Merge branch 'core/iommu' into core/urgent
[linux-2.6.git] / kernel / futex.c
1 /*
2  *  Fast Userspace Mutexes (which I call "Futexes!").
3  *  (C) Rusty Russell, IBM 2002
4  *
5  *  Generalized futexes, futex requeueing, misc fixes by Ingo Molnar
6  *  (C) Copyright 2003 Red Hat Inc, All Rights Reserved
7  *
8  *  Removed page pinning, fix privately mapped COW pages and other cleanups
9  *  (C) Copyright 2003, 2004 Jamie Lokier
10  *
11  *  Robust futex support started by Ingo Molnar
12  *  (C) Copyright 2006 Red Hat Inc, All Rights Reserved
13  *  Thanks to Thomas Gleixner for suggestions, analysis and fixes.
14  *
15  *  PI-futex support started by Ingo Molnar and Thomas Gleixner
16  *  Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
17  *  Copyright (C) 2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com>
18  *
19  *  PRIVATE futexes by Eric Dumazet
20  *  Copyright (C) 2007 Eric Dumazet <dada1@cosmosbay.com>
21  *
22  *  Thanks to Ben LaHaise for yelling "hashed waitqueues" loudly
23  *  enough at me, Linus for the original (flawed) idea, Matthew
24  *  Kirkwood for proof-of-concept implementation.
25  *
26  *  "The futexes are also cursed."
27  *  "But they come in a choice of three flavours!"
28  *
29  *  This program is free software; you can redistribute it and/or modify
30  *  it under the terms of the GNU General Public License as published by
31  *  the Free Software Foundation; either version 2 of the License, or
32  *  (at your option) any later version.
33  *
34  *  This program is distributed in the hope that it will be useful,
35  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
36  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
37  *  GNU General Public License for more details.
38  *
39  *  You should have received a copy of the GNU General Public License
40  *  along with this program; if not, write to the Free Software
41  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
42  */
43 #include <linux/slab.h>
44 #include <linux/poll.h>
45 #include <linux/fs.h>
46 #include <linux/file.h>
47 #include <linux/jhash.h>
48 #include <linux/init.h>
49 #include <linux/futex.h>
50 #include <linux/mount.h>
51 #include <linux/pagemap.h>
52 #include <linux/syscalls.h>
53 #include <linux/signal.h>
54 #include <linux/module.h>
55 #include <linux/magic.h>
56 #include <linux/pid.h>
57 #include <linux/nsproxy.h>
58
59 #include <asm/futex.h>
60
61 #include "rtmutex_common.h"
62
63 int __read_mostly futex_cmpxchg_enabled;
64
65 #define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8)
66
67 /*
68  * Priority Inheritance state:
69  */
70 struct futex_pi_state {
71         /*
72          * list of 'owned' pi_state instances - these have to be
73          * cleaned up in do_exit() if the task exits prematurely:
74          */
75         struct list_head list;
76
77         /*
78          * The PI object:
79          */
80         struct rt_mutex pi_mutex;
81
82         struct task_struct *owner;
83         atomic_t refcount;
84
85         union futex_key key;
86 };
87
88 /*
89  * We use this hashed waitqueue instead of a normal wait_queue_t, so
90  * we can wake only the relevant ones (hashed queues may be shared).
91  *
92  * A futex_q has a woken state, just like tasks have TASK_RUNNING.
93  * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0.
94  * The order of wakup is always to make the first condition true, then
95  * wake up q->waiter, then make the second condition true.
96  */
97 struct futex_q {
98         struct plist_node list;
99         /* There can only be a single waiter */
100         wait_queue_head_t waiter;
101
102         /* Which hash list lock to use: */
103         spinlock_t *lock_ptr;
104
105         /* Key which the futex is hashed on: */
106         union futex_key key;
107
108         /* Optional priority inheritance state: */
109         struct futex_pi_state *pi_state;
110         struct task_struct *task;
111
112         /* Bitset for the optional bitmasked wakeup */
113         u32 bitset;
114 };
115
116 /*
117  * Split the global futex_lock into every hash list lock.
118  */
119 struct futex_hash_bucket {
120         spinlock_t lock;
121         struct plist_head chain;
122 };
123
124 static struct futex_hash_bucket futex_queues[1<<FUTEX_HASHBITS];
125
126 /*
127  * We hash on the keys returned from get_futex_key (see below).
128  */
129 static struct futex_hash_bucket *hash_futex(union futex_key *key)
130 {
131         u32 hash = jhash2((u32*)&key->both.word,
132                           (sizeof(key->both.word)+sizeof(key->both.ptr))/4,
133                           key->both.offset);
134         return &futex_queues[hash & ((1 << FUTEX_HASHBITS)-1)];
135 }
136
137 /*
138  * Return 1 if two futex_keys are equal, 0 otherwise.
139  */
140 static inline int match_futex(union futex_key *key1, union futex_key *key2)
141 {
142         return (key1->both.word == key2->both.word
143                 && key1->both.ptr == key2->both.ptr
144                 && key1->both.offset == key2->both.offset);
145 }
146
147 /*
148  * Take a reference to the resource addressed by a key.
149  * Can be called while holding spinlocks.
150  *
151  */
152 static void get_futex_key_refs(union futex_key *key)
153 {
154         if (!key->both.ptr)
155                 return;
156
157         switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
158         case FUT_OFF_INODE:
159                 atomic_inc(&key->shared.inode->i_count);
160                 break;
161         case FUT_OFF_MMSHARED:
162                 atomic_inc(&key->private.mm->mm_count);
163                 break;
164         }
165 }
166
167 /*
168  * Drop a reference to the resource addressed by a key.
169  * The hash bucket spinlock must not be held.
170  */
171 static void drop_futex_key_refs(union futex_key *key)
172 {
173         if (!key->both.ptr)
174                 return;
175
176         switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
177         case FUT_OFF_INODE:
178                 iput(key->shared.inode);
179                 break;
180         case FUT_OFF_MMSHARED:
181                 mmdrop(key->private.mm);
182                 break;
183         }
184 }
185
186 /**
187  * get_futex_key - Get parameters which are the keys for a futex.
188  * @uaddr: virtual address of the futex
189  * @shared: NULL for a PROCESS_PRIVATE futex,
190  *      &current->mm->mmap_sem for a PROCESS_SHARED futex
191  * @key: address where result is stored.
192  *
193  * Returns a negative error code or 0
194  * The key words are stored in *key on success.
195  *
196  * For shared mappings, it's (page->index, vma->vm_file->f_path.dentry->d_inode,
197  * offset_within_page).  For private mappings, it's (uaddr, current->mm).
198  * We can usually work out the index without swapping in the page.
199  *
200  * fshared is NULL for PROCESS_PRIVATE futexes
201  * For other futexes, it points to &current->mm->mmap_sem and
202  * caller must have taken the reader lock. but NOT any spinlocks.
203  */
204 static int get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key)
205 {
206         unsigned long address = (unsigned long)uaddr;
207         struct mm_struct *mm = current->mm;
208         struct page *page;
209         int err;
210
211         /*
212          * The futex address must be "naturally" aligned.
213          */
214         key->both.offset = address % PAGE_SIZE;
215         if (unlikely((address % sizeof(u32)) != 0))
216                 return -EINVAL;
217         address -= key->both.offset;
218
219         /*
220          * PROCESS_PRIVATE futexes are fast.
221          * As the mm cannot disappear under us and the 'key' only needs
222          * virtual address, we dont even have to find the underlying vma.
223          * Note : We do have to check 'uaddr' is a valid user address,
224          *        but access_ok() should be faster than find_vma()
225          */
226         if (!fshared) {
227                 if (unlikely(!access_ok(VERIFY_WRITE, uaddr, sizeof(u32))))
228                         return -EFAULT;
229                 key->private.mm = mm;
230                 key->private.address = address;
231                 get_futex_key_refs(key);
232                 return 0;
233         }
234
235 again:
236         err = get_user_pages_fast(address, 1, 0, &page);
237         if (err < 0)
238                 return err;
239
240         lock_page(page);
241         if (!page->mapping) {
242                 unlock_page(page);
243                 put_page(page);
244                 goto again;
245         }
246
247         /*
248          * Private mappings are handled in a simple way.
249          *
250          * NOTE: When userspace waits on a MAP_SHARED mapping, even if
251          * it's a read-only handle, it's expected that futexes attach to
252          * the object not the particular process.
