$ time ./pthread # main uses lots of CPU time

real    0m2.003s
user    0m1.048s
sys     0m0.955s

At the same time in another window:
$ mpstat -P ALL 1 1
12:39:08 PM  CPU    %usr   %nice    %sys %iowait    %irq   %soft  %steal  %guest  %gnice   %idle
12:39:09 PM  all   13.22    0.00   11.47    0.00    0.00    0.00    0.00    0.00    0.00   75.31
12:39:09 PM    0    0.00    0.00    0.00    0.00    0.00    0.00    0.00    0.00    0.00  100.00
12:39:09 PM    1    0.99    0.00    0.99    0.00    0.00    0.00    0.00    0.00    0.00   98.02
12:39:09 PM    2   50.00    0.00   45.00    0.00    0.00    0.00    0.00    0.00    0.00    5.00
12:39:09 PM    3    1.00    0.00    0.00    0.00    0.00    0.00    0.00    0.00    0.00   99.00

###

$ time ./pthread_cond # almost no CPU usage

real    0m2.004s
user    0m0.001s
sys     0m0.004s

###

$ time ./pthread_pipe # almost no CPU usage

real    0m2.004s
user    0m0.004s
sys     0m0.000s