PROBLEM: 4.15.0-rc3 APIC causes lockups on Core 2 Duo laptop

[Alexandru Chirvasitu]

On Sat, Dec 23, 2017 at 02:32:52PM +0100, Thomas Gleixner wrote:
> On Sat, 23 Dec 2017, Dexuan Cui wrote:
> 
> > > From: Alexandru Chirvasitu [mailto:achirvasub at gmail.com]
> > > Sent: Friday, December 22, 2017 14:29
> > > 
> > > The output of that precise command run just now on a freshly-compiled
> > > copy of that commit is attached.
> > > 
> > > On Fri, Dec 22, 2017 at 09:31:28PM +0000, Dexuan Cui wrote:
> > > > > From: Alexandru Chirvasitu [mailto:achirvasub at gmail.com]
> > > > > Sent: Friday, December 22, 2017 06:21
> > > > >
> > > > > In the absence of logs, the best I can do at the moment is attach a
> > > > > picture of the screen I am presented with on the apic=debug boot
> > > > > attempt.
> > > > > Alex
> > > >
> > > > The panic happens in irq_matrix_assign_system+0x4e/0xd0 in your picture.
> > > > IMO we should find which line of code causes the panic. I suppose
> > > > "objdump -D kernel/irq/matrix.o" can help to do that.
> > > >
> > > > Thanks,
> > > > -- Dexuan
> > 
> > The BUG_ON panic happens at line 147:
> >                    BUG_ON(!test_and_clear_bit(bit, cm->alloc_map));
> > 
> > I'm sure Thomas and Dou know it better than me. 
> 
> I'll have a look after the holidays.
>

Thanks for that!

A quick follow-up on my inability to make kexec / kdump work in order
to perhaps produce better logs: I've done another bisect for that with
this result:

# first bad commit: [e802a51ede91350438c051da2f238f5e8c918ead] x86/idt: Consolidate IDT invalidation

I am quite certain this is the one for that issue. Its only parent is

# good: [8f55868f9e42fea56021b17421914b9e4fda4960] x86/idt: Remove unused set_trap_gate()

(i.e. one of the "good" commits I hit upon during the bisect).

On the core 2 duo machine I've been referring to e802a51 and later
commits simply return me to a regular BIOS boot when issuing either
kexec -e on a loaded crash kernel or crashing with echo c >
/proc/sysrq-trigger.


Alex