Root/
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 | /* Maximum msec timeout value storeable in a long int */ |
81 | #define EP_MAX_MSTIMEO min(1000ULL * MAX_SCHEDULE_TIMEOUT / HZ, (LONG_MAX - 999ULL) / HZ) |
82 | |
83 | #define EP_MAX_EVENTS (INT_MAX / sizeof(struct epoll_event)) |
84 | |
85 | #define EP_UNACTIVE_PTR ((void *) -1L) |
86 | |
87 | #define EP_ITEM_COST (sizeof(struct epitem) + sizeof(struct eppoll_entry)) |
88 | |
89 | struct epoll_filefd { |
90 | struct file *file; |
91 | int fd; |
92 | }; |
93 | |
94 | /* |
95 | * Structure used to track possible nested calls, for too deep recursions |
96 | * and loop cycles. |
97 | */ |
98 | struct nested_call_node { |
99 | struct list_head llink; |
100 | void *cookie; |
101 | void *ctx; |
102 | }; |
103 | |
104 | /* |
105 | * This structure is used as collector for nested calls, to check for |
106 | * maximum recursion dept and loop cycles. |
107 | */ |
108 | struct nested_calls { |
109 | struct list_head tasks_call_list; |
110 | spinlock_t lock; |
111 | }; |
112 | |
113 | /* |
114 | * Each file descriptor added to the eventpoll interface will |
115 | * have an entry of this type linked to the "rbr" RB tree. |
116 | */ |
117 | struct epitem { |
118 | /* RB tree node used to link this structure to the eventpoll RB tree */ |
119 | struct rb_node rbn; |
120 | |
121 | /* List header used to link this structure to the eventpoll ready list */ |
122 | struct list_head rdllink; |
123 | |
124 | /* |
125 | * Works together "struct eventpoll"->ovflist in keeping the |
126 | * single linked chain of items. |
127 | */ |
128 | struct epitem *next; |
129 | |
130 | /* The file descriptor information this item refers to */ |
131 | struct epoll_filefd ffd; |
132 | |
133 | /* Number of active wait queue attached to poll operations */ |
134 | int nwait; |
135 | |
136 | /* List containing poll wait queues */ |
137 | struct list_head pwqlist; |
138 | |
139 | /* The "container" of this item */ |
140 | struct eventpoll *ep; |
141 | |
142 | /* List header used to link this item to the "struct file" items list */ |
143 | struct list_head fllink; |
144 | |
145 | /* The structure that describe the interested events and the source fd */ |
146 | struct epoll_event event; |
147 | }; |
148 | |
149 | /* |
150 | * This structure is stored inside the "private_data" member of the file |
151 | * structure and rapresent the main data sructure for the eventpoll |
152 | * interface. |
153 | */ |
154 | struct eventpoll { |
155 | /* Protect the this structure access */ |
156 | spinlock_t lock; |
157 | |
158 | /* |
159 | * This mutex is used to ensure that files are not removed |
160 | * while epoll is using them. This is held during the event |
161 | * collection loop, the file cleanup path, the epoll file exit |
162 | * code and the ctl operations. |
163 | */ |
164 | struct mutex mtx; |
165 | |
166 | /* Wait queue used by sys_epoll_wait() */ |
167 | wait_queue_head_t wq; |
168 | |
169 | /* Wait queue used by file->poll() */ |
170 | wait_queue_head_t poll_wait; |
171 | |
172 | /* List of ready file descriptors */ |
173 | struct list_head rdllist; |
174 | |
175 | /* RB tree root used to store monitored fd structs */ |
176 | struct rb_root rbr; |
177 | |
178 | /* |
179 | * This is a single linked list that chains all the "struct epitem" that |
180 | * happened while transfering ready events to userspace w/out |
181 | * holding ->lock. |
182 | */ |
183 | struct epitem *ovflist; |
184 | |
185 | /* The user that created the eventpoll descriptor */ |
186 | struct user_struct *user; |
187 | }; |
188 | |
189 | /* Wait structure used by the poll hooks */ |
190 | struct eppoll_entry { |
191 | /* List header used to link this structure to the "struct epitem" */ |
192 | struct list_head llink; |
193 | |
194 | /* The "base" pointer is set to the container "struct epitem" */ |
195 | struct epitem *base; |
196 | |
197 | /* |
198 | * Wait queue item that will be linked to the target file wait |
199 | * queue head. |
200 | */ |
201 | wait_queue_t wait; |
202 | |
203 | /* The wait queue head that linked the "wait" wait queue item */ |
204 | wait_queue_head_t *whead; |
205 | }; |
206 | |
207 | /* Wrapper struct used by poll queueing */ |
208 | struct ep_pqueue { |
209 | poll_table pt; |
210 | struct epitem *epi; |
211 | }; |
212 | |
213 | /* Used by the ep_send_events() function as callback private data */ |
214 | struct ep_send_events_data { |
215 | int maxevents; |
216 | struct epoll_event __user *events; |
217 | }; |
218 | |
219 | /* |
220 | * Configuration options available inside /proc/sys/fs/epoll/ |
221 | */ |
222 | /* Maximum number of epoll watched descriptors, per user */ |
223 | static int max_user_watches __read_mostly; |
224 | |
225 | /* |
226 | * This mutex is used to serialize ep_free() and eventpoll_release_file(). |
227 | */ |
228 | static DEFINE_MUTEX(epmutex); |
229 | |
230 | /* Used for safe wake up implementation */ |
231 | static struct nested_calls poll_safewake_ncalls; |
232 | |
233 | /* Used to call file's f_op->poll() under the nested calls boundaries */ |
234 | static struct nested_calls poll_readywalk_ncalls; |
235 | |
236 | /* Slab cache used to allocate "struct epitem" */ |
237 | static struct kmem_cache *epi_cache __read_mostly; |
238 | |
239 | /* Slab cache used to allocate "struct eppoll_entry" */ |
240 | static struct kmem_cache *pwq_cache __read_mostly; |
241 | |
242 | #ifdef CONFIG_SYSCTL |
243 | |
244 | #include <linux/sysctl.h> |
245 | |
246 | static int zero; |
247 | |
248 | ctl_table epoll_table[] = { |
249 | { |
250 | .procname = "max_user_watches", |
251 | .data = &max_user_watches, |
252 | .maxlen = sizeof(int), |
253 | .mode = 0644, |
254 | .proc_handler = &proc_dointvec_minmax, |
255 | .extra1 = &zero, |
256 | }, |
257 | { .ctl_name = 0 } |
258 | }; |
259 | #endif /* CONFIG_SYSCTL */ |
260 | |
261 | |
262 | /* Setup the structure that is used as key for the RB tree */ |
263 | static inline void ep_set_ffd(struct epoll_filefd *ffd, |
264 | struct file *file, int fd) |
265 | { |
266 | ffd->file = file; |
267 | ffd->fd = fd; |
268 | } |
269 | |
270 | /* Compare RB tree keys */ |
271 | static inline int ep_cmp_ffd(struct epoll_filefd *p1, |
272 | struct epoll_filefd *p2) |
273 | { |
274 | return (p1->file > p2->file ? +1: |
275 | (p1->file < p2->file ? -1 : p1->fd - p2->fd)); |
276 | } |
277 | |
278 | /* Tells us if the item is currently linked */ |
279 | static inline int ep_is_linked(struct list_head *p) |
280 | { |
281 | return !list_empty(p); |
282 | } |
283 | |
284 | /* Get the "struct epitem" from a wait queue pointer */ |
285 | static inline struct epitem *ep_item_from_wait(wait_queue_t *p) |
286 | { |
287 | return container_of(p, struct eppoll_entry, wait)->base; |
288 | } |
289 | |
290 | /* Get the "struct epitem" from an epoll queue wrapper */ |
291 | static inline struct epitem *ep_item_from_epqueue(poll_table *p) |
292 | { |
293 | return container_of(p, struct ep_pqueue, pt)->epi; |
294 | } |
295 | |
296 | /* Tells if the epoll_ctl(2) operation needs an event copy from userspace */ |
297 | static inline int ep_op_has_event(int op) |
298 | { |
299 | return op != EPOLL_CTL_DEL; |
300 | } |
301 | |
302 | /* Initialize the poll safe wake up structure */ |
303 | static void ep_nested_calls_init(struct nested_calls *ncalls) |
304 | { |
305 | INIT_LIST_HEAD(&ncalls->tasks_call_list); |
306 | spin_lock_init(&ncalls->lock); |
307 | } |
308 | |
309 | /** |
310 | * ep_call_nested - Perform a bound (possibly) nested call, by checking |
311 | * that the recursion limit is not exceeded, and that |
312 | * the same nested call (by the meaning of same cookie) is |
313 | * no re-entered. |
314 | * |
315 | * @ncalls: Pointer to the nested_calls structure to be used for this call. |
316 | * @max_nests: Maximum number of allowed nesting calls. |
317 | * @nproc: Nested call core function pointer. |
318 | * @priv: Opaque data to be passed to the @nproc callback. |
319 | * @cookie: Cookie to be used to identify this nested call. |
320 | * @ctx: This instance context. |
321 | * |
322 | * Returns: Returns the code returned by the @nproc callback, or -1 if |
323 | * the maximum recursion limit has been exceeded. |
324 | */ |
325 | static int ep_call_nested(struct nested_calls *ncalls, int max_nests, |
326 | int (*nproc)(void *, void *, int), void *priv, |
327 | void *cookie, void *ctx) |
328 | { |
329 | int error, call_nests = 0; |
330 | unsigned long flags; |
331 | struct list_head *lsthead = &ncalls->tasks_call_list; |
332 | struct nested_call_node *tncur; |
333 | struct nested_call_node tnode; |
334 | |
335 | spin_lock_irqsave(&ncalls->lock, flags); |
336 | |
337 | /* |
338 | * Try to see if the current task is already inside this wakeup call. |
339 | * We use a list here, since the population inside this set is always |
340 | * very much limited. |
341 | */ |
342 | list_for_each_entry(tncur, lsthead, llink) { |
343 | if (tncur->ctx == ctx && |
344 | (tncur->cookie == cookie || ++call_nests > max_nests)) { |
345 | /* |
346 | * Ops ... loop detected or maximum nest level reached. |
347 | * We abort this wake by breaking the cycle itself. |
348 | */ |
349 | error = -1; |
350 | goto out_unlock; |
351 | } |
352 | } |
353 | |
354 | /* Add the current task and cookie to the list */ |
355 | tnode.ctx = ctx; |
356 | tnode.cookie = cookie; |
357 | list_add(&tnode.llink, lsthead); |
358 | |
359 | spin_unlock_irqrestore(&ncalls->lock, flags); |
360 | |
361 | /* Call the nested function */ |
362 | error = (*nproc)(priv, cookie, call_nests); |
363 | |
364 | /* Remove the current task from the list */ |
365 | spin_lock_irqsave(&ncalls->lock, flags); |
366 | list_del(&tnode.llink); |
367 | out_unlock: |
368 | spin_unlock_irqrestore(&ncalls->lock, flags); |
369 | |
370 | return error; |
371 | } |
372 | |
373 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
374 | static inline void ep_wake_up_nested(wait_queue_head_t *wqueue, |
375 | unsigned long events, int subclass) |
376 | { |
377 | unsigned long flags; |
378 | |
379 | spin_lock_irqsave_nested(&wqueue->lock, flags, subclass); |
380 | wake_up_locked_poll(wqueue, events); |
381 | spin_unlock_irqrestore(&wqueue->lock, flags); |
382 | } |
383 | #else |
384 | static inline void ep_wake_up_nested(wait_queue_head_t *wqueue, |
385 | unsigned long events, int subclass) |
386 | { |
387 | wake_up_poll(wqueue, events); |
388 | } |
389 | #endif |
390 | |
391 | static int ep_poll_wakeup_proc(void *priv, void *cookie, int call_nests) |
392 | { |
393 | ep_wake_up_nested((wait_queue_head_t *) cookie, POLLIN, |
394 | 1 + call_nests); |
395 | return 0; |
396 | } |
397 | |
398 | /* |
399 | * Perform a safe wake up of the poll wait list. The problem is that |
400 | * with the new callback'd wake up system, it is possible that the |
401 | * poll callback is reentered from inside the call to wake_up() done |
402 | * on the poll wait queue head. The rule is that we cannot reenter the |
403 | * wake up code from the same task more than EP_MAX_NESTS times, |
404 | * and we cannot reenter the same wait queue head at all. This will |
405 | * enable to have a hierarchy of epoll file descriptor of no more than |
406 | * EP_MAX_NESTS deep. |
407 | */ |
408 | static void ep_poll_safewake(wait_queue_head_t *wq) |
409 | { |
410 | int this_cpu = get_cpu(); |
411 | |
412 | ep_call_nested(&poll_safewake_ncalls, EP_MAX_NESTS, |
413 | ep_poll_wakeup_proc, NULL, wq, (void *) (long) this_cpu); |
414 | |
415 | put_cpu(); |
416 | } |
417 | |
418 | /* |
419 | * This function unregisters poll callbacks from the associated file |
420 | * descriptor. Must be called with "mtx" held (or "epmutex" if called from |
