| 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 | * |
| 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 | * |
| 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 | * |
| 19 | * PRIVATE futexes by Eric Dumazet |
| 20 | * Copyright (C) 2007 Eric Dumazet <dada1@cosmosbay.com> |
| 21 | * |
| 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 | * |
| 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> |
| 57 | #include <linux/signal.h> |
| 58 | #include <linux/export.h> |
| 59 | #include <linux/magic.h> |
| 60 | #include <linux/pid.h> |
| 61 | #include <linux/nsproxy.h> |
| 62 | #include <linux/ptrace.h> |
| 63 | #include <linux/sched/rt.h> |
| 64 | #include <linux/hugetlb.h> |
| 65 | #include <linux/freezer.h> |
| 66 | |
| 67 | #include <asm/futex.h> |
| 68 | |
| 69 | #include "rtmutex_common.h" |
| 70 | |
| 71 | #ifndef CONFIG_HAVE_FUTEX_CMPXCHG |
| 72 | int __read_mostly futex_cmpxchg_enabled; |
| 73 | #endif |
| 74 | |
| 75 | #define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8) |
| 76 | |
| 77 | /* |
| 78 | * Futex flags used to encode options to functions and preserve them across |
| 79 | * restarts. |
| 80 | */ |
| 81 | #define FLAGS_SHARED 0x01 |
| 82 | #define FLAGS_CLOCKRT 0x02 |
| 83 | #define FLAGS_HAS_TIMEOUT 0x04 |
| 84 | |
| 85 | /* |
| 86 | * Priority Inheritance state: |
| 87 | */ |
| 88 | struct futex_pi_state { |
| 89 | /* |
| 90 | * list of 'owned' pi_state instances - these have to be |
| 91 | * cleaned up in do_exit() if the task exits prematurely: |
| 92 | */ |
| 93 | struct list_head list; |
| 94 | |
| 95 | /* |
| 96 | * The PI object: |
| 97 | */ |
| 98 | struct rt_mutex pi_mutex; |
| 99 | |
| 100 | struct task_struct *owner; |
| 101 | atomic_t refcount; |
| 102 | |
| 103 | union futex_key key; |
| 104 | }; |
| 105 | |
| 106 | /** |
| 107 | * struct futex_q - The hashed futex queue entry, one per waiting task |
| 108 | * @list: priority-sorted list of tasks waiting on this futex |
| 109 | * @task: the task waiting on the futex |
| 110 | * @lock_ptr: the hash bucket lock |
| 111 | * @key: the key the futex is hashed on |
| 112 | * @pi_state: optional priority inheritance state |
| 113 | * @rt_waiter: rt_waiter storage for use with requeue_pi |
| 114 | * @requeue_pi_key: the requeue_pi target futex key |
| 115 | * @bitset: bitset for the optional bitmasked wakeup |
| 116 | * |
| 117 | * We use this hashed waitqueue, instead of a normal wait_queue_t, so |
| 118 | * we can wake only the relevant ones (hashed queues may be shared). |
| 119 | * |
| 120 | * A futex_q has a woken state, just like tasks have TASK_RUNNING. |
| 121 | * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0. |
| 122 | * The order of wakeup is always to make the first condition true, then |
| 123 | * the second. |
| 124 | * |
| 125 | * PI futexes are typically woken before they are removed from the hash list via |
| 126 | * the rt_mutex code. See unqueue_me_pi(). |
| 127 | */ |
| 128 | struct futex_q { |
| 129 | struct plist_node list; |
| 130 | |
| 131 | struct task_struct *task; |
| 132 | spinlock_t *lock_ptr; |
| 133 | union futex_key key; |
| 134 | struct futex_pi_state *pi_state; |
| 135 | struct rt_mutex_waiter *rt_waiter; |
| 136 | union futex_key *requeue_pi_key; |
| 137 | u32 bitset; |
| 138 | }; |
| 139 | |
| 140 | static const struct futex_q futex_q_init = { |
| 141 | /* list gets initialized in queue_me()*/ |
| 142 | .key = FUTEX_KEY_INIT, |
| 143 | .bitset = FUTEX_BITSET_MATCH_ANY |
| 144 | }; |
| 145 | |
| 146 | /* |
| 147 | * Hash buckets are shared by all the futex_keys that hash to the same |
| 148 | * location. Each key may have multiple futex_q structures, one for each task |
| 149 | * waiting on a futex. |
| 150 | */ |
| 151 | struct futex_hash_bucket { |
| 152 | spinlock_t lock; |
| 153 | struct plist_head chain; |
| 154 | }; |
| 155 | |
| 156 | static struct futex_hash_bucket futex_queues[1<<FUTEX_HASHBITS]; |
| 157 | |
| 158 | /* |
| 159 | * We hash on the keys returned from get_futex_key (see below). |
| 160 | */ |
| 161 | static struct futex_hash_bucket *hash_futex(union futex_key *key) |
| 162 | { |
| 163 | u32 hash = jhash2((u32*)&key->both.word, |
| 164 | (sizeof(key->both.word)+sizeof(key->both.ptr))/4, |
| 165 | key->both.offset); |
| 166 | return &futex_queues[hash & ((1 << FUTEX_HASHBITS)-1)]; |
| 167 | } |
| 168 | |
| 169 | /* |
| 170 | * Return 1 if two futex_keys are equal, 0 otherwise. |
| 171 | */ |
| 172 | static inline int match_futex(union futex_key *key1, union futex_key *key2) |
| 173 | { |
| 174 | return (key1 && key2 |
| 175 | && key1->both.word == key2->both.word |
| 176 | && key1->both.ptr == key2->both.ptr |
| 177 | && key1->both.offset == key2->both.offset); |
| 178 | } |
| 179 | |
| 180 | /* |
| 181 | * Take a reference to the resource addressed by a key. |
| 182 | * Can be called while holding spinlocks. |
| 183 | * |
| 184 | */ |
| 185 | static void get_futex_key_refs(union futex_key *key) |
| 186 | { |
| 187 | if (!key->both.ptr) |
| 188 | return; |
| 189 | |
| 190 | switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { |
| 191 | case FUT_OFF_INODE: |
| 192 | ihold(key->shared.inode); |
| 193 | break; |
| 194 | case FUT_OFF_MMSHARED: |
| 195 | atomic_inc(&key->private.mm->mm_count); |
| 196 | break; |
| 197 | } |
| 198 | } |
| 199 | |
| 200 | /* |
| 201 | * Drop a reference to the resource addressed by a key. |
| 202 | * The hash bucket spinlock must not be held. |
| 203 | */ |
| 204 | static void drop_futex_key_refs(union futex_key *key) |
| 205 | { |
| 206 | if (!key->both.ptr) { |
| 207 | /* If we're here then we tried to put a key we failed to get */ |
| 208 | WARN_ON_ONCE(1); |
| 209 | return; |
| 210 | } |
| 211 | |
| 212 | switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { |
| 213 | case FUT_OFF_INODE: |
| 214 | iput(key->shared.inode); |
| 215 | break; |
| 216 | case FUT_OFF_MMSHARED: |
| 217 | mmdrop(key->private.mm); |
| 218 | break; |
| 219 | } |
| 220 | } |
| 221 | |
| 222 | /** |
| 223 | * get_futex_key() - Get parameters which are the keys for a futex |
| 224 | * @uaddr: virtual address of the futex |
| 225 | * @fshared: 0 for a PROCESS_PRIVATE futex, 1 for PROCESS_SHARED |
| 226 | * @key: address where result is stored. |
| 227 | * @rw: mapping needs to be read/write (values: VERIFY_READ, |
| 228 | * VERIFY_WRITE) |
| 229 | * |
| 230 | * Return: a negative error code or 0 |
| 231 | * |
| 232 | * The key words are stored in *key on success. |
| 233 | * |
| 234 | * For shared mappings, it's (page->index, file_inode(vma->vm_file), |
| 235 | * offset_within_page). For private mappings, it's (uaddr, current->mm). |
| 236 | * We can usually work out the index without swapping in the page. |
| 237 | * |
| 238 | * lock_page() might sleep, the caller should not hold a spinlock. |
| 239 | */ |
| 240 | static int |
| 241 | get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key, int rw) |
| 242 | { |
| 243 | unsigned long address = (unsigned long)uaddr; |
| 244 | struct mm_struct *mm = current->mm; |
| 245 | struct page *page, *page_head; |
| 246 | int err, ro = 0; |
| 247 | |
| 248 | /* |
| 249 | * The futex address must be "naturally" aligned. |
| 250 | */ |
| 251 | key->both.offset = address % PAGE_SIZE; |
| 252 | if (unlikely((address % sizeof(u32)) != 0)) |
| 253 | return -EINVAL; |
| 254 | address -= key->both.offset; |
| 255 | |
| 256 | /* |
| 257 | * PROCESS_PRIVATE futexes are fast. |
| 258 | * As the mm cannot disappear under us and the 'key' only needs |
| 259 | * virtual address, we dont even have to find the underlying vma. |
| 260 | * Note : We do have to check 'uaddr' is a valid user address, |
| 261 | * but access_ok() should be faster than find_vma() |
| 262 | */ |
| 263 | if (!fshared) { |
| 264 | if (unlikely(!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))) |
| 265 | return -EFAULT; |
| 266 | key->private.mm = mm; |
| 267 | key->private.address = address; |
| 268 | get_futex_key_refs(key); |
| 269 | return 0; |
| 270 | } |
| 271 | |
| 272 | again: |
| 273 | err = get_user_pages_fast(address, 1, 1, &page); |
| 274 | /* |
| 275 | * If write access is not required (eg. FUTEX_WAIT), try |
| 276 | * and get read-only access. |
| 277 | */ |
| 278 | if (err == -EFAULT && rw == VERIFY_READ) { |
| 279 | err = get_user_pages_fast(address, 1, 0, &page); |
| 280 | ro = 1; |
| 281 | } |
| 282 | if (err < 0) |
| 283 | return err; |
| 284 | else |
| 285 | err = 0; |
| 286 | |
| 287 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE |
| 288 | page_head = page; |
| 289 | if (unlikely(PageTail(page))) { |
| 290 | put_page(page); |
| 291 | /* serialize against __split_huge_page_splitting() */ |
| 292 | local_irq_disable(); |
| 293 | if (likely(__get_user_pages_fast(address, 1, !ro, &page) == 1)) { |
| 294 | page_head = compound_head(page); |
| 295 | /* |
| 296 | * page_head is valid pointer but we must pin |
| 297 | * it before taking the PG_lock and/or |
| 298 | * PG_compound_lock. The moment we re-enable |
| 299 | * irqs __split_huge_page_splitting() can |
| 300 | * return and the head page can be freed from |
| 301 | * under us. We can't take the PG_lock and/or |
| 302 | * PG_compound_lock on a page that could be |
| 303 | * freed from under us. |
| 304 | */ |
| 305 | if (page != page_head) { |
| 306 | get_page(page_head); |
| 307 | put_page(page); |
| 308 | } |
| 309 | local_irq_enable(); |
| 310 | } else { |
| 311 | local_irq_enable(); |
| 312 | goto again; |
| 313 | } |
| 314 | } |
| 315 | #else |
| 316 | page_head = compound_head(page); |
| 317 | if (page != page_head) { |
| 318 | get_page(page_head); |
| 319 | put_page(page); |
| 320 | } |
| 321 | #endif |
| 322 | |
| 323 | lock_page(page_head); |
| 324 | |
| 325 | /* |
| 326 | * If page_head->mapping is NULL, then it cannot be a PageAnon |
| 327 | * page; but it might be the ZERO_PAGE or in the gate area or |
| 328 | * in a special mapping (all cases which we are happy to fail); |
| 329 | * or it may have been a good file page when get_user_pages_fast |
| 330 | * found it, but truncated or holepunched or subjected to |
| 331 | * invalidate_complete_page2 before we got the page lock (also |
| 332 | * cases which we are happy to fail). And we hold a reference, |
| 333 | * so refcount care in invalidate_complete_page's remove_mapping |
| 334 | * prevents drop_caches from setting mapping to NULL beneath us. |
| 335 | * |
| 336 | * The case we do have to guard against is when memory pressure made |
| 337 | * shmem_writepage move it from filecache to swapcache beneath us: |
| 338 | * an unlikely race, but we do need to retry for page_head->mapping. |
| 339 | */ |
| 340 | if (!page_head->mapping) { |
| 341 | int shmem_swizzled = PageSwapCache(page_head); |
| 342 | unlock_page(page_head); |
| 343 | put_page(page_head); |
| 344 | if (shmem_swizzled) |
| 345 | goto again; |
| 346 | return -EFAULT; |
| 347 | } |
| 348 | |
| 349 | /* |
| 350 | * Private mappings are handled in a simple way. |
| 351 | * |
| 352 | * NOTE: When userspace waits on a MAP_SHARED mapping, even if |
| 353 | * it's a read-only handle, it's expected that futexes attach to |
| 354 | * the object not the particular process. |
| 355 | */ |
| 356 | if (PageAnon(page_head)) { |
| 357 | /* |
| 358 | * A RO anonymous page will never change and thus doesn't make |
| 359 | * sense for futex operations. |
| 360 | */ |
| 361 | if (ro) { |
| 362 | err = -EFAULT; |
| 363 | goto out; |
| 364 | } |
| 365 | |
| 366 | key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */ |
| 367 | key->private.mm = mm; |
| 368 | key->private.address = address; |
| 369 | } else { |
| 370 | key->both.offset |= FUT_OFF_INODE; /* inode-based key */ |
| 371 | key->shared.inode = page_head->mapping->host; |
| 372 | key->shared.pgoff = basepage_index(page); |
| 373 | } |
| 374 | |
| 375 | get_futex_key_refs(key); |
| 376 | |
| 377 | out: |
| 378 | unlock_page(page_head); |
| 379 | put_page(page_head); |
| 380 | return err; |
| 381 | } |
| 382 | |
| 383 | static inline void put_futex_key(union futex_key *key) |
| 384 | { |
| 385 | drop_futex_key_refs(key); |
| 386 | } |
| 387 | |
| 388 | /** |
| 389 | * fault_in_user_writeable() - Fault in user address and verify RW access |
| 390 | * @uaddr: pointer to faulting user space address |
| 391 | * |
| 392 | * Slow path to fixup the fault we just took in the atomic write |
| 393 | * access to @uaddr. |
| 394 | * |
| 395 | * We have no generic implementation of a non-destructive write to the |
| 396 | * user address. We know that we faulted in the atomic pagefault |
| 397 | * disabled section so we can as well avoid the #PF overhead by |
| 398 | * calling get_user_pages() right away. |
| 399 | */ |
| 400 | static int fault_in_user_writeable(u32 __user *uaddr) |
| 401 | { |
| 402 | struct mm_struct *mm = current->mm; |
| 403 | int ret; |
| 404 | |
| 405 | down_read(&mm->mmap_sem); |
| 406 | ret = fixup_user_fault(current, mm, (unsigned long)uaddr, |
| 407 | FAULT_FLAG_WRITE); |
| 408 | up_read(&mm->mmap_sem); |
| 409 | |
| 410 | return ret < 0 ? ret : 0; |
| 411 | } |
| 412 | |
| 413 | /** |
| 414 | * futex_top_waiter() - Return the highest priority waiter on a futex |
| 415 | * @hb: the hash bucket the futex_q's reside in |
| 416 | * @key: the futex key (to distinguish it from other futex futex_q's) |
| 417 | * |
| 418 | * Must be called with the hb lock held. |
| 419 | */ |
| 420 | static struct futex_q *futex_top_waiter(struct futex_hash_bucket *hb, |
| 421 | union futex_key *key) |
| 422 | { |
| 423 | struct futex_q *this; |
| 424 | |
| 425 | plist_for_each_entry(this, &hb->chain, list) { |
| 426 | if (match_futex(&this->key, key)) |
| 427 | return this; |
| 428 | } |
| 429 | return NULL; |
| 430 | } |
| 431 | |
| 432 | static int cmpxchg_futex_value_locked(u32 *curval, u32 __user *uaddr, |
| 433 | u32 uval, u32 newval) |
| 434 | { |
| 435 | int ret; |
| 436 | |
| 437 | pagefault_disable(); |
| 438 | ret = futex_atomic_cmpxchg_inatomic(curval, uaddr, uval, newval); |
| 439 | pagefault_enable(); |
| 440 | |
| 441 | return ret; |
| 442 | } |
| 443 | |
| 444 | static int get_futex_value_locked(u32 *dest, u32 __user *from) |
| 445 | { |
| 446 | int ret; |
| 447 | |
| 448 | pagefault_disable(); |
| 449 | ret = __copy_from_user_inatomic(dest, from, sizeof(u32)); |
| 450 | pagefault_enable(); |
| 451 | |
| 452 | return ret ? -EFAULT : 0; |
| 453 | } |
| 454 | |
| 455 | |
| 456 | /* |
| 457 | * PI code: |
| 458 | */ |
| 459 | static int refill_pi_state_cache(void) |
| 460 | { |
| 461 | struct futex_pi_state *pi_state; |
| 462 | |
| 463 | if (likely(current->pi_state_cache)) |
| 464 | return 0; |
| 465 | |
| 466 | pi_state = kzalloc(sizeof(*pi_state), GFP_KERNEL); |
| 467 | |
| 468 | if (!pi_state) |
| 469 | return -ENOMEM; |
| 470 | |
| 471 | INIT_LIST_HEAD(&pi_state->list); |
| 472 | /* pi_mutex gets initialized later */ |
| 473 | pi_state->owner = NULL; |
| 474 | atomic_set(&pi_state->refcount, 1); |
| 475 | pi_state->key = FUTEX_KEY_INIT; |
| 476 | |
| 477 | current->pi_state_cache = pi_state; |
| 478 | |
| 479 | return 0; |
| 480 | } |
| 481 | |
| 482 | static struct futex_pi_state * alloc_pi_state(void) |
| 483 | { |
| 484 | struct futex_pi_state *pi_state = current->pi_state_cache; |
| 485 | |
| 486 | WARN_ON(!pi_state); |
| 487 | current->pi_state_cache = NULL; |
| 488 | |
| 489 | return pi_state; |
| 490 | } |
| 491 | |
| 492 | static void free_pi_state(struct futex_pi_state *pi_state) |
| 493 | { |
| 494 | if (!atomic_dec_and_test(&pi_state->refcount)) |
| 495 | return; |
| 496 | |
| 497 | /* |
| 498 | * If pi_state->owner is NULL, the owner is most probably dying |
| 499 | * and has cleaned up the pi_state already |
| 500 | */ |
| 501 | if (pi_state->owner) { |
| 502 | raw_spin_lock_irq(&pi_state->owner->pi_lock); |
| 503 | list_del_init(&pi_state->list); |
| 504 | raw_spin_unlock_irq(&pi_state->owner->pi_lock); |
| 505 | |
| 506 | rt_mutex_proxy_unlock(&pi_state->pi_mutex, pi_state->owner); |
| 507 | } |
| 508 | |
| 509 | if (current->pi_state_cache) |
| 510 | kfree(pi_state); |
| 511 | else { |
| 512 | /* |
| 513 | * pi_state->list is already empty. |
| 514 | * clear pi_state->owner. |
| 515 | * refcount is at 0 - put it back to 1. |
| 516 | */ |
| 517 | pi_state->owner = NULL; |
| 518 | atomic_set(&pi_state->refcount, 1); |
| 519 | current->pi_state_cache = pi_state; |
| 520 | } |
| 521 | } |
| 522 | |
| 523 | /* |
| 524 | * Look up the task based on what TID userspace gave us. |
| 525 | * We dont trust it. |
| 526 | */ |
| 527 | static struct task_struct * futex_find_get_task(pid_t pid) |
| 528 | { |
| 529 | struct task_struct *p; |
| 530 | |
| 531 | rcu_read_lock(); |
| 532 | p = find_task_by_vpid(pid); |
| 533 | if (p) |
| 534 | get_task_struct(p); |
| 535 | |
| 536 | rcu_read_unlock(); |
| 537 | |
| 538 | return p; |
| 539 | } |
| 540 | |
| 541 | /* |
| 542 | * This task is holding PI mutexes at exit time => bad. |
| 543 | * Kernel cleans up PI-state, but userspace is likely hosed. |
| 544 | * (Robust-futex cleanup is separate and might save the day for userspace.) |
| 545 | */ |
| 546 | void exit_pi_state_list(struct task_struct *curr) |
| 547 | { |
| 548 | struct list_head *next, *head = &curr->pi_state_list; |
| 549 | struct futex_pi_state *pi_state; |
| 550 | struct futex_hash_bucket *hb; |
| 551 | union futex_key key = FUTEX_KEY_INIT; |
| 552 | |
| 553 | if (!futex_cmpxchg_enabled) |
| 554 | return; |
| 555 | /* |
| 556 | * We are a ZOMBIE and nobody can enqueue itself on |
| 557 | * pi_state_list anymore, but we have to be careful |
| 558 | * versus waiters unqueueing themselves: |
| 559 | */ |
| 560 | raw_spin_lock_irq(&curr->pi_lock); |
| 561 | while (!list_empty(head)) { |
| 562 | |
| 563 | next = head->next; |
| 564 | pi_state = list_entry(next, struct futex_pi_state, list); |
| 565 | key = pi_state->key; |
| 566 | hb = hash_futex(&key); |
| 567 | raw_spin_unlock_irq(&curr->pi_lock); |
| 568 | |
| 569 | spin_lock(&hb->lock); |
| 570 | |
| 571 | raw_spin_lock_irq(&curr->pi_lock); |
| 572 | /* |
| 573 | * We dropped the pi-lock, so re-check whether this |
| 574 | * task still owns the PI-state: |
| 575 | */ |
| 576 | if (head->next != next) { |
| 577 | spin_unlock(&hb->lock); |
| 578 | continue; |
| 579 | } |
| 580 | |
| 581 | WARN_ON(pi_state->owner != curr); |
| 582 | WARN_ON(list_empty(&pi_state->list)); |
| 583 | list_del_init(&pi_state->list); |
| 584 | pi_state->owner = NULL; |
| 585 | raw_spin_unlock_irq(&curr->pi_lock); |
| 586 | |
| 587 | rt_mutex_unlock(&pi_state->pi_mutex); |
| 588 | |
| 589 | spin_unlock(&hb->lock); |
| 590 | |
| 591 | raw_spin_lock_irq(&curr->pi_lock); |
| 592 | } |
| 593 | raw_spin_unlock_irq(&curr->pi_lock); |
| 594 | } |
| 595 | |
| 596 | /* |
| 597 | * We need to check the following states: |
| 598 | * |
| 599 | * Waiter | pi_state | pi->owner | uTID | uODIED | ? |
| 600 | * |
| 601 | * [1] NULL | --- | --- | 0 | 0/1 | Valid |
| 602 | * [2] NULL | --- | --- | >0 | 0/1 | Valid |
| 603 | * |
| 604 | * [3] Found | NULL | -- | Any | 0/1 | Invalid |
| 605 | * |
| 606 | * [4] Found | Found | NULL | 0 | 1 | Valid |
| 607 | * [5] Found | Found | NULL | >0 | 1 | Invalid |
| 608 | * |
| 609 | * [6] Found | Found | task | 0 | 1 | Valid |
| 610 | * |
| 611 | * [7] Found | Found | NULL | Any | 0 | Invalid |
| 612 | * |
| 613 | * [8] Found | Found | task | ==taskTID | 0/1 | Valid |
| 614 | * [9] Found | Found | task | 0 | 0 | Invalid |
| 615 | * [10] Found | Found | task | !=taskTID | 0/1 | Invalid |
| 616 | * |
| 617 | * [1] Indicates that the kernel can acquire the futex atomically. We |
| 618 | * came came here due to a stale FUTEX_WAITERS/FUTEX_OWNER_DIED bit. |
| 619 | * |
| 620 | * [2] Valid, if TID does not belong to a kernel thread. If no matching |
| 621 | * thread is found then it indicates that the owner TID has died. |
| 622 | * |
| 623 | * [3] Invalid. The waiter is queued on a non PI futex |
| 624 | * |
| 625 | * [4] Valid state after exit_robust_list(), which sets the user space |
| 626 | * value to FUTEX_WAITERS | FUTEX_OWNER_DIED. |
| 627 | * |
| 628 | * [5] The user space value got manipulated between exit_robust_list() |
| 629 | * and exit_pi_state_list() |
| 630 | * |
| 631 | * [6] Valid state after exit_pi_state_list() which sets the new owner in |
| 632 | * the pi_state but cannot access the user space value. |
| 633 | * |
| 634 | * [7] pi_state->owner can only be NULL when the OWNER_DIED bit is set. |
| 635 | * |
| 636 | * [8] Owner and user space value match |
| 637 | * |
| 638 | * [9] There is no transient state which sets the user space TID to 0 |
| 639 | * except exit_robust_list(), but this is indicated by the |
| 640 | * FUTEX_OWNER_DIED bit. See [4] |
| 641 | * |
| 642 | * [10] There is no transient state which leaves owner and user space |
| 643 | * TID out of sync. |
| 644 | */ |
| 645 | static int |
| 646 | lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, |
| 647 | union futex_key *key, struct futex_pi_state **ps) |
| 648 | { |
| 649 | struct futex_pi_state *pi_state = NULL; |
| 650 | struct futex_q *this, *next; |
| 651 | struct plist_head *head; |
| 652 | struct task_struct *p; |
| 653 | pid_t pid = uval & FUTEX_TID_MASK; |
| 654 | |
| 655 | head = &hb->chain; |
| 656 | |
| 657 | plist_for_each_entry_safe(this, next, head, list) { |
| 658 | if (match_futex(&this->key, key)) { |
| 659 | /* |
| 660 | * Sanity check the waiter before increasing |
| 661 | * the refcount and attaching to it. |
| 662 | */ |
| 663 | pi_state = this->pi_state; |
| 664 | /* |
| 665 | * Userspace might have messed up non-PI and |
| 666 | * PI futexes [3] |
| 667 | */ |
| 668 | if (unlikely(!pi_state)) |
| 669 | return -EINVAL; |
| 670 | |
| 671 | WARN_ON(!atomic_read(&pi_state->refcount)); |
| 672 | |
| 673 | /* |
| 674 | * Handle the owner died case: |
| 675 | */ |
| 676 | if (uval & FUTEX_OWNER_DIED) { |
| 677 | /* |
| 678 | * exit_pi_state_list sets owner to NULL and |
| 679 | * wakes the topmost waiter. The task which |
| 680 | * acquires the pi_state->rt_mutex will fixup |
| 681 | * owner. |
| 682 | */ |
| 683 | if (!pi_state->owner) { |
| 684 | /* |
| 685 | * No pi state owner, but the user |
| 686 | * space TID is not 0. Inconsistent |
| 687 | * state. [5] |
| 688 | */ |
| 689 | if (pid) |
| 690 | return -EINVAL; |
| 691 | /* |
| 692 | * Take a ref on the state and |
| 693 | * return. [4] |
| 694 | */ |
| 695 | goto out_state; |
| 696 | } |
| 697 | |
| 698 | /* |
| 699 | * If TID is 0, then either the dying owner |
| 700 | * has not yet executed exit_pi_state_list() |
| 701 | * or some waiter acquired the rtmutex in the |
| 702 | * pi state, but did not yet fixup the TID in |
| 703 | * user space. |
| 704 | * |
| 705 | * Take a ref on the state and return. [6] |
| 706 | */ |
| 707 | if (!pid) |
| 708 | goto out_state; |
| 709 | } else { |
| 710 | /* |
| 711 | * If the owner died bit is not set, |
| 712 | * then the pi_state must have an |
| 713 | * owner. [7] |
| 714 | */ |
| 715 | if (!pi_state->owner) |
| 716 | return -EINVAL; |
| 717 | } |
| 718 | |
| 719 | /* |
| 720 | * Bail out if user space manipulated the |
| 721 | * futex value. If pi state exists then the |
| 722 | * owner TID must be the same as the user |
| 723 | * space TID. [9/10] |
| 724 | */ |
| 725 | if (pid != task_pid_vnr(pi_state->owner)) |
| 726 | return -EINVAL; |
| 727 | |
| 728 | out_state: |
| 729 | atomic_inc(&pi_state->refcount); |
| 730 | *ps = pi_state; |
| 731 | return 0; |
| 732 | } |
| 733 | } |
| 734 | |
| 735 | /* |
| 736 | * We are the first waiter - try to look up the real owner and attach |
| 737 | * the new pi_state to it, but bail out when TID = 0 [1] |
| 738 | */ |
| 739 | if (!pid) |
| 740 | return -ESRCH; |
| 741 | p = futex_find_get_task(pid); |
| 742 | if (!p) |
| 743 | return -ESRCH; |
| 744 | |
| 745 | if (!p->mm) { |
| 746 | put_task_struct(p); |
| 747 | return -EPERM; |
| 748 | } |
| 749 | |
| 750 | /* |
| 751 | * We need to look at the task state flags to figure out, |
| 752 | * whether the task is exiting. To protect against the do_exit |
| 753 | * change of the task flags, we do this protected by |
| 754 | * p->pi_lock: |
| 755 | */ |
| 756 | raw_spin_lock_irq(&p->pi_lock); |
| 757 | if (unlikely(p->flags & PF_EXITING)) { |
| 758 | /* |
| 759 | * The task is on the way out. When PF_EXITPIDONE is |
| 760 | * set, we know that the task has finished the |
| 761 | * cleanup: |
| 762 | */ |
| 763 | int ret = (p->flags & PF_EXITPIDONE) ? -ESRCH : -EAGAIN; |
| 764 | |
| 765 | raw_spin_unlock_irq(&p->pi_lock); |
| 766 | put_task_struct(p); |
| 767 | return ret; |
| 768 | } |
| 769 | |
| 770 | /* |
| 771 | * No existing pi state. First waiter. [2] |
| 772 | */ |
| 773 | pi_state = alloc_pi_state(); |
| 774 | |
| 775 | /* |
| 776 | * Initialize the pi_mutex in locked state and make 'p' |
| 777 | * the owner of it: |
| 778 | */ |
| 779 | rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p); |
| 780 | |
| 781 | /* Store the key for possible exit cleanups: */ |
| 782 | pi_state->key = *key; |
| 783 | |
| 784 | WARN_ON(!list_empty(&pi_state->list)); |
| 785 | list_add(&pi_state->list, &p->pi_state_list); |
| 786 | pi_state->owner = p; |
| 787 | raw_spin_unlock_irq(&p->pi_lock); |
| 788 | |
| 789 | put_task_struct(p); |
| 790 | |
| 791 | *ps = pi_state; |
| 792 | |
| 793 | return 0; |
