Merge branch 'v2.1' into v2.2

[makedoc]

CHANGES/v2.1.txt

@@ -233,6 +233,8 @@ For users:
 - Fixed erroneously reported message about MPI at the end of ./configure.
 - Changed warning message about undocumented components.
 - PLUMED now says in the log file if it was compiled from a dirty git repository.
+- Fixed a problem leading to rare random crashes when using \ref METAD with WALKERS_MPI and multiple
+  processors per replica.
 
 
 */

src/bias/MetaD.cpp

@@ -665,6 +665,9 @@ last_step_warn_grid(0)
    }
   }
 
+  comm.Barrier();
+  if(comm.Get_rank()==0) multi_sim_comm.Barrier();
+
 // open hills file for writing
   hillsOfile_.link(*this);
   if(walkers_mpi){