1 files changed, 34 insertions, 2 deletions

diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h
index 4c2a0189e748..9c990df880d1 100644
--- a/kernel/rcu/tree_exp.h
+++ b/kernel/rcu/tree_exp.h
@@ -10,6 +10,7 @@
 #include <linux/lockdep.h>
 
 static void rcu_exp_handler(void *unused);
+static int rcu_print_task_exp_stall(struct rcu_node *rnp);
 
 /*
  * Record the start of an expedited grace period.
@@ -633,7 +634,7 @@ static void rcu_exp_handler(void *unused)
                 raw_spin_lock_irqsave_rcu_node(rnp, flags);
                 if (rnp->expmask & rdp->grpmask) {
                         rdp->deferred_qs = true;
-                        WRITE_ONCE(t->rcu_read_unlock_special.b.exp_hint, true);
+                        t->rcu_read_unlock_special.b.exp_hint = true;
                 }
                 raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
                 return;
@@ -648,7 +649,7 @@ static void rcu_exp_handler(void *unused)
          *
          * If the CPU is fully enabled (or if some buggy RCU-preempt
          * read-side critical section is being used from idle), just
-         * invoke rcu_preempt_defer_qs() to immediately report the
+         * invoke rcu_preempt_deferred_qs() to immediately report the
          * quiescent state.  We cannot use rcu_read_unlock_special()
          * because we are in an interrupt handler, which will cause that
          * function to take an early exit without doing anything.
@@ -670,6 +671,27 @@ static void sync_sched_exp_online_cleanup(int cpu)
 {
 }
 
+/*
+ * Scan the current list of tasks blocked within RCU read-side critical
+ * sections, printing out the tid of each that is blocking the current
+ * expedited grace period.
+ */
+static int rcu_print_task_exp_stall(struct rcu_node *rnp)
+{
+        struct task_struct *t;
+        int ndetected = 0;
+
+        if (!rnp->exp_tasks)
+                return 0;
+        t = list_entry(rnp->exp_tasks->prev,
+                       struct task_struct, rcu_node_entry);
+        list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) {
+                pr_cont(" P%d", t->pid);
+                ndetected++;
+        }
+        return ndetected;
+}
+
 #else /* #ifdef CONFIG_PREEMPT_RCU */
 
 /* Invoked on each online non-idle CPU for expedited quiescent state. */
@@ -709,6 +731,16 @@ static void sync_sched_exp_online_cleanup(int cpu)
         WARN_ON_ONCE(ret);
 }
 
+/*
+ * Because preemptible RCU does not exist, we never have to check for
+ * tasks blocked within RCU read-side critical sections that are
+ * blocking the current expedited grace period.
+ */
+static int rcu_print_task_exp_stall(struct rcu_node *rnp)
+{
+        return 0;
+}
+
 #endif /* #else #ifdef CONFIG_PREEMPT_RCU */
 
 /**