timerfd: Add tests

Take Jan Kokemuller's timerfd tests from the epoll-shim project,
stripping out code that isn't directly related to FreeBSD.

Reviewed by:		markj
Differential Revision:	https://reviews.freebsd.org/D55789
MFC after:		2 weeks

2 files changed, 1321 insertions, 0 deletions

diff --git a/tests/sys/kern/Makefile b/tests/sys/kern/Makefile
index 6d59a752bb4f..0e505d6cb51a 100644
--- a/tests/sys/kern/Makefile
+++ b/tests/sys/kern/Makefile
@@ -53,6 +53,9 @@ ATF_TESTS_C+=	subr_physmem_test
 PLAIN_TESTS_C+=	subr_unit_test
 ATF_TESTS_C+=	sysctl_kern_proc
 ATF_TESTS_C+=	sys_getrandom
+ATF_TESTS_C+=	timerfd
+CFLAGS.timerfd+=	-I${.CURDIR}
+LIBADD.timerfd+=	pthread
 ATF_TESTS_C+=	tty_pts
 ATF_TESTS_C+=	unix_dgram
 ATF_TESTS_C+=	unix_passfd_dgram
diff --git a/tests/sys/kern/timerfd.c b/tests/sys/kern/timerfd.c
new file mode 100644
index 000000000000..37cb4924faf1
--- /dev/null
+++ b/tests/sys/kern/timerfd.c
@@ -0,0 +1,1318 @@
+/*-
+ * SPDX-License-Identifier: MIT
+ *
+ * Copyright (c) 2016 Jan Kokemüller
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include <atf-c.h>
+
+#include <sys/types.h>
+
+#include <sys/event.h>
+#include <sys/param.h>
+#include <sys/select.h>
+#include <sys/time.h>
+
+#include <errno.h>
+#include <signal.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <err.h>
+#include <poll.h>
+#include <pthread.h>
+#include <time.h>
+#include <unistd.h>
+
+#include <sys/timerfd.h>
+
+/* Time in ns that sleeps are allowed to take longer for in unit tests. */
+#define TIMER_SLACK (90000000)
+
+ATF_TC_WITHOUT_HEAD(timerfd__many_timers);
+ATF_TC_BODY(timerfd__many_timers, tc)
+{
+	int timer_fds[256];
+	int i;
+
+	for (i = 0; i < (int)nitems(timer_fds); ++i) {
+		timer_fds[i] = timerfd_create(CLOCK_MONOTONIC, /**/
+		    TFD_CLOEXEC | TFD_NONBLOCK);
+		if (timer_fds[i] < 0 && errno == EMFILE) {
+			atf_tc_skip("timerfd_create: EMFILE");
+		}
+		ATF_REQUIRE_MSG(timer_fds[i] >= 0, "errno: %d", errno);
+	}
+}
+
+static uint64_t
+wait_for_timerfd(int timerfd)
+{
+	struct pollfd pfd = { .fd = timerfd, .events = POLLIN };
+
+	ATF_REQUIRE(poll(&pfd, 1, -1) == 1);
+
+	uint64_t timeouts;
+	ssize_t r = read(timerfd, &timeouts, sizeof(timeouts));
+
+	ATF_REQUIRE_MSG(r == (ssize_t)sizeof(timeouts), "%d %d", (int)r, errno);
+	ATF_REQUIRE(timeouts > 0);
+	return timeouts;
+}
+
+ATF_TC_WITHOUT_HEAD(timerfd__simple_timer);
+ATF_TC_BODY(timerfd__simple_timer, tc)
+{
+	int timerfd = timerfd_create(CLOCK_MONOTONIC, /**/
+	    TFD_CLOEXEC | TFD_NONBLOCK);
+
+	ATF_REQUIRE(timerfd >= 0);
+
+	struct itimerspec time = {
+		.it_value.tv_sec = 0,
+		.it_value.tv_nsec = 100000000,
+	};
+
+	struct timespec b, e;
+	ATF_REQUIRE(clock_gettime(CLOCK_MONOTONIC, &b) == 0);
+
+	ATF_REQUIRE(timerfd_settime(timerfd, 0, &time, NULL) == 0);
+	(void)wait_for_timerfd(timerfd);
+
+	ATF_REQUIRE(clock_gettime(CLOCK_MONOTONIC, &e) == 0);
+	timespecsub(&e, &b, &e);
+
+	ATF_REQUIRE((e.tv_sec == 0 && e.tv_nsec >= 100000000) || e.tv_sec > 0);
+	ATF_REQUIRE(e.tv_sec == 0 && e.tv_nsec < 100000000 + TIMER_SLACK);
+
+	ATF_REQUIRE(close(timerfd) == 0);
+}
+
+ATF_TC_WITHOUT_HEAD(timerfd__simple_periodic_timer);
+ATF_TC_BODY(timerfd__simple_periodic_timer, tc)
+{
+	int timerfd = timerfd_create(CLOCK_MONOTONIC, /**/
+	    TFD_CLOEXEC | TFD_NONBLOCK);
+
+	ATF_REQUIRE(timerfd >= 0);
+
+	struct itimerspec time = {
+		.it_value.tv_sec = 0,
+		.it_value.tv_nsec = 200000000,
+		.it_interval.tv_sec = 0,
+		.it_interval.tv_nsec = 200000000,
+	};
+
+	struct timespec b, e;
+	ATF_REQUIRE(clock_gettime(CLOCK_MONOTONIC, &b) == 0);
+
+	ATF_REQUIRE(timerfd_settime(timerfd, 0, &time, NULL) == 0);
+	uint64_t timeouts = wait_for_timerfd(timerfd);
+
+	ATF_REQUIRE(clock_gettime(CLOCK_MONOTONIC, &e) == 0);
+	timespecsub(&e, &b, &e);
+
+	ATF_REQUIRE((e.tv_sec == 0 && e.tv_nsec >= 200000000) || e.tv_sec > 0);
+	ATF_REQUIRE(timeouts >= 1);
+	ATF_REQUIRE(e.tv_sec == 0 && e.tv_nsec < 200000000 + TIMER_SLACK);
+	ATF_REQUIRE(timeouts == 1);
+
+	usleep(400000);
+
+	ATF_REQUIRE(read(timerfd, &timeouts, sizeof(timeouts)) ==
+	    (ssize_t)sizeof(timeouts));
+	ATF_REQUIRE(timeouts >= 2);
