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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> | |
60063497 | 40 | #include <linux/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 | |
bf6a41db | 65 | * close()d without a previous call to epoll_ctl(EPOLL_CTL_DEL). |
22bacca4 DL |
66 | * It is also acquired when inserting an epoll fd onto another epoll |
67 | * fd. We do this so that we walk the epoll tree and ensure that this | |
68 | * insertion does not create a cycle of epoll file descriptors, which | |
69 | * could lead to deadlock. We need a global mutex to prevent two | |
70 | * simultaneous inserts (A into B and B into A) from racing and | |
71 | * constructing a cycle without either insert observing that it is | |
72 | * going to. | |
d8805e63 NE |
73 | * It is necessary to acquire multiple "ep->mtx"es at once in the |
74 | * case when one epoll fd is added to another. In this case, we | |
75 | * always acquire the locks in the order of nesting (i.e. after | |
76 | * epoll_ctl(e1, EPOLL_CTL_ADD, e2), e1->mtx will always be acquired | |
77 | * before e2->mtx). Since we disallow cycles of epoll file | |
78 | * descriptors, this ensures that the mutexes are well-ordered. In | |
79 | * order to communicate this nesting to lockdep, when walking a tree | |
80 | * of epoll file descriptors, we use the current recursion depth as | |
81 | * the lockdep subkey. | |
d47de16c DL |
82 | * It is possible to drop the "ep->mtx" and to use the global |
83 | * mutex "epmutex" (together with "ep->lock") to have it working, | |
84 | * but having "ep->mtx" will make the interface more scalable. | |
144efe3e | 85 | * Events that require holding "epmutex" are very rare, while for |
d47de16c DL |
86 | * normal operations the epoll private "ep->mtx" will guarantee |
87 | * a better scalability. | |
1da177e4 LT |
88 | */ |
89 | ||
1da177e4 LT |
90 | /* Epoll private bits inside the event mask */ |
91 | #define EP_PRIVATE_BITS (EPOLLONESHOT | EPOLLET) | |
92 | ||
5071f97e DL |
93 | /* Maximum number of nesting allowed inside epoll sets */ |
94 | #define EP_MAX_NESTS 4 | |
1da177e4 | 95 | |
b611967d DL |
96 | #define EP_MAX_EVENTS (INT_MAX / sizeof(struct epoll_event)) |
97 | ||
d47de16c DL |
98 | #define EP_UNACTIVE_PTR ((void *) -1L) |
99 | ||
7ef9964e DL |
100 | #define EP_ITEM_COST (sizeof(struct epitem) + sizeof(struct eppoll_entry)) |
101 | ||
1da177e4 LT |
102 | struct epoll_filefd { |
103 | struct file *file; | |
104 | int fd; | |
105 | }; | |
106 | ||
107 | /* | |
5071f97e DL |
108 | * Structure used to track possible nested calls, for too deep recursions |
109 | * and loop cycles. | |
1da177e4 | 110 | */ |
5071f97e | 111 | struct nested_call_node { |
1da177e4 | 112 | struct list_head llink; |
5071f97e | 113 | void *cookie; |
3fe4a975 | 114 | void *ctx; |
1da177e4 LT |
115 | }; |
116 | ||
117 | /* | |
5071f97e DL |
118 | * This structure is used as collector for nested calls, to check for |
119 | * maximum recursion dept and loop cycles. | |
1da177e4 | 120 | */ |
5071f97e DL |
121 | struct nested_calls { |
122 | struct list_head tasks_call_list; | |
1da177e4 LT |
123 | spinlock_t lock; |
124 | }; | |
125 | ||
d47de16c DL |
126 | /* |
127 | * Each file descriptor added to the eventpoll interface will | |
128 | * have an entry of this type linked to the "rbr" RB tree. | |
129 | */ | |
130 | struct epitem { | |
67647d0f | 131 | /* RB tree node used to link this structure to the eventpoll RB tree */ |
d47de16c DL |
132 | struct rb_node rbn; |
133 | ||
134 | /* List header used to link this structure to the eventpoll ready list */ | |
135 | struct list_head rdllink; | |
136 | ||
c7ea7630 DL |
137 | /* |
138 | * Works together "struct eventpoll"->ovflist in keeping the | |
139 | * single linked chain of items. | |
140 | */ | |
141 | struct epitem *next; | |
142 | ||
d47de16c DL |
143 | /* The file descriptor information this item refers to */ |
144 | struct epoll_filefd ffd; | |
145 | ||
146 | /* Number of active wait queue attached to poll operations */ | |
147 | int nwait; | |
148 | ||
149 | /* List containing poll wait queues */ | |
150 | struct list_head pwqlist; | |
151 | ||
152 | /* The "container" of this item */ | |
153 | struct eventpoll *ep; | |
154 | ||
d47de16c DL |
155 | /* List header used to link this item to the "struct file" items list */ |
156 | struct list_head fllink; | |
157 | ||
c7ea7630 DL |
158 | /* The structure that describe the interested events and the source fd */ |
159 | struct epoll_event event; | |
d47de16c DL |
160 | }; |
161 | ||
1da177e4 LT |
162 | /* |
163 | * This structure is stored inside the "private_data" member of the file | |
bf6a41db | 164 | * structure and represents the main data structure for the eventpoll |
1da177e4 LT |
165 | * interface. |
166 | */ | |
167 | struct eventpoll { | |
bf6a41db | 168 | /* Protect the access to this structure */ |
c7ea7630 | 169 | spinlock_t lock; |
1da177e4 LT |
170 | |
171 | /* | |
d47de16c DL |
172 | * This mutex is used to ensure that files are not removed |
173 | * while epoll is using them. This is held during the event | |
174 | * collection loop, the file cleanup path, the epoll file exit | |
175 | * code and the ctl operations. | |
1da177e4 | 176 | */ |
d47de16c | 177 | struct mutex mtx; |
1da177e4 LT |
178 | |
179 | /* Wait queue used by sys_epoll_wait() */ | |
180 | wait_queue_head_t wq; | |
181 | ||
182 | /* Wait queue used by file->poll() */ | |
183 | wait_queue_head_t poll_wait; | |
184 | ||
185 | /* List of ready file descriptors */ | |
186 | struct list_head rdllist; | |
187 | ||
67647d0f | 188 | /* RB tree root used to store monitored fd structs */ |
1da177e4 | 189 | struct rb_root rbr; |
d47de16c DL |
190 | |
191 | /* | |
192 | * This is a single linked list that chains all the "struct epitem" that | |
25985edc | 193 | * happened while transferring ready events to userspace w/out |
d47de16c DL |
194 | * holding ->lock. |
195 | */ | |
196 | struct epitem *ovflist; | |
7ef9964e DL |
197 | |
198 | /* The user that created the eventpoll descriptor */ | |
199 | struct user_struct *user; | |
28d82dc1 JB |
200 | |
201 | struct file *file; | |
202 | ||
203 | /* used to optimize loop detection check */ | |
204 | int visited; | |
205 | struct list_head visited_list_link; | |
1da177e4 LT |
206 | }; |
207 | ||
208 | /* Wait structure used by the poll hooks */ | |
209 | struct eppoll_entry { | |
210 | /* List header used to link this structure to the "struct epitem" */ | |
211 | struct list_head llink; | |
212 | ||
213 | /* The "base" pointer is set to the container "struct epitem" */ | |
4f0989db | 214 | struct epitem *base; |
1da177e4 LT |
215 | |
216 | /* | |
217 | * Wait queue item that will be linked to the target file wait | |
218 | * queue head. | |
219 | */ | |
220 | wait_queue_t wait; | |
221 | ||
222 | /* The wait queue head that linked the "wait" wait queue item */ | |
223 | wait_queue_head_t *whead; | |
224 | }; | |
225 | ||
1da177e4 LT |
226 | /* Wrapper struct used by poll queueing */ |
227 | struct ep_pqueue { | |
228 | poll_table pt; | |
229 | struct epitem *epi; | |
230 | }; | |
231 | ||
5071f97e DL |
232 | /* Used by the ep_send_events() function as callback private data */ |
233 | struct ep_send_events_data { | |
234 | int maxevents; | |
235 | struct epoll_event __user *events; | |
236 | }; | |
237 | ||
7ef9964e DL |
238 | /* |
239 | * Configuration options available inside /proc/sys/fs/epoll/ | |
240 | */ | |
7ef9964e | 241 | /* Maximum number of epoll watched descriptors, per user */ |
52bd19f7 | 242 | static long max_user_watches __read_mostly; |
7ef9964e | 243 | |
1da177e4 | 244 | /* |
d47de16c | 245 | * This mutex is used to serialize ep_free() and eventpoll_release_file(). |
1da177e4 | 246 | */ |
7ef9964e | 247 | static DEFINE_MUTEX(epmutex); |
1da177e4 | 248 | |
22bacca4 DL |
249 | /* Used to check for epoll file descriptor inclusion loops */ |
250 | static struct nested_calls poll_loop_ncalls; | |
251 | ||
5071f97e DL |
252 | /* Used for safe wake up implementation */ |
253 | static struct nested_calls poll_safewake_ncalls; | |
254 | ||
255 | /* Used to call file's f_op->poll() under the nested calls boundaries */ | |
256 | static struct nested_calls poll_readywalk_ncalls; | |
1da177e4 LT |
257 | |
258 | /* Slab cache used to allocate "struct epitem" */ | |
e18b890b | 259 | static struct kmem_cache *epi_cache __read_mostly; |
1da177e4 LT |
260 | |
261 | /* Slab cache used to allocate "struct eppoll_entry" */ | |
e18b890b | 262 | static struct kmem_cache *pwq_cache __read_mostly; |
1da177e4 | 263 | |
28d82dc1 JB |
264 | /* Visited nodes during ep_loop_check(), so we can unset them when we finish */ |
265 | static LIST_HEAD(visited_list); | |
266 | ||
267 | /* | |
268 | * List of files with newly added links, where we may need to limit the number | |
269 | * of emanating paths. Protected by the epmutex. | |
