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Source at commit cdde9cf73945d547acd3e96f9508c79e84ad0bf1 created 12 years 9 months ago. By Maarten ter Huurne, MMC: JZ4740: Added support for CPU frequency changing | |
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1 | /* |
2 | * fs/eventpoll.c (Efficient event retrieval implementation) |
3 | * Copyright (C) 2001,...,2009 Davide Libenzi |
4 | * |
5 | * This program is free software; you can redistribute it and/or modify |
6 | * it under the terms of the GNU General Public License as published by |
7 | * the Free Software Foundation; either version 2 of the License, or |
8 | * (at your option) any later version. |
9 | * |
10 | * Davide Libenzi <davidel@xmailserver.org> |
11 | * |
12 | */ |
13 | |
14 | #include <linux/init.h> |
15 | #include <linux/kernel.h> |
16 | #include <linux/sched.h> |
17 | #include <linux/fs.h> |
18 | #include <linux/file.h> |
19 | #include <linux/signal.h> |
20 | #include <linux/errno.h> |
21 | #include <linux/mm.h> |
22 | #include <linux/slab.h> |
23 | #include <linux/poll.h> |
24 | #include <linux/string.h> |
25 | #include <linux/list.h> |
26 | #include <linux/hash.h> |
27 | #include <linux/spinlock.h> |
28 | #include <linux/syscalls.h> |
29 | #include <linux/rbtree.h> |
30 | #include <linux/wait.h> |
31 | #include <linux/eventpoll.h> |
32 | #include <linux/mount.h> |
33 | #include <linux/bitops.h> |
34 | #include <linux/mutex.h> |
35 | #include <linux/anon_inodes.h> |
36 | #include <linux/device.h> |
37 | #include <asm/uaccess.h> |
38 | #include <asm/io.h> |
39 | #include <asm/mman.h> |
40 | #include <linux/atomic.h> |
41 | |
42 | /* |
43 | * LOCKING: |
44 | * There are three level of locking required by epoll : |
45 | * |
46 | * 1) epmutex (mutex) |
47 | * 2) ep->mtx (mutex) |
48 | * 3) ep->lock (spinlock) |
49 | * |
50 | * The acquire order is the one listed above, from 1 to 3. |
51 | * We need a spinlock (ep->lock) because we manipulate objects |
52 | * from inside the poll callback, that might be triggered from |
53 | * a wake_up() that in turn might be called from IRQ context. |
54 | * So we can't sleep inside the poll callback and hence we need |
55 | * a spinlock. During the event transfer loop (from kernel to |
56 | * user space) we could end up sleeping due a copy_to_user(), so |
57 | * we need a lock that will allow us to sleep. This lock is a |
58 | * mutex (ep->mtx). It is acquired during the event transfer loop, |
59 | * during epoll_ctl(EPOLL_CTL_DEL) and during eventpoll_release_file(). |
60 | * Then we also need a global mutex to serialize eventpoll_release_file() |
61 | * and ep_free(). |
62 | * This mutex is acquired by ep_free() during the epoll file |
63 | * cleanup path and it is also acquired by eventpoll_release_file() |
64 | * if a file has been pushed inside an epoll set and it is then |
65 | * close()d without a previous call to epoll_ctl(EPOLL_CTL_DEL). |
66 | * It is also acquired when inserting an epoll fd onto another epoll |
67 | * fd. We do this so that we walk the epoll tree and ensure that this |
68 | * insertion does not create a cycle of epoll file descriptors, which |
69 | * could lead to deadlock. We need a global mutex to prevent two |
70 | * simultaneous inserts (A into B and B into A) from racing and |
71 | * constructing a cycle without either insert observing that it is |
72 | * going to. |
73 | * It is necessary to acquire multiple "ep->mtx"es at once in the |
74 | * case when one epoll fd is added to another. In this case, we |
75 | * always acquire the locks in the order of nesting (i.e. after |
76 | * epoll_ctl(e1, EPOLL_CTL_ADD, e2), e1->mtx will always be acquired |
77 | * before e2->mtx). Since we disallow cycles of epoll file |
78 | * descriptors, this ensures that the mutexes are well-ordered. In |
79 | * order to communicate this nesting to lockdep, when walking a tree |
80 | * of epoll file descriptors, we use the current recursion depth as |
81 | * the lockdep subkey. |
82 | * It is possible to drop the "ep->mtx" and to use the global |
83 | * mutex "epmutex" (together with "ep->lock") to have it working, |
84 | * but having "ep->mtx" will make the interface more scalable. |
85 | * Events that require holding "epmutex" are very rare, while for |
86 | * normal operations the epoll private "ep->mtx" will guarantee |
87 | * a better scalability. |
88 | */ |
89 | |
90 | /* Epoll private bits inside the event mask */ |
91 | #define EP_PRIVATE_BITS (EPOLLWAKEUP | EPOLLONESHOT | EPOLLET) |
92 | |
93 | /* Maximum number of nesting allowed inside epoll sets */ |
94 | #define EP_MAX_NESTS 4 |
95 | |
96 | #define EP_MAX_EVENTS (INT_MAX / sizeof(struct epoll_event)) |
97 | |
98 | #define EP_UNACTIVE_PTR ((void *) -1L) |
99 | |
100 | #define EP_ITEM_COST (sizeof(struct epitem) + sizeof(struct eppoll_entry)) |
101 | |
102 | struct epoll_filefd { |
103 | struct file *file; |
104 | int fd; |
105 | }; |
106 | |
107 | /* |
108 | * Structure used to track possible nested calls, for too deep recursions |
109 | * and loop cycles. |
110 | */ |
111 | struct nested_call_node { |
112 | struct list_head llink; |
113 | void *cookie; |
114 | void *ctx; |
115 | }; |
116 | |
117 | /* |
118 | * This structure is used as collector for nested calls, to check for |
119 | * maximum recursion dept and loop cycles. |
120 | */ |
121 | struct nested_calls { |
122 | struct list_head tasks_call_list; |
123 | spinlock_t lock; |
124 | }; |
125 | |
126 | /* |
127 | * Each file descriptor added to the eventpoll interface will |
128 | * have an entry of this type linked to the "rbr" RB tree. |
129 | */ |
130 | struct epitem { |
131 | /* RB tree node used to link this structure to the eventpoll RB tree */ |
132 | struct rb_node rbn; |
133 | |
134 | /* List header used to link this structure to the eventpoll ready list */ |
135 | struct list_head rdllink; |
136 | |
137 | /* |
138 | * Works together "struct eventpoll"->ovflist in keeping the |
139 | * single linked chain of items. |
140 | */ |
141 | struct epitem *next; |
142 | |
143 | /* The file descriptor information this item refers to */ |
144 | struct epoll_filefd ffd; |
145 | |
146 | /* Number of active wait queue attached to poll operations */ |
147 | int nwait; |
148 | |
149 | /* List containing poll wait queues */ |
150 | struct list_head pwqlist; |
151 | |
152 | /* The "container" of this item */ |
153 | struct eventpoll *ep; |
154 | |
155 | /* List header used to link this item to the "struct file" items list */ |
156 | struct list_head fllink; |
157 | |
158 | /* wakeup_source used when EPOLLWAKEUP is set */ |
159 | struct wakeup_source *ws; |
160 | |
161 | /* The structure that describe the interested events and the source fd */ |
162 | struct epoll_event event; |
163 | }; |
164 | |
165 | /* |
166 | * This structure is stored inside the "private_data" member of the file |
167 | * structure and represents the main data structure for the eventpoll |
168 | * interface. |
169 | */ |
170 | struct eventpoll { |
171 | /* Protect the access to this structure */ |
172 | spinlock_t lock; |
173 | |
174 | /* |
175 | * This mutex is used to ensure that files are not removed |
176 | * while epoll is using them. This is held during the event |
177 | * collection loop, the file cleanup path, the epoll file exit |
178 | * code and the ctl operations. |
179 | */ |
180 | struct mutex mtx; |
181 | |
182 | /* Wait queue used by sys_epoll_wait() */ |
183 | wait_queue_head_t wq; |
184 | |
185 | /* Wait queue used by file->poll() */ |
186 | wait_queue_head_t poll_wait; |
187 | |
188 | /* List of ready file descriptors */ |
189 | struct list_head rdllist; |
190 | |
191 | /* RB tree root used to store monitored fd structs */ |
192 | struct rb_root rbr; |
193 | |
194 | /* |
195 | * This is a single linked list that chains all the "struct epitem" that |
196 | * happened while transferring ready events to userspace w/out |
197 | * holding ->lock. |
198 | */ |
199 | struct epitem *ovflist; |
200 | |
201 | /* wakeup_source used when ep_scan_ready_list is running */ |
202 | struct wakeup_source *ws; |
203 | |
204 | /* The user that created the eventpoll descriptor */ |
205 | struct user_struct *user; |
206 | |
207 | struct file *file; |
208 | |
209 | /* used to optimize loop detection check */ |
210 | int visited; |
211 | struct list_head visited_list_link; |
212 | }; |
213 | |
214 | /* Wait structure used by the poll hooks */ |
215 | struct eppoll_entry { |
216 | /* List header used to link this structure to the "struct epitem" */ |
