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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 | 195 | * @key: address where result is stored. |
64d1304a | 196 | * @rw: mapping needs to be read/write (values: VERIFY_READ, VERIFY_WRITE) |
34f01cc1 ED |
197 | * |
198 | * Returns a negative error code or 0 | |
199 | * The key words are stored in *key on success. | |
1da177e4 | 200 | * |
f3a43f3f | 201 | * For shared mappings, it's (page->index, vma->vm_file->f_path.dentry->d_inode, |
1da177e4 LT |
202 | * offset_within_page). For private mappings, it's (uaddr, current->mm). |
203 | * We can usually work out the index without swapping in the page. | |
204 | * | |
b2d0994b | 205 | * lock_page() might sleep, the caller should not hold a spinlock. |
1da177e4 | 206 | */ |
64d1304a TG |
207 | static int |
208 | get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key, int rw) | |
1da177e4 | 209 | { |
e2970f2f | 210 | unsigned long address = (unsigned long)uaddr; |
1da177e4 | 211 | struct mm_struct *mm = current->mm; |
1da177e4 LT |
212 | struct page *page; |
213 | int err; | |
214 | ||
215 | /* | |
216 | * The futex address must be "naturally" aligned. | |
217 | */ | |
e2970f2f | 218 | key->both.offset = address % PAGE_SIZE; |
34f01cc1 | 219 | if (unlikely((address % sizeof(u32)) != 0)) |
1da177e4 | 220 | return -EINVAL; |
e2970f2f | 221 | address -= key->both.offset; |
1da177e4 | 222 | |
34f01cc1 ED |
223 | /* |
224 | * PROCESS_PRIVATE futexes are fast. | |
225 | * As the mm cannot disappear under us and the 'key' only needs | |
226 | * virtual address, we dont even have to find the underlying vma. | |
227 | * Note : We do have to check 'uaddr' is a valid user address, | |
228 | * but access_ok() should be faster than find_vma() | |
229 | */ | |
230 | if (!fshared) { | |
64d1304a | 231 | if (unlikely(!access_ok(rw, uaddr, sizeof(u32)))) |
34f01cc1 ED |
232 | return -EFAULT; |
233 | key->private.mm = mm; | |
234 | key->private.address = address; | |
42569c39 | 235 | get_futex_key_refs(key); |
34f01cc1 ED |
236 | return 0; |
237 | } | |
1da177e4 | 238 | |
38d47c1b | 239 | again: |
64d1304a | 240 | err = get_user_pages_fast(address, 1, rw == VERIFY_WRITE, &page); |
38d47c1b PZ |
241 | if (err < 0) |
242 | return err; | |
243 | ||
244 | lock_page(page); | |
245 | if (!page->mapping) { | |
246 | unlock_page(page); | |
247 | put_page(page); | |
248 | goto again; | |
249 | } | |
1da177e4 LT |
250 | |
251 | /* | |
252 | * Private mappings are handled in a simple way. | |
253 | * | |
254 | * NOTE: When userspace waits on a MAP_SHARED mapping, even if | |
255 | * it's a read-only handle, it's expected that futexes attach to | |
38d47c1b | 256 | * the object not the particular process. |
1da177e4 | 257 | */ |
38d47c1b PZ |
258 | if (PageAnon(page)) { |
259 | key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */ | |
1da177e4 | 260 | key->private.mm = mm; |
e2970f2f | 261 | key->private.address = address; |
38d47c1b PZ |
262 | } else { |
263 | key->both.offset |= FUT_OFF_INODE; /* inode-based key */ | |
264 | key->shared.inode = page->mapping->host; | |
265 | key->shared.pgoff = page->index; | |
1da177e4 LT |
266 | } |
267 | ||
38d47c1b | 268 | get_futex_key_refs(key); |
1da177e4 | 269 | |
38d47c1b PZ |
270 | unlock_page(page); |
271 | put_page(page); | |
272 | return 0; | |
1da177e4 LT |
273 | } |
274 | ||
38d47c1b | 275 | static inline |
c2f9f201 | 276 | void put_futex_key(int fshared, union futex_key *key) |
1da177e4 | 277 | { |
38d47c1b | 278 | drop_futex_key_refs(key); |
1da177e4 LT |
279 | } |
280 | ||
36cf3b5c TG |
281 | static u32 cmpxchg_futex_value_locked(u32 __user *uaddr, u32 uval, u32 newval) |
282 | { | |
283 | u32 curval; | |
284 | ||
285 | pagefault_disable(); | |
286 | curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval); | |
287 | pagefault_enable(); | |
288 | ||
289 | return curval; | |
290 | } | |
291 | ||
292 | static int get_futex_value_locked(u32 *dest, u32 __user *from) | |
1da177e4 LT |
293 | { |
294 | int ret; | |
295 | ||
a866374a | 296 | pagefault_disable(); |
e2970f2f | 297 | ret = __copy_from_user_inatomic(dest, from, sizeof(u32)); |
a866374a | 298 | pagefault_enable(); |
1da177e4 LT |
299 | |
300 | return ret ? -EFAULT : 0; | |
301 | } | |
302 | ||
c87e2837 IM |
303 | |
304 | /* | |
305 | * PI code: | |
306 | */ | |
307 | static int refill_pi_state_cache(void) | |
308 | { | |
309 | struct futex_pi_state *pi_state; | |
310 | ||
311 | if (likely(current->pi_state_cache)) | |
312 | return 0; | |
313 | ||
4668edc3 | 314 | pi_state = kzalloc(sizeof(*pi_state), GFP_KERNEL); |
c87e2837 IM |
315 | |
316 | if (!pi_state) | |
317 | return -ENOMEM; | |
318 | ||
c87e2837 IM |
319 | INIT_LIST_HEAD(&pi_state->list); |
320 | /* pi_mutex gets initialized later */ | |
321 | pi_state->owner = NULL; | |
322 | atomic_set(&pi_state->refcount, 1); | |
38d47c1b | 323 | pi_state->key = FUTEX_KEY_INIT; |
c87e2837 IM |
324 | |
325 | current->pi_state_cache = pi_state; | |
326 | ||
327 | return 0; | |
328 | } | |
329 | ||
330 | static struct futex_pi_state * alloc_pi_state(void) | |
331 | { | |
332 | struct futex_pi_state *pi_state = current->pi_state_cache; | |
333 | ||
334 | WARN_ON(!pi_state); | |
335 | current->pi_state_cache = NULL; | |
336 | ||
337 | return pi_state; | |
338 | } | |
339 | ||
340 | static void free_pi_state(struct futex_pi_state *pi_state) | |
341 | { | |
342 | if (!atomic_dec_and_test(&pi_state->refcount)) | |
343 | return; | |
344 | ||
345 | /* | |
346 | * If pi_state->owner is NULL, the owner is most probably dying | |
347 | * and has cleaned up the pi_state already | |
348 | */ | |
349 | if (pi_state->owner) { | |
350 | spin_lock_irq(&pi_state->owner->pi_lock); | |
351 | list_del_init(&pi_state->list); | |
352 | spin_unlock_irq(&pi_state->owner->pi_lock); | |
353 | ||
354 | rt_mutex_proxy_unlock(&pi_state->pi_mutex, pi_state->owner); | |
355 | } | |
356 | ||
357 | if (current->pi_state_cache) | |
358 | kfree(pi_state); | |
359 | else { | |
360 | /* | |
361 | * pi_state->list is already empty. | |
362 | * clear pi_state->owner. | |
363 | * refcount is at 0 - put it back to 1. | |
364 | */ | |
365 | pi_state->owner = NULL; | |
366 | atomic_set(&pi_state->refcount, 1); | |
367 | current->pi_state_cache = pi_state; | |
368 | } | |
369 | } | |
370 | ||
371 | /* | |
372 | * Look up the task based on what TID userspace gave us. | |
373 | * We dont trust it. | |
374 | */ | |
375 | static struct task_struct * futex_find_get_task(pid_t pid) | |
376 | { | |
377 | struct task_struct *p; | |
c69e8d9c | 378 | const struct cred *cred = current_cred(), *pcred; |
c87e2837 | 379 | |
d359b549 | 380 | rcu_read_lock(); |
228ebcbe | 381 | p = find_task_by_vpid(pid); |
c69e8d9c | 382 | if (!p) { |
a06381fe | 383 | p = ERR_PTR(-ESRCH); |
c69e8d9c DH |
384 | } else { |
385 | pcred = __task_cred(p); | |
386 | if (cred->euid != pcred->euid && | |
387 | cred->euid != pcred->uid) | |
388 | p = ERR_PTR(-ESRCH); | |
389 | else | |
390 | get_task_struct(p); | |
391 | } | |
a06381fe | 392 | |
d359b549 | 393 | rcu_read_unlock(); |
c87e2837 IM |
394 | |
395 | return p; | |
396 | } | |
397 | ||
398 | /* | |
399 | * This task is holding PI mutexes at exit time => bad. | |
400 | * Kernel cleans up PI-state, but userspace is likely hosed. | |
401 | * (Robust-futex cleanup is separate and might save the day for userspace.) | |
402 | */ | |
403 | void exit_pi_state_list(struct task_struct *curr) | |
404 | { | |
c87e2837 IM |
405 | struct list_head *next, *head = &curr->pi_state_list; |
406 | struct futex_pi_state *pi_state; | |
627371d7 | 407 | struct futex_hash_bucket *hb; |
38d47c1b | 408 | union futex_key key = FUTEX_KEY_INIT; |
c87e2837 | 409 | |
a0c1e907 TG |
410 | if (!futex_cmpxchg_enabled) |
411 | return; | |
c87e2837 IM |
412 | /* |
413 | * We are a ZOMBIE and nobody can enqueue itself on | |
414 | * pi_state_list anymore, but we have to be careful | |
627371d7 | 415 | * versus waiters unqueueing themselves: |
c87e2837 IM |
416 | */ |
417 | spin_lock_irq(&curr->pi_lock); | |
418 | while (!list_empty(head)) { | |
419 | ||
420 | next = head->next; | |
421 | pi_state = list_entry(next, struct futex_pi_state, list); | |
422 | key = pi_state->key; | |
627371d7 | 423 | hb = hash_futex(&key); |
c87e2837 IM |
424 | spin_unlock_irq(&curr->pi_lock); |
425 | ||
c87e2837 IM |
426 | spin_lock(&hb->lock); |
427 | ||
428 | spin_lock_irq(&curr->pi_lock); | |
627371d7 IM |
429 | /* |
430 | * We dropped the pi-lock, so re-check whether this | |