270 | */ | |
271 | static LIST_HEAD(tfile_check_list); | |
272 | ||
7ef9964e DL |
273 | #ifdef CONFIG_SYSCTL |
274 | ||
275 | #include <linux/sysctl.h> | |
276 | ||
52bd19f7 RH |
277 | static long zero; |
278 | static long long_max = LONG_MAX; | |
7ef9964e DL |
279 | |
280 | ctl_table epoll_table[] = { | |
7ef9964e DL |
281 | { |
282 | .procname = "max_user_watches", | |
283 | .data = &max_user_watches, | |
52bd19f7 | 284 | .maxlen = sizeof(max_user_watches), |
7ef9964e | 285 | .mode = 0644, |
52bd19f7 | 286 | .proc_handler = proc_doulongvec_minmax, |
7ef9964e | 287 | .extra1 = &zero, |
52bd19f7 | 288 | .extra2 = &long_max, |
7ef9964e | 289 | }, |
ab09203e | 290 | { } |
7ef9964e DL |
291 | }; |
292 | #endif /* CONFIG_SYSCTL */ | |
293 | ||
28d82dc1 JB |
294 | static const struct file_operations eventpoll_fops; |
295 | ||
296 | static inline int is_file_epoll(struct file *f) | |
297 | { | |
298 | return f->f_op == &eventpoll_fops; | |
299 | } | |
b030a4dd | 300 | |
67647d0f | 301 | /* Setup the structure that is used as key for the RB tree */ |
b030a4dd PE |
302 | static inline void ep_set_ffd(struct epoll_filefd *ffd, |
303 | struct file *file, int fd) | |
304 | { | |
305 | ffd->file = file; | |
306 | ffd->fd = fd; | |
307 | } | |
308 | ||
67647d0f | 309 | /* Compare RB tree keys */ |
b030a4dd PE |
310 | static inline int ep_cmp_ffd(struct epoll_filefd *p1, |
311 | struct epoll_filefd *p2) | |
312 | { | |
313 | return (p1->file > p2->file ? +1: | |
314 | (p1->file < p2->file ? -1 : p1->fd - p2->fd)); | |
315 | } | |
316 | ||
b030a4dd PE |
317 | /* Tells us if the item is currently linked */ |
318 | static inline int ep_is_linked(struct list_head *p) | |
319 | { | |
320 | return !list_empty(p); | |
321 | } | |
322 | ||
971316f0 ON |
323 | static inline struct eppoll_entry *ep_pwq_from_wait(wait_queue_t *p) |
324 | { | |
325 | return container_of(p, struct eppoll_entry, wait); | |
326 | } | |
327 | ||
b030a4dd | 328 | /* Get the "struct epitem" from a wait queue pointer */ |
cdac75e6 | 329 | static inline struct epitem *ep_item_from_wait(wait_queue_t *p) |
b030a4dd PE |
330 | { |
331 | return container_of(p, struct eppoll_entry, wait)->base; | |
332 | } | |
333 | ||
334 | /* Get the "struct epitem" from an epoll queue wrapper */ | |
cdac75e6 | 335 | static inline struct epitem *ep_item_from_epqueue(poll_table *p) |
b030a4dd PE |
336 | { |
337 | return container_of(p, struct ep_pqueue, pt)->epi; | |
338 | } | |
339 | ||
340 | /* Tells if the epoll_ctl(2) operation needs an event copy from userspace */ | |
6192bd53 | 341 | static inline int ep_op_has_event(int op) |
b030a4dd PE |
342 | { |
343 | return op != EPOLL_CTL_DEL; | |
344 | } | |
345 | ||
1da177e4 | 346 | /* Initialize the poll safe wake up structure */ |
5071f97e | 347 | static void ep_nested_calls_init(struct nested_calls *ncalls) |
1da177e4 | 348 | { |
5071f97e DL |
349 | INIT_LIST_HEAD(&ncalls->tasks_call_list); |
350 | spin_lock_init(&ncalls->lock); | |
1da177e4 LT |
351 | } |
352 | ||
3fb0e584 DL |
353 | /** |
354 | * ep_events_available - Checks if ready events might be available. | |
355 | * | |
356 | * @ep: Pointer to the eventpoll context. | |
357 | * | |
358 | * Returns: Returns a value different than zero if ready events are available, | |
359 | * or zero otherwise. | |
360 | */ | |
361 | static inline int ep_events_available(struct eventpoll *ep) | |
362 | { | |
363 | return !list_empty(&ep->rdllist) || ep->ovflist != EP_UNACTIVE_PTR; | |
364 | } | |
365 | ||
5071f97e DL |
366 | /** |
367 | * ep_call_nested - Perform a bound (possibly) nested call, by checking | |
368 | * that the recursion limit is not exceeded, and that | |
369 | * the same nested call (by the meaning of same cookie) is | |
370 | * no re-entered. | |
371 | * | |
372 | * @ncalls: Pointer to the nested_calls structure to be used for this call. | |
373 | * @max_nests: Maximum number of allowed nesting calls. | |
374 | * @nproc: Nested call core function pointer. | |
375 | * @priv: Opaque data to be passed to the @nproc callback. | |
376 | * @cookie: Cookie to be used to identify this nested call. | |
3fe4a975 | 377 | * @ctx: This instance context. |
5071f97e DL |
378 | * |
379 | * Returns: Returns the code returned by the @nproc callback, or -1 if | |
380 | * the maximum recursion limit has been exceeded. | |
1da177e4 | 381 | */ |
5071f97e DL |
382 | static int ep_call_nested(struct nested_calls *ncalls, int max_nests, |
383 | int (*nproc)(void *, void *, int), void *priv, | |
3fe4a975 | 384 | void *cookie, void *ctx) |
1da177e4 | 385 | { |
5071f97e | 386 | int error, call_nests = 0; |
1da177e4 | 387 | unsigned long flags; |
5071f97e DL |
388 | struct list_head *lsthead = &ncalls->tasks_call_list; |
389 | struct nested_call_node *tncur; | |
390 | struct nested_call_node tnode; | |
1da177e4 | 391 | |
5071f97e | 392 | spin_lock_irqsave(&ncalls->lock, flags); |
1da177e4 | 393 | |
5071f97e DL |
394 | /* |
395 | * Try to see if the current task is already inside this wakeup call. | |
396 | * We use a list here, since the population inside this set is always | |
397 | * very much limited. | |
398 | */ | |
b70c3940 | 399 | list_for_each_entry(tncur, lsthead, llink) { |
3fe4a975 | 400 | if (tncur->ctx == ctx && |
5071f97e | 401 | (tncur->cookie == cookie || ++call_nests > max_nests)) { |
1da177e4 LT |
402 | /* |
403 | * Ops ... loop detected or maximum nest level reached. | |
404 | * We abort this wake by breaking the cycle itself. | |
405 | */ | |
abff55ce TB |
406 | error = -1; |
407 | goto out_unlock; | |
1da177e4 LT |
408 | } |
409 | } | |
410 | ||
5071f97e | 411 | /* Add the current task and cookie to the list */ |
3fe4a975 | 412 | tnode.ctx = ctx; |
5071f97e | 413 | tnode.cookie = cookie; |
1da177e4 LT |
414 | list_add(&tnode.llink, lsthead); |
415 | ||
5071f97e | 416 | spin_unlock_irqrestore(&ncalls->lock, flags); |
1da177e4 | 417 | |
5071f97e DL |
418 | /* Call the nested function */ |
419 | error = (*nproc)(priv, cookie, call_nests); | |
1da177e4 LT |
420 | |
421 | /* Remove the current task from the list */ | |
5071f97e | 422 | spin_lock_irqsave(&ncalls->lock, flags); |
1da177e4 | 423 | list_del(&tnode.llink); |
3fe4a975 | 424 | out_unlock: |
5071f97e DL |
425 | spin_unlock_irqrestore(&ncalls->lock, flags); |
426 | ||
427 | return error; | |
428 | } | |
429 | ||
2dfa4eea DL |
430 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
431 | static inline void ep_wake_up_nested(wait_queue_head_t *wqueue, | |
432 | unsigned long events, int subclass) | |
433 | { | |
434 | unsigned long flags; | |
435 | ||
436 | spin_lock_irqsave_nested(&wqueue->lock, flags, subclass); | |
437 | wake_up_locked_poll(wqueue, events); | |
438 | spin_unlock_irqrestore(&wqueue->lock, flags); | |
439 | } | |
440 | #else | |
441 | static inline void ep_wake_up_nested(wait_queue_head_t *wqueue, | |
442 | unsigned long events, int subclass) | |
443 | { | |
444 | wake_up_poll(wqueue, events); | |
445 | } | |
446 | #endif | |
447 | ||
5071f97e DL |
448 | static int ep_poll_wakeup_proc(void *priv, void *cookie, int call_nests) |
449 | { | |
2dfa4eea DL |
450 | ep_wake_up_nested((wait_queue_head_t *) cookie, POLLIN, |
451 | 1 + call_nests); | |
5071f97e DL |
452 | return 0; |
453 | } | |
454 | ||
455 | /* | |
456 | * Perform a safe wake up of the poll wait list. The problem is that | |
457 | * with the new callback'd wake up system, it is possible that the | |
458 | * poll callback is reentered from inside the call to wake_up() done | |
459 | * on the poll wait queue head. The rule is that we cannot reenter the | |
460 | * wake up code from the same task more than EP_MAX_NESTS times, | |
461 | * and we cannot reenter the same wait queue head at all. This will | |
462 | * enable to have a hierarchy of epoll file descriptor of no more than | |
463 | * EP_MAX_NESTS deep. | |
464 | */ | |
465 | static void ep_poll_safewake(wait_queue_head_t *wq) | |
466 | { | |
3fe4a975 DL |
467 | int this_cpu = get_cpu(); |
468 | ||
5071f97e | 469 | ep_call_nested(&poll_safewake_ncalls, EP_MAX_NESTS, |
3fe4a975 DL |
470 | ep_poll_wakeup_proc, NULL, wq, (void *) (long) this_cpu); |
471 | ||
472 | put_cpu(); | |
1da177e4 LT |
473 | } |
474 | ||
971316f0 ON |
475 | static void ep_remove_wait_queue(struct eppoll_entry *pwq) |
476 | { | |
477 | wait_queue_head_t *whead; | |
478 | ||
479 | rcu_read_lock(); | |
480 | /* If it is cleared by POLLFREE, it should be rcu-safe */ | |
481 | whead = rcu_dereference(pwq->whead); | |
482 | if (whead) | |
483 | remove_wait_queue(whead, &pwq->wait); | |
484 | rcu_read_unlock(); | |
485 | } | |
486 | ||
1da177e4 | 487 | /* |
d1bc90dd TB |
488 | * This function unregisters poll callbacks from the associated file |
489 | * descriptor. Must be called with "mtx" held (or "epmutex" if called from | |
490 | * ep_free). | |
1da177e4 | 491 | */ |
