linux-toradex.git/include/linux/timekeeper_internal.h, branch v5.12-rc6

timekeeping/vsyscall: Prevent math overflow in BOOTTIME update

2019-08-23T00:12:11+00:00

The VDSO update for CLOCK_BOOTTIME has a overflow issue as it shifts the
nanoseconds based boot time offset left by the clocksource shift. That
overflows once the boot time offset becomes large enough. As a consequence
CLOCK_BOOTTIME in the VDSO becomes a random number causing applications to
misbehave.

Fix it by storing a timespec64 representation of the offset when boot time
is adjusted and add that to the MONOTONIC base time value in the vdso data
page. Using the timespec64 representation avoids a 64bit division in the
update code.

Fixes: 44f57d788e7d ("timekeeping: Provide a generic update_vsyscall() implementation")
Reported-by: Chris Clayton 
Signed-off-by: Thomas Gleixner 
Tested-by: Chris Clayton 
Tested-by: Vincenzo Frascino 
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1908221257580.1983@nanos.tec.linutronix.de

Revert: Unify CLOCK_MONOTONIC and CLOCK_BOOTTIME

2018-04-26T12:53:32+00:00

Revert commits

92af4dcb4e1c ("tracing: Unify the "boot" and "mono" tracing clocks")
127bfa5f4342 ("hrtimer: Unify MONOTONIC and BOOTTIME clock behavior")
7250a4047aa6 ("posix-timers: Unify MONOTONIC and BOOTTIME clock behavior")
d6c7270e913d ("timekeeping: Remove boot time specific code")
f2d6fdbfd238 ("Input: Evdev - unify MONOTONIC and BOOTTIME clock behavior")
d6ed449afdb3 ("timekeeping: Make the MONOTONIC clock behave like the BOOTTIME clock")
72199320d49d ("timekeeping: Add the new CLOCK_MONOTONIC_ACTIVE clock")

As stated in the pull request for the unification of CLOCK_MONOTONIC and
CLOCK_BOOTTIME, it was clear that we might have to revert the change.

As reported by several folks systemd and other applications rely on the
documented behaviour of CLOCK_MONOTONIC on Linux and break with the above
changes. After resume daemons time out and other timeout related issues are
observed. Rafael compiled this list:

* systemd kills daemons on resume, after >WatchdogSec seconds
  of suspending (Genki Sky).  [Verified that that's because systemd uses
  CLOCK_MONOTONIC and expects it to not include the suspend time.]

* systemd-journald misbehaves after resume:
  systemd-journald[7266]: File /var/log/journal/016627c3c4784cd4812d4b7e96a34226/system.journal
corrupted or uncleanly shut down, renaming and replacing.
  (Mike Galbraith).

* NetworkManager reports "networking disabled" and networking is broken
  after resume 50% of the time (Pavel).  [May be because of systemd.]

* MATE desktop dims the display and starts the screensaver right after
  system resume (Pavel).

* Full system hang during resume (me).  [May be due to systemd or NM or both.]

That happens on debian and open suse systems.

It's sad, that these problems were neither catched in -next nor by those
folks who expressed interest in this change.

Reported-by: Rafael J. Wysocki 
Reported-by: Genki Sky ,
Reported-by: Pavel Machek 
Signed-off-by: Thomas Gleixner 
Cc: Dmitry Torokhov 
Cc: John Stultz 
Cc: Jonathan Corbet 
Cc: Kevin Easton 
Cc: Linus Torvalds 
Cc: Mark Salyzyn 
Cc: Michael Kerrisk 
Cc: Peter Zijlstra 
Cc: Petr Mladek 
Cc: Prarit Bhargava 
Cc: Sergey Senozhatsky 
Cc: Steven Rostedt

timekeeping: Add the new CLOCK_MONOTONIC_ACTIVE clock

2018-03-13T06:34:21+00:00

The planned change to unify the behaviour of the MONOTONIC and BOOTTIME
clocks vs. suspend removes the ability to retrieve the active
non-suspended time of a system.

Provide a new CLOCK_MONOTONIC_ACTIVE clock which returns the active
non-suspended time of the system via clock_gettime().

