kernel/linux.git/include/linux/timekeeping.h, branch v6.6.132

timekeeping: Introduce fast accessor to clock tai

2022-04-14T14:19:30+00:00

Introduce fast/NMI safe accessor to clock tai for tracing. The Linux kernel tracing infrastructure has support for using different clocks to generate timestamps for trace events. Especially in TSN networks it's useful to have TAI as trace clock, because the application scheduling is done in accordance to the network time, which is based on TAI. With a tai trace_clock in place, it becomes very convenient to correlate network activity with Linux kernel application traces. Use the same implementation as ktime_get_boot_fast_ns() does by reading the monotonic time and adding the TAI offset. The same limitations as for the fast boot implementation apply. The TAI offset may change at run time e.g., by setting the time or using adjtimex() with an offset. However, these kind of offset changes are rare events. Nevertheless, the user has to be aware and deal with it in post processing. An alternative approach would be to use the same implementation as ktime_get_real_fast_ns() does. However, this requires to add an additional u64 member to the tk_read_base struct. This struct together with a seqcount is designed to fit into a single cache line on 64 bit architectures. Adding a new member would violate this constraint. Signed-off-by: Kurt Kanzenbach Signed-off-by: Thomas Gleixner Cc: Steven Rostedt Link: https://lore.kernel.org/r/20220414091805.89667-2-kurt@linutronix.de

time: Add mechanism to recognize clocksource in time_get_snapshot

2021-04-07T15:33:20+00:00

System time snapshots are not conveying information about the current clocksource which was used, but callers like the PTP KVM guest implementation have the requirement to evaluate the clocksource type to select the appropriate mechanism. Introduce a clocksource id field in struct clocksource which is by default set to CSID_GENERIC (0). Clocksource implementations can set that field to a value which allows to identify the clocksource. Store the clocksource id of the current clocksource in the system_time_snapshot so callers can evaluate which clocksource was used to take the snapshot and act accordingly. Signed-off-by: Thomas Gleixner Signed-off-by: Jianyong Wu Signed-off-by: Marc Zyngier Link: https://lore.kernel.org/r/20201209060932.212364-5-jianyong.wu@arm.com

Merge tag 'asm-generic-timers-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic

2020-12-16T08:07:17+00:00

Pull asm-generic cross-architecture timer cleanup from Arnd Bergmann: "This cleans up two ancient timer features that were never completed in the past, CONFIG_GENERIC_CLOCKEVENTS and CONFIG_ARCH_USES_GETTIMEOFFSET. There was only one user left for the ARCH_USES_GETTIMEOFFSET variant of clocksource implementations, the ARM EBSA110 platform. Rather than changing to use modern timekeeping, we remove the platform entirely as Russell no longer uses his machine and nobody else seems to have one any more. The conditional code for using arch_gettimeoffset() is removed as a result. For CONFIG_GENERIC_CLOCKEVENTS, there are still a couple of platforms not using clockevent drivers: parisc, ia64, most of m68k, and one Arm platform. These all do timer ticks slighly differently, and this gets cleaned up to the point they at least all call the same helper function. Instead of most platforms using 'select GENERIC_CLOCKEVENTS' in Kconfig, the polarity is now reversed, with the few remaining ones selecting LEGACY_TIMER_TICK instead" * tag 'asm-generic-timers-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic: timekeeping: default GENERIC_CLOCKEVENTS to enabled timekeeping: remove xtime_update m68k: remove timer_interrupt() function m68k: change remaining timers to legacy_timer_tick m68k: m68328: use legacy_timer_tick() m68k: sun3/sun3c: use legacy_timer_tick m68k: split heartbeat out of timer function m68k: coldfire: use legacy_timer_tick() parisc: use legacy_timer_tick ARM: rpc: use legacy_timer_tick ia64: convert to legacy_timer_tick timekeeping: add CONFIG_LEGACY_TIMER_TICK timekeeping: remove arch_gettimeoffset net: remove am79c961a driver ARM: remove ebsa110 platform

ntp: Fix prototype in the !CONFIG_GENERIC_CMOS_UPDATE case

2020-12-13T09:16:31+00:00

In the !CONFIG_GENERIC_CMOS_UPDATE case the update_persistent_clock64() function gets defined as a stub in ntp.c - make the prototype in conditional on CONFIG_GENERIC_CMOS_UPDATE as well. Fixes: 76e87d96b30b5 ("ntp: Consolidate the RTC update implementation") Signed-off-by: Ingo Molnar Acked-by: Thomas Gleixner

