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2024-04-28sched/isolation: Prevent boot crash when the boot CPU is nohz_fullOleg Nesterov
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 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/
2021-11-30rcu: Remove the RCU_FAST_NO_HZ Kconfig optionPaul E. McKenney
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>
2021-09-27Documentation/no_hz: Introduce "dyntick-idle mode" before using itBorislav Petkov
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>
2021-05-10Documentation: drop optional BOMsRandy Dunlap
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>
2020-07-23docs: timers: drop documentation about LB_BIASJulia Lawall
The LB_BIAS feature was removed in commit 1c1b8a7b03ef ("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>
2019-06-14docs: timers: convert docs to ReST and rename to *.rstMauro Carvalho Chehab
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>