Commit | Line | Data |
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1da177e4 LT |
1 | /* |
2 | * Fast Userspace Mutexes (which I call "Futexes!"). | |
3 | * (C) Rusty Russell, IBM 2002 | |
4 | * | |
5 | * Generalized futexes, futex requeueing, misc fixes by Ingo Molnar | |
6 | * (C) Copyright 2003 Red Hat Inc, All Rights Reserved | |
7 | * | |
8 | * Removed page pinning, fix privately mapped COW pages and other cleanups | |
9 | * (C) Copyright 2003, 2004 Jamie Lokier | |
10 | * | |
0771dfef IM |
11 | * Robust futex support started by Ingo Molnar |
12 | * (C) Copyright 2006 Red Hat Inc, All Rights Reserved | |
13 | * Thanks to Thomas Gleixner for suggestions, analysis and fixes. | |
14 | * | |
c87e2837 IM |
15 | * PI-futex support started by Ingo Molnar and Thomas Gleixner |
16 | * Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> | |
17 | * Copyright (C) 2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com> | |
18 | * | |
34f01cc1 ED |
19 | * PRIVATE futexes by Eric Dumazet |
20 | * Copyright (C) 2007 Eric Dumazet <dada1@cosmosbay.com> | |
21 | * | |
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> |
9984de1a | 58 | #include <linux/export.h> |
fd5eea42 | 59 | #include <linux/magic.h> |
b488893a PE |
60 | #include <linux/pid.h> |
61 | #include <linux/nsproxy.h> | |
bdbb776f | 62 | #include <linux/ptrace.h> |
8bd75c77 | 63 | #include <linux/sched/rt.h> |
13d60f4b | 64 | #include <linux/hugetlb.h> |
88c8004f | 65 | #include <linux/freezer.h> |
a52b89eb | 66 | #include <linux/bootmem.h> |
b488893a | 67 | |
4732efbe | 68 | #include <asm/futex.h> |
1da177e4 | 69 | |
1696a8be | 70 | #include "locking/rtmutex_common.h" |
c87e2837 | 71 | |
99b60ce6 | 72 | /* |
d7e8af1a DB |
73 | * READ this before attempting to hack on futexes! |
74 | * | |
75 | * Basic futex operation and ordering guarantees | |
76 | * ============================================= | |
99b60ce6 TG |
77 | * |
78 | * The waiter reads the futex value in user space and calls | |
79 | * futex_wait(). This function computes the hash bucket and acquires | |
80 | * the hash bucket lock. After that it reads the futex user space value | |
b0c29f79 DB |
81 | * again and verifies that the data has not changed. If it has not changed |
82 | * it enqueues itself into the hash bucket, releases the hash bucket lock | |
83 | * and schedules. | |
99b60ce6 TG |
84 | * |
85 | * The waker side modifies the user space value of the futex and calls | |
b0c29f79 DB |
86 | * futex_wake(). This function computes the hash bucket and acquires the |
87 | * hash bucket lock. Then it looks for waiters on that futex in the hash | |
88 | * bucket and wakes them. | |
99b60ce6 | 89 | * |
b0c29f79 DB |
90 | * In futex wake up scenarios where no tasks are blocked on a futex, taking |
91 | * the hb spinlock can be avoided and simply return. In order for this | |
92 | * optimization to work, ordering guarantees must exist so that the waiter | |
93 | * being added to the list is acknowledged when the list is concurrently being | |
94 | * checked by the waker, avoiding scenarios like the following: | |
99b60ce6 TG |
95 | * |
96 | * CPU 0 CPU 1 | |
97 | * val = *futex; | |
98 | * sys_futex(WAIT, futex, val); | |
99 | * futex_wait(futex, val); | |
100 | * uval = *futex; | |
101 | * *futex = newval; | |
102 | * sys_futex(WAKE, futex); | |
103 | * futex_wake(futex); | |
104 | * if (queue_empty()) | |
105 | * return; | |
106 | * if (uval == val) | |
107 | * lock(hash_bucket(futex)); | |
108 | * queue(); | |
109 | * unlock(hash_bucket(futex)); | |
110 | * schedule(); | |
111 | * | |
112 | * This would cause the waiter on CPU 0 to wait forever because it | |
113 | * missed the transition of the user space value from val to newval | |
114 | * and the waker did not find the waiter in the hash bucket queue. | |
99b60ce6 | 115 | * |
b0c29f79 DB |
116 | * The correct serialization ensures that a waiter either observes |
117 | * the changed user space value before blocking or is woken by a | |
118 | * concurrent waker: | |
119 | * | |
120 | * CPU 0 CPU 1 | |
99b60ce6 TG |
121 | * val = *futex; |
122 | * sys_futex(WAIT, futex, val); | |
123 | * futex_wait(futex, val); | |
b0c29f79 | 124 | * |
d7e8af1a | 125 | * waiters++; (a) |
b0c29f79 DB |
126 | * mb(); (A) <-- paired with -. |
127 | * | | |
128 | * lock(hash_bucket(futex)); | | |
129 | * | | |
130 | * uval = *futex; | | |
131 | * | *futex = newval; | |
132 | * | sys_futex(WAKE, futex); | |
133 | * | futex_wake(futex); | |
134 | * | | |
135 | * `-------> mb(); (B) | |
99b60ce6 | 136 | * if (uval == val) |
b0c29f79 | 137 | * queue(); |
99b60ce6 | 138 | * unlock(hash_bucket(futex)); |
b0c29f79 DB |
139 | * schedule(); if (waiters) |
140 | * lock(hash_bucket(futex)); | |
d7e8af1a DB |
141 | * else wake_waiters(futex); |
142 | * waiters--; (b) unlock(hash_bucket(futex)); | |
b0c29f79 | 143 | * |
d7e8af1a DB |
144 | * Where (A) orders the waiters increment and the futex value read through |
145 | * atomic operations (see hb_waiters_inc) and where (B) orders the write | |
146 | * to futex and the waiters read -- this is done by the barriers in | |
147 | * get_futex_key_refs(), through either ihold or atomic_inc, depending on the | |
148 | * futex type. | |
b0c29f79 DB |
149 | * |
150 | * This yields the following case (where X:=waiters, Y:=futex): | |
151 | * | |
152 | * X = Y = 0 | |
153 | * | |
154 | * w[X]=1 w[Y]=1 | |
155 | * MB MB | |
156 | * r[Y]=y r[X]=x | |
157 | * | |
158 | * Which guarantees that x==0 && y==0 is impossible; which translates back into | |
159 | * the guarantee that we cannot both miss the futex variable change and the | |
160 | * enqueue. | |
d7e8af1a DB |
161 | * |
162 | * Note that a new waiter is accounted for in (a) even when it is possible that | |
163 | * the wait call can return error, in which case we backtrack from it in (b). | |
164 | * Refer to the comment in queue_lock(). | |
165 | * | |
166 | * Similarly, in order to account for waiters being requeued on another | |
167 | * address we always increment the waiters for the destination bucket before | |
168 | * acquiring the lock. It then decrements them again after releasing it - | |
169 | * the code that actually moves the futex(es) between hash buckets (requeue_futex) | |
170 | * will do the additional required waiter count housekeeping. This is done for | |
171 | * double_lock_hb() and double_unlock_hb(), respectively. | |
99b60ce6 TG |
172 | */ |
173 | ||
03b8c7b6 | 174 | #ifndef CONFIG_HAVE_FUTEX_CMPXCHG |
a0c1e907 | 175 | int __read_mostly futex_cmpxchg_enabled; |
03b8c7b6 | 176 | #endif |
a0c1e907 | 177 | |
b41277dc DH |
178 | /* |
179 | * Futex flags used to encode options to functions and preserve them across | |
180 | * restarts. | |
181 | */ | |
182 | #define FLAGS_SHARED 0x01 | |
183 | #define FLAGS_CLOCKRT 0x02 | |
184 | #define FLAGS_HAS_TIMEOUT 0x04 | |
185 | ||
c87e2837 IM |
186 | /* |
187 | * Priority Inheritance state: | |
188 | */ | |
189 | struct futex_pi_state { | |
190 | /* | |
191 | * list of 'owned' pi_state instances - these have to be | |
192 | * cleaned up in do_exit() if the task exits prematurely: | |
193 | */ | |
194 | struct list_head list; | |
195 | ||
196 | /* | |
197 | * The PI object: | |
198 | */ | |
199 | struct rt_mutex pi_mutex; | |
200 | ||
201 | struct task_struct *owner; | |
202 | atomic_t refcount; | |
203 | ||
204 | union futex_key key; | |
205 | }; | |
206 | ||
d8d88fbb DH |
207 | /** |
208 | * struct futex_q - The hashed futex queue entry, one per waiting task | |
fb62db2b | 209 | * @list: priority-sorted list of tasks waiting on this futex |
d8d88fbb DH |
210 | * @task: the task waiting on the futex |
211 | * @lock_ptr: the hash bucket lock | |
212 | * @key: the key the futex is hashed on | |
213 | * @pi_state: optional priority inheritance state | |
214 | * @rt_waiter: rt_waiter storage for use with requeue_pi | |
215 | * @requeue_pi_key: the requeue_pi target futex key | |
216 | * @bitset: bitset for the optional bitmasked wakeup | |
217 | * | |
218 | * We use this hashed waitqueue, instead of a normal wait_queue_t, so | |
1da177e4 LT |
219 | * we can wake only the relevant ones (hashed queues may be shared). |
220 | * | |
221 | * A futex_q has a woken state, just like tasks have TASK_RUNNING. | |
ec92d082 | 222 | * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0. |
fb62db2b | 223 | * The order of wakeup is always to make the first condition true, then |
d8d88fbb DH |
224 | * the second. |
225 | * | |
226 | * PI futexes are typically woken before they are removed from the hash list via | |
227 | * the rt_mutex code. See unqueue_me_pi(). | |
1da177e4 LT |
228 | */ |
229 | struct futex_q { | |
ec92d082 | 230 | struct plist_node list; |
1da177e4 | 231 | |
d8d88fbb | 232 | struct task_struct *task; |
1da177e4 | 233 | spinlock_t *lock_ptr; |
1da177e4 | 234 | union futex_key key; |
c87e2837 | 235 | struct futex_pi_state *pi_state; |
52400ba9 | 236 | struct rt_mutex_waiter *rt_waiter; |
84bc4af5 | 237 | union futex_key *requeue_pi_key; |
cd689985 | 238 | u32 bitset; |
1da177e4 LT |
239 | }; |
240 | ||
5bdb05f9 DH |
241 | static const struct futex_q futex_q_init = { |
242 | /* list gets initialized in queue_me()*/ | |
243 | .key = FUTEX_KEY_INIT, | |
244 | .bitset = FUTEX_BITSET_MATCH_ANY | |
245 | }; | |
246 | ||
1da177e4 | 247 | /* |
b2d0994b DH |
248 | * Hash buckets are shared by all the futex_keys that hash to the same |
249 | * location. Each key may have multiple futex_q structures, one for each task | |
250 | * waiting on a futex. | |
1da177e4 LT |
251 | */ |
252 | struct futex_hash_bucket { | |
11d4616b | 253 | atomic_t waiters; |
ec92d082 PP |
254 | spinlock_t lock; |
255 | struct plist_head chain; | |
a52b89eb | 256 | } ____cacheline_aligned_in_smp; |
1da177e4 | 257 | |
a52b89eb DB |
258 | static unsigned long __read_mostly futex_hashsize; |
259 | ||
260 | static struct futex_hash_bucket *futex_queues; | |
1da177e4 | 261 | |
b0c29f79 DB |
262 | static inline void futex_get_mm(union futex_key *key) |
263 | { | |
264 | atomic_inc(&key->private.mm->mm_count); | |
265 | /* | |
266 | * Ensure futex_get_mm() implies a full barrier such that | |
267 | * get_futex_key() implies a full barrier. This is relied upon | |
268 | * as full barrier (B), see the ordering comment above. | |
269 | */ | |
270 | smp_mb__after_atomic_inc(); | |
271 | } | |
272 | ||
11d4616b LT |
273 | /* |
274 | * Reflects a new waiter being added to the waitqueue. | |
275 | */ | |
276 | static inline void hb_waiters_inc(struct futex_hash_bucket *hb) | |
b0c29f79 DB |
277 | { |
278 | #ifdef CONFIG_SMP | |
11d4616b | 279 | atomic_inc(&hb->waiters); |
b0c29f79 | 280 | /* |
11d4616b | 281 | * Full barrier (A), see the ordering comment above. |
b0c29f79 | 282 | */ |
11d4616b LT |
283 | smp_mb__after_atomic_inc(); |
284 | #endif | |
285 | } | |
286 | ||
287 | /* | |
288 | * Reflects a waiter being removed from the waitqueue by wakeup | |
289 | * paths. | |
290 | */ | |
291 | static inline void hb_waiters_dec(struct futex_hash_bucket *hb) | |
292 | { | |
293 | #ifdef CONFIG_SMP | |
294 | atomic_dec(&hb->waiters); | |
295 | #endif | |
296 | } | |
b0c29f79 | 297 | |
11d4616b LT |
298 | static inline int hb_waiters_pending(struct futex_hash_bucket *hb) |
299 | { | |
300 | #ifdef CONFIG_SMP | |
301 | return atomic_read(&hb->waiters); | |
b0c29f79 | 302 | #else |
11d4616b | 303 | return 1; |
b0c29f79 DB |
304 | #endif |
305 | } | |
306 | ||
1da177e4 LT |
307 | /* |
308 | * We hash on the keys returned from get_futex_key (see below). | |
309 | */ | |
310 | static struct futex_hash_bucket *hash_futex(union futex_key *key) | |
311 | { | |
312 | u32 hash = jhash2((u32*)&key->both.word, | |
313 | (sizeof(key->both.word)+sizeof(key->both.ptr))/4, | |
314 | key->both.offset); | |
a52b89eb | 315 | return &futex_queues[hash & (futex_hashsize - 1)]; |
1da177e4 LT |
316 | } |
317 | ||
318 | /* | |
319 | * Return 1 if two futex_keys are equal, 0 otherwise. | |
320 | */ | |
321 | static inline int match_futex(union futex_key *key1, union futex_key *key2) | |
322 | { | |
2bc87203 DH |
323 | return (key1 && key2 |
324 | && key1->both.word == key2->both.word | |
1da177e4 LT |
325 | && key1->both.ptr == key2->both.ptr |
326 | && key1->both.offset == key2->both.offset); | |
327 | } | |
328 | ||
38d47c1b PZ |
329 | /* |
330 | * Take a reference to the resource addressed by a key. | |
331 | * Can be called while holding spinlocks. | |
332 | * | |
333 | */ | |
334 | static void get_futex_key_refs(union futex_key *key) | |
335 | { | |
336 | if (!key->both.ptr) | |
337 | return; | |
338 | ||
339 | switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { | |
340 | case FUT_OFF_INODE: | |
b0c29f79 | 341 | ihold(key->shared.inode); /* implies MB (B) */ |
38d47c1b PZ |
342 | break; |
343 | case FUT_OFF_MMSHARED: | |
b0c29f79 | 344 | futex_get_mm(key); /* implies MB (B) */ |
38d47c1b PZ |
345 | break; |
346 | } | |
347 | } | |
348 | ||
349 | /* | |
350 | * Drop a reference to the resource addressed by a key. | |
351 | * The hash bucket spinlock must not be held. | |
352 | */ | |
353 | static void drop_futex_key_refs(union futex_key *key) | |
354 | { | |
90621c40 DH |
355 | if (!key->both.ptr) { |
356 | /* If we're here then we tried to put a key we failed to get */ | |
357 | WARN_ON_ONCE(1); | |
38d47c1b | 358 | return; |
90621c40 | 359 | } |
38d47c1b PZ |
360 | |
361 | switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { | |
362 | case FUT_OFF_INODE: | |
363 | iput(key->shared.inode); | |
364 | break; | |
365 | case FUT_OFF_MMSHARED: | |
366 | mmdrop(key->private.mm); | |
367 | break; | |
368 | } | |
369 | } | |
370 | ||
34f01cc1 | 371 | /** |
d96ee56c DH |
372 | * get_futex_key() - Get parameters which are the keys for a futex |
373 | * @uaddr: virtual address of the futex | |
374 | * @fshared: 0 for a PROCESS_PRIVATE futex, 1 for PROCESS_SHARED | |
375 | * @key: address where result is stored. | |
9ea71503 SB |
376 | * @rw: mapping needs to be read/write (values: VERIFY_READ, |
377 | * VERIFY_WRITE) | |
34f01cc1 | 378 | * |
6c23cbbd RD |
379 | * Return: a negative error code or 0 |
380 | * | |
34f01cc1 | 381 | * The key words are stored in *key on success. |
1da177e4 | 382 | * |
6131ffaa | 383 | * For shared mappings, it's (page->index, file_inode(vma->vm_file), |
1da177e4 LT |
384 | * offset_within_page). For private mappings, it's (uaddr, current->mm). |
385 | * We can usually work out the index without swapping in the page. | |
386 | * | |
b2d0994b | 387 | * lock_page() might sleep, the caller should not hold a spinlock. |
