From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.devel Subject: Re: wait_reading_process_ouput hangs in certain cases (w/ patches) Date: Tue, 14 Nov 2017 18:03:33 +0200 Message-ID: <83vaickfu2.fsf@gnu.org> References: <83lgjz8eiy.fsf@gnu.org> <831slp98ut.fsf@gnu.org> <83tvyj62qg.fsf@gnu.org> <83r2tetf90.fsf@gnu.org> <5150d198-8dd3-9cf4-5914-b7e945294452@binary-island.eu> <83tvy7s6wi.fsf@gnu.org> <83inemrqid.fsf@gnu.org> <398f8d17-b727-d5d6-4a31-772448c7ca0d@binary-island.eu> <56e722a6-95a4-0e42-185c-f26845d4f4bf@binary-island.eu> <21237e45-a353-92f9-01ec-7b51640d2031@cs.ucla.edu> Reply-To: Eli Zaretskii NNTP-Posting-Host: blaine.gmane.org X-Trace: blaine.gmane.org 1510675459 17727 195.159.176.226 (14 Nov 2017 16:04:19 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Tue, 14 Nov 2017 16:04:19 +0000 (UTC) Cc: ml_emacs-lists@binary-island.eu, emacs-devel@gnu.org To: Paul Eggert Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Tue Nov 14 17:04:08 2017 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1eEdh1-0003yU-6Y for ged-emacs-devel@m.gmane.org; Tue, 14 Nov 2017 17:04:07 +0100 Original-Received: from localhost ([::1]:60510 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eEdh7-00051E-Vs for ged-emacs-devel@m.gmane.org; Tue, 14 Nov 2017 11:04:14 -0500 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:50877) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eEdgP-0004xY-Ep for emacs-devel@gnu.org; Tue, 14 Nov 2017 11:03:36 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eEdgK-0005hL-UY for emacs-devel@gnu.org; Tue, 14 Nov 2017 11:03:29 -0500 Original-Received: from fencepost.gnu.org ([2001:4830:134:3::e]:33781) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eEdgK-0005h5-Ra; Tue, 14 Nov 2017 11:03:24 -0500 Original-Received: from [176.228.60.248] (port=3513 helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:RSA_AES_256_CBC_SHA1:256) (Exim 4.82) (envelope-from ) id 1eEdgK-0000t0-AB; Tue, 14 Nov 2017 11:03:24 -0500 In-reply-to: <21237e45-a353-92f9-01ec-7b51640d2031@cs.ucla.edu> (message from Paul Eggert on Tue, 14 Nov 2017 07:24:31 -0800) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 2001:4830:134:3::e X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.21 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.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.org gmane.emacs.devel:220183 Archived-At: > Cc: emacs-devel@gnu.org > From: Paul Eggert > Date: Tue, 14 Nov 2017 07:24:31 -0800 > > On 11/14/2017 06:58 AM, Matthias Dahl wrote: > > If during an active > > call to wait_... all recursive calls happen to read exactly 2**32 (or > > whatever bit depths EMACS_UINT is) bytes back, then we will miss it > > completely and stall. > > First, this means that the companion idea of subtracting the two > counters to yield a byte count is also buggy because the byte count will > be wrong for this call. This would be a bug that could happen whenever a > successful recursive call occurs, which apparently is quite common. So > if we stick with the current approach, we definitely should be dropping > the requirement that Eli was thinking of, which says that a positive > number returned by wait_reading_process_output indicates the number of > bytes read for this call. No, I'm not dropping that requirement. > Second, I don't leaving a known bug in the code, even if the bug is > unlikely. Too often, these extreme cases occur anyway (e.g., due to a > network attack). I'd prefer a slightly-more-complicated solution where > the bug cannot occur. It can't be that hard to fix. Please describe such a solution, or show the code.