1 /* 2 * fs/eventpoll.c ( Efficent event polling implementation ) 3 * Copyright (C) 2001,...,2003 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/module.h> 15 #include <linux/init.h> 16 #include <linux/kernel.h> 17 #include <linux/sched.h> 18 #include <linux/fs.h> 19 #include <linux/file.h> 20 #include <linux/signal.h> 21 #include <linux/errno.h> 22 #include <linux/mm.h> 23 #include <linux/slab.h> 24 #include <linux/poll.h> 25 #include <linux/smp_lock.h> 26 #include <linux/string.h> 27 #include <linux/list.h> 28 #include <linux/hash.h> 29 #include <linux/spinlock.h> 30 #include <linux/syscalls.h> 31 #include <linux/rwsem.h> 32 #include <linux/rbtree.h> 33 #include <linux/wait.h> 34 #include <linux/eventpoll.h> 35 #include <linux/mount.h> 36 #include <linux/bitops.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 /* 46 * LOCKING: 47 * There are three level of locking required by epoll : 48 * 49 * 1) epsem (semaphore) 50 * 2) ep->sem (rw_semaphore) 51 * 3) ep->lock (rw_lock) 52 * 53 * The acquire order is the one listed above, from 1 to 3. 54 * We need a spinlock (ep->lock) because we manipulate objects 55 * from inside the poll callback, that might be triggered from 56 * a wake_up() that in turn might be called from IRQ context. 57 * So we can't sleep inside the poll callback and hence we need 58 * a spinlock. During the event transfer loop (from kernel to 59 * user space) we could end up sleeping due a copy_to_user(), so 60 * we need a lock that will allow us to sleep. This lock is a 61 * read-write semaphore (ep->sem). It is acquired on read during 62 * the event transfer loop and in write during epoll_ctl(EPOLL_CTL_DEL) 63 * and during eventpoll_release_file(). Then we also need a global 64 * semaphore to serialize eventpoll_release_file() and ep_free(). 65 * This semaphore is acquired by ep_free() during the epoll file 66 * cleanup path and it is also acquired by eventpoll_release_file() 67 * if a file has been pushed inside an epoll set and it is then 68 * close()d without a previous call toepoll_ctl(EPOLL_CTL_DEL). 69 * It is possible to drop the "ep->sem" and to use the global 70 * semaphore "epsem" (together with "ep->lock") to have it working, 71 * but having "ep->sem" will make the interface more scalable. 72 * Events that require holding "epsem" are very rare, while for 73 * normal operations the epoll private "ep->sem" will guarantee 74 * a greater scalability. 75 */ 76 77 78 #define EVENTPOLLFS_MAGIC 0x03111965 /* My birthday should work for this :) */ 79 80 #define DEBUG_EPOLL 0 81 82 #if DEBUG_EPOLL > 0 83 #define DPRINTK(x) printk x 84 #define DNPRINTK(n, x) do { if ((n) <= DEBUG_EPOLL) printk x; } while (0) 85 #else /* #if DEBUG_EPOLL > 0 */ 86 #define DPRINTK(x) (void) 0 87 #define DNPRINTK(n, x) (void) 0 88 #endif /* #if DEBUG_EPOLL > 0 */ 89 90 #define DEBUG_EPI 0 91 92 #if DEBUG_EPI != 0 93 #define EPI_SLAB_DEBUG (SLAB_DEBUG_FREE | SLAB_RED_ZONE /* | SLAB_POISON */) 94 #else /* #if DEBUG_EPI != 0 */ 95 #define EPI_SLAB_DEBUG 0 96 #endif /* #if DEBUG_EPI != 0 */ 97 98 /* Epoll private bits inside the event mask */ 99 #define EP_PRIVATE_BITS (EPOLLONESHOT | EPOLLET) 100 101 /* Maximum number of poll wake up nests we are allowing */ 102 #define EP_MAX_POLLWAKE_NESTS 4 103 104 /* Maximum msec timeout value storeable in a long int */ 105 #define EP_MAX_MSTIMEO min(1000ULL * MAX_SCHEDULE_TIMEOUT / HZ, (LONG_MAX - 999ULL) / HZ) 106 107 108 struct epoll_filefd { 109 struct file *file; 110 int fd; 111 }; 112 113 /* 114 * Node that is linked into the "wake_task_list" member of the "struct poll_safewake". 115 * It is used to keep track on all tasks that are currently inside the wake_up() code 116 * to 1) short-circuit the one coming from the same task and same wait queue head 117 * ( loop ) 2) allow a maximum number of epoll descriptors inclusion nesting 118 * 3) let go the ones coming from other tasks. 119 */ 120 struct wake_task_node { 121 struct list_head llink; 122 task_t *task; 123 wait_queue_head_t *wq; 124 }; 125 126 /* 127 * This is used to implement the safe poll wake up avoiding to reenter 128 * the poll callback from inside wake_up(). 129 */ 130 struct poll_safewake { 131 struct list_head wake_task_list; 132 spinlock_t lock; 133 }; 134 135 /* 136 * This structure is stored inside the "private_data" member of the file 137 * structure and rapresent the main data sructure for the eventpoll 138 * interface. 139 */ 140 struct eventpoll { 141 /* Protect the this structure access */ 142 rwlock_t lock; 143 144 /* 145 * This semaphore is used to ensure that files are not removed 146 * while epoll is using them. This is read-held during the event 147 * collection loop and it is write-held during the file cleanup 148 * path, the epoll file exit code and the ctl operations. 149 */ 150 struct rw_semaphore sem; 151 152 /* Wait queue used by sys_epoll_wait() */ 153 wait_queue_head_t wq; 154 155 /* Wait queue used by file->poll() */ 156 wait_queue_head_t poll_wait; 157 158 /* List of ready file descriptors */ 159 struct list_head rdllist; 160 161 /* RB-Tree root used to store monitored fd structs */ 162 struct rb_root rbr; 163 }; 164 165 /* Wait structure used by the poll hooks */ 166 struct eppoll_entry { 167 /* List header used to link this structure to the "struct epitem" */ 168 struct list_head llink; 169 170 /* The "base" pointer is set to the container "struct epitem" */ 171 void *base; 172 173 /* 174 * Wait queue item that will be linked to the target file wait 175 * queue head. 176 */ 177 wait_queue_t wait; 178 179 /* The wait queue head that linked the "wait" wait queue item */ 180 wait_queue_head_t *whead; 181 }; 182 183 /* 184 * Each file descriptor added to the eventpoll interface will 185 * have an entry of this type linked to the hash. 186 */ 187 struct epitem { 188 /* RB-Tree node used to link this structure to the eventpoll rb-tree */ 189 struct rb_node rbn; 190 191 /* List header used to link this structure to the eventpoll ready list */ 192 struct list_head rdllink; 193 194 /* The file descriptor information this item refers to */ 195 struct epoll_filefd ffd; 196 197 /* Number of active wait queue attached to poll operations */ 198 int nwait; 199 200 /* List containing poll wait queues */ 201 struct list_head pwqlist; 202 203 /* The "container" of this item */ 204 struct eventpoll *ep; 205 206 /* The structure that describe the interested events and the source fd */ 207 struct epoll_event event; 208 209 /* 210 * Used to keep track of the usage count of the structure. This avoids 211 * that the structure will desappear from underneath our processing. 