From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [patch][rfc] mm: have expand_stack honour VM_LOCKED From: Lee Schermerhorn In-Reply-To: <20081017093701.GA14409@wotan.suse.de> References: <20081017142346.FAA6.KOSAKI.MOTOHIRO@jp.fujitsu.com> <20081017090813.GA32554@wotan.suse.de> <20081017182737.E23C.KOSAKI.MOTOHIRO@jp.fujitsu.com> <20081017093701.GA14409@wotan.suse.de> Content-Type: text/plain Date: Fri, 17 Oct 2008 08:50:41 -0400 Message-Id: <1224247841.1736.24.camel@lts-notebook> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: KOSAKI Motohiro , Hugh Dickins , Linux Memory Management List List-ID: On Fri, 2008-10-17 at 11:37 +0200, Nick Piggin wrote: > On Fri, Oct 17, 2008 at 06:32:07PM +0900, KOSAKI Motohiro wrote: > > > > Hi Nick, > > > > > > > > > Is this valid? > > > > > > > > > > > > > > > It appears that direct callers of expand_stack may not properly lock the newly > > > > > expanded stack if they don't call make_pages_present (page fault handlers do > > > > > this). > > > > > > > > When happend this issue? > > > > > > > > I think... > > > > > > > > case 1. explit mlock to stack > > > > > > > > 1. mlock to stack > > > > -> make_pages_present is called via mlock(2). > > > > 2. stack increased > > > > -> no page fault happened. > > > > > > > > case 2. swapout and mlock stack > > > > > > > > 1. stack swap out > > > > 2. mlock to stack > > > > -> the page doesn't swap in at the time. > > > > 3. page fault in the stack > > > > -> the page swap in > > > > (no need make_present_page()) > > > > > > > > > > > > So, it seems this patch isn't necessary. > > > > > > What if you you page fault the stack further than a single page down? > > > > > > > I see. thanks. > > > > But unfortunately, this patch conflicted against unevictable patch series. > > I'll make for -mm version patch few days after if you don't like do that. > > Well, it's not a big deal. I just wanted to get some comments to see whether > the patch seems to be valid. Let's wait and see what gets merged in this > window, then I'll resubmit this patch unless anybody sees a problem with it. > > Thanks for looking at it, Hmmm. guess I should drain my inbox--not to mention a couple more cups of coffee--before responding... Lee -- 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