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linux-next/kernel/time
Kurt Kanzenbach 3dc6ffae2d timekeeping: Introduce fast accessor to clock tai
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 <kurt@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/20220414091805.89667-2-kurt@linutronix.de
2022-04-14 16:19:30 +02:00
..
alarmtimer.c alarmtimer: Check RTC features instead of ops 2021-05-11 21:28:04 +02:00
clockevents.c clockevents: Use list_move() instead of list_del()/list_add() 2021-06-22 17:16:46 +02:00
clocksource-wdtest.c clocksource: Make clocksource watchdog test safe for slow-HZ systems 2021-08-28 17:01:32 +02:00
clocksource.c clocksource: Add a Kconfig option for WATCHDOG_MAX_SKEW 2022-02-01 17:35:43 -08:00
hrtimer.c hrtimer: Unbreak hrtimer_force_reprogram() 2021-08-12 22:34:40 +02:00
itimer.c time: Prevent undefined behaviour in timespec64_to_ns() 2020-10-26 11:48:11 +01:00
jiffies.c clocksource: Make clocksource watchdog test safe for slow-HZ systems 2021-08-28 17:01:32 +02:00
Kconfig clocksource: Add a Kconfig option for WATCHDOG_MAX_SKEW 2022-02-01 17:35:43 -08:00
Makefile time: Improve performance of time64_to_tm() 2021-06-24 11:51:59 +02:00
namespace.c memcg: enable accounting for new namesapces and struct nsproxy 2021-09-03 09:58:12 -07:00
ntp_internal.h ntp: Make the RTC synchronization more reliable 2020-12-11 10:40:52 +01:00
ntp.c timekeeping, clocksource: Fix various typos in comments 2021-03-22 23:06:48 +01:00
posix-clock.c posix-clocks: Rename the clock_get() callback to clock_get_timespec() 2020-01-14 12:20:49 +01:00
posix-cpu-timers.c ptrace: Cleanups for v5.18 2022-03-28 17:29:53 -07:00
posix-stubs.c posix-timers: Make clock_nanosleep() time namespace aware 2020-01-14 12:20:55 +01:00
posix-timers.c Merge branch 'akpm' (patches from Andrew) 2021-09-03 10:08:28 -07:00
posix-timers.h posix-clocks: Introduce clock_get_ktime() callback 2020-01-14 12:20:51 +01:00
sched_clock.c time/sched_clock: Mark sched_clock_read_begin/retry() as notrace 2020-10-26 11:34:31 +01:00
test_udelay.c time/debug: Remove dentry pointer for debugfs 2021-03-18 11:20:26 +01:00
tick-broadcast-hrtimer.c timekeeping, clocksource: Fix various typos in comments 2021-03-22 23:06:48 +01:00
tick-broadcast.c timer_list: Print name of per-cpu wakeup device 2021-05-31 17:04:49 +02:00
tick-common.c timekeeping: Distangle resume and clock-was-set events 2021-08-10 17:57:23 +02:00
tick-internal.h clocksource: Make clocksource watchdog test safe for slow-HZ systems 2021-08-28 17:01:32 +02:00
tick-legacy.c timekeeping: remove xtime_update 2020-10-30 21:57:07 +01:00
tick-oneshot.c timekeeping, clocksource: Fix various typos in comments 2021-03-22 23:06:48 +01:00
tick-sched.c tick/rcu: Stop allowing RCU_SOFTIRQ in idle 2022-03-07 23:01:34 +01:00
tick-sched.h tick: Detect and fix jiffies update stall 2022-03-07 23:01:19 +01:00
time_test.c time/kunit: Add missing MODULE_LICENSE() 2021-06-28 07:40:23 +02:00
time.c timekeeping, clocksource: Fix various typos in comments 2021-03-22 23:06:48 +01:00
timeconst.bc time: Add SPDX license identifiers 2018-11-23 11:51:20 +01:00
timeconv.c time: Improve performance of time64_to_tm() 2021-06-24 11:51:59 +02:00
timecounter.c time/timecounter: Mark 1st argument of timecounter_cyc2time() as const 2021-04-16 21:03:50 +02:00
timekeeping_debug.c timekeeping/debug: No need to check return value of debugfs_create functions 2019-01-29 20:08:41 +01:00
timekeeping_internal.h timekeeping/vsyscall: Provide vdso_update_begin/end() 2020-08-06 10:57:30 +02:00
timekeeping.c timekeeping: Introduce fast accessor to clock tai 2022-04-14 16:19:30 +02:00
timekeeping.h asm-generic: cross-architecture timer cleanup 2020-12-16 00:07:17 -08:00
timer_list.c timer_list: Print name of per-cpu wakeup device 2021-05-31 17:04:49 +02:00
timer.c timers: implement usleep_idle_range() 2021-12-10 17:10:55 -08:00
vsyscall.c timekeeping, clocksource: Fix various typos in comments 2021-03-22 23:06:48 +01:00