tracing: Reset the function filter after completing trampoline/graph selftest

The direct trampoline and graph coexistence test sets global_ops to
trace only 'trace_selftest_dynamic_test_func', but does not reset it
after the test is completed, resulting in the function filter being set
already after the system starts. Although it can be reset through the
tracefs interface, it is more or less confusing to the user, and we
should reset it to trace all functions after the trampoline/graph test
completes.

Link: https://lkml.kernel.org/r/20220427034119.24668-1-lihuafei1@huawei.com
Link: https://lore.kernel.org/all/20220418073958.104029-1-lihuafei1@huawei.com/

Fixes: 130c080658 ("tracing: Add trampoline/graph selftest")
Signed-off-by: Li Huafei <lihuafei1@huawei.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

kernel/trace/trace_selftest.c

@@ -895,6 +895,9 @@ trace_selftest_startup_function_graph(struct tracer *trace,
 		ret = -1;
 		goto out;
 	}
+
+	/* Enable tracing on all functions again */
+	ftrace_set_global_filter(NULL, 0, 1);
 #endif
 
 	/* Don't test dynamic tracing, the function tracer already did */