From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [RFC] page fault retry with NOPAGE_RETRY From: Benjamin Herrenschmidt In-Reply-To: <20060921154105.904313f7.akpm@osdl.org> References: <1158274508.14473.88.camel@localhost.localdomain> <20060915001151.75f9a71b.akpm@osdl.org> <45107ECE.5040603@google.com> <1158709835.6002.203.camel@localhost.localdomain> <1158710712.6002.216.camel@localhost.localdomain> <20060919172105.bad4a89e.akpm@osdl.org> <1158717429.6002.231.camel@localhost.localdomain> <20060919200533.2874ce36.akpm@osdl.org> <1158728665.6002.262.camel@localhost.localdomain> <20060919222656.52fadf3c.akpm@osdl.org> <1158735299.6002.273.camel@localhost.localdomain> <20060920105317.7c3eb5f4.akpm@osdl.org> <1158876304.26347.129.camel@localhost.localdomain> <20060921154105.904313f7.akpm@osdl.org> Content-Type: text/plain Date: Fri, 22 Sep 2006 09:09:25 +1000 Message-Id: <1158880165.26347.132.camel@localhost.localdomain> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton Cc: Mike Waychison , linux-mm@kvack.org, Linux Kernel list , Linus Torvalds List-ID: On Thu, 2006-09-21 at 15:41 -0700, Andrew Morton wrote: > On Fri, 22 Sep 2006 08:05:04 +1000 > Benjamin Herrenschmidt wrote: > > > > So I think there's a nasty DoS here if we permit infinite retries. But > > > it's not just that - there might be other situations under really heavy > > > memory pressure where livelocks like this can occur. It's just a general > > > robustness-of-implementation issue. > > > > Got it. Now, changing args to no_page() will be a pretty big task.... > > > > Not as big as removing the pt_regs arg from every interrupt handler ;) Which is a change I'm not 100% convinced about btw ... I remember actually using that in a few occasions... mostly for debugging though. Bah, anyway, I suppose we can always have a per-cpu global with the last irq pt_regs pointer if really needed for debug. > But pretty mechanical. Problem is, I don't think we have our mechanic. Yup, we would need to decide what to put in there.... Ben. -- 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