Re: [PATCH] rcuscale: fix building with RCU_TINY

[Paul E. McKenney]

On Fri, Jun 09, 2023 at 02:05:14PM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@xxxxxxxx>
> 
> Both the CONFIG_TASKS_RCU and CONFIG_TASKS_RUDE_RCU options
> are broken when RCU_TINY is enabled as well, as some functions
> are missing a declaration.
> 
> In file included from kernel/rcu/update.c:649:
> kernel/rcu/tasks.h:1271:21: error: no previous prototype for 'get_rcu_tasks_rude_gp_kthread' [-Werror=missing-prototypes]
>  1271 | struct task_struct *get_rcu_tasks_rude_gp_kthread(void)
>       |                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> kernel/rcu/rcuscale.c:330:27: error: 'get_rcu_tasks_rude_gp_kthread' undeclared here (not in a function); did you mean 'get_rcu_tasks_trace_gp_kthread'?
>   330 |         .rso_gp_kthread = get_rcu_tasks_rude_gp_kthread,
>       |                           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>       |                           get_rcu_tasks_trace_gp_kthread
> 
> In file included from /home/arnd/arm-soc/kernel/rcu/update.c:649:
> kernel/rcu/tasks.h:1113:21: error: no previous prototype for 'get_rcu_tasks_gp_kthread' [-Werror=missing-prototypes]
>  1113 | struct task_struct *get_rcu_tasks_gp_kthread(void)
>       |                     ^~~~~~~~~~~~~~~~~~~~~~~~
> 
> Also, building with CONFIG_TASKS_RUDE_RCU but not CONFIG_TASKS_RCU is
> broken because of some missing stub functions:
> 
> kernel/rcu/rcuscale.c:322:27: error: 'tasks_scale_read_lock' undeclared here (not in a function); did you mean 'srcu_scale_read_lock'?
>   322 |         .readlock       = tasks_scale_read_lock,
>       |                           ^~~~~~~~~~~~~~~~~~~~~
>       |                           srcu_scale_read_lock
> kernel/rcu/rcuscale.c:323:27: error: 'tasks_scale_read_unlock' undeclared here (not in a function); did you mean 'srcu_scale_read_unlock'?
>   323 |         .readunlock     = tasks_scale_read_unlock,
>       |                           ^~~~~~~~~~~~~~~~~~~~~~~
>       |                           srcu_scale_read_unlock
> 
> Move the declarations outside of the RCU_TINY #ifdef and duplicate the
> shared stub functions to address all of the above.
> 
> Fixes: 88d7ff818f0ce ("rcuscale: Add RCU Tasks Rude testing")
> Fixes: 755f1c5eb416b ("rcuscale: Measure RCU Tasks Trace grace-period kthread CPU time")
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>

Queued and pushed, thank you!

I clearly need to improve my Kconfig coverage here...

							Thanx, Paul

> ---
>  kernel/rcu/rcu.h      | 14 ++++++++------
>  kernel/rcu/rcuscale.c | 13 +++++++++++--
>  2 files changed, 19 insertions(+), 8 deletions(-)
> 
> diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
> index 9829d8161b213..5befd8780dcd3 100644
> --- a/kernel/rcu/rcu.h
> +++ b/kernel/rcu/rcu.h
> @@ -505,18 +505,20 @@ void rcu_async_relax(void);
>  void rcupdate_announce_bootup_oddness(void);
>  #ifdef CONFIG_TASKS_RCU_GENERIC
>  void show_rcu_tasks_gp_kthreads(void);
> -# ifdef CONFIG_TASKS_RCU
> -struct task_struct *get_rcu_tasks_gp_kthread(void);
> -# endif // # ifdef CONFIG_TASKS_RCU
> -# ifdef CONFIG_TASKS_RUDE_RCU
> -struct task_struct *get_rcu_tasks_rude_gp_kthread(void);
> -# endif // # ifdef CONFIG_TASKS_RUDE_RCU
>  #else /* #ifdef CONFIG_TASKS_RCU_GENERIC */
>  static inline void show_rcu_tasks_gp_kthreads(void) {}
>  #endif /* #else #ifdef CONFIG_TASKS_RCU_GENERIC */
>  void rcu_request_urgent_qs_task(struct task_struct *t);
>  #endif /* #else #ifdef CONFIG_TINY_RCU */
>  
> +#ifdef CONFIG_TASKS_RCU
> +struct task_struct *get_rcu_tasks_gp_kthread(void);
> +#endif // # ifdef CONFIG_TASKS_RCU
> +
> +#ifdef CONFIG_TASKS_RUDE_RCU
> +struct task_struct *get_rcu_tasks_rude_gp_kthread(void);
> +#endif // # ifdef CONFIG_TASKS_RUDE_RCU
> +
>  #define RCU_SCHEDULER_INACTIVE	0
>  #define RCU_SCHEDULER_INIT	1
>  #define RCU_SCHEDULER_RUNNING	2
> diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
> index 5ce3b4e7ce711..a0eae19007088 100644
> --- a/kernel/rcu/rcuscale.c
> +++ b/kernel/rcu/rcuscale.c
> @@ -316,11 +316,20 @@ static struct rcu_scale_ops tasks_ops = {
>   * Definitions for RCU-tasks-rude scalability testing.
>   */
>  
> +static int tasks_rude_scale_read_lock(void)
> +{
> +	return 0;
> +}
> +
> +static void tasks_rude_scale_read_unlock(int idx)
> +{
> +}
> +
>  static struct rcu_scale_ops tasks_rude_ops = {
>  	.ptype		= RCU_TASKS_RUDE_FLAVOR,
>  	.init		= rcu_sync_scale_init,
> -	.readlock	= tasks_scale_read_lock,
> -	.readunlock	= tasks_scale_read_unlock,
> +	.readlock	= tasks_rude_scale_read_lock,
> +	.readunlock	= tasks_rude_scale_read_unlock,
>  	.get_gp_seq	= rcu_no_completed,
>  	.gp_diff	= rcu_seq_diff,
>  	.async		= call_rcu_tasks_rude,
> -- 
> 2.39.2
>