| Allegro CL version 10.0 Unrevised from 9.0 to 10.0. 9.0 version | ||||||||||
Arguments: (object &key type block non-smp typecheck timeout) &body body
This macro expands into code that waits until the executing process acquires control of the object, then evaluates the forms in the body as an implicit progn. It then releases control of the object and returns whatever values the last form in the body returned.
The arguments are:
lockable-object or of a
subclass of lockable-object unless the type argument is
included and specifies otherwise. Object can also be a class object
(an instance of standard-class). The instances of such
classes are not necessarily lockable; the class would need to inherit
from
lockable-object for the
instances to be lockable.
:clos (the default): the object form must evaluate
to an instance of lockable-object or of a subclass of
lockable-object.
:struct: the object form must evaluate to an
instance of synchronizing-structure or of a subtype of
synchronizing-structure.
:without-scheduling to get the equivalent of
(without-scheduling . body)
:without-interrupts to get the equivalent of
(with-delayed-interrupts . body)
:atomically (only valid when
the type argument is
:struct) to get the equivalent
of (fast-and-clean . body)
nil, the generated code does not include
an explicit typecheck of the object. If specified as
non-nil the generated code checks that the
object is of the appropriate type. If typecheck
is ommitted, the type check code is generated unless the type argument
is :clos (explicitly or by default)
nil or a real
number. If nil (or unspecified), the body
will be evaluated if and when the lock is acquired. A value greater
than 0 specifies a timeout of that many seconds; when the timeout
occurs before the lock is acquired, the body is not evaluated and the
entire form evaluates to nil. A value less
than or equal to 0 specifies an immediate timeout; the body is
evaluated only if the lock can be acquired with no delay. If the body
itself return nil, one cannot then tell from
the return value whether the body executed or not. See
mp:with-process-lock for
an example where timing out causes additional code to run which can
make clear whether the body did or did not execute.
It is not an error for a process that already owns an object to try to lock it again. When this happens, the object is not released until the outermost lock form is exited.
The release of the object is performed in an unwind-protect cleanup form, so non-local exits from body are allowed.
See smp.htm and multiprocessing.htm for more information on this macro and on multiprocessing.
Copyright (c) 1998-2019, Franz Inc. Oakland, CA., USA. All rights reserved.
This page was not revised from the 9.0 page.
Created 2015.5.21.
| Allegro CL version 10.0 Unrevised from 9.0 to 10.0. 9.0 version | ||||||||||