1 files changed, 136 insertions, 215 deletions

diff --git a/kernel/futex.c b/kernel/futex.c
index 4fe790e89d0f..7c6cbabe52b3 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;
@@ -123,24 +124,6 @@ struct futex_hash_bucket {
 static struct futex_hash_bucket futex_queues[1<<FUTEX_HASHBITS];
 
 /*
- * Take mm->mmap_sem, when futex is shared
- */
-static inline void futex_lock_mm(struct rw_semaphore *fshared)
-{
-        if (fshared)
-                down_read(fshared);
-}
-
-/*
- * Release mm->mmap_sem, when the futex is shared
- */
-static inline void futex_unlock_mm(struct rw_semaphore *fshared)
-{
-        if (fshared)
-                up_read(fshared);
-}
-
-/*
  * We hash on the keys returned from get_futex_key (see below).
  */
 static struct futex_hash_bucket *hash_futex(union futex_key *key)
@@ -161,6 +144,45 @@ static inline int match_futex(union futex_key *key1, union futex_key *key2)
                 && key1->both.offset == key2->both.offset);
 }
 
+/*
+ * Take a reference to the resource addressed by a key.
+ * Can be called while holding spinlocks.
+ *
+ */
+static void get_futex_key_refs(union futex_key *key)
+{
+        if (!key->both.ptr)
+                return;
+
+        switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
+        case FUT_OFF_INODE:
+                atomic_inc(&key->shared.inode->i_count);
+                break;
+        case FUT_OFF_MMSHARED:
+                atomic_inc(&key->private.mm->mm_count);
+                break;
+        }
+}
+
+/*
+ * Drop a reference to the resource addressed by a key.
+ * The hash bucket spinlock must not be held.
+ */
+static void drop_futex_key_refs(union futex_key *key)
+{
+        if (!key->both.ptr)
+                return;
+
+        switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
+        case FUT_OFF_INODE:
+                iput(key->shared.inode);
+                break;
+        case FUT_OFF_MMSHARED:
+                mmdrop(key->private.mm);
+                break;
+        }
+}
+
 /**
  * get_futex_key - Get parameters which are the keys for a futex.
  * @uaddr: virtual address of the futex
@@ -179,12 +201,10 @@ static inline int match_futex(union futex_key *key1, union futex_key *key2)
  * For other futexes, it points to &current->mm->mmap_sem and
  * caller must have taken the reader lock. but NOT any spinlocks.
  */
-static int get_futex_key(u32 __user *uaddr, struct rw_semaphore *fshared,
-                         union futex_key *key)
+static int get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key)
 {
         unsigned long address = (unsigned long)uaddr;
         struct mm_struct *mm = current->mm;
-        struct vm_area_struct *vma;
         struct page *page;
         int err;
 
@@ -208,100 +228,50 @@ static int get_futex_key(u32 __user *uaddr, struct rw_semaphore *fshared,
                         return -EFAULT;
                 key->private.mm = mm;
                 key->private.address = address;
+                get_futex_key_refs(key);
                 return 0;
         }
-        /*
-         * The futex is hashed differently depending on whether
-         * it's in a shared or private mapping.  So check vma first.
-         */
-        vma = find_extend_vma(mm, address);
-        if (unlikely(!vma))
-                return -EFAULT;
 
-        /*
-         * Permissions.
-         */
-        if (unlikely((vma->vm_flags & (VM_IO|VM_READ)) != VM_READ))
-                return (vma->vm_flags & VM_IO) ? -EPERM : -EACCES;
+again:
+        err = get_user_pages_fast(address, 1, 0, &page);
+        if (err < 0)
+                return err;
+
+        lock_page(page);
+        if (!page->mapping) {
+                unlock_page(page);
+                put_page(page);
+                goto again;
+        }
 
