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    SubjectRe: 2.6.9-rc2-mm4 ps hang ?
    Badari Pulavarty <pbadari@us.ibm.com> wrote:
    >
    >
    > On Fri, 2004-10-01 at 16:49, Andrew Morton wrote:
    > > Badari Pulavarty <pbadari@us.ibm.com> wrote:
    > > >
    > > > Here is the full sysrq-t output.
    > >
    > > What's this guy up to?
    > ...
    > >
    > > Something is seriously screwed up if it's stuck in try_to_wake_up(). Tried
    > > generating a few extra traces?
    > >
    > > Then again, maybe we're missing an up_read() somewhere. hrm, I'll check.
    > >
    >
    > It reproduced again. I think this is the one causing all the troubles..
    >
    > db2fmcd D ffffffff80132e2a 0 10854 7636
    > (NOTLB)
    > 00000101bae85ef8 0000000000000002 0000020800000018 00000101d9ddd550
    > 0000000100000084 000001016d490e20 000001016d491158
    > 00000101d9ddd550
    > 0000000000000206 ffffffff801353cb
    > Call Trace:<ffffffff801353cb>{try_to_wake_up+971}
    > <ffffffff804455f0>{__down_write+128}
    > <ffffffff80125e6f>{sys32_mmap+143}
    > <ffffffff80124af1>{ia32_sysret+0}
    >
    > when I tried looking at /proc/10854 - it hung.

    OK, so maybe that CPU is spinning in try_to_wake_up(). Can you tell if one
    CPU is busy when this happens?

    Or you could try Peter's suggestion:

    --- 25/kernel/sched.c~a 2004-10-01 17:43:32.500700488 -0700
    +++ 25-akpm/kernel/sched.c 2004-10-01 17:43:34.754357880 -0700
    @@ -1606,7 +1606,7 @@ out_set_cpu:
    task_rq_unlock(rql, &flags);
    /* might preempt at this point */
    rql = task_rq_lock(p, &flags);
    - adjust_sched_timestamp(p, old_rq);
    +// adjust_sched_timestamp(p, old_rq);
    old_state = p->state;
    if (!(old_state & state))
    goto out;
    _
    -
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