1 /* 2 * fs/eventpoll.c (Efficent event polling implementation) 3 * Copyright (C) 2001,...,2007 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/rbtree.h> 30 #include <linux/wait.h> 31 #include <linux/eventpoll.h> 32 #include <linux/mount.h> 33 #include <linux/bitops.h> 34 #include <linux/mutex.h> 35 #include <linux/anon_inodes.h> 36 #include <asm/uaccess.h> 37 #include <asm/system.h> 38 #include <asm/io.h> 39 #include <asm/mman.h> 40 #include <asm/atomic.h> 41 42 /* 43 * LOCKING: 44 * There are three level of locking required by epoll : 45 * 46 * 1) epmutex (mutex) 47 * 2) ep->mtx (mutex) 48 * 3) ep->lock (spinlock) 49 * 50 * The acquire order is the one listed above, from 1 to 3. 51 * We need a spinlock (ep->lock) because we manipulate objects 52 * from inside the poll callback, that might be triggered from 53 * a wake_up() that in turn might be called from IRQ context. 54 * So we can't sleep inside the poll callback and hence we need 55 * a spinlock. During the event transfer loop (from kernel to 56 * user space) we could end up sleeping due a copy_to_user(), so 57 * we need a lock that will allow us to sleep. This lock is a 58 * mutex (ep->mtx). It is acquired during the event transfer loop, 59 * during epoll_ctl(EPOLL_CTL_DEL) and during eventpoll_release_file(). 60 * Then we also need a global mutex to serialize eventpoll_release_file() 61 * and ep_free(). 62 * This mutex is acquired by ep_free() during the epoll file 63 * cleanup path and it is also acquired by eventpoll_release_file() 64 * if a file has been pushed inside an epoll set and it is then 65 * close()d without a previous call toepoll_ctl(EPOLL_CTL_DEL). 66 * It is possible to drop the "ep->mtx" and to use the global 67 * mutex "epmutex" (together with "ep->lock") to have it working, 68 * but having "ep->mtx" will make the interface more scalable. 69 * Events that require holding "epmutex" are very rare, while for 70 * normal operations the epoll private "ep->mtx" will guarantee 71 * a better scalability. 72 */ 73 74 #define DEBUG_EPOLL 0 75 76 #if DEBUG_EPOLL > 0 77 #define DPRINTK(x) printk x 78 #define DNPRINTK(n, x) do { if ((n) <= DEBUG_EPOLL) printk x; } while (0) 79 #else /* #if DEBUG_EPOLL > 0 */ 80 #define DPRINTK(x) (void) 0 81 #define DNPRINTK(n, x) (void) 0 82 #endif /* #if DEBUG_EPOLL > 0 */ 83 84 #define DEBUG_EPI 0 85 86 #if DEBUG_EPI != 0 87 #define EPI_SLAB_DEBUG (SLAB_DEBUG_FREE | SLAB_RED_ZONE /* | SLAB_POISON */) 88 #else /* #if DEBUG_EPI != 0 */ 89 #define EPI_SLAB_DEBUG 0 90 #endif /* #if DEBUG_EPI != 0 */ 91 92 /* Epoll private bits inside the event mask */ 93 #define EP_PRIVATE_BITS (EPOLLONESHOT | EPOLLET) 94 95 /* Maximum number of poll wake up nests we are allowing */ 96 #define EP_MAX_POLLWAKE_NESTS 4 97 98 /* Maximum msec timeout value storeable in a long int */ 99 #define EP_MAX_MSTIMEO min(1000ULL * MAX_SCHEDULE_TIMEOUT / HZ, (LONG_MAX - 999ULL) / HZ) 100 101 #define EP_MAX_EVENTS (INT_MAX / sizeof(struct epoll_event)) 102 103 #define EP_UNACTIVE_PTR ((void *) -1L) 104 105 #define EP_ITEM_COST (sizeof(struct epitem) + sizeof(struct eppoll_entry)) 106 107 struct epoll_filefd { 108 struct file *file; 109 int fd; 110 }; 111 112 /* 113 * Node that is linked into the "wake_task_list" member of the "struct poll_safewake". 114 * It is used to keep track on all tasks that are currently inside the wake_up() code 115 * to 1) short-circuit the one coming from the same task and same wait queue head 116 * (loop) 2) allow a maximum number of epoll descriptors inclusion nesting 117 * 3) let go the ones coming from other tasks. 118 */ 119 struct wake_task_node { 120 struct list_head llink; 121 struct task_struct *task; 122 wait_queue_head_t *wq; 123 }; 124 125 /* 126 * This is used to implement the safe poll wake up avoiding to reenter 127 * the poll callback from inside wake_up(). 128 */ 129 struct poll_safewake { 130 struct list_head wake_task_list; 131 spinlock_t lock; 132 }; 133 134 /* 135 * Each file descriptor added to the eventpoll interface will 136 * have an entry of this type linked to the "rbr" RB tree. 137 */ 138 struct epitem { 139 /* RB tree node used to link this structure to the eventpoll RB tree */ 140 struct rb_node rbn; 141 142 /* List header used to link this structure to the eventpoll ready list */ 143 struct list_head rdllink; 144 145 /* 146 * Works together "struct eventpoll"->ovflist in keeping the 147 * single linked chain of items. 148 */ 149 struct epitem *next; 150 151 /* The file descriptor information this item refers to */ 152 struct epoll_filefd ffd; 153 154 /* Number of active wait queue attached to poll operations */ 155 int nwait; 156 157 /* List containing poll wait queues */ 158 struct list_head pwqlist; 159 160 /* The "container" of this item */ 161 struct eventpoll *ep; 162 163 /* List header used to link this item to the "struct file" items list */ 164 struct list_head fllink; 165 166 /* The structure that describe the interested events and the source fd */ 167 struct epoll_event event; 168 }; 169 170 /* 171 * This structure is stored inside the "private_data" member of the file 172 * structure and rapresent the main data sructure for the eventpoll 173 * interface. 