rcu: Add a trace event for kfree_rcu() use of kfree_bulk()

The event is given three parameters, first one is the name
of RCU flavour, second one is the number of elements in array
for free and last one is an address of the array holding
pointers to be freed by the kfree_bulk() function.

To enable the trace event your kernel has to be build with
CONFIG_RCU_TRACE=y, after that it is possible to track the
events using ftrace subsystem.

Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
index 5e49b06e810445f2d07e1144f7d176a7cf0697c2..49a49e68b916f3e86d1053e713fc26d4839970b2 100644 (file)
--- a/include/trace/events/rcu.h
+++ b/include/trace/events/rcu.h
@@ -623,6 +623,34 @@ TRACE_EVENT_RCU(rcu_invoke_kfree_callback,
                  __entry->rcuname, __entry->rhp, __entry->offset)
 );
 
+/*
+ * Tracepoint for the invocation of a single RCU callback of the special
+ * kfree_bulk() form. The first argument is the RCU flavor, the second
+ * argument is a number of elements in array to free, the third is an
+ * address of the array holding nr_records entries.
+ */
+TRACE_EVENT_RCU(rcu_invoke_kfree_bulk_callback,
+
+       TP_PROTO(const char *rcuname, unsigned long nr_records, void **p),
+
+       TP_ARGS(rcuname, nr_records, p),
+
+       TP_STRUCT__entry(
+               __field(const char *, rcuname)
+               __field(unsigned long, nr_records)
+               __field(void **, p)
+       ),
+
+       TP_fast_assign(
+               __entry->rcuname = rcuname;
+               __entry->nr_records = nr_records;
+               __entry->p = p;
+       ),
+
+       TP_printk("%s bulk=0x%p nr_records=%lu",
+               __entry->rcuname, __entry->p, __entry->nr_records)
+);
+
 /*
  * Tracepoint for exiting rcu_do_batch after RCU callbacks have been
  * invoked.  The first argument is the name of the RCU flavor,

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 51a3aa884a7c60a0bdcd52676774143b9ba26e57..909f97efb1ed26d4f35e1b00cff2c7969ca83a93 100644 (file)
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2792,6 +2792,9 @@ static void kfree_rcu_work(struct work_struct *work)
                debug_rcu_head_unqueue_bulk(bhead->head_free_debug);
 
                rcu_lock_acquire(&rcu_callback_map);
+               trace_rcu_invoke_kfree_bulk_callback(rcu_state.name,
+                       bhead->nr_records, bhead->records);
+
                kfree_bulk(bhead->nr_records, bhead->records);
                rcu_lock_release(&rcu_callback_map);