Patchwork [01/40] PCI: fix default vga ref_count

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Submitter Yinghai Lu
Date Sept. 19, 2012, 6:54 p.m.
Message ID <1348080894-23412-2-git-send-email-yinghai@kernel.org>
Download mbox | patch
Permalink /patch/185143/
State Accepted
Headers show

Comments

Yinghai Lu - Sept. 19, 2012, 6:54 p.m.
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@kernel.org>
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>
---
 drivers/gpu/vga/vgaarb.c |   14 +++++++++-----
 1 files changed, 9 insertions(+), 5 deletions(-)
Bjorn Helgaas - Sept. 21, 2012, 8:52 p.m.
On Wed, Sep 19, 2012 at 12:54 PM, Yinghai Lu <yinghai@kernel.org> 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@kernel.org>
> 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>
> ---
>  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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Yinghai Lu - Sept. 21, 2012, 9:18 p.m.
On Fri, Sep 21, 2012 at 1:52 PM, Bjorn Helgaas <bhelgaas@google.com> wrote:
> On Wed, Sep 19, 2012 at 12:54 PM, Yinghai Lu <yinghai@kernel.org> wrote:
>> --- 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);

ah, i missed that, pci_dev_put and pci_dev_get check that inside.

>
> I haven't seen an answer to Matthew's question about whether we want
> to check for "vga_default == pdev".

yes, that could avoid the extra put/get pair.

Please check updated version.

-Yinghai
Jiang Liu - Sept. 23, 2012, 3:25 p.m.
On 09/20/2012 02:54 AM, Yinghai Lu 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@kernel.org>
> 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>
> ---
>  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;
>  }
Seems it could be simplified as
void vga_set_default_device(struct pci_dev *pdev)
{
	pci_dev_put(vga_default);
 	vga_default = pci_dev_get(pdev);
}
--Gerry

>  #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))
> 

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Patch

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;
 }
 #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))