253          */
254         if (PageAnon(page)) {
255                 key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */
256                 key->private.mm = mm;
257                 key->private.address = address;
258         } else {
259                 key->both.offset |= FUT_OFF_INODE; /* inode-based key */
260                 key->shared.inode = page->mapping->host;
261                 key->shared.pgoff = page->index;
262         }
263
264         get_futex_key_refs(key);
265
266         unlock_page(page);
267         put_page(page);
268         return 0;
269 }
270
271 static inline
272 void put_futex_key(int fshared, union futex_key *key)
273 {
274         drop_futex_key_refs(key);
275 }
276
277 static u32 cmpxchg_futex_value_locked(u32 __user *uaddr, u32 uval, u32 newval)
278 {
279         u32 curval;
280
281         pagefault_disable();
282         curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval);
283         pagefault_enable();
284
285         return curval;
286 }
287
288 static int get_futex_value_locked(u32 *dest, u32 __user *from)
289 {
290         int ret;
291
292         pagefault_disable();
293         ret = __copy_from_user_inatomic(dest, from, sizeof(u32));
294         pagefault_enable();
295
296         return ret ? -EFAULT : 0;
297 }
298
299 /*
300  * Fault handling.
301  */
302 static int futex_handle_fault(unsigned long address, int attempt)
303 {
304         struct vm_area_struct * vma;
305         struct mm_struct *mm = current->mm;
306         int ret = -EFAULT;
307
308         if (attempt > 2)
309                 return ret;
310
311         down_read(&mm->mmap_sem);
312         vma = find_vma(mm, address);
313         if (vma && address >= vma->vm_start &&
314             (vma->vm_flags & VM_WRITE)) {
315                 int fault;
316                 fault = handle_mm_fault(mm, vma, address, 1);
317                 if (unlikely((fault & VM_FAULT_ERROR))) {
318 #if 0
319                         /* XXX: let's do this when we verify it is OK */
320                         if (ret & VM_FAULT_OOM)
321                                 ret = -ENOMEM;
322 #endif
323                 } else {
324                         ret = 0;
325                         if (fault & VM_FAULT_MAJOR)
326                                 current->maj_flt++;
327                         else
328                                 current->min_flt++;
329                 }
330         }
331         up_read(&mm->mmap_sem);
332         return ret;
333 }
334
335 /*
336  * PI code:
337  */
338 static int refill_pi_state_cache(void)
339 {
340         struct futex_pi_state *pi_state;
341
342         if (likely(current->pi_state_cache))
343                 return 0;
344
345         pi_state = kzalloc(sizeof(*pi_state), GFP_KERNEL);
346
347         if (!pi_state)
348                 return -ENOMEM;
349
350         INIT_LIST_HEAD(&pi_state->list);
351         /* pi_mutex gets initialized later */
352         pi_state->owner = NULL;
353         atomic_set(&pi_state->refcount, 1);
354         pi_state->key = FUTEX_KEY_INIT;
355
356         current->pi_state_cache = pi_state;
357
358         return 0;
359 }
360
361 static struct futex_pi_state * alloc_pi_state(void)
362 {
363         struct futex_pi_state *pi_state = current->pi_state_cache;
364
365         WARN_ON(!pi_state);
366         current->pi_state_cache = NULL;
367
368         return pi_state;
369 }
370
371 static void free_pi_state(struct futex_pi_state *pi_state)
372 {
373         if (!atomic_dec_and_test(&pi_state->refcount))
374                 return;
375
376         /*
377          * If pi_state->owner is NULL, the owner is most probably dying
378          * and has cleaned up the pi_state already
379          */
380         if (pi_state->owner) {
381                 spin_lock_irq(&pi_state->owner->pi_lock);
382                 list_del_init(&pi_state->list);
383                 spin_unlock_irq(&pi_state->owner->pi_lock);
384
385                 rt_mutex_proxy_unlock(&pi_state->pi_mutex, pi_state->owner);
386         }
387
388         if (current->pi_state_cache)
389                 kfree(pi_state);
390         else {
391                 /*
392                  * pi_state->list is already empty.
393                  * clear pi_state->owner.
394                  * refcount is at 0 - put it back to 1.
395                  */
396                 pi_state->owner = NULL;
397                 atomic_set(&pi_state->refcount, 1);
398                 current->pi_state_cache = pi_state;
399         }
400 }
401
402 /*
403  * Look up the task based on what TID userspace gave us.
404  * We dont trust it.
405  */
406 static struct task_struct * futex_find_get_task(pid_t pid)
407 {
408         struct task_struct *p;
409         const struct cred *cred = current_cred(), *pcred;
410
411         rcu_read_lock();
412         p = find_task_by_vpid(pid);
413         if (!p) {
414                 p = ERR_PTR(-ESRCH);
415         } else {
416                 pcred = __task_cred(p);
417                 if (cred->euid != pcred->euid &&
418                     cred->euid != pcred->uid)
419                         p = ERR_PTR(-ESRCH);
420                 else
421                         get_task_struct(p);
422         }
423
424         rcu_read_unlock();
425
426         return p;
427 }
428
429 /*
430  * This task is holding PI mutexes at exit time => bad.
431  * Kernel cleans up PI-state, but userspace is likely hosed.
432  * (Robust-futex cleanup is separate and might save the day for userspace.)
433  */
434 void exit_pi_state_list(struct task_struct *curr)
435 {
436         struct list_head *next, *head = &curr->pi_state_list;
437         struct futex_pi_state *pi_state;
438         struct futex_hash_bucket *hb;
439         union futex_key key = FUTEX_KEY_INIT;
440
441         if (!futex_cmpxchg_enabled)
442                 return;
443         /*
444          * We are a ZOMBIE and nobody can enqueue itself on
445          * pi_state_list anymore, but we have to be careful
446          * versus waiters unqueueing themselves:
447          */
448         spin_lock_irq(&curr->pi_lock);
449         while (!list_empty(head)) {
450
451                 next = head->next;
452                 pi_state = list_entry(next, struct futex_pi_state, list);
453                 key = pi_state->key;
454                 hb = hash_futex(&key);
455                 spin_unlock_irq(&curr->pi_lock);
456
457                 spin_lock(&hb->lock);
458
459                 spin_lock_irq(&curr->pi_lock);
460                 /*
461                  * We dropped the pi-lock, so re-check whether this
462                  * task still owns the PI-state:
463                  */
464                 if (head->next != next) {
465                         spin_unlock(&hb->lock);
466                         continue;
467                 }
468
469                 WARN_ON(pi_state->owner != curr);
470                 WARN_ON(list_empty(&pi_state->list));
471                 list_del_init(&pi_state->list);
472                 pi_state->owner = NULL;
473                 spin_unlock_irq(&curr->pi_lock);
474
475                 rt_mutex_unlock(&pi_state->pi_mutex);
476
477                 spin_unlock(&hb->lock);
478
479                 spin_lock_irq(&curr->pi_lock);
480         }
481         spin_unlock_irq(&curr->pi_lock);
482 }
483
484 static int
485 lookup_pi_state(u32 uval, struct futex_hash_bucket *hb,
486                 union futex_key *key, struct futex_pi_state **ps)
487 {
488         struct futex_pi_state *pi_state = NULL;
489         struct futex_q *this, *next;
490         struct plist_head *head;
491         struct task_struct *p;
492         pid_t pid = uval & FUTEX_TID_MASK;
493
494         head = &hb->chain;
495
496         plist_for_each_entry_safe(this, next, head, list) {
497                 if (match_futex(&this->key, key)) {
498                         /*
499                          * Another waiter already exists - bump up
500                          * the refcount and return its pi_state:
501                          */
502                         pi_state = this->pi_state;
503                         /*
504                          * Userspace might have messed up non PI and PI futexes
505                          */
506                         if (unlikely(!pi_state))
507                                 return -EINVAL;
508
509                         WARN_ON(!atomic_read(&pi_state->refcount));
510                         WARN_ON(pid && pi_state->owner &&
511                                 pi_state->owner->pid != pid);
512
513                         atomic_inc(&pi_state->refcount);
514                         *ps = pi_state;
515
516                         return 0;
517                 }
518         }
519
520         /*
521          * We are the first waiter - try to look up the real owner and attach
522          * the new pi_state to it, but bail out when TID = 0
523          */
524         if (!pid)
525                 return -ESRCH;
526         p = futex_find_get_task(pid);
527         if (IS_ERR(p))
528                 return PTR_ERR(p);
529
530         /*
531          * We need to look at the task state flags to figure out,
532          * whether the task is exiting. To protect against the do_exit
533          * change of the task flags, we do this protected by
534          * p->pi_lock:
535          */
536         spin_lock_irq(&p->pi_lock);
537         if (unlikely(p->flags & PF_EXITING)) {
538                 /*
539                  * The task is on the way out. When PF_EXITPIDONE is
540                  * set, we know that the task has finished the
541                  * cleanup:
542                  */
543                 int ret = (p->flags & PF_EXITPIDONE) ? -ESRCH : -EAGAIN;
544
545                 spin_unlock_irq(&p->pi_lock);
546                 put_task_struct(p);
547                 return ret;
548         }
549
550         pi_state = alloc_pi_state();
551
552         /*
553          * Initialize the pi_mutex in locked state and make 'p'
554          * the owner of it:
555          */
556         rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p);
557
558         /* Store the key for possible exit cleanups: */
559         pi_state->key = *key;
560
561         WARN_ON(!list_empty(&pi_state->list));
562         list_add(&pi_state->list, &p->pi_state_list);
563         pi_state->owner = p;
564         spin_unlock_irq(&p->pi_lock);
565
566         put_task_struct(p);
567
568         *ps = pi_state;
569
570         return 0;
571 }
572
573 /*
574  * The hash bucket lock must be held when this is called.
