Linux kernel upgrade broke named pipes

We noticed a change with named pipes after a linux kernel upgrade. Using the scripts from http://www.linuxjournal.com/content/using-named-pipes-fifos-bash, we were able to replicate the issue. The scripts work on

Linux TEST05 3.13.0-55-generic #94-Ubuntu SMP Thu Jun 18 00:27:10 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

but hang on

Linux TEST01 3.13.0-65-generic #106-Ubuntu SMP Fri Oct 2 22:08:27 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

There seems to be a difference in how named pipes work. Is that intentional or not?

We captured the two scripts as pipe_reader.sh:

#!/bin/bash

pipe=/tmp/testpipe

trap "rm -f $pipe" EXIT

if [[ ! -p $pipe ]]; then
    mkfifo $pipe
fi

while true
do
    if read line <$pipe; then
        if [[ "$line" == 'quit' ]]; then
            break
        fi
        echo $line
    fi
done

echo "Reader exiting"

and pipe_writer.sh:

#!/bin/bash

pipe=/tmp/testpipe

if [[ ! -p $pipe ]]; then
    echo "Reader not running"
    exit 1
fi


if [[ "$1" ]]; then
    echo "$1" >$pipe
else
    echo "Hello from $$" >$pipe
fi

Is there a fix?

EDIT:

We're running each script in its own terminal. They hang in the sense that the writer script never exists, and the reader script never shows the normal "Hello from..." output. We're executing them in an identical fashion under both kernel versions, so it's not an issue of running one script more than once, or any other procedural differences.