From 543487c7a2670bb0d96c00673a44b74360e3b6c1 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Tue, 16 Jul 2013 10:22:12 -0400 Subject: [PATCH 1/2] nohz: Do not warn about unstable tsc unless user uses nohz_full 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 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index e80183f4a6c4..1102534a1a57 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; } #endif From ca06416b2b4fa562cd3c3f9eb4198c3b2a983342 Mon Sep 17 00:00:00 2001 From: Li Zhong Date: Tue, 16 Jul 2013 12:18:47 +0800 Subject: [PATCH 2/2] nohz: fix compile warning in tick_nohz_init() cpu is not used after commit 5b8621a68fdcd2baf1d3b413726f913a5254d46a Signed-off-by: Li Zhong Cc: 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 | 2 -- 1 file changed, 2 deletions(-) diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 1102534a1a57..9563c744dad2 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -344,8 +344,6 @@ static int tick_nohz_init_all(void) void __init tick_nohz_init(void) { - int cpu; - if (!have_nohz_full_mask) { if (tick_nohz_init_all() < 0) return;