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1da177e4 | 1 | /* |
5071f97e DL |
2 | * fs/eventpoll.c (Efficient event retrieval implementation) |
3 | * Copyright (C) 2001,...,2009 Davide Libenzi | |
1da177e4 LT |
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 | ||
1da177e4 LT |
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> | |
1da177e4 LT |
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> | |
1da177e4 LT |
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> | |
144efe3e | 34 | #include <linux/mutex.h> |
da66f7cb | 35 | #include <linux/anon_inodes.h> |
1da177e4 LT |
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> | |
1da177e4 | 41 | |
1da177e4 LT |
42 | /* |
43 | * LOCKING: | |
44 | * There are three level of locking required by epoll : | |
45 | * | |
144efe3e | 46 | * 1) epmutex (mutex) |
c7ea7630 DL |
47 | * 2) ep->mtx (mutex) |
48 | * 3) ep->lock (spinlock) | |
1da177e4 LT |
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 | |
d47de16c DL |
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 | |
1da177e4 LT |
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). | |
d47de16c DL |
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. | |
144efe3e | 69 | * Events that require holding "epmutex" are very rare, while for |
d47de16c DL |
70 | * normal operations the epoll private "ep->mtx" will guarantee |
71 | * a better scalability. | |
1da177e4 LT |
72 | */ |
73 | ||
1da177e4 LT |
74 | /* Epoll private bits inside the event mask */ |
75 | #define EP_PRIVATE_BITS (EPOLLONESHOT | EPOLLET) | |
76 | ||
5071f97e DL |
77 | /* Maximum number of nesting allowed inside epoll sets */ |
78 | #define EP_MAX_NESTS 4 | |
1da177e4 | 79 | |
e3306dd5 DL |
80 | /* Maximum msec timeout value storeable in a long int */ |
81 | #define EP_MAX_MSTIMEO min(1000ULL * MAX_SCHEDULE_TIMEOUT / HZ, (LONG_MAX - 999ULL) / HZ) | |
82 | ||
b611967d DL |
83 | #define EP_MAX_EVENTS (INT_MAX / sizeof(struct epoll_event)) |
84 | ||
d47de16c DL |
85 | #define EP_UNACTIVE_PTR ((void *) -1L) |
86 | ||
7ef9964e DL |
87 | #define EP_ITEM_COST (sizeof(struct epitem) + sizeof(struct eppoll_entry)) |
88 | ||
1da177e4 LT |
89 | struct epoll_filefd { |
90 | struct file *file; | |
91 | int fd; | |
92 | }; | |
93 | ||
94 | /* | |
5071f97e DL |
95 | * Structure used to track possible nested calls, for too deep recursions |
96 | * and loop cycles. | |
1da177e4 | 97 | */ |
5071f97e | 98 | struct nested_call_node { |
1da177e4 | 99 | struct list_head llink; |
5071f97e | 100 | void *cookie; |
abff55ce | 101 | int cpu; |
1da177e4 LT |
102 | }; |
103 | ||
104 | /* | |
5071f97e DL |
105 | * This structure is used as collector for nested calls, to check for |
106 | * maximum recursion dept and loop cycles. | |
1da177e4 | 107 | */ |
5071f97e DL |
108 | struct nested_calls { |
109 | struct list_head tasks_call_list; | |
1da177e4 LT |
110 | spinlock_t lock; |
111 | }; | |
112 | ||
d47de16c DL |
113 | /* |
114 | * Each file descriptor added to the eventpoll interface will | |
115 | * have an entry of this type linked to the "rbr" RB tree. | |
116 | */ | |
117 | struct epitem { | |
67647d0f | 118 | /* RB tree node used to link this structure to the eventpoll RB tree */ |
d47de16c DL |
119 | struct rb_node rbn; |
120 | ||
121 | /* List header used to link this structure to the eventpoll ready list */ | |
122 | struct list_head rdllink; | |
123 | ||
c7ea7630 DL |
124 | /* |
125 | * Works together "struct eventpoll"->ovflist in keeping the | |
126 | * single linked chain of items. | |
127 | */ | |
128 | struct epitem *next; | |
129 | ||
d47de16c DL |
130 | /* The file descriptor information this item refers to */ |
131 | struct epoll_filefd ffd; | |
132 | ||
133 | /* Number of active wait queue attached to poll operations */ | |
134 | int nwait; | |
135 | ||
136 | /* List containing poll wait queues */ | |
137 | struct list_head pwqlist; | |
138 | ||
139 | /* The "container" of this item */ | |
140 | struct eventpoll *ep; | |
141 | ||
d47de16c DL |
142 | /* List header used to link this item to the "struct file" items list */ |
143 | struct list_head fllink; | |
144 | ||
c7ea7630 DL |
145 | /* The structure that describe the interested events and the source fd */ |
146 | struct epoll_event event; | |
d47de16c DL |
147 | }; |
148 | ||
1da177e4 LT |
149 | /* |
150 | * This structure is stored inside the "private_data" member of the file | |
151 | * structure and rapresent the main data sructure for the eventpoll | |
152 | * interface. | |
153 | */ | |
154 | struct eventpoll { | |
155 | /* Protect the this structure access */ | |
c7ea7630 | 156 | spinlock_t lock; |
1da177e4 LT |
157 | |
158 | /* | |
d47de16c DL |
159 | * This mutex is used to ensure that files are not removed |
160 | * while epoll is using them. This is held during the event | |
161 | * collection loop, the file cleanup path, the epoll file exit | |
162 | * code and the ctl operations. | |
1da177e4 | 163 | */ |
d47de16c | 164 | struct mutex mtx; |
1da177e4 LT |
165 | |
166 | /* Wait queue used by sys_epoll_wait() */ | |
167 | wait_queue_head_t wq; | |
168 | ||
169 | /* Wait queue used by file->poll() */ | |
170 | wait_queue_head_t poll_wait; | |
171 | ||
172 | /* List of ready file descriptors */ | |
173 | struct list_head rdllist; | |
174 | ||
67647d0f | 175 | /* RB tree root used to store monitored fd structs */ |
1da177e4 | 176 | struct rb_root rbr; |
d47de16c DL |
177 | |
178 | /* | |
179 | * This is a single linked list that chains all the "struct epitem" that | |
180 | * happened while transfering ready events to userspace w/out | |
181 | * holding ->lock. | |
182 | */ | |
183 | struct epitem *ovflist; | |
7ef9964e DL |
184 | |
185 | /* The user that created the eventpoll descriptor */ | |
186 | struct user_struct *user; | |
1da177e4 LT |
187 | }; |
188 | ||
189 | /* Wait structure used by the poll hooks */ | |
190 | struct eppoll_entry { | |
191 | /* List header used to link this structure to the "struct epitem" */ | |
192 | struct list_head llink; | |
193 | ||
194 | /* The "base" pointer is set to the container "struct epitem" */ | |
195 | void *base; | |
196 | ||
197 | /* | |
198 | * Wait queue item that will be linked to the target file wait | |
199 | * queue head. | |
200 | */ | |
201 | wait_queue_t wait; | |
202 | ||
203 | /* The wait queue head that linked the "wait" wait queue item */ | |
204 | wait_queue_head_t *whead; | |
205 | }; | |
206 | ||
1da177e4 LT |
207 | /* Wrapper struct used by poll queueing */ |
208 | struct ep_pqueue { | |
209 | poll_table pt; | |
210 | struct epitem *epi; | |
211 | }; | |
212 | ||
5071f97e DL |
213 | /* Used by the ep_send_events() function as callback private data */ |
214 | struct ep_send_events_data { | |
215 | int maxevents; | |
216 | struct epoll_event __user *events; | |
217 | }; | |
218 | ||
7ef9964e DL |
