1 /* 2 * fs/eventpoll.c ( Efficent event polling implementation ) 3 * Copyright (C) 2001,...,2006 Davide Libenzi 4 * 5 * This program is free software; you can redistribute it and/or modify 6 * it under the terms of the GNU General Public License as published by 7 * the Free Software Foundation; either version 2 of the License, or 8 * (at your option) any later version. 9 * 10 * Davide Libenzi <davidel@xmailserver.org> 11 * 12 */ 13 14 #include <linux/init.h> 15 #include <linux/kernel.h> 16 #include <linux/sched.h> 17 #include <linux/fs.h> 18 #include <linux/file.h> 19 #include <linux/signal.h> 20 #include <linux/errno.h> 21 #include <linux/mm.h> 22 #include <linux/slab.h> 23 #include <linux/poll.h> 24 #include <linux/string.h> 25 #include <linux/list.h> 26 #include <linux/hash.h> 27 #include <linux/spinlock.h> 28 #include <linux/syscalls.h> 29 #include <linux/rwsem.h> 30 #include <linux/rbtree.h> 31 #include <linux/wait.h> 32 #include <linux/eventpoll.h> 33 #include <linux/mount.h> 34 #include <linux/bitops.h> 35 #include <linux/mutex.h> 36 #include <linux/anon_inodes.h> 37 #include <asm/uaccess.h> 38 #include <asm/system.h> 39 #include <asm/io.h> 40 #include <asm/mman.h> 41 #include <asm/atomic.h> 42 #include <asm/semaphore.h> 43 44 /* 45 * LOCKING: 46 * There are three level of locking required by epoll : 47 * 48 * 1) epmutex (mutex) 49 * 2) ep->sem (rw_semaphore) 50 * 3) ep->lock (rw_lock) 51 * 52 * The acquire order is the one listed above, from 1 to 3. 53 * We need a spinlock (ep->lock) because we manipulate objects 54 * from inside the poll callback, that might be triggered from 55 * a wake_up() that in turn might be called from IRQ context. 56 * So we can't sleep inside the poll callback and hence we need 57 * a spinlock. During the event transfer loop (from kernel to 58 * user space) we could end up sleeping due a copy_to_user(), so 59 * we need a lock that will allow us to sleep. This lock is a 60 * read-write semaphore (ep->sem). It is acquired on read during 61 * the event transfer loop and in write during epoll_ctl(EPOLL_CTL_DEL) 62 * and during eventpoll_release_file(). Then we also need a global 63 * semaphore to serialize eventpoll_release_file() and ep_free(). 64 * This semaphore is acquired by ep_free() during the epoll file 65 * cleanup path and it is also acquired by eventpoll_release_file() 66 * if a file has been pushed inside an epoll set and it is then 67 * close()d without a previous call toepoll_ctl(EPOLL_CTL_DEL). 68 * It is possible to drop the "ep->sem" and to use the global 69 * semaphore "epmutex" (together with "ep->lock") to have it working, 70 * but having "ep->sem" will make the interface more scalable. 71 * Events that require holding "epmutex" are very rare, while for 72 * normal operations the epoll private "ep->sem" will guarantee 73 * a greater scalability. 74 */ 75 76 #define DEBUG_EPOLL 0 77 78 #if DEBUG_EPOLL > 0 79 #define DPRINTK(x) printk x 80 #define DNPRINTK(n, x) do { if ((n) <= DEBUG_EPOLL) printk x; } while (0) 81 #else /* #if DEBUG_EPOLL > 0 */ 82 #define DPRINTK(x) (void) 0 83 #define DNPRINTK(n, x) (void) 0 84 #endif /* #if DEBUG_EPOLL > 0 */ 85 86 #define DEBUG_EPI 0 87 88 #if DEBUG_EPI != 0 89 #define EPI_SLAB_DEBUG (SLAB_DEBUG_FREE | SLAB_RED_ZONE /* | SLAB_POISON */) 90 #else /* #if DEBUG_EPI != 0 */ 91 #define EPI_SLAB_DEBUG 0 92 #endif /* #if DEBUG_EPI != 0 */ 93 94 /* Epoll private bits inside the event mask */ 95 #define EP_PRIVATE_BITS (EPOLLONESHOT | EPOLLET) 96 97 /* Maximum number of poll wake up nests we are allowing */ 98 #define EP_MAX_POLLWAKE_NESTS 4 99 100 /* Maximum msec timeout value storeable in a long int */ 101 #define EP_MAX_MSTIMEO min(1000ULL * MAX_SCHEDULE_TIMEOUT / HZ, (LONG_MAX - 999ULL) / HZ) 102 103 #define EP_MAX_EVENTS (INT_MAX / sizeof(struct epoll_event)) 104 105 struct epoll_filefd { 106 struct file *file; 107 int fd; 108 }; 109 110 /* 111 * Node that is linked into the "wake_task_list" member of the "struct poll_safewake". 112 * It is used to keep track on all tasks that are currently inside the wake_up() code 113 * to 1) short-circuit the one coming from the same task and same wait queue head 114 * ( loop ) 2) allow a maximum number of epoll descriptors inclusion nesting 115 * 3) let go the ones coming from other tasks. 116 */ 117 struct wake_task_node { 118 struct list_head llink; 119 struct task_struct *task; 120 wait_queue_head_t *wq; 121 }; 122 123 /* 124 * This is used to implement the safe poll wake up avoiding to reenter 125 * the poll callback from inside wake_up(). 126 */ 127 struct poll_safewake { 128 struct list_head wake_task_list; 129 spinlock_t lock; 130 }; 131 132 /* 133 * This structure is stored inside the "private_data" member of the file 134 * structure and rapresent the main data sructure for the eventpoll 135 * interface. 136 */ 137 struct eventpoll { 138 /* Protect the this structure access */ 139 rwlock_t lock; 140 141 /* 142 * This semaphore is used to ensure that files are not removed 143 * while epoll is using them. This is read-held during the event 144 * collection loop and it is write-held during the file cleanup 145 * path, the epoll file exit code and the ctl operations. 