575  * Afterwards, the futex_q must not be accessed.
576  */
577 static void wake_futex(struct futex_q *q)
578 {
579         plist_del(&q->list, &q->list.plist);
580         /*
581          * The lock in wake_up_all() is a crucial memory barrier after the
582          * plist_del() and also before assigning to q->lock_ptr.
583          */
584         wake_up(&q->waiter);
585         /*
586          * The waiting task can free the futex_q as soon as this is written,
587          * without taking any locks.  This must come last.
588          *
589          * A memory barrier is required here to prevent the following store
590          * to lock_ptr from getting ahead of the wakeup. Clearing the lock
591          * at the end of wake_up_all() does not prevent this store from
592          * moving.
593          */
594         smp_wmb();
595         q->lock_ptr = NULL;
596 }
597
598 static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this)
599 {
600         struct task_struct *new_owner;
601         struct futex_pi_state *pi_state = this->pi_state;
602         u32 curval, newval;
603
604         if (!pi_state)
605                 return -EINVAL;
606
607         spin_lock(&pi_state->pi_mutex.wait_lock);
608         new_owner = rt_mutex_next_owner(&pi_state->pi_mutex);
609
610         /*
611          * This happens when we have stolen the lock and the original
612          * pending owner did not enqueue itself back on the rt_mutex.
613          * Thats not a tragedy. We know that way, that a lock waiter
614          * is on the fly. We make the futex_q waiter the pending owner.
615          */
616         if (!new_owner)
617                 new_owner = this->task;
618
619         /*
620          * We pass it to the next owner. (The WAITERS bit is always
621          * kept enabled while there is PI state around. We must also
622          * preserve the owner died bit.)
623          */
624         if (!(uval & FUTEX_OWNER_DIED)) {
625                 int ret = 0;
626
627                 newval = FUTEX_WAITERS | task_pid_vnr(new_owner);
628
629                 curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
630
631                 if (curval == -EFAULT)
632                         ret = -EFAULT;
633                 else if (curval != uval)
634                         ret = -EINVAL;
635                 if (ret) {
636                         spin_unlock(&pi_state->pi_mutex.wait_lock);
637                         return ret;
638                 }
639         }
640
641         spin_lock_irq(&pi_state->owner->pi_lock);
642         WARN_ON(list_empty(&pi_state->list));
643         list_del_init(&pi_state->list);
644         spin_unlock_irq(&pi_state->owner->pi_lock);
645
646         spin_lock_irq(&new_owner->pi_lock);
647         WARN_ON(!list_empty(&pi_state->list));
648         list_add(&pi_state->list, &new_owner->pi_state_list);
649         pi_state->owner = new_owner;
650         spin_unlock_irq(&new_owner->pi_lock);
651
652         spin_unlock(&pi_state->pi_mutex.wait_lock);
653         rt_mutex_unlock(&pi_state->pi_mutex);
654
655         return 0;
656 }
657
658 static int unlock_futex_pi(u32 __user *uaddr, u32 uval)
659 {
660         u32 oldval;
661
662         /*
663          * There is no waiter, so we unlock the futex. The owner died
664          * bit has not to be preserved here. We are the owner:
665          */
666         oldval = cmpxchg_futex_value_locked(uaddr, uval, 0);
667
668         if (oldval == -EFAULT)
669                 return oldval;
670         if (oldval != uval)
671                 return -EAGAIN;
672
673         return 0;
674 }
675
676 /*
677  * Express the locking dependencies for lockdep:
678  */
679 static inline void
680 double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
681 {
682         if (hb1 <= hb2) {
683                 spin_lock(&hb1->lock);
684                 if (hb1 < hb2)
685                         spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING);
686         } else { /* hb1 > hb2 */
687                 spin_lock(&hb2->lock);
688                 spin_lock_nested(&hb1->lock, SINGLE_DEPTH_NESTING);
689         }
690 }
691
692 /*
693  * Wake up all waiters hashed on the physical page that is mapped
694  * to this virtual address:
695  */
696 static int futex_wake(u32 __user *uaddr, int fshared, int nr_wake, u32 bitset)
697 {
698         struct futex_hash_bucket *hb;
699         struct futex_q *this, *next;
700         struct plist_head *head;
701         union futex_key key = FUTEX_KEY_INIT;
702         int ret;
703
704         if (!bitset)
705                 return -EINVAL;
706
707         ret = get_futex_key(uaddr, fshared, &key);
708         if (unlikely(ret != 0))
709                 goto out;
710
711         hb = hash_futex(&key);
712         spin_lock(&hb->lock);
713         head = &hb->chain;
714
715         plist_for_each_entry_safe(this, next, head, list) {
716                 if (match_futex (&this->key, &key)) {
717                         if (this->pi_state) {
718                                 ret = -EINVAL;
719                                 break;
720                         }
721
722                         /* Check if one of the bits is set in both bitsets */
723                         if (!(this->bitset & bitset))
724                                 continue;
725
726                         wake_futex(this);
727                         if (++ret >= nr_wake)
728                                 break;
729                 }
730         }
731
732         spin_unlock(&hb->lock);
733 out:
734         put_futex_key(fshared, &key);
735         return ret;
736 }
737
738 /*
739  * Wake up all waiters hashed on the physical page that is mapped
740  * to this virtual address:
741  */
742 static int
743 futex_wake_op(u32 __user *uaddr1, int fshared, u32 __user *uaddr2,
744               int nr_wake, int nr_wake2, int op)
745 {
746         union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT;
747         struct futex_hash_bucket *hb1, *hb2;
748         struct plist_head *head;
749         struct futex_q *this, *next;
750         int ret, op_ret, attempt = 0;
751
752 retryfull:
753         ret = get_futex_key(uaddr1, fshared, &key1);
754         if (unlikely(ret != 0))
755                 goto out;
756         ret = get_futex_key(uaddr2, fshared, &key2);
757         if (unlikely(ret != 0))
758                 goto out;
759
760         hb1 = hash_futex(&key1);
761         hb2 = hash_futex(&key2);
762
763 retry:
764         double_lock_hb(hb1, hb2);
765
766         op_ret = futex_atomic_op_inuser(op, uaddr2);
767         if (unlikely(op_ret < 0)) {
768                 u32 dummy;
769
770                 spin_unlock(&hb1->lock);
771                 if (hb1 != hb2)
772                         spin_unlock(&hb2->lock);
773
774 #ifndef CONFIG_MMU
775                 /*
776                  * we don't get EFAULT from MMU faults if we don't have an MMU,
777                  * but we might get them from range checking
778                  */
779                 ret = op_ret;
780                 goto out;
781 #endif
782
783                 if (unlikely(op_ret != -EFAULT)) {
784                         ret = op_ret;
785                         goto out;
786                 }
787
788                 /*
789                  * futex_atomic_op_inuser needs to both read and write
790                  * *(int __user *)uaddr2, but we can't modify it
791                  * non-atomically.  Therefore, if get_user below is not
792                  * enough, we need to handle the fault ourselves, while
793                  * still holding the mmap_sem.
