diff mbox

[v2,02/13] drm/vmwgfx: Stop using plane->fb in vmw_kms_helper_dirty()

Message ID 20180525185045.29689-3-ville.syrjala@linux.intel.com (mailing list archive)
State New, archived
Headers show

Commit Message

Ville Syrjälä May 25, 2018, 6:50 p.m. UTC 
From: Ville Syrjälä <ville.syrjala@linux.intel.com>

Instead of plane->fb (which we're going to deprecate for atomic drivers)
we need to look at plane->state->fb. The maze of code leading to
vmw_kms_helper_dirty() wasn't particularly clear, but my analysis
concluded that the calls originating from vmw_*_primary_plane_atomic_update()
all pass in the crtc which means we'll never end up in this branch
of the function. All other callers use drm_modeset_lock_all() somewhere
higher up, which means accessing plane->state is safe. We'll toss in
a lockdep assert to catch wrongdoers.

v2: Drop the comment and make the code do what it did before (Thomas)

Cc: Deepak Rawat <drawat@vmware.com>
Cc: Thomas Hellstrom <thellstrom@vmware.com>
Cc: Sinclair Yeh <syeh@vmware.com>
Cc: VMware Graphics <linux-graphics-maintainer@vmware.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_kms.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

Comments

Ville Syrjälä May 30, 2018, 8:08 p.m. UTC | #1 
On Fri, May 25, 2018 at 09:50:34PM +0300, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> Instead of plane->fb (which we're going to deprecate for atomic drivers)
> we need to look at plane->state->fb. The maze of code leading to
> vmw_kms_helper_dirty() wasn't particularly clear, but my analysis
> concluded that the calls originating from vmw_*_primary_plane_atomic_update()
> all pass in the crtc which means we'll never end up in this branch
> of the function. All other callers use drm_modeset_lock_all() somewhere
> higher up, which means accessing plane->state is safe. We'll toss in
> a lockdep assert to catch wrongdoers.
> 
> v2: Drop the comment and make the code do what it did before (Thomas)
> 
> Cc: Deepak Rawat <drawat@vmware.com>
> Cc: Thomas Hellstrom <thellstrom@vmware.com>
> Cc: Sinclair Yeh <syeh@vmware.com>
> Cc: VMware Graphics <linux-graphics-maintainer@vmware.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/vmwgfx/vmwgfx_kms.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
> index 2e4c38bb846d..5417eb1b486e 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
> @@ -2326,9 +2326,12 @@ int vmw_kms_helper_dirty(struct vmw_private *dev_priv,
>  	} else {
>  		list_for_each_entry(crtc, &dev_priv->dev->mode_config.crtc_list,
>  				    head) {
> -			if (crtc->primary->fb != &framebuffer->base)
> -				continue;
> -			units[num_units++] = vmw_crtc_to_du(crtc);
> +			struct drm_plane *plane = crtc->primary;
> +
> +			lockdep_assert_held(&plane->mutex);

kbuild test robot told me
>> include/linux/lockdep.h:347:52: error: 'struct drm_modeset_lock' has
>> no member named 'dep_map'                      
    #define lockdep_is_held(lock)  lock_is_held(&(lock)->dep_map)                                                      

Maybe I'll just drop the asserts? Or do people really want them
(in which case I gues I need to dig out the underlying mutex)?

> +
> +			if (plane->state->fb == &framebuffer->base)
> +				units[num_units++] = vmw_crtc_to_du(crtc);
>  		}
>  	}
>  
> -- 
> 2.16.1
Sinclair Yeh June 4, 2018, 6:13 p.m. UTC | #2 
On Wed, May 30, 2018 at 11:08:57PM +0300, Ville Syrjälä wrote:
> On Fri, May 25, 2018 at 09:50:34PM +0300, Ville Syrjala wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > Instead of plane->fb (which we're going to deprecate for atomic drivers)
> > we need to look at plane->state->fb. The maze of code leading to
> > vmw_kms_helper_dirty() wasn't particularly clear, but my analysis
> > concluded that the calls originating from vmw_*_primary_plane_atomic_update()
> > all pass in the crtc which means we'll never end up in this branch
> > of the function. All other callers use drm_modeset_lock_all() somewhere
> > higher up, which means accessing plane->state is safe. We'll toss in
> > a lockdep assert to catch wrongdoers.
> > 
> > v2: Drop the comment and make the code do what it did before (Thomas)
> > 
> > Cc: Deepak Rawat <drawat@vmware.com>
> > Cc: Thomas Hellstrom <thellstrom@vmware.com>
> > Cc: Sinclair Yeh <syeh@vmware.com>
> > Cc: VMware Graphics <linux-graphics-maintainer@vmware.com>
> > Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> >  drivers/gpu/drm/vmwgfx/vmwgfx_kms.c | 9 ++++++---
> >  1 file changed, 6 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
> > index 2e4c38bb846d..5417eb1b486e 100644
> > --- a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
> > +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
> > @@ -2326,9 +2326,12 @@ int vmw_kms_helper_dirty(struct vmw_private *dev_priv,
> >  	} else {
> >  		list_for_each_entry(crtc, &dev_priv->dev->mode_config.crtc_list,
> >  				    head) {
> > -			if (crtc->primary->fb != &framebuffer->base)
> > -				continue;
> > -			units[num_units++] = vmw_crtc_to_du(crtc);
> > +			struct drm_plane *plane = crtc->primary;
> > +
> > +			lockdep_assert_held(&plane->mutex);
> 
> kbuild test robot told me
> >> include/linux/lockdep.h:347:52: error: 'struct drm_modeset_lock' has
> >> no member named 'dep_map'                      
>     #define lockdep_is_held(lock)  lock_is_held(&(lock)->dep_map)                                                      
> 
> Maybe I'll just drop the asserts? Or do people really want them
> (in which case I gues I need to dig out the underlying mutex)?