219 | /* |
220 | * Configuration options available inside /proc/sys/fs/epoll/ | |
221 | */ | |
7ef9964e DL |
222 | /* Maximum number of epoll watched descriptors, per user */ |
223 | static int max_user_watches __read_mostly; | |
224 | ||
1da177e4 | 225 | /* |
d47de16c | 226 | * This mutex is used to serialize ep_free() and eventpoll_release_file(). |
1da177e4 | 227 | */ |
7ef9964e | 228 | static DEFINE_MUTEX(epmutex); |
1da177e4 | 229 | |
5071f97e DL |
230 | /* Used for safe wake up implementation */ |
231 | static struct nested_calls poll_safewake_ncalls; | |
232 | ||
233 | /* Used to call file's f_op->poll() under the nested calls boundaries */ | |
234 | static struct nested_calls poll_readywalk_ncalls; | |
1da177e4 LT |
235 | |
236 | /* Slab cache used to allocate "struct epitem" */ | |
e18b890b | 237 | static struct kmem_cache *epi_cache __read_mostly; |
1da177e4 LT |
238 | |
239 | /* Slab cache used to allocate "struct eppoll_entry" */ | |
e18b890b | 240 | static struct kmem_cache *pwq_cache __read_mostly; |
1da177e4 | 241 | |
7ef9964e DL |
242 | #ifdef CONFIG_SYSCTL |
243 | ||
244 | #include <linux/sysctl.h> | |
245 | ||
246 | static int zero; | |
247 | ||
248 | ctl_table epoll_table[] = { | |
7ef9964e DL |
249 | { |
250 | .procname = "max_user_watches", | |
251 | .data = &max_user_watches, | |
252 | .maxlen = sizeof(int), | |
253 | .mode = 0644, | |
254 | .proc_handler = &proc_dointvec_minmax, | |
255 | .extra1 = &zero, | |
256 | }, | |
257 | { .ctl_name = 0 } | |
258 | }; | |
259 | #endif /* CONFIG_SYSCTL */ | |
260 | ||
b030a4dd | 261 | |
67647d0f | 262 | /* Setup the structure that is used as key for the RB tree */ |
b030a4dd PE |
263 | static inline void ep_set_ffd(struct epoll_filefd *ffd, |
264 | struct file *file, int fd) | |
265 | { | |
266 | ffd->file = file; | |
267 | ffd->fd = fd; | |
268 | } | |
269 | ||
67647d0f | 270 | /* Compare RB tree keys */ |
b030a4dd PE |
271 | static inline int ep_cmp_ffd(struct epoll_filefd *p1, |
272 | struct epoll_filefd *p2) | |
273 | { | |
274 | return (p1->file > p2->file ? +1: | |
275 | (p1->file < p2->file ? -1 : p1->fd - p2->fd)); | |
276 | } | |
277 | ||
b030a4dd PE |
278 | /* Tells us if the item is currently linked */ |
279 | static inline int ep_is_linked(struct list_head *p) | |
280 | { | |
281 | return !list_empty(p); | |
282 | } | |
283 | ||
284 | /* Get the "struct epitem" from a wait queue pointer */ | |
cdac75e6 | 285 | static inline struct epitem *ep_item_from_wait(wait_queue_t *p) |
b030a4dd PE |
286 | { |
287 | return container_of(p, struct eppoll_entry, wait)->base; | |
288 | } | |
289 | ||
290 | /* Get the "struct epitem" from an epoll queue wrapper */ | |
cdac75e6 | 291 | static inline struct epitem *ep_item_from_epqueue(poll_table *p) |
b030a4dd PE |
292 | { |
293 | return container_of(p, struct ep_pqueue, pt)->epi; | |
294 | } | |
295 | ||
296 | /* Tells if the epoll_ctl(2) operation needs an event copy from userspace */ | |
6192bd53 | 297 | static inline int ep_op_has_event(int op) |
b030a4dd PE |
298 | { |
299 | return op != EPOLL_CTL_DEL; | |
300 | } | |
301 | ||
1da177e4 | 302 | /* Initialize the poll safe wake up structure */ |
5071f97e | 303 | static void ep_nested_calls_init(struct nested_calls *ncalls) |
1da177e4 | 304 | { |
5071f97e DL |
305 | INIT_LIST_HEAD(&ncalls->tasks_call_list); |
306 | spin_lock_init(&ncalls->lock); | |
1da177e4 LT |
307 | } |
308 | ||
5071f97e DL |
309 | /** |
310 | * ep_call_nested - Perform a bound (possibly) nested call, by checking | |
311 | * that the recursion limit is not exceeded, and that | |
312 | * the same nested call (by the meaning of same cookie) is | |
313 | * no re-entered. | |
314 | * | |
315 | * @ncalls: Pointer to the nested_calls structure to be used for this call. | |
316 | * @max_nests: Maximum number of allowed nesting calls. | |
317 | * @nproc: Nested call core function pointer. | |
318 | * @priv: Opaque data to be passed to the @nproc callback. | |
319 | * @cookie: Cookie to be used to identify this nested call. | |
320 | * | |
321 | * Returns: Returns the code returned by the @nproc callback, or -1 if | |
322 | * the maximum recursion limit has been exceeded. | |
1da177e4 | 323 | */ |
5071f97e DL |
324 | static int ep_call_nested(struct nested_calls *ncalls, int max_nests, |
325 | int (*nproc)(void *, void *, int), void *priv, | |
326 | void *cookie) | |
1da177e4 | 327 | { |
5071f97e | 328 | int error, call_nests = 0; |
1da177e4 | 329 | unsigned long flags; |
abff55ce | 330 | int this_cpu = get_cpu(); |
5071f97e DL |
331 | struct list_head *lsthead = &ncalls->tasks_call_list; |
332 | struct nested_call_node *tncur; | |
333 | struct nested_call_node tnode; | |
1da177e4 | 334 | |
5071f97e | 335 | spin_lock_irqsave(&ncalls->lock, flags); |
1da177e4 | 336 | |
5071f97e DL |
337 | /* |
338 | * Try to see if the current task is already inside this wakeup call. | |
339 | * We use a list here, since the population inside this set is always | |
340 | * very much limited. | |
341 | */ | |
b70c3940 | 342 | list_for_each_entry(tncur, lsthead, llink) { |
abff55ce | 343 | if (tncur->cpu == this_cpu && |
5071f97e | 344 | (tncur->cookie == cookie || ++call_nests > max_nests)) { |
1da177e4 LT |
345 | /* |
346 | * Ops ... loop detected or maximum nest level reached. | |
347 | * We abort this wake by breaking the cycle itself. | |
348 | */ | |
abff55ce TB |
349 | error = -1; |
350 | goto out_unlock; | |
1da177e4 LT |
351 | } |
352 | } | |
353 | ||
5071f97e | 354 | /* Add the current task and cookie to the list */ |
abff55ce | 355 | tnode.cpu = this_cpu; |
5071f97e | 356 | tnode.cookie = cookie; |
1da177e4 LT |
357 | list_add(&tnode.llink, lsthead); |
358 | ||
5071f97e | 359 | spin_unlock_irqrestore(&ncalls->lock, flags); |
1da177e4 | 360 | |
5071f97e DL |
361 | /* Call the nested function */ |
362 | error = (*nproc)(priv, cookie, call_nests); | |
1da177e4 LT |
363 | |
364 | /* Remove the current task from the list */ | |
5071f97e | 365 | spin_lock_irqsave(&ncalls->lock, flags); |
1da177e4 | 366 | list_del(&tnode.llink); |
abff55ce | 367 | out_unlock: |
5071f97e DL |
368 | spin_unlock_irqrestore(&ncalls->lock, flags); |
369 | ||
abff55ce | 370 | put_cpu(); |
5071f97e DL |
371 | return error; |
372 | } | |
373 | ||
374 | static int ep_poll_wakeup_proc(void *priv, void *cookie, int call_nests) | |
375 | { | |
376 | wake_up_nested((wait_queue_head_t *) cookie, 1 + call_nests); | |
377 | return 0; | |
378 | } | |
379 | ||
380 | /* | |
381 | * Perform a safe wake up of the poll wait list. The problem is that | |
382 | * with the new callback'd wake up system, it is possible that the | |
383 | * poll callback is reentered from inside the call to wake_up() done | |
384 | * on the poll wait queue head. The rule is that we cannot reenter the | |
385 | * wake up code from the same task more than EP_MAX_NESTS times, | |
