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.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: x86@kernel.org
Cc: Dave Airlie <airlied@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Julia Lawall <julia@diku.dk>
Cc: Matthew Garrett <mjg@redhat.com>

1 files changed, 8 insertions, 6 deletions

diff --git a/drivers/gpu/vga/vgaarb.c b/drivers/gpu/vga/vgaarb.c
index 3df8fc0ec01a..7a439b84dd42 100644
--- a/drivers/gpu/vga/vgaarb.c
+++ b/drivers/gpu/vga/vgaarb.c
@@ -141,7 +141,11 @@ EXPORT_SYMBOL_GPL(vga_default_device);
 
 void vga_set_default_device(struct pci_dev *pdev)
 {
-        vga_default = pdev;
+        if (vga_default == pdev)
+                return;
+
+        pci_dev_put(vga_default);
+        vga_default = pci_dev_get(pdev);
 }
 #endif
 
@@ -577,7 +581,7 @@ static bool vga_arbiter_add_pci_device(struct pci_dev *pdev)
 #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 +617,8 @@ static bool vga_arbiter_del_pci_device(struct pci_dev *pdev)
         }
 
 #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))