Message-ID: <20161020174810.GB7165@e106950-lin.cambridge.arm.com>
Date:   Thu, 20 Oct 2016 18:48:10 +0100
From:   Brian Starkey <brian.starkey@....com>
To:     Gustavo Padovan <gustavo@...ovan.org>
Cc:     dri-devel@...ts.freedesktop.org, marcheu@...gle.com,
        Daniel Stone <daniels@...labora.com>, seanpaul@...gle.com,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        linux-kernel@...r.kernel.org, laurent.pinchart@...asonboard.com,
        Gustavo Padovan <gustavo.padovan@...labora.co.uk>,
        John Harrison <John.C.Harrison@...el.com>, m.chehab@...sung.com
Subject: Re: [PATCH v5 4/4] drm/fence: add out-fences support

Hi Gustavo,

I notice your branch has the sync_file refcount change in, but this
doesn't seem to take account for that. Will you be dropping that
change to match the semantics of fence_array?

Couple more comments below.

On Thu, Oct 20, 2016 at 12:50:05PM -0200, Gustavo Padovan wrote:
>From: Gustavo Padovan <gustavo.padovan@...labora.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.
>
>In case of error userspace should receive a fd number of -1.
>
>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.
>
>Signed-off-by: Gustavo Padovan <gustavo.padovan@...labora.co.uk>
>---
> drivers/gpu/drm/drm_atomic.c | 116 ++++++++++++++++++++++++++++++++++---------
> drivers/gpu/drm/drm_crtc.c   |   8 +++
> include/drm/drm_crtc.h       |  19 +++++++
> 3 files changed, 119 insertions(+), 24 deletions(-)
>
>diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
>index b3284b2..07775fc 100644
>--- a/drivers/gpu/drm/drm_atomic.c
>+++ b/drivers/gpu/drm/drm_atomic.c
>@@ -490,6 +490,8 @@ 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) {
>+		state->out_fence_ptr = u64_to_user_ptr(val);
> 	} else if (crtc->funcs->atomic_set_property)
> 		return crtc->funcs->atomic_set_property(crtc, state, property, val);
> 	else
>@@ -532,6 +534,8 @@ 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
>@@ -1474,11 +1478,9 @@ EXPORT_SYMBOL(drm_atomic_nonblocking_commit);
>  */
>
> static struct drm_pending_vblank_event *create_vblank_event(
>-		struct drm_device *dev, struct drm_file *file_priv,
>-		struct 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)
>@@ -1488,17 +1490,6 @@ 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;
> }
>
>@@ -1603,6 +1594,40 @@ void drm_atomic_clean_old_fb(struct drm_device *dev,
> }
> EXPORT_SYMBOL(drm_atomic_clean_old_fb);
>
>+static int crtc_setup_out_fence(struct drm_crtc *crtc,
>+				struct drm_crtc_state *crtc_state,
>+				struct drm_out_fence_state *fence_state)
>+{
>+	struct fence *fence;
>+
>+	fence_state->fd = get_unused_fd_flags(O_CLOEXEC);
>+	if (fence_state->fd < 0) {
>+		return fence_state->fd;
>+	}
>+
>+	fence_state->out_fence_ptr = crtc_state->out_fence_ptr;
>+	crtc_state->out_fence_ptr = NULL;
>+
>+	if (put_user(fence_state->fd, fence_state->out_fence_ptr))
>+		return -EFAULT;
>+
>+	fence = kzalloc(sizeof(*fence), GFP_KERNEL);
>+	if (!fence)
>+		return -ENOMEM;
>+
>+	fence_init(fence, &drm_crtc_fence_ops, &crtc->fence_lock,
>+		   crtc->fence_context, ++crtc->fence_seqno);
>+
>+	fence_state->sync_file = sync_file_create(fence);
>+	if(!fence_state->sync_file) {
>+		fence_put(fence);
>+		return -ENOMEM;
>+	}
>+
>+	crtc_state->event->base.fence = fence_get(fence);
>+	return 0;
>+}
>+
> int drm_mode_atomic_ioctl(struct drm_device *dev,
> 			  void *data, struct drm_file *file_priv)
> {
>@@ -1617,9 +1642,10 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
> 	struct drm_plane *plane;
> 	struct drm_crtc *crtc;
> 	struct drm_crtc_state *crtc_state;
>+	struct drm_out_fence_state *fence_state;
> 	unsigned plane_mask;
> 	int ret = 0;
>-	unsigned int i, j;
>+	unsigned int i, j, fence_idx = 0;
>
> 	/* disallow for drivers not supporting atomic: */
> 	if (!drm_core_check_feature(dev, DRIVER_ATOMIC))
>@@ -1734,12 +1760,19 @@ retry:
> 		drm_mode_object_unreference(obj);
> 	}
>
>-	if (arg->flags & DRM_MODE_PAGE_FLIP_EVENT) {
>-		for_each_crtc_in_state(state, crtc, crtc_state, i) {
>+	fence_state = kcalloc(dev->mode_config.num_crtc, sizeof(*fence_state),
>+			      GFP_KERNEL);
>+	if (!fence_state) {
>+		ret = -ENOMEM;
>+		goto out;
>+	}
>+
>+	for_each_crtc_in_state(state, crtc, crtc_state, i) {
>+		if (arg->flags & DRM_MODE_PAGE_FLIP_EVENT ||
>+		    crtc_state->out_fence_ptr) {
> 			struct drm_pending_vblank_event *e;
>
>-			e = create_vblank_event(dev, file_priv, NULL,
>-						arg->user_data);
>+			e = create_vblank_event(dev, arg->user_data);
> 			if (!e) {
> 				ret = -ENOMEM;
> 				goto out;
>@@ -1747,6 +1780,28 @@ retry:
>
> 			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;
>+				goto out;
>+			}
>+		}
>+
>+		if (crtc_state->out_fence_ptr) {
>+			ret = crtc_setup_out_fence(crtc, crtc_state,
>+						   &fence_state[fence_idx++]);
>+			if (ret)
>+				goto out;
>+		}
> 	}
>
> 	if (arg->flags & DRM_MODE_ATOMIC_TEST_ONLY) {
>@@ -1761,24 +1816,37 @@ retry:
> 		ret = drm_atomic_commit(state);
> 	}
>
>+	for (i = 0; i < fence_idx; i++)
>+		fd_install(fence_state[i].fd, fence_state[i].sync_file->file);
>+
> out:
> 	drm_atomic_clean_old_fb(dev, plane_mask, ret);
>
>-	if (ret && arg->flags & DRM_MODE_PAGE_FLIP_EVENT) {
>+	for_each_crtc_in_state(state, crtc, crtc_state, i) {