217 | struct list_head llink; |
218 | |
219 | /* The "base" pointer is set to the container "struct epitem" */ |
220 | struct epitem *base; |
221 | |
222 | /* |
223 | * Wait queue item that will be linked to the target file wait |
224 | * queue head. |
225 | */ |
226 | wait_queue_t wait; |
227 | |
228 | /* The wait queue head that linked the "wait" wait queue item */ |
229 | wait_queue_head_t *whead; |
230 | }; |
231 | |
232 | /* Wrapper struct used by poll queueing */ |
233 | struct ep_pqueue { |
234 | poll_table pt; |
235 | struct epitem *epi; |
236 | }; |
237 | |
238 | /* Used by the ep_send_events() function as callback private data */ |
239 | struct ep_send_events_data { |
240 | int maxevents; |
241 | struct epoll_event __user *events; |
242 | }; |
243 | |
244 | /* |
245 | * Configuration options available inside /proc/sys/fs/epoll/ |
246 | */ |
247 | /* Maximum number of epoll watched descriptors, per user */ |
248 | static long max_user_watches __read_mostly; |
249 | |
250 | /* |
251 | * This mutex is used to serialize ep_free() and eventpoll_release_file(). |
252 | */ |
253 | static DEFINE_MUTEX(epmutex); |
254 | |
255 | /* Used to check for epoll file descriptor inclusion loops */ |
256 | static struct nested_calls poll_loop_ncalls; |
257 | |
258 | /* Used for safe wake up implementation */ |
259 | static struct nested_calls poll_safewake_ncalls; |
260 | |
261 | /* Used to call file's f_op->poll() under the nested calls boundaries */ |
262 | static struct nested_calls poll_readywalk_ncalls; |
263 | |
264 | /* Slab cache used to allocate "struct epitem" */ |
265 | static struct kmem_cache *epi_cache __read_mostly; |
266 | |
267 | /* Slab cache used to allocate "struct eppoll_entry" */ |
268 | static struct kmem_cache *pwq_cache __read_mostly; |
269 | |
270 | /* Visited nodes during ep_loop_check(), so we can unset them when we finish */ |
271 | static LIST_HEAD(visited_list); |
272 | |
273 | /* |
274 | * List of files with newly added links, where we may need to limit the number |
275 | * of emanating paths. Protected by the epmutex. |
276 | */ |
277 | static LIST_HEAD(tfile_check_list); |
278 | |
279 | #ifdef CONFIG_SYSCTL |
280 | |
281 | #include <linux/sysctl.h> |
282 | |
283 | static long zero; |
284 | static long long_max = LONG_MAX; |
285 | |
286 | ctl_table epoll_table[] = { |
287 | { |
288 | .procname = "max_user_watches", |
289 | .data = &max_user_watches, |
290 | .maxlen = sizeof(max_user_watches), |
291 | .mode = 0644, |
292 | .proc_handler = proc_doulongvec_minmax, |
293 | .extra1 = &zero, |
294 | .extra2 = &long_max, |
295 | }, |
296 | { } |
297 | }; |
298 | #endif /* CONFIG_SYSCTL */ |
299 | |
300 | static const struct file_operations eventpoll_fops; |
301 | |
302 | static inline int is_file_epoll(struct file *f) |
303 | { |
304 | return f->f_op == &eventpoll_fops; |
305 | } |
306 | |
307 | /* Setup the structure that is used as key for the RB tree */ |
308 | static inline void ep_set_ffd(struct epoll_filefd *ffd, |
309 | struct file *file, int fd) |
310 | { |
311 | ffd->file = file; |
312 | ffd->fd = fd; |
313 | } |
314 | |
315 | /* Compare RB tree keys */ |
316 | static inline int ep_cmp_ffd(struct epoll_filefd *p1, |
317 | struct epoll_filefd *p2) |
318 | { |
319 | return (p1->file > p2->file ? +1: |
320 | (p1->file < p2->file ? -1 : p1->fd - p2->fd)); |
321 | } |
322 | |
323 | /* Tells us if the item is currently linked */ |
324 | static inline int ep_is_linked(struct list_head *p) |
325 | { |
326 | return !list_empty(p); |
327 | } |
328 | |
329 | static inline struct eppoll_entry *ep_pwq_from_wait(wait_queue_t *p) |
330 | { |
331 | return container_of(p, struct eppoll_entry, wait); |
332 | } |
333 | |
334 | /* Get the "struct epitem" from a wait queue pointer */ |
335 | static inline struct epitem *ep_item_from_wait(wait_queue_t *p) |
336 | { |
337 | return container_of(p, struct eppoll_entry, wait)->base; |
338 | } |
339 | |
340 | /* Get the "struct epitem" from an epoll queue wrapper */ |
341 | static inline struct epitem *ep_item_from_epqueue(poll_table *p) |
342 | { |
343 | return container_of(p, struct ep_pqueue, pt)->epi; |
344 | } |
345 | |
346 | /* Tells if the epoll_ctl(2) operation needs an event copy from userspace */ |
347 | static inline int ep_op_has_event(int op) |
348 | { |
349 | return op != EPOLL_CTL_DEL; |
350 | } |
351 | |
352 | /* Initialize the poll safe wake up structure */ |
353 | static void ep_nested_calls_init(struct nested_calls *ncalls) |
354 | { |
355 | INIT_LIST_HEAD(&ncalls->tasks_call_list); |
356 | spin_lock_init(&ncalls->lock); |
357 | } |
358 | |
359 | /** |
360 | * ep_events_available - Checks if ready events might be available. |
361 | * |
362 | * @ep: Pointer to the eventpoll context. |
363 | * |
364 | * Returns: Returns a value different than zero if ready events are available, |
365 | * or zero otherwise. |
366 | */ |
367 | static inline int ep_events_available(struct eventpoll *ep) |
368 | { |
369 | return !list_empty(&ep->rdllist) || ep->ovflist != EP_UNACTIVE_PTR; |
370 | } |
371 | |
372 | /** |
373 | * ep_call_nested - Perform a bound (possibly) nested call, by checking |
374 | * that the recursion limit is not exceeded, and that |
375 | * the same nested call (by the meaning of same cookie) is |
376 | * no re-entered. |
377 | * |
378 | * @ncalls: Pointer to the nested_calls structure to be used for this call. |
379 | * @max_nests: Maximum number of allowed nesting calls. |
380 | * @nproc: Nested call core function pointer. |
381 | * @priv: Opaque data to be passed to the @nproc callback. |
382 | * @cookie: Cookie to be used to identify this nested call. |
383 | * @ctx: This instance context. |
384 | * |
385 | * Returns: Returns the code returned by the @nproc callback, or -1 if |
386 | * the maximum recursion limit has been exceeded. |
387 | */ |
388 | static int ep_call_nested(struct nested_calls *ncalls, int max_nests, |
389 | int (*nproc)(void *, void *, int), void *priv, |
390 | void *cookie, void *ctx) |
391 | { |
392 | int error, call_nests = 0; |
393 | unsigned long flags; |
394 | struct list_head *lsthead = &ncalls->tasks_call_list; |
395 | struct nested_call_node *tncur; |
396 | struct nested_call_node tnode; |
397 | |
398 | spin_lock_irqsave(&ncalls->lock, flags); |
399 | |
400 | /* |
401 | * Try to see if the current task is already inside this wakeup call. |
402 | * We use a list here, since the population inside this set is always |
403 | * very much limited. |
404 | */ |
405 | list_for_each_entry(tncur, lsthead, llink) { |
406 | if (tncur->ctx == ctx && |
407 | (tncur->cookie == cookie || ++call_nests > max_nests)) { |
408 | /* |
409 | * Ops ... loop detected or maximum nest level reached. |
410 | * We abort this wake by breaking the cycle itself. |
411 | */ |
412 | error = -1; |
413 | goto out_unlock; |
414 | } |
415 | } |
416 | |
417 | /* Add the current task and cookie to the list */ |
418 | tnode.ctx = ctx; |
419 | tnode.cookie = cookie; |
420 | list_add(&tnode.llink, lsthead); |
421 | |
422 | spin_unlock_irqrestore(&ncalls->lock, flags); |
423 | |
424 | /* Call the nested function */ |
425 | error = (*nproc)(priv, cookie, call_nests); |
426 | |
427 | /* Remove the current task from the list */ |
428 | spin_lock_irqsave(&ncalls->lock, flags); |
429 | list_del(&tnode.llink); |
430 | out_unlock: |
431 | spin_unlock_irqrestore(&ncalls->lock, flags); |
432 | |
433 | return error; |
434 | } |
435 | |
436 | /* |
437 | * As described in commit 0ccf831cb lockdep: annotate epoll |
438 | * the use of wait queues used by epoll is done in a very controlled |
439 | * manner. Wake ups can nest inside each other, but are never done |
440 | * with the same locking. For example: |
441 | * |
442 | * dfd = socket(...); |
443 | * efd1 = epoll_create(); |
444 | * efd2 = epoll_create(); |
445 | * epoll_ctl(efd1, EPOLL_CTL_ADD, dfd, ...); |
446 | * epoll_ctl(efd2, EPOLL_CTL_ADD, efd1, ...); |
447 | * |
448 | * When a packet arrives to the device underneath "dfd", the net code will |
449 | * issue a wake_up() on its poll wake list. Epoll (efd1) has installed a |
450 | * callback wakeup entry on that queue, and the wake_up() performed by the |
451 | * "dfd" net code will end up in ep_poll_callback(). At this point epoll |
452 | * (efd1) notices that it may have some event ready, so it needs to wake up |
453 | * the waiters on its poll wait list (efd2). So it calls ep_poll_safewake() |
454 | * that ends up in another wake_up(), after having checked about the |
