ftrace: fix comm on function trace output

In cleaning up of the sched_switch code, the function trace recording
of task comms was removed. This patch adds back the recording of comms
for function trace. The output of ftrace now has the task comm instead
of <...>.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 5 insertions, 2 deletions

diff --git a/kernel/trace/trace_sched_switch.c b/kernel/trace/trace_sched_switch.c
index 5671db0e182..a3376478fc2 100644
--- a/kernel/trace/trace_sched_switch.c
+++ b/kernel/trace/trace_sched_switch.c
@@ -29,8 +29,6 @@ ctx_switch_func(void *__rq, struct task_struct *prev, struct task_struct *next)
         if (!tracer_enabled)
                 return;
 
-        tracing_record_cmdline(prev);
-
         local_irq_save(flags);
         cpu = raw_smp_processor_id();
         data = tr->data[cpu];
@@ -73,6 +71,9 @@ void
 ftrace_ctx_switch(void *__rq, struct task_struct *prev,
                   struct task_struct *next)
 {
+        if (unlikely(atomic_read(&trace_record_cmdline_enabled)))
+                tracing_record_cmdline(prev);
+
         /*
          * If tracer_switch_func only points to the local
          * switch func, it still needs the ptr passed to it.
@@ -134,11 +135,13 @@ static void sched_switch_reset(struct trace_array *tr)
 static void start_sched_trace(struct trace_array *tr)
 {
         sched_switch_reset(tr);
+        atomic_inc(&trace_record_cmdline_enabled);
         tracer_enabled = 1;
 }
 
 static void stop_sched_trace(struct trace_array *tr)
 {
+        atomic_dec(&trace_record_cmdline_enabled);
         tracer_enabled = 0;
 }