It appears that when a config change commit is initiated, but is unsuccessful in completion (for one of a few reasons), a hung thread for 'sudo write' to return a message to the pty of the user committing the change occurs.
The configuration subsystem then becomes inoperable until hung threads are cleaned up.
bbabich@pauseq4rbdr1# commit
^C^C^C
^Z
[1]+ Stopped /opt/vyatta/sbin/my_commit "${args[@]}" 2>&1
[edit]
bbabich@pauseq4rbdr1# ps -ef | grep -i commit
bbabich 35765 35503 0 00:29 pts/0 00:00:00 /opt/vyatta/sbin/my_commit
bbabich 35923 35503 0 00:30 pts/0 00:00:00 grep -i commit
[edit]
bbabich@pauseq4rbdr1# kill -9 35765
[edit]
bbabich@pauseq4rbdr1# compare
[1]+ Killed /opt/vyatta/sbin/my_commit "${args[@]}" 2>&1
...
bbabich@pauseq4rbdr1:~$ ps -ef | grep -i bbabich
root 10974 2753 0 Jan04 ? 00:00:00 sshd: bbabich [priv]
bbabich 10982 10974 0 Jan04 ? 00:00:00 sshd: bbabich@pts/2
bbabich 10983 10982 0 Jan04 pts/2 00:00:00 -vbash
bbabich 11102 11101 0 Jan04 pts/2 00:00:00 vbash
root 22485 1 0 Jan04 ? 00:00:00 sudo write bbabich pts/2
root 22486 22485 0 Jan04 ? 00:00:00 write bbabich pts/2
root 22922 2753 0 Jan04 ? 00:00:00 sshd: bbabich [priv]
bbabich 22928 22922 0 Jan04 ? 00:00:00 sshd: bbabich@pts/1
bbabich 22929 22928 0 Jan04 pts/1 00:00:00 -vbash
root 25712 1 0 Jan04 ? 00:00:00 sudo write bbabich pts/2
root 25713 25712 0 Jan04 ? 00:00:00 write bbabich pts/2
root 26430 1 0 Jan04 ? 00:00:00 sudo write bbabich pts/2
root 26431 26430 0 Jan04 ? 00:00:00 write bbabich pts/2
root 27135 1 0 Jan04 ? 00:00:00 sudo write bbabich pts/2
root 27136 27135 0 Jan04 ? 00:00:00 write bbabich pts/2
root 28109 1 0 Jan04 ? 00:00:00 sudo write bbabich pts/2
root 28110 28109 0 Jan04 ? 00:00:00 write bbabich pts/2
root 28663 1 0 Jan04 ? 00:00:00 sudo write bbabich pts/2
root 28664 28663 0 Jan04 ? 00:00:00 write bbabich pts/2
root 29526 1 0 Jan04 ? 00:00:00 sudo write bbabich pts/2
root 29527 29526 0 Jan04 ? 00:00:00 write bbabich pts/2
root 30490 1 0 Jan04 ? 00:00:00 sudo write bbabich pts/2
root 30491 30490 0 Jan04 ? 00:00:00 write bbabich pts/2
root 30819 1 0 Jan04 ? 00:00:00 sudo write bbabich pts/2
root 30820 30819 0 Jan04 ? 00:00:00 write bbabich pts/2
root 33242 1 0 00:09 ? 00:00:00 sudo write bbabich pts/2
root 33243 33242 0 00:09 ? 00:00:00 write bbabich pts/2
root 34145 1 0 00:15 ? 00:00:00 sudo write bbabich pts/2
root 34146 34145 0 00:15 ? 00:00:00 write bbabich pts/2
root 34648 1 0 00:20 ? 00:00:00 sudo write bbabich pts/2
root 34649 34648 0 00:20 ? 00:00:00 write bbabich pts/2
root 35377 2753 0 00:28 ? 00:00:00 sshd: bbabich [priv]
bbabich 35381 35377 0 00:28 ? 00:00:00 sshd: bbabich@pts/0
bbabich 35382 35381 0 00:28 pts/0 00:00:00 -vbash
root 35812 1 0 00:29 pts/0 00:00:00 sudo write bbabich pts/2
root 35813 35812 0 00:29 pts/0 00:00:00 write bbabich pts/2
root 49999 1 0 03:30 pts/0 00:00:00 sudo write bbabich pts/2
root 50000 49999 0 03:30 pts/0 00:00:00 write bbabich pts/2
root 53824 53811 0 04:22 pts/1 00:00:00 sudo write bbabich pts/2
root 53825 53824 0 04:22 pts/1 00:00:00 write bbabich pts/2
bbabich 54033 35382 0 04:25 pts/0 00:00:00 ps -ef
bbabich 54034 35382 0 04:25 pts/0 00:00:00 grep -i bbabich
bbabich@pauseq4rbdr1:~$ ps -ef | grep -i bbabich | awk '{print $2}' | xargs kill
Connection to 10.0.222.141 closed by remote host.
Connection to 10.0.222.141 closed.
...