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 TG |
72 | /* |
73 | * Basic futex operation and ordering guarantees: | |
74 | * | |
75 | * The waiter reads the futex value in user space and calls | |
76 | * futex_wait(). This function computes the hash bucket and acquires | |
77 | * the hash bucket lock. After that it reads the futex user space value | |
b0c29f79 DB |
78 | * again and verifies that the data has not changed. If it has not changed |
79 | * it enqueues itself into the hash bucket, releases the hash bucket lock | |
80 | * and schedules. | |
99b60ce6 TG |
81 | * |
82 | * The waker side modifies the user space value of the futex and calls | |
b0c29f79 DB |
83 | * futex_wake(). This function computes the hash bucket and acquires the |
84 | * hash bucket lock. Then it looks for waiters on that futex in the hash | |
85 | * bucket and wakes them. | |
99b60ce6 | 86 | * |
b0c29f79 DB |
87 | * In futex wake up scenarios where no tasks are blocked on a futex, taking |
88 | * the hb spinlock can be avoided and simply return. In order for this | |
89 | * optimization to work, ordering guarantees must exist so that the waiter | |
90 | * being added to the list is acknowledged when the list is concurrently being | |
91 | * checked by the waker, avoiding scenarios like the following: | |
99b60ce6 TG |
92 | * |
93 | * CPU 0 CPU 1 | |
94 | * val = *futex; | |
95 | * sys_futex(WAIT, futex, val); | |
96 | * futex_wait(futex, val); | |
97 | * uval = *futex; | |
98 | * *futex = newval; | |
99 | * sys_futex(WAKE, futex); | |
100 | * futex_wake(futex); | |
101 | * if (queue_empty()) | |
102 | * return; | |
103 | * if (uval == val) | |
104 | * lock(hash_bucket(futex)); | |
105 | * queue(); | |
106 | * unlock(hash_bucket(futex)); | |
107 | * schedule(); | |
108 | * | |
109 | * This would cause the waiter on CPU 0 to wait forever because it | |
110 | * missed the transition of the user space value from val to newval | |
111 | * and the waker did not find the waiter in the hash bucket queue. | |
99b60ce6 | 112 | * |
b0c29f79 DB |
113 | * The correct serialization ensures that a waiter either observes |
114 | * the changed user space value before blocking or is woken by a | |
115 | * concurrent waker: | |
116 | * | |
117 | * CPU 0 CPU 1 | |
99b60ce6 TG |
118 | * val = *futex; |
119 | * sys_futex(WAIT, futex, val); | |
120 | * futex_wait(futex, val); | |
b0c29f79 DB |
121 | * |
122 | * waiters++; | |
123 | * mb(); (A) <-- paired with -. | |
124 | * | | |
125 | * lock(hash_bucket(futex)); | | |
126 | * | | |
127 | * uval = *futex; | | |
128 | * | *futex = newval; | |
129 | * | sys_futex(WAKE, futex); | |
130 | * | futex_wake(futex); | |
131 | * | | |
132 | * `-------> mb(); (B) | |
99b60ce6 | 133 | * if (uval == val) |
b0c29f79 | 134 | * queue(); |
99b60ce6 | 135 | * unlock(hash_bucket(futex)); |
b0c29f79 DB |
136 | * schedule(); if (waiters) |
137 | * lock(hash_bucket(futex)); | |
138 | * wake_waiters(futex); | |
139 | * unlock(hash_bucket(futex)); | |
140 | * | |
141 | * Where (A) orders the waiters increment and the futex value read -- this | |
142 | * is guaranteed by the head counter in the hb spinlock; and where (B) | |
143 | * orders the write to futex and the waiters read -- this is done by the | |
144 | * barriers in get_futex_key_refs(), through either ihold or atomic_inc, | |
145 | * depending on the futex type. | |
146 | * | |
147 | * This yields the following case (where X:=waiters, Y:=futex): | |
148 | * | |
149 | * X = Y = 0 | |
150 | * | |
151 | * w[X]=1 w[Y]=1 | |
152 | * MB MB | |
153 | * r[Y]=y r[X]=x | |
154 | * | |
155 | * Which guarantees that x==0 && y==0 is impossible; which translates back into | |
156 | * the guarantee that we cannot both miss the futex variable change and the | |
157 | * enqueue. | |
99b60ce6 TG |
158 | */ |
159 | ||
a0c1e907 TG |
160 | int __read_mostly futex_cmpxchg_enabled; |
161 | ||
b41277dc DH |
162 | /* |
163 | * Futex flags used to encode options to functions and preserve them across | |
164 | * restarts. | |
165 | */ | |
166 | #define FLAGS_SHARED 0x01 | |
167 | #define FLAGS_CLOCKRT 0x02 | |
168 | #define FLAGS_HAS_TIMEOUT 0x04 | |
169 | ||
c87e2837 IM |
170 | /* |
171 | * Priority Inheritance state: | |
172 | */ | |
173 | struct futex_pi_state { | |
174 | /* | |
175 | * list of 'owned' pi_state instances - these have to be | |
176 | * cleaned up in do_exit() if the task exits prematurely: | |
177 | */ | |
178 | struct list_head list; | |
179 | ||
180 | /* | |
181 | * The PI object: | |
182 | */ | |
183 | struct rt_mutex pi_mutex; | |
184 | ||
185 | struct task_struct *owner; | |
186 | atomic_t refcount; | |
187 | ||
188 | union futex_key key; | |
189 | }; | |
190 | ||
d8d88fbb DH |
191 | /** |
192 | * struct futex_q - The hashed futex queue entry, one per waiting task | |
fb62db2b | 193 | * @list: priority-sorted list of tasks waiting on this futex |
d8d88fbb DH |
194 | * @task: the task waiting on the futex |
195 | * @lock_ptr: the hash bucket lock | |
196 | * @key: the key the futex is hashed on | |
197 | * @pi_state: optional priority inheritance state | |
198 | * @rt_waiter: rt_waiter storage for use with requeue_pi | |
199 | * @requeue_pi_key: the requeue_pi target futex key | |
200 | * @bitset: bitset for the optional bitmasked wakeup | |
201 | * | |
202 | * We use this hashed waitqueue, instead of a normal wait_queue_t, so | |
1da177e4 LT |
203 | * we can wake only the relevant ones (hashed queues may be shared). |
204 | * | |
205 | * A futex_q has a woken state, just like tasks have TASK_RUNNING. | |
ec92d082 | 206 | * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0. |
fb62db2b | 207 | * The order of wakeup is always to make the first condition true, then |
d8d88fbb DH |
208 | * the second. |
209 | * | |
210 | * PI futexes are typically woken before they are removed from the hash list via | |
211 | * the rt_mutex code. See unqueue_me_pi(). | |
1da177e4 LT |
212 | */ |
213 | struct futex_q { | |
ec92d082 | 214 | struct plist_node list; |
1da177e4 | 215 | |
d8d88fbb | 216 | struct task_struct *task; |
1da177e4 | 217 | spinlock_t *lock_ptr; |
1da177e4 | 218 | union futex_key key; |
c87e2837 | 219 | struct futex_pi_state *pi_state; |
52400ba9 | 220 | struct rt_mutex_waiter *rt_waiter; |
84bc4af5 | 221 | union futex_key *requeue_pi_key; |
cd689985 | 222 | u32 bitset; |
1da177e4 LT |
223 | }; |
224 | ||
5bdb05f9 DH |
225 | static const struct futex_q futex_q_init = { |
226 | /* list gets initialized in queue_me()*/ | |
227 | .key = FUTEX_KEY_INIT, | |
228 | .bitset = FUTEX_BITSET_MATCH_ANY | |
229 | }; | |
230 | ||
1da177e4 | 231 | /* |
b2d0994b DH |
232 | * Hash buckets are shared by all the futex_keys that hash to the same |
233 | * location. Each key may have multiple futex_q structures, one for each task | |
234 | * waiting on a futex. | |
1da177e4 LT |
235 | */ |
236 | struct futex_hash_bucket { | |
11d4616b | 237 | atomic_t waiters; |
ec92d082 PP |
238 | spinlock_t lock; |
239 | struct plist_head chain; | |
a52b89eb | 240 | } ____cacheline_aligned_in_smp; |
1da177e4 | 241 | |
a52b89eb DB |
242 | static unsigned long __read_mostly futex_hashsize; |
243 | ||
244 | static struct futex_hash_bucket *futex_queues; | |
1da177e4 | 245 | |
b0c29f79 DB |
246 | static inline void futex_get_mm(union futex_key *key) |
247 | { | |
248 | atomic_inc(&key->private.mm->mm_count); | |
249 | /* | |
250 | * Ensure futex_get_mm() implies a full barrier such that | |
251 | * get_futex_key() implies a full barrier. This is relied upon | |
252 | * as full barrier (B), see the ordering comment above. | |
253 | */ | |
254 | smp_mb__after_atomic_inc(); | |
255 | } | |
256 | ||
11d4616b LT |
257 | /* |
258 | * Reflects a new waiter being added to the waitqueue. | |
259 | */ | |
260 | static inline void hb_waiters_inc(struct futex_hash_bucket *hb) | |
b0c29f79 DB |
261 | { |
262 | #ifdef CONFIG_SMP | |
11d4616b | 263 | atomic_inc(&hb->waiters); |
b0c29f79 | 264 | /* |
11d4616b | 265 | * Full barrier (A), see the ordering comment above. |
b0c29f79 | 266 | */ |
11d4616b LT |
267 | smp_mb__after_atomic_inc(); |
268 | #endif | |
269 | } | |
270 | ||
271 | /* | |
272 | * Reflects a waiter being removed from the waitqueue by wakeup | |
273 | * paths. | |
274 | */ | |
275 | static inline void hb_waiters_dec(struct futex_hash_bucket *hb) | |
276 | { | |
277 | #ifdef CONFIG_SMP | |
278 | atomic_dec(&hb->waiters); | |
279 | #endif | |
280 | } | |
b0c29f79 | 281 | |
11d4616b LT |
282 | static inline int hb_waiters_pending(struct futex_hash_bucket *hb) |
283 | { | |
284 | #ifdef CONFIG_SMP | |
285 | return atomic_read(&hb->waiters); | |
b0c29f79 | 286 | #else |
11d4616b | 287 | return 1; |
b0c29f79 DB |
288 | #endif |
289 | } | |
290 | ||
1da177e4 LT |
291 | /* |
292 | * We hash on the keys returned from get_futex_key (see below). | |
293 | */ | |
294 | static struct futex_hash_bucket *hash_futex(union futex_key *key) | |
295 | { | |
296 | u32 hash = jhash2((u32*)&key->both.word, | |
297 | (sizeof(key->both.word)+sizeof(key->both.ptr))/4, | |
298 | key->both.offset); | |
a52b89eb | 299 | return &futex_queues[hash & (futex_hashsize - 1)]; |
1da177e4 LT |
300 | } |
301 | ||
302 | /* | |
303 | * Return 1 if two futex_keys are equal, 0 otherwise. | |
304 | */ | |
305 | static inline int match_futex(union futex_key *key1, union futex_key *key2) | |
306 | { | |
2bc87203 DH |
307 | return (key1 && key2 |
308 | && key1->both.word == key2->both.word | |
1da177e4 LT |
309 | && key1->both.ptr == key2->both.ptr |
310 | && key1->both.offset == key2->both.offset); | |
311 | } | |
312 | ||
38d47c1b PZ |
313 | /* |
314 | * Take a reference to the resource addressed by a key. | |
315 | * Can be called while holding spinlocks. | |
316 | * | |
317 | */ | |
318 | static void get_futex_key_refs(union futex_key *key) | |
319 | { | |
320 | if (!key->both.ptr) | |
321 | return; | |
322 | ||
323 | switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { | |
324 | case FUT_OFF_INODE: | |
b0c29f79 | 325 | ihold(key->shared.inode); /* implies MB (B) */ |
38d47c1b PZ |
326 | break; |
327 | case FUT_OFF_MMSHARED: | |
b0c29f79 | 328 | futex_get_mm(key); /* implies MB (B) */ |
38d47c1b PZ |
329 | break; |
330 | } | |
331 | } | |
332 | ||
333 | /* | |
334 | * Drop a reference to the resource addressed by a key. | |
335 | * The hash bucket spinlock must not be held. | |
336 | */ | |
337 | static void drop_futex_key_refs(union futex_key *key) | |
338 | { | |
90621c40 DH |
339 | if (!key->both.ptr) { |
340 | /* If we're here then we tried to put a key we failed to get */ | |
341 | WARN_ON_ONCE(1); | |
38d47c1b | 342 | return; |
90621c40 | 343 | } |
38d47c1b PZ |
344 | |
345 | switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { | |
346 | case FUT_OFF_INODE: | |
347 | iput(key->shared.inode); | |
348 | break; | |
349 | case FUT_OFF_MMSHARED: | |
350 | mmdrop(key->private.mm); | |
351 | break; | |
352 | } | |
353 | } | |
354 | ||
34f01cc1 | 355 | /** |
d96ee56c DH |
356 | * get_futex_key() - Get parameters which are the keys for a futex |
357 | * @uaddr: virtual address of the futex | |
358 | * @fshared: 0 for a PROCESS_PRIVATE futex, 1 for PROCESS_SHARED | |
359 | * @key: address where result is stored. | |
9ea71503 SB |
360 | * @rw: mapping needs to be read/write (values: VERIFY_READ, |
361 | * VERIFY_WRITE) | |
34f01cc1 | 362 | * |
6c23cbbd RD |
363 | * Return: a negative error code or 0 |
364 | * | |
34f01cc1 | 365 | * The key words are stored in *key on success. |
1da177e4 | 366 | * |
6131ffaa | 367 | * For shared mappings, it's (page->index, file_inode(vma->vm_file), |
1da177e4 LT |
368 | * offset_within_page). For private mappings, it's (uaddr, current->mm). |
369 | * We can usually work out the index without swapping in the page. | |
370 | * | |
b2d0994b | 371 | * lock_page() might sleep, the caller should not hold a spinlock. |
1da177e4 | 372 | */ |
64d1304a | 373 | static int |
9ea71503 | 374 | get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key, int rw) |
1da177e4 | 375 | { |
e2970f2f | 376 | unsigned long address = (unsigned long)uaddr; |
1da177e4 | 377 | struct mm_struct *mm = current->mm; |
a5b338f2 | 378 | struct page *page, *page_head; |
9ea71503 | 379 | int err, ro = 0; |
1da177e4 LT |
380 | |
381 | /* | |
382 | * The futex address must be "naturally" aligned. | |
383 | */ | |
e2970f2f | 384 | key->both.offset = address % PAGE_SIZE; |
34f01cc1 | 385 | if (unlikely((address % sizeof(u32)) != 0)) |
1da177e4 | 386 | return -EINVAL; |
e2970f2f | 387 | address -= key->both.offset; |
1da177e4 | 388 | |
5cdec2d8 LT |
389 | if (unlikely(!access_ok(rw, uaddr, sizeof(u32)))) |
390 | return -EFAULT; | |
391 | ||
34f01cc1 ED |
392 | /* |
393 | * PROCESS_PRIVATE futexes are fast. | |
394 | * As the mm cannot disappear under us and the 'key' only needs | |
395 | * virtual address, we dont even have to find the underlying vma. | |
396 | * Note : We do have to check 'uaddr' is a valid user address, | |
397 | * but access_ok() should be faster than find_vma() | |
398 | */ | |
399 | if (!fshared) { | |
34f01cc1 ED |
400 | key->private.mm = mm; |
401 | key->private.address = address; | |
b0c29f79 | 402 | get_futex_key_refs(key); /* implies MB (B) */ |
34f01cc1 ED |
403 | return 0; |
404 | } | |
1da177e4 | 405 | |
38d47c1b | 406 | again: |
7485d0d3 | 407 | err = get_user_pages_fast(address, 1, 1, &page); |
9ea71503 SB |
408 | /* |
409 | * If write access is not required (eg. FUTEX_WAIT), try | |
410 | * and get read-only access. | |
411 | */ | |
412 | if (err == -EFAULT && rw == VERIFY_READ) { | |
413 | err = get_user_pages_fast(address, 1, 0, &page); | |
414 | ro = 1; | |
415 | } | |
38d47c1b PZ |
416 | if (err < 0) |
417 | return err; | |
9ea71503 SB |
418 | else |
419 | err = 0; | |
38d47c1b | 420 | |
a5b338f2 AA |
421 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE |
422 | page_head = page; | |
423 | if (unlikely(PageTail(page))) { | |
38d47c1b | 424 | put_page(page); |
a5b338f2 AA |
425 | /* serialize against __split_huge_page_splitting() */ |
426 | local_irq_disable(); | |
f12d5bfc | 427 | if (likely(__get_user_pages_fast(address, 1, !ro, &page) == 1)) { |
a5b338f2 AA |
428 | page_head = compound_head(page); |
429 | /* | |
430 | * page_head is valid pointer but we must pin | |
431 | * it before taking the PG_lock and/or | |
432 | * PG_compound_lock. The moment we re-enable | |
433 | * irqs __split_huge_page_splitting() can | |
434 | * return and the head page can be freed from | |
435 | * under us. We can't take the PG_lock and/or | |
436 | * PG_compound_lock on a page that could be | |
437 | * freed from under us. | |
438 | */ | |
439 | if (page != page_head) { | |
440 | get_page(page_head); | |
441 | put_page(page); | |
442 | } | |
443 | local_irq_enable(); | |
444 | } else { | |
445 | local_irq_enable(); | |
446 | goto again; | |
447 | } | |
448 | } | |
449 | #else | |
450 | page_head = compound_head(page); | |
451 | if (page != page_head) { | |
452 | get_page(page_head); | |
453 | put_page(page); | |
454 | } | |
455 | #endif | |
456 | ||
457 | lock_page(page_head); | |
e6780f72 HD |
458 | |
459 | /* | |
460 | * If page_head->mapping is NULL, then it cannot be a PageAnon | |
461 | * page; but it might be the ZERO_PAGE or in the gate area or | |
462 | * in a special mapping (all cases which we are happy to fail); | |
463 | * or it may have been a good file page when get_user_pages_fast | |
464 | * found it, but truncated or holepunched or subjected to | |
465 | * invalidate_complete_page2 before we got the page lock (also | |
466 | * cases which we are happy to fail). And we hold a reference, | |
467 | * so refcount care in invalidate_complete_page's remove_mapping | |
468 | * prevents drop_caches from setting mapping to NULL beneath us. | |
469 | * | |
470 | * The case we do have to guard against is when memory pressure made | |
471 | * shmem_writepage move it from filecache to swapcache beneath us: | |
472 | * an unlikely race, but we do need to retry for page_head->mapping. | |
473 | */ | |
a5b338f2 | 474 | if (!page_head->mapping) { |
e6780f72 | 475 | int shmem_swizzled = PageSwapCache(page_head); |
a5b338f2 AA |
476 | unlock_page(page_head); |
477 | put_page(page_head); | |
e6780f72 HD |
478 | if (shmem_swizzled) |
479 | goto again; | |
480 | return -EFAULT; | |
38d47c1b | 481 | } |
1da177e4 LT |
482 | |
483 | /* | |
484 | * Private mappings are handled in a simple way. | |
485 | * | |
486 | * NOTE: When userspace waits on a MAP_SHARED mapping, even if | |
487 | * it's a read-only handle, it's expected that futexes attach to | |
38d47c1b | 488 | * the object not the particular process. |
1da177e4 | 489 | */ |
a5b338f2 | 490 | if (PageAnon(page_head)) { |
9ea71503 SB |
491 | /* |
492 | * A RO anonymous page will never change and thus doesn't make | |
493 | * sense for futex operations. | |
494 | */ | |
495 | if (ro) { | |
496 | err = -EFAULT; | |
497 | goto out; | |
498 | } | |
499 | ||
38d47c1b | 500 | key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */ |
1da177e4 | 501 | key->private.mm = mm; |
e2970f2f | 502 | key->private.address = address; |
38d47c1b PZ |
503 | } else { |
504 | key->both.offset |= FUT_OFF_INODE; /* inode-based key */ | |
a5b338f2 | 505 | key->shared.inode = page_head->mapping->host; |
13d60f4b | 506 | key->shared.pgoff = basepage_index(page); |
1da177e4 LT |
507 | } |
508 | ||
b0c29f79 | 509 | get_futex_key_refs(key); /* implies MB (B) */ |
1da177e4 | 510 | |
9ea71503 | 511 | out: |
a5b338f2 AA |
512 | unlock_page(page_head); |
513 | put_page(page_head); | |
9ea71503 | 514 | return err; |
1da177e4 LT |
515 | } |
516 | ||
ae791a2d | 517 | static inline void put_futex_key(union futex_key *key) |
1da177e4 | 518 | { |
38d47c1b | 519 | drop_futex_key_refs(key); |
1da177e4 LT |
520 | } |
521 | ||
d96ee56c DH |
522 | /** |
523 | * fault_in_user_writeable() - Fault in user address and verify RW access | |
d0725992 TG |
524 | * @uaddr: pointer to faulting user space address |
525 | * | |
526 | * Slow path to fixup the fault we just took in the atomic write | |
527 | * access to @uaddr. | |
528 | * | |
fb62db2b | 529 | * We have no generic implementation of a non-destructive write to the |
d0725992 TG |
530 | * user address. We know that we faulted in the atomic pagefault |
531 | * disabled section so we can as well avoid the #PF overhead by | |
532 | * calling get_user_pages() right away. | |
533 | */ | |
534 | static int fault_in_user_writeable(u32 __user *uaddr) | |
535 | { | |
722d0172 AK |
536 | struct mm_struct *mm = current->mm; |
537 | int ret; | |
538 | ||
539 | down_read(&mm->mmap_sem); | |
2efaca92 BH |
540 | ret = fixup_user_fault(current, mm, (unsigned long)uaddr, |
541 | FAULT_FLAG_WRITE); | |
722d0172 AK |
542 | up_read(&mm->mmap_sem); |
543 | ||
d0725992 TG |
544 | return ret < 0 ? ret : 0; |
545 | } | |
546 | ||
4b1c486b DH |
547 | /** |
548 | * futex_top_waiter() - Return the highest priority waiter on a futex | |
d96ee56c DH |
549 | * @hb: the hash bucket the futex_q's reside in |
550 | * @key: the futex key (to distinguish it from other futex futex_q's) | |
4b1c486b DH |
551 | * |
552 | * Must be called with the hb lock held. | |
553 | */ | |
554 | static struct futex_q *futex_top_waiter(struct futex_hash_bucket *hb, | |
555 | union futex_key *key) | |
556 | { | |
557 | struct futex_q *this; | |
558 | ||
559 | plist_for_each_entry(this, &hb->chain, list) { | |
560 | if (match_futex(&this->key, key)) | |
561 | return this; | |
562 | } | |
563 | return NULL; | |
564 | } | |
565 | ||
37a9d912 ML |
566 | static int cmpxchg_futex_value_locked(u32 *curval, u32 __user *uaddr, |
567 | u32 uval, u32 newval) | |
36cf3b5c | 568 | { |
37a9d912 | 569 | int ret; |
36cf3b5c TG |
570 | |
571 | pagefault_disable(); | |
37a9d912 | 572 | ret = futex_atomic_cmpxchg_inatomic(curval, uaddr, uval, newval); |
36cf3b5c TG |
573 | pagefault_enable(); |
574 | ||
37a9d912 | 575 | return ret; |
36cf3b5c TG |
576 | } |
577 | ||
578 | static int get_futex_value_locked(u32 *dest, u32 __user *from) | |
1da177e4 LT |
579 | { |
580 | int ret; | |
581 | ||
a866374a | 582 | pagefault_disable(); |
e2970f2f | 583 | ret = __copy_from_user_inatomic(dest, from, sizeof(u32)); |
a866374a | 584 | pagefault_enable(); |
1da177e4 LT |
585 | |
586 | return ret ? -EFAULT : 0; | |
587 | } | |
588 | ||
c87e2837 IM |
589 | |
590 | /* | |
591 | * PI code: | |
592 | */ | |
593 | static int refill_pi_state_cache(void) | |
594 | { | |
595 | struct futex_pi_state *pi_state; | |
596 | ||
597 | if (likely(current->pi_state_cache)) | |
598 | return 0; | |
599 | ||
4668edc3 | 600 | pi_state = kzalloc(sizeof(*pi_state), GFP_KERNEL); |
c87e2837 IM |
601 | |
602 | if (!pi_state) | |
603 | return -ENOMEM; | |
604 | ||
c87e2837 IM |
605 | INIT_LIST_HEAD(&pi_state->list); |
606 | /* pi_mutex gets initialized later */ | |
607 | pi_state->owner = NULL; | |
608 | atomic_set(&pi_state->refcount, 1); | |
38d47c1b | 609 | pi_state->key = FUTEX_KEY_INIT; |
c87e2837 IM |
610 | |
611 | current->pi_state_cache = pi_state; | |
612 | ||
613 | return 0; | |
614 | } | |
615 | ||
616 | static struct futex_pi_state * alloc_pi_state(void) | |
617 | { | |
618 | struct futex_pi_state *pi_state = current->pi_state_cache; | |
619 | ||
620 | WARN_ON(!pi_state); | |
621 | current->pi_state_cache = NULL; | |
622 | ||
623 | return pi_state; | |
624 | } | |
625 | ||
626 | static void free_pi_state(struct futex_pi_state *pi_state) | |
627 | { | |
628 | if (!atomic_dec_and_test(&pi_state->refcount)) | |
629 | return; | |
630 | ||
631 | /* | |
632 | * If pi_state->owner is NULL, the owner is most probably dying | |
633 | * and has cleaned up the pi_state already | |
634 | */ | |
635 | if (pi_state->owner) { | |
1d615482 | 636 | raw_spin_lock_irq(&pi_state->owner->pi_lock); |
c87e2837 | 637 | list_del_init(&pi_state->list); |
1d615482 | 638 | raw_spin_unlock_irq(&pi_state->owner->pi_lock); |
c87e2837 IM |
639 | |
640 | rt_mutex_proxy_unlock(&pi_state->pi_mutex, pi_state->owner); | |
641 | } | |
642 | ||
643 | if (current->pi_state_cache) | |
644 | kfree(pi_state); | |
645 | else { | |
646 | /* | |
647 | * pi_state->list is already empty. | |
648 | * clear pi_state->owner. | |
649 | * refcount is at 0 - put it back to 1. | |
650 | */ | |
651 | pi_state->owner = NULL; | |
652 | atomic_set(&pi_state->refcount, 1); | |
653 | current->pi_state_cache = pi_state; | |
654 | } | |
655 | } | |
656 | ||
657 | /* | |
658 | * Look up the task based on what TID userspace gave us. | |
659 | * We dont trust it. | |
660 | */ | |
661 | static struct task_struct * futex_find_get_task(pid_t pid) | |
662 | { | |
663 | struct task_struct *p; | |
664 | ||
d359b549 | 665 | rcu_read_lock(); |
228ebcbe | 666 | p = find_task_by_vpid(pid); |
7a0ea09a MH |
667 | if (p) |
668 | get_task_struct(p); | |
a06381fe | 669 | |
d359b549 | 670 | rcu_read_unlock(); |
c87e2837 IM |
671 | |
672 | return p; | |
673 | } | |
674 | ||
675 | /* | |
676 | * This task is holding PI mutexes at exit time => bad. | |
677 | * Kernel cleans up PI-state, but userspace is likely hosed. | |
678 | * (Robust-futex cleanup is separate and might save the day for userspace.) | |
679 | */ | |
680 | void exit_pi_state_list(struct task_struct *curr) | |
681 | { | |
c87e2837 IM |
682 | struct list_head *next, *head = &curr->pi_state_list; |
683 | struct futex_pi_state *pi_state; | |
627371d7 | 684 | struct futex_hash_bucket *hb; |
38d47c1b | 685 | union futex_key key = FUTEX_KEY_INIT; |
c87e2837 | 686 | |
a0c1e907 TG |
687 | if (!futex_cmpxchg_enabled) |
688 | return; | |
c87e2837 IM |
689 | /* |
690 | * We are a ZOMBIE and nobody can enqueue itself on | |
691 | * pi_state_list anymore, but we have to be careful | |
627371d7 | 692 | * versus waiters unqueueing themselves: |
c87e2837 | 693 | */ |
1d615482 | 694 | raw_spin_lock_irq(&curr->pi_lock); |
c87e2837 IM |
695 | while (!list_empty(head)) { |
696 | ||
697 | next = head->next; | |
698 | pi_state = list_entry(next, struct futex_pi_state, list); | |
699 | key = pi_state->key; | |
627371d7 | 700 | hb = hash_futex(&key); |
1d615482 | 701 | raw_spin_unlock_irq(&curr->pi_lock); |
c87e2837 | 702 | |
c87e2837 IM |
703 | spin_lock(&hb->lock); |
704 | ||
1d615482 | 705 | raw_spin_lock_irq(&curr->pi_lock); |
627371d7 IM |
706 | /* |
707 | * We dropped the pi-lock, so re-check whether this | |
708 | * task still owns the PI-state: | |
709 | */ | |
c87e2837 IM |
710 | if (head->next != next) { |
711 | spin_unlock(&hb->lock); | |
712 | continue; | |
713 | } | |
714 | ||
c87e2837 | 715 | WARN_ON(pi_state->owner != curr); |
627371d7 IM |
716 | WARN_ON(list_empty(&pi_state->list)); |
717 | list_del_init(&pi_state->list); | |
c87e2837 | 718 | pi_state->owner = NULL; |
1d615482 | 719 | raw_spin_unlock_irq(&curr->pi_lock); |
c87e2837 IM |
720 | |
721 | rt_mutex_unlock(&pi_state->pi_mutex); | |
722 | ||
723 | spin_unlock(&hb->lock); | |
724 | ||
1d615482 | 725 | raw_spin_lock_irq(&curr->pi_lock); |
c87e2837 | 726 | } |
1d615482 | 727 | raw_spin_unlock_irq(&curr->pi_lock); |
c87e2837 IM |
728 | } |
729 | ||
730 | static int | |
d0aa7a70 PP |
731 | lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, |
732 | union futex_key *key, struct futex_pi_state **ps) | |
c87e2837 IM |
733 | { |
734 | struct futex_pi_state *pi_state = NULL; | |
735 | struct futex_q *this, *next; | |
c87e2837 | 736 | struct task_struct *p; |
778e9a9c | 737 | pid_t pid = uval & FUTEX_TID_MASK; |
c87e2837 | 738 | |
0d00c7b2 | 739 | plist_for_each_entry_safe(this, next, &hb->chain, list) { |
d0aa7a70 | 740 | if (match_futex(&this->key, key)) { |
c87e2837 IM |
741 | /* |
742 | * Another waiter already exists - bump up | |
743 | * the refcount and return its pi_state: | |
744 | */ | |
745 | pi_state = this->pi_state; | |
06a9ec29 | 746 | /* |
fb62db2b | 747 | * Userspace might have messed up non-PI and PI futexes |
06a9ec29 TG |
748 | */ |
749 | if (unlikely(!pi_state)) | |
750 | return -EINVAL; | |
751 | ||
627371d7 | 752 | WARN_ON(!atomic_read(&pi_state->refcount)); |
59647b6a TG |
753 | |
754 | /* | |
755 | * When pi_state->owner is NULL then the owner died | |
756 | * and another waiter is on the fly. pi_state->owner | |
757 | * is fixed up by the task which acquires | |
758 | * pi_state->rt_mutex. | |
759 | * | |
760 | * We do not check for pid == 0 which can happen when | |
761 | * the owner died and robust_list_exit() cleared the | |
762 | * TID. | |
763 | */ | |
764 | if (pid && pi_state->owner) { | |
765 | /* | |
766 | * Bail out if user space manipulated the | |
767 | * futex value. | |
768 | */ | |
769 | if (pid != task_pid_vnr(pi_state->owner)) | |
770 | return -EINVAL; | |
771 | } | |
627371d7 | 772 | |
c87e2837 | 773 | atomic_inc(&pi_state->refcount); |
d0aa7a70 | 774 | *ps = pi_state; |
c87e2837 IM |
775 | |
776 | return 0; | |
777 | } | |
778 | } | |
779 | ||
780 | /* | |
e3f2ddea | 781 | * We are the first waiter - try to look up the real owner and attach |
778e9a9c | 782 | * the new pi_state to it, but bail out when TID = 0 |
c87e2837 | 783 | */ |
778e9a9c | 784 | if (!pid) |
e3f2ddea | 785 | return -ESRCH; |
c87e2837 | 786 | p = futex_find_get_task(pid); |
7a0ea09a MH |
787 | if (!p) |
788 | return -ESRCH; | |
778e9a9c AK |
789 | |
790 | /* | |
791 | * We need to look at the task state flags to figure out, | |
792 | * whether the task is exiting. To protect against the do_exit | |
793 | * change of the task flags, we do this protected by | |
794 | * p->pi_lock: | |
795 | */ | |
1d615482 | 796 | raw_spin_lock_irq(&p->pi_lock); |
778e9a9c AK |
797 | if (unlikely(p->flags & PF_EXITING)) { |
798 | /* | |
799 | * The task is on the way out. When PF_EXITPIDONE is | |
800 | * set, we know that the task has finished the | |
801 | * cleanup: | |
802 | */ | |
803 | int ret = (p->flags & PF_EXITPIDONE) ? -ESRCH : -EAGAIN; | |
804 | ||
1d615482 | 805 | raw_spin_unlock_irq(&p->pi_lock); |
778e9a9c AK |
806 | put_task_struct(p); |
807 | return ret; | |
808 | } | |
c87e2837 IM |
809 | |
810 | pi_state = alloc_pi_state(); | |
811 | ||
812 | /* | |
813 | * Initialize the pi_mutex in locked state and make 'p' | |
