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1 | /* | |
2 | * fs/eventpoll.c (Efficient event retrieval implementation) | |
3 | * Copyright (C) 2001,...,2009 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 | /* Epoll private bits inside the event mask */ | |
75 | #define EP_PRIVATE_BITS (EPOLLONESHOT | EPOLLET) | |
76 | ||
77 | /* Maximum number of nesting allowed inside epoll sets */ | |
78 | #define EP_MAX_NESTS 4 | |
79 | ||
80 | #define EP_MAX_EVENTS (INT_MAX / sizeof(struct epoll_event)) | |
81 | ||
82 | #define EP_UNACTIVE_PTR ((void *) -1L) | |
83 | ||
84 | #define EP_ITEM_COST (sizeof(struct epitem) + sizeof(struct eppoll_entry)) | |
85 | ||
86 | struct epoll_filefd { | |
87 | struct file *file; | |
88 | int fd; | |
89 | }; | |
90 | ||
91 | /* | |
92 | * Structure used to track possible nested calls, for too deep recursions | |
93 | * and loop cycles. | |
94 | */ | |
95 | struct nested_call_node { | |
96 | struct list_head llink; | |
97 | void *cookie; | |
98 | void *ctx; | |
99 | }; | |
100 | ||
101 | /* | |
102 | * This structure is used as collector for nested calls, to check for | |
103 | * maximum recursion dept and loop cycles. | |
104 | */ | |
105 | struct nested_calls { | |
106 | struct list_head tasks_call_list; | |
107 | spinlock_t lock; | |
108 | }; | |
109 | ||
110 | /* | |
111 | * Each file descriptor added to the eventpoll interface will | |
112 | * have an entry of this type linked to the "rbr" RB tree. | |
113 | */ | |
114 | struct epitem { | |
115 | /* RB tree node used to link this structure to the eventpoll RB tree */ | |
116 | struct rb_node rbn; | |
117 | ||
118 | /* List header used to link this structure to the eventpoll ready list */ | |
119 | struct list_head rdllink; | |
120 | ||
121 | /* | |
122 | * Works together "struct eventpoll"->ovflist in keeping the | |
123 | * single linked chain of items. | |
124 | */ | |
125 | struct epitem *next; | |
126 | ||
127 | /* The file descriptor information this item refers to */ | |
128 | struct epoll_filefd ffd; | |
129 | ||
130 | /* Number of active wait queue attached to poll operations */ | |
131 | int nwait; | |
132 | ||
133 | /* List containing poll wait queues */ | |
134 | struct list_head pwqlist; | |
135 | ||
136 | /* The "container" of this item */ | |
137 | struct eventpoll *ep; | |
138 | ||
139 | /* List header used to link this item to the "struct file" items list */ | |
140 | struct list_head fllink; | |
141 | ||
142 | /* The structure that describe the interested events and the source fd */ | |
143 | struct epoll_event event; | |
144 | }; | |
145 | ||
146 | /* | |
147 | * This structure is stored inside the "private_data" member of the file | |
148 | * structure and rapresent the main data sructure for the eventpoll | |
149 | * interface. | |
150 | */ | |
151 | struct eventpoll { | |
152 | /* Protect the this structure access */ | |
153 | spinlock_t lock; | |
154 | ||
155 | /* | |
156 | * This mutex is used to ensure that files are not removed | |
157 | * while epoll is using them. This is held during the event | |
158 | * collection loop, the file cleanup path, the epoll file exit | |
159 | * code and the ctl operations. | |
160 | */ | |
161 | struct mutex mtx; | |
162 | ||
163 | /* Wait queue used by sys_epoll_wait() */ | |
164 | wait_queue_head_t wq; | |
165 | ||
166 | /* Wait queue used by file->poll() */ | |
167 | wait_queue_head_t poll_wait; | |
168 | ||
169 | /* List of ready file descriptors */ | |
170 | struct list_head rdllist; | |
171 | ||
172 | /* RB tree root used to store monitored fd structs */ | |
173 | struct rb_root rbr; | |
174 | ||
175 | /* | |
176 | * This is a single linked list that chains all the "struct epitem" that | |
177 | * happened while transfering ready events to userspace w/out | |
178 | * holding ->lock. | |
179 | */ | |
180 | struct epitem *ovflist; | |
181 | ||
182 | /* The user that created the eventpoll descriptor */ | |
183 | struct user_struct *user; | |
184 | }; | |
185 | ||
186 | /* Wait structure used by the poll hooks */ | |
187 | struct eppoll_entry { | |
188 | /* List header used to link this structure to the "struct epitem" */ | |
189 | struct list_head llink; | |
190 | ||
191 | /* The "base" pointer is set to the container "struct epitem" */ | |
192 | struct epitem *base; | |
193 | ||
194 | /* | |
195 | * Wait queue item that will be linked to the target file wait | |
196 | * queue head. | |
197 | */ | |
198 | wait_queue_t wait; | |
199 | ||
200 | /* The wait queue head that linked the "wait" wait queue item */ | |
201 | wait_queue_head_t *whead; | |
202 | }; | |
203 | ||
204 | /* Wrapper struct used by poll queueing */ | |
205 | struct ep_pqueue { | |
206 | poll_table pt; | |
207 | struct epitem *epi; | |
208 | }; | |
209 | ||
210 | /* Used by the ep_send_events() function as callback private data */ | |
211 | struct ep_send_events_data { | |
212 | int maxevents; | |
213 | struct epoll_event __user *events; | |
214 | }; | |
215 | ||
216 | /* | |
217 | * Configuration options available inside /proc/sys/fs/epoll/ | |
218 | */ | |
219 | /* Maximum number of epoll watched descriptors, per user */ | |
220 | static int max_user_watches __read_mostly; | |
221 | ||
222 | /* | |
223 | * This mutex is used to serialize ep_free() and eventpoll_release_file(). | |
224 | */ | |
225 | static DEFINE_MUTEX(epmutex); | |
226 | ||
227 | /* Used for safe wake up implementation */ | |
228 | static struct nested_calls poll_safewake_ncalls; | |
229 | ||
230 | /* Used to call file's f_op->poll() under the nested calls boundaries */ | |
231 | static struct nested_calls poll_readywalk_ncalls; | |
232 | ||
233 | /* Slab cache used to allocate "struct epitem" */ | |
234 | static struct kmem_cache *epi_cache __read_mostly; | |
235 | ||
236 | /* Slab cache used to allocate "struct eppoll_entry" */ | |
237 | static struct kmem_cache *pwq_cache __read_mostly; | |
238 | ||
239 | #ifdef CONFIG_SYSCTL | |
240 | ||
241 | #include <linux/sysctl.h> | |
242 | ||
243 | static int zero; | |
244 | ||
245 | ctl_table epoll_table[] = { | |
246 | { | |
247 | .procname = "max_user_watches", | |
248 | .data = &max_user_watches, | |
