1. 19 6月, 2013 1 次提交
  2. 16 3月, 2013 2 次提交
  3. 22 2月, 2013 1 次提交
  4. 09 2月, 2013 1 次提交
    • P
      time, Fix setting of hardware clock in NTP code · 84e345e4
      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
  5. 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
  6. 16 3月, 2012 1 次提交
  7. 31 10月, 2011 1 次提交
  8. 21 9月, 2011 1 次提交
  9. 02 2月, 2011 1 次提交
  10. 31 1月, 2011 1 次提交
  11. 26 1月, 2011 1 次提交
  12. 29 11月, 2010 1 次提交
    • J
      Kill off a bunch of warning: ‘inline’ is not at beginning of declaration · fa9f90be
      Jesper Juhl 提交于
      These warnings are spewed during a build of a 'allnoconfig' kernel
      (especially the ones from u64_stats_sync.h show up a lot) when building
      with -Wextra (which I often do)..
      They are
        a) annoying
        b) easy to get rid of.
      This patch kills them off.
      
      include/linux/u64_stats_sync.h:70:1: warning: ‘inline’ is not at beginning of declaration
      include/linux/u64_stats_sync.h:77:1: warning: ‘inline’ is not at beginning of declaration
      include/linux/u64_stats_sync.h:84:1: warning: ‘inline’ is not at beginning of declaration
      include/linux/u64_stats_sync.h:96:1: warning: ‘inline’ is not at beginning of declaration
      include/linux/u64_stats_sync.h:115:1: warning: ‘inline’ is not at beginning of declaration
      include/linux/u64_stats_sync.h:127:1: warning: ‘inline’ is not at beginning of declaration
      kernel/time.c:241:1: warning: ‘inline’ is not at beginning of declaration
      kernel/time.c:257:1: warning: ‘inline’ is not at beginning of declaration
      kernel/perf_event.c:4513:1: warning: ‘inline’ is not at beginning of declaration
      mm/page_alloc.c:4012:1: warning: ‘inline’ is not at beginning of declaration
      Signed-off-by: NJesper Juhl <jj@chaosbits.net>
      Signed-off-by: NJiri Kosina <jkosina@suse.cz>
      fa9f90be
  13. 27 7月, 2010 1 次提交
  14. 24 5月, 2010 1 次提交
  15. 30 3月, 2010 1 次提交
    • T
      include cleanup: Update gfp.h and slab.h includes to prepare for breaking... · 5a0e3ad6
      Tejun Heo 提交于
      include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h
      
      percpu.h is included by sched.h and module.h and thus ends up being
      included when building most .c files.  percpu.h includes slab.h which
      in turn includes gfp.h making everything defined by the two files
      universally available and complicating inclusion dependencies.
      
      percpu.h -> slab.h dependency is about to be removed.  Prepare for
      this change by updating users of gfp and slab facilities include those
      headers directly instead of assuming availability.  As this conversion
      needs to touch large number of source files, the following script is
      used as the basis of conversion.
      
        http://userweb.kernel.org/~tj/misc/slabh-sweep.py
      
      The script does the followings.
      
      * Scan files for gfp and slab usages and update includes such that
        only the necessary includes are there.  ie. if only gfp is used,
        gfp.h, if slab is used, slab.h.
      
      * When the script inserts a new include, it looks at the include
        blocks and try to put the new include such that its order conforms
        to its surrounding.  It's put in the include block which contains
        core kernel includes, in the same order that the rest are ordered -
        alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
        doesn't seem to be any matching order.
      
      * If the script can't find a place to put a new include (mostly
        because the file doesn't have fitting include block), it prints out
        an error message indicating which .h file needs to be added to the
        file.
      
      The conversion was done in the following steps.
      
      1. The initial automatic conversion of all .c files updated slightly
         over 4000 files, deleting around 700 includes and adding ~480 gfp.h
         and ~3000 slab.h inclusions.  The script emitted errors for ~400
         files.
      
      2. Each error was manually checked.  Some didn't need the inclusion,
         some needed manual addition while adding it to implementation .h or
         embedding .c file was more appropriate for others.  This step added
         inclusions to around 150 files.
      
      3. The script was run again and the output was compared to the edits
         from #2 to make sure no file was left behind.
      
