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    SubjectRe: [2.6.30-rc1] RCU detected CPU 1 stall
    On Fri, Apr 10, 2009 at 04:03:53PM +0100, Al Viro wrote:
    > On Fri, Apr 10, 2009 at 07:22:03AM -0700, Paul E. McKenney wrote:
    >
    > > Hmmmm... This indicates that CPU 1 was spinning in the kernel for
    > > a long time. At 250 HZ, 32,565 jiffies is 130 seconds, or just over
    > > two -minutes-. Ouch!!!
    > >
    > > The interrupt happened on the stalled CPU, so we know that interrupts
    > > were enabled. Because we have CONFIG_PREEMPT_NONE=y, there is no
    > > preemption, so preemption need not be disabled. This could be due
    > > to lock contention, or even a simple infinite loop.
    > >
    > > The timer interrupt (apic_timer_interrupt) occurred in either
    > > __bprm_mm_init(), __get_user_4(), count(), or do_execve(). There
    > > have been some recent changes around check_unsafe_exec() -- any
    > > possibility that these introduced excessive lock contention or
    > > an infinite loop? Ditto for the recent security fixes?
    >
    > Oh, joy... the loop in there is this:
    > for (t = next_thread(p); t != p; t = next_thread(t)) {
    > if (t->fs == p->fs)
    > n_fs++;
    > }
    > I find it hard to believe that it can take two minutes, though.

    Tetsuo, how many tasks did you have on this machine?

    Though I too find it hard to believe that there were enough to chew up
    two minutes. Maybe the list got corrupted so that it has a loop?

    Thanx, Paul


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