249 | .maxlen = sizeof(int), | |
250 | .mode = 0644, | |
251 | .proc_handler = proc_dointvec_minmax, | |
252 | .extra1 = &zero, | |
253 | }, | |
254 | { } | |
255 | }; | |
256 | #endif /* CONFIG_SYSCTL */ | |
257 | ||
258 | ||
259 | /* Setup the structure that is used as key for the RB tree */ | |
260 | static inline void ep_set_ffd(struct epoll_filefd *ffd, | |
261 | struct file *file, int fd) | |
262 | { | |
263 | ffd->file = file; | |
264 | ffd->fd = fd; | |
265 | } | |
266 | ||
267 | /* Compare RB tree keys */ | |
268 | static inline int ep_cmp_ffd(struct epoll_filefd *p1, | |
269 | struct epoll_filefd *p2) | |
270 | { | |
271 | return (p1->file > p2->file ? +1: | |
272 | (p1->file < p2->file ? -1 : p1->fd - p2->fd)); | |
273 | } | |
274 | ||
275 | /* Tells us if the item is currently linked */ | |
276 | static inline int ep_is_linked(struct list_head *p) | |
277 | { | |
278 | return !list_empty(p); | |
279 | } | |
280 | ||
281 | /* Get the "struct epitem" from a wait queue pointer */ | |
282 | static inline struct epitem *ep_item_from_wait(wait_queue_t *p) | |
283 | { | |
284 | return container_of(p, struct eppoll_entry, wait)->base; | |
285 | } | |
286 | ||
287 | /* Get the "struct epitem" from an epoll queue wrapper */ | |
288 | static inline struct epitem *ep_item_from_epqueue(poll_table *p) | |
289 | { | |
290 | return container_of(p, struct ep_pqueue, pt)->epi; | |
291 | } | |
292 | ||
293 | /* Tells if the epoll_ctl(2) operation needs an event copy from userspace */ | |
294 | static inline int ep_op_has_event(int op) | |
295 | { | |
296 | return op != EPOLL_CTL_DEL; | |
297 | } | |
298 | ||
299 | /* Initialize the poll safe wake up structure */ | |
300 | static void ep_nested_calls_init(struct nested_calls *ncalls) | |
301 | { | |
302 | INIT_LIST_HEAD(&ncalls->tasks_call_list); | |
303 | spin_lock_init(&ncalls->lock); | |
304 | } | |
305 | ||
306 | /** | |
307 | * ep_call_nested - Perform a bound (possibly) nested call, by checking | |
308 | * that the recursion limit is not exceeded, and that | |
309 | * the same nested call (by the meaning of same cookie) is | |
310 | * no re-entered. | |
311 | * | |
312 | * @ncalls: Pointer to the nested_calls structure to be used for this call. | |
313 | * @max_nests: Maximum number of allowed nesting calls. | |
314 | * @nproc: Nested call core function pointer. | |
315 | * @priv: Opaque data to be passed to the @nproc callback. | |
316 | * @cookie: Cookie to be used to identify this nested call. | |
317 | * @ctx: This instance context. | |
318 | * | |
319 | * Returns: Returns the code returned by the @nproc callback, or -1 if | |
320 | * the maximum recursion limit has been exceeded. | |
321 | */ | |
322 | static int ep_call_nested(struct nested_calls *ncalls, int max_nests, | |
323 | int (*nproc)(void *, void *, int), void *priv, | |
324 | void *cookie, void *ctx) | |
325 | { | |
326 | int error, call_nests = 0; | |
327 | unsigned long flags; | |
328 | struct list_head *lsthead = &ncalls->tasks_call_list; | |
329 | struct nested_call_node *tncur; | |
330 | struct nested_call_node tnode; | |
331 | ||
332 | spin_lock_irqsave(&ncalls->lock, flags); | |
333 | ||
334 | /* | |
335 | * Try to see if the current task is already inside this wakeup call. | |
336 | * We use a list here, since the population inside this set is always | |
337 | * very much limited. | |
338 | */ | |
339 | list_for_each_entry(tncur, lsthead, llink) { | |
340 | if (tncur->ctx == ctx && | |
341 | (tncur->cookie == cookie || ++call_nests > max_nests)) { | |
342 | /* | |
343 | * Ops ... loop detected or maximum nest level reached. | |
344 | * We abort this wake by breaking the cycle itself. | |
345 | */ | |
346 | error = -1; | |
347 | goto out_unlock; | |
348 | } | |
349 | } | |
350 | ||
351 | /* Add the current task and cookie to the list */ | |
352 | tnode.ctx = ctx; | |
353 | tnode.cookie = cookie; | |
354 | list_add(&tnode.llink, lsthead); | |
355 | ||
356 | spin_unlock_irqrestore(&ncalls->lock, flags); | |
357 | ||
358 | /* Call the nested function */ | |
359 | error = (*nproc)(priv, cookie, call_nests); | |
360 | ||
361 | /* Remove the current task from the list */ | |
362 | spin_lock_irqsave(&ncalls->lock, flags); | |
363 | list_del(&tnode.llink); | |
364 | out_unlock: | |
365 | spin_unlock_irqrestore(&ncalls->lock, flags); | |
366 | ||
367 | return error; | |
368 | } | |
369 | ||
370 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
371 | static inline void ep_wake_up_nested(wait_queue_head_t *wqueue, | |
372 | unsigned long events, int subclass) | |
373 | { | |
374 | unsigned long flags; | |
375 | ||
376 | spin_lock_irqsave_nested(&wqueue->lock, flags, subclass); | |
377 | wake_up_locked_poll(wqueue, events); | |
378 | spin_unlock_irqrestore(&wqueue->lock, flags); | |
379 | } | |
380 | #else | |
381 | static inline void ep_wake_up_nested(wait_queue_head_t *wqueue, | |
382 | unsigned long events, int subclass) | |
383 | { | |
384 | wake_up_poll(wqueue, events); | |
385 | } | |
386 | #endif | |
387 | ||
388 | static int ep_poll_wakeup_proc(void *priv, void *cookie, int call_nests) | |
389 | { | |
390 | ep_wake_up_nested((wait_queue_head_t *) cookie, POLLIN, | |
391 | 1 + call_nests); | |
392 | return 0; | |
393 | } | |
394 | ||
395 | /* | |
396 | * Perform a safe wake up of the poll wait list. The problem is that | |
397 | * with the new callback'd wake up system, it is possible that the | |
398 | * poll callback is reentered from inside the call to wake_up() done | |
399 | * on the poll wait queue head. The rule is that we cannot reenter the | |
400 | * wake up code from the same task more than EP_MAX_NESTS times, | |
401 | * and we cannot reenter the same wait queue head at all. This will | |
402 | * enable to have a hierarchy of epoll file descriptor of no more than | |
403 | * EP_MAX_NESTS deep. | |
404 | */ | |
405 | static void ep_poll_safewake(wait_queue_head_t *wq) | |
406 | { | |
407 | int this_cpu = get_cpu(); | |
408 | ||
409 | ep_call_nested(&poll_safewake_ncalls, EP_MAX_NESTS, | |
410 | ep_poll_wakeup_proc, NULL, wq, (void *) (long) this_cpu); | |
411 | ||
412 | put_cpu(); | |
413 | } | |