212 */ 213 atomic_t usecnt; 214 215 /* List header used to link this item to the "struct file" items list */ 216 struct list_head fllink; 217 218 /* List header used to link the item to the transfer list */ 219 struct list_head txlink; 220 221 /* 222 * This is used during the collection/transfer of events to userspace 223 * to pin items empty events set. 224 */ 225 unsigned int revents; 226 }; 227 228 /* Wrapper struct used by poll queueing */ 229 struct ep_pqueue { 230 poll_table pt; 231 struct epitem *epi; 232 }; 233 234 235 236 static void ep_poll_safewake_init(struct poll_safewake *psw); 237 static void ep_poll_safewake(struct poll_safewake *psw, wait_queue_head_t *wq); 238 static int ep_getfd(int *efd, struct inode **einode, struct file **efile, 239 struct eventpoll *ep); 240 static int ep_alloc(struct eventpoll **pep); 241 static void ep_free(struct eventpoll *ep); 242 static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd); 243 static void ep_use_epitem(struct epitem *epi); 244 static void ep_release_epitem(struct epitem *epi); 245 static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, 246 poll_table *pt); 247 static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi); 248 static int ep_insert(struct eventpoll *ep, struct epoll_event *event, 249 struct file *tfile, int fd); 250 static int ep_modify(struct eventpoll *ep, struct epitem *epi, 251 struct epoll_event *event); 252 static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi); 253 static int ep_unlink(struct eventpoll *ep, struct epitem *epi); 254 static int ep_remove(struct eventpoll *ep, struct epitem *epi); 255 static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *key); 256 static int ep_eventpoll_close(struct inode *inode, struct file *file); 257 static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait); 258 static int ep_collect_ready_items(struct eventpoll *ep, 259 struct list_head *txlist, int maxevents); 260 static int ep_send_events(struct eventpoll *ep, struct list_head *txlist, 261 struct epoll_event __user *events); 262 static void ep_reinject_items(struct eventpoll *ep, struct list_head *txlist); 263 static int ep_events_transfer(struct eventpoll *ep, 264 struct epoll_event __user *events, 265 int maxevents); 266 static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, 267 int maxevents, long timeout); 268 static int eventpollfs_delete_dentry(struct dentry *dentry); 269 static struct inode *ep_eventpoll_inode(void); 270 static struct super_block *eventpollfs_get_sb(struct file_system_type *fs_type, 271 int flags, const char *dev_name, 272 void *data); 273 274 /* 275 * This semaphore is used to serialize ep_free() and eventpoll_release_file(). 276 */ 277 static struct semaphore epsem; 278 279 /* Safe wake up implementation */ 280 static struct poll_safewake psw; 281 282 /* Slab cache used to allocate "struct epitem" */ 283 static kmem_cache_t *epi_cache; 284 285 /* Slab cache used to allocate "struct eppoll_entry" */ 286 static kmem_cache_t *pwq_cache; 287 288 /* Virtual fs used to allocate inodes for eventpoll files */ 289 static struct vfsmount *eventpoll_mnt; 290 291 /* File callbacks that implement the eventpoll file behaviour */ 292 static struct file_operations eventpoll_fops = { 293 .release = ep_eventpoll_close, 294 .poll = ep_eventpoll_poll 295 }; 296 297 /* 298 * This is used to register the virtual file system from where 299 * eventpoll inodes are allocated. 300 */ 301 static struct file_system_type eventpoll_fs_type = { 302 .name = "eventpollfs", 303 .get_sb = eventpollfs_get_sb, 304 .kill_sb = kill_anon_super, 305 }; 306 307 /* Very basic directory entry operations for the eventpoll virtual file system */ 308 static struct dentry_operations eventpollfs_dentry_operations = { 309 .d_delete = eventpollfs_delete_dentry, 310 }; 311 312 313 314 /* Fast test to see if the file is an evenpoll file */ 315 static inline int is_file_epoll(struct file *f) 316 { 317 return f->f_op == &eventpoll_fops; 318 } 319 320 /* Setup the structure that is used as key for the rb-tree */ 321 static inline void ep_set_ffd(struct epoll_filefd *ffd, 322 struct file *file, int fd) 323 { 324 ffd->file = file; 325 ffd->fd = fd; 326 } 327 328 /* Compare rb-tree keys */ 329 static inline int ep_cmp_ffd(struct epoll_filefd *p1, 330 struct epoll_filefd *p2) 331 { 332 return (p1->file > p2->file ? +1: 333 (p1->file < p2->file ? -1 : p1->fd - p2->fd)); 334 } 335 336 /* Special initialization for the rb-tree node to detect linkage */ 337 static inline void ep_rb_initnode(struct rb_node *n) 338 { 339 n->rb_parent = n; 340 } 341 342 /* Removes a node from the rb-tree and marks it for a fast is-linked check */ 343 static inline void ep_rb_erase(struct rb_node *n, struct rb_root *r) 344 { 345 rb_erase(n, r); 346 n->rb_parent = n; 347 } 348 349 /* Fast check to verify that the item is linked to the main rb-tree */ 350 static inline int ep_rb_linked(struct rb_node *n) 351 { 352 return n->rb_parent != n; 353 } 354 355 /* 356 * Remove the item from the list and perform its initialization. 357 * This is useful for us because we can test if the item is linked 358 * using "ep_is_linked(p)". 