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Date: Fri, 21 Jan 2011 08:25:28 +0200
From: Onkalo Samu <samu.p.onkalo@...ia.com>
To: ext Peter Zijlstra <peterz@...radead.org>
Cc: Yong Zhang <yong.zhang0@...il.com>, mingo@...e.hu,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
tglx <tglx@...utronix.de>, Steven Rostedt <rostedt@...dmis.org>
Subject: Re: Bug in scheduler when using rt_mutex
On Thu, 2011-01-20 at 09:07 +0200, Onkalo Samu wrote:
> On Wed, 2011-01-19 at 14:30 +0100, ext Peter Zijlstra wrote:
> > On Wed, 2011-01-19 at 15:13 +0200, Onkalo Samu wrote:
> > >
> > > When the task is sleeping rt_mutex_setprio
> > > doesn't call check_class_changed since the task is not
> > > in queue at that moment I think.
> >
> > Ah, indeed, more changes then..
> >
> > (I think we can also remove the prio_changed_idle thing, since I think
> > we killed that hotplug usage)
>
> Doesn't compile because kernel/sched_idletask.c
> functions still use "running" parameter which was removed.
>
I made similar corrections to sched_idletask.c as you did for other
functions. Seems to work for us.
-Samu
> >
>
> >
> > ---
> > Index: linux-2.6/kernel/sched.c
> > ===================================================================
> > --- linux-2.6.orig/kernel/sched.c
> > +++ linux-2.6/kernel/sched.c
> > @@ -2025,14 +2025,14 @@ inline int task_curr(const struct task_s
> >
> > static inline void check_class_changed(struct rq *rq, struct task_struct *p,
> > const struct sched_class *prev_class,
> > - int oldprio, int running)
> > + int oldprio)
> > {
> > if (prev_class != p->sched_class) {
> > if (prev_class->switched_from)
> > - prev_class->switched_from(rq, p, running);
> > - p->sched_class->switched_to(rq, p, running);
> > - } else
> > - p->sched_class->prio_changed(rq, p, oldprio, running);
> > + prev_class->switched_from(rq, p);
> > + p->sched_class->switched_to(rq, p);
> > + } else if (oldprio != p->prio)
> > + p->sched_class->prio_changed(rq, p, oldprio);
> > }
> >
> > static void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
> > @@ -4570,11 +4570,10 @@ void rt_mutex_setprio(struct task_struct
> >
> > if (running)
> > p->sched_class->set_curr_task(rq);
> > - if (on_rq) {
> > + if (on_rq)
> > enqueue_task(rq, p, oldprio < prio ? ENQUEUE_HEAD : 0);
> >
> > - check_class_changed(rq, p, prev_class, oldprio, running);
> > - }
> > + check_class_changed(rq, p, prev_class, oldprio);
> > task_rq_unlock(rq, &flags);
> > }
> >
> > @@ -4902,11 +4901,10 @@ static int __sched_setscheduler(struct t
> >
> > if (running)
> > p->sched_class->set_curr_task(rq);
> > - if (on_rq) {
> > + if (on_rq)
> > activate_task(rq, p, 0);
> >
> > - check_class_changed(rq, p, prev_class, oldprio, running);
> > - }
> > + check_class_changed(rq, p, prev_class, oldprio);
> > __task_rq_unlock(rq);
> > raw_spin_unlock_irqrestore(&p->pi_lock, flags);
> >
> > @@ -8109,6 +8107,8 @@ EXPORT_SYMBOL(__might_sleep);
> > #ifdef CONFIG_MAGIC_SYSRQ
> > static void normalize_task(struct rq *rq, struct task_struct *p)
> > {
> > + struct sched_class *prev_class = p->sched_class;
> > + int old_prio = p->prio;
> > int on_rq;
> >
> > on_rq = p->se.on_rq;
> > @@ -8119,6 +8119,8 @@ static void normalize_task(struct rq *rq
> > activate_task(rq, p, 0);
> > resched_task(rq->curr);
> > }
> > +
> > + check_class_changed(rq, p, prev_class, old_prio);
> > }
> >
> > void normalize_rt_tasks(void)
> > Index: linux-2.6/kernel/sched_fair.c
> > ===================================================================
> > --- linux-2.6.orig/kernel/sched_fair.c
> > +++ linux-2.6/kernel/sched_fair.c
> > @@ -4054,33 +4054,56 @@ static void task_fork_fair(struct task_s
> > * Priority of the task has changed. Check to see if we preempt
> > * the current task.
