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    SubjectRe: linux-next-20110923: warning kernel/rcutree.c:1833
    On Fri, Sep 30, 2011 at 12:24:38PM -0700, Paul E. McKenney wrote:
    > +#ifdef CONFIG_PROVE_RCU
    > +
    > +/*
    > + * Test whether the current CPU is idle.
    > + */
    > +int rcu_is_cpu_idle(void)
    > +{
    > + return !rcu_dynticks_nesting;
    > +}

    Seems that's not used in the patch.

    > +
    > +#endif /* #ifdef CONFIG_PROVE_RCU */
    <snip>
    > +#ifdef CONFIG_PROVE_RCU
    > +
    > /**
    > - * rcu_irq_enter - inform RCU of entry to hard irq context
    > + * rcu_is_cpu_idle - see if RCU thinks that the current CPU is idle
    > *
    > - * If the CPU was idle with dynamic ticks active, this updates the
    > - * rdtp->dynticks to let the RCU handling know that the CPU is active.
    > + * If the current CPU is in its idle loop and is neither in an interrupt
    > + * or NMI handler, return true. The caller must have at least disabled
    > + * preemption.
    > */
    > -void rcu_irq_enter(void)
    > +int rcu_is_cpu_idle(void)
    > {
    > - rcu_exit_nohz();
    > + return (atomic_read(&__get_cpu_var(rcu_dynticks).dynticks) & 0x1) == 0;
    > }

    So that's not used in this patch but it's interesting for me
    to backport "rcu: Detect illegal rcu dereference in extended quiescent state".

    The above should be read from a preempt disabled section though
    (remember "rcu: Fix preempt-unsafe debug check of rcu extended quiescent state")

    Those functions should probably lay in a separate patch. But I don't mind
    much keeping the things as is and use these APIs in my next patches though.
    I'll just fix the preempt enabled thing above.


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