Re: [RFC PATCH] mm: silence soft lockups from unlock_page

[Michal Hocko]

On Tue 21-07-20 07:44:07, Qian Cai wrote:
> 
> 
> > On Jul 21, 2020, at 7:25 AM, Michal Hocko <mhocko@xxxxxxxxxx> wrote:
> > 
> > Are these really important? I believe I can dig that out from the bug
> > report but I didn't really consider that important enough.
> 
> Please dig them out. We have also been running those things on
> âlargeâ powerpc as well and never saw such soft-lockups. Those
> details may give us some clues about the actual problem.

I strongly suspect this is not really relevant but just FYI this is
16Node, 11.9TB with 1536CPUs system.

> Once we
> understand the problem better, we may judge if this âhackâ is
> really worth it.

I do not have access to the machine so I can only judge from the boot
log I have in hands. And from that it is pretty clear that 
$ grep BUG tmp/attachment.txt | wc -l
896

$ grep BUG tmp/attachment.txt | grep "\[systemd" | wc -l
860

$ grep do_fault+0x448 tmp/attachment.txt | wc -l
860

that the boot struggles, lockups happen from udev workers and most of
them are stuck at the very same place which is unlock_page. The rest is
a part of the changelog.
-- 
Michal Hocko
SUSE Labs