414 | ||
415 | /* | |
416 | * This function unregisters poll callbacks from the associated file | |
417 | * descriptor. Must be called with "mtx" held (or "epmutex" if called from | |
418 | * ep_free). | |
419 | */ | |
420 | static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi) | |
421 | { | |
422 | struct list_head *lsthead = &epi->pwqlist; | |
423 | struct eppoll_entry *pwq; | |
424 | ||
425 | while (!list_empty(lsthead)) { | |
426 | pwq = list_first_entry(lsthead, struct eppoll_entry, llink); | |
427 | ||
428 | list_del(&pwq->llink); | |
429 | remove_wait_queue(pwq->whead, &pwq->wait); | |
430 | kmem_cache_free(pwq_cache, pwq); | |
431 | } | |
432 | } | |
433 | ||
434 | /** | |
435 | * ep_scan_ready_list - Scans the ready list in a way that makes possible for | |
436 | * the scan code, to call f_op->poll(). Also allows for | |
437 | * O(NumReady) performance. | |
438 | * | |
439 | * @ep: Pointer to the epoll private data structure. | |
440 | * @sproc: Pointer to the scan callback. | |
441 | * @priv: Private opaque data passed to the @sproc callback. | |
442 | * | |
443 | * Returns: The same integer error code returned by the @sproc callback. | |
444 | */ | |
445 | static int ep_scan_ready_list(struct eventpoll *ep, | |
446 | int (*sproc)(struct eventpoll *, | |
447 | struct list_head *, void *), | |
448 | void *priv) | |
449 | { | |
450 | int error, pwake = 0; | |
451 | unsigned long flags; | |
452 | struct epitem *epi, *nepi; | |
453 | LIST_HEAD(txlist); | |
454 | ||
455 | /* | |
456 | * We need to lock this because we could be hit by | |
457 | * eventpoll_release_file() and epoll_ctl(). | |
458 | */ | |
459 | mutex_lock(&ep->mtx); | |
460 | ||
461 | /* | |
462 | * Steal the ready list, and re-init the original one to the | |
463 | * empty list. Also, set ep->ovflist to NULL so that events | |
464 | * happening while looping w/out locks, are not lost. We cannot | |
465 | * have the poll callback to queue directly on ep->rdllist, | |
466 | * because we want the "sproc" callback to be able to do it | |
467 | * in a lockless way. | |
468 | */ | |
469 | spin_lock_irqsave(&ep->lock, flags); | |
470 | list_splice_init(&ep->rdllist, &txlist); | |
471 | ep->ovflist = NULL; | |
472 | spin_unlock_irqrestore(&ep->lock, flags); | |
473 | ||
474 | /* | |
475 | * Now call the callback function. | |
476 | */ | |
477 | error = (*sproc)(ep, &txlist, priv); | |
478 | ||
479 | spin_lock_irqsave(&ep->lock, flags); | |
480 | /* | |
481 | * During the time we spent inside the "sproc" callback, some | |
482 | * other events might have been queued by the poll callback. | |
483 | * We re-insert them inside the main ready-list here. | |
484 | */ | |
485 | for (nepi = ep->ovflist; (epi = nepi) != NULL; | |
486 | nepi = epi->next, epi->next = EP_UNACTIVE_PTR) { | |
487 | /* | |
488 | * We need to check if the item is already in the list. | |
489 | * During the "sproc" callback execution time, items are | |
490 | * queued into ->ovflist but the "txlist" might already | |
491 | * contain them, and the list_splice() below takes care of them. | |
492 | */ | |
493 | if (!ep_is_linked(&epi->rdllink)) | |
494 | list_add_tail(&epi->rdllink, &ep->rdllist); | |
495 | } | |
496 | /* | |
497 | * We need to set back ep->ovflist to EP_UNACTIVE_PTR, so that after | |
498 | * releasing the lock, events will be queued in the normal way inside | |
499 | * ep->rdllist. | |
500 | */ | |
501 | ep->ovflist = EP_UNACTIVE_PTR; | |
502 | ||
503 | /* | |
504 | * Quickly re-inject items left on "txlist". | |
505 | */ | |
506 | list_splice(&txlist, &ep->rdllist); | |
507 | ||
508 | if (!list_empty(&ep->rdllist)) { | |
509 | /* | |
510 | * Wake up (if active) both the eventpoll wait list and | |
511 | * the ->poll() wait list (delayed after we release the lock). | |
512 | */ | |
513 | if (waitqueue_active(&ep->wq)) | |
514 | wake_up_locked(&ep->wq); | |
515 | if (waitqueue_active(&ep->poll_wait)) | |
516 | pwake++; | |
517 | } | |
518 | spin_unlock_irqrestore(&ep->lock, flags); | |
519 | ||
520 | mutex_unlock(&ep->mtx); | |
521 | ||
522 | /* We have to call this outside the lock */ | |
523 | if (pwake) | |
524 | ep_poll_safewake(&ep->poll_wait); | |
525 | ||
526 | return error; | |
527 | } | |
528 | ||
529 | /* | |
530 | * Removes a "struct epitem" from the eventpoll RB tree and deallocates | |
531 | * all the associated resources. Must be called with "mtx" held. | |
532 | */ | |
533 | static int ep_remove(struct eventpoll *ep, struct epitem *epi) | |
534 | { | |
535 | unsigned long flags; | |
536 | struct file *file = epi->ffd.file; | |
537 | ||
538 | /* | |
539 | * Removes poll wait queue hooks. We _have_ to do this without holding | |
540 | * the "ep->lock" otherwise a deadlock might occur. This because of the | |
541 | * sequence of the lock acquisition. Here we do "ep->lock" then the wait | |
542 | * queue head lock when unregistering the wait queue. The wakeup callback | |
543 | * will run by holding the wait queue head lock and will call our callback | |
544 | * that will try to get "ep->lock". | |
545 | */ | |
546 | ep_unregister_pollwait(ep, epi); | |
547 | ||
548 | /* Remove the current item from the list of epoll hooks */ | |
549 | spin_lock(&file->f_lock); | |
550 | if (ep_is_linked(&epi->fllink)) | |
551 | list_del_init(&epi->fllink); | |
552 | spin_unlock(&file->f_lock); | |
553 | ||
554 | rb_erase(&epi->rbn, &ep->rbr); | |
555 | ||
556 | spin_lock_irqsave(&ep->lock, flags); | |
557 | if (ep_is_linked(&epi->rdllink)) | |
558 | list_del_init(&epi->rdllink); | |
559 | spin_unlock_irqrestore(&ep->lock, flags); | |
560 | ||
561 | /* At this point it is safe to free the eventpoll item */ | |
562 | kmem_cache_free(epi_cache, epi); | |
563 | ||
564 | atomic_dec(&ep->user->epoll_watches); | |
565 | ||
566 | return 0; | |
567 | } | |
568 | ||
569 | static void ep_free(struct eventpoll *ep) | |
570 | { | |
571 | struct rb_node *rbp; | |
572 | struct epitem *epi; | |
573 | ||
574 | /* We need to release all tasks waiting for these file */ | |
575 | if (waitqueue_active(&ep->poll_wait)) | |
576 | ep_poll_safewake(&ep->poll_wait); | |
577 | ||
578 | /* | |
579 | * We need to lock this because we could be hit by | |
580 | * eventpoll_release_file() while we're freeing the "struct eventpoll". | |
581 | * We do not need to hold "ep->mtx" here because the epoll file | |
582 | * is on the way to be removed and no one has references to it | |
583 | * anymore. The only hit might come from eventpoll_release_file() but | |
584 | * holding "epmutex" is sufficent here. | |
585 | */ | |
586 | mutex_lock(&epmutex); | |
587 | ||
588 | /* | |
589 | * Walks through the whole tree by unregistering poll callbacks. | |
590 | */ | |
591 | for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { | |
592 | epi = rb_entry(rbp, struct epitem, rbn); | |
593 | ||
594 | ep_unregister_pollwait(ep, epi); | |
595 | } | |
596 | ||
597 | /* | |
598 | * Walks through the whole tree by freeing each "struct epitem". At this | |
599 | * point we are sure no poll callbacks will be lingering around, and also by | |
600 | * holding "epmutex" we can be sure that no file cleanup code will hit | |
601 | * us during this operation. So we can avoid the lock on "ep->lock". | |
602 | */ | |
603 | while ((rbp = rb_first(&ep->rbr)) != NULL) { | |
604 | epi = rb_entry(rbp, struct epitem, rbn); | |
605 | ep_remove(ep, epi); | |
606 | } | |
607 | ||
608 | mutex_unlock(&epmutex); | |
609 | mutex_destroy(&ep->mtx); | |
610 | free_uid(ep->user); | |
611 | kfree(ep); | |
612 | } | |
613 | ||
614 | static int ep_eventpoll_release(struct inode *inode, struct file *file) | |
615 | { | |
616 | struct eventpoll *ep = file->private_data; | |
617 | ||
618 | if (ep) | |
619 | ep_free(ep); | |
620 | ||
621 | return 0; | |
622 | } | |
623 | ||
624 | static int ep_read_events_proc(struct eventpoll *ep, struct list_head *head, | |
625 | void *priv) | |
626 | { | |
627 | struct epitem *epi, *tmp; | |
628 | ||
629 | list_for_each_entry_safe(epi, tmp, head, rdllink) { | |
630 | if (epi->ffd.file->f_op->poll(epi->ffd.file, NULL) & | |
631 | epi->event.events) | |
632 | return POLLIN | POLLRDNORM; | |
633 | else { | |
634 | /* | |
635 | * Item has been dropped into the ready list by the poll | |
636 | * callback, but it's not actually ready, as far as | |
637 | * caller requested events goes. We can remove it here. | |
638 | */ | |
639 | list_del_init(&epi->rdllink); | |
640 | } | |
641 | } | |
642 | ||
643 | return 0; | |
644 | } | |
645 | ||
646 | static int ep_poll_readyevents_proc(void *priv, void *cookie, int call_nests) | |
647 | { | |
648 | return ep_scan_ready_list(priv, ep_read_events_proc, NULL); | |
649 | } | |
650 | ||
651 | static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait) | |
652 | { | |
653 | int pollflags; | |
654 | struct eventpoll *ep = file->private_data; | |
655 | ||
656 | /* Insert inside our poll wait queue */ | |
657 | poll_wait(file, &ep->poll_wait, wait); | |
658 | ||
659 | /* | |
660 | * Proceed to find out if wanted events are really available inside | |
661 | * the ready list. This need to be done under ep_call_nested() | |
662 | * supervision, since the call to f_op->poll() done on listed files | |
663 | * could re-enter here. | |
664 | */ | |
665 | pollflags = ep_call_nested(&poll_readywalk_ncalls, EP_MAX_NESTS, | |
666 | ep_poll_readyevents_proc, ep, ep, current); | |
667 | ||
668 | return pollflags != -1 ? pollflags : 0; | |
669 | } | |
670 | ||
671 | /* File callbacks that implement the eventpoll file behaviour */ | |
672 | static const struct file_operations eventpoll_fops = { | |
673 | .release = ep_eventpoll_release, | |
674 | .poll = ep_eventpoll_poll, | |
675 | .llseek = noop_llseek, | |
676 | }; | |
677 | ||
678 | /* Fast test to see if the file is an evenpoll file */ | |
679 | static inline int is_file_epoll(struct file *f) | |
680 | { | |
681 | return f->f_op == &eventpoll_fops; | |
682 | } | |
683 | ||
684 | /* | |
685 | * This is called from eventpoll_release() to unlink files from the eventpoll | |
686 | * interface. We need to have this facility to cleanup correctly files that are | |
687 | * closed without being removed from the eventpoll interface. | |
688 | */ | |
689 | void eventpoll_release_file(struct file *file) | |
690 | { | |
691 | struct list_head *lsthead = &file->f_ep_links; | |
692 | struct eventpoll *ep; | |
693 | struct epitem *epi; | |
694 | ||
695 | /* | |
696 | * We don't want to get "file->f_lock" because it is not | |
697 | * necessary. It is not necessary because we're in the "struct file" | |
698 | * cleanup path, and this means that noone is using this file anymore. | |
699 | * So, for example, epoll_ctl() cannot hit here since if we reach this | |
700 | * point, the file counter already went to zero and fget() would fail. | |
701 | * The only hit might come from ep_free() but by holding the mutex | |
702 | * will correctly serialize the operation. We do need to acquire | |
703 | * "ep->mtx" after "epmutex" because ep_remove() requires it when called | |
704 | * from anywhere but ep_free(). | |
705 | * | |
706 | * Besides, ep_remove() acquires the lock, so we can't hold it here. | |
707 | */ | |
708 | mutex_lock(&epmutex); | |
709 | ||
710 | while (!list_empty(lsthead)) { | |
711 | epi = list_first_entry(lsthead, struct epitem, fllink); | |
712 | ||
713 | ep = epi->ep; | |
714 | list_del_init(&epi->fllink); | |
715 | mutex_lock(&ep->mtx); | |
716 | ep_remove(ep, epi); | |
717 | mutex_unlock(&ep->mtx); | |
718 | } | |
719 | ||
720 | mutex_unlock(&epmutex); | |
721 | } | |
722 | ||
723 | static int ep_alloc(struct eventpoll **pep) | |
724 | { | |
725 | int error; | |
726 | struct user_struct *user; | |
727 | struct eventpoll *ep; | |
728 | ||
729 | user = get_current_user(); | |
730 | error = -ENOMEM; | |
731 | ep = kzalloc(sizeof(*ep), GFP_KERNEL); | |
732 | if (unlikely(!ep)) | |
733 | goto free_uid; | |
734 | ||
735 | spin_lock_init(&ep->lock); | |
736 | mutex_init(&ep->mtx); | |
737 | init_waitqueue_head(&ep->wq); | |
738 | init_waitqueue_head(&ep->poll_wait); | |
739 | INIT_LIST_HEAD(&ep->rdllist); | |
740 | ep->rbr = RB_ROOT; | |
741 | ep->ovflist = EP_UNACTIVE_PTR; | |
742 | ep->user = user; | |
743 | ||
744 | *pep = ep; | |
745 | ||
746 | return 0; | |
747 | ||
748 | free_uid: | |
