| 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 | * Thanks to Ben LaHaise for yelling "hashed waitqueues" loudly |
| 20 | * enough at me, Linus for the original (flawed) idea, Matthew |
| 21 | * Kirkwood for proof-of-concept implementation. |
| 22 | * |
| 23 | * "The futexes are also cursed." |
| 24 | * "But they come in a choice of three flavours!" |
| 25 | * |
| 26 | * This program is free software; you can redistribute it and/or modify |
| 27 | * it under the terms of the GNU General Public License as published by |
| 28 | * the Free Software Foundation; either version 2 of the License, or |
| 29 | * (at your option) any later version. |
| 30 | * |
| 31 | * This program is distributed in the hope that it will be useful, |
| 32 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 33 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 34 | * GNU General Public License for more details. |
| 35 | * |
| 36 | * You should have received a copy of the GNU General Public License |
| 37 | * along with this program; if not, write to the Free Software |
| 38 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
| 39 | */ |
| 40 | #include <linux/slab.h> |
| 41 | #include <linux/poll.h> |
| 42 | #include <linux/fs.h> |
| 43 | #include <linux/file.h> |
| 44 | #include <linux/jhash.h> |
| 45 | #include <linux/init.h> |
| 46 | #include <linux/futex.h> |
| 47 | #include <linux/mount.h> |
| 48 | #include <linux/pagemap.h> |
| 49 | #include <linux/syscalls.h> |
| 50 | #include <linux/signal.h> |
| 51 | #include <asm/futex.h> |
| 52 | |
| 53 | #include "rtmutex_common.h" |
| 54 | |
| 55 | #define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8) |
| 56 | |
| 57 | /* |
| 58 | * Futexes are matched on equal values of this key. |
| 59 | * The key type depends on whether it's a shared or private mapping. |
| 60 | * Don't rearrange members without looking at hash_futex(). |
| 61 | * |
| 62 | * offset is aligned to a multiple of sizeof(u32) (== 4) by definition. |
| 63 | * We set bit 0 to indicate if it's an inode-based key. |
| 64 | */ |
| 65 | union futex_key { |
| 66 | struct { |
| 67 | unsigned long pgoff; |
| 68 | struct inode *inode; |
| 69 | int offset; |
| 70 | } shared; |
| 71 | struct { |
| 72 | unsigned long address; |
| 73 | struct mm_struct *mm; |
| 74 | int offset; |
| 75 | } private; |
| 76 | struct { |
| 77 | unsigned long word; |
| 78 | void *ptr; |
| 79 | int offset; |
| 80 | } both; |
| 81 | }; |
| 82 | |
| 83 | /* |
| 84 | * Priority Inheritance state: |
| 85 | */ |
| 86 | struct futex_pi_state { |
| 87 | /* |
| 88 | * list of 'owned' pi_state instances - these have to be |
| 89 | * cleaned up in do_exit() if the task exits prematurely: |
| 90 | */ |
| 91 | struct list_head list; |
| 92 | |
| 93 | /* |
| 94 | * The PI object: |
| 95 | */ |
| 96 | struct rt_mutex pi_mutex; |
| 97 | |
| 98 | struct task_struct *owner; |
| 99 | atomic_t refcount; |
| 100 | |
| 101 | union futex_key key; |
| 102 | }; |
| 103 | |
| 104 | /* |
| 105 | * We use this hashed waitqueue instead of a normal wait_queue_t, so |
| 106 | * we can wake only the relevant ones (hashed queues may be shared). |
| 107 | * |
| 108 | * A futex_q has a woken state, just like tasks have TASK_RUNNING. |
| 109 | * It is considered woken when list_empty(&q->list) || q->lock_ptr == 0. |
| 110 | * The order of wakup is always to make the first condition true, then |
| 111 | * wake up q->waiters, then make the second condition true. |
| 112 | */ |
| 113 | struct futex_q { |
| 114 | struct list_head list; |
| 115 | wait_queue_head_t waiters; |
| 116 | |
| 117 | /* Which hash list lock to use: */ |
| 118 | spinlock_t *lock_ptr; |
| 119 | |
| 120 | /* Key which the futex is hashed on: */ |
| 121 | union futex_key key; |
| 122 | |
| 123 | /* For fd, sigio sent using these: */ |
| 124 | int fd; |
| 125 | struct file *filp; |
| 126 | |
| 127 | /* Optional priority inheritance state: */ |
| 128 | struct futex_pi_state *pi_state; |
| 129 | struct task_struct *task; |
| 130 | }; |
| 131 | |
| 132 | /* |
| 133 | * Split the global futex_lock into every hash list lock. |
| 134 | */ |
| 135 | struct futex_hash_bucket { |
| 136 | spinlock_t lock; |
| 137 | struct list_head chain; |
| 138 | }; |
| 139 | |
| 140 | static struct futex_hash_bucket futex_queues[1<<FUTEX_HASHBITS]; |
| 141 | |
| 142 | /* Futex-fs vfsmount entry: */ |
| 143 | static struct vfsmount *futex_mnt; |
| 144 | |
| 145 | /* |
| 146 | * We hash on the keys returned from get_futex_key (see below). |
| 147 | */ |
| 148 | static struct futex_hash_bucket *hash_futex(union futex_key *key) |
| 149 | { |
| 150 | u32 hash = jhash2((u32*)&key->both.word, |
| 151 | (sizeof(key->both.word)+sizeof(key->both.ptr))/4, |
| 152 | key->both.offset); |
| 153 | return &futex_queues[hash & ((1 << FUTEX_HASHBITS)-1)]; |
| 154 | } |
| 155 | |
| 156 | /* |
| 157 | * Return 1 if two futex_keys are equal, 0 otherwise. |
| 158 | */ |
| 159 | static inline int match_futex(union futex_key *key1, union futex_key *key2) |
| 160 | { |
| 161 | return (key1->both.word == key2->both.word |
| 162 | && key1->both.ptr == key2->both.ptr |
| 163 | && key1->both.offset == key2->both.offset); |
| 164 | } |
| 165 | |
| 166 | /* |
| 167 | * Get parameters which are the keys for a futex. |
| 168 | * |
| 169 | * For shared mappings, it's (page->index, vma->vm_file->f_dentry->d_inode, |
| 170 | * offset_within_page). For private mappings, it's (uaddr, current->mm). |
| 171 | * We can usually work out the index without swapping in the page. |
| 172 | * |
| 173 | * Returns: 0, or negative error code. |
| 174 | * The key words are stored in *key on success. |
| 175 | * |
| 176 | * Should be called with ¤t->mm->mmap_sem but NOT any spinlocks. |
| 177 | */ |
| 178 | static int get_futex_key(u32 __user *uaddr, union futex_key *key) |
| 179 | { |
| 180 | unsigned long address = (unsigned long)uaddr; |
| 181 | struct mm_struct *mm = current->mm; |
| 182 | struct vm_area_struct *vma; |
| 183 | struct page *page; |
| 184 | int err; |
| 185 | |
| 186 | /* |
| 187 | * The futex address must be "naturally" aligned. |
| 188 | */ |
| 189 | key->both.offset = address % PAGE_SIZE; |
| 190 | if (unlikely((key->both.offset % sizeof(u32)) != 0)) |
| 191 | return -EINVAL; |
| 192 | address -= key->both.offset; |
| 193 | |
| 194 | /* |
| 195 | * The futex is hashed differently depending on whether |
| 196 | * it's in a shared or private mapping. So check vma first. |
| 197 | */ |
| 198 | vma = find_extend_vma(mm, address); |
| 199 | if (unlikely(!vma)) |
| 200 | return -EFAULT; |
| 201 | |
| 202 | /* |
| 203 | * Permissions. |
| 204 | */ |
| 205 | if (unlikely((vma->vm_flags & (VM_IO|VM_READ)) != VM_READ)) |
| 206 | return (vma->vm_flags & VM_IO) ? -EPERM : -EACCES; |
| 207 | |
| 208 | /* |
| 209 | * Private mappings are handled in a simple way. |
| 210 | * |
| 211 | * NOTE: When userspace waits on a MAP_SHARED mapping, even if |
| 212 | * it's a read-only handle, it's expected that futexes attach to |
| 213 | * the object not the particular process. Therefore we use |
| 214 | * VM_MAYSHARE here, not VM_SHARED which is restricted to shared |
| 215 | * mappings of _writable_ handles. |
| 216 | */ |
| 217 | if (likely(!(vma->vm_flags & VM_MAYSHARE))) { |
| 218 | key->private.mm = mm; |
| 219 | key->private.address = address; |
| 220 | return 0; |
| 221 | } |
| 222 | |
| 223 | /* |
| 224 | * Linear file mappings are also simple. |
| 225 | */ |
| 226 | key->shared.inode = vma->vm_file->f_dentry->d_inode; |
