X-Git-Url: http://pileus.org/git/?a=blobdiff_plain;f=kernel%2Frcupdate.c;h=2c7b8457d0d234203517f7aa6a1ddc6b724ef447;hb=574bbe782057fdf0490dc7dec906a2dc26363e20;hp=d92a76a881aa47a9aa059c3221910834f6c50cf8;hpb=f45ac22ae2b8fc5b4c32d9b8d17ea419a8701d89;p=~andy%2Flinux

diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index d92a76a881a..2c7b8457d0d 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -44,6 +44,7 @@
 #include <linux/cpu.h>
 #include <linux/mutex.h>
 #include <linux/module.h>
+#include <linux/kernel_stat.h>
 
 enum rcu_barrier {
 	RCU_BARRIER_STD,
@@ -55,6 +56,7 @@ 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;
 
 /*
  * Awaken the corresponding synchronize_rcu() instance now that a
@@ -80,6 +82,10 @@ void wakeme_after_rcu(struct rcu_head  *head)
 void synchronize_rcu(void)
 {
 	struct rcu_synchronize rcu;
+
+	if (rcu_blocking_is_gp())
+		return;
+
 	init_completion(&rcu.completion);
 	/* Will wake me after RCU finished. */
 	call_rcu(&rcu.head, wakeme_after_rcu);
@@ -116,6 +122,8 @@ static void rcu_barrier_func(void *type)
 	}
 }
 
+static inline void wait_migrated_callbacks(void);
+
 /*
  * Orchestrate the specified type of RCU barrier, waiting for all
  * RCU callbacks of the specified type to complete.
@@ -141,6 +149,7 @@ static void _rcu_barrier(enum rcu_barrier type)
 		complete(&rcu_barrier_completion);
 	wait_for_completion(&rcu_barrier_completion);
 	mutex_unlock(&rcu_barrier_mutex);
+	wait_migrated_callbacks();
 }
 
 /**
@@ -170,8 +179,55 @@ void rcu_barrier_sched(void)
 }
 EXPORT_SYMBOL_GPL(rcu_barrier_sched);
 
+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_migrate_callback(struct rcu_head *notused)
+{
+	if (atomic_dec_and_test(&rcu_migrate_type_count))
+		wake_up(&rcu_migrate_wq);
+}
+
+static inline void wait_migrated_callbacks(void)
+{
+	wait_event(rcu_migrate_wq, !atomic_read(&rcu_migrate_type_count));
+}
+
+static int __cpuinit rcu_barrier_cpu_hotplug(struct notifier_block *self,
+		unsigned long action, void *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_POST_DEAD) {
+		/* rcu_migrate_head is protected by cpu_add_remove_lock */
+		wait_migrated_callbacks();
+	}
+
+	return NOTIFY_OK;
+}
+
 void __init rcu_init(void)
 {
 	__rcu_init();
+	hotcpu_notifier(rcu_barrier_cpu_hotplug, 0);
 }
 
+void rcu_scheduler_starting(void)
+{
+	WARN_ON(num_online_cpus() != 1);
+	WARN_ON(nr_context_switches() > 0);
+	rcu_scheduler_active = 1;
+}