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.
Reviewed-by: James Clark james.clark@linaro.org Signed-off-by: Leo Yan leo.yan@arm.com --- tools/perf/util/cs-etm.c | 45 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+)
diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c index ba9ffb7bdb4bd95c9dc6c323c0d56f516aae56b8..996317687ce7b241afed83444b554155edb09564 100644 --- a/tools/perf/util/cs-etm.c +++ b/tools/perf/util/cs-etm.c @@ -2033,6 +2033,45 @@ 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; + + switch (pid_fmt) { + case CS_ETM_PIDFMT_CTXTID2: + /* Clear the guest stack if virtualization is supported */ + cs_etm__flush_machine_stack(etmq, DEFAULT_GUEST_KERNEL_ID); + fallthrough; + case CS_ETM_PIDFMT_CTXTID: + cs_etm__flush_machine_stack(etmq, HOST_KERNEL_ID); + break; + case CS_ETM_PIDFMT_NONE: + default: + break; + + } +} + /* * cs_etm__get_data_block: Fetch a block from the auxtrace_buffer queue * if need be. @@ -2055,6 +2094,12 @@ 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;