From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with ESMTP id 321266B0085 for ; Mon, 8 Nov 2010 17:29:06 -0500 (EST) From: Greg Thelen Subject: Re: [patch 2/4] memcg: catch negative per-cpu sums in dirty info References: <1288973333-7891-1-git-send-email-minchan.kim@gmail.com> <20101106010357.GD23393@cmpxchg.org> <20101107215030.007259800@cmpxchg.org> <20101107220353.414283590@cmpxchg.org> Date: Mon, 08 Nov 2010 14:28:46 -0800 In-Reply-To: (Minchan Kim's message of "Mon, 8 Nov 2010 08:26:29 +0900") Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org To: Minchan Kim Cc: Johannes Weiner , Andrew Morton , Dave Young , Andrea Righi , KAMEZAWA Hiroyuki , Daisuke Nishimura , Balbir Singh , Wu Fengguang , linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: Minchan Kim writes: > On Mon, Nov 8, 2010 at 7:14 AM, Johannes Weiner wrote: >> Folding the per-cpu counters can yield a negative value in case of >> accounting races between CPUs. >> >> When collecting the dirty info, the code would read those sums into an >> unsigned variable and then check for it being negative, which can not >> work. >> >> Instead, fold the counters into a signed local variable, make the >> check, and only then assign it. >> >> This way, the function signals correctly when there are insane values >> instead of leaking them out to the caller. >> >> Signed-off-by: Johannes Weiner > Reviewed-by: Minchan Kim Reviewed-by: Greg Thelen -- 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