| 227 | key->both.offset++; /* Bit 0 of offset indicates inode-based key. */ |
| 228 | if (likely(!(vma->vm_flags & VM_NONLINEAR))) { |
| 229 | key->shared.pgoff = (((address - vma->vm_start) >> PAGE_SHIFT) |
| 230 | + vma->vm_pgoff); |
| 231 | return 0; |
| 232 | } |
| 233 | |
| 234 | /* |
| 235 | * We could walk the page table to read the non-linear |
| 236 | * pte, and get the page index without fetching the page |
| 237 | * from swap. But that's a lot of code to duplicate here |
| 238 | * for a rare case, so we simply fetch the page. |
| 239 | */ |
| 240 | err = get_user_pages(current, mm, address, 1, 0, 0, &page, NULL); |
| 241 | if (err >= 0) { |
| 242 | key->shared.pgoff = |
| 243 | page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); |
| 244 | put_page(page); |
| 245 | return 0; |
| 246 | } |
| 247 | return err; |
| 248 | } |
| 249 | |
| 250 | /* |
| 251 | * Take a reference to the resource addressed by a key. |
| 252 | * Can be called while holding spinlocks. |
| 253 | * |
| 254 | * NOTE: mmap_sem MUST be held between get_futex_key() and calling this |
| 255 | * function, if it is called at all. mmap_sem keeps key->shared.inode valid. |
| 256 | */ |
| 257 | static inline void get_key_refs(union futex_key *key) |
| 258 | { |
| 259 | if (key->both.ptr != 0) { |
| 260 | if (key->both.offset & 1) |
| 261 | atomic_inc(&key->shared.inode->i_count); |
| 262 | else |
| 263 | atomic_inc(&key->private.mm->mm_count); |
| 264 | } |
| 265 | } |
| 266 | |
| 267 | /* |
| 268 | * Drop a reference to the resource addressed by a key. |
| 269 | * The hash bucket spinlock must not be held. |
| 270 | */ |
| 271 | static void drop_key_refs(union futex_key *key) |
| 272 | { |
| 273 | if (key->both.ptr != 0) { |
| 274 | if (key->both.offset & 1) |
| 275 | iput(key->shared.inode); |
| 276 | else |
| 277 | mmdrop(key->private.mm); |
| 278 | } |
| 279 | } |
| 280 | |
| 281 | static inline int get_futex_value_locked(u32 *dest, u32 __user *from) |
| 282 | { |
| 283 | int ret; |
| 284 | |
| 285 | inc_preempt_count(); |
| 286 | ret = __copy_from_user_inatomic(dest, from, sizeof(u32)); |
| 287 | dec_preempt_count(); |
| 288 | |
| 289 | return ret ? -EFAULT : 0; |
| 290 | } |
| 291 | |
| 292 | /* |
| 293 | * Fault handling. Called with current->mm->mmap_sem held. |
| 294 | */ |
| 295 | static int futex_handle_fault(unsigned long address, int attempt) |
| 296 | { |
| 297 | struct vm_area_struct * vma; |
| 298 | struct mm_struct *mm = current->mm; |
| 299 | |
| 300 | if (attempt > 2 || !(vma = find_vma(mm, address)) || |
| 301 | vma->vm_start > address || !(vma->vm_flags & VM_WRITE)) |
| 302 | return -EFAULT; |
| 303 | |
| 304 | switch (handle_mm_fault(mm, vma, address, 1)) { |
| 305 | case VM_FAULT_MINOR: |
| 306 | current->min_flt++; |
| 307 | break; |
| 308 | case VM_FAULT_MAJOR: |
| 309 | current->maj_flt++; |
| 310 | break; |
| 311 | default: |
| 312 | return -EFAULT; |
| 313 | } |
| 314 | return 0; |
| 315 | } |
| 316 | |
| 317 | /* |
| 318 | * PI code: |
| 319 | */ |
| 320 | static int refill_pi_state_cache(void) |
| 321 | { |
| 322 | struct futex_pi_state *pi_state; |
| 323 | |
| 324 | if (likely(current->pi_state_cache)) |
| 325 | return 0; |
| 326 | |
| 327 | pi_state = kmalloc(sizeof(*pi_state), GFP_KERNEL); |
| 328 | |
| 329 | if (!pi_state) |
| 330 | return -ENOMEM; |
| 331 | |
| 332 | memset(pi_state, 0, sizeof(*pi_state)); |
| 333 | INIT_LIST_HEAD(&pi_state->list); |
| 334 | /* pi_mutex gets initialized later */ |
| 335 | pi_state->owner = NULL; |
| 336 | atomic_set(&pi_state->refcount, 1); |
| 337 | |
| 338 | current->pi_state_cache = pi_state; |
| 339 | |
| 340 | return 0; |
| 341 | } |
| 342 | |
| 343 | static struct futex_pi_state * alloc_pi_state(void) |
| 344 | { |
| 345 | struct futex_pi_state *pi_state = current->pi_state_cache; |
| 346 | |
| 347 | WARN_ON(!pi_state); |
| 348 | current->pi_state_cache = NULL; |
| 349 | |
| 350 | return pi_state; |
| 351 | } |
| 352 | |
| 353 | static void free_pi_state(struct futex_pi_state *pi_state) |
| 354 | { |
| 355 | if (!atomic_dec_and_test(&pi_state->refcount)) |
| 356 | return; |
| 357 | |
| 358 | /* |
| 359 | * If pi_state->owner is NULL, the owner is most probably dying |
| 360 | * and has cleaned up the pi_state already |
| 361 | */ |
| 362 | if (pi_state->owner) { |
| 363 | spin_lock_irq(&pi_state->owner->pi_lock); |
| 364 | list_del_init(&pi_state->list); |
| 365 | spin_unlock_irq(&pi_state->owner->pi_lock); |
| 366 | |
| 367 | rt_mutex_proxy_unlock(&pi_state->pi_mutex, pi_state->owner); |
| 368 | } |
| 369 | |
| 370 | if (current->pi_state_cache) |
| 371 | kfree(pi_state); |
| 372 | else { |
| 373 | /* |
| 374 | * pi_state->list is already empty. |
| 375 | * clear pi_state->owner. |
| 376 | * refcount is at 0 - put it back to 1. |
| 377 | */ |
| 378 | pi_state->owner = NULL; |
| 379 | atomic_set(&pi_state->refcount, 1); |
| 380 | current->pi_state_cache = pi_state; |
| 381 | } |
| 382 | } |
| 383 | |
| 384 | /* |
| 385 | * Look up the task based on what TID userspace gave us. |
| 386 | * We dont trust it. |
| 387 | */ |
| 388 | static struct task_struct * futex_find_get_task(pid_t pid) |
| 389 | { |
| 390 | struct task_struct *p; |
| 391 | |
| 392 | read_lock(&tasklist_lock); |
| 393 | p = find_task_by_pid(pid); |
| 394 | if (!p) |
| 395 | goto out_unlock; |
| 396 | if ((current->euid != p->euid) && (current->euid != p->uid)) { |
| 397 | p = NULL; |
| 398 | goto out_unlock; |
| 399 | } |
| 400 | if (p->exit_state != 0) { |
| 401 | p = NULL; |
| 402 | goto out_unlock; |
| 403 | } |
| 404 | get_task_struct(p); |
| 405 | out_unlock: |
| 406 | read_unlock(&tasklist_lock); |
| 407 | |
| 408 | return p; |
| 409 | } |
| 410 | |
| 411 | /* |
| 412 | * This task is holding PI mutexes at exit time => bad. |
| 413 | * Kernel cleans up PI-state, but userspace is likely hosed. |
| 414 | * (Robust-futex cleanup is separate and might save the day for userspace.) |
| 415 | */ |
| 416 | void exit_pi_state_list(struct task_struct *curr) |
| 417 | { |
| 418 | struct list_head *next, *head = &curr->pi_state_list; |
| 419 | struct futex_pi_state *pi_state; |
| 420 | struct futex_hash_bucket *hb; |
| 421 | union futex_key key; |
| 422 | |
| 423 | /* |
| 424 | * We are a ZOMBIE and nobody can enqueue itself on |
| 425 | * pi_state_list anymore, but we have to be careful |
| 426 | * versus waiters unqueueing themselves: |
| 427 | */ |
| 428 | spin_lock_irq(&curr->pi_lock); |
| 429 | while (!list_empty(head)) { |
| 430 | |
| 431 | next = head->next; |
| 432 | pi_state = list_entry(next, struct futex_pi_state, list); |
| 433 | key = pi_state->key; |
| 434 | hb = hash_futex(&key); |
| 435 | spin_unlock_irq(&curr->pi_lock); |
| 436 | |
| 437 | spin_lock(&hb->lock); |
| 438 | |
| 439 | spin_lock_irq(&curr->pi_lock); |
| 440 | /* |
| 441 | * We dropped the pi-lock, so re-check whether this |
| 442 | * task still owns the PI-state: |
| 443 | */ |
| 444 | if (head->next != next) { |
| 445 | spin_unlock(&hb->lock); |
| 446 | continue; |
| 447 | } |
| 448 | |
| 449 | WARN_ON(pi_state->owner != curr); |
| 450 | WARN_ON(list_empty(&pi_state->list)); |
| 451 | list_del_init(&pi_state->list); |
| 452 | pi_state->owner = NULL; |
| 453 | spin_unlock_irq(&curr->pi_lock); |
| 454 | |
| 455 | rt_mutex_unlock(&pi_state->pi_mutex); |
| 456 | |
| 457 | spin_unlock(&hb->lock); |
| 458 | |
| 459 | spin_lock_irq(&curr->pi_lock); |
| 460 | } |
| 461 | spin_unlock_irq(&curr->pi_lock); |
| 462 | } |
| 463 | |
| 464 | static int |
| 465 | lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, struct futex_q *me) |
