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Re: [PATCH] mips: work-around R10k ll/sc errata
- From: Matt Turner <mattst88 at gmail dot com>
- To: "Joseph S. Myers" <joseph at codesourcery dot com>
- Cc: Ralf Baechle <ralf at linux-mips dot org>, libc-ports at sourceware dot org, Joshua Kinard <kumba at gentoo dot org>, Tom de Vries <tom at codesourcery dot com>, macro at linux-mips dot org
- Date: Thu, 28 Jul 2011 01:45:26 -0400
- Subject: Re: [PATCH] mips: work-around R10k ll/sc errata
- References: <email@example.com> <Pine.LNX.firstname.lastname@example.org> <BANLkTik66=75x5S7Ah1tuX6v4uTXOi2KVQ@mail.gmail.com> <Pine.LNX.email@example.com> <20110629180430.GA8274@linux-mips.org> <Pine.LNX.firstname.lastname@example.org> <BANLkTimrbv37ByhLOSVd_27JX14XpuMK6g@mail.gmail.com>
On Thu, Jun 30, 2011 at 1:17 PM, Matt Turner <email@example.com> wrote:
> On Wed, Jun 29, 2011 at 3:34 PM, Joseph S. Myers
> <firstname.lastname@example.org> wrote:
>> On Wed, 29 Jun 2011, Ralf Baechle wrote:
>>> > I didn't get any sense of consensus in the previous discussion (which
>>> > extended to at least Jan 2009) and several people there are rather more
>>> > expert in the MIPS variants than me. ?Perhaps someone would care to put
>>> > together a compilation of all the points raised and explain how the patch
>>> > addresses them or at least leaves things no worse off - in particular
>>> > detailing the circumstances (compiler options) under which the patch
>>> > results in any change to the code in glibc.
>>> Do you have a pointer to that old discussion?
>>> To summarize, I think the patch should be applied but the mentioned issues
>>> may deserve documentation.
>> Thanks. ?Maciej, do you have any comments on this latest patch?
>>> As more of a general question, Is there a point in eventually moving this
>>> sort of stuff into a VDSO? ?It would allow the kernel to provide suitable
>>> definitions of common LL/SC constructs without having to modify glibc.
>> I don't think it's easy for GCC to generate calls to a vDSO directly from
>> __sync_* intrinsics, and __sync_* intrinsics (or in future an
>> implementation of the C1X and C++0X atomics functionality using new
>> versions of those intrinsics) are what we want code to use.
> I don't mean to speak for Maciej, but in the last email link you
> provided, both he and Daniel Jacobowitz seem to be in favor of a patch
> that only affected the code when specifically requested.
>> Please don't activate this workaround on builds that won't run on an R10K
So it doesn't look like we should be expecting a response from Maciej
The patch only modifies behavior when specifically prompted, namely
-march=r10k, and Ralf says it should be applied. I don't see any