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 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 rapresent the main data sructure for the eventpoll |
156 | * interface. |
157 | */ |
158 | struct eventpoll { |
159 | /* Protect the this structure access */ |
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 | * machanism. 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 trasfering 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 happens 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); |
1556 |
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