timekeeping: remove xtime_update

2020-10-30T20:57:07+00:00

There are no more users of xtime_update aside from legacy_timer_tick(), so fold it into that function and remove the declaration. update_process_times() is now only called inside of the kernel/time/ code, so the declaration can be moved there. Reviewed-by: Geert Uytterhoeven Tested-by: Geert Uytterhoeven Reviewed-by: Linus Walleij Signed-off-by: Arnd Bergmann

timekeeping: add CONFIG_LEGACY_TIMER_TICK

2020-10-30T20:57:04+00:00

All platforms that currently do not use generic clockevents roughly call the same set of functions in their timer interrupts: xtime_update(), update_process_times() and profile_tick(), sometimes in a different sequence. Add a helper function that performs all three of them, to make the callers more uniform and simplify the interface. Reviewed-by: Geert Uytterhoeven Reviewed-by: Linus Walleij Signed-off-by: Arnd Bergmann

timekeeping: Provide multi-timestamp accessor to NMI safe timekeeper

2020-08-23T08:38:24+00:00

printk wants to store various timestamps (MONOTONIC, REALTIME, BOOTTIME) to make correlation of dmesg from several systems easier. Provide an interface to retrieve all three timestamps in one go. There are some caveats: 1) Boot time and late sleep time injection Boot time is a racy access on 32bit systems if the sleep time injection happens late during resume and not in timekeeping_resume(). That could be avoided by expanding struct tk_read_base with boot offset for 32bit and adding more overhead to the update. As this is a hard to observe once per resume event which can be filtered with reasonable effort using the accurate mono/real timestamps, it's probably not worth the trouble. Aside of that it might be possible on 32 and 64 bit to observe the following when the sleep time injection happens late: CPU 0 CPU 1 timekeeping_resume() ktime_get_fast_timestamps() mono, real = __ktime_get_real_fast() inject_sleep_time() update boot offset boot = mono + bootoffset; That means that boot time already has the sleep time adjustment, but real time does not. On the next readout both are in sync again. Preventing this for 64bit is not really feasible without destroying the careful cache layout of the timekeeper because the sequence count and struct tk_read_base would then need two cache lines instead of one. 2) Suspend/resume timestamps Access to the time keeper clock source is disabled accross the innermost steps of suspend/resume. The accessors still work, but the timestamps are frozen until time keeping is resumed which happens very early. For regular suspend/resume there is no observable difference vs. sched clock, but it might affect some of the nasty low level debug printks. OTOH, access to sched clock is not guaranteed accross suspend/resume on all systems either so it depends on the hardware in use. If that turns out to be a real problem then this could be mitigated by using sched clock in a similar way as during early boot. But it's not as trivial as on early boot because it needs some careful protection against the clock monotonic timestamp jumping backwards on resume. Signed-off-by: Thomas Gleixner Tested-by: Petr Mladek Link: https://lore.kernel.org/r/20200814115512.159981360@linutronix.de

timekeeping: Fix kerneldoc system_device_crosststamp & al

2020-06-18T09:37:03+00:00

Make kernel doc comments actually work and fix the syncronized typo. [ tglx: Added the missing /** and fixed up formatting ] Signed-off-by: Kurt Kanzenbach Signed-off-by: Thomas Gleixner Link: https://lkml.kernel.org/r/20200609081726.5657-1-kurt@linutronix.de

timekeeping: Boot should be boottime for coarse ns accessor

2019-06-25T06:54:51+00:00

Somewhere in all the patchsets before, this cleanup got lost. Signed-off-by: Jason A. Donenfeld Signed-off-by: Thomas Gleixner Cc: Arnd Bergmann Link: https://lkml.kernel.org/r/20190624091539.13512-1-Jason@zx2c4.com

timekeeping: Add missing _ns functions for coarse accessors

2019-06-22T10:11:28+00:00

This further unifies the accessors for the fast and coarse functions, so that the same types of functions are available for each. There was also a bit of confusion with the documentation, which prior advertised a function that has never existed. Finally, the vanilla ktime_get_coarse() was omitted from the API originally, so this fills this oversight. Signed-off-by: Jason A. Donenfeld Signed-off-by: Thomas Gleixner Reviewed-by: Arnd Bergmann Link: https://lkml.kernel.org/r/20190621203249.3909-3-Jason@zx2c4.com