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From: Guenter Roeck <linux@roeck-us.net>
To: Tobias Klauser <tklauser@distanz.ch>
Cc: Sven Schmidt <4sschmid@informatik.uni-hamburg.de>,
	Arnd Bergmann <arnd@arndb.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-kernel@vger.kernel.org, Ley Foon Tan <lftan@altera.com>,
	nios2-dev@lists.rocketboards.org,
	Sandra Loosemore <sandra@codesourcery.com>
Subject: Re: nios2 crash/hang in mainline due to 'lib: update LZ4 compressor module'
Date: Tue, 28 Feb 2017 09:57:25 -0800
Message-ID: <20170228175725.GB13455@roeck-us.net> (raw)
In-Reply-To: <20170228155331.GC27998@distanz.ch>

On Tue, Feb 28, 2017 at 04:53:31PM +0100, 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@roeck-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.
> 

I tried the following combinations of gcc and binutils:
	gcc 6.1.0; binutils 2.26.1
	gcc 6.3.0; binutils 2.25.1
	gcc 6.3.0; binutils 2.26.1
	gcc 6.3.0; binutils 2.27

I used buildroot 2017.02-rc3 to build the toolchains. All have the problem.

Another data point, confirming what you say above: I am relatively (99%)
sure that the code in question is not actually called. I added reference
counters to make sure that this is the case. Just the existence of the
LZ4 decompression code appears to be sufficient to cause the boot failure.
Weird.

I just hope this only affects nios2.

Guenter

      parent reply index

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-02-26 21:03 Guenter Roeck
2017-02-27 19:34 ` Sven Schmidt
2017-02-27 20:37   ` Guenter Roeck
2017-02-28 15:53 ` Tobias Klauser
2017-02-28 17:53   ` Sandra Loosemore
2017-02-28 18:14     ` Guenter Roeck
2017-03-01 18:58       ` Sven Schmidt
2017-03-01 19:45         ` Guenter Roeck
2017-03-02 16:38           ` Tobias Klauser
2017-03-03  3:04             ` Guenter Roeck
2017-03-07 12:46               ` Tobias Klauser
2017-03-08  4:12                 ` Guenter Roeck
2017-03-09 13:20                 ` Guenter Roeck
2017-03-09 14:43                   ` Tobias Klauser
2017-03-09 18:49                     ` Guenter Roeck
2017-03-01 22:50         ` Sandra Loosemore
2017-03-02 13:30           ` Tobias Klauser
2017-02-28 17:57   ` Guenter Roeck [this message]

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