Re: [PATCH 4/4] mm, oom: Fix unnecessary killing of additional processes.

On 2018/09/06 21:05, Michal Hocko wrote:

quoted

If you are too busy, please show "the point of no-blocking" using source code
instead. If such "the point of no-blocking" really exists, it can be executed
by allocating threads.

I would have to study this much deeper but I _suspect_ that we are not
taking any blocking locks right after we return from unmap_vmas. In
other words the place we used to have synchronization with the
oom_reaper in the past.

See commit 97b1255cb27c551d ("mm,oom_reaper: check for MMF_OOM_SKIP before
complaining"). Since this dependency is inode-based (i.e. irrelevant with
OOM victims), waiting for this lock can livelock.

So, where is safe "the point of no-blocking" ?