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Date:   Fri, 21 Oct 2022 11:00:40 -0700
From:   "Paul E. McKenney" <paulmck@kernel.org>
To:     Willy Tarreau <w@1wt.eu>
Cc:     Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] selftests/nolibc: add 7 tests for memcmp()
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On Fri, Oct 21, 2022 at 07:20:26PM +0200, Willy Tarreau wrote:
> On Fri, Oct 21, 2022 at 10:07:38AM -0700, Paul E. McKenney wrote:
> > > I see. In the worst case, a preliminary "make clean" will do it. We just
> > > need to decide what's the best solution for everyone (i.e. not waste too
> > > much time between tests while not getting misleading results by accident).
> > 
> > Maybe just document the careful/slow way, then people doing it more
> > frequently can do it the clever/fast way.
> > 
> > My guess is that the careful/slow is this:
> > 
> > 	pushd tools/include/nolibc
> > 	make clean
> > 	make
> > 	popd
> > 	pushd tools/testing/selftests/nolibc
> > 	make clean
> > 	make -j32 run
> > 
> > Or did I miss a turn in there somewhere?
> 
> It's even easier, you don't even need the clean phase in include/nolibc.
> I'm doing this and it's sufficient:
> 
>   make -C tools/testing/selftests/nolibc clean
>   make -C tools/testing/selftests/nolibc nolibc-test
>   tools/testing/selftests/nolibc/nolibc-test
> 
> Or for the test under QEMU, which involves a kernel build:
> 
>   make -C tools/testing/selftests/nolibc clean
>   make -C tools/testing/selftests/nolibc -j $(nproc) run
> 
> Where would you first look for such a hint ? Maybe the help output of
> the default "make" command could send as a hint that a clean is needed
> after patching nolibc and that could be sufficient ? I just want to make
> sure users don't waste their time trying to find what they could be doing
> wrong.

Maybe it suffices for the near term for me to put this information in
the signed tag for the pull request?

Another approach would be to remind about "make clean" in the case of
a test failure.  Or make test failure combined with a detected change
trigger an automatic "make clean" and a retry.  Or other schemes of
increasing complexity and fragility.  ;-)

Other approaches?

							Thanx, Paul