[PATCH 04/10] m68k: fix livelock in uaccess

[Linus Torvalds]

On Sat, Feb 4, 2023 at 10:16 PM Finn Thain <fthain at linux-m68k.org> wrote:
>
> That could be a bug I was chasing back in 2021 but never found. The mmap
> stressors in stress-ng were triggering a crash on a Mac Quadras, though
> only rarely. Sometimes it would run all day without a failure.
>
> Last year when I started using GCC 12 to build the kernel, I saw the same
> workload fail again but the failure mode had become a silent hang/livelock
> instead of the oopses I got with GCC 6.
>
> When I press the NMI button after the livelock I always see
> do_page_fault() in the backtrace. So I've been testing your patch. I've
> been running the same stress-ng reproducer for about 12 hours now with no
> failures which looks promising.
>
> In case that stress-ng testing is of use:
> Tested-by: Finn Thain <fthain at linux-m68k.org>

Could you test the thing that Mark Rutland pointed to? He had an
actual test-case for this for the arm64 fixes some years ago.

See

   https://lore.kernel.org/all/Y9pD+TMP+%2FSyfeJm@FVFF77S0Q05N/

for his email with links to his old test-case?

                Linus