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> |
ab51fbab | 67 | #include <linux/fault-inject.h> |
b488893a | 68 | |
4732efbe | 69 | #include <asm/futex.h> |
1da177e4 | 70 | |
1696a8be | 71 | #include "locking/rtmutex_common.h" |
c87e2837 | 72 | |
99b60ce6 | 73 | /* |
d7e8af1a DB |
74 | * READ this before attempting to hack on futexes! |
75 | * | |
76 | * Basic futex operation and ordering guarantees | |
77 | * ============================================= | |
99b60ce6 TG |
78 | * |
79 | * The waiter reads the futex value in user space and calls | |
80 | * futex_wait(). This function computes the hash bucket and acquires | |
81 | * the hash bucket lock. After that it reads the futex user space value | |
b0c29f79 DB |
82 | * again and verifies that the data has not changed. If it has not changed |
83 | * it enqueues itself into the hash bucket, releases the hash bucket lock | |
84 | * and schedules. | |
99b60ce6 TG |
85 | * |
86 | * The waker side modifies the user space value of the futex and calls | |
b0c29f79 DB |
87 | * futex_wake(). This function computes the hash bucket and acquires the |
88 | * hash bucket lock. Then it looks for waiters on that futex in the hash | |
89 | * bucket and wakes them. | |
99b60ce6 | 90 | * |
b0c29f79 DB |
91 | * In futex wake up scenarios where no tasks are blocked on a futex, taking |
92 | * the hb spinlock can be avoided and simply return. In order for this | |
93 | * optimization to work, ordering guarantees must exist so that the waiter | |
94 | * being added to the list is acknowledged when the list is concurrently being | |
95 | * checked by the waker, avoiding scenarios like the following: | |
99b60ce6 TG |
96 | * |
97 | * CPU 0 CPU 1 | |
98 | * val = *futex; | |
99 | * sys_futex(WAIT, futex, val); | |
100 | * futex_wait(futex, val); | |
101 | * uval = *futex; | |
102 | * *futex = newval; | |
103 | * sys_futex(WAKE, futex); | |
104 | * futex_wake(futex); | |
105 | * if (queue_empty()) | |
106 | * return; | |
107 | * if (uval == val) | |
108 | * lock(hash_bucket(futex)); | |
109 | * queue(); | |
110 | * unlock(hash_bucket(futex)); | |
111 | * schedule(); | |
112 | * | |
113 | * This would cause the waiter on CPU 0 to wait forever because it | |
114 | * missed the transition of the user space value from val to newval | |
115 | * and the waker did not find the waiter in the hash bucket queue. | |
99b60ce6 | 116 | * |
b0c29f79 DB |
117 | * The correct serialization ensures that a waiter either observes |
118 | * the changed user space value before blocking or is woken by a | |
119 | * concurrent waker: | |
120 | * | |
121 | * CPU 0 CPU 1 | |
99b60ce6 TG |
122 | * val = *futex; |
123 | * sys_futex(WAIT, futex, val); | |
124 | * futex_wait(futex, val); | |
b0c29f79 | 125 | * |
d7e8af1a | 126 | * waiters++; (a) |
b0c29f79 DB |
127 | * mb(); (A) <-- paired with -. |
128 | * | | |
129 | * lock(hash_bucket(futex)); | | |
130 | * | | |
131 | * uval = *futex; | | |
132 | * | *futex = newval; | |
133 | * | sys_futex(WAKE, futex); | |
134 | * | futex_wake(futex); | |
135 | * | | |
136 | * `-------> mb(); (B) | |
99b60ce6 | 137 | * if (uval == val) |
b0c29f79 | 138 | * queue(); |
99b60ce6 | 139 | * unlock(hash_bucket(futex)); |
b0c29f79 DB |
140 | * schedule(); if (waiters) |
141 | * lock(hash_bucket(futex)); | |
d7e8af1a DB |
142 | * else wake_waiters(futex); |
143 | * waiters--; (b) unlock(hash_bucket(futex)); | |
b0c29f79 | 144 | * |
d7e8af1a DB |
145 | * Where (A) orders the waiters increment and the futex value read through |
146 | * atomic operations (see hb_waiters_inc) and where (B) orders the write | |
993b2ff2 DB |
147 | * to futex and the waiters read -- this is done by the barriers for both |
148 | * shared and private futexes in get_futex_key_refs(). | |
b0c29f79 DB |
149 | * |
150 | * This yields the following case (where X:=waiters, Y:=futex): | |
151 | * | |
152 | * X = Y = 0 | |
153 | * | |
154 | * w[X]=1 w[Y]=1 | |
155 | * MB MB | |
156 | * r[Y]=y r[X]=x | |
157 | * | |
158 | * Which guarantees that x==0 && y==0 is impossible; which translates back into | |
159 | * the guarantee that we cannot both miss the futex variable change and the | |
160 | * enqueue. | |
d7e8af1a DB |
161 | * |
162 | * Note that a new waiter is accounted for in (a) even when it is possible that | |
163 | * the wait call can return error, in which case we backtrack from it in (b). | |
164 | * Refer to the comment in queue_lock(). | |
165 | * | |
166 | * Similarly, in order to account for waiters being requeued on another | |
167 | * address we always increment the waiters for the destination bucket before | |
168 | * acquiring the lock. It then decrements them again after releasing it - | |
169 | * the code that actually moves the futex(es) between hash buckets (requeue_futex) | |
170 | * will do the additional required waiter count housekeeping. This is done for | |
171 | * double_lock_hb() and double_unlock_hb(), respectively. | |
99b60ce6 TG |
172 | */ |
173 | ||
03b8c7b6 | 174 | #ifndef CONFIG_HAVE_FUTEX_CMPXCHG |
a0c1e907 | 175 | int __read_mostly futex_cmpxchg_enabled; |
03b8c7b6 | 176 | #endif |
a0c1e907 | 177 | |
b41277dc DH |
178 | /* |
179 | * Futex flags used to encode options to functions and preserve them across | |
180 | * restarts. | |
181 | */ | |
182 | #define FLAGS_SHARED 0x01 | |
183 | #define FLAGS_CLOCKRT 0x02 | |
184 | #define FLAGS_HAS_TIMEOUT 0x04 | |
185 | ||
c87e2837 IM |
186 | /* |
187 | * Priority Inheritance state: | |
188 | */ | |
189 | struct futex_pi_state { | |
190 | /* | |
191 | * list of 'owned' pi_state instances - these have to be | |
192 | * cleaned up in do_exit() if the task exits prematurely: | |
193 | */ | |
194 | struct list_head list; | |
195 | ||
196 | /* | |
197 | * The PI object: | |
198 | */ | |
199 | struct rt_mutex pi_mutex; | |
200 | ||
201 | struct task_struct *owner; | |
202 | atomic_t refcount; | |
203 | ||
204 | union futex_key key; | |
205 | }; | |
206 | ||
d8d88fbb DH |
207 | /** |
208 | * struct futex_q - The hashed futex queue entry, one per waiting task | |
fb62db2b | 209 | * @list: priority-sorted list of tasks waiting on this futex |
d8d88fbb DH |
210 | * @task: the task waiting on the futex |
211 | * @lock_ptr: the hash bucket lock | |
212 | * @key: the key the futex is hashed on | |
213 | * @pi_state: optional priority inheritance state | |
214 | * @rt_waiter: rt_waiter storage for use with requeue_pi | |
215 | * @requeue_pi_key: the requeue_pi target futex key | |
216 | * @bitset: bitset for the optional bitmasked wakeup | |
217 | * | |
218 | * We use this hashed waitqueue, instead of a normal wait_queue_t, so | |
1da177e4 LT |
219 | * we can wake only the relevant ones (hashed queues may be shared). |
220 | * | |
221 | * A futex_q has a woken state, just like tasks have TASK_RUNNING. | |
ec92d082 | 222 | * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0. |
fb62db2b | 223 | * The order of wakeup is always to make the first condition true, then |
d8d88fbb DH |
224 | * the second. |
225 | * | |
226 | * PI futexes are typically woken before they are removed from the hash list via | |
227 | * the rt_mutex code. See unqueue_me_pi(). | |
1da177e4 LT |
228 | */ |
229 | struct futex_q { | |
ec92d082 | 230 | struct plist_node list; |
1da177e4 | 231 | |
d8d88fbb | 232 | struct task_struct *task; |
1da177e4 | 233 | spinlock_t *lock_ptr; |
1da177e4 | 234 | union futex_key key; |
c87e2837 | 235 | struct futex_pi_state *pi_state; |
52400ba9 | 236 | struct rt_mutex_waiter *rt_waiter; |
84bc4af5 | 237 | union futex_key *requeue_pi_key; |
cd689985 | 238 | u32 bitset; |
1da177e4 LT |
239 | }; |
240 | ||
5bdb05f9 DH |
241 | static const struct futex_q futex_q_init = { |
242 | /* list gets initialized in queue_me()*/ | |
243 | .key = FUTEX_KEY_INIT, | |
244 | .bitset = FUTEX_BITSET_MATCH_ANY | |
245 | }; | |
246 | ||
1da177e4 | 247 | /* |
b2d0994b DH |
248 | * Hash buckets are shared by all the futex_keys that hash to the same |
249 | * location. Each key may have multiple futex_q structures, one for each task | |
250 | * waiting on a futex. | |
1da177e4 LT |
251 | */ |
252 | struct futex_hash_bucket { | |
11d4616b | 253 | atomic_t waiters; |
ec92d082 PP |
254 | spinlock_t lock; |
255 | struct plist_head chain; | |
a52b89eb | 256 | } ____cacheline_aligned_in_smp; |
1da177e4 | 257 | |
ac742d37 RV |
258 | /* |
259 | * The base of the bucket array and its size are always used together | |
260 | * (after initialization only in hash_futex()), so ensure that they | |
261 | * reside in the same cacheline. | |
262 | */ | |
263 | static struct { | |
264 | struct futex_hash_bucket *queues; | |
265 | unsigned long hashsize; | |
266 | } __futex_data __read_mostly __aligned(2*sizeof(long)); | |
267 | #define futex_queues (__futex_data.queues) | |
268 | #define futex_hashsize (__futex_data.hashsize) | |
a52b89eb | 269 | |
1da177e4 | 270 | |
ab51fbab DB |
271 | /* |
272 | * Fault injections for futexes. | |
273 | */ | |
274 | #ifdef CONFIG_FAIL_FUTEX | |
275 | ||
276 | static struct { | |
277 | struct fault_attr attr; | |
278 | ||
621a5f7a | 279 | bool ignore_private; |
ab51fbab DB |
280 | } fail_futex = { |
281 | .attr = FAULT_ATTR_INITIALIZER, | |
621a5f7a | 282 | .ignore_private = false, |
ab51fbab DB |
283 | }; |
284 | ||
285 | static int __init setup_fail_futex(char *str) | |
286 | { | |
287 | return setup_fault_attr(&fail_futex.attr, str); | |
288 | } | |
289 | __setup("fail_futex=", setup_fail_futex); | |
290 | ||
5d285a7f | 291 | static bool should_fail_futex(bool fshared) |
ab51fbab DB |
292 | { |
293 | if (fail_futex.ignore_private && !fshared) | |
294 | return false; | |
295 | ||
296 | return should_fail(&fail_futex.attr, 1); | |
297 | } | |
298 | ||
299 | #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS | |
300 | ||
301 | static int __init fail_futex_debugfs(void) | |
302 | { | |
303 | umode_t mode = S_IFREG | S_IRUSR | S_IWUSR; | |
304 | struct dentry *dir; | |
305 | ||
306 | dir = fault_create_debugfs_attr("fail_futex", NULL, | |
307 | &fail_futex.attr); | |
308 | if (IS_ERR(dir)) | |
309 | return PTR_ERR(dir); | |
310 | ||
311 | if (!debugfs_create_bool("ignore-private", mode, dir, | |
312 | &fail_futex.ignore_private)) { | |
313 | debugfs_remove_recursive(dir); | |
314 | return -ENOMEM; | |
315 | } | |
316 | ||
317 | return 0; | |
318 | } | |
319 | ||
320 | late_initcall(fail_futex_debugfs); | |
321 | ||
322 | #endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */ | |
323 | ||
324 | #else | |
325 | static inline bool should_fail_futex(bool fshared) | |
326 | { | |
327 | return false; | |
328 | } | |
329 | #endif /* CONFIG_FAIL_FUTEX */ | |
330 | ||
b0c29f79 DB |
331 | static inline void futex_get_mm(union futex_key *key) |
332 | { | |
333 | atomic_inc(&key->private.mm->mm_count); | |
334 | /* | |
335 | * Ensure futex_get_mm() implies a full barrier such that | |
336 | * get_futex_key() implies a full barrier. This is relied upon | |
337 | * as full barrier (B), see the ordering comment above. | |
338 | */ | |
4e857c58 | 339 | smp_mb__after_atomic(); |
b0c29f79 DB |
340 | } |
341 | ||
11d4616b LT |
342 | /* |
343 | * Reflects a new waiter being added to the waitqueue. | |
344 | */ | |
345 | static inline void hb_waiters_inc(struct futex_hash_bucket *hb) | |
b0c29f79 DB |
346 | { |
347 | #ifdef CONFIG_SMP | |
11d4616b | 348 | atomic_inc(&hb->waiters); |
b0c29f79 | 349 | /* |
11d4616b | 350 | * Full barrier (A), see the ordering comment above. |
b0c29f79 | 351 | */ |
4e857c58 | 352 | smp_mb__after_atomic(); |
11d4616b LT |
353 | #endif |
354 | } | |
355 | ||
356 | /* | |
357 | * Reflects a waiter being removed from the waitqueue by wakeup | |
358 | * paths. | |
359 | */ | |
360 | static inline void hb_waiters_dec(struct futex_hash_bucket *hb) | |
361 | { | |
362 | #ifdef CONFIG_SMP | |
363 | atomic_dec(&hb->waiters); | |
364 | #endif | |
365 | } | |
b0c29f79 | 366 | |
11d4616b LT |
367 | static inline int hb_waiters_pending(struct futex_hash_bucket *hb) |
368 | { | |
369 | #ifdef CONFIG_SMP | |
370 | return atomic_read(&hb->waiters); | |
b0c29f79 | 371 | #else |
11d4616b | 372 | return 1; |
b0c29f79 DB |
373 | #endif |
374 | } | |
375 | ||
1da177e4 LT |
376 | /* |
377 | * We hash on the keys returned from get_futex_key (see below). | |
378 | */ | |
379 | static struct futex_hash_bucket *hash_futex(union futex_key *key) | |
380 | { | |
381 | u32 hash = jhash2((u32*)&key->both.word, | |
382 | (sizeof(key->both.word)+sizeof(key->both.ptr))/4, | |
383 | key->both.offset); | |
a52b89eb | 384 | return &futex_queues[hash & (futex_hashsize - 1)]; |
1da177e4 LT |
385 | } |
386 | ||
387 | /* | |
388 | * Return 1 if two futex_keys are equal, 0 otherwise. | |
389 | */ | |
390 | static inline int match_futex(union futex_key *key1, union futex_key *key2) | |
391 | { | |
2bc87203 DH |
392 | return (key1 && key2 |
393 | && key1->both.word == key2->both.word | |
1da177e4 LT |
394 | && key1->both.ptr == key2->both.ptr |
395 | && key1->both.offset == key2->both.offset); | |
396 | } | |
397 | ||
38d47c1b PZ |
398 | /* |
399 | * Take a reference to the resource addressed by a key. | |
400 | * Can be called while holding spinlocks. | |
401 | * | |
402 | */ | |
403 | static void get_futex_key_refs(union futex_key *key) | |
404 | { | |
405 | if (!key->both.ptr) | |
406 | return; | |
407 | ||
408 | switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { | |
409 | case FUT_OFF_INODE: | |
b0c29f79 | 410 | ihold(key->shared.inode); /* implies MB (B) */ |
38d47c1b PZ |
411 | break; |
412 | case FUT_OFF_MMSHARED: | |
b0c29f79 | 413 | futex_get_mm(key); /* implies MB (B) */ |
38d47c1b | 414 | break; |
76835b0e | 415 | default: |
993b2ff2 DB |
416 | /* |
417 | * Private futexes do not hold reference on an inode or | |
418 | * mm, therefore the only purpose of calling get_futex_key_refs | |
419 | * is because we need the barrier for the lockless waiter check. | |
420 | */ | |
76835b0e | 421 | smp_mb(); /* explicit MB (B) */ |
38d47c1b PZ |
422 | } |
423 | } | |
424 | ||
425 | /* | |
426 | * Drop a reference to the resource addressed by a key. | |
993b2ff2 DB |
427 | * The hash bucket spinlock must not be held. This is |
428 | * a no-op for private futexes, see comment in the get | |
429 | * counterpart. | |
38d47c1b PZ |
430 | */ |
431 | static void drop_futex_key_refs(union futex_key *key) | |
432 | { | |
90621c40 DH |
433 | if (!key->both.ptr) { |
434 | /* If we're here then we tried to put a key we failed to get */ | |
435 | WARN_ON_ONCE(1); | |
38d47c1b | 436 | return; |
90621c40 | 437 | } |
38d47c1b PZ |
438 | |
439 | switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { | |
440 | case FUT_OFF_INODE: | |
441 | iput(key->shared.inode); | |
442 | break; | |
443 | case FUT_OFF_MMSHARED: | |
444 | mmdrop(key->private.mm); | |
445 | break; | |
446 | } | |
447 | } | |
448 | ||
34f01cc1 | 449 | /** |
d96ee56c DH |
450 | * get_futex_key() - Get parameters which are the keys for a futex |
451 | * @uaddr: virtual address of the futex | |
452 | * @fshared: 0 for a PROCESS_PRIVATE futex, 1 for PROCESS_SHARED | |
453 | * @key: address where result is stored. | |
9ea71503 SB |
454 | * @rw: mapping needs to be read/write (values: VERIFY_READ, |
455 | * VERIFY_WRITE) | |
34f01cc1 | 456 | * |
6c23cbbd RD |
457 | * Return: a negative error code or 0 |
458 | * | |
34f01cc1 | 459 | * The key words are stored in *key on success. |
1da177e4 | 460 | * |
6131ffaa | 461 | * For shared mappings, it's (page->index, file_inode(vma->vm_file), |
1da177e4 LT |
462 | * offset_within_page). For private mappings, it's (uaddr, current->mm). |
463 | * We can usually work out the index without swapping in the page. | |
