diff --git a/cpp/src/io/parquet/page_data.cu b/cpp/src/io/parquet/page_data.cu
index 12bf5e860fe..e1ed4ac3aa0 100644
--- a/cpp/src/io/parquet/page_data.cu
+++ b/cpp/src/io/parquet/page_data.cu
@@ -482,7 +482,7 @@ __global__ void __launch_bounds__(decode_block_size)
       target_pos = min(s->nz_count, src_pos + decode_block_size - out_thread0);
       if (out_thread0 > 32) { target_pos = min(target_pos, s->dict_pos); }
     }
-    // TODO(ets): see if this sync can be removed
+    // this needs to be here to prevent warp 3 modifying src_pos before all threads have read it
     __syncthreads();
     if (t < 32) {
       // decode repetition and definition levels.
diff --git a/cpp/src/io/parquet/page_delta_decode.cu b/cpp/src/io/parquet/page_delta_decode.cu
index c2a7deedb80..528048d2fe6 100644
--- a/cpp/src/io/parquet/page_delta_decode.cu
+++ b/cpp/src/io/parquet/page_delta_decode.cu
@@ -365,7 +365,7 @@ __global__ void __launch_bounds__(96)
     } else {  // warp2
       target_pos = min(s->nz_count, src_pos + batch_size);
     }
-    // TODO(ets): see if this sync can be removed
+    // this needs to be here to prevent warp 2 modifying src_pos before all threads have read it
     __syncthreads();
 
     // warp0 will decode the rep/def levels, warp1 will unpack a mini-batch of deltas.
@@ -507,7 +507,7 @@ __global__ void __launch_bounds__(decode_block_size)
     } else {  // warp 3
       target_pos = min(s->nz_count, src_pos + batch_size);
     }
-    // TODO(ets): see if this sync can be removed
+    // this needs to be here to prevent warp 3 modifying src_pos before all threads have read it
     __syncthreads();
 
     // warp0 will decode the rep/def levels, warp1 will unpack a mini-batch of prefixes, warp 2 will