On Thu, May 03, 2007 at 12:19:32AM +0200, Bernhard Walle wrote:
> * Vivek Goyal <[email protected]> [2007-04-30 10:48]:
> >
> > handle_edge_irq() already makes sure that desc->action is not null, still
> > note_interrupt() is receiving desc->action as null, that's strange. On my
> > system this is happening for irq 4 and /proc/interrupt shows that it is
> > coming from "serial".
>
> Unfortunately, I couldn't reproduce this here. Vivek, do you have time
> to take a look at this at your site? For the meanwhile, should I
> create a patch that checks for desc->action in note_interrupt(), too?
>
Hi Bernhard,
I can reproduce this problem only on one machine. I think there is some
race condition and your code somehow just exposes it.
I put few WARN_ON(!desc->action) in handle_edge_irq() and what I find
that after handle_IRQ_event(), desc->action has become null. That means
in the meantime somebody has gone ahead and modified the desc. This must
have happened because we have release desc->lock while running
handle_IRQ_event().
This means there is a race somewhere. It is verified by the fact that
this problem does not occur if same system is booted with only one
cpu (maxcpus=1).
Thanks
Vivek
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