464 | * | |
b2d0994b | 465 | * lock_page() might sleep, the caller should not hold a spinlock. |
1da177e4 | 466 | */ |
64d1304a | 467 | static int |
9ea71503 | 468 | get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key, int rw) |
1da177e4 | 469 | { |
e2970f2f | 470 | unsigned long address = (unsigned long)uaddr; |
1da177e4 | 471 | struct mm_struct *mm = current->mm; |
14d27abd KS |
472 | struct page *page; |
473 | struct address_space *mapping; | |
9ea71503 | 474 | int err, ro = 0; |
1da177e4 LT |
475 | |
476 | /* | |
477 | * The futex address must be "naturally" aligned. | |
478 | */ | |
e2970f2f | 479 | key->both.offset = address % PAGE_SIZE; |
34f01cc1 | 480 | if (unlikely((address % sizeof(u32)) != 0)) |
1da177e4 | 481 | return -EINVAL; |
e2970f2f | 482 | address -= key->both.offset; |
1da177e4 | 483 | |
5cdec2d8 LT |
484 | if (unlikely(!access_ok(rw, uaddr, sizeof(u32)))) |
485 | return -EFAULT; | |
486 | ||
ab51fbab DB |
487 | if (unlikely(should_fail_futex(fshared))) |
488 | return -EFAULT; | |
489 | ||
34f01cc1 ED |
490 | /* |
491 | * PROCESS_PRIVATE futexes are fast. | |
492 | * As the mm cannot disappear under us and the 'key' only needs | |
493 | * virtual address, we dont even have to find the underlying vma. | |
494 | * Note : We do have to check 'uaddr' is a valid user address, | |
495 | * but access_ok() should be faster than find_vma() | |
496 | */ | |
497 | if (!fshared) { | |
34f01cc1 ED |
498 | key->private.mm = mm; |
499 | key->private.address = address; | |
b0c29f79 | 500 | get_futex_key_refs(key); /* implies MB (B) */ |
34f01cc1 ED |
501 | return 0; |
502 | } | |
1da177e4 | 503 | |
38d47c1b | 504 | again: |
ab51fbab DB |
505 | /* Ignore any VERIFY_READ mapping (futex common case) */ |
506 | if (unlikely(should_fail_futex(fshared))) | |
507 | return -EFAULT; | |
508 | ||
7485d0d3 | 509 | err = get_user_pages_fast(address, 1, 1, &page); |
9ea71503 SB |
510 | /* |
511 | * If write access is not required (eg. FUTEX_WAIT), try | |
512 | * and get read-only access. | |
513 | */ | |
514 | if (err == -EFAULT && rw == VERIFY_READ) { | |
515 | err = get_user_pages_fast(address, 1, 0, &page); | |
516 | ro = 1; | |
517 | } | |
38d47c1b PZ |
518 | if (err < 0) |
519 | return err; | |
9ea71503 SB |
520 | else |
521 | err = 0; | |
38d47c1b | 522 | |
14d27abd | 523 | lock_page(page); |
e6780f72 | 524 | /* |
14d27abd | 525 | * If page->mapping is NULL, then it cannot be a PageAnon |
e6780f72 HD |
526 | * page; but it might be the ZERO_PAGE or in the gate area or |
527 | * in a special mapping (all cases which we are happy to fail); | |
528 | * or it may have been a good file page when get_user_pages_fast | |
529 | * found it, but truncated or holepunched or subjected to | |
530 | * invalidate_complete_page2 before we got the page lock (also | |
531 | * cases which we are happy to fail). And we hold a reference, | |
532 | * so refcount care in invalidate_complete_page's remove_mapping | |
533 | * prevents drop_caches from setting mapping to NULL beneath us. | |
534 | * | |
535 | * The case we do have to guard against is when memory pressure made | |
536 | * shmem_writepage move it from filecache to swapcache beneath us: | |
14d27abd | 537 | * an unlikely race, but we do need to retry for page->mapping. |
e6780f72 | 538 | */ |
14d27abd KS |
539 | mapping = compound_head(page)->mapping; |
540 | if (!mapping) { | |
541 | int shmem_swizzled = PageSwapCache(page); | |
542 | unlock_page(page); | |
543 | put_page(page); | |
e6780f72 HD |
544 | if (shmem_swizzled) |
545 | goto again; | |
546 | return -EFAULT; | |
38d47c1b | 547 | } |
1da177e4 LT |
548 | |
549 | /* | |
550 | * Private mappings are handled in a simple way. | |
551 | * | |
552 | * NOTE: When userspace waits on a MAP_SHARED mapping, even if | |
553 | * it's a read-only handle, it's expected that futexes attach to | |
38d47c1b | 554 | * the object not the particular process. |
1da177e4 | 555 | */ |
14d27abd | 556 | if (PageAnon(page)) { |
9ea71503 SB |
557 | /* |
558 | * A RO anonymous page will never change and thus doesn't make | |
559 | * sense for futex operations. | |
560 | */ | |
ab51fbab | 561 | if (unlikely(should_fail_futex(fshared)) || ro) { |
9ea71503 SB |
562 | err = -EFAULT; |
563 | goto out; | |
564 | } | |
565 | ||
38d47c1b | 566 | key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */ |
1da177e4 | 567 | key->private.mm = mm; |
e2970f2f | 568 | key->private.address = address; |
38d47c1b PZ |
569 | } else { |
570 | key->both.offset |= FUT_OFF_INODE; /* inode-based key */ | |
14d27abd | 571 | key->shared.inode = mapping->host; |
13d60f4b | 572 | key->shared.pgoff = basepage_index(page); |
1da177e4 LT |
573 | } |
574 | ||
b0c29f79 | 575 | get_futex_key_refs(key); /* implies MB (B) */ |
1da177e4 | 576 | |
9ea71503 | 577 | out: |
14d27abd KS |
578 | unlock_page(page); |
579 | put_page(page); | |
9ea71503 | 580 | return err; |
1da177e4 LT |
581 | } |
582 | ||
ae791a2d | 583 | static inline void put_futex_key(union futex_key *key) |
1da177e4 | 584 | { |
38d47c1b | 585 | drop_futex_key_refs(key); |
1da177e4 LT |
586 | } |
587 | ||
d96ee56c DH |
588 | /** |
589 | * fault_in_user_writeable() - Fault in user address and verify RW access | |
d0725992 TG |
590 | * @uaddr: pointer to faulting user space address |
591 | * | |
592 | * Slow path to fixup the fault we just took in the atomic write | |
593 | * access to @uaddr. | |
594 | * | |
fb62db2b | 595 | * We have no generic implementation of a non-destructive write to the |
d0725992 TG |
596 | * user address. We know that we faulted in the atomic pagefault |
597 | * disabled section so we can as well avoid the #PF overhead by | |
598 | * calling get_user_pages() right away. | |
599 | */ | |
600 | static int fault_in_user_writeable(u32 __user *uaddr) | |
601 | { | |
722d0172 AK |
602 | struct mm_struct *mm = current->mm; |
603 | int ret; | |
604 | ||
605 | down_read(&mm->mmap_sem); | |
2efaca92 | 606 | ret = fixup_user_fault(current, mm, (unsigned long)uaddr, |
4a9e1cda | 607 | FAULT_FLAG_WRITE, NULL); |
722d0172 AK |
608 | up_read(&mm->mmap_sem); |
609 | ||
d0725992 TG |
610 | return ret < 0 ? ret : 0; |
611 | } | |
612 | ||
4b1c486b DH |
613 | /** |
614 | * futex_top_waiter() - Return the highest priority waiter on a futex | |
d96ee56c DH |
615 | * @hb: the hash bucket the futex_q's reside in |
616 | * @key: the futex key (to distinguish it from other futex futex_q's) | |
4b1c486b DH |
617 | * |
618 | * Must be called with the hb lock held. | |
619 | */ | |
620 | static struct futex_q *futex_top_waiter(struct futex_hash_bucket *hb, | |
621 | union futex_key *key) | |
622 | { | |
623 | struct futex_q *this; | |
624 | ||
625 | plist_for_each_entry(this, &hb->chain, list) { | |
626 | if (match_futex(&this->key, key)) | |
627 | return this; | |
628 | } | |
629 | return NULL; | |
630 | } | |
631 | ||
37a9d912 ML |
632 | static int cmpxchg_futex_value_locked(u32 *curval, u32 __user *uaddr, |
633 | u32 uval, u32 newval) | |
36cf3b5c | 634 | { |
37a9d912 | 635 | int ret; |
36cf3b5c TG |
636 | |
637 | pagefault_disable(); | |
37a9d912 | 638 | ret = futex_atomic_cmpxchg_inatomic(curval, uaddr, uval, newval); |
36cf3b5c TG |
639 | pagefault_enable(); |
640 | ||
37a9d912 | 641 | return ret; |
36cf3b5c TG |
642 | } |
643 | ||
644 | static int get_futex_value_locked(u32 *dest, u32 __user *from) | |
1da177e4 LT |
645 | { |
646 | int ret; | |
647 | ||
a866374a | 648 | pagefault_disable(); |
e2970f2f | 649 | ret = __copy_from_user_inatomic(dest, from, sizeof(u32)); |
a866374a | 650 | pagefault_enable(); |
1da177e4 LT |
651 | |
652 | return ret ? -EFAULT : 0; | |
653 | } | |
654 | ||
c87e2837 IM |
655 | |
656 | /* | |
657 | * PI code: | |
658 | */ | |
659 | static int refill_pi_state_cache(void) | |
660 | { | |
661 | struct futex_pi_state *pi_state; | |
662 | ||
663 | if (likely(current->pi_state_cache)) | |
664 | return 0; | |
665 | ||
4668edc3 | 666 | pi_state = kzalloc(sizeof(*pi_state), GFP_KERNEL); |
c87e2837 IM |
667 | |
668 | if (!pi_state) | |
669 | return -ENOMEM; | |
670 | ||
c87e2837 IM |
671 | INIT_LIST_HEAD(&pi_state->list); |
672 | /* pi_mutex gets initialized later */ | |
673 | pi_state->owner = NULL; | |
674 | atomic_set(&pi_state->refcount, 1); | |
38d47c1b | 675 | pi_state->key = FUTEX_KEY_INIT; |
c87e2837 IM |
676 | |
677 | current->pi_state_cache = pi_state; | |
678 | ||
679 | return 0; | |
680 | } | |
681 | ||
682 | static struct futex_pi_state * alloc_pi_state(void) | |
683 | { | |
684 | struct futex_pi_state *pi_state = current->pi_state_cache; | |
685 | ||
686 | WARN_ON(!pi_state); | |
687 | current->pi_state_cache = NULL; | |
688 | ||
689 | return pi_state; | |
690 | } | |
691 | ||
30a6b803 | 692 | /* |
29e9ee5d TG |
693 | * Drops a reference to the pi_state object and frees or caches it |
694 | * when the last reference is gone. | |
695 | * | |
30a6b803 BS |
696 | * Must be called with the hb lock held. |
697 | */ | |
29e9ee5d | 698 | static void put_pi_state(struct futex_pi_state *pi_state) |
c87e2837 | 699 | { |
30a6b803 BS |
700 | if (!pi_state) |
701 | return; | |
702 | ||
c87e2837 IM |
703 | if (!atomic_dec_and_test(&pi_state->refcount)) |
704 | return; | |
705 | ||
706 | /* | |
707 | * If pi_state->owner is NULL, the owner is most probably dying | |
708 | * and has cleaned up the pi_state already | |
709 | */ | |
710 | if (pi_state->owner) { | |
1d615482 | 711 | raw_spin_lock_irq(&pi_state->owner->pi_lock); |
c87e2837 | 712 | list_del_init(&pi_state->list); |
1d615482 | 713 | raw_spin_unlock_irq(&pi_state->owner->pi_lock); |
c87e2837 IM |
714 | |
715 | rt_mutex_proxy_unlock(&pi_state->pi_mutex, pi_state->owner); | |
716 | } | |
717 | ||
718 | if (current->pi_state_cache) | |
719 | kfree(pi_state); | |
720 | else { | |
721 | /* | |
722 | * pi_state->list is already empty. | |
723 | * clear pi_state->owner. | |
724 | * refcount is at 0 - put it back to 1. | |
725 | */ | |
726 | pi_state->owner = NULL; | |
727 | atomic_set(&pi_state->refcount, 1); | |
728 | current->pi_state_cache = pi_state; | |
729 | } | |
730 | } | |
731 | ||
732 | /* | |
733 | * Look up the task based on what TID userspace gave us. | |
734 | * We dont trust it. | |
735 | */ | |
736 | static struct task_struct * futex_find_get_task(pid_t pid) | |
737 | { | |
738 | struct task_struct *p; | |
739 | ||
d359b549 | 740 | rcu_read_lock(); |
228ebcbe | 741 | p = find_task_by_vpid(pid); |
7a0ea09a MH |
742 | if (p) |
743 | get_task_struct(p); | |
a06381fe | 744 | |
d359b549 | 745 | rcu_read_unlock(); |
c87e2837 IM |
746 | |
747 | return p; | |
748 | } | |
749 | ||
750 | /* | |
751 | * This task is holding PI mutexes at exit time => bad. | |
752 | * Kernel cleans up PI-state, but userspace is likely hosed. | |
753 | * (Robust-futex cleanup is separate and might save the day for userspace.) | |
754 | */ | |
755 | void exit_pi_state_list(struct task_struct *curr) | |
756 | { | |
c87e2837 IM |
757 | struct list_head *next, *head = &curr->pi_state_list; |
758 | struct futex_pi_state *pi_state; | |
627371d7 | 759 | struct futex_hash_bucket *hb; |
38d47c1b | 760 | union futex_key key = FUTEX_KEY_INIT; |
c87e2837 | 761 | |
a0c1e907 TG |
762 | if (!futex_cmpxchg_enabled) |
763 | return; | |
c87e2837 IM |
764 | /* |
765 | * We are a ZOMBIE and nobody can enqueue itself on | |
766 | * pi_state_list anymore, but we have to be careful | |
627371d7 | 767 | * versus waiters unqueueing themselves: |
c87e2837 | 768 | */ |
1d615482 | 769 | raw_spin_lock_irq(&curr->pi_lock); |
c87e2837 IM |
770 | while (!list_empty(head)) { |
771 | ||
772 | next = head->next; | |
773 | pi_state = list_entry(next, struct futex_pi_state, list); | |
774 | key = pi_state->key; | |
627371d7 | 775 | hb = hash_futex(&key); |
1d615482 | 776 | raw_spin_unlock_irq(&curr->pi_lock); |
c87e2837 | 777 | |
c87e2837 IM |
778 | spin_lock(&hb->lock); |
779 | ||
1d615482 | 780 | raw_spin_lock_irq(&curr->pi_lock); |
627371d7 IM |
781 | /* |
782 | * We dropped the pi-lock, so re-check whether this | |
783 | * task still owns the PI-state: | |
784 | */ | |
c87e2837 IM |
785 | if (head->next != next) { |
786 | spin_unlock(&hb->lock); | |
787 | continue; | |
788 | } | |
789 | ||
c87e2837 | 790 | WARN_ON(pi_state->owner != curr); |
627371d7 IM |
791 | WARN_ON(list_empty(&pi_state->list)); |
792 | list_del_init(&pi_state->list); | |
c87e2837 | 793 | pi_state->owner = NULL; |
1d615482 | 794 | raw_spin_unlock_irq(&curr->pi_lock); |
c87e2837 IM |
795 | |
796 | rt_mutex_unlock(&pi_state->pi_mutex); | |
797 | ||
798 | spin_unlock(&hb->lock); | |
799 | ||
1d615482 | 800 | raw_spin_lock_irq(&curr->pi_lock); |
c87e2837 | 801 | } |
1d615482 | 802 | raw_spin_unlock_irq(&curr->pi_lock); |
c87e2837 IM |
803 | } |
804 | ||
54a21788 TG |
805 | /* |
806 | * We need to check the following states: | |
807 | * | |
808 | * Waiter | pi_state | pi->owner | uTID | uODIED | ? | |
809 | * | |
810 | * [1] NULL | --- | --- | 0 | 0/1 | Valid | |
811 | * [2] NULL | --- | --- | >0 | 0/1 | Valid | |
812 | * | |
813 | * [3] Found | NULL | -- | Any | 0/1 | Invalid | |
814 | * | |
815 | * [4] Found | Found | NULL | 0 | 1 | Valid | |
816 | * [5] Found | Found | NULL | >0 | 1 | Invalid | |
817 | * | |
818 | * [6] Found | Found | task | 0 | 1 | Valid | |
819 | * | |
820 | * [7] Found | Found | NULL | Any | 0 | Invalid | |
821 | * | |
822 | * [8] Found | Found | task | ==taskTID | 0/1 | Valid | |
823 | * [9] Found | Found | task | 0 | 0 | Invalid | |
824 | * [10] Found | Found | task | !=taskTID | 0/1 | Invalid | |
825 | * | |
826 | * [1] Indicates that the kernel can acquire the futex atomically. We | |
827 | * came came here due to a stale FUTEX_WAITERS/FUTEX_OWNER_DIED bit. | |
828 | * | |
829 | * [2] Valid, if TID does not belong to a kernel thread. If no matching | |
830 | * thread is found then it indicates that the owner TID has died. | |
831 | * | |
832 | * [3] Invalid. The waiter is queued on a non PI futex | |
833 | * | |
834 | * [4] Valid state after exit_robust_list(), which sets the user space | |
835 | * value to FUTEX_WAITERS | FUTEX_OWNER_DIED. | |
836 | * | |
837 | * [5] The user space value got manipulated between exit_robust_list() | |
838 | * and exit_pi_state_list() | |
839 | * | |
840 | * [6] Valid state after exit_pi_state_list() which sets the new owner in | |
841 | * the pi_state but cannot access the user space value. | |
842 | * | |
843 | * [7] pi_state->owner can only be NULL when the OWNER_DIED bit is set. | |
844 | * | |
845 | * [8] Owner and user space value match | |
846 | * | |
847 | * [9] There is no transient state which sets the user space TID to 0 | |
848 | * except exit_robust_list(), but this is indicated by the | |
849 | * FUTEX_OWNER_DIED bit. See [4] | |
850 | * | |
851 | * [10] There is no transient state which leaves owner and user space | |
852 | * TID out of sync. | |
853 | */ | |
e60cbc5c TG |
854 | |
855 | /* | |
856 | * Validate that the existing waiter has a pi_state and sanity check | |
857 | * the pi_state against the user space value. If correct, attach to | |
858 | * it. | |
859 | */ | |
860 | static int attach_to_pi_state(u32 uval, struct futex_pi_state *pi_state, | |
861 | struct futex_pi_state **ps) | |
c87e2837 | 862 | { |
778e9a9c | 863 | pid_t pid = uval & FUTEX_TID_MASK; |
c87e2837 | 864 | |
e60cbc5c TG |
865 | /* |
866 | * Userspace might have messed up non-PI and PI futexes [3] | |
867 | */ | |
868 | if (unlikely(!pi_state)) | |
869 | return -EINVAL; | |
06a9ec29 | 870 | |
e60cbc5c | 871 | WARN_ON(!atomic_read(&pi_state->refcount)); |
59647b6a | 872 | |
e60cbc5c TG |
873 | /* |
874 | * Handle the owner died case: | |
875 | */ | |
876 | if (uval & FUTEX_OWNER_DIED) { | |