794                  */
795                 if (attempt++) {
796                         ret = futex_handle_fault((unsigned long)uaddr2,
797                                                  attempt);
798                         if (ret)
799                                 goto out;
800                         goto retry;
801                 }
802
803                 ret = get_user(dummy, uaddr2);
804                 if (ret)
805                         return ret;
806
807                 goto retryfull;
808         }
809
810         head = &hb1->chain;
811
812         plist_for_each_entry_safe(this, next, head, list) {
813                 if (match_futex (&this->key, &key1)) {
814                         wake_futex(this);
815                         if (++ret >= nr_wake)
816                                 break;
817                 }
818         }
819
820         if (op_ret > 0) {
821                 head = &hb2->chain;
822
823                 op_ret = 0;
824                 plist_for_each_entry_safe(this, next, head, list) {
825                         if (match_futex (&this->key, &key2)) {
826                                 wake_futex(this);
827                                 if (++op_ret >= nr_wake2)
828                                         break;
829                         }
830                 }
831                 ret += op_ret;
832         }
833
834         spin_unlock(&hb1->lock);
835         if (hb1 != hb2)
836                 spin_unlock(&hb2->lock);
837 out:
838         put_futex_key(fshared, &key2);
839         put_futex_key(fshared, &key1);
840
841         return ret;
842 }
843
844 /*
845  * Requeue all waiters hashed on one physical page to another
846  * physical page.
847  */
848 static int futex_requeue(u32 __user *uaddr1, int fshared, u32 __user *uaddr2,
849                          int nr_wake, int nr_requeue, u32 *cmpval)
850 {
851         union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT;
852         struct futex_hash_bucket *hb1, *hb2;
853         struct plist_head *head1;
854         struct futex_q *this, *next;
855         int ret, drop_count = 0;
856
857  retry:
858         ret = get_futex_key(uaddr1, fshared, &key1);
859         if (unlikely(ret != 0))
860                 goto out;
861         ret = get_futex_key(uaddr2, fshared, &key2);
862         if (unlikely(ret != 0))
863                 goto out;
864
865         hb1 = hash_futex(&key1);
866         hb2 = hash_futex(&key2);
867
868         double_lock_hb(hb1, hb2);
869
870         if (likely(cmpval != NULL)) {
871                 u32 curval;
872
873                 ret = get_futex_value_locked(&curval, uaddr1);
874
875                 if (unlikely(ret)) {
876                         spin_unlock(&hb1->lock);
877                         if (hb1 != hb2)
878                                 spin_unlock(&hb2->lock);
879
880                         ret = get_user(curval, uaddr1);
881
882                         if (!ret)
883                                 goto retry;
884
885                         return ret;
886                 }
887                 if (curval != *cmpval) {
888                         ret = -EAGAIN;
889                         goto out_unlock;
890                 }
891         }
892
893         head1 = &hb1->chain;
894         plist_for_each_entry_safe(this, next, head1, list) {
895                 if (!match_futex (&this->key, &key1))
896                         continue;
897                 if (++ret <= nr_wake) {
898                         wake_futex(this);
899                 } else {
900                         /*
901                          * If key1 and key2 hash to the same bucket, no need to
902                          * requeue.
903                          */
904                         if (likely(head1 != &hb2->chain)) {
905                                 plist_del(&this->list, &hb1->chain);
906                                 plist_add(&this->list, &hb2->chain);
907                                 this->lock_ptr = &hb2->lock;
908 #ifdef CONFIG_DEBUG_PI_LIST
909                                 this->list.plist.lock = &hb2->lock;
910 #endif
911                         }
912                         this->key = key2;
913                         get_futex_key_refs(&key2);
914                         drop_count++;
915
916                         if (ret - nr_wake >= nr_requeue)
917                                 break;
918                 }
919         }
920
921 out_unlock:
922         spin_unlock(&hb1->lock);
923         if (hb1 != hb2)
924                 spin_unlock(&hb2->lock);
925
926         /* drop_futex_key_refs() must be called outside the spinlocks. */
927         while (--drop_count >= 0)
928                 drop_futex_key_refs(&key1);
929
930 out:
931         put_futex_key(fshared, &key2);
932         put_futex_key(fshared, &key1);
933         return ret;
934 }
935
936 /* The key must be already stored in q->key. */
937 static inline struct futex_hash_bucket *queue_lock(struct futex_q *q)
938 {
939         struct futex_hash_bucket *hb;
940
941         init_waitqueue_head(&q->waiter);
942
943         get_futex_key_refs(&q->key);
944         hb = hash_futex(&q->key);
945         q->lock_ptr = &hb->lock;
946
947         spin_lock(&hb->lock);
948         return hb;
949 }
950
951 static inline void queue_me(struct futex_q *q, struct futex_hash_bucket *hb)
952 {
953         int prio;
954
955         /*
956          * The priority used to register this element is
957          * - either the real thread-priority for the real-time threads
958          * (i.e. threads with a priority lower than MAX_RT_PRIO)
959          * - or MAX_RT_PRIO for non-RT threads.
960          * Thus, all RT-threads are woken first in priority order, and
961          * the others are woken last, in FIFO order.
962          */
963         prio = min(current->normal_prio, MAX_RT_PRIO);
964
965         plist_node_init(&q->list, prio);
966 #ifdef CONFIG_DEBUG_PI_LIST
967         q->list.plist.lock = &hb->lock;
968 #endif
969         plist_add(&q->list, &hb->chain);
970         q->task = current;
971         spin_unlock(&hb->lock);
972 }
973
974 static inline void
975 queue_unlock(struct futex_q *q, struct futex_hash_bucket *hb)
976 {
977         spin_unlock(&hb->lock);
978         drop_futex_key_refs(&q->key);
979 }
980
981 /*
982  * queue_me and unqueue_me must be called as a pair, each
983  * exactly once.  They are called with the hashed spinlock held.
984  */
985
986 /* Return 1 if we were still queued (ie. 0 means we were woken) */
987 static int unqueue_me(struct futex_q *q)
988 {
989         spinlock_t *lock_ptr;
990         int ret = 0;
991
992         /* In the common case we don't take the spinlock, which is nice. */
993  retry:
994         lock_ptr = q->lock_ptr;
995         barrier();
996         if (lock_ptr != NULL) {
997                 spin_lock(lock_ptr);
998                 /*
999                  * q->lock_ptr can change between reading it and
1000                  * spin_lock(), causing us to take the wrong lock.  This
1001                  * corrects the race condition.
1002                  *
1003                  * Reasoning goes like this: if we have the wrong lock,
1004                  * q->lock_ptr must have changed (maybe several times)
1005                  * between reading it and the spin_lock().  It can
1006                  * change again after the spin_lock() but only if it was
1007                  * already changed before the spin_lock().  It cannot,
1008                  * however, change back to the original value.  Therefore
1009                  * we can detect whether we acquired the correct lock.
1010                  */
1011                 if (unlikely(lock_ptr != q->lock_ptr)) {
1012                         spin_unlock(lock_ptr);
1013                         goto retry;
1014                 }
1015                 WARN_ON(plist_node_empty(&q->list));
1016                 plist_del(&q->list, &q->list.plist);
1017
1018                 BUG_ON(q->pi_state);
1019
1020                 spin_unlock(lock_ptr);
1021                 ret = 1;
1022         }
1023
1024         drop_futex_key_refs(&q->key);
1025         return ret;
1026 }
1027
1028 /*
1029  * PI futexes can not be requeued and must remove themself from the
1030  * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry
1031  * and dropped here.
1032  */
1033 static void unqueue_me_pi(struct futex_q *q)
1034 {
1035         WARN_ON(plist_node_empty(&q->list));
1036         plist_del(&q->list, &q->list.plist);
1037
1038         BUG_ON(!q->pi_state);
1039         free_pi_state(q->pi_state);
1040         q->pi_state = NULL;
1041
1042         spin_unlock(q->lock_ptr);
1043
1044         drop_futex_key_refs(&q->key);
1045 }
1046
1047 /*
1048  * Fixup the pi_state owner with the new owner.
1049  *
1050  * Must be called with hash bucket lock held and mm->sem held for non
1051  * private futexes.
1052  */
1053 static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
1054                                 struct task_struct *newowner, int fshared)
1055 {
1056         u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS;
1057         struct futex_pi_state *pi_state = q->pi_state;
1058         struct task_struct *oldowner = pi_state->owner;
1059         u32 uval, curval, newval;
1060         int ret, attempt = 0;
1061
1062         /* Owner died? */
1063         if (!pi_state->owner)
1064                 newtid |= FUTEX_OWNER_DIED;
1065
1066         /*
1067          * We are here either because we stole the rtmutex from the
1068          * pending owner or we are the pending owner which failed to
1069          * get the rtmutex. We have to replace the pending owner TID
1070          * in the user space variable. This must be atomic as we have
1071          * to preserve the owner died bit here.
