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authorFrederic Weisbecker <fweisbec@gmail.com>2013-06-07 13:35:42 +0200
committerFrederic Weisbecker <fweisbec@gmail.com>2013-06-20 15:46:32 +0200
commit940be35ac0139530d7554aa2352a8388e3d4adca (patch)
tree5da95cdb511ed220e02bae139eddb49d5e57d5b3
parent3c00ea82c724fab0b98f15428a804cb45eb9ad38 (diff)
downloadlinux-940be35ac0139530d7554aa2352a8388e3d4adca.tar.bz2
watchdog: Boot-disable by default on full dynticks
When the watchdog runs, it prevents the full dynticks CPUs from stopping their tick because the hard lockup detector uses perf events internally, which in turn rely on the periodic tick. Since this is a rather confusing behaviour that is not easy to track down and identify for those who want to test CONFIG_NO_HZ_FULL, let's default disable the watchdog on boot time when full dynticks is enabled. The user can still enable it later on runtime using proc or sysctl. Reported-by: Steven Rostedt <rostedt@goodmis.org> Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: 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: Peter Zijlstra <peterz@infradead.org> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Don Zickus <dzickus@redhat.com> Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Cc: Anish Singh <anish198519851985@gmail.com>
-rw-r--r--kernel/watchdog.c8
1 files changed, 8 insertions, 0 deletions
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 51c4f34d258e..1241d8c91d5e 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -553,6 +553,14 @@ void __init lockup_detector_init(void)
{
set_sample_period();
+#ifdef CONFIG_NO_HZ_FULL
+ if (watchdog_user_enabled) {
+ watchdog_user_enabled = 0;
+ pr_warning("Disabled lockup detectors by default for full dynticks\n");
+ pr_warning("You can reactivate it with 'sysctl -w kernel.watchdog=1'\n");
+ }
+#endif
+
if (watchdog_user_enabled)
watchdog_enable_all_cpus();
}