Commit f4493771 authored by Mike Galbraith's avatar Mike Galbraith Committed by Ingo Molnar
Browse files

sched, autogroup: Fix CONFIG_RT_GROUP_SCHED sched_setscheduler() failure 



If CONFIG_RT_GROUP_SCHED is set, __sched_setscheduler() fails due to autogroup
not allocating rt_runtime.  Free unused/unusable rt_se and rt_rq, redirect RT
tasks to the root task group, and tell __sched_setscheduler() that it's ok.

Reported-and-tested-by: default avatarBharata B Rao <bharata@linux.vnet.ibm.com>
Signed-off-by: default avatarMike Galbraith <efault@gmx.de>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1294890890.8089.39.camel@marge.simson.net>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 8ecedd7a

kernel/sched.c

+2 −1
Original line number Diff line number Diff line
@@ -4871,7 +4871,8 @@ recheck: 
		 * assigned.

		 */

		if (rt_bandwidth_enabled() && rt_policy(policy) &&

				task_group(p)->rt_bandwidth.rt_runtime == 0) {

				task_group(p)->rt_bandwidth.rt_runtime == 0 &&

				!task_group_is_autogroup(task_group(p))) {

			__task_rq_unlock(rq);

			raw_spin_unlock_irqrestore(&p->pi_lock, flags);

			return -EPERM;

kernel/sched_autogroup.c

+27 −0
Original line number Diff line number Diff line
@@ -27,6 +27,11 @@ static inline void autogroup_destroy(struct kref *kref) 
{

	struct autogroup *ag = container_of(kref, struct autogroup, kref);



#ifdef CONFIG_RT_GROUP_SCHED

	/* We've redirected RT tasks to the root task group... */

	ag->tg->rt_se = NULL;

	ag->tg->rt_rq = NULL;

#endif

	sched_destroy_group(ag->tg);

}
@@ -55,6 +60,10 @@ static inline struct autogroup *autogroup_task_get(struct task_struct *p) 
	return ag;

}



#ifdef CONFIG_RT_GROUP_SCHED

static void free_rt_sched_group(struct task_group *tg);

#endif



static inline struct autogroup *autogroup_create(void)

{

	struct autogroup *ag = kzalloc(sizeof(*ag), GFP_KERNEL);
@@ -72,6 +81,19 @@ static inline struct autogroup *autogroup_create(void) 
	init_rwsem(&ag->lock);

	ag->id = atomic_inc_return(&autogroup_seq_nr);

	ag->tg = tg;

#ifdef CONFIG_RT_GROUP_SCHED

	/*

	 * Autogroup RT tasks are redirected to the root task group

	 * so we don't have to move tasks around upon policy change,

	 * or flail around trying to allocate bandwidth on the fly.

	 * A bandwidth exception in __sched_setscheduler() allows

	 * the policy change to proceed.  Thereafter, task_group()

	 * returns &root_task_group, so zero bandwidth is required.

	 */

	free_rt_sched_group(tg);

	tg->rt_se = root_task_group.rt_se;

	tg->rt_rq = root_task_group.rt_rq;

#endif

	tg->autogroup = ag;



	return ag;
@@ -106,6 +128,11 @@ task_wants_autogroup(struct task_struct *p, struct task_group *tg) 
	return true;

}



static inline bool task_group_is_autogroup(struct task_group *tg)

{

	return tg != &root_task_group && tg->autogroup;

}



static inline struct task_group *

autogroup_task_group(struct task_struct *p, struct task_group *tg)

{

kernel/sched_autogroup.h

+4 −0
Original line number Diff line number Diff line
@@ -15,6 +15,10 @@ autogroup_task_group(struct task_struct *p, struct task_group *tg); 


static inline void autogroup_init(struct task_struct *init_task) {  }

static inline void autogroup_free(struct task_group *tg) { }

static inline bool task_group_is_autogroup(struct task_group *tg)

{

	return 0;

}



static inline struct task_group *

autogroup_task_group(struct task_struct *p, struct task_group *tg)

CRA Git | Maintained and supported by SUSTech CRA and CCSE