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. :-/
