3 files changed, 36 insertions, 10 deletions

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index b0e9467922e1..d24e4339b46d 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -4188,7 +4188,7 @@ void debug_show_held_locks(struct task_struct *task)
 }
 EXPORT_SYMBOL_GPL(debug_show_held_locks);
 
-asmlinkage void lockdep_sys_exit(void)
+asmlinkage __visible void lockdep_sys_exit(void)
 {
         struct task_struct *curr = current;
 
diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index f26b1a18e34e..0955b885d0dc 100644
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -82,14 +82,14 @@ struct lock_writer_stress_stats {
 };
 static struct lock_writer_stress_stats *lwsa;
 
-#if defined(MODULE) || defined(CONFIG_LOCK_TORTURE_TEST_RUNNABLE)
+#if defined(MODULE)
 #define LOCKTORTURE_RUNNABLE_INIT 1
 #else
 #define LOCKTORTURE_RUNNABLE_INIT 0
 #endif
 int locktorture_runnable = LOCKTORTURE_RUNNABLE_INIT;
 module_param(locktorture_runnable, int, 0444);
-MODULE_PARM_DESC(locktorture_runnable, "Start locktorture at boot");
+MODULE_PARM_DESC(locktorture_runnable, "Start locktorture at module init");
 
 /* Forward reference. */
 static void lock_torture_cleanup(void);
@@ -216,10 +216,11 @@ static int lock_torture_writer(void *arg)
         static DEFINE_TORTURE_RANDOM(rand);
 
         VERBOSE_TOROUT_STRING("lock_torture_writer task started");
-        set_user_nice(current, 19);
+        set_user_nice(current, MAX_NICE);
 
         do {
-                schedule_timeout_uninterruptible(1);
+                if ((torture_random(&rand) & 0xfffff) == 0)
+                        schedule_timeout_uninterruptible(1);
                 cur_ops->writelock();
                 if (WARN_ON_ONCE(lock_is_write_held))
                         lwsp->n_write_lock_fail++;
@@ -354,7 +355,8 @@ static int __init lock_torture_init(void)
                 &lock_busted_ops, &spin_lock_ops, &spin_lock_irq_ops,
         };
 
-        torture_init_begin(torture_type, verbose, &locktorture_runnable);
+        if (!torture_init_begin(torture_type, verbose, &locktorture_runnable))
+                return -EBUSY;
 
         /* Process args and tell the world that the torturer is on the job. */
         for (i = 0; i < ARRAY_SIZE(torture_ops); i++) {
diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index aa4dff04b594..a620d4d08ca6 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -343,9 +343,16 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task,
          * top_waiter can be NULL, when we are in the deboosting
          * mode!
          */
-        if (top_waiter && (!task_has_pi_waiters(task) ||
-                           top_waiter != task_top_pi_waiter(task)))
-                goto out_unlock_pi;
+        if (top_waiter) {
+                if (!task_has_pi_waiters(task))
+                        goto out_unlock_pi;
+                /*
+                 * If deadlock detection is off, we stop here if we
+                 * are not the top pi waiter of the task.
+                 */
+                if (!detect_deadlock && top_waiter != task_top_pi_waiter(task))
+                        goto out_unlock_pi;
+        }
 
         /*
          * When deadlock detection is off then we check, if further
@@ -361,7 +368,12 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task,
                 goto retry;
         }
 
-        /* Deadlock detection */
+        /*
+         * Deadlock detection. If the lock is the same as the original
+         * lock which caused us to walk the lock chain or if the
+         * current lock is owned by the task which initiated the chain
+         * walk, we detected a deadlock.
+         */
         if (lock == orig_lock || rt_mutex_owner(lock) == top_task) {
                 debug_rt_mutex_deadlock(deadlock_detect, orig_waiter, lock);
                 raw_spin_unlock(&lock->wait_lock);
@@ -527,6 +539,18 @@ static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
         unsigned long flags;
         int chain_walk = 0, res;
 
+        /*
+         * Early deadlock detection. We really don't want the task to
+         * enqueue on itself just to untangle the mess later. It's not
+         * only an optimization. We drop the locks, so another waiter
+         * can come in before the chain walk detects the deadlock. So
+         * the other will detect the deadlock and return -EDEADLOCK,
+         * which is wrong, as the other waiter is not in a deadlock
+         * situation.
+         */
+        if (detect_deadlock && owner == task)
+                return -EDEADLK;
+
         raw_spin_lock_irqsave(&task->pi_lock, flags);
         __rt_mutex_adjust_prio(task);
         waiter->task = task;