The following commit has been merged into the timers/core branch of tip:

Commit-ID:     f4b58f61da79032b03d25f8f1a5a697db84a46f3
Gitweb:        https://git.kernel.org/tip/f4b58f61da79032b03d25f8f1a5a697db84a46f3
Author:        Thomas Gleixner <tglx@kernel.org>
AuthorDate:    Wed, 08 Apr 2026 13:54:16 +02:00
Committer:     Thomas Gleixner <tglx@kernel.org>
CommitterDate: Fri, 01 May 2026 21:36:13 +02:00

alarmtimer: Convert posix timer functions to alarm_start_timer()

Use the new alarm_start_timer() for arming and rearming posix interval
timers and for clock_nanosleep() so that already expired timers do not go
through the full timer interrupt cycle.

Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: John Stultz <jstultz@google.com>
Link: https://patch.msgid.link/20260408114952.400451460@kernel.org
---
 kernel/time/alarmtimer.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c
index 2348b08..9baa69c 100644
--- a/kernel/time/alarmtimer.c
+++ b/kernel/time/alarmtimer.c
@@ -560,8 +560,7 @@ static bool alarm_timer_rearm(struct k_itimer *timr)
 	struct alarm *alarm = &timr->it.alarm.alarmtimer;
 
 	timr->it_overrun += alarm_forward_now(alarm, timr->it_interval);
-	alarm_start(alarm, alarm->node.expires);
-	return true;
+	return alarm_start_timer(alarm, alarm->node.expires, false);
 }
 
 /**
@@ -625,11 +624,16 @@ static bool alarm_timer_arm(struct k_itimer *timr, ktime_t expires,
 
 	if (!absolute)
 		expires = ktime_add_safe(expires, base->get_ktime());
-	if (sigev_none)
+
+	/*
+	 * sigev_none needs to update the expires value and pretend
+	 * that the timer is queued
+	 */
+	if (sigev_none) {
 		alarm->node.expires = expires;
-	else
-		alarm_start(&timr->it.alarm.alarmtimer, expires);
-	return true;
+		return true;
+	}
+	return alarm_start_timer(&timr->it.alarm.alarmtimer, expires, false);
 }
 
 /**
@@ -736,7 +740,9 @@ static int alarmtimer_do_nsleep(struct alarm *alarm, ktime_t absexp,
 	alarm->data = (void *)current;
 	do {
 		set_current_state(TASK_INTERRUPTIBLE);
-		alarm_start(alarm, absexp);
+		if (!alarm_start_timer(alarm, absexp, false))
+			alarm->data = NULL;
+
 		if (likely(alarm->data))
 			schedule();