timekeeping: Always check for negative motion

clocksource_delta() has two variants. One with a check for negative motion,
which is only selected by x86. This is a historic leftover as this function

timekeeping: Always check for negative motion

clocksource_delta() has two variants. One with a check for negative motion,
which is only selected by x86. This is a historic leftover as this function
was previously used in the time getter hot paths.

Since 135225a363ae timekeeping_cycles_to_ns() has unconditional protection
against this as a by-product of the protection against 64bit math overflow.

clocksource_delta() is only used in the clocksource watchdog and in
timekeeping_advance(). The extra conditional there is not hurting anyone.

Remove the config option and unconditionally prevent negative motion of the
readout.

Signed-off-by: Thomas Gleixner <[email protected]>
Acked-by: John Stultz <[email protected]>
Link: https://lore.kernel.org/all/[email protected]

show more ...

clocksource: Make the int help prompt unit readable in ncurses

When doing

make menuconfig

and searching for the CLOCKSOURCE_WATCHDOG_MAX_SKEW_US config item, the
help says:

│ Symbol: CLOCKSOU

clocksource: Make the int help prompt unit readable in ncurses

When doing

make menuconfig

and searching for the CLOCKSOURCE_WATCHDOG_MAX_SKEW_US config item, the
help says:

│ Symbol: CLOCKSOURCE_WATCHDOG_MAX_SKEW_US [=125]
│ Type : integer
│ Range : [50 1000]
│ Defined at kernel/time/Kconfig:204
│ Prompt: Clocksource watchdog maximum allowable skew (in s)
^^^

│ Depends on: GENERIC_CLOCKEVENTS [=y] && CLOCKSOURCE_WATCHDOG [=y]

because on some terminals, it cannot display the 'μ' char, unicode
number 0x3bc.

So simply write it out so that there's no trouble.

Signed-off-by: Borislav Petkov (AMD) <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Acked-by: Paul E. McKenney <[email protected]>
Acked-by: Randy Dunlap <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

show more ...

sched/idle: Conditionally handle tick broadcast in default_idle_call()

The x86 architecture has an idle routine for AMD CPUs which are affected
by erratum 400. On the affected CPUs the local APIC ti

sched/idle: Conditionally handle tick broadcast in default_idle_call()

The x86 architecture has an idle routine for AMD CPUs which are affected
by erratum 400. On the affected CPUs the local APIC timer stops in the
C1E halt state.

It therefore requires tick broadcasting. The invocation of
tick_broadcast_enter()/exit() from this function violates the RCU
constraints because it can end up in lockdep or tracing, which
rightfully triggers a warning.

tick_broadcast_enter()/exit() must be invoked before ct_cpuidle_enter()
and after ct_cpuidle_exit() in default_idle_call().

Add a static branch conditional invocation of tick_broadcast_enter()/exit()
into this function to allow X86 to replace the AMD specific idle code. It's
guarded by a config switch which will be selected by x86. Otherwise it's
a NOOP.

Reported-by: Borislav Petkov <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

show more ...

clocksource: Loosen clocksource watchdog constraints

Currently, MAX_SKEW_USEC is set to 100 microseconds, which has worked
reasonably well. However, NTP is willing to tolerate 500 microseconds
of s

clocksource: Loosen clocksource watchdog constraints

Currently, MAX_SKEW_USEC is set to 100 microseconds, which has worked
reasonably well. However, NTP is willing to tolerate 500 microseconds
of skew per second, and a clocksource that is good enough for NTP should
be good enough for the clocksource watchdog. The watchdog's skew is
controlled by MAX_SKEW_USEC and the CLOCKSOURCE_WATCHDOG_MAX_SKEW_US
Kconfig option. However, these values are doubled before being associated
with a clocksource's ->uncertainty_margin, and the ->uncertainty_margin
values of the pair of clocksource's being compared are summed before
checking against the skew.

