linux-toradex.git/kernel/time/timekeeping.c, branch T30_LinuxImageV2.0Beta2_20130626

clocksource: Avoid selecting mult values that might overflow when adjusted

2011-12-09T16:54:24+00:00

commit d65670a78cdbfae94f20a9e05ec705871d7cdf2b upstream.

For some frequencies, the clocks_calc_mult_shift() function will
unfortunately select mult values very close to 0xffffffff.  This
has the potential to overflow when NTP adjusts the clock, adding
to the mult value.

This patch adds a clocksource.maxadj value, which provides
an approximation of an 11% adjustment(NTP limits adjustments to
500ppm and the tick adjustment is limited to 10%), which could
be made to the clocksource.mult value. This is then used to both
check that the current mult value won't overflow/underflow, as
well as warning us if the timekeeping_adjust() code pushes over
that 11% boundary.

v2: Fix max_adjustment calculation, and improve WARN_ONCE
messages.

v3: Don't warn before maxadj has actually been set

CC: Yong Zhang 
CC: David Daney 
CC: Thomas Gleixner 
CC: Chen Jie 
CC: zhangfx 
Reported-by: Chen Jie 
Reported-by: zhangfx 
Tested-by: Yong Zhang 
Signed-off-by: John Stultz 
Signed-off-by: Greg Kroah-Hartman

timekeeping: add arch_offset hook to ktime_get functions

2011-12-09T16:54:23+00:00

commit d004e024058a0eaca097513ce62cbcf978913e0a upstream.

ktime_get and ktime_get_ts were calling timekeeping_get_ns()
but later they were not calling arch_gettimeoffset() so architectures
using this mechanism returned 0 ns when calling these functions.

This happened for example when running Busybox's ping which calls
syscall(__NR_clock_gettime, CLOCK_MONOTONIC, ts) which eventually
calls ktime_get. As a result the returned ping travel time was zero.

Signed-off-by: Hector Palacios 
Signed-off-by: John Stultz 
Signed-off-by: Greg Kroah-Hartman

time: Fix stupid KERN_WARN compile issue

2011-07-20T22:42:55+00:00

Terribly embarassing. Don't know how I committed this, but its
KERN_WARNING not KERN_WARN.

This fixes the following compile error:
kernel/time/timekeeping.c: In function ‘__timekeeping_inject_sleeptime’:
kernel/time/timekeeping.c:608: error: ‘KERN_WARN’ undeclared (first use in this function)
kernel/time/timekeeping.c:608: error: (Each undeclared identifier is reported only once
kernel/time/timekeeping.c:608: error: for each function it appears in.)
kernel/time/timekeeping.c:608: error: expected ‘)’ before string constant
make[2]: *** [kernel/time/timekeeping.o] Error 1

Reported-by: Ingo Molnar 
Signed-off-by: John Stultz

time: Avoid accumulating time drift in suspend/resume

2011-06-21T23:55:37+00:00

Because the read_persistent_clock interface is usually backed by
only a second granular interface, each time we read from the persistent
clock for suspend/resume, we introduce a half second (on average) of error.

In order to avoid this error accumulating as the system is suspended
over and over, this patch measures the time delta between the persistent
clock and the system CLOCK_REALTIME.

If the delta is less then 2 seconds from the last suspend, we compensate
by using the previous time delta (keeping it close). If it is larger
then 2 seconds, we assume the clock was set or has been changed, so we
do no correction and update the delta.

Note: If NTP is running, ths could seem to "fight" with the NTP corrected
time, where as if the system time was off by 1 second, and NTP slewed the
value in, a suspend/resume cycle could undo this correction, by trying to
restore the previous offset from the persistent clock.  However, without
this patch, since each read could cause almost a full second worth of
error, its possible to get almost 2 seconds of error just from the
suspend/resume cycle alone, so this about equal to any offset added by
the compensation.

Further on systems that suspend/resume frequently, this should keep time
closer then NTP could compensate for if the errors were allowed to
accumulate.

Credits to Arve Hjønnevåg for suggesting this solution.

