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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> |
4d7e30d9 | 36 | #include <linux/device.h> |
1da177e4 | 37 | #include <asm/uaccess.h> |
1da177e4 LT |
38 | #include <asm/io.h> |
39 | #include <asm/mman.h> | |
60063497 | 40 | #include <linux/atomic.h> |
138d22b5 CG |
41 | #include <linux/proc_fs.h> |
42 | #include <linux/seq_file.h> | |
35280bd4 | 43 | #include <linux/compat.h> |
ae10b2b4 | 44 | #include <linux/rculist.h> |
1da177e4 | 45 | |
1da177e4 LT |
46 | /* |
47 | * LOCKING: | |
48 | * There are three level of locking required by epoll : | |
49 | * | |
144efe3e | 50 | * 1) epmutex (mutex) |
c7ea7630 DL |
51 | * 2) ep->mtx (mutex) |
52 | * 3) ep->lock (spinlock) | |
1da177e4 LT |
53 | * |
54 | * The acquire order is the one listed above, from 1 to 3. | |
55 | * We need a spinlock (ep->lock) because we manipulate objects | |
56 | * from inside the poll callback, that might be triggered from | |
57 | * a wake_up() that in turn might be called from IRQ context. | |
58 | * So we can't sleep inside the poll callback and hence we need | |
59 | * a spinlock. During the event transfer loop (from kernel to | |
60 | * user space) we could end up sleeping due a copy_to_user(), so | |
61 | * we need a lock that will allow us to sleep. This lock is a | |
d47de16c DL |
62 | * mutex (ep->mtx). It is acquired during the event transfer loop, |
63 | * during epoll_ctl(EPOLL_CTL_DEL) and during eventpoll_release_file(). | |
64 | * Then we also need a global mutex to serialize eventpoll_release_file() | |
65 | * and ep_free(). | |
66 | * This mutex is acquired by ep_free() during the epoll file | |
1da177e4 LT |
67 | * cleanup path and it is also acquired by eventpoll_release_file() |
68 | * if a file has been pushed inside an epoll set and it is then | |
bf6a41db | 69 | * close()d without a previous call to epoll_ctl(EPOLL_CTL_DEL). |
22bacca4 DL |
70 | * It is also acquired when inserting an epoll fd onto another epoll |
71 | * fd. We do this so that we walk the epoll tree and ensure that this | |
72 | * insertion does not create a cycle of epoll file descriptors, which | |
73 | * could lead to deadlock. We need a global mutex to prevent two | |
74 | * simultaneous inserts (A into B and B into A) from racing and | |
75 | * constructing a cycle without either insert observing that it is | |
76 | * going to. | |
d8805e63 NE |
77 | * It is necessary to acquire multiple "ep->mtx"es at once in the |
78 | * case when one epoll fd is added to another. In this case, we | |
79 | * always acquire the locks in the order of nesting (i.e. after | |
80 | * epoll_ctl(e1, EPOLL_CTL_ADD, e2), e1->mtx will always be acquired | |
81 | * before e2->mtx). Since we disallow cycles of epoll file | |
82 | * descriptors, this ensures that the mutexes are well-ordered. In | |
83 | * order to communicate this nesting to lockdep, when walking a tree | |
84 | * of epoll file descriptors, we use the current recursion depth as | |
85 | * the lockdep subkey. | |
d47de16c DL |
86 | * It is possible to drop the "ep->mtx" and to use the global |
87 | * mutex "epmutex" (together with "ep->lock") to have it working, | |
88 | * but having "ep->mtx" will make the interface more scalable. | |
144efe3e | 89 | * Events that require holding "epmutex" are very rare, while for |
