linux-stable.git/kernel/time, branch v4.14.22

hrtimer: Reset hrtimer cpu base proper on CPU hotplug

2018-01-31T13:03:49+00:00

commit d5421ea43d30701e03cadc56a38854c36a8b4433 upstream.

The hrtimer interrupt code contains a hang detection and mitigation
mechanism, which prevents that a long delayed hrtimer interrupt causes a
continous retriggering of interrupts which prevent the system from making
progress. If a hang is detected then the timer hardware is programmed with
a certain delay into the future and a flag is set in the hrtimer cpu base
which prevents newly enqueued timers from reprogramming the timer hardware
prior to the chosen delay. The subsequent hrtimer interrupt after the delay
clears the flag and resumes normal operation.

If such a hang happens in the last hrtimer interrupt before a CPU is
unplugged then the hang_detected flag is set and stays that way when the
CPU is plugged in again. At that point the timer hardware is not armed and
it cannot be armed because the hang_detected flag is still active, so
nothing clears that flag. As a consequence the CPU does not receive hrtimer
interrupts and no timers expire on that CPU which results in RCU stalls and
other malfunctions.

Clear the flag along with some other less critical members of the hrtimer
cpu base to ensure starting from a clean state when a CPU is plugged in.

Thanks to Paul, Sebastian and Anna-Maria for their help to get down to the
root cause of that hard to reproduce heisenbug. Once understood it's
trivial and certainly justifies a brown paperbag.

Fixes: 41d2e4949377 ("hrtimer: Tune hrtimer_interrupt hang logic")
Reported-by: Paul E. McKenney 
Signed-off-by: Thomas Gleixner 
Cc: Peter Zijlstra 
Cc: Sebastian Sewior 
Cc: Anna-Maria Gleixner 
Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1801261447590.2067@nanos
Signed-off-by: Greg Kroah-Hartman

timers: Unconditionally check deferrable base

2018-01-23T18:58:12+00:00

commit ed4bbf7910b28ce3c691aef28d245585eaabda06 upstream.

When the timer base is checked for expired timers then the deferrable base
must be checked as well. This was missed when making the deferrable base
independent of base::nohz_active.

Fixes: ced6d5c11d3e ("timers: Use deferrable base independent of base::nohz_active")
Signed-off-by: Thomas Gleixner 
Cc: Anna-Maria Gleixner 
Cc: Frederic Weisbecker 
Cc: Peter Zijlstra 
Cc: Sebastian Siewior 
Cc: Paul McKenney 
Cc: rt@linutronix.de
Signed-off-by: Greg Kroah-Hartman

nohz: Prevent a timer interrupt storm in tick_nohz_stop_sched_tick()

2018-01-02T19:31:16+00:00

commit 5d62c183f9e9df1deeea0906d099a94e8a43047a upstream.

The conditions in irq_exit() to invoke tick_nohz_irq_exit() which
subsequently invokes tick_nohz_stop_sched_tick() are:

  if ((idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu))

If need_resched() is not set, but a timer softirq is pending then this is
an indication that the softirq code punted and delegated the execution to
softirqd. need_resched() is not true because the current interrupted task
takes precedence over softirqd.

Invoking tick_nohz_irq_exit() in this case can cause an endless loop of
timer interrupts because the timer wheel contains an expired timer, but
softirqs are not yet executed. So it returns an immediate expiry request,
which causes the timer to fire immediately again. Lather, rinse and
repeat....

Prevent that by adding a check for a pending timer soft interrupt to the
conditions in tick_nohz_stop_sched_tick() which avoid calling
get_next_timer_interrupt(). That keeps the tick sched timer on the tick and
prevents a repetitive programming of an already expired timer.

Reported-by: Sebastian Siewior 
Signed-off-by: Thomas Gleixner 
Acked-by: Frederic Weisbecker 
Cc: Peter Zijlstra 
Cc: Paul McKenney 
Cc: Anna-Maria Gleixner 
Cc: Sebastian Siewior 
Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1712272156050.2431@nanos
Signed-off-by: Greg Kroah-Hartman

timers: Reinitialize per cpu bases on hotplug

2018-01-02T19:31:15+00:00

commit 26456f87aca7157c057de65c9414b37f1ab881d1 upstream.

The timer wheel bases are not (re)initialized on CPU hotplug. That leaves
them with a potentially stale clk and next_expiry valuem, which can cause
trouble then the CPU is plugged.

Add a prepare callback which forwards the clock, sets next_expiry to far in
the future and reset the control flags to a known state.

Set base->must_forward_clk so the first timer which is queued will try to
forward the clock to current jiffies.

