Re: Duplicate headers in tools/testing/shared directory diverged - rcupdate.h

[Marco Elver]

> On Wed, 15 Apr 2026 at 18:39, Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx> wrote:
>
> All,
>
> I am sending this email to you all because you touched tools/testing/shared
> and its sub directories and show up in
>
> get_maintainer.pl -f tools/testing/shared/ output
>
> rbtree compile failed as it couldn't find urcu.h
>
> cc -I../shared -I. -I../../include -I../../arch/x86/include -I../../../lib -g -Og -Wall -D_LGPL_SOURCE -fsanitize=address -fsanitize=undefined    -c -o rbtree_test.o rbtree_test.c
> In file included from ../shared/shared.h:11,
>                   from rbtree_test.c:9:
> ../shared/linux/rcupdate.h:5:10: fatal error: urcu.h: No such file or directory
>      5 | #include <urcu.h>
>        |          ^~~~~~~~
> compilation terminated.
>
> This sent me down the path to look at the duplicate headers in tools/testing/shared
> especially rcupdate.h which is under tools/testing/shared/linux
>
> It appears this file is an exact copy of include/linux/rcupdate.h and now it
> diverged. Why do we have these duplicate headers here in this shared
> directory - it appears they are out of date and lead to maintenance problems.

I tripped over this recently, too - my archeology concluded that
<urcu.h> comes from a user space library (which I installed to fix the
breakage):

  % dpkg -S /usr/include/x86_64-linux-gnu/urcu.h
  liburcu-dev:amd64: /usr/include/x86_64-linux-gnu/urcu.h

This version of rcupdate.h originally came out of
tools/testing/radix-tree/ and was moved in 74579d8dab47 ("tools:
separate out shared radix-tree components").

Maybe the targets that depend on liburcu should be configured to build
only when it's installed?