Re: [PATCH v8 3/3] drm/fence: add out-fences support

[Sean Paul]

On Fri, Nov 11, 2016 at 9:15 AM, Gustavo Padovan <gustavo@xxxxxxxxxxx> wrote:
> From: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
>
> Support DRM out-fences by creating a sync_file with a fence for each CRTC
> that sets the OUT_FENCE_PTR property.
>
> We use the out_fence pointer received in the OUT_FENCE_PTR prop to send
> the sync_file fd back to userspace.
>
> The sync_file and fd are allocated/created before commit, but the
> fd_install operation only happens after we know that commit succeed.
>
> v2: Comment by Rob Clark:
>         - Squash commit that adds DRM_MODE_ATOMIC_OUT_FENCE flag here.
>
>     Comment by Daniel Vetter:
>         - Add clean up code for out_fences
>
> v3: Comments by Daniel Vetter:
>         - create DRM_MODE_ATOMIC_EVENT_MASK
>         - userspace should fill out_fences_ptr with the crtc_ids for which
>         it wants fences back.
>
> v4: Create OUT_FENCE_PTR properties and remove old approach.
>
> v5: Comments by Brian Starkey:
>         - Remove extra fence_get() in atomic_ioctl()
>         - Check ret before iterating on the crtc_state
>         - check ret before fd_install
>         - set fence_state to NULL at the beginning
>         - check fence_state->out_fence_ptr before put_user()
>         - change order of fput() and put_unused_fd() on failure
>
>      - Add access_ok() check to the out_fence_ptr received
>      - Rebase after fence -> dma_fence rename
>      - Store out_fence_ptr in the drm_atomic_state
>      - Split crtc_setup_out_fence()
>      - return -1 as out_fence with TEST_ONLY flag
>
> v6: Comments by Daniel Vetter
>         - Add prepare/unprepare_crtc_signaling()
>         - move struct drm_out_fence_state to drm_atomic.c
>         - mark get_crtc_fence() as static
>
>     Comments by Brian Starkey
>         - proper set fence_ptr fence_state array
>         - isolate fence_idx increment
>
>     - improve error handling
>
> v7: Comments by Daniel Vetter
>         - remove prefix from internal functions
>         - make out_fence_ptr an s64 pointer
>         - degrade DRM_INFO to DRM_DEBUG_ATOMIC when put_user fail
>         - fix doc issues
>         - filter out OUT_FENCE_PTR == NULL and do not fail in this case
>         - add complete_crtc_signalling()
>         - krealloc fence_state on demand
>
>     Comment by Brian Starkey
>         - remove unused crtc_state arg from get_out_fence()
>
> v8: Comment by Brian Starkey
>         - cancel events before check for !fence_state
>         - convert a few lefovers u64 types for out_fence_ptr
>         - fix memleak by assign fence_state earlier after realloc
>         - proper accout num_fences in case of error
>
> Signed-off-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>