| 794 | } |
| 795 | |
| 796 | /** |
| 797 | * futex_lock_pi_atomic() - Atomic work required to acquire a pi aware futex |
| 798 | * @uaddr: the pi futex user address |
| 799 | * @hb: the pi futex hash bucket |
| 800 | * @key: the futex key associated with uaddr and hb |
| 801 | * @ps: the pi_state pointer where we store the result of the |
| 802 | * lookup |
| 803 | * @task: the task to perform the atomic lock work for. This will |
| 804 | * be "current" except in the case of requeue pi. |
| 805 | * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0) |
| 806 | * |
| 807 | * Return: |
| 808 | * 0 - ready to wait; |
| 809 | * 1 - acquired the lock; |
| 810 | * <0 - error |
| 811 | * |
| 812 | * The hb->lock and futex_key refs shall be held by the caller. |
| 813 | */ |
| 814 | static int futex_lock_pi_atomic(u32 __user *uaddr, struct futex_hash_bucket *hb, |
| 815 | union futex_key *key, |
| 816 | struct futex_pi_state **ps, |
| 817 | struct task_struct *task, int set_waiters) |
| 818 | { |
| 819 | int lock_taken, ret, force_take = 0; |
| 820 | u32 uval, newval, curval, vpid = task_pid_vnr(task); |
| 821 | |
| 822 | retry: |
| 823 | ret = lock_taken = 0; |
| 824 | |
| 825 | /* |
| 826 | * To avoid races, we attempt to take the lock here again |
| 827 | * (by doing a 0 -> TID atomic cmpxchg), while holding all |
| 828 | * the locks. It will most likely not succeed. |
| 829 | */ |
| 830 | newval = vpid; |
| 831 | if (set_waiters) |
| 832 | newval |= FUTEX_WAITERS; |
| 833 | |
| 834 | if (unlikely(cmpxchg_futex_value_locked(&curval, uaddr, 0, newval))) |
| 835 | return -EFAULT; |
| 836 | |
| 837 | /* |
| 838 | * Detect deadlocks. |
| 839 | */ |
| 840 | if ((unlikely((curval & FUTEX_TID_MASK) == vpid))) |
| 841 | return -EDEADLK; |
| 842 | |
| 843 | /* |
| 844 | * Surprise - we got the lock, but we do not trust user space at all. |
| 845 | */ |
| 846 | if (unlikely(!curval)) { |
| 847 | /* |
| 848 | * We verify whether there is kernel state for this |
| 849 | * futex. If not, we can safely assume, that the 0 -> |
| 850 | * TID transition is correct. If state exists, we do |
| 851 | * not bother to fixup the user space state as it was |
| 852 | * corrupted already. |
| 853 | */ |
| 854 | return futex_top_waiter(hb, key) ? -EINVAL : 1; |
| 855 | } |
| 856 | |
| 857 | uval = curval; |
| 858 | |
| 859 | /* |
| 860 | * Set the FUTEX_WAITERS flag, so the owner will know it has someone |
| 861 | * to wake at the next unlock. |
| 862 | */ |
| 863 | newval = curval | FUTEX_WAITERS; |
| 864 | |
| 865 | /* |
| 866 | * Should we force take the futex? See below. |
| 867 | */ |
| 868 | if (unlikely(force_take)) { |
| 869 | /* |
| 870 | * Keep the OWNER_DIED and the WAITERS bit and set the |
| 871 | * new TID value. |
| 872 | */ |
| 873 | newval = (curval & ~FUTEX_TID_MASK) | vpid; |
| 874 | force_take = 0; |
| 875 | lock_taken = 1; |
| 876 | } |
| 877 | |
| 878 | if (unlikely(cmpxchg_futex_value_locked(&curval, uaddr, uval, newval))) |
| 879 | return -EFAULT; |
| 880 | if (unlikely(curval != uval)) |
| 881 | goto retry; |
| 882 | |
| 883 | /* |
| 884 | * We took the lock due to forced take over. |
| 885 | */ |
| 886 | if (unlikely(lock_taken)) |
| 887 | return 1; |
| 888 | |
| 889 | /* |
| 890 | * We dont have the lock. Look up the PI state (or create it if |
| 891 | * we are the first waiter): |
| 892 | */ |
| 893 | ret = lookup_pi_state(uval, hb, key, ps); |
| 894 | |
| 895 | if (unlikely(ret)) { |
| 896 | switch (ret) { |
| 897 | case -ESRCH: |
| 898 | /* |
| 899 | * We failed to find an owner for this |
| 900 | * futex. So we have no pi_state to block |
| 901 | * on. This can happen in two cases: |
| 902 | * |
| 903 | * 1) The owner died |
| 904 | * 2) A stale FUTEX_WAITERS bit |
| 905 | * |
| 906 | * Re-read the futex value. |
| 907 | */ |
| 908 | if (get_futex_value_locked(&curval, uaddr)) |
| 909 | return -EFAULT; |
| 910 | |
| 911 | /* |
| 912 | * If the owner died or we have a stale |
| 913 | * WAITERS bit the owner TID in the user space |
| 914 | * futex is 0. |
| 915 | */ |
| 916 | if (!(curval & FUTEX_TID_MASK)) { |
| 917 | force_take = 1; |
| 918 | goto retry; |
| 919 | } |
| 920 | default: |
| 921 | break; |
| 922 | } |
| 923 | } |
| 924 | |
| 925 | return ret; |
| 926 | } |
| 927 | |
| 928 | /** |
| 929 | * __unqueue_futex() - Remove the futex_q from its futex_hash_bucket |
| 930 | * @q: The futex_q to unqueue |
| 931 | * |
| 932 | * The q->lock_ptr must not be NULL and must be held by the caller. |
| 933 | */ |
| 934 | static void __unqueue_futex(struct futex_q *q) |
| 935 | { |
| 936 | struct futex_hash_bucket *hb; |
| 937 | |
| 938 | if (WARN_ON_SMP(!q->lock_ptr || !spin_is_locked(q->lock_ptr)) |
| 939 | || WARN_ON(plist_node_empty(&q->list))) |
| 940 | return; |
| 941 | |
| 942 | hb = container_of(q->lock_ptr, struct futex_hash_bucket, lock); |
| 943 | plist_del(&q->list, &hb->chain); |
| 944 | } |
| 945 | |
| 946 | /* |
| 947 | * The hash bucket lock must be held when this is called. |
| 948 | * Afterwards, the futex_q must not be accessed. |
| 949 | */ |
| 950 | static void wake_futex(struct futex_q *q) |
| 951 | { |
| 952 | struct task_struct *p = q->task; |
| 953 | |
| 954 | if (WARN(q->pi_state || q->rt_waiter, "refusing to wake PI futex\n")) |
| 955 | return; |
| 956 | |
| 957 | /* |
| 958 | * We set q->lock_ptr = NULL _before_ we wake up the task. If |
| 959 | * a non-futex wake up happens on another CPU then the task |
| 960 | * might exit and p would dereference a non-existing task |
| 961 | * struct. Prevent this by holding a reference on p across the |
| 962 | * wake up. |
| 963 | */ |
| 964 | get_task_struct(p); |
| 965 | |
| 966 | __unqueue_futex(q); |
| 967 | /* |
| 968 | * The waiting task can free the futex_q as soon as |
| 969 | * q->lock_ptr = NULL is written, without taking any locks. A |
| 970 | * memory barrier is required here to prevent the following |
| 971 | * store to lock_ptr from getting ahead of the plist_del. |
| 972 | */ |
| 973 | smp_wmb(); |
| 974 | q->lock_ptr = NULL; |
| 975 | |
| 976 | wake_up_state(p, TASK_NORMAL); |
| 977 | put_task_struct(p); |
| 978 | } |
| 979 | |
| 980 | static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this) |
| 981 | { |
| 982 | struct task_struct *new_owner; |
| 983 | struct futex_pi_state *pi_state = this->pi_state; |
| 984 | u32 uninitialized_var(curval), newval; |
| 985 | int ret = 0; |
| 986 | |
| 987 | if (!pi_state) |
| 988 | return -EINVAL; |
| 989 | |
| 990 | /* |
| 991 | * If current does not own the pi_state then the futex is |
| 992 | * inconsistent and user space fiddled with the futex value. |
| 993 | */ |
| 994 | if (pi_state->owner != current) |
| 995 | return -EINVAL; |
| 996 | |
| 997 | raw_spin_lock(&pi_state->pi_mutex.wait_lock); |
| 998 | new_owner = rt_mutex_next_owner(&pi_state->pi_mutex); |
| 999 | |
| 1000 | /* |
| 1001 | * It is possible that the next waiter (the one that brought |
| 1002 | * this owner to the kernel) timed out and is no longer |
| 1003 | * waiting on the lock. |
| 1004 | */ |
| 1005 | if (!new_owner) |
| 1006 | new_owner = this->task; |
| 1007 | |
| 1008 | /* |
| 1009 | * We pass it to the next owner. The WAITERS bit is always |
| 1010 | * kept enabled while there is PI state around. We cleanup the |
| 1011 | * owner died bit, because we are the owner. |
| 1012 | */ |
| 1013 | newval = FUTEX_WAITERS | task_pid_vnr(new_owner); |
| 1014 | |
| 1015 | if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval)) |
| 1016 | ret = -EFAULT; |
| 1017 | else if (curval != uval) |
| 1018 | ret = -EINVAL; |
| 1019 | if (ret) { |
| 1020 | raw_spin_unlock(&pi_state->pi_mutex.wait_lock); |
| 1021 | return ret; |
| 1022 | } |
| 1023 | |
| 1024 | raw_spin_lock_irq(&pi_state->owner->pi_lock); |
| 1025 | WARN_ON(list_empty(&pi_state->list)); |
| 1026 | list_del_init(&pi_state->list); |
| 1027 | raw_spin_unlock_irq(&pi_state->owner->pi_lock); |
| 1028 | |
| 1029 | raw_spin_lock_irq(&new_owner->pi_lock); |
| 1030 | WARN_ON(!list_empty(&pi_state->list)); |
| 1031 | list_add(&pi_state->list, &new_owner->pi_state_list); |
| 1032 | pi_state->owner = new_owner; |
| 1033 | raw_spin_unlock_irq(&new_owner->pi_lock); |
| 1034 | |
| 1035 | raw_spin_unlock(&pi_state->pi_mutex.wait_lock); |
| 1036 | rt_mutex_unlock(&pi_state->pi_mutex); |
| 1037 | |
| 1038 | return 0; |
| 1039 | } |
| 1040 | |
| 1041 | static int unlock_futex_pi(u32 __user *uaddr, u32 uval) |
| 1042 | { |
| 1043 | u32 uninitialized_var(oldval); |
| 1044 | |
| 1045 | /* |
| 1046 | * There is no waiter, so we unlock the futex. The owner died |
| 1047 | * bit has not to be preserved here. We are the owner: |
| 1048 | */ |
| 1049 | if (cmpxchg_futex_value_locked(&oldval, uaddr, uval, 0)) |
| 1050 | return -EFAULT; |
| 1051 | if (oldval != uval) |
| 1052 | return -EAGAIN; |
| 1053 | |
| 1054 | return 0; |
| 1055 | } |
| 1056 | |
| 1057 | /* |
| 1058 | * Express the locking dependencies for lockdep: |
| 1059 | */ |
| 1060 | static inline void |
| 1061 | double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) |
| 1062 | { |
| 1063 | if (hb1 <= hb2) { |
| 1064 | spin_lock(&hb1->lock); |
| 1065 | if (hb1 < hb2) |
| 1066 | spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING); |
| 1067 | } else { /* hb1 > hb2 */ |
| 1068 | spin_lock(&hb2->lock); |
| 1069 | spin_lock_nested(&hb1->lock, SINGLE_DEPTH_NESTING); |
| 1070 | } |
| 1071 | } |
| 1072 | |
| 1073 | static inline void |
| 1074 | double_unlock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) |
| 1075 | { |
| 1076 | spin_unlock(&hb1->lock); |
| 1077 | if (hb1 != hb2) |
| 1078 | spin_unlock(&hb2->lock); |
| 1079 | } |
| 1080 | |
| 1081 | /* |
| 1082 | * Wake up waiters matching bitset queued on this futex (uaddr). |
| 1083 | */ |
| 1084 | static int |
| 1085 | futex_wake(u32 __user *uaddr, unsigned int flags, int nr_wake, u32 bitset) |
| 1086 | { |
| 1087 | struct futex_hash_bucket *hb; |
| 1088 | struct futex_q *this, *next; |
| 1089 | struct plist_head *head; |
| 1090 | union futex_key key = FUTEX_KEY_INIT; |
| 1091 | int ret; |
| 1092 | |
| 1093 | if (!bitset) |
| 1094 | return -EINVAL; |
| 1095 | |
| 1096 | ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key, VERIFY_READ); |
| 1097 | if (unlikely(ret != 0)) |
| 1098 | goto out; |
| 1099 | |
| 1100 | hb = hash_futex(&key); |
| 1101 | spin_lock(&hb->lock); |
| 1102 | head = &hb->chain; |
| 1103 | |
| 1104 | plist_for_each_entry_safe(this, next, head, list) { |
| 1105 | if (match_futex (&this->key, &key)) { |
| 1106 | if (this->pi_state || this->rt_waiter) { |
| 1107 | ret = -EINVAL; |
| 1108 | break; |
| 1109 | } |
| 1110 | |
| 1111 | /* Check if one of the bits is set in both bitsets */ |
| 1112 | if (!(this->bitset & bitset)) |
| 1113 | continue; |
| 1114 | |
| 1115 | wake_futex(this); |
| 1116 | if (++ret >= nr_wake) |
| 1117 | break; |
| 1118 | } |
| 1119 | } |
| 1120 | |
| 1121 | spin_unlock(&hb->lock); |
| 1122 | put_futex_key(&key); |
| 1123 | out: |
| 1124 | return ret; |
| 1125 | } |
| 1126 | |
| 1127 | /* |
| 1128 | * Wake up all waiters hashed on the physical page that is mapped |
| 1129 | * to this virtual address: |
| 1130 | */ |
| 1131 | static int |
| 1132 | futex_wake_op(u32 __user *uaddr1, unsigned int flags, u32 __user *uaddr2, |
| 1133 | int nr_wake, int nr_wake2, int op) |
| 1134 | { |
| 1135 | union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT; |
| 1136 | struct futex_hash_bucket *hb1, *hb2; |
| 1137 | struct plist_head *head; |
| 1138 | struct futex_q *this, *next; |
| 1139 | int ret, op_ret; |
| 1140 | |
| 1141 | retry: |
| 1142 | ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1, VERIFY_READ); |
| 1143 | if (unlikely(ret != 0)) |
| 1144 | goto out; |
| 1145 | ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, VERIFY_WRITE); |
| 1146 | if (unlikely(ret != 0)) |
| 1147 | goto out_put_key1; |
| 1148 | |
| 1149 | hb1 = hash_futex(&key1); |
| 1150 | hb2 = hash_futex(&key2); |
| 1151 | |
| 1152 | retry_private: |
| 1153 | double_lock_hb(hb1, hb2); |
| 1154 | op_ret = futex_atomic_op_inuser(op, uaddr2); |
| 1155 | if (unlikely(op_ret < 0)) { |
| 1156 | |
| 1157 | double_unlock_hb(hb1, hb2); |
| 1158 | |
| 1159 | #ifndef CONFIG_MMU |
| 1160 | /* |
| 1161 | * we don't get EFAULT from MMU faults if we don't have an MMU, |
| 1162 | * but we might get them from range checking |
| 1163 | */ |
| 1164 | ret = op_ret; |
| 1165 | goto out_put_keys; |
| 1166 | #endif |
| 1167 | |
| 1168 | if (unlikely(op_ret != -EFAULT)) { |
| 1169 | ret = op_ret; |
| 1170 | goto out_put_keys; |
| 1171 | } |
| 1172 | |
| 1173 | ret = fault_in_user_writeable(uaddr2); |
| 1174 | if (ret) |
| 1175 | goto out_put_keys; |
