perf intel-pt: Fix timestamp following overflow

commit 91d29b288aed3406caf7c454bf2b898c96cfd177 upstream.

timestamp_insn_cnt is used to estimate the timestamp based on the number of
instructions since the last known timestamp.

If the estimate is not accurate enough decoding might not be correctly
synchronized with side-band events causing more trace errors.

However there are always timestamps following an overflow, so the
estimate is not needed and can indeed result in more errors.

Suppress the estimate by setting timestamp_insn_cnt to zero.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1520431349-30689-5-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
index 1d0ea0c78d0c0fd5365b3eb4fe8e0edca1b46ffa..cac39532c0574ae005ba9620987a2b30b7f73e7a 100644 (file)
--- a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
+++ b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
@@ -1300,6 +1300,7 @@ static int intel_pt_overflow(struct intel_pt_decoder *decoder)
        intel_pt_clear_tx_flags(decoder);
        decoder->have_tma = false;
        decoder->cbr = 0;
+       decoder->timestamp_insn_cnt = 0;
        decoder->pkt_state = INTEL_PT_STATE_ERR_RESYNC;
        decoder->overflow = true;
        return -EOVERFLOW;