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From:   Kalle Valo <kvalo@codeaurora.org>
To:     Arnd Bergmann <arnd@arndb.de>
Cc:     linux-wireless <linux-wireless@vger.kernel.org>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: gcc-10: kernel stack is corrupted and fails to boot
References: <20200509120707.188595-1-arnd@arndb.de>
        <20200509120707.188595-2-arnd@arndb.de>
        <87v9l24qz6.fsf@kamboji.qca.qualcomm.com>
        <87r1vq4qev.fsf@kamboji.qca.qualcomm.com>
        <87d078tjl0.fsf_-_@kamboji.qca.qualcomm.com>
        <CAK8P3a1dxJAHCZ19=sPUkDi5wLWeJ6KKtD09Wmjqkz27TQN6Xw@mail.gmail.com>
        <87zhacrokl.fsf@kamboji.qca.qualcomm.com>
        <CAK8P3a1mMcpVE5kLv-krjL_ZjqfRXDK4e3fChzuom_QFRtTJqw@mail.gmail.com>
Date:   Wed, 13 May 2020 18:31:19 +0300
In-Reply-To: <CAK8P3a1mMcpVE5kLv-krjL_ZjqfRXDK4e3fChzuom_QFRtTJqw@mail.gmail.com>
        (Arnd Bergmann's message of "Wed, 13 May 2020 15:45:47 +0200")
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Arnd Bergmann <arnd@arndb.de> writes:

> On Wed, May 13, 2020 at 2:57 PM Kalle Valo <kvalo@codeaurora.org> wrote:
>>
>> Arnd Bergmann <arnd@arndb.de> writes:
>>
>> > On Wed, May 13, 2020 at 8:50 AM Kalle Valo <kvalo@codeaurora.org> wrote:
>> >>
>> >> Kalle Valo <kvalo@codeaurora.org> writes:
>> >
>> > At least if it fails reproducibly, it's probably not too hard to drill
>> > down further. Some ideas:
>> >
>> > * I'd first try to reproduce it in qemu. Since you don't even need
>> >   any user space or modules, I would simply try
>> >   $ qemu-system-x86_64 -nographic -monitor none -append
>> > "console=ttyS0" -serial stdio -smp 4 -kernel arch/x86/boot/bzImage
>> >   I tried it here with an x86 defconfig linux-next kernel but did not
>> >   run into the problem you described.
>>
>> Thanks, I'll try that but I expect it will take few days before I can do
>> it.
>>
>> > If you share your .config, I can try reproducing with that as well.
>> > Once there is a reproducer in qemu, it should be trivial to step
>> > through it using gdb.
>>
>> I have attached the .config I used with GCC 10.1. If you are able to
>> test it please do let me know how it went.
>
> Yes, I see the same problem now, but have not investigated
> any further.

Great, so it's not a problem due to my setup.

>> > * There are still two prerelease compiler versions on kernel.org,
>> >   from February and from April. You can try each one to see
>> >   if this was a recent regression. It's also possible that there is
>> >   a problem with my specific builds of gcc-10.1, and that the
>> >   compiler is actually fine for others.The gcc-10 packages in
>> >   Fedora/Debian/Ubuntu are probably better tested.
>>
>> I'm still using Ubuntu 16.04 so not sure how easy it is to find a
>> package for that, but maybe this is a good reason to finally my upgrade
>> my laptop :)
>
> I checked with the gcc-10 package from Ubuntu 20.04, same
> result as with my version, at least that indicates it's not my fault ;-)

That's good to know as well. And now I can delay my laptop upgrade even
more ;)

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