| 1176 | |
| 1177 | if (!(flags & FLAGS_SHARED)) |
| 1178 | goto retry_private; |
| 1179 | |
| 1180 | put_futex_key(&key2); |
| 1181 | put_futex_key(&key1); |
| 1182 | goto retry; |
| 1183 | } |
| 1184 | |
| 1185 | head = &hb1->chain; |
| 1186 | |
| 1187 | plist_for_each_entry_safe(this, next, head, list) { |
| 1188 | if (match_futex (&this->key, &key1)) { |
| 1189 | if (this->pi_state || this->rt_waiter) { |
| 1190 | ret = -EINVAL; |
| 1191 | goto out_unlock; |
| 1192 | } |
| 1193 | wake_futex(this); |
| 1194 | if (++ret >= nr_wake) |
| 1195 | break; |
| 1196 | } |
| 1197 | } |
| 1198 | |
| 1199 | if (op_ret > 0) { |
| 1200 | head = &hb2->chain; |
| 1201 | |
| 1202 | op_ret = 0; |
| 1203 | plist_for_each_entry_safe(this, next, head, list) { |
| 1204 | if (match_futex (&this->key, &key2)) { |
| 1205 | if (this->pi_state || this->rt_waiter) { |
| 1206 | ret = -EINVAL; |
| 1207 | goto out_unlock; |
| 1208 | } |
| 1209 | wake_futex(this); |
| 1210 | if (++op_ret >= nr_wake2) |
| 1211 | break; |
| 1212 | } |
| 1213 | } |
| 1214 | ret += op_ret; |
| 1215 | } |
| 1216 | |
| 1217 | out_unlock: |
| 1218 | double_unlock_hb(hb1, hb2); |
| 1219 | out_put_keys: |
| 1220 | put_futex_key(&key2); |
| 1221 | out_put_key1: |
| 1222 | put_futex_key(&key1); |
| 1223 | out: |
| 1224 | return ret; |
| 1225 | } |
| 1226 | |
| 1227 | /** |
| 1228 | * requeue_futex() - Requeue a futex_q from one hb to another |
| 1229 | * @q: the futex_q to requeue |
| 1230 | * @hb1: the source hash_bucket |
| 1231 | * @hb2: the target hash_bucket |
| 1232 | * @key2: the new key for the requeued futex_q |
| 1233 | */ |
| 1234 | static inline |
| 1235 | void requeue_futex(struct futex_q *q, struct futex_hash_bucket *hb1, |
| 1236 | struct futex_hash_bucket *hb2, union futex_key *key2) |
| 1237 | { |
| 1238 | |
| 1239 | /* |
| 1240 | * If key1 and key2 hash to the same bucket, no need to |
| 1241 | * requeue. |
| 1242 | */ |
| 1243 | if (likely(&hb1->chain != &hb2->chain)) { |
| 1244 | plist_del(&q->list, &hb1->chain); |
| 1245 | plist_add(&q->list, &hb2->chain); |
| 1246 | q->lock_ptr = &hb2->lock; |
| 1247 | } |
| 1248 | get_futex_key_refs(key2); |
| 1249 | q->key = *key2; |
| 1250 | } |
| 1251 | |
| 1252 | /** |
| 1253 | * requeue_pi_wake_futex() - Wake a task that acquired the lock during requeue |
| 1254 | * @q: the futex_q |
| 1255 | * @key: the key of the requeue target futex |
| 1256 | * @hb: the hash_bucket of the requeue target futex |
| 1257 | * |
| 1258 | * During futex_requeue, with requeue_pi=1, it is possible to acquire the |
| 1259 | * target futex if it is uncontended or via a lock steal. Set the futex_q key |
| 1260 | * to the requeue target futex so the waiter can detect the wakeup on the right |
| 1261 | * futex, but remove it from the hb and NULL the rt_waiter so it can detect |
| 1262 | * atomic lock acquisition. Set the q->lock_ptr to the requeue target hb->lock |
| 1263 | * to protect access to the pi_state to fixup the owner later. Must be called |
| 1264 | * with both q->lock_ptr and hb->lock held. |
| 1265 | */ |
| 1266 | static inline |
| 1267 | void requeue_pi_wake_futex(struct futex_q *q, union futex_key *key, |
| 1268 | struct futex_hash_bucket *hb) |
| 1269 | { |
| 1270 | get_futex_key_refs(key); |
| 1271 | q->key = *key; |
| 1272 | |
| 1273 | __unqueue_futex(q); |
| 1274 | |
| 1275 | WARN_ON(!q->rt_waiter); |
| 1276 | q->rt_waiter = NULL; |
| 1277 | |
| 1278 | q->lock_ptr = &hb->lock; |
| 1279 | |
| 1280 | wake_up_state(q->task, TASK_NORMAL); |
| 1281 | } |
| 1282 | |
| 1283 | /** |
| 1284 | * futex_proxy_trylock_atomic() - Attempt an atomic lock for the top waiter |
| 1285 | * @pifutex: the user address of the to futex |
| 1286 | * @hb1: the from futex hash bucket, must be locked by the caller |
| 1287 | * @hb2: the to futex hash bucket, must be locked by the caller |
| 1288 | * @key1: the from futex key |
| 1289 | * @key2: the to futex key |
| 1290 | * @ps: address to store the pi_state pointer |
| 1291 | * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0) |
| 1292 | * |
| 1293 | * Try and get the lock on behalf of the top waiter if we can do it atomically. |
| 1294 | * Wake the top waiter if we succeed. If the caller specified set_waiters, |
| 1295 | * then direct futex_lock_pi_atomic() to force setting the FUTEX_WAITERS bit. |
| 1296 | * hb1 and hb2 must be held by the caller. |
| 1297 | * |
| 1298 | * Return: |
| 1299 | * 0 - failed to acquire the lock atomically; |
| 1300 | * >0 - acquired the lock, return value is vpid of the top_waiter |
| 1301 | * <0 - error |
| 1302 | */ |
| 1303 | static int futex_proxy_trylock_atomic(u32 __user *pifutex, |
| 1304 | struct futex_hash_bucket *hb1, |
| 1305 | struct futex_hash_bucket *hb2, |
| 1306 | union futex_key *key1, union futex_key *key2, |
| 1307 | struct futex_pi_state **ps, int set_waiters) |
| 1308 | { |
| 1309 | struct futex_q *top_waiter = NULL; |
| 1310 | u32 curval; |
| 1311 | int ret, vpid; |
| 1312 | |
| 1313 | if (get_futex_value_locked(&curval, pifutex)) |
| 1314 | return -EFAULT; |
| 1315 | |
| 1316 | /* |
| 1317 | * Find the top_waiter and determine if there are additional waiters. |
| 1318 | * If the caller intends to requeue more than 1 waiter to pifutex, |
| 1319 | * force futex_lock_pi_atomic() to set the FUTEX_WAITERS bit now, |
| 1320 | * as we have means to handle the possible fault. If not, don't set |
| 1321 | * the bit unecessarily as it will force the subsequent unlock to enter |
| 1322 | * the kernel. |
| 1323 | */ |
| 1324 | top_waiter = futex_top_waiter(hb1, key1); |
| 1325 | |
| 1326 | /* There are no waiters, nothing for us to do. */ |
| 1327 | if (!top_waiter) |
| 1328 | return 0; |
| 1329 | |
| 1330 | /* Ensure we requeue to the expected futex. */ |
| 1331 | if (!match_futex(top_waiter->requeue_pi_key, key2)) |
| 1332 | return -EINVAL; |
| 1333 | |
| 1334 | /* |
| 1335 | * Try to take the lock for top_waiter. Set the FUTEX_WAITERS bit in |
| 1336 | * the contended case or if set_waiters is 1. The pi_state is returned |
| 1337 | * in ps in contended cases. |
| 1338 | */ |
| 1339 | vpid = task_pid_vnr(top_waiter->task); |
| 1340 | ret = futex_lock_pi_atomic(pifutex, hb2, key2, ps, top_waiter->task, |
| 1341 | set_waiters); |
| 1342 | if (ret == 1) { |
| 1343 | requeue_pi_wake_futex(top_waiter, key2, hb2); |
| 1344 | return vpid; |
| 1345 | } |
| 1346 | return ret; |
| 1347 | } |
| 1348 | |
| 1349 | /** |
| 1350 | * futex_requeue() - Requeue waiters from uaddr1 to uaddr2 |
| 1351 | * @uaddr1: source futex user address |
| 1352 | * @flags: futex flags (FLAGS_SHARED, etc.) |
| 1353 | * @uaddr2: target futex user address |
| 1354 | * @nr_wake: number of waiters to wake (must be 1 for requeue_pi) |
| 1355 | * @nr_requeue: number of waiters to requeue (0-INT_MAX) |
| 1356 | * @cmpval: @uaddr1 expected value (or %NULL) |
| 1357 | * @requeue_pi: if we are attempting to requeue from a non-pi futex to a |
| 1358 | * pi futex (pi to pi requeue is not supported) |
| 1359 | * |
| 1360 | * Requeue waiters on uaddr1 to uaddr2. In the requeue_pi case, try to acquire |
| 1361 | * uaddr2 atomically on behalf of the top waiter. |
| 1362 | * |
| 1363 | * Return: |
| 1364 | * >=0 - on success, the number of tasks requeued or woken; |
| 1365 | * <0 - on error |
| 1366 | */ |
| 1367 | static int futex_requeue(u32 __user *uaddr1, unsigned int flags, |
| 1368 | u32 __user *uaddr2, int nr_wake, int nr_requeue, |
| 1369 | u32 *cmpval, int requeue_pi) |
| 1370 | { |
| 1371 | union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT; |
| 1372 | int drop_count = 0, task_count = 0, ret; |
| 1373 | struct futex_pi_state *pi_state = NULL; |
| 1374 | struct futex_hash_bucket *hb1, *hb2; |
| 1375 | struct plist_head *head1; |
| 1376 | struct futex_q *this, *next; |
| 1377 | |
| 1378 | if (requeue_pi) { |
| 1379 | /* |
| 1380 | * Requeue PI only works on two distinct uaddrs. This |
| 1381 | * check is only valid for private futexes. See below. |
| 1382 | */ |
| 1383 | if (uaddr1 == uaddr2) |
| 1384 | return -EINVAL; |
| 1385 | |
| 1386 | /* |
| 1387 | * requeue_pi requires a pi_state, try to allocate it now |
| 1388 | * without any locks in case it fails. |
| 1389 | */ |
| 1390 | if (refill_pi_state_cache()) |
| 1391 | return -ENOMEM; |
| 1392 | /* |
| 1393 | * requeue_pi must wake as many tasks as it can, up to nr_wake |
| 1394 | * + nr_requeue, since it acquires the rt_mutex prior to |
| 1395 | * returning to userspace, so as to not leave the rt_mutex with |
| 1396 | * waiters and no owner. However, second and third wake-ups |
| 1397 | * cannot be predicted as they involve race conditions with the |
| 1398 | * first wake and a fault while looking up the pi_state. Both |
| 1399 | * pthread_cond_signal() and pthread_cond_broadcast() should |
| 1400 | * use nr_wake=1. |
| 1401 | */ |
| 1402 | if (nr_wake != 1) |
| 1403 | return -EINVAL; |
| 1404 | } |
| 1405 | |
| 1406 | retry: |
| 1407 | if (pi_state != NULL) { |
| 1408 | /* |
| 1409 | * We will have to lookup the pi_state again, so free this one |
| 1410 | * to keep the accounting correct. |
| 1411 | */ |
| 1412 | free_pi_state(pi_state); |
| 1413 | pi_state = NULL; |
| 1414 | } |
| 1415 | |
| 1416 | ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1, VERIFY_READ); |
| 1417 | if (unlikely(ret != 0)) |
| 1418 | goto out; |
| 1419 | ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, |
| 1420 | requeue_pi ? VERIFY_WRITE : VERIFY_READ); |
| 1421 | if (unlikely(ret != 0)) |
| 1422 | goto out_put_key1; |
| 1423 | |
| 1424 | /* |
| 1425 | * The check above which compares uaddrs is not sufficient for |
| 1426 | * shared futexes. We need to compare the keys: |
| 1427 | */ |
| 1428 | if (requeue_pi && match_futex(&key1, &key2)) { |
| 1429 | ret = -EINVAL; |
| 1430 | goto out_put_keys; |
| 1431 | } |
| 1432 | |
| 1433 | hb1 = hash_futex(&key1); |
| 1434 | hb2 = hash_futex(&key2); |
| 1435 | |
| 1436 | retry_private: |
| 1437 | double_lock_hb(hb1, hb2); |
| 1438 | |
| 1439 | if (likely(cmpval != NULL)) { |
| 1440 | u32 curval; |
| 1441 | |
| 1442 | ret = get_futex_value_locked(&curval, uaddr1); |
| 1443 | |
| 1444 | if (unlikely(ret)) { |
| 1445 | double_unlock_hb(hb1, hb2); |
| 1446 | |
| 1447 | ret = get_user(curval, uaddr1); |
| 1448 | if (ret) |
| 1449 | goto out_put_keys; |
| 1450 | |
| 1451 | if (!(flags & FLAGS_SHARED)) |
| 1452 | goto retry_private; |
| 1453 | |
| 1454 | put_futex_key(&key2); |
| 1455 | put_futex_key(&key1); |
| 1456 | goto retry; |
| 1457 | } |
| 1458 | if (curval != *cmpval) { |
| 1459 | ret = -EAGAIN; |
| 1460 | goto out_unlock; |
| 1461 | } |
| 1462 | } |
| 1463 | |
| 1464 | if (requeue_pi && (task_count - nr_wake < nr_requeue)) { |
| 1465 | /* |
| 1466 | * Attempt to acquire uaddr2 and wake the top waiter. If we |
| 1467 | * intend to requeue waiters, force setting the FUTEX_WAITERS |
| 1468 | * bit. We force this here where we are able to easily handle |
| 1469 | * faults rather in the requeue loop below. |
| 1470 | */ |
| 1471 | ret = futex_proxy_trylock_atomic(uaddr2, hb1, hb2, &key1, |
| 1472 | &key2, &pi_state, nr_requeue); |
| 1473 | |
| 1474 | /* |
| 1475 | * At this point the top_waiter has either taken uaddr2 or is |
| 1476 | * waiting on it. If the former, then the pi_state will not |
| 1477 | * exist yet, look it up one more time to ensure we have a |
| 1478 | * reference to it. If the lock was taken, ret contains the |
| 1479 | * vpid of the top waiter task. |
| 1480 | */ |
| 1481 | if (ret > 0) { |
| 1482 | WARN_ON(pi_state); |
| 1483 | drop_count++; |
| 1484 | task_count++; |
| 1485 | /* |
| 1486 | * If we acquired the lock, then the user |
| 1487 | * space value of uaddr2 should be vpid. It |
| 1488 | * cannot be changed by the top waiter as it |
| 1489 | * is blocked on hb2 lock if it tries to do |
| 1490 | * so. If something fiddled with it behind our |
| 1491 | * back the pi state lookup might unearth |
| 1492 | * it. So we rather use the known value than |
| 1493 | * rereading and handing potential crap to |
| 1494 | * lookup_pi_state. |
| 1495 | */ |
| 1496 | ret = lookup_pi_state(ret, hb2, &key2, &pi_state); |
| 1497 | } |
| 1498 | |
| 1499 | switch (ret) { |
| 1500 | case 0: |
| 1501 | break; |
| 1502 | case -EFAULT: |
| 1503 | double_unlock_hb(hb1, hb2); |
| 1504 | put_futex_key(&key2); |
| 1505 | put_futex_key(&key1); |
| 1506 | ret = fault_in_user_writeable(uaddr2); |
| 1507 | if (!ret) |
| 1508 | goto retry; |
| 1509 | goto out; |
| 1510 | case -EAGAIN: |
| 1511 | /* The owner was exiting, try again. */ |
| 1512 | double_unlock_hb(hb1, hb2); |
| 1513 | put_futex_key(&key2); |
| 1514 | put_futex_key(&key1); |
| 1515 | cond_resched(); |