         /*
          * Private mappings are handled in a simple way.
          *
          * NOTE: When userspace waits on a MAP_SHARED mapping, even if
          * it's a read-only handle, it's expected that futexes attach to
-         * the object not the particular process.  Therefore we use
-         * VM_MAYSHARE here, not VM_SHARED which is restricted to shared
-         * mappings of _writable_ handles.
+         * the object not the particular process.
          */
-        if (likely(!(vma->vm_flags & VM_MAYSHARE))) {
-                key->both.offset |= FUT_OFF_MMSHARED; /* reference taken on mm */
+        if (PageAnon(page)) {
+                key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */
                 key->private.mm = mm;
                 key->private.address = address;
-                return 0;
+        } else {
+                key->both.offset |= FUT_OFF_INODE; /* inode-based key */
+                key->shared.inode = page->mapping->host;
+                key->shared.pgoff = page->index;
         }
 
-        /*
-         * Linear file mappings are also simple.
-         */
-        key->shared.inode = vma->vm_file->f_path.dentry->d_inode;
-        key->both.offset |= FUT_OFF_INODE; /* inode-based key. */
-        if (likely(!(vma->vm_flags & VM_NONLINEAR))) {
-                key->shared.pgoff = (((address - vma->vm_start) >> PAGE_SHIFT)
-                                     + vma->vm_pgoff);
-                return 0;
-        }
+        get_futex_key_refs(key);
 
-        /*
-         * We could walk the page table to read the non-linear
-         * pte, and get the page index without fetching the page
-         * from swap.  But that's a lot of code to duplicate here
-         * for a rare case, so we simply fetch the page.
-         */
-        err = get_user_pages(current, mm, address, 1, 0, 0, &page, NULL);
-        if (err >= 0) {
-                key->shared.pgoff =
-                        page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
-                put_page(page);
-                return 0;
-        }
-        return err;
-}
-
-/*
- * Take a reference to the resource addressed by a key.
- * Can be called while holding spinlocks.
- *
- */
-static void get_futex_key_refs(union futex_key *key)
-{
-        if (key->both.ptr == NULL)
-                return;
-        switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
-                case FUT_OFF_INODE:
-                        atomic_inc(&key->shared.inode->i_count);
-                        break;
-                case FUT_OFF_MMSHARED:
-                        atomic_inc(&key->private.mm->mm_count);
-                        break;
-        }
+        unlock_page(page);
+        put_page(page);
+        return 0;
 }
 
-/*
- * Drop a reference to the resource addressed by a key.
- * The hash bucket spinlock must not be held.
- */
-static void drop_futex_key_refs(union futex_key *key)
+static inline
+void put_futex_key(int fshared, union futex_key *key)
 {
-        if (!key->both.ptr)
-                return;
-        switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
-                case FUT_OFF_INODE:
-                        iput(key->shared.inode);
-                        break;
-                case FUT_OFF_MMSHARED:
-                        mmdrop(key->private.mm);
-                        break;
-        }
+        drop_futex_key_refs(key);
 }
 
 static u32 cmpxchg_futex_value_locked(u32 __user *uaddr, u32 uval, u32 newval)
@@ -328,10 +298,8 @@ static int get_futex_value_locked(u32 *dest, u32 __user *from)
 
 /*
  * Fault handling.
- * if fshared is non NULL, current->mm->mmap_sem is already held
  */
-static int futex_handle_fault(unsigned long address,
-                              struct rw_semaphore *fshared, int attempt)
+static int futex_handle_fault(unsigned long address, int attempt)
 {
         struct vm_area_struct * vma;
         struct mm_struct *mm = current->mm;
@@ -340,8 +308,7 @@ static int futex_handle_fault(unsigned long address,
         if (attempt > 2)
                 return ret;
 
-        if (!fshared)
-                down_read(&mm->mmap_sem);
+        down_read(&mm->mmap_sem);
         vma = find_vma(mm, address);
         if (vma && address >= vma->vm_start &&
             (vma->vm_flags & VM_WRITE)) {
@@ -361,8 +328,7 @@ static int futex_handle_fault(unsigned long address,
                                 current->min_flt++;
                 }
         }
-        if (!fshared)
-                up_read(&mm->mmap_sem);
+        up_read(&mm->mmap_sem);
         return ret;
 }
 
@@ -385,6 +351,7 @@ static int refill_pi_state_cache(void)
         /* pi_mutex gets initialized later */
         pi_state->owner = NULL;
         atomic_set(&pi_state->refcount, 1);
+        pi_state->key = FUTEX_KEY_INIT;
 
         current->pi_state_cache = pi_state;
 
@@ -469,7 +436,7 @@ void exit_pi_state_list(struct task_struct *curr)
         struct list_head *next, *head = &curr->pi_state_list;
         struct futex_pi_state *pi_state;
         struct futex_hash_bucket *hb;
-        union futex_key key;
+        union futex_key key = FUTEX_KEY_INIT;
 
         if (!futex_cmpxchg_enabled)
                 return;
@@ -614,7 +581,7 @@ 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.
@@ -726,20 +693,17 @@ double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
  * Wake up all waiters hashed on the physical page that is mapped
  * to this virtual address:
  */
-static int futex_wake(u32 __user *uaddr, struct rw_semaphore *fshared,
-                      int nr_wake, u32 bitset)
+static int futex_wake(u32 __user *uaddr, int fshared, int nr_wake, u32 bitset)
 {
         struct futex_hash_bucket *hb;
         struct futex_q *this, *next;
         struct plist_head *head;
-        union futex_key key;
+        union futex_key key = FUTEX_KEY_INIT;
         int ret;
 
         if (!bitset)
                 return -EINVAL;
 
-        futex_lock_mm(fshared);
-
         ret = get_futex_key(uaddr, fshared, &key);
         if (unlikely(ret != 0))
                 goto out;
@@ -767,7 +731,7 @@ static int futex_wake(u32 __user *uaddr, struct rw_semaphore *fshared,
 
         spin_unlock(&hb->lock);
 out:
-        futex_unlock_mm(fshared);
+        put_futex_key(fshared, &key);
         return ret;
 }
 
@@ -776,19 +740,16 @@ out:
  * to this virtual address:
  */
 static int
-futex_wake_op(u32 __user *uaddr1, struct rw_semaphore *fshared,
-              u32 __user *uaddr2,
+futex_wake_op(u32 __user *uaddr1, int fshared, u32 __user *uaddr2,
               int nr_wake, int nr_wake2, int op)
 {
-        union futex_key key1, key2;
+        union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT;
         struct futex_hash_bucket *hb1, *hb2;
         struct plist_head *head;
         struct futex_q *this, *next;
         int ret, op_ret, attempt = 0;
 
 retryfull:
-        futex_lock_mm(fshared);
-
         ret = get_futex_key(uaddr1, fshared, &key1);
         if (unlikely(ret != 0))
                 goto out;
@@ -833,18 +794,12 @@ retry:
                  */
                 if (attempt++) {
                         ret = futex_handle_fault((unsigned long)uaddr2,
-                                                 fshared, attempt);
+                                                 attempt);
                         if (ret)
                                 goto out;
                         goto retry;
                 }
 
-                /*
-                 * If we would have faulted, release mmap_sem,
-                 * fault it in and start all over again.
-                 */
-                futex_unlock_mm(fshared);
-
                 ret = get_user(dummy, uaddr2);
                 if (ret)
                         return ret;
@@ -880,7 +835,8 @@ retry:
         if (hb1 != hb2)
                 spin_unlock(&hb2->lock);
 out:
-        futex_unlock_mm(fshared);
+        put_futex_key(fshared, &key2);
+        put_futex_key(fshared, &key1);
 
