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  1. 24 7月, 2014 1 次提交
  3. 21 5月, 2014 1 次提交
  5. 31 7月, 2013 1 次提交
  7. 05 7月, 2013 1 次提交
    • T
      clocksource: Reselect clocksource when watchdog validated high-res capability · 332962f2
      由 Thomas Gleixner 提交于 
      Up to commit 5d33b883 (clocksource: Always verify highres capability)
we had no sanity check when selecting a clocksource, which prevented
that a non highres capable clocksource is used when the system already
switched to highres/nohz mode.

The new sanity check works as Alex and Tim found out. It prevents the
TSC from being used. This happens because on x86 the boot process
looks like this:

 tsc_start_freqency_validation(TSC);
 clocksource_register(HPET);
 clocksource_done_booting();
	clocksource_select()
		Selects HPET which is valid for high-res

 switch_to_highres();

 clocksource_register(TSC);
 	TSC is not selected, because it is not yet
	flagged as VALID_HIGH_RES

 clocksource_watchdog()
	Validates TSC for highres, but that does not make TSC
	the current clocksource.

Before the sanity check was added, we installed TSC unvalidated which
worked most of the time. If the TSC was really detected as unstable,
then the unstable logic removed it and installed HPET again.

The sanity check is correct and needed. So the watchdog needs to kick
a reselection of the clocksource, when it qualifies TSC as a valid
high res clocksource.

To solve this, we mark the clocksource which got the flag
CLOCK_SOURCE_VALID_FOR_HRES set by the watchdog with an new flag
CLOCK_SOURCE_RESELECT and trigger the watchdog thread. The watchdog
thread evaluates the flag and invokes clocksource_select() when set.

To avoid that the clocksource_done_booting() code, which is about to
install the first real clocksource anyway, needs to go through
clocksource_select and tick_oneshot_notify() pointlessly, split out
the clocksource_watchdog_kthread() list walk code and invoke the
select/notify only when called from clocksource_watchdog_kthread().

So clocksource_done_booting() can utilize the same splitout code
without the select/notify invocation and the clocksource_mutex
unlock/relock dance.
Reported-and-tested-by: NAlex Shi <alex.shi@intel.com>
Cc: Hans Peter Anvin <hpa@linux.intel.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Andi Kleen <andi.kleen@intel.com>
Tested-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: John Stultz <john.stultz@linaro.org>
Link: http://lkml.kernel.org/r/alpine.DEB.2.02.1307042239150.11637@ionos.tec.linutronix.deSigned-off-by: NThomas Gleixner <tglx@linutronix.de>
      332962f2
  9. 16 5月, 2013 3 次提交
  11. 28 3月, 2013 1 次提交
  13. 20 3月, 2013 1 次提交
  15. 16 3月, 2013 1 次提交
  17. 11 3月, 2013 1 次提交
  19. 01 2月, 2013 1 次提交
  21. 03 1月, 2013 1 次提交
    • S
      clocksource: add common of_clksrc_init() function · ae278a93
      由 Stephen Warren 提交于 
      It is desirable to move all clocksource drivers to drivers/clocksource,
yet each requires its own initialization function. We'd rather not
pollute <linux/> with a header for each function. Instead, create a
single of_clksrc_init() function which will determine which clocksource
driver to initialize based on device tree.

Based on a similar patch for drivers/irqchip by Thomas Petazzoni.
Signed-off-by: NStephen Warren <swarren@nvidia.com>
      ae278a93
  23. 25 9月, 2012 1 次提交
    • J
      time: Move update_vsyscall definitions to timekeeper_internal.h · 189374ae
      由 John Stultz 提交于 
      Since users will need to include timekeeper_internal.h, move
update_vsyscall definitions to timekeeper_internal.h.

Cc: Tony Luck <tony.luck@intel.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Paul Turner <pjt@google.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: NJohn Stultz <john.stultz@linaro.org>
      189374ae
  25. 02 2月, 2012 1 次提交
  27. 19 12月, 2011 1 次提交
  29. 11 11月, 2011 1 次提交
    • J
      clocksource: Avoid selecting mult values that might overflow when adjusted · d65670a7
      由 John Stultz 提交于 
      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 <yong.zhang0@gmail.com>
CC: David Daney <ddaney.cavm@gmail.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Chen Jie <chenj@lemote.com>
CC: zhangfx <zhangfx@lemote.com>
CC: stable@kernel.org
Reported-by: NChen Jie <chenj@lemote.com>
Reported-by: Nzhangfx <zhangfx@lemote.com>
Tested-by: NYong Zhang <yong.zhang0@gmail.com>
Signed-off-by: NJohn Stultz <john.stultz@linaro.org>
      d65670a7
  31. 22 7月, 2011 1 次提交
  33. 15 7月, 2011 1 次提交
  35. 14 7月, 2011 1 次提交
  37. 17 6月, 2011 1 次提交
    • T
      clocksource: Make watchdog robust vs. interruption · b5199515
      由 Thomas Gleixner 提交于 
      The clocksource watchdog code is interruptible and it has been
observed that this can trigger false positives which disable the TSC.

