[ltt-dev] [PATCH 07/10] call_rcu: remove write-only qlen variable

[Mathieu Desnoyers]

* Paolo Bonzini (pbonzini at redhat.com) wrote:
> The qlen variable is write-only, we can remove it easily.

I defer to Paul for this one: he likes keeping qlen there so the
debugger can show the list state, which is useful for debugging. I'll
let you two figure out how to come to an agreement. ;)

Mathieu

> 
> Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
> ---
>  urcu-call-rcu-impl.h |    9 ---------
>  1 files changed, 0 insertions(+), 9 deletions(-)
> 
> diff --git a/urcu-call-rcu-impl.h b/urcu-call-rcu-impl.h
> index 7e6acdd..ca597d0 100644
> --- a/urcu-call-rcu-impl.h
> +++ b/urcu-call-rcu-impl.h
> @@ -47,7 +47,6 @@ struct call_rcu_data {
>  	struct cds_wfq_queue cbs;
>  	unsigned long flags;
>  	int futex;
> -	unsigned long qlen;
>  	pthread_t tid;
>  	int cpu_affinity;
>  	struct cds_list_head list;
> @@ -198,7 +197,6 @@ int set_thread_cpu_affinity(struct call_rcu_data *crdp)
>  
>  static void *call_rcu_thread(void *arg)
>  {
> -	unsigned long cbcount;
>  	struct cds_wfq_node *cbs;
>  	struct cds_wfq_node **cbs_tail;
>  	struct call_rcu_data *crdp = (struct call_rcu_data *)arg;
> @@ -218,7 +216,6 @@ static void *call_rcu_thread(void *arg)
>  			cbs_tail = (struct cds_wfq_node **)
>  				uatomic_xchg(&crdp->cbs.tail, &crdp->cbs.head);
>  			synchronize_rcu();
> -			cbcount = 0;
>  			do {
>  				while (cbs->next == NULL &&
>  				       &cbs->next != cbs_tail)
> @@ -230,9 +227,7 @@ static void *call_rcu_thread(void *arg)
>  				rhp = (struct rcu_head *)cbs;
>  				cbs = cbs->next;
>  				rhp->func(rhp);
> -				cbcount++;
>  			} while (cbs != NULL);
> -			uatomic_sub(&crdp->qlen, cbcount);
>  		}
>  		if (uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOP)
>  			break;
> @@ -267,7 +262,6 @@ static void call_rcu_data_init(struct call_rcu_data **crdpp,
>  	}
>  	memset(crdp, '\0', sizeof(*crdp));
>  	cds_wfq_init(&crdp->cbs);
> -	crdp->qlen = 0;
>  	crdp->futex = 0;
>  	crdp->flags = flags;
>  	cds_list_add(&crdp->list, &call_rcu_data_list);
> @@ -519,7 +513,6 @@ void call_rcu(struct rcu_head *head,
>  	head->func = func;
>  	crdp = get_call_rcu_data();
>  	cds_wfq_enqueue(&crdp->cbs, &head->next);
> -	uatomic_inc(&crdp->qlen);
>  	wake_call_rcu_thread(crdp);
>  }
>  
> @@ -565,8 +558,6 @@ void call_rcu_data_free(struct call_rcu_data *crdp)
>  		cbs_endprev = (struct cds_wfq_node **)
>  			uatomic_xchg(&default_call_rcu_data, cbs_tail);
>  		*cbs_endprev = cbs;
> -		uatomic_add(&default_call_rcu_data->qlen,
> -			    uatomic_read(&crdp->qlen));
>  		cds_list_del(&crdp->list);
>  		free(crdp);
>  	}
> -- 
> 1.7.4.4
> 
> 
> 
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> 

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com