linux-kernel - Re: refcount leak in pci_get

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Message-ID: <20080821202504.GU8318@parisc-linux.org>
Date:	Thu, 21 Aug 2008 14:25:04 -0600
From:	Matthew Wilcox <matthew@....cx>
To:	Alex Chiang <achiang@...com>, gregkh@...e.de,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: refcount leak in pci_get_device()?

On Thu, Aug 21, 2008 at 02:19:18PM -0600, Alex Chiang wrote:
> #define for_each_pci_dev(d) while ((d = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, d)) != NULL)
> 
> That eventually calls pci_get_dev_by_id(), which increases the
> refcount on the device, but never decrements it.
> 
> Looks like that change in behavior happened here:
> 
> 	PCI: clean up search.c a lot
> 	95247b57ed844511a212265b45cf9a919753aea1
> 
> pci_get_device() used to decrement the refcount, but no longer
> does.
> 
> Thanks to Matthew Wilcox for helping me get this far...
> 
> Like I said, I'm still trying to track down my particular issue,
> but I'd like to get your opinion on this.

In particular, I'd like to know whether this should be fixed by
pci_get_dev_by_id() decrementing the refcount of from/dev_start,
pci_get_subsys() decrementing 'from', or by bus_find_device()
decrementing 'start'.  It looks like bus_find_device() is the place
where this should logically happen, but the kerneldoc doesn't document
the intended behaviour.

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."
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