238609294, 286331153, }; -static void activate_task(struct rq *rq, struct task_struct *p, int wakeup); +static void activate_task(struct rq *rq, struct task_struct *p, int flags); /* * runqueue iterator, to support SMP load-balancing between different @@ -1542,16 +1542,16 @@ static void set_load_weight(struct task_struct *p) p->se.load.inv_weight = prio_to_wmult[p->static_prio - MAX_RT_PRIO]; } -static void enqueue_task(struct rq *rq, struct task_struct *p, int wakeup) +static void enqueue_task(struct rq *rq, struct task_struct *p, int flags) { sched_info_queued(p); - p->sched_class->enqueue_task(rq, p, wakeup); + p->sched_class->enqueue_task(rq, p, flags); p->se.on_rq = 1; } -static void dequeue_task(struct rq *rq, struct task_struct *p, int sleep) +static void dequeue_task(struct rq *rq, struct task_struct *p, int flags) { - p->sched_class->dequeue_task(rq, p, sleep); + p->sched_class->dequeue_task(rq, p, flags); p->se.on_rq = 0; } @@ -1604,24 +1604,24 @@ static int effective_prio(struct task_struct *p) /* * activate_task - move a task to the runqueue. */ -static void activate_task(struct rq *rq, struct task_struct *p, int wakeup) +static void activate_task(struct rq *rq, struct task_struct *p, int flags) { if (task_contributes_to_load(p)) rq->nr_uninterruptible--; - enqueue_task(rq, p, wakeup); + enqueue_task(rq, p, flags); inc_nr_running(p, rq); } /* * deactivate_task - remove a task from the runqueue. */ -static void deactivate_task(struct rq *rq, struct task_struct *p, int sleep) +static void deactivate_task(struct rq *rq, struct task_struct *p, int flags) { if (task_contributes_to_load(p)) rq->nr_uninterruptible++; - dequeue_task(rq, p, sleep); + dequeue_task(rq, p, flags); dec_nr_running(p, rq); } @@ -2143,7 +2143,7 @@ out_activate: else schedstat_inc(p, se.nr_wakeups_remote); update_rq_clock(rq); - activate_task(rq, p, 1); + activate_task(rq, p, ENQUEUE_WAKEUP); success = 1; out_running: @@ -4170,7 +4170,7 @@ need_resched_nonpreemptible: if (unlikely(signal_pending_state(prev->state, prev))) prev->state = TASK_RUNNING; else - deactivate_task(rq, prev, 1); + deactivate_task(rq, prev, DEQUEUE_SLEEP); switch_count = &prev->nvcsw; } @@ -4525,7 +4525,7 @@ EXPORT_SYMBOL(sleep_on_timeout); void rt_mutex_setprio(struct task_struct *p, int prio) { unsigned long flags; - int oldprio, on_rq, running; + int oldprio, on_rq, running, down; struct rq *rq; const struct sched_class *prev_class = p->sched_class; @@ -4547,12 +4547,13 @@ void rt_mutex_setprio(struct task_struct *p, int prio) else p->sched_class = &fair_sched_class; + down = (prio > p->prio) ? ENQUEUE_HEAD : 0; p->prio = prio; if (running) p->sched_class->set_curr_task(rq); if (on_rq) { - enqueue_task(rq, p, 0); + enqueue_task(rq, p, down); check_class_changed(rq, p, prev_class, oldprio, running); } diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index 08ae848..b545eeb 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -847,10 +847,11 @@ hrtick_start_fair(struct rq *rq, struct task_struct *p) * increased. Here we update the fair scheduling stats and * then put the task into the rbtree: */ -static void enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup) +static void enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) { struct cfs_rq *cfs_rq; struct sched_entity *se = &p->se; + int wakeup = flags & ENQUEUE_WAKEUP; for_each_sched_entity(se) { if (se->on_rq) @@ -868,10 +869,11 @@ static void enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup) * decreased. We remove the task from the rbtree and * update the fair