[PATCH tip/core/rcu 07/22] rcu: Move rcu_barrier_cpu_count to rcu_state structure

Paul E. McKenney
2012-06-22T15:33:27Z

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 cb2d35d..592c43f 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