[PATCH v3] drm/syncobj: add IOCTL to register an eventfd
Simon Ser
contact at emersion.fr
Tue Jul 11 14:28:11 UTC 2023
Introduce a new DRM_IOCTL_SYNCOBJ_EVENTFD IOCTL which signals an
eventfd from a syncobj.
This is useful for Wayland compositors to handle wait-before-submit.
Wayland clients can send a timeline point to the compositor
before the point has materialized yet, then compositors can wait
for the point to materialize via this new IOCTL.
The existing DRM_IOCTL_SYNCOBJ_TIMELINE_WAIT IOCTL is not suitable
because it blocks. Compositors want to integrate the wait with
their poll(2)-based event loop.
Requirements for new uAPI:
- User-space patch: https://gitlab.freedesktop.org/wlroots/wlroots/-/merge_requests/4262
- IGT: https://lists.freedesktop.org/archives/igt-dev/2023-July/057866.html
v2:
- Wait for fence when flags is zero
- Improve documentation (Pekka)
- Rename IOCTL (Christian)
- Fix typo in drm_syncobj_add_eventfd() (Christian)
v3:
- Link user-space + IGT patches
- Add reference from overview docs
Signed-off-by: Simon Ser <contact at emersion.fr>
Reviewed-by: Christian König <christian.koenig at amd.com>
Acked-by: Pekka Paalanen <pekka.paalanen at collabora.com>
Cc: Jason Ekstrand <jason at jlekstrand.net>
Cc: Daniel Vetter <daniel at ffwll.ch>
Cc: Bas Nieuwenhuizen <bas at basnieuwenhuizen.nl>
Cc: Daniel Stone <daniel at fooishbar.org>
Cc: James Jones <jajones at nvidia.com>
Cc: Austin Shafer <ashafer at nvidia.com>
---
drivers/gpu/drm/drm_internal.h | 2 +
drivers/gpu/drm/drm_ioctl.c | 2 +
drivers/gpu/drm/drm_syncobj.c | 147 +++++++++++++++++++++++++++++++--
include/drm/drm_syncobj.h | 6 +-
include/uapi/drm/drm.h | 22 +++++
5 files changed, 172 insertions(+), 7 deletions(-)
diff --git a/drivers/gpu/drm/drm_internal.h b/drivers/gpu/drm/drm_internal.h
index d7e023bbb0d5..ba12acd55139 100644
--- a/drivers/gpu/drm/drm_internal.h
+++ b/drivers/gpu/drm/drm_internal.h
@@ -245,6 +245,8 @@ int drm_syncobj_wait_ioctl(struct drm_device *dev, void *data,
struct drm_file *file_private);
int drm_syncobj_timeline_wait_ioctl(struct drm_device *dev, void *data,
struct drm_file *file_private);
+int drm_syncobj_eventfd_ioctl(struct drm_device *dev, void *data,
+ struct drm_file *file_private);
int drm_syncobj_reset_ioctl(struct drm_device *dev, void *data,
struct drm_file *file_private);
int drm_syncobj_signal_ioctl(struct drm_device *dev, void *data,
diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index 8e9afe7af19c..f03ffbacfe9b 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -701,6 +701,8 @@ static const struct drm_ioctl_desc drm_ioctls[] = {
DRM_RENDER_ALLOW),
DRM_IOCTL_DEF(DRM_IOCTL_SYNCOBJ_TIMELINE_WAIT, drm_syncobj_timeline_wait_ioctl,
DRM_RENDER_ALLOW),
+ DRM_IOCTL_DEF(DRM_IOCTL_SYNCOBJ_EVENTFD, drm_syncobj_eventfd_ioctl,
+ DRM_RENDER_ALLOW),
DRM_IOCTL_DEF(DRM_IOCTL_SYNCOBJ_RESET, drm_syncobj_reset_ioctl,
DRM_RENDER_ALLOW),
DRM_IOCTL_DEF(DRM_IOCTL_SYNCOBJ_SIGNAL, drm_syncobj_signal_ioctl,
diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c
index 0c2be8360525..0f1cb70413af 100644
--- a/drivers/gpu/drm/drm_syncobj.c
+++ b/drivers/gpu/drm/drm_syncobj.c
@@ -136,6 +136,10 @@
* requirement is inherited from the wait-before-signal behavior required by
* the Vulkan timeline semaphore API.
