From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx146.postini.com [74.125.245.146]) by kanga.kvack.org (Postfix) with SMTP id 824036B005D for ; Mon, 23 Jul 2012 21:10:21 -0400 (EDT) From: Minchan Kim Subject: [PATCH 2/3] mm: Warn if pg_data_t isn't initialized with zero Date: Tue, 24 Jul 2012 10:10:34 +0900 Message-Id: <1343092235-13399-2-git-send-email-minchan@kernel.org> In-Reply-To: <1343092235-13399-1-git-send-email-minchan@kernel.org> References: <1343092235-13399-1-git-send-email-minchan@kernel.org> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Tejun Heo , Yinghai Lu , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Minchan Kim , linux-arch This patch warns if memory-hotplug/boot code doesn't initialize pg_data_t with zero when it's allocated. As I looked arch code and memory hotplug, they already seem to initiailize pg_data_t. So this warning should be never happen. It needs double check and let's add checking garbage with warn. I select fields randomly nearyby begin/middle/end of pg_data_t for checking garbage. If we are very unlucky, those garbage might be zero but it's very unlikely, I hope. This patch isn't for performance but removing initialization code which is necessary to add whenever we adds new field to pg_data_t or zone. It's rather bothersome and error-prone about compile at least as I had experienced. Firstly, Andrew suggested clearing out of pg_data_t in MM core part but Tejun doesn't like it because in the future, some archs can initialize some fields in arch code and pass them into general MM part so blindly clearing it out in mm core part would be very annoying. Cc: Tejun Heo Cc: Andrew Morton Cc: linux-arch Signed-off-by: Minchan Kim --- mm/page_alloc.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index b65c362..2037eeb 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -4517,6 +4517,9 @@ void __paginginit free_area_init_node(int nid, unsigned long *zones_size, { pg_data_t *pgdat = NODE_DATA(nid); + /* pg_data_t should be reset to zero when it's allocated */ + WARN_ON(pgdat->nr_zones || pgdat->node_start_pfn || pgdat->classzone_idx); + pgdat->node_id = nid; pgdat->node_start_pfn = node_start_pfn; calculate_node_totalpages(pgdat, zones_size, zholes_size); -- 1.7.9.5 -- 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