Re: [driver-core:driver-core-testing 1/4] include/linux/rcupdate.h:510:9: error: dereferencing pointer to incomplete type 'struct revocable_provider'

[Tzung-Bi Shih <tzungbi@kernel.org>]

On Wed, Feb 04, 2026 at 12:48:55AM +0800, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/driver-core/driver-core.git driver-core-testing
> head:   988357628c2c84e891f5992c4f5cfb31fb3bd27b
> commit: 4d7dc4d1a62dbb22b1178dddeeb7a22d0272df77 [1/4] revocable: Fix races in revocable_alloc() using RCU
> config: sparc-randconfig-001-20260203 (https://download.01.org/0day-ci/archive/20260204/202602040048.R81E8WaK-lkp@intel.com/config)
> compiler: sparc-linux-gcc (GCC) 8.5.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260204/202602040048.R81E8WaK-lkp@intel.com/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202602040048.R81E8WaK-lkp@intel.com/
> 
> All error/warnings (new ones prefixed by >>):
> 
>    In file included from drivers/base/revocable_test.c:19:
>    drivers/base/revocable_test.c: In function 'revocable_test_basic':
> >> include/linux/rcupdate.h:510:9: error: dereferencing pointer to incomplete type 'struct revocable_provider'
>      typeof(*p) *local = (typeof(*p) *__force)(p);   \
>    include/kunit/test.h:839:15: note: in definition of macro 'KUNIT_BASE_BINARY_ASSERTION'
>      const typeof(left) __left = (left);           \
>                   ^~~~
>    include/kunit/test.h:1056:2: note: in expansion of macro 'KUNIT_BINARY_PTR_ASSERTION'
>      KUNIT_BINARY_PTR_ASSERTION(test,           \
>      ^~~~~~~~~~~~~~~~~~~~~~~~~~
>    include/kunit/test.h:1053:2: note: in expansion of macro 'KUNIT_EXPECT_PTR_EQ_MSG'
>      KUNIT_EXPECT_PTR_EQ_MSG(test, left, right, NULL)
>      ^~~~~~~~~~~~~~~~~~~~~~~
>    drivers/base/revocable_test.c:40:2: note: in expansion of macro 'KUNIT_EXPECT_PTR_EQ'
>      KUNIT_EXPECT_PTR_EQ(test, unrcu_pointer(rp), NULL);
>      ^~~~~~~~~~~~~~~~~~~
>    include/linux/rcupdate.h:521:26: note: in expansion of macro '__unrcu_pointer'
>     #define unrcu_pointer(p) __unrcu_pointer(p, __UNIQUE_ID(rcu))
>                              ^~~~~~~~~~~~~~~
>    drivers/base/revocable_test.c:40:28: note: in expansion of macro 'unrcu_pointer'
>      KUNIT_EXPECT_PTR_EQ(test, unrcu_pointer(rp), NULL);
>                                ^~~~~~~~~~~~~

This warning seems to be reproducible only with older toolchain.

`struct revocable_provider` is an opaque type.  Possible fixes: make it
a non-opaque type, or move the type definition to revocable_internal.h
and include the header in the KUnit test, or don't use unrcu_pointer()
at all.

I'll address other reported comments first, and evaluate this later.