d47de16c DL |
90 | * normal operations the epoll private "ep->mtx" will guarantee |
91 | * a better scalability. | |
1da177e4 LT |
92 | */ |
93 | ||
1da177e4 | 94 | /* Epoll private bits inside the event mask */ |
4d7e30d9 | 95 | #define EP_PRIVATE_BITS (EPOLLWAKEUP | EPOLLONESHOT | EPOLLET) |
1da177e4 | 96 | |
5071f97e DL |
97 | /* Maximum number of nesting allowed inside epoll sets */ |
98 | #define EP_MAX_NESTS 4 | |
1da177e4 | 99 | |
b611967d DL |
100 | #define EP_MAX_EVENTS (INT_MAX / sizeof(struct epoll_event)) |
101 | ||
d47de16c DL |
102 | #define EP_UNACTIVE_PTR ((void *) -1L) |
103 | ||
7ef9964e DL |
104 | #define EP_ITEM_COST (sizeof(struct epitem) + sizeof(struct eppoll_entry)) |
105 | ||
1da177e4 LT |
106 | struct epoll_filefd { |
107 | struct file *file; | |
108 | int fd; | |
39732ca5 | 109 | } __packed; |
1da177e4 LT |
110 | |
111 | /* | |
5071f97e DL |
112 | * Structure used to track possible nested calls, for too deep recursions |
113 | * and loop cycles. | |
1da177e4 | 114 | */ |
5071f97e | 115 | struct nested_call_node { |
1da177e4 | 116 | struct list_head llink; |
5071f97e | 117 | void *cookie; |
3fe4a975 | 118 | void *ctx; |
1da177e4 LT |
119 | }; |
120 | ||
121 | /* | |
5071f97e DL |
122 | * This structure is used as collector for nested calls, to check for |
123 | * maximum recursion dept and loop cycles. | |
1da177e4 | 124 | */ |
5071f97e DL |
125 | struct nested_calls { |
126 | struct list_head tasks_call_list; | |
1da177e4 LT |
127 | spinlock_t lock; |
128 | }; | |
129 | ||
d47de16c DL |
130 | /* |
131 | * Each file descriptor added to the eventpoll interface will | |
132 | * have an entry of this type linked to the "rbr" RB tree. | |
39732ca5 EW |
133 | * Avoid increasing the size of this struct, there can be many thousands |
134 | * of these on a server and we do not want this to take another cache line. | |
d47de16c DL |
135 | */ |
136 | struct epitem { | |
ae10b2b4 JB |
137 | union { |
138 | /* RB tree node links this structure to the eventpoll RB tree */ | |
139 | struct rb_node rbn; | |
140 | /* Used to free the struct epitem */ | |
141 | struct rcu_head rcu; | |
142 | }; | |
d47de16c DL |
143 | |
144 | /* List header used to link this structure to the eventpoll ready list */ | |
145 | struct list_head rdllink; | |
146 | ||
c7ea7630 DL |
147 | /* |
148 | * Works together "struct eventpoll"->ovflist in keeping the | |
149 | * single linked chain of items. | |
150 | */ | |
151 | struct epitem *next; | |
152 | ||
d47de16c DL |
153 | /* The file descriptor information this item refers to */ |
154 | struct epoll_filefd ffd; | |
155 | ||
156 | /* Number of active wait queue attached to poll operations */ | |
157 | int nwait; | |
158 | ||
159 | /* List containing poll wait queues */ | |
160 | struct list_head pwqlist; | |
161 | ||
162 | /* The "container" of this item */ | |
163 | struct eventpoll *ep; | |
164 | ||
d47de16c DL |
165 | /* List header used to link this item to the "struct file" items list */ |
166 | struct list_head fllink; | |
167 | ||
4d7e30d9 | 168 | /* wakeup_source used when EPOLLWAKEUP is set */ |
eea1d585 | 169 | struct wakeup_source __rcu *ws; |
4d7e30d9 | 170 | |
c7ea7630 DL |
171 | /* The structure that describe the interested events and the source fd */ |
172 | struct epoll_event event; | |
d47de16c DL |