| 466 | { |
| 467 | struct futex_pi_state *pi_state = NULL; |
| 468 | struct futex_q *this, *next; |
| 469 | struct list_head *head; |
| 470 | struct task_struct *p; |
| 471 | pid_t pid; |
| 472 | |
| 473 | head = &hb->chain; |
| 474 | |
| 475 | list_for_each_entry_safe(this, next, head, list) { |
| 476 | if (match_futex(&this->key, &me->key)) { |
| 477 | /* |
| 478 | * Another waiter already exists - bump up |
| 479 | * the refcount and return its pi_state: |
| 480 | */ |
| 481 | pi_state = this->pi_state; |
| 482 | /* |
| 483 | * Userspace might have messed up non PI and PI futexes |
| 484 | */ |
| 485 | if (unlikely(!pi_state)) |
| 486 | return -EINVAL; |
| 487 | |
| 488 | WARN_ON(!atomic_read(&pi_state->refcount)); |
| 489 | |
| 490 | atomic_inc(&pi_state->refcount); |
| 491 | me->pi_state = pi_state; |
| 492 | |
| 493 | return 0; |
| 494 | } |
| 495 | } |
| 496 | |
| 497 | /* |
| 498 | * We are the first waiter - try to look up the real owner and attach |
| 499 | * the new pi_state to it, but bail out when the owner died bit is set |
| 500 | * and TID = 0: |
| 501 | */ |
| 502 | pid = uval & FUTEX_TID_MASK; |
| 503 | if (!pid && (uval & FUTEX_OWNER_DIED)) |
| 504 | return -ESRCH; |
| 505 | p = futex_find_get_task(pid); |
| 506 | if (!p) |
| 507 | return -ESRCH; |
| 508 | |
| 509 | pi_state = alloc_pi_state(); |
| 510 | |
| 511 | /* |
| 512 | * Initialize the pi_mutex in locked state and make 'p' |
| 513 | * the owner of it: |
| 514 | */ |
| 515 | rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p); |
| 516 | |
| 517 | /* Store the key for possible exit cleanups: */ |
| 518 | pi_state->key = me->key; |
| 519 | |
| 520 | spin_lock_irq(&p->pi_lock); |
| 521 | WARN_ON(!list_empty(&pi_state->list)); |
| 522 | list_add(&pi_state->list, &p->pi_state_list); |
| 523 | pi_state->owner = p; |
| 524 | spin_unlock_irq(&p->pi_lock); |
| 525 | |
| 526 | put_task_struct(p); |
| 527 | |
| 528 | me->pi_state = pi_state; |
| 529 | |
| 530 | return 0; |
| 531 | } |
| 532 | |
| 533 | /* |
| 534 | * The hash bucket lock must be held when this is called. |
| 535 | * Afterwards, the futex_q must not be accessed. |
| 536 | */ |
| 537 | static void wake_futex(struct futex_q *q) |
| 538 | { |
| 539 | list_del_init(&q->list); |
| 540 | if (q->filp) |
| 541 | send_sigio(&q->filp->f_owner, q->fd, POLL_IN); |
| 542 | /* |
| 543 | * The lock in wake_up_all() is a crucial memory barrier after the |
| 544 | * list_del_init() and also before assigning to q->lock_ptr. |
| 545 | */ |
| 546 | wake_up_all(&q->waiters); |
| 547 | /* |
| 548 | * The waiting task can free the futex_q as soon as this is written, |
| 549 | * without taking any locks. This must come last. |
| 550 | * |
| 551 | * A memory barrier is required here to prevent the following store |
| 552 | * to lock_ptr from getting ahead of the wakeup. Clearing the lock |
| 553 | * at the end of wake_up_all() does not prevent this store from |
| 554 | * moving. |
| 555 | */ |
| 556 | wmb(); |
| 557 | q->lock_ptr = NULL; |
| 558 | } |
| 559 | |
| 560 | static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this) |
| 561 | { |
| 562 | struct task_struct *new_owner; |
| 563 | struct futex_pi_state *pi_state = this->pi_state; |
| 564 | u32 curval, newval; |
| 565 | |
| 566 | if (!pi_state) |
| 567 | return -EINVAL; |
| 568 | |
| 569 | new_owner = rt_mutex_next_owner(&pi_state->pi_mutex); |
| 570 | |
| 571 | /* |
| 572 | * This happens when we have stolen the lock and the original |
| 573 | * pending owner did not enqueue itself back on the rt_mutex. |
| 574 | * Thats not a tragedy. We know that way, that a lock waiter |
| 575 | * is on the fly. We make the futex_q waiter the pending owner. |
| 576 | */ |
| 577 | if (!new_owner) |
| 578 | new_owner = this->task; |
| 579 | |
| 580 | /* |
| 581 | * We pass it to the next owner. (The WAITERS bit is always |
| 582 | * kept enabled while there is PI state around. We must also |
| 583 | * preserve the owner died bit.) |
| 584 | */ |
| 585 | if (!(uval & FUTEX_OWNER_DIED)) { |
| 586 | newval = FUTEX_WAITERS | new_owner->pid; |
| 587 | |
| 588 | inc_preempt_count(); |
| 589 | curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval); |
| 590 | dec_preempt_count(); |
| 591 | if (curval == -EFAULT) |
| 592 | return -EFAULT; |
| 593 | if (curval != uval) |
| 594 | return -EINVAL; |
| 595 | } |
| 596 | |
| 597 | spin_lock_irq(&pi_state->owner->pi_lock); |
| 598 | WARN_ON(list_empty(&pi_state->list)); |
| 599 | list_del_init(&pi_state->list); |
| 600 | spin_unlock_irq(&pi_state->owner->pi_lock); |
| 601 | |
| 602 | spin_lock_irq(&new_owner->pi_lock); |
| 603 | WARN_ON(!list_empty(&pi_state->list)); |
| 604 | list_add(&pi_state->list, &new_owner->pi_state_list); |
| 605 | pi_state->owner = new_owner; |
| 606 | spin_unlock_irq(&new_owner->pi_lock); |
| 607 | |
| 608 | rt_mutex_unlock(&pi_state->pi_mutex); |
| 609 | |
| 610 | return 0; |
| 611 | } |
| 612 | |
| 613 | static int unlock_futex_pi(u32 __user *uaddr, u32 uval) |
| 614 | { |
| 615 | u32 oldval; |
| 616 | |
| 617 | /* |
| 618 | * There is no waiter, so we unlock the futex. The owner died |
| 619 | * bit has not to be preserved here. We are the owner: |
| 620 | */ |
| 621 | inc_preempt_count(); |
| 622 | oldval = futex_atomic_cmpxchg_inatomic(uaddr, uval, 0); |
| 623 | dec_preempt_count(); |
| 624 | |
| 625 | if (oldval == -EFAULT) |
| 626 | return oldval; |
| 627 | if (oldval != uval) |
| 628 | return -EAGAIN; |
| 629 | |
| 630 | return 0; |
| 631 | } |
| 632 | |
| 633 | /* |
| 634 | * Express the locking dependencies for lockdep: |
| 635 | */ |
| 636 | static inline void |
| 637 | double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) |
| 638 | { |
| 639 | if (hb1 <= hb2) { |
| 640 | spin_lock(&hb1->lock); |
| 641 | if (hb1 < hb2) |
| 642 | spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING); |
| 643 | } else { /* hb1 > hb2 */ |
| 644 | spin_lock(&hb2->lock); |
| 645 | spin_lock_nested(&hb1->lock, SINGLE_DEPTH_NESTING); |
| 646 | } |
| 647 | } |
| 648 | |
| 649 | /* |
| 650 | * Wake up all waiters hashed on the physical page that is mapped |
| 651 | * to this virtual address: |
| 652 | */ |
| 653 | static int futex_wake(u32 __user *uaddr, int nr_wake) |
| 654 | { |
| 655 | struct futex_hash_bucket *hb; |
| 656 | struct futex_q *this, *next; |
| 657 | struct list_head *head; |
| 658 | union futex_key key; |
| 659 | int ret; |
| 660 | |
| 661 | down_read(¤t->mm->mmap_sem); |
| 662 | |
| 663 | ret = get_futex_key(uaddr, &key); |
| 664 | if (unlikely(ret != 0)) |
| 665 | goto out; |
| 666 | |
| 667 | hb = hash_futex(&key); |
| 668 | spin_lock(&hb->lock); |
| 669 | head = &hb->chain; |
| 670 | |
| 671 | list_for_each_entry_safe(this, next, head, list) { |
| 672 | if (match_futex (&this->key, &key)) { |
| 673 | if (this->pi_state) { |
| 674 | ret = -EINVAL; |
| 675 | break; |
| 676 | } |
| 677 | wake_futex(this); |
| 678 | if (++ret >= nr_wake) |
| 679 | break; |
| 680 | } |
| 681 | } |
| 682 | |
| 683 | spin_unlock(&hb->lock); |
| 684 | out: |
| 685 | up_read(¤t->mm->mmap_sem); |
| 686 | return ret; |
| 687 | } |
| 688 | |
| 689 | /* |
| 690 | * Wake up all waiters hashed on the physical page that is mapped |
| 691 | * to this virtual address: |
| 692 | */ |
| 693 | static int |
| 694 | futex_wake_op(u32 __user *uaddr1, u32 __user *uaddr2, |
| 695 | int nr_wake, int nr_wake2, int op) |
| 696 | { |
| 697 | union futex_key key1, key2; |
| 698 | struct futex_hash_bucket *hb1, *hb2; |
| 699 | struct list_head *head; |