421 | * ep_free). |
422 | */ |
423 | static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi) |
424 | { |
425 | struct list_head *lsthead = &epi->pwqlist; |
426 | struct eppoll_entry *pwq; |
427 | |
428 | while (!list_empty(lsthead)) { |
429 | pwq = list_first_entry(lsthead, struct eppoll_entry, llink); |
430 | |
431 | list_del(&pwq->llink); |
432 | remove_wait_queue(pwq->whead, &pwq->wait); |
433 | kmem_cache_free(pwq_cache, pwq); |
434 | } |
435 | } |
436 | |
437 | /** |
438 | * ep_scan_ready_list - Scans the ready list in a way that makes possible for |
439 | * the scan code, to call f_op->poll(). Also allows for |
440 | * O(NumReady) performance. |
441 | * |
442 | * @ep: Pointer to the epoll private data structure. |
443 | * @sproc: Pointer to the scan callback. |
444 | * @priv: Private opaque data passed to the @sproc callback. |
445 | * |
446 | * Returns: The same integer error code returned by the @sproc callback. |
447 | */ |
448 | static int ep_scan_ready_list(struct eventpoll *ep, |
449 | int (*sproc)(struct eventpoll *, |
450 | struct list_head *, void *), |
451 | void *priv) |
452 | { |
453 | int error, pwake = 0; |
454 | unsigned long flags; |
455 | struct epitem *epi, *nepi; |
456 | LIST_HEAD(txlist); |
457 | |
458 | /* |
459 | * We need to lock this because we could be hit by |
460 | * eventpoll_release_file() and epoll_ctl(). |
461 | */ |
462 | mutex_lock(&ep->mtx); |
463 | |
464 | /* |
465 | * Steal the ready list, and re-init the original one to the |
466 | * empty list. Also, set ep->ovflist to NULL so that events |
467 | * happening while looping w/out locks, are not lost. We cannot |
468 | * have the poll callback to queue directly on ep->rdllist, |
469 | * because we want the "sproc" callback to be able to do it |
470 | * in a lockless way. |
471 | */ |
472 | spin_lock_irqsave(&ep->lock, flags); |
473 | list_splice_init(&ep->rdllist, &txlist); |
474 | ep->ovflist = NULL; |
475 | spin_unlock_irqrestore(&ep->lock, flags); |
476 | |
477 | /* |
478 | * Now call the callback function. |
479 | */ |
480 | error = (*sproc)(ep, &txlist, priv); |
481 | |
482 | spin_lock_irqsave(&ep->lock, flags); |
483 | /* |
484 | * During the time we spent inside the "sproc" callback, some |
485 | * other events might have been queued by the poll callback. |
486 | * We re-insert them inside the main ready-list here. |
487 | */ |
488 | for (nepi = ep->ovflist; (epi = nepi) != NULL; |
489 | nepi = epi->next, epi->next = EP_UNACTIVE_PTR) { |
490 | /* |
491 | * We need to check if the item is already in the list. |
492 | * During the "sproc" callback execution time, items are |
493 | * queued into ->ovflist but the "txlist" might already |
494 | * contain them, and the list_splice() below takes care of them. |
495 | */ |
496 | if (!ep_is_linked(&epi->rdllink)) |
497 | list_add_tail(&epi->rdllink, &ep->rdllist); |
498 | } |
499 | /* |
500 | * We need to set back ep->ovflist to EP_UNACTIVE_PTR, so that after |
501 | * releasing the lock, events will be queued in the normal way inside |
502 | * ep->rdllist. |
503 | */ |
504 | ep->ovflist = EP_UNACTIVE_PTR; |
505 | |
506 | /* |
507 | * Quickly re-inject items left on "txlist". |
508 | */ |
509 | list_splice(&txlist, &ep->rdllist); |
510 | |
511 | if (!list_empty(&ep->rdllist)) { |
512 | /* |
513 | * Wake up (if active) both the eventpoll wait list and |
514 | * the ->poll() wait list (delayed after we release the lock). |
515 | */ |
516 | if (waitqueue_active(&ep->wq)) |
517 | wake_up_locked(&ep->wq); |
518 | if (waitqueue_active(&ep->poll_wait)) |
519 | pwake++; |
520 | } |
521 | spin_unlock_irqrestore(&ep->lock, flags); |
522 | |
523 | mutex_unlock(&ep->mtx); |
524 | |
525 | /* We have to call this outside the lock */ |
526 | if (pwake) |
527 | ep_poll_safewake(&ep->poll_wait); |
528 | |
529 | return error; |
530 | } |
531 | |
532 | /* |
533 | * Removes a "struct epitem" from the eventpoll RB tree and deallocates |
534 | * all the associated resources. Must be called with "mtx" held. |
535 | */ |
536 | static int ep_remove(struct eventpoll *ep, struct epitem *epi) |
537 | { |
538 | unsigned long flags; |
539 | struct file *file = epi->ffd.file; |
540 | |
541 | /* |
542 | * Removes poll wait queue hooks. We _have_ to do this without holding |
543 | * the "ep->lock" otherwise a deadlock might occur. This because of the |
544 | * sequence of the lock acquisition. Here we do "ep->lock" then the wait |
545 | * queue head lock when unregistering the wait queue. The wakeup callback |
546 | * will run by holding the wait queue head lock and will call our callback |
547 | * that will try to get "ep->lock". |
548 | */ |
549 | ep_unregister_pollwait(ep, epi); |
550 | |
551 | /* Remove the current item from the list of epoll hooks */ |
552 | spin_lock(&file->f_lock); |
553 | if (ep_is_linked(&epi->fllink)) |
554 | list_del_init(&epi->fllink); |
555 | spin_unlock(&file->f_lock); |
556 | |
557 | rb_erase(&epi->rbn, &ep->rbr); |
558 | |
559 | spin_lock_irqsave(&ep->lock, flags); |
560 | if (ep_is_linked(&epi->rdllink)) |
561 | list_del_init(&epi->rdllink); |
562 | spin_unlock_irqrestore(&ep->lock, flags); |
563 | |
564 | /* At this point it is safe to free the eventpoll item */ |
565 | kmem_cache_free(epi_cache, epi); |
566 | |
567 | atomic_dec(&ep->user->epoll_watches); |
568 | |
569 | return 0; |
570 | } |
571 | |
572 | static void ep_free(struct eventpoll *ep) |
573 | { |
574 | struct rb_node *rbp; |
575 | struct epitem *epi; |
576 | |
577 | /* We need to release all tasks waiting for these file */ |
578 | if (waitqueue_active(&ep->poll_wait)) |
579 | ep_poll_safewake(&ep->poll_wait); |
580 | |
581 | /* |
582 | * We need to lock this because we could be hit by |
583 | * eventpoll_release_file() while we're freeing the "struct eventpoll". |
584 | * We do not need to hold "ep->mtx" here because the epoll file |
