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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 | ||
a0c1e907 TG |
63 | int __read_mostly futex_cmpxchg_enabled; |
64 | ||
1da177e4 LT |
65 | #define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8) |
66 | ||
c87e2837 IM |
67 | /* |
68 | * Priority Inheritance state: | |
69 | */ | |
70 | struct futex_pi_state { | |
71 | /* | |
72 | * list of 'owned' pi_state instances - these have to be | |
73 | * cleaned up in do_exit() if the task exits prematurely: | |
74 | */ | |
75 | struct list_head list; | |
76 | ||
77 | /* | |
78 | * The PI object: | |
79 | */ | |
80 | struct rt_mutex pi_mutex; | |
81 | ||
82 | struct task_struct *owner; | |
83 | atomic_t refcount; | |
84 | ||
85 | union futex_key key; | |
86 | }; | |
87 | ||
1da177e4 LT |
88 | /* |
89 | * We use this hashed waitqueue instead of a normal wait_queue_t, so | |
90 | * we can wake only the relevant ones (hashed queues may be shared). | |
91 | * | |
92 | * A futex_q has a woken state, just like tasks have TASK_RUNNING. | |
ec92d082 | 93 | * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0. |
1da177e4 | 94 | * The order of wakup is always to make the first condition true, then |
73500ac5 | 95 | * wake up q->waiter, then make the second condition true. |
1da177e4 LT |
96 | */ |
97 | struct futex_q { | |
ec92d082 | 98 | struct plist_node list; |
73500ac5 DH |
99 | /* There can only be a single waiter */ |
100 | wait_queue_head_t waiter; | |
1da177e4 | 101 | |
e2970f2f | 102 | /* Which hash list lock to use: */ |
1da177e4 LT |
103 | spinlock_t *lock_ptr; |
104 | ||
e2970f2f | 105 | /* Key which the futex is hashed on: */ |
1da177e4 LT |
106 | union futex_key key; |
107 | ||
c87e2837 IM |
108 | /* Optional priority inheritance state: */ |
109 | struct futex_pi_state *pi_state; | |
110 | struct task_struct *task; | |
cd689985 TG |
111 | |
112 | /* Bitset for the optional bitmasked wakeup */ | |
113 | u32 bitset; | |
1da177e4 LT |
114 | }; |
115 | ||
116 | /* | |
b2d0994b DH |
117 | * Hash buckets are shared by all the futex_keys that hash to the same |
118 | * location. Each key may have multiple futex_q structures, one for each task | |
119 | * waiting on a futex. | |
1da177e4 LT |
120 | */ |
121 | struct futex_hash_bucket { | |
ec92d082 PP |
122 | spinlock_t lock; |
123 | struct plist_head chain; | |
1da177e4 LT |
124 | }; |
125 | ||
126 | static struct futex_hash_bucket futex_queues[1<<FUTEX_HASHBITS]; | |
127 | ||
1da177e4 LT |
128 | /* |
129 | * We hash on the keys returned from get_futex_key (see below). | |
130 | */ | |
131 | static struct futex_hash_bucket *hash_futex(union futex_key *key) | |
132 | { | |
133 | u32 hash = jhash2((u32*)&key->both.word, | |
134 | (sizeof(key->both.word)+sizeof(key->both.ptr))/4, | |
135 | key->both.offset); | |
136 | return &futex_queues[hash & ((1 << FUTEX_HASHBITS)-1)]; | |
137 | } | |
138 | ||
139 | /* | |
140 | * Return 1 if two futex_keys are equal, 0 otherwise. | |
141 | */ | |
142 | static inline int match_futex(union futex_key *key1, union futex_key *key2) | |
143 | { | |
144 | return (key1->both.word == key2->both.word | |
145 | && key1->both.ptr == key2->both.ptr | |
146 | && key1->both.offset == key2->both.offset); | |
147 | } | |
148 | ||
38d47c1b PZ |
149 | /* |
150 | * Take a reference to the resource addressed by a key. | |
151 | * Can be called while holding spinlocks. | |
152 | * | |
153 | */ | |
154 | static void get_futex_key_refs(union futex_key *key) | |
155 | { | |
156 | if (!key->both.ptr) | |
157 | return; | |
158 | ||
159 | switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { | |
160 | case FUT_OFF_INODE: | |
161 | atomic_inc(&key->shared.inode->i_count); | |
162 | break; | |
163 | case FUT_OFF_MMSHARED: | |
164 | atomic_inc(&key->private.mm->mm_count); | |
165 | break; | |
166 | } | |
167 | } | |
168 | ||
169 | /* | |
170 | * Drop a reference to the resource addressed by a key. | |
171 | * The hash bucket spinlock must not be held. | |
172 | */ | |
173 | static void drop_futex_key_refs(union futex_key *key) | |
174 | { | |
90621c40 DH |
175 | if (!key->both.ptr) { |
176 | /* If we're here then we tried to put a key we failed to get */ | |
177 | WARN_ON_ONCE(1); | |
38d47c1b | 178 | return; |
90621c40 | 179 | } |
38d47c1b PZ |
180 | |
181 | switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { | |
182 | case FUT_OFF_INODE: | |
183 | iput(key->shared.inode); | |
184 | break; | |
185 | case FUT_OFF_MMSHARED: | |
186 | mmdrop(key->private.mm); | |
187 | break; | |
188 | } | |
189 | } | |
190 | ||
34f01cc1 ED |
191 | /** |
192 | * get_futex_key - Get parameters which are the keys for a futex. | |
193 | * @uaddr: virtual address of the futex | |
b2d0994b | 194 | * @fshared: 0 for a PROCESS_PRIVATE futex, 1 for PROCESS_SHARED |
34f01cc1 ED |
195 | * @key: address where result is stored. |
196 | * | |
197 | * Returns a negative error code or 0 | |
198 | * The key words are stored in *key on success. | |
1da177e4 | 199 | * |
f3a43f3f | 200 | * For shared mappings, it's (page->index, vma->vm_file->f_path.dentry->d_inode, |
1da177e4 LT |
201 | * offset_within_page). For private mappings, it's (uaddr, current->mm). |
202 | * We can usually work out the index without swapping in the page. | |
203 | * | |
b2d0994b | 204 | * lock_page() might sleep, the caller should not hold a spinlock. |
1da177e4 | 205 | */ |
c2f9f201 | 206 | static int get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key) |
1da177e4 | 207 | { |
e2970f2f | 208 | unsigned long address = (unsigned long)uaddr; |
1da177e4 | 209 | struct mm_struct *mm = current->mm; |
1da177e4 LT |
210 | struct page *page; |
211 | int err; | |
212 | ||
213 | /* | |
214 | * The futex address must be "naturally" aligned. | |
215 | */ | |
e2970f2f | 216 | key->both.offset = address % PAGE_SIZE; |
34f01cc1 | 217 | if (unlikely((address % sizeof(u32)) != 0)) |
1da177e4 | 218 | return -EINVAL; |
e2970f2f | 219 | address -= key->both.offset; |
1da177e4 | 220 | |
34f01cc1 ED |
221 | /* |
222 | * PROCESS_PRIVATE futexes are fast. | |
223 | * As the mm cannot disappear under us and the 'key' only needs | |
224 | * virtual address, we dont even have to find the underlying vma. | |
225 | * Note : We do have to check 'uaddr' is a valid user address, | |
226 | * but access_ok() should be faster than find_vma() | |
227 | */ | |
228 | if (!fshared) { | |
229 | if (unlikely(!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))) | |
230 | return -EFAULT; | |
231 | key->private.mm = mm; | |
232 | key->private.address = address; | |
42569c39 | 233 | get_futex_key_refs(key); |
34f01cc1 ED |
234 | return 0; |
235 | } | |
1da177e4 | 236 | |
38d47c1b | 237 | again: |
734b05b1 | 238 | err = get_user_pages_fast(address, 1, 0, &page); |
38d47c1b PZ |
239 | if (err < 0) |
240 | return err; | |
241 | ||
242 | lock_page(page); | |
243 | if (!page->mapping) { | |
244 | unlock_page(page); | |
245 | put_page(page); | |
246 | goto again; | |
247 | } | |
1da177e4 LT |
248 | |
249 | /* | |
250 | * Private mappings are handled in a simple way. | |
251 | * | |
252 | * NOTE: When userspace waits on a MAP_SHARED mapping, even if | |
253 | * it's a read-only handle, it's expected that futexes attach to | |
38d47c1b | 254 | * the object not the particular process. |
1da177e4 | 255 | */ |
38d47c1b PZ |
256 | if (PageAnon(page)) { |
257 | key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */ | |
1da177e4 | 258 | key->private.mm = mm; |
e2970f2f | 259 | key->private.address = address; |
38d47c1b PZ |
260 | } else { |
261 | key->both.offset |= FUT_OFF_INODE; /* inode-based key */ | |
262 | key->shared.inode = page->mapping->host; | |
263 | key->shared.pgoff = page->index; | |
1da177e4 LT |
264 | } |
265 | ||
38d47c1b | 266 | get_futex_key_refs(key); |
1da177e4 | 267 | |
38d47c1b PZ |
268 | unlock_page(page); |
269 | put_page(page); | |
270 | return 0; | |
1da177e4 LT |
271 | } |
272 | ||
38d47c1b | 273 | static inline |
c2f9f201 | 274 | void put_futex_key(int fshared, union futex_key *key) |
1da177e4 | 275 | { |
38d47c1b | 276 | drop_futex_key_refs(key); |
1da177e4 LT |
277 | } |
278 | ||
36cf3b5c TG |
279 | static u32 cmpxchg_futex_value_locked(u32 __user *uaddr, u32 uval, u32 newval) |
280 | { | |
281 | u32 curval; | |
282 | ||
283 | pagefault_disable(); | |
284 | curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval); | |
285 | pagefault_enable(); | |
286 | ||
287 | return curval; | |
288 | } | |
289 | ||
290 | static int get_futex_value_locked(u32 *dest, u32 __user *from) | |
1da177e4 LT |
291 | { |
292 | int ret; | |
293 | ||
a866374a | 294 | pagefault_disable(); |
e2970f2f | 295 | ret = __copy_from_user_inatomic(dest, from, sizeof(u32)); |
a866374a | 296 | pagefault_enable(); |
1da177e4 LT |
297 | |
298 | return ret ? -EFAULT : 0; | |
299 | } | |
300 | ||
c87e2837 | 301 | /* |
34f01cc1 | 302 | * Fault handling. |
c87e2837 | 303 | */ |
c2f9f201 | 304 | static int futex_handle_fault(unsigned long address, int attempt) |
c87e2837 IM |
305 | { |
306 | struct vm_area_struct * vma; | |
307 | struct mm_struct *mm = current->mm; | |
34f01cc1 | 308 | int ret = -EFAULT; |
c87e2837 | 309 | |
34f01cc1 ED |
310 | if (attempt > 2) |
311 | return ret; | |
c87e2837 | 312 | |
61270708 | 313 | down_read(&mm->mmap_sem); |