+	ATF_REQUIRE(timeouts == 2);
+
+	ATF_REQUIRE(close(timerfd) == 0);
+}
+
+ATF_TC_WITHOUT_HEAD(timerfd__complex_periodic_timer);
+ATF_TC_BODY(timerfd__complex_periodic_timer, tc)
+{
+	int timerfd = timerfd_create(CLOCK_MONOTONIC, /**/
+	    TFD_CLOEXEC | TFD_NONBLOCK);
+
+	ATF_REQUIRE(timerfd >= 0);
+
+	struct itimerspec time = {
+		.it_value.tv_sec = 0,
+		.it_value.tv_nsec = 100000000,
+		.it_interval.tv_sec = 0,
+		.it_interval.tv_nsec = 200000001,
+	};
+
+	struct timespec b, e;
+	ATF_REQUIRE(clock_gettime(CLOCK_MONOTONIC, &b) == 0);
+
+	ATF_REQUIRE(timerfd_settime(timerfd, 0, &time, NULL) == 0);
+	uint64_t timeouts = wait_for_timerfd(timerfd);
+
+	ATF_REQUIRE(clock_gettime(CLOCK_MONOTONIC, &e) == 0);
+	timespecsub(&e, &b, &e);
+
+	ATF_REQUIRE((e.tv_sec == 0 && e.tv_nsec >= 100000000) || e.tv_sec > 0);
+	ATF_REQUIRE(timeouts >= 1);
+	ATF_REQUIRE_MSG(e.tv_sec == 0 && e.tv_nsec >= 100000000 &&
+		e.tv_nsec < 100000000 + TIMER_SLACK,
+	    "%ld", (long)e.tv_nsec);
+	ATF_REQUIRE(timeouts == 1);
+
+	usleep(401000);
+
+	ATF_REQUIRE(read(timerfd, &timeouts, sizeof(timeouts)) ==
+	    (ssize_t)sizeof(timeouts));
+	ATF_REQUIRE_MSG(timeouts >= 2, "%d", (int)timeouts);
+	ATF_REQUIRE_MSG(timeouts == 2, "%d", (int)timeouts);
+
+	ATF_REQUIRE(close(timerfd) == 0);
+}
+
+ATF_TC_WITHOUT_HEAD(timerfd__reset_periodic_timer);
+ATF_TC_BODY(timerfd__reset_periodic_timer, tc)
+{
+	int timerfd = timerfd_create(CLOCK_MONOTONIC, /**/
+	    TFD_CLOEXEC | TFD_NONBLOCK);
+
+	ATF_REQUIRE(timerfd >= 0);
+
+	struct itimerspec time = {
+		.it_value.tv_sec = 0,
+		.it_value.tv_nsec = 100000000,
+		.it_interval.tv_sec = 0,
+		.it_interval.tv_nsec = 100000000,
+	};
+
+	struct timespec b, e;
+	ATF_REQUIRE(clock_gettime(CLOCK_MONOTONIC, &b) == 0);
+
+	ATF_REQUIRE(timerfd_settime(timerfd, 0, &time, NULL) == 0);
+	(void)wait_for_timerfd(timerfd);
+
+	time = (struct itimerspec) {
+		.it_value.tv_sec = 0,
+		.it_value.tv_nsec = 50000000,
+		.it_interval.tv_sec = 0,
+		.it_interval.tv_nsec = 100000000,
+	};
+
+	ATF_REQUIRE(timerfd_settime(timerfd, 0, &time, NULL) == 0);
+
+	uint64_t timeouts = wait_for_timerfd(timerfd);
+	ATF_REQUIRE(timeouts >= 1);
+	ATF_REQUIRE(timeouts == 1);
+
+	ATF_REQUIRE(clock_gettime(CLOCK_MONOTONIC, &e) == 0);
+	timespecsub(&e, &b, &e);
+	ATF_REQUIRE((e.tv_sec == 0 && e.tv_nsec >= 150000000) || e.tv_sec > 0);
+	ATF_REQUIRE(e.tv_sec == 0 && e.tv_nsec >= 150000000 &&
+	    e.tv_nsec < 150000000 + TIMER_SLACK * 2);
+
+	ATF_REQUIRE(close(timerfd) == 0);
+}
+
+ATF_TC_WITHOUT_HEAD(timerfd__reenable_periodic_timer);
+ATF_TC_BODY(timerfd__reenable_periodic_timer, tc)
+{
+	int timerfd = timerfd_create(CLOCK_MONOTONIC, /**/
+	    TFD_CLOEXEC | TFD_NONBLOCK);
+
+	ATF_REQUIRE(timerfd >= 0);
+
+	struct itimerspec time = {
+		.it_value.tv_sec = 0,
+		.it_value.tv_nsec = 100000000,
+		.it_interval.tv_sec = 0,
+		.it_interval.tv_nsec = 100000000,
+	};
+
+	struct timespec b, e;
+	ATF_REQUIRE(clock_gettime(CLOCK_MONOTONIC, &b) == 0);
+
+	ATF_REQUIRE(timerfd_settime(timerfd, 0, &time, NULL) == 0);
+	uint64_t timeouts = wait_for_timerfd(timerfd);
+
+	ATF_REQUIRE(timeouts >= 1);
+	ATF_REQUIRE(timeouts == 1);
+
+	time = (struct itimerspec) {
+		.it_value.tv_sec = 0,
+		.it_value.tv_nsec = 0,
+		.it_interval.tv_sec = 0,
+		.it_interval.tv_nsec = 0,
+	};
+
+	ATF_REQUIRE(timerfd_settime(timerfd, 0, &time, NULL) == 0);
+
+	struct pollfd pfd = { .fd = timerfd, .events = POLLIN };
+	ATF_REQUIRE(poll(&pfd, 1, 250) == 0);
+
+	ATF_REQUIRE(clock_gettime(CLOCK_MONOTONIC, &e) == 0);
+	timespecsub(&e, &b, &e);
+
+	ATF_REQUIRE((e.tv_sec == 0 && e.tv_nsec >= 350000000) || e.tv_sec > 0);
+	ATF_REQUIRE(e.tv_sec == 0 && e.tv_nsec >= 350000000 &&
+	    e.tv_nsec < 350000000 + TIMER_SLACK * 2);
+
+	time = (struct itimerspec) {
+		.it_value.tv_sec = 1,
+		.it_value.tv_nsec = 0,
+		.it_interval.tv_sec = 1,
+		.it_interval.tv_nsec = 0,
+	};
+	ATF_REQUIRE(timerfd_settime(timerfd, 0, &time, NULL) == 0);
+
+	ATF_REQUIRE(close(timerfd) == 0);
+}
+
+/*
+ * Adapted from sghctoma's example here:
+ * https://github.com/jiixyj/epoll-shim/issues/2
+ *
+ * The SIGUSR1 signal should not kill the process.