814 | * the owner of it: | |
815 | */ | |
816 | rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p); | |
817 | ||
818 | /* Store the key for possible exit cleanups: */ | |
d0aa7a70 | 819 | pi_state->key = *key; |
c87e2837 | 820 | |
627371d7 | 821 | WARN_ON(!list_empty(&pi_state->list)); |
c87e2837 IM |
822 | list_add(&pi_state->list, &p->pi_state_list); |
823 | pi_state->owner = p; | |
1d615482 | 824 | raw_spin_unlock_irq(&p->pi_lock); |
c87e2837 IM |
825 | |
826 | put_task_struct(p); | |
827 | ||
d0aa7a70 | 828 | *ps = pi_state; |
c87e2837 IM |
829 | |
830 | return 0; | |
831 | } | |
832 | ||
1a52084d | 833 | /** |
d96ee56c | 834 | * futex_lock_pi_atomic() - Atomic work required to acquire a pi aware futex |
bab5bc9e DH |
835 | * @uaddr: the pi futex user address |
836 | * @hb: the pi futex hash bucket | |
837 | * @key: the futex key associated with uaddr and hb | |
838 | * @ps: the pi_state pointer where we store the result of the | |
839 | * lookup | |
840 | * @task: the task to perform the atomic lock work for. This will | |
841 | * be "current" except in the case of requeue pi. | |
842 | * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0) | |
1a52084d | 843 | * |
6c23cbbd RD |
844 | * Return: |
845 | * 0 - ready to wait; | |
846 | * 1 - acquired the lock; | |
1a52084d DH |
847 | * <0 - error |
848 | * | |
849 | * The hb->lock and futex_key refs shall be held by the caller. | |
850 | */ | |
851 | static int futex_lock_pi_atomic(u32 __user *uaddr, struct futex_hash_bucket *hb, | |
852 | union futex_key *key, | |
853 | struct futex_pi_state **ps, | |
bab5bc9e | 854 | struct task_struct *task, int set_waiters) |
1a52084d | 855 | { |
59fa6245 | 856 | int lock_taken, ret, force_take = 0; |
c0c9ed15 | 857 | u32 uval, newval, curval, vpid = task_pid_vnr(task); |
1a52084d DH |
858 | |
859 | retry: | |
860 | ret = lock_taken = 0; | |
861 | ||
862 | /* | |
863 | * To avoid races, we attempt to take the lock here again | |
864 | * (by doing a 0 -> TID atomic cmpxchg), while holding all | |
865 | * the locks. It will most likely not succeed. | |
866 | */ | |
c0c9ed15 | 867 | newval = vpid; |
bab5bc9e DH |
868 | if (set_waiters) |
869 | newval |= FUTEX_WAITERS; | |
1a52084d | 870 | |
37a9d912 | 871 | if (unlikely(cmpxchg_futex_value_locked(&curval, uaddr, 0, newval))) |
1a52084d DH |
872 | return -EFAULT; |
873 | ||
874 | /* | |
875 | * Detect deadlocks. | |
876 | */ | |
c0c9ed15 | 877 | if ((unlikely((curval & FUTEX_TID_MASK) == vpid))) |
1a52084d DH |
878 | return -EDEADLK; |
879 | ||
880 | /* | |
881 | * Surprise - we got the lock. Just return to userspace: | |
882 | */ | |
883 | if (unlikely(!curval)) | |
884 | return 1; | |
885 | ||
886 | uval = curval; | |
887 | ||
888 | /* | |
889 | * Set the FUTEX_WAITERS flag, so the owner will know it has someone | |
890 | * to wake at the next unlock. | |
891 | */ | |
892 | newval = curval | FUTEX_WAITERS; | |
893 | ||
894 | /* | |
59fa6245 | 895 | * Should we force take the futex? See below. |
1a52084d | 896 | */ |
59fa6245 TG |
897 | if (unlikely(force_take)) { |
898 | /* | |
899 | * Keep the OWNER_DIED and the WAITERS bit and set the | |
900 | * new TID value. | |
901 | */ | |
c0c9ed15 | 902 | newval = (curval & ~FUTEX_TID_MASK) | vpid; |
59fa6245 | 903 | force_take = 0; |
1a52084d DH |
904 | lock_taken = 1; |
905 | } | |
906 | ||
37a9d912 | 907 | if (unlikely(cmpxchg_futex_value_locked(&curval, uaddr, uval, newval))) |
1a52084d DH |
908 | return -EFAULT; |
909 | if (unlikely(curval != uval)) | |
910 | goto retry; | |
911 | ||
912 | /* | |
59fa6245 | 913 | * We took the lock due to forced take over. |
1a52084d DH |
914 | */ |
915 | if (unlikely(lock_taken)) | |
916 | return 1; | |
917 | ||
918 | /* | |
919 | * We dont have the lock. Look up the PI state (or create it if | |
920 | * we are the first waiter): | |
921 | */ | |
922 | ret = lookup_pi_state(uval, hb, key, ps); | |
923 | ||
924 | if (unlikely(ret)) { | |
925 | switch (ret) { | |
926 | case -ESRCH: | |
927 | /* | |
59fa6245 TG |
928 | * We failed to find an owner for this |
929 | * futex. So we have no pi_state to block | |
930 | * on. This can happen in two cases: | |
931 | * | |
932 | * 1) The owner died | |
933 | * 2) A stale FUTEX_WAITERS bit | |
934 | * | |
935 | * Re-read the futex value. | |
1a52084d DH |
936 | */ |
937 | if (get_futex_value_locked(&curval, uaddr)) | |
938 | return -EFAULT; | |
939 | ||
940 | /* | |
59fa6245 TG |
941 | * If the owner died or we have a stale |
942 | * WAITERS bit the owner TID in the user space | |
943 | * futex is 0. | |
1a52084d | 944 | */ |
59fa6245 TG |
945 | if (!(curval & FUTEX_TID_MASK)) { |
946 | force_take = 1; | |
1a52084d DH |
947 | goto retry; |
948 | } | |
949 | default: | |
950 | break; | |
951 | } | |
952 | } | |
953 | ||
954 | return ret; | |
955 | } | |
956 | ||
2e12978a LJ |
957 | /** |
958 | * __unqueue_futex() - Remove the futex_q from its futex_hash_bucket | |
959 | * @q: The futex_q to unqueue | |
960 | * | |
961 | * The q->lock_ptr must not be NULL and must be held by the caller. | |
962 | */ | |
963 | static void __unqueue_futex(struct futex_q *q) | |
964 | { | |
965 | struct futex_hash_bucket *hb; | |
966 | ||
29096202 SR |
967 | if (WARN_ON_SMP(!q->lock_ptr || !spin_is_locked(q->lock_ptr)) |
968 | || WARN_ON(plist_node_empty(&q->list))) | |
2e12978a LJ |
969 | return; |
970 | ||
971 | hb = container_of(q->lock_ptr, struct futex_hash_bucket, lock); | |
972 | plist_del(&q->list, &hb->chain); | |
11d4616b | 973 | hb_waiters_dec(hb); |
2e12978a LJ |
974 | } |
975 | ||
1da177e4 LT |
976 | /* |
977 | * The hash bucket lock must be held when this is called. | |
978 | * Afterwards, the futex_q must not be accessed. | |
979 | */ | |
980 | static void wake_futex(struct futex_q *q) | |
981 | { | |
f1a11e05 TG |
982 | struct task_struct *p = q->task; |
983 | ||
aa10990e DH |
984 | if (WARN(q->pi_state || q->rt_waiter, "refusing to wake PI futex\n")) |
985 | return; | |
986 | ||
1da177e4 | 987 | /* |
f1a11e05 | 988 | * We set q->lock_ptr = NULL _before_ we wake up the task. If |
fb62db2b RD |
989 | * a non-futex wake up happens on another CPU then the task |
990 | * might exit and p would dereference a non-existing task | |
f1a11e05 TG |
991 | * struct. Prevent this by holding a reference on p across the |
992 | * wake up. | |
1da177e4 | 993 | */ |
f1a11e05 TG |
994 | get_task_struct(p); |
995 | ||
2e12978a | 996 | __unqueue_futex(q); |
1da177e4 | 997 | /* |
f1a11e05 TG |
998 | * The waiting task can free the futex_q as soon as |
999 | * q->lock_ptr = NULL is written, without taking any locks. A | |
1000 | * memory barrier is required here to prevent the following | |
1001 | * store to lock_ptr from getting ahead of the plist_del. | |
1da177e4 | 1002 | */ |
ccdea2f8 | 1003 | smp_wmb(); |
1da177e4 | 1004 | q->lock_ptr = NULL; |
f1a11e05 TG |
1005 | |
1006 | wake_up_state(p, TASK_NORMAL); | |
1007 | put_task_struct(p); | |
1da177e4 LT |
1008 | } |
1009 | ||
c87e2837 IM |
1010 | static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this) |
1011 | { | |
1012 | struct task_struct *new_owner; | |
1013 | struct futex_pi_state *pi_state = this->pi_state; | |
7cfdaf38 | 1014 | u32 uninitialized_var(curval), newval; |
c87e2837 IM |
1015 | |
1016 | if (!pi_state) | |
1017 | return -EINVAL; | |
1018 | ||
51246bfd TG |
1019 | /* |
1020 | * If current does not own the pi_state then the futex is | |
1021 | * inconsistent and user space fiddled with the futex value. | |
1022 | */ | |
1023 | if (pi_state->owner != current) | |
1024 | return -EINVAL; | |
1025 | ||
d209d74d | 1026 | raw_spin_lock(&pi_state->pi_mutex.wait_lock); |
c87e2837 IM |
1027 | new_owner = rt_mutex_next_owner(&pi_state->pi_mutex); |
1028 | ||
1029 | /* | |
f123c98e SR |
1030 | * It is possible that the next waiter (the one that brought |
1031 | * this owner to the kernel) timed out and is no longer | |
1032 | * waiting on the lock. | |
c87e2837 IM |
1033 | */ |
1034 | if (!new_owner) | |
1035 | new_owner = this->task; | |
1036 | ||
1037 | /* | |
1038 | * We pass it to the next owner. (The WAITERS bit is always | |
1039 | * kept enabled while there is PI state around. We must also | |
1040 | * preserve the owner died bit.) | |
1041 | */ | |
e3f2ddea | 1042 | if (!(uval & FUTEX_OWNER_DIED)) { |
778e9a9c AK |
1043 | int ret = 0; |
1044 | ||
b488893a | 1045 | newval = FUTEX_WAITERS | task_pid_vnr(new_owner); |
e3f2ddea | 1046 | |
37a9d912 | 1047 | if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval)) |
778e9a9c | 1048 | ret = -EFAULT; |
cde898fa | 1049 | else if (curval != uval) |
778e9a9c AK |
1050 | ret = -EINVAL; |
1051 | if (ret) { | |
d209d74d | 1052 | raw_spin_unlock(&pi_state->pi_mutex.wait_lock); |
778e9a9c AK |
1053 | return ret; |
1054 | } | |
e3f2ddea | 1055 | } |
c87e2837 | 1056 | |
1d615482 | 1057 | raw_spin_lock_irq(&pi_state->owner->pi_lock); |
627371d7 IM |
1058 | WARN_ON(list_empty(&pi_state->list)); |
1059 | list_del_init(&pi_state->list); | |
1d615482 | 1060 | raw_spin_unlock_irq(&pi_state->owner->pi_lock); |
627371d7 | 1061 | |
1d615482 | 1062 | raw_spin_lock_irq(&new_owner->pi_lock); |
627371d7 | 1063 | WARN_ON(!list_empty(&pi_state->list)); |
c87e2837 IM |
1064 | list_add(&pi_state->list, &new_owner->pi_state_list); |
1065 | pi_state->owner = new_owner; | |
1d615482 | 1066 | raw_spin_unlock_irq(&new_owner->pi_lock); |
627371d7 | 1067 | |
d209d74d | 1068 | raw_spin_unlock(&pi_state->pi_mutex.wait_lock); |
c87e2837 IM |
1069 | rt_mutex_unlock(&pi_state->pi_mutex); |
1070 | ||
1071 | return 0; | |
1072 | } | |
1073 | ||
1074 | static int unlock_futex_pi(u32 __user *uaddr, u32 uval) | |
1075 | { | |
7cfdaf38 | 1076 | u32 uninitialized_var(oldval); |
c87e2837 IM |
1077 | |
1078 | /* | |
1079 | * There is no waiter, so we unlock the futex. The owner died | |
1080 | * bit has not to be preserved here. We are the owner: | |
1081 | */ | |
37a9d912 ML |
1082 | if (cmpxchg_futex_value_locked(&oldval, uaddr, uval, 0)) |
1083 | return -EFAULT; | |
c87e2837 IM |
1084 | if (oldval != uval) |
1085 | return -EAGAIN; | |
1086 | ||
1087 | return 0; | |
1088 | } | |
1089 | ||
8b8f319f IM |
1090 | /* |
1091 | * Express the locking dependencies for lockdep: | |
1092 | */ | |
1093 | static inline void | |
1094 | double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) | |
1095 | { | |
1096 | if (hb1 <= hb2) { | |
1097 | spin_lock(&hb1->lock); | |
1098 | if (hb1 < hb2) | |
1099 | spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING); | |
1100 | } else { /* hb1 > hb2 */ | |
1101 | spin_lock(&hb2->lock); | |
1102 | spin_lock_nested(&hb1->lock, SINGLE_DEPTH_NESTING); | |
1103 | } | |
1104 | } | |
1105 | ||
5eb3dc62 DH |
1106 | static inline void |
1107 | double_unlock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) | |
1108 | { | |
f061d351 | 1109 | spin_unlock(&hb1->lock); |
88f502fe IM |
1110 | if (hb1 != hb2) |
1111 | spin_unlock(&hb2->lock); | |
5eb3dc62 DH |
1112 | } |
1113 | ||
1da177e4 | 1114 | /* |
b2d0994b | 1115 | * Wake up waiters matching bitset queued on this futex (uaddr). |
1da177e4 | 1116 | */ |
b41277dc DH |
1117 | static int |
1118 | futex_wake(u32 __user *uaddr, unsigned int flags, int nr_wake, u32 bitset) | |
1da177e4 | 1119 | { |
e2970f2f | 1120 | struct futex_hash_bucket *hb; |
1da177e4 | 1121 | struct futex_q *this, *next; |
38d47c1b | 1122 | union futex_key key = FUTEX_KEY_INIT; |
1da177e4 LT |
1123 | int ret; |
1124 | ||
cd689985 TG |
1125 | if (!bitset) |
1126 | return -EINVAL; | |
1127 | ||
9ea71503 | 1128 | ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key, VERIFY_READ); |
1da177e4 LT |
1129 | if (unlikely(ret != 0)) |
1130 | goto out; | |
1131 | ||
e2970f2f | 1132 | hb = hash_futex(&key); |
b0c29f79 DB |
1133 | |
1134 | /* Make sure we really have tasks to wakeup */ | |
1135 | if (!hb_waiters_pending(hb)) | |
1136 | goto out_put_key; | |
1137 | ||
e2970f2f | 1138 | spin_lock(&hb->lock); |
1da177e4 | 1139 | |
0d00c7b2 | 1140 | plist_for_each_entry_safe(this, next, &hb->chain, list) { |
1da177e4 | 1141 | if (match_futex (&this->key, &key)) { |
52400ba9 | 1142 | if (this->pi_state || this->rt_waiter) { |
ed6f7b10 IM |
1143 | ret = -EINVAL; |
1144 | break; | |
1145 | } | |
cd689985 TG |
1146 | |
1147 | /* Check if one of the bits is set in both bitsets */ | |
1148 | if (!(this->bitset & bitset)) | |
1149 | continue; | |
1150 | ||
1da177e4 LT |
1151 | wake_futex(this); |
1152 | if (++ret >= nr_wake) | |
1153 | break; | |
1154 | } | |
1155 | } | |
1156 | ||
e2970f2f | 1157 | spin_unlock(&hb->lock); |
b0c29f79 | 1158 | out_put_key: |
ae791a2d | 1159 | put_futex_key(&key); |
42d35d48 | 1160 | out: |
1da177e4 LT |
1161 | return ret; |
1162 | } | |
1163 | ||
4732efbe JJ |
1164 | /* |
1165 | * Wake up all waiters hashed on the physical page that is mapped | |
1166 | * to this virtual address: | |
1167 | */ | |
e2970f2f | 1168 | static int |
b41277dc | 1169 | futex_wake_op(u32 __user *uaddr1, unsigned int flags, u32 __user *uaddr2, |
e2970f2f | 1170 | int nr_wake, int nr_wake2, int op) |
4732efbe | 1171 | { |
38d47c1b | 1172 | union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT; |
e2970f2f | 1173 | struct futex_hash_bucket *hb1, *hb2; |
4732efbe | 1174 | struct futex_q *this, *next; |
e4dc5b7a | 1175 | int ret, op_ret; |
4732efbe | 1176 | |
e4dc5b7a | 1177 | retry: |
9ea71503 | 1178 | ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1, VERIFY_READ); |
4732efbe JJ |
1179 | if (unlikely(ret != 0)) |
1180 | goto out; | |
9ea71503 | 1181 | ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, VERIFY_WRITE); |
4732efbe | 1182 | if (unlikely(ret != 0)) |
42d35d48 | 1183 | goto out_put_key1; |
4732efbe | 1184 | |
e2970f2f IM |
1185 | hb1 = hash_futex(&key1); |
1186 | hb2 = hash_futex(&key2); | |
4732efbe | 1187 | |
e4dc5b7a | 1188 | retry_private: |
eaaea803 | 1189 | double_lock_hb(hb1, hb2); |
e2970f2f | 1190 | op_ret = futex_atomic_op_inuser(op, uaddr2); |
4732efbe | 1191 | if (unlikely(op_ret < 0)) { |
4732efbe | 1192 | |
5eb3dc62 | 1193 | double_unlock_hb(hb1, hb2); |
4732efbe | 1194 | |
7ee1dd3f | 1195 | #ifndef CONFIG_MMU |
e2970f2f IM |
1196 | /* |
1197 | * we don't get EFAULT from MMU faults if we don't have an MMU, | |
1198 | * but we might get them from range checking | |
1199 | */ | |
7ee1dd3f | 1200 | ret = op_ret; |
42d35d48 | 1201 | goto out_put_keys; |
7ee1dd3f DH |
1202 | #endif |
1203 | ||
796f8d9b DG |
1204 | if (unlikely(op_ret != -EFAULT)) { |
1205 | ret = op_ret; | |
42d35d48 | 1206 | goto out_put_keys; |
796f8d9b DG |
1207 | } |
1208 | ||
d0725992 | 1209 | ret = fault_in_user_writeable(uaddr2); |
4732efbe | 1210 | if (ret) |
de87fcc1 | 1211 | goto out_put_keys; |
4732efbe | 1212 | |
b41277dc | 1213 | if (!(flags & FLAGS_SHARED)) |
e4dc5b7a DH |
1214 | goto retry_private; |
1215 | ||
ae791a2d TG |
1216 | put_futex_key(&key2); |
1217 | put_futex_key(&key1); | |
e4dc5b7a | 1218 | goto retry; |
4732efbe JJ |
1219 | } |
1220 | ||
0d00c7b2 | 1221 | plist_for_each_entry_safe(this, next, &hb1->chain, list) { |
4732efbe | 1222 | if (match_futex (&this->key, &key1)) { |
aa10990e DH |
1223 | if (this->pi_state || this->rt_waiter) { |
1224 | ret = -EINVAL; | |
1225 | goto out_unlock; | |
1226 | } | |
4732efbe JJ |
1227 | wake_futex(this); |
1228 | if (++ret >= nr_wake) | |
1229 | break; | |
1230 | } | |
1231 | } | |
1232 | ||
1233 | if (op_ret > 0) { | |
4732efbe | 1234 | op_ret = 0; |
0d00c7b2 | 1235 | plist_for_each_entry_safe(this, next, &hb2->chain, list) { |
4732efbe | 1236 | if (match_futex (&this->key, &key2)) { |
aa10990e DH |
1237 | if (this->pi_state || this->rt_waiter) { |
1238 | ret = -EINVAL; | |
1239 | goto out_unlock; | |
1240 | } | |
4732efbe JJ |
1241 | wake_futex(this); |
1242 | if (++op_ret >= nr_wake2) | |
1243 | break; | |
1244 | } | |
1245 | } | |
1246 | ret += op_ret; | |
1247 | } | |
1248 | ||
aa10990e | 1249 | out_unlock: |
5eb3dc62 | 1250 | double_unlock_hb(hb1, hb2); |
42d35d48 | 1251 | out_put_keys: |
ae791a2d | 1252 | put_futex_key(&key2); |
42d35d48 | 1253 | out_put_key1: |
ae791a2d | 1254 | put_futex_key(&key1); |
42d35d48 | 1255 | out: |
4732efbe JJ |
1256 | return ret; |
1257 | } | |
1258 | ||
9121e478 DH |
1259 | /** |
1260 | * requeue_futex() - Requeue a futex_q from one hb to another | |
1261 | * @q: the futex_q to requeue | |
1262 | * @hb1: the source hash_bucket | |
1263 | * @hb2: the target hash_bucket | |
1264 | * @key2: the new key for the requeued futex_q | |
1265 | */ | |
1266 | static inline | |
1267 | void requeue_futex(struct futex_q *q, struct futex_hash_bucket *hb1, | |
1268 | struct futex_hash_bucket *hb2, union futex_key *key2) | |
1269 | { | |
1270 | ||
1271 | /* | |
1272 | * If key1 and key2 hash to the same bucket, no need to | |
1273 | * requeue. | |
1274 | */ | |
1275 | if (likely(&hb1->chain != &hb2->chain)) { | |
1276 | plist_del(&q->list, &hb1->chain); | |
11d4616b | 1277 | hb_waiters_dec(hb1); |
9121e478 | 1278 | plist_add(&q->list, &hb2->chain); |
11d4616b | 1279 | hb_waiters_inc(hb2); |
9121e478 | 1280 | q->lock_ptr = &hb2->lock; |
9121e478 DH |
1281 | } |
1282 | get_futex_key_refs(key2); | |
1283 | q->key = *key2; | |
1284 | } | |
1285 | ||
52400ba9 DH |
1286 | /** |
1287 | * requeue_pi_wake_futex() - Wake a task that acquired the lock during requeue | |
d96ee56c DH |
1288 | * @q: the futex_q |
1289 | * @key: the key of the requeue target futex | |
1290 | * @hb: the hash_bucket of the requeue target futex | |
52400ba9 DH |
1291 | * |
1292 | * During futex_requeue, with requeue_pi=1, it is possible to acquire the | |
1293 | * target futex if it is uncontended or via a lock steal. Set the futex_q key | |
1294 | * to the requeue target futex so the waiter can detect the wakeup on the right | |
1295 | * futex, but remove it from the hb and NULL the rt_waiter so it can detect | |
beda2c7e DH |
1296 | * atomic lock acquisition. Set the q->lock_ptr to the requeue target hb->lock |
1297 | * to protect access to the pi_state to fixup the owner later. Must be called | |
1298 | * with both q->lock_ptr and hb->lock held. | |
52400ba9 DH |
1299 | */ |
1300 | static inline | |
beda2c7e DH |
1301 | void requeue_pi_wake_futex(struct futex_q *q, union futex_key *key, |
1302 | struct futex_hash_bucket *hb) | |
52400ba9 | 1303 | { |
52400ba9 DH |
1304 | get_futex_key_refs(key); |
1305 | q->key = *key; | |
1306 | ||
2e12978a | 1307 | __unqueue_futex(q); |
52400ba9 DH |
1308 | |
1309 | WARN_ON(!q->rt_waiter); | |
1310 | q->rt_waiter = NULL; | |
1311 | ||
beda2c7e | 1312 | q->lock_ptr = &hb->lock; |
beda2c7e | 1313 | |
f1a11e05 | 1314 | wake_up_state(q->task, TASK_NORMAL); |
52400ba9 DH |
1315 | } |
1316 | ||
1317 | /** | |
1318 | * futex_proxy_trylock_atomic() - Attempt an atomic lock for the top waiter | |
bab5bc9e DH |
1319 | * @pifutex: the user address of the to futex |
1320 | * @hb1: the from futex hash bucket, must be locked by the caller | |
1321 | * @hb2: the to futex hash bucket, must be locked by the caller | |
1322 | * @key1: the from futex key | |
1323 | * @key2: the to futex key | |
1324 | * @ps: address to store the pi_state pointer | |
1325 | * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0) | |
52400ba9 DH |
1326 | * |
1327 | * Try and get the lock on behalf of the top waiter if we can do it atomically. | |
bab5bc9e DH |
1328 | * Wake the top waiter if we succeed. If the caller specified set_waiters, |
1329 | * then direct futex_lock_pi_atomic() to force setting the FUTEX_WAITERS bit. | |
1330 | * hb1 and hb2 must be held by the caller. | |
52400ba9 | 1331 | * |
6c23cbbd RD |
1332 | * Return: |
1333 | * 0 - failed to acquire the lock atomically; | |
1334 | * 1 - acquired the lock; | |
52400ba9 DH |
1335 | * <0 - error |
1336 | */ | |
1337 | static int futex_proxy_trylock_atomic(u32 __user *pifutex, | |
1338 | struct futex_hash_bucket *hb1, | |
1339 | struct futex_hash_bucket *hb2, | |
1340 | union futex_key *key1, union futex_key *key2, | |
bab5bc9e | 1341 | struct futex_pi_state **ps, int set_waiters) |
52400ba9 | 1342 | { |
bab5bc9e | 1343 | struct futex_q *top_waiter = NULL; |
52400ba9 DH |
1344 | u32 curval; |
1345 | int ret; | |
1346 | ||
1347 | if (get_futex_value_locked(&curval, pifutex)) | |
1348 | return -EFAULT; | |
1349 | ||
bab5bc9e DH |
1350 | /* |
1351 | * Find the top_waiter and determine if there are additional waiters. | |
1352 | * If the caller intends to requeue more than 1 waiter to pifutex, | |
1353 | * force futex_lock_pi_atomic() to set the FUTEX_WAITERS bit now, | |
1354 | * as we have means to handle the possible fault. If not, don't set | |
1355 | * the bit unecessarily as it will force the subsequent unlock to enter | |
1356 | * the kernel. | |
1357 | */ | |
52400ba9 DH |
1358 | top_waiter = futex_top_waiter(hb1, key1); |
1359 | ||
1360 | /* There are no waiters, nothing for us to do. */ | |
1361 | if (!top_waiter) | |
1362 | return 0; | |
1363 | ||
84bc4af5 DH |
1364 | /* Ensure we requeue to the expected futex. */ |
1365 | if (!match_futex(top_waiter->requeue_pi_key, key2)) | |
1366 | return -EINVAL; | |
1367 | ||
52400ba9 | 1368 | /* |
bab5bc9e DH |
1369 | * Try to take the lock for top_waiter. Set the FUTEX_WAITERS bit in |
1370 | * the contended case or if set_waiters is 1. The pi_state is returned | |
1371 | * in ps in contended cases. | |
52400ba9 | 1372 | */ |
bab5bc9e DH |
1373 | ret = futex_lock_pi_atomic(pifutex, hb2, key2, ps, top_waiter->task, |
1374 | set_waiters); | |
52400ba9 | 1375 | if (ret == 1) |
beda2c7e | 1376 | requeue_pi_wake_futex(top_waiter, key2, hb2); |
52400ba9 DH |
1377 | |
1378 | return ret; | |
1379 | } | |
1380 | ||
1381 | /** | |
1382 | * futex_requeue() - Requeue waiters from uaddr1 to uaddr2 | |
fb62db2b | 1383 | * @uaddr1: source futex user address |
b41277dc | 1384 | * @flags: futex flags (FLAGS_SHARED, etc.) |
fb62db2b RD |
1385 | * @uaddr2: target futex user address |
1386 | * @nr_wake: number of waiters to wake (must be 1 for requeue_pi) | |
1387 | * @nr_requeue: number of waiters to requeue (0-INT_MAX) | |
1388 | * @cmpval: @uaddr1 expected value (or %NULL) | |
1389 | * @requeue_pi: if we are attempting to requeue from a non-pi futex to a | |
b41277dc | 1390 | * pi futex (pi to pi requeue is not supported) |
52400ba9 DH |
1391 | * |
1392 | * Requeue waiters on uaddr1 to uaddr2. In the requeue_pi case, try to acquire | |
1393 | * uaddr2 atomically on behalf of the top waiter. | |
1394 | * | |
6c23cbbd RD |
1395 | * Return: |
1396 | * >=0 - on success, the number of tasks requeued or woken; | |
52400ba9 | 1397 | * <0 - on error |
1da177e4 | 1398 | */ |
b41277dc DH |
1399 | static int futex_requeue(u32 __user *uaddr1, unsigned int flags, |
1400 | u32 __user *uaddr2, int nr_wake, int nr_requeue, | |
1401 | u32 *cmpval, int requeue_pi) | |
1da177e4 | 1402 | { |
38d47c1b | 1403 | union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT; |
52400ba9 DH |
1404 | int drop_count = 0, task_count = 0, ret; |
1405 | struct futex_pi_state *pi_state = NULL; | |
e2970f2f | 1406 | struct futex_hash_bucket *hb1, *hb2; |
1da177e4 | 1407 | struct futex_q *this, *next; |
52400ba9 DH |
1408 | u32 curval2; |
1409 | ||
1410 | if (requeue_pi) { | |
1411 | /* | |
1412 | * requeue_pi requires a pi_state, try to allocate it now | |
1413 | * without any locks in case it fails. | |
1414 | */ | |
1415 | if (refill_pi_state_cache()) | |
1416 | return -ENOMEM; | |
1417 | /* | |
1418 | * requeue_pi must wake as many tasks as it can, up to nr_wake | |
1419 | * + nr_requeue, since it acquires the rt_mutex prior to | |
1420 | * returning to userspace, so as to not leave the rt_mutex with | |
1421 | * waiters and no owner. However, second and third wake-ups | |
1422 | * cannot be predicted as they involve race conditions with the | |
1423 | * first wake and a fault while looking up the pi_state. Both | |
1424 | * pthread_cond_signal() and pthread_cond_broadcast() should | |
1425 | * use nr_wake=1. | |
1426 | */ | |
1427 | if (nr_wake != 1) | |
1428 | return -EINVAL; | |
1429 | } | |
1da177e4 | 1430 | |
42d35d48 | 1431 | retry: |
52400ba9 DH |
1432 | if (pi_state != NULL) { |
1433 | /* | |
1434 | * We will have to lookup the pi_state again, so free this one | |
1435 | * to keep the accounting correct. | |
1436 | */ | |
1437 | free_pi_state(pi_state); | |
1438 | pi_state = NULL; | |
1439 | } | |
1440 | ||
9ea71503 | 1441 | ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1, VERIFY_READ); |
1da177e4 LT |
1442 | if (unlikely(ret != 0)) |
1443 | goto out; | |
9ea71503 SB |
1444 | ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, |
1445 | requeue_pi ? VERIFY_WRITE : VERIFY_READ); | |
1da177e4 | 1446 | if (unlikely(ret != 0)) |
42d35d48 | 1447 | goto out_put_key1; |
1da177e4 | 1448 | |
e2970f2f IM |
1449 | hb1 = hash_futex(&key1); |
1450 | hb2 = hash_futex(&key2); | |
1da177e4 | 1451 | |
e4dc5b7a | 1452 | retry_private: |
8b8f319f | 1453 | double_lock_hb(hb1, hb2); |
1da177e4 | 1454 | |
e2970f2f IM |
1455 | if (likely(cmpval != NULL)) { |
1456 | u32 curval; | |
1da177e4 | 1457 | |
e2970f2f | 1458 | ret = get_futex_value_locked(&curval, uaddr1); |
1da177e4 LT |
1459 | |
1460 | if (unlikely(ret)) { | |
5eb3dc62 | 1461 | double_unlock_hb(hb1, hb2); |
1da177e4 | 1462 | |
e2970f2f | 1463 | ret = get_user(curval, uaddr1); |
e4dc5b7a DH |
1464 | if (ret) |
1465 | goto out_put_keys; | |
1da177e4 | 1466 | |
b41277dc | 1467 | if (!(flags & FLAGS_SHARED)) |
e4dc5b7a | 1468 | goto retry_private; |
1da177e4 | 1469 | |
ae791a2d TG |
1470 | put_futex_key(&key2); |
1471 | put_futex_key(&key1); | |
e4dc5b7a | 1472 | goto retry; |
1da177e4 | 1473 | } |
e2970f2f | 1474 | if (curval != *cmpval) { |
1da177e4 LT |
1475 | ret = -EAGAIN; |
1476 | goto out_unlock; | |
1477 | } | |
1478 | } | |
1479 | ||
52400ba9 | 1480 | if (requeue_pi && (task_count - nr_wake < nr_requeue)) { |
bab5bc9e DH |
1481 | /* |
1482 | * Attempt to acquire uaddr2 and wake the top waiter. If we | |
1483 | * intend to requeue waiters, force setting the FUTEX_WAITERS | |
1484 | * bit. We force this here where we are able to easily handle | |
1485 | * faults rather in the requeue loop below. | |
1486 | */ | |
52400ba9 | 1487 | ret = futex_proxy_trylock_atomic(uaddr2, hb1, hb2, &key1, |
bab5bc9e | 1488 | &key2, &pi_state, nr_requeue); |
52400ba9 DH |
1489 | |
1490 | /* | |
1491 | * At this point the top_waiter has either taken uaddr2 or is | |
1492 | * waiting on it. If the former, then the pi_state will not | |
1493 | * exist yet, look it up one more time to ensure we have a | |
1494 | * reference to it. | |
1495 | */ | |
1496 | if (ret == 1) { | |
1497 | WARN_ON(pi_state); | |
89061d3d | 1498 | drop_count++; |
52400ba9 DH |
1499 | task_count++; |
1500 | ret = get_futex_value_locked(&curval2, uaddr2); | |
1501 | if (!ret) | |
1502 | ret = lookup_pi_state(curval2, hb2, &key2, | |
1503 | &pi_state); | |
1504 | } | |
1505 | ||
1506 | switch (ret) { | |
1507 | case 0: | |
1508 | break; | |
1509 | case -EFAULT: | |
1510 | double_unlock_hb(hb1, hb2); | |
ae791a2d TG |
1511 | put_futex_key(&key2); |
1512 | put_futex_key(&key1); | |
d0725992 | 1513 | ret = fault_in_user_writeable(uaddr2); |
52400ba9 DH |
1514 | if (!ret) |
1515 | goto retry; | |
1516 | goto out; | |
1517 | case -EAGAIN: | |
1518 | /* The owner was exiting, try again. */ | |
1519 | double_unlock_hb(hb1, hb2); | |
ae791a2d TG |
1520 | put_futex_key(&key2); |
1521 | put_futex_key(&key1); | |
52400ba9 DH |
1522 | cond_resched(); |
1523 | goto retry; | |
1524 | default: | |
1525 | goto out_unlock; | |
1526 | } | |
1527 | } | |
1528 | ||
0d00c7b2 | 1529 | plist_for_each_entry_safe(this, next, &hb1->chain, list) { |
52400ba9 DH |
1530 | if (task_count - nr_wake >= nr_requeue) |
1531 | break; | |
1532 | ||
1533 | if (!match_futex(&this->key, &key1)) | |
1da177e4 | 1534 | continue; |
52400ba9 | 1535 | |
392741e0 DH |
1536 | /* |
1537 | * FUTEX_WAIT_REQEUE_PI and FUTEX_CMP_REQUEUE_PI should always | |
1538 | * be paired with each other and no other futex ops. | |
aa10990e DH |
1539 | * |
1540 | * We should never be requeueing a futex_q with a pi_state, | |
1541 | * which is awaiting a futex_unlock_pi(). | |
392741e0 DH |
1542 | */ |
1543 | if ((requeue_pi && !this->rt_waiter) || | |
aa10990e DH |
1544 | (!requeue_pi && this->rt_waiter) || |
1545 | this->pi_state) { | |
392741e0 DH |
1546 | ret = -EINVAL; |
1547 | break; | |
1548 | } | |
52400ba9 DH |
1549 | |
1550 | /* | |
1551 | * Wake nr_wake waiters. For requeue_pi, if we acquired the | |
1552 | * lock, we already woke the top_waiter. If not, it will be | |
1553 | * woken by futex_unlock_pi(). | |
1554 | */ | |
1555 | if (++task_count <= nr_wake && !requeue_pi) { | |
1da177e4 | 1556 | wake_futex(this); |
52400ba9 DH |
1557 | continue; |
1558 | } | |
1da177e4 | 1559 | |
84bc4af5 DH |
1560 | /* Ensure we requeue to the expected futex for requeue_pi. */ |
1561 | if (requeue_pi && !match_futex(this->requeue_pi_key, &key2)) { | |
1562 | ret = -EINVAL; | |
1563 | break; | |
1564 | } | |
1565 | ||
52400ba9 DH |
1566 | /* |
1567 | * Requeue nr_requeue waiters and possibly one more in the case | |
1568 | * of requeue_pi if we couldn't acquire the lock atomically. | |
1569 | */ | |
1570 | if (requeue_pi) { | |
1571 | /* Prepare the waiter to take the rt_mutex. */ | |
1572 | atomic_inc(&pi_state->refcount); | |
1573 | this->pi_state = pi_state; | |
1574 | ret = rt_mutex_start_proxy_lock(&pi_state->pi_mutex, | |
1575 | this->rt_waiter, | |
1576 | this->task, 1); | |
1577 | if (ret == 1) { | |
1578 | /* We got the lock. */ | |
beda2c7e | 1579 | requeue_pi_wake_futex(this, &key2, hb2); |
89061d3d | 1580 | drop_count++; |
52400ba9 DH |
1581 | continue; |
1582 | } else if (ret) { | |
1583 | /* -EDEADLK */ | |
1584 | this->pi_state = NULL; | |
1585 | free_pi_state(pi_state); | |
1586 | goto out_unlock; | |
1587 | } | |
1da177e4 | 1588 | } |
52400ba9 DH |
1589 | requeue_futex(this, hb1, hb2, &key2); |
1590 | drop_count++; | |
1da177e4 LT |
1591 | } |
1592 | ||
1593 | out_unlock: | |
5eb3dc62 | 1594 | double_unlock_hb(hb1, hb2); |
1da177e4 | 1595 | |
cd84a42f DH |
1596 | /* |
1597 | * drop_futex_key_refs() must be called outside the spinlocks. During | |
1598 | * the requeue we moved futex_q's from the hash bucket at key1 to the | |
1599 | * one at key2 and updated their key pointer. We no longer need to | |
1600 | * hold the references to key1. | |
1601 | */ | |
1da177e4 | 1602 | while (--drop_count >= 0) |
9adef58b | 1603 | drop_futex_key_refs(&key1); |
1da177e4 | 1604 | |
42d35d48 | 1605 | out_put_keys: |
ae791a2d | 1606 | put_futex_key(&key2); |
42d35d48 | 1607 | out_put_key1: |
ae791a2d | 1608 | put_futex_key(&key1); |
42d35d48 | 1609 | out: |
52400ba9 DH |
1610 | if (pi_state != NULL) |
1611 | free_pi_state(pi_state); | |
1612 | return ret ? ret : task_count; | |
1da177e4 LT |
1613 | } |
1614 | ||
1615 | /* The key must be already stored in q->key. */ | |
82af7aca | 1616 | static inline struct futex_hash_bucket *queue_lock(struct futex_q *q) |
15e408cd | 1617 | __acquires(&hb->lock) |
1da177e4 | 1618 | { |
e2970f2f | 1619 | struct futex_hash_bucket *hb; |
1da177e4 | 1620 | |
e2970f2f | 1621 | hb = hash_futex(&q->key); |
11d4616b LT |
1622 | |
1623 | /* | |
1624 | * Increment the counter before taking the lock so that | |
1625 | * a potential waker won't miss a to-be-slept task that is | |
1626 | * waiting for the spinlock. This is safe as all queue_lock() | |
1627 | * users end up calling queue_me(). Similarly, for housekeeping, | |
1628 | * decrement the counter at queue_unlock() when some error has | |
1629 | * occurred and we don't end up adding the task to the list. | |
1630 | */ | |
1631 | hb_waiters_inc(hb); | |
1632 | ||
e2970f2f | 1633 | q->lock_ptr = &hb->lock; |
1da177e4 | 1634 | |
b0c29f79 | 1635 | spin_lock(&hb->lock); /* implies MB (A) */ |
e2970f2f | 1636 | return hb; |
1da177e4 LT |
1637 | } |
1638 | ||
d40d65c8 | 1639 | static inline void |
0d00c7b2 | 1640 | queue_unlock(struct futex_hash_bucket *hb) |
15e408cd | 1641 | __releases(&hb->lock) |
d40d65c8 DH |
1642 | { |
1643 | spin_unlock(&hb->lock); | |
11d4616b | 1644 | hb_waiters_dec(hb); |
d40d65c8 DH |
1645 | } |
1646 | ||
1647 | /** | |
1648 | * queue_me() - Enqueue the futex_q on the futex_hash_bucket | |
1649 | * @q: The futex_q to enqueue | |
1650 | * @hb: The destination hash bucket | |
1651 | * | |
1652 | * The hb->lock must be held by the caller, and is released here. A call to | |
1653 | * queue_me() is typically paired with exactly one call to unqueue_me(). The | |
1654 | * exceptions involve the PI related operations, which may use unqueue_me_pi() | |
1655 | * or nothing if the unqueue is done as part of the wake process and the unqueue | |
1656 | * state is implicit in the state of woken task (see futex_wait_requeue_pi() for | |
1657 | * an example). | |
1658 | */ | |
82af7aca | 1659 | static inline void queue_me(struct futex_q *q, struct futex_hash_bucket *hb) |
15e408cd | 1660 | __releases(&hb->lock) |
1da177e4 | 1661 | { |
ec92d082 PP |
1662 | int prio; |
1663 | ||
1664 | /* | |
1665 | * The priority used to register this element is | |
1666 | * - either the real thread-priority for the real-time threads | |
1667 | * (i.e. threads with a priority lower than MAX_RT_PRIO) | |
1668 | * - or MAX_RT_PRIO for non-RT threads. | |
1669 | * Thus, all RT-threads are woken first in priority order, and | |
1670 | * the others are woken last, in FIFO order. | |
1671 | */ | |
1672 | prio = min(current->normal_prio, MAX_RT_PRIO); | |
1673 | ||
1674 | plist_node_init(&q->list, prio); | |
ec92d082 | 1675 | plist_add(&q->list, &hb->chain); |
c87e2837 | 1676 | q->task = current; |
e2970f2f | 1677 | spin_unlock(&hb->lock); |
1da177e4 LT |
1678 | } |
1679 | ||
d40d65c8 DH |
1680 | /** |
1681 | * unqueue_me() - Remove the futex_q from its futex_hash_bucket | |
1682 | * @q: The futex_q to unqueue | |
1683 | * | |
1684 | * The q->lock_ptr must not be held by the caller. A call to unqueue_me() must | |
1685 | * be paired with exactly one earlier call to queue_me(). | |
1686 | * | |
6c23cbbd RD |
1687 | * Return: |
1688 | * 1 - if the futex_q was still queued (and we removed unqueued it); | |
d40d65c8 | 1689 | * 0 - if the futex_q was already removed by the waking thread |
1da177e4 | 1690 | */ |
1da177e4 LT |
1691 | static int unqueue_me(struct futex_q *q) |
1692 | { | |
1da177e4 | 1693 | spinlock_t *lock_ptr; |
e2970f2f | 1694 | int ret = 0; |
1da177e4 LT |
1695 | |
1696 | /* In the common case we don't take the spinlock, which is nice. */ | |
42d35d48 | 1697 | retry: |
1da177e4 | 1698 | lock_ptr = q->lock_ptr; |
e91467ec | 1699 | barrier(); |
c80544dc | 1700 | if (lock_ptr != NULL) { |
1da177e4 LT |
1701 | spin_lock(lock_ptr); |
1702 | /* | |
1703 | * q->lock_ptr can change between reading it and | |
1704 | * spin_lock(), causing us to take the wrong lock. This | |
1705 | * corrects the race condition. | |
1706 | * | |
1707 | * Reasoning goes like this: if we have the wrong lock, | |
1708 | * q->lock_ptr must have changed (maybe several times) | |
1709 | * between reading it and the spin_lock(). It can | |
1710 | * change again after the spin_lock() but only if it was | |
1711 | * already changed before the spin_lock(). It cannot, | |
1712 | * however, change back to the original value. Therefore | |
1713 | * we can detect whether we acquired the correct lock. | |
1714 | */ | |
1715 | if (unlikely(lock_ptr != q->lock_ptr)) { | |
1716 | spin_unlock(lock_ptr); | |
1717 | goto retry; | |
1718 | } | |
2e12978a | 1719 | __unqueue_futex(q); |
c87e2837 IM |
1720 | |
1721 | BUG_ON(q->pi_state); | |
1722 | ||
1da177e4 LT |
1723 | spin_unlock(lock_ptr); |
1724 | ret = 1; | |
1725 | } | |
1726 | ||
9adef58b | 1727 | drop_futex_key_refs(&q->key); |
1da177e4 LT |
1728 | return ret; |
1729 | } | |
1730 | ||
c87e2837 IM |
1731 | /* |
1732 | * PI futexes can not be requeued and must remove themself from the | |
d0aa7a70 PP |
1733 | * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry |
1734 | * and dropped here. | |
c87e2837 | 1735 | */ |
d0aa7a70 | 1736 | static void unqueue_me_pi(struct futex_q *q) |
15e408cd | 1737 | __releases(q->lock_ptr) |
c87e2837 | 1738 | { |
2e12978a | 1739 | __unqueue_futex(q); |
c87e2837 IM |
1740 | |
1741 | BUG_ON(!q->pi_state); | |
1742 | free_pi_state(q->pi_state); | |
1743 | q->pi_state = NULL; | |
1744 | ||
d0aa7a70 | 1745 | spin_unlock(q->lock_ptr); |
c87e2837 IM |
1746 | } |
1747 | ||
d0aa7a70 | 1748 | /* |
cdf71a10 | 1749 | * Fixup the pi_state owner with the new owner. |
d0aa7a70 | 1750 | * |
778e9a9c AK |
1751 | * Must be called with hash bucket lock held and mm->sem held for non |
1752 | * private futexes. | |
d0aa7a70 | 1753 | */ |
778e9a9c | 1754 | static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q, |
ae791a2d | 1755 | struct task_struct *newowner) |
d0aa7a70 | 1756 | { |
cdf71a10 | 1757 | u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS; |
d0aa7a70 | 1758 | struct futex_pi_state *pi_state = q->pi_state; |
1b7558e4 | 1759 | struct task_struct *oldowner = pi_state->owner; |
7cfdaf38 | 1760 | u32 uval, uninitialized_var(curval), newval; |
e4dc5b7a | 1761 | int ret; |
d0aa7a70 PP |
1762 | |
1763 | /* Owner died? */ | |
1b7558e4 TG |
1764 | if (!pi_state->owner) |
1765 | newtid |= FUTEX_OWNER_DIED; | |
1766 | ||
1767 | /* | |
1768 | * We are here either because we stole the rtmutex from the | |
8161239a LJ |
1769 | * previous highest priority waiter or we are the highest priority |
1770 | * waiter but failed to get the rtmutex the first time. | |
1771 | * We have to replace the newowner TID in the user space variable. | |
1772 | * This must be atomic as we have to preserve the owner died bit here. | |
1b7558e4 | 1773 | * |
b2d0994b DH |
1774 | * Note: We write the user space value _before_ changing the pi_state |
1775 | * because we can fault here. Imagine swapped out pages or a fork | |
1776 | * that marked all the anonymous memory readonly for cow. | |
1b7558e4 TG |
1777 | * |
1778 | * Modifying pi_state _before_ the user space value would | |
1779 | * leave the pi_state in an inconsistent state when we fault | |
1780 | * here, because we need to drop the hash bucket lock to | |
1781 | * handle the fault. This might be observed in the PID check | |
1782 | * in lookup_pi_state. | |
1783 | */ | |
1784 | retry: | |
1785 | if (get_futex_value_locked(&uval, uaddr)) | |
1786 | goto handle_fault; | |
1787 | ||
1788 | while (1) { | |
1789 | newval = (uval & FUTEX_OWNER_DIED) | newtid; | |
1790 | ||
37a9d912 | 1791 | if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval)) |
1b7558e4 TG |
1792 | goto handle_fault; |
1793 | if (curval == uval) | |
1794 | break; | |
1795 | uval = curval; | |
1796 | } | |
1797 | ||
1798 | /* | |
1799 | * We fixed up user space. Now we need to fix the pi_state | |
1800 | * itself. | |
1801 | */ | |
d0aa7a70 | 1802 | if (pi_state->owner != NULL) { |
1d615482 | 1803 | raw_spin_lock_irq(&pi_state->owner->pi_lock); |
d0aa7a70 PP |
1804 | WARN_ON(list_empty(&pi_state->list)); |
1805 | list_del_init(&pi_state->list); | |
1d615482 | 1806 | raw_spin_unlock_irq(&pi_state->owner->pi_lock); |
1b7558e4 | 1807 | } |
d0aa7a70 | 1808 | |
cdf71a10 | 1809 | pi_state->owner = newowner; |
d0aa7a70 | 1810 | |
1d615482 | 1811 | raw_spin_lock_irq(&newowner->pi_lock); |
d0aa7a70 | 1812 | WARN_ON(!list_empty(&pi_state->list)); |
cdf71a10 | 1813 | list_add(&pi_state->list, &newowner->pi_state_list); |
1d615482 | 1814 | raw_spin_unlock_irq(&newowner->pi_lock); |
1b7558e4 | 1815 | return 0; |
d0aa7a70 | 1816 | |
d0aa7a70 | 1817 | /* |
1b7558e4 | 1818 | * To handle the page fault we need to drop the hash bucket |
8161239a LJ |
1819 | * lock here. That gives the other task (either the highest priority |
1820 | * waiter itself or the task which stole the rtmutex) the | |
1b7558e4 TG |
1821 | * chance to try the fixup of the pi_state. So once we are |
1822 | * back from handling the fault we need to check the pi_state | |
1823 | * after reacquiring the hash bucket lock and before trying to | |
1824 | * do another fixup. When the fixup has been done already we | |
1825 | * simply return. | |
d0aa7a70 | 1826 | */ |
1b7558e4 TG |
1827 | handle_fault: |
1828 | spin_unlock(q->lock_ptr); | |
778e9a9c | 1829 | |
d0725992 | 1830 | ret = fault_in_user_writeable(uaddr); |
778e9a9c | 1831 | |
1b7558e4 | 1832 | spin_lock(q->lock_ptr); |
778e9a9c | 1833 | |
1b7558e4 TG |
1834 | /* |
1835 | * Check if someone else fixed it for us: | |
1836 | */ | |
1837 | if (pi_state->owner != oldowner) | |
1838 | return 0; | |
1839 | ||
1840 | if (ret) | |
1841 | return ret; | |
1842 | ||
1843 | goto retry; | |
d0aa7a70 PP |
1844 | } |
1845 | ||
72c1bbf3 | 1846 | static long futex_wait_restart(struct restart_block *restart); |
36cf3b5c | 1847 | |
dd973998 DH |
1848 | /** |
1849 | * fixup_owner() - Post lock pi_state and corner case management | |
1850 | * @uaddr: user address of the futex | |
dd973998 DH |
1851 | * @q: futex_q (contains pi_state and access to the rt_mutex) |
1852 | * @locked: if the attempt to take the rt_mutex succeeded (1) or not (0) | |
1853 | * | |
1854 | * After attempting to lock an rt_mutex, this function is called to cleanup | |
1855 | * the pi_state owner as well as handle race conditions that may allow us to | |
1856 | * acquire the lock. Must be called with the hb lock held. | |
1857 | * | |
6c23cbbd RD |
1858 | * Return: |
1859 | * 1 - success, lock taken; | |
1860 | * 0 - success, lock not taken; | |
dd973998 DH |
1861 | * <0 - on error (-EFAULT) |
1862 | */ | |
ae791a2d | 1863 | static int fixup_owner(u32 __user *uaddr, struct futex_q *q, int locked) |
dd973998 DH |
1864 | { |
1865 | struct task_struct *owner; | |
1866 | int ret = 0; | |
1867 | ||
1868 | if (locked) { | |
1869 | /* | |
1870 | * Got the lock. We might not be the anticipated owner if we | |
1871 | * did a lock-steal - fix up the PI-state in that case: | |
1872 | */ | |
1873 | if (q->pi_state->owner != current) | |
ae791a2d | 1874 | ret = fixup_pi_state_owner(uaddr, q, current); |
dd973998 DH |
1875 | goto out; |
1876 | } | |
1877 | ||
1878 | /* | |
1879 | * Catch the rare case, where the lock was released when we were on the | |
1880 | * way back before we locked the hash bucket. | |