1da177e4 | 388 | */ |
64d1304a | 389 | static int |
9ea71503 | 390 | get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key, int rw) |
1da177e4 | 391 | { |
e2970f2f | 392 | unsigned long address = (unsigned long)uaddr; |
1da177e4 | 393 | struct mm_struct *mm = current->mm; |
a5b338f2 | 394 | struct page *page, *page_head; |
9ea71503 | 395 | int err, ro = 0; |
1da177e4 LT |
396 | |
397 | /* | |
398 | * The futex address must be "naturally" aligned. | |
399 | */ | |
e2970f2f | 400 | key->both.offset = address % PAGE_SIZE; |
34f01cc1 | 401 | if (unlikely((address % sizeof(u32)) != 0)) |
1da177e4 | 402 | return -EINVAL; |
e2970f2f | 403 | address -= key->both.offset; |
1da177e4 | 404 | |
5cdec2d8 LT |
405 | if (unlikely(!access_ok(rw, uaddr, sizeof(u32)))) |
406 | return -EFAULT; | |
407 | ||
34f01cc1 ED |
408 | /* |
409 | * PROCESS_PRIVATE futexes are fast. | |
410 | * As the mm cannot disappear under us and the 'key' only needs | |
411 | * virtual address, we dont even have to find the underlying vma. | |
412 | * Note : We do have to check 'uaddr' is a valid user address, | |
413 | * but access_ok() should be faster than find_vma() | |
414 | */ | |
415 | if (!fshared) { | |
34f01cc1 ED |
416 | key->private.mm = mm; |
417 | key->private.address = address; | |
b0c29f79 | 418 | get_futex_key_refs(key); /* implies MB (B) */ |
34f01cc1 ED |
419 | return 0; |
420 | } | |
1da177e4 | 421 | |
38d47c1b | 422 | again: |
7485d0d3 | 423 | err = get_user_pages_fast(address, 1, 1, &page); |
9ea71503 SB |
424 | /* |
425 | * If write access is not required (eg. FUTEX_WAIT), try | |
426 | * and get read-only access. | |
427 | */ | |
428 | if (err == -EFAULT && rw == VERIFY_READ) { | |
429 | err = get_user_pages_fast(address, 1, 0, &page); | |
430 | ro = 1; | |
431 | } | |
38d47c1b PZ |
432 | if (err < 0) |
433 | return err; | |
9ea71503 SB |
434 | else |
435 | err = 0; | |
38d47c1b | 436 | |
a5b338f2 AA |
437 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE |
438 | page_head = page; | |
439 | if (unlikely(PageTail(page))) { | |
38d47c1b | 440 | put_page(page); |
a5b338f2 AA |
441 | /* serialize against __split_huge_page_splitting() */ |
442 | local_irq_disable(); | |
f12d5bfc | 443 | if (likely(__get_user_pages_fast(address, 1, !ro, &page) == 1)) { |
a5b338f2 AA |
444 | page_head = compound_head(page); |
445 | /* | |
446 | * page_head is valid pointer but we must pin | |
447 | * it before taking the PG_lock and/or | |
448 | * PG_compound_lock. The moment we re-enable | |
449 | * irqs __split_huge_page_splitting() can | |
450 | * return and the head page can be freed from | |
451 | * under us. We can't take the PG_lock and/or | |
452 | * PG_compound_lock on a page that could be | |
453 | * freed from under us. | |
454 | */ | |
455 | if (page != page_head) { | |
456 | get_page(page_head); | |
457 | put_page(page); | |
458 | } | |
459 | local_irq_enable(); | |
460 | } else { | |
461 | local_irq_enable(); | |
462 | goto again; | |
463 | } | |
464 | } | |
465 | #else | |
466 | page_head = compound_head(page); | |
467 | if (page != page_head) { | |
468 | get_page(page_head); | |
469 | put_page(page); | |
470 | } | |
471 | #endif | |
472 | ||
473 | lock_page(page_head); | |
e6780f72 HD |
474 | |
475 | /* | |
476 | * If page_head->mapping is NULL, then it cannot be a PageAnon | |
477 | * page; but it might be the ZERO_PAGE or in the gate area or | |
478 | * in a special mapping (all cases which we are happy to fail); | |
479 | * or it may have been a good file page when get_user_pages_fast | |
480 | * found it, but truncated or holepunched or subjected to | |
481 | * invalidate_complete_page2 before we got the page lock (also | |
482 | * cases which we are happy to fail). And we hold a reference, | |
483 | * so refcount care in invalidate_complete_page's remove_mapping | |
484 | * prevents drop_caches from setting mapping to NULL beneath us. | |
485 | * | |
486 | * The case we do have to guard against is when memory pressure made | |
487 | * shmem_writepage move it from filecache to swapcache beneath us: | |
488 | * an unlikely race, but we do need to retry for page_head->mapping. | |
489 | */ | |
a5b338f2 | 490 | if (!page_head->mapping) { |
e6780f72 | 491 | int shmem_swizzled = PageSwapCache(page_head); |
a5b338f2 AA |
492 | unlock_page(page_head); |
493 | put_page(page_head); | |
e6780f72 HD |
494 | if (shmem_swizzled) |
495 | goto again; | |
496 | return -EFAULT; | |
38d47c1b | 497 | } |
1da177e4 LT |
498 | |
499 | /* | |
500 | * Private mappings are handled in a simple way. | |
501 | * | |
502 | * NOTE: When userspace waits on a MAP_SHARED mapping, even if | |
503 | * it's a read-only handle, it's expected that futexes attach to | |
38d47c1b | 504 | * the object not the particular process. |
1da177e4 | 505 | */ |
a5b338f2 | 506 | if (PageAnon(page_head)) { |
9ea71503 SB |
507 | /* |
508 | * A RO anonymous page will never change and thus doesn't make | |
509 | * sense for futex operations. | |
510 | */ | |
511 | if (ro) { | |
512 | err = -EFAULT; | |
513 | goto out; | |
514 | } | |
515 | ||
38d47c1b | 516 | key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */ |
1da177e4 | 517 | key->private.mm = mm; |
e2970f2f | 518 | key->private.address = address; |
38d47c1b PZ |
519 | } else { |
520 | key->both.offset |= FUT_OFF_INODE; /* inode-based key */ | |
a5b338f2 | 521 | key->shared.inode = page_head->mapping->host; |
13d60f4b | 522 | key->shared.pgoff = basepage_index(page); |
1da177e4 LT |
523 | } |
524 | ||
b0c29f79 | 525 | get_futex_key_refs(key); /* implies MB (B) */ |
1da177e4 | 526 | |
9ea71503 | 527 | out: |
a5b338f2 AA |
528 | unlock_page(page_head); |
529 | put_page(page_head); | |
9ea71503 | 530 | return err; |
1da177e4 LT |
531 | } |
532 | ||
ae791a2d | 533 | static inline void put_futex_key(union futex_key *key) |
1da177e4 | 534 | { |
38d47c1b | 535 | drop_futex_key_refs(key); |
1da177e4 LT |
536 | } |
537 | ||
d96ee56c DH |
538 | /** |
539 | * fault_in_user_writeable() - Fault in user address and verify RW access | |
d0725992 TG |
540 | * @uaddr: pointer to faulting user space address |
541 | * | |
542 | * Slow path to fixup the fault we just took in the atomic write | |
543 | * access to @uaddr. | |
544 | * | |
fb62db2b | 545 | * We have no generic implementation of a non-destructive write to the |
d0725992 TG |
546 | * user address. We know that we faulted in the atomic pagefault |
547 | * disabled section so we can as well avoid the #PF overhead by | |
548 | * calling get_user_pages() right away. | |
549 | */ | |
550 | static int fault_in_user_writeable(u32 __user *uaddr) | |
551 | { | |
722d0172 AK |
552 | struct mm_struct *mm = current->mm; |
553 | int ret; | |
554 | ||
555 | down_read(&mm->mmap_sem); | |
2efaca92 BH |
556 | ret = fixup_user_fault(current, mm, (unsigned long)uaddr, |
557 | FAULT_FLAG_WRITE); | |
722d0172 AK |
558 | up_read(&mm->mmap_sem); |
559 | ||
d0725992 TG |
560 | return ret < 0 ? ret : 0; |
561 | } | |
562 | ||
4b1c486b DH |
563 | /** |
564 | * futex_top_waiter() - Return the highest priority waiter on a futex | |
d96ee56c DH |
565 | * @hb: the hash bucket the futex_q's reside in |
566 | * @key: the futex key (to distinguish it from other futex futex_q's) | |
4b1c486b DH |
567 | * |
568 | * Must be called with the hb lock held. | |
569 | */ | |
570 | static struct futex_q *futex_top_waiter(struct futex_hash_bucket *hb, | |
571 | union futex_key *key) | |
572 | { | |
573 | struct futex_q *this; | |
574 | ||
575 | plist_for_each_entry(this, &hb->chain, list) { | |
576 | if (match_futex(&this->key, key)) | |
577 | return this; | |
578 | } | |
579 | return NULL; | |
580 | } | |
581 | ||
37a9d912 ML |
582 | static int cmpxchg_futex_value_locked(u32 *curval, u32 __user *uaddr, |
583 | u32 uval, u32 newval) | |
36cf3b5c | 584 | { |
37a9d912 | 585 | int ret; |
36cf3b5c TG |
586 | |
587 | pagefault_disable(); | |
37a9d912 | 588 | ret = futex_atomic_cmpxchg_inatomic(curval, uaddr, uval, newval); |
36cf3b5c TG |
589 | pagefault_enable(); |
590 | ||
37a9d912 | 591 | return ret; |
36cf3b5c TG |
592 | } |
593 | ||
594 | static int get_futex_value_locked(u32 *dest, u32 __user *from) | |
1da177e4 LT |
595 | { |
596 | int ret; | |
597 | ||
a866374a | 598 | pagefault_disable(); |
e2970f2f | 599 | ret = __copy_from_user_inatomic(dest, from, sizeof(u32)); |
a866374a | 600 | pagefault_enable(); |
1da177e4 LT |
601 | |
602 | return ret ? -EFAULT : 0; | |
603 | } | |
604 | ||
c87e2837 IM |
605 | |
606 | /* | |
607 | * PI code: | |
608 | */ | |
609 | static int refill_pi_state_cache(void) | |
610 | { | |
611 | struct futex_pi_state *pi_state; | |
612 | ||
613 | if (likely(current->pi_state_cache)) | |
614 | return 0; | |
615 | ||
4668edc3 | 616 | pi_state = kzalloc(sizeof(*pi_state), GFP_KERNEL); |
c87e2837 IM |
617 | |
618 | if (!pi_state) | |
619 | return -ENOMEM; | |
620 | ||
c87e2837 IM |
621 | INIT_LIST_HEAD(&pi_state->list); |
622 | /* pi_mutex gets initialized later */ | |
623 | pi_state->owner = NULL; | |
624 | atomic_set(&pi_state->refcount, 1); | |
38d47c1b | 625 | pi_state->key = FUTEX_KEY_INIT; |
c87e2837 IM |
626 | |
627 | current->pi_state_cache = pi_state; | |
628 | ||
629 | return 0; | |
630 | } | |
631 | ||
632 | static struct futex_pi_state * alloc_pi_state(void) | |
633 | { | |
634 | struct futex_pi_state *pi_state = current->pi_state_cache; | |
635 | ||
636 | WARN_ON(!pi_state); | |
637 | current->pi_state_cache = NULL; | |
638 | ||
639 | return pi_state; | |
640 | } | |
641 | ||
642 | static void free_pi_state(struct futex_pi_state *pi_state) | |
643 | { | |
644 | if (!atomic_dec_and_test(&pi_state->refcount)) | |
645 | return; | |
646 | ||
647 | /* | |
648 | * If pi_state->owner is NULL, the owner is most probably dying | |
649 | * and has cleaned up the pi_state already | |
650 | */ | |
651 | if (pi_state->owner) { | |
1d615482 | 652 | raw_spin_lock_irq(&pi_state->owner->pi_lock); |
c87e2837 | 653 | list_del_init(&pi_state->list); |
1d615482 | 654 | raw_spin_unlock_irq(&pi_state->owner->pi_lock); |
c87e2837 IM |
655 | |
656 | rt_mutex_proxy_unlock(&pi_state->pi_mutex, pi_state->owner); | |
657 | } | |
658 | ||
659 | if (current->pi_state_cache) | |
660 | kfree(pi_state); | |
661 | else { | |
662 | /* | |
663 | * pi_state->list is already empty. | |
664 | * clear pi_state->owner. | |
665 | * refcount is at 0 - put it back to 1. | |
666 | */ | |
667 | pi_state->owner = NULL; | |
668 | atomic_set(&pi_state->refcount, 1); | |
669 | current->pi_state_cache = pi_state; | |
670 | } | |
671 | } | |
672 | ||
673 | /* | |
674 | * Look up the task based on what TID userspace gave us. | |
675 | * We dont trust it. | |
676 | */ | |
677 | static struct task_struct * futex_find_get_task(pid_t pid) | |
678 | { | |
679 | struct task_struct *p; | |
680 | ||
d359b549 | 681 | rcu_read_lock(); |
228ebcbe | 682 | p = find_task_by_vpid(pid); |
7a0ea09a MH |
683 | if (p) |
684 | get_task_struct(p); | |
a06381fe | 685 | |
d359b549 | 686 | rcu_read_unlock(); |
c87e2837 IM |
687 | |
688 | return p; | |
689 | } | |
690 | ||
691 | /* | |
692 | * This task is holding PI mutexes at exit time => bad. | |
693 | * Kernel cleans up PI-state, but userspace is likely hosed. | |
694 | * (Robust-futex cleanup is separate and might save the day for userspace.) | |
695 | */ | |
696 | void exit_pi_state_list(struct task_struct *curr) | |
697 | { | |
c87e2837 IM |
698 | struct list_head *next, *head = &curr->pi_state_list; |
699 | struct futex_pi_state *pi_state; | |
627371d7 | 700 | struct futex_hash_bucket *hb; |
38d47c1b | 701 | union futex_key key = FUTEX_KEY_INIT; |
c87e2837 | 702 | |
a0c1e907 TG |
703 | if (!futex_cmpxchg_enabled) |
704 | return; | |
c87e2837 IM |
705 | /* |
706 | * We are a ZOMBIE and nobody can enqueue itself on | |
707 | * pi_state_list anymore, but we have to be careful | |
627371d7 | 708 | * versus waiters unqueueing themselves: |
c87e2837 | 709 | */ |
1d615482 | 710 | raw_spin_lock_irq(&curr->pi_lock); |
c87e2837 IM |
711 | while (!list_empty(head)) { |
712 | ||
713 | next = head->next; | |
714 | pi_state = list_entry(next, struct futex_pi_state, list); | |
715 | key = pi_state->key; | |
627371d7 | 716 | hb = hash_futex(&key); |
1d615482 | 717 | raw_spin_unlock_irq(&curr->pi_lock); |
c87e2837 | 718 | |
c87e2837 IM |
719 | spin_lock(&hb->lock); |
720 | ||
1d615482 | 721 | raw_spin_lock_irq(&curr->pi_lock); |
627371d7 IM |
722 | /* |
723 | * We dropped the pi-lock, so re-check whether this | |
724 | * task still owns the PI-state: | |
725 | */ | |
c87e2837 IM |
726 | if (head->next != next) { |
727 | spin_unlock(&hb->lock); | |
728 | continue; | |
729 | } | |
730 | ||
c87e2837 | 731 | WARN_ON(pi_state->owner != curr); |
627371d7 IM |
732 | WARN_ON(list_empty(&pi_state->list)); |
733 | list_del_init(&pi_state->list); | |
c87e2837 | 734 | pi_state->owner = NULL; |
1d615482 | 735 | raw_spin_unlock_irq(&curr->pi_lock); |
c87e2837 IM |
736 | |
737 | rt_mutex_unlock(&pi_state->pi_mutex); | |
738 | ||
739 | spin_unlock(&hb->lock); | |
740 | ||
1d615482 | 741 | raw_spin_lock_irq(&curr->pi_lock); |
c87e2837 | 742 | } |
1d615482 | 743 | raw_spin_unlock_irq(&curr->pi_lock); |
c87e2837 IM |
744 | } |
745 | ||
746 | static int | |
d0aa7a70 | 747 | lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, |
866293ee TG |
748 | union futex_key *key, struct futex_pi_state **ps, |
749 | struct task_struct *task) | |
c87e2837 IM |
750 | { |
751 | struct futex_pi_state *pi_state = NULL; | |
752 | struct futex_q *this, *next; | |
c87e2837 | 753 | struct task_struct *p; |
778e9a9c | 754 | pid_t pid = uval & FUTEX_TID_MASK; |
c87e2837 | 755 | |
0d00c7b2 | 756 | plist_for_each_entry_safe(this, next, &hb->chain, list) { |
d0aa7a70 | 757 | if (match_futex(&this->key, key)) { |
c87e2837 IM |
758 | /* |
759 | * Another waiter already exists - bump up | |
760 | * the refcount and return its pi_state: | |
761 | */ | |
762 | pi_state = this->pi_state; | |
06a9ec29 | 763 | /* |
fb62db2b | 764 | * Userspace might have messed up non-PI and PI futexes |
06a9ec29 TG |
765 | */ |
766 | if (unlikely(!pi_state)) | |
767 | return -EINVAL; | |
768 | ||
627371d7 | 769 | WARN_ON(!atomic_read(&pi_state->refcount)); |
59647b6a TG |
770 | |
771 | /* | |
772 | * When pi_state->owner is NULL then the owner died | |
773 | * and another waiter is on the fly. pi_state->owner | |
774 | * is fixed up by the task which acquires | |
775 | * pi_state->rt_mutex. | |
776 | * | |
777 | * We do not check for pid == 0 which can happen when | |
778 | * the owner died and robust_list_exit() cleared the | |
779 | * TID. | |
780 | */ | |