386 | * and we cannot reenter the same wait queue head at all. This will | |
387 | * enable to have a hierarchy of epoll file descriptor of no more than | |
388 | * EP_MAX_NESTS deep. | |
389 | */ | |
390 | static void ep_poll_safewake(wait_queue_head_t *wq) | |
391 | { | |
392 | ep_call_nested(&poll_safewake_ncalls, EP_MAX_NESTS, | |
393 | ep_poll_wakeup_proc, NULL, wq); | |
1da177e4 LT |
394 | } |
395 | ||
1da177e4 | 396 | /* |
7699acd1 DL |
397 | * This function unregister poll callbacks from the associated file descriptor. |
398 | * Since this must be called without holding "ep->lock" the atomic exchange trick | |
399 | * will protect us from multiple unregister. | |
1da177e4 | 400 | */ |
7699acd1 | 401 | static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi) |
1da177e4 | 402 | { |
7699acd1 DL |
403 | int nwait; |
404 | struct list_head *lsthead = &epi->pwqlist; | |
405 | struct eppoll_entry *pwq; | |
1da177e4 | 406 | |
7699acd1 DL |
407 | /* This is called without locks, so we need the atomic exchange */ |
408 | nwait = xchg(&epi->nwait, 0); | |
1da177e4 | 409 | |
7699acd1 DL |
410 | if (nwait) { |
411 | while (!list_empty(lsthead)) { | |
412 | pwq = list_first_entry(lsthead, struct eppoll_entry, llink); | |
1da177e4 | 413 | |
7699acd1 DL |
414 | list_del_init(&pwq->llink); |
415 | remove_wait_queue(pwq->whead, &pwq->wait); | |
416 | kmem_cache_free(pwq_cache, pwq); | |
417 | } | |
1da177e4 | 418 | } |
1da177e4 LT |
419 | } |
420 | ||
5071f97e DL |
421 | /** |
422 | * ep_scan_ready_list - Scans the ready list in a way that makes possible for | |
423 | * the scan code, to call f_op->poll(). Also allows for | |
424 | * O(NumReady) performance. | |
425 | * | |
426 | * @ep: Pointer to the epoll private data structure. | |
427 | * @sproc: Pointer to the scan callback. | |
428 | * @priv: Private opaque data passed to the @sproc callback. | |
429 | * | |
430 | * Returns: The same integer error code returned by the @sproc callback. | |
431 | */ | |
432 | static int ep_scan_ready_list(struct eventpoll *ep, | |
433 | int (*sproc)(struct eventpoll *, | |
434 | struct list_head *, void *), | |
435 | void *priv) | |
436 | { | |
437 | int error, pwake = 0; | |
438 | unsigned long flags; | |
439 | struct epitem *epi, *nepi; | |
296e236e | 440 | LIST_HEAD(txlist); |
5071f97e DL |
441 | |
442 | /* | |
443 | * We need to lock this because we could be hit by | |
444 | * eventpoll_release_file() and epoll_ctl(EPOLL_CTL_DEL). | |
445 | */ | |
446 | mutex_lock(&ep->mtx); | |
447 | ||
448 | /* | |
449 | * Steal the ready list, and re-init the original one to the | |
450 | * empty list. Also, set ep->ovflist to NULL so that events | |
451 | * happening while looping w/out locks, are not lost. We cannot | |
452 | * have the poll callback to queue directly on ep->rdllist, | |
453 | * because we want the "sproc" callback to be able to do it | |
454 | * in a lockless way. | |
455 | */ | |
456 | spin_lock_irqsave(&ep->lock, flags); | |
296e236e | 457 | list_splice_init(&ep->rdllist, &txlist); |
5071f97e DL |
458 | ep->ovflist = NULL; |
459 | spin_unlock_irqrestore(&ep->lock, flags); | |
460 | ||
461 | /* | |
462 | * Now call the callback function. | |
463 | */ | |
464 | error = (*sproc)(ep, &txlist, priv); | |
465 | ||
466 | spin_lock_irqsave(&ep->lock, flags); | |
467 | /* | |
468 | * During the time we spent inside the "sproc" callback, some | |
469 | * other events might have been queued by the poll callback. | |
470 | * We re-insert them inside the main ready-list here. | |
471 | */ | |
472 | for (nepi = ep->ovflist; (epi = nepi) != NULL; | |
473 | nepi = epi->next, epi->next = EP_UNACTIVE_PTR) { | |
474 | /* | |
475 | * We need to check if the item is already in the list. | |
476 | * During the "sproc" callback execution time, items are | |
477 | * queued into ->ovflist but the "txlist" might already | |
478 | * contain them, and the list_splice() below takes care of them. | |
479 | */ | |
480 | if (!ep_is_linked(&epi->rdllink)) | |
481 | list_add_tail(&epi->rdllink, &ep->rdllist); | |
482 | } | |
483 | /* | |
484 | * We need to set back ep->ovflist to EP_UNACTIVE_PTR, so that after | |
485 | * releasing the lock, events will be queued in the normal way inside | |
486 | * ep->rdllist. | |
487 | */ | |
488 | ep->ovflist = EP_UNACTIVE_PTR; | |
489 | ||
490 | /* | |
491 | * Quickly re-inject items left on "txlist". | |
492 | */ | |
493 | list_splice(&txlist, &ep->rdllist); | |
494 | ||
495 | if (!list_empty(&ep->rdllist)) { | |
496 | /* | |
296e236e DL |
497 | * Wake up (if active) both the eventpoll wait list and |
498 | * the ->poll() wait list (delayed after we release the lock). | |
5071f97e DL |
499 | */ |
500 | if (waitqueue_active(&ep->wq)) | |
501 | wake_up_locked(&ep->wq); | |
502 | if (waitqueue_active(&ep->poll_wait)) | |
503 | pwake++; | |
504 | } | |
505 | spin_unlock_irqrestore(&ep->lock, flags); | |
506 | ||
507 | mutex_unlock(&ep->mtx); | |
508 | ||
509 | /* We have to call this outside the lock */ | |
510 | if (pwake) | |
511 | ep_poll_safewake(&ep->poll_wait); | |
512 | ||
513 | return error; | |
514 | } | |
515 | ||
7699acd1 DL |
516 | /* |
517 | * Removes a "struct epitem" from the eventpoll RB tree and deallocates | |
c7ea7630 | 518 | * all the associated resources. Must be called with "mtx" held. |
7699acd1 DL |
519 | */ |
520 | static int ep_remove(struct eventpoll *ep, struct epitem *epi) | |
521 | { | |
7699acd1 DL |
522 | unsigned long flags; |
523 | struct file *file = epi->ffd.file; | |
1da177e4 LT |
524 | |
525 | /* | |
7699acd1 DL |
526 | * Removes poll wait queue hooks. We _have_ to do this without holding |
527 | * the "ep->lock" otherwise a deadlock might occur. This because of the | |
528 | * sequence of the lock acquisition. Here we do "ep->lock" then the wait | |
529 | * queue head lock when unregistering the wait queue. The wakeup callback | |
530 | * will run by holding the wait queue head lock and will call our callback | |
531 | * that will try to get "ep->lock". | |
1da177e4 | 532 | */ |
7699acd1 | 533 | ep_unregister_pollwait(ep, epi); |
1da177e4 | 534 | |
7699acd1 | 535 | /* Remove the current item from the list of epoll hooks */ |
68499914 | 536 | spin_lock(&file->f_lock); |
7699acd1 DL |
537 | if (ep_is_linked(&epi->fllink)) |
538 | list_del_init(&epi->fllink); | |
68499914 | 539 | spin_unlock(&file->f_lock); |
1da177e4 | 540 | |
cdac75e6 | 541 | rb_erase(&epi->rbn, &ep->rbr); |
1da177e4 | 542 | |
c7ea7630 DL |
543 | spin_lock_irqsave(&ep->lock, flags); |
544 | if (ep_is_linked(&epi->rdllink)) | |
545 | list_del_init(&epi->rdllink); | |
546 | spin_unlock_irqrestore(&ep->lock, flags); | |
1da177e4 | 547 | |
7699acd1 | 548 | /* At this point it is safe to free the eventpoll item */ |
c7ea7630 | 549 | kmem_cache_free(epi_cache, epi); |
1da177e4 | 550 | |
7ef9964e DL |