         return ret;
 }
@@ -889,19 +845,16 @@ out:
  * Requeue all waiters hashed on one physical page to another
  * physical page.
  */
-static int futex_requeue(u32 __user *uaddr1, struct rw_semaphore *fshared,
-                         u32 __user *uaddr2,
+static int futex_requeue(u32 __user *uaddr1, int fshared, u32 __user *uaddr2,
                          int nr_wake, int nr_requeue, u32 *cmpval)
 {
-        union futex_key key1, key2;
+        union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT;
         struct futex_hash_bucket *hb1, *hb2;
         struct plist_head *head1;
         struct futex_q *this, *next;
         int ret, drop_count = 0;
 
  retry:
-        futex_lock_mm(fshared);
-
         ret = get_futex_key(uaddr1, fshared, &key1);
         if (unlikely(ret != 0))
                 goto out;
@@ -924,12 +877,6 @@ static int futex_requeue(u32 __user *uaddr1, struct rw_semaphore *fshared,
                         if (hb1 != hb2)
                                 spin_unlock(&hb2->lock);
 
-                        /*
-                         * If we would have faulted, release mmap_sem, fault
-                         * it in and start all over again.
-                         */
-                        futex_unlock_mm(fshared);
-
                         ret = get_user(curval, uaddr1);
 
                         if (!ret)
@@ -981,7 +928,8 @@ out_unlock:
                 drop_futex_key_refs(&key1);
 
 out:
-        futex_unlock_mm(fshared);
+        put_futex_key(fshared, &key2);
+        put_futex_key(fshared, &key1);
         return ret;
 }
 
@@ -990,7 +938,7 @@ 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);
@@ -1103,8 +1051,7 @@ static void unqueue_me_pi(struct futex_q *q)
  * private futexes.
  */
 static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
-                                struct task_struct *newowner,
-                                struct rw_semaphore *fshared)
+                                struct task_struct *newowner, int fshared)
 {
         u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS;
         struct futex_pi_state *pi_state = q->pi_state;
@@ -1183,7 +1130,7 @@ retry:
 handle_fault:
         spin_unlock(q->lock_ptr);
 
-        ret = futex_handle_fault((unsigned long)uaddr, fshared, attempt++);
+        ret = futex_handle_fault((unsigned long)uaddr, attempt++);
 
         spin_lock(q->lock_ptr);
 
@@ -1203,12 +1150,13 @@ 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, struct rw_semaphore *fshared,
-                      u32 val, ktime_t *abs_time, u32 bitset)
+static int futex_wait(u32 __user *uaddr, int fshared,
+                      u32 val, ktime_t *abs_time, u32 bitset, int clockrt)
 {
         struct task_struct *curr = current;
         DECLARE_WAITQUEUE(wait, curr);
@@ -1225,8 +1173,7 @@ static int futex_wait(u32 __user *uaddr, struct rw_semaphore *fshared,
         q.pi_state = NULL;
         q.bitset = bitset;
  retry:
-        futex_lock_mm(fshared);
-
+        q.key = FUTEX_KEY_INIT;
         ret = get_futex_key(uaddr, fshared, &q.key);
         if (unlikely(ret != 0))
                 goto out_release_sem;
@@ -1258,12 +1205,6 @@ static int futex_wait(u32 __user *uaddr, struct rw_semaphore *fshared,
         if (unlikely(ret)) {
                 queue_unlock(&q, hb);
 
-                /*
-                 * If we would have faulted, release mmap_sem, fault it in and
-                 * start all over again.
-                 */
-                futex_unlock_mm(fshared);
-
                 ret = get_user(uval, uaddr);
 
                 if (!ret)
@@ -1278,12 +1219,6 @@ static int futex_wait(u32 __user *uaddr, struct rw_semaphore *fshared,
         queue_me(&q, hb);
 