1881 | */ | |
1882 | if (q->pi_state->owner == current) { | |
1883 | /* | |
1884 | * Try to get the rt_mutex now. This might fail as some other | |
1885 | * task acquired the rt_mutex after we removed ourself from the | |
1886 | * rt_mutex waiters list. | |
1887 | */ | |
1888 | if (rt_mutex_trylock(&q->pi_state->pi_mutex)) { | |
1889 | locked = 1; | |
1890 | goto out; | |
1891 | } | |
1892 | ||
1893 | /* | |
1894 | * pi_state is incorrect, some other task did a lock steal and | |
1895 | * we returned due to timeout or signal without taking the | |
8161239a | 1896 | * rt_mutex. Too late. |
dd973998 | 1897 | */ |
8161239a | 1898 | raw_spin_lock(&q->pi_state->pi_mutex.wait_lock); |
dd973998 | 1899 | owner = rt_mutex_owner(&q->pi_state->pi_mutex); |
8161239a LJ |
1900 | if (!owner) |
1901 | owner = rt_mutex_next_owner(&q->pi_state->pi_mutex); | |
1902 | raw_spin_unlock(&q->pi_state->pi_mutex.wait_lock); | |
ae791a2d | 1903 | ret = fixup_pi_state_owner(uaddr, q, owner); |
dd973998 DH |
1904 | goto out; |
1905 | } | |
1906 | ||
1907 | /* | |
1908 | * Paranoia check. If we did not take the lock, then we should not be | |
8161239a | 1909 | * the owner of the rt_mutex. |
dd973998 DH |
1910 | */ |
1911 | if (rt_mutex_owner(&q->pi_state->pi_mutex) == current) | |
1912 | printk(KERN_ERR "fixup_owner: ret = %d pi-mutex: %p " | |
1913 | "pi-state %p\n", ret, | |
1914 | q->pi_state->pi_mutex.owner, | |
1915 | q->pi_state->owner); | |
1916 | ||
1917 | out: | |
1918 | return ret ? ret : locked; | |
1919 | } | |
1920 | ||
ca5f9524 DH |
1921 | /** |
1922 | * futex_wait_queue_me() - queue_me() and wait for wakeup, timeout, or signal | |
1923 | * @hb: the futex hash bucket, must be locked by the caller | |
1924 | * @q: the futex_q to queue up on | |
1925 | * @timeout: the prepared hrtimer_sleeper, or null for no timeout | |
ca5f9524 DH |
1926 | */ |
1927 | static void futex_wait_queue_me(struct futex_hash_bucket *hb, struct futex_q *q, | |
f1a11e05 | 1928 | struct hrtimer_sleeper *timeout) |
ca5f9524 | 1929 | { |
9beba3c5 DH |
1930 | /* |
1931 | * The task state is guaranteed to be set before another task can | |
1932 | * wake it. set_current_state() is implemented using set_mb() and | |
1933 | * queue_me() calls spin_unlock() upon completion, both serializing | |
1934 | * access to the hash list and forcing another memory barrier. | |
1935 | */ | |
f1a11e05 | 1936 | set_current_state(TASK_INTERRUPTIBLE); |
0729e196 | 1937 | queue_me(q, hb); |
ca5f9524 DH |
1938 | |
1939 | /* Arm the timer */ | |
1940 | if (timeout) { | |
1941 | hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS); | |
1942 | if (!hrtimer_active(&timeout->timer)) | |
1943 | timeout->task = NULL; | |
1944 | } | |
1945 | ||
1946 | /* | |
0729e196 DH |
1947 | * If we have been removed from the hash list, then another task |
1948 | * has tried to wake us, and we can skip the call to schedule(). | |
ca5f9524 DH |
1949 | */ |
1950 | if (likely(!plist_node_empty(&q->list))) { | |
1951 | /* | |
1952 | * If the timer has already expired, current will already be | |
1953 | * flagged for rescheduling. Only call schedule if there | |
1954 | * is no timeout, or if it has yet to expire. | |
1955 | */ | |
1956 | if (!timeout || timeout->task) | |
88c8004f | 1957 | freezable_schedule(); |
ca5f9524 DH |
1958 | } |
1959 | __set_current_state(TASK_RUNNING); | |
1960 | } | |
1961 | ||
f801073f DH |
1962 | /** |
1963 | * futex_wait_setup() - Prepare to wait on a futex | |
1964 | * @uaddr: the futex userspace address | |
1965 | * @val: the expected value | |
b41277dc | 1966 | * @flags: futex flags (FLAGS_SHARED, etc.) |
f801073f DH |
1967 | * @q: the associated futex_q |
1968 | * @hb: storage for hash_bucket pointer to be returned to caller | |
1969 | * | |
1970 | * Setup the futex_q and locate the hash_bucket. Get the futex value and | |
1971 | * compare it with the expected value. Handle atomic faults internally. | |
1972 | * Return with the hb lock held and a q.key reference on success, and unlocked | |
1973 | * with no q.key reference on failure. | |
1974 | * | |
6c23cbbd RD |
1975 | * Return: |
1976 | * 0 - uaddr contains val and hb has been locked; | |
ca4a04cf | 1977 | * <1 - -EFAULT or -EWOULDBLOCK (uaddr does not contain val) and hb is unlocked |
f801073f | 1978 | */ |
b41277dc | 1979 | static int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags, |
f801073f | 1980 | struct futex_q *q, struct futex_hash_bucket **hb) |
1da177e4 | 1981 | { |
e2970f2f IM |
1982 | u32 uval; |
1983 | int ret; | |
1da177e4 | 1984 | |
1da177e4 | 1985 | /* |
b2d0994b | 1986 | * Access the page AFTER the hash-bucket is locked. |
1da177e4 LT |
1987 | * Order is important: |
1988 | * | |
1989 | * Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val); | |
1990 | * Userspace waker: if (cond(var)) { var = new; futex_wake(&var); } | |
1991 | * | |
1992 | * The basic logical guarantee of a futex is that it blocks ONLY | |
1993 | * if cond(var) is known to be true at the time of blocking, for | |
8fe8f545 ML |
1994 | * any cond. If we locked the hash-bucket after testing *uaddr, that |
1995 | * would open a race condition where we could block indefinitely with | |
1da177e4 LT |
1996 | * cond(var) false, which would violate the guarantee. |
1997 | * | |
8fe8f545 ML |
1998 | * On the other hand, we insert q and release the hash-bucket only |
1999 | * after testing *uaddr. This guarantees that futex_wait() will NOT | |
2000 | * absorb a wakeup if *uaddr does not match the desired values | |
2001 | * while the syscall executes. | |
1da177e4 | 2002 | */ |
f801073f | 2003 | retry: |
9ea71503 | 2004 | ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q->key, VERIFY_READ); |
f801073f | 2005 | if (unlikely(ret != 0)) |
a5a2a0c7 | 2006 | return ret; |
f801073f DH |
2007 | |
2008 | retry_private: | |
2009 | *hb = queue_lock(q); | |
2010 | ||
e2970f2f | 2011 | ret = get_futex_value_locked(&uval, uaddr); |
1da177e4 | 2012 | |
f801073f | 2013 | if (ret) { |
0d00c7b2 | 2014 | queue_unlock(*hb); |
1da177e4 | 2015 | |
e2970f2f | 2016 | ret = get_user(uval, uaddr); |
e4dc5b7a | 2017 | if (ret) |
f801073f | 2018 | goto out; |
1da177e4 | 2019 | |
b41277dc | 2020 | if (!(flags & FLAGS_SHARED)) |
e4dc5b7a DH |
2021 | goto retry_private; |
2022 | ||
ae791a2d | 2023 | put_futex_key(&q->key); |
e4dc5b7a | 2024 | goto retry; |
1da177e4 | 2025 | } |
ca5f9524 | 2026 | |
f801073f | 2027 | if (uval != val) { |
0d00c7b2 | 2028 | queue_unlock(*hb); |
f801073f | 2029 | ret = -EWOULDBLOCK; |
2fff78c7 | 2030 | } |
1da177e4 | 2031 | |
f801073f DH |
2032 | out: |
2033 | if (ret) | |
ae791a2d | 2034 | put_futex_key(&q->key); |
f801073f DH |
2035 | return ret; |
2036 | } | |
2037 | ||
b41277dc DH |
2038 | static int futex_wait(u32 __user *uaddr, unsigned int flags, u32 val, |
2039 | ktime_t *abs_time, u32 bitset) | |
f801073f DH |
2040 | { |
2041 | struct hrtimer_sleeper timeout, *to = NULL; | |
f801073f DH |
2042 | struct restart_block *restart; |
2043 | struct futex_hash_bucket *hb; | |
5bdb05f9 | 2044 | struct futex_q q = futex_q_init; |
f801073f DH |
2045 | int ret; |
2046 | ||
2047 | if (!bitset) | |
2048 | return -EINVAL; | |
f801073f DH |
2049 | q.bitset = bitset; |
2050 | ||
2051 | if (abs_time) { | |
2052 | to = &timeout; | |
2053 | ||
b41277dc DH |
2054 | hrtimer_init_on_stack(&to->timer, (flags & FLAGS_CLOCKRT) ? |
2055 | CLOCK_REALTIME : CLOCK_MONOTONIC, | |
2056 | HRTIMER_MODE_ABS); | |
f801073f DH |
2057 | hrtimer_init_sleeper(to, current); |
2058 | hrtimer_set_expires_range_ns(&to->timer, *abs_time, | |
2059 | current->timer_slack_ns); | |
2060 | } | |
2061 | ||
d58e6576 | 2062 | retry: |
7ada876a DH |
2063 | /* |
2064 | * Prepare to wait on uaddr. On success, holds hb lock and increments | |
2065 | * q.key refs. | |
2066 | */ | |
b41277dc | 2067 | ret = futex_wait_setup(uaddr, val, flags, &q, &hb); |
f801073f DH |
2068 | if (ret) |
2069 | goto out; | |
2070 | ||
ca5f9524 | 2071 | /* queue_me and wait for wakeup, timeout, or a signal. */ |
f1a11e05 | 2072 | futex_wait_queue_me(hb, &q, to); |
1da177e4 LT |
2073 | |
2074 | /* If we were woken (and unqueued), we succeeded, whatever. */ | |
2fff78c7 | 2075 | ret = 0; |
7ada876a | 2076 | /* unqueue_me() drops q.key ref */ |
1da177e4 | 2077 | if (!unqueue_me(&q)) |
7ada876a | 2078 | goto out; |
2fff78c7 | 2079 | ret = -ETIMEDOUT; |
ca5f9524 | 2080 | if (to && !to->task) |
7ada876a | 2081 | goto out; |
72c1bbf3 | 2082 | |
e2970f2f | 2083 | /* |
d58e6576 TG |
2084 | * We expect signal_pending(current), but we might be the |
2085 | * victim of a spurious wakeup as well. | |
e2970f2f | 2086 | */ |
7ada876a | 2087 | if (!signal_pending(current)) |
d58e6576 | 2088 | goto retry; |
d58e6576 | 2089 | |
2fff78c7 | 2090 | ret = -ERESTARTSYS; |
c19384b5 | 2091 | if (!abs_time) |
7ada876a | 2092 | goto out; |
1da177e4 | 2093 | |
2fff78c7 PZ |
2094 | restart = ¤t_thread_info()->restart_block; |
2095 | restart->fn = futex_wait_restart; | |
a3c74c52 | 2096 | restart->futex.uaddr = uaddr; |
2fff78c7 PZ |
2097 | restart->futex.val = val; |
2098 | restart->futex.time = abs_time->tv64; | |
2099 | restart->futex.bitset = bitset; | |
0cd9c649 | 2100 | restart->futex.flags = flags | FLAGS_HAS_TIMEOUT; |
42d35d48 | 2101 | |
2fff78c7 PZ |
2102 | ret = -ERESTART_RESTARTBLOCK; |
2103 | ||
42d35d48 | 2104 | out: |
ca5f9524 DH |
2105 | if (to) { |
2106 | hrtimer_cancel(&to->timer); | |
2107 | destroy_hrtimer_on_stack(&to->timer); | |
2108 | } | |
c87e2837 IM |
2109 | return ret; |
2110 | } | |
2111 | ||
72c1bbf3 NP |
2112 | |
2113 | static long futex_wait_restart(struct restart_block *restart) | |
2114 | { | |
a3c74c52 | 2115 | u32 __user *uaddr = restart->futex.uaddr; |
a72188d8 | 2116 | ktime_t t, *tp = NULL; |
72c1bbf3 | 2117 | |
a72188d8 DH |
2118 | if (restart->futex.flags & FLAGS_HAS_TIMEOUT) { |
2119 | t.tv64 = restart->futex.time; | |
2120 | tp = &t; | |
2121 | } | |
72c1bbf3 | 2122 | restart->fn = do_no_restart_syscall; |
b41277dc DH |
2123 | |
2124 | return (long)futex_wait(uaddr, restart->futex.flags, | |
2125 | restart->futex.val, tp, restart->futex.bitset); | |
72c1bbf3 NP |
2126 | } |
2127 | ||
2128 | ||
c87e2837 IM |
2129 | /* |
2130 | * Userspace tried a 0 -> TID atomic transition of the futex value | |
2131 | * and failed. The kernel side here does the whole locking operation: | |
2132 | * if there are waiters then it will block, it does PI, etc. (Due to | |
2133 | * races the kernel might see a 0 value of the futex too.) | |
2134 | */ | |
b41277dc DH |
2135 | static int futex_lock_pi(u32 __user *uaddr, unsigned int flags, int detect, |
2136 | ktime_t *time, int trylock) | |
c87e2837 | 2137 | { |
c5780e97 | 2138 | struct hrtimer_sleeper timeout, *to = NULL; |
c87e2837 | 2139 | struct futex_hash_bucket *hb; |
5bdb05f9 | 2140 | struct futex_q q = futex_q_init; |
dd973998 | 2141 | int res, ret; |
c87e2837 IM |
2142 | |
2143 | if (refill_pi_state_cache()) | |
2144 | return -ENOMEM; | |
2145 | ||
c19384b5 | 2146 | if (time) { |
c5780e97 | 2147 | to = &timeout; |
237fc6e7 TG |
2148 | hrtimer_init_on_stack(&to->timer, CLOCK_REALTIME, |
2149 | HRTIMER_MODE_ABS); | |
c5780e97 | 2150 | hrtimer_init_sleeper(to, current); |
cc584b21 | 2151 | hrtimer_set_expires(&to->timer, *time); |
c5780e97 TG |
2152 | } |
2153 | ||
42d35d48 | 2154 | retry: |
9ea71503 | 2155 | ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q.key, VERIFY_WRITE); |
c87e2837 | 2156 | if (unlikely(ret != 0)) |
42d35d48 | 2157 | goto out; |
c87e2837 | 2158 | |
e4dc5b7a | 2159 | retry_private: |
82af7aca | 2160 | hb = queue_lock(&q); |
c87e2837 | 2161 | |
bab5bc9e | 2162 | ret = futex_lock_pi_atomic(uaddr, hb, &q.key, &q.pi_state, current, 0); |
c87e2837 | 2163 | if (unlikely(ret)) { |
778e9a9c | 2164 | switch (ret) { |
1a52084d DH |
2165 | case 1: |
2166 | /* We got the lock. */ | |
2167 | ret = 0; | |
2168 | goto out_unlock_put_key; | |
2169 | case -EFAULT: | |
2170 | goto uaddr_faulted; | |
778e9a9c AK |
2171 | case -EAGAIN: |
2172 | /* | |
2173 | * Task is exiting and we just wait for the | |
2174 | * exit to complete. | |
2175 | */ | |
0d00c7b2 | 2176 | queue_unlock(hb); |
ae791a2d | 2177 | put_futex_key(&q.key); |
778e9a9c AK |
2178 | cond_resched(); |
2179 | goto retry; | |
778e9a9c | 2180 | default: |
42d35d48 | 2181 | goto out_unlock_put_key; |
c87e2837 | 2182 | } |
c87e2837 IM |
2183 | } |
2184 | ||
2185 | /* | |
2186 | * Only actually queue now that the atomic ops are done: | |
2187 | */ | |
82af7aca | 2188 | queue_me(&q, hb); |
c87e2837 | 2189 | |
c87e2837 IM |
2190 | WARN_ON(!q.pi_state); |
2191 | /* | |
2192 | * Block on the PI mutex: | |
2193 | */ | |
2194 | if (!trylock) | |
2195 | ret = rt_mutex_timed_lock(&q.pi_state->pi_mutex, to, 1); | |
2196 | else { | |
2197 | ret = rt_mutex_trylock(&q.pi_state->pi_mutex); | |
2198 | /* Fixup the trylock return value: */ | |
2199 | ret = ret ? 0 : -EWOULDBLOCK; | |
2200 | } | |
2201 | ||
a99e4e41 | 2202 | spin_lock(q.lock_ptr); |
dd973998 DH |
2203 | /* |
2204 | * Fixup the pi_state owner and possibly acquire the lock if we | |
2205 | * haven't already. | |
2206 | */ | |
ae791a2d | 2207 | res = fixup_owner(uaddr, &q, !ret); |
dd973998 DH |
2208 | /* |
2209 | * If fixup_owner() returned an error, proprogate that. If it acquired | |
2210 | * the lock, clear our -ETIMEDOUT or -EINTR. | |
2211 | */ | |
2212 | if (res) | |
2213 | ret = (res < 0) ? res : 0; | |
c87e2837 | 2214 | |
e8f6386c | 2215 | /* |
dd973998 DH |
2216 | * If fixup_owner() faulted and was unable to handle the fault, unlock |
2217 | * it and return the fault to userspace. | |
e8f6386c DH |
2218 | */ |
2219 | if (ret && (rt_mutex_owner(&q.pi_state->pi_mutex) == current)) | |
2220 | rt_mutex_unlock(&q.pi_state->pi_mutex); | |
2221 | ||
778e9a9c AK |
2222 | /* Unqueue and drop the lock */ |
2223 | unqueue_me_pi(&q); | |
c87e2837 | 2224 | |
5ecb01cf | 2225 | goto out_put_key; |
c87e2837 | 2226 | |
42d35d48 | 2227 | out_unlock_put_key: |
0d00c7b2 | 2228 | queue_unlock(hb); |
c87e2837 | 2229 | |
42d35d48 | 2230 | out_put_key: |
ae791a2d | 2231 | put_futex_key(&q.key); |
