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

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Em Mon, Apr 10, 2017 at 01:14:31PM -0700, David Carrillo-Cisneros escreveu:
> A common pattern in in pipe-mode bugs is accessing an empty evlist.
> Return NULL to make it easier to catch this problems.

This one is far reaching, we need to take care handling all places using
these functions, albeit probably most cases will always have an evsel, I
looked at builtin-top.c for instance, and I think we need to be more
careful here, will leave this for later.

- Arnaldo
 
> 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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