Commit | Line | Data |
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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 LT |
94 | * The order of wakup is always to make the first condition true, then |
95 | * wake up q->waiters, then make the second condition true. | |
96 | */ | |
97 | struct futex_q { | |
ec92d082 | 98 | struct plist_node list; |
1da177e4 LT |
99 | wait_queue_head_t waiters; |
100 | ||
e2970f2f | 101 | /* Which hash list lock to use: */ |
1da177e4 LT |
102 | spinlock_t *lock_ptr; |
103 | ||
e2970f2f | 104 | /* Key which the futex is hashed on: */ |
1da177e4 LT |
105 | union futex_key key; |
106 | ||
c87e2837 IM |
107 | /* Optional priority inheritance state: */ |
108 | struct futex_pi_state *pi_state; | |
109 | struct task_struct *task; | |
cd689985 TG |
110 | |
111 | /* Bitset for the optional bitmasked wakeup */ | |
112 | u32 bitset; | |
1da177e4 LT |
113 | }; |
114 | ||
115 | /* | |
116 | * Split the global futex_lock into every hash list lock. | |
117 | */ | |
118 | struct futex_hash_bucket { | |
ec92d082 PP |
119 | spinlock_t lock; |
120 | struct plist_head chain; | |
1da177e4 LT |
121 | }; |
122 | ||
123 | static struct futex_hash_bucket futex_queues[1<<FUTEX_HASHBITS]; | |
124 | ||
1da177e4 LT |
125 | /* |
126 | * We hash on the keys returned from get_futex_key (see below). | |
127 | */ | |
128 | static struct futex_hash_bucket *hash_futex(union futex_key *key) | |
129 | { | |
130 | u32 hash = jhash2((u32*)&key->both.word, | |
131 | (sizeof(key->both.word)+sizeof(key->both.ptr))/4, | |
132 | key->both.offset); | |
133 | return &futex_queues[hash & ((1 << FUTEX_HASHBITS)-1)]; | |
134 | } | |
135 | ||
136 | /* | |
137 | * Return 1 if two futex_keys are equal, 0 otherwise. | |
138 | */ | |
139 | static inline int match_futex(union futex_key *key1, union futex_key *key2) | |
140 | { | |
141 | return (key1->both.word == key2->both.word | |
142 | && key1->both.ptr == key2->both.ptr | |
143 | && key1->both.offset == key2->both.offset); | |
144 | } | |
145 | ||
38d47c1b PZ |
146 | /* |
147 | * Take a reference to the resource addressed by a key. | |
148 | * Can be called while holding spinlocks. | |
149 | * | |
150 | */ | |
151 | static void get_futex_key_refs(union futex_key *key) | |
152 | { | |
153 | if (!key->both.ptr) | |
154 | return; | |
155 | ||
156 | switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { | |
157 | case FUT_OFF_INODE: | |
158 | atomic_inc(&key->shared.inode->i_count); | |
159 | break; | |
160 | case FUT_OFF_MMSHARED: | |
161 | atomic_inc(&key->private.mm->mm_count); | |
162 | break; | |
163 | } | |
164 | } | |
165 | ||
166 | /* | |
167 | * Drop a reference to the resource addressed by a key. | |
168 | * The hash bucket spinlock must not be held. | |
169 | */ | |
170 | static void drop_futex_key_refs(union futex_key *key) | |
171 | { | |
172 | if (!key->both.ptr) | |
173 | return; | |
174 | ||
175 | switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { | |
176 | case FUT_OFF_INODE: | |
177 | iput(key->shared.inode); | |
178 | break; | |
179 | case FUT_OFF_MMSHARED: | |
180 | mmdrop(key->private.mm); | |
181 | break; | |
182 | } | |
183 | } | |
184 | ||
34f01cc1 ED |
185 | /** |
186 | * get_futex_key - Get parameters which are the keys for a futex. | |
187 | * @uaddr: virtual address of the futex | |
188 | * @shared: NULL for a PROCESS_PRIVATE futex, | |
189 | * ¤t->mm->mmap_sem for a PROCESS_SHARED futex | |
190 | * @key: address where result is stored. | |
191 | * | |
192 | * Returns a negative error code or 0 | |
193 | * The key words are stored in *key on success. | |
1da177e4 | 194 | * |
f3a43f3f | 195 | * For shared mappings, it's (page->index, vma->vm_file->f_path.dentry->d_inode, |
1da177e4 LT |
196 | * offset_within_page). For private mappings, it's (uaddr, current->mm). |
197 | * We can usually work out the index without swapping in the page. | |
198 | * | |
34f01cc1 ED |
199 | * fshared is NULL for PROCESS_PRIVATE futexes |
200 | * For other futexes, it points to ¤t->mm->mmap_sem and | |
201 | * caller must have taken the reader lock. but NOT any spinlocks. | |
1da177e4 | 202 | */ |
fad23fc7 AB |
203 | static int get_futex_key(u32 __user *uaddr, struct rw_semaphore *fshared, |
204 | union futex_key *key) | |
1da177e4 | 205 | { |
e2970f2f | 206 | unsigned long address = (unsigned long)uaddr; |
1da177e4 | 207 | struct mm_struct *mm = current->mm; |
1da177e4 LT |
208 | struct page *page; |
209 | int err; | |
210 | ||
211 | /* | |
212 | * The futex address must be "naturally" aligned. | |
213 | */ | |
e2970f2f | 214 | key->both.offset = address % PAGE_SIZE; |
34f01cc1 | 215 | if (unlikely((address % sizeof(u32)) != 0)) |
1da177e4 | 216 | return -EINVAL; |
e2970f2f | 217 | address -= key->both.offset; |
1da177e4 | 218 | |
34f01cc1 ED |
219 | /* |
220 | * PROCESS_PRIVATE futexes are fast. | |
221 | * As the mm cannot disappear under us and the 'key' only needs | |
222 | * virtual address, we dont even have to find the underlying vma. | |
223 | * Note : We do have to check 'uaddr' is a valid user address, | |
224 | * but access_ok() should be faster than find_vma() | |
225 | */ | |
226 | if (!fshared) { | |
227 | if (unlikely(!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))) | |
228 | return -EFAULT; | |
229 | key->private.mm = mm; | |
230 | key->private.address = address; | |
231 | return 0; | |
232 | } | |
1da177e4 | 233 | |
38d47c1b | 234 | again: |
61270708 | 235 | down_read(&mm->mmap_sem); |
38d47c1b | 236 | err = get_user_pages(current, mm, address, 1, 0, 0, &page, NULL); |
61270708 | 237 | up_read(&mm->mmap_sem); |
38d47c1b PZ |
238 | if (err < 0) |
239 | return err; | |
240 | ||
241 | lock_page(page); | |
242 | if (!page->mapping) { | |
243 | unlock_page(page); | |
244 | put_page(page); | |
245 | goto again; | |
246 | } | |
1da177e4 LT |
247 | |
248 | /* | |
249 | * Private mappings are handled in a simple way. | |
250 | * | |
251 | * NOTE: When userspace waits on a MAP_SHARED mapping, even if | |
252 | * it's a read-only handle, it's expected that futexes attach to | |
38d47c1b | 253 | * the object not the particular process. |
1da177e4 | 254 | */ |
38d47c1b PZ |
255 | if (PageAnon(page)) { |
256 | key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */ | |
1da177e4 | 257 | key->private.mm = mm; |
e2970f2f | 258 | key->private.address = address; |
38d47c1b PZ |
259 | } else { |
260 | key->both.offset |= FUT_OFF_INODE; /* inode-based key */ | |
261 | key->shared.inode = page->mapping->host; | |
262 | key->shared.pgoff = page->index; | |
1da177e4 LT |
263 | } |
264 | ||
38d47c1b | 265 | get_futex_key_refs(key); |
1da177e4 | 266 | |
38d47c1b PZ |
267 | unlock_page(page); |
268 | put_page(page); | |
269 | return 0; | |
1da177e4 LT |
270 | } |
271 | ||
38d47c1b PZ |
272 | static inline |
273 | void put_futex_key(struct rw_semaphore *fshared, union futex_key *key) | |
1da177e4 | 274 | { |
38d47c1b | 275 | drop_futex_key_refs(key); |
1da177e4 LT |
276 | } |
277 | ||
36cf3b5c TG |
278 | static u32 cmpxchg_futex_value_locked(u32 __user *uaddr, u32 uval, u32 newval) |
279 | { | |
280 | u32 curval; | |
281 | ||
282 | pagefault_disable(); | |
283 | curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval); | |
284 | pagefault_enable(); | |
285 | ||
286 | return curval; | |
287 | } | |
288 | ||
289 | static int get_futex_value_locked(u32 *dest, u32 __user *from) | |
1da177e4 LT |
290 | { |
291 | int ret; | |
292 | ||
a866374a | 293 | pagefault_disable(); |
e2970f2f | 294 | ret = __copy_from_user_inatomic(dest, from, sizeof(u32)); |
a866374a | 295 | pagefault_enable(); |
1da177e4 LT |
296 | |
297 | return ret ? -EFAULT : 0; | |
298 | } | |
299 | ||
c87e2837 | 300 | /* |
34f01cc1 ED |
301 | * Fault handling. |
302 | * if fshared is non NULL, current->mm->mmap_sem is already held | |
c87e2837 | 303 | */ |
34f01cc1 ED |
304 | static int futex_handle_fault(unsigned long address, |
305 | struct rw_semaphore *fshared, int attempt) | |
c87e2837 IM |
306 | { |
307 | struct vm_area_struct * vma; | |
308 | struct mm_struct *mm = current->mm; | |
34f01cc1 | 309 | int ret = -EFAULT; |
c87e2837 | 310 | |
34f01cc1 ED |
311 | if (attempt > 2) |
312 | return ret; | |
c87e2837 | 313 | |
61270708 | 314 | down_read(&mm->mmap_sem); |
34f01cc1 ED |
315 | vma = find_vma(mm, address); |
316 | if (vma && address >= vma->vm_start && | |
317 | (vma->vm_flags & VM_WRITE)) { | |
83c54070 NP |
318 | int fault; |
319 | fault = handle_mm_fault(mm, vma, address, 1); | |
320 | if (unlikely((fault & VM_FAULT_ERROR))) { | |
321 | #if 0 | |
322 | /* XXX: let's do this when we verify it is OK */ | |
323 | if (ret & VM_FAULT_OOM) | |
324 | ret = -ENOMEM; | |
325 | #endif | |
326 | } else { | |
34f01cc1 | 327 | ret = 0; |
