linux-toradex.git/kernel/time/timekeeping.c, branch v4.4.39

timekeeping: Fix __ktime_get_fast_ns() regression

2016-10-16T15:36:14+00:00

commit 58bfea9532552d422bde7afa207e1a0f08dffa7d upstream.

In commit 27727df240c7 ("Avoid taking lock in NMI path with
CONFIG_DEBUG_TIMEKEEPING"), I changed the logic to open-code
the timekeeping_get_ns() function, but I forgot to include
the unit conversion from cycles to nanoseconds, breaking the
function's output, which impacts users like perf.

This results in bogus perf timestamps like:
 swapper     0 [000]   253.427536:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]   254.426573:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]   254.426687:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]   254.426800:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]   254.426905:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]   254.427022:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]   254.427127:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]   254.427239:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]   254.427346:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]   254.427463:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]   255.426572:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])

Instead of more reasonable expected timestamps like:
 swapper     0 [000]    39.953768:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]    40.064839:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]    40.175956:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]    40.287103:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]    40.398217:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]    40.509324:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]    40.620437:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]    40.731546:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]    40.842654:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]    40.953772:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]    41.064881:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])

Add the proper use of timekeeping_delta_to_ns() to convert
the cycle delta to nanoseconds as needed.

Thanks to Brendan and Alexei for finding this quickly after
the v4.8 release. Unfortunately the problematic commit has
landed in some -stable trees so they'll need this fix as
well.

Many apologies for this mistake. I'll be looking to add a
perf-clock sanity test to the kselftest timers tests soon.

Fixes: 27727df240c7 "timekeeping: Avoid taking lock in NMI path with CONFIG_DEBUG_TIMEKEEPING"
Reported-by: Brendan Gregg 
Reported-by: Alexei Starovoitov 
Tested-and-reviewed-by: Mathieu Desnoyers 
Signed-off-by: John Stultz 
Cc: Peter Zijlstra 
Cc: Steven Rostedt 
Link: http://lkml.kernel.org/r/1475636148-26539-1-git-send-email-john.stultz@linaro.org
Signed-off-by: Thomas Gleixner 
Cc: Mathieu Desnoyers 
Signed-off-by: Greg Kroah-Hartman

time: Add cycles to nanoseconds translation

2016-10-16T15:36:14+00:00

commit 6bd58f09e1d8cc6c50a824c00bf0d617919986a1 upstream.

The timekeeping code does not currently provide a way to translate
externally provided clocksource cycles to system time. The cycle count
is always provided by the result clocksource read() method internal to
the timekeeping code. The added function timekeeping_cycles_to_ns()
calculated a nanosecond value from a cycle count that can be added to
tk_read_base.base value yielding the current system time. This allows
clocksource cycle values external to the timekeeping code to provide a
cycle count that can be transformed to system time.

Cc: Prarit Bhargava 
Cc: Richard Cochran 
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: Andy Lutomirski 
Cc: kevin.b.stanton@intel.com
Cc: kevin.j.clarke@intel.com
Cc: hpa@zytor.com
Cc: jeffrey.t.kirsher@intel.com
Cc: netdev@vger.kernel.org
Reviewed-by: Thomas Gleixner 
Signed-off-by: Christopher S. Hall 
Signed-off-by: John Stultz 
Signed-off-by: Greg Kroah-Hartman

timekeeping: Avoid taking lock in NMI path with CONFIG_DEBUG_TIMEKEEPING

2016-09-15T06:27:52+00:00

commit 27727df240c7cc84f2ba6047c6f18d5addfd25ef upstream.

When I added some extra sanity checking in timekeeping_get_ns() under
CONFIG_DEBUG_TIMEKEEPING, I missed that the NMI safe __ktime_get_fast_ns()
method was using timekeeping_get_ns().

Thus the locking added to the debug checks broke the NMI-safety of
__ktime_get_fast_ns().

This patch open-codes the timekeeping_get_ns() logic for
__ktime_get_fast_ns(), so can avoid any deadlocks in NMI.

Fixes: 4ca22c2648f9 "timekeeping: Add warnings when overflows or underflows are observed"
Reported-by: Steven Rostedt 
Reported-by: Peter Zijlstra 
Signed-off-by: John Stultz 
Link: http://lkml.kernel.org/r/1471993702-29148-2-git-send-email-john.stultz@linaro.org
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

time: Verify time values in adjtimex ADJ_SETOFFSET to avoid overflow

2016-09-15T06:27:47+00:00

[ Upstream commit 37cf4dc3370fbca0344e23bb96446eb2c3548ba7 ]

For adjtimex()'s ADJ_SETOFFSET, make sure the tv_usec value is
sane. We might multiply them later which can cause an overflow
and undefined behavior.

This patch introduces new helper functions to simplify the
checking code and adds comments to clarify

Orginally this patch was by Sasha Levin, but I've basically
rewritten it, so he should get credit for finding the issue
and I should get the blame for any mistakes made since.

Also, credit to Richard Cochran for the phrasing used in the
comment for what is considered valid here.

Cc: Sasha Levin 
Cc: Richard Cochran 
Cc: Thomas Gleixner 
Reported-by: Sasha Levin 
Signed-off-by: John Stultz 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

time: Avoid signed overflow in timekeeping_get_ns()

2016-03-03T23:07:16+00:00

commit 35a4933a895927990772ae96fdcfd2f806929ee2 upstream.