749 | free_uid(user); | |
750 | return error; | |
751 | } | |
752 | ||
753 | /* | |
754 | * Search the file inside the eventpoll tree. The RB tree operations | |
755 | * are protected by the "mtx" mutex, and ep_find() must be called with | |
756 | * "mtx" held. | |
757 | */ | |
758 | static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd) | |
759 | { | |
760 | int kcmp; | |
761 | struct rb_node *rbp; | |
762 | struct epitem *epi, *epir = NULL; | |
763 | struct epoll_filefd ffd; | |
764 | ||
765 | ep_set_ffd(&ffd, file, fd); | |
766 | for (rbp = ep->rbr.rb_node; rbp; ) { | |
767 | epi = rb_entry(rbp, struct epitem, rbn); | |
768 | kcmp = ep_cmp_ffd(&ffd, &epi->ffd); | |
769 | if (kcmp > 0) | |
770 | rbp = rbp->rb_right; | |
771 | else if (kcmp < 0) | |
772 | rbp = rbp->rb_left; | |
773 | else { | |
774 | epir = epi; | |
775 | break; | |
776 | } | |
777 | } | |
778 | ||
779 | return epir; | |
780 | } | |
781 | ||
782 | /* | |
783 | * This is the callback that is passed to the wait queue wakeup | |
784 | * machanism. It is called by the stored file descriptors when they | |
785 | * have events to report. | |
786 | */ | |
787 | static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *key) | |
788 | { | |
789 | int pwake = 0; | |
790 | unsigned long flags; | |
791 | struct epitem *epi = ep_item_from_wait(wait); | |
792 | struct eventpoll *ep = epi->ep; | |
793 | ||
794 | spin_lock_irqsave(&ep->lock, flags); | |
795 | ||
796 | /* | |
797 | * If the event mask does not contain any poll(2) event, we consider the | |
798 | * descriptor to be disabled. This condition is likely the effect of the | |
799 | * EPOLLONESHOT bit that disables the descriptor when an event is received, | |
800 | * until the next EPOLL_CTL_MOD will be issued. | |
801 | */ | |
802 | if (!(epi->event.events & ~EP_PRIVATE_BITS)) | |
803 | goto out_unlock; | |
804 | ||
805 | /* | |
806 | * Check the events coming with the callback. At this stage, not | |
807 | * every device reports the events in the "key" parameter of the | |
808 | * callback. We need to be able to handle both cases here, hence the | |
809 | * test for "key" != NULL before the event match test. | |
810 | */ | |
811 | if (key && !((unsigned long) key & epi->event.events)) | |
812 | goto out_unlock; | |
813 | ||
814 | /* | |
815 | * If we are trasfering events to userspace, we can hold no locks | |
816 | * (because we're accessing user memory, and because of linux f_op->poll() | |
817 | * semantics). All the events that happens during that period of time are | |
818 | * chained in ep->ovflist and requeued later on. | |
819 | */ | |
820 | if (unlikely(ep->ovflist != EP_UNACTIVE_PTR)) { | |
821 | if (epi->next == EP_UNACTIVE_PTR) { | |
822 | epi->next = ep->ovflist; | |
823 | ep->ovflist = epi; | |
824 | } | |
825 | goto out_unlock; | |
826 | } | |
827 | ||
828 | /* If this file is already in the ready list we exit soon */ | |
829 | if (!ep_is_linked(&epi->rdllink)) | |
830 | list_add_tail(&epi->rdllink, &ep->rdllist); | |
831 | ||
832 | /* | |
833 | * Wake up ( if active ) both the eventpoll wait list and the ->poll() | |
834 | * wait list. | |
835 | */ | |
836 | if (waitqueue_active(&ep->wq)) | |
837 | wake_up_locked(&ep->wq); | |
838 | if (waitqueue_active(&ep->poll_wait)) | |
839 | pwake++; | |
840 | ||
841 | out_unlock: | |
842 | spin_unlock_irqrestore(&ep->lock, flags); | |
843 | ||
844 | /* We have to call this outside the lock */ | |
845 | if (pwake) | |
846 | ep_poll_safewake(&ep->poll_wait); | |
847 | ||
848 | return 1; | |
849 | } | |
850 | ||
851 | /* | |
852 | * This is the callback that is used to add our wait queue to the | |
853 | * target file wakeup lists. | |
854 | */ | |
855 | static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, | |
856 | poll_table *pt) | |
857 | { | |
858 | struct epitem *epi = ep_item_from_epqueue(pt); | |
859 | struct eppoll_entry *pwq; | |
860 | ||
861 | if (epi->nwait >= 0 && (pwq = kmem_cache_alloc(pwq_cache, GFP_KERNEL))) { | |
862 | init_waitqueue_func_entry(&pwq->wait, ep_poll_callback); | |
863 | pwq->whead = whead; | |
864 | pwq->base = epi; | |
865 | add_wait_queue(whead, &pwq->wait); | |
866 | list_add_tail(&pwq->llink, &epi->pwqlist); | |
867 | epi->nwait++; | |
868 | } else { | |
869 | /* We have to signal that an error occurred */ | |
870 | epi->nwait = -1; | |
871 | } | |
872 | } | |
873 | ||
874 | static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi) | |
875 | { | |
876 | int kcmp; | |
877 | struct rb_node **p = &ep->rbr.rb_node, *parent = NULL; | |
878 | struct epitem *epic; | |
879 | ||
880 | while (*p) { | |
881 | parent = *p; | |
882 | epic = rb_entry(parent, struct epitem, rbn); | |
883 | kcmp = ep_cmp_ffd(&epi->ffd, &epic->ffd); | |
884 | if (kcmp > 0) | |
885 | p = &parent->rb_right; | |
886 | else | |
887 | p = &parent->rb_left; | |
888 | } | |
889 | rb_link_node(&epi->rbn, parent, p); | |
890 | rb_insert_color(&epi->rbn, &ep->rbr); | |
891 | } | |
892 | ||
893 | /* | |
894 | * Must be called with "mtx" held. | |
895 | */ | |
896 | static int ep_insert(struct eventpoll *ep, struct epoll_event *event, | |
897 | struct file *tfile, int fd) | |
898 | { | |
899 | int error, revents, pwake = 0; | |
900 | unsigned long flags; | |
901 | struct epitem *epi; | |
902 | struct ep_pqueue epq; | |
903 | ||
904 | if (unlikely(atomic_read(&ep->user->epoll_watches) >= | |
905 | max_user_watches)) | |
906 | return -ENOSPC; | |
907 | if (!(epi = kmem_cache_alloc(epi_cache, GFP_KERNEL))) | |
908 | return -ENOMEM; | |
909 | ||
910 | /* Item initialization follow here ... */ | |
911 | INIT_LIST_HEAD(&epi->rdllink); | |
912 | INIT_LIST_HEAD(&epi->fllink); | |
913 | INIT_LIST_HEAD(&epi->pwqlist); | |
914 | epi->ep = ep; | |
915 | ep_set_ffd(&epi->ffd, tfile, fd); | |
916 | epi->event = *event; | |
917 | epi->nwait = 0; | |
918 | epi->next = EP_UNACTIVE_PTR; | |
919 | ||
920 | /* Initialize the poll table using the queue callback */ | |
921 | epq.epi = epi; | |
922 | init_poll_funcptr(&epq.pt, ep_ptable_queue_proc); | |
923 | ||
924 | /* | |
925 | * Attach the item to the poll hooks and get current event bits. | |