431 | * task still owns the PI-state: | |
432 | */ | |
c87e2837 IM |
433 | if (head->next != next) { |
434 | spin_unlock(&hb->lock); | |
435 | continue; | |
436 | } | |
437 | ||
c87e2837 | 438 | WARN_ON(pi_state->owner != curr); |
627371d7 IM |
439 | WARN_ON(list_empty(&pi_state->list)); |
440 | list_del_init(&pi_state->list); | |
c87e2837 IM |
441 | pi_state->owner = NULL; |
442 | spin_unlock_irq(&curr->pi_lock); | |
443 | ||
444 | rt_mutex_unlock(&pi_state->pi_mutex); | |
445 | ||
446 | spin_unlock(&hb->lock); | |
447 | ||
448 | spin_lock_irq(&curr->pi_lock); | |
449 | } | |
450 | spin_unlock_irq(&curr->pi_lock); | |
451 | } | |
452 | ||
453 | static int | |
d0aa7a70 PP |
454 | lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, |
455 | union futex_key *key, struct futex_pi_state **ps) | |
c87e2837 IM |
456 | { |
457 | struct futex_pi_state *pi_state = NULL; | |
458 | struct futex_q *this, *next; | |
ec92d082 | 459 | struct plist_head *head; |
c87e2837 | 460 | struct task_struct *p; |
778e9a9c | 461 | pid_t pid = uval & FUTEX_TID_MASK; |
c87e2837 IM |
462 | |
463 | head = &hb->chain; | |
464 | ||
ec92d082 | 465 | plist_for_each_entry_safe(this, next, head, list) { |
d0aa7a70 | 466 | if (match_futex(&this->key, key)) { |
c87e2837 IM |
467 | /* |
468 | * Another waiter already exists - bump up | |
469 | * the refcount and return its pi_state: | |
470 | */ | |
471 | pi_state = this->pi_state; | |
06a9ec29 TG |
472 | /* |
473 | * Userspace might have messed up non PI and PI futexes | |
474 | */ | |
475 | if (unlikely(!pi_state)) | |
476 | return -EINVAL; | |
477 | ||
627371d7 | 478 | WARN_ON(!atomic_read(&pi_state->refcount)); |
778e9a9c AK |
479 | WARN_ON(pid && pi_state->owner && |
480 | pi_state->owner->pid != pid); | |
627371d7 | 481 | |
c87e2837 | 482 | atomic_inc(&pi_state->refcount); |
d0aa7a70 | 483 | *ps = pi_state; |
c87e2837 IM |
484 | |
485 | return 0; | |
486 | } | |
487 | } | |
488 | ||
489 | /* | |
e3f2ddea | 490 | * We are the first waiter - try to look up the real owner and attach |
778e9a9c | 491 | * the new pi_state to it, but bail out when TID = 0 |
c87e2837 | 492 | */ |
778e9a9c | 493 | if (!pid) |
e3f2ddea | 494 | return -ESRCH; |
c87e2837 | 495 | p = futex_find_get_task(pid); |
778e9a9c AK |
496 | if (IS_ERR(p)) |
497 | return PTR_ERR(p); | |
498 | ||
499 | /* | |
500 | * We need to look at the task state flags to figure out, | |
501 | * whether the task is exiting. To protect against the do_exit | |
502 | * change of the task flags, we do this protected by | |
503 | * p->pi_lock: | |
504 | */ | |
505 | spin_lock_irq(&p->pi_lock); | |
506 | if (unlikely(p->flags & PF_EXITING)) { | |
507 | /* | |
508 | * The task is on the way out. When PF_EXITPIDONE is | |
509 | * set, we know that the task has finished the | |
510 | * cleanup: | |
511 | */ | |
512 | int ret = (p->flags & PF_EXITPIDONE) ? -ESRCH : -EAGAIN; | |
513 | ||
514 | spin_unlock_irq(&p->pi_lock); | |
515 | put_task_struct(p); | |
516 | return ret; | |
517 | } | |
c87e2837 IM |
518 | |
519 | pi_state = alloc_pi_state(); | |
520 | ||
521 | /* | |
522 | * Initialize the pi_mutex in locked state and make 'p' | |
523 | * the owner of it: | |
524 | */ | |
525 | rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p); | |
526 | ||
527 | /* Store the key for possible exit cleanups: */ | |
d0aa7a70 | 528 | pi_state->key = *key; |
c87e2837 | 529 | |
627371d7 | 530 | WARN_ON(!list_empty(&pi_state->list)); |
c87e2837 IM |
531 | list_add(&pi_state->list, &p->pi_state_list); |
532 | pi_state->owner = p; | |
533 | spin_unlock_irq(&p->pi_lock); | |
534 | ||
535 | put_task_struct(p); | |
536 | ||
d0aa7a70 | 537 | *ps = pi_state; |
c87e2837 IM |
538 | |
539 | return 0; | |
540 | } | |
541 | ||
1da177e4 LT |
542 | /* |
543 | * The hash bucket lock must be held when this is called. | |
544 | * Afterwards, the futex_q must not be accessed. | |
545 | */ | |
546 | static void wake_futex(struct futex_q *q) | |
547 | { | |
ec92d082 | 548 | plist_del(&q->list, &q->list.plist); |
1da177e4 LT |
549 | /* |
550 | * The lock in wake_up_all() is a crucial memory barrier after the | |
ec92d082 | 551 | * plist_del() and also before assigning to q->lock_ptr. |
1da177e4 | 552 | */ |
73500ac5 | 553 | wake_up(&q->waiter); |
1da177e4 LT |
554 | /* |
555 | * The waiting task can free the futex_q as soon as this is written, | |
556 | * without taking any locks. This must come last. | |
8e31108b | 557 | * |
b2d0994b DH |
558 | * A memory barrier is required here to prevent the following store to |
559 | * lock_ptr from getting ahead of the wakeup. Clearing the lock at the | |
560 | * end of wake_up() does not prevent this store from moving. | |
1da177e4 | 561 | */ |
ccdea2f8 | 562 | smp_wmb(); |
1da177e4 LT |
563 | q->lock_ptr = NULL; |
564 | } | |
565 | ||
c87e2837 IM |
566 | static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this) |
567 | { | |
568 | struct task_struct *new_owner; | |
569 | struct futex_pi_state *pi_state = this->pi_state; | |
570 | u32 curval, newval; | |
571 | ||
572 | if (!pi_state) | |
573 | return -EINVAL; | |
574 | ||
21778867 | 575 | spin_lock(&pi_state->pi_mutex.wait_lock); |
c87e2837 IM |
576 | new_owner = rt_mutex_next_owner(&pi_state->pi_mutex); |
577 | ||
578 | /* | |
579 | * This happens when we have stolen the lock and the original | |
580 | * pending owner did not enqueue itself back on the rt_mutex. | |
581 | * Thats not a tragedy. We know that way, that a lock waiter | |
582 | * is on the fly. We make the futex_q waiter the pending owner. | |
583 | */ | |
584 | if (!new_owner) | |
585 | new_owner = this->task; | |
586 | ||
587 | /* | |
588 | * We pass it to the next owner. (The WAITERS bit is always | |
589 | * kept enabled while there is PI state around. We must also | |
590 | * preserve the owner died bit.) | |
591 | */ | |
e3f2ddea | 592 | if (!(uval & FUTEX_OWNER_DIED)) { |
778e9a9c AK |
593 | int ret = 0; |
594 | ||
b488893a | 595 | newval = FUTEX_WAITERS | task_pid_vnr(new_owner); |
e3f2ddea | 596 | |
36cf3b5c | 597 | curval = cmpxchg_futex_value_locked(uaddr, uval, newval); |
778e9a9c | 598 | |
e3f2ddea | 599 | if (curval == -EFAULT) |
778e9a9c | 600 | ret = -EFAULT; |
cde898fa | 601 | else if (curval != uval) |
778e9a9c AK |
602 | ret = -EINVAL; |
603 | if (ret) { | |
604 | spin_unlock(&pi_state->pi_mutex.wait_lock); | |
605 | return ret; | |
606 | } | |
e3f2ddea | 607 | } |
c87e2837 | 608 | |
627371d7 IM |
609 | spin_lock_irq(&pi_state->owner->pi_lock); |
610 | WARN_ON(list_empty(&pi_state->list)); | |
611 | list_del_init(&pi_state->list); | |
612 | spin_unlock_irq(&pi_state->owner->pi_lock); | |
613 | ||
614 | spin_lock_irq(&new_owner->pi_lock); | |
615 | WARN_ON(!list_empty(&pi_state->list)); | |
c87e2837 IM |
616 | list_add(&pi_state->list, &new_owner->pi_state_list); |
617 | pi_state->owner = new_owner; | |
627371d7 IM |
618 | spin_unlock_irq(&new_owner->pi_lock); |
619 | ||
21778867 | 620 | spin_unlock(&pi_state->pi_mutex.wait_lock); |
c87e2837 IM |
621 | rt_mutex_unlock(&pi_state->pi_mutex); |
622 | ||
623 | return 0; | |
624 | } | |
625 | ||
626 | static int unlock_futex_pi(u32 __user *uaddr, u32 uval) | |
627 | { | |
628 | u32 oldval; | |
629 | ||
630 | /* | |
631 | * There is no waiter, so we unlock the futex. The owner died | |
632 | * bit has not to be preserved here. We are the owner: | |
633 | */ | |
36cf3b5c | 634 | oldval = cmpxchg_futex_value_locked(uaddr, uval, 0); |
c87e2837 IM |
635 | |
636 | if (oldval == -EFAULT) | |
637 | return oldval; | |
638 | if (oldval != uval) | |
639 | return -EAGAIN; | |
640 | ||
641 | return 0; | |
642 | } | |
643 | ||
8b8f319f IM |
644 | /* |
645 | * Express the locking dependencies for lockdep: | |
646 | */ | |
647 | static inline void | |
648 | double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) | |
649 | { | |
650 | if (hb1 <= hb2) { | |
651 | spin_lock(&hb1->lock); | |
652 | if (hb1 < hb2) | |
653 | spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING); | |
654 | } else { /* hb1 > hb2 */ | |
655 | spin_lock(&hb2->lock); | |
656 | spin_lock_nested(&hb1->lock, SINGLE_DEPTH_NESTING); | |
657 | } | |
658 | } | |
659 | ||
5eb3dc62 DH |
660 | static inline void |
661 | double_unlock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) | |
662 | { | |
f061d351 | 663 | spin_unlock(&hb1->lock); |
88f502fe IM |
664 | if (hb1 != hb2) |
665 | spin_unlock(&hb2->lock); | |
5eb3dc62 DH |
666 | } |
667 | ||
1da177e4 | 668 | /* |
b2d0994b | 669 | * Wake up waiters matching bitset queued on this futex (uaddr). |