1e75fa8 "time: Condense timekeeper.xtime into xtime_sec" replaced a call to
clocksource_cyc2ns() from timekeeping_get_ns() with an open-coded version
of the same logic to avoid keeping a semi-redundant struct timespec
in struct timekeeper.

However, the commit also introduced a subtle semantic change - where
clocksource_cyc2ns() uses purely unsigned math, the new version introduces
a signed temporary, meaning that if (delta * tk->mult) has a 63-bit
overflow the following shift will still give a negative result.  The
choice of 'maxsec' in __clocksource_updatefreq_scale() means this will
generally happen if there's a ~10 minute pause in examining the
clocksource.

This can be triggered on a powerpc KVM guest by stopping it from qemu for
a bit over 10 minutes.  After resuming time has jumped backwards several
minutes causing numerous problems (jiffies does not advance, msleep()s can
be extended by minutes..).  It doesn't happen on x86 KVM guests, because
the guest TSC is effectively frozen while the guest is stopped, which is
not the case for the powerpc timebase.

Obviously an unsigned (64 bit) overflow will only take twice as long as a
signed, 63-bit overflow.  I don't know the time code well enough to know
if that will still cause incorrect calculations, or if a 64-bit overflow
is avoided elsewhere.

Still, an incorrect forwards clock adjustment will cause less trouble than
time going backwards.  So, this patch removes the potential for
intermediate signed overflow.

Suggested-by: Laurent Vivier 
Tested-by: Laurent Vivier 
Signed-off-by: David Gibson 
Signed-off-by: John Stultz 
Signed-off-by: Greg Kroah-Hartman

remove abs64()

2015-11-09T23:11:24+00:00

Switch everything to the new and more capable implementation of abs().
Mainly to give the new abs() a bit of a workout.

Cc: Michal Nazarewicz 
Cc: John Stultz 
Cc: Ingo Molnar 
Cc: Steven Rostedt 
Cc: Peter Zijlstra 
Cc: Masami Hiramatsu 
Cc: Peter Zijlstra 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

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

2015-11-03T22:13:41+00:00

Pull timer updates from Thomas Gleixner:
 "The timer departement provides:

   - More y2038 work in the area of ntp and pps.

   - Optimization of posix cpu timers

   - New time related selftests

   - Some new clocksource drivers

   - The usual pile of fixes, cleanups and improvements"

* 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (25 commits)
  timeconst: Update path in comment
  timers/x86/hpet: Type adjustments
  clocksource/drivers/armada-370-xp: Implement ARM delay timer
  clocksource/drivers/tango_xtal: Add new timer for Tango SoCs
  clocksource/drivers/imx: Allow timer irq affinity change
  clocksource/drivers/exynos_mct: Use container_of() instead of this_cpu_ptr()
  clocksource/drivers/h8300_*: Remove unneeded memset()s
  clocksource/drivers/sh_cmt: Remove unneeded memset() in sh_cmt_setup()
  clocksource/drivers/em_sti: Remove unneeded memset()s
  clocksource/drivers/mediatek: Use GPT as sched clock source
  clockevents/drivers/mtk: Fix spurious interrupt leading to crash
  posix_cpu_timer: Reduce unnecessary sighand lock contention
  posix_cpu_timer: Convert cputimer->running to bool
  posix_cpu_timer: Check thread timers only when there are active thread timers
  posix_cpu_timer: Optimize fastpath_timer_check()
  timers, kselftest: Add 'adjtick' test to validate adjtimex() tick adjustments
  timers: Use __fls in apply_slack()
  clocksource: Remove return statement from void functions
  net: sfc: avoid using timespec
  ntp/pps: use y2038 safe types in pps_event_time
  ...

Merge branch 'fortglx/4.4/time' of https://git.linaro.org/people/john.stultz/linux into timers/core

2015-10-20T10:36:37+00:00

Time updates from John Stultz:

     - More 2038 work from Arnd Bergmann around ntp and pps

timekeeping: Increment clock_was_set_seq in timekeeping_init()

2015-10-16T13:50:22+00:00

timekeeping_init() can set the wall time offset, so we need to
increment the clock_was_set_seq counter. That way hrtimers will pick
up the early offset immediately. Otherwise on a machine which does not
set wall time later in the boot process the hrtimer offset is stale at
0 and wall time timers are going to expire with a delay of 45 years.

Fixes: 868a3e915f7f "hrtimer: Make offset update smarter"
Reported-and-tested-by: Heiko Carstens 
Signed-off-by: Thomas Gleixner 
Cc: Stefan Liebler 
Cc: Peter Zijlstra 
Cc: John Stultz

ntp/pps: replace getnstime_raw_and_real with 64-bit version

2015-10-01T16:59:01+00:00

There is exactly one caller of getnstime_raw_and_real in the kernel,
which is the pps_get_ts function. This changes the caller and
the implementation to work on timespec64 types rather than timespec,
to avoid the time_t overflow on 32-bit architectures.

For consistency with the other new functions (ktime_get_seconds,
ktime_get_real_*, ...), I'm renaming the function to
ktime_get_raw_and_real_ts64.

We still need to convert from the internal 64-bit type to 32 bit
types in the caller, but this conversion is now pushed out from
getnstime_raw_and_real to pps_get_ts. A follow-up patch changes
the remaining pps code to completely avoid the conversion.

Acked-by: Richard Cochran 
Acked-by: David S. Miller 
Reviewed-by: Thomas Gleixner 
Signed-off-by: Arnd Bergmann 
Signed-off-by: John Stultz