bd1dbcc6 | 877 | /* |
e60cbc5c TG |
878 | * exit_pi_state_list sets owner to NULL and wakes the |
879 | * topmost waiter. The task which acquires the | |
880 | * pi_state->rt_mutex will fixup owner. | |
bd1dbcc6 | 881 | */ |
e60cbc5c | 882 | if (!pi_state->owner) { |
59647b6a | 883 | /* |
e60cbc5c TG |
884 | * No pi state owner, but the user space TID |
885 | * is not 0. Inconsistent state. [5] | |
59647b6a | 886 | */ |
e60cbc5c TG |
887 | if (pid) |
888 | return -EINVAL; | |
bd1dbcc6 | 889 | /* |
e60cbc5c | 890 | * Take a ref on the state and return success. [4] |
866293ee | 891 | */ |
e60cbc5c | 892 | goto out_state; |
c87e2837 | 893 | } |
bd1dbcc6 TG |
894 | |
895 | /* | |
e60cbc5c TG |
896 | * If TID is 0, then either the dying owner has not |
897 | * yet executed exit_pi_state_list() or some waiter | |
898 | * acquired the rtmutex in the pi state, but did not | |
899 | * yet fixup the TID in user space. | |
900 | * | |
901 | * Take a ref on the state and return success. [6] | |
902 | */ | |
903 | if (!pid) | |
904 | goto out_state; | |
905 | } else { | |
906 | /* | |
907 | * If the owner died bit is not set, then the pi_state | |
908 | * must have an owner. [7] | |
bd1dbcc6 | 909 | */ |
e60cbc5c | 910 | if (!pi_state->owner) |
bd1dbcc6 | 911 | return -EINVAL; |
c87e2837 IM |
912 | } |
913 | ||
e60cbc5c TG |
914 | /* |
915 | * Bail out if user space manipulated the futex value. If pi | |
916 | * state exists then the owner TID must be the same as the | |
917 | * user space TID. [9/10] | |
918 | */ | |
919 | if (pid != task_pid_vnr(pi_state->owner)) | |
920 | return -EINVAL; | |
921 | out_state: | |
922 | atomic_inc(&pi_state->refcount); | |
923 | *ps = pi_state; | |
924 | return 0; | |
925 | } | |
926 | ||
04e1b2e5 TG |
927 | /* |
928 | * Lookup the task for the TID provided from user space and attach to | |
929 | * it after doing proper sanity checks. | |
930 | */ | |
931 | static int attach_to_pi_owner(u32 uval, union futex_key *key, | |
932 | struct futex_pi_state **ps) | |
e60cbc5c | 933 | { |
e60cbc5c | 934 | pid_t pid = uval & FUTEX_TID_MASK; |
04e1b2e5 TG |
935 | struct futex_pi_state *pi_state; |
936 | struct task_struct *p; | |
e60cbc5c | 937 | |
c87e2837 | 938 | /* |
e3f2ddea | 939 | * We are the first waiter - try to look up the real owner and attach |
54a21788 | 940 | * the new pi_state to it, but bail out when TID = 0 [1] |
c87e2837 | 941 | */ |
778e9a9c | 942 | if (!pid) |
e3f2ddea | 943 | return -ESRCH; |
c87e2837 | 944 | p = futex_find_get_task(pid); |
7a0ea09a MH |
945 | if (!p) |
946 | return -ESRCH; | |
778e9a9c | 947 | |
a2129464 | 948 | if (unlikely(p->flags & PF_KTHREAD)) { |
f0d71b3d TG |
949 | put_task_struct(p); |
950 | return -EPERM; | |
951 | } | |
952 | ||
778e9a9c AK |
953 | /* |
954 | * We need to look at the task state flags to figure out, | |
955 | * whether the task is exiting. To protect against the do_exit | |
956 | * change of the task flags, we do this protected by | |
957 | * p->pi_lock: | |
958 | */ | |
1d615482 | 959 | raw_spin_lock_irq(&p->pi_lock); |
778e9a9c AK |
960 | if (unlikely(p->flags & PF_EXITING)) { |
961 | /* | |
962 | * The task is on the way out. When PF_EXITPIDONE is | |
963 | * set, we know that the task has finished the | |
964 | * cleanup: | |
965 | */ | |
966 | int ret = (p->flags & PF_EXITPIDONE) ? -ESRCH : -EAGAIN; | |
967 | ||
1d615482 | 968 | raw_spin_unlock_irq(&p->pi_lock); |
778e9a9c AK |
969 | put_task_struct(p); |
970 | return ret; | |
971 | } | |
c87e2837 | 972 | |
54a21788 TG |
973 | /* |
974 | * No existing pi state. First waiter. [2] | |
975 | */ | |
c87e2837 IM |
976 | pi_state = alloc_pi_state(); |
977 | ||
978 | /* | |
04e1b2e5 | 979 | * Initialize the pi_mutex in locked state and make @p |
c87e2837 IM |
980 | * the owner of it: |
981 | */ | |
982 | rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p); | |
983 | ||
984 | /* Store the key for possible exit cleanups: */ | |
d0aa7a70 | 985 | pi_state->key = *key; |
c87e2837 | 986 | |
627371d7 | 987 | WARN_ON(!list_empty(&pi_state->list)); |
c87e2837 IM |
988 | list_add(&pi_state->list, &p->pi_state_list); |
989 | pi_state->owner = p; | |
1d615482 | 990 | raw_spin_unlock_irq(&p->pi_lock); |
c87e2837 IM |
991 | |
992 | put_task_struct(p); | |
993 | ||
d0aa7a70 | 994 | *ps = pi_state; |
c87e2837 IM |
995 | |
996 | return 0; | |
997 | } | |
998 | ||
04e1b2e5 TG |
999 | static int lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, |
1000 | union futex_key *key, struct futex_pi_state **ps) | |
1001 | { | |
1002 | struct futex_q *match = futex_top_waiter(hb, key); | |
1003 | ||
1004 | /* | |
1005 | * If there is a waiter on that futex, validate it and | |
1006 | * attach to the pi_state when the validation succeeds. | |
1007 | */ | |
1008 | if (match) | |
1009 | return attach_to_pi_state(uval, match->pi_state, ps); | |
1010 | ||
1011 | /* | |
1012 | * We are the first waiter - try to look up the owner based on | |
1013 | * @uval and attach to it. | |
1014 | */ | |
1015 | return attach_to_pi_owner(uval, key, ps); | |
1016 | } | |
1017 | ||
af54d6a1 TG |
1018 | static int lock_pi_update_atomic(u32 __user *uaddr, u32 uval, u32 newval) |
1019 | { | |
1020 | u32 uninitialized_var(curval); | |
1021 | ||
ab51fbab DB |
1022 | if (unlikely(should_fail_futex(true))) |
1023 | return -EFAULT; | |
1024 | ||
af54d6a1 TG |
1025 | if (unlikely(cmpxchg_futex_value_locked(&curval, uaddr, uval, newval))) |
1026 | return -EFAULT; | |
1027 | ||
1028 | /*If user space value changed, let the caller retry */ | |
1029 | return curval != uval ? -EAGAIN : 0; | |
1030 | } | |
1031 | ||
1a52084d | 1032 | /** |
d96ee56c | 1033 | * futex_lock_pi_atomic() - Atomic work required to acquire a pi aware futex |
bab5bc9e DH |
1034 | * @uaddr: the pi futex user address |
1035 | * @hb: the pi futex hash bucket | |
1036 | * @key: the futex key associated with uaddr and hb | |
1037 | * @ps: the pi_state pointer where we store the result of the | |
1038 | * lookup | |
1039 | * @task: the task to perform the atomic lock work for. This will | |
1040 | * be "current" except in the case of requeue pi. | |
1041 | * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0) | |
1a52084d | 1042 | * |
6c23cbbd RD |
1043 | * Return: |
1044 | * 0 - ready to wait; | |
1045 | * 1 - acquired the lock; | |
1a52084d DH |
1046 | * <0 - error |
1047 | * | |
1048 | * The hb->lock and futex_key refs shall be held by the caller. | |
1049 | */ | |
1050 | static int futex_lock_pi_atomic(u32 __user *uaddr, struct futex_hash_bucket *hb, | |
1051 | union futex_key *key, | |
1052 | struct futex_pi_state **ps, | |
bab5bc9e | 1053 | struct task_struct *task, int set_waiters) |
1a52084d | 1054 | { |
af54d6a1 TG |
1055 | u32 uval, newval, vpid = task_pid_vnr(task); |
1056 | struct futex_q *match; | |
1057 | int ret; | |
1a52084d DH |
1058 | |
1059 | /* | |
af54d6a1 TG |
1060 | * Read the user space value first so we can validate a few |
1061 | * things before proceeding further. | |
1a52084d | 1062 | */ |
af54d6a1 | 1063 | if (get_futex_value_locked(&uval, uaddr)) |
1a52084d DH |
1064 | return -EFAULT; |
1065 | ||
ab51fbab DB |
1066 | if (unlikely(should_fail_futex(true))) |
1067 | return -EFAULT; | |
1068 | ||
1a52084d DH |
1069 | /* |
1070 | * Detect deadlocks. | |
1071 | */ | |
af54d6a1 | 1072 | if ((unlikely((uval & FUTEX_TID_MASK) == vpid))) |
1a52084d DH |
1073 | return -EDEADLK; |
1074 | ||
ab51fbab DB |
1075 | if ((unlikely(should_fail_futex(true)))) |
1076 | return -EDEADLK; | |
1077 | ||
1a52084d | 1078 | /* |
af54d6a1 TG |
1079 | * Lookup existing state first. If it exists, try to attach to |
1080 | * its pi_state. | |
1a52084d | 1081 | */ |
af54d6a1 TG |
1082 | match = futex_top_waiter(hb, key); |
1083 | if (match) | |
1084 | return attach_to_pi_state(uval, match->pi_state, ps); | |
1a52084d DH |
1085 | |
1086 | /* | |
af54d6a1 TG |
1087 | * No waiter and user TID is 0. We are here because the |
1088 | * waiters or the owner died bit is set or called from | |
1089 | * requeue_cmp_pi or for whatever reason something took the | |
1090 | * syscall. | |
1a52084d | 1091 | */ |
af54d6a1 | 1092 | if (!(uval & FUTEX_TID_MASK)) { |
59fa6245 | 1093 | /* |
af54d6a1 TG |
1094 | * We take over the futex. No other waiters and the user space |
1095 | * TID is 0. We preserve the owner died bit. | |
59fa6245 | 1096 | */ |
af54d6a1 TG |
1097 | newval = uval & FUTEX_OWNER_DIED; |
1098 | newval |= vpid; | |
1a52084d | 1099 | |
af54d6a1 TG |
1100 | /* The futex requeue_pi code can enforce the waiters bit */ |
1101 | if (set_waiters) | |
1102 | newval |= FUTEX_WAITERS; | |
1103 | ||
1104 | ret = lock_pi_update_atomic(uaddr, uval, newval); | |
1105 | /* If the take over worked, return 1 */ | |
1106 | return ret < 0 ? ret : 1; | |
1107 | } | |
1a52084d DH |
1108 | |
1109 | /* | |
af54d6a1 TG |
1110 | * First waiter. Set the waiters bit before attaching ourself to |
1111 | * the owner. If owner tries to unlock, it will be forced into | |
1112 | * the kernel and blocked on hb->lock. | |
1a52084d | 1113 | */ |
af54d6a1 TG |
1114 | newval = uval | FUTEX_WAITERS; |
1115 | ret = lock_pi_update_atomic(uaddr, uval, newval); | |
1116 | if (ret) | |
1117 | return ret; | |
1a52084d | 1118 | /* |
af54d6a1 TG |
1119 | * If the update of the user space value succeeded, we try to |
1120 | * attach to the owner. If that fails, no harm done, we only | |
1121 | * set the FUTEX_WAITERS bit in the user space variable. | |
1a52084d | 1122 | */ |
af54d6a1 | 1123 | return attach_to_pi_owner(uval, key, ps); |
1a52084d DH |
1124 | } |
1125 | ||
2e12978a LJ |
1126 | /** |
1127 | * __unqueue_futex() - Remove the futex_q from its futex_hash_bucket | |
1128 | * @q: The futex_q to unqueue | |
1129 | * | |
1130 | * The q->lock_ptr must not be NULL and must be held by the caller. | |
1131 | */ | |
1132 | static void __unqueue_futex(struct futex_q *q) | |
1133 | { | |
1134 | struct futex_hash_bucket *hb; | |
1135 | ||
29096202 SR |
1136 | if (WARN_ON_SMP(!q->lock_ptr || !spin_is_locked(q->lock_ptr)) |
1137 | || WARN_ON(plist_node_empty(&q->list))) | |
2e12978a LJ |
1138 | return; |
1139 | ||
1140 | hb = container_of(q->lock_ptr, struct futex_hash_bucket, lock); | |
1141 | plist_del(&q->list, &hb->chain); | |
11d4616b | 1142 | hb_waiters_dec(hb); |
2e12978a LJ |
1143 | } |
1144 | ||
1da177e4 LT |
1145 | /* |
1146 | * The hash bucket lock must be held when this is called. | |
1d0dcb3a DB |
1147 | * Afterwards, the futex_q must not be accessed. Callers |
1148 | * must ensure to later call wake_up_q() for the actual | |
1149 | * wakeups to occur. | |
1da177e4 | 1150 | */ |
1d0dcb3a | 1151 | static void mark_wake_futex(struct wake_q_head *wake_q, struct futex_q *q) |
1da177e4 | 1152 | { |
f1a11e05 TG |
1153 | struct task_struct *p = q->task; |
1154 | ||
aa10990e DH |
1155 | if (WARN(q->pi_state || q->rt_waiter, "refusing to wake PI futex\n")) |
1156 | return; | |
1157 | ||
1da177e4 | 1158 | /* |
1d0dcb3a DB |
1159 | * Queue the task for later wakeup for after we've released |
1160 | * the hb->lock. wake_q_add() grabs reference to p. | |
1da177e4 | 1161 | */ |
1d0dcb3a | 1162 | wake_q_add(wake_q, p); |
2e12978a | 1163 | __unqueue_futex(q); |
1da177e4 | 1164 | /* |
f1a11e05 TG |
1165 | * The waiting task can free the futex_q as soon as |
1166 | * q->lock_ptr = NULL is written, without taking any locks. A | |
1167 | * memory barrier is required here to prevent the following | |
1168 | * store to lock_ptr from getting ahead of the plist_del. | |
1da177e4 | 1169 | */ |
ccdea2f8 | 1170 | smp_wmb(); |
1da177e4 LT |
1171 | q->lock_ptr = NULL; |
1172 | } | |
1173 | ||
802ab58d SAS |
1174 | static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this, |
1175 | struct futex_hash_bucket *hb) | |
c87e2837 IM |
1176 | { |
1177 | struct task_struct *new_owner; | |
1178 | struct futex_pi_state *pi_state = this->pi_state; | |
7cfdaf38 | 1179 | u32 uninitialized_var(curval), newval; |
802ab58d SAS |
1180 | WAKE_Q(wake_q); |
1181 | bool deboost; | |
13fbca4c | 1182 | int ret = 0; |
c87e2837 IM |
1183 | |
1184 | if (!pi_state) | |
1185 | return -EINVAL; | |
1186 | ||
51246bfd TG |
1187 | /* |
1188 | * If current does not own the pi_state then the futex is | |
1189 | * inconsistent and user space fiddled with the futex value. | |
1190 | */ | |
1191 | if (pi_state->owner != current) | |
1192 | return -EINVAL; | |
1193 | ||
b4abf910 | 1194 | raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock); |
c87e2837 IM |
1195 | new_owner = rt_mutex_next_owner(&pi_state->pi_mutex); |
1196 | ||
1197 | /* | |
f123c98e SR |
1198 | * It is possible that the next waiter (the one that brought |
1199 | * this owner to the kernel) timed out and is no longer | |
1200 | * waiting on the lock. | |
c87e2837 IM |
1201 | */ |
1202 | if (!new_owner) | |
1203 | new_owner = this->task; | |
1204 | ||
1205 | /* | |
13fbca4c TG |
1206 | * We pass it to the next owner. The WAITERS bit is always |
1207 | * kept enabled while there is PI state around. We cleanup the | |
1208 | * owner died bit, because we are the owner. | |
c87e2837 | 1209 | */ |
13fbca4c | 1210 | newval = FUTEX_WAITERS | task_pid_vnr(new_owner); |
e3f2ddea | 1211 | |
ab51fbab DB |
1212 | if (unlikely(should_fail_futex(true))) |
1213 | ret = -EFAULT; | |
1214 | ||
13fbca4c TG |
1215 | if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval)) |
1216 | ret = -EFAULT; | |
1217 | else if (curval != uval) | |
1218 | ret = -EINVAL; | |
1219 | if (ret) { | |
b4abf910 | 1220 | raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock); |
13fbca4c | 1221 | return ret; |
e3f2ddea | 1222 | } |
c87e2837 | 1223 | |
b4abf910 | 1224 | raw_spin_lock(&pi_state->owner->pi_lock); |
627371d7 IM |
1225 | WARN_ON(list_empty(&pi_state->list)); |
1226 | list_del_init(&pi_state->list); | |
b4abf910 | 1227 | raw_spin_unlock(&pi_state->owner->pi_lock); |
627371d7 | 1228 | |
b4abf910 | 1229 | raw_spin_lock(&new_owner->pi_lock); |
627371d7 | 1230 | WARN_ON(!list_empty(&pi_state->list)); |
c87e2837 IM |
1231 | list_add(&pi_state->list, &new_owner->pi_state_list); |
1232 | pi_state->owner = new_owner; | |
b4abf910 | 1233 | raw_spin_unlock(&new_owner->pi_lock); |
627371d7 | 1234 | |
b4abf910 | 1235 | raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock); |
802ab58d SAS |
1236 | |
1237 | deboost = rt_mutex_futex_unlock(&pi_state->pi_mutex, &wake_q); | |
1238 | ||
1239 | /* | |
1240 | * First unlock HB so the waiter does not spin on it once he got woken | |
1241 | * up. Second wake up the waiter before the priority is adjusted. If we | |
1242 | * deboost first (and lose our higher priority), then the task might get | |
1243 | * scheduled away before the wake up can take place. | |
1244 | */ | |
1245 | spin_unlock(&hb->lock); | |
1246 | wake_up_q(&wake_q); | |
1247 | if (deboost) | |
1248 | rt_mutex_adjust_prio(current); | |
c87e2837 IM |
1249 | |
1250 | return 0; | |
1251 | } | |
1252 | ||
8b8f319f IM |
1253 | /* |
1254 | * Express the locking dependencies for lockdep: | |
1255 | */ | |
1256 | static inline void | |
1257 | double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) | |
1258 | { | |
1259 | if (hb1 <= hb2) { | |
1260 | spin_lock(&hb1->lock); | |
1261 | if (hb1 < hb2) | |
1262 | spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING); | |
1263 | } else { /* hb1 > hb2 */ | |
1264 | spin_lock(&hb2->lock); | |
1265 | spin_lock_nested(&hb1->lock, SINGLE_DEPTH_NESTING); | |
1266 | } | |
1267 | } | |
1268 | ||
5eb3dc62 DH |
1269 | static inline void |
1270 | double_unlock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) | |
1271 | { | |
f061d351 | 1272 | spin_unlock(&hb1->lock); |
88f502fe IM |
1273 | if (hb1 != hb2) |
1274 | spin_unlock(&hb2->lock); | |
5eb3dc62 DH |
1275 | } |
1276 | ||
1da177e4 | 1277 | /* |
b2d0994b | 1278 | * Wake up waiters matching bitset queued on this futex (uaddr). |
1da177e4 | 1279 | */ |
b41277dc DH |
1280 | static int |
1281 | futex_wake(u32 __user *uaddr, unsigned int flags, int nr_wake, u32 bitset) | |
1da177e4 | 1282 | { |
e2970f2f | 1283 | struct futex_hash_bucket *hb; |
1da177e4 | 1284 | struct futex_q *this, *next; |
38d47c1b | 1285 | union futex_key key = FUTEX_KEY_INIT; |
1da177e4 | 1286 | int ret; |
1d0dcb3a | 1287 | WAKE_Q(wake_q); |
1da177e4 | 1288 | |
cd689985 TG |
1289 | if (!bitset) |
1290 | return -EINVAL; | |
1291 | ||
9ea71503 | 1292 | ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key, VERIFY_READ); |
1da177e4 LT |
1293 | if (unlikely(ret != 0)) |
1294 | goto out; | |
1295 | ||
e2970f2f | 1296 | hb = hash_futex(&key); |
b0c29f79 DB |
1297 | |
1298 | /* Make sure we really have tasks to wakeup */ | |
1299 | if (!hb_waiters_pending(hb)) | |
1300 | goto out_put_key; | |
1301 | ||
e2970f2f | 1302 | spin_lock(&hb->lock); |
1da177e4 | 1303 | |
0d00c7b2 | 1304 | plist_for_each_entry_safe(this, next, &hb->chain, list) { |
1da177e4 | 1305 | if (match_futex (&this->key, &key)) { |
52400ba9 | 1306 | if (this->pi_state || this->rt_waiter) { |
ed6f7b10 IM |
1307 | ret = -EINVAL; |
1308 | break; | |
1309 | } | |
cd689985 TG |
1310 | |
1311 | /* Check if one of the bits is set in both bitsets */ | |
1312 | if (!(this->bitset & bitset)) | |
1313 | continue; | |
1314 | ||
1d0dcb3a | 1315 | mark_wake_futex(&wake_q, this); |
1da177e4 LT |
1316 | if (++ret >= nr_wake) |
1317 | break; | |
1318 | } | |
1319 | } | |
1320 | ||
e2970f2f | 1321 | spin_unlock(&hb->lock); |
1d0dcb3a | 1322 | wake_up_q(&wake_q); |
b0c29f79 | 1323 | out_put_key: |
ae791a2d | 1324 | put_futex_key(&key); |
42d35d48 | 1325 | out: |
1da177e4 LT |
1326 | return ret; |
1327 | } | |
1328 | ||
4732efbe JJ |
1329 | /* |
1330 | * Wake up all waiters hashed on the physical page that is mapped | |
1331 | * to this virtual address: | |
1332 | */ | |
e2970f2f | 1333 | static int |
b41277dc | 1334 | futex_wake_op(u32 __user *uaddr1, unsigned int flags, u32 __user *uaddr2, |
e2970f2f | 1335 | int nr_wake, int nr_wake2, int op) |
4732efbe | 1336 | { |
38d47c1b | 1337 | union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT; |
e2970f2f | 1338 | struct futex_hash_bucket *hb1, *hb2; |
4732efbe | 1339 | struct futex_q *this, *next; |
e4dc5b7a | 1340 | int ret, op_ret; |
1d0dcb3a | 1341 | WAKE_Q(wake_q); |
4732efbe | 1342 | |
e4dc5b7a | 1343 | retry: |
9ea71503 | 1344 | ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1, VERIFY_READ); |
4732efbe JJ |
1345 | if (unlikely(ret != 0)) |
1346 | goto out; | |
9ea71503 | 1347 | ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, VERIFY_WRITE); |
4732efbe | 1348 | if (unlikely(ret != 0)) |
42d35d48 | 1349 | goto out_put_key1; |
4732efbe | 1350 | |
e2970f2f IM |
1351 | hb1 = hash_futex(&key1); |
1352 | hb2 = hash_futex(&key2); | |
4732efbe | 1353 | |
e4dc5b7a | 1354 | retry_private: |
eaaea803 | 1355 | double_lock_hb(hb1, hb2); |
e2970f2f | 1356 | op_ret = futex_atomic_op_inuser(op, uaddr2); |
4732efbe | 1357 | if (unlikely(op_ret < 0)) { |
4732efbe | 1358 | |
5eb3dc62 | 1359 | double_unlock_hb(hb1, hb2); |
4732efbe | 1360 | |
7ee1dd3f | 1361 | #ifndef CONFIG_MMU |
e2970f2f IM |
1362 | /* |
1363 | * we don't get EFAULT from MMU faults if we don't have an MMU, | |
1364 | * but we might get them from range checking | |
1365 | */ | |
7ee1dd3f | 1366 | ret = op_ret; |
42d35d48 | 1367 | goto out_put_keys; |
7ee1dd3f DH |
1368 | #endif |
1369 | ||
796f8d9b DG |
1370 | if (unlikely(op_ret != -EFAULT)) { |
1371 | ret = op_ret; | |
42d35d48 | 1372 | goto out_put_keys; |
796f8d9b DG |
1373 | } |
1374 | ||
d0725992 | 1375 | ret = fault_in_user_writeable(uaddr2); |
4732efbe | 1376 | if (ret) |
de87fcc1 | 1377 | goto out_put_keys; |
4732efbe | 1378 | |
b41277dc | 1379 | if (!(flags & FLAGS_SHARED)) |
e4dc5b7a DH |
1380 | goto retry_private; |
1381 | ||
ae791a2d TG |
1382 | put_futex_key(&key2); |
1383 | put_futex_key(&key1); | |
e4dc5b7a | 1384 | goto retry; |
4732efbe JJ |
1385 | } |
1386 | ||
0d00c7b2 | 1387 | plist_for_each_entry_safe(this, next, &hb1->chain, list) { |
4732efbe | 1388 | if (match_futex (&this->key, &key1)) { |
aa10990e DH |
1389 | if (this->pi_state || this->rt_waiter) { |
1390 | ret = -EINVAL; | |
1391 | goto out_unlock; | |
1392 | } | |
1d0dcb3a | 1393 | mark_wake_futex(&wake_q, this); |
4732efbe JJ |
1394 | if (++ret >= nr_wake) |
1395 | break; | |
1396 | } | |
1397 | } | |
1398 | ||
1399 | if (op_ret > 0) { | |
4732efbe | 1400 | op_ret = 0; |
0d00c7b2 | 1401 | plist_for_each_entry_safe(this, next, &hb2->chain, list) { |
4732efbe | 1402 | if (match_futex (&this->key, &key2)) { |
aa10990e DH |
1403 | if (this->pi_state || this->rt_waiter) { |
1404 | ret = -EINVAL; | |
1405 | goto out_unlock; | |
1406 | } | |
1d0dcb3a | 1407 | mark_wake_futex(&wake_q, this); |
4732efbe JJ |
1408 | if (++op_ret >= nr_wake2) |
1409 | break; | |
1410 | } | |
1411 | } | |
1412 | ret += op_ret; | |
1413 | } | |
1414 | ||
aa10990e | 1415 | out_unlock: |
5eb3dc62 | 1416 | double_unlock_hb(hb1, hb2); |
1d0dcb3a | 1417 | wake_up_q(&wake_q); |
42d35d48 | 1418 | out_put_keys: |
ae791a2d | 1419 | put_futex_key(&key2); |
42d35d48 | 1420 | out_put_key1: |
ae791a2d | 1421 | put_futex_key(&key1); |
42d35d48 | 1422 | out: |
4732efbe JJ |
1423 | return ret; |
1424 | } | |
1425 | ||
9121e478 DH |
1426 | /** |
1427 | * requeue_futex() - Requeue a futex_q from one hb to another | |
1428 | * @q: the futex_q to requeue | |
1429 | * @hb1: the source hash_bucket | |
1430 | * @hb2: the target hash_bucket | |
1431 | * @key2: the new key for the requeued futex_q | |
1432 | */ | |
1433 | static inline | |
1434 | void requeue_futex(struct futex_q *q, struct futex_hash_bucket *hb1, | |
1435 | struct futex_hash_bucket *hb2, union futex_key *key2) | |
1436 | { | |
1437 | ||
1438 | /* | |
1439 | * If key1 and key2 hash to the same bucket, no need to | |
1440 | * requeue. | |
1441 | */ | |
1442 | if (likely(&hb1->chain != &hb2->chain)) { | |
1443 | plist_del(&q->list, &hb1->chain); | |
11d4616b | 1444 | hb_waiters_dec(hb1); |
9121e478 | 1445 | plist_add(&q->list, &hb2->chain); |
11d4616b | 1446 | hb_waiters_inc(hb2); |
9121e478 | 1447 | q->lock_ptr = &hb2->lock; |
9121e478 DH |
1448 | } |
1449 | get_futex_key_refs(key2); | |
1450 | q->key = *key2; | |
1451 | } | |
1452 | ||
52400ba9 DH |
1453 | /** |
1454 | * requeue_pi_wake_futex() - Wake a task that acquired the lock during requeue | |
d96ee56c DH |
1455 | * @q: the futex_q |
1456 | * @key: the key of the requeue target futex | |
1457 | * @hb: the hash_bucket of the requeue target futex | |
52400ba9 DH |
1458 | * |
1459 | * During futex_requeue, with requeue_pi=1, it is possible to acquire the | |
1460 | * target futex if it is uncontended or via a lock steal. Set the futex_q key | |
1461 | * to the requeue target futex so the waiter can detect the wakeup on the right | |
1462 | * futex, but remove it from the hb and NULL the rt_waiter so it can detect | |
beda2c7e DH |
1463 | * atomic lock acquisition. Set the q->lock_ptr to the requeue target hb->lock |
1464 | * to protect access to the pi_state to fixup the owner later. Must be called | |
1465 | * with both q->lock_ptr and hb->lock held. | |
52400ba9 DH |
1466 | */ |
1467 | static inline | |
beda2c7e DH |
1468 | void requeue_pi_wake_futex(struct futex_q *q, union futex_key *key, |
1469 | struct futex_hash_bucket *hb) | |
52400ba9 | 1470 | { |
52400ba9 DH |
1471 | get_futex_key_refs(key); |
1472 | q->key = *key; | |
1473 | ||
2e12978a | 1474 | __unqueue_futex(q); |
52400ba9 DH |
1475 | |
1476 | WARN_ON(!q->rt_waiter); | |
1477 | q->rt_waiter = NULL; | |
1478 | ||
beda2c7e | 1479 | q->lock_ptr = &hb->lock; |
beda2c7e | 1480 | |
f1a11e05 | 1481 | wake_up_state(q->task, TASK_NORMAL); |
52400ba9 DH |
1482 | } |
1483 | ||
1484 | /** | |
1485 | * futex_proxy_trylock_atomic() - Attempt an atomic lock for the top waiter | |
bab5bc9e DH |
1486 | * @pifutex: the user address of the to futex |
1487 | * @hb1: the from futex hash bucket, must be locked by the caller | |
1488 | * @hb2: the to futex hash bucket, must be locked by the caller | |
1489 | * @key1: the from futex key | |
1490 | * @key2: the to futex key | |
1491 | * @ps: address to store the pi_state pointer | |
1492 | * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0) | |
52400ba9 DH |
1493 | * |
1494 | * Try and get the lock on behalf of the top waiter if we can do it atomically. | |
bab5bc9e DH |
1495 | * Wake the top waiter if we succeed. If the caller specified set_waiters, |
1496 | * then direct futex_lock_pi_atomic() to force setting the FUTEX_WAITERS bit. | |
1497 | * hb1 and hb2 must be held by the caller. | |
52400ba9 | 1498 | * |
6c23cbbd RD |
1499 | * Return: |
1500 | * 0 - failed to acquire the lock atomically; | |
866293ee | 1501 | * >0 - acquired the lock, return value is vpid of the top_waiter |
52400ba9 DH |
1502 | * <0 - error |
1503 | */ | |
1504 | static int futex_proxy_trylock_atomic(u32 __user *pifutex, | |
1505 | struct futex_hash_bucket *hb1, | |
1506 | struct futex_hash_bucket *hb2, | |
1507 | union futex_key *key1, union futex_key *key2, | |
bab5bc9e | 1508 | struct futex_pi_state **ps, int set_waiters) |
52400ba9 | 1509 | { |
bab5bc9e | 1510 | struct futex_q *top_waiter = NULL; |
52400ba9 | 1511 | u32 curval; |
866293ee | 1512 | int ret, vpid; |
52400ba9 DH |
1513 | |
1514 | if (get_futex_value_locked(&curval, pifutex)) | |
1515 | return -EFAULT; | |
1516 | ||
ab51fbab DB |
1517 | if (unlikely(should_fail_futex(true))) |
1518 | return -EFAULT; | |
1519 | ||
bab5bc9e DH |
1520 | /* |
1521 | * Find the top_waiter and determine if there are additional waiters. | |
1522 | * If the caller intends to requeue more than 1 waiter to pifutex, | |
1523 | * force futex_lock_pi_atomic() to set the FUTEX_WAITERS bit now, | |
1524 | * as we have means to handle the possible fault. If not, don't set | |
1525 | * the bit unecessarily as it will force the subsequent unlock to enter | |
1526 | * the kernel. | |
1527 | */ | |
52400ba9 DH |
1528 | top_waiter = futex_top_waiter(hb1, key1); |
1529 | ||
1530 | /* There are no waiters, nothing for us to do. */ | |
1531 | if (!top_waiter) | |
1532 | return 0; | |
1533 | ||
84bc4af5 DH |
1534 | /* Ensure we requeue to the expected futex. */ |
1535 | if (!match_futex(top_waiter->requeue_pi_key, key2)) | |
1536 | return -EINVAL; | |
1537 | ||
52400ba9 | 1538 | /* |
bab5bc9e DH |
1539 | * Try to take the lock for top_waiter. Set the FUTEX_WAITERS bit in |
1540 | * the contended case or if set_waiters is 1. The pi_state is returned | |
1541 | * in ps in contended cases. | |
52400ba9 | 1542 | */ |
866293ee | 1543 | vpid = task_pid_vnr(top_waiter->task); |
bab5bc9e DH |
1544 | ret = futex_lock_pi_atomic(pifutex, hb2, key2, ps, top_waiter->task, |
1545 | set_waiters); | |
866293ee | 1546 | if (ret == 1) { |
beda2c7e | 1547 | requeue_pi_wake_futex(top_waiter, key2, hb2); |
866293ee TG |
1548 | return vpid; |
1549 | } | |
52400ba9 DH |
1550 | return ret; |
1551 | } | |
1552 | ||
1553 | /** | |
1554 | * futex_requeue() - Requeue waiters from uaddr1 to uaddr2 | |
fb62db2b | 1555 | * @uaddr1: source futex user address |
b41277dc | 1556 | * @flags: futex flags (FLAGS_SHARED, etc.) |
fb62db2b RD |
1557 | * @uaddr2: target futex user address |
1558 | * @nr_wake: number of waiters to wake (must be 1 for requeue_pi) | |
1559 | * @nr_requeue: number of waiters to requeue (0-INT_MAX) | |
1560 | * @cmpval: @uaddr1 expected value (or %NULL) | |
1561 | * @requeue_pi: if we are attempting to requeue from a non-pi futex to a | |
b41277dc | 1562 | * pi futex (pi to pi requeue is not supported) |
52400ba9 DH |
1563 | * |
1564 | * Requeue waiters on uaddr1 to uaddr2. In the requeue_pi case, try to acquire | |
1565 | * uaddr2 atomically on behalf of the top waiter. | |
1566 | * | |
6c23cbbd RD |
1567 | * Return: |
1568 | * >=0 - on success, the number of tasks requeued or woken; | |
52400ba9 | 1569 | * <0 - on error |
1da177e4 | 1570 | */ |
b41277dc DH |
1571 | static int futex_requeue(u32 __user *uaddr1, unsigned int flags, |
1572 | u32 __user *uaddr2, int nr_wake, int nr_requeue, | |
1573 | u32 *cmpval, int requeue_pi) | |
1da177e4 | 1574 | { |
38d47c1b | 1575 | union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT; |
52400ba9 DH |
1576 | int drop_count = 0, task_count = 0, ret; |
1577 | struct futex_pi_state *pi_state = NULL; | |
e2970f2f | 1578 | struct futex_hash_bucket *hb1, *hb2; |
1da177e4 | 1579 | struct futex_q *this, *next; |
1d0dcb3a | 1580 | WAKE_Q(wake_q); |
52400ba9 DH |
1581 | |
1582 | if (requeue_pi) { | |
e9c243a5 TG |
1583 | /* |
1584 | * Requeue PI only works on two distinct uaddrs. This | |
1585 | * check is only valid for private futexes. See below. | |
1586 | */ | |
1587 | if (uaddr1 == uaddr2) | |
1588 | return -EINVAL; | |
1589 | ||
52400ba9 DH |
1590 | /* |
1591 | * requeue_pi requires a pi_state, try to allocate it now | |
1592 | * without any locks in case it fails. | |
1593 | */ | |
1594 | if (refill_pi_state_cache()) | |
1595 | return -ENOMEM; | |
1596 | /* | |
1597 | * requeue_pi must wake as many tasks as it can, up to nr_wake | |
1598 | * + nr_requeue, since it acquires the rt_mutex prior to | |
1599 | * returning to userspace, so as to not leave the rt_mutex with | |
1600 | * waiters and no owner. However, second and third wake-ups | |
1601 | * cannot be predicted as they involve race conditions with the | |
1602 | * first wake and a fault while looking up the pi_state. Both | |
1603 | * pthread_cond_signal() and pthread_cond_broadcast() should | |
1604 | * use nr_wake=1. | |
1605 | */ | |
1606 | if (nr_wake != 1) | |
1607 | return -EINVAL; | |
1608 | } | |
1da177e4 | 1609 | |
42d35d48 | 1610 | retry: |
9ea71503 | 1611 | ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1, VERIFY_READ); |
1da177e4 LT |
1612 | if (unlikely(ret != 0)) |
1613 | goto out; | |
9ea71503 SB |
1614 | ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, |
1615 | requeue_pi ? VERIFY_WRITE : VERIFY_READ); | |
1da177e4 | 1616 | if (unlikely(ret != 0)) |
42d35d48 | 1617 | goto out_put_key1; |
1da177e4 | 1618 | |
e9c243a5 TG |
1619 | /* |
1620 | * The check above which compares uaddrs is not sufficient for | |
1621 | * shared futexes. We need to compare the keys: | |
1622 | */ | |
1623 | if (requeue_pi && match_futex(&key1, &key2)) { | |
1624 | ret = -EINVAL; | |
1625 | goto out_put_keys; | |
1626 | } | |
1627 | ||
e2970f2f IM |
1628 | hb1 = hash_futex(&key1); |
1629 | hb2 = hash_futex(&key2); | |
1da177e4 | 1630 | |
e4dc5b7a | 1631 | retry_private: |
69cd9eba | 1632 | hb_waiters_inc(hb2); |
8b8f319f | 1633 | double_lock_hb(hb1, hb2); |
1da177e4 | 1634 | |
e2970f2f IM |
1635 | if (likely(cmpval != NULL)) { |
1636 | u32 curval; | |
1da177e4 | 1637 | |
e2970f2f | 1638 | ret = get_futex_value_locked(&curval, uaddr1); |
1da177e4 LT |
1639 | |
1640 | if (unlikely(ret)) { | |
5eb3dc62 | 1641 | double_unlock_hb(hb1, hb2); |
69cd9eba | 1642 | hb_waiters_dec(hb2); |
1da177e4 | 1643 | |
e2970f2f | 1644 | ret = get_user(curval, uaddr1); |
e4dc5b7a DH |
1645 | if (ret) |
1646 | goto out_put_keys; | |
1da177e4 | 1647 | |
b41277dc | 1648 | if (!(flags & FLAGS_SHARED)) |
e4dc5b7a | 1649 | goto retry_private; |
1da177e4 | 1650 | |
ae791a2d TG |
1651 | put_futex_key(&key2); |
1652 | put_futex_key(&key1); | |
e4dc5b7a | 1653 | goto retry; |
1da177e4 | 1654 | } |
e2970f2f | 1655 | if (curval != *cmpval) { |
1da177e4 LT |
1656 | ret = -EAGAIN; |
1657 | goto out_unlock; | |
1658 | } | |