174 */ 175 struct eventpoll { 176 /* Protect the this structure access */ 177 spinlock_t lock; 178 179 /* 180 * This mutex is used to ensure that files are not removed 181 * while epoll is using them. This is held during the event 182 * collection loop, the file cleanup path, the epoll file exit 183 * code and the ctl operations. 184 */ 185 struct mutex mtx; 186 187 /* Wait queue used by sys_epoll_wait() */ 188 wait_queue_head_t wq; 189 190 /* Wait queue used by file->poll() */ 191 wait_queue_head_t poll_wait; 192 193 /* List of ready file descriptors */ 194 struct list_head rdllist; 195 196 /* RB tree root used to store monitored fd structs */ 197 struct rb_root rbr; 198 199 /* 200 * This is a single linked list that chains all the "struct epitem" that 201 * happened while transfering ready events to userspace w/out 202 * holding ->lock. 203 */ 204 struct epitem *ovflist; 205 206 /* The user that created the eventpoll descriptor */ 207 struct user_struct *user; 208 }; 209 210 /* Wait structure used by the poll hooks */ 211 struct eppoll_entry { 212 /* List header used to link this structure to the "struct epitem" */ 213 struct list_head llink; 214 215 /* The "base" pointer is set to the container "struct epitem" */ 216 void *base; 217 218 /* 219 * Wait queue item that will be linked to the target file wait 220 * queue head. 221 */ 222 wait_queue_t wait; 223 224 /* The wait queue head that linked the "wait" wait queue item */ 225 wait_queue_head_t *whead; 226 }; 227 228 /* Wrapper struct used by poll queueing */ 229 struct ep_pqueue { 230 poll_table pt; 231 struct epitem *epi; 232 }; 233 234 /* 235 * Configuration options available inside /proc/sys/fs/epoll/ 236 */ 237 /* Maximum number of epoll devices, per user */ 238 static int max_user_instances __read_mostly; 239 /* Maximum number of epoll watched descriptors, per user */ 240 static int max_user_watches __read_mostly; 241 242 /* 243 * This mutex is used to serialize ep_free() and eventpoll_release_file(). 244 */ 245 static DEFINE_MUTEX(epmutex); 246 247 /* Safe wake up implementation */ 248 static struct poll_safewake psw; 249 250 /* Slab cache used to allocate "struct epitem" */ 251 static struct kmem_cache *epi_cache __read_mostly; 252 253 /* Slab cache used to allocate "struct eppoll_entry" */ 254 static struct kmem_cache *pwq_cache __read_mostly; 255 256 #ifdef CONFIG_SYSCTL 257 258 #include <linux/sysctl.h> 259 260 static int zero; 261 262 ctl_table epoll_table[] = { 263 { 264 .procname = "max_user_instances", 265 .data = &max_user_instances, 266 .maxlen = sizeof(int), 267 .mode = 0644, 268 .proc_handler = &proc_dointvec_minmax, 269 .extra1 = &zero, 270 }, 271 { 272 .procname = "max_user_watches", 273 .data = &max_user_watches, 274 .maxlen = sizeof(int), 275 .mode = 0644, 276 .proc_handler = &proc_dointvec_minmax, 277 .extra1 = &zero, 278 }, 279 { .ctl_name = 0 } 280 }; 281 #endif /* CONFIG_SYSCTL */ 282 283 284 /* Setup the structure that is used as key for the RB tree */ 285 static inline void ep_set_ffd(struct epoll_filefd *ffd, 286 struct file *file, int fd) 287 { 288 ffd->file = file; 289 ffd->fd = fd; 290 } 291 292 /* Compare RB tree keys */ 293 static inline int ep_cmp_ffd(struct epoll_filefd *p1, 294 struct epoll_filefd *p2) 295 { 296 return (p1->file > p2->file ? +1: 297 (p1->file < p2->file ? -1 : p1->fd - p2->fd)); 298 } 299 300 /* Tells us if the item is currently linked */ 301 static inline int ep_is_linked(struct list_head *p) 302 { 303 return !list_empty(p); 304 } 305 306 /* Get the "struct epitem" from a wait queue pointer */ 307 static inline struct epitem *ep_item_from_wait(wait_queue_t *p) 308 { 309 return container_of(p, struct eppoll_entry, wait)->base; 310 } 311 312 /* Get the "struct epitem" from an epoll queue wrapper */ 313 static inline struct epitem *ep_item_from_epqueue(poll_table *p) 314 { 315 return container_of(p, struct ep_pqueue, pt)->epi; 316 } 317 318 /* Tells if the epoll_ctl(2) operation needs an event copy from userspace */ 319 static inline int ep_op_has_event(int op) 320 { 321 return op != EPOLL_CTL_DEL; 322 } 323 324 /* Initialize the poll safe wake up structure */ 325 static void ep_poll_safewake_init(struct poll_safewake *psw) 326 { 327 328 INIT_LIST_HEAD(&psw->wake_task_list); 329 spin_lock_init(&psw->lock); 330 } 331 332 /* 333 * Perform a safe wake up of the poll wait list. The problem is that 334 * with the new callback'd wake up system, it is possible that the 335 * poll callback is reentered from inside the call to wake_up() done 336 * on the poll wait queue head. The rule is that we cannot reenter the 337 * wake up code from the same task more than EP_MAX_POLLWAKE_NESTS times, 338 * and we cannot reenter the same wait queue head at all. This will 339 * enable to have a hierarchy of epoll file descriptor of no more than 340 * EP_MAX_POLLWAKE_NESTS deep. We need the irq version of the spin lock 341 * because this one gets called by the poll callback, that in turn is called 342 * from inside a wake_up(), that might be called from irq context. 