83c54070 NP |
328 | if (fault & VM_FAULT_MAJOR) |
329 | current->maj_flt++; | |
330 | else | |
331 | current->min_flt++; | |
34f01cc1 | 332 | } |
c87e2837 | 333 | } |
61270708 | 334 | up_read(&mm->mmap_sem); |
34f01cc1 | 335 | return ret; |
c87e2837 IM |
336 | } |
337 | ||
338 | /* | |
339 | * PI code: | |
340 | */ | |
341 | static int refill_pi_state_cache(void) | |
342 | { | |
343 | struct futex_pi_state *pi_state; | |
344 | ||
345 | if (likely(current->pi_state_cache)) | |
346 | return 0; | |
347 | ||
4668edc3 | 348 | pi_state = kzalloc(sizeof(*pi_state), GFP_KERNEL); |
c87e2837 IM |
349 | |
350 | if (!pi_state) | |
351 | return -ENOMEM; | |
352 | ||
c87e2837 IM |
353 | INIT_LIST_HEAD(&pi_state->list); |
354 | /* pi_mutex gets initialized later */ | |
355 | pi_state->owner = NULL; | |
356 | atomic_set(&pi_state->refcount, 1); | |
38d47c1b | 357 | pi_state->key = FUTEX_KEY_INIT; |
c87e2837 IM |
358 | |
359 | current->pi_state_cache = pi_state; | |
360 | ||
361 | return 0; | |
362 | } | |
363 | ||
364 | static struct futex_pi_state * alloc_pi_state(void) | |
365 | { | |
366 | struct futex_pi_state *pi_state = current->pi_state_cache; | |
367 | ||
368 | WARN_ON(!pi_state); | |
369 | current->pi_state_cache = NULL; | |
370 | ||
371 | return pi_state; | |
372 | } | |
373 | ||
374 | static void free_pi_state(struct futex_pi_state *pi_state) | |
375 | { | |
376 | if (!atomic_dec_and_test(&pi_state->refcount)) | |
377 | return; | |
378 | ||
379 | /* | |
380 | * If pi_state->owner is NULL, the owner is most probably dying | |
381 | * and has cleaned up the pi_state already | |
382 | */ | |
383 | if (pi_state->owner) { | |
384 | spin_lock_irq(&pi_state->owner->pi_lock); | |
385 | list_del_init(&pi_state->list); | |
386 | spin_unlock_irq(&pi_state->owner->pi_lock); | |
387 | ||
388 | rt_mutex_proxy_unlock(&pi_state->pi_mutex, pi_state->owner); | |
389 | } | |
390 | ||
391 | if (current->pi_state_cache) | |
392 | kfree(pi_state); | |
393 | else { | |
394 | /* | |
395 | * pi_state->list is already empty. | |
396 | * clear pi_state->owner. | |
397 | * refcount is at 0 - put it back to 1. | |
398 | */ | |
399 | pi_state->owner = NULL; | |
400 | atomic_set(&pi_state->refcount, 1); | |
401 | current->pi_state_cache = pi_state; | |
402 | } | |
403 | } | |
404 | ||
405 | /* | |
406 | * Look up the task based on what TID userspace gave us. | |
407 | * We dont trust it. | |
408 | */ | |
409 | static struct task_struct * futex_find_get_task(pid_t pid) | |
410 | { | |
411 | struct task_struct *p; | |
412 | ||
d359b549 | 413 | rcu_read_lock(); |
228ebcbe | 414 | p = find_task_by_vpid(pid); |
a06381fe TG |
415 | if (!p || ((current->euid != p->euid) && (current->euid != p->uid))) |
416 | p = ERR_PTR(-ESRCH); | |
417 | else | |
418 | get_task_struct(p); | |
419 | ||
d359b549 | 420 | rcu_read_unlock(); |
c87e2837 IM |
421 | |
422 | return p; | |
423 | } | |
424 | ||
425 | /* | |
426 | * This task is holding PI mutexes at exit time => bad. | |
427 | * Kernel cleans up PI-state, but userspace is likely hosed. | |
428 | * (Robust-futex cleanup is separate and might save the day for userspace.) | |
429 | */ | |
430 | void exit_pi_state_list(struct task_struct *curr) | |
431 | { | |
c87e2837 IM |
432 | struct list_head *next, *head = &curr->pi_state_list; |
433 | struct futex_pi_state *pi_state; | |
627371d7 | 434 | struct futex_hash_bucket *hb; |
38d47c1b | 435 | union futex_key key = FUTEX_KEY_INIT; |
c87e2837 | 436 | |
a0c1e907 TG |
437 | if (!futex_cmpxchg_enabled) |
438 | return; | |
c87e2837 IM |
439 | /* |
440 | * We are a ZOMBIE and nobody can enqueue itself on | |
441 | * pi_state_list anymore, but we have to be careful | |
627371d7 | 442 | * versus waiters unqueueing themselves: |
c87e2837 IM |
443 | */ |
444 | spin_lock_irq(&curr->pi_lock); | |
445 | while (!list_empty(head)) { | |
446 | ||
447 | next = head->next; | |
448 | pi_state = list_entry(next, struct futex_pi_state, list); | |
449 | key = pi_state->key; | |
627371d7 | 450 | hb = hash_futex(&key); |
c87e2837 IM |
451 | spin_unlock_irq(&curr->pi_lock); |
452 | ||
c87e2837 IM |
453 | spin_lock(&hb->lock); |
454 | ||
455 | spin_lock_irq(&curr->pi_lock); | |
627371d7 IM |
456 | /* |
457 | * We dropped the pi-lock, so re-check whether this | |
458 | * task still owns the PI-state: | |
459 | */ | |
c87e2837 IM |
460 | if (head->next != next) { |
461 | spin_unlock(&hb->lock); | |
462 | continue; | |
463 | } | |
464 | ||
c87e2837 | 465 | WARN_ON(pi_state->owner != curr); |
627371d7 IM |
466 | WARN_ON(list_empty(&pi_state->list)); |
467 | list_del_init(&pi_state->list); | |
c87e2837 IM |
468 | pi_state->owner = NULL; |
469 | spin_unlock_irq(&curr->pi_lock); | |
470 | ||
471 | rt_mutex_unlock(&pi_state->pi_mutex); | |
472 | ||
473 | spin_unlock(&hb->lock); | |
474 | ||
475 | spin_lock_irq(&curr->pi_lock); | |
476 | } | |
477 | spin_unlock_irq(&curr->pi_lock); | |
478 | } | |
479 | ||
480 | static int | |
d0aa7a70 PP |
481 | lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, |
482 | union futex_key *key, struct futex_pi_state **ps) | |
c87e2837 IM |
483 | { |
484 | struct futex_pi_state *pi_state = NULL; | |
485 | struct futex_q *this, *next; | |
ec92d082 | 486 | struct plist_head *head; |
c87e2837 | 487 | struct task_struct *p; |
778e9a9c | 488 | pid_t pid = uval & FUTEX_TID_MASK; |
c87e2837 IM |
489 | |
490 | head = &hb->chain; | |
491 | ||
ec92d082 | 492 | plist_for_each_entry_safe(this, next, head, list) { |
d0aa7a70 | 493 | if (match_futex(&this->key, key)) { |
c87e2837 IM |
494 | /* |
495 | * Another waiter already exists - bump up | |
496 | * the refcount and return its pi_state: | |
497 | */ | |
498 | pi_state = this->pi_state; | |
06a9ec29 TG |
499 | /* |
500 | * Userspace might have messed up non PI and PI futexes | |
501 | */ | |
502 | if (unlikely(!pi_state)) | |
503 | return -EINVAL; | |
504 | ||
627371d7 | 505 | WARN_ON(!atomic_read(&pi_state->refcount)); |
778e9a9c AK |
506 | WARN_ON(pid && pi_state->owner && |
507 | pi_state->owner->pid != pid); | |
627371d7 | 508 | |
c87e2837 | 509 | atomic_inc(&pi_state->refcount); |
d0aa7a70 | 510 | *ps = pi_state; |
c87e2837 IM |
511 | |
512 | return 0; | |
513 | } | |
514 | } | |
515 | ||
516 | /* | |
e3f2ddea | 517 | * We are the first waiter - try to look up the real owner and attach |
778e9a9c | 518 | * the new pi_state to it, but bail out when TID = 0 |
c87e2837 | 519 | */ |
778e9a9c | 520 | if (!pid) |
e3f2ddea | 521 | return -ESRCH; |
c87e2837 | 522 | p = futex_find_get_task(pid); |
778e9a9c AK |
523 | if (IS_ERR(p)) |
524 | return PTR_ERR(p); | |
525 | ||
526 | /* | |
527 | * We need to look at the task state flags to figure out, | |
528 | * whether the task is exiting. To protect against the do_exit | |
529 | * change of the task flags, we do this protected by | |
530 | * p->pi_lock: | |
531 | */ | |
532 | spin_lock_irq(&p->pi_lock); | |
533 | if (unlikely(p->flags & PF_EXITING)) { | |
534 | /* | |
535 | * The task is on the way out. When PF_EXITPIDONE is | |
536 | * set, we know that the task has finished the | |
537 | * cleanup: | |
538 | */ | |
539 | int ret = (p->flags & PF_EXITPIDONE) ? -ESRCH : -EAGAIN; | |
540 | ||
541 | spin_unlock_irq(&p->pi_lock); | |
542 | put_task_struct(p); | |
543 | return ret; | |
544 | } | |
c87e2837 IM |
545 | |
546 | pi_state = alloc_pi_state(); | |
547 | ||
548 | /* | |
549 | * Initialize the pi_mutex in locked state and make 'p' | |
550 | * the owner of it: | |
551 | */ | |
552 | rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p); | |
553 | ||
554 | /* Store the key for possible exit cleanups: */ | |
d0aa7a70 | 555 | pi_state->key = *key; |
c87e2837 | 556 | |
627371d7 | 557 | WARN_ON(!list_empty(&pi_state->list)); |
c87e2837 IM |
558 | list_add(&pi_state->list, &p->pi_state_list); |
559 | pi_state->owner = p; | |
560 | spin_unlock_irq(&p->pi_lock); | |
561 | ||
562 | put_task_struct(p); | |
563 | ||
d0aa7a70 | 564 | *ps = pi_state; |
c87e2837 IM |
565 | |
566 | return 0; | |
567 | } | |
568 | ||
1da177e4 LT |
569 | /* |
570 | * The hash bucket lock must be held when this is called. | |
571 | * Afterwards, the futex_q must not be accessed. | |
572 | */ | |
573 | static void wake_futex(struct futex_q *q) | |
574 | { | |
ec92d082 | 575 | plist_del(&q->list, &q->list.plist); |
1da177e4 LT |
576 | /* |
577 | * The lock in wake_up_all() is a crucial memory barrier after the | |
ec92d082 | 578 | * plist_del() and also before assigning to q->lock_ptr. |
1da177e4 LT |
579 | */ |
580 | wake_up_all(&q->waiters); | |
581 | /* | |
582 | * The waiting task can free the futex_q as soon as this is written, | |
583 | * without taking any locks. This must come last. | |
8e31108b AM |
584 | * |
