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SubjectRe: [PATCH] sched_rt: fix overload bug on rt group scheduling -v2
Peter Zijlstra wrote:
> Greg, how's this?
>

Hi Peter,
Sorry for the delay getting back to you.

I can't vouch specifically for the rt-group specific part, but as far as
the general balancer modifications to the migration code, it looks good.

> ---
> Subject: sched_rt: fix overload bug on rt group scheduling
> From: Peter Zijlstra <peterz@infradead.org>
> Date: Wed, 01 Apr 2009 18:40:15 +0200
>
> Fixes an easily triggerable BUG() when setting process affinities.
>
> Make sure to count the number of migratable tasks in the same place:
> the root rt_rq. Otherwise the number doesn't make sense and we'll hit
> the BUG in set_cpus_allowed_rt().
>
> Also, make sure we only count tasks, not groups (this is probably
> already taken care of by the fact that rt_se->nr_cpus_allowed will be 0
> for groups, but be more explicit)
>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
>

Acked-by: Gregory Haskins <ghaskins@novell.com>

> ---
> kernel/sched_rt.c | 18 +++++++++++++++++-
> 1 file changed, 17 insertions(+), 1 deletion(-)
>
> Index: linux-2.6/kernel/sched_rt.c
> ===================================================================
> --- linux-2.6.orig/kernel/sched_rt.c
> +++ linux-2.6/kernel/sched_rt.c
> @@ -10,6 +10,8 @@ static inline struct task_struct *rt_tas
>
> #ifdef CONFIG_RT_GROUP_SCHED
>
> +#define rt_entity_is_task(rt_se) (!(rt_se)->my_q)
> +
> static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
> {
> return rt_rq->rq;
> @@ -22,6 +24,8 @@ static inline struct rt_rq *rt_rq_of_se(
>
> #else /* CONFIG_RT_GROUP_SCHED */
>
> +#define rt_entity_is_task(rt_se) (1)
> +
> static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
> {
> return container_of(rt_rq, struct rq, rt);
> @@ -73,7 +77,7 @@ static inline void rt_clear_overload(str
>
> static void update_rt_migration(struct rt_rq *rt_rq)
> {
> - if (rt_rq->rt_nr_migratory && (rt_rq->rt_nr_running > 1)) {
> + if (rt_rq->rt_nr_migratory && rt_rq->rt_nr_total > 1) {
> if (!rt_rq->overloaded) {
> rt_set_overload(rq_of_rt_rq(rt_rq));
> rt_rq->overloaded = 1;
> @@ -86,6 +90,12 @@ static void update_rt_migration(struct r
>
> static void inc_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
> {
> + if (!rt_entity_is_task(rt_se))
> + return;
> +
> + rt_rq = &rq_of_rt_rq(rt_rq)->rt;
> +
> + rt_rq->rt_nr_total++;
> if (rt_se->nr_cpus_allowed > 1)
> rt_rq->rt_nr_migratory++;
>
> @@ -94,6 +104,12 @@ static void inc_rt_migration(struct sche
>
> static void dec_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
> {
> + if (!rt_entity_is_task(rt_se))
> + return;
> +
> + rt_rq = &rq_of_rt_rq(rt_rq)->rt;
> +
> + rt_rq->rt_nr_total--;
> if (rt_se->nr_cpus_allowed > 1)
> rt_rq->rt_nr_migratory--;
>
> diff --git a/kernel/sched.c b/kernel/sched.c
> index fd3ac58..a07d520 100644
> --- a/kernel/sched.c
> +++ b/kernel/sched.c
> @@ -493,6 +493,7 @@ struct rt_rq {
> #endif
> #ifdef CONFIG_SMP
> unsigned long rt_nr_migratory;
> + unsigned long rt_nr_total;
> int overloaded;
> struct plist_head pushable_tasks;
> #endif
>
>


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