Re: [ammarfaizi2-block:paulmck/linux-rcu/dev 82/84] kernel/rcu/tree.c:2678:17: error: implicit declaration of function 'rcu_tasks_classic_qs'

["Paul E. McKenney" <paulmck@kernel.org>]

On Tue, Mar 08, 2022 at 09:15:35PM +0800, kernel test robot wrote:
> tree:   https://github.com/ammarfaizi2/linux-block paulmck/linux-rcu/dev
> head:   fb8d1afe45bd6fcb50dff8bac4636725358fde94
> commit: c8c42c80febd4e6d346f7f62958300eb8205aa31 [82/84] rcu-tasks: Make Tasks RCU account for userspace execution
> config: arm-oxnas_v6_defconfig (https://download.01.org/0day-ci/archive/20220308/202203082147.h7DGjo3z-lkp@intel.com/config)
> compiler: arm-linux-gnueabi-gcc (GCC) 11.2.0
> 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://github.com/ammarfaizi2/linux-block/commit/c8c42c80febd4e6d346f7f62958300eb8205aa31
>         git remote add ammarfaizi2-block https://github.com/ammarfaizi2/linux-block
>         git fetch --no-tags ammarfaizi2-block paulmck/linux-rcu/dev
>         git checkout c8c42c80febd4e6d346f7f62958300eb8205aa31
>         # save the config file to linux build tree
>         mkdir build_dir
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross O=build_dir ARCH=arm SHELL=/bin/bash
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
> 
> All errors (new ones prefixed by >>):
> 
>    kernel/rcu/tree.c: In function 'rcu_sched_clock_irq':
> >> kernel/rcu/tree.c:2678:17: error: implicit declaration of function 'rcu_tasks_classic_qs' [-Werror=implicit-function-declaration]
>     2678 |                 rcu_tasks_classic_qs(current, false);
>          |                 ^~~~~~~~~~~~~~~~~~~~
>    cc1: some warnings being treated as errors

Good catch!  Does the patch below fix this for you?

							Thanx, Paul

------------------------------------------------------------------------

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index e7c39c200e2b0..1a32036c918cd 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -196,6 +196,7 @@ void synchronize_rcu_tasks_rude(void);
 void exit_tasks_rcu_start(void);
 void exit_tasks_rcu_finish(void);
 #else /* #ifdef CONFIG_TASKS_RCU_GENERIC */
+#define rcu_tasks_classic_qs(t, preempt) do { } while (0)
 #define rcu_tasks_qs(t, preempt) do { } while (0)
 #define rcu_note_voluntary_context_switch(t) do { } while (0)
 #define call_rcu_tasks call_rcu