2 files changed, 37 insertions, 27 deletions

diff --git a/include/linux/futex.h b/include/linux/futex.h
index 8f627b9ae2b1..3bf5bb5a34f9 100644
--- a/include/linux/futex.h
+++ b/include/linux/futex.h
@@ -25,7 +25,8 @@ union ktime;
 #define FUTEX_WAKE_BITSET       10
 
 #define FUTEX_PRIVATE_FLAG      128
-#define FUTEX_CMD_MASK          ~FUTEX_PRIVATE_FLAG
+#define FUTEX_CLOCK_REALTIME    256
+#define FUTEX_CMD_MASK          ~(FUTEX_PRIVATE_FLAG | FUTEX_CLOCK_REALTIME)
 
 #define FUTEX_WAIT_PRIVATE      (FUTEX_WAIT | FUTEX_PRIVATE_FLAG)
 #define FUTEX_WAKE_PRIVATE      (FUTEX_WAKE | FUTEX_PRIVATE_FLAG)
diff --git a/kernel/futex.c b/kernel/futex.c
index e10c5c8786a6..b4f87bac91c1 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -92,11 +92,12 @@ struct futex_pi_state {
  * A futex_q has a woken state, just like tasks have TASK_RUNNING.
  * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0.
  * The order of wakup is always to make the first condition true, then
- * wake up q->waiters, then make the second condition true.
+ * wake up q->waiter, then make the second condition true.
  */
 struct futex_q {
         struct plist_node list;
-        wait_queue_head_t waiters;
+        /* There can only be a single waiter */
+        wait_queue_head_t waiter;
 
         /* Which hash list lock to use: */
         spinlock_t *lock_ptr;
@@ -573,7 +574,7 @@ static void wake_futex(struct futex_q *q)
          * The lock in wake_up_all() is a crucial memory barrier after the
          * plist_del() and also before assigning to q->lock_ptr.
          */
-        wake_up_all(&q->waiters);
+        wake_up(&q->waiter);
         /*
          * The waiting task can free the futex_q as soon as this is written,
          * without taking any locks.  This must come last.
@@ -930,7 +931,7 @@ static inline struct futex_hash_bucket *queue_lock(struct futex_q *q)
 {
         struct futex_hash_bucket *hb;
 
-        init_waitqueue_head(&q->waiters);
+        init_waitqueue_head(&q->waiter);
 
         get_futex_key_refs(&q->key);
         hb = hash_futex(&q->key);
@@ -1142,12 +1143,13 @@ handle_fault:
  * In case we must use restart_block to restart a futex_wait,
  * we encode in the 'flags' shared capability
  */
-#define FLAGS_SHARED  1
+#define FLAGS_SHARED            0x01
+#define FLAGS_CLOCKRT           0x02
 
 static long futex_wait_restart(struct restart_block *restart);
 
 static int futex_wait(u32 __user *uaddr, int fshared,
-                      u32 val, ktime_t *abs_time, u32 bitset)
+                      u32 val, ktime_t *abs_time, u32 bitset, int clockrt)
 {
         struct task_struct *curr = current;
         DECLARE_WAITQUEUE(wait, curr);
@@ -1220,7 +1222,7 @@ static int futex_wait(u32 __user *uaddr, int fshared,
 
         /* add_wait_queue is the barrier after __set_current_state. */
         __set_current_state(TASK_INTERRUPTIBLE);
-        add_wait_queue(&q.waiters, &wait);
+        add_wait_queue(&q.waiter, &wait);
         /*
          * !plist_node_empty() is safe here without any lock.
          * q.lock_ptr != 0 is not safe, because of ordering against wakeup.
@@ -1233,8 +1235,10 @@ static int futex_wait(u32 __user *uaddr, int fshared,
                         slack = current->timer_slack_ns;
                         if (rt_task(current))
                                 slack = 0;
-                        hrtimer_init_on_stack(&t.timer, CLOCK_MONOTONIC,
-                                                HRTIMER_MODE_ABS);
+                        hrtimer_init_on_stack(&t.timer,
+                                              clockrt ? CLOCK_REALTIME :
+                                              CLOCK_MONOTONIC,
+                                              HRTIMER_MODE_ABS);
                         hrtimer_init_sleeper(&t, current);
                         hrtimer_set_expires_range_ns(&t.timer, *abs_time, slack);
 
