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Sebastian Andrzej Siewior a55050c798 tick/common: Align tick period with the HZ tick. 
[ Upstream commit e9523a0d81 ]

With HIGHRES enabled tick_sched_timer() is programmed every jiffy to
expire the timer_list timers. This timer is programmed accurate in
respect to CLOCK_MONOTONIC so that 0 seconds and nanoseconds is the
first tick and the next one is 1000/CONFIG_HZ ms later. For HZ=250 it is
every 4 ms and so based on the current time the next tick can be
computed.

This accuracy broke since the commit mentioned below because the jiffy
based clocksource is initialized with higher accuracy in
read_persistent_wall_and_boot_offset(). This higher accuracy is
inherited during the setup in tick_setup_device(). The timer still fires
every 4ms with HZ=250 but timer is no longer aligned with
CLOCK_MONOTONIC with 0 as it origin but has an offset in the us/ns part
of the timestamp. The offset differs with every boot and makes it
impossible for user land to align with the tick.

Align the tick period with CLOCK_MONOTONIC ensuring that it is always a
multiple of 1000/CONFIG_HZ ms.

Fixes: 857baa87b6 ("sched/clock: Enable sched clock early")
Reported-by: Gusenleitner Klaus <gus@keba.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/20230406095735.0_14edn3@linutronix.de
Link: https://lore.kernel.org/r/20230418122639.ikgfvu3f@linutronix.de
Signed-off-by: Sasha Levin <sashal@kernel.org>
2023-05-11 23:00:25 +09:00
arch arm64: kgdb: Set PSTATE.SS to 1 to re-enable single-step 2023-05-11 23:00:24 +09:00
block blk-crypto: make blk_crypto_evict_key() more robust 2023-05-11 23:00:16 +09:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:22:01 +02:00
crypto crypto: api - Demote BUG_ON() in crypto_unregister_alg() to a WARN_ON() 2023-05-11 23:00:17 +09:00
Documentation riscv: Move early dtb mapping into the fixmap region 2023-05-01 08:23:24 +09:00
drivers drm/i915: Make intel_get_crtc_new_encoder() less oopsy 2023-05-11 23:00:25 +09:00
fs erofs: fix potential overflow calculating xattr_isize 2023-05-11 23:00:20 +09:00
include platform: Provide a remove callback that returns no value 2023-05-11 23:00:24 +09:00
init kbuild: Add CONFIG_PAHOLE_VERSION 2023-02-25 12:06:45 +01:00
io_uring io_uring: avoid null-ptr-deref in io_arm_poll_handler 2023-03-22 13:31:37 +01:00
ipc ipc/sem: Fix dangling sem_array access in semtimedop race 2022-12-08 11:28:45 +01:00
kernel tick/common: Align tick period with the HZ tick. 2023-05-11 23:00:25 +09:00
lib debugobject: Prevent init race with static objects 2023-05-11 23:00:25 +09:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm writeback, cgroup: fix null-ptr-deref write in bdi_split_work_to_wbs 2023-05-11 23:00:18 +09:00
net bluetooth: Perform careful capability checks in hci_sock_ioctl() 2023-05-01 08:23:23 +09:00
samples samples: vfio-mdev: Fix missing pci_disable_device() in mdpy_fb_probe() 2022-12-31 13:14:31 +01:00
scripts ASN.1: Fix check for strdup() success 2023-04-26 13:51:56 +02:00
security selinux: ensure av_permissions.h is built when needed 2023-05-11 23:00:19 +09:00
sound sound/oss/dmasound: fix build when drivers are mixed =y/=m 2023-05-11 23:00:19 +09:00
tools tools/x86/kcpuid: Fix avx512bw and avx512lvl fields in Fn00000007 2023-05-11 23:00:20 +09:00
usr usr/include/Makefile: add linux/nfc.h to the compile-test coverage 2022-02-01 17:27:15 +01:00
virt KVM: fix memoryleak in kvm_init() 2023-03-17 08:49:04 +01:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS counter: Internalize sysfs interface code 2023-04-20 12:13:55 +02:00
Makefile Linux 5.15.110 2023-05-01 08:23:24 +09:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.