343 */ 344 static void ep_poll_safewake(struct poll_safewake *psw, wait_queue_head_t *wq) 345 { 346 int wake_nests = 0; 347 unsigned long flags; 348 struct task_struct *this_task = current; 349 struct list_head *lsthead = &psw->wake_task_list; 350 struct wake_task_node *tncur; 351 struct wake_task_node tnode; 352 353 spin_lock_irqsave(&psw->lock, flags); 354 355 /* Try to see if the current task is already inside this wakeup call */ 356 list_for_each_entry(tncur, lsthead, llink) { 357 358 if (tncur->wq == wq || 359 (tncur->task == this_task && ++wake_nests > EP_MAX_POLLWAKE_NESTS)) { 360 /* 361 * Ops ... loop detected or maximum nest level reached. 362 * We abort this wake by breaking the cycle itself. 363 */ 364 spin_unlock_irqrestore(&psw->lock, flags); 365 return; 366 } 367 } 368 369 /* Add the current task to the list */ 370 tnode.task = this_task; 371 tnode.wq = wq; 372 list_add(&tnode.llink, lsthead); 373 374 spin_unlock_irqrestore(&psw->lock, flags); 375 376 /* Do really wake up now */ 377 wake_up_nested(wq, 1 + wake_nests); 378 379 /* Remove the current task from the list */ 380 spin_lock_irqsave(&psw->lock, flags); 381 list_del(&tnode.llink); 382 spin_unlock_irqrestore(&psw->lock, flags); 383 } 384 385 /* 386 * This function unregister poll callbacks from the associated file descriptor. 387 * Since this must be called without holding "ep->lock" the atomic exchange trick 388 * will protect us from multiple unregister. 389 */ 390 static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi) 391 { 392 int nwait; 393 struct list_head *lsthead = &epi->pwqlist; 394 struct eppoll_entry *pwq; 395 396 /* This is called without locks, so we need the atomic exchange */ 397 nwait = xchg(&epi->nwait, 0); 398 399 if (nwait) { 400 while (!list_empty(lsthead)) { 401 pwq = list_first_entry(lsthead, struct eppoll_entry, llink); 402 403 list_del_init(&pwq->llink); 404 remove_wait_queue(pwq->whead, &pwq->wait); 405 kmem_cache_free(pwq_cache, pwq); 406 } 407 } 408 } 409 410 /* 411 * Removes a "struct epitem" from the eventpoll RB tree and deallocates 412 * all the associated resources. Must be called with "mtx" held. 413 */ 414 static int ep_remove(struct eventpoll *ep, struct epitem *epi) 415 { 416 unsigned long flags; 417 struct file *file = epi->ffd.file; 418 419 /* 420 * Removes poll wait queue hooks. We _have_ to do this without holding 421 * the "ep->lock" otherwise a deadlock might occur. This because of the 422 * sequence of the lock acquisition. Here we do "ep->lock" then the wait 423 * queue head lock when unregistering the wait queue. The wakeup callback 424 * will run by holding the wait queue head lock and will call our callback 425 * that will try to get "ep->lock". 426 */ 427 ep_unregister_pollwait(ep, epi); 428 429 /* Remove the current item from the list of epoll hooks */ 430 spin_lock(&file->f_ep_lock); 431 if (ep_is_linked(&epi->fllink)) 432 list_del_init(&epi->fllink); 433 spin_unlock(&file->f_ep_lock); 434 435 rb_erase(&epi->rbn, &ep->rbr); 436 437 spin_lock_irqsave(&ep->lock, flags); 438 if (ep_is_linked(&epi->rdllink)) 439 list_del_init(&epi->rdllink); 440 spin_unlock_irqrestore(&ep->lock, flags); 441 442 /* At this point it is safe to free the eventpoll item */ 443 kmem_cache_free(epi_cache, epi); 444 445 atomic_dec(&ep->user->epoll_watches); 446 447 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_remove(%p, %p)\n", 448 current, ep, file)); 449 450 return 0; 451 } 452 453 static void ep_free(struct eventpoll *ep) 454 { 455 struct rb_node *rbp; 456 struct epitem *epi; 457 458 /* We need to release all tasks waiting for these file */ 459 if (waitqueue_active(&ep->poll_wait)) 460 ep_poll_safewake(&psw, &ep->poll_wait); 461 462 /* 463 * We need to lock this because we could be hit by 464 * eventpoll_release_file() while we're freeing the "struct eventpoll". 465 * We do not need to hold "ep->mtx" here because the epoll file 466 * is on the way to be removed and no one has references to it 467 * anymore. The only hit might come from eventpoll_release_file() but 468 * holding "epmutex" is sufficent here. 469 */ 470 mutex_lock(&epmutex); 471 472 /* 473 * Walks through the whole tree by unregistering poll callbacks. 474 */ 475 for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { 476 epi = rb_entry(rbp, struct epitem, rbn); 477 478 ep_unregister_pollwait(ep, epi); 479 } 480 481 /* 482 * Walks through the whole tree by freeing each "struct epitem". At this 483 * point we are sure no poll callbacks will be lingering around, and also by 484 * holding "epmutex" we can be sure that no file cleanup code will hit 485 * us during this operation. So we can avoid the lock on "ep->lock". 