[tip:perf/core] perf tools: Do backtrace post unwind only if we regs and stack were captured

[tip-bot for Jiri Olsa <jolsa@redhat.com>]

Commit-ID:  bdde37163e1fd474509aab90f5eaacee46100107
Gitweb:     http://git.kernel.org/tip/bdde37163e1fd474509aab90f5eaacee46100107
Author:     Jiri Olsa <jolsa@redhat.com>
AuthorDate: Mon, 10 Sep 2012 18:50:16 +0200
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Tue, 11 Sep 2012 12:01:15 -0300

perf tools: Do backtrace post unwind only if we regs and stack were captured

Bail out without error if we want to do backtrace post unwind, but were
not able to capture user registers or user stack during the record
phase, which is possible and valid case.

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1347295819-23177-2-git-send-email-jolsa@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/session.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 3806ea4..0ecd62b 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -388,6 +388,11 @@ int machine__resolve_callchain(struct machine *machine,
 	      (evsel->attr.sample_type & PERF_SAMPLE_STACK_USER)))
 		return 0;
 
+	/* Bail out if nothing was captured. */
+	if ((!sample->user_regs.regs) ||
+	    (!sample->user_stack.size))
+		return 0;
+
 	return unwind__get_entries(unwind_entry, &callchain_cursor, machine,
 				   thread, evsel->attr.sample_regs_user,
 				   sample);