On Thu 06-09-18 22:40:24, Tetsuo Handa wrote:
> On 2018/09/06 21:05, Michal Hocko wrote:
> >> 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" ?
Ohh, right unlink_file_vma and its i_mmap_rwsem lock. As I've said I
have to think about that some more. Maybe we can split those into two parts.
--
Michal Hocko
SUSE Labs
