rcu: Consolidate tree/tiny __rcu_read_{,un}lock() implementations

[~andy/linux] / kernel / rcupdate.c

diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index 95cba41ce1e9a10568bf17a403b637b57a822d62..4e6a61b15e86fe0e27fc30d80775de4f4c8c47e6 100644 (file)
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -53,6 +53,50 @@
 
 #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(ACCESS_ONCE(t->rcu_read_unlock_special)))
+                       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 = ACCESS_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);
+
 /*
  * Check for a task exiting while in a preemptible-RCU read-side
  * critical section, clean up if so.  No need to issue warnings,