From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753001AbXJGGcE (ORCPT ); Sun, 7 Oct 2007 02:32:04 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750803AbXJGGby (ORCPT ); Sun, 7 Oct 2007 02:31:54 -0400 Received: from gw.goop.org ([64.81.55.164]:37289 "EHLO mail.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751353AbXJGGbx (ORCPT ); Sun, 7 Oct 2007 02:31:53 -0400 Message-ID: <47087D45.2010904@goop.org> Date: Sat, 06 Oct 2007 23:31:33 -0700 From: Jeremy Fitzhardinge User-Agent: Thunderbird 2.0.0.5 (X11/20070727) MIME-Version: 1.0 To: Ingo Molnar CC: Linux Kernel Mailing List Subject: lockdep: how to tell it multiple pte locks is OK? X-Enigmail-Version: 0.95.3 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org I'm writing some code which is doing some batch processing on pte pages, and so wants to hold multiple pte locks at once. This seems OK, but lockdep is giving me the warning: ============================================= [ INFO: possible recursive locking detected ] 2.6.23-rc9-paravirt #1673 --------------------------------------------- init/1 is trying to acquire lock: (__pte_lockptr(new)){--..}, at: [] lock_pte+0x10/0x15 but task is already holding lock: (__pte_lockptr(new)){--..}, at: [] lock_pte+0x10/0x15 other info that might help us debug this: 4 locks held by init/1: #0: (&mm->mmap_sem){----}, at: [] copy_process+0xab4/0x12bf #1: (&mm->mmap_sem/1){--..}, at: [] copy_process+0xac4/0x12bf #2: (&mm->page_table_lock){--..}, at: [] xen_dup_mmap+0x11/0x24 #3: (__pte_lockptr(new)){--..}, at: [] lock_pte+0x10/0x15 stack backtrace: [] show_trace_log_lvl+0x1a/0x2f [] show_trace+0x12/0x14 [] dump_stack+0x16/0x18 [] __lock_acquire+0x195/0xc5f [] lock_acquire+0x88/0xac [] _spin_lock+0x35/0x42 [] lock_pte+0x10/0x15 [] pin_page+0x67/0x17e [] pgd_walk+0x168/0x1ba [] xen_pgd_pin+0x42/0xf8 [] xen_dup_mmap+0x19/0x24 [] copy_process+0xc79/0x12bf [] do_fork+0x99/0x1bf [] sys_clone+0x33/0x39 [] syscall_call+0x7/0xb ======================= I presume this is because I'm holding multiple pte locks (class "__pte_lockptr(new)"). Is there some way I can tell lockdep this is OK? I'm presume I'm the first person to try holding multiple pte locks at once, so there's no existing locking order for these locks. I'm always traversing and locking the pagetable in virtual address order (and this seems like a sane-enough rule for anyone else who wants to hold multiple pte locks). Thanks, J