From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C1086C433FE for ; Tue, 1 Nov 2022 18:26:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229875AbiKAS0X (ORCPT ); Tue, 1 Nov 2022 14:26:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46154 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229531AbiKAS0W (ORCPT ); Tue, 1 Nov 2022 14:26:22 -0400 Received: from mail-oi1-x229.google.com (mail-oi1-x229.google.com [IPv6:2607:f8b0:4864:20::229]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 56FB5D13B for ; Tue, 1 Nov 2022 11:26:21 -0700 (PDT) Received: by mail-oi1-x229.google.com with SMTP id v81so8121044oie.5 for ; Tue, 01 Nov 2022 11:26:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:from:to:cc:subject:date:message-id :reply-to; bh=j13+RdBhueYLBa+gZTK00atTbWK5kdZidNW/hkmhbwQ=; b=n2AxkPgmqto4tH3j65TvYJJyeMZJOVrWyPOTduayeVrDeBcpKWdmWFwoHGWu5y8DA1 5jtIiKmupXbwBLpA+WJAOWp5QwFhIbliflFMC5lsflDQZdQ5qhc5WncGaoaZH/9Szosk Rz5a+oL5bAOZbpijyokB10EwLigXhTIDyecgpuiYbNBd3XULrX0iFx7V+5m1RaKIXSBx n+4E6hMf2G6qvlpDsyOeLgdwnmMF0fWygDhiZHPZqJ2dfkxIVOBXq3L/xE5u0n9eRtO8 6HMp8zRL78azl2vMwIBuOV7feNoZU51aC4JhXlJc9dh06PmVErVKStpm66wFqtDaelgc qkbQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=j13+RdBhueYLBa+gZTK00atTbWK5kdZidNW/hkmhbwQ=; b=A3BNanA+xK9Khdx9zsXURPoIsHBfz27wbu8LAwS59DsSp8ww56naVYXB8em3aIV0Ok eDGQvoEzV1rWhyhl4PPXMCMkrNRxz9AeFMyxJQc6eCu+t/rnv/SnFI9s78VUocogiy0T mQec9wfsX8Op3ZaLylz4tIpjTbKzykcj/hM0oaRqICS074Xsb2gIeK6tvEuw1jFlb6lr uAaKtx70Uv4IkOPjMKKLNqddIA8zihz8Mg5x9ZUNTOKdOtst/7Ra+eXnJbgnJUheY+KS W6C2BSkk53O+13FqtvdWOW93tDauqOrvANWhKzLzKPV9Rxaxbnl9PElA/NNriO3gSjH9 Qi4w== X-Gm-Message-State: ACrzQf06F9I40tDPNUPGm90IQ7aBfP8VBp16i40peA+bhRWpRrejuAI4 EhRbdfiZGGikFnRVToUCYtLl8t6c0mc= X-Google-Smtp-Source: AMsMyM6Z5x00Xi5CAwkr3wcF2tRHOLJPjfrS373frSb9omJXx41PIPu5dtQdCFJ8FRJrVXBVQXaIlA== X-Received: by 2002:a05:6808:2023:b0:359:c826:8085 with SMTP id q35-20020a056808202300b00359c8268085mr10947774oiw.156.1667327180648; Tue, 01 Nov 2022 11:26:20 -0700 (PDT) Received: from server.roeck-us.net ([2600:1700:e321:62f0:329c:23ff:fee3:9d7c]) by smtp.gmail.com with ESMTPSA id k29-20020a056870959d00b0012c52bd4369sm4810311oao.19.2022.11.01.11.26.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 01 Nov 2022 11:26:19 -0700 (PDT) Sender: Guenter Roeck Date: Tue, 1 Nov 2022 11:26:16 -0700 From: Guenter Roeck To: Arnd Bergmann Cc: Linus Torvalds , Russell King , Masahiro Yamada , Linux Kernel Mailing List , Miguel Ojeda Subject: Re: Linux 6.1-rc3 Message-ID: <20221101182616.GA1328619@roeck-us.net> References: <20221101170015.GA1314742@roeck-us.net> <29d07648-29a9-432a-a666-f9c9e55c32f6@app.fastmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <29d07648-29a9-432a-a666-f9c9e55c32f6@app.fastmail.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 01, 2022 at 06:57:41PM +0100, Arnd Bergmann wrote: > On Tue, Nov 1, 2022, at 18:29, Linus Torvalds wrote: > > > IOW, I expect it is - once again - some random linker-generated stub > > that ends up causing problems, where the re-link stage ends up being > > unstable because of some subtle alignment issue or other. I think > > zero-sized symbols have often been involved. > > Linker-generated symbols are usually the cause, but those tend to > be fixed with the extra pass, and Guenter said that doing an extra > pass does not avoid the issue here. > > I have not tried to understand what the 73bbb94466fd patch actually does, > but as the description explains that it uses either 1-byte or > 2-byte encodings for some symbols, I suspect this is related to > the new problem here, possibly it gets into an oscillating state > where making the symbol table shorter causes a symbol to use the > longer representation in the next round, which in turn makes the > table longer again. > > What I've done in the past to debug this was to change > scripts/link-vmlinux.sh to use a larger number of steps, > mainly to see if it eventually converges, grows indefinitely > or oscillates. After that I would compare the temporary files > from the last two different steps to see which symbols are > actually different. Unfortunately, there is no built-in > debugging mode in kallsyms, so this is a rather manual process. > I have been doing the same, but so far I never encountered the oscillating situation. In those all I can find is that some symbol addresses keep changing, but I have not been able to track down the cause. The possible explanation above makes sense to me, but do you have an idea how I could track down what actually happens ? Thanks, Guenter