455 | * recursion constraints. That are, no more than EP_MAX_POLLWAKE_NESTS, to |
456 | * avoid stack blasting. |
457 | * |
458 | * When CONFIG_DEBUG_LOCK_ALLOC is enabled, make sure lockdep can handle |
459 | * this special case of epoll. |
460 | */ |
461 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
462 | static inline void ep_wake_up_nested(wait_queue_head_t *wqueue, |
463 | unsigned long events, int subclass) |
464 | { |
465 | unsigned long flags; |
466 | |
467 | spin_lock_irqsave_nested(&wqueue->lock, flags, subclass); |
468 | wake_up_locked_poll(wqueue, events); |
469 | spin_unlock_irqrestore(&wqueue->lock, flags); |
470 | } |
471 | #else |
472 | static inline void ep_wake_up_nested(wait_queue_head_t *wqueue, |
473 | unsigned long events, int subclass) |
474 | { |
475 | wake_up_poll(wqueue, events); |
476 | } |
477 | #endif |
478 | |
479 | static int ep_poll_wakeup_proc(void *priv, void *cookie, int call_nests) |
480 | { |
481 | ep_wake_up_nested((wait_queue_head_t *) cookie, POLLIN, |
482 | 1 + call_nests); |
483 | return 0; |
484 | } |
485 | |
486 | /* |
487 | * Perform a safe wake up of the poll wait list. The problem is that |
488 | * with the new callback'd wake up system, it is possible that the |
489 | * poll callback is reentered from inside the call to wake_up() done |
490 | * on the poll wait queue head. The rule is that we cannot reenter the |
491 | * wake up code from the same task more than EP_MAX_NESTS times, |
492 | * and we cannot reenter the same wait queue head at all. This will |
493 | * enable to have a hierarchy of epoll file descriptor of no more than |
494 | * EP_MAX_NESTS deep. |
495 | */ |
496 | static void ep_poll_safewake(wait_queue_head_t *wq) |
497 | { |
498 | int this_cpu = get_cpu(); |
499 | |
500 | ep_call_nested(&poll_safewake_ncalls, EP_MAX_NESTS, |
501 | ep_poll_wakeup_proc, NULL, wq, (void *) (long) this_cpu); |
502 | |
503 | put_cpu(); |
504 | } |
505 | |
506 | static void ep_remove_wait_queue(struct eppoll_entry *pwq) |
507 | { |
508 | wait_queue_head_t *whead; |
509 | |
510 | rcu_read_lock(); |
511 | /* If it is cleared by POLLFREE, it should be rcu-safe */ |
512 | whead = rcu_dereference(pwq->whead); |
513 | if (whead) |
514 | remove_wait_queue(whead, &pwq->wait); |
515 | rcu_read_unlock(); |
516 | } |
517 | |
518 | /* |
519 | * This function unregisters poll callbacks from the associated file |
520 | * descriptor. Must be called with "mtx" held (or "epmutex" if called from |
521 | * ep_free). |
522 | */ |
523 | static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi) |
524 | { |
525 | struct list_head *lsthead = &epi->pwqlist; |
526 | struct eppoll_entry *pwq; |
527 | |
528 | while (!list_empty(lsthead)) { |
529 | pwq = list_first_entry(lsthead, struct eppoll_entry, llink); |
530 | |
531 | list_del(&pwq->llink); |
532 | ep_remove_wait_queue(pwq); |
533 | kmem_cache_free(pwq_cache, pwq); |
534 | } |
535 | } |
536 | |
537 | /** |
538 | * ep_scan_ready_list - Scans the ready list in a way that makes possible for |
539 | * the scan code, to call f_op->poll(). Also allows for |
540 | * O(NumReady) performance. |
541 | * |
542 | * @ep: Pointer to the epoll private data structure. |
543 | * @sproc: Pointer to the scan callback. |
544 | * @priv: Private opaque data passed to the @sproc callback. |
545 | * @depth: The current depth of recursive f_op->poll calls. |
546 | * |
547 | * Returns: The same integer error code returned by the @sproc callback. |
548 | */ |
549 | static int ep_scan_ready_list(struct eventpoll *ep, |
550 | int (*sproc)(struct eventpoll *, |
551 | struct list_head *, void *), |
552 | void *priv, |
553 | int depth) |
554 | { |
555 | int error, pwake = 0; |
556 | unsigned long flags; |
557 | struct epitem *epi, *nepi; |
558 | LIST_HEAD(txlist); |
559 | |
560 | /* |
561 | * We need to lock this because we could be hit by |
562 | * eventpoll_release_file() and epoll_ctl(). |
563 | */ |
564 | mutex_lock_nested(&ep->mtx, depth); |
565 | |
566 | /* |
567 | * Steal the ready list, and re-init the original one to the |
568 | * empty list. Also, set ep->ovflist to NULL so that events |
569 | * happening while looping w/out locks, are not lost. We cannot |
570 | * have the poll callback to queue directly on ep->rdllist, |
571 | * because we want the "sproc" callback to be able to do it |
572 | * in a lockless way. |
573 | */ |
574 | spin_lock_irqsave(&ep->lock, flags); |
575 | list_splice_init(&ep->rdllist, &txlist); |
576 | ep->ovflist = NULL; |
577 | spin_unlock_irqrestore(&ep->lock, flags); |
578 | |
579 | /* |
580 | * Now call the callback function. |
581 | */ |
582 | error = (*sproc)(ep, &txlist, priv); |
583 | |
584 | spin_lock_irqsave(&ep->lock, flags); |
585 | /* |
586 | * During the time we spent inside the "sproc" callback, some |
587 | * other events might have been queued by the poll callback. |
588 | * We re-insert them inside the main ready-list here. |
589 | */ |
590 | for (nepi = ep->ovflist; (epi = nepi) != NULL; |
591 | nepi = epi->next, epi->next = EP_UNACTIVE_PTR) { |
592 | /* |
593 | * We need to check if the item is already in the list. |
594 | * During the "sproc" callback execution time, items are |
595 | * queued into ->ovflist but the "txlist" might already |
596 | * contain them, and the list_splice() below takes care of them. |
597 | */ |
598 | if (!ep_is_linked(&epi->rdllink)) { |
599 | list_add_tail(&epi->rdllink, &ep->rdllist); |
600 | __pm_stay_awake(epi->ws); |
601 | } |
602 | } |
603 | /* |
604 | * We need to set back ep->ovflist to EP_UNACTIVE_PTR, so that after |
605 | * releasing the lock, events will be queued in the normal way inside |
606 | * ep->rdllist. |
607 | */ |
608 | ep->ovflist = EP_UNACTIVE_PTR; |
609 | |
610 | /* |
611 | * Quickly re-inject items left on "txlist". |
612 | */ |
613 | list_splice(&txlist, &ep->rdllist); |
614 | __pm_relax(ep->ws); |
615 | |
616 | if (!list_empty(&ep->rdllist)) { |
617 | /* |
618 | * Wake up (if active) both the eventpoll wait list and |
619 | * the ->poll() wait list (delayed after we release the lock). |
620 | */ |
621 | if (waitqueue_active(&ep->wq)) |
622 | wake_up_locked(&ep->wq); |
623 | if (waitqueue_active(&ep->poll_wait)) |
624 | pwake++; |
625 | } |
626 | spin_unlock_irqrestore(&ep->lock, flags); |
627 | |
628 | mutex_unlock(&ep->mtx); |
629 | |
630 | /* We have to call this outside the lock */ |
631 | if (pwake) |
632 | ep_poll_safewake(&ep->poll_wait); |
633 | |
634 | return error; |
635 | } |
636 | |
637 | /* |
638 | * Removes a "struct epitem" from the eventpoll RB tree and deallocates |
639 | * all the associated resources. Must be called with "mtx" held. |
640 | */ |
641 | static int ep_remove(struct eventpoll *ep, struct epitem *epi) |
642 | { |
643 | unsigned long flags; |
644 | struct file *file = epi->ffd.file; |
645 | |
646 | /* |
647 | * Removes poll wait queue hooks. We _have_ to do this without holding |
648 | * the "ep->lock" otherwise a deadlock might occur. This because of the |
649 | * sequence of the lock acquisition. Here we do "ep->lock" then the wait |
650 | * queue head lock when unregistering the wait queue. The wakeup callback |
651 | * will run by holding the wait queue head lock and will call our callback |
652 | * that will try to get "ep->lock". |
653 | */ |
654 | ep_unregister_pollwait(ep, epi); |
655 | |
656 | /* Remove the current item from the list of epoll hooks */ |
657 | spin_lock(&file->f_lock); |
658 | if (ep_is_linked(&epi->fllink)) |
659 | list_del_init(&epi->fllink); |
660 | spin_unlock(&file->f_lock); |
661 | |
662 | rb_erase(&epi->rbn, &ep->rbr); |
663 | |
664 | spin_lock_irqsave(&ep->lock, flags); |
665 | if (ep_is_linked(&epi->rdllink)) |
666 | list_del_init(&epi->rdllink); |
667 | spin_unlock_irqrestore(&ep->lock, flags); |
668 | |
669 | wakeup_source_unregister(epi->ws); |
670 | |
671 | /* At this point it is safe to free the eventpoll item */ |
672 | kmem_cache_free(epi_cache, epi); |
673 | |
674 | atomic_long_dec(&ep->user->epoll_watches); |
675 | |
676 | return 0; |
677 | } |
678 | |
679 | static void ep_free(struct eventpoll *ep) |
680 | { |
681 | struct rb_node *rbp; |
682 | struct epitem *epi; |
683 | |
684 | /* We need to release all tasks waiting for these file */ |
685 | if (waitqueue_active(&ep->poll_wait)) |
686 | ep_poll_safewake(&ep->poll_wait); |
687 | |
688 | /* |
689 | * We need to lock this because we could be hit by |
690 | * eventpoll_release_file() while we're freeing the "struct eventpoll". |
691 | * We do not need to hold "ep->mtx" here because the epoll file |
