From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kanoj Sarcar Message-Id: <200010131819.LAA39874@google.engr.sgi.com> Subject: Re: Updated Linux 2.4 Status/TODO List (from the ALS show) Date: Fri, 13 Oct 2000 11:19:06 -0700 (PDT) In-Reply-To: from "Linus Torvalds" at Oct 12, 2000 10:05:19 PM MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Linus Torvalds Cc: "David S. Miller" , saw@saw.sw.com.sg, davej@suse.de, linux-kernel@vger.kernel.org, linux-mm@kvack.org, tytso@mit.edu List-ID: > > > On Thu, 12 Oct 2000, David S. Miller wrote: > > > > page_table_lock is supposed to protect normal page table activity (like > > what's done in page fault handler) from swapping out. > > However, grabbing this lock in swap-out code is completely missing! > > > > Audrey, vmlist_access_{un,}lock == unlocking/locking page_table_lock. > > Yeah, it's an easy mistake to make. > > I've made it myself - grepping for page_table_lock and coming up empty in > places where I expected it to be. > > In fact, if somebody sends me patches to remove the "vmlist_access_lock()" > stuff completely, and replace them with explicit page_table_lock things, > I'll apply it pretty much immediately. I don't like information hiding, > and right now that's the only thing that the vmlist_access_lock() stuff is > doing. Linus, I came up with the vmlist_access_lock/vmlist_modify_lock names early in 2.3. The reasoning behind that was that in most places where the "vmlist lock" was being taken was to protect the vmlist chain, vma_t fields or mm_struct fields. The fact that implementation wise this lock could be the same as page_table_lock was a good idea that you suggested. Nevertheless, the name was chosen to indicate what type of things it was guarding. For example, in the future, you might actually have a different (possibly sleeping) lock to guard the vmachain etc, but still have a spin lock for the page_table_lock (No, I don't want to be drawn into a discussion of why this might be needed right now). Some of this is mentioned in Documentation/vm/locking. Just thought I would mention, in case you don't recollect some of this history. Of course, I understand the "information hiding" part. Kanoj -- 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.eu.org/Linux-MM/