-clockid_t clock_boottime_or_monotonic(void) {
- static clockid_t clock = -1;
- int fd;
-
- if (clock != -1)
- return clock;
-
- fd = timerfd_create(CLOCK_BOOTTIME, TFD_NONBLOCK|TFD_CLOEXEC);
- if (fd < 0)
- clock = CLOCK_MONOTONIC;
- else {
- safe_close(fd);
- clock = CLOCK_BOOTTIME;
+bool clock_boottime_supported(void) {
+ static int supported = -1;
+
+ /* Note that this checks whether CLOCK_BOOTTIME is available in general as well as available for timerfds()! */
+
+ if (supported < 0) {
+ int fd;
+
+ fd = timerfd_create(CLOCK_BOOTTIME, TFD_NONBLOCK|TFD_CLOEXEC);
+ if (fd < 0)
+ supported = false;
+ else {
+ safe_close(fd);
+ supported = true;
+ }