1 files changed, 24 insertions, 1 deletions

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 74df86bd9204..e78538712df0 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -873,6 +873,29 @@ static void record_gp_stall_check_time(struct rcu_state *rsp)
         rsp->jiffies_stall = jiffies + jiffies_till_stall_check();
 }
 
+/*
+ * Dump stacks of all tasks running on stalled CPUs.  This is a fallback
+ * for architectures that do not implement trigger_all_cpu_backtrace().
+ * The NMI-triggered stack traces are more accurate because they are
+ * printed by the target CPU.
+ */
+static void rcu_dump_cpu_stacks(struct rcu_state *rsp)
+{
+        int cpu;
+        unsigned long flags;
+        struct rcu_node *rnp;
+
+        rcu_for_each_leaf_node(rsp, rnp) {
+                raw_spin_lock_irqsave(&rnp->lock, flags);
+                if (rnp->qsmask != 0) {
+                        for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++)
+                                if (rnp->qsmask & (1UL << cpu))
+                                        dump_cpu_task(rnp->grplo + cpu);
+                }
+                raw_spin_unlock_irqrestore(&rnp->lock, flags);
+        }
+}
+
 static void print_other_cpu_stall(struct rcu_state *rsp)
 {
         int cpu;
@@ -929,7 +952,7 @@ static void print_other_cpu_stall(struct rcu_state *rsp)
         if (ndetected == 0)
                 printk(KERN_ERR "INFO: Stall ended before state dump start\n");
         else if (!trigger_all_cpu_backtrace())
-                dump_stack();
+                rcu_dump_cpu_stacks(rsp);
 
         /* Complain about tasks blocking the grace period. */