tracing: Clear trace_state when starting trace

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.

Link: http://lkml.kernel.org/r/158193315899.8868.1781259176894639952.stgit@devnote2
Reviewed-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index f068d55..9d87aa1 100644 (file)
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -1824,6 +1824,8 @@ __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
@@ -2063,8 +2065,6 @@ 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 */