From b40c927345a91e687eac4c3c5ca03a99643cd0c4 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 8 Apr 2026 13:53:52 +0200 Subject: [PATCH] hrtimer: Use hrtimer_start_expires_user() for hrtimer sleepers Most hrtimer sleepers are user controlled and user space can hand arbitrary expiry values in as long as they are valid timespecs. If the expiry value is in the past then this requires a full loop through reprogramming the clock event device, taking the hrtimer interrupt, waking the task and reprogram again. Use hrtimer_start_expires_user() which avoids the full round trip by checking the timer for expiry on enqueue. Signed-off-by: Thomas Gleixner Tested-by: Calvin Owens Reviewed-by: Frederic Weisbecker Acked-by: Peter Zijlstra (Intel) Link: https://patch.msgid.link/20260408114952.062400833@kernel.org --- kernel/time/hrtimer.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c index 79aaac471164..8cfc7aacece1 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -2315,7 +2315,11 @@ void hrtimer_sleeper_start_expires(struct hrtimer_sleeper *sl, enum hrtimer_mode if (IS_ENABLED(CONFIG_PREEMPT_RT) && sl->timer.is_hard) mode |= HRTIMER_MODE_HARD; - hrtimer_start_expires(&sl->timer, mode); + /* If already expired, clear the task pointer and set current state to running */ + if (!hrtimer_start_expires_user(&sl->timer, mode)) { + sl->task = NULL; + __set_current_state(TASK_RUNNING); + } } EXPORT_SYMBOL_GPL(hrtimer_sleeper_start_expires);