7699acd1 | 492 | static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi) |
1da177e4 | 493 | { |
7699acd1 DL |
494 | struct list_head *lsthead = &epi->pwqlist; |
495 | struct eppoll_entry *pwq; | |
1da177e4 | 496 | |
d1bc90dd TB |
497 | while (!list_empty(lsthead)) { |
498 | pwq = list_first_entry(lsthead, struct eppoll_entry, llink); | |
1da177e4 | 499 | |
d1bc90dd | 500 | list_del(&pwq->llink); |
971316f0 | 501 | ep_remove_wait_queue(pwq); |
d1bc90dd | 502 | kmem_cache_free(pwq_cache, pwq); |
1da177e4 | 503 | } |
1da177e4 LT |
504 | } |
505 | ||
5071f97e DL |
506 | /** |
507 | * ep_scan_ready_list - Scans the ready list in a way that makes possible for | |
508 | * the scan code, to call f_op->poll(). Also allows for | |
509 | * O(NumReady) performance. | |
510 | * | |
511 | * @ep: Pointer to the epoll private data structure. | |
512 | * @sproc: Pointer to the scan callback. | |
513 | * @priv: Private opaque data passed to the @sproc callback. | |
d8805e63 | 514 | * @depth: The current depth of recursive f_op->poll calls. |
5071f97e DL |
515 | * |
516 | * Returns: The same integer error code returned by the @sproc callback. | |
517 | */ | |
518 | static int ep_scan_ready_list(struct eventpoll *ep, | |
519 | int (*sproc)(struct eventpoll *, | |
520 | struct list_head *, void *), | |
d8805e63 NE |
521 | void *priv, |
522 | int depth) | |
5071f97e DL |
523 | { |
524 | int error, pwake = 0; | |
525 | unsigned long flags; | |
526 | struct epitem *epi, *nepi; | |
296e236e | 527 | LIST_HEAD(txlist); |
5071f97e DL |
528 | |
529 | /* | |
530 | * We need to lock this because we could be hit by | |
e057e15f | 531 | * eventpoll_release_file() and epoll_ctl(). |
5071f97e | 532 | */ |
d8805e63 | 533 | mutex_lock_nested(&ep->mtx, depth); |
5071f97e DL |
534 | |
535 | /* | |
536 | * Steal the ready list, and re-init the original one to the | |
537 | * empty list. Also, set ep->ovflist to NULL so that events | |
538 | * happening while looping w/out locks, are not lost. We cannot | |
539 | * have the poll callback to queue directly on ep->rdllist, | |
540 | * because we want the "sproc" callback to be able to do it | |
541 | * in a lockless way. | |
542 | */ | |
543 | spin_lock_irqsave(&ep->lock, flags); | |
296e236e | 544 | list_splice_init(&ep->rdllist, &txlist); |
5071f97e DL |
545 | ep->ovflist = NULL; |
546 | spin_unlock_irqrestore(&ep->lock, flags); | |
547 | ||
548 | /* | |
549 | * Now call the callback function. | |
550 | */ | |
551 | error = (*sproc)(ep, &txlist, priv); | |
552 | ||
553 | spin_lock_irqsave(&ep->lock, flags); | |
554 | /* | |
555 | * During the time we spent inside the "sproc" callback, some | |
556 | * other events might have been queued by the poll callback. | |
557 | * We re-insert them inside the main ready-list here. | |
558 | */ | |
559 | for (nepi = ep->ovflist; (epi = nepi) != NULL; | |
560 | nepi = epi->next, epi->next = EP_UNACTIVE_PTR) { | |
561 | /* | |
562 | * We need to check if the item is already in the list. | |
563 | * During the "sproc" callback execution time, items are | |
564 | * queued into ->ovflist but the "txlist" might already | |
565 | * contain them, and the list_splice() below takes care of them. | |
566 | */ | |
567 | if (!ep_is_linked(&epi->rdllink)) | |
568 | list_add_tail(&epi->rdllink, &ep->rdllist); | |
569 | } | |
570 | /* | |
571 | * We need to set back ep->ovflist to EP_UNACTIVE_PTR, so that after | |
572 | * releasing the lock, events will be queued in the normal way inside | |
573 | * ep->rdllist. | |
574 | */ | |
575 | ep->ovflist = EP_UNACTIVE_PTR; | |
576 | ||
577 | /* | |
578 | * Quickly re-inject items left on "txlist". | |
579 | */ | |
580 | list_splice(&txlist, &ep->rdllist); | |
581 | ||
582 | if (!list_empty(&ep->rdllist)) { | |
583 | /* | |
296e236e DL |
584 | * Wake up (if active) both the eventpoll wait list and |
585 | * the ->poll() wait list (delayed after we release the lock). | |
5071f97e DL |
586 | */ |
587 | if (waitqueue_active(&ep->wq)) | |
588 | wake_up_locked(&ep->wq); | |
589 | if (waitqueue_active(&ep->poll_wait)) | |
590 | pwake++; | |
591 | } | |
592 | spin_unlock_irqrestore(&ep->lock, flags); | |
593 | ||
594 | mutex_unlock(&ep->mtx); | |
595 | ||
596 | /* We have to call this outside the lock */ | |
597 | if (pwake) | |
598 | ep_poll_safewake(&ep->poll_wait); | |
599 | ||
600 | return error; | |
601 | } | |
602 | ||
7699acd1 DL |
603 | /* |
604 | * Removes a "struct epitem" from the eventpoll RB tree and deallocates | |
c7ea7630 | 605 | * all the associated resources. Must be called with "mtx" held. |
7699acd1 DL |
606 | */ |
607 | static int ep_remove(struct eventpoll *ep, struct epitem *epi) | |
608 | { | |
7699acd1 DL |
609 | unsigned long flags; |
610 | struct file *file = epi->ffd.file; | |
1da177e4 LT |
611 | |
612 | /* | |
7699acd1 DL |
613 | * Removes poll wait queue hooks. We _have_ to do this without holding |
614 | * the "ep->lock" otherwise a deadlock might occur. This because of the | |
615 | * sequence of the lock acquisition. Here we do "ep->lock" then the wait | |
616 | * queue head lock when unregistering the wait queue. The wakeup callback | |
617 | * will run by holding the wait queue head lock and will call our callback | |
618 | * that will try to get "ep->lock". | |
1da177e4 | 619 | */ |
7699acd1 | 620 | ep_unregister_pollwait(ep, epi); |
1da177e4 | 621 | |
7699acd1 | 622 | /* Remove the current item from the list of epoll hooks */ |
68499914 | 623 | spin_lock(&file->f_lock); |
7699acd1 DL |
624 | if (ep_is_linked(&epi->fllink)) |
625 | list_del_init(&epi->fllink); | |
68499914 | 626 | spin_unlock(&file->f_lock); |
1da177e4 | 627 | |
cdac75e6 | 628 | rb_erase(&epi->rbn, &ep->rbr); |
1da177e4 | 629 | |
c7ea7630 DL |
630 | spin_lock_irqsave(&ep->lock, flags); |
631 | if (ep_is_linked(&epi->rdllink)) | |
632 | list_del_init(&epi->rdllink); | |
633 | spin_unlock_irqrestore(&ep->lock, flags); | |
1da177e4 | 634 | |
7699acd1 | 635 | /* At this point it is safe to free the eventpoll item */ |
c7ea7630 | 636 | kmem_cache_free(epi_cache, epi); |
1da177e4 | 637 | |
52bd19f7 | 638 | atomic_long_dec(&ep->user->epoll_watches); |
7ef9964e | 639 | |
c7ea7630 | 640 | return 0; |
1da177e4 LT |
641 | } |
642 | ||
7699acd1 | 643 | static void ep_free(struct eventpoll *ep) |
1da177e4 | 644 | { |
7699acd1 DL |
645 | struct rb_node *rbp; |
646 | struct epitem *epi; | |
1da177e4 | 647 | |
7699acd1 DL |
648 | /* We need to release all tasks waiting for these file */ |
649 | if (waitqueue_active(&ep->poll_wait)) | |
5071f97e | 650 | ep_poll_safewake(&ep->poll_wait); |
1da177e4 | 651 | |
7699acd1 DL |
652 | /* |
653 | * We need to lock this because we could be hit by | |
654 | * eventpoll_release_file() while we're freeing the "struct eventpoll". | |
d47de16c | 655 | * We do not need to hold "ep->mtx" here because the epoll file |
7699acd1 DL |
656 | * is on the way to be removed and no one has references to it |
657 | * anymore. The only hit might come from eventpoll_release_file() but | |
25985edc | 658 | * holding "epmutex" is sufficient here. |
7699acd1 DL |
659 | */ |
660 | mutex_lock(&epmutex); | |
1da177e4 LT |
661 | |
662 | /* | |
7699acd1 | 663 | * Walks through the whole tree by unregistering poll callbacks. |
1da177e4 | 664 | */ |
7699acd1 DL |
665 | for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { |
666 | epi = rb_entry(rbp, struct epitem, rbn); | |
667 | ||
668 | ep_unregister_pollwait(ep, epi); | |
669 | } | |
1da177e4 LT |
670 | |
671 | /* | |
7699acd1 DL |
672 | * Walks through the whole tree by freeing each "struct epitem". At this |
673 | * point we are sure no poll callbacks will be lingering around, and also by | |
d47de16c | 674 | * holding "epmutex" we can be sure that no file cleanup code will hit |
7699acd1 | 675 | * us during this operation. So we can avoid the lock on "ep->lock". |
1da177e4 | 676 | */ |
c80544dc | 677 | while ((rbp = rb_first(&ep->rbr)) != NULL) { |
7699acd1 DL |
678 | epi = rb_entry(rbp, struct epitem, rbn); |
679 | ep_remove(ep, epi); | |
680 | } | |
1da177e4 | 681 | |
7699acd1 | 682 | mutex_unlock(&epmutex); |
d47de16c | 683 | mutex_destroy(&ep->mtx); |
7ef9964e | 684 | free_uid(ep->user); |
f0ee9aab | 685 | kfree(ep); |
7699acd1 | 686 | } |
1da177e4 | 687 | |
7699acd1 DL |
688 | static int ep_eventpoll_release(struct inode *inode, struct file *file) |
689 | { | |
690 | struct eventpoll *ep = file->private_data; | |
1da177e4 | 691 | |
f0ee9aab | 692 | if (ep) |
7699acd1 | 693 | ep_free(ep); |
7699acd1 | 694 | |
7699acd1 | 695 | return 0; |
1da177e4 LT |
696 | } |
697 | ||
296e236e DL |
698 | static int ep_read_events_proc(struct eventpoll *ep, struct list_head *head, |
699 | void *priv) | |
5071f97e DL |
700 | { |
701 | struct epitem *epi, *tmp; | |
702 | ||
703 | list_for_each_entry_safe(epi, tmp, head, rdllink) { | |
704 | if (epi->ffd.file->f_op->poll(epi->ffd.file, NULL) & | |
705 | epi->event.events) | |
