Re: [PATCH v3 3/3] selftests: pidfd: add tests for PIDFD_SELF_*

Peter Zijlstra
2026-02-13T11:02:50Z

On Thu, May 01, 2025 at 02:46:46PM +0200, Peter Zijlstra wrote:
> On Thu, May 01, 2025 at 01:42:35PM +0200, Peter Zijlstra wrote:
> > On Wed, Oct 16, 2024 at 07:14:34PM -0700, John Hubbard wrote:
> > > On 10/16/24 3:06 PM, Lorenzo Stoakes wrote:
> > > > On Wed, Oct 16, 2024 at 02:00:27PM -0600, Shuah Khan wrote:
> > > > > On 10/16/24 04:20, Lorenzo Stoakes wrote:
> > > ...
> > > > > > diff --git a/tools/testing/selftests/pidfd/pidfd.h b/tools/testing/selftests/pidfd/pidfd.h
> > > > > > index 88d6830ee004..1640b711889b 100644
> > > > > > --- a/tools/testing/selftests/pidfd/pidfd.h
> > > > > > +++ b/tools/testing/selftests/pidfd/pidfd.h
> > > > > > @@ -50,6 +50,14 @@
> > > > > > #define PIDFD_NONBLOCK O_NONBLOCK
> > > > > > #endif
> > > > > > +/* System header file may not have this available. */
> > > > > > +#ifndef PIDFD_SELF_THREAD
> > > > > > +#define PIDFD_SELF_THREAD -100
> > > > > > +#endif
> > > > > > +#ifndef PIDFD_SELF_THREAD_GROUP
> > > > > > +#define PIDFD_SELF_THREAD_GROUP -200
> > > > > > +#endif
> > > > > > +
> > > > >
> > > > > As mentioned in my response to v1 patch:
> > > > >
> > > > > kselftest has dependency on "make headers" and tests include
> > > > > headers from linux/ directory
> > > >
> > > > Right but that assumes you install the kernel headers on the build system,
> > > > which is quite a painful thing to have to do when you are quickly iterating
> > > > on a qemu setup.
> > > >
> > > > This is a use case I use all the time so not at all theoretical.
> > > >
> > >
> > > This is turning out to be a fairly typical reaction from kernel
> > > developers, when presented with the "you must first run make headers"
> > > requirement for kselftests.
> > >
> > > Peter Zijlstra's "NAK NAK NAK" response [1] last year was the most
> > > colorful, so I'll helpfully cite it here. :)
> >
> > Let me re-try this.
> >
> > This is driving me insane. I've spend the past _TWO_ days trying to
> > build KVM selftests and I'm still failing.
> >
> > This is absolute atrocious crap and is costing me valuable time.
> >
> > Please fix this fucking selftests shit to just build. This is unusable
> > garbage.
>
> So after spending more time trying to remember how to debug Makefiles (I
> hate my life), I found that not only do I need this headers shit, the
> kvm selftests Makefile is actively broken if you use: make O=foo
>
> -INSTALL_HDR_PATH = $(top_srcdir)/usr
> +INSTALL_HDR_PATH = $(top_srcdir)/$(O)/usr
>
>
> And then finally, I can do:
>
> make O=foo headers_install
> make O=foo -C tools/testing/selftests/kvm/
>
> So yeah, thank you very much for wasting my time *AGAIN*.

And *AGAIN*.. this is still the state of things. Selftests are still
hopelessly broken and useless.

Maybe we should just delete the lot?