[Small-cl-src-discuss] Re: [Small-cl-src] Re: simple locking retry

Nathan Froyd froydnj at cs.rice.edu
Sun Jun 27 20:44:10 UTC 2004

On Sun, Jun 27, 2004 at 02:36:06PM -0400, Randall Randall wrote:
> On Jun 27, 2004, at 8:58 AM, Joe Marshall wrote:
> >This isn't thread safe.  If two processes attempted to enter the queue
> >simultaneously, one could get lost.
> Because the second could run between evaluation of
> ,queue and evaluation of APPEND?  Okay.  Is there
> an atomic way to do that append such that it is
> thread safe without using specialized machinery not
> available with serve-event?

CMUCL under x86 supports several "set place atomically" primitives
that use the processor's cmpxchg instruction to provide true
atomicity.  (apropos "ATOMIC-") to have a peek at what's there.
Since you're on PPC, this may not help that much...
Nathan | From Man's effeminate slackness it begins.  --Paradise Lost

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