Re: [PATCH v3] drm/syncobj: use newly allocated stub fences

Pushing to drm-misc-next works for me. Thanks for the quick responses.

-David

On Thu, Apr 8, 2021 at 6:56 PM Christian König christian.koenig@amd.com wrote:

Am 08.04.21 um 11:54 schrieb David Stevens:

...

From: David Stevens stevensd@chromium.org

Allocate a new private stub fence in drm_syncobj_assign_null_handle, instead of using a static stub fence.

When userspace creates a fence with DRM_SYNCOBJ_CREATE_SIGNALED or when userspace signals a fence via DRM_IOCTL_SYNCOBJ_SIGNAL, the timestamp obtained when the fence is exported and queried with SYNC_IOC_FILE_INFO should match when the fence's status was changed from the perspective of userspace, which is during the respective ioctl.

When a static stub fence started being used in by these ioctls, this behavior changed. Instead, the timestamp returned by SYNC_IOC_FILE_INFO became the first time anything used the static stub fence, which has no meaning to userspace.

Signed-off-by: David Stevens stevensd@chromium.org

Reviewed-by: Christian König christian.koenig@amd.com

Should I push this to drm-misc-next or how do you want to upstream it?

Thanks, Christian.

...

---

v2 -> v3:

• reuse the static stub spinlock

v1 -> v2:

• checkpatch style fixes

drivers/dma-buf/dma-fence.c | 27 ++++++++++++++++++++++++++- drivers/gpu/drm/drm_syncobj.c | 25 +++++++++++++++++++------ include/linux/dma-fence.h | 1 + 3 files changed, 46 insertions(+), 7 deletions(-)

diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c index d64fc03929be..ce0f5eff575d 100644 --- a/drivers/dma-buf/dma-fence.c +++ b/drivers/dma-buf/dma-fence.c @@ -123,7 +123,9 @@ static const struct dma_fence_ops dma_fence_stub_ops = { /**

• dma_fence_get_stub - return a signaled fence

• • Return a stub fence which is already signaled.

• • Return a stub fence which is already signaled. The fence's
• • timestamp corresponds to the first time after boot this
• • function is called.
  */ struct dma_fence *dma_fence_get_stub(void) {

@@ -141,6 +143,29 @@ struct dma_fence *dma_fence_get_stub(void) } EXPORT_SYMBOL(dma_fence_get_stub);

+/**

• • dma_fence_allocate_private_stub - return a private, signaled fence
• • Return a newly allocated and signaled stub fence.
• */

+struct dma_fence *dma_fence_allocate_private_stub(void) +{

• struct dma_fence *fence;
  

• fence = kzalloc(sizeof(*fence), GFP_KERNEL);
  

• if (fence == NULL)
  

•         return ERR_PTR(-ENOMEM);
  

• dma_fence_init(fence,
  

•                &dma_fence_stub_ops,
  

•                &dma_fence_stub_lock,
  

•                0, 0);
  

• dma_fence_signal(fence);
  

• return fence;
  

+} +EXPORT_SYMBOL(dma_fence_allocate_private_stub);

• /**
  • dma_fence_context_alloc - allocate an array of fence contexts
  • @num: amount of contexts to allocate

diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c index 349146049849..a54aa850d143 100644 --- a/drivers/gpu/drm/drm_syncobj.c +++ b/drivers/gpu/drm/drm_syncobj.c @@ -350,12 +350,16 @@ EXPORT_SYMBOL(drm_syncobj_replace_fence);

• Assign a already signaled stub fence to the sync object.

*/ -static void drm_syncobj_assign_null_handle(struct drm_syncobj *syncobj) +static int drm_syncobj_assign_null_handle(struct drm_syncobj *syncobj) {

• struct dma_fence *fence = dma_fence_get_stub();
  

• struct dma_fence *fence = dma_fence_allocate_private_stub();
  

• if (IS_ERR(fence))
  

•         return PTR_ERR(fence);
  
  drm_syncobj_replace_fence(syncobj, fence);
  dma_fence_put(fence);
  

• return 0;
  

  }

  /* 5s default for wait submission */

@@ -469,6 +473,7 @@ EXPORT_SYMBOL(drm_syncobj_free); int drm_syncobj_create(struct drm_syncobj **out_syncobj, uint32_t flags, struct dma_fence *fence) {

• int ret;
  struct drm_syncobj *syncobj;
  
  syncobj = kzalloc(sizeof(struct drm_syncobj), GFP_KERNEL);
  

@@ -479,8 +484,13 @@ int drm_syncobj_create(struct drm_syncobj **out_syncobj, uint32_t flags, INIT_LIST_HEAD(&syncobj->cb_list); spin_lock_init(&syncobj->lock);

• if (flags & DRM_SYNCOBJ_CREATE_SIGNALED)
  

•         drm_syncobj_assign_null_handle(syncobj);
  

• if (flags & DRM_SYNCOBJ_CREATE_SIGNALED) {
  

•         ret = drm_syncobj_assign_null_handle(syncobj);
  

•         if (ret < 0) {
  

•                 drm_syncobj_put(syncobj);
  

•                 return ret;
  

•         }
  

• }
  
  if (fence)
          drm_syncobj_replace_fence(syncobj, fence);
  

@@ -1322,8 +1332,11 @@ drm_syncobj_signal_ioctl(struct drm_device *dev, void *data, if (ret < 0) return ret;

• for (i = 0; i < args->count_handles; i++)
  

•         drm_syncobj_assign_null_handle(syncobjs[i]);
  

• for (i = 0; i < args->count_handles; i++) {
  

•         ret = drm_syncobj_assign_null_handle(syncobjs[i]);
  

•         if (ret < 0)
  

•                 break;
  

• }
  
  drm_syncobj_array_free(syncobjs, args->count_handles);
  
  

diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h index 9f12efaaa93a..6ffb4b2c6371 100644 --- a/include/linux/dma-fence.h +++ b/include/linux/dma-fence.h @@ -587,6 +587,7 @@ static inline signed long dma_fence_wait(struct dma_fence *fence, bool intr) }

struct dma_fence *dma_fence_get_stub(void); +struct dma_fence *dma_fence_allocate_private_stub(void); u64 dma_fence_context_alloc(unsigned num);

#define DMA_FENCE_TRACE(f, fmt, args...) \