+ */
+ATF_TC_WITHOUT_HEAD(timerfd__expire_five);
+ATF_TC_BODY(timerfd__expire_five, tc)
+{
+	int fd;
+	struct itimerspec value;
+	uint64_t total_exp = 0;
+
+	fd = timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC | TFD_NONBLOCK);
+	ATF_REQUIRE(fd >= 0);
+
+	value.it_value.tv_sec = 3;
+	value.it_value.tv_nsec = 0;
+	value.it_interval.tv_sec = 1;
+	value.it_interval.tv_nsec = 0;
+
+	ATF_REQUIRE(timerfd_settime(fd, 0, &value, NULL) == 0);
+
+	sigset_t sigs;
+	sigemptyset(&sigs);
+	sigaddset(&sigs, SIGUSR1);
+	sigprocmask(SIG_BLOCK, &sigs, NULL);
+
+	kill(getpid(), SIGUSR1);
+
+	for (;;) {
+		uint64_t exp = wait_for_timerfd(fd);
+
+		printf("timer expired %u times\n", (unsigned)exp);
+
+		total_exp += exp;
+		if (total_exp >= 5) {
+			break;
+		}
+	}
+
+	ATF_REQUIRE(close(fd) == 0);
+}
+
+ATF_TC_WITHOUT_HEAD(timerfd__simple_gettime);
+ATF_TC_BODY(timerfd__simple_gettime, tc)
+{
+	struct itimerspec curr_value;
+
+	int fd = timerfd_create(CLOCK_MONOTONIC, 0);
+	ATF_REQUIRE(fd >= 0);
+
+	ATF_REQUIRE(timerfd_gettime(fd, &curr_value) == 0);
+
+	ATF_REQUIRE(curr_value.it_value.tv_sec == 0);
+	ATF_REQUIRE(curr_value.it_value.tv_nsec == 0);
+	ATF_REQUIRE(curr_value.it_interval.tv_sec == 0);
+	ATF_REQUIRE(curr_value.it_interval.tv_nsec == 0);
+
+	struct itimerspec time = {
+		.it_value.tv_sec = 0,
+		.it_value.tv_nsec = 100000000,
+		.it_interval.tv_sec = 0,
+		.it_interval.tv_nsec = 100000000,
+	};
+
+	curr_value = time;
+	ATF_REQUIRE(timerfd_settime(fd, 0, &time, &curr_value) == 0);
+	ATF_REQUIRE(curr_value.it_value.tv_sec == 0);
+	ATF_REQUIRE(curr_value.it_value.tv_nsec == 0);
+	ATF_REQUIRE(curr_value.it_interval.tv_sec == 0);
+	ATF_REQUIRE(curr_value.it_interval.tv_nsec == 0);
+
+	ATF_REQUIRE(close(fd) == 0);
+}
+
+ATF_TC_WITHOUT_HEAD(timerfd__simple_blocking_periodic_timer);
+ATF_TC_BODY(timerfd__simple_blocking_periodic_timer, tc)
+{
+	int timerfd = timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC);
+
+	ATF_REQUIRE(timerfd >= 0);
+
+	struct itimerspec time = {
+		.it_value.tv_sec = 0,
+		.it_value.tv_nsec = 100000000,
+		.it_interval.tv_sec = 0,
+		.it_interval.tv_nsec = 100000000,
+	};
+
+	struct timespec b, e;
+	ATF_REQUIRE(clock_gettime(CLOCK_MONOTONIC, &b) == 0);
+
+	ATF_REQUIRE(timerfd_settime(timerfd, 0, &time, NULL) == 0);
+
+	uint64_t timeouts = 0;
+	int num_loop_iterations = 0;
+
+	while (timeouts < 3) {
+		uint64_t timeouts_local;
+		ATF_REQUIRE(
+		    read(timerfd, &timeouts_local, sizeof(timeouts_local)) ==
+		    (ssize_t)sizeof(timeouts_local));
+		ATF_REQUIRE(timeouts_local > 0);
+
+		++num_loop_iterations;
+		timeouts += timeouts_local;
+	}
+
+	ATF_REQUIRE(clock_gettime(CLOCK_MONOTONIC, &e) == 0);
+	timespecsub(&e, &b, &e);
+
+	ATF_REQUIRE((e.tv_sec == 0 && e.tv_nsec >= 300000000) || e.tv_sec > 0);
+	ATF_REQUIRE(e.tv_sec == 0 && e.tv_nsec >= 300000000 &&
+	    e.tv_nsec < 300000000 + TIMER_SLACK);
+
+	ATF_REQUIRE(num_loop_iterations <= 3);
+
+	ATF_REQUIRE(close(timerfd) == 0);
+}
+
+ATF_TC_WITHOUT_HEAD(timerfd__argument_checks);
+ATF_TC_BODY(timerfd__argument_checks, tc)
+{
+	int timerfd = timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC);
+	ATF_REQUIRE(timerfd >= 0);
+
+	struct itimerspec time = {
+		.it_value.tv_sec = 0,
+		.it_value.tv_nsec = 100000000,
+		.it_interval.tv_sec = 0,
+		.it_interval.tv_nsec = 100000000,
+	};
+
+	ATF_REQUIRE_ERRNO(EFAULT, timerfd_settime(timerfd, 0, NULL, NULL) < 0);
+	ATF_REQUIRE_ERRNO(EFAULT, timerfd_settime(-2, 0, NULL, NULL) < 0);
+	ATF_REQUIRE_ERRNO(EBADF, timerfd_settime(-2, 0, &time, NULL) < 0);
+	ATF_REQUIRE_ERRNO(EFAULT, timerfd_settime(-2, 42, NULL, NULL) < 0);
+	ATF_REQUIRE_ERRNO(EINVAL, timerfd_settime(-2, 42, &time, NULL) < 0);
+	ATF_REQUIRE_ERRNO(EINVAL,
+	    timerfd_settime(timerfd, 42, &time, NULL) < 0);
+
+	{
+		time = (struct itimerspec) {
+			.it_value.tv_sec = -1,
+			.it_value.tv_nsec = 100000000,
+			.it_interval.tv_sec = 0,
+			.it_interval.tv_nsec = 100000000,
+		};
+		ATF_REQUIRE_ERRNO(EINVAL,
+		    timerfd_settime(timerfd, 0, &time, NULL) < 0);
+	}
+	{
+		time = (struct itimerspec) {
+			.it_value.tv_sec = 0,
+			.it_value.tv_nsec = -1,
+			.it_interval.tv_sec = 0,
+			.it_interval.tv_nsec = 100000000,
+		};
+		ATF_REQUIRE_ERRNO(EINVAL,
+		    timerfd_settime(timerfd, 0, &time, NULL) < 0);
+	}
+	{
+		time = (struct itimerspec) {
+			.it_value.tv_sec = 0,
+			.it_value.tv_nsec = 100000000,
+			.it_interval.tv_sec = -1,
+			.it_interval.tv_nsec = 100000000,
+		};
+		ATF_REQUIRE_ERRNO(EINVAL,
+		    timerfd_settime(timerfd, 0, &time, NULL) < 0);
+	}
+	{
+		time = (struct itimerspec) {
+			.it_value.tv_sec = 0,
+			.it_value.tv_nsec = 100000000,
+			.it_interval.tv_sec = 0,
+			.it_interval.tv_nsec = -1,
+		};
+		ATF_REQUIRE_ERRNO(EINVAL,
+		    timerfd_settime(timerfd, 0, &time, NULL) < 0);
+	}
+	{
+		time = (struct itimerspec) {