1072          *
1073          * Note: We write the user space value _before_ changing the
1074          * pi_state because we can fault here. Imagine swapped out
1075          * pages or a fork, which was running right before we acquired
1076          * mmap_sem, that marked all the anonymous memory readonly for
1077          * cow.
1078          *
1079          * Modifying pi_state _before_ the user space value would
1080          * leave the pi_state in an inconsistent state when we fault
1081          * here, because we need to drop the hash bucket lock to
1082          * handle the fault. This might be observed in the PID check
1083          * in lookup_pi_state.
1084          */
1085 retry:
1086         if (get_futex_value_locked(&uval, uaddr))
1087                 goto handle_fault;
1088
1089         while (1) {
1090                 newval = (uval & FUTEX_OWNER_DIED) | newtid;
1091
1092                 curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
1093
1094                 if (curval == -EFAULT)
1095                         goto handle_fault;
1096                 if (curval == uval)
1097                         break;
1098                 uval = curval;
1099         }
1100
1101         /*
1102          * We fixed up user space. Now we need to fix the pi_state
1103          * itself.
1104          */
1105         if (pi_state->owner != NULL) {
1106                 spin_lock_irq(&pi_state->owner->pi_lock);
1107                 WARN_ON(list_empty(&pi_state->list));
1108                 list_del_init(&pi_state->list);
1109                 spin_unlock_irq(&pi_state->owner->pi_lock);
1110         }
1111
1112         pi_state->owner = newowner;
1113
1114         spin_lock_irq(&newowner->pi_lock);
1115         WARN_ON(!list_empty(&pi_state->list));
1116         list_add(&pi_state->list, &newowner->pi_state_list);
1117         spin_unlock_irq(&newowner->pi_lock);
1118         return 0;
1119
1120         /*
1121          * To handle the page fault we need to drop the hash bucket
1122          * lock here. That gives the other task (either the pending
1123          * owner itself or the task which stole the rtmutex) the
1124          * chance to try the fixup of the pi_state. So once we are
1125          * back from handling the fault we need to check the pi_state
1126          * after reacquiring the hash bucket lock and before trying to
1127          * do another fixup. When the fixup has been done already we
1128          * simply return.
1129          */
1130 handle_fault:
1131         spin_unlock(q->lock_ptr);
1132
1133         ret = futex_handle_fault((unsigned long)uaddr, attempt++);
1134
1135         spin_lock(q->lock_ptr);
1136
1137         /*
1138          * Check if someone else fixed it for us:
1139          */
1140         if (pi_state->owner != oldowner)
1141                 return 0;
1142
1143         if (ret)
1144                 return ret;
1145
1146         goto retry;
1147 }
1148
1149 /*
1150  * In case we must use restart_block to restart a futex_wait,
1151  * we encode in the 'flags' shared capability
1152  */
1153 #define FLAGS_SHARED            0x01
1154 #define FLAGS_CLOCKRT           0x02
1155
1156 static long futex_wait_restart(struct restart_block *restart);
1157
1158 static int futex_wait(u32 __user *uaddr, int fshared,
1159                       u32 val, ktime_t *abs_time, u32 bitset, int clockrt)
1160 {
1161         struct task_struct *curr = current;
1162         DECLARE_WAITQUEUE(wait, curr);
1163         struct futex_hash_bucket *hb;
1164         struct futex_q q;
1165         u32 uval;
1166         int ret;
1167         struct hrtimer_sleeper t;
1168         int rem = 0;
1169
1170         if (!bitset)
1171                 return -EINVAL;
1172
1173         q.pi_state = NULL;
1174         q.bitset = bitset;
1175  retry:
1176         q.key = FUTEX_KEY_INIT;
1177         ret = get_futex_key(uaddr, fshared, &q.key);
1178         if (unlikely(ret != 0))
1179                 goto out_release_sem;
1180
1181         hb = queue_lock(&q);
1182
1183         /*
1184          * Access the page AFTER the futex is queued.
1185          * Order is important:
1186          *
1187          *   Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val);
1188          *   Userspace waker:  if (cond(var)) { var = new; futex_wake(&var); }
1189          *
1190          * The basic logical guarantee of a futex is that it blocks ONLY
1191          * if cond(var) is known to be true at the time of blocking, for
1192          * any cond.  If we queued after testing *uaddr, that would open
1193          * a race condition where we could block indefinitely with
1194          * cond(var) false, which would violate the guarantee.
1195          *
1196          * A consequence is that futex_wait() can return zero and absorb
1197          * a wakeup when *uaddr != val on entry to the syscall.  This is
1198          * rare, but normal.
1199          *
1200          * for shared futexes, we hold the mmap semaphore, so the mapping
1201          * cannot have changed since we looked it up in get_futex_key.
1202          */
1203         ret = get_futex_value_locked(&uval, uaddr);
1204
1205         if (unlikely(ret)) {
1206                 queue_unlock(&q, hb);
1207
1208                 ret = get_user(uval, uaddr);
1209
1210                 if (!ret)
1211                         goto retry;
1212                 return ret;
1213         }
1214         ret = -EWOULDBLOCK;
1215         if (uval != val)
1216                 goto out_unlock_release_sem;
1217
1218         /* Only actually queue if *uaddr contained val.  */
1219         queue_me(&q, hb);
1220
1221         /*
1222          * There might have been scheduling since the queue_me(), as we
1223          * cannot hold a spinlock across the get_user() in case it
1224          * faults, and we cannot just set TASK_INTERRUPTIBLE state when
1225          * queueing ourselves into the futex hash.  This code thus has to
1226          * rely on the futex_wake() code removing us from hash when it
1227          * wakes us up.
1228          */
1229
1230         /* add_wait_queue is the barrier after __set_current_state. */
1231         __set_current_state(TASK_INTERRUPTIBLE);
1232         add_wait_queue(&q.waiter, &wait);
1233         /*
1234          * !plist_node_empty() is safe here without any lock.
1235          * q.lock_ptr != 0 is not safe, because of ordering against wakeup.
1236          */
1237         if (likely(!plist_node_empty(&q.list))) {
1238                 if (!abs_time)
1239                         schedule();
1240                 else {
1241                         unsigned long slack;
1242                         slack = current->timer_slack_ns;
1243                         if (rt_task(current))
1244                                 slack = 0;
1245                         hrtimer_init_on_stack(&t.timer,
1246                                               clockrt ? CLOCK_REALTIME :
1247                                               CLOCK_MONOTONIC,
1248                                               HRTIMER_MODE_ABS);
1249                         hrtimer_init_sleeper(&t, current);
1250                         hrtimer_set_expires_range_ns(&t.timer, *abs_time, slack);
1251
1252                         hrtimer_start_expires(&t.timer, HRTIMER_MODE_ABS);
1253                         if (!hrtimer_active(&t.timer))
1254                                 t.task = NULL;
1255
1256                         /*
1257                          * the timer could have already expired, in which
1258                          * case current would be flagged for rescheduling.
1259                          * Don't bother calling schedule.
1260                          */
1261                         if (likely(t.task))
1262                                 schedule();
1263
1264                         hrtimer_cancel(&t.timer);
1265
1266                         /* Flag if a timeout occured */
1267                         rem = (t.task == NULL);
1268
1269                         destroy_hrtimer_on_stack(&t.timer);
1270                 }
1271         }
1272         __set_current_state(TASK_RUNNING);
1273
1274         /*
1275          * NOTE: we don't remove ourselves from the waitqueue because
1276          * we are the only user of it.
1277          */
1278
1279         /* If we were woken (and unqueued), we succeeded, whatever. */
1280         if (!unqueue_me(&q))
1281                 return 0;
1282         if (rem)
1283                 return -ETIMEDOUT;
1284
1285         /*
1286          * We expect signal_pending(current), but another thread may
1287          * have handled it for us already.
