]>
Commit | Line | Data |
---|---|---|
1da177e4 LT |
1 | /* |
2 | * Fast Userspace Mutexes (which I call "Futexes!"). | |
3 | * (C) Rusty Russell, IBM 2002 | |
4 | * | |
5 | * Generalized futexes, futex requeueing, misc fixes by Ingo Molnar | |
6 | * (C) Copyright 2003 Red Hat Inc, All Rights Reserved | |
7 | * | |
8 | * Removed page pinning, fix privately mapped COW pages and other cleanups | |
9 | * (C) Copyright 2003, 2004 Jamie Lokier | |
10 | * | |
0771dfef IM |
11 | * Robust futex support started by Ingo Molnar |
12 | * (C) Copyright 2006 Red Hat Inc, All Rights Reserved | |
13 | * Thanks to Thomas Gleixner for suggestions, analysis and fixes. | |
14 | * | |
c87e2837 IM |
15 | * PI-futex support started by Ingo Molnar and Thomas Gleixner |
16 | * Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> | |
17 | * Copyright (C) 2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com> | |
18 | * | |
34f01cc1 ED |
19 | * PRIVATE futexes by Eric Dumazet |
20 | * Copyright (C) 2007 Eric Dumazet <dada1@cosmosbay.com> | |
21 | * | |
52400ba9 DH |
22 | * Requeue-PI support by Darren Hart <dvhltc@us.ibm.com> |
23 | * Copyright (C) IBM Corporation, 2009 | |
24 | * Thanks to Thomas Gleixner for conceptual design and careful reviews. | |
25 | * | |
1da177e4 LT |
26 | * Thanks to Ben LaHaise for yelling "hashed waitqueues" loudly |
27 | * enough at me, Linus for the original (flawed) idea, Matthew | |
28 | * Kirkwood for proof-of-concept implementation. | |
29 | * | |
30 | * "The futexes are also cursed." | |
31 | * "But they come in a choice of three flavours!" | |
32 | * | |
33 | * This program is free software; you can redistribute it and/or modify | |
34 | * it under the terms of the GNU General Public License as published by | |
35 | * the Free Software Foundation; either version 2 of the License, or | |
36 | * (at your option) any later version. | |
37 | * | |
38 | * This program is distributed in the hope that it will be useful, | |
39 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
40 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
41 | * GNU General Public License for more details. | |
42 | * | |
43 | * You should have received a copy of the GNU General Public License | |
44 | * along with this program; if not, write to the Free Software | |
45 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA | |
46 | */ | |
47 | #include <linux/slab.h> | |
48 | #include <linux/poll.h> | |
49 | #include <linux/fs.h> | |
50 | #include <linux/file.h> | |
51 | #include <linux/jhash.h> | |
52 | #include <linux/init.h> | |
53 | #include <linux/futex.h> | |
54 | #include <linux/mount.h> | |
55 | #include <linux/pagemap.h> | |
56 | #include <linux/syscalls.h> | |
7ed20e1a | 57 | #include <linux/signal.h> |
9adef58b | 58 | #include <linux/module.h> |
fd5eea42 | 59 | #include <linux/magic.h> |
b488893a PE |
60 | #include <linux/pid.h> |
61 | #include <linux/nsproxy.h> | |
62 | ||
4732efbe | 63 | #include <asm/futex.h> |
1da177e4 | 64 | |
c87e2837 IM |
65 | #include "rtmutex_common.h" |
66 | ||
a0c1e907 TG |
67 | int __read_mostly futex_cmpxchg_enabled; |
68 | ||
1da177e4 LT |
69 | #define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8) |
70 | ||
b41277dc DH |
71 | /* |
72 | * Futex flags used to encode options to functions and preserve them across | |
73 | * restarts. | |
74 | */ | |
75 | #define FLAGS_SHARED 0x01 | |
76 | #define FLAGS_CLOCKRT 0x02 | |
77 | #define FLAGS_HAS_TIMEOUT 0x04 | |
78 | ||
c87e2837 IM |
79 | /* |
80 | * Priority Inheritance state: | |
81 | */ | |
82 | struct futex_pi_state { | |
83 | /* | |
84 | * list of 'owned' pi_state instances - these have to be | |
85 | * cleaned up in do_exit() if the task exits prematurely: | |
86 | */ | |
87 | struct list_head list; | |
88 | ||
89 | /* | |
90 | * The PI object: | |
91 | */ | |
92 | struct rt_mutex pi_mutex; | |
93 | ||
94 | struct task_struct *owner; | |
95 | atomic_t refcount; | |
96 | ||
97 | union futex_key key; | |
98 | }; | |
99 | ||
d8d88fbb DH |
100 | /** |
101 | * struct futex_q - The hashed futex queue entry, one per waiting task | |
fb62db2b | 102 | * @list: priority-sorted list of tasks waiting on this futex |
d8d88fbb DH |
103 | * @task: the task waiting on the futex |
104 | * @lock_ptr: the hash bucket lock | |
105 | * @key: the key the futex is hashed on | |
106 | * @pi_state: optional priority inheritance state | |
107 | * @rt_waiter: rt_waiter storage for use with requeue_pi | |
108 | * @requeue_pi_key: the requeue_pi target futex key | |
109 | * @bitset: bitset for the optional bitmasked wakeup | |
110 | * | |
111 | * We use this hashed waitqueue, instead of a normal wait_queue_t, so | |
1da177e4 LT |
112 | * we can wake only the relevant ones (hashed queues may be shared). |
113 | * | |
114 | * A futex_q has a woken state, just like tasks have TASK_RUNNING. | |
ec92d082 | 115 | * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0. |
fb62db2b | 116 | * The order of wakeup is always to make the first condition true, then |
d8d88fbb DH |
117 | * the second. |
118 | * | |
119 | * PI futexes are typically woken before they are removed from the hash list via | |
120 | * the rt_mutex code. See unqueue_me_pi(). | |
1da177e4 LT |
121 | */ |
122 | struct futex_q { | |
ec92d082 | 123 | struct plist_node list; |
1da177e4 | 124 | |
d8d88fbb | 125 | struct task_struct *task; |
1da177e4 | 126 | spinlock_t *lock_ptr; |
1da177e4 | 127 | union futex_key key; |
c87e2837 | 128 | struct futex_pi_state *pi_state; |
52400ba9 | 129 | struct rt_mutex_waiter *rt_waiter; |
84bc4af5 | 130 | union futex_key *requeue_pi_key; |
cd689985 | 131 | u32 bitset; |
1da177e4 LT |
132 | }; |
133 | ||
134 | /* | |
b2d0994b DH |
135 | * Hash buckets are shared by all the futex_keys that hash to the same |
136 | * location. Each key may have multiple futex_q structures, one for each task | |
137 | * waiting on a futex. | |
1da177e4 LT |
138 | */ |
139 | struct futex_hash_bucket { | |
ec92d082 PP |
140 | spinlock_t lock; |
141 | struct plist_head chain; | |
1da177e4 LT |
142 | }; |
143 | ||
144 | static struct futex_hash_bucket futex_queues[1<<FUTEX_HASHBITS]; | |
145 | ||
1da177e4 LT |
146 | /* |
147 | * We hash on the keys returned from get_futex_key (see below). | |
148 | */ | |
149 | static struct futex_hash_bucket *hash_futex(union futex_key *key) | |
150 | { | |
151 | u32 hash = jhash2((u32*)&key->both.word, | |
152 | (sizeof(key->both.word)+sizeof(key->both.ptr))/4, | |
153 | key->both.offset); | |
154 | return &futex_queues[hash & ((1 << FUTEX_HASHBITS)-1)]; | |
155 | } | |
156 | ||
157 | /* | |
158 | * Return 1 if two futex_keys are equal, 0 otherwise. | |
159 | */ | |
160 | static inline int match_futex(union futex_key *key1, union futex_key *key2) | |
161 | { | |
2bc87203 DH |
162 | return (key1 && key2 |
163 | && key1->both.word == key2->both.word | |
1da177e4 LT |
164 | && key1->both.ptr == key2->both.ptr |
165 | && key1->both.offset == key2->both.offset); | |
166 | } | |
167 | ||
38d47c1b PZ |
168 | /* |
169 | * Take a reference to the resource addressed by a key. | |
170 | * Can be called while holding spinlocks. | |
171 | * | |
172 | */ | |
173 | static void get_futex_key_refs(union futex_key *key) | |
174 | { | |
175 | if (!key->both.ptr) | |
176 | return; | |
177 | ||
178 | switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { | |
179 | case FUT_OFF_INODE: | |
7de9c6ee | 180 | ihold(key->shared.inode); |
38d47c1b PZ |
181 | break; |
182 | case FUT_OFF_MMSHARED: | |
183 | atomic_inc(&key->private.mm->mm_count); | |
184 | break; | |
185 | } | |
186 | } | |
187 | ||
188 | /* | |
189 | * Drop a reference to the resource addressed by a key. | |
190 | * The hash bucket spinlock must not be held. | |
191 | */ | |
192 | static void drop_futex_key_refs(union futex_key *key) | |
193 | { | |
90621c40 DH |
194 | if (!key->both.ptr) { |
195 | /* If we're here then we tried to put a key we failed to get */ | |
196 | WARN_ON_ONCE(1); | |
38d47c1b | 197 | return; |
90621c40 | 198 | } |
38d47c1b PZ |
199 | |
200 | switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { | |
201 | case FUT_OFF_INODE: | |
202 | iput(key->shared.inode); | |
203 | break; | |
204 | case FUT_OFF_MMSHARED: | |
205 | mmdrop(key->private.mm); | |
206 | break; | |
207 | } | |
208 | } | |
209 | ||
34f01cc1 | 210 | /** |
d96ee56c DH |
211 | * get_futex_key() - Get parameters which are the keys for a futex |
212 | * @uaddr: virtual address of the futex | |
213 | * @fshared: 0 for a PROCESS_PRIVATE futex, 1 for PROCESS_SHARED | |
214 | * @key: address where result is stored. | |
34f01cc1 ED |
215 | * |
216 | * Returns a negative error code or 0 | |
217 | * The key words are stored in *key on success. | |
1da177e4 | 218 | * |
f3a43f3f | 219 | * For shared mappings, it's (page->index, vma->vm_file->f_path.dentry->d_inode, |
1da177e4 LT |
220 | * offset_within_page). For private mappings, it's (uaddr, current->mm). |
221 | * We can usually work out the index without swapping in the page. | |
222 | * | |
b2d0994b | 223 | * lock_page() might sleep, the caller should not hold a spinlock. |
1da177e4 | 224 | */ |
64d1304a | 225 | static int |
7485d0d3 | 226 | get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key) |
1da177e4 | 227 | { |
e2970f2f | 228 | unsigned long address = (unsigned long)uaddr; |
1da177e4 | 229 | struct mm_struct *mm = current->mm; |
1da177e4 LT |
230 | struct page *page; |
231 | int err; | |
232 | ||
233 | /* | |
234 | * The futex address must be "naturally" aligned. | |
235 | */ | |
e2970f2f | 236 | key->both.offset = address % PAGE_SIZE; |
34f01cc1 | 237 | if (unlikely((address % sizeof(u32)) != 0)) |
1da177e4 | 238 | return -EINVAL; |
e2970f2f | 239 | address -= key->both.offset; |
1da177e4 | 240 | |
34f01cc1 ED |
241 | /* |
242 | * PROCESS_PRIVATE futexes are fast. | |
243 | * As the mm cannot disappear under us and the 'key' only needs | |
244 | * virtual address, we dont even have to find the underlying vma. | |
245 | * Note : We do have to check 'uaddr' is a valid user address, | |
246 | * but access_ok() should be faster than find_vma() | |
247 | */ | |
248 | if (!fshared) { | |
7485d0d3 | 249 | if (unlikely(!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))) |
34f01cc1 ED |
250 | return -EFAULT; |
251 | key->private.mm = mm; | |
252 | key->private.address = address; | |
42569c39 | 253 | get_futex_key_refs(key); |
34f01cc1 ED |
254 | return 0; |
255 | } | |
1da177e4 | 256 | |
38d47c1b | 257 | again: |
7485d0d3 | 258 | err = get_user_pages_fast(address, 1, 1, &page); |
38d47c1b PZ |
259 | if (err < 0) |
260 | return err; | |
261 | ||
ce2ae53b | 262 | page = compound_head(page); |
38d47c1b PZ |
263 | lock_page(page); |
264 | if (!page->mapping) { | |
265 | unlock_page(page); | |
266 | put_page(page); | |
267 | goto again; | |
268 | } | |
1da177e4 LT |
269 | |
270 | /* | |
271 | * Private mappings are handled in a simple way. | |
272 | * | |
273 | * NOTE: When userspace waits on a MAP_SHARED mapping, even if | |
274 | * it's a read-only handle, it's expected that futexes attach to | |
38d47c1b | 275 | * the object not the particular process. |
1da177e4 | 276 | */ |
38d47c1b PZ |
277 | if (PageAnon(page)) { |
278 | key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */ | |
1da177e4 | 279 | key->private.mm = mm; |
e2970f2f | 280 | key->private.address = address; |
38d47c1b PZ |
281 | } else { |
282 | key->both.offset |= FUT_OFF_INODE; /* inode-based key */ | |
283 | key->shared.inode = page->mapping->host; | |
284 | key->shared.pgoff = page->index; | |
1da177e4 LT |
285 | } |
286 | ||
38d47c1b | 287 | get_futex_key_refs(key); |
1da177e4 | 288 | |
38d47c1b PZ |
289 | unlock_page(page); |
290 | put_page(page); | |
291 | return 0; | |
1da177e4 LT |
292 | } |
293 | ||
ae791a2d | 294 | static inline void put_futex_key(union futex_key *key) |
1da177e4 | 295 | { |
38d47c1b | 296 | drop_futex_key_refs(key); |
1da177e4 LT |
297 | } |
298 | ||
d96ee56c DH |
299 | /** |
300 | * fault_in_user_writeable() - Fault in user address and verify RW access | |
d0725992 TG |
301 | * @uaddr: pointer to faulting user space address |
302 | * | |
303 | * Slow path to fixup the fault we just took in the atomic write | |
304 | * access to @uaddr. | |
305 | * | |
fb62db2b | 306 | * We have no generic implementation of a non-destructive write to the |
d0725992 TG |
307 | * user address. We know that we faulted in the atomic pagefault |
308 | * disabled section so we can as well avoid the #PF overhead by | |
309 | * calling get_user_pages() right away. | |
310 | */ | |
311 | static int fault_in_user_writeable(u32 __user *uaddr) | |
312 | { | |
722d0172 AK |
313 | struct mm_struct *mm = current->mm; |
314 | int ret; | |
315 | ||
316 | down_read(&mm->mmap_sem); | |
317 | ret = get_user_pages(current, mm, (unsigned long)uaddr, | |
318 | 1, 1, 0, NULL, NULL); | |
319 | up_read(&mm->mmap_sem); | |
320 | ||
d0725992 TG |
321 | return ret < 0 ? ret : 0; |
