Comment 2 for bug 1512815

This is a reproducer for the stall problem in drivers/tty/n_tty.c

To reproduce the problem, save the program below as pty.c, compile it,
and run it in parallel.

# cc -o pty pty.c
# for i in {1..16}; do ./pty& done; wait
The problem can be reproduced on a multi-socket server with recent CPUs.
The program always stalled during the first run when I used a server
with the following CPU.
  Intel(R) Xeon(R) CPU E5-2698 v3 @ 2.30GHz
  2-sockets x 16-cores x 2-threads