146 */ 147 struct rw_semaphore sem; 148 149 /* Wait queue used by sys_epoll_wait() */ 150 wait_queue_head_t wq; 151 152 /* Wait queue used by file->poll() */ 153 wait_queue_head_t poll_wait; 154 155 /* List of ready file descriptors */ 156 struct list_head rdllist; 157 158 /* RB-Tree root used to store monitored fd structs */ 159 struct rb_root rbr; 160 }; 161 162 /* Wait structure used by the poll hooks */ 163 struct eppoll_entry { 164 /* List header used to link this structure to the "struct epitem" */ 165 struct list_head llink; 166 167 /* The "base" pointer is set to the container "struct epitem" */ 168 void *base; 169 170 /* 171 * Wait queue item that will be linked to the target file wait 172 * queue head. 173 */ 174 wait_queue_t wait; 175 176 /* The wait queue head that linked the "wait" wait queue item */ 177 wait_queue_head_t *whead; 178 }; 179 180 /* 181 * Each file descriptor added to the eventpoll interface will 182 * have an entry of this type linked to the "rbr" RB tree. 183 */ 184 struct epitem { 185 /* RB-Tree node used to link this structure to the eventpoll rb-tree */ 186 struct rb_node rbn; 187 188 /* List header used to link this structure to the eventpoll ready list */ 189 struct list_head rdllink; 190 191 /* The file descriptor information this item refers to */ 192 struct epoll_filefd ffd; 193 194 /* Number of active wait queue attached to poll operations */ 195 int nwait; 196 197 /* List containing poll wait queues */ 198 struct list_head pwqlist; 199 200 /* The "container" of this item */ 201 struct eventpoll *ep; 202 203 /* The structure that describe the interested events and the source fd */ 204 struct epoll_event event; 205 206 /* 207 * Used to keep track of the usage count of the structure. This avoids 208 * that the structure will desappear from underneath our processing. 209 */ 210 atomic_t usecnt; 211 212 /* List header used to link this item to the "struct file" items list */ 213 struct list_head fllink; 214 }; 215 216 /* Wrapper struct used by poll queueing */ 217 struct ep_pqueue { 218 poll_table pt; 219 struct epitem *epi; 220 }; 221 222 /* 223 * This semaphore is used to serialize ep_free() and eventpoll_release_file(). 224 */ 225 static struct mutex epmutex; 226 227 /* Safe wake up implementation */ 228 static struct poll_safewake psw; 229 230 /* Slab cache used to allocate "struct epitem" */ 231 static struct kmem_cache *epi_cache __read_mostly; 232 233 /* Slab cache used to allocate "struct eppoll_entry" */ 234 static struct kmem_cache *pwq_cache __read_mostly; 235 236 237 /* Setup the structure that is used as key for the rb-tree */ 238 static inline void ep_set_ffd(struct epoll_filefd *ffd, 239 struct file *file, int fd) 240 { 241 ffd->file = file; 242 ffd->fd = fd; 243 } 244 245 /* Compare rb-tree keys */ 246 static inline int ep_cmp_ffd(struct epoll_filefd *p1, 247 struct epoll_filefd *p2) 248 { 249 return (p1->file > p2->file ? +1: 250 (p1->file < p2->file ? -1 : p1->fd - p2->fd)); 251 } 252 253 /* Special initialization for the rb-tree node to detect linkage */ 254 static inline void ep_rb_initnode(struct rb_node *n) 255 { 256 rb_set_parent(n, n); 257 } 258 259 /* Removes a node from the rb-tree and marks it for a fast is-linked check */ 260 static inline void ep_rb_erase(struct rb_node *n, struct rb_root *r) 261 { 262 rb_erase(n, r); 263 rb_set_parent(n, n); 264 } 265 266 /* Fast check to verify that the item is linked to the main rb-tree */ 267 static inline int ep_rb_linked(struct rb_node *n) 268 { 269 return rb_parent(n) != n; 270 } 271 272 /* Tells us if the item is currently linked */ 273 static inline int ep_is_linked(struct list_head *p) 274 { 275 return !list_empty(p); 276 } 277 278 /* Get the "struct epitem" from a wait queue pointer */ 279 static inline struct epitem * ep_item_from_wait(wait_queue_t *p) 280 { 281 return container_of(p, struct eppoll_entry, wait)->base; 282 } 283 284 /* Get the "struct epitem" from an epoll queue wrapper */ 285 static inline struct epitem * ep_item_from_epqueue(poll_table *p) 286 { 287 return container_of(p, struct ep_pqueue, pt)->epi; 288 } 289 290 /* Tells if the epoll_ctl(2) operation needs an event copy from userspace */ 291 static inline int ep_op_has_event(int op) 292 { 293 return op != EPOLL_CTL_DEL; 294 } 295 296 /* Initialize the poll safe wake up structure */ 297 static void ep_poll_safewake_init(struct poll_safewake *psw) 298 { 299 300 INIT_LIST_HEAD(&psw->wake_task_list); 301 spin_lock_init(&psw->lock); 302 } 303 304 /* 305 * Perform a safe wake up of the poll wait list. The problem is that 306 * with the new callback'd wake up system, it is possible that the 307 * poll callback is reentered from inside the call to wake_up() done 308 * on the poll wait queue head. The rule is that we cannot reenter the 309 * wake up code from the same task more than EP_MAX_POLLWAKE_NESTS times, 310 * and we cannot reenter the same wait queue head at all. This will 311 * enable to have a hierarchy of epoll file descriptor of no more than 312 * EP_MAX_POLLWAKE_NESTS deep. We need the irq version of the spin lock 313 * because this one gets called by the poll callback, that in turn is called 314 * from inside a wake_up(), that might be called from irq context. 315 */ 316 static void ep_poll_safewake(struct poll_safewake *psw, wait_queue_head_t *wq) 317 { 318 int wake_nests = 0; 319 unsigned long flags; 320 struct task_struct *this_task = current; 321 struct list_head *lsthead = &psw->wake_task_list, *lnk; 322 struct wake_task_node *tncur; 323 struct wake_task_node tnode; 324 325 spin_lock_irqsave(&psw->lock, flags); 326 327 /* Try to see if the current task is already inside this wakeup call */ 328 list_for_each(lnk, lsthead) { 329 tncur = list_entry(lnk, struct wake_task_node, llink); 330 331 if (tncur->wq == wq || 332 (tncur->task == this_task && ++wake_nests > EP_MAX_POLLWAKE_NESTS)) { 333 /* 334 * Ops ... loop detected or maximum nest level reached. 