linux-kernel - Re: Regression with commit f9cde5f in 2.6.30-gitX

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Message-Id: <1245860100.3216.7.camel@localhost.localdomain>
Date:	Wed, 24 Jun 2009 21:45:00 +0530
From:	Jaswinder Singh Rajput <jaswinder@...nel.org>
To:	Gary Hade <garyhade@...ibm.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Larry Finger <Larry.Finger@...inger.net>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	x86 maintainers <x86@...nel.org>, Len Brown <lenb@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: Regression with commit f9cde5f in 2.6.30-gitX

On Wed, 2009-06-24 at 08:56 -0700, Gary Hade wrote:
> On Wed, Jun 24, 2009 at 04:51:48PM +0200, Thomas Gleixner wrote:
> > On Wed, 24 Jun 2009, Jaswinder Singh Rajput wrote:
> > > Reported-by: Larry Finger <Larry.Finger@...inger.net>
> > > Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@...il.com>
> > > ---
> > >  arch/x86/pci/acpi.c |   16 ++++++++++------
> > >  1 files changed, 10 insertions(+), 6 deletions(-)
> > > 
> > > diff --git a/arch/x86/pci/acpi.c b/arch/x86/pci/acpi.c
> > > index 16c3fda..0bc015f 100644
> > > --- a/arch/x86/pci/acpi.c
> > > +++ b/arch/x86/pci/acpi.c
> > > @@ -69,6 +69,9 @@ setup_resource(struct acpi_resource *acpi_res, void *data)
> > >  	struct resource *root;
> > >  	int max_root_bus_resources = PCI_BUS_NUM_RESOURCES;
> > >  
> > > +	if (info->res_num >= PCI_BUS_NUM_RESOURCES)
> > > +		return AE_OK;
> > > +
> > >  	status = resource_to_addr(acpi_res, &addr);
> > >  	if (!ACPI_SUCCESS(status))
> > >  		return AE_OK;
> > > @@ -94,17 +97,18 @@ setup_resource(struct acpi_resource *acpi_res, void *data)
> > >  	if (bus_has_transparent_bridge(info->bus))
> > >  		max_root_bus_resources -= 3;
> > >  	if (info->res_num >= max_root_bus_resources) {
> > > -		printk(KERN_WARNING "PCI: Failed to allocate 0x%lx-0x%lx "
> > > -			"from %s for %s due to _CRS returning more than "
> > > -			"%d resource descriptors\n", (unsigned long) res->start,
> > > -			(unsigned long) res->end, root->name, info->name,
> > > -			max_root_bus_resources);
> > > +		pr_warning("PCI: Failed to allocate 0x%lx-0x%lx "
> > > +			   "from %s for %s due to _CRS returning more than "
> > > +			   "%d resource descriptors\n",
> > > +			   (unsigned long)res->start, (unsigned long)res->end,
> > > +			   root->name, info->name, max_root_bus_resources);
> > 
> > Can you please avoid mixing cleanup patches with bug fixes ? I almost
> > did not see the line below.
> > 
> > > +		info->bus->resource[info->res_num] = res;
> > 
> > Storing the resource in defeats the purpose of the original patch,
> > which makes sure that we do _NOT_ use the last 3 slots of the resource
> > array for a root bus with a transparent bridge.
> > 
> > >  		info->res_num++;
> > 
> > This is the real bug. info->res_num should not be incremented when we
> > run out of resources already.
> 
> This probably isn't needed but I don't think it is the cause of
> the problem.  It is just counting the number of _CRS returned
> resources and I believe subsequent visits to setup_resource()
> for additional returned resources will generate the same warning
> as it also would if the instruction were removed and no longer
> being used to keep an accurate count.
> 

Yes, this count is needed to avoid PCI failure.

Thanks,
--
JSR

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