Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull perf tooling fixes from Thomas Gleixner:

 - fix 'perf test Session topology' segfault on s390 (Thomas Richter)

 - fix NULL return handling in bpf__prepare_load() (YueHaibing)

 - fix indexing on Coresight ETM packet queue decoder (Mathieu Poirier)

 - fix perf.data format description of NRCPUS header (Arnaldo Carvalho
   de Melo)

 - update perf.data documentation section on cpu topology

 - handle uncore event aliases in small groups properly (Kan Liang)

 - add missing perf_sample.addr into python sample dictionary (Leo Yan)

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf tools: Fix perf.data format description of NRCPUS header
  perf script python: Add addr into perf sample dict
  perf data: Update documentation section on cpu topology
  perf cs-etm: Fix indexing for decoder packet queue
  perf bpf: Fix NULL return handling in bpf__prepare_load()
  perf test: "Session topology" dumps core on s390
  perf parse-events: Handle uncore event aliases in small groups properly

1 files changed, 10 insertions, 2 deletions

diff --git a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
index c8b98fa22997..4d5fc374e730 100644
--- a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
+++ b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
@@ -96,11 +96,19 @@ int cs_etm_decoder__get_packet(struct cs_etm_decoder *decoder,
 	/* Nothing to do, might as well just return */
 	if (decoder->packet_count == 0)
 		return 0;
+	/*
+	 * The queueing process in function cs_etm_decoder__buffer_packet()
+	 * increments the tail *before* using it.  This is somewhat counter
+	 * intuitive but it has the advantage of centralizing tail management
+	 * at a single location.  Because of that we need to follow the same
+	 * heuristic with the head, i.e we increment it before using its
+	 * value.  Otherwise the first element of the packet queue is not
+	 * used.
+	 */
+	decoder->head = (decoder->head + 1) & (MAX_BUFFER - 1);
 
 	*packet = decoder->packet_buffer[decoder->head];
 
-	decoder->head = (decoder->head + 1) & (MAX_BUFFER - 1);
-
 	decoder->packet_count--;
 
 	return 1;