From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-4.0 required=3.0 tests=AWL,BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI shortcircuit=no autolearn=ham autolearn_force=no version=3.4.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id 73BB01F405 for ; Thu, 9 Aug 2018 21:32:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727274AbeHIX6p (ORCPT ); Thu, 9 Aug 2018 19:58:45 -0400 Received: from cloud.peff.net ([104.130.231.41]:49100 "HELO cloud.peff.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1727240AbeHIX6p (ORCPT ); Thu, 9 Aug 2018 19:58:45 -0400 Received: (qmail 5242 invoked by uid 109); 9 Aug 2018 21:32:03 -0000 Received: from Unknown (HELO peff.net) (10.0.1.2) by cloud.peff.net (qpsmtpd/0.94) with SMTP; Thu, 09 Aug 2018 21:32:03 +0000 Authentication-Results: cloud.peff.net; auth=none Received: (qmail 13868 invoked by uid 111); 9 Aug 2018 21:32:05 -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, 09 Aug 2018 17:32:05 -0400 Authentication-Results: peff.net; auth=none Received: by sigill.intra.peff.net (sSMTP sendmail emulation); Thu, 09 Aug 2018 17:32:01 -0400 Date: Thu, 9 Aug 2018 17:32:01 -0400 From: Jeff King To: Junio C Hamano Cc: Johannes Schindelin via GitGitGadget , git@vger.kernel.org Subject: Re: [PATCH 0/4] t5552: fix flakiness by introducing proper locking for GIT_TRACE Message-ID: <20180809213201.GB11342@sigill.intra.peff.net> References: <20180809194712.GC32376@sigill.intra.peff.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Thu, Aug 09, 2018 at 02:08:56PM -0700, Junio C Hamano wrote: > > Correct. But I am more worried about the "mixed/overwriting" > > breakage, if there is one; it means we may need to be prepared for > > systems that lack O_APPEND that works correctly. I initially just > > assumed that it was what Dscho was seeing, but after re-reading his > > message, I am not sure anymore. > > > > I think the "do not trace the other side" approach you suggest for > > these tests that only care about one side is more appropriate > > solution for this particular case. We then do not have to worry > > about overwriting or output from both sides mixed randomly. > > A concluding sentence I forgot to add, after saying "this is simpler > and better to fix test breakage", was > > But if we really are seeing O_APPEND breakage, a mandatory > locking mechanism like this one might be necessary to work > around it (I seriously hope we do not have to, though). > > Sorry for an additional noise. Yeah, my earlier email said "if we just care about this test, then...". But if we do care about making this multiple-tracing case work all the time, then we'd need some solution. If there's something that can work like O_APPEND, even if we have to make some system-specific call, I'd prefer that to locking. I did some searching for atomic append on Windows and got mixed reports on whether their FILE_DATA_APPEND does what we want or not. Knowing nothing about msys, I'd _assume_ that O_APPEND would get translated to that flag, but I got lost trying to find it in git-for-windows/msys2-runtime. Wouldn't it be wonderful if the solution were as simple as making sure that flag was plumbed through? I seriously doubt it will be that easy, though. :) -Peff