From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 16 Oct 2002 16:08:17 +0100 (BST) From: Hugh Dickins Subject: Re: [PATCH 2.5.42-mm3] Fix mremap for shared page tables In-Reply-To: <291360000.1034721127@baldur.austin.ibm.com> Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Sender: owner-linux-mm@kvack.org Return-Path: To: Dave McCracken Cc: Andrew Morton , Linux Kernel , Linux Memory Management List-ID: On Tue, 15 Oct 2002, Dave McCracken wrote: > > Hugh Dickens was right. mremap was broken wrt shared page tables. i Sorry, Dave, I only mentioned mremap as one _example_. You have changed the locking rules for ptes in page tables in two or three sources, but there's a number more which need to be updated too. Please don't ask me to list which, it's a matter of looking at all the uses of ->page_table_lock and whether those places need to be changed to fit the new locking scheme - some of the uses are quite irrelevant, some may be obscure, some may be historic, some must be changed. I wouldn't mind if it was just broken wrt shared page tables, CONFIG_SHAREPTE is easily made experimental. But the locking rules have (rightly) been changed in all cases, so -mm tree is now unsafe. A stopgap measure might be to hold on to page_table_lock for as long as before, then fix sources up piecemeal - but that approach would still leave CONFIG_SHAREPTE y broken for a while. Let me say again, that I have _not_ actually observed any problem yet: we're talking about races and correctness, I don't mean to be alarmist. Hugh -- 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/