A few people using Postfix for mail have reported system hangs at irregular intervals; Joerg Sonnenberger and Matt Dillon have been trying to track this down. Joerg posted these steps to take if you are so fortunate as to encounter this problem:

“Please try to provide the following for us for download:

• a tarball of your /var/spool/postfix [if this doesn’t contain private mail, save it and try to remove them as long as the problem persists]
• a crash dump of the system when it hangs and the kernel.debug, please test that ‘gdb -k kernel.debug vmcore.X‘ actually works and gdb doesn’t crash.
• if you can easily reproduce the problem, compile kern/kern_lockf.c with -DLOCKF_DEBUG, use the ddb command ‘w lf_print_ranges 1‘ to set the lockf debugging and give us the /var/log/messages.

I really want to fix this, but neither Matt nor I can reproduce this problem and the code is not obviously bad. There is some interaction going on, but the crash dump we had so far doesn’t work (see above about testing). It would be nice, if you can use bzip2 or gzip on all this data.”