486 */ 487 while ((rbp = rb_first(&ep->rbr)) != NULL) { 488 epi = rb_entry(rbp, struct epitem, rbn); 489 ep_remove(ep, epi); 490 } 491 492 mutex_unlock(&epmutex); 493 mutex_destroy(&ep->mtx); 494 atomic_dec(&ep->user->epoll_devs); 495 free_uid(ep->user); 496 kfree(ep); 497 } 498 499 static int ep_eventpoll_release(struct inode *inode, struct file *file) 500 { 501 struct eventpoll *ep = file->private_data; 502 503 if (ep) 504 ep_free(ep); 505 506 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: close() ep=%p\n", current, ep)); 507 return 0; 508 } 509 510 static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait) 511 { 512 unsigned int pollflags = 0; 513 unsigned long flags; 514 struct eventpoll *ep = file->private_data; 515 516 /* Insert inside our poll wait queue */ 517 poll_wait(file, &ep->poll_wait, wait); 518 519 /* Check our condition */ 520 spin_lock_irqsave(&ep->lock, flags); 521 if (!list_empty(&ep->rdllist)) 522 pollflags = POLLIN | POLLRDNORM; 523 spin_unlock_irqrestore(&ep->lock, flags); 524 525 return pollflags; 526 } 527 528 /* File callbacks that implement the eventpoll file behaviour */ 529 static const struct file_operations eventpoll_fops = { 530 .release = ep_eventpoll_release, 531 .poll = ep_eventpoll_poll 532 }; 533 534 /* Fast test to see if the file is an evenpoll file */ 535 static inline int is_file_epoll(struct file *f) 536 { 537 return f->f_op == &eventpoll_fops; 538 } 539 540 /* 541 * This is called from eventpoll_release() to unlink files from the eventpoll 542 * interface. We need to have this facility to cleanup correctly files that are 543 * closed without being removed from the eventpoll interface. 544 */ 545 void eventpoll_release_file(struct file *file) 546 { 547 struct list_head *lsthead = &file->f_ep_links; 548 struct eventpoll *ep; 549 struct epitem *epi; 550 551 /* 552 * We don't want to get "file->f_ep_lock" because it is not 553 * necessary. It is not necessary because we're in the "struct file" 554 * cleanup path, and this means that noone is using this file anymore. 555 * So, for example, epoll_ctl() cannot hit here sicne if we reach this 556 * point, the file counter already went to zero and fget() would fail. 557 * The only hit might come from ep_free() but by holding the mutex 558 * will correctly serialize the operation. We do need to acquire 559 * "ep->mtx" after "epmutex" because ep_remove() requires it when called 560 * from anywhere but ep_free(). 561 */ 562 mutex_lock(&epmutex); 563 564 while (!list_empty(lsthead)) { 565 epi = list_first_entry(lsthead, struct epitem, fllink); 566 567 ep = epi->ep; 568 list_del_init(&epi->fllink); 569 mutex_lock(&ep->mtx); 570 ep_remove(ep, epi); 571 mutex_unlock(&ep->mtx); 572 } 573 574 mutex_unlock(&epmutex); 575 } 576 577 static int ep_alloc(struct eventpoll **pep) 578 { 579 int error; 580 struct user_struct *user; 581 struct eventpoll *ep; 582 583 user = get_current_user(); 584 error = -EMFILE; 585 if (unlikely(atomic_read(&user->epoll_devs) >= 586 max_user_instances)) 587 goto free_uid; 588 error = -ENOMEM; 589 ep = kzalloc(sizeof(*ep), GFP_KERNEL); 590 if (unlikely(!ep)) 591 goto free_uid; 592 593 spin_lock_init(&ep->lock); 594 mutex_init(&ep->mtx); 595 init_waitqueue_head(&ep->wq); 596 init_waitqueue_head(&ep->poll_wait); 597 INIT_LIST_HEAD(&ep->rdllist); 598 ep->rbr = RB_ROOT; 599 ep->ovflist = EP_UNACTIVE_PTR; 600 ep->user = user; 601 602 *pep = ep; 603 604 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_alloc() ep=%p\n", 605 current, ep)); 606 return 0; 607 608 free_uid: 609 free_uid(user); 610 return error; 611 } 612 613 /* 614 * Search the file inside the eventpoll tree. The RB tree operations 615 * are protected by the "mtx" mutex, and ep_find() must be called with 616 * "mtx" held. 617 */ 618 static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd) 619 { 620 int kcmp; 621 struct rb_node *rbp; 622 struct epitem *epi, *epir = NULL; 623 struct epoll_filefd ffd; 624 625 ep_set_ffd(&ffd, file, fd); 626 for (rbp = ep->rbr.rb_node; rbp; ) { 627 epi = rb_entry(rbp, struct epitem, rbn); 628 kcmp = ep_cmp_ffd(&ffd, &epi->ffd); 629 if (kcmp > 0) 630 rbp = rbp->rb_right; 631 else if (kcmp < 0) 632 rbp = rbp->rb_left; 633 else { 634 epir = epi; 635 break; 636 } 637 } 638 639 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_find(%p) -> %p\n", 640 current, file, epir)); 641 642 return epir; 643 } 644 645 /* 646 * This is the callback that is passed to the wait queue wakeup 647 * machanism. It is called by the stored file descriptors when they 648 * have events to report. 649 */ 650 static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *key) 651 { 652 int pwake = 0; 653 unsigned long flags; 654 struct epitem *epi = ep_item_from_wait(wait); 655 struct eventpoll *ep = epi->ep; 656 657 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: poll_callback(%p) epi=%p ep=%p\n", 658 current, epi->ffd.file, epi, ep)); 659 660 spin_lock_irqsave(&ep->lock, flags); 661 662 /* 663 * If the event mask does not contain any poll(2) event, we consider the 664 * descriptor to be disabled. This condition is likely the effect of the 665 * EPOLLONESHOT bit that disables the descriptor when an event is received, 666 * until the next EPOLL_CTL_MOD will be issued. 667 */ 668 if (!