linux.git/kernel/time, branch v4.1.29

posix-clock: Fix return code on the poll method's error path

2016-02-01T19:46:08+00:00

[ Upstream commit 1b9f23727abb92c5e58f139e7d180befcaa06fe0 ]

The posix_clock_poll function is supposed to return a bit mask of
POLLxxx values.  However, in case the hardware has disappeared (due to
hot plugging for example) this code returns -ENODEV in a futile
attempt to throw an error at the file descriptor level.  The kernel's
file_operations interface does not accept such error codes from the
poll method.  Instead, this function aught to return POLLERR.

The value -ENODEV does, in fact, contain the POLLERR bit (and almost
all the other POLLxxx bits as well), but only by chance.  This patch
fixes code to return a proper bit mask.

Credit goes to Markus Elfring for pointing out the suspicious
signed/unsigned mismatch.

Reported-by: Markus Elfring 
igned-off-by: Richard Cochran 
Cc: John Stultz 
Cc: Julia Lawall 
Link: http://lkml.kernel.org/r/1450819198-17420-1-git-send-email-richardcochran@gmail.com
Cc: stable@vger.kernel.org
Signed-off-by: Thomas Gleixner 
Signed-off-by: Sasha Levin

time: Avoid signed overflow in timekeeping_get_ns()

2016-02-01T16:37:05+00:00

[ Upstream commit 35a4933a895927990772ae96fdcfd2f806929ee2 ]

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.

Cc: stable@vger.kernel.org  (3.7+)
Suggested-by: Laurent Vivier 
Tested-by: Laurent Vivier 
Signed-off-by: David Gibson 
Signed-off-by: John Stultz 
Signed-off-by: Sasha Levin

time: Fix timekeeping_freqadjust()'s incorrect use of abs() instead of abs64()

2015-10-22T21:43:11+00:00

commit 2619d7e9c92d524cb155ec89fd72875321512e5b upstream.

The internal clocksteering done for fine-grained error
correction uses a logarithmic approximation, so any time
adjtimex() adjusts the clock steering, timekeeping_freqadjust()
quickly approximates the correct clock frequency over a series
of ticks.

Unfortunately, the logic in timekeeping_freqadjust(), introduced
in commit:

  dc491596f639 ("timekeeping: Rework frequency adjustments to work better w/ nohz")

used the abs() function with a s64 error value to calculate the
size of the approximated adjustment to be made.

Per include/linux/kernel.h:

  "abs() should not be used for 64-bit types (s64, u64, long long) - use abs64()".

Thus on 32-bit platforms, this resulted in the clocksteering to
take a quite dampended random walk trying to converge on the
proper frequency, which caused the adjustments to be made much
slower then intended (most easily observed when large
adjustments are made).

This patch fixes the issue by using abs64() instead.

Reported-by: Nuno Gonçalves 
Tested-by: Nuno Goncalves 
Signed-off-by: John Stultz 
Cc: Linus Torvalds 
Cc: Miroslav Lichvar 
Cc: Peter Zijlstra 
Cc: Prarit Bhargava 
Cc: Richard Cochran 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1441840051-20244-1-git-send-email-john.stultz@linaro.org
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

ktime: Fix ktime_divns to do signed division

2015-05-13T08:19:35+00:00

It was noted that the 32bit implementation of ktime_divns()
was doing unsigned division and didn't properly handle
negative values.

And when a ktime helper was changed to utilize
ktime_divns, it caused a regression on some IR blasters.
See the following bugzilla for details:
  https://bugzilla.redhat.com/show_bug.cgi?id=1200353

This patch fixes the problem in ktime_divns by checking
and preserving the sign bit, and then reapplying it if
appropriate after the division, it also changes the return
type to a s64 to make it more obvious this is expected.

Nicolas also pointed out that negative dividers would
cause infinite loops on 32bit systems, negative dividers
is unlikely for users of this function, but out of caution
this patch adds checks for negative dividers for both
32-bit (BUG_ON) and 64-bit(WARN_ON) versions to make sure
no such use cases creep in.

