Re: [Xen-devel] [PATCH v4 2/2] x86: add accessors for scratch cpu mask

[Jan Beulich <jbeulich@xxxxxxxx>]

On 28.02.2020 11:31, Roger Pau Monné wrote:
> On Fri, Feb 28, 2020 at 11:16:55AM +0100, Jan Beulich wrote:
>> On 28.02.2020 10:33, Roger Pau Monne wrote:
>>> +    /*
>>> +     * Due to reentrancy scratch cpumask cannot be used in IRQ, #MC or #NMI
>>> +     * context.
>>> +     */
>>> +    BUG_ON(in_irq() || in_mce_handler() || in_nmi_handler());
>>> +
>>> +    if ( use && unlikely(this_cpu(scratch_cpumask_use)) )
>>> +    {
>>> +        printk("scratch CPU mask already in use by %ps (%p)\n",
>>> +               this_cpu(scratch_cpumask_use), 
>>> this_cpu(scratch_cpumask_use));
>>
>> Why the raw %p as well? We don't do so elsewhere, I think. Yes,
>> it's debugging code only, but I wonder anyway.
> 
> I use addr2line to find the offending line, and it's much easier to do
> so if you have the address directly, rather than having to use nm in
> order to figure out the address of the symbol and then add the offset.
> 
> Maybe I'm missing some other way to do this more easily?

In such a case we may want to consider making %ps (and %pS)
print a hex presentation next to the decoded one, in debug
builds at least. Andrew, thoughts? (There may be cases where
this is not wanted, bit if we made this a debug mode only
feature, I think it wouldn't do too much harm.)

Jan

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