From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-3.4 required=3.0 tests=AWL,BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,RCVD_IN_DNSWL_HI,T_RP_MATCHES_RCVD shortcircuit=no autolearn=ham autolearn_force=no version=3.4.0 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id A8A811F404 for ; Thu, 5 Apr 2018 16:39:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751344AbeDEQj4 (ORCPT ); Thu, 5 Apr 2018 12:39:56 -0400 Received: from cloud.peff.net ([104.130.231.41]:54706 "HELO cloud.peff.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751251AbeDEQjz (ORCPT ); Thu, 5 Apr 2018 12:39:55 -0400 Received: (qmail 29826 invoked by uid 109); 5 Apr 2018 16:39:55 -0000 Received: from Unknown (HELO peff.net) (10.0.1.2) by cloud.peff.net (qpsmtpd/0.94) with SMTP; Thu, 05 Apr 2018 16:39:55 +0000 Authentication-Results: cloud.peff.net; auth=none Received: (qmail 16814 invoked by uid 111); 5 Apr 2018 16:40:56 -0000 Received: from sigill.intra.peff.net (HELO sigill.intra.peff.net) (10.0.0.7) by peff.net (qpsmtpd/0.94) with (ECDHE-RSA-AES256-GCM-SHA384 encrypted) SMTP; Thu, 05 Apr 2018 12:40:56 -0400 Authentication-Results: peff.net; auth=none Received: by sigill.intra.peff.net (sSMTP sendmail emulation); Thu, 05 Apr 2018 12:39:53 -0400 Date: Thu, 5 Apr 2018 12:39:53 -0400 From: Jeff King To: Jan Palus Cc: git@vger.kernel.org Subject: Re: Timing issue in t5570 "daemon log records all attributes" Message-ID: <20180405163953.GB25224@sigill.intra.peff.net> References: <1522783990.964448.1325338528.0D49CC15@webmail.messagingengine.com> <20180403203233.GB15157@sigill.intra.peff.net> <20180404215752.6qsipaaskrzwiv4q@kalarepa> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20180404215752.6qsipaaskrzwiv4q@kalarepa> Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Wed, Apr 04, 2018 at 11:57:52PM +0200, Jan Palus wrote: > On 03.04.2018 16:32, Jeff King wrote: > > I'm tempted to say we should just scrap this test. It was added > > relatively recently and only shows the fix for a pretty minor bug. > > It's probably not worth the contortions to make it race-proof. > > Thanks for your reply Jeff. > > It appears race condition in reading/writing daemon.log is not the only issue of > t5570. On a different machine I've just randomly got: > > t5570-git-daemon.sh[163]: can't create git_daemon_output: Interrupted system call > > which I believe might also be associated with concurrent processing of piped > data connected with a fact that test restarts daemon few times. I can barely > wrap my head around it but I guess it's somewhat around "shell still tries to > read fifo while attempt to create new one is made". That sounds more like your system doesn't handle EINTR gracefully (presumably it's getting SIGCLD during the mknod() call). Normally that would be done by an external program, but is mkfifo perhaps a builtin in your shell? If I run t5570 on a loop on a loaded system[1], I can't seem to provoke any failures, using dash. -Peff [1] The script I use is: https://github.com/peff/git/blob/meta/stress which runs the test script over and over in parallel. That's usually enough to exhibit practical races, since it creates enough load to show timing effects.