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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 to epoll_ctl(EPOLL_CTL_DEL). | |
66 | * It is also acquired when inserting an epoll fd onto another epoll | |
67 | * fd. We do this so that we walk the epoll tree and ensure that this | |
68 | * insertion does not create a cycle of epoll file descriptors, which | |
69 | * could lead to deadlock. We need a global mutex to prevent two | |
70 | * simultaneous inserts (A into B and B into A) from racing and | |
71 | * constructing a cycle without either insert observing that it is | |
72 | * going to. | |
73 | * It is possible to drop the "ep->mtx" and to use the global | |
74 | * mutex "epmutex" (together with "ep->lock") to have it working, | |
75 | * but having "ep->mtx" will make the interface more scalable. | |
76 | * Events that require holding "epmutex" are very rare, while for | |
77 | * normal operations the epoll private "ep->mtx" will guarantee | |
78 | * a better scalability. | |
79 | */ | |
80 | ||
81 | /* Epoll private bits inside the event mask */ | |
82 | #define EP_PRIVATE_BITS (EPOLLONESHOT | EPOLLET) | |
83 | ||
84 | /* Maximum number of nesting allowed inside epoll sets */ | |
85 | #define EP_MAX_NESTS 4 | |
86 | ||
87 | #define EP_MAX_EVENTS (INT_MAX / sizeof(struct epoll_event)) | |
88 | ||
89 | #define EP_UNACTIVE_PTR ((void *) -1L) | |
90 | ||
91 | #define EP_ITEM_COST (sizeof(struct epitem) + sizeof(struct eppoll_entry)) | |
92 | ||
93 | struct epoll_filefd { | |
94 | struct file *file; | |
95 | int fd; | |
96 | }; | |
97 | ||
98 | /* | |
99 | * Structure used to track possible nested calls, for too deep recursions | |
100 | * and loop cycles. | |
101 | */ | |
102 | struct nested_call_node { | |
103 | struct list_head llink; | |
104 | void *cookie; | |
105 | void *ctx; | |
106 | }; | |
107 | ||
108 | /* | |
109 | * This structure is used as collector for nested calls, to check for | |
110 | * maximum recursion dept and loop cycles. | |
111 | */ | |
112 | struct nested_calls { | |
113 | struct list_head tasks_call_list; | |
114 | spinlock_t lock; | |
115 | }; | |
116 | ||
117 | /* | |
118 | * Each file descriptor added to the eventpoll interface will | |
119 | * have an entry of this type linked to the "rbr" RB tree. | |
120 | */ | |
121 | struct epitem { | |
122 | /* RB tree node used to link this structure to the eventpoll RB tree */ | |
123 | struct rb_node rbn; | |
124 | ||
125 | /* List header used to link this structure to the eventpoll ready list */ | |
126 | struct list_head rdllink; | |
127 | ||
128 | /* | |
129 | * Works together "struct eventpoll"->ovflist in keeping the | |
130 | * single linked chain of items. | |
131 | */ | |
132 | struct epitem *next; | |
133 | ||
134 | /* The file descriptor information this item refers to */ | |
135 | struct epoll_filefd ffd; | |
136 | ||
137 | /* Number of active wait queue attached to poll operations */ | |
138 | int nwait; | |
139 | ||
140 | /* List containing poll wait queues */ | |
141 | struct list_head pwqlist; | |
142 | ||
143 | /* The "container" of this item */ | |
144 | struct eventpoll *ep; | |
145 | ||
146 | /* List header used to link this item to the "struct file" items list */ | |
147 | struct list_head fllink; | |
148 | ||
149 | /* The structure that describe the interested events and the source fd */ | |
150 | struct epoll_event event; | |
151 | }; | |
152 | ||
153 | /* | |
154 | * This structure is stored inside the "private_data" member of the file | |
155 | * structure and represents the main data structure for the eventpoll | |
156 | * interface. | |
157 | */ | |
158 | struct eventpoll { | |
159 | /* Protect the access to this structure */ | |
160 | spinlock_t lock; | |
161 | ||
162 | /* | |
163 | * This mutex is used to ensure that files are not removed | |
164 | * while epoll is using them. This is held during the event | |
165 | * collection loop, the file cleanup path, the epoll file exit | |
166 | * code and the ctl operations. | |
167 | */ | |
168 | struct mutex mtx; | |
169 | ||
170 | /* Wait queue used by sys_epoll_wait() */ | |
171 | wait_queue_head_t wq; | |
172 | ||
173 | /* Wait queue used by file->poll() */ | |
174 | wait_queue_head_t poll_wait; | |
175 | ||
176 | /* List of ready file descriptors */ | |
177 | struct list_head rdllist; | |
178 | ||
179 | /* RB tree root used to store monitored fd structs */ | |
180 | struct rb_root rbr; | |
181 | ||
182 | /* | |
183 | * This is a single linked list that chains all the "struct epitem" that | |
184 | * happened while transfering ready events to userspace w/out | |
185 | * holding ->lock. | |
186 | */ | |
187 | struct epitem *ovflist; | |
188 | ||
189 | /* The user that created the eventpoll descriptor */ | |
190 | struct user_struct *user; | |
191 | }; | |
192 | ||
193 | /* Wait structure used by the poll hooks */ | |
194 | struct eppoll_entry { | |
195 | /* List header used to link this structure to the "struct epitem" */ | |
196 | struct list_head llink; | |
197 | ||
198 | /* The "base" pointer is set to the container "struct epitem" */ | |
199 | struct epitem *base; | |
200 | ||
201 | /* | |
202 | * Wait queue item that will be linked to the target file wait | |
203 | * queue head. | |
204 | */ | |
205 | wait_queue_t wait; | |
206 | ||
207 | /* The wait queue head that linked the "wait" wait queue item */ | |
208 | wait_queue_head_t *whead; | |
209 | }; | |
210 | ||
211 | /* Wrapper struct used by poll queueing */ | |
212 | struct ep_pqueue { | |
213 | poll_table pt; | |
214 | struct epitem *epi; | |
215 | }; | |
216 | ||
217 | /* Used by the ep_send_events() function as callback private data */ | |
218 | struct ep_send_events_data { | |
219 | int maxevents; | |
220 | struct epoll_event __user *events; | |
221 | }; | |
222 | ||
223 | /* | |
224 | * Configuration options available inside /proc/sys/fs/epoll/ | |
225 | */ | |
226 | /* Maximum number of epoll watched descriptors, per user */ | |
227 | static long max_user_watches __read_mostly; | |
228 | ||
229 | /* | |
230 | * This mutex is used to serialize ep_free() and eventpoll_release_file(). | |
231 | */ | |
232 | static DEFINE_MUTEX(epmutex); | |
233 | ||
234 | /* Used to check for epoll file descriptor inclusion loops */ | |
235 | static struct nested_calls poll_loop_ncalls; | |
236 | ||
237 | /* Used for safe wake up implementation */ | |
238 | static struct nested_calls poll_safewake_ncalls; | |
239 | ||
240 | /* Used to call file's f_op->poll() under the nested calls boundaries */ | |
241 | static struct nested_calls poll_readywalk_ncalls; | |
242 | ||
243 | /* Slab cache used to allocate "struct epitem" */ | |
244 | static struct kmem_cache *epi_cache __read_mostly; | |
245 | ||
246 | /* Slab cache used to allocate "struct eppoll_entry" */ | |