| 700 | struct futex_q *this, *next; |
| 701 | int ret, op_ret, attempt = 0; |
| 702 | |
| 703 | retryfull: |
| 704 | down_read(¤t->mm->mmap_sem); |
| 705 | |
| 706 | ret = get_futex_key(uaddr1, &key1); |
| 707 | if (unlikely(ret != 0)) |
| 708 | goto out; |
| 709 | ret = get_futex_key(uaddr2, &key2); |
| 710 | if (unlikely(ret != 0)) |
| 711 | goto out; |
| 712 | |
| 713 | hb1 = hash_futex(&key1); |
| 714 | hb2 = hash_futex(&key2); |
| 715 | |
| 716 | retry: |
| 717 | double_lock_hb(hb1, hb2); |
| 718 | |
| 719 | op_ret = futex_atomic_op_inuser(op, uaddr2); |
| 720 | if (unlikely(op_ret < 0)) { |
| 721 | u32 dummy; |
| 722 | |
| 723 | spin_unlock(&hb1->lock); |
| 724 | if (hb1 != hb2) |
| 725 | spin_unlock(&hb2->lock); |
| 726 | |
| 727 | #ifndef CONFIG_MMU |
| 728 | /* |
| 729 | * we don't get EFAULT from MMU faults if we don't have an MMU, |
| 730 | * but we might get them from range checking |
| 731 | */ |
| 732 | ret = op_ret; |
| 733 | goto out; |
| 734 | #endif |
| 735 | |
| 736 | if (unlikely(op_ret != -EFAULT)) { |
| 737 | ret = op_ret; |
| 738 | goto out; |
| 739 | } |
| 740 | |
| 741 | /* |
| 742 | * futex_atomic_op_inuser needs to both read and write |
| 743 | * *(int __user *)uaddr2, but we can't modify it |
| 744 | * non-atomically. Therefore, if get_user below is not |
| 745 | * enough, we need to handle the fault ourselves, while |
| 746 | * still holding the mmap_sem. |
| 747 | */ |
| 748 | if (attempt++) { |
| 749 | if (futex_handle_fault((unsigned long)uaddr2, |
| 750 | attempt)) { |
| 751 | ret = -EFAULT; |
| 752 | goto out; |
| 753 | } |
| 754 | goto retry; |
| 755 | } |
| 756 | |
| 757 | /* |
| 758 | * If we would have faulted, release mmap_sem, |
| 759 | * fault it in and start all over again. |
| 760 | */ |
| 761 | up_read(¤t->mm->mmap_sem); |
| 762 | |
| 763 | ret = get_user(dummy, uaddr2); |
| 764 | if (ret) |
| 765 | return ret; |
| 766 | |
| 767 | goto retryfull; |
| 768 | } |
| 769 | |
| 770 | head = &hb1->chain; |
| 771 | |
| 772 | list_for_each_entry_safe(this, next, head, list) { |
| 773 | if (match_futex (&this->key, &key1)) { |
| 774 | wake_futex(this); |
| 775 | if (++ret >= nr_wake) |
| 776 | break; |
| 777 | } |
| 778 | } |
| 779 | |
| 780 | if (op_ret > 0) { |
| 781 | head = &hb2->chain; |
| 782 | |
| 783 | op_ret = 0; |
| 784 | list_for_each_entry_safe(this, next, head, list) { |
| 785 | if (match_futex (&this->key, &key2)) { |
| 786 | wake_futex(this); |
| 787 | if (++op_ret >= nr_wake2) |
| 788 | break; |
| 789 | } |
| 790 | } |
| 791 | ret += op_ret; |
| 792 | } |
| 793 | |
| 794 | spin_unlock(&hb1->lock); |
| 795 | if (hb1 != hb2) |
| 796 | spin_unlock(&hb2->lock); |
| 797 | out: |
| 798 | up_read(¤t->mm->mmap_sem); |
| 799 | return ret; |
| 800 | } |
| 801 | |
| 802 | /* |
| 803 | * Requeue all waiters hashed on one physical page to another |
| 804 | * physical page. |
| 805 | */ |
| 806 | static int futex_requeue(u32 __user *uaddr1, u32 __user *uaddr2, |
| 807 | int nr_wake, int nr_requeue, u32 *cmpval) |
| 808 | { |
| 809 | union futex_key key1, key2; |
| 810 | struct futex_hash_bucket *hb1, *hb2; |
| 811 | struct list_head *head1; |
| 812 | struct futex_q *this, *next; |
| 813 | int ret, drop_count = 0; |
| 814 | |
| 815 | retry: |
| 816 | down_read(¤t->mm->mmap_sem); |
| 817 | |
| 818 | ret = get_futex_key(uaddr1, &key1); |
| 819 | if (unlikely(ret != 0)) |
| 820 | goto out; |
| 821 | ret = get_futex_key(uaddr2, &key2); |
| 822 | if (unlikely(ret != 0)) |
| 823 | goto out; |
| 824 | |
| 825 | hb1 = hash_futex(&key1); |
| 826 | hb2 = hash_futex(&key2); |
| 827 | |
| 828 | double_lock_hb(hb1, hb2); |
| 829 | |
| 830 | if (likely(cmpval != NULL)) { |
| 831 | u32 curval; |
| 832 | |
| 833 | ret = get_futex_value_locked(&curval, uaddr1); |
| 834 | |
| 835 | if (unlikely(ret)) { |
| 836 | spin_unlock(&hb1->lock); |
| 837 | if (hb1 != hb2) |
| 838 | spin_unlock(&hb2->lock); |
| 839 | |
| 840 | /* |
| 841 | * If we would have faulted, release mmap_sem, fault |
| 842 | * it in and start all over again. |
| 843 | */ |
| 844 | up_read(¤t->mm->mmap_sem); |
| 845 | |
| 846 | ret = get_user(curval, uaddr1); |
| 847 | |
| 848 | if (!ret) |
| 849 | goto retry; |
| 850 | |
| 851 | return ret; |
| 852 | } |
| 853 | if (curval != *cmpval) { |
| 854 | ret = -EAGAIN; |
| 855 | goto out_unlock; |
| 856 | } |
| 857 | } |
| 858 | |
| 859 | head1 = &hb1->chain; |
| 860 | list_for_each_entry_safe(this, next, head1, list) { |
| 861 | if (!match_futex (&this->key, &key1)) |
| 862 | continue; |
| 863 | if (++ret <= nr_wake) { |
| 864 | wake_futex(this); |
| 865 | } else { |
| 866 | /* |
| 867 | * If key1 and key2 hash to the same bucket, no need to |
| 868 | * requeue. |
| 869 | */ |
| 870 | if (likely(head1 != &hb2->chain)) { |
| 871 | list_move_tail(&this->list, &hb2->chain); |
| 872 | this->lock_ptr = &hb2->lock; |
| 873 | } |
| 874 | this->key = key2; |
| 875 | get_key_refs(&key2); |
| 876 | drop_count++; |
| 877 | |
| 878 | if (ret - nr_wake >= nr_requeue) |
| 879 | break; |
| 880 | } |
| 881 | } |
| 882 | |
| 883 | out_unlock: |
| 884 | spin_unlock(&hb1->lock); |
| 885 | if (hb1 != hb2) |
| 886 | spin_unlock(&hb2->lock); |
| 887 | |
| 888 | /* drop_key_refs() must be called outside the spinlocks. */ |
| 889 | while (--drop_count >= 0) |
| 890 | drop_key_refs(&key1); |
| 891 | |
| 892 | out: |
| 893 | up_read(¤t->mm->mmap_sem); |
| 894 | return ret; |
| 895 | } |
| 896 | |
| 897 | /* The key must be already stored in q->key. */ |
| 898 | static inline struct futex_hash_bucket * |
| 899 | queue_lock(struct futex_q *q, int fd, struct file *filp) |
| 900 | { |
| 901 | struct futex_hash_bucket *hb; |
| 902 | |
| 903 | q->fd = fd; |
| 904 | q->filp = filp; |
| 905 | |
| 906 | init_waitqueue_head(&q->waiters); |
| 907 | |
| 908 | get_key_refs(&q->key); |
| 909 | hb = hash_futex(&q->key); |
| 910 | q->lock_ptr = &hb->lock; |
| 911 | |
| 912 | spin_lock(&hb->lock); |
| 913 | return hb; |
| 914 | } |
| 915 | |
| 916 | static inline void __queue_me(struct futex_q *q, struct futex_hash_bucket *hb) |
| 917 | { |
| 918 | list_add_tail(&q->list, &hb->chain); |
| 919 | q->task = current; |
| 920 | spin_unlock(&hb->lock); |
| 921 | } |
| 922 | |
| 923 | static inline void |
| 924 | queue_unlock(struct futex_q *q, struct futex_hash_bucket *hb) |
| 925 | { |
| 926 | spin_unlock(&hb->lock); |
| 927 | drop_key_refs(&q->key); |
| 928 | } |
| 929 | |
| 930 | /* |
| 931 | * queue_me and unqueue_me must be called as a pair, each |
| 932 | * exactly once. They are called with the hashed spinlock held. |
| 933 | */ |
| 934 | |
| 935 | /* The key must be already stored in q->key. */ |
| 936 | static void queue_me(struct futex_q *q, int fd, struct file *filp) |
| 937 | { |
| 938 | struct futex_hash_bucket *hb; |
| 939 | |
| 940 | hb = queue_lock(q, fd, filp); |
| 941 | __queue_me(q, hb); |
| 942 | } |
| 943 | |
| 944 | /* Return 1 if we were still queued (ie. 0 means we were woken) */ |
| 945 | static int unqueue_me(struct futex_q *q) |
| 946 | { |
| 947 | spinlock_t *lock_ptr; |
| 948 | int ret = 0; |
| 949 | |
| 950 | /* In the common case we don't take the spinlock, which is nice. */ |
| 951 | retry: |
| 952 | lock_ptr = q->lock_ptr; |
| 953 | barrier(); |
| 954 | if (lock_ptr != 0) { |
| 955 | spin_lock(lock_ptr); |
| 956 | /* |
| 957 | * q->lock_ptr can change between reading it and |
| 958 | * spin_lock(), causing us to take the wrong lock. This |
| 959 | * corrects the race condition. |
| 960 | * |
| 961 | * Reasoning goes like this: if we have the wrong lock, |
