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Filename Latest commit message Latest commit date
Sebastian Andrzej Siewior a3e7a3d472 tick/common: Align tick period with the HZ tick.
[ Upstream commit e9523a0d81899361214d118ad60ef76f0e92f71d ]

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>
2023-05-17 11:35:40 +02:00
arch arm64: kgdb: Set PSTATE.SS to 1 to re-enable single-step 2023-05-17 11:35:39 +02:00
block blk-iocost: fix divide by 0 error in calc_lcoefs() 2023-03-11 16:43:54 +01:00
certs
crypto asymmetric_keys: log on fatal failures in PE/pkcs7 2023-04-20 12:07:36 +02:00
Documentation media: uapi: add MEDIA_BUS_FMT_METADATA_FIXED media bus format. 2023-05-17 11:35:36 +02:00
drivers regulator: stm32-pwr: fix of_iomap leak 2023-05-17 11:35:38 +02:00
fs erofs: fix potential overflow calculating xattr_isize 2023-05-17 11:35:35 +02:00
include media: uapi: add MEDIA_BUS_FMT_METADATA_FIXED media bus format. 2023-05-17 11:35:36 +02:00
init
ipc
kernel tick/common: Align tick period with the HZ tick. 2023-05-17 11:35:40 +02:00
lib debugobject: Prevent init race with static objects 2023-05-17 11:35:39 +02:00
LICENSES
mm mm/swap: fix swap_info_struct race between swapoff and get_swap_pages() 2023-04-20 12:07:35 +02:00
net bluetooth: Perform careful capability checks in hci_sock_ioctl() 2023-05-17 11:35:31 +02:00
samples
scripts ASN.1: Fix check for strdup() success 2023-04-26 11:24:06 +02:00
security selinux: ensure av_permissions.h is built when needed 2023-05-17 11:35:34 +02:00
sound ASoC: Intel: bytcr_rt5640: Add quirk for the Acer Iconia One 7 B1-750 2023-05-17 11:35:31 +02:00
tools perf sched: Cast PTHREAD_STACK_MIN to int as it may turn into sysconf(__SC_THREAD_STACK_MIN_VALUE) 2023-05-17 11:35:32 +02:00
usr
virt KVM: Destroy target device if coalesced MMIO unregistration fails 2023-03-11 16:44:01 +01:00
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Makefile Linux 5.4.242 2023-04-26 11:24:06 +02:00
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.