nohz: Warn if the machine can not perform nohz_full

[~andy/linux] / kernel / time / tick-sched.c

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index f4208138fbf4cd1a72791f99c31adcbea9180e3e..d87d22cb9bf2baeb31d854c3c731e70ee402f3da 100644 (file)
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -178,6 +178,11 @@ static bool can_stop_full_tick(void)
         */
        if (!sched_clock_stable) {
                trace_tick_stop(0, "unstable sched clock\n");
+               /*
+                * Don't allow the user to think they can get
+                * full NO_HZ with this machine.
+                */
+               WARN_ONCE(1, "NO_HZ FULL will not work with unstable sched clock");
                return false;
        }
 #endif