692 | * is on the way to be removed and no one has references to it |
693 | * anymore. The only hit might come from eventpoll_release_file() but |
694 | * holding "epmutex" is sufficient here. |
695 | */ |
696 | mutex_lock(&epmutex); |
697 | |
698 | /* |
699 | * Walks through the whole tree by unregistering poll callbacks. |
700 | */ |
701 | for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { |
702 | epi = rb_entry(rbp, struct epitem, rbn); |
703 | |
704 | ep_unregister_pollwait(ep, epi); |
705 | } |
706 | |
707 | /* |
708 | * Walks through the whole tree by freeing each "struct epitem". At this |
709 | * point we are sure no poll callbacks will be lingering around, and also by |
710 | * holding "epmutex" we can be sure that no file cleanup code will hit |
711 | * us during this operation. So we can avoid the lock on "ep->lock". |
712 | */ |
713 | while ((rbp = rb_first(&ep->rbr)) != NULL) { |
714 | epi = rb_entry(rbp, struct epitem, rbn); |
715 | ep_remove(ep, epi); |
716 | } |
717 | |
718 | mutex_unlock(&epmutex); |
719 | mutex_destroy(&ep->mtx); |
720 | free_uid(ep->user); |
721 | wakeup_source_unregister(ep->ws); |
722 | kfree(ep); |
723 | } |
724 | |
725 | static int ep_eventpoll_release(struct inode *inode, struct file *file) |
726 | { |
727 | struct eventpoll *ep = file->private_data; |
728 | |
729 | if (ep) |
730 | ep_free(ep); |
731 | |
732 | return 0; |
733 | } |
734 | |
735 | static int ep_read_events_proc(struct eventpoll *ep, struct list_head *head, |
736 | void *priv) |
737 | { |
738 | struct epitem *epi, *tmp; |
739 | poll_table pt; |
740 | |
741 | init_poll_funcptr(&pt, NULL); |
742 | list_for_each_entry_safe(epi, tmp, head, rdllink) { |
743 | pt._key = epi->event.events; |
744 | if (epi->ffd.file->f_op->poll(epi->ffd.file, &pt) & |
745 | epi->event.events) |
746 | return POLLIN | POLLRDNORM; |
747 | else { |
748 | /* |
749 | * Item has been dropped into the ready list by the poll |
750 | * callback, but it's not actually ready, as far as |
751 | * caller requested events goes. We can remove it here. |
752 | */ |
753 | __pm_relax(epi->ws); |
754 | list_del_init(&epi->rdllink); |
755 | } |
756 | } |
757 | |
758 | return 0; |
759 | } |
760 | |
761 | static int ep_poll_readyevents_proc(void *priv, void *cookie, int call_nests) |
762 | { |
763 | return ep_scan_ready_list(priv, ep_read_events_proc, NULL, call_nests + 1); |
764 | } |
765 | |
766 | static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait) |
767 | { |
768 | int pollflags; |
769 | struct eventpoll *ep = file->private_data; |
770 | |
771 | /* Insert inside our poll wait queue */ |
772 | poll_wait(file, &ep->poll_wait, wait); |
773 | |
774 | /* |
775 | * Proceed to find out if wanted events are really available inside |
776 | * the ready list. This need to be done under ep_call_nested() |
777 | * supervision, since the call to f_op->poll() done on listed files |
778 | * could re-enter here. |
779 | */ |
780 | pollflags = ep_call_nested(&poll_readywalk_ncalls, EP_MAX_NESTS, |
781 | ep_poll_readyevents_proc, ep, ep, current); |
782 | |
783 | return pollflags != -1 ? pollflags : 0; |
784 | } |
785 | |
786 | /* File callbacks that implement the eventpoll file behaviour */ |
787 | static const struct file_operations eventpoll_fops = { |
788 | .release = ep_eventpoll_release, |
789 | .poll = ep_eventpoll_poll, |
790 | .llseek = noop_llseek, |
791 | }; |
792 | |
793 | /* |
794 | * This is called from eventpoll_release() to unlink files from the eventpoll |
795 | * interface. We need to have this facility to cleanup correctly files that are |
796 | * closed without being removed from the eventpoll interface. |
797 | */ |
798 | void eventpoll_release_file(struct file *file) |
799 | { |
800 | struct list_head *lsthead = &file->f_ep_links; |
801 | struct eventpoll *ep; |
802 | struct epitem *epi; |
803 | |
804 | /* |
805 | * We don't want to get "file->f_lock" because it is not |
806 | * necessary. It is not necessary because we're in the "struct file" |
807 | * cleanup path, and this means that no one is using this file anymore. |
808 | * So, for example, epoll_ctl() cannot hit here since if we reach this |
809 | * point, the file counter already went to zero and fget() would fail. |
810 | * The only hit might come from ep_free() but by holding the mutex |
811 | * will correctly serialize the operation. We do need to acquire |
812 | * "ep->mtx" after "epmutex" because ep_remove() requires it when called |
813 | * from anywhere but ep_free(). |
814 | * |
815 | * Besides, ep_remove() acquires the lock, so we can't hold it here. |
816 | */ |
817 | mutex_lock(&epmutex); |
818 | |
819 | while (!list_empty(lsthead)) { |
820 | epi = list_first_entry(lsthead, struct epitem, fllink); |
821 | |
822 | ep = epi->ep; |
823 | list_del_init(&epi->fllink); |
824 | mutex_lock_nested(&ep->mtx, 0); |
825 | ep_remove(ep, epi); |
826 | mutex_unlock(&ep->mtx); |
827 | } |
828 | |
829 | mutex_unlock(&epmutex); |
830 | } |
831 | |
832 | static int ep_alloc(struct eventpoll **pep) |
833 | { |
834 | int error; |
835 | struct user_struct *user; |
836 | struct eventpoll *ep; |
837 | |
838 | user = get_current_user(); |
839 | error = -ENOMEM; |
840 | ep = kzalloc(sizeof(*ep), GFP_KERNEL); |
841 | if (unlikely(!ep)) |
842 | goto free_uid; |
843 | |
844 | spin_lock_init(&ep->lock); |
845 | mutex_init(&ep->mtx); |
846 | init_waitqueue_head(&ep->wq); |
847 | init_waitqueue_head(&ep->poll_wait); |
848 | INIT_LIST_HEAD(&ep->rdllist); |
849 | ep->rbr = RB_ROOT; |
850 | ep->ovflist = EP_UNACTIVE_PTR; |
851 | ep->user = user; |
852 | |
853 | *pep = ep; |
854 | |
855 | return 0; |
856 | |
857 | free_uid: |
858 | free_uid(user); |
859 | return error; |
860 | } |
861 | |
862 | /* |
863 | * Search the file inside the eventpoll tree. The RB tree operations |
864 | * are protected by the "mtx" mutex, and ep_find() must be called with |
865 | * "mtx" held. |
866 | */ |
867 | static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd) |
868 | { |
869 | int kcmp; |
870 | struct rb_node *rbp; |
871 | struct epitem *epi, *epir = NULL; |
872 | struct epoll_filefd ffd; |
873 | |
874 | ep_set_ffd(&ffd, file, fd); |
875 | for (rbp = ep->rbr.rb_node; rbp; ) { |
876 | epi = rb_entry(rbp, struct epitem, rbn); |
877 | kcmp = ep_cmp_ffd(&ffd, &epi->ffd); |
878 | if (kcmp > 0) |
879 | rbp = rbp->rb_right; |
880 | else if (kcmp < 0) |
881 | rbp = rbp->rb_left; |
882 | else { |
883 | epir = epi; |
884 | break; |
885 | } |
886 | } |
887 | |
888 | return epir; |
889 | } |
890 | |
891 | /* |
892 | * This is the callback that is passed to the wait queue wakeup |
893 | * mechanism. It is called by the stored file descriptors when they |
894 | * have events to report. |
895 | */ |
896 | static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *key) |
897 | { |
898 | int pwake = 0; |
899 | unsigned long flags; |
900 | struct epitem *epi = ep_item_from_wait(wait); |
901 | struct eventpoll *ep = epi->ep; |
902 | |
903 | if ((unsigned long)key & POLLFREE) { |
904 | ep_pwq_from_wait(wait)->whead = NULL; |
905 | /* |
906 | * whead = NULL above can race with ep_remove_wait_queue() |
907 | * which can do another remove_wait_queue() after us, so we |
908 | * can't use __remove_wait_queue(). whead->lock is held by |
909 | * the caller. |
910 | */ |
911 | list_del_init(&wait->task_list); |
912 | } |
913 | |
914 | spin_lock_irqsave(&ep->lock, flags); |
915 | |
916 | /* |
917 | * If the event mask does not contain any poll(2) event, we consider the |
918 | * descriptor to be disabled. This condition is likely the effect of the |
919 | * EPOLLONESHOT bit that disables the descriptor when an event is received, |
920 | * until the next EPOLL_CTL_MOD will be issued. |
921 | */ |
922 | if (!(epi->event.events & ~EP_PRIVATE_BITS)) |
923 | goto out_unlock; |
924 | |
925 | /* |
926 | * Check the events coming with the callback. At this stage, not |
927 | * every device reports the events in the "key" parameter of the |
928 | * callback. We need to be able to handle both cases here, hence the |
929 | * test for "key" != NULL before the event match test. |
930 | */ |
931 | if (key && !((unsigned long) key & epi->event.events)) |
932 | goto out_unlock; |
933 | |
934 | /* |
935 | * If we are transferring events to userspace, we can hold no locks |
936 | * (because we're accessing user memory, and because of linux f_op->poll() |
937 | * semantics). All the events that happen during that period of time are |
938 | * chained in ep->ovflist and requeued later on. |
939 | */ |
