Changes in Kconfig

c163e40a - timekeeping: Always check for negative motion

Thu, 31 Oct 2024 12:04:08 +0000

timekeeping: Always check for negative motionclocksource_delta() has two variants. One with a check for negative motion,which is only selected by x86. This is a historic leftover as this functionwas previously used in the time getter hot paths.Since 135225a363ae timekeeping_cycles_to_ns() has unconditional protectionagainst this as a by-product of the protection against 64bit math overflow.clocksource_delta() is only used in the clocksource watchdog and intimekeeping_advance(). The extra conditional there is not hurting anyone.Remove the config option and unconditionally prevent negative motion of thereadout.Signed-off-by: Thomas Gleixner Acked-by: John Stultz Link: https://lore.kernel.org/all/20241031120328.599430157@linutronix.de List of files: /linux-6.15/kernel/time/Kconfig

54db412e - clocksource: Make the int help prompt unit readable in ncurses

Sun, 28 Apr 2024 10:21:43 +0000

clocksource: Make the int help prompt unit readable in ncursesWhen doing make menuconfigand searching for the CLOCKSOURCE_WATCHDOG_MAX_SKEW_US config item, thehelp says: │ Symbol: CLOCKSOURCE_WATCHDOG_MAX_SKEW_US [=125] │ Type : integer │ Range : [50 1000] │ Defined at kernel/time/Kconfig:204 │ Prompt: Clocksource watchdog maximum allowable skew (in s) ^^^ │ Depends on: GENERIC_CLOCKEVENTS [=y] && CLOCKSOURCE_WATCHDOG [=y]because on some terminals, it cannot display the 'μ' char, unicodenumber 0x3bc.So simply write it out so that there's no trouble.Signed-off-by: Borislav Petkov (AMD) Signed-off-by: Thomas Gleixner Acked-by: Paul E. McKenney Acked-by: Randy Dunlap Link: https://lore.kernel.org/r/20240428102143.26764-1-bp@kernel.org List of files: /linux-6.15/kernel/time/Kconfig

2be2a197 - sched/idle: Conditionally handle tick broadcast in default_idle_call()

Thu, 29 Feb 2024 14:23:36 +0000

sched/idle: Conditionally handle tick broadcast in default_idle_call()The x86 architecture has an idle routine for AMD CPUs which are affectedby erratum 400. On the affected CPUs the local APIC timer stops in theC1E halt state.It therefore requires tick broadcasting. The invocation oftick_broadcast_enter()/exit() from this function violates the RCUconstraints because it can end up in lockdep or tracing, whichrightfully triggers a warning.tick_broadcast_enter()/exit() must be invoked before ct_cpuidle_enter()and after ct_cpuidle_exit() in default_idle_call().Add a static branch conditional invocation of tick_broadcast_enter()/exit()into this function to allow X86 to replace the AMD specific idle code. It'sguarded by a config switch which will be selected by x86. Otherwise it'sa NOOP.Reported-by: Borislav Petkov Signed-off-by: Thomas Gleixner Signed-off-by: Borislav Petkov (AMD) Link: https://lore.kernel.org/r/20240229142248.266708822@linutronix.de List of files: /linux-6.15/kernel/time/Kconfig

c37e85c1 - clocksource: Loosen clocksource watchdog constraints

Wed, 07 Dec 2022 03:36:10 +0000

clocksource: Loosen clocksource watchdog constraintsCurrently, MAX_SKEW_USEC is set to 100 microseconds, which has workedreasonably well. However, NTP is willing to tolerate 500 microsecondsof skew per second, and a clocksource that is good enough for NTP shouldbe good enough for the clocksource watchdog. The watchdog's skew iscontrolled by MAX_SKEW_USEC and the CLOCKSOURCE_WATCHDOG_MAX_SKEW_USKconfig option. However, these values are doubled before being associatedwith a clocksource's ->uncertainty_margin, and the ->uncertainty_marginvalues of the pair of clocksource's being compared are summed beforechecking against the skew.Therefore, set both MAX_SKEW_USEC and the default for theCLOCKSOURCE_WATCHDOG_MAX_SKEW_US Kconfig option to 125 microseconds ofskew per second, resulting in 500 microseconds of skew per second inthe clocksource watchdog's skew comparison.Suggested-by Rik van Riel Signed-off-by: Paul E. McKenney List of files: /linux-6.15/kernel/time/Kconfig