335 * We abort this wake by breaking the cycle itself. 336 */ 337 spin_unlock_irqrestore(&psw->lock, flags); 338 return; 339 } 340 } 341 342 /* Add the current task to the list */ 343 tnode.task = this_task; 344 tnode.wq = wq; 345 list_add(&tnode.llink, lsthead); 346 347 spin_unlock_irqrestore(&psw->lock, flags); 348 349 /* Do really wake up now */ 350 wake_up(wq); 351 352 /* Remove the current task from the list */ 353 spin_lock_irqsave(&psw->lock, flags); 354 list_del(&tnode.llink); 355 spin_unlock_irqrestore(&psw->lock, flags); 356 } 357 358 /* 359 * This function unregister poll callbacks from the associated file descriptor. 360 * Since this must be called without holding "ep->lock" the atomic exchange trick 361 * will protect us from multiple unregister. 362 */ 363 static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi) 364 { 365 int nwait; 366 struct list_head *lsthead = &epi->pwqlist; 367 struct eppoll_entry *pwq; 368 369 /* This is called without locks, so we need the atomic exchange */ 370 nwait = xchg(&epi->nwait, 0); 371 372 if (nwait) { 373 while (!list_empty(lsthead)) { 374 pwq = list_first_entry(lsthead, struct eppoll_entry, llink); 375 376 list_del_init(&pwq->llink); 377 remove_wait_queue(pwq->whead, &pwq->wait); 378 kmem_cache_free(pwq_cache, pwq); 379 } 380 } 381 } 382 383 /* 384 * Unlink the "struct epitem" from all places it might have been hooked up. 385 * This function must be called with write IRQ lock on "ep->lock". 386 */ 387 static int ep_unlink(struct eventpoll *ep, struct epitem *epi) 388 { 389 int error; 390 391 /* 392 * It can happen that this one is called for an item already unlinked. 393 * The check protect us from doing a double unlink ( crash ). 394 */ 395 error = -ENOENT; 396 if (!ep_rb_linked(&epi->rbn)) 397 goto error_return; 398 399 /* 400 * Clear the event mask for the unlinked item. This will avoid item 401 * notifications to be sent after the unlink operation from inside 402 * the kernel->userspace event transfer loop. 403 */ 404 epi->event.events = 0; 405 406 /* 407 * At this point is safe to do the job, unlink the item from our rb-tree. 408 * This operation togheter with the above check closes the door to 409 * double unlinks. 410 */ 411 ep_rb_erase(&epi->rbn, &ep->rbr); 412 413 /* 414 * If the item we are going to remove is inside the ready file descriptors 415 * we want to remove it from this list to avoid stale events. 416 */ 417 if (ep_is_linked(&epi->rdllink)) 418 list_del_init(&epi->rdllink); 419 420 error = 0; 421 error_return: 422 423 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_unlink(%p, %p) = %d\n", 424 current, ep, epi->ffd.file, error)); 425 426 return error; 427 } 428 429 /* 430 * Increment the usage count of the "struct epitem" making it sure 431 * that the user will have a valid pointer to reference. 432 */ 433 static void ep_use_epitem(struct epitem *epi) 434 { 435 atomic_inc(&epi->usecnt); 436 } 437 438 /* 439 * Decrement ( release ) the usage count by signaling that the user 440 * has finished using the structure. It might lead to freeing the 441 * structure itself if the count goes to zero. 442 */ 443 static void ep_release_epitem(struct epitem *epi) 444 { 445 if (atomic_dec_and_test(&epi->usecnt)) 446 kmem_cache_free(epi_cache, epi); 447 } 448 449 /* 450 * Removes a "struct epitem" from the eventpoll RB tree and deallocates 451 * all the associated resources. 452 */ 453 static int ep_remove(struct eventpoll *ep, struct epitem *epi) 454 { 455 int error; 456 unsigned long flags; 457 struct file *file = epi->ffd.file; 458 459 /* 460 * Removes poll wait queue hooks. We _have_ to do this without holding 461 * the "ep->lock" otherwise a deadlock might occur. This because of the 462 * sequence of the lock acquisition. Here we do "ep->lock" then the wait 463 * queue head lock when unregistering the wait queue. The wakeup callback 464 * will run by holding the wait queue head lock and will call our callback 465 * that will try to get "ep->lock". 466 */ 467 ep_unregister_pollwait(ep, epi); 468 469 /* Remove the current item from the list of epoll hooks */ 470 spin_lock(&file->f_ep_lock); 471 if (ep_is_linked(&epi->fllink)) 472 list_del_init(&epi->fllink); 473 spin_unlock(&file->f_ep_lock); 474 475 /* We need to acquire the write IRQ lock before calling ep_unlink() */ 476 write_lock_irqsave(&ep->lock, flags); 477 478 /* Really unlink the item from the RB tree */ 479 error = ep_unlink(ep, epi); 480 481 write_unlock_irqrestore(&ep->lock, flags); 482 483 if (error) 484 goto error_return; 485 486 /* At this point it is safe to free the eventpoll item */ 487 ep_release_epitem(epi); 488 489 error = 0; 490 error_return: 491 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_remove(%p, %p) = %d\n", 492 current, ep, file, error)); 493 494 return error; 495 } 496 497 static void ep_free(struct eventpoll *ep) 498 { 499 struct rb_node *rbp; 500 struct epitem *epi; 501 502 /* We need to release all tasks waiting for these file */ 503 if (waitqueue_active(&ep->poll_wait)) 504 ep_poll_safewake(&psw, &ep->poll_wait); 505 506 /* 507 * We need to lock this because we could be hit by 508 * eventpoll_release_file() while we're freeing the "struct eventpoll". 