A couple of nits below, other than that, looks good to me

> ---
>  drivers/gpu/drm/drm_atomic.c | 243 +++++++++++++++++++++++++++++++++++--------
>  drivers/gpu/drm/drm_crtc.c   |   8 ++
>  include/drm/drm_atomic.h     |   1 +
>  include/drm/drm_crtc.h       |   6 ++
>  4 files changed, 213 insertions(+), 45 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index 8e26ad1..34cdc6e 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -290,6 +290,23 @@ drm_atomic_get_crtc_state(struct drm_atomic_state *state,
>  }
>  EXPORT_SYMBOL(drm_atomic_get_crtc_state);
>
> +static void set_out_fence_for_crtc(struct drm_atomic_state *state,
> +                                  struct drm_crtc *crtc, s64 __user *fence_ptr)
> +{
> +       state->crtcs[drm_crtc_index(crtc)].out_fence_ptr = fence_ptr;
> +}
> +
> +static s64 __user * get_out_fence_for_crtc(struct drm_atomic_state *state,
> +                                          struct drm_crtc *crtc)
> +{
> +       s64 __user *fence_ptr;
> +
> +       fence_ptr = state->crtcs[drm_crtc_index(crtc)].out_fence_ptr;
> +       state->crtcs[drm_crtc_index(crtc)].out_fence_ptr = NULL;
> +
> +       return fence_ptr;
> +}
> +
>  /**
>   * drm_atomic_set_mode_for_crtc - set mode for CRTC
>   * @state: the CRTC whose incoming state to update
> @@ -491,6 +508,16 @@ int drm_atomic_crtc_set_property(struct drm_crtc *crtc,
>                                         &replaced);
>                 state->color_mgmt_changed |= replaced;
>                 return ret;
> +       } else if (property == config->prop_out_fence_ptr) {
> +               s64 __user *fence_ptr = u64_to_user_ptr(val);
> +
> +               if (!fence_ptr)
> +                       return 0;
> +
> +               if (!access_ok(VERIFY_WRITE, fence_ptr, sizeof(*fence_ptr)))
> +                       return -EFAULT;
> +
> +               set_out_fence_for_crtc(state->state, crtc, fence_ptr);
>         } else if (crtc->funcs->atomic_set_property)
>                 return crtc->funcs->atomic_set_property(crtc, state, property, val);
>         else
> @@ -533,6 +560,8 @@ drm_atomic_crtc_get_property(struct drm_crtc *crtc,
>                 *val = (state->ctm) ? state->ctm->base.id : 0;
>         else if (property == config->gamma_lut_property)
>                 *val = (state->gamma_lut) ? state->gamma_lut->base.id : 0;
> +       else if (property == config->prop_out_fence_ptr)
> +               *val = 0;
>         else if (crtc->funcs->atomic_get_property)
>                 return crtc->funcs->atomic_get_property(crtc, state, property, val);
>         else
> @@ -1659,11 +1688,9 @@ int drm_atomic_debugfs_init(struct drm_minor *minor)
>   */
>
>  static struct drm_pending_vblank_event *create_vblank_event(
> -               struct drm_device *dev, struct drm_file *file_priv,
> -               struct dma_fence *fence, uint64_t user_data)
> +               struct drm_device *dev, uint64_t user_data)
>  {
>         struct drm_pending_vblank_event *e = NULL;
> -       int ret;
>
>         e = kzalloc(sizeof *e, GFP_KERNEL);
>         if (!e)
> @@ -1673,17 +1700,6 @@ static struct drm_pending_vblank_event *create_vblank_event(
>         e->event.base.length = sizeof(e->event);
>         e->event.user_data = user_data;
>
> -       if (file_priv) {
> -               ret = drm_event_reserve_init(dev, file_priv, &e->base,
> -                                            &e->event.base);
> -               if (ret) {
> -                       kfree(e);
> -                       return NULL;
> -               }
> -       }
> -
> -       e->base.fence = fence;
> -
>         return e;
>  }
>
> @@ -1788,6 +1804,167 @@ void drm_atomic_clean_old_fb(struct drm_device *dev,
>  }
>  EXPORT_SYMBOL(drm_atomic_clean_old_fb);
>
> +static struct dma_fence *get_crtc_fence(struct drm_crtc *crtc)
> +{
> +       struct dma_fence *fence;
> +
> +       fence = kzalloc(sizeof(*fence), GFP_KERNEL);
> +       if (!fence)
> +               return NULL;
> +
> +       dma_fence_init(fence, &drm_crtc_fence_ops, &crtc->fence_lock,
> +                      crtc->fence_context, ++crtc->fence_seqno);
> +
> +       return fence;
> +}
> +
> +struct drm_out_fence_state {
> +       s64 __user *out_fence_ptr;
> +       struct sync_file *sync_file;
> +       int fd;
> +};
> +
> +static int setup_out_fence(struct drm_out_fence_state *fence_state,
> +                          struct dma_fence *fence)
> +{
> +       fence_state->fd = get_unused_fd_flags(O_CLOEXEC);
> +       if (fence_state->fd < 0)
> +               return fence_state->fd;
> +
> +       if (put_user(fence_state->fd, fence_state->out_fence_ptr))
> +               return -EFAULT;
> +
> +       fence_state->sync_file = sync_file_create(fence);
> +       if(!fence_state->sync_file)
> +               return -ENOMEM;
> +
> +       return 0;
> +}
> +
> +static int prepare_crtc_signaling(struct drm_device *dev,
> +                                 struct drm_atomic_state *state,
> +                                 struct drm_mode_atomic *arg,
> +                                 struct drm_file *file_priv,
> +                                 struct drm_out_fence_state **fence_state,
> +                                 unsigned int *num_fences)
> +{
> +       struct drm_crtc *crtc;
> +       struct drm_crtc_state *crtc_state;
> +       int i, ret;
> +
> +       for_each_crtc_in_state(state, crtc, crtc_state, i) {
> +               u64 __user *fence_ptr;
> +
> +               fence_ptr = get_out_fence_for_crtc(crtc_state->state, crtc);
> +
> +               if (arg->flags & DRM_MODE_ATOMIC_TEST_ONLY && fence_ptr) {
> +                       if (put_user(-1, fence_ptr))
> +                               return -EFAULT;
> +
> +                       continue;
> +               }
> +
> +               if (arg->flags & DRM_MODE_PAGE_FLIP_EVENT || fence_ptr) {

pedantic suggestion: If you did the inverse, you could just continue
and save yourself some indentation (and instantiate e once). ie:

if (!(arg->flags & DRM_MODE_PAGE_FLIP_EVENT) && !fence_ptr)
        continue;

...


