Re: [PATCH 3/4] selftests/lib.mk: set PWD from CURDIR to avoid wrong extmod path

[Li Wang]

On Mon, Mar 30, 2026 at 10:30:25PM -0700, Andrew Morton wrote:
> On Tue, 31 Mar 2026 12:01:55 +0800 Li Wang <liwang@xxxxxxxxxx> wrote:
> 
> > When running selftests from the kernel top-level (e.g. make kselftest-all),
> > sub-makes might still inherit the caller's PWD from the environment.
> > 
> > Some selftests use $(PWD) in recursive kbuild invocations, which can
> > then incorrectly resolve to the kernel top directory instead of the
> > current test directory.
> > 
> > In that case, kbuild may generate an external-module wrapper Makefile in
> > the wrong location, potentially clobbering the top-level Makefile and
> > causing recursive include failures ("Too many open files").
> > 
> > Export PWD := $(CURDIR) in selftests/lib.mk so $(PWD) always matches the
> > actual current selftest directory.
> > 
> > Reported-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Li Wang <liwang@xxxxxxxxxx>
> 
> I couldn't clearly figure out what I was doing to cause kbuild to
> destroy my top-level Makefile.  It happened three times and it wasn't
> fun so I Stopped Doing That.  
> 
> I tried a bunch of things *without* this patch and of course, Makefile
> is still intact.  So I cannot confirm or deny, sorry.
> 
> I've switched my script so I'll henceforth be running -j100, shall keep
> an eye on things.

No problem, actually I wasn't able to reproduce it, the patch just worked
out based on your description. We can kick out it from patchset unless
someone confirm it is needed.

-- 
Regards,
Li Wang