Failing to show 'Password:' prompt

[Nikos Vassiliadis]

Manolis Kiagias wrote:
> This morning my server was unresponsive both from ssh and through http. 
> The only thing that is different on this system on a 1st of month, is a 
> dump job that runs through periodic (on a mostly inactive system).
> 
> Visiting the console, I discovered the system was still up and 
> displaying login prompt on all vtys, but after typing a username, the 
> password prompt would never appear. Keyboard was responsive and I could 
> even switch between keyboard layouts (English/Greek). Plugging and and 
> unplugging an external USB drive, showed the kernel messages on tty0. 
> Still, I could not get it to display a password prompt and had to hard 
> reboot it.
> 
> I can't find anything in /var/log/messages either - it stops at 5.25 in 
> the morning.  And the dump was not performed either (and there are no 
> traces about it in the log).
> 
> What kind of crash could cause the password prompt to not display? Ideas?

Geia Manoli,

A deadlock somewhere in the filesystem code would expose
such behavior. Other subsystems may continue to work, but
some operations, somehow related to that filesystem code,
will wait - forever - for some locks to be released.

I've seen such behavior in early RELENG_6 branch with regard
to UFS snapshots.

Nikos