Re: IRQ behaivour has been changed from v4.14 to v4.15-rc1

[Thomas Gleixner]

On Thu, 28 Dec 2017, Andy Shevchenko wrote:
> On Thu, 2017-12-28 at 18:21 +0100, Thomas Gleixner wrote:
> > > [   85.167061] spurious APIC interrupt through vector ff on CPU#0,
> > > should never happen.
> > > [   85.199886] atomisp-isp2 0000:00:03.0: stream[0] started.
> > > 
> > > and Ctrl+C does NOT work. Machine just hangs.
> > > 
> > > It might be related to this:
> > > https://lkml.org/lkml/2017/12/22/697
> > 
> > I don't think so.
> > 
> > Does the patch below cure it?
> 
> Unfortunately, no.
> 
> Same behaviour.
> 
> Tell me if I need to provide some debug before it hangs. For now I have
> apic=debug (AFAIR it doesn't affect this).

The interesting question is why that spurious APIC interrupt through vector
ff happens. Can you please add the following to the kernel command line:

 'trace_events=irq_vectors:* ftrace_dump_on_oops'

and apply the patch below. That should spill out the trace over serial (I
hope you have that ...)

Thanks,

        tglx

8<---------------
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1978,6 +1978,8 @@ void __init register_lapic_address(unsig
        /* see sw-dev-man vol 3, chapter 7.4.13.5 */
        pr_info("spurious APIC interrupt through vector %02x on CPU#%d, "
                "should never happen.\n", vector, smp_processor_id());
+       tracing_off();
+       BUG();
 
        trace_spurious_apic_exit(vector);
        exiting_irq();