perf evsel: Dummy events never triggers, no need to ask for PERF_SAMPLE_BRANCH_STACK

A dummy event never triggers any actual counter and therefore cannot be
used with branch_stack
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/20200422173615.59436-1-irogers@google.com
[ split from a larger patch ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/evsel.c

@@ -1153,11 +1153,14 @@ void evsel__config(struct evsel *evsel, struct record_opts *opts,
 	}
 
 	/*
+	 * A dummy event never triggers any actual counter and therefore
+	 * cannot be used with branch_stack.
+	 *
 	 * For initial_delay, a dummy event is added implicitly.
 	 * The software event will trigger -EOPNOTSUPP error out,
 	 * if BRANCH_STACK bit is set.
 	 */
-	if (opts->initial_delay && is_dummy_event(evsel))
+	if (is_dummy_event(evsel))
 		evsel__reset_sample_bit(evsel, BRANCH_STACK);
 }