/bin/login hangs if an NFS server down?

[Dan Kegel]

We run Solbourne's SunOS 4.0.1, without quotas.  Whenever an NFS server on
my network is down, logins seem to take forever even if the filesystem
provided by the server has nothing to do with the user who is logging in.


Here is part of the output of trace -t /bin/login when a server is down:

10:20:11 open ("/etc/motd", 0, 0666) = 3
10:20:11 ioctl (3, 0x40125401, 0xf7fffaa6) = -1 ENOTTY (Inappropriate ioctl for device)
10:20:11 fstat (3, 0xf7fffb18) = 0
10:20:11 read (3, "OS/MP 4.0B (GENERIC/root) #1: Tu".., 8192) = 60
10:20:11 write (1, "OS/MP 4.0B (GENERIC/root) #1: Tu".., 59) = 59
10:20:11 write (1, "\n", 1) = 1
10:20:11 read (3, "", 8192) = 0
10:20:11 close (3) = 0
10:20:11 sigvec (2, 0xf7fffb34, 0xf7fffba0) = 0
10:20:11 stat ("/var/spool/mail/dank", 0xf7fffc88) = 0
10:20:11 write (1, "You have new mail.\n", 19) = 19
10:20:11 vfork () = 3639
10:20:11 wait4 (0, 0, 0, 0) = 0
10:21:27 - SIGCHLD (20)
10:21:27 wait4 (0, 0, 0, 0) = 3639
10:21:27 sigvec (14, 0xf7fffb94, 0xf7fffc00) = 0
10:21:27 sigvec (3, 0xf7fffb94, 0xf7fffc00) = 0
10:21:27 sigvec (2, 0xf7fffb94, 0xf7fffc00) = 0
10:21:27 sigvec (18, 0xf7fffb94, 0xf7fffc00) = 0
10:21:27 execve ("/bin/csh", 0xf7fffc60, 0x8958) = 0

If I unmount the offending file system, the output is the same except that
wait4() completes immediately.

Does anybody know what the heck /bin/login is doing in that child process
that takes 1'16" to terminate?  Is it secretly doing a df?

Please reply by e-mail, and I'll summarize.
- Dan Kegel (dank at moc.jpl.nasa.gov)