critical-section

Arguments: (&key block non-smp) &body body

This macro was added by a patch released in July, 2009. This macro will not be defined if that patch has not been installed. See sys:update-allegro for information on downloading patches.

This macro expands into code that uses a unique basic-lock associated with the expansion to control execution of the body code. Only one process at a time can acquire ownership of the lock and execute the forms in body. Ownership of the lock is relinquished when control leaves body by falling through or by non-local exit. The result of evaluating the critical-section code is the result of the last form in body.

The arguments are:

• block: used for special internal functions. Users should not specify this.
• non-smp: what code to generate in a non-smp lisp. Legal values are:
  • :without-scheduling to get the equivalent of (mp:without-scheduling . body)
  • :without-interrupts to get the equivalent of (excl:without-interrupts . body)
  • :atomically: to get the equivalent of (excl::atomically . body)
• [omitted]: to get object-locking code like smp. This may be inefficient or even problematic in a non-smp lisp.

See smp.htm and multiprocessing.htm for more information on this macro and on multiprocessing.

Copyright (c) 1998-2009, Franz Inc. Oakland, CA., USA. All rights reserved.
Documentation for Allegro CL version 8.1. This page is new in the 8.1 release.
Created 2007.4.30.