Fixes: 500462a9de65 ("timers: Switch to a non-cascading wheel")
Reported-by: Paul E. McKenney 
Signed-off-by: Thomas Gleixner 
Cc: Peter Zijlstra 
Cc: Frederic Weisbecker 
Cc: Sebastian Siewior 
Cc: Anna-Maria Gleixner 
Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1712272152200.2431@nanos
Signed-off-by: Greg Kroah-Hartman

timers: Invoke timer_start_debug() where it makes sense

2018-01-02T19:31:15+00:00

commit fd45bb77ad682be728d1002431d77b8c73342836 upstream.

The timer start debug function is called before the proper timer base is
set. As a consequence the trace data contains the stale CPU and flags
values.

Call the debug function after setting the new base and flags.

Fixes: 500462a9de65 ("timers: Switch to a non-cascading wheel")
Signed-off-by: Thomas Gleixner 
Cc: Peter Zijlstra 
Cc: Frederic Weisbecker 
Cc: Sebastian Siewior 
Cc: rt@linutronix.de
Cc: Paul McKenney 
Cc: Anna-Maria Gleixner 
Link: https://lkml.kernel.org/r/20171222145337.792907137@linutronix.de
Signed-off-by: Greg Kroah-Hartman

timers: Use deferrable base independent of base::nohz_active

2018-01-02T19:31:15+00:00

commit ced6d5c11d3e7b342f1a80f908e6756ebd4b8ddd upstream.

During boot and before base::nohz_active is set in the timer bases, deferrable
timers are enqueued into the standard timer base. This works correctly as
long as base::nohz_active is false.

Once it base::nohz_active is set and a timer which was enqueued before that
is accessed the lock selector code choses the lock of the deferred
base. This causes unlocked access to the standard base and in case the
timer is removed it does not clear the pending flag in the standard base
bitmap which causes get_next_timer_interrupt() to return bogus values.

To prevent that, the deferrable timers must be enqueued in the deferrable
base, even when base::nohz_active is not set. Those deferrable timers also
need to be expired unconditional.

Fixes: 500462a9de65 ("timers: Switch to a non-cascading wheel")
Signed-off-by: Anna-Maria Gleixner 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Frederic Weisbecker 
Cc: Peter Zijlstra 
Cc: Sebastian Siewior 
Cc: rt@linutronix.de
Cc: Paul McKenney 
Link: https://lkml.kernel.org/r/20171222145337.633328378@linutronix.de
Signed-off-by: Greg Kroah-Hartman

cpufreq: schedutil: Use idle_calls counter of the remote CPU

2018-01-02T19:31:05+00:00

commit 466a2b42d67644447a1765276259a3ea5531ddff upstream.

Since the recent remote cpufreq callback work, its possible that a cpufreq
update is triggered from a remote CPU. For single policies however, the current
code uses the local CPU when trying to determine if the remote sg_cpu entered
idle or is busy. This is incorrect. To remedy this, compare with the nohz tick
idle_calls counter of the remote CPU.

Fixes: 674e75411fc2 (sched: cpufreq: Allow remote cpufreq callbacks)
Acked-by: Viresh Kumar 
Acked-by: Peter Zijlstra (Intel) 
Signed-off-by: Joel Fernandes 
Signed-off-by: Rafael J. Wysocki 
Signed-off-by: Greg Kroah-Hartman

posix-timer: Properly check sigevent->sigev_notify

2017-12-20T09:10:21+00:00

commit cef31d9af908243421258f1df35a4a644604efbe upstream.

timer_create() specifies via sigevent->sigev_notify the signal delivery for
the new timer. The valid modes are SIGEV_NONE, SIGEV_SIGNAL, SIGEV_THREAD
and (SIGEV_SIGNAL | SIGEV_THREAD_ID).

The sanity check in good_sigevent() is only checking the valid combination
for the SIGEV_THREAD_ID bit, i.e. SIGEV_SIGNAL, but if SIGEV_THREAD_ID is
not set it accepts any random value.

This has no real effects on the posix timer and signal delivery code, but
it affects show_timer() which handles the output of /proc/$PID/timers. That
function uses a string array to pretty print sigev_notify. The access to
that array has no bound checks, so random sigev_notify cause access beyond
the array bounds.

Add proper checks for the valid notify modes and remove the SIGEV_THREAD_ID
masking from various code pathes as SIGEV_NONE can never be set in
combination with SIGEV_THREAD_ID.