| 1516 | goto retry; |
| 1517 | default: |
| 1518 | goto out_unlock; |
| 1519 | } |
| 1520 | } |
| 1521 | |
| 1522 | head1 = &hb1->chain; |
| 1523 | plist_for_each_entry_safe(this, next, head1, list) { |
| 1524 | if (task_count - nr_wake >= nr_requeue) |
| 1525 | break; |
| 1526 | |
| 1527 | if (!match_futex(&this->key, &key1)) |
| 1528 | continue; |
| 1529 | |
| 1530 | /* |
| 1531 | * FUTEX_WAIT_REQEUE_PI and FUTEX_CMP_REQUEUE_PI should always |
| 1532 | * be paired with each other and no other futex ops. |
| 1533 | * |
| 1534 | * We should never be requeueing a futex_q with a pi_state, |
| 1535 | * which is awaiting a futex_unlock_pi(). |
| 1536 | */ |
| 1537 | if ((requeue_pi && !this->rt_waiter) || |
| 1538 | (!requeue_pi && this->rt_waiter) || |
| 1539 | this->pi_state) { |
| 1540 | ret = -EINVAL; |
| 1541 | break; |
| 1542 | } |
| 1543 | |
| 1544 | /* |
| 1545 | * Wake nr_wake waiters. For requeue_pi, if we acquired the |
| 1546 | * lock, we already woke the top_waiter. If not, it will be |
| 1547 | * woken by futex_unlock_pi(). |
| 1548 | */ |
| 1549 | if (++task_count <= nr_wake && !requeue_pi) { |
| 1550 | wake_futex(this); |
| 1551 | continue; |
| 1552 | } |
| 1553 | |
| 1554 | /* Ensure we requeue to the expected futex for requeue_pi. */ |
| 1555 | if (requeue_pi && !match_futex(this->requeue_pi_key, &key2)) { |
| 1556 | ret = -EINVAL; |
| 1557 | break; |
| 1558 | } |
| 1559 | |
| 1560 | /* |
| 1561 | * Requeue nr_requeue waiters and possibly one more in the case |
| 1562 | * of requeue_pi if we couldn't acquire the lock atomically. |
| 1563 | */ |
| 1564 | if (requeue_pi) { |
| 1565 | /* Prepare the waiter to take the rt_mutex. */ |
| 1566 | atomic_inc(&pi_state->refcount); |
| 1567 | this->pi_state = pi_state; |
| 1568 | ret = rt_mutex_start_proxy_lock(&pi_state->pi_mutex, |
| 1569 | this->rt_waiter, |
| 1570 | this->task, 1); |
| 1571 | if (ret == 1) { |
| 1572 | /* We got the lock. */ |
| 1573 | requeue_pi_wake_futex(this, &key2, hb2); |
| 1574 | drop_count++; |
| 1575 | continue; |
| 1576 | } else if (ret) { |
| 1577 | /* -EDEADLK */ |
| 1578 | this->pi_state = NULL; |
| 1579 | free_pi_state(pi_state); |
| 1580 | goto out_unlock; |
| 1581 | } |
| 1582 | } |
| 1583 | requeue_futex(this, hb1, hb2, &key2); |
| 1584 | drop_count++; |
| 1585 | } |
| 1586 | |
| 1587 | out_unlock: |
| 1588 | double_unlock_hb(hb1, hb2); |
| 1589 | |
| 1590 | /* |
| 1591 | * drop_futex_key_refs() must be called outside the spinlocks. During |
| 1592 | * the requeue we moved futex_q's from the hash bucket at key1 to the |
| 1593 | * one at key2 and updated their key pointer. We no longer need to |
| 1594 | * hold the references to key1. |
| 1595 | */ |
| 1596 | while (--drop_count >= 0) |
| 1597 | drop_futex_key_refs(&key1); |
| 1598 | |
| 1599 | out_put_keys: |
| 1600 | put_futex_key(&key2); |
| 1601 | out_put_key1: |
| 1602 | put_futex_key(&key1); |
| 1603 | out: |
| 1604 | if (pi_state != NULL) |
| 1605 | free_pi_state(pi_state); |
| 1606 | return ret ? ret : task_count; |
| 1607 | } |
| 1608 | |
| 1609 | /* The key must be already stored in q->key. */ |
| 1610 | static inline struct futex_hash_bucket *queue_lock(struct futex_q *q) |
| 1611 | __acquires(&hb->lock) |
| 1612 | { |
| 1613 | struct futex_hash_bucket *hb; |
| 1614 | |
| 1615 | hb = hash_futex(&q->key); |
| 1616 | q->lock_ptr = &hb->lock; |
| 1617 | |
| 1618 | spin_lock(&hb->lock); |
| 1619 | return hb; |
| 1620 | } |
| 1621 | |
| 1622 | static inline void |
| 1623 | queue_unlock(struct futex_q *q, struct futex_hash_bucket *hb) |
| 1624 | __releases(&hb->lock) |
| 1625 | { |
| 1626 | spin_unlock(&hb->lock); |
| 1627 | } |
| 1628 | |
| 1629 | /** |
| 1630 | * queue_me() - Enqueue the futex_q on the futex_hash_bucket |
| 1631 | * @q: The futex_q to enqueue |
| 1632 | * @hb: The destination hash bucket |
| 1633 | * |
| 1634 | * The hb->lock must be held by the caller, and is released here. A call to |
| 1635 | * queue_me() is typically paired with exactly one call to unqueue_me(). The |
| 1636 | * exceptions involve the PI related operations, which may use unqueue_me_pi() |
| 1637 | * or nothing if the unqueue is done as part of the wake process and the unqueue |
| 1638 | * state is implicit in the state of woken task (see futex_wait_requeue_pi() for |
| 1639 | * an example). |
| 1640 | */ |
| 1641 | static inline void queue_me(struct futex_q *q, struct futex_hash_bucket *hb) |
| 1642 | __releases(&hb->lock) |
| 1643 | { |
| 1644 | int prio; |
| 1645 | |
| 1646 | /* |
| 1647 | * The priority used to register this element is |
| 1648 | * - either the real thread-priority for the real-time threads |
| 1649 | * (i.e. threads with a priority lower than MAX_RT_PRIO) |
| 1650 | * - or MAX_RT_PRIO for non-RT threads. |
| 1651 | * Thus, all RT-threads are woken first in priority order, and |
| 1652 | * the others are woken last, in FIFO order. |
| 1653 | */ |
| 1654 | prio = min(current->normal_prio, MAX_RT_PRIO); |
| 1655 | |
| 1656 | plist_node_init(&q->list, prio); |
| 1657 | plist_add(&q->list, &hb->chain); |
| 1658 | q->task = current; |
| 1659 | spin_unlock(&hb->lock); |
| 1660 | } |
| 1661 | |
| 1662 | /** |
| 1663 | * unqueue_me() - Remove the futex_q from its futex_hash_bucket |
| 1664 | * @q: The futex_q to unqueue |
| 1665 | * |
| 1666 | * The q->lock_ptr must not be held by the caller. A call to unqueue_me() must |
| 1667 | * be paired with exactly one earlier call to queue_me(). |
| 1668 | * |
| 1669 | * Return: |
| 1670 | * 1 - if the futex_q was still queued (and we removed unqueued it); |
| 1671 | * 0 - if the futex_q was already removed by the waking thread |
| 1672 | */ |
| 1673 | static int unqueue_me(struct futex_q *q) |
| 1674 | { |
| 1675 | spinlock_t *lock_ptr; |
| 1676 | int ret = 0; |
| 1677 | |
| 1678 | /* In the common case we don't take the spinlock, which is nice. */ |
| 1679 | retry: |
| 1680 | lock_ptr = q->lock_ptr; |
| 1681 | barrier(); |
| 1682 | if (lock_ptr != NULL) { |
| 1683 | spin_lock(lock_ptr); |
| 1684 | /* |
| 1685 | * q->lock_ptr can change between reading it and |
| 1686 | * spin_lock(), causing us to take the wrong lock. This |
| 1687 | * corrects the race condition. |
| 1688 | * |
| 1689 | * Reasoning goes like this: if we have the wrong lock, |
| 1690 | * q->lock_ptr must have changed (maybe several times) |
| 1691 | * between reading it and the spin_lock(). It can |
| 1692 | * change again after the spin_lock() but only if it was |
| 1693 | * already changed before the spin_lock(). It cannot, |
| 1694 | * however, change back to the original value. Therefore |
| 1695 | * we can detect whether we acquired the correct lock. |
| 1696 | */ |
| 1697 | if (unlikely(lock_ptr != q->lock_ptr)) { |
| 1698 | spin_unlock(lock_ptr); |
| 1699 | goto retry; |
| 1700 | } |
| 1701 | __unqueue_futex(q); |
| 1702 | |
| 1703 | BUG_ON(q->pi_state); |
| 1704 | |
| 1705 | spin_unlock(lock_ptr); |
| 1706 | ret = 1; |
| 1707 | } |
| 1708 | |
| 1709 | drop_futex_key_refs(&q->key); |
| 1710 | return ret; |
| 1711 | } |
| 1712 | |
| 1713 | /* |
| 1714 | * PI futexes can not be requeued and must remove themself from the |
| 1715 | * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry |
| 1716 | * and dropped here. |
| 1717 | */ |
| 1718 | static void unqueue_me_pi(struct futex_q *q) |
| 1719 | __releases(q->lock_ptr) |
| 1720 | { |
| 1721 | __unqueue_futex(q); |
| 1722 | |
| 1723 | BUG_ON(!q->pi_state); |
| 1724 | free_pi_state(q->pi_state); |
| 1725 | q->pi_state = NULL; |
| 1726 | |
| 1727 | spin_unlock(q->lock_ptr); |
| 1728 | } |
| 1729 | |
| 1730 | /* |
| 1731 | * Fixup the pi_state owner with the new owner. |
| 1732 | * |
| 1733 | * Must be called with hash bucket lock held and mm->sem held for non |
| 1734 | * private futexes. |
| 1735 | */ |
| 1736 | static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q, |
| 1737 | struct task_struct *newowner) |
| 1738 | { |
| 1739 | u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS; |
| 1740 | struct futex_pi_state *pi_state = q->pi_state; |
| 1741 | struct task_struct *oldowner = pi_state->owner; |
| 1742 | u32 uval, uninitialized_var(curval), newval; |
| 1743 | int ret; |
| 1744 | |
| 1745 | /* Owner died? */ |
| 1746 | if (!pi_state->owner) |
| 1747 | newtid |= FUTEX_OWNER_DIED; |
| 1748 | |
| 1749 | /* |
| 1750 | * We are here either because we stole the rtmutex from the |
| 1751 | * previous highest priority waiter or we are the highest priority |
| 1752 | * waiter but failed to get the rtmutex the first time. |
| 1753 | * We have to replace the newowner TID in the user space variable. |
| 1754 | * This must be atomic as we have to preserve the owner died bit here. |
| 1755 | * |
| 1756 | * Note: We write the user space value _before_ changing the pi_state |
| 1757 | * because we can fault here. Imagine swapped out pages or a fork |
| 1758 | * that marked all the anonymous memory readonly for cow. |
| 1759 | * |
| 1760 | * Modifying pi_state _before_ the user space value would |
| 1761 | * leave the pi_state in an inconsistent state when we fault |
| 1762 | * here, because we need to drop the hash bucket lock to |
| 1763 | * handle the fault. This might be observed in the PID check |
| 1764 | * in lookup_pi_state. |
| 1765 | */ |
| 1766 | retry: |
| 1767 | if (get_futex_value_locked(&uval, uaddr)) |
| 1768 | goto handle_fault; |
| 1769 | |
| 1770 | while (1) { |
| 1771 | newval = (uval & FUTEX_OWNER_DIED) | newtid; |
| 1772 | |
| 1773 | if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval)) |
| 1774 | goto handle_fault; |
| 1775 | if (curval == uval) |
| 1776 | break; |
| 1777 | uval = curval; |
| 1778 | } |
| 1779 | |
| 1780 | /* |
| 1781 | * We fixed up user space. Now we need to fix the pi_state |
| 1782 | * itself. |
| 1783 | */ |
| 1784 | if (pi_state->owner != NULL) { |
| 1785 | raw_spin_lock_irq(&pi_state->owner->pi_lock); |
| 1786 | WARN_ON(list_empty(&pi_state->list)); |
| 1787 | list_del_init(&pi_state->list); |
| 1788 | raw_spin_unlock_irq(&pi_state->owner->pi_lock); |
| 1789 | } |
| 1790 | |
| 1791 | pi_state->owner = newowner; |
| 1792 | |
| 1793 | raw_spin_lock_irq(&newowner->pi_lock); |
| 1794 | WARN_ON(!list_empty(&pi_state->list)); |
| 1795 | list_add(&pi_state->list, &newowner->pi_state_list); |
| 1796 | raw_spin_unlock_irq(&newowner->pi_lock); |
| 1797 | return 0; |
| 1798 | |
| 1799 | /* |
| 1800 | * To handle the page fault we need to drop the hash bucket |
| 1801 | * lock here. That gives the other task (either the highest priority |
| 1802 | * waiter itself or the task which stole the rtmutex) the |
| 1803 | * chance to try the fixup of the pi_state. So once we are |
| 1804 | * back from handling the fault we need to check the pi_state |
| 1805 | * after reacquiring the hash bucket lock and before trying to |
| 1806 | * do another fixup. When the fixup has been done already we |
| 1807 | * simply return. |
| 1808 | */ |
| 1809 | handle_fault: |
| 1810 | spin_unlock(q->lock_ptr); |
| 1811 | |
| 1812 | ret = fault_in_user_writeable(uaddr); |
| 1813 | |
| 1814 | spin_lock(q->lock_ptr); |
| 1815 | |
| 1816 | /* |
| 1817 | * Check if someone else fixed it for us: |
| 1818 | */ |
| 1819 | if (pi_state->owner != oldowner) |
| 1820 | return 0; |
| 1821 | |
| 1822 | if (ret) |
| 1823 | return ret; |
| 1824 | |
| 1825 | goto retry; |
| 1826 | } |
| 1827 | |
| 1828 | static long futex_wait_restart(struct restart_block *restart); |
| 1829 | |
| 1830 | /** |
| 1831 | * fixup_owner() - Post lock pi_state and corner case management |
| 1832 | * @uaddr: user address of the futex |
| 1833 | * @q: futex_q (contains pi_state and access to the rt_mutex) |
| 1834 | * @locked: if the attempt to take the rt_mutex succeeded (1) or not (0) |
| 1835 | * |
| 1836 | * After attempting to lock an rt_mutex, this function is called to cleanup |
| 1837 | * the pi_state owner as well as handle race conditions that may allow us to |
| 1838 | * acquire the lock. Must be called with the hb lock held. |
| 1839 | * |
| 1840 | * Return: |
| 1841 | * 1 - success, lock taken; |
| 1842 | * 0 - success, lock not taken; |
| 1843 | * <0 - on error (-EFAULT) |
| 1844 | */ |
| 1845 | static int fixup_owner(u32 __user *uaddr, struct futex_q *q, int locked) |
| 1846 | { |
| 1847 | struct task_struct *owner; |
| 1848 | int ret = 0; |
| 1849 | |
| 1850 | if (locked) { |
| 1851 | /* |
| 1852 | * Got the lock. We might not be the anticipated owner if we |
| 1853 | * did a lock-steal - fix up the PI-state in that case: |
| 1854 | */ |
| 1855 | if (q->pi_state->owner != current) |
| 1856 | ret = fixup_pi_state_owner(uaddr, q, current); |
| 1857 | goto out; |
| 1858 | } |
| 1859 | |
| 1860 | /* |
