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1da177e4 LT |
1 | /* |
2 | * Fast Userspace Mutexes (which I call "Futexes!"). | |
3 | * (C) Rusty Russell, IBM 2002 | |
4 | * | |
5 | * Generalized futexes, futex requeueing, misc fixes by Ingo Molnar | |
6 | * (C) Copyright 2003 Red Hat Inc, All Rights Reserved | |
7 | * | |
8 | * Removed page pinning, fix privately mapped COW pages and other cleanups | |
9 | * (C) Copyright 2003, 2004 Jamie Lokier | |
10 | * | |
0771dfef IM |
11 | * Robust futex support started by Ingo Molnar |
12 | * (C) Copyright 2006 Red Hat Inc, All Rights Reserved | |
13 | * Thanks to Thomas Gleixner for suggestions, analysis and fixes. | |
14 | * | |
c87e2837 IM |
15 | * PI-futex support started by Ingo Molnar and Thomas Gleixner |
16 | * Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> | |
17 | * Copyright (C) 2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com> | |
18 | * | |
34f01cc1 ED |
19 | * PRIVATE futexes by Eric Dumazet |
20 | * Copyright (C) 2007 Eric Dumazet <dada1@cosmosbay.com> | |
21 | * | |
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 | ||
c87e2837 IM |
71 | /* |
72 | * Priority Inheritance state: | |
73 | */ | |
74 | struct futex_pi_state { | |
75 | /* | |
76 | * list of 'owned' pi_state instances - these have to be | |
77 | * cleaned up in do_exit() if the task exits prematurely: | |
78 | */ | |
79 | struct list_head list; | |
80 | ||
81 | /* | |
82 | * The PI object: | |
83 | */ | |
84 | struct rt_mutex pi_mutex; | |
85 | ||
86 | struct task_struct *owner; | |
87 | atomic_t refcount; | |
88 | ||
89 | union futex_key key; | |
90 | }; | |
91 | ||
d8d88fbb DH |
92 | /** |
93 | * struct futex_q - The hashed futex queue entry, one per waiting task | |
94 | * @task: the task waiting on the futex | |
95 | * @lock_ptr: the hash bucket lock | |
96 | * @key: the key the futex is hashed on | |
97 | * @pi_state: optional priority inheritance state | |
98 | * @rt_waiter: rt_waiter storage for use with requeue_pi | |
99 | * @requeue_pi_key: the requeue_pi target futex key | |
100 | * @bitset: bitset for the optional bitmasked wakeup | |
101 | * | |
102 | * We use this hashed waitqueue, instead of a normal wait_queue_t, so | |
1da177e4 LT |
103 | * we can wake only the relevant ones (hashed queues may be shared). |
104 | * | |
105 | * A futex_q has a woken state, just like tasks have TASK_RUNNING. | |
ec92d082 | 106 | * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0. |
1da177e4 | 107 | * The order of wakup is always to make the first condition true, then |
d8d88fbb DH |
108 | * the second. |
109 | * | |
110 | * PI futexes are typically woken before they are removed from the hash list via | |
111 | * the rt_mutex code. See unqueue_me_pi(). | |
1da177e4 LT |
112 | */ |
113 | struct futex_q { | |
ec92d082 | 114 | struct plist_node list; |
1da177e4 | 115 | |
d8d88fbb | 116 | struct task_struct *task; |
1da177e4 | 117 | spinlock_t *lock_ptr; |
1da177e4 | 118 | union futex_key key; |
c87e2837 | 119 | struct futex_pi_state *pi_state; |
52400ba9 | 120 | struct rt_mutex_waiter *rt_waiter; |
84bc4af5 | 121 | union futex_key *requeue_pi_key; |
cd689985 | 122 | u32 bitset; |
1da177e4 LT |
123 | }; |
124 | ||
125 | /* | |
b2d0994b DH |
126 | * Hash buckets are shared by all the futex_keys that hash to the same |
127 | * location. Each key may have multiple futex_q structures, one for each task | |
128 | * waiting on a futex. | |
1da177e4 LT |
129 | */ |
130 | struct futex_hash_bucket { | |
ec92d082 PP |
131 | spinlock_t lock; |
132 | struct plist_head chain; | |
1da177e4 LT |
133 | }; |
134 | ||
135 | static struct futex_hash_bucket futex_queues[1<<FUTEX_HASHBITS]; | |
136 | ||
1da177e4 LT |
137 | /* |
138 | * We hash on the keys returned from get_futex_key (see below). | |
139 | */ | |
140 | static struct futex_hash_bucket *hash_futex(union futex_key *key) | |
141 | { | |
142 | u32 hash = jhash2((u32*)&key->both.word, | |
143 | (sizeof(key->both.word)+sizeof(key->both.ptr))/4, | |
144 | key->both.offset); | |
145 | return &futex_queues[hash & ((1 << FUTEX_HASHBITS)-1)]; | |
146 | } | |
147 | ||
148 | /* | |
149 | * Return 1 if two futex_keys are equal, 0 otherwise. | |
150 | */ | |
151 | static inline int match_futex(union futex_key *key1, union futex_key *key2) | |
152 | { | |
2bc87203 DH |
153 | return (key1 && key2 |
154 | && key1->both.word == key2->both.word | |
1da177e4 LT |
155 | && key1->both.ptr == key2->both.ptr |
156 | && key1->both.offset == key2->both.offset); | |
157 | } | |
158 | ||
38d47c1b PZ |
159 | /* |
160 | * Take a reference to the resource addressed by a key. | |
161 | * Can be called while holding spinlocks. | |
162 | * | |
163 | */ | |
164 | static void get_futex_key_refs(union futex_key *key) | |
165 | { | |
166 | if (!key->both.ptr) | |
167 | return; | |
168 | ||
169 | switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { | |
170 | case FUT_OFF_INODE: | |
171 | atomic_inc(&key->shared.inode->i_count); | |
172 | break; | |
173 | case FUT_OFF_MMSHARED: | |
174 | atomic_inc(&key->private.mm->mm_count); | |
175 | break; | |
176 | } | |
177 | } | |
178 | ||
179 | /* | |
180 | * Drop a reference to the resource addressed by a key. | |
181 | * The hash bucket spinlock must not be held. | |
182 | */ | |
183 | static void drop_futex_key_refs(union futex_key *key) | |
184 | { | |
90621c40 DH |
185 | if (!key->both.ptr) { |
186 | /* If we're here then we tried to put a key we failed to get */ | |
187 | WARN_ON_ONCE(1); | |
38d47c1b | 188 | return; |
90621c40 | 189 | } |
38d47c1b PZ |
190 | |
191 | switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { | |
192 | case FUT_OFF_INODE: | |
193 | iput(key->shared.inode); | |
194 | break; | |
195 | case FUT_OFF_MMSHARED: | |
196 | mmdrop(key->private.mm); | |
197 | break; | |
198 | } | |
199 | } | |
200 | ||
34f01cc1 | 201 | /** |
d96ee56c DH |
202 | * get_futex_key() - Get parameters which are the keys for a futex |
203 | * @uaddr: virtual address of the futex | |
204 | * @fshared: 0 for a PROCESS_PRIVATE futex, 1 for PROCESS_SHARED | |
205 | * @key: address where result is stored. | |
34f01cc1 ED |
206 | * |
207 | * Returns a negative error code or 0 | |
208 | * The key words are stored in *key on success. | |
1da177e4 | 209 | * |
f3a43f3f | 210 | * For shared mappings, it's (page->index, vma->vm_file->f_path.dentry->d_inode, |
1da177e4 LT |
211 | * offset_within_page). For private mappings, it's (uaddr, current->mm). |
212 | * We can usually work out the index without swapping in the page. | |
213 | * | |
b2d0994b | 214 | * lock_page() might sleep, the caller should not hold a spinlock. |
1da177e4 | 215 | */ |
64d1304a | 216 | static int |
7485d0d3 | 217 | get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key) |
1da177e4 | 218 | { |
e2970f2f | 219 | unsigned long address = (unsigned long)uaddr; |
1da177e4 | 220 | struct mm_struct *mm = current->mm; |
1da177e4 LT |
221 | struct page *page; |
222 | int err; | |
223 | ||
224 | /* | |
225 | * The futex address must be "naturally" aligned. | |
226 | */ | |
e2970f2f | 227 | key->both.offset = address % PAGE_SIZE; |
34f01cc1 | 228 | if (unlikely((address % sizeof(u32)) != 0)) |
1da177e4 | 229 | return -EINVAL; |
e2970f2f | 230 | address -= key->both.offset; |
1da177e4 | 231 | |
34f01cc1 ED |
232 | /* |
233 | * PROCESS_PRIVATE futexes are fast. | |
234 | * As the mm cannot disappear under us and the 'key' only needs | |
235 | * virtual address, we dont even have to find the underlying vma. | |
236 | * Note : We do have to check 'uaddr' is a valid user address, | |
237 | * but access_ok() should be faster than find_vma() | |
238 | */ | |
239 | if (!fshared) { | |
7485d0d3 | 240 | if (unlikely(!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))) |
34f01cc1 ED |
241 | return -EFAULT; |
242 | key->private.mm = mm; | |
243 | key->private.address = address; | |
42569c39 | 244 | get_futex_key_refs(key); |
34f01cc1 ED |
245 | return 0; |
246 | } | |
1da177e4 | 247 | |
38d47c1b | 248 | again: |
7485d0d3 | 249 | err = get_user_pages_fast(address, 1, 1, &page); |
38d47c1b PZ |
250 | if (err < 0) |
251 | return err; | |
252 | ||
ce2ae53b | 253 | page = compound_head(page); |
38d47c1b PZ |
254 | lock_page(page); |
255 | if (!page->mapping) { | |
256 | unlock_page(page); | |
257 | put_page(page); | |
258 | goto again; | |
259 | } | |
1da177e4 LT |
260 | |
261 | /* | |
262 | * Private mappings are handled in a simple way. | |
263 | * | |
264 | * NOTE: When userspace waits on a MAP_SHARED mapping, even if | |
265 | * it's a read-only handle, it's expected that futexes attach to | |
38d47c1b | 266 | * the object not the particular process. |
1da177e4 | 267 | */ |
38d47c1b PZ |
268 | if (PageAnon(page)) { |
269 | key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */ | |
1da177e4 | 270 | key->private.mm = mm; |
e2970f2f | 271 | key->private.address = address; |
38d47c1b PZ |
272 | } else { |
273 | key->both.offset |= FUT_OFF_INODE; /* inode-based key */ | |
274 | key->shared.inode = page->mapping->host; | |
275 | key->shared.pgoff = page->index; | |
1da177e4 LT |
276 | } |
277 | ||
38d47c1b | 278 | get_futex_key_refs(key); |
1da177e4 | 279 | |
38d47c1b PZ |
280 | unlock_page(page); |
281 | put_page(page); | |
282 | return 0; | |
1da177e4 LT |
283 | } |
284 | ||
38d47c1b | 285 | static inline |
c2f9f201 | 286 | void put_futex_key(int fshared, union futex_key *key) |
1da177e4 | 287 | { |
38d47c1b | 288 | drop_futex_key_refs(key); |
1da177e4 LT |
289 | } |
290 | ||
d96ee56c DH |
291 | /** |
292 | * fault_in_user_writeable() - Fault in user address and verify RW access | |
d0725992 TG |
293 | * @uaddr: pointer to faulting user space address |
294 | * | |
295 | * Slow path to fixup the fault we just took in the atomic write | |
296 | * access to @uaddr. | |
297 | * | |
298 | * We have no generic implementation of a non destructive write to the | |
299 | * user address. We know that we faulted in the atomic pagefault | |
300 | * disabled section so we can as well avoid the #PF overhead by | |
301 | * calling get_user_pages() right away. | |
302 | */ | |
303 | static int fault_in_user_writeable(u32 __user *uaddr) | |
304 | { | |
722d0172 AK |
305 | struct mm_struct *mm = current->mm; |
306 | int ret; | |
307 | ||
308 | down_read(&mm->mmap_sem); | |
309 | ret = get_user_pages(current, mm, (unsigned long)uaddr, | |
310 | 1, 1, 0, NULL, NULL); | |
311 | up_read(&mm->mmap_sem); | |
312 | ||
d0725992 TG |
313 | return ret < 0 ? ret : 0; |
314 | } | |
315 | ||
4b1c486b DH |
316 | /** |
317 | * futex_top_waiter() - Return the highest priority waiter on a futex | |
d96ee56c DH |
318 | * @hb: the hash bucket the futex_q's reside in |
319 | * @key: the futex key (to distinguish it from other futex futex_q's) | |
4b1c486b DH |
320 | * |
321 | * Must be called with the hb lock held. | |
322 | */ | |
323 | static struct futex_q *futex_top_waiter(struct futex_hash_bucket *hb, | |
324 | union futex_key *key) | |
325 | { | |
326 | struct futex_q *this; | |
327 | ||
328 | plist_for_each_entry(this, &hb->chain, list) { | |
329 | if (match_futex(&this->key, key)) | |
330 | return this; | |
331 | } | |
332 | return NULL; | |
333 | } | |
334 | ||
36cf3b5c TG |
335 | static u32 cmpxchg_futex_value_locked(u32 __user *uaddr, u32 uval, u32 newval) |
336 | { | |
337 | u32 curval; | |
338 | ||
339 | pagefault_disable(); | |
340 | curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval); | |
341 | pagefault_enable(); | |
342 | ||
343 | return curval; | |
344 | } | |
345 | ||
346 | static int get_futex_value_locked(u32 *dest, u32 __user *from) | |
1da177e4 LT |
347 | { |
348 | int ret; | |
349 | ||
a866374a | 350 | pagefault_disable(); |
e2970f2f | 351 | ret = __copy_from_user_inatomic(dest, from, sizeof(u32)); |
a866374a | 352 | pagefault_enable(); |
1da177e4 LT |
353 | |
354 | return ret ? -EFAULT : 0; | |
355 | } | |
356 | ||
c87e2837 IM |
357 | |
358 | /* | |
359 | * PI code: | |
360 | */ | |
361 | static int refill_pi_state_cache(void) | |
362 | { | |
363 | struct futex_pi_state *pi_state; | |
364 | ||
365 | if (likely(current->pi_state_cache)) | |
366 | return 0; | |
367 | ||
4668edc3 | 368 | pi_state = kzalloc(sizeof(*pi_state), GFP_KERNEL); |
c87e2837 IM |
369 | |
370 | if (!pi_state) | |
371 | return -ENOMEM; | |
372 | ||
c87e2837 IM |
373 | INIT_LIST_HEAD(&pi_state->list); |
374 | /* pi_mutex gets initialized later */ | |
375 | pi_state->owner = NULL; | |
376 | atomic_set(&pi_state->refcount, 1); | |
38d47c1b | 377 | pi_state->key = FUTEX_KEY_INIT; |
c87e2837 IM |