34f01cc1 ED |
314 | vma = find_vma(mm, address); |
315 | if (vma && address >= vma->vm_start && | |
316 | (vma->vm_flags & VM_WRITE)) { | |
83c54070 NP |
317 | int fault; |
318 | fault = handle_mm_fault(mm, vma, address, 1); | |
319 | if (unlikely((fault & VM_FAULT_ERROR))) { | |
320 | #if 0 | |
321 | /* XXX: let's do this when we verify it is OK */ | |
322 | if (ret & VM_FAULT_OOM) | |
323 | ret = -ENOMEM; | |
324 | #endif | |
325 | } else { | |
34f01cc1 | 326 | ret = 0; |
83c54070 NP |
327 | if (fault & VM_FAULT_MAJOR) |
328 | current->maj_flt++; | |
329 | else | |
330 | current->min_flt++; | |
34f01cc1 | 331 | } |
c87e2837 | 332 | } |
61270708 | 333 | up_read(&mm->mmap_sem); |
34f01cc1 | 334 | return ret; |
c87e2837 IM |
335 | } |
336 | ||
337 | /* | |
338 | * PI code: | |
339 | */ | |
340 | static int refill_pi_state_cache(void) | |
341 | { | |
342 | struct futex_pi_state *pi_state; | |
343 | ||
344 | if (likely(current->pi_state_cache)) | |
345 | return 0; | |
346 | ||
4668edc3 | 347 | pi_state = kzalloc(sizeof(*pi_state), GFP_KERNEL); |
c87e2837 IM |
348 | |
349 | if (!pi_state) | |
350 | return -ENOMEM; | |
351 | ||
c87e2837 IM |
352 | INIT_LIST_HEAD(&pi_state->list); |
353 | /* pi_mutex gets initialized later */ | |
354 | pi_state->owner = NULL; | |
355 | atomic_set(&pi_state->refcount, 1); | |
38d47c1b | 356 | pi_state->key = FUTEX_KEY_INIT; |
c87e2837 IM |
357 | |
358 | current->pi_state_cache = pi_state; | |
359 | ||
360 | return 0; | |
361 | } | |
362 | ||
363 | static struct futex_pi_state * alloc_pi_state(void) | |
364 | { | |
365 | struct futex_pi_state *pi_state = current->pi_state_cache; | |
366 | ||
367 | WARN_ON(!pi_state); | |
368 | current->pi_state_cache = NULL; | |
369 | ||
370 | return pi_state; | |
371 | } | |
372 | ||
373 | static void free_pi_state(struct futex_pi_state *pi_state) | |
374 | { | |
375 | if (!atomic_dec_and_test(&pi_state->refcount)) | |
376 | return; | |
377 | ||
378 | /* | |
379 | * If pi_state->owner is NULL, the owner is most probably dying | |
380 | * and has cleaned up the pi_state already | |
381 | */ | |
382 | if (pi_state->owner) { | |
383 | spin_lock_irq(&pi_state->owner->pi_lock); | |
384 | list_del_init(&pi_state->list); | |
385 | spin_unlock_irq(&pi_state->owner->pi_lock); | |
386 | ||
387 | rt_mutex_proxy_unlock(&pi_state->pi_mutex, pi_state->owner); | |
388 | } | |
389 | ||
390 | if (current->pi_state_cache) | |
391 | kfree(pi_state); | |
392 | else { | |
393 | /* | |
394 | * pi_state->list is already empty. | |
395 | * clear pi_state->owner. | |
396 | * refcount is at 0 - put it back to 1. | |
397 | */ | |
398 | pi_state->owner = NULL; | |
399 | atomic_set(&pi_state->refcount, 1); | |
400 | current->pi_state_cache = pi_state; | |
401 | } | |
402 | } | |
403 | ||
404 | /* | |
405 | * Look up the task based on what TID userspace gave us. | |
406 | * We dont trust it. | |
407 | */ | |
408 | static struct task_struct * futex_find_get_task(pid_t pid) | |
409 | { | |
410 | struct task_struct *p; | |
c69e8d9c | 411 | const struct cred *cred = current_cred(), *pcred; |
c87e2837 | 412 | |
d359b549 | 413 | rcu_read_lock(); |
228ebcbe | 414 | p = find_task_by_vpid(pid); |
c69e8d9c | 415 | if (!p) { |
a06381fe | 416 | p = ERR_PTR(-ESRCH); |
c69e8d9c DH |
417 | } else { |
418 | pcred = __task_cred(p); | |
419 | if (cred->euid != pcred->euid && | |
420 | cred->euid != pcred->uid) | |
421 | p = ERR_PTR(-ESRCH); | |
422 | else | |
423 | get_task_struct(p); | |
424 | } | |
a06381fe | 425 | |
d359b549 | 426 | rcu_read_unlock(); |
c87e2837 IM |
427 | |
428 | return p; | |
429 | } | |
430 | ||
431 | /* | |
432 | * This task is holding PI mutexes at exit time => bad. | |
433 | * Kernel cleans up PI-state, but userspace is likely hosed. | |
434 | * (Robust-futex cleanup is separate and might save the day for userspace.) | |
435 | */ | |
436 | void exit_pi_state_list(struct task_struct *curr) | |
437 | { | |
c87e2837 IM |
438 | struct list_head *next, *head = &curr->pi_state_list; |
439 | struct futex_pi_state *pi_state; | |
627371d7 | 440 | struct futex_hash_bucket *hb; |
38d47c1b | 441 | union futex_key key = FUTEX_KEY_INIT; |
c87e2837 | 442 | |
a0c1e907 TG |
443 | if (!futex_cmpxchg_enabled) |
444 | return; | |
c87e2837 IM |
445 | /* |
446 | * We are a ZOMBIE and nobody can enqueue itself on | |
447 | * pi_state_list anymore, but we have to be careful | |
627371d7 | 448 | * versus waiters unqueueing themselves: |
c87e2837 IM |
449 | */ |
450 | spin_lock_irq(&curr->pi_lock); | |
451 | while (!list_empty(head)) { | |
452 | ||
453 | next = head->next; | |
454 | pi_state = list_entry(next, struct futex_pi_state, list); | |
455 | key = pi_state->key; | |
627371d7 | 456 | hb = hash_futex(&key); |
c87e2837 IM |
457 | spin_unlock_irq(&curr->pi_lock); |
458 | ||
c87e2837 IM |
459 | spin_lock(&hb->lock); |
460 | ||
461 | spin_lock_irq(&curr->pi_lock); | |
627371d7 IM |
462 | /* |
463 | * We dropped the pi-lock, so re-check whether this | |
464 | * task still owns the PI-state: | |
465 | */ | |
c87e2837 IM |
466 | if (head->next != next) { |
467 | spin_unlock(&hb->lock); | |
468 | continue; | |
469 | } | |
470 | ||
c87e2837 | 471 | WARN_ON(pi_state->owner != curr); |
627371d7 IM |
472 | WARN_ON(list_empty(&pi_state->list)); |
473 | list_del_init(&pi_state->list); | |
c87e2837 IM |
474 | pi_state->owner = NULL; |
475 | spin_unlock_irq(&curr->pi_lock); | |
476 | ||
477 | rt_mutex_unlock(&pi_state->pi_mutex); | |
478 | ||
479 | spin_unlock(&hb->lock); | |
480 | ||
481 | spin_lock_irq(&curr->pi_lock); | |
482 | } | |
483 | spin_unlock_irq(&curr->pi_lock); | |
484 | } | |
485 | ||
486 | static int | |
d0aa7a70 PP |
487 | lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, |
488 | union futex_key *key, struct futex_pi_state **ps) | |
c87e2837 IM |
489 | { |
490 | struct futex_pi_state *pi_state = NULL; | |
491 | struct futex_q *this, *next; | |
ec92d082 | 492 | struct plist_head *head; |
c87e2837 | 493 | struct task_struct *p; |
778e9a9c | 494 | pid_t pid = uval & FUTEX_TID_MASK; |
c87e2837 IM |
495 | |
496 | head = &hb->chain; | |
497 | ||
ec92d082 | 498 | plist_for_each_entry_safe(this, next, head, list) { |
d0aa7a70 | 499 | if (match_futex(&this->key, key)) { |
c87e2837 IM |
500 | /* |
501 | * Another waiter already exists - bump up | |
502 | * the refcount and return its pi_state: | |
503 | */ | |
504 | pi_state = this->pi_state; | |
06a9ec29 TG |
505 | /* |
506 | * Userspace might have messed up non PI and PI futexes | |
507 | */ | |
508 | if (unlikely(!pi_state)) | |
509 | return -EINVAL; | |
510 | ||
627371d7 | 511 | WARN_ON(!atomic_read(&pi_state->refcount)); |
778e9a9c AK |
512 | WARN_ON(pid && pi_state->owner && |
513 | pi_state->owner->pid != pid); | |
627371d7 | 514 | |
c87e2837 | 515 | atomic_inc(&pi_state->refcount); |
d0aa7a70 | 516 | *ps = pi_state; |
c87e2837 IM |
517 | |
518 | return 0; | |
519 | } | |
520 | } | |
521 | ||
522 | /* | |
e3f2ddea | 523 | * We are the first waiter - try to look up the real owner and attach |
778e9a9c | 524 | * the new pi_state to it, but bail out when TID = 0 |
c87e2837 | 525 | */ |
778e9a9c | 526 | if (!pid) |
e3f2ddea | 527 | return -ESRCH; |
c87e2837 | 528 | p = futex_find_get_task(pid); |
778e9a9c AK |
529 | if (IS_ERR(p)) |
530 | return PTR_ERR(p); | |
531 | ||
532 | /* | |
533 | * We need to look at the task state flags to figure out, | |
534 | * whether the task is exiting. To protect against the do_exit | |
535 | * change of the task flags, we do this protected by | |
536 | * p->pi_lock: | |
537 | */ | |
538 | spin_lock_irq(&p->pi_lock); | |
539 | if (unlikely(p->flags & PF_EXITING)) { | |
540 | /* | |
541 | * The task is on the way out. When PF_EXITPIDONE is | |
542 | * set, we know that the task has finished the | |
543 | * cleanup: | |
544 | */ | |
545 | int ret = (p->flags & PF_EXITPIDONE) ? -ESRCH : -EAGAIN; | |
546 | ||
547 | spin_unlock_irq(&p->pi_lock); | |
548 | put_task_struct(p); | |
549 | return ret; | |
550 | } | |
c87e2837 IM |
551 | |
552 | pi_state = alloc_pi_state(); | |
553 | ||
554 | /* | |
555 | * Initialize the pi_mutex in locked state and make 'p' | |
556 | * the owner of it: | |
557 | */ | |
558 | rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p); | |
559 | ||
560 | /* Store the key for possible exit cleanups: */ | |
d0aa7a70 | 561 | pi_state->key = *key; |
c87e2837 | 562 | |
627371d7 | 563 | WARN_ON(!list_empty(&pi_state->list)); |
c87e2837 IM |
564 | list_add(&pi_state->list, &p->pi_state_list); |
565 | pi_state->owner = p; | |
566 | spin_unlock_irq(&p->pi_lock); | |
567 | ||
568 | put_task_struct(p); | |
569 | ||
d0aa7a70 | 570 | *ps = pi_state; |
c87e2837 IM |
571 | |
572 | return 0; | |
573 | } | |
574 | ||
1da177e4 LT |
575 | /* |
576 | * The hash bucket lock must be held when this is called. | |
577 | * Afterwards, the futex_q must not be accessed. | |
578 | */ | |
579 | static void wake_futex(struct futex_q *q) | |
580 | { | |
ec92d082 | 581 | plist_del(&q->list, &q->list.plist); |
1da177e4 LT |
582 | /* |
583 | * The lock in wake_up_all() is a crucial memory barrier after the | |
ec92d082 | 584 | * plist_del() and also before assigning to q->lock_ptr. |
1da177e4 | 585 | */ |
73500ac5 | 586 | wake_up(&q->waiter); |
1da177e4 LT |
587 | /* |
588 | * The waiting task can free the futex_q as soon as this is written, | |
