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1 | /* | |
2 | * fs/eventpoll.c (Efficent event polling implementation) | |
3 | * Copyright (C) 2001,...,2007 Davide Libenzi | |
4 | * | |
5 | * This program is free software; you can redistribute it and/or modify | |
6 | * it under the terms of the GNU General Public License as published by | |
7 | * the Free Software Foundation; either version 2 of the License, or | |
8 | * (at your option) any later version. | |
9 | * | |
10 | * Davide Libenzi <davidel@xmailserver.org> | |
11 | * | |
12 | */ | |
13 | ||
14 | #include <linux/init.h> | |
15 | #include <linux/kernel.h> | |
16 | #include <linux/sched.h> | |
17 | #include <linux/fs.h> | |
18 | #include <linux/file.h> | |
19 | #include <linux/signal.h> | |
20 | #include <linux/errno.h> | |
21 | #include <linux/mm.h> | |
22 | #include <linux/slab.h> | |
23 | #include <linux/poll.h> | |
24 | #include <linux/string.h> | |
25 | #include <linux/list.h> | |
26 | #include <linux/hash.h> | |
27 | #include <linux/spinlock.h> | |
28 | #include <linux/syscalls.h> | |
29 | #include <linux/rbtree.h> | |
30 | #include <linux/wait.h> | |
31 | #include <linux/eventpoll.h> | |
32 | #include <linux/mount.h> | |
33 | #include <linux/bitops.h> | |
34 | #include <linux/mutex.h> | |
35 | #include <linux/anon_inodes.h> | |
36 | #include <asm/uaccess.h> | |
37 | #include <asm/system.h> | |
38 | #include <asm/io.h> | |
39 | #include <asm/mman.h> | |
40 | #include <asm/atomic.h> | |
41 | ||
42 | /* | |
43 | * LOCKING: | |
44 | * There are three level of locking required by epoll : | |
45 | * | |
46 | * 1) epmutex (mutex) | |
47 | * 2) ep->mtx (mutex) | |
48 | * 3) ep->lock (spinlock) | |
49 | * | |
50 | * The acquire order is the one listed above, from 1 to 3. | |
51 | * We need a spinlock (ep->lock) because we manipulate objects | |
52 | * from inside the poll callback, that might be triggered from | |
53 | * a wake_up() that in turn might be called from IRQ context. | |
54 | * So we can't sleep inside the poll callback and hence we need | |
55 | * a spinlock. During the event transfer loop (from kernel to | |
56 | * user space) we could end up sleeping due a copy_to_user(), so | |
57 | * we need a lock that will allow us to sleep. This lock is a | |
58 | * mutex (ep->mtx). It is acquired during the event transfer loop, | |
59 | * during epoll_ctl(EPOLL_CTL_DEL) and during eventpoll_release_file(). | |
60 | * Then we also need a global mutex to serialize eventpoll_release_file() | |
61 | * and ep_free(). | |
62 | * This mutex is acquired by ep_free() during the epoll file | |
63 | * cleanup path and it is also acquired by eventpoll_release_file() | |
64 | * if a file has been pushed inside an epoll set and it is then | |
65 | * close()d without a previous call toepoll_ctl(EPOLL_CTL_DEL). | |
66 | * It is possible to drop the "ep->mtx" and to use the global | |
67 | * mutex "epmutex" (together with "ep->lock") to have it working, | |
68 | * but having "ep->mtx" will make the interface more scalable. | |
69 | * Events that require holding "epmutex" are very rare, while for | |
70 | * normal operations the epoll private "ep->mtx" will guarantee | |
71 | * a better scalability. | |
72 | */ | |
73 | ||
74 | #define DEBUG_EPOLL 0 | |
75 | ||
76 | #if DEBUG_EPOLL > 0 | |
77 | #define DPRINTK(x) printk x | |
78 | #define DNPRINTK(n, x) do { if ((n) <= DEBUG_EPOLL) printk x; } while (0) | |
79 | #else /* #if DEBUG_EPOLL > 0 */ | |
80 | #define DPRINTK(x) (void) 0 | |
81 | #define DNPRINTK(n, x) (void) 0 | |
82 | #endif /* #if DEBUG_EPOLL > 0 */ | |
83 | ||
84 | #define DEBUG_EPI 0 | |
85 | ||
86 | #if DEBUG_EPI != 0 | |
87 | #define EPI_SLAB_DEBUG (SLAB_DEBUG_FREE | SLAB_RED_ZONE /* | SLAB_POISON */) | |
88 | #else /* #if DEBUG_EPI != 0 */ | |
89 | #define EPI_SLAB_DEBUG 0 | |
90 | #endif /* #if DEBUG_EPI != 0 */ | |
91 | ||
92 | /* Epoll private bits inside the event mask */ | |
93 | #define EP_PRIVATE_BITS (EPOLLONESHOT | EPOLLET) | |
94 | ||
95 | /* Maximum number of poll wake up nests we are allowing */ | |
96 | #define EP_MAX_POLLWAKE_NESTS 4 | |
97 | ||
98 | /* Maximum msec timeout value storeable in a long int */ | |
99 | #define EP_MAX_MSTIMEO min(1000ULL * MAX_SCHEDULE_TIMEOUT / HZ, (LONG_MAX - 999ULL) / HZ) | |
100 | ||
101 | #define EP_MAX_EVENTS (INT_MAX / sizeof(struct epoll_event)) | |
102 | ||
103 | #define EP_UNACTIVE_PTR ((void *) -1L) | |
104 | ||
105 | struct epoll_filefd { | |
106 | struct file *file; | |
107 | int fd; | |
108 | }; | |
109 | ||
110 | /* | |
111 | * Node that is linked into the "wake_task_list" member of the "struct poll_safewake". | |
112 | * It is used to keep track on all tasks that are currently inside the wake_up() code | |
113 | * to 1) short-circuit the one coming from the same task and same wait queue head | |
114 | * (loop) 2) allow a maximum number of epoll descriptors inclusion nesting | |
115 | * 3) let go the ones coming from other tasks. | |
116 | */ | |
117 | struct wake_task_node { | |
118 | struct list_head llink; | |
119 | struct task_struct *task; | |
120 | wait_queue_head_t *wq; | |
121 | }; | |
122 | ||
123 | /* | |
124 | * This is used to implement the safe poll wake up avoiding to reenter | |
125 | * the poll callback from inside wake_up(). | |
126 | */ | |
127 | struct poll_safewake { | |
128 | struct list_head wake_task_list; | |
129 | spinlock_t lock; | |
130 | }; | |
131 | ||
132 | /* | |
133 | * Each file descriptor added to the eventpoll interface will | |
134 | * have an entry of this type linked to the "rbr" RB tree. | |
135 | */ | |
136 | struct epitem { | |
137 | /* RB tree node used to link this structure to the eventpoll RB tree */ | |
138 | struct rb_node rbn; | |
139 | ||
140 | /* List header used to link this structure to the eventpoll ready list */ | |
141 | struct list_head rdllink; | |
142 | ||
143 | /* | |
144 | * Works together "struct eventpoll"->ovflist in keeping the | |
145 | * single linked chain of items. | |
146 | */ | |
147 | struct epitem *next; | |
148 | ||
149 | /* The file descriptor information this item refers to */ | |
150 | struct epoll_filefd ffd; | |
151 | ||
152 | /* Number of active wait queue attached to poll operations */ | |
153 | int nwait; | |
154 | ||
155 | /* List containing poll wait queues */ | |
156 | struct list_head pwqlist; | |
157 | ||
158 | /* The "container" of this item */ | |
159 | struct eventpoll *ep; | |
160 | ||
161 | /* List header used to link this item to the "struct file" items list */ | |
162 | struct list_head fllink; | |
163 | ||
164 | /* The structure that describe the interested events and the source fd */ | |
165 | struct epoll_event event; | |
166 | }; | |
167 | ||
168 | /* | |
169 | * This structure is stored inside the "private_data" member of the file | |
170 | * structure and rapresent the main data sructure for the eventpoll | |
171 | * interface. | |
172 | */ | |
173 | struct eventpoll { | |
174 | /* Protect the this structure access */ | |
175 | spinlock_t lock; | |
176 | ||
177 | /* | |
178 | * This mutex is used to ensure that files are not removed | |
179 | * while epoll is using them. This is held during the event | |
180 | * collection loop, the file cleanup path, the epoll file exit | |
181 | * code and the ctl operations. | |
182 | */ | |
183 | struct mutex mtx; | |
184 | ||
185 | /* Wait queue used by sys_epoll_wait() */ | |
186 | wait_queue_head_t wq; | |
187 | ||
188 | /* Wait queue used by file->poll() */ | |
189 | wait_queue_head_t poll_wait; | |
190 | ||
191 | /* List of ready file descriptors */ | |
192 | struct list_head rdllist; | |
193 | ||
194 | /* RB tree root used to store monitored fd structs */ | |
195 | struct rb_root rbr; | |
196 | ||
197 | /* | |
198 | * This is a single linked list that chains all the "struct epitem" that | |
199 | * happened while transfering ready events to userspace w/out | |
200 | * holding ->lock. | |
201 | */ | |
202 | struct epitem *ovflist; | |
203 | }; | |
204 | ||
205 | /* Wait structure used by the poll hooks */ | |
206 | struct eppoll_entry { | |
207 | /* List header used to link this structure to the "struct epitem" */ | |
208 | struct list_head llink; | |
209 | ||
210 | /* The "base" pointer is set to the container "struct epitem" */ | |
211 | void *base; | |
212 | ||
213 | /* | |
214 | * Wait queue item that will be linked to the target file wait | |
215 | * queue head. | |
216 | */ | |
217 | wait_queue_t wait; | |
218 | ||
219 | /* The wait queue head that linked the "wait" wait queue item */ | |
220 | wait_queue_head_t *whead; | |
221 | }; | |
222 | ||
223 | /* Wrapper struct used by poll queueing */ | |
224 | struct ep_pqueue { | |
225 | poll_table pt; | |
226 | struct epitem *epi; | |
227 | }; | |
228 | ||
229 | /* | |
230 | * This mutex is used to serialize ep_free() and eventpoll_release_file(). | |
231 | */ | |
232 | static struct mutex epmutex; | |
233 | ||
234 | /* Safe wake up implementation */ | |
235 | static struct poll_safewake psw; | |
236 | ||
237 | /* Slab cache used to allocate "struct epitem" */ | |
238 | static struct kmem_cache *epi_cache __read_mostly; | |
239 | ||
240 | /* Slab cache used to allocate "struct eppoll_entry" */ | |
241 | static struct kmem_cache *pwq_cache __read_mostly; | |
242 | ||
243 | ||
244 | /* Setup the structure that is used as key for the RB tree */ | |
245 | static inline void ep_set_ffd(struct epoll_filefd *ffd, | |
246 | struct file *file, int fd) | |
247 | { | |
248 | ffd->file = file; | |
249 | ffd->fd = fd; | |
250 | } | |
251 | ||
252 | /* Compare RB tree keys */ | |
253 | static inline int ep_cmp_ffd(struct epoll_filefd *p1, | |
254 | struct epoll_filefd *p2) | |
255 | { | |
256 | return (p1->file > p2->file ? +1: | |
257 | (p1->file < p2->file ? -1 : p1->fd - p2->fd)); | |
258 | } | |
259 | ||
260 | /* Special initialization for the RB tree node to detect linkage */ | |
261 | static inline void ep_rb_initnode(struct rb_node *n) | |
262 | { | |
263 | rb_set_parent(n, n); | |
264 | } | |
265 | ||
266 | /* Removes a node from the RB tree and marks it for a fast is-linked check */ | |
267 | static inline void ep_rb_erase(struct rb_node *n, struct rb_root *r) | |
268 | { | |
269 | rb_erase(n, r); | |
270 | rb_set_parent(n, n); | |
271 | } | |
272 | ||
273 | /* Fast check to verify that the item is linked to the main RB tree */ | |
274 | static inline int ep_rb_linked(struct rb_node *n) | |
275 | { | |
276 | return rb_parent(n) != n; | |
277 | } | |
278 | ||
279 | /* Tells us if the item is currently linked */ | |
280 | static inline int ep_is_linked(struct list_head *p) | |
281 | { | |
282 | return !list_empty(p); | |
283 | } | |
284 | ||
285 | /* Get the "struct epitem" from a wait queue pointer */ | |
286 | static inline struct epitem * ep_item_from_wait(wait_queue_t *p) | |
287 | { | |
288 | return container_of(p, struct eppoll_entry, wait)->base; | |
289 | } | |
290 | ||
291 | /* Get the "struct epitem" from an epoll queue wrapper */ | |
292 | static inline struct epitem * ep_item_from_epqueue(poll_table *p) | |
293 | { | |
294 | return container_of(p, struct ep_pqueue, pt)->epi; | |
295 | } | |
296 | ||
297 | /* Tells if the epoll_ctl(2) operation needs an event copy from userspace */ | |
298 | static inline int ep_op_has_event(int op) | |
299 | { | |
300 | return op != EPOLL_CTL_DEL; | |
301 | } | |
302 | ||
303 | /* Initialize the poll safe wake up structure */ | |
304 | static void ep_poll_safewake_init(struct poll_safewake *psw) | |
305 | { | |
306 | ||
307 | INIT_LIST_HEAD(&psw->wake_task_list); | |
308 | spin_lock_init(&psw->lock); | |
309 | } | |
310 | ||
311 | /* | |
312 | * Perform a safe wake up of the poll wait list. The problem is that | |
313 | * with the new callback'd wake up system, it is possible that the | |
314 | * poll callback is reentered from inside the call to wake_up() done | |
315 | * on the poll wait queue head. The rule is that we cannot reenter the | |
316 | * wake up code from the same task more than EP_MAX_POLLWAKE_NESTS times, | |
317 | * and we cannot reenter the same wait queue head at all. This will | |
318 | * enable to have a hierarchy of epoll file descriptor of no more than | |
319 | * EP_MAX_POLLWAKE_NESTS deep. We need the irq version of the spin lock | |
320 | * because this one gets called by the poll callback, that in turn is called | |
