From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 17 Oct 2008 11:08:13 +0200 From: Nick Piggin Subject: Re: [patch][rfc] mm: have expand_stack honour VM_LOCKED Message-ID: <20081017090813.GA32554@wotan.suse.de> References: <20081017050120.GA28605@wotan.suse.de> <20081017142346.FAA6.KOSAKI.MOTOHIRO@jp.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20081017142346.FAA6.KOSAKI.MOTOHIRO@jp.fujitsu.com> Sender: owner-linux-mm@kvack.org Return-Path: To: KOSAKI Motohiro Cc: Hugh Dickins , Linux Memory Management List List-ID: On Fri, Oct 17, 2008 at 02:41:31PM +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? -- 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