378 | |
379 | current->pi_state_cache = pi_state; | |
380 | ||
381 | return 0; | |
382 | } | |
383 | ||
384 | static struct futex_pi_state * alloc_pi_state(void) | |
385 | { | |
386 | struct futex_pi_state *pi_state = current->pi_state_cache; | |
387 | ||
388 | WARN_ON(!pi_state); | |
389 | current->pi_state_cache = NULL; | |
390 | ||
391 | return pi_state; | |
392 | } | |
393 | ||
394 | static void free_pi_state(struct futex_pi_state *pi_state) | |
395 | { | |
396 | if (!atomic_dec_and_test(&pi_state->refcount)) | |
397 | return; | |
398 | ||
399 | /* | |
400 | * If pi_state->owner is NULL, the owner is most probably dying | |
401 | * and has cleaned up the pi_state already | |
402 | */ | |
403 | if (pi_state->owner) { | |
1d615482 | 404 | raw_spin_lock_irq(&pi_state->owner->pi_lock); |
c87e2837 | 405 | list_del_init(&pi_state->list); |
1d615482 | 406 | raw_spin_unlock_irq(&pi_state->owner->pi_lock); |
c87e2837 IM |
407 | |
408 | rt_mutex_proxy_unlock(&pi_state->pi_mutex, pi_state->owner); | |
409 | } | |
410 | ||
411 | if (current->pi_state_cache) | |
412 | kfree(pi_state); | |
413 | else { | |
414 | /* | |
415 | * pi_state->list is already empty. | |
416 | * clear pi_state->owner. | |
417 | * refcount is at 0 - put it back to 1. | |
418 | */ | |
419 | pi_state->owner = NULL; | |
420 | atomic_set(&pi_state->refcount, 1); | |
421 | current->pi_state_cache = pi_state; | |
422 | } | |
423 | } | |
424 | ||
425 | /* | |
426 | * Look up the task based on what TID userspace gave us. | |
427 | * We dont trust it. | |
428 | */ | |
429 | static struct task_struct * futex_find_get_task(pid_t pid) | |
430 | { | |
431 | struct task_struct *p; | |
c69e8d9c | 432 | const struct cred *cred = current_cred(), *pcred; |
c87e2837 | 433 | |
d359b549 | 434 | rcu_read_lock(); |
228ebcbe | 435 | p = find_task_by_vpid(pid); |
c69e8d9c | 436 | if (!p) { |
a06381fe | 437 | p = ERR_PTR(-ESRCH); |
c69e8d9c DH |
438 | } else { |
439 | pcred = __task_cred(p); | |
440 | if (cred->euid != pcred->euid && | |
441 | cred->euid != pcred->uid) | |
442 | p = ERR_PTR(-ESRCH); | |
443 | else | |
444 | get_task_struct(p); | |
445 | } | |
a06381fe | 446 | |
d359b549 | 447 | rcu_read_unlock(); |
c87e2837 IM |
448 | |
449 | return p; | |
450 | } | |
451 | ||
452 | /* | |
453 | * This task is holding PI mutexes at exit time => bad. | |
454 | * Kernel cleans up PI-state, but userspace is likely hosed. | |
455 | * (Robust-futex cleanup is separate and might save the day for userspace.) | |
456 | */ | |
457 | void exit_pi_state_list(struct task_struct *curr) | |
458 | { | |
c87e2837 IM |
459 | struct list_head *next, *head = &curr->pi_state_list; |
460 | struct futex_pi_state *pi_state; | |
627371d7 | 461 | struct futex_hash_bucket *hb; |
38d47c1b | 462 | union futex_key key = FUTEX_KEY_INIT; |
c87e2837 | 463 | |
a0c1e907 TG |
464 | if (!futex_cmpxchg_enabled) |
465 | return; | |
c87e2837 IM |
466 | /* |
467 | * We are a ZOMBIE and nobody can enqueue itself on | |
468 | * pi_state_list anymore, but we have to be careful | |
627371d7 | 469 | * versus waiters unqueueing themselves: |
c87e2837 | 470 | */ |
1d615482 | 471 | raw_spin_lock_irq(&curr->pi_lock); |
c87e2837 IM |
472 | while (!list_empty(head)) { |
473 | ||
474 | next = head->next; | |
475 | pi_state = list_entry(next, struct futex_pi_state, list); | |
476 | key = pi_state->key; | |
627371d7 | 477 | hb = hash_futex(&key); |
1d615482 | 478 | raw_spin_unlock_irq(&curr->pi_lock); |
c87e2837 | 479 | |
c87e2837 IM |
480 | spin_lock(&hb->lock); |
481 | ||
1d615482 | 482 | raw_spin_lock_irq(&curr->pi_lock); |
627371d7 IM |
483 | /* |
484 | * We dropped the pi-lock, so re-check whether this | |
485 | * task still owns the PI-state: | |
486 | */ | |
c87e2837 IM |
487 | if (head->next != next) { |
488 | spin_unlock(&hb->lock); | |
489 | continue; | |
490 | } | |
491 | ||
c87e2837 | 492 | WARN_ON(pi_state->owner != curr); |
627371d7 IM |
493 | WARN_ON(list_empty(&pi_state->list)); |
494 | list_del_init(&pi_state->list); | |
c87e2837 | 495 | pi_state->owner = NULL; |
1d615482 | 496 | raw_spin_unlock_irq(&curr->pi_lock); |
c87e2837 IM |
497 | |
498 | rt_mutex_unlock(&pi_state->pi_mutex); | |
499 | ||
500 | spin_unlock(&hb->lock); | |
501 | ||
1d615482 | 502 | raw_spin_lock_irq(&curr->pi_lock); |
c87e2837 | 503 | } |
1d615482 | 504 | raw_spin_unlock_irq(&curr->pi_lock); |
c87e2837 IM |
505 | } |
506 | ||
507 | static int | |
d0aa7a70 PP |
508 | lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, |
509 | union futex_key *key, struct futex_pi_state **ps) | |
c87e2837 IM |
510 | { |
511 | struct futex_pi_state *pi_state = NULL; | |
512 | struct futex_q *this, *next; | |
ec92d082 | 513 | struct plist_head *head; |
c87e2837 | 514 | struct task_struct *p; |
778e9a9c | 515 | pid_t pid = uval & FUTEX_TID_MASK; |
c87e2837 IM |
516 | |
517 | head = &hb->chain; | |
518 | ||
ec92d082 | 519 | plist_for_each_entry_safe(this, next, head, list) { |
d0aa7a70 | 520 | if (match_futex(&this->key, key)) { |
c87e2837 IM |
521 | /* |
522 | * Another waiter already exists - bump up | |
523 | * the refcount and return its pi_state: | |
524 | */ | |
525 | pi_state = this->pi_state; | |
06a9ec29 TG |
526 | /* |
527 | * Userspace might have messed up non PI and PI futexes | |
528 | */ | |
529 | if (unlikely(!pi_state)) | |
530 | return -EINVAL; | |
531 | ||
627371d7 | 532 | WARN_ON(!atomic_read(&pi_state->refcount)); |
778e9a9c AK |
533 | WARN_ON(pid && pi_state->owner && |
534 | pi_state->owner->pid != pid); | |
627371d7 | 535 | |
c87e2837 | 536 | atomic_inc(&pi_state->refcount); |
d0aa7a70 | 537 | *ps = pi_state; |
c87e2837 IM |
538 | |
539 | return 0; | |
540 | } | |
541 | } | |
542 | ||
543 | /* | |
e3f2ddea | 544 | * We are the first waiter - try to look up the real owner and attach |
778e9a9c | 545 | * the new pi_state to it, but bail out when TID = 0 |
c87e2837 | 546 | */ |
778e9a9c | 547 | if (!pid) |
e3f2ddea | 548 | return -ESRCH; |
c87e2837 | 549 | p = futex_find_get_task(pid); |
778e9a9c AK |
550 | if (IS_ERR(p)) |
551 | return PTR_ERR(p); | |
552 | ||
553 | /* | |
554 | * We need to look at the task state flags to figure out, | |
555 | * whether the task is exiting. To protect against the do_exit | |
556 | * change of the task flags, we do this protected by | |
557 | * p->pi_lock: | |
558 | */ | |
1d615482 | 559 | raw_spin_lock_irq(&p->pi_lock); |
778e9a9c AK |
560 | if (unlikely(p->flags & PF_EXITING)) { |
561 | /* | |
562 | * The task is on the way out. When PF_EXITPIDONE is | |
563 | * set, we know that the task has finished the | |
564 | * cleanup: | |
565 | */ | |
566 | int ret = (p->flags & PF_EXITPIDONE) ? -ESRCH : -EAGAIN; | |
567 | ||
1d615482 | 568 | raw_spin_unlock_irq(&p->pi_lock); |
778e9a9c AK |
569 | put_task_struct(p); |
570 | return ret; | |
571 | } | |
c87e2837 IM |
572 | |
573 | pi_state = alloc_pi_state(); | |
574 | ||
575 | /* | |
576 | * Initialize the pi_mutex in locked state and make 'p' | |
577 | * the owner of it: | |
578 | */ | |
579 | rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p); | |
580 | ||
581 | /* Store the key for possible exit cleanups: */ | |
d0aa7a70 | 582 | pi_state->key = *key; |
c87e2837 | 583 | |
627371d7 | 584 | WARN_ON(!list_empty(&pi_state->list)); |
c87e2837 IM |
585 | list_add(&pi_state->list, &p->pi_state_list); |
586 | pi_state->owner = p; | |
1d615482 | 587 | raw_spin_unlock_irq(&p->pi_lock); |
c87e2837 IM |
588 | |
589 | put_task_struct(p); | |
590 | ||
d0aa7a70 | 591 | *ps = pi_state; |
c87e2837 IM |
592 | |
593 | return 0; | |
594 | } | |
595 | ||
1a52084d | 596 | /** |
d96ee56c | 597 | * futex_lock_pi_atomic() - Atomic work required to acquire a pi aware futex |
bab5bc9e DH |
598 | * @uaddr: the pi futex user address |
599 | * @hb: the pi futex hash bucket | |
600 | * @key: the futex key associated with uaddr and hb | |
601 | * @ps: the pi_state pointer where we store the result of the | |
602 | * lookup | |
603 | * @task: the task to perform the atomic lock work for. This will | |
604 | * be "current" except in the case of requeue pi. | |
605 | * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0) | |
1a52084d DH |
606 | * |
607 | * Returns: | |
608 | * 0 - ready to wait | |
609 | * 1 - acquired the lock | |
610 | * <0 - error | |
611 | * | |
612 | * The hb->lock and futex_key refs shall be held by the caller. | |
613 | */ | |
614 | static int futex_lock_pi_atomic(u32 __user *uaddr, struct futex_hash_bucket *hb, | |
615 | union futex_key *key, | |
616 | struct futex_pi_state **ps, | |
bab5bc9e | 617 | struct task_struct *task, int set_waiters) |
1a52084d DH |
618 | { |
619 | int lock_taken, ret, ownerdied = 0; | |
620 | u32 uval, newval, curval; | |
621 | ||
622 | retry: | |
623 | ret = lock_taken = 0; | |
624 | ||
625 | /* | |
626 | * To avoid races, we attempt to take the lock here again | |
627 | * (by doing a 0 -> TID atomic cmpxchg), while holding all | |
628 | * the locks. It will most likely not succeed. | |
629 | */ | |
630 | newval = task_pid_vnr(task); | |
bab5bc9e DH |
631 | if (set_waiters) |
632 | newval |= FUTEX_WAITERS; | |
1a52084d DH |
633 | |
634 | curval = cmpxchg_futex_value_locked(uaddr, 0, newval); | |
635 | ||
636 | if (unlikely(curval == -EFAULT)) | |
637 | return -EFAULT; | |
638 | ||
639 | /* | |
640 | * Detect deadlocks. | |
641 | */ | |
642 | if ((unlikely((curval & FUTEX_TID_MASK) == task_pid_vnr(task)))) | |
643 | return -EDEADLK; | |
644 | ||
645 | /* | |
646 | * Surprise - we got the lock. Just return to userspace: | |
647 | */ | |
648 | if (unlikely(!curval)) | |
649 | return 1; | |
650 | ||
651 | uval = curval; | |
652 | ||
653 | /* | |
654 | * Set the FUTEX_WAITERS flag, so the owner will know it has someone | |
655 | * to wake at the next unlock. | |
656 | */ | |
657 | newval = curval | FUTEX_WAITERS; | |
658 | ||
659 | /* | |
660 | * There are two cases, where a futex might have no owner (the | |
661 | * owner TID is 0): OWNER_DIED. We take over the futex in this | |
662 | * case. We also do an unconditional take over, when the owner | |
663 | * of the futex died. | |
664 | * | |
665 | * This is safe as we are protected by the hash bucket lock ! | |
666 | */ | |
667 | if (unlikely(ownerdied || !(curval & FUTEX_TID_MASK))) { | |
668 | /* Keep the OWNER_DIED bit */ | |
669 | newval = (curval & ~FUTEX_TID_MASK) | task_pid_vnr(task); | |
670 | ownerdied = 0; | |
671 | lock_taken = 1; | |
672 | } | |
673 | ||
674 | curval = cmpxchg_futex_value_locked(uaddr, uval, newval); | |
675 | ||
676 | if (unlikely(curval == -EFAULT)) | |
677 | return -EFAULT; | |
678 | if (unlikely(curval != uval)) | |
679 | goto retry; | |
680 | ||
681 | /* | |
682 | * We took the lock due to owner died take over. | |
683 | */ | |
684 | if (unlikely(lock_taken)) | |
685 | return 1; | |
686 | ||
687 | /* | |
688 | * We dont have the lock. Look up the PI state (or create it if | |
689 | * we are the first waiter): | |
690 | */ | |
691 | ret = lookup_pi_state(uval, hb, key, ps); | |
692 | ||
693 | if (unlikely(ret)) { | |
694 | switch (ret) { | |
695 | case -ESRCH: | |
696 | /* | |
697 | * No owner found for this futex. Check if the | |
698 | * OWNER_DIED bit is set to figure out whether | |
699 | * this is a robust futex or not. | |
700 | */ | |
701 | if (get_futex_value_locked(&curval, uaddr)) | |
702 | return -EFAULT; | |
703 | ||
704 | /* | |
705 | * We simply start over in case of a robust | |
706 | * futex. The code above will take the futex | |
707 | * and return happy. | |
708 | */ | |
709 | if (curval & FUTEX_OWNER_DIED) { | |
710 | ownerdied = 1; | |
711 | goto retry; | |
712 | } | |
713 | default: | |
714 | break; | |
715 | } | |
716 | } | |
717 | ||
718 | return ret; | |
719 | } | |
720 | ||
1da177e4 LT |
721 | /* |
722 | * The hash bucket lock must be held when this is called. | |
723 | * Afterwards, the futex_q must not be accessed. | |
724 | */ | |
725 | static void wake_futex(struct futex_q *q) | |
726 | { | |
f1a11e05 TG |
727 | struct task_struct *p = q->task; |
728 | ||
1da177e4 | 729 | /* |
f1a11e05 TG |
730 | * We set q->lock_ptr = NULL _before_ we wake up the task. If |
731 | * a non futex wake up happens on another CPU then the task | |
732 | * might exit and p would dereference a non existing task | |
733 | * struct. Prevent this by holding a reference on p across the | |
734 | * wake up. | |
1da177e4 | 735 | */ |
f1a11e05 TG |
736 | get_task_struct(p); |
737 | ||
738 | plist_del(&q->list, &q->list.plist); | |
1da177e4 | 739 | /* |
f1a11e05 TG |
740 | * The waiting task can free the futex_q as soon as |