509 * We do not need to hold "ep->sem" here because the epoll file 510 * is on the way to be removed and no one has references to it 511 * anymore. The only hit might come from eventpoll_release_file() but 512 * holding "epmutex" is sufficent here. 513 */ 514 mutex_lock(&epmutex); 515 516 /* 517 * Walks through the whole tree by unregistering poll callbacks. 518 */ 519 for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { 520 epi = rb_entry(rbp, struct epitem, rbn); 521 522 ep_unregister_pollwait(ep, epi); 523 } 524 525 /* 526 * Walks through the whole tree by freeing each "struct epitem". At this 527 * point we are sure no poll callbacks will be lingering around, and also by 528 * write-holding "sem" we can be sure that no file cleanup code will hit 529 * us during this operation. So we can avoid the lock on "ep->lock". 530 */ 531 while ((rbp = rb_first(&ep->rbr)) != 0) { 532 epi = rb_entry(rbp, struct epitem, rbn); 533 ep_remove(ep, epi); 534 } 535 536 mutex_unlock(&epmutex); 537 } 538 539 static int ep_eventpoll_release(struct inode *inode, struct file *file) 540 { 541 struct eventpoll *ep = file->private_data; 542 543 if (ep) { 544 ep_free(ep); 545 kfree(ep); 546 } 547 548 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: close() ep=%p\n", current, ep)); 549 return 0; 550 } 551 552 static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait) 553 { 554 unsigned int pollflags = 0; 555 unsigned long flags; 556 struct eventpoll *ep = file->private_data; 557 558 /* Insert inside our poll wait queue */ 559 poll_wait(file, &ep->poll_wait, wait); 560 561 /* Check our condition */ 562 read_lock_irqsave(&ep->lock, flags); 563 if (!list_empty(&ep->rdllist)) 564 pollflags = POLLIN | POLLRDNORM; 565 read_unlock_irqrestore(&ep->lock, flags); 566 567 return pollflags; 568 } 569 570 /* File callbacks that implement the eventpoll file behaviour */ 571 static const struct file_operations eventpoll_fops = { 572 .release = ep_eventpoll_release, 573 .poll = ep_eventpoll_poll 574 }; 575 576 /* Fast test to see if the file is an evenpoll file */ 577 static inline int is_file_epoll(struct file *f) 578 { 579 return f->f_op == &eventpoll_fops; 580 } 581 582 /* 583 * This is called from eventpoll_release() to unlink files from the eventpoll 584 * interface. We need to have this facility to cleanup correctly files that are 585 * closed without being removed from the eventpoll interface. 586 */ 587 void eventpoll_release_file(struct file *file) 588 { 589 struct list_head *lsthead = &file->f_ep_links; 590 struct eventpoll *ep; 591 struct epitem *epi; 592 593 /* 594 * We don't want to get "file->f_ep_lock" because it is not 595 * necessary. It is not necessary because we're in the "struct file" 596 * cleanup path, and this means that noone is using this file anymore. 597 * The only hit might come from ep_free() but by holding the semaphore 598 * will correctly serialize the operation. We do need to acquire 599 * "ep->sem" after "epmutex" because ep_remove() requires it when called 600 * from anywhere but ep_free(). 601 */ 602 mutex_lock(&epmutex); 603 604 while (!list_empty(lsthead)) { 605 epi = list_first_entry(lsthead, struct epitem, fllink); 606 607 ep = epi->ep; 608 list_del_init(&epi->fllink); 609 down_write(&ep->sem); 610 ep_remove(ep, epi); 611 up_write(&ep->sem); 612 } 613 614 mutex_unlock(&epmutex); 615 } 616 617 static int ep_alloc(struct eventpoll **pep) 618 { 619 struct eventpoll *ep = kzalloc(sizeof(*ep), GFP_KERNEL); 620 621 if (!ep) 622 return -ENOMEM; 623 624 rwlock_init(&ep->lock); 625 init_rwsem(&ep->sem); 626 init_waitqueue_head(&ep->wq); 627 init_waitqueue_head(&ep->poll_wait); 628 INIT_LIST_HEAD(&ep->rdllist); 629 ep->rbr = RB_ROOT; 630 631 *pep = ep; 632 633 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_alloc() ep=%p\n", 634 current, ep)); 635 return 0; 636 } 637 638 /* 639 * Search the file inside the eventpoll tree. It add usage count to 640 * the returned item, so the caller must call ep_release_epitem() 641 * after finished using the "struct epitem". 642 */ 643 static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd) 644 { 645 int kcmp; 646 unsigned long flags; 647 struct rb_node *rbp; 648 struct epitem *epi, *epir = NULL; 649 struct epoll_filefd ffd; 650 651 ep_set_ffd(&ffd, file, fd); 652 read_lock_irqsave(&ep->lock, flags); 653 for (rbp = ep->rbr.rb_node; rbp; ) { 654 epi = rb_entry(rbp, struct epitem, rbn); 655 kcmp = ep_cmp_ffd(&ffd, &epi->ffd); 656 if (kcmp > 0) 657 rbp = rbp->rb_right; 658 else if (kcmp < 0) 659 rbp = rbp->rb_left; 660 else { 661 ep_use_epitem(epi); 662 epir = epi; 663 break; 664 } 665 } 666 read_unlock_irqrestore(&ep->lock, flags); 667 668 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_find(%p) -> %p\n", 669 current, file, epir)); 670 671 return epir; 672 } 673 674 /* 675 * This is the callback that is passed to the wait queue wakeup 676 * machanism. It is called by the stored file descriptors when they 677 * have events to report. 678 */ 679 static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *key) 680 { 681 int pwake = 0; 682 unsigned long flags; 683 struct epitem *epi = ep_item_from_wait(wait); 684 struct eventpoll *ep = epi->ep; 685 686 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: poll_callback(%p) epi=%p ep=%p\n", 687 current, epi->ffd.file, epi, ep)); 688 689 write_lock_irqsave(&ep->lock, flags); 690 691 /* 692 * If the event mask does not contain any poll(2) event, we consider the 693 * descriptor to be disabled. This condition is likely the effect of the 694 * EPOLLONESHOT bit that disables the descriptor when an event is received, 695 * until the next EPOLL_CTL_MOD will be issued. 