From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-vk1-xa2d.google.com (mail-vk1-xa2d.google.com [IPv6:2607:f8b0:4864:20::a2d]) by sourceware.org (Postfix) with ESMTPS id 515D33892015 for ; Fri, 16 Apr 2021 10:54:55 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 515D33892015 Received: by mail-vk1-xa2d.google.com with SMTP id q143so1198541vka.13 for ; Fri, 16 Apr 2021 03:54:55 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=EBu6MkZmS8djDa+Z+ZIc5mqdEAqsaGBj0XXfCOljAMQ=; b=RzkTxEEhsQngUtOFjrzWh7vrYAAwLC87gzyEiqxSnyLetQ5/M0FgMW84pRXrYgUWKT vOioql5usmDb0Ki9Y9aV96XUuN8JccOgakcbw9UX4JAIOyclpSYxfY6/59Y6Sa5CmS/o I1oIDjO5JXwyxuNBnmzkE+hHH0HsVsRBazs18wa81KF0M3k1m+LVrkB83Ad3et64YTlN E7zXTAdZ2tRoHmhlXSPlcDmsUSs1Dc+3qQWsKomJGTM6QphzR6JGmX2QrZDHm+PqOA33 /vFkSIqZ2TVkKdJ2jcgkLhKeu4CH6ovJcMuUBI7tJxNNZ+yBBOD6tsFSgwQtU8jEJwSi sysw== X-Gm-Message-State: AOAM532ObuojXdeth+7qP7oC12eoOQ2Mm43wN2s0DSFXlYJO3KacRlBq BXg+Q9I7n2ecKrbgS2uIWDFx1Bp49b4xJl9g26RylY7swgqTSA== X-Google-Smtp-Source: ABdhPJy0B2tDK4fQYDftQ7DZ34wP5Sb1fmn4NQrqQCKturxK0RvaLgFIKCjn8EsipZB7+egdp5REedY6sbtaDfCGCuU= X-Received: by 2002:ac5:cde5:: with SMTP id v5mr6198793vkn.16.1618570494907; Fri, 16 Apr 2021 03:54:54 -0700 (PDT) MIME-Version: 1.0 References: <87y2dizkxp.fsf@oldenburg.str.redhat.com> In-Reply-To: <87y2dizkxp.fsf@oldenburg.str.redhat.com> From: Emil Velikov Date: Fri, 16 Apr 2021 11:54:43 +0100 Message-ID: Subject: Re: Glibc commit causing regression in gdb To: Florian Weimer Cc: Emil Velikov via Libc-alpha Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Spam-Status: No, score=-1.3 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_FROM, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 16 Apr 2021 10:54:56 -0000 Hi Florian, On Fri, 16 Apr 2021 at 09:35, Florian Weimer wrote: > > * Emil Velikov via Libc-alpha: > > > We have recently received a regression report in Arch Linux, where gdb > > attach fails with some applications. > > In particular, the issue originates in glibc 2.33, while gdb used is > > 10.1 and is 100% reproducible (here) with steam and gimp. > > > > Note that explicitly rebuilding gdb explicitly against the glibc does n= ot help. > > > > After some digging I found the offending glibc commit > > 1daccf403b1bd86370eb94edca794dc106d02039 ("nptl: Move stack list > > variables into _rtld_global"). With the said commit the > > td_ta_map_lwp2thr() call in GDB fails, resulting in the infamous > > > > Error while reading shared library symbols for /usr/lib/libpthread.so.0= : > > Cannot find user-level thread for LWP 2999060: generic error > > > Can anyone confirm if the issue is reproducible with other distros? > > There's a separate thread about this on the gdb-patches list, under the > slightly misleading subject of =E2=80=9CGDB 10.2 Release -- 2021-04-11 up= date=E2=80=9D: > > > > I believe there was an earlier discussion as well, but I can't find it > right now. > Thanks for the link and tips. Reading through the thread and related discussions it seems that a gdb-side fix is far from trivial. With your glibc developer hat on, how crazy^Wstupid of an idea is to carry a revert locally until a proper gdb fix is available? Say on the scale of 1 to 10. I am going through the glibc/gdb test suites with the revert, although I don't know if there are extra subtleties which won't be caught by the tests. Thanks again, Emil