1659 | } | |
1660 | ||
52400ba9 | 1661 | if (requeue_pi && (task_count - nr_wake < nr_requeue)) { |
bab5bc9e DH |
1662 | /* |
1663 | * Attempt to acquire uaddr2 and wake the top waiter. If we | |
1664 | * intend to requeue waiters, force setting the FUTEX_WAITERS | |
1665 | * bit. We force this here where we are able to easily handle | |
1666 | * faults rather in the requeue loop below. | |
1667 | */ | |
52400ba9 | 1668 | ret = futex_proxy_trylock_atomic(uaddr2, hb1, hb2, &key1, |
bab5bc9e | 1669 | &key2, &pi_state, nr_requeue); |
52400ba9 DH |
1670 | |
1671 | /* | |
1672 | * At this point the top_waiter has either taken uaddr2 or is | |
1673 | * waiting on it. If the former, then the pi_state will not | |
1674 | * exist yet, look it up one more time to ensure we have a | |
866293ee TG |
1675 | * reference to it. If the lock was taken, ret contains the |
1676 | * vpid of the top waiter task. | |
ecb38b78 TG |
1677 | * If the lock was not taken, we have pi_state and an initial |
1678 | * refcount on it. In case of an error we have nothing. | |
52400ba9 | 1679 | */ |
866293ee | 1680 | if (ret > 0) { |
52400ba9 | 1681 | WARN_ON(pi_state); |
89061d3d | 1682 | drop_count++; |
52400ba9 | 1683 | task_count++; |
866293ee | 1684 | /* |
ecb38b78 TG |
1685 | * If we acquired the lock, then the user space value |
1686 | * of uaddr2 should be vpid. It cannot be changed by | |
1687 | * the top waiter as it is blocked on hb2 lock if it | |
1688 | * tries to do so. If something fiddled with it behind | |
1689 | * our back the pi state lookup might unearth it. So | |
1690 | * we rather use the known value than rereading and | |
1691 | * handing potential crap to lookup_pi_state. | |
1692 | * | |
1693 | * If that call succeeds then we have pi_state and an | |
1694 | * initial refcount on it. | |
866293ee | 1695 | */ |
54a21788 | 1696 | ret = lookup_pi_state(ret, hb2, &key2, &pi_state); |
52400ba9 DH |
1697 | } |
1698 | ||
1699 | switch (ret) { | |
1700 | case 0: | |
ecb38b78 | 1701 | /* We hold a reference on the pi state. */ |
52400ba9 | 1702 | break; |
4959f2de TG |
1703 | |
1704 | /* If the above failed, then pi_state is NULL */ | |
52400ba9 DH |
1705 | case -EFAULT: |
1706 | double_unlock_hb(hb1, hb2); | |
69cd9eba | 1707 | hb_waiters_dec(hb2); |
ae791a2d TG |
1708 | put_futex_key(&key2); |
1709 | put_futex_key(&key1); | |
d0725992 | 1710 | ret = fault_in_user_writeable(uaddr2); |
52400ba9 DH |
1711 | if (!ret) |
1712 | goto retry; | |
1713 | goto out; | |
1714 | case -EAGAIN: | |
af54d6a1 TG |
1715 | /* |
1716 | * Two reasons for this: | |
1717 | * - Owner is exiting and we just wait for the | |
1718 | * exit to complete. | |
1719 | * - The user space value changed. | |
1720 | */ | |
52400ba9 | 1721 | double_unlock_hb(hb1, hb2); |
69cd9eba | 1722 | hb_waiters_dec(hb2); |
ae791a2d TG |
1723 | put_futex_key(&key2); |
1724 | put_futex_key(&key1); | |
52400ba9 DH |
1725 | cond_resched(); |
1726 | goto retry; | |
1727 | default: | |
1728 | goto out_unlock; | |
1729 | } | |
1730 | } | |
1731 | ||
0d00c7b2 | 1732 | plist_for_each_entry_safe(this, next, &hb1->chain, list) { |
52400ba9 DH |
1733 | if (task_count - nr_wake >= nr_requeue) |
1734 | break; | |
1735 | ||
1736 | if (!match_futex(&this->key, &key1)) | |
1da177e4 | 1737 | continue; |
52400ba9 | 1738 | |
392741e0 DH |
1739 | /* |
1740 | * FUTEX_WAIT_REQEUE_PI and FUTEX_CMP_REQUEUE_PI should always | |
1741 | * be paired with each other and no other futex ops. | |
aa10990e DH |
1742 | * |
1743 | * We should never be requeueing a futex_q with a pi_state, | |
1744 | * which is awaiting a futex_unlock_pi(). | |
392741e0 DH |
1745 | */ |
1746 | if ((requeue_pi && !this->rt_waiter) || | |
aa10990e DH |
1747 | (!requeue_pi && this->rt_waiter) || |
1748 | this->pi_state) { | |
392741e0 DH |
1749 | ret = -EINVAL; |
1750 | break; | |
1751 | } | |
52400ba9 DH |
1752 | |
1753 | /* | |
1754 | * Wake nr_wake waiters. For requeue_pi, if we acquired the | |
1755 | * lock, we already woke the top_waiter. If not, it will be | |
1756 | * woken by futex_unlock_pi(). | |
1757 | */ | |
1758 | if (++task_count <= nr_wake && !requeue_pi) { | |
1d0dcb3a | 1759 | mark_wake_futex(&wake_q, this); |
52400ba9 DH |
1760 | continue; |
1761 | } | |
1da177e4 | 1762 | |
84bc4af5 DH |
1763 | /* Ensure we requeue to the expected futex for requeue_pi. */ |
1764 | if (requeue_pi && !match_futex(this->requeue_pi_key, &key2)) { | |
1765 | ret = -EINVAL; | |
1766 | break; | |
1767 | } | |
1768 | ||
52400ba9 DH |
1769 | /* |
1770 | * Requeue nr_requeue waiters and possibly one more in the case | |
1771 | * of requeue_pi if we couldn't acquire the lock atomically. | |
1772 | */ | |
1773 | if (requeue_pi) { | |
ecb38b78 TG |
1774 | /* |
1775 | * Prepare the waiter to take the rt_mutex. Take a | |
1776 | * refcount on the pi_state and store the pointer in | |
1777 | * the futex_q object of the waiter. | |
1778 | */ | |
52400ba9 DH |
1779 | atomic_inc(&pi_state->refcount); |
1780 | this->pi_state = pi_state; | |
1781 | ret = rt_mutex_start_proxy_lock(&pi_state->pi_mutex, | |
1782 | this->rt_waiter, | |
c051b21f | 1783 | this->task); |
52400ba9 | 1784 | if (ret == 1) { |
ecb38b78 TG |
1785 | /* |
1786 | * We got the lock. We do neither drop the | |
1787 | * refcount on pi_state nor clear | |
1788 | * this->pi_state because the waiter needs the | |
1789 | * pi_state for cleaning up the user space | |
1790 | * value. It will drop the refcount after | |
1791 | * doing so. | |
1792 | */ | |
beda2c7e | 1793 | requeue_pi_wake_futex(this, &key2, hb2); |
89061d3d | 1794 | drop_count++; |
52400ba9 DH |
1795 | continue; |
1796 | } else if (ret) { | |
ecb38b78 TG |
1797 | /* |
1798 | * rt_mutex_start_proxy_lock() detected a | |
1799 | * potential deadlock when we tried to queue | |
1800 | * that waiter. Drop the pi_state reference | |
1801 | * which we took above and remove the pointer | |
1802 | * to the state from the waiters futex_q | |
1803 | * object. | |
1804 | */ | |
52400ba9 | 1805 | this->pi_state = NULL; |
29e9ee5d | 1806 | put_pi_state(pi_state); |
885c2cb7 TG |
1807 | /* |
1808 | * We stop queueing more waiters and let user | |
1809 | * space deal with the mess. | |
1810 | */ | |
1811 | break; | |
52400ba9 | 1812 | } |
1da177e4 | 1813 | } |
52400ba9 DH |
1814 | requeue_futex(this, hb1, hb2, &key2); |
1815 | drop_count++; | |
1da177e4 LT |
1816 | } |
1817 | ||
ecb38b78 TG |
1818 | /* |
1819 | * We took an extra initial reference to the pi_state either | |
1820 | * in futex_proxy_trylock_atomic() or in lookup_pi_state(). We | |
1821 | * need to drop it here again. | |
1822 | */ | |
29e9ee5d | 1823 | put_pi_state(pi_state); |
885c2cb7 TG |
1824 | |
1825 | out_unlock: | |
5eb3dc62 | 1826 | double_unlock_hb(hb1, hb2); |
1d0dcb3a | 1827 | wake_up_q(&wake_q); |
69cd9eba | 1828 | hb_waiters_dec(hb2); |
1da177e4 | 1829 | |
cd84a42f DH |
1830 | /* |
1831 | * drop_futex_key_refs() must be called outside the spinlocks. During | |
1832 | * the requeue we moved futex_q's from the hash bucket at key1 to the | |
1833 | * one at key2 and updated their key pointer. We no longer need to | |
1834 | * hold the references to key1. | |
1835 | */ | |
1da177e4 | 1836 | while (--drop_count >= 0) |
9adef58b | 1837 | drop_futex_key_refs(&key1); |
1da177e4 | 1838 | |
42d35d48 | 1839 | out_put_keys: |
ae791a2d | 1840 | put_futex_key(&key2); |
42d35d48 | 1841 | out_put_key1: |
ae791a2d | 1842 | put_futex_key(&key1); |
42d35d48 | 1843 | out: |
52400ba9 | 1844 | return ret ? ret : task_count; |
1da177e4 LT |
1845 | } |
1846 | ||
1847 | /* The key must be already stored in q->key. */ | |
82af7aca | 1848 | static inline struct futex_hash_bucket *queue_lock(struct futex_q *q) |
15e408cd | 1849 | __acquires(&hb->lock) |
1da177e4 | 1850 | { |
e2970f2f | 1851 | struct futex_hash_bucket *hb; |
1da177e4 | 1852 | |
e2970f2f | 1853 | hb = hash_futex(&q->key); |
11d4616b LT |
1854 | |
1855 | /* | |
1856 | * Increment the counter before taking the lock so that | |
1857 | * a potential waker won't miss a to-be-slept task that is | |
1858 | * waiting for the spinlock. This is safe as all queue_lock() | |
1859 | * users end up calling queue_me(). Similarly, for housekeeping, | |
1860 | * decrement the counter at queue_unlock() when some error has | |
1861 | * occurred and we don't end up adding the task to the list. | |
1862 | */ | |
1863 | hb_waiters_inc(hb); | |
1864 | ||
e2970f2f | 1865 | q->lock_ptr = &hb->lock; |
1da177e4 | 1866 | |
b0c29f79 | 1867 | spin_lock(&hb->lock); /* implies MB (A) */ |
e2970f2f | 1868 | return hb; |
1da177e4 LT |
1869 | } |
1870 | ||
d40d65c8 | 1871 | static inline void |
0d00c7b2 | 1872 | queue_unlock(struct futex_hash_bucket *hb) |
15e408cd | 1873 | __releases(&hb->lock) |
d40d65c8 DH |
1874 | { |
1875 | spin_unlock(&hb->lock); | |
11d4616b | 1876 | hb_waiters_dec(hb); |
d40d65c8 DH |
1877 | } |
1878 | ||
1879 | /** | |
1880 | * queue_me() - Enqueue the futex_q on the futex_hash_bucket | |
1881 | * @q: The futex_q to enqueue | |
1882 | * @hb: The destination hash bucket | |
1883 | * | |
1884 | * The hb->lock must be held by the caller, and is released here. A call to | |
1885 | * queue_me() is typically paired with exactly one call to unqueue_me(). The | |
1886 | * exceptions involve the PI related operations, which may use unqueue_me_pi() | |
1887 | * or nothing if the unqueue is done as part of the wake process and the unqueue | |
1888 | * state is implicit in the state of woken task (see futex_wait_requeue_pi() for | |
1889 | * an example). | |
1890 | */ | |
82af7aca | 1891 | static inline void queue_me(struct futex_q *q, struct futex_hash_bucket *hb) |
15e408cd | 1892 | __releases(&hb->lock) |
1da177e4 | 1893 | { |
ec92d082 PP |
1894 | int prio; |
1895 | ||
1896 | /* | |
1897 | * The priority used to register this element is | |
1898 | * - either the real thread-priority for the real-time threads | |
1899 | * (i.e. threads with a priority lower than MAX_RT_PRIO) | |
1900 | * - or MAX_RT_PRIO for non-RT threads. | |
1901 | * Thus, all RT-threads are woken first in priority order, and | |
1902 | * the others are woken last, in FIFO order. | |
1903 | */ | |
1904 | prio = min(current->normal_prio, MAX_RT_PRIO); | |
1905 | ||
1906 | plist_node_init(&q->list, prio); | |
ec92d082 | 1907 | plist_add(&q->list, &hb->chain); |
c87e2837 | 1908 | q->task = current; |
e2970f2f | 1909 | spin_unlock(&hb->lock); |
1da177e4 LT |
1910 | } |
1911 | ||
d40d65c8 DH |
1912 | /** |
1913 | * unqueue_me() - Remove the futex_q from its futex_hash_bucket | |
1914 | * @q: The futex_q to unqueue | |
1915 | * | |
1916 | * The q->lock_ptr must not be held by the caller. A call to unqueue_me() must | |
1917 | * be paired with exactly one earlier call to queue_me(). | |
1918 | * | |
6c23cbbd RD |
1919 | * Return: |
1920 | * 1 - if the futex_q was still queued (and we removed unqueued it); | |
d40d65c8 | 1921 | * 0 - if the futex_q was already removed by the waking thread |
1da177e4 | 1922 | */ |
1da177e4 LT |
1923 | static int unqueue_me(struct futex_q *q) |
1924 | { | |
1da177e4 | 1925 | spinlock_t *lock_ptr; |
e2970f2f | 1926 | int ret = 0; |
1da177e4 LT |
1927 | |
1928 | /* In the common case we don't take the spinlock, which is nice. */ | |
42d35d48 | 1929 | retry: |
1da177e4 | 1930 | lock_ptr = q->lock_ptr; |
e91467ec | 1931 | barrier(); |
c80544dc | 1932 | if (lock_ptr != NULL) { |
1da177e4 LT |
1933 | spin_lock(lock_ptr); |
1934 | /* | |
1935 | * q->lock_ptr can change between reading it and | |
1936 | * spin_lock(), causing us to take the wrong lock. This | |
1937 | * corrects the race condition. | |
1938 | * | |
1939 | * Reasoning goes like this: if we have the wrong lock, | |
1940 | * q->lock_ptr must have changed (maybe several times) | |
1941 | * between reading it and the spin_lock(). It can | |
1942 | * change again after the spin_lock() but only if it was | |
1943 | * already changed before the spin_lock(). It cannot, | |
1944 | * however, change back to the original value. Therefore | |
1945 | * we can detect whether we acquired the correct lock. | |
1946 | */ | |
1947 | if (unlikely(lock_ptr != q->lock_ptr)) { | |
1948 | spin_unlock(lock_ptr); | |
1949 | goto retry; | |
1950 | } | |
2e12978a | 1951 | __unqueue_futex(q); |
c87e2837 IM |
1952 | |
1953 | BUG_ON(q->pi_state); | |
1954 | ||
1da177e4 LT |
1955 | spin_unlock(lock_ptr); |
1956 | ret = 1; | |
1957 | } | |
1958 | ||
9adef58b | 1959 | drop_futex_key_refs(&q->key); |
1da177e4 LT |
1960 | return ret; |
1961 | } | |
1962 | ||
c87e2837 IM |
1963 | /* |
1964 | * PI futexes can not be requeued and must remove themself from the | |
d0aa7a70 PP |
1965 | * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry |
1966 | * and dropped here. | |
c87e2837 | 1967 | */ |
d0aa7a70 | 1968 | static void unqueue_me_pi(struct futex_q *q) |
15e408cd | 1969 | __releases(q->lock_ptr) |
c87e2837 | 1970 | { |
2e12978a | 1971 | __unqueue_futex(q); |
c87e2837 IM |
1972 | |
1973 | BUG_ON(!q->pi_state); | |
29e9ee5d | 1974 | put_pi_state(q->pi_state); |
c87e2837 IM |
1975 | q->pi_state = NULL; |
1976 | ||
d0aa7a70 | 1977 | spin_unlock(q->lock_ptr); |
c87e2837 IM |
1978 | } |
1979 | ||
d0aa7a70 | 1980 | /* |
cdf71a10 | 1981 | * Fixup the pi_state owner with the new owner. |
d0aa7a70 | 1982 | * |
778e9a9c AK |
1983 | * Must be called with hash bucket lock held and mm->sem held for non |
1984 | * private futexes. | |
d0aa7a70 | 1985 | */ |
778e9a9c | 1986 | static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q, |
ae791a2d | 1987 | struct task_struct *newowner) |
d0aa7a70 | 1988 | { |
cdf71a10 | 1989 | u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS; |
d0aa7a70 | 1990 | struct futex_pi_state *pi_state = q->pi_state; |
1b7558e4 | 1991 | struct task_struct *oldowner = pi_state->owner; |
7cfdaf38 | 1992 | u32 uval, uninitialized_var(curval), newval; |
e4dc5b7a | 1993 | int ret; |
d0aa7a70 PP |
1994 | |
1995 | /* Owner died? */ | |
1b7558e4 TG |
1996 | if (!pi_state->owner) |
1997 | newtid |= FUTEX_OWNER_DIED; | |
1998 | ||
1999 | /* | |
2000 | * We are here either because we stole the rtmutex from the | |
8161239a LJ |
2001 | * previous highest priority waiter or we are the highest priority |
2002 | * waiter but failed to get the rtmutex the first time. | |
2003 | * We have to replace the newowner TID in the user space variable. | |
2004 | * This must be atomic as we have to preserve the owner died bit here. | |
1b7558e4 | 2005 | * |
b2d0994b DH |
2006 | * Note: We write the user space value _before_ changing the pi_state |
2007 | * because we can fault here. Imagine swapped out pages or a fork | |
2008 | * that marked all the anonymous memory readonly for cow. | |
1b7558e4 TG |
2009 | * |
2010 | * Modifying pi_state _before_ the user space value would | |
2011 | * leave the pi_state in an inconsistent state when we fault | |
2012 | * here, because we need to drop the hash bucket lock to | |
2013 | * handle the fault. This might be observed in the PID check | |
2014 | * in lookup_pi_state. | |
2015 | */ | |
2016 | retry: | |
2017 | if (get_futex_value_locked(&uval, uaddr)) | |
2018 | goto handle_fault; | |
2019 | ||
2020 | while (1) { | |
2021 | newval = (uval & FUTEX_OWNER_DIED) | newtid; | |
2022 | ||
37a9d912 | 2023 | if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval)) |
1b7558e4 TG |
2024 | goto handle_fault; |
2025 | if (curval == uval) | |
2026 | break; | |
2027 | uval = curval; | |
2028 | } | |
2029 | ||
2030 | /* | |
2031 | * We fixed up user space. Now we need to fix the pi_state | |
2032 | * itself. | |
2033 | */ | |
d0aa7a70 | 2034 | if (pi_state->owner != NULL) { |
1d615482 | 2035 | raw_spin_lock_irq(&pi_state->owner->pi_lock); |
