Gérard Roudier wrote:
> 
> So, why not using a pure software flag in memory and only tampering the
> things if the offending interrupt is actually delivered ? If the given
> interrupt is delivered and the software mask is set we could simply do:
> 
> - MASK the given interrupt
> - EOI it.
> - return
>
Good idea.
I implemented it, and it was a full success: not it always locks up :-(

If I apply the attached patch, then I get a lockup after ~ 100 packets
flood ping.
I've also attached the dmesg print.
I know that startup is currently wrong (must set trigger to level), but
that doesn't matter since I only ifup once.

But I think we can change the bug description:

If an io apic io redirection entry is unmasked while the irq pin is
active, then the io apic sends out the interrupt as edge triggered, but
nevertheless sets the IRR bit.

In a second test run I checked the TMR bit in the local apics: the bit
on the cpu that received the last interrupt is really 0.

I'll not try a 2 step enable:
* unmask.
* io_apic_sync()
* set trigger mode to level.

--
	Manfred