781 | if (pid && pi_state->owner) { | |
782 | /* | |
783 | * Bail out if user space manipulated the | |
784 | * futex value. | |
785 | */ | |
786 | if (pid != task_pid_vnr(pi_state->owner)) | |
787 | return -EINVAL; | |
788 | } | |
627371d7 | 789 | |
866293ee TG |
790 | /* |
791 | * Protect against a corrupted uval. If uval | |
792 | * is 0x80000000 then pid is 0 and the waiter | |
793 | * bit is set. So the deadlock check in the | |
794 | * calling code has failed and we did not fall | |
795 | * into the check above due to !pid. | |
796 | */ | |
797 | if (task && pi_state->owner == task) | |
798 | return -EDEADLK; | |
799 | ||
c87e2837 | 800 | atomic_inc(&pi_state->refcount); |
d0aa7a70 | 801 | *ps = pi_state; |
c87e2837 IM |
802 | |
803 | return 0; | |
804 | } | |
805 | } | |
806 | ||
807 | /* | |
e3f2ddea | 808 | * We are the first waiter - try to look up the real owner and attach |
778e9a9c | 809 | * the new pi_state to it, but bail out when TID = 0 |
c87e2837 | 810 | */ |
778e9a9c | 811 | if (!pid) |
e3f2ddea | 812 | return -ESRCH; |
c87e2837 | 813 | p = futex_find_get_task(pid); |
7a0ea09a MH |
814 | if (!p) |
815 | return -ESRCH; | |
778e9a9c AK |
816 | |
817 | /* | |
818 | * We need to look at the task state flags to figure out, | |
819 | * whether the task is exiting. To protect against the do_exit | |
820 | * change of the task flags, we do this protected by | |
821 | * p->pi_lock: | |
822 | */ | |
1d615482 | 823 | raw_spin_lock_irq(&p->pi_lock); |
778e9a9c AK |
824 | if (unlikely(p->flags & PF_EXITING)) { |
825 | /* | |
826 | * The task is on the way out. When PF_EXITPIDONE is | |
827 | * set, we know that the task has finished the | |
828 | * cleanup: | |
829 | */ | |
830 | int ret = (p->flags & PF_EXITPIDONE) ? -ESRCH : -EAGAIN; | |
831 | ||
1d615482 | 832 | raw_spin_unlock_irq(&p->pi_lock); |
778e9a9c AK |
833 | put_task_struct(p); |
834 | return ret; | |
835 | } | |
c87e2837 IM |
836 | |
837 | pi_state = alloc_pi_state(); | |
838 | ||
839 | /* | |
840 | * Initialize the pi_mutex in locked state and make 'p' | |
841 | * the owner of it: | |
842 | */ | |
843 | rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p); | |
844 | ||
845 | /* Store the key for possible exit cleanups: */ | |
d0aa7a70 | 846 | pi_state->key = *key; |
c87e2837 | 847 | |
627371d7 | 848 | WARN_ON(!list_empty(&pi_state->list)); |
c87e2837 IM |
849 | list_add(&pi_state->list, &p->pi_state_list); |
850 | pi_state->owner = p; | |
1d615482 | 851 | raw_spin_unlock_irq(&p->pi_lock); |
c87e2837 IM |
852 | |
853 | put_task_struct(p); | |
854 | ||
d0aa7a70 | 855 | *ps = pi_state; |
c87e2837 IM |
856 | |
857 | return 0; | |
858 | } | |
859 | ||
1a52084d | 860 | /** |
d96ee56c | 861 | * futex_lock_pi_atomic() - Atomic work required to acquire a pi aware futex |
bab5bc9e DH |
862 | * @uaddr: the pi futex user address |
863 | * @hb: the pi futex hash bucket | |
864 | * @key: the futex key associated with uaddr and hb | |
865 | * @ps: the pi_state pointer where we store the result of the | |
866 | * lookup | |
867 | * @task: the task to perform the atomic lock work for. This will | |
868 | * be "current" except in the case of requeue pi. | |
869 | * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0) | |
1a52084d | 870 | * |
6c23cbbd RD |
871 | * Return: |
872 | * 0 - ready to wait; | |
873 | * 1 - acquired the lock; | |
1a52084d DH |
874 | * <0 - error |
875 | * | |
876 | * The hb->lock and futex_key refs shall be held by the caller. | |
877 | */ | |
878 | static int futex_lock_pi_atomic(u32 __user *uaddr, struct futex_hash_bucket *hb, | |
879 | union futex_key *key, | |
880 | struct futex_pi_state **ps, | |
bab5bc9e | 881 | struct task_struct *task, int set_waiters) |
1a52084d | 882 | { |
59fa6245 | 883 | int lock_taken, ret, force_take = 0; |
c0c9ed15 | 884 | u32 uval, newval, curval, vpid = task_pid_vnr(task); |
1a52084d DH |
885 | |
886 | retry: | |
887 | ret = lock_taken = 0; | |
888 | ||
889 | /* | |
890 | * To avoid races, we attempt to take the lock here again | |
891 | * (by doing a 0 -> TID atomic cmpxchg), while holding all | |
892 | * the locks. It will most likely not succeed. | |
893 | */ | |
c0c9ed15 | 894 | newval = vpid; |
bab5bc9e DH |
895 | if (set_waiters) |
896 | newval |= FUTEX_WAITERS; | |
1a52084d | 897 | |
37a9d912 | 898 | if (unlikely(cmpxchg_futex_value_locked(&curval, uaddr, 0, newval))) |
1a52084d DH |
899 | return -EFAULT; |
900 | ||
901 | /* | |
902 | * Detect deadlocks. | |
903 | */ | |
c0c9ed15 | 904 | if ((unlikely((curval & FUTEX_TID_MASK) == vpid))) |
1a52084d DH |
905 | return -EDEADLK; |
906 | ||
907 | /* | |
908 | * Surprise - we got the lock. Just return to userspace: | |
909 | */ | |
910 | if (unlikely(!curval)) | |
911 | return 1; | |
912 | ||
913 | uval = curval; | |
914 | ||
915 | /* | |
916 | * Set the FUTEX_WAITERS flag, so the owner will know it has someone | |
917 | * to wake at the next unlock. | |
918 | */ | |
919 | newval = curval | FUTEX_WAITERS; | |
920 | ||
921 | /* | |
59fa6245 | 922 | * Should we force take the futex? See below. |
1a52084d | 923 | */ |
59fa6245 TG |
924 | if (unlikely(force_take)) { |
925 | /* | |
926 | * Keep the OWNER_DIED and the WAITERS bit and set the | |
927 | * new TID value. | |
928 | */ | |
c0c9ed15 | 929 | newval = (curval & ~FUTEX_TID_MASK) | vpid; |
59fa6245 | 930 | force_take = 0; |
1a52084d DH |
931 | lock_taken = 1; |
932 | } | |
933 | ||
37a9d912 | 934 | if (unlikely(cmpxchg_futex_value_locked(&curval, uaddr, uval, newval))) |
1a52084d DH |
935 | return -EFAULT; |
936 | if (unlikely(curval != uval)) | |
937 | goto retry; | |
938 | ||
939 | /* | |
59fa6245 | 940 | * We took the lock due to forced take over. |
1a52084d DH |
941 | */ |
942 | if (unlikely(lock_taken)) | |
943 | return 1; | |
944 | ||
945 | /* | |
946 | * We dont have the lock. Look up the PI state (or create it if | |
947 | * we are the first waiter): | |
948 | */ | |
866293ee | 949 | ret = lookup_pi_state(uval, hb, key, ps, task); |
1a52084d DH |
950 | |
951 | if (unlikely(ret)) { | |
952 | switch (ret) { | |
953 | case -ESRCH: | |
954 | /* | |
59fa6245 TG |
955 | * We failed to find an owner for this |
956 | * futex. So we have no pi_state to block | |
957 | * on. This can happen in two cases: | |
958 | * | |
959 | * 1) The owner died | |
960 | * 2) A stale FUTEX_WAITERS bit | |
961 | * | |
962 | * Re-read the futex value. | |
1a52084d DH |
963 | */ |
964 | if (get_futex_value_locked(&curval, uaddr)) | |
965 | return -EFAULT; | |
966 | ||
967 | /* | |
59fa6245 TG |
968 | * If the owner died or we have a stale |
969 | * WAITERS bit the owner TID in the user space | |
970 | * futex is 0. | |
1a52084d | 971 | */ |
59fa6245 TG |
972 | if (!(curval & FUTEX_TID_MASK)) { |
973 | force_take = 1; | |
1a52084d DH |
974 | goto retry; |
975 | } | |
976 | default: | |
977 | break; | |
978 | } | |
979 | } | |
980 | ||
981 | return ret; | |
982 | } | |
983 | ||
2e12978a LJ |
984 | /** |
985 | * __unqueue_futex() - Remove the futex_q from its futex_hash_bucket | |
986 | * @q: The futex_q to unqueue | |
987 | * | |
988 | * The q->lock_ptr must not be NULL and must be held by the caller. | |
989 | */ | |
990 | static void __unqueue_futex(struct futex_q *q) | |
991 | { | |
992 | struct futex_hash_bucket *hb; | |
993 | ||
29096202 SR |
994 | if (WARN_ON_SMP(!q->lock_ptr || !spin_is_locked(q->lock_ptr)) |
995 | || WARN_ON(plist_node_empty(&q->list))) | |
2e12978a LJ |
996 | return; |
997 | ||
998 | hb = container_of(q->lock_ptr, struct futex_hash_bucket, lock); | |
999 | plist_del(&q->list, &hb->chain); | |
11d4616b | 1000 | hb_waiters_dec(hb); |
2e12978a LJ |
1001 | } |
1002 | ||
1da177e4 LT |
1003 | /* |
1004 | * The hash bucket lock must be held when this is called. | |
1005 | * Afterwards, the futex_q must not be accessed. | |
1006 | */ | |
1007 | static void wake_futex(struct futex_q *q) | |
1008 | { | |
f1a11e05 TG |
1009 | struct task_struct *p = q->task; |
1010 | ||
aa10990e DH |
1011 | if (WARN(q->pi_state || q->rt_waiter, "refusing to wake PI futex\n")) |
1012 | return; | |
1013 | ||
1da177e4 | 1014 | /* |
f1a11e05 | 1015 | * We set q->lock_ptr = NULL _before_ we wake up the task. If |
fb62db2b RD |
1016 | * a non-futex wake up happens on another CPU then the task |
1017 | * might exit and p would dereference a non-existing task | |
f1a11e05 TG |
1018 | * struct. Prevent this by holding a reference on p across the |
1019 | * wake up. | |
1da177e4 | 1020 | */ |
f1a11e05 TG |
1021 | get_task_struct(p); |
1022 | ||
2e12978a | 1023 | __unqueue_futex(q); |
1da177e4 | 1024 | /* |
f1a11e05 TG |
1025 | * The waiting task can free the futex_q as soon as |
1026 | * q->lock_ptr = NULL is written, without taking any locks. A | |
1027 | * memory barrier is required here to prevent the following | |
1028 | * store to lock_ptr from getting ahead of the plist_del. | |
1da177e4 | 1029 | */ |
ccdea2f8 | 1030 | smp_wmb(); |
1da177e4 | 1031 | q->lock_ptr = NULL; |
f1a11e05 TG |
1032 | |
1033 | wake_up_state(p, TASK_NORMAL); | |
1034 | put_task_struct(p); | |
1da177e4 LT |
1035 | } |
1036 | ||
c87e2837 IM |
1037 | static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this) |
1038 | { | |
1039 | struct task_struct *new_owner; | |
1040 | struct futex_pi_state *pi_state = this->pi_state; | |
7cfdaf38 | 1041 | u32 uninitialized_var(curval), newval; |
c87e2837 IM |
1042 | |
1043 | if (!pi_state) | |
1044 | return -EINVAL; | |
1045 | ||
51246bfd TG |
1046 | /* |
1047 | * If current does not own the pi_state then the futex is | |
1048 | * inconsistent and user space fiddled with the futex value. | |
1049 | */ | |
1050 | if (pi_state->owner != current) | |
1051 | return -EINVAL; | |
1052 | ||
d209d74d | 1053 | raw_spin_lock(&pi_state->pi_mutex.wait_lock); |
c87e2837 IM |
1054 | new_owner = rt_mutex_next_owner(&pi_state->pi_mutex); |
1055 | ||
1056 | /* | |
f123c98e SR |
1057 | * It is possible that the next waiter (the one that brought |
1058 | * this owner to the kernel) timed out and is no longer | |
1059 | * waiting on the lock. | |
c87e2837 IM |
1060 | */ |
1061 | if (!new_owner) | |
1062 | new_owner = this->task; | |
1063 | ||
1064 | /* | |
1065 | * We pass it to the next owner. (The WAITERS bit is always | |
1066 | * kept enabled while there is PI state around. We must also | |
1067 | * preserve the owner died bit.) | |
1068 | */ | |
e3f2ddea | 1069 | if (!(uval & FUTEX_OWNER_DIED)) { |
778e9a9c AK |
1070 | int ret = 0; |
1071 | ||
b488893a | 1072 | newval = FUTEX_WAITERS | task_pid_vnr(new_owner); |
e3f2ddea | 1073 | |
37a9d912 | 1074 | if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval)) |
778e9a9c | 1075 | ret = -EFAULT; |
cde898fa | 1076 | else if (curval != uval) |
778e9a9c AK |
1077 | ret = -EINVAL; |
1078 | if (ret) { | |
d209d74d | 1079 | raw_spin_unlock(&pi_state->pi_mutex.wait_lock); |
778e9a9c AK |
1080 | return ret; |
1081 | } | |
e3f2ddea | 1082 | } |
c87e2837 | 1083 | |
1d615482 | 1084 | raw_spin_lock_irq(&pi_state->owner->pi_lock); |
627371d7 IM |
1085 | WARN_ON(list_empty(&pi_state->list)); |
1086 | list_del_init(&pi_state->list); | |
1d615482 | 1087 | raw_spin_unlock_irq(&pi_state->owner->pi_lock); |
627371d7 | 1088 | |
1d615482 | 1089 | raw_spin_lock_irq(&new_owner->pi_lock); |
627371d7 | 1090 | WARN_ON(!list_empty(&pi_state->list)); |
c87e2837 IM |
1091 | list_add(&pi_state->list, &new_owner->pi_state_list); |
1092 | pi_state->owner = new_owner; | |
1d615482 | 1093 | raw_spin_unlock_irq(&new_owner->pi_lock); |
627371d7 | 1094 | |
d209d74d | 1095 | raw_spin_unlock(&pi_state->pi_mutex.wait_lock); |
c87e2837 IM |
1096 | rt_mutex_unlock(&pi_state->pi_mutex); |
1097 | ||
1098 | return 0; | |
1099 | } | |
1100 | ||
1101 | static int unlock_futex_pi(u32 __user *uaddr, u32 uval) | |
1102 | { | |
7cfdaf38 | 1103 | u32 uninitialized_var(oldval); |
c87e2837 IM |
1104 | |
1105 | /* | |
1106 | * There is no waiter, so we unlock the futex. The owner died | |
1107 | * bit has not to be preserved here. We are the owner: | |
1108 | */ | |
37a9d912 ML |
1109 | if (cmpxchg_futex_value_locked(&oldval, uaddr, uval, 0)) |
1110 | return -EFAULT; | |
c87e2837 IM |
1111 | if (oldval != uval) |
1112 | return -EAGAIN; | |
1113 | ||
1114 | return 0; | |
1115 | } | |
1116 | ||
8b8f319f IM |
1117 | /* |
1118 | * Express the locking dependencies for lockdep: | |
1119 | */ | |
1120 | static inline void | |
1121 | double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) | |
1122 | { | |
1123 | if (hb1 <= hb2) { | |
1124 | spin_lock(&hb1->lock); | |
1125 | if (hb1 < hb2) | |
1126 | spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING); | |
1127 | } else { /* hb1 > hb2 */ | |
1128 | spin_lock(&hb2->lock); | |
1129 | spin_lock_nested(&hb1->lock, SINGLE_DEPTH_NESTING); | |
1130 | } | |
1131 | } | |
1132 | ||
5eb3dc62 DH |
1133 | static inline void |
1134 | double_unlock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) | |
1135 | { | |
f061d351 | 1136 | spin_unlock(&hb1->lock); |
88f502fe IM |
1137 | if (hb1 != hb2) |
1138 | spin_unlock(&hb2->lock); | |
5eb3dc62 DH |
1139 | } |
1140 | ||
1da177e4 | 1141 | /* |
b2d0994b | 1142 | * Wake up waiters matching bitset queued on this futex (uaddr). |
1da177e4 | 1143 | */ |
b41277dc DH |
1144 | static int |
1145 | futex_wake(u32 __user *uaddr, unsigned int flags, int nr_wake, u32 bitset) | |
1da177e4 | 1146 | { |
e2970f2f | 1147 | struct futex_hash_bucket *hb; |
1da177e4 | 1148 | struct futex_q *this, *next; |
38d47c1b | 1149 | union futex_key key = FUTEX_KEY_INIT; |
1da177e4 LT |
1150 | int ret; |
1151 | ||
cd689985 TG |
1152 | if (!bitset) |
1153 | return -EINVAL; | |
1154 | ||
9ea71503 | 1155 | ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key, VERIFY_READ); |
1da177e4 LT |
1156 | if (unlikely(ret != 0)) |
1157 | goto out; | |
1158 | ||
e2970f2f | 1159 | hb = hash_futex(&key); |
b0c29f79 DB |
1160 | |
1161 | /* Make sure we really have tasks to wakeup */ | |
1162 | if (!hb_waiters_pending(hb)) | |
1163 | goto out_put_key; | |
1164 | ||
e2970f2f | 1165 | spin_lock(&hb->lock); |
1da177e4 | 1166 | |
0d00c7b2 | 1167 | plist_for_each_entry_safe(this, next, &hb->chain, list) { |
1da177e4 | 1168 | if (match_futex (&this->key, &key)) { |
52400ba9 | 1169 | if (this->pi_state || this->rt_waiter) { |
ed6f7b10 IM |
1170 | ret = -EINVAL; |
1171 | break; | |
1172 | } | |
cd689985 TG |
1173 | |
1174 | /* Check if one of the bits is set in both bitsets */ | |
1175 | if (!(this->bitset & bitset)) | |
1176 | continue; | |
1177 | ||
1da177e4 LT |
1178 | wake_futex(this); |
1179 | if (++ret >= nr_wake) | |
1180 | break; | |
1181 | } | |