359 */ 360 static inline void ep_list_del(struct list_head *p) 361 { 362 list_del(p); 363 INIT_LIST_HEAD(p); 364 } 365 366 /* Tells us if the item is currently linked */ 367 static inline int ep_is_linked(struct list_head *p) 368 { 369 return !list_empty(p); 370 } 371 372 /* Get the "struct epitem" from a wait queue pointer */ 373 static inline struct epitem * ep_item_from_wait(wait_queue_t *p) 374 { 375 return container_of(p, struct eppoll_entry, wait)->base; 376 } 377 378 /* Get the "struct epitem" from an epoll queue wrapper */ 379 static inline struct epitem * ep_item_from_epqueue(poll_table *p) 380 { 381 return container_of(p, struct ep_pqueue, pt)->epi; 382 } 383 384 /* Tells if the epoll_ctl(2) operation needs an event copy from userspace */ 385 static inline int ep_op_hash_event(int op) 386 { 387 return op != EPOLL_CTL_DEL; 388 } 389 390 /* Initialize the poll safe wake up structure */ 391 static void ep_poll_safewake_init(struct poll_safewake *psw) 392 { 393 394 INIT_LIST_HEAD(&psw->wake_task_list); 395 spin_lock_init(&psw->lock); 396 } 397 398 399 /* 400 * Perform a safe wake up of the poll wait list. The problem is that 401 * with the new callback'd wake up system, it is possible that the 402 * poll callback is reentered from inside the call to wake_up() done 403 * on the poll wait queue head. The rule is that we cannot reenter the 404 * wake up code from the same task more than EP_MAX_POLLWAKE_NESTS times, 405 * and we cannot reenter the same wait queue head at all. This will 406 * enable to have a hierarchy of epoll file descriptor of no more than 407 * EP_MAX_POLLWAKE_NESTS deep. We need the irq version of the spin lock 408 * because this one gets called by the poll callback, that in turn is called 409 * from inside a wake_up(), that might be called from irq context. 410 */ 411 static void ep_poll_safewake(struct poll_safewake *psw, wait_queue_head_t *wq) 412 { 413 int wake_nests = 0; 414 unsigned long flags; 415 task_t *this_task = current; 416 struct list_head *lsthead = &psw->wake_task_list, *lnk; 417 struct wake_task_node *tncur; 418 struct wake_task_node tnode; 419 420 spin_lock_irqsave(&psw->lock, flags); 421 422 /* Try to see if the current task is already inside this wakeup call */ 423 list_for_each(lnk, lsthead) { 424 tncur = list_entry(lnk, struct wake_task_node, llink); 425 426 if (tncur->wq == wq || 427 (tncur->task == this_task && ++wake_nests > EP_MAX_POLLWAKE_NESTS)) { 428 /* 429 * Ops ... loop detected or maximum nest level reached. 430 * We abort this wake by breaking the cycle itself. 431 */ 432 spin_unlock_irqrestore(&psw->lock, flags); 433 return; 434 } 435 } 436 437 /* Add the current task to the list */ 438 tnode.task = this_task; 439 tnode.wq = wq; 440 list_add(&tnode.llink, lsthead); 441 442 spin_unlock_irqrestore(&psw->lock, flags); 443 444 /* Do really wake up now */ 445 wake_up(wq); 446 447 /* Remove the current task from the list */ 448 spin_lock_irqsave(&psw->lock, flags); 449 list_del(&tnode.llink); 450 spin_unlock_irqrestore(&psw->lock, flags); 451 } 452 453 454 /* Used to initialize the epoll bits inside the "struct file" */ 455 void eventpoll_init_file(struct file *file) 456 { 457 458 INIT_LIST_HEAD(&file->f_ep_links); 459 spin_lock_init(&file->f_ep_lock); 460 } 461 462 463 /* 464 * This is called from eventpoll_release() to unlink files from the eventpoll 465 * interface. We need to have this facility to cleanup correctly files that are 466 * closed without being removed from the eventpoll interface. 467 */ 468 void eventpoll_release_file(struct file *file) 469 { 470 struct list_head *lsthead = &file->f_ep_links; 471 struct eventpoll *ep; 472 struct epitem *epi; 473 474 /* 475 * We don't want to get "file->f_ep_lock" because it is not 476 * necessary. It is not necessary because we're in the "struct file" 477 * cleanup path, and this means that noone is using this file anymore. 478 * The only hit might come from ep_free() but by holding the semaphore 479 * will correctly serialize the operation. We do need to acquire 480 * "ep->sem" after "epsem" because ep_remove() requires it when called 481 * from anywhere but ep_free(). 482 */ 483 down(&epsem); 484 485 while (!list_empty(lsthead)) { 486 epi = list_entry(lsthead->next, struct epitem, fllink); 487 488 ep = epi->ep; 489 ep_list_del(&epi->fllink); 490 down_write(&ep->sem); 491 ep_remove(ep, epi); 492 up_write(&ep->sem); 493 } 494 495 up(&epsem); 496 } 497 498 499 /* 500 * It opens an eventpoll file descriptor by suggesting a storage of "size" 501 * file descriptors. The size parameter is just an hint about how to size 502 * data structures. It won't prevent the user to store more than "size" 503 * file descriptors inside the epoll interface. It is the kernel part of 504 * the userspace epoll_create(2). 505 */ 506 asmlinkage long sys_epoll_create(int size) 507 { 508 int error, fd; 509 struct eventpoll *ep; 510 struct inode *inode; 511 struct file *file; 512 513 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d)\n", 514 current, size)); 515 516 /* 517 * Sanity check on the size parameter, and create the internal data 518 * structure ( "struct eventpoll" ). 519 */ 520 error = -EINVAL; 521 if (size <= 0 || (error = ep_alloc(&ep)) != 0) 522 goto eexit_1; 523 524 /* 525 * Creates all the items needed to setup an eventpoll file. That is, 526 * a file structure, and inode and a free file descriptor. 527 */ 528 error = ep_getfd(&fd, &inode, &file, ep); 529 if (error) 530 goto eexit_2; 531 532 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n", 533 current, size, fd)); 534 535 return fd; 536 537 eexit_2: 538 ep_free(ep); 539 kfree(ep); 540 eexit_1: 541 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n", 542 current, size, error)); 543 return error; 544 } 545 546 547 /* 548 * The following function implements the controller interface for 549 * the eventpoll file that enables the insertion/removal/change of 550 * file descriptors inside the interest set. It represents 551 * the kernel part of the user space epoll_ctl(2). 552 */ 553 asmlinkage long 554 sys_epoll_ctl(int epfd, int op, int fd, struct epoll_event __user *event) 555 { 556 int error; 557 struct file *file, *tfile; 558 struct eventpoll *ep; 559 struct epitem *epi; 560 struct epoll_event epds; 561 562 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %p)\n", 563 current, epfd, op, fd, event)); 564 565 error = -EFAULT; 566 if (ep_op_hash_event(op) && 567 copy_from_user(&epds, event, sizeof(struct epoll_event))) 568 goto eexit_1; 569 570 /* Get the "struct file *" for the eventpoll file */ 571 error = -EBADF; 572 file = fget(epfd); 573 if (!file) 574 goto eexit_1; 575 576 /* Get the "struct file *" for the target file */ 577 tfile = fget(fd); 578 if (!tfile) 579 goto eexit_2; 580 581 /* The target file descriptor must support poll */ 582 error = -EPERM; 583 if (!tfile->f_op || !tfile->f_op->poll) 584 goto eexit_3; 585 586 /* 587 * We have to check that the file structure underneath the file descriptor 588 * the user passed to us _is_ an eventpoll file. And also we do not permit 589 * adding an epoll file descriptor inside itself. 