> > */
> > -static void prio_changed_fair(struct rq *rq, struct task_struct *p,
> > - int oldprio, int running)
> > +static void
> > +prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
> > {
> > + if (!p->se.on_rq)
> > + return;
> > +
> > /*
> > * 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
> > */
> > - if (running) {
> > + if (rq->curr == p) {
> > if (p->prio > oldprio)
> > resched_task(rq->curr);
> > } else
> > check_preempt_curr(rq, p, 0);
> > }
> >
> > +static void switched_from_fair(struct rq *rq, struct task_struct *p)
> > +{
> > + struct sched_entity *se = &p->se;
> > + struct cfs_rq *cfs_rq = cfs_rq_of(se);
> > +
> > + /*
> > + * Ensure the task's vruntime is normalized, so that when its
> > + * switched back to the fair class the enqueue_entity(.flags=0) will
> > + * do the right thing.
> > + *
> > + * If it was on_rq, then the dequeue_entity(.flags=0) will already
> > + * have normalized the vruntime, if it was !on_rq, then only when
> > + * the task is sleeping will it still have non-normalized vruntime.
> > + */
> > + if (!se->on_rq && p->state != TASK_RUNNING)
> > + se->vruntime -= cfs_rq->min_vruntime;
> > +}
> > +
> > /*
> > * We switched to the sched_fair class.
> > */
> > -static void switched_to_fair(struct rq *rq, struct task_struct *p,
> > - int running)
> > +static void switched_to_fair(struct rq *rq, struct task_struct *p)
> > {
> > + if (!p->se.on_rq)
> > + return;
> > +
> > /*
> > * We were most likely switched from sched_rt, so
> > * kick off the schedule if running, otherwise just see
> > * if we can still preempt the current task.
> > */
> > - if (running)
> > + if (rq->curr == p)
> > resched_task(rq->curr);
> > else
> > check_preempt_curr(rq, p, 0);
> > @@ -4166,6 +4189,7 @@ static const struct sched_class fair_sch
> > .task_fork = task_fork_fair,
> >
> > .prio_changed = prio_changed_fair,
> > + .switched_from = switched_from_fair,
> > .switched_to = switched_to_fair,
> >
> > .get_rr_interval = get_rr_interval_fair,
> > Index: linux-2.6/include/linux/sched.h
> > ===================================================================
> > --- linux-2.6.orig/include/linux/sched.h
> > +++ linux-2.6/include/linux/sched.h
> > @@ -1084,12 +1084,10 @@ struct sched_class {
> > void (*task_tick) (struct rq *rq, struct task_struct *p, int queued);
> > void (*task_fork) (struct task_struct *p);
> >
> > - void (*switched_from) (struct rq *this_rq, struct task_struct *task,
> > - int running);
> > - void (*switched_to) (struct rq *this_rq, struct task_struct *task,
> > - int running);
> > + void (*switched_from) (struct rq *this_rq, struct task_struct *task);
> > + void (*switched_to) (struct rq *this_rq, struct task_struct *task);
> > void (*prio_changed) (struct rq *this_rq, struct task_struct *task,
> > - int oldprio, int running);
> > + int oldprio);
> >
> > unsigned int (*get_rr_interval) (struct rq *rq,
> > struct task_struct *task);
> > Index: linux-2.6/kernel/sched_idletask.c
> > ===================================================================
> > --- linux-2.6.orig/kernel/sched_idletask.c
> > +++ linux-2.6/kernel/sched_idletask.c
> > @@ -52,8 +52,7 @@ static void set_curr_task_idle(struct rq
> > {
> > }
> >
> > -static void switched_to_idle(struct rq *rq, struct task_struct *p,
> > - int running)
> > +static void switched_to_idle(struct rq *rq, struct task_struct *p)
> > {
> > /* Can this actually happen?? */
> > if (running)
> > @@ -62,8 +61,8 @@ static void switched_to_idle(struct rq *
> > check_preempt_curr(rq, p, 0);
> > }
> >
> > -static void prio_changed_idle(struct rq *rq, struct task_struct *p,
> > - int oldprio, int running)
> > +static void
> > +prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio)
> > {
> > /* This can happen for hot plug CPUS */
> >
> > Index: linux-2.6/kernel/sched_rt.c
> > ===================================================================
> > --- linux-2.6.orig/kernel/sched_rt.c
> > +++ linux-2.6/kernel/sched_rt.c
> > @@ -1595,8 +1595,7 @@ static void rq_offline_rt(struct rq *rq)
> > * When switch from the rt queue, we bring ourselves to a position
> > * that we might want to pull RT tasks from other runqueues.
