tracing/sysprof: add missing tracing_{start,stop}_record_cmdline()

Add the missing pair tracing_{start,stop}_record_cmdline() to record well
the cmdline associated with pid.

Changes in v2:

- fix a build error, the sched_switch tracer is needed to record the
  cmdline.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/trace/Kconfig

@@ -134,6 +134,7 @@ config SYSPROF_TRACER
 	bool "Sysprof Tracer"
 	depends on X86
 	select TRACING
+	select CONTEXT_SWITCH_TRACER
 	help
 	  This tracer provides the trace needed by the 'Sysprof' userspace
 	  tool.

kernel/trace/trace_sysprof.c

@@ -238,6 +238,8 @@ static int stack_trace_init(struct trace_array *tr)
 {
 	sysprof_trace = tr;
 
+	tracing_start_cmdline_record();
+
 	mutex_lock(&sample_timer_lock);
 	start_stack_timers();
 	tracer_enabled = 1;
@@ -247,6 +249,7 @@ static int stack_trace_init(struct trace_array *tr)
 
 static void stack_trace_reset(struct trace_array *tr)
 {
+	tracing_stop_cmdline_record();
 	stop_stack_trace(tr);
 }