From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from madras.collabora.co.uk (madras.collabora.co.uk [46.235.227.172]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7661A1E501; Tue, 23 May 2023 10:27:19 +0000 (UTC) Received: from [IPV6:2405:201:0:21ea:e49:10dd:40c0:e842] (unknown [IPv6:2405:201:0:21ea:e49:10dd:40c0:e842]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (No client certificate requested) (Authenticated sender: shreeya) by madras.collabora.co.uk (Postfix) with ESMTPSA id 9FE4A6606E75; Tue, 23 May 2023 11:27:09 +0100 (BST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1684837632; bh=/cZpY/DKk5fAZOo6SiYRERzxSUjyx353F4endTRRSo4=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=btnZAAQPlKxgroncGmTp3yjgSRL5MgT6cZvPcPX4larqhFPob0jvaz5BeIOl18OPl PZd+Pbf8QIJY5xSHJ6y57ZzWy3167LwYDoLqg3ENVXMBaBsDVZ5R3fJBJDu+ePfeKi Frh1Mc313r6OdfIUrP1trhhPaqCXTlOWfwecZgDZwd3tkNNp36VndrF8XXwgYVYMGc MjoDNgU78Aza3z8wgCJhMaffnZFAWFhqdDVzLFYgmivitI403nWwNZbb2oNXJeQKDG ZLUcrBeZT51Pw5gLMhdvqLf60ndM2RWjKiSgmILIOKmpI7cU/v+nf5+KAw3wn1SGmQ 3fyLvdowXCRyw== Message-ID: Date: Tue, 23 May 2023 15:57:06 +0530 Precedence: bulk X-Mailing-List: kernelci@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Subject: Re: [PATCH v4] Makefile.compiler: replace cc-ifversion with compiler-specific macros Content-Language: en-US To: Nick Desaulniers , Masahiro Yamada , Greg KH , Maksim Panchenko , =?UTF-8?Q?Ricardo_Ca=c3=b1uelo?= Cc: Michal Marek , Linux Kernel Mailing List , clang-built-linux , Bill Wendling , Nathan Chancellor , regressions@lists.linux.dev, "gustavo.padovan@collabora.com" , Guillaume Charles Tucker , denys.f@collabora.com, kernelci@lists.linux.dev References: <17c91d37-7d9c-0df4-2438-2b30ca0b5777@collabora.com> <878rdlk9bi.fsf@rcn-XPS-13-9305.i-did-not-set--mail-host-address--so-tickle-me> <875y8ok9b5.fsf@rcn-XPS-13-9305.i-did-not-set--mail-host-address--so-tickle-me> <87353ok78h.fsf@rcn-XPS-13-9305.i-did-not-set--mail-host-address--so-tickle-me> <2023052247-bobtail-factsheet-d104@gregkh> From: Shreeya Patel In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Hi Nick and Masahiro, On 23/05/23 01:22, Nick Desaulniers wrote: > On Mon, May 22, 2023 at 9:52 AM Greg KH wrote: >> On Mon, May 22, 2023 at 12:09:34PM +0200, Ricardo Cañuelo wrote: >>> On vie, may 19 2023 at 08:57:24, Nick Desaulniers wrote: >>>> It could be; if the link order was changed, it's possible that this >>>> target may be hitting something along the lines of: >>>> https://isocpp.org/wiki/faq/ctors#static-init-order i.e. the "static >>>> initialization order fiasco" >>>> >>>> I'm struggling to think of how this appears in C codebases, but I >>>> swear years ago I had a discussion with GKH (maybe?) about this. I >>>> think I was playing with converting Kbuild to use Ninja rather than >>>> Make; the resulting kernel image wouldn't boot because I had modified >>>> the order the object files were linked in. If you were to randomly >>>> shuffle the object files in the kernel, I recall some hazard that may >>>> prevent boot. >>> I thought that was specifically a C++ problem? But then again, the >>> kernel docs explicitly say that the ordering of obj-y goals in kbuild is >>> significant in some instances [1]: >> Yes, it matters, you can not change it. If you do, systems will break. >> It is the only way we have of properly ordering our init calls within >> the same "level". > Ah, right it was the initcall ordering. Thanks for the reminder. > > (There's a joke in there similar to the use of regexes to solve a > problem resulting in two new problems; initcalls have levels for > ordering, but we still have (unexpressed) dependencies between calls > of the same level; brittle!). > > +Maksim, since that might be relevant info for the BOLT+Kernel work. > > Ricardo, > https://elinux.org/images/e/e8/2020_ELCE_initcalls_myjosserand.pdf > mentions that there's a kernel command line param `initcall_debug`. > Perhaps that can be used to see if > 5750121ae7382ebac8d47ce6d68012d6cd1d7926 somehow changed initcall > ordering, resulting in a config that cannot boot? Here are the links to Lava jobs ran with initcall_debug added to the kernel command line. 1. Where regression happens (5750121ae7382ebac8d47ce6d68012d6cd1d7926) https://lava.collabora.dev/scheduler/job/10417706 2. With a revert of the commit 5750121ae7382ebac8d47ce6d68012d6cd1d7926 https://lava.collabora.dev/scheduler/job/10418012 Thanks, Shreeya Patel