1da177e4 | 670 | */ |
c2f9f201 | 671 | static int futex_wake(u32 __user *uaddr, int fshared, int nr_wake, u32 bitset) |
1da177e4 | 672 | { |
e2970f2f | 673 | struct futex_hash_bucket *hb; |
1da177e4 | 674 | struct futex_q *this, *next; |
ec92d082 | 675 | struct plist_head *head; |
38d47c1b | 676 | union futex_key key = FUTEX_KEY_INIT; |
1da177e4 LT |
677 | int ret; |
678 | ||
cd689985 TG |
679 | if (!bitset) |
680 | return -EINVAL; | |
681 | ||
64d1304a | 682 | ret = get_futex_key(uaddr, fshared, &key, VERIFY_READ); |
1da177e4 LT |
683 | if (unlikely(ret != 0)) |
684 | goto out; | |
685 | ||
e2970f2f IM |
686 | hb = hash_futex(&key); |
687 | spin_lock(&hb->lock); | |
688 | head = &hb->chain; | |
1da177e4 | 689 | |
ec92d082 | 690 | plist_for_each_entry_safe(this, next, head, list) { |
1da177e4 | 691 | if (match_futex (&this->key, &key)) { |
ed6f7b10 IM |
692 | if (this->pi_state) { |
693 | ret = -EINVAL; | |
694 | break; | |
695 | } | |
cd689985 TG |
696 | |
697 | /* Check if one of the bits is set in both bitsets */ | |
698 | if (!(this->bitset & bitset)) | |
699 | continue; | |
700 | ||
1da177e4 LT |
701 | wake_futex(this); |
702 | if (++ret >= nr_wake) | |
703 | break; | |
704 | } | |
705 | } | |
706 | ||
e2970f2f | 707 | spin_unlock(&hb->lock); |
38d47c1b | 708 | put_futex_key(fshared, &key); |
42d35d48 | 709 | out: |
1da177e4 LT |
710 | return ret; |
711 | } | |
712 | ||
4732efbe JJ |
713 | /* |
714 | * Wake up all waiters hashed on the physical page that is mapped | |
715 | * to this virtual address: | |
716 | */ | |
e2970f2f | 717 | static int |
c2f9f201 | 718 | futex_wake_op(u32 __user *uaddr1, int fshared, u32 __user *uaddr2, |
e2970f2f | 719 | int nr_wake, int nr_wake2, int op) |
4732efbe | 720 | { |
38d47c1b | 721 | union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT; |
e2970f2f | 722 | struct futex_hash_bucket *hb1, *hb2; |
ec92d082 | 723 | struct plist_head *head; |
4732efbe | 724 | struct futex_q *this, *next; |
e4dc5b7a | 725 | int ret, op_ret; |
4732efbe | 726 | |
e4dc5b7a | 727 | retry: |
64d1304a | 728 | ret = get_futex_key(uaddr1, fshared, &key1, VERIFY_READ); |
4732efbe JJ |
729 | if (unlikely(ret != 0)) |
730 | goto out; | |
64d1304a | 731 | ret = get_futex_key(uaddr2, fshared, &key2, VERIFY_WRITE); |
4732efbe | 732 | if (unlikely(ret != 0)) |
42d35d48 | 733 | goto out_put_key1; |
4732efbe | 734 | |
e2970f2f IM |
735 | hb1 = hash_futex(&key1); |
736 | hb2 = hash_futex(&key2); | |
4732efbe | 737 | |
8b8f319f | 738 | double_lock_hb(hb1, hb2); |
e4dc5b7a | 739 | retry_private: |
e2970f2f | 740 | op_ret = futex_atomic_op_inuser(op, uaddr2); |
4732efbe | 741 | if (unlikely(op_ret < 0)) { |
e2970f2f | 742 | u32 dummy; |
4732efbe | 743 | |
5eb3dc62 | 744 | double_unlock_hb(hb1, hb2); |
4732efbe | 745 | |
7ee1dd3f | 746 | #ifndef CONFIG_MMU |
e2970f2f IM |
747 | /* |
748 | * we don't get EFAULT from MMU faults if we don't have an MMU, | |
749 | * but we might get them from range checking | |
750 | */ | |
7ee1dd3f | 751 | ret = op_ret; |
42d35d48 | 752 | goto out_put_keys; |
7ee1dd3f DH |
753 | #endif |
754 | ||
796f8d9b DG |
755 | if (unlikely(op_ret != -EFAULT)) { |
756 | ret = op_ret; | |
42d35d48 | 757 | goto out_put_keys; |
796f8d9b DG |
758 | } |
759 | ||
e2970f2f | 760 | ret = get_user(dummy, uaddr2); |
4732efbe | 761 | if (ret) |
de87fcc1 | 762 | goto out_put_keys; |
4732efbe | 763 | |
e4dc5b7a DH |
764 | if (!fshared) |
765 | goto retry_private; | |
766 | ||
de87fcc1 DH |
767 | put_futex_key(fshared, &key2); |
768 | put_futex_key(fshared, &key1); | |
e4dc5b7a | 769 | goto retry; |
4732efbe JJ |
770 | } |
771 | ||
e2970f2f | 772 | head = &hb1->chain; |
4732efbe | 773 | |
ec92d082 | 774 | plist_for_each_entry_safe(this, next, head, list) { |
4732efbe JJ |
775 | if (match_futex (&this->key, &key1)) { |
776 | wake_futex(this); | |
777 | if (++ret >= nr_wake) | |
778 | break; | |
779 | } | |
780 | } | |
781 | ||
782 | if (op_ret > 0) { | |
e2970f2f | 783 | head = &hb2->chain; |
4732efbe JJ |
784 | |
785 | op_ret = 0; | |
ec92d082 | 786 | plist_for_each_entry_safe(this, next, head, list) { |
4732efbe JJ |
787 | if (match_futex (&this->key, &key2)) { |
788 | wake_futex(this); | |
789 | if (++op_ret >= nr_wake2) | |
790 | break; | |
791 | } | |
792 | } | |
793 | ret += op_ret; | |
794 | } | |
795 | ||
5eb3dc62 | 796 | double_unlock_hb(hb1, hb2); |
42d35d48 | 797 | out_put_keys: |
38d47c1b | 798 | put_futex_key(fshared, &key2); |
42d35d48 | 799 | out_put_key1: |
38d47c1b | 800 | put_futex_key(fshared, &key1); |
42d35d48 | 801 | out: |
4732efbe JJ |
802 | return ret; |
803 | } | |
804 | ||
1da177e4 LT |
805 | /* |
806 | * Requeue all waiters hashed on one physical page to another | |
807 | * physical page. | |
808 | */ | |
c2f9f201 | 809 | static int futex_requeue(u32 __user *uaddr1, int fshared, u32 __user *uaddr2, |
e2970f2f | 810 | int nr_wake, int nr_requeue, u32 *cmpval) |
1da177e4 | 811 | { |
38d47c1b | 812 | union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT; |
e2970f2f | 813 | struct futex_hash_bucket *hb1, *hb2; |
ec92d082 | 814 | struct plist_head *head1; |
1da177e4 LT |
815 | struct futex_q *this, *next; |
816 | int ret, drop_count = 0; | |
817 | ||
42d35d48 | 818 | retry: |
64d1304a | 819 | ret = get_futex_key(uaddr1, fshared, &key1, VERIFY_READ); |
1da177e4 LT |
820 | if (unlikely(ret != 0)) |
821 | goto out; | |
64d1304a | 822 | ret = get_futex_key(uaddr2, fshared, &key2, VERIFY_READ); |
1da177e4 | 823 | if (unlikely(ret != 0)) |
42d35d48 | 824 | goto out_put_key1; |
1da177e4 | 825 | |
e2970f2f IM |
826 | hb1 = hash_futex(&key1); |
827 | hb2 = hash_futex(&key2); | |
1da177e4 | 828 | |
e4dc5b7a | 829 | retry_private: |
8b8f319f | 830 | double_lock_hb(hb1, hb2); |
1da177e4 | 831 | |
e2970f2f IM |
832 | if (likely(cmpval != NULL)) { |
833 | u32 curval; | |
1da177e4 | 834 | |
e2970f2f | 835 | ret = get_futex_value_locked(&curval, uaddr1); |
1da177e4 LT |
836 | |
837 | if (unlikely(ret)) { | |
5eb3dc62 | 838 | double_unlock_hb(hb1, hb2); |
1da177e4 | 839 | |
e2970f2f | 840 | ret = get_user(curval, uaddr1); |
e4dc5b7a DH |
841 | if (ret) |
842 | goto out_put_keys; | |
1da177e4 | 843 | |
e4dc5b7a DH |
844 | if (!fshared) |
845 | goto retry_private; | |
1da177e4 | 846 | |
e4dc5b7a DH |
847 | put_futex_key(fshared, &key2); |
848 | put_futex_key(fshared, &key1); | |
849 | goto retry; | |
1da177e4 | 850 | } |
e2970f2f | 851 | if (curval != *cmpval) { |
1da177e4 LT |
852 | ret = -EAGAIN; |
853 | goto out_unlock; | |
854 | } | |
855 | } | |
856 | ||
e2970f2f | 857 | head1 = &hb1->chain; |
ec92d082 | 858 | plist_for_each_entry_safe(this, next, head1, list) { |
1da177e4 LT |
859 | if (!match_futex (&this->key, &key1)) |
860 | continue; | |
861 | if (++ret <= nr_wake) { | |
862 | wake_futex(this); | |
863 | } else { | |
59e0e0ac SD |
864 | /* |
865 | * If key1 and key2 hash to the same bucket, no need to | |
866 | * requeue. | |
867 | */ | |
868 | if (likely(head1 != &hb2->chain)) { | |
ec92d082 PP |
869 | plist_del(&this->list, &hb1->chain); |
870 | plist_add(&this->list, &hb2->chain); | |
59e0e0ac | 871 | this->lock_ptr = &hb2->lock; |
ec92d082 PP |
872 | #ifdef CONFIG_DEBUG_PI_LIST |
873 | this->list.plist.lock = &hb2->lock; | |
874 | #endif | |
778e9a9c | 875 | } |
1da177e4 | 876 | this->key = key2; |
9adef58b | 877 | get_futex_key_refs(&key2); |
1da177e4 LT |
878 | drop_count++; |
879 | ||
880 | if (ret - nr_wake >= nr_requeue) | |
881 | break; | |
1da177e4 LT |
882 | } |
883 | } | |
884 | ||
885 | out_unlock: | |
5eb3dc62 | 886 | double_unlock_hb(hb1, hb2); |
1da177e4 | 887 | |
cd84a42f DH |
888 | /* |
889 | * drop_futex_key_refs() must be called outside the spinlocks. During | |
890 | * the requeue we moved futex_q's from the hash bucket at key1 to the | |
891 | * one at key2 and updated their key pointer. We no longer need to | |
892 | * hold the references to key1. | |
893 | */ | |
1da177e4 | 894 | while (--drop_count >= 0) |
9adef58b | 895 | drop_futex_key_refs(&key1); |
1da177e4 | 896 | |
42d35d48 | 897 | out_put_keys: |
38d47c1b | 898 | put_futex_key(fshared, &key2); |
42d35d48 | 899 | out_put_key1: |
38d47c1b | 900 | put_futex_key(fshared, &key1); |
42d35d48 | 901 | out: |
1da177e4 LT |
902 | return ret; |
903 | } | |
904 | ||
905 | /* The key must be already stored in q->key. */ | |
82af7aca | 906 | static inline struct futex_hash_bucket *queue_lock(struct futex_q *q) |
1da177e4 | 907 | { |
e2970f2f | 908 | struct futex_hash_bucket *hb; |
1da177e4 | 909 | |
