]>
Commit | Line | Data |
---|---|---|
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 | ||
4b1c486b DH |
279 | /** |
280 | * futex_top_waiter() - Return the highest priority waiter on a futex | |
281 | * @hb: the hash bucket the futex_q's reside in | |
282 | * @key: the futex key (to distinguish it from other futex futex_q's) | |
283 | * | |
284 | * Must be called with the hb lock held. | |
285 | */ | |
286 | static struct futex_q *futex_top_waiter(struct futex_hash_bucket *hb, | |
287 | union futex_key *key) | |
288 | { | |
289 | struct futex_q *this; | |
290 | ||
291 | plist_for_each_entry(this, &hb->chain, list) { | |
292 | if (match_futex(&this->key, key)) | |
293 | return this; | |
294 | } | |
295 | return NULL; | |
296 | } | |
297 | ||
36cf3b5c TG |
298 | static u32 cmpxchg_futex_value_locked(u32 __user *uaddr, u32 uval, u32 newval) |
299 | { | |
300 | u32 curval; | |
301 | ||
302 | pagefault_disable(); | |
303 | curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval); | |
304 | pagefault_enable(); | |
305 | ||
306 | return curval; | |
307 | } | |
308 | ||
309 | static int get_futex_value_locked(u32 *dest, u32 __user *from) | |
1da177e4 LT |
310 | { |
311 | int ret; | |
312 | ||
a866374a | 313 | pagefault_disable(); |
e2970f2f | 314 | ret = __copy_from_user_inatomic(dest, from, sizeof(u32)); |
a866374a | 315 | pagefault_enable(); |
1da177e4 LT |
316 | |
317 | return ret ? -EFAULT : 0; | |
318 | } | |
319 | ||
c87e2837 IM |
320 | |
321 | /* | |
322 | * PI code: | |
323 | */ | |
324 | static int refill_pi_state_cache(void) | |
325 | { | |
326 | struct futex_pi_state *pi_state; | |
327 | ||
328 | if (likely(current->pi_state_cache)) | |
329 | return 0; | |
330 | ||
4668edc3 | 331 | pi_state = kzalloc(sizeof(*pi_state), GFP_KERNEL); |
c87e2837 IM |
332 | |
333 | if (!pi_state) | |
334 | return -ENOMEM; | |
335 | ||
c87e2837 IM |
336 | INIT_LIST_HEAD(&pi_state->list); |
337 | /* pi_mutex gets initialized later */ | |
338 | pi_state->owner = NULL; | |
339 | atomic_set(&pi_state->refcount, 1); | |
38d47c1b | 340 | pi_state->key = FUTEX_KEY_INIT; |
c87e2837 IM |
341 | |
342 | current->pi_state_cache = pi_state; | |
343 | ||
344 | return 0; | |
345 | } | |
346 | ||
347 | static struct futex_pi_state * alloc_pi_state(void) | |
348 | { | |
349 | struct futex_pi_state *pi_state = current->pi_state_cache; | |
350 | ||
351 | WARN_ON(!pi_state); | |
352 | current->pi_state_cache = NULL; | |
353 | ||
354 | return pi_state; | |
355 | } | |
356 | ||
357 | static void free_pi_state(struct futex_pi_state *pi_state) | |
358 | { | |
359 | if (!atomic_dec_and_test(&pi_state->refcount)) | |
360 | return; | |
361 | ||
362 | /* | |
363 | * If pi_state->owner is NULL, the owner is most probably dying | |
364 | * and has cleaned up the pi_state already | |
365 | */ | |
366 | if (pi_state->owner) { | |
367 | spin_lock_irq(&pi_state->owner->pi_lock); | |
368 | list_del_init(&pi_state->list); | |
369 | spin_unlock_irq(&pi_state->owner->pi_lock); | |
370 | ||
371 | rt_mutex_proxy_unlock(&pi_state->pi_mutex, pi_state->owner); | |
372 | } | |
373 | ||
374 | if (current->pi_state_cache) | |
375 | kfree(pi_state); | |
376 | else { | |
377 | /* | |
378 | * pi_state->list is already empty. | |
379 | * clear pi_state->owner. | |
380 | * refcount is at 0 - put it back to 1. | |
381 | */ | |
382 | pi_state->owner = NULL; | |
383 | atomic_set(&pi_state->refcount, 1); | |
384 | current->pi_state_cache = pi_state; | |
385 | } | |
386 | } | |
387 | ||
388 | /* | |
389 | * Look up the task based on what TID userspace gave us. | |
390 | * We dont trust it. | |
391 | */ | |
392 | static struct task_struct * futex_find_get_task(pid_t pid) | |
393 | { | |
394 | struct task_struct *p; | |
c69e8d9c | 395 | const struct cred *cred = current_cred(), *pcred; |
c87e2837 | 396 | |
d359b549 | 397 | rcu_read_lock(); |
228ebcbe | 398 | p = find_task_by_vpid(pid); |
c69e8d9c | 399 | if (!p) { |
a06381fe | 400 | p = ERR_PTR(-ESRCH); |
c69e8d9c DH |
401 | } else { |
402 | pcred = __task_cred(p); | |
403 | if (cred->euid != pcred->euid && | |
404 | cred->euid != pcred->uid) | |
405 | p = ERR_PTR(-ESRCH); | |
406 | else | |
407 | get_task_struct(p); | |
408 | } | |
a06381fe | 409 | |
d359b549 | 410 | rcu_read_unlock(); |
c87e2837 IM |
411 | |
412 | return p; | |
413 | } | |
414 | ||
415 | /* | |
416 | * This task is holding PI mutexes at exit time => bad. | |
417 | * Kernel cleans up PI-state, but userspace is likely hosed. | |
418 | * (Robust-futex cleanup is separate and might save the day for userspace.) | |
419 | */ | |
420 | void exit_pi_state_list(struct task_struct *curr) | |
421 | { | |
c87e2837 IM |
422 | struct list_head *next, *head = &curr->pi_state_list; |
423 | struct futex_pi_state *pi_state; | |
627371d7 | 424 | struct futex_hash_bucket *hb; |
38d47c1b | 425 | union futex_key key = FUTEX_KEY_INIT; |
c87e2837 | 426 | |
a0c1e907 TG |
427 | if (!futex_cmpxchg_enabled) |
428 | return; | |
c87e2837 IM |
429 | /* |
430 | * We are a ZOMBIE and nobody can enqueue itself on | |
431 | * pi_state_list anymore, but we have to be careful | |
627371d7 | 432 | * versus waiters unqueueing themselves: |
c87e2837 IM |
433 | */ |
434 | spin_lock_irq(&curr->pi_lock); | |
435 | while (!list_empty(head)) { | |
436 | ||
437 | next = head->next; | |
438 | pi_state = list_entry(next, struct futex_pi_state, list); | |
439 | key = pi_state->key; | |
627371d7 | 440 | hb = hash_futex(&key); |
c87e2837 IM |
441 | spin_unlock_irq(&curr->pi_lock); |
442 | ||
c87e2837 IM |
443 | spin_lock(&hb->lock); |
444 | ||
445 | spin_lock_irq(&curr->pi_lock); | |
627371d7 IM |
446 | /* |
447 | * We dropped the pi-lock, so re-check whether this | |
448 | * task still owns the PI-state: | |
449 | */ | |
c87e2837 IM |
450 | if (head->next != next) { |
451 | spin_unlock(&hb->lock); | |
452 | continue; | |
453 | } | |
454 | ||
c87e2837 | 455 | WARN_ON(pi_state->owner != curr); |
627371d7 IM |
456 | WARN_ON(list_empty(&pi_state->list)); |
457 | list_del_init(&pi_state->list); | |
c87e2837 IM |
458 | pi_state->owner = NULL; |
459 | spin_unlock_irq(&curr->pi_lock); | |
460 | ||
461 | rt_mutex_unlock(&pi_state->pi_mutex); | |
462 | ||
463 | spin_unlock(&hb->lock); | |
464 | ||
465 | spin_lock_irq(&curr->pi_lock); | |
466 | } | |
467 | spin_unlock_irq(&curr->pi_lock); | |
468 | } | |
469 | ||
470 | static int | |
d0aa7a70 PP |
471 | lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, |
472 | union futex_key *key, struct futex_pi_state **ps) | |
c87e2837 IM |
473 | { |
474 | struct futex_pi_state *pi_state = NULL; | |
475 | struct futex_q *this, *next; | |
ec92d082 | 476 | struct plist_head *head; |
c87e2837 | 477 | struct task_struct *p; |
778e9a9c | 478 | pid_t pid = uval & FUTEX_TID_MASK; |
c87e2837 IM |
479 | |
480 | head = &hb->chain; | |
481 | ||
ec92d082 | 482 | plist_for_each_entry_safe(this, next, head, list) { |
d0aa7a70 | 483 | if (match_futex(&this->key, key)) { |
c87e2837 IM |
484 | /* |
485 | * Another waiter already exists - bump up | |
486 | * the refcount and return its pi_state: | |
487 | */ | |
488 | pi_state = this->pi_state; | |
06a9ec29 TG |
489 | /* |
490 | * Userspace might have messed up non PI and PI futexes | |
491 | */ | |
492 | if (unlikely(!pi_state)) | |
493 | return -EINVAL; | |
494 | ||
627371d7 | 495 | WARN_ON(!atomic_read(&pi_state->refcount)); |
778e9a9c AK |
496 | WARN_ON(pid && pi_state->owner && |
497 | pi_state->owner->pid != pid); | |
627371d7 | 498 | |
c87e2837 | 499 | atomic_inc(&pi_state->refcount); |
d0aa7a70 | 500 | *ps = pi_state; |
c87e2837 IM |
501 | |
502 | return 0; | |
503 | } | |
504 | } | |
505 | ||
506 | /* | |
e3f2ddea | 507 | * We are the first waiter - try to look up the real owner and attach |
778e9a9c | 508 | * the new pi_state to it, but bail out when TID = 0 |
c87e2837 | 509 | */ |
778e9a9c | 510 | if (!pid) |
e3f2ddea | 511 | return -ESRCH; |
c87e2837 | 512 | p = futex_find_get_task(pid); |
778e9a9c AK |
513 | if (IS_ERR(p)) |
514 | return PTR_ERR(p); | |
515 | ||
516 | /* | |
517 | * We need to look at the task state flags to figure out, | |
518 | * whether the task is exiting. To protect against the do_exit | |