585 | * A memory barrier is required here to prevent the following store | |
586 | * to lock_ptr from getting ahead of the wakeup. Clearing the lock | |
587 | * at the end of wake_up_all() does not prevent this store from | |
588 | * moving. | |
1da177e4 | 589 | */ |
ccdea2f8 | 590 | smp_wmb(); |
1da177e4 LT |
591 | q->lock_ptr = NULL; |
592 | } | |
593 | ||
c87e2837 IM |
594 | static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this) |
595 | { | |
596 | struct task_struct *new_owner; | |
597 | struct futex_pi_state *pi_state = this->pi_state; | |
598 | u32 curval, newval; | |
599 | ||
600 | if (!pi_state) | |
601 | return -EINVAL; | |
602 | ||
21778867 | 603 | spin_lock(&pi_state->pi_mutex.wait_lock); |
c87e2837 IM |
604 | new_owner = rt_mutex_next_owner(&pi_state->pi_mutex); |
605 | ||
606 | /* | |
607 | * This happens when we have stolen the lock and the original | |
608 | * pending owner did not enqueue itself back on the rt_mutex. | |
609 | * Thats not a tragedy. We know that way, that a lock waiter | |
610 | * is on the fly. We make the futex_q waiter the pending owner. | |
611 | */ | |
612 | if (!new_owner) | |
613 | new_owner = this->task; | |
614 | ||
615 | /* | |
616 | * We pass it to the next owner. (The WAITERS bit is always | |
617 | * kept enabled while there is PI state around. We must also | |
618 | * preserve the owner died bit.) | |
619 | */ | |
e3f2ddea | 620 | if (!(uval & FUTEX_OWNER_DIED)) { |
778e9a9c AK |
621 | int ret = 0; |
622 | ||
b488893a | 623 | newval = FUTEX_WAITERS | task_pid_vnr(new_owner); |
e3f2ddea | 624 | |
36cf3b5c | 625 | curval = cmpxchg_futex_value_locked(uaddr, uval, newval); |
778e9a9c | 626 | |
e3f2ddea | 627 | if (curval == -EFAULT) |
778e9a9c | 628 | ret = -EFAULT; |
cde898fa | 629 | else if (curval != uval) |
778e9a9c AK |
630 | ret = -EINVAL; |
631 | if (ret) { | |
632 | spin_unlock(&pi_state->pi_mutex.wait_lock); | |
633 | return ret; | |
634 | } | |
e3f2ddea | 635 | } |
c87e2837 | 636 | |
627371d7 IM |
637 | spin_lock_irq(&pi_state->owner->pi_lock); |
638 | WARN_ON(list_empty(&pi_state->list)); | |
639 | list_del_init(&pi_state->list); | |
640 | spin_unlock_irq(&pi_state->owner->pi_lock); | |
641 | ||
642 | spin_lock_irq(&new_owner->pi_lock); | |
643 | WARN_ON(!list_empty(&pi_state->list)); | |
c87e2837 IM |
644 | list_add(&pi_state->list, &new_owner->pi_state_list); |
645 | pi_state->owner = new_owner; | |
627371d7 IM |
646 | spin_unlock_irq(&new_owner->pi_lock); |
647 | ||
21778867 | 648 | spin_unlock(&pi_state->pi_mutex.wait_lock); |
c87e2837 IM |
649 | rt_mutex_unlock(&pi_state->pi_mutex); |
650 | ||
651 | return 0; | |
652 | } | |
653 | ||
654 | static int unlock_futex_pi(u32 __user *uaddr, u32 uval) | |
655 | { | |
656 | u32 oldval; | |
657 | ||
658 | /* | |
659 | * There is no waiter, so we unlock the futex. The owner died | |
660 | * bit has not to be preserved here. We are the owner: | |
661 | */ | |
36cf3b5c | 662 | oldval = cmpxchg_futex_value_locked(uaddr, uval, 0); |
c87e2837 IM |
663 | |
664 | if (oldval == -EFAULT) | |
665 | return oldval; | |
666 | if (oldval != uval) | |
667 | return -EAGAIN; | |
668 | ||
669 | return 0; | |
670 | } | |
671 | ||
8b8f319f IM |
672 | /* |
673 | * Express the locking dependencies for lockdep: | |
674 | */ | |
675 | static inline void | |
676 | double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) | |
677 | { | |
678 | if (hb1 <= hb2) { | |
679 | spin_lock(&hb1->lock); | |
680 | if (hb1 < hb2) | |
681 | spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING); | |
682 | } else { /* hb1 > hb2 */ | |
683 | spin_lock(&hb2->lock); | |
684 | spin_lock_nested(&hb1->lock, SINGLE_DEPTH_NESTING); | |
685 | } | |
686 | } | |
687 | ||
1da177e4 LT |
688 | /* |
689 | * Wake up all waiters hashed on the physical page that is mapped | |
690 | * to this virtual address: | |
691 | */ | |
34f01cc1 | 692 | static int futex_wake(u32 __user *uaddr, struct rw_semaphore *fshared, |
cd689985 | 693 | int nr_wake, u32 bitset) |
1da177e4 | 694 | { |
e2970f2f | 695 | struct futex_hash_bucket *hb; |
1da177e4 | 696 | struct futex_q *this, *next; |
ec92d082 | 697 | struct plist_head *head; |
38d47c1b | 698 | union futex_key key = FUTEX_KEY_INIT; |
1da177e4 LT |
699 | int ret; |
700 | ||
cd689985 TG |
701 | if (!bitset) |
702 | return -EINVAL; | |
703 | ||
34f01cc1 | 704 | ret = get_futex_key(uaddr, fshared, &key); |
1da177e4 LT |
705 | if (unlikely(ret != 0)) |
706 | goto out; | |
707 | ||
e2970f2f IM |
708 | hb = hash_futex(&key); |
709 | spin_lock(&hb->lock); | |
710 | head = &hb->chain; | |
1da177e4 | 711 | |
ec92d082 | 712 | plist_for_each_entry_safe(this, next, head, list) { |
1da177e4 | 713 | if (match_futex (&this->key, &key)) { |
ed6f7b10 IM |
714 | if (this->pi_state) { |
715 | ret = -EINVAL; | |
716 | break; | |
717 | } | |
cd689985 TG |
718 | |
719 | /* Check if one of the bits is set in both bitsets */ | |
720 | if (!(this->bitset & bitset)) | |
721 | continue; | |
722 | ||
1da177e4 LT |
723 | wake_futex(this); |
724 | if (++ret >= nr_wake) | |
725 | break; | |
726 | } | |
727 | } | |
728 | ||
e2970f2f | 729 | spin_unlock(&hb->lock); |
1da177e4 | 730 | out: |
38d47c1b | 731 | put_futex_key(fshared, &key); |
1da177e4 LT |
732 | return ret; |
733 | } | |
734 | ||
4732efbe JJ |
735 | /* |
736 | * Wake up all waiters hashed on the physical page that is mapped | |
737 | * to this virtual address: | |
738 | */ | |
e2970f2f | 739 | static int |
34f01cc1 ED |
740 | futex_wake_op(u32 __user *uaddr1, struct rw_semaphore *fshared, |
741 | u32 __user *uaddr2, | |
e2970f2f | 742 | int nr_wake, int nr_wake2, int op) |
4732efbe | 743 | { |
38d47c1b | 744 | union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT; |
e2970f2f | 745 | struct futex_hash_bucket *hb1, *hb2; |
ec92d082 | 746 | struct plist_head *head; |
4732efbe JJ |
747 | struct futex_q *this, *next; |
748 | int ret, op_ret, attempt = 0; | |
749 | ||
750 | retryfull: | |
34f01cc1 | 751 | ret = get_futex_key(uaddr1, fshared, &key1); |
4732efbe JJ |
752 | if (unlikely(ret != 0)) |
753 | goto out; | |
34f01cc1 | 754 | ret = get_futex_key(uaddr2, fshared, &key2); |
4732efbe JJ |
755 | if (unlikely(ret != 0)) |
756 | goto out; | |
757 | ||
e2970f2f IM |
758 | hb1 = hash_futex(&key1); |
759 | hb2 = hash_futex(&key2); | |
4732efbe JJ |
760 | |
761 | retry: | |
8b8f319f | 762 | double_lock_hb(hb1, hb2); |
4732efbe | 763 | |
e2970f2f | 764 | op_ret = futex_atomic_op_inuser(op, uaddr2); |
4732efbe | 765 | if (unlikely(op_ret < 0)) { |
e2970f2f | 766 | u32 dummy; |
4732efbe | 767 | |
e2970f2f IM |
768 | spin_unlock(&hb1->lock); |
769 | if (hb1 != hb2) | |
770 | spin_unlock(&hb2->lock); | |
4732efbe | 771 | |
7ee1dd3f | 772 | #ifndef CONFIG_MMU |
e2970f2f IM |
773 | /* |
774 | * we don't get EFAULT from MMU faults if we don't have an MMU, | |
775 | * but we might get them from range checking | |
776 | */ | |
7ee1dd3f DH |
777 | ret = op_ret; |
778 | goto out; | |
779 | #endif | |
780 | ||
796f8d9b DG |
781 | if (unlikely(op_ret != -EFAULT)) { |
782 | ret = op_ret; | |
783 | goto out; | |
784 | } | |
785 | ||
e2970f2f IM |
786 | /* |
787 | * futex_atomic_op_inuser needs to both read and write | |
4732efbe JJ |
788 | * *(int __user *)uaddr2, but we can't modify it |
789 | * non-atomically. Therefore, if get_user below is not | |
790 | * enough, we need to handle the fault ourselves, while | |
e2970f2f IM |
791 | * still holding the mmap_sem. |
792 | */ | |
4732efbe | 793 | if (attempt++) { |
34f01cc1 | 794 | ret = futex_handle_fault((unsigned long)uaddr2, |
36cf3b5c | 795 | fshared, attempt); |
34f01cc1 | 796 | if (ret) |
4732efbe | 797 | goto out; |
4732efbe JJ |
798 | goto retry; |
799 | } | |
800 | ||
e2970f2f | 801 | ret = get_user(dummy, uaddr2); |
4732efbe JJ |
802 | if (ret) |
803 | return ret; | |
804 | ||
805 | goto retryfull; | |
806 | } | |
807 | ||
e2970f2f | 808 | head = &hb1->chain; |
4732efbe | 809 | |
ec92d082 | 810 | plist_for_each_entry_safe(this, next, head, list) { |
4732efbe JJ |
811 | if (match_futex (&this->key, &key1)) { |
812 | wake_futex(this); | |
813 | if (++ret >= nr_wake) | |
814 | break; | |
815 | } | |
816 | } | |
817 | ||
818 | if (op_ret > 0) { | |
e2970f2f | 819 | head = &hb2->chain; |
4732efbe JJ |
820 | |
821 | op_ret = 0; | |
ec92d082 | 822 | plist_for_each_entry_safe(this, next, head, list) { |
4732efbe JJ |
823 | if (match_futex (&this->key, &key2)) { |
824 | wake_futex(this); | |
825 | if (++op_ret >= nr_wake2) | |
826 | break; | |
827 | } | |
828 | } | |
829 | ret += op_ret; | |
830 | } | |
831 | ||
e2970f2f IM |
832 | spin_unlock(&hb1->lock); |
833 | if (hb1 != hb2) | |
834 | spin_unlock(&hb2->lock); | |
4732efbe | 835 | out: |
38d47c1b PZ |
836 | put_futex_key(fshared, &key2); |
837 | put_futex_key(fshared, &key1); | |
36cf3b5c | 838 | |
4732efbe JJ |
839 | return ret; |
840 | } | |
841 | ||
1da177e4 LT |
842 | /* |
843 | * Requeue all waiters hashed on one physical page to another | |
844 | * physical page. | |
845 | */ | |
34f01cc1 ED |
846 | static int futex_requeue(u32 __user *uaddr1, struct rw_semaphore *fshared, |
847 | u32 __user *uaddr2, | |
e2970f2f | 848 | int nr_wake, int nr_requeue, u32 *cmpval) |
1da177e4 | 849 | { |
38d47c1b | 850 | union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT; |
e2970f2f | 851 | struct futex_hash_bucket *hb1, *hb2; |
ec92d082 | 852 | struct plist_head *head1; |
1da177e4 LT |
853 | struct futex_q *this, *next; |
854 | int ret, drop_count = 0; | |
855 | ||
856 | retry: | |
34f01cc1 | 857 | ret = get_futex_key(uaddr1, fshared, &key1); |
1da177e4 LT |
858 | if (unlikely(ret != 0)) |
859 | goto out; | |
34f01cc1 | 860 | ret = get_futex_key(uaddr2, fshared, &key2); |
1da177e4 LT |
861 | if (unlikely(ret != 0)) |
862 | goto out; | |
863 | ||
e2970f2f IM |
864 | hb1 = hash_futex(&key1); |
865 | hb2 = hash_futex(&key2); | |
1da177e4 | 866 | |
8b8f319f | 867 | double_lock_hb(hb1, hb2); |
1da177e4 | 868 | |
e2970f2f IM |
869 | if (likely(cmpval != NULL)) { |
870 | u32 curval; | |
1da177e4 | 871 | |
e2970f2f | 872 | ret = get_futex_value_locked(&curval, uaddr1); |
1da177e4 LT |
873 | |
874 | if (unlikely(ret)) { | |
e2970f2f IM |
875 | spin_unlock(&hb1->lock); |
876 | if (hb1 != hb2) | |
877 | spin_unlock(&hb2->lock); | |
1da177e4 | 878 | |
e2970f2f | 879 | ret = get_user(curval, uaddr1); |
1da177e4 LT |
880 | |
881 | if (!ret) | |
882 | goto retry; | |
883 | ||
884 | return ret; | |
885 | } | |
e2970f2f | 886 | if (curval != *cmpval) { |
1da177e4 LT |
887 | ret = -EAGAIN; |
888 | goto out_unlock; | |
889 | } | |
890 | } | |
891 | ||
e2970f2f | 892 | head1 = &hb1->chain; |
ec92d082 | 893 | plist_for_each_entry_safe(this, next, head1, list) { |
1da177e4 LT |
894 | if (!match_futex (&this->key, &key1)) |
895 | continue; | |
896 | if (++ret <= nr_wake) { | |
897 | wake_futex(this); | |
898 | } else { | |
59e0e0ac SD |
899 | /* |
900 | * If key1 and key2 hash to the same bucket, no need to | |
901 | * requeue. | |
902 | */ | |
903 | if (likely(head1 != &hb2->chain)) { | |
ec92d082 PP |
904 | plist_del(&this->list, &hb1->chain); |
905 | plist_add(&this->list, &hb2->chain); | |
59e0e0ac | 906 | this->lock_ptr = &hb2->lock; |
ec92d082 PP |
907 | #ifdef CONFIG_DEBUG_PI_LIST |
908 | this->list.plist.lock = &hb2->lock; | |
909 | #endif | |
778e9a9c | 910 | } |
1da177e4 | 911 | this->key = key2; |
9adef58b | 912 | get_futex_key_refs(&key2); |
1da177e4 LT |
913 | drop_count++; |
914 | ||
915 | if (ret - nr_wake >= nr_requeue) | |
916 | break; | |
1da177e4 LT |
917 | } |
918 | } | |
919 | ||
920 | out_unlock: | |
e2970f2f IM |
921 | spin_unlock(&hb1->lock); |
922 | if (hb1 != hb2) | |
923 | spin_unlock(&hb2->lock); | |
1da177e4 | 924 | |
9adef58b | 925 | /* drop_futex_key_refs() must be called outside the spinlocks. */ |
1da177e4 | 926 | while (--drop_count >= 0) |
9adef58b | 927 | drop_futex_key_refs(&key1); |
1da177e4 LT |
928 | |
929 | out: | |
38d47c1b PZ |
930 | put_futex_key(fshared, &key2); |
931 | put_futex_key(fshared, &key1); | |
1da177e4 LT |
932 | return ret; |
933 | } | |
934 | ||
935 | /* The key must be already stored in q->key. */ | |
82af7aca | 936 | static inline struct futex_hash_bucket *queue_lock(struct futex_q *q) |
1da177e4 | 937 | { |
e2970f2f | 938 | struct futex_hash_bucket *hb; |
1da177e4 | 939 | |
1da177e4 LT |
940 | init_waitqueue_head(&q->waiters); |
941 | ||
9adef58b | 942 | get_futex_key_refs(&q->key); |
e2970f2f IM |
943 | hb = hash_futex(&q->key); |
944 | q->lock_ptr = &hb->lock; | |
1da177e4 | 945 | |
e2970f2f IM |
946 | spin_lock(&hb->lock); |
947 | return hb; | |
1da177e4 LT |
948 | } |
949 | ||
82af7aca | 950 | static inline void queue_me(struct futex_q *q, struct futex_hash_bucket *hb) |
1da177e4 | 951 | { |
ec92d082 PP |
952 | int prio; |
953 | ||
954 | /* | |
955 | * The priority used to register this element is | |
956 | * - either the real thread-priority for the real-time threads | |
957 | * (i.e. threads with a priority lower than MAX_RT_PRIO) | |
958 | * - or MAX_RT_PRIO for non-RT threads. | |
959 | * Thus, all RT-threads are woken first in priority order, and | |
960 | * the others are woken last, in FIFO order. | |
961 | */ | |
962 | prio = min(current->normal_prio, MAX_RT_PRIO); | |
963 | ||
964 | plist_node_init(&q->list, prio); | |
965 | #ifdef CONFIG_DEBUG_PI_LIST | |
966 | q->list.plist.lock = &hb->lock; | |
967 | #endif | |
968 | plist_add(&q->list, &hb->chain); | |
c87e2837 | 969 | q->task = current; |
e2970f2f | 970 | spin_unlock(&hb->lock); |
1da177e4 LT |
971 | } |
972 | ||
973 | static inline void | |
e2970f2f | 974 | queue_unlock(struct futex_q *q, struct futex_hash_bucket *hb) |
1da177e4 | 975 | { |
e2970f2f | 976 | spin_unlock(&hb->lock); |
9adef58b | 977 | drop_futex_key_refs(&q->key); |
1da177e4 LT |
978 | } |
979 | ||
980 | /* | |
981 | * queue_me and unqueue_me must be called as a pair, each | |
982 | * exactly once. They are called with the hashed spinlock held. | |
983 | */ | |
984 | ||
1da177e4 LT |
985 | /* Return 1 if we were still queued (ie. 0 means we were woken) */ |
986 | static int unqueue_me(struct futex_q *q) | |
987 | { | |
1da177e4 | 988 | spinlock_t *lock_ptr; |
e2970f2f | 989 | int ret = 0; |
1da177e4 LT |
990 | |
991 | /* In the common case we don't take the spinlock, which is nice. */ | |
992 | retry: | |
993 | lock_ptr = q->lock_ptr; | |
e91467ec | 994 | barrier(); |
c80544dc | 995 | if (lock_ptr != NULL) { |
1da177e4 LT |
996 | spin_lock(lock_ptr); |
997 | /* | |
998 | * q->lock_ptr can change between reading it and | |
999 | * spin_lock(), causing us to take the wrong lock. This | |
1000 | * corrects the race condition. | |
1001 | * | |
1002 | * Reasoning goes like this: if we have the wrong lock, | |
1003 | * q->lock_ptr must have changed (maybe several times) | |
1004 | * between reading it and the spin_lock(). It can | |
1005 | * change again after the spin_lock() but only if it was | |
1006 | * already changed before the spin_lock(). It cannot, | |
1007 | * however, change back to the original value. Therefore | |
1008 | * we can detect whether we acquired the correct lock. | |
1009 | */ | |
1010 | if (unlikely(lock_ptr != q->lock_ptr)) { | |
1011 | spin_unlock(lock_ptr); | |
1012 | goto retry; | |
1013 | } | |
ec92d082 PP |
1014 | WARN_ON(plist_node_empty(&q->list)); |
1015 | plist_del(&q->list, &q->list.plist); | |
c87e2837 IM |
1016 | |
1017 | BUG_ON(q->pi_state); | |
1018 | ||
1da177e4 LT |
1019 | spin_unlock(lock_ptr); |
1020 | ret = 1; | |
1021 | } | |
1022 | ||
9adef58b | 1023 | drop_futex_key_refs(&q->key); |
1da177e4 LT |
1024 | return ret; |
1025 | } | |
1026 | ||
c87e2837 IM |
1027 | /* |
1028 | * PI futexes can not be requeued and must remove themself from the | |
d0aa7a70 PP |
1029 | * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry |
1030 | * and dropped here. | |
c87e2837 | 1031 | */ |
d0aa7a70 | 1032 | static void unqueue_me_pi(struct futex_q *q) |
c87e2837 | 1033 | { |
ec92d082 PP |
1034 | WARN_ON(plist_node_empty(&q->list)); |
1035 | plist_del(&q->list, &q->list.plist); | |
c87e2837 IM |
1036 | |
1037 | BUG_ON(!q->pi_state); | |
1038 | free_pi_state(q->pi_state); | |
1039 | q->pi_state = NULL; | |
1040 | ||
d0aa7a70 | 1041 | spin_unlock(q->lock_ptr); |
c87e2837 | 1042 | |
9adef58b | 1043 | drop_futex_key_refs(&q->key); |
c87e2837 IM |
1044 | } |
1045 | ||
d0aa7a70 | 1046 | /* |
cdf71a10 | 1047 | * Fixup the pi_state owner with the new owner. |
d0aa7a70 | 1048 | * |
778e9a9c AK |
1049 | * Must be called with hash bucket lock held and mm->sem held for non |
1050 | * private futexes. | |
d0aa7a70 | 1051 | */ |
778e9a9c | 1052 | static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q, |
1b7558e4 TG |
1053 | struct task_struct *newowner, |
1054 | struct rw_semaphore *fshared) | |
d0aa7a70 | 1055 | { |
cdf71a10 | 1056 | u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS; |
d0aa7a70 | 1057 | struct futex_pi_state *pi_state = q->pi_state; |
1b7558e4 | 1058 | struct task_struct *oldowner = pi_state->owner; |
d0aa7a70 | 1059 | u32 uval, curval, newval; |
1b7558e4 | 1060 | int ret, attempt = 0; |
d0aa7a70 PP |
1061 | |
1062 | /* Owner died? */ | |
1b7558e4 TG |
1063 | if (!pi_state->owner) |
1064 | newtid |= FUTEX_OWNER_DIED; | |
1065 | ||
1066 | /* | |
1067 | * We are here either because we stole the rtmutex from the | |
1068 | * pending owner or we are the pending owner which failed to | |
1069 | * get the rtmutex. We have to replace the pending owner TID | |
1070 | * in the user space variable. This must be atomic as we have | |