73500ac5 | 910 | init_waitqueue_head(&q->waiter); |
1da177e4 | 911 | |
9adef58b | 912 | get_futex_key_refs(&q->key); |
e2970f2f IM |
913 | hb = hash_futex(&q->key); |
914 | q->lock_ptr = &hb->lock; | |
1da177e4 | 915 | |
e2970f2f IM |
916 | spin_lock(&hb->lock); |
917 | return hb; | |
1da177e4 LT |
918 | } |
919 | ||
82af7aca | 920 | static inline void queue_me(struct futex_q *q, struct futex_hash_bucket *hb) |
1da177e4 | 921 | { |
ec92d082 PP |
922 | int prio; |
923 | ||
924 | /* | |
925 | * The priority used to register this element is | |
926 | * - either the real thread-priority for the real-time threads | |
927 | * (i.e. threads with a priority lower than MAX_RT_PRIO) | |
928 | * - or MAX_RT_PRIO for non-RT threads. | |
929 | * Thus, all RT-threads are woken first in priority order, and | |
930 | * the others are woken last, in FIFO order. | |
931 | */ | |
932 | prio = min(current->normal_prio, MAX_RT_PRIO); | |
933 | ||
934 | plist_node_init(&q->list, prio); | |
935 | #ifdef CONFIG_DEBUG_PI_LIST | |
936 | q->list.plist.lock = &hb->lock; | |
937 | #endif | |
938 | plist_add(&q->list, &hb->chain); | |
c87e2837 | 939 | q->task = current; |
e2970f2f | 940 | spin_unlock(&hb->lock); |
1da177e4 LT |
941 | } |
942 | ||
943 | static inline void | |
e2970f2f | 944 | queue_unlock(struct futex_q *q, struct futex_hash_bucket *hb) |
1da177e4 | 945 | { |
e2970f2f | 946 | spin_unlock(&hb->lock); |
9adef58b | 947 | drop_futex_key_refs(&q->key); |
1da177e4 LT |
948 | } |
949 | ||
950 | /* | |
951 | * queue_me and unqueue_me must be called as a pair, each | |
952 | * exactly once. They are called with the hashed spinlock held. | |
953 | */ | |
954 | ||
1da177e4 LT |
955 | /* Return 1 if we were still queued (ie. 0 means we were woken) */ |
956 | static int unqueue_me(struct futex_q *q) | |
957 | { | |
1da177e4 | 958 | spinlock_t *lock_ptr; |
e2970f2f | 959 | int ret = 0; |
1da177e4 LT |
960 | |
961 | /* In the common case we don't take the spinlock, which is nice. */ | |
42d35d48 | 962 | retry: |
1da177e4 | 963 | lock_ptr = q->lock_ptr; |
e91467ec | 964 | barrier(); |
c80544dc | 965 | if (lock_ptr != NULL) { |
1da177e4 LT |
966 | spin_lock(lock_ptr); |
967 | /* | |
968 | * q->lock_ptr can change between reading it and | |
969 | * spin_lock(), causing us to take the wrong lock. This | |
970 | * corrects the race condition. | |
971 | * | |
972 | * Reasoning goes like this: if we have the wrong lock, | |
973 | * q->lock_ptr must have changed (maybe several times) | |
974 | * between reading it and the spin_lock(). It can | |
975 | * change again after the spin_lock() but only if it was | |
976 | * already changed before the spin_lock(). It cannot, | |
977 | * however, change back to the original value. Therefore | |
978 | * we can detect whether we acquired the correct lock. | |
979 | */ | |
980 | if (unlikely(lock_ptr != q->lock_ptr)) { | |
981 | spin_unlock(lock_ptr); | |
982 | goto retry; | |
983 | } | |
ec92d082 PP |
984 | WARN_ON(plist_node_empty(&q->list)); |
985 | plist_del(&q->list, &q->list.plist); | |
c87e2837 IM |
986 | |
987 | BUG_ON(q->pi_state); | |
988 | ||
1da177e4 LT |
989 | spin_unlock(lock_ptr); |
990 | ret = 1; | |
991 | } | |
992 | ||
9adef58b | 993 | drop_futex_key_refs(&q->key); |
1da177e4 LT |
994 | return ret; |
995 | } | |
996 | ||
c87e2837 IM |
997 | /* |
998 | * PI futexes can not be requeued and must remove themself from the | |
d0aa7a70 PP |
999 | * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry |
1000 | * and dropped here. | |
c87e2837 | 1001 | */ |
d0aa7a70 | 1002 | static void unqueue_me_pi(struct futex_q *q) |
c87e2837 | 1003 | { |
ec92d082 PP |
1004 | WARN_ON(plist_node_empty(&q->list)); |
1005 | plist_del(&q->list, &q->list.plist); | |
c87e2837 IM |
1006 | |
1007 | BUG_ON(!q->pi_state); | |
1008 | free_pi_state(q->pi_state); | |
1009 | q->pi_state = NULL; | |
1010 | ||
d0aa7a70 | 1011 | spin_unlock(q->lock_ptr); |
c87e2837 | 1012 | |
9adef58b | 1013 | drop_futex_key_refs(&q->key); |
c87e2837 IM |
1014 | } |
1015 | ||
d0aa7a70 | 1016 | /* |
cdf71a10 | 1017 | * Fixup the pi_state owner with the new owner. |
d0aa7a70 | 1018 | * |
778e9a9c AK |
1019 | * Must be called with hash bucket lock held and mm->sem held for non |
1020 | * private futexes. | |
d0aa7a70 | 1021 | */ |
778e9a9c | 1022 | static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q, |
c2f9f201 | 1023 | struct task_struct *newowner, int fshared) |
d0aa7a70 | 1024 | { |
cdf71a10 | 1025 | u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS; |
d0aa7a70 | 1026 | struct futex_pi_state *pi_state = q->pi_state; |
1b7558e4 | 1027 | struct task_struct *oldowner = pi_state->owner; |
d0aa7a70 | 1028 | u32 uval, curval, newval; |
e4dc5b7a | 1029 | int ret; |
d0aa7a70 PP |
1030 | |
1031 | /* Owner died? */ | |
1b7558e4 TG |
1032 | if (!pi_state->owner) |
1033 | newtid |= FUTEX_OWNER_DIED; | |
1034 | ||
1035 | /* | |
1036 | * We are here either because we stole the rtmutex from the | |
1037 | * pending owner or we are the pending owner which failed to | |
1038 | * get the rtmutex. We have to replace the pending owner TID | |
1039 | * in the user space variable. This must be atomic as we have | |
1040 | * to preserve the owner died bit here. | |
1041 | * | |
b2d0994b DH |
1042 | * Note: We write the user space value _before_ changing the pi_state |
1043 | * because we can fault here. Imagine swapped out pages or a fork | |
1044 | * that marked all the anonymous memory readonly for cow. | |
1b7558e4 TG |
1045 | * |
1046 | * Modifying pi_state _before_ the user space value would | |
1047 | * leave the pi_state in an inconsistent state when we fault | |
1048 | * here, because we need to drop the hash bucket lock to | |
1049 | * handle the fault. This might be observed in the PID check | |
1050 | * in lookup_pi_state. | |
1051 | */ | |
1052 | retry: | |
1053 | if (get_futex_value_locked(&uval, uaddr)) | |
1054 | goto handle_fault; | |
1055 | ||
1056 | while (1) { | |
1057 | newval = (uval & FUTEX_OWNER_DIED) | newtid; | |
1058 | ||
1059 | curval = cmpxchg_futex_value_locked(uaddr, uval, newval); | |
1060 | ||
1061 | if (curval == -EFAULT) | |
1062 | goto handle_fault; | |
1063 | if (curval == uval) | |
1064 | break; | |
1065 | uval = curval; | |
1066 | } | |
1067 | ||
1068 | /* | |
1069 | * We fixed up user space. Now we need to fix the pi_state | |
1070 | * itself. | |
1071 | */ | |
d0aa7a70 PP |
1072 | if (pi_state->owner != NULL) { |
1073 | spin_lock_irq(&pi_state->owner->pi_lock); | |
1074 | WARN_ON(list_empty(&pi_state->list)); | |
1075 | list_del_init(&pi_state->list); | |
1076 | spin_unlock_irq(&pi_state->owner->pi_lock); | |
1b7558e4 | 1077 | } |
d0aa7a70 | 1078 | |
cdf71a10 | 1079 | pi_state->owner = newowner; |
d0aa7a70 | 1080 | |
cdf71a10 | 1081 | spin_lock_irq(&newowner->pi_lock); |
d0aa7a70 | 1082 | WARN_ON(!list_empty(&pi_state->list)); |
cdf71a10 TG |
1083 | list_add(&pi_state->list, &newowner->pi_state_list); |
1084 | spin_unlock_irq(&newowner->pi_lock); | |
1b7558e4 | 1085 | return 0; |
d0aa7a70 | 1086 | |
d0aa7a70 | 1087 | /* |
1b7558e4 TG |
1088 | * To handle the page fault we need to drop the hash bucket |
1089 | * lock here. That gives the other task (either the pending | |
1090 | * owner itself or the task which stole the rtmutex) the | |
1091 | * chance to try the fixup of the pi_state. So once we are | |
1092 | * back from handling the fault we need to check the pi_state | |
1093 | * after reacquiring the hash bucket lock and before trying to | |
1094 | * do another fixup. When the fixup has been done already we | |
1095 | * simply return. | |
d0aa7a70 | 1096 | */ |
1b7558e4 TG |
1097 | handle_fault: |
1098 | spin_unlock(q->lock_ptr); | |
778e9a9c | 1099 | |
e4dc5b7a | 1100 | ret = get_user(uval, uaddr); |
778e9a9c | 1101 | |
1b7558e4 | 1102 | spin_lock(q->lock_ptr); |
778e9a9c | 1103 | |
1b7558e4 TG |
1104 | /* |
1105 | * Check if someone else fixed it for us: | |
1106 | */ | |
1107 | if (pi_state->owner != oldowner) | |
1108 | return 0; | |
1109 | ||
1110 | if (ret) | |
1111 | return ret; | |
1112 | ||
1113 | goto retry; | |
d0aa7a70 PP |
1114 | } |
1115 | ||
34f01cc1 ED |
1116 | /* |
1117 | * In case we must use restart_block to restart a futex_wait, | |
ce6bd420 | 1118 | * we encode in the 'flags' shared capability |
34f01cc1 | 1119 | */ |
1acdac10 TG |
1120 | #define FLAGS_SHARED 0x01 |
1121 | #define FLAGS_CLOCKRT 0x02 | |
34f01cc1 | 1122 | |
72c1bbf3 | 1123 | static long futex_wait_restart(struct restart_block *restart); |
