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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 IM |
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 IM |
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 | * | |
34f01cc1 ED |
19 | * PRIVATE futexes by Eric Dumazet |
20 | * Copyright (C) 2007 Eric Dumazet <dada1@cosmosbay.com> | |
21 | * | |
1da177e4 LT |
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> | |
7ed20e1a | 53 | #include <linux/signal.h> |
9adef58b | 54 | #include <linux/module.h> |
fd5eea42 | 55 | #include <linux/magic.h> |
b488893a PE |
56 | #include <linux/pid.h> |
57 | #include <linux/nsproxy.h> | |
58 | ||
4732efbe | 59 | #include <asm/futex.h> |
1da177e4 | 60 | |
c87e2837 IM |
61 | #include "rtmutex_common.h" |
62 | ||
1da177e4 LT |
63 | #define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8) |
64 | ||
c87e2837 IM |
65 | /* |
66 | * Priority Inheritance state: | |
67 | */ | |
68 | struct futex_pi_state { | |
69 | /* | |
70 | * list of 'owned' pi_state instances - these have to be | |
71 | * cleaned up in do_exit() if the task exits prematurely: | |
72 | */ | |
73 | struct list_head list; | |
74 | ||
75 | /* | |
76 | * The PI object: | |
77 | */ | |
78 | struct rt_mutex pi_mutex; | |
79 | ||
80 | struct task_struct *owner; | |
81 | atomic_t refcount; | |
82 | ||
83 | union futex_key key; | |
84 | }; | |
85 | ||
1da177e4 LT |
86 | /* |
87 | * We use this hashed waitqueue instead of a normal wait_queue_t, so | |
88 | * we can wake only the relevant ones (hashed queues may be shared). | |
89 | * | |
90 | * A futex_q has a woken state, just like tasks have TASK_RUNNING. | |
ec92d082 | 91 | * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0. |
1da177e4 LT |
92 | * The order of wakup is always to make the first condition true, then |
93 | * wake up q->waiters, then make the second condition true. | |
94 | */ | |
95 | struct futex_q { | |
ec92d082 | 96 | struct plist_node list; |
1da177e4 LT |
97 | wait_queue_head_t waiters; |
98 | ||
e2970f2f | 99 | /* Which hash list lock to use: */ |
1da177e4 LT |
100 | spinlock_t *lock_ptr; |
101 | ||
e2970f2f | 102 | /* Key which the futex is hashed on: */ |
1da177e4 LT |
103 | union futex_key key; |
104 | ||
e2970f2f | 105 | /* For fd, sigio sent using these: */ |
1da177e4 LT |
106 | int fd; |
107 | struct file *filp; | |
c87e2837 IM |
108 | |
109 | /* Optional priority inheritance state: */ | |
110 | struct futex_pi_state *pi_state; | |
111 | struct task_struct *task; | |
1da177e4 LT |
112 | }; |
113 | ||
114 | /* | |
115 | * Split the global futex_lock into every hash list lock. | |
116 | */ | |
117 | struct futex_hash_bucket { | |
ec92d082 PP |
118 | spinlock_t lock; |
119 | struct plist_head chain; | |
1da177e4 LT |
120 | }; |
121 | ||
122 | static struct futex_hash_bucket futex_queues[1<<FUTEX_HASHBITS]; | |
123 | ||
124 | /* Futex-fs vfsmount entry: */ | |
125 | static struct vfsmount *futex_mnt; | |
126 | ||
36cf3b5c TG |
127 | /* |
128 | * Take mm->mmap_sem, when futex is shared | |
129 | */ | |
130 | static inline void futex_lock_mm(struct rw_semaphore *fshared) | |
131 | { | |
132 | if (fshared) | |
133 | down_read(fshared); | |
134 | } | |
135 | ||
136 | /* | |
137 | * Release mm->mmap_sem, when the futex is shared | |
138 | */ | |
139 | static inline void futex_unlock_mm(struct rw_semaphore *fshared) | |
140 | { | |
141 | if (fshared) | |
142 | up_read(fshared); | |
143 | } | |
144 | ||
1da177e4 LT |
145 | /* |
146 | * We hash on the keys returned from get_futex_key (see below). | |
147 | */ | |
148 | static 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 | */ | |
159 | static 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 | ||
34f01cc1 ED |
166 | /** |
167 | * get_futex_key - Get parameters which are the keys for a futex. | |
168 | * @uaddr: virtual address of the futex | |
169 | * @shared: NULL for a PROCESS_PRIVATE futex, | |
170 | * ¤t->mm->mmap_sem for a PROCESS_SHARED futex | |
171 | * @key: address where result is stored. | |
172 | * | |
173 | * Returns a negative error code or 0 | |
174 | * The key words are stored in *key on success. | |
1da177e4 | 175 | * |
f3a43f3f | 176 | * For shared mappings, it's (page->index, vma->vm_file->f_path.dentry->d_inode, |
1da177e4 LT |
177 | * offset_within_page). For private mappings, it's (uaddr, current->mm). |
178 | * We can usually work out the index without swapping in the page. | |
179 | * | |
34f01cc1 ED |
180 | * fshared is NULL for PROCESS_PRIVATE futexes |
181 | * For other futexes, it points to ¤t->mm->mmap_sem and | |
182 | * caller must have taken the reader lock. but NOT any spinlocks. | |
1da177e4 | 183 | */ |
fad23fc7 AB |
184 | static int get_futex_key(u32 __user *uaddr, struct rw_semaphore *fshared, |
185 | union futex_key *key) | |
1da177e4 | 186 | { |
e2970f2f | 187 | unsigned long address = (unsigned long)uaddr; |
1da177e4 LT |
188 | struct mm_struct *mm = current->mm; |
189 | struct vm_area_struct *vma; | |
190 | struct page *page; | |
191 | int err; | |
192 | ||
193 | /* | |
194 | * The futex address must be "naturally" aligned. | |
195 | */ | |
e2970f2f | 196 | key->both.offset = address % PAGE_SIZE; |
34f01cc1 | 197 | if (unlikely((address % sizeof(u32)) != 0)) |
1da177e4 | 198 | return -EINVAL; |
e2970f2f | 199 | address -= key->both.offset; |
1da177e4 | 200 | |
34f01cc1 ED |
201 | /* |
202 | * PROCESS_PRIVATE futexes are fast. | |
203 | * As the mm cannot disappear under us and the 'key' only needs | |
204 | * virtual address, we dont even have to find the underlying vma. | |
205 | * Note : We do have to check 'uaddr' is a valid user address, | |
206 | * but access_ok() should be faster than find_vma() | |
207 | */ | |
208 | if (!fshared) { | |
209 | if (unlikely(!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))) | |
210 | return -EFAULT; | |
211 | key->private.mm = mm; | |
212 | key->private.address = address; | |
213 | return 0; | |
214 | } | |
1da177e4 LT |
215 | /* |
216 | * The futex is hashed differently depending on whether | |
217 | * it's in a shared or private mapping. So check vma first. | |
218 | */ | |
e2970f2f | 219 | vma = find_extend_vma(mm, address); |
1da177e4 LT |
220 | if (unlikely(!vma)) |
221 | return -EFAULT; | |
222 | ||
223 | /* | |
224 | * Permissions. | |
225 | */ | |
226 | if (unlikely((vma->vm_flags & (VM_IO|VM_READ)) != VM_READ)) | |
227 | return (vma->vm_flags & VM_IO) ? -EPERM : -EACCES; | |
228 | ||
229 | /* | |
230 | * Private mappings are handled in a simple way. | |
231 | * | |
232 | * NOTE: When userspace waits on a MAP_SHARED mapping, even if | |
233 | * it's a read-only handle, it's expected that futexes attach to | |
234 | * the object not the particular process. Therefore we use | |
235 | * VM_MAYSHARE here, not VM_SHARED which is restricted to shared | |
236 | * mappings of _writable_ handles. | |
237 | */ | |
238 | if (likely(!(vma->vm_flags & VM_MAYSHARE))) { | |
34f01cc1 | 239 | key->both.offset |= FUT_OFF_MMSHARED; /* reference taken on mm */ |
1da177e4 | 240 | key->private.mm = mm; |
e2970f2f | 241 | key->private.address = address; |
1da177e4 LT |
242 | return 0; |
243 | } | |
244 | ||
245 | /* | |
246 | * Linear file mappings are also simple. | |
247 | */ | |
f3a43f3f | 248 | key->shared.inode = vma->vm_file->f_path.dentry->d_inode; |
34f01cc1 | 249 | key->both.offset |= FUT_OFF_INODE; /* inode-based key. */ |
1da177e4 | 250 | if (likely(!(vma->vm_flags & VM_NONLINEAR))) { |
e2970f2f | 251 | key->shared.pgoff = (((address - vma->vm_start) >> PAGE_SHIFT) |
1da177e4 LT |
252 | + vma->vm_pgoff); |
253 | return 0; | |
254 | } | |
255 | ||
256 | /* | |
257 | * We could walk the page table to read the non-linear | |
258 | * pte, and get the page index without fetching the page | |
259 | * from swap. But that's a lot of code to duplicate here | |
260 | * for a rare case, so we simply fetch the page. | |
261 | */ | |
e2970f2f | 262 | err = get_user_pages(current, mm, address, 1, 0, 0, &page, NULL); |
1da177e4 LT |
263 | if (err >= 0) { |
264 | key->shared.pgoff = | |
265 | page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); | |
266 | put_page(page); | |
267 | return 0; | |
268 | } | |
269 | return err; | |
270 | } | |
271 | ||
272 | /* | |
273 | * Take a reference to the resource addressed by a key. | |
274 | * Can be called while holding spinlocks. | |
275 | * | |
1da177e4 | 276 | */ |
fad23fc7 | 277 | static void get_futex_key_refs(union futex_key *key) |
1da177e4 | 278 | { |
34f01cc1 ED |
279 | if (key->both.ptr == 0) |
280 | return; | |
281 | switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { | |
282 | case FUT_OFF_INODE: | |
1da177e4 | 283 | atomic_inc(&key->shared.inode->i_count); |
34f01cc1 ED |
284 | break; |
285 | case FUT_OFF_MMSHARED: | |
1da177e4 | 286 | atomic_inc(&key->private.mm->mm_count); |
34f01cc1 | 287 | break; |
1da177e4 LT |
288 | } |
289 | } | |
290 | ||
291 | /* | |
292 | * Drop a reference to the resource addressed by a key. | |
293 | * The hash bucket spinlock must not be held. | |
294 | */ | |
fad23fc7 | 295 | static void drop_futex_key_refs(union futex_key *key) |
1da177e4 | 296 | { |
c80544dc | 297 | if (!key->both.ptr) |
34f01cc1 ED |
298 | return; |
299 | switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { | |
300 | case FUT_OFF_INODE: | |
1da177e4 | 301 | iput(key->shared.inode); |
34f01cc1 ED |
302 | break; |
303 | case FUT_OFF_MMSHARED: | |
1da177e4 | 304 | mmdrop(key->private.mm); |
34f01cc1 | 305 | break; |
1da177e4 LT |
306 | } |
307 | } | |
308 | ||
36cf3b5c TG |
309 | static u32 cmpxchg_futex_value_locked(u32 __user *uaddr, u32 uval, u32 newval) |
310 | { | |
311 | u32 curval; | |
312 | ||
313 | pagefault_disable(); | |
314 | curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval); | |
315 | pagefault_enable(); | |
316 | ||
317 | return curval; | |
318 | } | |
319 | ||
320 | static int get_futex_value_locked(u32 *dest, u32 __user *from) | |
1da177e4 LT |
321 | { |
322 | int ret; | |
323 | ||
a866374a | 324 | pagefault_disable(); |
e2970f2f | 325 | ret = __copy_from_user_inatomic(dest, from, sizeof(u32)); |
a866374a | 326 | pagefault_enable(); |
1da177e4 LT |
327 | |
328 | return ret ? -EFAULT : 0; | |
329 | } | |
330 | ||
c87e2837 | 331 | /* |
34f01cc1 ED |
332 | * Fault handling. |
333 | * if fshared is non NULL, current->mm->mmap_sem is already held | |
c87e2837 | 334 | */ |
34f01cc1 ED |
335 | static int futex_handle_fault(unsigned long address, |
336 | struct rw_semaphore *fshared, int attempt) | |
c87e2837 IM |
337 | { |
338 | struct vm_area_struct * vma; | |
339 | struct mm_struct *mm = current->mm; | |
34f01cc1 | 340 | int ret = -EFAULT; |
c87e2837 | 341 | |
34f01cc1 ED |
342 | if (attempt > 2) |
343 | return ret; | |
c87e2837 | 344 | |
34f01cc1 ED |
345 | if (!fshared) |
346 | down_read(&mm->mmap_sem); | |
347 | vma = find_vma(mm, address); | |
348 | if (vma && address >= vma->vm_start && | |
349 | (vma->vm_flags & VM_WRITE)) { | |
83c54070 NP |
350 | int fault; |
351 | fault = handle_mm_fault(mm, vma, address, 1); | |
352 | if (unlikely((fault & VM_FAULT_ERROR))) { | |
353 | #if 0 | |
354 | /* XXX: let's do this when we verify it is OK */ | |
355 | if (ret & VM_FAULT_OOM) | |
356 | ret = -ENOMEM; | |
357 | #endif | |
358 | } else { | |
34f01cc1 | 359 | ret = 0; |
83c54070 NP |
360 | if (fault & VM_FAULT_MAJOR) |
361 | current->maj_flt++; | |
362 | else | |
363 | current->min_flt++; | |
34f01cc1 | 364 | } |
c87e2837 | 365 | } |
34f01cc1 ED |
366 | if (!fshared) |
367 | up_read(&mm->mmap_sem); | |
368 | return ret; | |
c87e2837 IM |
369 | } |
370 | ||
371 | /* | |
372 | * PI code: | |
373 | */ | |
374 | static int refill_pi_state_cache(void) | |
375 | { | |
376 | struct futex_pi_state *pi_state; | |
377 | ||
378 | if (likely(current->pi_state_cache)) | |
379 | return 0; | |
380 | ||
4668edc3 | 381 | pi_state = kzalloc(sizeof(*pi_state), GFP_KERNEL); |
c87e2837 IM |
382 | |
383 | if (!pi_state) | |
384 | return -ENOMEM; | |
385 | ||
c87e2837 IM |
386 | INIT_LIST_HEAD(&pi_state->list); |
387 | /* pi_mutex gets initialized later */ | |
388 | pi_state->owner = NULL; | |
389 | atomic_set(&pi_state->refcount, 1); | |
390 | ||
391 | current->pi_state_cache = pi_state; | |
392 | ||
393 | return 0; | |
394 | } | |
395 | ||
396 | static struct futex_pi_state * alloc_pi_state(void) | |
397 | { | |
398 | struct futex_pi_state *pi_state = current->pi_state_cache; | |
399 | ||
400 | WARN_ON(!pi_state); | |
401 | current->pi_state_cache = NULL; | |
402 | ||
403 | return pi_state; | |
404 | } | |
405 | ||
406 | static void free_pi_state(struct futex_pi_state *pi_state) | |
407 | { | |
408 | if (!atomic_dec_and_test(&pi_state->refcount)) | |
409 | return; | |
410 | ||
411 | /* | |
412 | * If pi_state->owner is NULL, the owner is most probably dying | |
413 | * and has cleaned up the pi_state already | |
414 | */ | |
415 | if (pi_state->owner) { | |
416 | spin_lock_irq(&pi_state->owner->pi_lock); | |
417 | list_del_init(&pi_state->list); | |
418 | spin_unlock_irq(&pi_state->owner->pi_lock); | |
419 | ||
420 | rt_mutex_proxy_unlock(&pi_state->pi_mutex, pi_state->owner); | |
421 | } | |
422 | ||
423 | if (current->pi_state_cache) | |
424 | kfree(pi_state); | |
425 | else { | |
426 | /* | |
427 | * pi_state->list is already empty. | |
428 | * clear pi_state->owner. | |
429 | * refcount is at 0 - put it back to 1. | |
430 | */ | |
431 | pi_state->owner = NULL; | |
432 | atomic_set(&pi_state->refcount, 1); | |
433 | current->pi_state_cache = pi_state; | |
434 | } | |
435 | } | |
436 | ||
437 | /* | |
438 | * Look up the task based on what TID userspace gave us. | |
439 | * We dont trust it. | |
440 | */ | |
441 | static struct task_struct * futex_find_get_task(pid_t pid) | |
442 | { | |
443 | struct task_struct *p; | |
444 | ||
d359b549 | 445 | rcu_read_lock(); |
228ebcbe | 446 | p = find_task_by_vpid(pid); |
a06381fe TG |
447 | if (!p || ((current->euid != p->euid) && (current->euid != p->uid))) |
448 | p = ERR_PTR(-ESRCH); | |
449 | else | |
450 | get_task_struct(p); | |
451 | ||
d359b549 | 452 | rcu_read_unlock(); |
c87e2837 IM |
453 | |
454 | return p; | |
455 | } | |
456 | ||
457 | /* | |
458 | * This task is holding PI mutexes at exit time => bad. | |
459 | * Kernel cleans up PI-state, but userspace is likely hosed. | |
460 | * (Robust-futex cleanup is separate and might save the day for userspace.) | |
461 | */ | |
462 | void exit_pi_state_list(struct task_struct *curr) | |
463 | { | |
c87e2837 IM |
464 | struct list_head *next, *head = &curr->pi_state_list; |
465 | struct futex_pi_state *pi_state; | |
627371d7 | 466 | struct futex_hash_bucket *hb; |
c87e2837 IM |
467 | union futex_key key; |
468 | ||
469 | /* | |
470 | * We are a ZOMBIE and nobody can enqueue itself on | |
471 | * pi_state_list anymore, but we have to be careful | |
627371d7 | 472 | * versus waiters unqueueing themselves: |
c87e2837 IM |
473 | */ |
474 | spin_lock_irq(&curr->pi_lock); | |
475 | while (!list_empty(head)) { | |
476 | ||
477 | next = head->next; | |
478 | pi_state = list_entry(next, struct futex_pi_state, list); | |
479 | key = pi_state->key; | |
627371d7 | 480 | hb = hash_futex(&key); |
c87e2837 IM |
481 | spin_unlock_irq(&curr->pi_lock); |
482 | ||
c87e2837 IM |
483 | spin_lock(&hb->lock); |
484 | ||
485 | spin_lock_irq(&curr->pi_lock); | |
627371d7 IM |
486 | /* |
487 | * We dropped the pi-lock, so re-check whether this | |
488 | * task still owns the PI-state: | |
489 | */ | |
c87e2837 IM |
490 | if (head->next != next) { |
491 | spin_unlock(&hb->lock); | |
492 | continue; | |
493 | } | |
494 | ||
c87e2837 | 495 | WARN_ON(pi_state->owner != curr); |
627371d7 IM |
496 | WARN_ON(list_empty(&pi_state->list)); |
497 | list_del_init(&pi_state->list); | |
c87e2837 IM |
498 | pi_state->owner = NULL; |
499 | spin_unlock_irq(&curr->pi_lock); | |
500 | ||
501 | rt_mutex_unlock(&pi_state->pi_mutex); | |
502 | ||
503 | spin_unlock(&hb->lock); | |
504 | ||
505 | spin_lock_irq(&curr->pi_lock); | |
506 | } | |
507 | spin_unlock_irq(&curr->pi_lock); | |
508 | } | |
509 | ||
510 | static int | |
d0aa7a70 PP |
511 | lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, |
512 | union futex_key *key, struct futex_pi_state **ps) | |
c87e2837 IM |
513 | { |
514 | struct futex_pi_state *pi_state = NULL; | |
515 | struct futex_q *this, *next; | |
ec92d082 | 516 | struct plist_head *head; |
c87e2837 | 517 | struct task_struct *p; |
778e9a9c | 518 | pid_t pid = uval & FUTEX_TID_MASK; |
c87e2837 IM |
519 | |
520 | head = &hb->chain; | |
521 | ||
ec92d082 | 522 | plist_for_each_entry_safe(this, next, head, list) { |
d0aa7a70 | 523 | if (match_futex(&this->key, key)) { |
c87e2837 IM |
524 | /* |
525 | * Another waiter already exists - bump up | |
526 | * the refcount and return its pi_state: | |
527 | */ | |
528 | pi_state = this->pi_state; | |
06a9ec29 TG |
529 | /* |
530 | * Userspace might have messed up non PI and PI futexes | |
531 | */ | |
532 | if (unlikely(!pi_state)) | |
533 | return -EINVAL; | |
534 | ||
627371d7 | 535 | WARN_ON(!atomic_read(&pi_state->refcount)); |
778e9a9c AK |
536 | WARN_ON(pid && pi_state->owner && |
537 | pi_state->owner->pid != pid); | |
627371d7 | 538 | |
c87e2837 | 539 | atomic_inc(&pi_state->refcount); |
d0aa7a70 | 540 | *ps = pi_state; |
c87e2837 IM |
541 | |
542 | return 0; | |
543 | } | |
544 | } | |
545 | ||
546 | /* | |
e3f2ddea | 547 | * We are the first waiter - try to look up the real owner and attach |
778e9a9c | 548 | * the new pi_state to it, but bail out when TID = 0 |
c87e2837 | 549 | */ |
778e9a9c | 550 | if (!pid) |
e3f2ddea | 551 | return -ESRCH; |
c87e2837 | 552 | p = futex_find_get_task(pid); |
778e9a9c AK |
553 | if (IS_ERR(p)) |
554 | return PTR_ERR(p); | |
555 | ||
556 | /* | |
557 | * We need to look at the task state flags to figure out, | |
558 | * whether the task is exiting. To protect against the do_exit | |
559 | * change of the task flags, we do this protected by | |
560 | * p->pi_lock: | |
561 | */ | |
562 | spin_lock_irq(&p->pi_lock); | |
563 | if (unlikely(p->flags & PF_EXITING)) { | |
564 | /* | |
565 | * The task is on the way out. When PF_EXITPIDONE is | |
566 | * set, we know that the task has finished the | |
567 | * cleanup: | |
568 | */ | |
569 | int ret = (p->flags & PF_EXITPIDONE) ? -ESRCH : -EAGAIN; | |
570 | ||
571 | spin_unlock_irq(&p->pi_lock); | |
572 | put_task_struct(p); | |
573 | return ret; | |
574 | } | |
c87e2837 IM |
575 | |
576 | pi_state = alloc_pi_state(); | |
577 | ||
578 | /* | |
579 | * Initialize the pi_mutex in locked state and make 'p' | |
