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

[Neeraj Upadhyay <neeraju@codeaurora.org>]

On 7/1/2021 10:01 PM, Paul E. McKenney wrote:
> On Thu, Jul 01, 2021 at 08:24:32PM +0530, Neeraj Upadhyay wrote:
>>
>>
>> On 6/30/2021 7:38 PM, 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.
>>>
>>
>> Minor: Can we also add below statement?
>> "This patch doesn't introduce any functional change."
>>
>>> Signed-off-by: Liu Song <liu.song11@zte.com.cn>
> 
> Applied with the usual wordsmithing, including adding words to this
> effect, so thank you all!  I removed the obsolete chunk that Neeraj
> pointed out as well.
> 
> Please take a look and check to see if all is well.
> 

Looks good to me

Thanks
Neeraj

> 							Thanx, Paul
> 
> ------------------------------------------------------------------------
> 
> commit 9a6b5a10785f4d9b4f073736e6648fa3851882bd
> Author: Liu Song <liu.song11@zte.com.cn>
> Date:   Wed Jun 30 22:08:02 2021 +0800
> 
>      rcu: Use per_cpu_ptr to get the pointer of per_cpu variable
>      
>      There are a few remaining locations in kernel/rcu that still use
>      "&per_cpu()".  This commit replaces them with "per_cpu_ptr(&)", and does
>      not introduce any functional change..
>      
>      Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
>      Reviewed-by: Neeraj Upadhyay <neeraju@codeaurora.org>
>      Signed-off-by: Liu Song <liu.song11@zte.com.cn>
>      Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
> 
> diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
> index f9f52daacd1c..806160c44b17 100644
> --- a/kernel/rcu/tasks.h
> +++ b/kernel/rcu/tasks.h
> @@ -923,7 +923,7 @@ 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 a627a200a5ae..f42b98af3ed3 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -1290,7 +1290,7 @@ 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 a8d0fcf0826f..677ee3d8671b 100644
> --- a/kernel/rcu/tree_stall.h
> +++ b/kernel/rcu/tree_stall.h
> @@ -351,7 +351,7 @@ 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,
> 

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