From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pb0-f41.google.com (mail-pb0-f41.google.com [209.85.160.41]) by kanga.kvack.org (Postfix) with ESMTP id 17BB66B0039 for ; Mon, 3 Feb 2014 19:06:54 -0500 (EST) Received: by mail-pb0-f41.google.com with SMTP id up15so7751732pbc.28 for ; Mon, 03 Feb 2014 16:06:53 -0800 (PST) Received: from mail-pa0-x22f.google.com (mail-pa0-x22f.google.com [2607:f8b0:400e:c03::22f]) by mx.google.com with ESMTPS id of8si9536953pbc.133.2014.02.03.16.06.52 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 03 Feb 2014 16:06:53 -0800 (PST) Received: by mail-pa0-f47.google.com with SMTP id kp14so7681575pab.6 for ; Mon, 03 Feb 2014 16:06:52 -0800 (PST) Date: Mon, 3 Feb 2014 16:06:51 -0800 (PST) From: David Rientjes Subject: Re: Need help in bug in isolate_migratepages_range In-Reply-To: <52EFC93D.3030106@suse.cz> Message-ID: References: <20140203122052.GC2495@dhcp22.suse.cz> <20140203162036.GJ2495@dhcp22.suse.cz> <52EFC93D.3030106@suse.cz> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka Cc: Michal Hocko , Holger Kiehl , linux-kernel , Mel Gorman , linux-mm@kvack.org On Mon, 3 Feb 2014, Vlastimil Babka wrote: > It seems to come from balloon_page_movable() and its test page_count(page) == > 1. > Hmm, I think it might be because compound_head() == NULL here. Holger, this looks like a race condition when allocating a compound page, did you only see it once or is it actually reproducible? I think this happens when a new compound page is allocated and PageBuddy is cleared before prep_compound_page() and then we see PageTail(p) set but p->first_page is not yet initialized. Is there any way to avoid memory barriers in compound_page()? -- 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