@@ -1289,6 +1293,8 @@ static int futex_wait(u32 __user *uaddr, int fshared,
 
                 if (fshared)
                         restart->futex.flags |= FLAGS_SHARED;
+                if (clockrt)
+                        restart->futex.flags |= FLAGS_CLOCKRT;
                 return -ERESTART_RESTARTBLOCK;
         }
 
@@ -1312,7 +1318,8 @@ static long futex_wait_restart(struct restart_block *restart)
         if (restart->futex.flags & FLAGS_SHARED)
                 fshared = 1;
         return (long)futex_wait(uaddr, fshared, restart->futex.val, &t,
-                                restart->futex.bitset);
+                                restart->futex.bitset,
+                                restart->futex.flags & FLAGS_CLOCKRT);
 }
 
 
@@ -1558,12 +1565,11 @@ static int futex_lock_pi(u32 __user *uaddr, int fshared,
 
  uaddr_faulted:
         /*
-         * We have to r/w  *(int __user *)uaddr, but we can't modify it
-         * non-atomically.  Therefore, if get_user below is not
-         * enough, we need to handle the fault ourselves, while
-         * still holding the mmap_sem.
-         *
-         * ... and hb->lock. :-) --ANK
+         * We have to r/w  *(int __user *)uaddr, and we have to modify it
+         * atomically.  Therefore, if we continue to fault after get_user()
+         * below, we need to handle the fault ourselves, while still holding
+         * the mmap_sem.  This can occur if the uaddr is under contention as
+         * we have to drop the mmap_sem in order to call get_user().
          */
         queue_unlock(&q, hb);
 
@@ -1575,7 +1581,7 @@ static int futex_lock_pi(u32 __user *uaddr, int fshared,
         }
 
         ret = get_user(uval, uaddr);
-        if (!ret && (uval != -EFAULT))
+        if (!ret)
                 goto retry;
 
         if (to)
@@ -1669,12 +1675,11 @@ out:
 
 pi_faulted:
         /*
-         * We have to r/w  *(int __user *)uaddr, but we can't modify it
-         * non-atomically.  Therefore, if get_user below is not
-         * enough, we need to handle the fault ourselves, while
-         * still holding the mmap_sem.
-         *
-         * ... and hb->lock. --ANK
+         * We have to r/w  *(int __user *)uaddr, and we have to modify it
+         * atomically.  Therefore, if we continue to fault after get_user()
+         * below, we need to handle the fault ourselves, while still holding
+         * the mmap_sem.  This can occur if the uaddr is under contention as
+         * we have to drop the mmap_sem in order to call get_user().
          */
         spin_unlock(&hb->lock);
 
@@ -1687,7 +1692,7 @@ pi_faulted:
         }
 
         ret = get_user(uval, uaddr);
-        if (!ret && (uval != -EFAULT))
+        if (!ret)
                 goto retry;
 
         return ret;
@@ -1905,18 +1910,22 @@ void exit_robust_list(struct task_struct *curr)
 long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
                 u32 __user *uaddr2, u32 val2, u32 val3)
 {
-        int ret = -ENOSYS;
+        int clockrt, ret = -ENOSYS;
         int cmd = op & FUTEX_CMD_MASK;
         int fshared = 0;
 
         if (!(op & FUTEX_PRIVATE_FLAG))
                 fshared = 1;
 
+        clockrt = op & FUTEX_CLOCK_REALTIME;
+        if (clockrt && cmd != FUTEX_WAIT_BITSET)
+                return -ENOSYS;
+
         switch (cmd) {
         case FUTEX_WAIT:
                 val3 = FUTEX_BITSET_MATCH_ANY;
         case FUTEX_WAIT_BITSET:
-                ret = futex_wait(uaddr, fshared, val, timeout, val3);
+                ret = futex_wait(uaddr, fshared, val, timeout, val3, clockrt);
                 break;
         case FUTEX_WAKE:
                 val3 = FUTEX_BITSET_MATCH_ANY;