From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Date: Thu, 1 Oct 2015 17:38:16 +0000 (-0700)
Subject: rcutorture:  Dump stack when GP kthread stalls
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=b1adb3e2736b695821badc715d2c7a5d873b8b94;p=linux-beck.git

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 e2315fb57b23..7b78c88e19a3 100644
--- 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);
+	}
 }
 
 /*