linux-kernel - [PATCH] PCI: fix default vga ref

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Date:	Tue, 18 Sep 2012 16:44:42 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	Yinghai Lu <yinghai@...nel.org>, x86@...nel.org,
	Dave Airlie <airlied@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Julia Lawall <julia@...u.dk>, Matthew Garrett <mjg@...hat.com>
Subject: [PATCH] PCI: fix default vga ref_count

when __ARCH_HAS_VGA_DEFAULT_DEVICE is not defined, aka EFIFB is not used,
for static path, vga_default setting is through vga_arbiter_add_pci_device.
and later x86 pci_fixup_video, will skip setting again.
- subsys_initcall(vga_arb_device_init) come first to call vga_arbiter_add_pci_device. It will call pci_get_dev to hold one reference.

for hotplug add path, even vga_arbiter_add_pci_device is called via notifier,
but it will check VGA_RSRC_LEGACY_MASK that is not set for hotplug path.
So x86 pci_fixup_video will take over to call vga_set_default_device().
It will not hold one refrence.

Later for hotplug remove path, vga_arbiter_del_pci_device that does not check
VGA_RSRC_LEGACY_MASK will call put_device and it will cause ref_count to
decrease extra. that will have that pci device get deleted early wrongly.

Need to make get/put balance for both cases.

-v2: According to Bjorn, update vga_set_default_device instead...

Signed-off-by: Yinghai Lu <yinghai@...nel.org>
Cc: x86@...nel.org
Cc: Dave Airlie <airlied@...hat.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Julia Lawall <julia@...u.dk>
Cc: Matthew Garrett <mjg@...hat.com>

---
 drivers/gpu/vga/vgaarb.c |   14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

Index: linux-2.6/drivers/gpu/vga/vgaarb.c
===================================================================
--- linux-2.6.orig/drivers/gpu/vga/vgaarb.c
+++ linux-2.6/drivers/gpu/vga/vgaarb.c
@@ -141,6 +141,12 @@ EXPORT_SYMBOL_GPL(vga_default_device);
 
 void vga_set_default_device(struct pci_dev *pdev)
 {
+	if (vga_default)
+		pci_dev_put(vga_default);
+
+	if (pdev)
+		pdev = pci_dev_get(pdev);
+
 	vga_default = pdev;
 }
 #endif
@@ -577,7 +583,7 @@ static bool vga_arbiter_add_pci_device(s
 #ifndef __ARCH_HAS_VGA_DEFAULT_DEVICE
 	if (vga_default == NULL &&
 	    ((vgadev->owns & VGA_RSRC_LEGACY_MASK) == VGA_RSRC_LEGACY_MASK))
-		vga_default = pci_dev_get(pdev);
+		vga_set_default_device(pdev);
 #endif
 
 	vga_arbiter_check_bridge_sharing(vgadev);
@@ -613,10 +619,8 @@ static bool vga_arbiter_del_pci_device(s
 	}
 
 #ifndef __ARCH_HAS_VGA_DEFAULT_DEVICE
-	if (vga_default == pdev) {
-		pci_dev_put(vga_default);
-		vga_default = NULL;
-	}
+	if (vga_default == pdev)
+		vga_set_default_device(NULL);
 #endif
 
 	if (vgadev->decodes & (VGA_RSRC_LEGACY_IO | VGA_RSRC_LEGACY_MEM))
--
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