551 | atomic_dec(&ep->user->epoll_watches); |
552 | ||
c7ea7630 | 553 | return 0; |
1da177e4 LT |
554 | } |
555 | ||
7699acd1 | 556 | static void ep_free(struct eventpoll *ep) |
1da177e4 | 557 | { |
7699acd1 DL |
558 | struct rb_node *rbp; |
559 | struct epitem *epi; | |
1da177e4 | 560 | |
7699acd1 DL |
561 | /* We need to release all tasks waiting for these file */ |
562 | if (waitqueue_active(&ep->poll_wait)) | |
5071f97e | 563 | ep_poll_safewake(&ep->poll_wait); |
1da177e4 | 564 | |
7699acd1 DL |
565 | /* |
566 | * We need to lock this because we could be hit by | |
567 | * eventpoll_release_file() while we're freeing the "struct eventpoll". | |
d47de16c | 568 | * We do not need to hold "ep->mtx" here because the epoll file |
7699acd1 DL |
569 | * is on the way to be removed and no one has references to it |
570 | * anymore. The only hit might come from eventpoll_release_file() but | |
571 | * holding "epmutex" is sufficent here. | |
572 | */ | |
573 | mutex_lock(&epmutex); | |
1da177e4 LT |
574 | |
575 | /* | |
7699acd1 | 576 | * Walks through the whole tree by unregistering poll callbacks. |
1da177e4 | 577 | */ |
7699acd1 DL |
578 | for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { |
579 | epi = rb_entry(rbp, struct epitem, rbn); | |
580 | ||
581 | ep_unregister_pollwait(ep, epi); | |
582 | } | |
1da177e4 LT |
583 | |
584 | /* | |
7699acd1 DL |
585 | * Walks through the whole tree by freeing each "struct epitem". At this |
586 | * point we are sure no poll callbacks will be lingering around, and also by | |
d47de16c | 587 | * holding "epmutex" we can be sure that no file cleanup code will hit |
7699acd1 | 588 | * us during this operation. So we can avoid the lock on "ep->lock". |
1da177e4 | 589 | */ |
c80544dc | 590 | while ((rbp = rb_first(&ep->rbr)) != NULL) { |
7699acd1 DL |
591 | epi = rb_entry(rbp, struct epitem, rbn); |
592 | ep_remove(ep, epi); | |
593 | } | |
1da177e4 | 594 | |
7699acd1 | 595 | mutex_unlock(&epmutex); |
d47de16c | 596 | mutex_destroy(&ep->mtx); |
7ef9964e | 597 | free_uid(ep->user); |
f0ee9aab | 598 | kfree(ep); |
7699acd1 | 599 | } |
1da177e4 | 600 | |
7699acd1 DL |
601 | static int ep_eventpoll_release(struct inode *inode, struct file *file) |
602 | { | |
603 | struct eventpoll *ep = file->private_data; | |
1da177e4 | 604 | |
f0ee9aab | 605 | if (ep) |
7699acd1 | 606 | ep_free(ep); |
7699acd1 | 607 | |
7699acd1 | 608 | return 0; |
1da177e4 LT |
609 | } |
610 | ||
296e236e DL |
611 | static int ep_read_events_proc(struct eventpoll *ep, struct list_head *head, |
612 | void *priv) | |
5071f97e DL |
613 | { |
614 | struct epitem *epi, *tmp; | |
615 | ||
616 | list_for_each_entry_safe(epi, tmp, head, rdllink) { | |
617 | if (epi->ffd.file->f_op->poll(epi->ffd.file, NULL) & | |
618 | epi->event.events) | |
619 | return POLLIN | POLLRDNORM; | |
296e236e | 620 | else { |
5071f97e DL |
621 | /* |
622 | * Item has been dropped into the ready list by the poll | |
623 | * callback, but it's not actually ready, as far as | |
624 | * caller requested events goes. We can remove it here. | |
625 | */ | |
626 | list_del_init(&epi->rdllink); | |
296e236e | 627 | } |
5071f97e DL |
628 | } |
629 | ||
630 | return 0; | |
631 | } | |
632 | ||
633 | static int ep_poll_readyevents_proc(void *priv, void *cookie, int call_nests) | |
634 | { | |
635 | return ep_scan_ready_list(priv, ep_read_events_proc, NULL); | |
636 | } | |
637 | ||
7699acd1 DL |
638 | static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait) |
639 | { | |
5071f97e | 640 | int pollflags; |
7699acd1 | 641 | struct eventpoll *ep = file->private_data; |
1da177e4 | 642 | |
7699acd1 DL |
643 | /* Insert inside our poll wait queue */ |
644 | poll_wait(file, &ep->poll_wait, wait); | |
645 | ||
5071f97e DL |
646 | /* |
647 | * Proceed to find out if wanted events are really available inside | |
648 | * the ready list. This need to be done under ep_call_nested() | |
649 | * supervision, since the call to f_op->poll() done on listed files | |
650 | * could re-enter here. | |
651 | */ | |
652 | pollflags = ep_call_nested(&poll_readywalk_ncalls, EP_MAX_NESTS, | |
653 | ep_poll_readyevents_proc, ep, ep); | |
7699acd1 | 654 | |
296e236e | 655 | return pollflags != -1 ? pollflags : 0; |
7699acd1 DL |
656 | } |
657 | ||
658 | /* File callbacks that implement the eventpoll file behaviour */ | |
659 | static const struct file_operations eventpoll_fops = { | |
660 | .release = ep_eventpoll_release, | |
661 | .poll = ep_eventpoll_poll | |
662 | }; | |
663 | ||
664 | /* Fast test to see if the file is an evenpoll file */ | |
665 | static inline int is_file_epoll(struct file *f) | |
666 | { | |
667 | return f->f_op == &eventpoll_fops; | |
668 | } | |
b611967d DL |
669 | |
670 | /* | |
7699acd1 DL |
671 | * This is called from eventpoll_release() to unlink files from the eventpoll |
672 | * interface. We need to have this facility to cleanup correctly files that are | |
673 | * closed without being removed from the eventpoll interface. | |
b611967d | 674 | */ |
7699acd1 | 675 | void eventpoll_release_file(struct file *file) |
b611967d | 676 | { |
7699acd1 DL |
677 | struct list_head *lsthead = &file->f_ep_links; |
678 | struct eventpoll *ep; | |
679 | struct epitem *epi; | |
b611967d DL |
680 | |
681 | /* | |
68499914 | 682 | * We don't want to get "file->f_lock" because it is not |
7699acd1 DL |
683 | * necessary. It is not necessary because we're in the "struct file" |
684 | * cleanup path, and this means that noone is using this file anymore. | |
5071f97e | 685 | * So, for example, epoll_ctl() cannot hit here since if we reach this |
67647d0f | 686 | * point, the file counter already went to zero and fget() would fail. |
d47de16c | 687 | * The only hit might come from ep_free() but by holding the mutex |
7699acd1 | 688 | * will correctly serialize the operation. We do need to acquire |
d47de16c | 689 | * "ep->mtx" after "epmutex" because ep_remove() requires it when called |
7699acd1 | 690 | * from anywhere but ep_free(). |
68499914 JC |
691 | * |
692 | * Besides, ep_remove() acquires the lock, so we can't hold it here. | |
b611967d | 693 | */ |
7699acd1 | 694 | mutex_lock(&epmutex); |
b611967d | 695 | |
7699acd1 DL |
696 | while (!list_empty(lsthead)) { |
697 | epi = list_first_entry(lsthead, struct epitem, fllink); | |
b611967d | 698 | |
7699acd1 DL |
699 | ep = epi->ep; |
700 | list_del_init(&epi->fllink); | |
d47de16c | 701 | mutex_lock(&ep->mtx); |
7699acd1 | 702 | ep_remove(ep, epi); |
d47de16c | 703 | mutex_unlock(&ep->mtx); |
b611967d DL |
704 | } |
705 | ||
7699acd1 | 706 | mutex_unlock(&epmutex); |
b611967d DL |
707 | } |
708 | ||
53d2be79 | 709 | static int ep_alloc(struct eventpoll **pep) |
1da177e4 | 710 | { |
7ef9964e DL |
711 | int error; |
712 | struct user_struct *user; | |
713 | struct eventpoll *ep; | |
1da177e4 | 714 | |
