drm: introduce sync objects (v4)

Sync objects are new toplevel drm object, that contain a
pointer to a fence. This fence can be updated via command
submission ioctls via drivers.

There is also a generic wait obj API modelled on the vulkan
wait API (with code modelled on some amdgpu code).

These objects can be converted to an opaque fd that can be
passes between processes.

v2: rename reference/unreference to put/get (Chris)
fix leaked reference (David Zhou)
drop mutex in favour of cmpxchg (Chris)
v3: cleanups from danvet, rebase on drm_fops rename
check fd_flags is 0 in ioctls.
v4: export find/free, change replace fence to take a
syncobj. In order to support lookup first, replace
later semantics which seem in the end to be cleaner.

Reviewed-by: Sean Paul <[e-mail]>
Reviewed-by: Chris Wilson <[e-mail]>
Signed-off-by: Dave Airlie <[e-mail]>

Documentation/gpu/drm-internals.rst

···
     implement appropriate obj->atomic_get_property() vfuncs for any
     modeset objects with driver specific properties.
 
+DRIVER_SYNCOBJ
+    Driver support drm sync objects.
+
 Major, Minor and Patchlevel
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

Documentation/gpu/drm-mm.rst

···
 
 .. kernel-doc:: drivers/gpu/drm/drm_cache.c
    :export:
+
+DRM Sync Objects
+===========================
+
+.. kernel-doc:: drivers/gpu/drm/drm_syncobj.c
+   :doc: Overview
+
+.. kernel-doc:: include/drm/drm_syncobj.h
+   :export:
+
+.. kernel-doc:: drivers/gpu/drm/drm_syncobj.c
+   :export:

drivers/gpu/drm/Makefile

···
 		drm_framebuffer.o drm_connector.o drm_blend.o \
 		drm_encoder.o drm_mode_object.o drm_property.o \
 		drm_plane.o drm_color_mgmt.o drm_print.o \
-		drm_dumb_buffers.o drm_mode_config.o drm_vblank.o
+		drm_dumb_buffers.o drm_mode_config.o drm_vblank.o \
+		drm_syncobj.o
 
 drm-$(CONFIG_DRM_LIB_RANDOM) += lib/drm_random.o
 drm-$(CONFIG_DRM_VM) += drm_vm.o

drivers/gpu/drm/drm_file.c

···
 	if (drm_core_check_feature(dev, DRIVER_GEM))
 		drm_gem_open(dev, priv);
 
+	if (drm_core_check_feature(dev, DRIVER_SYNCOBJ))
+		drm_syncobj_open(priv);
+
 	if (drm_core_check_feature(dev, DRIVER_PRIME))
 		drm_prime_init_file_private(&priv->prime);
 
···
 out_prime_destroy:
 	if (drm_core_check_feature(dev, DRIVER_PRIME))
 		drm_prime_destroy_file_private(&priv->prime);
+	if (drm_core_check_feature(dev, DRIVER_SYNCOBJ))
+		drm_syncobj_release(priv);
 	if (drm_core_check_feature(dev, DRIVER_GEM))
 		drm_gem_release(dev, priv);
 	put_pid(priv->pid);
···
 		drm_fb_release(file_priv);
 		drm_property_destroy_user_blobs(dev, file_priv);
 	}
+
+	if (drm_core_check_feature(dev, DRIVER_SYNCOBJ))
+		drm_syncobj_release(file_priv);
 
 	if (drm_core_check_feature(dev, DRIVER_GEM))
 		drm_gem_release(dev, file_priv);

drivers/gpu/drm/drm_internal.h

···
 {
 	return 0;
 }
+
 #endif
+
+/* drm_syncobj.c */
+void drm_syncobj_open(struct drm_file *file_private);
+void drm_syncobj_release(struct drm_file *file_private);
+int drm_syncobj_create_ioctl(struct drm_device *dev, void *data,
+			     struct drm_file *file_private);
+int drm_syncobj_destroy_ioctl(struct drm_device *dev, void *data,
+			      struct drm_file *file_private);
+int drm_syncobj_handle_to_fd_ioctl(struct drm_device *dev, void *data,
+				   struct drm_file *file_private);
+int drm_syncobj_fd_to_handle_ioctl(struct drm_device *dev, void *data,
+				   struct drm_file *file_private);

drivers/gpu/drm/drm_ioctl.c

···
 		req->value |= dev->driver->prime_fd_to_handle ? DRM_PRIME_CAP_IMPORT : 0;
 		req->value |= dev->driver->prime_handle_to_fd ? DRM_PRIME_CAP_EXPORT : 0;
 		return 0;
+	case DRM_CAP_SYNCOBJ:
+		req->value = drm_core_check_feature(dev, DRIVER_SYNCOBJ);
+		return 0;
 	}
 
 	/* Other caps only work with KMS drivers */
···
 	DRM_IOCTL_DEF(DRM_IOCTL_MODE_ATOMIC, drm_mode_atomic_ioctl, DRM_MASTER|DRM_CONTROL_ALLOW|DRM_UNLOCKED),
 	DRM_IOCTL_DEF(DRM_IOCTL_MODE_CREATEPROPBLOB, drm_mode_createblob_ioctl, DRM_CONTROL_ALLOW|DRM_UNLOCKED),
 	DRM_IOCTL_DEF(DRM_IOCTL_MODE_DESTROYPROPBLOB, drm_mode_destroyblob_ioctl, DRM_CONTROL_ALLOW|DRM_UNLOCKED),
+
+	DRM_IOCTL_DEF(DRM_IOCTL_SYNCOBJ_CREATE, drm_syncobj_create_ioctl,
+		      DRM_UNLOCKED|DRM_RENDER_ALLOW),
+	DRM_IOCTL_DEF(DRM_IOCTL_SYNCOBJ_DESTROY, drm_syncobj_destroy_ioctl,
+		      DRM_UNLOCKED|DRM_RENDER_ALLOW),
+	DRM_IOCTL_DEF(DRM_IOCTL_SYNCOBJ_HANDLE_TO_FD, drm_syncobj_handle_to_fd_ioctl,
+		      DRM_UNLOCKED|DRM_RENDER_ALLOW),
+	DRM_IOCTL_DEF(DRM_IOCTL_SYNCOBJ_FD_TO_HANDLE, drm_syncobj_fd_to_handle_ioctl,
+		      DRM_UNLOCKED|DRM_RENDER_ALLOW),
 };
 
 #define DRM_CORE_IOCTL_COUNT	ARRAY_SIZE( drm_ioctls )

