Re: [PATCH] rethook: Use __rcu pointer for rethook::handler

[Masami Hiramatsu (Google) <mhiramat@kernel.org>]

On Fri, 24 Nov 2023 23:40:57 +0800
kernel test robot <lkp@intel.com> wrote:

> Hi Masami,
> 
> kernel test robot noticed the following build warnings:
> 
> [auto build test WARNING on linus/master]
> [also build test WARNING on v6.7-rc2 next-20231124]
> [If your patch is applied to the wrong git tree, kindly drop us a note.
> And when submitting patch, we suggest to use '--base' as documented in
> https://git-scm.com/docs/git-format-patch#_base_tree_information]
> 
> url:    https://github.com/intel-lab-lkp/linux/commits/Masami-Hiramatsu-Google/rethook-Use-__rcu-pointer-for-rethook-handler/20231124-090634
> base:   linus/master
> patch link:    https://lore.kernel.org/r/170078778632.209874.7893551840863388753.stgit%40devnote2
> patch subject: [PATCH] rethook: Use __rcu pointer for rethook::handler
> config: x86_64-randconfig-r113-20231124 (https://download.01.org/0day-ci/archive/20231124/202311241808.rv9ceuAh-lkp@intel.com/config)
> compiler: clang version 16.0.4 (https://github.com/llvm/llvm-project.git ae42196bc493ffe877a7e3dff8be32035dea4d07)
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231124/202311241808.rv9ceuAh-lkp@intel.com/reproduce)

Let me fix this issue. It seems that sparse with function pointer
needs a special care.

Thank you,

> 
> 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/202311241808.rv9ceuAh-lkp@intel.com/
> 
> sparse warnings: (new ones prefixed by >>)
> >> kernel/trace/rethook.c:51:9: sparse: sparse: incompatible types in comparison expression (different address spaces):
> >> kernel/trace/rethook.c:51:9: sparse:    void ( [noderef] __rcu * )( ... )
> >> kernel/trace/rethook.c:51:9: sparse:    void ( * )( ... )
>    kernel/trace/rethook.c:66:9: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    kernel/trace/rethook.c:66:9: sparse:    void ( [noderef] __rcu * )( ... )
>    kernel/trace/rethook.c:66:9: sparse:    void ( * )( ... )
>    kernel/trace/rethook.c:110:9: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    kernel/trace/rethook.c:110:9: sparse:    void ( [noderef] __rcu * )( ... )
>    kernel/trace/rethook.c:110:9: sparse:    void ( * )( ... )
>    kernel/trace/rethook.c:140:19: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    kernel/trace/rethook.c:140:19: sparse:    void ( [noderef] __rcu * )( ... )
>    kernel/trace/rethook.c:140:19: sparse:    void ( * )( ... )
>    kernel/trace/rethook.c:161:19: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    kernel/trace/rethook.c:161:19: sparse:    void ( [noderef] __rcu * )( ... )
>    kernel/trace/rethook.c:161:19: sparse:    void ( * )( ... )
>    kernel/trace/rethook.c:305:27: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    kernel/trace/rethook.c:305:27: sparse:    void ( [noderef] __rcu * )( ... )
>    kernel/trace/rethook.c:305:27: sparse:    void ( * )( ... )
> 
> vim +51 kernel/trace/rethook.c
> 
>     40	
>     41	/**
>     42	 * rethook_stop() - Stop using a rethook.
>     43	 * @rh: the struct rethook to stop.
>     44	 *
>     45	 * Stop using a rethook to prepare for freeing it. If you want to wait for
>     46	 * all running rethook handler before calling rethook_free(), you need to
>     47	 * call this first and wait RCU, and call rethook_free().
>     48	 */
>     49	void rethook_stop(struct rethook *rh)
>     50	{
>   > 51		rcu_assign_pointer(rh->handler, NULL);
>     52	}
>     53	
> 
> -- 
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki


-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>