1 files changed, 9 insertions, 4 deletions

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 9970116163ba..ade788320dd6 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -545,6 +545,7 @@ static void print_other_cpu_stall(struct rcu_state *rsp)
         int cpu;
         long delta;
         unsigned long flags;
+        int ndetected;
         struct rcu_node *rnp = rcu_get_root(rsp);
 
         /* Only let one CPU complain about others per time interval. */
@@ -561,7 +562,7 @@ static void print_other_cpu_stall(struct rcu_state *rsp)
          * Now rat on any tasks that got kicked up to the root rcu_node
          * due to CPU offlining.
          */
-        rcu_print_task_stall(rnp);
+        ndetected = rcu_print_task_stall(rnp);
         raw_spin_unlock_irqrestore(&rnp->lock, flags);
 
         /*
@@ -573,17 +574,21 @@ static void print_other_cpu_stall(struct rcu_state *rsp)
                rsp->name);
         rcu_for_each_leaf_node(rsp, rnp) {
                 raw_spin_lock_irqsave(&rnp->lock, flags);
-                rcu_print_task_stall(rnp);
+                ndetected += rcu_print_task_stall(rnp);
                 raw_spin_unlock_irqrestore(&rnp->lock, flags);
                 if (rnp->qsmask == 0)
                         continue;
                 for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++)
-                        if (rnp->qsmask & (1UL << cpu))
+                        if (rnp->qsmask & (1UL << cpu)) {
                                 printk(" %d", rnp->grplo + cpu);
+                                ndetected++;
+                        }
         }
         printk("} (detected by %d, t=%ld jiffies)\n",
                smp_processor_id(), (long)(jiffies - rsp->gp_start));
-        if (!trigger_all_cpu_backtrace())
+        if (ndetected == 0)
+                printk(KERN_ERR "INFO: Stall ended before state dump start\n");
+        else if (!trigger_all_cpu_backtrace())
                 dump_stack();
 
         /* If so configured, complain about tasks blocking the grace period. */