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

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Date:   Tue, 28 Feb 2017 16:53:31 +0100
From:   Tobias Klauser <tklauser@...tanz.ch>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Sven Schmidt <4sschmid@...ormatik.uni-hamburg.de>,
        Arnd Bergmann <arnd@...db.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, Ley Foon Tan <lftan@...era.com>,
        nios2-dev@...ts.rocketboards.org,
        Sandra Loosemore <sandra@...esourcery.com>
Subject: Re: nios2 crash/hang in mainline due to 'lib: update LZ4 compressor
 module'

(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@...ck-us.net> 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.

Thanks
Tobias