321 | * from inside a wake_up(), that might be called from irq context. | |
322 | */ | |
323 | static void ep_poll_safewake(struct poll_safewake *psw, wait_queue_head_t *wq) | |
324 | { | |
325 | int wake_nests = 0; | |
326 | unsigned long flags; | |
327 | struct task_struct *this_task = current; | |
328 | struct list_head *lsthead = &psw->wake_task_list; | |
329 | struct wake_task_node *tncur; | |
330 | struct wake_task_node tnode; | |
331 | ||
332 | spin_lock_irqsave(&psw->lock, flags); | |
333 | ||
334 | /* Try to see if the current task is already inside this wakeup call */ | |
335 | list_for_each_entry(tncur, lsthead, llink) { | |
336 | ||
337 | if (tncur->wq == wq || | |
338 | (tncur->task == this_task && ++wake_nests > EP_MAX_POLLWAKE_NESTS)) { | |
339 | /* | |
340 | * Ops ... loop detected or maximum nest level reached. | |
341 | * We abort this wake by breaking the cycle itself. | |
342 | */ | |
343 | spin_unlock_irqrestore(&psw->lock, flags); | |
344 | return; | |
345 | } | |
346 | } | |
347 | ||
348 | /* Add the current task to the list */ | |
349 | tnode.task = this_task; | |
350 | tnode.wq = wq; | |
351 | list_add(&tnode.llink, lsthead); | |
352 | ||
353 | spin_unlock_irqrestore(&psw->lock, flags); | |
354 | ||
355 | /* Do really wake up now */ | |
356 | wake_up(wq); | |
357 | ||
358 | /* Remove the current task from the list */ | |
359 | spin_lock_irqsave(&psw->lock, flags); | |
360 | list_del(&tnode.llink); | |
361 | spin_unlock_irqrestore(&psw->lock, flags); | |
362 | } | |
363 | ||
364 | /* | |
365 | * This function unregister poll callbacks from the associated file descriptor. | |
366 | * Since this must be called without holding "ep->lock" the atomic exchange trick | |
367 | * will protect us from multiple unregister. | |
368 | */ | |
369 | static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi) | |
370 | { | |
371 | int nwait; | |
372 | struct list_head *lsthead = &epi->pwqlist; | |
373 | struct eppoll_entry *pwq; | |
374 | ||
375 | /* This is called without locks, so we need the atomic exchange */ | |
376 | nwait = xchg(&epi->nwait, 0); | |
377 | ||
378 | if (nwait) { | |
379 | while (!list_empty(lsthead)) { | |
380 | pwq = list_first_entry(lsthead, struct eppoll_entry, llink); | |
381 | ||
382 | list_del_init(&pwq->llink); | |
383 | remove_wait_queue(pwq->whead, &pwq->wait); | |
384 | kmem_cache_free(pwq_cache, pwq); | |
385 | } | |
386 | } | |
387 | } | |
388 | ||
389 | /* | |
390 | * Removes a "struct epitem" from the eventpoll RB tree and deallocates | |
391 | * all the associated resources. Must be called with "mtx" held. | |
392 | */ | |
393 | static int ep_remove(struct eventpoll *ep, struct epitem *epi) | |
394 | { | |
395 | unsigned long flags; | |
396 | struct file *file = epi->ffd.file; | |
397 | ||
398 | /* | |
399 | * Removes poll wait queue hooks. We _have_ to do this without holding | |
400 | * the "ep->lock" otherwise a deadlock might occur. This because of the | |
401 | * sequence of the lock acquisition. Here we do "ep->lock" then the wait | |
402 | * queue head lock when unregistering the wait queue. The wakeup callback | |
403 | * will run by holding the wait queue head lock and will call our callback | |
404 | * that will try to get "ep->lock". | |
405 | */ | |
406 | ep_unregister_pollwait(ep, epi); | |
407 | ||
408 | /* Remove the current item from the list of epoll hooks */ | |
409 | spin_lock(&file->f_ep_lock); | |
410 | if (ep_is_linked(&epi->fllink)) | |
411 | list_del_init(&epi->fllink); | |
412 | spin_unlock(&file->f_ep_lock); | |
413 | ||
414 | if (ep_rb_linked(&epi->rbn)) | |
415 | ep_rb_erase(&epi->rbn, &ep->rbr); | |
416 | ||
417 | spin_lock_irqsave(&ep->lock, flags); | |
418 | if (ep_is_linked(&epi->rdllink)) | |
419 | list_del_init(&epi->rdllink); | |
420 | spin_unlock_irqrestore(&ep->lock, flags); | |
421 | ||
422 | /* At this point it is safe to free the eventpoll item */ | |
423 | kmem_cache_free(epi_cache, epi); | |
424 | ||
425 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_remove(%p, %p)\n", | |
426 | current, ep, file)); | |
427 | ||
428 | return 0; | |
429 | } | |
430 | ||
431 | static void ep_free(struct eventpoll *ep) | |
432 | { | |
433 | struct rb_node *rbp; | |
434 | struct epitem *epi; | |
435 | ||
436 | /* We need to release all tasks waiting for these file */ | |
437 | if (waitqueue_active(&ep->poll_wait)) | |
438 | ep_poll_safewake(&psw, &ep->poll_wait); | |
439 | ||
440 | /* | |
441 | * We need to lock this because we could be hit by | |
442 | * eventpoll_release_file() while we're freeing the "struct eventpoll". | |
443 | * We do not need to hold "ep->mtx" here because the epoll file | |
444 | * is on the way to be removed and no one has references to it | |
445 | * anymore. The only hit might come from eventpoll_release_file() but | |
446 | * holding "epmutex" is sufficent here. | |
447 | */ | |
448 | mutex_lock(&epmutex); | |
449 | ||
450 | /* | |
451 | * Walks through the whole tree by unregistering poll callbacks. | |
452 | */ | |
453 | for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { | |
454 | epi = rb_entry(rbp, struct epitem, rbn); | |
455 | ||
456 | ep_unregister_pollwait(ep, epi); | |
457 | } | |
458 | ||
459 | /* | |
460 | * Walks through the whole tree by freeing each "struct epitem". At this | |
461 | * point we are sure no poll callbacks will be lingering around, and also by | |
462 | * holding "epmutex" we can be sure that no file cleanup code will hit | |
463 | * us during this operation. So we can avoid the lock on "ep->lock". | |
464 | */ | |
465 | while ((rbp = rb_first(&ep->rbr)) != NULL) { | |
466 | epi = rb_entry(rbp, struct epitem, rbn); | |
467 | ep_remove(ep, epi); | |
468 | } | |
469 | ||
470 | mutex_unlock(&epmutex); | |
471 | mutex_destroy(&ep->mtx); | |
472 | kfree(ep); | |
473 | } | |
474 | ||
475 | static int ep_eventpoll_release(struct inode *inode, struct file *file) | |
476 | { | |
477 | struct eventpoll *ep = file->private_data; | |
478 | ||
479 | if (ep) | |
480 | ep_free(ep); | |
481 | ||
482 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: close() ep=%p\n", current, ep)); | |
