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Thomas Weißschuh (Schneider Electric)
0f474ee80c selftests: timers: nsleep-lat: Reuse kselftest error numbers
The test currently defines its own custom error numbers.
These mirror the semantics from the standard KFST_* constants.

To make the code easier to read, use the standard result constants.

Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Acked-by: John Stultz <jstultz@google.com>
Link: https://patch.msgid.link/20260803-auxclock-nanosleep-prep-v2-16-910cbd485390@linutronix.de
2026-08-11 18:11:21 +02:00
Thomas Weißschuh (Schneider Electric)
187ac443ed selftests: timers: nsleep-lat: Explicitly list the tested clocks
The test relies on the numeric values of the clockids.
As not all clocks are meant to be tested, this requires skipping some
clocks unconditionally, cluttering the result.

Use an equivalent, explicit list instead.

In addition to CLOCK_PROCESS_CPUTIME_ID, CLOCK_THREAD_CPUTIME_ID and
CLOCK_HWSPECIFIC which were unconditionally skipped before, this also
unconditionally skips CLOCK_MONOTONIC_RAW, CLOCK_MONOTONIC_COARSE and
CLOCK_REALTIME_COARSE. clock_nanosleep() is not supported for those.

Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Acked-by: John Stultz <jstultz@google.com>
Link: https://patch.msgid.link/20260803-auxclock-nanosleep-prep-v2-15-910cbd485390@linutronix.de
2026-08-11 18:11:21 +02:00
Thomas Weißschuh (Schneider Electric)
a00f90877d selftests: timers: nsleep-lat: Use NSEC_PER_MSEC define for unreasonable latency
Use the predefined symbol to make the code easier to understand.

Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Acked-by: John Stultz <jstultz@google.com>
Link: https://patch.msgid.link/20260803-auxclock-nanosleep-prep-v2-14-910cbd485390@linutronix.de
2026-08-11 18:11:21 +02:00
Thomas Weißschuh (Schneider Electric)
a121128823 selftests: timers: nanosleep: Report each test separately
Currently the test for the sleep functionality itself and the one for
the remaining time are reported together. This makes the test output a
bit confusing, especially as the upcoming tests for auxiliary clocks
will have different results between the two parts.

Report each test part on its own.

This also allows continuing testing other clocks after a single one
has failed.

Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260803-auxclock-nanosleep-prep-v2-13-910cbd485390@linutronix.de
2026-08-11 18:11:21 +02:00
Thomas Weißschuh (Schneider Electric)
f2ff28a522 selftests: timers: nanosleep: Explicitly handle timer_delete() failure
An upcoming patch will remove the early exit on failure of a single
testcase. If a test fails because a timeout timer could not be deleted,
then that timeout timer might interfere with the following tettcases.

Exit the whole test case with a clear error message in this case.

Other failures are not problematic:
* If timer_settime() fails, a harmless unarmed timer is left around.
* The SIGALRM handler reconfigured for each call to
  nanosleep_test_remaining() anyways.

Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260803-auxclock-nanosleep-prep-v2-12-910cbd485390@linutronix.de
2026-08-11 18:11:21 +02:00
Thomas Weißschuh (Schneider Electric)
061341a568 selftests: timers: nanosleep: Move all single clock tests out of the loop in main()
Make the code easier to read by avoiding a goto.

Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Acked-by: John Stultz <jstultz@google.com>
Link: https://patch.msgid.link/20260803-auxclock-nanosleep-prep-v2-11-910cbd485390@linutronix.de
2026-08-11 18:11:20 +02:00
Thomas Weißschuh (Schneider Electric)
bfe5bf0c5f selftests: timers: nanosleep: Reuse kselftest error numbers
The test currently defines its own custom error numbers.
These mirror the semantics from the standard KFST_* constants.

To make the code easier to read, use the standard result constants.

Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Acked-by: John Stultz <jstultz@google.com>
Link: https://patch.msgid.link/20260803-auxclock-nanosleep-prep-v2-10-910cbd485390@linutronix.de
2026-08-11 18:11:20 +02:00
Thomas Weißschuh (Schneider Electric)
2999620932 selftests: timers: nanosleep: Explicitly list the tested clocks
The test relies on the numeric values of the clockids.
As not all clocks are meant to be tested, this requires skipping some
clocks unconditionally, cluttering the result.

Use an equivalent, explicit list instead.

In addition to CLOCK_PROCESS_CPUTIME_ID, CLOCK_THREAD_CPUTIME_ID and
CLOCK_HWSPECIFIC which were unconditionally skipped before, this also
unconditionally skips CLOCK_MONOTONIC_RAW, CLOCK_MONOTONIC_COARSE and
CLOCK_REALTIME_COARSE. clock_nanosleep() is not supported for those.

Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Acked-by: John Stultz <jstultz@google.com>
Link: https://patch.msgid.link/20260803-auxclock-nanosleep-prep-v2-9-910cbd485390@linutronix.de
2026-08-11 18:11:20 +02:00
Thomas Weißschuh (Schneider Electric)
142a2d312e selftests: timers: nanosleep: Drop output alignment
The padding of the clock name is pointless as nothing else is printed.

Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260803-auxclock-nanosleep-prep-v2-8-910cbd485390@linutronix.de
2026-08-11 18:11:20 +02:00
Thomas Weißschuh (Schneider Electric)
54200b8748 selftests: timers: Use clock_name() and constants from clock-helpers.h
Replace the many repetitions of custom clockid_t to string translation
with the clock_name() helper from clock-helpers.h.
Also drop the custom ?SEC_PER_?SEC definitions.

Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Acked-by: John Stultz <jstultz@google.com>
Link: https://patch.msgid.link/20260803-auxclock-nanosleep-prep-v2-7-910cbd485390@linutronix.de
2026-08-11 18:11:20 +02:00
Thomas Weißschuh (Schneider Electric)
431012dd0a selftests: Add clock-helpers.h
Multiple selftests duplicate various clock-related functionality.
Add a new header to collect and deduplicate those.

Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Acked-by: John Stultz <jstultz@google.com>
Link: https://patch.msgid.link/20260803-auxclock-nanosleep-prep-v2-6-910cbd485390@linutronix.de
2026-08-11 18:11:20 +02:00
Thomas Weißschuh (Schneider Electric)
859b069ec5 timer_list: Use ktime_t over nanoseconds
hrtimers use ktime_t in their implementation and API.
The timer list performs a lot of unnecessary conversion to nanoseconds
which make the code harder to read and are also wrong in case the values
ever become negative.

Remove the conversions.

Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260803-auxclock-nanosleep-prep-v2-5-910cbd485390@linutronix.de
2026-08-11 18:11:20 +02:00
Thomas Weißschuh (Schneider Electric)
40e05cf391 timer_list: Use standard 'long long' format placeholders
'%Ld' and '%Lu' are GNU extensions. While they do work for kernel code,
checkpatch complains about them all the time. Replace them with the
standard placeholders for 'long long' types, namely '%lld' and '%llu'.

Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260803-auxclock-nanosleep-prep-v2-4-910cbd485390@linutronix.de
2026-08-11 18:11:20 +02:00
Thomas Weißschuh (Schneider Electric)
d2e6ee3ecb hrtimer: Add a lockdep assertion to hrtimer_update_base()
Document and verify that the hrtimer_cpu_base::lock is held at this point.

Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260803-auxclock-nanosleep-prep-v2-3-910cbd485390@linutronix.de
2026-08-11 18:11:20 +02:00
Thomas Weißschuh (Schneider Electric)
406a037ce7 timekeeping: Use u32 for clock_was_set_seq
Use an explicitly sized type to make the code a bit more consistent
with other fields of the datastructure and other sequence counters.

Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260803-auxclock-nanosleep-prep-v2-2-910cbd485390@linutronix.de
2026-08-11 18:11:20 +02:00
Thomas Weißschuh (Schneider Electric)
4f39d3c19b timekeeping: Rename clockid_aux_valid() to clockid_is_aux_clock()
The current name is not clear about its behavior.

Rename it.

Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260803-auxclock-nanosleep-prep-v2-1-910cbd485390@linutronix.de
2026-08-11 18:11:19 +02:00
Liang Hao
32a05ba399 hrtimer: Account nr_retries on recovered interrupt retries
Re-arranging hrtimer_interrupt() switched the retry path to a local
counter and dropped the update of cpu_base->nr_retries, leaving the
field exported via /proc/timer_list stuck at zero.

Increment nr_retries only when another pass through the expiry loop
is started; the third attempt that falls through to hang handling is
still accounted by nr_hangs alone.

Fixes: 2889243848 ("hrtimer: Re-arrange hrtimer_interrupt()")
Signed-off-by: Liang Hao <haohlliang@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260731150408.19554-1-haohlliang@gmail.com
2026-08-11 18:08:24 +02:00
Jérémy Jean
18c7d85864 timers/itimer: Zero-init old itimerval before copy to userspace
On native sparc64, struct __kernel_old_timeval contains a four-byte hole
after tv_usec because tv_sec is 64-bit while __kernel_suseconds_t is 32-bit.
put_itimerval() fills only the named fields in a stack-allocated
__kernel_old_itimerval and copies the entire object to userspace, so
getitimer() can expose the two padding holes.