7ef9964e | 715 | user = get_current_user(); |
7ef9964e DL |
716 | error = -ENOMEM; |
717 | ep = kzalloc(sizeof(*ep), GFP_KERNEL); | |
718 | if (unlikely(!ep)) | |
719 | goto free_uid; | |
1da177e4 | 720 | |
c7ea7630 | 721 | spin_lock_init(&ep->lock); |
d47de16c | 722 | mutex_init(&ep->mtx); |
1da177e4 LT |
723 | init_waitqueue_head(&ep->wq); |
724 | init_waitqueue_head(&ep->poll_wait); | |
725 | INIT_LIST_HEAD(&ep->rdllist); | |
726 | ep->rbr = RB_ROOT; | |
d47de16c | 727 | ep->ovflist = EP_UNACTIVE_PTR; |
7ef9964e | 728 | ep->user = user; |
1da177e4 | 729 | |
53d2be79 | 730 | *pep = ep; |
1da177e4 | 731 | |
1da177e4 | 732 | return 0; |
7ef9964e DL |
733 | |
734 | free_uid: | |
735 | free_uid(user); | |
736 | return error; | |
1da177e4 LT |
737 | } |
738 | ||
1da177e4 | 739 | /* |
c7ea7630 DL |
740 | * Search the file inside the eventpoll tree. The RB tree operations |
741 | * are protected by the "mtx" mutex, and ep_find() must be called with | |
742 | * "mtx" held. | |
1da177e4 LT |
743 | */ |
744 | static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd) | |
745 | { | |
746 | int kcmp; | |
1da177e4 LT |
747 | struct rb_node *rbp; |
748 | struct epitem *epi, *epir = NULL; | |
749 | struct epoll_filefd ffd; | |
750 | ||
b030a4dd | 751 | ep_set_ffd(&ffd, file, fd); |
1da177e4 LT |
752 | for (rbp = ep->rbr.rb_node; rbp; ) { |
753 | epi = rb_entry(rbp, struct epitem, rbn); | |
b030a4dd | 754 | kcmp = ep_cmp_ffd(&ffd, &epi->ffd); |
1da177e4 LT |
755 | if (kcmp > 0) |
756 | rbp = rbp->rb_right; | |
757 | else if (kcmp < 0) | |
758 | rbp = rbp->rb_left; | |
759 | else { | |
1da177e4 LT |
760 | epir = epi; |
761 | break; | |
762 | } | |
763 | } | |
1da177e4 | 764 | |
1da177e4 LT |
765 | return epir; |
766 | } | |
767 | ||
1da177e4 | 768 | /* |
7699acd1 DL |
769 | * This is the callback that is passed to the wait queue wakeup |
770 | * machanism. It is called by the stored file descriptors when they | |
771 | * have events to report. | |
1da177e4 | 772 | */ |
7699acd1 | 773 | static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *key) |
1da177e4 | 774 | { |
7699acd1 DL |
775 | int pwake = 0; |
776 | unsigned long flags; | |
777 | struct epitem *epi = ep_item_from_wait(wait); | |
778 | struct eventpoll *ep = epi->ep; | |
1da177e4 | 779 | |
c7ea7630 | 780 | spin_lock_irqsave(&ep->lock, flags); |
1da177e4 | 781 | |
7699acd1 DL |
782 | /* |
783 | * If the event mask does not contain any poll(2) event, we consider the | |
784 | * descriptor to be disabled. This condition is likely the effect of the | |
785 | * EPOLLONESHOT bit that disables the descriptor when an event is received, | |
786 | * until the next EPOLL_CTL_MOD will be issued. | |
787 | */ | |
788 | if (!(epi->event.events & ~EP_PRIVATE_BITS)) | |
d47de16c DL |
789 | goto out_unlock; |
790 | ||
791 | /* | |
792 | * If we are trasfering events to userspace, we can hold no locks | |
793 | * (because we're accessing user memory, and because of linux f_op->poll() | |
794 | * semantics). All the events that happens during that period of time are | |
795 | * chained in ep->ovflist and requeued later on. | |
796 | */ | |
797 | if (unlikely(ep->ovflist != EP_UNACTIVE_PTR)) { | |
798 | if (epi->next == EP_UNACTIVE_PTR) { | |
799 | epi->next = ep->ovflist; | |
800 | ep->ovflist = epi; | |
801 | } | |
802 | goto out_unlock; | |
803 | } | |
1da177e4 | 804 | |
7699acd1 | 805 | /* If this file is already in the ready list we exit soon */ |
5071f97e DL |
806 | if (!ep_is_linked(&epi->rdllink)) |
807 | list_add_tail(&epi->rdllink, &ep->rdllist); | |
7699acd1 | 808 | |
7699acd1 DL |
809 | /* |
810 | * Wake up ( if active ) both the eventpoll wait list and the ->poll() | |
811 | * wait list. | |
812 | */ | |
813 | if (waitqueue_active(&ep->wq)) | |
4a6e9e2c | 814 | wake_up_locked(&ep->wq); |
7699acd1 DL |
815 | if (waitqueue_active(&ep->poll_wait)) |
816 | pwake++; | |
817 | ||
d47de16c | 818 | out_unlock: |
c7ea7630 | 819 | spin_unlock_irqrestore(&ep->lock, flags); |
1da177e4 | 820 | |
7699acd1 DL |
821 | /* We have to call this outside the lock */ |
822 | if (pwake) | |
5071f97e | 823 | ep_poll_safewake(&ep->poll_wait); |
7699acd1 DL |
824 | |
825 | return 1; | |
826 | } | |
1da177e4 LT |
827 | |
828 | /* | |
829 | * This is the callback that is used to add our wait queue to the | |
830 | * target file wakeup lists. | |
831 | */ | |
832 | static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, | |
833 | poll_table *pt) | |
834 | { | |
b030a4dd | 835 | struct epitem *epi = ep_item_from_epqueue(pt); |
1da177e4 LT |
836 | struct eppoll_entry *pwq; |
837 | ||
e94b1766 | 838 | if (epi->nwait >= 0 && (pwq = kmem_cache_alloc(pwq_cache, GFP_KERNEL))) { |
1da177e4 LT |
839 | init_waitqueue_func_entry(&pwq->wait, ep_poll_callback); |
840 | pwq->whead = whead; | |
841 | pwq->base = epi; | |
842 | add_wait_queue(whead, &pwq->wait); | |
843 | list_add_tail(&pwq->llink, &epi->pwqlist); | |
844 | epi->nwait++; | |
296e236e | 845 | } else { |
1da177e4 LT |
846 | /* We have to signal that an error occurred */ |
847 | epi->nwait = -1; | |
296e236e | 848 | } |
1da177e4 LT |
849 | } |
850 | ||
1da177e4 LT |
851 | static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi) |
852 | { | |
853 | int kcmp; | |
854 | struct rb_node **p = &ep->rbr.rb_node, *parent = NULL; | |
855 | struct epitem *epic; | |
856 | ||
857 | while (*p) { | |
858 | parent = *p; | |
859 | epic = rb_entry(parent, struct epitem, rbn); | |
b030a4dd | 860 | kcmp = ep_cmp_ffd(&epi->ffd, &epic->ffd); |
1da177e4 LT |
861 | if (kcmp > 0) |
862 | p = &parent->rb_right; | |
863 | else | |
864 | p = &parent->rb_left; | |
865 | } | |
866 | rb_link_node(&epi->rbn, parent, p); | |
867 | rb_insert_color(&epi->rbn, &ep->rbr); | |
868 | } | |
869 | ||
c7ea7630 DL |
870 | /* |
871 | * Must be called with "mtx" held. | |
872 | */ | |
1da177e4 LT |
873 | static int ep_insert(struct eventpoll *ep, struct epoll_event *event, |
874 | struct file *tfile, int fd) | |
875 | { | |
876 | int error, revents, pwake = 0; | |
877 | unsigned long flags; | |
878 | struct epitem *epi; | |
879 | struct ep_pqueue epq; | |
880 | ||
7ef9964e DL |
881 | if (unlikely(atomic_read(&ep->user->epoll_watches) >= |
882 | max_user_watches)) | |
883 | return -ENOSPC; | |
e94b1766 | 884 | if (!(epi = kmem_cache_alloc(epi_cache, GFP_KERNEL))) |
7ef9964e | 885 | return -ENOMEM; |
1da177e4 LT |
886 | |
887 | /* Item initialization follow here ... */ | |
1da177e4 LT |
888 | INIT_LIST_HEAD(&epi->rdllink); |
889 | INIT_LIST_HEAD(&epi->fllink); | |
1da177e4 LT |
890 | INIT_LIST_HEAD(&epi->pwqlist); |
891 | epi->ep = ep; | |
b030a4dd | 892 | ep_set_ffd(&epi->ffd, tfile, fd); |
1da177e4 | 893 | epi->event = *event; |
1da177e4 | 894 | epi->nwait = 0; |
d47de16c | 895 | epi->next = EP_UNACTIVE_PTR; |
1da177e4 LT |
896 | |
897 | /* Initialize the poll table using the queue callback */ | |
