[BUG] Build failure in next-20261007 and next-20261008

[Paul E. McKenney]

Hello!

Building a kernel on CentOS Stream 9 from next-20261007 and next-20261008
(and maybe others?)  on an x86 or arm64 system results in a strange
build failure featuring:

WARNING: Unable to reopen jobserver read-side pipe: FileNotFoundError(2, 'No such file or directory')

However, a kernel really is built, and restarting the build immediately
after a failure succeeds and generates a good kernel.  Doing a "make
clean" causes the next build to fail, as does changing a sufficient
number of source files.

My reproducer is:

tools/testing/selftests/rcutorture/bin/kvm.sh --build-only --allcpus --configs TREE02 --trust-make

But a simple "make -jN" suffices.

Bisection converged on this commit:

48ebe1cbbeb5 ("kbuild: compress the kernel with pigz if available")

Reverting this commit gets rid of the bug.

The bug does not happen on my ancient Ubuntu laptop.

The failing systems have a pigz command (which complains bitterly when
run without arguments), and the immune system does not.  On the failing
systems, "pigz --version" gives me "pigz 2.5".

Do I need a specific version of pigz?  Does this commit need a
version-number check?  Are my systems pigz-intolerant?  ;-)

Less flippantly, is this a known problem?  If not, what debugging
information can I provide?

							Thanx, Paul