perf: Handle stopped state with tracepoints

commit a0f7d0f7 upstream.

We toggle the state from start and stop callbacks but actually
don't check it when the event triggers. Do it so that
these callbacks actually work.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1299529629-18280-2-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

kernel/perf_event.c

@@ -4167,6 +4167,8 @@ static void tp_perf_event_destroy(struct perf_event *event)
 
 static const struct pmu *tp_perf_event_init(struct perf_event *event)
 {
+	if (event->hw.state & PERF_HES_STOPPED)
+		return 0;
 	/*
 	 * Raw tracepoint data is a severe data leak, only allow root to
 	 * have these.