898 | epq.epi = epi; | |
899 | init_poll_funcptr(&epq.pt, ep_ptable_queue_proc); | |
900 | ||
901 | /* | |
902 | * Attach the item to the poll hooks and get current event bits. | |
903 | * We can safely use the file* here because its usage count has | |
c7ea7630 DL |
904 | * been increased by the caller of this function. Note that after |
905 | * this operation completes, the poll callback can start hitting | |
906 | * the new item. | |
1da177e4 LT |
907 | */ |
908 | revents = tfile->f_op->poll(tfile, &epq.pt); | |
909 | ||
910 | /* | |
911 | * We have to check if something went wrong during the poll wait queue | |
912 | * install process. Namely an allocation for a wait queue failed due | |
913 | * high memory pressure. | |
914 | */ | |
7ef9964e | 915 | error = -ENOMEM; |
1da177e4 | 916 | if (epi->nwait < 0) |
7699acd1 | 917 | goto error_unregister; |
1da177e4 LT |
918 | |
919 | /* Add the current item to the list of active epoll hook for this file */ | |
68499914 | 920 | spin_lock(&tfile->f_lock); |
1da177e4 | 921 | list_add_tail(&epi->fllink, &tfile->f_ep_links); |
68499914 | 922 | spin_unlock(&tfile->f_lock); |
1da177e4 | 923 | |
c7ea7630 DL |
924 | /* |
925 | * Add the current item to the RB tree. All RB tree operations are | |
926 | * protected by "mtx", and ep_insert() is called with "mtx" held. | |
927 | */ | |
1da177e4 LT |
928 | ep_rbtree_insert(ep, epi); |
929 | ||
c7ea7630 DL |
930 | /* We have to drop the new item inside our item list to keep track of it */ |
931 | spin_lock_irqsave(&ep->lock, flags); | |
932 | ||
1da177e4 | 933 | /* If the file is already "ready" we drop it inside the ready list */ |
b030a4dd | 934 | if ((revents & event->events) && !ep_is_linked(&epi->rdllink)) { |
1da177e4 LT |
935 | list_add_tail(&epi->rdllink, &ep->rdllist); |
936 | ||
937 | /* Notify waiting tasks that events are available */ | |
938 | if (waitqueue_active(&ep->wq)) | |
4a6e9e2c | 939 | wake_up_locked(&ep->wq); |
1da177e4 LT |
940 | if (waitqueue_active(&ep->poll_wait)) |
941 | pwake++; | |
942 | } | |
943 | ||
c7ea7630 | 944 | spin_unlock_irqrestore(&ep->lock, flags); |
1da177e4 | 945 | |
7ef9964e DL |
946 | atomic_inc(&ep->user->epoll_watches); |
947 | ||
1da177e4 LT |
948 | /* We have to call this outside the lock */ |
949 | if (pwake) | |
5071f97e | 950 | ep_poll_safewake(&ep->poll_wait); |
1da177e4 | 951 | |
1da177e4 LT |
952 | return 0; |
953 | ||
7699acd1 | 954 | error_unregister: |
1da177e4 LT |
955 | ep_unregister_pollwait(ep, epi); |
956 | ||
957 | /* | |
958 | * We need to do this because an event could have been arrived on some | |
67647d0f DL |
959 | * allocated wait queue. Note that we don't care about the ep->ovflist |
960 | * list, since that is used/cleaned only inside a section bound by "mtx". | |
961 | * And ep_insert() is called with "mtx" held. | |
1da177e4 | 962 | */ |
c7ea7630 | 963 | spin_lock_irqsave(&ep->lock, flags); |
b030a4dd | 964 | if (ep_is_linked(&epi->rdllink)) |
6192bd53 | 965 | list_del_init(&epi->rdllink); |
c7ea7630 | 966 | spin_unlock_irqrestore(&ep->lock, flags); |
1da177e4 | 967 | |
b030a4dd | 968 | kmem_cache_free(epi_cache, epi); |
7ef9964e | 969 | |
1da177e4 LT |
970 | return error; |
971 | } | |
972 | ||
1da177e4 LT |
973 | /* |
974 | * Modify the interest event mask by dropping an event if the new mask | |
c7ea7630 | 975 | * has a match in the current file status. Must be called with "mtx" held. |
1da177e4 LT |
976 | */ |
977 | static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_event *event) | |
978 | { | |
979 | int pwake = 0; | |
980 | unsigned int revents; | |
981 | unsigned long flags; | |
982 | ||
983 | /* | |
984 | * Set the new event interest mask before calling f_op->poll(), otherwise | |
985 | * a potential race might occur. In fact if we do this operation inside | |
986 | * the lock, an event might happen between the f_op->poll() call and the | |
987 | * new event set registering. | |
988 | */ | |
989 | epi->event.events = event->events; | |
990 | ||
991 | /* | |
992 | * Get current event bits. We can safely use the file* here because | |
993 | * its usage count has been increased by the caller of this function. | |
994 | */ | |
995 | revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL); | |
996 | ||
c7ea7630 | 997 | spin_lock_irqsave(&ep->lock, flags); |
1da177e4 LT |
998 | |
999 | /* Copy the data member from inside the lock */ | |
1000 | epi->event.data = event->data; | |
1001 | ||
1002 | /* | |
c7ea7630 | 1003 | * If the item is "hot" and it is not registered inside the ready |
67647d0f | 1004 | * list, push it inside. |
1da177e4 | 1005 | */ |
c7ea7630 DL |
1006 | if (revents & event->events) { |
1007 | if (!ep_is_linked(&epi->rdllink)) { | |
1008 | list_add_tail(&epi->rdllink, &ep->rdllist); | |
1009 | ||
1010 | /* Notify waiting tasks that events are available */ | |
1011 | if (waitqueue_active(&ep->wq)) | |
4a6e9e2c | 1012 | wake_up_locked(&ep->wq); |
c7ea7630 DL |
1013 | if (waitqueue_active(&ep->poll_wait)) |
1014 | pwake++; | |
7699acd1 DL |
1015 | } |
1016 | } | |
c7ea7630 | 1017 | spin_unlock_irqrestore(&ep->lock, flags); |
1da177e4 | 1018 | |
7699acd1 DL |
1019 | /* We have to call this outside the lock */ |
1020 | if (pwake) | |
5071f97e | 1021 | ep_poll_safewake(&ep->poll_wait); |
1da177e4 | 1022 | |
7699acd1 | 1023 | return 0; |
1da177e4 LT |
1024 | } |
1025 | ||
296e236e DL |
1026 | static int ep_send_events_proc(struct eventpoll *ep, struct list_head *head, |
1027 | void *priv) | |
1da177e4 | 1028 | { |
5071f97e DL |
1029 | struct ep_send_events_data *esed = priv; |
1030 | int eventcnt; | |
296e236e | 1031 | unsigned int revents; |
5071f97e DL |
1032 | struct epitem *epi; |
1033 | struct epoll_event __user *uevent; | |
1da177e4 | 1034 | |
296e236e | 1035 | /* |
5071f97e DL |
1036 | * We can loop without lock because we are passed a task private list. |
1037 | * Items cannot vanish during the loop because ep_scan_ready_list() is | |
1038 | * holding "mtx" during this call. | |
296e236e | 1039 | */ |
5071f97e DL |
1040 | for (eventcnt = 0, uevent = esed->events; |
1041 | !list_empty(head) && eventcnt < esed->maxevents;) { | |
1042 | epi = list_first_entry(head, struct epitem, rdllink); | |
d47de16c DL |
1043 | |
1044 | list_del_init(&epi->rdllink); | |
1da177e4 | 1045 | |
296e236e DL |
1046 | revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL) & |
1047 | epi->event.events; | |
5071f97e | 1048 | |
296e236e | 1049 | /* |
5071f97e DL |
1050 | * If the event mask intersect the caller-requested one, |
1051 | * deliver the event to userspace. Again, ep_scan_ready_list() | |
1052 | * is holding "mtx", so no operations coming from userspace | |
1053 | * can change the item. | |
296e236e DL |
1054 | */ |
1055 | if (revents) { | |
5071f97e DL |
1056 | if (__put_user(revents, &uevent->events) || |
1057 | __put_user(epi->event.data, &uevent->data)) | |
296e236e DL |
1058 | return eventcnt ? eventcnt : -EFAULT; |
1059 | eventcnt++; | |
5071f97e | 1060 | uevent++; |
296e236e DL |
1061 | if (epi->event.events & EPOLLONESHOT) |
1062 | epi->event.events &= EP_PRIVATE_BITS; | |
1063 | else if (!(epi->event.events & EPOLLET)) { | |
1064 | /* | |
1065 | * If this file has been added with Level | |
1066 | * Trigger mode, we need to insert back inside | |
1067 | * the ready list, so that the next call to | |
1068 | * epoll_wait() will check again the events | |
1069 | * availability. At this point, noone can insert | |
1070 | * into ep->rdllist besides us. The epoll_ctl() | |
1071 | * callers are locked out by | |
1072 | * ep_scan_ready_list() holding "mtx" and the | |
1073 | * poll callback will queue them in ep->ovflist. | |
1074 | */ | |
1075 | list_add_tail(&epi->rdllink, &ep->rdllist); | |
1076 | } | |
1077 | } | |
1078 | } | |
5071f97e DL |
1079 | |
1080 | return eventcnt; | |
1081 | } | |
d47de16c | 1082 | |
296e236e DL |
1083 | static int ep_send_events(struct eventpoll *ep, |
1084 | struct epoll_event __user *events, int maxevents) | |
5071f97e DL |
1085 | { |
1086 | struct ep_send_events_data esed; | |
1da177e4 | 1087 | |
5071f97e DL |
1088 | esed.maxevents = maxevents; |
1089 | esed.events = events; | |
6192bd53 | 1090 | |
5071f97e | 1091 | return ep_scan_ready_list(ep, ep_send_events_proc, &esed); |
1da177e4 LT |
1092 | } |
1093 | ||
1da177e4 LT |
1094 | static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, |
1095 | int maxevents, long timeout) | |
1096 | { | |
1097 | int res, eavail; | |
1098 | unsigned long flags; | |
1099 | long jtimeout; | |
1100 | wait_queue_t wait; | |
1101 | ||
1102 | /* | |
5071f97e | 1103 | * Calculate the timeout by checking for the "infinite" value (-1) |
1da177e4 LT |
1104 | * and the overflow condition. The passed timeout is in milliseconds, |
1105 | * that why (t * HZ) / 1000. | |
1106 | */ | |
e3306dd5 DL |
1107 | jtimeout = (timeout < 0 || timeout >= EP_MAX_MSTIMEO) ? |
1108 | MAX_SCHEDULE_TIMEOUT : (timeout * HZ + 999) / 1000; | |
1da177e4 LT |
1109 | |
1110 | retry: | |
c7ea7630 | 1111 | spin_lock_irqsave(&ep->lock, flags); |
1da177e4 LT |
1112 | |
1113 | res = 0; | |
1114 | if (list_empty(&ep->rdllist)) { | |
1115 | /* | |
1116 | * We don't have any available event to return to the caller. | |
1117 | * We need to sleep here, and we will be wake up by | |
1118 | * ep_poll_callback() when events will become available. | |
1119 | */ | |
1120 | init_waitqueue_entry(&wait, current); | |
d47de16c | 1121 | wait.flags |= WQ_FLAG_EXCLUSIVE; |
3419b23a | 1122 | __add_wait_queue(&ep->wq, &wait); |
1da177e4 LT |
1123 | |
1124 | for (;;) { | |
1125 | /* | |
1126 | * We don't want to sleep if the ep_poll_callback() sends us | |
1127 | * a wakeup in between. That's why we set the task state | |
1128 | * to TASK_INTERRUPTIBLE before doing the checks. | |
1129 | */ | |
1130 | set_current_state(TASK_INTERRUPTIBLE); | |
1131 | if (!list_empty(&ep->rdllist) || !jtimeout) | |
1132 | break; | |
1133 | if (signal_pending(current)) { | |
1134 | res = -EINTR; | |
1135 | break; | |
1136 | } | |
1137 | ||
c7ea7630 | 1138 | spin_unlock_irqrestore(&ep->lock, flags); |
1da177e4 | 1139 | jtimeout = schedule_timeout(jtimeout); |
c7ea7630 | 1140 | spin_lock_irqsave(&ep->lock, flags); |
1da177e4 | 1141 | } |
3419b23a | 1142 | __remove_wait_queue(&ep->wq, &wait); |
1da177e4 LT |
1143 | |
1144 | set_current_state(TASK_RUNNING); | |
1145 | } | |
1da177e4 | 1146 | /* Is it worth to try to dig for events ? */ |
5071f97e | 1147 | eavail = !list_empty(&ep->rdllist) || ep->ovflist != EP_UNACTIVE_PTR; |
1da177e4 | 1148 | |
c7ea7630 | 1149 | spin_unlock_irqrestore(&ep->lock, flags); |
1da177e4 LT |
1150 | |
1151 | /* | |
1152 | * Try to transfer events to user space. In case we get 0 events and | |
1153 | * there's still timeout left over, we go trying again in search of | |
1154 | * more luck. | |
1155 | */ | |
1156 | if (!res && eavail && | |
d47de16c | 1157 | !(res = ep_send_events(ep, events, maxevents)) && jtimeout) |
1da177e4 LT |
1158 | goto retry; |
1159 | ||
1160 | return res; | |
1161 | } | |
1162 | ||
7699acd1 | 1163 | /* |
523723bb | 1164 | * Open an eventpoll file descriptor. |
7699acd1 | 1165 | */ |
5a8a82b1 | 1166 | SYSCALL_DEFINE1(epoll_create1, int, flags) |
7699acd1 | 1167 | { |
bb57c3ed DL |
1168 | int error; |
1169 | struct eventpoll *ep = NULL; | |
7699acd1 | 1170 | |
e38b36f3 UD |
1171 | /* Check the EPOLL_* constant for consistency. */ |
1172 | BUILD_BUG_ON(EPOLL_CLOEXEC != O_CLOEXEC); | |
1173 | ||
296e236e DL |
1174 | if (flags & ~EPOLL_CLOEXEC) |
1175 | return -EINVAL; | |
7699acd1 | 1176 | /* |
bb57c3ed | 1177 | * Create the internal data structure ("struct eventpoll"). |
7699acd1 | 1178 | */ |
9fe5ad9c | 1179 | error = ep_alloc(&ep); |
bb57c3ed DL |
1180 | if (error < 0) |
1181 | return error; | |
7699acd1 DL |
1182 | /* |
1183 | * Creates all the items needed to setup an eventpoll file. That is, | |
2030a42c | 1184 | * a file structure and a free file descriptor. |
7699acd1 | 1185 | */ |
bb57c3ed DL |
1186 | error = anon_inode_getfd("[eventpoll]", &eventpoll_fops, ep, |
1187 | flags & O_CLOEXEC); | |
1188 | if (error < 0) | |
2030a42c | 1189 | ep_free(ep); |
7699acd1 | 1190 | |
bb57c3ed | 1191 | return error; |
7699acd1 DL |
1192 | } |
1193 | ||
5a8a82b1 | 1194 | SYSCALL_DEFINE1(epoll_create, int, size) |
a0998b50 | 1195 | { |
9fe5ad9c UD |
1196 | if (size < 0) |
1197 | return -EINVAL; | |
1198 | ||
1199 | return sys_epoll_create1(0); | |
a0998b50 UD |
1200 | } |
1201 | ||
7699acd1 DL |
1202 | /* |
1203 | * The following function implements the controller interface for | |
1204 | * the eventpoll file that enables the insertion/removal/change of | |
67647d0f | 1205 | * file descriptors inside the interest set. |
7699acd1 | 1206 | */ |
5a8a82b1 HC |
1207 | SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd, |
1208 | struct epoll_event __user *, event) | |
7699acd1 DL |
1209 | { |
1210 | int error; | |
1211 | struct file *file, *tfile; | |
1212 | struct eventpoll *ep; | |
1213 | struct epitem *epi; | |
1214 | struct epoll_event epds; | |
1215 | ||
7699acd1 DL |
1216 | error = -EFAULT; |
1217 | if (ep_op_has_event(op) && | |
1218 | copy_from_user(&epds, event, sizeof(struct epoll_event))) | |
1219 | goto error_return; | |
1220 | ||
1221 | /* Get the "struct file *" for the eventpoll file */ | |
1222 | error = -EBADF; | |
1223 | file = fget(epfd); | |
1224 | if (!file) | |
1225 | goto error_return; | |
1226 | ||
1227 | /* Get the "struct file *" for the target file */ | |
1228 | tfile = fget(fd); | |
1229 | if (!tfile) | |
1230 | goto error_fput; | |
1231 | ||
1232 | /* The target file descriptor must support poll */ | |
1233 | error = -EPERM; | |
1234 | if (!tfile->f_op || !tfile->f_op->poll) | |
