Musing about arcane (?) topics...

"David McClain (as dbm at refined-audiometrics dot com)" <[email protected]> Sat, 20 Jun 2026 05:20:55 -0700
Newsgroups gmane.lisp.lispworks.general
Message-ID <[email protected]>
Maybe not so arcane… 

The ARM architecture supports DCAS - double-wide CAS (compare and swap). This would be useful to help avoid the ABA problem that might occur, fooling a single-wide CAS into thinging that the internal state had not changed.

By using a 2nd word for tag info - incrementing with every state change, we can avoid this blindness on the part of CAS.

So… anyone have an implementation of ARM DCAS for LW?

- DM

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