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

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

[Shuah Khan]

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directory - it appears they are out of date and lead to maintenance problems.

thanks,
-- Shuah

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

[Marco Elver]

> On Wed, 15 Apr 2026 at 18:39, Shuah Khan <skhan@linuxfoundation.org> 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 directory - it appears they are out of date and lead to maintenance problems.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?

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

[Lorenzo Stoakes]

On Wed, Apr 15, 2026 at 10:39:05AM -0600, Shuah Khan wrote:
> All,
>
> I am sending this email to you all because you touched tools/testing/shared
> and its sub directories and show up in

We need to add these to somewhere in MAINTAINERS...

>
> get_maintainer.pl -f tools/testing/shared/ output
>
> rbtree compile failed as it couldn't find urcu.h

Presumably liburcu is not installed.

>
> 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

$ wc -l tools/testing/shared/linux/rcupdate.h
12 tools/testing/shared/linux/rcupdate.h
$ wc -l include/linux/rcupdate.h
1196 include/linux/rcupdate.h

Umm, no?

> 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.

Because they're not duplicates of one another? One is a wrapper around urcu,
your problem is you don't have that library installed.

Unless I'm missing something?

>
> thanks,
> -- Shuah

Thanks, Lorenzo

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

[Shuah Khan]

On 4/15/26 10:50, Lorenzo Stoakes wrote:
> On Wed, Apr 15, 2026 at 10:39:05AM -0600, Shuah Khan wrote:
>> All,
>>
>> I am sending this email to you all because you touched tools/testing/shared
>> and its sub directories and show up in
> 
> We need to add these to somewhere in MAINTAINERS...
> 
>>
>> get_maintainer.pl -f tools/testing/shared/ output
>>
>> rbtree compile failed as it couldn't find urcu.h
> 
> Presumably liburcu is not installed.
> 
>>
>> 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
> 
> $ wc -l tools/testing/shared/linux/rcupdate.h
> 12 tools/testing/shared/linux/rcupdate.h
> $ wc -l include/linux/rcupdate.h
> 1196 include/linux/rcupdate.h
> 
> Umm, no?

My bad - I looked at diff wrong. You can ignore the duplicate headers
stuff.

> 
>> 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.
> 
> Because they're not duplicates of one another? One is a wrapper around urcu,
> your problem is you don't have that library installed.

It would have been nice to find a different name for this header and also
have some information about its purpose? It says nothing.


/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _RCUPDATE_H
#define _RCUPDATE_H

#include <urcu.h>

#define rcu_dereference_raw(p) rcu_dereference(p)
#define rcu_dereference_protected(p, cond) rcu_dereference(p)
#define rcu_dereference_check(p, cond) rcu_dereference(p)
#define RCU_INIT_POINTER(p, v)  do { (p) = (v); } while (0)

#endif

That solved one problem - still seeing others:

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 rbtree_test.c:11:
../../../lib/rbtree_test.c: In function ‘rbtree_test_init’:
../../../lib/rbtree_test.c:402:17: error: implicit declaration of function ‘kmalloc_objs’; did you mean ‘kzalloc_obj’? [-Wimplicit-function-declaration]
   402 |         nodes = kmalloc_objs(*nodes, nnodes);
       |                 ^~~~~~~~~~~~
       |                 kzalloc_obj
../../../lib/rbtree_test.c:402:15: error: assignment to ‘struct test_node *’ from ‘int’ makes pointer from integer without a cast [-Wint-conversion]
   402 |         nodes = kmalloc_objs(*nodes, nnodes);
       |               ^

thanks,
-- Shuah