1235 | goto error_tgt_fput; | |
1236 | ||
1237 | /* | |
1238 | * We have to check that the file structure underneath the file descriptor | |
1239 | * the user passed to us _is_ an eventpoll file. And also we do not permit | |
1240 | * adding an epoll file descriptor inside itself. | |
1241 | */ | |
1242 | error = -EINVAL; | |
1243 | if (file == tfile || !is_file_epoll(file)) | |
1244 | goto error_tgt_fput; | |
1245 | ||
1246 | /* | |
1247 | * At this point it is safe to assume that the "private_data" contains | |
1248 | * our own data structure. | |
1249 | */ | |
1250 | ep = file->private_data; | |
1251 | ||
d47de16c | 1252 | mutex_lock(&ep->mtx); |
7699acd1 | 1253 | |
67647d0f DL |
1254 | /* |
1255 | * Try to lookup the file inside our RB tree, Since we grabbed "mtx" | |
1256 | * above, we can be sure to be able to use the item looked up by | |
1257 | * ep_find() till we release the mutex. | |
1258 | */ | |
7699acd1 DL |
1259 | epi = ep_find(ep, tfile, fd); |
1260 | ||
1261 | error = -EINVAL; | |
1262 | switch (op) { | |
1263 | case EPOLL_CTL_ADD: | |
1264 | if (!epi) { | |
1265 | epds.events |= POLLERR | POLLHUP; | |
1266 | ||
1267 | error = ep_insert(ep, &epds, tfile, fd); | |
1268 | } else | |
1269 | error = -EEXIST; | |
1270 | break; | |
1271 | case EPOLL_CTL_DEL: | |
1272 | if (epi) | |
1273 | error = ep_remove(ep, epi); | |
1274 | else | |
1275 | error = -ENOENT; | |
1276 | break; | |
1277 | case EPOLL_CTL_MOD: | |
1278 | if (epi) { | |
1279 | epds.events |= POLLERR | POLLHUP; | |
1280 | error = ep_modify(ep, epi, &epds); | |
1281 | } else | |
1282 | error = -ENOENT; | |
1283 | break; | |
1284 | } | |
d47de16c | 1285 | mutex_unlock(&ep->mtx); |
7699acd1 DL |
1286 | |
1287 | error_tgt_fput: | |
1288 | fput(tfile); | |
1289 | error_fput: | |
1290 | fput(file); | |
1291 | error_return: | |
7699acd1 DL |
1292 | |
1293 | return error; | |
1294 | } | |
1295 | ||
1296 | /* | |
1297 | * Implement the event wait interface for the eventpoll file. It is the kernel | |
1298 | * part of the user space epoll_wait(2). | |
1299 | */ | |
5a8a82b1 HC |
1300 | SYSCALL_DEFINE4(epoll_wait, int, epfd, struct epoll_event __user *, events, |
1301 | int, maxevents, int, timeout) | |
7699acd1 DL |
1302 | { |
1303 | int error; | |
1304 | struct file *file; | |
1305 | struct eventpoll *ep; | |
1306 | ||
7699acd1 DL |
1307 | /* The maximum number of event must be greater than zero */ |
1308 | if (maxevents <= 0 || maxevents > EP_MAX_EVENTS) | |
1309 | return -EINVAL; | |
1310 | ||
1311 | /* Verify that the area passed by the user is writeable */ | |
1312 | if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event))) { | |
1313 | error = -EFAULT; | |
1314 | goto error_return; | |
1315 | } | |
1316 | ||
1317 | /* Get the "struct file *" for the eventpoll file */ | |
1318 | error = -EBADF; | |
1319 | file = fget(epfd); | |
1320 | if (!file) | |
1321 | goto error_return; | |
1322 | ||
1323 | /* | |
1324 | * We have to check that the file structure underneath the fd | |
1325 | * the user passed to us _is_ an eventpoll file. | |
1326 | */ | |
1327 | error = -EINVAL; | |
1328 | if (!is_file_epoll(file)) | |
1329 | goto error_fput; | |
1330 | ||
1331 | /* | |
1332 | * At this point it is safe to assume that the "private_data" contains | |
1333 | * our own data structure. | |
1334 | */ | |
1335 | ep = file->private_data; | |
1336 | ||
1337 | /* Time to fish for events ... */ | |
1338 | error = ep_poll(ep, events, maxevents, timeout); | |
1339 | ||
1340 | error_fput: | |
1341 | fput(file); | |
1342 | error_return: | |
7699acd1 DL |
1343 | |
1344 | return error; | |
1345 | } | |
1346 | ||
f3de272b | 1347 | #ifdef HAVE_SET_RESTORE_SIGMASK |
7699acd1 DL |
1348 | |
1349 | /* | |
1350 | * Implement the event wait interface for the eventpoll file. It is the kernel | |
1351 | * part of the user space epoll_pwait(2). | |
1352 | */ | |
5a8a82b1 HC |
1353 | SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events, |
1354 | int, maxevents, int, timeout, const sigset_t __user *, sigmask, | |
1355 | size_t, sigsetsize) | |
7699acd1 DL |
1356 | { |
1357 | int error; | |
1358 | sigset_t ksigmask, sigsaved; | |
1359 | ||
1360 | /* | |
1361 | * If the caller wants a certain signal mask to be set during the wait, | |
1362 | * we apply it here. | |
1363 | */ | |
1364 | if (sigmask) { | |
1365 | if (sigsetsize != sizeof(sigset_t)) | |
1366 | return -EINVAL; | |
1367 | if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) | |
1368 | return -EFAULT; | |
1369 | sigdelsetmask(&ksigmask, sigmask(SIGKILL) | sigmask(SIGSTOP)); | |
1370 | sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); | |
1371 | } | |
1372 | ||
1373 | error = sys_epoll_wait(epfd, events, maxevents, timeout); | |
1374 | ||
1375 | /* | |
1376 | * If we changed the signal mask, we need to restore the original one. | |
1377 | * In case we've got a signal while waiting, we do not restore the | |
1378 | * signal mask yet, and we allow do_signal() to deliver the signal on | |
1379 | * the way back to userspace, before the signal mask is restored. | |
1380 | */ | |
1381 | if (sigmask) { | |
1382 | if (error == -EINTR) { | |
1383 | memcpy(¤t->saved_sigmask, &sigsaved, | |
c7ea7630 | 1384 | sizeof(sigsaved)); |
4e4c22c7 | 1385 | set_restore_sigmask(); |
7699acd1 DL |
1386 | } else |
1387 | sigprocmask(SIG_SETMASK, &sigsaved, NULL); | |
1388 | } | |
1389 | ||
1390 | return error; | |
1391 | } | |
1392 | ||
f3de272b | 1393 | #endif /* HAVE_SET_RESTORE_SIGMASK */ |
7699acd1 | 1394 | |
1da177e4 LT |
1395 | static int __init eventpoll_init(void) |
1396 | { | |
7ef9964e DL |
1397 | struct sysinfo si; |
1398 | ||
1399 | si_meminfo(&si); | |
9df04e1f DL |
1400 | /* |
1401 | * Allows top 4% of lomem to be allocated for epoll watches (per user). | |
1402 | */ | |
1403 | max_user_watches = (((si.totalram - si.totalhigh) / 25) << PAGE_SHIFT) / | |
7ef9964e | 1404 | EP_ITEM_COST; |
1da177e4 LT |
1405 | |
1406 | /* Initialize the structure used to perform safe poll wait head wake ups */ | |
5071f97e DL |
1407 | ep_nested_calls_init(&poll_safewake_ncalls); |
1408 | ||
1409 | /* Initialize the structure used to perform file's f_op->poll() calls */ | |
1410 | ep_nested_calls_init(&poll_readywalk_ncalls); | |
1da177e4 LT |
1411 | |
1412 | /* Allocates slab cache used to allocate "struct epitem" items */ | |
1413 | epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem), | |
bb57c3ed | 1414 | 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); |
1da177e4 LT |
1415 | |
1416 | /* Allocates slab cache used to allocate "struct eppoll_entry" */ | |
1417 | pwq_cache = kmem_cache_create("eventpoll_pwq", | |
bb57c3ed | 1418 | sizeof(struct eppoll_entry), 0, SLAB_PANIC, NULL); |
1da177e4 | 1419 | |
1da177e4 | 1420 | return 0; |
1da177e4 | 1421 | } |
cea69241 | 1422 | fs_initcall(eventpoll_init); |