: spl is probably fundamentally wrong for SMP.  I haven't thought much
: about what to use instead.

The Solbourne people might disagree with you.  As might the VMS
Digitial people.  Both groups used a scheme where you would raise the
spl *AND* grab access locks to data structures (I think the latter was
optional on VMS depending on the, as I recall it, NCPU SYSGEN
parameter).  Both these systems used fairly fine grained locking and
took a lot of time to get right and robust.  Sun, when they were
writing Solaris, is rumored to have produced "warlock."  This program
would go through all your sources and warn of potential deadlock
situations in them.  They never released it as they considered it a
competitive advantage to them...

There is no other way to do MP synchronization than using some kind of
explicit locking that doesn't rely on the interrupt level.[*]

Warner

[*] Or I'd like ot be pointed at something that proves this statement
wrong.