247 | static struct kmem_cache *pwq_cache __read_mostly; | |
248 | ||
249 | #ifdef CONFIG_SYSCTL | |
250 | ||
251 | #include <linux/sysctl.h> | |
252 | ||
253 | static long zero; | |
254 | static long long_max = LONG_MAX; | |
255 | ||
256 | ctl_table epoll_table[] = { | |
257 | { | |
258 | .procname = "max_user_watches", | |
259 | .data = &max_user_watches, | |
260 | .maxlen = sizeof(max_user_watches), | |
261 | .mode = 0644, | |
262 | .proc_handler = proc_doulongvec_minmax, | |
263 | .extra1 = &zero, | |
264 | .extra2 = &long_max, | |
265 | }, | |
266 | { } | |
267 | }; | |
268 | #endif /* CONFIG_SYSCTL */ | |
269 | ||
270 | ||
271 | /* Setup the structure that is used as key for the RB tree */ | |
272 | static inline void ep_set_ffd(struct epoll_filefd *ffd, | |
273 | struct file *file, int fd) | |
274 | { | |
275 | ffd->file = file; | |
276 | ffd->fd = fd; | |
277 | } | |
278 | ||
279 | /* Compare RB tree keys */ | |
280 | static inline int ep_cmp_ffd(struct epoll_filefd *p1, | |
281 | struct epoll_filefd *p2) | |
282 | { | |
283 | return (p1->file > p2->file ? +1: | |
284 | (p1->file < p2->file ? -1 : p1->fd - p2->fd)); | |
285 | } | |
286 | ||
287 | /* Tells us if the item is currently linked */ | |
288 | static inline int ep_is_linked(struct list_head *p) | |
289 | { | |
290 | return !list_empty(p); | |
291 | } | |
292 | ||
293 | /* Get the "struct epitem" from a wait queue pointer */ | |
294 | static inline struct epitem *ep_item_from_wait(wait_queue_t *p) | |
295 | { | |
296 | return container_of(p, struct eppoll_entry, wait)->base; | |
297 | } | |
298 | ||
299 | /* Get the "struct epitem" from an epoll queue wrapper */ | |
300 | static inline struct epitem *ep_item_from_epqueue(poll_table *p) | |
301 | { | |
302 | return container_of(p, struct ep_pqueue, pt)->epi; | |
303 | } | |
304 | ||
305 | /* Tells if the epoll_ctl(2) operation needs an event copy from userspace */ | |
306 | static inline int ep_op_has_event(int op) | |
307 | { | |
308 | return op != EPOLL_CTL_DEL; | |
309 | } | |
310 | ||
311 | /* Initialize the poll safe wake up structure */ | |
312 | static void ep_nested_calls_init(struct nested_calls *ncalls) | |
313 | { | |
314 | INIT_LIST_HEAD(&ncalls->tasks_call_list); | |
315 | spin_lock_init(&ncalls->lock); | |
316 | } | |
317 | ||
318 | /** | |
319 | * ep_call_nested - Perform a bound (possibly) nested call, by checking | |
320 | * that the recursion limit is not exceeded, and that | |
321 | * the same nested call (by the meaning of same cookie) is | |
322 | * no re-entered. | |
323 | * | |
324 | * @ncalls: Pointer to the nested_calls structure to be used for this call. | |
325 | * @max_nests: Maximum number of allowed nesting calls. | |
326 | * @nproc: Nested call core function pointer. | |
327 | * @priv: Opaque data to be passed to the @nproc callback. | |
328 | * @cookie: Cookie to be used to identify this nested call. | |
329 | * @ctx: This instance context. | |
330 | * | |
331 | * Returns: Returns the code returned by the @nproc callback, or -1 if | |
332 | * the maximum recursion limit has been exceeded. | |
333 | */ | |
334 | static int ep_call_nested(struct nested_calls *ncalls, int max_nests, | |
335 | int (*nproc)(void *, void *, int), void *priv, | |
336 | void *cookie, void *ctx) | |
337 | { | |
338 | int error, call_nests = 0; | |
339 | unsigned long flags; | |
340 | struct list_head *lsthead = &ncalls->tasks_call_list; | |
341 | struct nested_call_node *tncur; | |
342 | struct nested_call_node tnode; | |
343 | ||
344 | spin_lock_irqsave(&ncalls->lock, flags); | |
345 | ||
346 | /* | |
347 | * Try to see if the current task is already inside this wakeup call. | |
348 | * We use a list here, since the population inside this set is always | |
349 | * very much limited. | |
350 | */ | |
351 | list_for_each_entry(tncur, lsthead, llink) { | |
352 | if (tncur->ctx == ctx && | |
353 | (tncur->cookie == cookie || ++call_nests > max_nests)) { | |
354 | /* | |
355 | * Ops ... loop detected or maximum nest level reached. | |
356 | * We abort this wake by breaking the cycle itself. | |
357 | */ | |
358 | error = -1; | |
359 | goto out_unlock; | |
360 | } | |
361 | } | |
362 | ||
363 | /* Add the current task and cookie to the list */ | |
364 | tnode.ctx = ctx; | |
365 | tnode.cookie = cookie; | |
366 | list_add(&tnode.llink, lsthead); | |
367 | ||
368 | spin_unlock_irqrestore(&ncalls->lock, flags); | |
369 | ||
370 | /* Call the nested function */ | |
371 | error = (*nproc)(priv, cookie, call_nests); | |
372 | ||
373 | /* Remove the current task from the list */ | |
374 | spin_lock_irqsave(&ncalls->lock, flags); | |
375 | list_del(&tnode.llink); | |
376 | out_unlock: | |
377 | spin_unlock_irqrestore(&ncalls->lock, flags); | |
378 | ||
379 | return error; | |
380 | } | |
381 | ||
382 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
383 | static inline void ep_wake_up_nested(wait_queue_head_t *wqueue, | |
384 | unsigned long events, int subclass) | |
385 | { | |
386 | unsigned long flags; | |
387 | ||
388 | spin_lock_irqsave_nested(&wqueue->lock, flags, subclass); | |
389 | wake_up_locked_poll(wqueue, events); | |
390 | spin_unlock_irqrestore(&wqueue->lock, flags); | |
391 | } | |
392 | #else | |
393 | static inline void ep_wake_up_nested(wait_queue_head_t *wqueue, | |
394 | unsigned long events, int subclass) | |
395 | { | |
396 | wake_up_poll(wqueue, events); | |
397 | } | |
398 | #endif | |
399 | ||
400 | static int ep_poll_wakeup_proc(void *priv, void *cookie, int call_nests) | |
401 | { | |
402 | ep_wake_up_nested((wait_queue_head_t *) cookie, POLLIN, | |
403 | 1 + call_nests); | |
404 | return 0; | |
405 | } | |
406 | ||
407 | /* | |
408 | * Perform a safe wake up of the poll wait list. The problem is that | |
409 | * with the new callback'd wake up system, it is possible that the | |
410 | * poll callback is reentered from inside the call to wake_up() done | |
411 | * on the poll wait queue head. The rule is that we cannot reenter the | |
412 | * wake up code from the same task more than EP_MAX_NESTS times, | |
413 | * and we cannot reenter the same wait queue head at all. This will | |
414 | * enable to have a hierarchy of epoll file descriptor of no more than | |
415 | * EP_MAX_NESTS deep. | |
416 | */ | |
417 | static void ep_poll_safewake(wait_queue_head_t *wq) | |
418 | { | |
419 | int this_cpu = get_cpu(); | |
420 | ||
421 | ep_call_nested(&poll_safewake_ncalls, EP_MAX_NESTS, | |
422 | ep_poll_wakeup_proc, NULL, wq, (void *) (long) this_cpu); | |
423 | ||
424 | put_cpu(); | |
425 | } | |
426 | ||
427 | /* | |
428 | * This function unregisters poll callbacks from the associated file | |
429 | * descriptor. Must be called with "mtx" held (or "epmutex" if called from | |
430 | * ep_free). | |
431 | */ | |
432 | static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi) | |
433 | { | |
434 | struct list_head *lsthead = &epi->pwqlist; | |
435 | struct eppoll_entry *pwq; | |
436 | ||
437 | while (!list_empty(lsthead)) { | |
438 | pwq = list_first_entry(lsthead, struct eppoll_entry, llink); | |
439 | ||
440 | list_del(&pwq->llink); | |
441 | remove_wait_queue(pwq->whead, &pwq->wait); | |
442 | kmem_cache_free(pwq_cache, pwq); | |
443 | } | |
444 | } | |
445 | ||
446 | /** | |
447 | * ep_scan_ready_list - Scans the ready list in a way that makes possible for | |
448 | * the scan code, to call f_op->poll(). Also allows for | |
449 | * O(NumReady) performance. | |
450 | * | |
451 | * @ep: Pointer to the epoll private data structure. | |
452 | * @sproc: Pointer to the scan callback. | |
453 | * @priv: Private opaque data passed to the @sproc callback. | |
454 | * | |
455 | * Returns: The same integer error code returned by the @sproc callback. | |
456 | */ | |
457 | static int ep_scan_ready_list(struct eventpoll *ep, | |
458 | int (*sproc)(struct eventpoll *, | |
459 | struct list_head *, void *), | |
460 | void *priv) | |
461 | { | |
462 | int error, pwake = 0; | |
463 | unsigned long flags; | |
464 | struct epitem *epi, *nepi; | |
465 | LIST_HEAD(txlist); | |
466 | ||
467 | /* | |
468 | * We need to lock this because we could be hit by | |
469 | * eventpoll_release_file() and epoll_ctl(). | |
470 | */ | |
471 | mutex_lock(&ep->mtx); | |
472 | ||
473 | /* | |
474 | * Steal the ready list, and re-init the original one to the | |
475 | * empty list. Also, set ep->ovflist to NULL so that events | |
476 | * happening while looping w/out locks, are not lost. We cannot | |
477 | * have the poll callback to queue directly on ep->rdllist, | |
478 | * because we want the "sproc" callback to be able to do it | |
479 | * in a lockless way. | |
480 | */ | |
481 | spin_lock_irqsave(&ep->lock, flags); | |
482 | list_splice_init(&ep->rdllist, &txlist); | |
483 | ep->ovflist = NULL; | |
484 | spin_unlock_irqrestore(&ep->lock, flags); | |
485 | ||
486 | /* | |
487 | * Now call the callback function. | |
488 | */ | |
489 | error = (*sproc)(ep, &txlist, priv); | |
490 | ||
491 | spin_lock_irqsave(&ep->lock, flags); | |
492 | /* | |
493 | * During the time we spent inside the "sproc" callback, some | |
494 | * other events might have been queued by the poll callback. | |
495 | * We re-insert them inside the main ready-list here. | |
496 | */ | |
497 | for (nepi = ep->ovflist; (epi = nepi) != NULL; | |
498 | nepi = epi->next, epi->next = EP_UNACTIVE_PTR) { | |
499 | /* | |
500 | * We need to check if the item is already in the list. | |
501 | * During the "sproc" callback execution time, items are | |
502 | * queued into ->ovflist but the "txlist" might already | |
503 | * contain them, and the list_splice() below takes care of them. | |
504 | */ | |
505 | if (!ep_is_linked(&epi->rdllink)) | |
506 | list_add_tail(&epi->rdllink, &ep->rdllist); | |
507 | } | |
508 | /* | |
509 | * We need to set back ep->ovflist to EP_UNACTIVE_PTR, so that after | |
510 | * releasing the lock, events will be queued in the normal way inside | |
511 | * ep->rdllist. | |
512 | */ | |
513 | ep->ovflist = EP_UNACTIVE_PTR; | |
514 | ||
515 | /* | |
516 | * Quickly re-inject items left on "txlist". | |
517 | */ | |
518 | list_splice(&txlist, &ep->rdllist); | |
519 | ||
520 | if (!list_empty(&ep->rdllist)) { | |
521 | /* | |
522 | * Wake up (if active) both the eventpoll wait list and | |
523 | * the ->poll() wait list (delayed after we release the lock). | |
524 | */ | |
525 | if (waitqueue_active(&ep->wq)) | |
526 | wake_up_locked(&ep->wq); | |
527 | if (waitqueue_active(&ep->poll_wait)) | |
528 | pwake++; | |
529 | } | |
530 | spin_unlock_irqrestore(&ep->lock, flags); | |
531 | ||
532 | mutex_unlock(&ep->mtx); | |
533 | ||
534 | /* We have to call this outside the lock */ | |
535 | if (pwake) | |
536 | ep_poll_safewake(&ep->poll_wait); | |
537 | ||
538 | return error; | |
539 | } | |
540 | ||
541 | /* | |
542 | * Removes a "struct epitem" from the eventpoll RB tree and deallocates | |
543 | * all the associated resources. Must be called with "mtx" held. | |
544 | */ | |
545 | static int ep_remove(struct eventpoll *ep, struct epitem *epi) | |
546 | { | |
547 | unsigned long flags; | |
548 | struct file *file = epi->ffd.file; | |
549 | ||
550 | /* | |
551 | * Removes poll wait queue hooks. We _have_ to do this without holding | |
552 | * the "ep->lock" otherwise a deadlock might occur. This because of the | |
553 | * sequence of the lock acquisition. Here we do "ep->lock" then the wait | |
554 | * queue head lock when unregistering the wait queue. The wakeup callback | |
555 | * will run by holding the wait queue head lock and will call our callback | |
556 | * that will try to get "ep->lock". | |
557 | */ | |
558 | ep_unregister_pollwait(ep, epi); | |
559 | ||
560 | /* Remove the current item from the list of epoll hooks */ | |
561 | spin_lock(&file->f_lock); | |
562 | if (ep_is_linked(&epi->fllink)) | |
563 | list_del_init(&epi->fllink); | |
564 | spin_unlock(&file->f_lock); | |
565 | ||
566 | rb_erase(&epi->rbn, &ep->rbr); | |
567 | ||
568 | spin_lock_irqsave(&ep->lock, flags); | |
569 | if (ep_is_linked(&epi->rdllink)) | |
570 | list_del_init(&epi->rdllink); | |
571 | spin_unlock_irqrestore(&ep->lock, flags); | |
572 | ||
573 | /* At this point it is safe to free the eventpoll item */ | |
574 | kmem_cache_free(epi_cache, epi); | |
575 | ||
576 | atomic_long_dec(&ep->user->epoll_watches); | |
577 | ||
578 | return 0; | |
579 | } | |
580 | ||
581 | static void ep_free(struct eventpoll *ep) | |
582 | { | |
583 | struct rb_node *rbp; | |
584 | struct epitem *epi; | |
585 | ||
586 | /* We need to release all tasks waiting for these file */ | |
587 | if (waitqueue_active(&ep->poll_wait)) | |
588 | ep_poll_safewake(&ep->poll_wait); | |
589 | ||
590 | /* | |
591 | * We need to lock this because we could be hit by | |
592 | * eventpoll_release_file() while we're freeing the "struct eventpoll". | |
593 | * We do not need to hold "ep->mtx" here because the epoll file | |
594 | * is on the way to be removed and no one has references to it | |
595 | * anymore. The only hit might come from eventpoll_release_file() but | |
596 | * holding "epmutex" is sufficent here. | |
597 | */ | |
598 | mutex_lock(&epmutex); | |
599 | ||
600 | /* | |
601 | * Walks through the whole tree by unregistering poll callbacks. | |
602 | */ | |
603 | for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { | |
604 | epi = rb_entry(rbp, struct epitem, rbn); | |
605 | ||
606 | ep_unregister_pollwait(ep, epi); | |
607 | } | |
608 | ||
609 | /* | |
610 | * Walks through the whole tree by freeing each "struct epitem". At this | |
611 | * point we are sure no poll callbacks will be lingering around, and also by | |
612 | * holding "epmutex" we can be sure that no file cleanup code will hit | |
613 | * us during this operation. So we can avoid the lock on "ep->lock". | |
614 | */ | |
615 | while ((rbp = rb_first(&ep->rbr)) != NULL) { | |
616 | epi = rb_entry(rbp, struct epitem, rbn); | |
617 | ep_remove(ep, epi); | |
618 | } | |
619 | ||
620 | mutex_unlock(&epmutex); | |
621 | mutex_destroy(&ep->mtx); | |
622 | free_uid(ep->user); | |
623 | kfree(ep); | |
624 | } | |
625 | ||
626 | static int ep_eventpoll_release(struct inode *inode, struct file *file) | |
627 | { | |
628 | struct eventpoll *ep = file->private_data; | |
629 | ||
630 | if (ep) | |
631 | ep_free(ep); | |
632 | ||
633 | return 0; | |
634 | } | |
635 | ||
636 | static int ep_read_events_proc(struct eventpoll *ep, struct list_head *head, | |
637 | void *priv) | |
638 | { | |
639 | struct epitem *epi, *tmp; | |
640 | ||
641 | list_for_each_entry_safe(epi, tmp, head, rdllink) { | |
642 | if (epi->ffd.file->f_op->poll(epi->ffd.file, NULL) & | |
643 | epi->event.events) | |
644 | return POLLIN | POLLRDNORM; | |
645 | else { | |
646 | /* | |
647 | * Item has been dropped into the ready list by the poll | |
648 | * callback, but it's not actually ready, as far as | |
649 | * caller requested events goes. We can remove it here. | |
650 | */ | |
651 | list_del_init(&epi->rdllink); | |
652 | } | |
653 | } | |
654 | ||
655 | return 0; | |
656 | } | |
657 | ||
658 | static int ep_poll_readyevents_proc(void *priv, void *cookie, int call_nests) | |
659 | { | |
660 | return ep_scan_ready_list(priv, ep_read_events_proc, NULL); | |
661 | } | |
662 | ||
663 | static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait) | |
664 | { | |
665 | int pollflags; | |
666 | struct eventpoll *ep = file->private_data; | |
667 | ||
668 | /* Insert inside our poll wait queue */ | |
669 | poll_wait(file, &ep->poll_wait, wait); | |
670 | ||
671 | /* | |
672 | * Proceed to find out if wanted events are really available inside | |
673 | * the ready list. This need to be done under ep_call_nested() | |
674 | * supervision, since the call to f_op->poll() done on listed files | |
675 | * could re-enter here. | |
676 | */ | |
677 | pollflags = ep_call_nested(&poll_readywalk_ncalls, EP_MAX_NESTS, | |
678 | ep_poll_readyevents_proc, ep, ep, current); | |
679 | ||
680 | return pollflags != -1 ? pollflags : 0; | |
681 | } | |
682 | ||
683 | /* File callbacks that implement the eventpoll file behaviour */ | |
684 | static const struct file_operations eventpoll_fops = { | |
685 | .release = ep_eventpoll_release, | |
686 | .poll = ep_eventpoll_poll, | |
687 | .llseek = noop_llseek, | |
688 | }; | |
689 | ||
690 | /* Fast test to see if the file is an evenpoll file */ | |
691 | static inline int is_file_epoll(struct file *f) | |
692 | { | |
693 | return f->f_op == &eventpoll_fops; | |
694 | } | |
695 | ||
696 | /* | |
697 | * This is called from eventpoll_release() to unlink files from the eventpoll | |
698 | * interface. We need to have this facility to cleanup correctly files that are | |
699 | * closed without being removed from the eventpoll interface. | |
700 | */ | |
701 | void eventpoll_release_file(struct file *file) | |
702 | { | |
703 | struct list_head *lsthead = &file->f_ep_links; | |
704 | struct eventpoll *ep; | |
705 | struct epitem *epi; | |
706 | ||
707 | /* | |
708 | * We don't want to get "file->f_lock" because it is not | |
709 | * necessary. It is not necessary because we're in the "struct file" | |
710 | * cleanup path, and this means that noone is using this file anymore. | |
711 | * So, for example, epoll_ctl() cannot hit here since if we reach this | |
712 | * point, the file counter already went to zero and fget() would fail. | |
713 | * The only hit might come from ep_free() but by holding the mutex | |
714 | * will correctly serialize the operation. We do need to acquire | |
715 | * "ep->mtx" after "epmutex" because ep_remove() requires it when called | |
716 | * from anywhere but ep_free(). | |
717 | * | |
718 | * Besides, ep_remove() acquires the lock, so we can't hold it here. | |
719 | */ | |
720 | mutex_lock(&epmutex); | |
721 | ||
722 | while (!list_empty(lsthead)) { | |
723 | epi = list_first_entry(lsthead, struct epitem, fllink); | |
724 | ||
725 | ep = epi->ep; | |
726 | list_del_init(&epi->fllink); | |
727 | mutex_lock(&ep->mtx); | |
728 | ep_remove(ep, epi); | |
729 | mutex_unlock(&ep->mtx); | |
730 | } | |
731 | ||
732 | mutex_unlock(&epmutex); | |
733 | } | |
734 | ||
735 | static int ep_alloc(struct eventpoll **pep) | |
736 | { | |
737 | int error; | |
738 | struct user_struct *user; | |
739 | struct eventpoll *ep; | |
740 | ||
741 | user = get_current_user(); | |
742 | error = -ENOMEM; | |
743 | ep = kzalloc(sizeof(*ep), GFP_KERNEL); | |
744 | if (unlikely(!ep)) | |
745 | goto free_uid; | |
746 | ||
747 | spin_lock_init(&ep->lock); | |
748 | mutex_init(&ep->mtx); | |
749 | init_waitqueue_head(&ep->wq); | |
750 | init_waitqueue_head(&ep->poll_wait); | |
751 | INIT_LIST_HEAD(&ep->rdllist); | |
752 | ep->rbr = RB_ROOT; | |
753 | ep->ovflist = EP_UNACTIVE_PTR; | |
754 | ep->user = user; | |
755 | ||
756 | *pep = ep; | |
757 | ||
758 | return 0; | |
759 | ||
760 | free_uid: | |
761 | free_uid(user); | |
762 | return error; | |
763 | } | |
764 | ||
765 | /* | |
766 | * Search the file inside the eventpoll tree. The RB tree operations | |
767 | * are protected by the "mtx" mutex, and ep_find() must be called with | |
768 | * "mtx" held. | |
769 | */ | |
770 | static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd) | |
771 | { | |
772 | int kcmp; | |
773 | struct rb_node *rbp; | |
774 | struct epitem *epi, *epir = NULL; | |
775 | struct epoll_filefd ffd; | |
776 | ||
777 | ep_set_ffd(&ffd, file, fd); | |
778 | for (rbp = ep->rbr.rb_node; rbp; ) { | |
779 | epi = rb_entry(rbp, struct epitem, rbn); | |
780 | kcmp = ep_cmp_ffd(&ffd, &epi->ffd); | |
781 | if (kcmp > 0) | |
782 | rbp = rbp->rb_right; | |
783 | else if (kcmp < 0) | |
784 | rbp = rbp->rb_left; | |
785 | else { | |
786 | epir = epi; | |
787 | break; | |
788 | } | |
789 | } | |
790 | ||
791 | return epir; | |
792 | } | |
793 | ||
794 | /* | |
795 | * This is the callback that is passed to the wait queue wakeup | |
796 | * mechanism. It is called by the stored file descriptors when they | |
797 | * have events to report. | |
798 | */ | |
799 | static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *key) | |
800 | { | |
801 | int pwake = 0; | |
802 | unsigned long flags; | |
803 | struct epitem *epi = ep_item_from_wait(wait); | |
804 | struct eventpoll *ep = epi->ep; | |
805 | ||
806 | spin_lock_irqsave(&ep->lock, flags); | |
807 | ||
808 | /* | |
809 | * If the event mask does not contain any poll(2) event, we consider the | |
810 | * descriptor to be disabled. This condition is likely the effect of the | |
811 | * EPOLLONESHOT bit that disables the descriptor when an event is received, | |
812 | * until the next EPOLL_CTL_MOD will be issued. | |
813 | */ | |
814 | if (!(epi->event.events & ~EP_PRIVATE_BITS)) | |
815 | goto out_unlock; | |
816 | ||
817 | /* | |
818 | * Check the events coming with the callback. At this stage, not | |
819 | * every device reports the events in the "key" parameter of the | |
820 | * callback. We need to be able to handle both cases here, hence the | |
821 | * test for "key" != NULL before the event match test. | |
822 | */ | |
823 | if (key && !((unsigned long) key & epi->event.events)) | |
824 | goto out_unlock; | |
825 | ||
826 | /* | |
827 | * If we are transferring events to userspace, we can hold no locks | |
828 | * (because we're accessing user memory, and because of linux f_op->poll() | |
829 | * semantics). All the events that happen during that period of time are | |
830 | * chained in ep->ovflist and requeued later on. | |
831 | */ | |
832 | if (unlikely(ep->ovflist != EP_UNACTIVE_PTR)) { | |
833 | if (epi->next == EP_UNACTIVE_PTR) { | |
834 | epi->next = ep->ovflist; | |
835 | ep->ovflist = epi; | |
836 | } | |
837 | goto out_unlock; | |
838 | } | |
839 | ||
840 | /* If this file is already in the ready list we exit soon */ | |
841 | if (!ep_is_linked(&epi->rdllink)) | |
842 | list_add_tail(&epi->rdllink, &ep->rdllist); | |
843 | ||
844 | /* | |
845 | * Wake up ( if active ) both the eventpoll wait list and the ->poll() | |
846 | * wait list. | |
847 | */ | |
848 | if (waitqueue_active(&ep->wq)) | |
849 | wake_up_locked(&ep->wq); | |
850 | if (waitqueue_active(&ep->poll_wait)) | |
851 | pwake++; | |
852 | ||
853 | out_unlock: | |
854 | spin_unlock_irqrestore(&ep->lock, flags); | |
855 | ||
856 | /* We have to call this outside the lock */ | |
857 | if (pwake) | |
858 | ep_poll_safewake(&ep->poll_wait); | |
859 | ||
860 | return 1; | |
861 | } | |
862 | ||
863 | /* | |
864 | * This is the callback that is used to add our wait queue to the | |
865 | * target file wakeup lists. | |
866 | */ | |
867 | static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, | |
868 | poll_table *pt) | |
869 | { | |
870 | struct epitem *epi = ep_item_from_epqueue(pt); | |
871 | struct eppoll_entry *pwq; | |
872 | ||
873 | if (epi->nwait >= 0 && (pwq = kmem_cache_alloc(pwq_cache, GFP_KERNEL))) { | |
874 | init_waitqueue_func_entry(&pwq->wait, ep_poll_callback); | |
875 | pwq->whead = whead; | |
876 | pwq->base = epi; | |
877 | add_wait_queue(whead, &pwq->wait); | |
878 | list_add_tail(&pwq->llink, &epi->pwqlist); | |
879 | epi->nwait++; | |
880 | } else { | |
881 | /* We have to signal that an error occurred */ | |
882 | epi->nwait = -1; | |
883 | } | |
884 | } | |
885 | ||
886 | static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi) | |
887 | { | |
888 | int kcmp; | |
889 | struct rb_node **p = &ep->rbr.rb_node, *parent = NULL; | |
890 | struct epitem *epic; | |
891 | ||
892 | while (*p) { | |
893 | parent = *p; | |
894 | epic = rb_entry(parent, struct epitem, rbn); | |
895 | kcmp = ep_cmp_ffd(&epi->ffd, &epic->ffd); | |
896 | if (kcmp > 0) | |
897 | p = &parent->rb_right; | |
898 | else | |
899 | p = &parent->rb_left; | |
900 | } | |
901 | rb_link_node(&epi->rbn, parent, p); | |
902 | rb_insert_color(&epi->rbn, &ep->rbr); | |
903 | } | |
904 | ||
905 | /* | |
906 | * Must be called with "mtx" held. | |
907 | */ | |
908 | static int ep_insert(struct eventpoll *ep, struct epoll_event *event, | |
909 | struct file *tfile, int fd) | |
910 | { | |
911 | int error, revents, pwake = 0; | |
912 | unsigned long flags; | |
913 | long user_watches; | |
914 | struct epitem *epi; | |
915 | struct ep_pqueue epq; | |
916 | ||
917 | user_watches = atomic_long_read(&ep->user->epoll_watches); | |
918 | if (unlikely(user_watches >= max_user_watches)) | |
919 | return -ENOSPC; | |
920 | if (!(epi = kmem_cache_alloc(epi_cache, GFP_KERNEL))) | |
921 | return -ENOMEM; | |
922 | ||
923 | /* Item initialization follow here ... */ | |
924 | INIT_LIST_HEAD(&epi->rdllink); | |
925 | INIT_LIST_HEAD(&epi->fllink); | |
926 | INIT_LIST_HEAD(&epi->pwqlist); | |
927 | epi->ep = ep; | |
928 | ep_set_ffd(&epi->ffd, tfile, fd); | |
929 | epi->event = *event; | |
930 | epi->nwait = 0; | |
931 | epi->next = EP_UNACTIVE_PTR; | |
932 | ||
933 | /* Initialize the poll table using the queue callback */ | |
934 | epq.epi = epi; | |
935 | init_poll_funcptr(&epq.pt, ep_ptable_queue_proc); | |
936 | ||
937 | /* | |
938 | * Attach the item to the poll hooks and get current event bits. | |
939 | * We can safely use the file* here because its usage count has | |
940 | * been increased by the caller of this function. Note that after | |
941 | * this operation completes, the poll callback can start hitting | |
942 | * the new item. | |
943 | */ | |
944 | revents = tfile->f_op->poll(tfile, &epq.pt); | |
945 | ||
946 | /* | |
947 | * We have to check if something went wrong during the poll wait queue | |
948 | * install process. Namely an allocation for a wait queue failed due | |
949 | * high memory pressure. | |
950 | */ | |
951 | error = -ENOMEM; | |
952 | if (epi->nwait < 0) | |
953 | goto error_unregister; | |
954 | ||
955 | /* Add the current item to the list of active epoll hook for this file */ | |
956 | spin_lock(&tfile->f_lock); | |
957 | list_add_tail(&epi->fllink, &tfile->f_ep_links); | |
958 | spin_unlock(&tfile->f_lock); | |
959 | ||
960 | /* | |
961 | * Add the current item to the RB tree. All RB tree operations are | |
962 | * protected by "mtx", and ep_insert() is called with "mtx" held. | |
963 | */ | |
964 | ep_rbtree_insert(ep, epi); | |
965 | ||
966 | /* We have to drop the new item inside our item list to keep track of it */ | |
967 | spin_lock_irqsave(&ep->lock, flags); | |
968 | ||
969 | /* If the file is already "ready" we drop it inside the ready list */ | |
970 | if ((revents & event->events) && !ep_is_linked(&epi->rdllink)) { | |
971 | list_add_tail(&epi->rdllink, &ep->rdllist); | |
972 | ||
973 | /* Notify waiting tasks that events are available */ | |
974 | if (waitqueue_active(&ep->wq)) | |
975 | wake_up_locked(&ep->wq); | |
976 | if (waitqueue_active(&ep->poll_wait)) | |
977 | pwake++; | |
978 | } | |
979 | ||
980 | spin_unlock_irqrestore(&ep->lock, flags); | |
981 | ||
982 | atomic_long_inc(&ep->user->epoll_watches); | |
983 | ||
984 | /* We have to call this outside the lock */ | |
985 | if (pwake) | |
986 | ep_poll_safewake(&ep->poll_wait); | |
987 | ||
988 | return 0; | |
989 | ||
990 | error_unregister: | |
991 | ep_unregister_pollwait(ep, epi); | |
992 | ||
993 | /* | |