      4. Several build tests were done and a couple of problems were fixed.
         e.g. lib/decompress_*.c used malloc/free() wrappers around slab
         APIs requiring slab.h to be added manually.
      
      5. The script was run on all .h files but without automatically
         editing them as sprinkling gfp.h and slab.h inclusions around .h
         files could easily lead to inclusion dependency hell.  Most gfp.h
         inclusion directives were ignored as stuff from gfp.h was usually
         wildly available and often used in preprocessor macros.  Each
         slab.h inclusion directive was examined and added manually as
         necessary.
      
      6. percpu.h was updated not to include slab.h.
      
      7. Build test were done on the following configurations and failures
         were fixed.  CONFIG_GCOV_KERNEL was turned off for all tests (as my
         distributed build env didn't work with gcov compiles) and a few
         more options had to be turned off depending on archs to make things
         build (like ipr on powerpc/64 which failed due to missing writeq).
      
         * x86 and x86_64 UP and SMP allmodconfig and a custom test config.
         * powerpc and powerpc64 SMP allmodconfig
         * sparc and sparc64 SMP allmodconfig
         * ia64 SMP allmodconfig
         * s390 SMP allmodconfig
         * alpha SMP allmodconfig
         * um on x86_64 SMP allmodconfig
      
      8. percpu.h modifications were reverted so that it could be applied as
         a separate patch and serve as bisection point.
      
      Given the fact that I had only a couple of failures from tests on step
      6, I'm fairly confident about the coverage of this conversion patch.
      If there is a breakage, it's likely to be something in one of the arch
      headers which should be easily discoverable easily on most builds of
      the specific arch.
      Signed-off-by: NTejun Heo <tj@kernel.org>
      Guess-its-ok-by: NChristoph Lameter <cl@linux-foundation.org>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
      5a0e3ad6
  16. 13 3月, 2010 1 次提交
  17. 23 12月, 2009 1 次提交
    • L
      Revert "time: Remove xtime_cache" · 83f57a11
      Linus Torvalds 提交于
      This reverts commit 7bc7d637, as
      requested by John Stultz. Quoting John:
      
       "Petr Titěra reported an issue where he saw odd atime regressions with
        2.6.33 where there were a full second worth of nanoseconds in the
        nanoseconds field.
      
        He also reviewed the time code and narrowed down the problem: unhandled
        overflow of the nanosecond field caused by rounding up the
        sub-nanosecond accumulated time.
      
        Details:
      
         * At the end of update_wall_time(), we currently round up the
        sub-nanosecond portion of accumulated time when storing it into xtime.
        This was added to avoid time inconsistencies caused when the
        sub-nanosecond portion was truncated when storing into xtime.
        Unfortunately we don't handle the possible second overflow caused by
        that rounding.
      
         * Previously the xtime_cache code hid this overflow by normalizing the
        xtime value when storing into the xtime_cache.
      
         * We could try to handle the second overflow after the rounding up, but
        since this affects the timekeeping's internal state, this would further
        complicate the next accumulation cycle, causing small errors in ntp
        steering. As much as I'd like to get rid of it, the xtime_cache code is
        known to work.
      
         * The correct fix is really to include the sub-nanosecond portion in the
        timekeeping accessor function, so we don't need to round up at during
        accumulation. This would greatly simplify the accumulation code.
        Unfortunately, we can't do this safely until the last three
        non-GENERIC_TIME arches (sparc32, arm, cris) are converted  (those
        patches are in -mm) and we kill off the spots where arches set xtime
        directly. This is all 2.6.34 material, so I think reverting the
        xtime_cache change is the best approach for now.
      
        Many thanks to Petr for both reporting and finding the issue!"
      Reported-by: NPetr Titěra <P.Titera@century.cz>
      Requested-by: Njohn stultz <johnstul@us.ibm.com>
      Cc: Ingo Molnar <mingo@elte.hu>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      83f57a11
  18. 26 11月, 2009 1 次提交
    • H
      sched, time: Define nsecs_to_jiffies() · b7b20df9
      Hidetoshi Seto 提交于
      Use of msecs_to_jiffies() for nsecs_to_cputime() have some
      problems:
      
       - The type of msecs_to_jiffies()'s argument is unsigned int, so
         it cannot convert msecs greater than UINT_MAX = about 49.7 days.
      