e67198cc - context_tracking: Take idle eqs entrypoints over RCU

Wed, 08 Jun 2022 14:40:25 +0000

context_tracking: Take idle eqs entrypoints over RCUThe RCU dynticks counter is going to be merged into the context trackingsubsystem. Start with moving the idle extended quiescent statesentrypoints to context tracking. For now those are dumb redirections toexisting RCU calls.[ paulmck: Apply kernel test robot feedback. ]Signed-off-by: Frederic Weisbecker Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Neeraj Upadhyay Cc: Uladzislau Rezki Cc: Joel Fernandes Cc: Boqun Feng Cc: Nicolas Saenz Julienne Cc: Marcelo Tosatti Cc: Xiongfeng Wang Cc: Yu Liao Cc: Phil Auld Cc: Paul GortmakerCc: Alex Belits Signed-off-by: Paul E. McKenney Reviewed-by: Nicolas Saenz Julienne Tested-by: Nicolas Saenz Julienne List of files: /linux-6.15/kernel/time/Kconfig

24a9c541 - context_tracking: Split user tracking Kconfig

Wed, 08 Jun 2022 14:40:24 +0000

context_tracking: Split user tracking KconfigContext tracking is going to be used not only to track user transitionsbut also idle/IRQs/NMIs. The user tracking part will then become aseparate feature. Prepare Kconfig for that.[ frederic: Apply Max Filippov feedback. ]Signed-off-by: Frederic Weisbecker Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Neeraj Upadhyay Cc: Uladzislau Rezki Cc: Joel Fernandes Cc: Boqun Feng Cc: Nicolas Saenz Julienne Cc: Marcelo Tosatti Cc: Xiongfeng Wang Cc: Yu Liao Cc: Phil Auld Cc: Paul GortmakerCc: Alex Belits Signed-off-by: Paul E. McKenney Reviewed-by: Nicolas Saenz Julienne Tested-by: Nicolas Saenz Julienne List of files: /linux-6.15/kernel/time/Kconfig

fc153c1c - clocksource: Add a Kconfig option for WATCHDOG_MAX_SKEW

Mon, 06 Dec 2021 03:38:15 +0000

clocksource: Add a Kconfig option for WATCHDOG_MAX_SKEWA watchdog maximum skew of 100us may still be too small forsome systems or archs. It may also be too small when some kerneldebug config options are enabled. So add a new Kconfig optionCLOCKSOURCE_WATCHDOG_MAX_SKEW_US to allow kernel builders to have morecontrol on the threshold for marking clocksource as unstable.Signed-off-by: Waiman Long Signed-off-by: Paul E. McKenney List of files: /linux-6.15/kernel/time/Kconfig

27601055 - time: Improve performance of time64_to_tm()

Tue, 22 Jun 2021 21:36:16 +0000

time: Improve performance of time64_to_tm()The current implementation of time64_to_tm() contains unnecessary loops,branches and look-up tables. The new one uses an arithmetic-based algorithmappeared in [1] and is approximately 3x faster (YMMV).The drawback is that the new code isn't intuitive and contains many 'magicnumbers' (not unusual for this type of algorithm). However, [1] justifiesall those numbers and, given this function's history, the code is unlikelyto need much maintenance, if any at all.Add a KUnit test for it which checks every day in a 160,000 years intervalcentered at 1970-01-01 against the expected result.[1] Neri, Schneider, "Euclidean Affine Functions and Applications toCalendar Algorithms". https://arxiv.org/abs/2102.06959Signed-off-by: Cassio Neri Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20210622213616.313046-1-cassio.neri@gmail.com List of files: /linux-6.15/kernel/time/Kconfig