This preserves the old behaviour of CLOCK_MONOTONIC before the
BOOTTIME/MONOTONIC unification.

This new clock also allows applications to detect programmatically that
the MONOTONIC and BOOTTIME clocks are identical.

Signed-off-by: Thomas Gleixner 
Cc: Dmitry Torokhov 
Cc: John Stultz 
Cc: Jonathan Corbet 
Cc: Kevin Easton 
Cc: Linus Torvalds 
Cc: Mark Salyzyn 
Cc: Michael Kerrisk 
Cc: Peter Zijlstra 
Cc: Petr Mladek 
Cc: Prarit Bhargava 
Cc: Sergey Senozhatsky 
Cc: Steven Rostedt 
Link: http://lkml.kernel.org/r/20180301165149.965235774@linutronix.de
Signed-off-by: Ingo Molnar

timekeeping/ntp: Determine the multiplier directly from NTP tick length

2018-03-10T08:12:41+00:00

When the length of the NTP tick changes significantly, e.g. when an
NTP/PTP application is correcting the initial offset of the clock, a
large value may accumulate in the NTP error before the multiplier
converges to the correct value. It may then take a very long time (hours
or even days) before the error is corrected. This causes the clock to
have an unstable frequency offset, which has a negative impact on the
stability of synchronization with precise time sources (e.g. NTP/PTP
using hardware timestamping or the PTP KVM clock).

Use division to determine the correct multiplier directly from the NTP
tick length and replace the iterative approach. This removes the last
major source of the NTP error. The only remaining source is now limited
resolution of the multiplier, which is corrected by adding 1 to the
multiplier when the system clock is behind the NTP time.

Signed-off-by: Miroslav Lichvar 
Signed-off-by: John Stultz 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Prarit Bhargava 
Cc: Richard Cochran 
Cc: Stephen Boyd 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1520620971-9567-3-git-send-email-john.stultz@linaro.org
Signed-off-by: Ingo Molnar

timekeeping: Remove CONFIG_GENERIC_TIME_VSYSCALL_OLD

2017-11-14T10:20:25+00:00

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 
Signed-off-by: John Stultz 
Signed-off-by: Thomas Gleixner 
Cc: Prarit Bhargava 
Cc: Tony Luck 
Cc: Richard Cochran 
Cc: Stephen Boyd 
Link: https://lkml.kernel.org/r/1510613491-16695-1-git-send-email-john.stultz@linaro.org

Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2017-11-14T01:56:58+00:00

Pull timer updates from Thomas Gleixner:
 "Yet another big pile of changes:

   - More year 2038 work from Arnd slowly reaching the point where we
     need to think about the syscalls themself.

   - A new timer function which allows to conditionally (re)arm a timer
     only when it's either not running or the new expiry time is sooner
     than the armed expiry time. This allows to use a single timer for
     multiple timeout requirements w/o caring about the first expiry
     time at the call site.

   - A new NMI safe accessor to clock real time for the printk timestamp
     work. Can be used by tracing, perf as well if required.

   - A large number of timer setup conversions from Kees which got
     collected here because either maintainers requested so or they
     simply got ignored. As Kees pointed out already there are a few
     trivial merge conflicts and some redundant commits which was
     unavoidable due to the size of this conversion effort.

   - Avoid a redundant iteration in the timer wheel softirq processing.

   - Provide a mechanism to treat RTC implementations depending on their
     hardware properties, i.e. don't inflict the write at the 0.5
     seconds boundary which originates from the PC CMOS RTC to all RTCs.
     No functional change as drivers need to be updated separately.