706 | return POLLIN | POLLRDNORM; | |
296e236e | 707 | else { |
5071f97e DL |
708 | /* |
709 | * Item has been dropped into the ready list by the poll | |
710 | * callback, but it's not actually ready, as far as | |
711 | * caller requested events goes. We can remove it here. | |
712 | */ | |
713 | list_del_init(&epi->rdllink); | |
296e236e | 714 | } |
5071f97e DL |
715 | } |
716 | ||
717 | return 0; | |
718 | } | |
719 | ||
720 | static int ep_poll_readyevents_proc(void *priv, void *cookie, int call_nests) | |
721 | { | |
d8805e63 | 722 | return ep_scan_ready_list(priv, ep_read_events_proc, NULL, call_nests + 1); |
5071f97e DL |
723 | } |
724 | ||
7699acd1 DL |
725 | static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait) |
726 | { | |
5071f97e | 727 | int pollflags; |
7699acd1 | 728 | struct eventpoll *ep = file->private_data; |
1da177e4 | 729 | |
7699acd1 DL |
730 | /* Insert inside our poll wait queue */ |
731 | poll_wait(file, &ep->poll_wait, wait); | |
732 | ||
5071f97e DL |
733 | /* |
734 | * Proceed to find out if wanted events are really available inside | |
735 | * the ready list. This need to be done under ep_call_nested() | |
736 | * supervision, since the call to f_op->poll() done on listed files | |
737 | * could re-enter here. | |
738 | */ | |
739 | pollflags = ep_call_nested(&poll_readywalk_ncalls, EP_MAX_NESTS, | |
3fe4a975 | 740 | ep_poll_readyevents_proc, ep, ep, current); |
7699acd1 | 741 | |
296e236e | 742 | return pollflags != -1 ? pollflags : 0; |
7699acd1 DL |
743 | } |
744 | ||
745 | /* File callbacks that implement the eventpoll file behaviour */ | |
746 | static const struct file_operations eventpoll_fops = { | |
747 | .release = ep_eventpoll_release, | |
6038f373 AB |
748 | .poll = ep_eventpoll_poll, |
749 | .llseek = noop_llseek, | |
7699acd1 DL |
750 | }; |
751 | ||
b611967d | 752 | /* |
7699acd1 DL |
753 | * This is called from eventpoll_release() to unlink files from the eventpoll |
754 | * interface. We need to have this facility to cleanup correctly files that are | |
755 | * closed without being removed from the eventpoll interface. | |
b611967d | 756 | */ |
7699acd1 | 757 | void eventpoll_release_file(struct file *file) |
b611967d | 758 | { |
7699acd1 DL |
759 | struct list_head *lsthead = &file->f_ep_links; |
760 | struct eventpoll *ep; | |
761 | struct epitem *epi; | |
b611967d DL |
762 | |
763 | /* | |
68499914 | 764 | * We don't want to get "file->f_lock" because it is not |
7699acd1 | 765 | * necessary. It is not necessary because we're in the "struct file" |
25985edc | 766 | * cleanup path, and this means that no one is using this file anymore. |
5071f97e | 767 | * So, for example, epoll_ctl() cannot hit here since if we reach this |
67647d0f | 768 | * point, the file counter already went to zero and fget() would fail. |
d47de16c | 769 | * The only hit might come from ep_free() but by holding the mutex |
7699acd1 | 770 | * will correctly serialize the operation. We do need to acquire |
d47de16c | 771 | * "ep->mtx" after "epmutex" because ep_remove() requires it when called |
7699acd1 | 772 | * from anywhere but ep_free(). |
68499914 JC |
773 | * |
774 | * Besides, ep_remove() acquires the lock, so we can't hold it here. | |
b611967d | 775 | */ |
7699acd1 | 776 | mutex_lock(&epmutex); |
b611967d | 777 | |
7699acd1 DL |
778 | while (!list_empty(lsthead)) { |
779 | epi = list_first_entry(lsthead, struct epitem, fllink); | |
b611967d | 780 | |
7699acd1 DL |
781 | ep = epi->ep; |
782 | list_del_init(&epi->fllink); | |
d8805e63 | 783 | mutex_lock_nested(&ep->mtx, 0); |
7699acd1 | 784 | ep_remove(ep, epi); |
d47de16c | 785 | mutex_unlock(&ep->mtx); |
b611967d DL |
786 | } |
787 | ||
7699acd1 | 788 | mutex_unlock(&epmutex); |
b611967d DL |
789 | } |
790 | ||
53d2be79 | 791 | static int ep_alloc(struct eventpoll **pep) |
1da177e4 | 792 | { |
7ef9964e DL |
793 | int error; |
794 | struct user_struct *user; | |
795 | struct eventpoll *ep; | |
1da177e4 | 796 | |
7ef9964e | 797 | user = get_current_user(); |
7ef9964e DL |
798 | error = -ENOMEM; |
799 | ep = kzalloc(sizeof(*ep), GFP_KERNEL); | |
800 | if (unlikely(!ep)) | |
801 | goto free_uid; | |
1da177e4 | 802 | |
c7ea7630 | 803 | spin_lock_init(&ep->lock); |
d47de16c | 804 | mutex_init(&ep->mtx); |
1da177e4 LT |
805 | init_waitqueue_head(&ep->wq); |
806 | init_waitqueue_head(&ep->poll_wait); | |
807 | INIT_LIST_HEAD(&ep->rdllist); | |
808 | ep->rbr = RB_ROOT; | |
d47de16c | 809 | ep->ovflist = EP_UNACTIVE_PTR; |
7ef9964e | 810 | ep->user = user; |
1da177e4 | 811 | |
53d2be79 | 812 | *pep = ep; |
1da177e4 | 813 | |
1da177e4 | 814 | return 0; |
7ef9964e DL |
815 | |
816 | free_uid: | |
817 | free_uid(user); | |
818 | return error; | |
1da177e4 LT |
819 | } |
820 | ||
1da177e4 | 821 | /* |
c7ea7630 DL |
822 | * Search the file inside the eventpoll tree. The RB tree operations |
823 | * are protected by the "mtx" mutex, and ep_find() must be called with | |
824 | * "mtx" held. | |
1da177e4 LT |
825 | */ |
826 | static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd) | |
827 | { | |
828 | int kcmp; | |
1da177e4 LT |
829 | struct rb_node *rbp; |
830 | struct epitem *epi, *epir = NULL; | |
831 | struct epoll_filefd ffd; | |
832 | ||
b030a4dd | 833 | ep_set_ffd(&ffd, file, fd); |
1da177e4 LT |
834 | for (rbp = ep->rbr.rb_node; rbp; ) { |
835 | epi = rb_entry(rbp, struct epitem, rbn); | |
b030a4dd | 836 | kcmp = ep_cmp_ffd(&ffd, &epi->ffd); |
1da177e4 LT |
837 | if (kcmp > 0) |
838 | rbp = rbp->rb_right; | |
839 | else if (kcmp < 0) | |
840 | rbp = rbp->rb_left; | |
841 | else { | |
1da177e4 LT |
842 | epir = epi; |
843 | break; | |
844 | } | |
845 | } | |
1da177e4 | 846 | |
1da177e4 LT |
847 | return epir; |
848 | } | |
849 | ||
1da177e4 | 850 | /* |
7699acd1 | 851 | * This is the callback that is passed to the wait queue wakeup |
bf6a41db | 852 | * mechanism. It is called by the stored file descriptors when they |
7699acd1 | 853 | * have events to report. |
1da177e4 | 854 | */ |
7699acd1 | 855 | static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *key) |
1da177e4 | 856 | { |
7699acd1 DL |
857 | int pwake = 0; |
858 | unsigned long flags; | |
859 | struct epitem *epi = ep_item_from_wait(wait); | |
860 | struct eventpoll *ep = epi->ep; | |
1da177e4 | 861 | |
971316f0 ON |
862 | if ((unsigned long)key & POLLFREE) { |
863 | ep_pwq_from_wait(wait)->whead = NULL; | |
864 | /* | |
865 | * whead = NULL above can race with ep_remove_wait_queue() | |
866 | * which can do another remove_wait_queue() after us, so we | |
867 | * can't use __remove_wait_queue(). whead->lock is held by | |
868 | * the caller. | |
869 | */ | |
d80e731e | 870 | list_del_init(&wait->task_list); |
971316f0 | 871 | } |
d80e731e | 872 | |
c7ea7630 | 873 | spin_lock_irqsave(&ep->lock, flags); |
1da177e4 | 874 | |
7699acd1 DL |
875 | /* |
876 | * If the event mask does not contain any poll(2) event, we consider the | |
877 | * descriptor to be disabled. This condition is likely the effect of the | |
878 | * EPOLLONESHOT bit that disables the descriptor when an event is received, | |
879 | * until the next EPOLL_CTL_MOD will be issued. | |
880 | */ | |
881 | if (!(epi->event.events & ~EP_PRIVATE_BITS)) | |
d47de16c DL |
882 | goto out_unlock; |
883 | ||
2dfa4eea DL |
884 | /* |
885 | * Check the events coming with the callback. At this stage, not | |
886 | * every device reports the events in the "key" parameter of the | |
887 | * callback. We need to be able to handle both cases here, hence the | |
888 | * test for "key" != NULL before the event match test. | |
889 | */ | |
890 | if (key && !((unsigned long) key & epi->event.events)) | |
891 | goto out_unlock; | |
892 | ||
d47de16c | 893 | /* |
bf6a41db | 894 | * If we are transferring events to userspace, we can hold no locks |
d47de16c | 895 | * (because we're accessing user memory, and because of linux f_op->poll() |
bf6a41db | 896 | * semantics). All the events that happen during that period of time are |
d47de16c DL |
897 | * chained in ep->ovflist and requeued later on. |
898 | */ | |
899 | if (unlikely(ep->ovflist != EP_UNACTIVE_PTR)) { | |
900 | if (epi->next == EP_UNACTIVE_PTR) { | |
901 | epi->next = ep->ovflist; | |
902 | ep->ovflist = epi; | |
903 | } | |
904 | goto out_unlock; | |
905 | } | |
1da177e4 | 906 | |
7699acd1 | 907 | /* If this file is already in the ready list we exit soon */ |
5071f97e DL |
908 | if (!ep_is_linked(&epi->rdllink)) |
909 | list_add_tail(&epi->rdllink, &ep->rdllist); | |
7699acd1 | 910 | |
7699acd1 DL |
911 | /* |
912 | * Wake up ( if active ) both the eventpoll wait list and the ->poll() | |
913 | * wait list. | |
914 | */ | |
915 | if (waitqueue_active(&ep->wq)) | |
4a6e9e2c | 916 | wake_up_locked(&ep->wq); |
7699acd1 DL |
917 | if (waitqueue_active(&ep->poll_wait)) |
918 | pwake++; | |
919 | ||
d47de16c | 920 | out_unlock: |
