From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754237AbaHKSoY (ORCPT ); Mon, 11 Aug 2014 14:44:24 -0400 Received: from mx1.redhat.com ([209.132.183.28]:1063 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752799AbaHKSoX (ORCPT ); Mon, 11 Aug 2014 14:44:23 -0400 Date: Mon, 11 Aug 2014 14:44:01 -0400 From: Vivek Goyal To: Richard Weinberger Cc: "akpm@linux-foundation.org" , "linux-kernel@vger.kernel.org" , user-mode-linux-devel , sahne@0x90.at Subject: Re: "resource: provide new functions to walk through resources" breaks UML Message-ID: <20140811184401.GE1863@redhat.com> References: <53E7A42E.4090702@nod.at> <20140811122229.GA26869@redhat.com> <53E8B654.2000807@nod.at> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53E8B654.2000807@nod.at> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 11, 2014 at 02:25:56PM +0200, Richard Weinberger wrote: > Hi Vivek, > > Am 11.08.2014 14:22, schrieb Vivek Goyal: > > On Sun, Aug 10, 2014 at 06:56:14PM +0200, Richard Weinberger wrote: > >> Hi Vivek, > >> > >> Daniel Walter reported that UML is currently broken. > >> The offending commit is: > >> > > > > Hi Richard, > > > > Thanks for pointing it out. I will look into it. > > > > Would you have link to the report Daniel sent. I am interested in > > looking at backtrace. > > he reported it on IRC to me. > > Here is a backtrace: > RIP: 0033:[<0000000060039b9f>] > RSP: 0000000081459da0 EFLAGS: 00010202 > RAX: 0000000000000000 RBX: 00000000219b3fff RCX: 000000006010d1d9 > RDX: 0000000000000001 RSI: 00000000602dfb94 RDI: 0000000081459df8 > RBP: 0000000081459de0 R08: 00000000601b59f4 R09: ffffffff0000ff00 > R10: ffffffff0000ff00 R11: 0000000081459e88 R12: 0000000081459df8 > R13: 00000000219b3fff R14: 00000000602dfb94 R15: 0000000000000000 > Kernel panic - not syncing: Segfault with no mm > CPU: 0 PID: 1 Comm: swapper Not tainted 3.16.0-10454-g58d08e3 #13 > Stack: > 00000000 000080d0 81459df0 219b3fff > 81459e70 6010d1d9 ffffffff 6033e010 > 81459e50 6003a269 81459e30 00000000 > Call Trace: > [<6010d1d9>] ? kclist_add_private+0x0/0xe7 > [<6003a269>] walk_system_ram_range+0x61/0xb7 > [<6000e859>] ? proc_kcore_init+0x0/0xf1 > [<6010d574>] kcore_update_ram+0x4c/0x168 > [<6010d72e>] ? kclist_add+0x0/0x2e > [<6000e943>] proc_kcore_init+0xea/0xf1 > [<6000e859>] ? proc_kcore_init+0x0/0xf1 > [<6000e859>] ? proc_kcore_init+0x0/0xf1 > [<600189f0>] do_one_initcall+0x13c/0x204 > [<6004ca46>] ? parse_args+0x1df/0x2e0 > [<6004c82d>] ? parameq+0x0/0x3a > [<601b5990>] ? strcpy+0x0/0x18 > [<60001e1a>] kernel_init_freeable+0x240/0x31e > [<6026f1c0>] kernel_init+0x12/0x148 > [<60019fad>] new_thread_handler+0x81/0xa3 > > RIP is at kernel/resource.c:66. Hi Richard, Can you please give the attached patch a try and see if it fixes the UML issue. I noticed that previous code had a for() loop which will not execute if p was null. I have resorted back to same code now. Thanks Vivek --- kernel/resource.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) Index: linux-2.6/kernel/resource.c =================================================================== --- linux-2.6.orig/kernel/resource.c 2014-08-11 13:36:19.942423192 -0400 +++ linux-2.6/kernel/resource.c 2014-08-11 13:50:20.529387653 -0400 @@ -351,15 +351,12 @@ static int find_next_iomem_res(struct re end = res->end; BUG_ON(start >= end); - read_lock(&resource_lock); - - if (first_level_children_only) { - p = iomem_resource.child; + if (first_level_children_only) sibling_only = true; - } else - p = &iomem_resource; - while ((p = next_resource(p, sibling_only))) { + read_lock(&resource_lock); + + for (p = iomem_resource.child; p; p = next_resource(p, sibling_only)) { if (p->flags != res->flags) continue; if (name && strcmp(p->name, name))