watchdog: Make it work under full dynticks

A perf event can be used without forcing the tick to
stay alive if it doesn't use a frequency but a sample
period and if it doesn't throttle (raise storm of events).

Since the lockup detector neither use a perf event frequency
nor should ever throttle due to its high period, it can now
run concurrently with the full dynticks feature.

So remove the hack that disabled the watchdog.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Anish Singh <anish198519851985@gmail.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1374539466-4799-9-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

kernel/watchdog.c

@@ -553,14 +553,6 @@ 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();
 }