user/sven/linux.git/include/linux/timekeeping.h, branch v6.15.1

timekeeping: Remove unused ktime_get_fast_timestamps()

2025-01-15T18:49:14Z

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

2024-10-06T19:00:01Z

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

timekeeping: Add percpu counter for tracking floor swap events

2024-10-06T18:56:07Z

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

2024-10-06T18:56:07Z

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

2024-10-02T15:10:41Z

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

2024-06-03T09:18:51Z

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

timekeeping: Provide infrastructure for converting to/from a base clock

2024-06-03T09:18:50Z

Hardware time stamps like provided by PTP clock implementations are based on a clock which feeds both the PCIe device and the system clock. For further processing the underlying hardwarre clock timestamp must be converted to the system clock. Right now this requires drivers to invoke an architecture specific conversion function, e.g. to convert the ART (Always Running Timer) timestamp to a TSC timestamp. As the system clock is aware of the underlying base clock, this can be moved to the core code by providing a base clock property for the system clock which contains the conversion factors and assigning a clocksource ID to the base clock. Add the required data structures and the conversion infrastructure in the core code to prepare for converting X86 and the related PTP drivers over. [ tglx: Added a missing READ_ONCE(). Massaged change log ] 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/20240513103813.5666-2-lakshmi.sowjanya.d@intel.com

time/timekeeping: Fix kernel-doc warnings and typos

2024-04-01T08:36:34Z

Fix punctuation, spellos, and kernel-doc warnings: timekeeping.h:79: warning: No description found for return value of 'ktime_get_real' timekeeping.h:95: warning: No description found for return value of 'ktime_get_boottime' timekeeping.h:108: warning: No description found for return value of 'ktime_get_clocktai' timekeeping.h:149: warning: Function parameter or struct member 'mono' not described in 'ktime_mono_to_real' timekeeping.h:149: warning: No description found for return value of 'ktime_mono_to_real' timekeeping.h:255: warning: Function parameter or struct member 'cs_id' not described in 'system_time_snapshot' Signed-off-by: Randy Dunlap Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20240331172652.14086-3-rdunlap@infradead.org

treewide: Remove system_counterval_t.cs, which is never read

2024-02-07T16:05:21Z

The clocksource pointer in struct system_counterval_t is not evaluated any more. Remove the code setting the member, and the member itself. Signed-off-by: Peter Hilber Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20240201010453.2212371-8-peter.hilber@opensynergy.com

timekeeping: Evaluate system_counterval_t.cs_id instead of .cs

2024-02-07T16:05:21Z

Clocksource pointers can be problematic to obtain for drivers which are not clocksource drivers themselves. In particular, the RFC virtio_rtc driver [1] would require a new helper function to obtain a pointer to the ARM Generic Timer clocksource. The ptp_kvm driver also required a similar workaround. Address this by evaluating the clocksource ID, rather than the clocksource pointer, of struct system_counterval_t. By this, setting the clocksource pointer becomes unneeded, and get_device_system_crosststamp() callers will no longer need to supply clocksource pointers. All relevant clocksource drivers provide the ID, so this change is not changing the behaviour. [1] https://lore.kernel.org/lkml/20231218073849.35294-1-peter.hilber@opensynergy.com/ Signed-off-by: Peter Hilber Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20240201010453.2212371-7-peter.hilber@opensynergy.com