1071 | * to preserve the owner died bit here. | |
1072 | * | |
1073 | * Note: We write the user space value _before_ changing the | |
1074 | * pi_state because we can fault here. Imagine swapped out | |
1075 | * pages or a fork, which was running right before we acquired | |
1076 | * mmap_sem, that marked all the anonymous memory readonly for | |
1077 | * cow. | |
1078 | * | |
1079 | * Modifying pi_state _before_ the user space value would | |
1080 | * leave the pi_state in an inconsistent state when we fault | |
1081 | * here, because we need to drop the hash bucket lock to | |
1082 | * handle the fault. This might be observed in the PID check | |
1083 | * in lookup_pi_state. | |
1084 | */ | |
1085 | retry: | |
1086 | if (get_futex_value_locked(&uval, uaddr)) | |
1087 | goto handle_fault; | |
1088 | ||
1089 | while (1) { | |
1090 | newval = (uval & FUTEX_OWNER_DIED) | newtid; | |
1091 | ||
1092 | curval = cmpxchg_futex_value_locked(uaddr, uval, newval); | |
1093 | ||
1094 | if (curval == -EFAULT) | |
1095 | goto handle_fault; | |
1096 | if (curval == uval) | |
1097 | break; | |
1098 | uval = curval; | |
1099 | } | |
1100 | ||
1101 | /* | |
1102 | * We fixed up user space. Now we need to fix the pi_state | |
1103 | * itself. | |
1104 | */ | |
d0aa7a70 PP |
1105 | if (pi_state->owner != NULL) { |
1106 | spin_lock_irq(&pi_state->owner->pi_lock); | |
1107 | WARN_ON(list_empty(&pi_state->list)); | |
1108 | list_del_init(&pi_state->list); | |
1109 | spin_unlock_irq(&pi_state->owner->pi_lock); | |
1b7558e4 | 1110 | } |
d0aa7a70 | 1111 | |
cdf71a10 | 1112 | pi_state->owner = newowner; |
d0aa7a70 | 1113 | |
cdf71a10 | 1114 | spin_lock_irq(&newowner->pi_lock); |
d0aa7a70 | 1115 | WARN_ON(!list_empty(&pi_state->list)); |
cdf71a10 TG |
1116 | list_add(&pi_state->list, &newowner->pi_state_list); |
1117 | spin_unlock_irq(&newowner->pi_lock); | |
1b7558e4 | 1118 | return 0; |
d0aa7a70 | 1119 | |
d0aa7a70 | 1120 | /* |
1b7558e4 TG |
1121 | * To handle the page fault we need to drop the hash bucket |
1122 | * lock here. That gives the other task (either the pending | |
1123 | * owner itself or the task which stole the rtmutex) the | |
1124 | * chance to try the fixup of the pi_state. So once we are | |
1125 | * back from handling the fault we need to check the pi_state | |
1126 | * after reacquiring the hash bucket lock and before trying to | |
1127 | * do another fixup. When the fixup has been done already we | |
1128 | * simply return. | |
d0aa7a70 | 1129 | */ |
1b7558e4 TG |
1130 | handle_fault: |
1131 | spin_unlock(q->lock_ptr); | |
778e9a9c | 1132 | |
1b7558e4 | 1133 | ret = futex_handle_fault((unsigned long)uaddr, fshared, attempt++); |
778e9a9c | 1134 | |
1b7558e4 | 1135 | spin_lock(q->lock_ptr); |
778e9a9c | 1136 | |
1b7558e4 TG |
1137 | /* |
1138 | * Check if someone else fixed it for us: | |
1139 | */ | |
1140 | if (pi_state->owner != oldowner) | |
1141 | return 0; | |
1142 | ||
1143 | if (ret) | |
1144 | return ret; | |
1145 | ||
1146 | goto retry; | |
d0aa7a70 PP |
1147 | } |
1148 | ||
34f01cc1 ED |
1149 | /* |
1150 | * In case we must use restart_block to restart a futex_wait, | |
ce6bd420 | 1151 | * we encode in the 'flags' shared capability |
34f01cc1 | 1152 | */ |
ce6bd420 | 1153 | #define FLAGS_SHARED 1 |
34f01cc1 | 1154 | |
72c1bbf3 | 1155 | static long futex_wait_restart(struct restart_block *restart); |
36cf3b5c | 1156 | |
34f01cc1 | 1157 | static int futex_wait(u32 __user *uaddr, struct rw_semaphore *fshared, |
cd689985 | 1158 | u32 val, ktime_t *abs_time, u32 bitset) |
1da177e4 | 1159 | { |
c87e2837 IM |
1160 | struct task_struct *curr = current; |
1161 | DECLARE_WAITQUEUE(wait, curr); | |
e2970f2f | 1162 | struct futex_hash_bucket *hb; |
1da177e4 | 1163 | struct futex_q q; |
e2970f2f IM |
1164 | u32 uval; |
1165 | int ret; | |
bd197234 | 1166 | struct hrtimer_sleeper t; |
c19384b5 | 1167 | int rem = 0; |
1da177e4 | 1168 | |
cd689985 TG |
1169 | if (!bitset) |
1170 | return -EINVAL; | |
1171 | ||
c87e2837 | 1172 | q.pi_state = NULL; |
cd689985 | 1173 | q.bitset = bitset; |
1da177e4 | 1174 | retry: |
38d47c1b | 1175 | q.key = FUTEX_KEY_INIT; |
34f01cc1 | 1176 | ret = get_futex_key(uaddr, fshared, &q.key); |
1da177e4 LT |
1177 | if (unlikely(ret != 0)) |
1178 | goto out_release_sem; | |
1179 | ||
82af7aca | 1180 | hb = queue_lock(&q); |
1da177e4 LT |
1181 | |
1182 | /* | |
1183 | * Access the page AFTER the futex is queued. | |
1184 | * Order is important: | |
1185 | * | |
1186 | * Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val); | |
1187 | * Userspace waker: if (cond(var)) { var = new; futex_wake(&var); } | |
1188 | * | |
1189 | * The basic logical guarantee of a futex is that it blocks ONLY | |
1190 | * if cond(var) is known to be true at the time of blocking, for | |
1191 | * any cond. If we queued after testing *uaddr, that would open | |
1192 | * a race condition where we could block indefinitely with | |
1193 | * cond(var) false, which would violate the guarantee. | |
1194 | * | |
1195 | * A consequence is that futex_wait() can return zero and absorb | |
1196 | * a wakeup when *uaddr != val on entry to the syscall. This is | |
1197 | * rare, but normal. | |
1198 | * | |
34f01cc1 ED |
1199 | * for shared futexes, we hold the mmap semaphore, so the mapping |
1200 | * cannot have changed since we looked it up in get_futex_key. | |
1da177e4 | 1201 | */ |
e2970f2f | 1202 | ret = get_futex_value_locked(&uval, uaddr); |
1da177e4 LT |
1203 | |
1204 | if (unlikely(ret)) { | |
e2970f2f | 1205 | queue_unlock(&q, hb); |
1da177e4 | 1206 | |
e2970f2f | 1207 | ret = get_user(uval, uaddr); |
1da177e4 LT |
1208 | |
1209 | if (!ret) | |
1210 | goto retry; | |
1211 | return ret; | |
1212 | } | |
c87e2837 IM |
1213 | ret = -EWOULDBLOCK; |
1214 | if (uval != val) | |
1215 | goto out_unlock_release_sem; | |
1da177e4 LT |
1216 | |
1217 | /* Only actually queue if *uaddr contained val. */ | |
82af7aca | 1218 | queue_me(&q, hb); |
1da177e4 | 1219 | |
1da177e4 LT |
1220 | /* |
1221 | * There might have been scheduling since the queue_me(), as we | |
1222 | * cannot hold a spinlock across the get_user() in case it | |
1223 | * faults, and we cannot just set TASK_INTERRUPTIBLE state when | |
1224 | * queueing ourselves into the futex hash. This code thus has to | |
1225 | * rely on the futex_wake() code removing us from hash when it | |
1226 | * wakes us up. | |
1227 | */ | |
1228 | ||
1229 | /* add_wait_queue is the barrier after __set_current_state. */ | |
1230 | __set_current_state(TASK_INTERRUPTIBLE); | |
1231 | add_wait_queue(&q.waiters, &wait); | |
1232 | /* | |
ec92d082 | 1233 | * !plist_node_empty() is safe here without any lock. |
1da177e4 LT |
1234 | * q.lock_ptr != 0 is not safe, because of ordering against wakeup. |
1235 | */ | |
ec92d082 | 1236 | if (likely(!plist_node_empty(&q.list))) { |
c19384b5 PP |
1237 | if (!abs_time) |
1238 | schedule(); | |
1239 | else { | |
237fc6e7 TG |
1240 | hrtimer_init_on_stack(&t.timer, CLOCK_MONOTONIC, |
1241 | HRTIMER_MODE_ABS); | |
c19384b5 PP |
1242 | hrtimer_init_sleeper(&t, current); |
1243 | t.timer.expires = *abs_time; | |
1244 | ||
237fc6e7 TG |
1245 | hrtimer_start(&t.timer, t.timer.expires, |
1246 | HRTIMER_MODE_ABS); | |
3588a085 PZ |
1247 | if (!hrtimer_active(&t.timer)) |
1248 | t.task = NULL; | |
c19384b5 PP |
1249 | |
1250 | /* | |
1251 | * the timer could have already expired, in which | |
1252 | * case current would be flagged for rescheduling. | |
1253 | * Don't bother calling schedule. | |
1254 | */ | |
1255 | if (likely(t.task)) | |
1256 | schedule(); | |
1257 | ||
1258 | hrtimer_cancel(&t.timer); | |
72c1bbf3 | 1259 | |
c19384b5 PP |
1260 | /* Flag if a timeout occured */ |
1261 | rem = (t.task == NULL); | |
237fc6e7 TG |
1262 | |
1263 | destroy_hrtimer_on_stack(&t.timer); | |
c19384b5 | 1264 | } |
72c1bbf3 | 1265 | } |
1da177e4 LT |
1266 | __set_current_state(TASK_RUNNING); |
1267 | ||
1268 | /* | |
1269 | * NOTE: we don't remove ourselves from the waitqueue because | |
1270 | * we are the only user of it. | |
1271 | */ | |
1272 | ||
1273 | /* If we were woken (and unqueued), we succeeded, whatever. */ | |
1274 | if (!unqueue_me(&q)) | |
1275 | return 0; | |
c19384b5 | 1276 | if (rem) |
1da177e4 | 1277 | return -ETIMEDOUT; |
72c1bbf3 | 1278 | |
e2970f2f IM |
1279 | /* |
1280 | * We expect signal_pending(current), but another thread may | |
1281 | * have handled it for us already. | |
1282 | */ | |
c19384b5 | 1283 | if (!abs_time) |
72c1bbf3 NP |
1284 | return -ERESTARTSYS; |
1285 | else { | |
1286 | struct restart_block *restart; | |
1287 | restart = ¤t_thread_info()->restart_block; | |
1288 | restart->fn = futex_wait_restart; | |
ce6bd420 SR |
1289 | restart->futex.uaddr = (u32 *)uaddr; |
