On Mon, May 20, 2013 at 06:01:51PM +0200, Frederic Weisbecker wrote: > 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.
I thought Peter committed a patch to perf so that this isn't needed any more? Cheers, Don > > Reported-by: Steven Rostedt <[email protected]> > Suggested-by: Peter Zijlstra <[email protected]> > Signed-off-by: Frederic Weisbecker <[email protected]> > Cc: Steven Rostedt <[email protected]> > Cc: Paul E. McKenney <[email protected]> > Cc: Ingo Molnar <[email protected]> > Cc: Andrew Morton <[email protected]> > Cc: Thomas Gleixner <[email protected]> > Cc: Peter Zijlstra <[email protected]> > Cc: Li Zhong <[email protected]> > Cc: Don Zickus <[email protected]> > --- > kernel/watchdog.c | 6 ++++++ > 1 files changed, 6 insertions(+), 0 deletions(-) > > diff --git a/kernel/watchdog.c b/kernel/watchdog.c > index 05039e3..7e1a021 100644 > --- a/kernel/watchdog.c > +++ b/kernel/watchdog.c > @@ -543,6 +543,12 @@ static struct smp_hotplug_thread watchdog_threads = { > > void __init lockup_detector_init(void) > { > +#ifdef CONFIG_NO_HZ_FULL > + watchdog_enabled = 0; > + watchdog_disabled = 1; > + pr_warning("Disabled lockup detectors by default because of full > dynticks\n"); > + pr_warning("You can overwrite that with 'sysctl -w > kernel.watchdog=1'\n"); > +#endif > set_sample_period(); > if (smpboot_register_percpu_thread(&watchdog_threads)) { > pr_err("Failed to create watchdog threads, disabled\n"); > -- > 1.7.5.4 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
