linux-kernel - Re: ACPI hotplug panic with current git head

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Date:	Thu, 15 Jan 2009 15:12:27 -0500
From:	James Bottomley <James.Bottomley@...senPartnership.com>
To:	Len Brown <lenb@...nel.org>
Cc:	linux-acpi@...r.kernel.org,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-pci@...r.kernel.org,
	"Barnes, Jesse" <jesse.barnes@...el.com>,
	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>,
	shaohua.li@...el.com
Subject: Re: ACPI hotplug panic with current git head

On Thu, 2009-01-15 at 14:54 -0500, James Bottomley wrote:
> On Thu, 2009-01-15 at 14:22 -0500, Len Brown wrote:
> > On Thu, 15 Jan 2009, James Bottomley wrote:
> > 
> > > On Mon, 2009-01-12 at 18:48 -0600, James Bottomley wrote:
> > > > On Mon, 2009-01-12 at 16:16 -0500, Len Brown wrote:
> > > > > > This is on an IBM Maia system with the calgary IOMMU enabled. It's a
> > > > > > fatal boot up panic.
> > > > > > 
> > > > > 
> > > > > James,
> > > > > A guided bisect...
> > > > > Please let me know which of these fail
> > > > > 
> > > > > a3a798c88a14b35e5d4ca30716dbc9eb9a1ddfe2 is 2.6.29 at ACPI merge
> > > > > efcb3cf7f00c3c424db012380a8a974c2676a3c8 is 2.6.29 before ACPI merge
> > > > 
> > > > Didn't try these (being after the failure)
> > > > 
> > > > > ec9f168fcc344d2ffec1c8c822076bf22dab5c33 is 2.6.28 with most ACPI
> > > > 
> > > > This is the failing one.
> > > > 
> > > > > e8443c358c34f3fe65236e24147ddf0cd0e61b08 is 2.6.28 plus just ACPICA
> > > > 
> > > > This one boots fine.
> > > > 
> > > > > Please test the "2.6.28+ACPICA" one first.
> > > > > If it fails, we are close so you can skip the others above
> > > > > and bisect between that and 2.6.28.
> > > > 
> > > > I'll try bisecting between ec9f168fcc344d2ffec1c8c822076bf22dab5c33 and
> > > > e8443c358c34f3fe65236e24147ddf0cd0e61b08.
> > > 
> > > OK, bisection complete.  It's not actually coming from the ACPI tree but
> > > from the PCI one (appropriate CC's added).
> > > 
> > > The commit causing the boot panic is:
> > > 
> > > commit e8c331e963c58b83db24b7d0e39e8c07f687dbc6
> > > Author: Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>
> > > Date:   Wed Dec 17 12:09:12 2008 +0900
> > > 
> > >     PCI hotplug: introduce functions for ACPI slot detection
> > > 
> > > I'm still not sure why, though
> > 
> > Nothing jumped out at me in the patch.
> > Does reverting e8c331e963c58b83db24b7d0e39e8c07f687dbc6
> > make the boot crash go away?
> 
> Yes, but then it would ... the call sequence is through the reverted
> code.

It looks like acpi_pci_get_bridge_handle() is returning NULL, so this is
the fix that works for me.

James

---

diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c
index f09b101..803d9dd 100644
--- a/drivers/pci/hotplug/acpiphp_glue.c
+++ b/drivers/pci/hotplug/acpiphp_glue.c
@@ -266,6 +266,8 @@ static int detect_ejectable_slots(struct pci_bus *pbus)
 	int found = acpi_pci_detect_ejectable(pbus);
 	if (!found) {
 		acpi_handle bridge_handle = acpi_pci_get_bridge_handle(pbus);
+		if (!bridge_handle)
+			return 0;
 		acpi_walk_namespace(ACPI_TYPE_DEVICE, bridge_handle, (u32)1,
 				    is_pci_dock_device, (void *)&found, NULL);
 	}


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