1288          */
1289         if (!abs_time)
1290                 return -ERESTARTSYS;
1291         else {
1292                 struct restart_block *restart;
1293                 restart = &current_thread_info()->restart_block;
1294                 restart->fn = futex_wait_restart;
1295                 restart->futex.uaddr = (u32 *)uaddr;
1296                 restart->futex.val = val;
1297                 restart->futex.time = abs_time->tv64;
1298                 restart->futex.bitset = bitset;
1299                 restart->futex.flags = 0;
1300
1301                 if (fshared)
1302                         restart->futex.flags |= FLAGS_SHARED;
1303                 if (clockrt)
1304                         restart->futex.flags |= FLAGS_CLOCKRT;
1305                 return -ERESTART_RESTARTBLOCK;
1306         }
1307
1308  out_unlock_release_sem:
1309         queue_unlock(&q, hb);
1310
1311  out_release_sem:
1312         put_futex_key(fshared, &q.key);
1313         return ret;
1314 }
1315
1316
1317 static long futex_wait_restart(struct restart_block *restart)
1318 {
1319         u32 __user *uaddr = (u32 __user *)restart->futex.uaddr;
1320         int fshared = 0;
1321         ktime_t t;
1322
1323         t.tv64 = restart->futex.time;
1324         restart->fn = do_no_restart_syscall;
1325         if (restart->futex.flags & FLAGS_SHARED)
1326                 fshared = 1;
1327         return (long)futex_wait(uaddr, fshared, restart->futex.val, &t,
1328                                 restart->futex.bitset,
1329                                 restart->futex.flags & FLAGS_CLOCKRT);
1330 }
1331
1332
1333 /*
1334  * Userspace tried a 0 -> TID atomic transition of the futex value
1335  * and failed. The kernel side here does the whole locking operation:
1336  * if there are waiters then it will block, it does PI, etc. (Due to
1337  * races the kernel might see a 0 value of the futex too.)
1338  */
1339 static int futex_lock_pi(u32 __user *uaddr, int fshared,
1340                          int detect, ktime_t *time, int trylock)
1341 {
1342         struct hrtimer_sleeper timeout, *to = NULL;
1343         struct task_struct *curr = current;
1344         struct futex_hash_bucket *hb;
1345         u32 uval, newval, curval;
1346         struct futex_q q;
1347         int ret, lock_taken, ownerdied = 0, attempt = 0;
1348
1349         if (refill_pi_state_cache())
1350                 return -ENOMEM;
1351
1352         if (time) {
1353                 to = &timeout;
1354                 hrtimer_init_on_stack(&to->timer, CLOCK_REALTIME,
1355                                       HRTIMER_MODE_ABS);
1356                 hrtimer_init_sleeper(to, current);
1357                 hrtimer_set_expires(&to->timer, *time);
1358         }
1359
1360         q.pi_state = NULL;
1361  retry:
1362         q.key = FUTEX_KEY_INIT;
1363         ret = get_futex_key(uaddr, fshared, &q.key);
1364         if (unlikely(ret != 0))
1365                 goto out_release_sem;
1366
1367  retry_unlocked:
1368         hb = queue_lock(&q);
1369
1370  retry_locked:
1371         ret = lock_taken = 0;
1372
1373         /*
1374          * To avoid races, we attempt to take the lock here again
1375          * (by doing a 0 -> TID atomic cmpxchg), while holding all
1376          * the locks. It will most likely not succeed.
1377          */
1378         newval = task_pid_vnr(current);
1379
1380         curval = cmpxchg_futex_value_locked(uaddr, 0, newval);
1381
1382         if (unlikely(curval == -EFAULT))
1383                 goto uaddr_faulted;
1384
1385         /*
1386          * Detect deadlocks. In case of REQUEUE_PI this is a valid
1387          * situation and we return success to user space.
1388          */
1389         if (unlikely((curval & FUTEX_TID_MASK) == task_pid_vnr(current))) {
1390                 ret = -EDEADLK;
1391                 goto out_unlock_release_sem;
1392         }
1393
1394         /*
1395          * Surprise - we got the lock. Just return to userspace:
1396          */
1397         if (unlikely(!curval))
1398                 goto out_unlock_release_sem;
1399
1400         uval = curval;
1401
1402         /*
1403          * Set the WAITERS flag, so the owner will know it has someone
1404          * to wake at next unlock
1405          */
1406         newval = curval | FUTEX_WAITERS;
1407
1408         /*
1409          * There are two cases, where a futex might have no owner (the
1410          * owner TID is 0): OWNER_DIED. We take over the futex in this
1411          * case. We also do an unconditional take over, when the owner
1412          * of the futex died.
1413          *
1414          * This is safe as we are protected by the hash bucket lock !
1415          */
1416         if (unlikely(ownerdied || !(curval & FUTEX_TID_MASK))) {
1417                 /* Keep the OWNER_DIED bit */
1418                 newval = (curval & ~FUTEX_TID_MASK) | task_pid_vnr(current);
1419                 ownerdied = 0;
1420                 lock_taken = 1;
1421         }
1422
1423         curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
1424
1425         if (unlikely(curval == -EFAULT))
1426                 goto uaddr_faulted;
1427         if (unlikely(curval != uval))
1428                 goto retry_locked;
1429
1430         /*
1431          * We took the lock due to owner died take over.
1432          */
1433         if (unlikely(lock_taken))
1434                 goto out_unlock_release_sem;
1435
1436         /*
1437          * We dont have the lock. Look up the PI state (or create it if
1438          * we are the first waiter):
1439          */
1440         ret = lookup_pi_state(uval, hb, &q.key, &q.pi_state);
1441
1442         if (unlikely(ret)) {
1443                 switch (ret) {
1444
1445                 case -EAGAIN:
1446                         /*
1447                          * Task is exiting and we just wait for the
1448                          * exit to complete.
1449                          */
1450                         queue_unlock(&q, hb);
1451                         cond_resched();
1452                         goto retry;
1453
1454                 case -ESRCH:
1455                         /*
1456                          * No owner found for this futex. Check if the
1457                          * OWNER_DIED bit is set to figure out whether
1458                          * this is a robust futex or not.
1459                          */
1460                         if (get_futex_value_locked(&curval, uaddr))
1461                                 goto uaddr_faulted;
1462
1463                         /*
1464                          * We simply start over in case of a robust
1465                          * futex. The code above will take the futex
1466                          * and return happy.
1467                          */
1468                         if (curval & FUTEX_OWNER_DIED) {
1469                                 ownerdied = 1;
1470                                 goto retry_locked;
1471                         }
1472                 default:
1473                         goto out_unlock_release_sem;
1474                 }
1475         }
1476
1477         /*
1478          * Only actually queue now that the atomic ops are done:
1479          */
1480         queue_me(&q, hb);
1481
1482         WARN_ON(!q.pi_state);
1483         /*
1484          * Block on the PI mutex:
1485          */
1486         if (!trylock)
1487                 ret = rt_mutex_timed_lock(&q.pi_state->pi_mutex, to, 1);
1488         else {
1489                 ret = rt_mutex_trylock(&q.pi_state->pi_mutex);
1490                 /* Fixup the trylock return value: */
1491                 ret = ret ? 0 : -EWOULDBLOCK;
1492         }
1493
1494         spin_lock(q.lock_ptr);
1495
1496         if (!ret) {
1497                 /*
1498                  * Got the lock. We might not be the anticipated owner
1499                  * if we did a lock-steal - fix up the PI-state in
1500                  * that case:
1501                  */
1502                 if (q.pi_state->owner != curr)
1503                         ret = fixup_pi_state_owner(uaddr, &q, curr, fshared);
1504         } else {
1505                 /*
1506                  * Catch the rare case, where the lock was released
1507                  * when we were on the way back before we locked the
1508                  * hash bucket.
1509                  */
1510                 if (q.pi_state->owner == curr) {
1511                         /*
1512                          * Try to get the rt_mutex now. This might
1513                          * fail as some other task acquired the
1514                          * rt_mutex after we removed ourself from the
1515                          * rt_mutex waiters list.
1516                          */
1517                         if (rt_mutex_trylock(&q.pi_state->pi_mutex))
1518                                 ret = 0;
1519                         else {
1520                                 /*
1521                                  * pi_state is incorrect, some other
1522                                  * task did a lock steal and we
1523                                  * returned due to timeout or signal
1524                                  * without taking the rt_mutex. Too
1525                                  * late. We can access the
1526                                  * rt_mutex_owner without locking, as
1527                                  * the other task is now blocked on
1528                                  * the hash bucket lock. Fix the state
1529                                  * up.