176b8906 - tick/nohz: Update nohz_full Kconfig help

Wed, 12 May 2021 23:29:19 +0000

tick/nohz: Update nohz_full Kconfig helpCONFIG_NO_HZ_FULL behaves just like CONFIG_NO_HZ_IDLE by default.Reassure distros about it.Signed-off-by: Frederic Weisbecker Signed-off-by: Ingo Molnar Acked-by: Peter Zijlstra Link: https://lore.kernel.org/r/20210512232924.150322-6-frederic@kernel.org List of files: /linux-6.15/kernel/time/Kconfig

f6f5cd84 - timekeeping: Fix spelling mistake in Kconfig "fullfill" -> "fulfill"

Thu, 17 Dec 2020 17:17:05 +0000

timekeeping: Fix spelling mistake in Kconfig "fullfill" -> "fulfill"There is a spelling mistake in the Kconfig help text. Fix it.Signed-off-by: Colin Ian King Signed-off-by: Thomas Gleixner Acked-by: Linus Walleij Link: https://lore.kernel.org/r/20201217171705.57586-1-colin.king@canonical.com List of files: /linux-6.15/kernel/time/Kconfig

0774a6ed - timekeeping: default GENERIC_CLOCKEVENTS to enabled

Thu, 24 Sep 2020 09:32:40 +0000

timekeeping: default GENERIC_CLOCKEVENTS to enabledAlmost all machines use GENERIC_CLOCKEVENTS, so it feels wrong torequire each one to select that symbol manually.Instead, enable it whenever CONFIG_LEGACY_TIMER_TICK is disabled asa simplification. It should be possible to select bothGENERIC_CLOCKEVENTS and LEGACY_TIMER_TICK from an architecture nowand decide at runtime between the two.For the clockevents arch-support.txt file, this means that additionalarchitectures are marked as TODO when they have at least one machinethat still uses LEGACY_TIMER_TICK, rather than being marked 'ok' whenat least one machine has been converted. This means that both m68k andarm (for riscpc) revert to TODO.At this point, we could just always enable CONFIG_GENERIC_CLOCKEVENTSrather than leaving it off when not needed. I built an m68kdefconfig kernel (using gcc-10.1.0) and found that this would addaround 5.5KB in kernel image size: text data bss dec hex filename3861936 1092236 196656 5150828 4e986c obj-m68k/vmlinux-no-clockevent3866201 1093832 196184 5156217 4ead79 obj-m68k/vmlinux-clockeventOn Arm (MACH_RPC), that difference appears to be twice as large,around 11KB on top of an 6MB vmlinux.Reviewed-by: Geert Uytterhoeven Acked-by: Geert Uytterhoeven Tested-by: Geert Uytterhoeven Reviewed-by: Linus Walleij Signed-off-by: Arnd Bergmann List of files: /linux-6.15/kernel/time/Kconfig

b3550164 - timekeeping: add CONFIG_LEGACY_TIMER_TICK

Thu, 24 Sep 2020 13:21:43 +0000

timekeeping: add CONFIG_LEGACY_TIMER_TICKAll platforms that currently do not use generic clockevents roughly callthe same set of functions in their timer interrupts: xtime_update(),update_process_times() and profile_tick(), sometimes in a differentsequence.Add a helper function that performs all three of them, to make thecallers more uniform and simplify the interface.Reviewed-by: Geert Uytterhoeven Reviewed-by: Linus Walleij Signed-off-by: Arnd Bergmann List of files: /linux-6.15/kernel/time/Kconfig

77f6c0b8 - timekeeping: remove arch_gettimeoffset

Thu, 24 Sep 2020 10:30:50 +0000

timekeeping: remove arch_gettimeoffsetWith Arm EBSA110 gone, nothing uses it any more, so the correspondingcode and the Kconfig option can be removed.Acked-by: Thomas Gleixner Reviewed-by: Linus Walleij Signed-off-by: Arnd Bergmann List of files: /linux-6.15/kernel/time/Kconfig

1fb497dd - posix-cpu-timers: Provide mechanisms to defer timer handling to task_work

