From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with ESMTP id 77D0E6B0071 for ; Tue, 23 Nov 2010 17:23:00 -0500 (EST) Date: Tue, 23 Nov 2010 14:22:47 -0800 From: Andrew Morton Subject: Re: [PATCH] [BUG] memcg: fix false positive VM_BUG on non-SMP Message-Id: <20101123142247.e8566e3e.akpm@linux-foundation.org> In-Reply-To: <20101123210255.GA22484@cmpxchg.org> References: <1290520130-9990-1-git-send-email-kirill@shutemov.name> <20101123121606.c07197e5.akpm@linux-foundation.org> <20101123210255.GA22484@cmpxchg.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Johannes Weiner Cc: "Kirill A. Shutsemov" , Balbir Singh , Daisuke Nishimura , KAMEZAWA Hiroyuki , KOSAKI Motohiro , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Tue, 23 Nov 2010 22:02:55 +0100 Johannes Weiner wrote: > On Tue, Nov 23, 2010 at 12:16:06PM -0800, Andrew Morton wrote: > > On Tue, 23 Nov 2010 15:48:50 +0200 > > "Kirill A. Shutsemov" wrote: > > > > > ------------[ cut here ]------------ > > > kernel BUG at mm/memcontrol.c:2155! > > > > This bug has been there for a year, from which I conclude people don't > > run memcg on uniprocessor machines a lot. > > > > Which is a bit sad, really. Small machines need resource control too, > > perhaps more than large ones.. > > Admittedly, this patch is compile-tested on UP only, but it should be > obvious enough. > > --- > From: Johannes Weiner > Subject: [patch] memcg: fix page cgroup lock assert on UP > > Page cgroup locking primitives use the bit spinlock API functions, > which do nothing on UP. > > Thus, checking the lock state can not be done by looking at the bit > directly, but one has to go through the bit spinlock API as well. > > This fixes a guaranteed UP bug, where asserting the page cgroup lock > bit as a sanity check crashes the kernel. > hm, your patch is the same as Kirill's, except you named it page_is_cgroup_locked() rather than is_page_cgroup_locked(). I guess page_is_cgroup_locked() is a bit better. -- 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/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org