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SubjectRe: [PATCH -v2] pci: Check bridge resources after resource allocation.
On Mon, May 16, 2011 at 01:55:38PM -0700, Yinghai Lu wrote:
> 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.


Ack. You are right.

Linus/Jesse: can we consider this patch for 2.6.39? It is the simplest fix to the problem.

Reviewed-by: Ram Pai <linuxram@us.ibm.com>

RP


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