posix: implement timer_getoverrun()

include/zephyr/posix/time.h

@@ -94,6 +94,7 @@ int timer_delete(timer_t timerid);
 int timer_gettime(timer_t timerid, struct itimerspec *its);
 int timer_settime(timer_t timerid, int flags, const struct itimerspec *value,
 		  struct itimerspec *ovalue);
+int timer_getoverrun(timer_t timerid);
 int nanosleep(const struct timespec *rqtp, struct timespec *rmtp);
 
 #ifdef __cplusplus

lib/posix/Kconfig.timer

@@ -14,3 +14,10 @@ config TIMER_CREATE_WAIT
 	help
 	  This controls how long to wait for resources to come available to create
 	  a new timer in POSIX compliant application
+
+config TIMER_DELAYTIMER_MAX
+	int "Maximum count returned my timer_getoverrun() in POSIX application"
+	default 20
+	help
+	  This controls the maximum number of times a timer can overrun before
+	  timer_getoverrun() in POSIX compliant application.

lib/posix/timer.c

@@ -179,6 +179,29 @@ int timer_settime(timer_t timerid, int flags, const struct itimerspec *value,
 	return 0;
 }
 
+/**
+ * @brief Returns the timer expiration overrun count.
+ *
+ * See IEEE 1003.1
+ */
+int timer_getoverrun(timer_t timerid)
+{
+	struct timer_obj *timer = (struct timer_obj *) timerid;
+
+	if (timer == NULL) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	int overruns = k_timer_status_get(&timer->ztimer) - 1;
+
+	if (overruns > CONFIG_TIMER_DELAYTIMER_MAX) {
+		overruns = CONFIG_TIMER_DELAYTIMER_MAX;
+	}
+
+	return overruns;
+}
+
 /**
  * @brief Delete a per-process timer.
  *

tests/posix/common/src/timer.c

@@ -68,6 +68,7 @@ ZTEST(posix_apis, test_timer)
 	sleep(SECS_TO_SLEEP);
 
 	clock_gettime(CLOCK_MONOTONIC, &te);
+	zassert_equal(ret, 0, "Number of timer overruns is incorrect");
 	timer_delete(timerid);
 
 	if (te.tv_nsec >= ts.tv_nsec) {
@@ -83,7 +84,32 @@ ZTEST(posix_apis, test_timer)
 			    (value.it_interval.tv_sec * NSEC_PER_SEC +
 			     value.it_interval.tv_nsec)) / NSEC_PER_SEC;
 
+
 	/*TESTPOINT: Check if POSIX timer test passed*/
 	zassert_equal(total_secs_timer, secs_elapsed,
 		      "POSIX timer test has failed");
 }
+
+ZTEST(posix_apis, test_timer_overrun)
+{
+	timer_t timerid;
+	struct sigevent sig = { 0 };
+	struct itimerspec value;
+
+	sig.sigev_notify = SIGEV_NONE;
+
+	timer_create(CLOCK_MONOTONIC, &sig, &timerid);
+
+	/*Set the timer to expire every 500 milliseconds*/
+	value.it_interval.tv_sec = 0;
+	value.it_interval.tv_nsec = 500000000;
+	value.it_value.tv_sec = 0;
+	value.it_value.tv_nsec = 500000000;
+	timer_settime(timerid, 0, &value, NULL);
+	k_sleep(K_MSEC(2500));
+
+	int overruns = timer_getoverrun(timerid);
+
+	timer_delete(timerid);
+	zassert_equal(overruns, 4, "Number of overruns is incorrect");
+}