d0aa7a70 PP |
2036 | WARN_ON(list_empty(&pi_state->list)); |
2037 | list_del_init(&pi_state->list); | |
1d615482 | 2038 | raw_spin_unlock_irq(&pi_state->owner->pi_lock); |
1b7558e4 | 2039 | } |
d0aa7a70 | 2040 | |
cdf71a10 | 2041 | pi_state->owner = newowner; |
d0aa7a70 | 2042 | |
1d615482 | 2043 | raw_spin_lock_irq(&newowner->pi_lock); |
d0aa7a70 | 2044 | WARN_ON(!list_empty(&pi_state->list)); |
cdf71a10 | 2045 | list_add(&pi_state->list, &newowner->pi_state_list); |
1d615482 | 2046 | raw_spin_unlock_irq(&newowner->pi_lock); |
1b7558e4 | 2047 | return 0; |
d0aa7a70 | 2048 | |
d0aa7a70 | 2049 | /* |
1b7558e4 | 2050 | * To handle the page fault we need to drop the hash bucket |
8161239a LJ |
2051 | * lock here. That gives the other task (either the highest priority |
2052 | * waiter itself or the task which stole the rtmutex) the | |
1b7558e4 TG |
2053 | * chance to try the fixup of the pi_state. So once we are |
2054 | * back from handling the fault we need to check the pi_state | |
2055 | * after reacquiring the hash bucket lock and before trying to | |
2056 | * do another fixup. When the fixup has been done already we | |
2057 | * simply return. | |
d0aa7a70 | 2058 | */ |
1b7558e4 TG |
2059 | handle_fault: |
2060 | spin_unlock(q->lock_ptr); | |
778e9a9c | 2061 | |
d0725992 | 2062 | ret = fault_in_user_writeable(uaddr); |
778e9a9c | 2063 | |
1b7558e4 | 2064 | spin_lock(q->lock_ptr); |
778e9a9c | 2065 | |
1b7558e4 TG |
2066 | /* |
2067 | * Check if someone else fixed it for us: | |
2068 | */ | |
2069 | if (pi_state->owner != oldowner) | |
2070 | return 0; | |
2071 | ||
2072 | if (ret) | |
2073 | return ret; | |
2074 | ||
2075 | goto retry; | |
d0aa7a70 PP |
2076 | } |
2077 | ||
72c1bbf3 | 2078 | static long futex_wait_restart(struct restart_block *restart); |
36cf3b5c | 2079 | |
dd973998 DH |
2080 | /** |
2081 | * fixup_owner() - Post lock pi_state and corner case management | |
2082 | * @uaddr: user address of the futex | |
dd973998 DH |
2083 | * @q: futex_q (contains pi_state and access to the rt_mutex) |
2084 | * @locked: if the attempt to take the rt_mutex succeeded (1) or not (0) | |
2085 | * | |
2086 | * After attempting to lock an rt_mutex, this function is called to cleanup | |
2087 | * the pi_state owner as well as handle race conditions that may allow us to | |
2088 | * acquire the lock. Must be called with the hb lock held. | |
2089 | * | |
6c23cbbd RD |
2090 | * Return: |
2091 | * 1 - success, lock taken; | |
2092 | * 0 - success, lock not taken; | |
dd973998 DH |
2093 | * <0 - on error (-EFAULT) |
2094 | */ | |
ae791a2d | 2095 | static int fixup_owner(u32 __user *uaddr, struct futex_q *q, int locked) |
dd973998 DH |
2096 | { |
2097 | struct task_struct *owner; | |
2098 | int ret = 0; | |
2099 | ||
2100 | if (locked) { | |
2101 | /* | |
2102 | * Got the lock. We might not be the anticipated owner if we | |
2103 | * did a lock-steal - fix up the PI-state in that case: | |
2104 | */ | |
2105 | if (q->pi_state->owner != current) | |
ae791a2d | 2106 | ret = fixup_pi_state_owner(uaddr, q, current); |
dd973998 DH |
2107 | goto out; |
2108 | } | |
2109 | ||
2110 | /* | |
2111 | * Catch the rare case, where the lock was released when we were on the | |
2112 | * way back before we locked the hash bucket. | |
2113 | */ | |
2114 | if (q->pi_state->owner == current) { | |
2115 | /* | |
2116 | * Try to get the rt_mutex now. This might fail as some other | |
2117 | * task acquired the rt_mutex after we removed ourself from the | |
2118 | * rt_mutex waiters list. | |
2119 | */ | |
2120 | if (rt_mutex_trylock(&q->pi_state->pi_mutex)) { | |
2121 | locked = 1; | |
2122 | goto out; | |
2123 | } | |
2124 | ||
2125 | /* | |
2126 | * pi_state is incorrect, some other task did a lock steal and | |
2127 | * we returned due to timeout or signal without taking the | |
8161239a | 2128 | * rt_mutex. Too late. |
dd973998 | 2129 | */ |
b4abf910 | 2130 | raw_spin_lock_irq(&q->pi_state->pi_mutex.wait_lock); |
dd973998 | 2131 | owner = rt_mutex_owner(&q->pi_state->pi_mutex); |
8161239a LJ |
2132 | if (!owner) |
2133 | owner = rt_mutex_next_owner(&q->pi_state->pi_mutex); | |
b4abf910 | 2134 | raw_spin_unlock_irq(&q->pi_state->pi_mutex.wait_lock); |
ae791a2d | 2135 | ret = fixup_pi_state_owner(uaddr, q, owner); |
dd973998 DH |
2136 | goto out; |
2137 | } | |
2138 | ||
2139 | /* | |
2140 | * Paranoia check. If we did not take the lock, then we should not be | |
8161239a | 2141 | * the owner of the rt_mutex. |
dd973998 DH |
2142 | */ |
2143 | if (rt_mutex_owner(&q->pi_state->pi_mutex) == current) | |
2144 | printk(KERN_ERR "fixup_owner: ret = %d pi-mutex: %p " | |
2145 | "pi-state %p\n", ret, | |
2146 | q->pi_state->pi_mutex.owner, | |
2147 | q->pi_state->owner); | |
2148 | ||
2149 | out: | |
2150 | return ret ? ret : locked; | |
2151 | } | |
2152 | ||
ca5f9524 DH |
2153 | /** |
2154 | * futex_wait_queue_me() - queue_me() and wait for wakeup, timeout, or signal | |
2155 | * @hb: the futex hash bucket, must be locked by the caller | |
2156 | * @q: the futex_q to queue up on | |
2157 | * @timeout: the prepared hrtimer_sleeper, or null for no timeout | |
ca5f9524 DH |
2158 | */ |
2159 | static void futex_wait_queue_me(struct futex_hash_bucket *hb, struct futex_q *q, | |
f1a11e05 | 2160 | struct hrtimer_sleeper *timeout) |
ca5f9524 | 2161 | { |
9beba3c5 DH |
2162 | /* |
2163 | * The task state is guaranteed to be set before another task can | |
b92b8b35 | 2164 | * wake it. set_current_state() is implemented using smp_store_mb() and |
9beba3c5 DH |
2165 | * queue_me() calls spin_unlock() upon completion, both serializing |
2166 | * access to the hash list and forcing another memory barrier. | |
2167 | */ | |
f1a11e05 | 2168 | set_current_state(TASK_INTERRUPTIBLE); |
0729e196 | 2169 | queue_me(q, hb); |
ca5f9524 DH |
2170 | |
2171 | /* Arm the timer */ | |
2e4b0d3f | 2172 | if (timeout) |
ca5f9524 | 2173 | hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS); |
ca5f9524 DH |
2174 | |
2175 | /* | |
0729e196 DH |
2176 | * If we have been removed from the hash list, then another task |
2177 | * has tried to wake us, and we can skip the call to schedule(). | |
ca5f9524 DH |
2178 | */ |
2179 | if (likely(!plist_node_empty(&q->list))) { | |
2180 | /* | |
2181 | * If the timer has already expired, current will already be | |
2182 | * flagged for rescheduling. Only call schedule if there | |
2183 | * is no timeout, or if it has yet to expire. | |
2184 | */ | |
2185 | if (!timeout || timeout->task) | |
88c8004f | 2186 | freezable_schedule(); |
ca5f9524 DH |
2187 | } |
2188 | __set_current_state(TASK_RUNNING); | |
2189 | } | |
2190 | ||
f801073f DH |
2191 | /** |
2192 | * futex_wait_setup() - Prepare to wait on a futex | |
2193 | * @uaddr: the futex userspace address | |
2194 | * @val: the expected value | |
b41277dc | 2195 | * @flags: futex flags (FLAGS_SHARED, etc.) |
f801073f DH |
2196 | * @q: the associated futex_q |
2197 | * @hb: storage for hash_bucket pointer to be returned to caller | |
2198 | * | |
2199 | * Setup the futex_q and locate the hash_bucket. Get the futex value and | |
2200 | * compare it with the expected value. Handle atomic faults internally. | |
2201 | * Return with the hb lock held and a q.key reference on success, and unlocked | |
2202 | * with no q.key reference on failure. | |
2203 | * | |
6c23cbbd RD |
2204 | * Return: |
2205 | * 0 - uaddr contains val and hb has been locked; | |
ca4a04cf | 2206 | * <1 - -EFAULT or -EWOULDBLOCK (uaddr does not contain val) and hb is unlocked |
f801073f | 2207 | */ |
b41277dc | 2208 | static int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags, |
f801073f | 2209 | struct futex_q *q, struct futex_hash_bucket **hb) |
1da177e4 | 2210 | { |
e2970f2f IM |
2211 | u32 uval; |
2212 | int ret; | |
1da177e4 | 2213 | |
1da177e4 | 2214 | /* |
b2d0994b | 2215 | * Access the page AFTER the hash-bucket is locked. |
1da177e4 LT |
2216 | * Order is important: |
2217 | * | |
2218 | * Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val); | |
2219 | * Userspace waker: if (cond(var)) { var = new; futex_wake(&var); } | |
2220 | * | |
2221 | * The basic logical guarantee of a futex is that it blocks ONLY | |
2222 | * if cond(var) is known to be true at the time of blocking, for | |
8fe8f545 ML |
2223 | * any cond. If we locked the hash-bucket after testing *uaddr, that |
2224 | * would open a race condition where we could block indefinitely with | |
1da177e4 LT |
2225 | * cond(var) false, which would violate the guarantee. |
2226 | * | |
8fe8f545 ML |
2227 | * On the other hand, we insert q and release the hash-bucket only |
2228 | * after testing *uaddr. This guarantees that futex_wait() will NOT | |
2229 | * absorb a wakeup if *uaddr does not match the desired values | |
2230 | * while the syscall executes. | |
1da177e4 | 2231 | */ |
f801073f | 2232 | retry: |
9ea71503 | 2233 | ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q->key, VERIFY_READ); |
f801073f | 2234 | if (unlikely(ret != 0)) |
a5a2a0c7 | 2235 | return ret; |
f801073f DH |
2236 | |
2237 | retry_private: | |
2238 | *hb = queue_lock(q); | |
2239 | ||
e2970f2f | 2240 | ret = get_futex_value_locked(&uval, uaddr); |
1da177e4 | 2241 | |
f801073f | 2242 | if (ret) { |
0d00c7b2 | 2243 | queue_unlock(*hb); |
1da177e4 | 2244 | |
e2970f2f | 2245 | ret = get_user(uval, uaddr); |
e4dc5b7a | 2246 | if (ret) |
f801073f | 2247 | goto out; |
1da177e4 | 2248 | |
b41277dc | 2249 | if (!(flags & FLAGS_SHARED)) |
e4dc5b7a DH |
2250 | goto retry_private; |
2251 | ||
ae791a2d | 2252 | put_futex_key(&q->key); |
e4dc5b7a | 2253 | goto retry; |
1da177e4 | 2254 | } |
ca5f9524 | 2255 | |
f801073f | 2256 | if (uval != val) { |
0d00c7b2 | 2257 | queue_unlock(*hb); |
f801073f | 2258 | ret = -EWOULDBLOCK; |
2fff78c7 | 2259 | } |
1da177e4 | 2260 | |
f801073f DH |
2261 | out: |
2262 | if (ret) | |
ae791a2d | 2263 | put_futex_key(&q->key); |
f801073f DH |
2264 | return ret; |
2265 | } | |
2266 | ||
b41277dc DH |
2267 | static int futex_wait(u32 __user *uaddr, unsigned int flags, u32 val, |
2268 | ktime_t *abs_time, u32 bitset) | |
f801073f DH |
2269 | { |
2270 | struct hrtimer_sleeper timeout, *to = NULL; | |
f801073f DH |
2271 | struct restart_block *restart; |
2272 | struct futex_hash_bucket *hb; | |
5bdb05f9 | 2273 | struct futex_q q = futex_q_init; |
f801073f DH |
2274 | int ret; |
2275 | ||
2276 | if (!bitset) | |
2277 | return -EINVAL; | |
f801073f DH |
2278 | q.bitset = bitset; |
2279 | ||
2280 | if (abs_time) { | |
2281 | to = &timeout; | |
2282 | ||
b41277dc DH |
2283 | hrtimer_init_on_stack(&to->timer, (flags & FLAGS_CLOCKRT) ? |
2284 | CLOCK_REALTIME : CLOCK_MONOTONIC, | |
2285 | HRTIMER_MODE_ABS); | |
f801073f DH |
2286 | hrtimer_init_sleeper(to, current); |
2287 | hrtimer_set_expires_range_ns(&to->timer, *abs_time, | |
2288 | current->timer_slack_ns); | |
2289 | } | |
2290 | ||
d58e6576 | 2291 | retry: |
7ada876a DH |
2292 | /* |
2293 | * Prepare to wait on uaddr. On success, holds hb lock and increments | |
2294 | * q.key refs. | |
2295 | */ | |
b41277dc | 2296 | ret = futex_wait_setup(uaddr, val, flags, &q, &hb); |
f801073f DH |
2297 | if (ret) |
2298 | goto out; | |
2299 | ||
ca5f9524 | 2300 | /* queue_me and wait for wakeup, timeout, or a signal. */ |
f1a11e05 | 2301 | futex_wait_queue_me(hb, &q, to); |
1da177e4 LT |
2302 | |
2303 | /* If we were woken (and unqueued), we succeeded, whatever. */ | |
2fff78c7 | 2304 | ret = 0; |
7ada876a | 2305 | /* unqueue_me() drops q.key ref */ |
1da177e4 | 2306 | if (!unqueue_me(&q)) |
7ada876a | 2307 | goto out; |
2fff78c7 | 2308 | ret = -ETIMEDOUT; |
ca5f9524 | 2309 | if (to && !to->task) |
7ada876a | 2310 | goto out; |
72c1bbf3 | 2311 | |
e2970f2f | 2312 | /* |
d58e6576 TG |
2313 | * We expect signal_pending(current), but we might be the |
2314 | * victim of a spurious wakeup as well. | |
e2970f2f | 2315 | */ |
7ada876a | 2316 | if (!signal_pending(current)) |
d58e6576 | 2317 | goto retry; |
d58e6576 | 2318 | |
2fff78c7 | 2319 | ret = -ERESTARTSYS; |
c19384b5 | 2320 | if (!abs_time) |
7ada876a | 2321 | goto out; |
1da177e4 | 2322 | |
f56141e3 | 2323 | restart = ¤t->restart_block; |
2fff78c7 | 2324 | restart->fn = futex_wait_restart; |
a3c74c52 | 2325 | restart->futex.uaddr = uaddr; |
2fff78c7 PZ |
2326 | restart->futex.val = val; |
2327 | restart->futex.time = abs_time->tv64; | |
2328 | restart->futex.bitset = bitset; | |
0cd9c649 | 2329 | restart->futex.flags = flags | FLAGS_HAS_TIMEOUT; |
42d35d48 | 2330 | |
2fff78c7 PZ |
2331 | ret = -ERESTART_RESTARTBLOCK; |
2332 | ||
42d35d48 | 2333 | out: |
ca5f9524 DH |
2334 | if (to) { |
2335 | hrtimer_cancel(&to->timer); | |
2336 | destroy_hrtimer_on_stack(&to->timer); | |
2337 | } | |
c87e2837 IM |
2338 | return ret; |
2339 | } | |
2340 | ||
72c1bbf3 NP |
2341 | |
2342 | static long futex_wait_restart(struct restart_block *restart) | |
2343 | { | |
a3c74c52 | 2344 | u32 __user *uaddr = restart->futex.uaddr; |
a72188d8 | 2345 | ktime_t t, *tp = NULL; |
72c1bbf3 | 2346 | |
a72188d8 DH |
2347 | if (restart->futex.flags & FLAGS_HAS_TIMEOUT) { |
2348 | t.tv64 = restart->futex.time; | |
2349 | tp = &t; | |
2350 | } | |
72c1bbf3 | 2351 | restart->fn = do_no_restart_syscall; |
b41277dc DH |
2352 | |
2353 | return (long)futex_wait(uaddr, restart->futex.flags, | |
2354 | restart->futex.val, tp, restart->futex.bitset); | |
72c1bbf3 NP |
2355 | } |
2356 | ||
2357 | ||
c87e2837 IM |
2358 | /* |
2359 | * Userspace tried a 0 -> TID atomic transition of the futex value | |
2360 | * and failed. The kernel side here does the whole locking operation: | |
767f509c DB |
2361 | * if there are waiters then it will block as a consequence of relying |
2362 | * on rt-mutexes, it does PI, etc. (Due to races the kernel might see | |
2363 | * a 0 value of the futex too.). | |
2364 | * | |
2365 | * Also serves as futex trylock_pi()'ing, and due semantics. | |
c87e2837 | 2366 | */ |
996636dd | 2367 | static int futex_lock_pi(u32 __user *uaddr, unsigned int flags, |
b41277dc | 2368 | ktime_t *time, int trylock) |
c87e2837 | 2369 | { |
c5780e97 | 2370 | struct hrtimer_sleeper timeout, *to = NULL; |
c87e2837 | 2371 | struct futex_hash_bucket *hb; |
5bdb05f9 | 2372 | struct futex_q q = futex_q_init; |
dd973998 | 2373 | int res, ret; |
c87e2837 IM |
2374 | |
2375 | if (refill_pi_state_cache()) | |
2376 | return -ENOMEM; | |
2377 | ||
c19384b5 | 2378 | if (time) { |
c5780e97 | 2379 | to = &timeout; |
237fc6e7 TG |
2380 | hrtimer_init_on_stack(&to->timer, CLOCK_REALTIME, |
2381 | HRTIMER_MODE_ABS); | |
c5780e97 | 2382 | hrtimer_init_sleeper(to, current); |
cc584b21 | 2383 | hrtimer_set_expires(&to->timer, *time); |
c5780e97 TG |
2384 | } |
2385 | ||
42d35d48 | 2386 | retry: |
9ea71503 | 2387 | ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q.key, VERIFY_WRITE); |
c87e2837 | 2388 | if (unlikely(ret != 0)) |
42d35d48 | 2389 | goto out; |
c87e2837 | 2390 | |
e4dc5b7a | 2391 | retry_private: |
82af7aca | 2392 | hb = queue_lock(&q); |
c87e2837 | 2393 | |
bab5bc9e | 2394 | ret = futex_lock_pi_atomic(uaddr, hb, &q.key, &q.pi_state, current, 0); |
c87e2837 | 2395 | if (unlikely(ret)) { |
767f509c DB |
2396 | /* |
2397 | * Atomic work succeeded and we got the lock, | |
2398 | * or failed. Either way, we do _not_ block. | |
2399 | */ | |
778e9a9c | 2400 | switch (ret) { |
1a52084d DH |
2401 | case 1: |
2402 | /* We got the lock. */ | |
2403 | ret = 0; | |
2404 | goto out_unlock_put_key; | |
2405 | case -EFAULT: | |
2406 | goto uaddr_faulted; | |
778e9a9c AK |
2407 | case -EAGAIN: |
2408 | /* | |
af54d6a1 TG |
2409 | * Two reasons for this: |
2410 | * - Task is exiting and we just wait for the | |
2411 | * exit to complete. | |
2412 | * - The user space value changed. | |
778e9a9c | 2413 | */ |
0d00c7b2 | 2414 | queue_unlock(hb); |
ae791a2d | 2415 | put_futex_key(&q.key); |
778e9a9c AK |
2416 | cond_resched(); |
2417 | goto retry; | |
778e9a9c | 2418 | default: |
42d35d48 | 2419 | goto out_unlock_put_key; |
c87e2837 | 2420 | } |
c87e2837 IM |
2421 | } |
2422 | ||
2423 | /* | |
2424 | * Only actually queue now that the atomic ops are done: | |
2425 | */ | |
82af7aca | 2426 | queue_me(&q, hb); |
c87e2837 | 2427 | |
c87e2837 IM |
2428 | WARN_ON(!q.pi_state); |
2429 | /* | |
2430 | * Block on the PI mutex: | |
2431 | */ | |
c051b21f TG |
2432 | if (!trylock) { |
2433 | ret = rt_mutex_timed_futex_lock(&q.pi_state->pi_mutex, to); | |
2434 | } else { | |
c87e2837 IM |
2435 | ret = rt_mutex_trylock(&q.pi_state->pi_mutex); |
2436 | /* Fixup the trylock return value: */ | |
2437 | ret = ret ? 0 : -EWOULDBLOCK; | |
2438 | } | |
2439 | ||
a99e4e41 | 2440 | spin_lock(q.lock_ptr); |
dd973998 DH |
2441 | /* |
2442 | * Fixup the pi_state owner and possibly acquire the lock if we | |
2443 | * haven't already. | |
2444 | */ | |
ae791a2d | 2445 | res = fixup_owner(uaddr, &q, !ret); |
dd973998 DH |
2446 | /* |
2447 | * If fixup_owner() returned an error, proprogate that. If it acquired | |
2448 | * the lock, clear our -ETIMEDOUT or -EINTR. | |
2449 | */ | |
2450 | if (res) | |
2451 | ret = (res < 0) ? res : 0; | |
c87e2837 | 2452 | |
e8f6386c | 2453 | /* |
dd973998 DH |
2454 | * If fixup_owner() faulted and was unable to handle the fault, unlock |
2455 | * it and return the fault to userspace. | |
e8f6386c DH |
2456 | */ |
2457 | if (ret && (rt_mutex_owner(&q.pi_state->pi_mutex) == current)) | |
2458 | rt_mutex_unlock(&q.pi_state->pi_mutex); | |
2459 | ||
778e9a9c AK |
2460 | /* Unqueue and drop the lock */ |
2461 | unqueue_me_pi(&q); | |
c87e2837 | 2462 | |
5ecb01cf | 2463 | goto out_put_key; |
c87e2837 | 2464 | |
42d35d48 | 2465 | out_unlock_put_key: |
0d00c7b2 | 2466 | queue_unlock(hb); |
c87e2837 | 2467 | |
42d35d48 | 2468 | out_put_key: |
ae791a2d | 2469 | put_futex_key(&q.key); |
42d35d48 | 2470 | out: |
237fc6e7 TG |
2471 | if (to) |
2472 | destroy_hrtimer_on_stack(&to->timer); | |
dd973998 | 2473 | return ret != -EINTR ? ret : -ERESTARTNOINTR; |
c87e2837 | 2474 | |
42d35d48 | 2475 | uaddr_faulted: |
0d00c7b2 | 2476 | queue_unlock(hb); |
778e9a9c | 2477 | |
d0725992 | 2478 | ret = fault_in_user_writeable(uaddr); |
e4dc5b7a DH |
2479 | if (ret) |
2480 | goto out_put_key; | |
c87e2837 | 2481 | |
b41277dc | 2482 | if (!(flags & FLAGS_SHARED)) |
e4dc5b7a DH |
2483 | goto retry_private; |
2484 | ||
ae791a2d | 2485 | put_futex_key(&q.key); |
e4dc5b7a | 2486 | goto retry; |
c87e2837 IM |
2487 | } |
2488 | ||
c87e2837 IM |
2489 | /* |
2490 | * Userspace attempted a TID -> 0 atomic transition, and failed. | |
2491 | * This is the in-kernel slowpath: we look up the PI state (if any), | |
2492 | * and do the rt-mutex unlock. | |
2493 | */ | |
b41277dc | 2494 | static int futex_unlock_pi(u32 __user *uaddr, unsigned int flags) |
c87e2837 | 2495 | { |
ccf9e6a8 | 2496 | u32 uninitialized_var(curval), uval, vpid = task_pid_vnr(current); |
38d47c1b | 2497 | union futex_key key = FUTEX_KEY_INIT; |
ccf9e6a8 TG |
2498 | struct futex_hash_bucket *hb; |
2499 | struct futex_q *match; | |
e4dc5b7a | 2500 | int ret; |
c87e2837 IM |
2501 | |
2502 | retry: | |
2503 | if (get_user(uval, uaddr)) | |
2504 | return -EFAULT; | |
2505 | /* | |
2506 | * We release only a lock we actually own: | |
2507 | */ | |
c0c9ed15 | 2508 | if ((uval & FUTEX_TID_MASK) != vpid) |
c87e2837 | 2509 | return -EPERM; |
c87e2837 | 2510 | |
9ea71503 | 2511 | ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key, VERIFY_WRITE); |
ccf9e6a8 TG |
2512 | if (ret) |
2513 | return ret; | |
c87e2837 IM |
2514 | |
2515 | hb = hash_futex(&key); | |
2516 | spin_lock(&hb->lock); | |
2517 | ||
c87e2837 | 2518 | /* |
ccf9e6a8 TG |
2519 | * Check waiters first. We do not trust user space values at |
2520 | * all and we at least want to know if user space fiddled | |
2521 | * with the futex value instead of blindly unlocking. | |
c87e2837 | 2522 | */ |
ccf9e6a8 TG |
2523 | match = futex_top_waiter(hb, &key); |
2524 | if (match) { | |
802ab58d SAS |
2525 | ret = wake_futex_pi(uaddr, uval, match, hb); |
2526 | /* | |
2527 | * In case of success wake_futex_pi dropped the hash | |
2528 | * bucket lock. | |
2529 | */ | |
2530 | if (!ret) | |
2531 | goto out_putkey; | |
c87e2837 | 2532 | /* |
ccf9e6a8 TG |
2533 | * The atomic access to the futex value generated a |
2534 | * pagefault, so retry the user-access and the wakeup: | |
c87e2837 IM |
2535 | */ |
2536 | if (ret == -EFAULT) | |
2537 | goto pi_faulted; | |
802ab58d SAS |
2538 | /* |
2539 | * wake_futex_pi has detected invalid state. Tell user | |
2540 | * space. | |
2541 | */ | |
c87e2837 IM |
2542 | goto out_unlock; |
2543 | } | |
ccf9e6a8 | 2544 | |
c87e2837 | 2545 | /* |
ccf9e6a8 TG |
2546 | * We have no kernel internal state, i.e. no waiters in the |
2547 | * kernel. Waiters which are about to queue themselves are stuck | |
2548 | * on hb->lock. So we can safely ignore them. We do neither | |
2549 | * preserve the WAITERS bit not the OWNER_DIED one. We are the | |
2550 | * owner. | |
c87e2837 | 2551 | */ |
ccf9e6a8 | 2552 | if (cmpxchg_futex_value_locked(&curval, uaddr, uval, 0)) |
13fbca4c | 2553 | goto pi_faulted; |
c87e2837 | 2554 | |
ccf9e6a8 TG |
2555 | /* |
2556 | * If uval has changed, let user space handle it. | |
2557 | */ | |
2558 | ret = (curval == uval) ? 0 : -EAGAIN; | |
2559 | ||
c87e2837 IM |
2560 | out_unlock: |
2561 | spin_unlock(&hb->lock); | |
802ab58d | 2562 | out_putkey: |
ae791a2d | 2563 | put_futex_key(&key); |
c87e2837 IM |
2564 | return ret; |
2565 | ||
2566 | pi_faulted: | |
778e9a9c | 2567 | spin_unlock(&hb->lock); |
ae791a2d | 2568 | put_futex_key(&key); |
c87e2837 | 2569 | |
d0725992 | 2570 | ret = fault_in_user_writeable(uaddr); |
b5686363 | 2571 | if (!ret) |
c87e2837 IM |
2572 | goto retry; |
2573 | ||
1da177e4 LT |
2574 | return ret; |
2575 | } | |
2576 | ||
52400ba9 DH |
2577 | /** |
2578 | * handle_early_requeue_pi_wakeup() - Detect early wakeup on the initial futex | |
2579 | * @hb: the hash_bucket futex_q was original enqueued on | |
2580 | * @q: the futex_q woken while waiting to be requeued | |
2581 | * @key2: the futex_key of the requeue target futex | |
2582 | * @timeout: the timeout associated with the wait (NULL if none) | |
2583 | * | |
2584 | * Detect if the task was woken on the initial futex as opposed to the requeue | |
2585 | * target futex. If so, determine if it was a timeout or a signal that caused | |
2586 | * the wakeup and return the appropriate error code to the caller. Must be | |
2587 | * called with the hb lock held. | |
2588 | * | |
6c23cbbd RD |
2589 | * Return: |
2590 | * 0 = no early wakeup detected; | |
2591 | * <0 = -ETIMEDOUT or -ERESTARTNOINTR | |
52400ba9 DH |
2592 | */ |
2593 | static inline | |
2594 | int handle_early_requeue_pi_wakeup(struct futex_hash_bucket *hb, | |
2595 | struct futex_q *q, union futex_key *key2, | |
2596 | struct hrtimer_sleeper *timeout) | |
2597 | { | |
2598 | int ret = 0; | |
2599 | ||
2600 | /* | |
2601 | * With the hb lock held, we avoid races while we process the wakeup. | |
2602 | * We only need to hold hb (and not hb2) to ensure atomicity as the | |
2603 | * wakeup code can't change q.key from uaddr to uaddr2 if we hold hb. | |
2604 | * It can't be requeued from uaddr2 to something else since we don't | |
2605 | * support a PI aware source futex for requeue. | |
2606 | */ | |
2607 | if (!match_futex(&q->key, key2)) { | |
2608 | WARN_ON(q->lock_ptr && (&hb->lock != q->lock_ptr)); | |
2609 | /* | |
2610 | * We were woken prior to requeue by a timeout or a signal. | |
2611 | * Unqueue the futex_q and determine which it was. | |
2612 | */ | |
2e12978a | 2613 | plist_del(&q->list, &hb->chain); |
11d4616b | 2614 | hb_waiters_dec(hb); |
52400ba9 | 2615 | |
d58e6576 | 2616 | /* Handle spurious wakeups gracefully */ |
11df6ddd | 2617 | ret = -EWOULDBLOCK; |
52400ba9 DH |
2618 | if (timeout && !timeout->task) |
2619 | ret = -ETIMEDOUT; | |
d58e6576 | 2620 | else if (signal_pending(current)) |
1c840c14 | 2621 | ret = -ERESTARTNOINTR; |
52400ba9 DH |
2622 | } |
2623 | return ret; | |
2624 | } | |
2625 | ||
2626 | /** | |
2627 | * futex_wait_requeue_pi() - Wait on uaddr and take uaddr2 | |
56ec1607 | 2628 | * @uaddr: the futex we initially wait on (non-pi) |
b41277dc | 2629 | * @flags: futex flags (FLAGS_SHARED, FLAGS_CLOCKRT, etc.), they must be |
ab51fbab | 2630 | * the same type, no requeueing from private to shared, etc. |
52400ba9 DH |
2631 | * @val: the expected value of uaddr |
2632 | * @abs_time: absolute timeout | |
56ec1607 | 2633 | * @bitset: 32 bit wakeup bitset set by userspace, defaults to all |
52400ba9 DH |
2634 | * @uaddr2: the pi futex we will take prior to returning to user-space |
2635 | * | |
2636 | * The caller will wait on uaddr and will be requeued by futex_requeue() to | |
6f7b0a2a DH |
2637 | * uaddr2 which must be PI aware and unique from uaddr. Normal wakeup will wake |
2638 | * on uaddr2 and complete the acquisition of the rt_mutex prior to returning to | |
2639 | * userspace. This ensures the rt_mutex maintains an owner when it has waiters; | |
2640 | * without one, the pi logic would not know which task to boost/deboost, if | |
2641 | * there was a need to. | |
52400ba9 DH |
2642 | * |
2643 | * We call schedule in futex_wait_queue_me() when we enqueue and return there | |
6c23cbbd | 2644 | * via the following-- |
52400ba9 | 2645 | * 1) wakeup on uaddr2 after an atomic lock acquisition by futex_requeue() |
cc6db4e6 DH |
2646 | * 2) wakeup on uaddr2 after a requeue |
2647 | * 3) signal | |
2648 | * 4) timeout | |
52400ba9 | 2649 | * |
cc6db4e6 | 2650 | * If 3, cleanup and return -ERESTARTNOINTR. |
52400ba9 DH |
2651 | * |
2652 | * If 2, we may then block on trying to take the rt_mutex and return via: | |
2653 | * 5) successful lock | |
2654 | * 6) signal | |
2655 | * 7) timeout | |
2656 | * 8) other lock acquisition failure | |
2657 | * | |
cc6db4e6 | 2658 | * If 6, return -EWOULDBLOCK (restarting the syscall would do the same). |
52400ba9 DH |
2659 | * |
2660 | * If 4 or 7, we cleanup and return with -ETIMEDOUT. | |
2661 | * | |
6c23cbbd RD |
2662 | * Return: |
2663 | * 0 - On success; | |
52400ba9 DH |
2664 | * <0 - On error |
2665 | */ | |
b41277dc | 2666 | static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags, |
52400ba9 | 2667 | u32 val, ktime_t *abs_time, u32 bitset, |
b41277dc | 2668 | u32 __user *uaddr2) |
52400ba9 DH |
2669 | { |
2670 | struct hrtimer_sleeper timeout, *to = NULL; | |
2671 | struct rt_mutex_waiter rt_waiter; | |
2672 | struct rt_mutex *pi_mutex = NULL; | |
52400ba9 | 2673 | struct futex_hash_bucket *hb; |
5bdb05f9 DH |
2674 | union futex_key key2 = FUTEX_KEY_INIT; |
2675 | struct futex_q q = futex_q_init; | |
52400ba9 | 2676 | int res, ret; |
52400ba9 | 2677 | |
6f7b0a2a DH |
2678 | if (uaddr == uaddr2) |
2679 | return -EINVAL; | |
2680 | ||
52400ba9 DH |
2681 | if (!bitset) |
2682 | return -EINVAL; | |
2683 | ||
2684 | if (abs_time) { | |
2685 | to = &timeout; | |
b41277dc DH |
2686 | hrtimer_init_on_stack(&to->timer, (flags & FLAGS_CLOCKRT) ? |
2687 | CLOCK_REALTIME : CLOCK_MONOTONIC, | |
2688 | HRTIMER_MODE_ABS); | |
52400ba9 DH |
2689 | hrtimer_init_sleeper(to, current); |
2690 | hrtimer_set_expires_range_ns(&to->timer, *abs_time, | |
2691 | current->timer_slack_ns); | |
2692 | } | |
2693 | ||
2694 | /* | |
2695 | * The waiter is allocated on our stack, manipulated by the requeue | |
2696 | * code while we sleep on uaddr. | |
2697 | */ | |
2698 | debug_rt_mutex_init_waiter(&rt_waiter); | |
fb00aca4 PZ |
2699 | RB_CLEAR_NODE(&rt_waiter.pi_tree_entry); |
2700 | RB_CLEAR_NODE(&rt_waiter.tree_entry); | |
52400ba9 DH |
2701 | rt_waiter.task = NULL; |
2702 | ||
9ea71503 | 2703 | ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, VERIFY_WRITE); |
52400ba9 DH |
2704 | if (unlikely(ret != 0)) |
2705 | goto out; | |
2706 | ||
84bc4af5 DH |
2707 | q.bitset = bitset; |
2708 | q.rt_waiter = &rt_waiter; | |
2709 | q.requeue_pi_key = &key2; | |
2710 | ||
7ada876a DH |
2711 | /* |
2712 | * Prepare to wait on uaddr. On success, increments q.key (key1) ref | |
2713 | * count. | |
2714 | */ | |
b41277dc | 2715 | ret = futex_wait_setup(uaddr, val, flags, &q, &hb); |
c8b15a70 TG |
2716 | if (ret) |
2717 | goto out_key2; | |
52400ba9 | 2718 | |
e9c243a5 TG |
2719 | /* |
2720 | * The check above which compares uaddrs is not sufficient for | |
2721 | * shared futexes. We need to compare the keys: | |
2722 | */ | |
2723 | if (match_futex(&q.key, &key2)) { | |
13c42c2f | 2724 | queue_unlock(hb); |
e9c243a5 TG |
2725 | ret = -EINVAL; |
2726 | goto out_put_keys; | |
2727 | } | |
2728 | ||
52400ba9 | 2729 | /* Queue the futex_q, drop the hb lock, wait for wakeup. */ |
f1a11e05 | 2730 | futex_wait_queue_me(hb, &q, to); |
52400ba9 DH |
2731 | |
2732 | spin_lock(&hb->lock); | |
2733 | ret = handle_early_requeue_pi_wakeup(hb, &q, &key2, to); | |
2734 | spin_unlock(&hb->lock); | |
2735 | if (ret) | |
2736 | goto out_put_keys; | |
2737 | ||
2738 | /* | |
2739 | * In order for us to be here, we know our q.key == key2, and since | |
2740 | * we took the hb->lock above, we also know that futex_requeue() has | |
2741 | * completed and we no longer have to concern ourselves with a wakeup | |
7ada876a DH |
2742 | * race with the atomic proxy lock acquisition by the requeue code. The |
2743 | * futex_requeue dropped our key1 reference and incremented our key2 | |
2744 | * reference count. | |
52400ba9 DH |
2745 | */ |
2746 | ||
2747 | /* Check if the requeue code acquired the second futex for us. */ | |
2748 | if (!q.rt_waiter) { | |
2749 | /* | |
2750 | * Got the lock. We might not be the anticipated owner if we | |
2751 | * did a lock-steal - fix up the PI-state in that case. | |
2752 | */ | |
2753 | if (q.pi_state && (q.pi_state->owner != current)) { | |
2754 | spin_lock(q.lock_ptr); | |
ae791a2d | 2755 | ret = fixup_pi_state_owner(uaddr2, &q, current); |
fb75a428 TG |
2756 | /* |
2757 | * Drop the reference to the pi state which | |
2758 | * the requeue_pi() code acquired for us. | |
2759 | */ | |
29e9ee5d | 2760 | put_pi_state(q.pi_state); |
52400ba9 DH |
2761 | spin_unlock(q.lock_ptr); |
2762 | } | |
2763 | } else { | |
2764 | /* | |
2765 | * We have been woken up by futex_unlock_pi(), a timeout, or a | |
2766 | * signal. futex_unlock_pi() will not destroy the lock_ptr nor | |
2767 | * the pi_state. | |
2768 | */ | |
f27071cb | 2769 | WARN_ON(!q.pi_state); |
52400ba9 | 2770 | pi_mutex = &q.pi_state->pi_mutex; |
c051b21f | 2771 | ret = rt_mutex_finish_proxy_lock(pi_mutex, to, &rt_waiter); |
52400ba9 DH |
2772 | debug_rt_mutex_free_waiter(&rt_waiter); |
2773 | ||
2774 | spin_lock(q.lock_ptr); | |
2775 | /* | |
2776 | * Fixup the pi_state owner and possibly acquire the lock if we | |
2777 | * haven't already. | |
2778 | */ | |
ae791a2d | 2779 | res = fixup_owner(uaddr2, &q, !ret); |
52400ba9 DH |
2780 | /* |
2781 | * If fixup_owner() returned an error, proprogate that. If it | |
56ec1607 | 2782 | * acquired the lock, clear -ETIMEDOUT or -EINTR. |
52400ba9 DH |
2783 | */ |
2784 | if (res) | |
2785 | ret = (res < 0) ? res : 0; | |
2786 | ||
2787 | /* Unqueue and drop the lock. */ | |
2788 | unqueue_me_pi(&q); | |
2789 | } | |
2790 | ||
2791 | /* | |
2792 | * If fixup_pi_state_owner() faulted and was unable to handle the | |
2793 | * fault, unlock the rt_mutex and return the fault to userspace. | |
2794 | */ | |
2795 | if (ret == -EFAULT) { | |
