[PATCH] drm/omap: Take a fb reference in omap_plane_update()
When userspace calls SET_PLANE ioctl, drm core takes a reference of the fb and
passes control to the update_plane op defined by the drm driver.
In omapdrm, we have a worker thread which queues framebuffers objects received
from update_plane and displays them at the appropriate time.
It is possible that the framebuffer is destoryed by userspace between the time
of calling the ioctl and apply-worker being scheduled. If this happens, the
apply-worker holds a pointer to a framebuffer which is already destroyed.
Take an extra refernece/unreference of the fb in omap_plane_update() to prevent
this from happening. A reference is taken of the fb passed to update_plane(),
the previous framebuffer (held by plane-fb) is unreferenced. This will prevent
drm from destroying the framebuffer till the time it's unreferenced by the
apply-worker.
This is in addition to the exisitng reference/unreference in update_pin(),
which is taken for the scanout of the plane's current framebuffer, and an
unreference the previous framebuffer.
Signed-off-by: Archit Taneja arc...@ti.com
Cc: Rob Clark robdcl...@gmail.com
---
drivers/gpu/drm/omapdrm/omap_plane.c |6 ++
1 file changed, 6 insertions(+)
diff --git a/drivers/gpu/drm/omapdrm/omap_plane.c
b/drivers/gpu/drm/omapdrm/omap_plane.c
index 2882cda..8d225d7 100644
--- a/drivers/gpu/drm/omapdrm/omap_plane.c
+++ b/drivers/gpu/drm/omapdrm/omap_plane.c
@@ -247,6 +247,12 @@ static int omap_plane_update(struct drm_plane *plane,
{
struct omap_plane *omap_plane = to_omap_plane(plane);
omap_plane-enabled = true;
+
+ if (plane-fb)
+ drm_framebuffer_unreference(plane-fb);
+
+ drm_framebuffer_reference(fb);
+
return omap_plane_mode_set(plane, crtc, fb,
crtc_x, crtc_y, crtc_w, crtc_h,
src_x, src_y, src_w, src_h,
--
1.7.10.4
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Re: [PATCH] drm/omap: Take a fb reference in omap_plane_update()
On Tue, Apr 9, 2013 at 8:26 AM, Archit Taneja arc...@ti.com wrote:
When userspace calls SET_PLANE ioctl, drm core takes a reference of the fb and
passes control to the update_plane op defined by the drm driver.
In omapdrm, we have a worker thread which queues framebuffers objects received
from update_plane and displays them at the appropriate time.
It is possible that the framebuffer is destoryed by userspace between the time
of calling the ioctl and apply-worker being scheduled. If this happens, the
apply-worker holds a pointer to a framebuffer which is already destroyed.
Take an extra refernece/unreference of the fb in omap_plane_update() to
prevent
this from happening. A reference is taken of the fb passed to update_plane(),
the previous framebuffer (held by plane-fb) is unreferenced. This will
prevent
drm from destroying the framebuffer till the time it's unreferenced by the
apply-worker.
This is in addition to the exisitng reference/unreference in update_pin(),
which is taken for the scanout of the plane's current framebuffer, and an
unreference the previous framebuffer.
Signed-off-by: Archit Taneja arc...@ti.com
Cc: Rob Clark robdcl...@gmail.com
Good catch
Signed-off-by: Rob Clark robdcl...@gmail.com
---
drivers/gpu/drm/omapdrm/omap_plane.c |6 ++
1 file changed, 6 insertions(+)
diff --git a/drivers/gpu/drm/omapdrm/omap_plane.c
b/drivers/gpu/drm/omapdrm/omap_plane.c
index 2882cda..8d225d7 100644
--- a/drivers/gpu/drm/omapdrm/omap_plane.c
+++ b/drivers/gpu/drm/omapdrm/omap_plane.c
@@ -247,6 +247,12 @@ static int omap_plane_update(struct drm_plane *plane,
{
struct omap_plane *omap_plane = to_omap_plane(plane);
omap_plane-enabled = true;
+
+ if (plane-fb)
+ drm_framebuffer_unreference(plane-fb);
+
+ drm_framebuffer_reference(fb);
+
return omap_plane_mode_set(plane, crtc, fb,
crtc_x, crtc_y, crtc_w, crtc_h,
src_x, src_y, src_w, src_h,
--
1.7.10.4
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Re: [PATCH] drm/omap: Take a fb reference in omap_plane_update()
On Tue, Apr 09, 2013 at 05:56:02PM +0530, Archit Taneja wrote:
When userspace calls SET_PLANE ioctl, drm core takes a reference of the fb and
passes control to the update_plane op defined by the drm driver.
In omapdrm, we have a worker thread which queues framebuffers objects received
from update_plane and displays them at the appropriate time.
It is possible that the framebuffer is destoryed by userspace between the time
of calling the ioctl and apply-worker being scheduled. If this happens, the
apply-worker holds a pointer to a framebuffer which is already destroyed.
Take an extra refernece/unreference of the fb in omap_plane_update() to
prevent
this from happening. A reference is taken of the fb passed to update_plane(),
the previous framebuffer (held by plane-fb) is unreferenced. This will
prevent
drm from destroying the framebuffer till the time it's unreferenced by the
apply-worker.
This is in addition to the exisitng reference/unreference in update_pin(),
which is taken for the scanout of the plane's current framebuffer, and an
unreference the previous framebuffer.