519 | * change of the task flags, we do this protected by | |
520 | * p->pi_lock: | |
521 | */ | |
522 | spin_lock_irq(&p->pi_lock); | |
523 | if (unlikely(p->flags & PF_EXITING)) { | |
524 | /* | |
525 | * The task is on the way out. When PF_EXITPIDONE is | |
526 | * set, we know that the task has finished the | |
527 | * cleanup: | |
528 | */ | |
529 | int ret = (p->flags & PF_EXITPIDONE) ? -ESRCH : -EAGAIN; | |
530 | ||
531 | spin_unlock_irq(&p->pi_lock); | |
532 | put_task_struct(p); | |
533 | return ret; | |
534 | } | |
c87e2837 IM |
535 | |
536 | pi_state = alloc_pi_state(); | |
537 | ||
538 | /* | |
539 | * Initialize the pi_mutex in locked state and make 'p' | |
540 | * the owner of it: | |
541 | */ | |
542 | rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p); | |
543 | ||
544 | /* Store the key for possible exit cleanups: */ | |
d0aa7a70 | 545 | pi_state->key = *key; |
c87e2837 | 546 | |
627371d7 | 547 | WARN_ON(!list_empty(&pi_state->list)); |
c87e2837 IM |
548 | list_add(&pi_state->list, &p->pi_state_list); |
549 | pi_state->owner = p; | |
550 | spin_unlock_irq(&p->pi_lock); | |
551 | ||
552 | put_task_struct(p); | |
553 | ||
d0aa7a70 | 554 | *ps = pi_state; |
c87e2837 IM |
555 | |
556 | return 0; | |
557 | } | |
558 | ||
1da177e4 LT |
559 | /* |
560 | * The hash bucket lock must be held when this is called. | |
561 | * Afterwards, the futex_q must not be accessed. | |
562 | */ | |
563 | static void wake_futex(struct futex_q *q) | |
564 | { | |
ec92d082 | 565 | plist_del(&q->list, &q->list.plist); |
1da177e4 LT |
566 | /* |
567 | * The lock in wake_up_all() is a crucial memory barrier after the | |
ec92d082 | 568 | * plist_del() and also before assigning to q->lock_ptr. |
1da177e4 | 569 | */ |
73500ac5 | 570 | wake_up(&q->waiter); |
1da177e4 LT |
571 | /* |
572 | * The waiting task can free the futex_q as soon as this is written, | |
573 | * without taking any locks. This must come last. | |
8e31108b | 574 | * |
b2d0994b DH |
575 | * A memory barrier is required here to prevent the following store to |
576 | * lock_ptr from getting ahead of the wakeup. Clearing the lock at the | |
577 | * end of wake_up() does not prevent this store from moving. | |
1da177e4 | 578 | */ |
ccdea2f8 | 579 | smp_wmb(); |
1da177e4 LT |
580 | q->lock_ptr = NULL; |
581 | } | |
582 | ||
c87e2837 IM |
583 | static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this) |
584 | { | |
585 | struct task_struct *new_owner; | |
586 | struct futex_pi_state *pi_state = this->pi_state; | |
587 | u32 curval, newval; | |
588 | ||
589 | if (!pi_state) | |
590 | return -EINVAL; | |
591 | ||
21778867 | 592 | spin_lock(&pi_state->pi_mutex.wait_lock); |
c87e2837 IM |
593 | new_owner = rt_mutex_next_owner(&pi_state->pi_mutex); |
594 | ||
595 | /* | |
596 | * This happens when we have stolen the lock and the original | |
597 | * pending owner did not enqueue itself back on the rt_mutex. | |
598 | * Thats not a tragedy. We know that way, that a lock waiter | |
599 | * is on the fly. We make the futex_q waiter the pending owner. | |
600 | */ | |
601 | if (!new_owner) | |
602 | new_owner = this->task; | |
603 | ||
604 | /* | |
605 | * We pass it to the next owner. (The WAITERS bit is always | |
606 | * kept enabled while there is PI state around. We must also | |
607 | * preserve the owner died bit.) | |
608 | */ | |
e3f2ddea | 609 | if (!(uval & FUTEX_OWNER_DIED)) { |
778e9a9c AK |
610 | int ret = 0; |
611 | ||
b488893a | 612 | newval = FUTEX_WAITERS | task_pid_vnr(new_owner); |
e3f2ddea | 613 | |
36cf3b5c | 614 | curval = cmpxchg_futex_value_locked(uaddr, uval, newval); |
778e9a9c | 615 | |
e3f2ddea | 616 | if (curval == -EFAULT) |
778e9a9c | 617 | ret = -EFAULT; |
cde898fa | 618 | else if (curval != uval) |
778e9a9c AK |
619 | ret = -EINVAL; |
620 | if (ret) { | |
621 | spin_unlock(&pi_state->pi_mutex.wait_lock); | |
622 | return ret; | |
623 | } | |
e3f2ddea | 624 | } |
c87e2837 | 625 | |
627371d7 IM |
626 | spin_lock_irq(&pi_state->owner->pi_lock); |
627 | WARN_ON(list_empty(&pi_state->list)); | |
628 | list_del_init(&pi_state->list); | |
629 | spin_unlock_irq(&pi_state->owner->pi_lock); | |
630 | ||
631 | spin_lock_irq(&new_owner->pi_lock); | |
632 | WARN_ON(!list_empty(&pi_state->list)); | |
c87e2837 IM |
633 | list_add(&pi_state->list, &new_owner->pi_state_list); |
634 | pi_state->owner = new_owner; | |
627371d7 IM |
635 | spin_unlock_irq(&new_owner->pi_lock); |
636 | ||
21778867 | 637 | spin_unlock(&pi_state->pi_mutex.wait_lock); |
c87e2837 IM |
638 | rt_mutex_unlock(&pi_state->pi_mutex); |
639 | ||
640 | return 0; | |
641 | } | |
642 | ||
643 | static int unlock_futex_pi(u32 __user *uaddr, u32 uval) | |
644 | { | |
645 | u32 oldval; | |
646 | ||
647 | /* | |
648 | * There is no waiter, so we unlock the futex. The owner died | |
649 | * bit has not to be preserved here. We are the owner: | |
650 | */ | |
36cf3b5c | 651 | oldval = cmpxchg_futex_value_locked(uaddr, uval, 0); |
c87e2837 IM |
652 | |
653 | if (oldval == -EFAULT) | |
654 | return oldval; | |
655 | if (oldval != uval) | |
656 | return -EAGAIN; | |
657 | ||
658 | return 0; | |
659 | } | |
660 | ||
8b8f319f IM |
661 | /* |
662 | * Express the locking dependencies for lockdep: | |
663 | */ | |
664 | static inline void | |
665 | double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) | |
666 | { | |
667 | if (hb1 <= hb2) { | |
668 | spin_lock(&hb1->lock); | |
669 | if (hb1 < hb2) | |
670 | spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING); | |
671 | } else { /* hb1 > hb2 */ | |
672 | spin_lock(&hb2->lock); | |
673 | spin_lock_nested(&hb1->lock, SINGLE_DEPTH_NESTING); | |
674 | } | |
675 | } | |
676 | ||
5eb3dc62 DH |
677 | static inline void |
678 | double_unlock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) | |
679 | { | |
f061d351 | 680 | spin_unlock(&hb1->lock); |
88f502fe IM |
681 | if (hb1 != hb2) |
682 | spin_unlock(&hb2->lock); | |
5eb3dc62 DH |
683 | } |
684 | ||
1da177e4 | 685 | /* |
b2d0994b | 686 | * Wake up waiters matching bitset queued on this futex (uaddr). |
1da177e4 | 687 | */ |
c2f9f201 | 688 | static int futex_wake(u32 __user *uaddr, int fshared, int nr_wake, u32 bitset) |
1da177e4 | 689 | { |
e2970f2f | 690 | struct futex_hash_bucket *hb; |
1da177e4 | 691 | struct futex_q *this, *next; |
ec92d082 | 692 | struct plist_head *head; |
38d47c1b | 693 | union futex_key key = FUTEX_KEY_INIT; |
1da177e4 LT |
694 | int ret; |
695 | ||
cd689985 TG |
696 | if (!bitset) |
697 | return -EINVAL; | |
698 | ||
34f01cc1 | 699 | ret = get_futex_key(uaddr, fshared, &key); |
1da177e4 LT |
700 | if (unlikely(ret != 0)) |
701 | goto out; | |
702 | ||
e2970f2f IM |
703 | hb = hash_futex(&key); |
704 | spin_lock(&hb->lock); | |
705 | head = &hb->chain; | |
1da177e4 | 706 | |
ec92d082 | 707 | plist_for_each_entry_safe(this, next, head, list) { |
1da177e4 | 708 | if (match_futex (&this->key, &key)) { |
ed6f7b10 IM |
709 | if (this->pi_state) { |
710 | ret = -EINVAL; | |
711 | break; | |
712 | } | |
cd689985 TG |
713 | |
714 | /* Check if one of the bits is set in both bitsets */ | |
715 | if (!(this->bitset & bitset)) | |
716 | continue; | |
717 | ||
1da177e4 LT |
718 | wake_futex(this); |
719 | if (++ret >= nr_wake) | |
720 | break; | |
721 | } | |
722 | } | |
723 | ||
e2970f2f | 724 | spin_unlock(&hb->lock); |
38d47c1b | 725 | put_futex_key(fshared, &key); |
42d35d48 | 726 | out: |
1da177e4 LT |
727 | return ret; |
728 | } | |
729 | ||
4732efbe JJ |
730 | /* |
731 | * Wake up all waiters hashed on the physical page that is mapped | |
732 | * to this virtual address: | |
733 | */ | |
e2970f2f | 734 | static int |
c2f9f201 | 735 | futex_wake_op(u32 __user *uaddr1, int fshared, u32 __user *uaddr2, |
e2970f2f | 736 | int nr_wake, int nr_wake2, int op) |
4732efbe | 737 | { |
38d47c1b | 738 | union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT; |
e2970f2f | 739 | struct futex_hash_bucket *hb1, *hb2; |
ec92d082 | 740 | struct plist_head *head; |
4732efbe | 741 | struct futex_q *this, *next; |
e4dc5b7a | 742 | int ret, op_ret; |
4732efbe | 743 | |
e4dc5b7a | 744 | retry: |
34f01cc1 | 745 | ret = get_futex_key(uaddr1, fshared, &key1); |
4732efbe JJ |
746 | if (unlikely(ret != 0)) |
747 | goto out; | |
34f01cc1 | 748 | ret = get_futex_key(uaddr2, fshared, &key2); |
4732efbe | 749 | if (unlikely(ret != 0)) |
42d35d48 | 750 | goto out_put_key1; |
4732efbe | 751 | |
e2970f2f IM |
752 | hb1 = hash_futex(&key1); |
753 | hb2 = hash_futex(&key2); | |
4732efbe | 754 | |
8b8f319f | 755 | double_lock_hb(hb1, hb2); |
e4dc5b7a | 756 | retry_private: |
e2970f2f | 757 | op_ret = futex_atomic_op_inuser(op, uaddr2); |
4732efbe | 758 | if (unlikely(op_ret < 0)) { |
e2970f2f | 759 | u32 dummy; |
4732efbe | 760 | |
5eb3dc62 | 761 | double_unlock_hb(hb1, hb2); |
4732efbe | 762 | |
7ee1dd3f | 763 | #ifndef CONFIG_MMU |
e2970f2f IM |
764 | /* |
765 | * we don't get EFAULT from MMU faults if we don't have an MMU, | |
766 | * but we might get them from range checking | |
767 | */ | |
7ee1dd3f | 768 | ret = op_ret; |
42d35d48 | 769 | goto out_put_keys; |
7ee1dd3f DH |
770 | #endif |
771 | ||
796f8d9b DG |
772 | if (unlikely(op_ret != -EFAULT)) { |
773 | ret = op_ret; | |
42d35d48 | 774 | goto out_put_keys; |
796f8d9b DG |
775 | } |
776 | ||
e2970f2f | 777 | ret = get_user(dummy, uaddr2); |
4732efbe | 778 | if (ret) |
de87fcc1 | 779 | goto out_put_keys; |
4732efbe | 780 | |
e4dc5b7a DH |
781 | if (!fshared) |
782 | goto retry_private; | |
783 | ||
de87fcc1 DH |
784 | put_futex_key(fshared, &key2); |
785 | put_futex_key(fshared, &key1); | |
e4dc5b7a | 786 | goto retry; |
4732efbe JJ |
787 | } |
788 | ||
e2970f2f | 789 | head = &hb1->chain; |
4732efbe | 790 | |
ec92d082 | 791 | plist_for_each_entry_safe(this, next, head, list) { |
4732efbe JJ |
792 | if (match_futex (&this->key, &key1)) { |
793 | wake_futex(this); | |
794 | if (++ret >= nr_wake) | |
795 | break; | |
796 | } | |
797 | } | |
798 | ||
799 | if (op_ret > 0) { | |
e2970f2f | 800 | head = &hb2->chain; |
4732efbe JJ |
801 | |
802 | op_ret = 0; | |
ec92d082 | 803 | plist_for_each_entry_safe(this, next, head, list) { |
4732efbe JJ |
804 | if (match_futex (&this->key, &key2)) { |
805 | wake_futex(this); | |
806 | if (++op_ret >= nr_wake2) | |
807 | break; | |
808 | } | |
809 | } | |
810 | ret += op_ret; | |
811 | } | |
812 | ||
5eb3dc62 | 813 | double_unlock_hb(hb1, hb2); |
42d35d48 | 814 | out_put_keys: |
38d47c1b | 815 | put_futex_key(fshared, &key2); |
42d35d48 | 816 | out_put_key1: |
38d47c1b | 817 | put_futex_key(fshared, &key1); |
42d35d48 | 818 | out: |
4732efbe JJ |
819 | return ret; |
820 | } | |
821 | ||
1da177e4 LT |
822 | /* |
823 | * Requeue all waiters hashed on one physical page to another | |
824 | * physical page. | |
825 | */ | |
c2f9f201 | 826 | static int futex_requeue(u32 __user *uaddr1, int fshared, u32 __user *uaddr2, |
e2970f2f | 827 | int nr_wake, int nr_requeue, u32 *cmpval) |
1da177e4 | 828 | { |
38d47c1b | 829 | union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT; |
e2970f2f | 830 | struct futex_hash_bucket *hb1, *hb2; |
ec92d082 | 831 | struct plist_head *head1; |
1da177e4 LT |
832 | struct futex_q *this, *next; |
833 | int ret, drop_count = 0; | |
834 | ||
42d35d48 | 835 | retry: |
34f01cc1 | 836 | ret = get_futex_key(uaddr1, fshared, &key1); |
1da177e4 LT |
837 | if (unlikely(ret != 0)) |
838 | goto out; | |
34f01cc1 | 839 | ret = get_futex_key(uaddr2, fshared, &key2); |
1da177e4 | 840 | if (unlikely(ret != 0)) |
42d35d48 | 841 | goto out_put_key1; |
1da177e4 | 842 | |
e2970f2f IM |
843 | hb1 = hash_futex(&key1); |
844 | hb2 = hash_futex(&key2); | |
1da177e4 | 845 | |
e4dc5b7a | 846 | retry_private: |
8b8f319f | 847 | double_lock_hb(hb1, hb2); |
1da177e4 | 848 | |
e2970f2f IM |
849 | if (likely(cmpval != NULL)) { |
850 | u32 curval; | |
1da177e4 | 851 | |
e2970f2f | 852 | ret = get_futex_value_locked(&curval, uaddr1); |
1da177e4 LT |
853 | |
854 | if (unlikely(ret)) { | |
5eb3dc62 | 855 | double_unlock_hb(hb1, hb2); |
1da177e4 | 856 | |
e2970f2f | 857 | ret = get_user(curval, uaddr1); |
e4dc5b7a DH |
858 | if (ret) |
859 | goto out_put_keys; | |
1da177e4 | 860 | |
e4dc5b7a DH |
861 | if (!fshared) |
862 | goto retry_private; | |
1da177e4 | 863 | |
e4dc5b7a DH |
864 | put_futex_key(fshared, &key2); |
865 | put_futex_key(fshared, &key1); | |
866 | goto retry; | |
1da177e4 | 867 | } |
e2970f2f | 868 | if (curval != *cmpval) { |
1da177e4 LT |
869 | ret = -EAGAIN; |
870 | goto out_unlock; | |
871 | } | |
872 | } | |
873 | ||
e2970f2f | 874 | head1 = &hb1->chain; |
ec92d082 | 875 | plist_for_each_entry_safe(this, next, head1, list) { |
1da177e4 LT |
876 | if (!match_futex (&this->key, &key1)) |
877 | continue; | |
878 | if (++ret <= nr_wake) { | |
879 | wake_futex(this); | |
880 | } else { | |
59e0e0ac SD |
881 | /* |
882 | * If key1 and key2 hash to the same bucket, no need to | |
883 | * requeue. | |
884 | */ | |
885 | if (likely(head1 != &hb2->chain)) { | |
ec92d082 PP |
886 | plist_del(&this->list, &hb1->chain); |
887 | plist_add(&this->list, &hb2->chain); | |
59e0e0ac | 888 | this->lock_ptr = &hb2->lock; |
ec92d082 PP |
889 | #ifdef CONFIG_DEBUG_PI_LIST |
890 | this->list.plist.lock = &hb2->lock; | |
891 | #endif | |
778e9a9c | 892 | } |
1da177e4 | 893 | this->key = key2; |
9adef58b | 894 | get_futex_key_refs(&key2); |
1da177e4 LT |
895 | drop_count++; |
896 | ||
897 | if (ret - nr_wake >= nr_requeue) | |
898 | break; | |
1da177e4 LT |
899 | } |
900 | } | |
901 | ||
902 | out_unlock: | |
5eb3dc62 | 903 | double_unlock_hb(hb1, hb2); |
1da177e4 | 904 | |
9adef58b | 905 | /* drop_futex_key_refs() must be called outside the spinlocks. */ |
1da177e4 | 906 | while (--drop_count >= 0) |
9adef58b | 907 | drop_futex_key_refs(&key1); |
1da177e4 | 908 | |
42d35d48 | 909 | out_put_keys: |
38d47c1b | 910 | put_futex_key(fshared, &key2); |
42d35d48 | 911 | out_put_key1: |
38d47c1b | 912 | put_futex_key(fshared, &key1); |
42d35d48 | 913 | out: |
1da177e4 LT |
914 | return ret; |
915 | } | |
916 | ||
917 | /* The key must be already stored in q->key. */ | |
82af7aca | 918 | static inline struct futex_hash_bucket *queue_lock(struct futex_q *q) |
1da177e4 | 919 | { |
e2970f2f | 920 | struct futex_hash_bucket *hb; |
1da177e4 | 921 | |
73500ac5 | 922 | init_waitqueue_head(&q->waiter); |
1da177e4 | 923 | |
9adef58b | 924 | get_futex_key_refs(&q->key); |
e2970f2f IM |
925 | hb = hash_futex(&q->key); |
926 | q->lock_ptr = &hb->lock; | |
1da177e4 | 927 | |
e2970f2f IM |
928 | spin_lock(&hb->lock); |
929 | return hb; | |
1da177e4 LT |
930 | } |
931 | ||
82af7aca | 932 | static inline void queue_me(struct futex_q *q, struct futex_hash_bucket *hb) |
1da177e4 | 933 | { |
ec92d082 PP |
934 | int prio; |
935 | ||
936 | /* | |
937 | * The priority used to register this element is | |
938 | * - either the real thread-priority for the real-time threads | |
939 | * (i.e. threads with a priority lower than MAX_RT_PRIO) | |
940 | * - or MAX_RT_PRIO for non-RT threads. | |
941 | * Thus, all RT-threads are woken first in priority order, and | |
942 | * the others are woken last, in FIFO order. | |
943 | */ | |
944 | prio = min(current->normal_prio, MAX_RT_PRIO); | |
945 | ||
946 | plist_node_init(&q->list, prio); | |
947 | #ifdef CONFIG_DEBUG_PI_LIST | |
948 | q->list.plist.lock = &hb->lock; | |
949 | #endif | |
950 | plist_add(&q->list, &hb->chain); | |
c87e2837 | 951 | q->task = current; |
e2970f2f | 952 | spin_unlock(&hb->lock); |
1da177e4 LT |
953 | } |
954 | ||
955 | static inline void | |
e2970f2f | 956 | queue_unlock(struct futex_q *q, struct futex_hash_bucket *hb) |
1da177e4 | 957 | { |
e2970f2f | 958 | spin_unlock(&hb->lock); |
9adef58b | 959 | drop_futex_key_refs(&q->key); |
1da177e4 LT |
960 | } |
961 | ||
962 | /* | |
963 | * queue_me and unqueue_me must be called as a pair, each | |
964 | * exactly once. They are called with the hashed spinlock held. | |
965 | */ | |
966 | ||
1da177e4 LT |
967 | /* Return 1 if we were still queued (ie. 0 means we were woken) */ |
968 | static int unqueue_me(struct futex_q *q) | |
969 | { | |
1da177e4 | 970 | spinlock_t *lock_ptr; |
e2970f2f | 971 | int ret = 0; |
1da177e4 LT |
972 | |
973 | /* In the common case we don't take the spinlock, which is nice. */ | |
42d35d48 | 974 | retry: |
1da177e4 | 975 | lock_ptr = q->lock_ptr; |
e91467ec | 976 | barrier(); |
c80544dc | 977 | if (lock_ptr != NULL) { |
1da177e4 LT |
