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SubjectRe: [patch] Re: autogroup: sched_setscheduler() fails
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On Mon, 2011-01-10 at 11:59 +0100, Peter Zijlstra wrote:
> On Mon, 2011-01-10 at 11:29 +0100, Mike Galbraith wrote:
> >
> > Autogroup does not support realtime task groups, so make selection of
> > SCHED_AUTOGROUP exclude RT_GROUP_SCHED.
> >

> Uhm, no. The right way is to put tasks back into the root group and then
> perform sched_setscheduler().

I think that would take more lines, this look like a right way too?

sched, autogroup: move tasks to the appropriate runqueue on policy change.

If CONFIG_RT_GROUP_SCHED is set, sched_setscheduler() fails due to autogroup
not allocating rt_runtime. Fool __sched_setscheduler() into proceeding on, and
move tasks to the appropriate runqueue upon policy change.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Reported-by: Bharata B Rao <bharata@linux.vnet.ibm.com>

---
kernel/sched.c | 9 ++++++---
kernel/sched_autogroup.c | 18 ++++++++++++++++++
kernel/sched_autogroup.h | 1 +
3 files changed, 25 insertions(+), 3 deletions(-)

Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -4571,6 +4571,8 @@ void rt_mutex_setprio(struct task_struct

p->prio = prio;

+ autogroup_setscheduler(p, on_rq);
+
if (running)
p->sched_class->set_curr_task(rq);
if (on_rq) {
@@ -4738,7 +4740,7 @@ static struct task_struct *find_process_

/* Actually do priority change: must hold rq lock. */
static void
-__setscheduler(struct rq *rq, struct task_struct *p, int policy, int prio)
+__setscheduler(struct rq *rq, struct task_struct *p, int policy, int prio, int on_rq)
{
BUG_ON(p->se.on_rq);

@@ -4752,6 +4754,7 @@ __setscheduler(struct rq *rq, struct tas
else
p->sched_class = &fair_sched_class;
set_load_weight(p);
+ autogroup_setscheduler(p, on_rq);
}

/*
@@ -4900,7 +4903,7 @@ recheck:

oldprio = p->prio;
prev_class = p->sched_class;
- __setscheduler(rq, p, policy, param->sched_priority);
+ __setscheduler(rq, p, policy, param->sched_priority, on_rq);

if (running)
p->sched_class->set_curr_task(rq);
@@ -8116,7 +8119,7 @@ static void normalize_task(struct rq *rq
on_rq = p->se.on_rq;
if (on_rq)
deactivate_task(rq, p, 0);
- __setscheduler(rq, p, SCHED_NORMAL, 0);
+ __setscheduler(rq, p, SCHED_NORMAL, 0, on_rq);
if (on_rq) {
activate_task(rq, p, 0);
resched_task(rq->curr);
Index: linux-2.6/kernel/sched_autogroup.c
===================================================================
--- linux-2.6.orig/kernel/sched_autogroup.c
+++ linux-2.6/kernel/sched_autogroup.c
@@ -73,6 +73,15 @@ static inline struct autogroup *autogrou
ag->id = atomic_inc_return(&autogroup_seq_nr);
ag->tg = tg;
tg->autogroup = ag;
+#ifdef CONFIG_RT_GROUP_SCHED
+ /*
+ * HACK: autogroup RT tasks run in the root task group.
+ * This fools __sched_setscheduler() into proceeding on
+ * so we can move the task to the appropriate runqueue
+ * upon scheduling policy change.
+ */
+ tg->rt_bandwidth.rt_runtime = RUNTIME_INF;
+#endif

return ag;

@@ -143,6 +152,15 @@ autogroup_move_group(struct task_struct
autogroup_kref_put(prev);
}

+static inline void
+autogroup_setscheduler(struct task_struct *p, int on_rq)
+{
+ if (p->sched_class->task_move_group)
+ p->sched_class->task_move_group(p, on_rq);
+ else
+ set_task_rq(p, task_cpu(p));
+}
+
/* Allocates GFP_KERNEL, cannot be called under any spinlock */
void sched_autogroup_create_attach(struct task_struct *p)
{
Index: linux-2.6/kernel/sched_autogroup.h
===================================================================
--- linux-2.6.orig/kernel/sched_autogroup.h
+++ linux-2.6/kernel/sched_autogroup.h
@@ -15,6 +15,7 @@ autogroup_task_group(struct task_struct

static inline void autogroup_init(struct task_struct *init_task) { }
static inline void autogroup_free(struct task_group *tg) { }
+static inline void autogroup_setscheduler(struct task_struct *p, int on_rq) { }

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



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