741 | * q->lock_ptr = NULL is written, without taking any locks. A | |
742 | * memory barrier is required here to prevent the following | |
743 | * store to lock_ptr from getting ahead of the plist_del. | |
1da177e4 | 744 | */ |
ccdea2f8 | 745 | smp_wmb(); |
1da177e4 | 746 | q->lock_ptr = NULL; |
f1a11e05 TG |
747 | |
748 | wake_up_state(p, TASK_NORMAL); | |
749 | put_task_struct(p); | |
1da177e4 LT |
750 | } |
751 | ||
c87e2837 IM |
752 | static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this) |
753 | { | |
754 | struct task_struct *new_owner; | |
755 | struct futex_pi_state *pi_state = this->pi_state; | |
756 | u32 curval, newval; | |
757 | ||
758 | if (!pi_state) | |
759 | return -EINVAL; | |
760 | ||
51246bfd TG |
761 | /* |
762 | * If current does not own the pi_state then the futex is | |
763 | * inconsistent and user space fiddled with the futex value. | |
764 | */ | |
765 | if (pi_state->owner != current) | |
766 | return -EINVAL; | |
767 | ||
d209d74d | 768 | raw_spin_lock(&pi_state->pi_mutex.wait_lock); |
c87e2837 IM |
769 | new_owner = rt_mutex_next_owner(&pi_state->pi_mutex); |
770 | ||
771 | /* | |
772 | * This happens when we have stolen the lock and the original | |
773 | * pending owner did not enqueue itself back on the rt_mutex. | |
774 | * Thats not a tragedy. We know that way, that a lock waiter | |
775 | * is on the fly. We make the futex_q waiter the pending owner. | |
776 | */ | |
777 | if (!new_owner) | |
778 | new_owner = this->task; | |
779 | ||
780 | /* | |
781 | * We pass it to the next owner. (The WAITERS bit is always | |
782 | * kept enabled while there is PI state around. We must also | |
783 | * preserve the owner died bit.) | |
784 | */ | |
e3f2ddea | 785 | if (!(uval & FUTEX_OWNER_DIED)) { |
778e9a9c AK |
786 | int ret = 0; |
787 | ||
b488893a | 788 | newval = FUTEX_WAITERS | task_pid_vnr(new_owner); |
e3f2ddea | 789 | |
36cf3b5c | 790 | curval = cmpxchg_futex_value_locked(uaddr, uval, newval); |
778e9a9c | 791 | |
e3f2ddea | 792 | if (curval == -EFAULT) |
778e9a9c | 793 | ret = -EFAULT; |
cde898fa | 794 | else if (curval != uval) |
778e9a9c AK |
795 | ret = -EINVAL; |
796 | if (ret) { | |
d209d74d | 797 | raw_spin_unlock(&pi_state->pi_mutex.wait_lock); |
778e9a9c AK |
798 | return ret; |
799 | } | |
e3f2ddea | 800 | } |
c87e2837 | 801 | |
1d615482 | 802 | raw_spin_lock_irq(&pi_state->owner->pi_lock); |
627371d7 IM |
803 | WARN_ON(list_empty(&pi_state->list)); |
804 | list_del_init(&pi_state->list); | |
1d615482 | 805 | raw_spin_unlock_irq(&pi_state->owner->pi_lock); |
627371d7 | 806 | |
1d615482 | 807 | raw_spin_lock_irq(&new_owner->pi_lock); |
627371d7 | 808 | WARN_ON(!list_empty(&pi_state->list)); |
c87e2837 IM |
809 | list_add(&pi_state->list, &new_owner->pi_state_list); |
810 | pi_state->owner = new_owner; | |
1d615482 | 811 | raw_spin_unlock_irq(&new_owner->pi_lock); |
627371d7 | 812 | |
d209d74d | 813 | raw_spin_unlock(&pi_state->pi_mutex.wait_lock); |
c87e2837 IM |
814 | rt_mutex_unlock(&pi_state->pi_mutex); |
815 | ||
816 | return 0; | |
817 | } | |
818 | ||
819 | static int unlock_futex_pi(u32 __user *uaddr, u32 uval) | |
820 | { | |
821 | u32 oldval; | |
822 | ||
823 | /* | |
824 | * There is no waiter, so we unlock the futex. The owner died | |
825 | * bit has not to be preserved here. We are the owner: | |
826 | */ | |
36cf3b5c | 827 | oldval = cmpxchg_futex_value_locked(uaddr, uval, 0); |
c87e2837 IM |
828 | |
829 | if (oldval == -EFAULT) | |
830 | return oldval; | |
831 | if (oldval != uval) | |
832 | return -EAGAIN; | |
833 | ||
834 | return 0; | |
835 | } | |
836 | ||
8b8f319f IM |
837 | /* |
838 | * Express the locking dependencies for lockdep: | |
839 | */ | |
840 | static inline void | |
841 | double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) | |
842 | { | |
843 | if (hb1 <= hb2) { | |
844 | spin_lock(&hb1->lock); | |
845 | if (hb1 < hb2) | |
846 | spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING); | |
847 | } else { /* hb1 > hb2 */ | |
848 | spin_lock(&hb2->lock); | |
849 | spin_lock_nested(&hb1->lock, SINGLE_DEPTH_NESTING); | |
850 | } | |
851 | } | |
852 | ||
5eb3dc62 DH |
853 | static inline void |
854 | double_unlock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) | |
855 | { | |
f061d351 | 856 | spin_unlock(&hb1->lock); |
88f502fe IM |
857 | if (hb1 != hb2) |
858 | spin_unlock(&hb2->lock); | |
5eb3dc62 DH |
859 | } |
860 | ||
1da177e4 | 861 | /* |
b2d0994b | 862 | * Wake up waiters matching bitset queued on this futex (uaddr). |
1da177e4 | 863 | */ |
c2f9f201 | 864 | static int futex_wake(u32 __user *uaddr, int fshared, int nr_wake, u32 bitset) |
1da177e4 | 865 | { |
e2970f2f | 866 | struct futex_hash_bucket *hb; |
1da177e4 | 867 | struct futex_q *this, *next; |
ec92d082 | 868 | struct plist_head *head; |
38d47c1b | 869 | union futex_key key = FUTEX_KEY_INIT; |
1da177e4 LT |
870 | int ret; |
871 | ||
cd689985 TG |
872 | if (!bitset) |
873 | return -EINVAL; | |
874 | ||
7485d0d3 | 875 | ret = get_futex_key(uaddr, fshared, &key); |
1da177e4 LT |
876 | if (unlikely(ret != 0)) |
877 | goto out; | |
878 | ||
e2970f2f IM |
879 | hb = hash_futex(&key); |
880 | spin_lock(&hb->lock); | |
881 | head = &hb->chain; | |
1da177e4 | 882 | |
ec92d082 | 883 | plist_for_each_entry_safe(this, next, head, list) { |
1da177e4 | 884 | if (match_futex (&this->key, &key)) { |
52400ba9 | 885 | if (this->pi_state || this->rt_waiter) { |
ed6f7b10 IM |
886 | ret = -EINVAL; |
887 | break; | |
888 | } | |
cd689985 TG |
889 | |
890 | /* Check if one of the bits is set in both bitsets */ | |
891 | if (!(this->bitset & bitset)) | |
892 | continue; | |
893 | ||
1da177e4 LT |
894 | wake_futex(this); |
895 | if (++ret >= nr_wake) | |
896 | break; | |
897 | } | |
898 | } | |
899 | ||
e2970f2f | 900 | spin_unlock(&hb->lock); |
38d47c1b | 901 | put_futex_key(fshared, &key); |
42d35d48 | 902 | out: |
1da177e4 LT |
903 | return ret; |
904 | } | |
905 | ||
4732efbe JJ |
906 | /* |
907 | * Wake up all waiters hashed on the physical page that is mapped | |
908 | * to this virtual address: | |
909 | */ | |
e2970f2f | 910 | static int |
c2f9f201 | 911 | futex_wake_op(u32 __user *uaddr1, int fshared, u32 __user *uaddr2, |
e2970f2f | 912 | int nr_wake, int nr_wake2, int op) |
4732efbe | 913 | { |
38d47c1b | 914 | union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT; |
e2970f2f | 915 | struct futex_hash_bucket *hb1, *hb2; |
ec92d082 | 916 | struct plist_head *head; |
4732efbe | 917 | struct futex_q *this, *next; |
e4dc5b7a | 918 | int ret, op_ret; |
4732efbe | 919 | |
e4dc5b7a | 920 | retry: |
7485d0d3 | 921 | ret = get_futex_key(uaddr1, fshared, &key1); |
4732efbe JJ |
922 | if (unlikely(ret != 0)) |
923 | goto out; | |
7485d0d3 | 924 | ret = get_futex_key(uaddr2, fshared, &key2); |
4732efbe | 925 | if (unlikely(ret != 0)) |
42d35d48 | 926 | goto out_put_key1; |
4732efbe | 927 | |
e2970f2f IM |
928 | hb1 = hash_futex(&key1); |
929 | hb2 = hash_futex(&key2); | |
4732efbe | 930 | |
e4dc5b7a | 931 | retry_private: |
eaaea803 | 932 | double_lock_hb(hb1, hb2); |
e2970f2f | 933 | op_ret = futex_atomic_op_inuser(op, uaddr2); |
4732efbe | 934 | if (unlikely(op_ret < 0)) { |
4732efbe | 935 | |
5eb3dc62 | 936 | double_unlock_hb(hb1, hb2); |
4732efbe | 937 | |
7ee1dd3f | 938 | #ifndef CONFIG_MMU |
e2970f2f IM |
939 | /* |
940 | * we don't get EFAULT from MMU faults if we don't have an MMU, | |
941 | * but we might get them from range checking | |
942 | */ | |
7ee1dd3f | 943 | ret = op_ret; |
42d35d48 | 944 | goto out_put_keys; |
7ee1dd3f DH |
945 | #endif |
946 | ||
796f8d9b DG |
947 | if (unlikely(op_ret != -EFAULT)) { |
948 | ret = op_ret; | |
42d35d48 | 949 | goto out_put_keys; |
796f8d9b DG |
950 | } |
951 | ||
d0725992 | 952 | ret = fault_in_user_writeable(uaddr2); |
4732efbe | 953 | if (ret) |
de87fcc1 | 954 | goto out_put_keys; |
4732efbe | 955 | |
e4dc5b7a DH |
956 | if (!fshared) |
957 | goto retry_private; | |
958 | ||
de87fcc1 DH |
959 | put_futex_key(fshared, &key2); |
960 | put_futex_key(fshared, &key1); | |
e4dc5b7a | 961 | goto retry; |
4732efbe JJ |
962 | } |
963 | ||
e2970f2f | 964 | head = &hb1->chain; |
4732efbe | 965 | |
ec92d082 | 966 | plist_for_each_entry_safe(this, next, head, list) { |
4732efbe JJ |
967 | if (match_futex (&this->key, &key1)) { |
968 | wake_futex(this); | |
969 | if (++ret >= nr_wake) | |
970 | break; | |
971 | } | |
972 | } | |
973 | ||
974 | if (op_ret > 0) { | |
e2970f2f | 975 | head = &hb2->chain; |
4732efbe JJ |
976 | |
977 | op_ret = 0; | |
ec92d082 | 978 | plist_for_each_entry_safe(this, next, head, list) { |
4732efbe JJ |
979 | if (match_futex (&this->key, &key2)) { |
980 | wake_futex(this); | |
981 | if (++op_ret >= nr_wake2) | |
982 | break; | |
983 | } | |
984 | } | |
985 | ret += op_ret; | |
986 | } | |
987 | ||
5eb3dc62 | 988 | double_unlock_hb(hb1, hb2); |
42d35d48 | 989 | out_put_keys: |
38d47c1b | 990 | put_futex_key(fshared, &key2); |
42d35d48 | 991 | out_put_key1: |
38d47c1b | 992 | put_futex_key(fshared, &key1); |
42d35d48 | 993 | out: |
4732efbe JJ |
994 | return ret; |
995 | } | |
996 | ||
9121e478 DH |
997 | /** |
998 | * requeue_futex() - Requeue a futex_q from one hb to another | |
999 | * @q: the futex_q to requeue | |
1000 | * @hb1: the source hash_bucket | |
1001 | * @hb2: the target hash_bucket | |
1002 | * @key2: the new key for the requeued futex_q | |
1003 | */ | |
1004 | static inline | |
1005 | void requeue_futex(struct futex_q *q, struct futex_hash_bucket *hb1, | |
1006 | struct futex_hash_bucket *hb2, union futex_key *key2) | |
1007 | { | |
1008 | ||
1009 | /* | |
1010 | * If key1 and key2 hash to the same bucket, no need to | |
1011 | * requeue. | |
1012 | */ | |
1013 | if (likely(&hb1->chain != &hb2->chain)) { | |
1014 | plist_del(&q->list, &hb1->chain); | |
1015 | plist_add(&q->list, &hb2->chain); | |
1016 | q->lock_ptr = &hb2->lock; | |
1017 | #ifdef CONFIG_DEBUG_PI_LIST | |
a2672459 | 1018 | q->list.plist.spinlock = &hb2->lock; |
9121e478 DH |
1019 | #endif |
1020 | } | |
1021 | get_futex_key_refs(key2); | |
1022 | q->key = *key2; | |
1023 | } | |
1024 | ||
52400ba9 DH |
1025 | /** |
1026 | * requeue_pi_wake_futex() - Wake a task that acquired the lock during requeue | |
d96ee56c DH |
1027 | * @q: the futex_q |
1028 | * @key: the key of the requeue target futex | |
1029 | * @hb: the hash_bucket of the requeue target futex | |
52400ba9 DH |
1030 | * |
1031 | * During futex_requeue, with requeue_pi=1, it is possible to acquire the | |
1032 | * target futex if it is uncontended or via a lock steal. Set the futex_q key | |
1033 | * to the requeue target futex so the waiter can detect the wakeup on the right | |
1034 | * futex, but remove it from the hb and NULL the rt_waiter so it can detect | |
beda2c7e DH |
1035 | * atomic lock acquisition. Set the q->lock_ptr to the requeue target hb->lock |
1036 | * to protect access to the pi_state to fixup the owner later. Must be called | |
1037 | * with both q->lock_ptr and hb->lock held. | |
52400ba9 DH |
1038 | */ |
1039 | static inline | |
beda2c7e DH |
1040 | void requeue_pi_wake_futex(struct futex_q *q, union futex_key *key, |
1041 | struct futex_hash_bucket *hb) | |
52400ba9 | 1042 | { |
52400ba9 DH |
1043 | get_futex_key_refs(key); |
1044 | q->key = *key; | |
1045 | ||
1046 | WARN_ON(plist_node_empty(&q->list)); | |
1047 | plist_del(&q->list, &q->list.plist); | |
1048 | ||
1049 | WARN_ON(!q->rt_waiter); | |
1050 | q->rt_waiter = NULL; | |
1051 | ||
beda2c7e DH |
1052 | q->lock_ptr = &hb->lock; |
1053 | #ifdef CONFIG_DEBUG_PI_LIST | |
a2672459 | 1054 | q->list.plist.spinlock = &hb->lock; |
beda2c7e DH |
1055 | #endif |
1056 | ||
f1a11e05 | 1057 | wake_up_state(q->task, TASK_NORMAL); |
52400ba9 DH |
1058 | } |
1059 | ||
1060 | /** | |
1061 | * futex_proxy_trylock_atomic() - Attempt an atomic lock for the top waiter | |
bab5bc9e DH |
1062 | * @pifutex: the user address of the to futex |
1063 | * @hb1: the from futex hash bucket, must be locked by the caller | |
1064 | * @hb2: the to futex hash bucket, must be locked by the caller | |
1065 | * @key1: the from futex key | |
1066 | * @key2: the to futex key | |
1067 | * @ps: address to store the pi_state pointer | |
1068 | * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0) | |
52400ba9 DH |
1069 | * |
1070 | * Try and get the lock on behalf of the top waiter if we can do it atomically. | |
bab5bc9e DH |
1071 | * Wake the top waiter if we succeed. If the caller specified set_waiters, |
1072 | * then direct futex_lock_pi_atomic() to force setting the FUTEX_WAITERS bit. | |
