Re: [PATCH] mm: avoid blocking lock_page() in kcompactd

[Cong Wang]

On Thu, Jan 9, 2020 at 5:01 PM Cong Wang <xiyou.wangcong@xxxxxxxxx> wrote:
> I tried to dump the process stacks after we saw the hung task
> with /proc/X/stack (apparently sysrq is not an option for production),
> but I didn't find anything useful. I didn't see any other process
> hung in lock_page() either, all mm-related kernel threads were sleeping
> (non-D) at the time I debugged. So, it is possible there was some place
> missing a unlock_page() too, which is too late to debug after the hung
> task was reported.

Never mind. I found the process locking the page, /proc/X/stack apparently
fools me by hiding page fault stack. :-/