[ tglx: Hand an u64 to do_div() to avoid the compiler warning ]

Fixes: 166afb64511e 'ktime: Sanitize ktime_to_us/ms conversion'
Reported-and-tested-by: Trevor Cordes 
Signed-off-by: John Stultz 
Acked-by: Nicolas Pitre 
Cc: Ingo Molnar 
Cc: Josh Boyer 
Cc: One Thousand Gnomes 
Cc: 
Link: http://lkml.kernel.org/r/1431118043-23452-1-git-send-email-john.stultz@linaro.org
Signed-off-by: Thomas Gleixner

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

2015-05-09T21:57:49+00:00

Pull timer fix from Thomas Gleixner:
 "A simple fix to actually shut down a detached device instead of
  keeping it active"

* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  clockevents: Shutdown detached clockevent device

clockevents: Shutdown detached clockevent device

2015-04-24T19:01:48+00:00

A clockevent device is marked DETACHED when it is replaced by another
clockevent device.

The device is shutdown properly for drivers that implement legacy
->set_mode() callback, as we call ->set_mode() for CLOCK_EVT_MODE_UNUSED
as well.

But for the new per-state callback interface, we skip shutting down the
device, as we thought its an internal state change. That wasn't correct.

The effect is that the device is left programmed in oneshot or periodic
mode.

Fall-back to 'case CLOCK_EVT_STATE_SHUTDOWN', to shutdown the device.

Fixes: bd624d75db21 "clockevents: Introduce mode specific callbacks"
Reported-by: Daniel Lezcano 
Signed-off-by: Viresh Kumar 
Cc: linaro-kernel@lists.linaro.org
Cc: Peter Zijlstra 
Link: http://lkml.kernel.org/r/eef0a91c51b74d4e52c8e5a95eca27b5a0563f07.1428650683.git.viresh.kumar@linaro.org
Signed-off-by: Thomas Gleixner

Merge tag 'char-misc-4.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc

2015-04-21T16:42:58+00:00

Pull char/misc driver updates from Greg KH:
 "Here's the big char/misc driver patchset for 4.1-rc1.

  Lots of different driver subsystem updates here, nothing major, full
  details are in the shortlog.

  All of this has been in linux-next for a while"

* tag 'char-misc-4.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc: (133 commits)
  mei: trace: remove unused TRACE_SYSTEM_STRING
  DTS: ARM: OMAP3-N900: Add lis3lv02d support
  Documentation: DT: lis302: update wakeup binding
  lis3lv02d: DT: add wakeup unit 2 and wakeup threshold
  lis3lv02d: DT: use s32 to support negative values
  Drivers: hv: hv_balloon: correctly handle num_pages>INT_MAX case
  Drivers: hv: hv_balloon: correctly handle val.freeram

timers/PM: Drop unnecessary braces from tick_freeze()

2015-04-03T13:15:52+00:00

Some braces in tick_freeze() are not necessary, so drop them.

Signed-off-by: Rafael J. Wysocki 
Cc: peterz@infradead.org
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1534128.H5hN3KBFB4@vostro.rjw.lan
Signed-off-by: Ingo Molnar

timers/PM: Fix up tick_unfreeze()

2015-04-03T13:15:51+00:00

A recent conflict resolution has left tick_resume() in
tick_unfreeze() which leads to an unbalanced execution of
tick_resume_broadcast() every time that function runs.

Fix that by replacing the tick_resume() in tick_unfreeze()
with tick_resume_local() as appropriate.

Signed-off-by: Rafael J. Wysocki 
Cc: boris.ostrovsky@oracle.com
Cc: david.vrabel@citrix.com
Cc: konrad.wilk@oracle.com
Cc: peterz@infradead.org
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/8099075.V0LvN3pQAV@vostro.rjw.lan
Signed-off-by: Ingo Molnar

timekeeping: Get rid of stale comment

2015-04-03T06:44:37+00:00

Arch specific management of xtime/jiffies/wall_to_monotonic is
gone for quite a while. Zap the stale comment.

Signed-off-by: Thomas Gleixner 
Signed-off-by: Rafael J. Wysocki 
Acked-by: John Stultz 
Cc: Peter Zijlstra 
Cc: John Stultz 
Link: http://lkml.kernel.org/r/2422730.dmO29q661S@vostro.rjw.lan
Signed-off-by: Ingo Molnar