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:
aae17ebb53 ("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: aae17ebb53 ("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/
All of the uses of CONFIG_RCU_FAST_NO_HZ=y that I have seen involve
systems with RCU callbacks offloaded. In this situation, all that this
Kconfig option does is slow down idle entry/exit with an additional
allways-taken early exit. If this is the only use case, then this
Kconfig option nothing but an attractive nuisance that needs to go away.
This commit therefore removes the RCU_FAST_NO_HZ Kconfig option.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The CONFIG_NO_HZ_IDLE paragraph is using "dyntick-idle mode" before
having defined it while the definition comes a couple of paragraphs
later.
That is leaving the reader with scratching head what that dyntick-idle
mode might be. Pull its definition up so that it is clear.
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20210914203355.21360-1-bp@alien8.de
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
A few of the Documentation .rst files begin with a Unicode
byte order mark (BOM). The BOM may signify endianess for
16-bit or 32-bit encodings or indicate that the text stream
is indeed Unicode. We don't need it for either of those uses.
It may also interfere with (confuse) some software.
Since we don't need it and its use is optional, just delete
the uses of it in Documentation/.
https://en.wikipedia.org/wiki/Byte_order_mark
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Link: https://lore.kernel.org/r/20210506231907.14359-1-rdunlap@infradead.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
The LB_BIAS feature was removed in commit 1c1b8a7b03 ("sched/fair:
Replace source_load() & target_load() with weighted_cpuload()"), so drop
the mention that it is disabled in the no_hz case.
Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Link: https://lore.kernel.org/r/1595088518-28116-1-git-send-email-Julia.Lawall@inria.fr
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
The conversion here is really trivial: just a bunch of title
markups and very few puntual changes is enough to make it to
be parsed by Sphinx and generate a nice html.
The conversion is actually:
- add blank lines and identation in order to identify paragraphs;
- fix tables markups;
- add some lists markups;
- mark literal blocks;
- adjust title markups.
At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Acked-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Oleg Nesterov