ftrace: add thread comm to function graph tracer

Impact: enhancement to function graph tracer

Export the trace_find_cmdline so the function graph tracer can
use it to print the comms of the threads.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

3 files changed, 18 insertions, 6 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 9d5f7c94f251..5811e0a5f732 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -804,7 +804,7 @@ static void trace_save_cmdline(struct task_struct *tsk)
         spin_unlock(&trace_cmdline_lock);
 }
 
-static char *trace_find_cmdline(int pid)
+char *trace_find_cmdline(int pid)
 {
         char *cmdline = "<...>";
         unsigned map;
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index ffe1bb1eb620..7adacf349ef7 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -450,6 +450,7 @@ struct tracer_switch_ops {
         struct tracer_switch_ops        *next;
 };
 
+char *trace_find_cmdline(int pid);
 #endif /* CONFIG_CONTEXT_SWITCH_TRACER */
 
 #ifdef CONFIG_DYNAMIC_FTRACE
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index b6f0cc2a00cb..bbb81e7b6c40 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -32,29 +32,40 @@ static pid_t last_pid = -1;
 
 static int graph_trace_init(struct trace_array *tr)
 {
-        int cpu;
+        int cpu, ret;
+
         for_each_online_cpu(cpu)
                 tracing_reset(tr, cpu);
 
-        return register_ftrace_graph(&trace_graph_return,
+        ret = register_ftrace_graph(&trace_graph_return,
                                         &trace_graph_entry);
+        if (ret)
+                return ret;
+        tracing_start_cmdline_record();
+
+        return 0;
 }
 
 static void graph_trace_reset(struct trace_array *tr)
 {
-                unregister_ftrace_graph();
+        tracing_stop_cmdline_record();
+        unregister_ftrace_graph();
 }
 
 /* If the pid changed since the last trace, output this event */
 static int verif_pid(struct trace_seq *s, pid_t pid)
 {
+        char *comm;
+
         if (last_pid != -1 && last_pid == pid)
                 return 1;
 
         last_pid = pid;
-        return trace_seq_printf(s, "\n------------8<---------- thread %d"
+        comm = trace_find_cmdline(pid);
+
+        return trace_seq_printf(s, "\n------------8<---------- thread %s-%d"
                                     " ------------8<----------\n\n",
-                                  pid);
+                                    comm, pid);
 }
 
 static enum print_line_t