Restore check for lowest id. It prevents livelock situation if multiple threads

are inside the function and they failed to obtain new cid the first time around.

This commit was SVN r16090.

ompi/communicator/comm_cid.c

@@ -171,6 +171,15 @@ int ompi_comm_nextcid ( ompi_communicator_t* newcomm,
              * This is the real algorithm described in the doc 
              */
             
+            OPAL_THREAD_LOCK(&ompi_cid_lock);
+            if (comm->c_contextid != ompi_comm_lowest_cid() ) {
+                /* if not lowest cid, we do not continue, but sleep and try again */
+                OPAL_THREAD_UNLOCK(&ompi_cid_lock);
+                continue;
+            }
+            OPAL_THREAD_UNLOCK(&ompi_cid_lock);
+            
+            
             for (i=start; i < mca_pml.pml_max_contextid ; i++) {
                 flag=ompi_pointer_array_test_and_set_item(&ompi_mpi_communicators, 
                                                           i, comm);