[PATCH v3 3/8] rcutorture: Don't try to disable to RT throttling.

[Sebastian Andrzej Siewior <bigeasy@linutronix.de>]

Commit 450efca7182a5 ("rcutorture: Disable RT throttling for boost
tests") added the ability to disable RT throttling while rcutorture was
run.

Since v6.12 the DL fair_server takes control of throttling and this
interface no longer serves this purpose. That sysctl control still
exists but serves a different cause.

There is no in-kernel interface to provide this feature, one needs to
echo 0 to each /sys/kernel/debug/sched/fair_server/cpu*/runtime file.

Since sysctl_sched_rt_runtime does not do what it once did, remove it
from rcutorture.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 kernel/rcu/rcu.h        |  2 --
 kernel/rcu/rcutorture.c | 35 -----------------------------------
 2 files changed, 37 deletions(-)

diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index d60444bf3a02d..6d1034e49d411 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -69,8 +69,6 @@
 /* A complete grace period count */
 #define RCU_SEQ_GP (RCU_SEQ_STATE_MASK + 1)
 
-extern int sysctl_sched_rt_runtime;
-
 /*
  * Return the counter portion of a sequence number previously returned
  * by rcu_seq_snap() or rcu_seq_current().
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 93ca7f06371e4..aecc4da7161bb 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1333,39 +1333,6 @@ static unsigned long rcutorture_seq_diff(unsigned long new, unsigned long old)
 	return cur_ops->gp_diff(new, old);
 }
 
-/*
- * RCU torture priority-boost testing.  Runs one real-time thread per
- * CPU for moderate bursts, repeatedly starting grace periods and waiting
- * for them to complete.  If a given grace period takes too long, we assume
- * that priority inversion has occurred.
- */
-
-static int old_rt_runtime = -1;
-
-static void rcu_torture_disable_rt_throttle(void)
-{
-	/*
-	 * Disable RT throttling so that rcutorture's boost threads don't get
-	 * throttled. Only possible if rcutorture is built-in otherwise the
-	 * user should manually do this by setting the sched_rt_period_us and
-	 * sched_rt_runtime sysctls.
-	 */
-	if (!IS_BUILTIN(CONFIG_RCU_TORTURE_TEST) || old_rt_runtime != -1)
-		return;
-
-	old_rt_runtime = sysctl_sched_rt_runtime;
-	sysctl_sched_rt_runtime = -1;
-}
-
-static void rcu_torture_enable_rt_throttle(void)
-{
-	if (!IS_BUILTIN(CONFIG_RCU_TORTURE_TEST) || old_rt_runtime == -1)
-		return;
-
-	sysctl_sched_rt_runtime = old_rt_runtime;
-	old_rt_runtime = -1;
-}
-
 static bool rcu_torture_boost_failed(unsigned long gp_state, unsigned long *start)
 {
 	int cpu;
@@ -3390,7 +3357,6 @@ static int rcutorture_booster_cleanup(unsigned int cpu)
 	mutex_lock(&boost_mutex);
 	t = boost_tasks[cpu];
 	boost_tasks[cpu] = NULL;
-	rcu_torture_enable_rt_throttle();
 	mutex_unlock(&boost_mutex);
 
 	/* This must be outside of the mutex, otherwise deadlock! */
@@ -3428,7 +3394,6 @@ static int rcutorture_booster_init(unsigned int cpu)
 
 	/* Don't allow time recalculation while creating a new task. */
 	mutex_lock(&boost_mutex);
-	rcu_torture_disable_rt_throttle();
 	VERBOSE_TOROUT_STRING("Creating rcu_torture_boost task");
 	boost_tasks[cpu] = kthread_run_on_cpu(rcu_torture_boost, NULL,
 					      cpu, "rcu_torture_boost_%u");

-- 
2.55.0