drivers/gpu/drm/drm_syncobj.c

···
+/*
+ * Copyright 2017 Red Hat
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ *
+ * Authors:
+ *
+ */
+
+/**
+ * DOC: Overview
+ *
+ * DRM synchronisation objects (syncobj) are a persistent objects,
+ * that contain an optional fence. The fence can be updated with a new
+ * fence, or be NULL.
+ *
+ * syncobj's can be export to fd's and back, these fd's are opaque and
+ * have no other use case, except passing the syncobj between processes.
+ *
+ * Their primary use-case is to implement Vulkan fences and semaphores.
+ *
+ * syncobj have a kref reference count, but also have an optional file.
+ * The file is only created once the syncobj is exported.
+ * The file takes a reference on the kref.
+ */
+
+#include <drm/drmP.h>
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/anon_inodes.h>
+
+#include "drm_internal.h"
+#include <drm/drm_syncobj.h>
+
+/**
+ * drm_syncobj_find - lookup and reference a sync object.
+ * @file_private: drm file private pointer
+ * @handle: sync object handle to lookup.
+ *
+ * Returns a reference to the syncobj pointed to by handle or NULL.
+ */
+struct drm_syncobj *drm_syncobj_find(struct drm_file *file_private,
+				     u32 handle)
+{
+	struct drm_syncobj *syncobj;
+
+	spin_lock(&file_private->syncobj_table_lock);
+
+	/* Check if we currently have a reference on the object */
+	syncobj = idr_find(&file_private->syncobj_idr, handle);
+	if (syncobj)
+		drm_syncobj_get(syncobj);
+
+	spin_unlock(&file_private->syncobj_table_lock);
+
+	return syncobj;
+}
+EXPORT_SYMBOL(drm_syncobj_find);
+
+/**
+ * drm_syncobj_replace_fence - replace fence in a sync object.
+ * @file_private: drm file private pointer.
+ * @syncobj: Sync object to replace fence in
+ * @fence: fence to install in sync file.
+ *
+ * This replaces the fence on a sync object.
+ */
+void drm_syncobj_replace_fence(struct drm_file *file_private,
+			       struct drm_syncobj *syncobj,
+			       struct dma_fence *fence)
+{
+	struct dma_fence *old_fence = NULL;
+
+	if (fence)
+		dma_fence_get(fence);
+	old_fence = xchg(&syncobj->fence, fence);
+
+	dma_fence_put(old_fence);
+}
+EXPORT_SYMBOL(drm_syncobj_replace_fence);
+
+int drm_syncobj_fence_get(struct drm_file *file_private,
+			  u32 handle,
+			  struct dma_fence **fence)
+{
+	struct drm_syncobj *syncobj = drm_syncobj_find(file_private, handle);
+	int ret = 0;
+
+	if (!syncobj)
+		return -ENOENT;
+
+	*fence = dma_fence_get(syncobj->fence);
+	if (!*fence) {
+		ret = -EINVAL;
+	}
+	drm_syncobj_put(syncobj);
+	return ret;
+}
+EXPORT_SYMBOL(drm_syncobj_fence_get);
+
+/**
+ * drm_syncobj_free - free a sync object.
+ * @kref: kref to free.
+ *
+ * Only to be called from kref_put in drm_syncobj_put.
+ */
+void drm_syncobj_free(struct kref *kref)
+{
+	struct drm_syncobj *syncobj = container_of(kref,
+						   struct drm_syncobj,
+						   refcount);
+	dma_fence_put(syncobj->fence);
+	kfree(syncobj);
+}
+EXPORT_SYMBOL(drm_syncobj_free);
+
+static int drm_syncobj_create(struct drm_file *file_private,
+			      u32 *handle)
+{
+	int ret;
+	struct drm_syncobj *syncobj;
+
+	syncobj = kzalloc(sizeof(struct drm_syncobj), GFP_KERNEL);
+	if (!syncobj)
+		return -ENOMEM;
+
+	kref_init(&syncobj->refcount);
+
+	idr_preload(GFP_KERNEL);
+	spin_lock(&file_private->syncobj_table_lock);
+	ret = idr_alloc(&file_private->syncobj_idr, syncobj, 1, 0, GFP_NOWAIT);
+	spin_unlock(&file_private->syncobj_table_lock);
+
+	idr_preload_end();
+
+	if (ret < 0) {
+		drm_syncobj_put(syncobj);
+		return ret;
+	}
+
+	*handle = ret;
+	return 0;
+}
+
+static int drm_syncobj_destroy(struct drm_file *file_private,
+			       u32 handle)
+{
+	struct drm_syncobj *syncobj;
+
+	spin_lock(&file_private->syncobj_table_lock);
+	syncobj = idr_remove(&file_private->syncobj_idr, handle);
+	spin_unlock(&file_private->syncobj_table_lock);
+
+	if (!syncobj)
+		return -EINVAL;
+
+	drm_syncobj_put(syncobj);
+	return 0;
+}
+
+static int drm_syncobj_file_release(struct inode *inode, struct file *file)
+{
+	struct drm_syncobj *syncobj = file->private_data;
+
+	drm_syncobj_put(syncobj);
+	return 0;
+}
+
+static const struct file_operations drm_syncobj_file_fops = {
+	.release = drm_syncobj_file_release,
+};
+
+static int drm_syncobj_alloc_file(struct drm_syncobj *syncobj)
+{
+	struct file *file = anon_inode_getfile("syncobj_file",
