From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 101735 invoked by alias); 25 Oct 2016 14:34:20 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Received: (qmail 101672 invoked by uid 89); 25 Oct 2016 14:34:20 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.5 required=5.0 tests=AWL,BAYES_00,KAM_LAZY_DOMAIN_SECURITY,RCVD_IN_DNSWL_LOW autolearn=no version=3.3.2 spammy=Riegel, seconded, riegel, effortlessly X-HELO: mx2.bahnhof.se X-Spam-Score: 0.668 Message-ID: <580F6D5E.6050600@gaisler.com> Date: Tue, 25 Oct 2016 14:34:00 -0000 From: Andreas Larsson User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 MIME-Version: 1.0 To: Adhemerval Zanella , Torvald Riegel CC: GNU C Library , David Miller , "software@gaisler.com" Subject: Re: Remove sparcv8 support References: <48cdf008-b66a-d411-a07a-5a38595978b9@linaro.org> <5809D90E.1090005@gaisler.com> <1477329945.7146.95.camel@localhost.localdomain> <8224de36-8a30-980c-697b-8e4cae481184@linaro.org> In-Reply-To: <8224de36-8a30-980c-697b-8e4cae481184@linaro.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-SW-Source: 2016-10/txt/msg00426.txt.bz2 On 2016-10-24 19:42, Adhemerval Zanella wrote: > > > On 24/10/2016 15:25, Torvald Riegel wrote: >> On Fri, 2016-10-21 at 10:59 +0200, Andreas Larsson wrote: >>> On 2016-10-20 21:47, Adhemerval Zanella wrote: >>>> The sparcv8 build is broken since GLIBC 2.23 due the new pthread >>>> barrier implementation [1] and since then there is no thread or >>>> interest on fixing it (Torvald has suggested some options on >>>> 2.23 release thread). It won't help with both new pthread rdlock >>>> and cond implementation, although I would expect that it relies >>>> on same atomic primitive that was not present for pthread barrier. >>>> >>>> AFAIK, recent commercial sparc chips from Oracle all supports >>>> sparcv9. The only somewhat recent sparc chip with just sparcv8 >>>> support is LEON4, which I really doubt it cares for glibc support. >>> >>> Hi! >>> >>> We do care about GLIBC support for many different LEON3 and LEON4 >>> systems. GLIBC support for sparcv8 is important for us and it is >>> important for our customers. Both LEON3 and LEON4 are continuously used >>> in new hardware designs. >> >> If you do care about it, it would be nice if you could (help) maintain >> sparcv8 (e.g., regularly testing most recent glibc on sparcv8, at the >> very least early during the freeze of each release). This ensures that >> you won't get surprises such as this one, when nobody else is spending >> resources on it. >> >>> We are not always using the latest version of GLIBC (the latest step we >>> took was to GLIBC 2.20), so unfortunately we missed this issue. We will >>> look into what the extent of the missing support is. Any pointers are >>> most welcome. >>> >>> Do you have a link to the suggested options on the 2.23 release thread? >>> I dug around a bit in the archives, but did not find it. >>> >>> (As a side note, most of the recent LEON3 and LEON4 chips have CAS >>> instruction support, but pure sparcv8 support is of course the baseline.) >> >> Yes, the lack of CAS is the major problem I am aware of. If the chips >> you mention do support CAS, then a patch that adds support for the >> CAS-based atomic operations in glibc would fix the barrier problem >> (because the generic barrier should just work). The patch would also >> have to add configure bits or whatever would be appropriate so that >> glibc can figure out whether it is supposed to be run on a sparcv8 with >> or without CAS. >> >> What about stopping support for plain sparcv8, and keeping to support >> sparcv8+CAS provided that we have a (group of) maintainer(s) for the >> latter that can tend to the minimal responsibilities of an arch >> maintainer and has the time to do that? > > At least the build for sparcv9-linux-gnu with -mcpu=leon3 finishes, > although I am not sure if it correctly runs on leon processors. > And I seconded Tovarld's suggestion about stop maintaining plain > sparcv8 and set sparcv8+CAS as the base supported sparc32. I have mixed feelings about this, but it is certainly better than throwing out sparcv8 outright. > As pointed out by David Miller, correct support for plain sparcv8 > could really only be provided with kernel supported. And when > it lands on kernel side, it should work effortlessly with a > sparcv8 + cas glibc build. What do you mean by "work effortlessly with a sparcv8 + cas glibc build"? Best regards, Andreas Larsson