       - msecs_to_jiffies() returns MAX_JIFFY_OFFSET if MSB of argument
         is set, assuming that input was negative value.  So it cannot
         convert msecs greater than INT_MAX = about 24.8 days too.
      
      This patch defines a new function nsecs_to_jiffies() that can
      deal greater values, and that can deal all incoming values as
      unsigned.
      Signed-off-by: NHidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
      Acked-by: NPeter Zijlstra <peterz@infradead.org>
      Cc: Stanislaw Gruszka <sgruszka@redhat.com>
      Cc: Spencer Candland <spencer@bluehost.com>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Cc: Balbir Singh <balbir@in.ibm.com>
      Cc: Amrico Wang <xiyou.wangcong@gmail.com>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: John Stultz <johnstul@linux.vnet.ibm.com>
      LKML-Reference: <4B0E16E7.5070307@jp.fujitsu.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      b7b20df9
  19. 05 10月, 2009 1 次提交
    • J
      time: Remove xtime_cache · 7bc7d637
      john stultz 提交于
      With the prior logarithmic time accumulation patch, xtime will now
      always be within one "tick" of the current time, instead of
      possibly half a second off.
      
      This removes the need for the xtime_cache value, which always
      stored the time at the last interrupt, so this patch cleans that up
      removing the xtime_cache related code.
      
      This is a bit simpler, but still could use some wider testing.
      Signed-off-by: NJohn Stultz <johnstul@us.ibm.com>
      Acked-by: NThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: NJohn Kacur <jkacur@redhat.com>
      Cc: Clark Williams <williams@redhat.com>
      Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      LKML-Reference: <1254525855.7741.95.camel@localhost.localdomain>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      7bc7d637
  20. 15 9月, 2009 1 次提交
    • T
      time: Prevent 32 bit overflow with set_normalized_timespec() · 12e09337
      Thomas Gleixner 提交于
      set_normalized_timespec() nsec argument is of type long. The recent
      timekeeping changes of ktime_get_ts() feed 
      
      	ts->tv_nsec + tomono.tv_nsec + nsecs
      
      to set_normalized_timespec(). On 32 bit machines that sum can be
      larger than (1 << 31) and therefor result in a negative value which
      screws up the result completely.
      
      Make the nsec argument of set_normalized_timespec() s64 to fix the
      problem at hand. This also prevents similar problems for future users
      of set_normalized_timespec().
      Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
      Tested-by: NCarsten Emde <carsten.emde@osadl.org>
      LKML-Reference: <new-submission>
      Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
      Cc: John Stultz <johnstul@us.ibm.com>
      12e09337
  21. 14 1月, 2009 1 次提交
  22. 07 1月, 2009 1 次提交
    • P
      Allow times and time system calls to return small negative values · e3d5a27d
      Paul Mackerras 提交于
      At the moment, the times() system call will appear to fail for a period
      shortly after boot, while the value it want to return is between -4095 and
      -1.  The same thing will also happen for the time() system call on 32-bit
      platforms some time in 2106 or so.
      
      On some platforms, such as x86, this is unavoidable because of the system
      call ABI, but other platforms such as powerpc have a separate error
      indication from the return value, so system calls can in fact return small
      negative values without indicating an error.  On those platforms,
      force_successful_syscall_return() provides a way to indicate that the
      system call return value should not be treated as an error even if it is
      in the range which would normally be taken as a negative error number.
      
      This adds a force_successful_syscall_return() call to the time() and
      times() system calls plus their 32-bit compat versions, so that they don't
      erroneously indicate an error on those platforms whose system call ABI has
      a separate error indication.  This will not affect anything on other
      platforms.
      
      Joakim Tjernlund added the fix for time() and the compat versions of
      time() and times(), after I did the fix for times().
      Signed-off-by: NJoakim Tjernlund <Joakim.Tjernlund@transmode.se>
      Signed-off-by: NPaul Mackerras <paulus@samba.org>
      Acked-by: NDavid S. Miller <davem@davemloft.net>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      e3d5a27d
  23. 06 9月, 2008 1 次提交
  24. 03 5月, 2008 1 次提交
    • H
      Make constants in kernel/timeconst.h fixed 64 bits · b9095fd8
      H. Peter Anvin 提交于
      Force constants in kernel/timeconst.h (except shift counts) to be 64 bits,
      using U64_C() constructor macros, and eliminate constants that cannot
      be represented at all in 64 bits.  This avoids warnings with some gcc
      versions.
      
