On Tue, Apr 10, 2018 at 01:10:01PM +0200, Michal Hocko wrote: > > > > Because do_brk does vma manipulations, for this reason it's > > running under down_write_killable(&mm->mmap_sem). Or you > > mean something else? > > Yes, all we need the new lock for is to get a consistent view on brk > values. I am simply asking whether there is something fundamentally > wrong by doing the update inside the new lock while keeping the original > mmap_sem locking in the brk path. That would allow us to drop the > mmap_sem lock in the proc path when looking at brk values.
Michal gimme some time. I guess we might do so, but I need some spare time to take more precise look into the code, hopefully today evening. Also I've a suspicion that we've wracked check_data_rlimit with this new lock in prctl. Need to verify it again.