| 962 | * q->lock_ptr must have changed (maybe several times) |
| 963 | * between reading it and the spin_lock(). It can |
| 964 | * change again after the spin_lock() but only if it was |
| 965 | * already changed before the spin_lock(). It cannot, |
| 966 | * however, change back to the original value. Therefore |
| 967 | * we can detect whether we acquired the correct lock. |
| 968 | */ |
| 969 | if (unlikely(lock_ptr != q->lock_ptr)) { |
| 970 | spin_unlock(lock_ptr); |
| 971 | goto retry; |
| 972 | } |
| 973 | WARN_ON(list_empty(&q->list)); |
| 974 | list_del(&q->list); |
| 975 | |
| 976 | BUG_ON(q->pi_state); |
| 977 | |
| 978 | spin_unlock(lock_ptr); |
| 979 | ret = 1; |
| 980 | } |
| 981 | |
| 982 | drop_key_refs(&q->key); |
| 983 | return ret; |
| 984 | } |
| 985 | |
| 986 | /* |
| 987 | * PI futexes can not be requeued and must remove themself from the |
| 988 | * hash bucket. The hash bucket lock is held on entry and dropped here. |
| 989 | */ |
| 990 | static void unqueue_me_pi(struct futex_q *q, struct futex_hash_bucket *hb) |
| 991 | { |
| 992 | WARN_ON(list_empty(&q->list)); |
| 993 | list_del(&q->list); |
| 994 | |
| 995 | BUG_ON(!q->pi_state); |
| 996 | free_pi_state(q->pi_state); |
| 997 | q->pi_state = NULL; |
| 998 | |
| 999 | spin_unlock(&hb->lock); |
| 1000 | |
| 1001 | drop_key_refs(&q->key); |
| 1002 | } |
| 1003 | |
| 1004 | static int futex_wait(u32 __user *uaddr, u32 val, unsigned long time) |
| 1005 | { |
| 1006 | struct task_struct *curr = current; |
| 1007 | DECLARE_WAITQUEUE(wait, curr); |
| 1008 | struct futex_hash_bucket *hb; |
| 1009 | struct futex_q q; |
| 1010 | u32 uval; |
| 1011 | int ret; |
| 1012 | |
| 1013 | q.pi_state = NULL; |
| 1014 | retry: |
| 1015 | down_read(&curr->mm->mmap_sem); |
| 1016 | |
| 1017 | ret = get_futex_key(uaddr, &q.key); |
| 1018 | if (unlikely(ret != 0)) |
| 1019 | goto out_release_sem; |
| 1020 | |
| 1021 | hb = queue_lock(&q, -1, NULL); |
| 1022 | |
| 1023 | /* |
| 1024 | * Access the page AFTER the futex is queued. |
| 1025 | * Order is important: |
| 1026 | * |
| 1027 | * Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val); |
| 1028 | * Userspace waker: if (cond(var)) { var = new; futex_wake(&var); } |
| 1029 | * |
| 1030 | * The basic logical guarantee of a futex is that it blocks ONLY |
| 1031 | * if cond(var) is known to be true at the time of blocking, for |
| 1032 | * any cond. If we queued after testing *uaddr, that would open |
| 1033 | * a race condition where we could block indefinitely with |
| 1034 | * cond(var) false, which would violate the guarantee. |
| 1035 | * |
| 1036 | * A consequence is that futex_wait() can return zero and absorb |
| 1037 | * a wakeup when *uaddr != val on entry to the syscall. This is |
| 1038 | * rare, but normal. |
| 1039 | * |
| 1040 | * We hold the mmap semaphore, so the mapping cannot have changed |
| 1041 | * since we looked it up in get_futex_key. |
| 1042 | */ |
| 1043 | ret = get_futex_value_locked(&uval, uaddr); |
| 1044 | |
| 1045 | if (unlikely(ret)) { |
| 1046 | queue_unlock(&q, hb); |
| 1047 | |
| 1048 | /* |
| 1049 | * If we would have faulted, release mmap_sem, fault it in and |
| 1050 | * start all over again. |
| 1051 | */ |
| 1052 | up_read(&curr->mm->mmap_sem); |
| 1053 | |
| 1054 | ret = get_user(uval, uaddr); |
| 1055 | |
| 1056 | if (!ret) |
| 1057 | goto retry; |
| 1058 | return ret; |
| 1059 | } |
| 1060 | ret = -EWOULDBLOCK; |
| 1061 | if (uval != val) |
| 1062 | goto out_unlock_release_sem; |
| 1063 | |
| 1064 | /* Only actually queue if *uaddr contained val. */ |
| 1065 | __queue_me(&q, hb); |
| 1066 | |
| 1067 | /* |
| 1068 | * Now the futex is queued and we have checked the data, we |
| 1069 | * don't want to hold mmap_sem while we sleep. |
| 1070 | */ |
| 1071 | up_read(&curr->mm->mmap_sem); |
| 1072 | |
| 1073 | /* |
| 1074 | * There might have been scheduling since the queue_me(), as we |
| 1075 | * cannot hold a spinlock across the get_user() in case it |
| 1076 | * faults, and we cannot just set TASK_INTERRUPTIBLE state when |
| 1077 | * queueing ourselves into the futex hash. This code thus has to |
| 1078 | * rely on the futex_wake() code removing us from hash when it |
| 1079 | * wakes us up. |
| 1080 | */ |
| 1081 | |
| 1082 | /* add_wait_queue is the barrier after __set_current_state. */ |
| 1083 | __set_current_state(TASK_INTERRUPTIBLE); |
| 1084 | add_wait_queue(&q.waiters, &wait); |
| 1085 | /* |
| 1086 | * !list_empty() is safe here without any lock. |
| 1087 | * q.lock_ptr != 0 is not safe, because of ordering against wakeup. |
| 1088 | */ |
| 1089 | if (likely(!list_empty(&q.list))) |
| 1090 | time = schedule_timeout(time); |
| 1091 | __set_current_state(TASK_RUNNING); |
| 1092 | |
| 1093 | /* |
| 1094 | * NOTE: we don't remove ourselves from the waitqueue because |
| 1095 | * we are the only user of it. |
| 1096 | */ |
| 1097 | |
| 1098 | /* If we were woken (and unqueued), we succeeded, whatever. */ |
| 1099 | if (!unqueue_me(&q)) |
| 1100 | return 0; |
| 1101 | if (time == 0) |
| 1102 | return -ETIMEDOUT; |
| 1103 | /* |
| 1104 | * We expect signal_pending(current), but another thread may |
| 1105 | * have handled it for us already. |
| 1106 | */ |
| 1107 | return -EINTR; |
| 1108 | |
| 1109 | out_unlock_release_sem: |
| 1110 | queue_unlock(&q, hb); |
| 1111 | |
| 1112 | out_release_sem: |
| 1113 | up_read(&curr->mm->mmap_sem); |
| 1114 | return ret; |
| 1115 | } |
| 1116 | |
| 1117 | /* |
| 1118 | * Userspace tried a 0 -> TID atomic transition of the futex value |
| 1119 | * and failed. The kernel side here does the whole locking operation: |
| 1120 | * if there are waiters then it will block, it does PI, etc. (Due to |
| 1121 | * races the kernel might see a 0 value of the futex too.) |
| 1122 | */ |
| 1123 | static int futex_lock_pi(u32 __user *uaddr, int detect, unsigned long sec, |
| 1124 | long nsec, int trylock) |
| 1125 | { |
| 1126 | struct hrtimer_sleeper timeout, *to = NULL; |
| 1127 | struct task_struct *curr = current; |
| 1128 | struct futex_hash_bucket *hb; |
| 1129 | u32 uval, newval, curval; |
| 1130 | struct futex_q q; |
| 1131 | int ret, attempt = 0; |
| 1132 | |
| 1133 | if (refill_pi_state_cache()) |
| 1134 | return -ENOMEM; |
| 1135 | |
| 1136 | if (sec != MAX_SCHEDULE_TIMEOUT) { |
| 1137 | to = &timeout; |
| 1138 | hrtimer_init(&to->timer, CLOCK_REALTIME, HRTIMER_ABS); |
| 1139 | hrtimer_init_sleeper(to, current); |
| 1140 | to->timer.expires = ktime_set(sec, nsec); |
| 1141 | } |
| 1142 | |
| 1143 | q.pi_state = NULL; |
| 1144 | retry: |
| 1145 | down_read(&curr->mm->mmap_sem); |
| 1146 | |
| 1147 | ret = get_futex_key(uaddr, &q.key); |
| 1148 | if (unlikely(ret != 0)) |
| 1149 | goto out_release_sem; |
| 1150 | |
| 1151 | hb = queue_lock(&q, -1, NULL); |
| 1152 | |
| 1153 | retry_locked: |
| 1154 | /* |
| 1155 | * To avoid races, we attempt to take the lock here again |
| 1156 | * (by doing a 0 -> TID atomic cmpxchg), while holding all |
| 1157 | * the locks. It will most likely not succeed. |
| 1158 | */ |
| 1159 | newval = current->pid; |
| 1160 | |
| 1161 | inc_preempt_count(); |
| 1162 | curval = futex_atomic_cmpxchg_inatomic(uaddr, 0, newval); |
| 1163 | dec_preempt_count(); |
| 1164 | |
| 1165 | if (unlikely(curval == -EFAULT)) |
| 1166 | goto uaddr_faulted; |
| 1167 | |
| 1168 | /* We own the lock already */ |
| 1169 | if (unlikely((curval & FUTEX_TID_MASK) == current->pid)) { |
| 1170 | if (!detect && 0) |
| 1171 | force_sig(SIGKILL, current); |
| 1172 | ret = -EDEADLK; |
| 1173 | goto out_unlock_release_sem; |
| 1174 | } |
| 1175 | |
| 1176 | /* |
| 1177 | * Surprise - we got the lock. Just return |
| 1178 | * to userspace: |
| 1179 | */ |
| 1180 | if (unlikely(!curval)) |
| 1181 | goto out_unlock_release_sem; |
| 1182 | |
| 1183 | uval = curval; |
| 1184 | newval = uval | FUTEX_WAITERS; |
| 1185 | |
| 1186 | inc_preempt_count(); |
| 1187 | curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval); |
| 1188 | dec_preempt_count(); |
| 1189 | |
| 1190 | if (unlikely(curval == -EFAULT)) |
| 1191 | goto uaddr_faulted; |
| 1192 | if (unlikely(curval != uval)) |
| 1193 | goto retry_locked; |
| 1194 | |
| 1195 | /* |
| 1196 | * We dont have the lock. Look up the PI state (or create it if |
| 1197 | * we are the first waiter): |
| 1198 | */ |
| 1199 | ret = lookup_pi_state(uval, hb, &q); |
| 1200 | |
| 1201 | if (unlikely(ret)) { |
| 1202 | /* |
| 1203 | * There were no waiters and the owner task lookup |
| 1204 | * failed. When the OWNER_DIED bit is set, then we |
| 1205 | * know that this is a robust futex and we actually |
| 1206 | * take the lock. This is safe as we are protected by |
| 1207 | * the hash bucket lock. We also set the waiters bit |
| 1208 | * unconditionally here, to simplify glibc handling of |
| 1209 | * multiple tasks racing to acquire the lock and |
| 1210 | * cleanup the problems which were left by the dead |
| 1211 | * owner. |
| 1212 | */ |
| 1213 | if (curval & FUTEX_OWNER_DIED) { |
| 1214 | uval = newval; |
| 1215 | newval = current->pid | |
| 1216 | FUTEX_OWNER_DIED | FUTEX_WAITERS; |
| 1217 | |
| 1218 | inc_preempt_count(); |
| 1219 | curval = futex_atomic_cmpxchg_inatomic(uaddr, |
| 1220 | uval, newval); |
| 1221 | dec_preempt_count(); |
| 1222 | |
| 1223 | if (unlikely(curval == -EFAULT)) |
| 1224 | goto uaddr_faulted; |
| 1225 | if (unlikely(curval != uval)) |
| 1226 | goto retry_locked; |
| 1227 | ret = 0; |
| 1228 | } |
| 1229 | goto out_unlock_release_sem; |
| 1230 | } |
| 1231 | |
| 1232 | /* |
| 1233 | * Only actually queue now that the atomic ops are done: |
| 1234 | */ |
| 1235 | __queue_me(&q, hb); |
| 1236 | |
| 1237 | /* |
| 1238 | * Now the futex is queued and we have checked the data, we |
| 1239 | * don't want to hold mmap_sem while we sleep. |
| 1240 | */ |
| 1241 | up_read(&curr->mm->mmap_sem); |
| 1242 | |
| 1243 | WARN_ON(!q.pi_state); |
| 1244 | /* |
| 1245 | * Block on the PI mutex: |
| 1246 | */ |
| 1247 | if (!trylock) |
| 1248 | ret = rt_mutex_timed_lock(&q.pi_state->pi_mutex, to, 1); |
| 1249 | else { |
| 1250 | ret = rt_mutex_trylock(&q.pi_state->pi_mutex); |
| 1251 | /* Fixup the trylock return value: */ |
| 1252 | ret = ret ? 0 : -EWOULDBLOCK; |
| 1253 | } |
| 1254 | |
| 1255 | down_read(&curr->mm->mmap_sem); |
| 1256 | spin_lock(q.lock_ptr); |
| 1257 | |
| 1258 | /* |
| 1259 | * Got the lock. We might not be the anticipated owner if we |
| 1260 | * did a lock-steal - fix up the PI-state in that case. |
| 1261 | */ |
| 1262 | if (!ret && q.pi_state->owner != curr) { |
| 1263 | u32 newtid = current->pid | FUTEX_WAITERS; |
| 1264 | |
| 1265 | /* Owner died? */ |
| 1266 | if (q.pi_state->owner != NULL) { |
| 1267 | spin_lock_irq(&q.pi_state->owner->pi_lock); |
| 1268 | WARN_ON(list_empty(&q.pi_state->list)); |
| 1269 | list_del_init(&q.pi_state->list); |
| 1270 | spin_unlock_irq(&q.pi_state->owner->pi_lock); |
| 1271 | } else |
| 1272 | newtid |= FUTEX_OWNER_DIED; |
| 1273 | |
| 1274 | q.pi_state->owner = current; |
| 1275 | |
| 1276 | spin_lock_irq(¤t->pi_lock); |
| 1277 | WARN_ON(!list_empty(&q.pi_state->list)); |
| 1278 | list_add(&q.pi_state->list, ¤t->pi_state_list); |
| 1279 | spin_unlock_irq(¤t->pi_lock); |
| 1280 | |
| 1281 | /* Unqueue and drop the lock */ |
| 1282 | unqueue_me_pi(&q, hb); |
| 1283 | up_read(&curr->mm->mmap_sem); |
| 1284 | /* |
| 1285 | * We own it, so we have to replace the pending owner |
| 1286 | * TID. This must be atomic as we have preserve the |
| 1287 | * owner died bit here. |
| 1288 | */ |
| 1289 | ret = get_user(uval, uaddr); |
| 1290 | while (!ret) { |
| 1291 | newval = (uval & FUTEX_OWNER_DIED) | newtid; |
| 1292 | curval = futex_atomic_cmpxchg_inatomic(uaddr, |
| 1293 | uval, newval); |
| 1294 | if (curval == -EFAULT) |
| 1295 | ret = -EFAULT; |
| 1296 | if (curval == uval) |
| 1297 | break; |
| 1298 | uval = curval; |
| 1299 | } |
| 1300 | } else { |
| 1301 | /* |
| 1302 | * Catch the rare case, where the lock was released |
| 1303 | * when we were on the way back before we locked |
| 1304 | * the hash bucket. |
| 1305 | */ |
| 1306 | if (ret && q.pi_state->owner == curr) { |
| 1307 | if (rt_mutex_trylock(&q.pi_state->pi_mutex)) |
| 1308 | ret = 0; |
| 1309 | } |
| 1310 | /* Unqueue and drop the lock */ |
| 1311 | unqueue_me_pi(&q, hb); |
| 1312 | up_read(&curr->mm->mmap_sem); |
| 1313 | } |
| 1314 | |
| 1315 | if (!detect && ret == -EDEADLK && 0) |
| 1316 | force_sig(SIGKILL, current); |
| 1317 | |
| 1318 | return ret != -EINTR ? ret : -ERESTARTNOINTR; |
| 1319 | |
| 1320 | out_unlock_release_sem: |
| 1321 | queue_unlock(&q, hb); |
| 1322 | |
| 1323 | out_release_sem: |
| 1324 | up_read(&curr->mm->mmap_sem); |
| 1325 | return ret; |
| 1326 | |
| 1327 | uaddr_faulted: |
| 1328 | /* |
| 1329 | * We have to r/w *(int __user *)uaddr, but we can't modify it |
| 1330 | * non-atomically. Therefore, if get_user below is not |
| 1331 | * enough, we need to handle the fault ourselves, while |
| 1332 | * still holding the mmap_sem. |
| 1333 | */ |
| 1334 | if (attempt++) { |
| 1335 | if (futex_handle_fault((unsigned long)uaddr, attempt)) { |
| 1336 | ret = -EFAULT; |
| 1337 | goto out_unlock_release_sem; |
| 1338 | } |
| 1339 | goto retry_locked; |
| 1340 | } |
| 1341 | |
| 1342 | queue_unlock(&q, hb); |
| 1343 | up_read(&curr->mm->mmap_sem); |
| 1344 | |
| 1345 | ret = get_user(uval, uaddr); |
| 1346 | if (!ret && (uval != -EFAULT)) |
| 1347 | goto retry; |
| 1348 | |
| 1349 | return ret; |
| 1350 | } |
| 1351 | |
| 1352 | /* |
| 1353 | * Userspace attempted a TID -> 0 atomic transition, and failed. |
| 1354 | * This is the in-kernel slowpath: we look up the PI state (if any), |
| 1355 | * and do the rt-mutex unlock. |
| 1356 | */ |
| 1357 | static int futex_unlock_pi(u32 __user *uaddr) |
| 1358 | { |
| 1359 | struct futex_hash_bucket *hb; |
| 1360 | struct futex_q *this, *next; |
| 1361 | u32 uval; |
| 1362 | struct list_head *head; |
| 1363 | union futex_key key; |
| 1364 | int ret, attempt = 0; |
| 1365 | |
| 1366 | retry: |
| 1367 | if (get_user(uval, uaddr)) |
| 1368 | return -EFAULT; |
| 1369 | /* |
| 1370 | * We release only a lock we actually own: |
| 1371 | */ |
| 1372 | if ((uval & FUTEX_TID_MASK) != current->pid) |
| 1373 | return -EPERM; |
| 1374 | /* |
| 1375 | * First take all the futex related locks: |
| 1376 | */ |
| 1377 | down_read(¤t->mm->mmap_sem); |
| 1378 | |
| 1379 | ret = get_futex_key(uaddr, &key); |
| 1380 | if (unlikely(ret != 0)) |
| 1381 | goto out; |
| 1382 | |
| 1383 | hb = hash_futex(&key); |
| 1384 | spin_lock(&hb->lock); |
| 1385 | |
| 1386 | retry_locked: |
| 1387 | /* |
| 1388 | * To avoid races, try to do the TID -> 0 atomic transition |
| 1389 | * again. If it succeeds then we can return without waking |
| 1390 | * anyone else up: |
| 1391 | */ |
| 1392 | if (!(uval & FUTEX_OWNER_DIED)) { |
| 1393 | inc_preempt_count(); |
| 1394 | uval = futex_atomic_cmpxchg_inatomic(uaddr, current->pid, 0); |
| 1395 | dec_preempt_count(); |
| 1396 | } |
| 1397 | |
| 1398 | if (unlikely(uval == -EFAULT)) |
| 1399 | goto pi_faulted; |
| 1400 | /* |
| 1401 | * Rare case: we managed to release the lock atomically, |
| 1402 | * no need to wake anyone else up: |
| 1403 | */ |
| 1404 | if (unlikely(uval == current->pid)) |
| 1405 | goto out_unlock; |
| 1406 | |
| 1407 | /* |
| 1408 | * Ok, other tasks may need to be woken up - check waiters |
| 1409 | * and do the wakeup if necessary: |
| 1410 | */ |
| 1411 | head = &hb->chain; |
| 1412 | |
| 1413 | list_for_each_entry_safe(this, next, head, list) { |
| 1414 | if (!match_futex (&this->key, &key)) |
| 1415 | continue; |
| 1416 | ret = wake_futex_pi(uaddr, uval, this); |
| 1417 | /* |
| 1418 | * The atomic access to the futex value |
| 1419 | * generated a pagefault, so retry the |
| 1420 | * user-access and the wakeup: |
| 1421 | */ |
| 1422 | if (ret == -EFAULT) |
| 1423 | goto pi_faulted; |
| 1424 | goto out_unlock; |
| 1425 | } |
| 1426 | /* |
| 1427 | * No waiters - kernel unlocks the futex: |
| 1428 | */ |
| 1429 | if (!(uval & FUTEX_OWNER_DIED)) { |
| 1430 | ret = unlock_futex_pi(uaddr, uval); |
| 1431 | if (ret == -EFAULT) |
| 1432 | goto pi_faulted; |
| 1433 | } |
| 1434 | |
| 1435 | out_unlock: |
| 1436 | spin_unlock(&hb->lock); |
| 1437 | out: |
| 1438 | up_read(¤t->mm->mmap_sem); |
| 1439 | |
| 1440 | return ret; |
| 1441 | |
| 1442 | pi_faulted: |
| 1443 | /* |
| 1444 | * We have to r/w *(int __user *)uaddr, but we can't modify it |
| 1445 | * non-atomically. Therefore, if get_user below is not |
| 1446 | * enough, we need to handle the fault ourselves, while |
| 1447 | * still holding the mmap_sem. |
| 1448 | */ |
| 1449 | if (attempt++) { |
| 1450 | if (futex_handle_fault((unsigned long)uaddr, attempt)) { |
| 1451 | ret = -EFAULT; |
| 1452 | goto out_unlock; |
| 1453 | } |
| 1454 | goto retry_locked; |
| 1455 | } |
| 1456 | |
| 1457 | spin_unlock(&hb->lock); |
| 1458 | up_read(¤t->mm->mmap_sem); |
| 1459 | |
| 1460 | ret = get_user(uval, uaddr); |
| 1461 | if (!ret && (uval != -EFAULT)) |
| 1462 | goto retry; |
| 1463 | |
| 1464 | return ret; |
| 1465 | } |
| 1466 | |
| 1467 | static int futex_close(struct inode *inode, struct file *filp) |
| 1468 | { |
| 1469 | struct futex_q *q = filp->private_data; |
| 1470 | |
| 1471 | unqueue_me(q); |
| 1472 | kfree(q); |
| 1473 | |
| 1474 | return 0; |
| 1475 | } |
| 1476 | |
| 1477 | /* This is one-shot: once it's gone off you need a new fd */ |
| 1478 | static unsigned int futex_poll(struct file *filp, |
| 1479 | struct poll_table_struct *wait) |
| 1480 | { |
| 1481 | struct futex_q *q = filp->private_data; |
| 1482 | int ret = 0; |
| 1483 | |
| 1484 | poll_wait(filp, &q->waiters, wait); |
| 1485 | |
| 1486 | /* |
| 1487 | * list_empty() is safe here without any lock. |
| 1488 | * q->lock_ptr != 0 is not safe, because of ordering against wakeup. |
| 1489 | */ |
| 1490 | if (list_empty(&q->list)) |
| 1491 | ret = POLLIN | POLLRDNORM; |
| 1492 | |
| 1493 | return ret; |
| 1494 | } |
| 1495 | |
| 1496 | static struct file_operations futex_fops = { |
| 1497 | .release = futex_close, |
| 1498 | .poll = futex_poll, |
| 1499 | }; |
| 1500 | |
| 1501 | /* |
| 1502 | * Signal allows caller to avoid the race which would occur if they |
| 1503 | * set the sigio stuff up afterwards. |
| 1504 | */ |
| 1505 | static int futex_fd(u32 __user *uaddr, int signal) |
| 1506 | { |
| 1507 | struct futex_q *q; |
| 1508 | struct file *filp; |
| 1509 | int ret, err; |
| 1510 | |
| 1511 | ret = -EINVAL; |
| 1512 | if (!valid_signal(signal)) |
| 1513 | goto out; |
| 1514 | |
| 1515 | ret = get_unused_fd(); |
| 1516 | if (ret < 0) |
| 1517 | goto out; |
| 1518 | filp = get_empty_filp(); |
| 1519 | if (!filp) { |
| 1520 | put_unused_fd(ret); |
| 1521 | ret = -ENFILE; |
| 1522 | goto out; |
| 1523 | } |
| 1524 | filp->f_op = &futex_fops; |
| 1525 | filp->f_vfsmnt = mntget(futex_mnt); |
| 1526 | filp->f_dentry = dget(futex_mnt->mnt_root); |
| 1527 | filp->f_mapping = filp->f_dentry->d_inode->i_mapping; |
| 1528 | |
| 1529 | if (signal) { |
| 1530 | err = f_setown(filp, current->pid, 1); |
| 1531 | if (err < 0) { |
| 1532 | goto error; |
| 1533 | } |
| 1534 | filp->f_owner.signum = signal; |
| 1535 | } |
| 1536 | |
| 1537 | q = kmalloc(sizeof(*q), GFP_KERNEL); |
| 1538 | if (!q) { |
| 1539 | err = -ENOMEM; |
| 1540 | goto error; |
| 1541 | } |
| 1542 | q->pi_state = NULL; |
| 1543 | |
| 1544 | down_read(¤t->mm->mmap_sem); |
| 1545 | err = get_futex_key(uaddr, &q->key); |
| 1546 | |
| 1547 | if (unlikely(err != 0)) { |
| 1548 | up_read(¤t->mm->mmap_sem); |
| 1549 | kfree(q); |
| 1550 | goto error; |
| 1551 | } |
| 1552 | |
| 1553 | /* |
| 1554 | * queue_me() must be called before releasing mmap_sem, because |
| 1555 | * key->shared.inode needs to be referenced while holding it. |
| 1556 | */ |
| 1557 | filp->private_data = q; |
| 1558 | |
| 1559 | queue_me(q, ret, filp); |
| 1560 | up_read(¤t->mm->mmap_sem); |
| 1561 | |
| 1562 | /* Now we map fd to filp, so userspace can access it */ |
| 1563 | fd_install(ret, filp); |
| 1564 | out: |
| 1565 | return ret; |
| 1566 | error: |
| 1567 | put_unused_fd(ret); |
| 1568 | put_filp(filp); |
| 1569 | ret = err; |
| 1570 | goto out; |
| 1571 | } |
| 1572 | |
| 1573 | /* |
| 1574 | * Support for robust futexes: the kernel cleans up held futexes at |
| 1575 | * thread exit time. |
| 1576 | * |
| 1577 | * Implementation: user-space maintains a per-thread list of locks it |
| 1578 | * is holding. Upon do_exit(), the kernel carefully walks this list, |
| 1579 | * and marks all locks that are owned by this thread with the |
| 1580 | * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is |
| 1581 | * always manipulated with the lock held, so the list is private and |
| 1582 | * per-thread. Userspace also maintains a per-thread 'list_op_pending' |
| 1583 | * field, to allow the kernel to clean up if the thread dies after |
| 1584 | * acquiring the lock, but just before it could have added itself to |
| 1585 | * the list. There can only be one such pending lock. |
| 1586 | */ |
| 1587 | |
| 1588 | /** |
| 1589 | * sys_set_robust_list - set the robust-futex list head of a task |
| 1590 | * @head: pointer to the list-head |
| 1591 | * @len: length of the list-head, as userspace expects |
| 1592 | */ |
| 1593 | asmlinkage long |
| 1594 | sys_set_robust_list(struct robust_list_head __user *head, |
| 1595 | size_t len) |
| 1596 | { |
| 1597 | /* |
| 1598 | * The kernel knows only one size for now: |
| 1599 | */ |
| 1600 | if (unlikely(len != sizeof(*head))) |
| 1601 | return -EINVAL; |
| 1602 | |
| 1603 | current->robust_list = head; |
| 1604 | |
| 1605 | return 0; |
| 1606 | } |
| 1607 | |
| 1608 | /** |
| 1609 | * sys_get_robust_list - get the robust-futex list head of a task |
| 1610 | * @pid: pid of the process [zero for current task] |
| 1611 | * @head_ptr: pointer to a list-head pointer, the kernel fills it in |
| 1612 | * @len_ptr: pointer to a length field, the kernel fills in the header size |
| 1613 | */ |
| 1614 | asmlinkage long |
| 1615 | sys_get_robust_list(int pid, struct robust_list_head __user **head_ptr, |
| 1616 | size_t __user *len_ptr) |
| 1617 | { |
| 1618 | struct robust_list_head *head; |
| 1619 | unsigned long ret; |
| 1620 | |
| 1621 | if (!pid) |
| 1622 | head = current->robust_list; |
| 1623 | else { |
| 1624 | struct task_struct *p; |
| 1625 | |
| 1626 | ret = -ESRCH; |
| 1627 | read_lock(&tasklist_lock); |
| 1628 | p = find_task_by_pid(pid); |
| 1629 | if (!p) |
| 1630 | goto err_unlock; |
| 1631 | ret = -EPERM; |
| 1632 | if ((current->euid != p->euid) && (current->euid != p->uid) && |
| 1633 | !capable(CAP_SYS_PTRACE)) |
| 1634 | goto err_unlock; |
