[tip:core/rcu] rcu: Distinguish between NOCB and non-NOCB rcu_callback trace events

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Commit-ID:  756cbf6befe6f59b0b3e0967d92a66c11e2566ed
Gitweb:     http://git.kernel.org/tip/756cbf6befe6f59b0b3e0967d92a66c11e2566ed
Author:     Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Thu, 15 Aug 2013 10:12:12 -0700
Committer:  Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Mon, 23 Sep 2013 09:18:14 -0700

rcu: Distinguish between NOCB and non-NOCB rcu_callback trace events

One way to distinguish between NOCB and non-NOCB rcu_callback trace
events is that the former always print zero for the lazy and non-lazy
queue lengths.  Unfortunately, this also means that we cannot see the NOCB
queue lengths.  This commit therefore accesses the NOCB queue lengths,
but negates them.  NOCB rcu_callback trace events should therefore have
negative queue lengths.

Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
[ paulmck: Match operand size per kbuild test robot's advice. ]
---
 kernel/rcutree_plugin.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index f4ed24b..24b01b6 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -2147,10 +2147,12 @@ static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp,
 	if (__is_kfree_rcu_offset((unsigned long)rhp->func))
 		trace_rcu_kfree_callback(rdp->rsp->name, rhp,
 					 (unsigned long)rhp->func,
-					 rdp->qlen_lazy, rdp->qlen);
+					 -atomic_long_read(&rdp->nocb_q_count_lazy),
+					 -atomic_long_read(&rdp->nocb_q_count));
 	else
 		trace_rcu_callback(rdp->rsp->name, rhp,
-				   rdp->qlen_lazy, rdp->qlen);
+				   -atomic_long_read(&rdp->nocb_q_count_lazy),
+				   -atomic_long_read(&rdp->nocb_q_count));
 	return 1;
 }
 
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