From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 25 Jan 2001 12:05:30 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 25 Jan 2001 12:05:20 -0500 Received: from cmn2.cmn.net ([206.168.145.10]:13896 "EHLO cmn2.cmn.net") by vger.kernel.org with ESMTP id ; Thu, 25 Jan 2001 12:05:03 -0500 Message-ID: <3A705CAF.70909@valinux.com> Date: Thu, 25 Jan 2001 10:04:47 -0700 From: Jeff Hartmann User-Agent: Mozilla/5.0 (X11; U; Linux 2.2.12-20smp i686; en-US; m18) Gecko/20001107 Netscape6/6.0 X-Accept-Language: en MIME-Version: 1.0 To: Timur Tabi CC: Roman Zippel , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: ioremap_nocache problem? In-Reply-To: <3A6D5D28.C132D416@sangate.com> <20010123165117Z131182-221+34@kanga.kvack.org> <20010123165117Z131182-221+34@kanga.kvack.org> ; from ttabi@interactivesi.com on Tue, Jan 23, 2001 at 10:53:51AM -0600 <20010125155345Z131181-221+38@kanga.kvack.org> <20010125165001Z132264-460+11@vger.kernel.org> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Timur Tabi wrote: > ** Reply to message from Roman Zippel on Thu, 25 Jan 2001 > 17:44:51 +0100 > > > >> set_bit(PG_reserved, &page->flags); >> ioremap(); >> ... >> iounmap(); >> clear_bit(PG_reserved, &page->flags); > > > The problem with this is that between the ioremap and iounmap, the page is > reserved. What happens if that page belongs to some disk buffer or user > process, and some other process tries to free it. Won't that cause a problem? The page can't belong to some other process/kernel component. You own the page if you allocated it. The kernel will only muck with memory you allocated if its GFP_HIGHMEM, or under certain circumstances if you map it into a user process (There are several rules here and I won't go into them, look at the DRM mmap setup for a start if your interested.) This is the correct ordering of the calls (I was the one who added support to the kernel to ioremap real ram, trust me.) -Jeff - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/