590 */ 591 error = -EINVAL; 592 if (file == tfile || !is_file_epoll(file)) 593 goto eexit_3; 594 595 /* 596 * At this point it is safe to assume that the "private_data" contains 597 * our own data structure. 598 */ 599 ep = file->private_data; 600 601 down_write(&ep->sem); 602 603 /* Try to lookup the file inside our hash table */ 604 epi = ep_find(ep, tfile, fd); 605 606 error = -EINVAL; 607 switch (op) { 608 case EPOLL_CTL_ADD: 609 if (!epi) { 610 epds.events |= POLLERR | POLLHUP; 611 612 error = ep_insert(ep, &epds, tfile, fd); 613 } else 614 error = -EEXIST; 615 break; 616 case EPOLL_CTL_DEL: 617 if (epi) 618 error = ep_remove(ep, epi); 619 else 620 error = -ENOENT; 621 break; 622 case EPOLL_CTL_MOD: 623 if (epi) { 624 epds.events |= POLLERR | POLLHUP; 625 error = ep_modify(ep, epi, &epds); 626 } else 627 error = -ENOENT; 628 break; 629 } 630 631 /* 632 * The function ep_find() increments the usage count of the structure 633 * so, if this is not NULL, we need to release it. 634 */ 635 if (epi) 636 ep_release_epitem(epi); 637 638 up_write(&ep->sem); 639 640 eexit_3: 641 fput(tfile); 642 eexit_2: 643 fput(file); 644 eexit_1: 645 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %p) = %d\n", 646 current, epfd, op, fd, event, error)); 647 648 return error; 649 } 650 651 #define MAX_EVENTS (INT_MAX / sizeof(struct epoll_event)) 652 653 /* 654 * Implement the event wait interface for the eventpoll file. It is the kernel 655 * part of the user space epoll_wait(2). 656 */ 657 asmlinkage long sys_epoll_wait(int epfd, struct epoll_event __user *events, 658 int maxevents, int timeout) 659 { 660 int error; 661 struct file *file; 662 struct eventpoll *ep; 663 664 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_wait(%d, %p, %d, %d)\n", 665 current, epfd, events, maxevents, timeout)); 666 667 /* The maximum number of event must be greater than zero */ 668 if (maxevents <= 0 || maxevents > MAX_EVENTS) 669 return -EINVAL; 670 671 /* Verify that the area passed by the user is writeable */ 672 if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event))) { 673 error = -EFAULT; 674 goto eexit_1; 675 } 676 677 /* Get the "struct file *" for the eventpoll file */ 678 error = -EBADF; 679 file = fget(epfd); 680 if (!file) 681 goto eexit_1; 682 683 /* 684 * We have to check that the file structure underneath the fd 685 * the user passed to us _is_ an eventpoll file. 686 */ 687 error = -EINVAL; 688 if (!is_file_epoll(file)) 689 goto eexit_2; 690 691 /* 692 * At this point it is safe to assume that the "private_data" contains 693 * our own data structure. 694 */ 695 ep = file->private_data; 696 697 /* Time to fish for events ... */ 698 error = ep_poll(ep, events, maxevents, timeout); 699 700 eexit_2: 701 fput(file); 702 eexit_1: 703 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_wait(%d, %p, %d, %d) = %d\n", 704 current, epfd, events, maxevents, timeout, error)); 705 706 return error; 707 } 708 709 710 /* 711 * Creates the file descriptor to be used by the epoll interface. 712 */ 713 static int ep_getfd(int *efd, struct inode **einode, struct file **efile, 714 struct eventpoll *ep) 715 { 716 struct qstr this; 717 char name[32]; 718 struct dentry *dentry; 719 struct inode *inode; 720 struct file *file; 721 int error, fd; 722 723 /* Get an ready to use file */ 724 error = -ENFILE; 725 file = get_empty_filp(); 726 if (!file) 727 goto eexit_1; 728 729 /* Allocates an inode from the eventpoll file system */ 730 inode = ep_eventpoll_inode(); 731 error = PTR_ERR(inode); 732 if (IS_ERR(inode)) 733 goto eexit_2; 734 735 /* Allocates a free descriptor to plug the file onto */ 736 error = get_unused_fd(); 737 if (error < 0) 738 goto eexit_3; 739 fd = error; 740 741 /* 742 * Link the inode to a directory entry by creating a unique name 743 * using the inode number. 744 */ 745 error = -ENOMEM; 746 sprintf(name, "[%lu]", inode->i_ino); 747 this.name = name; 748 this.len = strlen(name); 749 this.hash = inode->i_ino; 750 dentry = d_alloc(eventpoll_mnt->mnt_sb->s_root, &this); 751 if (!dentry) 752 goto eexit_4; 753 dentry->d_op = &eventpollfs_dentry_operations; 754 d_add(dentry, inode); 755 file->f_vfsmnt = mntget(eventpoll_mnt); 756 file->f_dentry = dentry; 757 file->f_mapping = inode->i_mapping; 758 759 file->f_pos = 0; 760 file->f_flags = O_RDONLY; 761 file->f_op = &eventpoll_fops; 762 file->f_mode = FMODE_READ; 763 file->f_version = 0; 764 file->private_data = ep; 765 766 /* Install the new setup file into the allocated fd. */ 767 fd_install(fd, file); 768 769 *efd = fd; 770 *einode = inode; 771 *efile = file; 772 return 0; 773 774 eexit_4: 775 put_unused_fd(fd); 776 eexit_3: 777 iput(inode); 778 eexit_2: 779 put_filp(file); 780 eexit_1: 781 return error; 782 } 783 784 785 static int ep_alloc(struct eventpoll **pep) 786 { 787 struct eventpoll *ep = kzalloc(sizeof(*ep), GFP_KERNEL); 788 789 if (!ep) 790 return -ENOMEM; 791 792 rwlock_init(&ep->lock); 793 init_rwsem(&ep->sem); 794 init_waitqueue_head(&ep->wq); 795 init_waitqueue_head(&ep->poll_wait); 796 INIT_LIST_HEAD(&ep->rdllist); 797 ep->rbr = RB_ROOT; 798 799 *pep = ep; 800 801 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_alloc() ep=%p\n", 802 current, ep)); 803 return 0; 804 } 805 806 807 static void ep_free(struct eventpoll *ep) 808 { 809 struct rb_node *rbp; 810 struct epitem *epi; 811 812 /* We need to release all tasks waiting for these file */ 813 if (waitqueue_active(&ep->poll_wait)) 814 ep_poll_safewake(&psw, &ep->poll_wait); 815 816 /* 817 * We need to lock this because we could be hit by 818 * eventpoll_release_file() while we're freeing the "struct eventpoll". 819 * We do not need to hold "ep->sem" here because the epoll file 820 * is on the way to be removed and no one has references to it 821 * anymore. The only hit might come from eventpoll_release_file() but 822 * holding "epsem" is sufficent here. 823 */ 824 down(&epsem); 825 826 /* 827 * Walks through the whole tree by unregistering poll callbacks. 