linux-kernel - Re: [PATCH] xarray: port tests to kunit

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Message-ID: <CAMuHMdVUZQTgLpa9L9R117s39nEqxdGy=CJLyLQaTv_16EDhZg@mail.gmail.com>
Date: Thu, 30 Jan 2025 15:24:45 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: "Liam R. Howlett" <Liam.Howlett@...cle.com>
Cc: Sidhartha Kumar <sidhartha.kumar@...cle.com>, akpm@...ux-foundation.org, 
	christophe.leroy@...roup.eu, justinstitt@...gle.com, 
	linux-kernel@...r.kernel.org, linux-m68k@...ts.linux-m68k.org, 
	linuxppc-dev@...ts.ozlabs.org, llvm@...ts.linux.dev, maddy@...ux.ibm.com, 
	morbo@...gle.com, mpe@...erman.id.au, nathan@...nel.org, naveen@...nel.org, 
	ndesaulniers@...gle.com, npiggin@...il.com, 
	Matthew Wilcox <willy@...radead.org>, linux-mm@...ck.org
Subject: Re: [PATCH] xarray: port tests to kunit

Hi Liam,

On Thu, 30 Jan 2025 at 15:06, Liam R. Howlett <Liam.Howlett@...cle.com> wrote:
> * Geert Uytterhoeven <geert@...ux-m68k.org> [250130 08:26]:
> > On Thu, 30 Jan 2025 at 13:52, Liam R. Howlett <Liam.Howlett@...cle.com> wrote:
> > > * Geert Uytterhoeven <geert@...ux-m68k.org> [250130 03:21]:
> > > > On Wed, 29 Jan 2025 at 23:26, Liam R. Howlett <Liam.Howlett@...cle.com> wrote:
> > > > > I've never used the kunit testing of xarray and have used the userspace
> > > > > testing instead, so I can't speak to the obscure invocation as both
> > > > > commands seem insanely long and obscure to me.
> > > >
> > > > The long and obscure command line is a red herring: a simple
> > > > "modprobe test_xarray" is all it takes...
> > >
> > > That command worked before too...
> >
> > Exactly, great!
> >
> > > > > You should look at the userspace testing (that this broke) as it has
> > > > > been really useful in certain scenarios.
> > > >
> > > > BTW, how do I even build tools/testing/radix-tree?
> > > > "make tools/help" doesn't show the radix-tree test.
> > > > "make tools/all" doesn't seem to try to build it.
> > > > Same for "make kselftest-all".
> > >
> > > make
> >
> > Where?
> > > > BTW, how do I even build tools/testing/radix-tree?
>                                 ^^^^^^^^^^^^^^^^^^^^^^^

Things like "make -C drivers/net/ethernet/" stopped working
ca. 20y ago.

> > > Or look at the make file and stop guessing.  Considering how difficult
> >
> > There is no Makefile referencing tools/testing/radix-tree or the
> > radix-tree subdir. That's why I asked...
> >
> > Oh, I am supposed to run make in tools/testing/radix-tree/?
> > What a surprise!
> >
> > Which is a pain when building in a separate output directory, as you
> > cannot just do "make -C tools/testing/radix-tree" there, but have to
> > type the full "make -C tools/testing/radix-tree O=..." (and optionally
> > ARCH=... and CROSS_COMPILE=...; oh wait, these are ignored :-( in the
> > source directory instead...
>
> I'll await your patch to link all this together.  Please Cc the authors.

I gave it a try for kselftests a few years ago.
https://lore.kernel.org/all/20190114135144.26096-1-geert+renesas@glider.be
Unfortunately only one patch was applied...

> > > it is to get m68k to build, you should probably know how to read a
> > > makefile.
> >
> > Like all other kernel cross-compilation? Usually you don't even have
> > to know where your cross-compiler is living:
> >
> >     make ARCH=m68k
>
> Ignoring that I had to make a config - which asked challenging
> questions...

make ARCH=m68k defconfig

> And ignoring the steps to get m68k compiler...

apt install gcc-m68k-linux-gnu?

> > > > When trying the above, and ignoring failures due to missing packages
> > > > on my host:
> > > >   - there are several weird build errors,
> > > >   - this doesn't play well with O=,
> > > >   - lots of scary warnings when building for 32-bit,
> > > >   - ...
> > > >
>
> In file included from ./include/linux/sched.h:12,
>                  from arch/m68k/kernel/asm-offsets.c:15:
> ./arch/m68k/include/asm/current.h:7:30: error: invalid register name for ‘current’
>     7 | register struct task_struct *current __asm__("%a2");

Which compiler are you using?

> > > > At least the kunit tests build (and run[1] ;-) most of the time...
> > >
> > > Do they?  How about you break something in xarray and then try to boot
> > > the kunit, or try to boot to load that module.
> >
> > If you break the kernel beyond the point of booting, you can indeed
> > not run any test modules...
>
> Which is extremely easy when you are changing code that runs so early in
> the boot.
>
> My code found a compiler issue because it's the first function that
> returns a boolean.  This is stupid.

Sorry. I don't understand this comment.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds