1 files changed, 73 insertions, 117 deletions

diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index a967c9feb90a..400183346ad2 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -19,7 +19,7 @@
  *
  * Authors: Dipankar Sarma <dipankar@in.ibm.com>
  *          Manfred Spraul <manfred@colorfullife.com>
- * 
+ *
  * Based on the original work by Paul McKenney <paulmck@us.ibm.com>
  * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
  * Papers:
@@ -27,7 +27,7 @@
  * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
  *
  * For detailed explanation of Read-Copy Update mechanism see -
- *              http://lse.sourceforge.net/locking/rcupdate.html
+ *              http://lse.sourceforge.net/locking/rcupdate.html
  *
  */
 #include <linux/types.h>
@@ -46,22 +46,15 @@
 #include <linux/module.h>
 #include <linux/kernel_stat.h>
 
-enum rcu_barrier {
-        RCU_BARRIER_STD,
-        RCU_BARRIER_BH,
-        RCU_BARRIER_SCHED,
-};
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+static struct lock_class_key rcu_lock_key;
+struct lockdep_map rcu_lock_map =
+        STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key);
+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.
@@ -74,6 +67,8 @@ void wakeme_after_rcu(struct rcu_head  *head)
         complete(&rcu->completion);
 }
 
+#ifdef CONFIG_TREE_PREEMPT_RCU
+
 /**
  * synchronize_rcu - wait until a grace period has elapsed.
  *
@@ -87,7 +82,7 @@ void synchronize_rcu(void)
 {
         struct rcu_synchronize rcu;
 
-        if (rcu_blocking_is_gp())
+        if (!rcu_scheduler_active)
                 return;
 
         init_completion(&rcu.completion);
@@ -98,129 +93,90 @@ void synchronize_rcu(void)
 }
 EXPORT_SYMBOL_GPL(synchronize_rcu);
 
-static void rcu_barrier_callback(struct rcu_head *notused)
-{
-        if (atomic_dec_and_test(&rcu_barrier_cpu_count))
-                complete(&rcu_barrier_completion);
-}
+#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
 
-/*
- * Called with preemption disabled, and from cross-cpu IRQ context.
+/**
+ * synchronize_sched - wait until an rcu-sched grace period has elapsed.
+ *
+ * Control will return to the caller some time after a full rcu-sched
+ * grace period has elapsed, in other words after all currently executing
+ * rcu-sched read-side critical sections have completed.   These read-side
+ * critical sections are delimited by rcu_read_lock_sched() and
+ * rcu_read_unlock_sched(), and may be nested.  Note that preempt_disable(),
+ * local_irq_disable(), and so on may be used in place of
+ * rcu_read_lock_sched().
+ *
+ * This means that all preempt_disable code sequences, including NMI and
+ * hardware-interrupt handlers, in progress on entry will have completed
+ * before this primitive returns.  However, this does not guarantee that
+ * softirq handlers will have completed, since in some kernels, these
+ * handlers can run in process context, and can block.
+ *
+ * This primitive provides the guarantees made by the (now removed)
+ * synchronize_kernel() API.  In contrast, synchronize_rcu() only
+ * guarantees that rcu_read_lock() sections will have completed.
+ * In "classic RCU", these two guarantees happen to be one and
+ * the same, but can differ in realtime RCU implementations.
  */
-static void rcu_barrier_func(void *type)
-{
-        int cpu = smp_processor_id();
-        struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu);
-
-        atomic_inc(&rcu_barrier_cpu_count);
-        switch ((enum rcu_barrier)type) {
-        case RCU_BARRIER_STD:
-                call_rcu(head, rcu_barrier_callback);
-                break;
-        case RCU_BARRIER_BH:
-                call_rcu_bh(head, rcu_barrier_callback);
-                break;
-        case RCU_BARRIER_SCHED:
-                call_rcu_sched(head, rcu_barrier_callback);
-                break;
-        }
-}
-
-static inline void wait_migrated_callbacks(void)
+void synchronize_sched(void)
 {
-        wait_event(rcu_migrate_wq, !atomic_read(&rcu_migrate_type_count));
-}
+        struct rcu_synchronize rcu;
 
-/*
- * Orchestrate the specified type of RCU barrier, waiting for all
- * RCU callbacks of the specified type to complete.
- */
-static void _rcu_barrier(enum rcu_barrier type)
-{
-        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 *)type, 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();
-}
+        if (rcu_blocking_is_gp())
+                return;
 
-/**
- * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete.
- */
-void rcu_barrier(void)
-{
-        _rcu_barrier(RCU_BARRIER_STD);
+        init_completion(&rcu.completion);
+        /* Will wake me after RCU finished. */
+        call_rcu_sched(&rcu.head, wakeme_after_rcu);
+        /* Wait for it. */
+        wait_for_completion(&rcu.completion);
 }
-EXPORT_SYMBOL_GPL(rcu_barrier);
+EXPORT_SYMBOL_GPL(synchronize_sched);
 
 /**
- * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete.
+ * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed.
+ *
+ * Control will return to the caller some time after a full rcu_bh grace
+ * period has elapsed, in other words after all currently executing rcu_bh
+ * read-side critical sections have completed.  RCU read-side critical
+ * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(),
+ * and may be nested.
  */
-void rcu_barrier_bh(void)
+void synchronize_rcu_bh(void)
 {
-        _rcu_barrier(RCU_BARRIER_BH);
-}
-EXPORT_SYMBOL_GPL(rcu_barrier_bh);
+        struct rcu_synchronize rcu;
 
-/**
- * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks.
- */
-void rcu_barrier_sched(void)
-{
-        _rcu_barrier(RCU_BARRIER_SCHED);
-}
-EXPORT_SYMBOL_GPL(rcu_barrier_sched);
+        if (rcu_blocking_is_gp())
+                return;
 
-static void rcu_migrate_callback(struct rcu_head *notused)
-{
-        if (atomic_dec_and_test(&rcu_migrate_type_count))
-                wake_up(&rcu_migrate_wq);
+        init_completion(&rcu.completion);
+        /* Will wake me after RCU finished. */
+        call_rcu_bh(&rcu.head, wakeme_after_rcu);
+        /* Wait for it. */
+        wait_for_completion(&rcu.completion);
 }
+EXPORT_SYMBOL_GPL(synchronize_rcu_bh);
 
 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;
+        return rcu_cpu_notify(self, action, hcpu);
 }
 
 void __init rcu_init(void)
 {
+        int i;
+
         __rcu_init();
-        hotcpu_notifier(rcu_barrier_cpu_hotplug, 0);
+        cpu_notifier(rcu_barrier_cpu_hotplug, 0);
+
+        /*
+         * We don't need protection against CPU-hotplug here because
+         * this is called early in boot, before either interrupts
+         * or the scheduler are operational.
+         */
+        for_each_online_cpu(i)
+                rcu_barrier_cpu_hotplug(NULL, CPU_UP_PREPARE, (void *)(long)i);
 }
 
 void rcu_scheduler_starting(void)