I think a check on ret is still needed before you iterate the CRTCs.
If the commit is successful then state has already been freed by this
point, and I get a splat.

> 		/*
> 		 * 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 (ret && crtc_state->event)
>+			drm_event_cancel_free(dev, &crtc_state->event->base);
>+	}
>
>-		for_each_crtc_in_state(state, crtc, crtc_state, i) {
>-			if (!crtc_state->event)
>-				continue;
>+	if (ret && fence_state) {
>+		for (i = 0; i < fence_idx; i++) {
>+			if (fence_state[i].fd >= 0)
>+				put_unused_fd(fence_state[i].fd);
>+			if (fence_state[i].sync_file)
>+				fput(fence_state[i].sync_file->file);
>
>-			drm_event_cancel_free(dev, &crtc_state->event->base);
>+			/* If this fails, there's not much we can do about it */
>+			if (put_user(-1, fence_state->out_fence_ptr))
>+				DRM_ERROR("Couldn't clear out_fence_ptr\n");
> 		}
> 	}
>
>+	kfree(fence_state);
>+
> 	if (ret == -EDEADLK) {
> 		drm_atomic_state_clear(state);
> 		drm_modeset_backoff(&ctx);
>diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
>index b99090f..40bce97 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_crtc.h b/include/drm/drm_crtc.h
>index 657a33a..b898604 100644
>--- a/include/drm/drm_crtc.h
>+++ b/include/drm/drm_crtc.h
>@@ -165,6 +165,8 @@ struct drm_crtc_state {
> 	struct drm_property_blob *ctm;
> 	struct drm_property_blob *gamma_lut;
>
>+	u64 __user *out_fence_ptr;
>+

I'm somewhat not convinced about stashing a __user pointer in the
CRTC atomic state. I know it gets cleared before the driver sees it,
but if anything I think that hints that this isn't the right place to
store it.

I've been trying to think of other ways to get from a property to
something drm_mode_atomic_ioctl can use - maybe we can store some
stuff in drm_atomic_state which only lives for the length of the ioctl
call and put this pointer in there.

Thanks,
Brian

> 	/**
> 	 * @event:
> 	 *
>@@ -748,6 +750,18 @@ static inline struct drm_crtc *fence_to_crtc(struct fence *fence)
> }
>
> /**
>+ * struct drm_out_fence_state - store out_fence data for install and clean up
>+ * @out_fence_ptr: user pointer to store the fence fd in.
>+ * @sync_file: sync_file related to the out_fence
>+ * @fd: file descriptor to installed on the sync_file.
>+ */
>+struct drm_out_fence_state {
>+	u64 __user *out_fence_ptr;
>+	struct sync_file *sync_file;
>+	int fd;
>+};
>+
>+/*
>  * struct drm_mode_set - new values for a CRTC config change
>  * @fb: framebuffer to use for new config
>  * @crtc: CRTC whose configuration we're about to change
>@@ -1230,6 +1244,11 @@ 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.
>+	 */
>+	struct drm_property *prop_out_fence_ptr;
>+	/**
> 	 * @prop_crtc_id: Default atomic plane property to specify the
> 	 * &drm_crtc.
> 	 */
>-- 
>2.5.5
>
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