June 2004 - small-cl-src-discuss@lists.common-lisp.net

[Small-cl-src-discuss] Re: [Small-cl-src] Re: simple locking retry
by Randall Randall 27 Jun '04

27 Jun '04

On Jun 27, 2004, at 8:58 AM, Joe Marshall wrote: > Randall Randall <randall(a)randallsquared.com> writes: > >> Second try; let's see if I get it right this time: >> >> This is intended to be a simple locking protocol for >> systems that need to be usable on both serve-event-only >> systems, like CMUCL on PPC, and more ordinary >> multi-processing systems. I'm currently using it as >> part of PSILISP, my webapp framework. >> >> This seems to work, and people I've run it by agree >> that it seems to work, but there could be some serious >> problem with it, so use at your own risk. I am only >> an egg. >> >> This code is released as public domain. >> >> (defmacro enqueue (queue) >> "Appends a unique ID to a queue." >> (let ((id (gensym))) >> `(let ((,id (gensym))) >> (setf ,queue (append ,queue (list ,id))) >> ,id))) > > 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? Alternatively, I guess I could use more #+ expressions. -- Randall Randall <randall(a)randallsquared.com> Property law should use #'EQ , not #'EQUAL .

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[Small-cl-src-discuss] simple locking
by Randall Randall 27 Jun '04

27 Jun '04

This is intended to be a simple locking protocol for systems that need to be usable on both serve-event-only systems, like CMUCL on PPC, and more ordinary multi-processing systems. I'm currently using it as part of PSILISP, my webapp framework. This seems to work, and people I've run it by agree that it seems to work, but there could be some serious problem with it, so use at your own risk. I am only an egg. (defmacro enqueue (queue) "Appends a unique ID to a queue." (let ((id (gensym))) `(let ((,id (gensym))) (setf ,queue (append ,queue (list ,id))) ,id))) (defmacro lock (queue) "Waits in turn in the activity queue until all previous members have exited." (let ((id (gensym))) `(let* ((,id (enqueue ,queue))) #+(and acl-compat (not allegro) (not cmu)) ; CMUCL on PPC doesn't have MP, so we have to use serve-event (ACL-COMPAT.MP:process-wait "waiting for lock" #'eq ,id (car ,queue)) #+allegro (MP:process-wait "waiting for lock" #'eq ,id (car ,queue)) #+cmu (do () ((eq ,id (car ,queue))) (sys:serve-event 0)) ,id))) (defmacro unlock (queue) `(pop ,queue)) Use example, which assumes a WIDGET structure or class, with a MYWIDGET instance, and a WIDGET-LOCK accessor. (defmacro with-locked-widget ((lock-id-var queue) &body body) "Provides a method of locking a widget while in use, if everyone uses this." `(let ((,lock-id-var (lock ,queue))) (unwind-protect (progn ,@body) (unlock ,queue)))) (with-locked-widget (l-id (widget-lock mywidget)) ; do stuff ) -- Randall Randall <randall(a)randallsquared.com> Property law should use #'EQ , not #'EQUAL .

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[Small-cl-src-discuss] Eye-candy for gnus users.
by Lawrence Mitchell 11 Jun '04

11 Jun '04

For those of you who use Gnus, this little snippet of elisp, which can sit in your ~/.gnus makes postings to small-cl-src, should they match the regexp "^;;;" font-locked as lisp-mode buffers. Yes, yes, it's not CL, I claim something or other... (add-to-list 'mailcap-mime-extensions '(".lisp" . "application/lisp")) (add-to-list 'mm-automatic-display "application/lisp") (add-to-list 'mm-inlined-types "application/lisp") (add-to-list 'mm-inline-media-tests '("application/lisp" my-display-lisp-inline identity)) (add-to-list 'mm-uu-type-alist '(small-cl-src "^;;;" nil my-mm-small-cl-src-extract nil my-mm-small-cl-src-test)) (eval-after-load "mm-uu" '(mm-uu-configure)) (defun my-mm-small-cl-src-test () (and gnus-newsgroup-name ;; replace this with whatever your small-cl-src's ;; `gnus-newsgroup-name' is. (string-equal gnus-newsgroup-name "gmane.lisp.sources.code"))) (defun my-mm-small-cl-src-extract () (mm-make-handle (mm-uu-copy-to-buffer start-point end-point) '("application/lisp") nil nil (list mm-dissect-disposition (cons 'filename "Lisp source file")))) (defun my-display-lisp-inline (handle) (mm-display-inline-fontify handle 'lisp-mode)) -- Lawrence Mitchell <wence(a)gmx.li>

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[Small-cl-src-discuss] Web page revamp (and possible default-license-change)
by Ingvar 04 Jun '04

04 Jun '04

Now that Actual Round Tuits seem to have arrived, so I have done some changes taht I think are in line with what we discussed before. The following text should now appear on the "small-cl-src" information page: ----------------------------------- This mailing list is intended for "small" Common Lisp sources. For now, "small" is defined as single-file, less than 64 KB, in plain text. Unless other is specified, anything posted to the list from 2004-07-01 is presumed to be "copyright owner, use as you want, keep the copyright notice on relevant code" unless explicitly noted otherwise. Anything posted prior to this date can be presumed to be "ask poster, do no assume a license". ------------------------------------ If people are unhappy with that, I am willing to change it. I think it's more-or-less in line with what was opreviously discussed. //Ingvar

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