lkml.org 
[lkml]   [2007]   [Mar]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [BUG 2.6.21-rc2] divide error: 0000
    On Fri, Mar 02, 2007 at 10:19:17AM +0100, Thomas Gleixner wrote:
    > On Fri, 2007-03-02 at 07:11 +0100, Willy Tarreau wrote:
    > > > Call Trace:
    > > > [<c0127d49>] posix_cpu_clock_get+0x47/0xdc
    > > > [<c0125bf3>] sys_clock_gettime+0x80/0x82
    > > > [<c0103bfc>] syscall_call+0x7/0xb
    > > > [<c02f0000>] svc_ioctl+0xc2/0x261
    > > > =======================
    > > > Code: 0b eb fe 57 56 53 89 cb 89 d1 8b 74 24 10 83 e0 03 83 f8 02 74 0c 89 f2 89 c8 5b 5e 5f e9 ee 3f ff ff bf 00 ca 9a 3b 89 d0 89 da <f7> f7 89 56 04 89 06 5b 5e 5f c3 55 57 56 53 89 c7 89 d6 89 cb
    > > > EIP: [<c0126a07>] sample_to_timespec+0x28/0x33 SS:ESP 0068:d4a56f74
    > > >
    > > > The instruction is:
    > > >
    > > > div %edi
    > > >
    > > > And edi is 1e9 (0x3b9aca00). I don't understand why this results in an
    > > > divide error.
    > >
    > > It does this because 'div' does an unsigned divide of edx:eax by edi.
    > > Here, edx=fffffffa and eax is 63b5a669. Clearly, such a number cannot
    > > be divided by 1e9 to return a 32 bits value.
    > >
    > > Given the values we see here, I suspect the code should have used an
    > > integer divide (idiv). This means that something in the code implies
    > > that the result is unsigned while it should be signed.
    >
    > The question is why do we have this negative value in the dividend. I
    > suspect this is related to
    >
    > http://marc.theaimsgroup.com/?l=linux-kernel&m=117210430112543&w=2
    >
    > Sean, can you please retest with that patch applied, which hit mainline
    > after 2.6.21-rc2

    Yup, this fixes it. And clock_gettime(CLOCK_THREAD_CPUTIME_ID) returns
    nice high resolution times. :)

    Thanks
    Sean
    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2007-03-02 10:41    [W:0.020 / U:118.588 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site