+			.it_value.tv_sec = 0,
+			.it_value.tv_nsec = 1000000000,
+			.it_interval.tv_sec = 0,
+			.it_interval.tv_nsec = 100000000,
+		};
+		ATF_REQUIRE_ERRNO(EINVAL,
+		    timerfd_settime(timerfd, 0, &time, NULL) < 0);
+	}
+	{
+		time = (struct itimerspec) {
+			.it_value.tv_sec = 0,
+			.it_value.tv_nsec = 100000000,
+			.it_interval.tv_sec = 0,
+			.it_interval.tv_nsec = 1000000000,
+		};
+		ATF_REQUIRE_ERRNO(EINVAL,
+		    timerfd_settime(timerfd, 0, &time, NULL) < 0);
+	}
+
+	ATF_REQUIRE_ERRNO(EINVAL,
+	    timerfd_create(CLOCK_MONOTONIC | 42, TFD_CLOEXEC));
+	ATF_REQUIRE_ERRNO(EINVAL,
+	    timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC | 42));
+
+	ATF_REQUIRE(close(timerfd) == 0);
+
+	struct itimerspec itimerspec;
+	ATF_REQUIRE_ERRNO(EBADF, timerfd_gettime(timerfd, &itimerspec) < 0);
+	ATF_REQUIRE_ERRNO(EINVAL,
+	    timerfd_settime(timerfd, 0, &itimerspec, NULL) < 0);
+}
+
+ATF_TC_WITHOUT_HEAD(timerfd__upgrade_simple_to_complex);
+ATF_TC_BODY(timerfd__upgrade_simple_to_complex, tc)
+{
+	int timerfd = timerfd_create(CLOCK_MONOTONIC, /**/
+	    TFD_CLOEXEC | TFD_NONBLOCK);
+
+	ATF_REQUIRE(timerfd >= 0);
+
+	struct itimerspec time = {
+		.it_value.tv_sec = 0,
+		.it_value.tv_nsec = 100000000,
+		.it_interval.tv_sec = 0,
+		.it_interval.tv_nsec = 100000000,
+	};
+
+	ATF_REQUIRE(timerfd_settime(timerfd, 0, &time, NULL) == 0);
+	(void)wait_for_timerfd(timerfd);
+
+	time = (struct itimerspec) {
+		.it_value.tv_sec = 0,
+		.it_value.tv_nsec = 50000000,
+		.it_interval.tv_sec = 0,
+		.it_interval.tv_nsec = 95000000,
+	};
+
+	struct timespec b, e;
+	ATF_REQUIRE(clock_gettime(CLOCK_MONOTONIC, &b) == 0);
+
+	ATF_REQUIRE(timerfd_settime(timerfd, 0, &time, NULL) == 0);
+
+	uint64_t timeouts = wait_for_timerfd(timerfd);
+	ATF_REQUIRE(timeouts >= 1);
+	ATF_REQUIRE(timeouts == 1);
+
+	ATF_REQUIRE(clock_gettime(CLOCK_MONOTONIC, &e) == 0);
+	timespecsub(&e, &b, &e);
+	ATF_REQUIRE((e.tv_sec == 0 && e.tv_nsec >= 50000000) || e.tv_sec > 0);
+	ATF_REQUIRE_MSG(e.tv_sec == 0 && e.tv_nsec < 50000000 + TIMER_SLACK,
+	    "%ld", e.tv_nsec);
+
+	timeouts = wait_for_timerfd(timerfd);
+	ATF_REQUIRE(timeouts >= 1);
+	ATF_REQUIRE(timeouts == 1);
+
+	ATF_REQUIRE(clock_gettime(CLOCK_MONOTONIC, &e) == 0);
+	timespecsub(&e, &b, &e);
+	ATF_REQUIRE((e.tv_sec == 0 && e.tv_nsec >= 145000000) || e.tv_sec > 0);
+	ATF_REQUIRE(e.tv_sec == 0 && e.tv_nsec >= 145000000 &&
+	    e.tv_nsec < 145000000 + TIMER_SLACK);
+
+	ATF_REQUIRE(close(timerfd) == 0);
+}
+
+ATF_TC_WITHOUT_HEAD(timerfd__absolute_timer);
+ATF_TC_BODY(timerfd__absolute_timer, tc)
+{
+	int timerfd = timerfd_create(CLOCK_MONOTONIC, /**/
+	    TFD_CLOEXEC | TFD_NONBLOCK);
+
+	ATF_REQUIRE(timerfd >= 0);
+
+	struct timespec b, e;
+	ATF_REQUIRE(clock_gettime(CLOCK_MONOTONIC, &b) == 0);
+
+	struct itimerspec time = {
+		.it_value = b,
+		.it_interval.tv_sec = 0,
+		.it_interval.tv_nsec = 0,
+	};
+
+	struct timespec ts_600ms = {
+		.tv_sec = 0,
+		.tv_nsec = 600000000,
+	};
+
+	timespecadd(&time.it_value, &ts_600ms, &time.it_value);
+
+	ATF_REQUIRE(timerfd_settime(timerfd, /**/
+			TFD_TIMER_ABSTIME, &time, NULL) == 0);
+
+	struct pollfd pfd = { .fd = timerfd, .events = POLLIN };
+	ATF_REQUIRE(poll(&pfd, 1, -1) == 1);
+
+	// Don't read(2) here!
+
+	ATF_REQUIRE(clock_gettime(CLOCK_MONOTONIC, &e) == 0);
+	timespecsub(&e, &b, &e);
+	ATF_REQUIRE(e.tv_sec == 0 &&
+	    /* Don't check for this because of spurious wakeups. */
+	    /* e.tv_nsec >= 600000000 && */
+	    e.tv_nsec < 600000000 + TIMER_SLACK);
+
+	struct itimerspec zeroed_its = {
+		.it_value.tv_sec = 0,
+		.it_value.tv_nsec = 0,
+		.it_interval.tv_sec = 0,
+		.it_interval.tv_nsec = 0,
+	};
+	ATF_REQUIRE(timerfd_settime(timerfd, 0, &zeroed_its, NULL) == 0);
+
+	uint64_t timeouts;
+	ATF_REQUIRE_ERRNO(EAGAIN,
+	    read(timerfd, &timeouts, sizeof(timeouts)) < 0);
+
+	ATF_REQUIRE(poll(&pfd, 1, 0) == 0);
+
+	ATF_REQUIRE(close(timerfd) == 0);
+}
+
+ATF_TC_WITHOUT_HEAD(timerfd__absolute_timer_in_the_past);
+ATF_TC_BODY(timerfd__absolute_timer_in_the_past, tc)
+{
+	int timerfd = timerfd_create(CLOCK_MONOTONIC, /**/
+	    TFD_CLOEXEC | TFD_NONBLOCK);
+
+	ATF_REQUIRE(timerfd >= 0);
+
+	struct timespec b;
+	ATF_REQUIRE(clock_gettime(CLOCK_MONOTONIC, &b) == 0);
+
+	{
+		struct itimerspec time = {
+			.it_value = b,
+			.it_interval.tv_sec = 10,
+			.it_interval.tv_nsec = 0,
+		};
+		time.it_value.tv_sec -= 1;
+
+		ATF_REQUIRE(timerfd_settime(timerfd, /**/
+				TFD_TIMER_ABSTIME, &time, NULL) == 0);
+
+		struct pollfd pfd = { .fd = timerfd, .events = POLLIN };
+		ATF_REQUIRE(poll(&pfd, 1, 1000) == 1);
+	}
+
+	{
+		struct itimerspec time = {
+			.it_value = b,
+			.it_interval.tv_sec = 0,
+			.it_interval.tv_nsec = 10000000,
+		};
+		time.it_value.tv_sec -= 1;
+
+		ATF_REQUIRE(timerfd_settime(timerfd, /**/
+				TFD_TIMER_ABSTIME, &time, NULL) == 0);
