linux-kernel - Re: [PATCH 0/7] Fixups for duplicate slot names

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Date:	Mon, 11 Aug 2008 10:19:06 +0900
From:	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>
To:	Alex Chiang <achiang@...com>,
	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>,
	Matthew Wilcox <matthew@....cx>,
	Pierre Ossman <drzeus-list@...eus.cx>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	LKML <linux-kernel@...r.kernel.org>, linux-pci@...r.kernel.org
Subject: Re: [PATCH 0/7] Fixups for duplicate slot names

Alex Chiang wrote:
> * Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>:
>> Hi Alex-san,
>>
>> Thank you for patches!
>>
>> I looked at your patches and it looks good. But I have only one
>> concern about how to allocate/free memory for slot name.
>>
>> With your change, memory region for slot name will be allocated
>> by hotplug *controller* driver and it can be freed using kfree()
>> by hotplug *core* driver (not hotplug controller driver). So all
>> hotplug controller drivers including drivers implemented in the
>> future need to take it into account.
>>
>> I think it will be more robust if we can allocate and free memory
>> in the same component (maybe hotplug core driver in this case).
> 
> Hm, I didn't think this would be a problem. The sequence is:
> 
> 	- controller allocates memory for slot name
> 	- if core detects a collision:
> 		- it frees the name
> 		- it allocates new memory for name
> 		- it assigns that memory to the name parameter
> 	- controller->release will eventually free the name
> 
> So it shouldn't matter if the core frees the original name
> pointer and allocates new memory, because the core will change
> the pointer for the controller.
> 
> This is why I had to change the interface of pci_create_slot()
> from taking a const char *name to a char *name.
> 
> Is there something I'm missing?
> 
> /ac

I'm worrying about the following cases for example:

 - hotplug controller driver allocates memory for slot name using
   other than kmalloc().

 - hotplug controller driver allocates memory for slot name as
   a part of another data structure.

Thanks,
Kenji Kaneshige


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