589 | * without taking any locks. This must come last. | |
8e31108b | 590 | * |
b2d0994b DH |
591 | * A memory barrier is required here to prevent the following store to |
592 | * lock_ptr from getting ahead of the wakeup. Clearing the lock at the | |
593 | * end of wake_up() does not prevent this store from moving. | |
1da177e4 | 594 | */ |
ccdea2f8 | 595 | smp_wmb(); |
1da177e4 LT |
596 | q->lock_ptr = NULL; |
597 | } | |
598 | ||
c87e2837 IM |
599 | static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this) |
600 | { | |
601 | struct task_struct *new_owner; | |
602 | struct futex_pi_state *pi_state = this->pi_state; | |
603 | u32 curval, newval; | |
604 | ||
605 | if (!pi_state) | |
606 | return -EINVAL; | |
607 | ||
21778867 | 608 | spin_lock(&pi_state->pi_mutex.wait_lock); |
c87e2837 IM |
609 | new_owner = rt_mutex_next_owner(&pi_state->pi_mutex); |
610 | ||
611 | /* | |
612 | * This happens when we have stolen the lock and the original | |
613 | * pending owner did not enqueue itself back on the rt_mutex. | |
614 | * Thats not a tragedy. We know that way, that a lock waiter | |
615 | * is on the fly. We make the futex_q waiter the pending owner. | |
616 | */ | |
617 | if (!new_owner) | |
618 | new_owner = this->task; | |
619 | ||
620 | /* | |
621 | * We pass it to the next owner. (The WAITERS bit is always | |
622 | * kept enabled while there is PI state around. We must also | |
623 | * preserve the owner died bit.) | |
624 | */ | |
e3f2ddea | 625 | if (!(uval & FUTEX_OWNER_DIED)) { |
778e9a9c AK |
626 | int ret = 0; |
627 | ||
b488893a | 628 | newval = FUTEX_WAITERS | task_pid_vnr(new_owner); |
e3f2ddea | 629 | |
36cf3b5c | 630 | curval = cmpxchg_futex_value_locked(uaddr, uval, newval); |
778e9a9c | 631 | |
e3f2ddea | 632 | if (curval == -EFAULT) |
778e9a9c | 633 | ret = -EFAULT; |
cde898fa | 634 | else if (curval != uval) |
778e9a9c AK |
635 | ret = -EINVAL; |
636 | if (ret) { | |
637 | spin_unlock(&pi_state->pi_mutex.wait_lock); | |
638 | return ret; | |
639 | } | |
e3f2ddea | 640 | } |
c87e2837 | 641 | |
627371d7 IM |
642 | spin_lock_irq(&pi_state->owner->pi_lock); |
643 | WARN_ON(list_empty(&pi_state->list)); | |
644 | list_del_init(&pi_state->list); | |
645 | spin_unlock_irq(&pi_state->owner->pi_lock); | |
646 | ||
647 | spin_lock_irq(&new_owner->pi_lock); | |
648 | WARN_ON(!list_empty(&pi_state->list)); | |
c87e2837 IM |
649 | list_add(&pi_state->list, &new_owner->pi_state_list); |
650 | pi_state->owner = new_owner; | |
627371d7 IM |
651 | spin_unlock_irq(&new_owner->pi_lock); |
652 | ||
21778867 | 653 | spin_unlock(&pi_state->pi_mutex.wait_lock); |
c87e2837 IM |
654 | rt_mutex_unlock(&pi_state->pi_mutex); |
655 | ||
656 | return 0; | |
657 | } | |
658 | ||
659 | static int unlock_futex_pi(u32 __user *uaddr, u32 uval) | |
660 | { | |
661 | u32 oldval; | |
662 | ||
663 | /* | |
664 | * There is no waiter, so we unlock the futex. The owner died | |
665 | * bit has not to be preserved here. We are the owner: | |
666 | */ | |
36cf3b5c | 667 | oldval = cmpxchg_futex_value_locked(uaddr, uval, 0); |
c87e2837 IM |
668 | |
669 | if (oldval == -EFAULT) | |
670 | return oldval; | |
671 | if (oldval != uval) | |
672 | return -EAGAIN; | |
673 | ||
674 | return 0; | |
675 | } | |
676 | ||
8b8f319f IM |
677 | /* |
678 | * Express the locking dependencies for lockdep: | |
679 | */ | |
680 | static inline void | |
681 | double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) | |
682 | { | |
683 | if (hb1 <= hb2) { | |
684 | spin_lock(&hb1->lock); | |
685 | if (hb1 < hb2) | |
686 | spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING); | |
687 | } else { /* hb1 > hb2 */ | |
688 | spin_lock(&hb2->lock); | |
689 | spin_lock_nested(&hb1->lock, SINGLE_DEPTH_NESTING); | |
690 | } | |
691 | } | |
692 | ||
5eb3dc62 DH |
693 | static inline void |
694 | double_unlock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) | |
695 | { | |
696 | if (hb1 <= hb2) { | |
697 | spin_unlock(&hb2->lock); | |
698 | if (hb1 < hb2) | |
699 | spin_unlock(&hb1->lock); | |
700 | } else { /* hb1 > hb2 */ | |
701 | spin_unlock(&hb1->lock); | |
702 | spin_unlock(&hb2->lock); | |
703 | } | |
704 | } | |
705 | ||
1da177e4 | 706 | /* |
b2d0994b | 707 | * Wake up waiters matching bitset queued on this futex (uaddr). |
1da177e4 | 708 | */ |
c2f9f201 | 709 | static int futex_wake(u32 __user *uaddr, int fshared, int nr_wake, u32 bitset) |
1da177e4 | 710 | { |
e2970f2f | 711 | struct futex_hash_bucket *hb; |
1da177e4 | 712 | struct futex_q *this, *next; |
ec92d082 | 713 | struct plist_head *head; |
38d47c1b | 714 | union futex_key key = FUTEX_KEY_INIT; |
1da177e4 LT |
715 | int ret; |
716 | ||
cd689985 TG |
717 | if (!bitset) |
718 | return -EINVAL; | |
719 | ||
34f01cc1 | 720 | ret = get_futex_key(uaddr, fshared, &key); |
1da177e4 LT |
721 | if (unlikely(ret != 0)) |
722 | goto out; | |
723 | ||
e2970f2f IM |
724 | hb = hash_futex(&key); |
725 | spin_lock(&hb->lock); | |
726 | head = &hb->chain; | |
1da177e4 | 727 | |
ec92d082 | 728 | plist_for_each_entry_safe(this, next, head, list) { |
1da177e4 | 729 | if (match_futex (&this->key, &key)) { |
ed6f7b10 IM |
730 | if (this->pi_state) { |
731 | ret = -EINVAL; | |
732 | break; | |
733 | } | |
cd689985 TG |
734 | |
735 | /* Check if one of the bits is set in both bitsets */ | |
736 | if (!(this->bitset & bitset)) | |
737 | continue; | |
738 | ||
1da177e4 LT |
739 | wake_futex(this); |
740 | if (++ret >= nr_wake) | |
741 | break; | |
742 | } | |
743 | } | |
744 | ||
e2970f2f | 745 | spin_unlock(&hb->lock); |
38d47c1b | 746 | put_futex_key(fshared, &key); |
42d35d48 | 747 | out: |
1da177e4 LT |
748 | return ret; |
749 | } | |
750 | ||
4732efbe JJ |
751 | /* |
752 | * Wake up all waiters hashed on the physical page that is mapped | |
753 | * to this virtual address: | |
754 | */ | |
e2970f2f | 755 | static int |
c2f9f201 | 756 | futex_wake_op(u32 __user *uaddr1, int fshared, u32 __user *uaddr2, |
e2970f2f | 757 | int nr_wake, int nr_wake2, int op) |
4732efbe | 758 | { |
38d47c1b | 759 | union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT; |
e2970f2f | 760 | struct futex_hash_bucket *hb1, *hb2; |
ec92d082 | 761 | struct plist_head *head; |
4732efbe JJ |
762 | struct futex_q *this, *next; |
763 | int ret, op_ret, attempt = 0; | |
764 | ||
765 | retryfull: | |
34f01cc1 | 766 | ret = get_futex_key(uaddr1, fshared, &key1); |
4732efbe JJ |
767 | if (unlikely(ret != 0)) |
768 | goto out; | |
34f01cc1 | 769 | ret = get_futex_key(uaddr2, fshared, &key2); |
4732efbe | 770 | if (unlikely(ret != 0)) |
42d35d48 | 771 | goto out_put_key1; |
4732efbe | 772 | |
e2970f2f IM |
773 | hb1 = hash_futex(&key1); |
774 | hb2 = hash_futex(&key2); | |
4732efbe JJ |
775 | |
776 | retry: | |
8b8f319f | 777 | double_lock_hb(hb1, hb2); |
4732efbe | 778 | |
e2970f2f | 779 | op_ret = futex_atomic_op_inuser(op, uaddr2); |
4732efbe | 780 | if (unlikely(op_ret < 0)) { |
e2970f2f | 781 | u32 dummy; |
4732efbe | 782 | |
5eb3dc62 | 783 | double_unlock_hb(hb1, hb2); |
4732efbe | 784 | |
7ee1dd3f | 785 | #ifndef CONFIG_MMU |
e2970f2f IM |
786 | /* |
787 | * we don't get EFAULT from MMU faults if we don't have an MMU, | |
788 | * but we might get them from range checking | |
789 | */ | |
7ee1dd3f | 790 | ret = op_ret; |
42d35d48 | 791 | goto out_put_keys; |
7ee1dd3f DH |
792 | #endif |
793 | ||
796f8d9b DG |
794 | if (unlikely(op_ret != -EFAULT)) { |
795 | ret = op_ret; | |
42d35d48 | 796 | goto out_put_keys; |
796f8d9b DG |
797 | } |
798 | ||
e2970f2f IM |
799 | /* |
800 | * futex_atomic_op_inuser needs to both read and write | |
4732efbe JJ |
801 | * *(int __user *)uaddr2, but we can't modify it |
802 | * non-atomically. Therefore, if get_user below is not | |
803 | * enough, we need to handle the fault ourselves, while | |
e2970f2f IM |
804 | * still holding the mmap_sem. |
805 | */ | |
4732efbe | 806 | if (attempt++) { |
34f01cc1 | 807 | ret = futex_handle_fault((unsigned long)uaddr2, |
c2f9f201 | 808 | attempt); |
34f01cc1 | 809 | if (ret) |
42d35d48 | 810 | goto out_put_keys; |
4732efbe JJ |
811 | goto retry; |
812 | } | |
813 | ||
e2970f2f | 814 | ret = get_user(dummy, uaddr2); |
4732efbe | 815 | if (ret) |
de87fcc1 | 816 | goto out_put_keys; |
4732efbe | 817 | |
de87fcc1 DH |
818 | put_futex_key(fshared, &key2); |
819 | put_futex_key(fshared, &key1); | |
4732efbe JJ |
820 | goto retryfull; |
821 | } | |
822 | ||
e2970f2f | 823 | head = &hb1->chain; |
4732efbe | 824 | |
ec92d082 | 825 | plist_for_each_entry_safe(this, next, head, list) { |
4732efbe JJ |
826 | if (match_futex (&this->key, &key1)) { |
827 | wake_futex(this); | |
828 | if (++ret >= nr_wake) | |
829 | break; | |
830 | } | |
831 | } | |
832 | ||
833 | if (op_ret > 0) { | |
e2970f2f | 834 | head = &hb2->chain; |
4732efbe JJ |
835 | |
836 | op_ret = 0; | |
ec92d082 | 837 | plist_for_each_entry_safe(this, next, head, list) { |
4732efbe JJ |
838 | if (match_futex (&this->key, &key2)) { |
839 | wake_futex(this); | |
840 | if (++op_ret >= nr_wake2) | |
841 | break; | |
842 | } | |
843 | } | |
844 | ret += op_ret; | |
845 | } | |
846 | ||
5eb3dc62 | 847 | double_unlock_hb(hb1, hb2); |
42d35d48 | 848 | out_put_keys: |
38d47c1b | 849 | put_futex_key(fshared, &key2); |
42d35d48 | 850 | out_put_key1: |
38d47c1b | 851 | put_futex_key(fshared, &key1); |
42d35d48 | 852 | out: |
4732efbe JJ |
853 | return ret; |
854 | } | |
855 | ||
1da177e4 LT |
856 | /* |
857 | * Requeue all waiters hashed on one physical page to another | |
858 | * physical page. | |
859 | */ | |
c2f9f201 | 860 | static int futex_requeue(u32 __user *uaddr1, int fshared, u32 __user *uaddr2, |
e2970f2f | 861 | int nr_wake, int nr_requeue, u32 *cmpval) |
1da177e4 | 862 | { |
38d47c1b | 863 | union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT; |
e2970f2f | 864 | struct futex_hash_bucket *hb1, *hb2; |
ec92d082 | 865 | struct plist_head *head1; |
1da177e4 LT |
866 | struct futex_q *this, *next; |
867 | int ret, drop_count = 0; | |
868 | ||
42d35d48 | 869 | retry: |
34f01cc1 | 870 | ret = get_futex_key(uaddr1, fshared, &key1); |
1da177e4 LT |
871 | if (unlikely(ret != 0)) |
872 | goto out; | |
34f01cc1 | 873 | ret = get_futex_key(uaddr2, fshared, &key2); |
1da177e4 | 874 | if (unlikely(ret != 0)) |
42d35d48 | 875 | goto out_put_key1; |
1da177e4 | 876 | |
e2970f2f IM |
877 | hb1 = hash_futex(&key1); |
878 | hb2 = hash_futex(&key2); | |
1da177e4 | 879 | |
8b8f319f | 880 | double_lock_hb(hb1, hb2); |
1da177e4 | 881 | |
e2970f2f IM |
882 | if (likely(cmpval != NULL)) { |
883 | u32 curval; | |
1da177e4 | 884 | |
e2970f2f | 885 | ret = get_futex_value_locked(&curval, uaddr1); |
1da177e4 LT |
886 | |
887 | if (unlikely(ret)) { | |
5eb3dc62 | 888 | double_unlock_hb(hb1, hb2); |
1da177e4 | 889 | |
de87fcc1 DH |
890 | put_futex_key(fshared, &key2); |
891 | put_futex_key(fshared, &key1); | |
892 | ||
e2970f2f | 893 | ret = get_user(curval, uaddr1); |
1da177e4 LT |
894 | |
895 | if (!ret) | |
896 | goto retry; | |
897 | ||
42d35d48 | 898 | goto out_put_keys; |
1da177e4 | 899 | } |
e2970f2f | 900 | if (curval != *cmpval) { |
1da177e4 LT |
901 | ret = -EAGAIN; |
902 | goto out_unlock; | |
903 | } | |
904 | } | |
905 | ||
e2970f2f | 906 | head1 = &hb1->chain; |
ec92d082 | 907 | plist_for_each_entry_safe(this, next, head1, list) { |
1da177e4 LT |
908 | if (!match_futex (&this->key, &key1)) |
909 | continue; | |
910 | if (++ret <= nr_wake) { | |
911 | wake_futex(this); | |
912 | } else { | |
59e0e0ac SD |
913 | /* |
914 | * If key1 and key2 hash to the same bucket, no need to | |
915 | * requeue. | |
916 | */ | |
917 | if (likely(head1 != &hb2->chain)) { | |
ec92d082 PP |
918 | plist_del(&this->list, &hb1->chain); |
919 | plist_add(&this->list, &hb2->chain); | |
59e0e0ac | 920 | this->lock_ptr = &hb2->lock; |
ec92d082 PP |
921 | #ifdef CONFIG_DEBUG_PI_LIST |
922 | this->list.plist.lock = &hb2->lock; | |
923 | #endif | |
778e9a9c | 924 | } |
1da177e4 | 925 | this->key = key2; |
9adef58b | 926 | get_futex_key_refs(&key2); |
1da177e4 LT |
927 | drop_count++; |
928 | ||
929 | if (ret - nr_wake >= nr_requeue) | |
930 | break; | |
1da177e4 LT |
931 | } |
932 | } | |
933 | ||
934 | out_unlock: | |
5eb3dc62 | 935 | double_unlock_hb(hb1, hb2); |
1da177e4 | 936 | |
9adef58b | 937 | /* drop_futex_key_refs() must be called outside the spinlocks. */ |
1da177e4 | 938 | while (--drop_count >= 0) |
9adef58b | 939 | drop_futex_key_refs(&key1); |
1da177e4 | 940 | |
42d35d48 | 941 | out_put_keys: |
38d47c1b | 942 | put_futex_key(fshared, &key2); |
42d35d48 | 943 | out_put_key1: |
38d47c1b | 944 | put_futex_key(fshared, &key1); |
42d35d48 | 945 | out: |
1da177e4 LT |
946 | return ret; |
947 | } | |
948 | ||
949 | /* The key must be already stored in q->key. */ | |
82af7aca | 950 | static inline struct futex_hash_bucket *queue_lock(struct futex_q *q) |
1da177e4 | 951 | { |
e2970f2f | 952 | struct futex_hash_bucket *hb; |
1da177e4 | 953 | |
73500ac5 | 954 | init_waitqueue_head(&q->waiter); |
1da177e4 | 955 | |
9adef58b | 956 | get_futex_key_refs(&q->key); |
e2970f2f IM |
957 | hb = hash_futex(&q->key); |
958 | q->lock_ptr = &hb->lock; | |
1da177e4 | 959 | |
e2970f2f IM |
960 | spin_lock(&hb->lock); |
961 | return hb; | |
1da177e4 LT |
962 | } |
963 | ||
82af7aca | 964 | static inline void queue_me(struct futex_q *q, struct futex_hash_bucket *hb) |
1da177e4 | 965 | { |
ec92d082 PP |
966 | int prio; |
967 | ||
968 | /* | |
969 | * The priority used to register this element is | |
970 | * - either the real thread-priority for the real-time threads | |
971 | * (i.e. threads with a priority lower than MAX_RT_PRIO) | |
972 | * - or MAX_RT_PRIO for non-RT threads. | |
973 | * Thus, all RT-threads are woken first in priority order, and | |
974 | * the others are woken last, in FIFO order. | |
975 | */ | |
976 | prio = min(current->normal_prio, MAX_RT_PRIO); | |
977 | ||
978 | plist_node_init(&q->list, prio); | |
979 | #ifdef CONFIG_DEBUG_PI_LIST | |
980 | q->list.plist.lock = &hb->lock; | |
981 | #endif | |
982 | plist_add(&q->list, &hb->chain); | |
c87e2837 | 983 | q->task = current; |
e2970f2f | 984 | spin_unlock(&hb->lock); |
1da177e4 LT |
985 | } |
986 | ||
987 | static inline void | |
e2970f2f | 988 | queue_unlock(struct futex_q *q, struct futex_hash_bucket *hb) |
1da177e4 | 989 | { |
e2970f2f | 990 | spin_unlock(&hb->lock); |
9adef58b | 991 | drop_futex_key_refs(&q->key); |
1da177e4 LT |
992 | } |
993 | ||
994 | /* | |
995 | * queue_me and unqueue_me must be called as a pair, each | |
996 | * exactly once. They are called with the hashed spinlock held. | |
997 | */ | |
998 | ||
1da177e4 LT |
999 | /* Return 1 if we were still queued (ie. 0 means we were woken) */ |
1000 | static int unqueue_me(struct futex_q *q) | |
1001 | { | |
1da177e4 | 1002 | spinlock_t *lock_ptr; |
e2970f2f | 1003 | int ret = 0; |
1da177e4 LT |
1004 | |
1005 | /* In the common case we don't take the spinlock, which is nice. */ | |
42d35d48 | 1006 | retry: |
1da177e4 | 1007 | lock_ptr = q->lock_ptr; |
e91467ec | 1008 | barrier(); |
c80544dc | 1009 | if (lock_ptr != NULL) { |
1da177e4 LT |
1010 | spin_lock(lock_ptr); |
1011 | /* | |
1012 | * q->lock_ptr can change between reading it and | |
1013 | * spin_lock(), causing us to take the wrong lock. This | |
1014 | * corrects the race condition. | |
1015 | * | |
1016 | * Reasoning goes like this: if we have the wrong lock, | |
1017 | * q->lock_ptr must have changed (maybe several times) | |
1018 | * between reading it and the spin_lock(). It can | |
1019 | * change again after the spin_lock() but only if it was | |
1020 | * already changed before the spin_lock(). It cannot, | |
1021 | * however, change back to the original value. Therefore | |
1022 | * we can detect whether we acquired the correct lock. | |
1023 | */ | |
1024 | if (unlikely(lock_ptr != q->lock_ptr)) { | |
1025 | spin_unlock(lock_ptr); | |
1026 | goto retry; | |
1027 | } | |
ec92d082 PP |
1028 | WARN_ON(plist_node_empty(&q->list)); |
1029 | plist_del(&q->list, &q->list.plist); | |
c87e2837 IM |
1030 | |
1031 | BUG_ON(q->pi_state); | |
1032 | ||
1da177e4 LT |
1033 | spin_unlock(lock_ptr); |
1034 | ret = 1; | |
1035 | } | |
1036 | ||
9adef58b | 1037 | drop_futex_key_refs(&q->key); |
1da177e4 LT |
1038 | return ret; |
1039 | } | |
1040 | ||
c87e2837 IM |
1041 | /* |
1042 | * PI futexes can not be requeued and must remove themself from the | |
d0aa7a70 PP |
1043 | * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry |
1044 | * and dropped here. | |
c87e2837 | 1045 | */ |
d0aa7a70 | 1046 | static void unqueue_me_pi(struct futex_q *q) |
c87e2837 | 1047 | { |
ec92d082 PP |
1048 | WARN_ON(plist_node_empty(&q->list)); |
1049 | plist_del(&q->list, &q->list.plist); | |
c87e2837 IM |
1050 | |
1051 | BUG_ON(!q->pi_state); | |
1052 | free_pi_state(q->pi_state); | |
1053 | q->pi_state = NULL; | |
1054 | ||
d0aa7a70 | 1055 | spin_unlock(q->lock_ptr); |
c87e2837 | 1056 | |
9adef58b | 1057 | drop_futex_key_refs(&q->key); |
c87e2837 IM |
1058 | } |
1059 | ||
d0aa7a70 | 1060 | /* |
cdf71a10 | 1061 | * Fixup the pi_state owner with the new owner. |
d0aa7a70 | 1062 | * |
778e9a9c AK |
1063 | * Must be called with hash bucket lock held and mm->sem held for non |
1064 | * private futexes. | |
d0aa7a70 | 1065 | */ |
778e9a9c | 1066 | static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q, |
c2f9f201 | 1067 | struct task_struct *newowner, int fshared) |
d0aa7a70 | 1068 | { |
cdf71a10 | 1069 | u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS; |
d0aa7a70 | 1070 | struct futex_pi_state *pi_state = q->pi_state; |
1b7558e4 | 1071 | struct task_struct *oldowner = pi_state->owner; |
d0aa7a70 | 1072 | u32 uval, curval, newval; |
1b7558e4 | 1073 | int ret, attempt = 0; |
d0aa7a70 PP |
1074 | |
1075 | /* Owner died? */ | |
1b7558e4 TG |
1076 | if (!pi_state->owner) |
1077 | newtid |= FUTEX_OWNER_DIED; | |
1078 | ||
1079 | /* | |
1080 | * We are here either because we stole the rtmutex from the | |
1081 | * pending owner or we are the pending owner which failed to | |
1082 | * get the rtmutex. We have to replace the pending owner TID | |
1083 | * in the user space variable. This must be atomic as we have | |
1084 | * to preserve the owner died bit here. | |
1085 | * | |
b2d0994b DH |
1086 | * Note: We write the user space value _before_ changing the pi_state |
1087 | * because we can fault here. Imagine swapped out pages or a fork | |
1088 | * that marked all the anonymous memory readonly for cow. | |
1b7558e4 TG |
1089 | * |
1090 | * Modifying pi_state _before_ the user space value would | |
1091 | * leave the pi_state in an inconsistent state when we fault | |