978 | spin_lock(lock_ptr); |
979 | /* | |
980 | * q->lock_ptr can change between reading it and | |
981 | * spin_lock(), causing us to take the wrong lock. This | |
982 | * corrects the race condition. | |
983 | * | |
984 | * Reasoning goes like this: if we have the wrong lock, | |
985 | * q->lock_ptr must have changed (maybe several times) | |
986 | * between reading it and the spin_lock(). It can | |
987 | * change again after the spin_lock() but only if it was | |
988 | * already changed before the spin_lock(). It cannot, | |
989 | * however, change back to the original value. Therefore | |
990 | * we can detect whether we acquired the correct lock. | |
991 | */ | |
992 | if (unlikely(lock_ptr != q->lock_ptr)) { | |
993 | spin_unlock(lock_ptr); | |
994 | goto retry; | |
995 | } | |
ec92d082 PP |
996 | WARN_ON(plist_node_empty(&q->list)); |
997 | plist_del(&q->list, &q->list.plist); | |
c87e2837 IM |
998 | |
999 | BUG_ON(q->pi_state); | |
1000 | ||
1da177e4 LT |
1001 | spin_unlock(lock_ptr); |
1002 | ret = 1; | |
1003 | } | |
1004 | ||
9adef58b | 1005 | drop_futex_key_refs(&q->key); |
1da177e4 LT |
1006 | return ret; |
1007 | } | |
1008 | ||
c87e2837 IM |
1009 | /* |
1010 | * PI futexes can not be requeued and must remove themself from the | |
d0aa7a70 PP |
1011 | * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry |
1012 | * and dropped here. | |
c87e2837 | 1013 | */ |
d0aa7a70 | 1014 | static void unqueue_me_pi(struct futex_q *q) |
c87e2837 | 1015 | { |
ec92d082 PP |
1016 | WARN_ON(plist_node_empty(&q->list)); |
1017 | plist_del(&q->list, &q->list.plist); | |
c87e2837 IM |
1018 | |
1019 | BUG_ON(!q->pi_state); | |
1020 | free_pi_state(q->pi_state); | |
1021 | q->pi_state = NULL; | |
1022 | ||
d0aa7a70 | 1023 | spin_unlock(q->lock_ptr); |
c87e2837 | 1024 | |
9adef58b | 1025 | drop_futex_key_refs(&q->key); |
c87e2837 IM |
1026 | } |
1027 | ||
d0aa7a70 | 1028 | /* |
cdf71a10 | 1029 | * Fixup the pi_state owner with the new owner. |
d0aa7a70 | 1030 | * |
778e9a9c AK |
1031 | * Must be called with hash bucket lock held and mm->sem held for non |
1032 | * private futexes. | |
d0aa7a70 | 1033 | */ |
778e9a9c | 1034 | static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q, |
c2f9f201 | 1035 | struct task_struct *newowner, int fshared) |
d0aa7a70 | 1036 | { |
cdf71a10 | 1037 | u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS; |
d0aa7a70 | 1038 | struct futex_pi_state *pi_state = q->pi_state; |
1b7558e4 | 1039 | struct task_struct *oldowner = pi_state->owner; |
d0aa7a70 | 1040 | u32 uval, curval, newval; |
e4dc5b7a | 1041 | int ret; |
d0aa7a70 PP |
1042 | |
1043 | /* Owner died? */ | |
1b7558e4 TG |
1044 | if (!pi_state->owner) |
1045 | newtid |= FUTEX_OWNER_DIED; | |
1046 | ||
1047 | /* | |
1048 | * We are here either because we stole the rtmutex from the | |
1049 | * pending owner or we are the pending owner which failed to | |
1050 | * get the rtmutex. We have to replace the pending owner TID | |
1051 | * in the user space variable. This must be atomic as we have | |
1052 | * to preserve the owner died bit here. | |
1053 | * | |
b2d0994b DH |
1054 | * Note: We write the user space value _before_ changing the pi_state |
1055 | * because we can fault here. Imagine swapped out pages or a fork | |
1056 | * that marked all the anonymous memory readonly for cow. | |
1b7558e4 TG |
1057 | * |
1058 | * Modifying pi_state _before_ the user space value would | |
1059 | * leave the pi_state in an inconsistent state when we fault | |
1060 | * here, because we need to drop the hash bucket lock to | |
1061 | * handle the fault. This might be observed in the PID check | |
1062 | * in lookup_pi_state. | |
1063 | */ | |
1064 | retry: | |
1065 | if (get_futex_value_locked(&uval, uaddr)) | |
1066 | goto handle_fault; | |
1067 | ||
1068 | while (1) { | |
1069 | newval = (uval & FUTEX_OWNER_DIED) | newtid; | |
1070 | ||
1071 | curval = cmpxchg_futex_value_locked(uaddr, uval, newval); | |
1072 | ||
1073 | if (curval == -EFAULT) | |
1074 | goto handle_fault; | |
1075 | if (curval == uval) | |
1076 | break; | |
1077 | uval = curval; | |
1078 | } | |
1079 | ||
1080 | /* | |
1081 | * We fixed up user space. Now we need to fix the pi_state | |
1082 | * itself. | |
1083 | */ | |
d0aa7a70 PP |
1084 | if (pi_state->owner != NULL) { |
1085 | spin_lock_irq(&pi_state->owner->pi_lock); | |
1086 | WARN_ON(list_empty(&pi_state->list)); | |
1087 | list_del_init(&pi_state->list); | |
1088 | spin_unlock_irq(&pi_state->owner->pi_lock); | |
1b7558e4 | 1089 | } |
d0aa7a70 | 1090 | |
cdf71a10 | 1091 | pi_state->owner = newowner; |
d0aa7a70 | 1092 | |
cdf71a10 | 1093 | spin_lock_irq(&newowner->pi_lock); |
d0aa7a70 | 1094 | WARN_ON(!list_empty(&pi_state->list)); |
cdf71a10 TG |
1095 | list_add(&pi_state->list, &newowner->pi_state_list); |
1096 | spin_unlock_irq(&newowner->pi_lock); | |
1b7558e4 | 1097 | return 0; |
d0aa7a70 | 1098 | |
d0aa7a70 | 1099 | /* |
1b7558e4 TG |
1100 | * To handle the page fault we need to drop the hash bucket |
1101 | * lock here. That gives the other task (either the pending | |
1102 | * owner itself or the task which stole the rtmutex) the | |
1103 | * chance to try the fixup of the pi_state. So once we are | |
1104 | * back from handling the fault we need to check the pi_state | |
1105 | * after reacquiring the hash bucket lock and before trying to | |
1106 | * do another fixup. When the fixup has been done already we | |
1107 | * simply return. | |
d0aa7a70 | 1108 | */ |
1b7558e4 TG |
1109 | handle_fault: |
1110 | spin_unlock(q->lock_ptr); | |
778e9a9c | 1111 | |
e4dc5b7a | 1112 | ret = get_user(uval, uaddr); |
778e9a9c | 1113 | |
1b7558e4 | 1114 | spin_lock(q->lock_ptr); |
778e9a9c | 1115 | |
1b7558e4 TG |
1116 | /* |
1117 | * Check if someone else fixed it for us: | |
1118 | */ | |
1119 | if (pi_state->owner != oldowner) | |
1120 | return 0; | |
1121 | ||
1122 | if (ret) | |
1123 | return ret; | |
1124 | ||
1125 | goto retry; | |
d0aa7a70 PP |
1126 | } |
1127 | ||
34f01cc1 ED |
1128 | /* |
1129 | * In case we must use restart_block to restart a futex_wait, | |
ce6bd420 | 1130 | * we encode in the 'flags' shared capability |
34f01cc1 | 1131 | */ |
1acdac10 TG |
1132 | #define FLAGS_SHARED 0x01 |
1133 | #define FLAGS_CLOCKRT 0x02 | |
34f01cc1 | 1134 | |
72c1bbf3 | 1135 | static long futex_wait_restart(struct restart_block *restart); |
36cf3b5c | 1136 | |
ca5f9524 DH |
1137 | /** |
1138 | * futex_wait_queue_me() - queue_me() and wait for wakeup, timeout, or signal | |
1139 | * @hb: the futex hash bucket, must be locked by the caller | |
1140 | * @q: the futex_q to queue up on | |
1141 | * @timeout: the prepared hrtimer_sleeper, or null for no timeout | |
1142 | * @wait: the wait_queue to add to the futex_q after queueing in the hb | |
1143 | */ | |
1144 | static void futex_wait_queue_me(struct futex_hash_bucket *hb, struct futex_q *q, | |
1145 | struct hrtimer_sleeper *timeout, | |
1146 | wait_queue_t *wait) | |
1147 | { | |
1148 | queue_me(q, hb); | |
1149 | ||
1150 | /* | |
1151 | * There might have been scheduling since the queue_me(), as we | |
1152 | * cannot hold a spinlock across the get_user() in case it | |
1153 | * faults, and we cannot just set TASK_INTERRUPTIBLE state when | |
1154 | * queueing ourselves into the futex hash. This code thus has to | |
1155 | * rely on the futex_wake() code removing us from hash when it | |
1156 | * wakes us up. | |
1157 | */ | |
1158 | ||
1159 | /* add_wait_queue is the barrier after __set_current_state. */ | |
1160 | __set_current_state(TASK_INTERRUPTIBLE); | |
1161 | ||
1162 | /* | |
1163 | * Add current as the futex_q waiter. We don't remove ourselves from | |
1164 | * the wait_queue because we are the only user of it. | |
1165 | */ | |
1166 | add_wait_queue(&q->waiter, wait); | |
1167 | ||
1168 | /* Arm the timer */ | |
1169 | if (timeout) { | |
1170 | hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS); | |
1171 | if (!hrtimer_active(&timeout->timer)) | |
1172 | timeout->task = NULL; | |
1173 | } | |
1174 | ||
1175 | /* | |
1176 | * !plist_node_empty() is safe here without any lock. | |
1177 | * q.lock_ptr != 0 is not safe, because of ordering against wakeup. | |
1178 | */ | |
1179 | if (likely(!plist_node_empty(&q->list))) { | |
1180 | /* | |
1181 | * If the timer has already expired, current will already be | |
1182 | * flagged for rescheduling. Only call schedule if there | |
1183 | * is no timeout, or if it has yet to expire. | |
1184 | */ | |
1185 | if (!timeout || timeout->task) | |
1186 | schedule(); | |
1187 | } | |
1188 | __set_current_state(TASK_RUNNING); | |
1189 | } | |
1190 | ||
c2f9f201 | 1191 | static int futex_wait(u32 __user *uaddr, int fshared, |
1acdac10 | 1192 | u32 val, ktime_t *abs_time, u32 bitset, int clockrt) |
1da177e4 | 1193 | { |
ca5f9524 DH |
1194 | struct hrtimer_sleeper timeout, *to = NULL; |
1195 | DECLARE_WAITQUEUE(wait, current); | |
2fff78c7 | 1196 | struct restart_block *restart; |
e2970f2f | 1197 | struct futex_hash_bucket *hb; |
1da177e4 | 1198 | struct futex_q q; |
e2970f2f IM |
1199 | u32 uval; |
1200 | int ret; | |
1da177e4 | 1201 | |
cd689985 TG |
1202 | if (!bitset) |
1203 | return -EINVAL; | |
1204 | ||
c87e2837 | 1205 | q.pi_state = NULL; |
cd689985 | 1206 | q.bitset = bitset; |
ca5f9524 DH |
1207 | |
1208 | if (abs_time) { | |
1209 | to = &timeout; | |
1210 | ||
1211 | hrtimer_init_on_stack(&to->timer, clockrt ? CLOCK_REALTIME : | |
1212 | CLOCK_MONOTONIC, HRTIMER_MODE_ABS); | |
1213 | hrtimer_init_sleeper(to, current); | |
1214 | hrtimer_set_expires_range_ns(&to->timer, *abs_time, | |
1215 | current->timer_slack_ns); | |
1216 | } | |
1217 | ||
42d35d48 | 1218 | retry: |
38d47c1b | 1219 | q.key = FUTEX_KEY_INIT; |
34f01cc1 | 1220 | ret = get_futex_key(uaddr, fshared, &q.key); |
1da177e4 | 1221 | if (unlikely(ret != 0)) |
42d35d48 | 1222 | goto out; |
1da177e4 | 1223 | |
e4dc5b7a | 1224 | retry_private: |
82af7aca | 1225 | hb = queue_lock(&q); |
1da177e4 LT |
1226 | |
1227 | /* | |
b2d0994b | 1228 | * Access the page AFTER the hash-bucket is locked. |
1da177e4 LT |
1229 | * Order is important: |
1230 | * | |
1231 | * Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val); | |
1232 | * Userspace waker: if (cond(var)) { var = new; futex_wake(&var); } | |
1233 | * | |
1234 | * The basic logical guarantee of a futex is that it blocks ONLY | |
1235 | * if cond(var) is known to be true at the time of blocking, for | |
1236 | * any cond. If we queued after testing *uaddr, that would open | |
1237 | * a race condition where we could block indefinitely with | |
1238 | * cond(var) false, which would violate the guarantee. | |
1239 | * | |
1240 | * A consequence is that futex_wait() can return zero and absorb | |
1241 | * a wakeup when *uaddr != val on entry to the syscall. This is | |
1242 | * rare, but normal. | |
1243 | * | |
b2d0994b | 1244 | * For shared futexes, we hold the mmap semaphore, so the mapping |
34f01cc1 | 1245 | * cannot have changed since we looked it up in get_futex_key. |
1da177e4 | 1246 | */ |
e2970f2f | 1247 | ret = get_futex_value_locked(&uval, uaddr); |
1da177e4 LT |
1248 | |
1249 | if (unlikely(ret)) { | |
e2970f2f | 1250 | queue_unlock(&q, hb); |
1da177e4 | 1251 | |
e2970f2f | 1252 | ret = get_user(uval, uaddr); |
e4dc5b7a DH |
1253 | if (ret) |
1254 | goto out_put_key; | |
1da177e4 | 1255 | |
e4dc5b7a DH |
1256 | if (!fshared) |
1257 | goto retry_private; | |
1258 | ||
1259 | put_futex_key(fshared, &q.key); | |
1260 | goto retry; | |
1da177e4 | 1261 | } |
c87e2837 | 1262 | ret = -EWOULDBLOCK; |
ca5f9524 DH |
1263 | |
1264 | /* Only actually queue if *uaddr contained val. */ | |
2fff78c7 PZ |
1265 | if (unlikely(uval != val)) { |
1266 | queue_unlock(&q, hb); | |
1267 | goto out_put_key; | |
1268 | } | |
1da177e4 | 1269 | |
ca5f9524 DH |
1270 | /* queue_me and wait for wakeup, timeout, or a signal. */ |
1271 | futex_wait_queue_me(hb, &q, to, &wait); | |
1da177e4 LT |
1272 | |
1273 | /* If we were woken (and unqueued), we succeeded, whatever. */ | |
2fff78c7 | 1274 | ret = 0; |
1da177e4 | 1275 | if (!unqueue_me(&q)) |
2fff78c7 PZ |
1276 | goto out_put_key; |
1277 | ret = -ETIMEDOUT; | |
ca5f9524 | 1278 | if (to && !to->task) |
2fff78c7 | 1279 | goto out_put_key; |
72c1bbf3 | 1280 | |
e2970f2f IM |
1281 | /* |
1282 | * We expect signal_pending(current), but another thread may | |
1283 | * have handled it for us already. | |
1284 | */ | |
2fff78c7 | 1285 | ret = -ERESTARTSYS; |
c19384b5 | 1286 | if (!abs_time) |
2fff78c7 | 1287 | goto out_put_key; |
1da177e4 | 1288 | |
2fff78c7 PZ |
1289 | restart = ¤t_thread_info()->restart_block; |
1290 | restart->fn = futex_wait_restart; | |
1291 | restart->futex.uaddr = (u32 *)uaddr; | |
1292 | restart->futex.val = val; | |
1293 | restart->futex.time = abs_time->tv64; | |
1294 | restart->futex.bitset = bitset; | |
1295 | restart->futex.flags = 0; | |
1296 | ||
1297 | if (fshared) | |
1298 | restart->futex.flags |= FLAGS_SHARED; | |
1299 | if (clockrt) | |
1300 | restart->futex.flags |= FLAGS_CLOCKRT; | |
42d35d48 | 1301 | |
2fff78c7 PZ |
1302 | ret = -ERESTART_RESTARTBLOCK; |
1303 | ||
1304 | out_put_key: | |
1305 | put_futex_key(fshared, &q.key); | |
42d35d48 | 1306 | out: |
ca5f9524 DH |
1307 | if (to) { |
1308 | hrtimer_cancel(&to->timer); | |
1309 | destroy_hrtimer_on_stack(&to->timer); | |
1310 | } | |
c87e2837 IM |
1311 | return ret; |
1312 | } | |
1313 | ||
72c1bbf3 NP |
1314 | |
1315 | static long futex_wait_restart(struct restart_block *restart) | |
1316 | { | |
ce6bd420 | 1317 | u32 __user *uaddr = (u32 __user *)restart->futex.uaddr; |
c2f9f201 | 1318 | int fshared = 0; |
ce6bd420 | 1319 | ktime_t t; |
72c1bbf3 | 1320 | |
ce6bd420 | 1321 | t.tv64 = restart->futex.time; |
72c1bbf3 | 1322 | restart->fn = do_no_restart_syscall; |
ce6bd420 | 1323 | if (restart->futex.flags & FLAGS_SHARED) |
c2f9f201 | 1324 | fshared = 1; |
cd689985 | 1325 | return (long)futex_wait(uaddr, fshared, restart->futex.val, &t, |
1acdac10 TG |
1326 | restart->futex.bitset, |
1327 | restart->futex.flags & FLAGS_CLOCKRT); | |
72c1bbf3 NP |
1328 | } |
1329 | ||
1330 | ||
c87e2837 IM |
1331 | /* |
1332 | * Userspace tried a 0 -> TID atomic transition of the futex value | |
1333 | * and failed. The kernel side here does the whole locking operation: | |
1334 | * if there are waiters then it will block, it does PI, etc. (Due to | |
1335 | * races the kernel might see a 0 value of the futex too.) | |
1336 | */ | |
c2f9f201 | 1337 | static int futex_lock_pi(u32 __user *uaddr, int fshared, |
34f01cc1 | 1338 | int detect, ktime_t *time, int trylock) |
c87e2837 | 1339 | { |
c5780e97 | 1340 | struct hrtimer_sleeper timeout, *to = NULL; |
c87e2837 IM |
1341 | struct task_struct *curr = current; |
1342 | struct futex_hash_bucket *hb; | |
1343 | u32 uval, newval, curval; | |
1344 | struct futex_q q; | |
e4dc5b7a | 1345 | int ret, lock_taken, ownerdied = 0; |
c87e2837 IM |
1346 | |
1347 | if (refill_pi_state_cache()) | |
1348 | return -ENOMEM; | |
1349 | ||
c19384b5 | 1350 | if (time) { |
c5780e97 | 1351 | to = &timeout; |
237fc6e7 TG |
1352 | hrtimer_init_on_stack(&to->timer, CLOCK_REALTIME, |
1353 | HRTIMER_MODE_ABS); | |
c5780e97 | 1354 | hrtimer_init_sleeper(to, current); |
cc584b21 | 1355 | hrtimer_set_expires(&to->timer, *time); |
c5780e97 TG |
1356 | } |
1357 | ||
c87e2837 | 1358 | q.pi_state = NULL; |
42d35d48 | 1359 | retry: |
38d47c1b | 1360 | q.key = FUTEX_KEY_INIT; |
34f01cc1 | 1361 | ret = get_futex_key(uaddr, fshared, &q.key); |
c87e2837 | 1362 | if (unlikely(ret != 0)) |
42d35d48 | 1363 | goto out; |
c87e2837 | 1364 | |
e4dc5b7a | 1365 | retry_private: |
82af7aca | 1366 | hb = queue_lock(&q); |
c87e2837 | 1367 | |
42d35d48 | 1368 | retry_locked: |
778e9a9c | 1369 | ret = lock_taken = 0; |
d0aa7a70 | 1370 | |
c87e2837 IM |
1371 | /* |
1372 | * To avoid races, we attempt to take the lock here again | |
1373 | * (by doing a 0 -> TID atomic cmpxchg), while holding all | |
1374 | * the locks. It will most likely not succeed. | |
1375 | */ | |
b488893a | 1376 | newval = task_pid_vnr(current); |
c87e2837 | 1377 | |
36cf3b5c | 1378 | curval = cmpxchg_futex_value_locked(uaddr, 0, newval); |
c87e2837 IM |
1379 | |
1380 | if (unlikely(curval == -EFAULT)) | |
1381 | goto uaddr_faulted; | |
1382 | ||
778e9a9c AK |
1383 | /* |
1384 | * Detect deadlocks. In case of REQUEUE_PI this is a valid | |
1385 | * situation and we return success to user space. | |
1386 | */ | |
b488893a | 1387 | if (unlikely((curval & FUTEX_TID_MASK) == task_pid_vnr(current))) { |
bd197234 | 1388 | ret = -EDEADLK; |
42d35d48 | 1389 | goto out_unlock_put_key; |
c87e2837 IM |
1390 | } |
1391 | ||
1392 | /* | |
778e9a9c | 1393 | * Surprise - we got the lock. Just return to userspace: |
c87e2837 IM |
1394 | */ |
1395 | if (unlikely(!curval)) | |
42d35d48 | 1396 | goto out_unlock_put_key; |
c87e2837 IM |
1397 | |
1398 | uval = curval; | |
778e9a9c | 1399 | |
d0aa7a70 | 1400 | /* |
778e9a9c AK |
1401 | * Set the WAITERS flag, so the owner will know it has someone |
1402 | * to wake at next unlock | |
d0aa7a70 | 1403 | */ |
778e9a9c AK |
1404 | newval = curval | FUTEX_WAITERS; |
1405 | ||
1406 | /* | |
1407 | * There are two cases, where a futex might have no owner (the | |
bd197234 TG |
1408 | * owner TID is 0): OWNER_DIED. We take over the futex in this |
1409 | * case. We also do an unconditional take over, when the owner | |
1410 | * of the futex died. | |
778e9a9c AK |
1411 | * |
1412 | * This is safe as we are protected by the hash bucket lock ! | |
1413 | */ | |
1414 | if (unlikely(ownerdied || !(curval & FUTEX_TID_MASK))) { | |
bd197234 | 1415 | /* Keep the OWNER_DIED bit */ |
b488893a | 1416 | newval = (curval & ~FUTEX_TID_MASK) | task_pid_vnr(current); |
778e9a9c AK |
1417 | ownerdied = 0; |
1418 | lock_taken = 1; | |
1419 | } | |
c87e2837 | 1420 | |
36cf3b5c | 1421 | curval = cmpxchg_futex_value_locked(uaddr, uval, newval); |
c87e2837 IM |
1422 | |
1423 | if (unlikely(curval == -EFAULT)) | |
1424 | goto uaddr_faulted; | |
1425 | if (unlikely(curval != uval)) | |
1426 | goto retry_locked; | |
1427 | ||
778e9a9c | 1428 | /* |
bd197234 | 1429 | * We took the lock due to owner died take over. |
778e9a9c | 1430 | */ |
bd197234 | 1431 | if (unlikely(lock_taken)) |
42d35d48 | 1432 | goto out_unlock_put_key; |
d0aa7a70 | 1433 | |
c87e2837 IM |
1434 | /* |
1435 | * We dont have the lock. Look up the PI state (or create it if | |
1436 | * we are the first waiter): | |
1437 | */ | |
d0aa7a70 | 1438 | ret = lookup_pi_state(uval, hb, &q.key, &q.pi_state); |
c87e2837 IM |
1439 | |
1440 | if (unlikely(ret)) { | |
778e9a9c | 1441 | switch (ret) { |
c87e2837 | 1442 | |
778e9a9c AK |
1443 | case -EAGAIN: |
1444 | /* | |
1445 | * Task is exiting and we just wait for the | |
1446 | * exit to complete. | |
1447 | */ | |
1448 | queue_unlock(&q, hb); | |
de87fcc1 | 1449 | put_futex_key(fshared, &q.key); |
778e9a9c AK |
1450 | cond_resched(); |
1451 | goto retry; | |
c87e2837 | 1452 | |
778e9a9c AK |
1453 | case -ESRCH: |
1454 | /* | |
1455 | * No owner found for this futex. Check if the | |
1456 | * OWNER_DIED bit is set to figure out whether | |
1457 | * this is a robust futex or not. | |
1458 | */ | |
1459 | if (get_futex_value_locked(&curval, uaddr)) | |
c87e2837 | 1460 | goto uaddr_faulted; |
778e9a9c AK |
1461 | |
1462 | /* | |
1463 | * We simply start over in case of a robust | |
1464 | * futex. The code above will take the futex | |
1465 | * and return happy. | |
1466 | */ | |
1467 | if (curval & FUTEX_OWNER_DIED) { | |
1468 | ownerdied = 1; | |
c87e2837 | 1469 | goto retry_locked; |
778e9a9c AK |
1470 | } |
1471 | default: | |
42d35d48 | 1472 | goto out_unlock_put_key; |
c87e2837 | 1473 | } |
c87e2837 IM |
1474 | } |
1475 | ||
1476 | /* | |
1477 | * Only actually queue now that the atomic ops are done: | |
1478 | */ | |
82af7aca | 1479 | queue_me(&q, hb); |
c87e2837 | 1480 | |
c87e2837 IM |
1481 | WARN_ON(!q.pi_state); |
1482 | /* | |
1483 | * Block on the PI mutex: | |
1484 | */ | |
1485 | if (!trylock) | |
1486 | ret = rt_mutex_timed_lock(&q.pi_state->pi_mutex, to, 1); | |
1487 | else { | |
1488 | ret = rt_mutex_trylock(&q.pi_state->pi_mutex); | |
1489 | /* Fixup the trylock return value: */ | |
1490 | ret = ret ? 0 : -EWOULDBLOCK; | |
1491 | } | |
1492 | ||
a99e4e41 | 1493 | spin_lock(q.lock_ptr); |
c87e2837 | 1494 | |
778e9a9c AK |
1495 | if (!ret) { |
1496 | /* | |
1497 | * Got the lock. We might not be the anticipated owner | |
1498 | * if we did a lock-steal - fix up the PI-state in | |
1499 | * that case: | |
1500 | */ | |
1501 | if (q.pi_state->owner != curr) | |
1b7558e4 | 1502 | ret = fixup_pi_state_owner(uaddr, &q, curr, fshared); |
778e9a9c | 1503 | } else { |
c87e2837 IM |
1504 | /* |
1505 | * Catch the rare case, where the lock was released | |
778e9a9c AK |
1506 | * when we were on the way back before we locked the |
1507 | * hash bucket. | |
c87e2837 | 1508 | */ |
cdf71a10 TG |
1509 | if (q.pi_state->owner == curr) { |
1510 | /* | |
1511 | * Try to get the rt_mutex now. This might | |
1512 | * fail as some other task acquired the | |
1513 | * rt_mutex after we removed ourself from the | |
1514 | * rt_mutex waiters list. | |
1515 | */ | |
1516 | if (rt_mutex_trylock(&q.pi_state->pi_mutex)) | |
1517 | ret = 0; | |
1518 | else { | |
1519 | /* | |
1520 | * pi_state is incorrect, some other | |
1521 | * task did a lock steal and we | |
1522 | * returned due to timeout or signal | |
1523 | * without taking the rt_mutex. Too | |
1524 | * late. We can access the | |
1525 | * rt_mutex_owner without locking, as | |
1526 | * the other task is now blocked on | |
1527 | * the hash bucket lock. Fix the state | |
1528 | * up. | |
1529 | */ | |
1530 | struct task_struct *owner; | |
1531 | int res; | |
1532 | ||
1533 | owner = rt_mutex_owner(&q.pi_state->pi_mutex); | |
1b7558e4 TG |
1534 | res = fixup_pi_state_owner(uaddr, &q, owner, |
1535 | fshared); | |
cdf71a10 | 1536 | |
cdf71a10 TG |
1537 | /* propagate -EFAULT, if the fixup failed */ |
1538 | if (res) | |
1539 | ret = res; | |
1540 | } | |
778e9a9c AK |
1541 | } else { |
1542 | /* | |
1543 | * Paranoia check. If we did not take the lock | |
1544 | * in the trylock above, then we should not be | |
1545 | * the owner of the rtmutex, neither the real | |
1546 | * nor the pending one: | |
1547 | */ | |
1548 | if (rt_mutex_owner(&q.pi_state->pi_mutex) == curr) | |
1549 | printk(KERN_ERR "futex_lock_pi: ret = %d " | |
1550 | "pi-mutex: %p pi-state %p\n", ret, | |
1551 | q.pi_state->pi_mutex.owner, | |
1552 | q.pi_state->owner); | |
c87e2837 | 1553 | } |
c87e2837 IM |
1554 | } |
1555 | ||
e8f6386c DH |
1556 | /* |
1557 | * If fixup_pi_state_owner() faulted and was unable to handle the | |
1558 | * fault, unlock it and return the fault to userspace. | |
1559 | */ | |
1560 | if (ret && (rt_mutex_owner(&q.pi_state->pi_mutex) == current)) | |
1561 | rt_mutex_unlock(&q.pi_state->pi_mutex); | |
1562 | ||
778e9a9c AK |
1563 | /* Unqueue and drop the lock */ |
1564 | unqueue_me_pi(&q); | |
c87e2837 | 1565 | |
237fc6e7 TG |
1566 | if (to) |
1567 | destroy_hrtimer_on_stack(&to->timer); | |
c5780e97 | 1568 | return ret != -EINTR ? ret : -ERESTARTNOINTR; |
c87e2837 | 1569 | |
42d35d48 | 1570 | out_unlock_put_key: |
c87e2837 IM |
1571 | queue_unlock(&q, hb); |
1572 | ||
42d35d48 | 1573 | out_put_key: |
38d47c1b | 1574 | put_futex_key(fshared, &q.key); |
42d35d48 | 1575 | out: |
237fc6e7 TG |
1576 | if (to) |
1577 | destroy_hrtimer_on_stack(&to->timer); | |
c87e2837 IM |
1578 | return ret; |
1579 | ||
42d35d48 | 1580 | uaddr_faulted: |
c87e2837 | 1581 | /* |
b5686363 DH |
1582 | * We have to r/w *(int __user *)uaddr, and we have to modify it |
1583 | * atomically. Therefore, if we continue to fault after get_user() | |
1584 | * below, we need to handle the fault ourselves, while still holding | |
1585 | * the mmap_sem. This can occur if the uaddr is under contention as | |
1586 | * we have to drop the mmap_sem in order to call get_user(). | |
c87e2837 | 1587 | */ |
778e9a9c AK |
1588 | queue_unlock(&q, hb); |
1589 | ||
c87e2837 | 1590 | ret = get_user(uval, uaddr); |
e4dc5b7a DH |
1591 | if (ret) |
1592 | goto out_put_key; | |
c87e2837 | 1593 | |
e4dc5b7a DH |
1594 | if (!fshared) |
1595 | goto retry_private; | |
1596 | ||
1597 | put_futex_key(fshared, &q.key); | |
1598 | goto retry; | |
c87e2837 IM |
1599 | } |
1600 | ||
de87fcc1 | 1601 | |
c87e2837 IM |
1602 | /* |
1603 | * Userspace attempted a TID -> 0 atomic transition, and failed. | |
1604 | * This is the in-kernel slowpath: we look up the PI state (if any), | |
1605 | * and do the rt-mutex unlock. | |
1606 | */ | |
c2f9f201 | 1607 | static int futex_unlock_pi(u32 __user *uaddr, int fshared) |
c87e2837 IM |
1608 | { |
1609 | struct futex_hash_bucket *hb; | |
1610 | struct futex_q *this, *next; | |
1611 | u32 uval; | |
ec92d082 | 1612 | struct plist_head *head; |
38d47c1b | 1613 | union futex_key key = FUTEX_KEY_INIT; |
e4dc5b7a | 1614 | int ret; |
c87e2837 IM |
1615 | |
1616 | retry: | |
1617 | if (get_user(uval, uaddr)) | |
1618 | return -EFAULT; | |
1619 | /* | |
1620 | * We release only a lock we actually own: | |
1621 | */ | |
b488893a | 1622 | if ((uval & FUTEX_TID_MASK) != task_pid_vnr(current)) |
c87e2837 | 1623 | return -EPERM; |
c87e2837 | 1624 | |
34f01cc1 | 1625 | ret = get_futex_key(uaddr, fshared, &key); |
c87e2837 IM |
1626 | if (unlikely(ret != 0)) |
1627 | goto out; | |
1628 | ||
1629 | hb = hash_futex(&key); | |
1630 | spin_lock(&hb->lock); | |
1631 | ||
c87e2837 IM |
1632 | /* |
1633 | * To avoid races, try to do the TID -> 0 atomic transition | |
1634 | * again. If it succeeds then we can return without waking | |
1635 | * anyone else up: | |
1636 | */ | |
36cf3b5c | 1637 | if (!(uval & FUTEX_OWNER_DIED)) |
b488893a | 1638 | uval = cmpxchg_futex_value_locked(uaddr, task_pid_vnr(current), 0); |
36cf3b5c | 1639 | |
c87e2837 IM |
1640 | |
1641 | if (unlikely(uval == -EFAULT)) | |
1642 | goto pi_faulted; | |
1643 | /* | |
1644 | * Rare case: we managed to release the lock atomically, | |
1645 | * no need to wake anyone else up: | |
1646 | */ | |
b488893a | 1647 | if (unlikely(uval == task_pid_vnr(current))) |
c87e2837 IM |
1648 | goto out_unlock; |
1649 | ||
1650 | /* | |
1651 | * Ok, other tasks may need to be woken up - check waiters | |
1652 | * and do the wakeup if necessary: | |
1653 | */ | |
1654 | head = &hb->chain; | |
1655 | ||
ec92d082 | 1656 | plist_for_each_entry_safe(this, next, head, list) { |
c87e2837 IM |
1657 | if (!match_futex (&this->key, &key)) |
1658 | continue; | |
1659 | ret = wake_futex_pi(uaddr, uval, this); | |
1660 | /* | |
1661 | * The atomic access to the futex value | |
1662 | * generated a pagefault, so retry the | |
1663 | * user-access and the wakeup: | |
1664 | */ | |
1665 | if (ret == -EFAULT) | |
1666 | goto pi_faulted; | |
1667 | goto out_unlock; | |
1668 | } | |
1669 | /* | |
1670 | * No waiters - kernel unlocks the futex: | |
1671 | */ | |
e3f2ddea IM |
1672 | if (!(uval & FUTEX_OWNER_DIED)) { |
1673 | ret = unlock_futex_pi(uaddr, uval); | |
1674 | if (ret == -EFAULT) | |
1675 | goto pi_faulted; | |
1676 | } | |
c87e2837 IM |
1677 | |
1678 | out_unlock: | |
1679 | spin_unlock(&hb->lock); | |
38d47c1b | 1680 | put_futex_key(fshared, &key); |
c87e2837 | 1681 | |
42d35d48 | 1682 | out: |
c87e2837 IM |
1683 | return ret; |
1684 | ||
1685 | pi_faulted: | |
1686 | /* | |
b5686363 DH |
1687 | * We have to r/w *(int __user *)uaddr, and we have to modify it |
1688 | * atomically. Therefore, if we continue to fault after get_user() | |
1689 | * below, we need to handle the fault ourselves, while still holding | |
1690 | * the mmap_sem. This can occur if the uaddr is under contention as | |
1691 | * we have to drop the mmap_sem in order to call get_user(). | |
c87e2837 | 1692 | */ |
778e9a9c | 1693 | spin_unlock(&hb->lock); |
e4dc5b7a | 1694 | put_futex_key(fshared, &key); |
c87e2837 | 1695 | |
c87e2837 | 1696 | ret = get_user(uval, uaddr); |
b5686363 | 1697 | if (!ret) |
c87e2837 IM |
1698 | goto retry; |
1699 | ||
1da177e4 LT |
1700 | return ret; |
1701 | } | |
1702 | ||
0771dfef IM |
1703 | /* |
1704 | * Support for robust futexes: the kernel cleans up held futexes at | |
1705 | * thread exit time. | |
1706 | * | |
1707 | * Implementation: user-space maintains a per-thread list of locks it | |
1708 | * is holding. Upon do_exit(), the kernel carefully walks this list, | |
1709 | * and marks all locks that are owned by this thread with the | |
c87e2837 | 1710 | * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is |
0771dfef IM |
1711 | * always manipulated with the lock held, so the list is private and |
1712 | * per-thread. Userspace also maintains a per-thread 'list_op_pending' | |
1713 | * field, to allow the kernel to clean up if the thread dies after | |
1714 | * acquiring the lock, but just before it could have added itself to | |
1715 | * the list. There can only be one such pending lock. | |
1716 | */ | |
1717 | ||
1718 | /** | |
1719 | * sys_set_robust_list - set the robust-futex list head of a task | |
1720 | * @head: pointer to the list-head | |
1721 | * @len: length of the list-head, as userspace expects | |
1722 | */ | |
836f92ad HC |
1723 | SYSCALL_DEFINE2(set_robust_list, struct robust_list_head __user *, head, |
1724 | size_t, len) | |
0771dfef | 1725 | { |
a0c1e907 TG |
1726 | if (!futex_cmpxchg_enabled) |
1727 | return -ENOSYS; | |
0771dfef IM |
1728 | /* |
1729 | * The kernel knows only one size for now: | |
1730 | */ | |
1731 | if (unlikely(len != sizeof(*head))) | |
1732 | return -EINVAL; | |
1733 | ||
1734 | current->robust_list = head; | |
1735 | ||
1736 | return 0; | |
1737 | } | |
1738 | ||
1739 | /** | |
1740 | * sys_get_robust_list - get the robust-futex list head of a task | |
1741 | * @pid: pid of the process [zero for current task] | |
1742 | * @head_ptr: pointer to a list-head pointer, the kernel fills it in | |
1743 | * @len_ptr: pointer to a length field, the kernel fills in the header size | |
1744 | */ | |
836f92ad HC |
1745 | SYSCALL_DEFINE3(get_robust_list, int, pid, |
1746 | struct robust_list_head __user * __user *, head_ptr, | |
1747 | size_t __user *, len_ptr) | |
0771dfef | 1748 | { |
ba46df98 | 1749 | struct robust_list_head __user *head; |
0771dfef | 1750 | unsigned long ret; |
c69e8d9c | 1751 | const struct cred *cred = current_cred(), *pcred; |
0771dfef | 1752 | |
a0c1e907 TG |
1753 | if (!futex_cmpxchg_enabled) |
1754 | return -ENOSYS; | |
1755 | ||
0771dfef IM |
1756 | if (!pid) |
1757 | head = current->robust_list; | |
1758 | else { | |
1759 | struct task_struct *p; | |
1760 | ||
1761 | ret = -ESRCH; | |
aaa2a97e | 1762 | rcu_read_lock(); |
228ebcbe | 1763 | p = find_task_by_vpid(pid); |
0771dfef IM |
1764 | if (!p) |
1765 | goto err_unlock; | |
1766 | ret = -EPERM; | |
c69e8d9c DH |
1767 | pcred = __task_cred(p); |
1768 | if (cred->euid != pcred->euid && | |
1769 | cred->euid != pcred->uid && | |
76aac0e9 | 1770 | !capable(CAP_SYS_PTRACE)) |
0771dfef IM |
1771 | goto err_unlock; |
1772 | head = p->robust_list; | |
aaa2a97e | 1773 | rcu_read_unlock(); |
0771dfef IM |
1774 | } |
1775 | ||
1776 | if (put_user(sizeof(*head), len_ptr)) | |
1777 | return -EFAULT; | |
1778 | return put_user(head, head_ptr); | |
1779 | ||
1780 | err_unlock: | |
aaa2a97e | 1781 | rcu_read_unlock(); |
0771dfef IM |
1782 | |
1783 | return ret; | |
1784 | } | |
1785 | ||
1786 | /* | |
1787 | * Process a futex-list entry, check whether it's owned by the | |
1788 | * dying task, and do notification if so: | |
1789 | */ | |
e3f2ddea | 1790 | int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi) |
0771dfef | 1791 | { |
e3f2ddea | 1792 | u32 uval, nval, mval; |
0771dfef | 1793 | |
8f17d3a5 IM |
1794 | retry: |
1795 | if (get_user(uval, uaddr)) | |
0771dfef IM |
1796 | return -1; |
1797 | ||
b488893a | 1798 | if ((uval & FUTEX_TID_MASK) == task_pid_vnr(curr)) { |
0771dfef IM |
1799 | /* |
1800 | * Ok, this dying thread is truly holding a futex | |
1801 | * of interest. Set the OWNER_DIED bit atomically | |
1802 | * via cmpxchg, and if the value had FUTEX_WAITERS | |
1803 | * set, wake up a waiter (if any). (We have to do a | |
1804 | * futex_wake() even if OWNER_DIED is already set - | |
1805 | * to handle the rare but possible case of recursive | |
1806 | * thread-death.) The rest of the cleanup is done in | |
1807 | * userspace. | |
1808 | */ | |
e3f2ddea IM |
1809 | mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED; |
1810 | nval = futex_atomic_cmpxchg_inatomic(uaddr, uval, mval); | |
1811 | ||
c87e2837 IM |
1812 | if (nval == -EFAULT) |
1813 | return -1; | |
1814 | ||
1815 | if (nval != uval) | |
8f17d3a5 | 1816 | goto retry; |
0771dfef | 1817 | |
e3f2ddea IM |
1818 | /* |
1819 | * Wake robust non-PI futexes here. The wakeup of | |
1820 | * PI futexes happens in exit_pi_state(): | |
1821 | */ | |
36cf3b5c | 1822 | if (!pi && (uval & FUTEX_WAITERS)) |
c2f9f201 | 1823 | futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY); |
0771dfef IM |
1824 | } |
1825 | return 0; | |
1826 | } | |
1827 | ||
e3f2ddea IM |
1828 | /* |
1829 | * Fetch a robust-list pointer. Bit 0 signals PI futexes: | |
1830 | */ | |
1831 | static inline int fetch_robust_entry(struct robust_list __user **entry, | |
ba46df98 AV |
1832 | struct robust_list __user * __user *head, |
1833 | int *pi) | |
e3f2ddea IM |
1834 | { |
1835 | unsigned long uentry; | |
1836 | ||
ba46df98 | 1837 | if (get_user(uentry, (unsigned long __user *)head)) |
e3f2ddea IM |
1838 | return -EFAULT; |
1839 | ||
ba46df98 | 1840 | *entry = (void __user *)(uentry & ~1UL); |
e3f2ddea IM |
1841 | *pi = uentry & 1; |
1842 | ||
1843 | return 0; | |
1844 | } | |
1845 | ||
0771dfef IM |
1846 | /* |
1847 | * Walk curr->robust_list (very carefully, it's a userspace list!) | |
1848 | * and mark any locks found there dead, and notify any waiters. | |
1849 | * | |
1850 | * We silently return on any sign of list-walking problem. | |
1851 | */ | |
1852 | void exit_robust_list(struct task_struct *curr) | |
1853 | { | |
1854 | struct robust_list_head __user *head = curr->robust_list; | |
9f96cb1e MS |
1855 | struct robust_list __user *entry, *next_entry, *pending; |
1856 | unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip; | |
0771dfef | 1857 | unsigned long futex_offset; |
9f96cb1e | 1858 | int rc; |
0771dfef | 1859 | |
a0c1e907 TG |
1860 | if (!futex_cmpxchg_enabled) |
1861 | return; | |
1862 | ||
0771dfef IM |
1863 | /* |
1864 | * Fetch the list head (which was registered earlier, via | |
1865 | * sys_set_robust_list()): | |
1866 | */ | |
e3f2ddea | 1867 | if (fetch_robust_entry(&entry, &head->list.next, &pi)) |
0771dfef IM |
1868 | return; |
1869 | /* | |
1870 | * Fetch the relative futex offset: | |
1871 | */ | |
1872 | if (get_user(futex_offset, &head->futex_offset)) | |
1873 | return; | |
1874 | /* | |
1875 | * Fetch any possibly pending lock-add first, and handle it | |
1876 | * if it exists: | |
1877 | */ | |
e3f2ddea | 1878 | if (fetch_robust_entry(&pending, &head->list_op_pending, &pip)) |
0771dfef | 1879 | return; |
e3f2ddea | 1880 | |
9f96cb1e | 1881 | next_entry = NULL; /* avoid warning with gcc */ |
0771dfef | 1882 | while (entry != &head->list) { |
9f96cb1e MS |
1883 | /* |
1884 | * Fetch the next entry in the list before calling | |
1885 | * handle_futex_death: | |
1886 | */ | |
1887 | rc = fetch_robust_entry(&next_entry, &entry->next, &next_pi); | |
0771dfef IM |
1888 | /* |
1889 | * A pending lock might already be on the list, so | |
c87e2837 | 1890 | * don't process it twice: |
0771dfef IM |
1891 | */ |
1892 | if (entry != pending) | |
ba46df98 | 1893 | if (handle_futex_death((void __user *)entry + futex_offset, |
e3f2ddea | 1894 | curr, pi)) |
0771dfef | 1895 | return; |
9f96cb1e | 1896 | if (rc) |
0771dfef | 1897 | return; |
9f96cb1e MS |
1898 | entry = next_entry; |
1899 | pi = next_pi; | |
0771dfef IM |
1900 | /* |
1901 | * Avoid excessively long or circular lists: | |
1902 | */ | |
1903 | if (!--limit) | |
1904 | break; | |
1905 | ||
1906 | cond_resched(); | |
1907 | } | |
9f96cb1e MS |
1908 | |
1909 | if (pending) | |
1910 | handle_futex_death((void __user *)pending + futex_offset, | |
1911 | curr, pip); | |
0771dfef IM |
1912 | } |
1913 | ||
c19384b5 | 1914 | long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout, |
e2970f2f | 1915 | u32 __user *uaddr2, u32 val2, u32 val3) |
1da177e4 | 1916 | { |
1acdac10 | 1917 | int clockrt, ret = -ENOSYS; |
34f01cc1 | 1918 | int cmd = op & FUTEX_CMD_MASK; |
c2f9f201 | 1919 | int fshared = 0; |
34f01cc1 ED |
1920 | |
1921 | if (!(op & FUTEX_PRIVATE_FLAG)) | |
c2f9f201 | 1922 | fshared = 1; |
1da177e4 | 1923 | |
1acdac10 TG |
1924 | clockrt = op & FUTEX_CLOCK_REALTIME; |
1925 | if (clockrt && cmd != FUTEX_WAIT_BITSET) | |
1926 | return -ENOSYS; | |
1da177e4 | 1927 | |
34f01cc1 | 1928 | switch (cmd) { |
1da177e4 | 1929 | case FUTEX_WAIT: |
cd689985 TG |
1930 | val3 = FUTEX_BITSET_MATCH_ANY; |
1931 | case FUTEX_WAIT_BITSET: | |
1acdac10 | 1932 | ret = futex_wait(uaddr, fshared, val, timeout, val3, clockrt); |
1da177e4 LT |
1933 | break; |
1934 | case FUTEX_WAKE: | |
cd689985 TG |
1935 | val3 = FUTEX_BITSET_MATCH_ANY; |
1936 | case FUTEX_WAKE_BITSET: | |
1937 | ret = futex_wake(uaddr, fshared, val, val3); | |
1da177e4 | 1938 | break; |
1da177e4 | 1939 | case FUTEX_REQUEUE: |
34f01cc1 | 1940 | ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, NULL); |
1da177e4 LT |
1941 | break; |
1942 | case FUTEX_CMP_REQUEUE: | |
34f01cc1 | 1943 | ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, &val3); |
1da177e4 | 1944 | break; |
4732efbe | 1945 | case FUTEX_WAKE_OP: |
34f01cc1 | 1946 | ret = futex_wake_op(uaddr, fshared, uaddr2, val, val2, val3); |
4732efbe | 1947 | break; |
c87e2837 | 1948 | case FUTEX_LOCK_PI: |
a0c1e907 TG |
1949 | if (futex_cmpxchg_enabled) |
1950 | ret = futex_lock_pi(uaddr, fshared, val, timeout, 0); | |
c87e2837 IM |
1951 | break; |
1952 | case FUTEX_UNLOCK_PI: | |
a0c1e907 TG |
1953 | if (futex_cmpxchg_enabled) |
1954 | ret = futex_unlock_pi(uaddr, fshared); | |
c87e2837 IM |
1955 | break; |
1956 | case FUTEX_TRYLOCK_PI: | |
a0c1e907 TG |
1957 | if (futex_cmpxchg_enabled) |
1958 | ret = futex_lock_pi(uaddr, fshared, 0, timeout, 1); | |
c87e2837 | 1959 | break; |
1da177e4 LT |
1960 | default: |
1961 | ret = -ENOSYS; | |
1962 | } | |
1963 | return ret; | |
1964 | } | |
1965 | ||
1966 | ||
17da2bd9 HC |
1967 | SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val, |
1968 | struct timespec __user *, utime, u32 __user *, uaddr2, | |
1969 | u32, val3) | |
1da177e4 | 1970 | { |
c19384b5 PP |
1971 | struct timespec ts; |
1972 | ktime_t t, *tp = NULL; | |
e2970f2f | 1973 | u32 val2 = 0; |
34f01cc1 | 1974 | int cmd = op & FUTEX_CMD_MASK; |
1da177e4 | 1975 | |
cd689985 TG |
1976 | if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI || |
1977 | cmd == FUTEX_WAIT_BITSET)) { | |
c19384b5 | 1978 | if (copy_from_user(&ts, utime, sizeof(ts)) != 0) |
1da177e4 | 1979 | return -EFAULT; |
c19384b5 | 1980 | if (!timespec_valid(&ts)) |
9741ef96 | 1981 | return -EINVAL; |
c19384b5 PP |
1982 | |
1983 | t = timespec_to_ktime(ts); | |
34f01cc1 | 1984 | if (cmd == FUTEX_WAIT) |
5a7780e7 | 1985 | t = ktime_add_safe(ktime_get(), t); |
c19384b5 | 1986 | tp = &t; |
1da177e4 LT |
1987 | } |
1988 | /* | |
34f01cc1 | 1989 | * requeue parameter in 'utime' if cmd == FUTEX_REQUEUE. |
f54f0986 | 1990 | * number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP. |
1da177e4 | 1991 | */ |
f54f0986 AS |
1992 | if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE || |
1993 | cmd == FUTEX_WAKE_OP) | |
e2970f2f | 1994 | val2 = (u32) (unsigned long) utime; |
1da177e4 | 1995 | |
c19384b5 | 1996 | return do_futex(uaddr, op, val, tp, uaddr2, val2, val3); |
1da177e4 LT |
1997 | } |
1998 | ||
f6d107fb | 1999 | static int __init futex_init(void) |
1da177e4 | 2000 | { |
a0c1e907 | 2001 | u32 curval; |
3e4ab747 | 2002 | int i; |
95362fa9 | 2003 | |
a0c1e907 TG |
2004 | /* |
2005 | * This will fail and we want it. Some arch implementations do | |
2006 | * runtime detection of the futex_atomic_cmpxchg_inatomic() | |
2007 | * functionality. We want to know that before we call in any | |
2008 | * of the complex code paths. Also we want to prevent | |
2009 | * registration of robust lists in that case. NULL is | |
2010 | * guaranteed to fault and we get -EFAULT on functional | |
2011 | * implementation, the non functional ones will return | |
2012 | * -ENOSYS. | |
2013 | */ | |
2014 | curval = cmpxchg_futex_value_locked(NULL, 0, 0); | |
2015 | if (curval == -EFAULT) | |
2016 | futex_cmpxchg_enabled = 1; | |
2017 | ||
3e4ab747 TG |
2018 | for (i = 0; i < ARRAY_SIZE(futex_queues); i++) { |
2019 | plist_head_init(&futex_queues[i].chain, &futex_queues[i].lock); | |
2020 | spin_lock_init(&futex_queues[i].lock); | |
2021 | } | |
2022 | ||
1da177e4 LT |
2023 | return 0; |
2024 | } | |
f6d107fb | 2025 | __initcall(futex_init); |