linux-kernel - Re: [PATCH] x86, reboot: skip reboot

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Message-ID: <CAErSpo5_dgH1Au3QChVrhqBY_Fm54+Aw_ZiwGf2JSsgQaR1dug@mail.gmail.com>
Date:	Thu, 24 Jan 2013 10:45:13 -0700
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Joonsoo Kim <js1304@...il.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
	x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH] x86, reboot: skip reboot_fixups in early boot phase

On Fri, Dec 28, 2012 at 6:50 AM, Joonsoo Kim <js1304@...il.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 <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Signed-off-by: Joonsoo Kim <js1304@...il.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.

Bjorn
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