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diff --git a/source/base/data_out_base.cc b/source/base/data_out_base.cc
index a7bbb7d98ceef4e820cccb0e1f0b27fc33d31cd4..b7ea069b18deacb6ae13f587d7d2126a672bb1e1 100644 (file)
--- a/source/base/data_out_base.cc
+++ b/source/base/data_out_base.cc
@@ -7786,9 +7786,11 @@ DataOutInterface<dim, spacedim>::write_vtu_in_parallel(
       }
   }
 
-  // Make sure we sync to disk. This ensures that the change in file
-  // size caused by the write_at() for the footer is visible for all
-  // ranks. Otherwise, the footer is sometimes lost.
+  // Make sure we sync to disk. As written in the standard,
+  // MPI_File_close() actually already implies a sync but there seems
+  // to be a bug on at least one configuration (running with multiple
+  // nodes using OpenMPI 4.1) that requires it. Without this call, the
+  // footer is sometimes missing.
   ierr = MPI_File_sync(fh);
   AssertThrowMPI(ierr);