322 | } | |
323 | ||
4b1c486b DH |
324 | /** |
325 | * futex_top_waiter() - Return the highest priority waiter on a futex | |
d96ee56c DH |
326 | * @hb: the hash bucket the futex_q's reside in |
327 | * @key: the futex key (to distinguish it from other futex futex_q's) | |
4b1c486b DH |
328 | * |
329 | * Must be called with the hb lock held. | |
330 | */ | |
331 | static struct futex_q *futex_top_waiter(struct futex_hash_bucket *hb, | |
332 | union futex_key *key) | |
333 | { | |
334 | struct futex_q *this; | |
335 | ||
336 | plist_for_each_entry(this, &hb->chain, list) { | |
337 | if (match_futex(&this->key, key)) | |
338 | return this; | |
339 | } | |
340 | return NULL; | |
341 | } | |
342 | ||
36cf3b5c TG |
343 | static u32 cmpxchg_futex_value_locked(u32 __user *uaddr, u32 uval, u32 newval) |
344 | { | |
345 | u32 curval; | |
346 | ||
347 | pagefault_disable(); | |
348 | curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval); | |
349 | pagefault_enable(); | |
350 | ||
351 | return curval; | |
352 | } | |
353 | ||
354 | static int get_futex_value_locked(u32 *dest, u32 __user *from) | |
1da177e4 LT |
355 | { |
356 | int ret; | |
357 | ||
a866374a | 358 | pagefault_disable(); |
e2970f2f | 359 | ret = __copy_from_user_inatomic(dest, from, sizeof(u32)); |
a866374a | 360 | pagefault_enable(); |
1da177e4 LT |
361 | |
362 | return ret ? -EFAULT : 0; | |
363 | } | |
364 | ||
c87e2837 IM |
365 | |
366 | /* | |
367 | * PI code: | |
368 | */ | |
369 | static int refill_pi_state_cache(void) | |
370 | { | |
371 | struct futex_pi_state *pi_state; | |
372 | ||
373 | if (likely(current->pi_state_cache)) | |
374 | return 0; | |
375 | ||
4668edc3 | 376 | pi_state = kzalloc(sizeof(*pi_state), GFP_KERNEL); |
c87e2837 IM |
377 | |
378 | if (!pi_state) | |
379 | return -ENOMEM; | |
380 | ||
c87e2837 IM |
381 | INIT_LIST_HEAD(&pi_state->list); |
382 | /* pi_mutex gets initialized later */ | |
383 | pi_state->owner = NULL; | |
384 | atomic_set(&pi_state->refcount, 1); | |
38d47c1b | 385 | pi_state->key = FUTEX_KEY_INIT; |
c87e2837 IM |
386 | |
387 | current->pi_state_cache = pi_state; | |
388 | ||
389 | return 0; | |
390 | } | |
391 | ||
392 | static struct futex_pi_state * alloc_pi_state(void) | |
393 | { | |
394 | struct futex_pi_state *pi_state = current->pi_state_cache; | |
395 | ||
396 | WARN_ON(!pi_state); | |
397 | current->pi_state_cache = NULL; | |
398 | ||
399 | return pi_state; | |
400 | } | |
401 | ||
402 | static void free_pi_state(struct futex_pi_state *pi_state) | |
403 | { | |
404 | if (!atomic_dec_and_test(&pi_state->refcount)) | |
405 | return; | |
406 | ||
407 | /* | |
408 | * If pi_state->owner is NULL, the owner is most probably dying | |
409 | * and has cleaned up the pi_state already | |
410 | */ | |
411 | if (pi_state->owner) { | |
1d615482 | 412 | raw_spin_lock_irq(&pi_state->owner->pi_lock); |
c87e2837 | 413 | list_del_init(&pi_state->list); |
1d615482 | 414 | raw_spin_unlock_irq(&pi_state->owner->pi_lock); |
c87e2837 IM |
415 | |
416 | rt_mutex_proxy_unlock(&pi_state->pi_mutex, pi_state->owner); | |
417 | } | |
418 | ||
419 | if (current->pi_state_cache) | |
420 | kfree(pi_state); | |
421 | else { | |
422 | /* | |
423 | * pi_state->list is already empty. | |
424 | * clear pi_state->owner. | |
425 | * refcount is at 0 - put it back to 1. | |
426 | */ | |
427 | pi_state->owner = NULL; | |
428 | atomic_set(&pi_state->refcount, 1); | |
429 | current->pi_state_cache = pi_state; | |
430 | } | |
431 | } | |
432 | ||
433 | /* | |
434 | * Look up the task based on what TID userspace gave us. | |
435 | * We dont trust it. | |
436 | */ | |
437 | static struct task_struct * futex_find_get_task(pid_t pid) | |
438 | { | |
439 | struct task_struct *p; | |
440 | ||
d359b549 | 441 | rcu_read_lock(); |
228ebcbe | 442 | p = find_task_by_vpid(pid); |
7a0ea09a MH |
443 | if (p) |
444 | get_task_struct(p); | |
a06381fe | 445 | |
d359b549 | 446 | rcu_read_unlock(); |
c87e2837 IM |
447 | |
448 | return p; | |
449 | } | |
450 | ||
451 | /* | |
452 | * This task is holding PI mutexes at exit time => bad. | |
453 | * Kernel cleans up PI-state, but userspace is likely hosed. | |
454 | * (Robust-futex cleanup is separate and might save the day for userspace.) | |
455 | */ | |
456 | void exit_pi_state_list(struct task_struct *curr) | |
457 | { | |
c87e2837 IM |
458 | struct list_head *next, *head = &curr->pi_state_list; |
459 | struct futex_pi_state *pi_state; | |
627371d7 | 460 | struct futex_hash_bucket *hb; |
38d47c1b | 461 | union futex_key key = FUTEX_KEY_INIT; |
c87e2837 | 462 | |
a0c1e907 TG |
463 | if (!futex_cmpxchg_enabled) |
464 | return; | |
c87e2837 IM |
465 | /* |
466 | * We are a ZOMBIE and nobody can enqueue itself on | |
467 | * pi_state_list anymore, but we have to be careful | |
627371d7 | 468 | * versus waiters unqueueing themselves: |
c87e2837 | 469 | */ |
1d615482 | 470 | raw_spin_lock_irq(&curr->pi_lock); |
c87e2837 IM |
471 | while (!list_empty(head)) { |
472 | ||
473 | next = head->next; | |
474 | pi_state = list_entry(next, struct futex_pi_state, list); | |
475 | key = pi_state->key; | |
627371d7 | 476 | hb = hash_futex(&key); |
1d615482 | 477 | raw_spin_unlock_irq(&curr->pi_lock); |
c87e2837 | 478 | |
c87e2837 IM |
479 | spin_lock(&hb->lock); |
480 | ||
1d615482 | 481 | raw_spin_lock_irq(&curr->pi_lock); |
627371d7 IM |
482 | /* |
483 | * We dropped the pi-lock, so re-check whether this | |
484 | * task still owns the PI-state: | |
485 | */ | |
c87e2837 IM |
486 | if (head->next != next) { |
487 | spin_unlock(&hb->lock); | |
488 | continue; | |
489 | } | |
490 | ||
c87e2837 | 491 | WARN_ON(pi_state->owner != curr); |
627371d7 IM |
492 | WARN_ON(list_empty(&pi_state->list)); |
493 | list_del_init(&pi_state->list); | |
c87e2837 | 494 | pi_state->owner = NULL; |
1d615482 | 495 | raw_spin_unlock_irq(&curr->pi_lock); |
c87e2837 IM |
496 | |
497 | rt_mutex_unlock(&pi_state->pi_mutex); | |
498 | ||
499 | spin_unlock(&hb->lock); | |
500 | ||
1d615482 | 501 | raw_spin_lock_irq(&curr->pi_lock); |
c87e2837 | 502 | } |
1d615482 | 503 | raw_spin_unlock_irq(&curr->pi_lock); |
c87e2837 IM |
504 | } |
505 | ||
506 | static int | |
d0aa7a70 PP |
507 | lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, |
508 | union futex_key *key, struct futex_pi_state **ps) | |
c87e2837 IM |
509 | { |
510 | struct futex_pi_state *pi_state = NULL; | |
511 | struct futex_q *this, *next; | |
ec92d082 | 512 | struct plist_head *head; |
c87e2837 | 513 | struct task_struct *p; |
778e9a9c | 514 | pid_t pid = uval & FUTEX_TID_MASK; |
c87e2837 IM |
515 | |
516 | head = &hb->chain; | |
517 | ||
ec92d082 | 518 | plist_for_each_entry_safe(this, next, head, list) { |
d0aa7a70 | 519 | if (match_futex(&this->key, key)) { |
c87e2837 IM |
520 | /* |
521 | * Another waiter already exists - bump up | |
522 | * the refcount and return its pi_state: | |
523 | */ | |
524 | pi_state = this->pi_state; | |
06a9ec29 | 525 | /* |
fb62db2b | 526 | * Userspace might have messed up non-PI and PI futexes |
06a9ec29 TG |
527 | */ |
528 | if (unlikely(!pi_state)) | |
529 | return -EINVAL; | |
530 | ||
627371d7 | 531 | WARN_ON(!atomic_read(&pi_state->refcount)); |
59647b6a TG |
532 | |
533 | /* | |
534 | * When pi_state->owner is NULL then the owner died | |
535 | * and another waiter is on the fly. pi_state->owner | |
536 | * is fixed up by the task which acquires | |
537 | * pi_state->rt_mutex. | |
538 | * | |
539 | * We do not check for pid == 0 which can happen when | |
540 | * the owner died and robust_list_exit() cleared the | |
541 | * TID. | |
542 | */ | |
543 | if (pid && pi_state->owner) { | |
544 | /* | |
545 | * Bail out if user space manipulated the | |
546 | * futex value. | |
547 | */ | |
548 | if (pid != task_pid_vnr(pi_state->owner)) | |
549 | return -EINVAL; | |
550 | } | |
627371d7 | 551 | |
c87e2837 | 552 | atomic_inc(&pi_state->refcount); |
d0aa7a70 | 553 | *ps = pi_state; |
c87e2837 IM |
554 | |
555 | return 0; | |
556 | } | |
557 | } | |
558 | ||
559 | /* | |
e3f2ddea | 560 | * We are the first waiter - try to look up the real owner and attach |
778e9a9c | 561 | * the new pi_state to it, but bail out when TID = 0 |
c87e2837 | 562 | */ |
778e9a9c | 563 | if (!pid) |
e3f2ddea | 564 | return -ESRCH; |
c87e2837 | 565 | p = futex_find_get_task(pid); |
7a0ea09a MH |
566 | if (!p) |
567 | return -ESRCH; | |
778e9a9c AK |
568 | |
569 | /* | |
570 | * We need to look at the task state flags to figure out, | |
571 | * whether the task is exiting. To protect against the do_exit | |
572 | * change of the task flags, we do this protected by | |
573 | * p->pi_lock: | |
574 | */ | |
1d615482 | 575 | raw_spin_lock_irq(&p->pi_lock); |
778e9a9c AK |
576 | if (unlikely(p->flags & PF_EXITING)) { |
577 | /* | |
578 | * The task is on the way out. When PF_EXITPIDONE is | |
579 | * set, we know that the task has finished the | |
580 | * cleanup: | |
581 | */ | |
582 | int ret = (p->flags & PF_EXITPIDONE) ? -ESRCH : -EAGAIN; | |
583 | ||
1d615482 | 584 | raw_spin_unlock_irq(&p->pi_lock); |
778e9a9c AK |
585 | put_task_struct(p); |
586 | return ret; | |
587 | } | |
c87e2837 IM |
588 | |
589 | pi_state = alloc_pi_state(); | |
590 | ||
591 | /* | |
592 | * Initialize the pi_mutex in locked state and make 'p' | |
593 | * the owner of it: | |
594 | */ | |
595 | rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p); | |
596 | ||
597 | /* Store the key for possible exit cleanups: */ | |
d0aa7a70 | 598 | pi_state->key = *key; |
c87e2837 | 599 | |
627371d7 | 600 | WARN_ON(!list_empty(&pi_state->list)); |
c87e2837 IM |
601 | list_add(&pi_state->list, &p->pi_state_list); |
602 | pi_state->owner = p; | |
1d615482 | 603 | raw_spin_unlock_irq(&p->pi_lock); |
c87e2837 IM |
604 | |
605 | put_task_struct(p); | |
606 | ||
d0aa7a70 | 607 | *ps = pi_state; |
c87e2837 IM |
608 | |
609 | return 0; | |
610 | } | |
611 | ||
1a52084d | 612 | /** |
d96ee56c | 613 | * futex_lock_pi_atomic() - Atomic work required to acquire a pi aware futex |
bab5bc9e DH |
614 | * @uaddr: the pi futex user address |
615 | * @hb: the pi futex hash bucket | |
616 | * @key: the futex key associated with uaddr and hb | |
617 | * @ps: the pi_state pointer where we store the result of the | |
618 | * lookup | |
619 | * @task: the task to perform the atomic lock work for. This will | |
620 | * be "current" except in the case of requeue pi. | |
621 | * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0) | |
1a52084d DH |
622 | * |
623 | * Returns: | |
624 | * 0 - ready to wait | |
625 | * 1 - acquired the lock | |
626 | * <0 - error | |
627 | * | |
628 | * The hb->lock and futex_key refs shall be held by the caller. | |
629 | */ | |
630 | static int futex_lock_pi_atomic(u32 __user *uaddr, struct futex_hash_bucket *hb, | |
631 | union futex_key *key, | |
632 | struct futex_pi_state **ps, | |
bab5bc9e | 633 | struct task_struct *task, int set_waiters) |
1a52084d DH |
634 | { |
635 | int lock_taken, ret, ownerdied = 0; | |
636 | u32 uval, newval, curval; | |
637 | ||
638 | retry: | |
639 | ret = lock_taken = 0; | |
640 | ||
641 | /* | |
642 | * To avoid races, we attempt to take the lock here again | |
643 | * (by doing a 0 -> TID atomic cmpxchg), while holding all | |
644 | * the locks. It will most likely not succeed. | |
645 | */ | |
646 | newval = task_pid_vnr(task); | |
bab5bc9e DH |
647 | if (set_waiters) |
648 | newval |= FUTEX_WAITERS; | |
1a52084d DH |
649 | |
650 | curval = cmpxchg_futex_value_locked(uaddr, 0, newval); | |
651 | ||
652 | if (unlikely(curval == -EFAULT)) | |
653 | return -EFAULT; | |
654 | ||
655 | /* | |
656 | * Detect deadlocks. | |
657 | */ | |
658 | if ((unlikely((curval & FUTEX_TID_MASK) == task_pid_vnr(task)))) | |
659 | return -EDEADLK; | |
660 | ||
661 | /* | |
662 | * Surprise - we got the lock. Just return to userspace: | |
663 | */ | |
664 | if (unlikely(!curval)) | |
665 | return 1; | |
666 | ||
667 | uval = curval; | |
668 | ||
669 | /* | |
670 | * Set the FUTEX_WAITERS flag, so the owner will know it has someone | |
671 | * to wake at the next unlock. | |
672 | */ | |
673 | newval = curval | FUTEX_WAITERS; | |
674 | ||
675 | /* | |
676 | * There are two cases, where a futex might have no owner (the | |
677 | * owner TID is 0): OWNER_DIED. We take over the futex in this | |
678 | * case. We also do an unconditional take over, when the owner | |
679 | * of the futex died. | |
680 | * | |
681 | * This is safe as we are protected by the hash bucket lock ! | |
682 | */ | |
683 | if (unlikely(ownerdied || !(curval & FUTEX_TID_MASK))) { | |
684 | /* Keep the OWNER_DIED bit */ | |
685 | newval = (curval & ~FUTEX_TID_MASK) | task_pid_vnr(task); | |
686 | ownerdied = 0; | |
687 | lock_taken = 1; | |
688 | } | |
689 | ||
690 | curval = cmpxchg_futex_value_locked(uaddr, uval, newval); | |
691 | ||
692 | if (unlikely(curval == -EFAULT)) | |
693 | return -EFAULT; | |
694 | if (unlikely(curval != uval)) | |
695 | goto retry; | |
