NFS Locking + Kubuntu

This afternoon, I went off to UCT, to help Arno out with a sudden problem in TSL: When you try and log into KDE, it just hangs. And if you try and run a KDE application from Gnome, it hangs...

I straced startkde, and spotted a hang that looked lock-related:

[pid  5726] open("/home/stefanor/.qt/.qt_plugins_3.3rc.lock", O_RDWR|O_CREAT|O_LARGEFILE, 0600) = 9
[pid  5726] fcntl64(9, F_SETLKW64, {type=F_WRLCK, whence=SEEK_SET, start=0, len=0} <unfinished ...>
[pid  5725] <... select resumed> )      = 0 (Timeout)
[pid  5725] gettimeofday({1190991469, 364681}, NULL) = 0
[pid  5725] ioctl(3, FIONREAD, [0])     = 0
[pid  5725] gettimeofday({1190991469, 364908}, NULL) = 0
[pid  5725] select(9, [3 4 6 8], [], [], {0, 120271}) = 0 (Timeout)

After some trial and error, it turned out, that the problem was the NFS mounted /home. KDE wants it to be mounted with the options async,lock. Then it's happy. I don't why how this turned up in a routine nightly Ubuntu feisty update. Maybe it was a backport?

Anyway, there you go: KDE is fussy about its locks.