585 | * is on the way to be removed and no one has references to it |
586 | * anymore. The only hit might come from eventpoll_release_file() but |
587 | * holding "epmutex" is sufficent here. |
588 | */ |
589 | mutex_lock(&epmutex); |
590 | |
591 | /* |
592 | * Walks through the whole tree by unregistering poll callbacks. |
593 | */ |
594 | for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { |
595 | epi = rb_entry(rbp, struct epitem, rbn); |
596 | |
597 | ep_unregister_pollwait(ep, epi); |
598 | } |
599 | |
600 | /* |
601 | * Walks through the whole tree by freeing each "struct epitem". At this |
602 | * point we are sure no poll callbacks will be lingering around, and also by |
603 | * holding "epmutex" we can be sure that no file cleanup code will hit |
604 | * us during this operation. So we can avoid the lock on "ep->lock". |
605 | */ |
606 | while ((rbp = rb_first(&ep->rbr)) != NULL) { |
607 | epi = rb_entry(rbp, struct epitem, rbn); |
608 | ep_remove(ep, epi); |
609 | } |
610 | |
611 | mutex_unlock(&epmutex); |
612 | mutex_destroy(&ep->mtx); |
613 | free_uid(ep->user); |
614 | kfree(ep); |
615 | } |
616 | |
617 | static int ep_eventpoll_release(struct inode *inode, struct file *file) |
618 | { |
619 | struct eventpoll *ep = file->private_data; |
620 | |
621 | if (ep) |
622 | ep_free(ep); |
623 | |
624 | return 0; |
625 | } |
626 | |
627 | static int ep_read_events_proc(struct eventpoll *ep, struct list_head *head, |
628 | void *priv) |
629 | { |
630 | struct epitem *epi, *tmp; |
631 | |
632 | list_for_each_entry_safe(epi, tmp, head, rdllink) { |
633 | if (epi->ffd.file->f_op->poll(epi->ffd.file, NULL) & |
634 | epi->event.events) |
635 | return POLLIN | POLLRDNORM; |
636 | else { |
637 | /* |
638 | * Item has been dropped into the ready list by the poll |
639 | * callback, but it's not actually ready, as far as |
640 | * caller requested events goes. We can remove it here. |
641 | */ |
642 | list_del_init(&epi->rdllink); |
643 | } |
644 | } |
645 | |
646 | return 0; |
647 | } |
648 | |
649 | static int ep_poll_readyevents_proc(void *priv, void *cookie, int call_nests) |
650 | { |
651 | return ep_scan_ready_list(priv, ep_read_events_proc, NULL); |
652 | } |
653 | |
654 | static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait) |
655 | { |
656 | int pollflags; |
657 | struct eventpoll *ep = file->private_data; |
658 | |
659 | /* Insert inside our poll wait queue */ |
660 | poll_wait(file, &ep->poll_wait, wait); |
661 | |
662 | /* |
663 | * Proceed to find out if wanted events are really available inside |
664 | * the ready list. This need to be done under ep_call_nested() |
665 | * supervision, since the call to f_op->poll() done on listed files |
666 | * could re-enter here. |
667 | */ |
668 | pollflags = ep_call_nested(&poll_readywalk_ncalls, EP_MAX_NESTS, |
669 | ep_poll_readyevents_proc, ep, ep, current); |
670 | |
671 | return pollflags != -1 ? pollflags : 0; |
672 | } |
673 | |
674 | /* File callbacks that implement the eventpoll file behaviour */ |
675 | static const struct file_operations eventpoll_fops = { |
676 | .release = ep_eventpoll_release, |
677 | .poll = ep_eventpoll_poll |
678 | }; |
679 | |
680 | /* Fast test to see if the file is an evenpoll file */ |
681 | static inline int is_file_epoll(struct file *f) |
682 | { |
683 | return f->f_op == &eventpoll_fops; |
684 | } |
685 | |
686 | /* |
687 | * This is called from eventpoll_release() to unlink files from the eventpoll |
688 | * interface. We need to have this facility to cleanup correctly files that are |
689 | * closed without being removed from the eventpoll interface. |
690 | */ |
691 | void eventpoll_release_file(struct file *file) |
692 | { |
693 | struct list_head *lsthead = &file->f_ep_links; |
694 | struct eventpoll *ep; |
695 | struct epitem *epi; |
696 | |
697 | /* |
698 | * We don't want to get "file->f_lock" because it is not |
699 | * necessary. It is not necessary because we're in the "struct file" |
700 | * cleanup path, and this means that noone is using this file anymore. |
701 | * So, for example, epoll_ctl() cannot hit here since if we reach this |
702 | * point, the file counter already went to zero and fget() would fail. |
703 | * The only hit might come from ep_free() but by holding the mutex |
704 | * will correctly serialize the operation. We do need to acquire |
705 | * "ep->mtx" after "epmutex" because ep_remove() requires it when called |
706 | * from anywhere but ep_free(). |
707 | * |
708 | * Besides, ep_remove() acquires the lock, so we can't hold it here. |
709 | */ |
710 | mutex_lock(&epmutex); |
711 | |
712 | while (!list_empty(lsthead)) { |
713 | epi = list_first_entry(lsthead, struct epitem, fllink); |
714 | |
715 | ep = epi->ep; |
716 | list_del_init(&epi->fllink); |
717 | mutex_lock(&ep->mtx); |
718 | ep_remove(ep, epi); |
719 | mutex_unlock(&ep->mtx); |
720 | } |
721 | |
722 | mutex_unlock(&epmutex); |
723 | } |
724 | |
725 | static int ep_alloc(struct eventpoll **pep) |
726 | { |
727 | int error; |
728 | struct user_struct *user; |
729 | struct eventpoll *ep; |
730 | |
731 | user = get_current_user(); |
732 | error = -ENOMEM; |
733 | ep = kzalloc(sizeof(*ep), GFP_KERNEL); |
734 | if (unlikely(!ep)) |
735 | goto free_uid; |
736 | |
737 | spin_lock_init(&ep->lock); |
738 | mutex_init(&ep->mtx); |
739 | init_waitqueue_head(&ep->wq); |
740 | init_waitqueue_head(&ep->poll_wait); |
741 | INIT_LIST_HEAD(&ep->rdllist); |
742 | ep->rbr = RB_ROOT; |
743 | ep->ovflist = EP_UNACTIVE_PTR; |
744 | ep->user = user; |
745 | |
746 | *pep = ep; |
747 | |
748 | return 0; |
749 | |
750 | free_uid: |
751 | free_uid(user); |
752 | return error; |
753 | } |
754 | |
755 | /* |
756 | * Search the file inside the eventpoll tree. The RB tree operations |
757 | * are protected by the "mtx" mutex, and ep_find() must be called with |
758 | * "mtx" held. |
759 | */ |
760 | static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd) |
761 | { |
762 | int kcmp; |
763 | struct rb_node *rbp; |
764 | struct epitem *epi, *epir = NULL; |
765 | struct epoll_filefd ffd; |
766 | |
767 | ep_set_ffd(&ffd, file, fd); |
768 | for (rbp = ep->rbr.rb_node; rbp; ) { |
769 | epi = rb_entry(rbp, struct epitem, rbn); |
770 | kcmp = ep_cmp_ffd(&ffd, &epi->ffd); |
771 | if (kcmp > 0) |
772 | rbp = rbp->rb_right; |
773 | else if (kcmp < 0) |
774 | rbp = rbp->rb_left; |
775 | else { |
776 | epir = epi; |
777 | break; |
778 | } |
779 | } |
780 | |
781 | return epir; |
782 | } |
783 | |
784 | /* |
785 | * This is the callback that is passed to the wait queue wakeup |
786 | * machanism. It is called by the stored file descriptors when they |
787 | * have events to report. |
788 | */ |
789 | static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *key) |
790 | { |
791 | int pwake = 0; |
792 | unsigned long flags; |
793 | struct epitem *epi = ep_item_from_wait(wait); |
794 | struct eventpoll *ep = epi->ep; |
795 | |
796 | spin_lock_irqsave(&ep->lock, flags); |
797 | |
798 | /* |
799 | * If the event mask does not contain any poll(2) event, we consider the |
800 | * descriptor to be disabled. This condition is likely the effect of the |
801 | * EPOLLONESHOT bit that disables the descriptor when an event is received, |
802 | * until the next EPOLL_CTL_MOD will be issued. |
803 | */ |
804 | if (!(epi->event.events & ~EP_PRIVATE_BITS)) |
805 | goto out_unlock; |
806 | |
807 | /* |
808 | * Check the events coming with the callback. At this stage, not |
809 | * every device reports the events in the "key" parameter of the |
810 | * callback. We need to be able to handle both cases here, hence the |
811 | * test for "key" != NULL before the event match test. |
812 | */ |
813 | if (key && !((unsigned long) key & epi->event.events)) |
814 | goto out_unlock; |
815 | |
816 | /* |
817 | * If we are trasfering events to userspace, we can hold no locks |
818 | * (because we're accessing user memory, and because of linux f_op->poll() |
819 | * semantics). All the events that happens during that period of time are |
820 | * chained in ep->ovflist and requeued later on. |
821 | */ |
822 | if (unlikely(ep->ovflist != EP_UNACTIVE_PTR)) { |
823 | if (epi->next == EP_UNACTIVE_PTR) { |
824 | epi->next = ep->ovflist; |
825 | ep->ovflist = epi; |
826 | } |
827 | goto out_unlock; |
828 | } |
829 | |
830 | /* If this file is already in the ready list we exit soon */ |
831 | if (!ep_is_linked(&epi->rdllink)) |
832 | list_add_tail(&epi->rdllink, &ep->rdllist); |
833 | |
834 | /* |
835 | * Wake up ( if active ) both the eventpoll wait list and the ->poll() |
836 | * wait list. |
837 | */ |
838 | if (waitqueue_active(&ep->wq)) |
839 | wake_up_locked(&ep->wq); |
840 | if (waitqueue_active(&ep->poll_wait)) |
841 | pwake++; |
842 | |
843 | out_unlock: |
844 | spin_unlock_irqrestore(&ep->lock, flags); |
845 | |
846 | /* We have to call this outside the lock */ |
847 | if (pwake) |
848 | ep_poll_safewake(&ep->poll_wait); |
849 | |
850 | return 1; |
851 | } |
852 | |
853 | /* |
854 | * This is the callback that is used to add our wait queue to the |
855 | * target file wakeup lists. |
856 | */ |
857 | static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, |
858 | poll_table *pt) |
859 | { |
860 | struct epitem *epi = ep_item_from_epqueue(pt); |
861 | struct eppoll_entry *pwq; |
862 | |
863 | if (epi->nwait >= 0 && (pwq = kmem_cache_alloc(pwq_cache, GFP_KERNEL))) { |
864 | init_waitqueue_func_entry(&pwq->wait, ep_poll_callback); |
865 | pwq->whead = whead; |
866 | pwq->base = epi; |
867 | add_wait_queue(whead, &pwq->wait); |
868 | list_add_tail(&pwq->llink, &epi->pwqlist); |
869 | epi->nwait++; |
870 | } else { |
871 | /* We have to signal that an error occurred */ |
872 | epi->nwait = -1; |
873 | } |
874 | } |
875 | |
876 | static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi) |
877 | { |
878 | int kcmp; |
879 | struct rb_node **p = &ep->rbr.rb_node, *parent = NULL; |
880 | struct epitem *epic; |
881 | |
882 | while (*p) { |
883 | parent = *p; |
884 | epic = rb_entry(parent, struct epitem, rbn); |
885 | kcmp = ep_cmp_ffd(&epi->ffd, &epic->ffd); |
886 | if (kcmp > 0) |
887 | p = &parent->rb_right; |
888 | else |
889 | p = &parent->rb_left; |
890 | } |
891 | rb_link_node(&epi->rbn, parent, p); |
892 | rb_insert_color(&epi->rbn, &ep->rbr); |
893 | } |
894 | |
895 | /* |
896 | * Must be called with "mtx" held. |
897 | */ |
898 | static int ep_insert(struct eventpoll *ep, struct epoll_event *event, |
899 | struct file *tfile, int fd) |
900 | { |
901 | int error, revents, pwake = 0; |
902 | unsigned long flags; |
903 | struct epitem *epi; |
904 | struct ep_pqueue epq; |
905 | |
906 | if (unlikely(atomic_read(&ep->user->epoll_watches) >= |
907 | max_user_watches)) |
908 | return -ENOSPC; |
909 | if (!(epi = kmem_cache_alloc(epi_cache, GFP_KERNEL))) |
910 | return -ENOMEM; |
911 | |
912 | /* Item initialization follow here ... */ |
913 | INIT_LIST_HEAD(&epi->rdllink); |
914 | INIT_LIST_HEAD(&epi->fllink); |
915 | INIT_LIST_HEAD(&epi->pwqlist); |
916 | epi->ep = ep; |
917 | ep_set_ffd(&epi->ffd, tfile, fd); |
918 | epi->event = *event; |
919 | epi->nwait = 0; |
920 | epi->next = EP_UNACTIVE_PTR; |
921 | |
922 | /* Initialize the poll table using the queue callback */ |
923 | epq.epi = epi; |
924 | init_poll_funcptr(&epq.pt, ep_ptable_queue_proc); |
925 | |
926 | /* |
927 | * Attach the item to the poll hooks and get current event bits. |
928 | * We can safely use the file* here because its usage count has |
929 | * been increased by the caller of this function. Note that after |
930 | * this operation completes, the poll callback can start hitting |
931 | * the new item. |
932 | */ |
