From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx178.postini.com [74.125.245.178]) by kanga.kvack.org (Postfix) with SMTP id 8ED126B005D for ; Wed, 19 Dec 2012 20:42:19 -0500 (EST) Received: by mail-pb0-f46.google.com with SMTP id wy7so1596542pbc.19 for ; Wed, 19 Dec 2012 17:42:18 -0800 (PST) Date: Wed, 19 Dec 2012 17:42:16 -0800 (PST) From: Hugh Dickins Subject: [PATCH] sched: numa: ksm: fix oops in task_numa_placment() Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: Linus Torvalds , Andrew Morton , Ingo Molnar , Sasha Levin , Petr Holasek , linux-kernel@vger.kernel.org, linux-mm@kvack.org task_numa_placement() oopsed on NULL p->mm when task_numa_fault() got called in the handling of break_ksm() for ksmd. That might be a peculiar case, which perhaps KSM could takes steps to avoid? but it's more robust if task_numa_placement() allows for such a possibility. Signed-off-by: Hugh Dickins --- kernel/sched/fair.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- 3.7+git/kernel/sched/fair.c 2012-12-16 16:35:08.724441527 -0800 +++ linux/kernel/sched/fair.c 2012-12-18 21:37:24.727964195 -0800 @@ -793,8 +793,11 @@ unsigned int sysctl_numa_balancing_scan_ static void task_numa_placement(struct task_struct *p) { - int seq = ACCESS_ONCE(p->mm->numa_scan_seq); + int seq; + if (!p->mm) /* for example, ksmd faulting in a user's mm */ + return; + seq = ACCESS_ONCE(p->mm->numa_scan_seq); if (p->numa_scan_seq == seq) return; p->numa_scan_seq = seq; -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org