1290 | restart->futex.val = val; | |
1291 | restart->futex.time = abs_time->tv64; | |
cd689985 | 1292 | restart->futex.bitset = bitset; |
ce6bd420 SR |
1293 | restart->futex.flags = 0; |
1294 | ||
34f01cc1 | 1295 | if (fshared) |
ce6bd420 | 1296 | restart->futex.flags |= FLAGS_SHARED; |
72c1bbf3 NP |
1297 | return -ERESTART_RESTARTBLOCK; |
1298 | } | |
1da177e4 | 1299 | |
c87e2837 IM |
1300 | out_unlock_release_sem: |
1301 | queue_unlock(&q, hb); | |
1302 | ||
1da177e4 | 1303 | out_release_sem: |
38d47c1b | 1304 | put_futex_key(fshared, &q.key); |
c87e2837 IM |
1305 | return ret; |
1306 | } | |
1307 | ||
72c1bbf3 NP |
1308 | |
1309 | static long futex_wait_restart(struct restart_block *restart) | |
1310 | { | |
ce6bd420 | 1311 | u32 __user *uaddr = (u32 __user *)restart->futex.uaddr; |
34f01cc1 | 1312 | struct rw_semaphore *fshared = NULL; |
ce6bd420 | 1313 | ktime_t t; |
72c1bbf3 | 1314 | |
ce6bd420 | 1315 | t.tv64 = restart->futex.time; |
72c1bbf3 | 1316 | restart->fn = do_no_restart_syscall; |
ce6bd420 | 1317 | if (restart->futex.flags & FLAGS_SHARED) |
34f01cc1 | 1318 | fshared = ¤t->mm->mmap_sem; |
cd689985 TG |
1319 | return (long)futex_wait(uaddr, fshared, restart->futex.val, &t, |
1320 | restart->futex.bitset); | |
72c1bbf3 NP |
1321 | } |
1322 | ||
1323 | ||
c87e2837 IM |
1324 | /* |
1325 | * Userspace tried a 0 -> TID atomic transition of the futex value | |
1326 | * and failed. The kernel side here does the whole locking operation: | |
1327 | * if there are waiters then it will block, it does PI, etc. (Due to | |
1328 | * races the kernel might see a 0 value of the futex too.) | |
1329 | */ | |
34f01cc1 ED |
1330 | static int futex_lock_pi(u32 __user *uaddr, struct rw_semaphore *fshared, |
1331 | int detect, ktime_t *time, int trylock) | |
c87e2837 | 1332 | { |
c5780e97 | 1333 | struct hrtimer_sleeper timeout, *to = NULL; |
c87e2837 IM |
1334 | struct task_struct *curr = current; |
1335 | struct futex_hash_bucket *hb; | |
1336 | u32 uval, newval, curval; | |
1337 | struct futex_q q; | |
778e9a9c | 1338 | int ret, lock_taken, ownerdied = 0, attempt = 0; |
c87e2837 IM |
1339 | |
1340 | if (refill_pi_state_cache()) | |
1341 | return -ENOMEM; | |
1342 | ||
c19384b5 | 1343 | if (time) { |
c5780e97 | 1344 | to = &timeout; |
237fc6e7 TG |
1345 | hrtimer_init_on_stack(&to->timer, CLOCK_REALTIME, |
1346 | HRTIMER_MODE_ABS); | |
c5780e97 | 1347 | hrtimer_init_sleeper(to, current); |
c19384b5 | 1348 | to->timer.expires = *time; |
c5780e97 TG |
1349 | } |
1350 | ||
c87e2837 IM |
1351 | q.pi_state = NULL; |
1352 | retry: | |
38d47c1b | 1353 | q.key = FUTEX_KEY_INIT; |
34f01cc1 | 1354 | ret = get_futex_key(uaddr, fshared, &q.key); |
c87e2837 IM |
1355 | if (unlikely(ret != 0)) |
1356 | goto out_release_sem; | |
1357 | ||
778e9a9c | 1358 | retry_unlocked: |
82af7aca | 1359 | hb = queue_lock(&q); |
c87e2837 IM |
1360 | |
1361 | retry_locked: | |
778e9a9c | 1362 | ret = lock_taken = 0; |
d0aa7a70 | 1363 | |
c87e2837 IM |
1364 | /* |
1365 | * To avoid races, we attempt to take the lock here again | |
1366 | * (by doing a 0 -> TID atomic cmpxchg), while holding all | |
1367 | * the locks. It will most likely not succeed. | |
1368 | */ | |
b488893a | 1369 | newval = task_pid_vnr(current); |
c87e2837 | 1370 | |
36cf3b5c | 1371 | curval = cmpxchg_futex_value_locked(uaddr, 0, newval); |
c87e2837 IM |
1372 | |
1373 | if (unlikely(curval == -EFAULT)) | |
1374 | goto uaddr_faulted; | |
1375 | ||
778e9a9c AK |
1376 | /* |
1377 | * Detect deadlocks. In case of REQUEUE_PI this is a valid | |
1378 | * situation and we return success to user space. | |
1379 | */ | |
b488893a | 1380 | if (unlikely((curval & FUTEX_TID_MASK) == task_pid_vnr(current))) { |
bd197234 | 1381 | ret = -EDEADLK; |
c87e2837 IM |
1382 | goto out_unlock_release_sem; |
1383 | } | |
1384 | ||
1385 | /* | |
778e9a9c | 1386 | * Surprise - we got the lock. Just return to userspace: |
c87e2837 IM |
1387 | */ |
1388 | if (unlikely(!curval)) | |
1389 | goto out_unlock_release_sem; | |
1390 | ||
1391 | uval = curval; | |
778e9a9c | 1392 | |
d0aa7a70 | 1393 | /* |
778e9a9c AK |
1394 | * Set the WAITERS flag, so the owner will know it has someone |
1395 | * to wake at next unlock | |
d0aa7a70 | 1396 | */ |
778e9a9c AK |
1397 | newval = curval | FUTEX_WAITERS; |
1398 | ||
1399 | /* | |
1400 | * There are two cases, where a futex might have no owner (the | |
bd197234 TG |
1401 | * owner TID is 0): OWNER_DIED. We take over the futex in this |
1402 | * case. We also do an unconditional take over, when the owner | |
1403 | * of the futex died. | |
778e9a9c AK |
1404 | * |
1405 | * This is safe as we are protected by the hash bucket lock ! | |
1406 | */ | |
1407 | if (unlikely(ownerdied || !(curval & FUTEX_TID_MASK))) { | |
bd197234 | 1408 | /* Keep the OWNER_DIED bit */ |
b488893a | 1409 | newval = (curval & ~FUTEX_TID_MASK) | task_pid_vnr(current); |
778e9a9c AK |
1410 | ownerdied = 0; |
1411 | lock_taken = 1; | |
1412 | } | |
c87e2837 | 1413 | |
36cf3b5c | 1414 | curval = cmpxchg_futex_value_locked(uaddr, uval, newval); |
c87e2837 IM |
1415 | |
1416 | if (unlikely(curval == -EFAULT)) | |
1417 | goto uaddr_faulted; | |
1418 | if (unlikely(curval != uval)) | |
1419 | goto retry_locked; | |
1420 | ||
778e9a9c | 1421 | /* |
bd197234 | 1422 | * We took the lock due to owner died take over. |
778e9a9c | 1423 | */ |
bd197234 | 1424 | if (unlikely(lock_taken)) |
d0aa7a70 | 1425 | goto out_unlock_release_sem; |
d0aa7a70 | 1426 | |
c87e2837 IM |
1427 | /* |
1428 | * We dont have the lock. Look up the PI state (or create it if | |
1429 | * we are the first waiter): | |
1430 | */ | |
d0aa7a70 | 1431 | ret = lookup_pi_state(uval, hb, &q.key, &q.pi_state); |
c87e2837 IM |
1432 | |
1433 | if (unlikely(ret)) { | |
778e9a9c | 1434 | switch (ret) { |
c87e2837 | 1435 | |
778e9a9c AK |
1436 | case -EAGAIN: |
1437 | /* | |
1438 | * Task is exiting and we just wait for the | |
1439 | * exit to complete. | |
1440 | */ | |
1441 | queue_unlock(&q, hb); | |
778e9a9c AK |
1442 | cond_resched(); |
1443 | goto retry; | |
c87e2837 | 1444 | |
778e9a9c AK |
1445 | case -ESRCH: |
1446 | /* | |
1447 | * No owner found for this futex. Check if the | |
1448 | * OWNER_DIED bit is set to figure out whether | |
1449 | * this is a robust futex or not. | |
1450 | */ | |
1451 | if (get_futex_value_locked(&curval, uaddr)) | |
c87e2837 | 1452 | goto uaddr_faulted; |
778e9a9c AK |
1453 | |
1454 | /* | |
1455 | * We simply start over in case of a robust | |
1456 | * futex. The code above will take the futex | |
1457 | * and return happy. | |
1458 | */ | |
1459 | if (curval & FUTEX_OWNER_DIED) { | |
1460 | ownerdied = 1; | |
c87e2837 | 1461 | goto retry_locked; |
778e9a9c AK |
1462 | } |
1463 | default: | |
1464 | goto out_unlock_release_sem; | |
c87e2837 | 1465 | } |
c87e2837 IM |
1466 | } |
1467 | ||
1468 | /* | |
1469 | * Only actually queue now that the atomic ops are done: | |
1470 | */ | |
82af7aca | 1471 | queue_me(&q, hb); |
c87e2837 | 1472 | |
c87e2837 IM |
1473 | WARN_ON(!q.pi_state); |
1474 | /* | |
1475 | * Block on the PI mutex: | |
1476 | */ | |
1477 | if (!trylock) | |
1478 | ret = rt_mutex_timed_lock(&q.pi_state->pi_mutex, to, 1); | |
1479 | else { | |
1480 | ret = rt_mutex_trylock(&q.pi_state->pi_mutex); | |
1481 | /* Fixup the trylock return value: */ | |
1482 | ret = ret ? 0 : -EWOULDBLOCK; | |
1483 | } | |
1484 | ||
a99e4e41 | 1485 | spin_lock(q.lock_ptr); |
c87e2837 | 1486 | |
778e9a9c AK |
1487 | if (!ret) { |
1488 | /* | |
1489 | * Got the lock. We might not be the anticipated owner | |
1490 | * if we did a lock-steal - fix up the PI-state in | |
1491 | * that case: | |
1492 | */ | |
1493 | if (q.pi_state->owner != curr) | |
1b7558e4 | 1494 | ret = fixup_pi_state_owner(uaddr, &q, curr, fshared); |
778e9a9c | 1495 | } else { |
c87e2837 IM |
1496 | /* |
1497 | * Catch the rare case, where the lock was released | |
778e9a9c AK |
1498 | * when we were on the way back before we locked the |
1499 | * hash bucket. | |
c87e2837 | 1500 | */ |
cdf71a10 TG |
1501 | if (q.pi_state->owner == curr) { |
1502 | /* | |
1503 | * Try to get the rt_mutex now. This might | |
1504 | * fail as some other task acquired the | |
1505 | * rt_mutex after we removed ourself from the | |
1506 | * rt_mutex waiters list. | |
1507 | */ | |
1508 | if (rt_mutex_trylock(&q.pi_state->pi_mutex)) | |
1509 | ret = 0; | |
1510 | else { | |
1511 | /* | |
1512 | * pi_state is incorrect, some other | |
1513 | * task did a lock steal and we | |
1514 | * returned due to timeout or signal | |
1515 | * without taking the rt_mutex. Too | |
1516 | * late. We can access the | |
1517 | * rt_mutex_owner without locking, as | |
1518 | * the other task is now blocked on | |