Thu, 30 Jul 2020 10:14:06 +0000

posix-cpu-timers: Provide mechanisms to defer timer handling to task_workRunning posix CPU timers in hard interrupt context has a few downsides: - For PREEMPT_RT it cannot work as the expiry code needs to take sighand lock, which is a 'sleeping spinlock' in RT. The original RT approach of offloading the posix CPU timer handling into a high priority thread was clumsy and provided no real benefit in general. - For fine grained accounting it's just wrong to run this in context of the timer interrupt because that way a process specific CPU time is accounted to the timer interrupt. - Long running timer interrupts caused by a large amount of expiring timers which can be created and armed by unpriviledged user space.There is no hard requirement to expire them in interrupt context.If the signal is targeted at the task itself then it won't be deliveredbefore the task returns to user space anyway. If the signal is targeted ata supervisor process then it might be slightly delayed, but posix CPUtimers are inaccurate anyway due to the fact that they are tied to thetick.Provide infrastructure to schedule task work which allows splitting theposix CPU timer code into a quick check in interrupt context and a threadcontext expiry and signal delivery function. This has to be enabled byarchitectures as it requires that the architecture specific KVMimplementation handles pending task work before exiting to guest mode.Signed-off-by: Thomas Gleixner Signed-off-by: Ingo Molnar Reviewed-by: Oleg Nesterov Acked-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20200730102337.783470146@linutronix.de List of files: /linux-6.15/kernel/time/Kconfig

ec8f24b7 - treewide: Add SPDX license identifier - Makefile/Kconfig

Sun, 19 May 2019 12:07:45 +0000

treewide: Add SPDX license identifier - Makefile/KconfigAdd SPDX license identifiers to all Make/Kconfig files which: - Have no license information of any formThese files fall under the project license, GPL v2 only. The resulting SPDXlicense identifier is: GPL-2.0-onlySigned-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman List of files: /linux-6.15/kernel/time/Kconfig

a4cffdad - time: Move CONTEXT_TRACKING to kernel/time/Kconfig

Thu, 20 Dec 2018 17:05:25 +0000

time: Move CONTEXT_TRACKING to kernel/time/KconfigBoth CONTEXT_TRACKING and CONTEXT_TRACKING_FORCE are currently definedin kernel/rcu/kconfig, which might have made sense at some point, butno longer does given that RCU refers to neither of these Kconfig options.Therefore move them to kernel/time/Kconfig, where the rest of theNO_HZ_FULL Kconfig options live.Signed-off-by: Paul E. McKenney Signed-off-by: Thomas Gleixner Cc: Frederic Weisbecker Link: https://lkml.kernel.org/r/20181220170525.GA12579@linux.ibm.com List of files: /linux-6.15/kernel/time/Kconfig

d67f34c1 - clocksource: Provide clocksource_arch_init()

Mon, 17 Sep 2018 12:45:34 +0000

clocksource: Provide clocksource_arch_init()Architectures have extra archdata in the clocksource, e.g. for VDSOsupport. There are no sanity checks or general initializations for thisavailable. Add support for that.Signed-off-by: Thomas Gleixner Acked-by: Andy Lutomirski Acked-by: John Stultz Cc: Peter Zijlstra Cc: Matt Rickard Cc: Stephen Boyd Cc: Florian Weimer Cc: "K. Y. Srinivasan" Cc: Vitaly Kuznetsov Cc: devel@linuxdriverproject.orgCc: virtualization@lists.linux-foundation.orgCc: Paolo Bonzini Cc: Arnd Bergmann Cc: Juergen Gross Link: https://lkml.kernel.org/r/20180917130706.973042587@linutronix.de List of files: /linux-6.15/kernel/time/Kconfig

