[PATCH] WorkStruct: Use direct assignment rather than cmpxchg()
[linux-block.git] / kernel / futex.c
CommitLineData
1da177e4
LT
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 *
0771dfef
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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 *
c87e2837
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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 *
1da177e4
LT
19 * Thanks to Ben LaHaise for yelling "hashed waitqueues" loudly
20 * enough at me, Linus for the original (flawed) idea, Matthew
21 * Kirkwood for proof-of-concept implementation.
22 *
23 * "The futexes are also cursed."
24 * "But they come in a choice of three flavours!"
25 *
26 * This program is free software; you can redistribute it and/or modify
27 * it under the terms of the GNU General Public License as published by
28 * the Free Software Foundation; either version 2 of the License, or
29 * (at your option) any later version.
30 *
31 * This program is distributed in the hope that it will be useful,
32 * but WITHOUT ANY WARRANTY; without even the implied warranty of
33 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
34 * GNU General Public License for more details.
35 *
36 * You should have received a copy of the GNU General Public License
37 * along with this program; if not, write to the Free Software
38 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
39 */
40#include <linux/slab.h>
41#include <linux/poll.h>
42#include <linux/fs.h>
43#include <linux/file.h>
44#include <linux/jhash.h>
45#include <linux/init.h>
46#include <linux/futex.h>
47#include <linux/mount.h>
48#include <linux/pagemap.h>
49#include <linux/syscalls.h>
7ed20e1a 50#include <linux/signal.h>
4732efbe 51#include <asm/futex.h>
1da177e4 52
c87e2837
IM
53#include "rtmutex_common.h"
54
1da177e4
LT
55#define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8)
56
57/*
58 * Futexes are matched on equal values of this key.
59 * The key type depends on whether it's a shared or private mapping.
60 * Don't rearrange members without looking at hash_futex().
61 *
62 * offset is aligned to a multiple of sizeof(u32) (== 4) by definition.
63 * We set bit 0 to indicate if it's an inode-based key.
64 */
65union futex_key {
66 struct {
67 unsigned long pgoff;
68 struct inode *inode;
69 int offset;
70 } shared;
71 struct {
e2970f2f 72 unsigned long address;
1da177e4
LT
73 struct mm_struct *mm;
74 int offset;
75 } private;
76 struct {
77 unsigned long word;
78 void *ptr;
79 int offset;
80 } both;
81};
82
c87e2837
IM
83/*
84 * Priority Inheritance state:
85 */
86struct futex_pi_state {
87 /*
88 * list of 'owned' pi_state instances - these have to be
89 * cleaned up in do_exit() if the task exits prematurely:
90 */
91 struct list_head list;
92
93 /*
94 * The PI object:
95 */
96 struct rt_mutex pi_mutex;
97
98 struct task_struct *owner;
99 atomic_t refcount;
100
101 union futex_key key;
102};
103
1da177e4
LT
104/*
105 * We use this hashed waitqueue instead of a normal wait_queue_t, so
106 * we can wake only the relevant ones (hashed queues may be shared).
107 *
108 * A futex_q has a woken state, just like tasks have TASK_RUNNING.
109 * It is considered woken when list_empty(&q->list) || q->lock_ptr == 0.
110 * The order of wakup is always to make the first condition true, then
111 * wake up q->waiters, then make the second condition true.
112 */
113struct futex_q {
114 struct list_head list;
115 wait_queue_head_t waiters;
116
e2970f2f 117 /* Which hash list lock to use: */
1da177e4
LT
118 spinlock_t *lock_ptr;
119
e2970f2f 120 /* Key which the futex is hashed on: */
1da177e4
LT
121 union futex_key key;
122
e2970f2f 123 /* For fd, sigio sent using these: */
1da177e4
LT
124 int fd;
125 struct file *filp;
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126
127 /* Optional priority inheritance state: */
128 struct futex_pi_state *pi_state;
129 struct task_struct *task;
1da177e4
LT
130};
131
132/*
133 * Split the global futex_lock into every hash list lock.
134 */
135struct futex_hash_bucket {
136 spinlock_t lock;
137 struct list_head chain;
138};
139
140static struct futex_hash_bucket futex_queues[1<<FUTEX_HASHBITS];
141
142/* Futex-fs vfsmount entry: */
143static struct vfsmount *futex_mnt;
144
145/*
146 * We hash on the keys returned from get_futex_key (see below).
147 */
148static struct futex_hash_bucket *hash_futex(union futex_key *key)
149{
150 u32 hash = jhash2((u32*)&key->both.word,
151 (sizeof(key->both.word)+sizeof(key->both.ptr))/4,
152 key->both.offset);
153 return &futex_queues[hash & ((1 << FUTEX_HASHBITS)-1)];
154}
155
156/*
157 * Return 1 if two futex_keys are equal, 0 otherwise.
158 */
159static inline int match_futex(union futex_key *key1, union futex_key *key2)
160{
161 return (key1->both.word == key2->both.word
162 && key1->both.ptr == key2->both.ptr
163 && key1->both.offset == key2->both.offset);
164}
165
166/*
167 * Get parameters which are the keys for a futex.
168 *
f3a43f3f 169 * For shared mappings, it's (page->index, vma->vm_file->f_path.dentry->d_inode,
1da177e4
LT
170 * offset_within_page). For private mappings, it's (uaddr, current->mm).
171 * We can usually work out the index without swapping in the page.
172 *
173 * Returns: 0, or negative error code.
174 * The key words are stored in *key on success.
175 *
176 * Should be called with &current->mm->mmap_sem but NOT any spinlocks.
177 */
e2970f2f 178static int get_futex_key(u32 __user *uaddr, union futex_key *key)
1da177e4 179{
e2970f2f 180 unsigned long address = (unsigned long)uaddr;
1da177e4
LT
181 struct mm_struct *mm = current->mm;
182 struct vm_area_struct *vma;
183 struct page *page;
184 int err;
185
186 /*
187 * The futex address must be "naturally" aligned.
188 */
e2970f2f 189 key->both.offset = address % PAGE_SIZE;
1da177e4
LT
190 if (unlikely((key->both.offset % sizeof(u32)) != 0))
191 return -EINVAL;
e2970f2f 192 address -= key->both.offset;
1da177e4
LT
193
194 /*
195 * The futex is hashed differently depending on whether
196 * it's in a shared or private mapping. So check vma first.
197 */
e2970f2f 198 vma = find_extend_vma(mm, address);
1da177e4
LT
199 if (unlikely(!vma))
200 return -EFAULT;
201
202 /*
203 * Permissions.
204 */
205 if (unlikely((vma->vm_flags & (VM_IO|VM_READ)) != VM_READ))
206 return (vma->vm_flags & VM_IO) ? -EPERM : -EACCES;
207
208 /*
209 * Private mappings are handled in a simple way.
210 *
211 * NOTE: When userspace waits on a MAP_SHARED mapping, even if
212 * it's a read-only handle, it's expected that futexes attach to
213 * the object not the particular process. Therefore we use
214 * VM_MAYSHARE here, not VM_SHARED which is restricted to shared
215 * mappings of _writable_ handles.
216 */
217 if (likely(!(vma->vm_flags & VM_MAYSHARE))) {
218 key->private.mm = mm;
e2970f2f 219 key->private.address = address;
1da177e4
LT
220 return 0;
221 }
222
223 /*
224 * Linear file mappings are also simple.
225 */
f3a43f3f 226 key->shared.inode = vma->vm_file->f_path.dentry->d_inode;
1da177e4
LT
227 key->both.offset++; /* Bit 0 of offset indicates inode-based key. */
228 if (likely(!(vma->vm_flags & VM_NONLINEAR))) {
e2970f2f 229 key->shared.pgoff = (((address - vma->vm_start) >> PAGE_SHIFT)
1da177e4
LT
230 + vma->vm_pgoff);
231 return 0;
232 }
233
234 /*
235 * We could walk the page table to read the non-linear
236 * pte, and get the page index without fetching the page
237 * from swap. But that's a lot of code to duplicate here
238 * for a rare case, so we simply fetch the page.
239 */
e2970f2f 240 err = get_user_pages(current, mm, address, 1, 0, 0, &page, NULL);
1da177e4
LT
241 if (err >= 0) {
242 key->shared.pgoff =
243 page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
244 put_page(page);
245 return 0;
246 }
247 return err;
248}
249
250/*
251 * Take a reference to the resource addressed by a key.
252 * Can be called while holding spinlocks.
253 *
254 * NOTE: mmap_sem MUST be held between get_futex_key() and calling this
255 * function, if it is called at all. mmap_sem keeps key->shared.inode valid.
256 */
257static inline void get_key_refs(union futex_key *key)
258{
259 if (key->both.ptr != 0) {
260 if (key->both.offset & 1)
261 atomic_inc(&key->shared.inode->i_count);
262 else
263 atomic_inc(&key->private.mm->mm_count);
264 }
265}
266
267/*
268 * Drop a reference to the resource addressed by a key.
269 * The hash bucket spinlock must not be held.
270 */
271static void drop_key_refs(union futex_key *key)
272{
273 if (key->both.ptr != 0) {
274 if (key->both.offset & 1)
275 iput(key->shared.inode);
276 else
277 mmdrop(key->private.mm);
278 }
279}
280
e2970f2f 281static inline int get_futex_value_locked(u32 *dest, u32 __user *from)
1da177e4
LT
282{
283 int ret;
284
a866374a 285 pagefault_disable();
e2970f2f 286 ret = __copy_from_user_inatomic(dest, from, sizeof(u32));
a866374a 287 pagefault_enable();
1da177e4
LT
288
289 return ret ? -EFAULT : 0;
290}
291
c87e2837
IM
292/*
293 * Fault handling. Called with current->mm->mmap_sem held.
294 */
295static int futex_handle_fault(unsigned long address, int attempt)
296{
297 struct vm_area_struct * vma;
298 struct mm_struct *mm = current->mm;
299
e579dcbf 300 if (attempt > 2 || !(vma = find_vma(mm, address)) ||
c87e2837
IM
301 vma->vm_start > address || !(vma->vm_flags & VM_WRITE))
302 return -EFAULT;
303
304 switch (handle_mm_fault(mm, vma, address, 1)) {
305 case VM_FAULT_MINOR:
306 current->min_flt++;
307 break;
308 case VM_FAULT_MAJOR:
309 current->maj_flt++;
310 break;
311 default:
312 return -EFAULT;
313 }
314 return 0;
315}
316
317/*
318 * PI code:
319 */
320static int refill_pi_state_cache(void)
321{
322 struct futex_pi_state *pi_state;
323
324 if (likely(current->pi_state_cache))
325 return 0;
326
4668edc3 327 pi_state = kzalloc(sizeof(*pi_state), GFP_KERNEL);
c87e2837
IM
328
329 if (!pi_state)
330 return -ENOMEM;
331
c87e2837
IM
332 INIT_LIST_HEAD(&pi_state->list);
333 /* pi_mutex gets initialized later */
334 pi_state->owner = NULL;
335 atomic_set(&pi_state->refcount, 1);
336
337 current->pi_state_cache = pi_state;
338
339 return 0;
340}
341
342static struct futex_pi_state * alloc_pi_state(void)
343{
344 struct futex_pi_state *pi_state = current->pi_state_cache;
345
346 WARN_ON(!pi_state);
347 current->pi_state_cache = NULL;
348
349 return pi_state;
350}
351
352static void free_pi_state(struct futex_pi_state *pi_state)
353{
354 if (!atomic_dec_and_test(&pi_state->refcount))
355 return;
356
357 /*
358 * If pi_state->owner is NULL, the owner is most probably dying
359 * and has cleaned up the pi_state already
360 */
361 if (pi_state->owner) {
362 spin_lock_irq(&pi_state->owner->pi_lock);
363 list_del_init(&pi_state->list);
364 spin_unlock_irq(&pi_state->owner->pi_lock);
365
366 rt_mutex_proxy_unlock(&pi_state->pi_mutex, pi_state->owner);
367 }
368
369 if (current->pi_state_cache)
370 kfree(pi_state);
371 else {
372 /*
373 * pi_state->list is already empty.
374 * clear pi_state->owner.
375 * refcount is at 0 - put it back to 1.
376 */
377 pi_state->owner = NULL;
378 atomic_set(&pi_state->refcount, 1);
379 current->pi_state_cache = pi_state;
380 }
381}
382
383/*
384 * Look up the task based on what TID userspace gave us.
385 * We dont trust it.
386 */
387static struct task_struct * futex_find_get_task(pid_t pid)
388{
389 struct task_struct *p;
390
d359b549 391 rcu_read_lock();
c87e2837
IM
392 p = find_task_by_pid(pid);
393 if (!p)
394 goto out_unlock;
395 if ((current->euid != p->euid) && (current->euid != p->uid)) {
396 p = NULL;
397 goto out_unlock;
398 }
d015baeb 399 if (p->exit_state != 0) {
c87e2837
IM
400 p = NULL;
401 goto out_unlock;
402 }
403 get_task_struct(p);
404out_unlock:
d359b549 405 rcu_read_unlock();
c87e2837
IM
406
407 return p;
408}
409
410/*
411 * This task is holding PI mutexes at exit time => bad.
412 * Kernel cleans up PI-state, but userspace is likely hosed.
413 * (Robust-futex cleanup is separate and might save the day for userspace.)
414 */
415void exit_pi_state_list(struct task_struct *curr)
416{
c87e2837
IM
417 struct list_head *next, *head = &curr->pi_state_list;
418 struct futex_pi_state *pi_state;
627371d7 419 struct futex_hash_bucket *hb;
c87e2837
IM
420 union futex_key key;
421
422 /*
423 * We are a ZOMBIE and nobody can enqueue itself on
424 * pi_state_list anymore, but we have to be careful
627371d7 425 * versus waiters unqueueing themselves:
c87e2837
IM
426 */
427 spin_lock_irq(&curr->pi_lock);
428 while (!list_empty(head)) {
429
430 next = head->next;
431 pi_state = list_entry(next, struct futex_pi_state, list);
432 key = pi_state->key;
627371d7 433 hb = hash_futex(&key);
c87e2837
IM
434 spin_unlock_irq(&curr->pi_lock);
435
c87e2837
IM
436 spin_lock(&hb->lock);
437
438 spin_lock_irq(&curr->pi_lock);
627371d7
IM
439 /*
440 * We dropped the pi-lock, so re-check whether this
441 * task still owns the PI-state:
442 */
c87e2837
IM
443 if (head->next != next) {
444 spin_unlock(&hb->lock);
445 continue;
446 }
447
c87e2837 448 WARN_ON(pi_state->owner != curr);
627371d7
IM
449 WARN_ON(list_empty(&pi_state->list));
450 list_del_init(&pi_state->list);
c87e2837
IM
451 pi_state->owner = NULL;
452 spin_unlock_irq(&curr->pi_lock);
453
454 rt_mutex_unlock(&pi_state->pi_mutex);
455
456 spin_unlock(&hb->lock);
457
458 spin_lock_irq(&curr->pi_lock);
459 }
460 spin_unlock_irq(&curr->pi_lock);
461}
462
463static int
464lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, struct futex_q *me)
465{
466 struct futex_pi_state *pi_state = NULL;
467 struct futex_q *this, *next;
468 struct list_head *head;
469 struct task_struct *p;
470 pid_t pid;
471
472 head = &hb->chain;
473
474 list_for_each_entry_safe(this, next, head, list) {
627371d7 475 if (match_futex(&this->key, &me->key)) {
c87e2837
IM
476 /*
477 * Another waiter already exists - bump up
478 * the refcount and return its pi_state:
479 */
480 pi_state = this->pi_state;
06a9ec29
TG
481 /*
482 * Userspace might have messed up non PI and PI futexes
483 */
484 if (unlikely(!pi_state))
485 return -EINVAL;
486
627371d7
IM
487 WARN_ON(!atomic_read(&pi_state->refcount));
488
c87e2837
IM
489 atomic_inc(&pi_state->refcount);
490 me->pi_state = pi_state;
491
492 return 0;
493 }
494 }
495
496 /*
e3f2ddea
IM
497 * We are the first waiter - try to look up the real owner and attach
498 * the new pi_state to it, but bail out when the owner died bit is set
499 * and TID = 0:
c87e2837
IM
500 */
501 pid = uval & FUTEX_TID_MASK;
e3f2ddea
IM
502 if (!pid && (uval & FUTEX_OWNER_DIED))
503 return -ESRCH;
c87e2837
IM
504 p = futex_find_get_task(pid);
505 if (!p)
506 return -ESRCH;
507
508 pi_state = alloc_pi_state();
509
510 /*
511 * Initialize the pi_mutex in locked state and make 'p'
512 * the owner of it:
513 */
514 rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p);
515
516 /* Store the key for possible exit cleanups: */
517 pi_state->key = me->key;
518
519 spin_lock_irq(&p->pi_lock);
627371d7 520 WARN_ON(!list_empty(&pi_state->list));
c87e2837
IM
521 list_add(&pi_state->list, &p->pi_state_list);
522 pi_state->owner = p;
523 spin_unlock_irq(&p->pi_lock);
524
525 put_task_struct(p);
526
527 me->pi_state = pi_state;
528
529 return 0;
530}
531
1da177e4
LT
532/*
533 * The hash bucket lock must be held when this is called.
534 * Afterwards, the futex_q must not be accessed.
535 */
536static void wake_futex(struct futex_q *q)
537{
538 list_del_init(&q->list);
539 if (q->filp)
540 send_sigio(&q->filp->f_owner, q->fd, POLL_IN);
541 /*
542 * The lock in wake_up_all() is a crucial memory barrier after the
543 * list_del_init() and also before assigning to q->lock_ptr.
544 */
545 wake_up_all(&q->waiters);
546 /*
547 * The waiting task can free the futex_q as soon as this is written,
548 * without taking any locks. This must come last.
8e31108b
AM
549 *
550 * A memory barrier is required here to prevent the following store
551 * to lock_ptr from getting ahead of the wakeup. Clearing the lock
552 * at the end of wake_up_all() does not prevent this store from
553 * moving.
1da177e4 554 */
ccdea2f8 555 smp_wmb();
1da177e4
LT
556 q->lock_ptr = NULL;
557}
558
c87e2837
IM
559static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this)
560{
561 struct task_struct *new_owner;
562 struct futex_pi_state *pi_state = this->pi_state;
563 u32 curval, newval;
564
565 if (!pi_state)
566 return -EINVAL;
567
568 new_owner = rt_mutex_next_owner(&pi_state->pi_mutex);
569
570 /*
571 * This happens when we have stolen the lock and the original
572 * pending owner did not enqueue itself back on the rt_mutex.
573 * Thats not a tragedy. We know that way, that a lock waiter
574 * is on the fly. We make the futex_q waiter the pending owner.
575 */
576 if (!new_owner)
577 new_owner = this->task;
578
579 /*
580 * We pass it to the next owner. (The WAITERS bit is always
581 * kept enabled while there is PI state around. We must also
582 * preserve the owner died bit.)
583 */
e3f2ddea
IM
584 if (!(uval & FUTEX_OWNER_DIED)) {
585 newval = FUTEX_WAITERS | new_owner->pid;
586
a866374a 587 pagefault_disable();
e3f2ddea 588 curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval);
a866374a 589 pagefault_enable();
e3f2ddea
IM
590 if (curval == -EFAULT)
591 return -EFAULT;
592 if (curval != uval)
593 return -EINVAL;
594 }
c87e2837 595
627371d7
IM
596 spin_lock_irq(&pi_state->owner->pi_lock);
597 WARN_ON(list_empty(&pi_state->list));
598 list_del_init(&pi_state->list);
599 spin_unlock_irq(&pi_state->owner->pi_lock);
600
601 spin_lock_irq(&new_owner->pi_lock);
602 WARN_ON(!list_empty(&pi_state->list));
c87e2837
IM
603 list_add(&pi_state->list, &new_owner->pi_state_list);
604 pi_state->owner = new_owner;
627371d7
IM
605 spin_unlock_irq(&new_owner->pi_lock);
606
c87e2837
IM
607 rt_mutex_unlock(&pi_state->pi_mutex);
608
609 return 0;
610}
611
612static int unlock_futex_pi(u32 __user *uaddr, u32 uval)
613{
614 u32 oldval;
615
616 /*
617 * There is no waiter, so we unlock the futex. The owner died
618 * bit has not to be preserved here. We are the owner:
619 */
a866374a 620 pagefault_disable();
c87e2837 621 oldval = futex_atomic_cmpxchg_inatomic(uaddr, uval, 0);
a866374a 622 pagefault_enable();
c87e2837
IM
623
624 if (oldval == -EFAULT)
625 return oldval;
626 if (oldval != uval)
627 return -EAGAIN;
628
629 return 0;
630}
631
8b8f319f
IM
632/*
633 * Express the locking dependencies for lockdep:
634 */
635static inline void
636double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
637{
638 if (hb1 <= hb2) {
639 spin_lock(&hb1->lock);
640 if (hb1 < hb2)
641 spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING);
642 } else { /* hb1 > hb2 */
643 spin_lock(&hb2->lock);
644 spin_lock_nested(&hb1->lock, SINGLE_DEPTH_NESTING);
645 }
646}
647
1da177e4
LT
648/*
649 * Wake up all waiters hashed on the physical page that is mapped
650 * to this virtual address:
651 */
e2970f2f 652static int futex_wake(u32 __user *uaddr, int nr_wake)
1da177e4 653{
e2970f2f 654 struct futex_hash_bucket *hb;
1da177e4 655 struct futex_q *this, *next;
e2970f2f
IM
656 struct list_head *head;
657 union futex_key key;
1da177e4
LT
658 int ret;
659
660 down_read(&current->mm->mmap_sem);
661
662 ret = get_futex_key(uaddr, &key);
663 if (unlikely(ret != 0))
664 goto out;
665
e2970f2f
IM
666 hb = hash_futex(&key);
667 spin_lock(&hb->lock);
668 head = &hb->chain;
1da177e4
LT
669
670 list_for_each_entry_safe(this, next, head, list) {
671 if (match_futex (&this->key, &key)) {
ed6f7b10
IM
672 if (this->pi_state) {
673 ret = -EINVAL;
674 break;
675 }
1da177e4
LT
676 wake_futex(this);
677 if (++ret >= nr_wake)
678 break;
679 }
680 }
681
e2970f2f 682 spin_unlock(&hb->lock);
1da177e4
LT
683out:
684 up_read(&current->mm->mmap_sem);
685 return ret;
686}
687
4732efbe
JJ
688/*
689 * Wake up all waiters hashed on the physical page that is mapped
690 * to this virtual address:
691 */
e2970f2f
IM
692static int
693futex_wake_op(u32 __user *uaddr1, u32 __user *uaddr2,
694 int nr_wake, int nr_wake2, int op)
4732efbe
JJ
695{
696 union futex_key key1, key2;
e2970f2f 697 struct futex_hash_bucket *hb1, *hb2;
4732efbe
JJ
698 struct list_head *head;
699 struct futex_q *this, *next;
700 int ret, op_ret, attempt = 0;
701
702retryfull:
703 down_read(&current->mm->mmap_sem);
704
705 ret = get_futex_key(uaddr1, &key1);
706 if (unlikely(ret != 0))
707 goto out;
708 ret = get_futex_key(uaddr2, &key2);
709 if (unlikely(ret != 0))
710 goto out;
711
e2970f2f
IM
712 hb1 = hash_futex(&key1);
713 hb2 = hash_futex(&key2);
4732efbe
JJ
714
715retry:
8b8f319f 716 double_lock_hb(hb1, hb2);
4732efbe 717
e2970f2f 718 op_ret = futex_atomic_op_inuser(op, uaddr2);
4732efbe 719 if (unlikely(op_ret < 0)) {
e2970f2f 720 u32 dummy;
4732efbe 721
e2970f2f
IM
722 spin_unlock(&hb1->lock);
723 if (hb1 != hb2)
724 spin_unlock(&hb2->lock);
4732efbe 725
7ee1dd3f 726#ifndef CONFIG_MMU
e2970f2f
IM
727 /*
728 * we don't get EFAULT from MMU faults if we don't have an MMU,
729 * but we might get them from range checking
730 */
7ee1dd3f
DH
731 ret = op_ret;
732 goto out;
733#endif
734
796f8d9b
DG
735 if (unlikely(op_ret != -EFAULT)) {
736 ret = op_ret;
737 goto out;
738 }
739
e2970f2f
IM
740 /*
741 * futex_atomic_op_inuser needs to both read and write
4732efbe
JJ
742 * *(int __user *)uaddr2, but we can't modify it
743 * non-atomically. Therefore, if get_user below is not
744 * enough, we need to handle the fault ourselves, while
e2970f2f
IM
745 * still holding the mmap_sem.
