linux-kernel - Re: [PATCH v3 3/3] selftests: pidfd: add tests for PIDFD_SELF

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Message-ID: <20250501124646.GC4356@noisy.programming.kicks-ass.net>
Date: Thu, 1 May 2025 14:46:46 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: John Hubbard <jhubbard@...dia.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Shuah Khan <skhan@...uxfoundation.org>,
	Christian Brauner <christian@...uner.io>,
	Shuah Khan <shuah@...nel.org>,
	"Liam R . Howlett" <Liam.Howlett@...cle.com>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Vlastimil Babka <vbabka@...e.cz>, pedro.falcato@...il.com,
	linux-kselftest@...r.kernel.org, linux-mm@...ck.org,
	linux-fsdevel@...r.kernel.org, linux-api@...r.kernel.org,
	linux-kernel@...r.kernel.org, Oliver Sang <oliver.sang@...el.com>,
	seanjc@...gle.com
Subject: Re: [PATCH v3 3/3] selftests: pidfd: add tests for PIDFD_SELF_*

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*.


Seriously, I want to be able to do:

  cd tools/testing/selftests/foo; make

and have it just work. I would strongly suggest every subsystem to
reclaim their selftests and make it so again.

And on that, let me go merge the fixes I need to have x86 and futex
build without this headers shit.