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Groups > linux.kernel > #1620708

[PATCH 6/7] perf tool: protect empty evlists

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A common pattern in in pipe-mode bugs is accessing an empty evlist.
Return NULL to make it easier to catch this problems.

Signed-off-by: David Carrillo-Cisneros <davidcc@google.com>
---
 tools/perf/util/evlist.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index 39942995f537..ba4788462325 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -257,11 +257,15 @@ void perf_evlist__splice_list_tail(struct perf_evlist *evlist,
 
 static inline struct perf_evsel *perf_evlist__first(struct perf_evlist *evlist)
 {
+	if (list_empty(&evlist->entries))
+		return NULL;
 	return list_entry(evlist->entries.next, struct perf_evsel, node);
 }
 
 static inline struct perf_evsel *perf_evlist__last(struct perf_evlist *evlist)
 {
+	if (list_empty(&evlist->entries))
+		return NULL;
 	return list_entry(evlist->entries.prev, struct perf_evsel, node);
 }
 
-- 
2.12.2.715.g7642488e1d-goog

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[PATCH 0/7] perf tool: pipe-mode fixes David Carrillo-Cisneros <davidcc@google.com> - 2017-04-10 22:20 +0200
  [PATCH 1/7] perf inject: don't proceed if perf_session__process_event fails David Carrillo-Cisneros <davidcc@google.com> - 2017-04-10 22:20 +0200
    [tip:perf/core] perf inject: Don't proceed if  perf_session__process_event() fails tip-bot for David Carrillo-Cisneros <tipbot@zytor.com> - 2017-04-12 07:50 +0200
  [PATCH 2/7] perf inject: copy events when reordering events in pipe mode David Carrillo-Cisneros <davidcc@google.com> - 2017-04-10 22:20 +0200
    Re: [PATCH 2/7] perf inject: copy events when reordering events in  pipe mode Jiri Olsa <jolsa@redhat.com> - 2017-04-11 11:50 +0200
      Re: [PATCH 2/7] perf inject: copy events when reordering events in  pipe mode David Carrillo-Cisneros <davidcc@google.com> - 2017-04-11 21:00 +0200
    [tip:perf/core] perf inject: Copy events when reordering events in  pipe mode tip-bot for David Carrillo-Cisneros <tipbot@zytor.com> - 2017-04-12 07:50 +0200
  [PATCH 4/7] perf annotate: process attr and build_id records David Carrillo-Cisneros <davidcc@google.com> - 2017-04-10 22:20 +0200
    [tip:perf/core] perf annotate: Process attr and build_id records tip-bot for David Carrillo-Cisneros <tipbot@zytor.com> - 2017-04-12 07:50 +0200
  [PATCH 6/7] perf tool: protect empty evlists David Carrillo-Cisneros <davidcc@google.com> - 2017-04-10 22:20 +0200
    Re: [PATCH 6/7] perf tool: protect empty evlists Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-04-11 20:20 +0200
      Re: [PATCH 6/7] perf tool: protect empty evlists David Carrillo-Cisneros <davidcc@google.com> - 2017-04-11 20:40 +0200
  [PATCH 7/7] perf tool: do not print missing features in pipe-mode David Carrillo-Cisneros <davidcc@google.com> - 2017-04-10 22:20 +0200
    [tip:perf/core] perf tools: Do not print missing features in  pipe-mode tip-bot for David Carrillo-Cisneros <tipbot@zytor.com> - 2017-04-12 07:50 +0200
  [PATCH 5/7] perf session: don't rely on evlist in pipe mode David Carrillo-Cisneros <davidcc@google.com> - 2017-04-10 22:20 +0200
    Re: [PATCH 5/7] perf session: don't rely on evlist in pipe mode Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-04-11 20:50 +0200
      Re: [PATCH 5/7] perf session: don't rely on evlist in pipe mode David Carrillo-Cisneros <davidcc@google.com> - 2017-04-11 21:00 +0200
        Re: [PATCH 5/7] perf session: don't rely on evlist in pipe mode Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-04-11 21:50 +0200
    Re: [PATCH 5/7] perf session: don't rely on evlist in pipe mode Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-04-11 20:50 +0200
    Re: [PATCH 5/7] perf session: don't rely on evlist in pipe mode Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-04-11 20:50 +0200
    [tip:perf/core] perf session: Don't rely on evlist in pipe mode tip-bot for David Carrillo-Cisneros <tipbot@zytor.com> - 2017-04-12 07:50 +0200
  Re: [PATCH 0/7] perf tool: pipe-mode fixes Jiri Olsa <jolsa@redhat.com> - 2017-04-11 11:50 +0200
    Re: [PATCH 0/7] perf tool: pipe-mode fixes Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-04-11 20:20 +0200

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