Simultaneous mv's cause crash

[obrien at CSNET-SH.ARPA]

From:  Mike O'Brien <obrien at CSNET-SH.ARPA>

	I saw this once at Rand, and just last night here at BBN.  Now,
at Rand, we put in a whole bunch of fixes from the Usenet, including some
having to do with reference counts.  We never saw one after that, but then,
we weren't exactly trying to cause them, either!

	Does anyone out there know specifically which glitch it is that
causes this one?  I've always seen it as due to the same operation: two
processes unlinking the same file at the 'same' time.