696 | ||
697 | /* | |
698 | * We took the lock due to owner died take over. | |
699 | */ | |
700 | if (unlikely(lock_taken)) | |
701 | return 1; | |
702 | ||
703 | /* | |
704 | * We dont have the lock. Look up the PI state (or create it if | |
705 | * we are the first waiter): | |
706 | */ | |
707 | ret = lookup_pi_state(uval, hb, key, ps); | |
708 | ||
709 | if (unlikely(ret)) { | |
710 | switch (ret) { | |
711 | case -ESRCH: | |
712 | /* | |
713 | * No owner found for this futex. Check if the | |
714 | * OWNER_DIED bit is set to figure out whether | |
715 | * this is a robust futex or not. | |
716 | */ | |
717 | if (get_futex_value_locked(&curval, uaddr)) | |
718 | return -EFAULT; | |
719 | ||
720 | /* | |
721 | * We simply start over in case of a robust | |
722 | * futex. The code above will take the futex | |
723 | * and return happy. | |
724 | */ | |
725 | if (curval & FUTEX_OWNER_DIED) { | |
726 | ownerdied = 1; | |
727 | goto retry; | |
728 | } | |
729 | default: | |
730 | break; | |
731 | } | |
732 | } | |
733 | ||
734 | return ret; | |
735 | } | |
736 | ||
1da177e4 LT |
737 | /* |
738 | * The hash bucket lock must be held when this is called. | |
739 | * Afterwards, the futex_q must not be accessed. | |
740 | */ | |
741 | static void wake_futex(struct futex_q *q) | |
742 | { | |
f1a11e05 TG |
743 | struct task_struct *p = q->task; |
744 | ||
1da177e4 | 745 | /* |
f1a11e05 | 746 | * We set q->lock_ptr = NULL _before_ we wake up the task. If |
fb62db2b RD |
747 | * a non-futex wake up happens on another CPU then the task |
748 | * might exit and p would dereference a non-existing task | |
f1a11e05 TG |
749 | * struct. Prevent this by holding a reference on p across the |
750 | * wake up. | |
1da177e4 | 751 | */ |
f1a11e05 TG |
752 | get_task_struct(p); |
753 | ||
754 | plist_del(&q->list, &q->list.plist); | |
1da177e4 | 755 | /* |
f1a11e05 TG |
756 | * The waiting task can free the futex_q as soon as |
757 | * q->lock_ptr = NULL is written, without taking any locks. A | |
758 | * memory barrier is required here to prevent the following | |
759 | * store to lock_ptr from getting ahead of the plist_del. | |
1da177e4 | 760 | */ |
ccdea2f8 | 761 | smp_wmb(); |
1da177e4 | 762 | q->lock_ptr = NULL; |
f1a11e05 TG |
763 | |
764 | wake_up_state(p, TASK_NORMAL); | |
765 | put_task_struct(p); | |
1da177e4 LT |
766 | } |
767 | ||
c87e2837 IM |
768 | static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this) |
769 | { | |
770 | struct task_struct *new_owner; | |
771 | struct futex_pi_state *pi_state = this->pi_state; | |
772 | u32 curval, newval; | |
773 | ||
774 | if (!pi_state) | |
775 | return -EINVAL; | |
776 | ||
51246bfd TG |
777 | /* |
778 | * If current does not own the pi_state then the futex is | |
779 | * inconsistent and user space fiddled with the futex value. | |
780 | */ | |
781 | if (pi_state->owner != current) | |
782 | return -EINVAL; | |
783 | ||
d209d74d | 784 | raw_spin_lock(&pi_state->pi_mutex.wait_lock); |
c87e2837 IM |
785 | new_owner = rt_mutex_next_owner(&pi_state->pi_mutex); |
786 | ||
787 | /* | |
788 | * This happens when we have stolen the lock and the original | |
789 | * pending owner did not enqueue itself back on the rt_mutex. | |
790 | * Thats not a tragedy. We know that way, that a lock waiter | |
791 | * is on the fly. We make the futex_q waiter the pending owner. | |
792 | */ | |
793 | if (!new_owner) | |
794 | new_owner = this->task; | |
795 | ||
796 | /* | |
797 | * We pass it to the next owner. (The WAITERS bit is always | |
798 | * kept enabled while there is PI state around. We must also | |
799 | * preserve the owner died bit.) | |
800 | */ | |
e3f2ddea | 801 | if (!(uval & FUTEX_OWNER_DIED)) { |
778e9a9c AK |
802 | int ret = 0; |
803 | ||
b488893a | 804 | newval = FUTEX_WAITERS | task_pid_vnr(new_owner); |
e3f2ddea | 805 | |
36cf3b5c | 806 | curval = cmpxchg_futex_value_locked(uaddr, uval, newval); |
778e9a9c | 807 | |
e3f2ddea | 808 | if (curval == -EFAULT) |
778e9a9c | 809 | ret = -EFAULT; |
cde898fa | 810 | else if (curval != uval) |
778e9a9c AK |
811 | ret = -EINVAL; |
812 | if (ret) { | |
d209d74d | 813 | raw_spin_unlock(&pi_state->pi_mutex.wait_lock); |
778e9a9c AK |
814 | return ret; |
815 | } | |
e3f2ddea | 816 | } |
c87e2837 | 817 | |
1d615482 | 818 | raw_spin_lock_irq(&pi_state->owner->pi_lock); |
627371d7 IM |
819 | WARN_ON(list_empty(&pi_state->list)); |
820 | list_del_init(&pi_state->list); | |
1d615482 | 821 | raw_spin_unlock_irq(&pi_state->owner->pi_lock); |
627371d7 | 822 | |
1d615482 | 823 | raw_spin_lock_irq(&new_owner->pi_lock); |
627371d7 | 824 | WARN_ON(!list_empty(&pi_state->list)); |
c87e2837 IM |
825 | list_add(&pi_state->list, &new_owner->pi_state_list); |
826 | pi_state->owner = new_owner; | |
1d615482 | 827 | raw_spin_unlock_irq(&new_owner->pi_lock); |
627371d7 | 828 | |
d209d74d | 829 | raw_spin_unlock(&pi_state->pi_mutex.wait_lock); |
c87e2837 IM |
830 | rt_mutex_unlock(&pi_state->pi_mutex); |
831 | ||
832 | return 0; | |
833 | } | |
834 | ||
835 | static int unlock_futex_pi(u32 __user *uaddr, u32 uval) | |
836 | { | |
837 | u32 oldval; | |
838 | ||
839 | /* | |
840 | * There is no waiter, so we unlock the futex. The owner died | |
841 | * bit has not to be preserved here. We are the owner: | |
842 | */ | |
36cf3b5c | 843 | oldval = cmpxchg_futex_value_locked(uaddr, uval, 0); |
c87e2837 IM |
844 | |
845 | if (oldval == -EFAULT) | |
846 | return oldval; | |
847 | if (oldval != uval) | |
848 | return -EAGAIN; | |
849 | ||
850 | return 0; | |
851 | } | |
852 | ||
8b8f319f IM |
853 | /* |
854 | * Express the locking dependencies for lockdep: | |
855 | */ | |
856 | static inline void | |
857 | double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) | |
858 | { | |
859 | if (hb1 <= hb2) { | |
860 | spin_lock(&hb1->lock); | |
861 | if (hb1 < hb2) | |
862 | spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING); | |
863 | } else { /* hb1 > hb2 */ | |
864 | spin_lock(&hb2->lock); | |
865 | spin_lock_nested(&hb1->lock, SINGLE_DEPTH_NESTING); | |
866 | } | |
867 | } | |
868 | ||
5eb3dc62 DH |
869 | static inline void |
870 | double_unlock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) | |
871 | { | |
f061d351 | 872 | spin_unlock(&hb1->lock); |
88f502fe IM |
873 | if (hb1 != hb2) |
874 | spin_unlock(&hb2->lock); | |
5eb3dc62 DH |
875 | } |
876 | ||
1da177e4 | 877 | /* |
b2d0994b | 878 | * Wake up waiters matching bitset queued on this futex (uaddr). |
1da177e4 | 879 | */ |
b41277dc DH |
880 | static int |
881 | futex_wake(u32 __user *uaddr, unsigned int flags, int nr_wake, u32 bitset) | |
1da177e4 | 882 | { |
e2970f2f | 883 | struct futex_hash_bucket *hb; |
1da177e4 | 884 | struct futex_q *this, *next; |
ec92d082 | 885 | struct plist_head *head; |
38d47c1b | 886 | union futex_key key = FUTEX_KEY_INIT; |
1da177e4 LT |
887 | int ret; |
888 | ||
cd689985 TG |
889 | if (!bitset) |
890 | return -EINVAL; | |
891 | ||
b41277dc | 892 | ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key); |
1da177e4 LT |
893 | if (unlikely(ret != 0)) |
894 | goto out; | |
895 | ||
e2970f2f IM |
896 | hb = hash_futex(&key); |
897 | spin_lock(&hb->lock); | |
898 | head = &hb->chain; | |
1da177e4 | 899 | |
ec92d082 | 900 | plist_for_each_entry_safe(this, next, head, list) { |
1da177e4 | 901 | if (match_futex (&this->key, &key)) { |
52400ba9 | 902 | if (this->pi_state || this->rt_waiter) { |
ed6f7b10 IM |
903 | ret = -EINVAL; |
904 | break; | |
905 | } | |
cd689985 TG |
906 | |
907 | /* Check if one of the bits is set in both bitsets */ | |
908 | if (!(this->bitset & bitset)) | |
909 | continue; | |
910 | ||
1da177e4 LT |
911 | wake_futex(this); |
912 | if (++ret >= nr_wake) | |
913 | break; | |
914 | } | |
915 | } | |
916 | ||
e2970f2f | 917 | spin_unlock(&hb->lock); |
ae791a2d | 918 | put_futex_key(&key); |
42d35d48 | 919 | out: |
1da177e4 LT |
920 | return ret; |
921 | } | |
922 | ||
4732efbe JJ |
923 | /* |
924 | * Wake up all waiters hashed on the physical page that is mapped | |
925 | * to this virtual address: | |
926 | */ | |
e2970f2f | 927 | static int |
b41277dc | 928 | futex_wake_op(u32 __user *uaddr1, unsigned int flags, u32 __user *uaddr2, |
e2970f2f | 929 | int nr_wake, int nr_wake2, int op) |
4732efbe | 930 | { |
38d47c1b | 931 | union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT; |
e2970f2f | 932 | struct futex_hash_bucket *hb1, *hb2; |
ec92d082 | 933 | struct plist_head *head; |
4732efbe | 934 | struct futex_q *this, *next; |
e4dc5b7a | 935 | int ret, op_ret; |
4732efbe | 936 | |
e4dc5b7a | 937 | retry: |
b41277dc | 938 | ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1); |
4732efbe JJ |
939 | if (unlikely(ret != 0)) |
940 | goto out; | |
b41277dc | 941 | ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2); |
4732efbe | 942 | if (unlikely(ret != 0)) |
42d35d48 | 943 | goto out_put_key1; |
4732efbe | 944 | |
e2970f2f IM |
945 | hb1 = hash_futex(&key1); |
946 | hb2 = hash_futex(&key2); | |
4732efbe | 947 | |
e4dc5b7a | 948 | retry_private: |
eaaea803 | 949 | double_lock_hb(hb1, hb2); |
e2970f2f | 950 | op_ret = futex_atomic_op_inuser(op, uaddr2); |
4732efbe | 951 | if (unlikely(op_ret < 0)) { |
4732efbe | 952 | |
5eb3dc62 | 953 | double_unlock_hb(hb1, hb2); |
4732efbe | 954 | |
7ee1dd3f | 955 | #ifndef CONFIG_MMU |
e2970f2f IM |
956 | /* |
957 | * we don't get EFAULT from MMU faults if we don't have an MMU, | |
958 | * but we might get them from range checking | |
959 | */ | |
7ee1dd3f | 960 | ret = op_ret; |
42d35d48 | 961 | goto out_put_keys; |
7ee1dd3f DH |
962 | #endif |
963 | ||
796f8d9b DG |
964 | if (unlikely(op_ret != -EFAULT)) { |
965 | ret = op_ret; | |
42d35d48 | 966 | goto out_put_keys; |
796f8d9b DG |
967 | } |
968 | ||
d0725992 | 969 | ret = fault_in_user_writeable(uaddr2); |
4732efbe | 970 | if (ret) |
de87fcc1 | 971 | goto out_put_keys; |
4732efbe | 972 | |
b41277dc | 973 | if (!(flags & FLAGS_SHARED)) |
e4dc5b7a DH |
974 | goto retry_private; |
975 | ||
ae791a2d TG |
976 | put_futex_key(&key2); |
977 | put_futex_key(&key1); | |
e4dc5b7a | 978 | goto retry; |
4732efbe JJ |
979 | } |
980 | ||
e2970f2f | 981 | head = &hb1->chain; |
4732efbe | 982 | |
ec92d082 | 983 | plist_for_each_entry_safe(this, next, head, list) { |
4732efbe JJ |
984 | if (match_futex (&this->key, &key1)) { |
985 | wake_futex(this); | |
986 | if (++ret >= nr_wake) | |
987 | break; | |
988 | } | |
989 | } | |
990 | ||
991 | if (op_ret > 0) { | |
e2970f2f | 992 | head = &hb2->chain; |
4732efbe JJ |
993 | |
994 | op_ret = 0; | |
ec92d082 | 995 | plist_for_each_entry_safe(this, next, head, list) { |
4732efbe JJ |
996 | if (match_futex (&this->key, &key2)) { |
997 | wake_futex(this); | |
998 | if (++op_ret >= nr_wake2) | |
999 | break; | |
1000 | } | |
1001 | } | |
1002 | ret += op_ret; | |
1003 | } | |
1004 | ||
5eb3dc62 | 1005 | double_unlock_hb(hb1, hb2); |
42d35d48 | 1006 | out_put_keys: |
ae791a2d | 1007 | put_futex_key(&key2); |
42d35d48 | 1008 | out_put_key1: |
ae791a2d | 1009 | put_futex_key(&key1); |
42d35d48 | 1010 | out: |
4732efbe JJ |
1011 | return ret; |
1012 | } | |
1013 | ||
9121e478 DH |
1014 | /** |
1015 | * requeue_futex() - Requeue a futex_q from one hb to another | |
1016 | * @q: the futex_q to requeue | |
1017 | * @hb1: the source hash_bucket | |
1018 | * @hb2: the target hash_bucket | |
1019 | * @key2: the new key for the requeued futex_q | |
1020 | */ | |
1021 | static inline | |
1022 | void requeue_futex(struct futex_q *q, struct futex_hash_bucket *hb1, | |
1023 | struct futex_hash_bucket *hb2, union futex_key *key2) | |
1024 | { | |
1025 | ||
1026 | /* | |
1027 | * If key1 and key2 hash to the same bucket, no need to | |
1028 | * requeue. | |
1029 | */ | |
1030 | if (likely(&hb1->chain != &hb2->chain)) { | |
1031 | plist_del(&q->list, &hb1->chain); | |
1032 | plist_add(&q->list, &hb2->chain); | |
1033 | q->lock_ptr = &hb2->lock; | |
1034 | #ifdef CONFIG_DEBUG_PI_LIST | |
a2672459 | 1035 | q->list.plist.spinlock = &hb2->lock; |
9121e478 DH |
1036 | #endif |
1037 | } | |
1038 | get_futex_key_refs(key2); | |
1039 | q->key = *key2; | |
1040 | } | |
1041 | ||
52400ba9 DH |
1042 | /** |
1043 | * requeue_pi_wake_futex() - Wake a task that acquired the lock during requeue | |
d96ee56c DH |
1044 | * @q: the futex_q |
1045 | * @key: the key of the requeue target futex | |
1046 | * @hb: the hash_bucket of the requeue target futex | |
52400ba9 DH |
1047 | * |
1048 | * During futex_requeue, with requeue_pi=1, it is possible to acquire the | |
1049 | * target futex if it is uncontended or via a lock steal. Set the futex_q key | |
1050 | * to the requeue target futex so the waiter can detect the wakeup on the right | |
1051 | * futex, but remove it from the hb and NULL the rt_waiter so it can detect | |
beda2c7e DH |
1052 | * atomic lock acquisition. Set the q->lock_ptr to the requeue target hb->lock |
1053 | * to protect access to the pi_state to fixup the owner later. Must be called | |
