Re: [PATCH] selftests: more general make nesting support

[Shuah Khan]

On 8/5/20 1:36 PM, Greg Thelen wrote:
> On Tue, Jul 28, 2020 at 12:32 AM Greg Thelen <gthelen@xxxxxxxxxx> wrote:
> > selftests can be built from the toplevel kernel makefile (e.g. make
> > kselftest-all) or directly (make -C tools/testing/selftests all).
> >
> > The toplevel kernel makefile explicitly disables implicit rules with
> > "MAKEFLAGS += -rR", which is passed to tools/testing/selftests.  Some
> > selftest makefiles require implicit make rules, which is why
> > commit 67d8712dcc70 ("selftests: Fix build failures when invoked from
> > kselftest target") reenables implicit rules by clearing MAKEFLAGS if
> > MAKELEVEL=1.
> >
> > So far so good.  However, if the toplevel makefile is called from an
> > outer makefile then MAKELEVEL will be elevated, which breaks the
> > MAKELEVEL equality test.
> > Example wrapped makefile error:
> >    $ cat ~/Makefile
> >    all:
> >          $(MAKE) defconfig
> >          $(MAKE) kselftest-all
> >    $ make -sf ~/Makefile
> >      futex_wait_timeout.c /src/tools/testing/selftests/kselftest_harness.h   /src/tools/testing/selftests/kselftest.h ../include/futextest.h ../include/atomic.h ../include/logging.h -lpthread -lrt -o /src/tools/testing/selftests/futex/functional/futex_wait_timeout
> >    make[4]: futex_wait_timeout.c: Command not found
> >
> > Rather than checking $(MAKELEVEL), check for $(LINK.c), which is a more
> > direct side effect of "make -R".  This enables arbitrary makefile
> > nesting.
> >
> > Signed-off-by: Greg Thelen <gthelen@xxxxxxxxxx>
> > ---
> >   tools/testing/selftests/Makefile | 8 ++++----
> >   1 file changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
> > index 1195bd85af38..289a2e4b3f6f 100644
> > --- a/tools/testing/selftests/Makefile
> > +++ b/tools/testing/selftests/Makefile
> > @@ -84,10 +84,10 @@ endif
> >   # of the targets gets built.
> >   FORCE_TARGETS ?=
> >
> > -# Clear LDFLAGS and MAKEFLAGS if called from main
> > -# Makefile to avoid test build failures when test
> > -# Makefile doesn't have explicit build rules.
> > -ifeq (1,$(MAKELEVEL))
> > +# Clear LDFLAGS and MAKEFLAGS when implicit rules are missing.  This provides
> > +# implicit rules to sub-test Makefiles which avoids build failures in test
> > +# Makefile that don't have explicit build rules.
> > +ifeq (,$(LINK.c))
> >   override LDFLAGS =
> >   override MAKEFLAGS =
> >   endif
> > --
> > 2.28.0.rc0.142.g3c755180ce-goog
>
> Is there any feedback on this patch?  It's not high priority but something that
> will help me make more use of selftests.

No issues with the patch. I will apply it once the merge window ends.

thanks,
-- Shuah