$ $SG_TEST_EXENV ${bindir:=.}/s4u-mutex
> [Jupiter:worker:(2) 0.000000] [s4u_test/INFO] Hello s4u, I'm ready to compute after a lock_guard
$ $SG_TEST_EXENV ${bindir:=.}/s4u-mutex
> [Jupiter:worker:(2) 0.000000] [s4u_test/INFO] Hello s4u, I'm ready to compute after a lock_guard