1182 | } | |
1183 | ||
e2970f2f | 1184 | spin_unlock(&hb->lock); |
b0c29f79 | 1185 | out_put_key: |
ae791a2d | 1186 | put_futex_key(&key); |
42d35d48 | 1187 | out: |
1da177e4 LT |
1188 | return ret; |
1189 | } | |
1190 | ||
4732efbe JJ |
1191 | /* |
1192 | * Wake up all waiters hashed on the physical page that is mapped | |
1193 | * to this virtual address: | |
1194 | */ | |
e2970f2f | 1195 | static int |
b41277dc | 1196 | futex_wake_op(u32 __user *uaddr1, unsigned int flags, u32 __user *uaddr2, |
e2970f2f | 1197 | int nr_wake, int nr_wake2, int op) |
4732efbe | 1198 | { |
38d47c1b | 1199 | union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT; |
e2970f2f | 1200 | struct futex_hash_bucket *hb1, *hb2; |
4732efbe | 1201 | struct futex_q *this, *next; |
e4dc5b7a | 1202 | int ret, op_ret; |
4732efbe | 1203 | |
e4dc5b7a | 1204 | retry: |
9ea71503 | 1205 | ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1, VERIFY_READ); |
4732efbe JJ |
1206 | if (unlikely(ret != 0)) |
1207 | goto out; | |
9ea71503 | 1208 | ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, VERIFY_WRITE); |
4732efbe | 1209 | if (unlikely(ret != 0)) |
42d35d48 | 1210 | goto out_put_key1; |
4732efbe | 1211 | |
e2970f2f IM |
1212 | hb1 = hash_futex(&key1); |
1213 | hb2 = hash_futex(&key2); | |
4732efbe | 1214 | |
e4dc5b7a | 1215 | retry_private: |
eaaea803 | 1216 | double_lock_hb(hb1, hb2); |
e2970f2f | 1217 | op_ret = futex_atomic_op_inuser(op, uaddr2); |
4732efbe | 1218 | if (unlikely(op_ret < 0)) { |
4732efbe | 1219 | |
5eb3dc62 | 1220 | double_unlock_hb(hb1, hb2); |
4732efbe | 1221 | |
7ee1dd3f | 1222 | #ifndef CONFIG_MMU |
e2970f2f IM |
1223 | /* |
1224 | * we don't get EFAULT from MMU faults if we don't have an MMU, | |
1225 | * but we might get them from range checking | |
1226 | */ | |
7ee1dd3f | 1227 | ret = op_ret; |
42d35d48 | 1228 | goto out_put_keys; |
7ee1dd3f DH |
1229 | #endif |
1230 | ||
796f8d9b DG |
1231 | if (unlikely(op_ret != -EFAULT)) { |
1232 | ret = op_ret; | |
42d35d48 | 1233 | goto out_put_keys; |
796f8d9b DG |
1234 | } |
1235 | ||
d0725992 | 1236 | ret = fault_in_user_writeable(uaddr2); |
4732efbe | 1237 | if (ret) |
de87fcc1 | 1238 | goto out_put_keys; |
4732efbe | 1239 | |
b41277dc | 1240 | if (!(flags & FLAGS_SHARED)) |
e4dc5b7a DH |
1241 | goto retry_private; |
1242 | ||
ae791a2d TG |
1243 | put_futex_key(&key2); |
1244 | put_futex_key(&key1); | |
e4dc5b7a | 1245 | goto retry; |
4732efbe JJ |
1246 | } |
1247 | ||
0d00c7b2 | 1248 | plist_for_each_entry_safe(this, next, &hb1->chain, list) { |
4732efbe | 1249 | if (match_futex (&this->key, &key1)) { |
aa10990e DH |
1250 | if (this->pi_state || this->rt_waiter) { |
1251 | ret = -EINVAL; | |
1252 | goto out_unlock; | |
1253 | } | |
4732efbe JJ |
1254 | wake_futex(this); |
1255 | if (++ret >= nr_wake) | |
1256 | break; | |
1257 | } | |
1258 | } | |
1259 | ||
1260 | if (op_ret > 0) { | |
4732efbe | 1261 | op_ret = 0; |
0d00c7b2 | 1262 | plist_for_each_entry_safe(this, next, &hb2->chain, list) { |
4732efbe | 1263 | if (match_futex (&this->key, &key2)) { |
aa10990e DH |
1264 | if (this->pi_state || this->rt_waiter) { |
1265 | ret = -EINVAL; | |
1266 | goto out_unlock; | |
1267 | } | |
4732efbe JJ |
1268 | wake_futex(this); |
1269 | if (++op_ret >= nr_wake2) | |
1270 | break; | |
1271 | } | |
1272 | } | |
1273 | ret += op_ret; | |
1274 | } | |
1275 | ||
aa10990e | 1276 | out_unlock: |
5eb3dc62 | 1277 | double_unlock_hb(hb1, hb2); |
42d35d48 | 1278 | out_put_keys: |
ae791a2d | 1279 | put_futex_key(&key2); |
42d35d48 | 1280 | out_put_key1: |
ae791a2d | 1281 | put_futex_key(&key1); |
42d35d48 | 1282 | out: |
4732efbe JJ |
1283 | return ret; |
1284 | } | |
1285 | ||
9121e478 DH |
1286 | /** |
1287 | * requeue_futex() - Requeue a futex_q from one hb to another | |
1288 | * @q: the futex_q to requeue | |
1289 | * @hb1: the source hash_bucket | |
1290 | * @hb2: the target hash_bucket | |
1291 | * @key2: the new key for the requeued futex_q | |
1292 | */ | |
1293 | static inline | |
1294 | void requeue_futex(struct futex_q *q, struct futex_hash_bucket *hb1, | |
1295 | struct futex_hash_bucket *hb2, union futex_key *key2) | |
1296 | { | |
1297 | ||
1298 | /* | |
1299 | * If key1 and key2 hash to the same bucket, no need to | |
1300 | * requeue. | |
1301 | */ | |
1302 | if (likely(&hb1->chain != &hb2->chain)) { | |
1303 | plist_del(&q->list, &hb1->chain); | |
11d4616b | 1304 | hb_waiters_dec(hb1); |
9121e478 | 1305 | plist_add(&q->list, &hb2->chain); |
11d4616b | 1306 | hb_waiters_inc(hb2); |
9121e478 | 1307 | q->lock_ptr = &hb2->lock; |
9121e478 DH |
1308 | } |
1309 | get_futex_key_refs(key2); | |
1310 | q->key = *key2; | |
1311 | } | |
1312 | ||
52400ba9 DH |
1313 | /** |
1314 | * requeue_pi_wake_futex() - Wake a task that acquired the lock during requeue | |
d96ee56c DH |
1315 | * @q: the futex_q |
1316 | * @key: the key of the requeue target futex | |
1317 | * @hb: the hash_bucket of the requeue target futex | |
52400ba9 DH |
1318 | * |
1319 | * During futex_requeue, with requeue_pi=1, it is possible to acquire the | |
1320 | * target futex if it is uncontended or via a lock steal. Set the futex_q key | |
1321 | * to the requeue target futex so the waiter can detect the wakeup on the right | |
1322 | * futex, but remove it from the hb and NULL the rt_waiter so it can detect | |
beda2c7e DH |
1323 | * atomic lock acquisition. Set the q->lock_ptr to the requeue target hb->lock |
1324 | * to protect access to the pi_state to fixup the owner later. Must be called | |
1325 | * with both q->lock_ptr and hb->lock held. | |
52400ba9 DH |
1326 | */ |
1327 | static inline | |
beda2c7e DH |
1328 | void requeue_pi_wake_futex(struct futex_q *q, union futex_key *key, |
1329 | struct futex_hash_bucket *hb) | |
52400ba9 | 1330 | { |
52400ba9 DH |
1331 | get_futex_key_refs(key); |
1332 | q->key = *key; | |
1333 | ||
2e12978a | 1334 | __unqueue_futex(q); |
52400ba9 DH |
1335 | |
1336 | WARN_ON(!q->rt_waiter); | |
1337 | q->rt_waiter = NULL; | |
1338 | ||
beda2c7e | 1339 | q->lock_ptr = &hb->lock; |
beda2c7e | 1340 | |
f1a11e05 | 1341 | wake_up_state(q->task, TASK_NORMAL); |
52400ba9 DH |
1342 | } |
1343 | ||
1344 | /** | |
1345 | * futex_proxy_trylock_atomic() - Attempt an atomic lock for the top waiter | |
bab5bc9e DH |
1346 | * @pifutex: the user address of the to futex |
1347 | * @hb1: the from futex hash bucket, must be locked by the caller | |
1348 | * @hb2: the to futex hash bucket, must be locked by the caller | |
1349 | * @key1: the from futex key | |
1350 | * @key2: the to futex key | |
1351 | * @ps: address to store the pi_state pointer | |
1352 | * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0) | |
52400ba9 DH |
1353 | * |
1354 | * Try and get the lock on behalf of the top waiter if we can do it atomically. | |
bab5bc9e DH |
1355 | * Wake the top waiter if we succeed. If the caller specified set_waiters, |
1356 | * then direct futex_lock_pi_atomic() to force setting the FUTEX_WAITERS bit. | |
1357 | * hb1 and hb2 must be held by the caller. | |
52400ba9 | 1358 | * |
6c23cbbd RD |
1359 | * Return: |
1360 | * 0 - failed to acquire the lock atomically; | |
866293ee | 1361 | * >0 - acquired the lock, return value is vpid of the top_waiter |
52400ba9 DH |
1362 | * <0 - error |
1363 | */ | |
1364 | static int futex_proxy_trylock_atomic(u32 __user *pifutex, | |
1365 | struct futex_hash_bucket *hb1, | |
1366 | struct futex_hash_bucket *hb2, | |
1367 | union futex_key *key1, union futex_key *key2, | |
bab5bc9e | 1368 | struct futex_pi_state **ps, int set_waiters) |
52400ba9 | 1369 | { |
bab5bc9e | 1370 | struct futex_q *top_waiter = NULL; |
52400ba9 | 1371 | u32 curval; |
866293ee | 1372 | int ret, vpid; |
52400ba9 DH |
1373 | |
1374 | if (get_futex_value_locked(&curval, pifutex)) | |
1375 | return -EFAULT; | |
1376 | ||
bab5bc9e DH |
1377 | /* |
1378 | * Find the top_waiter and determine if there are additional waiters. | |
1379 | * If the caller intends to requeue more than 1 waiter to pifutex, | |
1380 | * force futex_lock_pi_atomic() to set the FUTEX_WAITERS bit now, | |
1381 | * as we have means to handle the possible fault. If not, don't set | |
1382 | * the bit unecessarily as it will force the subsequent unlock to enter | |
1383 | * the kernel. | |
1384 | */ | |
52400ba9 DH |
1385 | top_waiter = futex_top_waiter(hb1, key1); |
1386 | ||
1387 | /* There are no waiters, nothing for us to do. */ | |
1388 | if (!top_waiter) | |
1389 | return 0; | |
1390 | ||
84bc4af5 DH |
1391 | /* Ensure we requeue to the expected futex. */ |
1392 | if (!match_futex(top_waiter->requeue_pi_key, key2)) | |
1393 | return -EINVAL; | |
1394 | ||
52400ba9 | 1395 | /* |
bab5bc9e DH |
1396 | * Try to take the lock for top_waiter. Set the FUTEX_WAITERS bit in |
1397 | * the contended case or if set_waiters is 1. The pi_state is returned | |
1398 | * in ps in contended cases. | |
52400ba9 | 1399 | */ |
866293ee | 1400 | vpid = task_pid_vnr(top_waiter->task); |
bab5bc9e DH |
1401 | ret = futex_lock_pi_atomic(pifutex, hb2, key2, ps, top_waiter->task, |
1402 | set_waiters); | |
866293ee | 1403 | if (ret == 1) { |
beda2c7e | 1404 | requeue_pi_wake_futex(top_waiter, key2, hb2); |
866293ee TG |
1405 | return vpid; |
1406 | } | |
52400ba9 DH |
1407 | return ret; |
1408 | } | |
1409 | ||
1410 | /** | |
1411 | * futex_requeue() - Requeue waiters from uaddr1 to uaddr2 | |
fb62db2b | 1412 | * @uaddr1: source futex user address |
b41277dc | 1413 | * @flags: futex flags (FLAGS_SHARED, etc.) |
fb62db2b RD |
1414 | * @uaddr2: target futex user address |
1415 | * @nr_wake: number of waiters to wake (must be 1 for requeue_pi) | |
1416 | * @nr_requeue: number of waiters to requeue (0-INT_MAX) | |
1417 | * @cmpval: @uaddr1 expected value (or %NULL) | |
1418 | * @requeue_pi: if we are attempting to requeue from a non-pi futex to a | |
b41277dc | 1419 | * pi futex (pi to pi requeue is not supported) |
52400ba9 DH |
1420 | * |
1421 | * Requeue waiters on uaddr1 to uaddr2. In the requeue_pi case, try to acquire | |
1422 | * uaddr2 atomically on behalf of the top waiter. | |
1423 | * | |
6c23cbbd RD |
1424 | * Return: |
1425 | * >=0 - on success, the number of tasks requeued or woken; | |
52400ba9 | 1426 | * <0 - on error |
1da177e4 | 1427 | */ |
b41277dc DH |
1428 | static int futex_requeue(u32 __user *uaddr1, unsigned int flags, |
1429 | u32 __user *uaddr2, int nr_wake, int nr_requeue, | |
1430 | u32 *cmpval, int requeue_pi) | |
1da177e4 | 1431 | { |
38d47c1b | 1432 | union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT; |
52400ba9 DH |
1433 | int drop_count = 0, task_count = 0, ret; |
1434 | struct futex_pi_state *pi_state = NULL; | |
e2970f2f | 1435 | struct futex_hash_bucket *hb1, *hb2; |
1da177e4 | 1436 | struct futex_q *this, *next; |
52400ba9 DH |
1437 | |
1438 | if (requeue_pi) { | |
1439 | /* | |
1440 | * requeue_pi requires a pi_state, try to allocate it now | |
1441 | * without any locks in case it fails. | |
1442 | */ | |
1443 | if (refill_pi_state_cache()) | |
1444 | return -ENOMEM; | |
1445 | /* | |
1446 | * requeue_pi must wake as many tasks as it can, up to nr_wake | |
1447 | * + nr_requeue, since it acquires the rt_mutex prior to | |
1448 | * returning to userspace, so as to not leave the rt_mutex with | |
1449 | * waiters and no owner. However, second and third wake-ups | |
1450 | * cannot be predicted as they involve race conditions with the | |
1451 | * first wake and a fault while looking up the pi_state. Both | |
1452 | * pthread_cond_signal() and pthread_cond_broadcast() should | |
1453 | * use nr_wake=1. | |
1454 | */ | |
1455 | if (nr_wake != 1) | |
1456 | return -EINVAL; | |
1457 | } | |
1da177e4 | 1458 | |
42d35d48 | 1459 | retry: |
52400ba9 DH |
1460 | if (pi_state != NULL) { |
1461 | /* | |
1462 | * We will have to lookup the pi_state again, so free this one | |
1463 | * to keep the accounting correct. | |
1464 | */ | |
1465 | free_pi_state(pi_state); | |
1466 | pi_state = NULL; | |
1467 | } | |
1468 | ||
9ea71503 | 1469 | ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1, VERIFY_READ); |
1da177e4 LT |
1470 | if (unlikely(ret != 0)) |
1471 | goto out; | |
9ea71503 SB |
1472 | ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, |
1473 | requeue_pi ? VERIFY_WRITE : VERIFY_READ); | |
1da177e4 | 1474 | if (unlikely(ret != 0)) |
42d35d48 | 1475 | goto out_put_key1; |
1da177e4 | 1476 | |
e2970f2f IM |
1477 | hb1 = hash_futex(&key1); |
1478 | hb2 = hash_futex(&key2); | |
1da177e4 | 1479 | |
e4dc5b7a | 1480 | retry_private: |
69cd9eba | 1481 | hb_waiters_inc(hb2); |
8b8f319f | 1482 | double_lock_hb(hb1, hb2); |
1da177e4 | 1483 | |
e2970f2f IM |
1484 | if (likely(cmpval != NULL)) { |
1485 | u32 curval; | |
1da177e4 | 1486 | |
e2970f2f | 1487 | ret = get_futex_value_locked(&curval, uaddr1); |
1da177e4 LT |
1488 | |
1489 | if (unlikely(ret)) { | |
5eb3dc62 | 1490 | double_unlock_hb(hb1, hb2); |
69cd9eba | 1491 | hb_waiters_dec(hb2); |
1da177e4 | 1492 | |
e2970f2f | 1493 | ret = get_user(curval, uaddr1); |
e4dc5b7a DH |
1494 | if (ret) |
1495 | goto out_put_keys; | |
1da177e4 | 1496 | |
b41277dc | 1497 | if (!(flags & FLAGS_SHARED)) |
e4dc5b7a | 1498 | goto retry_private; |
1da177e4 | 1499 | |
ae791a2d TG |
1500 | put_futex_key(&key2); |
1501 | put_futex_key(&key1); | |
e4dc5b7a | 1502 | goto retry; |
1da177e4 | 1503 | } |
e2970f2f | 1504 | if (curval != *cmpval) { |
1da177e4 LT |
1505 | ret = -EAGAIN; |
1506 | goto out_unlock; | |
1507 | } | |
1508 | } | |
1509 | ||
52400ba9 | 1510 | if (requeue_pi && (task_count - nr_wake < nr_requeue)) { |
bab5bc9e DH |
1511 | /* |
1512 | * Attempt to acquire uaddr2 and wake the top waiter. If we | |
1513 | * intend to requeue waiters, force setting the FUTEX_WAITERS | |
1514 | * bit. We force this here where we are able to easily handle | |
1515 | * faults rather in the requeue loop below. | |
1516 | */ | |
52400ba9 | 1517 | ret = futex_proxy_trylock_atomic(uaddr2, hb1, hb2, &key1, |
bab5bc9e | 1518 | &key2, &pi_state, nr_requeue); |
52400ba9 DH |
1519 | |
1520 | /* | |
1521 | * At this point the top_waiter has either taken uaddr2 or is | |
1522 | * waiting on it. If the former, then the pi_state will not | |
1523 | * exist yet, look it up one more time to ensure we have a | |
866293ee TG |
1524 | * reference to it. If the lock was taken, ret contains the |
1525 | * vpid of the top waiter task. | |
52400ba9 | 1526 | */ |
866293ee | 1527 | if (ret > 0) { |
52400ba9 | 1528 | WARN_ON(pi_state); |
89061d3d | 1529 | drop_count++; |
52400ba9 | 1530 | task_count++; |
866293ee TG |
1531 | /* |
1532 | * If we acquired the lock, then the user | |
1533 | * space value of uaddr2 should be vpid. It | |
1534 | * cannot be changed by the top waiter as it | |
1535 | * is blocked on hb2 lock if it tries to do | |
1536 | * so. If something fiddled with it behind our | |
1537 | * back the pi state lookup might unearth | |
1538 | * it. So we rather use the known value than | |
1539 | * rereading and handing potential crap to | |
1540 | * lookup_pi_state. | |
1541 | */ | |
1542 | ret = lookup_pi_state(ret, hb2, &key2, &pi_state, NULL); | |
52400ba9 DH |
1543 | } |
1544 | ||
1545 | switch (ret) { | |
1546 | case 0: | |
1547 | break; | |
1548 | case -EFAULT: | |
1549 | double_unlock_hb(hb1, hb2); | |
69cd9eba | 1550 | hb_waiters_dec(hb2); |
ae791a2d TG |
1551 | put_futex_key(&key2); |
1552 | put_futex_key(&key1); | |
d0725992 | 1553 | ret = fault_in_user_writeable(uaddr2); |
52400ba9 DH |
1554 | if (!ret) |
1555 | goto retry; | |
1556 | goto out; | |
1557 | case -EAGAIN: | |
1558 | /* The owner was exiting, try again. */ | |
1559 | double_unlock_hb(hb1, hb2); | |
69cd9eba | 1560 | hb_waiters_dec(hb2); |
ae791a2d TG |
1561 | put_futex_key(&key2); |
1562 | put_futex_key(&key1); | |
52400ba9 DH |
1563 | cond_resched(); |
1564 | goto retry; | |
1565 | default: | |
1566 | goto out_unlock; | |
1567 | } | |
1568 | } | |
1569 | ||
0d00c7b2 | 1570 | plist_for_each_entry_safe(this, next, &hb1->chain, list) { |
52400ba9 DH |
1571 | if (task_count - nr_wake >= nr_requeue) |
1572 | break; | |
1573 | ||
1574 | if (!match_futex(&this->key, &key1)) | |
1da177e4 | 1575 | continue; |
52400ba9 | 1576 | |
392741e0 DH |
1577 | /* |
1578 | * FUTEX_WAIT_REQEUE_PI and FUTEX_CMP_REQUEUE_PI should always | |
1579 | * be paired with each other and no other futex ops. | |
aa10990e DH |
1580 | * |
1581 | * We should never be requeueing a futex_q with a pi_state, | |
1582 | * which is awaiting a futex_unlock_pi(). | |
392741e0 DH |
1583 | */ |
1584 | if ((requeue_pi && !this->rt_waiter) || | |
aa10990e DH |
1585 | (!requeue_pi && this->rt_waiter) || |
1586 | this->pi_state) { | |
392741e0 DH |
1587 | ret = -EINVAL; |
1588 | break; | |
1589 | } | |
52400ba9 DH |
1590 | |
1591 | /* | |
1592 | * Wake nr_wake waiters. For requeue_pi, if we acquired the | |
1593 | * lock, we already woke the top_waiter. If not, it will be | |
1594 | * woken by futex_unlock_pi(). | |
1595 | */ | |
1596 | if (++task_count <= nr_wake && !requeue_pi) { | |
1da177e4 | 1597 | wake_futex(this); |
52400ba9 DH |
1598 | continue; |
1599 | } | |
1da177e4 | 1600 | |
84bc4af5 DH |
1601 | /* Ensure we requeue to the expected futex for requeue_pi. */ |
1602 | if (requeue_pi && !match_futex(this->requeue_pi_key, &key2)) { | |
1603 | ret = -EINVAL; | |
1604 | break; | |
1605 | } | |
1606 | ||
52400ba9 DH |
1607 | /* |
1608 | * Requeue nr_requeue waiters and possibly one more in the case | |
1609 | * of requeue_pi if we couldn't acquire the lock atomically. | |
1610 | */ | |
1611 | if (requeue_pi) { | |
1612 | /* Prepare the waiter to take the rt_mutex. */ | |
1613 | atomic_inc(&pi_state->refcount); | |
1614 | this->pi_state = pi_state; | |
1615 | ret = rt_mutex_start_proxy_lock(&pi_state->pi_mutex, | |
1616 | this->rt_waiter, | |
1617 | this->task, 1); | |
1618 | if (ret == 1) { | |
1619 | /* We got the lock. */ | |
beda2c7e | 1620 | requeue_pi_wake_futex(this, &key2, hb2); |
89061d3d | 1621 | drop_count++; |
52400ba9 DH |
1622 | continue; |
1623 | } else if (ret) { | |
1624 | /* -EDEADLK */ | |
1625 | this->pi_state = NULL; | |
1626 | free_pi_state(pi_state); | |
1627 | goto out_unlock; | |
1628 | } | |
1da177e4 | 1629 | } |
52400ba9 DH |
1630 | requeue_futex(this, hb1, hb2, &key2); |
1631 | drop_count++; | |
1da177e4 LT |
1632 | } |
1633 | ||
1634 | out_unlock: | |
5eb3dc62 | 1635 | double_unlock_hb(hb1, hb2); |
69cd9eba | 1636 | hb_waiters_dec(hb2); |
1da177e4 | 1637 | |
cd84a42f DH |
1638 | /* |
1639 | * drop_futex_key_refs() must be called outside the spinlocks. During | |
1640 | * the requeue we moved futex_q's from the hash bucket at key1 to the | |
1641 | * one at key2 and updated their key pointer. We no longer need to | |
1642 | * hold the references to key1. | |
1643 | */ | |
1da177e4 | 1644 | while (--drop_count >= 0) |
9adef58b | 1645 | drop_futex_key_refs(&key1); |
1da177e4 | 1646 | |
42d35d48 | 1647 | out_put_keys: |
ae791a2d | 1648 | put_futex_key(&key2); |
42d35d48 | 1649 | out_put_key1: |
ae791a2d | 1650 | put_futex_key(&key1); |
42d35d48 | 1651 | out: |
52400ba9 DH |
1652 | if (pi_state != NULL) |
1653 | free_pi_state(pi_state); | |
1654 | return ret ? ret : task_count; | |
1da177e4 LT |
1655 | } |
1656 | ||
1657 | /* The key must be already stored in q->key. */ | |
82af7aca | 1658 | static inline struct futex_hash_bucket *queue_lock(struct futex_q *q) |
15e408cd | 1659 | __acquires(&hb->lock) |
1da177e4 | 1660 | { |
e2970f2f | 1661 | struct futex_hash_bucket *hb; |
1da177e4 | 1662 | |
e2970f2f | 1663 | hb = hash_futex(&q->key); |
11d4616b LT |
1664 | |
1665 | /* | |
1666 | * Increment the counter before taking the lock so that | |
1667 | * a potential waker won't miss a to-be-slept task that is | |
1668 | * waiting for the spinlock. This is safe as all queue_lock() | |
1669 | * users end up calling queue_me(). Similarly, for housekeeping, | |
1670 | * decrement the counter at queue_unlock() when some error has | |
1671 | * occurred and we don't end up adding the task to the list. | |
1672 | */ | |
1673 | hb_waiters_inc(hb); | |
1674 | ||
e2970f2f | 1675 | q->lock_ptr = &hb->lock; |
1da177e4 | 1676 | |
b0c29f79 | 1677 | spin_lock(&hb->lock); /* implies MB (A) */ |
e2970f2f | 1678 | return hb; |
1da177e4 LT |
1679 | } |
1680 | ||
d40d65c8 | 1681 | static inline void |
0d00c7b2 | 1682 | queue_unlock(struct futex_hash_bucket *hb) |
15e408cd | 1683 | __releases(&hb->lock) |
d40d65c8 DH |
1684 | { |
1685 | spin_unlock(&hb->lock); | |
11d4616b | 1686 | hb_waiters_dec(hb); |
d40d65c8 DH |
1687 | } |
1688 | ||
1689 | /** | |
1690 | * queue_me() - Enqueue the futex_q on the futex_hash_bucket | |
1691 | * @q: The futex_q to enqueue | |
1692 | * @hb: The destination hash bucket | |
1693 | * | |
1694 | * The hb->lock must be held by the caller, and is released here. A call to | |
1695 | * queue_me() is typically paired with exactly one call to unqueue_me(). The | |
1696 | * exceptions involve the PI related operations, which may use unqueue_me_pi() | |
1697 | * or nothing if the unqueue is done as part of the wake process and the unqueue | |
1698 | * state is implicit in the state of woken task (see futex_wait_requeue_pi() for | |
1699 | * an example). | |
1700 | */ | |
82af7aca | 1701 | static inline void queue_me(struct futex_q *q, struct futex_hash_bucket *hb) |
15e408cd | 1702 | __releases(&hb->lock) |
1da177e4 | 1703 | { |
ec92d082 PP |
1704 | int prio; |
1705 | ||
1706 | /* | |
1707 | * The priority used to register this element is | |
1708 | * - either the real thread-priority for the real-time threads | |
1709 | * (i.e. threads with a priority lower than MAX_RT_PRIO) | |
1710 | * - or MAX_RT_PRIO for non-RT threads. | |
1711 | * Thus, all RT-threads are woken first in priority order, and | |
1712 | * the others are woken last, in FIFO order. | |
1713 | */ | |
1714 | prio = min(current->normal_prio, MAX_RT_PRIO); | |
1715 | ||
1716 | plist_node_init(&q->list, prio); | |
ec92d082 | 1717 | plist_add(&q->list, &hb->chain); |
c87e2837 | 1718 | q->task = current; |
e2970f2f | 1719 | spin_unlock(&hb->lock); |
1da177e4 LT |
1720 | } |
1721 | ||
d40d65c8 DH |
1722 | /** |
1723 | * unqueue_me() - Remove the futex_q from its futex_hash_bucket | |
1724 | * @q: The futex_q to unqueue | |
1725 | * | |
1726 | * The q->lock_ptr must not be held by the caller. A call to unqueue_me() must | |
1727 | * be paired with exactly one earlier call to queue_me(). | |
1728 | * | |
6c23cbbd RD |
1729 | * Return: |
1730 | * 1 - if the futex_q was still queued (and we removed unqueued it); | |
d40d65c8 | 1731 | * 0 - if the futex_q was already removed by the waking thread |
1da177e4 | 1732 | */ |
1da177e4 LT |
1733 | static int unqueue_me(struct futex_q *q) |
1734 | { | |
1da177e4 | 1735 | spinlock_t *lock_ptr; |
e2970f2f | 1736 | int ret = 0; |
1da177e4 LT |
1737 | |
1738 | /* In the common case we don't take the spinlock, which is nice. */ | |
42d35d48 | 1739 | retry: |
1da177e4 | 1740 | lock_ptr = q->lock_ptr; |
e91467ec | 1741 | barrier(); |
c80544dc | 1742 | if (lock_ptr != NULL) { |
1da177e4 LT |
1743 | spin_lock(lock_ptr); |
1744 | /* | |
1745 | * q->lock_ptr can change between reading it and | |
1746 | * spin_lock(), causing us to take the wrong lock. This | |
1747 | * corrects the race condition. | |
1748 | * | |
1749 | * Reasoning goes like this: if we have the wrong lock, | |
1750 | * q->lock_ptr must have changed (maybe several times) | |
1751 | * between reading it and the spin_lock(). It can | |
1752 | * change again after the spin_lock() but only if it was | |
1753 | * already changed before the spin_lock(). It cannot, | |
1754 | * however, change back to the original value. Therefore | |
1755 | * we can detect whether we acquired the correct lock. | |
1756 | */ | |
1757 | if (unlikely(lock_ptr != q->lock_ptr)) { | |
1758 | spin_unlock(lock_ptr); | |
1759 | goto retry; | |
1760 | } | |
2e12978a | 1761 | __unqueue_futex(q); |
c87e2837 IM |
1762 | |
1763 | BUG_ON(q->pi_state); | |
1764 | ||
1da177e4 LT |
1765 | spin_unlock(lock_ptr); |
1766 | ret = 1; | |
1767 | } | |
1768 | ||
9adef58b | 1769 | drop_futex_key_refs(&q->key); |
1da177e4 LT |
1770 | return ret; |
1771 | } | |
1772 | ||
c87e2837 IM |
1773 | /* |
1774 | * PI futexes can not be requeued and must remove themself from the | |
d0aa7a70 PP |
1775 | * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry |
1776 | * and dropped here. | |
c87e2837 | 1777 | */ |
d0aa7a70 | 1778 | static void unqueue_me_pi(struct futex_q *q) |
15e408cd | 1779 | __releases(q->lock_ptr) |
c87e2837 | 1780 | { |
2e12978a | 1781 | __unqueue_futex(q); |
c87e2837 IM |
1782 | |
1783 | BUG_ON(!q->pi_state); | |
1784 | free_pi_state(q->pi_state); | |
1785 | q->pi_state = NULL; | |
1786 | ||
d0aa7a70 | 1787 | spin_unlock(q->lock_ptr); |
c87e2837 IM |
1788 | } |
1789 | ||
d0aa7a70 | 1790 | /* |
cdf71a10 | 1791 | * Fixup the pi_state owner with the new owner. |
d0aa7a70 | 1792 | * |
778e9a9c AK |
1793 | * Must be called with hash bucket lock held and mm->sem held for non |
1794 | * private futexes. | |
d0aa7a70 | 1795 | */ |
778e9a9c | 1796 | static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q, |
ae791a2d | 1797 | struct task_struct *newowner) |
d0aa7a70 | 1798 | { |
cdf71a10 | 1799 | u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS; |
d0aa7a70 | 1800 | struct futex_pi_state *pi_state = q->pi_state; |
1b7558e4 | 1801 | struct task_struct *oldowner = pi_state->owner; |
7cfdaf38 | 1802 | u32 uval, uninitialized_var(curval), newval; |
e4dc5b7a | 1803 | int ret; |
d0aa7a70 PP |
1804 | |
1805 | /* Owner died? */ | |
1b7558e4 TG |
1806 | if (!pi_state->owner) |
1807 | newtid |= FUTEX_OWNER_DIED; | |
1808 | ||
1809 | /* | |
1810 | * We are here either because we stole the rtmutex from the | |
8161239a LJ |
1811 | * previous highest priority waiter or we are the highest priority |
1812 | * waiter but failed to get the rtmutex the first time. | |
1813 | * We have to replace the newowner TID in the user space variable. | |
1814 | * This must be atomic as we have to preserve the owner died bit here. | |
1b7558e4 | 1815 | * |
b2d0994b DH |
1816 | * Note: We write the user space value _before_ changing the pi_state |
1817 | * because we can fault here. Imagine swapped out pages or a fork | |
1818 | * that marked all the anonymous memory readonly for cow. | |
1b7558e4 TG |
1819 | * |
1820 | * Modifying pi_state _before_ the user space value would | |
1821 | * leave the pi_state in an inconsistent state when we fault | |
1822 | * here, because we need to drop the hash bucket lock to | |
1823 | * handle the fault. This might be observed in the PID check | |
1824 | * in lookup_pi_state. | |
1825 | */ | |
1826 | retry: | |
1827 | if (get_futex_value_locked(&uval, uaddr)) | |
1828 | goto handle_fault; | |
1829 | ||
1830 | while (1) { | |
1831 | newval = (uval & FUTEX_OWNER_DIED) | newtid; | |
1832 | ||
37a9d912 | 1833 | if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval)) |
1b7558e4 TG |
1834 | goto handle_fault; |
1835 | if (curval == uval) | |
1836 | break; | |
1837 | uval = curval; | |
1838 | } | |
1839 | ||
1840 | /* | |
1841 | * We fixed up user space. Now we need to fix the pi_state | |
1842 | * itself. | |
1843 | */ | |
d0aa7a70 | 1844 | if (pi_state->owner != NULL) { |
1d615482 | 1845 | raw_spin_lock_irq(&pi_state->owner->pi_lock); |
d0aa7a70 PP |
1846 | WARN_ON(list_empty(&pi_state->list)); |
1847 | list_del_init(&pi_state->list); | |
1d615482 | 1848 | raw_spin_unlock_irq(&pi_state->owner->pi_lock); |
1b7558e4 | 1849 | } |
d0aa7a70 | 1850 | |
cdf71a10 | 1851 | pi_state->owner = newowner; |
d0aa7a70 | 1852 | |
1d615482 | 1853 | raw_spin_lock_irq(&newowner->pi_lock); |
d0aa7a70 | 1854 | WARN_ON(!list_empty(&pi_state->list)); |
cdf71a10 | 1855 | list_add(&pi_state->list, &newowner->pi_state_list); |
1d615482 | 1856 | raw_spin_unlock_irq(&newowner->pi_lock); |
1b7558e4 | 1857 | return 0; |
d0aa7a70 | 1858 | |
d0aa7a70 | 1859 | /* |
1b7558e4 | 1860 | * To handle the page fault we need to drop the hash bucket |
8161239a LJ |
1861 | * lock here. That gives the other task (either the highest priority |
1862 | * waiter itself or the task which stole the rtmutex) the | |
1b7558e4 TG |
1863 | * chance to try the fixup of the pi_state. So once we are |
1864 | * back from handling the fault we need to check the pi_state | |
1865 | * after reacquiring the hash bucket lock and before trying to | |
1866 | * do another fixup. When the fixup has been done already we | |
1867 | * simply return. | |
d0aa7a70 | 1868 | */ |
1b7558e4 TG |
1869 | handle_fault: |
1870 | spin_unlock(q->lock_ptr); | |
778e9a9c | 1871 | |
d0725992 | 1872 | ret = fault_in_user_writeable(uaddr); |
778e9a9c | 1873 | |
1b7558e4 | 1874 | spin_lock(q->lock_ptr); |
778e9a9c | 1875 | |
1b7558e4 TG |
1876 | /* |
1877 | * Check if someone else fixed it for us: | |
1878 | */ | |
1879 | if (pi_state->owner != oldowner) | |
1880 | return 0; | |
1881 | ||
1882 | if (ret) | |
1883 | return ret; | |
1884 | ||
1885 | goto retry; | |
d0aa7a70 PP |
1886 | } |
1887 | ||
72c1bbf3 | 1888 | static long futex_wait_restart(struct restart_block *restart); |
36cf3b5c | 1889 | |
dd973998 DH |
1890 | /** |