42d35d48 | 2232 | out: |
237fc6e7 TG |
2233 | if (to) |
2234 | destroy_hrtimer_on_stack(&to->timer); | |
dd973998 | 2235 | return ret != -EINTR ? ret : -ERESTARTNOINTR; |
c87e2837 | 2236 | |
42d35d48 | 2237 | uaddr_faulted: |
0d00c7b2 | 2238 | queue_unlock(hb); |
778e9a9c | 2239 | |
d0725992 | 2240 | ret = fault_in_user_writeable(uaddr); |
e4dc5b7a DH |
2241 | if (ret) |
2242 | goto out_put_key; | |
c87e2837 | 2243 | |
b41277dc | 2244 | if (!(flags & FLAGS_SHARED)) |
e4dc5b7a DH |
2245 | goto retry_private; |
2246 | ||
ae791a2d | 2247 | put_futex_key(&q.key); |
e4dc5b7a | 2248 | goto retry; |
c87e2837 IM |
2249 | } |
2250 | ||
c87e2837 IM |
2251 | /* |
2252 | * Userspace attempted a TID -> 0 atomic transition, and failed. | |
2253 | * This is the in-kernel slowpath: we look up the PI state (if any), | |
2254 | * and do the rt-mutex unlock. | |
2255 | */ | |
b41277dc | 2256 | static int futex_unlock_pi(u32 __user *uaddr, unsigned int flags) |
c87e2837 IM |
2257 | { |
2258 | struct futex_hash_bucket *hb; | |
2259 | struct futex_q *this, *next; | |
38d47c1b | 2260 | union futex_key key = FUTEX_KEY_INIT; |
c0c9ed15 | 2261 | u32 uval, vpid = task_pid_vnr(current); |
e4dc5b7a | 2262 | int ret; |
c87e2837 IM |
2263 | |
2264 | retry: | |
2265 | if (get_user(uval, uaddr)) | |
2266 | return -EFAULT; | |
2267 | /* | |
2268 | * We release only a lock we actually own: | |
2269 | */ | |
c0c9ed15 | 2270 | if ((uval & FUTEX_TID_MASK) != vpid) |
c87e2837 | 2271 | return -EPERM; |
c87e2837 | 2272 | |
9ea71503 | 2273 | ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key, VERIFY_WRITE); |
c87e2837 IM |
2274 | if (unlikely(ret != 0)) |
2275 | goto out; | |
2276 | ||
2277 | hb = hash_futex(&key); | |
2278 | spin_lock(&hb->lock); | |
2279 | ||
c87e2837 IM |
2280 | /* |
2281 | * To avoid races, try to do the TID -> 0 atomic transition | |
2282 | * again. If it succeeds then we can return without waking | |
2283 | * anyone else up: | |
2284 | */ | |
37a9d912 ML |
2285 | if (!(uval & FUTEX_OWNER_DIED) && |
2286 | cmpxchg_futex_value_locked(&uval, uaddr, vpid, 0)) | |
c87e2837 IM |
2287 | goto pi_faulted; |
2288 | /* | |
2289 | * Rare case: we managed to release the lock atomically, | |
2290 | * no need to wake anyone else up: | |
2291 | */ | |
c0c9ed15 | 2292 | if (unlikely(uval == vpid)) |
c87e2837 IM |
2293 | goto out_unlock; |
2294 | ||
2295 | /* | |
2296 | * Ok, other tasks may need to be woken up - check waiters | |
2297 | * and do the wakeup if necessary: | |
2298 | */ | |
0d00c7b2 | 2299 | plist_for_each_entry_safe(this, next, &hb->chain, list) { |
c87e2837 IM |
2300 | if (!match_futex (&this->key, &key)) |
2301 | continue; | |
2302 | ret = wake_futex_pi(uaddr, uval, this); | |
2303 | /* | |
2304 | * The atomic access to the futex value | |
2305 | * generated a pagefault, so retry the | |
2306 | * user-access and the wakeup: | |
2307 | */ | |
2308 | if (ret == -EFAULT) | |
2309 | goto pi_faulted; | |
2310 | goto out_unlock; | |
2311 | } | |
2312 | /* | |
2313 | * No waiters - kernel unlocks the futex: | |
2314 | */ | |
e3f2ddea IM |
2315 | if (!(uval & FUTEX_OWNER_DIED)) { |
2316 | ret = unlock_futex_pi(uaddr, uval); | |
2317 | if (ret == -EFAULT) | |
2318 | goto pi_faulted; | |
2319 | } | |
c87e2837 IM |
2320 | |
2321 | out_unlock: | |
2322 | spin_unlock(&hb->lock); | |
ae791a2d | 2323 | put_futex_key(&key); |
c87e2837 | 2324 | |
42d35d48 | 2325 | out: |
c87e2837 IM |
2326 | return ret; |
2327 | ||
2328 | pi_faulted: | |
778e9a9c | 2329 | spin_unlock(&hb->lock); |
ae791a2d | 2330 | put_futex_key(&key); |
c87e2837 | 2331 | |
d0725992 | 2332 | ret = fault_in_user_writeable(uaddr); |
b5686363 | 2333 | if (!ret) |
c87e2837 IM |
2334 | goto retry; |
2335 | ||
1da177e4 LT |
2336 | return ret; |
2337 | } | |
2338 | ||
52400ba9 DH |
2339 | /** |
2340 | * handle_early_requeue_pi_wakeup() - Detect early wakeup on the initial futex | |
2341 | * @hb: the hash_bucket futex_q was original enqueued on | |
2342 | * @q: the futex_q woken while waiting to be requeued | |
2343 | * @key2: the futex_key of the requeue target futex | |
2344 | * @timeout: the timeout associated with the wait (NULL if none) | |
2345 | * | |
2346 | * Detect if the task was woken on the initial futex as opposed to the requeue | |
2347 | * target futex. If so, determine if it was a timeout or a signal that caused | |
2348 | * the wakeup and return the appropriate error code to the caller. Must be | |
2349 | * called with the hb lock held. | |
2350 | * | |
6c23cbbd RD |
2351 | * Return: |
2352 | * 0 = no early wakeup detected; | |
2353 | * <0 = -ETIMEDOUT or -ERESTARTNOINTR | |
52400ba9 DH |
2354 | */ |
2355 | static inline | |
2356 | int handle_early_requeue_pi_wakeup(struct futex_hash_bucket *hb, | |
2357 | struct futex_q *q, union futex_key *key2, | |
2358 | struct hrtimer_sleeper *timeout) | |
2359 | { | |
2360 | int ret = 0; | |
2361 | ||
2362 | /* | |
2363 | * With the hb lock held, we avoid races while we process the wakeup. | |
2364 | * We only need to hold hb (and not hb2) to ensure atomicity as the | |
2365 | * wakeup code can't change q.key from uaddr to uaddr2 if we hold hb. | |
2366 | * It can't be requeued from uaddr2 to something else since we don't | |
2367 | * support a PI aware source futex for requeue. | |
2368 | */ | |
2369 | if (!match_futex(&q->key, key2)) { | |
2370 | WARN_ON(q->lock_ptr && (&hb->lock != q->lock_ptr)); | |
2371 | /* | |
2372 | * We were woken prior to requeue by a timeout or a signal. | |
2373 | * Unqueue the futex_q and determine which it was. | |
2374 | */ | |
2e12978a | 2375 | plist_del(&q->list, &hb->chain); |
11d4616b | 2376 | hb_waiters_dec(hb); |
52400ba9 | 2377 | |
d58e6576 | 2378 | /* Handle spurious wakeups gracefully */ |
11df6ddd | 2379 | ret = -EWOULDBLOCK; |
52400ba9 DH |
2380 | if (timeout && !timeout->task) |
2381 | ret = -ETIMEDOUT; | |
d58e6576 | 2382 | else if (signal_pending(current)) |
1c840c14 | 2383 | ret = -ERESTARTNOINTR; |
52400ba9 DH |
2384 | } |
2385 | return ret; | |
2386 | } | |
2387 | ||
2388 | /** | |
2389 | * futex_wait_requeue_pi() - Wait on uaddr and take uaddr2 | |
56ec1607 | 2390 | * @uaddr: the futex we initially wait on (non-pi) |
b41277dc | 2391 | * @flags: futex flags (FLAGS_SHARED, FLAGS_CLOCKRT, etc.), they must be |
52400ba9 DH |
2392 | * the same type, no requeueing from private to shared, etc. |
2393 | * @val: the expected value of uaddr | |
2394 | * @abs_time: absolute timeout | |
56ec1607 | 2395 | * @bitset: 32 bit wakeup bitset set by userspace, defaults to all |
52400ba9 DH |
2396 | * @uaddr2: the pi futex we will take prior to returning to user-space |
2397 | * | |
2398 | * The caller will wait on uaddr and will be requeued by futex_requeue() to | |
6f7b0a2a DH |
2399 | * uaddr2 which must be PI aware and unique from uaddr. Normal wakeup will wake |
2400 | * on uaddr2 and complete the acquisition of the rt_mutex prior to returning to | |
2401 | * userspace. This ensures the rt_mutex maintains an owner when it has waiters; | |
2402 | * without one, the pi logic would not know which task to boost/deboost, if | |
2403 | * there was a need to. | |
52400ba9 DH |
2404 | * |
2405 | * We call schedule in futex_wait_queue_me() when we enqueue and return there | |
6c23cbbd | 2406 | * via the following-- |
52400ba9 | 2407 | * 1) wakeup on uaddr2 after an atomic lock acquisition by futex_requeue() |
cc6db4e6 DH |
2408 | * 2) wakeup on uaddr2 after a requeue |
2409 | * 3) signal | |
2410 | * 4) timeout | |
52400ba9 | 2411 | * |
cc6db4e6 | 2412 | * If 3, cleanup and return -ERESTARTNOINTR. |
52400ba9 DH |
2413 | * |
2414 | * If 2, we may then block on trying to take the rt_mutex and return via: | |
2415 | * 5) successful lock | |
2416 | * 6) signal | |
2417 | * 7) timeout | |
2418 | * 8) other lock acquisition failure | |
2419 | * | |
cc6db4e6 | 2420 | * If 6, return -EWOULDBLOCK (restarting the syscall would do the same). |
52400ba9 DH |
2421 | * |
2422 | * If 4 or 7, we cleanup and return with -ETIMEDOUT. | |
2423 | * | |
6c23cbbd RD |
2424 | * Return: |
2425 | * 0 - On success; | |
52400ba9 DH |
2426 | * <0 - On error |
2427 | */ | |
b41277dc | 2428 | static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags, |
52400ba9 | 2429 | u32 val, ktime_t *abs_time, u32 bitset, |
b41277dc | 2430 | u32 __user *uaddr2) |
52400ba9 DH |
2431 | { |
2432 | struct hrtimer_sleeper timeout, *to = NULL; | |
2433 | struct rt_mutex_waiter rt_waiter; | |
2434 | struct rt_mutex *pi_mutex = NULL; | |
52400ba9 | 2435 | struct futex_hash_bucket *hb; |
5bdb05f9 DH |
2436 | union futex_key key2 = FUTEX_KEY_INIT; |
2437 | struct futex_q q = futex_q_init; | |
52400ba9 | 2438 | int res, ret; |
52400ba9 | 2439 | |
6f7b0a2a DH |
2440 | if (uaddr == uaddr2) |
2441 | return -EINVAL; | |
2442 | ||
52400ba9 DH |
2443 | if (!bitset) |
2444 | return -EINVAL; | |
2445 | ||
2446 | if (abs_time) { | |
2447 | to = &timeout; | |
b41277dc DH |
2448 | hrtimer_init_on_stack(&to->timer, (flags & FLAGS_CLOCKRT) ? |
2449 | CLOCK_REALTIME : CLOCK_MONOTONIC, | |
2450 | HRTIMER_MODE_ABS); | |
52400ba9 DH |
2451 | hrtimer_init_sleeper(to, current); |
2452 | hrtimer_set_expires_range_ns(&to->timer, *abs_time, | |
2453 | current->timer_slack_ns); | |
2454 | } | |
2455 | ||
2456 | /* | |
2457 | * The waiter is allocated on our stack, manipulated by the requeue | |
2458 | * code while we sleep on uaddr. | |
2459 | */ | |
2460 | debug_rt_mutex_init_waiter(&rt_waiter); | |
fb00aca4 PZ |
2461 | RB_CLEAR_NODE(&rt_waiter.pi_tree_entry); |
2462 | RB_CLEAR_NODE(&rt_waiter.tree_entry); | |
52400ba9 DH |
2463 | rt_waiter.task = NULL; |
2464 | ||
9ea71503 | 2465 | ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, VERIFY_WRITE); |
52400ba9 DH |
2466 | if (unlikely(ret != 0)) |
2467 | goto out; | |
2468 | ||
84bc4af5 DH |
2469 | q.bitset = bitset; |
2470 | q.rt_waiter = &rt_waiter; | |
2471 | q.requeue_pi_key = &key2; | |
2472 | ||
7ada876a DH |
2473 | /* |
2474 | * Prepare to wait on uaddr. On success, increments q.key (key1) ref | |
2475 | * count. | |
2476 | */ | |
b41277dc | 2477 | ret = futex_wait_setup(uaddr, val, flags, &q, &hb); |
c8b15a70 TG |
2478 | if (ret) |
2479 | goto out_key2; | |
52400ba9 DH |
2480 | |
2481 | /* Queue the futex_q, drop the hb lock, wait for wakeup. */ | |
f1a11e05 | 2482 | futex_wait_queue_me(hb, &q, to); |
52400ba9 DH |
2483 | |
2484 | spin_lock(&hb->lock); | |
2485 | ret = handle_early_requeue_pi_wakeup(hb, &q, &key2, to); | |
2486 | spin_unlock(&hb->lock); | |
2487 | if (ret) | |
2488 | goto out_put_keys; | |
2489 | ||
2490 | /* | |
2491 | * In order for us to be here, we know our q.key == key2, and since | |
2492 | * we took the hb->lock above, we also know that futex_requeue() has | |
2493 | * completed and we no longer have to concern ourselves with a wakeup | |
7ada876a DH |
2494 | * race with the atomic proxy lock acquisition by the requeue code. The |
2495 | * futex_requeue dropped our key1 reference and incremented our key2 | |
2496 | * reference count. | |
52400ba9 DH |
2497 | */ |
2498 | ||
2499 | /* Check if the requeue code acquired the second futex for us. */ | |
2500 | if (!q.rt_waiter) { | |
2501 | /* | |
2502 | * Got the lock. We might not be the anticipated owner if we | |
2503 | * did a lock-steal - fix up the PI-state in that case. | |
2504 | */ | |
2505 | if (q.pi_state && (q.pi_state->owner != current)) { | |
2506 | spin_lock(q.lock_ptr); | |
ae791a2d | 2507 | ret = fixup_pi_state_owner(uaddr2, &q, current); |
52400ba9 DH |
2508 | spin_unlock(q.lock_ptr); |
2509 | } | |
2510 | } else { | |
2511 | /* | |
2512 | * We have been woken up by futex_unlock_pi(), a timeout, or a | |
2513 | * signal. futex_unlock_pi() will not destroy the lock_ptr nor | |
2514 | * the pi_state. | |
2515 | */ | |
f27071cb | 2516 | WARN_ON(!q.pi_state); |
52400ba9 DH |
2517 | pi_mutex = &q.pi_state->pi_mutex; |
2518 | ret = rt_mutex_finish_proxy_lock(pi_mutex, to, &rt_waiter, 1); | |
2519 | debug_rt_mutex_free_waiter(&rt_waiter); | |
2520 | ||
2521 | spin_lock(q.lock_ptr); | |
2522 | /* | |
2523 | * Fixup the pi_state owner and possibly acquire the lock if we | |
2524 | * haven't already. | |
2525 | */ | |
ae791a2d | 2526 | res = fixup_owner(uaddr2, &q, !ret); |
52400ba9 DH |
2527 | /* |
2528 | * If fixup_owner() returned an error, proprogate that. If it | |
56ec1607 | 2529 | * acquired the lock, clear -ETIMEDOUT or -EINTR. |
52400ba9 DH |
2530 | */ |
2531 | if (res) | |
2532 | ret = (res < 0) ? res : 0; | |
2533 | ||
2534 | /* Unqueue and drop the lock. */ | |
2535 | unqueue_me_pi(&q); | |
2536 | } | |
2537 | ||
2538 | /* | |
2539 | * If fixup_pi_state_owner() faulted and was unable to handle the | |
2540 | * fault, unlock the rt_mutex and return the fault to userspace. | |
2541 | */ | |
2542 | if (ret == -EFAULT) { | |
b6070a8d | 2543 | if (pi_mutex && rt_mutex_owner(pi_mutex) == current) |
52400ba9 DH |
2544 | rt_mutex_unlock(pi_mutex); |
2545 | } else if (ret == -EINTR) { | |
52400ba9 | 2546 | /* |
cc6db4e6 DH |
2547 | * We've already been requeued, but cannot restart by calling |
2548 | * futex_lock_pi() directly. We could restart this syscall, but | |
2549 | * it would detect that the user space "val" changed and return | |
2550 | * -EWOULDBLOCK. Save the overhead of the restart and return | |
2551 | * -EWOULDBLOCK directly. | |
52400ba9 | 2552 | */ |
2070887f | 2553 | ret = -EWOULDBLOCK; |
52400ba9 DH |
2554 | } |
2555 | ||
2556 | out_put_keys: | |
ae791a2d | 2557 | put_futex_key(&q.key); |
c8b15a70 | 2558 | out_key2: |
ae791a2d | 2559 | put_futex_key(&key2); |
52400ba9 DH |
2560 | |
2561 | out: | |
2562 | if (to) { | |
2563 | hrtimer_cancel(&to->timer); | |
2564 | destroy_hrtimer_on_stack(&to->timer); | |
2565 | } | |
2566 | return ret; | |
2567 | } | |
2568 | ||
0771dfef IM |
2569 | /* |
2570 | * Support for robust futexes: the kernel cleans up held futexes at | |
2571 | * thread exit time. | |
2572 | * | |
2573 | * Implementation: user-space maintains a per-thread list of locks it | |
2574 | * is holding. Upon do_exit(), the kernel carefully walks this list, | |
