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-rw-r--r--kernel/time/posix-timers.c13
1 files changed, 13 insertions, 0 deletions
diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
index 88517dcfe0ca..58c0f60b132f 100644
--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -72,6 +72,7 @@ static DEFINE_SPINLOCK(hash_lock);
static const struct k_clock * const posix_clocks[];
static const struct k_clock *clockid_to_kclock(const clockid_t id);
+static const struct k_clock clock_realtime, clock_monotonic;
/*
* we assume that the new SIGEV_THREAD_ID shares no bits with the other
@@ -750,6 +751,18 @@ static void common_hrtimer_arm(struct k_itimer *timr, ktime_t expires,
enum hrtimer_mode mode;
mode = absolute ? HRTIMER_MODE_ABS : HRTIMER_MODE_REL;
+ /*
+ * Posix magic: Relative CLOCK_REALTIME timers are not affected by
+ * clock modifications, so they become CLOCK_MONOTONIC based under the
+ * hood. See hrtimer_init(). Update timr->kclock, so the generic
+ * functions which use timr->kclock->clock_get() work.
+ *
+ * Note: it_clock stays unmodified, because the next timer_set() might
+ * use ABSTIME, so it needs to switch back.
+ */
+ if (timr->it_clock == CLOCK_REALTIME)
+ timr->kclock = absolute ? &clock_realtime : &clock_monotonic;
+
hrtimer_init(&timr->it.real.timer, timr->it_clock, mode);
timr->it.real.timer.function = posix_timer_fn;