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@linux.vnet.ibm.com>
[ paulmck: Match operand size per kbuild test robot's advice. ]

1 files changed, 4 insertions, 2 deletions

diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index f4ed24b18e77..24b01b69be92 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;
 }