926 | * We can safely use the file* here because its usage count has | |
927 | * been increased by the caller of this function. Note that after | |
928 | * this operation completes, the poll callback can start hitting | |
929 | * the new item. | |
930 | */ | |
931 | revents = tfile->f_op->poll(tfile, &epq.pt); | |
932 | ||
933 | /* | |
934 | * We have to check if something went wrong during the poll wait queue | |
935 | * install process. Namely an allocation for a wait queue failed due | |
936 | * high memory pressure. | |
937 | */ | |
938 | error = -ENOMEM; | |
939 | if (epi->nwait < 0) | |
940 | goto error_unregister; | |
941 | ||
942 | /* Add the current item to the list of active epoll hook for this file */ | |
943 | spin_lock(&tfile->f_lock); | |
944 | list_add_tail(&epi->fllink, &tfile->f_ep_links); | |
945 | spin_unlock(&tfile->f_lock); | |
946 | ||
947 | /* | |
948 | * Add the current item to the RB tree. All RB tree operations are | |
949 | * protected by "mtx", and ep_insert() is called with "mtx" held. | |
950 | */ | |
951 | ep_rbtree_insert(ep, epi); | |
952 | ||
953 | /* We have to drop the new item inside our item list to keep track of it */ | |
954 | spin_lock_irqsave(&ep->lock, flags); | |
955 | ||
956 | /* If the file is already "ready" we drop it inside the ready list */ | |
957 | if ((revents & event->events) && !ep_is_linked(&epi->rdllink)) { | |
958 | list_add_tail(&epi->rdllink, &ep->rdllist); | |
959 | ||
960 | /* Notify waiting tasks that events are available */ | |
961 | if (waitqueue_active(&ep->wq)) | |
962 | wake_up_locked(&ep->wq); | |
963 | if (waitqueue_active(&ep->poll_wait)) | |
964 | pwake++; | |
965 | } | |
966 | ||
967 | spin_unlock_irqrestore(&ep->lock, flags); | |
968 | ||
969 | atomic_inc(&ep->user->epoll_watches); | |
970 | ||
971 | /* We have to call this outside the lock */ | |
972 | if (pwake) | |
973 | ep_poll_safewake(&ep->poll_wait); | |
974 | ||
975 | return 0; | |
976 | ||
977 | error_unregister: | |
978 | ep_unregister_pollwait(ep, epi); | |
979 | ||
980 | /* | |
981 | * We need to do this because an event could have been arrived on some | |
982 | * allocated wait queue. Note that we don't care about the ep->ovflist | |
983 | * list, since that is used/cleaned only inside a section bound by "mtx". | |
984 | * And ep_insert() is called with "mtx" held. | |
985 | */ | |
986 | spin_lock_irqsave(&ep->lock, flags); | |
987 | if (ep_is_linked(&epi->rdllink)) | |
988 | list_del_init(&epi->rdllink); | |
989 | spin_unlock_irqrestore(&ep->lock, flags); | |
990 | ||
991 | kmem_cache_free(epi_cache, epi); | |
992 | ||
993 | return error; | |
994 | } | |
995 | ||
996 | /* | |
997 | * Modify the interest event mask by dropping an event if the new mask | |
998 | * has a match in the current file status. Must be called with "mtx" held. | |
999 | */ | |
1000 | static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_event *event) | |
1001 | { | |
1002 | int pwake = 0; | |
1003 | unsigned int revents; | |
1004 | ||
1005 | /* | |
1006 | * Set the new event interest mask before calling f_op->poll(); | |
1007 | * otherwise we might miss an event that happens between the | |
1008 | * f_op->poll() call and the new event set registering. | |
1009 | */ | |
1010 | epi->event.events = event->events; | |
1011 | epi->event.data = event->data; /* protected by mtx */ | |
1012 | ||
1013 | /* | |
1014 | * Get current event bits. We can safely use the file* here because | |
1015 | * its usage count has been increased by the caller of this function. | |
1016 | */ | |
1017 | revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL); | |
1018 | ||
1019 | /* | |
1020 | * If the item is "hot" and it is not registered inside the ready | |
1021 | * list, push it inside. | |
1022 | */ | |
1023 | if (revents & event->events) { | |
1024 | spin_lock_irq(&ep->lock); | |
1025 | if (!ep_is_linked(&epi->rdllink)) { | |
1026 | list_add_tail(&epi->rdllink, &ep->rdllist); | |
1027 | ||
1028 | /* Notify waiting tasks that events are available */ | |
1029 | if (waitqueue_active(&ep->wq)) | |
1030 | wake_up_locked(&ep->wq); | |
1031 | if (waitqueue_active(&ep->poll_wait)) | |
1032 | pwake++; | |
1033 | } | |
1034 | spin_unlock_irq(&ep->lock); | |
1035 | } | |
1036 | ||
1037 | /* We have to call this outside the lock */ | |
1038 | if (pwake) | |
1039 | ep_poll_safewake(&ep->poll_wait); | |
1040 | ||
1041 | return 0; | |
1042 | } | |
1043 | ||
1044 | static int ep_send_events_proc(struct eventpoll *ep, struct list_head *head, | |
1045 | void *priv) | |
1046 | { | |
1047 | struct ep_send_events_data *esed = priv; | |
1048 | int eventcnt; | |
1049 | unsigned int revents; | |
1050 | struct epitem *epi; | |
1051 | struct epoll_event __user *uevent; | |
1052 | ||
1053 | /* | |
1054 | * We can loop without lock because we are passed a task private list. | |
1055 | * Items cannot vanish during the loop because ep_scan_ready_list() is | |
1056 | * holding "mtx" during this call. | |
1057 | */ | |
1058 | for (eventcnt = 0, uevent = esed->events; | |
1059 | !list_empty(head) && eventcnt < esed->maxevents;) { | |
1060 | epi = list_first_entry(head, struct epitem, rdllink); | |
1061 | ||
1062 | list_del_init(&epi->rdllink); | |
1063 | ||
1064 | revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL) & | |
1065 | epi->event.events; | |
1066 | ||
1067 | /* | |
1068 | * If the event mask intersect the caller-requested one, | |
1069 | * deliver the event to userspace. Again, ep_scan_ready_list() | |
1070 | * is holding "mtx", so no operations coming from userspace | |
1071 | * can change the item. | |
1072 | */ | |
1073 | if (revents) { | |
1074 | if (__put_user(revents, &uevent->events) || | |
1075 | __put_user(epi->event.data, &uevent->data)) { | |
1076 | list_add(&epi->rdllink, head); | |
1077 | return eventcnt ? eventcnt : -EFAULT; | |
1078 | } | |
1079 | eventcnt++; | |
1080 | uevent++; | |
1081 | if (epi->event.events & EPOLLONESHOT) | |
1082 | epi->event.events &= EP_PRIVATE_BITS; | |
1083 | else if (!(epi->event.events & EPOLLET)) { | |
1084 | /* | |
1085 | * If this file has been added with Level | |
1086 | * Trigger mode, we need to insert back inside | |
