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drm/syncobj: add IOCTL to register an eventfd 

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/057893.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

v4: fix IOCTL number conflict with GETFB2 (Nicholas Choi, Vitaly Prosyak)

Signed-off-by: Simon Ser <contact@emersion.fr>
Reviewed-by: Christian König <christian.koenig@amd.com>
Acked-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Cc: Jason Ekstrand <jason@jlekstrand.net>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Cc: Daniel Stone <daniel@fooishbar.org>
Cc: James Jones <jajones@nvidia.com>
Cc: Austin Shafer <ashafer@nvidia.com>
Cc: Vitaly Prosyak <vprosyak@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230714111257.11940-1-contact@emersion.fr
This commit is contained in:
Simon Ser 2023-07-14 11:13:03 +00:00
parent 4f66feeab1
commit c7a4722971
5 changed files with 174 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/gpu/drm/drm_internal.h
View File

@ -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,

2
drivers/gpu/drm/drm_ioctl.c
View File

@ -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,

148
drivers/gpu/drm/drm_syncobj.c
View File

@ -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 +293,28 @@ 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 +329,8 @@ 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 +344,10 @@ 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 +367,8 @@ 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 +380,10 @@ 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 +519,13 @@ 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 +554,7 @@ 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 +1358,88 @@ 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,

6
include/drm/drm_syncobj.h
View File

@ -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;
/**

23
include/uapi/drm/drm.h
View File

@ -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;
@ -1169,6 +1190,8 @@ extern "C" {
*/
#define DRM_IOCTL_MODE_GETFB2 DRM_IOWR(0xCE, struct drm_mode_fb_cmd2)
#define DRM_IOCTL_SYNCOBJ_EVENTFD DRM_IOWR(0xCF, struct drm_syncobj_eventfd)
/*
* Device specific ioctls should only be in their respective headers
* The device specific ioctl range is from 0x40 to 0x9f.