994 | * We need to do this because an event could have been arrived on some | |
995 | * allocated wait queue. Note that we don't care about the ep->ovflist | |
996 | * list, since that is used/cleaned only inside a section bound by "mtx". | |
997 | * And ep_insert() is called with "mtx" held. | |
998 | */ | |
999 | spin_lock_irqsave(&ep->lock, flags); | |
1000 | if (ep_is_linked(&epi->rdllink)) | |
1001 | list_del_init(&epi->rdllink); | |
1002 | spin_unlock_irqrestore(&ep->lock, flags); | |
1003 | ||
1004 | kmem_cache_free(epi_cache, epi); | |
1005 | ||
1006 | return error; | |
1007 | } | |
1008 | ||
1009 | /* | |
1010 | * Modify the interest event mask by dropping an event if the new mask | |
1011 | * has a match in the current file status. Must be called with "mtx" held. | |
1012 | */ | |
1013 | static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_event *event) | |
1014 | { | |
1015 | int pwake = 0; | |
1016 | unsigned int revents; | |
1017 | ||
1018 | /* | |
1019 | * Set the new event interest mask before calling f_op->poll(); | |
1020 | * otherwise we might miss an event that happens between the | |
1021 | * f_op->poll() call and the new event set registering. | |
1022 | */ | |
1023 | epi->event.events = event->events; | |
1024 | epi->event.data = event->data; /* protected by mtx */ | |
1025 | ||
1026 | /* | |
1027 | * Get current event bits. We can safely use the file* here because | |
1028 | * its usage count has been increased by the caller of this function. | |
1029 | */ | |
1030 | revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL); | |
1031 | ||
1032 | /* | |
1033 | * If the item is "hot" and it is not registered inside the ready | |
1034 | * list, push it inside. | |
1035 | */ | |
1036 | if (revents & event->events) { | |
1037 | spin_lock_irq(&ep->lock); | |
1038 | if (!ep_is_linked(&epi->rdllink)) { | |
1039 | list_add_tail(&epi->rdllink, &ep->rdllist); | |
1040 | ||
1041 | /* Notify waiting tasks that events are available */ | |
1042 | if (waitqueue_active(&ep->wq)) | |
1043 | wake_up_locked(&ep->wq); | |
1044 | if (waitqueue_active(&ep->poll_wait)) | |
1045 | pwake++; | |
1046 | } | |
1047 | spin_unlock_irq(&ep->lock); | |
1048 | } | |
1049 | ||
1050 | /* We have to call this outside the lock */ | |
1051 | if (pwake) | |
1052 | ep_poll_safewake(&ep->poll_wait); | |
1053 | ||
1054 | return 0; | |
1055 | } | |
1056 | ||
1057 | static int ep_send_events_proc(struct eventpoll *ep, struct list_head *head, | |
1058 | void *priv) | |
1059 | { | |
1060 | struct ep_send_events_data *esed = priv; | |
1061 | int eventcnt; | |
1062 | unsigned int revents; | |
1063 | struct epitem *epi; | |
1064 | struct epoll_event __user *uevent; | |
1065 | ||
1066 | /* | |
1067 | * We can loop without lock because we are passed a task private list. | |
1068 | * Items cannot vanish during the loop because ep_scan_ready_list() is | |
1069 | * holding "mtx" during this call. | |
1070 | */ | |
1071 | for (eventcnt = 0, uevent = esed->events; | |
1072 | !list_empty(head) && eventcnt < esed->maxevents;) { | |
1073 | epi = list_first_entry(head, struct epitem, rdllink); | |
1074 | ||
1075 | list_del_init(&epi->rdllink); | |
1076 | ||
1077 | revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL) & | |
1078 | epi->event.events; | |
1079 | ||
1080 | /* | |
1081 | * If the event mask intersect the caller-requested one, | |
1082 | * deliver the event to userspace. Again, ep_scan_ready_list() | |
1083 | * is holding "mtx", so no operations coming from userspace | |
1084 | * can change the item. | |
1085 | */ | |
1086 | if (revents) { | |
1087 | if (__put_user(revents, &uevent->events) || | |
1088 | __put_user(epi->event.data, &uevent->data)) { | |
1089 | list_add(&epi->rdllink, head); | |
1090 | return eventcnt ? eventcnt : -EFAULT; | |
1091 | } | |
1092 | eventcnt++; | |
1093 | uevent++; | |
1094 | if (epi->event.events & EPOLLONESHOT) | |
1095 | epi->event.events &= EP_PRIVATE_BITS; | |
1096 | else if (!(epi->event.events & EPOLLET)) { | |
1097 | /* | |
1098 | * If this file has been added with Level | |
1099 | * Trigger mode, we need to insert back inside | |
1100 | * the ready list, so that the next call to | |
1101 | * epoll_wait() will check again the events | |
1102 | * availability. At this point, noone can insert | |
1103 | * into ep->rdllist besides us. The epoll_ctl() | |
1104 | * callers are locked out by | |
1105 | * ep_scan_ready_list() holding "mtx" and the | |
1106 | * poll callback will queue them in ep->ovflist. | |
1107 | */ | |
1108 | list_add_tail(&epi->rdllink, &ep->rdllist); | |
1109 | } | |
1110 | } | |
1111 | } | |
1112 | ||
1113 | return eventcnt; | |
1114 | } | |
1115 | ||
1116 | static int ep_send_events(struct eventpoll *ep, | |
1117 | struct epoll_event __user *events, int maxevents) | |
1118 | { | |
1119 | struct ep_send_events_data esed; | |
1120 | ||
1121 | esed.maxevents = maxevents; | |
1122 | esed.events = events; | |
1123 | ||
1124 | return ep_scan_ready_list(ep, ep_send_events_proc, &esed); | |
1125 | } | |
1126 | ||
1127 | static inline struct timespec ep_set_mstimeout(long ms) | |
1128 | { | |
1129 | struct timespec now, ts = { | |
1130 | .tv_sec = ms / MSEC_PER_SEC, | |
1131 | .tv_nsec = NSEC_PER_MSEC * (ms % MSEC_PER_SEC), | |
1132 | }; | |
1133 | ||
1134 | ktime_get_ts(&now); | |
1135 | return timespec_add_safe(now, ts); | |
1136 | } | |
1137 | ||
1138 | static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, | |
1139 | int maxevents, long timeout) | |
1140 | { | |
1141 | int res, eavail, timed_out = 0; | |
1142 | unsigned long flags; | |
1143 | long slack; | |
1144 | wait_queue_t wait; | |
1145 | ktime_t expires, *to = NULL; | |
1146 | ||
1147 | if (timeout > 0) { | |
1148 | struct timespec end_time = ep_set_mstimeout(timeout); | |
1149 | ||
1150 | slack = select_estimate_accuracy(&end_time); | |
1151 | to = &expires; | |
1152 | *to = timespec_to_ktime(end_time); | |
1153 | } else if (timeout == 0) { | |
1154 | timed_out = 1; | |
1155 | } | |
1156 | ||
1157 | retry: | |
1158 | spin_lock_irqsave(&ep->lock, flags); | |
1159 | ||
1160 | res = 0; | |
1161 | if (list_empty(&ep->rdllist)) { | |
1162 | /* | |
1163 | * We don't have any available event to return to the caller. | |
1164 | * We need to sleep here, and we will be wake up by | |
1165 | * ep_poll_callback() when events will become available. | |
1166 | */ | |
1167 | init_waitqueue_entry(&wait, current); | |
1168 | __add_wait_queue_exclusive(&ep->wq, &wait); | |
1169 | ||
1170 | for (;;) { | |
1171 | /* | |
1172 | * We don't want to sleep if the ep_poll_callback() sends us | |
1173 | * a wakeup in between. That's why we set the task state | |
1174 | * to TASK_INTERRUPTIBLE before doing the checks. | |
1175 | */ | |
1176 | set_current_state(TASK_INTERRUPTIBLE); | |
1177 | if (!list_empty(&ep->rdllist) || timed_out) | |
1178 | break; | |
1179 | if (signal_pending(current)) { | |
1180 | res = -EINTR; | |
1181 | break; | |
1182 | } | |
1183 | ||
1184 | spin_unlock_irqrestore(&ep->lock, flags); | |
1185 | if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS)) | |
1186 | timed_out = 1; | |
1187 | ||
1188 | spin_lock_irqsave(&ep->lock, flags); | |
1189 | } | |
1190 | __remove_wait_queue(&ep->wq, &wait); | |
1191 | ||
1192 | set_current_state(TASK_RUNNING); | |
1193 | } | |
1194 | /* Is it worth to try to dig for events ? */ | |
1195 | eavail = !list_empty(&ep->rdllist) || ep->ovflist != EP_UNACTIVE_PTR; | |
1196 | ||
1197 | spin_unlock_irqrestore(&ep->lock, flags); | |
1198 | ||
1199 | /* | |
1200 | * Try to transfer events to user space. In case we get 0 events and | |
1201 | * there's still timeout left over, we go trying again in search of | |
1202 | * more luck. | |
1203 | */ | |
1204 | if (!res && eavail && | |
1205 | !(res = ep_send_events(ep, events, maxevents)) && !timed_out) | |
1206 | goto retry; | |
1207 | ||
1208 | return res; | |
1209 | } | |
1210 | ||
1211 | /** | |
1212 | * ep_loop_check_proc - Callback function to be passed to the @ep_call_nested() | |
1213 | * API, to verify that adding an epoll file inside another | |
1214 | * epoll structure, does not violate the constraints, in | |
1215 | * terms of closed loops, or too deep chains (which can | |
1216 | * result in excessive stack usage). | |
1217 | * | |
1218 | * @priv: Pointer to the epoll file to be currently checked. | |
1219 | * @cookie: Original cookie for this call. This is the top-of-the-chain epoll | |
1220 | * data structure pointer. | |
1221 | * @call_nests: Current dept of the @ep_call_nested() call stack. | |
1222 | * | |
1223 | * Returns: Returns zero if adding the epoll @file inside current epoll | |
1224 | * structure @ep does not violate the constraints, or -1 otherwise. | |
1225 | */ | |
1226 | static int ep_loop_check_proc(void *priv, void *cookie, int call_nests) | |
1227 | { | |
1228 | int error = 0; | |
1229 | struct file *file = priv; | |
1230 | struct eventpoll *ep = file->private_data; | |
1231 | struct rb_node *rbp; | |
1232 | struct epitem *epi; | |
1233 | ||
1234 | mutex_lock(&ep->mtx); | |
1235 | for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { | |
1236 | epi = rb_entry(rbp, struct epitem, rbn); | |
1237 | if (unlikely(is_file_epoll(epi->ffd.file))) { | |
1238 | error = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, | |
1239 | ep_loop_check_proc, epi->ffd.file, | |
1240 | epi->ffd.file->private_data, current); | |
1241 | if (error != 0) | |
1242 | break; | |
1243 | } | |
1244 | } | |
1245 | mutex_unlock(&ep->mtx); | |
1246 | ||
1247 | return error; | |
1248 | } | |
1249 | ||
1250 | /** | |
1251 | * ep_loop_check - Performs a check to verify that adding an epoll file (@file) | |
1252 | * another epoll file (represented by @ep) does not create | |
1253 | * closed loops or too deep chains. | |
1254 | * | |
1255 | * @ep: Pointer to the epoll private data structure. | |
1256 | * @file: Pointer to the epoll file to be checked. | |
1257 | * | |
1258 | * Returns: Returns zero if adding the epoll @file inside current epoll | |
1259 | * structure @ep does not violate the constraints, or -1 otherwise. | |
1260 | */ | |
1261 | static int ep_loop_check(struct eventpoll *ep, struct file *file) | |
1262 | { | |
1263 | return ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, | |
1264 | ep_loop_check_proc, file, ep, current); | |
1265 | } | |
1266 | ||
1267 | /* | |
1268 | * Open an eventpoll file descriptor. | |
1269 | */ | |
1270 | SYSCALL_DEFINE1(epoll_create1, int, flags) | |
1271 | { | |
1272 | int error; | |
1273 | struct eventpoll *ep = NULL; | |
1274 | ||
1275 | /* Check the EPOLL_* constant for consistency. */ | |
1276 | BUILD_BUG_ON(EPOLL_CLOEXEC != O_CLOEXEC); | |
1277 | ||
1278 | if (flags & ~EPOLL_CLOEXEC) | |
1279 | return -EINVAL; | |
1280 | /* | |
1281 | * Create the internal data structure ("struct eventpoll"). | |
1282 | */ | |
1283 | error = ep_alloc(&ep); | |
1284 | if (error < 0) | |
1285 | return error; | |
1286 | /* | |
1287 | * Creates all the items needed to setup an eventpoll file. That is, | |
1288 | * a file structure and a free file descriptor. | |
1289 | */ | |
1290 | error = anon_inode_getfd("[eventpoll]", &eventpoll_fops, ep, | |
1291 | O_RDWR | (flags & O_CLOEXEC)); | |
1292 | if (error < 0) | |
1293 | ep_free(ep); | |
1294 | ||
1295 | return error; | |
1296 | } | |
1297 | ||
1298 | SYSCALL_DEFINE1(epoll_create, int, size) | |
1299 | { | |
1300 | if (size <= 0) | |
1301 | return -EINVAL; | |
1302 | ||
1303 | return sys_epoll_create1(0); | |
1304 | } | |
1305 | ||
1306 | /* | |
1307 | * The following function implements the controller interface for | |
1308 | * the eventpoll file that enables the insertion/removal/change of | |
1309 | * file descriptors inside the interest set. | |
1310 | */ | |
1311 | SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd, | |
1312 | struct epoll_event __user *, event) | |
1313 | { | |
1314 | int error; | |
1315 | int did_lock_epmutex = 0; | |
1316 | struct file *file, *tfile; | |
1317 | struct eventpoll *ep; | |
1318 | struct epitem *epi; | |
1319 | struct epoll_event epds; | |
1320 | ||
1321 | error = -EFAULT; | |
1322 | if (ep_op_has_event(op) && | |
1323 | copy_from_user(&epds, event, sizeof(struct epoll_event))) | |
1324 | goto error_return; | |
1325 | ||
1326 | /* Get the "struct file *" for the eventpoll file */ | |
1327 | error = -EBADF; | |
1328 | file = fget(epfd); | |
1329 | if (!file) | |
1330 | goto error_return; | |
1331 | ||
1332 | /* Get the "struct file *" for the target file */ | |
1333 | tfile = fget(fd); | |
1334 | if (!tfile) | |
1335 | goto error_fput; | |
1336 | ||
1337 | /* The target file descriptor must support poll */ | |
1338 | error = -EPERM; | |
1339 | if (!tfile->f_op || !tfile->f_op->poll) | |
1340 | goto error_tgt_fput; | |
1341 | ||
1342 | /* | |
1343 | * We have to check that the file structure underneath the file descriptor | |
1344 | * the user passed to us _is_ an eventpoll file. And also we do not permit | |
1345 | * adding an epoll file descriptor inside itself. | |
1346 | */ | |
1347 | error = -EINVAL; | |
1348 | if (file == tfile || !is_file_epoll(file)) | |
1349 | goto error_tgt_fput; | |
1350 | ||
1351 | /* | |
1352 | * At this point it is safe to assume that the "private_data" contains | |
1353 | * our own data structure. | |
1354 | */ | |
1355 | ep = file->private_data; | |
1356 | ||
1357 | /* | |
1358 | * When we insert an epoll file descriptor, inside another epoll file | |
1359 | * descriptor, there is the change of creating closed loops, which are | |
1360 | * better be handled here, than in more critical paths. | |
1361 | * | |
1362 | * We hold epmutex across the loop check and the insert in this case, in | |
1363 | * order to prevent two separate inserts from racing and each doing the | |
1364 | * insert "at the same time" such that ep_loop_check passes on both | |
1365 | * before either one does the insert, thereby creating a cycle. | |
1366 | */ | |
1367 | if (unlikely(is_file_epoll(tfile) && op == EPOLL_CTL_ADD)) { | |
1368 | mutex_lock(&epmutex); | |
1369 | did_lock_epmutex = 1; | |
1370 | error = -ELOOP; | |
1371 | if (ep_loop_check(ep, tfile) != 0) | |
1372 | goto error_tgt_fput; | |
1373 | } | |
1374 | ||
1375 | ||
1376 | mutex_lock(&ep->mtx); | |
1377 | ||
1378 | /* | |
1379 | * Try to lookup the file inside our RB tree, Since we grabbed "mtx" | |
1380 | * above, we can be sure to be able to use the item looked up by | |
1381 | * ep_find() till we release the mutex. | |
1382 | */ | |
1383 | epi = ep_find(ep, tfile, fd); | |
1384 | ||
1385 | error = -EINVAL; | |
1386 | switch (op) { | |
1387 | case EPOLL_CTL_ADD: | |
1388 | if (!epi) { | |
1389 | epds.events |= POLLERR | POLLHUP; | |
1390 | error = ep_insert(ep, &epds, tfile, fd); | |
1391 | } else | |
1392 | error = -EEXIST; | |
1393 | break; | |
1394 | case EPOLL_CTL_DEL: | |
1395 | if (epi) | |
1396 | error = ep_remove(ep, epi); | |
1397 | else | |
1398 | error = -ENOENT; | |
1399 | break; | |
1400 | case EPOLL_CTL_MOD: | |
1401 | if (epi) { | |
1402 | epds.events |= POLLERR | POLLHUP; | |
1403 | error = ep_modify(ep, epi, &epds); | |
1404 | } else | |
1405 | error = -ENOENT; | |
1406 | break; | |
1407 | } | |
1408 | mutex_unlock(&ep->mtx); | |
1409 | ||
1410 | error_tgt_fput: | |
1411 | if (unlikely(did_lock_epmutex)) | |
1412 | mutex_unlock(&epmutex); | |
1413 | ||
1414 | fput(tfile); | |
1415 | error_fput: | |
1416 | fput(file); | |
1417 | error_return: | |
1418 | ||
1419 | return error; | |
1420 | } | |
1421 | ||
1422 | /* | |
1423 | * Implement the event wait interface for the eventpoll file. It is the kernel | |
1424 | * part of the user space epoll_wait(2). | |
1425 | */ | |
1426 | SYSCALL_DEFINE4(epoll_wait, int, epfd, struct epoll_event __user *, events, | |
1427 | int, maxevents, int, timeout) | |
1428 | { | |
1429 | int error; | |
1430 | struct file *file; | |
1431 | struct eventpoll *ep; | |
1432 | ||
1433 | /* The maximum number of event must be greater than zero */ | |
1434 | if (maxevents <= 0 || maxevents > EP_MAX_EVENTS) | |
1435 | return -EINVAL; | |
1436 | ||
1437 | /* Verify that the area passed by the user is writeable */ | |
1438 | if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event))) { | |
1439 | error = -EFAULT; | |
1440 | goto error_return; | |
1441 | } | |
1442 | ||
1443 | /* Get the "struct file *" for the eventpoll file */ | |
1444 | error = -EBADF; | |
1445 | file = fget(epfd); | |
1446 | if (!file) | |
1447 | goto error_return; | |
1448 | ||
1449 | /* | |
1450 | * We have to check that the file structure underneath the fd | |
1451 | * the user passed to us _is_ an eventpoll file. | |
1452 | */ | |
1453 | error = -EINVAL; | |
1454 | if (!is_file_epoll(file)) | |
1455 | goto error_fput; | |
1456 | ||
1457 | /* | |
1458 | * At this point it is safe to assume that the "private_data" contains | |
1459 | * our own data structure. | |
1460 | */ | |
1461 | ep = file->private_data; | |
1462 | ||
1463 | /* Time to fish for events ... */ | |
1464 | error = ep_poll(ep, events, maxevents, timeout); | |
1465 | ||
1466 | error_fput: | |
1467 | fput(file); | |
1468 | error_return: | |
1469 | ||
1470 | return error; | |
1471 | } | |
1472 | ||
1473 | #ifdef HAVE_SET_RESTORE_SIGMASK | |
1474 | ||
1475 | /* | |
1476 | * Implement the event wait interface for the eventpoll file. It is the kernel | |
1477 | * part of the user space epoll_pwait(2). | |
1478 | */ | |
1479 | SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events, | |
1480 | int, maxevents, int, timeout, const sigset_t __user *, sigmask, | |
1481 | size_t, sigsetsize) | |
1482 | { | |
1483 | int error; | |
1484 | sigset_t ksigmask, sigsaved; | |
1485 | ||
1486 | /* | |
1487 | * If the caller wants a certain signal mask to be set during the wait, | |
1488 | * we apply it here. | |
1489 | */ | |
1490 | if (sigmask) { | |
1491 | if (sigsetsize != sizeof(sigset_t)) | |
1492 | return -EINVAL; | |
1493 | if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) | |
1494 | return -EFAULT; | |
1495 | sigdelsetmask(&ksigmask, sigmask(SIGKILL) | sigmask(SIGSTOP)); | |
1496 | sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); | |
1497 | } | |
1498 | ||
1499 | error = sys_epoll_wait(epfd, events, maxevents, timeout); | |
1500 | ||
1501 | /* | |
1502 | * If we changed the signal mask, we need to restore the original one. | |
1503 | * In case we've got a signal while waiting, we do not restore the | |
1504 | * signal mask yet, and we allow do_signal() to deliver the signal on | |
1505 | * the way back to userspace, before the signal mask is restored. | |
1506 | */ | |
1507 | if (sigmask) { | |
1508 | if (error == -EINTR) { | |
1509 | memcpy(¤t->saved_sigmask, &sigsaved, | |
1510 | sizeof(sigsaved)); | |
1511 | set_restore_sigmask(); | |
1512 | } else | |
1513 | sigprocmask(SIG_SETMASK, &sigsaved, NULL); | |
1514 | } | |
1515 | ||
1516 | return error; | |
1517 | } | |
1518 | ||
1519 | #endif /* HAVE_SET_RESTORE_SIGMASK */ | |
1520 | ||
1521 | static int __init eventpoll_init(void) | |
1522 | { | |
1523 | struct sysinfo si; | |
1524 | ||
1525 | si_meminfo(&si); | |
1526 | /* | |
1527 | * Allows top 4% of lomem to be allocated for epoll watches (per user). | |
1528 | */ | |
1529 | max_user_watches = (((si.totalram - si.totalhigh) / 25) << PAGE_SHIFT) / | |
1530 | EP_ITEM_COST; | |
1531 | BUG_ON(max_user_watches < 0); | |
1532 | ||
1533 | /* | |
1534 | * Initialize the structure used to perform epoll file descriptor | |
1535 | * inclusion loops checks. | |
1536 | */ | |
1537 | ep_nested_calls_init(&poll_loop_ncalls); | |
1538 | ||
1539 | /* Initialize the structure used to perform safe poll wait head wake ups */ | |
1540 | ep_nested_calls_init(&poll_safewake_ncalls); | |
1541 | ||
1542 | /* Initialize the structure used to perform file's f_op->poll() calls */ | |
1543 | ep_nested_calls_init(&poll_readywalk_ncalls); | |
1544 | ||
1545 | /* Allocates slab cache used to allocate "struct epitem" items */ | |
1546 | epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem), | |
1547 | 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); | |
1548 | ||
1549 | /* Allocates slab cache used to allocate "struct eppoll_entry" */ | |
1550 | pwq_cache = kmem_cache_create("eventpoll_pwq", | |
1551 | sizeof(struct eppoll_entry), 0, SLAB_PANIC, NULL); | |
1552 | ||
1553 | return 0; | |
1554 | } | |
1555 | fs_initcall(eventpoll_init); |