Reported-by: Eric Biggers 
Reported-by: Dmitry Vyukov 
Reported-by: Alexey Dobriyan 
Signed-off-by: Thomas Gleixner 
Cc: John Stultz 
Signed-off-by: Greg Kroah-Hartman

License cleanup: add SPDX GPL-2.0 license identifier to files with no license

2017-11-02T10:10:55+00:00

Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.

By default all files without license information are under the default
license of the kernel, which is GPL version 2.

Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier.  The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.

How this work was done:

Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
 - file had no licensing information it it.
 - file was a */uapi/* one with no licensing information in it,
 - file was a */uapi/* one with existing licensing information,

Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.

The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne.  Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.

The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed.  Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.

Criteria used to select files for SPDX license identifier tagging was:
 - Files considered eligible had to be source code files.
 - Make and config files were included as candidates if they contained >5
   lines of source
 - File already had some variant of a license header in it (even if <5
   lines).

All documentation files were explicitly excluded.

The following heuristics were used to determine which SPDX license
identifiers to apply.

 - when both scanners couldn't find any license traces, file was
   considered to have no license information in it, and the top level
   COPYING file license applied.

   For non */uapi/* files that summary was:

   SPDX license identifier                            # files
   ---------------------------------------------------|-------
   GPL-2.0                                              11139

   and resulted in the first patch in this series.

   If that file was a */uapi/* path one, it was "GPL-2.0 WITH
   Linux-syscall-note" otherwise it was "GPL-2.0".  Results of that was:

   SPDX license identifier                            # files
   ---------------------------------------------------|-------
   GPL-2.0 WITH Linux-syscall-note                        930

   and resulted in the second patch in this series.

 - if a file had some form of licensing information in it, and was one
   of the */uapi/* ones, it was denoted with the Linux-syscall-note if
   any GPL family license was found in the file or had no licensing in
   it (per prior point).  Results summary:

   SPDX license identifier                            # files
   ---------------------------------------------------|------
   GPL-2.0 WITH Linux-syscall-note                       270
   GPL-2.0+ WITH Linux-syscall-note                      169
   ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause)    21
   ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)    17
   LGPL-2.1+ WITH Linux-syscall-note                      15
   GPL-1.0+ WITH Linux-syscall-note                       14
   ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause)    5
   LGPL-2.0+ WITH Linux-syscall-note                       4
   LGPL-2.1 WITH Linux-syscall-note                        3
   ((GPL-2.0 WITH Linux-syscall-note) OR MIT)              3
   ((GPL-2.0 WITH Linux-syscall-note) AND MIT)             1

   and that resulted in the third patch in this series.

 - when the two scanners agreed on the detected license(s), that became
   the concluded license(s).

 - when there was disagreement between the two scanners (one detected a
   license but the other didn't, or they both detected different
   licenses) a manual inspection of the file occurred.

 - In most cases a manual inspection of the information in the file
   resulted in a clear resolution of the license that should apply (and
   which scanner probably needed to revisit its heuristics).

 - When it was not immediately clear, the license identifier was
   confirmed with lawyers working with the Linux Foundation.

 - If there was any question as to the appropriate license identifier,
   the file was flagged for further research and to be revisited later
   in time.

In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.

Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights.  The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.

Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.

In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.

Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
 - a full scancode scan run, collecting the matched texts, detected
   license ids and scores
 - reviewing anything where there was a license detected (about 500+
   files) to ensure that the applied SPDX license was correct
 - reviewing anything where there was no detection but the patch license
   was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
   SPDX license was correct

This produced a worksheet with 20 files needing minor correction.  This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.

These .csv files were then reviewed by Greg.  Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected.  This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.)  Finally Greg ran the script using the .csv files to
generate the patches.

Reviewed-by: Kate Stewart 
Reviewed-by: Philippe Ombredanne 
Reviewed-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

drivers/pps: aesthetic tweaks to PPS-related content

2017-09-09T01:26:51+00:00

Collection of aesthetic adjustments to various PPS-related files,
directories and Documentation, some quite minor just for the sake of
consistency, including:

 * Updated example of pps device tree node (courtesy Rodolfo G.)
 * "PPS-API" -> "PPS API"
 * "pps_source_info_s" -> "pps_source_info"
 * "ktimer driver" -> "pps-ktimer driver"
 * "ppstest /dev/pps0" -> "ppstest /dev/pps1" to match example
 * Add missing PPS-related entries to MAINTAINERS file
 * Other trivialities

Link: http://lkml.kernel.org/r/alpine.LFD.2.20.1708261048220.8106@localhost.localdomain
Signed-off-by: Robert P. J. Day 
Acked-by: Rodolfo Giometti 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds