Contents of /alx-src/tags/kernel26-2.6.12-alx-r9/kernel/futex.c
Parent Directory | Revision Log
Revision 630 -
(show annotations)
(download)
Wed Mar 4 11:03:09 2009 UTC (15 years, 6 months ago) by niro
File MIME type: text/plain
File size: 19796 byte(s)
Wed Mar 4 11:03:09 2009 UTC (15 years, 6 months ago) by niro
File MIME type: text/plain
File size: 19796 byte(s)
Tag kernel26-2.6.12-alx-r9
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 | * Thanks to Ben LaHaise for yelling "hashed waitqueues" loudly |
12 | * enough at me, Linus for the original (flawed) idea, Matthew |
13 | * Kirkwood for proof-of-concept implementation. |
14 | * |
15 | * "The futexes are also cursed." |
16 | * "But they come in a choice of three flavours!" |
17 | * |
18 | * This program is free software; you can redistribute it and/or modify |
19 | * it under the terms of the GNU General Public License as published by |
20 | * the Free Software Foundation; either version 2 of the License, or |
21 | * (at your option) any later version. |
22 | * |
23 | * This program is distributed in the hope that it will be useful, |
24 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
25 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
26 | * GNU General Public License for more details. |
27 | * |
28 | * You should have received a copy of the GNU General Public License |
29 | * along with this program; if not, write to the Free Software |
30 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
31 | */ |
32 | #include <linux/slab.h> |
33 | #include <linux/poll.h> |
34 | #include <linux/fs.h> |
35 | #include <linux/file.h> |
36 | #include <linux/jhash.h> |
37 | #include <linux/init.h> |
38 | #include <linux/futex.h> |
39 | #include <linux/mount.h> |
40 | #include <linux/pagemap.h> |
41 | #include <linux/syscalls.h> |
42 | #include <linux/signal.h> |
43 | |
44 | #define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8) |
45 | |
46 | /* |
47 | * Futexes are matched on equal values of this key. |
48 | * The key type depends on whether it's a shared or private mapping. |
49 | * Don't rearrange members without looking at hash_futex(). |
50 | * |
51 | * offset is aligned to a multiple of sizeof(u32) (== 4) by definition. |
52 | * We set bit 0 to indicate if it's an inode-based key. |
53 | */ |
54 | union futex_key { |
55 | struct { |
56 | unsigned long pgoff; |
57 | struct inode *inode; |
58 | int offset; |
59 | } shared; |
60 | struct { |
61 | unsigned long uaddr; |
62 | struct mm_struct *mm; |
63 | int offset; |
64 | } private; |
65 | struct { |
66 | unsigned long word; |
67 | void *ptr; |
68 | int offset; |
69 | } both; |
70 | }; |
71 | |
72 | /* |
73 | * We use this hashed waitqueue instead of a normal wait_queue_t, so |
74 | * we can wake only the relevant ones (hashed queues may be shared). |
75 | * |
76 | * A futex_q has a woken state, just like tasks have TASK_RUNNING. |
77 | * It is considered woken when list_empty(&q->list) || q->lock_ptr == 0. |
78 | * The order of wakup is always to make the first condition true, then |
79 | * wake up q->waiters, then make the second condition true. |
80 | */ |
81 | struct futex_q { |
82 | struct list_head list; |
83 | wait_queue_head_t waiters; |
84 | |
85 | /* Which hash list lock to use. */ |
86 | spinlock_t *lock_ptr; |
87 | |
88 | /* Key which the futex is hashed on. */ |
89 | union futex_key key; |
90 | |
91 | /* For fd, sigio sent using these. */ |
92 | int fd; |
93 | struct file *filp; |
94 | }; |
95 | |
96 | /* |
97 | * Split the global futex_lock into every hash list lock. |
98 | */ |
99 | struct futex_hash_bucket { |
100 | spinlock_t lock; |
101 | struct list_head chain; |
102 | }; |
103 | |
104 | static struct futex_hash_bucket futex_queues[1<<FUTEX_HASHBITS]; |
105 | |
106 | /* Futex-fs vfsmount entry: */ |
107 | static struct vfsmount *futex_mnt; |
108 | |
109 | /* |
110 | * We hash on the keys returned from get_futex_key (see below). |
111 | */ |
112 | static struct futex_hash_bucket *hash_futex(union futex_key *key) |
113 | { |
114 | u32 hash = jhash2((u32*)&key->both.word, |
115 | (sizeof(key->both.word)+sizeof(key->both.ptr))/4, |
116 | key->both.offset); |
117 | return &futex_queues[hash & ((1 << FUTEX_HASHBITS)-1)]; |
118 | } |
119 | |
120 | /* |
121 | * Return 1 if two futex_keys are equal, 0 otherwise. |
122 | */ |
123 | static inline int match_futex(union futex_key *key1, union futex_key *key2) |
124 | { |
125 | return (key1->both.word == key2->both.word |
126 | && key1->both.ptr == key2->both.ptr |
127 | && key1->both.offset == key2->both.offset); |
128 | } |
129 | |
130 | /* |
131 | * Get parameters which are the keys for a futex. |
132 | * |
133 | * For shared mappings, it's (page->index, vma->vm_file->f_dentry->d_inode, |
134 | * offset_within_page). For private mappings, it's (uaddr, current->mm). |
135 | * We can usually work out the index without swapping in the page. |
136 | * |
137 | * Returns: 0, or negative error code. |
138 | * The key words are stored in *key on success. |
139 | * |
140 | * Should be called with ¤t->mm->mmap_sem but NOT any spinlocks. |
141 | */ |
142 | static int get_futex_key(unsigned long uaddr, union futex_key *key) |
143 | { |
144 | struct mm_struct *mm = current->mm; |
145 | struct vm_area_struct *vma; |
146 | struct page *page; |
147 | int err; |
148 | |
149 | /* |
150 | * The futex address must be "naturally" aligned. |
151 | */ |
152 | key->both.offset = uaddr % PAGE_SIZE; |
153 | if (unlikely((key->both.offset % sizeof(u32)) != 0)) |
154 | return -EINVAL; |
155 | uaddr -= key->both.offset; |
156 | |
157 | /* |
158 | * The futex is hashed differently depending on whether |
159 | * it's in a shared or private mapping. So check vma first. |
160 | */ |
161 | vma = find_extend_vma(mm, uaddr); |
162 | if (unlikely(!vma)) |
163 | return -EFAULT; |
164 | |
165 | /* |
166 | * Permissions. |
167 | */ |
168 | if (unlikely((vma->vm_flags & (VM_IO|VM_READ)) != VM_READ)) |
169 | return (vma->vm_flags & VM_IO) ? -EPERM : -EACCES; |
170 | |
171 | /* |
172 | * Private mappings are handled in a simple way. |
173 | * |
174 | * NOTE: When userspace waits on a MAP_SHARED mapping, even if |
175 | * it's a read-only handle, it's expected that futexes attach to |
176 | * the object not the particular process. Therefore we use |
177 | * VM_MAYSHARE here, not VM_SHARED which is restricted to shared |
178 | * mappings of _writable_ handles. |
179 | */ |
180 | if (likely(!(vma->vm_flags & VM_MAYSHARE))) { |
181 | key->private.mm = mm; |
182 | key->private.uaddr = uaddr; |
183 | return 0; |
184 | } |
185 | |
186 | /* |
187 | * Linear file mappings are also simple. |
188 | */ |
189 | key->shared.inode = vma->vm_file->f_dentry->d_inode; |
190 | key->both.offset++; /* Bit 0 of offset indicates inode-based key. */ |
191 | if (likely(!(vma->vm_flags & VM_NONLINEAR))) { |
192 | key->shared.pgoff = (((uaddr - vma->vm_start) >> PAGE_SHIFT) |
193 | + vma->vm_pgoff); |
194 | return 0; |
195 | } |
196 | |
197 | /* |
198 | * We could walk the page table to read the non-linear |
199 | * pte, and get the page index without fetching the page |