Zero-initialize the aggregate before assigning the fields so implicit
padding is deterministic before it crosses the user/kernel boundary.

Signed-off-by: Jérémy Jean <Jeremy.Jean@oss.cyber.gouv.fr>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Assisted-by: Codex:gpt-5
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260809190428.1523014-1-Jeremy.Jean@oss.cyber.gouv.fr
2026-08-11 15:43:12 +02:00
Julian Braha
b17006b452 nohz: Replace dead select with choice default
'select' does not work on config options in a 'choice', so currently the
'select VIRT_CPU_ACCOUNTING_GEN' for NO_HZ_FULL is dead, with the choice
option VIRT_CPU_ACCOUNTING_GEN only being enabled when NO_HZ_FULL=y because
the other choice members depend on NO_HZ_FULL=n.

Remove the dead select, and encode this relationship as a default of the
choice, instead.

This dead select was found by kconfirm, a static analysis tool for Kconfig.

Signed-off-by: Julian Braha <julianbraha@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Reviewed-by: Bradley Morgan <include@grrlz.net>
Reviewed-by: Nicolas Schier <nsc@kernel.org>
Link: https://patch.msgid.link/20260801160140.2391000-1-julianbraha@gmail.com
2026-08-11 15:37:23 +02:00
Thomas Weißschuh (Schneider Electric)
2838bdb772 timekeeping: Annotate auxiliary clock accessors with __must_check
In contrast to the system time accessors, the ones for auxiliary clocks can
fail.

Make sure the callers check for this.

Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260731-timekeeping-aux-must-check-v1-2-11ae93068497@linutronix.de
2026-08-11 11:12:43 +02:00
Thomas Weißschuh (Schneider Electric)
1b51577187 timekeeping: Remove the unused ktime_get_clock_ts64()
The last user was removed in commit a6d799608e ("ptp: Switch to
ktime_get_snapshot_id() for pre/post timestamps").

Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260731-timekeeping-aux-must-check-v1-1-11ae93068497@linutronix.de
2026-08-11 11:12:43 +02:00
Thomas Weißschuh (Schneider Electric)
4b61084b11 timekeeping: Check the return value of tk_get_aux_ts64 in __do_adjtimex()
If the auxiliary clock is disabled during tk_get_aux_ts64() but is enabled
before tks->clock_valid is checked, then uninitialized stackdata will be
used in the calculations and indirectly leaked to userspace.

The same race window also exists after this change and also for the core
timekeeper. But in these cases the only effect would be incorrect
adjustments and this is userspace's responsibility to avoid this.

Fixes: 4eca49d0b6 ("timekeeping: Prepare do_adtimex() for auxiliary clocks")
Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260731-timekeeping-aux-adjtimex-return-v1-1-b7fea4692886@linutronix.de
2026-08-10 22:16:34 +02:00
Dennis Moshegov
d7fc133bf9 timekeeping: Use READ_ONCE/WRITE_ONCE() for xtime_sec to prevent tearing
The timekeeper update path uses a bulk memcpy() to synchronize the
timekeeper structure, which is not guaranteed to be atomic. This allows for
torn reads in ktime_get_real_seconds() on 64-bit systems, where the
sequence counter protection is bypassed for performance.

To prevent reading a torn 64-bit xtime_sec value, enforce atomic-like
access by using WRITE_ONCE() for the critical field before the bulk
memcpy() in timekeeping_update_from_shadow(). Correspondingly, use
READ_ONCE() in ktime_get_real_seconds() to ensure a fresh, consistent load
from memory.

[ tglx: Format changelog and add comment ]

Reported-by: syzbot+72789cd1697965e714ca@syzkaller.appspotmail.com
Signed-off-by: Dennis Moshegov <dennis@xzync.uk>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260724154405.70-1-dennis@xzync.uk
Closes: https://syzkaller.appspot.com/bug?extid=72789cd1697965e714ca
2026-08-10 17:52:19 +02:00
Babanpreet Singh
ecc330e309 timers/migration: Fix bad line kernel-doc warning in struct tmigr_cpu
Running kernel-doc on timer_migration.h reports:

  Warning: kernel/time/timer_migration.h:105 bad line:

The empty line separating the @available paragraph from the @idle
member documentation in the struct tmigr_cpu kernel-doc block lacks
the " *" line prefix that kernel-doc requires on every line inside a
block. The header is not scanned by the build-time kernel-doc checks,
so the warning only shows up when kernel-doc is invoked on the file
directly.

Add the missing prefix. The empty line was introduced when the
@available documentation was expanded by commit 45a13ba52c
("timers/migration: Update stale @online doc to @available").