1073 | * hb1 and hb2 must be held by the caller. | |
52400ba9 DH |
1074 | * |
1075 | * Returns: | |
1076 | * 0 - failed to acquire the lock atomicly | |
1077 | * 1 - acquired the lock | |
1078 | * <0 - error | |
1079 | */ | |
1080 | static int futex_proxy_trylock_atomic(u32 __user *pifutex, | |
1081 | struct futex_hash_bucket *hb1, | |
1082 | struct futex_hash_bucket *hb2, | |
1083 | union futex_key *key1, union futex_key *key2, | |
bab5bc9e | 1084 | struct futex_pi_state **ps, int set_waiters) |
52400ba9 | 1085 | { |
bab5bc9e | 1086 | struct futex_q *top_waiter = NULL; |
52400ba9 DH |
1087 | u32 curval; |
1088 | int ret; | |
1089 | ||
1090 | if (get_futex_value_locked(&curval, pifutex)) | |
1091 | return -EFAULT; | |
1092 | ||
bab5bc9e DH |
1093 | /* |
1094 | * Find the top_waiter and determine if there are additional waiters. | |
1095 | * If the caller intends to requeue more than 1 waiter to pifutex, | |
1096 | * force futex_lock_pi_atomic() to set the FUTEX_WAITERS bit now, | |
1097 | * as we have means to handle the possible fault. If not, don't set | |
1098 | * the bit unecessarily as it will force the subsequent unlock to enter | |
1099 | * the kernel. | |
1100 | */ | |
52400ba9 DH |
1101 | top_waiter = futex_top_waiter(hb1, key1); |
1102 | ||
1103 | /* There are no waiters, nothing for us to do. */ | |
1104 | if (!top_waiter) | |
1105 | return 0; | |
1106 | ||
84bc4af5 DH |
1107 | /* Ensure we requeue to the expected futex. */ |
1108 | if (!match_futex(top_waiter->requeue_pi_key, key2)) | |
1109 | return -EINVAL; | |
1110 | ||
52400ba9 | 1111 | /* |
bab5bc9e DH |
1112 | * Try to take the lock for top_waiter. Set the FUTEX_WAITERS bit in |
1113 | * the contended case or if set_waiters is 1. The pi_state is returned | |
1114 | * in ps in contended cases. | |
52400ba9 | 1115 | */ |
bab5bc9e DH |
1116 | ret = futex_lock_pi_atomic(pifutex, hb2, key2, ps, top_waiter->task, |
1117 | set_waiters); | |
52400ba9 | 1118 | if (ret == 1) |
beda2c7e | 1119 | requeue_pi_wake_futex(top_waiter, key2, hb2); |
52400ba9 DH |
1120 | |
1121 | return ret; | |
1122 | } | |
1123 | ||
1124 | /** | |
1125 | * futex_requeue() - Requeue waiters from uaddr1 to uaddr2 | |
1126 | * uaddr1: source futex user address | |
1127 | * uaddr2: target futex user address | |
1128 | * nr_wake: number of waiters to wake (must be 1 for requeue_pi) | |
1129 | * nr_requeue: number of waiters to requeue (0-INT_MAX) | |
1130 | * requeue_pi: if we are attempting to requeue from a non-pi futex to a | |
1131 | * pi futex (pi to pi requeue is not supported) | |
1132 | * | |
1133 | * Requeue waiters on uaddr1 to uaddr2. In the requeue_pi case, try to acquire | |
1134 | * uaddr2 atomically on behalf of the top waiter. | |
1135 | * | |
1136 | * Returns: | |
1137 | * >=0 - on success, the number of tasks requeued or woken | |
1138 | * <0 - on error | |
1da177e4 | 1139 | */ |
c2f9f201 | 1140 | static int futex_requeue(u32 __user *uaddr1, int fshared, u32 __user *uaddr2, |
52400ba9 DH |
1141 | int nr_wake, int nr_requeue, u32 *cmpval, |
1142 | int requeue_pi) | |
1da177e4 | 1143 | { |
38d47c1b | 1144 | union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT; |
52400ba9 DH |
1145 | int drop_count = 0, task_count = 0, ret; |
1146 | struct futex_pi_state *pi_state = NULL; | |
e2970f2f | 1147 | struct futex_hash_bucket *hb1, *hb2; |
ec92d082 | 1148 | struct plist_head *head1; |
1da177e4 | 1149 | struct futex_q *this, *next; |
52400ba9 DH |
1150 | u32 curval2; |
1151 | ||
1152 | if (requeue_pi) { | |
1153 | /* | |
1154 | * requeue_pi requires a pi_state, try to allocate it now | |
1155 | * without any locks in case it fails. | |
1156 | */ | |
1157 | if (refill_pi_state_cache()) | |
1158 | return -ENOMEM; | |
1159 | /* | |
1160 | * requeue_pi must wake as many tasks as it can, up to nr_wake | |
1161 | * + nr_requeue, since it acquires the rt_mutex prior to | |
1162 | * returning to userspace, so as to not leave the rt_mutex with | |
1163 | * waiters and no owner. However, second and third wake-ups | |
1164 | * cannot be predicted as they involve race conditions with the | |
1165 | * first wake and a fault while looking up the pi_state. Both | |
1166 | * pthread_cond_signal() and pthread_cond_broadcast() should | |
1167 | * use nr_wake=1. | |
1168 | */ | |
1169 | if (nr_wake != 1) | |
1170 | return -EINVAL; | |
1171 | } | |
1da177e4 | 1172 | |
42d35d48 | 1173 | retry: |
52400ba9 DH |
1174 | if (pi_state != NULL) { |
1175 | /* | |
1176 | * We will have to lookup the pi_state again, so free this one | |
1177 | * to keep the accounting correct. | |
1178 | */ | |
1179 | free_pi_state(pi_state); | |
1180 | pi_state = NULL; | |
1181 | } | |
1182 | ||
7485d0d3 | 1183 | ret = get_futex_key(uaddr1, fshared, &key1); |
1da177e4 LT |
1184 | if (unlikely(ret != 0)) |
1185 | goto out; | |
7485d0d3 | 1186 | ret = get_futex_key(uaddr2, fshared, &key2); |
1da177e4 | 1187 | if (unlikely(ret != 0)) |
42d35d48 | 1188 | goto out_put_key1; |
1da177e4 | 1189 | |
e2970f2f IM |
1190 | hb1 = hash_futex(&key1); |
1191 | hb2 = hash_futex(&key2); | |
1da177e4 | 1192 | |
e4dc5b7a | 1193 | retry_private: |
8b8f319f | 1194 | double_lock_hb(hb1, hb2); |
1da177e4 | 1195 | |
e2970f2f IM |
1196 | if (likely(cmpval != NULL)) { |
1197 | u32 curval; | |
1da177e4 | 1198 | |
e2970f2f | 1199 | ret = get_futex_value_locked(&curval, uaddr1); |
1da177e4 LT |
1200 | |
1201 | if (unlikely(ret)) { | |
5eb3dc62 | 1202 | double_unlock_hb(hb1, hb2); |
1da177e4 | 1203 | |
e2970f2f | 1204 | ret = get_user(curval, uaddr1); |
e4dc5b7a DH |
1205 | if (ret) |
1206 | goto out_put_keys; | |
1da177e4 | 1207 | |
e4dc5b7a DH |
1208 | if (!fshared) |
1209 | goto retry_private; | |
1da177e4 | 1210 | |
e4dc5b7a DH |
1211 | put_futex_key(fshared, &key2); |
1212 | put_futex_key(fshared, &key1); | |
1213 | goto retry; | |
1da177e4 | 1214 | } |
e2970f2f | 1215 | if (curval != *cmpval) { |
1da177e4 LT |
1216 | ret = -EAGAIN; |
1217 | goto out_unlock; | |
1218 | } | |
1219 | } | |
1220 | ||
52400ba9 | 1221 | if (requeue_pi && (task_count - nr_wake < nr_requeue)) { |
bab5bc9e DH |
1222 | /* |
1223 | * Attempt to acquire uaddr2 and wake the top waiter. If we | |
1224 | * intend to requeue waiters, force setting the FUTEX_WAITERS | |
1225 | * bit. We force this here where we are able to easily handle | |
1226 | * faults rather in the requeue loop below. | |
1227 | */ | |
52400ba9 | 1228 | ret = futex_proxy_trylock_atomic(uaddr2, hb1, hb2, &key1, |
bab5bc9e | 1229 | &key2, &pi_state, nr_requeue); |
52400ba9 DH |
1230 | |
1231 | /* | |
1232 | * At this point the top_waiter has either taken uaddr2 or is | |
1233 | * waiting on it. If the former, then the pi_state will not | |
1234 | * exist yet, look it up one more time to ensure we have a | |
1235 | * reference to it. | |
1236 | */ | |
1237 | if (ret == 1) { | |
1238 | WARN_ON(pi_state); | |
89061d3d | 1239 | drop_count++; |
52400ba9 DH |
1240 | task_count++; |
1241 | ret = get_futex_value_locked(&curval2, uaddr2); | |
1242 | if (!ret) | |
1243 | ret = lookup_pi_state(curval2, hb2, &key2, | |
1244 | &pi_state); | |
1245 | } | |
1246 | ||
1247 | switch (ret) { | |
1248 | case 0: | |
1249 | break; | |
1250 | case -EFAULT: | |
1251 | double_unlock_hb(hb1, hb2); | |
1252 | put_futex_key(fshared, &key2); | |
1253 | put_futex_key(fshared, &key1); | |
d0725992 | 1254 | ret = fault_in_user_writeable(uaddr2); |
52400ba9 DH |
1255 | if (!ret) |
1256 | goto retry; | |
1257 | goto out; | |
1258 | case -EAGAIN: | |
1259 | /* The owner was exiting, try again. */ | |
1260 | double_unlock_hb(hb1, hb2); | |
1261 | put_futex_key(fshared, &key2); | |
1262 | put_futex_key(fshared, &key1); | |
1263 | cond_resched(); | |
1264 | goto retry; | |
1265 | default: | |
1266 | goto out_unlock; | |
1267 | } | |
1268 | } | |
1269 | ||
e2970f2f | 1270 | head1 = &hb1->chain; |
ec92d082 | 1271 | plist_for_each_entry_safe(this, next, head1, list) { |
52400ba9 DH |
1272 | if (task_count - nr_wake >= nr_requeue) |
1273 | break; | |
1274 | ||
1275 | if (!match_futex(&this->key, &key1)) | |
1da177e4 | 1276 | continue; |
52400ba9 | 1277 | |
392741e0 DH |
1278 | /* |
1279 | * FUTEX_WAIT_REQEUE_PI and FUTEX_CMP_REQUEUE_PI should always | |
1280 | * be paired with each other and no other futex ops. | |
1281 | */ | |
1282 | if ((requeue_pi && !this->rt_waiter) || | |
1283 | (!requeue_pi && this->rt_waiter)) { | |
1284 | ret = -EINVAL; | |
1285 | break; | |
1286 | } | |
52400ba9 DH |
1287 | |
1288 | /* | |
1289 | * Wake nr_wake waiters. For requeue_pi, if we acquired the | |
1290 | * lock, we already woke the top_waiter. If not, it will be | |
1291 | * woken by futex_unlock_pi(). | |
1292 | */ | |
1293 | if (++task_count <= nr_wake && !requeue_pi) { | |
1da177e4 | 1294 | wake_futex(this); |
52400ba9 DH |
1295 | continue; |
1296 | } | |
1da177e4 | 1297 | |
84bc4af5 DH |
1298 | /* Ensure we requeue to the expected futex for requeue_pi. */ |
1299 | if (requeue_pi && !match_futex(this->requeue_pi_key, &key2)) { | |
1300 | ret = -EINVAL; | |
1301 | break; | |
1302 | } | |
1303 | ||
52400ba9 DH |
1304 | /* |
1305 | * Requeue nr_requeue waiters and possibly one more in the case | |
1306 | * of requeue_pi if we couldn't acquire the lock atomically. | |
1307 | */ | |
1308 | if (requeue_pi) { | |
1309 | /* Prepare the waiter to take the rt_mutex. */ | |
1310 | atomic_inc(&pi_state->refcount); | |
1311 | this->pi_state = pi_state; | |
1312 | ret = rt_mutex_start_proxy_lock(&pi_state->pi_mutex, | |
1313 | this->rt_waiter, | |
1314 | this->task, 1); | |
1315 | if (ret == 1) { | |
1316 | /* We got the lock. */ | |
beda2c7e | 1317 | requeue_pi_wake_futex(this, &key2, hb2); |
89061d3d | 1318 | drop_count++; |
52400ba9 DH |
1319 | continue; |
1320 | } else if (ret) { | |
1321 | /* -EDEADLK */ | |
1322 | this->pi_state = NULL; | |
1323 | free_pi_state(pi_state); | |
1324 | goto out_unlock; | |
1325 | } | |
1da177e4 | 1326 | } |
52400ba9 DH |
1327 | requeue_futex(this, hb1, hb2, &key2); |
1328 | drop_count++; | |
1da177e4 LT |
1329 | } |
1330 | ||
1331 | out_unlock: | |
5eb3dc62 | 1332 | double_unlock_hb(hb1, hb2); |
1da177e4 | 1333 | |
cd84a42f DH |
1334 | /* |
1335 | * drop_futex_key_refs() must be called outside the spinlocks. During | |
1336 | * the requeue we moved futex_q's from the hash bucket at key1 to the | |
1337 | * one at key2 and updated their key pointer. We no longer need to | |
1338 | * hold the references to key1. | |
1339 | */ | |
1da177e4 | 1340 | while (--drop_count >= 0) |
9adef58b | 1341 | drop_futex_key_refs(&key1); |
1da177e4 | 1342 | |
42d35d48 | 1343 | out_put_keys: |
38d47c1b | 1344 | put_futex_key(fshared, &key2); |
42d35d48 | 1345 | out_put_key1: |
38d47c1b | 1346 | put_futex_key(fshared, &key1); |
42d35d48 | 1347 | out: |
52400ba9 DH |
1348 | if (pi_state != NULL) |
1349 | free_pi_state(pi_state); | |
1350 | return ret ? ret : task_count; | |
1da177e4 LT |
1351 | } |
1352 | ||
1353 | /* The key must be already stored in q->key. */ | |
82af7aca | 1354 | static inline struct futex_hash_bucket *queue_lock(struct futex_q *q) |
1da177e4 | 1355 | { |
e2970f2f | 1356 | struct futex_hash_bucket *hb; |
1da177e4 | 1357 | |
9adef58b | 1358 | get_futex_key_refs(&q->key); |
e2970f2f IM |
1359 | hb = hash_futex(&q->key); |
1360 | q->lock_ptr = &hb->lock; | |
1da177e4 | 1361 | |
e2970f2f IM |
1362 | spin_lock(&hb->lock); |
1363 | return hb; | |
1da177e4 LT |
1364 | } |
1365 | ||
d40d65c8 DH |
1366 | static inline void |
1367 | queue_unlock(struct futex_q *q, struct futex_hash_bucket *hb) | |
1368 | { | |
1369 | spin_unlock(&hb->lock); | |
1370 | drop_futex_key_refs(&q->key); | |
1371 | } | |
1372 | ||
1373 | /** | |
1374 | * queue_me() - Enqueue the futex_q on the futex_hash_bucket | |
1375 | * @q: The futex_q to enqueue | |
1376 | * @hb: The destination hash bucket | |
1377 | * | |
1378 | * The hb->lock must be held by the caller, and is released here. A call to | |
1379 | * queue_me() is typically paired with exactly one call to unqueue_me(). The | |
1380 | * exceptions involve the PI related operations, which may use unqueue_me_pi() | |
1381 | * or nothing if the unqueue is done as part of the wake process and the unqueue | |
1382 | * state is implicit in the state of woken task (see futex_wait_requeue_pi() for | |
1383 | * an example). | |
1384 | */ | |
82af7aca | 1385 | static inline void queue_me(struct futex_q *q, struct futex_hash_bucket *hb) |
1da177e4 | 1386 | { |
ec92d082 PP |
1387 | int prio; |
1388 | ||
1389 | /* | |
1390 | * The priority used to register this element is | |
1391 | * - either the real thread-priority for the real-time threads | |
1392 | * (i.e. threads with a priority lower than MAX_RT_PRIO) | |
1393 | * - or MAX_RT_PRIO for non-RT threads. | |
1394 | * Thus, all RT-threads are woken first in priority order, and | |
1395 | * the others are woken last, in FIFO order. | |
1396 | */ | |
1397 | prio = min(current->normal_prio, MAX_RT_PRIO); | |
1398 | ||
1399 | plist_node_init(&q->list, prio); | |
1400 | #ifdef CONFIG_DEBUG_PI_LIST | |
a2672459 | 1401 | q->list.plist.spinlock = &hb->lock; |
ec92d082 PP |
1402 | #endif |
1403 | plist_add(&q->list, &hb->chain); | |
c87e2837 | 1404 | q->task = current; |
e2970f2f | 1405 | spin_unlock(&hb->lock); |
1da177e4 LT |
1406 | } |
1407 | ||
d40d65c8 DH |
1408 | /** |
1409 | * unqueue_me() - Remove the futex_q from its futex_hash_bucket | |
1410 | * @q: The futex_q to unqueue | |
1411 | * | |
1412 | * The q->lock_ptr must not be held by the caller. A call to unqueue_me() must | |
1413 | * be paired with exactly one earlier call to queue_me(). | |
1414 | * | |
1415 | * Returns: | |
1416 | * 1 - if the futex_q was still queued (and we removed unqueued it) | |
1417 | * 0 - if the futex_q was already removed by the waking thread | |
1da177e4 | 1418 | */ |
1da177e4 LT |
1419 | static int unqueue_me(struct futex_q *q) |
1420 | { | |
1da177e4 | 1421 | spinlock_t *lock_ptr; |
e2970f2f | 1422 | int ret = 0; |
1da177e4 LT |
1423 | |
1424 | /* In the common case we don't take the spinlock, which is nice. */ | |
42d35d48 | 1425 | retry: |
1da177e4 | 1426 | lock_ptr = q->lock_ptr; |
e91467ec | 1427 | barrier(); |
c80544dc | 1428 | if (lock_ptr != NULL) { |
1da177e4 LT |
1429 | spin_lock(lock_ptr); |
1430 | /* | |
1431 | * q->lock_ptr can change between reading it and | |
1432 | * spin_lock(), causing us to take the wrong lock. This | |
1433 | * corrects the race condition. | |
1434 | * | |
1435 | * Reasoning goes like this: if we have the wrong lock, | |
1436 | * q->lock_ptr must have changed (maybe several times) | |
1437 | * between reading it and the spin_lock(). It can | |
1438 | * change again after the spin_lock() but only if it was | |
1439 | * already changed before the spin_lock(). It cannot, | |
1440 | * however, change back to the original value. Therefore | |
1441 | * we can detect whether we acquired the correct lock. | |
1442 | */ | |
1443 | if (unlikely(lock_ptr != q->lock_ptr)) { | |
1444 | spin_unlock(lock_ptr); | |
1445 | goto retry; | |
1446 | } | |
ec92d082 PP |
1447 | WARN_ON(plist_node_empty(&q->list)); |
1448 | plist_del(&q->list, &q->list.plist); | |
c87e2837 IM |
1449 | |
1450 | BUG_ON(q->pi_state); | |
1451 | ||
1da177e4 LT |
1452 | spin_unlock(lock_ptr); |
1453 | ret = 1; | |
1454 | } | |
1455 | ||
9adef58b | 1456 | drop_futex_key_refs(&q->key); |
1da177e4 LT |
1457 | return ret; |
1458 | } | |
1459 | ||
c87e2837 IM |
1460 | /* |
1461 | * PI futexes can not be requeued and must remove themself from the | |
d0aa7a70 PP |
1462 | * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry |
1463 | * and dropped here. | |
c87e2837 | 1464 | */ |
d0aa7a70 | 1465 | static void unqueue_me_pi(struct futex_q *q) |
c87e2837 | 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 | free_pi_state(q->pi_state); | |
1472 | q->pi_state = NULL; | |
1473 | ||
d0aa7a70 | 1474 | spin_unlock(q->lock_ptr); |
c87e2837 | 1475 | |
9adef58b | 1476 | drop_futex_key_refs(&q->key); |
c87e2837 IM |
1477 | } |
1478 | ||
d0aa7a70 | 1479 | /* |
cdf71a10 | 1480 | * Fixup the pi_state owner with the new owner. |
d0aa7a70 | 1481 | * |
778e9a9c AK |
1482 | * Must be called with hash bucket lock held and mm->sem held for non |
1483 | * private futexes. | |
d0aa7a70 | 1484 | */ |
778e9a9c | 1485 | static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q, |
c2f9f201 | 1486 | struct task_struct *newowner, int fshared) |
d0aa7a70 | 1487 | { |
cdf71a10 | 1488 | u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS; |
d0aa7a70 | 1489 | struct futex_pi_state *pi_state = q->pi_state; |
1b7558e4 | 1490 | struct task_struct *oldowner = pi_state->owner; |
d0aa7a70 | 1491 | u32 uval, curval, newval; |
e4dc5b7a | 1492 | int ret; |
d0aa7a70 PP |
1493 | |
1494 | /* Owner died? */ | |
1b7558e4 TG |
1495 | if (!pi_state->owner) |
1496 | newtid |= FUTEX_OWNER_DIED; | |
1497 | ||
1498 | /* | |
1499 | * We are here either because we stole the rtmutex from the | |
1500 | * pending owner or we are the pending owner which failed to | |
1501 | * get the rtmutex. We have to replace the pending owner TID | |
1502 | * in the user space variable. This must be atomic as we have | |
1503 | * to preserve the owner died bit here. | |
1504 | * | |
b2d0994b DH |
1505 | * Note: We write the user space value _before_ changing the pi_state |
1506 | * because we can fault here. Imagine swapped out pages or a fork | |
1507 | * that marked all the anonymous memory readonly for cow. | |
1b7558e4 TG |
1508 | * |
1509 | * Modifying pi_state _before_ the user space value would | |
1510 | * leave the pi_state in an inconsistent state when we fault | |
1511 | * here, because we need to drop the hash bucket lock to | |
1512 | * handle the fault. This might be observed in the PID check | |
1513 | * in lookup_pi_state. | |
1514 | */ | |
1515 | retry: | |
1516 | if (get_futex_value_locked(&uval, uaddr)) | |
1517 | goto handle_fault; | |
1518 | ||
1519 | while (1) { | |
1520 | newval = (uval & FUTEX_OWNER_DIED) | newtid; | |
1521 | ||
1522 | curval = cmpxchg_futex_value_locked(uaddr, uval, newval); | |
1523 | ||
1524 | if (curval == -EFAULT) | |
1525 | goto handle_fault; | |
1526 | if (curval == uval) | |
1527 | break; | |
1528 | uval = curval; | |
1529 | } | |
1530 | ||
1531 | /* | |
1532 | * We fixed up user space. Now we need to fix the pi_state | |
1533 | * itself. | |
1534 | */ | |
d0aa7a70 | 1535 | if (pi_state->owner != NULL) { |
1d615482 | 1536 | raw_spin_lock_irq(&pi_state->owner->pi_lock); |
d0aa7a70 PP |
1537 | WARN_ON(list_empty(&pi_state->list)); |
1538 | list_del_init(&pi_state->list); | |
1d615482 | 1539 | raw_spin_unlock_irq(&pi_state->owner->pi_lock); |
1b7558e4 | 1540 | } |
d0aa7a70 | 1541 | |
cdf71a10 | 1542 | pi_state->owner = newowner; |
d0aa7a70 | 1543 | |
1d615482 | 1544 | raw_spin_lock_irq(&newowner->pi_lock); |
d0aa7a70 | 1545 | WARN_ON(!list_empty(&pi_state->list)); |
cdf71a10 | 1546 | list_add(&pi_state->list, &newowner->pi_state_list); |
1d615482 | 1547 | raw_spin_unlock_irq(&newowner->pi_lock); |
1b7558e4 | 1548 | return 0; |
d0aa7a70 | 1549 | |
d0aa7a70 | 1550 | /* |
1b7558e4 TG |
1551 | * To handle the page fault we need to drop the hash bucket |
1552 | * lock here. That gives the other task (either the pending | |
1553 | * owner itself or the task which stole the rtmutex) the | |
1554 | * chance to try the fixup of the pi_state. So once we are | |
1555 | * back from handling the fault we need to check the pi_state | |
1556 | * after reacquiring the hash bucket lock and before trying to | |
1557 | * do another fixup. When the fixup has been done already we | |
1558 | * simply return. | |
d0aa7a70 | 1559 | */ |
1b7558e4 TG |
1560 | handle_fault: |
1561 | spin_unlock(q->lock_ptr); | |
778e9a9c | 1562 | |
d0725992 | 1563 | ret = fault_in_user_writeable(uaddr); |
778e9a9c | 1564 | |
1b7558e4 | 1565 | spin_lock(q->lock_ptr); |
778e9a9c | 1566 | |
1b7558e4 TG |
1567 | /* |
1568 | * Check if someone else fixed it for us: | |
1569 | */ | |
1570 | if (pi_state->owner != oldowner) | |
1571 | return 0; | |
1572 | ||
1573 | if (ret) | |
1574 | return ret; | |
1575 | ||
1576 | goto retry; | |
d0aa7a70 PP |
1577 | } |
1578 | ||
34f01cc1 ED |
1579 | /* |
1580 | * In case we must use restart_block to restart a futex_wait, | |
ce6bd420 | 1581 | * we encode in the 'flags' shared capability |
34f01cc1 | 1582 | */ |
1acdac10 TG |
1583 | #define FLAGS_SHARED 0x01 |
1584 | #define FLAGS_CLOCKRT 0x02 | |
a72188d8 | 1585 | #define FLAGS_HAS_TIMEOUT 0x04 |
34f01cc1 | 1586 | |
72c1bbf3 | 1587 | static long futex_wait_restart(struct restart_block *restart); |
36cf3b5c | 1588 | |
dd973998 DH |
1589 | /** |
1590 | * fixup_owner() - Post lock pi_state and corner case management | |
1591 | * @uaddr: user address of the futex | |
1592 | * @fshared: whether the futex is shared (1) or not (0) | |
1593 | * @q: futex_q (contains pi_state and access to the rt_mutex) | |
1594 | * @locked: if the attempt to take the rt_mutex succeeded (1) or not (0) | |
1595 | * | |
1596 | * After attempting to lock an rt_mutex, this function is called to cleanup | |
1597 | * the pi_state owner as well as handle race conditions that may allow us to | |
1598 | * acquire the lock. Must be called with the hb lock held. | |
1599 | * | |
1600 | * Returns: | |
1601 | * 1 - success, lock taken | |
1602 | * 0 - success, lock not taken | |
1603 | * <0 - on error (-EFAULT) | |
1604 | */ | |
1605 | static int fixup_owner(u32 __user *uaddr, int fshared, struct futex_q *q, | |
1606 | int locked) | |
1607 | { | |
1608 | struct task_struct *owner; | |
1609 | int ret = 0; | |
1610 | ||
1611 | if (locked) { | |
1612 | /* | |
1613 | * Got the lock. We might not be the anticipated owner if we | |
1614 | * did a lock-steal - fix up the PI-state in that case: | |
1615 | */ | |
1616 | if (q->pi_state->owner != current) | |
1617 | ret = fixup_pi_state_owner(uaddr, q, current, fshared); | |
1618 | goto out; | |
1619 | } | |
1620 | ||
1621 | /* | |
1622 | * Catch the rare case, where the lock was released when we were on the | |
1623 | * way back before we locked the hash bucket. | |
1624 | */ | |
1625 | if (q->pi_state->owner == current) { | |
1626 | /* | |
1627 | * Try to get the rt_mutex now. This might fail as some other | |
1628 | * task acquired the rt_mutex after we removed ourself from the | |
1629 | * rt_mutex waiters list. | |
1630 | */ | |
1631 | if (rt_mutex_trylock(&q->pi_state->pi_mutex)) { | |
1632 | locked = 1; | |
1633 | goto out; | |
1634 | } | |
1635 | ||
1636 | /* | |
1637 | * pi_state is incorrect, some other task did a lock steal and | |
1638 | * we returned due to timeout or signal without taking the | |
1639 | * rt_mutex. Too late. We can access the rt_mutex_owner without | |
1640 | * locking, as the other task is now blocked on the hash bucket | |
1641 | * lock. Fix the state up. | |
1642 | */ | |
1643 | owner = rt_mutex_owner(&q->pi_state->pi_mutex); | |
1644 | ret = fixup_pi_state_owner(uaddr, q, owner, fshared); | |
1645 | goto out; | |
1646 | } | |
1647 | ||
1648 | /* | |
1649 | * Paranoia check. If we did not take the lock, then we should not be | |
1650 | * the owner, nor the pending owner, of the rt_mutex. | |
1651 | */ | |
1652 | if (rt_mutex_owner(&q->pi_state->pi_mutex) == current) | |
1653 | printk(KERN_ERR "fixup_owner: ret = %d pi-mutex: %p " | |
1654 | "pi-state %p\n", ret, | |
1655 | q->pi_state->pi_mutex.owner, | |
1656 | q->pi_state->owner); | |
1657 | ||
1658 | out: | |
1659 | return ret ? ret : locked; | |
1660 | } | |
1661 | ||
ca5f9524 DH |
1662 | /** |
1663 | * futex_wait_queue_me() - queue_me() and wait for wakeup, timeout, or signal | |
1664 | * @hb: the futex hash bucket, must be locked by the caller | |
1665 | * @q: the futex_q to queue up on | |
1666 | * @timeout: the prepared hrtimer_sleeper, or null for no timeout | |
ca5f9524 DH |
1667 | */ |
1668 | static void futex_wait_queue_me(struct futex_hash_bucket *hb, struct futex_q *q, | |
f1a11e05 | 1669 | struct hrtimer_sleeper *timeout) |
ca5f9524 | 1670 | { |
9beba3c5 DH |
1671 | /* |
1672 | * The task state is guaranteed to be set before another task can | |
1673 | * wake it. set_current_state() is implemented using set_mb() and | |
1674 | * queue_me() calls spin_unlock() upon completion, both serializing | |
1675 | * access to the hash list and forcing another memory barrier. | |
1676 | */ | |
f1a11e05 | 1677 | set_current_state(TASK_INTERRUPTIBLE); |
0729e196 | 1678 | queue_me(q, hb); |
ca5f9524 DH |
1679 | |
1680 | /* Arm the timer */ | |
1681 | if (timeout) { | |
1682 | hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS); | |
1683 | if (!hrtimer_active(&timeout->timer)) | |
1684 | timeout->task = NULL; | |
1685 | } | |
1686 | ||
1687 | /* | |
0729e196 DH |
1688 | * If we have been removed from the hash list, then another task |
1689 | * has tried to wake us, and we can skip the call to schedule(). | |
ca5f9524 DH |
1690 | */ |
1691 | if (likely(!plist_node_empty(&q->list))) { | |
1692 | /* | |
1693 | * If the timer has already expired, current will already be | |
1694 | * flagged for rescheduling. Only call schedule if there | |
1695 | * is no timeout, or if it has yet to expire. | |
1696 | */ | |
1697 | if (!timeout || timeout->task) | |
1698 | schedule(); | |
1699 | } | |
1700 | __set_current_state(TASK_RUNNING); | |
1701 | } | |
1702 | ||
f801073f DH |
1703 | /** |
1704 | * futex_wait_setup() - Prepare to wait on a futex | |
1705 | * @uaddr: the futex userspace address | |
1706 | * @val: the expected value | |
1707 | * @fshared: whether the futex is shared (1) or not (0) | |
1708 | * @q: the associated futex_q | |
1709 | * @hb: storage for hash_bucket pointer to be returned to caller | |
1710 | * | |
1711 | * Setup the futex_q and locate the hash_bucket. Get the futex value and | |
1712 | * compare it with the expected value. Handle atomic faults internally. | |
1713 | * Return with the hb lock held and a q.key reference on success, and unlocked | |
1714 | * with no q.key reference on failure. | |
1715 | * | |
1716 | * Returns: | |
1717 | * 0 - uaddr contains val and hb has been locked | |
1718 | * <1 - -EFAULT or -EWOULDBLOCK (uaddr does not contain val) and hb is unlcoked | |
1719 | */ | |
1720 | static int futex_wait_setup(u32 __user *uaddr, u32 val, int fshared, | |
1721 | struct futex_q *q, struct futex_hash_bucket **hb) | |
1da177e4 | 1722 | { |
e2970f2f IM |
1723 | u32 uval; |
1724 | int ret; | |
1da177e4 | 1725 | |
1da177e4 | 1726 | /* |
b2d0994b | 1727 | * Access the page AFTER the hash-bucket is locked. |
1da177e4 LT |
1728 | * Order is important: |
1729 | * | |
1730 | * Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val); | |
1731 | * Userspace waker: if (cond(var)) { var = new; futex_wake(&var); } | |
1732 | * | |
1733 | * The basic logical guarantee of a futex is that it blocks ONLY | |
1734 | * if cond(var) is known to be true at the time of blocking, for | |
1735 | * any cond. If we queued after testing *uaddr, that would open | |
1736 | * a race condition where we could block indefinitely with | |
1737 | * cond(var) false, which would violate the guarantee. | |
1738 | * | |
1739 | * A consequence is that futex_wait() can return zero and absorb | |
1740 | * a wakeup when *uaddr != val on entry to the syscall. This is | |
1741 | * rare, but normal. | |
1da177e4 | 1742 | */ |
f801073f DH |
1743 | retry: |
1744 | q->key = FUTEX_KEY_INIT; | |
7485d0d3 | 1745 | ret = get_futex_key(uaddr, fshared, &q->key); |
f801073f | 1746 | if (unlikely(ret != 0)) |
a5a2a0c7 | 1747 | return ret; |
f801073f DH |
1748 | |
1749 | retry_private: | |
1750 | *hb = queue_lock(q); | |
1751 | ||
e2970f2f | 1752 | ret = get_futex_value_locked(&uval, uaddr); |
1da177e4 | 1753 | |
f801073f DH |
1754 | if (ret) { |
1755 | queue_unlock(q, *hb); | |
1da177e4 | 1756 | |
e2970f2f | 1757 | ret = get_user(uval, uaddr); |
e4dc5b7a | 1758 | if (ret) |
f801073f | 1759 | goto out; |
1da177e4 | 1760 | |
e4dc5b7a DH |
1761 | if (!fshared) |
1762 | goto retry_private; | |
1763 | ||
f801073f | 1764 | put_futex_key(fshared, &q->key); |
e4dc5b7a | 1765 | goto retry; |
1da177e4 | 1766 | } |
ca5f9524 | 1767 | |
f801073f DH |
1768 | if (uval != val) { |
1769 | queue_unlock(q, *hb); | |
1770 | ret = -EWOULDBLOCK; | |
2fff78c7 | 1771 | } |
1da177e4 | 1772 | |
f801073f DH |
1773 | out: |
1774 | if (ret) | |
1775 | put_futex_key(fshared, &q->key); | |
1776 | return ret; | |
1777 | } | |
1778 | ||
1779 | static int futex_wait(u32 __user *uaddr, int fshared, | |
1780 | u32 val, ktime_t *abs_time, u32 bitset, int clockrt) | |
1781 | { | |
1782 | struct hrtimer_sleeper timeout, *to = NULL; | |
f801073f DH |
1783 | struct restart_block *restart; |
1784 | struct futex_hash_bucket *hb; | |
1785 | struct futex_q q; | |
1786 | int ret; | |
1787 | ||
1788 | if (!bitset) | |
1789 | return -EINVAL; | |
1790 | ||
1791 | q.pi_state = NULL; | |
1792 | q.bitset = bitset; | |
52400ba9 | 1793 | q.rt_waiter = NULL; |
84bc4af5 | 1794 | q.requeue_pi_key = NULL; |
f801073f DH |
1795 | |
1796 | if (abs_time) { | |
1797 | to = &timeout; | |
1798 | ||
1799 | hrtimer_init_on_stack(&to->timer, clockrt ? CLOCK_REALTIME : | |
1800 | CLOCK_MONOTONIC, HRTIMER_MODE_ABS); | |
1801 | hrtimer_init_sleeper(to, current); | |
1802 | hrtimer_set_expires_range_ns(&to->timer, *abs_time, | |
1803 | current->timer_slack_ns); | |
1804 | } | |
1805 | ||
d58e6576 | 1806 | retry: |
f801073f DH |
1807 | /* Prepare to wait on uaddr. */ |
1808 | ret = futex_wait_setup(uaddr, val, fshared, &q, &hb); | |
1809 | if (ret) | |
1810 | goto out; | |
1811 | ||
ca5f9524 | 1812 | /* queue_me and wait for wakeup, timeout, or a signal. */ |
f1a11e05 | 1813 | futex_wait_queue_me(hb, &q, to); |
1da177e4 LT |
1814 | |
1815 | /* If we were woken (and unqueued), we succeeded, whatever. */ | |
2fff78c7 | 1816 | ret = 0; |
1da177e4 | 1817 | if (!unqueue_me(&q)) |
2fff78c7 PZ |
1818 | goto out_put_key; |
1819 | ret = -ETIMEDOUT; | |
ca5f9524 | 1820 | if (to && !to->task) |
2fff78c7 | 1821 | goto out_put_key; |
72c1bbf3 | 1822 | |
e2970f2f | 1823 | /* |
d58e6576 TG |
1824 | * We expect signal_pending(current), but we might be the |
1825 | * victim of a spurious wakeup as well. | |
e2970f2f | 1826 | */ |
d58e6576 TG |
1827 | if (!signal_pending(current)) { |
1828 | put_futex_key(fshared, &q.key); | |
1829 | goto retry; | |
1830 | } | |
1831 | ||
2fff78c7 | 1832 | ret = -ERESTARTSYS; |
c19384b5 | 1833 | if (!abs_time) |
2fff78c7 | 1834 | goto out_put_key; |
1da177e4 | 1835 | |
2fff78c7 PZ |
1836 | restart = ¤t_thread_info()->restart_block; |
1837 | restart->fn = futex_wait_restart; | |
1838 | restart->futex.uaddr = (u32 *)uaddr; | |
1839 | restart->futex.val = val; | |
1840 | restart->futex.time = abs_time->tv64; | |
1841 | restart->futex.bitset = bitset; | |
a72188d8 | 1842 | restart->futex.flags = FLAGS_HAS_TIMEOUT; |
2fff78c7 PZ |
1843 | |
1844 | if (fshared) | |
1845 | restart->futex.flags |= FLAGS_SHARED; | |
1846 | if (clockrt) | |
1847 | restart->futex.flags |= FLAGS_CLOCKRT; | |
42d35d48 | 1848 | |
2fff78c7 PZ |
1849 | ret = -ERESTART_RESTARTBLOCK; |
1850 | ||
1851 | out_put_key: | |
1852 | put_futex_key(fshared, &q.key); | |
42d35d48 | 1853 | out: |
ca5f9524 DH |
1854 | if (to) { |
1855 | hrtimer_cancel(&to->timer); | |
1856 | destroy_hrtimer_on_stack(&to->timer); | |
1857 | } | |
c87e2837 IM |
1858 | return ret; |
1859 | } | |
1860 | ||
72c1bbf3 NP |
1861 | |
1862 | static long futex_wait_restart(struct restart_block *restart) | |
1863 | { | |
ce6bd420 | 1864 | u32 __user *uaddr = (u32 __user *)restart->futex.uaddr; |
c2f9f201 | 1865 | int fshared = 0; |
a72188d8 | 1866 | ktime_t t, *tp = NULL; |
72c1bbf3 | 1867 | |
a72188d8 DH |
1868 | if (restart->futex.flags & FLAGS_HAS_TIMEOUT) { |
1869 | t.tv64 = restart->futex.time; | |
1870 | tp = &t; | |
1871 | } | |
72c1bbf3 | 1872 | restart->fn = do_no_restart_syscall; |
ce6bd420 | 1873 | if (restart->futex.flags & FLAGS_SHARED) |
c2f9f201 | 1874 | fshared = 1; |
a72188d8 | 1875 | return (long)futex_wait(uaddr, fshared, restart->futex.val, tp, |
1acdac10 TG |
1876 | restart->futex.bitset, |
1877 | restart->futex.flags & FLAGS_CLOCKRT); | |
72c1bbf3 NP |
1878 | } |
1879 | ||
1880 | ||
c87e2837 IM |
1881 | /* |
1882 | * Userspace tried a 0 -> TID atomic transition of the futex value | |
1883 | * and failed. The kernel side here does the whole locking operation: | |
1884 | * if there are waiters then it will block, it does PI, etc. (Due to | |
1885 | * races the kernel might see a 0 value of the futex too.) | |
1886 | */ | |
c2f9f201 | 1887 | static int futex_lock_pi(u32 __user *uaddr, int fshared, |
34f01cc1 | 1888 | int detect, ktime_t *time, int trylock) |
c87e2837 | 1889 | { |
c5780e97 | 1890 | struct hrtimer_sleeper timeout, *to = NULL; |
c87e2837 | 1891 | struct futex_hash_bucket *hb; |
c87e2837 | 1892 | struct futex_q q; |
dd973998 | 1893 | int res, ret; |
c87e2837 IM |
1894 | |
1895 | if (refill_pi_state_cache()) | |
1896 | return -ENOMEM; | |
1897 | ||
c19384b5 | 1898 | if (time) { |
c5780e97 | 1899 | to = &timeout; |
237fc6e7 TG |
1900 | hrtimer_init_on_stack(&to->timer, CLOCK_REALTIME, |
1901 | HRTIMER_MODE_ABS); | |
c5780e97 | 1902 | hrtimer_init_sleeper(to, current); |
cc584b21 | 1903 | hrtimer_set_expires(&to->timer, *time); |
c5780e97 TG |
1904 | } |
1905 | ||
c87e2837 | 1906 | q.pi_state = NULL; |
52400ba9 | 1907 | q.rt_waiter = NULL; |
84bc4af5 | 1908 | q.requeue_pi_key = NULL; |
42d35d48 | 1909 | retry: |
38d47c1b | 1910 | q.key = FUTEX_KEY_INIT; |
7485d0d3 | 1911 | ret = get_futex_key(uaddr, fshared, &q.key); |
c87e2837 | 1912 | if (unlikely(ret != 0)) |
42d35d48 | 1913 | goto out; |
c87e2837 | 1914 | |
e4dc5b7a | 1915 | retry_private: |
82af7aca | 1916 | hb = queue_lock(&q); |
c87e2837 | 1917 | |
bab5bc9e | 1918 | ret = futex_lock_pi_atomic(uaddr, hb, &q.key, &q.pi_state, current, 0); |
c87e2837 | 1919 | if (unlikely(ret)) { |
778e9a9c | 1920 | switch (ret) { |
1a52084d DH |
1921 | case 1: |
1922 | /* We got the lock. */ | |
1923 | ret = 0; | |
1924 | goto out_unlock_put_key; | |
1925 | case -EFAULT: | |
1926 | goto uaddr_faulted; | |
778e9a9c AK |
1927 | case -EAGAIN: |
1928 | /* | |
1929 | * Task is exiting and we just wait for the | |
1930 | * exit to complete. | |
1931 | */ | |
1932 | queue_unlock(&q, hb); | |
de87fcc1 | 1933 | put_futex_key(fshared, &q.key); |
778e9a9c AK |
1934 | cond_resched(); |
1935 | goto retry; | |
778e9a9c | 1936 | default: |
42d35d48 | 1937 | goto out_unlock_put_key; |
c87e2837 | 1938 | } |
c87e2837 IM |
1939 | } |
1940 | ||
1941 | /* | |
1942 | * Only actually queue now that the atomic ops are done: | |
1943 | */ | |
82af7aca | 1944 | queue_me(&q, hb); |
c87e2837 | 1945 | |
c87e2837 IM |
1946 | WARN_ON(!q.pi_state); |
1947 | /* | |
1948 | * Block on the PI mutex: | |
1949 | */ | |
1950 | if (!trylock) | |
1951 | ret = rt_mutex_timed_lock(&q.pi_state->pi_mutex, to, 1); | |
1952 | else { | |
1953 | ret = rt_mutex_trylock(&q.pi_state->pi_mutex); | |
1954 | /* Fixup the trylock return value: */ | |
1955 | ret = ret ? 0 : -EWOULDBLOCK; | |
1956 | } | |
1957 | ||
a99e4e41 | 1958 | spin_lock(q.lock_ptr); |
dd973998 DH |
1959 | /* |
1960 | * Fixup the pi_state owner and possibly acquire the lock if we | |
1961 | * haven't already. | |
1962 | */ | |
1963 | res = fixup_owner(uaddr, fshared, &q, !ret); | |
1964 | /* | |
1965 | * If fixup_owner() returned an error, proprogate that. If it acquired | |
1966 | * the lock, clear our -ETIMEDOUT or -EINTR. | |
1967 | */ | |
1968 | if (res) | |
1969 | ret = (res < 0) ? res : 0; | |
c87e2837 | 1970 | |
e8f6386c | 1971 | /* |
dd973998 DH |
1972 | * If fixup_owner() faulted and was unable to handle the fault, unlock |
1973 | * it and return the fault to userspace. | |
e8f6386c DH |
1974 | */ |
1975 | if (ret && (rt_mutex_owner(&q.pi_state->pi_mutex) == current)) | |
1976 | rt_mutex_unlock(&q.pi_state->pi_mutex); | |
1977 | ||
778e9a9c AK |
1978 | /* Unqueue and drop the lock */ |
1979 | unqueue_me_pi(&q); | |
c87e2837 | 1980 | |
5ecb01cf | 1981 | goto out_put_key; |
c87e2837 | 1982 | |
42d35d48 | 1983 | out_unlock_put_key: |
c87e2837 IM |
1984 | queue_unlock(&q, hb); |
1985 | ||
42d35d48 | 1986 | out_put_key: |
38d47c1b | 1987 | put_futex_key(fshared, &q.key); |
42d35d48 | 1988 | out: |
237fc6e7 TG |
1989 | if (to) |
1990 | destroy_hrtimer_on_stack(&to->timer); | |
dd973998 | 1991 | return ret != -EINTR ? ret : -ERESTARTNOINTR; |
c87e2837 | 1992 | |
42d35d48 | 1993 | uaddr_faulted: |
778e9a9c AK |
1994 | queue_unlock(&q, hb); |
1995 | ||
d0725992 | 1996 | ret = fault_in_user_writeable(uaddr); |
e4dc5b7a DH |
1997 | if (ret) |
1998 | goto out_put_key; | |
c87e2837 | 1999 | |
e4dc5b7a DH |
2000 | if (!fshared) |
2001 | goto retry_private; | |
2002 | ||
2003 | put_futex_key(fshared, &q.key); | |
2004 | goto retry; | |
c87e2837 IM |
2005 | } |
2006 | ||
c87e2837 IM |
2007 | /* |
2008 | * Userspace attempted a TID -> 0 atomic transition, and failed. | |
2009 | * This is the in-kernel slowpath: we look up the PI state (if any), | |
2010 | * and do the rt-mutex unlock. | |
2011 | */ | |
c2f9f201 | 2012 | static int futex_unlock_pi(u32 __user *uaddr, int fshared) |
c87e2837 IM |
2013 | { |
2014 | struct futex_hash_bucket *hb; | |
2015 | struct futex_q *this, *next; | |
2016 | u32 uval; | |
ec92d082 | 2017 | struct plist_head *head; |
38d47c1b | 2018 | union futex_key key = FUTEX_KEY_INIT; |
e4dc5b7a | 2019 | int ret; |
c87e2837 IM |
2020 | |
2021 | retry: | |
2022 | if (get_user(uval, uaddr)) | |
2023 | return -EFAULT; | |
2024 | /* | |
2025 | * We release only a lock we actually own: | |
2026 | */ | |
b488893a | 2027 | if ((uval & FUTEX_TID_MASK) != task_pid_vnr(current)) |
c87e2837 | 2028 | return -EPERM; |
c87e2837 | 2029 | |