*
+ * Alternatively, &DRM_IOCTL_SYNCOBJ_EVENTFD can be used to wait without
+ * blocking: an eventfd will be signaled when the syncobj is. This is useful to
+ * integrate the wait in an event loop.
+ *
*
* Import/export of syncobjs
* -------------------------
@@ -185,6 +189,7 @@
#include <linux/anon_inodes.h>
#include <linux/dma-fence-unwrap.h>
+#include <linux/eventfd.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/sched/signal.h>
@@ -212,6 +217,20 @@ struct syncobj_wait_entry {
static void syncobj_wait_syncobj_func(struct drm_syncobj *syncobj,
struct syncobj_wait_entry *wait);
+struct syncobj_eventfd_entry {
+ struct list_head node;
+ struct dma_fence *fence;
+ struct dma_fence_cb fence_cb;
+ struct drm_syncobj *syncobj;
+ struct eventfd_ctx *ev_fd_ctx;
+ u64 point;
+ u32 flags;
+};
+
+static void
+syncobj_eventfd_entry_func(struct drm_syncobj *syncobj,
+ struct syncobj_eventfd_entry *entry);
+
/**
* drm_syncobj_find - lookup and reference a sync object.
* @file_private: drm file private pointer
@@ -274,6 +293,27 @@ static void drm_syncobj_remove_wait(struct drm_syncobj *syncobj,
spin_unlock(&syncobj->lock);
}
+static void
+syncobj_eventfd_entry_free(struct syncobj_eventfd_entry *entry)
+{
+ eventfd_ctx_put(entry->ev_fd_ctx);
+ dma_fence_put(entry->fence);
+ /* This happens either inside the syncobj lock, or after the node has
+ * already been removed from the list */
+ list_del(&entry->node);
+ kfree(entry);
+}
+
+static void
+drm_syncobj_add_eventfd(struct drm_syncobj *syncobj,
+ struct syncobj_eventfd_entry *entry)
+{
+ spin_lock(&syncobj->lock);
+ list_add_tail(&entry->node, &syncobj->ev_fd_list);
+ syncobj_eventfd_entry_func(syncobj, entry);
+ spin_unlock(&syncobj->lock);
+}
+
/**
* drm_syncobj_add_point - add new timeline point to the syncobj
* @syncobj: sync object to add timeline point do
@@ -288,7 +328,8 @@ void drm_syncobj_add_point(struct drm_syncobj *syncobj,
struct dma_fence *fence,
uint64_t point)
{
- struct syncobj_wait_entry *cur, *tmp;
+ struct syncobj_wait_entry *wait_cur, *wait_tmp;
+ struct syncobj_eventfd_entry *ev_fd_cur, *ev_fd_tmp;
struct dma_fence *prev;
dma_fence_get(fence);
@@ -302,8 +343,10 @@ void drm_syncobj_add_point(struct drm_syncobj *syncobj,
dma_fence_chain_init(chain, prev, fence, point);
rcu_assign_pointer(syncobj->fence, &chain->base);
- list_for_each_entry_safe(cur, tmp, &syncobj->cb_list, node)
- syncobj_wait_syncobj_func(syncobj, cur);
+ list_for_each_entry_safe(wait_cur, wait_tmp, &syncobj->cb_list, node)
+ syncobj_wait_syncobj_func(syncobj, wait_cur);
+ list_for_each_entry_safe(ev_fd_cur, ev_fd_tmp, &syncobj->ev_fd_list, node)
+ syncobj_eventfd_entry_func(syncobj, ev_fd_cur);
spin_unlock(&syncobj->lock);
/* Walk the chain once to trigger garbage collection */