No functional change.

Signed-off-by: Babanpreet Singh <bbnpreetsingh@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Assisted-by: Claude:claude-sonnet-5
Link: https://patch.msgid.link/20260717035947.7-1-bbnpreetsingh@gmail.com
2026-07-20 16:07:39 +02:00
Randy Dunlap
98680a85df posix-cpu-timers: Avoid kernel-doc warnings
Use the struct keyword when describing a struct. Without that, the
type defaults to function.

Warning: ./include/linux/posix-timers_types.h:40 cannot understand
 function prototype: 'struct posix_cputimer_base'
Warning: ./include/linux/posix-timers_types.h:55 cannot understand
 function prototype: 'struct posix_cputimers'
Warning: ./include/linux/posix-timers_types.h:67 cannot understand
 function prototype: 'struct posix_cputimers_work'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260720031236.3070575-2-rdunlap@infradead.org
2026-07-20 16:05:42 +02:00
Randy Dunlap
151ce4cf88 posix-timers: Clean up kernel-doc warnings
Use the struct keyword when describing a struct.
Add missing kernel-doc for @it_pid_type.

Warning: ./include/linux/posix-timers.h:58 cannot understand
 function prototype: 'struct cpu_timer'
Warning: ./include/linux/posix-timers.h:222 struct member
 'it_pid_type' not described in 'k_itimer'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260720031236.3070575-1-rdunlap@infradead.org
2026-07-20 16:05:42 +02:00
Wake Liu
f44ce7fdbd selftests: timers: Partially revert "Remove local NSEC_PER_SEC and USEC_PER_SEC defines"
This partially reverts commit 80fa614e2f ("selftests: timers: Remove
local NSEC_PER_SEC and USEC_PER_SEC defines").

The original commit removed local definitions of NSEC_PER_SEC and
USEC_PER_SEC in favor of including <include/vdso/time64.h>. However,
NSEC_PER_SEC in vdso/time64.h is defined as 1000000000L, which is
32-bit on 32-bit architectures. This causes integer overflow warnings
in several timer tests when doing arithmetic like NSEC_PER_SEC * 10 on
32-bit systems.

To fix this, restore the local definitions of NSEC_PER_SEC and
USEC_PER_SEC in the test files, but use "LL" suffix consistently
(1000000000LL and 1000000LL) to ensure 64-bit arithmetic and avoid
overflows.

We keep the cleanup from the original commit that renamed plural
definitions (NSECS_PER_SEC/USECS_PER_SEC) to singular ones in
posix_timers.c, but we now define them locally there as well.
This also removes the dependency of the selftests on the internal
kernel header <include/vdso/time64.h>.

Signed-off-by: Wake Liu <wakel@google.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Acked-by: John Stultz <jstultz@google.com>
Link: https://patch.msgid.link/20260610014721.718362-1-wakel@google.com
2026-07-10 09:20:55 +02:00
David Woodhouse
794ddd6e15 ntp: Remove tick_length_base, use tick_length directly
Now that nothing inflates tick_length beyond tick_length_base (the
adjtime path was converted to use time_offset in the previous commit),
the two fields are always equal.

Remove tick_length_base and keep tick_length as the single field.
Remove the per-second reset and the delta update in
ntp_update_frequency() since there is no separate base to track.

No functional change intended.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Assisted-by: Kiro:claude-opus-4.6-1m
Link: https://patch.msgid.link/20260621220051.1030462-8-dwmw2@infradead.org
2026-07-10 09:20:55 +02:00
David Woodhouse
34ce97c33d timekeeping: Settle competing time_offset and time_adjust skew
time_offset (the exponential PLL phase slew) and time_adjust (the
linear adjtime() slew) can be asked to move the clock in opposite
directions. second_overflow() folds only their *net* into the per-tick
skew_delta, so the cancelling overlap would never be drained from
either tracker by the per-tick code — and if they cancel exactly,
skew_delta is zero and neither converges at all.

Arguably we could just let one of them entirely cancel out the other
immediately, but that would be a change in userspace-visible behaviour.

Instead, preserve the existing behaviour by calculating the "conflict"
portion between the opposing skew each second, and transferring that
amount directly from one tracker to the other.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Assisted-by: Kiro:claude-opus-4.8
Link: https://patch.msgid.link/20260621220051.1030462-7-dwmw2@infradead.org
2026-07-10 09:20:55 +02:00
David Woodhouse
289d175949 timekeeping: Drive time_adjust skew via per-tick ntp_error transfer
The legacy adjtime() slew (ADJ_OFFSET_SINGLESHOT) was the last user of
tick_length != tick_length_base: it slewed the clock by inflating
tick_length directly, which delivered the correction imprecisely (e.g.
delivering only 4997.5µs when asked for a 5ms skew).