940 | if (unlikely(ep->ovflist != EP_UNACTIVE_PTR)) { |
941 | if (epi->next == EP_UNACTIVE_PTR) { |
942 | epi->next = ep->ovflist; |
943 | ep->ovflist = epi; |
944 | if (epi->ws) { |
945 | /* |
946 | * Activate ep->ws since epi->ws may get |
947 | * deactivated at any time. |
948 | */ |
949 | __pm_stay_awake(ep->ws); |
950 | } |
951 | |
952 | } |
953 | goto out_unlock; |
954 | } |
955 | |
956 | /* If this file is already in the ready list we exit soon */ |
957 | if (!ep_is_linked(&epi->rdllink)) { |
958 | list_add_tail(&epi->rdllink, &ep->rdllist); |
959 | __pm_stay_awake(epi->ws); |
960 | } |
961 | |
962 | /* |
963 | * Wake up ( if active ) both the eventpoll wait list and the ->poll() |
964 | * wait list. |
965 | */ |
966 | if (waitqueue_active(&ep->wq)) |
967 | wake_up_locked(&ep->wq); |
968 | if (waitqueue_active(&ep->poll_wait)) |
969 | pwake++; |
970 | |
971 | out_unlock: |
972 | spin_unlock_irqrestore(&ep->lock, flags); |
973 | |
974 | /* We have to call this outside the lock */ |
975 | if (pwake) |
976 | ep_poll_safewake(&ep->poll_wait); |
977 | |
978 | return 1; |
979 | } |
980 | |
981 | /* |
982 | * This is the callback that is used to add our wait queue to the |
983 | * target file wakeup lists. |
984 | */ |
985 | static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, |
986 | poll_table *pt) |
987 | { |
988 | struct epitem *epi = ep_item_from_epqueue(pt); |
989 | struct eppoll_entry *pwq; |
990 | |
991 | if (epi->nwait >= 0 && (pwq = kmem_cache_alloc(pwq_cache, GFP_KERNEL))) { |
992 | init_waitqueue_func_entry(&pwq->wait, ep_poll_callback); |
993 | pwq->whead = whead; |
994 | pwq->base = epi; |
995 | add_wait_queue(whead, &pwq->wait); |
996 | list_add_tail(&pwq->llink, &epi->pwqlist); |
997 | epi->nwait++; |
998 | } else { |
999 | /* We have to signal that an error occurred */ |
1000 | epi->nwait = -1; |
1001 | } |
1002 | } |
1003 | |
1004 | static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi) |
1005 | { |
1006 | int kcmp; |
1007 | struct rb_node **p = &ep->rbr.rb_node, *parent = NULL; |
1008 | struct epitem *epic; |
1009 | |
1010 | while (*p) { |
1011 | parent = *p; |
1012 | epic = rb_entry(parent, struct epitem, rbn); |
1013 | kcmp = ep_cmp_ffd(&epi->ffd, &epic->ffd); |
1014 | if (kcmp > 0) |
1015 | p = &parent->rb_right; |
1016 | else |
1017 | p = &parent->rb_left; |
1018 | } |
1019 | rb_link_node(&epi->rbn, parent, p); |
1020 | rb_insert_color(&epi->rbn, &ep->rbr); |
1021 | } |
1022 | |
1023 | |
1024 | |
1025 | #define PATH_ARR_SIZE 5 |
1026 | /* |
1027 | * These are the number paths of length 1 to 5, that we are allowing to emanate |
1028 | * from a single file of interest. For example, we allow 1000 paths of length |
1029 | * 1, to emanate from each file of interest. This essentially represents the |
1030 | * potential wakeup paths, which need to be limited in order to avoid massive |
1031 | * uncontrolled wakeup storms. The common use case should be a single ep which |
1032 | * is connected to n file sources. In this case each file source has 1 path |
1033 | * of length 1. Thus, the numbers below should be more than sufficient. These |
1034 | * path limits are enforced during an EPOLL_CTL_ADD operation, since a modify |
1035 | * and delete can't add additional paths. Protected by the epmutex. |
1036 | */ |
1037 | static const int path_limits[PATH_ARR_SIZE] = { 1000, 500, 100, 50, 10 }; |
1038 | static int path_count[PATH_ARR_SIZE]; |
1039 | |
1040 | static int path_count_inc(int nests) |
1041 | { |
1042 | /* Allow an arbitrary number of depth 1 paths */ |
1043 | if (nests == 0) |
1044 | return 0; |
1045 | |
1046 | if (++path_count[nests] > path_limits[nests]) |
1047 | return -1; |
1048 | return 0; |
1049 | } |
1050 | |
1051 | static void path_count_init(void) |
1052 | { |
1053 | int i; |
1054 | |
1055 | for (i = 0; i < PATH_ARR_SIZE; i++) |
1056 | path_count[i] = 0; |
1057 | } |
1058 | |
1059 | static int reverse_path_check_proc(void *priv, void *cookie, int call_nests) |
1060 | { |
1061 | int error = 0; |
1062 | struct file *file = priv; |
1063 | struct file *child_file; |
1064 | struct epitem *epi; |
1065 | |
1066 | list_for_each_entry(epi, &file->f_ep_links, fllink) { |
1067 | child_file = epi->ep->file; |
1068 | if (is_file_epoll(child_file)) { |
1069 | if (list_empty(&child_file->f_ep_links)) { |
1070 | if (path_count_inc(call_nests)) { |
1071 | error = -1; |
1072 | break; |
1073 | } |
1074 | } else { |
1075 | error = ep_call_nested(&poll_loop_ncalls, |
1076 | EP_MAX_NESTS, |
1077 | reverse_path_check_proc, |
1078 | child_file, child_file, |
1079 | current); |
1080 | } |
1081 | if (error != 0) |
1082 | break; |
1083 | } else { |
1084 | printk(KERN_ERR "reverse_path_check_proc: " |
1085 | "file is not an ep!\n"); |
1086 | } |
1087 | } |
1088 | return error; |
1089 | } |
1090 | |
1091 | /** |
1092 | * reverse_path_check - The tfile_check_list is list of file *, which have |
1093 | * links that are proposed to be newly added. We need to |
1094 | * make sure that those added links don't add too many |
1095 | * paths such that we will spend all our time waking up |
1096 | * eventpoll objects. |
1097 | * |
1098 | * Returns: Returns zero if the proposed links don't create too many paths, |
1099 | * -1 otherwise. |
1100 | */ |
1101 | static int reverse_path_check(void) |
1102 | { |
1103 | int error = 0; |
1104 | struct file *current_file; |
1105 | |
1106 | /* let's call this for all tfiles */ |
1107 | list_for_each_entry(current_file, &tfile_check_list, f_tfile_llink) { |
1108 | path_count_init(); |
1109 | error = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, |
1110 | reverse_path_check_proc, current_file, |
1111 | current_file, current); |
1112 | if (error) |
1113 | break; |
1114 | } |
1115 | return error; |
1116 | } |
1117 | |
1118 | static int ep_create_wakeup_source(struct epitem *epi) |
1119 | { |
1120 | const char *name; |
1121 | |
1122 | if (!epi->ep->ws) { |
1123 | epi->ep->ws = wakeup_source_register("eventpoll"); |
1124 | if (!epi->ep->ws) |
1125 | return -ENOMEM; |
1126 | } |
1127 | |
1128 | name = epi->ffd.file->f_path.dentry->d_name.name; |
1129 | epi->ws = wakeup_source_register(name); |
1130 | if (!epi->ws) |
1131 | return -ENOMEM; |
1132 | |
1133 | return 0; |
1134 | } |
1135 | |
1136 | static void ep_destroy_wakeup_source(struct epitem *epi) |
1137 | { |
1138 | wakeup_source_unregister(epi->ws); |
1139 | epi->ws = NULL; |
1140 | } |
1141 | |
1142 | /* |
1143 | * Must be called with "mtx" held. |
1144 | */ |
1145 | static int ep_insert(struct eventpoll *ep, struct epoll_event *event, |
1146 | struct file *tfile, int fd) |
1147 | { |
1148 | int error, revents, pwake = 0; |
1149 | unsigned long flags; |
1150 | long user_watches; |
1151 | struct epitem *epi; |
1152 | struct ep_pqueue epq; |
1153 | |
1154 | user_watches = atomic_long_read(&ep->user->epoll_watches); |
1155 | if (unlikely(user_watches >= max_user_watches)) |
1156 | return -ENOSPC; |
1157 | if (!(epi = kmem_cache_alloc(epi_cache, GFP_KERNEL))) |
1158 | return -ENOMEM; |
1159 | |
1160 | /* Item initialization follow here ... */ |
1161 | INIT_LIST_HEAD(&epi->rdllink); |
1162 | INIT_LIST_HEAD(&epi->fllink); |
1163 | INIT_LIST_HEAD(&epi->pwqlist); |
1164 | epi->ep = ep; |
1165 | ep_set_ffd(&epi->ffd, tfile, fd); |
1166 | epi->event = *event; |
1167 | epi->nwait = 0; |
1168 | epi->next = EP_UNACTIVE_PTR; |
1169 | if (epi->event.events & EPOLLWAKEUP) { |
1170 | error = ep_create_wakeup_source(epi); |
1171 | if (error) |
1172 | goto error_create_wakeup_source; |
1173 | } else { |
1174 | epi->ws = NULL; |
1175 | } |
1176 | |
1177 | /* Initialize the poll table using the queue callback */ |
1178 | epq.epi = epi; |
1179 | init_poll_funcptr(&epq.pt, ep_ptable_queue_proc); |
1180 | epq.pt._key = event->events; |
1181 | |
1182 | /* |
1183 | * Attach the item to the poll hooks and get current event bits. |
1184 | * We can safely use the file* here because its usage count has |
1185 | * been increased by the caller of this function. Note that after |
1186 | * this operation completes, the poll callback can start hitting |
1187 | * the new item. |
1188 | */ |
1189 | revents = tfile->f_op->poll(tfile, &epq.pt); |
1190 | |
1191 | /* |
1192 | * We have to check if something went wrong during the poll wait queue |
1193 | * install process. Namely an allocation for a wait queue failed due |
1194 | * high memory pressure. |
1195 | */ |
1196 | error = -ENOMEM; |
1197 | if (epi->nwait < 0) |
1198 | goto error_unregister; |
1199 | |
1200 | /* Add the current item to the list of active epoll hook for this file */ |
1201 | spin_lock(&tfile->f_lock); |
1202 | list_add_tail(&epi->fllink, &tfile->f_ep_links); |
1203 | spin_unlock(&tfile->f_lock); |
1204 | |
1205 | /* |
1206 | * Add the current item to the RB tree. All RB tree operations are |
1207 | * protected by "mtx", and ep_insert() is called with "mtx" held. |
1208 | */ |
1209 | ep_rbtree_insert(ep, epi); |
1210 | |
1211 | /* now check if we've created too many backpaths */ |
1212 | error = -EINVAL; |
1213 | if (reverse_path_check()) |
1214 | goto error_remove_epi; |
1215 | |
1216 | /* We have to drop the new item inside our item list to keep track of it */ |
1217 | spin_lock_irqsave(&ep->lock, flags); |
1218 | |
1219 | /* If the file is already "ready" we drop it inside the ready list */ |
1220 | if ((revents & event->events) && !ep_is_linked(&epi->rdllink)) { |
1221 | list_add_tail(&epi->rdllink, &ep->rdllist); |
1222 | __pm_stay_awake(epi->ws); |
1223 | |
1224 | /* Notify waiting tasks that events are available */ |
1225 | if (waitqueue_active(&ep->wq)) |
1226 | wake_up_locked(&ep->wq); |
1227 | if (waitqueue_active(&ep->poll_wait)) |
1228 | pwake++; |
1229 | } |
1230 | |
1231 | spin_unlock_irqrestore(&ep->lock, flags); |
1232 | |
1233 | atomic_long_inc(&ep->user->epoll_watches); |
1234 | |
1235 | /* We have to call this outside the lock */ |
1236 | if (pwake) |
1237 | ep_poll_safewake(&ep->poll_wait); |
1238 | |
1239 | return 0; |
1240 | |
1241 | error_remove_epi: |
1242 | spin_lock(&tfile->f_lock); |
1243 | if (ep_is_linked(&epi->fllink)) |
1244 | list_del_init(&epi->fllink); |
1245 | spin_unlock(&tfile->f_lock); |
1246 | |
1247 | rb_erase(&epi->rbn, &ep->rbr); |
1248 | |
1249 | error_unregister: |
1250 | ep_unregister_pollwait(ep, epi); |
1251 | |
1252 | /* |
1253 | * We need to do this because an event could have been arrived on some |
1254 | * allocated wait queue. Note that we don't care about the ep->ovflist |
1255 | * list, since that is used/cleaned only inside a section bound by "mtx". |
1256 | * And ep_insert() is called with "mtx" held. |
1257 | */ |
1258 | spin_lock_irqsave(&ep->lock, flags); |
1259 | if (ep_is_linked(&epi->rdllink)) |
1260 | list_del_init(&epi->rdllink); |
1261 | spin_unlock_irqrestore(&ep->lock, flags); |
1262 | |
1263 | wakeup_source_unregister(epi->ws); |
1264 | |
1265 | error_create_wakeup_source: |
1266 | kmem_cache_free(epi_cache, epi); |
1267 | |
1268 | return error; |
1269 | } |
1270 | |
1271 | /* |
1272 | * Modify the interest event mask by dropping an event if the new mask |
1273 | * has a match in the current file status. Must be called with "mtx" held. |
1274 | */ |
1275 | static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_event *event) |
1276 | { |
1277 | int pwake = 0; |
1278 | unsigned int revents; |
1279 | poll_table pt; |
1280 | |
1281 | init_poll_funcptr(&pt, NULL); |
1282 | |
1283 | /* |
1284 | * Set the new event interest mask before calling f_op->poll(); |
1285 | * otherwise we might miss an event that happens between the |
1286 | * f_op->poll() call and the new event set registering. |
1287 | */ |
1288 | epi->event.events = event->events; |
1289 | pt._key = event->events; |
1290 | epi->event.data = event->data; /* protected by mtx */ |
1291 | if (epi->event.events & EPOLLWAKEUP) { |
1292 | if (!epi->ws) |
1293 | ep_create_wakeup_source(epi); |
1294 | } else if (epi->ws) { |
1295 | ep_destroy_wakeup_source(epi); |
1296 | } |
1297 | |
1298 | /* |
1299 | * Get current event bits. We can safely use the file* here because |
1300 | * its usage count has been increased by the caller of this function. |
1301 | */ |
1302 | revents = epi->ffd.file->f_op->poll(epi->ffd.file, &pt); |
1303 | |
1304 | /* |
1305 | * If the item is "hot" and it is not registered inside the ready |
1306 | * list, push it inside. |
1307 | */ |
1308 | if (revents & event->events) { |
1309 | spin_lock_irq(&ep->lock); |
1310 | if (!ep_is_linked(&epi->rdllink)) { |
1311 | list_add_tail(&epi->rdllink, &ep->rdllist); |
1312 | __pm_stay_awake(epi->ws); |
1313 | |
1314 | /* Notify waiting tasks that events are available */ |
1315 | if (waitqueue_active(&ep->wq)) |
1316 | wake_up_locked(&ep->wq); |
1317 | if (waitqueue_active(&ep->poll_wait)) |
1318 | pwake++; |
1319 | } |
1320 | spin_unlock_irq(&ep->lock); |
1321 | } |
1322 | |
1323 | /* We have to call this outside the lock */ |
1324 | if (pwake) |
1325 | ep_poll_safewake(&ep->poll_wait); |
1326 | |
1327 | return 0; |
1328 | } |
1329 | |
1330 | static int ep_send_events_proc(struct eventpoll *ep, struct list_head *head, |
1331 | void *priv) |
1332 | { |
1333 | struct ep_send_events_data *esed = priv; |
1334 | int eventcnt; |
1335 | unsigned int revents; |
1336 | struct epitem *epi; |
1337 | struct epoll_event __user *uevent; |
1338 | poll_table pt; |
1339 | |
1340 | init_poll_funcptr(&pt, NULL); |
1341 | |
1342 | /* |
1343 | * We can loop without lock because we are passed a task private list. |
1344 | * Items cannot vanish during the loop because ep_scan_ready_list() is |
1345 | * holding "mtx" during this call. |
1346 | */ |
1347 | for (eventcnt = 0, uevent = esed->events; |
1348 | !list_empty(head) && eventcnt < esed->maxevents;) { |
1349 | epi = list_first_entry(head, struct epitem, rdllink); |
1350 | |
1351 | /* |
1352 | * Activate ep->ws before deactivating epi->ws to prevent |
1353 | * triggering auto-suspend here (in case we reactive epi->ws |
1354 | * below). |
1355 | * |
1356 | * This could be rearranged to delay the deactivation of epi->ws |
1357 | * instead, but then epi->ws would temporarily be out of sync |
1358 | * with ep_is_linked(). |
1359 | */ |
1360 | if (epi->ws && epi->ws->active) |
1361 | __pm_stay_awake(ep->ws); |
1362 | __pm_relax(epi->ws); |
1363 | list_del_init(&epi->rdllink); |
1364 | |
1365 | pt._key = epi->event.events; |
1366 | revents = epi->ffd.file->f_op->poll(epi->ffd.file, &pt) & |
1367 | epi->event.events; |
1368 | |
1369 | /* |
1370 | * If the event mask intersect the caller-requested one, |
1371 | * deliver the event to userspace. Again, ep_scan_ready_list() |
1372 | * is holding "mtx", so no operations coming from userspace |
1373 | * can change the item. |
1374 | */ |
1375 | if (revents) { |
1376 | if (__put_user(revents, &uevent->events) || |
1377 | __put_user(epi->event.data, &uevent->data)) { |
1378 | list_add(&epi->rdllink, head); |
1379 | __pm_stay_awake(epi->ws); |
1380 | return eventcnt ? eventcnt : -EFAULT; |
1381 | } |
1382 | eventcnt++; |
1383 | uevent++; |
1384 | if (epi->event.events & EPOLLONESHOT) |
1385 | epi->event.events &= EP_PRIVATE_BITS; |
1386 | else if (!(epi->event.events & EPOLLET)) { |
1387 | /* |
1388 | * If this file has been added with Level |
1389 | * Trigger mode, we need to insert back inside |
1390 | * the ready list, so that the next call to |
1391 | * epoll_wait() will check again the events |
1392 | * availability. At this point, no one can insert |
1393 | * into ep->rdllist besides us. The epoll_ctl() |
1394 | * callers are locked out by |
1395 | * ep_scan_ready_list() holding "mtx" and the |
1396 | * poll callback will queue them in ep->ovflist. |
1397 | */ |
1398 | list_add_tail(&epi->rdllink, &ep->rdllist); |
1399 | __pm_stay_awake(epi->ws); |
1400 | } |
1401 | } |
1402 | } |
1403 | |
1404 | return eventcnt; |
1405 | } |
1406 | |
1407 | static int ep_send_events(struct eventpoll *ep, |
1408 | struct epoll_event __user *events, int maxevents) |
1409 | { |
1410 | struct ep_send_events_data esed; |
1411 | |
1412 | esed.maxevents = maxevents; |
1413 | esed.events = events; |
1414 | |
1415 | return ep_scan_ready_list(ep, ep_send_events_proc, &esed, 0); |
1416 | } |
1417 | |
1418 | static inline struct timespec ep_set_mstimeout(long ms) |
1419 | { |
1420 | struct timespec now, ts = { |
1421 | .tv_sec = ms / MSEC_PER_SEC, |
1422 | .tv_nsec = NSEC_PER_MSEC * (ms % MSEC_PER_SEC), |
1423 | }; |
1424 | |
1425 | ktime_get_ts(&now); |
1426 | return timespec_add_safe(now, ts); |
1427 | } |
1428 | |
1429 | /** |
1430 | * ep_poll - Retrieves ready events, and delivers them to the caller supplied |
1431 | * event buffer. |
1432 | * |
1433 | * @ep: Pointer to the eventpoll context. |
1434 | * @events: Pointer to the userspace buffer where the ready events should be |
1435 | * stored. |
1436 | * @maxevents: Size (in terms of number of events) of the caller event buffer. |
1437 | * @timeout: Maximum timeout for the ready events fetch operation, in |
1438 | * milliseconds. If the @timeout is zero, the function will not block, |