+
+		struct pollfd pfd = { .fd = timerfd, .events = POLLIN };
+		ATF_REQUIRE(poll(&pfd, 1, -1) == 1);
+	}
+
+	uint64_t timeouts;
+	ATF_REQUIRE(read(timerfd, &timeouts, sizeof(timeouts)) ==
+	    (ssize_t)sizeof(timeouts));
+
+	ATF_REQUIRE_MSG(timeouts >= 101, "%d", (int)timeouts);
+
+	ATF_REQUIRE(close(timerfd) == 0);
+}
+
+ATF_TC_WITHOUT_HEAD(timerfd__reset_absolute);
+ATF_TC_BODY(timerfd__reset_absolute, tc)
+{
+	int timerfd = timerfd_create(CLOCK_MONOTONIC, /**/
+	    TFD_CLOEXEC | TFD_NONBLOCK);
+
+	ATF_REQUIRE(timerfd >= 0);
+
+	struct timespec b;
+	ATF_REQUIRE(clock_gettime(CLOCK_MONOTONIC, &b) == 0);
+
+	{
+		struct itimerspec time = {
+			.it_value = b,
+		};
+		time.it_value.tv_sec += 10;
+
+		ATF_REQUIRE(timerfd_settime(timerfd, /**/
+				TFD_TIMER_ABSTIME, &time, NULL) == 0);
+
+		struct pollfd pfd = { .fd = timerfd, .events = POLLIN };
+		ATF_REQUIRE(poll(&pfd, 1, 100) == 0);
+	}
+
+	{
+		struct itimerspec time = {
+			.it_value = b,
+		};
+		time.it_value.tv_nsec += 500000000;
+		if (time.it_value.tv_nsec >= 1000000000) {
+			time.it_value.tv_nsec -= 1000000000;
+			time.it_value.tv_sec += 1;
+		}
+
+		ATF_REQUIRE(timerfd_settime(timerfd, /**/
+				TFD_TIMER_ABSTIME, &time, NULL) == 0);
+
+		struct pollfd pfd = { .fd = timerfd, .events = POLLIN };
+		ATF_REQUIRE(poll(&pfd, 1, 1000) == 1);
+	}
+
+	uint64_t timeouts;
+	ATF_REQUIRE(read(timerfd, &timeouts, sizeof(timeouts)) ==
+	    (ssize_t)sizeof(timeouts));
+
+	ATF_REQUIRE_MSG(timeouts == 1, "%d", (int)timeouts);
+
+	ATF_REQUIRE(close(timerfd) == 0);
+}
+
+ATF_TC(timerfd__periodic_timer_performance);
+ATF_TC_HEAD(timerfd__periodic_timer_performance, tc)
+{
+	atf_tc_set_md_var(tc, "timeout", "1");
+}
+ATF_TC_BODY(timerfd__periodic_timer_performance, tc)
+{
+	int timerfd = timerfd_create(CLOCK_MONOTONIC, /**/
+	    TFD_CLOEXEC | TFD_NONBLOCK);
+
+	ATF_REQUIRE(timerfd >= 0);
+
+	struct itimerspec time = {
+		.it_value.tv_sec = 0,
+		.it_value.tv_nsec = 1,
+		.it_interval.tv_sec = 0,
+		.it_interval.tv_nsec = 1,
+	};
+
+	ATF_REQUIRE(timerfd_settime(timerfd, 0, &time, NULL) == 0);
+
+	usleep(400000);
+
+	struct pollfd pfd = { .fd = timerfd, .events = POLLIN };
+	ATF_REQUIRE(poll(&pfd, 1, -1) == 1);
+
+	uint64_t timeouts;
+	ATF_REQUIRE(read(timerfd, &timeouts, sizeof(timeouts)) ==
+	    (ssize_t)sizeof(timeouts));
+	ATF_REQUIRE_MSG(timeouts >= 400000000, "%ld", (long)timeouts);
+
+	ATF_REQUIRE(close(timerfd) == 0);
+}
+
+ATF_TC_WITHOUT_HEAD(timerfd__argument_overflow);
+ATF_TC_BODY(timerfd__argument_overflow, tc)
+{
+	int timerfd = timerfd_create(CLOCK_MONOTONIC, /**/
+	    TFD_CLOEXEC | TFD_NONBLOCK);
+	ATF_REQUIRE(timerfd >= 0);
+	{
+		struct itimerspec time = {
+			.it_value.tv_sec = 0,
+			.it_value.tv_nsec = 1,
+		};
+
+		ATF_REQUIRE(timerfd_settime(timerfd, /**/
+				TFD_TIMER_ABSTIME, &time, NULL) == 0);
+
+		struct pollfd pfd = { .fd = timerfd, .events = POLLIN };
+		ATF_REQUIRE(poll(&pfd, 1, -1) == 1);
+
+		uint64_t timeouts;
+		ATF_REQUIRE(read(timerfd, &timeouts, sizeof(timeouts)) ==
+		    (ssize_t)sizeof(timeouts));
+		ATF_REQUIRE(timeouts == 1);
+
+		ATF_REQUIRE(read(timerfd, &timeouts, sizeof(timeouts)) < 0);
+	}
+	{
+		struct itimerspec time = {
+			.it_value.tv_sec = LONG_MAX,
+			.it_value.tv_nsec = 999999999,
+		};
+
+		ATF_REQUIRE(timerfd_settime(timerfd, /**/
+				TFD_TIMER_ABSTIME, &time, NULL) == 0);
+
+		struct pollfd pfd = { .fd = timerfd, .events = POLLIN };
+		ATF_REQUIRE(poll(&pfd, 1, 500) == 0);
+
+		uint64_t timeouts;
+		ATF_REQUIRE(read(timerfd, &timeouts, sizeof(timeouts)) < 0);
+	}
+
+	ATF_REQUIRE(close(timerfd) == 0);
+}
+
+ATF_TC(timerfd__short_evfilt_timer_timeout);
+ATF_TC_HEAD(timerfd__short_evfilt_timer_timeout, tc)
+{
+	atf_tc_set_md_var(tc, "timeout", "30");
+}
+ATF_TC_BODY(timerfd__short_evfilt_timer_timeout, tc)
+{
+	int kq = kqueue();
+	ATF_REQUIRE(kq >= 0);
+
+	bool returns_early = false;
+
+	for (int l = 0; l < 10; ++l) {
+		for (int i = 1; i <= 17; ++i) {
+			struct kevent kev;
+			EV_SET(&kev, 0, EVFILT_TIMER, EV_ADD | EV_ONESHOT, 0, i,
+			    0);
+
+			struct timespec b;
+			ATF_REQUIRE(clock_gettime(CLOCK_MONOTONIC, &b) == 0);
+
+			ATF_REQUIRE(kevent(kq, &kev, 1, NULL, 0, NULL) == 0);
+
+			ATF_REQUIRE(kevent(kq, NULL, 0, &kev, 1, NULL) == 1);
+
+			struct timespec e;
+			ATF_REQUIRE(clock_gettime(CLOCK_MONOTONIC, &e) == 0);
+
+			struct timespec diff;
+			timespecsub(&e, &b, &diff);
+
+			if (diff.tv_sec != 0 || diff.tv_nsec < i * 1000000) {
+				fprintf(stderr,
+				    "expected: %lldns, got: %lldns\n",
+				    (long long)(i * 1000000LL),
+				    (long long)diff.tv_nsec);
+				returns_early = true;
+				goto check;
+			}
+		}
+	}
+
+check:
+	ATF_REQUIRE(!returns_early);
+
+	ATF_REQUIRE(close(kq) == 0);
+
+	/*
+	 * timerfd's should never return early, regardless of how
+	 * EVFILT_TIMER behaves.
