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  1. 12 9月, 2013 1 次提交
    • J
      timekeeping: Fix HRTICK related deadlock from ntp lock changes · 7bd36014
      由 John Stultz 提交于 
      Gerlando Falauto reported that when HRTICK is enabled, it is
possible to trigger system deadlocks. These were hard to
reproduce, as HRTICK has been broken in the past, but seemed
to be connected to the timekeeping_seq lock.

Since seqlock/seqcount's aren't supported w/ lockdep, I added
some extra spinlock based locking and triggered the following
lockdep output:

[   15.849182] ntpd/4062 is trying to acquire lock:
[   15.849765]  (&(&pool->lock)->rlock){..-...}, at: [<ffffffff810aa9b5>] __queue_work+0x145/0x480
[   15.850051]
[   15.850051] but task is already holding lock:
[   15.850051]  (timekeeper_lock){-.-.-.}, at: [<ffffffff810df6df>] do_adjtimex+0x7f/0x100

<snip>

[   15.850051] Chain exists of: &(&pool->lock)->rlock --> &p->pi_lock --> timekeeper_lock
[   15.850051]  Possible unsafe locking scenario:
[   15.850051]
[   15.850051]        CPU0                    CPU1
[   15.850051]        ----                    ----
[   15.850051]   lock(timekeeper_lock);
[   15.850051]                                lock(&p->pi_lock);
[   15.850051] lock(timekeeper_lock);
[   15.850051] lock(&(&pool->lock)->rlock);
[   15.850051]
[   15.850051]  *** DEADLOCK ***

The deadlock was introduced by 06c017fd ("timekeeping:
Hold timekeepering locks in do_adjtimex and hardpps") in 3.10

This patch avoids this deadlock, by moving the call to
schedule_delayed_work() outside of the timekeeper lock
critical section.
Reported-by: NGerlando Falauto <gerlando.falauto@keymile.com>
Tested-by: NLin Ming <minggr@gmail.com>
Signed-off-by: NJohn Stultz <john.stultz@linaro.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: stable <stable@vger.kernel.org> #3.11, 3.10
Link: http://lkml.kernel.org/r/1378943457-27314-1-git-send-email-john.stultz@linaro.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>
      7bd36014
  3. 23 8月, 2013 1 次提交
    • M
      ntp: Make periodic RTC update more reliable · a97ad0c4
      由 Miroslav Lichvar 提交于 
      The current code requires that the scheduled update of the RTC happens
in the closest tick to the half of the second. This seems to be
difficult to achieve reliably. The scheduled work may be missing the
target time by a tick or two and be constantly rescheduled every second.

Relax the limit to 10 ticks. As a typical RTC drifts in the 11-minute
update interval by several milliseconds, this shouldn't affect the
overall accuracy of the RTC much.
Signed-off-by: NMiroslav Lichvar <mlichvar@redhat.com>
Signed-off-by: NJohn Stultz <john.stultz@linaro.org>
      a97ad0c4
  5. 29 5月, 2013 1 次提交
  7. 05 4月, 2013 6 次提交
  9. 23 3月, 2013 1 次提交
  11. 19 2月, 2013 1 次提交
  13. 09 2月, 2013 1 次提交
    • P
      time, Fix setting of hardware clock in NTP code · 84e345e4
      由 Prarit Bhargava 提交于 
      At init time, if the system time is "warped" forward in warp_clock()
it will differ from the hardware clock by sys_tz.tz_minuteswest.  This time
difference is not taken into account when ntp updates the hardware clock,
and this causes the system time to jump forward by this offset every reboot.

The kernel must take this offset into account when writing the system time
to the hardware clock in the ntp code.  This patch adds
persistent_clock_is_local which indicates that an offset has been applied
in warp_clock() and accounts for the "warp" before writing the hardware
clock.

x86 does not have this problem as rtc writes are software limited to a
+/-15 minute window relative to the current rtc time.  Other arches, such
as powerpc, however do a full synchronization of the system time to the
rtc and will see this problem.

