[PATCH tip/core/rcu 07/10] rcu: Distinguish between NOCB and non-NOCB rcu_callback trace events

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>

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@linux.vnet.ibm.com>
[ 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;
 }
 
-- 
1.8.1.5