[3.8.y.z extended stable] Patch "i7core_edac: Fix PCI device reference count" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    i7core_edac: Fix PCI device reference count

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.20.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 607a1b80ee3792268c3828d3b3a628d3e3f4eee2 Mon Sep 17 00:00:00 2001
From: Jean Delvare <jdelvare at suse.de>
Date: Mon, 24 Feb 2014 09:39:27 +0100
Subject: i7core_edac: Fix PCI device reference count

commit c0f5eeed0f4cef4f05b74883a7160e7edde58b6a upstream.

The reference count changes done by pci_get_device can be a little
misleading when the usage diverges from the most common scheme. The
reference count of the device passed as the last parameter is always
decreased, even if the function returns no new device. So if we are
going to try alternative device IDs, we must manually increment the
device reference count before each retry. If we don't, we end up
decreasing the reference count, and after a few modprobe/rmmod cycles
the PCI devices will vanish.

In other words and as Alan put it: without this fix the EDAC code
corrupts the PCI device list.

This fixes kernel bug #50491:
https://bugzilla.kernel.org/show_bug.cgi?id=50491

Signed-off-by: Jean Delvare <jdelvare at suse.de>
Link: http://lkml.kernel.org/r/20140224093927.7659dd9d@endymion.delvare
Reviewed-by: Alan Cox <alan at linux.intel.com>
Cc: Mauro Carvalho Chehab <m.chehab at samsung.com>
Cc: Doug Thompson <dougthompson at xmission.com>
Signed-off-by: Borislav Petkov <bp at suse.de>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/edac/i7core_edac.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/edac/i7core_edac.c b/drivers/edac/i7core_edac.c
index e213d03..04e7b9b 100644
--- a/drivers/edac/i7core_edac.c
+++ b/drivers/edac/i7core_edac.c
@@ -1334,14 +1334,19 @@ static int i7core_get_onedevice(struct pci_dev **prev,
 	 * is at addr 8086:2c40, instead of 8086:2c41. So, we need
 	 * to probe for the alternate address in case of failure
 	 */
-	if (dev_descr->dev_id == PCI_DEVICE_ID_INTEL_I7_NONCORE && !pdev)
+	if (dev_descr->dev_id == PCI_DEVICE_ID_INTEL_I7_NONCORE && !pdev) {
+		pci_dev_get(*prev);	/* pci_get_device will put it */
 		pdev = pci_get_device(PCI_VENDOR_ID_INTEL,
 				      PCI_DEVICE_ID_INTEL_I7_NONCORE_ALT, *prev);
+	}

-	if (dev_descr->dev_id == PCI_DEVICE_ID_INTEL_LYNNFIELD_NONCORE && !pdev)
+	if (dev_descr->dev_id == PCI_DEVICE_ID_INTEL_LYNNFIELD_NONCORE &&
+	    !pdev) {
+		pci_dev_get(*prev);	/* pci_get_device will put it */
 		pdev = pci_get_device(PCI_VENDOR_ID_INTEL,
 				      PCI_DEVICE_ID_INTEL_LYNNFIELD_NONCORE_ALT,
 				      *prev);
+	}

 	if (!pdev) {
 		if (*prev) {
--
1.8.3.2