2575 | * and marks all locks that are owned by this thread with the | |
c87e2837 | 2576 | * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is |
0771dfef IM |
2577 | * always manipulated with the lock held, so the list is private and |
2578 | * per-thread. Userspace also maintains a per-thread 'list_op_pending' | |
2579 | * field, to allow the kernel to clean up if the thread dies after | |
2580 | * acquiring the lock, but just before it could have added itself to | |
2581 | * the list. There can only be one such pending lock. | |
2582 | */ | |
2583 | ||
2584 | /** | |
d96ee56c DH |
2585 | * sys_set_robust_list() - Set the robust-futex list head of a task |
2586 | * @head: pointer to the list-head | |
2587 | * @len: length of the list-head, as userspace expects | |
0771dfef | 2588 | */ |
836f92ad HC |
2589 | SYSCALL_DEFINE2(set_robust_list, struct robust_list_head __user *, head, |
2590 | size_t, len) | |
0771dfef | 2591 | { |
a0c1e907 TG |
2592 | if (!futex_cmpxchg_enabled) |
2593 | return -ENOSYS; | |
0771dfef IM |
2594 | /* |
2595 | * The kernel knows only one size for now: | |
2596 | */ | |
2597 | if (unlikely(len != sizeof(*head))) | |
2598 | return -EINVAL; | |
2599 | ||
2600 | current->robust_list = head; | |
2601 | ||
2602 | return 0; | |
2603 | } | |
2604 | ||
2605 | /** | |
d96ee56c DH |
2606 | * sys_get_robust_list() - Get the robust-futex list head of a task |
2607 | * @pid: pid of the process [zero for current task] | |
2608 | * @head_ptr: pointer to a list-head pointer, the kernel fills it in | |
2609 | * @len_ptr: pointer to a length field, the kernel fills in the header size | |
0771dfef | 2610 | */ |
836f92ad HC |
2611 | SYSCALL_DEFINE3(get_robust_list, int, pid, |
2612 | struct robust_list_head __user * __user *, head_ptr, | |
2613 | size_t __user *, len_ptr) | |
0771dfef | 2614 | { |
ba46df98 | 2615 | struct robust_list_head __user *head; |
0771dfef | 2616 | unsigned long ret; |
bdbb776f | 2617 | struct task_struct *p; |
0771dfef | 2618 | |
a0c1e907 TG |
2619 | if (!futex_cmpxchg_enabled) |
2620 | return -ENOSYS; | |
2621 | ||
bdbb776f KC |
2622 | rcu_read_lock(); |
2623 | ||
2624 | ret = -ESRCH; | |
0771dfef | 2625 | if (!pid) |
bdbb776f | 2626 | p = current; |
0771dfef | 2627 | else { |
228ebcbe | 2628 | p = find_task_by_vpid(pid); |
0771dfef IM |
2629 | if (!p) |
2630 | goto err_unlock; | |
0771dfef IM |
2631 | } |
2632 | ||
bdbb776f KC |
2633 | ret = -EPERM; |
2634 | if (!ptrace_may_access(p, PTRACE_MODE_READ)) | |
2635 | goto err_unlock; | |
2636 | ||
2637 | head = p->robust_list; | |
2638 | rcu_read_unlock(); | |
2639 | ||
0771dfef IM |
2640 | if (put_user(sizeof(*head), len_ptr)) |
2641 | return -EFAULT; | |
2642 | return put_user(head, head_ptr); | |
2643 | ||
2644 | err_unlock: | |
aaa2a97e | 2645 | rcu_read_unlock(); |
0771dfef IM |
2646 | |
2647 | return ret; | |
2648 | } | |
2649 | ||
2650 | /* | |
2651 | * Process a futex-list entry, check whether it's owned by the | |
2652 | * dying task, and do notification if so: | |
2653 | */ | |
e3f2ddea | 2654 | int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi) |
0771dfef | 2655 | { |
7cfdaf38 | 2656 | u32 uval, uninitialized_var(nval), mval; |
0771dfef | 2657 | |
8f17d3a5 IM |
2658 | retry: |
2659 | if (get_user(uval, uaddr)) | |
0771dfef IM |
2660 | return -1; |
2661 | ||
b488893a | 2662 | if ((uval & FUTEX_TID_MASK) == task_pid_vnr(curr)) { |
0771dfef IM |
2663 | /* |
2664 | * Ok, this dying thread is truly holding a futex | |
2665 | * of interest. Set the OWNER_DIED bit atomically | |
2666 | * via cmpxchg, and if the value had FUTEX_WAITERS | |
2667 | * set, wake up a waiter (if any). (We have to do a | |
2668 | * futex_wake() even if OWNER_DIED is already set - | |
2669 | * to handle the rare but possible case of recursive | |
2670 | * thread-death.) The rest of the cleanup is done in | |
2671 | * userspace. | |
2672 | */ | |
e3f2ddea | 2673 | mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED; |
6e0aa9f8 TG |
2674 | /* |
2675 | * We are not holding a lock here, but we want to have | |
2676 | * the pagefault_disable/enable() protection because | |
2677 | * we want to handle the fault gracefully. If the | |
2678 | * access fails we try to fault in the futex with R/W | |
2679 | * verification via get_user_pages. get_user() above | |
2680 | * does not guarantee R/W access. If that fails we | |
2681 | * give up and leave the futex locked. | |
2682 | */ | |
2683 | if (cmpxchg_futex_value_locked(&nval, uaddr, uval, mval)) { | |
2684 | if (fault_in_user_writeable(uaddr)) | |
2685 | return -1; | |
2686 | goto retry; | |
2687 | } | |
c87e2837 | 2688 | if (nval != uval) |
8f17d3a5 | 2689 | goto retry; |
0771dfef | 2690 | |
e3f2ddea IM |
2691 | /* |
2692 | * Wake robust non-PI futexes here. The wakeup of | |
2693 | * PI futexes happens in exit_pi_state(): | |
2694 | */ | |
36cf3b5c | 2695 | if (!pi && (uval & FUTEX_WAITERS)) |
c2f9f201 | 2696 | futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY); |
0771dfef IM |
2697 | } |
2698 | return 0; | |
2699 | } | |
2700 | ||
e3f2ddea IM |
2701 | /* |
2702 | * Fetch a robust-list pointer. Bit 0 signals PI futexes: | |
2703 | */ | |
2704 | static inline int fetch_robust_entry(struct robust_list __user **entry, | |
ba46df98 | 2705 | struct robust_list __user * __user *head, |
1dcc41bb | 2706 | unsigned int *pi) |
e3f2ddea IM |
2707 | { |
2708 | unsigned long uentry; | |
2709 | ||
ba46df98 | 2710 | if (get_user(uentry, (unsigned long __user *)head)) |
e3f2ddea IM |
2711 | return -EFAULT; |
2712 | ||
ba46df98 | 2713 | *entry = (void __user *)(uentry & ~1UL); |
e3f2ddea IM |
2714 | *pi = uentry & 1; |
2715 | ||
2716 | return 0; | |
2717 | } | |
2718 | ||
0771dfef IM |
2719 | /* |
2720 | * Walk curr->robust_list (very carefully, it's a userspace list!) | |
2721 | * and mark any locks found there dead, and notify any waiters. | |
2722 | * | |
2723 | * We silently return on any sign of list-walking problem. | |
2724 | */ | |
2725 | void exit_robust_list(struct task_struct *curr) | |
2726 | { | |
2727 | struct robust_list_head __user *head = curr->robust_list; | |
9f96cb1e | 2728 | struct robust_list __user *entry, *next_entry, *pending; |
4c115e95 DH |
2729 | unsigned int limit = ROBUST_LIST_LIMIT, pi, pip; |
2730 | unsigned int uninitialized_var(next_pi); | |
0771dfef | 2731 | unsigned long futex_offset; |
9f96cb1e | 2732 | int rc; |
0771dfef | 2733 | |
a0c1e907 TG |
2734 | if (!futex_cmpxchg_enabled) |
2735 | return; | |
2736 | ||
0771dfef IM |
2737 | /* |
2738 | * Fetch the list head (which was registered earlier, via | |
2739 | * sys_set_robust_list()): | |
2740 | */ | |
e3f2ddea | 2741 | if (fetch_robust_entry(&entry, &head->list.next, &pi)) |
0771dfef IM |
2742 | return; |
2743 | /* | |
2744 | * Fetch the relative futex offset: | |
2745 | */ | |
2746 | if (get_user(futex_offset, &head->futex_offset)) | |
2747 | return; | |
2748 | /* | |
2749 | * Fetch any possibly pending lock-add first, and handle it | |
2750 | * if it exists: | |
2751 | */ | |
e3f2ddea | 2752 | if (fetch_robust_entry(&pending, &head->list_op_pending, &pip)) |
0771dfef | 2753 | return; |
e3f2ddea | 2754 | |
9f96cb1e | 2755 | next_entry = NULL; /* avoid warning with gcc */ |
0771dfef | 2756 | while (entry != &head->list) { |
9f96cb1e MS |
2757 | /* |
2758 | * Fetch the next entry in the list before calling | |
2759 | * handle_futex_death: | |
2760 | */ | |
2761 | rc = fetch_robust_entry(&next_entry, &entry->next, &next_pi); | |
0771dfef IM |
2762 | /* |
2763 | * A pending lock might already be on the list, so | |
c87e2837 | 2764 | * don't process it twice: |
0771dfef IM |
2765 | */ |
2766 | if (entry != pending) | |
ba46df98 | 2767 | if (handle_futex_death((void __user *)entry + futex_offset, |
e3f2ddea | 2768 | curr, pi)) |
0771dfef | 2769 | return; |
9f96cb1e | 2770 | if (rc) |
0771dfef | 2771 | return; |
9f96cb1e MS |
2772 | entry = next_entry; |
2773 | pi = next_pi; | |
0771dfef IM |
2774 | /* |
2775 | * Avoid excessively long or circular lists: | |
2776 | */ | |
2777 | if (!--limit) | |
2778 | break; | |
2779 | ||
2780 | cond_resched(); | |
2781 | } | |
9f96cb1e MS |
2782 | |
2783 | if (pending) | |
2784 | handle_futex_death((void __user *)pending + futex_offset, | |
2785 | curr, pip); | |
0771dfef IM |
2786 | } |
2787 | ||
c19384b5 | 2788 | long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout, |
e2970f2f | 2789 | u32 __user *uaddr2, u32 val2, u32 val3) |
1da177e4 | 2790 | { |
81b40539 | 2791 | int cmd = op & FUTEX_CMD_MASK; |
b41277dc | 2792 | unsigned int flags = 0; |
34f01cc1 ED |
2793 | |
2794 | if (!(op & FUTEX_PRIVATE_FLAG)) | |
b41277dc | 2795 | flags |= FLAGS_SHARED; |
1da177e4 | 2796 | |
b41277dc DH |
2797 | if (op & FUTEX_CLOCK_REALTIME) { |
2798 | flags |= FLAGS_CLOCKRT; | |
2799 | if (cmd != FUTEX_WAIT_BITSET && cmd != FUTEX_WAIT_REQUEUE_PI) | |
2800 | return -ENOSYS; | |
2801 | } | |
1da177e4 | 2802 | |
59263b51 TG |
2803 | switch (cmd) { |
2804 | case FUTEX_LOCK_PI: | |
2805 | case FUTEX_UNLOCK_PI: | |
2806 | case FUTEX_TRYLOCK_PI: | |
2807 | case FUTEX_WAIT_REQUEUE_PI: | |
2808 | case FUTEX_CMP_REQUEUE_PI: | |
2809 | if (!futex_cmpxchg_enabled) | |
2810 | return -ENOSYS; | |
2811 | } | |
2812 | ||
34f01cc1 | 2813 | switch (cmd) { |
1da177e4 | 2814 | case FUTEX_WAIT: |
cd689985 TG |
2815 | val3 = FUTEX_BITSET_MATCH_ANY; |
2816 | case FUTEX_WAIT_BITSET: | |
81b40539 | 2817 | return futex_wait(uaddr, flags, val, timeout, val3); |
1da177e4 | 2818 | case FUTEX_WAKE: |
cd689985 TG |
2819 | val3 = FUTEX_BITSET_MATCH_ANY; |
2820 | case FUTEX_WAKE_BITSET: | |
81b40539 | 2821 | return futex_wake(uaddr, flags, val, val3); |
1da177e4 | 2822 | case FUTEX_REQUEUE: |
81b40539 | 2823 | return futex_requeue(uaddr, flags, uaddr2, val, val2, NULL, 0); |
1da177e4 | 2824 | case FUTEX_CMP_REQUEUE: |
81b40539 | 2825 | return futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 0); |
4732efbe | 2826 | case FUTEX_WAKE_OP: |
81b40539 | 2827 | return futex_wake_op(uaddr, flags, uaddr2, val, val2, val3); |
c87e2837 | 2828 | case FUTEX_LOCK_PI: |
81b40539 | 2829 | return futex_lock_pi(uaddr, flags, val, timeout, 0); |
c87e2837 | 2830 | case FUTEX_UNLOCK_PI: |
81b40539 | 2831 | return futex_unlock_pi(uaddr, flags); |
c87e2837 | 2832 | case FUTEX_TRYLOCK_PI: |
81b40539 | 2833 | return futex_lock_pi(uaddr, flags, 0, timeout, 1); |
52400ba9 DH |
2834 | case FUTEX_WAIT_REQUEUE_PI: |
2835 | val3 = FUTEX_BITSET_MATCH_ANY; | |
81b40539 TG |
2836 | return futex_wait_requeue_pi(uaddr, flags, val, timeout, val3, |
2837 | uaddr2); | |
52400ba9 | 2838 | case FUTEX_CMP_REQUEUE_PI: |
81b40539 | 2839 | return futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 1); |
1da177e4 | 2840 | } |
81b40539 | 2841 | return -ENOSYS; |
1da177e4 LT |
2842 | } |
2843 | ||
2844 | ||
17da2bd9 HC |
2845 | SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val, |
2846 | struct timespec __user *, utime, u32 __user *, uaddr2, | |
2847 | u32, val3) | |
1da177e4 | 2848 | { |
c19384b5 PP |
2849 | struct timespec ts; |
2850 | ktime_t t, *tp = NULL; | |
e2970f2f | 2851 | u32 val2 = 0; |
34f01cc1 | 2852 | int cmd = op & FUTEX_CMD_MASK; |
1da177e4 | 2853 | |
cd689985 | 2854 | if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI || |
52400ba9 DH |
2855 | cmd == FUTEX_WAIT_BITSET || |
2856 | cmd == FUTEX_WAIT_REQUEUE_PI)) { | |
c19384b5 | 2857 | if (copy_from_user(&ts, utime, sizeof(ts)) != 0) |
1da177e4 | 2858 | return -EFAULT; |
c19384b5 | 2859 | if (!timespec_valid(&ts)) |
9741ef96 | 2860 | return -EINVAL; |
c19384b5 PP |
2861 | |
2862 | t = timespec_to_ktime(ts); | |
34f01cc1 | 2863 | if (cmd == FUTEX_WAIT) |
5a7780e7 | 2864 | t = ktime_add_safe(ktime_get(), t); |
c19384b5 | 2865 | tp = &t; |
1da177e4 LT |
2866 | } |
2867 | /* | |
52400ba9 | 2868 | * requeue parameter in 'utime' if cmd == FUTEX_*_REQUEUE_*. |
f54f0986 | 2869 | * number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP. |
1da177e4 | 2870 | */ |
f54f0986 | 2871 | if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE || |
ba9c22f2 | 2872 | cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP) |
e2970f2f | 2873 | val2 = (u32) (unsigned long) utime; |
1da177e4 | 2874 | |
c19384b5 | 2875 | return do_futex(uaddr, op, val, tp, uaddr2, val2, val3); |
1da177e4 LT |
2876 | } |
2877 | ||
f6d107fb | 2878 | static int __init futex_init(void) |
1da177e4 | 2879 | { |
a0c1e907 | 2880 | u32 curval; |
63b1a816 | 2881 | unsigned int futex_shift; |
a52b89eb DB |
2882 | unsigned long i; |
2883 | ||
2884 | #if CONFIG_BASE_SMALL | |
2885 | futex_hashsize = 16; | |
2886 | #else | |
2887 | futex_hashsize = roundup_pow_of_two(256 * num_possible_cpus()); | |
2888 | #endif | |
2889 | ||
2890 | futex_queues = alloc_large_system_hash("futex", sizeof(*futex_queues), | |
2891 | futex_hashsize, 0, | |
2892 | futex_hashsize < 256 ? HASH_SMALL : 0, | |
63b1a816 HC |
2893 | &futex_shift, NULL, |
2894 | futex_hashsize, futex_hashsize); | |
2895 | futex_hashsize = 1UL << futex_shift; | |
a0c1e907 TG |
2896 | /* |
2897 | * This will fail and we want it. Some arch implementations do | |
2898 | * runtime detection of the futex_atomic_cmpxchg_inatomic() | |
2899 | * functionality. We want to know that before we call in any | |
2900 | * of the complex code paths. Also we want to prevent | |
2901 | * registration of robust lists in that case. NULL is | |
2902 | * guaranteed to fault and we get -EFAULT on functional | |
fb62db2b | 2903 | * implementation, the non-functional ones will return |
a0c1e907 TG |
2904 | * -ENOSYS. |
2905 | */ | |
37a9d912 | 2906 | if (cmpxchg_futex_value_locked(&curval, NULL, 0, 0) == -EFAULT) |
a0c1e907 TG |
2907 | futex_cmpxchg_enabled = 1; |
2908 | ||
a52b89eb | 2909 | for (i = 0; i < futex_hashsize; i++) { |
11d4616b | 2910 | atomic_set(&futex_queues[i].waiters, 0); |
732375c6 | 2911 | plist_head_init(&futex_queues[i].chain); |
3e4ab747 TG |
2912 | spin_lock_init(&futex_queues[i].lock); |
2913 | } | |
2914 | ||
1da177e4 LT |
2915 | return 0; |
2916 | } | |
f6d107fb | 2917 | __initcall(futex_init); |