Signed-off-by: Archit Taneja arc...@ti.com
Cc: Rob Clark robdcl...@gmail.com
---
drivers/gpu/drm/omapdrm/omap_plane.c |6 ++
1 file changed, 6 insertions(+)
diff --git a/drivers/gpu/drm/omapdrm/omap_plane.c
b/drivers/gpu/drm/omapdrm/omap_plane.c
index 2882cda..8d225d7 100644
--- a/drivers/gpu/drm/omapdrm/omap_plane.c
+++ b/drivers/gpu/drm/omapdrm/omap_plane.c
@@ -247,6 +247,12 @@ static int omap_plane_update(struct drm_plane *plane,
{
struct omap_plane *omap_plane = to_omap_plane(plane);
omap_plane-enabled = true;
+
+ if (plane-fb)
+ drm_framebuffer_unreference(plane-fb);
Shouldn't the unref only happen once the flip has completed? Otherwise we
might free the memory which is still being scanned out and put some other
crap there.
Note that I've been too lazy to read the code, but I expected the unref of
the old one to happen after the ref-taking for the new one, with a vblank
wait/delay in between ... Might be that I'm completely off ;-)
-Daniel
+
+ drm_framebuffer_reference(fb);
+
return omap_plane_mode_set(plane, crtc, fb,
crtc_x, crtc_y, crtc_w, crtc_h,
src_x, src_y, src_w, src_h,
--
1.7.10.4
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+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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Re: [PATCH] drm/omap: Take a fb reference in omap_plane_update()
On Tue, Apr 9, 2013 at 8:53 AM, Daniel Vetter dan...@ffwll.ch wrote:
On Tue, Apr 09, 2013 at 05:56:02PM +0530, Archit Taneja wrote:
When userspace calls SET_PLANE ioctl, drm core takes a reference of the fb
and
passes control to the update_plane op defined by the drm driver.
In omapdrm, we have a worker thread which queues framebuffers objects
received
from update_plane and displays them at the appropriate time.
It is possible that the framebuffer is destoryed by userspace between the
time
of calling the ioctl and apply-worker being scheduled. If this happens, the
apply-worker holds a pointer to a framebuffer which is already destroyed.
Take an extra refernece/unreference of the fb in omap_plane_update() to
prevent
this from happening. A reference is taken of the fb passed to update_plane(),
the previous framebuffer (held by plane-fb) is unreferenced. This will
prevent
drm from destroying the framebuffer till the time it's unreferenced by the
apply-worker.
This is in addition to the exisitng reference/unreference in update_pin(),
which is taken for the scanout of the plane's current framebuffer, and an
unreference the previous framebuffer.
Signed-off-by: Archit Taneja arc...@ti.com
Cc: Rob Clark robdcl...@gmail.com
---
drivers/gpu/drm/omapdrm/omap_plane.c |6 ++
1 file changed, 6 insertions(+)
diff --git a/drivers/gpu/drm/omapdrm/omap_plane.c
b/drivers/gpu/drm/omapdrm/omap_plane.c
index 2882cda..8d225d7 100644
--- a/drivers/gpu/drm/omapdrm/omap_plane.c
+++ b/drivers/gpu/drm/omapdrm/omap_plane.c
@@ -247,6 +247,12 @@ static int omap_plane_update(struct drm_plane *plane,
{
struct omap_plane *omap_plane = to_omap_plane(plane);
omap_plane-enabled = true;
+
+ if (plane-fb)
+ drm_framebuffer_unreference(plane-fb);
Shouldn't the unref only happen once the flip has completed? Otherwise we
might free the memory which is still being scanned out and put some other
crap there.
yup, there is a 2nd ref grabbed when we start scanout and dropped when
we finish scanout.. so that part was already covered. What wasn't
covered before was the time between the ioctl and the worker thread
(which was grabbing/dropping the scanout ref)
BR,
-R
Note that I've been too lazy to read the code, but I expected the unref of
the old one to happen after the ref-taking for the new one, with a vblank
wait/delay in between ... Might be that I'm completely off ;-)
-Daniel
+
+ drm_framebuffer_reference(fb);
+
return omap_plane_mode_set(plane, crtc, fb,
crtc_x, crtc_y, crtc_w, crtc_h,
src_x, src_y, src_w, src_h,
--
1.7.10.4
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Re: [PATCH] drm/omap: Take a fb reference in omap_plane_update()
On Tue, Apr 9, 2013 at 3:17 PM, Rob Clark robdcl...@gmail.com wrote:
diff --git a/drivers/gpu/drm/omapdrm/omap_plane.c
b/drivers/gpu/drm/omapdrm/omap_plane.c
index 2882cda..8d225d7 100644
--- a/drivers/gpu/drm/omapdrm/omap_plane.c
+++ b/drivers/gpu/drm/omapdrm/omap_plane.c
@@ -247,6 +247,12 @@ static int omap_plane_update(struct drm_plane *plane,
{
struct omap_plane *omap_plane = to_omap_plane(plane);
omap_plane-enabled = true;
+
+ if (plane-fb)
+ drm_framebuffer_unreference(plane-fb);
Shouldn't the unref only happen once the flip has completed? Otherwise we
might free the memory which is still being scanned out and put some other
crap there.
yup, there is a 2nd ref grabbed when we start scanout and dropped when
we finish scanout.. so that part was already covered. What wasn't
covered before was the time between the ioctl and the worker thread
(which was grabbing/dropping the scanout ref)
Ah, I see. And the ordering doesn't seem to matter here since it's all
protected by locks (against races with the worker thread) anyway.
Thanks for the explanation.
-Daniel
--
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Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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