| 1861 | * Catch the rare case, where the lock was released when we were on the |
| 1862 | * way back before we locked the hash bucket. |
| 1863 | */ |
| 1864 | if (q->pi_state->owner == current) { |
| 1865 | /* |
| 1866 | * Try to get the rt_mutex now. This might fail as some other |
| 1867 | * task acquired the rt_mutex after we removed ourself from the |
| 1868 | * rt_mutex waiters list. |
| 1869 | */ |
| 1870 | if (rt_mutex_trylock(&q->pi_state->pi_mutex)) { |
| 1871 | locked = 1; |
| 1872 | goto out; |
| 1873 | } |
| 1874 | |
| 1875 | /* |
| 1876 | * pi_state is incorrect, some other task did a lock steal and |
| 1877 | * we returned due to timeout or signal without taking the |
| 1878 | * rt_mutex. Too late. |
| 1879 | */ |
| 1880 | raw_spin_lock(&q->pi_state->pi_mutex.wait_lock); |
| 1881 | owner = rt_mutex_owner(&q->pi_state->pi_mutex); |
| 1882 | if (!owner) |
| 1883 | owner = rt_mutex_next_owner(&q->pi_state->pi_mutex); |
| 1884 | raw_spin_unlock(&q->pi_state->pi_mutex.wait_lock); |
| 1885 | ret = fixup_pi_state_owner(uaddr, q, owner); |
| 1886 | goto out; |
| 1887 | } |
| 1888 | |
| 1889 | /* |
| 1890 | * Paranoia check. If we did not take the lock, then we should not be |
| 1891 | * the owner of the rt_mutex. |
| 1892 | */ |
| 1893 | if (rt_mutex_owner(&q->pi_state->pi_mutex) == current) |
| 1894 | printk(KERN_ERR "fixup_owner: ret = %d pi-mutex: %p " |
| 1895 | "pi-state %p\n", ret, |
| 1896 | q->pi_state->pi_mutex.owner, |
| 1897 | q->pi_state->owner); |
| 1898 | |
| 1899 | out: |
| 1900 | return ret ? ret : locked; |
| 1901 | } |
| 1902 | |
| 1903 | /** |
| 1904 | * futex_wait_queue_me() - queue_me() and wait for wakeup, timeout, or signal |
| 1905 | * @hb: the futex hash bucket, must be locked by the caller |
| 1906 | * @q: the futex_q to queue up on |
| 1907 | * @timeout: the prepared hrtimer_sleeper, or null for no timeout |
| 1908 | */ |
| 1909 | static void futex_wait_queue_me(struct futex_hash_bucket *hb, struct futex_q *q, |
| 1910 | struct hrtimer_sleeper *timeout) |
| 1911 | { |
| 1912 | /* |
| 1913 | * The task state is guaranteed to be set before another task can |
| 1914 | * wake it. set_current_state() is implemented using set_mb() and |
| 1915 | * queue_me() calls spin_unlock() upon completion, both serializing |
| 1916 | * access to the hash list and forcing another memory barrier. |
| 1917 | */ |
| 1918 | set_current_state(TASK_INTERRUPTIBLE); |
| 1919 | queue_me(q, hb); |
| 1920 | |
| 1921 | /* Arm the timer */ |
| 1922 | if (timeout) { |
| 1923 | hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS); |
| 1924 | if (!hrtimer_active(&timeout->timer)) |
| 1925 | timeout->task = NULL; |
| 1926 | } |
| 1927 | |
| 1928 | /* |
| 1929 | * If we have been removed from the hash list, then another task |
| 1930 | * has tried to wake us, and we can skip the call to schedule(). |
| 1931 | */ |
| 1932 | if (likely(!plist_node_empty(&q->list))) { |
| 1933 | /* |
| 1934 | * If the timer has already expired, current will already be |
| 1935 | * flagged for rescheduling. Only call schedule if there |
| 1936 | * is no timeout, or if it has yet to expire. |
| 1937 | */ |
| 1938 | if (!timeout || timeout->task) |
| 1939 | freezable_schedule(); |
| 1940 | } |
| 1941 | __set_current_state(TASK_RUNNING); |
| 1942 | } |
| 1943 | |
| 1944 | /** |
| 1945 | * futex_wait_setup() - Prepare to wait on a futex |
| 1946 | * @uaddr: the futex userspace address |
| 1947 | * @val: the expected value |
| 1948 | * @flags: futex flags (FLAGS_SHARED, etc.) |
| 1949 | * @q: the associated futex_q |
| 1950 | * @hb: storage for hash_bucket pointer to be returned to caller |
| 1951 | * |
| 1952 | * Setup the futex_q and locate the hash_bucket. Get the futex value and |
| 1953 | * compare it with the expected value. Handle atomic faults internally. |
| 1954 | * Return with the hb lock held and a q.key reference on success, and unlocked |
| 1955 | * with no q.key reference on failure. |
| 1956 | * |
| 1957 | * Return: |
| 1958 | * 0 - uaddr contains val and hb has been locked; |
| 1959 | * <1 - -EFAULT or -EWOULDBLOCK (uaddr does not contain val) and hb is unlocked |
| 1960 | */ |
| 1961 | static int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags, |
| 1962 | struct futex_q *q, struct futex_hash_bucket **hb) |
| 1963 | { |
| 1964 | u32 uval; |
| 1965 | int ret; |
| 1966 | |
| 1967 | /* |
| 1968 | * Access the page AFTER the hash-bucket is locked. |
| 1969 | * Order is important: |
| 1970 | * |
| 1971 | * Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val); |
| 1972 | * Userspace waker: if (cond(var)) { var = new; futex_wake(&var); } |
| 1973 | * |
| 1974 | * The basic logical guarantee of a futex is that it blocks ONLY |
| 1975 | * if cond(var) is known to be true at the time of blocking, for |
| 1976 | * any cond. If we locked the hash-bucket after testing *uaddr, that |
| 1977 | * would open a race condition where we could block indefinitely with |
| 1978 | * cond(var) false, which would violate the guarantee. |
| 1979 | * |
| 1980 | * On the other hand, we insert q and release the hash-bucket only |
| 1981 | * after testing *uaddr. This guarantees that futex_wait() will NOT |
| 1982 | * absorb a wakeup if *uaddr does not match the desired values |
| 1983 | * while the syscall executes. |
| 1984 | */ |
| 1985 | retry: |
| 1986 | ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q->key, VERIFY_READ); |
| 1987 | if (unlikely(ret != 0)) |
| 1988 | return ret; |
| 1989 | |
| 1990 | retry_private: |
| 1991 | *hb = queue_lock(q); |
| 1992 | |
| 1993 | ret = get_futex_value_locked(&uval, uaddr); |
| 1994 | |
| 1995 | if (ret) { |
| 1996 | queue_unlock(q, *hb); |
| 1997 | |
| 1998 | ret = get_user(uval, uaddr); |
| 1999 | if (ret) |
| 2000 | goto out; |
| 2001 | |
| 2002 | if (!(flags & FLAGS_SHARED)) |
| 2003 | goto retry_private; |
| 2004 | |
| 2005 | put_futex_key(&q->key); |
| 2006 | goto retry; |
| 2007 | } |
| 2008 | |
| 2009 | if (uval != val) { |
| 2010 | queue_unlock(q, *hb); |
| 2011 | ret = -EWOULDBLOCK; |
| 2012 | } |
| 2013 | |
| 2014 | out: |
| 2015 | if (ret) |
| 2016 | put_futex_key(&q->key); |
| 2017 | return ret; |
| 2018 | } |
| 2019 | |
| 2020 | static int futex_wait(u32 __user *uaddr, unsigned int flags, u32 val, |
| 2021 | ktime_t *abs_time, u32 bitset) |
| 2022 | { |
| 2023 | struct hrtimer_sleeper timeout, *to = NULL; |
| 2024 | struct restart_block *restart; |
| 2025 | struct futex_hash_bucket *hb; |
| 2026 | struct futex_q q = futex_q_init; |
| 2027 | int ret; |
| 2028 | |
| 2029 | if (!bitset) |
| 2030 | return -EINVAL; |
| 2031 | q.bitset = bitset; |
| 2032 | |
| 2033 | if (abs_time) { |
| 2034 | to = &timeout; |
| 2035 | |
| 2036 | hrtimer_init_on_stack(&to->timer, (flags & FLAGS_CLOCKRT) ? |
| 2037 | CLOCK_REALTIME : CLOCK_MONOTONIC, |
| 2038 | HRTIMER_MODE_ABS); |
| 2039 | hrtimer_init_sleeper(to, current); |
| 2040 | hrtimer_set_expires_range_ns(&to->timer, *abs_time, |
| 2041 | current->timer_slack_ns); |
| 2042 | } |
| 2043 | |
| 2044 | retry: |
| 2045 | /* |
| 2046 | * Prepare to wait on uaddr. On success, holds hb lock and increments |
| 2047 | * q.key refs. |
| 2048 | */ |
| 2049 | ret = futex_wait_setup(uaddr, val, flags, &q, &hb); |
| 2050 | if (ret) |
| 2051 | goto out; |
| 2052 | |
| 2053 | /* queue_me and wait for wakeup, timeout, or a signal. */ |
| 2054 | futex_wait_queue_me(hb, &q, to); |
| 2055 | |
| 2056 | /* If we were woken (and unqueued), we succeeded, whatever. */ |
| 2057 | ret = 0; |
| 2058 | /* unqueue_me() drops q.key ref */ |
| 2059 | if (!unqueue_me(&q)) |
| 2060 | goto out; |
| 2061 | ret = -ETIMEDOUT; |
| 2062 | if (to && !to->task) |
| 2063 | goto out; |
| 2064 | |
| 2065 | /* |
| 2066 | * We expect signal_pending(current), but we might be the |
| 2067 | * victim of a spurious wakeup as well. |
| 2068 | */ |
| 2069 | if (!signal_pending(current)) |
| 2070 | goto retry; |
| 2071 | |
| 2072 | ret = -ERESTARTSYS; |
| 2073 | if (!abs_time) |
| 2074 | goto out; |
| 2075 | |
| 2076 | restart = ¤t_thread_info()->restart_block; |
| 2077 | restart->fn = futex_wait_restart; |
| 2078 | restart->futex.uaddr = uaddr; |
| 2079 | restart->futex.val = val; |
| 2080 | restart->futex.time = abs_time->tv64; |
| 2081 | restart->futex.bitset = bitset; |
| 2082 | restart->futex.flags = flags | FLAGS_HAS_TIMEOUT; |
| 2083 | |
| 2084 | ret = -ERESTART_RESTARTBLOCK; |
| 2085 | |
| 2086 | out: |
| 2087 | if (to) { |
| 2088 | hrtimer_cancel(&to->timer); |
| 2089 | destroy_hrtimer_on_stack(&to->timer); |
| 2090 | } |
| 2091 | return ret; |
| 2092 | } |
| 2093 | |
| 2094 | |
| 2095 | static long futex_wait_restart(struct restart_block *restart) |
| 2096 | { |
| 2097 | u32 __user *uaddr = restart->futex.uaddr; |
| 2098 | ktime_t t, *tp = NULL; |
| 2099 | |
| 2100 | if (restart->futex.flags & FLAGS_HAS_TIMEOUT) { |
| 2101 | t.tv64 = restart->futex.time; |
| 2102 | tp = &t; |
| 2103 | } |
| 2104 | restart->fn = do_no_restart_syscall; |
| 2105 | |
| 2106 | return (long)futex_wait(uaddr, restart->futex.flags, |
| 2107 | restart->futex.val, tp, restart->futex.bitset); |
| 2108 | } |
| 2109 | |
| 2110 | |
| 2111 | /* |
| 2112 | * Userspace tried a 0 -> TID atomic transition of the futex value |
| 2113 | * and failed. The kernel side here does the whole locking operation: |
| 2114 | * if there are waiters then it will block, it does PI, etc. (Due to |
| 2115 | * races the kernel might see a 0 value of the futex too.) |
| 2116 | */ |
| 2117 | static int futex_lock_pi(u32 __user *uaddr, unsigned int flags, int detect, |
| 2118 | ktime_t *time, int trylock) |
| 2119 | { |
| 2120 | struct hrtimer_sleeper timeout, *to = NULL; |
| 2121 | struct futex_hash_bucket *hb; |
| 2122 | struct futex_q q = futex_q_init; |
| 2123 | int res, ret; |
| 2124 | |
| 2125 | if (refill_pi_state_cache()) |
| 2126 | return -ENOMEM; |
| 2127 | |
| 2128 | if (time) { |
| 2129 | to = &timeout; |
| 2130 | hrtimer_init_on_stack(&to->timer, CLOCK_REALTIME, |
| 2131 | HRTIMER_MODE_ABS); |
| 2132 | hrtimer_init_sleeper(to, current); |
| 2133 | hrtimer_set_expires(&to->timer, *time); |
| 2134 | } |
| 2135 | |
| 2136 | retry: |
| 2137 | ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q.key, VERIFY_WRITE); |
| 2138 | if (unlikely(ret != 0)) |
| 2139 | goto out; |
| 2140 | |
| 2141 | retry_private: |
| 2142 | hb = queue_lock(&q); |
| 2143 | |
| 2144 | ret = futex_lock_pi_atomic(uaddr, hb, &q.key, &q.pi_state, current, 0); |
| 2145 | if (unlikely(ret)) { |
| 2146 | switch (ret) { |
| 2147 | case 1: |
| 2148 | /* We got the lock. */ |
| 2149 | ret = 0; |
| 2150 | goto out_unlock_put_key; |
| 2151 | case -EFAULT: |
| 2152 | goto uaddr_faulted; |
| 2153 | case -EAGAIN: |
| 2154 | /* |
| 2155 | * Task is exiting and we just wait for the |
| 2156 | * exit to complete. |
| 2157 | */ |
| 2158 | queue_unlock(&q, hb); |
| 2159 | put_futex_key(&q.key); |
| 2160 | cond_resched(); |
| 2161 | goto retry; |
| 2162 | default: |
| 2163 | goto out_unlock_put_key; |
| 2164 | } |
| 2165 | } |
| 2166 | |
| 2167 | /* |
| 2168 | * Only actually queue now that the atomic ops are done: |
| 2169 | */ |
| 2170 | queue_me(&q, hb); |
| 2171 | |
| 2172 | WARN_ON(!q.pi_state); |
| 2173 | /* |
| 2174 | * Block on the PI mutex: |
| 2175 | */ |
| 2176 | if (!trylock) |
| 2177 | ret = rt_mutex_timed_lock(&q.pi_state->pi_mutex, to, 1); |
| 2178 | else { |
| 2179 | ret = rt_mutex_trylock(&q.pi_state->pi_mutex); |
| 2180 | /* Fixup the trylock return value: */ |
| 2181 | ret = ret ? 0 : -EWOULDBLOCK; |
| 2182 | } |
| 2183 | |
| 2184 | spin_lock(q.lock_ptr); |
| 2185 | /* |
| 2186 | * Fixup the pi_state owner and possibly acquire the lock if we |
| 2187 | * haven't already. |
| 2188 | */ |
| 2189 | res = fixup_owner(uaddr, &q, !ret); |
| 2190 | /* |
| 2191 | * If fixup_owner() returned an error, proprogate that. If it acquired |
| 2192 | * the lock, clear our -ETIMEDOUT or -EINTR. |
| 2193 | */ |
| 2194 | if (res) |
| 2195 | ret = (res < 0) ? res : 0; |
| 2196 | |
| 2197 | /* |
| 2198 | * If fixup_owner() faulted and was unable to handle the fault, unlock |
| 2199 | * it and return the fault to userspace. |
| 2200 | */ |
| 2201 | if (ret && (rt_mutex_owner(&q.pi_state->pi_mutex) == current)) |
| 2202 | rt_mutex_unlock(&q.pi_state->pi_mutex); |
| 2203 | |
| 2204 | /* Unqueue and drop the lock */ |
| 2205 | unqueue_me_pi(&q); |
| 2206 | |
| 2207 | goto out_put_key; |
| 2208 | |
| 2209 | out_unlock_put_key: |
| 2210 | queue_unlock(&q, hb); |
| 2211 | |
| 2212 | out_put_key: |
| 2213 | put_futex_key(&q.key); |
| 2214 | out: |
| 2215 | if (to) |
| 2216 | destroy_hrtimer_on_stack(&to->timer); |
| 2217 | return ret != -EINTR ? ret : -ERESTARTNOINTR; |
