[PATCH tip/core/rcu 06/22] rcu: Move _rcu_barrier()'s rcu_head structures to rcu_data structures

Paul E. McKenney
2012-06-22T15:25:11Z

From: "Paul E. McKenney" <paul.mckenney@linaro.org>

In order for multiple flavors of RCU to each concurrently run one
rcu_barrier(), each flavor needs its own per-CPU set of rcu_head
structures. This commit therefore moves _rcu_barrier()'s set of
per-CPU rcu_head structures from per-CPU variables to the existing
per-CPU and per-RCU-flavor rcu_data structures.

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 | 6 ++----
kernel/rcutree.h | 3 +++
2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 24cd2f0..cb2d35d 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 DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL};
static atomic_t rcu_barrier_cpu_count;
static DEFINE_MUTEX(rcu_barrier_mutex);
static struct completion rcu_barrier_completion;
@@ -2279,12 +2278,11 @@ static void rcu_barrier_callback(struct rcu_head *notused)
*/
static void rcu_barrier_func(void *type)
{
- int cpu = smp_processor_id();
- struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu);
struct rcu_state *rsp = type;
+ struct rcu_data *rdp = __this_cpu_ptr(rsp->rda);

atomic_inc(&rcu_barrier_cpu_count);
- rsp->call(head, rcu_barrier_callback);
+ rsp->call(&rdp->barrier_head, rcu_barrier_callback);
}

/*
diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index 15837d7..1783eae 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -300,6 +300,9 @@ struct rcu_data {
unsigned long n_rp_need_fqs;
unsigned long n_rp_need_nothing;

+ /* 6) _rcu_barrier() callback. */
+ struct rcu_head barrier_head;
+
int cpu;
struct rcu_state *rsp;
};
--
1.7.8