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Oleg Nesterov c3997fe80e sched/isolation: Prevent boot crash when the boot CPU is nohz_full 
JIRA: https://issues.redhat.com/browse/RHEL-30589

commit 5097cbcb38e6e0d2627c9dde1985e91d2c9f880e
Author: Oleg Nesterov <oleg@redhat.com>
Date:   Thu Apr 11 16:39:05 2024 +0200

    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:

      08ae95f4fd ("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
    logic.

    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 <crecklin@redhat.com>
    Signed-off-by: Oleg Nesterov <oleg@redhat.com>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Reviewed-by: Phil Auld <pauld@redhat.com>
    Acked-by: Frederic Weisbecker <frederic@kernel.org>
    Link: https://lore.kernel.org/r/20240411143905.GA19288@redhat.com
    Closes: https://lore.kernel.org/all/20240402105847.GA24832@redhat.com/

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
 		2024-07-25 09:48:26 +02:00
..
highres.rst
…
hpet.rst
…
hrtimers.rst
…
index.rst docs: add some directories to the main documentation index 2019-07-15 11:03:03 -03:00
no_hz.rst sched/isolation: Prevent boot crash when the boot CPU is nohz_full 2024-07-25 09:48:26 +02:00
timekeeping.rst
…
timers-howto.rst Documentation: Replace lkml.org links with lore 2021-01-11 12:47:38 -07:00