36cf3b5c | 1124 | |
c2f9f201 | 1125 | static int futex_wait(u32 __user *uaddr, int fshared, |
1acdac10 | 1126 | u32 val, ktime_t *abs_time, u32 bitset, int clockrt) |
1da177e4 | 1127 | { |
c87e2837 | 1128 | struct task_struct *curr = current; |
2fff78c7 | 1129 | struct restart_block *restart; |
c87e2837 | 1130 | DECLARE_WAITQUEUE(wait, curr); |
e2970f2f | 1131 | struct futex_hash_bucket *hb; |
1da177e4 | 1132 | struct futex_q q; |
e2970f2f IM |
1133 | u32 uval; |
1134 | int ret; | |
bd197234 | 1135 | struct hrtimer_sleeper t; |
c19384b5 | 1136 | int rem = 0; |
1da177e4 | 1137 | |
cd689985 TG |
1138 | if (!bitset) |
1139 | return -EINVAL; | |
1140 | ||
c87e2837 | 1141 | q.pi_state = NULL; |
cd689985 | 1142 | q.bitset = bitset; |
42d35d48 | 1143 | retry: |
38d47c1b | 1144 | q.key = FUTEX_KEY_INIT; |
64d1304a | 1145 | ret = get_futex_key(uaddr, fshared, &q.key, VERIFY_READ); |
1da177e4 | 1146 | if (unlikely(ret != 0)) |
42d35d48 | 1147 | goto out; |
1da177e4 | 1148 | |
e4dc5b7a | 1149 | retry_private: |
82af7aca | 1150 | hb = queue_lock(&q); |
1da177e4 LT |
1151 | |
1152 | /* | |
b2d0994b | 1153 | * Access the page AFTER the hash-bucket is locked. |
1da177e4 LT |
1154 | * Order is important: |
1155 | * | |
1156 | * Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val); | |
1157 | * Userspace waker: if (cond(var)) { var = new; futex_wake(&var); } | |
1158 | * | |
1159 | * The basic logical guarantee of a futex is that it blocks ONLY | |
1160 | * if cond(var) is known to be true at the time of blocking, for | |
1161 | * any cond. If we queued after testing *uaddr, that would open | |
1162 | * a race condition where we could block indefinitely with | |
1163 | * cond(var) false, which would violate the guarantee. | |
1164 | * | |
1165 | * A consequence is that futex_wait() can return zero and absorb | |
1166 | * a wakeup when *uaddr != val on entry to the syscall. This is | |
1167 | * rare, but normal. | |
1168 | * | |
b2d0994b | 1169 | * For shared futexes, we hold the mmap semaphore, so the mapping |
34f01cc1 | 1170 | * cannot have changed since we looked it up in get_futex_key. |
1da177e4 | 1171 | */ |
e2970f2f | 1172 | ret = get_futex_value_locked(&uval, uaddr); |
1da177e4 LT |
1173 | |
1174 | if (unlikely(ret)) { | |
e2970f2f | 1175 | queue_unlock(&q, hb); |
1da177e4 | 1176 | |
e2970f2f | 1177 | ret = get_user(uval, uaddr); |
e4dc5b7a DH |
1178 | if (ret) |
1179 | goto out_put_key; | |
1da177e4 | 1180 | |
e4dc5b7a DH |
1181 | if (!fshared) |
1182 | goto retry_private; | |
1183 | ||
1184 | put_futex_key(fshared, &q.key); | |
1185 | goto retry; | |
1da177e4 | 1186 | } |
c87e2837 | 1187 | ret = -EWOULDBLOCK; |
2fff78c7 PZ |
1188 | if (unlikely(uval != val)) { |
1189 | queue_unlock(&q, hb); | |
1190 | goto out_put_key; | |
1191 | } | |
1da177e4 LT |
1192 | |
1193 | /* Only actually queue if *uaddr contained val. */ | |
82af7aca | 1194 | queue_me(&q, hb); |
1da177e4 | 1195 | |
1da177e4 LT |
1196 | /* |
1197 | * There might have been scheduling since the queue_me(), as we | |
1198 | * cannot hold a spinlock across the get_user() in case it | |
1199 | * faults, and we cannot just set TASK_INTERRUPTIBLE state when | |
1200 | * queueing ourselves into the futex hash. This code thus has to | |
1201 | * rely on the futex_wake() code removing us from hash when it | |
1202 | * wakes us up. | |
1203 | */ | |
1204 | ||
1205 | /* add_wait_queue is the barrier after __set_current_state. */ | |
1206 | __set_current_state(TASK_INTERRUPTIBLE); | |
73500ac5 | 1207 | add_wait_queue(&q.waiter, &wait); |
1da177e4 | 1208 | /* |
ec92d082 | 1209 | * !plist_node_empty() is safe here without any lock. |
1da177e4 LT |
1210 | * q.lock_ptr != 0 is not safe, because of ordering against wakeup. |
1211 | */ | |
ec92d082 | 1212 | if (likely(!plist_node_empty(&q.list))) { |
c19384b5 PP |
1213 | if (!abs_time) |
1214 | schedule(); | |
1215 | else { | |
1acdac10 TG |
1216 | hrtimer_init_on_stack(&t.timer, |
1217 | clockrt ? CLOCK_REALTIME : | |
1218 | CLOCK_MONOTONIC, | |
1219 | HRTIMER_MODE_ABS); | |
c19384b5 | 1220 | hrtimer_init_sleeper(&t, current); |
16f4993f DH |
1221 | hrtimer_set_expires_range_ns(&t.timer, *abs_time, |
1222 | current->timer_slack_ns); | |
c19384b5 | 1223 | |
cc584b21 | 1224 | hrtimer_start_expires(&t.timer, HRTIMER_MODE_ABS); |
3588a085 PZ |
1225 | if (!hrtimer_active(&t.timer)) |
1226 | t.task = NULL; | |
c19384b5 PP |
1227 | |
1228 | /* | |
1229 | * the timer could have already expired, in which | |
1230 | * case current would be flagged for rescheduling. | |
1231 | * Don't bother calling schedule. | |
1232 | */ | |
1233 | if (likely(t.task)) | |
1234 | schedule(); | |
1235 | ||
1236 | hrtimer_cancel(&t.timer); | |
72c1bbf3 | 1237 | |
c19384b5 PP |
1238 | /* Flag if a timeout occured */ |
1239 | rem = (t.task == NULL); | |
237fc6e7 TG |
1240 | |
1241 | destroy_hrtimer_on_stack(&t.timer); | |
c19384b5 | 1242 | } |
72c1bbf3 | 1243 | } |
1da177e4 LT |
1244 | __set_current_state(TASK_RUNNING); |
1245 | ||
1246 | /* | |
1247 | * NOTE: we don't remove ourselves from the waitqueue because | |
1248 | * we are the only user of it. | |
1249 | */ | |
1250 | ||
1251 | /* If we were woken (and unqueued), we succeeded, whatever. */ | |
2fff78c7 | 1252 | ret = 0; |
1da177e4 | 1253 | if (!unqueue_me(&q)) |
2fff78c7 PZ |
1254 | goto out_put_key; |
1255 | ret = -ETIMEDOUT; | |
c19384b5 | 1256 | if (rem) |
2fff78c7 | 1257 | goto out_put_key; |
72c1bbf3 | 1258 | |
e2970f2f IM |
1259 | /* |
1260 | * We expect signal_pending(current), but another thread may | |
1261 | * have handled it for us already. | |
1262 | */ | |
2fff78c7 | 1263 | ret = -ERESTARTSYS; |
c19384b5 | 1264 | if (!abs_time) |
2fff78c7 | 1265 | goto out_put_key; |
1da177e4 | 1266 | |
2fff78c7 PZ |
1267 | restart = ¤t_thread_info()->restart_block; |
1268 | restart->fn = futex_wait_restart; | |
1269 | restart->futex.uaddr = (u32 *)uaddr; | |
1270 | restart->futex.val = val; | |
1271 | restart->futex.time = abs_time->tv64; | |
1272 | restart->futex.bitset = bitset; | |
1273 | restart->futex.flags = 0; | |
1274 | ||
1275 | if (fshared) | |
1276 | restart->futex.flags |= FLAGS_SHARED; | |
1277 | if (clockrt) | |
1278 | restart->futex.flags |= FLAGS_CLOCKRT; | |
42d35d48 | 1279 | |
2fff78c7 PZ |
1280 | ret = -ERESTART_RESTARTBLOCK; |
1281 | ||
1282 | out_put_key: | |
1283 | put_futex_key(fshared, &q.key); | |
42d35d48 | 1284 | out: |
c87e2837 IM |
1285 | return ret; |
1286 | } | |
1287 | ||
72c1bbf3 NP |
1288 | |
1289 | static long futex_wait_restart(struct restart_block *restart) | |
1290 | { | |
ce6bd420 | 1291 | u32 __user *uaddr = (u32 __user *)restart->futex.uaddr; |
c2f9f201 | 1292 | int fshared = 0; |
ce6bd420 | 1293 | ktime_t t; |
72c1bbf3 | 1294 | |
ce6bd420 | 1295 | t.tv64 = restart->futex.time; |
72c1bbf3 | 1296 | restart->fn = do_no_restart_syscall; |
ce6bd420 | 1297 | if (restart->futex.flags & FLAGS_SHARED) |
c2f9f201 | 1298 | fshared = 1; |
cd689985 | 1299 | return (long)futex_wait(uaddr, fshared, restart->futex.val, &t, |
1acdac10 TG |
1300 | restart->futex.bitset, |
1301 | restart->futex.flags & FLAGS_CLOCKRT); | |
72c1bbf3 NP |
1302 | } |
1303 | ||
1304 | ||
c87e2837 IM |
1305 | /* |
1306 | * Userspace tried a 0 -> TID atomic transition of the futex value | |
1307 | * and failed. The kernel side here does the whole locking operation: | |
1308 | * if there are waiters then it will block, it does PI, etc. (Due to | |
1309 | * races the kernel might see a 0 value of the futex too.) | |
1310 | */ | |
c2f9f201 | 1311 | static int futex_lock_pi(u32 __user *uaddr, int fshared, |
34f01cc1 | 1312 | int detect, ktime_t *time, int trylock) |
c87e2837 | 1313 | { |
c5780e97 | 1314 | struct hrtimer_sleeper timeout, *to = NULL; |
c87e2837 IM |
1315 | struct task_struct *curr = current; |
1316 | struct futex_hash_bucket *hb; | |
1317 | u32 uval, newval, curval; | |
1318 | struct futex_q q; | |
e4dc5b7a | 1319 | int ret, lock_taken, ownerdied = 0; |
c87e2837 IM |
1320 | |
1321 | if (refill_pi_state_cache()) | |
1322 | return -ENOMEM; | |
1323 | ||
c19384b5 | 1324 | if (time) { |
c5780e97 | 1325 | to = &timeout; |
237fc6e7 TG |
1326 | hrtimer_init_on_stack(&to->timer, CLOCK_REALTIME, |
1327 | HRTIMER_MODE_ABS); | |
c5780e97 | 1328 | hrtimer_init_sleeper(to, current); |
cc584b21 | 1329 | hrtimer_set_expires(&to->timer, *time); |
c5780e97 TG |
1330 | } |
1331 | ||
c87e2837 | 1332 | q.pi_state = NULL; |
42d35d48 | 1333 | retry: |
38d47c1b | 1334 | q.key = FUTEX_KEY_INIT; |