1054 | * with both q->lock_ptr and hb->lock held. | |
52400ba9 DH |
1055 | */ |
1056 | static inline | |
beda2c7e DH |
1057 | void requeue_pi_wake_futex(struct futex_q *q, union futex_key *key, |
1058 | struct futex_hash_bucket *hb) | |
52400ba9 | 1059 | { |
52400ba9 DH |
1060 | get_futex_key_refs(key); |
1061 | q->key = *key; | |
1062 | ||
1063 | WARN_ON(plist_node_empty(&q->list)); | |
1064 | plist_del(&q->list, &q->list.plist); | |
1065 | ||
1066 | WARN_ON(!q->rt_waiter); | |
1067 | q->rt_waiter = NULL; | |
1068 | ||
beda2c7e DH |
1069 | q->lock_ptr = &hb->lock; |
1070 | #ifdef CONFIG_DEBUG_PI_LIST | |
a2672459 | 1071 | q->list.plist.spinlock = &hb->lock; |
beda2c7e DH |
1072 | #endif |
1073 | ||
f1a11e05 | 1074 | wake_up_state(q->task, TASK_NORMAL); |
52400ba9 DH |
1075 | } |
1076 | ||
1077 | /** | |
1078 | * futex_proxy_trylock_atomic() - Attempt an atomic lock for the top waiter | |
bab5bc9e DH |
1079 | * @pifutex: the user address of the to futex |
1080 | * @hb1: the from futex hash bucket, must be locked by the caller | |
1081 | * @hb2: the to futex hash bucket, must be locked by the caller | |
1082 | * @key1: the from futex key | |
1083 | * @key2: the to futex key | |
1084 | * @ps: address to store the pi_state pointer | |
1085 | * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0) | |
52400ba9 DH |
1086 | * |
1087 | * Try and get the lock on behalf of the top waiter if we can do it atomically. | |
bab5bc9e DH |
1088 | * Wake the top waiter if we succeed. If the caller specified set_waiters, |
1089 | * then direct futex_lock_pi_atomic() to force setting the FUTEX_WAITERS bit. | |
1090 | * hb1 and hb2 must be held by the caller. | |
52400ba9 DH |
1091 | * |
1092 | * Returns: | |
1093 | * 0 - failed to acquire the lock atomicly | |
1094 | * 1 - acquired the lock | |
1095 | * <0 - error | |
1096 | */ | |
1097 | static int futex_proxy_trylock_atomic(u32 __user *pifutex, | |
1098 | struct futex_hash_bucket *hb1, | |
1099 | struct futex_hash_bucket *hb2, | |
1100 | union futex_key *key1, union futex_key *key2, | |
bab5bc9e | 1101 | struct futex_pi_state **ps, int set_waiters) |
52400ba9 | 1102 | { |
bab5bc9e | 1103 | struct futex_q *top_waiter = NULL; |
52400ba9 DH |
1104 | u32 curval; |
1105 | int ret; | |
1106 | ||
1107 | if (get_futex_value_locked(&curval, pifutex)) | |
1108 | return -EFAULT; | |
1109 | ||
bab5bc9e DH |
1110 | /* |
1111 | * Find the top_waiter and determine if there are additional waiters. | |
1112 | * If the caller intends to requeue more than 1 waiter to pifutex, | |
1113 | * force futex_lock_pi_atomic() to set the FUTEX_WAITERS bit now, | |
1114 | * as we have means to handle the possible fault. If not, don't set | |
1115 | * the bit unecessarily as it will force the subsequent unlock to enter | |
1116 | * the kernel. | |
1117 | */ | |
52400ba9 DH |
1118 | top_waiter = futex_top_waiter(hb1, key1); |
1119 | ||
1120 | /* There are no waiters, nothing for us to do. */ | |
1121 | if (!top_waiter) | |
1122 | return 0; | |
1123 | ||
84bc4af5 DH |
1124 | /* Ensure we requeue to the expected futex. */ |
1125 | if (!match_futex(top_waiter->requeue_pi_key, key2)) | |
1126 | return -EINVAL; | |
1127 | ||
52400ba9 | 1128 | /* |
bab5bc9e DH |
1129 | * Try to take the lock for top_waiter. Set the FUTEX_WAITERS bit in |
1130 | * the contended case or if set_waiters is 1. The pi_state is returned | |
1131 | * in ps in contended cases. | |
52400ba9 | 1132 | */ |
bab5bc9e DH |
1133 | ret = futex_lock_pi_atomic(pifutex, hb2, key2, ps, top_waiter->task, |
1134 | set_waiters); | |
52400ba9 | 1135 | if (ret == 1) |
beda2c7e | 1136 | requeue_pi_wake_futex(top_waiter, key2, hb2); |
52400ba9 DH |
1137 | |
1138 | return ret; | |
1139 | } | |
1140 | ||
1141 | /** | |
1142 | * futex_requeue() - Requeue waiters from uaddr1 to uaddr2 | |
fb62db2b | 1143 | * @uaddr1: source futex user address |
b41277dc | 1144 | * @flags: futex flags (FLAGS_SHARED, etc.) |
fb62db2b RD |
1145 | * @uaddr2: target futex user address |
1146 | * @nr_wake: number of waiters to wake (must be 1 for requeue_pi) | |
1147 | * @nr_requeue: number of waiters to requeue (0-INT_MAX) | |
1148 | * @cmpval: @uaddr1 expected value (or %NULL) | |
1149 | * @requeue_pi: if we are attempting to requeue from a non-pi futex to a | |
b41277dc | 1150 | * pi futex (pi to pi requeue is not supported) |
52400ba9 DH |
1151 | * |
1152 | * Requeue waiters on uaddr1 to uaddr2. In the requeue_pi case, try to acquire | |
1153 | * uaddr2 atomically on behalf of the top waiter. | |
1154 | * | |
1155 | * Returns: | |
1156 | * >=0 - on success, the number of tasks requeued or woken | |
1157 | * <0 - on error | |
1da177e4 | 1158 | */ |
b41277dc DH |
1159 | static int futex_requeue(u32 __user *uaddr1, unsigned int flags, |
1160 | u32 __user *uaddr2, int nr_wake, int nr_requeue, | |
1161 | u32 *cmpval, int requeue_pi) | |
1da177e4 | 1162 | { |
38d47c1b | 1163 | union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT; |
52400ba9 DH |
1164 | int drop_count = 0, task_count = 0, ret; |
1165 | struct futex_pi_state *pi_state = NULL; | |
e2970f2f | 1166 | struct futex_hash_bucket *hb1, *hb2; |
ec92d082 | 1167 | struct plist_head *head1; |
1da177e4 | 1168 | struct futex_q *this, *next; |
52400ba9 DH |
1169 | u32 curval2; |
1170 | ||
1171 | if (requeue_pi) { | |
1172 | /* | |
1173 | * requeue_pi requires a pi_state, try to allocate it now | |
1174 | * without any locks in case it fails. | |
1175 | */ | |
1176 | if (refill_pi_state_cache()) | |
1177 | return -ENOMEM; | |
1178 | /* | |
1179 | * requeue_pi must wake as many tasks as it can, up to nr_wake | |
1180 | * + nr_requeue, since it acquires the rt_mutex prior to | |
1181 | * returning to userspace, so as to not leave the rt_mutex with | |
1182 | * waiters and no owner. However, second and third wake-ups | |
1183 | * cannot be predicted as they involve race conditions with the | |
1184 | * first wake and a fault while looking up the pi_state. Both | |
1185 | * pthread_cond_signal() and pthread_cond_broadcast() should | |
1186 | * use nr_wake=1. | |
1187 | */ | |
1188 | if (nr_wake != 1) | |
1189 | return -EINVAL; | |
1190 | } | |
1da177e4 | 1191 | |
42d35d48 | 1192 | retry: |
52400ba9 DH |
1193 | if (pi_state != NULL) { |
1194 | /* | |
1195 | * We will have to lookup the pi_state again, so free this one | |
1196 | * to keep the accounting correct. | |
1197 | */ | |
1198 | free_pi_state(pi_state); | |
1199 | pi_state = NULL; | |
1200 | } | |
1201 | ||
b41277dc | 1202 | ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1); |
1da177e4 LT |
1203 | if (unlikely(ret != 0)) |
1204 | goto out; | |
b41277dc | 1205 | ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2); |
1da177e4 | 1206 | if (unlikely(ret != 0)) |
42d35d48 | 1207 | goto out_put_key1; |
1da177e4 | 1208 | |
e2970f2f IM |
1209 | hb1 = hash_futex(&key1); |
1210 | hb2 = hash_futex(&key2); | |
1da177e4 | 1211 | |
e4dc5b7a | 1212 | retry_private: |
8b8f319f | 1213 | double_lock_hb(hb1, hb2); |
1da177e4 | 1214 | |
e2970f2f IM |
1215 | if (likely(cmpval != NULL)) { |
1216 | u32 curval; | |
1da177e4 | 1217 | |
e2970f2f | 1218 | ret = get_futex_value_locked(&curval, uaddr1); |
1da177e4 LT |
1219 | |
1220 | if (unlikely(ret)) { | |
5eb3dc62 | 1221 | double_unlock_hb(hb1, hb2); |
1da177e4 | 1222 | |
e2970f2f | 1223 | ret = get_user(curval, uaddr1); |
e4dc5b7a DH |
1224 | if (ret) |
1225 | goto out_put_keys; | |
1da177e4 | 1226 | |
b41277dc | 1227 | if (!(flags & FLAGS_SHARED)) |
e4dc5b7a | 1228 | goto retry_private; |
1da177e4 | 1229 | |
ae791a2d TG |
1230 | put_futex_key(&key2); |
1231 | put_futex_key(&key1); | |
e4dc5b7a | 1232 | goto retry; |
1da177e4 | 1233 | } |
e2970f2f | 1234 | if (curval != *cmpval) { |
1da177e4 LT |
1235 | ret = -EAGAIN; |
1236 | goto out_unlock; | |
1237 | } | |
1238 | } | |
1239 | ||
52400ba9 | 1240 | if (requeue_pi && (task_count - nr_wake < nr_requeue)) { |
bab5bc9e DH |
1241 | /* |
1242 | * Attempt to acquire uaddr2 and wake the top waiter. If we | |
1243 | * intend to requeue waiters, force setting the FUTEX_WAITERS | |
1244 | * bit. We force this here where we are able to easily handle | |
1245 | * faults rather in the requeue loop below. | |
1246 | */ | |
52400ba9 | 1247 | ret = futex_proxy_trylock_atomic(uaddr2, hb1, hb2, &key1, |
bab5bc9e | 1248 | &key2, &pi_state, nr_requeue); |
52400ba9 DH |
1249 | |
1250 | /* | |
1251 | * At this point the top_waiter has either taken uaddr2 or is | |
1252 | * waiting on it. If the former, then the pi_state will not | |
1253 | * exist yet, look it up one more time to ensure we have a | |
1254 | * reference to it. | |
1255 | */ | |
1256 | if (ret == 1) { | |
1257 | WARN_ON(pi_state); | |
89061d3d | 1258 | drop_count++; |
52400ba9 DH |
1259 | task_count++; |
1260 | ret = get_futex_value_locked(&curval2, uaddr2); | |
1261 | if (!ret) | |
1262 | ret = lookup_pi_state(curval2, hb2, &key2, | |
1263 | &pi_state); | |
1264 | } | |
1265 | ||
1266 | switch (ret) { | |
1267 | case 0: | |
1268 | break; | |
1269 | case -EFAULT: | |
1270 | double_unlock_hb(hb1, hb2); | |
ae791a2d TG |
1271 | put_futex_key(&key2); |
1272 | put_futex_key(&key1); | |
d0725992 | 1273 | ret = fault_in_user_writeable(uaddr2); |
52400ba9 DH |
1274 | if (!ret) |
1275 | goto retry; | |
1276 | goto out; | |
1277 | case -EAGAIN: | |
1278 | /* The owner was exiting, try again. */ | |
1279 | double_unlock_hb(hb1, hb2); | |
ae791a2d TG |
1280 | put_futex_key(&key2); |
1281 | put_futex_key(&key1); | |
52400ba9 DH |
1282 | cond_resched(); |
1283 | goto retry; | |
1284 | default: | |
1285 | goto out_unlock; | |
1286 | } | |
1287 | } | |
1288 | ||
e2970f2f | 1289 | head1 = &hb1->chain; |
ec92d082 | 1290 | plist_for_each_entry_safe(this, next, head1, list) { |
52400ba9 DH |
1291 | if (task_count - nr_wake >= nr_requeue) |
1292 | break; | |
1293 | ||
1294 | if (!match_futex(&this->key, &key1)) | |
1da177e4 | 1295 | continue; |
52400ba9 | 1296 | |
392741e0 DH |
1297 | /* |
1298 | * FUTEX_WAIT_REQEUE_PI and FUTEX_CMP_REQUEUE_PI should always | |
1299 | * be paired with each other and no other futex ops. | |
1300 | */ | |
1301 | if ((requeue_pi && !this->rt_waiter) || | |
1302 | (!requeue_pi && this->rt_waiter)) { | |
1303 | ret = -EINVAL; | |
1304 | break; | |
1305 | } | |
52400ba9 DH |
1306 | |
1307 | /* | |
1308 | * Wake nr_wake waiters. For requeue_pi, if we acquired the | |
1309 | * lock, we already woke the top_waiter. If not, it will be | |
1310 | * woken by futex_unlock_pi(). | |
1311 | */ | |
1312 | if (++task_count <= nr_wake && !requeue_pi) { | |
1da177e4 | 1313 | wake_futex(this); |
52400ba9 DH |
1314 | continue; |
1315 | } | |
1da177e4 | 1316 | |
84bc4af5 DH |
1317 | /* Ensure we requeue to the expected futex for requeue_pi. */ |
1318 | if (requeue_pi && !match_futex(this->requeue_pi_key, &key2)) { | |
1319 | ret = -EINVAL; | |
1320 | break; | |
1321 | } | |
1322 | ||
52400ba9 DH |
1323 | /* |
1324 | * Requeue nr_requeue waiters and possibly one more in the case | |
1325 | * of requeue_pi if we couldn't acquire the lock atomically. | |
1326 | */ | |
1327 | if (requeue_pi) { | |
1328 | /* Prepare the waiter to take the rt_mutex. */ | |
1329 | atomic_inc(&pi_state->refcount); | |
1330 | this->pi_state = pi_state; | |
1331 | ret = rt_mutex_start_proxy_lock(&pi_state->pi_mutex, | |
1332 | this->rt_waiter, | |
1333 | this->task, 1); | |
1334 | if (ret == 1) { | |
1335 | /* We got the lock. */ | |
beda2c7e | 1336 | requeue_pi_wake_futex(this, &key2, hb2); |
89061d3d | 1337 | drop_count++; |
52400ba9 DH |
1338 | continue; |
1339 | } else if (ret) { | |
1340 | /* -EDEADLK */ | |
1341 | this->pi_state = NULL; | |
1342 | free_pi_state(pi_state); | |
1343 | goto out_unlock; | |
1344 | } | |
1da177e4 | 1345 | } |
52400ba9 DH |
1346 | requeue_futex(this, hb1, hb2, &key2); |
1347 | drop_count++; | |
1da177e4 LT |
1348 | } |
1349 | ||
1350 | out_unlock: | |
5eb3dc62 | 1351 | double_unlock_hb(hb1, hb2); |
1da177e4 | 1352 | |
cd84a42f DH |
1353 | /* |
1354 | * drop_futex_key_refs() must be called outside the spinlocks. During | |
1355 | * the requeue we moved futex_q's from the hash bucket at key1 to the | |
1356 | * one at key2 and updated their key pointer. We no longer need to | |
1357 | * hold the references to key1. | |
1358 | */ | |
1da177e4 | 1359 | while (--drop_count >= 0) |
9adef58b | 1360 | drop_futex_key_refs(&key1); |
1da177e4 | 1361 | |
42d35d48 | 1362 | out_put_keys: |
ae791a2d | 1363 | put_futex_key(&key2); |
42d35d48 | 1364 | out_put_key1: |
ae791a2d | 1365 | put_futex_key(&key1); |
42d35d48 | 1366 | out: |
52400ba9 DH |
1367 | if (pi_state != NULL) |
1368 | free_pi_state(pi_state); | |
1369 | return ret ? ret : task_count; | |
1da177e4 LT |
1370 | } |
1371 | ||
1372 | /* The key must be already stored in q->key. */ | |
82af7aca | 1373 | static inline struct futex_hash_bucket *queue_lock(struct futex_q *q) |
15e408cd | 1374 | __acquires(&hb->lock) |
1da177e4 | 1375 | { |