+	 */
+
+	int timerfd = timerfd_create(CLOCK_MONOTONIC, /**/
+	    TFD_CLOEXEC | TFD_NONBLOCK);
+
+	ATF_REQUIRE(timerfd >= 0);
+
+	for (int l = 0; l < 10; ++l) {
+		for (int i = 1; i <= 17; ++i) {
+			struct itimerspec time = {
+				.it_value.tv_sec = 0,
+				.it_value.tv_nsec = i * 1000000,
+			};
+
+			struct timespec b;
+			ATF_REQUIRE(clock_gettime(CLOCK_MONOTONIC, &b) == 0);
+
+			ATF_REQUIRE(
+			    timerfd_settime(timerfd, 0, &time, NULL) == 0);
+			(void)wait_for_timerfd(timerfd);
+
+			struct timespec e;
+			ATF_REQUIRE(clock_gettime(CLOCK_MONOTONIC, &e) == 0);
+
+			struct timespec diff;
+			timespecsub(&e, &b, &diff);
+
+			ATF_REQUIRE(
+			    diff.tv_sec == 0 && diff.tv_nsec >= i * 1000000);
+			fprintf(stderr, "%dms, waited %lldns\n", i,
+			    (long long)diff.tv_nsec);
+		}
+	}
+
+	ATF_REQUIRE(close(timerfd) == 0);
+}
+
+ATF_TC_WITHOUT_HEAD(timerfd__unmodified_errno);
+ATF_TC_BODY(timerfd__unmodified_errno, tc)
+{
+	ATF_REQUIRE(errno == 0);
+	int timerfd = timerfd_create(CLOCK_MONOTONIC, /**/
+	    TFD_CLOEXEC | TFD_NONBLOCK);
+	ATF_REQUIRE(timerfd >= 0);
+	ATF_REQUIRE(errno == 0);
+
+	ATF_REQUIRE(timerfd_settime(timerfd, 0,
+			&(struct itimerspec) {
+			    .it_value.tv_sec = 0,
+			    .it_value.tv_nsec = 100000000,
+			},
+			NULL) == 0);
+	ATF_REQUIRE(errno == 0);
+	(void)wait_for_timerfd(timerfd);
+	ATF_REQUIRE(errno == 0);
+
+	ATF_REQUIRE(timerfd_settime(timerfd, 0,
+			&(struct itimerspec) {
+			    .it_value.tv_sec = 0,
+			    .it_value.tv_nsec = 0,
+			},
+			NULL) == 0);
+	ATF_REQUIRE(errno == 0);
+
+	ATF_REQUIRE(timerfd_settime(timerfd, 0,
+			&(struct itimerspec) {
+			    .it_value.tv_sec = 0,
+			    .it_value.tv_nsec = 0,
+			},
+			NULL) == 0);
+	ATF_REQUIRE(errno == 0);
+
+	ATF_REQUIRE(close(timerfd) == 0);
+	ATF_REQUIRE(errno == 0);
+}
+
+ATF_TC_WITHOUT_HEAD(timerfd__reset_to_very_long);
+ATF_TC_BODY(timerfd__reset_to_very_long, tc)
+{
+	ATF_REQUIRE(errno == 0);
+	int timerfd = timerfd_create(CLOCK_MONOTONIC, /**/
+	    TFD_CLOEXEC | TFD_NONBLOCK);
+	ATF_REQUIRE(timerfd >= 0);
+	ATF_REQUIRE(errno == 0);
+
+	ATF_REQUIRE(timerfd_settime(timerfd, 0,
+			&(struct itimerspec) {
+			    .it_value.tv_sec = 0,
+			    .it_value.tv_nsec = 100000000,
+			},
+			NULL) == 0);
+	ATF_REQUIRE(errno == 0);
+
+	ATF_REQUIRE(timerfd_settime(timerfd, 0,
+			&(struct itimerspec) {
+			    .it_value.tv_sec = 630720000,
+			    .it_value.tv_nsec = 0,
+			},
+			NULL) == 0);
+	ATF_REQUIRE(errno == 0);
+
+	struct pollfd pfd = { .fd = timerfd, .events = POLLIN };
+	ATF_REQUIRE(poll(&pfd, 1, 500) == 0);
+	uint64_t timeouts;
+	ssize_t r = read(timerfd, &timeouts, sizeof(timeouts));
+	ATF_REQUIRE_ERRNO(EAGAIN, r < 0);
+
+	ATF_REQUIRE(close(timerfd) == 0);
+	ATF_REQUIRE(errno == EAGAIN);
+}
+
+/*
+ * Tests requiring root (clock_settime on CLOCK_REALTIME).
+ * Tests gracefully skip if not running as root.
+ */
+
+static struct timespec current_time;
+static void
+reset_time(void)
+{
+	(void)clock_settime(CLOCK_REALTIME, &current_time);
+}
+
+static void
+clock_settime_or_skip_test(clockid_t clockid, struct timespec const *ts)
+{
+	int r = clock_settime(clockid, ts);
+	if (r < 0 && errno == EPERM) {
+		atf_tc_skip("root required");
+	}
+	ATF_REQUIRE(r == 0);
+}
+
+ATF_TC_WITHOUT_HEAD(timerfd_root__zero_read_on_abs_realtime);
+ATF_TC_BODY(timerfd_root__zero_read_on_abs_realtime, tc)
+{
+	int tfd = timerfd_create(CLOCK_REALTIME, TFD_CLOEXEC);
+	ATF_REQUIRE(tfd >= 0);
+
+	ATF_REQUIRE(clock_gettime(CLOCK_REALTIME, &current_time) == 0);
+	ATF_REQUIRE(atexit(reset_time) == 0);
+
+	ATF_REQUIRE(timerfd_settime(tfd, TFD_TIMER_ABSTIME,
+			&(struct itimerspec) {
+			    .it_value = current_time,
+			    .it_interval.tv_sec = 1,
+			    .it_interval.tv_nsec = 0,
+			},
+			NULL) == 0);
+
+	ATF_REQUIRE(
+	    poll(&(struct pollfd) { .fd = tfd, .events = POLLIN }, 1, -1) == 1);
+
+	clock_settime_or_skip_test(CLOCK_REALTIME,
+	    &(struct timespec) {
+		.tv_sec = current_time.tv_sec - 1,
+		.tv_nsec = current_time.tv_nsec,
+	    });
+
+	uint64_t exp;
+	ssize_t r = read(tfd, &exp, sizeof(exp));
+	ATF_REQUIRE_MSG(r == 0, "r: %d, errno: %d", (int)r, errno);
+
+	{
+		int r = fcntl(tfd, F_GETFL);
+		ATF_REQUIRE(r >= 0);
+		r = fcntl(tfd, F_SETFL, r | O_NONBLOCK);
+		ATF_REQUIRE(r >= 0);
+	}
+
+	r = read(tfd, &exp, sizeof(exp));
+	ATF_REQUIRE_ERRNO(EAGAIN, r < 0);
+
+	current_time.tv_sec += 1;
+	ATF_REQUIRE(poll(&(struct pollfd) { .fd = tfd, .events = POLLIN }, 1,
+			1800) == 1);