c7ea7630 | 921 | spin_unlock_irqrestore(&ep->lock, flags); |
1da177e4 | 922 | |
7699acd1 DL |
923 | /* We have to call this outside the lock */ |
924 | if (pwake) | |
5071f97e | 925 | ep_poll_safewake(&ep->poll_wait); |
7699acd1 DL |
926 | |
927 | return 1; | |
928 | } | |
1da177e4 LT |
929 | |
930 | /* | |
931 | * This is the callback that is used to add our wait queue to the | |
932 | * target file wakeup lists. | |
933 | */ | |
934 | static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, | |
935 | poll_table *pt) | |
936 | { | |
b030a4dd | 937 | struct epitem *epi = ep_item_from_epqueue(pt); |
1da177e4 LT |
938 | struct eppoll_entry *pwq; |
939 | ||
e94b1766 | 940 | if (epi->nwait >= 0 && (pwq = kmem_cache_alloc(pwq_cache, GFP_KERNEL))) { |
1da177e4 LT |
941 | init_waitqueue_func_entry(&pwq->wait, ep_poll_callback); |
942 | pwq->whead = whead; | |
943 | pwq->base = epi; | |
944 | add_wait_queue(whead, &pwq->wait); | |
945 | list_add_tail(&pwq->llink, &epi->pwqlist); | |
946 | epi->nwait++; | |
296e236e | 947 | } else { |
1da177e4 LT |
948 | /* We have to signal that an error occurred */ |
949 | epi->nwait = -1; | |
296e236e | 950 | } |
1da177e4 LT |
951 | } |
952 | ||
1da177e4 LT |
953 | static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi) |
954 | { | |
955 | int kcmp; | |
956 | struct rb_node **p = &ep->rbr.rb_node, *parent = NULL; | |
957 | struct epitem *epic; | |
958 | ||
959 | while (*p) { | |
960 | parent = *p; | |
961 | epic = rb_entry(parent, struct epitem, rbn); | |
b030a4dd | 962 | kcmp = ep_cmp_ffd(&epi->ffd, &epic->ffd); |
1da177e4 LT |
963 | if (kcmp > 0) |
964 | p = &parent->rb_right; | |
965 | else | |
966 | p = &parent->rb_left; | |
967 | } | |
968 | rb_link_node(&epi->rbn, parent, p); | |
969 | rb_insert_color(&epi->rbn, &ep->rbr); | |
970 | } | |
971 | ||
28d82dc1 JB |
972 | |
973 | ||
974 | #define PATH_ARR_SIZE 5 | |
975 | /* | |
976 | * These are the number paths of length 1 to 5, that we are allowing to emanate | |
977 | * from a single file of interest. For example, we allow 1000 paths of length | |
978 | * 1, to emanate from each file of interest. This essentially represents the | |
979 | * potential wakeup paths, which need to be limited in order to avoid massive | |
980 | * uncontrolled wakeup storms. The common use case should be a single ep which | |
981 | * is connected to n file sources. In this case each file source has 1 path | |
982 | * of length 1. Thus, the numbers below should be more than sufficient. These | |
983 | * path limits are enforced during an EPOLL_CTL_ADD operation, since a modify | |
984 | * and delete can't add additional paths. Protected by the epmutex. | |
985 | */ | |
986 | static const int path_limits[PATH_ARR_SIZE] = { 1000, 500, 100, 50, 10 }; | |
987 | static int path_count[PATH_ARR_SIZE]; | |
988 | ||
989 | static int path_count_inc(int nests) | |
990 | { | |
991 | if (++path_count[nests] > path_limits[nests]) | |
992 | return -1; | |
993 | return 0; | |
994 | } | |
995 | ||
996 | static void path_count_init(void) | |
997 | { | |
998 | int i; | |
999 | ||
1000 | for (i = 0; i < PATH_ARR_SIZE; i++) | |
1001 | path_count[i] = 0; | |
1002 | } | |
1003 | ||
1004 | static int reverse_path_check_proc(void *priv, void *cookie, int call_nests) | |
1005 | { | |
1006 | int error = 0; | |
1007 | struct file *file = priv; | |
1008 | struct file *child_file; | |
1009 | struct epitem *epi; | |
1010 | ||
1011 | list_for_each_entry(epi, &file->f_ep_links, fllink) { | |
1012 | child_file = epi->ep->file; | |
1013 | if (is_file_epoll(child_file)) { | |
1014 | if (list_empty(&child_file->f_ep_links)) { | |
1015 | if (path_count_inc(call_nests)) { | |
1016 | error = -1; | |
1017 | break; | |
1018 | } | |
1019 | } else { | |
1020 | error = ep_call_nested(&poll_loop_ncalls, | |
1021 | EP_MAX_NESTS, | |
1022 | reverse_path_check_proc, | |
1023 | child_file, child_file, | |
1024 | current); | |
1025 | } | |
1026 | if (error != 0) | |
1027 | break; | |
1028 | } else { | |
1029 | printk(KERN_ERR "reverse_path_check_proc: " | |
1030 | "file is not an ep!\n"); | |
1031 | } | |
1032 | } | |
1033 | return error; | |
1034 | } | |
1035 | ||
1036 | /** | |
1037 | * reverse_path_check - The tfile_check_list is list of file *, which have | |
1038 | * links that are proposed to be newly added. We need to | |
1039 | * make sure that those added links don't add too many | |
1040 | * paths such that we will spend all our time waking up | |
1041 | * eventpoll objects. | |
1042 | * | |
1043 | * Returns: Returns zero if the proposed links don't create too many paths, | |
1044 | * -1 otherwise. | |
1045 | */ | |
1046 | static int reverse_path_check(void) | |
1047 | { | |
1048 | int length = 0; | |
1049 | int error = 0; | |
1050 | struct file *current_file; | |
1051 | ||
1052 | /* let's call this for all tfiles */ | |
1053 | list_for_each_entry(current_file, &tfile_check_list, f_tfile_llink) { | |
1054 | length++; | |
1055 | path_count_init(); | |
1056 | error = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, | |
1057 | reverse_path_check_proc, current_file, | |
1058 | current_file, current); | |
1059 | if (error) | |
1060 | break; | |
1061 | } | |
1062 | return error; | |
1063 | } | |
1064 | ||
c7ea7630 DL |
1065 | /* |
1066 | * Must be called with "mtx" held. | |
1067 | */ | |
1da177e4 LT |
1068 | static int ep_insert(struct eventpoll *ep, struct epoll_event *event, |
1069 | struct file *tfile, int fd) | |
1070 | { | |
1071 | int error, revents, pwake = 0; | |
1072 | unsigned long flags; | |
52bd19f7 | 1073 | long user_watches; |
1da177e4 LT |
1074 | struct epitem *epi; |
1075 | struct ep_pqueue epq; | |
1076 | ||
52bd19f7 RH |
1077 | user_watches = atomic_long_read(&ep->user->epoll_watches); |
1078 | if (unlikely(user_watches >= max_user_watches)) | |
7ef9964e | 1079 | return -ENOSPC; |
e94b1766 | 1080 | if (!(epi = kmem_cache_alloc(epi_cache, GFP_KERNEL))) |
7ef9964e | 1081 | return -ENOMEM; |
1da177e4 LT |
1082 | |
1083 | /* Item initialization follow here ... */ | |
1da177e4 LT |
1084 | INIT_LIST_HEAD(&epi->rdllink); |
1085 | INIT_LIST_HEAD(&epi->fllink); | |
1da177e4 LT |
1086 | INIT_LIST_HEAD(&epi->pwqlist); |
1087 | epi->ep = ep; | |
b030a4dd | 1088 | ep_set_ffd(&epi->ffd, tfile, fd); |
1da177e4 | 1089 | epi->event = *event; |
1da177e4 | 1090 | epi->nwait = 0; |
d47de16c | 1091 | epi->next = EP_UNACTIVE_PTR; |
1da177e4 LT |
1092 | |
1093 | /* Initialize the poll table using the queue callback */ | |
1094 | epq.epi = epi; | |
1095 | init_poll_funcptr(&epq.pt, ep_ptable_queue_proc); | |
1096 | ||
1097 | /* | |
1098 | * Attach the item to the poll hooks and get current event bits. | |
1099 | * We can safely use the file* here because its usage count has | |
c7ea7630 DL |
1100 | * been increased by the caller of this function. Note that after |
1101 | * this operation completes, the poll callback can start hitting | |
1102 | * the new item. | |
1da177e4 LT |
1103 | */ |
1104 | revents = tfile->f_op->poll(tfile, &epq.pt); | |
1105 | ||
1106 | /* | |
1107 | * We have to check if something went wrong during the poll wait queue | |
1108 | * install process. Namely an allocation for a wait queue failed due | |
1109 | * high memory pressure. | |
1110 | */ | |
7ef9964e | 1111 | error = -ENOMEM; |
1da177e4 | 1112 | if (epi->nwait < 0) |
7699acd1 | 1113 | goto error_unregister; |
1da177e4 LT |
1114 | |
1115 | /* Add the current item to the list of active epoll hook for this file */ | |
68499914 | 1116 | spin_lock(&tfile->f_lock); |
1da177e4 | 1117 | list_add_tail(&epi->fllink, &tfile->f_ep_links); |
68499914 | 1118 | spin_unlock(&tfile->f_lock); |
1da177e4 | 1119 | |
c7ea7630 DL |
1120 | /* |
1121 | * Add the current item to the RB tree. All RB tree operations are | |
1122 | * protected by "mtx", and ep_insert() is called with "mtx" held. | |
1123 | */ | |
1da177e4 LT |
1124 | ep_rbtree_insert(ep, epi); |
1125 | ||
28d82dc1 JB |
1126 | /* now check if we've created too many backpaths */ |
1127 | error = -EINVAL; | |
1128 | if (reverse_path_check()) | |
1129 | goto error_remove_epi; | |
1130 | ||
c7ea7630 DL |
1131 | /* We have to drop the new item inside our item list to keep track of it */ |
1132 | spin_lock_irqsave(&ep->lock, flags); | |
1133 | ||
1da177e4 | 1134 | /* If the file is already "ready" we drop it inside the ready list */ |
b030a4dd | 1135 | if ((revents & event->events) && !ep_is_linked(&epi->rdllink)) { |
1da177e4 LT |
1136 | list_add_tail(&epi->rdllink, &ep->rdllist); |
1137 | ||
1138 | /* Notify waiting tasks that events are available */ | |
1139 | if (waitqueue_active(&ep->wq)) | |
4a6e9e2c | 1140 | wake_up_locked(&ep->wq); |
1da177e4 LT |
1141 | if (waitqueue_active(&ep->poll_wait)) |
1142 | pwake++; | |
1143 | } | |
1144 | ||
c7ea7630 | 1145 | spin_unlock_irqrestore(&ep->lock, flags); |
1da177e4 | 1146 | |
52bd19f7 | 1147 | atomic_long_inc(&ep->user->epoll_watches); |