Therefore, set both MAX_SKEW_USEC and the default for the
CLOCKSOURCE_WATCHDOG_MAX_SKEW_US Kconfig option to 125 microseconds of
skew per second, resulting in 500 microseconds of skew per second in
the clocksource watchdog's skew comparison.

Suggested-by Rik van Riel <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>

show more ...

context_tracking: Take idle eqs entrypoints over RCU

The RCU dynticks counter is going to be merged into the context tracking
subsystem. Start with moving the idle extended quiescent states
entrypoi

context_tracking: Take idle eqs entrypoints over RCU

The RCU dynticks counter is going to be merged into the context tracking
subsystem. Start with moving the idle extended quiescent states
entrypoints to context tracking. For now those are dumb redirections to
existing RCU calls.

[ paulmck: Apply kernel test robot feedback. ]

Signed-off-by: Frederic Weisbecker <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Neeraj Upadhyay <[email protected]>
Cc: Uladzislau Rezki <[email protected]>
Cc: Joel Fernandes <[email protected]>
Cc: Boqun Feng <[email protected]>
Cc: Nicolas Saenz Julienne <[email protected]>
Cc: Marcelo Tosatti <[email protected]>
Cc: Xiongfeng Wang <[email protected]>
Cc: Yu Liao <[email protected]>
Cc: Phil Auld <[email protected]>
Cc: Paul Gortmaker<[email protected]>
Cc: Alex Belits <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
Reviewed-by: Nicolas Saenz Julienne <[email protected]>
Tested-by: Nicolas Saenz Julienne <[email protected]>

show more ...

context_tracking: Split user tracking Kconfig

Context tracking is going to be used not only to track user transitions
but also idle/IRQs/NMIs. The user tracking part will then become a
separate feat

context_tracking: Split user tracking Kconfig

Context tracking is going to be used not only to track user transitions
but also idle/IRQs/NMIs. The user tracking part will then become a
separate feature. Prepare Kconfig for that.

[ frederic: Apply Max Filippov feedback. ]

Signed-off-by: Frederic Weisbecker <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Neeraj Upadhyay <[email protected]>
Cc: Uladzislau Rezki <[email protected]>
Cc: Joel Fernandes <[email protected]>
Cc: Boqun Feng <[email protected]>
Cc: Nicolas Saenz Julienne <[email protected]>
Cc: Marcelo Tosatti <[email protected]>
Cc: Xiongfeng Wang <[email protected]>
Cc: Yu Liao <[email protected]>
Cc: Phil Auld <[email protected]>
Cc: Paul Gortmaker<[email protected]>
Cc: Alex Belits <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
Reviewed-by: Nicolas Saenz Julienne <[email protected]>
Tested-by: Nicolas Saenz Julienne <[email protected]>

show more ...

clocksource: Add a Kconfig option for WATCHDOG_MAX_SKEW

A watchdog maximum skew of 100us may still be too small for
some systems or archs. It may also be too small when some kernel
debug config opti

clocksource: Add a Kconfig option for WATCHDOG_MAX_SKEW

A watchdog maximum skew of 100us may still be too small for
some systems or archs. It may also be too small when some kernel
debug config options are enabled. So add a new Kconfig option
CLOCKSOURCE_WATCHDOG_MAX_SKEW_US to allow kernel builders to have more
control on the threshold for marking clocksource as unstable.

Signed-off-by: Waiman Long <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>

show more ...

time: Improve performance of time64_to_tm()

The current implementation of time64_to_tm() contains unnecessary loops,
branches and look-up tables. The new one uses an arithmetic-based algorithm
appea

time: Improve performance of time64_to_tm()

The current implementation of time64_to_tm() contains unnecessary loops,
branches and look-up tables. The new one uses an arithmetic-based algorithm
appeared in [1] and is approximately 3x faster (YMMV).

The drawback is that the new code isn't intuitive and contains many 'magic
numbers' (not unusual for this type of algorithm). However, [1] justifies
all those numbers and, given this function's history, the code is unlikely
to need much maintenance, if any at all.

Add a KUnit test for it which checks every day in a 160,000 years interval
centered at 1970-01-01 against the expected result.

[1] Neri, Schneider, "Euclidean Affine Functions and Applications to
Calendar Algorithms". https://arxiv.org/abs/2102.06959

Signed-off-by: Cassio Neri <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

show more ...

tick/nohz: Update nohz_full Kconfig help

CONFIG_NO_HZ_FULL behaves just like CONFIG_NO_HZ_IDLE by default.
Reassure distros about it.

Signed-off-by: Frederic Weisbecker <[email protected]>
Signed

tick/nohz: Update nohz_full Kconfig help

CONFIG_NO_HZ_FULL behaves just like CONFIG_NO_HZ_IDLE by default.
Reassure distros about it.

Signed-off-by: Frederic Weisbecker <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Acked-by: Peter Zijlstra <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

show more ...

timekeeping: Fix spelling mistake in Kconfig "fullfill" -> "fulfill"

There is a spelling mistake in the Kconfig help text. Fix it.

Signed-off-by: Colin Ian King <[email protected]>
Signed-of

timekeeping: Fix spelling mistake in Kconfig "fullfill" -> "fulfill"

There is a spelling mistake in the Kconfig help text. Fix it.

Signed-off-by: Colin Ian King <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Acked-by: Linus Walleij <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

show more ...

timekeeping: default GENERIC_CLOCKEVENTS to enabled

Almost all machines use GENERIC_CLOCKEVENTS, so it feels wrong to
require each one to select that symbol manually.

Instead, enable it whenever CO

timekeeping: default GENERIC_CLOCKEVENTS to enabled

Almost all machines use GENERIC_CLOCKEVENTS, so it feels wrong to
require each one to select that symbol manually.

Instead, enable it whenever CONFIG_LEGACY_TIMER_TICK is disabled as
a simplification. It should be possible to select both
GENERIC_CLOCKEVENTS and LEGACY_TIMER_TICK from an architecture now
and decide at runtime between the two.

For the clockevents arch-support.txt file, this means that additional
architectures are marked as TODO when they have at least one machine
that still uses LEGACY_TIMER_TICK, rather than being marked 'ok' when
at least one machine has been converted. This means that both m68k and
arm (for riscpc) revert to TODO.

At this point, we could just always enable CONFIG_GENERIC_CLOCKEVENTS
rather than leaving it off when not needed. I built an m68k
defconfig kernel (using gcc-10.1.0) and found that this would add
around 5.5KB in kernel image size:

text data bss dec hex filename
3861936 1092236 196656 5150828 4e986c obj-m68k/vmlinux-no-clockevent
3866201 1093832 196184 5156217 4ead79 obj-m68k/vmlinux-clockevent

On Arm (MACH_RPC), that difference appears to be twice as large,
around 11KB on top of an 6MB vmlinux.

Reviewed-by: Geert Uytterhoeven <[email protected]>
Acked-by: Geert Uytterhoeven <[email protected]>
Tested-by: Geert Uytterhoeven <[email protected]>
Reviewed-by: Linus Walleij <[email protected]>
Signed-off-by: Arnd Bergmann <[email protected]>

show more ...

timekeeping: add CONFIG_LEGACY_TIMER_TICK

All platforms that currently do not use generic clockevents roughly call
the same set of functions in their timer interrupts: xtime_update(),
update_process

timekeeping: add CONFIG_LEGACY_TIMER_TICK

All platforms that currently do not use generic clockevents roughly call
the same set of functions in their timer interrupts: xtime_update(),
update_process_times() and profile_tick(), sometimes in a different
sequence.

Add a helper function that performs all three of them, to make the
callers more uniform and simplify the interface.

Reviewed-by: Geert Uytterhoeven <[email protected]>
Reviewed-by: Linus Walleij <[email protected]>
Signed-off-by: Arnd Bergmann <[email protected]>

show more ...

timekeeping: remove arch_gettimeoffset

With Arm EBSA110 gone, nothing uses it any more, so the corresponding
code and the Kconfig option can be removed.

