tracing/function-graph-tracer: handle ftrace_printk entries

Handle the TRACE_PRINT entries from the function grapg tracer
and output them as a C comment just below the function that called
it, as if it was a comment inside this function.

Example with an ftrace_printk inside might_sleep() function:

void __might_sleep(char *file, int line)
{
	static unsigned long prev_jiffy;	/* ratelimiting */

	ftrace_printk("Hi I'm a comment in might_sleep() :-)");

A chunk of a resulting trace:

 0)               |        _reiserfs_free_block() {
 0)               |          reiserfs_read_bitmap_block() {
 0)               |            __bread() {
 0)               |              __getblk() {
 0)               |                __find_get_block() {
 0)   0.698 us    |                  mark_page_accessed();
 0)   2.267 us    |                }
 0)               |                __might_sleep() {
 0)               |                  /* Hi I'm a comment in might_sleep() :-) */
 0)   1.321 us    |                }
 0)   5.872 us    |              }
 0)   7.313 us    |            }
 0)   8.718 us    |          }

And this patch brings two minor fixes:

- The newline after a switch-out task has disappeared
- The "|" sign just before the cpu number on task-switch has been deleted.

 0)   0.616 us    |                pick_next_task_rt();
 0)   1.457 us    |                _spin_trylock();
 0)   0.653 us    |                _spin_unlock();
 0)   0.728 us    |                _spin_trylock();
 0)   0.631 us    |                _spin_unlock();
 0)   0.729 us    |                native_load_sp0();
 0)   0.593 us    |                native_load_tls();
 ------------------------------------------
 0)    cat-2834    =>   migrati-3
 ------------------------------------------

 0)               |    finish_task_switch() {
 0)   0.841 us    |      _spin_unlock_irq();
 0)   0.616 us    |      post_schedule_rt();
 0)   3.882 us    |    }

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

1 files changed, 71 insertions, 1 deletions

diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index c66578f2fdc2..32b7fb9a19df 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -173,7 +173,7 @@ verif_pid(struct trace_seq *s, pid_t pid, int cpu)
 
  */
         ret = trace_seq_printf(s,
-                "\n ------------------------------------------\n |");
+                " ------------------------------------------\n");
         if (!ret)
                 TRACE_TYPE_PARTIAL_LINE;
 
@@ -477,6 +477,71 @@ print_graph_return(struct ftrace_graph_ret *trace, struct trace_seq *s,
         return TRACE_TYPE_HANDLED;
 }
 
+static enum print_line_t
+print_graph_comment(struct print_entry *trace, struct trace_seq *s,
+                   struct trace_entry *ent, struct trace_iterator *iter)
+{
+        int i;
+        int ret;
+
+        /* Pid */
+        if (verif_pid(s, ent->pid, iter->cpu) == TRACE_TYPE_PARTIAL_LINE)
+                return TRACE_TYPE_PARTIAL_LINE;
+
+        /* Cpu */
+        if (tracer_flags.val & TRACE_GRAPH_PRINT_CPU) {
+                ret = print_graph_cpu(s, iter->cpu);
+                if (ret == TRACE_TYPE_PARTIAL_LINE)
+                        return TRACE_TYPE_PARTIAL_LINE;
+        }
+
+        /* Proc */
+        if (tracer_flags.val & TRACE_GRAPH_PRINT_PROC) {
+                ret = print_graph_proc(s, ent->pid);
+                if (ret == TRACE_TYPE_PARTIAL_LINE)
+                        return TRACE_TYPE_PARTIAL_LINE;
+
+                ret = trace_seq_printf(s, " | ");
+                if (!ret)
+                        return TRACE_TYPE_PARTIAL_LINE;
+        }
+
+        /* No overhead */
+        if (tracer_flags.val & TRACE_GRAPH_PRINT_OVERHEAD) {
+                ret = trace_seq_printf(s, "  ");
+                if (!ret)
+                        return TRACE_TYPE_PARTIAL_LINE;
+        }
+
+        /* No time */
+        ret = trace_seq_printf(s, "            |  ");
+        if (!ret)
+                return TRACE_TYPE_PARTIAL_LINE;
+
+        /* Indentation */
+        if (trace->depth > 0)
+                for (i = 0; i < (trace->depth + 1) * TRACE_GRAPH_INDENT; i++) {
+                        ret = trace_seq_printf(s, " ");
+                        if (!ret)
+                                return TRACE_TYPE_PARTIAL_LINE;
+                }
+
+        /* The comment */
+        ret = trace_seq_printf(s, "/* %s", trace->buf);
+        if (!ret)
+                return TRACE_TYPE_PARTIAL_LINE;
+
+        if (ent->flags & TRACE_FLAG_CONT)
+                trace_seq_print_cont(s, iter);
+
+        ret = trace_seq_printf(s, " */\n");
+        if (!ret)
+                return TRACE_TYPE_PARTIAL_LINE;
+
+        return TRACE_TYPE_HANDLED;
+}
+
+
 enum print_line_t
 print_graph_function(struct trace_iterator *iter)
 {
@@ -495,6 +560,11 @@ print_graph_function(struct trace_iterator *iter)
                 trace_assign_type(field, entry);
                 return print_graph_return(&field->ret, s, entry, iter->cpu);
         }
+        case TRACE_PRINT: {
+                struct print_entry *field;
+                trace_assign_type(field, entry);
+                return print_graph_comment(field, s, entry, iter);
+        }
         default:
                 return TRACE_TYPE_UNHANDLED;
         }