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.
This variant works for me:
if (!new_plane_state || !new_plane_state->crtc)
return -EINVAL;
> funcs = plane->helper_private;
> if (!funcs->atomic_async_update)
> return -EINVAL;
>
> - if (plane_state->fence)
> + if (new_plane_state->fence)
> return -EINVAL;
>
> /*
> @@ -1424,31 +1420,11 @@ int drm_atomic_helper_async_check(struct drm_device *dev,
> * the plane. This prevents our async update's changes from getting
> * overridden by a previous synchronous update's state.
> */
> - for_each_new_crtc_in_state(state, crtc, crtc_state, i) {
> - if (plane->crtc != crtc)
> - continue;
> -
> - spin_lock(&crtc->commit_lock);
> - commit = list_first_entry_or_null(&crtc->commit_list,
> - struct drm_crtc_commit,
> - commit_entry);
> - if (!commit) {
> - spin_unlock(&crtc->commit_lock);
> - continue;
> - }
> - spin_unlock(&crtc->commit_lock);
> -
> - if (!crtc->state->state)
> - continue;
> + if (old_plane_state->commit &&
> + !try_wait_for_completion(&old_plane_state->commit->hw_done))
> + return -EBUSY;
>
> - for_each_plane_in_state(crtc->state->state, __plane,
> - __plane_state, j) {
> - if (__plane == plane)
> - return -EINVAL;
> - }
> - }
> -
> - return funcs->atomic_async_check(plane, plane_state);
> + return funcs->atomic_async_check(plane, new_plane_state);
> }
> EXPORT_SYMBOL(drm_atomic_helper_async_check);
>
> @@ -1814,9 +1790,10 @@ int drm_atomic_helper_setup_commit(struct drm_atomic_state *state,
> }
>
> for_each_oldnew_plane_in_state(state, plane, old_plane_state, new_plane_state, i) {
> - /* commit tracked through new_crtc_state->commit, no need to do it explicitly */
> - if (new_plane_state->crtc)
> - continue;
> + /*
> + * Unlike connectors, always track planes explicitly for
> + * async pageflip support.
> + */
>
> /* Userspace is not allowed to get ahead of the previous
> * commit with nonblocking ones. */
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 7abbc761a635..0add029d95f6 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -13064,6 +13064,14 @@ intel_legacy_cursor_update(struct drm_plane *plane,
> goto slow;
>
> old_plane_state = plane->state;
> + /*
> + * Don't do an async update if there is an outstanding commit modifying
> + * the plane. This prevents our async update's changes from getting
> + * overridden by a previous synchronous update's state.
> + */
> + if (old_plane_state->commit &&
> + !try_wait_for_completion(&old_plane_state->commit->hw_done))
> + goto slow;
>
> /*
> * If any parameters change that may affect watermarks,
> @@ -13125,19 +13133,12 @@ intel_legacy_cursor_update(struct drm_plane *plane,
> }
>
> old_fb = old_plane_state->fb;
> - old_vma = to_intel_plane_state(old_plane_state)->vma;
>
> i915_gem_track_fb(intel_fb_obj(old_fb), intel_fb_obj(fb),
> intel_plane->frontbuffer_bit);
>
> /* Swap plane state */
> - new_plane_state->fence = old_plane_state->fence;
> - new_plane_state->commit = old_plane_state->commit;
> - *to_intel_plane_state(old_plane_state) = *to_intel_plane_state(new_plane_state);
> - new_plane_state->fence = NULL;
> - new_plane_state->commit = NULL;
> - new_plane_state->fb = old_fb;
> - to_intel_plane_state(new_plane_state)->vma = NULL;
> + plane->state = new_plane_state;
>
> if (plane->state->visible) {
> trace_intel_update_plane(plane, to_intel_crtc(crtc));
> @@ -13149,13 +13150,19 @@ intel_legacy_cursor_update(struct drm_plane *plane,
> intel_plane->disable_plane(intel_plane, to_intel_crtc(crtc));
> }
>
> - if (old_vma)
> + old_vma = to_intel_plane_state(old_plane_state)->vma;
> + if (old_vma) {
> + to_intel_plane_state(old_plane_state)->vma = NULL;
> intel_unpin_fb_vma(old_vma);
> + }
>
> out_unlock:
> mutex_unlock(&dev_priv->drm.struct_mutex);
> out_free:
> - intel_plane_destroy_state(plane, new_plane_state);
> + if (ret)
> + intel_plane_destroy_state(plane, new_plane_state);
> + else
> + intel_plane_destroy_state(plane, old_plane_state);
> return ret;
>
> slow:
> diff --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h
> index 7d96116fd4c4..feb9941d0cdb 100644
> --- a/include/drm/drm_plane.h
> +++ b/include/drm/drm_plane.h
> @@ -124,9 +124,10 @@ struct drm_plane_state {
> bool visible;
>
> /**
> - * @commit: Tracks the pending commit to prevent use-after-free conditions.
> + * @commit: Tracks the pending commit to prevent use-after-free conditions,
> + * and for async plane updates.
> *
> - * Is only set when @crtc is NULL.
> + * May be NULL.
> */
> struct drm_crtc_commit *commit;
>
>
--
Dmitry
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