1439 | * while if the @timeout is less than zero, the function will block |
1440 | * until at least one event has been retrieved (or an error |
1441 | * occurred). |
1442 | * |
1443 | * Returns: Returns the number of ready events which have been fetched, or an |
1444 | * error code, in case of error. |
1445 | */ |
1446 | static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, |
1447 | int maxevents, long timeout) |
1448 | { |
1449 | int res = 0, eavail, timed_out = 0; |
1450 | unsigned long flags; |
1451 | long slack = 0; |
1452 | wait_queue_t wait; |
1453 | ktime_t expires, *to = NULL; |
1454 | |
1455 | if (timeout > 0) { |
1456 | struct timespec end_time = ep_set_mstimeout(timeout); |
1457 | |
1458 | slack = select_estimate_accuracy(&end_time); |
1459 | to = &expires; |
1460 | *to = timespec_to_ktime(end_time); |
1461 | } else if (timeout == 0) { |
1462 | /* |
1463 | * Avoid the unnecessary trip to the wait queue loop, if the |
1464 | * caller specified a non blocking operation. |
1465 | */ |
1466 | timed_out = 1; |
1467 | spin_lock_irqsave(&ep->lock, flags); |
1468 | goto check_events; |
1469 | } |
1470 | |
1471 | fetch_events: |
1472 | spin_lock_irqsave(&ep->lock, flags); |
1473 | |
1474 | if (!ep_events_available(ep)) { |
1475 | /* |
1476 | * We don't have any available event to return to the caller. |
1477 | * We need to sleep here, and we will be wake up by |
1478 | * ep_poll_callback() when events will become available. |
1479 | */ |
1480 | init_waitqueue_entry(&wait, current); |
1481 | __add_wait_queue_exclusive(&ep->wq, &wait); |
1482 | |
1483 | for (;;) { |
1484 | /* |
1485 | * We don't want to sleep if the ep_poll_callback() sends us |
1486 | * a wakeup in between. That's why we set the task state |
1487 | * to TASK_INTERRUPTIBLE before doing the checks. |
1488 | */ |
1489 | set_current_state(TASK_INTERRUPTIBLE); |
1490 | if (ep_events_available(ep) || timed_out) |
1491 | break; |
1492 | if (signal_pending(current)) { |
1493 | res = -EINTR; |
1494 | break; |
1495 | } |
1496 | |
1497 | spin_unlock_irqrestore(&ep->lock, flags); |
1498 | if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS)) |
1499 | timed_out = 1; |
1500 | |
1501 | spin_lock_irqsave(&ep->lock, flags); |
1502 | } |
1503 | __remove_wait_queue(&ep->wq, &wait); |
1504 | |
1505 | set_current_state(TASK_RUNNING); |
1506 | } |
1507 | check_events: |
1508 | /* Is it worth to try to dig for events ? */ |
1509 | eavail = ep_events_available(ep); |
1510 | |
1511 | spin_unlock_irqrestore(&ep->lock, flags); |
1512 | |
1513 | /* |
1514 | * Try to transfer events to user space. In case we get 0 events and |
1515 | * there's still timeout left over, we go trying again in search of |
1516 | * more luck. |
1517 | */ |
1518 | if (!res && eavail && |
1519 | !(res = ep_send_events(ep, events, maxevents)) && !timed_out) |
1520 | goto fetch_events; |
1521 | |
1522 | return res; |
1523 | } |
1524 | |
1525 | /** |
1526 | * ep_loop_check_proc - Callback function to be passed to the @ep_call_nested() |
1527 | * API, to verify that adding an epoll file inside another |
1528 | * epoll structure, does not violate the constraints, in |
1529 | * terms of closed loops, or too deep chains (which can |
1530 | * result in excessive stack usage). |
1531 | * |
1532 | * @priv: Pointer to the epoll file to be currently checked. |
1533 | * @cookie: Original cookie for this call. This is the top-of-the-chain epoll |
1534 | * data structure pointer. |
1535 | * @call_nests: Current dept of the @ep_call_nested() call stack. |
1536 | * |
1537 | * Returns: Returns zero if adding the epoll @file inside current epoll |
1538 | * structure @ep does not violate the constraints, or -1 otherwise. |
1539 | */ |
1540 | static int ep_loop_check_proc(void *priv, void *cookie, int call_nests) |
1541 | { |
1542 | int error = 0; |
1543 | struct file *file = priv; |
1544 | struct eventpoll *ep = file->private_data; |
1545 | struct eventpoll *ep_tovisit; |
1546 | struct rb_node *rbp; |
1547 | struct epitem *epi; |
1548 | |
1549 | mutex_lock_nested(&ep->mtx, call_nests + 1); |
1550 | ep->visited = 1; |
1551 | list_add(&ep->visited_list_link, &visited_list); |
1552 | for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { |
1553 | epi = rb_entry(rbp, struct epitem, rbn); |
1554 | if (unlikely(is_file_epoll(epi->ffd.file))) { |
1555 | ep_tovisit = epi->ffd.file->private_data; |
1556 | if (ep_tovisit->visited) |
1557 | continue; |
1558 | error = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, |
1559 | ep_loop_check_proc, epi->ffd.file, |
1560 | ep_tovisit, current); |
1561 | if (error != 0) |
1562 | break; |
1563 | } else { |
1564 | /* |
1565 | * If we've reached a file that is not associated with |
1566 | * an ep, then we need to check if the newly added |
1567 | * links are going to add too many wakeup paths. We do |
1568 | * this by adding it to the tfile_check_list, if it's |
1569 | * not already there, and calling reverse_path_check() |
1570 | * during ep_insert(). |
1571 | */ |
1572 | if (list_empty(&epi->ffd.file->f_tfile_llink)) |
1573 | list_add(&epi->ffd.file->f_tfile_llink, |
1574 | &tfile_check_list); |
1575 | } |
1576 | } |
1577 | mutex_unlock(&ep->mtx); |
1578 | |
1579 | return error; |
1580 | } |
1581 | |
1582 | /** |
1583 | * ep_loop_check - Performs a check to verify that adding an epoll file (@file) |
1584 | * another epoll file (represented by @ep) does not create |
1585 | * closed loops or too deep chains. |
1586 | * |
1587 | * @ep: Pointer to the epoll private data structure. |
1588 | * @file: Pointer to the epoll file to be checked. |
1589 | * |
1590 | * Returns: Returns zero if adding the epoll @file inside current epoll |
1591 | * structure @ep does not violate the constraints, or -1 otherwise. |
1592 | */ |
1593 | static int ep_loop_check(struct eventpoll *ep, struct file *file) |
1594 | { |
1595 | int ret; |
1596 | struct eventpoll *ep_cur, *ep_next; |
1597 | |
1598 | ret = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, |
1599 | ep_loop_check_proc, file, ep, current); |
1600 | /* clear visited list */ |
1601 | list_for_each_entry_safe(ep_cur, ep_next, &visited_list, |
1602 | visited_list_link) { |
1603 | ep_cur->visited = 0; |
1604 | list_del(&ep_cur->visited_list_link); |
1605 | } |
1606 | return ret; |
1607 | } |
1608 | |
1609 | static void clear_tfile_check_list(void) |
1610 | { |
1611 | struct file *file; |
1612 | |
1613 | /* first clear the tfile_check_list */ |
1614 | while (!list_empty(&tfile_check_list)) { |
1615 | file = list_first_entry(&tfile_check_list, struct file, |
1616 | f_tfile_llink); |
1617 | list_del_init(&file->f_tfile_llink); |
1618 | } |
1619 | INIT_LIST_HEAD(&tfile_check_list); |
1620 | } |
1621 | |
1622 | /* |
1623 | * Open an eventpoll file descriptor. |
1624 | */ |
1625 | SYSCALL_DEFINE1(epoll_create1, int, flags) |
1626 | { |
1627 | int error, fd; |
1628 | struct eventpoll *ep = NULL; |
1629 | struct file *file; |
1630 | |
1631 | /* Check the EPOLL_* constant for consistency. */ |
1632 | BUILD_BUG_ON(EPOLL_CLOEXEC != O_CLOEXEC); |
1633 | |
1634 | if (flags & ~EPOLL_CLOEXEC) |
1635 | return -EINVAL; |
1636 | /* |
1637 | * Create the internal data structure ("struct eventpoll"). |
1638 | */ |
1639 | error = ep_alloc(&ep); |
1640 | if (error < 0) |
1641 | return error; |
1642 | /* |
1643 | * Creates all the items needed to setup an eventpoll file. That is, |
1644 | * a file structure and a free file descriptor. |
1645 | */ |
1646 | fd = get_unused_fd_flags(O_RDWR | (flags & O_CLOEXEC)); |
1647 | if (fd < 0) { |
1648 | error = fd; |
1649 | goto out_free_ep; |
1650 | } |
1651 | file = anon_inode_getfile("[eventpoll]", &eventpoll_fops, ep, |
1652 | O_RDWR | (flags & O_CLOEXEC)); |
1653 | if (IS_ERR(file)) { |
1654 | error = PTR_ERR(file); |
1655 | goto out_free_fd; |
1656 | } |
1657 | ep->file = file; |
1658 | fd_install(fd, file); |
1659 | return fd; |
1660 | |
1661 | out_free_fd: |
1662 | put_unused_fd(fd); |
1663 | out_free_ep: |
1664 | ep_free(ep); |
1665 | return error; |
1666 | } |
1667 | |
1668 | SYSCALL_DEFINE1(epoll_create, int, size) |
1669 | { |
1670 | if (size <= 0) |
1671 | return -EINVAL; |
1672 | |
1673 | return sys_epoll_create1(0); |
1674 | } |
1675 | |
1676 | /* |
1677 | * The following function implements the controller interface for |
1678 | * the eventpoll file that enables the insertion/removal/change of |
1679 | * file descriptors inside the interest set. |
1680 | */ |
1681 | SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd, |