696 */ 697 if (!(epi->event.events & ~EP_PRIVATE_BITS)) 698 goto is_disabled; 699 700 /* If this file is already in the ready list we exit soon */ 701 if (ep_is_linked(&epi->rdllink)) 702 goto is_linked; 703 704 list_add_tail(&epi->rdllink, &ep->rdllist); 705 706 is_linked: 707 /* 708 * Wake up ( if active ) both the eventpoll wait list and the ->poll() 709 * wait list. 710 */ 711 if (waitqueue_active(&ep->wq)) 712 __wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE | 713 TASK_INTERRUPTIBLE); 714 if (waitqueue_active(&ep->poll_wait)) 715 pwake++; 716 717 is_disabled: 718 write_unlock_irqrestore(&ep->lock, flags); 719 720 /* We have to call this outside the lock */ 721 if (pwake) 722 ep_poll_safewake(&psw, &ep->poll_wait); 723 724 return 1; 725 } 726 727 /* 728 * This is the callback that is used to add our wait queue to the 729 * target file wakeup lists. 730 */ 731 static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, 732 poll_table *pt) 733 { 734 struct epitem *epi = ep_item_from_epqueue(pt); 735 struct eppoll_entry *pwq; 736 737 if (epi->nwait >= 0 && (pwq = kmem_cache_alloc(pwq_cache, GFP_KERNEL))) { 738 init_waitqueue_func_entry(&pwq->wait, ep_poll_callback); 739 pwq->whead = whead; 740 pwq->base = epi; 741 add_wait_queue(whead, &pwq->wait); 742 list_add_tail(&pwq->llink, &epi->pwqlist); 743 epi->nwait++; 744 } else { 745 /* We have to signal that an error occurred */ 746 epi->nwait = -1; 747 } 748 } 749 750 static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi) 751 { 752 int kcmp; 753 struct rb_node **p = &ep->rbr.rb_node, *parent = NULL; 754 struct epitem *epic; 755 756 while (*p) { 757 parent = *p; 758 epic = rb_entry(parent, struct epitem, rbn); 759 kcmp = ep_cmp_ffd(&epi->ffd, &epic->ffd); 760 if (kcmp > 0) 761 p = &parent->rb_right; 762 else 763 p = &parent->rb_left; 764 } 765 rb_link_node(&epi->rbn, parent, p); 766 rb_insert_color(&epi->rbn, &ep->rbr); 767 } 768 769 static int ep_insert(struct eventpoll *ep, struct epoll_event *event, 770 struct file *tfile, int fd) 771 { 772 int error, revents, pwake = 0; 773 unsigned long flags; 774 struct epitem *epi; 775 struct ep_pqueue epq; 776 777 error = -ENOMEM; 778 if (!(epi = kmem_cache_alloc(epi_cache, GFP_KERNEL))) 779 goto error_return; 780 781 /* Item initialization follow here ... */ 782 ep_rb_initnode(&epi->rbn); 783 INIT_LIST_HEAD(&epi->rdllink); 784 INIT_LIST_HEAD(&epi->fllink); 785 INIT_LIST_HEAD(&epi->pwqlist); 786 epi->ep = ep; 787 ep_set_ffd(&epi->ffd, tfile, fd); 788 epi->event = *event; 789 atomic_set(&epi->usecnt, 1); 790 epi->nwait = 0; 791 792 /* Initialize the poll table using the queue callback */ 793 epq.epi = epi; 794 init_poll_funcptr(&epq.pt, ep_ptable_queue_proc); 795 796 /* 797 * Attach the item to the poll hooks and get current event bits. 798 * We can safely use the file* here because its usage count has 799 * been increased by the caller of this function. 800 */ 801 revents = tfile->f_op->poll(tfile, &epq.pt); 802 803 /* 804 * We have to check if something went wrong during the poll wait queue 805 * install process. Namely an allocation for a wait queue failed due 806 * high memory pressure. 807 */ 808 if (epi->nwait < 0) 809 goto error_unregister; 810 811 /* Add the current item to the list of active epoll hook for this file */ 812 spin_lock(&tfile->f_ep_lock); 813 list_add_tail(&epi->fllink, &tfile->f_ep_links); 814 spin_unlock(&tfile->f_ep_lock); 815 816 /* We have to drop the new item inside our item list to keep track of it */ 817 write_lock_irqsave(&ep->lock, flags); 818 819 /* Add the current item to the rb-tree */ 820 ep_rbtree_insert(ep, epi); 821 822 /* If the file is already "ready" we drop it inside the ready list */ 823 if ((revents & event->events) && !ep_is_linked(&epi->rdllink)) { 824 list_add_tail(&epi->rdllink, &ep->rdllist); 825 826 /* Notify waiting tasks that events are available */ 827 if (waitqueue_active(&ep->wq)) 828 __wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE); 829 if (waitqueue_active(&ep->poll_wait)) 830 pwake++; 831 } 832 833 write_unlock_irqrestore(&ep->lock, flags); 834 835 /* We have to call this outside the lock */ 836 if (pwake) 837 ep_poll_safewake(&psw, &ep->poll_wait); 838 839 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_insert(%p, %p, %d)\n", 840 current, ep, tfile, fd)); 841 842 return 0; 843 844 error_unregister: 845 ep_unregister_pollwait(ep, epi); 846 847 /* 848 * We need to do this because an event could have been arrived on some 849 * allocated wait queue. 850 */ 851 write_lock_irqsave(&ep->lock, flags); 852 if (ep_is_linked(&epi->rdllink)) 853 list_del_init(&epi->rdllink); 854 write_unlock_irqrestore(&ep->lock, flags); 855 856 kmem_cache_free(epi_cache, epi); 857 error_return: 858 return error; 859 } 860 861 /* 862 * Modify the interest event mask by dropping an event if the new mask 863 * has a match in the current file status. 864 */ 865 static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_event *event) 866 { 867 int pwake = 0; 868 unsigned int revents; 869 unsigned long flags; 870 871 /* 872 * Set the new event interest mask before calling f_op->poll(), otherwise 873 * a potential race might occur. In fact if we do this operation inside 874 * the lock, an event might happen between the f_op->poll() call and the 875 * new event set registering. 