CC: Arve Hjønnevåg 
CC: Thomas Gleixner 
Signed-off-by: John Stultz

time: Catch invalid timespec sleep values in __timekeeping_inject_sleeptime

2011-06-21T23:55:36+00:00

Arve suggested making sure we catch possible negative sleep time
intervals that could be passed into timekeeping_inject_sleeptime.

CC: Arve Hjønnevåg 
CC: Thomas Gleixner 
Signed-off-by: John Stultz

timerfd: Allow timers to be cancelled when clock was set

2011-05-02T19:39:15+00:00

Some applications must be aware of clock realtime being set
backward. A simple example is a clock applet which arms a timer for
the next minute display. If clock realtime is set backward then the
applet displays a stale time for the amount of time which the clock
was set backwards. Due to that applications poll the time because we
don't have an interface.

Extend the timerfd interface by adding a flag which puts the timer
onto a different internal realtime clock. All timers on this clock are
expired whenever the clock was set.

The timerfd core records the monotonic offset when the timer is
created. When the timer is armed, then the current offset is compared
to the previous recorded offset. When it has changed, then
timerfd_settime returns -ECANCELED. When a timer is read the offset is
compared and if it changed -ECANCELED returned to user space. Periodic
timers are not rearmed in the cancelation case.

Signed-off-by: Thomas Gleixner 
Acked-by: John Stultz 
Cc: Chris Friesen 
Tested-by: Kay Sievers 
Cc: "Kirill A. Shutemov" 
Cc: Peter Zijlstra 
Cc: Davide Libenzi 
Reviewed-by: Alexander Shishkin 
Link: http://lkml.kernel.org/r/%3Calpine.LFD.2.02.1104271359580.3323%40ionos%3E
Signed-off-by: Thomas Gleixner

hrtimers: Prepare for cancel on clock was set timers

2011-05-02T19:37:58+00:00

Make clock_was_set() unconditional and rename hres_timers_resume to
hrtimers_resume. This is a preparatory patch for hrtimers which are
cancelled when clock realtime was set.

Signed-off-by: Thomas Gleixner

time: Add timekeeping_inject_sleeptime

2011-04-26T21:01:41+00:00

Some platforms cannot implement read_persistent_clock, as
their RTC devices are only accessible when interrupts are enabled.
This keeps them from being used by the timekeeping code on resume
to measure the time in suspend.

The RTC layer tries to work around this, by calling do_settimeofday
on resume after irqs are reenabled to set the time properly. However,
this only corrects CLOCK_REALTIME, and does not properly adjust
the sleep time value. This causes btime in /proc/stat to be incorrect
as well as making the new CLOCK_BOTTTIME inaccurate.

This patch resolves the issue by introducing a new timekeeping hook
to allow the RTC layer to inject the sleep time on resume.

The code also checks to make sure that read_persistent_clock is
nonfunctional before setting the sleep time, so that should the RTC's
HCTOSYS option be configured in on a system that does support
read_persistent_clock we will not increase the total_sleep_time twice.

CC: Arve Hjønnevåg 
CC: Thomas Gleixner 
Acked-by: Arnd Bergmann 
Signed-off-by: John Stultz

timekeeping: Use syscore_ops instead of sysdev class and sysdev

2011-03-23T21:16:04+00:00

The timekeeping subsystem uses a sysdev class and a sysdev for
executing timekeeping_suspend() after interrupts have been turned off
on the boot CPU (during system suspend) and for executing
timekeeping_resume() before turning on interrupts on the boot CPU
(during system resume).  However, since both of these functions
ignore their arguments, the entire mechanism may be replaced with a
struct syscore_ops object which is simpler.

Signed-off-by: Rafael J. Wysocki 
Reviewed-by: Thomas Gleixner

time: Extend get_xtime_and_monotonic_offset() to also return sleep

2011-02-21T20:53:07+00:00

Extend get_xtime_and_monotonic_offset to
get_xtime_and_monotonic_and_sleep_offset().

CC: Jamie Lokier 
CC: Thomas Gleixner 
CC: Alexander Shishkin 
CC: Arve Hjønnevåg 
Signed-off-by: John Stultz