Re: [PATCH] PCI Hotplug: acpiphp: don't store a pci_dev in acpiphp_func

[Matthew Wilcox <matthew@wil.cx>]

On Thu, May 21, 2009 at 04:21:15PM -0600, Alex Chiang wrote:
> In other words, if acpiphp has claimed a PCI device, and that
> device is logically removed, then acpiphp may oops when it
> attempts to access it again.
> 
> 	# echo 1 > /sys/bus/pci/devices/$device/remove
> 	# echo 0 > /sys/bus/pci/slots/$slot/power
> 
> The root cause of this oops is that the logical remove ("echo 1 >
> /sys/bus/pci/devices/$device/remove") destroyed the pci_dev. The
> pci_dev struct itself wasn't deallocated because acpiphp kept a
> reference, but some of its fields became invalid.
> 
> acpiphp doesn't have any real reason to keep a pointer to a
> pci_dev around. It can always derive it using pci_get_slot().
> 
> If a logical remove destroys the pci_dev, acpiphp won't find it
> and is thus prevented from causing mischief.
> 
> Reported-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
> Acked-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
> Signed-off-by: Alex Chiang <achiang@hp.com>

I think this is the right approach.  The more minimal way to fix this
would be to check that the pdev was valid before destroying it ... but
I approve of deleting more code from acpiphp ;-)  You do end up doing
slightly more work in the remove case, but this is such an infrequent
operation that it really doesn't matter.

Reviewed-by: Matthew Wilcox <willy@linux.intel.com>

-- 
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."