200 | * from swap. But that's a lot of code to duplicate here |
201 | * for a rare case, so we simply fetch the page. |
202 | */ |
203 | |
204 | /* |
205 | * Do a quick atomic lookup first - this is the fastpath. |
206 | */ |
207 | spin_lock(¤t->mm->page_table_lock); |
208 | page = follow_page(mm, uaddr, 0); |
209 | if (likely(page != NULL)) { |
210 | key->shared.pgoff = |
211 | page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); |
212 | spin_unlock(¤t->mm->page_table_lock); |
213 | return 0; |
214 | } |
215 | spin_unlock(¤t->mm->page_table_lock); |
216 | |
217 | /* |
218 | * Do it the general way. |
219 | */ |
220 | err = get_user_pages(current, mm, uaddr, 1, 0, 0, &page, NULL); |
221 | if (err >= 0) { |
222 | key->shared.pgoff = |
223 | page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); |
224 | put_page(page); |
225 | return 0; |
226 | } |
227 | return err; |
228 | } |
229 | |
230 | /* |
231 | * Take a reference to the resource addressed by a key. |
232 | * Can be called while holding spinlocks. |
233 | * |
234 | * NOTE: mmap_sem MUST be held between get_futex_key() and calling this |
235 | * function, if it is called at all. mmap_sem keeps key->shared.inode valid. |
236 | */ |
237 | static inline void get_key_refs(union futex_key *key) |
238 | { |
239 | if (key->both.ptr != 0) { |
240 | if (key->both.offset & 1) |
241 | atomic_inc(&key->shared.inode->i_count); |
242 | else |
243 | atomic_inc(&key->private.mm->mm_count); |
244 | } |
245 | } |
246 | |
247 | /* |
248 | * Drop a reference to the resource addressed by a key. |
249 | * The hash bucket spinlock must not be held. |
250 | */ |
251 | static void drop_key_refs(union futex_key *key) |
252 | { |
253 | if (key->both.ptr != 0) { |
254 | if (key->both.offset & 1) |
255 | iput(key->shared.inode); |
256 | else |
257 | mmdrop(key->private.mm); |
258 | } |
259 | } |
260 | |
261 | static inline int get_futex_value_locked(int *dest, int __user *from) |
262 | { |
263 | int ret; |
264 | |
265 | inc_preempt_count(); |
266 | ret = __copy_from_user_inatomic(dest, from, sizeof(int)); |
267 | dec_preempt_count(); |
268 | |
269 | return ret ? -EFAULT : 0; |
270 | } |
271 | |
272 | /* |
273 | * The hash bucket lock must be held when this is called. |
274 | * Afterwards, the futex_q must not be accessed. |
275 | */ |
276 | static void wake_futex(struct futex_q *q) |
277 | { |
278 | list_del_init(&q->list); |
279 | if (q->filp) |
280 | send_sigio(&q->filp->f_owner, q->fd, POLL_IN); |
281 | /* |
282 | * The lock in wake_up_all() is a crucial memory barrier after the |
283 | * list_del_init() and also before assigning to q->lock_ptr. |
284 | */ |
285 | wake_up_all(&q->waiters); |
286 | /* |
287 | * The waiting task can free the futex_q as soon as this is written, |
288 | * without taking any locks. This must come last. |
289 | */ |
290 | q->lock_ptr = NULL; |
291 | } |
292 | |
293 | /* |
294 | * Wake up all waiters hashed on the physical page that is mapped |
295 | * to this virtual address: |
296 | */ |
297 | static int futex_wake(unsigned long uaddr, int nr_wake) |
298 | { |
299 | union futex_key key; |
300 | struct futex_hash_bucket *bh; |
301 | struct list_head *head; |
302 | struct futex_q *this, *next; |
303 | int ret; |
304 | |
305 | down_read(¤t->mm->mmap_sem); |
306 | |
307 | ret = get_futex_key(uaddr, &key); |
308 | if (unlikely(ret != 0)) |
309 | goto out; |
310 | |
311 | bh = hash_futex(&key); |
312 | spin_lock(&bh->lock); |
313 | head = &bh->chain; |
314 | |
315 | list_for_each_entry_safe(this, next, head, list) { |