1891 | * fixup_owner() - Post lock pi_state and corner case management | |
1892 | * @uaddr: user address of the futex | |
dd973998 DH |
1893 | * @q: futex_q (contains pi_state and access to the rt_mutex) |
1894 | * @locked: if the attempt to take the rt_mutex succeeded (1) or not (0) | |
1895 | * | |
1896 | * After attempting to lock an rt_mutex, this function is called to cleanup | |
1897 | * the pi_state owner as well as handle race conditions that may allow us to | |
1898 | * acquire the lock. Must be called with the hb lock held. | |
1899 | * | |
6c23cbbd RD |
1900 | * Return: |
1901 | * 1 - success, lock taken; | |
1902 | * 0 - success, lock not taken; | |
dd973998 DH |
1903 | * <0 - on error (-EFAULT) |
1904 | */ | |
ae791a2d | 1905 | static int fixup_owner(u32 __user *uaddr, struct futex_q *q, int locked) |
dd973998 DH |
1906 | { |
1907 | struct task_struct *owner; | |
1908 | int ret = 0; | |
1909 | ||
1910 | if (locked) { | |
1911 | /* | |
1912 | * Got the lock. We might not be the anticipated owner if we | |
1913 | * did a lock-steal - fix up the PI-state in that case: | |
1914 | */ | |
1915 | if (q->pi_state->owner != current) | |
ae791a2d | 1916 | ret = fixup_pi_state_owner(uaddr, q, current); |
dd973998 DH |
1917 | goto out; |
1918 | } | |
1919 | ||
1920 | /* | |
1921 | * Catch the rare case, where the lock was released when we were on the | |
1922 | * way back before we locked the hash bucket. | |
1923 | */ | |
1924 | if (q->pi_state->owner == current) { | |
1925 | /* | |
1926 | * Try to get the rt_mutex now. This might fail as some other | |
1927 | * task acquired the rt_mutex after we removed ourself from the | |
1928 | * rt_mutex waiters list. | |
1929 | */ | |
1930 | if (rt_mutex_trylock(&q->pi_state->pi_mutex)) { | |
1931 | locked = 1; | |
1932 | goto out; | |
1933 | } | |
1934 | ||
1935 | /* | |
1936 | * pi_state is incorrect, some other task did a lock steal and | |
1937 | * we returned due to timeout or signal without taking the | |
8161239a | 1938 | * rt_mutex. Too late. |
dd973998 | 1939 | */ |
8161239a | 1940 | raw_spin_lock(&q->pi_state->pi_mutex.wait_lock); |
dd973998 | 1941 | owner = rt_mutex_owner(&q->pi_state->pi_mutex); |
8161239a LJ |
1942 | if (!owner) |
1943 | owner = rt_mutex_next_owner(&q->pi_state->pi_mutex); | |
1944 | raw_spin_unlock(&q->pi_state->pi_mutex.wait_lock); | |
ae791a2d | 1945 | ret = fixup_pi_state_owner(uaddr, q, owner); |
dd973998 DH |
1946 | goto out; |
1947 | } | |
1948 | ||
1949 | /* | |
1950 | * Paranoia check. If we did not take the lock, then we should not be | |
8161239a | 1951 | * the owner of the rt_mutex. |
dd973998 DH |
1952 | */ |
1953 | if (rt_mutex_owner(&q->pi_state->pi_mutex) == current) | |
1954 | printk(KERN_ERR "fixup_owner: ret = %d pi-mutex: %p " | |
1955 | "pi-state %p\n", ret, | |
1956 | q->pi_state->pi_mutex.owner, | |
1957 | q->pi_state->owner); | |
1958 | ||
1959 | out: | |
1960 | return ret ? ret : locked; | |
1961 | } | |
1962 | ||
ca5f9524 DH |
1963 | /** |
1964 | * futex_wait_queue_me() - queue_me() and wait for wakeup, timeout, or signal | |
1965 | * @hb: the futex hash bucket, must be locked by the caller | |
1966 | * @q: the futex_q to queue up on | |
1967 | * @timeout: the prepared hrtimer_sleeper, or null for no timeout | |
ca5f9524 DH |
1968 | */ |
1969 | static void futex_wait_queue_me(struct futex_hash_bucket *hb, struct futex_q *q, | |
f1a11e05 | 1970 | struct hrtimer_sleeper *timeout) |
ca5f9524 | 1971 | { |
9beba3c5 DH |
1972 | /* |
1973 | * The task state is guaranteed to be set before another task can | |
1974 | * wake it. set_current_state() is implemented using set_mb() and | |
1975 | * queue_me() calls spin_unlock() upon completion, both serializing | |
1976 | * access to the hash list and forcing another memory barrier. | |
1977 | */ | |
f1a11e05 | 1978 | set_current_state(TASK_INTERRUPTIBLE); |
0729e196 | 1979 | queue_me(q, hb); |
ca5f9524 DH |
1980 | |
1981 | /* Arm the timer */ | |
1982 | if (timeout) { | |
1983 | hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS); | |
1984 | if (!hrtimer_active(&timeout->timer)) | |
1985 | timeout->task = NULL; | |
1986 | } | |
1987 | ||
1988 | /* | |
0729e196 DH |
1989 | * If we have been removed from the hash list, then another task |
1990 | * has tried to wake us, and we can skip the call to schedule(). | |
ca5f9524 DH |
1991 | */ |
1992 | if (likely(!plist_node_empty(&q->list))) { | |
1993 | /* | |
1994 | * If the timer has already expired, current will already be | |
1995 | * flagged for rescheduling. Only call schedule if there | |
1996 | * is no timeout, or if it has yet to expire. | |
1997 | */ | |
1998 | if (!timeout || timeout->task) | |
88c8004f | 1999 | freezable_schedule(); |
ca5f9524 DH |
2000 | } |
2001 | __set_current_state(TASK_RUNNING); | |
2002 | } | |
2003 | ||
f801073f DH |
2004 | /** |
2005 | * futex_wait_setup() - Prepare to wait on a futex | |
2006 | * @uaddr: the futex userspace address | |
2007 | * @val: the expected value | |
b41277dc | 2008 | * @flags: futex flags (FLAGS_SHARED, etc.) |
f801073f DH |
2009 | * @q: the associated futex_q |
2010 | * @hb: storage for hash_bucket pointer to be returned to caller | |
2011 | * | |
2012 | * Setup the futex_q and locate the hash_bucket. Get the futex value and | |
2013 | * compare it with the expected value. Handle atomic faults internally. | |
2014 | * Return with the hb lock held and a q.key reference on success, and unlocked | |
2015 | * with no q.key reference on failure. | |
2016 | * | |
6c23cbbd RD |
2017 | * Return: |
2018 | * 0 - uaddr contains val and hb has been locked; | |
ca4a04cf | 2019 | * <1 - -EFAULT or -EWOULDBLOCK (uaddr does not contain val) and hb is unlocked |
f801073f | 2020 | */ |
b41277dc | 2021 | static int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags, |
f801073f | 2022 | struct futex_q *q, struct futex_hash_bucket **hb) |
1da177e4 | 2023 | { |
e2970f2f IM |
2024 | u32 uval; |
2025 | int ret; | |
1da177e4 | 2026 | |
1da177e4 | 2027 | /* |
b2d0994b | 2028 | * Access the page AFTER the hash-bucket is locked. |
1da177e4 LT |
2029 | * Order is important: |
2030 | * | |
2031 | * Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val); | |
2032 | * Userspace waker: if (cond(var)) { var = new; futex_wake(&var); } | |
2033 | * | |
2034 | * The basic logical guarantee of a futex is that it blocks ONLY | |
2035 | * if cond(var) is known to be true at the time of blocking, for | |
8fe8f545 ML |
2036 | * any cond. If we locked the hash-bucket after testing *uaddr, that |
2037 | * would open a race condition where we could block indefinitely with | |
1da177e4 LT |
2038 | * cond(var) false, which would violate the guarantee. |
2039 | * | |
8fe8f545 ML |
2040 | * On the other hand, we insert q and release the hash-bucket only |
2041 | * after testing *uaddr. This guarantees that futex_wait() will NOT | |
2042 | * absorb a wakeup if *uaddr does not match the desired values | |
2043 | * while the syscall executes. | |
1da177e4 | 2044 | */ |
f801073f | 2045 | retry: |
9ea71503 | 2046 | ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q->key, VERIFY_READ); |
f801073f | 2047 | if (unlikely(ret != 0)) |
a5a2a0c7 | 2048 | return ret; |
f801073f DH |
2049 | |
2050 | retry_private: | |
2051 | *hb = queue_lock(q); | |
2052 | ||
e2970f2f | 2053 | ret = get_futex_value_locked(&uval, uaddr); |
1da177e4 | 2054 | |
f801073f | 2055 | if (ret) { |
0d00c7b2 | 2056 | queue_unlock(*hb); |
1da177e4 | 2057 | |
e2970f2f | 2058 | ret = get_user(uval, uaddr); |
e4dc5b7a | 2059 | if (ret) |
f801073f | 2060 | goto out; |
1da177e4 | 2061 | |
b41277dc | 2062 | if (!(flags & FLAGS_SHARED)) |
e4dc5b7a DH |
2063 | goto retry_private; |
2064 | ||
ae791a2d | 2065 | put_futex_key(&q->key); |
e4dc5b7a | 2066 | goto retry; |
1da177e4 | 2067 | } |
ca5f9524 | 2068 | |
f801073f | 2069 | if (uval != val) { |
0d00c7b2 | 2070 | queue_unlock(*hb); |
f801073f | 2071 | ret = -EWOULDBLOCK; |
2fff78c7 | 2072 | } |
1da177e4 | 2073 | |
f801073f DH |
2074 | out: |
2075 | if (ret) | |
ae791a2d | 2076 | put_futex_key(&q->key); |
f801073f DH |
2077 | return ret; |
2078 | } | |
2079 | ||
b41277dc DH |
2080 | static int futex_wait(u32 __user *uaddr, unsigned int flags, u32 val, |
2081 | ktime_t *abs_time, u32 bitset) | |
f801073f DH |
2082 | { |
2083 | struct hrtimer_sleeper timeout, *to = NULL; | |
f801073f DH |
2084 | struct restart_block *restart; |
2085 | struct futex_hash_bucket *hb; | |
5bdb05f9 | 2086 | struct futex_q q = futex_q_init; |
f801073f DH |
2087 | int ret; |
2088 | ||
2089 | if (!bitset) | |
2090 | return -EINVAL; | |
f801073f DH |
2091 | q.bitset = bitset; |
2092 | ||
2093 | if (abs_time) { | |
2094 | to = &timeout; | |
2095 | ||
b41277dc DH |
2096 | hrtimer_init_on_stack(&to->timer, (flags & FLAGS_CLOCKRT) ? |
2097 | CLOCK_REALTIME : CLOCK_MONOTONIC, | |
2098 | HRTIMER_MODE_ABS); | |
f801073f DH |
2099 | hrtimer_init_sleeper(to, current); |
2100 | hrtimer_set_expires_range_ns(&to->timer, *abs_time, | |
2101 | current->timer_slack_ns); | |
2102 | } | |
2103 | ||
d58e6576 | 2104 | retry: |
7ada876a DH |
2105 | /* |
2106 | * Prepare to wait on uaddr. On success, holds hb lock and increments | |
2107 | * q.key refs. | |
2108 | */ | |
b41277dc | 2109 | ret = futex_wait_setup(uaddr, val, flags, &q, &hb); |
f801073f DH |
2110 | if (ret) |
2111 | goto out; | |
2112 | ||
ca5f9524 | 2113 | /* queue_me and wait for wakeup, timeout, or a signal. */ |
f1a11e05 | 2114 | futex_wait_queue_me(hb, &q, to); |
1da177e4 LT |
2115 | |
2116 | /* If we were woken (and unqueued), we succeeded, whatever. */ | |
2fff78c7 | 2117 | ret = 0; |
7ada876a | 2118 | /* unqueue_me() drops q.key ref */ |
1da177e4 | 2119 | if (!unqueue_me(&q)) |
7ada876a | 2120 | goto out; |
2fff78c7 | 2121 | ret = -ETIMEDOUT; |
ca5f9524 | 2122 | if (to && !to->task) |
7ada876a | 2123 | goto out; |
72c1bbf3 | 2124 | |
e2970f2f | 2125 | /* |
d58e6576 TG |
2126 | * We expect signal_pending(current), but we might be the |
2127 | * victim of a spurious wakeup as well. | |
e2970f2f | 2128 | */ |
7ada876a | 2129 | if (!signal_pending(current)) |
d58e6576 | 2130 | goto retry; |
d58e6576 | 2131 | |
2fff78c7 | 2132 | ret = -ERESTARTSYS; |
c19384b5 | 2133 | if (!abs_time) |
7ada876a | 2134 | goto out; |
1da177e4 | 2135 | |
2fff78c7 PZ |
2136 | restart = ¤t_thread_info()->restart_block; |
2137 | restart->fn = futex_wait_restart; | |
a3c74c52 | 2138 | restart->futex.uaddr = uaddr; |
2fff78c7 PZ |
2139 | restart->futex.val = val; |
2140 | restart->futex.time = abs_time->tv64; | |
2141 | restart->futex.bitset = bitset; | |
0cd9c649 | 2142 | restart->futex.flags = flags | FLAGS_HAS_TIMEOUT; |
42d35d48 | 2143 | |
2fff78c7 PZ |
2144 | ret = -ERESTART_RESTARTBLOCK; |
2145 | ||
42d35d48 | 2146 | out: |
ca5f9524 DH |
2147 | if (to) { |
2148 | hrtimer_cancel(&to->timer); | |
2149 | destroy_hrtimer_on_stack(&to->timer); | |
2150 | } | |
c87e2837 IM |
2151 | return ret; |
2152 | } | |
2153 | ||
72c1bbf3 NP |
2154 | |
2155 | static long futex_wait_restart(struct restart_block *restart) | |
2156 | { | |
a3c74c52 | 2157 | u32 __user *uaddr = restart->futex.uaddr; |
a72188d8 | 2158 | ktime_t t, *tp = NULL; |
72c1bbf3 | 2159 | |
a72188d8 DH |
2160 | if (restart->futex.flags & FLAGS_HAS_TIMEOUT) { |
2161 | t.tv64 = restart->futex.time; | |
2162 | tp = &t; | |
2163 | } | |
72c1bbf3 | 2164 | restart->fn = do_no_restart_syscall; |
b41277dc DH |
2165 | |
2166 | return (long)futex_wait(uaddr, restart->futex.flags, | |
2167 | restart->futex.val, tp, restart->futex.bitset); | |
72c1bbf3 NP |
2168 | } |
2169 | ||
2170 | ||
c87e2837 IM |
2171 | /* |
2172 | * Userspace tried a 0 -> TID atomic transition of the futex value | |
2173 | * and failed. The kernel side here does the whole locking operation: | |
2174 | * if there are waiters then it will block, it does PI, etc. (Due to | |
2175 | * races the kernel might see a 0 value of the futex too.) | |
2176 | */ | |
b41277dc DH |
2177 | static int futex_lock_pi(u32 __user *uaddr, unsigned int flags, int detect, |
2178 | ktime_t *time, int trylock) | |
c87e2837 | 2179 | { |
c5780e97 | 2180 | struct hrtimer_sleeper timeout, *to = NULL; |
c87e2837 | 2181 | struct futex_hash_bucket *hb; |
5bdb05f9 | 2182 | struct futex_q q = futex_q_init; |
dd973998 | 2183 | int res, ret; |
c87e2837 IM |
2184 | |
2185 | if (refill_pi_state_cache()) | |
2186 | return -ENOMEM; | |
2187 | ||
c19384b5 | 2188 | if (time) { |
c5780e97 | 2189 | to = &timeout; |
237fc6e7 TG |
2190 | hrtimer_init_on_stack(&to->timer, CLOCK_REALTIME, |
2191 | HRTIMER_MODE_ABS); | |
c5780e97 | 2192 | hrtimer_init_sleeper(to, current); |
cc584b21 | 2193 | hrtimer_set_expires(&to->timer, *time); |
c5780e97 TG |
2194 | } |
2195 | ||
42d35d48 | 2196 | retry: |
9ea71503 | 2197 | ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q.key, VERIFY_WRITE); |
c87e2837 | 2198 | if (unlikely(ret != 0)) |
42d35d48 | 2199 | goto out; |
c87e2837 | 2200 | |
e4dc5b7a | 2201 | retry_private: |
82af7aca | 2202 | hb = queue_lock(&q); |
c87e2837 | 2203 | |
bab5bc9e | 2204 | ret = futex_lock_pi_atomic(uaddr, hb, &q.key, &q.pi_state, current, 0); |
c87e2837 | 2205 | if (unlikely(ret)) { |
778e9a9c | 2206 | switch (ret) { |
1a52084d DH |
2207 | case 1: |
2208 | /* We got the lock. */ | |
2209 | ret = 0; | |
2210 | goto out_unlock_put_key; | |
2211 | case -EFAULT: | |
2212 | goto uaddr_faulted; | |
778e9a9c AK |
2213 | case -EAGAIN: |
2214 | /* | |
2215 | * Task is exiting and we just wait for the | |
2216 | * exit to complete. | |
2217 | */ | |
0d00c7b2 | 2218 | queue_unlock(hb); |
ae791a2d | 2219 | put_futex_key(&q.key); |
778e9a9c AK |
2220 | cond_resched(); |
2221 | goto retry; | |
778e9a9c | 2222 | default: |
42d35d48 | 2223 | goto out_unlock_put_key; |
c87e2837 | 2224 | } |
c87e2837 IM |
2225 | } |
2226 | ||
2227 | /* | |
2228 | * Only actually queue now that the atomic ops are done: | |
2229 | */ | |
82af7aca | 2230 | queue_me(&q, hb); |
c87e2837 | 2231 | |
c87e2837 IM |
2232 | WARN_ON(!q.pi_state); |
2233 | /* | |
2234 | * Block on the PI mutex: | |
2235 | */ | |
2236 | if (!trylock) | |
2237 | ret = rt_mutex_timed_lock(&q.pi_state->pi_mutex, to, 1); | |
2238 | else { | |
2239 | ret = rt_mutex_trylock(&q.pi_state->pi_mutex); | |
2240 | /* Fixup the trylock return value: */ | |
2241 | ret = ret ? 0 : -EWOULDBLOCK; | |
2242 | } | |
2243 | ||
a99e4e41 | 2244 | spin_lock(q.lock_ptr); |
dd973998 DH |
2245 | /* |
2246 | * Fixup the pi_state owner and possibly acquire the lock if we | |
2247 | * haven't already. | |
2248 | */ | |
ae791a2d | 2249 | res = fixup_owner(uaddr, &q, !ret); |
dd973998 DH |
2250 | /* |
