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

Brian Starkey
2016-11-11T11:41:22Z

Hi Gustavo,

On Fri, Nov 11, 2016 at 02:16:09PM +0900, Gustavo Padovan wrote:
>From: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
>
>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 fail in this case

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()
>
>Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>

From an integration with writeback point of view, this looks fine to
me - I can add writeback to this easily.

A few comments below though:

>---
> drivers/gpu/drm/drm_atomic.c | 242 +++++++++++++++++++++++++++++++++++--------
> drivers/gpu/drm/drm_crtc.c | 8 ++
> include/drm/drm_atomic.h | 1 +
> include/drm/drm_crtc.h | 6 ++
> 4 files changed, 212 insertions(+), 45 deletions(-)
>
>diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
>index 8e26ad1..cd39f13 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, u64 __user *fence_ptr)
>+{
>+ state->crtcs[drm_crtc_index(crtc)].out_fence_ptr = fence_ptr;
>+}
>+
>+static u64 __user * get_out_fence_for_crtc(struct drm_atomic_state *state,
>+ struct drm_crtc *crtc)
>+{
>+ u64 __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;
>+}
>+

You missed a couple of s/u64/s64/ in the two functions above.

> /**
> * 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 +1804,166 @@ 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) {
>+ 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 = get_crtc_fence(crtc);
>+ if (!fence)
>+ return -ENOMEM;
>+
>+ ret = setup_out_fence(&f[*num_fences], fence);
>+ if (ret) {
>+ dma_fence_put(fence);
>+ return ret;
>+ }

Looks to me that the cleanup path doesn't work here. If
setup_out_fence fails, you bail out before incrementing num_fences,
and so the cleanup loop will be an iteration short.

>+
>+ (*num_fences)++;
>+
>+ *fence_state = f;

I think this is problematic too. If I understand krealloc right, when
you bail out before here and f != *fence_state, then the old
*fence_state will have been already freed, and f is going to leak.

>+ 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) {
>+ for (i = 0; i < num_fences; i++)
>+ fd_install(fence_state[i].fd,
>+ fence_state[i].sync_file->file);
>+ return;
>+ }
>+
>+ if (!fence_state)
>+ 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);
>+ }

I think this event cleanup needs to be before the !fence_state check;
userspace can ask for events but no fences, and if that fails then the
events need to be freed.

Cheers,
-Brian

>+
>+ 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 +1976,10 @@ 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 +2094,10 @@ 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 +2117,7 @@ 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
>