Op 24-09-17 om 16:33 schreef Dmitry Osipenko:
> On 04.09.2017 13:48, Maarten Lankhorst wrote:
>> By always keeping track of the last commit in plane_state, we know
>> whether there is an active update on the plane or not. With that
>> information we can reject the fast update, and force the slowpath
>> to be used as was originally intended.
>>
>> We cannot use plane_state->crtc->state here, because this only mentions
>> the most recent commit for the crtc, but not the planes that were part
>> of it. We specifically care about what the last commit involving this
>> plane is, which can only be tracked with a pointer in the plane state.
>>
>> Changes since v1:
>> - Clean up the whole function here, instead of partially earlier.
>> - Add mention in the commit message why we need commit in plane_state.
>> - Swap plane->state in intel_legacy_cursor_update, instead of
>> reassigning all variables. With this commit We know that the cursor
>> is not part of any active commits so this hack can be removed.
>>
>> Cc: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxx>
>> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
>> Reviewed-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxx>
>> Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx> #v1
>> ---
>> drivers/gpu/drm/drm_atomic_helper.c | 53 ++++++++++--------------------------
>> drivers/gpu/drm/i915/intel_display.c | 27 +++++++++++-------
>> include/drm/drm_plane.h | 5 ++--
>> 3 files changed, 35 insertions(+), 50 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
>> index c81d46927a74..a2cd432d8b2d 100644
>> --- a/drivers/gpu/drm/drm_atomic_helper.c
>> +++ b/drivers/gpu/drm/drm_atomic_helper.c
>> @@ -1388,35 +1388,31 @@ int drm_atomic_helper_async_check(struct drm_device *dev,
>> {
>> struct drm_crtc *crtc;
>> struct drm_crtc_state *crtc_state;
>> - struct drm_crtc_commit *commit;
>> - struct drm_plane *__plane, *plane = NULL;
>> - struct drm_plane_state *__plane_state, *plane_state = NULL;
>> + struct drm_plane *plane;
>> + struct drm_plane_state *old_plane_state, *new_plane_state;
>> const struct drm_plane_helper_funcs *funcs;
>> - int i, j, n_planes = 0;
>> + int i, n_planes = 0;
>>
>> for_each_new_crtc_in_state(state, crtc, crtc_state, i) {
>> if (drm_atomic_crtc_needs_modeset(crtc_state))
>> return -EINVAL;
>> }
>>
>> - for_each_new_plane_in_state(state, __plane, __plane_state, i) {
>> + for_each_oldnew_plane_in_state(state, plane, old_plane_state, new_plane_state, i)
>> n_planes++;
>> - plane = __plane;
>> - plane_state = __plane_state;
>> - }
>>
>> /* FIXME: we support only single plane updates for now */
>> - if (!plane || n_planes != 1)
>> + if (n_planes != 1)
>> return -EINVAL;
>>
>> - if (!plane_state->crtc)
>> + if (!new_plane_state->crtc)
>> return -EINVAL;
>>
> Hello,
>
> It looks like a NULL-checking of new_plane_state is missed here.
>
> [ 70.138947] [<c03dd670>] (drm_atomic_helper_async_check) from [<c03e0424>]
> (drm_atomic_helper_check+0x4c/0x64)
> [ 70.138958] [<c03e0424>] (drm_atomic_helper_check) from [<c03fb6d4>]
> (drm_atomic_check_only+0x2f4/0x56c)
> [ 70.138969] [<c03fb6d4>] (drm_atomic_check_only) from [<c03fb95c>]
> (drm_atomic_commit+0x10/0x50)
> [ 70.138979] [<c03fb95c>] (drm_atomic_commit) from [<c03dde50>]
> (drm_atomic_helper_update_plane+0xf0/0x100)
> [ 70.138991] [<c03dde50>] (drm_atomic_helper_update_plane) from [<c0403548>]
> (__setplane_internal+0x178/0x214)
> [ 70.139003] [<c0403548>] (__setplane_internal) from [<c04036fc>]
> (drm_mode_cursor_universal+0x118/0x1a8)
> [ 70.139014] [<c04036fc>] (drm_mode_cursor_universal) from [<c0403900>]
> (drm_mode_cursor_common+0x174/0x1ec)
> [ 70.139026] [<c0403900>] (drm_mode_cursor_common) from [<c0403fa4>]
> (drm_mode_cursor_ioctl+0x58/0x60)
> [ 70.139036] [<c0403fa4>] (drm_mode_cursor_ioctl) from [<c03eb0b4>]
> (drm_ioctl+0x198/0x368)
> [ 70.139047] [<c03eb0b4>] (drm_ioctl) from [<c015fffc>] (do_vfs_ioctl+0x9c/0x8f0)
> [ 70.139058] [<c015fffc>] (do_vfs_ioctl) from [<c0160884>] (SyS_ioctl+0x34/0x5c)
> [ 70.139071] [<c0160884>] (SyS_ioctl) from [<c000f900>]
> (ret_fast_syscall+0x0/0x48)
>
> It's triggered by Tegra DRM driver on Xorg's startup. I also should notice that
> currently Tegra DRM doesn't have a working HW cursor, I'm going to send out
> Tegra cursor patches sometime soon.
Oops.. I messed up there.. for_each_new_plane_in_state overwrites the state internally..
----->8-----
for_each_oldnew_plane_in_state overwrites the iterator values internally, so we cannot rely
on it being set to the last valid plane. This was causing a NULL pointer deref when someone
tries to use the code. Save the plane and use the accessor functions to pull out the relevant
plane state.
Cc: Dmitry Osipenko <digetx@xxxxxxxxx>
Fixes: 669c9215afea ("drm/atomic: Make async plane update checks work as intended, v2.")
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
---
diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 32fb61169b4f..8573feaea8c0 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -1388,23 +1388,30 @@ int drm_atomic_helper_async_check(struct drm_device *dev,
{
struct drm_crtc *crtc;
struct drm_crtc_state *crtc_state;
- struct drm_plane *plane;
+ struct drm_plane *plane = NULL, *__plane;
struct drm_plane_state *old_plane_state, *new_plane_state;
const struct drm_plane_helper_funcs *funcs;
- int i, n_planes = 0;
+ int i;
for_each_new_crtc_in_state(state, crtc, crtc_state, i) {
if (drm_atomic_crtc_needs_modeset(crtc_state))
return -EINVAL;
}
- for_each_oldnew_plane_in_state(state, plane, old_plane_state, new_plane_state, i)
- n_planes++;
+ for_each_new_plane_in_state(state, __plane, new_plane_state, i) {
+ /* FIXME: we support only single plane updates for now */
+ if (plane)
+ return -EINVAL;
+
+ plane = __plane;
+ }
- /* FIXME: we support only single plane updates for now */
- if (n_planes != 1)
+ if (!plane)
return -EINVAL;
+ old_plane_state = drm_atomic_get_old_plane_state(state, plane);
+ new_plane_state = drm_atomic_get_new_plane_state(state, plane);
+
if (!new_plane_state->crtc)
return -EINVAL;
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