sched/isolation: Introduce housekeeping flags

Before we implement isolcpus under housekeeping, we need the isolation
features to be more finegrained. For example some people want NOHZ_FULL
without the full scheduler isolation, others want full scheduler
isolation without NOHZ_FULL.

So let's cut all these isolation features piecewise, at the risk of
overcutting it right now. We can still merge some flags later if they
always make sense together.

Signed-off-by: Frederic Weisbecker <[email protected]>
Acked-by: Thomas Gleixner <[email protected]>
Cc: Chris Metcalf <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Luiz Capitulino <[email protected]>
Cc: Mike Galbraith <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Wanpeng Li <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

kernel/watchdog.c

@@ -777,7 +777,8 @@ void __init lockup_detector_init(void)
 	if (tick_nohz_full_enabled())
 		pr_info("Disabling watchdog on nohz_full cores by default\n");
 
-	cpumask_copy(&watchdog_cpumask, housekeeping_cpumask());
+	cpumask_copy(&watchdog_cpumask,
+		     housekeeping_cpumask(HK_FLAG_TIMER));
 
 	if (!watchdog_nmi_probe())
 		nmi_watchdog_available = true;