tracing: Drop lock_acquired waittime field

Drop the waittime field from the lock_acquired event, we can
calculate it by substracting the lock_acquired event timestamp
with the matching lock_acquire one.

It is not needed and takes useless space in the traces.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp>
Cc: Steven Rostedt <rostedt@goodmis.org>

include/trace/events/lock.h

@@ -78,24 +78,21 @@ TRACE_EVENT(lock_contended,
 );
 
 TRACE_EVENT(lock_acquired,
-	TP_PROTO(struct lockdep_map *lock, unsigned long ip, s64 waittime),
+	TP_PROTO(struct lockdep_map *lock, unsigned long ip),
 
-	TP_ARGS(lock, ip, waittime),
+	TP_ARGS(lock, ip),
 
 	TP_STRUCT__entry(
 		__string(name, lock->name)
-		__field(s64, wait_nsec)
 		__field(void *, lockdep_addr)
 	),
 
 	TP_fast_assign(
 		__assign_str(name, lock->name);
-		__entry->wait_nsec = waittime;
 		__entry->lockdep_addr = lock;
 	),
-	TP_printk("%p %s (%llu ns)", __entry->lockdep_addr,
-		  __get_str(name),
-		  __entry->wait_nsec)
+	TP_printk("%p %s", __entry->lockdep_addr,
+		  __get_str(name))
 );
 
 #endif

kernel/lockdep.c

@@ -3380,7 +3380,7 @@ found_it:
 		hlock->holdtime_stamp = now;
 	}
 
-	trace_lock_acquired(lock, ip, waittime);
+	trace_lock_acquired(lock, ip);
 
 	stats = get_lock_stats(hlock_class(hlock));
 	if (waittime) {