> > */
> > -static void switched_from_rt(struct rq *rq, struct task_struct *p,
> > - int running)
> > +static void switched_from_rt(struct rq *rq, struct task_struct *p)
> > {
> > /*
> > * If there are other RT tasks then we will reschedule
> > @@ -1605,7 +1604,7 @@ static void switched_from_rt(struct rq *
> > * we may need to handle the pulling of RT tasks
> > * now.
> > */
> > - if (!rq->rt.rt_nr_running)
> > + if (p->se.on_rq && !rq->rt.rt_nr_running)
> > pull_rt_task(rq);
> > }
> >
> > @@ -1624,8 +1623,7 @@ static inline void init_sched_rt_class(v
> > * with RT tasks. In this case we try to push them off to
> > * other runqueues.
> > */
> > -static void switched_to_rt(struct rq *rq, struct task_struct *p,
> > - int running)
> > +static void switched_to_rt(struct rq *rq, struct task_struct *p)
> > {
> > int check_resched = 1;
> >
> > @@ -1636,7 +1634,7 @@ static void switched_to_rt(struct rq *rq
> > * If that current running task is also an RT task
> > * then see if we can move to another run queue.
> > */
> > - if (!running) {
> > + if (p->se.on_rq && rq->curr != p) {
> > #ifdef CONFIG_SMP
> > if (rq->rt.overloaded && push_rt_task(rq) &&
> > /* Don't resched if we changed runqueues */
> > @@ -1652,10 +1650,13 @@ static void switched_to_rt(struct rq *rq
> > * Priority of the task has changed. This may cause
> > * us to initiate a push or pull.
> > */
> > -static void prio_changed_rt(struct rq *rq, struct task_struct *p,
> > - int oldprio, int running)
> > +static void
> > +prio_changed_rt(struct rq *rq, struct task_struct *p, int oldprio)
> > {
> > - if (running) {
> > + if (!p->se.on_rq)
> > + return;
> > +
> > + if (rq->curr == p) {
> > #ifdef CONFIG_SMP
> > /*
> > * If our priority decreases while running, we
> > Index: linux-2.6/kernel/sched_stoptask.c
> > ===================================================================
> > --- linux-2.6.orig/kernel/sched_stoptask.c
> > +++ linux-2.6/kernel/sched_stoptask.c
> > @@ -59,14 +59,13 @@ static void set_curr_task_stop(struct rq
> > {
> > }
> >
> > -static void switched_to_stop(struct rq *rq, struct task_struct *p,
> > - int running)
> > +static void switched_to_stop(struct rq *rq, struct task_struct *p)
> > {
> > BUG(); /* its impossible to change to this class */
> > }
> >
> > -static void prio_changed_stop(struct rq *rq, struct task_struct *p,
> > - int oldprio, int running)
> > +static void
> > +prio_changed_stop(struct rq *rq, struct task_struct *p, int oldprio)
> > {
> > BUG(); /* how!?, what priority? */
> > }
> >
>
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