[PATCH v4 3/3] tracing/ftrace: Add support to record and display tgid

[Joel Fernandes]

Make function tracer able to record tgid if/when record-tgid is enabled.

Cc: kernel-t...@android.com
Cc: Steven Rostedt <rost...@goodmis.org>
Cc: Ingo Molnar <mi...@redhat.com>
Tested-by: Michael Sartain <mikes...@gmail.com>
Signed-off-by: Joel Fernandes <joe...@google.com>
---
 kernel/trace/trace_functions.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
index a3bddbfd0874..d6bdc38ab273 100644
--- a/kernel/trace/trace_functions.c
+++ b/kernel/trace/trace_functions.c
@@ -27,6 +27,7 @@ static void
 function_stack_trace_call(unsigned long ip, unsigned long parent_ip,
                          struct ftrace_ops *op, struct pt_regs *pt_regs);
 static struct tracer_flags func_flags;
+static bool tgid_recorded;
 
 /* Our option */
 enum {
@@ -104,6 +105,11 @@ static int function_trace_init(struct trace_array *tr)
        put_cpu();
 
        tracing_start_cmdline_record();
+
+       if (tr->trace_flags & TRACE_ITER_RECORD_TGID) {
+               tgid_recorded = true;
+               tracing_start_tgid_record();
+       }
        tracing_start_function_trace(tr);
        return 0;
 }
@@ -112,6 +118,10 @@ static void function_trace_reset(struct trace_array *tr)
 {
        tracing_stop_function_trace(tr);
        tracing_stop_cmdline_record();
+       if (tgid_recorded) {
+               tracing_stop_tgid_record();
+               tgid_recorded = false;
+       }
        ftrace_reset_array_ops(tr);
 }
 
@@ -252,6 +262,21 @@ func_set_flag(struct trace_array *tr, u32 old_flags, u32 
bit, int set)
        return 0;
 }
 
+static int
+func_tracer_flag_changed(struct trace_array *tr, unsigned int mask,
+                        int enabled)
+{
+       if (mask == TRACE_ITER_RECORD_TGID) {
+               tgid_recorded = !!enabled;
+               if (enabled)
+                       tracing_start_tgid_record();
+               else
+                       tracing_stop_tgid_record();
+       }
+
+       return 0;
+}
+
 static struct tracer function_trace __tracer_data =
 {
        .name           = "function",
@@ -260,6 +285,7 @@ static struct tracer function_trace __tracer_data =
        .start          = function_trace_start,
        .flags          = &func_flags,
        .set_flag       = func_set_flag,
+       .flag_changed   = func_tracer_flag_changed,
        .allow_instances = true,
 #ifdef CONFIG_FTRACE_SELFTEST
        .selftest       = trace_selftest_startup_function,
-- 
2.13.1.611.g7e3b11ae1-goog