Revert "rcu: Permit rt_mutex_unlock() with irqs disabled"

This reverts commit 5342e269b2b58ee0b0b4168a94087faaa60d0567.

The approach taken in this patch was deemed too abusive to mutexes,
and thus too likely to result in maintenance problems in the future.
Instead, we will disallow RCU read-side critical sections that partially
overlap with interrupt-disbled code segments.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 8cd9efe7e81f4f9fcc1c3ca062f5abd4cfb5b1d1..f55f10ba01f548279e48f06459a61703391c569d 100644 (file)
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -1165,8 +1165,6 @@ static void rcu_initiate_boost_trace(struct rcu_node *rnp)
 
 #endif /* #else #ifdef CONFIG_RCU_TRACE */
 
-static struct lock_class_key rcu_boost_class;
-
 /*
  * Carry out RCU priority boosting on the task indicated by ->exp_tasks
  * or ->boost_tasks, advancing the pointer to the next task in the
@@ -1229,9 +1227,6 @@ static int rcu_boost(struct rcu_node *rnp)
         */
        t = container_of(tb, struct task_struct, rcu_node_entry);
        rt_mutex_init_proxy_locked(&mtx, t);
-       /* Avoid lockdep false positives.  This rt_mutex is its own thing. */
-       lockdep_set_class_and_name(&mtx.wait_lock, &rcu_boost_class,
-                                  "rcu_boost_mutex");
        t->rcu_boost_mutex = &mtx;
        raw_spin_unlock_irqrestore(&rnp->lock, flags);
        rt_mutex_lock(&mtx);  /* Side effect: boosts task t's priority. */

diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c
index f9d8482dd4872f631b8bfb3524f5797b2eb711f4..a242e691c993038f35ace870d245487d44b5bc16 100644 (file)
--- a/kernel/rtmutex.c
+++ b/kernel/rtmutex.c
@@ -579,7 +579,6 @@ __rt_mutex_slowlock(struct rt_mutex *lock, int state,
                    struct rt_mutex_waiter *waiter)
 {
        int ret = 0;
-       int was_disabled;
 
        for (;;) {
                /* Try to acquire the lock: */
@@ -602,17 +601,10 @@ __rt_mutex_slowlock(struct rt_mutex *lock, int state,
 
                raw_spin_unlock(&lock->wait_lock);
 
-               was_disabled = irqs_disabled();
-               if (was_disabled)
-                       local_irq_enable();
-
                debug_rt_mutex_print_deadlock(waiter);
 
                schedule_rt_mutex(lock);
 
-               if (was_disabled)
-                       local_irq_disable();
-
                raw_spin_lock(&lock->wait_lock);
                set_current_state(state);
        }