linux-kernel - [PATCH tip/core/rcu 09/11] rcu/nocb: Rename and document no-CB CB kthread sleep trace event

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Message-Id: <20190801225028.18225-9-paulmck@linux.ibm.com>
Date:   Thu,  1 Aug 2019 15:50:26 -0700
From:   "Paul E. McKenney" <paulmck@...ux.ibm.com>
To:     rcu@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, mingo@...nel.org,
        jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
        rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
        fweisbec@...il.com, oleg@...hat.com, joel@...lfernandes.org,
        "Paul E. McKenney" <paulmck@...ux.ibm.com>
Subject: [PATCH tip/core/rcu 09/11] rcu/nocb: Rename and document no-CB CB kthread sleep trace event

The nocb_cb_wait() function traces a "FollowerSleep" trace_rcu_nocb_wake()
event, which never was documented and is now misleading.  This commit
therefore changes "FollowerSleep" to "CBSleep", documents this, and
updates the documentation for "Sleep" as well.

Signed-off-by: Paul E. McKenney <paulmck@...ux.ibm.com>
---
 include/trace/events/rcu.h | 3 ++-
 kernel/rcu/tree_plugin.h   | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
index 02a3f78f7cd8..313324d1b135 100644
--- a/include/trace/events/rcu.h
+++ b/include/trace/events/rcu.h
@@ -267,7 +267,8 @@ TRACE_EVENT_RCU(rcu_exp_funnel_lock,
  *	"WakeNotPoll": Don't wake rcuo kthread because it is polling.
  *	"DeferredWake": Carried out the "IsDeferred" wakeup.
  *	"Poll": Start of new polling cycle for rcu_nocb_poll.
- *	"Sleep": Sleep waiting for CBs for !rcu_nocb_poll.
+ *	"Sleep": Sleep waiting for GP for !rcu_nocb_poll.
+ *	"CBSleep": Sleep waiting for CBs for !rcu_nocb_poll.
  *	"WokeEmpty": rcuo kthread woke to find empty list.
  *	"WokeNonEmpty": rcuo kthread woke to find non-empty list.
  *	"WaitQueue": Enqueue partially done, timed wait for it to complete.
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 0af36e98e70f..be065aacd63b 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1891,7 +1891,7 @@ static int rcu_nocb_gp_kthread(void *arg)
  */
 static bool nocb_cb_wait(struct rcu_data *rdp)
 {
-	trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("FollowerSleep"));
+	trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("CBSleep"));
 	swait_event_interruptible_exclusive(rdp->nocb_cb_wq,
 				 READ_ONCE(rdp->nocb_cb_head));
 	if (smp_load_acquire(&rdp->nocb_cb_head)) { /* VVV */
-- 
2.17.1