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From: Sven Schmidt <>
To: Guenter Roeck <>
Cc: Arnd Bergmann <>,
	Andrew Morton <>,, Ley Foon Tan <>,
Subject: Re: nios2 crash/hang in mainline due to 'lib: update LZ4 compressor module'
Date: Mon, 27 Feb 2017 20:34:55 +0100
Message-ID: <20170227193455.GA25066@bierbaron.springfield.local> (raw)
In-Reply-To: <>

Hi Guenter,

thanks for your testing!

I must admit, I'm fairly new to kernel development and a little overwhelmed by all that tools used.
So I do not really know how to reproduce your test using your script. I installed qemu from the master branch and buildroot.
Unfortunately, that's the point I'm stuck. I would be grateful if you provide me some lead how to continue.
Would I make the kernel using ARCH=nios2 and a defconf and pass it to qemu? What arguments do I provide to that script
(especially, the machine param)?

On Sun, Feb 26, 2017 at 01:03:38PM -0800, Guenter Roeck 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.

So, seems like it's the decompressor? Which decompression code do you mean exactly? LZ4_decompress_fast/_safe/_generic?
Since the decompression functions worked fine in all previous tests, and this is a problem during boot, my first guess would
be the lib/decompress_unlz4.c, providing the functions for decompressing a lz4-compressed kernel image.
But then it should only result in problems when the kernel image is compressed, wouldn't it?

> 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
> Qemu is from qemu mainline or qemu v2.8 with nios2 patches applied.
> I tried to track down the problem, with no success. Just the presence
> of the LZ4 code seems to be sufficient to cause the problem; I have
> no idea why that would be the case.

Maybe there's someone who has an idea and/or is experiencing similar issues. Hopefully, we can track this down.

> Please let me know if there is anything I can do to help tracking down
> the problem.
> Thanks,
> Guenter
> ---
> # bad: [c4f3f22eddc982d247ffe2a6690c3e4a5c46dd09] Merge tag 'linux-kselftest-4.11-rc1' of git://
> # good: [9e314890292c0dd357eadef6a043704fa0b4c157] Merge tag 'openrisc-for-linus' of git://
> git bisect start 'HEAD' '9e31489'
> # bad: [7067739df23ffd641ca99c967830e0ed2ba39eab] Merge branch 'i2c/for-4.11' of git://
> git bisect bad 7067739df23ffd641ca99c967830e0ed2ba39eab
> # good: [c5adae9583ef6985875532904160c6bf9f07b453] lib: add CONFIG_TEST_SORT to enable self-test of sort()
> git bisect good c5adae9583ef6985875532904160c6bf9f07b453
> # bad: [edccb59429657b09806146339e2b27594c1d1da0] Merge tag 'fbdev-v4.11' of git://
> git bisect bad edccb59429657b09806146339e2b27594c1d1da0
> # good: [72db33355c1431fefcabb06c9c25705e8226eed5] fbdev: ssd1307fb: Start to use gpiod API for reset gpio
> git bisect good 72db33355c1431fefcabb06c9c25705e8226eed5
> # bad: [95330473636e5e4546f94874c957c3be66bb2140] checkpatch: remove false unbalanced braces warning
> git bisect bad 95330473636e5e4546f94874c957c3be66bb2140
> # bad: [69c78423b8f439b077929410bdf8f88e7031b891] lib/lz4: remove back-compat wrappers
> git bisect bad 69c78423b8f439b077929410bdf8f88e7031b891
> # bad: [e23d54e48346e775be53b3cc25a95d65da960393] lib/decompress_unlz4: change module to work with new LZ4 module version
> git bisect bad e23d54e48346e775be53b3cc25a95d65da960393
> # bad: [4e1a33b105ddf201f66dcc44490c6086a25eca0b] lib: update LZ4 compressor module
> git bisect bad 4e1a33b105ddf201f66dcc44490c6086a25eca0b
> # good: [8893f519330bb073a49c5b4676fce4be6f1be15d] lib/test_sort.c: make it explicitly non-modular
> git bisect good 8893f519330bb073a49c5b4676fce4be6f1be15d
> # first bad commit: [4e1a33b105ddf201f66dcc44490c6086a25eca0b] lib: update LZ4 compressor module

Thank you,


  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 [this message]
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

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