From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Paul Eggert Newsgroups: gmane.emacs.devel Subject: Re: some accept-process-output races fixed; Tramp FIXMEs Date: Wed, 16 Jan 2019 16:15:09 -0800 Organization: UCLA Computer Science Department Message-ID: References: <46ce72ef-c4cb-1cd1-566a-c305ca92e68c@cs.ucla.edu> <80d86b5a-efb7-87cc-a3db-0a6ad356274d@cs.ucla.edu> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Trace: blaine.gmane.org 1547684679 25084 195.159.176.226 (17 Jan 2019 00:24:39 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Thu, 17 Jan 2019 00:24:39 +0000 (UTC) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 To: emacs-devel@gnu.org Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Thu Jan 17 01:24:35 2019 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([209.51.188.17]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1gjvU2-0006PO-FA for ged-emacs-devel@m.gmane.org; Thu, 17 Jan 2019 01:24:34 +0100 Original-Received: from localhost ([127.0.0.1]:43186 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gjvW9-0008Bh-AF for ged-emacs-devel@m.gmane.org; Wed, 16 Jan 2019 19:26:45 -0500 Original-Received: from eggs.gnu.org ([209.51.188.92]:56008) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gjvL0-0000NJ-79 for emacs-devel@gnu.org; Wed, 16 Jan 2019 19:15:15 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gjvKz-0007e7-EZ for emacs-devel@gnu.org; Wed, 16 Jan 2019 19:15:14 -0500 Original-Received: from zimbra.cs.ucla.edu ([131.179.128.68]:57414) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gjvKz-0007Yp-5w for emacs-devel@gnu.org; Wed, 16 Jan 2019 19:15:13 -0500 Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id 2DD48160FE8 for ; Wed, 16 Jan 2019 16:15:10 -0800 (PST) Original-Received: from zimbra.cs.ucla.edu ([127.0.0.1]) by localhost (zimbra.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id 9I3C5BMGxWOX for ; Wed, 16 Jan 2019 16:15:09 -0800 (PST) Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id 62312160FEF for ; Wed, 16 Jan 2019 16:15:09 -0800 (PST) X-Virus-Scanned: amavisd-new at zimbra.cs.ucla.edu Original-Received: from zimbra.cs.ucla.edu ([127.0.0.1]) by localhost (zimbra.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id GlQXqaR5uE6R for ; Wed, 16 Jan 2019 16:15:09 -0800 (PST) Original-Received: from Penguin.CS.UCLA.EDU (Penguin.CS.UCLA.EDU [131.179.64.200]) by zimbra.cs.ucla.edu (Postfix) with ESMTPSA id 4A889160FDE for ; Wed, 16 Jan 2019 16:15:09 -0800 (PST) Openpgp: preference=signencrypt Autocrypt: addr=eggert@cs.ucla.edu; prefer-encrypt=mutual; keydata= xsFNBEyAcmQBEADAAyH2xoTu7ppG5D3a8FMZEon74dCvc4+q1XA2J2tBy2pwaTqfhpxxdGA9 Jj50UJ3PD4bSUEgN8tLZ0san47l5XTAFLi2456ciSl5m8sKaHlGdt9XmAAtmXqeZVIYX/UFS 96fDzf4xhEmm/y7LbYEPQdUdxu47xA5KhTYp5bltF3WYDz1Ygd7gx07Auwp7iw7eNvnoDTAl KAl8KYDZzbDNCQGEbpY3efZIvPdeI+FWQN4W+kghy+P6au6PrIIhYraeua7XDdb2LS1en3Ss mE3QjqfRqI/A2ue8JMwsvXe/WK38Ezs6x74iTaqI3AFH6ilAhDqpMnd/msSESNFt76DiO1ZK QMr9amVPknjfPmJISqdhgB1DlEdw34sROf6V8mZw0xfqT6PKE46LcFefzs0kbg4GORf8vjG2 Sf1tk5eU8MBiyN/bZ03bKNjNYMpODDQQwuP84kYLkX2wBxxMAhBxwbDVZudzxDZJ1C2VXujC OJVxq2kljBM9ETYuUGqd75AW2LXrLw6+MuIsHFAYAgRr7+KcwDgBAfwhPBYX34nSSiHlmLC+ KaHLeCLF5ZI2vKm3HEeCTtlOg7xZEONgwzL+fdKo+D6SoC8RRxJKs8a3sVfI4t6CnrQzvJbB n6gxdgCu5i29J1QCYrCYvql2UyFPAK+do99/1jOXT4m2836j1wARAQABzSBQYXVsIEVnZ2Vy dCA8ZWdnZXJ0QGNzLnVjbGEuZWR1PsLBfgQTAQIAKAUCTIByZAIbAwUJEswDAAYLCQgHAwIG FQgCCQoLBBYCAwECH In-Reply-To: Content-Language: en-US X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 131.179.128.68 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:232410 Archived-At: On 1/16/19 11:07 AM, Stefan Monnier wrote: > I think we should make sure that > > (if (not (process-live-p p)) > (progn > (accept-process-output p) > ;; Here we should be sure that we processed all the output > > whereas IIUC currently we need > > (if (not (process-live-p p)) > (progn > (while (accept-process-output p)) > ;; Here we are presumably sure that we processed all the output Both those approaches should work now. In my earlier email I was worried about the slightly-different case where P exits just before (accept-process-output P DELAY) is called. In this case accept-process-output might not slurp all the data from P even if P has already exited. However, in the above scenarios, where Emacs "knows" that P has exited before (accept-process-output P) is called with no DELAY, no data should go missing on any sane POSIX platform (though admittedly I can't cite chapter and verse on this and I suspect POSIX does not strictly require it). However, I'm still puzzled by Tramp's use of (while (or (accept-process-output p 0.1) (process-live-p p))) to get all P's output. Why not use (while (accept-process-output p)) instead, which is simpler and avoids the race condition I mentioned? Maybe something to do with timers? I'm at a loss there.