scheduling stats: */ -static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int sleep) +static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags) { struct cfs_rq *cfs_rq; struct sched_entity *se = &p->se; + int sleep = flags & DEQUEUE_SLEEP; for_each_sched_entity(se) { cfs_rq = cfs_rq_of(se); diff --git a/kernel/sched_idletask.c b/kernel/sched_idletask.c index 3a4f92d..0819086 100644 --- a/kernel/sched_idletask.c +++ b/kernel/sched_idletask.c @@ -31,7 +31,7 @@ static struct task_struct *pick_next_task_idle(struct rq *rq) * message if some code attempts to do it: */ static void -dequeue_task_idle(struct rq *rq, struct task_struct *p, int sleep) +dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags) { spin_unlock_irq(&rq->lock); printk(KERN_ERR "bad: scheduling from the idle thread!\n"); diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c index 3432d57..0134f7c 100644 --- a/kernel/sched_rt.c +++ b/kernel/sched_rt.c @@ -91,7 +91,7 @@ static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se) return rt_se->my_q; } -static void enqueue_rt_entity(struct sched_rt_entity *rt_se); +static void enqueue_rt_entity(struct sched_rt_entity *rt_se, int flags); static void dequeue_rt_entity(struct sched_rt_entity *rt_se); static void sched_rt_rq_enqueue(struct rt_rq *rt_rq) @@ -101,7 +101,7 @@ static void sched_rt_rq_enqueue(struct rt_rq *rt_rq) if (rt_se && !on_rt_rq(rt_se) && rt_rq->rt_nr_running) { struct task_struct *curr = rq_of_rt_rq(rt_rq)->curr; - enqueue_rt_entity(rt_se); + enqueue_rt_entity(rt_se, 0); if (rt_rq->highest_prio < curr->prio) resched_task(curr); } @@ -449,16 +449,21 @@ void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq) #endif } -static void enqueue_rt_entity(struct sched_rt_entity *rt_se) +static void enqueue_rt_entity(struct sched_rt_entity *rt_se, int flags) { struct rt_rq *rt_rq = rt_rq_of_se(rt_se); struct rt_prio_array *array = &rt_rq->active; struct rt_rq *group_rq = group_rt_rq(rt_se); + struct list_head *queue = array->queue + rt_se_prio(rt_se); if (group_rq && rt_rq_throttled(group_rq)) return; - list_add_tail(&rt_se->run_list, array->queue + rt_se_prio(rt_se)); + if (unlikely(flags & ENQUEUE_HEAD)) + list_add(&rt_se->run_list, queue); + else + list_add_tail(&rt_se->run_list, queue); + __set_bit(rt_se_prio(rt_se), array->bitmap); inc_rt_tasks(rt_se, rt_rq); @@ -499,29 +504,35 @@ static void dequeue_rt_stack(struct task_struct *p) /* * Adding/removing a task to/from a priority array: */ -static void enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup) +static void enqueue_task_rt(struct rq *rq, struct task_struct *p, int flags) { struct sched_rt_entity *rt_se = &p->rt; - if (wakeup) + if (flags & ENQUEUE_WAKEUP) rt_se->timeout = 0; + /* + * XXX: destroys queue order, how to fix? + */ dequeue_rt_stack(p); /* * enqueue everybody, bottom - up. */ for_each_sched_rt_entity(rt_se) - enqueue_rt_entity(rt_se); + enqueue_rt_entity(rt_se, flags & ENQUEUE_HEAD); } -static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int sleep) +static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int flags) { struct sched_rt_entity *rt_se = &p->rt; struct rt_rq *rt_rq; update_curr_rt(rq); + /* + * XXX: destroys queue order, how to fix? + */ dequeue_rt_stack(p); /* @@ -530,7 +541,7 @@ static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int sleep) for_each_sched_rt_entity(rt_se) { rt_rq = group_rt_rq(rt_se); if (rt_rq && rt_rq->rt_nr_running) - enqueue_rt_entity(rt_se); + enqueue_rt_entity(rt_se, 0); } }
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