Eitherway is fine with me.


> 
> > +
> > +			if (plane->state->fb == &framebuffer->base)
> > +				units[num_units++] = vmw_crtc_to_du(crtc);
> >  		}
> >  	}
> >  
> > -- 
> > 2.16.1
> 
> -- 
> Ville Syrjälä
> Intel
Ville Syrjälä June 11, 2018, 5:58 p.m. UTC | #3 
On Mon, Jun 04, 2018 at 11:13:53AM -0700, Sinclair Yeh wrote:
> On Wed, May 30, 2018 at 11:08:57PM +0300, Ville Syrjälä wrote:
> > On Fri, May 25, 2018 at 09:50:34PM +0300, Ville Syrjala wrote:
> > > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > 
> > > Instead of plane->fb (which we're going to deprecate for atomic drivers)
> > > we need to look at plane->state->fb. The maze of code leading to
> > > vmw_kms_helper_dirty() wasn't particularly clear, but my analysis
> > > concluded that the calls originating from vmw_*_primary_plane_atomic_update()
> > > all pass in the crtc which means we'll never end up in this branch
> > > of the function. All other callers use drm_modeset_lock_all() somewhere
> > > higher up, which means accessing plane->state is safe. We'll toss in
> > > a lockdep assert to catch wrongdoers.
> > > 
> > > v2: Drop the comment and make the code do what it did before (Thomas)
> > > 
> > > Cc: Deepak Rawat <drawat@vmware.com>
> > > Cc: Thomas Hellstrom <thellstrom@vmware.com>
> > > Cc: Sinclair Yeh <syeh@vmware.com>
> > > Cc: VMware Graphics <linux-graphics-maintainer@vmware.com>
> > > Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> > > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > ---
> > >  drivers/gpu/drm/vmwgfx/vmwgfx_kms.c | 9 ++++++---
> > >  1 file changed, 6 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
> > > index 2e4c38bb846d..5417eb1b486e 100644
> > > --- a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
> > > +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
> > > @@ -2326,9 +2326,12 @@ int vmw_kms_helper_dirty(struct vmw_private *dev_priv,
> > >  	} else {
> > >  		list_for_each_entry(crtc, &dev_priv->dev->mode_config.crtc_list,
> > >  				    head) {
> > > -			if (crtc->primary->fb != &framebuffer->base)
> > > -				continue;
> > > -			units[num_units++] = vmw_crtc_to_du(crtc);
> > > +			struct drm_plane *plane = crtc->primary;
> > > +
> > > +			lockdep_assert_held(&plane->mutex);
> > 
> > kbuild test robot told me
> > >> include/linux/lockdep.h:347:52: error: 'struct drm_modeset_lock' has
> > >> no member named 'dep_map'                      
> >     #define lockdep_is_held(lock)  lock_is_held(&(lock)->dep_map)                                                      
> > 
> > Maybe I'll just drop the asserts? Or do people really want them
> > (in which case I gues I need to dig out the underlying mutex)?
> 
> Eitherway is fine with me.

I just dropped them, and pushe the series to drm-misc-next. Thanks for
the reviews everyone.

Fingers crossed that no new uses of the legacy pointers have been added
in the meantime. A quick grep didn't seem to catch anything at least,
but selective blindness can occur sometimes. So just holler if
anything broke...
diff mbox

Patch

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
index 2e4c38bb846d..5417eb1b486e 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
@@ -2326,9 +2326,12 @@  int vmw_kms_helper_dirty(struct vmw_private *dev_priv,
 	} else {
 		list_for_each_entry(crtc, &dev_priv->dev->mode_config.crtc_list,
 				    head) {
-			if (crtc->primary->fb != &framebuffer->base)
-				continue;
-			units[num_units++] = vmw_crtc_to_du(crtc);
+			struct drm_plane *plane = crtc->primary;
+
+			lockdep_assert_held(&plane->mutex);
+
+			if (plane->state->fb == &framebuffer->base)
+				units[num_units++] = vmw_crtc_to_du(crtc);
 		}
 	}