e2970f2f | 1376 | struct futex_hash_bucket *hb; |
1da177e4 | 1377 | |
e2970f2f IM |
1378 | hb = hash_futex(&q->key); |
1379 | q->lock_ptr = &hb->lock; | |
1da177e4 | 1380 | |
e2970f2f IM |
1381 | spin_lock(&hb->lock); |
1382 | return hb; | |
1da177e4 LT |
1383 | } |
1384 | ||
d40d65c8 DH |
1385 | static inline void |
1386 | queue_unlock(struct futex_q *q, struct futex_hash_bucket *hb) | |
15e408cd | 1387 | __releases(&hb->lock) |
d40d65c8 DH |
1388 | { |
1389 | spin_unlock(&hb->lock); | |
d40d65c8 DH |
1390 | } |
1391 | ||
1392 | /** | |
1393 | * queue_me() - Enqueue the futex_q on the futex_hash_bucket | |
1394 | * @q: The futex_q to enqueue | |
1395 | * @hb: The destination hash bucket | |
1396 | * | |
1397 | * The hb->lock must be held by the caller, and is released here. A call to | |
1398 | * queue_me() is typically paired with exactly one call to unqueue_me(). The | |
1399 | * exceptions involve the PI related operations, which may use unqueue_me_pi() | |
1400 | * or nothing if the unqueue is done as part of the wake process and the unqueue | |
1401 | * state is implicit in the state of woken task (see futex_wait_requeue_pi() for | |
1402 | * an example). | |
1403 | */ | |
82af7aca | 1404 | static inline void queue_me(struct futex_q *q, struct futex_hash_bucket *hb) |
15e408cd | 1405 | __releases(&hb->lock) |
1da177e4 | 1406 | { |
ec92d082 PP |
1407 | int prio; |
1408 | ||
1409 | /* | |
1410 | * The priority used to register this element is | |
1411 | * - either the real thread-priority for the real-time threads | |
1412 | * (i.e. threads with a priority lower than MAX_RT_PRIO) | |
1413 | * - or MAX_RT_PRIO for non-RT threads. | |
1414 | * Thus, all RT-threads are woken first in priority order, and | |
1415 | * the others are woken last, in FIFO order. | |
1416 | */ | |
1417 | prio = min(current->normal_prio, MAX_RT_PRIO); | |
1418 | ||
1419 | plist_node_init(&q->list, prio); | |
1420 | #ifdef CONFIG_DEBUG_PI_LIST | |
a2672459 | 1421 | q->list.plist.spinlock = &hb->lock; |
ec92d082 PP |
1422 | #endif |
1423 | plist_add(&q->list, &hb->chain); | |
c87e2837 | 1424 | q->task = current; |
e2970f2f | 1425 | spin_unlock(&hb->lock); |
1da177e4 LT |
1426 | } |
1427 | ||
d40d65c8 DH |
1428 | /** |
1429 | * unqueue_me() - Remove the futex_q from its futex_hash_bucket | |
1430 | * @q: The futex_q to unqueue | |
1431 | * | |
1432 | * The q->lock_ptr must not be held by the caller. A call to unqueue_me() must | |
1433 | * be paired with exactly one earlier call to queue_me(). | |
1434 | * | |
1435 | * Returns: | |
1436 | * 1 - if the futex_q was still queued (and we removed unqueued it) | |
1437 | * 0 - if the futex_q was already removed by the waking thread | |
1da177e4 | 1438 | */ |
1da177e4 LT |
1439 | static int unqueue_me(struct futex_q *q) |
1440 | { | |
1da177e4 | 1441 | spinlock_t *lock_ptr; |
e2970f2f | 1442 | int ret = 0; |
1da177e4 LT |
1443 | |
1444 | /* In the common case we don't take the spinlock, which is nice. */ | |
42d35d48 | 1445 | retry: |
1da177e4 | 1446 | lock_ptr = q->lock_ptr; |
e91467ec | 1447 | barrier(); |
c80544dc | 1448 | if (lock_ptr != NULL) { |
1da177e4 LT |
1449 | spin_lock(lock_ptr); |
1450 | /* | |
1451 | * q->lock_ptr can change between reading it and | |
1452 | * spin_lock(), causing us to take the wrong lock. This | |
1453 | * corrects the race condition. | |
1454 | * | |
1455 | * Reasoning goes like this: if we have the wrong lock, | |
1456 | * q->lock_ptr must have changed (maybe several times) | |
1457 | * between reading it and the spin_lock(). It can | |
1458 | * change again after the spin_lock() but only if it was | |
1459 | * already changed before the spin_lock(). It cannot, | |
1460 | * however, change back to the original value. Therefore | |
1461 | * we can detect whether we acquired the correct lock. | |
1462 | */ | |
1463 | if (unlikely(lock_ptr != q->lock_ptr)) { | |
1464 | spin_unlock(lock_ptr); | |
1465 | goto retry; | |
1466 | } | |
ec92d082 PP |
1467 | WARN_ON(plist_node_empty(&q->list)); |
1468 | plist_del(&q->list, &q->list.plist); | |
c87e2837 IM |
1469 | |
1470 | BUG_ON(q->pi_state); | |
1471 | ||
1da177e4 LT |
1472 | spin_unlock(lock_ptr); |
1473 | ret = 1; | |
1474 | } | |
1475 | ||
9adef58b | 1476 | drop_futex_key_refs(&q->key); |
1da177e4 LT |
1477 | return ret; |
1478 | } | |
1479 | ||
c87e2837 IM |
1480 | /* |
1481 | * PI futexes can not be requeued and must remove themself from the | |
d0aa7a70 PP |
1482 | * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry |
1483 | * and dropped here. | |
c87e2837 | 1484 | */ |
d0aa7a70 | 1485 | static void unqueue_me_pi(struct futex_q *q) |
15e408cd | 1486 | __releases(q->lock_ptr) |
c87e2837 | 1487 | { |
ec92d082 PP |
1488 | WARN_ON(plist_node_empty(&q->list)); |
1489 | plist_del(&q->list, &q->list.plist); | |
c87e2837 IM |
1490 | |
1491 | BUG_ON(!q->pi_state); | |
1492 | free_pi_state(q->pi_state); | |
1493 | q->pi_state = NULL; | |
1494 | ||
d0aa7a70 | 1495 | spin_unlock(q->lock_ptr); |
c87e2837 IM |
1496 | } |
1497 | ||
d0aa7a70 | 1498 | /* |
cdf71a10 | 1499 | * Fixup the pi_state owner with the new owner. |
d0aa7a70 | 1500 | * |
778e9a9c AK |
1501 | * Must be called with hash bucket lock held and mm->sem held for non |
1502 | * private futexes. | |
d0aa7a70 | 1503 | */ |
778e9a9c | 1504 | static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q, |
ae791a2d | 1505 | struct task_struct *newowner) |
d0aa7a70 | 1506 | { |
cdf71a10 | 1507 | u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS; |
d0aa7a70 | 1508 | struct futex_pi_state *pi_state = q->pi_state; |
1b7558e4 | 1509 | struct task_struct *oldowner = pi_state->owner; |
d0aa7a70 | 1510 | u32 uval, curval, newval; |
e4dc5b7a | 1511 | int ret; |
d0aa7a70 PP |
1512 | |
1513 | /* Owner died? */ | |
1b7558e4 TG |
1514 | if (!pi_state->owner) |
1515 | newtid |= FUTEX_OWNER_DIED; | |
1516 | ||
1517 | /* | |
1518 | * We are here either because we stole the rtmutex from the | |
1519 | * pending owner or we are the pending owner which failed to | |
1520 | * get the rtmutex. We have to replace the pending owner TID | |
1521 | * in the user space variable. This must be atomic as we have | |
1522 | * to preserve the owner died bit here. | |
1523 | * | |
b2d0994b DH |
1524 | * Note: We write the user space value _before_ changing the pi_state |
1525 | * because we can fault here. Imagine swapped out pages or a fork | |
1526 | * that marked all the anonymous memory readonly for cow. | |
1b7558e4 TG |
1527 | * |
1528 | * Modifying pi_state _before_ the user space value would | |
1529 | * leave the pi_state in an inconsistent state when we fault | |
1530 | * here, because we need to drop the hash bucket lock to | |
1531 | * handle the fault. This might be observed in the PID check | |
1532 | * in lookup_pi_state. | |
1533 | */ | |
1534 | retry: | |
1535 | if (get_futex_value_locked(&uval, uaddr)) | |
1536 | goto handle_fault; | |
1537 | ||
1538 | while (1) { | |
1539 | newval = (uval & FUTEX_OWNER_DIED) | newtid; | |
1540 | ||
1541 | curval = cmpxchg_futex_value_locked(uaddr, uval, newval); | |
1542 | ||
1543 | if (curval == -EFAULT) | |
1544 | goto handle_fault; | |
1545 | if (curval == uval) | |
1546 | break; | |
1547 | uval = curval; | |
1548 | } | |
1549 | ||
1550 | /* | |
1551 | * We fixed up user space. Now we need to fix the pi_state | |
1552 | * itself. | |
1553 | */ | |
d0aa7a70 | 1554 | if (pi_state->owner != NULL) { |
1d615482 | 1555 | raw_spin_lock_irq(&pi_state->owner->pi_lock); |
d0aa7a70 PP |
1556 | WARN_ON(list_empty(&pi_state->list)); |
1557 | list_del_init(&pi_state->list); | |
1d615482 | 1558 | raw_spin_unlock_irq(&pi_state->owner->pi_lock); |
1b7558e4 | 1559 | } |
d0aa7a70 | 1560 | |
cdf71a10 | 1561 | pi_state->owner = newowner; |
d0aa7a70 | 1562 | |
1d615482 | 1563 | raw_spin_lock_irq(&newowner->pi_lock); |
d0aa7a70 | 1564 | WARN_ON(!list_empty(&pi_state->list)); |
cdf71a10 | 1565 | list_add(&pi_state->list, &newowner->pi_state_list); |
1d615482 | 1566 | raw_spin_unlock_irq(&newowner->pi_lock); |
1b7558e4 | 1567 | return 0; |
d0aa7a70 | 1568 | |
d0aa7a70 | 1569 | /* |
1b7558e4 TG |
1570 | * To handle the page fault we need to drop the hash bucket |
1571 | * lock here. That gives the other task (either the pending | |
1572 | * owner itself or the task which stole the rtmutex) the | |
1573 | * chance to try the fixup of the pi_state. So once we are | |
1574 | * back from handling the fault we need to check the pi_state | |
1575 | * after reacquiring the hash bucket lock and before trying to | |
1576 | * do another fixup. When the fixup has been done already we | |
1577 | * simply return. | |
d0aa7a70 | 1578 | */ |
1b7558e4 TG |
1579 | handle_fault: |
1580 | spin_unlock(q->lock_ptr); | |
778e9a9c | 1581 | |
d0725992 | 1582 | ret = fault_in_user_writeable(uaddr); |
778e9a9c | 1583 | |
1b7558e4 | 1584 | spin_lock(q->lock_ptr); |
778e9a9c | 1585 | |
1b7558e4 TG |
1586 | /* |
1587 | * Check if someone else fixed it for us: | |
1588 | */ | |
1589 | if (pi_state->owner != oldowner) | |
1590 | return 0; | |
1591 | ||
1592 | if (ret) | |
1593 | return ret; | |
1594 | ||
1595 | goto retry; | |
d0aa7a70 PP |
1596 | } |
1597 | ||
72c1bbf3 | 1598 | static long futex_wait_restart(struct restart_block *restart); |
36cf3b5c | 1599 | |
dd973998 DH |
1600 | /** |
1601 | * fixup_owner() - Post lock pi_state and corner case management | |
1602 | * @uaddr: user address of the futex | |
dd973998 DH |
1603 | * @q: futex_q (contains pi_state and access to the rt_mutex) |
1604 | * @locked: if the attempt to take the rt_mutex succeeded (1) or not (0) | |
1605 | * | |
1606 | * After attempting to lock an rt_mutex, this function is called to cleanup | |
1607 | * the pi_state owner as well as handle race conditions that may allow us to | |
1608 | * acquire the lock. Must be called with the hb lock held. | |
1609 | * | |
1610 | * Returns: | |
1611 | * 1 - success, lock taken | |
1612 | * 0 - success, lock not taken | |
1613 | * <0 - on error (-EFAULT) | |
1614 | */ | |
ae791a2d | 1615 | static int fixup_owner(u32 __user *uaddr, struct futex_q *q, int locked) |
dd973998 DH |
1616 | { |
1617 | struct task_struct *owner; | |
1618 | int ret = 0; | |
1619 | ||
1620 | if (locked) { | |
1621 | /* | |
1622 | * Got the lock. We might not be the anticipated owner if we | |
1623 | * did a lock-steal - fix up the PI-state in that case: | |
1624 | */ | |
1625 | if (q->pi_state->owner != current) | |
ae791a2d | 1626 | ret = fixup_pi_state_owner(uaddr, q, current); |
dd973998 DH |
1627 | goto out; |
1628 | } | |
1629 | ||
1630 | /* | |
1631 | * Catch the rare case, where the lock was released when we were on the | |
1632 | * way back before we locked the hash bucket. | |
1633 | */ | |
1634 | if (q->pi_state->owner == current) { | |
1635 | /* | |
1636 | * Try to get the rt_mutex now. This might fail as some other | |
1637 | * task acquired the rt_mutex after we removed ourself from the | |
1638 | * rt_mutex waiters list. | |
1639 | */ | |
1640 | if (rt_mutex_trylock(&q->pi_state->pi_mutex)) { | |
1641 | locked = 1; | |
1642 | goto out; | |
1643 | } | |
1644 | ||
1645 | /* | |
1646 | * pi_state is incorrect, some other task did a lock steal and | |
1647 | * we returned due to timeout or signal without taking the | |
1648 | * rt_mutex. Too late. We can access the rt_mutex_owner without | |
1649 | * locking, as the other task is now blocked on the hash bucket | |
1650 | * lock. Fix the state up. | |
1651 | */ | |
1652 | owner = rt_mutex_owner(&q->pi_state->pi_mutex); | |
ae791a2d | 1653 | ret = fixup_pi_state_owner(uaddr, q, owner); |
dd973998 DH |
1654 | goto out; |
1655 | } | |
1656 | ||
1657 | /* | |
1658 | * Paranoia check. If we did not take the lock, then we should not be | |
1659 | * the owner, nor the pending owner, of the rt_mutex. | |
1660 | */ | |
1661 | if (rt_mutex_owner(&q->pi_state->pi_mutex) == current) | |
1662 | printk(KERN_ERR "fixup_owner: ret = %d pi-mutex: %p " | |
1663 | "pi-state %p\n", ret, | |
1664 | q->pi_state->pi_mutex.owner, | |
1665 | q->pi_state->owner); | |
1666 | ||
1667 | out: | |
1668 | return ret ? ret : locked; | |
1669 | } | |
1670 | ||
ca5f9524 DH |
1671 | /** |
1672 | * futex_wait_queue_me() - queue_me() and wait for wakeup, timeout, or signal | |
1673 | * @hb: the futex hash bucket, must be locked by the caller | |
1674 | * @q: the futex_q to queue up on | |
1675 | * @timeout: the prepared hrtimer_sleeper, or null for no timeout | |
ca5f9524 DH |
1676 | */ |
1677 | static void futex_wait_queue_me(struct futex_hash_bucket *hb, struct futex_q *q, | |
f1a11e05 | 1678 | struct hrtimer_sleeper *timeout) |
ca5f9524 | 1679 | { |
9beba3c5 DH |
1680 | /* |
1681 | * The task state is guaranteed to be set before another task can | |
1682 | * wake it. set_current_state() is implemented using set_mb() and | |
1683 | * queue_me() calls spin_unlock() upon completion, both serializing | |
1684 | * access to the hash list and forcing another memory barrier. | |
1685 | */ | |
f1a11e05 | 1686 | set_current_state(TASK_INTERRUPTIBLE); |
0729e196 | 1687 | queue_me(q, hb); |
ca5f9524 DH |
1688 | |
1689 | /* Arm the timer */ | |
1690 | if (timeout) { | |
1691 | hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS); | |
1692 | if (!hrtimer_active(&timeout->timer)) | |
1693 | timeout->task = NULL; | |
1694 | } | |
1695 | ||
1696 | /* | |
0729e196 DH |
1697 | * If we have been removed from the hash list, then another task |
1698 | * has tried to wake us, and we can skip the call to schedule(). | |
ca5f9524 DH |
1699 | */ |
1700 | if (likely(!plist_node_empty(&q->list))) { | |
1701 | /* | |
1702 | * If the timer has already expired, current will already be | |
1703 | * flagged for rescheduling. Only call schedule if there | |
1704 | * is no timeout, or if it has yet to expire. | |
1705 | */ | |
1706 | if (!timeout || timeout->task) | |
1707 | schedule(); | |
1708 | } | |
1709 | __set_current_state(TASK_RUNNING); | |
1710 | } | |
1711 | ||
f801073f DH |
1712 | /** |
1713 | * futex_wait_setup() - Prepare to wait on a futex | |
1714 | * @uaddr: the futex userspace address | |
1715 | * @val: the expected value | |
b41277dc | 1716 | * @flags: futex flags (FLAGS_SHARED, etc.) |
f801073f DH |
1717 | * @q: the associated futex_q |
1718 | * @hb: storage for hash_bucket pointer to be returned to caller | |
1719 | * | |
1720 | * Setup the futex_q and locate the hash_bucket. Get the futex value and | |
1721 | * compare it with the expected value. Handle atomic faults internally. | |
1722 | * Return with the hb lock held and a q.key reference on success, and unlocked | |
1723 | * with no q.key reference on failure. | |
1724 | * | |
1725 | * Returns: | |
1726 | * 0 - uaddr contains val and hb has been locked | |
1727 | * <1 - -EFAULT or -EWOULDBLOCK (uaddr does not contain val) and hb is unlcoked | |
1728 | */ | |
b41277dc | 1729 | static int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags, |
f801073f | 1730 | struct futex_q *q, struct futex_hash_bucket **hb) |
1da177e4 | 1731 | { |
e2970f2f IM |
1732 | u32 uval; |
1733 | int ret; | |
1da177e4 | 1734 | |
1da177e4 | 1735 | /* |
b2d0994b | 1736 | * Access the page AFTER the hash-bucket is locked. |
1da177e4 LT |
1737 | * Order is important: |
1738 | * | |
1739 | * Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val); | |
1740 | * Userspace waker: if (cond(var)) { var = new; futex_wake(&var); } | |
1741 | * | |
1742 | * The basic logical guarantee of a futex is that it blocks ONLY | |
1743 | * if cond(var) is known to be true at the time of blocking, for | |
1744 | * any cond. If we queued after testing *uaddr, that would open | |
1745 | * a race condition where we could block indefinitely with | |
1746 | * cond(var) false, which would violate the guarantee. | |
1747 | * | |
1748 | * A consequence is that futex_wait() can return zero and absorb | |
1749 | * a wakeup when *uaddr != val on entry to the syscall. This is | |
1750 | * rare, but normal. | |
1da177e4 | 1751 | */ |
f801073f DH |
1752 | retry: |
1753 | q->key = FUTEX_KEY_INIT; | |
b41277dc | 1754 | ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q->key); |
f801073f | 1755 | if (unlikely(ret != 0)) |
a5a2a0c7 | 1756 | return ret; |
f801073f DH |
1757 | |
1758 | retry_private: | |
1759 | *hb = queue_lock(q); | |
1760 | ||
e2970f2f | 1761 | ret = get_futex_value_locked(&uval, uaddr); |
1da177e4 | 1762 | |
f801073f DH |
1763 | if (ret) { |
1764 | queue_unlock(q, *hb); | |
1da177e4 | 1765 | |
e2970f2f | 1766 | ret = get_user(uval, uaddr); |
e4dc5b7a | 1767 | if (ret) |
f801073f | 1768 | goto out; |
1da177e4 | 1769 | |
b41277dc | 1770 | if (!(flags & FLAGS_SHARED)) |
e4dc5b7a DH |
1771 | goto retry_private; |
1772 | ||
ae791a2d | 1773 | put_futex_key(&q->key); |
e4dc5b7a | 1774 | goto retry; |
1da177e4 | 1775 | } |
ca5f9524 | 1776 | |
f801073f DH |
1777 | if (uval != val) { |
1778 | queue_unlock(q, *hb); | |
1779 | ret = -EWOULDBLOCK; | |
2fff78c7 | 1780 | } |
1da177e4 | 1781 | |
f801073f DH |
1782 | out: |
1783 | if (ret) | |
ae791a2d | 1784 | put_futex_key(&q->key); |
f801073f DH |
1785 | return ret; |
1786 | } | |
1787 | ||
b41277dc DH |
1788 | static int futex_wait(u32 __user *uaddr, unsigned int flags, u32 val, |
1789 | ktime_t *abs_time, u32 bitset) | |
f801073f DH |
1790 | { |
1791 | struct hrtimer_sleeper timeout, *to = NULL; | |
f801073f DH |
1792 | struct restart_block *restart; |
1793 | struct futex_hash_bucket *hb; | |
1794 | struct futex_q q; | |
1795 | int ret; | |
1796 | ||
1797 | if (!bitset) | |
1798 | return -EINVAL; | |
1799 | ||
1800 | q.pi_state = NULL; | |
1801 | q.bitset = bitset; | |
52400ba9 | 1802 | q.rt_waiter = NULL; |
84bc4af5 | 1803 | q.requeue_pi_key = NULL; |
f801073f DH |
1804 | |
1805 | if (abs_time) { | |
1806 | to = &timeout; | |
1807 | ||
b41277dc DH |
1808 | hrtimer_init_on_stack(&to->timer, (flags & FLAGS_CLOCKRT) ? |
1809 | CLOCK_REALTIME : CLOCK_MONOTONIC, | |
1810 | HRTIMER_MODE_ABS); | |
f801073f DH |
1811 | hrtimer_init_sleeper(to, current); |
1812 | hrtimer_set_expires_range_ns(&to->timer, *abs_time, | |
1813 | current->timer_slack_ns); | |
1814 | } | |
1815 | ||
d58e6576 | 1816 | retry: |
7ada876a DH |
1817 | /* |
1818 | * Prepare to wait on uaddr. On success, holds hb lock and increments | |
1819 | * q.key refs. | |
1820 | */ | |
b41277dc | 1821 | ret = futex_wait_setup(uaddr, val, flags, &q, &hb); |
f801073f DH |
1822 | if (ret) |
1823 | goto out; | |
1824 | ||
ca5f9524 | 1825 | /* queue_me and wait for wakeup, timeout, or a signal. */ |
f1a11e05 | 1826 | futex_wait_queue_me(hb, &q, to); |
1da177e4 LT |
1827 | |
1828 | /* If we were woken (and unqueued), we succeeded, whatever. */ | |
2fff78c7 | 1829 | ret = 0; |
7ada876a | 1830 | /* unqueue_me() drops q.key ref */ |
1da177e4 | 1831 | if (!unqueue_me(&q)) |
7ada876a | 1832 | goto out; |
2fff78c7 | 1833 | ret = -ETIMEDOUT; |
ca5f9524 | 1834 | if (to && !to->task) |
7ada876a | 1835 | goto out; |
72c1bbf3 | 1836 | |
e2970f2f | 1837 | /* |
d58e6576 TG |
1838 | * We expect signal_pending(current), but we might be the |
1839 | * victim of a spurious wakeup as well. | |
e2970f2f | 1840 | */ |
7ada876a | 1841 | if (!signal_pending(current)) |
d58e6576 | 1842 | goto retry; |
d58e6576 | 1843 | |
2fff78c7 | 1844 | ret = -ERESTARTSYS; |
c19384b5 | 1845 | if (!abs_time) |
7ada876a | 1846 | goto out; |
1da177e4 | 1847 | |
2fff78c7 PZ |
1848 | restart = ¤t_thread_info()->restart_block; |
1849 | restart->fn = futex_wait_restart; | |
a3c74c52 | 1850 | restart->futex.uaddr = uaddr; |
2fff78c7 PZ |
1851 | restart->futex.val = val; |
1852 | restart->futex.time = abs_time->tv64; | |
1853 | restart->futex.bitset = bitset; | |
b41277dc | 1854 | restart->futex.flags = flags; |
42d35d48 | 1855 | |
2fff78c7 PZ |
1856 | ret = -ERESTART_RESTARTBLOCK; |
1857 | ||
42d35d48 | 1858 | out: |
ca5f9524 DH |
1859 | if (to) { |
1860 | hrtimer_cancel(&to->timer); | |
1861 | destroy_hrtimer_on_stack(&to->timer); | |
1862 | } | |
c87e2837 IM |
1863 | return ret; |
1864 | } | |
1865 | ||
72c1bbf3 NP |
1866 | |
1867 | static long futex_wait_restart(struct restart_block *restart) | |
1868 | { | |
a3c74c52 | 1869 | u32 __user *uaddr = restart->futex.uaddr; |
a72188d8 | 1870 | ktime_t t, *tp = NULL; |
72c1bbf3 | 1871 | |
a72188d8 DH |
1872 | if (restart->futex.flags & FLAGS_HAS_TIMEOUT) { |
1873 | t.tv64 = restart->futex.time; | |
1874 | tp = &t; | |
1875 | } | |
72c1bbf3 | 1876 | restart->fn = do_no_restart_syscall; |
b41277dc DH |
1877 | |
1878 | return (long)futex_wait(uaddr, restart->futex.flags, | |
1879 | restart->futex.val, tp, restart->futex.bitset); | |
72c1bbf3 NP |
1880 | } |
1881 | ||
1882 | ||
c87e2837 IM |
1883 | /* |
1884 | * Userspace tried a 0 -> TID atomic transition of the futex value | |
1885 | * and failed. The kernel side here does the whole locking operation: | |
1886 | * if there are waiters then it will block, it does PI, etc. (Due to | |
1887 | * races the kernel might see a 0 value of the futex too.) | |
1888 | */ | |
b41277dc DH |
1889 | static int futex_lock_pi(u32 __user *uaddr, unsigned int flags, int detect, |
1890 | ktime_t *time, int trylock) | |
c87e2837 | 1891 | { |
c5780e97 | 1892 | struct hrtimer_sleeper timeout, *to = NULL; |
c87e2837 | 1893 | struct futex_hash_bucket *hb; |
c87e2837 | 1894 | struct futex_q q; |
dd973998 | 1895 | int res, ret; |
c87e2837 IM |
1896 | |
1897 | if (refill_pi_state_cache()) | |
1898 | return -ENOMEM; | |
1899 | ||
c19384b5 | 1900 | if (time) { |
c5780e97 | 1901 | to = &timeout; |
237fc6e7 TG |
1902 | hrtimer_init_on_stack(&to->timer, CLOCK_REALTIME, |
1903 | HRTIMER_MODE_ABS); | |
c5780e97 | 1904 | hrtimer_init_sleeper(to, current); |
cc584b21 | 1905 | hrtimer_set_expires(&to->timer, *time); |
c5780e97 TG |
1906 | } |
1907 | ||
c87e2837 | 1908 | q.pi_state = NULL; |
52400ba9 | 1909 | q.rt_waiter = NULL; |
84bc4af5 | 1910 | q.requeue_pi_key = NULL; |
42d35d48 | 1911 | retry: |
38d47c1b | 1912 | q.key = FUTEX_KEY_INIT; |
b41277dc | 1913 | ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q.key); |
c87e2837 | 1914 | if (unlikely(ret != 0)) |
42d35d48 | 1915 | goto out; |
c87e2837 | 1916 | |
e4dc5b7a | 1917 | retry_private: |
82af7aca | 1918 | hb = queue_lock(&q); |
c87e2837 | 1919 | |
bab5bc9e | 1920 | ret = futex_lock_pi_atomic(uaddr, hb, &q.key, &q.pi_state, current, 0); |
c87e2837 | 1921 | if (unlikely(ret)) { |
778e9a9c | 1922 | switch (ret) { |
1a52084d DH |
1923 | case 1: |
1924 | /* We got the lock. */ | |
1925 | ret = 0; | |
1926 | goto out_unlock_put_key; | |
1927 | case -EFAULT: | |
1928 | goto uaddr_faulted; | |
778e9a9c AK |
1929 | case -EAGAIN: |
1930 | /* | |
1931 | * Task is exiting and we just wait for the | |
1932 | * exit to complete. | |
1933 | */ | |
1934 | queue_unlock(&q, hb); | |
ae791a2d | 1935 | put_futex_key(&q.key); |
778e9a9c AK |
1936 | cond_resched(); |
1937 | goto retry; | |
778e9a9c | 1938 | default: |
42d35d48 | 1939 | goto out_unlock_put_key; |
c87e2837 | 1940 | } |
c87e2837 IM |
1941 | } |
1942 | ||
1943 | /* | |
1944 | * Only actually queue now that the atomic ops are done: | |
1945 | */ | |
82af7aca | 1946 | queue_me(&q, hb); |
c87e2837 | 1947 | |
c87e2837 IM |
1948 | WARN_ON(!q.pi_state); |
1949 | /* | |
1950 | * Block on the PI mutex: | |
1951 | */ | |
1952 | if (!trylock) | |
1953 | ret = rt_mutex_timed_lock(&q.pi_state->pi_mutex, to, 1); | |
1954 | else { | |
1955 | ret = rt_mutex_trylock(&q.pi_state->pi_mutex); | |
1956 | /* Fixup the trylock return value: */ | |
1957 | ret = ret ? 0 : -EWOULDBLOCK; | |
1958 | } | |
1959 | ||
a99e4e41 | 1960 | spin_lock(q.lock_ptr); |
dd973998 DH |
1961 | /* |
1962 | * Fixup the pi_state owner and possibly acquire the lock if we | |
1963 | * haven't already. | |
1964 | */ | |
ae791a2d | 1965 | res = fixup_owner(uaddr, &q, !ret); |
dd973998 DH |
1966 | /* |
1967 | * If fixup_owner() returned an error, proprogate that. If it acquired | |
1968 | * the lock, clear our -ETIMEDOUT or -EINTR. | |
1969 | */ | |
1970 | if (res) | |
1971 | ret = (res < 0) ? res : 0; | |
c87e2837 | 1972 | |
e8f6386c | 1973 | /* |
dd973998 DH |
1974 | * If fixup_owner() faulted and was unable to handle the fault, unlock |
1975 | * it and return the fault to userspace. | |
e8f6386c DH |
1976 | */ |
1977 | if (ret && (rt_mutex_owner(&q.pi_state->pi_mutex) == current)) | |
1978 | rt_mutex_unlock(&q.pi_state->pi_mutex); | |
1979 | ||
778e9a9c AK |
1980 | /* Unqueue and drop the lock */ |
1981 | unqueue_me_pi(&q); | |
c87e2837 | 1982 | |
5ecb01cf | 1983 | goto out_put_key; |
c87e2837 | 1984 | |
42d35d48 | 1985 | out_unlock_put_key: |
c87e2837 IM |
1986 | queue_unlock(&q, hb); |
1987 | ||
42d35d48 | 1988 | out_put_key: |
ae791a2d | 1989 | put_futex_key(&q.key); |
42d35d48 | 1990 | out: |
237fc6e7 TG |
1991 | if (to) |
1992 | destroy_hrtimer_on_stack(&to->timer); | |
dd973998 | 1993 | return ret != -EINTR ? ret : -ERESTARTNOINTR; |
c87e2837 | 1994 | |
42d35d48 | 1995 | uaddr_faulted: |
778e9a9c AK |
1996 | queue_unlock(&q, hb); |
1997 | ||
d0725992 | 1998 | ret = fault_in_user_writeable(uaddr); |
e4dc5b7a DH |
1999 | if (ret) |
2000 | goto out_put_key; | |
c87e2837 | 2001 | |
b41277dc | 2002 | if (!(flags & FLAGS_SHARED)) |
e4dc5b7a DH |
2003 | goto retry_private; |
2004 | ||
ae791a2d | 2005 | put_futex_key(&q.key); |
e4dc5b7a | 2006 | goto retry; |
c87e2837 IM |
2007 | } |
2008 | ||
c87e2837 IM |
2009 | /* |
2010 | * Userspace attempted a TID -> 0 atomic transition, and failed. | |
2011 | * This is the in-kernel slowpath: we look up the PI state (if any), | |
2012 | * and do the rt-mutex unlock. | |
2013 | */ | |
b41277dc | 2014 | static int futex_unlock_pi(u32 __user *uaddr, unsigned int flags) |
c87e2837 IM |
2015 | { |
2016 | struct futex_hash_bucket *hb; | |
2017 | struct futex_q *this, *next; | |
2018 | u32 uval; | |
ec92d082 | 2019 | struct plist_head *head; |
38d47c1b | 2020 | union futex_key key = FUTEX_KEY_INIT; |
e4dc5b7a | 2021 | int ret; |
