rcu: Move rcu_barrier_mutex to rcu_state structure

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>

2 files changed, 4 insertions, 6 deletions

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index ca7d1678ac79..ff992ac24e73 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
@@ -2303,7 +2300,7 @@ 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. */
 
@@ -2380,7 +2377,7 @@ 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 d1ca4424122b..7641aec3e59c 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -400,6 +400,7 @@ 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 */