On Wed, Sep 19, 2012 at 12:54 PM, Yinghai Lu <yinghai@xxxxxxxxxx> wrote:
> 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@xxxxxxxxxx>
> Cc: x86@xxxxxxxxxx
> Cc: Dave Airlie <airlied@xxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Julia Lawall <julia@xxxxxxx>
> Cc: Matthew Garrett <mjg@xxxxxxxxxx>
> ---
> drivers/gpu/vga/vgaarb.c | 14 +++++++++-----
> 1 files changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/vga/vgaarb.c b/drivers/gpu/vga/vgaarb.c
> index b6852b7..0888951e 100644
> --- a/drivers/gpu/vga/vgaarb.c
> +++ b/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;
I think this is equivalent to:
pci_dev_put(vga_default);
vga_default = pci_dev_get(pdev);
I haven't seen an answer to Matthew's question about whether we want
to check for "vga_default == pdev".
> }
> #endif
> @@ -577,7 +583,7 @@ 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 +619,8 @@ 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))
> --
> 1.7.7
>
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