1530                                  */
1531                                 struct task_struct *owner;
1532                                 int res;
1533
1534                                 owner = rt_mutex_owner(&q.pi_state->pi_mutex);
1535                                 res = fixup_pi_state_owner(uaddr, &q, owner,
1536                                                            fshared);
1537
1538                                 /* propagate -EFAULT, if the fixup failed */
1539                                 if (res)
1540                                         ret = res;
1541                         }
1542                 } else {
1543                         /*
1544                          * Paranoia check. If we did not take the lock
1545                          * in the trylock above, then we should not be
1546                          * the owner of the rtmutex, neither the real
1547                          * nor the pending one:
1548                          */
1549                         if (rt_mutex_owner(&q.pi_state->pi_mutex) == curr)
1550                                 printk(KERN_ERR "futex_lock_pi: ret = %d "
1551                                        "pi-mutex: %p pi-state %p\n", ret,
1552                                        q.pi_state->pi_mutex.owner,
1553                                        q.pi_state->owner);
1554                 }
1555         }
1556
1557         /* Unqueue and drop the lock */
1558         unqueue_me_pi(&q);
1559
1560         if (to)
1561                 destroy_hrtimer_on_stack(&to->timer);
1562         return ret != -EINTR ? ret : -ERESTARTNOINTR;
1563
1564  out_unlock_release_sem:
1565         queue_unlock(&q, hb);
1566
1567  out_release_sem:
1568         put_futex_key(fshared, &q.key);
1569         if (to)
1570                 destroy_hrtimer_on_stack(&to->timer);
1571         return ret;
1572
1573  uaddr_faulted:
1574         /*
1575          * We have to r/w  *(int __user *)uaddr, and we have to modify it
1576          * atomically.  Therefore, if we continue to fault after get_user()
1577          * below, we need to handle the fault ourselves, while still holding
1578          * the mmap_sem.  This can occur if the uaddr is under contention as
1579          * we have to drop the mmap_sem in order to call get_user().
1580          */
1581         queue_unlock(&q, hb);
1582
1583         if (attempt++) {
1584                 ret = futex_handle_fault((unsigned long)uaddr, attempt);
1585                 if (ret)
1586                         goto out_release_sem;
1587                 goto retry_unlocked;
1588         }
1589
1590         ret = get_user(uval, uaddr);
1591         if (!ret)
1592                 goto retry;
1593
1594         if (to)
1595                 destroy_hrtimer_on_stack(&to->timer);
1596         return ret;
1597 }
1598
1599 /*
1600  * Userspace attempted a TID -> 0 atomic transition, and failed.
1601  * This is the in-kernel slowpath: we look up the PI state (if any),
1602  * and do the rt-mutex unlock.
1603  */
1604 static int futex_unlock_pi(u32 __user *uaddr, int fshared)
1605 {
1606         struct futex_hash_bucket *hb;
1607         struct futex_q *this, *next;
1608         u32 uval;
1609         struct plist_head *head;
1610         union futex_key key = FUTEX_KEY_INIT;
1611         int ret, attempt = 0;
1612
1613 retry:
1614         if (get_user(uval, uaddr))
1615                 return -EFAULT;
1616         /*
1617          * We release only a lock we actually own:
1618          */
1619         if ((uval & FUTEX_TID_MASK) != task_pid_vnr(current))
1620                 return -EPERM;
1621
1622         ret = get_futex_key(uaddr, fshared, &key);
1623         if (unlikely(ret != 0))
1624                 goto out;
1625
1626         hb = hash_futex(&key);
1627 retry_unlocked:
1628         spin_lock(&hb->lock);
1629
1630         /*
1631          * To avoid races, try to do the TID -> 0 atomic transition
1632          * again. If it succeeds then we can return without waking
1633          * anyone else up:
1634          */
1635         if (!(uval & FUTEX_OWNER_DIED))
1636                 uval = cmpxchg_futex_value_locked(uaddr, task_pid_vnr(current), 0);
1637
1638
1639         if (unlikely(uval == -EFAULT))
1640                 goto pi_faulted;
1641         /*
1642          * Rare case: we managed to release the lock atomically,
1643          * no need to wake anyone else up:
1644          */
1645         if (unlikely(uval == task_pid_vnr(current)))
1646                 goto out_unlock;
1647
1648         /*
1649          * Ok, other tasks may need to be woken up - check waiters
1650          * and do the wakeup if necessary:
1651          */
1652         head = &hb->chain;
1653
1654         plist_for_each_entry_safe(this, next, head, list) {
1655                 if (!match_futex (&this->key, &key))
1656                         continue;
1657                 ret = wake_futex_pi(uaddr, uval, this);
1658                 /*
1659                  * The atomic access to the futex value
1660                  * generated a pagefault, so retry the
1661                  * user-access and the wakeup:
1662                  */
1663                 if (ret == -EFAULT)
1664                         goto pi_faulted;
1665                 goto out_unlock;
1666         }
1667         /*
1668          * No waiters - kernel unlocks the futex:
1669          */
1670         if (!(uval & FUTEX_OWNER_DIED)) {
1671                 ret = unlock_futex_pi(uaddr, uval);
1672                 if (ret == -EFAULT)
1673                         goto pi_faulted;
1674         }
1675
1676 out_unlock:
1677         spin_unlock(&hb->lock);
1678 out:
1679         put_futex_key(fshared, &key);
1680
1681         return ret;
1682
1683 pi_faulted:
1684         /*
1685          * We have to r/w  *(int __user *)uaddr, and we have to modify it
1686          * atomically.  Therefore, if we continue to fault after get_user()
1687          * below, we need to handle the fault ourselves, while still holding
1688          * the mmap_sem.  This can occur if the uaddr is under contention as
1689          * we have to drop the mmap_sem in order to call get_user().
1690          */
1691         spin_unlock(&hb->lock);
1692
1693         if (attempt++) {
1694                 ret = futex_handle_fault((unsigned long)uaddr, attempt);
1695                 if (ret)
1696                         goto out;
1697                 uval = 0;
1698                 goto retry_unlocked;
1699         }
1700
1701         ret = get_user(uval, uaddr);
1702         if (!ret)
1703                 goto retry;
1704
1705         return ret;
1706 }
1707
1708 /*
1709  * Support for robust futexes: the kernel cleans up held futexes at
1710  * thread exit time.
1711  *
1712  * Implementation: user-space maintains a per-thread list of locks it
1713  * is holding. Upon do_exit(), the kernel carefully walks this list,
1714  * and marks all locks that are owned by this thread with the
1715  * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is
1716  * always manipulated with the lock held, so the list is private and
1717  * per-thread. Userspace also maintains a per-thread 'list_op_pending'
1718  * field, to allow the kernel to clean up if the thread dies after
1719  * acquiring the lock, but just before it could have added itself to
1720  * the list. There can only be one such pending lock.
1721  */
1722
1723 /**
1724  * sys_set_robust_list - set the robust-futex list head of a task
1725  * @head: pointer to the list-head
1726  * @len: length of the list-head, as userspace expects
1727  */
1728 asmlinkage long
1729 sys_set_robust_list(struct robust_list_head __user *head,
1730                     size_t len)
1731 {
1732         if (!futex_cmpxchg_enabled)
1733                 return -ENOSYS;
1734         /*
1735          * The kernel knows only one size for now:
1736          */
1737         if (unlikely(len != sizeof(*head)))
1738                 return -EINVAL;
1739
1740         current->robust_list = head;
1741
1742         return 0;
1743 }
1744
1745 /**
1746  * sys_get_robust_list - get the robust-futex list head of a task
1747  * @pid: pid of the process [zero for current task]
1748  * @head_ptr: pointer to a list-head pointer, the kernel fills it in
1749  * @len_ptr: pointer to a length field, the kernel fills in the header size
1750  */
1751 asmlinkage long
1752 sys_get_robust_list(int pid, struct robust_list_head __user * __user *head_ptr,
1753                     size_t __user *len_ptr)
1754 {
1755         struct robust_list_head __user *head;
1756         unsigned long ret;
1757         const struct cred *cred = current_cred(), *pcred;
1758
1759         if (!futex_cmpxchg_enabled)
1760                 return -ENOSYS;
1761
1762         if (!pid)
1763                 head = current->robust_list;
1764         else {
1765                 struct task_struct *p;
1766
1767                 ret = -ESRCH;
1768                 rcu_read_lock();
1769                 p = find_task_by_vpid(pid);
1770                 if (!p)
1771                         goto err_unlock;
1772                 ret = -EPERM;
1773                 pcred = __task_cred(p);
1774                 if (cred->euid != pcred->euid &&
1775                     cred->euid != pcred->uid &&
1776                     !capable(CAP_SYS_PTRACE))
1777                         goto err_unlock;
1778                 head = p->robust_list;
1779                 rcu_read_unlock();
1780         }
1781
1782         if (put_user(sizeof(*head), len_ptr))
1783                 return -EFAULT;
1784         return put_user(head, head_ptr);
1785
1786 err_unlock:
1787         rcu_read_unlock();
1788
1789         return ret;
1790 }
1791
1792 /*
1793  * Process a futex-list entry, check whether it's owned by the
1794  * dying task, and do notification if so:
1795  */
1796 int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi)
1797 {
1798         u32 uval, nval, mval;
1799
1800 retry:
1801         if (get_user(uval, uaddr))
1802                 return -1;
1803
1804         if ((uval & FUTEX_TID_MASK) == task_pid_vnr(curr)) {
1805                 /*
1806                  * Ok, this dying thread is truly holding a futex
1807                  * of interest. Set the OWNER_DIED bit atomically
1808                  * via cmpxchg, and if the value had FUTEX_WAITERS
1809                  * set, wake up a waiter (if any). (We have to do a
1810                  * futex_wake() even if OWNER_DIED is already set -
1811                  * to handle the rare but possible case of recursive
1812                  * thread-death.) The rest of the cleanup is done in
1813                  * userspace.
