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    SubjectRe: 2.6.16-rc2 powerpc timestamp skew
    Date
    Benjamin Herrenschmidt <benh@kernel.crashing.org> writes:

    > On Sun, 2006-02-12 at 17:13 +0000, Roger Leigh wrote:
    >> Hi folks,
    >>
    >> When running a 2.6.16-rc2 kernel on a powerpc system (Mac Mini;
    >> Freescale 7447A):
    >>
    >> $ date && touch f && ls -l f && rm -f f && date
    >> Sun Feb 12 12:20:14 GMT 2006
    >> -rw-r--r-- 1 rleigh rleigh 0 2006-02-12 12:23
    >> Sun Feb 12 12:20:14 GMT 2006
    >>
    >> Notice the timestamp is 3 minutes in the future compared with the
    >> system time. "make" is not a very happy bunny running on this kernel
    >> due to every touched file being 3 minutes in the future.
    >>
    >> When the same command is run on 2.6.15.3:
    >>
    >> $ date && touch f && ls -l f && rm -f f && date
    >> Sun Feb 12 14:27:27 GMT 2006
    >> -rw-r--r-- 1 rleigh rleigh 0 2006-02-12 14:27
    >> Sun Feb 12 14:27:27 GMT 2006
    >>
    >> In this case the times are identical, as you would expect.
    >>
    >> In both these cases, the chrony NTP daemon is running, if that might
    >> be a problem.
    >
    > Can you strace vs. ltrace and see if the gettimeofday or clock_gettime
    > syscalls are ever called ?

    | strace | ltrace
    -----------+---------------+------------------------------------
    2.6.15 | |
    date | clock_gettime | clock_gettime -> SYS_clock_gettime,
    | | localtime, strftime
    touch | utimes | futimes -> SYS_utimes
    | |
    2.6.16-rc2 | |
    date | clock_gettime | clock_gettime -> SYS_clock_gettime,
    | | localtime, strftime
    touch | utimes | futimes -> SYS_utimes

    [clock_gettime(CLOCK_REALTIME, {1139826613, 157402000}) = 0]

    > I wonder if you have a glibc new enough to
    > use the vDSO to obtain the time or if it's using the syscall... The vDSO
    > on ppc32 is very new.

    It's glibc 2.3.5 (Debian libc6 2.3.5-13).

    > Also, are your kernels built with ARCH=ppc or ARCH=powerpc ?

    ppc.


    Thanks,
    Roger

    --
    Roger Leigh
    Printing on GNU/Linux? http://gutenprint.sourceforge.net/
    Debian GNU/Linux http://www.debian.org/
    GPG Public Key: 0x25BFB848. Please sign and encrypt your mail.
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