diff --git a/fs/proc/base.c b/fs/proc/base.c
index dd579332a7f8..afe573e8d8f1 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2569,10 +2569,11 @@ static ssize_t timerslack_ns_write(struct file *file, const char __user *buf,
 	}
 
 	task_lock(p);
-	if (slack_ns == 0)
-		p->timer_slack_ns = p->default_timer_slack_ns;
-	else
-		p->timer_slack_ns = slack_ns;
+	if (task_is_realtime(p))
+		slack_ns = 0;
+	else if (slack_ns == 0)
+		slack_ns = p->default_timer_slack_ns;
+	p->timer_slack_ns = slack_ns;
 	task_unlock(p);
 
 out:
diff --git a/fs/select.c b/fs/select.c
index 9515c3fa1a03..ad171b7a5c11 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -77,19 +77,16 @@ u64 select_estimate_accuracy(struct timespec64 *tv)
 {
 	u64 ret;
 	struct timespec64 now;
+	u64 slack = current->timer_slack_ns;
 
-	/*
-	 * Realtime tasks get a slack of 0 for obvious reasons.
-	 */
-
-	if (rt_task(current))
+	if (slack == 0)
 		return 0;
 
 	ktime_get_ts64(&now);
 	now = timespec64_sub(*tv, now);
 	ret = __estimate_accuracy(&now);
-	if (ret < current->timer_slack_ns)
-		return current->timer_slack_ns;
+	if (ret < slack)
+		return slack;
 	return ret;
 }
 
diff --git a/kernel/sched/syscalls.c b/kernel/sched/syscalls.c
index ae1b42775ef9..195d2f2834a9 100644
--- a/kernel/sched/syscalls.c
+++ b/kernel/sched/syscalls.c
@@ -406,6 +406,14 @@ static void __setscheduler_params(struct task_struct *p,
 	else if (fair_policy(policy))
 		p->static_prio = NICE_TO_PRIO(attr->sched_nice);
 
+	/* rt-policy tasks do not have a timerslack */
+	if (task_is_realtime(p)) {
+		p->timer_slack_ns = 0;
+	} else if (p->timer_slack_ns == 0) {
+		/* when switching back to non-rt policy, restore timerslack */
+		p->timer_slack_ns = p->default_timer_slack_ns;
+	}
+
 	/*
 	 * __sched_setscheduler() ensures attr->sched_priority == 0 when
 	 * !rt_policy. Always setting this ensures that things like
diff --git a/kernel/sys.c b/kernel/sys.c
index 3a2df1bd9f64..e3c4cffb520c 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -2557,6 +2557,8 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
 			error = current->timer_slack_ns;
 		break;
 	case PR_SET_TIMERSLACK:
+		if (task_is_realtime(current))
+			break;
 		if (arg2 <= 0)
 			current->timer_slack_ns =
 					current->default_timer_slack_ns;
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index f56ef23aad90..a023946f8558 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -2074,14 +2074,9 @@ long hrtimer_nanosleep(ktime_t rqtp, const enum hrtimer_mode mode,
 	struct restart_block *restart;
 	struct hrtimer_sleeper t;
 	int ret = 0;
-	u64 slack;
-
-	slack = current->timer_slack_ns;
-	if (rt_task(current))
-		slack = 0;
 
 	hrtimer_init_sleeper_on_stack(&t, clockid, mode);
-	hrtimer_set_expires_range_ns(&t.timer, rqtp, slack);
+	hrtimer_set_expires_range_ns(&t.timer, rqtp, current->timer_slack_ns);
 	ret = do_nanosleep(&t, mode);
 	if (ret != -ERESTART_RESTARTBLOCK)
 		goto out;
@@ -2251,7 +2246,7 @@ void __init hrtimers_init(void)
 /**
  * schedule_hrtimeout_range_clock - sleep until timeout
  * @expires:	timeout value (ktime_t)
- * @delta:	slack in expires timeout (ktime_t) for SCHED_OTHER tasks
+ * @delta:	slack in expires timeout (ktime_t)
  * @mode:	timer mode
  * @clock_id:	timer clock to be used
  */
@@ -2278,13 +2273,6 @@ schedule_hrtimeout_range_clock(ktime_t *expires, u64 delta,
 		return -EINTR;
 	}
 
-	/*
-	 * Override any slack passed by the user if under
-	 * rt contraints.
-	 */
-	if (rt_task(current))
-		delta = 0;
-
 	hrtimer_init_sleeper_on_stack(&t, clock_id, mode);
 	hrtimer_set_expires_range_ns(&t.timer, *expires, delta);
 	hrtimer_sleeper_start_expires(&t, mode);
@@ -2304,7 +2292,7 @@ EXPORT_SYMBOL_GPL(schedule_hrtimeout_range_clock);
 /**
  * schedule_hrtimeout_range - sleep until timeout
  * @expires:	timeout value (ktime_t)
- * @delta:	slack in expires timeout (ktime_t) for SCHED_OTHER tasks
+ * @delta:	slack in expires timeout (ktime_t)
  * @mode:	timer mode
  *
  * Make the current task sleep until the given expiry time has