From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 71326 invoked by alias); 25 May 2016 15:22:49 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Received: (qmail 71311 invoked by uid 89); 25 May 2016 15:22:48 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-3.3 required=5.0 tests=BAYES_00,RP_MATCHES_RCVD,SPF_HELO_PASS autolearn=ham version=3.3.2 spammy=loud, fuller, recall, overnight X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES256-GCM-SHA384 encrypted) ESMTPS; Wed, 25 May 2016 15:22:40 +0000 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 8D1DDC05B1D1; Wed, 25 May 2016 15:22:39 +0000 (UTC) Received: from [127.0.0.1] (ovpn01.gateway.prod.ext.ams2.redhat.com [10.39.146.11]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u4PFMcpV025083; Wed, 25 May 2016 11:22:38 -0400 Subject: Re: gdb-7.11.1 - 2 weeks to go... To: Joel Brobecker References: <20160510161756.GB26324@adacore.com> <395c33b0-7071-ed80-915a-dd8dbefe2786@redhat.com> <20160520132452.GF26324@adacore.com> Cc: gdb-patches@sourceware.org From: Pedro Alves Message-ID: <512c2f2d-b85b-766e-99e0-d219fca20dc7@redhat.com> Date: Wed, 25 May 2016 15:22:00 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.1.0 MIME-Version: 1.0 In-Reply-To: <20160520132452.GF26324@adacore.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-SW-Source: 2016-05/txt/msg00449.txt.bz2 On 05/20/2016 02:24 PM, Joel Brobecker wrote: > Hi Pedro, > >> Odd, it definitely doesn't work for me on master. > > I don't recall exactly, but I must have thought it was fixed just > because I saw a commit. Sorry if that caused some confusion. No worries, no real confusion. >> Another option that just occurred to me, is to apply the fuller fix >> to the branch (patch #6 in the series), and disable the >> attach-many-short-lived-threads.exp test in the branch? GDB regresses >> in the use case of attaching to a program that is constantly spawning >> many threads in quick succession, though that's a contrived use case >> to expose problems. Probably no program in the wild is like that. >> I hope. Use cases like Go programs with tons of goroutines make me >> worry a bit. > > At this stage, I think we should only commit changes we are confident > about. If that leaves things broken and regressing, well, better > document them, especially if we have workarounds, or else direct > people to 7.10 or future releases. *nod* > > In this case, if you feel good about your simpler fix, we could go > with that on the branch, while we aim at getting your complete > series on master. Just thinking out loud. > Another option is doing nothing, To be clear, the reported bug is unrelated to attach-many-short-lived-threads.exp. It's just that fixing the bug surprisingly regresses attach-many-short-lived-threads.exp. > or disabling attach-many-short-lived-threads.exp. This > test is very good, but also not always representative of typical > programs. > Right. The full fix is in master since yesterday. I let the buildbot chew on it overnight, and looked at fail reports. Although some builders showed attach-many-short-lived-threads.exp failures, all I saw looked like pre-existing racy fails that also appear before the fixes. I've spent today trying to come up with a simpler fix, but all I tried has some significant drawback. E.g., I tried making the detach path cope with an lwp not in gdb's thread list (avoiding the PR gdb/19828 assertion), but then gdb crashes elsewhere. Disabling all-stop-on-top-of-non-stop would be another potential path forward, but although it'd be a one-liner, it's quite an invasive change to make in a patch release, as it completely changes how the infrun.c -> linux-nat.c cooperate... So all in all, I prefer the approach of pushing the fuller fix to the branch, without the invasive optimization bits, and disable the attach-many-short-lived-threads.exp test. I'll do that in a bit. Thanks, Pedro Alves