perf test: Fix dso cache testcase

The current dso cache permits to keep dso->data.fd is open under a half
of open file limit.  But test__dso_data_cache() sets dso_cnt to limit /
2 + 1 so it'll reach the limit in the loop even though the loop count is
one less than the dso_cnt and it makes the final dso__data_fd() after
the loop meaningless.

I guess the intention was dsos[0]->data.fd is open before the last open
and gets closed after it.  So add an assert before the last open.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1422585209-32742-1-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/tests/dso-data.c

@@ -243,8 +243,8 @@ int test__dso_data_cache(void)
 	limit = nr * 4;
 	TEST_ASSERT_VAL("failed to set file limit", !set_fd_limit(limit));
 
-	/* and this is now our dso open FDs limit + 1 extra */
-	dso_cnt = limit / 2 + 1;
+	/* and this is now our dso open FDs limit */
+	dso_cnt = limit / 2;
 	TEST_ASSERT_VAL("failed to create dsos\n",
 		!dsos__create(dso_cnt, TEST_FILE_SIZE));
 
@@ -268,7 +268,10 @@ int test__dso_data_cache(void)
 		}
 	}
 
-	/* open +1 dso over the allowed limit */
+	/* verify the first one is already open */
+	TEST_ASSERT_VAL("dsos[0] is not open", dsos[0]->data.fd != -1);
+
+	/* open +1 dso to reach the allowed limit */
 	fd = dso__data_fd(dsos[i], &machine);
 	TEST_ASSERT_VAL("failed to get fd", fd > 0);