On 20/09/2021 11:13, Christian König wrote:

Am 20.09.21 um 10:45 schrieb Tvrtko Ursulin:

quoted

On 17/09/2021 13:35, Christian König wrote:

quoted

This makes the function much simpler since the complex
retry logic is now handled else where.

Signed-off-by: Christian König <christian.koenig@amd.com>
---
  drivers/gpu/drm/i915/gem/i915_gem_busy.c | 32 ++++++++----------------
  1 file changed, 11 insertions(+), 21 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_busy.c 

b/drivers/gpu/drm/i915/gem/i915_gem_busy.c
index 6234e17259c1..b1cb7ba688da 100644

--- a/drivers/gpu/drm/i915/gem/i915_gem_busy.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_busy.c

@@ -82,8 +82,8 @@ i915_gem_busy_ioctl(struct drm_device *dev, void 

*data,
  {
      struct drm_i915_gem_busy *args = data;
      struct drm_i915_gem_object *obj;
-    struct dma_resv_list *list;
-    unsigned int seq;
+    struct dma_resv_iter cursor;
+    struct dma_fence *fence;
      int err;
        err = -ENOENT;

@@ -109,27 +109,17 @@ i915_gem_busy_ioctl(struct drm_device *dev, 

void *data,
       * to report the overall busyness. This is what the wait-ioctl 
does.
       *
       */
-retry:
-    seq = raw_read_seqcount(&obj->base.resv->seq);
-
-    /* Translate the exclusive fence to the READ *and* WRITE engine */
-    args->busy = 
busy_check_writer(dma_resv_excl_fence(obj->base.resv));
-
-    /* Translate shared fences to READ set of engines */
-    list = dma_resv_shared_list(obj->base.resv);
-    if (list) {
-        unsigned int shared_count = list->shared_count, i;
-
-        for (i = 0; i < shared_count; ++i) {
-            struct dma_fence *fence =
-                rcu_dereference(list->shared[i]);
-
+    args->busy = false;
+    dma_resv_iter_begin(&cursor, obj->base.resv, true);
+    dma_resv_for_each_fence_unlocked(&cursor, fence) {

You did not agree with my suggestion to reset args->busy on restart 
and so preserve current behaviour?

No, I want to keep the restart behavior internally to the dma_resv 
object and as far as I can see it should not make a difference here.

To be clear, on paper difference between old and new implementation is 
if the restart happens while processing the shared fences.

Old implementation unconditionally goes to "args->busy =
 >>> busy_check_writer(dma_resv_excl_fence(obj->base.resv));" and so 
overwrites the set of flags returned to userspace.

New implementation can merge new read flags to the old set of flags and 
so return a composition of past and current fences.

Maybe it does not matter hugely in this case, depends if userspace 
typically just restarts until flags are clear. But I am not sure.

On the higher level - what do you mean with wanting to keep the restart 
behaviour internal? Not providing iterators users means of detecting it? 
I think it has to be provided.

Regards,

Tvrtko

Regards,
Christian.

quoted

Regards,

Tvrtko

quoted

+        if (dma_resv_iter_is_exclusive(&cursor))
+            /* Translate the exclusive fence to the READ *and* WRITE 
engine */
+            args->busy = busy_check_writer(fence);
+        else
+            /* Translate shared fences to READ set of engines */
              args->busy |= busy_check_reader(fence);
-        }
      }
-
-    if (args->busy && read_seqcount_retry(&obj->base.resv->seq, seq))
-        goto retry;
+    dma_resv_iter_end(&cursor);
        err = 0;
  out: