rcu: Move rcu_barrier() to rcutree

Move the existing rcu_barrier() implementation to rcutree.c,
consistent with the fact that the rcu_barrier() implementation is
tied quite tightly to the RCU implementation.

This opens the way to simplify and fix rcutree.c's rcu_barrier()
implementation in a later patch.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: akpm@linux-foundation.org
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <12548908982563-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 120 insertions, 119 deletions

diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index e43242274466..400183346ad2 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -53,16 +53,8 @@ struct lockdep_map rcu_lock_map =
 EXPORT_SYMBOL_GPL(rcu_lock_map);
 #endif
 
-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;
 int rcu_scheduler_active __read_mostly;
 
-static atomic_t rcu_migrate_type_count = ATOMIC_INIT(0);
-static struct rcu_head rcu_migrate_head[3];
-static DECLARE_WAIT_QUEUE_HEAD(rcu_migrate_wq);
-
 /*
  * Awaken the corresponding synchronize_rcu() instance now that a
  * grace period has elapsed.
@@ -165,120 +157,10 @@ void synchronize_rcu_bh(void)
 }
 EXPORT_SYMBOL_GPL(synchronize_rcu_bh);
 
-static void rcu_barrier_callback(struct rcu_head *notused)
-{
-        if (atomic_dec_and_test(&rcu_barrier_cpu_count))
-                complete(&rcu_barrier_completion);
-}
-
-/*
- * Called with preemption disabled, and from cross-cpu IRQ context.
- */
-static void rcu_barrier_func(void *type)
-{
-        int cpu = smp_processor_id();
-        struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu);
-        void (*call_rcu_func)(struct rcu_head *head,
-                              void (*func)(struct rcu_head *head));
-
-        atomic_inc(&rcu_barrier_cpu_count);
-        call_rcu_func = type;
-        call_rcu_func(head, rcu_barrier_callback);
-}
-
-static inline void wait_migrated_callbacks(void)
-{
-        wait_event(rcu_migrate_wq, !atomic_read(&rcu_migrate_type_count));
-        smp_mb(); /* In case we didn't sleep. */
-}
-
-/*
- * Orchestrate the specified type of RCU barrier, waiting for all
- * RCU callbacks of the specified type to complete.
- */
-static void _rcu_barrier(void (*call_rcu_func)(struct rcu_head *head,
-                                               void (*func)(struct rcu_head *head)))
-{
-        BUG_ON(in_interrupt());
-        /* Take cpucontrol mutex to protect against CPU hotplug */
-        mutex_lock(&rcu_barrier_mutex);
-        init_completion(&rcu_barrier_completion);
-        /*
-         * Initialize rcu_barrier_cpu_count to 1, then invoke
-         * rcu_barrier_func() on each CPU, so that each CPU also has
-         * incremented rcu_barrier_cpu_count.  Only then is it safe to
-         * decrement rcu_barrier_cpu_count -- otherwise the first CPU
-         * might complete its grace period before all of the other CPUs
-         * did their increment, causing this function to return too
-         * early.
-         */
-        atomic_set(&rcu_barrier_cpu_count, 1);
-        on_each_cpu(rcu_barrier_func, (void *)call_rcu_func, 1);
-        if (atomic_dec_and_test(&rcu_barrier_cpu_count))
-                complete(&rcu_barrier_completion);
-        wait_for_completion(&rcu_barrier_completion);
-        mutex_unlock(&rcu_barrier_mutex);
-        wait_migrated_callbacks();
-}
-
-/**
- * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete.
- */
-void rcu_barrier(void)
-{
-        _rcu_barrier(call_rcu);
-}
-EXPORT_SYMBOL_GPL(rcu_barrier);
-
-/**
- * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete.
- */
-void rcu_barrier_bh(void)
-{
-        _rcu_barrier(call_rcu_bh);
-}
-EXPORT_SYMBOL_GPL(rcu_barrier_bh);
-
-/**
- * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks.
- */
-void rcu_barrier_sched(void)
-{
-        _rcu_barrier(call_rcu_sched);
-}
-EXPORT_SYMBOL_GPL(rcu_barrier_sched);
-
-static void rcu_migrate_callback(struct rcu_head *notused)
-{
-        if (atomic_dec_and_test(&rcu_migrate_type_count))
-                wake_up(&rcu_migrate_wq);
-}
-
 static int __cpuinit rcu_barrier_cpu_hotplug(struct notifier_block *self,
                 unsigned long action, void *hcpu)
 {
-        rcu_cpu_notify(self, action, hcpu);
-        if (action == CPU_DYING) {
-                /*
-                 * preempt_disable() in on_each_cpu() prevents stop_machine(),
-                 * so when "on_each_cpu(rcu_barrier_func, (void *)type, 1);"
-                 * returns, all online cpus have queued rcu_barrier_func(),
-                 * and the dead cpu(if it exist) queues rcu_migrate_callback()s.
-                 *
-                 * These callbacks ensure _rcu_barrier() waits for all
-                 * RCU callbacks of the specified type to complete.
-                 */
-                atomic_set(&rcu_migrate_type_count, 3);
-                call_rcu_bh(rcu_migrate_head, rcu_migrate_callback);
-                call_rcu_sched(rcu_migrate_head + 1, rcu_migrate_callback);
-                call_rcu(rcu_migrate_head + 2, rcu_migrate_callback);
-        } else if (action == CPU_DOWN_PREPARE) {
-                /* Don't need to wait until next removal operation. */
-                /* rcu_migrate_head is protected by cpu_add_remove_lock */
-                wait_migrated_callbacks();
-        }
-
-        return NOTIFY_OK;
+        return rcu_cpu_notify(self, action, hcpu);
 }
 
 void __init rcu_init(void)
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index e2e272b5c277..0108570a192c 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1363,6 +1363,103 @@ int rcu_needs_cpu(int cpu)
                rcu_preempt_needs_cpu(cpu);
 }
 
+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;
+static atomic_t rcu_migrate_type_count = ATOMIC_INIT(0);
+static struct rcu_head rcu_migrate_head[3];
+static DECLARE_WAIT_QUEUE_HEAD(rcu_migrate_wq);
+
+static void rcu_barrier_callback(struct rcu_head *notused)
+{
+        if (atomic_dec_and_test(&rcu_barrier_cpu_count))
+                complete(&rcu_barrier_completion);
+}
+
+/*
+ * Called with preemption disabled, and from cross-cpu IRQ context.
+ */
+static void rcu_barrier_func(void *type)
+{
+        int cpu = smp_processor_id();
+        struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu);
+        void (*call_rcu_func)(struct rcu_head *head,
+                              void (*func)(struct rcu_head *head));
+
+        atomic_inc(&rcu_barrier_cpu_count);
+        call_rcu_func = type;
+        call_rcu_func(head, rcu_barrier_callback);
+}
+
+static inline void wait_migrated_callbacks(void)
+{
+        wait_event(rcu_migrate_wq, !atomic_read(&rcu_migrate_type_count));
+        smp_mb(); /* In case we didn't sleep. */
+}
+
+/*
+ * Orchestrate the specified type of RCU barrier, waiting for all
+ * RCU callbacks of the specified type to complete.
+ */
+static void _rcu_barrier(void (*call_rcu_func)(struct rcu_head *head,
+                                               void (*func)(struct rcu_head *head)))
+{
+        BUG_ON(in_interrupt());
+        /* Take cpucontrol mutex to protect against CPU hotplug */
+        mutex_lock(&rcu_barrier_mutex);
+        init_completion(&rcu_barrier_completion);
+        /*
+         * Initialize rcu_barrier_cpu_count to 1, then invoke
+         * rcu_barrier_func() on each CPU, so that each CPU also has
+         * incremented rcu_barrier_cpu_count.  Only then is it safe to
+         * decrement rcu_barrier_cpu_count -- otherwise the first CPU
+         * might complete its grace period before all of the other CPUs
+         * did their increment, causing this function to return too
+         * early.
+         */
+        atomic_set(&rcu_barrier_cpu_count, 1);
+        on_each_cpu(rcu_barrier_func, (void *)call_rcu_func, 1);
+        if (atomic_dec_and_test(&rcu_barrier_cpu_count))
+                complete(&rcu_barrier_completion);
+        wait_for_completion(&rcu_barrier_completion);
+        mutex_unlock(&rcu_barrier_mutex);
+        wait_migrated_callbacks();
+}
+
+/**
+ * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete.
+ */
+void rcu_barrier(void)
+{
+        _rcu_barrier(call_rcu);
+}
+EXPORT_SYMBOL_GPL(rcu_barrier);
+
+/**
+ * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete.
+ */
+void rcu_barrier_bh(void)
+{
+        _rcu_barrier(call_rcu_bh);
+}
+EXPORT_SYMBOL_GPL(rcu_barrier_bh);
+
+/**
+ * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks.
+ */
+void rcu_barrier_sched(void)
+{
+        _rcu_barrier(call_rcu_sched);
+}
+EXPORT_SYMBOL_GPL(rcu_barrier_sched);
+
+static void rcu_migrate_callback(struct rcu_head *notused)
+{
+        if (atomic_dec_and_test(&rcu_migrate_type_count))
+                wake_up(&rcu_migrate_wq);
+}
+
 /*
  * Do boot-time initialization of a CPU's per-CPU RCU data.
  */
@@ -1459,6 +1556,28 @@ int __cpuinit rcu_cpu_notify(struct notifier_block *self,
         case CPU_UP_PREPARE_FROZEN:
                 rcu_online_cpu(cpu);
                 break;
+        case CPU_DOWN_PREPARE:
+        case CPU_DOWN_PREPARE_FROZEN:
+                /* Don't need to wait until next removal operation. */
+                /* rcu_migrate_head is protected by cpu_add_remove_lock */
+                wait_migrated_callbacks();
+                break;
+        case CPU_DYING:
+        case CPU_DYING_FROZEN:
+                /*
+                 * preempt_disable() in on_each_cpu() prevents stop_machine(),
+                 * so when "on_each_cpu(rcu_barrier_func, (void *)type, 1);"
+                 * returns, all online cpus have queued rcu_barrier_func(),
+                 * and the dead cpu(if it exist) queues rcu_migrate_callback()s.
+                 *
+                 * These callbacks ensure _rcu_barrier() waits for all
+                 * RCU callbacks of the specified type to complete.
+                 */
+                atomic_set(&rcu_migrate_type_count, 3);
+                call_rcu_bh(rcu_migrate_head, rcu_migrate_callback);
+                call_rcu_sched(rcu_migrate_head + 1, rcu_migrate_callback);
+                call_rcu(rcu_migrate_head + 2, rcu_migrate_callback);
+                break;
         case CPU_DEAD:
         case CPU_DEAD_FROZEN:
         case CPU_UP_CANCELED: