Messages in this thread | | | Date | Thu, 20 Aug 2020 16:36:27 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 1/1] mm, oom_adj: don't loop through tasks in __set_oom_adj when not necessary |
| |
On 08/20, Oleg Nesterov wrote: > > On 08/20, Eric W. Biederman wrote: > > > > --- a/fs/exec.c > > +++ b/fs/exec.c > > @@ -1139,6 +1139,10 @@ static int exec_mmap(struct mm_struct *mm) > > vmacache_flush(tsk); > > task_unlock(tsk); > > if (old_mm) { > > + mm->oom_score_adj = old_mm->oom_score_adj; > > + mm->oom_score_adj_min = old_mm->oom_score_adj_min; > > + if (tsk->vfork_done) > > + mm->oom_score_adj = tsk->vfork_oom_score_adj; > > too late, ->vfork_done is NULL after mm_release(). > > And this can race with __set_oom_adj(). Yes, the current code is racy too, > but this change adds another race, __set_oom_adj() could already observe > ->mm != NULL and update mm->oom_score_adj. ^^^^^^^^^^^^
I meant ->mm == new_mm.
And another problem. Suppose we have
if (!vfork()) { change_oom_score(); exec(); }
the parent can be killed before the child execs, in this case vfork_oom_score_adj will be lost.
Oleg.
| |