Re: [patch] 2.4.0, 2.4.0-ac12: APIC lock-ups

[Maciej W. Rozycki]

On Sat, 3 Feb 2001, Manfred Spraul wrote:

> I found another workaround:
> 8390.c currently calls
> 
> 	outb_p(ENISR_ALL, e8390_base + EN0_IMR);
> 	enable_irq(dev->irq);
> 
> and locks up after ~ 100 packets flood ping.
> 
> If I reorder these calls to
> 
> 	enable_irq(dev->irq);
> 	outb_p(ENISR_ALL, e8390_base + EN0_IMR);
> 	(and the correct spin_lock()'s)
> 
> the lockup disappears.

 Is it possible that asserting the IRQ when the mask is active makes it be
mishandled?

> Playing with the trigger mode is not 100% reliable - I assume it kicks
> the io apic only after several changes of the trigger mode bit. Maciej's
> patch switches that bit twice during every start_tx operation and thus
> doesn't lock up, my patch touches the redirection entry exactly once and
> reliably locks up - even if I change trigger mode, polarity, delivery
> mode and vector during enable_level_irq().

 I believe I recover from the lockup -- it's the mask function that
recovers.  But another one happens at the unmask time, I suppose.

> Any ideas?

 I'll implement the IRQ unlocker I was thinking first.  The idea is not to
try to prevent the lockup from happening as it might even be impossible
but to make the unlocker trigger after a lockup happens instead.  I should
have an implementation ready soon.

-- 
+  Maciej W. Rozycki, Technical University of Gdansk, Poland   +
+--------------------------------------------------------------+
+        e-mail: [e-mail], PGP key available        +