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[PATCH tip/core/rcu 6/6] rcu: Dump ftrace buffer when kicking grace-period kthread

From "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Newsgroups linux.kernel
Subject [PATCH tip/core/rcu 6/6] rcu: Dump ftrace buffer when kicking grace-period kthread
Date 2016-04-12 17:10 +0200
Message-ID <rn870-W0-27@gated-at.bofh.it> (permalink)
References <rn870-W0-5@gated-at.bofh.it>
Organization linux.* mail to news gateway

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If it is necessary to kick the grace-period kthread, that is a good
time to dump the trace buffer in order to learn why kicking was needed.
This commit therefore does the dump.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 kernel/rcu/tree.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index a739292be605..86edb92276d3 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1266,6 +1266,7 @@ static void rcu_stall_kick_kthreads(struct rcu_state *rsp)
 	j = READ_ONCE(rsp->jiffies_kick_kthreads);
 	if (time_after(jiffies, j) && rsp->gp_kthread) {
 		WARN_ONCE(1, "Kicking %s grace-period kthread\n", rsp->name);
+		rcu_ftrace_dump(DUMP_ALL);
 		wake_up_process(rsp->gp_kthread);
 		WRITE_ONCE(rsp->jiffies_kick_kthreads, j + HZ);
 	}
-- 
2.5.2

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Thread

[PATCH tip/core/rcu 0/6] Miscellaneous fixes for 4.7 "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-04-12 17:10 +0200
  [PATCH tip/core/rcu 4/6] rcu: Awaken grace-period kthread if too long since FQS "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-04-12 17:10 +0200
  [PATCH tip/core/rcu 6/6] rcu: Dump ftrace buffer when kicking grace-period kthread "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-04-12 17:10 +0200
  [PATCH tip/core/rcu 2/6] rcu: Awaken grace-period kthread when stalled "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-04-12 17:10 +0200
  [PATCH tip/core/rcu 5/6] rcu: Remove superfluous versions of rcu_read_lock_sched_held() "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-04-12 17:10 +0200
  [PATCH tip/core/rcu 1/6] rcu: Consolidate dumping of ftrace buffer "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-04-12 17:10 +0200

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