316 | if (match_futex (&this->key, &key)) { |
317 | wake_futex(this); |
318 | if (++ret >= nr_wake) |
319 | break; |
320 | } |
321 | } |
322 | |
323 | spin_unlock(&bh->lock); |
324 | out: |
325 | up_read(¤t->mm->mmap_sem); |
326 | return ret; |
327 | } |
328 | |
329 | /* |
330 | * Requeue all waiters hashed on one physical page to another |
331 | * physical page. |
332 | */ |
333 | static int futex_requeue(unsigned long uaddr1, unsigned long uaddr2, |
334 | int nr_wake, int nr_requeue, int *valp) |
335 | { |
336 | union futex_key key1, key2; |
337 | struct futex_hash_bucket *bh1, *bh2; |
338 | struct list_head *head1; |
339 | struct futex_q *this, *next; |
340 | int ret, drop_count = 0; |
341 | |
342 | retry: |
343 | down_read(¤t->mm->mmap_sem); |
344 | |
345 | ret = get_futex_key(uaddr1, &key1); |
346 | if (unlikely(ret != 0)) |
347 | goto out; |
348 | ret = get_futex_key(uaddr2, &key2); |
349 | if (unlikely(ret != 0)) |
350 | goto out; |
351 | |
352 | bh1 = hash_futex(&key1); |
353 | bh2 = hash_futex(&key2); |
354 | |
355 | if (bh1 < bh2) |
356 | spin_lock(&bh1->lock); |
357 | spin_lock(&bh2->lock); |
358 | if (bh1 > bh2) |
359 | spin_lock(&bh1->lock); |
360 | |
361 | if (likely(valp != NULL)) { |
362 | int curval; |
363 | |
364 | ret = get_futex_value_locked(&curval, (int __user *)uaddr1); |
365 | |
366 | if (unlikely(ret)) { |
367 | spin_unlock(&bh1->lock); |
368 | if (bh1 != bh2) |
369 | spin_unlock(&bh2->lock); |
370 | |
371 | /* If we would have faulted, release mmap_sem, fault |
372 | * it in and start all over again. |
373 | */ |
374 | up_read(¤t->mm->mmap_sem); |
375 | |
376 | ret = get_user(curval, (int __user *)uaddr1); |
377 | |
378 | if (!ret) |
379 | goto retry; |
380 | |
381 | return ret; |
382 | } |
383 | if (curval != *valp) { |
384 | ret = -EAGAIN; |
385 | goto out_unlock; |
386 | } |
387 | } |
388 | |
389 | head1 = &bh1->chain; |
390 | list_for_each_entry_safe(this, next, head1, list) { |
391 | if (!match_futex (&this->key, &key1)) |
392 | continue; |
393 | if (++ret <= nr_wake) { |
394 | wake_futex(this); |
395 | } else { |
396 | list_move_tail(&this->list, &bh2->chain); |
397 | this->lock_ptr = &bh2->lock; |
398 | this->key = key2; |
399 | get_key_refs(&key2); |
400 | drop_count++; |
401 | |
402 | if (ret - nr_wake >= nr_requeue) |
403 | break; |
404 | /* Make sure to stop if key1 == key2 */ |
405 | if (head1 == &bh2->chain && head1 != &next->list) |
406 | head1 = &this->list; |
407 | } |
408 | } |
409 | |
410 | out_unlock: |
411 | spin_unlock(&bh1->lock); |
412 | if (bh1 != bh2) |
413 | spin_unlock(&bh2->lock); |
414 | |
415 | /* drop_key_refs() must be called outside the spinlocks. */ |
416 | while (--drop_count >= 0) |
417 | drop_key_refs(&key1); |
418 | |
419 | out: |
420 | up_read(¤t->mm->mmap_sem); |
421 | return ret; |
422 | } |
423 | |
424 | /* The key must be already stored in q->key. */ |
425 | static inline struct futex_hash_bucket * |
426 | queue_lock(struct futex_q *q, int fd, struct file *filp) |
427 | { |
428 | struct futex_hash_bucket *bh; |
429 | |
430 | q->fd = fd; |
431 | q->filp = filp; |
432 | |
433 | init_waitqueue_head(&q->waiters); |
434 | |
435 | get_key_refs(&q->key); |
436 | bh = hash_futex(&q->key); |
437 | q->lock_ptr = &bh->lock; |
438 | |
439 | spin_lock(&bh->lock); |
440 | return bh; |
441 | } |
442 | |
443 | static inline void __queue_me(struct futex_q *q, struct futex_hash_bucket *bh) |
444 | { |
445 | list_add_tail(&q->list, &bh->chain); |
446 | spin_unlock(&bh->lock); |
447 | } |
448 | |
449 | static inline void |
450 | queue_unlock(struct futex_q *q, struct futex_hash_bucket *bh) |