+					       &drm_syncobj_file_fops,
+					       syncobj, 0);
+	if (IS_ERR(file))
+		return PTR_ERR(file);
+
+	drm_syncobj_get(syncobj);
+	if (cmpxchg(&syncobj->file, NULL, file)) {
+		/* lost the race */
+		fput(file);
+	}
+
+	return 0;
+}
+
+static int drm_syncobj_handle_to_fd(struct drm_file *file_private,
+				    u32 handle, int *p_fd)
+{
+	struct drm_syncobj *syncobj = drm_syncobj_find(file_private, handle);
+	int ret;
+	int fd;
+
+	if (!syncobj)
+		return -EINVAL;
+
+	fd = get_unused_fd_flags(O_CLOEXEC);
+	if (fd < 0) {
+		drm_syncobj_put(syncobj);
+		return fd;
+	}
+
+	if (!syncobj->file) {
+		ret = drm_syncobj_alloc_file(syncobj);
+		if (ret)
+			goto out_put_fd;
+	}
+	fd_install(fd, syncobj->file);
+	drm_syncobj_put(syncobj);
+	*p_fd = fd;
+	return 0;
+out_put_fd:
+	put_unused_fd(fd);
+	drm_syncobj_put(syncobj);
+	return ret;
+}
+
+static struct drm_syncobj *drm_syncobj_fdget(int fd)
+{
+	struct file *file = fget(fd);
+
+	if (!file)
+		return NULL;
+	if (file->f_op != &drm_syncobj_file_fops)
+		goto err;
+
+	return file->private_data;
+err:
+	fput(file);
+	return NULL;
+};
+
+static int drm_syncobj_fd_to_handle(struct drm_file *file_private,
+				    int fd, u32 *handle)
+{
+	struct drm_syncobj *syncobj = drm_syncobj_fdget(fd);
+	int ret;
+
+	if (!syncobj)
+		return -EINVAL;
+
+	/* take a reference to put in the idr */
+	drm_syncobj_get(syncobj);
+
+	idr_preload(GFP_KERNEL);
+	spin_lock(&file_private->syncobj_table_lock);
+	ret = idr_alloc(&file_private->syncobj_idr, syncobj, 1, 0, GFP_NOWAIT);
+	spin_unlock(&file_private->syncobj_table_lock);
+	idr_preload_end();
+
+	if (ret < 0) {
+		fput(syncobj->file);
+		return ret;
+	}
+	*handle = ret;
+	return 0;
+}
+
+/**
+ * drm_syncobj_open - initalizes syncobj file-private structures at devnode open time
+ * @dev: drm_device which is being opened by userspace
+ * @file_private: drm file-private structure to set up
+ *
+ * Called at device open time, sets up the structure for handling refcounting
+ * of sync objects.
+ */
+void
+drm_syncobj_open(struct drm_file *file_private)
+{
+	idr_init(&file_private->syncobj_idr);
+	spin_lock_init(&file_private->syncobj_table_lock);
+}
+
+static int
+drm_syncobj_release_handle(int id, void *ptr, void *data)
+{
+	struct drm_syncobj *syncobj = ptr;
+
+	drm_syncobj_put(syncobj);
+	return 0;
+}
+
+/**
+ * drm_syncobj_release - release file-private sync object resources
+ * @dev: drm_device which is being closed by userspace
+ * @file_private: drm file-private structure to clean up
+ *
+ * Called at close time when the filp is going away.
+ *
+ * Releases any remaining references on objects by this filp.
+ */
+void
+drm_syncobj_release(struct drm_file *file_private)
+{
+	idr_for_each(&file_private->syncobj_idr,
+		     &drm_syncobj_release_handle, file_private);
+	idr_destroy(&file_private->syncobj_idr);
+}
+
+int
+drm_syncobj_create_ioctl(struct drm_device *dev, void *data,
+			 struct drm_file *file_private)
+{
+	struct drm_syncobj_create *args = data;
+
+	if (!drm_core_check_feature(dev, DRIVER_SYNCOBJ))
+		return -ENODEV;
+
+	/* no valid flags yet */
+	if (args->flags)
+		return -EINVAL;
+
+	return drm_syncobj_create(file_private,
+				  &args->handle);
+}
+
+int
+drm_syncobj_destroy_ioctl(struct drm_device *dev, void *data,
+			  struct drm_file *file_private)
+{
+	struct drm_syncobj_destroy *args = data;
+
+	if (!drm_core_check_feature(dev, DRIVER_SYNCOBJ))
+		return -ENODEV;
+
+	/* make sure padding is empty */
+	if (args->pad)
+		return -EINVAL;
+	return drm_syncobj_destroy(file_private, args->handle);
+}
+
+int
+drm_syncobj_handle_to_fd_ioctl(struct drm_device *dev, void *data,
+				   struct drm_file *file_private)
+{
+	struct drm_syncobj_handle *args = data;
+
+	if (!drm_core_check_feature(dev, DRIVER_SYNCOBJ))
+		return -ENODEV;
+
+	if (args->pad || args->flags)
+		return -EINVAL;
+
+	return drm_syncobj_handle_to_fd(file_private, args->handle,
+					&args->fd);
+}
+
+int
+drm_syncobj_fd_to_handle_ioctl(struct drm_device *dev, void *data,
+				   struct drm_file *file_private)
+{
+	struct drm_syncobj_handle *args = data;
+
+	if (!drm_core_check_feature(dev, DRIVER_SYNCOBJ))
+		return -ENODEV;
+
+	if (args->pad || args->flags)
+		return -EINVAL;
+
+	return drm_syncobj_fd_to_handle(file_private, args->fd,
+					&args->handle);
+}

