[tip: timers/core] posix-cpu-timers: Handle interval timers correctly in timer_get()

[tip-bot2 for Thomas Gleixner]

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

Commit-ID:     1c5028425793ea98fcb403852331664662d97226
Gitweb:        https://git.kernel.org/tip/1c5028425793ea98fcb403852331664662d97226
Author:        Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate:    Mon, 10 Jun 2024 18:42:16 +02:00
Committer:     Frederic Weisbecker <frederic@xxxxxxxxxx>
CommitterDate: Mon, 29 Jul 2024 21:57:34 +02:00

posix-cpu-timers: Handle interval timers correctly in timer_get()

timer_gettime() must return the remaining time to the next expiry of a
timer or 0 if the timer is not armed and no signal pending, but posix CPU
timers fail to forward a timer which is already expired.

Add the required logic to address that.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
 kernel/time/posix-cpu-timers.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
index 5aac088..92222ca 100644
--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -787,8 +787,24 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
 
 static void __posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp, u64 now)
 {
-	u64 expires = cpu_timer_getexpires(&timer->it.cpu);
+	u64 expires, iv = timer->it_interval;
 
+	/*
+	 * Make sure that interval timers are moved forward for the
+	 * following cases:
+	 *  - Timers which expired, but the signal has not yet been
+	 *    delivered
+	 */
+	if (iv && (timer->it_requeue_pending & REQUEUE_PENDING))
+		expires = bump_cpu_timer(timer, now);
+	else
+		expires = cpu_timer_getexpires(&timer->it.cpu);
+
+	/*
+	 * Expired interval timers cannot have a remaining time <= 0.
+	 * The kernel has to move them forward so that the next
+	 * timer expiry is > @now.
+	 */
 	if (now < expires) {
 		itp->it_value = ns_to_timespec64(expires - now);
 	} else {