> +                       struct drm_pending_vblank_event *e;
> +
> +                       e = create_vblank_event(dev, arg->user_data);
> +                       if (!e)
> +                               return -ENOMEM;
> +
> +                       crtc_state->event = e;
> +               }
> +
> +               if (arg->flags & DRM_MODE_PAGE_FLIP_EVENT) {
> +                       struct drm_pending_vblank_event *e = crtc_state->event;
> +
> +                       if (!file_priv)
> +                               continue;
> +
> +                       ret = drm_event_reserve_init(dev, file_priv, &e->base,
> +                                                    &e->event.base);
> +                       if (ret) {
> +                               kfree(e);
> +                               crtc_state->event = NULL;
> +                               return ret;
> +                       }
> +               }
> +
> +               if (fence_ptr) {
> +                       struct dma_fence *fence;
> +                       struct drm_out_fence_state *f;
> +
> +                       f = krealloc(*fence_state, sizeof(**fence_state) *
> +                                    (*num_fences + 1), GFP_KERNEL);
> +                       if (!f)
> +                               return -ENOMEM;
> +
> +                       f[*num_fences].out_fence_ptr = fence_ptr;
> +                       *fence_state = f;
> +
> +                       fence = get_crtc_fence(crtc);
> +                       if (!fence) {
> +                               (*num_fences)++;
> +                               return -ENOMEM;
> +                       }
> +
> +                       ret = setup_out_fence(&f[(*num_fences)++], fence);
> +                       if (ret) {
> +                               dma_fence_put(fence);
> +                               return ret;
> +                       }
> +
> +                       crtc_state->event->base.fence = fence;
> +
> +               }
> +       }
> +
> +       return 0;
> +}
> +
> +static void complete_crtc_signaling(struct drm_device *dev,
> +                                    struct drm_atomic_state *state,
> +                                    struct drm_out_fence_state *fence_state,
> +                                    unsigned int num_fences, int ret)
> +{
> +       struct drm_crtc *crtc;
> +       struct drm_crtc_state *crtc_state;
> +       int i;
> +
> +       if (!ret) {

I don't think there's any reason to smash the fd install and clean-up
into one function. I think splitting into 2 functions and calling the
right one from atomic_ioctl would be better.