173 | }; |
174 | ||
1da177e4 LT |
175 | /* |
176 | * This structure is stored inside the "private_data" member of the file | |
bf6a41db | 177 | * structure and represents the main data structure for the eventpoll |
1da177e4 LT |
178 | * interface. |
179 | */ | |
180 | struct eventpoll { | |
bf6a41db | 181 | /* Protect the access to this structure */ |
c7ea7630 | 182 | spinlock_t lock; |
1da177e4 LT |
183 | |
184 | /* | |
d47de16c DL |
185 | * This mutex is used to ensure that files are not removed |
186 | * while epoll is using them. This is held during the event | |
187 | * collection loop, the file cleanup path, the epoll file exit | |
188 | * code and the ctl operations. | |
1da177e4 | 189 | */ |
d47de16c | 190 | struct mutex mtx; |
1da177e4 LT |
191 | |
192 | /* Wait queue used by sys_epoll_wait() */ | |
193 | wait_queue_head_t wq; | |
194 | ||
195 | /* Wait queue used by file->poll() */ | |
196 | wait_queue_head_t poll_wait; | |
197 | ||
198 | /* List of ready file descriptors */ | |
199 | struct list_head rdllist; | |
200 | ||
67647d0f | 201 | /* RB tree root used to store monitored fd structs */ |
1da177e4 | 202 | struct rb_root rbr; |
d47de16c DL |
203 | |
204 | /* | |
205 | * This is a single linked list that chains all the "struct epitem" that | |
25985edc | 206 | * happened while transferring ready events to userspace w/out |
d47de16c DL |
207 | * holding ->lock. |
208 | */ | |
209 | struct epitem *ovflist; | |
7ef9964e | 210 | |
4d7e30d9 AH |
211 | /* wakeup_source used when ep_scan_ready_list is running */ |
212 | struct wakeup_source *ws; | |
213 | ||
7ef9964e DL |
214 | /* The user that created the eventpoll descriptor */ |
215 | struct user_struct *user; | |
28d82dc1 JB |
216 | |
217 | struct file *file; | |
218 | ||
219 | /* used to optimize loop detection check */ | |
220 | int visited; | |
221 | struct list_head visited_list_link; | |
1da177e4 LT |
222 | }; |
223 | ||
224 | /* Wait structure used by the poll hooks */ | |
225 | struct eppoll_entry { | |
226 | /* List header used to link this structure to the "struct epitem" */ | |
227 | struct list_head llink; | |
228 | ||
229 | /* The "base" pointer is set to the container "struct epitem" */ | |
4f0989db | 230 | struct epitem *base; |
1da177e4 LT |
231 | |
232 | /* | |
233 | * Wait queue item that will be linked to the target file wait | |
234 | * queue head. | |
235 | */ | |
236 | wait_queue_t wait; | |
237 | ||
238 | /* The wait queue head that linked the "wait" wait queue item */ | |
239 | wait_queue_head_t *whead; | |
240 | }; | |
241 | ||
1da177e4 LT |
242 | /* Wrapper struct used by poll queueing */ |
243 | struct ep_pqueue { | |
244 | poll_table pt; | |
245 | struct epitem *epi; | |
246 | }; | |
247 | ||
5071f97e DL |
248 | /* Used by the ep_send_events() function as callback private data */ |
249 | struct ep_send_events_data { | |
250 | int maxevents; | |
251 | struct epoll_event __user *events; | |
252 | }; | |
253 | ||
7ef9964e DL |
254 | /* |
255 | * Configuration options available inside /proc/sys/fs/epoll/ | |
256 | */ | |
7ef9964e | 257 | /* Maximum number of epoll watched descriptors, per user */ |
52bd19f7 | 258 | static long max_user_watches __read_mostly; |
7ef9964e | 259 | |
1da177e4 | 260 | /* |
d47de16c | 261 | * This mutex is used to serialize ep_free() and eventpoll_release_file(). |
