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Merge tag 'timers-core-2021-06-29' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer updates from Thomas Gleixner:
"Time and clocksource/clockevent related updates:
Core changes:
- Infrastructure to support per CPU "broadcast" devices for per CPU
clockevent devices which stop in deep idle states. This allows us
to utilize the more efficient architected timer on certain ARM SoCs
for normal operation instead of permanentely using the slow to
access SoC specific clockevent device.
- Print the name of the broadcast/wakeup device in /proc/timer_list
- Make the clocksource watchdog more robust against delays between
reading the current active clocksource and the watchdog
clocksource. Such delays can be caused by NMIs, SMIs and vCPU
preemption.
Handle this by reading the watchdog clocksource twice, i.e. before
and after reading the current active clocksource. In case that the
two watchdog reads shows an excessive time delta, the read sequence
is repeated up to 3 times.
- Improve the debug output and add a test module for the watchdog
mechanism.
- Reimplementation of the venerable time64_to_tm() function with a
faster and significantly smaller version. Straight from the source,
i.e. the author of the related research paper contributed this!
Driver changes:
- No new drivers, not even new device tree bindings!
- Fixes, improvements and cleanups and all over the place"
* tag 'timers-core-2021-06-29' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (30 commits)
time/kunit: Add missing MODULE_LICENSE()
time: Improve performance of time64_to_tm()
clockevents: Use list_move() instead of list_del()/list_add()
clocksource: Print deviation in nanoseconds when a clocksource becomes unstable
clocksource: Provide kernel module to test clocksource watchdog
clocksource: Reduce clocksource-skew threshold
clocksource: Limit number of CPUs checked for clock synchronization
clocksource: Check per-CPU clock synchronization when marked unstable
clocksource: Retry clock read if long delays detected
clockevents: Add missing parameter documentation
clocksource/drivers/timer-ti-dm: Drop unnecessary restore
clocksource/arm_arch_timer: Improve Allwinner A64 timer workaround
clocksource/drivers/arm_global_timer: Remove duplicated argument in arm_global_timer
clocksource/drivers/arm_global_timer: Make symbol 'gt_clk_rate_change_nb' static
arm: zynq: don't disable CONFIG_ARM_GLOBAL_TIMER due to CONFIG_CPU_FREQ anymore
clocksource/drivers/arm_global_timer: Implement rate compensation whenever source clock changes
clocksource/drivers/ingenic: Rename unreasonable array names
clocksource/drivers/timer-ti-dm: Save and restore timer TIOCP_CFG
clocksource/drivers/mediatek: Ack and disable interrupts on suspend
clocksource/drivers/samsung_pwm: Constify source IO memory
...
5.1 KiB
SPDX-License-Identifier: GPL-2.0-only
Timer subsystem related configuration options
Options selectable by arch Kconfig
Watchdog function for clocksources to detect instabilities
config CLOCKSOURCE_WATCHDOG bool
Architecture has extra clocksource data
config ARCH_CLOCKSOURCE_DATA bool
Architecture has extra clocksource init called from registration
config ARCH_CLOCKSOURCE_INIT bool
Clocksources require validation of the clocksource against the last
cycle update - x86/TSC misfeature
config CLOCKSOURCE_VALIDATE_LAST_CYCLE bool
Timekeeping vsyscall support
config GENERIC_TIME_VSYSCALL bool
The generic clock events infrastructure
config GENERIC_CLOCKEVENTS def_bool !LEGACY_TIMER_TICK
Architecture can handle broadcast in a driver-agnostic way
config ARCH_HAS_TICK_BROADCAST bool
Clockevents broadcasting infrastructure
config GENERIC_CLOCKEVENTS_BROADCAST bool depends on GENERIC_CLOCKEVENTS
Automatically adjust the min. reprogramming time for
clock event device
config GENERIC_CLOCKEVENTS_MIN_ADJUST bool
Generic update of CMOS clock
config GENERIC_CMOS_UPDATE bool
Select to handle posix CPU timers from task_work
and not from the timer interrupt context
config HAVE_POSIX_CPU_TIMERS_TASK_WORK bool
config POSIX_CPU_TIMERS_TASK_WORK bool default y if POSIX_TIMERS && HAVE_POSIX_CPU_TIMERS_TASK_WORK
config LEGACY_TIMER_TICK bool help The legacy timer tick helper is used by platforms that lack support for the generic clockevent framework. New platforms should use generic clockevents instead.
config TIME_KUNIT_TEST tristate "KUnit test for kernel/time functions" if !KUNIT_ALL_TESTS depends on KUNIT default KUNIT_ALL_TESTS help Enable this option to test RTC library functions.
If unsure, say N.
if GENERIC_CLOCKEVENTS menu "Timers subsystem"
Core internal switch. Selected by NO_HZ_COMMON / HIGH_RES_TIMERS. This is
only related to the tick functionality. Oneshot clockevent devices
are supported independent of this.
config TICK_ONESHOT bool
config NO_HZ_COMMON bool select TICK_ONESHOT
choice prompt "Timer tick handling" default NO_HZ_IDLE if NO_HZ
config HZ_PERIODIC bool "Periodic timer ticks (constant rate, no dynticks)" help This option keeps the tick running periodically at a constant rate, even when the CPU doesn't need it.
config NO_HZ_IDLE bool "Idle dynticks system (tickless idle)" select NO_HZ_COMMON help This option enables a tickless idle system: timer interrupts will only trigger on an as-needed basis when the system is idle. This is usually interesting for energy saving.
Most of the time you want to say Y here.
config NO_HZ_FULL bool "Full dynticks system (tickless)" # NO_HZ_COMMON dependency # We need at least one periodic CPU for timekeeping depends on SMP depends on HAVE_CONTEXT_TRACKING # VIRT_CPU_ACCOUNTING_GEN dependency depends on HAVE_VIRT_CPU_ACCOUNTING_GEN select NO_HZ_COMMON select RCU_NOCB_CPU select VIRT_CPU_ACCOUNTING_GEN select IRQ_WORK select CPU_ISOLATION help Adaptively try to shutdown the tick whenever possible, even when the CPU is running tasks. Typically this requires running a single task on the CPU. Chances for running tickless are maximized when the task mostly runs in userspace and has few kernel activity.
You need to fill up the nohz_full boot parameter with the
desired range of dynticks CPUs to use it. This is implemented at
the expense of some overhead in user <-> kernel transitions:
syscalls, exceptions and interrupts.
By default, without passing the nohz_full parameter, this behaves just
like NO_HZ_IDLE.
If you're a distro say Y.
endchoice
config CONTEXT_TRACKING bool
config CONTEXT_TRACKING_FORCE bool "Force context tracking" depends on CONTEXT_TRACKING default y if !NO_HZ_FULL help The major pre-requirement for full dynticks to work is to support the context tracking subsystem. But there are also other dependencies to provide in order to make the full dynticks working.
This option stands for testing when an arch implements the
context tracking backend but doesn't yet fulfill all the
requirements to make the full dynticks feature working.
Without the full dynticks, there is no way to test the support
for context tracking and the subsystems that rely on it: RCU
userspace extended quiescent state and tickless cputime
accounting. This option copes with the absence of the full
dynticks subsystem by forcing the context tracking on all
CPUs in the system.
Say Y only if you're working on the development of an
architecture backend for the context tracking.
Say N otherwise, this option brings an overhead that you
don't want in production.
config NO_HZ bool "Old Idle dynticks config" help This is the old config entry that enables dynticks idle. We keep it around for a little while to enforce backward compatibility with older config files.
config HIGH_RES_TIMERS bool "High Resolution Timer Support" select TICK_ONESHOT help This option enables high resolution timer support. If your hardware is not capable then this option only increases the size of the kernel image.
endmenu endif