[PATCH 2/2] tracing: Clear trace_state when starting trace

[Masami Hiramatsu]

Clear trace_state data structure when starting trace
in __synth_event_trace_start() internal function.

Currently trace_state is initialized only in the
synth_event_trace_start() API, but the trace_state
in synth_event_trace() and synth_event_trace_array()
are on the stack without initialization.
This means those APIs will see wrong parameters and
wil skip closing process in __synth_event_trace_end()
because trace_state->disabled may be !0.

Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
---
 kernel/trace/trace_events_hist.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 7f0e5cdf17ae..9ec0a7551d62 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -1798,6 +1798,8 @@ __synth_event_trace_start(struct trace_event_file *file,
 	int entry_size, fields_size = 0;
 	int ret = 0;
 
+	memset(trace_state, '\0', sizeof(*trace_state));
+
 	/*
 	 * Normal event tracing doesn't get called at all unless the
 	 * ENABLED bit is set (which attaches the probe thus allowing
@@ -1993,8 +1995,6 @@ int synth_event_trace_start(struct trace_event_file *file,
 	if (!trace_state)
 		return -EINVAL;
 
-	memset(trace_state, '\0', sizeof(*trace_state));
-
 	ret = __synth_event_trace_start(file, trace_state);
 	if (ret == -ENOENT)
 		ret = 0; /* just disabled, not really an error */