sched,rt: fix isolated CPUs leaving root_task_group indefinitely throttled

[~andy/linux] / kernel / sched / rt.c

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 573e1ca01102066468e65aee96c57ea30cccd6de..944cb68420e957cbde71f9cacaaa4e81c4b1de20 100644 (file)
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -788,6 +788,19 @@ static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
        const struct cpumask *span;
 
        span = sched_rt_period_mask();
+#ifdef CONFIG_RT_GROUP_SCHED
+       /*
+        * FIXME: isolated CPUs should really leave the root task group,
+        * whether they are isolcpus or were isolated via cpusets, lest
+        * the timer run on a CPU which does not service all runqueues,
+        * potentially leaving other CPUs indefinitely throttled.  If
+        * isolation is really required, the user will turn the throttle
+        * off to kill the perturbations it causes anyway.  Meanwhile,
+        * this maintains functionality for boot and/or troubleshooting.
+        */
+       if (rt_b == &root_task_group.rt_bandwidth)
+               span = cpu_online_mask;
+#endif
        for_each_cpu(i, span) {
                int enqueue = 0;
                struct rt_rq *rt_rq = sched_rt_period_rt_rq(rt_b, i);