From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.devel Subject: Re: save-excursion and multi-thread? Date: Mon, 27 Sep 2021 15:35:37 -0400 Message-ID: References: <5713E898-28B8-456C-992C-F0332FACA9FF@mit.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="26991"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.0.50 (gnu/linux) Cc: "emacs-devel@gnu.org" To: Qiantan Hong Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Mon Sep 27 22:12:03 2021 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 1mUwyo-0006nH-Oq for ged-emacs-devel@m.gmane-mx.org; Mon, 27 Sep 2021 22:12:02 +0200 Original-Received: from localhost ([::1]:47620 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mUwyn-0003br-Oo for ged-emacs-devel@m.gmane-mx.org; Mon, 27 Sep 2021 16:12:01 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:59314) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mUwQH-0000ah-He for emacs-devel@gnu.org; Mon, 27 Sep 2021 15:36:22 -0400 Original-Received: from mailscanner.iro.umontreal.ca ([132.204.25.50]:65347) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mUwQF-0005s4-FM for emacs-devel@gnu.org; Mon, 27 Sep 2021 15:36:20 -0400 Original-Received: from pmg1.iro.umontreal.ca (localhost.localdomain [127.0.0.1]) by pmg1.iro.umontreal.ca (Proxmox) with ESMTP id 6E03C10021B; Mon, 27 Sep 2021 15:36:16 -0400 (EDT) Original-Received: from mail01.iro.umontreal.ca (unknown [172.31.2.1]) by pmg1.iro.umontreal.ca (Proxmox) with ESMTP id C6206100134; Mon, 27 Sep 2021 15:36:14 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=iro.umontreal.ca; s=mail; t=1632771374; bh=mauJYbrjDesVAThmMsFknj8Daoo2+QcsMnzACpSPMOs=; h=From:To:Cc:Subject:References:Date:In-Reply-To:From; b=A5GFBlGEhYoWDT7X2YFbCaOfZnlD3UGpkApuE3eKKsrld2kBtglyEBwyiXdhn/4GJ 8dkckB4i20TVno4w222sfNp1LXDdWRjnSEkk8Z9POl3uPso8T3ap4OhP4A+wfP6hjh S9dWnaTT0qqd7W7ecjdSluF3TzwzrWu/40jVUOfr8Ln/OhCX0OvmCpSAMS9ev3ae/h c3beXxfadh2VSE6JDGtEfhLl/pntg1UiQ33HR9pIqlKJsaulZk+j20KHhuEzKOY1Km HMt1BOZJCeGnPIElDhYCCcGz9cFCuZaONCw6ndD4mDAEa7iK5rCTRXI4Cz4mwQb/FP Vpc+y8d2kW5Pg== Original-Received: from alfajor (lechon.iro.umontreal.ca [132.204.27.242]) by mail01.iro.umontreal.ca (Postfix) with ESMTPSA id A77FD120298; Mon, 27 Sep 2021 15:36:14 -0400 (EDT) In-Reply-To: <5713E898-28B8-456C-992C-F0332FACA9FF@mit.edu> (Qiantan Hong's message of "Sun, 26 Sep 2021 17:41:17 +0000") Received-SPF: pass client-ip=132.204.25.50; envelope-from=monnier@iro.umontreal.ca; helo=mailscanner.iro.umontreal.ca X-Spam_score_int: -42 X-Spam_score: -4.3 X-Spam_bar: ---- X-Spam_report: (-4.3 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.23 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" Xref: news.gmane.io gmane.emacs.devel:275612 Archived-At: > Is this how save-excursion supposed to work? Good question. > It=E2=80=99s inconsistent with the behavior of special variable + dynamic= bindings, > which works currently under multi-thread. You might be right and maybe we should undo/redo such buffer movements when context-switching, just like we do for the let bindings. We already implement such undo/redo of this and similar forms in a different yet related context: when we evaluate a user-specified expression in a given stack frame (from the *Backtrace* debugger). See `backtrace-eval`. This said, your scenario smells like a race-condition to me, so maybe we should instead "lock" the buffer's point while we're inside the `save-excursion`. Stefan