   - The usual small updates to core code clocksource drivers. Nothing
     really exciting"

* 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (111 commits)
  timers: Add a function to start/reduce a timer
  pstore: Use ktime_get_real_fast_ns() instead of __getnstimeofday()
  timer: Prepare to change all DEFINE_TIMER() callbacks
  netfilter: ipvs: Convert timers to use timer_setup()
  scsi: qla2xxx: Convert timers to use timer_setup()
  block/aoe: discover_timer: Convert timers to use timer_setup()
  ide: Convert timers to use timer_setup()
  drbd: Convert timers to use timer_setup()
  mailbox: Convert timers to use timer_setup()
  crypto: Convert timers to use timer_setup()
  drivers/pcmcia: omap1: Fix error in automated timer conversion
  ARM: footbridge: Fix typo in timer conversion
  drivers/sgi-xp: Convert timers to use timer_setup()
  drivers/pcmcia: Convert timers to use timer_setup()
  drivers/memstick: Convert timers to use timer_setup()
  drivers/macintosh: Convert timers to use timer_setup()
  hwrng/xgene-rng: Convert timers to use timer_setup()
  auxdisplay: Convert timers to use timer_setup()
  sparc/led: Convert timers to use timer_setup()
  mips: ip22/32: Convert timers to use timer_setup()
  ...

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

timekeeping: Provide NMI safe access to clock realtime

2017-09-25T19:05:59+00:00

The configurable printk timestamping wants access to clock realtime. Right
now there is no ktime_get_real_fast_ns() accessor because reading the
monotonic base and the realtime offset cannot be done atomically. Contrary
to boot time this offset can change during runtime and cause half updated
readouts.

struct tk_read_base was fully packed when the fast timekeeper access was
implemented. commit ceea5e3771ed ("time: Fix clock->read(clock) race around
clocksource changes") removed the 'read' function pointer from the
structure, but of course left the comment stale.

So now the structure can fit a new 64bit member w/o violating the cache
line constraints.

Add real_base to tk_read_base and update it in the fast timekeeper update
sequence.

Implement an accessor which follows the same scheme as the accessor to
clock monotonic, but uses the new real_base to access clock real time.

The runtime overhead for updating real_base is minimal as it just adds two
cache hot values and stores them into an already dirtied cache line along
with the other fast timekeeper updates.

Signed-off-by: Thomas Gleixner 
Cc: Prarit Bhargava 
Cc: John Stultz 
Cc: Peter Zijlstra 
Link: https://lkml.kernel.org/r/1505757060-2004-3-git-send-email-prarit@redhat.com

time: Clean up CLOCK_MONOTONIC_RAW time handling

2017-06-21T05:13:59+00:00

Now that we fixed the sub-ns handling for CLOCK_MONOTONIC_RAW,
remove the duplicitive tk->raw_time.tv_nsec, which can be
stored in tk->tkr_raw.xtime_nsec (similarly to how its handled
for monotonic time).

Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: Miroslav Lichvar 
Cc: Richard Cochran 
Cc: Prarit Bhargava 
Cc: Stephen Boyd 
Cc: Kevin Brodsky 
Cc: Will Deacon 
Cc: Daniel Mentz 
Tested-by: Daniel Mentz 
Signed-off-by: John Stultz

time: Fix CLOCK_MONOTONIC_RAW sub-nanosecond accounting

2017-06-20T08:41:50+00:00

Due to how the MONOTONIC_RAW accumulation logic was handled,
there is the potential for a 1ns discontinuity when we do
accumulations. This small discontinuity has for the most part
gone un-noticed, but since ARM64 enabled CLOCK_MONOTONIC_RAW
in their vDSO clock_gettime implementation, we've seen failures
with the inconsistency-check test in kselftest.

This patch addresses the issue by using the same sub-ns
accumulation handling that CLOCK_MONOTONIC uses, which avoids
the issue for in-kernel users.

Since the ARM64 vDSO implementation has its own clock_gettime
calculation logic, this patch reduces the frequency of errors,
but failures are still seen. The ARM64 vDSO will need to be
updated to include the sub-nanosecond xtime_nsec values in its
calculation for this issue to be completely fixed.

Signed-off-by: John Stultz 
Tested-by: Daniel Mentz 
Cc: Prarit Bhargava 
Cc: Kevin Brodsky 
Cc: Richard Cochran 
Cc: Stephen Boyd 
Cc: Will Deacon 
Cc: "stable #4 . 8+" 
Cc: Miroslav Lichvar 
Link: http://lkml.kernel.org/r/1496965462-20003-3-git-send-email-john.stultz@linaro.org
Signed-off-by: Thomas Gleixner