7485d0d3 | 2030 | ret = get_futex_key(uaddr, fshared, &key); |
c87e2837 IM |
2031 | if (unlikely(ret != 0)) |
2032 | goto out; | |
2033 | ||
2034 | hb = hash_futex(&key); | |
2035 | spin_lock(&hb->lock); | |
2036 | ||
c87e2837 IM |
2037 | /* |
2038 | * To avoid races, try to do the TID -> 0 atomic transition | |
2039 | * again. If it succeeds then we can return without waking | |
2040 | * anyone else up: | |
2041 | */ | |
36cf3b5c | 2042 | if (!(uval & FUTEX_OWNER_DIED)) |
b488893a | 2043 | uval = cmpxchg_futex_value_locked(uaddr, task_pid_vnr(current), 0); |
36cf3b5c | 2044 | |
c87e2837 IM |
2045 | |
2046 | if (unlikely(uval == -EFAULT)) | |
2047 | goto pi_faulted; | |
2048 | /* | |
2049 | * Rare case: we managed to release the lock atomically, | |
2050 | * no need to wake anyone else up: | |
2051 | */ | |
b488893a | 2052 | if (unlikely(uval == task_pid_vnr(current))) |
c87e2837 IM |
2053 | goto out_unlock; |
2054 | ||
2055 | /* | |
2056 | * Ok, other tasks may need to be woken up - check waiters | |
2057 | * and do the wakeup if necessary: | |
2058 | */ | |
2059 | head = &hb->chain; | |
2060 | ||
ec92d082 | 2061 | plist_for_each_entry_safe(this, next, head, list) { |
c87e2837 IM |
2062 | if (!match_futex (&this->key, &key)) |
2063 | continue; | |
2064 | ret = wake_futex_pi(uaddr, uval, this); | |
2065 | /* | |
2066 | * The atomic access to the futex value | |
2067 | * generated a pagefault, so retry the | |
2068 | * user-access and the wakeup: | |
2069 | */ | |
2070 | if (ret == -EFAULT) | |
2071 | goto pi_faulted; | |
2072 | goto out_unlock; | |
2073 | } | |
2074 | /* | |
2075 | * No waiters - kernel unlocks the futex: | |
2076 | */ | |
e3f2ddea IM |
2077 | if (!(uval & FUTEX_OWNER_DIED)) { |
2078 | ret = unlock_futex_pi(uaddr, uval); | |
2079 | if (ret == -EFAULT) | |
2080 | goto pi_faulted; | |
2081 | } | |
c87e2837 IM |
2082 | |
2083 | out_unlock: | |
2084 | spin_unlock(&hb->lock); | |
38d47c1b | 2085 | put_futex_key(fshared, &key); |
c87e2837 | 2086 | |
42d35d48 | 2087 | out: |
c87e2837 IM |
2088 | return ret; |
2089 | ||
2090 | pi_faulted: | |
778e9a9c | 2091 | spin_unlock(&hb->lock); |
e4dc5b7a | 2092 | put_futex_key(fshared, &key); |
c87e2837 | 2093 | |
d0725992 | 2094 | ret = fault_in_user_writeable(uaddr); |
b5686363 | 2095 | if (!ret) |
c87e2837 IM |
2096 | goto retry; |
2097 | ||
1da177e4 LT |
2098 | return ret; |
2099 | } | |
2100 | ||
52400ba9 DH |
2101 | /** |
2102 | * handle_early_requeue_pi_wakeup() - Detect early wakeup on the initial futex | |
2103 | * @hb: the hash_bucket futex_q was original enqueued on | |
2104 | * @q: the futex_q woken while waiting to be requeued | |
2105 | * @key2: the futex_key of the requeue target futex | |
2106 | * @timeout: the timeout associated with the wait (NULL if none) | |
2107 | * | |
2108 | * Detect if the task was woken on the initial futex as opposed to the requeue | |
2109 | * target futex. If so, determine if it was a timeout or a signal that caused | |
2110 | * the wakeup and return the appropriate error code to the caller. Must be | |
2111 | * called with the hb lock held. | |
2112 | * | |
2113 | * Returns | |
2114 | * 0 - no early wakeup detected | |
1c840c14 | 2115 | * <0 - -ETIMEDOUT or -ERESTARTNOINTR |
52400ba9 DH |
2116 | */ |
2117 | static inline | |
2118 | int handle_early_requeue_pi_wakeup(struct futex_hash_bucket *hb, | |
2119 | struct futex_q *q, union futex_key *key2, | |
2120 | struct hrtimer_sleeper *timeout) | |
2121 | { | |
2122 | int ret = 0; | |
2123 | ||
2124 | /* | |
2125 | * With the hb lock held, we avoid races while we process the wakeup. | |
2126 | * We only need to hold hb (and not hb2) to ensure atomicity as the | |
2127 | * wakeup code can't change q.key from uaddr to uaddr2 if we hold hb. | |
2128 | * It can't be requeued from uaddr2 to something else since we don't | |
2129 | * support a PI aware source futex for requeue. | |
2130 | */ | |
2131 | if (!match_futex(&q->key, key2)) { | |
2132 | WARN_ON(q->lock_ptr && (&hb->lock != q->lock_ptr)); | |
2133 | /* | |
2134 | * We were woken prior to requeue by a timeout or a signal. | |
2135 | * Unqueue the futex_q and determine which it was. | |
2136 | */ | |
2137 | plist_del(&q->list, &q->list.plist); | |
52400ba9 | 2138 | |
d58e6576 | 2139 | /* Handle spurious wakeups gracefully */ |
11df6ddd | 2140 | ret = -EWOULDBLOCK; |
52400ba9 DH |
2141 | if (timeout && !timeout->task) |
2142 | ret = -ETIMEDOUT; | |
d58e6576 | 2143 | else if (signal_pending(current)) |
1c840c14 | 2144 | ret = -ERESTARTNOINTR; |
52400ba9 DH |
2145 | } |
2146 | return ret; | |
2147 | } | |
2148 | ||
2149 | /** | |
2150 | * futex_wait_requeue_pi() - Wait on uaddr and take uaddr2 | |
56ec1607 | 2151 | * @uaddr: the futex we initially wait on (non-pi) |
52400ba9 DH |
2152 | * @fshared: whether the futexes are shared (1) or not (0). They must be |
2153 | * the same type, no requeueing from private to shared, etc. | |
2154 | * @val: the expected value of uaddr | |
2155 | * @abs_time: absolute timeout | |
56ec1607 | 2156 | * @bitset: 32 bit wakeup bitset set by userspace, defaults to all |
52400ba9 DH |
2157 | * @clockrt: whether to use CLOCK_REALTIME (1) or CLOCK_MONOTONIC (0) |
2158 | * @uaddr2: the pi futex we will take prior to returning to user-space | |
2159 | * | |
2160 | * The caller will wait on uaddr and will be requeued by futex_requeue() to | |
2161 | * uaddr2 which must be PI aware. Normal wakeup will wake on uaddr2 and | |
2162 | * complete the acquisition of the rt_mutex prior to returning to userspace. | |
2163 | * This ensures the rt_mutex maintains an owner when it has waiters; without | |
2164 | * one, the pi logic wouldn't know which task to boost/deboost, if there was a | |
2165 | * need to. | |
2166 | * | |
2167 | * We call schedule in futex_wait_queue_me() when we enqueue and return there | |
2168 | * via the following: | |
2169 | * 1) wakeup on uaddr2 after an atomic lock acquisition by futex_requeue() | |
cc6db4e6 DH |
2170 | * 2) wakeup on uaddr2 after a requeue |
2171 | * 3) signal | |
2172 | * 4) timeout | |
52400ba9 | 2173 | * |
cc6db4e6 | 2174 | * If 3, cleanup and return -ERESTARTNOINTR. |
52400ba9 DH |
2175 | * |
2176 | * If 2, we may then block on trying to take the rt_mutex and return via: | |
2177 | * 5) successful lock | |
2178 | * 6) signal | |
2179 | * 7) timeout | |
2180 | * 8) other lock acquisition failure | |
2181 | * | |
cc6db4e6 | 2182 | * If 6, return -EWOULDBLOCK (restarting the syscall would do the same). |
52400ba9 DH |
2183 | * |
2184 | * If 4 or 7, we cleanup and return with -ETIMEDOUT. | |
2185 | * | |
2186 | * Returns: | |
2187 | * 0 - On success | |
2188 | * <0 - On error | |
2189 | */ | |
2190 | static int futex_wait_requeue_pi(u32 __user *uaddr, int fshared, | |
2191 | u32 val, ktime_t *abs_time, u32 bitset, | |
2192 | int clockrt, u32 __user *uaddr2) | |
2193 | { | |
2194 | struct hrtimer_sleeper timeout, *to = NULL; | |
2195 | struct rt_mutex_waiter rt_waiter; | |
2196 | struct rt_mutex *pi_mutex = NULL; | |
52400ba9 DH |
2197 | struct futex_hash_bucket *hb; |
2198 | union futex_key key2; | |
2199 | struct futex_q q; | |
2200 | int res, ret; | |
52400ba9 DH |
2201 | |
2202 | if (!bitset) | |
2203 | return -EINVAL; | |
2204 | ||
2205 | if (abs_time) { | |
2206 | to = &timeout; | |
2207 | hrtimer_init_on_stack(&to->timer, clockrt ? CLOCK_REALTIME : | |
2208 | CLOCK_MONOTONIC, HRTIMER_MODE_ABS); | |
2209 | hrtimer_init_sleeper(to, current); | |
2210 | hrtimer_set_expires_range_ns(&to->timer, *abs_time, | |
2211 | current->timer_slack_ns); | |
2212 | } | |
2213 | ||
2214 | /* | |
2215 | * The waiter is allocated on our stack, manipulated by the requeue | |
2216 | * code while we sleep on uaddr. | |
2217 | */ | |
2218 | debug_rt_mutex_init_waiter(&rt_waiter); | |
2219 | rt_waiter.task = NULL; | |
2220 | ||
52400ba9 | 2221 | key2 = FUTEX_KEY_INIT; |
7485d0d3 | 2222 | ret = get_futex_key(uaddr2, fshared, &key2); |
52400ba9 DH |
2223 | if (unlikely(ret != 0)) |
2224 | goto out; | |
2225 | ||
84bc4af5 DH |
2226 | q.pi_state = NULL; |
2227 | q.bitset = bitset; | |
2228 | q.rt_waiter = &rt_waiter; | |
2229 | q.requeue_pi_key = &key2; | |
2230 | ||
52400ba9 DH |
2231 | /* Prepare to wait on uaddr. */ |
2232 | ret = futex_wait_setup(uaddr, val, fshared, &q, &hb); | |
c8b15a70 TG |
2233 | if (ret) |
2234 | goto out_key2; | |
52400ba9 DH |
2235 | |
2236 | /* Queue the futex_q, drop the hb lock, wait for wakeup. */ | |
f1a11e05 | 2237 | futex_wait_queue_me(hb, &q, to); |
52400ba9 DH |
2238 | |
2239 | spin_lock(&hb->lock); | |
2240 | ret = handle_early_requeue_pi_wakeup(hb, &q, &key2, to); | |
2241 | spin_unlock(&hb->lock); | |
2242 | if (ret) | |
2243 | goto out_put_keys; | |
2244 | ||
2245 | /* | |
2246 | * In order for us to be here, we know our q.key == key2, and since | |
2247 | * we took the hb->lock above, we also know that futex_requeue() has | |
2248 | * completed and we no longer have to concern ourselves with a wakeup | |
2249 | * race with the atomic proxy lock acquition by the requeue code. | |
2250 | */ | |
2251 | ||
2252 | /* Check if the requeue code acquired the second futex for us. */ | |
2253 | if (!q.rt_waiter) { | |
2254 | /* | |
2255 | * Got the lock. We might not be the anticipated owner if we | |
2256 | * did a lock-steal - fix up the PI-state in that case. | |
2257 | */ | |
2258 | if (q.pi_state && (q.pi_state->owner != current)) { | |
2259 | spin_lock(q.lock_ptr); | |
2260 | ret = fixup_pi_state_owner(uaddr2, &q, current, | |
2261 | fshared); | |
2262 | spin_unlock(q.lock_ptr); | |
2263 | } | |
2264 | } else { | |
2265 | /* | |
2266 | * We have been woken up by futex_unlock_pi(), a timeout, or a | |
2267 | * signal. futex_unlock_pi() will not destroy the lock_ptr nor | |
2268 | * the pi_state. | |
2269 | */ | |
2270 | WARN_ON(!&q.pi_state); | |
2271 | pi_mutex = &q.pi_state->pi_mutex; | |
2272 | ret = rt_mutex_finish_proxy_lock(pi_mutex, to, &rt_waiter, 1); | |
2273 | debug_rt_mutex_free_waiter(&rt_waiter); | |
2274 | ||
2275 | spin_lock(q.lock_ptr); | |
2276 | /* | |
2277 | * Fixup the pi_state owner and possibly acquire the lock if we | |
2278 | * haven't already. | |
2279 | */ | |
2280 | res = fixup_owner(uaddr2, fshared, &q, !ret); | |
2281 | /* | |
2282 | * If fixup_owner() returned an error, proprogate that. If it | |
56ec1607 | 2283 | * acquired the lock, clear -ETIMEDOUT or -EINTR. |
52400ba9 DH |
2284 | */ |
2285 | if (res) | |
2286 | ret = (res < 0) ? res : 0; | |
2287 | ||
2288 | /* Unqueue and drop the lock. */ | |
2289 | unqueue_me_pi(&q); | |
2290 | } | |
2291 | ||
2292 | /* | |
2293 | * If fixup_pi_state_owner() faulted and was unable to handle the | |
2294 | * fault, unlock the rt_mutex and return the fault to userspace. | |
2295 | */ | |
2296 | if (ret == -EFAULT) { | |
2297 | if (rt_mutex_owner(pi_mutex) == current) | |
2298 | rt_mutex_unlock(pi_mutex); | |
2299 | } else if (ret == -EINTR) { | |
52400ba9 | 2300 | /* |
cc6db4e6 DH |
2301 | * We've already been requeued, but cannot restart by calling |
2302 | * futex_lock_pi() directly. We could restart this syscall, but | |
2303 | * it would detect that the user space "val" changed and return | |
2304 | * -EWOULDBLOCK. Save the overhead of the restart and return | |
2305 | * -EWOULDBLOCK directly. | |
52400ba9 | 2306 | */ |
2070887f | 2307 | ret = -EWOULDBLOCK; |
52400ba9 DH |
2308 | } |
2309 | ||
2310 | out_put_keys: | |
2311 | put_futex_key(fshared, &q.key); | |
c8b15a70 | 2312 | out_key2: |
52400ba9 DH |
2313 | put_futex_key(fshared, &key2); |
2314 | ||
2315 | out: | |
2316 | if (to) { | |
2317 | hrtimer_cancel(&to->timer); | |
2318 | destroy_hrtimer_on_stack(&to->timer); | |
2319 | } | |
2320 | return ret; | |
2321 | } | |
2322 | ||
0771dfef IM |
2323 | /* |
2324 | * Support for robust futexes: the kernel cleans up held futexes at | |
2325 | * thread exit time. | |
2326 | * | |
2327 | * Implementation: user-space maintains a per-thread list of locks it | |
2328 | * is holding. Upon do_exit(), the kernel carefully walks this list, | |
2329 | * and marks all locks that are owned by this thread with the | |
c87e2837 | 2330 | * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is |
0771dfef IM |
2331 | * always manipulated with the lock held, so the list is private and |
2332 | * per-thread. Userspace also maintains a per-thread 'list_op_pending' | |
2333 | * field, to allow the kernel to clean up if the thread dies after | |
2334 | * acquiring the lock, but just before it could have added itself to | |
2335 | * the list. There can only be one such pending lock. | |
