tick/sched: Remove bogus boot "safety" check

stable inclusion
from stable-5.10.5
commit 330c1ee7d59373ac91390779e2daddc5aa54deab
bugzilla: 46931

--------------------------------

[ Upstream commit ba8ea8e7 ]

can_stop_idle_tick() checks whether the do_timer() duty has been taken over
by a CPU on boot. That's silly because the boot CPU always takes over with
the initial clockevent device.

But even if no CPU would have installed a clockevent and taken over the
duty then the question whether the tick on the current CPU can be stopped
or not is moot. In that case the current CPU would have no clockevent
either, so there would be nothing to keep ticking.

Remove it.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Acked-by: NFrederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20201206212002.725238293@linutronix.deSigned-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>

kernel/time/tick-sched.c

@@ -941,13 +941,6 @@ static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
 		 */
 		if (tick_do_timer_cpu == cpu)
 			return false;
-		/*
-		 * Boot safety: make sure the timekeeping duty has been
-		 * assigned before entering dyntick-idle mode,
-		 * tick_do_timer_cpu is TICK_DO_TIMER_BOOT
-		 */
-		if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_BOOT))
-			return false;
 
 		/* Should not happen for nohz-full */
 		if (WARN_ON_ONCE(tick_do_timer_cpu == TICK_DO_TIMER_NONE))