         /*
-         * Now the futex is queued and we have checked the data, we
-         * don't want to hold mmap_sem while we sleep.
-         */
-        futex_unlock_mm(fshared);
-
-        /*
          * There might have been scheduling since the queue_me(), as we
          * cannot hold a spinlock across the get_user() in case it
          * faults, and we cannot just set TASK_INTERRUPTIBLE state when
@@ -1294,7 +1229,7 @@ static int futex_wait(u32 __user *uaddr, struct rw_semaphore *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.
@@ -1307,8 +1242,10 @@ static int futex_wait(u32 __user *uaddr, struct rw_semaphore *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);
 
@@ -1363,6 +1300,8 @@ static int futex_wait(u32 __user *uaddr, struct rw_semaphore *fshared,
 
                 if (fshared)
                         restart->futex.flags |= FLAGS_SHARED;
+                if (clockrt)
+                        restart->futex.flags |= FLAGS_CLOCKRT;
                 return -ERESTART_RESTARTBLOCK;
         }
 
@@ -1370,7 +1309,7 @@ static int futex_wait(u32 __user *uaddr, struct rw_semaphore *fshared,
         queue_unlock(&q, hb);
 
  out_release_sem:
-        futex_unlock_mm(fshared);
+        put_futex_key(fshared, &q.key);
         return ret;
 }
 
@@ -1378,15 +1317,16 @@ static int futex_wait(u32 __user *uaddr, struct rw_semaphore *fshared,
 static long futex_wait_restart(struct restart_block *restart)
 {
         u32 __user *uaddr = (u32 __user *)restart->futex.uaddr;
-        struct rw_semaphore *fshared = NULL;
+        int fshared = 0;
         ktime_t t;
 
         t.tv64 = restart->futex.time;
         restart->fn = do_no_restart_syscall;
         if (restart->futex.flags & FLAGS_SHARED)
-                fshared = &current->mm->mmap_sem;
+                fshared = 1;
         return (long)futex_wait(uaddr, fshared, restart->futex.val, &t,
-                                restart->futex.bitset);
+                                restart->futex.bitset,
+                                restart->futex.flags & FLAGS_CLOCKRT);
 }
 
 
@@ -1396,7 +1336,7 @@ static long futex_wait_restart(struct restart_block *restart)
  * if there are waiters then it will block, it does PI, etc. (Due to
  * races the kernel might see a 0 value of the futex too.)
  */
-static int futex_lock_pi(u32 __user *uaddr, struct rw_semaphore *fshared,
+static int futex_lock_pi(u32 __user *uaddr, int fshared,
                          int detect, ktime_t *time, int trylock)
 {
         struct hrtimer_sleeper timeout, *to = NULL;
@@ -1419,8 +1359,7 @@ static int futex_lock_pi(u32 __user *uaddr, struct rw_semaphore *fshared,
 
         q.pi_state = NULL;
  retry:
-        futex_lock_mm(fshared);
-
+        q.key = FUTEX_KEY_INIT;
         ret = get_futex_key(uaddr, fshared, &q.key);
         if (unlikely(ret != 0))
                 goto out_release_sem;
@@ -1509,7 +1448,6 @@ static int futex_lock_pi(u32 __user *uaddr, struct rw_semaphore *fshared,
                          * exit to complete.
                          */
                         queue_unlock(&q, hb);
-                        futex_unlock_mm(fshared);
                         cond_resched();
                         goto retry;
 
@@ -1541,12 +1479,6 @@ static int futex_lock_pi(u32 __user *uaddr, struct rw_semaphore *fshared,
          */
         queue_me(&q, hb);
 
-        /*
-         * Now the futex is queued and we have checked the data, we
-         * don't want to hold mmap_sem while we sleep.
-         */
-        futex_unlock_mm(fshared);
-
         WARN_ON(!q.pi_state);
         /*
          * Block on the PI mutex:
@@ -1559,7 +1491,6 @@ static int futex_lock_pi(u32 __user *uaddr, struct rw_semaphore *fshared,
                 ret = ret ? 0 : -EWOULDBLOCK;
         }
 