746 */
4732efbe 747 if (attempt++) {
c87e2837 748 if (futex_handle_fault((unsigned long)uaddr2,
e579dcbf 749 attempt)) {
750 ret = -EFAULT;
4732efbe 751 goto out;
e579dcbf 752 }
4732efbe
JJ
753 goto retry;
754 }
755
e2970f2f
IM
756 /*
757 * If we would have faulted, release mmap_sem,
758 * fault it in and start all over again.
759 */
4732efbe
JJ
760 up_read(&current->mm->mmap_sem);
761
e2970f2f 762 ret = get_user(dummy, uaddr2);
4732efbe
JJ
763 if (ret)
764 return ret;
765
766 goto retryfull;
767 }
768
e2970f2f 769 head = &hb1->chain;
4732efbe
JJ
770
771 list_for_each_entry_safe(this, next, head, list) {
772 if (match_futex (&this->key, &key1)) {
773 wake_futex(this);
774 if (++ret >= nr_wake)
775 break;
776 }
777 }
778
779 if (op_ret > 0) {
e2970f2f 780 head = &hb2->chain;
4732efbe
JJ
781
782 op_ret = 0;
783 list_for_each_entry_safe(this, next, head, list) {
784 if (match_futex (&this->key, &key2)) {
785 wake_futex(this);
786 if (++op_ret >= nr_wake2)
787 break;
788 }
789 }
790 ret += op_ret;
791 }
792
e2970f2f
IM
793 spin_unlock(&hb1->lock);
794 if (hb1 != hb2)
795 spin_unlock(&hb2->lock);
4732efbe
JJ
796out:
797 up_read(&current->mm->mmap_sem);
798 return ret;
799}
800
1da177e4
LT
801/*
802 * Requeue all waiters hashed on one physical page to another
803 * physical page.
804 */
e2970f2f
IM
805static int futex_requeue(u32 __user *uaddr1, u32 __user *uaddr2,
806 int nr_wake, int nr_requeue, u32 *cmpval)
1da177e4
LT
807{
808 union futex_key key1, key2;
e2970f2f 809 struct futex_hash_bucket *hb1, *hb2;
1da177e4
LT
810 struct list_head *head1;
811 struct futex_q *this, *next;
812 int ret, drop_count = 0;
813
814 retry:
815 down_read(&current->mm->mmap_sem);
816
817 ret = get_futex_key(uaddr1, &key1);
818 if (unlikely(ret != 0))
819 goto out;
820 ret = get_futex_key(uaddr2, &key2);
821 if (unlikely(ret != 0))
822 goto out;
823
e2970f2f
IM
824 hb1 = hash_futex(&key1);
825 hb2 = hash_futex(&key2);
1da177e4 826
8b8f319f 827 double_lock_hb(hb1, hb2);
1da177e4 828
e2970f2f
IM
829 if (likely(cmpval != NULL)) {
830 u32 curval;
1da177e4 831
e2970f2f 832 ret = get_futex_value_locked(&curval, uaddr1);
1da177e4
LT
833
834 if (unlikely(ret)) {
e2970f2f
IM
835 spin_unlock(&hb1->lock);
836 if (hb1 != hb2)
837 spin_unlock(&hb2->lock);
1da177e4 838
e2970f2f
IM
839 /*
840 * If we would have faulted, release mmap_sem, fault
1da177e4
LT
841 * it in and start all over again.
842 */
843 up_read(&current->mm->mmap_sem);
844
e2970f2f 845 ret = get_user(curval, uaddr1);
1da177e4
LT
846
847 if (!ret)
848 goto retry;
849
850 return ret;
851 }
e2970f2f 852 if (curval != *cmpval) {
1da177e4
LT
853 ret = -EAGAIN;
854 goto out_unlock;
855 }
856 }
857
e2970f2f 858 head1 = &hb1->chain;
1da177e4
LT
859 list_for_each_entry_safe(this, next, head1, list) {
860 if (!match_futex (&this->key, &key1))
861 continue;
862 if (++ret <= nr_wake) {
863 wake_futex(this);
864 } else {
59e0e0ac
SD
865 /*
866 * If key1 and key2 hash to the same bucket, no need to
867 * requeue.
868 */
869 if (likely(head1 != &hb2->chain)) {
870 list_move_tail(&this->list, &hb2->chain);
871 this->lock_ptr = &hb2->lock;
872 }
1da177e4
LT
873 this->key = key2;
874 get_key_refs(&key2);
875 drop_count++;
876
877 if (ret - nr_wake >= nr_requeue)
878 break;
1da177e4
LT
879 }
880 }
881
882out_unlock:
e2970f2f
IM
883 spin_unlock(&hb1->lock);
884 if (hb1 != hb2)
885 spin_unlock(&hb2->lock);
1da177e4
LT
886
887 /* drop_key_refs() must be called outside the spinlocks. */
888 while (--drop_count >= 0)
889 drop_key_refs(&key1);
890
891out:
892 up_read(&current->mm->mmap_sem);
893 return ret;
894}
895
896/* The key must be already stored in q->key. */
897static inline struct futex_hash_bucket *
898queue_lock(struct futex_q *q, int fd, struct file *filp)
899{
e2970f2f 900 struct futex_hash_bucket *hb;
1da177e4
LT
901
902 q->fd = fd;
903 q->filp = filp;
904
905 init_waitqueue_head(&q->waiters);
906
907 get_key_refs(&q->key);
e2970f2f
IM
908 hb = hash_futex(&q->key);
909 q->lock_ptr = &hb->lock;
1da177e4 910
e2970f2f
IM
911 spin_lock(&hb->lock);
912 return hb;
1da177e4
LT
913}
914
e2970f2f 915static inline void __queue_me(struct futex_q *q, struct futex_hash_bucket *hb)
1da177e4 916{
e2970f2f 917 list_add_tail(&q->list, &hb->chain);
c87e2837 918 q->task = current;
e2970f2f 919 spin_unlock(&hb->lock);
1da177e4
LT
920}
921
922static inline void
e2970f2f 923queue_unlock(struct futex_q *q, struct futex_hash_bucket *hb)
1da177e4 924{
e2970f2f 925 spin_unlock(&hb->lock);
1da177e4
LT
926 drop_key_refs(&q->key);
927}
928
929/*
930 * queue_me and unqueue_me must be called as a pair, each
931 * exactly once. They are called with the hashed spinlock held.
932 */
933
934/* The key must be already stored in q->key. */
935static void queue_me(struct futex_q *q, int fd, struct file *filp)
936{
e2970f2f
IM
937 struct futex_hash_bucket *hb;
938
939 hb = queue_lock(q, fd, filp);
940 __queue_me(q, hb);
1da177e4
LT
941}
942
943/* Return 1 if we were still queued (ie. 0 means we were woken) */
944static int unqueue_me(struct futex_q *q)
945{
1da177e4 946 spinlock_t *lock_ptr;
e2970f2f 947 int ret = 0;
1da177e4
LT
948
949 /* In the common case we don't take the spinlock, which is nice. */
950 retry:
951 lock_ptr = q->lock_ptr;
e91467ec 952 barrier();
1da177e4
LT
953 if (lock_ptr != 0) {
954 spin_lock(lock_ptr);
955 /*
956 * q->lock_ptr can change between reading it and
957 * spin_lock(), causing us to take the wrong lock. This
958 * corrects the race condition.
959 *
960 * Reasoning goes like this: if we have the wrong lock,
961 * q->lock_ptr must have changed (maybe several times)
962 * between reading it and the spin_lock(). It can
963 * change again after the spin_lock() but only if it was
964 * already changed before the spin_lock(). It cannot,
965 * however, change back to the original value. Therefore
966 * we can detect whether we acquired the correct lock.
967 */
968 if (unlikely(lock_ptr != q->lock_ptr)) {
969 spin_unlock(lock_ptr);
970 goto retry;
971 }
972 WARN_ON(list_empty(&q->list));
973 list_del(&q->list);
c87e2837
IM
974
975 BUG_ON(q->pi_state);
976
1da177e4
LT
977 spin_unlock(lock_ptr);
978 ret = 1;
979 }
980
981 drop_key_refs(&q->key);
982 return ret;
983}
984
c87e2837
IM
985/*
986 * PI futexes can not be requeued and must remove themself from the
987 * hash bucket. The hash bucket lock is held on entry and dropped here.
