Re: Hang on boot Was: [XenPPC] [xenppc-unstable] [POWERPC][XEN] Detect bad spurious interrupt condition and panic instead of hang

[Jimi Xenidis <jimix@xxxxxxxxxxxxxx>]

Yup Tony, thats it.
Beofre actually detecting this panic we uses to just "hang" with the  
last of the buffered output showing that Linux was processing the  
dt_* tree (IIRC), now at least the panic flushed out put and shows  
you why.
-JX
On Sep 14, 2006, at 3:11 AM, Tony Breeds wrote:

> On Tue, Sep 12, 2006 at 06:00:17PM +0200, Segher Boessenkool wrote:
> > > Sometimes when Xen is booted and we let Linux init the MPIC for
> > > "the second time" Xen could end up in a loop where the CPU is
> > > constantly being interrupted by the MPIC.
> > >
> > > Because of console buffering, the last message you see is some
> > > message from early kernel boot.
> > > Anyway.. we detect this now and you see a panic.
> > There seems to be a problem with the U3/U4 MPIC, where edge-
> > triggered interrupts are delivered to more than one CPU.  Every
> > CPU other than the one that ACKed it first, will get the spurious
> > vector (so functionally, the impact of this bug isn't that bad;
> > performance-wise it might be different).
> >
> > The UART IRQ [on JS2x and Maple] is an edge IRQ; if you produce
> > console output for every spurious interrupt, you'll get a nice
> > little storm.  Is that what's happening?
> >
> > > Yes, I believe, it has something to do with temperature.
> > Interesting observation, never thought of investigating that --
> > it's in line with my suspicion that something in the MPIC is
> > metastable though.
> I don't know if this is realted or something else but I just got:
> ---
> *** 0000 : Setup Done
> [boot]0015 Setup Done
> Built 1 zonelists.  Total pages: 49152
> Kernel command line: root=/dev/hda3 ro sysrq=1
> Sharing PIC with Xen -> maple_init_IRQ
> <6>mpic: Setting up MPIC "U3-MPIC" version 1.2 at f8040000, max 4 CPUs
> mpic: ISU size: 124, shift: 7, mask: 7f
> mpic: Initializing for 124 sources
> mpic: Setting up HT PICs workarounds for U3/U4
> mpic:   - HT:01.0 [0xb8] vendor 1022 device 7450 has 4 irqs
> mpic:   - HT:02.0 [0xb8] vendor 1022 device 7450 has 4 irqs
> mpic:   - HT:03.0 [0xf0] vendor 1022 device 7460 has 24 irqs
> (XEN)
> (XEN) ****************************************
> (XEN) Panic on CPU 0:
> (XEN) Too many (100) spurrious interrupts in a row
> (XEN)   Known problem, please halt and let machine idle/cool   then  
> reboot
> (XEN) ****************************************
> (XEN)
> (XEN) Reboot in five seconds...
> ---
>
> on my JS20, rebooting cleared the error.
>
> Yours Tony
>
>    linux.conf.au       http://linux.conf.au/ || http:// 
> lca2007.linux.org.au/
>    Jan 15-20 2007      The Australian Linux Technical Conference!

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