64d1304a | 1335 | ret = get_futex_key(uaddr, fshared, &q.key, VERIFY_WRITE); |
c87e2837 | 1336 | if (unlikely(ret != 0)) |
42d35d48 | 1337 | goto out; |
c87e2837 | 1338 | |
e4dc5b7a | 1339 | retry_private: |
82af7aca | 1340 | hb = queue_lock(&q); |
c87e2837 | 1341 | |
42d35d48 | 1342 | retry_locked: |
778e9a9c | 1343 | ret = lock_taken = 0; |
d0aa7a70 | 1344 | |
c87e2837 IM |
1345 | /* |
1346 | * To avoid races, we attempt to take the lock here again | |
1347 | * (by doing a 0 -> TID atomic cmpxchg), while holding all | |
1348 | * the locks. It will most likely not succeed. | |
1349 | */ | |
b488893a | 1350 | newval = task_pid_vnr(current); |
c87e2837 | 1351 | |
36cf3b5c | 1352 | curval = cmpxchg_futex_value_locked(uaddr, 0, newval); |
c87e2837 IM |
1353 | |
1354 | if (unlikely(curval == -EFAULT)) | |
1355 | goto uaddr_faulted; | |
1356 | ||
778e9a9c AK |
1357 | /* |
1358 | * Detect deadlocks. In case of REQUEUE_PI this is a valid | |
1359 | * situation and we return success to user space. | |
1360 | */ | |
b488893a | 1361 | if (unlikely((curval & FUTEX_TID_MASK) == task_pid_vnr(current))) { |
bd197234 | 1362 | ret = -EDEADLK; |
42d35d48 | 1363 | goto out_unlock_put_key; |
c87e2837 IM |
1364 | } |
1365 | ||
1366 | /* | |
778e9a9c | 1367 | * Surprise - we got the lock. Just return to userspace: |
c87e2837 IM |
1368 | */ |
1369 | if (unlikely(!curval)) | |
42d35d48 | 1370 | goto out_unlock_put_key; |
c87e2837 IM |
1371 | |
1372 | uval = curval; | |
778e9a9c | 1373 | |
d0aa7a70 | 1374 | /* |
778e9a9c AK |
1375 | * Set the WAITERS flag, so the owner will know it has someone |
1376 | * to wake at next unlock | |
d0aa7a70 | 1377 | */ |
778e9a9c AK |
1378 | newval = curval | FUTEX_WAITERS; |
1379 | ||
1380 | /* | |
1381 | * There are two cases, where a futex might have no owner (the | |
bd197234 TG |
1382 | * owner TID is 0): OWNER_DIED. We take over the futex in this |
1383 | * case. We also do an unconditional take over, when the owner | |
1384 | * of the futex died. | |
778e9a9c AK |
1385 | * |
1386 | * This is safe as we are protected by the hash bucket lock ! | |
1387 | */ | |
1388 | if (unlikely(ownerdied || !(curval & FUTEX_TID_MASK))) { | |
bd197234 | 1389 | /* Keep the OWNER_DIED bit */ |
b488893a | 1390 | newval = (curval & ~FUTEX_TID_MASK) | task_pid_vnr(current); |
778e9a9c AK |
1391 | ownerdied = 0; |
1392 | lock_taken = 1; | |
1393 | } | |
c87e2837 | 1394 | |
36cf3b5c | 1395 | curval = cmpxchg_futex_value_locked(uaddr, uval, newval); |
c87e2837 IM |
1396 | |
1397 | if (unlikely(curval == -EFAULT)) | |
1398 | goto uaddr_faulted; | |
1399 | if (unlikely(curval != uval)) | |
1400 | goto retry_locked; | |
1401 | ||
778e9a9c | 1402 | /* |
bd197234 | 1403 | * We took the lock due to owner died take over. |
778e9a9c | 1404 | */ |
bd197234 | 1405 | if (unlikely(lock_taken)) |
42d35d48 | 1406 | goto out_unlock_put_key; |
d0aa7a70 | 1407 | |
c87e2837 IM |
1408 | /* |
1409 | * We dont have the lock. Look up the PI state (or create it if | |
1410 | * we are the first waiter): | |
1411 | */ | |
d0aa7a70 | 1412 | ret = lookup_pi_state(uval, hb, &q.key, &q.pi_state); |
c87e2837 IM |
1413 | |
1414 | if (unlikely(ret)) { | |
778e9a9c | 1415 | switch (ret) { |
c87e2837 | 1416 | |
778e9a9c AK |
1417 | case -EAGAIN: |
1418 | /* | |
1419 | * Task is exiting and we just wait for the | |
1420 | * exit to complete. | |
1421 | */ | |
1422 | queue_unlock(&q, hb); | |
de87fcc1 | 1423 | put_futex_key(fshared, &q.key); |
778e9a9c AK |
1424 | cond_resched(); |
1425 | goto retry; | |
c87e2837 | 1426 | |
778e9a9c AK |
1427 | case -ESRCH: |
1428 | /* | |
1429 | * No owner found for this futex. Check if the | |
1430 | * OWNER_DIED bit is set to figure out whether | |
1431 | * this is a robust futex or not. | |
1432 | */ | |
1433 | if (get_futex_value_locked(&curval, uaddr)) | |
c87e2837 | 1434 | goto uaddr_faulted; |
778e9a9c AK |
1435 | |
1436 | /* | |
1437 | * We simply start over in case of a robust | |
1438 | * futex. The code above will take the futex | |
1439 | * and return happy. | |
1440 | */ | |
1441 | if (curval & FUTEX_OWNER_DIED) { | |
1442 | ownerdied = 1; | |
c87e2837 | 1443 | goto retry_locked; |
778e9a9c AK |
1444 | } |
1445 | default: | |
42d35d48 | 1446 | goto out_unlock_put_key; |
c87e2837 | 1447 | } |
c87e2837 IM |
1448 | } |
1449 | ||
1450 | /* | |
1451 | * Only actually queue now that the atomic ops are done: | |
1452 | */ | |
82af7aca | 1453 | queue_me(&q, hb); |
c87e2837 | 1454 | |
c87e2837 IM |
1455 | WARN_ON(!q.pi_state); |
1456 | /* | |
1457 | * Block on the PI mutex: | |
1458 | */ | |
1459 | if (!trylock) | |
1460 | ret = rt_mutex_timed_lock(&q.pi_state->pi_mutex, to, 1); | |
1461 | else { | |
1462 | ret = rt_mutex_trylock(&q.pi_state->pi_mutex); | |
1463 | /* Fixup the trylock return value: */ | |
1464 | ret = ret ? 0 : -EWOULDBLOCK; | |
1465 | } | |
1466 | ||
a99e4e41 | 1467 | spin_lock(q.lock_ptr); |
c87e2837 | 1468 | |
778e9a9c AK |
1469 | if (!ret) { |
1470 | /* | |
1471 | * Got the lock. We might not be the anticipated owner | |
1472 | * if we did a lock-steal - fix up the PI-state in | |
1473 | * that case: | |
1474 | */ | |
1475 | if (q.pi_state->owner != curr) | |
1b7558e4 | 1476 | ret = fixup_pi_state_owner(uaddr, &q, curr, fshared); |
778e9a9c | 1477 | } else { |
c87e2837 IM |
1478 | /* |
1479 | * Catch the rare case, where the lock was released | |
778e9a9c AK |
1480 | * when we were on the way back before we locked the |
1481 | * hash bucket. | |
c87e2837 | 1482 | */ |
cdf71a10 TG |
1483 | if (q.pi_state->owner == curr) { |
1484 | /* | |
1485 | * Try to get the rt_mutex now. This might | |
1486 | * fail as some other task acquired the | |
1487 | * rt_mutex after we removed ourself from the | |
1488 | * rt_mutex waiters list. | |
1489 | */ | |
1490 | if (rt_mutex_trylock(&q.pi_state->pi_mutex)) | |
1491 | ret = 0; | |
1492 | else { | |
1493 | /* | |
1494 | * pi_state is incorrect, some other | |
1495 | * task did a lock steal and we | |
1496 | * returned due to timeout or signal | |
1497 | * without taking the rt_mutex. Too | |
1498 | * late. We can access the | |
1499 | * rt_mutex_owner without locking, as | |
1500 | * the other task is now blocked on | |
1501 | * the hash bucket lock. Fix the state | |
1502 | * up. | |
1503 | */ | |
1504 | struct task_struct *owner; | |
1505 | int res; | |
1506 | ||
1507 | owner = rt_mutex_owner(&q.pi_state->pi_mutex); | |
1b7558e4 TG |
1508 | res = fixup_pi_state_owner(uaddr, &q, owner, |
1509 | fshared); | |
cdf71a10 | 1510 | |
cdf71a10 TG |
1511 | /* propagate -EFAULT, if the fixup failed */ |
1512 | if (res) | |
1513 | ret = res; | |
1514 | } | |
778e9a9c AK |
1515 | } else { |
1516 | /* | |
1517 | * Paranoia check. If we did not take the lock | |
1518 | * in the trylock above, then we should not be | |
1519 | * the owner of the rtmutex, neither the real | |
1520 | * nor the pending one: | |
1521 | */ | |
1522 | if (rt_mutex_owner(&q.pi_state->pi_mutex) == curr) | |
1523 | printk(KERN_ERR "futex_lock_pi: ret = %d " | |
1524 | "pi-mutex: %p pi-state %p\n", ret, | |
1525 | q.pi_state->pi_mutex.owner, | |
1526 | q.pi_state->owner); | |
c87e2837 | 1527 | } |
c87e2837 IM |
1528 | } |
1529 | ||
e8f6386c DH |
1530 | /* |
1531 | * If fixup_pi_state_owner() faulted and was unable to handle the | |
1532 | * fault, unlock it and return the fault to userspace. | |
1533 | */ | |
1534 | if (ret && (rt_mutex_owner(&q.pi_state->pi_mutex) == current)) | |
1535 | rt_mutex_unlock(&q.pi_state->pi_mutex); | |
1536 | ||
778e9a9c AK |
1537 | /* Unqueue and drop the lock */ |
1538 | unqueue_me_pi(&q); | |
c87e2837 | 1539 | |
237fc6e7 TG |
1540 | if (to) |
1541 | destroy_hrtimer_on_stack(&to->timer); | |
c5780e97 | 1542 | return ret != -EINTR ? ret : -ERESTARTNOINTR; |
c87e2837 | 1543 | |
42d35d48 | 1544 | out_unlock_put_key: |
c87e2837 IM |
1545 | queue_unlock(&q, hb); |
1546 | ||
42d35d48 | 1547 | out_put_key: |
38d47c1b | 1548 | put_futex_key(fshared, &q.key); |
42d35d48 | 1549 | out: |
237fc6e7 TG |
1550 | if (to) |
1551 | destroy_hrtimer_on_stack(&to->timer); | |
c87e2837 IM |
1552 | return ret; |
1553 | ||
42d35d48 | 1554 | uaddr_faulted: |
c87e2837 | 1555 | /* |
b5686363 DH |
1556 | * We have to r/w *(int __user *)uaddr, and we have to modify it |
1557 | * atomically. Therefore, if we continue to fault after get_user() | |
1558 | * below, we need to handle the fault ourselves, while still holding | |
1559 | * the mmap_sem. This can occur if the uaddr is under contention as | |
