1. 25 9月, 2012 1 次提交
    • J
      time: Move update_vsyscall definitions to timekeeper_internal.h · 189374ae
      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
  2. 02 2月, 2012 1 次提交
  3. 19 12月, 2011 1 次提交
  4. 11 11月, 2011 1 次提交
    • J
      clocksource: Avoid selecting mult values that might overflow when adjusted · d65670a7
      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
  5. 22 7月, 2011 1 次提交
  6. 15 7月, 2011 1 次提交
  7. 14 7月, 2011 1 次提交
  8. 17 6月, 2011 1 次提交
    • T
      clocksource: Make watchdog robust vs. interruption · b5199515
      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
  9. 24 5月, 2011 1 次提交
  10. 19 5月, 2011 1 次提交
  11. 14 5月, 2011 1 次提交
  12. 22 2月, 2011 1 次提交
  13. 27 7月, 2010 2 次提交
  14. 10 5月, 2010 1 次提交
    • J
      clocksource: Add clocksource_register_hz/khz interface · d7e81c26
      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
  15. 05 2月, 2010 2 次提交
  16. 17 11月, 2009 1 次提交
    • L
      timekeeping: Fix clock_gettime vsyscall time warp · 0696b711
      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
  17. 14 11月, 2009 2 次提交
    • J
      nohz: Prevent clocksource wrapping during idle · 98962465
      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
      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
  18. 29 8月, 2009 1 次提交
    • T
      clocksource: Resolve cpu hotplug dead lock with TSC unstable · 7285dd7f
      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
  19. 15 8月, 2009 6 次提交
  20. 31 7月, 2009 1 次提交
  21. 02 5月, 2009 1 次提交
    • M
      clocksource: setup mult_orig in clocksource_enable() · a25cbd04
      Magnus Damm 提交于
      Setup clocksource mult_orig in clocksource_enable().
      
      Clocksource drivers can save power by using keeping the
      device clock disabled while the clocksource is unused.
      
      In practice this means that the enable() and disable()
      callbacks perform clk_enable() and clk_disable().
      
      The enable() callback may also use clk_get_rate() to get
      the clock rate from the clock framework. This information
      can then be used to calculate the shift and mult variables.
      
      Currently the mult_orig variable is setup from mult at
      registration time only. This is conflicting with the above
      case since the clock is disabled and the mult variable is
      not yet calculated at the time of registration.
      
      Moving the mult_orig setup code to clocksource_enable()
      allows us to both handle the common case with no enable()
      callback and the mult-changed-after-enable() case.
      
      [ Impact: allow dynamic clock source usage ]
      Signed-off-by: NMagnus Damm <damm@igel.co.jp>
      LKML-Reference: <20090501054546.8193.10688.sendpatchset@rx1.opensource.se>
      Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
      a25cbd04
  22. 22 4月, 2009 2 次提交
  23. 16 2月, 2009 1 次提交
    • P
      clocksource: allow usage independent of timekeeping.c · a038a353
      Patrick Ohly 提交于
      So far struct clocksource acted as the interface between time/timekeeping.c
      and hardware. This patch generalizes the concept so that a similar
      interface can also be used in other contexts. For that it introduces
      new structures and related functions *without* touching the existing
      struct clocksource.
      
      The reasons for adding these new structures to clocksource.[ch] are
      * the APIs are clearly related
      * struct clocksource could be cleaned up to use the new structs
      * avoids proliferation of files with similar names (timesource.h?
        timecounter.h?)
      
      As outlined in the discussion with John Stultz, this patch adds
      * struct cyclecounter: stateless API to hardware which counts clock cycles
      * struct timecounter: stateful utility code built on a cyclecounter which
        provides a nanosecond counter
      * only the function to read the nanosecond counter; deltas are used internally
        and not exposed to users of timecounter
      
      The code does no locking of the shared state. It must be called at least
      as often as the cycle counter wraps around to detect these wrap arounds.
      Both is the responsibility of the timecounter user.
      Acked-by: NJohn Stultz <johnstul@us.ibm.com>
      Signed-off-by: NPatrick Ohly <patrick.ohly@intel.com>
      Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      a038a353
  24. 21 8月, 2008 2 次提交
    • J
      clocksource: introduce CLOCK_MONOTONIC_RAW · 2d42244a
      John Stultz 提交于
      In talking with Josip Loncaric, and his work on clock synchronization (see
      btime.sf.net), he mentioned that for really close synchronization, it is
      useful to have access to "hardware time", that is a notion of time that is
      not in any way adjusted by the clock slewing done to keep close time sync.
      
      Part of the issue is if we are using the kernel's ntp adjusted
      representation of time in order to measure how we should correct time, we
      can run into what Paul McKenney aptly described as "Painting a road using
      the lines we're painting as the guide".
      
      I had been thinking of a similar problem, and was trying to come up with a
      way to give users access to a purely hardware based time representation
      that avoided users having to know the underlying frequency and mask values
      needed to deal with the wide variety of possible underlying hardware
      counters.
      
      My solution is to introduce CLOCK_MONOTONIC_RAW.  This exposes a
      nanosecond based time value, that increments starting at bootup and has no
      frequency adjustments made to it what so ever.
      
      The time is accessed from userspace via the posix_clock_gettime() syscall,
      passing CLOCK_MONOTONIC_RAW as the clock_id.
      Signed-off-by: NJohn Stultz <johnstul@us.ibm.com>
      Signed-off-by: NRoman Zippel <zippel@linux-m68k.org>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      2d42244a
    • J
      clocksource: keep track of original clocksource frequency · 1aa5dfb7
      John Stultz 提交于
      The clocksource frequency is represented by
      clocksource->mult/2^(clocksource->shift).  Currently, when NTP makes
      adjustments to the clock frequency, they are made directly to the mult
      value.
      
      This has the drawback that once changed, we cannot know what the orignal
      mult value was, or how much adjustment has been applied.
      
      This property causes problems in calculating proper ntp intervals when
      switching back and forth between clocksources.
      
      This patch separates the current mult value into a mult and mult_orig
      pair.  The mult_orig value stays constant, while the ntp clocksource
      adjustments are done only to the mult value.
      
      This allows for correct ntp interval calculation and additionally lays the
      groundwork for a new notion of time, what I'm calling the monotonic-raw
      time, which is introduced in a following patch.
      Signed-off-by: NJohn Stultz <johnstul@us.ibm.com>
      Signed-off-by: NRoman Zippel <zippel@linux-m68k.org>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      1aa5dfb7
  25. 01 5月, 2008 1 次提交
  26. 18 4月, 2008 1 次提交
  27. 30 1月, 2008 2 次提交
  28. 19 10月, 2007 1 次提交
  29. 21 7月, 2007 1 次提交