netdev - Re: [proposed patch] via-rhine: prevent oops when requesting an IRQ

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Date:	Thu, 06 Nov 2008 01:07:41 -0500
From:	Jeff Garzik <jeff@...zik.org>
To:	Chuck Ebbert <cebbert@...hat.com>
CC:	netdev@...r.kernel.org
Subject: Re: [proposed patch] via-rhine: prevent oops when requesting an IRQ

Chuck Ebbert wrote:
> via-rhine: prevent oops when requesting an IRQ
> 
> via-rhine requests an IRQ before it's ready to handle an interrupt.
> It oopses when CONFIG_DEBUG_SHIRQ is enabled.
> 
> https://bugzilla.redhat.com/show_bug.cgi?id=469303
> 
> ---
> 
> NOTE: UNTESTED: Is it okay to init the hardware before requesting the
> IRQ, or should that be done afterward?

First of all, _ideally_ your interrupt handler should be able to any 
state of software initialization, once registers are mapped.  So I would 
first concentrate on "hardening" the interrupt handler, if feasible.

It is certainly a common technique to disable interrupts somehow, during 
initialization of the hardware.  Note, though, that doing things before 
request_irq() is no real guarantee you are out of danger -- you might be 
on a shared PCI irq, and your init causes that interrupt to "scream" 
even though your driver has not registered the irq.

	Jeff

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