1519 | * the hash bucket lock. Fix the state | |
1520 | * up. | |
1521 | */ | |
1522 | struct task_struct *owner; | |
1523 | int res; | |
1524 | ||
1525 | owner = rt_mutex_owner(&q.pi_state->pi_mutex); | |
1b7558e4 TG |
1526 | res = fixup_pi_state_owner(uaddr, &q, owner, |
1527 | fshared); | |
cdf71a10 | 1528 | |
cdf71a10 TG |
1529 | /* propagate -EFAULT, if the fixup failed */ |
1530 | if (res) | |
1531 | ret = res; | |
1532 | } | |
778e9a9c AK |
1533 | } else { |
1534 | /* | |
1535 | * Paranoia check. If we did not take the lock | |
1536 | * in the trylock above, then we should not be | |
1537 | * the owner of the rtmutex, neither the real | |
1538 | * nor the pending one: | |
1539 | */ | |
1540 | if (rt_mutex_owner(&q.pi_state->pi_mutex) == curr) | |
1541 | printk(KERN_ERR "futex_lock_pi: ret = %d " | |
1542 | "pi-mutex: %p pi-state %p\n", ret, | |
1543 | q.pi_state->pi_mutex.owner, | |
1544 | q.pi_state->owner); | |
c87e2837 | 1545 | } |
c87e2837 IM |
1546 | } |
1547 | ||
778e9a9c AK |
1548 | /* Unqueue and drop the lock */ |
1549 | unqueue_me_pi(&q); | |
c87e2837 | 1550 | |
237fc6e7 TG |
1551 | if (to) |
1552 | destroy_hrtimer_on_stack(&to->timer); | |
c5780e97 | 1553 | return ret != -EINTR ? ret : -ERESTARTNOINTR; |
c87e2837 IM |
1554 | |
1555 | out_unlock_release_sem: | |
1556 | queue_unlock(&q, hb); | |
1557 | ||
1558 | out_release_sem: | |
38d47c1b | 1559 | put_futex_key(fshared, &q.key); |
237fc6e7 TG |
1560 | if (to) |
1561 | destroy_hrtimer_on_stack(&to->timer); | |
c87e2837 IM |
1562 | return ret; |
1563 | ||
1564 | uaddr_faulted: | |
1565 | /* | |
1566 | * We have to r/w *(int __user *)uaddr, but we can't modify it | |
1567 | * non-atomically. Therefore, if get_user below is not | |
1568 | * enough, we need to handle the fault ourselves, while | |
1569 | * still holding the mmap_sem. | |
778e9a9c AK |
1570 | * |
1571 | * ... and hb->lock. :-) --ANK | |
c87e2837 | 1572 | */ |
778e9a9c AK |
1573 | queue_unlock(&q, hb); |
1574 | ||
c87e2837 | 1575 | if (attempt++) { |
34f01cc1 ED |
1576 | ret = futex_handle_fault((unsigned long)uaddr, fshared, |
1577 | attempt); | |
1578 | if (ret) | |
778e9a9c AK |
1579 | goto out_release_sem; |
1580 | goto retry_unlocked; | |
c87e2837 IM |
1581 | } |
1582 | ||
c87e2837 IM |
1583 | ret = get_user(uval, uaddr); |
1584 | if (!ret && (uval != -EFAULT)) | |
1585 | goto retry; | |
1586 | ||
237fc6e7 TG |
1587 | if (to) |
1588 | destroy_hrtimer_on_stack(&to->timer); | |
c87e2837 IM |
1589 | return ret; |
1590 | } | |
1591 | ||
c87e2837 IM |
1592 | /* |
1593 | * Userspace attempted a TID -> 0 atomic transition, and failed. | |
1594 | * This is the in-kernel slowpath: we look up the PI state (if any), | |
1595 | * and do the rt-mutex unlock. | |
1596 | */ | |
34f01cc1 | 1597 | static int futex_unlock_pi(u32 __user *uaddr, struct rw_semaphore *fshared) |
c87e2837 IM |
1598 | { |
1599 | struct futex_hash_bucket *hb; | |
1600 | struct futex_q *this, *next; | |
1601 | u32 uval; | |
ec92d082 | 1602 | struct plist_head *head; |
38d47c1b | 1603 | union futex_key key = FUTEX_KEY_INIT; |
c87e2837 IM |
1604 | int ret, attempt = 0; |
1605 | ||
1606 | retry: | |
1607 | if (get_user(uval, uaddr)) | |
1608 | return -EFAULT; | |
1609 | /* | |
1610 | * We release only a lock we actually own: | |
1611 | */ | |
b488893a | 1612 | if ((uval & FUTEX_TID_MASK) != task_pid_vnr(current)) |
c87e2837 | 1613 | return -EPERM; |
c87e2837 | 1614 | |
34f01cc1 | 1615 | ret = get_futex_key(uaddr, fshared, &key); |
c87e2837 IM |
1616 | if (unlikely(ret != 0)) |
1617 | goto out; | |
1618 | ||
1619 | hb = hash_futex(&key); | |
778e9a9c | 1620 | retry_unlocked: |
c87e2837 IM |
1621 | spin_lock(&hb->lock); |
1622 | ||
c87e2837 IM |
1623 | /* |
1624 | * To avoid races, try to do the TID -> 0 atomic transition | |
1625 | * again. If it succeeds then we can return without waking | |
1626 | * anyone else up: | |
1627 | */ | |
36cf3b5c | 1628 | if (!(uval & FUTEX_OWNER_DIED)) |
b488893a | 1629 | uval = cmpxchg_futex_value_locked(uaddr, task_pid_vnr(current), 0); |
36cf3b5c | 1630 | |
c87e2837 IM |
1631 | |
1632 | if (unlikely(uval == -EFAULT)) | |
1633 | goto pi_faulted; | |
1634 | /* | |
1635 | * Rare case: we managed to release the lock atomically, | |
1636 | * no need to wake anyone else up: | |
1637 | */ | |
b488893a | 1638 | if (unlikely(uval == task_pid_vnr(current))) |
c87e2837 IM |
1639 | goto out_unlock; |
1640 | ||
1641 | /* | |
1642 | * Ok, other tasks may need to be woken up - check waiters | |
1643 | * and do the wakeup if necessary: | |
1644 | */ | |
1645 | head = &hb->chain; | |
1646 | ||
ec92d082 | 1647 | plist_for_each_entry_safe(this, next, head, list) { |
c87e2837 IM |
1648 | if (!match_futex (&this->key, &key)) |
1649 | continue; | |
1650 | ret = wake_futex_pi(uaddr, uval, this); | |
1651 | /* | |
1652 | * The atomic access to the futex value | |
1653 | * generated a pagefault, so retry the | |
1654 | * user-access and the wakeup: | |
1655 | */ | |
1656 | if (ret == -EFAULT) | |
1657 | goto pi_faulted; | |
1658 | goto out_unlock; | |
1659 | } | |
1660 | /* | |
1661 | * No waiters - kernel unlocks the futex: | |
1662 | */ | |
e3f2ddea IM |
1663 | if (!(uval & FUTEX_OWNER_DIED)) { |
1664 | ret = unlock_futex_pi(uaddr, uval); | |
1665 | if (ret == -EFAULT) | |
1666 | goto pi_faulted; | |
1667 | } | |
c87e2837 IM |
1668 | |
1669 | out_unlock: | |
1670 | spin_unlock(&hb->lock); | |
1671 | out: | |
38d47c1b | 1672 | put_futex_key(fshared, &key); |
c87e2837 IM |
1673 | |
1674 | return ret; | |
1675 | ||
1676 | pi_faulted: | |
1677 | /* | |
1678 | * We have to r/w *(int __user *)uaddr, but we can't modify it | |
1679 | * non-atomically. Therefore, if get_user below is not | |
1680 | * enough, we need to handle the fault ourselves, while | |
1681 | * still holding the mmap_sem. | |
778e9a9c AK |
1682 | * |
1683 | * ... and hb->lock. --ANK | |
c87e2837 | 1684 | */ |
778e9a9c AK |
1685 | spin_unlock(&hb->lock); |
1686 | ||
c87e2837 | 1687 | if (attempt++) { |
34f01cc1 ED |
1688 | ret = futex_handle_fault((unsigned long)uaddr, fshared, |
1689 | attempt); | |
1690 | if (ret) | |
778e9a9c | 1691 | goto out; |
187226f5 | 1692 | uval = 0; |
778e9a9c | 1693 | goto retry_unlocked; |
c87e2837 IM |
1694 | } |
1695 | ||
c87e2837 IM |
1696 | ret = get_user(uval, uaddr); |
1697 | if (!ret && (uval != -EFAULT)) | |
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 | */ | |
1723 | asmlinkage long | |
1724 | sys_set_robust_list(struct robust_list_head __user *head, | |
1725 | size_t len) | |
1726 | { | |
a0c1e907 TG |
1727 | if (!futex_cmpxchg_enabled) |
1728 | return -ENOSYS; | |
0771dfef IM |
1729 | /* |
1730 | * The kernel knows only one size for now: | |
1731 | */ | |
1732 | if (unlikely(len != sizeof(*head))) | |
1733 | return -EINVAL; | |
1734 | ||
1735 | current->robust_list = head; | |
1736 | ||
1737 | return 0; | |
1738 | } | |
1739 | ||
1740 | /** | |
1741 | * sys_get_robust_list - get the robust-futex list head of a task | |
1742 | * @pid: pid of the process [zero for current task] | |
1743 | * @head_ptr: pointer to a list-head pointer, the kernel fills it in | |
1744 | * @len_ptr: pointer to a length field, the kernel fills in the header size | |
1745 | */ | |
1746 | asmlinkage long | |
ba46df98 | 1747 | sys_get_robust_list(int pid, struct robust_list_head __user * __user *head_ptr, |
0771dfef IM |
1748 | size_t __user *len_ptr) |
1749 | { | |
ba46df98 | 1750 | struct robust_list_head __user *head; |
0771dfef IM |
1751 | unsigned long ret; |
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; | |
1767 | if ((current->euid != p->euid) && (current->euid != p->uid) && | |
1768 | !capable(CAP_SYS_PTRACE)) | |
1769 | goto err_unlock; | |
1770 | head = p->robust_list; | |
aaa2a97e | 1771 | rcu_read_unlock(); |
0771dfef IM |
1772 | } |
1773 | ||
1774 | if (put_user(sizeof(*head), len_ptr)) | |
1775 | return -EFAULT; | |
1776 | return put_user(head, head_ptr); | |
1777 | ||
1778 | err_unlock: | |
aaa2a97e | 1779 | rcu_read_unlock(); |
0771dfef IM |
1780 | |
1781 | return ret; | |
1782 | } | |
1783 | ||
1784 | /* | |
1785 | * Process a futex-list entry, check whether it's owned by the | |
1786 | * dying task, and do notification if so: | |
1787 | */ | |
e3f2ddea | 1788 | int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi) |
0771dfef | 1789 | { |
e3f2ddea | 1790 | u32 uval, nval, mval; |
0771dfef | 1791 | |
8f17d3a5 IM |
1792 | retry: |
1793 | if (get_user(uval, uaddr)) | |
0771dfef IM |
1794 | return -1; |
1795 | ||
b488893a | 1796 | if ((uval & FUTEX_TID_MASK) == task_pid_vnr(curr)) { |
0771dfef IM |
1797 | /* |
1798 | * Ok, this dying thread is truly holding a futex | |
1799 | * of interest. Set the OWNER_DIED bit atomically | |