Acked-by: Thomas Gleixner <[email protected]

timekeeping: remove arch_gettimeoffset

With Arm EBSA110 gone, nothing uses it any more, so the corresponding
code and the Kconfig option can be removed.

Acked-by: Thomas Gleixner <[email protected]>
Reviewed-by: Linus Walleij <[email protected]>
Signed-off-by: Arnd Bergmann <[email protected]>

show more ...

posix-cpu-timers: Provide mechanisms to defer timer handling to task_work

Running posix CPU timers in hard interrupt context has a few downsides:

- For PREEMPT_RT it cannot work as the expiry code

posix-cpu-timers: Provide mechanisms to defer timer handling to task_work

Running posix CPU timers in hard interrupt context has a few downsides:

- For PREEMPT_RT it cannot work as the expiry code needs to take
sighand lock, which is a 'sleeping spinlock' in RT. The original RT
approach of offloading the posix CPU timer handling into a high
priority thread was clumsy and provided no real benefit in general.

- For fine grained accounting it's just wrong to run this in context of
the timer interrupt because that way a process specific CPU time is
accounted to the timer interrupt.

- Long running timer interrupts caused by a large amount of expiring
timers which can be created and armed by unpriviledged user space.

There is no hard requirement to expire them in interrupt context.

If the signal is targeted at the task itself then it won't be delivered
before the task returns to user space anyway. If the signal is targeted at
a supervisor process then it might be slightly delayed, but posix CPU
timers are inaccurate anyway due to the fact that they are tied to the
tick.

Provide infrastructure to schedule task work which allows splitting the
posix CPU timer code into a quick check in interrupt context and a thread
context expiry and signal delivery function. This has to be enabled by
architectures as it requires that the architecture specific KVM
implementation handles pending task work before exiting to guest mode.

Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Reviewed-by: Oleg Nesterov <[email protected]>
Acked-by: Peter Zijlstra (Intel) <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

show more ...

treewide: Add SPDX license identifier - Makefile/Kconfig

Add SPDX license identifiers to all Make/Kconfig files which:

- Have no license information of any form

These files fall under the project

treewide: Add SPDX license identifier - Makefile/Kconfig

Add SPDX license identifiers to all Make/Kconfig files which:

- Have no license information of any form

These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:

GPL-2.0-only

Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

show more ...

time: Move CONTEXT_TRACKING to kernel/time/Kconfig

Both CONTEXT_TRACKING and CONTEXT_TRACKING_FORCE are currently defined
in kernel/rcu/kconfig, which might have made sense at some point, but
no lon

time: Move CONTEXT_TRACKING to kernel/time/Kconfig

Both CONTEXT_TRACKING and CONTEXT_TRACKING_FORCE are currently defined
in kernel/rcu/kconfig, which might have made sense at some point, but
no longer does given that RCU refers to neither of these Kconfig options.

Therefore move them to kernel/time/Kconfig, where the rest of the
NO_HZ_FULL Kconfig options live.

Signed-off-by: Paul E. McKenney <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

show more ...

clocksource: Provide clocksource_arch_init()

Architectures have extra archdata in the clocksource, e.g. for VDSO
support. There are no sanity checks or general initializations for this
available. Ad

clocksource: Provide clocksource_arch_init()

Architectures have extra archdata in the clocksource, e.g. for VDSO
support. There are no sanity checks or general initializations for this
available. Add support for that.

