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SubjectRe: [PATCH -v2] pci: Check bridge resources after resource allocation.
On 05/16/2011 12:59 AM, Ram Pai wrote:
> On Fri, May 13, 2011 at 06:06:17PM -0700, Yinghai Lu wrote:
>> On 05/12/2011 12:34 PM, Jesse Barnes wrote:
>>> On Thu, 12 May 2011 12:18:43 -0700
>>> Linus Torvalds <torvalds@linux-foundation.org> wrote:
>>>
>>>> On Thu, May 12, 2011 at 11:37 AM, Jesse Barnes <jbarnes@virtuousgeek.org> wrote:
>>>>>
>>>>> Linus, I don't have anything else queued up, so you may as well take
>>>>> this one directly if you want it in 2.6.39. It's a regression fix, but
>>>>> resource changes always make me nervous. Alternately, I could put it
>>>>> into 2.6.40 instead, the backport to 2.6.39.x if it survives until
>>>>> 2.6.40-rc2 or so...
>>>>
>>>> Considering the trouble resource allocation always ends up being, I'd
>>>> almost prefer that "mark it for stable and put it in the 2.6.40
>>>> queue".
>>>>
>>>> Afaik this problem hasn't actually hit any "normal" users, has it? So ...
>>>
>>> Sounds good, thanks. Yeah I don't think it's hit anyone but Yinghai
>>> (at least I don't know of any other reports).
>>>
>>
>> please check this one, it should be safe for 2.6.39 ?
>
>> size0 = calculate_iosize(size, min_size, size1,
>> resource_size(b_res), 4096);
>> - size1 = !add_size? size0:
>> + size1 = (!add_head || (add_head && !add_size)) ? size0 :
>> calculate_iosize(size, min_size+add_size, size1,
>> resource_size(b_res), 4096);
>
> This solves the problem you encountered.
>
> But, I think, it still does not fix the following scenario:
>
> adjust_resource() failing to allocate additional resource to a hotplug bridge
> that has no children. In this case ->flags of that 'struct resource'
> continues to be set even when no resource is allocated to that hot-plug bridge.
>
that case: requested_size will be 0, but add_size will not be zero.

res->flags is not cleared in pbus_size_xx, so it will be put into head.
so it will go through first path.
...
if (!resource_size(res) && add_size) {
res->end = res->start + add_size - 1;
if(pci_assign_resource(list->dev, idx))
reset_resource(res);
} else if (add_size) {
adjust_resource(res, res->start,
resource_size(res) + add_size);
}

and if it fails to get assign, the flags will get clear in reset_resource.

so it should be ok. and testing in one my setup show those flags get clear correctly and does not emit any warning.

Thanks

Yinghai


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