a7c8655b - sched/isolation: Eliminate NO_HZ_FULL_ALL

Thu, 30 Nov 2017 23:36:35 +0000

sched/isolation: Eliminate NO_HZ_FULL_ALLCommit 6f1982fedd59 ("sched/isolation: Handle the nohz_full= parameter")broke CONFIG_NO_HZ_FULL_ALL=y kernels. This breakage is due to the codeunder CONFIG_NO_HZ_FULL_ALL failing to invoke the shiny new housekeepingfunctions. This means that rcutorture scenario TREE04 now emits RCU CPUstall warnings due to the RCU grace-period kthreads not being awakenedat a time of their choosing, or perhaps even not at all:[ 27.731422] rcu_bh kthread starved for 21001 jiffies! g18446744073709551369 c18446744073709551368 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x402 ->cpu=3[ 27.731423] rcu_bh I14936 9 2 0x80080000[ 27.731435] Call Trace:[ 27.731440] __schedule+0x31a/0x6d0[ 27.731442] schedule+0x31/0x80[ 27.731446] schedule_timeout+0x15a/0x320[ 27.731453] ? call_timer_fn+0x130/0x130[ 27.731457] rcu_gp_kthread+0x66c/0xea0[ 27.731458] ? rcu_gp_kthread+0x66c/0xea0Because no one has complained about CONFIG_NO_HZ_FULL_ALL=y being broken,I hypothesize that no one is in fact using it, other than rcutorture.This commit therefore eliminates CONFIG_NO_HZ_FULL_ALL and updatesrcutorture's config files to instead use the nohz_full= kernel parameterto put the desired CPUs into nohz_full mode.Fixes: 6f1982fedd59 ("sched/isolation: Handle the nohz_full= parameter")Reported-by: kernel test robot Signed-off-by: Paul E. McKenney Cc: Frederic Weisbecker Cc: Thomas Gleixner Cc: Chris Metcalf Cc: Christoph Lameter Cc: Linus Torvalds Cc: Luiz Capitulino Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Rik van Riel Cc: Wanpeng Li Cc: Ingo Molnar Cc: John Stultz Cc: Jonathan Corbet List of files: /linux-6.15/kernel/time/Kconfig

bf29cb23 - sched/isolation: Make CONFIG_NO_HZ_FULL select CONFIG_CPU_ISOLATION

Thu, 14 Dec 2017 18:18:25 +0000

sched/isolation: Make CONFIG_NO_HZ_FULL select CONFIG_CPU_ISOLATIONCONFIG_NO_HZ_FULL doesn't make sense without CONFIG_CPU_ISOLATION. Infact enabling the first without the second is a regression as nohz_full=boot parameter gets silently ignored.Besides this unnatural combination hangs RCU gp kthread when runningrcutorture for reasons that are not yet fully understood: rcu_preempt kthread starved for 9974 jiffies! g4294967208 +c4294967207 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x402 ->cpu=0 rcu_preempt I 7464 8 2 0x80000000 Call Trace: __schedule+0x493/0x620 schedule+0x24/0x40 schedule_timeout+0x330/0x3b0 ? preempt_count_sub+0xea/0x140 ? collect_expired_timers+0xb0/0xb0 rcu_gp_kthread+0x6bf/0xef0This commit therefore makes NO_HZ_FULL select CPU_ISOLATION, whichprevents all these bad behaviours.Reported-by: kernel test robot Signed-off-by: Paul E. McKenney Signed-off-by: Frederic Weisbecker Cc: Chris Metcalf Cc: Christoph Lameter Cc: John Stultz Cc: Linus Torvalds Cc: Luiz Capitulino Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Rik van Riel Cc: Thomas Gleixner Cc: Wanpeng Li Fixes: 5c4991e24c69 ("sched/isolation: Split out new CONFIG_CPU_ISOLATION=y config from CONFIG_NO_HZ_FULL")Link: http://lkml.kernel.org/r/1513275507-29200-2-git-send-email-frederic@kernel.orgSigned-off-by: Ingo Molnar List of files: /linux-6.15/kernel/time/Kconfig

aea3706c - timekeeping: Remove CONFIG_GENERIC_TIME_VSYSCALL_OLD

Mon, 13 Nov 2017 22:51:31 +0000

timekeeping: Remove CONFIG_GENERIC_TIME_VSYSCALL_OLDAs of d4d1fc61eb38f (ia64: Update fsyscall gettime to use modernvsyscall_update)the last user of CONFIG_GENERIC_TIME_VSYSCALL_OLDhave been updated, the legacy support for old-style vsyscallimplementations can be removed from the timekeeping code.(Thanks again to Tony Luck for helping remove the last user!)[jstultz: Commit message rework]Signed-off-by: Miroslav Lichvar Signed-off-by: John Stultz Signed-off-by: Thomas Gleixner Cc: Prarit Bhargava Cc: Tony Luck Cc: Richard Cochran Cc: Stephen Boyd Link: https://lkml.kernel.org/r/1510613491-16695-1-git-send-email-john.stultz@linaro.org List of files: /linux-6.15/kernel/time/Kconfig