As the sibling comment implies, I don't mean SMP anywhere in computing, I mean in the Unix world, which didn't even exist in the early 1960s. I'll grant that m

As the sibling comment implies, I don't mean SMP anywhere in computing, I mean in the Unix world, which didn't even exist in the early 1960s. I'll grant that my early Unix knowledge is far from comprehensive, primarily skewed toward hardware at certain universities and in the database industry, as well as mostly BSD, with little from the "AT&T side" before SVR3. Given that, I'd be hard-pressed to name a Unix port that supported SMP prior to 1983. And I didn't mean to equate SMP with threads, only that thread support wouldn't make much sense without hardware concurrency, of which multi-processor hardware was an early practical example in the Unix world. As such, it was merely a (failed) rhetorical device to illustrate how designers of filesystem locking might not even have a notion such as intra-process concurrency on their mental radar. Even if you are, pedantically, correct, it doesn't refute my overall suggestion.