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Subject[PATCH tip/core/rcu 09/22] rcu: Move rcu_barrier_mutex to rcu_state structure
Date
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_mutex global variable to a new ->barrier_mutex 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>
---
kernel/rcutree.c | 9 +++------
kernel/rcutree.h | 1 +
2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 5e087f9..ac6e0c2 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -71,6 +71,7 @@ static struct lock_class_key rcu_node_class[RCU_NUM_LVLS];
.onofflock = __RAW_SPIN_LOCK_UNLOCKED(&sname##_state.onofflock), \
.orphan_nxttail = &sname##_state.orphan_nxtlist, \
.orphan_donetail = &sname##_state.orphan_donelist, \
+ .barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \
.fqslock = __RAW_SPIN_LOCK_UNLOCKED(&sname##_state.fqslock), \
.n_force_qs = 0, \
.n_force_qs_ngp = 0, \
@@ -155,10 +156,6 @@ static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp);
unsigned long rcutorture_testseq;
unsigned long rcutorture_vernum;

-/* State information for rcu_barrier() and friends. */
-
-static DEFINE_MUTEX(rcu_barrier_mutex);
-
/*
* Return true if an RCU grace period is in progress. The ACCESS_ONCE()s
* permit this function to be invoked without holding the root rcu_node
@@ -2300,7 +2297,7 @@ static void _rcu_barrier(struct rcu_state *rsp)
init_rcu_head_on_stack(&rd.barrier_head);

/* Take mutex to serialize concurrent rcu_barrier() requests. */
- mutex_lock(&rcu_barrier_mutex);
+ mutex_lock(&rsp->barrier_mutex);

smp_mb(); /* Prevent any prior operations from leaking in. */

@@ -2377,7 +2374,7 @@ static void _rcu_barrier(struct rcu_state *rsp)
wait_for_completion(&rsp->barrier_completion);

/* Other rcu_barrier() invocations can now safely proceed. */
- mutex_unlock(&rcu_barrier_mutex);
+ mutex_unlock(&rsp->barrier_mutex);

destroy_rcu_head_on_stack(&rd.barrier_head);
}
diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index 56fb8d4..d9ac82f 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. */
+ struct mutex barrier_mutex; /* Guards barrier fields. */
atomic_t barrier_cpu_count; /* # CPUs waiting on. */
struct completion barrier_completion; /* Wake at barrier end. */
raw_spinlock_t fqslock; /* Only one task forcing */
--
1.7.8


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