linux-kernel - Re: [PATCH] pci: Fixing drivers/pci/search.c compilation warning.

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Date:	Mon, 27 Oct 2008 11:18:43 +0800
From:	"Zhao, Yu" <yu.zhao@...el.com>
To:	Matthew Wilcox <matthew@....cx>
CC:	Yu Zhao <yu.zhao@...scape.net>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"greg@...ah.com" <greg@...ah.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"stable@...nel.org" <stable@...nel.org>,
	Rakib Mullick <rakib.mullick@...il.com>
Subject: Re: [PATCH] pci: Fixing drivers/pci/search.c compilation warning.

Matthew Wilcox wrote:
> On Sun, Oct 26, 2008 at 08:51:25PM +0800, Yu Zhao wrote:
>> This reminds me of other problems of PCI search functions.
>>
>> The 'dev_start' is passed to bus_find_device(), and its 'knode_bus' 
>> reference count is decreased by klist_iter_init_node() in that function. 
>> The problem is the reference count may be already decrease to 0 because 
>> the PCI device 'from' is hot-plugged off (e.g., pci_remove_bus) when the 
>> search goes. A warning is fired when klist_iter_init_node() detects the 
>> reference count becomes 0.
>>
>> Some code uses pci_find_device() in a way that is not safe with the 
>> hotplug, because a device may be destroyed after bus_find_device() 
>> returns it and before it's held by pci_dev_get() in the next round. 
>> Following is an example from a random grep:
> 
> Yes, that's why pci_find_device() is deprecated.  But it doesn't also
> need to be buggy ;-)
> 

How about pci_get_bus_and_slot()? People would meet the problem with it 
anyway.

Thanks,
Yu
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