1087 | * the ready list, so that the next call to | |
1088 | * epoll_wait() will check again the events | |
1089 | * availability. At this point, noone can insert | |
1090 | * into ep->rdllist besides us. The epoll_ctl() | |
1091 | * callers are locked out by | |
1092 | * ep_scan_ready_list() holding "mtx" and the | |
1093 | * poll callback will queue them in ep->ovflist. | |
1094 | */ | |
1095 | list_add_tail(&epi->rdllink, &ep->rdllist); | |
1096 | } | |
1097 | } | |
1098 | } | |
1099 | ||
1100 | return eventcnt; | |
1101 | } | |
1102 | ||
1103 | static int ep_send_events(struct eventpoll *ep, | |
1104 | struct epoll_event __user *events, int maxevents) | |
1105 | { | |
1106 | struct ep_send_events_data esed; | |
1107 | ||
1108 | esed.maxevents = maxevents; | |
1109 | esed.events = events; | |
1110 | ||
1111 | return ep_scan_ready_list(ep, ep_send_events_proc, &esed); | |
1112 | } | |
1113 | ||
1114 | static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, | |
1115 | int maxevents, long timeout) | |
1116 | { | |
1117 | int res, eavail, timed_out = 0; | |
1118 | unsigned long flags; | |
1119 | long slack; | |
1120 | wait_queue_t wait; | |
1121 | struct timespec end_time; | |
1122 | ktime_t expires, *to = NULL; | |
1123 | ||
1124 | if (timeout > 0) { | |
1125 | ktime_get_ts(&end_time); | |
1126 | timespec_add_ns(&end_time, (u64)timeout * NSEC_PER_MSEC); | |
1127 | slack = select_estimate_accuracy(&end_time); | |
1128 | to = &expires; | |
1129 | *to = timespec_to_ktime(end_time); | |
1130 | } else if (timeout == 0) { | |
1131 | timed_out = 1; | |
1132 | } | |
1133 | ||
1134 | retry: | |
1135 | spin_lock_irqsave(&ep->lock, flags); | |
1136 | ||
1137 | res = 0; | |
1138 | if (list_empty(&ep->rdllist)) { | |
1139 | /* | |
1140 | * We don't have any available event to return to the caller. | |
1141 | * We need to sleep here, and we will be wake up by | |
1142 | * ep_poll_callback() when events will become available. | |
1143 | */ | |
1144 | init_waitqueue_entry(&wait, current); | |
1145 | __add_wait_queue_exclusive(&ep->wq, &wait); | |
1146 | ||
1147 | for (;;) { | |
1148 | /* | |
1149 | * We don't want to sleep if the ep_poll_callback() sends us | |
1150 | * a wakeup in between. That's why we set the task state | |
1151 | * to TASK_INTERRUPTIBLE before doing the checks. | |
1152 | */ | |
1153 | set_current_state(TASK_INTERRUPTIBLE); | |
1154 | if (!list_empty(&ep->rdllist) || timed_out) | |
1155 | break; | |
1156 | if (signal_pending(current)) { | |
1157 | res = -EINTR; | |
1158 | break; | |
1159 | } | |
1160 | ||
1161 | spin_unlock_irqrestore(&ep->lock, flags); | |
1162 | if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS)) | |
1163 | timed_out = 1; | |
1164 | ||
1165 | spin_lock_irqsave(&ep->lock, flags); | |
1166 | } | |
1167 | __remove_wait_queue(&ep->wq, &wait); | |
1168 | ||
1169 | set_current_state(TASK_RUNNING); | |
1170 | } | |
1171 | /* Is it worth to try to dig for events ? */ | |
1172 | eavail = !list_empty(&ep->rdllist) || ep->ovflist != EP_UNACTIVE_PTR; | |
1173 | ||
1174 | spin_unlock_irqrestore(&ep->lock, flags); | |
1175 | ||
1176 | /* | |
1177 | * Try to transfer events to user space. In case we get 0 events and | |
1178 | * there's still timeout left over, we go trying again in search of | |
1179 | * more luck. | |
1180 | */ | |
1181 | if (!res && eavail && | |
1182 | !(res = ep_send_events(ep, events, maxevents)) && !timed_out) | |
1183 | goto retry; | |
1184 | ||
1185 | return res; | |
1186 | } | |
1187 | ||
1188 | /* | |
1189 | * Open an eventpoll file descriptor. | |
1190 | */ | |
1191 | SYSCALL_DEFINE1(epoll_create1, int, flags) | |
1192 | { | |
1193 | int error; | |
1194 | struct eventpoll *ep = NULL; | |
1195 | ||
1196 | /* Check the EPOLL_* constant for consistency. */ | |
1197 | BUILD_BUG_ON(EPOLL_CLOEXEC != O_CLOEXEC); | |
1198 | ||
1199 | if (flags & ~EPOLL_CLOEXEC) | |
1200 | return -EINVAL; | |
1201 | /* | |
1202 | * Create the internal data structure ("struct eventpoll"). | |
1203 | */ | |
1204 | error = ep_alloc(&ep); | |
1205 | if (error < 0) | |
1206 | return error; | |
1207 | /* | |
1208 | * Creates all the items needed to setup an eventpoll file. That is, | |
1209 | * a file structure and a free file descriptor. | |
1210 | */ | |
1211 | error = anon_inode_getfd("[eventpoll]", &eventpoll_fops, ep, | |
1212 | O_RDWR | (flags & O_CLOEXEC)); | |
1213 | if (error < 0) | |
1214 | ep_free(ep); | |
1215 | ||
1216 | return error; | |
1217 | } | |
1218 | ||
1219 | SYSCALL_DEFINE1(epoll_create, int, size) | |
1220 | { | |
1221 | if (size <= 0) | |
1222 | return -EINVAL; | |
1223 | ||
1224 | return sys_epoll_create1(0); | |
1225 | } | |
1226 | ||
1227 | /* | |
1228 | * The following function implements the controller interface for | |
1229 | * the eventpoll file that enables the insertion/removal/change of | |
1230 | * file descriptors inside the interest set. | |
1231 | */ | |
1232 | SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd, | |
1233 | struct epoll_event __user *, event) | |
1234 | { | |
1235 | int error; | |
1236 | struct file *file, *tfile; | |
1237 | struct eventpoll *ep; | |
1238 | struct epitem *epi; | |
1239 | struct epoll_event epds; | |
1240 | ||
1241 | error = -EFAULT; | |
1242 | if (ep_op_has_event(op) && | |
1243 | copy_from_user(&epds, event, sizeof(struct epoll_event))) | |
1244 | goto error_return; | |
1245 | ||
1246 | /* Get the "struct file *" for the eventpoll file */ | |
1247 | error = -EBADF; | |
1248 | file = fget(epfd); | |
1249 | if (!file) | |
1250 | goto error_return; | |
1251 | ||
1252 | /* Get the "struct file *" for the target file */ | |
1253 | tfile = fget(fd); | |
1254 | if (!tfile) | |
1255 | goto error_fput; | |
1256 | ||
1257 | /* The target file descriptor must support poll */ | |
1258 | error = -EPERM; | |
1259 | if (!tfile->f_op || !tfile->f_op->poll) | |
1260 | goto error_tgt_fput; | |
1261 | ||
1262 | /* | |
1263 | * We have to check that the file structure underneath the file descriptor | |
1264 | * the user passed to us _is_ an eventpoll file. And also we do not permit | |
1265 | * adding an epoll file descriptor inside itself. | |
1266 | */ | |
