Merge remote-tracking branch 'rcu/rcu/next'

[karo-tx-linux.git] / kernel / rcupdate.c

diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index ddddb320be61ee463cc4e7ea163a379c908745de..1a491edd9c09b39a42afb90561b230c00bef32d5 100644 (file)
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -46,6 +46,11 @@
 #include <linux/module.h>
 #include <linux/hardirq.h>
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/rcu.h>
+
+#include "rcu.h"
+
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 static struct lock_class_key rcu_lock_key;
 struct lockdep_map rcu_lock_map =
@@ -82,23 +87,43 @@ EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled);
  * that require that they be called within an RCU read-side critical
  * section.
  *
- * Check debug_lockdep_rcu_enabled() to prevent false positives during boot.
+ * Check debug_lockdep_rcu_enabled() to prevent false positives during boot
+ * and while lockdep is disabled.
+ *
+ * Note that if the CPU is in an extended quiescent state, for example,
+ * if the CPU is in dyntick-idle mode, then rcu_read_lock_held() returns
+ * false even if the CPU did an rcu_read_lock().  The reason for this is
+ * that RCU ignores CPUs that are in extended quiescent states, so such
+ * a CPU is effectively never in an RCU read-side critical section
+ * regardless of what RCU primitives it invokes.  This state of affairs
+ * is required -- RCU would otherwise need to periodically wake up
+ * dyntick-idle CPUs, which would defeat the whole purpose of dyntick-idle
+ * mode.
  */
 int rcu_read_lock_bh_held(void)
 {
        if (!debug_lockdep_rcu_enabled())
                return 1;
+
+       if (rcu_check_extended_qs())
+               return 0;
+
        return in_softirq() || irqs_disabled();
 }
 EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);
 
 #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 
+struct rcu_synchronize {
+       struct rcu_head head;
+       struct completion completion;
+};
+
 /*
  * Awaken the corresponding synchronize_rcu() instance now that a
  * grace period has elapsed.
  */
-void wakeme_after_rcu(struct rcu_head  *head)
+static void wakeme_after_rcu(struct rcu_head  *head)
 {
        struct rcu_synchronize *rcu;
 
@@ -106,6 +131,20 @@ void wakeme_after_rcu(struct rcu_head  *head)
        complete(&rcu->completion);
 }
 
+void wait_rcu_gp(call_rcu_func_t crf)
+{
+       struct rcu_synchronize rcu;
+
+       init_rcu_head_on_stack(&rcu.head);
+       init_completion(&rcu.completion);
+       /* Will wake me after RCU finished. */
+       crf(&rcu.head, wakeme_after_rcu);
+       /* Wait for it. */
+       wait_for_completion(&rcu.completion);
+       destroy_rcu_head_on_stack(&rcu.head);
+}
+EXPORT_SYMBOL_GPL(wait_rcu_gp);
+
 #ifdef CONFIG_PROVE_RCU
 /*
  * wrapper function to avoid #include problems.