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    SubjectRe: [PATCH] [12/58] x86_64: Add vDSO for x86-64 with gettimeofday/clock_gettime/getcpu
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    On Thu, 2007-07-19 at 11:54 +0200, Andi Kleen wrote:
    > +
    > +static noinline int do_realtime(struct timespec *ts)
    > +{
    > + unsigned long seq, ns;
    > + do {
    > + seq = read_seqbegin(&gtod->lock);
    > + ts->tv_sec = gtod->wall_time_sec;
    > + ts->tv_nsec = gtod->wall_time_nsec;
    > + ns = vgetns();
    > + } while (unlikely(read_seqretry(&gtod->lock, seq)));
    > + timespec_add_ns(ts, ns);
    > + return 0;
    > +}

    Some thoughts ,

    In the -mm kernel there is some debugging that gets injected into the
    likely/unlikely macros .. If they get called from userspace it causes a
    hang .. We might want to add some new set of macros to specifically
    denote that they are called from userspace, not just likely/unlikely but
    all the macros so we don't get mixed usage ..

    Daniel

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