3 files changed, 37 insertions, 4 deletions

diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index 0453a7d12b3f..bee070979970 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -502,6 +502,7 @@ static inline void rcu_force_quiescent_state(void) { }
 static inline void rcu_bh_force_quiescent_state(void) { }
 static inline void rcu_sched_force_quiescent_state(void) { }
 static inline void show_rcu_gp_kthreads(void) { }
+static inline int rcu_get_gp_kthreads_prio(void) { return 0; }
 #else /* #ifdef CONFIG_TINY_RCU */
 unsigned long rcu_get_gp_seq(void);
 unsigned long rcu_bh_get_gp_seq(void);
@@ -510,6 +511,7 @@ unsigned long rcu_exp_batches_completed(void);
 unsigned long rcu_exp_batches_completed_sched(void);
 unsigned long srcu_batches_completed(struct srcu_struct *sp);
 void show_rcu_gp_kthreads(void);
+int rcu_get_gp_kthreads_prio(void);
 void rcu_force_quiescent_state(void);
 void rcu_bh_force_quiescent_state(void);
 void rcu_sched_force_quiescent_state(void);
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 049b3735dba8..e3d2d4f1d928 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1787,6 +1787,32 @@ static void rcu_torture_barrier_cleanup(void)
         }
 }
 
+static bool rcu_torture_can_boost(void)
+{
+        static int boost_warn_once;
+        int prio;
+
+        if (!(test_boost == 1 && cur_ops->can_boost) && test_boost != 2)
+                return false;
+
+        prio = rcu_get_gp_kthreads_prio();
+        if (!prio)
+                return false;
+
+        if (prio < 2) {
+                if (boost_warn_once  == 1)
+                        return false;
+
+                pr_alert("%s: WARN: RCU kthread priority too low to test boosting. "
+                         "Skipping RCU boost test. Try passing rcutree.kthread_prio > 1 "
+                         "on the kernel command line.\n", KBUILD_MODNAME);
+                boost_warn_once = 1;
+                return false;
+        }
+
+        return true;
+}
+
 static enum cpuhp_state rcutor_hp;
 
 static void
@@ -1831,8 +1857,7 @@ rcu_torture_cleanup(void)
         torture_stop_kthread(rcu_torture_fqs, fqs_task);
         for (i = 0; i < ncbflooders; i++)
                 torture_stop_kthread(rcu_torture_cbflood, cbflood_task[i]);
-        if ((test_boost == 1 && cur_ops->can_boost) ||
-            test_boost == 2)
+        if (rcu_torture_can_boost())
                 cpuhp_remove_state(rcutor_hp);
 
         /*
@@ -2056,8 +2081,7 @@ rcu_torture_init(void)
                 test_boost_interval = 1;
         if (test_boost_duration < 2)
                 test_boost_duration = 2;
-        if ((test_boost == 1 && cur_ops->can_boost) ||
-            test_boost == 2) {
+        if (rcu_torture_can_boost()) {
 
                 boost_starttime = jiffies + test_boost_interval * HZ;
 
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 65abb399b08d..b4bcb5e21ca6 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -180,6 +180,13 @@ module_param(gp_init_delay, int, 0444);
 static int gp_cleanup_delay;
 module_param(gp_cleanup_delay, int, 0444);
 
+/* Retreive RCU kthreads priority for rcutorture */
+int rcu_get_gp_kthreads_prio(void)
+{
+        return kthread_prio;
+}
+EXPORT_SYMBOL_GPL(rcu_get_gp_kthreads_prio);
+
 /*
  * Number of grace periods between delays, normalized by the duration of
  * the delay.  The longer the delay, the more the grace periods between