sched/isolation: Prevent boot crash when the boot CPU is nohz_full

Documentation/timers/no_hz.rst states that the "nohz_full=" mask must not
include the boot CPU, which is no longer true after:

  08ae95f4fd3b ("nohz_full: Allow the boot CPU to be nohz_full").

However after:

  aae17ebb53cd ("workqueue: Avoid using isolated cpus' timers on queue_delayed_work")

the kernel will crash at boot time in this case; housekeeping_any_cpu()
returns an invalid CPU number until smp_init() brings the first
housekeeping CPU up.

Change housekeeping_any_cpu() to check the result of cpumask_any_and() and
return smp_processor_id() in this case.

This is just the simple and backportable workaround which fixes the
symptom, but smp_processor_id() at boot time should be safe at least for
type == HK_TYPE_TIMER, this more or less matches the tick_do_timer_boot_cpu

There is no worry about cpu_down(); tick_nohz_cpu_down() will not allow to
offline tick_do_timer_cpu (the 1st online housekeeping CPU).

Fixes: aae17ebb53cd ("workqueue: Avoid using isolated cpus' timers on queue_delayed_work")
Reported-by: Chris von Recklinghausen <>
Signed-off-by: Oleg Nesterov <>
Signed-off-by: Thomas Gleixner <>
Signed-off-by: Ingo Molnar <>
Reviewed-by: Phil Auld <>
Acked-by: Frederic Weisbecker <>
2 files changed