rcutorture: Dump stack when GP kthread stalls

This commit increases debug information in the case where the grace-period
kthread is being prevented from running by dumping that kthread's stack.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Split into prior commit and this commit, as suggested by
  Josh Triplett. ]
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index e2315fb57b238b091243b8fcdbf7ac78bcded4db..7b78c88e19a30f86aa5797d0ba57edec1026f6ce 100644 (file)
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1196,12 +1196,15 @@ static void rcu_check_gp_kthread_starvation(struct rcu_state *rsp)
 
        j = jiffies;
        gpa = READ_ONCE(rsp->gp_activity);
-       if (j - gpa > 2 * HZ)
+       if (j - gpa > 2 * HZ) {
                pr_err("%s kthread starved for %ld jiffies! g%lu c%lu f%#x s%d ->state=%#lx\n",
                       rsp->name, j - gpa,
                       rsp->gpnum, rsp->completed,
                       rsp->gp_flags, rsp->gp_state,
                       rsp->gp_kthread ? rsp->gp_kthread->state : ~0);
+               if (rsp->gp_kthread)
+                       sched_show_task(rsp->gp_kthread);
+       }
 }
 
 /*