2251 | * If fixup_owner() returned an error, proprogate that. If it acquired | |
2252 | * the lock, clear our -ETIMEDOUT or -EINTR. | |
2253 | */ | |
2254 | if (res) | |
2255 | ret = (res < 0) ? res : 0; | |
c87e2837 | 2256 | |
e8f6386c | 2257 | /* |
dd973998 DH |
2258 | * If fixup_owner() faulted and was unable to handle the fault, unlock |
2259 | * it and return the fault to userspace. | |
e8f6386c DH |
2260 | */ |
2261 | if (ret && (rt_mutex_owner(&q.pi_state->pi_mutex) == current)) | |
2262 | rt_mutex_unlock(&q.pi_state->pi_mutex); | |
2263 | ||
778e9a9c AK |
2264 | /* Unqueue and drop the lock */ |
2265 | unqueue_me_pi(&q); | |
c87e2837 | 2266 | |
5ecb01cf | 2267 | goto out_put_key; |
c87e2837 | 2268 | |
42d35d48 | 2269 | out_unlock_put_key: |
0d00c7b2 | 2270 | queue_unlock(hb); |
c87e2837 | 2271 | |
42d35d48 | 2272 | out_put_key: |
ae791a2d | 2273 | put_futex_key(&q.key); |
42d35d48 | 2274 | out: |
237fc6e7 TG |
2275 | if (to) |
2276 | destroy_hrtimer_on_stack(&to->timer); | |
dd973998 | 2277 | return ret != -EINTR ? ret : -ERESTARTNOINTR; |
c87e2837 | 2278 | |
42d35d48 | 2279 | uaddr_faulted: |
0d00c7b2 | 2280 | queue_unlock(hb); |
778e9a9c | 2281 | |
d0725992 | 2282 | ret = fault_in_user_writeable(uaddr); |
e4dc5b7a DH |
2283 | if (ret) |
2284 | goto out_put_key; | |
c87e2837 | 2285 | |
b41277dc | 2286 | if (!(flags & FLAGS_SHARED)) |
e4dc5b7a DH |
2287 | goto retry_private; |
2288 | ||
ae791a2d | 2289 | put_futex_key(&q.key); |
e4dc5b7a | 2290 | goto retry; |
c87e2837 IM |
2291 | } |
2292 | ||
c87e2837 IM |
2293 | /* |
2294 | * Userspace attempted a TID -> 0 atomic transition, and failed. | |
2295 | * This is the in-kernel slowpath: we look up the PI state (if any), | |
2296 | * and do the rt-mutex unlock. | |
2297 | */ | |
b41277dc | 2298 | static int futex_unlock_pi(u32 __user *uaddr, unsigned int flags) |
c87e2837 IM |
2299 | { |
2300 | struct futex_hash_bucket *hb; | |
2301 | struct futex_q *this, *next; | |
38d47c1b | 2302 | union futex_key key = FUTEX_KEY_INIT; |
c0c9ed15 | 2303 | u32 uval, vpid = task_pid_vnr(current); |
e4dc5b7a | 2304 | int ret; |
c87e2837 IM |
2305 | |
2306 | retry: | |
2307 | if (get_user(uval, uaddr)) | |
2308 | return -EFAULT; | |
2309 | /* | |
2310 | * We release only a lock we actually own: | |
2311 | */ | |
c0c9ed15 | 2312 | if ((uval & FUTEX_TID_MASK) != vpid) |
c87e2837 | 2313 | return -EPERM; |
c87e2837 | 2314 | |
9ea71503 | 2315 | ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key, VERIFY_WRITE); |
c87e2837 IM |
2316 | if (unlikely(ret != 0)) |
2317 | goto out; | |
2318 | ||
2319 | hb = hash_futex(&key); | |
2320 | spin_lock(&hb->lock); | |
2321 | ||
c87e2837 IM |
2322 | /* |
2323 | * To avoid races, try to do the TID -> 0 atomic transition | |
2324 | * again. If it succeeds then we can return without waking | |
2325 | * anyone else up: | |
2326 | */ | |
37a9d912 ML |
2327 | if (!(uval & FUTEX_OWNER_DIED) && |
2328 | cmpxchg_futex_value_locked(&uval, uaddr, vpid, 0)) | |
c87e2837 IM |
2329 | goto pi_faulted; |
2330 | /* | |
2331 | * Rare case: we managed to release the lock atomically, | |
2332 | * no need to wake anyone else up: | |
2333 | */ | |
c0c9ed15 | 2334 | if (unlikely(uval == vpid)) |
c87e2837 IM |
2335 | goto out_unlock; |
2336 | ||
2337 | /* | |
2338 | * Ok, other tasks may need to be woken up - check waiters | |
2339 | * and do the wakeup if necessary: | |
2340 | */ | |
0d00c7b2 | 2341 | plist_for_each_entry_safe(this, next, &hb->chain, list) { |
c87e2837 IM |
2342 | if (!match_futex (&this->key, &key)) |
2343 | continue; | |
2344 | ret = wake_futex_pi(uaddr, uval, this); | |
2345 | /* | |
2346 | * The atomic access to the futex value | |
2347 | * generated a pagefault, so retry the | |
2348 | * user-access and the wakeup: | |
2349 | */ | |
2350 | if (ret == -EFAULT) | |
2351 | goto pi_faulted; | |
2352 | goto out_unlock; | |
2353 | } | |
2354 | /* | |
2355 | * No waiters - kernel unlocks the futex: | |
2356 | */ | |
e3f2ddea IM |
2357 | if (!(uval & FUTEX_OWNER_DIED)) { |
2358 | ret = unlock_futex_pi(uaddr, uval); | |
2359 | if (ret == -EFAULT) | |
2360 | goto pi_faulted; | |
2361 | } | |
c87e2837 IM |
2362 | |
2363 | out_unlock: | |
2364 | spin_unlock(&hb->lock); | |
ae791a2d | 2365 | put_futex_key(&key); |
c87e2837 | 2366 | |
42d35d48 | 2367 | out: |
c87e2837 IM |
2368 | return ret; |
2369 | ||
2370 | pi_faulted: | |
778e9a9c | 2371 | spin_unlock(&hb->lock); |
ae791a2d | 2372 | put_futex_key(&key); |
c87e2837 | 2373 | |
d0725992 | 2374 | ret = fault_in_user_writeable(uaddr); |
b5686363 | 2375 | if (!ret) |
c87e2837 IM |
2376 | goto retry; |
2377 | ||
1da177e4 LT |
2378 | return ret; |
2379 | } | |
2380 | ||
52400ba9 DH |
2381 | /** |
2382 | * handle_early_requeue_pi_wakeup() - Detect early wakeup on the initial futex | |
2383 | * @hb: the hash_bucket futex_q was original enqueued on | |
2384 | * @q: the futex_q woken while waiting to be requeued | |
2385 | * @key2: the futex_key of the requeue target futex | |
2386 | * @timeout: the timeout associated with the wait (NULL if none) | |
2387 | * | |
2388 | * Detect if the task was woken on the initial futex as opposed to the requeue | |
2389 | * target futex. If so, determine if it was a timeout or a signal that caused | |
2390 | * the wakeup and return the appropriate error code to the caller. Must be | |
2391 | * called with the hb lock held. | |
2392 | * | |
6c23cbbd RD |
2393 | * Return: |
2394 | * 0 = no early wakeup detected; | |
2395 | * <0 = -ETIMEDOUT or -ERESTARTNOINTR | |
52400ba9 DH |
2396 | */ |
2397 | static inline | |
2398 | int handle_early_requeue_pi_wakeup(struct futex_hash_bucket *hb, | |
2399 | struct futex_q *q, union futex_key *key2, | |
2400 | struct hrtimer_sleeper *timeout) | |
2401 | { | |
2402 | int ret = 0; | |
2403 | ||
2404 | /* | |
2405 | * With the hb lock held, we avoid races while we process the wakeup. | |
2406 | * We only need to hold hb (and not hb2) to ensure atomicity as the | |
2407 | * wakeup code can't change q.key from uaddr to uaddr2 if we hold hb. | |
2408 | * It can't be requeued from uaddr2 to something else since we don't | |
2409 | * support a PI aware source futex for requeue. | |
2410 | */ | |
2411 | if (!match_futex(&q->key, key2)) { | |
2412 | WARN_ON(q->lock_ptr && (&hb->lock != q->lock_ptr)); | |
2413 | /* | |
2414 | * We were woken prior to requeue by a timeout or a signal. | |
2415 | * Unqueue the futex_q and determine which it was. | |
2416 | */ | |
2e12978a | 2417 | plist_del(&q->list, &hb->chain); |
11d4616b | 2418 | hb_waiters_dec(hb); |
52400ba9 | 2419 | |
d58e6576 | 2420 | /* Handle spurious wakeups gracefully */ |
11df6ddd | 2421 | ret = -EWOULDBLOCK; |
52400ba9 DH |
2422 | if (timeout && !timeout->task) |
2423 | ret = -ETIMEDOUT; | |
d58e6576 | 2424 | else if (signal_pending(current)) |
1c840c14 | 2425 | ret = -ERESTARTNOINTR; |
52400ba9 DH |
2426 | } |
2427 | return ret; | |
2428 | } | |
2429 | ||
2430 | /** | |
2431 | * futex_wait_requeue_pi() - Wait on uaddr and take uaddr2 | |
56ec1607 | 2432 | * @uaddr: the futex we initially wait on (non-pi) |
b41277dc | 2433 | * @flags: futex flags (FLAGS_SHARED, FLAGS_CLOCKRT, etc.), they must be |
52400ba9 DH |
2434 | * the same type, no requeueing from private to shared, etc. |
2435 | * @val: the expected value of uaddr | |
2436 | * @abs_time: absolute timeout | |
56ec1607 | 2437 | * @bitset: 32 bit wakeup bitset set by userspace, defaults to all |
52400ba9 DH |
2438 | * @uaddr2: the pi futex we will take prior to returning to user-space |
2439 | * | |
2440 | * The caller will wait on uaddr and will be requeued by futex_requeue() to | |
6f7b0a2a DH |
2441 | * uaddr2 which must be PI aware and unique from uaddr. Normal wakeup will wake |
2442 | * on uaddr2 and complete the acquisition of the rt_mutex prior to returning to | |
2443 | * userspace. This ensures the rt_mutex maintains an owner when it has waiters; | |
2444 | * without one, the pi logic would not know which task to boost/deboost, if | |
2445 | * there was a need to. | |
52400ba9 DH |
2446 | * |
2447 | * We call schedule in futex_wait_queue_me() when we enqueue and return there | |
6c23cbbd | 2448 | * via the following-- |
52400ba9 | 2449 | * 1) wakeup on uaddr2 after an atomic lock acquisition by futex_requeue() |
cc6db4e6 DH |
2450 | * 2) wakeup on uaddr2 after a requeue |
2451 | * 3) signal | |
2452 | * 4) timeout | |
52400ba9 | 2453 | * |
cc6db4e6 | 2454 | * If 3, cleanup and return -ERESTARTNOINTR. |
52400ba9 DH |
2455 | * |
2456 | * If 2, we may then block on trying to take the rt_mutex and return via: | |
2457 | * 5) successful lock | |
2458 | * 6) signal | |
2459 | * 7) timeout | |
2460 | * 8) other lock acquisition failure | |
2461 | * | |
cc6db4e6 | 2462 | * If 6, return -EWOULDBLOCK (restarting the syscall would do the same). |
52400ba9 DH |
2463 | * |
2464 | * If 4 or 7, we cleanup and return with -ETIMEDOUT. | |
2465 | * | |
6c23cbbd RD |
2466 | * Return: |
2467 | * 0 - On success; | |
52400ba9 DH |
2468 | * <0 - On error |
2469 | */ | |
b41277dc | 2470 | static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags, |
52400ba9 | 2471 | u32 val, ktime_t *abs_time, u32 bitset, |
b41277dc | 2472 | u32 __user *uaddr2) |
52400ba9 DH |
2473 | { |
2474 | struct hrtimer_sleeper timeout, *to = NULL; | |
2475 | struct rt_mutex_waiter rt_waiter; | |
2476 | struct rt_mutex *pi_mutex = NULL; | |
52400ba9 | 2477 | struct futex_hash_bucket *hb; |
5bdb05f9 DH |
2478 | union futex_key key2 = FUTEX_KEY_INIT; |
2479 | struct futex_q q = futex_q_init; | |
52400ba9 | 2480 | int res, ret; |
52400ba9 | 2481 | |
6f7b0a2a DH |
2482 | if (uaddr == uaddr2) |
2483 | return -EINVAL; | |
2484 | ||
52400ba9 DH |
2485 | if (!bitset) |
2486 | return -EINVAL; | |
2487 | ||
2488 | if (abs_time) { | |
2489 | to = &timeout; | |
b41277dc DH |
2490 | hrtimer_init_on_stack(&to->timer, (flags & FLAGS_CLOCKRT) ? |
2491 | CLOCK_REALTIME : CLOCK_MONOTONIC, | |
2492 | HRTIMER_MODE_ABS); | |
52400ba9 DH |
2493 | hrtimer_init_sleeper(to, current); |
2494 | hrtimer_set_expires_range_ns(&to->timer, *abs_time, | |
2495 | current->timer_slack_ns); | |
2496 | } | |
2497 | ||
2498 | /* | |
2499 | * The waiter is allocated on our stack, manipulated by the requeue | |
2500 | * code while we sleep on uaddr. | |
2501 | */ | |
2502 | debug_rt_mutex_init_waiter(&rt_waiter); | |
fb00aca4 PZ |
2503 | RB_CLEAR_NODE(&rt_waiter.pi_tree_entry); |
2504 | RB_CLEAR_NODE(&rt_waiter.tree_entry); | |
52400ba9 DH |
2505 | rt_waiter.task = NULL; |
2506 | ||
9ea71503 | 2507 | ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, VERIFY_WRITE); |
52400ba9 DH |
2508 | if (unlikely(ret != 0)) |
2509 | goto out; | |
2510 | ||
84bc4af5 DH |
2511 | q.bitset = bitset; |
2512 | q.rt_waiter = &rt_waiter; | |
2513 | q.requeue_pi_key = &key2; | |
2514 | ||
7ada876a DH |
2515 | /* |
2516 | * Prepare to wait on uaddr. On success, increments q.key (key1) ref | |
2517 | * count. | |
2518 | */ | |
b41277dc | 2519 | ret = futex_wait_setup(uaddr, val, flags, &q, &hb); |
c8b15a70 TG |
2520 | if (ret) |
2521 | goto out_key2; | |
52400ba9 DH |
2522 | |
2523 | /* Queue the futex_q, drop the hb lock, wait for wakeup. */ | |
f1a11e05 | 2524 | futex_wait_queue_me(hb, &q, to); |
52400ba9 DH |
2525 | |
2526 | spin_lock(&hb->lock); | |
2527 | ret = handle_early_requeue_pi_wakeup(hb, &q, &key2, to); | |
2528 | spin_unlock(&hb->lock); | |
2529 | if (ret) | |
2530 | goto out_put_keys; | |
2531 | ||
2532 | /* | |
2533 | * In order for us to be here, we know our q.key == key2, and since | |
2534 | * we took the hb->lock above, we also know that futex_requeue() has | |
2535 | * completed and we no longer have to concern ourselves with a wakeup | |
7ada876a DH |
2536 | * race with the atomic proxy lock acquisition by the requeue code. The |
2537 | * futex_requeue dropped our key1 reference and incremented our key2 | |
2538 | * reference count. | |
52400ba9 DH |
2539 | */ |
2540 | ||
2541 | /* Check if the requeue code acquired the second futex for us. */ | |
2542 | if (!q.rt_waiter) { | |
2543 | /* | |
2544 | * Got the lock. We might not be the anticipated owner if we | |
2545 | * did a lock-steal - fix up the PI-state in that case. | |
2546 | */ | |
2547 | if (q.pi_state && (q.pi_state->owner != current)) { | |
2548 | spin_lock(q.lock_ptr); | |
ae791a2d | 2549 | ret = fixup_pi_state_owner(uaddr2, &q, current); |
52400ba9 DH |
2550 | spin_unlock(q.lock_ptr); |
2551 | } | |
2552 | } else { | |
2553 | /* | |
2554 | * We have been woken up by futex_unlock_pi(), a timeout, or a | |
2555 | * signal. futex_unlock_pi() will not destroy the lock_ptr nor | |
2556 | * the pi_state. | |
2557 | */ | |
f27071cb | 2558 | WARN_ON(!q.pi_state); |
52400ba9 DH |
2559 | pi_mutex = &q.pi_state->pi_mutex; |
2560 | ret = rt_mutex_finish_proxy_lock(pi_mutex, to, &rt_waiter, 1); | |
2561 | debug_rt_mutex_free_waiter(&rt_waiter); | |
2562 | ||
2563 | spin_lock(q.lock_ptr); | |
2564 | /* | |
2565 | * Fixup the pi_state owner and possibly acquire the lock if we | |
2566 | * haven't already. | |
2567 | */ | |
ae791a2d | 2568 | res = fixup_owner(uaddr2, &q, !ret); |
52400ba9 DH |
2569 | /* |
2570 | * If fixup_owner() returned an error, proprogate that. If it | |
56ec1607 | 2571 | * acquired the lock, clear -ETIMEDOUT or -EINTR. |
52400ba9 DH |
2572 | */ |
2573 | if (res) | |
2574 | ret = (res < 0) ? res : 0; | |
2575 | ||
2576 | /* Unqueue and drop the lock. */ | |
2577 | unqueue_me_pi(&q); | |
2578 | } | |
2579 | ||
2580 | /* | |
2581 | * If fixup_pi_state_owner() faulted and was unable to handle the | |
2582 | * fault, unlock the rt_mutex and return the fault to userspace. | |
2583 | */ | |
2584 | if (ret == -EFAULT) { | |
b6070a8d | 2585 | if (pi_mutex && rt_mutex_owner(pi_mutex) == current) |
52400ba9 DH |
2586 | rt_mutex_unlock(pi_mutex); |
2587 | } else if (ret == -EINTR) { | |
52400ba9 | 2588 | /* |
cc6db4e6 DH |
2589 | * We've already been requeued, but cannot restart by calling |
2590 | * futex_lock_pi() directly. We could restart this syscall, but | |
2591 | * it would detect that the user space "val" changed and return | |
2592 | * -EWOULDBLOCK. Save the overhead of the restart and return | |
2593 | * -EWOULDBLOCK directly. | |
52400ba9 | 2594 | */ |
2070887f | 2595 | ret = -EWOULDBLOCK; |
52400ba9 DH |
2596 | } |
2597 | ||
2598 | out_put_keys: | |
ae791a2d | 2599 | put_futex_key(&q.key); |
c8b15a70 | 2600 | out_key2: |
ae791a2d | 2601 | put_futex_key(&key2); |
52400ba9 DH |
2602 | |
2603 | out: | |
2604 | if (to) { | |
2605 | hrtimer_cancel(&to->timer); | |
2606 | destroy_hrtimer_on_stack(&to->timer); | |
2607 | } | |
