[PATCH RFC 1/3] locking: Add contended_release tracepoint

[Dmitry Ilvokhin <d@ilvokhin.com>]

Add the contended_release trace event. This tracepoint fires on the
holder side when a contended lock is released, complementing the
existing contention_begin/contention_end tracepoints which fire on the
waiter side.

This enables correlating lock hold time under contention with waiter
events by lock address. Subsequent patches wire this tracepoint into
the individual lock implementations.

Signed-off-by: Dmitry Ilvokhin <d@ilvokhin.com>
---
 include/trace/events/lock.h | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/include/trace/events/lock.h b/include/trace/events/lock.h
index 8e89baa3775f..4f28e41977ec 100644
--- a/include/trace/events/lock.h
+++ b/include/trace/events/lock.h
@@ -138,6 +138,23 @@ TRACE_EVENT(contention_end,
 	TP_printk("%p (ret=%d)", __entry->lock_addr, __entry->ret)
 );
 
+TRACE_EVENT(contended_release,
+
+	TP_PROTO(void *lock),
+
+	TP_ARGS(lock),
+
+	TP_STRUCT__entry(
+		__field(void *, lock_addr)
+	),
+
+	TP_fast_assign(
+		__entry->lock_addr = lock;
+	),
+
+	TP_printk("%p", __entry->lock_addr)
+);
+
 #endif /* _TRACE_LOCK_H */
 
 /* This part must be outside protection */
-- 
2.47.3