| 2218 | |
| 2219 | uaddr_faulted: |
| 2220 | queue_unlock(&q, hb); |
| 2221 | |
| 2222 | ret = fault_in_user_writeable(uaddr); |
| 2223 | if (ret) |
| 2224 | goto out_put_key; |
| 2225 | |
| 2226 | if (!(flags & FLAGS_SHARED)) |
| 2227 | goto retry_private; |
| 2228 | |
| 2229 | put_futex_key(&q.key); |
| 2230 | goto retry; |
| 2231 | } |
| 2232 | |
| 2233 | /* |
| 2234 | * Userspace attempted a TID -> 0 atomic transition, and failed. |
| 2235 | * This is the in-kernel slowpath: we look up the PI state (if any), |
| 2236 | * and do the rt-mutex unlock. |
| 2237 | */ |
| 2238 | static int futex_unlock_pi(u32 __user *uaddr, unsigned int flags) |
| 2239 | { |
| 2240 | struct futex_hash_bucket *hb; |
| 2241 | struct futex_q *this, *next; |
| 2242 | struct plist_head *head; |
| 2243 | union futex_key key = FUTEX_KEY_INIT; |
| 2244 | u32 uval, vpid = task_pid_vnr(current); |
| 2245 | int ret; |
| 2246 | |
| 2247 | retry: |
| 2248 | if (get_user(uval, uaddr)) |
| 2249 | return -EFAULT; |
| 2250 | /* |
| 2251 | * We release only a lock we actually own: |
| 2252 | */ |
| 2253 | if ((uval & FUTEX_TID_MASK) != vpid) |
| 2254 | return -EPERM; |
| 2255 | |
| 2256 | ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key, VERIFY_WRITE); |
| 2257 | if (unlikely(ret != 0)) |
| 2258 | goto out; |
| 2259 | |
| 2260 | hb = hash_futex(&key); |
| 2261 | spin_lock(&hb->lock); |
| 2262 | |
| 2263 | /* |
| 2264 | * To avoid races, try to do the TID -> 0 atomic transition |
| 2265 | * again. If it succeeds then we can return without waking |
| 2266 | * anyone else up. We only try this if neither the waiters nor |
| 2267 | * the owner died bit are set. |
| 2268 | */ |
| 2269 | if (!(uval & ~FUTEX_TID_MASK) && |
| 2270 | cmpxchg_futex_value_locked(&uval, uaddr, vpid, 0)) |
| 2271 | goto pi_faulted; |
| 2272 | /* |
| 2273 | * Rare case: we managed to release the lock atomically, |
| 2274 | * no need to wake anyone else up: |
| 2275 | */ |
| 2276 | if (unlikely(uval == vpid)) |
| 2277 | goto out_unlock; |
| 2278 | |
| 2279 | /* |
| 2280 | * Ok, other tasks may need to be woken up - check waiters |
| 2281 | * and do the wakeup if necessary: |
| 2282 | */ |
| 2283 | head = &hb->chain; |
| 2284 | |
| 2285 | plist_for_each_entry_safe(this, next, head, list) { |
| 2286 | if (!match_futex (&this->key, &key)) |
| 2287 | continue; |
| 2288 | ret = wake_futex_pi(uaddr, uval, this); |
| 2289 | /* |
| 2290 | * The atomic access to the futex value |
| 2291 | * generated a pagefault, so retry the |
| 2292 | * user-access and the wakeup: |
| 2293 | */ |
| 2294 | if (ret == -EFAULT) |
| 2295 | goto pi_faulted; |
| 2296 | goto out_unlock; |
| 2297 | } |
| 2298 | /* |
| 2299 | * No waiters - kernel unlocks the futex: |
| 2300 | */ |
| 2301 | ret = unlock_futex_pi(uaddr, uval); |
| 2302 | if (ret == -EFAULT) |
| 2303 | goto pi_faulted; |
| 2304 | |
| 2305 | out_unlock: |
| 2306 | spin_unlock(&hb->lock); |
| 2307 | put_futex_key(&key); |
| 2308 | |
| 2309 | out: |
| 2310 | return ret; |
| 2311 | |
| 2312 | pi_faulted: |
| 2313 | spin_unlock(&hb->lock); |
| 2314 | put_futex_key(&key); |
| 2315 | |
| 2316 | ret = fault_in_user_writeable(uaddr); |
| 2317 | if (!ret) |
| 2318 | goto retry; |
| 2319 | |
| 2320 | return ret; |
| 2321 | } |
| 2322 | |
| 2323 | /** |
| 2324 | * handle_early_requeue_pi_wakeup() - Detect early wakeup on the initial futex |
| 2325 | * @hb: the hash_bucket futex_q was original enqueued on |
| 2326 | * @q: the futex_q woken while waiting to be requeued |
| 2327 | * @key2: the futex_key of the requeue target futex |
| 2328 | * @timeout: the timeout associated with the wait (NULL if none) |
| 2329 | * |
| 2330 | * Detect if the task was woken on the initial futex as opposed to the requeue |
| 2331 | * target futex. If so, determine if it was a timeout or a signal that caused |
| 2332 | * the wakeup and return the appropriate error code to the caller. Must be |
| 2333 | * called with the hb lock held. |
| 2334 | * |
| 2335 | * Return: |
| 2336 | * 0 = no early wakeup detected; |
| 2337 | * <0 = -ETIMEDOUT or -ERESTARTNOINTR |
| 2338 | */ |
| 2339 | static inline |
| 2340 | int handle_early_requeue_pi_wakeup(struct futex_hash_bucket *hb, |
| 2341 | struct futex_q *q, union futex_key *key2, |
| 2342 | struct hrtimer_sleeper *timeout) |
| 2343 | { |
| 2344 | int ret = 0; |
| 2345 | |
| 2346 | /* |
| 2347 | * With the hb lock held, we avoid races while we process the wakeup. |
| 2348 | * We only need to hold hb (and not hb2) to ensure atomicity as the |
| 2349 | * wakeup code can't change q.key from uaddr to uaddr2 if we hold hb. |
| 2350 | * It can't be requeued from uaddr2 to something else since we don't |
| 2351 | * support a PI aware source futex for requeue. |
| 2352 | */ |
| 2353 | if (!match_futex(&q->key, key2)) { |
| 2354 | WARN_ON(q->lock_ptr && (&hb->lock != q->lock_ptr)); |
| 2355 | /* |
| 2356 | * We were woken prior to requeue by a timeout or a signal. |
| 2357 | * Unqueue the futex_q and determine which it was. |
| 2358 | */ |
| 2359 | plist_del(&q->list, &hb->chain); |
| 2360 | |
| 2361 | /* Handle spurious wakeups gracefully */ |
| 2362 | ret = -EWOULDBLOCK; |
| 2363 | if (timeout && !timeout->task) |
| 2364 | ret = -ETIMEDOUT; |
| 2365 | else if (signal_pending(current)) |
| 2366 | ret = -ERESTARTNOINTR; |
| 2367 | } |
| 2368 | return ret; |
| 2369 | } |
| 2370 | |
| 2371 | /** |
| 2372 | * futex_wait_requeue_pi() - Wait on uaddr and take uaddr2 |
| 2373 | * @uaddr: the futex we initially wait on (non-pi) |
| 2374 | * @flags: futex flags (FLAGS_SHARED, FLAGS_CLOCKRT, etc.), they must be |
| 2375 | * the same type, no requeueing from private to shared, etc. |
| 2376 | * @val: the expected value of uaddr |
| 2377 | * @abs_time: absolute timeout |
| 2378 | * @bitset: 32 bit wakeup bitset set by userspace, defaults to all |
| 2379 | * @uaddr2: the pi futex we will take prior to returning to user-space |
| 2380 | * |
| 2381 | * The caller will wait on uaddr and will be requeued by futex_requeue() to |
| 2382 | * uaddr2 which must be PI aware and unique from uaddr. Normal wakeup will wake |
| 2383 | * on uaddr2 and complete the acquisition of the rt_mutex prior to returning to |
| 2384 | * userspace. This ensures the rt_mutex maintains an owner when it has waiters; |
| 2385 | * without one, the pi logic would not know which task to boost/deboost, if |
| 2386 | * there was a need to. |
| 2387 | * |
| 2388 | * We call schedule in futex_wait_queue_me() when we enqueue and return there |
| 2389 | * via the following-- |
| 2390 | * 1) wakeup on uaddr2 after an atomic lock acquisition by futex_requeue() |
| 2391 | * 2) wakeup on uaddr2 after a requeue |
| 2392 | * 3) signal |
| 2393 | * 4) timeout |
| 2394 | * |
| 2395 | * If 3, cleanup and return -ERESTARTNOINTR. |
| 2396 | * |
| 2397 | * If 2, we may then block on trying to take the rt_mutex and return via: |
| 2398 | * 5) successful lock |
| 2399 | * 6) signal |
| 2400 | * 7) timeout |
| 2401 | * 8) other lock acquisition failure |
| 2402 | * |
| 2403 | * If 6, return -EWOULDBLOCK (restarting the syscall would do the same). |
| 2404 | * |
| 2405 | * If 4 or 7, we cleanup and return with -ETIMEDOUT. |
| 2406 | * |
| 2407 | * Return: |
| 2408 | * 0 - On success; |
| 2409 | * <0 - On error |
| 2410 | */ |
| 2411 | static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags, |
| 2412 | u32 val, ktime_t *abs_time, u32 bitset, |
| 2413 | u32 __user *uaddr2) |
| 2414 | { |
| 2415 | struct hrtimer_sleeper timeout, *to = NULL; |
| 2416 | struct rt_mutex_waiter rt_waiter; |
| 2417 | struct futex_hash_bucket *hb; |
| 2418 | union futex_key key2 = FUTEX_KEY_INIT; |
| 2419 | struct futex_q q = futex_q_init; |
| 2420 | int res, ret; |
| 2421 | |
| 2422 | if (uaddr == uaddr2) |
| 2423 | return -EINVAL; |
| 2424 | |
| 2425 | if (!bitset) |
| 2426 | return -EINVAL; |
| 2427 | |
| 2428 | if (abs_time) { |
| 2429 | to = &timeout; |
| 2430 | hrtimer_init_on_stack(&to->timer, (flags & FLAGS_CLOCKRT) ? |
| 2431 | CLOCK_REALTIME : CLOCK_MONOTONIC, |
| 2432 | HRTIMER_MODE_ABS); |
| 2433 | hrtimer_init_sleeper(to, current); |
| 2434 | hrtimer_set_expires_range_ns(&to->timer, *abs_time, |
| 2435 | current->timer_slack_ns); |
| 2436 | } |
| 2437 | |
| 2438 | /* |
| 2439 | * The waiter is allocated on our stack, manipulated by the requeue |
| 2440 | * code while we sleep on uaddr. |
| 2441 | */ |
| 2442 | debug_rt_mutex_init_waiter(&rt_waiter); |
| 2443 | rt_waiter.task = NULL; |
| 2444 | |
| 2445 | ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, VERIFY_WRITE); |
| 2446 | if (unlikely(ret != 0)) |
| 2447 | goto out; |
| 2448 | |
| 2449 | q.bitset = bitset; |
| 2450 | q.rt_waiter = &rt_waiter; |
| 2451 | q.requeue_pi_key = &key2; |
| 2452 | |
| 2453 | /* |
| 2454 | * Prepare to wait on uaddr. On success, increments q.key (key1) ref |
| 2455 | * count. |
| 2456 | */ |
| 2457 | ret = futex_wait_setup(uaddr, val, flags, &q, &hb); |
| 2458 | if (ret) |
| 2459 | goto out_key2; |
| 2460 | |
| 2461 | /* |
| 2462 | * The check above which compares uaddrs is not sufficient for |
| 2463 | * shared futexes. We need to compare the keys: |
| 2464 | */ |
| 2465 | if (match_futex(&q.key, &key2)) { |
| 2466 | ret = -EINVAL; |
| 2467 | goto out_put_keys; |
| 2468 | } |
| 2469 | |
| 2470 | /* Queue the futex_q, drop the hb lock, wait for wakeup. */ |
| 2471 | futex_wait_queue_me(hb, &q, to); |
| 2472 | |
| 2473 | spin_lock(&hb->lock); |
| 2474 | ret = handle_early_requeue_pi_wakeup(hb, &q, &key2, to); |
| 2475 | spin_unlock(&hb->lock); |
| 2476 | if (ret) |
| 2477 | goto out_put_keys; |
| 2478 | |
| 2479 | /* |
| 2480 | * In order for us to be here, we know our q.key == key2, and since |
| 2481 | * we took the hb->lock above, we also know that futex_requeue() has |
| 2482 | * completed and we no longer have to concern ourselves with a wakeup |
| 2483 | * race with the atomic proxy lock acquisition by the requeue code. The |
| 2484 | * futex_requeue dropped our key1 reference and incremented our key2 |
| 2485 | * reference count. |
| 2486 | */ |
| 2487 | |
| 2488 | /* Check if the requeue code acquired the second futex for us. */ |
| 2489 | if (!q.rt_waiter) { |
| 2490 | /* |
| 2491 | * Got the lock. We might not be the anticipated owner if we |
| 2492 | * did a lock-steal - fix up the PI-state in that case. |
| 2493 | */ |
| 2494 | if (q.pi_state && (q.pi_state->owner != current)) { |
| 2495 | spin_lock(q.lock_ptr); |
| 2496 | ret = fixup_pi_state_owner(uaddr2, &q, current); |
| 2497 | if (ret && rt_mutex_owner(&q.pi_state->pi_mutex) == current) |
| 2498 | rt_mutex_unlock(&q.pi_state->pi_mutex); |
| 2499 | /* |
| 2500 | * Drop the reference to the pi state which |
| 2501 | * the requeue_pi() code acquired for us. |
| 2502 | */ |
| 2503 | free_pi_state(q.pi_state); |
| 2504 | spin_unlock(q.lock_ptr); |
| 2505 | } |
| 2506 | } else { |
| 2507 | struct rt_mutex *pi_mutex; |
| 2508 | |
| 2509 | /* |
| 2510 | * We have been woken up by futex_unlock_pi(), a timeout, or a |
| 2511 | * signal. futex_unlock_pi() will not destroy the lock_ptr nor |
| 2512 | * the pi_state. |
| 2513 | */ |
| 2514 | WARN_ON(!q.pi_state); |
| 2515 | pi_mutex = &q.pi_state->pi_mutex; |
| 2516 | ret = rt_mutex_finish_proxy_lock(pi_mutex, to, &rt_waiter, 1); |
| 2517 | debug_rt_mutex_free_waiter(&rt_waiter); |
| 2518 | |
| 2519 | spin_lock(q.lock_ptr); |
| 2520 | /* |
| 2521 | * Fixup the pi_state owner and possibly acquire the lock if we |
| 2522 | * haven't already. |
| 2523 | */ |
| 2524 | res = fixup_owner(uaddr2, &q, !ret); |
| 2525 | /* |
| 2526 | * If fixup_owner() returned an error, proprogate that. If it |
| 2527 | * acquired the lock, clear -ETIMEDOUT or -EINTR. |
| 2528 | */ |
| 2529 | if (res) |
| 2530 | ret = (res < 0) ? res : 0; |
| 2531 | |
| 2532 | /* |
| 2533 | * If fixup_pi_state_owner() faulted and was unable to handle |
| 2534 | * the fault, unlock the rt_mutex and return the fault to |
| 2535 | * userspace. |
| 2536 | */ |
| 2537 | if (ret && rt_mutex_owner(pi_mutex) == current) |
| 2538 | rt_mutex_unlock(pi_mutex); |
| 2539 | |
| 2540 | /* Unqueue and drop the lock. */ |
| 2541 | unqueue_me_pi(&q); |
| 2542 | } |
| 2543 | |
| 2544 | if (ret == -EINTR) { |
| 2545 | /* |
| 2546 | * We've already been requeued, but cannot restart by calling |
| 2547 | * futex_lock_pi() directly. We could restart this syscall, but |
| 2548 | * it would detect that the user space "val" changed and return |
| 2549 | * -EWOULDBLOCK. Save the overhead of the restart and return |
| 2550 | * -EWOULDBLOCK directly. |
| 2551 | */ |
| 2552 | ret = -EWOULDBLOCK; |
| 2553 | } |
| 2554 | |
| 2555 | out_put_keys: |
