The call to __iter_div_u64_rem() in vdso_time_update_aux() is a wrapper
around subtraction. It cannot be used to divide large numbers, as that
introduces long, computationally expensive delays. A regular u64 division
is also not possible in the timekeeper update path as it can be too slow.
Instead of splitting the ktime_t offset into into second and subsecond
components during the timekeeper update fast-path, do it together with the
adjustment of tk->offs_aux in the slow-path. Equivalent to the handling of
offs_boot and monotonic_to_boot.
Reuse the storage of monotonic_to_boot for the new field, as it is not used
by auxiliary timekeepers.
Fixes: 380b84e168 ("vdso/vsyscall: Update auxiliary clock data in the datapage")
Reported-by: Miroslav Lichvar <mlichvar@redhat.com>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250825-vdso-auxclock-division-v1-1-a1d32a16a313@linutronix.de
Closes: https://lore.kernel.org/lkml/aKwsNNWsHJg8IKzj@localhost/
With the introduction of clone3 in commit 7f192e3cd3 ("fork: add
clone3") the effective bit width of clone_flags on all architectures was
increased from 32-bit to 64-bit, with a new type of u64 for the flags.
However, for most consumers of clone_flags the interface was not
changed from the previous type of unsigned long.
While this works fine as long as none of the new 64-bit flag bits
(CLONE_CLEAR_SIGHAND and CLONE_INTO_CGROUP) are evaluated, this is still
undesirable in terms of the principle of least surprise.
Thus, this commit fixes all relevant interfaces of callees to
sys_clone3/copy_process (excluding the architecture-specific
copy_thread) to consistently pass clone_flags as u64, so that
no truncation to 32-bit integers occurs on 32-bit architectures.
Signed-off-by: Simon Schuster <schuster.simon@siemens-energy.com>
Link: https://lore.kernel.org/20250901-nios2-implement-clone3-v2-2-53fcf5577d57@siemens-energy.com
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Pull bitmap updates from Yury Norov:
- find_random_bit() series (Yury)
- GENMASK() consolidation (Vincent)
- random cleanups (Shaopeng, Ben, Yury)
* tag 'bitmap-for-6.17' of https://github.com/norov/linux:
bitfield: Ensure the return values of helper functions are checked
test_bits: add tests for __GENMASK() and __GENMASK_ULL()
bits: unify the non-asm GENMASK*()
bits: split the definition of the asm and non-asm GENMASK*()
cpumask: Remove unnecessary cpumask_nth_andnot()
watchdog: fix opencoded cpumask_next_wrap() in watchdog_next_cpu()
clocksource: Improve randomness in clocksource_verify_choose_cpus()
cpumask: introduce cpumask_random()
bitmap: generalize node_random()
The current algorithm of picking a random CPU works OK for dense online
cpumask, but if cpumask is non-dense, the distribution of picked CPUs
is skewed.
For example, on 8-CPU board with CPUs 4-7 offlined, the probability of
selecting CPU 0 is 5/8. Accordingly, cpus 1, 2 and 3 are chosen with
probability 1/8 each. The proper algorithm should pick each online CPU
with probability 1/4.
Switch it to cpumask_random(), which has better statistical
characteristics.
CC: Andrew Morton <akpm@linux-foundation.org>
Acked-by: John Stultz <jstultz@google.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: "Yury Norov [NVIDIA]" <yury.norov@gmail.com>
Pull timekeeping and VDSO updates from Thomas Gleixner:
- Introduce support for auxiliary timekeepers
PTP clocks can be disconnected from the universal CLOCK_TAI reality
for various reasons including regularatory requirements for
functional safety redundancy.
The kernel so far only supports a single notion of time, which means
that all clocks are correlated in frequency and only differ by offset
to each other.
Access to non-correlated PTP clocks has been available so far only
through the file descriptor based "POSIX clock IDs", which are
subject to locking and have to go all the way out to the hardware.
The access is not only horribly slow, as it has to go all the way out
to the NIC/PTP hardware, but that also prevents the kernel to read
the time of such clocks e.g. from the network stack, where it is
required for TSN networking both on the transmit and receive side
unless the hardware provides offloading.
The auxiliary clocks provide a mechanism to support arbitrary clocks
which are not correlated to the system clock. This is not restricted
to the PTP use case on purpose as there is no kernel side association
of these clocks to a particular PTP device because that's a pure user
space configuration decision. Having them independent allows to
utilize them for other purposes and also enables them to be tested
without hardware dependencies.