1560 | * we have to drop the mmap_sem in order to call get_user(). | |
c87e2837 | 1561 | */ |
778e9a9c AK |
1562 | queue_unlock(&q, hb); |
1563 | ||
c87e2837 | 1564 | ret = get_user(uval, uaddr); |
e4dc5b7a DH |
1565 | if (ret) |
1566 | goto out_put_key; | |
c87e2837 | 1567 | |
e4dc5b7a DH |
1568 | if (!fshared) |
1569 | goto retry_private; | |
1570 | ||
1571 | put_futex_key(fshared, &q.key); | |
1572 | goto retry; | |
c87e2837 IM |
1573 | } |
1574 | ||
de87fcc1 | 1575 | |
c87e2837 IM |
1576 | /* |
1577 | * Userspace attempted a TID -> 0 atomic transition, and failed. | |
1578 | * This is the in-kernel slowpath: we look up the PI state (if any), | |
1579 | * and do the rt-mutex unlock. | |
1580 | */ | |
c2f9f201 | 1581 | static int futex_unlock_pi(u32 __user *uaddr, int fshared) |
c87e2837 IM |
1582 | { |
1583 | struct futex_hash_bucket *hb; | |
1584 | struct futex_q *this, *next; | |
1585 | u32 uval; | |
ec92d082 | 1586 | struct plist_head *head; |
38d47c1b | 1587 | union futex_key key = FUTEX_KEY_INIT; |
e4dc5b7a | 1588 | int ret; |
c87e2837 IM |
1589 | |
1590 | retry: | |
1591 | if (get_user(uval, uaddr)) | |
1592 | return -EFAULT; | |
1593 | /* | |
1594 | * We release only a lock we actually own: | |
1595 | */ | |
b488893a | 1596 | if ((uval & FUTEX_TID_MASK) != task_pid_vnr(current)) |
c87e2837 | 1597 | return -EPERM; |
c87e2837 | 1598 | |
64d1304a | 1599 | ret = get_futex_key(uaddr, fshared, &key, VERIFY_WRITE); |
c87e2837 IM |
1600 | if (unlikely(ret != 0)) |
1601 | goto out; | |
1602 | ||
1603 | hb = hash_futex(&key); | |
1604 | spin_lock(&hb->lock); | |
1605 | ||
c87e2837 IM |
1606 | /* |
1607 | * To avoid races, try to do the TID -> 0 atomic transition | |
1608 | * again. If it succeeds then we can return without waking | |
1609 | * anyone else up: | |
1610 | */ | |
36cf3b5c | 1611 | if (!(uval & FUTEX_OWNER_DIED)) |
b488893a | 1612 | uval = cmpxchg_futex_value_locked(uaddr, task_pid_vnr(current), 0); |
36cf3b5c | 1613 | |
c87e2837 IM |
1614 | |
1615 | if (unlikely(uval == -EFAULT)) | |
1616 | goto pi_faulted; | |
1617 | /* | |
1618 | * Rare case: we managed to release the lock atomically, | |
1619 | * no need to wake anyone else up: | |
1620 | */ | |
b488893a | 1621 | if (unlikely(uval == task_pid_vnr(current))) |
c87e2837 IM |
1622 | goto out_unlock; |
1623 | ||
1624 | /* | |
1625 | * Ok, other tasks may need to be woken up - check waiters | |
1626 | * and do the wakeup if necessary: | |
1627 | */ | |
1628 | head = &hb->chain; | |
1629 | ||
ec92d082 | 1630 | plist_for_each_entry_safe(this, next, head, list) { |
c87e2837 IM |
1631 | if (!match_futex (&this->key, &key)) |
1632 | continue; | |
1633 | ret = wake_futex_pi(uaddr, uval, this); | |
1634 | /* | |
1635 | * The atomic access to the futex value | |
1636 | * generated a pagefault, so retry the | |
1637 | * user-access and the wakeup: | |
1638 | */ | |
1639 | if (ret == -EFAULT) | |
1640 | goto pi_faulted; | |
1641 | goto out_unlock; | |
1642 | } | |
1643 | /* | |
1644 | * No waiters - kernel unlocks the futex: | |
1645 | */ | |
e3f2ddea IM |
1646 | if (!(uval & FUTEX_OWNER_DIED)) { |
1647 | ret = unlock_futex_pi(uaddr, uval); | |
1648 | if (ret == -EFAULT) | |
1649 | goto pi_faulted; | |
1650 | } | |
c87e2837 IM |
1651 | |
1652 | out_unlock: | |
1653 | spin_unlock(&hb->lock); | |
38d47c1b | 1654 | put_futex_key(fshared, &key); |
c87e2837 | 1655 | |
42d35d48 | 1656 | out: |
c87e2837 IM |
1657 | return ret; |
1658 | ||
1659 | pi_faulted: | |
1660 | /* | |
b5686363 DH |
1661 | * We have to r/w *(int __user *)uaddr, and we have to modify it |
1662 | * atomically. Therefore, if we continue to fault after get_user() | |
1663 | * below, we need to handle the fault ourselves, while still holding | |
1664 | * the mmap_sem. This can occur if the uaddr is under contention as | |
1665 | * we have to drop the mmap_sem in order to call get_user(). | |
c87e2837 | 1666 | */ |
778e9a9c | 1667 | spin_unlock(&hb->lock); |
e4dc5b7a | 1668 | put_futex_key(fshared, &key); |
c87e2837 | 1669 | |
c87e2837 | 1670 | ret = get_user(uval, uaddr); |
b5686363 | 1671 | if (!ret) |
c87e2837 IM |
1672 | goto retry; |
1673 | ||
1da177e4 LT |
1674 | return ret; |
1675 | } | |
1676 | ||
0771dfef IM |
1677 | /* |
1678 | * Support for robust futexes: the kernel cleans up held futexes at | |
1679 | * thread exit time. | |
1680 | * | |
1681 | * Implementation: user-space maintains a per-thread list of locks it | |
1682 | * is holding. Upon do_exit(), the kernel carefully walks this list, | |
1683 | * and marks all locks that are owned by this thread with the | |
c87e2837 | 1684 | * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is |
0771dfef IM |
1685 | * always manipulated with the lock held, so the list is private and |
1686 | * per-thread. Userspace also maintains a per-thread 'list_op_pending' | |
1687 | * field, to allow the kernel to clean up if the thread dies after | |
1688 | * acquiring the lock, but just before it could have added itself to | |
1689 | * the list. There can only be one such pending lock. | |
1690 | */ | |
1691 | ||
1692 | /** | |
1693 | * sys_set_robust_list - set the robust-futex list head of a task | |
1694 | * @head: pointer to the list-head | |
1695 | * @len: length of the list-head, as userspace expects | |
1696 | */ | |
836f92ad HC |
1697 | SYSCALL_DEFINE2(set_robust_list, struct robust_list_head __user *, head, |
1698 | size_t, len) | |
0771dfef | 1699 | { |
a0c1e907 TG |
1700 | if (!futex_cmpxchg_enabled) |
1701 | return -ENOSYS; | |
0771dfef IM |
1702 | /* |
1703 | * The kernel knows only one size for now: | |
1704 | */ | |
1705 | if (unlikely(len != sizeof(*head))) | |
1706 | return -EINVAL; | |
1707 | ||
1708 | current->robust_list = head; | |
1709 | ||
1710 | return 0; | |
1711 | } | |
1712 | ||
1713 | /** | |
1714 | * sys_get_robust_list - get the robust-futex list head of a task | |
1715 | * @pid: pid of the process [zero for current task] | |
1716 | * @head_ptr: pointer to a list-head pointer, the kernel fills it in | |
1717 | * @len_ptr: pointer to a length field, the kernel fills in the header size | |
1718 | */ | |
836f92ad HC |
1719 | SYSCALL_DEFINE3(get_robust_list, int, pid, |
1720 | struct robust_list_head __user * __user *, head_ptr, | |
1721 | size_t __user *, len_ptr) | |
0771dfef | 1722 | { |
ba46df98 | 1723 | struct robust_list_head __user *head; |
0771dfef | 1724 | unsigned long ret; |
c69e8d9c | 1725 | const struct cred *cred = current_cred(), *pcred; |
0771dfef | 1726 | |
a0c1e907 TG |
1727 | if (!futex_cmpxchg_enabled) |
1728 | return -ENOSYS; | |
1729 | ||
0771dfef IM |
1730 | if (!pid) |
1731 | head = current->robust_list; | |
1732 | else { | |
1733 | struct task_struct *p; | |
1734 | ||
1735 | ret = -ESRCH; | |
aaa2a97e | 1736 | rcu_read_lock(); |
228ebcbe | 1737 | p = find_task_by_vpid(pid); |
0771dfef IM |
1738 | if (!p) |
1739 | goto err_unlock; | |
1740 | ret = -EPERM; | |
c69e8d9c DH |
1741 | pcred = __task_cred(p); |
1742 | if (cred->euid != pcred->euid && | |
1743 | cred->euid != pcred->uid && | |
76aac0e9 | 1744 | !capable(CAP_SYS_PTRACE)) |
0771dfef IM |
1745 | goto err_unlock; |
1746 | head = p->robust_list; | |
aaa2a97e | 1747 | rcu_read_unlock(); |
0771dfef IM |
1748 | } |
1749 | ||
1750 | if (put_user(sizeof(*head), len_ptr)) | |
1751 | return -EFAULT; | |
1752 | return put_user(head, head_ptr); | |
1753 | ||
1754 | err_unlock: | |
aaa2a97e | 1755 | rcu_read_unlock(); |
0771dfef IM |
1756 | |
1757 | return ret; | |
1758 | } | |
1759 | ||
1760 | /* | |
1761 | * Process a futex-list entry, check whether it's owned by the | |
1762 | * dying task, and do notification if so: | |
1763 | */ | |
e3f2ddea | 1764 | int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi) |
0771dfef | 1765 | { |
e3f2ddea | 1766 | u32 uval, nval, mval; |
0771dfef | 1767 | |
8f17d3a5 IM |
1768 | retry: |
1769 | if (get_user(uval, uaddr)) | |
0771dfef IM |
1770 | return -1; |
1771 | ||
b488893a | 1772 | if ((uval & FUTEX_TID_MASK) == task_pid_vnr(curr)) { |
0771dfef IM |
1773 | /* |
1774 | * Ok, this dying thread is truly holding a futex | |
1775 | * of interest. Set the OWNER_DIED bit atomically | |
1776 | * via cmpxchg, and if the value had FUTEX_WAITERS | |
1777 | * set, wake up a waiter (if any). (We have to do a | |
1778 | * futex_wake() even if OWNER_DIED is already set - | |
1779 | * to handle the rare but possible case of recursive | |
1780 | * thread-death.) The rest of the cleanup is done in | |
1781 | * userspace. | |
1782 | */ | |
e3f2ddea IM |
