Re: nios2 crash/hang in mainline due to 'lib: update LZ4 compressor module'

[Guenter Roeck]

On Tue, Feb 28, 2017 at 10:53:56AM -0700, Sandra Loosemore wrote:
> On 02/28/2017 08:53 AM, Tobias Klauser wrote:
> >(adding Sandra Loosemore to Cc due to possible relation to gcc/binutils
> >for nios2)
> >
> >On 2017-02-26 at 22:03:38 +0100, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> >>Hi Sven,
> >>
> >>my qemu test for nios2 started failing with commit 4e1a33b105dd ("lib:
> >>update LZ4 compressor module"). The test hangs early during boot before
> >>any console output is seen. Reverting the offending patch as well as the
> >>subsequent lz4 related patches fixes the problem. Disabling CONFIG_RD_LZ4
> >>and with it other LZ4 options also fixes it (as does adding "return -EINVAL;"
> >>at the top of the LZ4 decompression code). For reference, bisect log
> >>is attached.
> >>
> >>I tried with buildroot toolchains using gcc 6.1.0 as well as 6.3.0
> >>and binutils 2.26.1. Scripts used to run the tests are available at
> >>https://github.com/groeck/linux-build-test/tree/master/rootfs/nios2.
> >>Qemu is from qemu mainline or qemu v2.8 with nios2 patches applied.
> >
> >Looks like this is somehow related to gcc/binutils. Using GCC 4.8.3 and
> >binutils 2.24.51 (both from from Sourcery CodeBench Lite 2014.05) I can
> >get a kernel booting on latest master branch. AFAICT, none of the
> >LZ4_decompress_* functions are called during boot.
> >
> >However, using a self-built GCC 7.0 (20161127) and binutils 2.27 I can
> >reproduce the problem you see using the instructions Guenter provided in
> >the reply to Sven.
> >
> >I'll try to dig a bit deeper from here on. Any suggestions on what to
> >look out for wrt the differences between the gcc/binutils version are
> >welcome of course.
> 
> This message doesn't give me enough context to know what is going on,
> especially without seeing the rest of the thread.  Generally speaking,
> Mentor recommends you use one of our stable releases instead of trying to
> roll your own from mainline sources.  As an upstream binutils and gcc
> maintainer I do try my best to look at bug reports for those components, but
> I need a reproducible standalone testcase and specific versions of the
> different components involved.
> 
The problem is also seen with Sourcery CodeBench Lite 2016.11-32 (gcc 6.2.0,
binutils 2.26.51). I can provide additional details if needed, but we don't
have a well enough understanding of the problem to be able to provide a
reduced size test case. The test used to reproduce the problem is available
at https://github.com/groeck/linux-build-test/tree/master/rootfs/nios2,
run on the ToT linux kernel.

Guenter