From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755551Ab3AYEMl (ORCPT ); Thu, 24 Jan 2013 23:12:41 -0500 Received: from mail.kernel.org ([198.145.19.201]:52045 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753657Ab3AYEMj (ORCPT ); Thu, 24 Jan 2013 23:12:39 -0500 Date: Thu, 24 Jan 2013 20:14:11 -0800 From: Greg Kroah-Hartman To: Bjorn Helgaas Cc: Joonsoo Kim , "H. Peter Anvin" , linux-kernel@vger.kernel.org, x86@kernel.org, Thomas Gleixner , Ingo Molnar Subject: Re: [PATCH] x86, reboot: skip reboot_fixups in early boot phase Message-ID: <20130125041411.GB12562@kroah.com> References: <1356702623-9430-1-git-send-email-js1304@gmail.com> <20130125011303.GA3401@lge.com> <20130125025901.GA26984@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130125025901.GA26984@google.com> 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 Thu, Jan 24, 2013 at 07:59:01PM -0700, Bjorn Helgaas wrote: > [+cc Greg for driver core] > > On Fri, Jan 25, 2013 at 10:13:03AM +0900, Joonsoo Kim wrote: > > Hello, Bjorn. > > > > On Thu, Jan 24, 2013 at 10:45:13AM -0700, Bjorn Helgaas wrote: > > > On Fri, Dec 28, 2012 at 6:50 AM, Joonsoo Kim wrote: > > > > During early boot phase, PCI bus subsystem is not yet initialized. > > > > If panic is occured in early boot phase and panic_timeout is set, > > > > code flow go into emergency_restart() and hit mach_reboot_fixups(), then > > > > encounter another panic. When second panic, we can't hold a panic_lock, so > > > > code flow go into panic_smp_self_stop() which prevent system to restart. > > > > > > > > For avoid second panic, skip reboot_fixups in early boot phase. > > > > It makes panic_timeout works in early boot phase. > > > > > > > > Cc: Thomas Gleixner > > > > Cc: Ingo Molnar > > > > Cc: "H. Peter Anvin" > > > > Signed-off-by: Joonsoo Kim > > > > > > > > diff --git a/arch/x86/kernel/reboot_fixups_32.c b/arch/x86/kernel/reboot_fixups_32.c > > > > index c8e41e9..b9b8ec9 100644 > > > > --- a/arch/x86/kernel/reboot_fixups_32.c > > > > +++ b/arch/x86/kernel/reboot_fixups_32.c > > > > @@ -89,6 +89,10 @@ void mach_reboot_fixups(void) > > > > if (in_interrupt()) > > > > return; > > > > > > > > + /* During early boot phase, PCI is not yet initialized */ > > > > + if (system_state == SYSTEM_BOOTING) > > > > + return; > > > > + > > > > for (i=0; i < ARRAY_SIZE(fixups_table); i++) { > > > > cur = &(fixups_table[i]); > > > > dev = pci_get_device(cur->vendor, cur->device, NULL); > > > > > > I guess you're saying that if we call pci_get_device() too early, it > > > panics? Did you figure out why that happens? > > > > > > If we call pci_get_device() before PCI has been initialized, it would > > > be good if it just returned NULL, indicating that we didn't find any > > > matching device. I looked briefly, and I thought that's what would > > > happen, but apparently I'm missing something. > > > > In bus_find_device(), klist_iter_init_node() is called with > > @bus->p->klist_device. Before initialization, bus->p is NULL, > > so panic is occured. > > I see. pci_bus_type.p is initialized by __bus_register() in this path: > > pci_driver_init # postcore_initcall > bus_register(&pci_bus_type) > __bus_register > priv = kzalloc(sizeof(struct subsys_private)) > bus->p = priv > klist_init(&priv->klist_devices, klist_devices_get, klist_devices_put) > > I was hoping we could statically initialize the klist, but that doesn't > seem likely. > > But I wonder if we could do something like the following. If we could, > then callers wouldn't have to worry about whether or not the bus has been > initialized. I have no objection to that patch, but really, someone wants to call pci_find_device() before PCI is initialized? Can't that be fixed instead, as that is the root problem, not the driver core. But, to paper over your subsystem's bugs, I guess I can take it :) Care to resend it in a format that I can apply it in? thanks, greg k-h