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Re: Math errors
- From: Alistair Francis <alistair23 at gmail dot com>
- To: Jonathan Nieder <jrnieder at gmail dot com>
- Cc: Jim Wilson <jimw at sifive dot com>, Joseph Myers <joseph at codesourcery dot com>, GNU C Library <libc-alpha at sourceware dot org>
- Date: Tue, 14 Jan 2020 14:57:14 +1000
- Subject: Re: Math errors
- References: <CAKmqyKNQXGVriszbWvfyAys-8aoe-ShWDqXr9H7fMs9M8Htm5A@mail.gmail.com> <alpine.DEB.2.21.1912302227040.17472@digraph.polyomino.org.uk> <alpine.DEB.2.21.1912302229041.17472@digraph.polyomino.org.uk> <CAKmqyKO6tkQjTkP85z3PoX13Y+Xgd1S6zZZo0HjZQsSMW=E=9A@mail.gmail.com> <CAFyWVaYqcvNuLM9oE2GYGN82CBGGHbYJz=cZQYGJNySzJzUbpA@mail.gmail.com> <CAKmqyKOfm8pcJYPkZyp89WL+t7WMnmRJL3rXALYokj1A3pdu8g@mail.gmail.com> <CAFyWVaYFRAVd7bWTGpw-iqYn3iwEVwT7B=PQpjaD_gOC+=Pcbg@mail.gmail.com> <CAKmqyKOSqsUeADkB3KDCxj67AHix7jrexDetRcG-xLbQVr3E7g@mail.gmail.com> <20200114022856.GA24302@google.com>
On Tue, Jan 14, 2020 at 12:28 PM Jonathan Nieder <jrnieder@gmail.com> wrote:
>
> Hi,
>
> Alistair Francis wrote:
> > On Wed, Jan 8, 2020 at 4:29 AM Jim Wilson <jimw@sifive.com> wrote:
> >> On Mon, Jan 6, 2020 at 5:33 PM Alistair Francis <alistair23@gmail.com> wrote:
>
> >>> I have the latest 5.4.x kernel, I'm not sure if that has it or not.
> >>
> >> I don't know. I don't follow linux kernel development that closely.
> >> But the failures I sometimes see are test-fenv and test-fpucw which I
> >> don't see in your list.
> >>
> >> I only run glibc testsuite on hardware though, and I've only been
> >> testing rv64gc support. I haven't tried qemu. In the RISC-V software
> >> meeting this morning, Palmer mentioned that there are some known
> >> RISC-V qemu FP bugs, for instance fcmp doesn't set the FP reg dirty
> >> bit when an exception flag is set, which could cause a testcase
> >> failure if a context switch happens at the wrong time. This could
> >
> > I have noticed that running the tests not in parallel gives much better results
>
> Interesting. Can you provide full "uname -r" output? What Linux
> distribution do you use?
I don't have it in front of me right now, but it's 5.4.x and built
from OpenEmbedded.
>
> I suspect the issue Jim mentioned is fixed by v5.3-rc5~12^2~1 ("riscv:
> Correct the initialized flow of FP register", 2019-08-14), which you
> would already have. That said, the 5.5-rc series has some more fp reg
> handling fixes.
It could be a QEMU issue:
https://lists.gnu.org/archive/html/qemu-devel/2020-01/msg02455.html
Alistair
>
> [...]
> >> Someone will have to look at the rv32gc math failures, and keep an
> >> open mind that they could be glibc, qemu, gcc, linux kernel, etc
> >
> > Yeah, that's what I was thinking. There are only a few math tests left
> > failing, so it's not too bad. Thanks for the information Jim.
>
> That it appears more often with threading does suggest some kind of FP
> register leakage.
>
> Thanks and happy hunting,
> Jonathan