Re: [PATCH] PHYLIB: IRQ event workqueue handling fixes

Maciej W. Rozycki
2007-10-16T17:19:58Z

On Tue, 16 Oct 2007, Jarek Poplawski wrote:

> Yes, it's all right here. Sorry for bothering - I should've found this
> by myself.

Ah, no problem -- even with the right keys you may sometimes get lost in
the results.

> I've still some doubts about this possible enable_irq() after
> free_irq(). If it's the only handler the status would be changed again
> and at least some of this code in check_irq_resend() would be run, but
> I can miss something again or/and this doesn't matter, as well.

Well, enable_irq() and disable_irq() themselves are nesting, so they are
not a problem. OTOH, free_irq() does not seem to maintain the depth count
correctly, which looks like a bug to me and which could trigger regardless
of whether flush_scheduled_work() or cancel_work_sync() was called.

The reason is CONFIG_DEBUG_SHIRQ which makes a simulated interrupt event
be sent at the end of free_irq(). It looks like a problem that is
complementary to one I signalled here:

http://lkml.org/lkml/2007/9/12/82

with respect to request_irq(), where, similarly, such an interrupt event
is sent at the beginning. It looks like nobody was concerned back then,
but perhaps it is time to do a better investigation now and propose a
solution.

I'll think about it and thanks for your inquisitiveness that has led to
these conclusions.

Maciej