linux-kernel - [patch 3.5-rc3] mm, oom: fix potential killing of thread that is disabled from oom killing

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Message-ID: <alpine.DEB.2.00.1206221443210.23486@chino.kir.corp.google.com>
Date:	Fri, 22 Jun 2012 14:44:34 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>
cc:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [patch 3.5-rc3] mm, oom: fix potential killing of thread that is
 disabled from oom killing

/proc/sys/vm/oom_kill_allocating_task will immediately kill current when
the oom killer is called to avoid a potentially expensive tasklist scan
for large systems.

Currently, however, it is not checking current's oom_score_adj value
which may be OOM_SCORE_ADJ_MIN, meaning that it has been disabled from
oom killing.

This patch avoids killing current in such a condition and simply falls
back to the tasklist scan since memory still needs to be freed.

Signed-off-by: David Rientjes <rientjes@...gle.com>
---
 mm/oom_kill.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -720,9 +720,9 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
 	check_panic_on_oom(constraint, gfp_mask, order, mpol_mask);
 
 	read_lock(&tasklist_lock);
-	if (sysctl_oom_kill_allocating_task &&
+	if (sysctl_oom_kill_allocating_task && current->mm &&
 	    !oom_unkillable_task(current, NULL, nodemask) &&
-	    current->mm) {
+	    current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
 		oom_kill_process(current, gfp_mask, order, 0, totalpages, NULL,
 				 nodemask,
 				 "Out of memory (oom_kill_allocating_task)");
--
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