2336 | */ | |
2337 | ||
2338 | /** | |
d96ee56c DH |
2339 | * sys_set_robust_list() - Set the robust-futex list head of a task |
2340 | * @head: pointer to the list-head | |
2341 | * @len: length of the list-head, as userspace expects | |
0771dfef | 2342 | */ |
836f92ad HC |
2343 | SYSCALL_DEFINE2(set_robust_list, struct robust_list_head __user *, head, |
2344 | size_t, len) | |
0771dfef | 2345 | { |
a0c1e907 TG |
2346 | if (!futex_cmpxchg_enabled) |
2347 | return -ENOSYS; | |
0771dfef IM |
2348 | /* |
2349 | * The kernel knows only one size for now: | |
2350 | */ | |
2351 | if (unlikely(len != sizeof(*head))) | |
2352 | return -EINVAL; | |
2353 | ||
2354 | current->robust_list = head; | |
2355 | ||
2356 | return 0; | |
2357 | } | |
2358 | ||
2359 | /** | |
d96ee56c DH |
2360 | * sys_get_robust_list() - Get the robust-futex list head of a task |
2361 | * @pid: pid of the process [zero for current task] | |
2362 | * @head_ptr: pointer to a list-head pointer, the kernel fills it in | |
2363 | * @len_ptr: pointer to a length field, the kernel fills in the header size | |
0771dfef | 2364 | */ |
836f92ad HC |
2365 | SYSCALL_DEFINE3(get_robust_list, int, pid, |
2366 | struct robust_list_head __user * __user *, head_ptr, | |
2367 | size_t __user *, len_ptr) | |
0771dfef | 2368 | { |
ba46df98 | 2369 | struct robust_list_head __user *head; |
0771dfef | 2370 | unsigned long ret; |
c69e8d9c | 2371 | const struct cred *cred = current_cred(), *pcred; |
0771dfef | 2372 | |
a0c1e907 TG |
2373 | if (!futex_cmpxchg_enabled) |
2374 | return -ENOSYS; | |
2375 | ||
0771dfef IM |
2376 | if (!pid) |
2377 | head = current->robust_list; | |
2378 | else { | |
2379 | struct task_struct *p; | |
2380 | ||
2381 | ret = -ESRCH; | |
aaa2a97e | 2382 | rcu_read_lock(); |
228ebcbe | 2383 | p = find_task_by_vpid(pid); |
0771dfef IM |
2384 | if (!p) |
2385 | goto err_unlock; | |
2386 | ret = -EPERM; | |
c69e8d9c DH |
2387 | pcred = __task_cred(p); |
2388 | if (cred->euid != pcred->euid && | |
2389 | cred->euid != pcred->uid && | |
76aac0e9 | 2390 | !capable(CAP_SYS_PTRACE)) |
0771dfef IM |
2391 | goto err_unlock; |
2392 | head = p->robust_list; | |
aaa2a97e | 2393 | rcu_read_unlock(); |
0771dfef IM |
2394 | } |
2395 | ||
2396 | if (put_user(sizeof(*head), len_ptr)) | |
2397 | return -EFAULT; | |
2398 | return put_user(head, head_ptr); | |
2399 | ||
2400 | err_unlock: | |
aaa2a97e | 2401 | rcu_read_unlock(); |
0771dfef IM |
2402 | |
2403 | return ret; | |
2404 | } | |
2405 | ||
2406 | /* | |
2407 | * Process a futex-list entry, check whether it's owned by the | |
2408 | * dying task, and do notification if so: | |
2409 | */ | |
e3f2ddea | 2410 | int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi) |
0771dfef | 2411 | { |
e3f2ddea | 2412 | u32 uval, nval, mval; |
0771dfef | 2413 | |
8f17d3a5 IM |
2414 | retry: |
2415 | if (get_user(uval, uaddr)) | |
0771dfef IM |
2416 | return -1; |
2417 | ||
b488893a | 2418 | if ((uval & FUTEX_TID_MASK) == task_pid_vnr(curr)) { |
0771dfef IM |
2419 | /* |
2420 | * Ok, this dying thread is truly holding a futex | |
2421 | * of interest. Set the OWNER_DIED bit atomically | |
2422 | * via cmpxchg, and if the value had FUTEX_WAITERS | |
2423 | * set, wake up a waiter (if any). (We have to do a | |
2424 | * futex_wake() even if OWNER_DIED is already set - | |
2425 | * to handle the rare but possible case of recursive | |
2426 | * thread-death.) The rest of the cleanup is done in | |
2427 | * userspace. | |
2428 | */ | |
e3f2ddea IM |
2429 | mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED; |
2430 | nval = futex_atomic_cmpxchg_inatomic(uaddr, uval, mval); | |
2431 | ||
c87e2837 IM |
2432 | if (nval == -EFAULT) |
2433 | return -1; | |
2434 | ||
2435 | if (nval != uval) | |
8f17d3a5 | 2436 | goto retry; |
0771dfef | 2437 | |
e3f2ddea IM |
2438 | /* |
2439 | * Wake robust non-PI futexes here. The wakeup of | |
2440 | * PI futexes happens in exit_pi_state(): | |
2441 | */ | |
36cf3b5c | 2442 | if (!pi && (uval & FUTEX_WAITERS)) |
c2f9f201 | 2443 | futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY); |
0771dfef IM |
2444 | } |
2445 | return 0; | |
2446 | } | |
2447 | ||
e3f2ddea IM |
2448 | /* |
2449 | * Fetch a robust-list pointer. Bit 0 signals PI futexes: | |
2450 | */ | |
2451 | static inline int fetch_robust_entry(struct robust_list __user **entry, | |
ba46df98 AV |
2452 | struct robust_list __user * __user *head, |
2453 | int *pi) | |
e3f2ddea IM |
2454 | { |
2455 | unsigned long uentry; | |
2456 | ||
ba46df98 | 2457 | if (get_user(uentry, (unsigned long __user *)head)) |
e3f2ddea IM |
2458 | return -EFAULT; |
2459 | ||
ba46df98 | 2460 | *entry = (void __user *)(uentry & ~1UL); |
e3f2ddea IM |
2461 | *pi = uentry & 1; |
2462 | ||
2463 | return 0; | |
2464 | } | |
2465 | ||
0771dfef IM |
2466 | /* |
2467 | * Walk curr->robust_list (very carefully, it's a userspace list!) | |
2468 | * and mark any locks found there dead, and notify any waiters. | |
2469 | * | |
2470 | * We silently return on any sign of list-walking problem. | |
2471 | */ | |
2472 | void exit_robust_list(struct task_struct *curr) | |
2473 | { | |
2474 | struct robust_list_head __user *head = curr->robust_list; | |
9f96cb1e MS |
2475 | struct robust_list __user *entry, *next_entry, *pending; |
2476 | unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip; | |
0771dfef | 2477 | unsigned long futex_offset; |
9f96cb1e | 2478 | int rc; |
0771dfef | 2479 | |
a0c1e907 TG |
2480 | if (!futex_cmpxchg_enabled) |
2481 | return; | |
2482 | ||
0771dfef IM |
2483 | /* |
2484 | * Fetch the list head (which was registered earlier, via | |
2485 | * sys_set_robust_list()): | |
2486 | */ | |
e3f2ddea | 2487 | if (fetch_robust_entry(&entry, &head->list.next, &pi)) |
0771dfef IM |
2488 | return; |
2489 | /* | |
2490 | * Fetch the relative futex offset: | |
2491 | */ | |
2492 | if (get_user(futex_offset, &head->futex_offset)) | |
2493 | return; | |
2494 | /* | |
2495 | * Fetch any possibly pending lock-add first, and handle it | |
2496 | * if it exists: | |
2497 | */ | |
e3f2ddea | 2498 | if (fetch_robust_entry(&pending, &head->list_op_pending, &pip)) |
0771dfef | 2499 | return; |
e3f2ddea | 2500 | |
9f96cb1e | 2501 | next_entry = NULL; /* avoid warning with gcc */ |
0771dfef | 2502 | while (entry != &head->list) { |
9f96cb1e MS |
2503 | /* |
2504 | * Fetch the next entry in the list before calling | |
2505 | * handle_futex_death: | |
2506 | */ | |
2507 | rc = fetch_robust_entry(&next_entry, &entry->next, &next_pi); | |
0771dfef IM |
2508 | /* |
2509 | * A pending lock might already be on the list, so | |
c87e2837 | 2510 | * don't process it twice: |
0771dfef IM |
2511 | */ |
2512 | if (entry != pending) | |
ba46df98 | 2513 | if (handle_futex_death((void __user *)entry + futex_offset, |
e3f2ddea | 2514 | curr, pi)) |
0771dfef | 2515 | return; |
9f96cb1e | 2516 | if (rc) |
0771dfef | 2517 | return; |
9f96cb1e MS |
2518 | entry = next_entry; |
2519 | pi = next_pi; | |
0771dfef IM |
2520 | /* |
2521 | * Avoid excessively long or circular lists: | |
2522 | */ | |
2523 | if (!--limit) | |
2524 | break; | |
2525 | ||
2526 | cond_resched(); | |
2527 | } | |
9f96cb1e MS |
2528 | |
2529 | if (pending) | |
2530 | handle_futex_death((void __user *)pending + futex_offset, | |
2531 | curr, pip); | |
0771dfef IM |
2532 | } |
2533 | ||
c19384b5 | 2534 | long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout, |
e2970f2f | 2535 | u32 __user *uaddr2, u32 val2, u32 val3) |
1da177e4 | 2536 | { |
1acdac10 | 2537 | int clockrt, ret = -ENOSYS; |
34f01cc1 | 2538 | int cmd = op & FUTEX_CMD_MASK; |
c2f9f201 | 2539 | int fshared = 0; |
34f01cc1 ED |
2540 | |
2541 | if (!(op & FUTEX_PRIVATE_FLAG)) | |
c2f9f201 | 2542 | fshared = 1; |
1da177e4 | 2543 | |
1acdac10 | 2544 | clockrt = op & FUTEX_CLOCK_REALTIME; |
52400ba9 | 2545 | if (clockrt && cmd != FUTEX_WAIT_BITSET && cmd != FUTEX_WAIT_REQUEUE_PI) |
1acdac10 | 2546 | return -ENOSYS; |
1da177e4 | 2547 | |
34f01cc1 | 2548 | switch (cmd) { |
1da177e4 | 2549 | case FUTEX_WAIT: |
cd689985 TG |
2550 | val3 = FUTEX_BITSET_MATCH_ANY; |
2551 | case FUTEX_WAIT_BITSET: | |
1acdac10 | 2552 | ret = futex_wait(uaddr, fshared, val, timeout, val3, clockrt); |
1da177e4 LT |
2553 | break; |
2554 | case FUTEX_WAKE: | |
cd689985 TG |
2555 | val3 = FUTEX_BITSET_MATCH_ANY; |
2556 | case FUTEX_WAKE_BITSET: | |
2557 | ret = futex_wake(uaddr, fshared, val, val3); | |
1da177e4 | 2558 | break; |
1da177e4 | 2559 | case FUTEX_REQUEUE: |
52400ba9 | 2560 | ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, NULL, 0); |
1da177e4 LT |
2561 | break; |
2562 | case FUTEX_CMP_REQUEUE: | |
52400ba9 DH |
2563 | ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, &val3, |
2564 | 0); | |
1da177e4 | 2565 | break; |
4732efbe | 2566 | case FUTEX_WAKE_OP: |
34f01cc1 | 2567 | ret = futex_wake_op(uaddr, fshared, uaddr2, val, val2, val3); |
4732efbe | 2568 | break; |
c87e2837 | 2569 | case FUTEX_LOCK_PI: |
a0c1e907 TG |
2570 | if (futex_cmpxchg_enabled) |
2571 | ret = futex_lock_pi(uaddr, fshared, val, timeout, 0); | |
c87e2837 IM |
2572 | break; |
2573 | case FUTEX_UNLOCK_PI: | |
a0c1e907 TG |
2574 | if (futex_cmpxchg_enabled) |
2575 | ret = futex_unlock_pi(uaddr, fshared); | |
c87e2837 IM |
2576 | break; |
2577 | case FUTEX_TRYLOCK_PI: | |
a0c1e907 TG |
2578 | if (futex_cmpxchg_enabled) |
2579 | ret = futex_lock_pi(uaddr, fshared, 0, timeout, 1); | |
c87e2837 | 2580 | break; |
52400ba9 DH |
2581 | case FUTEX_WAIT_REQUEUE_PI: |
2582 | val3 = FUTEX_BITSET_MATCH_ANY; | |
2583 | ret = futex_wait_requeue_pi(uaddr, fshared, val, timeout, val3, | |
2584 | clockrt, uaddr2); | |
2585 | break; | |
52400ba9 DH |
2586 | case FUTEX_CMP_REQUEUE_PI: |
2587 | ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, &val3, | |
2588 | 1); | |
2589 | break; | |
1da177e4 LT |
2590 | default: |
2591 | ret = -ENOSYS; | |
2592 | } | |
2593 | return ret; | |
2594 | } | |
2595 | ||
2596 | ||
17da2bd9 HC |
2597 | SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val, |
2598 | struct timespec __user *, utime, u32 __user *, uaddr2, | |
2599 | u32, val3) | |
1da177e4 | 2600 | { |
c19384b5 PP |
2601 | struct timespec ts; |
2602 | ktime_t t, *tp = NULL; | |
e2970f2f | 2603 | u32 val2 = 0; |
34f01cc1 | 2604 | int cmd = op & FUTEX_CMD_MASK; |
1da177e4 | 2605 | |
cd689985 | 2606 | if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI || |
52400ba9 DH |
2607 | cmd == FUTEX_WAIT_BITSET || |
2608 | cmd == FUTEX_WAIT_REQUEUE_PI)) { | |
c19384b5 | 2609 | if (copy_from_user(&ts, utime, sizeof(ts)) != 0) |
1da177e4 | 2610 | return -EFAULT; |
c19384b5 | 2611 | if (!timespec_valid(&ts)) |
9741ef96 | 2612 | return -EINVAL; |
c19384b5 PP |
2613 | |
2614 | t = timespec_to_ktime(ts); | |
34f01cc1 | 2615 | if (cmd == FUTEX_WAIT) |
5a7780e7 | 2616 | t = ktime_add_safe(ktime_get(), t); |
c19384b5 | 2617 | tp = &t; |
1da177e4 LT |
2618 | } |
2619 | /* | |
52400ba9 | 2620 | * requeue parameter in 'utime' if cmd == FUTEX_*_REQUEUE_*. |
f54f0986 | 2621 | * number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP. |
1da177e4 | 2622 | */ |
f54f0986 | 2623 | if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE || |
ba9c22f2 | 2624 | cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP) |
e2970f2f | 2625 | val2 = (u32) (unsigned long) utime; |
1da177e4 | 2626 | |
c19384b5 | 2627 | return do_futex(uaddr, op, val, tp, uaddr2, val2, val3); |
1da177e4 LT |
2628 | } |
2629 | ||
f6d107fb | 2630 | static int __init futex_init(void) |
1da177e4 | 2631 | { |
a0c1e907 | 2632 | u32 curval; |
3e4ab747 | 2633 | int i; |
95362fa9 | 2634 | |
a0c1e907 TG |
2635 | /* |
2636 | * This will fail and we want it. Some arch implementations do | |
2637 | * runtime detection of the futex_atomic_cmpxchg_inatomic() | |
2638 | * functionality. We want to know that before we call in any | |
2639 | * of the complex code paths. Also we want to prevent | |
2640 | * registration of robust lists in that case. NULL is | |
2641 | * guaranteed to fault and we get -EFAULT on functional | |
2642 | * implementation, the non functional ones will return | |
2643 | * -ENOSYS. | |
2644 | */ | |
2645 | curval = cmpxchg_futex_value_locked(NULL, 0, 0); | |
2646 | if (curval == -EFAULT) | |
2647 | futex_cmpxchg_enabled = 1; | |
2648 | ||
3e4ab747 TG |
2649 | for (i = 0; i < ARRAY_SIZE(futex_queues); i++) { |
2650 | plist_head_init(&futex_queues[i].chain, &futex_queues[i].lock); | |
2651 | spin_lock_init(&futex_queues[i].lock); | |
2652 | } | |
2653 | ||
1da177e4 LT |
2654 | return 0; |
2655 | } | |
f6d107fb | 2656 | __initcall(futex_init); |