rcu: Move __rcu_read_lock() and __rcu_read_unlock() to tree_plugin.h

The __rcu_read_lock() and __rcu_read_unlock() functions were moved
to kernel/rcu/update.c in order to implement tiny preemptible RCU.
However, tiny preemptible RCU was removed from the kernel a long time
ago, so this commit belatedly moves them back into the only remaining
preemptible-RCU code.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Nicholas Piggin <npiggin@gmail.com>

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index dfc42c3..ee24a5d 100644 (file)
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -383,6 +383,50 @@ static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp)
        return rnp->gp_tasks != NULL;
 }
 
+/*
+ * Preemptible RCU implementation for rcu_read_lock().
+ * Just increment ->rcu_read_lock_nesting, shared state will be updated
+ * if we block.
+ */
+void __rcu_read_lock(void)
+{
+       current->rcu_read_lock_nesting++;
+       barrier();  /* critical section after entry code. */
+}
+EXPORT_SYMBOL_GPL(__rcu_read_lock);
+
+/*
+ * Preemptible RCU implementation for rcu_read_unlock().
+ * Decrement ->rcu_read_lock_nesting.  If the result is zero (outermost
+ * rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then
+ * invoke rcu_read_unlock_special() to clean up after a context switch
+ * in an RCU read-side critical section and other special cases.
+ */
+void __rcu_read_unlock(void)
+{
+       struct task_struct *t = current;
+
+       if (t->rcu_read_lock_nesting != 1) {
+               --t->rcu_read_lock_nesting;
+       } else {
+               barrier();  /* critical section before exit code. */
+               t->rcu_read_lock_nesting = INT_MIN;
+               barrier();  /* assign before ->rcu_read_unlock_special load */
+               if (unlikely(READ_ONCE(t->rcu_read_unlock_special.s)))
+                       rcu_read_unlock_special(t);
+               barrier();  /* ->rcu_read_unlock_special load before assign */
+               t->rcu_read_lock_nesting = 0;
+       }
+#ifdef CONFIG_PROVE_LOCKING
+       {
+               int rrln = READ_ONCE(t->rcu_read_lock_nesting);
+
+               WARN_ON_ONCE(rrln < 0 && rrln > INT_MIN / 2);
+       }
+#endif /* #ifdef CONFIG_PROVE_LOCKING */
+}
+EXPORT_SYMBOL_GPL(__rcu_read_unlock);
+
 /*
  * Advance a ->blkd_tasks-list pointer to the next entry, instead
  * returning NULL if at the end of the list.

diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index e401960..4c230a6 100644 (file)
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -226,54 +226,6 @@ core_initcall(rcu_set_runtime_mode);
 
 #endif /* #if !defined(CONFIG_TINY_RCU) || defined(CONFIG_SRCU) */
 
-#ifdef CONFIG_PREEMPT_RCU
-
-/*
- * Preemptible RCU implementation for rcu_read_lock().
- * Just increment ->rcu_read_lock_nesting, shared state will be updated
- * if we block.
- */
-void __rcu_read_lock(void)
-{
-       current->rcu_read_lock_nesting++;
-       barrier();  /* critical section after entry code. */
-}
-EXPORT_SYMBOL_GPL(__rcu_read_lock);
-
-/*
- * Preemptible RCU implementation for rcu_read_unlock().
- * Decrement ->rcu_read_lock_nesting.  If the result is zero (outermost
- * rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then
- * invoke rcu_read_unlock_special() to clean up after a context switch
- * in an RCU read-side critical section and other special cases.
- */
-void __rcu_read_unlock(void)
-{
-       struct task_struct *t = current;
-
-       if (t->rcu_read_lock_nesting != 1) {
-               --t->rcu_read_lock_nesting;
-       } else {
-               barrier();  /* critical section before exit code. */
-               t->rcu_read_lock_nesting = INT_MIN;
-               barrier();  /* assign before ->rcu_read_unlock_special load */
-               if (unlikely(READ_ONCE(t->rcu_read_unlock_special.s)))
-                       rcu_read_unlock_special(t);
-               barrier();  /* ->rcu_read_unlock_special load before assign */
-               t->rcu_read_lock_nesting = 0;
-       }
-#ifdef CONFIG_PROVE_LOCKING
-       {
-               int rrln = READ_ONCE(t->rcu_read_lock_nesting);
-
-               WARN_ON_ONCE(rrln < 0 && rrln > INT_MIN / 2);
-       }
-#endif /* #ifdef CONFIG_PROVE_LOCKING */
-}
-EXPORT_SYMBOL_GPL(__rcu_read_unlock);
-
-#endif /* #ifdef CONFIG_PREEMPT_RCU */
-
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 static struct lock_class_key rcu_lock_key;
 struct lockdep_map rcu_lock_map =