Signed-off-by: Thomas Gleixner <[email protected]>
Acked-by: Andy Lutomirski <[email protected]>
Acked-by: John Stultz <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Matt Rickard <[email protected]>
Cc: Stephen Boyd <[email protected]>
Cc: Florian Weimer <[email protected]>
Cc: "K. Y. Srinivasan" <[email protected]>
Cc: Vitaly Kuznetsov <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: Paolo Bonzini <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Juergen Gross <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

show more ...

sched/isolation: Eliminate NO_HZ_FULL_ALL

Commit 6f1982fedd59 ("sched/isolation: Handle the nohz_full= parameter")
broke CONFIG_NO_HZ_FULL_ALL=y kernels. This breakage is due to the code
under CONF

sched/isolation: Eliminate NO_HZ_FULL_ALL

Commit 6f1982fedd59 ("sched/isolation: Handle the nohz_full= parameter")
broke CONFIG_NO_HZ_FULL_ALL=y kernels. This breakage is due to the code
under CONFIG_NO_HZ_FULL_ALL failing to invoke the shiny new housekeeping
functions. This means that rcutorture scenario TREE04 now emits RCU CPU
stall warnings due to the RCU grace-period kthreads not being awakened
at a time of their choosing, or perhaps even not at all:

[ 27.731422] rcu_bh kthread starved for 21001 jiffies! g18446744073709551369 c18446744073709551368 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x402 ->cpu=3
[ 27.731423] rcu_bh I14936 9 2 0x80080000
[ 27.731435] Call Trace:
[ 27.731440] __schedule+0x31a/0x6d0
[ 27.731442] schedule+0x31/0x80
[ 27.731446] schedule_timeout+0x15a/0x320
[ 27.731453] ? call_timer_fn+0x130/0x130
[ 27.731457] rcu_gp_kthread+0x66c/0xea0
[ 27.731458] ? rcu_gp_kthread+0x66c/0xea0

Because no one has complained about CONFIG_NO_HZ_FULL_ALL=y being broken,
I hypothesize that no one is in fact using it, other than rcutorture.
This commit therefore eliminates CONFIG_NO_HZ_FULL_ALL and updates
rcutorture's config files to instead use the nohz_full= kernel parameter
to put the desired CPUs into nohz_full mode.

Fixes: 6f1982fedd59 ("sched/isolation: Handle the nohz_full= parameter")

Reported-by: kernel test robot <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Chris Metcalf <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Luiz Capitulino <[email protected]>
Cc: Mike Galbraith <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Wanpeng Li <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: John Stultz <[email protected]>
Cc: Jonathan Corbet <[email protected]>

show more ...

sched/isolation: Make CONFIG_NO_HZ_FULL select CONFIG_CPU_ISOLATION

CONFIG_NO_HZ_FULL doesn't make sense without CONFIG_CPU_ISOLATION. In
fact enabling the first without the second is a regression a

sched/isolation: Make CONFIG_NO_HZ_FULL select CONFIG_CPU_ISOLATION

CONFIG_NO_HZ_FULL doesn't make sense without CONFIG_CPU_ISOLATION. In
fact enabling the first without the second is a regression as nohz_full=
boot parameter gets silently ignored.

Besides this unnatural combination hangs RCU gp kthread when running
rcutorture for reasons that are not yet fully understood:

rcu_preempt kthread starved for 9974 jiffies! g4294967208
+c4294967207 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x402 ->cpu=0
rcu_preempt I 7464 8 2 0x80000000
Call Trace:
__schedule+0x493/0x620
schedule+0x24/0x40
schedule_timeout+0x330/0x3b0
? preempt_count_sub+0xea/0x140
? collect_expired_timers+0xb0/0xb0
rcu_gp_kthread+0x6bf/0xef0

This commit therefore makes NO_HZ_FULL select CPU_ISOLATION, which
prevents all these bad behaviours.