| 1635 | head = p->robust_list; |
| 1636 | read_unlock(&tasklist_lock); |
| 1637 | } |
| 1638 | |
| 1639 | if (put_user(sizeof(*head), len_ptr)) |
| 1640 | return -EFAULT; |
| 1641 | return put_user(head, head_ptr); |
| 1642 | |
| 1643 | err_unlock: |
| 1644 | read_unlock(&tasklist_lock); |
| 1645 | |
| 1646 | return ret; |
| 1647 | } |
| 1648 | |
| 1649 | /* |
| 1650 | * Process a futex-list entry, check whether it's owned by the |
| 1651 | * dying task, and do notification if so: |
| 1652 | */ |
| 1653 | int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi) |
| 1654 | { |
| 1655 | u32 uval, nval, mval; |
| 1656 | |
| 1657 | retry: |
| 1658 | if (get_user(uval, uaddr)) |
| 1659 | return -1; |
| 1660 | |
| 1661 | if ((uval & FUTEX_TID_MASK) == curr->pid) { |
| 1662 | /* |
| 1663 | * Ok, this dying thread is truly holding a futex |
| 1664 | * of interest. Set the OWNER_DIED bit atomically |
| 1665 | * via cmpxchg, and if the value had FUTEX_WAITERS |
| 1666 | * set, wake up a waiter (if any). (We have to do a |
| 1667 | * futex_wake() even if OWNER_DIED is already set - |
| 1668 | * to handle the rare but possible case of recursive |
| 1669 | * thread-death.) The rest of the cleanup is done in |
| 1670 | * userspace. |
| 1671 | */ |
| 1672 | mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED; |
| 1673 | nval = futex_atomic_cmpxchg_inatomic(uaddr, uval, mval); |
| 1674 | |
| 1675 | if (nval == -EFAULT) |
| 1676 | return -1; |
| 1677 | |
| 1678 | if (nval != uval) |
| 1679 | goto retry; |
| 1680 | |
| 1681 | /* |
| 1682 | * Wake robust non-PI futexes here. The wakeup of |
| 1683 | * PI futexes happens in exit_pi_state(): |
| 1684 | */ |
| 1685 | if (!pi) { |
| 1686 | if (uval & FUTEX_WAITERS) |
| 1687 | futex_wake(uaddr, 1); |
| 1688 | } |
| 1689 | } |
| 1690 | return 0; |
| 1691 | } |
| 1692 | |
| 1693 | /* |
| 1694 | * Fetch a robust-list pointer. Bit 0 signals PI futexes: |
| 1695 | */ |
| 1696 | static inline int fetch_robust_entry(struct robust_list __user **entry, |
| 1697 | struct robust_list __user **head, int *pi) |
| 1698 | { |
| 1699 | unsigned long uentry; |
| 1700 | |
| 1701 | if (get_user(uentry, (unsigned long *)head)) |
| 1702 | return -EFAULT; |
| 1703 | |
| 1704 | *entry = (void *)(uentry & ~1UL); |
| 1705 | *pi = uentry & 1; |
| 1706 | |
| 1707 | return 0; |
| 1708 | } |
| 1709 | |
| 1710 | /* |
| 1711 | * Walk curr->robust_list (very carefully, it's a userspace list!) |
| 1712 | * and mark any locks found there dead, and notify any waiters. |
| 1713 | * |
| 1714 | * We silently return on any sign of list-walking problem. |
| 1715 | */ |
| 1716 | void exit_robust_list(struct task_struct *curr) |
| 1717 | { |
| 1718 | struct robust_list_head __user *head = curr->robust_list; |
| 1719 | struct robust_list __user *entry, *pending; |
| 1720 | unsigned int limit = ROBUST_LIST_LIMIT, pi, pip; |
| 1721 | unsigned long futex_offset; |
| 1722 | |
| 1723 | /* |
| 1724 | * Fetch the list head (which was registered earlier, via |
| 1725 | * sys_set_robust_list()): |
| 1726 | */ |
| 1727 | if (fetch_robust_entry(&entry, &head->list.next, &pi)) |
| 1728 | return; |
| 1729 | /* |
| 1730 | * Fetch the relative futex offset: |
| 1731 | */ |
| 1732 | if (get_user(futex_offset, &head->futex_offset)) |
| 1733 | return; |
| 1734 | /* |
| 1735 | * Fetch any possibly pending lock-add first, and handle it |
| 1736 | * if it exists: |
| 1737 | */ |
| 1738 | if (fetch_robust_entry(&pending, &head->list_op_pending, &pip)) |
| 1739 | return; |
| 1740 | |
| 1741 | if (pending) |
| 1742 | handle_futex_death((void *)pending + futex_offset, curr, pip); |
| 1743 | |
| 1744 | while (entry != &head->list) { |
| 1745 | /* |
| 1746 | * A pending lock might already be on the list, so |
| 1747 | * don't process it twice: |
| 1748 | */ |
| 1749 | if (entry != pending) |
| 1750 | if (handle_futex_death((void *)entry + futex_offset, |
| 1751 | curr, pi)) |
| 1752 | return; |
| 1753 | /* |
| 1754 | * Fetch the next entry in the list: |
| 1755 | */ |
| 1756 | if (fetch_robust_entry(&entry, &entry->next, &pi)) |
| 1757 | return; |
| 1758 | /* |
| 1759 | * Avoid excessively long or circular lists: |
| 1760 | */ |
| 1761 | if (!--limit) |
| 1762 | break; |
| 1763 | |
| 1764 | cond_resched(); |
| 1765 | } |
| 1766 | } |
| 1767 | |
| 1768 | long do_futex(u32 __user *uaddr, int op, u32 val, unsigned long timeout, |
| 1769 | u32 __user *uaddr2, u32 val2, u32 val3) |
| 1770 | { |
| 1771 | int ret; |
| 1772 | |
| 1773 | switch (op) { |
| 1774 | case FUTEX_WAIT: |
| 1775 | ret = futex_wait(uaddr, val, timeout); |
| 1776 | break; |
| 1777 | case FUTEX_WAKE: |
| 1778 | ret = futex_wake(uaddr, val); |
| 1779 | break; |
| 1780 | case FUTEX_FD: |
| 1781 | /* non-zero val means F_SETOWN(getpid()) & F_SETSIG(val) */ |
| 1782 | ret = futex_fd(uaddr, val); |
| 1783 | break; |
| 1784 | case FUTEX_REQUEUE: |
| 1785 | ret = futex_requeue(uaddr, uaddr2, val, val2, NULL); |
| 1786 | break; |
| 1787 | case FUTEX_CMP_REQUEUE: |
| 1788 | ret = futex_requeue(uaddr, uaddr2, val, val2, &val3); |
| 1789 | break; |
| 1790 | case FUTEX_WAKE_OP: |
| 1791 | ret = futex_wake_op(uaddr, uaddr2, val, val2, val3); |
| 1792 | break; |
| 1793 | case FUTEX_LOCK_PI: |
| 1794 | ret = futex_lock_pi(uaddr, val, timeout, val2, 0); |
| 1795 | break; |
| 1796 | case FUTEX_UNLOCK_PI: |
| 1797 | ret = futex_unlock_pi(uaddr); |
| 1798 | break; |
| 1799 | case FUTEX_TRYLOCK_PI: |
| 1800 | ret = futex_lock_pi(uaddr, 0, timeout, val2, 1); |
| 1801 | break; |
| 1802 | default: |
| 1803 | ret = -ENOSYS; |
| 1804 | } |
| 1805 | return ret; |
| 1806 | } |
| 1807 | |
| 1808 | |
| 1809 | asmlinkage long sys_futex(u32 __user *uaddr, int op, u32 val, |
| 1810 | struct timespec __user *utime, u32 __user *uaddr2, |
| 1811 | u32 val3) |
| 1812 | { |
| 1813 | struct timespec t; |
| 1814 | unsigned long timeout = MAX_SCHEDULE_TIMEOUT; |
| 1815 | u32 val2 = 0; |
| 1816 | |
| 1817 | if (utime && (op == FUTEX_WAIT || op == FUTEX_LOCK_PI)) { |
| 1818 | if (copy_from_user(&t, utime, sizeof(t)) != 0) |
| 1819 | return -EFAULT; |
| 1820 | if (!timespec_valid(&t)) |
| 1821 | return -EINVAL; |
| 1822 | if (op == FUTEX_WAIT) |
| 1823 | timeout = timespec_to_jiffies(&t) + 1; |
| 1824 | else { |
| 1825 | timeout = t.tv_sec; |
| 1826 | val2 = t.tv_nsec; |
| 1827 | } |
| 1828 | } |
| 1829 | /* |
| 1830 | * requeue parameter in 'utime' if op == FUTEX_REQUEUE. |
| 1831 | */ |
| 1832 | if (op == FUTEX_REQUEUE || op == FUTEX_CMP_REQUEUE) |
| 1833 | val2 = (u32) (unsigned long) utime; |
| 1834 | |
| 1835 | return do_futex(uaddr, op, val, timeout, uaddr2, val2, val3); |
| 1836 | } |
| 1837 | |
| 1838 | static int futexfs_get_sb(struct file_system_type *fs_type, |
| 1839 | int flags, const char *dev_name, void *data, |
| 1840 | struct vfsmount *mnt) |
| 1841 | { |
| 1842 | return get_sb_pseudo(fs_type, "futex", NULL, 0xBAD1DEA, mnt); |
| 1843 | } |
| 1844 | |
| 1845 | static struct file_system_type futex_fs_type = { |
| 1846 | .name = "futexfs", |
| 1847 | .get_sb = futexfs_get_sb, |
| 1848 | .kill_sb = kill_anon_super, |
| 1849 | }; |
| 1850 | |
| 1851 | static int __init init(void) |
| 1852 | { |
| 1853 | unsigned int i; |
| 1854 | |
| 1855 | register_filesystem(&futex_fs_type); |
| 1856 | futex_mnt = kern_mount(&futex_fs_type); |
| 1857 | |
| 1858 | for (i = 0; i < ARRAY_SIZE(futex_queues); i++) { |
| 1859 | INIT_LIST_HEAD(&futex_queues[i].chain); |
| 1860 | spin_lock_init(&futex_queues[i].lock); |
| 1861 | } |
| 1862 | return 0; |
| 1863 | } |
| 1864 | __initcall(init); |