1da177e4 | 262 | */ |
7ef9964e | 263 | static DEFINE_MUTEX(epmutex); |
1da177e4 | 264 | |
22bacca4 DL |
265 | /* Used to check for epoll file descriptor inclusion loops */ |
266 | static struct nested_calls poll_loop_ncalls; | |
267 | ||
5071f97e DL |
268 | /* Used for safe wake up implementation */ |
269 | static struct nested_calls poll_safewake_ncalls; | |
270 | ||
271 | /* Used to call file's f_op->poll() under the nested calls boundaries */ | |
272 | static struct nested_calls poll_readywalk_ncalls; | |
1da177e4 LT |
273 | |
274 | /* Slab cache used to allocate "struct epitem" */ | |
e18b890b | 275 | static struct kmem_cache *epi_cache __read_mostly; |
1da177e4 LT |
276 | |
277 | /* Slab cache used to allocate "struct eppoll_entry" */ | |
e18b890b | 278 | static struct kmem_cache *pwq_cache __read_mostly; |
1da177e4 | 279 | |
28d82dc1 JB |
280 | /* Visited nodes during ep_loop_check(), so we can unset them when we finish */ |
281 | static LIST_HEAD(visited_list); | |
282 | ||
283 | /* | |
284 | * List of files with newly added links, where we may need to limit the number | |
285 | * of emanating paths. Protected by the epmutex. | |
286 | */ | |
287 | static LIST_HEAD(tfile_check_list); | |
288 | ||
7ef9964e DL |
289 | #ifdef CONFIG_SYSCTL |
290 | ||
291 | #include <linux/sysctl.h> | |
292 | ||
52bd19f7 RH |
293 | static long zero; |
294 | static long long_max = LONG_MAX; | |
7ef9964e | 295 | |
1f7e0616 | 296 | struct ctl_table epoll_table[] = { |
7ef9964e DL |
297 | { |
298 | .procname = "max_user_watches", | |
299 | .data = &max_user_watches, | |
52bd19f7 | 300 | .maxlen = sizeof(max_user_watches), |
7ef9964e | 301 | .mode = 0644, |
52bd19f7 | 302 | .proc_handler = proc_doulongvec_minmax, |
7ef9964e | 303 | .extra1 = &zero, |
52bd19f7 | 304 | .extra2 = &long_max, |
7ef9964e | 305 | }, |
ab09203e | 306 | { } |
7ef9964e DL |
307 | }; |
308 | #endif /* CONFIG_SYSCTL */ | |
309 | ||
28d82dc1 JB |
310 | static const struct file_operations eventpoll_fops; |
311 | ||
312 | static inline int is_file_epoll(struct file *f) | |
313 | { | |
314 | return f->f_op == &eventpoll_fops; | |
315 | } | |
b030a4dd | 316 | |
67647d0f | 317 | /* Setup the structure that is used as key for the RB tree */ |
b030a4dd PE |
318 | static inline void ep_set_ffd(struct epoll_filefd *ffd, |
319 | struct file *file, int fd) | |
320 | { | |
321 | ffd->file = file; | |
322 | ffd->fd = fd; | |
323 | } | |
324 | ||
67647d0f | 325 | /* Compare RB tree keys */ |
b030a4dd PE |
326 | static inline int ep_cmp_ffd(struct epoll_filefd *p1, |
327 | struct epoll_filefd *p2) | |
328 | { | |
329 | return (p1->file > p2->file ? +1: | |
330 | (p1->file < p2->file ? -1 : p1->fd - p2->fd)); | |
331 | } | |
332 | ||
b030a4dd PE |
333 | /* Tells us if the item is currently linked */ |
334 | static inline int ep_is_linked(struct list_head *p) | |
335 | { | |
336 | return !list_empty(p); | |
337 | } | |
338 | ||
971316f0 ON |
339 | static inline struct eppoll_entry *ep_pwq_from_wait(wait_queue_t *p) |
340 | { | |
341 | return container_of(p, struct eppoll_entry, wait); | |
342 | } | |
343 | ||
b030a4dd | 344 | /* Get the "struct epitem" from a wait queue pointer */ |
cdac75e6 | 345 | static inline struct epitem *ep_item_from_wait(wait_queue_t *p) |
b030a4dd PE |
346 | { |
347 | return container_of(p, struct eppoll_entry, wait)->base; | |
