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 07:59:35 +0000 Message-ID: <87bkg0s9p4.fsf@localhost> References: <871qhnr4ty.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> <87mszk7glc.fsf@localhost> <877cqozc14.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="10295"; 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 10:00:29 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 1qOCy5-0002Sw-CT for ged-emacs-devel@m.gmane-mx.org; Tue, 25 Jul 2023 10:00:29 +0200 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qOCx8-0004un-Q5; Tue, 25 Jul 2023 03:59:30 -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 1qOCx6-0004uL-GY for emacs-devel@gnu.org; Tue, 25 Jul 2023 03:59:28 -0400 Original-Received: from mout02.posteo.de ([185.67.36.66]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qOCx4-0004i0-Pd for emacs-devel@gnu.org; Tue, 25 Jul 2023 03:59:28 -0400 Original-Received: from submission (posteo.de [185.67.36.169]) by mout02.posteo.de (Postfix) with ESMTPS id 8C550240103 for ; Tue, 25 Jul 2023 09:59:24 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=posteo.net; s=2017; t=1690271964; bh=qH/74BKQWu+ZMN3PvOUtKRDCzX7lLxYuABbIQdrIyy4=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:From; b=CxkNDO1MchQD7mttIWvnaBWKYe4qtoAsDMygx22yTA2yYjd9Dn2rGlkEkjhNx9oEh 4aLOR3pHfAFaf9QQXvdhRH01f37k9n7JPqEeslsv/K0IjwsrMQO6xnBmflGHtM/78K WiJ/GMTwQrEpfF36JRlKyVxZ9S6bM2wXmmCr6Wg3Dqv2fh9oKakJdzMtmlrR/o9GJn Qe+zEGrMV936bBI/iwtyv1kWm50tw/4rSke+9jmsPHEYwzzsylaHwIMzQnVTDmhCmB bEwPCcSwo8omzuxb+GwiVNYmP0ywrKMYmN17iM9MWwK2t0q+wShWNLm61mNH4fnz46 sH6Z+9ewKpDRA== Original-Received: from customer (localhost [127.0.0.1]) by submission (posteo.de) with ESMTPSA id 4R98Z22BV9z6ty5; Tue, 25 Jul 2023 09:59:22 +0200 (CEST) In-Reply-To: <877cqozc14.fsf@yahoo.com> Received-SPF: pass client-ip=185.67.36.66; envelope-from=yantar92@posteo.net; helo=mout02.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=ham 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:308078 Archived-At: Po Lu writes: >> There are known architectures where simultaneous read may result in >> mixing bits from the old and new values. > > Which architectures would that be? Unless you're describing unaligned > reads and writes, or for data types larger or smaller (on the 21064) > than a machine word. McKenney (2023) Is Parallel Programming Hard, And, If So, What Can You Do About It? p. 483 "For an example, consider embedded systems with 32-bit pointers and 16-bit busses. On such a system, a data race involving a store to and a load from a given pointer might well result in the load returning the low-order 16 bits of the old value of the pointer concatenated with the high-order 16 bits of the new value of the pointer." >>, unless we use READ_ONCE and WRITE_ONCE. > > Emacs is not the Linux kernel and is not subject to its considerations. > Besides, READ_ONCE and WRITE_ONCE involve _NO_ interlocking! Sure. I just meant that we need to avoid data races. Using READ/WRITE_ONCE or mutexes. READ/WRITE_ONCE should be actually avoided, AFAIK. They will degrade performance significantly (one-two orders of magnitude) for each individual operation (see Figure 5.1 in the McKenney's book) -- Ihor Radchenko // yantar92, Org mode contributor, Learn more about Org mode at . Support Org development at , or support my work at