Re: [PATCH tip/core/rcu 07/15] rcu: Move rcu_barrier_completion to rcu_state structure

[Josh Triplett <josh@joshtriplett.org>]

On Fri, Jun 15, 2012 at 02:06:02PM -0700, Paul E. McKenney wrote:
> From: "Paul E. McKenney" <paul.mckenney@linaro.org>
> 
> In order to allow each RCU flavor to concurrently execute its
> rcu_barrier() function, it is necessary to move the relevant
> state to the rcu_state structure.  This commit therefore moves the
> rcu_barrier_completion global variable to a new ->barrier_completion
> field in the rcu_state structure.
> 
> Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

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

>  kernel/rcutree.c |    9 ++++-----
>  kernel/rcutree.h |    1 +
>  2 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/kernel/rcutree.c b/kernel/rcutree.c
> index d363416..a946437 100644
> --- a/kernel/rcutree.c
> +++ b/kernel/rcutree.c
> @@ -158,7 +158,6 @@ unsigned long rcutorture_vernum;
>  /* State information for rcu_barrier() and friends. */
>  
>  static DEFINE_MUTEX(rcu_barrier_mutex);
> -static struct completion rcu_barrier_completion;
>  
>  /*
>   * Return true if an RCU grace period is in progress.  The ACCESS_ONCE()s
> @@ -2272,7 +2271,7 @@ static void rcu_barrier_callback(struct rcu_head *rhp)
>  	struct rcu_state *rsp = rdp->rsp;
>  
>  	if (atomic_dec_and_test(&rsp->barrier_cpu_count))
> -		complete(&rcu_barrier_completion);
> +		complete(&rsp->barrier_completion);
>  }
>  
>  /*
> @@ -2322,7 +2321,7 @@ static void _rcu_barrier(struct rcu_state *rsp)
>  	 * 6.	Both rcu_barrier_callback() callbacks are invoked, awakening
>  	 *	us -- but before CPU 1's orphaned callbacks are invoked!!!
>  	 */
> -	init_completion(&rcu_barrier_completion);
> +	init_completion(&rsp->barrier_completion);
>  	atomic_set(&rsp->barrier_cpu_count, 1);
>  	raw_spin_lock_irqsave(&rsp->onofflock, flags);
>  	rsp->rcu_barrier_in_progress = current;
> @@ -2372,10 +2371,10 @@ static void _rcu_barrier(struct rcu_state *rsp)
>  	 * CPU, and thus each counted, remove the initial count.
>  	 */
>  	if (atomic_dec_and_test(&rsp->barrier_cpu_count))
> -		complete(&rcu_barrier_completion);
> +		complete(&rsp->barrier_completion);
>  
>  	/* Wait for all rcu_barrier_callback() callbacks to be invoked. */
> -	wait_for_completion(&rcu_barrier_completion);
> +	wait_for_completion(&rsp->barrier_completion);
>  
>  	/* Other rcu_barrier() invocations can now safely proceed. */
>  	mutex_unlock(&rcu_barrier_mutex);
> diff --git a/kernel/rcutree.h b/kernel/rcutree.h
> index e7d29b7..56fb8d4 100644
> --- a/kernel/rcutree.h
> +++ b/kernel/rcutree.h
> @@ -387,6 +387,7 @@ struct rcu_state {
>  						/* Task doing rcu_barrier(), */
>  						/*  or NULL if no barrier. */
>  	atomic_t barrier_cpu_count;		/* # CPUs waiting on. */
> +	struct completion barrier_completion;	/* Wake at barrier end. */
>  	raw_spinlock_t fqslock;			/* Only one task forcing */
>  						/*  quiescent states. */
>  	unsigned long jiffies_force_qs;		/* Time at which to invoke */
> -- 
> 1.7.8
>