[PATCH v4 13/13] mm/debug_vm_pgtable: Avoid none pte in pte_clear_test

[Aneesh Kumar K.V]

Guenter Roeck <linux at roeck-us.net> writes:

> On Wed, Sep 02, 2020 at 05:12:22PM +0530, Aneesh Kumar K.V wrote:
>> pte_clear_tests operate on an existing pte entry. Make sure that
>> is not a none pte entry.
>> 
>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar at linux.ibm.com>
>
> This patch causes all riscv64 images to crash. Reverting it
> as well as the follow-up patch fixes the problem, but there are
> still several warning messages starting with
> 	BUG kmem_cache (Not tainted): Freechain corrupt
> I did not try to track down this other problem.
>
> A detailed crash log is at
> 	https://kerneltests.org/builders/qemu-riscv64-next/builds/523/steps/qemubuildcommand/logs/stdio
>
> Bisect log is attached.


https://lore.kernel.org/linux-mm/87zh5wx51b.fsf@linux.ibm.com

This was mentioned earlier. The RANDOM_OR_VALUE used is interacting with
some of the riscv page table accessors. 

-aneesh