483 | return 0; | |
484 | } | |
485 | ||
486 | static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait) | |
487 | { | |
488 | unsigned int pollflags = 0; | |
489 | unsigned long flags; | |
490 | struct eventpoll *ep = file->private_data; | |
491 | ||
492 | /* Insert inside our poll wait queue */ | |
493 | poll_wait(file, &ep->poll_wait, wait); | |
494 | ||
495 | /* Check our condition */ | |
496 | spin_lock_irqsave(&ep->lock, flags); | |
497 | if (!list_empty(&ep->rdllist)) | |
498 | pollflags = POLLIN | POLLRDNORM; | |
499 | spin_unlock_irqrestore(&ep->lock, flags); | |
500 | ||
501 | return pollflags; | |
502 | } | |
503 | ||
504 | /* File callbacks that implement the eventpoll file behaviour */ | |
505 | static const struct file_operations eventpoll_fops = { | |
506 | .release = ep_eventpoll_release, | |
507 | .poll = ep_eventpoll_poll | |
508 | }; | |
509 | ||
510 | /* Fast test to see if the file is an evenpoll file */ | |
511 | static inline int is_file_epoll(struct file *f) | |
512 | { | |
513 | return f->f_op == &eventpoll_fops; | |
514 | } | |
515 | ||
516 | /* | |
517 | * This is called from eventpoll_release() to unlink files from the eventpoll | |
518 | * interface. We need to have this facility to cleanup correctly files that are | |
519 | * closed without being removed from the eventpoll interface. | |
520 | */ | |
521 | void eventpoll_release_file(struct file *file) | |
522 | { | |
523 | struct list_head *lsthead = &file->f_ep_links; | |
524 | struct eventpoll *ep; | |
525 | struct epitem *epi; | |
526 | ||
527 | /* | |
528 | * We don't want to get "file->f_ep_lock" because it is not | |
529 | * necessary. It is not necessary because we're in the "struct file" | |
530 | * cleanup path, and this means that noone is using this file anymore. | |
531 | * So, for example, epoll_ctl() cannot hit here sicne if we reach this | |
532 | * point, the file counter already went to zero and fget() would fail. | |
533 | * The only hit might come from ep_free() but by holding the mutex | |
534 | * will correctly serialize the operation. We do need to acquire | |
535 | * "ep->mtx" after "epmutex" because ep_remove() requires it when called | |
536 | * from anywhere but ep_free(). | |
537 | */ | |
538 | mutex_lock(&epmutex); | |
539 | ||
540 | while (!list_empty(lsthead)) { | |
541 | epi = list_first_entry(lsthead, struct epitem, fllink); | |
542 | ||
543 | ep = epi->ep; | |
544 | list_del_init(&epi->fllink); | |
545 | mutex_lock(&ep->mtx); | |
546 | ep_remove(ep, epi); | |
547 | mutex_unlock(&ep->mtx); | |
548 | } | |
549 | ||
550 | mutex_unlock(&epmutex); | |
551 | } | |
552 | ||
553 | static int ep_alloc(struct eventpoll **pep) | |
554 | { | |
555 | struct eventpoll *ep = kzalloc(sizeof(*ep), GFP_KERNEL); | |
556 | ||
557 | if (!ep) | |
558 | return -ENOMEM; | |
559 | ||
560 | spin_lock_init(&ep->lock); | |
561 | mutex_init(&ep->mtx); | |
562 | init_waitqueue_head(&ep->wq); | |
563 | init_waitqueue_head(&ep->poll_wait); | |
564 | INIT_LIST_HEAD(&ep->rdllist); | |
565 | ep->rbr = RB_ROOT; | |
566 | ep->ovflist = EP_UNACTIVE_PTR; | |
567 | ||
568 | *pep = ep; | |
569 | ||
570 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_alloc() ep=%p\n", | |
571 | current, ep)); | |
572 | return 0; | |
573 | } | |
574 | ||
575 | /* | |
576 | * Search the file inside the eventpoll tree. The RB tree operations | |
577 | * are protected by the "mtx" mutex, and ep_find() must be called with | |
578 | * "mtx" held. | |
579 | */ | |
580 | static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd) | |
581 | { | |
582 | int kcmp; | |
583 | struct rb_node *rbp; | |
584 | struct epitem *epi, *epir = NULL; | |
585 | struct epoll_filefd ffd; | |
586 | ||
587 | ep_set_ffd(&ffd, file, fd); | |
588 | for (rbp = ep->rbr.rb_node; rbp; ) { | |
589 | epi = rb_entry(rbp, struct epitem, rbn); | |
590 | kcmp = ep_cmp_ffd(&ffd, &epi->ffd); | |
591 | if (kcmp > 0) | |
592 | rbp = rbp->rb_right; | |
593 | else if (kcmp < 0) | |
594 | rbp = rbp->rb_left; | |
595 | else { | |
596 | epir = epi; | |
597 | break; | |
598 | } | |
599 | } | |
600 | ||
601 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_find(%p) -> %p\n", | |
602 | current, file, epir)); | |
603 | ||
604 | return epir; | |
605 | } | |
606 | ||
607 | /* | |
608 | * This is the callback that is passed to the wait queue wakeup | |
609 | * machanism. It is called by the stored file descriptors when they | |
610 | * have events to report. | |
611 | */ | |
612 | static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *key) | |
613 | { | |
614 | int pwake = 0; | |
615 | unsigned long flags; | |
616 | struct epitem *epi = ep_item_from_wait(wait); | |
617 | struct eventpoll *ep = epi->ep; | |
618 | ||
619 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: poll_callback(%p) epi=%p ep=%p\n", | |
620 | current, epi->ffd.file, epi, ep)); | |
621 | ||
622 | spin_lock_irqsave(&ep->lock, flags); | |
623 | ||
624 | /* | |
625 | * If the event mask does not contain any poll(2) event, we consider the | |
626 | * descriptor to be disabled. This condition is likely the effect of the | |
627 | * EPOLLONESHOT bit that disables the descriptor when an event is received, | |
628 | * until the next EPOLL_CTL_MOD will be issued. | |
629 | */ | |
630 | if (!(epi->event.events & ~EP_PRIVATE_BITS)) | |
631 | goto out_unlock; | |
632 | ||
633 | /* | |
634 | * If we are trasfering events to userspace, we can hold no locks | |
635 | * (because we're accessing user memory, and because of linux f_op->poll() | |
636 | * semantics). All the events that happens during that period of time are | |
637 | * chained in ep->ovflist and requeued later on. | |
638 | */ | |
639 | if (unlikely(ep->ovflist != EP_UNACTIVE_PTR)) { | |
640 | if (epi->next == EP_UNACTIVE_PTR) { | |
641 | epi->next = ep->ovflist; | |
642 | ep->ovflist = epi; | |
643 | } | |
644 | goto out_unlock; | |
645 | } | |
646 | ||
647 | /* If this file is already in the ready list we exit soon */ | |
648 | if (ep_is_linked(&epi->rdllink)) | |
649 | goto is_linked; | |
650 | ||
651 | list_add_tail(&epi->rdllink, &ep->rdllist); | |
652 | ||
653 | is_linked: | |
654 | /* | |
655 | * Wake up ( if active ) both the eventpoll wait list and the ->poll() | |
656 | * wait list. | |
657 | */ | |
658 | if (waitqueue_active(&ep->wq)) | |
659 | __wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE | | |
660 | TASK_INTERRUPTIBLE); | |
661 | if (waitqueue_active(&ep->poll_wait)) | |
662 | pwake++; | |
663 | ||
664 | out_unlock: | |
665 | spin_unlock_irqrestore(&ep->lock, flags); | |
666 | ||
667 | /* We have to call this outside the lock */ | |
668 | if (pwake) | |
669 | ep_poll_safewake(&psw, &ep->poll_wait); | |
670 | ||
671 | return 1; | |
672 | } | |
673 | ||
674 | /* | |
675 | * This is the callback that is used to add our wait queue to the | |
676 | * target file wakeup lists. | |
677 | */ | |
678 | static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, | |
679 | poll_table *pt) | |
680 | { | |
681 | struct epitem *epi = ep_item_from_epqueue(pt); | |
682 | struct eppoll_entry *pwq; | |
683 | ||
684 | if (epi->nwait >= 0 && (pwq = kmem_cache_alloc(pwq_cache, GFP_KERNEL))) { | |
685 | init_waitqueue_func_entry(&pwq->wait, ep_poll_callback); | |
686 | pwq->whead = whead; | |
687 | pwq->base = epi; | |
688 | add_wait_queue(whead, &pwq->wait); | |
689 | list_add_tail(&pwq->llink, &epi->pwqlist); | |
690 | epi->nwait++; | |
691 | } else { | |
692 | /* We have to signal that an error occurred */ | |
693 | epi->nwait = -1; | |
694 | } | |
695 | } | |
696 | ||
697 | static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi) | |
698 | { | |
699 | int kcmp; | |
700 | struct rb_node **p = &ep->rbr.rb_node, *parent = NULL; | |
701 | struct epitem *epic; | |
702 | ||
703 | while (*p) { | |
704 | parent = *p; | |
705 | epic = rb_entry(parent, struct epitem, rbn); | |
706 | kcmp = ep_cmp_ffd(&epi->ffd, &epic->ffd); | |
707 | if (kcmp > 0) | |
708 | p = &parent->rb_right; | |
709 | else | |
710 | p = &parent->rb_left; | |
711 | } | |
712 | rb_link_node(&epi->rbn, parent, p); | |
713 | rb_insert_color(&epi->rbn, &ep->rbr); | |
714 | } | |
715 | ||
716 | /* | |
717 | * Must be called with "mtx" held. | |
718 | */ | |
719 | static int ep_insert(struct eventpoll *ep, struct epoll_event *event, | |
720 | struct file *tfile, int fd) | |
721 | { | |
722 | int error, revents, pwake = 0; | |
723 | unsigned long flags; | |
724 | struct epitem *epi; | |
725 | struct ep_pqueue epq; | |
726 | ||
727 | error = -ENOMEM; | |
728 | if (!(epi = kmem_cache_alloc(epi_cache, GFP_KERNEL))) | |
729 | goto error_return; | |
730 | ||
731 | /* Item initialization follow here ... */ | |
732 | ep_rb_initnode(&epi->rbn); | |
733 | INIT_LIST_HEAD(&epi->rdllink); | |
734 | INIT_LIST_HEAD(&epi->fllink); | |
735 | INIT_LIST_HEAD(&epi->pwqlist); | |
736 | epi->ep = ep; | |
737 | ep_set_ffd(&epi->ffd, tfile, fd); | |
738 | epi->event = *event; | |
739 | epi->nwait = 0; | |
740 | epi->next = EP_UNACTIVE_PTR; | |
741 | ||
742 | /* Initialize the poll table using the queue callback */ | |
743 | epq.epi = epi; | |
744 | init_poll_funcptr(&epq.pt, ep_ptable_queue_proc); | |
745 | ||
746 | /* | |
747 | * Attach the item to the poll hooks and get current event bits. | |
748 | * We can safely use the file* here because its usage count has | |
749 | * been increased by the caller of this function. Note that after | |
750 | * this operation completes, the poll callback can start hitting | |
751 | * the new item. | |
752 | */ | |
753 | revents = tfile->f_op->poll(tfile, &epq.pt); | |
754 | ||
755 | /* | |
756 | * We have to check if something went wrong during the poll wait queue | |
757 | * install process. Namely an allocation for a wait queue failed due | |
758 | * high memory pressure. | |
759 | */ | |
760 | if (epi->nwait < 0) | |
761 | goto error_unregister; | |
762 | ||
763 | /* Add the current item to the list of active epoll hook for this file */ | |
764 | spin_lock(&tfile->f_ep_lock); | |
765 | list_add_tail(&epi->fllink, &tfile->f_ep_links); | |
766 | spin_unlock(&tfile->f_ep_lock); | |
767 | ||
768 | /* | |
769 | * Add the current item to the RB tree. All RB tree operations are | |
770 | * protected by "mtx", and ep_insert() is called with "mtx" held. | |
771 | */ | |
772 | ep_rbtree_insert(ep, epi); | |
773 | ||
774 | /* We have to drop the new item inside our item list to keep track of it */ | |
775 | spin_lock_irqsave(&ep->lock, flags); | |
776 | ||
777 | /* If the file is already "ready" we drop it inside the ready list */ | |
778 | if ((revents & event->events) && !ep_is_linked(&epi->rdllink)) { | |
779 | list_add_tail(&epi->rdllink, &ep->rdllist); | |
780 | ||
781 | /* Notify waiting tasks that events are available */ | |
782 | if (waitqueue_active(&ep->wq)) | |
783 | __wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE); | |
784 | if (waitqueue_active(&ep->poll_wait)) | |
785 | pwake++; | |
786 | } | |
787 | ||
788 | spin_unlock_irqrestore(&ep->lock, flags); | |
789 | ||
790 | /* We have to call this outside the lock */ | |
791 | if (pwake) | |
792 | ep_poll_safewake(&psw, &ep->poll_wait); | |
793 | ||
794 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_insert(%p, %p, %d)\n", | |
795 | current, ep, tfile, fd)); | |
796 | ||
797 | return 0; | |
798 | ||
799 | error_unregister: | |
800 | ep_unregister_pollwait(ep, epi); | |
801 | ||
802 | /* | |
803 | * We need to do this because an event could have been arrived on some | |
804 | * allocated wait queue. Note that we don't care about the ep->ovflist | |
805 | * list, since that is used/cleaned only inside a section bound by "mtx". | |
806 | * And ep_insert() is called with "mtx" held. | |
807 | */ | |
808 | spin_lock_irqsave(&ep->lock, flags); | |
809 | if (ep_is_linked(&epi->rdllink)) | |
810 | list_del_init(&epi->rdllink); | |
811 | spin_unlock_irqrestore(&ep->lock, flags); | |
812 | ||
813 | kmem_cache_free(epi_cache, epi); | |
814 | error_return: | |
815 | return error; | |
816 | } | |
817 | ||
818 | /* | |
819 | * Modify the interest event mask by dropping an event if the new mask | |
820 | * has a match in the current file status. Must be called with "mtx" held. | |
821 | */ | |
822 | static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_event *event) | |
823 | { | |