Reported-by: kernel test robot <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
Signed-off-by: Frederic Weisbecker <[email protected]>
Cc: Chris Metcalf <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: John Stultz <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Luiz Capitulino <[email protected]>
Cc: Mike Galbraith <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Wanpeng Li <[email protected]>
Fixes: 5c4991e24c69 ("sched/isolation: Split out new CONFIG_CPU_ISOLATION=y config from CONFIG_NO_HZ_FULL")
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

show more ...

timekeeping: Remove CONFIG_GENERIC_TIME_VSYSCALL_OLD

As of d4d1fc61eb38f (ia64: Update fsyscall gettime to use modern
vsyscall_update)the last user of CONFIG_GENERIC_TIME_VSYSCALL_OLD
have been upda

timekeeping: Remove CONFIG_GENERIC_TIME_VSYSCALL_OLD

As of d4d1fc61eb38f (ia64: Update fsyscall gettime to use modern
vsyscall_update)the last user of CONFIG_GENERIC_TIME_VSYSCALL_OLD
have been updated, the legacy support for old-style vsyscall
implementations can be removed from the timekeeping code.

(Thanks again to Tony Luck for helping remove the last user!)

[jstultz: Commit message rework]

Signed-off-by: Miroslav Lichvar <[email protected]>
Signed-off-by: John Stultz <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: Prarit Bhargava <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Richard Cochran <[email protected]>
Cc: Stephen Boyd <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

show more ...

kernel/time/Kconfig: Fix typo in comment

Fix typo in Kconfig comment text.

Signed-off-by: Randy Dunlap <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: John Stultz <j

kernel/time/Kconfig: Fix typo in comment

Fix typo in Kconfig comment text.

Signed-off-by: Randy Dunlap <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: John Stultz <[email protected]>
Cc: Stephen Boyd <[email protected]>
Cc: Jiri Kosina <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

show more ...

rcu: Remove nohz_full full-system-idle state machine

The NO_HZ_FULL_SYSIDLE full-system-idle capability was added in 2013
by commit 0edd1b1784cb ("nohz_full: Add full-system-idle state machine"),
bu

rcu: Remove nohz_full full-system-idle state machine

The NO_HZ_FULL_SYSIDLE full-system-idle capability was added in 2013
by commit 0edd1b1784cb ("nohz_full: Add full-system-idle state machine"),
but has not been used. This commit therefore removes it.

If it turns out to be needed later, this commit can always be reverted.

Signed-off-by: Paul E. McKenney <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Ingo Molnar <[email protected]>
Acked-by: Linus Torvalds <[email protected]>

show more ...

rcu: Drop RCU_USER_QS in favor of NO_HZ_FULL

The RCU_USER_QS Kconfig parameter is now just a synonym for NO_HZ_FULL,
so this commit eliminates RCU_USER_QS, replacing all uses with NO_HZ_FULL.

Repor

rcu: Drop RCU_USER_QS in favor of NO_HZ_FULL

The RCU_USER_QS Kconfig parameter is now just a synonym for NO_HZ_FULL,
so this commit eliminates RCU_USER_QS, replacing all uses with NO_HZ_FULL.

Reported-by: Frederic Weisbecker <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
Acked-by: Frederic Weisbecker <[email protected]>

show more ...

clockevents: Remove CONFIG_GENERIC_CLOCKEVENTS_BUILD

This option was for simpler migration to the clock events code.
Most architectures have been converted and the option has been
disfunctional as a

clockevents: Remove CONFIG_GENERIC_CLOCKEVENTS_BUILD

This option was for simpler migration to the clock events code.
Most architectures have been converted and the option has been
disfunctional as a standalone option for quite some time. Remove
it.

Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: Rafael J. Wysocki <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

show more ...

clocksource: Move cycle_last validation to core code

The only user of the cycle_last validation is the x86 TSC. In order to
provide NMI safe accessor functions for clock monotonic and
monotonic_raw

clocksource: Move cycle_last validation to core code

The only user of the cycle_last validation is the x86 TSC. In order to
provide NMI safe accessor functions for clock monotonic and
monotonic_raw we need to do that in the core.

We can't do the TSC specific

if (now < cycle_last)
now = cycle_last;

for the other wrapping around clocksources, but TSC has
CLOCKSOURCE_MASK(64) which actually does not mask out anything so if
now is less than cycle_last the subtraction will give a negative
result. So we can check for that in clocksource_delta() and return 0
for that case.

Implement and enable it for x86

Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: John Stultz <[email protected]>

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