988 */
989static void unqueue_me_pi(struct futex_q *q, struct futex_hash_bucket *hb)
990{
991 WARN_ON(list_empty(&q->list));
992 list_del(&q->list);
993
994 BUG_ON(!q->pi_state);
995 free_pi_state(q->pi_state);
996 q->pi_state = NULL;
997
998 spin_unlock(&hb->lock);
999
1000 drop_key_refs(&q->key);
1001}
1002
e2970f2f 1003static int futex_wait(u32 __user *uaddr, u32 val, unsigned long time)
1da177e4 1004{
c87e2837
IM
1005 struct task_struct *curr = current;
1006 DECLARE_WAITQUEUE(wait, curr);
e2970f2f 1007 struct futex_hash_bucket *hb;
1da177e4 1008 struct futex_q q;
e2970f2f
IM
1009 u32 uval;
1010 int ret;
1da177e4 1011
c87e2837 1012 q.pi_state = NULL;
1da177e4 1013 retry:
c87e2837 1014 down_read(&curr->mm->mmap_sem);
1da177e4
LT
1015
1016 ret = get_futex_key(uaddr, &q.key);
1017 if (unlikely(ret != 0))
1018 goto out_release_sem;
1019
e2970f2f 1020 hb = queue_lock(&q, -1, NULL);
1da177e4
LT
1021
1022 /*
1023 * Access the page AFTER the futex is queued.
1024 * Order is important:
1025 *
1026 * Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val);
1027 * Userspace waker: if (cond(var)) { var = new; futex_wake(&var); }
1028 *
1029 * The basic logical guarantee of a futex is that it blocks ONLY
1030 * if cond(var) is known to be true at the time of blocking, for
1031 * any cond. If we queued after testing *uaddr, that would open
1032 * a race condition where we could block indefinitely with
1033 * cond(var) false, which would violate the guarantee.
1034 *
1035 * A consequence is that futex_wait() can return zero and absorb
1036 * a wakeup when *uaddr != val on entry to the syscall. This is
1037 * rare, but normal.
1038 *
1039 * We hold the mmap semaphore, so the mapping cannot have changed
1040 * since we looked it up in get_futex_key.
1041 */
e2970f2f 1042 ret = get_futex_value_locked(&uval, uaddr);
1da177e4
LT
1043
1044 if (unlikely(ret)) {
e2970f2f 1045 queue_unlock(&q, hb);
1da177e4 1046
e2970f2f
IM
1047 /*
1048 * If we would have faulted, release mmap_sem, fault it in and
1da177e4
LT
1049 * start all over again.
1050 */
c87e2837 1051 up_read(&curr->mm->mmap_sem);
1da177e4 1052
e2970f2f 1053 ret = get_user(uval, uaddr);
1da177e4
LT
1054
1055 if (!ret)
1056 goto retry;
1057 return ret;
1058 }
c87e2837
IM
1059 ret = -EWOULDBLOCK;
1060 if (uval != val)
1061 goto out_unlock_release_sem;
1da177e4
LT
1062
1063 /* Only actually queue if *uaddr contained val. */
e2970f2f 1064 __queue_me(&q, hb);
1da177e4
LT
1065
1066 /*
1067 * Now the futex is queued and we have checked the data, we
1068 * don't want to hold mmap_sem while we sleep.
c87e2837
IM
1069 */
1070 up_read(&curr->mm->mmap_sem);
1da177e4
LT
1071
1072 /*
1073 * There might have been scheduling since the queue_me(), as we
1074 * cannot hold a spinlock across the get_user() in case it
1075 * faults, and we cannot just set TASK_INTERRUPTIBLE state when
1076 * queueing ourselves into the futex hash. This code thus has to
1077 * rely on the futex_wake() code removing us from hash when it
1078 * wakes us up.
1079 */
1080
1081 /* add_wait_queue is the barrier after __set_current_state. */
1082 __set_current_state(TASK_INTERRUPTIBLE);
1083 add_wait_queue(&q.waiters, &wait);
1084 /*
1085 * !list_empty() is safe here without any lock.
1086 * q.lock_ptr != 0 is not safe, because of ordering against wakeup.
1087 */
1088 if (likely(!list_empty(&q.list)))
1089 time = schedule_timeout(time);
1090 __set_current_state(TASK_RUNNING);
1091
1092 /*
1093 * NOTE: we don't remove ourselves from the waitqueue because
1094 * we are the only user of it.
1095 */
1096
1097 /* If we were woken (and unqueued), we succeeded, whatever. */
1098 if (!unqueue_me(&q))
1099 return 0;
1100 if (time == 0)
1101 return -ETIMEDOUT;
e2970f2f
IM
1102 /*
1103 * We expect signal_pending(current), but another thread may
1104 * have handled it for us already.
1105 */
1da177e4
LT
1106 return -EINTR;
1107
c87e2837
IM
1108 out_unlock_release_sem:
1109 queue_unlock(&q, hb);
1110
1da177e4 1111 out_release_sem:
c87e2837
IM
1112 up_read(&curr->mm->mmap_sem);
1113 return ret;
1114}
1115
1116/*
1117 * Userspace tried a 0 -> TID atomic transition of the futex value
1118 * and failed. The kernel side here does the whole locking operation:
1119 * if there are waiters then it will block, it does PI, etc. (Due to
1120 * races the kernel might see a 0 value of the futex too.)
1121 */
c5780e97
TG
1122static int futex_lock_pi(u32 __user *uaddr, int detect, unsigned long sec,
1123 long nsec, int trylock)
c87e2837 1124{
c5780e97 1125 struct hrtimer_sleeper timeout, *to = NULL;
c87e2837
IM
1126 struct task_struct *curr = current;
1127 struct futex_hash_bucket *hb;
1128 u32 uval, newval, curval;
1129 struct futex_q q;
1130 int ret, attempt = 0;
1131
1132 if (refill_pi_state_cache())
1133 return -ENOMEM;
1134
c5780e97
TG
1135 if (sec != MAX_SCHEDULE_TIMEOUT) {
1136 to = &timeout;
1137 hrtimer_init(&to->timer, CLOCK_REALTIME, HRTIMER_ABS);
1138 hrtimer_init_sleeper(to, current);
1139 to->timer.expires = ktime_set(sec, nsec);
1140 }
1141
c87e2837
IM
1142 q.pi_state = NULL;
1143 retry:
1144 down_read(&curr->mm->mmap_sem);
1145
1146 ret = get_futex_key(uaddr, &q.key);
1147 if (unlikely(ret != 0))
1148 goto out_release_sem;
1149
1150 hb = queue_lock(&q, -1, NULL);
1151
1152 retry_locked:
1153 /*
1154 * To avoid races, we attempt to take the lock here again
1155 * (by doing a 0 -> TID atomic cmpxchg), while holding all
1156 * the locks. It will most likely not succeed.
1157 */
1158 newval = current->pid;
1159
a866374a 1160 pagefault_disable();
c87e2837 1161 curval = futex_atomic_cmpxchg_inatomic(uaddr, 0, newval);
a866374a 1162 pagefault_enable();
c87e2837
IM
1163
1164 if (unlikely(curval == -EFAULT))
1165 goto uaddr_faulted;
1166
1167 /* We own the lock already */
1168 if (unlikely((curval & FUTEX_TID_MASK) == current->pid)) {
1169 if (!detect && 0)
1170 force_sig(SIGKILL, current);
1171 ret = -EDEADLK;
1172 goto out_unlock_release_sem;
1173 }
1174
1175 /*
1176 * Surprise - we got the lock. Just return
1177 * to userspace:
1178 */
1179 if (unlikely(!curval))
1180 goto out_unlock_release_sem;
1181
1182 uval = curval;
1183 newval = uval | FUTEX_WAITERS;
1184
a866374a 1185 pagefault_disable();
c87e2837 1186 curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval);
a866374a 1187 pagefault_enable();
c87e2837
IM
1188
1189 if (unlikely(curval == -EFAULT))
1190 goto uaddr_faulted;
1191 if (unlikely(curval != uval))
1192 goto retry_locked;
1193
1194 /*
1195 * We dont have the lock. Look up the PI state (or create it if
1196 * we are the first waiter):
1197 */
1198 ret = lookup_pi_state(uval, hb, &q);
1199
1200 if (unlikely(ret)) {
1201 /*
1202 * There were no waiters and the owner task lookup
1203 * failed. When the OWNER_DIED bit is set, then we
1204 * know that this is a robust futex and we actually
1205 * take the lock. This is safe as we are protected by
1206 * the hash bucket lock. We also set the waiters bit
1207 * unconditionally here, to simplify glibc handling of
1208 * multiple tasks racing to acquire the lock and
1209 * cleanup the problems which were left by the dead
1210 * owner.
