From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AIpwx4/GkIi+LU+s1k9hOvvBfXOx0dAdKSsO6lUs4Y8ygzZbq4RifOnRs9oSLqDyMwX3wQkrGz76 ARC-Seal: i=1; a=rsa-sha256; t=1522834212; cv=none; d=google.com; s=arc-20160816; b=hH3Q7cA7QHnky+cOzeO9OT9qK691fAsBn+ELaXPZSnOW+svqaRupYMn1atjRWpb3Hb IBjxwix/XToMo663dG8YFaXjHAViDZP1AvXy23uZea2r2axKnCj05p/i9bDSlpall4IA nqHIHFT9NpbCkPbMIpRNGQWgVzYlRiKw2aQveHFb3iuK3q92sZ0fxxnhX7z7o0pYPJvt ZYndp7hlf9j1Z0hcU72Ne65Qrs0uZPQ8EKQv/FoQVgwomDfcKXxdQ4KoWlbvrkm2xJSo i8oJd3FNYPAx1RYQ7lvjEsosdtq7GTHZ4DKo9dEA26b8aeuUMSOX/27gLuEAHV4K7l5V CU1A== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date:dkim-signature :arc-authentication-results; bh=fFIBP+ahGIcIb6n4Cq6YRk3HktQqqw1YlPcY7vp3ac0=; b=dC2ZGCw28AGAHsKmImfXU3D6Wc8Y+ic9EZcM9x2K8yuH/dnvaxscL9jExDlabjN1SL IPNbV6nMebg16hjMIrHDyUaGfeDilExQPIEvYuVGu96BTMUnW066kHGtdqEfTJA9u5qE dv7EfnID3jDjMArdxlQvOEue+ThFJ9doBJvc5lp3aJylMXhmRpEvXADEeUl9e1+N09uw 3c2yatgBhwUjrZHkglylNkdXPHq4FbgBu4GpXF5d0P3MP4HzKiyrrp0uQkG0QFaaal4o T3A0IzmdtsmHMXDXijAIrG4W1/QDazkBDjBQ9knZRv0EgoAtNhUAQ6RR2GfKXkf92HWF RbrA== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b=LgF9+Vbe; spf=pass (google.com: best guess record for domain of peterz@infradead.org designates 198.137.202.133 as permitted sender) smtp.mailfrom=peterz@infradead.org Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b=LgF9+Vbe; spf=pass (google.com: best guess record for domain of peterz@infradead.org designates 198.137.202.133 as permitted sender) smtp.mailfrom=peterz@infradead.org Date: Wed, 4 Apr 2018 11:30:07 +0200 From: Peter Zijlstra To: Matthias Kaehlcke Cc: Ingo Molnar , Linus Torvalds , Linux Kernel Mailing List , Thomas Gleixner , Andrew Morton , James Y Knight , Chandler Carruth , Stephen Hines , Nick Desaulniers , Kees Cook , Guenter Roeck , Greg Hackmann , Greg Kroah-Hartman Subject: Re: [GIT PULL] x86/build changes for v4.17 Message-ID: <20180404093007.GI4082@hirez.programming.kicks-ass.net> References: <20180402095033.nfzcrmxvpm46dhbl@gmail.com> <20180403085904.GY4082@hirez.programming.kicks-ass.net> <20180403095118.rpf7tj577dppvx7d@gmail.com> <20180403180658.GE87376@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180403180658.GE87376@google.com> User-Agent: Mutt/1.9.3 (2018-01-21) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcSW1wb3J0YW50Ig==?= X-GMAIL-THRID: =?utf-8?q?1596675801568391777?= X-GMAIL-MSGID: =?utf-8?q?1596807406723415347?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Tue, Apr 03, 2018 at 11:06:58AM -0700, Matthias Kaehlcke wrote: > Yes, Chrome OS R67 (currently dev, soon beta) will ship a kernel built > with Clang for multiple x86 Chromebooks. But there are still _known_ miscompilations.... > Given that it takes time for distributions to roll out new compiler > versions I would like to ask for a longer period of 'exemption' from > asm-goto for Clang, at least if it isn't an actual burden for the > kernel, like preventing important features from being added. An ideal > time would be after the next-next LTS version, if this is considered > too far out, after the next LTS version would be the second best time > IMO. Let me be clear, this is *not* to delay the implementation of > asm-goto, but to facilitate the use of Clang-built kernels by other > projects and distributions, as well as automated builds of upstream > kernels with Clang, without requiring necessarily the very latest > version of Clang or extra patches. I don't think that's sane or realistic, given that the very latest clang is _known_ to miscompile the kernel. How can you want to support older compilers that are therefore also known to not work correctly. Next LTS is still a fair way out, if we take LTS release to be every ~5 releases, the next one would be ~.19, that's still 3 releases hence. That's a _long_ time. I don't see the point in waiting that long for a compiler that doesn't work even without asm-goto.