[lkml]   [2013]   [Jul]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
Subject[PATCH 1/2] nohz: Do not warn about unstable tsc unless user uses nohz_full
From: Steven Rostedt <>

If the user enables CONFIG_NO_HZ_FULL and runs the kernel on a machine
with an unstable TSC, it will produce a WARN_ON dump as well as taint
the kernel. This is a bit extreme for a kernel that just enables a
feature but doesn't use it.

The warning should only happen if the user tries to use the feature by
either adding nohz_full to the kernel command line, or by enabling
CONFIG_NO_HZ_FULL_ALL that makes nohz used on all CPUs at boot up. Note,
this second feature should not (yet) be used by distros or anyone that
doesn't care if NO_HZ is used or not.

Signed-off-by: Steven Rostedt <>
Cc: Paul E. McKenney <>
Cc: Ingo Molnar <>
Cc: Thomas Gleixner <>
Cc: Peter Zijlstra <>
Cc: Borislav Petkov <>
Cc: Li Zhong <>
Cc: Mike Galbraith <>
Cc: Kevin Hilman <>
Signed-off-by: Frederic Weisbecker <>
kernel/time/tick-sched.c | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index e80183f..1102534 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -182,7 +182,8 @@ static bool can_stop_full_tick(void)
* 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");
+ WARN_ONCE(have_nohz_full_mask,
+ "NO_HZ FULL will not work with unstable sched clock");
return false;

 \ /
  Last update: 2013-07-24 21:21    [W:0.059 / U:67.196 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site