[PATCH v2 3/4] ftrace: Have funcgraph-args take affect during tracing

Steven Rostedt
2024-12-23T20:14:50Z

From: Steven Rostedt <rostedt@goodmis.org>

Currently, when function_graph is started, it looks at the option
funcgraph-args, and if it is set, it will enable tracing of the arguments.

But if tracing is already running, and the user enables funcgraph-args, it
will have no effect. Instead, it should enable argument tracing when it is
enabled, even if it means disabling the function graph tracing for a short
time in order to do the transition.

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
kernel/trace/trace_functions_graph.c | 27 ++++++++++++++++++++++++++-
1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index c8eda9bebdf4..d1ee001f5a8e 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -469,7 +469,7 @@ static int graph_trace_init(struct trace_array *tr)
else
tr->gops->retfunc = trace_graph_return;

- /* Make gops functions are visible before we start tracing */
+ /* Make gops functions visible before we start tracing */
smp_mb();

ret = register_ftrace_graph(tr->gops);
@@ -480,6 +480,28 @@ static int graph_trace_init(struct trace_array *tr)
return 0;
}

+static int ftrace_graph_trace_args(struct trace_array *tr, int set)
+{
+ trace_func_graph_ent_t entry;
+
+ if (set)
+ entry = trace_graph_entry_args;
+ else
+ entry = trace_graph_entry;
+
+ /* See if there's any changes */
+ if (tr->gops->entryfunc == entry)
+ return 0;
+
+ unregister_ftrace_graph(tr->gops);
+
+ tr->gops->entryfunc = entry;
+
+ /* Make gops functions visible before we start tracing */
+ smp_mb();
+ return register_ftrace_graph(tr->gops);
+}
+
static void graph_trace_reset(struct trace_array *tr)
{
tracing_stop_cmdline_record();
@@ -1609,6 +1631,9 @@ func_graph_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set)
if (bit == TRACE_GRAPH_GRAPH_TIME)
ftrace_graph_graph_time_control(set);

+ if (bit == TRACE_GRAPH_ARGS)
+ return ftrace_graph_trace_args(tr, set);
+
return 0;
}

--
2.45.2