Deliver it accurately through the same per-tick mechanism that is now
used for time_offset, allowing it to contribute to skew_delta and thus
drive the delivery through ntp_error and mult selection.

To allow for accurate accounting, store the sub-microsecond part of
time_adjust is separately, while keeping time_adjust in microseconds
as that's the external API.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Assisted-by: Kiro:claude-opus-4.8
Link: https://patch.msgid.link/20260621220051.1030462-6-dwmw2@infradead.org
2026-07-10 09:20:54 +02:00
David Woodhouse
d375af5899 timekeeping: Drive time_offset skew via per-tick ntp_error transfer
Currently, the phase offset of time_offset and time_adjust is delivered
by adjusting tick_length in second_overflow(), and immediately draining
time_offset/time_adjust by the amount that the tick_length adjustment is
*estimated* to cause. This is fairly approximate, in part because it is
not always correct to assume that precisely NTP_INTERVAL_FREQ ticks will
occur between one call to second_overflow() and the next. It could also
over and under-run in the final second of delivery.

Instead of inflating tick_length, transfer the intended skew directly
into ntp_error each tick to achieve the desired rate.

In second_overflow(), calculate skew_delta which is the per-tick slew
rate, in the same units as time_offset: (ns << NTP_SCALE_SHIFT) / HZ.

In logarithmic_accumulation(), drain up to 'skew_delta' time units from
time_offset into ntp_error to drive the overall effective rate. The new
ntp_drain_skew() function returns the amount which is actually 'claimed'
by time_offset (and in a future patch, time_adjust). Any overrun which
is delivered by the changed 'mult' (as described below) but not claimed
by ntp_drain_skew() will remain in ntp_error to be corrected away in
subsequent ticks.

Simply transferring the precise amount from time_offset to ntp_error
would be sufficent to make the time *eventually* converge, however the
skew delivered is limited by the choice of { mult, mult+1 } each tick
and thus the convergence would be extremely slow.

In theory we could inflate ntp_err_mult with the magnitude of ntp_error
in the general case — but that would cause overcorrection in a tickless
kernel. Instead, in timekeeping_adjust(), take skew_delta into account
when calculating 'mult', such that the available {mult, mult+1} choices
bracket the overall effective rate *including* the skew, to avoid the
delta just building up in ntp_error.

The effect is that the inflated 'mult' causes ntp_error to grow because
xtime_interval is (e.g.) longer than the true tick_length. But then the
same delta is removed again as it's drained from time_offset.

This gives behaviour equivalent to the old tick_length += delta approach
but with exact per-tick accounting of the time_offset actually imparted
to the clock, and no overrun.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Assisted-by: Kiro:claude-opus-4.8
Link: https://patch.msgid.link/20260621220051.1030462-5-dwmw2@infradead.org
2026-07-10 09:20:54 +02:00
David Woodhouse
869a55e662 timekeeping: Account for clocksource tick quantisation via NTP
cycle_interval is an integer number of counter cycles per NTP interval,
so the real time it represents differs from the nominal
NTP_INTERVAL_LENGTH by up to half a counter period. For coarse
clocksources this is significant: the 3.579545 MHz ACPI PM timer at
HZ=1000 rounds 3579.545 cycles up to 3580, making each tick 1.000127 ms
(+127 PPM).

Commit a386b5af8e ("time: Compensate for rounding on odd-frequency
clocksources") introduced xtime_remainder to compensate for exactly
this, citing the same 127 PPM ACPI PM example. The compensation is
correct and necessary, but it was applied inside the timekeeping
accumulation in timekeeping.c: subtracted in the mult computation in
timekeeping_adjust() and folded into the ntp_error update in
logarithmic_accumulation(). That keeps the base rate correct and leaves
NTP its full symmetric +/-MAXFREQ range rather than +373/-627 PPM, but
the NTP code in ntp.c never sees it: tick_length is computed without the
correction, so ntp.c's notion of how long a tick is disagrees with the
rate timekeeping actually produces.