[v2]: generated against tip/timers/core
Signed-off-by: NPrarit Bhargava <prarit@redhat.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: NJohn Stultz <john.stultz@linaro.org>
      84e345e4
  15. 16 1月, 2013 1 次提交
    • J
      NTP: Add a CONFIG_RTC_SYSTOHC configuration · 023f333a
      由 Jason Gunthorpe 提交于 
      The purpose of this option is to allow ARM/etc systems that rely on the
class RTC subsystem to have the same kind of automatic NTP based
synchronization that we have on PC platforms. Today ARM does not
implement update_persistent_clock and makes extensive use of the class
RTC system.

When enabled CONFIG_RTC_SYSTOHC will provide a generic
rtc_update_persistent_clock that stores the current time in the RTC and
is intended complement the existing CONFIG_RTC_HCTOSYS option that loads
the RTC at boot.

Like with RTC_HCTOSYS the platform's update_persistent_clock is used
first, if it works. Platforms with mixed class RTC and non-RTC drivers
need to return ENODEV when class RTC should be used. Such an update for
PPC is included in this patch.

Long term, implementations of update_persistent_clock should migrate to
proper class RTC drivers and use CONFIG_RTC_SYSTOHC instead.

Tested on ARM kirkwood and PPC405
Signed-off-by: NJason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: NJohn Stultz <john.stultz@linaro.org>
      023f333a
  17. 31 7月, 2012 1 次提交
  19. 15 7月, 2012 1 次提交
  21. 22 5月, 2012 2 次提交
  23. 24 3月, 2012 1 次提交
  25. 23 3月, 2012 1 次提交
    • J
      ntp: Fix leap-second hrtimer livelock · 6b43ae8a
      由 John Stultz 提交于 
      Since commit 7dffa3c6 the ntp
subsystem has used an hrtimer for triggering the leapsecond
adjustment. However, this can cause a potential livelock.

Thomas diagnosed this as the following pattern:
CPU 0                                                    CPU 1
do_adjtimex()
  spin_lock_irq(&ntp_lock);
    process_adjtimex_modes();				 timer_interrupt()
      process_adj_status();                                do_timer()
        ntp_start_leap_timer();                             write_lock(&xtime_lock);
          hrtimer_start();                                  update_wall_time();
             hrtimer_reprogram();                            ntp_tick_length()
               tick_program_event()                            spin_lock(&ntp_lock);
                 clockevents_program_event()
		   ktime_get()
                     seq = req_seqbegin(xtime_lock);

This patch tries to avoid the problem by reverting back to not using
an hrtimer to inject leapseconds, and instead we handle the leapsecond
processing in the second_overflow() function.

The downside to this change is that on systems that support highres
timers, the leap second processing will occur on a HZ tick boundary,
(ie: ~1-10ms, depending on HZ)  after the leap second instead of
possibly sooner (~34us in my tests w/ x86_64 lapic).

This patch applies on top of tip/timers/core.

CC: Sasha Levin <levinsasha928@gmail.com>
CC: Thomas Gleixner <tglx@linutronix.de>
Reported-by: NSasha Levin <levinsasha928@gmail.com>
Diagnoised-by: NThomas Gleixner <tglx@linutronix.de>
Tested-by: NSasha Levin <levinsasha928@gmail.com>
Signed-off-by: NJohn Stultz <john.stultz@linaro.org>
      6b43ae8a
  27. 16 3月, 2012 1 次提交
  29. 27 1月, 2012 3 次提交
  31. 04 4月, 2011 1 次提交
  33. 19 2月, 2011 1 次提交
  35. 02 2月, 2011 1 次提交
  37. 01 2月, 2011 1 次提交
  39. 14 1月, 2011 1 次提交
    • A
      ntp: add hardpps implementation · 025b40ab
      由 Alexander Gordeev 提交于 
      This commit adds hardpps() implementation based upon the original one from
the NTPv4 reference kernel code from David Mills.  However, it is highly
optimized towards very fast syncronization and maximum stickness to PPS
signal.  The typical error is less then a microsecond.

To make it sync faster I had to throw away exponential phase filter so
that the full phase offset is corrected immediately.  Then I also had to
throw away median phase filter because it gives a bigger error itself if
used without exponential filter.

