2012-08-09 22:34:51

by Peter Boonstoppel

Subject: [PATCH 1/1] sched: unthrottle rt runqueues in __disable_runtime()

migrate_tasks() uses _pick_next_task_rt() to get tasks from the
real-time runqueues to be migrated. When rt_rq is throttled
_pick_next_task_rt() won't return anything, in which case
migrate_tasks() can't move all threads over and gets stuck in an
infinite loop.

Instead unthrottle rt runqueues before migrating tasks.

Additionally: move unthrottle_offline_cfs_rqs() to rq_offline_fair()

Signed-off-by: Peter Boonstoppel <[email protected]>
---
kernel/sched/core.c | 3 ---
kernel/sched/fair.c | 7 +++++--
kernel/sched/rt.c | 1 +
kernel/sched/sched.h | 1 -
4 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 2df035a..2e7ecff 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5221,9 +5221,6 @@ static void migrate_tasks(unsigned int dead_cpu)
*/
rq->stop = NULL;

- /* Ensure any throttled groups are reachable by pick_next_task */
- unthrottle_offline_cfs_rqs(rq);
-
for ( ; ; ) {
/*
* There's this thread running, bail when that's the only
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 3704ad3..dc8341b 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2057,7 +2057,7 @@ static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
hrtimer_cancel(&cfs_b->slack_timer);
}

-void unthrottle_offline_cfs_rqs(struct rq *rq)
+static void unthrottle_offline_cfs_rqs(struct rq *rq)
{
struct cfs_rq *cfs_rq;

@@ -2111,7 +2111,7 @@ static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
return NULL;
}
static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
-void unthrottle_offline_cfs_rqs(struct rq *rq) {}
+static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}

#endif /* CONFIG_CFS_BANDWIDTH */

@@ -5086,6 +5086,9 @@ static void rq_online_fair(struct rq *rq)
static void rq_offline_fair(struct rq *rq)
{
update_sysctl();
+
+ /* Ensure any throttled groups are reachable by pick_next_task */
+ unthrottle_offline_cfs_rqs(rq);
}

#endif /* CONFIG_SMP */
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 573e1ca..b9a94fb 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -691,6 +691,7 @@ balanced:
* runtime - in which case borrowing doesn't make sense.
*/
rt_rq->rt_runtime = RUNTIME_INF;
+ rt_rq->rt_throttled = 0;
raw_spin_unlock(&rt_rq->rt_runtime_lock);
raw_spin_unlock(&rt_b->rt_runtime_lock);
}
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 4134d37..5d9aabe 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1167,7 +1167,6 @@ extern void print_rt_stats(struct seq_file *m, int cpu);

extern void init_cfs_rq(struct cfs_rq *cfs_rq);
extern void init_rt_rq(struct rt_rq *rt_rq, struct rq *rq);
-extern void unthrottle_offline_cfs_rqs(struct rq *rq);

extern void account_cfs_bandwidth_used(int enabled, int was_enabled);

--
1.7.0.4-

2012-08-16 08:22:11

by Peter Zijlstra

Subject: Re: [PATCH 1/1] sched: unthrottle rt runqueues in __disable_runtime()

On Thu, 2012-08-09 at 15:34 -0700, Peter Boonstoppel wrote:
> migrate_tasks() uses _pick_next_task_rt() to get tasks from the
> real-time runqueues to be migrated. When rt_rq is throttled
> _pick_next_task_rt() won't return anything, in which case
> migrate_tasks() can't move all threads over and gets stuck in an
> infinite loop.
>
> Instead unthrottle rt runqueues before migrating tasks.
>
> Additionally: move unthrottle_offline_cfs_rqs() to rq_offline_fair()

Thanks!