Make the offset an explicit part of the NTP tick_length instead. Add
ntp_data::cs_tick_adj, a fixed per-second addend that
ntp_update_frequency() includes alongside ntp_tick_adj and time_freq.
tk_setup_internals() computes it from the difference between the real
cycle_interval duration and the nominal interval, stores it in the
timekeeper, and hands it to NTP through a new argument to ntp_clear() --
which already recomputes the frequency and is invoked after every
clocksource (re)configuration. timekeeping_init() now uses TK_UPDATE_ALL
for this; clearing NTP there is otherwise redundant since ntp_init() has
just initialised it.

ntp.c now computes the true tick rate, giving a single source of truth.
Like ntp_tick_adj, cs_tick_adj stays internal to the kernel: userspace
still sees the nominal 1.000000 ms tick via adjtimex and is unaware of
the addends. timekeeping_adjust() and logarithmic_accumulation() use
ntp_tick / xtime_interval directly, and xtime_remainder is removed.

The base-rate arithmetic is unchanged: ntp_tick becomes
xtime_interval << ntp_error_shift, so the mult division yields the same
base mult and the ntp_error accumulation still nets to zero per tick.

Beyond the cleanup of treating all the tick_length contributions
(nominal interval, ntp_tick_adj, cs_tick_adj, time_freq) consistently
as addends in one place, it also prepares for feed-forward discipline:
a future timekeeping_set_reference() will set tick_length to track an
absolute external reference such as a vmclock, and that path needs
ntp.c to own a tick_length that already reflects the clocksource
quantisation, with no hidden correction applied elsewhere.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Assisted-by: Kiro:claude-opus-4.8
Acked-by: John Stultz <jstultz@google.com>
Link: https://patch.msgid.link/20260621220051.1030462-4-dwmw2@infradead.org
2026-07-10 09:20:54 +02:00
David Woodhouse
b7befd6d91 timekeeping: Account for monotonicity adjustment in ntp_error
timekeeping_apply_adjustment() modifies xtime_nsec to ensure monotonicity
when mult changes:

    xtime_nsec -= offset

This ensures that the time reported to userspace does not jump when the
multiplier is adjusted from one tick to the next. However, the ntp_error
accumulator which tracks the difference between intended and actual
clock position was not being updated to reflect this additional
discrepancy.

An earlier attempt at this compensation existed as:

    ntp_error -= (interval - offset) << ntp_error_shift

but was removed in commit c2cda2a5bd ("timekeeping/ntp: Don't align
NTP frequency adjustments to ticks") because it was a major source of
NTP error. That's because (interval - offset) was wrong: the subtraction
of "interval" prematurely accounted for the changed xtime_interval of
the next tick, which would be correctly accounted in the next
accumulation anyway — a double subtraction.

What is actually needed is just the "offset" part: ntp_error must be
told that xtime_nsec moved by "offset" without a corresponding change
in the intended position. For the normal ±1 mult dithering this is
negligible (the adjustments cancel over time), but for larger mult
changes — such as when an external reference clock sets a new
frequency — the one-time uncompensated offset is significant.

Fix by adjusting ntp_error by the correct amount:

    ntp_error += offset << ntp_error_shift

This keeps ntp_error consistent with the actual xtime_nsec position
after the adjustment, and ensures the discrepancy is correctly smoothed
away over time and the clock returns to where it should have been.

Fixes: c2cda2a5bd ("timekeeping/ntp: Don't align NTP frequency adjustments to ticks")
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Assisted-by: Kiro:claude-opus-4.6-1m
Acked-by: John Stultz <jstultz@google.com>
Link: https://patch.msgid.link/20260621220051.1030462-3-dwmw2@infradead.org
2026-07-08 00:17:26 +02:00
David Woodhouse
79b8bd857b MAINTAINERS: Add Miroslav as timekeeping reviewer
If Thomas is going to nudge me on IRC to add Miroslav to Cc on
timekeeping patches, then he might as well actually be listed in the
MAINTAINERS file.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Acked-by: John Stultz <jstultz@google.com>
Link: https://patch.msgid.link/20260621220051.1030462-2-dwmw2@infradead.org
2026-07-08 00:17:26 +02:00
Thomas Weißschuh
79ced850e5 y2038: uapi: Use 64-bit __kernel_old_timespec::tv_nsec on x32
'struct __kernel_old_timespec' represents the 'native' time ABI of the
kernel. On 32-bit systems it uses 32-bit fields and on 64-bit systems
it uses 64-bit fields.

However the x86 x32 ABI uses the 64-bit time ABI natively.  This is
correctly handled for the 'tv_sec' fields, through the typedefs of
'__kernel_old_time_t' -> '__kernel_long_t' -> 'long long'. The same
treatment was missed for 'tv_nsec'.

In practice this might not make much of a difference as the value of
'tv_nsec' will always fit into 32 bits and the missing bits fall
into the padding of the structure.

When introspecting the structure however, a difference can be observed.

Switch to 64-bit tv_nsec on x32.  No other architectures or ABIs are
affected.