1211 */
1212 if (curval & FUTEX_OWNER_DIED) {
1213 uval = newval;
1214 newval = current->pid |
1215 FUTEX_OWNER_DIED | FUTEX_WAITERS;
1216
a866374a 1217 pagefault_disable();
c87e2837
IM
1218 curval = futex_atomic_cmpxchg_inatomic(uaddr,
1219 uval, newval);
a866374a 1220 pagefault_enable();
c87e2837
IM
1221
1222 if (unlikely(curval == -EFAULT))
1223 goto uaddr_faulted;
1224 if (unlikely(curval != uval))
1225 goto retry_locked;
1226 ret = 0;
1227 }
1228 goto out_unlock_release_sem;
1229 }
1230
1231 /*
1232 * Only actually queue now that the atomic ops are done:
1233 */
1234 __queue_me(&q, hb);
1235
1236 /*
1237 * Now the futex is queued and we have checked the data, we
1238 * don't want to hold mmap_sem while we sleep.
1239 */
1240 up_read(&curr->mm->mmap_sem);
1241
1242 WARN_ON(!q.pi_state);
1243 /*
1244 * Block on the PI mutex:
1245 */
1246 if (!trylock)
1247 ret = rt_mutex_timed_lock(&q.pi_state->pi_mutex, to, 1);
1248 else {
1249 ret = rt_mutex_trylock(&q.pi_state->pi_mutex);
1250 /* Fixup the trylock return value: */
1251 ret = ret ? 0 : -EWOULDBLOCK;
1252 }
1253
1254 down_read(&curr->mm->mmap_sem);
a99e4e41 1255 spin_lock(q.lock_ptr);
c87e2837
IM
1256
1257 /*
1258 * Got the lock. We might not be the anticipated owner if we
1259 * did a lock-steal - fix up the PI-state in that case.
1260 */
1261 if (!ret && q.pi_state->owner != curr) {
1262 u32 newtid = current->pid | FUTEX_WAITERS;
1263
1264 /* Owner died? */
1265 if (q.pi_state->owner != NULL) {
1266 spin_lock_irq(&q.pi_state->owner->pi_lock);
627371d7 1267 WARN_ON(list_empty(&q.pi_state->list));
c87e2837
IM
1268 list_del_init(&q.pi_state->list);
1269 spin_unlock_irq(&q.pi_state->owner->pi_lock);
1270 } else
1271 newtid |= FUTEX_OWNER_DIED;
1272
1273 q.pi_state->owner = current;
1274
1275 spin_lock_irq(&current->pi_lock);
627371d7 1276 WARN_ON(!list_empty(&q.pi_state->list));
c87e2837
IM
1277 list_add(&q.pi_state->list, &current->pi_state_list);
1278 spin_unlock_irq(&current->pi_lock);
1279
1280 /* Unqueue and drop the lock */
1281 unqueue_me_pi(&q, hb);
1282 up_read(&curr->mm->mmap_sem);
1283 /*
1284 * We own it, so we have to replace the pending owner
1285 * TID. This must be atomic as we have preserve the
1286 * owner died bit here.
1287 */
1288 ret = get_user(uval, uaddr);
1289 while (!ret) {
1290 newval = (uval & FUTEX_OWNER_DIED) | newtid;
1291 curval = futex_atomic_cmpxchg_inatomic(uaddr,
1292 uval, newval);
1293 if (curval == -EFAULT)
1294 ret = -EFAULT;
1295 if (curval == uval)
1296 break;
1297 uval = curval;
1298 }
1299 } else {
1300 /*
1301 * Catch the rare case, where the lock was released
1302 * when we were on the way back before we locked
1303 * the hash bucket.
1304 */
1305 if (ret && q.pi_state->owner == curr) {
1306 if (rt_mutex_trylock(&q.pi_state->pi_mutex))
1307 ret = 0;
1308 }
1309 /* Unqueue and drop the lock */
1310 unqueue_me_pi(&q, hb);
1311 up_read(&curr->mm->mmap_sem);
1312 }
1313
1314 if (!detect && ret == -EDEADLK && 0)
1315 force_sig(SIGKILL, current);
1316
c5780e97 1317 return ret != -EINTR ? ret : -ERESTARTNOINTR;
c87e2837
IM
1318
1319 out_unlock_release_sem:
1320 queue_unlock(&q, hb);
1321
1322 out_release_sem:
1323 up_read(&curr->mm->mmap_sem);
1324 return ret;
1325
1326 uaddr_faulted:
1327 /*
1328 * We have to r/w *(int __user *)uaddr, but we can't modify it
1329 * non-atomically. Therefore, if get_user below is not
1330 * enough, we need to handle the fault ourselves, while
1331 * still holding the mmap_sem.
1332 */
1333 if (attempt++) {
e579dcbf 1334 if (futex_handle_fault((unsigned long)uaddr, attempt)) {
1335 ret = -EFAULT;
c87e2837 1336 goto out_unlock_release_sem;
e579dcbf 1337 }
c87e2837
IM
1338 goto retry_locked;
1339 }
1340
1341 queue_unlock(&q, hb);
1342 up_read(&curr->mm->mmap_sem);
1343
1344 ret = get_user(uval, uaddr);
1345 if (!ret && (uval != -EFAULT))
1346 goto retry;
1347
1348 return ret;
1349}
1350
c87e2837
IM
1351/*
1352 * Userspace attempted a TID -> 0 atomic transition, and failed.
1353 * This is the in-kernel slowpath: we look up the PI state (if any),
1354 * and do the rt-mutex unlock.
1355 */
1356static int futex_unlock_pi(u32 __user *uaddr)
1357{
1358 struct futex_hash_bucket *hb;
1359 struct futex_q *this, *next;
1360 u32 uval;
1361 struct list_head *head;
1362 union futex_key key;
1363 int ret, attempt = 0;
1364
1365retry:
1366 if (get_user(uval, uaddr))
1367 return -EFAULT;
1368 /*
1369 * We release only a lock we actually own:
1370 */
1371 if ((uval & FUTEX_TID_MASK) != current->pid)
1372 return -EPERM;
1373 /*
1374 * First take all the futex related locks:
1375 */
1376 down_read(&current->mm->mmap_sem);
1377
1378 ret = get_futex_key(uaddr, &key);
1379 if (unlikely(ret != 0))
1380 goto out;
1381
1382 hb = hash_futex(&key);
1383 spin_lock(&hb->lock);
1384
1385retry_locked:
1386 /*
1387 * To avoid races, try to do the TID -> 0 atomic transition
1388 * again. If it succeeds then we can return without waking
1389 * anyone else up:
1390 */
e3f2ddea 1391 if (!(uval & FUTEX_OWNER_DIED)) {
a866374a 1392 pagefault_disable();
e3f2ddea 1393 uval = futex_atomic_cmpxchg_inatomic(uaddr, current->pid, 0);
a866374a 1394 pagefault_enable();
e3f2ddea 1395 }
c87e2837
IM
1396
1397 if (unlikely(uval == -EFAULT))
1398 goto pi_faulted;
1399 /*
1400 * Rare case: we managed to release the lock atomically,
1401 * no need to wake anyone else up:
1402 */
1403 if (unlikely(uval == current->pid))
1404 goto out_unlock;
1405
1406 /*
1407 * Ok, other tasks may need to be woken up - check waiters
1408 * and do the wakeup if necessary:
1409 */
1410 head = &hb->chain;
1411
1412 list_for_each_entry_safe(this, next, head, list) {
1413 if (!match_futex (&this->key, &key))
1414 continue;
1415 ret = wake_futex_pi(uaddr, uval, this);
1416 /*
1417 * The atomic access to the futex value
1418 * generated a pagefault, so retry the
1419 * user-access and the wakeup:
1420 */
1421 if (ret == -EFAULT)
1422 goto pi_faulted;
1423 goto out_unlock;
1424 }
1425 /*
1426 * No waiters - kernel unlocks the futex:
1427 */
e3f2ddea
IM
1428 if (!(uval & FUTEX_OWNER_DIED)) {
1429 ret = unlock_futex_pi(uaddr, uval);
1430 if (ret == -EFAULT)
1431 goto pi_faulted;
1432 }
c87e2837
IM
1433
1434out_unlock:
1435 spin_unlock(&hb->lock);
1436out:
1437 up_read(&current->mm->mmap_sem);
1438
1439 return ret;
1440
1441pi_faulted:
1442 /*
1443 * We have to r/w *(int __user *)uaddr, but we can't modify it
1444 * non-atomically. Therefore, if get_user below is not
1445 * enough, we need to handle the fault ourselves, while
1446 * still holding the mmap_sem.
