Commit d6404de9 authored by Leo Yan's avatar Leo Yan Committed by Greg Kroah-Hartman

perf cs-etm: Correct packets swapping in cs_etm__flush()

[ Upstream commit 43fd5666 ]

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

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: default avatarLeo Yan <>
Reviewed-by: default avatarMathieu Poirier <>
Cc: Alexander Shishkin <>
Cc: Jiri Olsa <>
Cc: Mike Leach <>
Cc: Namhyung Kim <>
Cc: Robert Walker <>
Link: default avatarArnaldo Carvalho de Melo <>
Signed-off-by: default avatarSasha Levin <>
parent 22b10bb1
......@@ -1005,7 +1005,7 @@ static int cs_etm__flush(struct cs_etm_queue *etmq)
if (etmq->etm->synth_opts.last_branch) {
if (etm->sample_branches || etm->synth_opts.last_branch) {
* the next incoming packet.
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