+	r = read(tfd, &exp, sizeof(exp));
+	ATF_REQUIRE(r == (ssize_t)sizeof(exp));
+	ATF_REQUIRE(exp == 1);
+
+	ATF_REQUIRE(close(tfd) == 0);
+}
+
+ATF_TC_WITHOUT_HEAD(timerfd_root__read_on_abs_realtime_no_interval);
+ATF_TC_BODY(timerfd_root__read_on_abs_realtime_no_interval, tc)
+{
+	int tfd = timerfd_create(CLOCK_REALTIME, TFD_CLOEXEC);
+	ATF_REQUIRE(tfd >= 0);
+
+	ATF_REQUIRE(clock_gettime(CLOCK_REALTIME, &current_time) == 0);
+	ATF_REQUIRE(atexit(reset_time) == 0);
+
+	ATF_REQUIRE(timerfd_settime(tfd, TFD_TIMER_ABSTIME,
+			&(struct itimerspec) {
+			    .it_value = current_time,
+			    .it_interval.tv_sec = 0,
+			    .it_interval.tv_nsec = 0,
+			},
+			NULL) == 0);
+
+	ATF_REQUIRE(
+	    poll(&(struct pollfd) { .fd = tfd, .events = POLLIN }, 1, -1) == 1);
+
+	clock_settime_or_skip_test(CLOCK_REALTIME,
+	    &(struct timespec) {
+		.tv_sec = current_time.tv_sec - 1,
+		.tv_nsec = current_time.tv_nsec,
+	    });
+
+	uint64_t exp;
+	ssize_t r = read(tfd, &exp, sizeof(exp));
+	ATF_REQUIRE(r == (ssize_t)sizeof(exp));
+	ATF_REQUIRE(exp == 1);
+
+	ATF_REQUIRE(close(tfd) == 0);
+}
+
+ATF_TC_WITHOUT_HEAD(timerfd_root__cancel_on_set);
+ATF_TC_BODY(timerfd_root__cancel_on_set, tc)
+{
+	int tfd = timerfd_create(CLOCK_REALTIME, TFD_CLOEXEC);
+	ATF_REQUIRE(tfd >= 0);
+
+	ATF_REQUIRE(clock_gettime(CLOCK_REALTIME, &current_time) == 0);
+	ATF_REQUIRE(atexit(reset_time) == 0);
+
+	ATF_REQUIRE(
+	    timerfd_settime(tfd, TFD_TIMER_ABSTIME | TFD_TIMER_CANCEL_ON_SET,
+		&(struct itimerspec) {
+		    .it_value.tv_sec = current_time.tv_sec + 10,
+		    .it_value.tv_nsec = current_time.tv_nsec,
+		    .it_interval.tv_sec = 0,
+		    .it_interval.tv_nsec = 0,
+		},
+		NULL) == 0);
+
+	clock_settime_or_skip_test(CLOCK_REALTIME, &current_time);
+
+	ATF_REQUIRE(
+	    poll(&(struct pollfd) { .fd = tfd, .events = POLLIN }, 1, -1) == 1);
+
+	{
+		int r = timerfd_settime(tfd,
+		    TFD_TIMER_ABSTIME | TFD_TIMER_CANCEL_ON_SET,
+		    &(struct itimerspec) {
+			.it_value.tv_sec = current_time.tv_sec,
+			.it_value.tv_nsec = current_time.tv_nsec,
+			.it_interval.tv_sec = 0,
+			.it_interval.tv_nsec = 0,
+		    },
+		    NULL);
+		ATF_REQUIRE_ERRNO(ECANCELED, r < 0);
+	}
+
+	ATF_REQUIRE(poll(&(struct pollfd) { .fd = tfd, .events = POLLIN }, 1,
+			800) == 1);
+
+	uint64_t exp;
+	ssize_t r;
+
+	r = read(tfd, &exp, sizeof(exp));
+	ATF_REQUIRE(r == (ssize_t)sizeof(exp));
+	ATF_REQUIRE(exp == 1);
+
+	ATF_REQUIRE(
+	    timerfd_settime(tfd, TFD_TIMER_ABSTIME | TFD_TIMER_CANCEL_ON_SET,
+		&(struct itimerspec) {
+		    .it_value.tv_sec = current_time.tv_sec + 1,
+		    .it_value.tv_nsec = current_time.tv_nsec,
+		    .it_interval.tv_sec = 1,
+		    .it_interval.tv_nsec = 0,
+		},
+		NULL) == 0);
+
+	clock_settime_or_skip_test(CLOCK_REALTIME, &current_time);
+
+	ATF_REQUIRE(
+	    poll(&(struct pollfd) { .fd = tfd, .events = POLLIN }, 1, -1) == 1);
+
+	r = read(tfd, &exp, sizeof(exp));
+	ATF_REQUIRE_ERRNO(ECANCELED, r < 0);
+
+	r = read(tfd, &exp, sizeof(exp));
+	current_time.tv_sec += 1;
+	ATF_REQUIRE_MSG(r == (ssize_t)sizeof(exp), "%d %d", (int)r, errno);
+	ATF_REQUIRE(exp == 1);
+
+	ATF_REQUIRE(
+	    timerfd_settime(tfd, TFD_TIMER_ABSTIME | TFD_TIMER_CANCEL_ON_SET,
+		&(struct itimerspec) {
+		    .it_value.tv_sec = current_time.tv_sec + 1,
+		    .it_value.tv_nsec = current_time.tv_nsec,
+		    .it_interval.tv_sec = 1,
+		    .it_interval.tv_nsec = 0,
+		},
+		NULL) == 0);
+
+	clock_settime_or_skip_test(CLOCK_REALTIME, &current_time);
+	current_time.tv_sec += 2;
+	ATF_REQUIRE(nanosleep(&(struct timespec) { .tv_sec = 2 }, NULL) == 0);
+
+	r = read(tfd, &exp, sizeof(exp));
+	ATF_REQUIRE_ERRNO(ECANCELED, r < 0);
+
+	r = poll(&(struct pollfd) { .fd = tfd, .events = POLLIN }, 1, 3000);
+	ATF_REQUIRE(r == 0);
+	current_time.tv_sec += 3;
+
+	ATF_REQUIRE(close(tfd) == 0);
+}
+
+ATF_TC_WITHOUT_HEAD(timerfd_root__cancel_on_set_init);
+ATF_TC_BODY(timerfd_root__cancel_on_set_init, tc)
+{
+	int tfd = timerfd_create(CLOCK_REALTIME, TFD_CLOEXEC);
+	ATF_REQUIRE(tfd >= 0);
+
+	ATF_REQUIRE(clock_gettime(CLOCK_REALTIME, &current_time) == 0);
+	ATF_REQUIRE(atexit(reset_time) == 0);
+
+	clock_settime_or_skip_test(CLOCK_REALTIME, &current_time);
+
+	ATF_REQUIRE(
+	    timerfd_settime(tfd, TFD_TIMER_ABSTIME | TFD_TIMER_CANCEL_ON_SET,
+		&(struct itimerspec) {
+		    .it_value.tv_sec = current_time.tv_sec + 10,
+		    .it_value.tv_nsec = current_time.tv_nsec,
+		    .it_interval.tv_sec = 0,
+		    .it_interval.tv_nsec = 0,