1447 */
1448 if (attempt++) {
e579dcbf 1449 if (futex_handle_fault((unsigned long)uaddr, attempt)) {
1450 ret = -EFAULT;
c87e2837 1451 goto out_unlock;
e579dcbf 1452 }
c87e2837
IM
1453 goto retry_locked;
1454 }
1455
1456 spin_unlock(&hb->lock);
1da177e4 1457 up_read(&current->mm->mmap_sem);
c87e2837
IM
1458
1459 ret = get_user(uval, uaddr);
1460 if (!ret && (uval != -EFAULT))
1461 goto retry;
1462
1da177e4
LT
1463 return ret;
1464}
1465
1466static int futex_close(struct inode *inode, struct file *filp)
1467{
1468 struct futex_q *q = filp->private_data;
1469
1470 unqueue_me(q);
1471 kfree(q);
e2970f2f 1472
1da177e4
LT
1473 return 0;
1474}
1475
1476/* This is one-shot: once it's gone off you need a new fd */
1477static unsigned int futex_poll(struct file *filp,
1478 struct poll_table_struct *wait)
1479{
1480 struct futex_q *q = filp->private_data;
1481 int ret = 0;
1482
1483 poll_wait(filp, &q->waiters, wait);
1484
1485 /*
1486 * list_empty() is safe here without any lock.
1487 * q->lock_ptr != 0 is not safe, because of ordering against wakeup.
1488 */
1489 if (list_empty(&q->list))
1490 ret = POLLIN | POLLRDNORM;
1491
1492 return ret;
1493}
1494
15ad7cdc 1495static const struct file_operations futex_fops = {
1da177e4
LT
1496 .release = futex_close,
1497 .poll = futex_poll,
1498};
1499
1500/*
1501 * Signal allows caller to avoid the race which would occur if they
1502 * set the sigio stuff up afterwards.
1503 */
e2970f2f 1504static int futex_fd(u32 __user *uaddr, int signal)
1da177e4
LT
1505{
1506 struct futex_q *q;
1507 struct file *filp;
1508 int ret, err;
19c6b6ed
AM
1509 static unsigned long printk_interval;
1510
1511 if (printk_timed_ratelimit(&printk_interval, 60 * 60 * 1000)) {
1512 printk(KERN_WARNING "Process `%s' used FUTEX_FD, which "
1513 "will be removed from the kernel in June 2007\n",
1514 current->comm);
1515 }
1da177e4
LT
1516
1517 ret = -EINVAL;
7ed20e1a 1518 if (!valid_signal(signal))
1da177e4
LT
1519 goto out;
1520
1521 ret = get_unused_fd();
1522 if (ret < 0)
1523 goto out;
1524 filp = get_empty_filp();
1525 if (!filp) {
1526 put_unused_fd(ret);
1527 ret = -ENFILE;
1528 goto out;
1529 }
1530 filp->f_op = &futex_fops;
f3a43f3f
JJS
1531 filp->f_path.mnt = mntget(futex_mnt);
1532 filp->f_path.dentry = dget(futex_mnt->mnt_root);
1533 filp->f_mapping = filp->f_path.dentry->d_inode->i_mapping;
1da177e4
LT
1534
1535 if (signal) {
609d7fa9 1536 err = __f_setown(filp, task_pid(current), PIDTYPE_PID, 1);
1da177e4 1537 if (err < 0) {
39ed3fde 1538 goto error;
1da177e4
LT
1539 }
1540 filp->f_owner.signum = signal;
1541 }
1542
1543 q = kmalloc(sizeof(*q), GFP_KERNEL);
1544 if (!q) {
39ed3fde
PE
1545 err = -ENOMEM;
1546 goto error;
1da177e4 1547 }
c87e2837 1548 q->pi_state = NULL;
1da177e4
LT
1549
1550 down_read(&current->mm->mmap_sem);
1551 err = get_futex_key(uaddr, &q->key);
1552
1553 if (unlikely(err != 0)) {
1554 up_read(&current->mm->mmap_sem);
1da177e4 1555 kfree(q);
39ed3fde 1556 goto error;
1da177e4
LT
1557 }
1558
1559 /*
1560 * queue_me() must be called before releasing mmap_sem, because
1561 * key->shared.inode needs to be referenced while holding it.
1562 */
1563 filp->private_data = q;
1564
1565 queue_me(q, ret, filp);
1566 up_read(&current->mm->mmap_sem);
1567
1568 /* Now we map fd to filp, so userspace can access it */
1569 fd_install(ret, filp);
1570out:
1571 return ret;
39ed3fde
PE
1572error:
1573 put_unused_fd(ret);
1574 put_filp(filp);
1575 ret = err;
1576 goto out;
1da177e4
LT
1577}
1578
0771dfef
IM
1579/*
1580 * Support for robust futexes: the kernel cleans up held futexes at
1581 * thread exit time.
1582 *
1583 * Implementation: user-space maintains a per-thread list of locks it
1584 * is holding. Upon do_exit(), the kernel carefully walks this list,
1585 * and marks all locks that are owned by this thread with the
c87e2837 1586 * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is
0771dfef
IM
1587 * always manipulated with the lock held, so the list is private and
1588 * per-thread. Userspace also maintains a per-thread 'list_op_pending'
1589 * field, to allow the kernel to clean up if the thread dies after
1590 * acquiring the lock, but just before it could have added itself to
1591 * the list. There can only be one such pending lock.
1592 */
1593
1594/**
1595 * sys_set_robust_list - set the robust-futex list head of a task
1596 * @head: pointer to the list-head
1597 * @len: length of the list-head, as userspace expects
1598 */
1599asmlinkage long
1600sys_set_robust_list(struct robust_list_head __user *head,
1601 size_t len)
1602{
1603 /*
1604 * The kernel knows only one size for now:
1605 */
1606 if (unlikely(len != sizeof(*head)))
1607 return -EINVAL;
1608
1609 current->robust_list = head;
1610
1611 return 0;
1612}
1613
1614/**
1615 * sys_get_robust_list - get the robust-futex list head of a task
1616 * @pid: pid of the process [zero for current task]
1617 * @head_ptr: pointer to a list-head pointer, the kernel fills it in
1618 * @len_ptr: pointer to a length field, the kernel fills in the header size
1619 */
1620asmlinkage long
ba46df98 1621sys_get_robust_list(int pid, struct robust_list_head __user * __user *head_ptr,
0771dfef
IM
1622 size_t __user *len_ptr)
1623{
ba46df98 1624 struct robust_list_head __user *head;
0771dfef
IM
1625 unsigned long ret;
1626
1627 if (!pid)
1628 head = current->robust_list;
1629 else {
1630 struct task_struct *p;
1631
1632 ret = -ESRCH;
aaa2a97e 1633 rcu_read_lock();
0771dfef
IM
1634 p = find_task_by_pid(pid);
1635 if (!p)
1636 goto err_unlock;
1637 ret = -EPERM;
1638 if ((current->euid != p->euid) && (current->euid != p->uid) &&
1639 !capable(CAP_SYS_PTRACE))
1640 goto err_unlock;
1641 head = p->robust_list;
aaa2a97e 1642 rcu_read_unlock();
0771dfef
IM
1643 }
1644
1645 if (put_user(sizeof(*head), len_ptr))
1646 return -EFAULT;
1647 return put_user(head, head_ptr);
1648
1649err_unlock:
aaa2a97e 1650 rcu_read_unlock();
0771dfef
IM
1651
1652 return ret;
1653}
1654
1655/*
1656 * Process a futex-list entry, check whether it's owned by the
1657 * dying task, and do notification if so:
1658 */
e3f2ddea 1659int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi)
0771dfef 1660{
e3f2ddea 1661 u32 uval, nval, mval;
0771dfef 1662
8f17d3a5
IM
1663retry:
1664 if (get_user(uval, uaddr))
0771dfef
IM
1665 return -1;
1666
8f17d3a5 1667 if ((uval & FUTEX_TID_MASK) == curr->pid) {
0771dfef
IM
1668 /*
1669 * Ok, this dying thread is truly holding a futex
1670 * of interest. Set the OWNER_DIED bit atomically
1671 * via cmpxchg, and if the value had FUTEX_WAITERS
1672 * set, wake up a waiter (if any). (We have to do a
1673 * futex_wake() even if OWNER_DIED is already set -
1674 * to handle the rare but possible case of recursive
1675 * thread-death.) The rest of the cleanup is done in
1676 * userspace.
