I was able to verify that deleting ftrace/test.d/kprobe/multiple_kprobes.tc allows the remaining ftrace selftests (from the cosmic kernel tree) to pass. That suggests that the "Register/unregister many kprobe events" (multiple_kprobes.tc) test is the test that puts the system into a bad state.
I was able to verify that deleting ftrace/ test.d/ kprobe/ multiple_ kprobes. tc allows the remaining ftrace selftests (from the cosmic kernel tree) to pass. That suggests that the "Register/ unregister many kprobe events" (multiple_ kprobes. tc) test is the test that puts the system into a bad state.