828 */ 829 for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { 830 epi = rb_entry(rbp, struct epitem, rbn); 831 832 ep_unregister_pollwait(ep, epi); 833 } 834 835 /* 836 * Walks through the whole hash by freeing each "struct epitem". At this 837 * point we are sure no poll callbacks will be lingering around, and also by 838 * write-holding "sem" we can be sure that no file cleanup code will hit 839 * us during this operation. So we can avoid the lock on "ep->lock". 840 */ 841 while ((rbp = rb_first(&ep->rbr)) != 0) { 842 epi = rb_entry(rbp, struct epitem, rbn); 843 ep_remove(ep, epi); 844 } 845 846 up(&epsem); 847 } 848 849 850 /* 851 * Search the file inside the eventpoll hash. It add usage count to 852 * the returned item, so the caller must call ep_release_epitem() 853 * after finished using the "struct epitem". 854 */ 855 static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd) 856 { 857 int kcmp; 858 unsigned long flags; 859 struct rb_node *rbp; 860 struct epitem *epi, *epir = NULL; 861 struct epoll_filefd ffd; 862 863 ep_set_ffd(&ffd, file, fd); 864 read_lock_irqsave(&ep->lock, flags); 865 for (rbp = ep->rbr.rb_node; rbp; ) { 866 epi = rb_entry(rbp, struct epitem, rbn); 867 kcmp = ep_cmp_ffd(&ffd, &epi->ffd); 868 if (kcmp > 0) 869 rbp = rbp->rb_right; 870 else if (kcmp < 0) 871 rbp = rbp->rb_left; 872 else { 873 ep_use_epitem(epi); 874 epir = epi; 875 break; 876 } 877 } 878 read_unlock_irqrestore(&ep->lock, flags); 879 880 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_find(%p) -> %p\n", 881 current, file, epir)); 882 883 return epir; 884 } 885 886 887 /* 888 * Increment the usage count of the "struct epitem" making it sure 889 * that the user will have a valid pointer to reference. 890 */ 891 static void ep_use_epitem(struct epitem *epi) 892 { 893 894 atomic_inc(&epi->usecnt); 895 } 896 897 898 /* 899 * Decrement ( release ) the usage count by signaling that the user 900 * has finished using the structure. It might lead to freeing the 901 * structure itself if the count goes to zero. 902 */ 903 static void ep_release_epitem(struct epitem *epi) 904 { 905 906 if (atomic_dec_and_test(&epi->usecnt)) 907 kmem_cache_free(epi_cache, epi); 908 } 909 910 911 /* 912 * This is the callback that is used to add our wait queue to the 913 * target file wakeup lists. 914 */ 915 static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, 916 poll_table *pt) 917 { 918 struct epitem *epi = ep_item_from_epqueue(pt); 919 struct eppoll_entry *pwq; 920 921 if (epi->nwait >= 0 && (pwq = kmem_cache_alloc(pwq_cache, SLAB_KERNEL))) { 922 init_waitqueue_func_entry(&pwq->wait, ep_poll_callback); 923 pwq->whead = whead; 924 pwq->base = epi; 925 add_wait_queue(whead, &pwq->wait); 926 list_add_tail(&pwq->llink, &epi->pwqlist); 927 epi->nwait++; 928 } else { 929 /* We have to signal that an error occurred */ 930 epi->nwait = -1; 931 } 932 } 933 934 935 static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi) 936 { 937 int kcmp; 938 struct rb_node **p = &ep->rbr.rb_node, *parent = NULL; 939 struct epitem *epic; 940 941 while (*p) { 942 parent = *p; 943 epic = rb_entry(parent, struct epitem, rbn); 944 kcmp = ep_cmp_ffd(&epi->ffd, &epic->ffd); 945 if (kcmp > 0) 946 p = &parent->rb_right; 947 else 948 p = &parent->rb_left; 949 } 950 rb_link_node(&epi->rbn, parent, p); 951 rb_insert_color(&epi->rbn, &ep->rbr); 952 } 953 954 955 static int ep_insert(struct eventpoll *ep, struct epoll_event *event, 956 struct file *tfile, int fd) 957 { 958 int error, revents, pwake = 0; 959 unsigned long flags; 960 struct epitem *epi; 961 struct ep_pqueue epq; 962 963 error = -ENOMEM; 964 if (!(epi = kmem_cache_alloc(epi_cache, SLAB_KERNEL))) 965 goto eexit_1; 966 967 /* Item initialization follow here ... */ 968 ep_rb_initnode(&epi->rbn); 969 INIT_LIST_HEAD(&epi->rdllink); 970 INIT_LIST_HEAD(&epi->fllink); 971 INIT_LIST_HEAD(&epi->txlink); 972 INIT_LIST_HEAD(&epi->pwqlist); 973 epi->ep = ep; 974 ep_set_ffd(&epi->ffd, tfile, fd); 975 epi->event = *event; 976 atomic_set(&epi->usecnt, 1); 977 epi->nwait = 0; 978 979 /* Initialize the poll table using the queue callback */ 980 epq.epi = epi; 981 init_poll_funcptr(&epq.pt, ep_ptable_queue_proc); 982 983 /* 984 * Attach the item to the poll hooks and get current event bits. 985 * We can safely use the file* here because its usage count has 986 * been increased by the caller of this function. 987 */ 988 revents = tfile->f_op->poll(tfile, &epq.pt); 989 990 /* 991 * We have to check if something went wrong during the poll wait queue 992 * install process. Namely an allocation for a wait queue failed due 993 * high memory pressure. 994 */ 995 if (epi->nwait < 0) 996 goto eexit_2; 997 998 /* Add the current item to the list of active epoll hook for this file */ 999 spin_lock(&tfile->f_ep_lock); 1000 list_add_tail(&epi->fllink, &tfile->f_ep_links); 1001 spin_unlock(&tfile->f_ep_lock); 1002 1003 /* We have to drop the new item inside our item list to keep track of it */ 1004 write_lock_irqsave(&ep->lock, flags); 1005 1006 /* Add the current item to the rb-tree */ 1007 ep_rbtree_insert(ep, epi); 1008 1009 /* If the file is already "ready" we drop it inside the ready list */ 1010 if ((revents & event->events) && !ep_is_linked(&epi->rdllink)) { 1011 list_add_tail(&epi->rdllink, &ep->rdllist); 1012 1013 /* Notify waiting tasks that events are available */ 1014 if (waitqueue_active(&ep->wq)) 1015 wake_up(&ep->wq); 1016 if (waitqueue_active(&ep->poll_wait)) 1017 pwake++; 1018 } 1019 1020 write_unlock_irqrestore(&ep->lock, flags); 1021 1022 /* We have to call this outside the lock */ 1023 if (pwake) 1024 ep_poll_safewake(&psw, &ep->poll_wait); 1025 1026 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_insert(%p, %p, %d)\n", 1027 current, ep, tfile, fd)); 1028 1029 return 0; 1030 1031 eexit_2: 1032 ep_unregister_pollwait(ep, epi); 1033 1034 /* 1035 * We need to do this because an event could have been arrived on some 1036 * allocated wait queue. 