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SubjectRe: [PATCH rcu 01/20] rcu-tasks: Fix warning for unused tasks_rcu_exit_srcu
On Thu, Mar 30, 2023 at 03:47:07PM -0700, Paul E. McKenney wrote:
> The tasks_rcu_exit_srcu variable is used only by kernels built
> with CONFIG_TASKS_RCU=y, but is defined for all kernesl with
> CONFIG_TASKS_RCU_GENERIC=y. Therefore, in kernels built with
> CONFIG_TASKS_RCU_GENERIC=y but CONFIG_TASKS_RCU=n, this gives
> a "defined but not used" warning.
>
> This commit therefore moves this variable under CONFIG_TASKS_RCU.
>
> Link: https://lore.kernel.org/oe-kbuild-all/202303191536.XzMSyzTl-lkp@intel.com/
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
> ---
> kernel/rcu/tasks.h | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
> index bfb5e1549f2b..185358c2f08d 100644
> --- a/kernel/rcu/tasks.h
> +++ b/kernel/rcu/tasks.h
> @@ -136,8 +136,10 @@ static struct rcu_tasks rt_name = \
> .kname = #rt_name, \
> }
>
> +#ifdef CONFIG_TASKS_RCU
> /* Track exiting tasks in order to allow them to be waited for. */
> DEFINE_STATIC_SRCU(tasks_rcu_exit_srcu);
> +#endif

Reviewed-by: Frederic Weisbecker <frederic@kernel.org>

BTW should exit_tasks_rcu_start/stop() be defined as static inline stubs
whenever !CONFIG_TASKS_RCU ? Currently:

* if CONFIG_TASKS_RCU_GENERIC=n, the stubs are as usual (static inline)

* if CONFIG_TASKS_RCU_GENERIC=y && CONFIG_TASKS_RCU=n, then the stubs are
defined as empty linked function (is the compiler smart enough to remove
the empty call?)

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