Reset to 3.12.19

1 files changed, 29 insertions, 67 deletions

diff --git a/kernel/futex.c b/kernel/futex.c
index 3b85a95..d8347b7 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -68,7 +68,9 @@
 
 #include "rtmutex_common.h"
 
+#ifndef CONFIG_HAVE_FUTEX_CMPXCHG
 int __read_mostly futex_cmpxchg_enabled;
+#endif
 
 #define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8)
 
@@ -573,9 +575,7 @@ void exit_pi_state_list(struct task_struct *curr)
 		 * task still owns the PI-state:
 		 */
 		if (head->next != next) {
-			raw_spin_unlock_irq(&curr->pi_lock);
 			spin_unlock(&hb->lock);
-			raw_spin_lock_irq(&curr->pi_lock);
 			continue;
 		}
 
@@ -1449,16 +1449,6 @@ retry_private:
 				requeue_pi_wake_futex(this, &key2, hb2);
 				drop_count++;
 				continue;
-			} else if (ret == -EAGAIN) {
-				/*
-				 * Waiter was woken by timeout or
-				 * signal and has set pi_blocked_on to
-				 * PI_WAKEUP_INPROGRESS before we
-				 * tried to enqueue it on the rtmutex.
-				 */
-				this->pi_state = NULL;
-				free_pi_state(pi_state);
-				continue;
 			} else if (ret) {
 				/* -EDEADLK */
 				this->pi_state = NULL;
@@ -2302,7 +2292,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
 	struct hrtimer_sleeper timeout, *to = NULL;
 	struct rt_mutex_waiter rt_waiter;
 	struct rt_mutex *pi_mutex = NULL;
-	struct futex_hash_bucket *hb, *hb2;
+	struct futex_hash_bucket *hb;
 	union futex_key key2 = FUTEX_KEY_INIT;
 	struct futex_q q = futex_q_init;
 	int res, ret;
@@ -2327,7 +2317,8 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
 	 * The waiter is allocated on our stack, manipulated by the requeue
 	 * code while we sleep on uaddr.
 	 */
-	rt_mutex_init_waiter(&rt_waiter, false);
+	debug_rt_mutex_init_waiter(&rt_waiter);
+	rt_waiter.task = NULL;
 
 	ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, VERIFY_WRITE);
 	if (unlikely(ret != 0))
@@ -2348,55 +2339,20 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
 	/* Queue the futex_q, drop the hb lock, wait for wakeup. */
 	futex_wait_queue_me(hb, &q, to);
 
-	/*
-	 * On RT we must avoid races with requeue and trying to block
-	 * on two mutexes (hb->lock and uaddr2's rtmutex) by
-	 * serializing access to pi_blocked_on with pi_lock.
-	 */
-	raw_spin_lock_irq(&current->pi_lock);
-	if (current->pi_blocked_on) {
-		/*
-		 * We have been requeued or are in the process of
-		 * being requeued.
-		 */
-		raw_spin_unlock_irq(&current->pi_lock);
-	} else {
-		/*
-		 * Setting pi_blocked_on to PI_WAKEUP_INPROGRESS
-		 * prevents a concurrent requeue from moving us to the
-		 * uaddr2 rtmutex. After that we can safely acquire
-		 * (and possibly block on) hb->lock.
-		 */
-		current->pi_blocked_on = PI_WAKEUP_INPROGRESS;
-		raw_spin_unlock_irq(&current->pi_lock);
-
-		spin_lock(&hb->lock);
-
-		/*
-		 * Clean up pi_blocked_on. We might leak it otherwise
-		 * when we succeeded with the hb->lock in the fast
-		 * path.
-		 */
-		raw_spin_lock_irq(&current->pi_lock);
-		current->pi_blocked_on = NULL;
-		raw_spin_unlock_irq(&current->pi_lock);
-
-		ret = handle_early_requeue_pi_wakeup(hb, &q, &key2, to);
-		spin_unlock(&hb->lock);
-		if (ret)
-			goto out_put_keys;
-	}
+	spin_lock(&hb->lock);
+	ret = handle_early_requeue_pi_wakeup(hb, &q, &key2, to);
+	spin_unlock(&hb->lock);
+	if (ret)
+		goto out_put_keys;
 
 	/*
-	 * In order to be here, we have either been requeued, are in
-	 * the process of being requeued, or requeue successfully
-	 * acquired uaddr2 on our behalf.  If pi_blocked_on was
-	 * non-null above, we may be racing with a requeue.  Do not
-	 * rely on q->lock_ptr to be hb2->lock until after blocking on
-	 * hb->lock or hb2->lock. The futex_requeue dropped our key1
-	 * reference and incremented our key2 reference count.
+	 * In order for us to be here, we know our q.key == key2, and since
+	 * we took the hb->lock above, we also know that futex_requeue() has
+	 * completed and we no longer have to concern ourselves with a wakeup
+	 * race with the atomic proxy lock acquisition by the requeue code. The
+	 * futex_requeue dropped our key1 reference and incremented our key2
+	 * reference count.
 	 */
-	hb2 = hash_futex(&key2);
 
 	/* Check if the requeue code acquired the second futex for us. */
 	if (!q.rt_waiter) {
@@ -2405,10 +2361,9 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
 		 * did a lock-steal - fix up the PI-state in that case.
 		 */
 		if (q.pi_state && (q.pi_state->owner != current)) {
-			spin_lock(&hb2->lock);
-			BUG_ON(&hb2->lock != q.lock_ptr);
+			spin_lock(q.lock_ptr);
 			ret = fixup_pi_state_owner(uaddr2, &q, current);
-			spin_unlock(&hb2->lock);
+			spin_unlock(q.lock_ptr);
 		}
 	} else {
 		/*
@@ -2421,8 +2376,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
 		ret = rt_mutex_finish_proxy_lock(pi_mutex, to, &rt_waiter, 1);
 		debug_rt_mutex_free_waiter(&rt_waiter);
 
-		spin_lock(&hb2->lock);
-		BUG_ON(&hb2->lock != q.lock_ptr);
+		spin_lock(q.lock_ptr);
 		/*
 		 * Fixup the pi_state owner and possibly acquire the lock if we
 		 * haven't already.
@@ -2779,10 +2733,10 @@ SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val,
 	return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
 }
 
-static int __init futex_init(void)
+static void __init futex_detect_cmpxchg(void)
 {
+#ifndef CONFIG_HAVE_FUTEX_CMPXCHG
 	u32 curval;
-	int i;
 
 	/*
 	 * This will fail and we want it. Some arch implementations do
@@ -2796,6 +2750,14 @@ static int __init futex_init(void)
 	 */
 	if (cmpxchg_futex_value_locked(&curval, NULL, 0, 0) == -EFAULT)
 		futex_cmpxchg_enabled = 1;
+#endif
+}
+
+static int __init futex_init(void)
+{
+	int i;
+
+	futex_detect_cmpxchg();
 
 	for (i = 0; i < ARRAY_SIZE(futex_queues); i++) {
 		plist_head_init(&futex_queues[i].chain);