824 | int pwake = 0; | |
825 | unsigned int revents; | |
826 | unsigned long flags; | |
827 | ||
828 | /* | |
829 | * Set the new event interest mask before calling f_op->poll(), otherwise | |
830 | * a potential race might occur. In fact if we do this operation inside | |
831 | * the lock, an event might happen between the f_op->poll() call and the | |
832 | * new event set registering. | |
833 | */ | |
834 | epi->event.events = event->events; | |
835 | ||
836 | /* | |
837 | * Get current event bits. We can safely use the file* here because | |
838 | * its usage count has been increased by the caller of this function. | |
839 | */ | |
840 | revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL); | |
841 | ||
842 | spin_lock_irqsave(&ep->lock, flags); | |
843 | ||
844 | /* Copy the data member from inside the lock */ | |
845 | epi->event.data = event->data; | |
846 | ||
847 | /* | |
848 | * If the item is "hot" and it is not registered inside the ready | |
849 | * list, push it inside. | |
850 | */ | |
851 | if (revents & event->events) { | |
852 | if (!ep_is_linked(&epi->rdllink)) { | |
853 | list_add_tail(&epi->rdllink, &ep->rdllist); | |
854 | ||
855 | /* Notify waiting tasks that events are available */ | |
856 | if (waitqueue_active(&ep->wq)) | |
857 | __wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE | | |
858 | TASK_INTERRUPTIBLE); | |
859 | if (waitqueue_active(&ep->poll_wait)) | |
860 | pwake++; | |
861 | } | |
862 | } | |
863 | spin_unlock_irqrestore(&ep->lock, flags); | |
864 | ||
865 | /* We have to call this outside the lock */ | |
866 | if (pwake) | |
867 | ep_poll_safewake(&psw, &ep->poll_wait); | |
868 | ||
869 | return 0; | |
870 | } | |
871 | ||
872 | static int ep_send_events(struct eventpoll *ep, struct epoll_event __user *events, | |
873 | int maxevents) | |
874 | { | |
875 | int eventcnt, error = -EFAULT, pwake = 0; | |
876 | unsigned int revents; | |
877 | unsigned long flags; | |
878 | struct epitem *epi, *nepi; | |
879 | struct list_head txlist; | |
880 | ||
881 | INIT_LIST_HEAD(&txlist); | |
882 | ||
883 | /* | |
884 | * We need to lock this because we could be hit by | |
885 | * eventpoll_release_file() and epoll_ctl(EPOLL_CTL_DEL). | |
886 | */ | |
887 | mutex_lock(&ep->mtx); | |
888 | ||
889 | /* | |
890 | * Steal the ready list, and re-init the original one to the | |
891 | * empty list. Also, set ep->ovflist to NULL so that events | |
892 | * happening while looping w/out locks, are not lost. We cannot | |
893 | * have the poll callback to queue directly on ep->rdllist, | |
894 | * because we are doing it in the loop below, in a lockless way. | |
895 | */ | |
896 | spin_lock_irqsave(&ep->lock, flags); | |
897 | list_splice(&ep->rdllist, &txlist); | |
898 | INIT_LIST_HEAD(&ep->rdllist); | |
899 | ep->ovflist = NULL; | |
900 | spin_unlock_irqrestore(&ep->lock, flags); | |
901 | ||
902 | /* | |
903 | * We can loop without lock because this is a task private list. | |
904 | * We just splice'd out the ep->rdllist in ep_collect_ready_items(). | |
905 | * Items cannot vanish during the loop because we are holding "mtx". | |
906 | */ | |
907 | for (eventcnt = 0; !list_empty(&txlist) && eventcnt < maxevents;) { | |
908 | epi = list_first_entry(&txlist, struct epitem, rdllink); | |
909 | ||
910 | list_del_init(&epi->rdllink); | |
911 | ||
912 | /* | |
913 | * Get the ready file event set. We can safely use the file | |
914 | * because we are holding the "mtx" and this will guarantee | |
915 | * that both the file and the item will not vanish. | |
916 | */ | |
917 | revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL); | |
918 | revents &= epi->event.events; | |
919 | ||
920 | /* | |
921 | * Is the event mask intersect the caller-requested one, | |
922 | * deliver the event to userspace. Again, we are holding | |
923 | * "mtx", so no operations coming from userspace can change | |
924 | * the item. | |
925 | */ | |
926 | if (revents) { | |
927 | if (__put_user(revents, | |
928 | &events[eventcnt].events) || | |
929 | __put_user(epi->event.data, | |
930 | &events[eventcnt].data)) | |
931 | goto errxit; | |
932 | if (epi->event.events & EPOLLONESHOT) | |
933 | epi->event.events &= EP_PRIVATE_BITS; | |
934 | eventcnt++; | |
935 | } | |
936 | /* | |
937 | * At this point, noone can insert into ep->rdllist besides | |
938 | * us. The epoll_ctl() callers are locked out by us holding | |
939 | * "mtx" and the poll callback will queue them in ep->ovflist. | |
940 | */ | |
941 | if (!(epi->event.events & EPOLLET) && | |
942 | (revents & epi->event.events)) | |
943 | list_add_tail(&epi->rdllink, &ep->rdllist); | |
944 | } | |
945 | error = 0; | |
946 | ||
947 | errxit: | |
948 | ||
949 | spin_lock_irqsave(&ep->lock, flags); | |
950 | /* | |
951 | * During the time we spent in the loop above, some other events | |
952 | * might have been queued by the poll callback. We re-insert them | |
953 | * here (in case they are not already queued, or they're one-shot). | |
954 | */ | |
955 | for (nepi = ep->ovflist; (epi = nepi) != NULL; | |
956 | nepi = epi->next, epi->next = EP_UNACTIVE_PTR) { | |
957 | if (!ep_is_linked(&epi->rdllink) && | |
958 | (epi->event.events & ~EP_PRIVATE_BITS)) | |
959 | list_add_tail(&epi->rdllink, &ep->rdllist); | |
960 | } | |
961 | /* | |
962 | * We need to set back ep->ovflist to EP_UNACTIVE_PTR, so that after | |
963 | * releasing the lock, events will be queued in the normal way inside | |
964 | * ep->rdllist. | |
965 | */ | |
966 | ep->ovflist = EP_UNACTIVE_PTR; | |
967 | ||
968 | /* | |
969 | * In case of error in the event-send loop, or in case the number of | |
970 | * ready events exceeds the userspace limit, we need to splice the | |
971 | * "txlist" back inside ep->rdllist. | |
972 | */ | |
973 | list_splice(&txlist, &ep->rdllist); | |
974 | ||
975 | if (!list_empty(&ep->rdllist)) { | |
976 | /* | |
977 | * Wake up (if active) both the eventpoll wait list and the ->poll() | |
978 | * wait list (delayed after we release the lock). | |
979 | */ | |
980 | if (waitqueue_active(&ep->wq)) | |
981 | __wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE | | |
982 | TASK_INTERRUPTIBLE); | |
