linux-stable.git/kernel/time/timekeeping.c, branch v4.19.232

timekeeping: Really make sure wall_to_monotonic isn't positive

2021-12-22T08:19:03+00:00

commit 4e8c11b6b3f0b6a283e898344f154641eda94266 upstream.

Even after commit e1d7ba873555 ("time: Always make sure wall_to_monotonic
isn't positive") it is still possible to make wall_to_monotonic positive
by running the following code:

    int main(void)
    {
        struct timespec time;

        clock_gettime(CLOCK_MONOTONIC, &time);
        time.tv_nsec = 0;
        clock_settime(CLOCK_REALTIME, &time);
        return 0;
    }

The reason is that the second parameter of timespec64_compare(), ts_delta,
may be unnormalized because the delta is calculated with an open coded
substraction which causes the comparison of tv_sec to yield the wrong
result:

  wall_to_monotonic = { .tv_sec = -10, .tv_nsec =  900000000 }
  ts_delta 	    = { .tv_sec =  -9, .tv_nsec = -900000000 }

That makes timespec64_compare() claim that wall_to_monotonic < ts_delta,
but actually the result should be wall_to_monotonic > ts_delta.

After normalization, the result of timespec64_compare() is correct because
the tv_sec comparison is not longer misleading:

  wall_to_monotonic = { .tv_sec = -10, .tv_nsec =  900000000 }
  ts_delta 	    = { .tv_sec = -10, .tv_nsec =  100000000 }

Use timespec64_sub() to ensure that ts_delta is normalized, which fixes the
issue.

Fixes: e1d7ba873555 ("time: Always make sure wall_to_monotonic isn't positive")
Signed-off-by: Yu Liao 
Signed-off-by: Thomas Gleixner 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20211213135727.1656662-1-liaoyu15@huawei.com
Signed-off-by: Greg Kroah-Hartman

timekeeping: Prevent 32bit truncation in scale64_check_overflow()

2020-10-01T11:14:36+00:00

[ Upstream commit 4cbbc3a0eeed675449b1a4d080008927121f3da3 ]

While unlikely the divisor in scale64_check_overflow() could be >= 32bit in
scale64_check_overflow(). do_div() truncates the divisor to 32bit at least
on 32bit platforms.

Use div64_u64() instead to avoid the truncation to 32-bit.

[ tglx: Massaged changelog ]

Signed-off-by: Wen Yang 
Signed-off-by: Thomas Gleixner 
Link: https://lkml.kernel.org/r/20200120100523.45656-1-wenyang@linux.alibaba.com
Signed-off-by: Sasha Levin

y2038: make do_gettimeofday() and get_seconds() inline

2019-11-20T17:45:24+00:00

[ Upstream commit 33e26418193f58d1895f2f968e1953b1caf8deb7 ]

get_seconds() and do_gettimeofday() are only used by a few modules now any
more (waiting for the respective patches to get accepted), and they are
among the last holdouts of code that is not y2038 safe in the core kernel.

Move the implementation into the timekeeping32.h header to clean up
the core kernel and isolate the old interfaces further.

Signed-off-by: Arnd Bergmann 
Signed-off-by: Sasha Levin

timekeeping: Use proper ktime_add when adding nsecs in coarse offset

2019-09-16T06:21:42+00:00

[ Upstream commit 0354c1a3cdf31f44b035cfad14d32282e815a572 ]

While this doesn't actually amount to a real difference, since the macro
evaluates to the same thing, every place else operates on ktime_t using
these functions, so let's not break the pattern.

Fixes: e3ff9c3678b4 ("timekeeping: Repair ktime_get_coarse*() granularity")
Signed-off-by: Jason A. Donenfeld 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Arnd Bergmann 
Link: https://lkml.kernel.org/r/20190621203249.3909-1-Jason@zx2c4.com
Signed-off-by: Sasha Levin

timekeeping: Repair ktime_get_coarse*() granularity

2019-06-19T06:18:06+00:00

commit e3ff9c3678b4d80e22d2557b68726174578eaf52 upstream.

Jason reported that the coarse ktime based time getters advance only once
per second and not once per tick as advertised.

The code reads only the monotonic base time, which advances once per
second. The nanoseconds are accumulated on every tick in xtime_nsec up to
a second and the regular time getters take this nanoseconds offset into
account, but the ktime_get_coarse*() implementation fails to do so.

Add the accumulated xtime_nsec value to the monotonic base time to get the
proper per tick advancing coarse tinme.

Fixes: b9ff604cff11 ("timekeeping: Add ktime_get_coarse_with_offset")
Reported-by: Jason A. Donenfeld 
Signed-off-by: Thomas Gleixner 
Tested-by: Jason A. Donenfeld 
Cc: Arnd Bergmann 
Cc: Peter Zijlstra 
Cc: Clemens Ladisch 
Cc: Sultan Alsawaf 
Cc: Waiman Long 
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1906132136280.1791@nanos.tec.linutronix.de
Signed-off-by: Greg Kroah-Hartman

timekeeping: Force upper bound for setting CLOCK_REALTIME

2019-05-31T13:46:29+00:00

[ Upstream commit 7a8e61f8478639072d402a26789055a4a4de8f77 ]

Several people reported testing failures after setting CLOCK_REALTIME close
to the limits of the kernel internal representation in nanoseconds,
i.e. year 2262.

The failures are exposed in subsequent operations, i.e. when arming timers
or when the advancing CLOCK_MONOTONIC makes the calculation of
CLOCK_REALTIME overflow into negative space.