580 | * the owner of it: | |
581 | */ | |
582 | rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p); | |
583 | ||
584 | /* Store the key for possible exit cleanups: */ | |
d0aa7a70 | 585 | pi_state->key = *key; |
c87e2837 | 586 | |
627371d7 | 587 | WARN_ON(!list_empty(&pi_state->list)); |
c87e2837 IM |
588 | list_add(&pi_state->list, &p->pi_state_list); |
589 | pi_state->owner = p; | |
590 | spin_unlock_irq(&p->pi_lock); | |
591 | ||
592 | put_task_struct(p); | |
593 | ||
d0aa7a70 | 594 | *ps = pi_state; |
c87e2837 IM |
595 | |
596 | return 0; | |
597 | } | |
598 | ||
1da177e4 LT |
599 | /* |
600 | * The hash bucket lock must be held when this is called. | |
601 | * Afterwards, the futex_q must not be accessed. | |
602 | */ | |
603 | static void wake_futex(struct futex_q *q) | |
604 | { | |
ec92d082 | 605 | plist_del(&q->list, &q->list.plist); |
1da177e4 LT |
606 | if (q->filp) |
607 | send_sigio(&q->filp->f_owner, q->fd, POLL_IN); | |
608 | /* | |
609 | * The lock in wake_up_all() is a crucial memory barrier after the | |
ec92d082 | 610 | * plist_del() and also before assigning to q->lock_ptr. |
1da177e4 LT |
611 | */ |
612 | wake_up_all(&q->waiters); | |
613 | /* | |
614 | * The waiting task can free the futex_q as soon as this is written, | |
615 | * without taking any locks. This must come last. | |
8e31108b AM |
616 | * |
617 | * A memory barrier is required here to prevent the following store | |
618 | * to lock_ptr from getting ahead of the wakeup. Clearing the lock | |
619 | * at the end of wake_up_all() does not prevent this store from | |
620 | * moving. | |
1da177e4 | 621 | */ |
ccdea2f8 | 622 | smp_wmb(); |
1da177e4 LT |
623 | q->lock_ptr = NULL; |
624 | } | |
625 | ||
c87e2837 IM |
626 | static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this) |
627 | { | |
628 | struct task_struct *new_owner; | |
629 | struct futex_pi_state *pi_state = this->pi_state; | |
630 | u32 curval, newval; | |
631 | ||
632 | if (!pi_state) | |
633 | return -EINVAL; | |
634 | ||
21778867 | 635 | spin_lock(&pi_state->pi_mutex.wait_lock); |
c87e2837 IM |
636 | new_owner = rt_mutex_next_owner(&pi_state->pi_mutex); |
637 | ||
638 | /* | |
639 | * This happens when we have stolen the lock and the original | |
640 | * pending owner did not enqueue itself back on the rt_mutex. | |
641 | * Thats not a tragedy. We know that way, that a lock waiter | |
642 | * is on the fly. We make the futex_q waiter the pending owner. | |
643 | */ | |
644 | if (!new_owner) | |
645 | new_owner = this->task; | |
646 | ||
647 | /* | |
648 | * We pass it to the next owner. (The WAITERS bit is always | |
649 | * kept enabled while there is PI state around. We must also | |
650 | * preserve the owner died bit.) | |
651 | */ | |
e3f2ddea | 652 | if (!(uval & FUTEX_OWNER_DIED)) { |
778e9a9c AK |
653 | int ret = 0; |
654 | ||
b488893a | 655 | newval = FUTEX_WAITERS | task_pid_vnr(new_owner); |
e3f2ddea | 656 | |
36cf3b5c | 657 | curval = cmpxchg_futex_value_locked(uaddr, uval, newval); |
778e9a9c | 658 | |
e3f2ddea | 659 | if (curval == -EFAULT) |
778e9a9c | 660 | ret = -EFAULT; |
cde898fa | 661 | else if (curval != uval) |
778e9a9c AK |
662 | ret = -EINVAL; |
663 | if (ret) { | |
664 | spin_unlock(&pi_state->pi_mutex.wait_lock); | |
665 | return ret; | |
666 | } | |
e3f2ddea | 667 | } |
c87e2837 | 668 | |
627371d7 IM |
669 | spin_lock_irq(&pi_state->owner->pi_lock); |
670 | WARN_ON(list_empty(&pi_state->list)); | |
671 | list_del_init(&pi_state->list); | |
672 | spin_unlock_irq(&pi_state->owner->pi_lock); | |
673 | ||
674 | spin_lock_irq(&new_owner->pi_lock); | |
675 | WARN_ON(!list_empty(&pi_state->list)); | |
c87e2837 IM |
676 | list_add(&pi_state->list, &new_owner->pi_state_list); |
677 | pi_state->owner = new_owner; | |
627371d7 IM |
678 | spin_unlock_irq(&new_owner->pi_lock); |
679 | ||
21778867 | 680 | spin_unlock(&pi_state->pi_mutex.wait_lock); |
c87e2837 IM |
681 | rt_mutex_unlock(&pi_state->pi_mutex); |
682 | ||
683 | return 0; | |
684 | } | |
685 | ||
686 | static int unlock_futex_pi(u32 __user *uaddr, u32 uval) | |
687 | { | |
688 | u32 oldval; | |
689 | ||
690 | /* | |
691 | * There is no waiter, so we unlock the futex. The owner died | |
692 | * bit has not to be preserved here. We are the owner: | |
693 | */ | |
36cf3b5c | 694 | oldval = cmpxchg_futex_value_locked(uaddr, uval, 0); |
c87e2837 IM |
695 | |
696 | if (oldval == -EFAULT) | |
697 | return oldval; | |
698 | if (oldval != uval) | |
699 | return -EAGAIN; | |
700 | ||
701 | return 0; | |
702 | } | |
703 | ||
8b8f319f IM |
704 | /* |
705 | * Express the locking dependencies for lockdep: | |
706 | */ | |
707 | static inline void | |
708 | double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) | |
709 | { | |
710 | if (hb1 <= hb2) { | |
711 | spin_lock(&hb1->lock); | |
712 | if (hb1 < hb2) | |
713 | spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING); | |
714 | } else { /* hb1 > hb2 */ | |
715 | spin_lock(&hb2->lock); | |
716 | spin_lock_nested(&hb1->lock, SINGLE_DEPTH_NESTING); | |
717 | } | |
718 | } | |
719 | ||
1da177e4 LT |
720 | /* |
721 | * Wake up all waiters hashed on the physical page that is mapped | |
722 | * to this virtual address: | |
723 | */ | |
34f01cc1 ED |
724 | static int futex_wake(u32 __user *uaddr, struct rw_semaphore *fshared, |
725 | int nr_wake) | |
1da177e4 | 726 | { |
e2970f2f | 727 | struct futex_hash_bucket *hb; |
1da177e4 | 728 | struct futex_q *this, *next; |
ec92d082 | 729 | struct plist_head *head; |
e2970f2f | 730 | union futex_key key; |
1da177e4 LT |
731 | int ret; |
732 | ||
36cf3b5c | 733 | futex_lock_mm(fshared); |
1da177e4 | 734 | |
34f01cc1 | 735 | ret = get_futex_key(uaddr, fshared, &key); |
1da177e4 LT |
736 | if (unlikely(ret != 0)) |
737 | goto out; | |
738 | ||
e2970f2f IM |
739 | hb = hash_futex(&key); |
740 | spin_lock(&hb->lock); | |
741 | head = &hb->chain; | |
1da177e4 | 742 | |
ec92d082 | 743 | plist_for_each_entry_safe(this, next, head, list) { |
1da177e4 | 744 | if (match_futex (&this->key, &key)) { |
ed6f7b10 IM |
745 | if (this->pi_state) { |
746 | ret = -EINVAL; | |
747 | break; | |
748 | } | |
1da177e4 LT |
749 | wake_futex(this); |
750 | if (++ret >= nr_wake) | |
751 | break; | |
752 | } | |
753 | } | |
754 | ||
e2970f2f | 755 | spin_unlock(&hb->lock); |
1da177e4 | 756 | out: |
36cf3b5c | 757 | futex_unlock_mm(fshared); |
1da177e4 LT |
758 | return ret; |
759 | } | |
760 | ||
4732efbe JJ |
761 | /* |
762 | * Wake up all waiters hashed on the physical page that is mapped | |
763 | * to this virtual address: | |
764 | */ | |
e2970f2f | 765 | static int |
34f01cc1 ED |
766 | futex_wake_op(u32 __user *uaddr1, struct rw_semaphore *fshared, |
767 | u32 __user *uaddr2, | |
e2970f2f | 768 | int nr_wake, int nr_wake2, int op) |
4732efbe JJ |
769 | { |
770 | union futex_key key1, key2; | |
e2970f2f | 771 | struct futex_hash_bucket *hb1, *hb2; |
ec92d082 | 772 | struct plist_head *head; |
4732efbe JJ |
773 | struct futex_q *this, *next; |
774 | int ret, op_ret, attempt = 0; | |
775 | ||
776 | retryfull: | |
36cf3b5c | 777 | futex_lock_mm(fshared); |
4732efbe | 778 | |
34f01cc1 | 779 | ret = get_futex_key(uaddr1, fshared, &key1); |
4732efbe JJ |
780 | if (unlikely(ret != 0)) |
781 | goto out; | |
34f01cc1 | 782 | ret = get_futex_key(uaddr2, fshared, &key2); |
4732efbe JJ |
783 | if (unlikely(ret != 0)) |
784 | goto out; | |
785 | ||
e2970f2f IM |
786 | hb1 = hash_futex(&key1); |
787 | hb2 = hash_futex(&key2); | |
4732efbe JJ |
788 | |
789 | retry: | |
8b8f319f | 790 | double_lock_hb(hb1, hb2); |
4732efbe | 791 | |
e2970f2f | 792 | op_ret = futex_atomic_op_inuser(op, uaddr2); |
4732efbe | 793 | if (unlikely(op_ret < 0)) { |
e2970f2f | 794 | u32 dummy; |
4732efbe | 795 | |
e2970f2f IM |
796 | spin_unlock(&hb1->lock); |
797 | if (hb1 != hb2) | |
798 | spin_unlock(&hb2->lock); | |
4732efbe | 799 | |
7ee1dd3f | 800 | #ifndef CONFIG_MMU |
e2970f2f IM |
801 | /* |
802 | * we don't get EFAULT from MMU faults if we don't have an MMU, | |
803 | * but we might get them from range checking | |
804 | */ | |
7ee1dd3f DH |
805 | ret = op_ret; |
806 | goto out; | |
807 | #endif | |
808 | ||
796f8d9b DG |
809 | if (unlikely(op_ret != -EFAULT)) { |
810 | ret = op_ret; | |
811 | goto out; | |
812 | } | |
813 | ||
e2970f2f IM |
814 | /* |
815 | * futex_atomic_op_inuser needs to both read and write | |
4732efbe JJ |
816 | * *(int __user *)uaddr2, but we can't modify it |
817 | * non-atomically. Therefore, if get_user below is not | |
818 | * enough, we need to handle the fault ourselves, while | |
e2970f2f IM |
819 | * still holding the mmap_sem. |
820 | */ | |
4732efbe | 821 | if (attempt++) { |
34f01cc1 | 822 | ret = futex_handle_fault((unsigned long)uaddr2, |
36cf3b5c | 823 | fshared, attempt); |
34f01cc1 | 824 | if (ret) |
4732efbe | 825 | goto out; |
4732efbe JJ |
826 | goto retry; |
827 | } | |
828 | ||
e2970f2f IM |
829 | /* |
830 | * If we would have faulted, release mmap_sem, | |
831 | * fault it in and start all over again. | |
832 | */ | |
36cf3b5c | 833 | futex_unlock_mm(fshared); |
4732efbe | 834 | |
e2970f2f | 835 | ret = get_user(dummy, uaddr2); |
4732efbe JJ |
836 | if (ret) |
837 | return ret; | |
838 | ||
839 | goto retryfull; | |
840 | } | |
841 | ||
e2970f2f | 842 | head = &hb1->chain; |
4732efbe | 843 | |
ec92d082 | 844 | plist_for_each_entry_safe(this, next, head, list) { |
4732efbe JJ |
845 | if (match_futex (&this->key, &key1)) { |
846 | wake_futex(this); | |
847 | if (++ret >= nr_wake) | |
848 | break; | |
849 | } | |
850 | } | |
851 | ||
852 | if (op_ret > 0) { | |
e2970f2f | 853 | head = &hb2->chain; |
4732efbe JJ |
854 | |
855 | op_ret = 0; | |
ec92d082 | 856 | plist_for_each_entry_safe(this, next, head, list) { |
4732efbe JJ |
857 | if (match_futex (&this->key, &key2)) { |
858 | wake_futex(this); | |
859 | if (++op_ret >= nr_wake2) | |
860 | break; | |
861 | } | |
862 | } | |
863 | ret += op_ret; | |
864 | } | |
865 | ||
e2970f2f IM |
866 | spin_unlock(&hb1->lock); |
867 | if (hb1 != hb2) | |
868 | spin_unlock(&hb2->lock); | |
4732efbe | 869 | out: |
36cf3b5c TG |
870 | futex_unlock_mm(fshared); |
871 | ||
4732efbe JJ |
872 | return ret; |
873 | } | |
874 | ||
1da177e4 LT |
875 | /* |
876 | * Requeue all waiters hashed on one physical page to another | |
877 | * physical page. | |
878 | */ | |
34f01cc1 ED |
879 | static int futex_requeue(u32 __user *uaddr1, struct rw_semaphore *fshared, |
880 | u32 __user *uaddr2, | |
e2970f2f | 881 | int nr_wake, int nr_requeue, u32 *cmpval) |
1da177e4 LT |
882 | { |
883 | union futex_key key1, key2; | |
e2970f2f | 884 | struct futex_hash_bucket *hb1, *hb2; |
ec92d082 | 885 | struct plist_head *head1; |
1da177e4 LT |
886 | struct futex_q *this, *next; |
887 | int ret, drop_count = 0; | |
888 | ||
889 | retry: | |
36cf3b5c | 890 | futex_lock_mm(fshared); |
1da177e4 | 891 | |
34f01cc1 | 892 | ret = get_futex_key(uaddr1, fshared, &key1); |
1da177e4 LT |
893 | if (unlikely(ret != 0)) |
894 | goto out; | |
34f01cc1 | 895 | ret = get_futex_key(uaddr2, fshared, &key2); |
1da177e4 LT |
896 | if (unlikely(ret != 0)) |
897 | goto out; | |
898 | ||
e2970f2f IM |
899 | hb1 = hash_futex(&key1); |
900 | hb2 = hash_futex(&key2); | |
1da177e4 | 901 | |
8b8f319f | 902 | double_lock_hb(hb1, hb2); |
1da177e4 | 903 | |
e2970f2f IM |
904 | if (likely(cmpval != NULL)) { |
905 | u32 curval; | |
1da177e4 | 906 | |
e2970f2f | 907 | ret = get_futex_value_locked(&curval, uaddr1); |
1da177e4 LT |
908 | |
909 | if (unlikely(ret)) { | |
e2970f2f IM |
910 | spin_unlock(&hb1->lock); |
911 | if (hb1 != hb2) | |
912 | spin_unlock(&hb2->lock); | |
1da177e4 | 913 | |
e2970f2f IM |
914 | /* |
915 | * If we would have faulted, release mmap_sem, fault | |
1da177e4 LT |
916 | * it in and start all over again. |
917 | */ | |
36cf3b5c | 918 | futex_unlock_mm(fshared); |
1da177e4 | 919 | |
e2970f2f | 920 | ret = get_user(curval, uaddr1); |
1da177e4 LT |
921 | |
922 | if (!ret) | |
923 | goto retry; | |
924 | ||
925 | return ret; | |
926 | } | |
e2970f2f | 927 | if (curval != *cmpval) { |
1da177e4 LT |
928 | ret = -EAGAIN; |
929 | goto out_unlock; | |
930 | } | |
931 | } | |
932 | ||
e2970f2f | 933 | head1 = &hb1->chain; |
ec92d082 | 934 | plist_for_each_entry_safe(this, next, head1, list) { |
1da177e4 LT |
935 | if (!match_futex (&this->key, &key1)) |
936 | continue; | |
937 | if (++ret <= nr_wake) { | |
938 | wake_futex(this); | |
939 | } else { | |
59e0e0ac SD |
940 | /* |
941 | * If key1 and key2 hash to the same bucket, no need to | |
942 | * requeue. | |
943 | */ | |
944 | if (likely(head1 != &hb2->chain)) { | |
ec92d082 PP |
945 | plist_del(&this->list, &hb1->chain); |
946 | plist_add(&this->list, &hb2->chain); | |
59e0e0ac | 947 | this->lock_ptr = &hb2->lock; |
ec92d082 PP |
948 | #ifdef CONFIG_DEBUG_PI_LIST |
949 | this->list.plist.lock = &hb2->lock; | |
950 | #endif | |
778e9a9c | 951 | } |
1da177e4 | 952 | this->key = key2; |
9adef58b | 953 | get_futex_key_refs(&key2); |
1da177e4 LT |
954 | drop_count++; |
955 | ||
956 | if (ret - nr_wake >= nr_requeue) | |
957 | break; | |
1da177e4 LT |
958 | } |
959 | } | |
960 | ||
961 | out_unlock: | |
e2970f2f IM |
962 | spin_unlock(&hb1->lock); |
963 | if (hb1 != hb2) | |
964 | spin_unlock(&hb2->lock); | |
1da177e4 | 965 | |
9adef58b | 966 | /* drop_futex_key_refs() must be called outside the spinlocks. */ |
1da177e4 | 967 | while (--drop_count >= 0) |
9adef58b | 968 | drop_futex_key_refs(&key1); |
1da177e4 LT |
969 | |
970 | out: | |
36cf3b5c | 971 | futex_unlock_mm(fshared); |
1da177e4 LT |
972 | return ret; |
973 | } | |
974 | ||
975 | /* The key must be already stored in q->key. */ | |
976 | static inline struct futex_hash_bucket * | |
977 | queue_lock(struct futex_q *q, int fd, struct file *filp) | |
978 | { | |
e2970f2f | 979 | struct futex_hash_bucket *hb; |
1da177e4 LT |
980 | |
981 | q->fd = fd; | |
982 | q->filp = filp; | |
983 | ||
984 | init_waitqueue_head(&q->waiters); | |
985 | ||
9adef58b | 986 | get_futex_key_refs(&q->key); |
e2970f2f IM |
987 | hb = hash_futex(&q->key); |
988 | q->lock_ptr = &hb->lock; | |
1da177e4 | 989 | |
e2970f2f IM |
990 | spin_lock(&hb->lock); |
991 | return hb; | |
1da177e4 LT |
992 | } |
993 | ||
e2970f2f | 994 | static inline void __queue_me(struct futex_q *q, struct futex_hash_bucket *hb) |
1da177e4 | 995 | { |
ec92d082 PP |
996 | int prio; |
997 | ||
998 | /* | |
999 | * The priority used to register this element is | |
1000 | * - either the real thread-priority for the real-time threads | |
1001 | * (i.e. threads with a priority lower than MAX_RT_PRIO) | |
1002 | * - or MAX_RT_PRIO for non-RT threads. | |
1003 | * Thus, all RT-threads are woken first in priority order, and | |
1004 | * the others are woken last, in FIFO order. | |
1005 | */ | |
1006 | prio = min(current->normal_prio, MAX_RT_PRIO); | |
1007 | ||
1008 | plist_node_init(&q->list, prio); | |
1009 | #ifdef CONFIG_DEBUG_PI_LIST | |
1010 | q->list.plist.lock = &hb->lock; | |
1011 | #endif | |
1012 | plist_add(&q->list, &hb->chain); | |
c87e2837 | 1013 | q->task = current; |
e2970f2f | 1014 | spin_unlock(&hb->lock); |
1da177e4 LT |
1015 | } |
1016 | ||
1017 | static inline void | |
e2970f2f | 1018 | queue_unlock(struct futex_q *q, struct futex_hash_bucket *hb) |
1da177e4 | 1019 | { |
e2970f2f | 1020 | spin_unlock(&hb->lock); |
9adef58b | 1021 | drop_futex_key_refs(&q->key); |
1da177e4 LT |
1022 | } |
1023 | ||
1024 | /* | |
1025 | * queue_me and unqueue_me must be called as a pair, each | |
1026 | * exactly once. They are called with the hashed spinlock held. | |
1027 | */ | |
1028 | ||
1029 | /* The key must be already stored in q->key. */ | |
1030 | static void queue_me(struct futex_q *q, int fd, struct file *filp) | |
1031 | { | |
e2970f2f IM |
1032 | struct futex_hash_bucket *hb; |
1033 | ||
1034 | hb = queue_lock(q, fd, filp); | |
1035 | __queue_me(q, hb); | |
1da177e4 LT |
1036 | } |
1037 | ||
1038 | /* Return 1 if we were still queued (ie. 0 means we were woken) */ | |
1039 | static int unqueue_me(struct futex_q *q) | |
1040 | { | |
1da177e4 | 1041 | spinlock_t *lock_ptr; |
e2970f2f | 1042 | int ret = 0; |
1da177e4 LT |
1043 | |
1044 | /* In the common case we don't take the spinlock, which is nice. */ | |
1045 | retry: | |
1046 | lock_ptr = q->lock_ptr; | |
e91467ec | 1047 | barrier(); |
c80544dc | 1048 | if (lock_ptr != NULL) { |
1da177e4 LT |
1049 | spin_lock(lock_ptr); |
1050 | /* | |
1051 | * q->lock_ptr can change between reading it and | |
1052 | * spin_lock(), causing us to take the wrong lock. This | |
1053 | * corrects the race condition. | |
1054 | * | |
1055 | * Reasoning goes like this: if we have the wrong lock, | |
1056 | * q->lock_ptr must have changed (maybe several times) | |
1057 | * between reading it and the spin_lock(). It can | |
1058 | * change again after the spin_lock() but only if it was | |
1059 | * already changed before the spin_lock(). It cannot, | |
1060 | * however, change back to the original value. Therefore | |
1061 | * we can detect whether we acquired the correct lock. | |
1062 | */ | |
1063 | if (unlikely(lock_ptr != q->lock_ptr)) { | |
1064 | spin_unlock(lock_ptr); | |
1065 | goto retry; | |
1066 | } | |
ec92d082 PP |
1067 | WARN_ON(plist_node_empty(&q->list)); |
1068 | plist_del(&q->list, &q->list.plist); | |
c87e2837 IM |
1069 | |
1070 | BUG_ON(q->pi_state); | |
1071 | ||
1da177e4 LT |
1072 | spin_unlock(lock_ptr); |
1073 | ret = 1; | |
1074 | } | |
1075 | ||
9adef58b | 1076 | drop_futex_key_refs(&q->key); |
1da177e4 LT |
1077 | return ret; |
1078 | } | |
1079 | ||
c87e2837 IM |
1080 | /* |
1081 | * PI futexes can not be requeued and must remove themself from the | |
d0aa7a70 PP |
1082 | * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry |
1083 | * and dropped here. | |
c87e2837 | 1084 | */ |
d0aa7a70 | 1085 | static void unqueue_me_pi(struct futex_q *q) |
c87e2837 | 1086 | { |
ec92d082 PP |
1087 | WARN_ON(plist_node_empty(&q->list)); |
1088 | plist_del(&q->list, &q->list.plist); | |
c87e2837 IM |
1089 | |
1090 | BUG_ON(!q->pi_state); | |
1091 | free_pi_state(q->pi_state); | |
1092 | q->pi_state = NULL; | |
1093 | ||
d0aa7a70 | 1094 | spin_unlock(q->lock_ptr); |
c87e2837 | 1095 | |
9adef58b | 1096 | drop_futex_key_refs(&q->key); |
c87e2837 IM |
1097 | } |
1098 | ||
d0aa7a70 PP |
1099 | /* |
1100 | * Fixup the pi_state owner with current. | |
1101 | * | |
778e9a9c AK |
1102 | * Must be called with hash bucket lock held and mm->sem held for non |
1103 | * private futexes. | |
d0aa7a70 | 1104 | */ |
778e9a9c | 1105 | static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q, |
d0aa7a70 PP |
1106 | struct task_struct *curr) |
1107 | { | |
b488893a | 1108 | u32 newtid = task_pid_vnr(curr) | FUTEX_WAITERS; |
d0aa7a70 PP |
1109 | struct futex_pi_state *pi_state = q->pi_state; |
1110 | u32 uval, curval, newval; | |
1111 | int ret; | |
1112 | ||
1113 | /* Owner died? */ | |
1114 | if (pi_state->owner != NULL) { | |
1115 | spin_lock_irq(&pi_state->owner->pi_lock); | |
1116 | WARN_ON(list_empty(&pi_state->list)); | |
1117 | list_del_init(&pi_state->list); | |
1118 | spin_unlock_irq(&pi_state->owner->pi_lock); | |
1119 | } else | |
1120 | newtid |= FUTEX_OWNER_DIED; | |
1121 | ||
1122 | pi_state->owner = curr; | |
1123 | ||
1124 | spin_lock_irq(&curr->pi_lock); | |
1125 | WARN_ON(!list_empty(&pi_state->list)); | |
1126 | list_add(&pi_state->list, &curr->pi_state_list); | |
1127 | spin_unlock_irq(&curr->pi_lock); | |
1128 | ||
d0aa7a70 PP |
1129 | /* |
1130 | * We own it, so we have to replace the pending owner | |
1131 | * TID. This must be atomic as we have preserve the | |
1132 | * owner died bit here. | |
1133 | */ | |
778e9a9c AK |
1134 | ret = get_futex_value_locked(&uval, uaddr); |
1135 | ||
d0aa7a70 PP |
1136 | while (!ret) { |
1137 | newval = (uval & FUTEX_OWNER_DIED) | newtid; | |
778e9a9c | 1138 | |
36cf3b5c | 1139 | curval = cmpxchg_futex_value_locked(uaddr, uval, newval); |
778e9a9c | 1140 | |
d0aa7a70 | 1141 | if (curval == -EFAULT) |
778e9a9c | 1142 | ret = -EFAULT; |
d0aa7a70 PP |
1143 | if (curval == uval) |
1144 | break; | |
1145 | uval = curval; | |
1146 | } | |
1147 | return ret; | |
1148 | } | |
1149 | ||
34f01cc1 ED |
1150 | /* |
1151 | * In case we must use restart_block to restart a futex_wait, | |
ce6bd420 | 1152 | * we encode in the 'flags' shared capability |
34f01cc1 | 1153 | */ |
ce6bd420 | 1154 | #define FLAGS_SHARED 1 |
34f01cc1 | 1155 | |
72c1bbf3 | 1156 | static long futex_wait_restart(struct restart_block *restart); |
36cf3b5c | 1157 | |
34f01cc1 ED |
1158 | static int futex_wait(u32 __user *uaddr, struct rw_semaphore *fshared, |
1159 | u32 val, ktime_t *abs_time) | |
1da177e4 | 1160 | { |
c87e2837 IM |
1161 | struct task_struct *curr = current; |
1162 | DECLARE_WAITQUEUE(wait, curr); | |
e2970f2f | 1163 | struct futex_hash_bucket *hb; |
1da177e4 | 1164 | struct futex_q q; |
e2970f2f IM |
1165 | u32 uval; |
1166 | int ret; | |
bd197234 | 1167 | struct hrtimer_sleeper t; |
c19384b5 | 1168 | int rem = 0; |
1da177e4 | 1169 | |
c87e2837 | 1170 | q.pi_state = NULL; |
1da177e4 | 1171 | retry: |
36cf3b5c | 1172 | futex_lock_mm(fshared); |
1da177e4 | 1173 | |
34f01cc1 | 1174 | ret = get_futex_key(uaddr, fshared, &q.key); |
1da177e4 LT |
1175 | if (unlikely(ret != 0)) |
1176 | goto out_release_sem; | |
1177 | ||
e2970f2f | 1178 | hb = queue_lock(&q, -1, NULL); |
1da177e4 LT |
1179 | |
1180 | /* | |
1181 | * Access the page AFTER the futex is queued. | |
1182 | * Order is important: | |
1183 | * | |
1184 | * Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val); | |
1185 | * Userspace waker: if (cond(var)) { var = new; futex_wake(&var); } | |
1186 | * | |
1187 | * The basic logical guarantee of a futex is that it blocks ONLY | |
1188 | * if cond(var) is known to be true at the time of blocking, for | |
1189 | * any cond. If we queued after testing *uaddr, that would open | |
1190 | * a race condition where we could block indefinitely with | |
1191 | * cond(var) false, which would violate the guarantee. | |
1192 | * | |
1193 | * A consequence is that futex_wait() can return zero and absorb | |
1194 | * a wakeup when *uaddr != val on entry to the syscall. This is | |
1195 | * rare, but normal. | |
1196 | * | |
34f01cc1 ED |
1197 | * for shared futexes, we hold the mmap semaphore, so the mapping |
1198 | * cannot have changed since we looked it up in get_futex_key. | |
1da177e4 | 1199 | */ |
e2970f2f | 1200 | ret = get_futex_value_locked(&uval, uaddr); |
1da177e4 LT |
1201 | |
1202 | if (unlikely(ret)) { | |
e2970f2f | 1203 | queue_unlock(&q, hb); |
1da177e4 | 1204 | |
e2970f2f IM |
1205 | /* |
1206 | * If we would have faulted, release mmap_sem, fault it in and | |
1da177e4 LT |
1207 | * start all over again. |
1208 | */ | |
36cf3b5c | 1209 | futex_unlock_mm(fshared); |
1da177e4 | 1210 | |
e2970f2f | 1211 | ret = get_user(uval, uaddr); |
1da177e4 LT |
1212 | |
1213 | if (!ret) | |
1214 | goto retry; | |
1215 | return ret; | |
1216 | } | |
c87e2837 IM |
1217 | ret = -EWOULDBLOCK; |
1218 | if (uval != val) | |
1219 | goto out_unlock_release_sem; | |
1da177e4 LT |
1220 | |
1221 | /* Only actually queue if *uaddr contained val. */ | |
e2970f2f | 1222 | __queue_me(&q, hb); |
1da177e4 LT |
1223 | |
1224 | /* | |
1225 | * Now the futex is queued and we have checked the data, we | |
1226 | * don't want to hold mmap_sem while we sleep. | |
c87e2837 | 1227 | */ |
36cf3b5c | 1228 | futex_unlock_mm(fshared); |
1da177e4 LT |
1229 | |
1230 | /* | |
1231 | * There might have been scheduling since the queue_me(), as we | |
1232 | * cannot hold a spinlock across the get_user() in case it | |
1233 | * faults, and we cannot just set TASK_INTERRUPTIBLE state when | |
1234 | * queueing ourselves into the futex hash. This code thus has to | |
1235 | * rely on the futex_wake() code removing us from hash when it | |
1236 | * wakes us up. | |
1237 | */ | |
1238 | ||
1239 | /* add_wait_queue is the barrier after __set_current_state. */ | |
1240 | __set_current_state(TASK_INTERRUPTIBLE); | |
1241 | add_wait_queue(&q.waiters, &wait); | |
1242 | /* | |
ec92d082 | 1243 | * !plist_node_empty() is safe here without any lock. |
1da177e4 LT |
1244 | * q.lock_ptr != 0 is not safe, because of ordering against wakeup. |
1245 | */ | |
ec92d082 | 1246 | if (likely(!plist_node_empty(&q.list))) { |
c19384b5 PP |
1247 | if (!abs_time) |
1248 | schedule(); | |
1249 | else { | |
1250 | hrtimer_init(&t.timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); | |
1251 | hrtimer_init_sleeper(&t, current); | |
1252 | t.timer.expires = *abs_time; | |
1253 | ||
1254 | hrtimer_start(&t.timer, t.timer.expires, HRTIMER_MODE_ABS); | |
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); | |
72c1bbf3 | 1265 | |
c19384b5 PP |
1266 | /* Flag if a timeout occured */ |
1267 | rem = (t.task == NULL); | |
1268 | } | |
72c1bbf3 | 1269 | } |
1da177e4 LT |
1270 | __set_current_state(TASK_RUNNING); |
1271 | ||
1272 | /* | |
1273 | * NOTE: we don't remove ourselves from the waitqueue because | |
1274 | * we are the only user of it. | |
1275 | */ | |
1276 | ||
1277 | /* If we were woken (and unqueued), we succeeded, whatever. */ | |
1278 | if (!unqueue_me(&q)) | |
1279 | return 0; | |
c19384b5 | 1280 | if (rem) |
1da177e4 | 1281 | return -ETIMEDOUT; |
72c1bbf3 | 1282 | |
e2970f2f IM |
1283 | /* |
1284 | * We expect signal_pending(current), but another thread may | |
1285 | * have handled it for us already. | |
1286 | */ | |
c19384b5 | 1287 | if (!abs_time) |
72c1bbf3 NP |
1288 | return -ERESTARTSYS; |
1289 | else { | |
1290 | struct restart_block *restart; | |
1291 | restart = ¤t_thread_info()->restart_block; | |
1292 | restart->fn = futex_wait_restart; | |
ce6bd420 SR |
1293 | restart->futex.uaddr = (u32 *)uaddr; |
1294 | restart->futex.val = val; | |
1295 | restart->futex.time = abs_time->tv64; | |
1296 | restart->futex.flags = 0; | |
1297 | ||
34f01cc1 | 1298 | if (fshared) |
ce6bd420 | 1299 | restart->futex.flags |= FLAGS_SHARED; |
72c1bbf3 NP |
1300 | return -ERESTART_RESTARTBLOCK; |
1301 | } | |
1da177e4 | 1302 | |
c87e2837 IM |
1303 | out_unlock_release_sem: |
1304 | queue_unlock(&q, hb); | |
1305 | ||
1da177e4 | 1306 | out_release_sem: |
36cf3b5c | 1307 | futex_unlock_mm(fshared); |
c87e2837 IM |
1308 | return ret; |
1309 | } | |
1310 | ||
72c1bbf3 NP |
1311 | |
1312 | static long futex_wait_restart(struct restart_block *restart) | |
1313 | { | |
ce6bd420 | 1314 | u32 __user *uaddr = (u32 __user *)restart->futex.uaddr; |
34f01cc1 | 1315 | struct rw_semaphore *fshared = NULL; |
ce6bd420 | 1316 | ktime_t t; |
72c1bbf3 | 1317 | |
ce6bd420 | 1318 | t.tv64 = restart->futex.time; |
72c1bbf3 | 1319 | restart->fn = do_no_restart_syscall; |
ce6bd420 | 1320 | if (restart->futex.flags & FLAGS_SHARED) |
34f01cc1 | 1321 | fshared = ¤t->mm->mmap_sem; |
ce6bd420 | 1322 | return (long)futex_wait(uaddr, fshared, restart->futex.val, &t); |
72c1bbf3 NP |
1323 | } |
1324 | ||
1325 | ||
c87e2837 IM |
1326 | /* |
1327 | * Userspace tried a 0 -> TID atomic transition of the futex value | |
1328 | * and failed. The kernel side here does the whole locking operation: | |
1329 | * if there are waiters then it will block, it does PI, etc. (Due to | |
1330 | * races the kernel might see a 0 value of the futex too.) | |
1331 | */ | |
34f01cc1 ED |
1332 | static int futex_lock_pi(u32 __user *uaddr, struct rw_semaphore *fshared, |
1333 | int detect, ktime_t *time, int trylock) | |
c87e2837 | 1334 | { |
c5780e97 | 1335 | struct hrtimer_sleeper timeout, *to = NULL; |
c87e2837 IM |
1336 | struct task_struct *curr = current; |
1337 | struct futex_hash_bucket *hb; | |
1338 | u32 uval, newval, curval; | |
1339 | struct futex_q q; | |
778e9a9c | 1340 | int ret, lock_taken, ownerdied = 0, attempt = 0; |
c87e2837 IM |
1341 | |
1342 | if (refill_pi_state_cache()) | |
1343 | return -ENOMEM; | |
1344 | ||
c19384b5 | 1345 | if (time) { |
c5780e97 | 1346 | to = &timeout; |
c9cb2e3d | 1347 | hrtimer_init(&to->timer, CLOCK_REALTIME, HRTIMER_MODE_ABS); |
c5780e97 | 1348 | hrtimer_init_sleeper(to, current); |
c19384b5 | 1349 | to->timer.expires = *time; |
c5780e97 TG |
1350 | } |
1351 | ||
c87e2837 IM |
1352 | q.pi_state = NULL; |
1353 | retry: | |
36cf3b5c | 1354 | futex_lock_mm(fshared); |
c87e2837 | 1355 | |
34f01cc1 | 1356 | ret = get_futex_key(uaddr, fshared, &q.key); |
c87e2837 IM |
1357 | if (unlikely(ret != 0)) |
1358 | goto out_release_sem; | |
1359 | ||
778e9a9c | 1360 | retry_unlocked: |
c87e2837 IM |
1361 | hb = queue_lock(&q, -1, NULL); |
1362 | ||
1363 | retry_locked: | |
778e9a9c | 1364 | ret = lock_taken = 0; |
d0aa7a70 | 1365 | |
c87e2837 IM |
1366 | /* |
1367 | * To avoid races, we attempt to take the lock here again | |
1368 | * (by doing a 0 -> TID atomic cmpxchg), while holding all | |
1369 | * the locks. It will most likely not succeed. | |
1370 | */ | |
b488893a | 1371 | newval = task_pid_vnr(current); |
c87e2837 | 1372 | |
36cf3b5c | 1373 | curval = cmpxchg_futex_value_locked(uaddr, 0, newval); |
c87e2837 IM |
1374 | |
1375 | if (unlikely(curval == -EFAULT)) | |
1376 | goto uaddr_faulted; | |
1377 | ||
778e9a9c AK |
1378 | /* |
1379 | * Detect deadlocks. In case of REQUEUE_PI this is a valid | |
1380 | * situation and we return success to user space. | |
1381 | */ | |
b488893a | 1382 | if (unlikely((curval & FUTEX_TID_MASK) == task_pid_vnr(current))) { |
bd197234 | 1383 | ret = -EDEADLK; |
c87e2837 IM |
1384 | goto out_unlock_release_sem; |
1385 | } | |
1386 | ||
1387 | /* | |
778e9a9c | 1388 | * Surprise - we got the lock. Just return to userspace: |
c87e2837 IM |
1389 | */ |
1390 | if (unlikely(!curval)) | |
1391 | goto out_unlock_release_sem; | |
1392 | ||
1393 | uval = curval; | |
778e9a9c | 1394 | |
d0aa7a70 | 1395 | /* |
778e9a9c AK |
1396 | * Set the WAITERS flag, so the owner will know it has someone |
1397 | * to wake at next unlock | |
d0aa7a70 | 1398 | */ |
778e9a9c AK |
1399 | newval = curval | FUTEX_WAITERS; |
1400 | ||
1401 | /* | |
1402 | * There are two cases, where a futex might have no owner (the | |
bd197234 TG |
1403 | * owner TID is 0): OWNER_DIED. We take over the futex in this |
1404 | * case. We also do an unconditional take over, when the owner | |
1405 | * of the futex died. | |
778e9a9c AK |
1406 | * |
1407 | * This is safe as we are protected by the hash bucket lock ! | |
1408 | */ | |
1409 | if (unlikely(ownerdied || !(curval & FUTEX_TID_MASK))) { | |
bd197234 | 1410 | /* Keep the OWNER_DIED bit */ |
b488893a | 1411 | newval = (curval & ~FUTEX_TID_MASK) | task_pid_vnr(current); |
778e9a9c AK |
1412 | ownerdied = 0; |
1413 | lock_taken = 1; | |
1414 | } | |
c87e2837 | 1415 | |
36cf3b5c | 1416 | curval = cmpxchg_futex_value_locked(uaddr, uval, newval); |
c87e2837 IM |
1417 | |
1418 | if (unlikely(curval == -EFAULT)) | |
1419 | goto uaddr_faulted; | |
1420 | if (unlikely(curval != uval)) | |
1421 | goto retry_locked; | |
1422 | ||
778e9a9c | 1423 | /* |
bd197234 | 1424 | * We took the lock due to owner died take over. |
778e9a9c | 1425 | */ |
bd197234 | 1426 | if (unlikely(lock_taken)) |
d0aa7a70 | 1427 | goto out_unlock_release_sem; |
d0aa7a70 | 1428 | |
c87e2837 IM |
1429 | /* |
1430 | * We dont have the lock. Look up the PI state (or create it if | |
1431 | * we are the first waiter): | |
1432 | */ | |
d0aa7a70 | 1433 | ret = lookup_pi_state(uval, hb, &q.key, &q.pi_state); |
c87e2837 IM |
1434 | |
1435 | if (unlikely(ret)) { | |
778e9a9c | 1436 | switch (ret) { |
c87e2837 | 1437 | |
778e9a9c AK |
1438 | case -EAGAIN: |
1439 | /* | |
1440 | * Task is exiting and we just wait for the | |
1441 | * exit to complete. | |
1442 | */ | |
1443 | queue_unlock(&q, hb); | |
36cf3b5c | 1444 | futex_unlock_mm(fshared); |
778e9a9c AK |
1445 | cond_resched(); |
1446 | goto retry; | |
c87e2837 | 1447 | |
778e9a9c AK |
1448 | case -ESRCH: |
1449 | /* | |
1450 | * No owner found for this futex. Check if the | |
1451 | * OWNER_DIED bit is set to figure out whether | |
1452 | * this is a robust futex or not. | |
1453 | */ | |
1454 | if (get_futex_value_locked(&curval, uaddr)) | |
c87e2837 | 1455 | goto uaddr_faulted; |
778e9a9c AK |
1456 | |
1457 | /* | |
1458 | * We simply start over in case of a robust | |
1459 | * futex. The code above will take the futex | |
1460 | * and return happy. | |
1461 | */ | |
1462 | if (curval & FUTEX_OWNER_DIED) { | |
1463 | ownerdied = 1; | |
c87e2837 | 1464 | goto retry_locked; |
778e9a9c AK |
1465 | } |
1466 | default: | |
1467 | goto out_unlock_release_sem; | |
c87e2837 | 1468 | } |
c87e2837 IM |
1469 | } |
1470 | ||
1471 | /* | |
1472 | * Only actually queue now that the atomic ops are done: | |
1473 | */ | |
1474 | __queue_me(&q, hb); | |
1475 | ||
1476 | /* | |
1477 | * Now the futex is queued and we have checked the data, we | |
1478 | * don't want to hold mmap_sem while we sleep. | |
1479 | */ | |
36cf3b5c | 1480 | futex_unlock_mm(fshared); |
c87e2837 IM |
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 | ||
36cf3b5c | 1494 | futex_lock_mm(fshared); |
a99e4e41 | 1495 | spin_lock(q.lock_ptr); |
c87e2837 | 1496 | |
778e9a9c AK |
1497 | if (!ret) { |
1498 | /* | |
1499 | * Got the lock. We might not be the anticipated owner | |
1500 | * if we did a lock-steal - fix up the PI-state in | |
1501 | * that case: | |
1502 | */ | |
1503 | if (q.pi_state->owner != curr) | |
1504 | ret = fixup_pi_state_owner(uaddr, &q, curr); | |
1505 | } else { | |
c87e2837 IM |
1506 | /* |
1507 | * Catch the rare case, where the lock was released | |
778e9a9c AK |
1508 | * when we were on the way back before we locked the |
1509 | * hash bucket. | |
c87e2837 | 1510 | */ |
778e9a9c AK |
1511 | if (q.pi_state->owner == curr && |
1512 | rt_mutex_trylock(&q.pi_state->pi_mutex)) { | |
1513 | ret = 0; | |
1514 | } else { | |
1515 | /* | |
1516 | * Paranoia check. If we did not take the lock | |
1517 | * in the trylock above, then we should not be | |
1518 | * the owner of the rtmutex, neither the real | |
1519 | * nor the pending one: | |
1520 | */ | |
1521 | if (rt_mutex_owner(&q.pi_state->pi_mutex) == curr) | |
1522 | printk(KERN_ERR "futex_lock_pi: ret = %d " | |
1523 | "pi-mutex: %p pi-state %p\n", ret, | |
1524 | q.pi_state->pi_mutex.owner, | |
1525 | q.pi_state->owner); | |
c87e2837 | 1526 | } |
c87e2837 IM |
1527 | } |
1528 | ||
778e9a9c AK |
1529 | /* Unqueue and drop the lock */ |
1530 | unqueue_me_pi(&q); | |
36cf3b5c | 1531 | futex_unlock_mm(fshared); |
c87e2837 | 1532 | |
c5780e97 | 1533 | return ret != -EINTR ? ret : -ERESTARTNOINTR; |
c87e2837 IM |
1534 | |
1535 | out_unlock_release_sem: | |
1536 | queue_unlock(&q, hb); | |
1537 | ||
1538 | out_release_sem: | |
36cf3b5c | 1539 | futex_unlock_mm(fshared); |
c87e2837 IM |
1540 | return ret; |
1541 | ||
1542 | uaddr_faulted: | |
1543 | /* | |
1544 | * We have to r/w *(int __user *)uaddr, but we can't modify it | |
1545 | * non-atomically. Therefore, if get_user below is not | |
1546 | * enough, we need to handle the fault ourselves, while | |
1547 | * still holding the mmap_sem. | |
778e9a9c AK |
1548 | * |
1549 | * ... and hb->lock. :-) --ANK | |
c87e2837 | 1550 | */ |
778e9a9c AK |
1551 | queue_unlock(&q, hb); |
1552 | ||
c87e2837 | 1553 | if (attempt++) { |
34f01cc1 ED |
1554 | ret = futex_handle_fault((unsigned long)uaddr, fshared, |
1555 | attempt); | |
1556 | if (ret) | |
778e9a9c AK |
1557 | goto out_release_sem; |
1558 | goto retry_unlocked; | |
c87e2837 IM |
1559 | } |
1560 | ||
36cf3b5c | 1561 | futex_unlock_mm(fshared); |
c87e2837 IM |
1562 | |
1563 | ret = get_user(uval, uaddr); | |
1564 | if (!ret && (uval != -EFAULT)) | |
1565 | goto retry; | |
1566 | ||
1567 | return ret; | |
1568 | } | |
1569 | ||
c87e2837 IM |
1570 | /* |
1571 | * Userspace attempted a TID -> 0 atomic transition, and failed. | |
1572 | * This is the in-kernel slowpath: we look up the PI state (if any), | |
1573 | * and do the rt-mutex unlock. | |
1574 | */ | |
34f01cc1 | 1575 | static int futex_unlock_pi(u32 __user *uaddr, struct rw_semaphore *fshared) |
c87e2837 IM |
1576 | { |
1577 | struct futex_hash_bucket *hb; | |
1578 | struct futex_q *this, *next; | |
1579 | u32 uval; | |
ec92d082 | 1580 | struct plist_head *head; |
c87e2837 IM |
1581 | union futex_key key; |
1582 | int ret, attempt = 0; | |
1583 | ||
1584 | retry: | |
1585 | if (get_user(uval, uaddr)) | |
1586 | return -EFAULT; | |
1587 | /* | |
1588 | * We release only a lock we actually own: | |
1589 | */ | |
b488893a | 1590 | if ((uval & FUTEX_TID_MASK) != task_pid_vnr(current)) |
c87e2837 IM |
1591 | return -EPERM; |
1592 | /* | |
1593 | * First take all the futex related locks: | |
1594 | */ | |
36cf3b5c | 1595 | futex_lock_mm(fshared); |
c87e2837 | 1596 | |
34f01cc1 | 1597 | ret = get_futex_key(uaddr, fshared, &key); |
c87e2837 IM |
1598 | if (unlikely(ret != 0)) |
1599 | goto out; | |
1600 | ||
1601 | hb = hash_futex(&key); | |
778e9a9c | 1602 | retry_unlocked: |
c87e2837 IM |
1603 | spin_lock(&hb->lock); |
1604 | ||
c87e2837 IM |
1605 | /* |
1606 | * To avoid races, try to do the TID -> 0 atomic transition | |
1607 | * again. If it succeeds then we can return without waking | |
1608 | * anyone else up: | |
1609 | */ | |
36cf3b5c | 1610 | if (!(uval & FUTEX_OWNER_DIED)) |
b488893a | 1611 | uval = cmpxchg_futex_value_locked(uaddr, task_pid_vnr(current), 0); |
36cf3b5c | 1612 | |
c87e2837 IM |
1613 | |
1614 | if (unlikely(uval == -EFAULT)) | |
1615 | goto pi_faulted; | |
1616 | /* | |
1617 | * Rare case: we managed to release the lock atomically, | |
1618 | * no need to wake anyone else up: | |
1619 | */ | |
b488893a | 1620 | if (unlikely(uval == task_pid_vnr(current))) |
c87e2837 IM |
1621 | goto out_unlock; |
1622 | ||
1623 | /* | |
1624 | * Ok, other tasks may need to be woken up - check waiters | |
1625 | * and do the wakeup if necessary: | |
1626 | */ | |
1627 | head = &hb->chain; | |
1628 | ||
ec92d082 | 1629 | plist_for_each_entry_safe(this, next, head, list) { |
c87e2837 IM |
1630 | if (!match_futex (&this->key, &key)) |
1631 | continue; | |
1632 | ret = wake_futex_pi(uaddr, uval, this); | |
1633 | /* | |
1634 | * The atomic access to the futex value | |
1635 | * generated a pagefault, so retry the | |
1636 | * user-access and the wakeup: | |
1637 | */ | |
1638 | if (ret == -EFAULT) | |
1639 | goto pi_faulted; | |
1640 | goto out_unlock; | |
1641 | } | |
1642 | /* | |
1643 | * No waiters - kernel unlocks the futex: | |
1644 | */ | |
e3f2ddea IM |
1645 | if (!(uval & FUTEX_OWNER_DIED)) { |
1646 | ret = unlock_futex_pi(uaddr, uval); | |
1647 | if (ret == -EFAULT) | |
1648 | goto pi_faulted; | |
1649 | } | |
c87e2837 IM |
1650 | |
1651 | out_unlock: | |
1652 | spin_unlock(&hb->lock); | |
1653 | out: | |
36cf3b5c | 1654 | futex_unlock_mm(fshared); |
c87e2837 IM |
1655 | |
1656 | return ret; | |
1657 | ||
1658 | pi_faulted: | |
1659 | /* | |
1660 | * We have to r/w *(int __user *)uaddr, but we can't modify it | |
1661 | * non-atomically. Therefore, if get_user below is not | |
1662 | * enough, we need to handle the fault ourselves, while | |
1663 | * still holding the mmap_sem. | |
778e9a9c AK |
1664 | * |
1665 | * ... and hb->lock. --ANK | |
c87e2837 | 1666 | */ |
778e9a9c AK |
1667 | spin_unlock(&hb->lock); |
1668 | ||
c87e2837 | 1669 | if (attempt++) { |
34f01cc1 ED |
1670 | ret = futex_handle_fault((unsigned long)uaddr, fshared, |
1671 | attempt); | |
1672 | if (ret) | |
778e9a9c | 1673 | goto out; |
187226f5 | 1674 | uval = 0; |
778e9a9c | 1675 | goto retry_unlocked; |
c87e2837 IM |
1676 | } |
1677 | ||
36cf3b5c | 1678 | futex_unlock_mm(fshared); |
c87e2837 IM |
1679 | |
1680 | ret = get_user(uval, uaddr); | |
1681 | if (!ret && (uval != -EFAULT)) | |
1682 | goto retry; | |
1683 | ||
1da177e4 LT |
1684 | return ret; |
1685 | } | |
1686 | ||
1687 | static int futex_close(struct inode *inode, struct file *filp) | |
1688 | { | |
1689 | struct futex_q *q = filp->private_data; | |
1690 | ||
1691 | unqueue_me(q); | |
1692 | kfree(q); | |
e2970f2f | 1693 | |
1da177e4 LT |
1694 | return 0; |
1695 | } | |
1696 | ||
1697 | /* This is one-shot: once it's gone off you need a new fd */ | |
1698 | static unsigned int futex_poll(struct file *filp, | |
1699 | struct poll_table_struct *wait) | |
1700 | { | |
1701 | struct futex_q *q = filp->private_data; | |
1702 | int ret = 0; | |
1703 | ||
1704 | poll_wait(filp, &q->waiters, wait); | |
1705 | ||
1706 | /* | |
ec92d082 | 1707 | * plist_node_empty() is safe here without any lock. |
1da177e4 LT |
1708 | * q->lock_ptr != 0 is not safe, because of ordering against wakeup. |
1709 | */ | |
ec92d082 | 1710 | if (plist_node_empty(&q->list)) |
1da177e4 LT |
1711 | ret = POLLIN | POLLRDNORM; |
1712 | ||
1713 | return ret; | |
1714 | } | |
1715 | ||
15ad7cdc | 1716 | static const struct file_operations futex_fops = { |
1da177e4 LT |
1717 | .release = futex_close, |
1718 | .poll = futex_poll, | |
1719 | }; | |
1720 | ||
1721 | /* | |
1722 | * Signal allows caller to avoid the race which would occur if they | |
1723 | * set the sigio stuff up afterwards. | |
1724 | */ | |
e2970f2f | 1725 | static int futex_fd(u32 __user *uaddr, int signal) |
1da177e4 LT |
1726 | { |
1727 | struct futex_q *q; | |
1728 | struct file *filp; | |
1729 | int ret, err; | |
34f01cc1 | 1730 | struct rw_semaphore *fshared; |
19c6b6ed AM |
1731 | static unsigned long printk_interval; |
1732 | ||
1733 | if (printk_timed_ratelimit(&printk_interval, 60 * 60 * 1000)) { | |
1734 | printk(KERN_WARNING "Process `%s' used FUTEX_FD, which " | |
36cf3b5c TG |
1735 | "will be removed from the kernel in June 2007\n", |
1736 | current->comm); | |
19c6b6ed | 1737 | } |
1da177e4 LT |
1738 | |
1739 | ret = -EINVAL; | |
7ed20e1a | 1740 | if (!valid_signal(signal)) |
1da177e4 LT |
1741 | goto out; |
1742 | ||
1743 | ret = get_unused_fd(); | |
1744 | if (ret < 0) | |
1745 | goto out; | |
1746 | filp = get_empty_filp(); | |
1747 | if (!filp) { | |
1748 | put_unused_fd(ret); | |
1749 | ret = -ENFILE; | |
1750 | goto out; | |
1751 | } | |
1752 | filp->f_op = &futex_fops; | |
f3a43f3f JJS |
1753 | filp->f_path.mnt = mntget(futex_mnt); |
1754 | filp->f_path.dentry = dget(futex_mnt->mnt_root); | |
1755 | filp->f_mapping = filp->f_path.dentry->d_inode->i_mapping; | |
1da177e4 LT |
1756 | |
1757 | if (signal) { | |
609d7fa9 | 1758 | err = __f_setown(filp, task_pid(current), PIDTYPE_PID, 1); |
1da177e4 | 1759 | if (err < 0) { |
39ed3fde | 1760 | goto error; |
1da177e4 LT |
1761 | } |
1762 | filp->f_owner.signum = signal; | |
1763 | } | |
1764 | ||
1765 | q = kmalloc(sizeof(*q), GFP_KERNEL); | |
1766 | if (!q) { | |
39ed3fde PE |
1767 | err = -ENOMEM; |
1768 | goto error; | |
1da177e4 | 1769 | } |
c87e2837 | 1770 | q->pi_state = NULL; |
1da177e4 | 1771 | |
34f01cc1 ED |
1772 | fshared = ¤t->mm->mmap_sem; |
1773 | down_read(fshared); | |
1774 | err = get_futex_key(uaddr, fshared, &q->key); | |
1da177e4 LT |
1775 | |
1776 | if (unlikely(err != 0)) { | |
34f01cc1 | 1777 | up_read(fshared); |
1da177e4 | 1778 | kfree(q); |
39ed3fde | 1779 | goto error; |
1da177e4 LT |
1780 | } |
1781 | ||
1782 | /* | |
1783 | * queue_me() must be called before releasing mmap_sem, because | |
1784 | * key->shared.inode needs to be referenced while holding it. | |
1785 | */ | |
1786 | filp->private_data = q; | |
1787 | ||
1788 | queue_me(q, ret, filp); | |
34f01cc1 | 1789 | up_read(fshared); |
1da177e4 LT |
1790 | |
1791 | /* Now we map fd to filp, so userspace can access it */ | |
1792 | fd_install(ret, filp); | |
1793 | out: | |
1794 | return ret; | |
39ed3fde PE |
1795 | error: |
1796 | put_unused_fd(ret); | |
1797 | put_filp(filp); | |
1798 | ret = err; | |
1799 | goto out; | |
1da177e4 LT |
1800 | } |
1801 | ||
0771dfef IM |
1802 | /* |
1803 | * Support for robust futexes: the kernel cleans up held futexes at | |
1804 | * thread exit time. | |
1805 | * | |
1806 | * Implementation: user-space maintains a per-thread list of locks it | |
1807 | * is holding. Upon do_exit(), the kernel carefully walks this list, | |
1808 | * and marks all locks that are owned by this thread with the | |
c87e2837 | 1809 | * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is |
0771dfef IM |
1810 | * always manipulated with the lock held, so the list is private and |
1811 | * per-thread. Userspace also maintains a per-thread 'list_op_pending' | |
1812 | * field, to allow the kernel to clean up if the thread dies after | |
1813 | * acquiring the lock, but just before it could have added itself to | |
1814 | * the list. There can only be one such pending lock. | |
1815 | */ | |
1816 | ||
1817 | /** | |
1818 | * sys_set_robust_list - set the robust-futex list head of a task | |
1819 | * @head: pointer to the list-head | |
1820 | * @len: length of the list-head, as userspace expects | |
1821 | */ | |
1822 | asmlinkage long | |
1823 | sys_set_robust_list(struct robust_list_head __user *head, | |
1824 | size_t len) | |
1825 | { | |
1826 | /* | |
1827 | * The kernel knows only one size for now: | |
1828 | */ | |
1829 | if (unlikely(len != sizeof(*head))) | |
1830 | return -EINVAL; | |
1831 | ||
1832 | current->robust_list = head; | |
1833 | ||
1834 | return 0; | |
1835 | } | |
1836 | ||
1837 | /** | |
1838 | * sys_get_robust_list - get the robust-futex list head of a task | |
1839 | * @pid: pid of the process [zero for current task] | |
1840 | * @head_ptr: pointer to a list-head pointer, the kernel fills it in | |
1841 | * @len_ptr: pointer to a length field, the kernel fills in the header size | |
1842 | */ | |
1843 | asmlinkage long | |
ba46df98 | 1844 | sys_get_robust_list(int pid, struct robust_list_head __user * __user *head_ptr, |
0771dfef IM |
1845 | size_t __user *len_ptr) |
1846 | { | |
ba46df98 | 1847 | struct robust_list_head __user *head; |
0771dfef IM |
1848 | unsigned long ret; |
1849 | ||
1850 | if (!pid) | |
1851 | head = current->robust_list; | |
1852 | else { | |
1853 | struct task_struct *p; | |
1854 | ||
1855 | ret = -ESRCH; | |
aaa2a97e | 1856 | rcu_read_lock(); |
228ebcbe | 1857 | p = find_task_by_vpid(pid); |
0771dfef IM |
1858 | if (!p) |
1859 | goto err_unlock; | |
1860 | ret = -EPERM; | |
1861 | if ((current->euid != p->euid) && (current->euid != p->uid) && | |
1862 | !capable(CAP_SYS_PTRACE)) | |
1863 | goto err_unlock; | |
1864 | head = p->robust_list; | |
aaa2a97e | 1865 | rcu_read_unlock(); |
0771dfef IM |
1866 | } |
1867 | ||
1868 | if (put_user(sizeof(*head), len_ptr)) | |
1869 | return -EFAULT; | |
1870 | return put_user(head, head_ptr); | |
