[08/10] drm/i915/gem: Teach execbuf how to wait on future syncobj
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Message ID 20200331212600.16654-8-chris@chris-wilson.co.uk
State New
Headers show
Series
  • [01/10] drm/i915/selftests: Add request throughput measurement to perf
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Commit Message

Chris Wilson March 31, 2020, 9:25 p.m. UTC
If a syncobj has not yet been assigned, treat it as a future fence and
install and wait upon a dma-fence-proxy. The proxy will be replace by
the real fence later, and that fence will be responsible for signaling
our waiter.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 .../gpu/drm/i915/gem/i915_gem_execbuffer.c    | 21 +++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

Patch
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diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index cda35e6dfc44..c367b1aa52f5 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -5,6 +5,7 @@ 
  */
 
 #include <linux/intel-iommu.h>
+#include <linux/dma-fence-proxy.h>
 #include <linux/dma-resv.h>
 #include <linux/sync_file.h>
 #include <linux/uaccess.h>
@@ -2318,8 +2319,24 @@  await_fence_array(struct i915_execbuffer *eb,
 			continue;
 
 		fence = drm_syncobj_fence_get(syncobj);
-		if (!fence)
-			return -EINVAL;
+		if (!fence) {
+			struct dma_fence *old;
+
+			fence = dma_fence_create_proxy();
+			if (!fence)
+				return -ENOMEM;
+
+			spin_lock(&syncobj->lock);
+			old = rcu_dereference_protected(syncobj->fence, true);
+			if (unlikely(old)) {
+				dma_fence_put(fence);
+				fence = dma_fence_get(old);
+			} else {
+				rcu_assign_pointer(syncobj->fence,
+						   dma_fence_get(fence));
+			}
+			spin_unlock(&syncobj->lock);
+		}
 
 		err = i915_request_await_dma_fence(eb->request, fence);
 		dma_fence_put(fence);