      Drop generating 64-bit constants, since we have no real hope of
      getting a full set (operation on 64-bit values requires a 128-bit
      intermediate result, which gcc only supports on 64-bit platforms, and
      only with libgcc support on some.)  Note that the use of these
      constants does not depend on if we are on a 32- or 64-bit architecture.
      
      This resolves Bugzilla 10153.
      Signed-off-by: NH. Peter Anvin <hpa@zytor.com>
      b9095fd8
  25. 01 5月, 2008 2 次提交
  26. 29 4月, 2008 1 次提交
  27. 22 4月, 2008 1 次提交
  28. 09 2月, 2008 2 次提交
    • H
      avoid overflows in kernel/time.c · bdc80787
      H. Peter Anvin 提交于
      When the conversion factor between jiffies and milli- or microseconds is
      not a single multiply or divide, as for the case of HZ == 300, we currently
      do a multiply followed by a divide.  The intervening result, however, is
      subject to overflows, especially since the fraction is not simplified (for
      HZ == 300, we multiply by 300 and divide by 1000).
      
      This is exposed to the user when passing a large timeout to poll(), for
      example.
      
      This patch replaces the multiply-divide with a reciprocal multiplication on
      32-bit platforms.  When the input is an unsigned long, there is no portable
      way to do this on 64-bit platforms there is no portable way to do this
      since it requires a 128-bit intermediate result (which gcc does support on
      64-bit platforms but may generate libgcc calls, e.g.  on 64-bit s390), but
      since the output is a 32-bit integer in the cases affected, just simplify
      the multiply-divide (*3/10 instead of *300/1000).
      
      The reciprocal multiply used can have off-by-one errors in the upper half
      of the valid output range.  This could be avoided at the expense of having
      to deal with a potential 65-bit intermediate result.  Since the intent is
      to avoid overflow problems and most of the other time conversions are only
      semiexact, the off-by-one errors were considered an acceptable tradeoff.
      
      At Ralf Baechle's suggestion, this version uses a Perl script to compute
      the necessary constants.  We already have dependencies on Perl for kernel
      compiles.  This does, however, require the Perl module Math::BigInt, which
      is included in the standard Perl distribution starting with version 5.8.0.
      In order to support older versions of Perl, include a table of canned
      constants in the script itself, and structure the script so that
      Math::BigInt isn't required if pulling values from said table.
      
      Running the script requires that the HZ value is available from the
      Makefile.  Thus, this patch also adds the Kconfig variable CONFIG_HZ to the
      architectures which didn't already have it (alpha, cris, frv, h8300, m32r,
      m68k, m68knommu, sparc, v850, and xtensa.) It does *not* touch the sh or
      sh64 architectures, since Paul Mundt has dealt with those separately in the
      sh tree.
      Signed-off-by: NH. Peter Anvin <hpa@zytor.com>
      Cc: Ralf Baechle <ralf@linux-mips.org>,
      Cc: Sam Ravnborg <sam@ravnborg.org>,
      Cc: Paul Mundt <lethal@linux-sh.org>,
      Cc: Richard Henderson <rth@twiddle.net>,
      Cc: Michael Starvik <starvik@axis.com>,
      Cc: David Howells <dhowells@redhat.com>,
      Cc: Yoshinori Sato <ysato@users.sourceforge.jp>,
      Cc: Hirokazu Takata <takata@linux-m32r.org>,
      Cc: Geert Uytterhoeven <geert@linux-m68k.org>,
      Cc: Roman Zippel <zippel@linux-m68k.org>,
      Cc: William L. Irwin <sparclinux@vger.kernel.org>,
      Cc: Chris Zankel <chris@zankel.net>,
      Cc: H. Peter Anvin <hpa@zytor.com>,
      Cc: Jan Engelhardt <jengelh@computergmbh.de>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      bdc80787
    • L
      time: fix typo in comments · 3eb05676
      Li Zefan 提交于
      Fix typo in comments.
      
