sched: rt: document the risk of small values in the bandwidth settings

[deliverable/linux.git] / kernel / sched.c

diff --git a/kernel/sched.c b/kernel/sched.c
index 54d67b94f1a9f159e7f9ea07f9ab0e2bc626c569..2a43a581ead32c2ae0396c8f13e3b484a89003c8 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -9917,6 +9917,13 @@ static int sched_rt_global_constraints(void)
        if (sysctl_sched_rt_period <= 0)
                return -EINVAL;
 
+       /*
+        * There's always some RT tasks in the root group
+        * -- migration, kstopmachine etc..
+        */
+       if (sysctl_sched_rt_runtime == 0)
+               return -EBUSY;
+
        spin_lock_irqsave(&def_rt_bandwidth.rt_runtime_lock, flags);
        for_each_possible_cpu(i) {
                struct rt_rq *rt_rq = &cpu_rq(i)->rt;