linux-kernel - [PATCH] oom: OOM-Killed process don't invoke pagefault-oom

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Message-Id: <20100114191940.6749.A69D9226@jp.fujitsu.com>
Date:	Thu, 14 Jan 2010 19:22:34 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Nick Piggin <npiggin@...e.de>, Jeff Dike <jdike@...toit.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>
Cc:	kosaki.motohiro@...fujitsu.com
Subject: [PATCH] oom: OOM-Killed process don't invoke pagefault-oom


Nick, I've found this issue by code review. I'm glad if you review this
patch.

Thanks.

=============================
commit 1c0fe6e3 (invoke oom-killer from page fault) created
page fault specific oom handler.

But If OOM occur, alloc_pages() in page fault might return
NULL. It mean page fault return VM_FAULT_OOM. But OOM Killer
itself sholdn't invoke next OOM Kill. it is obviously strange.

Plus, process exiting itself makes some free memory. we
don't need kill another process.

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc: Nick Piggin <npiggin@...e.de>
Cc: Jeff Dike <jdike@...toit.com>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Andrew Morton <akpm@...ux-foundation.org>
---
 mm/oom_kill.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 4f167b8..86cecdf 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -596,6 +596,15 @@ void pagefault_out_of_memory(void)
 {
 	unsigned long freed = 0;
 
+	/*
+	 * If the task was received SIGKILL while memory allocation, alloc_pages
+	 * might return NULL and it cause page fault return VM_FAULT_OOM. But
+	 * in such case, the task don't need kill any another task, it need
+	 * just die.
+	 */
+	if (fatal_signal_pending(current))
+		return;
+
 	blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
 	if (freed > 0)
 		/* Got some memory back in the last second. */
-- 
1.6.5.2



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