1037 */ 1038 write_lock_irqsave(&ep->lock, flags); 1039 if (ep_is_linked(&epi->rdllink)) 1040 ep_list_del(&epi->rdllink); 1041 write_unlock_irqrestore(&ep->lock, flags); 1042 1043 kmem_cache_free(epi_cache, epi); 1044 eexit_1: 1045 return error; 1046 } 1047 1048 1049 /* 1050 * Modify the interest event mask by dropping an event if the new mask 1051 * has a match in the current file status. 1052 */ 1053 static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_event *event) 1054 { 1055 int pwake = 0; 1056 unsigned int revents; 1057 unsigned long flags; 1058 1059 /* 1060 * Set the new event interest mask before calling f_op->poll(), otherwise 1061 * a potential race might occur. In fact if we do this operation inside 1062 * the lock, an event might happen between the f_op->poll() call and the 1063 * new event set registering. 1064 */ 1065 epi->event.events = event->events; 1066 1067 /* 1068 * Get current event bits. We can safely use the file* here because 1069 * its usage count has been increased by the caller of this function. 1070 */ 1071 revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL); 1072 1073 write_lock_irqsave(&ep->lock, flags); 1074 1075 /* Copy the data member from inside the lock */ 1076 epi->event.data = event->data; 1077 1078 /* 1079 * If the item is not linked to the hash it means that it's on its 1080 * way toward the removal. Do nothing in this case. 1081 */ 1082 if (ep_rb_linked(&epi->rbn)) { 1083 /* 1084 * If the item is "hot" and it is not registered inside the ready 1085 * list, push it inside. If the item is not "hot" and it is currently 1086 * registered inside the ready list, unlink it. 1087 */ 1088 if (revents & event->events) { 1089 if (!ep_is_linked(&epi->rdllink)) { 1090 list_add_tail(&epi->rdllink, &ep->rdllist); 1091 1092 /* Notify waiting tasks that events are available */ 1093 if (waitqueue_active(&ep->wq)) 1094 wake_up(&ep->wq); 1095 if (waitqueue_active(&ep->poll_wait)) 1096 pwake++; 1097 } 1098 } 1099 } 1100 1101 write_unlock_irqrestore(&ep->lock, flags); 1102 1103 /* We have to call this outside the lock */ 1104 if (pwake) 1105 ep_poll_safewake(&psw, &ep->poll_wait); 1106 1107 return 0; 1108 } 1109 1110 1111 /* 1112 * This function unregister poll callbacks from the associated file descriptor. 1113 * Since this must be called without holding "ep->lock" the atomic exchange trick 1114 * will protect us from multiple unregister. 1115 */ 1116 static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi) 1117 { 1118 int nwait; 1119 struct list_head *lsthead = &epi->pwqlist; 1120 struct eppoll_entry *pwq; 1121 1122 /* This is called without locks, so we need the atomic exchange */ 1123 nwait = xchg(&epi->nwait, 0); 1124 1125 if (nwait) { 1126 while (!list_empty(lsthead)) { 1127 pwq = list_entry(lsthead->next, struct eppoll_entry, llink); 1128 1129 ep_list_del(&pwq->llink); 1130 remove_wait_queue(pwq->whead, &pwq->wait); 1131 kmem_cache_free(pwq_cache, pwq); 1132 } 1133 } 1134 } 1135 1136 1137 /* 1138 * Unlink the "struct epitem" from all places it might have been hooked up. 1139 * This function must be called with write IRQ lock on "ep->lock". 1140 */ 1141 static int ep_unlink(struct eventpoll *ep, struct epitem *epi) 1142 { 1143 int error; 1144 1145 /* 1146 * It can happen that this one is called for an item already unlinked. 1147 * The check protect us from doing a double unlink ( crash ). 1148 */ 1149 error = -ENOENT; 1150 if (!ep_rb_linked(&epi->rbn)) 1151 goto eexit_1; 1152 1153 /* 1154 * Clear the event mask for the unlinked item. This will avoid item 1155 * notifications to be sent after the unlink operation from inside 1156 * the kernel->userspace event transfer loop. 1157 */ 1158 epi->event.events = 0; 1159 1160 /* 1161 * At this point is safe to do the job, unlink the item from our rb-tree. 1162 * This operation togheter with the above check closes the door to 1163 * double unlinks. 1164 */ 1165 ep_rb_erase(&epi->rbn, &ep->rbr); 1166 1167 /* 1168 * If the item we are going to remove is inside the ready file descriptors 1169 * we want to remove it from this list to avoid stale events. 1170 */ 1171 if (ep_is_linked(&epi->rdllink)) 1172 ep_list_del(&epi->rdllink); 1173 1174 error = 0; 1175 eexit_1: 1176 1177 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_unlink(%p, %p) = %d\n", 1178 current, ep, epi->file, error)); 1179 1180 return error; 1181 } 1182 1183 1184 /* 1185 * Removes a "struct epitem" from the eventpoll hash and deallocates 1186 * all the associated resources. 1187 */ 1188 static int ep_remove(struct eventpoll *ep, struct epitem *epi) 1189 { 1190 int error; 1191 unsigned long flags; 1192 struct file *file = epi->ffd.file; 1193 1194 /* 1195 * Removes poll wait queue hooks. We _have_ to do this without holding 1196 * the "ep->lock" otherwise a deadlock might occur. This because of the 1197 * sequence of the lock acquisition. Here we do "ep->lock" then the wait 1198 * queue head lock when unregistering the wait queue. The wakeup callback 1199 * will run by holding the wait queue head lock and will call our callback 1200 * that will try to get "ep->lock". 1201 */ 1202 ep_unregister_pollwait(ep, epi); 1203 1204 /* Remove the current item from the list of epoll hooks */ 1205 spin_lock(&file->f_ep_lock); 1206 if (ep_is_linked(&epi->fllink)) 1207 ep_list_del(&epi->fllink); 1208 spin_unlock(&file->f_ep_lock); 1209 1210 /* We need to acquire the write IRQ lock before calling ep_unlink() */ 1211 write_lock_irqsave(&ep->lock, flags); 1212 1213 /* Really unlink the item from the hash */ 1214 error = ep_unlink(ep, epi); 1215 1216 write_unlock_irqrestore(&ep->lock, flags); 1217 1218 if (error) 1219 goto eexit_1; 1220 1221 /* At this point it is safe to free the eventpoll item */ 1222 ep_release_epitem(epi); 1223 1224 error = 0; 1225 eexit_1: 1226 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_remove(%p, %p) = %d\n", 1227 current, ep, file, error)); 1228 1229 return error; 1230 } 1231 1232 1233 /* 1234 * This is the callback that is passed to the wait queue wakeup 1235 * machanism. It is called by the stored file descriptors when they 1236 * have events to report. 