7ef9964e | 1148 | |
1da177e4 LT |
1149 | /* We have to call this outside the lock */ |
1150 | if (pwake) | |
5071f97e | 1151 | ep_poll_safewake(&ep->poll_wait); |
1da177e4 | 1152 | |
1da177e4 LT |
1153 | return 0; |
1154 | ||
28d82dc1 JB |
1155 | error_remove_epi: |
1156 | spin_lock(&tfile->f_lock); | |
1157 | if (ep_is_linked(&epi->fllink)) | |
1158 | list_del_init(&epi->fllink); | |
1159 | spin_unlock(&tfile->f_lock); | |
1160 | ||
1161 | rb_erase(&epi->rbn, &ep->rbr); | |
1162 | ||
7699acd1 | 1163 | error_unregister: |
1da177e4 LT |
1164 | ep_unregister_pollwait(ep, epi); |
1165 | ||
1166 | /* | |
1167 | * We need to do this because an event could have been arrived on some | |
67647d0f DL |
1168 | * allocated wait queue. Note that we don't care about the ep->ovflist |
1169 | * list, since that is used/cleaned only inside a section bound by "mtx". | |
1170 | * And ep_insert() is called with "mtx" held. | |
1da177e4 | 1171 | */ |
c7ea7630 | 1172 | spin_lock_irqsave(&ep->lock, flags); |
b030a4dd | 1173 | if (ep_is_linked(&epi->rdllink)) |
6192bd53 | 1174 | list_del_init(&epi->rdllink); |
c7ea7630 | 1175 | spin_unlock_irqrestore(&ep->lock, flags); |
1da177e4 | 1176 | |
b030a4dd | 1177 | kmem_cache_free(epi_cache, epi); |
7ef9964e | 1178 | |
1da177e4 LT |
1179 | return error; |
1180 | } | |
1181 | ||
1da177e4 LT |
1182 | /* |
1183 | * Modify the interest event mask by dropping an event if the new mask | |
c7ea7630 | 1184 | * has a match in the current file status. Must be called with "mtx" held. |
1da177e4 LT |
1185 | */ |
1186 | static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_event *event) | |
1187 | { | |
1188 | int pwake = 0; | |
1189 | unsigned int revents; | |
1da177e4 LT |
1190 | |
1191 | /* | |
e057e15f TB |
1192 | * Set the new event interest mask before calling f_op->poll(); |
1193 | * otherwise we might miss an event that happens between the | |
1194 | * f_op->poll() call and the new event set registering. | |
1da177e4 LT |
1195 | */ |
1196 | epi->event.events = event->events; | |
e057e15f | 1197 | epi->event.data = event->data; /* protected by mtx */ |
1da177e4 LT |
1198 | |
1199 | /* | |
1200 | * Get current event bits. We can safely use the file* here because | |
1201 | * its usage count has been increased by the caller of this function. | |
1202 | */ | |
1203 | revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL); | |
1204 | ||
1da177e4 | 1205 | /* |
c7ea7630 | 1206 | * If the item is "hot" and it is not registered inside the ready |
67647d0f | 1207 | * list, push it inside. |
1da177e4 | 1208 | */ |
c7ea7630 | 1209 | if (revents & event->events) { |
e057e15f | 1210 | spin_lock_irq(&ep->lock); |
c7ea7630 DL |
1211 | if (!ep_is_linked(&epi->rdllink)) { |
1212 | list_add_tail(&epi->rdllink, &ep->rdllist); | |
1213 | ||
1214 | /* Notify waiting tasks that events are available */ | |
1215 | if (waitqueue_active(&ep->wq)) | |
4a6e9e2c | 1216 | wake_up_locked(&ep->wq); |
c7ea7630 DL |
1217 | if (waitqueue_active(&ep->poll_wait)) |
1218 | pwake++; | |
7699acd1 | 1219 | } |
e057e15f | 1220 | spin_unlock_irq(&ep->lock); |
7699acd1 | 1221 | } |
1da177e4 | 1222 | |
7699acd1 DL |
1223 | /* We have to call this outside the lock */ |
1224 | if (pwake) | |
5071f97e | 1225 | ep_poll_safewake(&ep->poll_wait); |
1da177e4 | 1226 | |
7699acd1 | 1227 | return 0; |
1da177e4 LT |
1228 | } |
1229 | ||
296e236e DL |
1230 | static int ep_send_events_proc(struct eventpoll *ep, struct list_head *head, |
1231 | void *priv) | |
1da177e4 | 1232 | { |
5071f97e DL |
1233 | struct ep_send_events_data *esed = priv; |
1234 | int eventcnt; | |
296e236e | 1235 | unsigned int revents; |
5071f97e DL |
1236 | struct epitem *epi; |
1237 | struct epoll_event __user *uevent; | |
1da177e4 | 1238 | |
296e236e | 1239 | /* |
5071f97e DL |
1240 | * We can loop without lock because we are passed a task private list. |
1241 | * Items cannot vanish during the loop because ep_scan_ready_list() is | |
1242 | * holding "mtx" during this call. | |
296e236e | 1243 | */ |
5071f97e DL |
1244 | for (eventcnt = 0, uevent = esed->events; |
1245 | !list_empty(head) && eventcnt < esed->maxevents;) { | |
1246 | epi = list_first_entry(head, struct epitem, rdllink); | |
d47de16c DL |
1247 | |
1248 | list_del_init(&epi->rdllink); | |
1da177e4 | 1249 | |
296e236e DL |
1250 | revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL) & |
1251 | epi->event.events; | |
5071f97e | 1252 | |
296e236e | 1253 | /* |
5071f97e DL |
1254 | * If the event mask intersect the caller-requested one, |
1255 | * deliver the event to userspace. Again, ep_scan_ready_list() | |
1256 | * is holding "mtx", so no operations coming from userspace | |
1257 | * can change the item. | |
296e236e DL |
1258 | */ |
1259 | if (revents) { | |
5071f97e | 1260 | if (__put_user(revents, &uevent->events) || |
d0305882 TB |
1261 | __put_user(epi->event.data, &uevent->data)) { |
1262 | list_add(&epi->rdllink, head); | |
296e236e | 1263 | return eventcnt ? eventcnt : -EFAULT; |
d0305882 | 1264 | } |
296e236e | 1265 | eventcnt++; |
5071f97e | 1266 | uevent++; |
296e236e DL |
1267 | if (epi->event.events & EPOLLONESHOT) |
1268 | epi->event.events &= EP_PRIVATE_BITS; | |
1269 | else if (!(epi->event.events & EPOLLET)) { | |
1270 | /* | |
1271 | * If this file has been added with Level | |
1272 | * Trigger mode, we need to insert back inside | |
1273 | * the ready list, so that the next call to | |
1274 | * epoll_wait() will check again the events | |
25985edc | 1275 | * availability. At this point, no one can insert |
296e236e DL |
1276 | * into ep->rdllist besides us. The epoll_ctl() |
1277 | * callers are locked out by | |
1278 | * ep_scan_ready_list() holding "mtx" and the | |
1279 | * poll callback will queue them in ep->ovflist. | |
1280 | */ | |
1281 | list_add_tail(&epi->rdllink, &ep->rdllist); | |
1282 | } | |
1283 | } | |
1284 | } | |
5071f97e DL |
1285 | |
1286 | return eventcnt; | |
1287 | } | |
d47de16c | 1288 | |
296e236e DL |
1289 | static int ep_send_events(struct eventpoll *ep, |
1290 | struct epoll_event __user *events, int maxevents) | |
5071f97e DL |
1291 | { |
1292 | struct ep_send_events_data esed; | |
1da177e4 | 1293 | |
5071f97e DL |
1294 | esed.maxevents = maxevents; |
1295 | esed.events = events; | |
6192bd53 | 1296 | |
d8805e63 | 1297 | return ep_scan_ready_list(ep, ep_send_events_proc, &esed, 0); |
1da177e4 LT |
1298 | } |
1299 | ||
0781b909 ED |
1300 | static inline struct timespec ep_set_mstimeout(long ms) |
1301 | { | |
1302 | struct timespec now, ts = { | |
1303 | .tv_sec = ms / MSEC_PER_SEC, | |
1304 | .tv_nsec = NSEC_PER_MSEC * (ms % MSEC_PER_SEC), | |
1305 | }; | |
1306 | ||
1307 | ktime_get_ts(&now); | |
1308 | return timespec_add_safe(now, ts); | |
1309 | } | |
1310 | ||
f4d93ad7 SB |
1311 | /** |
1312 | * ep_poll - Retrieves ready events, and delivers them to the caller supplied | |
1313 | * event buffer. | |
1314 | * | |
1315 | * @ep: Pointer to the eventpoll context. | |
1316 | * @events: Pointer to the userspace buffer where the ready events should be | |
1317 | * stored. | |
1318 | * @maxevents: Size (in terms of number of events) of the caller event buffer. | |
1319 | * @timeout: Maximum timeout for the ready events fetch operation, in | |
1320 | * milliseconds. If the @timeout is zero, the function will not block, | |
1321 | * while if the @timeout is less than zero, the function will block | |
1322 | * until at least one event has been retrieved (or an error | |
1323 | * occurred). | |
1324 | * | |
1325 | * Returns: Returns the number of ready events which have been fetched, or an | |
1326 | * error code, in case of error. | |
1327 | */ | |
1da177e4 LT |
1328 | static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, |
1329 | int maxevents, long timeout) | |
1330 | { | |
f4d93ad7 | 1331 | int res = 0, eavail, timed_out = 0; |
1da177e4 | 1332 | unsigned long flags; |
f4d93ad7 | 1333 | long slack = 0; |
1da177e4 | 1334 | wait_queue_t wait; |
95aac7b1 SB |
1335 | ktime_t expires, *to = NULL; |
1336 | ||
1337 | if (timeout > 0) { | |
0781b909 ED |
1338 | struct timespec end_time = ep_set_mstimeout(timeout); |
1339 | ||
95aac7b1 SB |
1340 | slack = select_estimate_accuracy(&end_time); |
1341 | to = &expires; | |
1342 | *to = timespec_to_ktime(end_time); | |
1343 | } else if (timeout == 0) { | |
f4d93ad7 SB |
1344 | /* |
1345 | * Avoid the unnecessary trip to the wait queue loop, if the | |
1346 | * caller specified a non blocking operation. | |
1347 | */ | |
95aac7b1 | 1348 | timed_out = 1; |
f4d93ad7 SB |
1349 | spin_lock_irqsave(&ep->lock, flags); |
1350 | goto check_events; | |
95aac7b1 | 1351 | } |
1da177e4 | 1352 | |
f4d93ad7 | 1353 | fetch_events: |
c7ea7630 | 1354 | spin_lock_irqsave(&ep->lock, flags); |
1da177e4 | 1355 | |
3fb0e584 | 1356 | if (!ep_events_available(ep)) { |
1da177e4 LT |
1357 | /* |
