From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261362AbTJCWXy (ORCPT ); Fri, 3 Oct 2003 18:23:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261364AbTJCWXx (ORCPT ); Fri, 3 Oct 2003 18:23:53 -0400 Received: from fw.osdl.org ([65.172.181.6]:52098 "EHLO mail.osdl.org") by vger.kernel.org with ESMTP id S261362AbTJCWXv (ORCPT ); Fri, 3 Oct 2003 18:23:51 -0400 Date: Fri, 3 Oct 2003 15:23:49 -0700 From: Andrew Morton To: Joe Korty Cc: linux-kernel@vger.kernel.org, riel@redhat.com, andrea@suse.de Subject: Re: mlockall and mmap of IO devices don't mix Message-Id: <20031003152349.7194b73d.akpm@osdl.org> In-Reply-To: <20031003214411.GA25802@rudolph.ccur.com> References: <20031003214411.GA25802@rudolph.ccur.com> X-Mailer: Sylpheed version 0.9.6 (GTK+ 1.2.10; i586-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Joe Korty wrote: > > 2.6.0-test6: the use of mlockall(2) in a process that has mmap(2)ed > the registers of an IO device will hang that process uninterruptibly. > The task runs in an infinite loop in get_user_pages(), invoking > follow_page() forever. whoops. I think the right fix is in get_user_pages(): if the region is VM_IO then don't call follow_page() at all. Something like this? 25-akpm/mm/memory.c | 15 +++++++++++---- 1 files changed, 11 insertions(+), 4 deletions(-) diff -puN mm/memory.c~get_user_pages-handle-VM_IO mm/memory.c --- 25/mm/memory.c~get_user_pages-handle-VM_IO Fri Oct 3 15:22:18 2003 +++ 25-akpm/mm/memory.c Fri Oct 3 15:22:18 2003 @@ -683,6 +683,7 @@ int get_user_pages(struct task_struct *t struct page **pages, struct vm_area_struct **vmas) { int i; + int vm_io; unsigned int flags; /* @@ -739,8 +740,8 @@ int get_user_pages(struct task_struct *t } #endif - if (!vma || (pages && (vma->vm_flags & VM_IO)) - || !(flags & vma->vm_flags)) + vm_io = vma->vm_flags & VM_IO; + if (!vma || (pages && vm_io) || !(flags & vma->vm_flags)) return i ? : -EFAULT; if (is_vm_hugetlb_page(vma)) { @@ -750,8 +751,14 @@ int get_user_pages(struct task_struct *t } spin_lock(&mm->page_table_lock); do { - struct page *map; - while (!(map = follow_page(mm, start, write))) { + struct page *map = NULL; + + /* + * We don't follow pagetables for VM_IO regions - they + * have no pageframes. And the caller passed NULL + * for `pages' anyway. + */ + while (!vm_io && !(map = follow_page(mm,start,write))) { spin_unlock(&mm->page_table_lock); switch (handle_mm_fault(mm,vma,start,write)) { case VM_FAULT_MINOR: _