1800 | * via cmpxchg, and if the value had FUTEX_WAITERS | |
1801 | * set, wake up a waiter (if any). (We have to do a | |
1802 | * futex_wake() even if OWNER_DIED is already set - | |
1803 | * to handle the rare but possible case of recursive | |
1804 | * thread-death.) The rest of the cleanup is done in | |
1805 | * userspace. | |
1806 | */ | |
e3f2ddea IM |
1807 | mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED; |
1808 | nval = futex_atomic_cmpxchg_inatomic(uaddr, uval, mval); | |
1809 | ||
c87e2837 IM |
1810 | if (nval == -EFAULT) |
1811 | return -1; | |
1812 | ||
1813 | if (nval != uval) | |
8f17d3a5 | 1814 | goto retry; |
0771dfef | 1815 | |
e3f2ddea IM |
1816 | /* |
1817 | * Wake robust non-PI futexes here. The wakeup of | |
1818 | * PI futexes happens in exit_pi_state(): | |
1819 | */ | |
36cf3b5c | 1820 | if (!pi && (uval & FUTEX_WAITERS)) |
cd689985 TG |
1821 | futex_wake(uaddr, &curr->mm->mmap_sem, 1, |
1822 | FUTEX_BITSET_MATCH_ANY); | |
0771dfef IM |
1823 | } |
1824 | return 0; | |
1825 | } | |
1826 | ||
e3f2ddea IM |
1827 | /* |
1828 | * Fetch a robust-list pointer. Bit 0 signals PI futexes: | |
1829 | */ | |
1830 | static inline int fetch_robust_entry(struct robust_list __user **entry, | |
ba46df98 AV |
1831 | struct robust_list __user * __user *head, |
1832 | int *pi) | |
e3f2ddea IM |
1833 | { |
1834 | unsigned long uentry; | |
1835 | ||
ba46df98 | 1836 | if (get_user(uentry, (unsigned long __user *)head)) |
e3f2ddea IM |
1837 | return -EFAULT; |
1838 | ||
ba46df98 | 1839 | *entry = (void __user *)(uentry & ~1UL); |
e3f2ddea IM |
1840 | *pi = uentry & 1; |
1841 | ||
1842 | return 0; | |
1843 | } | |
1844 | ||
0771dfef IM |
1845 | /* |
1846 | * Walk curr->robust_list (very carefully, it's a userspace list!) | |
1847 | * and mark any locks found there dead, and notify any waiters. | |
1848 | * | |
1849 | * We silently return on any sign of list-walking problem. | |
1850 | */ | |
1851 | void exit_robust_list(struct task_struct *curr) | |
1852 | { | |
1853 | struct robust_list_head __user *head = curr->robust_list; | |
9f96cb1e MS |
1854 | struct robust_list __user *entry, *next_entry, *pending; |
1855 | unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip; | |
0771dfef | 1856 | unsigned long futex_offset; |
9f96cb1e | 1857 | int rc; |
0771dfef | 1858 | |
a0c1e907 TG |
1859 | if (!futex_cmpxchg_enabled) |
1860 | return; | |
1861 | ||
0771dfef IM |
1862 | /* |
1863 | * Fetch the list head (which was registered earlier, via | |
1864 | * sys_set_robust_list()): | |
1865 | */ | |
e3f2ddea | 1866 | if (fetch_robust_entry(&entry, &head->list.next, &pi)) |
0771dfef IM |
1867 | return; |
1868 | /* | |
1869 | * Fetch the relative futex offset: | |
1870 | */ | |
1871 | if (get_user(futex_offset, &head->futex_offset)) | |
1872 | return; | |
1873 | /* | |
1874 | * Fetch any possibly pending lock-add first, and handle it | |
1875 | * if it exists: | |
1876 | */ | |
e3f2ddea | 1877 | if (fetch_robust_entry(&pending, &head->list_op_pending, &pip)) |
0771dfef | 1878 | return; |
e3f2ddea | 1879 | |
9f96cb1e | 1880 | next_entry = NULL; /* avoid warning with gcc */ |
0771dfef | 1881 | while (entry != &head->list) { |
9f96cb1e MS |
1882 | /* |
1883 | * Fetch the next entry in the list before calling | |
1884 | * handle_futex_death: | |
1885 | */ | |
1886 | rc = fetch_robust_entry(&next_entry, &entry->next, &next_pi); | |
0771dfef IM |
1887 | /* |
1888 | * A pending lock might already be on the list, so | |
c87e2837 | 1889 | * don't process it twice: |
0771dfef IM |
1890 | */ |
1891 | if (entry != pending) | |
ba46df98 | 1892 | if (handle_futex_death((void __user *)entry + futex_offset, |
e3f2ddea | 1893 | curr, pi)) |
0771dfef | 1894 | return; |
9f96cb1e | 1895 | if (rc) |
0771dfef | 1896 | return; |
9f96cb1e MS |
1897 | entry = next_entry; |
1898 | pi = next_pi; | |
0771dfef IM |
1899 | /* |
1900 | * Avoid excessively long or circular lists: | |
1901 | */ | |
1902 | if (!--limit) | |
1903 | break; | |
1904 | ||
1905 | cond_resched(); | |
1906 | } | |
9f96cb1e MS |
1907 | |
1908 | if (pending) | |
1909 | handle_futex_death((void __user *)pending + futex_offset, | |
1910 | curr, pip); | |
0771dfef IM |
1911 | } |
1912 | ||
c19384b5 | 1913 | long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout, |
e2970f2f | 1914 | u32 __user *uaddr2, u32 val2, u32 val3) |
1da177e4 | 1915 | { |
a0c1e907 | 1916 | int ret = -ENOSYS; |
34f01cc1 ED |
1917 | int cmd = op & FUTEX_CMD_MASK; |
1918 | struct rw_semaphore *fshared = NULL; | |
1919 | ||
1920 | if (!(op & FUTEX_PRIVATE_FLAG)) | |
1921 | fshared = ¤t->mm->mmap_sem; | |
1da177e4 | 1922 | |
34f01cc1 | 1923 | switch (cmd) { |
1da177e4 | 1924 | case FUTEX_WAIT: |
cd689985 TG |
1925 | val3 = FUTEX_BITSET_MATCH_ANY; |
1926 | case FUTEX_WAIT_BITSET: | |
1927 | ret = futex_wait(uaddr, fshared, val, timeout, val3); | |
1da177e4 LT |
1928 | break; |
1929 | case FUTEX_WAKE: | |
cd689985 TG |
1930 | val3 = FUTEX_BITSET_MATCH_ANY; |
1931 | case FUTEX_WAKE_BITSET: | |
1932 | ret = futex_wake(uaddr, fshared, val, val3); | |
1da177e4 | 1933 | break; |
1da177e4 | 1934 | case FUTEX_REQUEUE: |
34f01cc1 | 1935 | ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, NULL); |
1da177e4 LT |
1936 | break; |
1937 | case FUTEX_CMP_REQUEUE: | |
34f01cc1 | 1938 | ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, &val3); |
1da177e4 | 1939 | break; |
4732efbe | 1940 | case FUTEX_WAKE_OP: |
34f01cc1 | 1941 | ret = futex_wake_op(uaddr, fshared, uaddr2, val, val2, val3); |
4732efbe | 1942 | break; |
c87e2837 | 1943 | case FUTEX_LOCK_PI: |
a0c1e907 TG |
1944 | if (futex_cmpxchg_enabled) |
1945 | ret = futex_lock_pi(uaddr, fshared, val, timeout, 0); | |
c87e2837 IM |
1946 | break; |
1947 | case FUTEX_UNLOCK_PI: | |
a0c1e907 TG |
1948 | if (futex_cmpxchg_enabled) |
1949 | ret = futex_unlock_pi(uaddr, fshared); | |
c87e2837 IM |
1950 | break; |
1951 | case FUTEX_TRYLOCK_PI: | |
a0c1e907 TG |
1952 | if (futex_cmpxchg_enabled) |
1953 | ret = futex_lock_pi(uaddr, fshared, 0, timeout, 1); | |
c87e2837 | 1954 | break; |
1da177e4 LT |
1955 | default: |
1956 | ret = -ENOSYS; | |
1957 | } | |
1958 | return ret; | |
1959 | } | |
1960 | ||
1961 | ||
e2970f2f | 1962 | asmlinkage long sys_futex(u32 __user *uaddr, int op, u32 val, |
1da177e4 | 1963 | struct timespec __user *utime, u32 __user *uaddr2, |
e2970f2f | 1964 | u32 val3) |
1da177e4 | 1965 | { |
c19384b5 PP |
1966 | struct timespec ts; |
1967 | ktime_t t, *tp = NULL; | |
e2970f2f | 1968 | u32 val2 = 0; |
34f01cc1 | 1969 | int cmd = op & FUTEX_CMD_MASK; |
1da177e4 | 1970 | |
cd689985 TG |
1971 | if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI || |
1972 | cmd == FUTEX_WAIT_BITSET)) { | |
c19384b5 | 1973 | if (copy_from_user(&ts, utime, sizeof(ts)) != 0) |
1da177e4 | 1974 | return -EFAULT; |
c19384b5 | 1975 | if (!timespec_valid(&ts)) |
9741ef96 | 1976 | return -EINVAL; |
c19384b5 PP |
1977 | |
1978 | t = timespec_to_ktime(ts); | |
34f01cc1 | 1979 | if (cmd == FUTEX_WAIT) |
5a7780e7 | 1980 | t = ktime_add_safe(ktime_get(), t); |
c19384b5 | 1981 | tp = &t; |
1da177e4 LT |
1982 | } |
1983 | /* | |
34f01cc1 | 1984 | * requeue parameter in 'utime' if cmd == FUTEX_REQUEUE. |
f54f0986 | 1985 | * number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP. |
1da177e4 | 1986 | */ |
f54f0986 AS |
1987 | if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE || |
1988 | cmd == FUTEX_WAKE_OP) | |
e2970f2f | 1989 | val2 = (u32) (unsigned long) utime; |
1da177e4 | 1990 | |
c19384b5 | 1991 | return do_futex(uaddr, op, val, tp, uaddr2, val2, val3); |
1da177e4 LT |
1992 | } |
1993 | ||
f6d107fb | 1994 | static int __init futex_init(void) |
1da177e4 | 1995 | { |
a0c1e907 | 1996 | u32 curval; |
3e4ab747 | 1997 | int i; |
95362fa9 | 1998 | |
a0c1e907 TG |
1999 | /* |
2000 | * This will fail and we want it. Some arch implementations do | |
2001 | * runtime detection of the futex_atomic_cmpxchg_inatomic() | |
2002 | * functionality. We want to know that before we call in any | |
2003 | * of the complex code paths. Also we want to prevent | |
2004 | * registration of robust lists in that case. NULL is | |
2005 | * guaranteed to fault and we get -EFAULT on functional | |
2006 | * implementation, the non functional ones will return | |
2007 | * -ENOSYS. | |
2008 | */ | |
2009 | curval = cmpxchg_futex_value_locked(NULL, 0, 0); | |
2010 | if (curval == -EFAULT) | |
2011 | futex_cmpxchg_enabled = 1; | |
2012 | ||
3e4ab747 TG |
2013 | for (i = 0; i < ARRAY_SIZE(futex_queues); i++) { |
2014 | plist_head_init(&futex_queues[i].chain, &futex_queues[i].lock); | |
2015 | spin_lock_init(&futex_queues[i].lock); | |
2016 | } | |
2017 | ||
1da177e4 LT |
2018 | return 0; |
2019 | } | |
f6d107fb | 2020 | __initcall(futex_init); |