linux-kernel - Re: [BUG] irq_dispose_mapping after irq request failure

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Date:	Tue, 12 Feb 2013 19:53:37 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Michael Ellerman <michael@...erman.id.au>
Cc:	Grant Likely <grant.likely@...retlab.ca>,
	Baruch Siach <baruch@...s.co.il>,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [BUG] irq_dispose_mapping after irq request failure

On Tue, 2013-02-12 at 17:18 +1100, Michael Ellerman wrote:
> 
> I don't think you can, "active" is not well defined. Other code may have
> done nothing other than create the mapping and remembered the virq,
> which will break if you destroy the mapping. Or?

Active as in "requested". Yes there's a potential problems with multiple
requests for mappings & shared interrupts. This is not a problem for PCI
on powerpc because we don't free those mappings afaik.

> I agree refcounting is not fun. It'll end up with the same mess as
> of_node_get/put() where practically every 2nd piece of code leaks
> references.
> 
> I guess we can't go the other way, and say that mapping the same hwirq
> twice is an error.

Might be worth it, and force the sharing case to be handled at some kind
of upper level (bus or platform).

Ben.


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