| 2556 | put_futex_key(&q.key); |
| 2557 | out_key2: |
| 2558 | put_futex_key(&key2); |
| 2559 | |
| 2560 | out: |
| 2561 | if (to) { |
| 2562 | hrtimer_cancel(&to->timer); |
| 2563 | destroy_hrtimer_on_stack(&to->timer); |
| 2564 | } |
| 2565 | return ret; |
| 2566 | } |
| 2567 | |
| 2568 | /* |
| 2569 | * Support for robust futexes: the kernel cleans up held futexes at |
| 2570 | * thread exit time. |
| 2571 | * |
| 2572 | * Implementation: user-space maintains a per-thread list of locks it |
| 2573 | * is holding. Upon do_exit(), the kernel carefully walks this list, |
| 2574 | * and marks all locks that are owned by this thread with the |
| 2575 | * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is |
| 2576 | * always manipulated with the lock held, so the list is private and |
| 2577 | * per-thread. Userspace also maintains a per-thread 'list_op_pending' |
| 2578 | * field, to allow the kernel to clean up if the thread dies after |
| 2579 | * acquiring the lock, but just before it could have added itself to |
| 2580 | * the list. There can only be one such pending lock. |
| 2581 | */ |
| 2582 | |
| 2583 | /** |
| 2584 | * sys_set_robust_list() - Set the robust-futex list head of a task |
| 2585 | * @head: pointer to the list-head |
| 2586 | * @len: length of the list-head, as userspace expects |
| 2587 | */ |
| 2588 | SYSCALL_DEFINE2(set_robust_list, struct robust_list_head __user *, head, |
| 2589 | size_t, len) |
| 2590 | { |
| 2591 | if (!futex_cmpxchg_enabled) |
| 2592 | return -ENOSYS; |
| 2593 | /* |
| 2594 | * The kernel knows only one size for now: |
| 2595 | */ |
| 2596 | if (unlikely(len != sizeof(*head))) |
| 2597 | return -EINVAL; |
| 2598 | |
| 2599 | current->robust_list = head; |
| 2600 | |
| 2601 | return 0; |
| 2602 | } |
| 2603 | |
| 2604 | /** |
| 2605 | * sys_get_robust_list() - Get the robust-futex list head of a task |
| 2606 | * @pid: pid of the process [zero for current task] |
| 2607 | * @head_ptr: pointer to a list-head pointer, the kernel fills it in |
| 2608 | * @len_ptr: pointer to a length field, the kernel fills in the header size |
| 2609 | */ |
| 2610 | SYSCALL_DEFINE3(get_robust_list, int, pid, |
| 2611 | struct robust_list_head __user * __user *, head_ptr, |
| 2612 | size_t __user *, len_ptr) |
| 2613 | { |
| 2614 | struct robust_list_head __user *head; |
| 2615 | unsigned long ret; |
| 2616 | struct task_struct *p; |
| 2617 | |
| 2618 | if (!futex_cmpxchg_enabled) |
| 2619 | return -ENOSYS; |
| 2620 | |
| 2621 | rcu_read_lock(); |
| 2622 | |
| 2623 | ret = -ESRCH; |
| 2624 | if (!pid) |
| 2625 | p = current; |
| 2626 | else { |
| 2627 | p = find_task_by_vpid(pid); |
| 2628 | if (!p) |
| 2629 | goto err_unlock; |
| 2630 | } |
| 2631 | |
| 2632 | ret = -EPERM; |
| 2633 | if (!ptrace_may_access(p, PTRACE_MODE_READ_REALCREDS)) |
| 2634 | goto err_unlock; |
| 2635 | |
| 2636 | head = p->robust_list; |
| 2637 | rcu_read_unlock(); |
| 2638 | |
| 2639 | if (put_user(sizeof(*head), len_ptr)) |
| 2640 | return -EFAULT; |
| 2641 | return put_user(head, head_ptr); |
| 2642 | |
| 2643 | err_unlock: |
| 2644 | rcu_read_unlock(); |
| 2645 | |
| 2646 | return ret; |
| 2647 | } |
| 2648 | |
| 2649 | /* |
| 2650 | * Process a futex-list entry, check whether it's owned by the |
| 2651 | * dying task, and do notification if so: |
| 2652 | */ |
| 2653 | int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi) |
| 2654 | { |
| 2655 | u32 uval, uninitialized_var(nval), mval; |
| 2656 | |
| 2657 | retry: |
| 2658 | if (get_user(uval, uaddr)) |
| 2659 | return -1; |
| 2660 | |
| 2661 | if ((uval & FUTEX_TID_MASK) == task_pid_vnr(curr)) { |
| 2662 | /* |
| 2663 | * Ok, this dying thread is truly holding a futex |
| 2664 | * of interest. Set the OWNER_DIED bit atomically |
| 2665 | * via cmpxchg, and if the value had FUTEX_WAITERS |
| 2666 | * set, wake up a waiter (if any). (We have to do a |
| 2667 | * futex_wake() even if OWNER_DIED is already set - |
| 2668 | * to handle the rare but possible case of recursive |
| 2669 | * thread-death.) The rest of the cleanup is done in |
| 2670 | * userspace. |
| 2671 | */ |
| 2672 | mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED; |
| 2673 | /* |
| 2674 | * We are not holding a lock here, but we want to have |
| 2675 | * the pagefault_disable/enable() protection because |
| 2676 | * we want to handle the fault gracefully. If the |
| 2677 | * access fails we try to fault in the futex with R/W |
| 2678 | * verification via get_user_pages. get_user() above |
| 2679 | * does not guarantee R/W access. If that fails we |
| 2680 | * give up and leave the futex locked. |
| 2681 | */ |
| 2682 | if (cmpxchg_futex_value_locked(&nval, uaddr, uval, mval)) { |
| 2683 | if (fault_in_user_writeable(uaddr)) |
| 2684 | return -1; |
| 2685 | goto retry; |
| 2686 | } |
| 2687 | if (nval != uval) |
| 2688 | goto retry; |
| 2689 | |
| 2690 | /* |
| 2691 | * Wake robust non-PI futexes here. The wakeup of |
| 2692 | * PI futexes happens in exit_pi_state(): |
| 2693 | */ |
| 2694 | if (!pi && (uval & FUTEX_WAITERS)) |
| 2695 | futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY); |
| 2696 | } |
| 2697 | return 0; |
| 2698 | } |
| 2699 | |
| 2700 | /* |
| 2701 | * Fetch a robust-list pointer. Bit 0 signals PI futexes: |
| 2702 | */ |
| 2703 | static inline int fetch_robust_entry(struct robust_list __user **entry, |
| 2704 | struct robust_list __user * __user *head, |
| 2705 | unsigned int *pi) |
| 2706 | { |
| 2707 | unsigned long uentry; |
| 2708 | |
| 2709 | if (get_user(uentry, (unsigned long __user *)head)) |
| 2710 | return -EFAULT; |
| 2711 | |
| 2712 | *entry = (void __user *)(uentry & ~1UL); |
| 2713 | *pi = uentry & 1; |
| 2714 | |
| 2715 | return 0; |
| 2716 | } |
| 2717 | |
| 2718 | /* |
| 2719 | * Walk curr->robust_list (very carefully, it's a userspace list!) |
| 2720 | * and mark any locks found there dead, and notify any waiters. |
| 2721 | * |
| 2722 | * We silently return on any sign of list-walking problem. |
| 2723 | */ |
| 2724 | void exit_robust_list(struct task_struct *curr) |
| 2725 | { |
| 2726 | struct robust_list_head __user *head = curr->robust_list; |
| 2727 | struct robust_list __user *entry, *next_entry, *pending; |
| 2728 | unsigned int limit = ROBUST_LIST_LIMIT, pi, pip; |
| 2729 | unsigned int uninitialized_var(next_pi); |
| 2730 | unsigned long futex_offset; |
| 2731 | int rc; |
| 2732 | |
| 2733 | if (!futex_cmpxchg_enabled) |
| 2734 | return; |
| 2735 | |
| 2736 | /* |
| 2737 | * Fetch the list head (which was registered earlier, via |
| 2738 | * sys_set_robust_list()): |
| 2739 | */ |
| 2740 | if (fetch_robust_entry(&entry, &head->list.next, &pi)) |
| 2741 | return; |
| 2742 | /* |
| 2743 | * Fetch the relative futex offset: |
| 2744 | */ |
| 2745 | if (get_user(futex_offset, &head->futex_offset)) |
| 2746 | return; |
| 2747 | /* |
| 2748 | * Fetch any possibly pending lock-add first, and handle it |
| 2749 | * if it exists: |
| 2750 | */ |
| 2751 | if (fetch_robust_entry(&pending, &head->list_op_pending, &pip)) |
| 2752 | return; |
| 2753 | |
| 2754 | next_entry = NULL; /* avoid warning with gcc */ |
| 2755 | while (entry != &head->list) { |
| 2756 | /* |
| 2757 | * Fetch the next entry in the list before calling |
| 2758 | * handle_futex_death: |
| 2759 | */ |
| 2760 | rc = fetch_robust_entry(&next_entry, &entry->next, &next_pi); |
| 2761 | /* |
| 2762 | * A pending lock might already be on the list, so |
| 2763 | * don't process it twice: |
| 2764 | */ |
| 2765 | if (entry != pending) |
| 2766 | if (handle_futex_death((void __user *)entry + futex_offset, |
| 2767 | curr, pi)) |
| 2768 | return; |
| 2769 | if (rc) |
| 2770 | return; |
| 2771 | entry = next_entry; |
| 2772 | pi = next_pi; |
| 2773 | /* |
| 2774 | * Avoid excessively long or circular lists: |
| 2775 | */ |
| 2776 | if (!--limit) |
| 2777 | break; |
| 2778 | |
| 2779 | cond_resched(); |
| 2780 | } |
| 2781 | |
| 2782 | if (pending) |
| 2783 | handle_futex_death((void __user *)pending + futex_offset, |
| 2784 | curr, pip); |
| 2785 | } |
| 2786 | |
| 2787 | long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout, |
| 2788 | u32 __user *uaddr2, u32 val2, u32 val3) |
| 2789 | { |
| 2790 | int cmd = op & FUTEX_CMD_MASK; |
| 2791 | unsigned int flags = 0; |
| 2792 | |
| 2793 | if (!(op & FUTEX_PRIVATE_FLAG)) |
| 2794 | flags |= FLAGS_SHARED; |
| 2795 | |
| 2796 | if (op & FUTEX_CLOCK_REALTIME) { |
| 2797 | flags |= FLAGS_CLOCKRT; |
| 2798 | if (cmd != FUTEX_WAIT_BITSET && cmd != FUTEX_WAIT_REQUEUE_PI) |
| 2799 | return -ENOSYS; |
| 2800 | } |
| 2801 | |
| 2802 | switch (cmd) { |
| 2803 | case FUTEX_LOCK_PI: |
| 2804 | case FUTEX_UNLOCK_PI: |
| 2805 | case FUTEX_TRYLOCK_PI: |
| 2806 | case FUTEX_WAIT_REQUEUE_PI: |
| 2807 | case FUTEX_CMP_REQUEUE_PI: |
| 2808 | if (!futex_cmpxchg_enabled) |
| 2809 | return -ENOSYS; |
| 2810 | } |
| 2811 | |
| 2812 | switch (cmd) { |
| 2813 | case FUTEX_WAIT: |
| 2814 | val3 = FUTEX_BITSET_MATCH_ANY; |
| 2815 | case FUTEX_WAIT_BITSET: |
| 2816 | return futex_wait(uaddr, flags, val, timeout, val3); |
| 2817 | case FUTEX_WAKE: |
| 2818 | val3 = FUTEX_BITSET_MATCH_ANY; |
| 2819 | case FUTEX_WAKE_BITSET: |
| 2820 | return futex_wake(uaddr, flags, val, val3); |
| 2821 | case FUTEX_REQUEUE: |
| 2822 | return futex_requeue(uaddr, flags, uaddr2, val, val2, NULL, 0); |
| 2823 | case FUTEX_CMP_REQUEUE: |
| 2824 | return futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 0); |
| 2825 | case FUTEX_WAKE_OP: |
| 2826 | return futex_wake_op(uaddr, flags, uaddr2, val, val2, val3); |
| 2827 | case FUTEX_LOCK_PI: |
| 2828 | return futex_lock_pi(uaddr, flags, val, timeout, 0); |
| 2829 | case FUTEX_UNLOCK_PI: |
| 2830 | return futex_unlock_pi(uaddr, flags); |
| 2831 | case FUTEX_TRYLOCK_PI: |
| 2832 | return futex_lock_pi(uaddr, flags, 0, timeout, 1); |
| 2833 | case FUTEX_WAIT_REQUEUE_PI: |
| 2834 | val3 = FUTEX_BITSET_MATCH_ANY; |
| 2835 | return futex_wait_requeue_pi(uaddr, flags, val, timeout, val3, |
| 2836 | uaddr2); |
| 2837 | case FUTEX_CMP_REQUEUE_PI: |
| 2838 | return futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 1); |
| 2839 | } |
| 2840 | return -ENOSYS; |
| 2841 | } |
| 2842 | |
| 2843 | |
| 2844 | SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val, |
| 2845 | struct timespec __user *, utime, u32 __user *, uaddr2, |
| 2846 | u32, val3) |
| 2847 | { |
| 2848 | struct timespec ts; |
| 2849 | ktime_t t, *tp = NULL; |
| 2850 | u32 val2 = 0; |
| 2851 | int cmd = op & FUTEX_CMD_MASK; |
| 2852 | |
| 2853 | if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI || |
| 2854 | cmd == FUTEX_WAIT_BITSET || |
| 2855 | cmd == FUTEX_WAIT_REQUEUE_PI)) { |
| 2856 | if (copy_from_user(&ts, utime, sizeof(ts)) != 0) |
| 2857 | return -EFAULT; |
| 2858 | if (!timespec_valid(&ts)) |
| 2859 | return -EINVAL; |
| 2860 | |
| 2861 | t = timespec_to_ktime(ts); |
| 2862 | if (cmd == FUTEX_WAIT) |
| 2863 | t = ktime_add_safe(ktime_get(), t); |
| 2864 | tp = &t; |
| 2865 | } |
| 2866 | /* |
| 2867 | * requeue parameter in 'utime' if cmd == FUTEX_*_REQUEUE_*. |
| 2868 | * number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP. |
| 2869 | */ |
| 2870 | if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE || |
| 2871 | cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP) |
| 2872 | val2 = (u32) (unsigned long) utime; |
| 2873 | |
| 2874 | return do_futex(uaddr, op, val, tp, uaddr2, val2, val3); |
| 2875 | } |
| 2876 | |
| 2877 | static void __init futex_detect_cmpxchg(void) |
| 2878 | { |
| 2879 | #ifndef CONFIG_HAVE_FUTEX_CMPXCHG |
| 2880 | u32 curval; |
| 2881 | |
| 2882 | /* |
| 2883 | * This will fail and we want it. Some arch implementations do |
| 2884 | * runtime detection of the futex_atomic_cmpxchg_inatomic() |
| 2885 | * functionality. We want to know that before we call in any |
| 2886 | * of the complex code paths. Also we want to prevent |
| 2887 | * registration of robust lists in that case. NULL is |
| 2888 | * guaranteed to fault and we get -EFAULT on functional |
| 2889 | * implementation, the non-functional ones will return |
| 2890 | * -ENOSYS. |
| 2891 | */ |
| 2892 | if (cmpxchg_futex_value_locked(&curval, NULL, 0, 0) == -EFAULT) |
| 2893 | futex_cmpxchg_enabled = 1; |
| 2894 | #endif |
| 2895 | } |
| 2896 | |
| 2897 | static int __init futex_init(void) |
| 2898 | { |
| 2899 | int i; |
| 2900 | |
| 2901 | futex_detect_cmpxchg(); |
| 2902 | |
| 2903 | for (i = 0; i < ARRAY_SIZE(futex_queues); i++) { |
| 2904 | plist_head_init(&futex_queues[i].chain); |
| 2905 | spin_lock_init(&futex_queues[i].lock); |
| 2906 | } |
| 2907 | |
| 2908 | return 0; |
| 2909 | } |
| 2910 | core_initcall(futex_init); |