@@ -323,7 +366,8 @@ void drm_syncobj_replace_fence(struct drm_syncobj *syncobj,
struct dma_fence *fence)
{
struct dma_fence *old_fence;
- struct syncobj_wait_entry *cur, *tmp;
+ struct syncobj_wait_entry *wait_cur, *wait_tmp;
+ struct syncobj_eventfd_entry *ev_fd_cur, *ev_fd_tmp;
if (fence)
dma_fence_get(fence);
@@ -335,8 +379,10 @@ void drm_syncobj_replace_fence(struct drm_syncobj *syncobj,
rcu_assign_pointer(syncobj->fence, fence);
if (fence != old_fence) {
- list_for_each_entry_safe(cur, tmp, &syncobj->cb_list, node)
- syncobj_wait_syncobj_func(syncobj, cur);
+ list_for_each_entry_safe(wait_cur, wait_tmp, &syncobj->cb_list, node)
+ syncobj_wait_syncobj_func(syncobj, wait_cur);
+ list_for_each_entry_safe(ev_fd_cur, ev_fd_tmp, &syncobj->ev_fd_list, node)
+ syncobj_eventfd_entry_func(syncobj, ev_fd_cur);
}
spin_unlock(&syncobj->lock);
@@ -472,7 +518,13 @@ void drm_syncobj_free(struct kref *kref)
struct drm_syncobj *syncobj = container_of(kref,
struct drm_syncobj,
refcount);
+ struct syncobj_eventfd_entry *ev_fd_cur, *ev_fd_tmp;
+
drm_syncobj_replace_fence(syncobj, NULL);
+
+ list_for_each_entry_safe(ev_fd_cur, ev_fd_tmp, &syncobj->ev_fd_list, node)
+ syncobj_eventfd_entry_free(ev_fd_cur);
+
kfree(syncobj);
}
EXPORT_SYMBOL(drm_syncobj_free);
@@ -501,6 +553,7 @@ int drm_syncobj_create(struct drm_syncobj **out_syncobj, uint32_t flags,
kref_init(&syncobj->refcount);
INIT_LIST_HEAD(&syncobj->cb_list);
+ INIT_LIST_HEAD(&syncobj->ev_fd_list);
spin_lock_init(&syncobj->lock);
if (flags & DRM_SYNCOBJ_CREATE_SIGNALED) {
@@ -1304,6 +1357,88 @@ drm_syncobj_timeline_wait_ioctl(struct drm_device *dev, void *data,
return ret;
}
+static void syncobj_eventfd_entry_fence_func(struct dma_fence *fence,
+ struct dma_fence_cb *cb)
+{
+ struct syncobj_eventfd_entry *entry =
+ container_of(cb, struct syncobj_eventfd_entry, fence_cb);
+
+ eventfd_signal(entry->ev_fd_ctx, 1);
+ syncobj_eventfd_entry_free(entry);
+}
+
+static void
+syncobj_eventfd_entry_func(struct drm_syncobj *syncobj,
+ struct syncobj_eventfd_entry *entry)
+{
+ int ret;
+ struct dma_fence *fence;
+
+ /* This happens inside the syncobj lock */
+ fence = dma_fence_get(rcu_dereference_protected(syncobj->fence, 1));
+ ret = dma_fence_chain_find_seqno(&fence, entry->point);
+ if (ret != 0 || !fence) {
+ dma_fence_put(fence);
+ return;
+ }
+
+ list_del_init(&entry->node);
+ entry->fence = fence;
+
+ if (entry->flags & DRM_SYNCOBJ_WAIT_FLAGS_WAIT_AVAILABLE) {
+ eventfd_signal(entry->ev_fd_ctx, 1);
+ syncobj_eventfd_entry_free(entry);
+ } else {
+ ret = dma_fence_add_callback(fence, &entry->fence_cb,
+ syncobj_eventfd_entry_fence_func);
+ if (ret == -ENOENT) {
+ eventfd_signal(entry->ev_fd_ctx, 1);
+ syncobj_eventfd_entry_free(entry);
+ }
+ }
+}
+
+int
+drm_syncobj_eventfd_ioctl(struct drm_device *dev, void *data,