451 | { |
452 | spin_unlock(&bh->lock); |
453 | drop_key_refs(&q->key); |
454 | } |
455 | |
456 | /* |
457 | * queue_me and unqueue_me must be called as a pair, each |
458 | * exactly once. They are called with the hashed spinlock held. |
459 | */ |
460 | |
461 | /* The key must be already stored in q->key. */ |
462 | static void queue_me(struct futex_q *q, int fd, struct file *filp) |
463 | { |
464 | struct futex_hash_bucket *bh; |
465 | bh = queue_lock(q, fd, filp); |
466 | __queue_me(q, bh); |
467 | } |
468 | |
469 | /* Return 1 if we were still queued (ie. 0 means we were woken) */ |
470 | static int unqueue_me(struct futex_q *q) |
471 | { |
472 | int ret = 0; |
473 | spinlock_t *lock_ptr; |
474 | |
475 | /* In the common case we don't take the spinlock, which is nice. */ |
476 | retry: |
477 | lock_ptr = q->lock_ptr; |
478 | if (lock_ptr != 0) { |
479 | spin_lock(lock_ptr); |
480 | /* |
481 | * q->lock_ptr can change between reading it and |
482 | * spin_lock(), causing us to take the wrong lock. This |
483 | * corrects the race condition. |
484 | * |
485 | * Reasoning goes like this: if we have the wrong lock, |
486 | * q->lock_ptr must have changed (maybe several times) |
487 | * between reading it and the spin_lock(). It can |
488 | * change again after the spin_lock() but only if it was |
489 | * already changed before the spin_lock(). It cannot, |
490 | * however, change back to the original value. Therefore |
491 | * we can detect whether we acquired the correct lock. |
492 | */ |
493 | if (unlikely(lock_ptr != q->lock_ptr)) { |
494 | spin_unlock(lock_ptr); |
495 | goto retry; |
496 | } |
497 | WARN_ON(list_empty(&q->list)); |
498 | list_del(&q->list); |
499 | spin_unlock(lock_ptr); |
500 | ret = 1; |
501 | } |
502 | |
503 | drop_key_refs(&q->key); |
504 | return ret; |
505 | } |
506 | |
507 | static int futex_wait(unsigned long uaddr, int val, unsigned long time) |
508 | { |
509 | DECLARE_WAITQUEUE(wait, current); |
510 | int ret, curval; |
511 | struct futex_q q; |
512 | struct futex_hash_bucket *bh; |
513 | |
514 | retry: |
515 | down_read(¤t->mm->mmap_sem); |
516 | |
517 | ret = get_futex_key(uaddr, &q.key); |
518 | if (unlikely(ret != 0)) |
519 | goto out_release_sem; |
520 | |
521 | bh = queue_lock(&q, -1, NULL); |
522 | |
523 | /* |
524 | * Access the page AFTER the futex is queued. |
525 | * Order is important: |
526 | * |
527 | * Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val); |
528 | * Userspace waker: if (cond(var)) { var = new; futex_wake(&var); } |
529 | * |
530 | * The basic logical guarantee of a futex is that it blocks ONLY |
531 | * if cond(var) is known to be true at the time of blocking, for |
532 | * any cond. If we queued after testing *uaddr, that would open |
533 | * a race condition where we could block indefinitely with |
534 | * cond(var) false, which would violate the guarantee. |
535 | * |
536 | * A consequence is that futex_wait() can return zero and absorb |
537 | * a wakeup when *uaddr != val on entry to the syscall. This is |
538 | * rare, but normal. |
539 | * |
540 | * We hold the mmap semaphore, so the mapping cannot have changed |
541 | * since we looked it up in get_futex_key. |
542 | */ |
543 | |
544 | ret = get_futex_value_locked(&curval, (int __user *)uaddr); |
545 | |
546 | if (unlikely(ret)) { |
547 | queue_unlock(&q, bh); |
548 | |
549 | /* If we would have faulted, release mmap_sem, fault it in and |
550 | * start all over again. |
551 | */ |
552 | up_read(¤t->mm->mmap_sem); |
553 | |