c87e2837 IM |
2022 | |
2023 | retry: | |
2024 | if (get_user(uval, uaddr)) | |
2025 | return -EFAULT; | |
2026 | /* | |
2027 | * We release only a lock we actually own: | |
2028 | */ | |
b488893a | 2029 | if ((uval & FUTEX_TID_MASK) != task_pid_vnr(current)) |
c87e2837 | 2030 | return -EPERM; |
c87e2837 | 2031 | |
b41277dc | 2032 | ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key); |
c87e2837 IM |
2033 | if (unlikely(ret != 0)) |
2034 | goto out; | |
2035 | ||
2036 | hb = hash_futex(&key); | |
2037 | spin_lock(&hb->lock); | |
2038 | ||
c87e2837 IM |
2039 | /* |
2040 | * To avoid races, try to do the TID -> 0 atomic transition | |
2041 | * again. If it succeeds then we can return without waking | |
2042 | * anyone else up: | |
2043 | */ | |
36cf3b5c | 2044 | if (!(uval & FUTEX_OWNER_DIED)) |
b488893a | 2045 | uval = cmpxchg_futex_value_locked(uaddr, task_pid_vnr(current), 0); |
36cf3b5c | 2046 | |
c87e2837 IM |
2047 | |
2048 | if (unlikely(uval == -EFAULT)) | |
2049 | goto pi_faulted; | |
2050 | /* | |
2051 | * Rare case: we managed to release the lock atomically, | |
2052 | * no need to wake anyone else up: | |
2053 | */ | |
b488893a | 2054 | if (unlikely(uval == task_pid_vnr(current))) |
c87e2837 IM |
2055 | goto out_unlock; |
2056 | ||
2057 | /* | |
2058 | * Ok, other tasks may need to be woken up - check waiters | |
2059 | * and do the wakeup if necessary: | |
2060 | */ | |
2061 | head = &hb->chain; | |
2062 | ||
ec92d082 | 2063 | plist_for_each_entry_safe(this, next, head, list) { |
c87e2837 IM |
2064 | if (!match_futex (&this->key, &key)) |
2065 | continue; | |
2066 | ret = wake_futex_pi(uaddr, uval, this); | |
2067 | /* | |
2068 | * The atomic access to the futex value | |
2069 | * generated a pagefault, so retry the | |
2070 | * user-access and the wakeup: | |
2071 | */ | |
2072 | if (ret == -EFAULT) | |
2073 | goto pi_faulted; | |
2074 | goto out_unlock; | |
2075 | } | |
2076 | /* | |
2077 | * No waiters - kernel unlocks the futex: | |
2078 | */ | |
e3f2ddea IM |
2079 | if (!(uval & FUTEX_OWNER_DIED)) { |
2080 | ret = unlock_futex_pi(uaddr, uval); | |
2081 | if (ret == -EFAULT) | |
2082 | goto pi_faulted; | |
2083 | } | |
c87e2837 IM |
2084 | |
2085 | out_unlock: | |
2086 | spin_unlock(&hb->lock); | |
ae791a2d | 2087 | put_futex_key(&key); |
c87e2837 | 2088 | |
42d35d48 | 2089 | out: |
c87e2837 IM |
2090 | return ret; |
2091 | ||
2092 | pi_faulted: | |
778e9a9c | 2093 | spin_unlock(&hb->lock); |
ae791a2d | 2094 | put_futex_key(&key); |
c87e2837 | 2095 | |
d0725992 | 2096 | ret = fault_in_user_writeable(uaddr); |
b5686363 | 2097 | if (!ret) |
c87e2837 IM |
2098 | goto retry; |
2099 | ||
1da177e4 LT |
2100 | return ret; |
2101 | } | |
2102 | ||
52400ba9 DH |
2103 | /** |
2104 | * handle_early_requeue_pi_wakeup() - Detect early wakeup on the initial futex | |
2105 | * @hb: the hash_bucket futex_q was original enqueued on | |
2106 | * @q: the futex_q woken while waiting to be requeued | |
2107 | * @key2: the futex_key of the requeue target futex | |
2108 | * @timeout: the timeout associated with the wait (NULL if none) | |
2109 | * | |
2110 | * Detect if the task was woken on the initial futex as opposed to the requeue | |
2111 | * target futex. If so, determine if it was a timeout or a signal that caused | |
2112 | * the wakeup and return the appropriate error code to the caller. Must be | |
2113 | * called with the hb lock held. | |
2114 | * | |
2115 | * Returns | |
2116 | * 0 - no early wakeup detected | |
1c840c14 | 2117 | * <0 - -ETIMEDOUT or -ERESTARTNOINTR |
52400ba9 DH |
2118 | */ |
2119 | static inline | |
2120 | int handle_early_requeue_pi_wakeup(struct futex_hash_bucket *hb, | |
2121 | struct futex_q *q, union futex_key *key2, | |
2122 | struct hrtimer_sleeper *timeout) | |
2123 | { | |
2124 | int ret = 0; | |
2125 | ||
2126 | /* | |
2127 | * With the hb lock held, we avoid races while we process the wakeup. | |
2128 | * We only need to hold hb (and not hb2) to ensure atomicity as the | |
2129 | * wakeup code can't change q.key from uaddr to uaddr2 if we hold hb. | |
2130 | * It can't be requeued from uaddr2 to something else since we don't | |
2131 | * support a PI aware source futex for requeue. | |
2132 | */ | |
2133 | if (!match_futex(&q->key, key2)) { | |
2134 | WARN_ON(q->lock_ptr && (&hb->lock != q->lock_ptr)); | |
2135 | /* | |
2136 | * We were woken prior to requeue by a timeout or a signal. | |
2137 | * Unqueue the futex_q and determine which it was. | |
2138 | */ | |
2139 | plist_del(&q->list, &q->list.plist); | |
52400ba9 | 2140 | |
d58e6576 | 2141 | /* Handle spurious wakeups gracefully */ |
11df6ddd | 2142 | ret = -EWOULDBLOCK; |
52400ba9 DH |
2143 | if (timeout && !timeout->task) |
2144 | ret = -ETIMEDOUT; | |
d58e6576 | 2145 | else if (signal_pending(current)) |
1c840c14 | 2146 | ret = -ERESTARTNOINTR; |
52400ba9 DH |
2147 | } |
2148 | return ret; | |
2149 | } | |
2150 | ||
2151 | /** | |
2152 | * futex_wait_requeue_pi() - Wait on uaddr and take uaddr2 | |
56ec1607 | 2153 | * @uaddr: the futex we initially wait on (non-pi) |
b41277dc | 2154 | * @flags: futex flags (FLAGS_SHARED, FLAGS_CLOCKRT, etc.), they must be |
52400ba9 DH |
2155 | * the same type, no requeueing from private to shared, etc. |
2156 | * @val: the expected value of uaddr | |
2157 | * @abs_time: absolute timeout | |
56ec1607 | 2158 | * @bitset: 32 bit wakeup bitset set by userspace, defaults to all |
52400ba9 DH |
2159 | * @clockrt: whether to use CLOCK_REALTIME (1) or CLOCK_MONOTONIC (0) |
2160 | * @uaddr2: the pi futex we will take prior to returning to user-space | |
2161 | * | |
2162 | * The caller will wait on uaddr and will be requeued by futex_requeue() to | |
2163 | * uaddr2 which must be PI aware. Normal wakeup will wake on uaddr2 and | |
2164 | * complete the acquisition of the rt_mutex prior to returning to userspace. | |
2165 | * This ensures the rt_mutex maintains an owner when it has waiters; without | |
2166 | * one, the pi logic wouldn't know which task to boost/deboost, if there was a | |
2167 | * need to. | |
2168 | * | |
2169 | * We call schedule in futex_wait_queue_me() when we enqueue and return there | |
2170 | * via the following: | |
2171 | * 1) wakeup on uaddr2 after an atomic lock acquisition by futex_requeue() | |
cc6db4e6 DH |
2172 | * 2) wakeup on uaddr2 after a requeue |
2173 | * 3) signal | |
2174 | * 4) timeout | |
52400ba9 | 2175 | * |
cc6db4e6 | 2176 | * If 3, cleanup and return -ERESTARTNOINTR. |
52400ba9 DH |
2177 | * |
2178 | * If 2, we may then block on trying to take the rt_mutex and return via: | |
2179 | * 5) successful lock | |
2180 | * 6) signal | |
2181 | * 7) timeout | |
2182 | * 8) other lock acquisition failure | |
2183 | * | |
cc6db4e6 | 2184 | * If 6, return -EWOULDBLOCK (restarting the syscall would do the same). |
52400ba9 DH |
2185 | * |
2186 | * If 4 or 7, we cleanup and return with -ETIMEDOUT. | |
2187 | * | |
2188 | * Returns: | |
2189 | * 0 - On success | |
2190 | * <0 - On error | |
2191 | */ | |
b41277dc | 2192 | static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags, |
52400ba9 | 2193 | u32 val, ktime_t *abs_time, u32 bitset, |
b41277dc | 2194 | u32 __user *uaddr2) |
52400ba9 DH |
2195 | { |
2196 | struct hrtimer_sleeper timeout, *to = NULL; | |
2197 | struct rt_mutex_waiter rt_waiter; | |
2198 | struct rt_mutex *pi_mutex = NULL; | |
52400ba9 DH |
2199 | struct futex_hash_bucket *hb; |
2200 | union futex_key key2; | |
2201 | struct futex_q q; | |
2202 | int res, ret; | |
52400ba9 DH |
2203 | |
2204 | if (!bitset) | |
2205 | return -EINVAL; | |
2206 | ||
2207 | if (abs_time) { | |
2208 | to = &timeout; | |
b41277dc DH |
2209 | hrtimer_init_on_stack(&to->timer, (flags & FLAGS_CLOCKRT) ? |
2210 | CLOCK_REALTIME : CLOCK_MONOTONIC, | |
2211 | HRTIMER_MODE_ABS); | |
52400ba9 DH |
2212 | hrtimer_init_sleeper(to, current); |
2213 | hrtimer_set_expires_range_ns(&to->timer, *abs_time, | |
2214 | current->timer_slack_ns); | |
2215 | } | |
2216 | ||
2217 | /* | |
2218 | * The waiter is allocated on our stack, manipulated by the requeue | |
2219 | * code while we sleep on uaddr. | |
2220 | */ | |
2221 | debug_rt_mutex_init_waiter(&rt_waiter); | |
2222 | rt_waiter.task = NULL; | |
2223 | ||
52400ba9 | 2224 | key2 = FUTEX_KEY_INIT; |
b41277dc | 2225 | ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2); |
52400ba9 DH |
2226 | if (unlikely(ret != 0)) |
2227 | goto out; | |
2228 | ||
84bc4af5 DH |
2229 | q.pi_state = NULL; |
2230 | q.bitset = bitset; | |
2231 | q.rt_waiter = &rt_waiter; | |
2232 | q.requeue_pi_key = &key2; | |
2233 | ||
7ada876a DH |
2234 | /* |
2235 | * Prepare to wait on uaddr. On success, increments q.key (key1) ref | |
2236 | * count. | |
2237 | */ | |
b41277dc | 2238 | ret = futex_wait_setup(uaddr, val, flags, &q, &hb); |
c8b15a70 TG |
2239 | if (ret) |
2240 | goto out_key2; | |
52400ba9 DH |
2241 | |
2242 | /* Queue the futex_q, drop the hb lock, wait for wakeup. */ | |
f1a11e05 | 2243 | futex_wait_queue_me(hb, &q, to); |
52400ba9 DH |
2244 | |
2245 | spin_lock(&hb->lock); | |
2246 | ret = handle_early_requeue_pi_wakeup(hb, &q, &key2, to); | |
2247 | spin_unlock(&hb->lock); | |
2248 | if (ret) | |
2249 | goto out_put_keys; | |
2250 | ||
2251 | /* | |
2252 | * In order for us to be here, we know our q.key == key2, and since | |
2253 | * we took the hb->lock above, we also know that futex_requeue() has | |
2254 | * completed and we no longer have to concern ourselves with a wakeup | |
7ada876a DH |
2255 | * race with the atomic proxy lock acquisition by the requeue code. The |
2256 | * futex_requeue dropped our key1 reference and incremented our key2 | |
2257 | * reference count. | |
52400ba9 DH |
2258 | */ |
2259 | ||
2260 | /* Check if the requeue code acquired the second futex for us. */ | |
2261 | if (!q.rt_waiter) { | |
2262 | /* | |
2263 | * Got the lock. We might not be the anticipated owner if we | |
2264 | * did a lock-steal - fix up the PI-state in that case. | |
2265 | */ | |
2266 | if (q.pi_state && (q.pi_state->owner != current)) { | |
2267 | spin_lock(q.lock_ptr); | |
ae791a2d | 2268 | ret = fixup_pi_state_owner(uaddr2, &q, current); |
52400ba9 DH |
2269 | spin_unlock(q.lock_ptr); |
2270 | } | |
2271 | } else { | |
2272 | /* | |
2273 | * We have been woken up by futex_unlock_pi(), a timeout, or a | |
2274 | * signal. futex_unlock_pi() will not destroy the lock_ptr nor | |
2275 | * the pi_state. | |
2276 | */ | |
2277 | WARN_ON(!&q.pi_state); | |
2278 | pi_mutex = &q.pi_state->pi_mutex; | |
2279 | ret = rt_mutex_finish_proxy_lock(pi_mutex, to, &rt_waiter, 1); | |
2280 | debug_rt_mutex_free_waiter(&rt_waiter); | |
2281 | ||
2282 | spin_lock(q.lock_ptr); | |
2283 | /* | |
2284 | * Fixup the pi_state owner and possibly acquire the lock if we | |
2285 | * haven't already. | |
2286 | */ | |
ae791a2d | 2287 | res = fixup_owner(uaddr2, &q, !ret); |
52400ba9 DH |
2288 | /* |
2289 | * If fixup_owner() returned an error, proprogate that. If it | |
56ec1607 | 2290 | * acquired the lock, clear -ETIMEDOUT or -EINTR. |
52400ba9 DH |
2291 | */ |
2292 | if (res) | |
2293 | ret = (res < 0) ? res : 0; | |
2294 | ||
2295 | /* Unqueue and drop the lock. */ | |
2296 | unqueue_me_pi(&q); | |
2297 | } | |
2298 | ||
2299 | /* | |
2300 | * If fixup_pi_state_owner() faulted and was unable to handle the | |
2301 | * fault, unlock the rt_mutex and return the fault to userspace. | |
2302 | */ | |
2303 | if (ret == -EFAULT) { | |
2304 | if (rt_mutex_owner(pi_mutex) == current) | |
2305 | rt_mutex_unlock(pi_mutex); | |
2306 | } else if (ret == -EINTR) { | |
52400ba9 | 2307 | /* |
cc6db4e6 DH |
2308 | * We've already been requeued, but cannot restart by calling |
2309 | * futex_lock_pi() directly. We could restart this syscall, but | |
2310 | * it would detect that the user space "val" changed and return | |
2311 | * -EWOULDBLOCK. Save the overhead of the restart and return | |
2312 | * -EWOULDBLOCK directly. | |
52400ba9 | 2313 | */ |
2070887f | 2314 | ret = -EWOULDBLOCK; |
52400ba9 DH |
2315 | } |
2316 | ||
2317 | out_put_keys: | |
ae791a2d | 2318 | put_futex_key(&q.key); |
c8b15a70 | 2319 | out_key2: |
ae791a2d | 2320 | put_futex_key(&key2); |
52400ba9 DH |
2321 | |
2322 | out: | |
2323 | if (to) { | |
2324 | hrtimer_cancel(&to->timer); | |
2325 | destroy_hrtimer_on_stack(&to->timer); | |
2326 | } | |
2327 | return ret; | |
2328 | } | |
2329 | ||
0771dfef IM |
2330 | /* |
2331 | * Support for robust futexes: the kernel cleans up held futexes at | |
2332 | * thread exit time. | |
2333 | * | |
2334 | * Implementation: user-space maintains a per-thread list of locks it | |
2335 | * is holding. Upon do_exit(), the kernel carefully walks this list, | |
2336 | * and marks all locks that are owned by this thread with the | |
c87e2837 | 2337 | * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is |
0771dfef IM |
2338 | * always manipulated with the lock held, so the list is private and |