1092 | * here, because we need to drop the hash bucket lock to | |
1093 | * handle the fault. This might be observed in the PID check | |
1094 | * in lookup_pi_state. | |
1095 | */ | |
1096 | retry: | |
1097 | if (get_futex_value_locked(&uval, uaddr)) | |
1098 | goto handle_fault; | |
1099 | ||
1100 | while (1) { | |
1101 | newval = (uval & FUTEX_OWNER_DIED) | newtid; | |
1102 | ||
1103 | curval = cmpxchg_futex_value_locked(uaddr, uval, newval); | |
1104 | ||
1105 | if (curval == -EFAULT) | |
1106 | goto handle_fault; | |
1107 | if (curval == uval) | |
1108 | break; | |
1109 | uval = curval; | |
1110 | } | |
1111 | ||
1112 | /* | |
1113 | * We fixed up user space. Now we need to fix the pi_state | |
1114 | * itself. | |
1115 | */ | |
d0aa7a70 PP |
1116 | if (pi_state->owner != NULL) { |
1117 | spin_lock_irq(&pi_state->owner->pi_lock); | |
1118 | WARN_ON(list_empty(&pi_state->list)); | |
1119 | list_del_init(&pi_state->list); | |
1120 | spin_unlock_irq(&pi_state->owner->pi_lock); | |
1b7558e4 | 1121 | } |
d0aa7a70 | 1122 | |
cdf71a10 | 1123 | pi_state->owner = newowner; |
d0aa7a70 | 1124 | |
cdf71a10 | 1125 | spin_lock_irq(&newowner->pi_lock); |
d0aa7a70 | 1126 | WARN_ON(!list_empty(&pi_state->list)); |
cdf71a10 TG |
1127 | list_add(&pi_state->list, &newowner->pi_state_list); |
1128 | spin_unlock_irq(&newowner->pi_lock); | |
1b7558e4 | 1129 | return 0; |
d0aa7a70 | 1130 | |
d0aa7a70 | 1131 | /* |
1b7558e4 TG |
1132 | * To handle the page fault we need to drop the hash bucket |
1133 | * lock here. That gives the other task (either the pending | |
1134 | * owner itself or the task which stole the rtmutex) the | |
1135 | * chance to try the fixup of the pi_state. So once we are | |
1136 | * back from handling the fault we need to check the pi_state | |
1137 | * after reacquiring the hash bucket lock and before trying to | |
1138 | * do another fixup. When the fixup has been done already we | |
1139 | * simply return. | |
d0aa7a70 | 1140 | */ |
1b7558e4 TG |
1141 | handle_fault: |
1142 | spin_unlock(q->lock_ptr); | |
778e9a9c | 1143 | |
c2f9f201 | 1144 | ret = futex_handle_fault((unsigned long)uaddr, attempt++); |
778e9a9c | 1145 | |
1b7558e4 | 1146 | spin_lock(q->lock_ptr); |
778e9a9c | 1147 | |
1b7558e4 TG |
1148 | /* |
1149 | * Check if someone else fixed it for us: | |
1150 | */ | |
1151 | if (pi_state->owner != oldowner) | |
1152 | return 0; | |
1153 | ||
1154 | if (ret) | |
1155 | return ret; | |
1156 | ||
1157 | goto retry; | |
d0aa7a70 PP |
1158 | } |
1159 | ||
34f01cc1 ED |
1160 | /* |
1161 | * In case we must use restart_block to restart a futex_wait, | |
ce6bd420 | 1162 | * we encode in the 'flags' shared capability |
34f01cc1 | 1163 | */ |
1acdac10 TG |
1164 | #define FLAGS_SHARED 0x01 |
1165 | #define FLAGS_CLOCKRT 0x02 | |
34f01cc1 | 1166 | |
72c1bbf3 | 1167 | static long futex_wait_restart(struct restart_block *restart); |
36cf3b5c | 1168 | |
c2f9f201 | 1169 | static int futex_wait(u32 __user *uaddr, int fshared, |
1acdac10 | 1170 | u32 val, ktime_t *abs_time, u32 bitset, int clockrt) |
1da177e4 | 1171 | { |
c87e2837 | 1172 | struct task_struct *curr = current; |
2fff78c7 | 1173 | struct restart_block *restart; |
c87e2837 | 1174 | DECLARE_WAITQUEUE(wait, curr); |
e2970f2f | 1175 | struct futex_hash_bucket *hb; |
1da177e4 | 1176 | struct futex_q q; |
e2970f2f IM |
1177 | u32 uval; |
1178 | int ret; | |
bd197234 | 1179 | struct hrtimer_sleeper t; |
c19384b5 | 1180 | int rem = 0; |
1da177e4 | 1181 | |
cd689985 TG |
1182 | if (!bitset) |
1183 | return -EINVAL; | |
1184 | ||
c87e2837 | 1185 | q.pi_state = NULL; |
cd689985 | 1186 | q.bitset = bitset; |
42d35d48 | 1187 | retry: |
38d47c1b | 1188 | q.key = FUTEX_KEY_INIT; |
34f01cc1 | 1189 | ret = get_futex_key(uaddr, fshared, &q.key); |
1da177e4 | 1190 | if (unlikely(ret != 0)) |
42d35d48 | 1191 | goto out; |
1da177e4 | 1192 | |
82af7aca | 1193 | hb = queue_lock(&q); |
1da177e4 LT |
1194 | |
1195 | /* | |
b2d0994b | 1196 | * Access the page AFTER the hash-bucket is locked. |
1da177e4 LT |
1197 | * Order is important: |
1198 | * | |
1199 | * Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val); | |
1200 | * Userspace waker: if (cond(var)) { var = new; futex_wake(&var); } | |
1201 | * | |
1202 | * The basic logical guarantee of a futex is that it blocks ONLY | |
1203 | * if cond(var) is known to be true at the time of blocking, for | |
1204 | * any cond. If we queued after testing *uaddr, that would open | |
1205 | * a race condition where we could block indefinitely with | |
1206 | * cond(var) false, which would violate the guarantee. | |
1207 | * | |
1208 | * A consequence is that futex_wait() can return zero and absorb | |
1209 | * a wakeup when *uaddr != val on entry to the syscall. This is | |
1210 | * rare, but normal. | |
1211 | * | |
b2d0994b | 1212 | * For shared futexes, we hold the mmap semaphore, so the mapping |
34f01cc1 | 1213 | * cannot have changed since we looked it up in get_futex_key. |
1da177e4 | 1214 | */ |
e2970f2f | 1215 | ret = get_futex_value_locked(&uval, uaddr); |
1da177e4 LT |
1216 | |
1217 | if (unlikely(ret)) { | |
e2970f2f | 1218 | queue_unlock(&q, hb); |
42d35d48 | 1219 | put_futex_key(fshared, &q.key); |
1da177e4 | 1220 | |
e2970f2f | 1221 | ret = get_user(uval, uaddr); |
1da177e4 LT |
1222 | |
1223 | if (!ret) | |
1224 | goto retry; | |
2fff78c7 | 1225 | goto out; |
1da177e4 | 1226 | } |
c87e2837 | 1227 | ret = -EWOULDBLOCK; |
2fff78c7 PZ |
1228 | if (unlikely(uval != val)) { |
1229 | queue_unlock(&q, hb); | |
1230 | goto out_put_key; | |
1231 | } | |
1da177e4 LT |
1232 | |
1233 | /* Only actually queue if *uaddr contained val. */ | |
82af7aca | 1234 | queue_me(&q, hb); |
1da177e4 | 1235 | |
1da177e4 LT |
1236 | /* |
1237 | * There might have been scheduling since the queue_me(), as we | |
1238 | * cannot hold a spinlock across the get_user() in case it | |
1239 | * faults, and we cannot just set TASK_INTERRUPTIBLE state when | |
1240 | * queueing ourselves into the futex hash. This code thus has to | |
1241 | * rely on the futex_wake() code removing us from hash when it | |
1242 | * wakes us up. | |
1243 | */ | |
1244 | ||
1245 | /* add_wait_queue is the barrier after __set_current_state. */ | |
1246 | __set_current_state(TASK_INTERRUPTIBLE); | |
73500ac5 | 1247 | add_wait_queue(&q.waiter, &wait); |
1da177e4 | 1248 | /* |
ec92d082 | 1249 | * !plist_node_empty() is safe here without any lock. |
1da177e4 LT |
1250 | * q.lock_ptr != 0 is not safe, because of ordering against wakeup. |
1251 | */ | |
ec92d082 | 1252 | if (likely(!plist_node_empty(&q.list))) { |
c19384b5 PP |
1253 | if (!abs_time) |
1254 | schedule(); | |
1255 | else { | |
1acdac10 TG |
1256 | hrtimer_init_on_stack(&t.timer, |
1257 | clockrt ? CLOCK_REALTIME : | |
1258 | CLOCK_MONOTONIC, | |
1259 | HRTIMER_MODE_ABS); | |
c19384b5 | 1260 | hrtimer_init_sleeper(&t, current); |
16f4993f DH |
1261 | hrtimer_set_expires_range_ns(&t.timer, *abs_time, |
1262 | current->timer_slack_ns); | |
c19384b5 | 1263 | |
cc584b21 | 1264 | hrtimer_start_expires(&t.timer, HRTIMER_MODE_ABS); |
3588a085 PZ |
1265 | if (!hrtimer_active(&t.timer)) |
1266 | t.task = NULL; | |
c19384b5 PP |
1267 | |
1268 | /* | |
1269 | * the timer could have already expired, in which | |
1270 | * case current would be flagged for rescheduling. | |
1271 | * Don't bother calling schedule. | |
1272 | */ | |
1273 | if (likely(t.task)) | |
1274 | schedule(); | |
1275 | ||
1276 | hrtimer_cancel(&t.timer); | |
72c1bbf3 | 1277 | |
c19384b5 PP |
1278 | /* Flag if a timeout occured */ |
1279 | rem = (t.task == NULL); | |
237fc6e7 TG |
1280 | |
1281 | destroy_hrtimer_on_stack(&t.timer); | |
c19384b5 | 1282 | } |
72c1bbf3 | 1283 | } |
1da177e4 LT |
1284 | __set_current_state(TASK_RUNNING); |
1285 | ||
1286 | /* | |
1287 | * NOTE: we don't remove ourselves from the waitqueue because | |
1288 | * we are the only user of it. | |
1289 | */ | |
1290 | ||
1291 | /* If we were woken (and unqueued), we succeeded, whatever. */ | |
2fff78c7 | 1292 | ret = 0; |
1da177e4 | 1293 | if (!unqueue_me(&q)) |
2fff78c7 PZ |
1294 | goto out_put_key; |
1295 | ret = -ETIMEDOUT; | |
c19384b5 | 1296 | if (rem) |
2fff78c7 | 1297 | goto out_put_key; |
72c1bbf3 | 1298 | |
e2970f2f IM |
1299 | /* |
1300 | * We expect signal_pending(current), but another thread may | |
1301 | * have handled it for us already. | |
1302 | */ | |
2fff78c7 | 1303 | ret = -ERESTARTSYS; |
c19384b5 | 1304 | if (!abs_time) |
2fff78c7 | 1305 | goto out_put_key; |
1da177e4 | 1306 | |
2fff78c7 PZ |
1307 | restart = ¤t_thread_info()->restart_block; |
1308 | restart->fn = futex_wait_restart; | |
1309 | restart->futex.uaddr = (u32 *)uaddr; | |
1310 | restart->futex.val = val; | |
1311 | restart->futex.time = abs_time->tv64; | |
1312 | restart->futex.bitset = bitset; | |
1313 | restart->futex.flags = 0; | |
1314 | ||
1315 | if (fshared) | |
1316 | restart->futex.flags |= FLAGS_SHARED; | |
1317 | if (clockrt) | |
1318 | restart->futex.flags |= FLAGS_CLOCKRT; | |
42d35d48 | 1319 | |
2fff78c7 PZ |
1320 | ret = -ERESTART_RESTARTBLOCK; |
1321 | ||
1322 | out_put_key: | |
1323 | put_futex_key(fshared, &q.key); | |
42d35d48 | 1324 | out: |
c87e2837 IM |
1325 | return ret; |
1326 | } | |
1327 | ||
72c1bbf3 NP |
1328 | |
1329 | static long futex_wait_restart(struct restart_block *restart) | |
1330 | { | |
ce6bd420 | 1331 | u32 __user *uaddr = (u32 __user *)restart->futex.uaddr; |
c2f9f201 | 1332 | int fshared = 0; |
ce6bd420 | 1333 | ktime_t t; |
72c1bbf3 | 1334 | |
ce6bd420 | 1335 | t.tv64 = restart->futex.time; |
72c1bbf3 | 1336 | restart->fn = do_no_restart_syscall; |
ce6bd420 | 1337 | if (restart->futex.flags & FLAGS_SHARED) |
c2f9f201 | 1338 | fshared = 1; |
cd689985 | 1339 | return (long)futex_wait(uaddr, fshared, restart->futex.val, &t, |
1acdac10 TG |
1340 | restart->futex.bitset, |
1341 | restart->futex.flags & FLAGS_CLOCKRT); | |
72c1bbf3 NP |
1342 | } |
1343 | ||
1344 | ||
c87e2837 IM |
1345 | /* |
1346 | * Userspace tried a 0 -> TID atomic transition of the futex value | |
1347 | * and failed. The kernel side here does the whole locking operation: | |
1348 | * if there are waiters then it will block, it does PI, etc. (Due to | |
1349 | * races the kernel might see a 0 value of the futex too.) | |
1350 | */ | |
c2f9f201 | 1351 | static int futex_lock_pi(u32 __user *uaddr, int fshared, |
34f01cc1 | 1352 | int detect, ktime_t *time, int trylock) |
c87e2837 | 1353 | { |
c5780e97 | 1354 | struct hrtimer_sleeper timeout, *to = NULL; |
c87e2837 IM |
1355 | struct task_struct *curr = current; |
1356 | struct futex_hash_bucket *hb; | |
1357 | u32 uval, newval, curval; | |
1358 | struct futex_q q; | |
778e9a9c | 1359 | int ret, lock_taken, ownerdied = 0, attempt = 0; |
c87e2837 IM |
1360 | |
1361 | if (refill_pi_state_cache()) | |
1362 | return -ENOMEM; | |
1363 | ||
c19384b5 | 1364 | if (time) { |
c5780e97 | 1365 | to = &timeout; |
237fc6e7 TG |
1366 | hrtimer_init_on_stack(&to->timer, CLOCK_REALTIME, |
1367 | HRTIMER_MODE_ABS); | |
c5780e97 | 1368 | hrtimer_init_sleeper(to, current); |
cc584b21 | 1369 | hrtimer_set_expires(&to->timer, *time); |
c5780e97 TG |
1370 | } |
1371 | ||
c87e2837 | 1372 | q.pi_state = NULL; |
42d35d48 | 1373 | retry: |
38d47c1b | 1374 | q.key = FUTEX_KEY_INIT; |
34f01cc1 | 1375 | ret = get_futex_key(uaddr, fshared, &q.key); |
c87e2837 | 1376 | if (unlikely(ret != 0)) |
42d35d48 | 1377 | goto out; |
c87e2837 | 1378 | |
42d35d48 | 1379 | retry_unlocked: |
82af7aca | 1380 | hb = queue_lock(&q); |
c87e2837 | 1381 | |
42d35d48 | 1382 | retry_locked: |
778e9a9c | 1383 | ret = lock_taken = 0; |
d0aa7a70 | 1384 | |
c87e2837 IM |
1385 | /* |
1386 | * To avoid races, we attempt to take the lock here again | |
1387 | * (by doing a 0 -> TID atomic cmpxchg), while holding all | |
1388 | * the locks. It will most likely not succeed. | |
1389 | */ | |
b488893a | 1390 | newval = task_pid_vnr(current); |
c87e2837 | 1391 | |
36cf3b5c | 1392 | curval = cmpxchg_futex_value_locked(uaddr, 0, newval); |
c87e2837 IM |
1393 | |
1394 | if (unlikely(curval == -EFAULT)) | |
1395 | goto uaddr_faulted; | |
1396 | ||
778e9a9c AK |
1397 | /* |
1398 | * Detect deadlocks. In case of REQUEUE_PI this is a valid | |
1399 | * situation and we return success to user space. | |
1400 | */ | |
b488893a | 1401 | if (unlikely((curval & FUTEX_TID_MASK) == task_pid_vnr(current))) { |
bd197234 | 1402 | ret = -EDEADLK; |
42d35d48 | 1403 | goto out_unlock_put_key; |
c87e2837 IM |
1404 | } |
1405 | ||
1406 | /* | |
778e9a9c | 1407 | * Surprise - we got the lock. Just return to userspace: |
c87e2837 IM |
1408 | */ |
1409 | if (unlikely(!curval)) | |
42d35d48 | 1410 | goto out_unlock_put_key; |
c87e2837 IM |
1411 | |
1412 | uval = curval; | |
778e9a9c | 1413 | |
d0aa7a70 | 1414 | /* |
778e9a9c AK |
1415 | * Set the WAITERS flag, so the owner will know it has someone |
1416 | * to wake at next unlock | |
d0aa7a70 | 1417 | */ |
778e9a9c AK |
1418 | newval = curval | FUTEX_WAITERS; |
1419 | ||
1420 | /* | |
1421 | * There are two cases, where a futex might have no owner (the | |
bd197234 TG |
1422 | * owner TID is 0): OWNER_DIED. We take over the futex in this |
1423 | * case. We also do an unconditional take over, when the owner | |
1424 | * of the futex died. | |
778e9a9c AK |
1425 | * |
1426 | * This is safe as we are protected by the hash bucket lock ! | |
1427 | */ | |
1428 | if (unlikely(ownerdied || !(curval & FUTEX_TID_MASK))) { | |
bd197234 | 1429 | /* Keep the OWNER_DIED bit */ |
b488893a | 1430 | newval = (curval & ~FUTEX_TID_MASK) | task_pid_vnr(current); |
778e9a9c AK |
1431 | ownerdied = 0; |
1432 | lock_taken = 1; | |
1433 | } | |
c87e2837 | 1434 | |
36cf3b5c | 1435 | curval = cmpxchg_futex_value_locked(uaddr, uval, newval); |
c87e2837 IM |
1436 | |
1437 | if (unlikely(curval == -EFAULT)) | |
1438 | goto uaddr_faulted; | |
1439 | if (unlikely(curval != uval)) | |
1440 | goto retry_locked; | |
1441 | ||
778e9a9c | 1442 | /* |
bd197234 | 1443 | * We took the lock due to owner died take over. |
778e9a9c | 1444 | */ |
bd197234 | 1445 | if (unlikely(lock_taken)) |
42d35d48 | 1446 | goto out_unlock_put_key; |
d0aa7a70 | 1447 | |
c87e2837 IM |
1448 | /* |
1449 | * We dont have the lock. Look up the PI state (or create it if | |
1450 | * we are the first waiter): | |
1451 | */ | |
d0aa7a70 | 1452 | ret = lookup_pi_state(uval, hb, &q.key, &q.pi_state); |
c87e2837 IM |
1453 | |
1454 | if (unlikely(ret)) { | |
778e9a9c | 1455 | switch (ret) { |
c87e2837 | 1456 | |
778e9a9c AK |
1457 | case -EAGAIN: |
1458 | /* | |
1459 | * Task is exiting and we just wait for the | |
1460 | * exit to complete. | |
1461 | */ | |
1462 | queue_unlock(&q, hb); | |
de87fcc1 | 1463 | put_futex_key(fshared, &q.key); |
778e9a9c AK |
1464 | cond_resched(); |
1465 | goto retry; | |
c87e2837 | 1466 | |
778e9a9c AK |
1467 | case -ESRCH: |
1468 | /* | |
1469 | * No owner found for this futex. Check if the | |
1470 | * OWNER_DIED bit is set to figure out whether | |
1471 | * this is a robust futex or not. | |
1472 | */ | |
1473 | if (get_futex_value_locked(&curval, uaddr)) | |
c87e2837 | 1474 | goto uaddr_faulted; |
778e9a9c AK |
1475 | |
1476 | /* | |
1477 | * We simply start over in case of a robust | |
1478 | * futex. The code above will take the futex | |
1479 | * and return happy. | |
1480 | */ | |
1481 | if (curval & FUTEX_OWNER_DIED) { | |
1482 | ownerdied = 1; | |
c87e2837 | 1483 | goto retry_locked; |
778e9a9c AK |
1484 | } |
1485 | default: | |
42d35d48 | 1486 | goto out_unlock_put_key; |
c87e2837 | 1487 | } |
c87e2837 IM |
1488 | } |
1489 | ||
1490 | /* | |
1491 | * Only actually queue now that the atomic ops are done: | |
1492 | */ | |
82af7aca | 1493 | queue_me(&q, hb); |
c87e2837 | 1494 | |
c87e2837 IM |
1495 | WARN_ON(!q.pi_state); |
1496 | /* | |
1497 | * Block on the PI mutex: | |
1498 | */ | |
1499 | if (!trylock) | |
1500 | ret = rt_mutex_timed_lock(&q.pi_state->pi_mutex, to, 1); | |
1501 | else { | |
1502 | ret = rt_mutex_trylock(&q.pi_state->pi_mutex); | |
1503 | /* Fixup the trylock return value: */ | |
1504 | ret = ret ? 0 : -EWOULDBLOCK; | |
1505 | } | |
1506 | ||
a99e4e41 | 1507 | spin_lock(q.lock_ptr); |
c87e2837 | 1508 | |
778e9a9c AK |
1509 | if (!ret) { |
1510 | /* | |
1511 | * Got the lock. We might not be the anticipated owner | |
1512 | * if we did a lock-steal - fix up the PI-state in | |
1513 | * that case: | |
1514 | */ | |
1515 | if (q.pi_state->owner != curr) | |
1b7558e4 | 1516 | ret = fixup_pi_state_owner(uaddr, &q, curr, fshared); |
778e9a9c | 1517 | } else { |
c87e2837 IM |
1518 | /* |
1519 | * Catch the rare case, where the lock was released | |
778e9a9c AK |
1520 | * when we were on the way back before we locked the |
1521 | * hash bucket. | |
c87e2837 | 1522 | */ |
cdf71a10 TG |
1523 | if (q.pi_state->owner == curr) { |
1524 | /* | |
1525 | * Try to get the rt_mutex now. This might | |
1526 | * fail as some other task acquired the | |
1527 | * rt_mutex after we removed ourself from the | |
1528 | * rt_mutex waiters list. | |
1529 | */ | |
1530 | if (rt_mutex_trylock(&q.pi_state->pi_mutex)) | |
1531 | ret = 0; | |
1532 | else { | |
1533 | /* | |
1534 | * pi_state is incorrect, some other | |
1535 | * task did a lock steal and we | |
1536 | * returned due to timeout or signal | |
1537 | * without taking the rt_mutex. Too | |
1538 | * late. We can access the | |
1539 | * rt_mutex_owner without locking, as | |
1540 | * the other task is now blocked on | |
1541 | * the hash bucket lock. Fix the state | |
1542 | * up. | |
1543 | */ | |
1544 | struct task_struct *owner; | |
1545 | int res; | |
1546 | ||
1547 | owner = rt_mutex_owner(&q.pi_state->pi_mutex); | |
1b7558e4 TG |
1548 | res = fixup_pi_state_owner(uaddr, &q, owner, |
1549 | fshared); | |
cdf71a10 | 1550 | |
cdf71a10 TG |
1551 | /* propagate -EFAULT, if the fixup failed */ |
1552 | if (res) | |
1553 | ret = res; | |
1554 | } | |
778e9a9c AK |
1555 | } else { |
1556 | /* | |
1557 | * Paranoia check. If we did not take the lock | |
1558 | * in the trylock above, then we should not be | |
1559 | * the owner of the rtmutex, neither the real | |
1560 | * nor the pending one: | |
1561 | */ | |
1562 | if (rt_mutex_owner(&q.pi_state->pi_mutex) == curr) | |
1563 | printk(KERN_ERR "futex_lock_pi: ret = %d " | |
1564 | "pi-mutex: %p pi-state %p\n", ret, | |
1565 | q.pi_state->pi_mutex.owner, | |
1566 | q.pi_state->owner); | |
c87e2837 | 1567 | } |
c87e2837 IM |
1568 | } |
1569 | ||
e8f6386c DH |
1570 | /* |
1571 | * If fixup_pi_state_owner() faulted and was unable to handle the | |
1572 | * fault, unlock it and return the fault to userspace. | |
1573 | */ | |
1574 | if (ret && (rt_mutex_owner(&q.pi_state->pi_mutex) == current)) | |
1575 | rt_mutex_unlock(&q.pi_state->pi_mutex); | |
1576 | ||
778e9a9c AK |
1577 | /* Unqueue and drop the lock */ |
1578 | unqueue_me_pi(&q); | |
c87e2837 | 1579 | |
237fc6e7 TG |
1580 | if (to) |
1581 | destroy_hrtimer_on_stack(&to->timer); | |
c5780e97 | 1582 | return ret != -EINTR ? ret : -ERESTARTNOINTR; |
c87e2837 | 1583 | |
42d35d48 | 1584 | out_unlock_put_key: |
c87e2837 IM |
1585 | queue_unlock(&q, hb); |
1586 | ||
42d35d48 | 1587 | out_put_key: |
38d47c1b | 1588 | put_futex_key(fshared, &q.key); |
42d35d48 | 1589 | out: |
237fc6e7 TG |
1590 | if (to) |
1591 | destroy_hrtimer_on_stack(&to->timer); | |
c87e2837 IM |
1592 | return ret; |
1593 | ||
42d35d48 | 1594 | uaddr_faulted: |
c87e2837 | 1595 | /* |
b5686363 DH |
1596 | * We have to r/w *(int __user *)uaddr, and we have to modify it |
1597 | * atomically. Therefore, if we continue to fault after get_user() | |
1598 | * below, we need to handle the fault ourselves, while still holding | |
1599 | * the mmap_sem. This can occur if the uaddr is under contention as | |
1600 | * we have to drop the mmap_sem in order to call get_user(). | |
c87e2837 | 1601 | */ |
778e9a9c AK |
1602 | queue_unlock(&q, hb); |
1603 | ||
c87e2837 | 1604 | if (attempt++) { |
c2f9f201 | 1605 | ret = futex_handle_fault((unsigned long)uaddr, attempt); |
34f01cc1 | 1606 | if (ret) |
42d35d48 | 1607 | goto out_put_key; |
778e9a9c | 1608 | goto retry_unlocked; |
c87e2837 IM |
1609 | } |
1610 | ||
c87e2837 | 1611 | ret = get_user(uval, uaddr); |
b5686363 | 1612 | if (!ret) |
de87fcc1 | 1613 | goto retry_unlocked; |
c87e2837 | 1614 | |
de87fcc1 | 1615 | goto out_put_key; |
c87e2837 IM |
1616 | } |
1617 | ||
de87fcc1 | 1618 | |
c87e2837 IM |
1619 | /* |
1620 | * Userspace attempted a TID -> 0 atomic transition, and failed. | |
1621 | * This is the in-kernel slowpath: we look up the PI state (if any), | |
1622 | * and do the rt-mutex unlock. | |
1623 | */ | |
c2f9f201 | 1624 | static int futex_unlock_pi(u32 __user *uaddr, int fshared) |
c87e2837 IM |
1625 | { |
1626 | struct futex_hash_bucket *hb; | |
1627 | struct futex_q *this, *next; | |
1628 | u32 uval; | |
ec92d082 | 1629 | struct plist_head *head; |
38d47c1b | 1630 | union futex_key key = FUTEX_KEY_INIT; |
c87e2837 IM |
1631 | int ret, attempt = 0; |
1632 | ||
1633 | retry: | |
1634 | if (get_user(uval, uaddr)) | |
1635 | return -EFAULT; | |
1636 | /* | |
1637 | * We release only a lock we actually own: | |
1638 | */ | |
b488893a | 1639 | if ((uval & FUTEX_TID_MASK) != task_pid_vnr(current)) |
c87e2837 | 1640 | return -EPERM; |
c87e2837 | 1641 | |
34f01cc1 | 1642 | ret = get_futex_key(uaddr, fshared, &key); |
c87e2837 IM |
1643 | if (unlikely(ret != 0)) |
1644 | goto out; | |
1645 | ||
1646 | hb = hash_futex(&key); | |
778e9a9c | 1647 | retry_unlocked: |
c87e2837 IM |
1648 | spin_lock(&hb->lock); |
1649 | ||
c87e2837 IM |
1650 | /* |
1651 | * To avoid races, try to do the TID -> 0 atomic transition | |
1652 | * again. If it succeeds then we can return without waking | |
1653 | * anyone else up: | |
1654 | */ | |
36cf3b5c | 1655 | if (!(uval & FUTEX_OWNER_DIED)) |
b488893a | 1656 | uval = cmpxchg_futex_value_locked(uaddr, task_pid_vnr(current), 0); |
36cf3b5c | 1657 | |
c87e2837 IM |
1658 | |
1659 | if (unlikely(uval == -EFAULT)) | |
1660 | goto pi_faulted; | |
1661 | /* | |
1662 | * Rare case: we managed to release the lock atomically, | |
1663 | * no need to wake anyone else up: | |
1664 | */ | |
b488893a | 1665 | if (unlikely(uval == task_pid_vnr(current))) |
c87e2837 IM |
1666 | goto out_unlock; |
1667 | ||
1668 | /* | |
1669 | * Ok, other tasks may need to be woken up - check waiters | |
1670 | * and do the wakeup if necessary: | |
1671 | */ | |
1672 | head = &hb->chain; | |
1673 | ||
ec92d082 | 1674 | plist_for_each_entry_safe(this, next, head, list) { |
c87e2837 IM |
1675 | if (!match_futex (&this->key, &key)) |
1676 | continue; | |
1677 | ret = wake_futex_pi(uaddr, uval, this); | |
1678 | /* | |
1679 | * The atomic access to the futex value | |
1680 | * generated a pagefault, so retry the | |
1681 | * user-access and the wakeup: | |
1682 | */ | |
1683 | if (ret == -EFAULT) | |
1684 | goto pi_faulted; | |
1685 | goto out_unlock; | |
1686 | } | |
1687 | /* | |
1688 | * No waiters - kernel unlocks the futex: | |
1689 | */ | |
e3f2ddea IM |
1690 | if (!(uval & FUTEX_OWNER_DIED)) { |
1691 | ret = unlock_futex_pi(uaddr, uval); | |
1692 | if (ret == -EFAULT) | |
1693 | goto pi_faulted; | |
1694 | } | |
c87e2837 IM |
1695 | |
1696 | out_unlock: | |
1697 | spin_unlock(&hb->lock); | |
38d47c1b | 1698 | put_futex_key(fshared, &key); |
c87e2837 | 1699 | |
42d35d48 | 1700 | out: |
c87e2837 IM |
1701 | return ret; |
1702 | ||
1703 | pi_faulted: | |
1704 | /* | |
b5686363 DH |
1705 | * We have to r/w *(int __user *)uaddr, and we have to modify it |
1706 | * atomically. Therefore, if we continue to fault after get_user() | |
1707 | * below, we need to handle the fault ourselves, while still holding | |
1708 | * the mmap_sem. This can occur if the uaddr is under contention as | |
1709 | * we have to drop the mmap_sem in order to call get_user(). | |
c87e2837 | 1710 | */ |
778e9a9c AK |
1711 | spin_unlock(&hb->lock); |
1712 | ||
c87e2837 | 1713 | if (attempt++) { |
c2f9f201 | 1714 | ret = futex_handle_fault((unsigned long)uaddr, attempt); |
34f01cc1 | 1715 | if (ret) |
778e9a9c | 1716 | goto out; |
187226f5 | 1717 | uval = 0; |
778e9a9c | 1718 | goto retry_unlocked; |
c87e2837 IM |
1719 | } |
1720 | ||
c87e2837 | 1721 | ret = get_user(uval, uaddr); |
de87fcc1 | 1722 | put_futex_key(fshared, &key); |
b5686363 | 1723 | if (!ret) |
c87e2837 IM |
1724 | goto retry; |
1725 | ||
1da177e4 LT |
1726 | return ret; |
1727 | } | |
1728 | ||
0771dfef IM |
1729 | /* |
1730 | * Support for robust futexes: the kernel cleans up held futexes at | |
1731 | * thread exit time. | |
1732 | * | |
1733 | * Implementation: user-space maintains a per-thread list of locks it | |
1734 | * is holding. Upon do_exit(), the kernel carefully walks this list, | |
1735 | * and marks all locks that are owned by this thread with the | |
c87e2837 | 1736 | * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is |
0771dfef IM |
1737 | * always manipulated with the lock held, so the list is private and |
1738 | * per-thread. Userspace also maintains a per-thread 'list_op_pending' | |
1739 | * field, to allow the kernel to clean up if the thread dies after | |
1740 | * acquiring the lock, but just before it could have added itself to | |
1741 | * the list. There can only be one such pending lock. | |
1742 | */ | |
1743 | ||
1744 | /** | |
1745 | * sys_set_robust_list - set the robust-futex list head of a task | |
1746 | * @head: pointer to the list-head | |
1747 | * @len: length of the list-head, as userspace expects | |
1748 | */ | |
836f92ad HC |
1749 | SYSCALL_DEFINE2(set_robust_list, struct robust_list_head __user *, head, |
1750 | size_t, len) | |
0771dfef | 1751 | { |
a0c1e907 TG |
1752 | if (!futex_cmpxchg_enabled) |
1753 | return -ENOSYS; | |
0771dfef IM |
1754 | /* |
1755 | * The kernel knows only one size for now: | |
1756 | */ | |
1757 | if (unlikely(len != sizeof(*head))) | |
1758 | return -EINVAL; | |
1759 | ||
1760 | current->robust_list = head; | |
1761 | ||
1762 | return 0; | |
1763 | } | |
1764 | ||
1765 | /** | |
1766 | * sys_get_robust_list - get the robust-futex list head of a task | |
1767 | * @pid: pid of the process [zero for current task] | |
1768 | * @head_ptr: pointer to a list-head pointer, the kernel fills it in | |
1769 | * @len_ptr: pointer to a length field, the kernel fills in the header size | |
1770 | */ | |
836f92ad HC |
1771 | SYSCALL_DEFINE3(get_robust_list, int, pid, |
1772 | struct robust_list_head __user * __user *, head_ptr, | |
1773 | size_t __user *, len_ptr) | |
0771dfef | 1774 | { |
ba46df98 | 1775 | struct robust_list_head __user *head; |
0771dfef | 1776 | unsigned long ret; |
c69e8d9c | 1777 | const struct cred *cred = current_cred(), *pcred; |
0771dfef | 1778 | |
a0c1e907 TG |
1779 | if (!futex_cmpxchg_enabled) |
1780 | return -ENOSYS; | |
1781 | ||
0771dfef IM |
1782 | if (!pid) |
1783 | head = current->robust_list; | |
1784 | else { | |
1785 | struct task_struct *p; | |
1786 | ||
1787 | ret = -ESRCH; | |
aaa2a97e | 1788 | rcu_read_lock(); |
228ebcbe | 1789 | p = find_task_by_vpid(pid); |
0771dfef IM |
1790 | if (!p) |
1791 | goto err_unlock; | |
1792 | ret = -EPERM; | |
c69e8d9c DH |
1793 | pcred = __task_cred(p); |
1794 | if (cred->euid != pcred->euid && | |
1795 | cred->euid != pcred->uid && | |
76aac0e9 | 1796 | !capable(CAP_SYS_PTRACE)) |
0771dfef IM |
1797 | goto err_unlock; |
1798 | head = p->robust_list; | |
aaa2a97e | 1799 | rcu_read_unlock(); |
0771dfef IM |
1800 | } |
1801 | ||
1802 | if (put_user(sizeof(*head), len_ptr)) | |
1803 | return -EFAULT; | |
1804 | return put_user(head, head_ptr); | |
1805 | ||
1806 | err_unlock: | |
aaa2a97e | 1807 | rcu_read_unlock(); |
0771dfef IM |
1808 | |
1809 | return ret; | |
1810 | } | |
1811 | ||
1812 | /* | |
1813 | * Process a futex-list entry, check whether it's owned by the | |
1814 | * dying task, and do notification if so: | |
1815 | */ | |
e3f2ddea | 1816 | int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi) |
0771dfef | 1817 | { |
e3f2ddea | 1818 | u32 uval, nval, mval; |
0771dfef | 1819 | |
8f17d3a5 IM |
1820 | retry: |
1821 | if (get_user(uval, uaddr)) | |
0771dfef IM |
1822 | return -1; |
1823 | ||
b488893a | 1824 | if ((uval & FUTEX_TID_MASK) == task_pid_vnr(curr)) { |
0771dfef IM |
1825 | /* |
1826 | * Ok, this dying thread is truly holding a futex | |
1827 | * of interest. Set the OWNER_DIED bit atomically | |
1828 | * via cmpxchg, and if the value had FUTEX_WAITERS | |
1829 | * set, wake up a waiter (if any). (We have to do a | |
1830 | * futex_wake() even if OWNER_DIED is already set - | |
1831 | * to handle the rare but possible case of recursive | |
1832 | * thread-death.) The rest of the cleanup is done in | |
1833 | * userspace. | |
1834 | */ | |
e3f2ddea IM |
1835 | mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED; |
1836 | nval = futex_atomic_cmpxchg_inatomic(uaddr, uval, mval); | |
1837 | ||
c87e2837 IM |
1838 | if (nval == -EFAULT) |
1839 | return -1; | |
1840 | ||
1841 | if (nval != uval) | |
8f17d3a5 | 1842 | goto retry; |
0771dfef | 1843 | |
e3f2ddea IM |
1844 | /* |
1845 | * Wake robust non-PI futexes here. The wakeup of | |
1846 | * PI futexes happens in exit_pi_state(): | |
1847 | */ | |
36cf3b5c | 1848 | if (!pi && (uval & FUTEX_WAITERS)) |
c2f9f201 | 1849 | futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY); |
0771dfef IM |
1850 | } |
1851 | return 0; | |
1852 | } | |
1853 | ||
e3f2ddea IM |
1854 | /* |
1855 | * Fetch a robust-list pointer. Bit 0 signals PI futexes: | |
1856 | */ | |
1857 | static inline int fetch_robust_entry(struct robust_list __user **entry, | |
ba46df98 AV |
1858 | struct robust_list __user * __user *head, |
1859 | int *pi) | |
e3f2ddea IM |
1860 | { |
1861 | unsigned long uentry; | |
1862 | ||
ba46df98 | 1863 | if (get_user(uentry, (unsigned long __user *)head)) |
e3f2ddea IM |
1864 | return -EFAULT; |
1865 | ||
ba46df98 | 1866 | *entry = (void __user *)(uentry & ~1UL); |
e3f2ddea IM |
1867 | *pi = uentry & 1; |
1868 | ||
1869 | return 0; | |
1870 | } | |
1871 | ||
0771dfef IM |
1872 | /* |
1873 | * Walk curr->robust_list (very carefully, it's a userspace list!) | |
1874 | * and mark any locks found there dead, and notify any waiters. | |
1875 | * | |
1876 | * We silently return on any sign of list-walking problem. | |
1877 | */ | |
1878 | void exit_robust_list(struct task_struct *curr) | |
1879 | { | |
1880 | struct robust_list_head __user *head = curr->robust_list; | |
9f96cb1e MS |
1881 | struct robust_list __user *entry, *next_entry, *pending; |
1882 | unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip; | |
0771dfef | 1883 | unsigned long futex_offset; |
9f96cb1e | 1884 | int rc; |
0771dfef | 1885 | |
a0c1e907 TG |
1886 | if (!futex_cmpxchg_enabled) |
1887 | return; | |
1888 | ||
0771dfef IM |
1889 | /* |
1890 | * Fetch the list head (which was registered earlier, via | |
1891 | * sys_set_robust_list()): | |
1892 | */ | |
e3f2ddea | 1893 | if (fetch_robust_entry(&entry, &head->list.next, &pi)) |
0771dfef IM |
1894 | return; |
1895 | /* | |
1896 | * Fetch the relative futex offset: | |
1897 | */ | |
1898 | if (get_user(futex_offset, &head->futex_offset)) | |
1899 | return; | |
1900 | /* | |
1901 | * Fetch any possibly pending lock-add first, and handle it | |
1902 | * if it exists: | |
1903 | */ | |
e3f2ddea | 1904 | if (fetch_robust_entry(&pending, &head->list_op_pending, &pip)) |
0771dfef | 1905 | return; |
e3f2ddea | 1906 | |
9f96cb1e | 1907 | next_entry = NULL; /* avoid warning with gcc */ |
0771dfef | 1908 | while (entry != &head->list) { |
9f96cb1e MS |
1909 | /* |
1910 | * Fetch the next entry in the list before calling | |
1911 | * handle_futex_death: | |
1912 | */ | |
1913 | rc = fetch_robust_entry(&next_entry, &entry->next, &next_pi); | |
0771dfef IM |
1914 | /* |
1915 | * A pending lock might already be on the list, so | |
c87e2837 | 1916 | * don't process it twice: |
0771dfef IM |
1917 | */ |
1918 | if (entry != pending) | |
ba46df98 | 1919 | if (handle_futex_death((void __user *)entry + futex_offset, |
e3f2ddea | 1920 | curr, pi)) |
0771dfef | 1921 | return; |
9f96cb1e | 1922 | if (rc) |
0771dfef | 1923 | return; |
9f96cb1e MS |
1924 | entry = next_entry; |
1925 | pi = next_pi; | |
0771dfef IM |
1926 | /* |
1927 | * Avoid excessively long or circular lists: | |
1928 | */ | |
1929 | if (!--limit) | |
1930 | break; | |
1931 | ||
1932 | cond_resched(); | |
1933 | } | |
9f96cb1e MS |
1934 | |
1935 | if (pending) | |
1936 | handle_futex_death((void __user *)pending + futex_offset, | |
1937 | curr, pip); | |
0771dfef IM |
1938 | } |
1939 | ||
c19384b5 | 1940 | long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout, |
e2970f2f | 1941 | u32 __user *uaddr2, u32 val2, u32 val3) |
1da177e4 | 1942 | { |
1acdac10 | 1943 | int clockrt, ret = -ENOSYS; |
34f01cc1 | 1944 | int cmd = op & FUTEX_CMD_MASK; |
c2f9f201 | 1945 | int fshared = 0; |
34f01cc1 ED |
1946 | |
1947 | if (!(op & FUTEX_PRIVATE_FLAG)) | |
c2f9f201 | 1948 | fshared = 1; |
1da177e4 | 1949 | |
1acdac10 TG |
1950 | clockrt = op & FUTEX_CLOCK_REALTIME; |
1951 | if (clockrt && cmd != FUTEX_WAIT_BITSET) | |
1952 | return -ENOSYS; | |
1da177e4 | 1953 | |
34f01cc1 | 1954 | switch (cmd) { |
1da177e4 | 1955 | case FUTEX_WAIT: |
cd689985 TG |
1956 | val3 = FUTEX_BITSET_MATCH_ANY; |
1957 | case FUTEX_WAIT_BITSET: | |
1acdac10 | 1958 | ret = futex_wait(uaddr, fshared, val, timeout, val3, clockrt); |
1da177e4 LT |
1959 | break; |
1960 | case FUTEX_WAKE: | |
cd689985 TG |
1961 | val3 = FUTEX_BITSET_MATCH_ANY; |
1962 | case FUTEX_WAKE_BITSET: | |
1963 | ret = futex_wake(uaddr, fshared, val, val3); | |
1da177e4 | 1964 | break; |
1da177e4 | 1965 | case FUTEX_REQUEUE: |
34f01cc1 | 1966 | ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, NULL); |
1da177e4 LT |
1967 | break; |
1968 | case FUTEX_CMP_REQUEUE: | |
34f01cc1 | 1969 | ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, &val3); |
1da177e4 | 1970 | break; |
4732efbe | 1971 | case FUTEX_WAKE_OP: |
34f01cc1 | 1972 | ret = futex_wake_op(uaddr, fshared, uaddr2, val, val2, val3); |
4732efbe | 1973 | break; |
c87e2837 | 1974 | case FUTEX_LOCK_PI: |
a0c1e907 TG |
1975 | if (futex_cmpxchg_enabled) |
1976 | ret = futex_lock_pi(uaddr, fshared, val, timeout, 0); | |
c87e2837 IM |
1977 | break; |
1978 | case FUTEX_UNLOCK_PI: | |
a0c1e907 TG |
1979 | if (futex_cmpxchg_enabled) |
1980 | ret = futex_unlock_pi(uaddr, fshared); | |
c87e2837 IM |
1981 | break; |
1982 | case FUTEX_TRYLOCK_PI: | |
a0c1e907 TG |
1983 | if (futex_cmpxchg_enabled) |
1984 | ret = futex_lock_pi(uaddr, fshared, 0, timeout, 1); | |
c87e2837 | 1985 | break; |
1da177e4 LT |
1986 | default: |
1987 | ret = -ENOSYS; | |
1988 | } | |
1989 | return ret; | |
1990 | } | |
1991 | ||
1992 | ||
17da2bd9 HC |
1993 | SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val, |
1994 | struct timespec __user *, utime, u32 __user *, uaddr2, | |
1995 | u32, val3) | |
1da177e4 | 1996 | { |
c19384b5 PP |
1997 | struct timespec ts; |
1998 | ktime_t t, *tp = NULL; | |
e2970f2f | 1999 | u32 val2 = 0; |
34f01cc1 | 2000 | int cmd = op & FUTEX_CMD_MASK; |
1da177e4 | 2001 | |
cd689985 TG |
2002 | if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI || |
2003 | cmd == FUTEX_WAIT_BITSET)) { | |
c19384b5 | 2004 | if (copy_from_user(&ts, utime, sizeof(ts)) != 0) |
1da177e4 | 2005 | return -EFAULT; |
c19384b5 | 2006 | if (!timespec_valid(&ts)) |
9741ef96 | 2007 | return -EINVAL; |
c19384b5 PP |
2008 | |
2009 | t = timespec_to_ktime(ts); | |
34f01cc1 | 2010 | if (cmd == FUTEX_WAIT) |
5a7780e7 | 2011 | t = ktime_add_safe(ktime_get(), t); |
c19384b5 | 2012 | tp = &t; |
1da177e4 LT |
2013 | } |
2014 | /* | |
34f01cc1 | 2015 | * requeue parameter in 'utime' if cmd == FUTEX_REQUEUE. |
f54f0986 | 2016 | * number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP. |
1da177e4 | 2017 | */ |
f54f0986 AS |
2018 | if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE || |
2019 | cmd == FUTEX_WAKE_OP) | |
e2970f2f | 2020 | val2 = (u32) (unsigned long) utime; |
1da177e4 | 2021 | |
c19384b5 | 2022 | return do_futex(uaddr, op, val, tp, uaddr2, val2, val3); |
1da177e4 LT |
2023 | } |
2024 | ||
f6d107fb | 2025 | static int __init futex_init(void) |
1da177e4 | 2026 | { |
a0c1e907 | 2027 | u32 curval; |
3e4ab747 | 2028 | int i; |
95362fa9 | 2029 | |
a0c1e907 TG |
2030 | /* |
2031 | * This will fail and we want it. Some arch implementations do | |
2032 | * runtime detection of the futex_atomic_cmpxchg_inatomic() | |
2033 | * functionality. We want to know that before we call in any | |
2034 | * of the complex code paths. Also we want to prevent | |
2035 | * registration of robust lists in that case. NULL is | |
2036 | * guaranteed to fault and we get -EFAULT on functional | |
2037 | * implementation, the non functional ones will return | |
2038 | * -ENOSYS. | |
2039 | */ | |
2040 | curval = cmpxchg_futex_value_locked(NULL, 0, 0); | |
2041 | if (curval == -EFAULT) | |
2042 | futex_cmpxchg_enabled = 1; | |
2043 | ||
3e4ab747 TG |
2044 | for (i = 0; i < ARRAY_SIZE(futex_queues); i++) { |
2045 | plist_head_init(&futex_queues[i].chain, &futex_queues[i].lock); | |
2046 | spin_lock_init(&futex_queues[i].lock); | |
2047 | } | |
2048 | ||
1da177e4 LT |
2049 | return 0; |
2050 | } | |
f6d107fb | 2051 | __initcall(futex_init); |