554 | ret = get_user(curval, (int __user *)uaddr); |
555 | |
556 | if (!ret) |
557 | goto retry; |
558 | return ret; |
559 | } |
560 | if (curval != val) { |
561 | ret = -EWOULDBLOCK; |
562 | queue_unlock(&q, bh); |
563 | goto out_release_sem; |
564 | } |
565 | |
566 | /* Only actually queue if *uaddr contained val. */ |
567 | __queue_me(&q, bh); |
568 | |
569 | /* |
570 | * Now the futex is queued and we have checked the data, we |
571 | * don't want to hold mmap_sem while we sleep. |
572 | */ |
573 | up_read(¤t->mm->mmap_sem); |
574 | |
575 | /* |
576 | * There might have been scheduling since the queue_me(), as we |
577 | * cannot hold a spinlock across the get_user() in case it |
578 | * faults, and we cannot just set TASK_INTERRUPTIBLE state when |
579 | * queueing ourselves into the futex hash. This code thus has to |
580 | * rely on the futex_wake() code removing us from hash when it |
581 | * wakes us up. |
582 | */ |
583 | |
584 | /* add_wait_queue is the barrier after __set_current_state. */ |
585 | __set_current_state(TASK_INTERRUPTIBLE); |
586 | add_wait_queue(&q.waiters, &wait); |
587 | /* |
588 | * !list_empty() is safe here without any lock. |
589 | * q.lock_ptr != 0 is not safe, because of ordering against wakeup. |
590 | */ |
591 | if (likely(!list_empty(&q.list))) |
592 | time = schedule_timeout(time); |
593 | __set_current_state(TASK_RUNNING); |
594 | |
595 | /* |
596 | * NOTE: we don't remove ourselves from the waitqueue because |
597 | * we are the only user of it. |
598 | */ |
599 | |
600 | /* If we were woken (and unqueued), we succeeded, whatever. */ |
601 | if (!unqueue_me(&q)) |
602 | return 0; |
603 | if (time == 0) |
604 | return -ETIMEDOUT; |
605 | /* We expect signal_pending(current), but another thread may |
606 | * have handled it for us already. */ |
607 | return -EINTR; |
608 | |
609 | out_release_sem: |
610 | up_read(¤t->mm->mmap_sem); |
611 | return ret; |
612 | } |
613 | |
614 | static int futex_close(struct inode *inode, struct file *filp) |
615 | { |
616 | struct futex_q *q = filp->private_data; |
617 | |
618 | unqueue_me(q); |
619 | kfree(q); |
620 | return 0; |
621 | } |
622 | |
623 | /* This is one-shot: once it's gone off you need a new fd */ |
624 | static unsigned int futex_poll(struct file *filp, |
625 | struct poll_table_struct *wait) |
626 | { |
627 | struct futex_q *q = filp->private_data; |
628 | int ret = 0; |
629 | |
630 | poll_wait(filp, &q->waiters, wait); |
631 | |
632 | /* |
633 | * list_empty() is safe here without any lock. |
634 | * q->lock_ptr != 0 is not safe, because of ordering against wakeup. |
635 | */ |
636 | if (list_empty(&q->list)) |
637 | ret = POLLIN | POLLRDNORM; |
638 | |
639 | return ret; |
640 | } |
641 | |
642 | static struct file_operations futex_fops = { |
643 | .release = futex_close, |
644 | .poll = futex_poll, |
645 | }; |
646 | |
647 | /* |
648 | * Signal allows caller to avoid the race which would occur if they |
649 | * set the sigio stuff up afterwards. |
650 | */ |
651 | static int futex_fd(unsigned long uaddr, int signal) |
652 | { |
653 | struct futex_q *q; |
654 | struct file *filp; |
655 | int ret, err; |
656 | |
657 | ret = -EINVAL; |
658 | if (!valid_signal(signal)) |
659 | goto out; |
660 | |
661 | ret = get_unused_fd(); |
662 | if (ret < 0) |
663 | goto out; |
664 | filp = get_empty_filp(); |
665 | if (!filp) { |
666 | put_unused_fd(ret); |
667 | ret = -ENFILE; |
668 | goto out; |
669 | } |
670 | filp->f_op = &futex_fops; |
671 | filp->f_vfsmnt = mntget(futex_mnt); |
672 | filp->f_dentry = dget(futex_mnt->mnt_root); |
