mpi: add comments

mpi/src/mpi/starpu_mpi_early_data.h

@@ -63,6 +63,7 @@ struct _starpu_mpi_early_data_handle *_starpu_mpi_early_data_find(struct _starpu
 void _starpu_mpi_early_data_add(struct _starpu_mpi_early_data_handle *early_data_handle);
 void _starpu_mpi_early_data_delete(struct _starpu_mpi_early_data_handle *early_data_handle);
 
+// Not used now but needed for fault tolerance
 struct _starpu_mpi_early_data_handle_tag_hashlist *_starpu_mpi_early_data_extract(struct _starpu_mpi_node_tag *node_tag);
 
 #ifdef __cplusplus

mpi/src/mpi/starpu_mpi_early_request.h

@@ -47,6 +47,7 @@ void _starpu_mpi_early_request_check_termination(void);
 void _starpu_mpi_early_request_enqueue(struct _starpu_mpi_req *req);
 struct _starpu_mpi_req* _starpu_mpi_early_request_dequeue(starpu_mpi_tag_t data_tag, int source, MPI_Comm comm);
 
+// Not used now but needed for fault tolerance
 struct _starpu_mpi_early_request_tag_hashlist *_starpu_mpi_early_request_extract(starpu_mpi_tag_t data_tag, int source, MPI_Comm comm);
 
 #ifdef __cplusplus