[Bug 202149] New: NULL Pointer Dereference in __split_huge_pmd on PPC64LE

[Matt Corallo]

It's normal daily usage on a workstation (TALOS 2). I've seen it at least twice, both times in rustc, though I've run rustc more times than I can count. Note that the program that triggered it was running in lxc and it only happened after upgrading to 4.19.

> On Jan 9, 2019, at 06:50, Aneesh Kumar K.V <aneesh.kumar at linux.ibm.com> wrote:
> 
> Matt Corallo <kernel at bluematt.me> writes:
> 
>> .config follows. I have not tested with 64K pages as, sadly, I have a 
>> large BTRFS volume that was formatted on x86, and am thus stuck with 4K 
>> pages. Note that this is roughly the Debian kernel, so it has whatever 
>> patches Debian defaults to applying, a list of which follows.
>> 
> 
> What is the test you are running? I tried a 4K page size config on P9. I
> am running ltp test suite there. Also tried few thp memremap tests.
> Nothing hit that.
> 
> root@:~/tests/ltp/testcases/kernel/mem/thp# getconf  PAGESIZE
> 4096
> root at ltc-boston123:~/tests/ltp/testcases/kernel/mem/thp# grep thp /proc/vmstat 
> thp_fault_alloc 641141
> thp_fault_fallback 0
> thp_collapse_alloc 90
> thp_collapse_alloc_failed 0
> thp_file_alloc 0
> thp_file_mapped 0
> thp_split_page 1
> thp_split_page_failed 0
> thp_deferred_split_page 641150
> thp_split_pmd 24
> thp_zero_page_alloc 1
> thp_zero_page_alloc_failed 0
> thp_swpout 0
> thp_swpout_fallback 0
> root@:~/tests/ltp/testcases/kernel/mem/thp# 
> 
> -aneesh
>