2339 | * per-thread. Userspace also maintains a per-thread 'list_op_pending' | |
2340 | * field, to allow the kernel to clean up if the thread dies after | |
2341 | * acquiring the lock, but just before it could have added itself to | |
2342 | * the list. There can only be one such pending lock. | |
2343 | */ | |
2344 | ||
2345 | /** | |
d96ee56c DH |
2346 | * sys_set_robust_list() - Set the robust-futex list head of a task |
2347 | * @head: pointer to the list-head | |
2348 | * @len: length of the list-head, as userspace expects | |
0771dfef | 2349 | */ |
836f92ad HC |
2350 | SYSCALL_DEFINE2(set_robust_list, struct robust_list_head __user *, head, |
2351 | size_t, len) | |
0771dfef | 2352 | { |
a0c1e907 TG |
2353 | if (!futex_cmpxchg_enabled) |
2354 | return -ENOSYS; | |
0771dfef IM |
2355 | /* |
2356 | * The kernel knows only one size for now: | |
2357 | */ | |
2358 | if (unlikely(len != sizeof(*head))) | |
2359 | return -EINVAL; | |
2360 | ||
2361 | current->robust_list = head; | |
2362 | ||
2363 | return 0; | |
2364 | } | |
2365 | ||
2366 | /** | |
d96ee56c DH |
2367 | * sys_get_robust_list() - Get the robust-futex list head of a task |
2368 | * @pid: pid of the process [zero for current task] | |
2369 | * @head_ptr: pointer to a list-head pointer, the kernel fills it in | |
2370 | * @len_ptr: pointer to a length field, the kernel fills in the header size | |
0771dfef | 2371 | */ |
836f92ad HC |
2372 | SYSCALL_DEFINE3(get_robust_list, int, pid, |
2373 | struct robust_list_head __user * __user *, head_ptr, | |
2374 | size_t __user *, len_ptr) | |
0771dfef | 2375 | { |
ba46df98 | 2376 | struct robust_list_head __user *head; |
0771dfef | 2377 | unsigned long ret; |
c69e8d9c | 2378 | const struct cred *cred = current_cred(), *pcred; |
0771dfef | 2379 | |
a0c1e907 TG |
2380 | if (!futex_cmpxchg_enabled) |
2381 | return -ENOSYS; | |
2382 | ||
0771dfef IM |
2383 | if (!pid) |
2384 | head = current->robust_list; | |
2385 | else { | |
2386 | struct task_struct *p; | |
2387 | ||
2388 | ret = -ESRCH; | |
aaa2a97e | 2389 | rcu_read_lock(); |
228ebcbe | 2390 | p = find_task_by_vpid(pid); |
0771dfef IM |
2391 | if (!p) |
2392 | goto err_unlock; | |
2393 | ret = -EPERM; | |
c69e8d9c DH |
2394 | pcred = __task_cred(p); |
2395 | if (cred->euid != pcred->euid && | |
2396 | cred->euid != pcred->uid && | |
76aac0e9 | 2397 | !capable(CAP_SYS_PTRACE)) |
0771dfef IM |
2398 | goto err_unlock; |
2399 | head = p->robust_list; | |
aaa2a97e | 2400 | rcu_read_unlock(); |
0771dfef IM |
2401 | } |
2402 | ||
2403 | if (put_user(sizeof(*head), len_ptr)) | |
2404 | return -EFAULT; | |
2405 | return put_user(head, head_ptr); | |
2406 | ||
2407 | err_unlock: | |
aaa2a97e | 2408 | rcu_read_unlock(); |
0771dfef IM |
2409 | |
2410 | return ret; | |
2411 | } | |
2412 | ||
2413 | /* | |
2414 | * Process a futex-list entry, check whether it's owned by the | |
2415 | * dying task, and do notification if so: | |
2416 | */ | |
e3f2ddea | 2417 | int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi) |
0771dfef | 2418 | { |
e3f2ddea | 2419 | u32 uval, nval, mval; |
0771dfef | 2420 | |
8f17d3a5 IM |
2421 | retry: |
2422 | if (get_user(uval, uaddr)) | |
0771dfef IM |
2423 | return -1; |
2424 | ||
b488893a | 2425 | if ((uval & FUTEX_TID_MASK) == task_pid_vnr(curr)) { |
0771dfef IM |
2426 | /* |
2427 | * Ok, this dying thread is truly holding a futex | |
2428 | * of interest. Set the OWNER_DIED bit atomically | |
2429 | * via cmpxchg, and if the value had FUTEX_WAITERS | |
2430 | * set, wake up a waiter (if any). (We have to do a | |
2431 | * futex_wake() even if OWNER_DIED is already set - | |
2432 | * to handle the rare but possible case of recursive | |
2433 | * thread-death.) The rest of the cleanup is done in | |
2434 | * userspace. | |
2435 | */ | |
e3f2ddea IM |
2436 | mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED; |
2437 | nval = futex_atomic_cmpxchg_inatomic(uaddr, uval, mval); | |
2438 | ||
c87e2837 IM |
2439 | if (nval == -EFAULT) |
2440 | return -1; | |
2441 | ||
2442 | if (nval != uval) | |
8f17d3a5 | 2443 | goto retry; |
0771dfef | 2444 | |
e3f2ddea IM |
2445 | /* |
2446 | * Wake robust non-PI futexes here. The wakeup of | |
2447 | * PI futexes happens in exit_pi_state(): | |
2448 | */ | |
36cf3b5c | 2449 | if (!pi && (uval & FUTEX_WAITERS)) |
c2f9f201 | 2450 | futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY); |
0771dfef IM |
2451 | } |
2452 | return 0; | |
2453 | } | |
2454 | ||
e3f2ddea IM |
2455 | /* |
2456 | * Fetch a robust-list pointer. Bit 0 signals PI futexes: | |
2457 | */ | |
2458 | static inline int fetch_robust_entry(struct robust_list __user **entry, | |
ba46df98 | 2459 | struct robust_list __user * __user *head, |
1dcc41bb | 2460 | unsigned int *pi) |
e3f2ddea IM |
2461 | { |
2462 | unsigned long uentry; | |
2463 | ||
ba46df98 | 2464 | if (get_user(uentry, (unsigned long __user *)head)) |
e3f2ddea IM |
2465 | return -EFAULT; |
2466 | ||
ba46df98 | 2467 | *entry = (void __user *)(uentry & ~1UL); |
e3f2ddea IM |
2468 | *pi = uentry & 1; |
2469 | ||
2470 | return 0; | |
2471 | } | |
2472 | ||
0771dfef IM |
2473 | /* |
2474 | * Walk curr->robust_list (very carefully, it's a userspace list!) | |
2475 | * and mark any locks found there dead, and notify any waiters. | |
2476 | * | |
2477 | * We silently return on any sign of list-walking problem. | |
2478 | */ | |
2479 | void exit_robust_list(struct task_struct *curr) | |
2480 | { | |
2481 | struct robust_list_head __user *head = curr->robust_list; | |
9f96cb1e | 2482 | struct robust_list __user *entry, *next_entry, *pending; |
4c115e95 DH |
2483 | unsigned int limit = ROBUST_LIST_LIMIT, pi, pip; |
2484 | unsigned int uninitialized_var(next_pi); | |
0771dfef | 2485 | unsigned long futex_offset; |
9f96cb1e | 2486 | int rc; |
0771dfef | 2487 | |
a0c1e907 TG |
2488 | if (!futex_cmpxchg_enabled) |
2489 | return; | |
2490 | ||
0771dfef IM |
2491 | /* |
2492 | * Fetch the list head (which was registered earlier, via | |
2493 | * sys_set_robust_list()): | |
2494 | */ | |
e3f2ddea | 2495 | if (fetch_robust_entry(&entry, &head->list.next, &pi)) |
0771dfef IM |
2496 | return; |
2497 | /* | |
2498 | * Fetch the relative futex offset: | |
2499 | */ | |
2500 | if (get_user(futex_offset, &head->futex_offset)) | |
2501 | return; | |
2502 | /* | |
2503 | * Fetch any possibly pending lock-add first, and handle it | |
2504 | * if it exists: | |
2505 | */ | |
e3f2ddea | 2506 | if (fetch_robust_entry(&pending, &head->list_op_pending, &pip)) |
0771dfef | 2507 | return; |
e3f2ddea | 2508 | |
9f96cb1e | 2509 | next_entry = NULL; /* avoid warning with gcc */ |
0771dfef | 2510 | while (entry != &head->list) { |
9f96cb1e MS |
2511 | /* |
2512 | * Fetch the next entry in the list before calling | |
2513 | * handle_futex_death: | |
2514 | */ | |
2515 | rc = fetch_robust_entry(&next_entry, &entry->next, &next_pi); | |
0771dfef IM |
2516 | /* |
2517 | * A pending lock might already be on the list, so | |
c87e2837 | 2518 | * don't process it twice: |
0771dfef IM |
2519 | */ |
2520 | if (entry != pending) | |
ba46df98 | 2521 | if (handle_futex_death((void __user *)entry + futex_offset, |
e3f2ddea | 2522 | curr, pi)) |
0771dfef | 2523 | return; |
9f96cb1e | 2524 | if (rc) |
0771dfef | 2525 | return; |
9f96cb1e MS |
2526 | entry = next_entry; |
2527 | pi = next_pi; | |
0771dfef IM |
2528 | /* |
2529 | * Avoid excessively long or circular lists: | |
2530 | */ | |
2531 | if (!--limit) | |
2532 | break; | |
2533 | ||
2534 | cond_resched(); | |
2535 | } | |
9f96cb1e MS |
2536 | |
2537 | if (pending) | |
2538 | handle_futex_death((void __user *)pending + futex_offset, | |
2539 | curr, pip); | |
0771dfef IM |
2540 | } |
2541 | ||
c19384b5 | 2542 | long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout, |
e2970f2f | 2543 | u32 __user *uaddr2, u32 val2, u32 val3) |
1da177e4 | 2544 | { |
b41277dc DH |
2545 | int ret = -ENOSYS, cmd = op & FUTEX_CMD_MASK; |
2546 | unsigned int flags = 0; | |
34f01cc1 ED |
2547 | |
2548 | if (!(op & FUTEX_PRIVATE_FLAG)) | |
b41277dc | 2549 | flags |= FLAGS_SHARED; |
1da177e4 | 2550 | |
b41277dc DH |
2551 | if (op & FUTEX_CLOCK_REALTIME) { |
2552 | flags |= FLAGS_CLOCKRT; | |
2553 | if (cmd != FUTEX_WAIT_BITSET && cmd != FUTEX_WAIT_REQUEUE_PI) | |
2554 | return -ENOSYS; | |
2555 | } | |
1da177e4 | 2556 | |
34f01cc1 | 2557 | switch (cmd) { |
1da177e4 | 2558 | case FUTEX_WAIT: |
cd689985 TG |
2559 | val3 = FUTEX_BITSET_MATCH_ANY; |
2560 | case FUTEX_WAIT_BITSET: | |
b41277dc | 2561 | ret = futex_wait(uaddr, flags, val, timeout, val3); |
1da177e4 LT |
2562 | break; |
2563 | case FUTEX_WAKE: | |
cd689985 TG |
2564 | val3 = FUTEX_BITSET_MATCH_ANY; |
2565 | case FUTEX_WAKE_BITSET: | |
b41277dc | 2566 | ret = futex_wake(uaddr, flags, val, val3); |
1da177e4 | 2567 | break; |
1da177e4 | 2568 | case FUTEX_REQUEUE: |
b41277dc | 2569 | ret = futex_requeue(uaddr, flags, uaddr2, val, val2, NULL, 0); |
1da177e4 LT |
2570 | break; |
2571 | case FUTEX_CMP_REQUEUE: | |
b41277dc | 2572 | ret = futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 0); |
1da177e4 | 2573 | break; |
4732efbe | 2574 | case FUTEX_WAKE_OP: |
b41277dc | 2575 | ret = futex_wake_op(uaddr, flags, uaddr2, val, val2, val3); |
4732efbe | 2576 | break; |
c87e2837 | 2577 | case FUTEX_LOCK_PI: |
a0c1e907 | 2578 | if (futex_cmpxchg_enabled) |
b41277dc | 2579 | ret = futex_lock_pi(uaddr, flags, val, timeout, 0); |
c87e2837 IM |
2580 | break; |
2581 | case FUTEX_UNLOCK_PI: | |
a0c1e907 | 2582 | if (futex_cmpxchg_enabled) |
b41277dc | 2583 | ret = futex_unlock_pi(uaddr, flags); |
c87e2837 IM |
2584 | break; |
2585 | case FUTEX_TRYLOCK_PI: | |
a0c1e907 | 2586 | if (futex_cmpxchg_enabled) |
b41277dc | 2587 | ret = futex_lock_pi(uaddr, flags, 0, timeout, 1); |
c87e2837 | 2588 | break; |
52400ba9 DH |
2589 | case FUTEX_WAIT_REQUEUE_PI: |
2590 | val3 = FUTEX_BITSET_MATCH_ANY; | |
b41277dc DH |
2591 | ret = futex_wait_requeue_pi(uaddr, flags, val, timeout, val3, |
2592 | uaddr2); | |
52400ba9 | 2593 | break; |
52400ba9 | 2594 | case FUTEX_CMP_REQUEUE_PI: |
b41277dc | 2595 | ret = futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 1); |
52400ba9 | 2596 | break; |
1da177e4 LT |
2597 | default: |
2598 | ret = -ENOSYS; | |
2599 | } | |
2600 | return ret; | |
2601 | } | |
2602 | ||
2603 | ||
17da2bd9 HC |
2604 | SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val, |
2605 | struct timespec __user *, utime, u32 __user *, uaddr2, | |
2606 | u32, val3) | |
1da177e4 | 2607 | { |
c19384b5 PP |
2608 | struct timespec ts; |
2609 | ktime_t t, *tp = NULL; | |
e2970f2f | 2610 | u32 val2 = 0; |
34f01cc1 | 2611 | int cmd = op & FUTEX_CMD_MASK; |
1da177e4 | 2612 | |
cd689985 | 2613 | if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI || |
52400ba9 DH |
2614 | cmd == FUTEX_WAIT_BITSET || |
2615 | cmd == FUTEX_WAIT_REQUEUE_PI)) { | |
c19384b5 | 2616 | if (copy_from_user(&ts, utime, sizeof(ts)) != 0) |
1da177e4 | 2617 | return -EFAULT; |
c19384b5 | 2618 | if (!timespec_valid(&ts)) |
9741ef96 | 2619 | return -EINVAL; |
c19384b5 PP |
2620 | |
2621 | t = timespec_to_ktime(ts); | |
34f01cc1 | 2622 | if (cmd == FUTEX_WAIT) |
5a7780e7 | 2623 | t = ktime_add_safe(ktime_get(), t); |
c19384b5 | 2624 | tp = &t; |
1da177e4 LT |
2625 | } |
2626 | /* | |
52400ba9 | 2627 | * requeue parameter in 'utime' if cmd == FUTEX_*_REQUEUE_*. |
f54f0986 | 2628 | * number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP. |
1da177e4 | 2629 | */ |
f54f0986 | 2630 | if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE || |
ba9c22f2 | 2631 | cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP) |
e2970f2f | 2632 | val2 = (u32) (unsigned long) utime; |
1da177e4 | 2633 | |
c19384b5 | 2634 | return do_futex(uaddr, op, val, tp, uaddr2, val2, val3); |
1da177e4 LT |
2635 | } |
2636 | ||
f6d107fb | 2637 | static int __init futex_init(void) |
1da177e4 | 2638 | { |
a0c1e907 | 2639 | u32 curval; |
3e4ab747 | 2640 | int i; |
95362fa9 | 2641 | |
a0c1e907 TG |
2642 | /* |
2643 | * This will fail and we want it. Some arch implementations do | |
2644 | * runtime detection of the futex_atomic_cmpxchg_inatomic() | |
2645 | * functionality. We want to know that before we call in any | |
2646 | * of the complex code paths. Also we want to prevent | |
2647 | * registration of robust lists in that case. NULL is | |
2648 | * guaranteed to fault and we get -EFAULT on functional | |
fb62db2b | 2649 | * implementation, the non-functional ones will return |
a0c1e907 TG |
2650 | * -ENOSYS. |
2651 | */ | |
2652 | curval = cmpxchg_futex_value_locked(NULL, 0, 0); | |
2653 | if (curval == -EFAULT) | |
2654 | futex_cmpxchg_enabled = 1; | |
2655 | ||
3e4ab747 TG |
2656 | for (i = 0; i < ARRAY_SIZE(futex_queues); i++) { |
2657 | plist_head_init(&futex_queues[i].chain, &futex_queues[i].lock); | |
2658 | spin_lock_init(&futex_queues[i].lock); | |
2659 | } | |
2660 | ||
1da177e4 LT |
2661 | return 0; |
2662 | } | |
f6d107fb | 2663 | __initcall(futex_init); |