1358 | * We don't have any available event to return to the caller. | |
1359 | * We need to sleep here, and we will be wake up by | |
1360 | * ep_poll_callback() when events will become available. | |
1361 | */ | |
1362 | init_waitqueue_entry(&wait, current); | |
a93d2f17 | 1363 | __add_wait_queue_exclusive(&ep->wq, &wait); |
1da177e4 LT |
1364 | |
1365 | for (;;) { | |
1366 | /* | |
1367 | * We don't want to sleep if the ep_poll_callback() sends us | |
1368 | * a wakeup in between. That's why we set the task state | |
1369 | * to TASK_INTERRUPTIBLE before doing the checks. | |
1370 | */ | |
1371 | set_current_state(TASK_INTERRUPTIBLE); | |
3fb0e584 | 1372 | if (ep_events_available(ep) || timed_out) |
1da177e4 LT |
1373 | break; |
1374 | if (signal_pending(current)) { | |
1375 | res = -EINTR; | |
1376 | break; | |
1377 | } | |
1378 | ||
c7ea7630 | 1379 | spin_unlock_irqrestore(&ep->lock, flags); |
95aac7b1 SB |
1380 | if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS)) |
1381 | timed_out = 1; | |
1382 | ||
c7ea7630 | 1383 | spin_lock_irqsave(&ep->lock, flags); |
1da177e4 | 1384 | } |
3419b23a | 1385 | __remove_wait_queue(&ep->wq, &wait); |
1da177e4 LT |
1386 | |
1387 | set_current_state(TASK_RUNNING); | |
1388 | } | |
f4d93ad7 | 1389 | check_events: |
1da177e4 | 1390 | /* Is it worth to try to dig for events ? */ |
3fb0e584 | 1391 | eavail = ep_events_available(ep); |
1da177e4 | 1392 | |
c7ea7630 | 1393 | spin_unlock_irqrestore(&ep->lock, flags); |
1da177e4 LT |
1394 | |
1395 | /* | |
1396 | * Try to transfer events to user space. In case we get 0 events and | |
1397 | * there's still timeout left over, we go trying again in search of | |
1398 | * more luck. | |
1399 | */ | |
1400 | if (!res && eavail && | |
95aac7b1 | 1401 | !(res = ep_send_events(ep, events, maxevents)) && !timed_out) |
f4d93ad7 | 1402 | goto fetch_events; |
1da177e4 LT |
1403 | |
1404 | return res; | |
1405 | } | |
1406 | ||
22bacca4 DL |
1407 | /** |
1408 | * ep_loop_check_proc - Callback function to be passed to the @ep_call_nested() | |
1409 | * API, to verify that adding an epoll file inside another | |
1410 | * epoll structure, does not violate the constraints, in | |
1411 | * terms of closed loops, or too deep chains (which can | |
1412 | * result in excessive stack usage). | |
1413 | * | |
1414 | * @priv: Pointer to the epoll file to be currently checked. | |
1415 | * @cookie: Original cookie for this call. This is the top-of-the-chain epoll | |
1416 | * data structure pointer. | |
1417 | * @call_nests: Current dept of the @ep_call_nested() call stack. | |
1418 | * | |
1419 | * Returns: Returns zero if adding the epoll @file inside current epoll | |
1420 | * structure @ep does not violate the constraints, or -1 otherwise. | |
1421 | */ | |
1422 | static int ep_loop_check_proc(void *priv, void *cookie, int call_nests) | |
1423 | { | |
1424 | int error = 0; | |
1425 | struct file *file = priv; | |
1426 | struct eventpoll *ep = file->private_data; | |
28d82dc1 | 1427 | struct eventpoll *ep_tovisit; |
22bacca4 DL |
1428 | struct rb_node *rbp; |
1429 | struct epitem *epi; | |
1430 | ||
d8805e63 | 1431 | mutex_lock_nested(&ep->mtx, call_nests + 1); |
28d82dc1 JB |
1432 | ep->visited = 1; |
1433 | list_add(&ep->visited_list_link, &visited_list); | |
22bacca4 DL |
1434 | for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { |
1435 | epi = rb_entry(rbp, struct epitem, rbn); | |
1436 | if (unlikely(is_file_epoll(epi->ffd.file))) { | |
28d82dc1 JB |
1437 | ep_tovisit = epi->ffd.file->private_data; |
1438 | if (ep_tovisit->visited) | |
1439 | continue; | |
22bacca4 | 1440 | error = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, |
28d82dc1 JB |
1441 | ep_loop_check_proc, epi->ffd.file, |
1442 | ep_tovisit, current); | |
22bacca4 DL |
1443 | if (error != 0) |
1444 | break; | |
28d82dc1 JB |
1445 | } else { |
1446 | /* | |
1447 | * If we've reached a file that is not associated with | |
1448 | * an ep, then we need to check if the newly added | |
1449 | * links are going to add too many wakeup paths. We do | |
1450 | * this by adding it to the tfile_check_list, if it's | |
1451 | * not already there, and calling reverse_path_check() | |
1452 | * during ep_insert(). | |
1453 | */ | |
1454 | if (list_empty(&epi->ffd.file->f_tfile_llink)) | |
1455 | list_add(&epi->ffd.file->f_tfile_llink, | |
1456 | &tfile_check_list); | |
22bacca4 DL |
1457 | } |
1458 | } | |
1459 | mutex_unlock(&ep->mtx); | |
1460 | ||
1461 | return error; | |
1462 | } | |
1463 | ||
1464 | /** | |
1465 | * ep_loop_check - Performs a check to verify that adding an epoll file (@file) | |
1466 | * another epoll file (represented by @ep) does not create | |
1467 | * closed loops or too deep chains. | |
1468 | * | |
1469 | * @ep: Pointer to the epoll private data structure. | |
1470 | * @file: Pointer to the epoll file to be checked. | |
1471 | * | |
1472 | * Returns: Returns zero if adding the epoll @file inside current epoll | |
1473 | * structure @ep does not violate the constraints, or -1 otherwise. | |
1474 | */ | |
1475 | static int ep_loop_check(struct eventpoll *ep, struct file *file) | |
1476 | { | |
28d82dc1 JB |
1477 | int ret; |
1478 | struct eventpoll *ep_cur, *ep_next; | |
1479 | ||
1480 | ret = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, | |
22bacca4 | 1481 | ep_loop_check_proc, file, ep, current); |
28d82dc1 JB |
1482 | /* clear visited list */ |
1483 | list_for_each_entry_safe(ep_cur, ep_next, &visited_list, | |
1484 | visited_list_link) { | |
1485 | ep_cur->visited = 0; | |
1486 | list_del(&ep_cur->visited_list_link); | |
1487 | } | |
1488 | return ret; | |
1489 | } | |
1490 | ||
1491 | static void clear_tfile_check_list(void) | |
1492 | { | |
1493 | struct file *file; | |
1494 | ||
1495 | /* first clear the tfile_check_list */ | |
1496 | while (!list_empty(&tfile_check_list)) { | |
1497 | file = list_first_entry(&tfile_check_list, struct file, | |
1498 | f_tfile_llink); | |
1499 | list_del_init(&file->f_tfile_llink); | |
1500 | } | |
1501 | INIT_LIST_HEAD(&tfile_check_list); | |
22bacca4 DL |
1502 | } |
1503 | ||
7699acd1 | 1504 | /* |
523723bb | 1505 | * Open an eventpoll file descriptor. |
7699acd1 | 1506 | */ |
5a8a82b1 | 1507 | SYSCALL_DEFINE1(epoll_create1, int, flags) |
7699acd1 | 1508 | { |
28d82dc1 | 1509 | int error, fd; |
bb57c3ed | 1510 | struct eventpoll *ep = NULL; |
28d82dc1 | 1511 | struct file *file; |
7699acd1 | 1512 | |
e38b36f3 UD |
1513 | /* Check the EPOLL_* constant for consistency. */ |
1514 | BUILD_BUG_ON(EPOLL_CLOEXEC != O_CLOEXEC); | |
1515 | ||
296e236e DL |
1516 | if (flags & ~EPOLL_CLOEXEC) |
1517 | return -EINVAL; | |
7699acd1 | 1518 | /* |
bb57c3ed | 1519 | * Create the internal data structure ("struct eventpoll"). |
7699acd1 | 1520 | */ |
9fe5ad9c | 1521 | error = ep_alloc(&ep); |
bb57c3ed DL |
1522 | if (error < 0) |
1523 | return error; | |
7699acd1 DL |
1524 | /* |
1525 | * Creates all the items needed to setup an eventpoll file. That is, | |
2030a42c | 1526 | * a file structure and a free file descriptor. |
7699acd1 | 1527 | */ |
28d82dc1 JB |
1528 | fd = get_unused_fd_flags(O_RDWR | (flags & O_CLOEXEC)); |
1529 | if (fd < 0) { | |
1530 | error = fd; | |
1531 | goto out_free_ep; | |
1532 | } | |
1533 | file = anon_inode_getfile("[eventpoll]", &eventpoll_fops, ep, | |
628ff7c1 | 1534 | O_RDWR | (flags & O_CLOEXEC)); |
28d82dc1 JB |
1535 | if (IS_ERR(file)) { |
1536 | error = PTR_ERR(file); | |
1537 | goto out_free_fd; | |
1538 | } | |
1539 | fd_install(fd, file); | |
1540 | ep->file = file; | |
1541 | return fd; | |
1542 | ||
1543 | out_free_fd: | |
1544 | put_unused_fd(fd); | |
1545 | out_free_ep: | |
1546 | ep_free(ep); | |
bb57c3ed | 1547 | return error; |
7699acd1 DL |
1548 | } |
1549 | ||
5a8a82b1 | 1550 | SYSCALL_DEFINE1(epoll_create, int, size) |
a0998b50 | 1551 | { |
bfe3891a | 1552 | if (size <= 0) |
9fe5ad9c UD |
1553 | return -EINVAL; |
1554 | ||
1555 | return sys_epoll_create1(0); | |
a0998b50 UD |
1556 | } |
1557 | ||
7699acd1 DL |
1558 | /* |
1559 | * The following function implements the controller interface for | |
1560 | * the eventpoll file that enables the insertion/removal/change of | |
67647d0f | 1561 | * file descriptors inside the interest set. |
7699acd1 | 1562 | */ |
5a8a82b1 HC |
1563 | SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd, |
1564 | struct epoll_event __user *, event) | |
7699acd1 DL |
1565 | { |
1566 | int error; | |
22bacca4 | 1567 | int did_lock_epmutex = 0; |
7699acd1 DL |
1568 | struct file *file, *tfile; |
1569 | struct eventpoll *ep; | |
1570 | struct epitem *epi; | |
1571 | struct epoll_event epds; | |
1572 | ||
7699acd1 DL |
1573 | error = -EFAULT; |
1574 | if (ep_op_has_event(op) && | |
1575 | copy_from_user(&epds, event, sizeof(struct epoll_event))) | |
1576 | goto error_return; | |
1577 | ||
1578 | /* Get the "struct file *" for the eventpoll file */ | |
1579 | error = -EBADF; | |
