Sorry to waste your time - I will stop using rsync

[Paul Haas]

Looking at http://rsync.samba.org, we see under bug fixes for 2.5.5

      Fix situation where failure to fork (e.g. because out of process
      slots) would cause rsync to kill all processes owned by the
      current user.  Yes, really!  (Paul Haas, Martin Pool)

If rsync is running as root when it triggers this bug it will kill all
processes.  This is indistinguishable from a system crash.  Processes
running as root are allowed to shut down the system.  So this is not a
Kernel bug.

If you're still running 2.5.4, upgrade to 2.5.5.  If you're running 2.5.5,
try replacing the calls to kill() with an fprintf() to a logfile.  Then
manually kill any leftover rsync processes.

--
Paul Haas
paulh at hamjudo.com