While this could be interpreted as violating the POSIX requirement of
'timespec::tv_nsec' being 'long':

  * __kernel_old_timespec is not actually the POSIX timespec type

  * the requirement is gone in newer versions of POSIX

  * this matches glibc

Fixes: 94c467ddb2 ("y2038: add __kernel_old_timespec and __kernel_old_time_t")
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260504-timespec-x32-v2-1-0739c9047fc4@linutronix.de
2026-07-07 23:59:24 +02:00
Thomas Weißschuh
79bd39c58f timekeeping: Move the vDSO update declarations into a private header
All architectures are now fully using the generic vDSO infrastructure.
They don't need these declarations anymore to implement the functions
in architecture-specific code.

Move them to the private header.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260707-timekeeping-header-cleanup-v1-2-e85ad96409a9@linutronix.de
2026-07-07 23:48:08 +02:00
Thomas Weißschuh
6e43591139 timekeeping: Fold vdso_time_update_aux() declarations into the generic ifdeffery
The only caller of vdso_time_update_aux() is already gated behind
CONFIG_POSIX_AUX. The additional check in the header files is not
necessary.

Remove it and then fold the declarations into the existing
CONFIG_GENERIC_GETTIMEOFDAY ifdeffery.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260707-timekeeping-header-cleanup-v1-1-e85ad96409a9@linutronix.de
2026-07-07 23:48:08 +02:00
Thomas Weißschuh (Schneider Electric)
faef65e45a hrtimer: Remove inclusion of hrtimer_bases.h remove from hrtimer.h
hrtimer.h is used all over the kernel. Any change to hrtimer_bases.h
effectively triggers a full rebuild.

As all logical dependencies from hrtimer.h to hrtimer_bases.h have been
removed, the inclusion is now unncessary. Remove it.

Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260702-hrtimer-header-dependencies-v1-8-c50b19bda473@linutronix.de
2026-07-07 23:43:45 +02:00
Thomas Weißschuh (Schneider Electric)
0c31af3d23 x86/speculation: Explicitly include linux/types.h
The usage of 'bool' requires linux/types.h, which is currently only
included through a transitive dependency chain.

Include linux/types.h as that chain is going to go away.

Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260702-hrtimer-header-dependencies-v1-7-c50b19bda473@linutronix.de
2026-07-07 23:43:45 +02:00
Thomas Weißschuh (Schneider Electric)
071993aac7 hrtimer: Explicitly include some necessary headers in hrtimer_rearm.h
Multiple used types and symbols are only visible through transitive
dependency chains.

Include the headers explicitly as those chains are going to go away.

Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260702-hrtimer-header-dependencies-v1-6-c50b19bda473@linutronix.de
2026-07-07 23:43:45 +02:00
Thomas Weißschuh (Schneider Electric)
95cf8bbadd hrtimer: Explicitly include linux/hrtimer_bases.h
This header uses some definitions from linux/hrtimer_bases.h.
Currently this header is included transitively, which will change.

Include the header explicitly.

Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260702-hrtimer-header-dependencies-v1-5-c50b19bda473@linutronix.de
2026-07-07 23:43:44 +02:00
Thomas Weißschuh (Schneider Electric)
73fcec09d1 tick: Explicitly include linux/hrtimer_bases.h
This header uses some definitions from linux/hrtimer_bases.h.
Currently this header is included transitively, which will change.

Include the header explicitly.

Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260702-hrtimer-header-dependencies-v1-4-c50b19bda473@linutronix.de
2026-07-07 23:43:44 +02:00
Thomas Weißschuh (Schneider Electric)
a116c7582d hrtimer: Move hrtimer_update_function() to hrtimer.c
The usage of the hrtimer base forces hrtimer.h to also expose the base
structure definitions.

Move the function to hrtimer.c to avoid this.

Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260702-hrtimer-header-dependencies-v1-3-c50b19bda473@linutronix.de
2026-07-07 23:43:44 +02:00
Thomas Weißschuh (Schneider Electric)
d3dc7fabd4 hrtimer: Move hrtimer_callback_running() to hrtimer_bases.h
The usage of the hrtimer base introduces a dependency on the timer base
structure definitions from the widely-used hrtimer.h.

Move the helper to hrtimer_bases.h to trim this dependency.

Also adapt the two only callers to now include hrtimer_bases.h.

Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260702-hrtimer-header-dependencies-v1-2-c50b19bda473@linutronix.de
2026-07-07 23:43:44 +02:00
Thomas Weißschuh (Schneider Electric)
03b5d4c279 hrtimer: Rename hrtimer_defs.h to hrtimer_bases.h
This header was originally added for #defines and was later extended
with the hrtimer base structures. All the #defines have been removed
in the meantime, so the naming is off now.