983 | if (waitqueue_active(&ep->poll_wait)) | |
984 | pwake++; | |
985 | } | |
986 | spin_unlock_irqrestore(&ep->lock, flags); | |
987 | ||
988 | mutex_unlock(&ep->mtx); | |
989 | ||
990 | /* We have to call this outside the lock */ | |
991 | if (pwake) | |
992 | ep_poll_safewake(&psw, &ep->poll_wait); | |
993 | ||
994 | return eventcnt == 0 ? error: eventcnt; | |
995 | } | |
996 | ||
997 | static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, | |
998 | int maxevents, long timeout) | |
999 | { | |
1000 | int res, eavail; | |
1001 | unsigned long flags; | |
1002 | long jtimeout; | |
1003 | wait_queue_t wait; | |
1004 | ||
1005 | /* | |
1006 | * Calculate the timeout by checking for the "infinite" value ( -1 ) | |
1007 | * and the overflow condition. The passed timeout is in milliseconds, | |
1008 | * that why (t * HZ) / 1000. | |
1009 | */ | |
1010 | jtimeout = (timeout < 0 || timeout >= EP_MAX_MSTIMEO) ? | |
1011 | MAX_SCHEDULE_TIMEOUT : (timeout * HZ + 999) / 1000; | |
1012 | ||
1013 | retry: | |
1014 | spin_lock_irqsave(&ep->lock, flags); | |
1015 | ||
1016 | res = 0; | |
1017 | if (list_empty(&ep->rdllist)) { | |
1018 | /* | |
1019 | * We don't have any available event to return to the caller. | |
1020 | * We need to sleep here, and we will be wake up by | |
1021 | * ep_poll_callback() when events will become available. | |
1022 | */ | |
1023 | init_waitqueue_entry(&wait, current); | |
1024 | wait.flags |= WQ_FLAG_EXCLUSIVE; | |
1025 | __add_wait_queue(&ep->wq, &wait); | |
1026 | ||
1027 | for (;;) { | |
1028 | /* | |
1029 | * We don't want to sleep if the ep_poll_callback() sends us | |
1030 | * a wakeup in between. That's why we set the task state | |
1031 | * to TASK_INTERRUPTIBLE before doing the checks. | |
1032 | */ | |
1033 | set_current_state(TASK_INTERRUPTIBLE); | |
1034 | if (!list_empty(&ep->rdllist) || !jtimeout) | |
1035 | break; | |
1036 | if (signal_pending(current)) { | |
1037 | res = -EINTR; | |
1038 | break; | |
1039 | } | |
1040 | ||
1041 | spin_unlock_irqrestore(&ep->lock, flags); | |
1042 | jtimeout = schedule_timeout(jtimeout); | |
1043 | spin_lock_irqsave(&ep->lock, flags); | |
1044 | } | |
1045 | __remove_wait_queue(&ep->wq, &wait); | |
1046 | ||
1047 | set_current_state(TASK_RUNNING); | |
1048 | } | |
1049 | ||
1050 | /* Is it worth to try to dig for events ? */ | |
1051 | eavail = !list_empty(&ep->rdllist); | |
1052 | ||
1053 | spin_unlock_irqrestore(&ep->lock, flags); | |
1054 | ||
1055 | /* | |
1056 | * Try to transfer events to user space. In case we get 0 events and | |
1057 | * there's still timeout left over, we go trying again in search of | |
1058 | * more luck. | |
1059 | */ | |
1060 | if (!res && eavail && | |
1061 | !(res = ep_send_events(ep, events, maxevents)) && jtimeout) | |
1062 | goto retry; | |
1063 | ||
1064 | return res; | |
1065 | } | |
1066 | ||
1067 | /* | |
1068 | * It opens an eventpoll file descriptor. The "size" parameter is there | |
1069 | * for historical reasons, when epoll was using an hash instead of an | |
1070 | * RB tree. With the current implementation, the "size" parameter is ignored | |
1071 | * (besides sanity checks). | |
1072 | */ | |
1073 | asmlinkage long sys_epoll_create(int size) | |
1074 | { | |
1075 | int error, fd = -1; | |
1076 | struct eventpoll *ep; | |
1077 | struct inode *inode; | |
1078 | struct file *file; | |
1079 | ||
1080 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d)\n", | |
1081 | current, size)); | |
1082 | ||
1083 | /* | |
1084 | * Sanity check on the size parameter, and create the internal data | |
1085 | * structure ( "struct eventpoll" ). | |
1086 | */ | |
1087 | error = -EINVAL; | |
1088 | if (size <= 0 || (error = ep_alloc(&ep)) != 0) | |
1089 | goto error_return; | |
1090 | ||
1091 | /* | |
1092 | * Creates all the items needed to setup an eventpoll file. That is, | |
1093 | * a file structure, and inode and a free file descriptor. | |
1094 | */ | |
1095 | error = anon_inode_getfd(&fd, &inode, &file, "[eventpoll]", | |
1096 | &eventpoll_fops, ep); | |
1097 | if (error) | |
1098 | goto error_free; | |
1099 | ||
1100 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n", | |
1101 | current, size, fd)); | |
1102 | ||
1103 | return fd; | |
1104 | ||
1105 | error_free: | |
1106 | ep_free(ep); | |
1107 | error_return: | |
1108 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n", | |
1109 | current, size, error)); | |
1110 | return error; | |
1111 | } | |
1112 | ||
1113 | /* | |
1114 | * The following function implements the controller interface for | |
1115 | * the eventpoll file that enables the insertion/removal/change of | |
1116 | * file descriptors inside the interest set. | |
1117 | */ | |
1118 | asmlinkage long sys_epoll_ctl(int epfd, int op, int fd, | |
1119 | struct epoll_event __user *event) | |
1120 | { | |
1121 | int error; | |
1122 | struct file *file, *tfile; | |
1123 | struct eventpoll *ep; | |
1124 | struct epitem *epi; | |
1125 | struct epoll_event epds; | |
1126 | ||
1127 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %p)\n", | |
1128 | current, epfd, op, fd, event)); | |
1129 | ||
1130 | error = -EFAULT; | |
1131 | if (ep_op_has_event(op) && | |
1132 | copy_from_user(&epds, event, sizeof(struct epoll_event))) | |
1133 | goto error_return; | |
1134 | ||
1135 | /* Get the "struct file *" for the eventpoll file */ | |
1136 | error = -EBADF; | |
1137 | file = fget(epfd); | |
1138 | if (!file) | |
1139 | goto error_return; | |
1140 | ||
1141 | /* Get the "struct file *" for the target file */ | |
1142 | tfile = fget(fd); | |
1143 | if (!tfile) | |
1144 | goto error_fput; | |
1145 | ||
1146 | /* The target file descriptor must support poll */ | |
1147 | error = -EPERM; | |
1148 | if (!tfile->f_op || !tfile->f_op->poll) | |
1149 | goto error_tgt_fput; | |
1150 | ||
1151 | /* | |
1152 | * We have to check that the file structure underneath the file descriptor | |
1153 | * the user passed to us _is_ an eventpoll file. And also we do not permit | |
1154 | * adding an epoll file descriptor inside itself. | |
1155 | */ | |
1156 | error = -EINVAL; | |
1157 | if (file == tfile || !is_file_epoll(file)) | |
1158 | goto error_tgt_fput; | |
1159 | ||
1160 | /* | |
1161 | * At this point it is safe to assume that the "private_data" contains | |
1162 | * our own data structure. | |
1163 | */ | |
1164 | ep = file->private_data; | |
1165 | ||
1166 | mutex_lock(&ep->mtx); | |
1167 | ||
1168 | /* | |
1169 | * Try to lookup the file inside our RB tree, Since we grabbed "mtx" | |
1170 | * above, we can be sure to be able to use the item looked up by | |
1171 | * ep_find() till we release the mutex. | |
1172 | */ | |
1173 | epi = ep_find(ep, tfile, fd); | |
1174 | ||
1175 | error = -EINVAL; | |
1176 | switch (op) { | |
1177 | case EPOLL_CTL_ADD: | |
1178 | if (!epi) { | |
1179 | epds.events |= POLLERR | POLLHUP; | |
1180 | ||
1181 | error = ep_insert(ep, &epds, tfile, fd); | |
1182 | } else | |
1183 | error = -EEXIST; | |
1184 | break; | |
1185 | case EPOLL_CTL_DEL: | |
1186 | if (epi) | |
1187 | error = ep_remove(ep, epi); | |
1188 | else | |
1189 | error = -ENOENT; | |
1190 | break; | |
1191 | case EPOLL_CTL_MOD: | |
1192 | if (epi) { | |
1193 | epds.events |= POLLERR | POLLHUP; | |
1194 | error = ep_modify(ep, epi, &epds); | |
1195 | } else | |
1196 | error = -ENOENT; | |
1197 | break; | |
1198 | } | |
1199 | mutex_unlock(&ep->mtx); | |
1200 | ||
1201 | error_tgt_fput: | |
1202 | fput(tfile); | |
1203 | error_fput: | |
1204 | fput(file); | |
1205 | error_return: | |
1206 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %p) = %d\n", | |
1207 | current, epfd, op, fd, event, error)); | |
1208 | ||
1209 | return error; | |
1210 | } | |
1211 | ||
1212 | /* | |
1213 | * Implement the event wait interface for the eventpoll file. It is the kernel | |
1214 | * part of the user space epoll_wait(2). | |
1215 | */ | |
1216 | asmlinkage long sys_epoll_wait(int epfd, struct epoll_event __user *events, | |
1217 | int maxevents, int timeout) | |
1218 | { | |
1219 | int error; | |
1220 | struct file *file; | |
1221 | struct eventpoll *ep; | |
1222 | ||
1223 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_wait(%d, %p, %d, %d)\n", | |
1224 | current, epfd, events, maxevents, timeout)); | |
1225 | ||
1226 | /* The maximum number of event must be greater than zero */ | |
1227 | if (maxevents <= 0 || maxevents > EP_MAX_EVENTS) | |
1228 | return -EINVAL; | |
1229 | ||
1230 | /* Verify that the area passed by the user is writeable */ | |
1231 | if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event))) { | |
1232 | error = -EFAULT; | |
1233 | goto error_return; | |
1234 | } | |
1235 | ||
1236 | /* Get the "struct file *" for the eventpoll file */ | |
1237 | error = -EBADF; | |
1238 | file = fget(epfd); | |
1239 | if (!file) | |
1240 | goto error_return; | |
1241 | ||
1242 | /* | |
1243 | * We have to check that the file structure underneath the fd | |
1244 | * the user passed to us _is_ an eventpoll file. | |
1245 | */ | |
1246 | error = -EINVAL; | |
1247 | if (!is_file_epoll(file)) | |
1248 | goto error_fput; | |
1249 | ||
1250 | /* | |
1251 | * At this point it is safe to assume that the "private_data" contains | |
1252 | * our own data structure. | |
1253 | */ | |
1254 | ep = file->private_data; | |
1255 | ||
1256 | /* Time to fish for events ... */ | |
1257 | error = ep_poll(ep, events, maxevents, timeout); | |
1258 | ||
1259 | error_fput: | |
1260 | fput(file); | |
1261 | error_return: | |
1262 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_wait(%d, %p, %d, %d) = %d\n", | |
1263 | current, epfd, events, maxevents, timeout, error)); | |
1264 | ||
1265 | return error; | |
1266 | } | |
1267 | ||
1268 | #ifdef TIF_RESTORE_SIGMASK | |
1269 | ||
1270 | /* | |
1271 | * Implement the event wait interface for the eventpoll file. It is the kernel | |
1272 | * part of the user space epoll_pwait(2). | |
1273 | */ | |
1274 | asmlinkage long sys_epoll_pwait(int epfd, struct epoll_event __user *events, | |
1275 | int maxevents, int timeout, const sigset_t __user *sigmask, | |
1276 | size_t sigsetsize) | |
1277 | { | |
1278 | int error; | |
1279 | sigset_t ksigmask, sigsaved; | |
1280 | ||
1281 | /* | |
1282 | * If the caller wants a certain signal mask to be set during the wait, | |
1283 | * we apply it here. | |
1284 | */ | |
1285 | if (sigmask) { | |
1286 | if (sigsetsize != sizeof(sigset_t)) | |
1287 | return -EINVAL; | |
1288 | if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) | |
1289 | return -EFAULT; | |
1290 | sigdelsetmask(&ksigmask, sigmask(SIGKILL) | sigmask(SIGSTOP)); | |
1291 | sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); | |
1292 | } | |
1293 | ||
1294 | error = sys_epoll_wait(epfd, events, maxevents, timeout); | |
1295 | ||
1296 | /* | |
1297 | * If we changed the signal mask, we need to restore the original one. | |
1298 | * In case we've got a signal while waiting, we do not restore the | |
1299 | * signal mask yet, and we allow do_signal() to deliver the signal on | |
1300 | * the way back to userspace, before the signal mask is restored. | |
1301 | */ | |
1302 | if (sigmask) { | |
1303 | if (error == -EINTR) { | |
1304 | memcpy(¤t->saved_sigmask, &sigsaved, | |
1305 | sizeof(sigsaved)); | |
1306 | set_thread_flag(TIF_RESTORE_SIGMASK); | |
1307 | } else | |
1308 | sigprocmask(SIG_SETMASK, &sigsaved, NULL); | |
1309 | } | |
1310 | ||
1311 | return error; | |
1312 | } | |
1313 | ||
1314 | #endif /* #ifdef TIF_RESTORE_SIGMASK */ | |
1315 | ||
1316 | static int __init eventpoll_init(void) | |
1317 | { | |
1318 | mutex_init(&epmutex); | |
1319 | ||
1320 | /* Initialize the structure used to perform safe poll wait head wake ups */ | |
1321 | ep_poll_safewake_init(&psw); | |
1322 | ||
1323 | /* Allocates slab cache used to allocate "struct epitem" items */ | |
1324 | epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem), | |
1325 | 0, SLAB_HWCACHE_ALIGN|EPI_SLAB_DEBUG|SLAB_PANIC, | |
1326 | NULL); | |
1327 | ||
1328 | /* Allocates slab cache used to allocate "struct eppoll_entry" */ | |
1329 | pwq_cache = kmem_cache_create("eventpoll_pwq", | |
1330 | sizeof(struct eppoll_entry), 0, | |
1331 | EPI_SLAB_DEBUG|SLAB_PANIC, NULL); | |
1332 | ||
1333 | return 0; | |
1334 | } | |
1335 | fs_initcall(eventpoll_init); | |
1336 |