Now people start to paper over the underlying problem by clamping
calculations to the valid range, but that's just wrong because such
workarounds will prevent detection of real issues as well.

It is reasonable to force an upper bound for the various methods of setting
CLOCK_REALTIME. Year 2262 is the absolute upper bound. Assume a maximum
uptime of 30 years which is plenty enough even for esoteric embedded
systems. That results in an upper bound of year 2232 for setting the time.

Once that limit is reached in reality this limit is only a small part of
the problem space. But until then this stops people from trying to paper
over the problem at the wrong places.

Reported-by: Xiongfeng Wang 
Reported-by: Hongbo Yao 
Signed-off-by: Thomas Gleixner 
Cc: John Stultz 
Cc: Stephen Boyd 
Cc: Miroslav Lichvar 
Cc: Arnd Bergmann 
Cc: Richard Cochran 
Cc: Peter Zijlstra 
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1903231125480.2157@nanos.tec.linutronix.de
Signed-off-by: Sasha Levin

timekeeping: Use proper seqcount initializer

2019-02-12T18:47:05+00:00

[ Upstream commit ce10a5b3954f2514af726beb78ed8d7350c5e41c ]

tk_core.seq is initialized open coded, but that misses to initialize the
lockdep map when lockdep is enabled. Lockdep splats involving tk_core seq
consequently lack a name and are hard to read.

Use the proper initializer which takes care of the lockdep map
initialization.

[ tglx: Massaged changelog ]

Signed-off-by: Bart Van Assche 
Signed-off-by: Thomas Gleixner 
Cc: peterz@infradead.org
Cc: tj@kernel.org
Cc: johannes.berg@intel.com
Link: https://lkml.kernel.org/r/20181128234325.110011-12-bvanassche@acm.org
Signed-off-by: Sasha Levin

Merge branch 'x86-timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2018-08-14T01:28:19+00:00

Pull x86 timer updates from Thomas Gleixner:
 "Early TSC based time stamping to allow better boot time analysis.

  This comes with a general cleanup of the TSC calibration code which
  grew warts and duct taping over the years and removes 250 lines of
  code. Initiated and mostly implemented by Pavel with help from various
  folks"

* 'x86-timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (37 commits)
  x86/kvmclock: Mark kvm_get_preset_lpj() as __init
  x86/tsc: Consolidate init code
  sched/clock: Disable interrupts when calling generic_sched_clock_init()
  timekeeping: Prevent false warning when persistent clock is not available
  sched/clock: Close a hole in sched_clock_init()
  x86/tsc: Make use of tsc_calibrate_cpu_early()
  x86/tsc: Split native_calibrate_cpu() into early and late parts
  sched/clock: Use static key for sched_clock_running
  sched/clock: Enable sched clock early
  sched/clock: Move sched clock initialization and merge with generic clock
  x86/tsc: Use TSC as sched clock early
  x86/tsc: Initialize cyc2ns when tsc frequency is determined
  x86/tsc: Calibrate tsc only once
  ARM/time: Remove read_boot_clock64()
  s390/time: Remove read_boot_clock64()
  timekeeping: Default boot time offset to local_clock()
  timekeeping: Replace read_boot_clock64() with read_persistent_wall_and_boot_offset()
  s390/time: Add read_persistent_wall_and_boot_offset()
  x86/xen/time: Output xen sched_clock time from 0
  x86/xen/time: Initialize pv xen time in init_hypervisor_platform()
  ...

timekeeping: Prevent false warning when persistent clock is not available

2018-07-30T17:32:29+00:00

On arches with no persistent clock a message like this is printed during
boot:

[    0.000000] Persistent clock returned invalid value

The value is not invalid: Zero means that no persistent clock is available
and the absence of persistent clock should be quietly accepted.

Fixes: 3eca993740b8 ("timekeeping: Replace read_boot_clock64() with read_persistent_wall_and_boot_offset()")
Signed-off-by: Pavel Tatashin 
Signed-off-by: Thomas Gleixner 
Cc: steven.sistare@oracle.com
Cc: daniel.m.jordan@oracle.com
Cc: sboyd@kernel.org
Cc: john.stultz@linaro.org
Link: https://lkml.kernel.org/r/20180725200018.23722-1-pasha.tatashin@oracle.com

time: Introduce one suspend clocksource to compensate the suspend time

2018-07-20T00:08:52+00:00

On some hardware with multiple clocksources, we have coarse grained
clocksources that support the CLOCK_SOURCE_SUSPEND_NONSTOP flag, but
which are less than ideal for timekeeping whereas other clocksources
can be better candidates but halt on suspend.

Currently, the timekeeping core only supports timing suspend using
CLOCK_SOURCE_SUSPEND_NONSTOP clocksources if that clocksource is the
current clocksource for timekeeping.

As a result, some architectures try to implement read_persistent_clock64()
using those non-stop clocksources, but isn't really ideal, which will
introduce more duplicate code. To fix this, provide logic to allow a
registered SUSPEND_NONSTOP clocksource, which isn't the current
clocksource, to be used to calculate the suspend time.

Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: Miroslav Lichvar 
Cc: Richard Cochran 
Cc: Prarit Bhargava 
Cc: Stephen Boyd 
Cc: Daniel Lezcano 
Reviewed-by: Thomas Gleixner 
Reviewed-by: Daniel Lezcano 
Suggested-by: Thomas Gleixner 
Signed-off-by: Baolin Wang 
[jstultz: minor tweaks to merge with previous resume changes]
Signed-off-by: John Stultz