3 files changed, 42 insertions, 0 deletions

diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index d31e04ca8703..125150dc6e81 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -225,6 +225,12 @@ void cpuidle_uninstall_idle_handler(void)
                 initialized = 0;
                 wake_up_all_idle_cpus();
         }
+
+        /*
+         * Make sure external observers (such as the scheduler)
+         * are done looking at pointed idle states.
+         */
+        synchronize_rcu();
 }
 
 /**
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index 11e7bc434f43..c47fce75e666 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -147,6 +147,9 @@ use_default:
             clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &dev->cpu))
                 goto use_default;
 
+        /* Take note of the planned idle state. */
+        idle_set_state(this_rq(), &drv->states[next_state]);
+
         /*
          * Enter the idle state previously returned by the governor decision.
          * This function will block until an interrupt occurs and will take
@@ -154,6 +157,9 @@ use_default:
          */
         entered_state = cpuidle_enter(drv, dev, next_state);
 
+        /* The cpu is no longer idle or about to enter idle. */
+        idle_set_state(this_rq(), NULL);
+
         if (broadcast)
                 clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &dev->cpu);
 
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 76f3a38a401c..16e1ca9cb7e8 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -14,6 +14,7 @@
 #include "cpuacct.h"
 
 struct rq;
+struct cpuidle_state;
 
 /* task_struct::on_rq states: */
 #define TASK_ON_RQ_QUEUED       1
@@ -643,6 +644,11 @@ struct rq {
 #ifdef CONFIG_SMP
         struct llist_head wake_list;
 #endif
+
+#ifdef CONFIG_CPU_IDLE
+        /* Must be inspected within a rcu lock section */
+        struct cpuidle_state *idle_state;
+#endif
 };
 
 static inline int cpu_of(struct rq *rq)
@@ -1196,6 +1202,30 @@ static inline void idle_exit_fair(struct rq *rq) { }
 
 #endif
 
+#ifdef CONFIG_CPU_IDLE
+static inline void idle_set_state(struct rq *rq,
+                                  struct cpuidle_state *idle_state)
+{
+        rq->idle_state = idle_state;
+}
+
+static inline struct cpuidle_state *idle_get_state(struct rq *rq)
+{
+        WARN_ON(!rcu_read_lock_held());
+        return rq->idle_state;
+}
+#else
+static inline void idle_set_state(struct rq *rq,
+                                  struct cpuidle_state *idle_state)
+{
+}
+
+static inline struct cpuidle_state *idle_get_state(struct rq *rq)
+{
+        return NULL;
+}
+#endif
+
 extern void sysrq_sched_debug_show(void);
 extern void sched_init_granularity(void);
 extern void update_max_interval(void);