[Openmcl-devel] Is setf atomic?

Daniel Dickison danieldickison at gmail.com
Tue Nov 6 21:07:31 UTC 2007


On Nov 6, 2007, at 3:47 PM, Pascal Costanza wrote:

> So to get this straight - are you saying that even a setf on a simple
> variable, for example like (setf var 42) when var is not a symbol
> macro, is potentially not thread-safe?

I was actually wondering the same thing a year or so ago in order to  
implement a lock-free single-reader/single-writer queue.  I never  
actually figured it out, but I assumed it would be atomic as far as  
the actual assignment goes.

I guess the situation in question boils down to whether 'setq' is  
atomic or not.  I'm also curious about setf of svref and of car/cdr  
(i.e. rplaca/rplacd).

Daniel



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