sched: Remove sched_set_*() return value

Ingo suggested that since the new sched_set_*() functions are
implemented using the 'nocheck' variants, they really shouldn't ever
fail, so remove the return value.

Cc: axboe@kernel.dk
Cc: daniel.lezcano@linaro.org
Cc: sudeep.holla@arm.com
Cc: airlied@redhat.com
Cc: broonie@kernel.org
Cc: paulmck@kernel.org
Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ingo Molnar <mingo@kernel.org>

Author: Peter Zijlstra

drivers/block/drbd/drbd_receiver.c

@@ -6020,9 +6020,7 @@ int drbd_ack_receiver(struct drbd_thread *thi)
 	int expect   = header_size;
 	bool ping_timeout_active = false;
 
-	rv = sched_set_fifo_low(current);
-	if (rv < 0)
-		drbd_err(connection, "drbd_ack_receiver: ERROR set priority, ret=%d\n", rv);
+	sched_set_fifo_low(current);
 
 	while (get_t_state(thi) == RUNNING) {
 		drbd_thread_current_set_cpu(thi);

drivers/firmware/psci/psci_checker.c

@@ -281,8 +281,7 @@ static int suspend_test_thread(void *arg)
 	wait_for_completion(&suspend_threads_started);
 
 	/* Set maximum priority to preempt all other threads on this CPU. */
-	if (sched_set_fifo(current))
-		pr_warn("Failed to set suspend thread scheduler on CPU %d\n", cpu);
+	sched_set_fifo(current);
 
 	dev = this_cpu_read(cpuidle_devices);
 	drv = cpuidle_get_cpu_driver(dev);

drivers/gpu/drm/msm/msm_drv.c

@@ -509,10 +509,7 @@ static int msm_drm_init(struct device *dev, struct drm_driver *drv)
 			goto err_msm_uninit;
 		}
 
-		ret = sched_set_fifo(priv->event_thread[i].thread);
-		if (ret)
-			dev_warn(dev, "event_thread set priority failed:%d\n",
-				 ret);
+		sched_set_fifo(priv->event_thread[i].thread);
 	}
 
 	ret = drm_vblank_init(ddev, priv->num_crtcs);

drivers/platform/chrome/cros_ec_spi.c

@@ -725,10 +725,9 @@ static int cros_ec_spi_devm_high_pri_alloc(struct device *dev,
 	if (err)
 		return err;
 
-	err = sched_set_fifo(ec_spi->high_pri_worker->task);
-	if (err)
-		dev_err(dev, "Can't set cros_ec high pri priority: %d\n", err);
-	return err;
+	sched_set_fifo(ec_spi->high_pri_worker->task);
+
+	return 0;
 }
 
 static int cros_ec_spi_probe(struct spi_device *spi)

include/linux/sched.h

@@ -1653,9 +1653,9 @@ extern int idle_cpu(int cpu);
 extern int available_idle_cpu(int cpu);
 extern int sched_setscheduler(struct task_struct *, int, const struct sched_param *);
 extern int sched_setscheduler_nocheck(struct task_struct *, int, const struct sched_param *);
-extern int sched_set_fifo(struct task_struct *p);
-extern int sched_set_fifo_low(struct task_struct *p);
-extern int sched_set_normal(struct task_struct *p, int nice);
+extern void sched_set_fifo(struct task_struct *p);
+extern void sched_set_fifo_low(struct task_struct *p);
+extern void sched_set_normal(struct task_struct *p, int nice);
 extern int sched_setattr(struct task_struct *, const struct sched_attr *);
 extern int sched_setattr_nocheck(struct task_struct *, const struct sched_attr *);
 extern struct task_struct *idle_task(int cpu);

kernel/rcu/rcutorture.c

@@ -893,10 +893,7 @@ static int rcu_torture_boost(void *arg)
 	VERBOSE_TOROUT_STRING("rcu_torture_boost started");
 
 	/* Set real-time priority. */
-	if (sched_set_fifo_low(current) < 0) {
-		VERBOSE_TOROUT_STRING("rcu_torture_boost RT prio failed!");
-		n_rcu_torture_boost_rterror++;
-	}
+	sched_set_fifo_low(current);
 
 	init_rcu_head_on_stack(&rbi.rcu);
 	/* Each pass through the following loop does one boost-test cycle. */

kernel/sched/core.c

@@ -5183,30 +5183,30 @@ int sched_setscheduler_nocheck(struct task_struct *p, int policy,
  * The administrator _MUST_ configure the system, the kernel simply doesn't
  * know enough information to make a sensible choice.
  */
-int sched_set_fifo(struct task_struct *p)
+void sched_set_fifo(struct task_struct *p)
 {
 	struct sched_param sp = { .sched_priority = MAX_RT_PRIO / 2 };
-	return sched_setscheduler_nocheck(p, SCHED_FIFO, &sp);
+	WARN_ON_ONCE(sched_setscheduler_nocheck(p, SCHED_FIFO, &sp) != 0);
 }
 EXPORT_SYMBOL_GPL(sched_set_fifo);
 
 /*
  * For when you don't much care about FIFO, but want to be above SCHED_NORMAL.
  */
-int sched_set_fifo_low(struct task_struct *p)
+void sched_set_fifo_low(struct task_struct *p)
 {
 	struct sched_param sp = { .sched_priority = 1 };
-	return sched_setscheduler_nocheck(p, SCHED_FIFO, &sp);
+	WARN_ON_ONCE(sched_setscheduler_nocheck(p, SCHED_FIFO, &sp) != 0);
 }
 EXPORT_SYMBOL_GPL(sched_set_fifo_low);
 
-int sched_set_normal(struct task_struct *p, int nice)
+void sched_set_normal(struct task_struct *p, int nice)
 {
 	struct sched_attr attr = {
 		.sched_policy = SCHED_NORMAL,
 		.sched_nice = nice,
 	};
-	return sched_setattr_nocheck(p, &attr);
+	WARN_ON_ONCE(sched_setattr_nocheck(p, &attr) != 0);
 }
 EXPORT_SYMBOL_GPL(sched_set_normal);