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sched_rt: Fix overload bug on rt group scheduling

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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)

Tested-by: Thomas Gleixner <tglx@linutronix.de>
CC: stable@kernel.org
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Gregory Haskins <ghaskins@novell.com>
LKML-Reference: <1247067476.9777.57.camel@twins>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2009-04-01 18:40:15 +02:00 committed by Ingo Molnar
parent d4ec36bac3
commit a1ba4d8ba9
2 changed files with 18 additions and 1 deletions
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1
kernel/sched.c
View file

@ -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

18
kernel/sched_rt.c
View file

@ -10,6 +10,8 @@ static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
#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(struct sched_rt_entity *rt_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(struct rq *rq)
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 rt_rq *rt_rq)
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 sched_rt_entity *rt_se, struct rt_rq *rt_rq)
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--;