Re: [Xen-devel] Assertion 'cpu < nr_cpu_ids' failed at .../src/new/xen-unstable/xen/include/xen/cpumask.h:97

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 23.02.15 at 10:27, <linux@xxxxxxxxxxxxxx> wrote:
> While shutting down all guests to go for a host reboot i encountered the 
> splat below.
> This was running on Xen with:
> xen_changeset: Fri Feb 20 16:21:10 2015 +0100 git:24b2b8d-dirty

"-dirty" meaning what?

> (XEN) [2015-02-23 09:16:26.292] Assertion 'cpu < nr_cpu_ids' failed at 
> .../src/new/xen-unstable/xen/include/xen/cpumask.h:97

Since with debug=y the callstack entries should be reliable, I can't
see how this matches up with ...

> (XEN) [2015-02-23 09:16:26.292] Xen call trace:
> (XEN) [2015-02-23 09:16:26.292]    [<ffff82d08012c018>] 
> cpu_raise_softirq+0xd7/0xeb

... this, since

void cpu_raise_softirq(unsigned int cpu, unsigned int nr)
{
    unsigned int this_cpu = smp_processor_id();

    if ( test_and_set_bit(nr, &softirq_pending(cpu))
         || (cpu == this_cpu)
         || arch_skip_send_event_check(cpu) )
        return;

    if ( !per_cpu(batching, this_cpu) || in_irq() )
        smp_send_event_check_cpu(cpu);
    else
        set_bit(nr, &per_cpu(batch_mask, this_cpu));
}

doesn't indicate any use of cpumask functions. If, however,
arch_skip_send_event_check()'s call to cpumask_test_cpu()
didn't get inlined, that might be the cause. Albeit that would mean
smp_processor_id() returned an out-of-range value... In any
event we'll need to know what exactly above code location refers
to inside the entire function.

Jan


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