(epi->event.events & ~EP_PRIVATE_BITS)) 669 goto out_unlock; 670 671 /* 672 * If we are trasfering events to userspace, we can hold no locks 673 * (because we're accessing user memory, and because of linux f_op->poll() 674 * semantics). All the events that happens during that period of time are 675 * chained in ep->ovflist and requeued later on. 676 */ 677 if (unlikely(ep->ovflist != EP_UNACTIVE_PTR)) { 678 if (epi->next == EP_UNACTIVE_PTR) { 679 epi->next = ep->ovflist; 680 ep->ovflist = epi; 681 } 682 goto out_unlock; 683 } 684 685 /* If this file is already in the ready list we exit soon */ 686 if (ep_is_linked(&epi->rdllink)) 687 goto is_linked; 688 689 list_add_tail(&epi->rdllink, &ep->rdllist); 690 691 is_linked: 692 /* 693 * Wake up ( if active ) both the eventpoll wait list and the ->poll() 694 * wait list. 695 */ 696 if (waitqueue_active(&ep->wq)) 697 wake_up_locked(&ep->wq); 698 if (waitqueue_active(&ep->poll_wait)) 699 pwake++; 700 701 out_unlock: 702 spin_unlock_irqrestore(&ep->lock, flags); 703 704 /* We have to call this outside the lock */ 705 if (pwake) 706 ep_poll_safewake(&psw, &ep->poll_wait); 707 708 return 1; 709 } 710 711 /* 712 * This is the callback that is used to add our wait queue to the 713 * target file wakeup lists. 714 */ 715 static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, 716 poll_table *pt) 717 { 718 struct epitem *epi = ep_item_from_epqueue(pt); 719 struct eppoll_entry *pwq; 720 721 if (epi->nwait >= 0 && (pwq = kmem_cache_alloc(pwq_cache, GFP_KERNEL))) { 722 init_waitqueue_func_entry(&pwq->wait, ep_poll_callback); 723 pwq->whead = whead; 724 pwq->base = epi; 725 add_wait_queue(whead, &pwq->wait); 726 list_add_tail(&pwq->llink, &epi->pwqlist); 727 epi->nwait++; 728 } else { 729 /* We have to signal that an error occurred */ 730 epi->nwait = -1; 731 } 732 } 733 734 static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi) 735 { 736 int kcmp; 737 struct rb_node **p = &ep->rbr.rb_node, *parent = NULL; 738 struct epitem *epic; 739 740 while (*p) { 741 parent = *p; 742 epic = rb_entry(parent, struct epitem, rbn); 743 kcmp = ep_cmp_ffd(&epi->ffd, &epic->ffd); 744 if (kcmp > 0) 745 p = &parent->rb_right; 746 else 747 p = &parent->rb_left; 748 } 749 rb_link_node(&epi->rbn, parent, p); 750 rb_insert_color(&epi->rbn, &ep->rbr); 751 } 752 753 /* 754 * Must be called with "mtx" held. 755 */ 756 static int ep_insert(struct eventpoll *ep, struct epoll_event *event, 757 struct file *tfile, int fd) 758 { 759 int error, revents, pwake = 0; 760 unsigned long flags; 761 struct epitem *epi; 762 struct ep_pqueue epq; 763 764 if (unlikely(atomic_read(&ep->user->epoll_watches) >= 765 max_user_watches)) 766 return -ENOSPC; 767 if (!(epi = kmem_cache_alloc(epi_cache, GFP_KERNEL))) 768 return -ENOMEM; 769 770 /* Item initialization follow here ... */ 771 INIT_LIST_HEAD(&epi->rdllink); 772 INIT_LIST_HEAD(&epi->fllink); 773 INIT_LIST_HEAD(&epi->pwqlist); 774 epi->ep = ep; 775 ep_set_ffd(&epi->ffd, tfile, fd); 776 epi->event = *event; 777 epi->nwait = 0; 778 epi->next = EP_UNACTIVE_PTR; 779 780 /* Initialize the poll table using the queue callback */ 781 epq.epi = epi; 782 init_poll_funcptr(&epq.pt, ep_ptable_queue_proc); 783 784 /* 785 * Attach the item to the poll hooks and get current event bits. 786 * We can safely use the file* here because its usage count has 787 * been increased by the caller of this function. Note that after 788 * this operation completes, the poll callback can start hitting 789 * the new item. 790 */ 791 revents = tfile->f_op->poll(tfile, &epq.pt); 792 793 /* 794 * We have to check if something went wrong during the poll wait queue 795 * install process. Namely an allocation for a wait queue failed due 796 * high memory pressure. 797 */ 798 error = -ENOMEM; 799 if (epi->nwait < 0) 800 goto error_unregister; 801 802 /* Add the current item to the list of active epoll hook for this file */ 803 spin_lock(&tfile->f_ep_lock); 804 list_add_tail(&epi->fllink, &tfile->f_ep_links); 805 spin_unlock(&tfile->f_ep_lock); 806 807 /* 808 * Add the current item to the RB tree. All RB tree operations are 809 * protected by "mtx", and ep_insert() is called with "mtx" held. 810 */ 811 ep_rbtree_insert(ep, epi); 812 813 /* We have to drop the new item inside our item list to keep track of it */ 814 spin_lock_irqsave(&ep->lock, flags); 815 816 /* If the file is already "ready" we drop it inside the ready list */ 817 if ((revents & event->events) && !ep_is_linked(&epi->rdllink)) { 818 list_add_tail(&epi->rdllink, &ep->rdllist); 819 820 /* Notify waiting tasks that events are available */ 821 if (waitqueue_active(&ep->wq)) 822 wake_up_locked(&ep->wq); 823 if (waitqueue_active(&ep->poll_wait)) 824 pwake++; 825 } 826 827 spin_unlock_irqrestore(&ep->lock, flags); 828 829 atomic_inc(&ep->user->epoll_watches); 830 831 /* We have to call this outside the lock */ 832 if (pwake) 833 ep_poll_safewake(&psw, &ep->poll_wait); 834 835 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_insert(%p, %p, %d)\n", 836 current, ep, tfile, fd)); 837 838 return 0; 839 840 error_unregister: 841 ep_unregister_pollwait(ep, epi); 842 843 /* 844 * We need to do this because an event could have been arrived on some 845 * allocated wait queue. Note that we don't care about the ep->ovflist 846 * list, since that is used/cleaned only inside a section bound by "mtx". 847 * And ep_insert() is called with "mtx" held. 848 */ 849 spin_lock_irqsave(&ep->lock, flags); 850 if (ep_is_linked(&epi->rdllink)) 851 list_del_init(&epi->rdllink); 852 spin_unlock_irqrestore(&ep->lock, flags); 853 854 kmem_cache_free(epi_cache, epi); 855 856 return error; 857 } 858 859 /* 860 * Modify the interest event mask by dropping an event if the new mask 861 * has a match in the current file status. Must be called with "mtx" held. 862 */ 863 static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_event *event) 864 { 865 int pwake = 0; 866 unsigned int revents; 867 unsigned long flags; 868 869 /* 870 * Set the new event interest mask before calling f_op->poll(), otherwise 871 * a potential race might occur. In fact if we do this operation inside 872 * the lock, an event might happen between the f_op->poll() call and the 873 * new event set registering. 874 */ 875 epi->event.events = event->events; 876 877 /* 878 * Get current event bits. We can safely use the file* here because 879 * its usage count has been increased by the caller of this function. 880 */ 881 revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL); 882 883 spin_lock_irqsave(&ep->lock, flags); 884 885 /* Copy the data member from inside the lock */ 886 epi->event.data = event->data; 887 888 /* 889 * If the item is "hot" and it is not registered inside the ready 890 * list, push it inside. 891 */ 892 if (revents & event->events) { 893 if (!ep_is_linked(&epi->rdllink)) { 894 list_add_tail(&epi->rdllink, &ep->rdllist); 895 896 /* Notify waiting tasks that events are available */ 897 if (waitqueue_active(&ep->wq)) 898 wake_up_locked(&ep->wq); 899 if (waitqueue_active(&ep->poll_wait)) 900 pwake++; 901 } 902 } 903 spin_unlock_irqrestore(&ep->lock, flags); 904 905 /* We have to call this outside the lock */ 906 if (pwake) 907 ep_poll_safewake(&psw, &ep->poll_wait); 908 909 return 0; 910 } 911 912 static int ep_send_events(struct eventpoll *ep, struct epoll_event __user *events, 913 int maxevents) 914 { 915 int eventcnt, error = -EFAULT, pwake = 0; 916 unsigned int revents; 917 unsigned long flags; 918 struct epitem *epi, *nepi; 919 struct list_head txlist; 920 921 INIT_LIST_HEAD(&txlist); 922 923 /* 924 * We need to lock this because we could be hit by 925 * eventpoll_release_file() and epoll_ctl(EPOLL_CTL_DEL). 926 */ 927 mutex_lock(&ep->mtx); 928 929 /* 930 * Steal the ready list, and re-init the original one to the 931 * empty list. Also, set ep->ovflist to NULL so that events 932 * happening while looping w/out locks, are not lost. We cannot 933 * have the poll callback to queue directly on ep->rdllist, 934 * because we are doing it in the loop below, in a lockless way. 935 */ 936 spin_lock_irqsave(&ep->lock, flags); 937 list_splice(&ep->rdllist, &txlist); 938 INIT_LIST_HEAD(&ep->rdllist); 939 ep->ovflist = NULL; 940 spin_unlock_irqrestore(&ep->lock, flags); 941 942 /* 943 * We can loop without lock because this is a task private list. 944 * We just splice'd out the ep->rdllist in ep_collect_ready_items(). 945 * Items cannot vanish during the loop because we are holding "mtx". 946 */ 947 for (eventcnt = 0; !list_empty(&txlist) && eventcnt < maxevents;) { 948 epi = list_first_entry(&txlist, struct epitem, rdllink); 949 950 list_del_init(&epi->rdllink); 951 952 /* 953 * Get the ready file event set. We can safely use the file 954 * because we are holding the "mtx" and this will guarantee 955 * that both the file and the item will not vanish. 956 */ 957 revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL); 958 revents &= epi->event.events; 959 960 /* 961 * Is the event mask intersect the caller-requested one, 962 * deliver the event to userspace. Again, we are holding 963 * "mtx", so no operations coming from userspace can change 964 * the item. 965 */ 966 if (revents) { 967 if (__put_user(revents, 968 &events[eventcnt].events) || 969 __put_user(epi->event.data, 970 &events[eventcnt].data)) 971 goto errxit; 972 if (epi->event.events & EPOLLONESHOT) 973 epi->event.events &= EP_PRIVATE_BITS; 974 eventcnt++; 975 } 976 /* 977 * At this point, noone can insert into ep->rdllist besides 978 * us. The epoll_ctl() callers are locked out by us holding 979 * "mtx" and the poll callback will queue them in ep->ovflist. 980 */ 981 if (!(epi->event.events & EPOLLET) && 982 (revents & epi->event.events)) 983 list_add_tail(&epi->rdllink, &ep->rdllist); 984 } 985 error = 0; 986 987 errxit: 988 989 spin_lock_irqsave(&ep->lock, flags); 990 /* 991 * During the time we spent in the loop above, some other events 992 * might have been queued by the poll callback. We re-insert them 993 * inside the main ready-list here. 994 */ 995 for (nepi = ep->ovflist; (epi = nepi) != NULL; 996 nepi = epi->next, epi->next = EP_UNACTIVE_PTR) { 997 /* 998 * If the above loop quit with errors, the epoll item might still 999 * be linked to "txlist", and the list_splice() done below will 1000 * take care of those cases. 1001 */ 1002 if (!ep_is_linked(&epi->rdllink)) 1003 list_add_tail(&epi->rdllink, &ep->rdllist); 1004 } 1005 /* 1006 * We need to set back ep->ovflist to EP_UNACTIVE_PTR, so that after 1007 * releasing the lock, events will be queued in the normal way inside 1008 * ep->rdllist. 1009 */ 1010 ep->ovflist = EP_UNACTIVE_PTR; 1011 1012 /* 1013 * In case of error in the event-send loop, or in case the number of 1014 * ready events exceeds the userspace limit, we need to splice the 1015 * "txlist" back inside ep->rdllist. 1016 */ 1017 list_splice(&txlist, &ep->rdllist); 1018 1019 if (!list_empty(&ep->rdllist)) { 1020 /* 1021 * Wake up (if active) both the eventpoll wait list and the ->poll() 1022 * wait list (delayed after we release the lock). 