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authorSteven Rostedt <rostedt@goodmis.org>2013-05-10 17:12:28 -0400
committerFrederic Weisbecker <fweisbec@gmail.com>2013-06-20 01:15:51 +0200
commite12d0271774fea9fddf1e2a7952a0bffb2ee8e8b (patch)
tree6bd6a506cd535836ec419055cc4c20f0a6648224 /kernel/time
parent7d132055814ef17a6c7b69f342244c410a5e000f (diff)
nohz: Warn if the machine can not perform nohz_full
If the user configures NO_HZ_FULL and defines nohz_full=XXX on the kernel command line, or enables NO_HZ_FULL_ALL, but nohz fails due to the machine having a unstable clock, warn about it. We do not want users thinking that they are getting the benefit of nohz when their machine can not support it. Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Diffstat (limited to 'kernel/time')
-rw-r--r--kernel/time/tick-sched.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index f4208138fbf4..d87d22cb9bf2 100644
--- 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