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[209.85.218.44]) by smtp.gmail.com with ESMTPSA id d25sm4611897ejd.59.2021.05.02.14.14.56 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 02 May 2021 14:14:56 -0700 (PDT) Received: by mail-ej1-f44.google.com with SMTP id t4so5045156ejo.0 for ; Sun, 02 May 2021 14:14:56 -0700 (PDT) X-Received: by 2002:a2e:330f:: with SMTP id d15mr11126850ljc.251.1619989727157; Sun, 02 May 2021 14:08:47 -0700 (PDT) MIME-Version: 1.0 References: <20210501151538.145449-1-masahiroy@kernel.org> <3943bc020f6227c8801907317fc113aa13ad4bad.camel@perches.com> <20210502183030.GF10366@gate.crashing.org> <81a926a3bdb70debe3ae2b13655ea8d249fb9991.camel@perches.com> <20210502203253.GH10366@gate.crashing.org> In-Reply-To: <20210502203253.GH10366@gate.crashing.org> From: Linus Torvalds Date: Sun, 2 May 2021 14:08:31 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] Raise the minimum GCC version to 5.2 To: Segher Boessenkool Content-Type: text/plain; charset="UTF-8" X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Albert Ou , Catalin Marinas , Arnd Bergmann , Linux Kbuild mailing list , Greg Kroah-Hartman , Masahiro Yamada , Jonathan Corbet , Linux Doc Mailing List , linux-kernel , Miguel Ojeda , Will Deacon , Palmer Dabbelt , Paul Walmsley , Joe Perches , Paul Mackerras , linux-riscv@lists.infradead.org, Miguel Ojeda , linuxppc-dev , Linux ARM Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Sun, May 2, 2021 at 1:38 PM Segher Boessenkool wrote: > > The point is, you inconvenience users if you require a compiler version > they do not already have. Five years might be fine, but three years is > not. So this should be our main issue - not how old a compiler is, but how our compiler version limitations end up possibly making it harder for users to upgrade. Of course, one issue there is whether said users would have upgraded regardless - if you have a very old distribution, how likely are you to upgrade the kernel at all? But we do very much want to encourage people to upgrade their kernels, even if they might be running otherwise fairly old user space. If for no other reason than that it's good for our kernel coverage testing - the more different distributions people test a new kernel with, the better. And some of the less common architectures have their own issues, with distros possibly not even supporting them any more (if they ever did - considering all the odd ad-hoc cross-compiler builds people have had..) This is why "our clang support requires a very recent version of clang" is not relevant - distributions won't have old versions of clang anyway, and even if they do, such distributions will be gcc-based, so "build the kernel with clang" for that situation is perhaps an exercise for some intrepid person who is willing to do odd and unusual things, and might as well build their own clang version too. So I really wish people didn't get hung about some "three years ago" or similar. It's not relevant. What is relevant is what version of gcc various distributions actually have reasonably easily available, and how old and relevant the distributions are. We did decide that (just as an example) RHEL 7 was too old to worry about when we updated the gcc version requirement last time. Last year, Arnd and Kirill (maybe others were involved too) made a list of distros and older gcc versions. But I don't think anybody actually _maintains_ such a list. It would be perhaps interesting to have some way to check what compiler versions are being offered by different distros. Linus