876 */ 877 epi->event.events = event->events; 878 879 /* 880 * Get current event bits. We can safely use the file* here because 881 * its usage count has been increased by the caller of this function. 882 */ 883 revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL); 884 885 write_lock_irqsave(&ep->lock, flags); 886 887 /* Copy the data member from inside the lock */ 888 epi->event.data = event->data; 889 890 /* 891 * If the item is not linked to the RB tree it means that it's on its 892 * way toward the removal. Do nothing in this case. 893 */ 894 if (ep_rb_linked(&epi->rbn)) { 895 /* 896 * If the item is "hot" and it is not registered inside the ready 897 * list, push it inside. If the item is not "hot" and it is currently 898 * registered inside the ready list, unlink it. 899 */ 900 if (revents & event->events) { 901 if (!ep_is_linked(&epi->rdllink)) { 902 list_add_tail(&epi->rdllink, &ep->rdllist); 903 904 /* Notify waiting tasks that events are available */ 905 if (waitqueue_active(&ep->wq)) 906 __wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE | 907 TASK_INTERRUPTIBLE); 908 if (waitqueue_active(&ep->poll_wait)) 909 pwake++; 910 } 911 } 912 } 913 914 write_unlock_irqrestore(&ep->lock, flags); 915 916 /* We have to call this outside the lock */ 917 if (pwake) 918 ep_poll_safewake(&psw, &ep->poll_wait); 919 920 return 0; 921 } 922 923 /* 924 * This function is called without holding the "ep->lock" since the call to 925 * __copy_to_user() might sleep, and also f_op->poll() might reenable the IRQ 926 * because of the way poll() is traditionally implemented in Linux. 927 */ 928 static int ep_send_events(struct eventpoll *ep, struct list_head *txlist, 929 struct epoll_event __user *events, int maxevents) 930 { 931 int eventcnt, error = -EFAULT, pwake = 0; 932 unsigned int revents; 933 unsigned long flags; 934 struct epitem *epi; 935 struct list_head injlist; 936 937 INIT_LIST_HEAD(&injlist); 938 939 /* 940 * We can loop without lock because this is a task private list. 941 * We just splice'd out the ep->rdllist in ep_collect_ready_items(). 942 * Items cannot vanish during the loop because we are holding "sem" in 943 * read. 944 */ 945 for (eventcnt = 0; !list_empty(txlist) && eventcnt < maxevents;) { 946 epi = list_first_entry(txlist, struct epitem, rdllink); 947 prefetch(epi->rdllink.next); 948 949 /* 950 * Get the ready file event set. We can safely use the file 951 * because we are holding the "sem" in read and this will 952 * guarantee that both the file and the item will not vanish. 953 */ 954 revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL); 955 revents &= epi->event.events; 956 957 /* 958 * Is the event mask intersect the caller-requested one, 959 * deliver the event to userspace. Again, we are holding 960 * "sem" in read, so no operations coming from userspace 961 * can change the item. 962 */ 963 if (revents) { 964 if (__put_user(revents, 965 &events[eventcnt].events) || 966 __put_user(epi->event.data, 967 &events[eventcnt].data)) 968 goto errxit; 969 if (epi->event.events & EPOLLONESHOT) 970 epi->event.events &= EP_PRIVATE_BITS; 971 eventcnt++; 972 } 973 974 /* 975 * This is tricky. We are holding the "sem" in read, and this 976 * means that the operations that can change the "linked" status 977 * of the epoll item (epi->rbn and epi->rdllink), cannot touch 978 * them. Also, since we are "linked" from a epi->rdllink POV 979 * (the item is linked to our transmission list we just 980 * spliced), the ep_poll_callback() cannot touch us either, 981 * because of the check present in there. Another parallel 982 * epoll_wait() will not get the same result set, since we 983 * spliced the ready list before. Note that list_del() still 984 * shows the item as linked to the test in ep_poll_callback(). 985 */ 986 list_del(&epi->rdllink); 987 if (!(epi->event.events & EPOLLET) && 988 (revents & epi->event.events)) 989 list_add_tail(&epi->rdllink, &injlist); 990 else { 991 /* 992 * Be sure the item is totally detached before re-init 993 * the list_head. After INIT_LIST_HEAD() is committed, 994 * the ep_poll_callback() can requeue the item again, 995 * but we don't care since we are already past it. 996 */ 997 smp_mb(); 998 INIT_LIST_HEAD(&epi->rdllink); 999 } 1000 } 1001 error = 0; 1002 1003 errxit: 1004 1005 /* 1006 * If the re-injection list or the txlist are not empty, re-splice 1007 * them to the ready list and do proper wakeups. 1008 */ 1009 if (!list_empty(&injlist) || !list_empty(txlist)) { 1010 write_lock_irqsave(&ep->lock, flags); 1011 1012 list_splice(txlist, &ep->rdllist); 1013 list_splice(&injlist, &ep->rdllist); 1014 /* 1015 * Wake up ( if active ) both the eventpoll wait list and the ->poll() 1016 * wait list. 1017 */ 1018 if (waitqueue_active(&ep->wq)) 1019 __wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE | 1020 TASK_INTERRUPTIBLE); 1021 if (waitqueue_active(&ep->poll_wait)) 1022 pwake++; 1023 1024 write_unlock_irqrestore(&ep->lock, flags); 1025 } 1026 1027 /* We have to call this outside the lock */ 1028 if (pwake) 1029 ep_poll_safewake(&psw, &ep->poll_wait); 1030 1031 return eventcnt == 0 ? error: eventcnt; 1032 } 1033 1034 /* 1035 * Perform the transfer of events to user space. 