1580 | file = fget(epfd); | |
1581 | if (!file) | |
1582 | goto error_return; | |
1583 | ||
1584 | /* Get the "struct file *" for the target file */ | |
1585 | tfile = fget(fd); | |
1586 | if (!tfile) | |
1587 | goto error_fput; | |
1588 | ||
1589 | /* The target file descriptor must support poll */ | |
1590 | error = -EPERM; | |
1591 | if (!tfile->f_op || !tfile->f_op->poll) | |
1592 | goto error_tgt_fput; | |
1593 | ||
1594 | /* | |
1595 | * We have to check that the file structure underneath the file descriptor | |
1596 | * the user passed to us _is_ an eventpoll file. And also we do not permit | |
1597 | * adding an epoll file descriptor inside itself. | |
1598 | */ | |
1599 | error = -EINVAL; | |
1600 | if (file == tfile || !is_file_epoll(file)) | |
1601 | goto error_tgt_fput; | |
1602 | ||
1603 | /* | |
1604 | * At this point it is safe to assume that the "private_data" contains | |
1605 | * our own data structure. | |
1606 | */ | |
1607 | ep = file->private_data; | |
1608 | ||
22bacca4 DL |
1609 | /* |
1610 | * When we insert an epoll file descriptor, inside another epoll file | |
1611 | * descriptor, there is the change of creating closed loops, which are | |
28d82dc1 JB |
1612 | * better be handled here, than in more critical paths. While we are |
1613 | * checking for loops we also determine the list of files reachable | |
1614 | * and hang them on the tfile_check_list, so we can check that we | |
1615 | * haven't created too many possible wakeup paths. | |
22bacca4 | 1616 | * |
28d82dc1 JB |
1617 | * We need to hold the epmutex across both ep_insert and ep_remove |
1618 | * b/c we want to make sure we are looking at a coherent view of | |
1619 | * epoll network. | |
22bacca4 | 1620 | */ |
28d82dc1 | 1621 | if (op == EPOLL_CTL_ADD || op == EPOLL_CTL_DEL) { |
22bacca4 DL |
1622 | mutex_lock(&epmutex); |
1623 | did_lock_epmutex = 1; | |
22bacca4 | 1624 | } |
28d82dc1 JB |
1625 | if (op == EPOLL_CTL_ADD) { |
1626 | if (is_file_epoll(tfile)) { | |
1627 | error = -ELOOP; | |
1628 | if (ep_loop_check(ep, tfile) != 0) | |
1629 | goto error_tgt_fput; | |
1630 | } else | |
1631 | list_add(&tfile->f_tfile_llink, &tfile_check_list); | |
1632 | } | |
22bacca4 | 1633 | |
d8805e63 | 1634 | mutex_lock_nested(&ep->mtx, 0); |
7699acd1 | 1635 | |
67647d0f DL |
1636 | /* |
1637 | * Try to lookup the file inside our RB tree, Since we grabbed "mtx" | |
1638 | * above, we can be sure to be able to use the item looked up by | |
1639 | * ep_find() till we release the mutex. | |
1640 | */ | |
7699acd1 DL |
1641 | epi = ep_find(ep, tfile, fd); |
1642 | ||
1643 | error = -EINVAL; | |
1644 | switch (op) { | |
1645 | case EPOLL_CTL_ADD: | |
1646 | if (!epi) { | |
1647 | epds.events |= POLLERR | POLLHUP; | |
7699acd1 DL |
1648 | error = ep_insert(ep, &epds, tfile, fd); |
1649 | } else | |
1650 | error = -EEXIST; | |
28d82dc1 | 1651 | clear_tfile_check_list(); |
7699acd1 DL |
1652 | break; |
1653 | case EPOLL_CTL_DEL: | |
1654 | if (epi) | |
1655 | error = ep_remove(ep, epi); | |
1656 | else | |
1657 | error = -ENOENT; | |
1658 | break; | |
1659 | case EPOLL_CTL_MOD: | |
1660 | if (epi) { | |
1661 | epds.events |= POLLERR | POLLHUP; | |
1662 | error = ep_modify(ep, epi, &epds); | |
1663 | } else | |
1664 | error = -ENOENT; | |
1665 | break; | |
1666 | } | |
d47de16c | 1667 | mutex_unlock(&ep->mtx); |
7699acd1 DL |
1668 | |
1669 | error_tgt_fput: | |
28d82dc1 | 1670 | if (did_lock_epmutex) |
22bacca4 DL |
1671 | mutex_unlock(&epmutex); |
1672 | ||
7699acd1 DL |
1673 | fput(tfile); |
1674 | error_fput: | |
1675 | fput(file); | |
1676 | error_return: | |
7699acd1 DL |
1677 | |
1678 | return error; | |
1679 | } | |
1680 | ||
1681 | /* | |
1682 | * Implement the event wait interface for the eventpoll file. It is the kernel | |
1683 | * part of the user space epoll_wait(2). | |
1684 | */ | |
5a8a82b1 HC |
1685 | SYSCALL_DEFINE4(epoll_wait, int, epfd, struct epoll_event __user *, events, |
1686 | int, maxevents, int, timeout) | |
7699acd1 DL |
1687 | { |
1688 | int error; | |
1689 | struct file *file; | |
1690 | struct eventpoll *ep; | |
1691 | ||
7699acd1 DL |
1692 | /* The maximum number of event must be greater than zero */ |
1693 | if (maxevents <= 0 || maxevents > EP_MAX_EVENTS) | |
1694 | return -EINVAL; | |
1695 | ||
1696 | /* Verify that the area passed by the user is writeable */ | |
1697 | if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event))) { | |
1698 | error = -EFAULT; | |
1699 | goto error_return; | |
1700 | } | |
1701 | ||
1702 | /* Get the "struct file *" for the eventpoll file */ | |
1703 | error = -EBADF; | |
1704 | file = fget(epfd); | |
1705 | if (!file) | |
1706 | goto error_return; | |
1707 | ||
1708 | /* | |
1709 | * We have to check that the file structure underneath the fd | |
1710 | * the user passed to us _is_ an eventpoll file. | |
1711 | */ | |
1712 | error = -EINVAL; | |
1713 | if (!is_file_epoll(file)) | |
1714 | goto error_fput; | |
1715 | ||
1716 | /* | |
1717 | * At this point it is safe to assume that the "private_data" contains | |
1718 | * our own data structure. | |
1719 | */ | |
1720 | ep = file->private_data; | |
1721 | ||
1722 | /* Time to fish for events ... */ | |
1723 | error = ep_poll(ep, events, maxevents, timeout); | |
1724 | ||
1725 | error_fput: | |
1726 | fput(file); | |
1727 | error_return: | |
7699acd1 DL |
1728 | |
1729 | return error; | |
1730 | } | |
1731 | ||
f3de272b | 1732 | #ifdef HAVE_SET_RESTORE_SIGMASK |
7699acd1 DL |
1733 | |
1734 | /* | |
1735 | * Implement the event wait interface for the eventpoll file. It is the kernel | |
1736 | * part of the user space epoll_pwait(2). | |
1737 | */ | |
5a8a82b1 HC |
1738 | SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events, |
1739 | int, maxevents, int, timeout, const sigset_t __user *, sigmask, | |
1740 | size_t, sigsetsize) | |
7699acd1 DL |
1741 | { |
1742 | int error; | |
1743 | sigset_t ksigmask, sigsaved; | |
1744 | ||
1745 | /* | |
1746 | * If the caller wants a certain signal mask to be set during the wait, | |
1747 | * we apply it here. | |
1748 | */ | |
1749 | if (sigmask) { | |
1750 | if (sigsetsize != sizeof(sigset_t)) | |
1751 | return -EINVAL; | |
1752 | if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) | |
1753 | return -EFAULT; | |
1754 | sigdelsetmask(&ksigmask, sigmask(SIGKILL) | sigmask(SIGSTOP)); | |
1755 | sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); | |
1756 | } | |
1757 | ||
1758 | error = sys_epoll_wait(epfd, events, maxevents, timeout); | |
1759 | ||
1760 | /* | |
1761 | * If we changed the signal mask, we need to restore the original one. | |
1762 | * In case we've got a signal while waiting, we do not restore the | |
1763 | * signal mask yet, and we allow do_signal() to deliver the signal on | |
1764 | * the way back to userspace, before the signal mask is restored. | |
1765 | */ | |
1766 | if (sigmask) { | |
1767 | if (error == -EINTR) { | |
1768 | memcpy(¤t->saved_sigmask, &sigsaved, | |
c7ea7630 | 1769 | sizeof(sigsaved)); |
4e4c22c7 | 1770 | set_restore_sigmask(); |
7699acd1 DL |
1771 | } else |
1772 | sigprocmask(SIG_SETMASK, &sigsaved, NULL); | |
1773 | } | |
1774 | ||
1775 | return error; | |
1776 | } | |
1777 | ||
f3de272b | 1778 | #endif /* HAVE_SET_RESTORE_SIGMASK */ |
7699acd1 | 1779 | |
1da177e4 LT |
1780 | static int __init eventpoll_init(void) |
1781 | { | |
7ef9964e DL |
1782 | struct sysinfo si; |
1783 | ||
1784 | si_meminfo(&si); | |
9df04e1f DL |
1785 | /* |
1786 | * Allows top 4% of lomem to be allocated for epoll watches (per user). | |
1787 | */ | |
1788 | max_user_watches = (((si.totalram - si.totalhigh) / 25) << PAGE_SHIFT) / | |
7ef9964e | 1789 | EP_ITEM_COST; |
52bd19f7 | 1790 | BUG_ON(max_user_watches < 0); |
1da177e4 | 1791 | |
22bacca4 DL |
1792 | /* |
1793 | * Initialize the structure used to perform epoll file descriptor | |
1794 | * inclusion loops checks. | |
1795 | */ | |
1796 | ep_nested_calls_init(&poll_loop_ncalls); | |
1797 | ||
1da177e4 | 1798 | /* Initialize the structure used to perform safe poll wait head wake ups */ |
5071f97e DL |
1799 | ep_nested_calls_init(&poll_safewake_ncalls); |
1800 | ||
1801 | /* Initialize the structure used to perform file's f_op->poll() calls */ | |
1802 | ep_nested_calls_init(&poll_readywalk_ncalls); | |
1da177e4 LT |
1803 | |
1804 | /* Allocates slab cache used to allocate "struct epitem" items */ | |
1805 | epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem), | |
bb57c3ed | 1806 | 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); |
1da177e4 LT |
1807 | |
1808 | /* Allocates slab cache used to allocate "struct eppoll_entry" */ | |
1809 | pwq_cache = kmem_cache_create("eventpoll_pwq", | |
bb57c3ed | 1810 | sizeof(struct eppoll_entry), 0, SLAB_PANIC, NULL); |
1da177e4 | 1811 | |
1da177e4 | 1812 | return 0; |
1da177e4 | 1813 | } |
cea69241 | 1814 | fs_initcall(eventpoll_init); |