+ struct drm_file *file_private)
+{
+ struct drm_syncobj_eventfd *args = data;
+ struct drm_syncobj *syncobj;
+ struct eventfd_ctx *ev_fd_ctx;
+ struct syncobj_eventfd_entry *entry;
+
+ if (!drm_core_check_feature(dev, DRIVER_SYNCOBJ_TIMELINE))
+ return -EOPNOTSUPP;
+
+ if (args->flags & ~DRM_SYNCOBJ_WAIT_FLAGS_WAIT_AVAILABLE)
+ return -EINVAL;
+
+ if (args->pad)
+ return -EINVAL;
+
+ syncobj = drm_syncobj_find(file_private, args->handle);
+ if (!syncobj)
+ return -ENOENT;
+
+ ev_fd_ctx = eventfd_ctx_fdget(args->fd);
+ if (IS_ERR(ev_fd_ctx))
+ return PTR_ERR(ev_fd_ctx);
+
+ entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+ if (!entry) {
+ eventfd_ctx_put(ev_fd_ctx);
+ return -ENOMEM;
+ }
+ entry->syncobj = syncobj;
+ entry->ev_fd_ctx = ev_fd_ctx;
+ entry->point = args->point;
+ entry->flags = args->flags;
+
+ drm_syncobj_add_eventfd(syncobj, entry);
+ drm_syncobj_put(syncobj);
+
+ return 0;
+}
int
drm_syncobj_reset_ioctl(struct drm_device *dev, void *data,
diff --git a/include/drm/drm_syncobj.h b/include/drm/drm_syncobj.h
index 6cf7243a1dc5..b40052132e52 100644
--- a/include/drm/drm_syncobj.h
+++ b/include/drm/drm_syncobj.h
@@ -54,7 +54,11 @@ struct drm_syncobj {
*/
struct list_head cb_list;
/**
- * @lock: Protects &cb_list and write-locks &fence.
+ * @ev_fd_list: List of registered eventfd.
+ */
+ struct list_head ev_fd_list;
+ /**
+ * @lock: Protects &cb_list and &ev_fd_list, and write-locks &fence.
*/
spinlock_t lock;
/**
diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
index a87bbbbca2d4..73fc43e100bf 100644
--- a/include/uapi/drm/drm.h
+++ b/include/uapi/drm/drm.h
@@ -909,6 +909,27 @@ struct drm_syncobj_timeline_wait {
__u32 pad;
};
+/**
+ * struct drm_syncobj_eventfd
+ * @handle: syncobj handle.
+ * @flags: Zero to wait for the point to be signalled, or
+ * &DRM_SYNCOBJ_WAIT_FLAGS_WAIT_AVAILABLE to wait for a fence to be
+ * available for the point.
+ * @point: syncobj timeline point (set to zero for binary syncobjs).
+ * @fd: Existing eventfd to sent events to.
+ * @pad: Must be zero.
+ *
+ * Register an eventfd to be signalled by a syncobj. The eventfd counter will
+ * be incremented by one.
+ */
+struct drm_syncobj_eventfd {
+ __u32 handle;
+ __u32 flags;
+ __u64 point;
+ __s32 fd;
+ __u32 pad;
+};
+
struct drm_syncobj_array {
__u64 handles;
@@ -1138,6 +1159,7 @@ extern "C" {
#define DRM_IOCTL_SYNCOBJ_QUERY DRM_IOWR(0xCB, struct drm_syncobj_timeline_array)
#define DRM_IOCTL_SYNCOBJ_TRANSFER DRM_IOWR(0xCC, struct drm_syncobj_transfer)
#define DRM_IOCTL_SYNCOBJ_TIMELINE_SIGNAL DRM_IOWR(0xCD, struct drm_syncobj_timeline_array)
+#define DRM_IOCTL_SYNCOBJ_EVENTFD DRM_IOWR(0xCE, struct drm_syncobj_eventfd)
/**
* DRM_IOCTL_MODE_GETFB2 - Get framebuffer metadata.
--
2.41.0
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