From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with ESMTP id DD6776B0078 for ; Tue, 21 Sep 2010 04:12:27 -0400 (EDT) Message-ID: <562d0c45d5a10d80c3583c2fe1c318c7.squirrel@www.firstfloor.org> In-Reply-To: <20100921080459.GA29540@localhost> References: <20100921022112.GA10336@localhost> <20100921061310.GA11526@localhost> <20100921162316.3C03.A69D9226@jp.fujitsu.com> <31aed4ad96866a97dc791186303c5719.squirrel@www.firstfloor.org> <20100921080459.GA29540@localhost> Date: Tue, 21 Sep 2010 10:12:23 +0200 Subject: Re: Problem with debugfs From: "Andi Kleen" MIME-Version: 1.0 Content-Type: text/plain;charset=iso-8859-1 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org To: Wu Fengguang Cc: Andi Kleen , KOSAKI Motohiro , Kenneth , greg@kroah.com, linux-kernel@vger.kernel.org, Naoya Horiguchi , linux-mm List-ID: > > Thanks for the report. Did this show up as a real bug? What's your > use case? Or is it a theoretic concern raised when doing code review? I assume it was code review, right? > Yeah the hwpoison_filter_flags_* values are not referenced strictly > safe to concurrent updates. I didn't care it because the typical usage > is for hwpoison test tools to _first_ echo hwpoison_filter_flags_* > values into the debugfs and _then_ start injecting hwpoison errors. > Otherwise you cannot get reliable test results. The updated value is > guaranteed to be visible because there are file mutex UNLOCK and page > LOCK operations in between. Sorry that's not true -- all the x86 memory ordering constraints only apply to a single CPU or same address. But I agree it doesn't really matter for a debugging feature like this. So unless there's a very simple fix I would be inclined to leave it alone, perhaps with a comment added. Comments? -Andi -- 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