1023 */ 1024 if (waitqueue_active(&ep->wq)) 1025 wake_up_locked(&ep->wq); 1026 if (waitqueue_active(&ep->poll_wait)) 1027 pwake++; 1028 } 1029 spin_unlock_irqrestore(&ep->lock, flags); 1030 1031 mutex_unlock(&ep->mtx); 1032 1033 /* We have to call this outside the lock */ 1034 if (pwake) 1035 ep_poll_safewake(&psw, &ep->poll_wait); 1036 1037 return eventcnt == 0 ? error: eventcnt; 1038 } 1039 1040 static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, 1041 int maxevents, long timeout) 1042 { 1043 int res, eavail; 1044 unsigned long flags; 1045 long jtimeout; 1046 wait_queue_t wait; 1047 1048 /* 1049 * Calculate the timeout by checking for the "infinite" value ( -1 ) 1050 * and the overflow condition. The passed timeout is in milliseconds, 1051 * that why (t * HZ) / 1000. 1052 */ 1053 jtimeout = (timeout < 0 || timeout >= EP_MAX_MSTIMEO) ? 1054 MAX_SCHEDULE_TIMEOUT : (timeout * HZ + 999) / 1000; 1055 1056 retry: 1057 spin_lock_irqsave(&ep->lock, flags); 1058 1059 res = 0; 1060 if (list_empty(&ep->rdllist)) { 1061 /* 1062 * We don't have any available event to return to the caller. 1063 * We need to sleep here, and we will be wake up by 1064 * ep_poll_callback() when events will become available. 1065 */ 1066 init_waitqueue_entry(&wait, current); 1067 wait.flags |= WQ_FLAG_EXCLUSIVE; 1068 __add_wait_queue(&ep->wq, &wait); 1069 1070 for (;;) { 1071 /* 1072 * We don't want to sleep if the ep_poll_callback() sends us 1073 * a wakeup in between. That's why we set the task state 1074 * to TASK_INTERRUPTIBLE before doing the checks. 1075 */ 1076 set_current_state(TASK_INTERRUPTIBLE); 1077 if (!list_empty(&ep->rdllist) || !jtimeout) 1078 break; 1079 if (signal_pending(current)) { 1080 res = -EINTR; 1081 break; 1082 } 1083 1084 spin_unlock_irqrestore(&ep->lock, flags); 1085 jtimeout = schedule_timeout(jtimeout); 1086 spin_lock_irqsave(&ep->lock, flags); 1087 } 1088 __remove_wait_queue(&ep->wq, &wait); 1089 1090 set_current_state(TASK_RUNNING); 1091 } 1092 1093 /* Is it worth to try to dig for events ? */ 1094 eavail = !list_empty(&ep->rdllist); 1095 1096 spin_unlock_irqrestore(&ep->lock, flags); 1097 1098 /* 1099 * Try to transfer events to user space. In case we get 0 events and 1100 * there's still timeout left over, we go trying again in search of 1101 * more luck. 1102 */ 1103 if (!res && eavail && 1104 !(res = ep_send_events(ep, events, maxevents)) && jtimeout) 1105 goto retry; 1106 1107 return res; 1108 } 1109 1110 /* 1111 * Open an eventpoll file descriptor. 1112 */ 1113 SYSCALL_DEFINE1(epoll_create1, int, flags) 1114 { 1115 int error, fd = -1; 1116 struct eventpoll *ep; 1117 1118 /* Check the EPOLL_* constant for consistency. */ 1119 BUILD_BUG_ON(EPOLL_CLOEXEC != O_CLOEXEC); 1120 1121 if (flags & ~EPOLL_CLOEXEC) 1122 return -EINVAL; 1123 1124 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d)\n", 1125 current, flags)); 1126 1127 /* 1128 * Create the internal data structure ( "struct eventpoll" ). 1129 */ 1130 error = ep_alloc(&ep); 1131 if (error < 0) { 1132 fd = error; 1133 goto error_return; 1134 } 1135 1136 /* 1137 * Creates all the items needed to setup an eventpoll file. That is, 1138 * a file structure and a free file descriptor. 1139 */ 1140 fd = anon_inode_getfd("[eventpoll]", &eventpoll_fops, ep, 1141 flags & O_CLOEXEC); 1142 if (fd < 0) 1143 ep_free(ep); 1144 atomic_inc(&ep->user->epoll_devs); 1145 1146 error_return: 1147 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n", 1148 current, flags, fd)); 1149 1150 return fd; 1151 } 1152 1153 SYSCALL_DEFINE1(epoll_create, int, size) 1154 { 1155 if (size < 0) 1156 return -EINVAL; 1157 1158 return sys_epoll_create1(0); 1159 } 1160 1161 /* 1162 * The following function implements the controller interface for 1163 * the eventpoll file that enables the insertion/removal/change of 1164 * file descriptors inside the interest set. 1165 */ 1166 SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd, 1167 struct epoll_event __user *, event) 1168 { 1169 int error; 1170 struct file *file, *tfile; 1171 struct eventpoll *ep; 1172 struct epitem *epi; 1173 struct epoll_event epds; 1174 1175 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %p)\n", 1176 current, epfd, op, fd, event)); 1177 1178 error = -EFAULT; 1179 if (ep_op_has_event(op) && 1180 copy_from_user(&epds, event, sizeof(struct epoll_event))) 1181 goto error_return; 1182 1183 /* Get the "struct file *" for the eventpoll file */ 1184 error = -EBADF; 1185 file = fget(epfd); 1186 if (!file) 1187 goto error_return; 1188 1189 /* Get the "struct file *" for the target file */ 1190 tfile = fget(fd); 1191 if (!tfile) 1192 goto error_fput; 1193 1194 /* The target file descriptor must support poll */ 1195 error = -EPERM; 1196 if (!tfile->f_op || !tfile->f_op->poll) 1197 goto error_tgt_fput; 1198 1199 /* 1200 * We have to check that the file structure underneath the file descriptor 1201 * the user passed to us _is_ an eventpoll file. And also we do not permit 1202 * adding an epoll file descriptor inside itself. 1203 */ 1204 error = -EINVAL; 1205 if (file == tfile || !is_file_epoll(file)) 1206 goto error_tgt_fput; 1207 1208 /* 1209 * At this point it is safe to assume that the "private_data" contains 1210 * our own data structure. 