linux-kernel - Re: [PATCH 2/9] rcu: Remove superfluous local variable in rcu_init

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Message-ID: <20150307180337.GM5236@linux.vnet.ibm.com>
Date:	Sat, 7 Mar 2015 10:03:37 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Alexander Gordeev <agordeev@...hat.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/9] rcu: Remove superfluous local variable in
 rcu_init_geometry()

On Sat, Mar 07, 2015 at 06:03:37PM +0100, Alexander Gordeev wrote:
> Local variable 'n' mimics 'nr_cpu_ids' while the both are
> used within one function. There is no reason for 'n' to
> exist whatsoever.
> 
> Cc: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
> Signed-off-by: Alexander Gordeev <agordeev@...hat.com>

Good catch!  Could you please port this to branch rcu/next of
git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git?

							Thanx, Paul

> ---
>  kernel/rcu/tree.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 7588c7f..fb89630 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -3855,7 +3855,6 @@ static void __init rcu_init_geometry(void)
>  	ulong d;
>  	int i;
>  	int j;
> -	int n = nr_cpu_ids;
>  	int rcu_capacity[MAX_RCU_LVLS + 1];
> 
>  	/*
> @@ -3898,7 +3897,7 @@ static void __init rcu_init_geometry(void)
>  	 * the rcu_node masks.  Complain and fall back to the compile-
>  	 * time values if these limits are exceeded.
>  	 */
> -	if (n > rcu_capacity[MAX_RCU_LVLS])
> +	if (nr_cpu_ids > rcu_capacity[MAX_RCU_LVLS])
>  		panic("rcu_init_geometry: rcu_capacity[] is too small");
>  	else if (rcu_fanout_leaf < CONFIG_RCU_FANOUT_LEAF ||
>  		 rcu_fanout_leaf > sizeof(unsigned long) * 8) {
> @@ -3908,10 +3907,11 @@ static void __init rcu_init_geometry(void)
> 
>  	/* Calculate the number of rcu_nodes at each level of the tree. */
>  	for (i = 1; i <= MAX_RCU_LVLS; i++)
> -		if (n <= rcu_capacity[i]) {
> -			for (j = 0; j <= i; j++)
> -				num_rcu_lvl[j] =
> -					DIV_ROUND_UP(n, rcu_capacity[i - j]);
> +		if (nr_cpu_ids <= rcu_capacity[i]) {
> +			for (j = 0; j <= i; j++) {
> +				int cap = rcu_capacity[i - j];
> +				num_rcu_lvl[j] = DIV_ROUND_UP(nr_cpu_ids, cap);
> +			}
>  			rcu_num_lvls = i;
>  			for (j = i + 1; j <= MAX_RCU_LVLS; j++)
>  				num_rcu_lvl[j] = 0;
> @@ -3922,7 +3922,7 @@ static void __init rcu_init_geometry(void)
>  	rcu_num_nodes = 0;
>  	for (i = 0; i <= MAX_RCU_LVLS; i++)
>  		rcu_num_nodes += num_rcu_lvl[i];
> -	rcu_num_nodes -= n;
> +	rcu_num_nodes -= nr_cpu_ids;
>  }
> 
>  void __init rcu_init(void)
> -- 
> 1.8.3.1
> 

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