1814                  */
1815                 mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED;
1816                 nval = futex_atomic_cmpxchg_inatomic(uaddr, uval, mval);
1817
1818                 if (nval == -EFAULT)
1819                         return -1;
1820
1821                 if (nval != uval)
1822                         goto retry;
1823
1824                 /*
1825                  * Wake robust non-PI futexes here. The wakeup of
1826                  * PI futexes happens in exit_pi_state():
1827                  */
1828                 if (!pi && (uval & FUTEX_WAITERS))
1829                         futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY);
1830         }
1831         return 0;
1832 }
1833
1834 /*
1835  * Fetch a robust-list pointer. Bit 0 signals PI futexes:
1836  */
1837 static inline int fetch_robust_entry(struct robust_list __user **entry,
1838                                      struct robust_list __user * __user *head,
1839                                      int *pi)
1840 {
1841         unsigned long uentry;
1842
1843         if (get_user(uentry, (unsigned long __user *)head))
1844                 return -EFAULT;
1845
1846         *entry = (void __user *)(uentry & ~1UL);
1847         *pi = uentry & 1;
1848
1849         return 0;
1850 }
1851
1852 /*
1853  * Walk curr->robust_list (very carefully, it's a userspace list!)
1854  * and mark any locks found there dead, and notify any waiters.
1855  *
1856  * We silently return on any sign of list-walking problem.
1857  */
1858 void exit_robust_list(struct task_struct *curr)
1859 {
1860         struct robust_list_head __user *head = curr->robust_list;
1861         struct robust_list __user *entry, *next_entry, *pending;
1862         unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip;
1863         unsigned long futex_offset;
1864         int rc;
1865
1866         if (!futex_cmpxchg_enabled)
1867                 return;
1868
1869         /*
1870          * Fetch the list head (which was registered earlier, via
1871          * sys_set_robust_list()):
1872          */
1873         if (fetch_robust_entry(&entry, &head->list.next, &pi))
1874                 return;
1875         /*
1876          * Fetch the relative futex offset:
1877          */
1878         if (get_user(futex_offset, &head->futex_offset))
1879                 return;
1880         /*
1881          * Fetch any possibly pending lock-add first, and handle it
1882          * if it exists:
1883          */
1884         if (fetch_robust_entry(&pending, &head->list_op_pending, &pip))
1885                 return;
1886
1887         next_entry = NULL;      /* avoid warning with gcc */
1888         while (entry != &head->list) {
1889                 /*
1890                  * Fetch the next entry in the list before calling
1891                  * handle_futex_death:
1892                  */
1893                 rc = fetch_robust_entry(&next_entry, &entry->next, &next_pi);
1894                 /*
1895                  * A pending lock might already be on the list, so
1896                  * don't process it twice:
1897                  */
1898                 if (entry != pending)
1899                         if (handle_futex_death((void __user *)entry + futex_offset,
1900                                                 curr, pi))
1901                                 return;
1902                 if (rc)
1903                         return;
1904                 entry = next_entry;
1905                 pi = next_pi;
1906                 /*
1907                  * Avoid excessively long or circular lists:
1908                  */
1909                 if (!--limit)
1910                         break;
1911
1912                 cond_resched();
1913         }
1914
1915         if (pending)
1916                 handle_futex_death((void __user *)pending + futex_offset,
1917                                    curr, pip);
1918 }
1919
1920 long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
1921                 u32 __user *uaddr2, u32 val2, u32 val3)
1922 {
1923         int clockrt, ret = -ENOSYS;
1924         int cmd = op & FUTEX_CMD_MASK;
1925         int fshared = 0;
1926
1927         if (!(op & FUTEX_PRIVATE_FLAG))
1928                 fshared = 1;
1929
1930         clockrt = op & FUTEX_CLOCK_REALTIME;
1931         if (clockrt && cmd != FUTEX_WAIT_BITSET)
1932                 return -ENOSYS;
1933
1934         switch (cmd) {
1935         case FUTEX_WAIT:
1936                 val3 = FUTEX_BITSET_MATCH_ANY;
1937         case FUTEX_WAIT_BITSET:
1938                 ret = futex_wait(uaddr, fshared, val, timeout, val3, clockrt);
1939                 break;
1940         case FUTEX_WAKE:
1941                 val3 = FUTEX_BITSET_MATCH_ANY;
1942         case FUTEX_WAKE_BITSET:
1943                 ret = futex_wake(uaddr, fshared, val, val3);
1944                 break;
1945         case FUTEX_REQUEUE:
1946                 ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, NULL);
1947                 break;
1948         case FUTEX_CMP_REQUEUE:
1949                 ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, &val3);
1950                 break;
1951         case FUTEX_WAKE_OP:
1952                 ret = futex_wake_op(uaddr, fshared, uaddr2, val, val2, val3);
1953                 break;
1954         case FUTEX_LOCK_PI:
1955                 if (futex_cmpxchg_enabled)
1956                         ret = futex_lock_pi(uaddr, fshared, val, timeout, 0);
1957                 break;
1958         case FUTEX_UNLOCK_PI:
1959                 if (futex_cmpxchg_enabled)
1960                         ret = futex_unlock_pi(uaddr, fshared);
1961                 break;
1962         case FUTEX_TRYLOCK_PI:
1963                 if (futex_cmpxchg_enabled)
1964                         ret = futex_lock_pi(uaddr, fshared, 0, timeout, 1);
1965                 break;
1966         default:
1967                 ret = -ENOSYS;
1968         }
1969         return ret;
1970 }
1971
1972
1973 asmlinkage long sys_futex(u32 __user *uaddr, int op, u32 val,
1974                           struct timespec __user *utime, u32 __user *uaddr2,
1975                           u32 val3)
1976 {
1977         struct timespec ts;
1978         ktime_t t, *tp = NULL;
1979         u32 val2 = 0;
1980         int cmd = op & FUTEX_CMD_MASK;
1981
1982         if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
1983                       cmd == FUTEX_WAIT_BITSET)) {
1984                 if (copy_from_user(&ts, utime, sizeof(ts)) != 0)
1985                         return -EFAULT;
1986                 if (!timespec_valid(&ts))
1987                         return -EINVAL;
1988
1989                 t = timespec_to_ktime(ts);
1990                 if (cmd == FUTEX_WAIT)
1991                         t = ktime_add_safe(ktime_get(), t);
1992                 tp = &t;
1993         }
1994         /*
1995          * requeue parameter in 'utime' if cmd == FUTEX_REQUEUE.
1996          * number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP.
1997          */
1998         if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||
1999             cmd == FUTEX_WAKE_OP)
2000                 val2 = (u32) (unsigned long) utime;
2001
2002         return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
2003 }
2004
2005 static int __init futex_init(void)
2006 {
2007         u32 curval;
2008         int i;
2009
2010         /*
2011          * This will fail and we want it. Some arch implementations do
2012          * runtime detection of the futex_atomic_cmpxchg_inatomic()
2013          * functionality. We want to know that before we call in any
2014          * of the complex code paths. Also we want to prevent
2015          * registration of robust lists in that case. NULL is
2016          * guaranteed to fault and we get -EFAULT on functional
2017          * implementation, the non functional ones will return
2018          * -ENOSYS.
2019          */
2020         curval = cmpxchg_futex_value_locked(NULL, 0, 0);
2021         if (curval == -EFAULT)
2022                 futex_cmpxchg_enabled = 1;
2023
2024         for (i = 0; i < ARRAY_SIZE(futex_queues); i++) {
2025                 plist_head_init(&futex_queues[i].chain, &futex_queues[i].lock);
2026                 spin_lock_init(&futex_queues[i].lock);
2027         }
2028
2029         return 0;
2030 }
2031 __initcall(futex_init);