Commit-ID: 940be35ac0139530d7554aa2352a8388e3d4adca
Gitweb: http://git.kernel.org/tip/940be35ac0139530d7554aa2352a8388e3d4adca
Author: Frederic Weisbecker <fweisbec@xxxxxxxxx>
AuthorDate: Fri, 7 Jun 2013 13:35:42 +0200
Committer: Frederic Weisbecker <fweisbec@xxxxxxxxx>
CommitDate: Thu, 20 Jun 2013 15:46:32 +0200
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@xxxxxxxxxxx>
Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Li Zhong <zhong@xxxxxxxxxxxxxxxxxx>
Cc: Don Zickus <dzickus@xxxxxxxxxx>
Cc: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
Cc: Anish Singh <anish198519851985@xxxxxxxxx>
---
kernel/watchdog.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 51c4f34..1241d8c 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();
}
--
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