From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.devel Subject: Re: Insight into the mystery hangs Date: Mon, 12 Feb 2024 21:22:15 +0200 Message-ID: <86le7pqyhk.fsf@gnu.org> References: <20240211213737.3A38C18A1647@snark.thyrsus.com> <868r3psv2s.fsf@gnu.org> Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="23198"; mail-complaints-to="usenet@ciao.gmane.io" Cc: emacs-devel@gnu.org To: esr@thyrsus.com Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Mon Feb 12 20:22:57 2024 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 1rZbtJ-0005oW-3P for ged-emacs-devel@m.gmane-mx.org; Mon, 12 Feb 2024 20:22:57 +0100 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rZbsj-0000Zn-8Z; Mon, 12 Feb 2024 14:22:21 -0500 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 1rZbsg-0000ZI-W6 for emacs-devel@gnu.org; Mon, 12 Feb 2024 14:22:19 -0500 Original-Received: from fencepost.gnu.org ([2001:470:142:3::e]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rZbsg-000541-Gv; Mon, 12 Feb 2024 14:22:18 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=gnu.org; s=fencepost-gnu-org; h=References:Subject:In-Reply-To:To:From:Date: mime-version; bh=cvsmgtf9BFfL1ZJ/tMU7AOksOrwhvnu9gcyvKGMBXyM=; b=jYqZnvUe4UlH kktKvn7nAILuXAgj9CcsYBtzRMKI16ydb+3rud6XgA3MPRC9GlHiitpdXUFsekzjmEUCl5vviIaHB BRTloTYt+JqDHyyToBgt4B3R4Foi8fJ+ckGUFxDMq58a04OXqh/RNS0dEzKgB8pGnLOHKNfPjhWNi RbVh43ym6bltwNtDXdCWXGO34kjEKLTZTZ1pNO0MenGxwE0ubu4AZZzlskUnzUw8R3EUAJzf61aeW CAW2nTWDEsIH6pJZx5D+XDs26jyEeKPPWh9vcRd7TFj1SMf2S9UEjk6KdBvJgCgShvW0gx9x5jaxy h1kE2FH938OeuNFdXU8BUg==; In-Reply-To: (esr@thyrsus.com) 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:316148 Archived-At: > Date: Mon, 12 Feb 2024 13:26:16 -0500 > From: "Eric S. Raymond" > Cc: emacs-devel@gnu.org > > Eli Zaretskii : > > Isn't that call issued from the mode-line display? If so, that is > > done from redisplay, and redisplay cannot enter debugger, so it > > catches all errors. If you want to produce Lisp backtraces from Lisp > > code called by redisplay, you need to use the facilities documented in > > the node "Debugging Redisplay" in the ELisp Reference manual. > > 1. Thinking about it, I can see why redisplay can't be allowed to enter > the debugger. Infinite regress... > > 2. I don't know if that subprocess is called from the modeline > code. Probably, but I'd have to dig into vc.el to check. I won't have > time for that for a few days yet. > > 3. Assuming that it is called from the modeline code, the question > shifts from "Why did I have so much trouble generating a debug trace?" > to "How could I get one at all"?" There's some kind of timing issue, > I think. If you eventually can get Emacs into producing a backtrace, the facilities described in the node "Debugging Redisplay", mentioned above, should allow you to have it saved in a special buffer that you can then examine. > ...this directs my attention to the fact that that Emacs makes it > generally difficult to notice and diagnose ill-behaved subprocesses, > wuth problems behind the mode-line being the extreme case. Alas, I > don't know what to do about this other than windmill my arms at the > dev group. Not sure I understand what kind of features would you like to have to make this easier. To detect the fact that a sub-process takes most of the time you could use profiler.el -- the profile should show that a large portion of time is spent inside call-process or its ilk. Alternatively, you could use 'top' or a similar tool to see what the Emacs process and its subprocesses are doing.