1267 | error = -EINVAL; | |
1268 | if (file == tfile || !is_file_epoll(file)) | |
1269 | goto error_tgt_fput; | |
1270 | ||
1271 | /* | |
1272 | * At this point it is safe to assume that the "private_data" contains | |
1273 | * our own data structure. | |
1274 | */ | |
1275 | ep = file->private_data; | |
1276 | ||
1277 | mutex_lock(&ep->mtx); | |
1278 | ||
1279 | /* | |
1280 | * Try to lookup the file inside our RB tree, Since we grabbed "mtx" | |
1281 | * above, we can be sure to be able to use the item looked up by | |
1282 | * ep_find() till we release the mutex. | |
1283 | */ | |
1284 | epi = ep_find(ep, tfile, fd); | |
1285 | ||
1286 | error = -EINVAL; | |
1287 | switch (op) { | |
1288 | case EPOLL_CTL_ADD: | |
1289 | if (!epi) { | |
1290 | epds.events |= POLLERR | POLLHUP; | |
1291 | error = ep_insert(ep, &epds, tfile, fd); | |
1292 | } else | |
1293 | error = -EEXIST; | |
1294 | break; | |
1295 | case EPOLL_CTL_DEL: | |
1296 | if (epi) | |
1297 | error = ep_remove(ep, epi); | |
1298 | else | |
1299 | error = -ENOENT; | |
1300 | break; | |
1301 | case EPOLL_CTL_MOD: | |
1302 | if (epi) { | |
1303 | epds.events |= POLLERR | POLLHUP; | |
1304 | error = ep_modify(ep, epi, &epds); | |
1305 | } else | |
1306 | error = -ENOENT; | |
1307 | break; | |
1308 | } | |
1309 | mutex_unlock(&ep->mtx); | |
1310 | ||
1311 | error_tgt_fput: | |
1312 | fput(tfile); | |
1313 | error_fput: | |
1314 | fput(file); | |
1315 | error_return: | |
1316 | ||
1317 | return error; | |
1318 | } | |
1319 | ||
1320 | /* | |
1321 | * Implement the event wait interface for the eventpoll file. It is the kernel | |
1322 | * part of the user space epoll_wait(2). | |
1323 | */ | |
1324 | SYSCALL_DEFINE4(epoll_wait, int, epfd, struct epoll_event __user *, events, | |
1325 | int, maxevents, int, timeout) | |
1326 | { | |
1327 | int error; | |
1328 | struct file *file; | |
1329 | struct eventpoll *ep; | |
1330 | ||
1331 | /* The maximum number of event must be greater than zero */ | |
1332 | if (maxevents <= 0 || maxevents > EP_MAX_EVENTS) | |
1333 | return -EINVAL; | |
1334 | ||
1335 | /* Verify that the area passed by the user is writeable */ | |
1336 | if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event))) { | |
1337 | error = -EFAULT; | |
1338 | goto error_return; | |
1339 | } | |
1340 | ||
1341 | /* Get the "struct file *" for the eventpoll file */ | |
1342 | error = -EBADF; | |
1343 | file = fget(epfd); | |
1344 | if (!file) | |
1345 | goto error_return; | |
1346 | ||
1347 | /* | |
1348 | * We have to check that the file structure underneath the fd | |
1349 | * the user passed to us _is_ an eventpoll file. | |
1350 | */ | |
1351 | error = -EINVAL; | |
1352 | if (!is_file_epoll(file)) | |
1353 | goto error_fput; | |
1354 | ||
1355 | /* | |
1356 | * At this point it is safe to assume that the "private_data" contains | |
1357 | * our own data structure. | |
1358 | */ | |
1359 | ep = file->private_data; | |
1360 | ||
1361 | /* Time to fish for events ... */ | |
1362 | error = ep_poll(ep, events, maxevents, timeout); | |
1363 | ||
1364 | error_fput: | |
1365 | fput(file); | |
1366 | error_return: | |
1367 | ||
1368 | return error; | |
1369 | } | |
1370 | ||
1371 | #ifdef HAVE_SET_RESTORE_SIGMASK | |
1372 | ||
1373 | /* | |
1374 | * Implement the event wait interface for the eventpoll file. It is the kernel | |
1375 | * part of the user space epoll_pwait(2). | |
1376 | */ | |
1377 | SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events, | |
1378 | int, maxevents, int, timeout, const sigset_t __user *, sigmask, | |
1379 | size_t, sigsetsize) | |
1380 | { | |
1381 | int error; | |
1382 | sigset_t ksigmask, sigsaved; | |
1383 | ||
1384 | /* | |
1385 | * If the caller wants a certain signal mask to be set during the wait, | |
1386 | * we apply it here. | |
1387 | */ | |
1388 | if (sigmask) { | |
1389 | if (sigsetsize != sizeof(sigset_t)) | |
1390 | return -EINVAL; | |
1391 | if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) | |
1392 | return -EFAULT; | |
1393 | sigdelsetmask(&ksigmask, sigmask(SIGKILL) | sigmask(SIGSTOP)); | |
1394 | sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); | |
1395 | } | |
1396 | ||
1397 | error = sys_epoll_wait(epfd, events, maxevents, timeout); | |
1398 | ||
1399 | /* | |
1400 | * If we changed the signal mask, we need to restore the original one. | |
1401 | * In case we've got a signal while waiting, we do not restore the | |
1402 | * signal mask yet, and we allow do_signal() to deliver the signal on | |
1403 | * the way back to userspace, before the signal mask is restored. | |
1404 | */ | |
1405 | if (sigmask) { | |
1406 | if (error == -EINTR) { | |
1407 | memcpy(¤t->saved_sigmask, &sigsaved, | |
1408 | sizeof(sigsaved)); | |
1409 | set_restore_sigmask(); | |
1410 | } else | |
1411 | sigprocmask(SIG_SETMASK, &sigsaved, NULL); | |
1412 | } | |
1413 | ||
1414 | return error; | |
1415 | } | |
1416 | ||
1417 | #endif /* HAVE_SET_RESTORE_SIGMASK */ | |
1418 | ||
1419 | static int __init eventpoll_init(void) | |
1420 | { | |
1421 | struct sysinfo si; | |
1422 | ||
1423 | si_meminfo(&si); | |
1424 | /* | |
1425 | * Allows top 4% of lomem to be allocated for epoll watches (per user). | |
1426 | */ | |
1427 | max_user_watches = (((si.totalram - si.totalhigh) / 25) << PAGE_SHIFT) / | |
1428 | EP_ITEM_COST; | |
1429 | ||
1430 | /* Initialize the structure used to perform safe poll wait head wake ups */ | |
1431 | ep_nested_calls_init(&poll_safewake_ncalls); | |
1432 | ||
1433 | /* Initialize the structure used to perform file's f_op->poll() calls */ | |
1434 | ep_nested_calls_init(&poll_readywalk_ncalls); | |
1435 | ||
1436 | /* Allocates slab cache used to allocate "struct epitem" items */ | |
1437 | epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem), | |
1438 | 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); | |
1439 | ||
1440 | /* Allocates slab cache used to allocate "struct eppoll_entry" */ | |
1441 | pwq_cache = kmem_cache_create("eventpoll_pwq", | |
1442 | sizeof(struct eppoll_entry), 0, SLAB_PANIC, NULL); | |
1443 | ||
1444 | return 0; | |
1445 | } | |
1446 | fs_initcall(eventpoll_init); |