Re: [paulmck-rcu:rcu/next 19/19] kernel/rcu/rcuscale.c:340:20: error: use of undeclared identifier 'get_rcu_tasks_trace_gp_kthread'; did you mean 'show_rcu_tasks_trace_gp_kthread'?

[Yujie Liu <yujie.liu@intel.com>]

Hi Paul,

On Thu, May 18, 2023 at 07:11:33PM -0700, Paul E. McKenney wrote:
> On Fri, May 19, 2023 at 02:30:11AM +0800, kernel test robot wrote:
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git rcu/next
> > head:   9bb839a83e1bbbfd4f7f20827aafd0a39fad00c7
> > commit: 9bb839a83e1bbbfd4f7f20827aafd0a39fad00c7 [19/19] rcuscale: Measure grace-period kthread CPU time
> > config: x86_64-randconfig-a001
> > compiler: clang version 14.0.6 (https://github.com/llvm/llvm-project f28c006a5895fc0e329fe15fead81e37457cb1d1)
> > reproduce (this is a W=1 build):
> >         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> >         chmod +x ~/bin/make.cross
> >         # https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git/commit/?id=9bb839a83e1bbbfd4f7f20827aafd0a39fad00c7
> >         git remote add paulmck-rcu https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
> >         git fetch --no-tags paulmck-rcu rcu/next
> >         git checkout 9bb839a83e1bbbfd4f7f20827aafd0a39fad00c7
> >         # save the config file
> >         mkdir build_dir && cp config build_dir/.config
> >         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=x86_64 olddefconfig
> >         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash kernel/rcu/
> > 
> > If you fix the issue, kindly add following tag where applicable
> > | Reported-by: kernel test robot <lkp@intel.com>
> > | Closes: https://lore.kernel.org/oe-kbuild-all/202305190259.Rm6JC6Nz-lkp@intel.com/
> > 
> > All errors (new ones prefixed by >>):
> > 
> > >> kernel/rcu/rcuscale.c:340:20: error: use of undeclared identifier 'get_rcu_tasks_trace_gp_kthread'; did you mean 'show_rcu_tasks_trace_gp_kthread'?
> >            .rso_gp_kthread = get_rcu_tasks_trace_gp_kthread,
> >                              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >                              show_rcu_tasks_trace_gp_kthread
> >    kernel/rcu/rcu.h:642:20: note: 'show_rcu_tasks_trace_gp_kthread' declared here
> >    static inline void show_rcu_tasks_trace_gp_kthread(void) {}
> >                       ^
> > >> kernel/rcu/rcuscale.c:340:20: error: incompatible function pointer types initializing 'struct task_struct *(*)(void)' with an expression of type 'void (void)' [-Werror,-Wincompatible-function-pointer-types]
> >            .rso_gp_kthread = get_rcu_tasks_trace_gp_kthread,
> >                              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >    2 errors generated.
> 
> Apologies for the hassle!  Does the diff below help at your end?

Sorry for the late reply. We noticed that rcu/next branch was respined
and the diff below has been applied. We tested the new head commit
60901dadfadc ("rcuscale: Measure grace-period kthread CPU time")
and the build error is gone. Thanks.

Tested-by: Yujie Liu <yujie.liu@intel.com>

> 
> 						Thaxn, Paul
> 
> ------------------------------------------------------------------------
> 
> diff --git a/include/linux/rcupdate_trace.h b/include/linux/rcupdate_trace.h
> index 3a5a322939b6..eda493200663 100644
> --- a/include/linux/rcupdate_trace.h
> +++ b/include/linux/rcupdate_trace.h
> @@ -87,9 +87,7 @@ static inline void rcu_read_unlock_trace(void)
>  void call_rcu_tasks_trace(struct rcu_head *rhp, rcu_callback_t func);
>  void synchronize_rcu_tasks_trace(void);
>  void rcu_barrier_tasks_trace(void);
> -# ifdef CONFIG_RCU_SCALE_TEST
>  struct task_struct *get_rcu_tasks_trace_gp_kthread(void);
> -# endif
>  #else
>  /*
>   * The BPF JIT forms these addresses even when it doesn't call these
>