kernel/linux.git/include/linux/timekeeping.h, branch v6.19.11

timekeeping: Remove the temporary CLOCK_AUX workaround

2025-07-03T12:44:15+00:00

ktime_get_clock_ts64() was provided for the networking tree as a stand alone commit based on v6.16-rc1. It contains a temporary workaround for the CLOCK_AUX* defines, which are only available in the timekeeping tree. As this commit is now merged into the timers/ptp branch, which contains the real CLOCK_AUX* defines, the workaround is obsolete. Remove it. Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/all/20250701130923.579834908@linutronix.de

Merge tag 'ktime-get-clock-ts64-for-ptp' into timers/ptp

2025-07-03T12:35:53+00:00

Pull the base implementation of ktime_get_clock_ts64() for PTP, which contains a temporary CLOCK_AUX* workaround. That was created to allow integration of depending changes into the networking tree. The workaround is going to be removed in a subsequent change in the timekeeping tree. Signed-off-by: Thomas Gleixner

timekeeping: Provide ktime_get_clock_ts64()

2025-07-03T12:18:06+00:00

PTP implements an inline switch case for taking timestamps from various POSIX clock IDs, which already consumes quite some text space. Expanding it for auxiliary clocks really becomes too big for inlining. Provide a out of line version. The function invalidates the timestamp in case the clock is invalid. The invalidation allows to implement a validation check without the need to propagate a return value through deep existing call chains. Due to merge logistics this temporarily defines CLOCK_AUX[_LAST] if undefined, so that the plain branch, which does not contain any of the core timekeeper changes, can be pulled into the networking tree as prerequisite for the PTP side changes. These temporary defines are removed after that branch is merged into the tip::timers/ptp branch. That way the result in -next or upstream in the next merge window has zero dependencies. Signed-off-by: Thomas Gleixner Reviewed-by: Vadim Fedorenko Acked-by: John Stultz Link: https://lore.kernel.org/all/20250701132628.357686408@linutronix.de

timekeeping: Provide time getters for auxiliary clocks

2025-06-27T18:13:12+00:00

Provide interfaces similar to the ktime_get*() family which provide access to the auxiliary clocks. These interfaces have a boolean return value, which indicates whether the accessed clock is valid or not. Signed-off-by: Thomas Gleixner Acked-by: John Stultz Link: https://lore.kernel.org/all/20250625183757.868342628@linutronix.de

timekeeping: Remove unused ktime_get_fast_timestamps()

2025-01-15T18:49:14+00:00

ktime_get_fast_timestamps() was added in 2020 by commit e2d977c9f1ab ("timekeeping: Provide multi-timestamp accessor to NMI safe timekeeper") but has remained unused. Remove it. [ tglx: Fold the inline as David suggested in the submission ] Signed-off-by: Dr. David Alan Gilbert Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/all/20250112160132.450209-1-linux@treblig.org

Merge branch 'timers/vfs' into timers/core

2024-10-06T19:00:01+00:00

Pick up the VFS specific interfaces so further timekeeping changes can be based on them.

timekeeping: Add percpu counter for tracking floor swap events

2024-10-06T18:56:07+00:00

The mgtime_floor value is a global variable for tracking the latest fine-grained timestamp handed out. Because it's a global, track the number of times that a new floor value is assigned. Add a new percpu counter to the timekeeping code to track the number of floor swap events that have occurred. A later patch will add a debugfs file to display this counter alongside other stats involving multigrain timestamps. Signed-off-by: Jeff Layton Signed-off-by: Thomas Gleixner Tested-by: Randy Dunlap # documentation bits Link: https://lore.kernel.org/all/20241002-mgtime-v10-2-d1c4717f5284@kernel.org

timekeeping: Add interfaces for handling timestamps with a floor value

2024-10-06T18:56:07+00:00

Multigrain timestamps allow the kernel to use fine-grained timestamps when an inode's attributes is being actively observed via ->getattr(). With this support, it's possible for a file to get a fine-grained timestamp, and another modified after it to get a coarse-grained stamp that is earlier than the fine-grained time. If this happens then the files can appear to have been modified in reverse order, which breaks VFS ordering guarantees [1]. To prevent this, maintain a floor value for multigrain timestamps. Whenever a fine-grained timestamp is handed out, record it, and when later coarse-grained stamps are handed out, ensure they are not earlier than that value. If the coarse-grained timestamp is earlier than the fine-grained floor, return the floor value instead. Add a static singleton atomic64_t into timekeeper.c that is used to keep track of the latest fine-grained time ever handed out. This is tracked as a monotonic ktime_t value to ensure that it isn't affected by clock jumps. Because it is updated at different times than the rest of the timekeeper object, the floor value is managed independently of the timekeeper via a cmpxchg() operation, and sits on its own cacheline. Add two new public interfaces: - ktime_get_coarse_real_ts64_mg() fills a timespec64 with the later of the coarse-grained clock and the floor time - ktime_get_real_ts64_mg() gets the fine-grained clock value, and tries to swap it into the floor. A timespec64 is filled with the result. The floor value is global and updated via a single try_cmpxchg(). If that fails then the operation raced with a concurrent update. Any concurrent update must be later than the existing floor value, so any racing tasks can accept any resulting floor value without retrying. [1]: POSIX requires that files be stamped with realtime clock values, and makes no provision for dealing with backward clock jumps. If a backward realtime clock jump occurs, then files can appear to have been modified in reverse order. Signed-off-by: Jeff Layton Signed-off-by: Thomas Gleixner Tested-by: Randy Dunlap # documentation bits Acked-by: John Stultz Link: https://lore.kernel.org/all/20241002-mgtime-v10-1-d1c4717f5284@kernel.org

timekeeping: Add the boot clock to system time snapshot

2024-10-02T15:10:41+00:00

For tracing purpose, the boot clock is interesting as it doesn't stop on suspend. Export it as part of the time snapshot. This will later allow the hypervisor to add boot clock timestamps to its events. Signed-off-by: Vincent Donnefort Signed-off-by: Thomas Gleixner Acked-by: John Stultz Link: https://lore.kernel.org/all/20240911093029.3279154-5-vdonnefort@google.com

timekeeping: Add function to convert realtime to base clock

2024-06-03T09:18:51+00:00

PPS (Pulse Per Second) generates a hardware pulse every second based on CLOCK_REALTIME. This works fine when the pulse is generated in software from a hrtimer callback function. For hardware which generates the pulse by programming a timer it is required to convert CLOCK_REALTIME to the underlying hardware clock. The X86 Timed IO device is based on the Always Running Timer (ART), which is the base clock of the TSC, which is usually the system clocksource on X86. The core code already has functionality to convert base clock timestamps to system clocksource timestamps, but there is no support for converting the other way around. Provide the required functionality to support such devices in a generic way to avoid code duplication in drivers: 1) ktime_real_to_base_clock() to convert a CLOCK_REALTIME timestamp to a base clock timestamp 2) timekeeping_clocksource_has_base() to allow drivers to validate that the system clocksource is based on a particular clocksource ID. [ tglx: Simplify timekeeping_clocksource_has_base() and add missing READ_ONCE() ] Co-developed-by: Thomas Gleixner Signed-off-by: Thomas Gleixner Co-developed-by: Christopher S. Hall Signed-off-by: Christopher S. Hall Signed-off-by: Lakshmi Sowjanya D Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20240513103813.5666-10-lakshmi.sowjanya.d@intel.com