On 15/12/2023 06:42, Adrian Hunter wrote:

For discussion only, un-tested...

If anyone wants to test Coresight, the diff below is required to get the most basic use case working. It also probably needs more thought and some edge case handling:

diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c index 596c01e37624..bd0767356277 100644 --- a/drivers/hwtracing/coresight/coresight-etm-perf.c +++ b/drivers/hwtracing/coresight/coresight-etm-perf.c @@ -556,7 +556,8 @@ static void etm_event_stop(struct perf_event *event, int mode) struct etm_event_data *event_data; struct list_head *path;

- if (mode & PERF_EF_PAUSE && !READ_ONCE(ctxt->pr_allowed)) + if ((mode & PERF_EF_PAUSE && !READ_ONCE(ctxt->pr_allowed)) || + event->hw.state == PERF_HES_STOPPED) return;

WRITE_ONCE(ctxt->pr_allowed, 0); @@ -573,9 +574,6 @@ static void etm_event_stop(struct perf_event *event, int mode) /* Clear the event_data as this ETM is stopping the trace. */ ctxt->event_data = NULL;

- if (event->hw.state == PERF_HES_STOPPED) - goto out_pr_allowed; - /* We must have a valid event_data for a running event */ if (WARN_ON(!event_data)) return; @@ -586,7 +584,7 @@ static void etm_event_stop(struct perf_event *event, int mode) * nothing needs to be torn down other than outputting a * zero sized record. */ - if (handle->event && (mode & PERF_EF_UPDATE) && + if (handle->event && (mode & (PERF_EF_UPDATE | PERF_EF_PAUSE)) && !cpumask_test_cpu(cpu, &event_data->mask)) { event->hw.state = PERF_HES_STOPPED; perf_aux_output_end(handle, 0); @@ -616,7 +614,7 @@ static void etm_event_stop(struct perf_event *event, int mode) * handle due to lack of buffer space), we don't * have to do anything here. */ - if (handle->event && (mode & PERF_EF_UPDATE)) { + if (handle->event && (mode & (PERF_EF_UPDATE | PERF_EF_PAUSE))) { if (WARN_ON_ONCE(handle->event != event)) return;

@@ -646,7 +644,6 @@ static void etm_event_stop(struct perf_event *event, int mode) /* Disabling the path make its elements available to other sessions */ coresight_disable_path(path);

-out_pr_allowed: if (mode & PERF_EF_PAUSE) WRITE_ONCE(ctxt->pr_allowed, 1); } @@ -656,7 +653,7 @@ static int etm_event_add(struct perf_event *event, int mode) int ret = 0; struct hw_perf_event *hwc = &event->hw;

- if (mode & PERF_EF_START && !READ_ONCE(event->aux_paused)) { + if (mode & PERF_EF_START) { etm_event_start(event, 0); if (hwc->state & PERF_HES_STOPPED) ret = -EINVAL;