[PATCH 1/4] perf tools: Do backtrace post unwind only if we regs and stack were captured

[Jiri Olsa]

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

Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
 tools/perf/util/session.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 9453758..90278ee 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);
-- 
1.7.11.4

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