linux-kernel - [PATCH] memory hotplug: reset pgdat->kswapd to NULL if creating kernel thread fails

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Date:	Tue, 21 Aug 2012 14:31:19 +0800
From:	Wen Congyang <wency@...fujitsu.com>
To:	Andrew Morton <akpm@...ux-foundation.org>, mgorman@...e.de,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	hughd@...gle.com, minchan@...nel.org, linux-mm@...ck.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH] memory hotplug: reset pgdat->kswapd to NULL if creating kernel
 thread fails

If kthread_run() fails, pgdat->kswapd contains errno. When we stop
this thread, we only check whether pgdat->kswapd is NULL and access
it. If it contains errno, it will cause page fault. Reset pgdat->kswapd
to NULL when creating kernel thread fails can avoid this problem.

Signed-off-by: Wen Congyang <wency@...fujitsu.com>
---
 mm/vmscan.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 347b3ff..1e8e2aa 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2953,6 +2953,7 @@ int kswapd_run(int nid)
 		/* failure at boot is fatal */
 		BUG_ON(system_state == SYSTEM_BOOTING);
 		printk("Failed to start kswapd on node %d\n",nid);
+		pgdat->kswapd = NULL;
 		ret = -1;
 	}
 	return ret;
-- 
1.7.1
--
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