b6070a8d | 2796 | if (pi_mutex && rt_mutex_owner(pi_mutex) == current) |
52400ba9 DH |
2797 | rt_mutex_unlock(pi_mutex); |
2798 | } else if (ret == -EINTR) { | |
52400ba9 | 2799 | /* |
cc6db4e6 DH |
2800 | * We've already been requeued, but cannot restart by calling |
2801 | * futex_lock_pi() directly. We could restart this syscall, but | |
2802 | * it would detect that the user space "val" changed and return | |
2803 | * -EWOULDBLOCK. Save the overhead of the restart and return | |
2804 | * -EWOULDBLOCK directly. | |
52400ba9 | 2805 | */ |
2070887f | 2806 | ret = -EWOULDBLOCK; |
52400ba9 DH |
2807 | } |
2808 | ||
2809 | out_put_keys: | |
ae791a2d | 2810 | put_futex_key(&q.key); |
c8b15a70 | 2811 | out_key2: |
ae791a2d | 2812 | put_futex_key(&key2); |
52400ba9 DH |
2813 | |
2814 | out: | |
2815 | if (to) { | |
2816 | hrtimer_cancel(&to->timer); | |
2817 | destroy_hrtimer_on_stack(&to->timer); | |
2818 | } | |
2819 | return ret; | |
2820 | } | |
2821 | ||
0771dfef IM |
2822 | /* |
2823 | * Support for robust futexes: the kernel cleans up held futexes at | |
2824 | * thread exit time. | |
2825 | * | |
2826 | * Implementation: user-space maintains a per-thread list of locks it | |
2827 | * is holding. Upon do_exit(), the kernel carefully walks this list, | |
2828 | * and marks all locks that are owned by this thread with the | |
c87e2837 | 2829 | * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is |
0771dfef IM |
2830 | * always manipulated with the lock held, so the list is private and |
2831 | * per-thread. Userspace also maintains a per-thread 'list_op_pending' | |
2832 | * field, to allow the kernel to clean up if the thread dies after | |
2833 | * acquiring the lock, but just before it could have added itself to | |
2834 | * the list. There can only be one such pending lock. | |
2835 | */ | |
2836 | ||
2837 | /** | |
d96ee56c DH |
2838 | * sys_set_robust_list() - Set the robust-futex list head of a task |
2839 | * @head: pointer to the list-head | |
2840 | * @len: length of the list-head, as userspace expects | |
0771dfef | 2841 | */ |
836f92ad HC |
2842 | SYSCALL_DEFINE2(set_robust_list, struct robust_list_head __user *, head, |
2843 | size_t, len) | |
0771dfef | 2844 | { |
a0c1e907 TG |
2845 | if (!futex_cmpxchg_enabled) |
2846 | return -ENOSYS; | |
0771dfef IM |
2847 | /* |
2848 | * The kernel knows only one size for now: | |
2849 | */ | |
2850 | if (unlikely(len != sizeof(*head))) | |
2851 | return -EINVAL; | |
2852 | ||
2853 | current->robust_list = head; | |
2854 | ||
2855 | return 0; | |
2856 | } | |
2857 | ||
2858 | /** | |
d96ee56c DH |
2859 | * sys_get_robust_list() - Get the robust-futex list head of a task |
2860 | * @pid: pid of the process [zero for current task] | |
2861 | * @head_ptr: pointer to a list-head pointer, the kernel fills it in | |
2862 | * @len_ptr: pointer to a length field, the kernel fills in the header size | |
0771dfef | 2863 | */ |
836f92ad HC |
2864 | SYSCALL_DEFINE3(get_robust_list, int, pid, |
2865 | struct robust_list_head __user * __user *, head_ptr, | |
2866 | size_t __user *, len_ptr) | |
0771dfef | 2867 | { |
ba46df98 | 2868 | struct robust_list_head __user *head; |
0771dfef | 2869 | unsigned long ret; |
bdbb776f | 2870 | struct task_struct *p; |
0771dfef | 2871 | |
a0c1e907 TG |
2872 | if (!futex_cmpxchg_enabled) |
2873 | return -ENOSYS; | |
2874 | ||
bdbb776f KC |
2875 | rcu_read_lock(); |
2876 | ||
2877 | ret = -ESRCH; | |
0771dfef | 2878 | if (!pid) |
bdbb776f | 2879 | p = current; |
0771dfef | 2880 | else { |
228ebcbe | 2881 | p = find_task_by_vpid(pid); |
0771dfef IM |
2882 | if (!p) |
2883 | goto err_unlock; | |
0771dfef IM |
2884 | } |
2885 | ||
bdbb776f | 2886 | ret = -EPERM; |
caaee623 | 2887 | if (!ptrace_may_access(p, PTRACE_MODE_READ_REALCREDS)) |
bdbb776f KC |
2888 | goto err_unlock; |
2889 | ||
2890 | head = p->robust_list; | |
2891 | rcu_read_unlock(); | |
2892 | ||
0771dfef IM |
2893 | if (put_user(sizeof(*head), len_ptr)) |
2894 | return -EFAULT; | |
2895 | return put_user(head, head_ptr); | |
2896 | ||
2897 | err_unlock: | |
aaa2a97e | 2898 | rcu_read_unlock(); |
0771dfef IM |
2899 | |
2900 | return ret; | |
2901 | } | |
2902 | ||
2903 | /* | |
2904 | * Process a futex-list entry, check whether it's owned by the | |
2905 | * dying task, and do notification if so: | |
2906 | */ | |
e3f2ddea | 2907 | int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi) |
0771dfef | 2908 | { |
7cfdaf38 | 2909 | u32 uval, uninitialized_var(nval), mval; |
0771dfef | 2910 | |
8f17d3a5 IM |
2911 | retry: |
2912 | if (get_user(uval, uaddr)) | |
0771dfef IM |
2913 | return -1; |
2914 | ||
b488893a | 2915 | if ((uval & FUTEX_TID_MASK) == task_pid_vnr(curr)) { |
0771dfef IM |
2916 | /* |
2917 | * Ok, this dying thread is truly holding a futex | |
2918 | * of interest. Set the OWNER_DIED bit atomically | |
2919 | * via cmpxchg, and if the value had FUTEX_WAITERS | |
2920 | * set, wake up a waiter (if any). (We have to do a | |
2921 | * futex_wake() even if OWNER_DIED is already set - | |
2922 | * to handle the rare but possible case of recursive | |
2923 | * thread-death.) The rest of the cleanup is done in | |
2924 | * userspace. | |
2925 | */ | |
e3f2ddea | 2926 | mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED; |
6e0aa9f8 TG |
2927 | /* |
2928 | * We are not holding a lock here, but we want to have | |
2929 | * the pagefault_disable/enable() protection because | |
2930 | * we want to handle the fault gracefully. If the | |
2931 | * access fails we try to fault in the futex with R/W | |
2932 | * verification via get_user_pages. get_user() above | |
2933 | * does not guarantee R/W access. If that fails we | |
2934 | * give up and leave the futex locked. | |
2935 | */ | |
2936 | if (cmpxchg_futex_value_locked(&nval, uaddr, uval, mval)) { | |
2937 | if (fault_in_user_writeable(uaddr)) | |
2938 | return -1; | |
2939 | goto retry; | |
2940 | } | |
c87e2837 | 2941 | if (nval != uval) |
8f17d3a5 | 2942 | goto retry; |
0771dfef | 2943 | |
e3f2ddea IM |
2944 | /* |
2945 | * Wake robust non-PI futexes here. The wakeup of | |
2946 | * PI futexes happens in exit_pi_state(): | |
2947 | */ | |
36cf3b5c | 2948 | if (!pi && (uval & FUTEX_WAITERS)) |
c2f9f201 | 2949 | futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY); |
0771dfef IM |
2950 | } |
2951 | return 0; | |
2952 | } | |
2953 | ||
e3f2ddea IM |
2954 | /* |
2955 | * Fetch a robust-list pointer. Bit 0 signals PI futexes: | |
2956 | */ | |
2957 | static inline int fetch_robust_entry(struct robust_list __user **entry, | |
ba46df98 | 2958 | struct robust_list __user * __user *head, |
1dcc41bb | 2959 | unsigned int *pi) |
e3f2ddea IM |
2960 | { |
2961 | unsigned long uentry; | |
2962 | ||
ba46df98 | 2963 | if (get_user(uentry, (unsigned long __user *)head)) |
e3f2ddea IM |
2964 | return -EFAULT; |
2965 | ||
ba46df98 | 2966 | *entry = (void __user *)(uentry & ~1UL); |
e3f2ddea IM |
2967 | *pi = uentry & 1; |
2968 | ||
2969 | return 0; | |
2970 | } | |
2971 | ||
0771dfef IM |
2972 | /* |
2973 | * Walk curr->robust_list (very carefully, it's a userspace list!) | |
2974 | * and mark any locks found there dead, and notify any waiters. | |
2975 | * | |
2976 | * We silently return on any sign of list-walking problem. | |
2977 | */ | |
2978 | void exit_robust_list(struct task_struct *curr) | |
2979 | { | |
2980 | struct robust_list_head __user *head = curr->robust_list; | |
9f96cb1e | 2981 | struct robust_list __user *entry, *next_entry, *pending; |
4c115e95 DH |
2982 | unsigned int limit = ROBUST_LIST_LIMIT, pi, pip; |
2983 | unsigned int uninitialized_var(next_pi); | |
0771dfef | 2984 | unsigned long futex_offset; |
9f96cb1e | 2985 | int rc; |
0771dfef | 2986 | |
a0c1e907 TG |
2987 | if (!futex_cmpxchg_enabled) |
2988 | return; | |
2989 | ||
0771dfef IM |
2990 | /* |
2991 | * Fetch the list head (which was registered earlier, via | |
2992 | * sys_set_robust_list()): | |
2993 | */ | |
e3f2ddea | 2994 | if (fetch_robust_entry(&entry, &head->list.next, &pi)) |
0771dfef IM |
2995 | return; |
2996 | /* | |
2997 | * Fetch the relative futex offset: | |
2998 | */ | |
2999 | if (get_user(futex_offset, &head->futex_offset)) | |
3000 | return; | |
3001 | /* | |
3002 | * Fetch any possibly pending lock-add first, and handle it | |
3003 | * if it exists: | |
3004 | */ | |
e3f2ddea | 3005 | if (fetch_robust_entry(&pending, &head->list_op_pending, &pip)) |
0771dfef | 3006 | return; |
e3f2ddea | 3007 | |
9f96cb1e | 3008 | next_entry = NULL; /* avoid warning with gcc */ |
0771dfef | 3009 | while (entry != &head->list) { |
9f96cb1e MS |
3010 | /* |
3011 | * Fetch the next entry in the list before calling | |
3012 | * handle_futex_death: | |
3013 | */ | |
3014 | rc = fetch_robust_entry(&next_entry, &entry->next, &next_pi); | |
0771dfef IM |
3015 | /* |
3016 | * A pending lock might already be on the list, so | |
c87e2837 | 3017 | * don't process it twice: |
0771dfef IM |
3018 | */ |
3019 | if (entry != pending) | |
ba46df98 | 3020 | if (handle_futex_death((void __user *)entry + futex_offset, |
e3f2ddea | 3021 | curr, pi)) |
0771dfef | 3022 | return; |
9f96cb1e | 3023 | if (rc) |
0771dfef | 3024 | return; |
9f96cb1e MS |
3025 | entry = next_entry; |
3026 | pi = next_pi; | |
0771dfef IM |
3027 | /* |
3028 | * Avoid excessively long or circular lists: | |
3029 | */ | |
3030 | if (!--limit) | |
3031 | break; | |
3032 | ||
3033 | cond_resched(); | |
3034 | } | |
9f96cb1e MS |
3035 | |
3036 | if (pending) | |
3037 | handle_futex_death((void __user *)pending + futex_offset, | |
3038 | curr, pip); | |
0771dfef IM |
3039 | } |
3040 | ||
c19384b5 | 3041 | long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout, |
e2970f2f | 3042 | u32 __user *uaddr2, u32 val2, u32 val3) |
1da177e4 | 3043 | { |
81b40539 | 3044 | int cmd = op & FUTEX_CMD_MASK; |
b41277dc | 3045 | unsigned int flags = 0; |
34f01cc1 ED |
3046 | |
3047 | if (!(op & FUTEX_PRIVATE_FLAG)) | |
b41277dc | 3048 | flags |= FLAGS_SHARED; |
1da177e4 | 3049 | |
b41277dc DH |
3050 | if (op & FUTEX_CLOCK_REALTIME) { |
3051 | flags |= FLAGS_CLOCKRT; | |
337f1304 DH |
3052 | if (cmd != FUTEX_WAIT && cmd != FUTEX_WAIT_BITSET && \ |
3053 | cmd != FUTEX_WAIT_REQUEUE_PI) | |
b41277dc DH |
3054 | return -ENOSYS; |
3055 | } | |
1da177e4 | 3056 | |
59263b51 TG |
3057 | switch (cmd) { |
3058 | case FUTEX_LOCK_PI: | |
3059 | case FUTEX_UNLOCK_PI: | |
3060 | case FUTEX_TRYLOCK_PI: | |
3061 | case FUTEX_WAIT_REQUEUE_PI: | |
3062 | case FUTEX_CMP_REQUEUE_PI: | |
3063 | if (!futex_cmpxchg_enabled) | |
3064 | return -ENOSYS; | |
3065 | } | |
3066 | ||
34f01cc1 | 3067 | switch (cmd) { |
1da177e4 | 3068 | case FUTEX_WAIT: |
cd689985 TG |
3069 | val3 = FUTEX_BITSET_MATCH_ANY; |
3070 | case FUTEX_WAIT_BITSET: | |
81b40539 | 3071 | return futex_wait(uaddr, flags, val, timeout, val3); |
1da177e4 | 3072 | case FUTEX_WAKE: |
cd689985 TG |
3073 | val3 = FUTEX_BITSET_MATCH_ANY; |
3074 | case FUTEX_WAKE_BITSET: | |
81b40539 | 3075 | return futex_wake(uaddr, flags, val, val3); |
1da177e4 | 3076 | case FUTEX_REQUEUE: |
81b40539 | 3077 | return futex_requeue(uaddr, flags, uaddr2, val, val2, NULL, 0); |
1da177e4 | 3078 | case FUTEX_CMP_REQUEUE: |
81b40539 | 3079 | return futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 0); |
4732efbe | 3080 | case FUTEX_WAKE_OP: |
81b40539 | 3081 | return futex_wake_op(uaddr, flags, uaddr2, val, val2, val3); |
c87e2837 | 3082 | case FUTEX_LOCK_PI: |
996636dd | 3083 | return futex_lock_pi(uaddr, flags, timeout, 0); |
c87e2837 | 3084 | case FUTEX_UNLOCK_PI: |
81b40539 | 3085 | return futex_unlock_pi(uaddr, flags); |
c87e2837 | 3086 | case FUTEX_TRYLOCK_PI: |
996636dd | 3087 | return futex_lock_pi(uaddr, flags, NULL, 1); |
52400ba9 DH |
3088 | case FUTEX_WAIT_REQUEUE_PI: |
3089 | val3 = FUTEX_BITSET_MATCH_ANY; | |
81b40539 TG |
3090 | return futex_wait_requeue_pi(uaddr, flags, val, timeout, val3, |
3091 | uaddr2); | |
52400ba9 | 3092 | case FUTEX_CMP_REQUEUE_PI: |
81b40539 | 3093 | return futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 1); |
1da177e4 | 3094 | } |
81b40539 | 3095 | return -ENOSYS; |
1da177e4 LT |
3096 | } |
3097 | ||
3098 | ||
17da2bd9 HC |
3099 | SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val, |
3100 | struct timespec __user *, utime, u32 __user *, uaddr2, | |
3101 | u32, val3) | |
1da177e4 | 3102 | { |
c19384b5 PP |
3103 | struct timespec ts; |
3104 | ktime_t t, *tp = NULL; | |
e2970f2f | 3105 | u32 val2 = 0; |
34f01cc1 | 3106 | int cmd = op & FUTEX_CMD_MASK; |
1da177e4 | 3107 | |
cd689985 | 3108 | if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI || |
52400ba9 DH |
3109 | cmd == FUTEX_WAIT_BITSET || |
3110 | cmd == FUTEX_WAIT_REQUEUE_PI)) { | |
ab51fbab DB |
3111 | if (unlikely(should_fail_futex(!(op & FUTEX_PRIVATE_FLAG)))) |
3112 | return -EFAULT; | |
c19384b5 | 3113 | if (copy_from_user(&ts, utime, sizeof(ts)) != 0) |
1da177e4 | 3114 | return -EFAULT; |
c19384b5 | 3115 | if (!timespec_valid(&ts)) |
9741ef96 | 3116 | return -EINVAL; |
c19384b5 PP |
3117 | |
3118 | t = timespec_to_ktime(ts); | |
34f01cc1 | 3119 | if (cmd == FUTEX_WAIT) |
5a7780e7 | 3120 | t = ktime_add_safe(ktime_get(), t); |
c19384b5 | 3121 | tp = &t; |
1da177e4 LT |
3122 | } |
3123 | /* | |
52400ba9 | 3124 | * requeue parameter in 'utime' if cmd == FUTEX_*_REQUEUE_*. |
f54f0986 | 3125 | * number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP. |
1da177e4 | 3126 | */ |
f54f0986 | 3127 | if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE || |
ba9c22f2 | 3128 | cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP) |
e2970f2f | 3129 | val2 = (u32) (unsigned long) utime; |
1da177e4 | 3130 | |
c19384b5 | 3131 | return do_futex(uaddr, op, val, tp, uaddr2, val2, val3); |
1da177e4 LT |
3132 | } |
3133 | ||
03b8c7b6 | 3134 | static void __init futex_detect_cmpxchg(void) |
1da177e4 | 3135 | { |
03b8c7b6 | 3136 | #ifndef CONFIG_HAVE_FUTEX_CMPXCHG |
a0c1e907 | 3137 | u32 curval; |
03b8c7b6 HC |
3138 | |
3139 | /* | |
3140 | * This will fail and we want it. Some arch implementations do | |
3141 | * runtime detection of the futex_atomic_cmpxchg_inatomic() | |
3142 | * functionality. We want to know that before we call in any | |
3143 | * of the complex code paths. Also we want to prevent | |
3144 | * registration of robust lists in that case. NULL is | |
3145 | * guaranteed to fault and we get -EFAULT on functional | |
3146 | * implementation, the non-functional ones will return | |
3147 | * -ENOSYS. | |
3148 | */ | |
3149 | if (cmpxchg_futex_value_locked(&curval, NULL, 0, 0) == -EFAULT) | |
3150 | futex_cmpxchg_enabled = 1; | |
3151 | #endif | |
3152 | } | |
3153 | ||
3154 | static int __init futex_init(void) | |
3155 | { | |
63b1a816 | 3156 | unsigned int futex_shift; |
a52b89eb DB |
3157 | unsigned long i; |
3158 | ||
3159 | #if CONFIG_BASE_SMALL | |
3160 | futex_hashsize = 16; | |
3161 | #else | |
3162 | futex_hashsize = roundup_pow_of_two(256 * num_possible_cpus()); | |
3163 | #endif | |
3164 | ||
3165 | futex_queues = alloc_large_system_hash("futex", sizeof(*futex_queues), | |
3166 | futex_hashsize, 0, | |
3167 | futex_hashsize < 256 ? HASH_SMALL : 0, | |
63b1a816 HC |
3168 | &futex_shift, NULL, |
3169 | futex_hashsize, futex_hashsize); | |
3170 | futex_hashsize = 1UL << futex_shift; | |
03b8c7b6 HC |
3171 | |
3172 | futex_detect_cmpxchg(); | |
a0c1e907 | 3173 | |
a52b89eb | 3174 | for (i = 0; i < futex_hashsize; i++) { |
11d4616b | 3175 | atomic_set(&futex_queues[i].waiters, 0); |
732375c6 | 3176 | plist_head_init(&futex_queues[i].chain); |
3e4ab747 TG |
3177 | spin_lock_init(&futex_queues[i].lock); |
3178 | } | |
3179 | ||
1da177e4 LT |
3180 | return 0; |
3181 | } | |
f6d107fb | 3182 | __initcall(futex_init); |