> +               for (i = 0; i < num_fences; i++)
> +                       fd_install(fence_state[i].fd,
> +                                  fence_state[i].sync_file->file);
> +               return;
> +       }
> +
> +       for_each_crtc_in_state(state, crtc, crtc_state, i) {
> +               /*
> +                * TEST_ONLY and PAGE_FLIP_EVENT are mutually
> +                * exclusive, if they weren't, this code should be
> +                * called on success for TEST_ONLY too.
> +                */
> +               if (crtc_state->event)
> +                       drm_event_cancel_free(dev, &crtc_state->event->base);
> +       }
> +
> +       if (!fence_state)
> +               return;
> +
> +       for (i = 0; i < num_fences; i++) {
> +               if (fence_state[i].sync_file)
> +                       fput(fence_state[i].sync_file->file);
> +               if (fence_state[i].fd >= 0)
> +                       put_unused_fd(fence_state[i].fd);
> +
> +               /* If this fails log error to the user */
> +               if (fence_state[i].out_fence_ptr &&
> +                   put_user(-1, fence_state[i].out_fence_ptr))
> +                       DRM_DEBUG_ATOMIC("Couldn't clear out_fence_ptr\n");
> +       }
> +
> +       kfree(fence_state);
> +}
> +
>  int drm_mode_atomic_ioctl(struct drm_device *dev,
>                           void *data, struct drm_file *file_priv)
>  {
> @@ -1800,11 +1977,10 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
>         struct drm_atomic_state *state;
>         struct drm_modeset_acquire_ctx ctx;
>         struct drm_plane *plane;
> -       struct drm_crtc *crtc;
> -       struct drm_crtc_state *crtc_state;
> +       struct drm_out_fence_state *fence_state = NULL;
>         unsigned plane_mask;
>         int ret = 0;
> -       unsigned int i, j;
> +       unsigned int i, j, num_fences = 0;
>
>         /* disallow for drivers not supporting atomic: */
>         if (!drm_core_check_feature(dev, DRIVER_ATOMIC))
> @@ -1919,20 +2095,10 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
>                 drm_mode_object_unreference(obj);
>         }
>
> -       if (arg->flags & DRM_MODE_PAGE_FLIP_EVENT) {
> -               for_each_crtc_in_state(state, crtc, crtc_state, i) {
> -                       struct drm_pending_vblank_event *e;
> -
> -                       e = create_vblank_event(dev, file_priv, NULL,
> -                                               arg->user_data);
> -                       if (!e) {
> -                               ret = -ENOMEM;
> -                               goto out;
> -                       }
> -
> -                       crtc_state->event = e;
> -               }
> -       }
> +       ret = prepare_crtc_signaling(dev, state, arg, file_priv, &fence_state,
> +                                    &num_fences);
> +       if (ret)
> +               goto out;
>
>         if (arg->flags & DRM_MODE_ATOMIC_TEST_ONLY) {
>                 /*
> @@ -1952,20 +2118,7 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
>  out:
>         drm_atomic_clean_old_fb(dev, plane_mask, ret);
>
> -       if (ret && arg->flags & DRM_MODE_PAGE_FLIP_EVENT) {
> -               /*
> -                * TEST_ONLY and PAGE_FLIP_EVENT are mutually exclusive,
> -                * if they weren't, this code should be called on success
> -                * for TEST_ONLY too.
> -                */
> -
> -               for_each_crtc_in_state(state, crtc, crtc_state, i) {
> -                       if (!crtc_state->event)
> -                               continue;
> -
> -                       drm_event_cancel_free(dev, &crtc_state->event->base);
> -               }
> -       }
> +       complete_crtc_signaling(dev, state, fence_state, num_fences, ret);
>
>         if (ret == -EDEADLK) {
>                 drm_atomic_state_clear(state);
> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> index 9b9881b..e8bc1ae 100644
> --- a/drivers/gpu/drm/drm_crtc.c
> +++ b/drivers/gpu/drm/drm_crtc.c
> @@ -274,6 +274,8 @@ int drm_crtc_init_with_planes(struct drm_device *dev, struct drm_crtc *crtc,
>         if (drm_core_check_feature(dev, DRIVER_ATOMIC)) {
>                 drm_object_attach_property(&crtc->base, config->prop_active, 0);
>                 drm_object_attach_property(&crtc->base, config->prop_mode_id, 0);
> +               drm_object_attach_property(&crtc->base,
> +                                          config->prop_out_fence_ptr, 0);
>         }
>
>         return 0;
> @@ -434,6 +436,12 @@ static int drm_mode_create_standard_properties(struct drm_device *dev)
>                 return -ENOMEM;
>         dev->mode_config.prop_in_fence_fd = prop;
>
> +       prop = drm_property_create_range(dev, DRM_MODE_PROP_ATOMIC,
> +                       "OUT_FENCE_PTR", 0, U64_MAX);
> +       if (!prop)
> +               return -ENOMEM;
> +       dev->mode_config.prop_out_fence_ptr = prop;
> +
>         prop = drm_property_create_object(dev, DRM_MODE_PROP_ATOMIC,
>                         "CRTC_ID", DRM_MODE_OBJECT_CRTC);
>         if (!prop)
> diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h
> index 331bb10..c0eaec7 100644
> --- a/include/drm/drm_atomic.h
> +++ b/include/drm/drm_atomic.h
> @@ -144,6 +144,7 @@ struct __drm_crtcs_state {
>         struct drm_crtc *ptr;
>         struct drm_crtc_state *state;
>         struct drm_crtc_commit *commit;
> +       s64 __user *out_fence_ptr;
>  };
>
>  struct __drm_connnectors_state {
> diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
> index 0870de1..44571bc 100644
> --- a/include/drm/drm_crtc.h
> +++ b/include/drm/drm_crtc.h
> @@ -1264,6 +1264,12 @@ struct drm_mode_config {
>          */
>         struct drm_property *prop_in_fence_fd;
>         /**
> +        * @prop_out_fence_ptr: Sync File fd pointer representing the
> +        * outgoing fences for a CRTC. Userspace should provide a pointer to a
> +        * value of type s64, and then cast that pointer to u64.
> +        */
> +       struct drm_property *prop_out_fence_ptr;
> +       /**
>          * @prop_crtc_id: Default atomic plane property to specify the
>          * &drm_crtc.
>          */
> --
> 2.5.5
>