On 26/05/2026 5:59 pm, Leo Yan wrote:
Perf resets the CoreSight decoder when moving to a new AUX trace buffer, this causes trace discontinunity globally.
For callchain synthesis, keeping thread-stack state after decoder reset can leave stale call/return history attached to threads that are decoded later, producing incorrect synthesized callchains.
Flush all host thread stacks after a decoder reset. When virtualization is present, flush the guest thread stacks as well.
Signed-off-by: Leo Yan leo.yan@arm.com
tools/perf/util/cs-etm.c | 37 +++++++++++++++++++++++++++++++++++++ 1 file changed, 37 insertions(+)
diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c index 398ab3b7a429d402cc8e5f6cccb35c0b7c253732..ea2424175558ddc0a6f20a9de6c30f377facdc52 100644 --- a/tools/perf/util/cs-etm.c +++ b/tools/perf/util/cs-etm.c @@ -1956,6 +1956,37 @@ static int cs_etm__end_block(struct cs_etm_queue *etmq, return 0; }
+static int cs_etm__flush_stack_cb(struct thread *thread,
void *data __maybe_unused)+{
- thread_stack__flush(thread);
- return 0;
+}
+static void cs_etm__flush_machine_stack(struct cs_etm_queue *etmq, pid_t pid) +{
- struct machine *machine;
- machine = machines__find(&etmq->etm->session->machines, pid);
- if (machine)
machine__for_each_thread(machine, cs_etm__flush_stack_cb, NULL);+}
+static void cs_etm__flush_all_stack(struct cs_etm_queue *etmq) +{
- enum cs_etm_pid_fmt pid_fmt = cs_etm__get_pid_fmt(etmq);
- if (!etmq->etm->synth_opts.last_branch)
return;- cs_etm__flush_machine_stack(etmq, HOST_KERNEL_ID);
- /* Clear the guest stack if virtualization is supported */
- if (pid_fmt == CS_ETM_PIDFMT_CTXTID2)
cs_etm__flush_machine_stack(etmq, DEFAULT_GUEST_KERNEL_ID);+}
- /*
- cs_etm__get_data_block: Fetch a block from the auxtrace_buffer queue
if need be.@@ -1978,6 +2009,12 @@ static int cs_etm__get_data_block(struct cs_etm_queue *etmq) ret = cs_etm_decoder__reset(etmq->decoder); if (ret) return ret;
/** Since the decoder is reset, this causes a global trace* discontinuity. Flush all thread stacks.*/cs_etm__flush_all_stack(etmq);return etmq->buf_len;
Reviewed-by: James Clark james.clark@linaro.org