From acd1d7c1f8f3d848a3c5327dc09f8c1efb971678 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Mon, 23 Nov 2009 15:00:36 +0100 Subject: [PATCH] perf_events: Restore sanity to scaling land It is quite possible to call update_event_times() on a context that isn't actually running and thereby confuse the thing. perf stat was reporting !100% scale values for software counters (2e2af50b perf_events: Disable events when we detach them, solved the worst of that, but there was still some left). The thing that happens is that because we are not self-reaping (we have a caring parent) there is a time between the last schedule (out) and having do_exit() called which will detach the events. This period would be accounted as enabled,!running because the event->state==INACTIVE, even though !event->ctx->is_active. Similar issues could have been observed by calling read() on a event while the attached task was not scheduled in. Solve this by teaching update_event_times() about ctx->is_active. Signed-off-by: Peter Zijlstra Cc: Paul Mackerras Cc: Mike Galbraith Cc: Arnaldo Carvalho de Melo Cc: Frederic Weisbecker LKML-Reference: <1258984836.4531.480.camel@laptop> Signed-off-by: Ingo Molnar --- kernel/perf_event.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/kernel/perf_event.c b/kernel/perf_event.c index 0b0d5f72fe7d..0aafe85362fd 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -274,7 +274,12 @@ static void update_event_times(struct perf_event *event) event->group_leader->state < PERF_EVENT_STATE_INACTIVE) return; - event->total_time_enabled = ctx->time - event->tstamp_enabled; + if (ctx->is_active) + run_end = ctx->time; + else + run_end = event->tstamp_stopped; + + event->total_time_enabled = run_end - event->tstamp_enabled; if (event->state == PERF_EVENT_STATE_INACTIVE) run_end = event->tstamp_stopped; -- GitLab