linux-toradex.git/kernel/time/clockevents.c, branch v5.14-rc4

clockevents: Use list_move() instead of list_del()/list_add()

2021-06-22T15:16:46+00:00

Simplify the code.

Reported-by: Hulk Robot 
Signed-off-by: Baokun Li 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20210609070242.1322450-1-libaokun1@huawei.com

clockevents: Add missing parameter documentation

2021-06-22T14:33:16+00:00

Add the missing documentation for the @cpu parameter of
tick_cleanup_dead_cpu().

Signed-off-by: Baokun Li 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20210608024305.2750999-1-libaokun1@huawei.com

clockevents: Use DEVICE_ATTR_[RO|WO] macros

2021-05-31T15:04:42+00:00

Use the DEVICE_ATTR_[RO|WO] helpers instead of plain DEVICE_ATTR, which
makes the code a bit shorter and easier to read.

Signed-off-by: YueHaibing 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20210523065825.19684-1-yuehaibing@huawei.com

tick: Remove outgoing CPU from broadcast masks

2019-03-23T17:26:43+00:00

Valentin reported that unplugging a CPU occasionally results in a warning
in the tick broadcast code which is triggered when an offline CPU is in the
broadcast mask.

This happens because the outgoing CPU is not removing itself from the
broadcast masks, especially not from the broadcast_force_mask. The removal
happens on the control CPU after the outgoing CPU is dead. It's a long
standing issue, but the warning is harmless.

Rework the hotplug mechanism so that the outgoing CPU removes itself from
the broadcast masks after disabling interrupts and removing itself from the
online mask.

Reported-by: Valentin Schneider 
Signed-off-by: Thomas Gleixner 
Tested-by: Valentin Schneider 
Cc: Frederic Weisbecker 
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1903211540180.1784@nanos.tec.linutronix.de

hrtimers/tick/clockevents: Remove sloppy license references

2018-11-23T10:51:21+00:00

"For licencing details see kernel-base/COPYING" and similar license
references have no value over the SPDX identifier. Remove them.

Signed-off-by: Thomas Gleixner 
Acked-by: Kees Cook 
Acked-by: Ingo Molnar 
Acked-by: John Stultz 
Acked-by: Corey Minyard 
Cc: Peter Zijlstra 
Cc: Kate Stewart 
Cc: Philippe Ombredanne 
Cc: Peter Anvin 
Cc: Russell King 
Cc: Richard Cochran 
Cc: "Paul E. McKenney" 
Cc: Nicolas Pitre 
Cc: David Riley 
Cc: Colin Cross 
Cc: Mark Brown 
Link: https://lkml.kernel.org/r/20181031182252.963632760@linutronix.de

time: Add SPDX license identifiers

2018-11-23T10:51:20+00:00

Update the time(r) core files files with the correct SPDX license
identifier based on the license text in the file itself. The SPDX
identifier is a legally binding shorthand, which can be used instead of the
full boiler plate text.

This work is based on a script and data from Philippe Ombredanne, Kate
Stewart and myself. The data has been created with two independent license
scanners and manual inspection.

The following files do not contain any direct license information and have
been omitted from the big initial SPDX changes:

  timeconst.bc: The .bc files were not touched
  time.c, timer.c, timekeeping.c: Licence was deduced from EXPORT_SYMBOL_GPL

As those files do not contain direct license references they fall under the
project license, i.e. GPL V2 only.

Signed-off-by: Thomas Gleixner 
Acked-by: Kees Cook 
Acked-by: Ingo Molnar 
Acked-by: John Stultz 
Acked-by: Corey Minyard 
Cc: Peter Zijlstra 
Cc: Kate Stewart 
Cc: Philippe Ombredanne 
Cc: Russell King 
Cc: Richard Cochran 
Cc: Nicolas Pitre 
Cc: David Riley 
Cc: Colin Cross 
Cc: Mark Brown 
Cc: H. Peter Anvin 
Cc: Paul E. McKenney 
Link: https://lkml.kernel.org/r/20181031182252.879109557@linutronix.de

time: Remove useless filenames in top level comments

2018-11-23T10:51:20+00:00

Remove the pointless filenames in the top level comments. They have no
value at all and just occupy space. While at it tidy up some of the
comments and remove a stale one.

