Re: [PATCH 4/6] mm, oom: skip over vforked tasks

[Michal Hocko <mhocko@kernel.org>]

So I've ended up with a replacement for this patch which does the
following:
---
>From c40900923c78b51215794cc445d3f5a589b8f785 Mon Sep 17 00:00:00 2001
From: Michal Hocko <mhocko@suse.com>
Date: Mon, 30 May 2016 13:53:28 +0200
Subject: [PATCH] mm, oom: skip vforked tasks from being selected

vforked tasks are not really sitting on any memory. They are sharing
the mm with parent until they exec into a new code. Until then it is
just pinning the address space. OOM killer will kill the vforked task
along with its parent but we still can end up selecting vforked task
when the parent wouldn't be selected. E.g. init doing vfork to launch
a task or vforked being a child of oom unkillable task with an updated
oom_score_adj to be killable.

Make sure to not select vforked task as an oom victim by checking
vfork_done in oom_badness.

Signed-off-by: Michal Hocko <mhocko@suse.com>
---
 mm/oom_kill.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 7ba6bdf9ae94..36c821403d0f 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -176,11 +176,13 @@ unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg,
 
 	/*
 	 * Do not even consider tasks which are explicitly marked oom
-	 * unkillable or have been already oom reaped.
+	 * unkillable or have been already oom reaped or the are in
+	 * the middle of vfork
 	 */
 	adj = (long)p->signal->oom_score_adj;
 	if (adj == OOM_SCORE_ADJ_MIN ||
-			test_bit(MMF_OOM_REAPED, &p->mm->flags)) {
+			test_bit(MMF_OOM_REAPED, &p->mm->flags) ||
+			p->vfork_done) {
 		task_unlock(p);
 		return 0;
 	}
-- 
2.8.1

-- 
Michal Hocko
SUSE Labs