1871 | ||
1872 | err_unlock: | |
aaa2a97e | 1873 | rcu_read_unlock(); |
0771dfef IM |
1874 | |
1875 | return ret; | |
1876 | } | |
1877 | ||
1878 | /* | |
1879 | * Process a futex-list entry, check whether it's owned by the | |
1880 | * dying task, and do notification if so: | |
1881 | */ | |
e3f2ddea | 1882 | int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi) |
0771dfef | 1883 | { |
e3f2ddea | 1884 | u32 uval, nval, mval; |
0771dfef | 1885 | |
8f17d3a5 IM |
1886 | retry: |
1887 | if (get_user(uval, uaddr)) | |
0771dfef IM |
1888 | return -1; |
1889 | ||
b488893a | 1890 | if ((uval & FUTEX_TID_MASK) == task_pid_vnr(curr)) { |
0771dfef IM |
1891 | /* |
1892 | * Ok, this dying thread is truly holding a futex | |
1893 | * of interest. Set the OWNER_DIED bit atomically | |
1894 | * via cmpxchg, and if the value had FUTEX_WAITERS | |
1895 | * set, wake up a waiter (if any). (We have to do a | |
1896 | * futex_wake() even if OWNER_DIED is already set - | |
1897 | * to handle the rare but possible case of recursive | |
1898 | * thread-death.) The rest of the cleanup is done in | |
1899 | * userspace. | |
1900 | */ | |
e3f2ddea IM |
1901 | mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED; |
1902 | nval = futex_atomic_cmpxchg_inatomic(uaddr, uval, mval); | |
1903 | ||
c87e2837 IM |
1904 | if (nval == -EFAULT) |
1905 | return -1; | |
1906 | ||
1907 | if (nval != uval) | |
8f17d3a5 | 1908 | goto retry; |
0771dfef | 1909 | |
e3f2ddea IM |
1910 | /* |
1911 | * Wake robust non-PI futexes here. The wakeup of | |
1912 | * PI futexes happens in exit_pi_state(): | |
1913 | */ | |
36cf3b5c | 1914 | if (!pi && (uval & FUTEX_WAITERS)) |
34f01cc1 | 1915 | futex_wake(uaddr, &curr->mm->mmap_sem, 1); |
0771dfef IM |
1916 | } |
1917 | return 0; | |
1918 | } | |
1919 | ||
e3f2ddea IM |
1920 | /* |
1921 | * Fetch a robust-list pointer. Bit 0 signals PI futexes: | |
1922 | */ | |
1923 | static inline int fetch_robust_entry(struct robust_list __user **entry, | |
ba46df98 AV |
1924 | struct robust_list __user * __user *head, |
1925 | int *pi) | |
e3f2ddea IM |
1926 | { |
1927 | unsigned long uentry; | |
1928 | ||
ba46df98 | 1929 | if (get_user(uentry, (unsigned long __user *)head)) |
e3f2ddea IM |
1930 | return -EFAULT; |
1931 | ||
ba46df98 | 1932 | *entry = (void __user *)(uentry & ~1UL); |
e3f2ddea IM |
1933 | *pi = uentry & 1; |
1934 | ||
1935 | return 0; | |
1936 | } | |
1937 | ||
0771dfef IM |
1938 | /* |
1939 | * Walk curr->robust_list (very carefully, it's a userspace list!) | |
1940 | * and mark any locks found there dead, and notify any waiters. | |
1941 | * | |
1942 | * We silently return on any sign of list-walking problem. | |
1943 | */ | |
1944 | void exit_robust_list(struct task_struct *curr) | |
1945 | { | |
1946 | struct robust_list_head __user *head = curr->robust_list; | |
9f96cb1e MS |
1947 | struct robust_list __user *entry, *next_entry, *pending; |
1948 | unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip; | |
0771dfef | 1949 | unsigned long futex_offset; |
9f96cb1e | 1950 | int rc; |
0771dfef IM |
1951 | |
1952 | /* | |
1953 | * Fetch the list head (which was registered earlier, via | |
1954 | * sys_set_robust_list()): | |
1955 | */ | |
e3f2ddea | 1956 | if (fetch_robust_entry(&entry, &head->list.next, &pi)) |
0771dfef IM |
1957 | return; |
1958 | /* | |
1959 | * Fetch the relative futex offset: | |
1960 | */ | |
1961 | if (get_user(futex_offset, &head->futex_offset)) | |
1962 | return; | |
1963 | /* | |
1964 | * Fetch any possibly pending lock-add first, and handle it | |
1965 | * if it exists: | |
1966 | */ | |
e3f2ddea | 1967 | if (fetch_robust_entry(&pending, &head->list_op_pending, &pip)) |
0771dfef | 1968 | return; |
e3f2ddea | 1969 | |
9f96cb1e | 1970 | next_entry = NULL; /* avoid warning with gcc */ |
0771dfef | 1971 | while (entry != &head->list) { |
9f96cb1e MS |
1972 | /* |
1973 | * Fetch the next entry in the list before calling | |
1974 | * handle_futex_death: | |
1975 | */ | |
1976 | rc = fetch_robust_entry(&next_entry, &entry->next, &next_pi); | |
0771dfef IM |
1977 | /* |
1978 | * A pending lock might already be on the list, so | |
c87e2837 | 1979 | * don't process it twice: |
0771dfef IM |
1980 | */ |
1981 | if (entry != pending) | |
ba46df98 | 1982 | if (handle_futex_death((void __user *)entry + futex_offset, |
e3f2ddea | 1983 | curr, pi)) |
0771dfef | 1984 | return; |
9f96cb1e | 1985 | if (rc) |
0771dfef | 1986 | return; |
9f96cb1e MS |
1987 | entry = next_entry; |
1988 | pi = next_pi; | |
0771dfef IM |
1989 | /* |
1990 | * Avoid excessively long or circular lists: | |
1991 | */ | |
1992 | if (!--limit) | |
1993 | break; | |
1994 | ||
1995 | cond_resched(); | |
1996 | } | |
9f96cb1e MS |
1997 | |
1998 | if (pending) | |
1999 | handle_futex_death((void __user *)pending + futex_offset, | |
2000 | curr, pip); | |
0771dfef IM |
2001 | } |
2002 | ||
c19384b5 | 2003 | long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout, |
e2970f2f | 2004 | u32 __user *uaddr2, u32 val2, u32 val3) |
1da177e4 LT |
2005 | { |
2006 | int ret; | |
34f01cc1 ED |
2007 | int cmd = op & FUTEX_CMD_MASK; |
2008 | struct rw_semaphore *fshared = NULL; | |
2009 | ||
2010 | if (!(op & FUTEX_PRIVATE_FLAG)) | |
2011 | fshared = ¤t->mm->mmap_sem; | |
1da177e4 | 2012 | |
34f01cc1 | 2013 | switch (cmd) { |
1da177e4 | 2014 | case FUTEX_WAIT: |
34f01cc1 | 2015 | ret = futex_wait(uaddr, fshared, val, timeout); |
1da177e4 LT |
2016 | break; |
2017 | case FUTEX_WAKE: | |
34f01cc1 | 2018 | ret = futex_wake(uaddr, fshared, val); |
1da177e4 LT |
2019 | break; |
2020 | case FUTEX_FD: | |
2021 | /* non-zero val means F_SETOWN(getpid()) & F_SETSIG(val) */ | |
2022 | ret = futex_fd(uaddr, val); | |
2023 | break; | |
2024 | case FUTEX_REQUEUE: | |
34f01cc1 | 2025 | ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, NULL); |
1da177e4 LT |
2026 | break; |
2027 | case FUTEX_CMP_REQUEUE: | |
34f01cc1 | 2028 | ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, &val3); |
1da177e4 | 2029 | break; |
4732efbe | 2030 | case FUTEX_WAKE_OP: |
34f01cc1 | 2031 | ret = futex_wake_op(uaddr, fshared, uaddr2, val, val2, val3); |
4732efbe | 2032 | break; |
c87e2837 | 2033 | case FUTEX_LOCK_PI: |
34f01cc1 | 2034 | ret = futex_lock_pi(uaddr, fshared, val, timeout, 0); |
c87e2837 IM |
2035 | break; |
2036 | case FUTEX_UNLOCK_PI: | |
34f01cc1 | 2037 | ret = futex_unlock_pi(uaddr, fshared); |
c87e2837 IM |
2038 | break; |
2039 | case FUTEX_TRYLOCK_PI: | |
34f01cc1 | 2040 | ret = futex_lock_pi(uaddr, fshared, 0, timeout, 1); |
c87e2837 | 2041 | break; |
1da177e4 LT |
2042 | default: |
2043 | ret = -ENOSYS; | |
2044 | } | |
2045 | return ret; | |
2046 | } | |
2047 | ||
2048 | ||
e2970f2f | 2049 | asmlinkage long sys_futex(u32 __user *uaddr, int op, u32 val, |
1da177e4 | 2050 | struct timespec __user *utime, u32 __user *uaddr2, |
e2970f2f | 2051 | u32 val3) |
1da177e4 | 2052 | { |
c19384b5 PP |
2053 | struct timespec ts; |
2054 | ktime_t t, *tp = NULL; | |
e2970f2f | 2055 | u32 val2 = 0; |
34f01cc1 | 2056 | int cmd = op & FUTEX_CMD_MASK; |
1da177e4 | 2057 | |
34f01cc1 | 2058 | if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI)) { |
c19384b5 | 2059 | if (copy_from_user(&ts, utime, sizeof(ts)) != 0) |
1da177e4 | 2060 | return -EFAULT; |
c19384b5 | 2061 | if (!timespec_valid(&ts)) |
9741ef96 | 2062 | return -EINVAL; |
c19384b5 PP |
2063 | |
2064 | t = timespec_to_ktime(ts); | |
34f01cc1 | 2065 | if (cmd == FUTEX_WAIT) |
c19384b5 PP |
2066 | t = ktime_add(ktime_get(), t); |
2067 | tp = &t; | |
1da177e4 LT |
2068 | } |
2069 | /* | |
34f01cc1 | 2070 | * requeue parameter in 'utime' if cmd == FUTEX_REQUEUE. |
f54f0986 | 2071 | * number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP. |
1da177e4 | 2072 | */ |
f54f0986 AS |
2073 | if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE || |
2074 | cmd == FUTEX_WAKE_OP) | |
e2970f2f | 2075 | val2 = (u32) (unsigned long) utime; |
1da177e4 | 2076 | |
c19384b5 | 2077 | return do_futex(uaddr, op, val, tp, uaddr2, val2, val3); |
1da177e4 LT |
2078 | } |
2079 | ||
454e2398 DH |
2080 | static int futexfs_get_sb(struct file_system_type *fs_type, |
2081 | int flags, const char *dev_name, void *data, | |
2082 | struct vfsmount *mnt) | |
1da177e4 | 2083 | { |
fd5eea42 | 2084 | return get_sb_pseudo(fs_type, "futex", NULL, FUTEXFS_SUPER_MAGIC, mnt); |
1da177e4 LT |
2085 | } |
2086 | ||
2087 | static struct file_system_type futex_fs_type = { | |
2088 | .name = "futexfs", | |
2089 | .get_sb = futexfs_get_sb, | |
2090 | .kill_sb = kill_anon_super, | |
2091 | }; | |
2092 | ||
2093 | static int __init init(void) | |
2094 | { | |
95362fa9 AM |
2095 | int i = register_filesystem(&futex_fs_type); |
2096 | ||
2097 | if (i) | |
2098 | return i; | |
1da177e4 | 2099 | |
1da177e4 | 2100 | futex_mnt = kern_mount(&futex_fs_type); |
95362fa9 AM |
2101 | if (IS_ERR(futex_mnt)) { |
2102 | unregister_filesystem(&futex_fs_type); | |
2103 | return PTR_ERR(futex_mnt); | |
2104 | } | |
1da177e4 LT |
2105 | |
2106 | for (i = 0; i < ARRAY_SIZE(futex_queues); i++) { | |
ec92d082 | 2107 | plist_head_init(&futex_queues[i].chain, &futex_queues[i].lock); |
1da177e4 LT |
2108 | spin_lock_init(&futex_queues[i].lock); |
2109 | } | |
2110 | return 0; | |
2111 | } | |
2112 | __initcall(init); |