From 183d00b727139cf3b4be78d66a5602ce71a3acec Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 8 Apr 2026 13:54:11 +0200 Subject: [PATCH] alarmtimer: Provide alarm_start_timer() Alarm timers utilize hrtimers for normal operation and only switch to the RTC on suspend. In order to catch already expired timers early and without going through a timer interrupt cycle, provide a new start function which internally uses hrtimer_start_range_ns_user(). If hrtimer_start_range_ns_user() detects an already expired timer, it does not queue it. In that case remove the timer from the alarm base as well. Return the status queued or not back to the caller to handle the early expiry. Signed-off-by: Thomas Gleixner Reviewed-by: Frederic Weisbecker Acked-by: John Stultz Link: https://patch.msgid.link/20260408114952.332822525@kernel.org --- include/linux/alarmtimer.h | 6 ++++++ kernel/time/alarmtimer.c | 28 ++++++++++++++++++++++++++++ 2 files changed, 34 insertions(+) diff --git a/include/linux/alarmtimer.h b/include/linux/alarmtimer.h index 3ffa5341dce2..14d729fe0fd6 100644 --- a/include/linux/alarmtimer.h +++ b/include/linux/alarmtimer.h @@ -42,8 +42,14 @@ struct alarm { void *data; }; +static __always_inline ktime_t alarm_get_expires(struct alarm *alarm) +{ + return alarm->node.expires; +} + void alarm_init(struct alarm *alarm, enum alarmtimer_type type, void (*function)(struct alarm *, ktime_t)); +bool alarm_start_timer(struct alarm *alarm, ktime_t expires, bool relative); void alarm_start(struct alarm *alarm, ktime_t start); void alarm_start_relative(struct alarm *alarm, ktime_t start); void alarm_restart(struct alarm *alarm); diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c index e10021be190f..2348b0839114 100644 --- a/kernel/time/alarmtimer.c +++ b/kernel/time/alarmtimer.c @@ -369,6 +369,34 @@ void alarm_start_relative(struct alarm *alarm, ktime_t start) } EXPORT_SYMBOL_GPL(alarm_start_relative); +/** + * alarm_start_timer - Sets an alarm to fire + * @alarm: Pointer to alarm to set + * @expires: Expiry time + * @relative: True if @expires is relative + * + * Returns: True if the alarm was queued. False if it already expired + */ +bool alarm_start_timer(struct alarm *alarm, ktime_t expires, bool relative) +{ + struct alarm_base *base = &alarm_bases[alarm->type]; + + if (relative) + expires = ktime_add_safe(expires, base->get_ktime()); + + trace_alarmtimer_start(alarm, base->get_ktime()); + + guard(spinlock_irqsave)(&base->lock); + alarm->node.expires = expires; + alarmtimer_enqueue(base, alarm); + if (!hrtimer_start_range_ns_user(&alarm->timer, expires, 0, HRTIMER_MODE_ABS)) { + alarmtimer_dequeue(base, alarm); + return false; + } + return true; +} +EXPORT_SYMBOL_GPL(alarm_start_timer); + void alarm_restart(struct alarm *alarm) { struct alarm_base *base = &alarm_bases[alarm->type];