From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Mark H Weaver Newsgroups: gmane.lisp.guile.devel Subject: Concurrent MVars for Guile Date: Mon, 02 Sep 2013 03:55:07 -0400 Message-ID: <87fvtn1wv8.fsf@tines.lan> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="=-=-=" X-Trace: ger.gmane.org 1378108564 18364 80.91.229.3 (2 Sep 2013 07:56:04 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 2 Sep 2013 07:56:04 +0000 (UTC) To: guile-devel@gnu.org Original-X-From: guile-devel-bounces+guile-devel=m.gmane.org@gnu.org Mon Sep 02 09:56:06 2013 Return-path: Envelope-to: guile-devel@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1VGOzW-0005W3-5D for guile-devel@m.gmane.org; Mon, 02 Sep 2013 09:56:06 +0200 Original-Received: from localhost ([::1]:37645 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VGOzV-0001pr-Rz for guile-devel@m.gmane.org; Mon, 02 Sep 2013 03:56:05 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:33444) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VGOzK-0001pN-V2 for guile-devel@gnu.org; Mon, 02 Sep 2013 03:56:02 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VGOzD-00042E-KP for guile-devel@gnu.org; Mon, 02 Sep 2013 03:55:54 -0400 Original-Received: from world.peace.net ([96.39.62.75]:50191) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VGOzD-0003yy-5x for guile-devel@gnu.org; Mon, 02 Sep 2013 03:55:47 -0400 Original-Received: from c-98-217-64-74.hsd1.ma.comcast.net ([98.217.64.74] helo=tines.lan) by world.peace.net with esmtpsa (TLS1.0:DHE_RSA_AES_128_CBC_SHA1:16) (Exim 4.72) (envelope-from ) id 1VGOyi-0006YA-9K; Mon, 02 Sep 2013 03:55:17 -0400 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.6.x X-Received-From: 96.39.62.75 X-BeenThere: guile-devel@gnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: "Developers list for Guile, the GNU extensibility library" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: guile-devel-bounces+guile-devel=m.gmane.org@gnu.org Original-Sender: guile-devel-bounces+guile-devel=m.gmane.org@gnu.org Xref: news.gmane.org gmane.lisp.guile.devel:16608 Archived-At: --=-=-= Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Hello all, I've attached a preliminary implementation of MVars =C3=A0 la Concurrent Haskell for Guile. I made a few small changes to the API to better match Scheme conventions, and added atomicity guarantees for 'read-mvar' and 'swap-mvar'. I also added the interface 'try-read-mvar'. Note that the fairness of this implementation relies upon the fairness of Guile's mutexes and condition variables, which I have not checked. Comments and suggestions welcome. I was thinking that maybe we should add something like this to core Guile. What do you think? Mark --=-=-= Content-Type: text/plain Content-Disposition: inline; filename=mvars.scm Content-Description: MVars for Guile (define-module (ice-9 mvars) #:use-module (srfi srfi-8) ; receive #:use-module (srfi srfi-9) ; records #:use-module (srfi srfi-9 gnu) #:use-module (ice-9 threads) #:export (new-mvar mvar? mvar-empty? take-mvar put-mvar read-mvar swap-mvar try-take-mvar try-put-mvar try-read-mvar with-mvar modify-mvar modify-mvar*)) (define-record-type (make-mvar contents empty? mutex condvar) mvar? (contents mvar-contents set-mvar-contents!) (empty? mvar-empty? set-mvar-empty?!) (mutex mvar-mutex) (condvar mvar-condvar)) (set-record-type-printer! (lambda (mvar port) (display "#string (object-address mvar) 16) port) (display " " port) (write (receive (x full?) (try-read-mvar mvar) (if full? (list x) '())) port) (display ">" port))) (define new-mvar (case-lambda "Return a freshly allocated mvar. The optional argument, if provided,\n\ specifies the initial contents of the mvar, otherwise it will be empty." (() (make-mvar #f #t (make-mutex) (make-condition-variable))) ((x) (make-mvar x #f (make-mutex) (make-condition-variable))))) (define (take-mvar mvar) "Block until MVAR is full, then atomically remove and return its contents." (with-mutex (mvar-mutex mvar) (when (mvar-empty? mvar) (wait-condition-variable (mvar-condvar mvar) (mvar-mutex mvar)) (when (mvar-empty? mvar) (error "take-mvar: expected full mvar after waiting"))) (let ((x (mvar-contents mvar))) (set-mvar-contents! mvar #f) (set-mvar-empty?! mvar #t) (signal-condition-variable (mvar-condvar mvar)) x))) (define (put-mvar mvar x) "Block until MVAR is empty, then put X into it." (with-mutex (mvar-mutex mvar) (unless (mvar-empty? mvar) (wait-condition-variable (mvar-condvar mvar) (mvar-mutex mvar)) (unless (mvar-empty? mvar) (error "put-mvar: expected empty mvar after waiting"))) (set-mvar-contents! mvar x) (set-mvar-empty?! mvar #f) (signal-condition-variable (mvar-condvar mvar)) *unspecified*)) (define (read-mvar mvar) "Block until MVAR is full, then return its contents, leaving MVAR unchanged." (with-mutex (mvar-mutex mvar) (when (mvar-empty? mvar) (wait-condition-variable (mvar-condvar mvar) (mvar-mutex mvar)) (when (mvar-empty? mvar) (error "read-mvar: expected full mvar after waiting"))) (mvar-contents mvar))) (define (swap-mvar mvar new) "Block until MVAR is full, and then atomically swap its contents\n\ with NEW and return the previous contents." (with-mutex (mvar-mutex mvar) (when (mvar-empty? mvar) (wait-condition-variable (mvar-condvar mvar) (mvar-mutex mvar)) (when (mvar-empty? mvar) (error "swap-mvar: expected full mvar after waiting"))) (let ((old (mvar-contents mvar))) (set-mvar-contents! mvar new) old))) (define (try-take-mvar mvar) "If MVAR is full, return its contents and #t, else return #f and #f." (with-mutex (mvar-mutex mvar) (if (mvar-empty? mvar) (values #f #f) (let ((x (mvar-contents mvar))) (set-mvar-contents! mvar #f) (set-mvar-empty?! mvar #t) (signal-condition-variable (mvar-condvar mvar)) (values x #t))))) (define (try-put-mvar mvar x) "If MVAR is empty, put X into it and return #t, else return #f." (with-mutex (mvar-mutex mvar) (and (mvar-empty? mvar) (begin (set-mvar-contents! mvar x) (set-mvar-empty?! mvar #f) (signal-condition-variable (mvar-condvar mvar)) #t)))) (define (try-read-mvar mvar) "If MVAR is full, return its contents and #t, else return #f and #f." (with-mutex (mvar-mutex mvar) (if (mvar-empty? mvar) (values #f #f) (values (mvar-contents mvar) #t)))) (define (with-mvar mvar proc) "Take a value from MVAR and apply PROC to it. If an exception is raised,\n\ the original value is put back into MVAR. This procedure is atomic only if\n\ there are no other producers for MVAR." (let ((x (take-mvar mvar))) (catch #t (lambda () (proc x)) (lambda (key . args) (put-mvar mvar x) (apply throw key args))))) (define (modify-mvar mvar f) "Take a value x from MVAR, and then put back (F x). If an exception is\n\ raised, the original value is put back into MVAR. This procedure is\n\ atomic only if there are no other producers for MVAR." (let ((old (take-mvar mvar))) (catch #t (lambda () (put-mvar mvar (f old))) (lambda (key . args) (put-mvar mvar old) (apply throw key args))))) (define (modify-mvar* mvar f) "Take a value x from MVAR, and apply F to it. (F x) should return one\n\ or more values: the new value to be put back into MVAR, and zero or more\n\ additional values to be returned from MODIFY-MVAR*. If an exception is\n\ raised, the original value is put back into MVAR. This procedure is\n\ atomic only if there are no other producers for MVAR." (let ((old (take-mvar mvar))) (catch #t (lambda () (receive (new . results) (f old) (put-mvar mvar new) (apply values results))) (lambda (key . args) (put-mvar mvar old) (apply throw key args))))) --=-=-=--