The reason is that an interrupt storm or a long running interrupt
handler between the read of the watchdog source and the read of the
TSC brings the two far enough apart that the delta is larger than the
unstable treshold. Move both reads into a short interrupt disabled
region to avoid that.
Reported-and-tested-by: NVernon Mauery <vernux@us.ibm.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: stable@kernel.org
      b5199515
  39. 24 5月, 2011 1 次提交
  41. 19 5月, 2011 1 次提交
  43. 14 5月, 2011 1 次提交
  45. 22 2月, 2011 1 次提交
  47. 27 7月, 2010 2 次提交
  49. 10 5月, 2010 1 次提交
    • J
      clocksource: Add clocksource_register_hz/khz interface · d7e81c26
      由 John Stultz 提交于 
      How to pick good mult/shift pairs has always been difficult to
describe to folks writing clocksource drivers, since it requires
careful tradeoffs in adjustment accuracy vs overflow limits.

Now, with the clocks_calc_mult_shift function, its much
easier. However, not many clocksources have converted to using that
function, and there is still the issue of the max interval length
assumption being made by each clocksource driver independently.

So this patch simplifies the registration process by having
clocksources be registered with a hz/khz value and the registration
function taking care of setting mult/shift.

This should take most of the confusion out of writing a clocksource
driver.

Additionally it also keeps the shift size tradeoff (more accuracy vs
longer possible nohz times) centralized so the timekeeping core can
keep track of the assumptions being made.

[ tglx: Coding style and comments fixed ]
Signed-off-by: NJohn Stultz <johnstul@us.ibm.com>
LKML-Reference: <1273280858-30143-1-git-send-email-johnstul@us.ibm.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
      d7e81c26
  51. 05 2月, 2010 2 次提交
  53. 17 11月, 2009 1 次提交
    • L
      timekeeping: Fix clock_gettime vsyscall time warp · 0696b711
      由 Lin Ming 提交于 
      Since commit 0a544198 "timekeeping: Move NTP adjusted clock multiplier
to struct timekeeper" the clock multiplier of vsyscall is updated with
the unmodified clock multiplier of the clock source and not with the
NTP adjusted multiplier of the timekeeper.

This causes user space observerable time warps:
new CLOCK-warp maximum: 120 nsecs,  00000025c337c537 -> 00000025c337c4bf

Add a new argument "mult" to update_vsyscall() and hand in the
timekeeping internal NTP adjusted multiplier.
Signed-off-by: NLin Ming <ming.m.lin@intel.com>
Cc: "Zhang Yanmin" <yanmin_zhang@linux.intel.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Tony Luck <tony.luck@intel.com>
LKML-Reference: <1258436990.17765.83.camel@minggr.sh.intel.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
      0696b711
  55. 14 11月, 2009 2 次提交
    • J
      nohz: Prevent clocksource wrapping during idle · 98962465
      由 Jon Hunter 提交于 
      The dynamic tick allows the kernel to sleep for periods longer than a
single tick, but it does not limit the sleep time currently. In the
worst case the kernel could sleep longer than the wrap around time of
the time keeping clock source which would result in losing track of
time.

Prevent this by limiting it to the safe maximum sleep time of the
current time keeping clock source. The value is calculated when the
clock source is registered.

[ tglx: simplified the code a bit and massaged the commit msg ]
Signed-off-by: NJon Hunter <jon-hunter@ti.com>
Cc: John Stultz <johnstul@us.ibm.com>
LKML-Reference: <1250617512-23567-2-git-send-email-jon-hunter@ti.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
      98962465
    • T
      clocksource: Provide a generic mult/shift factor calculation · 7d2f944a
      由 Thomas Gleixner 提交于 
      MIPS has two functions to calculcate the mult/shift factors for clock
sources and clock events at run time. ARM needs such functions as
well.

Implement a function which calculates the mult/shift factors based on
the frequencies to which and from which is converted. The function
also has a parameter to specify the minimum conversion range in
seconds. This range is guaranteed not to produce a 64bit overflow when
a value is multiplied with the calculated mult factor. The larger the
conversion range the less becomes the conversion accuracy.

Provide two inline wrappers which handle clock events and clock
sources. For clock events the "from" frequency is nano seconds per
second which corresponds to 1GHz and "to" is the device frequency. For
clock sources "from" is the device frequency and "to" is nano seconds
per second.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Tested-by: NMikael Pettersson <mikpe@it.uu.se>
Acked-by: NRalf Baechle <ralf@linux-mips.org>
Acked-by: NLinus Walleij <linus.walleij@stericsson.com>
Cc: John Stultz <johnstul@us.ibm.com>
LKML-Reference: <20091111134229.766673305@linutronix.de>
      7d2f944a
  57. 29 8月, 2009 1 次提交
    • T
      clocksource: Resolve cpu hotplug dead lock with TSC unstable · 7285dd7f
      由 Thomas Gleixner 提交于 
      Martin Schwidefsky analyzed it:
To register a clocksource the clocksource_mutex is acquired and if
necessary timekeeping_notify is called to install the clocksource as
the timekeeper clock. timekeeping_notify uses stop_machine which needs
to take cpu_add_remove_lock mutex.
Starting a new cpu is done with the cpu_add_remove_lock mutex held.
native_cpu_up checks the tsc of the new cpu and if the tsc is no good
clocksource_change_rating is called. Which needs the clocksource_mutex
and the deadlock is complete.

The solution is to replace the TSC via the clocksource watchdog
mechanism. Mark the TSC as unstable and schedule the watchdog work so
it gets removed in the watchdog thread context.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
LKML-Reference: <new-submission>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: John Stultz <johnstul@us.ibm.com>
      7285dd7f
  59. 15 8月, 2009 6 次提交