      BTW: I have to fix coding style in arch/ia64/kernel/time.c also, otherwise
      checkpatch.pl will be complaining.
      Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: john stultz <johnstul@us.ibm.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      3eb05676
  29. 07 2月, 2008 2 次提交
  30. 02 2月, 2008 1 次提交
  31. 19 10月, 2007 2 次提交
  32. 17 10月, 2007 2 次提交
    • J
      Clean up duplicate includes in kernel/ · a9022e9c
      Jesper Juhl 提交于
      This patch cleans up duplicate includes in
      	kernel/
      Signed-off-by: NJesper Juhl <jesper.juhl@gmail.com>
      Acked-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      Reviewed-by: NSatyam Sharma <ssatyam@cse.iitk.ac.in>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      a9022e9c
    • I
      time: introduce xtime_seconds · f20bf612
      Ingo Molnar 提交于
      improve performance of sys_time(). sys_time() returns time in seconds,
      but it does so by calling do_gettimeofday() and then returning the
      tv_sec portion of the GTOD time. But the data structure "xtime", which
      is updated by every timer/scheduler tick, already offers HZ granularity
      time.
      
      the patch improves the sysbench oltp macrobenchmark by 4-5% on an AMD
      dual-core system:
      
      v2.6.23:
      
      #threads
      
         1:     transactions:                        4073   (407.23 per sec.)
         2:     transactions:                        8530   (852.81 per sec.)
         3:     transactions:                        8321   (831.88 per sec.)
         4:     transactions:                        8407   (840.58 per sec.)
         5:     transactions:                        8070   (806.74 per sec.)
      
      v2.6.23 + sys_time-speedup.patch:
      
         1:     transactions:                        4281   (428.09 per sec.)
         2:     transactions:                        8910   (890.85 per sec.)
         3:     transactions:                        8659   (865.79 per sec.)
         4:     transactions:                        8676   (867.34 per sec.)
         5:     transactions:                        8532   (852.91 per sec.)
      
      and by 4-5% on an Intel dual-core system too:
      
      2.6.23:
      
        1:     transactions:                        4560   (455.94 per sec.)
        2:     transactions:                        10094  (1009.30 per sec.)
        3:     transactions:                        9755   (975.36 per sec.)
        4:     transactions:                        9859   (985.78 per sec.)
        5:     transactions:                        9701   (969.72 per sec.)
      
      2.6.23 + sys_time-speedup.patch:
      
        1:     transactions:                        4779   (477.84 per sec.)
        2:     transactions:                        10103  (1010.14 per sec.)
        3:     transactions:                        10141  (1013.93 per sec.)
        4:     transactions:                        10371  (1036.89 per sec.)
        5:     transactions:                        10178  (1017.50 per sec.)
      
      (the more CPUs the system has, the more speedup this patch gives for
      this particular workload.)
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      f20bf612
  33. 26 7月, 2007 1 次提交
    • J
      Cleanup non-arch xtime uses, use get_seconds() or current_kernel_time(). · 2c6b47de
      john stultz 提交于
      This avoids use of the kernel-internal "xtime" variable directly outside
      of the actual time-related functions.  Instead, use the helper functions
      that we already have available to us.
      
      This doesn't actually change any behaviour, but this will allow us to
      fix the fact that "xtime" isn't updated very often with CONFIG_NO_HZ
      (because much of the realtime information is maintained as separate
      offsets to 'xtime'), which has caused interfaces that use xtime directly
      to get a time that is out of sync with the real-time clock by up to a
      third of a second or so.
      Signed-off-by: NJohn Stultz <johnstul@us.ibm.com>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      2c6b47de
  34. 21 7月, 2007 1 次提交
    • L
      Revert "sys_time() speedup" · 20082208
      Linus Torvalds 提交于
      This basically reverts commit 4e44f349,
      while waiting for it to be re-done more completely.  There are cases of
      people mixing "time()" with higher-resolution time sources, and we need
      to take the nanosecond offsets into account.
      
      Ingo has a patch that does that, but it's still under some discussion.
      In the meantime, just revert back to the old simple situation of just
      doing the whole exact timesource calculations.
      
      But rather than using do_gettimeofday(), use the internal nanosecond
      resolution getnstimeofday(), which at least avoids one unnecessary
      conversion (since we really don't care about whether the fractional
      seconds are nanoseconds or microseconds - we'll just throw them away).
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      20082208