1237 */ 1238 static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *key) 1239 { 1240 int pwake = 0; 1241 unsigned long flags; 1242 struct epitem *epi = ep_item_from_wait(wait); 1243 struct eventpoll *ep = epi->ep; 1244 1245 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: poll_callback(%p) epi=%p ep=%p\n", 1246 current, epi->file, epi, ep)); 1247 1248 write_lock_irqsave(&ep->lock, flags); 1249 1250 /* 1251 * If the event mask does not contain any poll(2) event, we consider the 1252 * descriptor to be disabled. This condition is likely the effect of the 1253 * EPOLLONESHOT bit that disables the descriptor when an event is received, 1254 * until the next EPOLL_CTL_MOD will be issued. 1255 */ 1256 if (!(epi->event.events & ~EP_PRIVATE_BITS)) 1257 goto is_disabled; 1258 1259 /* If this file is already in the ready list we exit soon */ 1260 if (ep_is_linked(&epi->rdllink)) 1261 goto is_linked; 1262 1263 list_add_tail(&epi->rdllink, &ep->rdllist); 1264 1265 is_linked: 1266 /* 1267 * Wake up ( if active ) both the eventpoll wait list and the ->poll() 1268 * wait list. 1269 */ 1270 if (waitqueue_active(&ep->wq)) 1271 wake_up(&ep->wq); 1272 if (waitqueue_active(&ep->poll_wait)) 1273 pwake++; 1274 1275 is_disabled: 1276 write_unlock_irqrestore(&ep->lock, flags); 1277 1278 /* We have to call this outside the lock */ 1279 if (pwake) 1280 ep_poll_safewake(&psw, &ep->poll_wait); 1281 1282 return 1; 1283 } 1284 1285 1286 static int ep_eventpoll_close(struct inode *inode, struct file *file) 1287 { 1288 struct eventpoll *ep = file->private_data; 1289 1290 if (ep) { 1291 ep_free(ep); 1292 kfree(ep); 1293 } 1294 1295 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: close() ep=%p\n", current, ep)); 1296 return 0; 1297 } 1298 1299 1300 static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait) 1301 { 1302 unsigned int pollflags = 0; 1303 unsigned long flags; 1304 struct eventpoll *ep = file->private_data; 1305 1306 /* Insert inside our poll wait queue */ 1307 poll_wait(file, &ep->poll_wait, wait); 1308 1309 /* Check our condition */ 1310 read_lock_irqsave(&ep->lock, flags); 1311 if (!list_empty(&ep->rdllist)) 1312 pollflags = POLLIN | POLLRDNORM; 1313 read_unlock_irqrestore(&ep->lock, flags); 1314 1315 return pollflags; 1316 } 1317 1318 1319 /* 1320 * Since we have to release the lock during the __copy_to_user() operation and 1321 * during the f_op->poll() call, we try to collect the maximum number of items 1322 * by reducing the irqlock/irqunlock switching rate. 1323 */ 1324 static int ep_collect_ready_items(struct eventpoll *ep, struct list_head *txlist, int maxevents) 1325 { 1326 int nepi; 1327 unsigned long flags; 1328 struct list_head *lsthead = &ep->rdllist, *lnk; 1329 struct epitem *epi; 1330 1331 write_lock_irqsave(&ep->lock, flags); 1332 1333 for (nepi = 0, lnk = lsthead->next; lnk != lsthead && nepi < maxevents;) { 1334 epi = list_entry(lnk, struct epitem, rdllink); 1335 1336 lnk = lnk->next; 1337 1338 /* If this file is already in the ready list we exit soon */ 1339 if (!ep_is_linked(&epi->txlink)) { 1340 /* 1341 * This is initialized in this way so that the default 1342 * behaviour of the reinjecting code will be to push back 1343 * the item inside the ready list. 1344 */ 1345 epi->revents = epi->event.events; 1346 1347 /* Link the ready item into the transfer list */ 1348 list_add(&epi->txlink, txlist); 1349 nepi++; 1350 1351 /* 1352 * Unlink the item from the ready list. 1353 */ 1354 ep_list_del(&epi->rdllink); 1355 } 1356 } 1357 1358 write_unlock_irqrestore(&ep->lock, flags); 1359 1360 return nepi; 1361 } 1362 1363 1364 /* 1365 * This function is called without holding the "ep->lock" since the call to 1366 * __copy_to_user() might sleep, and also f_op->poll() might reenable the IRQ 1367 * because of the way poll() is traditionally implemented in Linux. 1368 */ 1369 static int ep_send_events(struct eventpoll *ep, struct list_head *txlist, 1370 struct epoll_event __user *events) 1371 { 1372 int eventcnt = 0; 1373 unsigned int revents; 1374 struct list_head *lnk; 1375 struct epitem *epi; 1376 1377 /* 1378 * We can loop without lock because this is a task private list. 1379 * The test done during the collection loop will guarantee us that 1380 * another task will not try to collect this file. Also, items 1381 * cannot vanish during the loop because we are holding "sem". 1382 */ 1383 list_for_each(lnk, txlist) { 1384 epi = list_entry(lnk, struct epitem, txlink); 1385 1386 /* 1387 * Get the ready file event set. We can safely use the file 1388 * because we are holding the "sem" in read and this will 1389 * guarantee that both the file and the item will not vanish. 1390 */ 1391 revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL); 1392 1393 /* 1394 * Set the return event set for the current file descriptor. 1395 * Note that only the task task was successfully able to link 1396 * the item to its "txlist" will write this field. 1397 */ 1398 epi->revents = revents & epi->event.events; 1399 1400 if (epi->revents) { 1401 if (__put_user(epi->revents, 1402 &events[eventcnt].events) || 1403 __put_user(epi->event.data, 1404 &events[eventcnt].data)) 1405 return -EFAULT; 1406 if (epi->event.events & EPOLLONESHOT) 1407 epi->event.events &= EP_PRIVATE_BITS; 1408 eventcnt++; 1409 } 1410 } 1411 return eventcnt; 1412 } 1413 1414 1415 /* 1416 * Walk through the transfer list we collected with ep_collect_ready_items() 1417 * and, if 1) the item is still "alive" 2) its event set is not empty 3) it's 1418 * not already linked, links it to the ready list. Same as above, we are holding 1419 * "sem" so items cannot vanish underneath our nose. 1420 */ 1421 static void ep_reinject_items(struct eventpoll *ep, struct list_head *txlist) 1422 { 1423 int ricnt = 0, pwake = 0; 1424 unsigned long flags; 1425 struct epitem *epi; 1426 1427 write_lock_irqsave(&ep->lock, flags); 1428 1429 while (!list_empty(txlist)) { 1430 epi = list_entry(txlist->next, struct epitem, txlink); 1431 1432 /* Unlink the current item from the transfer list */ 1433 ep_list_del(&epi->txlink); 1434 1435 /* 1436 * If the item is no more linked to the interest set, we don't 1437 * have to push it inside the ready list because the following 1438 * ep_release_epitem() is going to drop it. Also, if the current 1439 * item is set to have an Edge Triggered behaviour, we don't have 1440 * to push it back either. 1441 */ 1442 if (ep_rb_linked(&epi->rbn) && !