nohz: Optimize full dynticks state checks with static keys

These APIs are frequenctly accessed and priority is given
to optimize the full dynticks off-case in order to let
distros enable this feature without suffering from
significant performance regressions.

Let's inline these APIs and optimize them with static keys.

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: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Kevin Hilman <khilman@linaro.org>

kernel/time/tick-sched.c

@@ -149,7 +149,7 @@ static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs)
 }
 
 #ifdef CONFIG_NO_HZ_FULL
-static cpumask_var_t tick_nohz_full_mask;
+cpumask_var_t tick_nohz_full_mask;
 bool tick_nohz_full_running;
 
 static bool can_stop_full_tick(void)
@@ -270,14 +270,6 @@ out:
 	local_irq_restore(flags);
 }
 
-int tick_nohz_full_cpu(int cpu)
-{
-	if (!tick_nohz_full_running)
-		return 0;
-
-	return cpumask_test_cpu(cpu, tick_nohz_full_mask);
-}
-
 /* Parse the boot-time nohz CPU list from the kernel parameters. */
 static int __init tick_nohz_full_setup(char *str)
 {
@@ -359,8 +351,6 @@ void __init tick_nohz_init(void)
 	cpulist_scnprintf(nohz_full_buf, sizeof(nohz_full_buf), tick_nohz_full_mask);
 	pr_info("NO_HZ: Full dynticks CPUs: %s.\n", nohz_full_buf);
 }
-#else
-#define tick_nohz_full_running (0)
 #endif
 
 /*
@@ -738,7 +728,7 @@ static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
 		return false;
 	}
 
-	if (tick_nohz_full_running) {
+	if (tick_nohz_full_enabled()) {
 		/*
 		 * Keep the tick alive to guarantee timekeeping progression
 		 * if there are full dynticks CPUs around