trace: Fix missing assignment in trace_ctxwake_*

The state char variable S should be reassigned, if S == 0.

We are missing the state of the task that is going to sleep for the
context switch events (in the raw mode).

Fortunately the problem arises with the sched_switch/wake_up
tracers, not the sched trace events.

The formers are legacy now. But still, that was buggy.
Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Cc: Steven Rostedt <srostedt@redhat.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4AC43118.6050409@ct.jp.nec.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/trace/trace_output.c

@@ -883,7 +883,7 @@ static int trace_ctxwake_raw(struct trace_iterator *iter, char S)
 	trace_assign_type(field, iter->ent);
 
 	if (!S)
-		task_state_char(field->prev_state);
+		S = task_state_char(field->prev_state);
 	T = task_state_char(field->next_state);
 	if (!trace_seq_printf(&iter->seq, "%d %d %c %d %d %d %c\n",
 			      field->prev_pid,
@@ -918,7 +918,7 @@ static int trace_ctxwake_hex(struct trace_iterator *iter, char S)
 	trace_assign_type(field, iter->ent);
 
 	if (!S)
-		task_state_char(field->prev_state);
+		S = task_state_char(field->prev_state);
 	T = task_state_char(field->next_state);
 
 	SEQ_PUT_HEX_FIELD_RET(s, field->prev_pid);