sigusr1_handler
ATF_REQUIRE(SIG_ERR != signal(SIGUSR1, sigusr1_handler));
ATF_REQUIRE(signal(SIGUSR1, sigusr1_handler) != SIG_ERR);
ATF_REQUIRE(signal(SIGUSR1, sigusr1_handler) != SIG_ERR);
ATF_REQUIRE(signal(SIGUSR1, sigusr1_handler) != SIG_ERR);
sa.sa_sigaction = sigusr1_handler;