Rename the header to fit its contents more.

This will also make the upcoming addition of some functions nicer.

Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260702-hrtimer-header-dependencies-v1-1-c50b19bda473@linutronix.de
2026-07-07 23:43:44 +02:00
Usama Arif
c4415c993f hrtimer: Don't take cpu_base::lock in hrtimer_get_next_event() when hres_active
hrtimer_get_next_event() runs on every tick-stop decision via
get_next_timer_interrupt() -> cmp_next_hrtimer_event().  When high
resolution timers are active it must return KTIME_MAX -- the caller
documents and depends on this.

The function takes cpu_base->lock, checks hres_active, and returns
KTIME_MAX.

Taking the lock is not required because cpu_base->hres_active is only
written by the local CPU in hrtimer_switch_to_hres() from hard interrupt
context and in hrtimers_cpu_starting() during bring-up.

All callers of hrtimer_get_next_event() reach it from the tick-stop /
cpuidle paths with interrupts disabled on that CPU. No writer can therefore
race with the read, so an unlocked hres_active check is stable and the lock
can be skipped in this case.

On a 176-thread AMD EPYC 9D64 running a production workload, bucketing
callers of native_queued_spin_lock_slowpath(), the slowpath had 199 samples
in total, of which 54 are attributed to hrtimer_get_next_event(), i.e. this
accounts for ~27% of slowpath hits on this specific workload.

Move the hres_active check before the lock guard region to address this.

[ tglx: Massaged change log and comments ]

Signed-off-by: Usama Arif <usama.arif@linux.dev>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260707153800.542394-1-usama.arif@linux.dev
2026-07-07 23:26:58 +02:00
Yu Peng
1d28a67d49 timer_list: Annotate print_cpu() diagnostic reads
print_cpu() prints hrtimer_cpu_base and tick_sched state without
synchronizing with concurrent updates. The output is diagnostic only, so
use data_race(READ_ONCE()) for these scalar reads to document the
intentional races and avoid KCSAN reports.

Reported-by: syzbot+8f0e958900a14d08a51d@syzkaller.appspotmail.com
Signed-off-by: Yu Peng <pengyu@kylinos.cn>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260707125813.2182532-1-pengyu@kylinos.cn
Closes: https://syzkaller.appspot.com/bug?extid=8f0e958900a14d08a51d
2026-07-07 23:26:58 +02:00
Malaya Kumar Rout
06aba58e58 time/namespace: Validate nanosecond field in proc_timens_set_offset()
The function validates tv_sec to be within [-KTIME_SEC_MAX, KTIME_SEC_MAX]
but never validates that tv_nsec is within the valid range of
[0, NSEC_PER_SEC-1] before using it in timespec64_add().

timespec64_add() expects both timespec64 structures to have normalized
values with tv_nsec in the range [0, 999999999]. If off->val.tv_nsec
contains invalid values (negative or >= NSEC_PER_SEC), it could lead to
incorrect calculations or unexpected behavior.

Add validation to ensure tv_nsec is within the valid range before
performing the addition.

Fixes: 04a8682a71 ("fs/proc: Introduce /proc/pid/timens_offsets")
Signed-off-by: Malaya Kumar Rout <malayarout91@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260704093429.89350-1-malayarout91@gmail.com
2026-07-07 23:26:58 +02:00
Malaya Kumar Rout
eddfded419 timers/migration: Fix memory leak in tmigr_setup_groups() error path
When the WARN_ON_ONCE(i >= tmigr_hierarchy_levels) assertion triggers,
the function returns -EINVAL without freeing the 'stack' memory allocated
via kzalloc_objs() at the beginning of the function.

Add kfree(stack) before returning to prevent the memory leak.

Fixes: 6c181b5667 ("timers/migration: Convert "while" loops to use "for"")
Signed-off-by: Malaya Kumar Rout <malayarout91@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260704085533.87098-1-malayarout91@gmail.com
2026-07-07 23:26:58 +02:00
Yuho Choi
f2eee7e31c timekeeping: Unwind aux clock sysfs children on failure
tk_aux_sysfs_init() creates one child kobject per auxiliary clock. If a
later child or sysfs group creation fails, the current error path only
puts the parent kobjects and leaves earlier children and groups behind.

Store the child kobjects during init and remove the successfully created
groups and kobjects on failure.

Fixes: 7b5ab04f03 ("timekeeping: Fix resource leak in tk_aux_sysfs_init() error paths")
Signed-off-by: Yuho Choi <dbgh9129@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260703165337.168445-1-dbgh9129@gmail.com
2026-07-07 23:26:58 +02:00