1 files changed, 35 insertions, 6 deletions

diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
index 0d918117a3e0..ee736861b18f 100644
--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -419,6 +419,20 @@ static struct posix_cputimer_base *timer_base(struct k_itimer *timer,
 }
 
 /*
+ * Force recalculating the base earliest expiration on the next tick.
+ * This will also re-evaluate the need to keep around the process wide
+ * cputime counter and tick dependency and eventually shut these down
+ * if necessary.
+ */
+static void trigger_base_recalc_expires(struct k_itimer *timer,
+					struct task_struct *tsk)
+{
+	struct posix_cputimer_base *base = timer_base(timer, tsk);
+
+	base->nextevt = 0;
+}
+
+/*
  * Dequeue the timer and reset the base if it was its earliest expiration.
  * It makes sure the next tick recalculates the base next expiration so we
  * don't keep the costly process wide cputime counter around for a random
@@ -438,7 +452,7 @@ static void disarm_timer(struct k_itimer *timer, struct task_struct *p)
 
 	base = timer_base(timer, p);
 	if (cpu_timer_getexpires(ctmr) == base->nextevt)
-		base->nextevt = 0;
+		trigger_base_recalc_expires(timer, p);
 }
 
 
@@ -734,13 +748,28 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
 	timer->it_overrun_last = 0;
 	timer->it_overrun = -1;
 
-	if (new_expires != 0 && !(val < new_expires)) {
+	if (val >= new_expires) {
+		if (new_expires != 0) {
+			/*
+			 * The designated time already passed, so we notify
+			 * immediately, even if the thread never runs to
+			 * accumulate more time on this clock.
+			 */
+			cpu_timer_fire(timer);
+		}
+
 		/*
-		 * The designated time already passed, so we notify
-		 * immediately, even if the thread never runs to
-		 * accumulate more time on this clock.
+		 * Make sure we don't keep around the process wide cputime
+		 * counter or the tick dependency if they are not necessary.
 		 */
-		cpu_timer_fire(timer);
+		sighand = lock_task_sighand(p, &flags);
+		if (!sighand)
+			goto out;
+
+		if (!cpu_timer_queued(ctmr))
+			trigger_base_recalc_expires(timer, p);
+
+		unlock_task_sighand(p, &flags);
 	}
  out:
 	rcu_read_unlock();