netdev - Re: [linux-pm] [PATCH] 3c59x: Get rid of "Trying to free already-free IRQ"

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Date:	Fri, 25 Sep 2009 00:43:47 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Anton Vorontsov <avorontsov@...mvista.com>
cc:	David Miller <davem@...emloft.net>, <netdev@...r.kernel.org>,
	<linux-pm@...ts.linux-foundation.org>
Subject: Re: [linux-pm] [PATCH] 3c59x: Get rid of "Trying to free already-free
 IRQ"

On Thu, 24 Sep 2009, Anton Vorontsov wrote:

> Though, there are few other issues with suspend/resume in this driver.
> The intention of calling free_irq() in suspend() was to avoid any
> possible spurious interrupts (see commit 5b039e681b8c5f30aac9cc04385
> "3c59x PM fixes"). But,
> 
> - On resume, the driver was requesting IRQ just after pci_set_master(),
>   but before vortex_up() (which actually resets 3c59x chips).

Shouldn't it be possible to reset the chip (or at least prevent it from 
generating spurious IRQs) during the early-resume phase?

> - Issuing free_irq() on a shared IRQ doesn't guarantee that a buggy
>   HW won't trigger spurious interrupts in another driver that
>   requested the same interrupt. So, if we want to protect from
>   unexpected interrupts, then on suspend we should issue disable_irq(),
>   not free_irq().

What if some other device shares the IRQ and still relies on receiving
interrupts when this code runs?  Won't disable_irq() mess up the other
device?

Alan Stern

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