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    SubjectRe: [BUG] sched: clock wrap bug in 2.6.35-stable kills scheduling
    On 2012-06-25 12:38, Peter Zijlstra wrote:
    > On Mon, 2012-06-25 at 11:45 +0200, Peter Zijlstra wrote:
    >> On Sun, 2012-06-24 at 19:32 +0200, Thomas Lange wrote:
    >>> Bug was introduced in 2.6.35.12 and is still present in linux-2.6.35.y HEAD.
    >>
    >> Ok, so nobody cares about that.. what does something recent like 3.5-rc4
    >> do?

    I haven't tested yet. I will try to find the time to do that.

    >> If that's fixed, find the patch that fixes it. If not, we'll have a
    >> look.

    Commit fe44d62 removed the if-clause that caused the problem. Most likely, this
    solved the problem.

    >
    >
    > If anything, I think something like the below ought to cure things.

    I agree. Either we make sure that sched_clock() never wraps or if it wraps,
    that it wraps shortly after boot to catch problems early.

    >
    > ---
    > kernel/sched/clock.c | 2 +-
    > 1 file changed, 1 insertion(+), 1 deletion(-)
    >
    > diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c
    > index c685e31..a1a128a 100644
    > --- a/kernel/sched/clock.c
    > +++ b/kernel/sched/clock.c
    > @@ -74,7 +74,7 @@
    > */
    > unsigned long long __attribute__((weak)) sched_clock(void)
    > {
    > - return (unsigned long long)(jiffies - INITIAL_JIFFIES)
    > + return (unsigned long long)(get_jiffies_64() - INITIAL_JIFFIES)
    > * (NSEC_PER_SEC / HZ);
    > }
    > EXPORT_SYMBOL_GPL(sched_clock);

    /Thomas


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