Signed-off-by: Thomas Gleixner 
Acked-by: Nicolas Pitre 
Acked-by: Kees Cook 
Acked-by: Ingo Molnar 
Acked-by: John Stultz 
Acked-by: Corey Minyard 
Cc: Peter Zijlstra 
Cc: Kate Stewart 
Cc: Philippe Ombredanne 
Cc: Peter Anvin 
Cc: Russell King 
Cc: Richard Cochran 
Cc: "Paul E. McKenney" 
Cc: David Riley 
Cc: Colin Cross 
Cc: Mark Brown 
Link: https://lkml.kernel.org/r/20181031182252.794898238@linutronix.de

clockevents: Remove unnecessary unlikely()

2018-11-05T13:22:54+00:00

WARN_ON() and WARN_ON_ONCE() already contains an unlikely(), so it's not
necessary to use unlikely.

Signed-off-by: Yangtao Li 
Signed-off-by: Thomas Gleixner 
Link: https://lkml.kernel.org/r/20181104023104.2572-1-tiny.windzz@gmail.com

clockevents: Warn if cpu_all_mask is used as cpumask

2018-08-02T12:55:53+00:00

Using cpu_all_mask in clockevents cpumask may result in issues while
comparing multiple clockevent devices to choose the preferred one.

On one of the platforms with 2 system (i.e. non per-CPU) timers with
different ratings, having cpu_all_mask for one of the device resulted in a
boot hang due to a endless loop in clockevents_notify_released() as both
were clocksources were selected as preferred.

In order to prevent such issues in the future, warn if any clockevent
driver sets cpu_all_mask as it's cpumask and just override it to use
cpu_possible_mask. All the existing occurrences of cpu_all_mask are already
replaced with cpu_possible_mask.

Signed-off-by: Sudeep Holla 
Signed-off-by: Thomas Gleixner 
Cc: linux-arm-kernel@lists.infradead.org
Link: https://lkml.kernel.org/r/1531308264-24220-3-git-send-email-sudeep.holla@arm.com

clockevents: Retry programming min delta up to 10 times

2017-10-19T14:29:15+00:00

When CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST=n, the call path
hrtimer_reprogram -> clockevents_program_event ->
clockevents_program_min_delta will not retry if the clock event driver
returns -ETIME.

If the driver could not satisfy the program_min_delta for any reason, the
lack of a retry means the CPU may not receive a tick interrupt, potentially
until the counter does a full period. This leads to rcu_sched timeout
messages as the stalled CPU is detected by other CPUs, and other issues if
the CPU is holding locks or other resources at the point at which it
stalls.

There have been a couple of observed mechanisms through which a clock event
driver could not satisfy the requested min_delta and return -ETIME.

With the MIPS GIC driver, the shared execution resource within MT cores
means inconventient latency due to execution of instructions from other
hardware threads in the core, within gic_next_event, can result in an event
being set in the past.

Additionally under virtualisation it is possible to get unexpected latency
during a clockevent device's set_next_event() callback which can make it
return -ETIME even for a delta based on min_delta_ns.

It isn't appropriate to use MIN_ADJUST in the virtualisation case as
occasional hypervisor induced high latency will cause min_delta_ns to
quickly increase to the maximum.

Instead, borrow the retry pattern from the MIN_ADJUST case, but without
making adjustments. Retry up to 10 times, each time increasing the
attempted delta by min_delta, before giving up.

[ Matt: Reworked the loop and made retry increase the delta. ]

Signed-off-by: James Hogan 
Signed-off-by: Matt Redfearn 
Signed-off-by: Thomas Gleixner 
Cc: linux-mips@linux-mips.org
Cc: Daniel Lezcano 
Cc: "Martin Schwidefsky" 
Cc: James Hogan 
Link: https://lkml.kernel.org/r/1508422643-6075-1-git-send-email-matt.redfearn@mips.com