On Tue 27-03-18 02:20:39, Yang Shi wrote: [...] The patch looks reasonable to me. Maybe it would be better to be more explicit about the purpose of the patch. As others noticed, this alone wouldn't solve the mmap_sem contention issues. I _think_ that if you were more explicit about the mmap_sem abuse it would trigger less questions. I have just one more question. Now that you are touching this area, would you be willing to remove the following ugliness? > diff --git a/kernel/sys.c b/kernel/sys.c > index f2289de..17bddd2 100644 > --- a/kernel/sys.c > +++ b/kernel/sys.c > @@ -1959,7 +1959,7 @@ static int prctl_set_mm_map(int opt, const void __user *addr, unsigned long data > return error; > } > > - down_write(&mm->mmap_sem); > + down_read(&mm->mmap_sem); Why do we need to hold mmap_sem here and call find_vma, when only PR_SET_MM_ENV_END: is consuming it? I guess we can replace it wit the new lock and take the mmap_sem only for PR_SET_MM_ENV_END. Thanks! -- Michal Hocko SUSE Labs
