* David Ahern <[email protected]> wrote:
> Recovery algorithm in __perf_session__process_events attempts to remap
> a perf.data file with a different file_offset and try again at a new head
> position. Both of these adjustment rely on page_offset. If page_offset is
> 0 then file_offset and head never change which means the remap attempt is
> the same and the fetch_mmaped_event is the same and the processing just
> loops forever.
>
> Detect this condition and warn the user.
>
> Signed-off-by: David Ahern <[email protected]>
> Cc: Arnaldo Carvalho de Melo <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: Frederic Weisbecker <[email protected]>
> Cc: Peter Zijlstra <[email protected]>
> Cc: Jiri Olsa <[email protected]>
> Cc: Namhyung Kim <[email protected]>
> Cc: Stephane Eranian <[email protected]>
> ---
> tools/perf/util/session.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
> index cf1fe01..1c4dc45 100644
> --- a/tools/perf/util/session.c
> +++ b/tools/perf/util/session.c
> @@ -1235,6 +1235,12 @@ more:
> }
>
> page_offset = page_size * (head / page_size);
> + /* catch looping where we never make forward progress. */
> + if (page_offset == 0) {
> + pr_err("Loop detection processing events. Is file
> corrupted?\n");
> + return -1;
> + }
> +
> file_offset += page_offset;
> head -= page_offset;
> goto remap;
Ah, nice!
Btw., would it make sense to emit a (once-only) warning and optimistically
fix page_offset up to 1 (or 4096) and let things continue with the next
set of data - can we recover most of the data in that case?
Thanks,
Ingo
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