Oleg Nesterov ba181019d1 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). [ Apply only documentation changes as commit which causes boot crash when boot CPU is nohz_full is not backported to stable kernels - Krishanth ] 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: Krishanth Jagaduri <Krishanth.Jagaduri@sony.com> [ strip out upstream commit and Fixes: so tools don't get confused that this commit actually does anything real - gregkh] Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2025-03-28 21:58:48 +01:00
..
highres.rst	docs: timers: convert docs to ReST and rename to *.rst	2019-06-14 14:31:48 -06:00
hpet.rst	docs: timers: convert docs to ReST and rename to *.rst	2019-06-14 14:31:48 -06:00
hrtimers.rst	docs: timers: convert docs to ReST and rename to *.rst	2019-06-14 14:31:48 -06:00
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	2025-03-28 21:58:48 +01:00
timekeeping.rst	docs: timers: convert docs to ReST and rename to *.rst	2019-06-14 14:31:48 -06:00
timers-howto.rst	Documentation: Replace lkml.org links with lore	2021-01-11 12:47:38 -07:00