1036 */ 1037 static int ep_events_transfer(struct eventpoll *ep, 1038 struct epoll_event __user *events, int maxevents) 1039 { 1040 int eventcnt; 1041 unsigned long flags; 1042 struct list_head txlist; 1043 1044 INIT_LIST_HEAD(&txlist); 1045 1046 /* 1047 * We need to lock this because we could be hit by 1048 * eventpoll_release_file() and epoll_ctl(EPOLL_CTL_DEL). 1049 */ 1050 down_read(&ep->sem); 1051 1052 /* 1053 * Steal the ready list, and re-init the original one to the 1054 * empty list. 1055 */ 1056 write_lock_irqsave(&ep->lock, flags); 1057 list_splice(&ep->rdllist, &txlist); 1058 INIT_LIST_HEAD(&ep->rdllist); 1059 write_unlock_irqrestore(&ep->lock, flags); 1060 1061 /* Build result set in userspace */ 1062 eventcnt = ep_send_events(ep, &txlist, events, maxevents); 1063 1064 up_read(&ep->sem); 1065 1066 return eventcnt; 1067 } 1068 1069 static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, 1070 int maxevents, long timeout) 1071 { 1072 int res, eavail; 1073 unsigned long flags; 1074 long jtimeout; 1075 wait_queue_t wait; 1076 1077 /* 1078 * Calculate the timeout by checking for the "infinite" value ( -1 ) 1079 * and the overflow condition. The passed timeout is in milliseconds, 1080 * that why (t * HZ) / 1000. 1081 */ 1082 jtimeout = (timeout < 0 || timeout >= EP_MAX_MSTIMEO) ? 1083 MAX_SCHEDULE_TIMEOUT : (timeout * HZ + 999) / 1000; 1084 1085 retry: 1086 write_lock_irqsave(&ep->lock, flags); 1087 1088 res = 0; 1089 if (list_empty(&ep->rdllist)) { 1090 /* 1091 * We don't have any available event to return to the caller. 1092 * We need to sleep here, and we will be wake up by 1093 * ep_poll_callback() when events will become available. 1094 */ 1095 init_waitqueue_entry(&wait, current); 1096 __add_wait_queue(&ep->wq, &wait); 1097 1098 for (;;) { 1099 /* 1100 * We don't want to sleep if the ep_poll_callback() sends us 1101 * a wakeup in between. That's why we set the task state 1102 * to TASK_INTERRUPTIBLE before doing the checks. 1103 */ 1104 set_current_state(TASK_INTERRUPTIBLE); 1105 if (!list_empty(&ep->rdllist) || !jtimeout) 1106 break; 1107 if (signal_pending(current)) { 1108 res = -EINTR; 1109 break; 1110 } 1111 1112 write_unlock_irqrestore(&ep->lock, flags); 1113 jtimeout = schedule_timeout(jtimeout); 1114 write_lock_irqsave(&ep->lock, flags); 1115 } 1116 __remove_wait_queue(&ep->wq, &wait); 1117 1118 set_current_state(TASK_RUNNING); 1119 } 1120 1121 /* Is it worth to try to dig for events ? */ 1122 eavail = !list_empty(&ep->rdllist); 1123 1124 write_unlock_irqrestore(&ep->lock, flags); 1125 1126 /* 1127 * Try to transfer events to user space. In case we get 0 events and 1128 * there's still timeout left over, we go trying again in search of 1129 * more luck. 1130 */ 1131 if (!res && eavail && 1132 !(res = ep_events_transfer(ep, events, maxevents)) && jtimeout) 1133 goto retry; 1134 1135 return res; 1136 } 1137 1138 /* 1139 * It opens an eventpoll file descriptor by suggesting a storage of "size" 1140 * file descriptors. The size parameter is just an hint about how to size 1141 * data structures. It won't prevent the user to store more than "size" 1142 * file descriptors inside the epoll interface. It is the kernel part of 1143 * the userspace epoll_create(2). 1144 */ 1145 asmlinkage long sys_epoll_create(int size) 1146 { 1147 int error, fd = -1; 1148 struct eventpoll *ep; 1149 struct inode *inode; 1150 struct file *file; 1151 1152 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d)\n", 1153 current, size)); 1154 1155 /* 1156 * Sanity check on the size parameter, and create the internal data 1157 * structure ( "struct eventpoll" ). 1158 */ 1159 error = -EINVAL; 1160 if (size <= 0 || (error = ep_alloc(&ep)) != 0) 1161 goto error_return; 1162 1163 /* 1164 * Creates all the items needed to setup an eventpoll file. That is, 1165 * a file structure, and inode and a free file descriptor. 1166 */ 1167 error = anon_inode_getfd(&fd, &inode, &file, "[eventpoll]", 1168 &eventpoll_fops, ep); 1169 if (error) 1170 goto error_free; 1171 1172 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n", 1173 current, size, fd)); 1174 1175 return fd; 1176 1177 error_free: 1178 ep_free(ep); 1179 kfree(ep); 1180 error_return: 1181 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n", 1182 current, size, error)); 1183 return error; 1184 } 1185 1186 /* 1187 * The following function implements the controller interface for 1188 * the eventpoll file that enables the insertion/removal/change of 1189 * file descriptors inside the interest set. It represents 1190 * the kernel part of the user space epoll_ctl(2). 1191 */ 1192 asmlinkage long sys_epoll_ctl(int epfd, int op, int fd, 1193 struct epoll_event __user *event) 1194 { 1195 int error; 1196 struct file *file, *tfile; 1197 struct eventpoll *ep; 1198 struct epitem *epi; 1199 struct epoll_event epds; 1200 1201 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %p)\n", 1202 current, epfd, op, fd, event)); 1203 1204 error = -EFAULT; 1205 if (ep_op_has_event(op) && 1206 copy_from_user(&epds, event, sizeof(struct epoll_event))) 1207 goto error_return; 1208 1209 /* Get the "struct file *" for the eventpoll file */ 1210 error = -EBADF; 1211 file = fget(epfd); 1212 if (!file) 1213 goto error_return; 1214 1215 /* Get the "struct file *" for the target file */ 1216 tfile = fget(fd); 1217 if (!tfile) 1218 goto error_fput; 1219 1220 /* The target file descriptor must support poll */ 1221 error = -EPERM; 1222 if (!tfile->f_op || !tfile->f_op->poll) 1223 goto error_tgt_fput; 1224 1225 /* 1226 * We have to check that the file structure underneath the file descriptor 1227 * the user passed to us _is_ an eventpoll file. And also we do not permit 1228 * adding an epoll file descriptor inside itself. 