673 | filp->f_mapping = filp->f_dentry->d_inode->i_mapping; |
674 | |
675 | if (signal) { |
676 | int err; |
677 | err = f_setown(filp, current->pid, 1); |
678 | if (err < 0) { |
679 | put_unused_fd(ret); |
680 | put_filp(filp); |
681 | ret = err; |
682 | goto out; |
683 | } |
684 | filp->f_owner.signum = signal; |
685 | } |
686 | |
687 | q = kmalloc(sizeof(*q), GFP_KERNEL); |
688 | if (!q) { |
689 | put_unused_fd(ret); |
690 | put_filp(filp); |
691 | ret = -ENOMEM; |
692 | goto out; |
693 | } |
694 | |
695 | down_read(¤t->mm->mmap_sem); |
696 | err = get_futex_key(uaddr, &q->key); |
697 | |
698 | if (unlikely(err != 0)) { |
699 | up_read(¤t->mm->mmap_sem); |
700 | put_unused_fd(ret); |
701 | put_filp(filp); |
702 | kfree(q); |
703 | return err; |
704 | } |
705 | |
706 | /* |
707 | * queue_me() must be called before releasing mmap_sem, because |
708 | * key->shared.inode needs to be referenced while holding it. |
709 | */ |
710 | filp->private_data = q; |
711 | |
712 | queue_me(q, ret, filp); |
713 | up_read(¤t->mm->mmap_sem); |
714 | |
715 | /* Now we map fd to filp, so userspace can access it */ |
716 | fd_install(ret, filp); |
717 | out: |
718 | return ret; |
719 | } |
720 | |
721 | long do_futex(unsigned long uaddr, int op, int val, unsigned long timeout, |
722 | unsigned long uaddr2, int val2, int val3) |
723 | { |
724 | int ret; |
725 | |
726 | switch (op) { |
727 | case FUTEX_WAIT: |
728 | ret = futex_wait(uaddr, val, timeout); |
729 | break; |
730 | case FUTEX_WAKE: |
731 | ret = futex_wake(uaddr, val); |
732 | break; |
733 | case FUTEX_FD: |
734 | /* non-zero val means F_SETOWN(getpid()) & F_SETSIG(val) */ |
735 | ret = futex_fd(uaddr, val); |
736 | break; |
737 | case FUTEX_REQUEUE: |
738 | ret = futex_requeue(uaddr, uaddr2, val, val2, NULL); |
739 | break; |
740 | case FUTEX_CMP_REQUEUE: |
741 | ret = futex_requeue(uaddr, uaddr2, val, val2, &val3); |
742 | break; |
743 | default: |
744 | ret = -ENOSYS; |
745 | } |
746 | return ret; |
747 | } |
748 | |
749 | |
750 | asmlinkage long sys_futex(u32 __user *uaddr, int op, int val, |
751 | struct timespec __user *utime, u32 __user *uaddr2, |
752 | int val3) |
753 | { |
754 | struct timespec t; |
755 | unsigned long timeout = MAX_SCHEDULE_TIMEOUT; |
756 | int val2 = 0; |
757 | |
758 | if ((op == FUTEX_WAIT) && utime) { |
759 | if (copy_from_user(&t, utime, sizeof(t)) != 0) |
760 | return -EFAULT; |
761 | timeout = timespec_to_jiffies(&t) + 1; |
762 | } |
763 | /* |
764 | * requeue parameter in 'utime' if op == FUTEX_REQUEUE. |
765 | */ |
766 | if (op >= FUTEX_REQUEUE) |
767 | val2 = (int) (unsigned long) utime; |
768 | |
769 | return do_futex((unsigned long)uaddr, op, val, timeout, |
770 | (unsigned long)uaddr2, val2, val3); |
771 | } |
772 | |
773 | static struct super_block * |
774 | futexfs_get_sb(struct file_system_type *fs_type, |
775 | int flags, const char *dev_name, void *data) |
776 | { |
777 | return get_sb_pseudo(fs_type, "futex", NULL, 0xBAD1DEA); |
778 | } |
779 | |
780 | static struct file_system_type futex_fs_type = { |
781 | .name = "futexfs", |
782 | .get_sb = futexfs_get_sb, |
783 | .kill_sb = kill_anon_super, |
784 | }; |
785 | |
786 | static int __init init(void) |
787 | { |
788 | unsigned int i; |
789 | |
790 | register_filesystem(&futex_fs_type); |
791 | futex_mnt = kern_mount(&futex_fs_type); |
792 | |
793 | for (i = 0; i < ARRAY_SIZE(futex_queues); i++) { |
794 | INIT_LIST_HEAD(&futex_queues[i].chain); |
795 | spin_lock_init(&futex_queues[i].lock); |
796 | } |
797 | return 0; |
798 | } |
799 | __initcall(init); |