1677 */
e3f2ddea
IM
1678 mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED;
1679 nval = futex_atomic_cmpxchg_inatomic(uaddr, uval, mval);
1680
c87e2837
IM
1681 if (nval == -EFAULT)
1682 return -1;
1683
1684 if (nval != uval)
8f17d3a5 1685 goto retry;
0771dfef 1686
e3f2ddea
IM
1687 /*
1688 * Wake robust non-PI futexes here. The wakeup of
1689 * PI futexes happens in exit_pi_state():
1690 */
1691 if (!pi) {
1692 if (uval & FUTEX_WAITERS)
1693 futex_wake(uaddr, 1);
1694 }
0771dfef
IM
1695 }
1696 return 0;
1697}
1698
e3f2ddea
IM
1699/*
1700 * Fetch a robust-list pointer. Bit 0 signals PI futexes:
1701 */
1702static inline int fetch_robust_entry(struct robust_list __user **entry,
ba46df98
AV
1703 struct robust_list __user * __user *head,
1704 int *pi)
e3f2ddea
IM
1705{
1706 unsigned long uentry;
1707
ba46df98 1708 if (get_user(uentry, (unsigned long __user *)head))
e3f2ddea
IM
1709 return -EFAULT;
1710
ba46df98 1711 *entry = (void __user *)(uentry & ~1UL);
e3f2ddea
IM
1712 *pi = uentry & 1;
1713
1714 return 0;
1715}
1716
0771dfef
IM
1717/*
1718 * Walk curr->robust_list (very carefully, it's a userspace list!)
1719 * and mark any locks found there dead, and notify any waiters.
1720 *
1721 * We silently return on any sign of list-walking problem.
1722 */
1723void exit_robust_list(struct task_struct *curr)
1724{
1725 struct robust_list_head __user *head = curr->robust_list;
1726 struct robust_list __user *entry, *pending;
e3f2ddea 1727 unsigned int limit = ROBUST_LIST_LIMIT, pi, pip;
0771dfef
IM
1728 unsigned long futex_offset;
1729
1730 /*
1731 * Fetch the list head (which was registered earlier, via
1732 * sys_set_robust_list()):
1733 */
e3f2ddea 1734 if (fetch_robust_entry(&entry, &head->list.next, &pi))
0771dfef
IM
1735 return;
1736 /*
1737 * Fetch the relative futex offset:
1738 */
1739 if (get_user(futex_offset, &head->futex_offset))
1740 return;
1741 /*
1742 * Fetch any possibly pending lock-add first, and handle it
1743 * if it exists:
1744 */
e3f2ddea 1745 if (fetch_robust_entry(&pending, &head->list_op_pending, &pip))
0771dfef 1746 return;
e3f2ddea 1747
0771dfef 1748 if (pending)
ba46df98 1749 handle_futex_death((void __user *)pending + futex_offset, curr, pip);
0771dfef
IM
1750
1751 while (entry != &head->list) {
1752 /*
1753 * A pending lock might already be on the list, so
c87e2837 1754 * don't process it twice:
0771dfef
IM
1755 */
1756 if (entry != pending)
ba46df98 1757 if (handle_futex_death((void __user *)entry + futex_offset,
e3f2ddea 1758 curr, pi))
0771dfef 1759 return;
0771dfef
IM
1760 /*
1761 * Fetch the next entry in the list:
1762 */
e3f2ddea 1763 if (fetch_robust_entry(&entry, &entry->next, &pi))
0771dfef
IM
1764 return;
1765 /*
1766 * Avoid excessively long or circular lists:
1767 */
1768 if (!--limit)
1769 break;
1770
1771 cond_resched();
1772 }
1773}
1774
e2970f2f
IM
1775long do_futex(u32 __user *uaddr, int op, u32 val, unsigned long timeout,
1776 u32 __user *uaddr2, u32 val2, u32 val3)
1da177e4
LT
1777{
1778 int ret;
1779
1780 switch (op) {
1781 case FUTEX_WAIT:
1782 ret = futex_wait(uaddr, val, timeout);
1783 break;
1784 case FUTEX_WAKE:
1785 ret = futex_wake(uaddr, val);
1786 break;
1787 case FUTEX_FD:
1788 /* non-zero val means F_SETOWN(getpid()) & F_SETSIG(val) */
1789 ret = futex_fd(uaddr, val);
1790 break;
1791 case FUTEX_REQUEUE:
1792 ret = futex_requeue(uaddr, uaddr2, val, val2, NULL);
1793 break;
1794 case FUTEX_CMP_REQUEUE:
1795 ret = futex_requeue(uaddr, uaddr2, val, val2, &val3);
1796 break;
4732efbe
JJ
1797 case FUTEX_WAKE_OP:
1798 ret = futex_wake_op(uaddr, uaddr2, val, val2, val3);
1799 break;
c87e2837
IM
1800 case FUTEX_LOCK_PI:
1801 ret = futex_lock_pi(uaddr, val, timeout, val2, 0);
1802 break;
1803 case FUTEX_UNLOCK_PI:
1804 ret = futex_unlock_pi(uaddr);
1805 break;
1806 case FUTEX_TRYLOCK_PI:
1807 ret = futex_lock_pi(uaddr, 0, timeout, val2, 1);
1808 break;
1da177e4
LT
1809 default:
1810 ret = -ENOSYS;
1811 }
1812 return ret;
1813}
1814
1815
e2970f2f 1816asmlinkage long sys_futex(u32 __user *uaddr, int op, u32 val,
1da177e4 1817 struct timespec __user *utime, u32 __user *uaddr2,
e2970f2f 1818 u32 val3)
1da177e4
LT
1819{
1820 struct timespec t;
1821 unsigned long timeout = MAX_SCHEDULE_TIMEOUT;
e2970f2f 1822 u32 val2 = 0;
1da177e4 1823
c87e2837 1824 if (utime && (op == FUTEX_WAIT || op == FUTEX_LOCK_PI)) {
1da177e4
LT
1825 if (copy_from_user(&t, utime, sizeof(t)) != 0)
1826 return -EFAULT;
9741ef96
TG
1827 if (!timespec_valid(&t))
1828 return -EINVAL;
c87e2837
IM
1829 if (op == FUTEX_WAIT)
1830 timeout = timespec_to_jiffies(&t) + 1;
1831 else {
1832 timeout = t.tv_sec;
1833 val2 = t.tv_nsec;
1834 }
1da177e4
LT
1835 }
1836 /*
1837 * requeue parameter in 'utime' if op == FUTEX_REQUEUE.
1838 */
c87e2837 1839 if (op == FUTEX_REQUEUE || op == FUTEX_CMP_REQUEUE)
e2970f2f 1840 val2 = (u32) (unsigned long) utime;
1da177e4 1841
e2970f2f 1842 return do_futex(uaddr, op, val, timeout, uaddr2, val2, val3);
1da177e4
LT
1843}
1844
454e2398
DH
1845static int futexfs_get_sb(struct file_system_type *fs_type,
1846 int flags, const char *dev_name, void *data,
1847 struct vfsmount *mnt)
1da177e4 1848{
454e2398 1849 return get_sb_pseudo(fs_type, "futex", NULL, 0xBAD1DEA, mnt);
1da177e4
LT
1850}
1851
1852static struct file_system_type futex_fs_type = {
1853 .name = "futexfs",
1854 .get_sb = futexfs_get_sb,
1855 .kill_sb = kill_anon_super,
1856};
1857
1858static int __init init(void)
1859{
95362fa9
AM
1860 int i = register_filesystem(&futex_fs_type);
1861
1862 if (i)
1863 return i;
1da177e4 1864
1da177e4 1865 futex_mnt = kern_mount(&futex_fs_type);
95362fa9
AM
1866 if (IS_ERR(futex_mnt)) {
1867 unregister_filesystem(&futex_fs_type);
1868 return PTR_ERR(futex_mnt);
1869 }
1da177e4
LT
1870
1871 for (i = 0; i < ARRAY_SIZE(futex_queues); i++) {
1872 INIT_LIST_HEAD(&futex_queues[i].chain);
1873 spin_lock_init(&futex_queues[i].lock);
1874 }
1875 return 0;
1876}
1877__initcall(init);