933 | revents = tfile->f_op->poll(tfile, &epq.pt); |
934 | |
935 | /* |
936 | * We have to check if something went wrong during the poll wait queue |
937 | * install process. Namely an allocation for a wait queue failed due |
938 | * high memory pressure. |
939 | */ |
940 | error = -ENOMEM; |
941 | if (epi->nwait < 0) |
942 | goto error_unregister; |
943 | |
944 | /* Add the current item to the list of active epoll hook for this file */ |
945 | spin_lock(&tfile->f_lock); |
946 | list_add_tail(&epi->fllink, &tfile->f_ep_links); |
947 | spin_unlock(&tfile->f_lock); |
948 | |
949 | /* |
950 | * Add the current item to the RB tree. All RB tree operations are |
951 | * protected by "mtx", and ep_insert() is called with "mtx" held. |
952 | */ |
953 | ep_rbtree_insert(ep, epi); |
954 | |
955 | /* We have to drop the new item inside our item list to keep track of it */ |
956 | spin_lock_irqsave(&ep->lock, flags); |
957 | |
958 | /* If the file is already "ready" we drop it inside the ready list */ |
959 | if ((revents & event->events) && !ep_is_linked(&epi->rdllink)) { |
960 | list_add_tail(&epi->rdllink, &ep->rdllist); |
961 | |
962 | /* Notify waiting tasks that events are available */ |
963 | if (waitqueue_active(&ep->wq)) |
964 | wake_up_locked(&ep->wq); |
965 | if (waitqueue_active(&ep->poll_wait)) |
966 | pwake++; |
967 | } |
968 | |
969 | spin_unlock_irqrestore(&ep->lock, flags); |
970 | |
971 | atomic_inc(&ep->user->epoll_watches); |
972 | |
973 | /* We have to call this outside the lock */ |
974 | if (pwake) |
975 | ep_poll_safewake(&ep->poll_wait); |
976 | |
977 | return 0; |
978 | |
979 | error_unregister: |
980 | ep_unregister_pollwait(ep, epi); |
981 | |
982 | /* |
983 | * We need to do this because an event could have been arrived on some |
984 | * allocated wait queue. Note that we don't care about the ep->ovflist |
985 | * list, since that is used/cleaned only inside a section bound by "mtx". |
986 | * And ep_insert() is called with "mtx" held. |
987 | */ |
988 | spin_lock_irqsave(&ep->lock, flags); |
989 | if (ep_is_linked(&epi->rdllink)) |
990 | list_del_init(&epi->rdllink); |
991 | spin_unlock_irqrestore(&ep->lock, flags); |
992 | |
993 | kmem_cache_free(epi_cache, epi); |
994 | |
995 | return error; |
996 | } |
997 | |
998 | /* |
999 | * Modify the interest event mask by dropping an event if the new mask |
1000 | * has a match in the current file status. Must be called with "mtx" held. |
1001 | */ |
1002 | static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_event *event) |
1003 | { |
1004 | int pwake = 0; |
1005 | unsigned int revents; |
1006 | |
1007 | /* |
1008 | * Set the new event interest mask before calling f_op->poll(); |
1009 | * otherwise we might miss an event that happens between the |
1010 | * f_op->poll() call and the new event set registering. |
1011 | */ |
1012 | epi->event.events = event->events; |
1013 | epi->event.data = event->data; /* protected by mtx */ |
1014 | |
1015 | /* |
1016 | * Get current event bits. We can safely use the file* here because |
1017 | * its usage count has been increased by the caller of this function. |
1018 | */ |
1019 | revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL); |
1020 | |
1021 | /* |
1022 | * If the item is "hot" and it is not registered inside the ready |
1023 | * list, push it inside. |
1024 | */ |
1025 | if (revents & event->events) { |
1026 | spin_lock_irq(&ep->lock); |
1027 | if (!ep_is_linked(&epi->rdllink)) { |
1028 | list_add_tail(&epi->rdllink, &ep->rdllist); |
1029 | |
1030 | /* Notify waiting tasks that events are available */ |
1031 | if (waitqueue_active(&ep->wq)) |
1032 | wake_up_locked(&ep->wq); |
1033 | if (waitqueue_active(&ep->poll_wait)) |
1034 | pwake++; |
1035 | } |
1036 | spin_unlock_irq(&ep->lock); |
1037 | } |
1038 | |
1039 | /* We have to call this outside the lock */ |
1040 | if (pwake) |
1041 | ep_poll_safewake(&ep->poll_wait); |
1042 | |
1043 | return 0; |
1044 | } |
1045 | |
1046 | static int ep_send_events_proc(struct eventpoll *ep, struct list_head *head, |
1047 | void *priv) |
1048 | { |
1049 | struct ep_send_events_data *esed = priv; |
1050 | int eventcnt; |
1051 | unsigned int revents; |
1052 | struct epitem *epi; |
1053 | struct epoll_event __user *uevent; |
1054 | |
1055 | /* |
1056 | * We can loop without lock because we are passed a task private list. |
1057 | * Items cannot vanish during the loop because ep_scan_ready_list() is |
1058 | * holding "mtx" during this call. |
1059 | */ |
1060 | for (eventcnt = 0, uevent = esed->events; |
1061 | !list_empty(head) && eventcnt < esed->maxevents;) { |
1062 | epi = list_first_entry(head, struct epitem, rdllink); |
1063 | |
1064 | list_del_init(&epi->rdllink); |
1065 | |
1066 | revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL) & |
1067 | epi->event.events; |
1068 | |
1069 | /* |
1070 | * If the event mask intersect the caller-requested one, |
1071 | * deliver the event to userspace. Again, ep_scan_ready_list() |
1072 | * is holding "mtx", so no operations coming from userspace |
1073 | * can change the item. |
1074 | */ |
1075 | if (revents) { |
1076 | if (__put_user(revents, &uevent->events) || |
1077 | __put_user(epi->event.data, &uevent->data)) { |
1078 | list_add(&epi->rdllink, head); |
1079 | return eventcnt ? eventcnt : -EFAULT; |
1080 | } |
1081 | eventcnt++; |
1082 | uevent++; |
1083 | if (epi->event.events & EPOLLONESHOT) |
1084 | epi->event.events &= EP_PRIVATE_BITS; |
1085 | else if (!(epi->event.events & EPOLLET)) { |
1086 | /* |
1087 | * If this file has been added with Level |
1088 | * Trigger mode, we need to insert back inside |
1089 | * the ready list, so that the next call to |
1090 | * epoll_wait() will check again the events |
1091 | * availability. At this point, noone can insert |
1092 | * into ep->rdllist besides us. The epoll_ctl() |
1093 | * callers are locked out by |
1094 | * ep_scan_ready_list() holding "mtx" and the |
1095 | * poll callback will queue them in ep->ovflist. |
1096 | */ |
1097 | list_add_tail(&epi->rdllink, &ep->rdllist); |
1098 | } |
1099 | } |
1100 | } |
1101 | |
1102 | return eventcnt; |
1103 | } |
1104 | |
1105 | static int ep_send_events(struct eventpoll *ep, |
1106 | struct epoll_event __user *events, int maxevents) |
1107 | { |
1108 | struct ep_send_events_data esed; |
1109 | |
1110 | esed.maxevents = maxevents; |
1111 | esed.events = events; |
1112 | |
1113 | return ep_scan_ready_list(ep, ep_send_events_proc, &esed); |
1114 | } |
1115 | |
1116 | static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, |
1117 | int maxevents, long timeout) |
1118 | { |
1119 | int res, eavail; |
1120 | unsigned long flags; |
1121 | long jtimeout; |
1122 | wait_queue_t wait; |
1123 | |
1124 | /* |
1125 | * Calculate the timeout by checking for the "infinite" value (-1) |
1126 | * and the overflow condition. The passed timeout is in milliseconds, |
1127 | * that why (t * HZ) / 1000. |
1128 | */ |
1129 | jtimeout = (timeout < 0 || timeout >= EP_MAX_MSTIMEO) ? |
1130 | MAX_SCHEDULE_TIMEOUT : (timeout * HZ + 999) / 1000; |
1131 | |
1132 | retry: |
1133 | spin_lock_irqsave(&ep->lock, flags); |
1134 | |
1135 | res = 0; |
1136 | if (list_empty(&ep->rdllist)) { |
1137 | /* |
1138 | * We don't have any available event to return to the caller. |
1139 | * We need to sleep here, and we will be wake up by |
1140 | * ep_poll_callback() when events will become available. |
1141 | */ |
1142 | init_waitqueue_entry(&wait, current); |
1143 | wait.flags |= WQ_FLAG_EXCLUSIVE; |
1144 | __add_wait_queue(&ep->wq, &wait); |
1145 | |
1146 | for (;;) { |
1147 | /* |
1148 | * We don't want to sleep if the ep_poll_callback() sends us |
1149 | * a wakeup in between. That's why we set the task state |
1150 | * to TASK_INTERRUPTIBLE before doing the checks. |
1151 | */ |
1152 | set_current_state(TASK_INTERRUPTIBLE); |
1153 | if (!list_empty(&ep->rdllist) || !jtimeout) |
1154 | break; |
1155 | if (signal_pending(current)) { |
1156 | res = -EINTR; |
1157 | break; |
1158 | } |
1159 | |
1160 | spin_unlock_irqrestore(&ep->lock, flags); |
1161 | jtimeout = schedule_timeout(jtimeout); |
1162 | spin_lock_irqsave(&ep->lock, flags); |
1163 | } |
1164 | __remove_wait_queue(&ep->wq, &wait); |
1165 | |
1166 | set_current_state(TASK_RUNNING); |
1167 | } |
1168 | /* Is it worth to try to dig for events ? */ |
1169 | eavail = !list_empty(&ep->rdllist) || ep->ovflist != EP_UNACTIVE_PTR; |
1170 | |
1171 | spin_unlock_irqrestore(&ep->lock, flags); |
1172 | |
1173 | /* |
1174 | * Try to transfer events to user space. In case we get 0 events and |
1175 | * there's still timeout left over, we go trying again in search of |
1176 | * more luck. |
1177 | */ |
1178 | if (!res && eavail && |
1179 | !(res = ep_send_events(ep, events, maxevents)) && jtimeout) |
1180 | goto retry; |
1181 | |
1182 | return res; |
1183 | } |
1184 | |
1185 | /* |
1186 | * Open an eventpoll file descriptor. |
1187 | */ |
1188 | SYSCALL_DEFINE1(epoll_create1, int, flags) |
1189 | { |
1190 | int error; |
1191 | struct eventpoll *ep = NULL; |
1192 | |
1193 | /* Check the EPOLL_* constant for consistency. */ |
1194 | BUILD_BUG_ON(EPOLL_CLOEXEC != O_CLOEXEC); |
1195 | |
1196 | if (flags & ~EPOLL_CLOEXEC) |
1197 | return -EINVAL; |
1198 | /* |
1199 | * Create the internal data structure ("struct eventpoll"). |
1200 | */ |
1201 | error = ep_alloc(&ep); |
1202 | if (error < 0) |
1203 | return error; |
1204 | /* |
1205 | * Creates all the items needed to setup an eventpoll file. That is, |
1206 | * a file structure and a free file descriptor. |
1207 | */ |
1208 | error = anon_inode_getfd("[eventpoll]", &eventpoll_fops, ep, |
1209 | flags & O_CLOEXEC); |
1210 | if (error < 0) |
1211 | ep_free(ep); |
1212 | |
1213 | return error; |
1214 | } |
1215 | |
1216 | SYSCALL_DEFINE1(epoll_create, int, size) |
1217 | { |
1218 | if (size <= 0) |
1219 | return -EINVAL; |
1220 | |
1221 | return sys_epoll_create1(0); |
1222 | } |
1223 | |
1224 | /* |
1225 | * The following function implements the controller interface for |
1226 | * the eventpoll file that enables the insertion/removal/change of |
1227 | * file descriptors inside the interest set. |
1228 | */ |
1229 | SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd, |
1230 | struct epoll_event __user *, event) |
1231 | { |
1232 | int error; |
1233 | struct file *file, *tfile; |
1234 | struct eventpoll *ep; |
1235 | struct epitem *epi; |
1236 | struct epoll_event epds; |
1237 | |
1238 | error = -EFAULT; |
1239 | if (ep_op_has_event(op) && |
1240 | copy_from_user(&epds, event, sizeof(struct epoll_event))) |
1241 | goto error_return; |
1242 | |
1243 | /* Get the "struct file *" for the eventpoll file */ |
1244 | error = -EBADF; |
1245 | file = fget(epfd); |
1246 | if (!file) |
1247 | goto error_return; |
1248 | |
1249 | /* Get the "struct file *" for the target file */ |
1250 | tfile = fget(fd); |
1251 | if (!tfile) |
1252 | goto error_fput; |
1253 | |
1254 | /* The target file descriptor must support poll */ |
1255 | error = -EPERM; |
1256 | if (!tfile->f_op || !tfile->f_op->poll) |
1257 | goto error_tgt_fput; |
1258 | |
1259 | /* |
1260 | * We have to check that the file structure underneath the file descriptor |
1261 | * the user passed to us _is_ an eventpoll file. And also we do not permit |
1262 | * adding an epoll file descriptor inside itself. |
1263 | */ |
1264 | error = -EINVAL; |
1265 | if (file == tfile || !is_file_epoll(file)) |
1266 | goto error_tgt_fput; |
1267 | |
1268 | /* |
1269 | * At this point it is safe to assume that the "private_data" contains |
1270 | * our own data structure. |
1271 | */ |
1272 | ep = file->private_data; |
1273 | |
1274 | mutex_lock(&ep->mtx); |
1275 | |
1276 | /* |
1277 | * Try to lookup the file inside our RB tree, Since we grabbed "mtx" |
1278 | * above, we can be sure to be able to use the item looked up by |
1279 | * ep_find() till we release the mutex. |
1280 | */ |
1281 | epi = ep_find(ep, tfile, fd); |
1282 | |
1283 | error = -EINVAL; |
1284 | switch (op) { |
1285 | case EPOLL_CTL_ADD: |
1286 | if (!epi) { |
1287 | epds.events |= POLLERR | POLLHUP; |
1288 | error = ep_insert(ep, &epds, tfile, fd); |
1289 | } else |
1290 | error = -EEXIST; |
1291 | break; |
1292 | case EPOLL_CTL_DEL: |
1293 | if (epi) |
1294 | error = ep_remove(ep, epi); |
1295 | else |
1296 | error = -ENOENT; |
1297 | break; |
1298 | case EPOLL_CTL_MOD: |
1299 | if (epi) { |
1300 | epds.events |= POLLERR | POLLHUP; |
1301 | error = ep_modify(ep, epi, &epds); |
1302 | } else |
1303 | error = -ENOENT; |
1304 | break; |
1305 | } |
1306 | mutex_unlock(&ep->mtx); |
1307 | |
1308 | error_tgt_fput: |
1309 | fput(tfile); |
1310 | error_fput: |
1311 | fput(file); |
1312 | error_return: |
1313 | |
1314 | return error; |
1315 | } |
1316 | |
1317 | /* |
1318 | * Implement the event wait interface for the eventpoll file. It is the kernel |
1319 | * part of the user space epoll_wait(2). |
1320 | */ |
1321 | SYSCALL_DEFINE4(epoll_wait, int, epfd, struct epoll_event __user *, events, |
1322 | int, maxevents, int, timeout) |
1323 | { |
1324 | int error; |
1325 | struct file *file; |
1326 | struct eventpoll *ep; |
1327 | |
1328 | /* The maximum number of event must be greater than zero */ |
1329 | if (maxevents <= 0 || maxevents > EP_MAX_EVENTS) |
1330 | return -EINVAL; |
1331 | |
1332 | /* Verify that the area passed by the user is writeable */ |
1333 | if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event))) { |
1334 | error = -EFAULT; |
1335 | goto error_return; |
1336 | } |
1337 | |
1338 | /* Get the "struct file *" for the eventpoll file */ |
1339 | error = -EBADF; |
1340 | file = fget(epfd); |
1341 | if (!file) |
1342 | goto error_return; |
1343 | |
1344 | /* |
1345 | * We have to check that the file structure underneath the fd |
1346 | * the user passed to us _is_ an eventpoll file. |
1347 | */ |
1348 | error = -EINVAL; |
1349 | if (!is_file_epoll(file)) |
1350 | goto error_fput; |
1351 | |
1352 | /* |
1353 | * At this point it is safe to assume that the "private_data" contains |
1354 | * our own data structure. |
1355 | */ |
1356 | ep = file->private_data; |
1357 | |
1358 | /* Time to fish for events ... */ |
1359 | error = ep_poll(ep, events, maxevents, timeout); |
1360 | |
1361 | error_fput: |
1362 | fput(file); |
1363 | error_return: |
1364 | |
1365 | return error; |
1366 | } |
1367 | |
1368 | #ifdef HAVE_SET_RESTORE_SIGMASK |
1369 | |
1370 | /* |
1371 | * Implement the event wait interface for the eventpoll file. It is the kernel |
1372 | * part of the user space epoll_pwait(2). |
1373 | */ |
1374 | SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events, |
1375 | int, maxevents, int, timeout, const sigset_t __user *, sigmask, |
1376 | size_t, sigsetsize) |
1377 | { |
1378 | int error; |
1379 | sigset_t ksigmask, sigsaved; |
1380 | |
1381 | /* |
1382 | * If the caller wants a certain signal mask to be set during the wait, |
1383 | * we apply it here. |
1384 | */ |
1385 | if (sigmask) { |
1386 | if (sigsetsize != sizeof(sigset_t)) |
1387 | return -EINVAL; |
1388 | if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) |
1389 | return -EFAULT; |
1390 | sigdelsetmask(&ksigmask, sigmask(SIGKILL) | sigmask(SIGSTOP)); |
1391 | sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); |
1392 | } |
1393 | |
1394 | error = sys_epoll_wait(epfd, events, maxevents, timeout); |
1395 | |
1396 | /* |
1397 | * If we changed the signal mask, we need to restore the original one. |
1398 | * In case we've got a signal while waiting, we do not restore the |
1399 | * signal mask yet, and we allow do_signal() to deliver the signal on |
1400 | * the way back to userspace, before the signal mask is restored. |
1401 | */ |
1402 | if (sigmask) { |
1403 | if (error == -EINTR) { |
1404 | memcpy(¤t->saved_sigmask, &sigsaved, |
1405 | sizeof(sigsaved)); |
1406 | set_restore_sigmask(); |
1407 | } else |
1408 | sigprocmask(SIG_SETMASK, &sigsaved, NULL); |
1409 | } |
1410 | |
1411 | return error; |
1412 | } |
1413 | |
1414 | #endif /* HAVE_SET_RESTORE_SIGMASK */ |
1415 | |
1416 | static int __init eventpoll_init(void) |
1417 | { |
1418 | struct sysinfo si; |
1419 | |
1420 | si_meminfo(&si); |
1421 | /* |
1422 | * Allows top 4% of lomem to be allocated for epoll watches (per user). |
1423 | */ |
1424 | max_user_watches = (((si.totalram - si.totalhigh) / 25) << PAGE_SHIFT) / |
1425 | EP_ITEM_COST; |
1426 | |
1427 | /* Initialize the structure used to perform safe poll wait head wake ups */ |
1428 | ep_nested_calls_init(&poll_safewake_ncalls); |
1429 | |
1430 | /* Initialize the structure used to perform file's f_op->poll() calls */ |
1431 | ep_nested_calls_init(&poll_readywalk_ncalls); |
1432 | |
1433 | /* Allocates slab cache used to allocate "struct epitem" items */ |
1434 | epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem), |
1435 | 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); |
1436 | |
1437 | /* Allocates slab cache used to allocate "struct eppoll_entry" */ |
1438 | pwq_cache = kmem_cache_create("eventpoll_pwq", |
1439 | sizeof(struct eppoll_entry), 0, SLAB_PANIC, NULL); |
1440 | |
1441 | return 0; |
1442 | } |
1443 | fs_initcall(eventpoll_init); |
1444 |
Branches:
ben-wpan
ben-wpan-stefan
javiroman/ks7010
jz-2.6.34
jz-2.6.34-rc5
jz-2.6.34-rc6
jz-2.6.34-rc7
jz-2.6.35
jz-2.6.36
jz-2.6.37
jz-2.6.38
jz-2.6.39
jz-3.0
jz-3.1
jz-3.11
jz-3.12
jz-3.13
jz-3.15
jz-3.16
jz-3.18-dt
jz-3.2
jz-3.3
jz-3.4
jz-3.5
jz-3.6
jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master
Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9