(epi->event.events & EPOLLET) && 1443 (epi->revents & epi->event.events) && !ep_is_linked(&epi->rdllink)) { 1444 list_add_tail(&epi->rdllink, &ep->rdllist); 1445 ricnt++; 1446 } 1447 } 1448 1449 if (ricnt) { 1450 /* 1451 * Wake up ( if active ) both the eventpoll wait list and the ->poll() 1452 * wait list. 1453 */ 1454 if (waitqueue_active(&ep->wq)) 1455 wake_up(&ep->wq); 1456 if (waitqueue_active(&ep->poll_wait)) 1457 pwake++; 1458 } 1459 1460 write_unlock_irqrestore(&ep->lock, flags); 1461 1462 /* We have to call this outside the lock */ 1463 if (pwake) 1464 ep_poll_safewake(&psw, &ep->poll_wait); 1465 } 1466 1467 1468 /* 1469 * Perform the transfer of events to user space. 1470 */ 1471 static int ep_events_transfer(struct eventpoll *ep, 1472 struct epoll_event __user *events, int maxevents) 1473 { 1474 int eventcnt = 0; 1475 struct list_head txlist; 1476 1477 INIT_LIST_HEAD(&txlist); 1478 1479 /* 1480 * We need to lock this because we could be hit by 1481 * eventpoll_release_file() and epoll_ctl(EPOLL_CTL_DEL). 1482 */ 1483 down_read(&ep->sem); 1484 1485 /* Collect/extract ready items */ 1486 if (ep_collect_ready_items(ep, &txlist, maxevents) > 0) { 1487 /* Build result set in userspace */ 1488 eventcnt = ep_send_events(ep, &txlist, events); 1489 1490 /* Reinject ready items into the ready list */ 1491 ep_reinject_items(ep, &txlist); 1492 } 1493 1494 up_read(&ep->sem); 1495 1496 return eventcnt; 1497 } 1498 1499 1500 static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, 1501 int maxevents, long timeout) 1502 { 1503 int res, eavail; 1504 unsigned long flags; 1505 long jtimeout; 1506 wait_queue_t wait; 1507 1508 /* 1509 * Calculate the timeout by checking for the "infinite" value ( -1 ) 1510 * and the overflow condition. The passed timeout is in milliseconds, 1511 * that why (t * HZ) / 1000. 1512 */ 1513 jtimeout = (timeout < 0 || timeout >= EP_MAX_MSTIMEO) ? 1514 MAX_SCHEDULE_TIMEOUT : (timeout * HZ + 999) / 1000; 1515 1516 retry: 1517 write_lock_irqsave(&ep->lock, flags); 1518 1519 res = 0; 1520 if (list_empty(&ep->rdllist)) { 1521 /* 1522 * We don't have any available event to return to the caller. 1523 * We need to sleep here, and we will be wake up by 1524 * ep_poll_callback() when events will become available. 1525 */ 1526 init_waitqueue_entry(&wait, current); 1527 add_wait_queue(&ep->wq, &wait); 1528 1529 for (;;) { 1530 /* 1531 * We don't want to sleep if the ep_poll_callback() sends us 1532 * a wakeup in between. That's why we set the task state 1533 * to TASK_INTERRUPTIBLE before doing the checks. 1534 */ 1535 set_current_state(TASK_INTERRUPTIBLE); 1536 if (!list_empty(&ep->rdllist) || !jtimeout) 1537 break; 1538 if (signal_pending(current)) { 1539 res = -EINTR; 1540 break; 1541 } 1542 1543 write_unlock_irqrestore(&ep->lock, flags); 1544 jtimeout = schedule_timeout(jtimeout); 1545 write_lock_irqsave(&ep->lock, flags); 1546 } 1547 remove_wait_queue(&ep->wq, &wait); 1548 1549 set_current_state(TASK_RUNNING); 1550 } 1551 1552 /* Is it worth to try to dig for events ? */ 1553 eavail = !list_empty(&ep->rdllist); 1554 1555 write_unlock_irqrestore(&ep->lock, flags); 1556 1557 /* 1558 * Try to transfer events to user space. In case we get 0 events and 1559 * there's still timeout left over, we go trying again in search of 1560 * more luck. 1561 */ 1562 if (!res && eavail && 1563 !(res = ep_events_transfer(ep, events, maxevents)) && jtimeout) 1564 goto retry; 1565 1566 return res; 1567 } 1568 1569 1570 static int eventpollfs_delete_dentry(struct dentry *dentry) 1571 { 1572 1573 return 1; 1574 } 1575 1576 1577 static struct inode *ep_eventpoll_inode(void) 1578 { 1579 int error = -ENOMEM; 1580 struct inode *inode = new_inode(eventpoll_mnt->mnt_sb); 1581 1582 if (!inode) 1583 goto eexit_1; 1584 1585 inode->i_fop = &eventpoll_fops; 1586 1587 /* 1588 * Mark the inode dirty from the very beginning, 1589 * that way it will never be moved to the dirty 1590 * list because mark_inode_dirty() will think 1591 * that it already _is_ on the dirty list. 1592 */ 1593 inode->i_state = I_DIRTY; 1594 inode->i_mode = S_IRUSR | S_IWUSR; 1595 inode->i_uid = current->fsuid; 1596 inode->i_gid = current->fsgid; 1597 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; 1598 inode->i_blksize = PAGE_SIZE; 1599 return inode; 1600 1601 eexit_1: 1602 return ERR_PTR(error); 1603 } 1604 1605 1606 static struct super_block * 1607 eventpollfs_get_sb(struct file_system_type *fs_type, int flags, 1608 const char *dev_name, void *data) 1609 { 1610 return get_sb_pseudo(fs_type, "eventpoll:", NULL, EVENTPOLLFS_MAGIC); 1611 } 1612 1613 1614 static int __init eventpoll_init(void) 1615 { 1616 int error; 1617 1618 init_MUTEX(&epsem); 1619 1620 /* Initialize the structure used to perform safe poll wait head wake ups */ 1621 ep_poll_safewake_init(&psw); 1622 1623 /* Allocates slab cache used to allocate "struct epitem" items */ 1624 epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem), 1625 0, SLAB_HWCACHE_ALIGN|EPI_SLAB_DEBUG|SLAB_PANIC, 1626 NULL, NULL); 1627 1628 /* Allocates slab cache used to allocate "struct eppoll_entry" */ 1629 pwq_cache = kmem_cache_create("eventpoll_pwq", 1630 sizeof(struct eppoll_entry), 0, 1631 EPI_SLAB_DEBUG|SLAB_PANIC, NULL, NULL); 1632 1633 /* 1634 * Register the virtual file system that will be the source of inodes 1635 * for the eventpoll files 1636 */ 1637 error = register_filesystem(&eventpoll_fs_type); 1638 if (error) 1639 goto epanic; 1640 1641 /* Mount the above commented virtual file system */ 1642 eventpoll_mnt = kern_mount(&eventpoll_fs_type); 1643 error = PTR_ERR(eventpoll_mnt); 1644 if (IS_ERR(eventpoll_mnt)) 1645 goto epanic; 1646 1647 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: successfully initialized.\n", 1648 current)); 1649 return 0; 1650 1651 epanic: 1652 panic("eventpoll_init() failed\n"); 1653 } 1654 1655 1656 static void __exit eventpoll_exit(void) 1657 { 1658 /* Undo all operations done inside eventpoll_init() */ 1659 unregister_filesystem(&eventpoll_fs_type); 1660 mntput(eventpoll_mnt); 1661 kmem_cache_destroy(pwq_cache); 1662 kmem_cache_destroy(epi_cache); 1663 } 1664 1665 module_init(eventpoll_init); 1666 module_exit(eventpoll_exit); 1667 1668 MODULE_LICENSE("GPL"); 1669