To avoid pointless overhead these clocks have to be enabled
individualy via a new sysfs interface to reduce the overhead to a
single compare in the hotpath if they are enabled at the Kconfig
level at all.
These clocks utilize the existing timekeeping/NTP infrastructures,
which has been made possible over the recent releases by incrementaly
converting these infrastructures over from a single static instance
to a multi-instance pointer based implementation without any
performance regression reported.
The auxiliary clocks provide the same "emulation" of a "correct"
clock as the existing CLOCK_* variants do with an independent
instance of data and provide the same steering mechanism through the
existing sys_clock_adjtime() interface, which has been confirmed to
work by the chronyd(8) maintainer.
That allows to provide lockless kernel internal and VDSO support so
that applications and kernel internal functionalities can access
these clocks without restrictions and at the same performance as the
existing system clocks.
- Avoid double notifications in the adjtimex() syscall. Not a big
issue, but a trivial to avoid latency source.
* tag 'timers-ptp-2025-07-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (39 commits)
vdso/gettimeofday: Add support for auxiliary clocks
vdso/vsyscall: Update auxiliary clock data in the datapage
vdso: Introduce aux_clock_resolution_ns()
vdso/gettimeofday: Introduce vdso_get_timestamp()
vdso/gettimeofday: Introduce vdso_set_timespec()
vdso/gettimeofday: Introduce vdso_clockid_valid()
vdso/gettimeofday: Return bool from clock_gettime() helpers
vdso/gettimeofday: Return bool from clock_getres() helpers
vdso/helpers: Add helpers for seqlocks of single vdso_clock
vdso/vsyscall: Split up __arch_update_vsyscall() into __arch_update_vdso_clock()
vdso/vsyscall: Introduce a helper to fill clock configurations
timekeeping: Remove the temporary CLOCK_AUX workaround
timekeeping: Provide ktime_get_clock_ts64()
timekeeping: Provide interface to control auxiliary clocks
timekeeping: Provide update for auxiliary timekeepers
timekeeping: Provide adjtimex() for auxiliary clocks
timekeeping: Prepare do_adtimex() for auxiliary clocks
timekeeping: Make do_adjtimex() reusable
timekeeping: Add auxiliary clock support to __timekeeping_inject_offset()
timekeeping: Make timekeeping_inject_offset() reusable
...
Pull timer core updates from Thomas Gleixner:
- Simplify the logic in the timer migration code
- Simplify the clocksource code by utilizing the more modern
cpumask+*() interfaces
* tag 'timers-core-2025-07-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
clocksource: Use cpumask_next_wrap() in clocksource_watchdog()
clocksource: Use cpumask_any_but() in clocksource_verify_choose_cpus()
timers/migration: Clean up the loop in tmigr_quick_check()
Pull timer cleanups from Thomas Gleixner:
"A treewide cleanup of struct cycle_counter const annotations.
The initial idea of making them const was correct as they were
seperate instances. When they got embedded into larger data
structures, which are even modified by the callback this got moot. The
only reason why this went unnoticed is that the required
container_of() casts the const attribute forcefully away.
Stop pretending that it is const"
* tag 'timers-cleanups-2025-07-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
time/timecounter: Fix the lie that struct cyclecounter is const
Most drivers only populate the fields cycles and cs_id of system_counterval
in their get_time_fn() callback for get_device_system_crosststamp(), unless
they explicitly provide nanosecond values.
When the use_nsecs field was added to struct system_counterval, most
drivers did not care. Clock sources other than CSID_GENERIC could then get
converted in convert_base_to_cs() based on an uninitialized use_nsecs field,
which usually results in -EINVAL during the following range check.
Pass in a fully zero initialized system_counterval_t to cure that.
Fixes: 6b2e299775 ("timekeeping: Provide infrastructure for converting to/from a base clock")
Signed-off-by: Markus Blöchl <markus@blochl.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20250720-timekeeping_uninit_crossts-v2-1-f513c885b7c2@blochl.de
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 <tglx@linutronix.de>
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 <tglx@linutronix.de>
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250701132628.357686408@linutronix.de
In both the read callback for struct cyclecounter, and in struct
timecounter, struct cyclecounter is declared as a const pointer.
Unfortunatly, a number of users of this pointer treat it as a non-const
pointer as it is burried in a larger structure that is heavily modified by
the callback function when accessed. This lie had been hidden by the fact
that container_of() "casts away" a const attribute of a pointer without any
compiler warning happening at all.
Fix this all up by removing the const attribute in the needed places so
that everyone can see that the structure really isn't const, but can,
and is, modified by the users of it.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/2025070124-backyard-hurt-783a@gregkh