1211 */ 1212 ep = file->private_data; 1213 1214 mutex_lock(&ep->mtx); 1215 1216 /* 1217 * Try to lookup the file inside our RB tree, Since we grabbed "mtx" 1218 * above, we can be sure to be able to use the item looked up by 1219 * ep_find() till we release the mutex. 1220 */ 1221 epi = ep_find(ep, tfile, fd); 1222 1223 error = -EINVAL; 1224 switch (op) { 1225 case EPOLL_CTL_ADD: 1226 if (!epi) { 1227 epds.events |= POLLERR | POLLHUP; 1228 1229 error = ep_insert(ep, &epds, tfile, fd); 1230 } else 1231 error = -EEXIST; 1232 break; 1233 case EPOLL_CTL_DEL: 1234 if (epi) 1235 error = ep_remove(ep, epi); 1236 else 1237 error = -ENOENT; 1238 break; 1239 case EPOLL_CTL_MOD: 1240 if (epi) { 1241 epds.events |= POLLERR | POLLHUP; 1242 error = ep_modify(ep, epi, &epds); 1243 } else 1244 error = -ENOENT; 1245 break; 1246 } 1247 mutex_unlock(&ep->mtx); 1248 1249 error_tgt_fput: 1250 fput(tfile); 1251 error_fput: 1252 fput(file); 1253 error_return: 1254 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %p) = %d\n", 1255 current, epfd, op, fd, event, error)); 1256 1257 return error; 1258 } 1259 1260 /* 1261 * Implement the event wait interface for the eventpoll file. It is the kernel 1262 * part of the user space epoll_wait(2). 1263 */ 1264 SYSCALL_DEFINE4(epoll_wait, int, epfd, struct epoll_event __user *, events, 1265 int, maxevents, int, timeout) 1266 { 1267 int error; 1268 struct file *file; 1269 struct eventpoll *ep; 1270 1271 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_wait(%d, %p, %d, %d)\n", 1272 current, epfd, events, maxevents, timeout)); 1273 1274 /* The maximum number of event must be greater than zero */ 1275 if (maxevents <= 0 || maxevents > EP_MAX_EVENTS) 1276 return -EINVAL; 1277 1278 /* Verify that the area passed by the user is writeable */ 1279 if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event))) { 1280 error = -EFAULT; 1281 goto error_return; 1282 } 1283 1284 /* Get the "struct file *" for the eventpoll file */ 1285 error = -EBADF; 1286 file = fget(epfd); 1287 if (!file) 1288 goto error_return; 1289 1290 /* 1291 * We have to check that the file structure underneath the fd 1292 * the user passed to us _is_ an eventpoll file. 1293 */ 1294 error = -EINVAL; 1295 if (!is_file_epoll(file)) 1296 goto error_fput; 1297 1298 /* 1299 * At this point it is safe to assume that the "private_data" contains 1300 * our own data structure. 1301 */ 1302 ep = file->private_data; 1303 1304 /* Time to fish for events ... */ 1305 error = ep_poll(ep, events, maxevents, timeout); 1306 1307 error_fput: 1308 fput(file); 1309 error_return: 1310 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_wait(%d, %p, %d, %d) = %d\n", 1311 current, epfd, events, maxevents, timeout, error)); 1312 1313 return error; 1314 } 1315 1316 #ifdef HAVE_SET_RESTORE_SIGMASK 1317 1318 /* 1319 * Implement the event wait interface for the eventpoll file. It is the kernel 1320 * part of the user space epoll_pwait(2). 1321 */ 1322 SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events, 1323 int, maxevents, int, timeout, const sigset_t __user *, sigmask, 1324 size_t, sigsetsize) 1325 { 1326 int error; 1327 sigset_t ksigmask, sigsaved; 1328 1329 /* 1330 * If the caller wants a certain signal mask to be set during the wait, 1331 * we apply it here. 1332 */ 1333 if (sigmask) { 1334 if (sigsetsize != sizeof(sigset_t)) 1335 return -EINVAL; 1336 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) 1337 return -EFAULT; 1338 sigdelsetmask(&ksigmask, sigmask(SIGKILL) | sigmask(SIGSTOP)); 1339 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); 1340 } 1341 1342 error = sys_epoll_wait(epfd, events, maxevents, timeout); 1343 1344 /* 1345 * If we changed the signal mask, we need to restore the original one. 1346 * In case we've got a signal while waiting, we do not restore the 1347 * signal mask yet, and we allow do_signal() to deliver the signal on 1348 * the way back to userspace, before the signal mask is restored. 1349 */ 1350 if (sigmask) { 1351 if (error == -EINTR) { 1352 memcpy(¤t->saved_sigmask, &sigsaved, 1353 sizeof(sigsaved)); 1354 set_restore_sigmask(); 1355 } else 1356 sigprocmask(SIG_SETMASK, &sigsaved, NULL); 1357 } 1358 1359 return error; 1360 } 1361 1362 #endif /* HAVE_SET_RESTORE_SIGMASK */ 1363 1364 static int __init eventpoll_init(void) 1365 { 1366 struct sysinfo si; 1367 1368 si_meminfo(&si); 1369 max_user_instances = 128; 1370 max_user_watches = (((si.totalram - si.totalhigh) / 32) << PAGE_SHIFT) / 1371 EP_ITEM_COST; 1372 1373 /* Initialize the structure used to perform safe poll wait head wake ups */ 1374 ep_poll_safewake_init(&psw); 1375 1376 /* Allocates slab cache used to allocate "struct epitem" items */ 1377 epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem), 1378 0, SLAB_HWCACHE_ALIGN|EPI_SLAB_DEBUG|SLAB_PANIC, 1379 NULL); 1380 1381 /* Allocates slab cache used to allocate "struct eppoll_entry" */ 1382 pwq_cache = kmem_cache_create("eventpoll_pwq", 1383 sizeof(struct eppoll_entry), 0, 1384 EPI_SLAB_DEBUG|SLAB_PANIC, NULL); 1385 1386 return 0; 1387 } 1388 fs_initcall(eventpoll_init); 1389