rcu: Revert "Allow post-unlock reference for rt_mutex" to avoid priority-inversion

[mirror_ubuntu-jammy-kernel.git] / kernel / rcu / tree_plugin.h

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 1fac68220999c31203156f2cf0a6238173c234aa..625e26040e6b548f1cdf07c74ed449b378f93c46 100644 (file)
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -429,10 +429,8 @@ void rcu_read_unlock_special(struct task_struct *t)
 
 #ifdef CONFIG_RCU_BOOST
                /* Unboost if we were boosted. */
-               if (drop_boost_mutex) {
+               if (drop_boost_mutex)
                        rt_mutex_unlock(&rnp->boost_mtx);
-                       complete(&rnp->boost_completion);
-               }
 #endif /* #ifdef CONFIG_RCU_BOOST */
 
                /*
@@ -1081,15 +1079,11 @@ static int rcu_boost(struct rcu_node *rnp)
         */
        t = container_of(tb, struct task_struct, rcu_node_entry);
        rt_mutex_init_proxy_locked(&rnp->boost_mtx, t);
-       init_completion(&rnp->boost_completion);
        raw_spin_unlock_irqrestore(&rnp->lock, flags);
        /* Lock only for side effect: boosts task t's priority. */
        rt_mutex_lock(&rnp->boost_mtx);
        rt_mutex_unlock(&rnp->boost_mtx);  /* Then keep lockdep happy. */
 
-       /* Wait for boostee to be done w/boost_mtx before reinitializing. */
-       wait_for_completion(&rnp->boost_completion);
-
        return ACCESS_ONCE(rnp->exp_tasks) != NULL ||
               ACCESS_ONCE(rnp->boost_tasks) != NULL;
 }