Re: [PATCH V8 1/4] perf/core: Add PERF_SAMPLE_DATA_PAGE_SIZE

[Dave Hansen]

On 9/30/20 12:15 AM, Stephane Eranian wrote:
>> +       /*
>> +        * Software page-table walkers must disable IRQs,
>> +        * which prevents any tear down of the page tables.
>> +        */
>> +       local_irq_save(flags);
>> +
>> +       size = __perf_get_page_size(current->active_mm, addr);
>> +
> When I tested on my kernel, it panicked because I suspect
> current->active_mm could be NULL. Adding a check for NULL avoided the
> problem. But I suspect this is not the correct solution.

Did you happen to capture the oops?  I can _imagine_ scenarios where
current->active_mm could be NULL, I just can't find any obvious ones in
the code.