1783 | mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED; |
1784 | nval = futex_atomic_cmpxchg_inatomic(uaddr, uval, mval); | |
1785 | ||
c87e2837 IM |
1786 | if (nval == -EFAULT) |
1787 | return -1; | |
1788 | ||
1789 | if (nval != uval) | |
8f17d3a5 | 1790 | goto retry; |
0771dfef | 1791 | |
e3f2ddea IM |
1792 | /* |
1793 | * Wake robust non-PI futexes here. The wakeup of | |
1794 | * PI futexes happens in exit_pi_state(): | |
1795 | */ | |
36cf3b5c | 1796 | if (!pi && (uval & FUTEX_WAITERS)) |
c2f9f201 | 1797 | futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY); |
0771dfef IM |
1798 | } |
1799 | return 0; | |
1800 | } | |
1801 | ||
e3f2ddea IM |
1802 | /* |
1803 | * Fetch a robust-list pointer. Bit 0 signals PI futexes: | |
1804 | */ | |
1805 | static inline int fetch_robust_entry(struct robust_list __user **entry, | |
ba46df98 AV |
1806 | struct robust_list __user * __user *head, |
1807 | int *pi) | |
e3f2ddea IM |
1808 | { |
1809 | unsigned long uentry; | |
1810 | ||
ba46df98 | 1811 | if (get_user(uentry, (unsigned long __user *)head)) |
e3f2ddea IM |
1812 | return -EFAULT; |
1813 | ||
ba46df98 | 1814 | *entry = (void __user *)(uentry & ~1UL); |
e3f2ddea IM |
1815 | *pi = uentry & 1; |
1816 | ||
1817 | return 0; | |
1818 | } | |
1819 | ||
0771dfef IM |
1820 | /* |
1821 | * Walk curr->robust_list (very carefully, it's a userspace list!) | |
1822 | * and mark any locks found there dead, and notify any waiters. | |
1823 | * | |
1824 | * We silently return on any sign of list-walking problem. | |
1825 | */ | |
1826 | void exit_robust_list(struct task_struct *curr) | |
1827 | { | |
1828 | struct robust_list_head __user *head = curr->robust_list; | |
9f96cb1e MS |
1829 | struct robust_list __user *entry, *next_entry, *pending; |
1830 | unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip; | |
0771dfef | 1831 | unsigned long futex_offset; |
9f96cb1e | 1832 | int rc; |
0771dfef | 1833 | |
a0c1e907 TG |
1834 | if (!futex_cmpxchg_enabled) |
1835 | return; | |
1836 | ||
0771dfef IM |
1837 | /* |
1838 | * Fetch the list head (which was registered earlier, via | |
1839 | * sys_set_robust_list()): | |
1840 | */ | |
e3f2ddea | 1841 | if (fetch_robust_entry(&entry, &head->list.next, &pi)) |
0771dfef IM |
1842 | return; |
1843 | /* | |
1844 | * Fetch the relative futex offset: | |
1845 | */ | |
1846 | if (get_user(futex_offset, &head->futex_offset)) | |
1847 | return; | |
1848 | /* | |
1849 | * Fetch any possibly pending lock-add first, and handle it | |
1850 | * if it exists: | |
1851 | */ | |
e3f2ddea | 1852 | if (fetch_robust_entry(&pending, &head->list_op_pending, &pip)) |
0771dfef | 1853 | return; |
e3f2ddea | 1854 | |
9f96cb1e | 1855 | next_entry = NULL; /* avoid warning with gcc */ |
0771dfef | 1856 | while (entry != &head->list) { |
9f96cb1e MS |
1857 | /* |
1858 | * Fetch the next entry in the list before calling | |
1859 | * handle_futex_death: | |
1860 | */ | |
1861 | rc = fetch_robust_entry(&next_entry, &entry->next, &next_pi); | |
0771dfef IM |
1862 | /* |
1863 | * A pending lock might already be on the list, so | |
c87e2837 | 1864 | * don't process it twice: |
0771dfef IM |
1865 | */ |
1866 | if (entry != pending) | |
ba46df98 | 1867 | if (handle_futex_death((void __user *)entry + futex_offset, |
e3f2ddea | 1868 | curr, pi)) |
0771dfef | 1869 | return; |
9f96cb1e | 1870 | if (rc) |
0771dfef | 1871 | return; |
9f96cb1e MS |
1872 | entry = next_entry; |
1873 | pi = next_pi; | |
0771dfef IM |
1874 | /* |
1875 | * Avoid excessively long or circular lists: | |
1876 | */ | |
1877 | if (!--limit) | |
1878 | break; | |
1879 | ||
1880 | cond_resched(); | |
1881 | } | |
9f96cb1e MS |
1882 | |
1883 | if (pending) | |
1884 | handle_futex_death((void __user *)pending + futex_offset, | |
1885 | curr, pip); | |
0771dfef IM |
1886 | } |
1887 | ||
c19384b5 | 1888 | long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout, |
e2970f2f | 1889 | u32 __user *uaddr2, u32 val2, u32 val3) |
1da177e4 | 1890 | { |
1acdac10 | 1891 | int clockrt, ret = -ENOSYS; |
34f01cc1 | 1892 | int cmd = op & FUTEX_CMD_MASK; |
c2f9f201 | 1893 | int fshared = 0; |
34f01cc1 ED |
1894 | |
1895 | if (!(op & FUTEX_PRIVATE_FLAG)) | |
c2f9f201 | 1896 | fshared = 1; |
1da177e4 | 1897 | |
1acdac10 TG |
1898 | clockrt = op & FUTEX_CLOCK_REALTIME; |
1899 | if (clockrt && cmd != FUTEX_WAIT_BITSET) | |
1900 | return -ENOSYS; | |
1da177e4 | 1901 | |
34f01cc1 | 1902 | switch (cmd) { |
1da177e4 | 1903 | case FUTEX_WAIT: |
cd689985 TG |
1904 | val3 = FUTEX_BITSET_MATCH_ANY; |
1905 | case FUTEX_WAIT_BITSET: | |
1acdac10 | 1906 | ret = futex_wait(uaddr, fshared, val, timeout, val3, clockrt); |
1da177e4 LT |
1907 | break; |
1908 | case FUTEX_WAKE: | |
cd689985 TG |
1909 | val3 = FUTEX_BITSET_MATCH_ANY; |
1910 | case FUTEX_WAKE_BITSET: | |
1911 | ret = futex_wake(uaddr, fshared, val, val3); | |
1da177e4 | 1912 | break; |
1da177e4 | 1913 | case FUTEX_REQUEUE: |
34f01cc1 | 1914 | ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, NULL); |
1da177e4 LT |
1915 | break; |
1916 | case FUTEX_CMP_REQUEUE: | |
34f01cc1 | 1917 | ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, &val3); |
1da177e4 | 1918 | break; |
4732efbe | 1919 | case FUTEX_WAKE_OP: |
34f01cc1 | 1920 | ret = futex_wake_op(uaddr, fshared, uaddr2, val, val2, val3); |
4732efbe | 1921 | break; |
c87e2837 | 1922 | case FUTEX_LOCK_PI: |
a0c1e907 TG |
1923 | if (futex_cmpxchg_enabled) |
1924 | ret = futex_lock_pi(uaddr, fshared, val, timeout, 0); | |
c87e2837 IM |
1925 | break; |
1926 | case FUTEX_UNLOCK_PI: | |
a0c1e907 TG |
1927 | if (futex_cmpxchg_enabled) |
1928 | ret = futex_unlock_pi(uaddr, fshared); | |
c87e2837 IM |
1929 | break; |
1930 | case FUTEX_TRYLOCK_PI: | |
a0c1e907 TG |
1931 | if (futex_cmpxchg_enabled) |
1932 | ret = futex_lock_pi(uaddr, fshared, 0, timeout, 1); | |
c87e2837 | 1933 | break; |
1da177e4 LT |
1934 | default: |
1935 | ret = -ENOSYS; | |
1936 | } | |
1937 | return ret; | |
1938 | } | |
1939 | ||
1940 | ||
17da2bd9 HC |
1941 | SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val, |
1942 | struct timespec __user *, utime, u32 __user *, uaddr2, | |
1943 | u32, val3) | |
1da177e4 | 1944 | { |
c19384b5 PP |
1945 | struct timespec ts; |
1946 | ktime_t t, *tp = NULL; | |
e2970f2f | 1947 | u32 val2 = 0; |
34f01cc1 | 1948 | int cmd = op & FUTEX_CMD_MASK; |
1da177e4 | 1949 | |
cd689985 TG |
1950 | if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI || |
1951 | cmd == FUTEX_WAIT_BITSET)) { | |
c19384b5 | 1952 | if (copy_from_user(&ts, utime, sizeof(ts)) != 0) |
1da177e4 | 1953 | return -EFAULT; |
c19384b5 | 1954 | if (!timespec_valid(&ts)) |
9741ef96 | 1955 | return -EINVAL; |
c19384b5 PP |
1956 | |
1957 | t = timespec_to_ktime(ts); | |
34f01cc1 | 1958 | if (cmd == FUTEX_WAIT) |
5a7780e7 | 1959 | t = ktime_add_safe(ktime_get(), t); |
c19384b5 | 1960 | tp = &t; |
1da177e4 LT |
1961 | } |
1962 | /* | |
34f01cc1 | 1963 | * requeue parameter in 'utime' if cmd == FUTEX_REQUEUE. |
f54f0986 | 1964 | * number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP. |
1da177e4 | 1965 | */ |
f54f0986 AS |
1966 | if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE || |
1967 | cmd == FUTEX_WAKE_OP) | |
e2970f2f | 1968 | val2 = (u32) (unsigned long) utime; |
1da177e4 | 1969 | |
c19384b5 | 1970 | return do_futex(uaddr, op, val, tp, uaddr2, val2, val3); |
1da177e4 LT |
1971 | } |
1972 | ||
f6d107fb | 1973 | static int __init futex_init(void) |
1da177e4 | 1974 | { |
a0c1e907 | 1975 | u32 curval; |
3e4ab747 | 1976 | int i; |
95362fa9 | 1977 | |
a0c1e907 TG |
1978 | /* |
1979 | * This will fail and we want it. Some arch implementations do | |
1980 | * runtime detection of the futex_atomic_cmpxchg_inatomic() | |
1981 | * functionality. We want to know that before we call in any | |
1982 | * of the complex code paths. Also we want to prevent | |
1983 | * registration of robust lists in that case. NULL is | |
1984 | * guaranteed to fault and we get -EFAULT on functional | |
1985 | * implementation, the non functional ones will return | |
1986 | * -ENOSYS. | |
1987 | */ | |
1988 | curval = cmpxchg_futex_value_locked(NULL, 0, 0); | |
1989 | if (curval == -EFAULT) | |
1990 | futex_cmpxchg_enabled = 1; | |
1991 | ||
3e4ab747 TG |
1992 | for (i = 0; i < ARRAY_SIZE(futex_queues); i++) { |
1993 | plist_head_init(&futex_queues[i].chain, &futex_queues[i].lock); | |
1994 | spin_lock_init(&futex_queues[i].lock); | |
1995 | } | |
1996 | ||
1da177e4 LT |
1997 | return 0; |
1998 | } | |
f6d107fb | 1999 | __initcall(futex_init); |