include/drm/drm_drv.h

···
 #define DRIVER_RENDER			0x8000
 #define DRIVER_ATOMIC			0x10000
 #define DRIVER_KMS_LEGACY_CONTEXT	0x20000
+#define DRIVER_SYNCOBJ                  0x40000
 
 /**
  * struct drm_driver - DRM driver structure

include/drm/drm_file.h

···
 	/** @table_lock: Protects @object_idr. */
 	spinlock_t table_lock;
 
+	/** @syncobj_idr: Mapping of sync object handles to object pointers. */
+	struct idr syncobj_idr;
+	/** @syncobj_table_lock: Protects @syncobj_idr. */
+	spinlock_t syncobj_table_lock;
+
 	/** @filp: Pointer to the core file structure. */
 	struct file *filp;
 

include/drm/drm_syncobj.h

···
+/*
+ * Copyright © 2017 Red Hat
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ *
+ * Authors:
+ *
+ */
+#ifndef __DRM_SYNCOBJ_H__
+#define __DRM_SYNCOBJ_H__
+
+#include "linux/dma-fence.h"
+
+/**
+ * struct drm_syncobj - sync object.
+ *
+ * This structure defines a generic sync object which wraps a dma fence.
+ */
+struct drm_syncobj {
+	/**
+	 * @refcount:
+	 *
+	 * Reference count of this object.
+	 */
+	struct kref refcount;
+	/**
+	 * @fence:
+	 * NULL or a pointer to the fence bound to this object.
+	 */
+	struct dma_fence *fence;
+	/**
+	 * @file:
+	 * a file backing for this syncobj.
+	 */
+	struct file *file;
+};
+
+void drm_syncobj_free(struct kref *kref);
+
+/**
+ * drm_syncobj_get - acquire a syncobj reference
+ * @obj: sync object
+ *
+ * This acquires additional reference to @obj. It is illegal to call this
+ * without already holding a reference. No locks required.
+ */
+static inline void
+drm_syncobj_get(struct drm_syncobj *obj)
+{
+	kref_get(&obj->refcount);
+}
+
+/**
+ * drm_syncobj_put - release a reference to a sync object.
+ * @obj: sync object.
+ */
+static inline void
+drm_syncobj_put(struct drm_syncobj *obj)
+{
+	kref_put(&obj->refcount, drm_syncobj_free);
+}
+
+struct drm_syncobj *drm_syncobj_find(struct drm_file *file_private,
+				     u32 handle);
+void drm_syncobj_replace_fence(struct drm_file *file_private,
+			       struct drm_syncobj *syncobj,
+			       struct dma_fence *fence);
+int drm_syncobj_fence_get(struct drm_file *file_private,
+			  u32 handle,
+			  struct dma_fence **fence);
+void drm_syncobj_free(struct kref *kref);
+
+#endif

include/uapi/drm/drm.h

···
 #define DRM_CAP_ADDFB2_MODIFIERS	0x10
 #define DRM_CAP_PAGE_FLIP_TARGET	0x11
 #define DRM_CAP_CRTC_IN_VBLANK_EVENT	0x12
+#define DRM_CAP_SYNCOBJ		0x13
 
 /** DRM_IOCTL_GET_CAP ioctl argument type */
 struct drm_get_cap {
···
 
 	/** Returned dmabuf file descriptor */
 	__s32 fd;
+};
+
+struct drm_syncobj_create {
+	__u32 handle;
+	__u32 flags;
+};
+
+struct drm_syncobj_destroy {
+	__u32 handle;
+	__u32 pad;
+};
+
+struct drm_syncobj_handle {
+	__u32 handle;
+	__u32 flags;
+
+	__s32 fd;
+	__u32 pad;
 };
 
 #if defined(__cplusplus)
···
 #define DRM_IOCTL_MODE_ATOMIC		DRM_IOWR(0xBC, struct drm_mode_atomic)
 #define DRM_IOCTL_MODE_CREATEPROPBLOB	DRM_IOWR(0xBD, struct drm_mode_create_blob)
 #define DRM_IOCTL_MODE_DESTROYPROPBLOB	DRM_IOWR(0xBE, struct drm_mode_destroy_blob)
+
+#define DRM_IOCTL_SYNCOBJ_CREATE	DRM_IOWR(0xBF, struct drm_syncobj_create)
+#define DRM_IOCTL_SYNCOBJ_DESTROY	DRM_IOWR(0xC0, struct drm_syncobj_destroy)
+#define DRM_IOCTL_SYNCOBJ_HANDLE_TO_FD	DRM_IOWR(0xC1, struct drm_syncobj_handle)
+#define DRM_IOCTL_SYNCOBJ_FD_TO_HANDLE	DRM_IOWR(0xC2, struct drm_syncobj_handle)
 
 /**
  * Device specific ioctls should only be in their respective headers