Re: [PATCH 01/26] dma-buf: add dma_resv_for_each_fence_unlocked v4

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Am 22.09.21 um 16:36 schrieb Tvrtko Ursulin:
+
+/**
+ * dma_resv_iter_first_unlocked - first fence in an unlocked dma_resv obj.
+ * @cursor: the cursor with the current position
+ *
+ * Returns the first fence from an unlocked dma_resv obj.
+ */
+struct dma_fence *dma_resv_iter_first_unlocked(struct dma_resv_iter *cursor)
+{
+    rcu_read_lock();
+    do {
+        dma_resv_iter_restart_unlocked(cursor);
+        dma_resv_iter_walk_unlocked(cursor);
+    } while (read_seqcount_retry(&cursor->obj->seq, cursor->seq));
+    rcu_read_unlock();
+
+    return cursor->fence;
+}
+EXPORT_SYMBOL(dma_resv_iter_first_unlocked);

Why is this one split from dma_resv_iter_begin and even exported?

I've split it to be able to use dma_resv_iter_begin in both the unlocked and locked iterator.

I couldn't find any users in the series.

This is used in the dma_resv_for_each_fence_unlocked() macro to return the first fence.


+
+/**
+ * dma_resv_iter_next_unlocked - next fence in an unlocked dma_resv obj.
+ * @cursor: the cursor with the current position
+ *
+ * Returns the next fence from an unlocked dma_resv obj.
+ */
+struct dma_fence *dma_resv_iter_next_unlocked(struct dma_resv_iter *cursor)
+{
+    bool restart;
+
+    rcu_read_lock();
+    cursor->is_restarted = false;
+    restart = read_seqcount_retry(&cursor->obj->seq, cursor->seq);
+    do {
+        if (restart)
+            dma_resv_iter_restart_unlocked(cursor);
+        dma_resv_iter_walk_unlocked(cursor);
+        restart = true;
+    } while (read_seqcount_retry(&cursor->obj->seq, cursor->seq));
+    rcu_read_unlock();
+
+    return cursor->fence;
+}
+EXPORT_SYMBOL(dma_resv_iter_next_unlocked);

Couldn't dma_resv_iter_first_unlocked and dma_resv_iter_next_unlocked share the same implementation? Especially if you are able to replace cursor->is_restarted with cursor->index == -1.

That's what I had initially, but Daniel disliked it for some reason. You then need a centralized walk function instead of first/next.

Thanks,
Christian.

Regards,

Tvrtko




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