1682 | struct epoll_event __user *, event) |
1683 | { |
1684 | int error; |
1685 | int did_lock_epmutex = 0; |
1686 | struct file *file, *tfile; |
1687 | struct eventpoll *ep; |
1688 | struct epitem *epi; |
1689 | struct epoll_event epds; |
1690 | |
1691 | error = -EFAULT; |
1692 | if (ep_op_has_event(op) && |
1693 | copy_from_user(&epds, event, sizeof(struct epoll_event))) |
1694 | goto error_return; |
1695 | |
1696 | /* Get the "struct file *" for the eventpoll file */ |
1697 | error = -EBADF; |
1698 | file = fget(epfd); |
1699 | if (!file) |
1700 | goto error_return; |
1701 | |
1702 | /* Get the "struct file *" for the target file */ |
1703 | tfile = fget(fd); |
1704 | if (!tfile) |
1705 | goto error_fput; |
1706 | |
1707 | /* The target file descriptor must support poll */ |
1708 | error = -EPERM; |
1709 | if (!tfile->f_op || !tfile->f_op->poll) |
1710 | goto error_tgt_fput; |
1711 | |
1712 | /* Check if EPOLLWAKEUP is allowed */ |
1713 | if ((epds.events & EPOLLWAKEUP) && !capable(CAP_BLOCK_SUSPEND)) |
1714 | epds.events &= ~EPOLLWAKEUP; |
1715 | |
1716 | /* |
1717 | * We have to check that the file structure underneath the file descriptor |
1718 | * the user passed to us _is_ an eventpoll file. And also we do not permit |
1719 | * adding an epoll file descriptor inside itself. |
1720 | */ |
1721 | error = -EINVAL; |
1722 | if (file == tfile || !is_file_epoll(file)) |
1723 | goto error_tgt_fput; |
1724 | |
1725 | /* |
1726 | * At this point it is safe to assume that the "private_data" contains |
1727 | * our own data structure. |
1728 | */ |
1729 | ep = file->private_data; |
1730 | |
1731 | /* |
1732 | * When we insert an epoll file descriptor, inside another epoll file |
1733 | * descriptor, there is the change of creating closed loops, which are |
1734 | * better be handled here, than in more critical paths. While we are |
1735 | * checking for loops we also determine the list of files reachable |
1736 | * and hang them on the tfile_check_list, so we can check that we |
1737 | * haven't created too many possible wakeup paths. |
1738 | * |
1739 | * We need to hold the epmutex across both ep_insert and ep_remove |
1740 | * b/c we want to make sure we are looking at a coherent view of |
1741 | * epoll network. |
1742 | */ |
1743 | if (op == EPOLL_CTL_ADD || op == EPOLL_CTL_DEL) { |
1744 | mutex_lock(&epmutex); |
1745 | did_lock_epmutex = 1; |
1746 | } |
1747 | if (op == EPOLL_CTL_ADD) { |
1748 | if (is_file_epoll(tfile)) { |
1749 | error = -ELOOP; |
1750 | if (ep_loop_check(ep, tfile) != 0) { |
1751 | clear_tfile_check_list(); |
1752 | goto error_tgt_fput; |
1753 | } |
1754 | } else |
1755 | list_add(&tfile->f_tfile_llink, &tfile_check_list); |
1756 | } |
1757 | |
1758 | mutex_lock_nested(&ep->mtx, 0); |
1759 | |
1760 | /* |
1761 | * Try to lookup the file inside our RB tree, Since we grabbed "mtx" |
1762 | * above, we can be sure to be able to use the item looked up by |
1763 | * ep_find() till we release the mutex. |
1764 | */ |
1765 | epi = ep_find(ep, tfile, fd); |
1766 | |
1767 | error = -EINVAL; |
1768 | switch (op) { |
1769 | case EPOLL_CTL_ADD: |
1770 | if (!epi) { |
1771 | epds.events |= POLLERR | POLLHUP; |
1772 | error = ep_insert(ep, &epds, tfile, fd); |
1773 | } else |
1774 | error = -EEXIST; |
1775 | clear_tfile_check_list(); |
1776 | break; |
1777 | case EPOLL_CTL_DEL: |
1778 | if (epi) |
1779 | error = ep_remove(ep, epi); |
1780 | else |
1781 | error = -ENOENT; |
1782 | break; |
1783 | case EPOLL_CTL_MOD: |
1784 | if (epi) { |
1785 | epds.events |= POLLERR | POLLHUP; |
1786 | error = ep_modify(ep, epi, &epds); |
1787 | } else |
1788 | error = -ENOENT; |
1789 | break; |
1790 | } |
1791 | mutex_unlock(&ep->mtx); |
1792 | |
1793 | error_tgt_fput: |
1794 | if (did_lock_epmutex) |
1795 | mutex_unlock(&epmutex); |
1796 | |
1797 | fput(tfile); |
1798 | error_fput: |
1799 | fput(file); |
1800 | error_return: |
1801 | |
1802 | return error; |
1803 | } |
1804 | |
1805 | /* |
1806 | * Implement the event wait interface for the eventpoll file. It is the kernel |
1807 | * part of the user space epoll_wait(2). |
1808 | */ |
1809 | SYSCALL_DEFINE4(epoll_wait, int, epfd, struct epoll_event __user *, events, |
1810 | int, maxevents, int, timeout) |
1811 | { |
1812 | int error; |
1813 | struct file *file; |
1814 | struct eventpoll *ep; |
1815 | |
1816 | /* The maximum number of event must be greater than zero */ |
1817 | if (maxevents <= 0 || maxevents > EP_MAX_EVENTS) |
1818 | return -EINVAL; |
1819 | |
1820 | /* Verify that the area passed by the user is writeable */ |
1821 | if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event))) { |
1822 | error = -EFAULT; |
1823 | goto error_return; |
1824 | } |
1825 | |
1826 | /* Get the "struct file *" for the eventpoll file */ |
1827 | error = -EBADF; |
1828 | file = fget(epfd); |
1829 | if (!file) |
1830 | goto error_return; |
1831 | |
1832 | /* |
1833 | * We have to check that the file structure underneath the fd |
1834 | * the user passed to us _is_ an eventpoll file. |
1835 | */ |
1836 | error = -EINVAL; |
1837 | if (!is_file_epoll(file)) |
1838 | goto error_fput; |
1839 | |
1840 | /* |
1841 | * At this point it is safe to assume that the "private_data" contains |
1842 | * our own data structure. |
1843 | */ |
1844 | ep = file->private_data; |
1845 | |
1846 | /* Time to fish for events ... */ |
1847 | error = ep_poll(ep, events, maxevents, timeout); |
1848 | |
1849 | error_fput: |
1850 | fput(file); |
1851 | error_return: |
1852 | |
1853 | return error; |
1854 | } |
1855 | |
1856 | /* |
1857 | * Implement the event wait interface for the eventpoll file. It is the kernel |
1858 | * part of the user space epoll_pwait(2). |
1859 | */ |
1860 | SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events, |
1861 | int, maxevents, int, timeout, const sigset_t __user *, sigmask, |
1862 | size_t, sigsetsize) |
1863 | { |
1864 | int error; |
1865 | sigset_t ksigmask, sigsaved; |
1866 | |
1867 | /* |
1868 | * If the caller wants a certain signal mask to be set during the wait, |
1869 | * we apply it here. |
1870 | */ |
1871 | if (sigmask) { |
1872 | if (sigsetsize != sizeof(sigset_t)) |
1873 | return -EINVAL; |
1874 | if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) |
1875 | return -EFAULT; |
1876 | sigdelsetmask(&ksigmask, sigmask(SIGKILL) | sigmask(SIGSTOP)); |
1877 | sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); |
1878 | } |
1879 | |
1880 | error = sys_epoll_wait(epfd, events, maxevents, timeout); |
1881 | |
1882 | /* |
1883 | * If we changed the signal mask, we need to restore the original one. |
1884 | * In case we've got a signal while waiting, we do not restore the |
1885 | * signal mask yet, and we allow do_signal() to deliver the signal on |
1886 | * the way back to userspace, before the signal mask is restored. |
1887 | */ |
1888 | if (sigmask) { |
1889 | if (error == -EINTR) { |
1890 | memcpy(¤t->saved_sigmask, &sigsaved, |
1891 | sizeof(sigsaved)); |
1892 | set_restore_sigmask(); |
1893 | } else |
1894 | sigprocmask(SIG_SETMASK, &sigsaved, NULL); |
1895 | } |
1896 | |
1897 | return error; |
1898 | } |
1899 | |
1900 | static int __init eventpoll_init(void) |
1901 | { |
1902 | struct sysinfo si; |
1903 | |
1904 | si_meminfo(&si); |
1905 | /* |
1906 | * Allows top 4% of lomem to be allocated for epoll watches (per user). |
1907 | */ |
1908 | max_user_watches = (((si.totalram - si.totalhigh) / 25) << PAGE_SHIFT) / |
1909 | EP_ITEM_COST; |
1910 | BUG_ON(max_user_watches < 0); |
1911 | |
1912 | /* |
1913 | * Initialize the structure used to perform epoll file descriptor |
1914 | * inclusion loops checks. |
1915 | */ |
1916 | ep_nested_calls_init(&poll_loop_ncalls); |
1917 | |
1918 | /* Initialize the structure used to perform safe poll wait head wake ups */ |
1919 | ep_nested_calls_init(&poll_safewake_ncalls); |
1920 | |
1921 | /* Initialize the structure used to perform file's f_op->poll() calls */ |
1922 | ep_nested_calls_init(&poll_readywalk_ncalls); |
1923 | |
1924 | /* Allocates slab cache used to allocate "struct epitem" items */ |
1925 | epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem), |
1926 | 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); |
1927 | |
1928 | /* Allocates slab cache used to allocate "struct eppoll_entry" */ |
1929 | pwq_cache = kmem_cache_create("eventpoll_pwq", |
1930 | sizeof(struct eppoll_entry), 0, SLAB_PANIC, NULL); |
1931 | |
1932 | return 0; |
1933 | } |
1934 | fs_initcall(eventpoll_init); |
1935 |
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