From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Mark H Weaver Newsgroups: gmane.emacs.bugs Subject: bug#46978: 27.1; Shell mode performs extremely poorly in Linux-libre 5.10.20 Date: Sun, 07 Mar 2021 03:50:15 -0500 Message-ID: <87y2ezgxel.fsf@netris.org> References: <878s6z25y4.fsf@netris.org> <87ft17it4a.fsf@netris.org> <83o8fvtqli.fsf@gnu.org> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="14311"; mail-complaints-to="usenet@ciao.gmane.io" Cc: 46978@debbugs.gnu.org To: Eli Zaretskii Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Sun Mar 07 09:52:13 2021 Return-path: Envelope-to: geb-bug-gnu-emacs@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 1lIp93-0003cp-Cj for geb-bug-gnu-emacs@m.gmane-mx.org; Sun, 07 Mar 2021 09:52:13 +0100 Original-Received: from localhost ([::1]:48814 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lIp91-0001XN-UK for geb-bug-gnu-emacs@m.gmane-mx.org; Sun, 07 Mar 2021 03:52:11 -0500 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:43278) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lIp8s-0001X9-1c for bug-gnu-emacs@gnu.org; Sun, 07 Mar 2021 03:52:02 -0500 Original-Received: from debbugs.gnu.org ([209.51.188.43]:55567) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1lIp8r-0000KT-Q2 for bug-gnu-emacs@gnu.org; Sun, 07 Mar 2021 03:52:01 -0500 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1lIp8r-0005Dg-OX for bug-gnu-emacs@gnu.org; Sun, 07 Mar 2021 03:52:01 -0500 X-Loop: help-debbugs@gnu.org Resent-From: Mark H Weaver Original-Sender: "Debbugs-submit" Resent-CC: bug-gnu-emacs@gnu.org Resent-Date: Sun, 07 Mar 2021 08:52:01 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 46978 X-GNU-PR-Package: emacs Original-Received: via spool by 46978-submit@debbugs.gnu.org id=B46978.161510710820043 (code B ref 46978); Sun, 07 Mar 2021 08:52:01 +0000 Original-Received: (at 46978) by debbugs.gnu.org; 7 Mar 2021 08:51:48 +0000 Original-Received: from localhost ([127.0.0.1]:38880 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1lIp8e-0005DC-5g for submit@debbugs.gnu.org; Sun, 07 Mar 2021 03:51:48 -0500 Original-Received: from world.peace.net ([64.112.178.59]:53992) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1lIp8d-0005D0-B3 for 46978@debbugs.gnu.org; Sun, 07 Mar 2021 03:51:47 -0500 Original-Received: from mhw by world.peace.net with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1lIp8X-0001m1-9T; Sun, 07 Mar 2021 03:51:41 -0500 In-Reply-To: <83o8fvtqli.fsf@gnu.org> X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list X-BeenThere: bug-gnu-emacs@gnu.org List-Id: "Bug reports for GNU Emacs, the Swiss army knife of text editors" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Original-Sender: "bug-gnu-emacs" Xref: news.gmane.io gmane.emacs.bugs:201733 Archived-At: Eli Zaretskii writes: >> From: Mark H Weaver >> Date: Sat, 06 Mar 2021 21:39:54 -0500 >> >> Mark H Weaver writes: >> >> > I've skimmed the list of changes between Linux 5.10.19 and 5.10.20, and >> > found these two commits that might be relevant: >> > >> > tty: implement read_iter >> > >> > >> > tty: convert tty_ldisc_ops 'read()' function to take a kernel pointer >> > >> > >> > These changes are also included in Linux-libre 5.11.3 (the newest >> > release), but I haven't yet tried that version. >> > >> > I'm currently building a variant of Linux-libre 5.10.20 with these two >> > commits reverted, to see if that makes the problem go away, and I will >> > report back when I have those results. >> >> Reverting the two commits cited above fixes the problem. > > So does this mean this isn't an Emacs issue, but the issue with that > kernel? That's not clear to me. What I know is that these changes to Linux's TTY subsystem, authored by Linus Torvalds himself and recently included in upstream Linux 5.11.3 and 5.10.20, have lead to this regression in Emacs. This might simply be a kernel bug, or it could be that Emacs is making an improper assumption about how the kernel behaves. > Or is there still something you'd like us to look into on the > Emacs side? I would suggest investigating to find out what's going wrong here, and then: (1) if it can reasonably be considered a kernel regression, submit a bug report to the Linux developers, and (2) if Emacs is found to behave suboptimally in its interactions with the kernel, or if the Linux developers do not soon deploy their own fix, modify Emacs as needed to avoid the problem. What do you think? Thanks, Mark