perf probe: Fix line walker to check CU correctly

Fix line walker to check whether a given DIE is CU or not.

Actually this function accepts CU, subprogram and inlined_subroutine
DIEs.

Without this fix, perf probe always fails to analyze lines on inlined
functions;

$ perf probe -L pre_schedule
Debuginfo analysis failed. (-2)
  Error: Failed to show lines. (-2)

This fixes that bug, as below.

$ perf probe -L pre_schedule
<pre_schedule@/home/mhiramat/ksrc/linux-2.6/kernel/sched.c:0>
      0  static inline void pre_schedule(struct rq *rq, struct task_struct *prev
         {
      2         if (prev->sched_class->pre_schedule)
      3                 prev->sched_class->pre_schedule(rq, prev);
         }

         /* rq->lock is NOT held, but preemption is disabled */

Changes from v1:
 - Update against current tip tree.(Fix dwarf-aux.c)

Cc: Frederic Weisbecker <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/20110811110235.19900.20614.stgit@fedora15
Signed-off-by: Masami Hiramatsu <[email protected]>
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

tools/perf/util/dwarf-aux.c

@@ -439,7 +439,7 @@ static int __die_walk_culines_cb(Dwarf_Die *sp_die, void *data)
 
 /**
  * die_walk_lines - Walk on lines inside given DIE
- * @rt_die: a root DIE (CU or subprogram)
+ * @rt_die: a root DIE (CU, subprogram or inlined_subroutine)
  * @callback: callback routine
  * @data: user data
  *
@@ -460,12 +460,12 @@ int die_walk_lines(Dwarf_Die *rt_die, line_walk_callback_t callback, void *data)
 	size_t nlines, i;
 
 	/* Get the CU die */
-	if (dwarf_tag(rt_die) == DW_TAG_subprogram)
+	if (dwarf_tag(rt_die) != DW_TAG_compile_unit)
 		cu_die = dwarf_diecu(rt_die, &die_mem, NULL, NULL);
 	else
 		cu_die = rt_die;
 	if (!cu_die) {
-		pr_debug2("Failed to get CU from subprogram\n");
+		pr_debug2("Failed to get CU from given DIE.\n");
 		return -EINVAL;
 	}