linux-kernel - Re: [PATCH tip/core/rcu 1/1] rcu: Remove unused variable rcu_perf_writer

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Date:   Wed, 7 Aug 2019 16:41:25 -0700
From:   "Paul E. McKenney" <paulmck@...ux.ibm.com>
To:     Ethan Hansen <1ethanhansen@...il.com>
Cc:     rcu@...r.kernel.org, linux-kernel@...r.kernel.org,
        dave@...olabs.net, josh@...htriplett.org, rostedt@...dmis.org,
        mathieu.desnoyers@...icios.com, jiangshanlai@...il.com,
        joel@...lfernandes.org
Subject: Re: [PATCH tip/core/rcu 1/1] rcu: Remove unused variable
 rcu_perf_writer_state

On Wed, Aug 07, 2019 at 04:26:55PM -0700, Ethan Hansen wrote:
> The variable rcu_perf_writer_state is declared and initialized,
> but is never actually referenced. Remove it to clean code.
> 
> Signed-off-by: Ethan Hansen <1ethanhansen@...il.com>

Good eyes, thank you!  One question below.

							Thanx, Paul

> ---
>  kernel/rcu/rcuperf.c | 8 --------
>  1 file changed, 8 deletions(-)
> 
> diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c
> index 5a879d0..ff02936 100644
> --- a/kernel/rcu/rcuperf.c
> +++ b/kernel/rcu/rcuperf.c
> @@ -109,7 +109,6 @@
>  static unsigned long b_rcu_perf_writer_finished;
>  static DEFINE_PER_CPU(atomic_t, n_async_inflight);
>  
> -static int rcu_perf_writer_state;
>  #define RTWS_INIT		0
>  #define RTWS_ASYNC		1
>  #define RTWS_BARRIER		2

Does removing this variable also mean that the RTWS_* C preprocessor
macros are now unused?

> @@ -404,25 +403,20 @@ static void rcu_perf_async_cb(struct rcu_head *rhp)
>  			if (!rhp)
>  				rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
>  			if (rhp && atomic_read(this_cpu_ptr(&n_async_inflight)) < gp_async_max) {
> -				rcu_perf_writer_state = RTWS_ASYNC;
>  				atomic_inc(this_cpu_ptr(&n_async_inflight));
>  				cur_ops->async(rhp, rcu_perf_async_cb);
>  				rhp = NULL;
>  			} else if (!kthread_should_stop()) {
> -				rcu_perf_writer_state = RTWS_BARRIER;
>  				cur_ops->gp_barrier();
>  				goto retry;
>  			} else {
>  				kfree(rhp); /* Because we are stopping. */
>  			}
>  		} else if (gp_exp) {
> -			rcu_perf_writer_state = RTWS_EXP_SYNC;
>  			cur_ops->exp_sync();
>  		} else {
> -			rcu_perf_writer_state = RTWS_SYNC;
>  			cur_ops->sync();
>  		}
> -		rcu_perf_writer_state = RTWS_IDLE;
>  		t = ktime_get_mono_fast_ns();
>  		*wdp = t - *wdp;
>  		i_max = i;
> @@ -463,10 +457,8 @@ static void rcu_perf_async_cb(struct rcu_head *rhp)
>  		rcu_perf_wait_shutdown();
>  	} while (!torture_must_stop());
>  	if (gp_async) {
> -		rcu_perf_writer_state = RTWS_BARRIER;
>  		cur_ops->gp_barrier();
>  	}
> -	rcu_perf_writer_state = RTWS_STOPPING;
>  	writer_n_durations[me] = i_max;
>  	torture_kthread_stopping("rcu_perf_writer");
>  	return 0;
> -- 
> 1.8.3.1
>