tick/sched: Remove bogus boot "safety" check

BugLink: https://bugs.launchpad.net/bugs/1910742
[ Upstream commit ba8ea8e7dd6e1662e34e730eadfc52aa6816f9dd ]

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: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20201206212002.725238293@linutronix.de
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 81632cd5e3b729568e86f80295a133410c905054..e8d351b7f9b03326c48630ffbb35851c991cbb10 100644 (file)
--- a/kernel/time/tick-sched.c
+++ b/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))