-        futex_lock_mm(fshared);
         spin_lock(q.lock_ptr);
 
         if (!ret) {
@@ -1625,7 +1556,6 @@ static int futex_lock_pi(u32 __user *uaddr, struct rw_semaphore *fshared,
 
         /* Unqueue and drop the lock */
         unqueue_me_pi(&q);
-        futex_unlock_mm(fshared);
 
         if (to)
                 destroy_hrtimer_on_stack(&to->timer);
@@ -1635,34 +1565,30 @@ static int futex_lock_pi(u32 __user *uaddr, struct rw_semaphore *fshared,
         queue_unlock(&q, hb);
 
  out_release_sem:
-        futex_unlock_mm(fshared);
+        put_futex_key(fshared, &q.key);
         if (to)
                 destroy_hrtimer_on_stack(&to->timer);
         return ret;
 
  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);
 
         if (attempt++) {
-                ret = futex_handle_fault((unsigned long)uaddr, fshared,
-                                         attempt);
+                ret = futex_handle_fault((unsigned long)uaddr, attempt);
                 if (ret)
                         goto out_release_sem;
                 goto retry_unlocked;
         }
 
-        futex_unlock_mm(fshared);
-
         ret = get_user(uval, uaddr);
-        if (!ret && (uval != -EFAULT))
+        if (!ret)
                 goto retry;
 
         if (to)
@@ -1675,13 +1601,13 @@ static int futex_lock_pi(u32 __user *uaddr, struct rw_semaphore *fshared,
  * This is the in-kernel slowpath: we look up the PI state (if any),
  * and do the rt-mutex unlock.
  */
-static int futex_unlock_pi(u32 __user *uaddr, struct rw_semaphore *fshared)
+static int futex_unlock_pi(u32 __user *uaddr, int fshared)
 {
         struct futex_hash_bucket *hb;
         struct futex_q *this, *next;
         u32 uval;
         struct plist_head *head;
-        union futex_key key;
+        union futex_key key = FUTEX_KEY_INIT;
         int ret, attempt = 0;
 
 retry:
@@ -1692,10 +1618,6 @@ retry:
          */
         if ((uval & FUTEX_TID_MASK) != task_pid_vnr(current))
                 return -EPERM;
-        /*
-         * First take all the futex related locks:
-         */
-        futex_lock_mm(fshared);
 
         ret = get_futex_key(uaddr, fshared, &key);
         if (unlikely(ret != 0))
@@ -1754,34 +1676,30 @@ retry_unlocked:
 out_unlock:
         spin_unlock(&hb->lock);
 out:
-        futex_unlock_mm(fshared);
+        put_futex_key(fshared, &key);
 
         return ret;
 
 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);
 
         if (attempt++) {
-                ret = futex_handle_fault((unsigned long)uaddr, fshared,
-                                         attempt);
+                ret = futex_handle_fault((unsigned long)uaddr, attempt);
                 if (ret)
                         goto out;
                 uval = 0;
                 goto retry_unlocked;
         }
 
-        futex_unlock_mm(fshared);
-
         ret = get_user(uval, uaddr);
-        if (!ret && (uval != -EFAULT))
+        if (!ret)
                 goto retry;
 
         return ret;
@@ -1908,8 +1826,7 @@ retry:
                  * PI futexes happens in exit_pi_state():
                  */
                 if (!pi && (uval & FUTEX_WAITERS))
-                        futex_wake(uaddr, &curr->mm->mmap_sem, 1,
-                                   FUTEX_BITSET_MATCH_ANY);
+                        futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY);
         }
         return 0;
 }
@@ -2003,18 +1920,22 @@ 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;
-        struct rw_semaphore *fshared = NULL;
+        int fshared = 0;
 
         if (!(op & FUTEX_PRIVATE_FLAG))
-                fshared = &current->mm->mmap_sem;
+                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;