2608 | return ret; | |
2609 | } | |
2610 | ||
0771dfef IM |
2611 | /* |
2612 | * Support for robust futexes: the kernel cleans up held futexes at | |
2613 | * thread exit time. | |
2614 | * | |
2615 | * Implementation: user-space maintains a per-thread list of locks it | |
2616 | * is holding. Upon do_exit(), the kernel carefully walks this list, | |
2617 | * and marks all locks that are owned by this thread with the | |
c87e2837 | 2618 | * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is |
0771dfef IM |
2619 | * always manipulated with the lock held, so the list is private and |
2620 | * per-thread. Userspace also maintains a per-thread 'list_op_pending' | |
2621 | * field, to allow the kernel to clean up if the thread dies after | |
2622 | * acquiring the lock, but just before it could have added itself to | |
2623 | * the list. There can only be one such pending lock. | |
2624 | */ | |
2625 | ||
2626 | /** | |
d96ee56c DH |
2627 | * sys_set_robust_list() - Set the robust-futex list head of a task |
2628 | * @head: pointer to the list-head | |
2629 | * @len: length of the list-head, as userspace expects | |
0771dfef | 2630 | */ |
836f92ad HC |
2631 | SYSCALL_DEFINE2(set_robust_list, struct robust_list_head __user *, head, |
2632 | size_t, len) | |
0771dfef | 2633 | { |
a0c1e907 TG |
2634 | if (!futex_cmpxchg_enabled) |
2635 | return -ENOSYS; | |
0771dfef IM |
2636 | /* |
2637 | * The kernel knows only one size for now: | |
2638 | */ | |
2639 | if (unlikely(len != sizeof(*head))) | |
2640 | return -EINVAL; | |
2641 | ||
2642 | current->robust_list = head; | |
2643 | ||
2644 | return 0; | |
2645 | } | |
2646 | ||
2647 | /** | |
d96ee56c DH |
2648 | * sys_get_robust_list() - Get the robust-futex list head of a task |
2649 | * @pid: pid of the process [zero for current task] | |
2650 | * @head_ptr: pointer to a list-head pointer, the kernel fills it in | |
2651 | * @len_ptr: pointer to a length field, the kernel fills in the header size | |
0771dfef | 2652 | */ |
836f92ad HC |
2653 | SYSCALL_DEFINE3(get_robust_list, int, pid, |
2654 | struct robust_list_head __user * __user *, head_ptr, | |
2655 | size_t __user *, len_ptr) | |
0771dfef | 2656 | { |
ba46df98 | 2657 | struct robust_list_head __user *head; |
0771dfef | 2658 | unsigned long ret; |
bdbb776f | 2659 | struct task_struct *p; |
0771dfef | 2660 | |
a0c1e907 TG |
2661 | if (!futex_cmpxchg_enabled) |
2662 | return -ENOSYS; | |
2663 | ||
bdbb776f KC |
2664 | rcu_read_lock(); |
2665 | ||
2666 | ret = -ESRCH; | |
0771dfef | 2667 | if (!pid) |
bdbb776f | 2668 | p = current; |
0771dfef | 2669 | else { |
228ebcbe | 2670 | p = find_task_by_vpid(pid); |
0771dfef IM |
2671 | if (!p) |
2672 | goto err_unlock; | |
0771dfef IM |
2673 | } |
2674 | ||
bdbb776f KC |
2675 | ret = -EPERM; |
2676 | if (!ptrace_may_access(p, PTRACE_MODE_READ)) | |
2677 | goto err_unlock; | |
2678 | ||
2679 | head = p->robust_list; | |
2680 | rcu_read_unlock(); | |
2681 | ||
0771dfef IM |
2682 | if (put_user(sizeof(*head), len_ptr)) |
2683 | return -EFAULT; | |
2684 | return put_user(head, head_ptr); | |
2685 | ||
2686 | err_unlock: | |
aaa2a97e | 2687 | rcu_read_unlock(); |
0771dfef IM |
2688 | |
2689 | return ret; | |
2690 | } | |
2691 | ||
2692 | /* | |
2693 | * Process a futex-list entry, check whether it's owned by the | |
2694 | * dying task, and do notification if so: | |
2695 | */ | |
e3f2ddea | 2696 | int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi) |
0771dfef | 2697 | { |
7cfdaf38 | 2698 | u32 uval, uninitialized_var(nval), mval; |
0771dfef | 2699 | |
8f17d3a5 IM |
2700 | retry: |
2701 | if (get_user(uval, uaddr)) | |
0771dfef IM |
2702 | return -1; |
2703 | ||
b488893a | 2704 | if ((uval & FUTEX_TID_MASK) == task_pid_vnr(curr)) { |
0771dfef IM |
2705 | /* |
2706 | * Ok, this dying thread is truly holding a futex | |
2707 | * of interest. Set the OWNER_DIED bit atomically | |
2708 | * via cmpxchg, and if the value had FUTEX_WAITERS | |
2709 | * set, wake up a waiter (if any). (We have to do a | |
2710 | * futex_wake() even if OWNER_DIED is already set - | |
2711 | * to handle the rare but possible case of recursive | |
2712 | * thread-death.) The rest of the cleanup is done in | |
2713 | * userspace. | |
2714 | */ | |
e3f2ddea | 2715 | mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED; |
6e0aa9f8 TG |
2716 | /* |
2717 | * We are not holding a lock here, but we want to have | |
2718 | * the pagefault_disable/enable() protection because | |
2719 | * we want to handle the fault gracefully. If the | |
2720 | * access fails we try to fault in the futex with R/W | |
2721 | * verification via get_user_pages. get_user() above | |
2722 | * does not guarantee R/W access. If that fails we | |
2723 | * give up and leave the futex locked. | |
2724 | */ | |
2725 | if (cmpxchg_futex_value_locked(&nval, uaddr, uval, mval)) { | |
2726 | if (fault_in_user_writeable(uaddr)) | |
2727 | return -1; | |
2728 | goto retry; | |
2729 | } | |
c87e2837 | 2730 | if (nval != uval) |
8f17d3a5 | 2731 | goto retry; |
0771dfef | 2732 | |
e3f2ddea IM |
2733 | /* |
2734 | * Wake robust non-PI futexes here. The wakeup of | |
2735 | * PI futexes happens in exit_pi_state(): | |
2736 | */ | |
36cf3b5c | 2737 | if (!pi && (uval & FUTEX_WAITERS)) |
c2f9f201 | 2738 | futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY); |
0771dfef IM |
2739 | } |
2740 | return 0; | |
2741 | } | |
2742 | ||
e3f2ddea IM |
2743 | /* |
2744 | * Fetch a robust-list pointer. Bit 0 signals PI futexes: | |
2745 | */ | |
2746 | static inline int fetch_robust_entry(struct robust_list __user **entry, | |
ba46df98 | 2747 | struct robust_list __user * __user *head, |
1dcc41bb | 2748 | unsigned int *pi) |
e3f2ddea IM |
2749 | { |
2750 | unsigned long uentry; | |
2751 | ||
ba46df98 | 2752 | if (get_user(uentry, (unsigned long __user *)head)) |
e3f2ddea IM |
2753 | return -EFAULT; |
2754 | ||
ba46df98 | 2755 | *entry = (void __user *)(uentry & ~1UL); |
e3f2ddea IM |
2756 | *pi = uentry & 1; |
2757 | ||
2758 | return 0; | |
2759 | } | |
2760 | ||
0771dfef IM |
2761 | /* |
2762 | * Walk curr->robust_list (very carefully, it's a userspace list!) | |
2763 | * and mark any locks found there dead, and notify any waiters. | |
2764 | * | |
2765 | * We silently return on any sign of list-walking problem. | |
2766 | */ | |
2767 | void exit_robust_list(struct task_struct *curr) | |
2768 | { | |
2769 | struct robust_list_head __user *head = curr->robust_list; | |
9f96cb1e | 2770 | struct robust_list __user *entry, *next_entry, *pending; |
4c115e95 DH |
2771 | unsigned int limit = ROBUST_LIST_LIMIT, pi, pip; |
2772 | unsigned int uninitialized_var(next_pi); | |
0771dfef | 2773 | unsigned long futex_offset; |
9f96cb1e | 2774 | int rc; |
0771dfef | 2775 | |
a0c1e907 TG |
2776 | if (!futex_cmpxchg_enabled) |
2777 | return; | |
2778 | ||
0771dfef IM |
2779 | /* |
2780 | * Fetch the list head (which was registered earlier, via | |
2781 | * sys_set_robust_list()): | |
2782 | */ | |
e3f2ddea | 2783 | if (fetch_robust_entry(&entry, &head->list.next, &pi)) |
0771dfef IM |
2784 | return; |
2785 | /* | |
2786 | * Fetch the relative futex offset: | |
2787 | */ | |
2788 | if (get_user(futex_offset, &head->futex_offset)) | |
2789 | return; | |
2790 | /* | |
2791 | * Fetch any possibly pending lock-add first, and handle it | |
2792 | * if it exists: | |
2793 | */ | |
e3f2ddea | 2794 | if (fetch_robust_entry(&pending, &head->list_op_pending, &pip)) |
0771dfef | 2795 | return; |
e3f2ddea | 2796 | |
9f96cb1e | 2797 | next_entry = NULL; /* avoid warning with gcc */ |
0771dfef | 2798 | while (entry != &head->list) { |
9f96cb1e MS |
2799 | /* |
2800 | * Fetch the next entry in the list before calling | |
2801 | * handle_futex_death: | |
2802 | */ | |
2803 | rc = fetch_robust_entry(&next_entry, &entry->next, &next_pi); | |
0771dfef IM |
2804 | /* |
2805 | * A pending lock might already be on the list, so | |
c87e2837 | 2806 | * don't process it twice: |
0771dfef IM |
2807 | */ |
2808 | if (entry != pending) | |
ba46df98 | 2809 | if (handle_futex_death((void __user *)entry + futex_offset, |
e3f2ddea | 2810 | curr, pi)) |
0771dfef | 2811 | return; |
9f96cb1e | 2812 | if (rc) |
0771dfef | 2813 | return; |
9f96cb1e MS |
2814 | entry = next_entry; |
2815 | pi = next_pi; | |
0771dfef IM |
2816 | /* |
2817 | * Avoid excessively long or circular lists: | |
2818 | */ | |
2819 | if (!--limit) | |
2820 | break; | |
2821 | ||
2822 | cond_resched(); | |
2823 | } | |
9f96cb1e MS |
2824 | |
2825 | if (pending) | |
2826 | handle_futex_death((void __user *)pending + futex_offset, | |
2827 | curr, pip); | |
0771dfef IM |
2828 | } |
2829 | ||
c19384b5 | 2830 | long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout, |
e2970f2f | 2831 | u32 __user *uaddr2, u32 val2, u32 val3) |
1da177e4 | 2832 | { |
81b40539 | 2833 | int cmd = op & FUTEX_CMD_MASK; |
b41277dc | 2834 | unsigned int flags = 0; |
34f01cc1 ED |
2835 | |
2836 | if (!(op & FUTEX_PRIVATE_FLAG)) | |
b41277dc | 2837 | flags |= FLAGS_SHARED; |
1da177e4 | 2838 | |
b41277dc DH |
2839 | if (op & FUTEX_CLOCK_REALTIME) { |
2840 | flags |= FLAGS_CLOCKRT; | |
2841 | if (cmd != FUTEX_WAIT_BITSET && cmd != FUTEX_WAIT_REQUEUE_PI) | |
2842 | return -ENOSYS; | |
2843 | } | |
1da177e4 | 2844 | |
59263b51 TG |
2845 | switch (cmd) { |
2846 | case FUTEX_LOCK_PI: | |
2847 | case FUTEX_UNLOCK_PI: | |
2848 | case FUTEX_TRYLOCK_PI: | |
2849 | case FUTEX_WAIT_REQUEUE_PI: | |
2850 | case FUTEX_CMP_REQUEUE_PI: | |
2851 | if (!futex_cmpxchg_enabled) | |
2852 | return -ENOSYS; | |
2853 | } | |
2854 | ||
34f01cc1 | 2855 | switch (cmd) { |
1da177e4 | 2856 | case FUTEX_WAIT: |
cd689985 TG |
2857 | val3 = FUTEX_BITSET_MATCH_ANY; |
2858 | case FUTEX_WAIT_BITSET: | |
81b40539 | 2859 | return futex_wait(uaddr, flags, val, timeout, val3); |
1da177e4 | 2860 | case FUTEX_WAKE: |
cd689985 TG |
2861 | val3 = FUTEX_BITSET_MATCH_ANY; |
2862 | case FUTEX_WAKE_BITSET: | |
81b40539 | 2863 | return futex_wake(uaddr, flags, val, val3); |
1da177e4 | 2864 | case FUTEX_REQUEUE: |
81b40539 | 2865 | return futex_requeue(uaddr, flags, uaddr2, val, val2, NULL, 0); |
1da177e4 | 2866 | case FUTEX_CMP_REQUEUE: |
81b40539 | 2867 | return futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 0); |
4732efbe | 2868 | case FUTEX_WAKE_OP: |
81b40539 | 2869 | return futex_wake_op(uaddr, flags, uaddr2, val, val2, val3); |
c87e2837 | 2870 | case FUTEX_LOCK_PI: |
81b40539 | 2871 | return futex_lock_pi(uaddr, flags, val, timeout, 0); |
c87e2837 | 2872 | case FUTEX_UNLOCK_PI: |
81b40539 | 2873 | return futex_unlock_pi(uaddr, flags); |
c87e2837 | 2874 | case FUTEX_TRYLOCK_PI: |
81b40539 | 2875 | return futex_lock_pi(uaddr, flags, 0, timeout, 1); |
52400ba9 DH |
2876 | case FUTEX_WAIT_REQUEUE_PI: |
2877 | val3 = FUTEX_BITSET_MATCH_ANY; | |
81b40539 TG |
2878 | return futex_wait_requeue_pi(uaddr, flags, val, timeout, val3, |
2879 | uaddr2); | |
52400ba9 | 2880 | case FUTEX_CMP_REQUEUE_PI: |
81b40539 | 2881 | return futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 1); |
1da177e4 | 2882 | } |
81b40539 | 2883 | return -ENOSYS; |
1da177e4 LT |
2884 | } |
2885 | ||
2886 | ||
17da2bd9 HC |
2887 | SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val, |
2888 | struct timespec __user *, utime, u32 __user *, uaddr2, | |
2889 | u32, val3) | |
1da177e4 | 2890 | { |
c19384b5 PP |
2891 | struct timespec ts; |
2892 | ktime_t t, *tp = NULL; | |
e2970f2f | 2893 | u32 val2 = 0; |
34f01cc1 | 2894 | int cmd = op & FUTEX_CMD_MASK; |
1da177e4 | 2895 | |
cd689985 | 2896 | if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI || |
52400ba9 DH |
2897 | cmd == FUTEX_WAIT_BITSET || |
2898 | cmd == FUTEX_WAIT_REQUEUE_PI)) { | |
c19384b5 | 2899 | if (copy_from_user(&ts, utime, sizeof(ts)) != 0) |
1da177e4 | 2900 | return -EFAULT; |
c19384b5 | 2901 | if (!timespec_valid(&ts)) |
9741ef96 | 2902 | return -EINVAL; |
c19384b5 PP |
2903 | |
2904 | t = timespec_to_ktime(ts); | |
34f01cc1 | 2905 | if (cmd == FUTEX_WAIT) |
5a7780e7 | 2906 | t = ktime_add_safe(ktime_get(), t); |
c19384b5 | 2907 | tp = &t; |
1da177e4 LT |
2908 | } |
2909 | /* | |
52400ba9 | 2910 | * requeue parameter in 'utime' if cmd == FUTEX_*_REQUEUE_*. |
f54f0986 | 2911 | * number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP. |
1da177e4 | 2912 | */ |
f54f0986 | 2913 | if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE || |
ba9c22f2 | 2914 | cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP) |
e2970f2f | 2915 | val2 = (u32) (unsigned long) utime; |
1da177e4 | 2916 | |
c19384b5 | 2917 | return do_futex(uaddr, op, val, tp, uaddr2, val2, val3); |
1da177e4 LT |
2918 | } |
2919 | ||
03b8c7b6 | 2920 | static void __init futex_detect_cmpxchg(void) |
1da177e4 | 2921 | { |
03b8c7b6 | 2922 | #ifndef CONFIG_HAVE_FUTEX_CMPXCHG |
a0c1e907 | 2923 | u32 curval; |
03b8c7b6 HC |
2924 | |
2925 | /* | |
2926 | * This will fail and we want it. Some arch implementations do | |
2927 | * runtime detection of the futex_atomic_cmpxchg_inatomic() | |
2928 | * functionality. We want to know that before we call in any | |
2929 | * of the complex code paths. Also we want to prevent | |
2930 | * registration of robust lists in that case. NULL is | |
2931 | * guaranteed to fault and we get -EFAULT on functional | |
2932 | * implementation, the non-functional ones will return | |
2933 | * -ENOSYS. | |
2934 | */ | |
2935 | if (cmpxchg_futex_value_locked(&curval, NULL, 0, 0) == -EFAULT) | |
2936 | futex_cmpxchg_enabled = 1; | |
2937 | #endif | |
2938 | } | |
2939 | ||
2940 | static int __init futex_init(void) | |
2941 | { | |
63b1a816 | 2942 | unsigned int futex_shift; |
a52b89eb DB |
2943 | unsigned long i; |
2944 | ||
2945 | #if CONFIG_BASE_SMALL | |
2946 | futex_hashsize = 16; | |
2947 | #else | |
2948 | futex_hashsize = roundup_pow_of_two(256 * num_possible_cpus()); | |
2949 | #endif | |
2950 | ||
2951 | futex_queues = alloc_large_system_hash("futex", sizeof(*futex_queues), | |
2952 | futex_hashsize, 0, | |
2953 | futex_hashsize < 256 ? HASH_SMALL : 0, | |
63b1a816 HC |
2954 | &futex_shift, NULL, |
2955 | futex_hashsize, futex_hashsize); | |
2956 | futex_hashsize = 1UL << futex_shift; | |
03b8c7b6 HC |
2957 | |
2958 | futex_detect_cmpxchg(); | |
a0c1e907 | 2959 | |
a52b89eb | 2960 | for (i = 0; i < futex_hashsize; i++) { |
11d4616b | 2961 | atomic_set(&futex_queues[i].waiters, 0); |
732375c6 | 2962 | plist_head_init(&futex_queues[i].chain); |
3e4ab747 TG |
2963 | spin_lock_init(&futex_queues[i].lock); |
2964 | } | |
2965 | ||
1da177e4 LT |
2966 | return 0; |
2967 | } | |
f6d107fb | 2968 | __initcall(futex_init); |