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SubjectRe: [PATCH tip/core/rcu 06/15] rcu: Move rcu_barrier_cpu_count to rcu_state structure
On Fri, Jun 15, 2012 at 02:06:01PM -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_cpu_count global
> variable to a new ->barrier_cpu_count 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 | 25 ++++++++++++++-----------
> kernel/rcutree.h | 1 +
> 2 files changed, 15 insertions(+), 11 deletions(-)
>
> diff --git a/kernel/rcutree.c b/kernel/rcutree.c
> index 2cfbdb8..d363416 100644
> --- a/kernel/rcutree.c
> +++ b/kernel/rcutree.c
> @@ -157,7 +157,6 @@ unsigned long rcutorture_vernum;
>
> /* State information for rcu_barrier() and friends. */
>
> -static atomic_t rcu_barrier_cpu_count;
> static DEFINE_MUTEX(rcu_barrier_mutex);
> static struct completion rcu_barrier_completion;
>
> @@ -2267,9 +2266,12 @@ static int rcu_cpu_has_callbacks(int cpu)
> * RCU callback function for _rcu_barrier(). If we are last, wake
> * up the task executing _rcu_barrier().
> */
> -static void rcu_barrier_callback(struct rcu_head *notused)
> +static void rcu_barrier_callback(struct rcu_head *rhp)
> {
> - if (atomic_dec_and_test(&rcu_barrier_cpu_count))
> + struct rcu_data *rdp = container_of(rhp, struct rcu_data, barrier_head);
> + struct rcu_state *rsp = rdp->rsp;
> +
> + if (atomic_dec_and_test(&rsp->barrier_cpu_count))
> complete(&rcu_barrier_completion);
> }
>
> @@ -2281,7 +2283,7 @@ static void rcu_barrier_func(void *type)
> struct rcu_state *rsp = type;
> struct rcu_data *rdp = __this_cpu_ptr(rsp->rda);
>
> - atomic_inc(&rcu_barrier_cpu_count);
> + atomic_inc(&rsp->barrier_cpu_count);
> rsp->call(&rdp->barrier_head, rcu_barrier_callback);
> }
>
> @@ -2294,9 +2296,9 @@ static void _rcu_barrier(struct rcu_state *rsp)
> int cpu;
> unsigned long flags;
> struct rcu_data *rdp;
> - struct rcu_head rh;
> + struct rcu_data rd;
>
> - init_rcu_head_on_stack(&rh);
> + init_rcu_head_on_stack(&rd.barrier_head);
>
> /* Take mutex to serialize concurrent rcu_barrier() requests. */
> mutex_lock(&rcu_barrier_mutex);
> @@ -2321,7 +2323,7 @@ static void _rcu_barrier(struct rcu_state *rsp)
> * us -- but before CPU 1's orphaned callbacks are invoked!!!
> */
> init_completion(&rcu_barrier_completion);
> - atomic_set(&rcu_barrier_cpu_count, 1);
> + atomic_set(&rsp->barrier_cpu_count, 1);
> raw_spin_lock_irqsave(&rsp->onofflock, flags);
> rsp->rcu_barrier_in_progress = current;
> raw_spin_unlock_irqrestore(&rsp->onofflock, flags);
> @@ -2360,15 +2362,16 @@ static void _rcu_barrier(struct rcu_state *rsp)
> rcu_adopt_orphan_cbs(rsp);
> rsp->rcu_barrier_in_progress = NULL;
> raw_spin_unlock_irqrestore(&rsp->onofflock, flags);
> - atomic_inc(&rcu_barrier_cpu_count);
> + atomic_inc(&rsp->barrier_cpu_count);
> smp_mb__after_atomic_inc(); /* Ensure atomic_inc() before callback. */
> - rsp->call(&rh, rcu_barrier_callback);
> + rd.rsp = rsp;
> + rsp->call(&rd.barrier_head, rcu_barrier_callback);
>
> /*
> * Now that we have an rcu_barrier_callback() callback on each
> * CPU, and thus each counted, remove the initial count.
> */
> - if (atomic_dec_and_test(&rcu_barrier_cpu_count))
> + if (atomic_dec_and_test(&rsp->barrier_cpu_count))
> complete(&rcu_barrier_completion);
>
> /* Wait for all rcu_barrier_callback() callbacks to be invoked. */
> @@ -2377,7 +2380,7 @@ static void _rcu_barrier(struct rcu_state *rsp)
> /* Other rcu_barrier() invocations can now safely proceed. */
> mutex_unlock(&rcu_barrier_mutex);
>
> - destroy_rcu_head_on_stack(&rh);
> + destroy_rcu_head_on_stack(&rd.barrier_head);
> }
>
> /**
> diff --git a/kernel/rcutree.h b/kernel/rcutree.h
> index 1783eae..e7d29b7 100644
> --- a/kernel/rcutree.h
> +++ b/kernel/rcutree.h
> @@ -386,6 +386,7 @@ struct rcu_state {
> struct task_struct *rcu_barrier_in_progress;
> /* Task doing rcu_barrier(), */
> /* or NULL if no barrier. */
> + atomic_t barrier_cpu_count; /* # CPUs waiting on. */
> raw_spinlock_t fqslock; /* Only one task forcing */
> /* quiescent states. */
> unsigned long jiffies_force_qs; /* Time at which to invoke */
> --
> 1.7.8
>


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