From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <43C9DD98.5000506@yahoo.com.au> Date: Sun, 15 Jan 2006 16:28:56 +1100 From: Nick Piggin MIME-Version: 1.0 Subject: Re: Race in new page migration code? References: <20060114155517.GA30543@wotan.suse.de> <20060114181949.GA27382@wotan.suse.de> In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: Nick Piggin , Andrew Morton , Linux Kernel Mailing List , Linux Memory Management List List-ID: Christoph Lameter wrote: > On Sat, 14 Jan 2006, Nick Piggin wrote: > > >>>We take that reference count on the page: >> >>Yes, after you have dropped all your claims to pin this page >>(ie. pte lock). You really can't take a refcount on a page that > > > Oh. Now I see. I screwed that up by a fix I added.... We cannot drop the > ptl here. So back to the way it was before. Remove the draining from > isolate_lru_page and do it before scanning for pages so that we do not > have to drop the ptl. > OK (either way is fine), but you should still drop the __isolate_lru_page nonsense and revert it like my patch does. > Also remove the WARN_ON since its now even possible that other actions of > the VM move the pages into the LRU lists while we scan for pages to > migrate. > Well, it has always been possible since vmscan started batching scans a long time ago. Actually seeing as you only take a read lock on the semaphore it is probably also possible to have a concurrent migrate operation cause this as well. Thanks, Nick -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com -- 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