+		},
+		NULL) == 0);
+
+	clock_settime_or_skip_test(CLOCK_REALTIME, &current_time);
+
+	int r = timerfd_settime(tfd,
+	    TFD_TIMER_ABSTIME | TFD_TIMER_CANCEL_ON_SET,
+	    &(struct itimerspec) {
+		.it_value.tv_sec = current_time.tv_sec + 10,
+		.it_value.tv_nsec = current_time.tv_nsec,
+		.it_interval.tv_sec = 0,
+		.it_interval.tv_nsec = 0,
+	    },
+	    NULL);
+	ATF_REQUIRE_ERRNO(ECANCELED, r < 0);
+	ATF_REQUIRE(close(tfd) == 0);
+}
+
+static void *
+clock_change_thread(void *arg)
+{
+	(void)arg;
+
+	fprintf(stderr, "clock change\n");
+	clock_settime_or_skip_test(CLOCK_REALTIME, &current_time);
+
+	current_time.tv_sec += 2;
+	ATF_REQUIRE(nanosleep(&(struct timespec) { .tv_sec = 2 }, NULL) == 0);
+
+	fprintf(stderr, "clock change\n");
+	clock_settime_or_skip_test(CLOCK_REALTIME, &current_time);
+
+	return NULL;
+}
+
+ATF_TC(timerfd_root__clock_change_notification);
+ATF_TC_HEAD(timerfd_root__clock_change_notification, tc)
+{
+	atf_tc_set_md_var(tc, "timeout", "10");
+}
+ATF_TC_BODY(timerfd_root__clock_change_notification, tc)
+{
+	ATF_REQUIRE(clock_gettime(CLOCK_REALTIME, &current_time) == 0);
+	ATF_REQUIRE(atexit(reset_time) == 0);
+
+	clock_settime_or_skip_test(CLOCK_REALTIME, &current_time);
+
+#define TIME_T_MAX (time_t)((UINTMAX_C(1) << ((sizeof(time_t) << 3) - 1)) - 1)
+	struct itimerspec its = {
+		.it_value.tv_sec = TIME_T_MAX,
+	};
+#undef TIME_T_MAX
+
+	int tfd = timerfd_create(CLOCK_REALTIME, TFD_CLOEXEC);
+	ATF_REQUIRE(tfd >= 0);
+
+	ATF_REQUIRE(
+	    timerfd_settime(tfd, TFD_TIMER_ABSTIME | TFD_TIMER_CANCEL_ON_SET,
+		&its, NULL) == 0);
+
+	pthread_t clock_changer;
+	ATF_REQUIRE(pthread_create(&clock_changer, NULL, /**/
+			clock_change_thread, NULL) == 0);
+
+	uint64_t exp;
+	ssize_t r;
+
+	r = read(tfd, &exp, sizeof(exp));
+	ATF_REQUIRE_ERRNO(ECANCELED, r < 0);
+	fprintf(stderr, "clock change detected\n");
+
+	r = read(tfd, &exp, sizeof(exp));
+	ATF_REQUIRE_ERRNO(ECANCELED, r < 0);
+	fprintf(stderr, "clock change detected\n");
+
+	ATF_REQUIRE(pthread_join(clock_changer, NULL) == 0);
+
+	ATF_REQUIRE(close(tfd) == 0);
+}
+
+ATF_TC_WITHOUT_HEAD(timerfd_root__advance_time_no_cancel);
+ATF_TC_BODY(timerfd_root__advance_time_no_cancel, tc)
+{
+	int tfd = timerfd_create(CLOCK_REALTIME, TFD_CLOEXEC);
+	ATF_REQUIRE(tfd >= 0);
+
+	ATF_REQUIRE(clock_gettime(CLOCK_REALTIME, &current_time) == 0);
+	ATF_REQUIRE(atexit(reset_time) == 0);
+
+	ATF_REQUIRE(timerfd_settime(tfd, TFD_TIMER_ABSTIME,
+			&(struct itimerspec) {
+			    .it_value.tv_sec = current_time.tv_sec + 10,
+			    .it_value.tv_nsec = current_time.tv_nsec,
+			    .it_interval.tv_sec = 0,
+			    .it_interval.tv_nsec = 0,
+			},
+			NULL) == 0);
+
+	current_time.tv_sec += 9;
+	clock_settime_or_skip_test(CLOCK_REALTIME, &current_time);
+	current_time.tv_sec -= 8;
+
+	{
+		int r = poll(&(struct pollfd) { .fd = tfd, .events = POLLIN },
+		    1, 1800);
+		ATF_REQUIRE(r == 1);
+	}
+
+	uint64_t exp;
+	ssize_t r;
+
+	r = read(tfd, &exp, sizeof(exp));
+	ATF_REQUIRE(r == (ssize_t)sizeof(exp));
+	ATF_REQUIRE(exp == 1);
+
+	ATF_REQUIRE(close(tfd) == 0);
+}
+
+ATF_TP_ADD_TCS(tp)
+{
+	ATF_TP_ADD_TC(tp, timerfd__many_timers);
+	ATF_TP_ADD_TC(tp, timerfd__simple_timer);
+	ATF_TP_ADD_TC(tp, timerfd__simple_periodic_timer);
+	ATF_TP_ADD_TC(tp, timerfd__complex_periodic_timer);
+	ATF_TP_ADD_TC(tp, timerfd__reset_periodic_timer);
+	ATF_TP_ADD_TC(tp, timerfd__reenable_periodic_timer);
+	ATF_TP_ADD_TC(tp, timerfd__expire_five);
+	ATF_TP_ADD_TC(tp, timerfd__simple_gettime);
+	ATF_TP_ADD_TC(tp, timerfd__simple_blocking_periodic_timer);
+	ATF_TP_ADD_TC(tp, timerfd__argument_checks);
+	ATF_TP_ADD_TC(tp, timerfd__upgrade_simple_to_complex);
+	ATF_TP_ADD_TC(tp, timerfd__absolute_timer);
+	ATF_TP_ADD_TC(tp, timerfd__absolute_timer_in_the_past);
+	ATF_TP_ADD_TC(tp, timerfd__reset_absolute);
+	ATF_TP_ADD_TC(tp, timerfd__periodic_timer_performance);
+	ATF_TP_ADD_TC(tp, timerfd__argument_overflow);
+	ATF_TP_ADD_TC(tp, timerfd__short_evfilt_timer_timeout);
+	ATF_TP_ADD_TC(tp, timerfd__unmodified_errno);
+	ATF_TP_ADD_TC(tp, timerfd__reset_to_very_long);
+
+	ATF_TP_ADD_TC(tp, timerfd_root__zero_read_on_abs_realtime);
+	ATF_TP_ADD_TC(tp, timerfd_root__read_on_abs_realtime_no_interval);
+	ATF_TP_ADD_TC(tp, timerfd_root__cancel_on_set);
+	ATF_TP_ADD_TC(tp, timerfd_root__cancel_on_set_init);
+	ATF_TP_ADD_TC(tp, timerfd_root__clock_change_notification);
+	ATF_TP_ADD_TC(tp, timerfd_root__advance_time_no_cancel);
+
+	return atf_no_error();
+}