Re: [PATCH] rcu: Use per_cpu_ptr to get the pointer of per_cpu variable

[Uladzislau Rezki <urezki@gmail.com>]

On Wed, Jun 30, 2021 at 10:08:02PM +0800, Liu Song wrote:
> From: Liu Song <liu.song11@zte.com.cn>
> 
> In rcu, most codes have used per_cpu_ptr to obtain per_cpu variable
> pointers. This patch adjusts a few codes that have not done so.
> 
> Signed-off-by: Liu Song <liu.song11@zte.com.cn>
> ---
>  kernel/rcu/tasks.h      | 2 +-
>  kernel/rcu/tree.c       | 4 ++--
>  kernel/rcu/tree_stall.h | 2 +-
>  3 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
> index 350ebf5051f9..0275217cb6e4 100644
> --- a/kernel/rcu/tasks.h
> +++ b/kernel/rcu/tasks.h
> @@ -875,7 +875,7 @@ static void trc_read_check_handler(void *t_in)
>  	// Allow future IPIs to be sent on CPU and for task.
>  	// Also order this IPI handler against any later manipulations of
>  	// the intended task.
> -	smp_store_release(&per_cpu(trc_ipi_to_cpu, smp_processor_id()), false); // ^^^
> +	smp_store_release(per_cpu_ptr(&trc_ipi_to_cpu, smp_processor_id()), false); // ^^^
>  	smp_store_release(&texp->trc_ipi_to_cpu, -1); // ^^^
>  }
>  
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 8e78b2430c16..5cab8e39a731 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -399,7 +399,7 @@ bool rcu_eqs_special_set(int cpu)
>  	int old;
>  	int new;
>  	int new_old;
> -	struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
> +	struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
>  
>  	new_old = atomic_read(&rdp->dynticks);
>  	do {
> @@ -1333,7 +1333,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
>  	 */
>  	jtsq = READ_ONCE(jiffies_to_sched_qs);
>  	ruqp = per_cpu_ptr(&rcu_data.rcu_urgent_qs, rdp->cpu);
> -	rnhqp = &per_cpu(rcu_data.rcu_need_heavy_qs, rdp->cpu);
> +	rnhqp = per_cpu_ptr(&rcu_data.rcu_need_heavy_qs, rdp->cpu);
>  	if (!READ_ONCE(*rnhqp) &&
>  	    (time_after(jiffies, rcu_state.gp_start + jtsq * 2) ||
>  	     time_after(jiffies, rcu_state.jiffies_resched) ||
> diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
> index 59b95cc5cbdf..990fdb793d57 100644
> --- a/kernel/rcu/tree_stall.h
> +++ b/kernel/rcu/tree_stall.h
> @@ -349,7 +349,7 @@ static void rcu_dump_cpu_stacks(void)
>  
>  static void print_cpu_stall_fast_no_hz(char *cp, int cpu)
>  {
> -	struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
> +	struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
>  
>  	sprintf(cp, "last_accelerate: %04lx/%04lx dyntick_enabled: %d",
>  		rdp->last_accelerate & 0xffff, jiffies & 0xffff,
> -- 
> 2.20.1
> 
To me it looks OK.

Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>

--
Vlad Rezki