[Openmcl-devel] Help with lap functions

[Taoufik Dachraoui]

Hi

Please I need help with creating 2 simple lapfunctions: acquire-lock-xchg
and free-lock-xchg

assembler pseudocode for both functions follow:

(deflapfunction acquire-lock-xchg (addr)
       mov 1 reg
       xchg addr reg
       ret reg  )

(deflapfunction free-lock-xchg (addr)
       mov 0 reg
       xchg addr reg
       ret
)

(defmacro with-critical-section (addr &body body)
   "lock on addr"
  `((loop when (= 1 (the fixnumm (acquire-lock-xchg ,addr))) return nil) ;
spin-wait           (unwind-protect
 (progn
           , at body)
      (free-lock-xchg ,addr))))

Usage:
   (let ((x '(1 nil . 0))) (with-critical-section (cddr x) (push 2 (cadr
x))))

Do you think that such code is robust and may be used in production? (I am
developing a new algorithm for persistent hash tables for multiprocessors
systems)

Kind regards
Taoufik
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