Maybe we will find an appropriate filtering scheme in the future but it's
not necessary if the signal quality is ok.
Signed-off-by: NAlexander Gordeev <lasaine@lvk.cs.msu.su>
Acked-by: NJohn Stultz <johnstul@us.ibm.com>
Cc: Rodolfo Giometti <giometti@enneenne.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      025b40ab
  41. 10 9月, 2010 1 次提交
  43. 24 3月, 2010 1 次提交
  45. 29 1月, 2010 2 次提交
  47. 15 8月, 2009 1 次提交
  49. 27 2月, 2009 1 次提交
  51. 26 2月, 2009 6 次提交
    • I
      time: ntp: clean up second_overflow() · 39854fe8
      由 Ingo Molnar 提交于 
      Impact: cleanup, no functionality changed

The 'time_adj' local variable is named in a very confusing
way because it almost shadows the 'time_adjust' global
variable - which is used in this same function.

Rename it to 'delta' - to make them stand apart more clearly.

kernel/time/ntp.o:

   text	   data	    bss	    dec	    hex	filename
   2545	    114	    144	   2803	    af3	ntp.o.before
   2545	    114	    144	   2803	    af3	ntp.o.after

md5:
   1bf0b3be564512279ba7cee299d1d2be  ntp.o.before.asm
   1bf0b3be564512279ba7cee299d1d2be  ntp.o.after.asm
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      39854fe8
    • I
      time: ntp: simplify ntp_tick_adj calculations · 069569e0
      由 Ingo Molnar 提交于 
      Impact: micro-optimization

Convert the (internal) ntp_tick_adj value we store from unscaled
units to scaled units. This is a constant that we never modify,
so scaling it up once during bootup is enough - we dont have to
do it for every adjustment step.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      069569e0
    • I
      time: ntp: make 64-bit constants more robust · 2b9d1496
      由 Ingo Molnar 提交于 
      Impact: cleanup, no functionality changed

 - make PPM_SCALE an explicit s64 constant, to
   remove (s64) casts from usage sites.

kernel/time/ntp.o:

   text	   data	    bss	    dec	    hex	filename
   2536	    114	    136	   2786	    ae2	ntp.o.before
   2536	    114	    136	   2786	    ae2	ntp.o.after

md5:
   40a7728d1188aa18e83e21a81fa7b150  ntp.o.before.asm
   40a7728d1188aa18e83e21a81fa7b150  ntp.o.after.asm
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      2b9d1496
    • I
      time: ntp: refactor do_adjtimex() some more · e9629165
      由 Ingo Molnar 提交于 
      Impact: cleanup, no functionality changed

Further simplify do_adjtimex():

 - introduce the ntp_start_leap_timer() helper function
 - eliminate the goto adj_done complication
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      e9629165
    • I
      time: ntp: refactor do_adjtimex() · 80f22571
      由 Ingo Molnar 提交于 
      Impact: cleanup, no functionality changed

do_adjtimex() is currently a monster function with a maze of
branches. Refactor the txc->modes setting aspects of it into
two new helper functions:

	process_adj_status()
	process_adjtimex_modes()

kernel/time/ntp.o:

   text	   data	    bss	    dec	    hex	filename
   2512	    114	    136	   2762	    aca	ntp.o.before
   2512	    114	    136	   2762	    aca	ntp.o.after
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      80f22571
    • I
      time: ntp: fix bug in ntp_update_offset() & do_adjtimex() · 10dd31a7
      由 Ingo Molnar 提交于 
      Impact: change (fix) the way the NTP PLL seconds offset is initialized/tracked

Fix a bug and do a micro-optimization:

When PLL is enabled we do not reset time_reftime. If the PLL
was off for a long time (for example after bootup), this is
arguably the wrong thing to do.

We already had a hack for the common boot-time case in
ntp_update_offset(), in form of:

	if (unlikely(time_status & STA_FREQHOLD || time_reftime == 0))
 		secs = 0;

But the update delta should be reset later on too - not just when
the PLL is enabled for the first time after bootup.

So do it on !STA_PLL -> STA_PLL transitions.

This changes behavior, as previously if ntpd was disabled for
a long time and we restarted it, we'd run from that last update,
with a very large delta.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      10dd31a7