From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Ihor Radchenko Newsgroups: gmane.emacs.devel Subject: Re: Concurrency via isolated process/thread Date: Tue, 25 Jul 2023 04:36:15 +0000 Message-ID: <87mszk7glc.fsf@localhost> References: <871qhnr4ty.fsf@localhost> <838rbrg4mg.fsf@gnu.org> <87ilavbvdr.fsf@localhost> <834jmffvhy.fsf@gnu.org> <878rbrbmwr.fsf@localhost> <83fs5zecpo.fsf@gnu.org> <87351zbi72.fsf@localhost> <83351yevde.fsf@gnu.org> <87cz12ad2w.fsf@localhost> <83a5w6cwdr.fsf@gnu.org> <87pm518m0g.fsf@localhost> <83o7kl9tyj.fsf@gnu.org> <874jmd89us.fsf@localhost> <878rb53dkj.fsf@localhost> <83edkxsclz.fsf@gnu.org> <87tttt1mzh.fsf@localhost> <83351ds9de.fsf@gnu.org> <87ila91j6n.fsf@localhost> <83y1j5qoyo.fsf@gnu.org> <87wmypi7s0.fsf@localhost> <87fs5czvs2.fsf@yahoo.com> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="1283"; mail-complaints-to="usenet@ciao.gmane.io" Cc: Eli Zaretskii , emacs-devel@gnu.org To: Po Lu Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Tue Jul 25 06:36:39 2023 Return-path: Envelope-to: ged-emacs-devel@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1qO9mp-00006t-Bo for ged-emacs-devel@m.gmane-mx.org; Tue, 25 Jul 2023 06:36:39 +0200 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qO9mN-00018x-7T; Tue, 25 Jul 2023 00:36:11 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qO9mH-00018k-RS for emacs-devel@gnu.org; Tue, 25 Jul 2023 00:36:06 -0400 Original-Received: from mout01.posteo.de ([185.67.36.65]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qO9mF-0005lT-Rq for emacs-devel@gnu.org; Tue, 25 Jul 2023 00:36:05 -0400 Original-Received: from submission (posteo.de [185.67.36.169]) by mout01.posteo.de (Postfix) with ESMTPS id A3AA5240027 for ; Tue, 25 Jul 2023 06:36:01 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=posteo.net; s=2017; t=1690259761; bh=3dzcgfMKvDvZWnxwDs2unQZ285vvGqH1U/bRji9pUjk=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:From; b=lpzGgnyQlTHSf80CQ6t7OHixsVS/d8Y+4tay+whZ3/bNMjpdfc0KnBsBc3E0uB/2v uWH73LfZBYgxY1RuqVfu0RJihDYYTHDBRPzaQX8EpJtSf0Uwpw9RmjwALumxeyCgd+ WsAWhdRKHhJctKLSVTiGp1x/Q7a2q/Ge7Mu1fkDatkpAUlgeeDNBW2ma2DF2uwvZJx L9D0JvKJvl9PHCBCXkT+XyzzxUw1bWpoXKGGeKpUIczh4FuDuUCoMavh+yroznTiSK uQadxUGiRY7KSdimIZIgkGEPogqU+lHgq3CnclJlk+miE06iPFKZFB1KkZu+L0mvgs dWpNpmhEpLe1g== Original-Received: from customer (localhost [127.0.0.1]) by submission (posteo.de) with ESMTPSA id 4R943P0KWTz9s2q; Tue, 25 Jul 2023 06:36:00 +0200 (CEST) In-Reply-To: <87fs5czvs2.fsf@yahoo.com> Received-SPF: pass client-ip=185.67.36.65; envelope-from=yantar92@posteo.net; helo=mout01.posteo.de X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Original-Sender: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Xref: news.gmane.io gmane.emacs.devel:308072 Archived-At: Po Lu writes: > Ihor Radchenko writes: > >> This problem is not limited to buffers - any low-level function that >> modifies C object struct must enforce the condition when other threads >> cannot modify the same object. For example SETCAR will have to mark the >> modified object non-writable first, set its car, and release the lock. > > No, because reading the car of a Lisp_Cons does not depend on any other > field within the Lisp_Cons. > > No interlocking is required to read from or write to machine word-sized > fields, as changes to such fields are always propagated coherently to > other CPUs. At worst, you will need to flush the write cache on any CPU > that has written to one such field. (Even these machines are rare -- I > don't think Emacs currently supports any.) This is a dangerous assumption. What if Emacs decides to support such architecture in future? Simultaneous write and read generally has undefined outcome, unless we use READ_ONCE and WRITE_ONCE. There are known architectures where simultaneous read may result in mixing bits from the old and new values. -- Ihor Radchenko // yantar92, Org mode contributor, Learn more about Org mode at . Support Org development at , or support my work at