Bash Scripting – How to Avoid Busy Waiting Without Sleep Command

I know I can wait on a condition to become true in bash by doing:

while true; do
  test_condition && break
  sleep 1
done

But it creates 1 sub-process at each iteration (sleep). I could avoid them by doing:

while true; do
  test_condition && break
done

But it uses lot of CPU (busy waiting). To avoid sub-processes and busy waiting, I came up with the solution bellow, but I find it ugly:

my_tmp_dir=$(mktemp -d --tmpdir=/tmp)    # Create a unique tmp dir for the fifo.
mkfifo $my_tmp_dir/fifo                  # Create an empty fifo for sleep by read.
exec 3<> $my_tmp_dir/fifo                # Open the fifo for reading and writing.

while true; do
  test_condition && break
  read -t 1 -u 3 var                     # Same as sleep 1, but without sub-process.
done

exec 3<&-                                # Closing the fifo.
rm $my_tmp_dir/fifo; rmdir $my_tmp_dir   # Cleanup, could be done in a trap.

Note: in the general case, I cannot simply use read -t 1 var without the fifo, because it will consume stdin, and will not work if stdin is not a terminal or a pipe.

Can I avoid sub-processes and busy waiting in a more elegant way ?