Re: [patch, -rc5-mm1] locking validator: special rule: 8390.c disable_irq()

[Ingo Molnar <mingo@elte.hu>]

* Arjan van de Ven <arjan@infradead.org> wrote:

> On Wed, 2006-05-31 at 22:02 +0200, Ingo Molnar wrote:
> > untested on 8390 hardware, but ought to solve the lockdep false 
> > positive.
> > 
> > -----------------
> > Subject: locking validator: special rule: 8390.c disable_irq()
> > From: Ingo Molnar <mingo@elte.hu>
> > 
> > 8390.c knows that ei_local->page_lock can only be used by an irq
> > context that it disabled -
> 
> btw I think this is no longer correct with the irq polling stuff Alan 
> added to the kernel recently...

hm, indeed. misrouted_irq() goes through all irq descriptors and ignores 
IRQ_DISABLED flag - rendering disable_irq() useless in essence, and 
introducing the kind of deadlocks that lockdep warned about.

Andrew, as far as i can see with irqfixup this isnt a lockdep false 
positive but a real deadlock scenario - a spurious IRQ might arrive 
during vortex_timer() execution and might cause the execution of 
misrouted_irq(), which could execute vortex_interrupt() => deadlock.

Alan, is this a necessary property of irqpoll/irqfixup? Shouldnt 
irqfixup leave irq descriptors alone that are disabled?

	Ingo
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