linux-kernel - Re: [PATCH tip/core/rcu 02/14] rcu: Consolidate duplicate callback-list initialization

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Message-ID: <20120615204214.GG31184@leaf>
Date:	Fri, 15 Jun 2012 13:42:14 -0700
From:	Josh Triplett <josh@...htriplett.org>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com,
	dipankar@...ibm.com, akpm@...ux-foundation.org,
	mathieu.desnoyers@...ymtl.ca, niv@...ibm.com, tglx@...utronix.de,
	peterz@...radead.org, rostedt@...dmis.org, Valdis.Kletnieks@...edu,
	dhowells@...hat.com, eric.dumazet@...il.com, darren@...art.com,
	fweisbec@...il.com, patches@...aro.org,
	"Paul E. McKenney" <paul.mckenney@...aro.org>
Subject: Re: [PATCH tip/core/rcu 02/14] rcu: Consolidate duplicate
 callback-list initialization

On Fri, Jun 15, 2012 at 01:13:03PM -0700, Paul E. McKenney wrote:
> From: "Paul E. McKenney" <paul.mckenney@...aro.org>
> 
> There are a couple of open-coded initializations of the rcu_data
> structure's RCU callback list.  This commit therefore consolidates
> them into a new init_callback_list() function.
> 
> Signed-off-by: Paul E. McKenney <paul.mckenney@...aro.org>
> Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

Reviewed-by: Josh Triplett <josh@...htriplett.org>

>  kernel/rcutree.c |   23 ++++++++++++++---------
>  1 files changed, 14 insertions(+), 9 deletions(-)
> 
> diff --git a/kernel/rcutree.c b/kernel/rcutree.c
> index 0f04480..d938671 100644
> --- a/kernel/rcutree.c
> +++ b/kernel/rcutree.c
> @@ -936,6 +936,18 @@ check_for_new_grace_period(struct rcu_state *rsp, struct rcu_data *rdp)
>  }
>  
>  /*
> + * Initialize the specified rcu_data structure's callback list to empty.
> + */
> +static void init_callback_list(struct rcu_data *rdp)
> +{
> +	int i;
> +
> +	rdp->nxtlist = NULL;
> +	for (i = 0; i < RCU_NEXT_SIZE; i++)
> +		rdp->nxttail[i] = &rdp->nxtlist;
> +}
> +
> +/*
>   * Advance this CPU's callbacks, but only if the current grace period
>   * has ended.  This may be called only from the CPU to whom the rdp
>   * belongs.  In addition, the corresponding leaf rcu_node structure's
> @@ -1327,8 +1339,6 @@ static void
>  rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp,
>  			  struct rcu_node *rnp, struct rcu_data *rdp)
>  {
> -	int i;
> -
>  	/*
>  	 * Orphan the callbacks.  First adjust the counts.  This is safe
>  	 * because ->onofflock excludes _rcu_barrier()'s adoption of
> @@ -1368,9 +1378,7 @@ rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp,
>  	}
>  
>  	/* Finally, initialize the rcu_data structure's list to empty.  */
> -	rdp->nxtlist = NULL;
> -	for (i = 0; i < RCU_NEXT_SIZE; i++)
> -		rdp->nxttail[i] = &rdp->nxtlist;
> +	init_callback_list(rdp);
>  }
>  
>  /*
> @@ -2404,16 +2412,13 @@ static void __init
>  rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
>  {
>  	unsigned long flags;
> -	int i;
>  	struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
>  	struct rcu_node *rnp = rcu_get_root(rsp);
>  
>  	/* Set up local state, ensuring consistent view of global state. */
>  	raw_spin_lock_irqsave(&rnp->lock, flags);
>  	rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo);
> -	rdp->nxtlist = NULL;
> -	for (i = 0; i < RCU_NEXT_SIZE; i++)
> -		rdp->nxttail[i] = &rdp->nxtlist;
> +	init_callback_list(rdp);
>  	rdp->qlen_lazy = 0;
>  	rdp->qlen = 0;
>  	rdp->dynticks = &per_cpu(rcu_dynticks, cpu);
> -- 
> 1.7.8
> 
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