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Re: mutexes, locks and so on...
> Hadn't it been much nicer of we just had the mutex and lock
> abstraction, and left the whole implementation to each MD part?
Exactly. Consider this hypothetical:
x86 does #define ATOMIC_OPS_USE_CAS and defines a CAS(); MI code
notices this and defines all the higher-level primitives (if that's not
too much of an oxymoron) in terms of CAS().
ppc, arm, all the arches sufficiently "modern" to have CAS, likewise.
Arches without a sufficiently general CAS[%] do not define
ATOMIC_OPS_USE_CAS and provides their own implementations of mutexes,
That seems to me like a mostly sane way to do it. If I can come up
with it in thirty seconds, it seems likely anyone capable of doing such
overhauls could come up with it.
Instead, all arches must implement a fully-general CAS. Seems to me
like a lose.
[%] It occurs to me, the VAX's BBSSI and BBCCI _are_ CAS, just
restricted to a one-bit-wide operand (and with the data-to-swap-in
specified by choice of instruction rather than an operand).
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