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Date:   Thu, 29 Apr 2021 00:35:10 -0300
From:   Marcelo Schmitt <marcelo.schmitt1@gmail.com>
To:     Masahiro Yamada <masahiroy@kernel.org>
Cc:     kunit-dev@googlegroups.com,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        andersonreisrosa@gmail.com
Subject: Re: Running kunit_tool on unclean trees
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On 04/26, Masahiro Yamada wrote:
> On Sun, Apr 25, 2021 at 4:05 AM Marcelo Schmitt
> <marcelo.schmitt1@gmail.com> wrote:
> >
> > Hi, a friend and I were chasing bug 205219 [1] listed in Bugzilla.
> > We step into something a little bit different when trying to reproduce
> > the buggy behavior. In our try, compilation failed with a message form
> > make asking us to clean the source tree. We couldn't run kunit_tool
> > after compiling the kernel for x86, as described by Ted in the
> > discussion pointed out by the bug report.
> >
> > Steps to reproduce:
> >
> > 0) Run kunit_tool
> > $ ./tools/testing/kunit/kunit.py run
> > Works fine with a clean tree.
> >
> > 1) Compile the kernel for some architecture (we did it for x86_64).
> >
> > 2) Run kunit_tool again
> > $ ./tools/testing/kunit/kunit.py run
> > Fails with a message form make asking us to clean the source tree.
> 
> This is probably because
> tools/testing/kunit/kunit_kernel.py
> runs make with O= option.
> 
> 
> 
> > Removing the clean source tree check from the top-level Makefile gives
> > us a similar error to what was described in the bug report. We see that
> > after running `git clean -fdx` kunit_tool runs nicely again. However,
> > this is not a real solution since some kernel binaries are erased by git.
> >
> > We also had a look into the commit messages of Masahiro Yamada but
> > couldn't quite grasp why the check for the tree to be clean was added.
> > We could invest more time in this issue but actually don't know how to
> > proceed. We'd be glad to receive any comment about it. We could also try
> > something else if it's a too hard issue for beginners.
> 
> I think you are talking about the following error message.
> 
> ***
> *** The source tree is not clean, please run 'make mrproper'
> *** in /home/masahiro/ref/linux
> ***
> 

Yes, I wanted to mean that message.

> 
> 
> Kbuild checks if the source tree is clean
> before starting the out-of-tree build
> because the out-of-tree build relies on VPATH.
> 
> This check has existed for a long time. (at least more than a decade)
> 
> If Kbuild started the O= build with a dirty source tree,
> some stale generated source files would have been remaining.
> (some *.c and *.h are generated by scripts)
> 
> Then, Kbuild would wrongly use stale source files in srctree
> instead of generating new ones in objtree.
> 

I see, we better try not to break stuff.
Well, I can't think of any means of fixing bug 205219 so we're probably
going to start looking forward to work on fixes for another one.


Thanks,

Marcelo

> 
> 
> 
> 
> > [1]: https://bugzilla.kernel.org/show_bug.cgi?id=205219
> >
> >
> > Best Regards,
> >
> > Marcelo
> 
> 
> 
> --
> Best Regards
> Masahiro Yamada
> 
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