sched: fix hotplug cpus on ia64
Cliff Wickman wrote:
> I built an ia64 kernel from Andrew's tree (2.6.26-rc2-mm1)
> and get a very predictable hotplug cpu problem.
> billberry1:/tmp/cpw # ./dis
> disabled cpu 17
> enabled cpu 17
> billberry1:/tmp/cpw # ./dis
> disabled cpu 17
> enabled cpu 17
> billberry1:/tmp/cpw # ./dis
>
> The script that disables the cpu always hangs (unkillable)
> on the 3rd attempt.
>
> And a bit further:
> The kstopmachine thread always sits on the run queue (real time) for about
> 30 minutes before running.
this fix solves some (but not all) issues between CPU hotplug and
RT bandwidth throttling.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index eaa6060..8ae3416 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -286,6 +286,9 @@
continue;
spin_lock(&iter->rt_runtime_lock);
+ if (iter->rt_runtime == RUNTIME_INF)
+ goto next;
+
diff = iter->rt_runtime - iter->rt_time;
if (diff > 0) {
do_div(diff, weight);
@@ -299,12 +302,105 @@
break;
}
}
+next:
spin_unlock(&iter->rt_runtime_lock);
}
spin_unlock(&rt_b->rt_runtime_lock);
return more;
}
+
+static void __disable_runtime(struct rq *rq)
+{
+ struct root_domain *rd = rq->rd;
+ struct rt_rq *rt_rq;
+
+ if (unlikely(!scheduler_running))
+ return;
+
+ for_each_leaf_rt_rq(rt_rq, rq) {
+ struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
+ s64 want;
+ int i;
+
+ spin_lock(&rt_b->rt_runtime_lock);
+ spin_lock(&rt_rq->rt_runtime_lock);
+ if (rt_rq->rt_runtime == RUNTIME_INF ||
+ rt_rq->rt_runtime == rt_b->rt_runtime)
+ goto balanced;
+ spin_unlock(&rt_rq->rt_runtime_lock);
+
+ want = rt_b->rt_runtime - rt_rq->rt_runtime;
+
+ for_each_cpu_mask(i, rd->span) {
+ struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
+ s64 diff;
+
+ if (iter == rt_rq)
+ continue;
+
+ spin_lock(&iter->rt_runtime_lock);
+ if (want > 0) {
+ diff = min_t(s64, iter->rt_runtime, want);
+ iter->rt_runtime -= diff;
+ want -= diff;
+ } else {
+ iter->rt_runtime -= want;
+ want -= want;
+ }
+ spin_unlock(&iter->rt_runtime_lock);
+
+ if (!want)
+ break;
+ }
+
+ spin_lock(&rt_rq->rt_runtime_lock);
+ BUG_ON(want);
+balanced:
+ rt_rq->rt_runtime = RUNTIME_INF;
+ spin_unlock(&rt_rq->rt_runtime_lock);
+ spin_unlock(&rt_b->rt_runtime_lock);
+ }
+}
+
+static void disable_runtime(struct rq *rq)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&rq->lock, flags);
+ __disable_runtime(rq);
+ spin_unlock_irqrestore(&rq->lock, flags);
+}
+
+static void __enable_runtime(struct rq *rq)
+{
+ struct root_domain *rd = rq->rd;
+ struct rt_rq *rt_rq;
+
+ if (unlikely(!scheduler_running))
+ return;
+
+ for_each_leaf_rt_rq(rt_rq, rq) {
+ struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
+
+ spin_lock(&rt_b->rt_runtime_lock);
+ spin_lock(&rt_rq->rt_runtime_lock);
+ rt_rq->rt_runtime = rt_b->rt_runtime;
+ rt_rq->rt_time = 0;
+ spin_unlock(&rt_rq->rt_runtime_lock);
+ spin_unlock(&rt_b->rt_runtime_lock);
+ }
+}
+
+static void enable_runtime(struct rq *rq)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&rq->lock, flags);
+ __enable_runtime(rq);
+ spin_unlock_irqrestore(&rq->lock, flags);
+}
+
#endif
static inline int rt_se_prio(struct sched_rt_entity *rt_se)
@@ -334,14 +430,13 @@
#ifdef CONFIG_SMP
if (rt_rq->rt_time > runtime) {
- int more;
-
spin_unlock(&rt_rq->rt_runtime_lock);
- more = balance_runtime(rt_rq);
+ balance_runtime(rt_rq);
spin_lock(&rt_rq->rt_runtime_lock);
- if (more)
- runtime = sched_rt_runtime(rt_rq);
+ runtime = sched_rt_runtime(rt_rq);
+ if (runtime == RUNTIME_INF)
+ return 0;
}
#endif
@@ -1174,6 +1269,8 @@
if (rq->rt.overloaded)
rt_set_overload(rq);
+ __enable_runtime(rq);
+
cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio);
}
@@ -1183,6 +1280,8 @@
if (rq->rt.overloaded)
rt_clear_overload(rq);
+ __disable_runtime(rq);
+
cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_INVALID);
}