From: Leo Yan leo.yan@linaro.org
The structure cs_etm_queue uses 'prev_packet' to point to previous packet, this can be used to combine with new coming packet to generate samples.
In function cs_etm__flush() it swaps packets only when the flag 'etm->synth_opts.last_branch' is true, this means that it will not swap packets if without option '--itrace=il' to generate last branch entries; thus for this case the 'prev_packet' doesn't point to the correct previous packet and the stale packet still will be used to generate sequential sample. Thus if dump trace with 'perf script' command we can see the incorrect flow with the stale packet's address info.
This patch corrects packets swapping in cs_etm__flush(); except using the flag 'etm->synth_opts.last_branch' it also checks the another flag 'etm->sample_branches', if any flag is true then it swaps packets so can save correct content to 'prev_packet'. Finally this can fix the wrong program flow dumping issue.
The patch has a minor refactoring to use 'etm->synth_opts.last_branch' instead of 'etmq->etm->synth_opts.last_branch' for condition checking, this is consistent with that is done in cs_etm__sample().
Signed-off-by: Leo Yan leo.yan@linaro.org Reviewed-by: Mathieu Poirier mathieu.poirier@linaro.org Cc: Alexander Shishkin alexander.shishkin@linux.intel.com Cc: Jiri Olsa jolsa@redhat.com Cc: Mike Leach mike.leach@linaro.org Cc: Namhyung Kim namhyung@kernel.org Cc: Robert Walker robert.walker@arm.com Cc: coresight@lists.linaro.org Cc: linux-arm-kernel@lists.infradead.org Link: http://lkml.kernel.org/r/1544513908-16805-2-git-send-email-leo.yan@linaro.or... Signed-off-by: Arnaldo Carvalho de Melo acme@redhat.com --- tools/perf/util/cs-etm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c index 23159c33db2a..789707bc4e9e 100644 --- a/tools/perf/util/cs-etm.c +++ b/tools/perf/util/cs-etm.c @@ -1042,7 +1042,7 @@ static int cs_etm__flush(struct cs_etm_queue *etmq) }
swap_packet: - if (etmq->etm->synth_opts.last_branch) { + if (etm->sample_branches || etm->synth_opts.last_branch) { /* * Swap PACKET with PREV_PACKET: PACKET becomes PREV_PACKET for * the next incoming packet.