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 <js1...@gmail.com> 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 <t...@linutronix.de>
> > > > Cc: Ingo Molnar <mi...@redhat.com>
> > > > Cc: "H. Peter Anvin" <h...@zytor.com>
> > > > Signed-off-by: Joonsoo Kim <js1...@gmail.com>
> > > >
> > > > 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.
<snip>
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
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