1229 */ 1230 error = -EINVAL; 1231 if (file == tfile || !is_file_epoll(file)) 1232 goto error_tgt_fput; 1233 1234 /* 1235 * At this point it is safe to assume that the "private_data" contains 1236 * our own data structure. 1237 */ 1238 ep = file->private_data; 1239 1240 down_write(&ep->sem); 1241 1242 /* Try to lookup the file inside our RB tree */ 1243 epi = ep_find(ep, tfile, fd); 1244 1245 error = -EINVAL; 1246 switch (op) { 1247 case EPOLL_CTL_ADD: 1248 if (!epi) { 1249 epds.events |= POLLERR | POLLHUP; 1250 1251 error = ep_insert(ep, &epds, tfile, fd); 1252 } else 1253 error = -EEXIST; 1254 break; 1255 case EPOLL_CTL_DEL: 1256 if (epi) 1257 error = ep_remove(ep, epi); 1258 else 1259 error = -ENOENT; 1260 break; 1261 case EPOLL_CTL_MOD: 1262 if (epi) { 1263 epds.events |= POLLERR | POLLHUP; 1264 error = ep_modify(ep, epi, &epds); 1265 } else 1266 error = -ENOENT; 1267 break; 1268 } 1269 /* 1270 * The function ep_find() increments the usage count of the structure 1271 * so, if this is not NULL, we need to release it. 1272 */ 1273 if (epi) 1274 ep_release_epitem(epi); 1275 up_write(&ep->sem); 1276 1277 error_tgt_fput: 1278 fput(tfile); 1279 error_fput: 1280 fput(file); 1281 error_return: 1282 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %p) = %d\n", 1283 current, epfd, op, fd, event, error)); 1284 1285 return error; 1286 } 1287 1288 /* 1289 * Implement the event wait interface for the eventpoll file. It is the kernel 1290 * part of the user space epoll_wait(2). 1291 */ 1292 asmlinkage long sys_epoll_wait(int epfd, struct epoll_event __user *events, 1293 int maxevents, int timeout) 1294 { 1295 int error; 1296 struct file *file; 1297 struct eventpoll *ep; 1298 1299 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_wait(%d, %p, %d, %d)\n", 1300 current, epfd, events, maxevents, timeout)); 1301 1302 /* The maximum number of event must be greater than zero */ 1303 if (maxevents <= 0 || maxevents > EP_MAX_EVENTS) 1304 return -EINVAL; 1305 1306 /* Verify that the area passed by the user is writeable */ 1307 if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event))) { 1308 error = -EFAULT; 1309 goto error_return; 1310 } 1311 1312 /* Get the "struct file *" for the eventpoll file */ 1313 error = -EBADF; 1314 file = fget(epfd); 1315 if (!file) 1316 goto error_return; 1317 1318 /* 1319 * We have to check that the file structure underneath the fd 1320 * the user passed to us _is_ an eventpoll file. 1321 */ 1322 error = -EINVAL; 1323 if (!is_file_epoll(file)) 1324 goto error_fput; 1325 1326 /* 1327 * At this point it is safe to assume that the "private_data" contains 1328 * our own data structure. 1329 */ 1330 ep = file->private_data; 1331 1332 /* Time to fish for events ... */ 1333 error = ep_poll(ep, events, maxevents, timeout); 1334 1335 error_fput: 1336 fput(file); 1337 error_return: 1338 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_wait(%d, %p, %d, %d) = %d\n", 1339 current, epfd, events, maxevents, timeout, error)); 1340 1341 return error; 1342 } 1343 1344 #ifdef TIF_RESTORE_SIGMASK 1345 1346 /* 1347 * Implement the event wait interface for the eventpoll file. It is the kernel 1348 * part of the user space epoll_pwait(2). 1349 */ 1350 asmlinkage long sys_epoll_pwait(int epfd, struct epoll_event __user *events, 1351 int maxevents, int timeout, const sigset_t __user *sigmask, 1352 size_t sigsetsize) 1353 { 1354 int error; 1355 sigset_t ksigmask, sigsaved; 1356 1357 /* 1358 * If the caller wants a certain signal mask to be set during the wait, 1359 * we apply it here. 1360 */ 1361 if (sigmask) { 1362 if (sigsetsize != sizeof(sigset_t)) 1363 return -EINVAL; 1364 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) 1365 return -EFAULT; 1366 sigdelsetmask(&ksigmask, sigmask(SIGKILL) | sigmask(SIGSTOP)); 1367 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); 1368 } 1369 1370 error = sys_epoll_wait(epfd, events, maxevents, timeout); 1371 1372 /* 1373 * If we changed the signal mask, we need to restore the original one. 1374 * In case we've got a signal while waiting, we do not restore the 1375 * signal mask yet, and we allow do_signal() to deliver the signal on 1376 * the way back to userspace, before the signal mask is restored. 1377 */ 1378 if (sigmask) { 1379 if (error == -EINTR) { 1380 memcpy(¤t->saved_sigmask, &sigsaved, 1381 sizeof(sigsaved)); 1382 set_thread_flag(TIF_RESTORE_SIGMASK); 1383 } else 1384 sigprocmask(SIG_SETMASK, &sigsaved, NULL); 1385 } 1386 1387 return error; 1388 } 1389 1390 #endif /* #ifdef TIF_RESTORE_SIGMASK */ 1391 1392 static int __init eventpoll_init(void) 1393 { 1394 mutex_init(&epmutex); 1395 1396 /* Initialize the structure used to perform safe poll wait head wake ups */ 1397 ep_poll_safewake_init(&psw); 1398 1399 /* Allocates slab cache used to allocate "struct epitem" items */ 1400 epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem), 1401 0, SLAB_HWCACHE_ALIGN|EPI_SLAB_DEBUG|SLAB_PANIC, 1402 NULL, NULL); 1403 1404 /* Allocates slab cache used to allocate "struct eppoll_entry" */ 1405 pwq_cache = kmem_cache_create("eventpoll_pwq", 1406 sizeof(struct eppoll_entry), 0, 1407 EPI_SLAB_DEBUG|SLAB_PANIC, NULL, NULL); 1408 1409 return 0; 1410 } 1411 fs_initcall(eventpoll_init); 1412 1413