348 | } | |
349 | ||
350 | /* Get the "struct epitem" from an epoll queue wrapper */ | |
cdac75e6 | 351 | static inline struct epitem *ep_item_from_epqueue(poll_table *p) |
b030a4dd PE |
352 | { |
353 | return container_of(p, struct ep_pqueue, pt)->epi; | |
354 | } | |
355 | ||
356 | /* Tells if the epoll_ctl(2) operation needs an event copy from userspace */ | |
6192bd53 | 357 | static inline int ep_op_has_event(int op) |
b030a4dd | 358 | { |
a80a6b85 | 359 | return op != EPOLL_CTL_DEL; |
b030a4dd PE |
360 | } |
361 | ||
1da177e4 | 362 | /* Initialize the poll safe wake up structure */ |
5071f97e | 363 | static void ep_nested_calls_init(struct nested_calls *ncalls) |
1da177e4 | 364 | { |
5071f97e DL |
365 | INIT_LIST_HEAD(&ncalls->tasks_call_list); |
366 | spin_lock_init(&ncalls->lock); | |
1da177e4 LT |
367 | } |
368 | ||
3fb0e584 DL |
369 | /** |
370 | * ep_events_available - Checks if ready events might be available. | |
371 | * | |
372 | * @ep: Pointer to the eventpoll context. | |
373 | * | |
374 | * Returns: Returns a value different than zero if ready events are available, | |
375 | * or zero otherwise. | |
376 | */ | |
377 | static inline int ep_events_available(struct eventpoll *ep) | |
378 | { | |
379 | return !list_empty(&ep->rdllist) || ep->ovflist != EP_UNACTIVE_PTR; | |
380 | } | |
381 | ||
5071f97e DL |
382 | /** |
383 | * ep_call_nested - Perform a bound (possibly) nested call, by checking | |
384 | * that the recursion limit is not exceeded, and that | |
385 | * the same nested call (by the meaning of same cookie) is | |
386 | * no re-entered. | |
387 | * | |
388 | * @ncalls: Pointer to the nested_calls structure to be used for this call. | |
389 | * @max_nests: Maximum number of allowed nesting calls. | |
390 | * @nproc: Nested call core function pointer. | |
391 | * @priv: Opaque data to be passed to the @nproc callback. | |
392 | * @cookie: Cookie to be used to identify this nested call. | |
3fe4a975 | 393 | * @ctx: This instance context. |
5071f97e DL |
394 | * |
395 | * Returns: Returns the code returned by the @nproc callback, or -1 if | |
396 | * the maximum recursion limit has been exceeded. | |
1da177e4 | 397 | */ |
5071f97e DL |
398 | static int ep_call_nested(struct nested_calls *ncalls, int max_nests, |
399 | int (*nproc)(void *, void *, int), void *priv, | |
3fe4a975 | 400 | void *cookie, void *ctx) |
1da177e4 | 401 | { |
5071f97e | 402 | int error, call_nests = 0; |
1da177e4 | 403 | unsigned long flags; |
5071f97e DL |
404 | struct list_head *lsthead = &ncalls->tasks_call_list; |
405 | struct nested_call_node *tncur; | |
406 | struct nested_call_node tnode; | |
1da177e4 | 407 | |
5071f97e | 408 | spin_lock_irqsave(&ncalls->lock, flags); |
1da177e4 | 409 | |
5071f97e DL |
410 | /* |
411 | * Try to see if the current task is already inside this wakeup call. | |
412 | * We use a list here, since the population inside this set is always | |
413 | * very much limited. | |
414 | */ | |
b70c3940 | 415 | list_for_each_entry(tncur, lsthead, llink) { |
3fe4a975 | 416 | if (tncur->ctx == ctx && |
5071f97e | 417 | (tncur->cookie == cookie || ++call_nests > max_nests)) { |
1da177e4 LT |
418 | /* |
419 | * Ops ... loop detected or maximum nest level reached. | |
420 | * We abort this wake by breaking the cycle itself. | |
421 | */ | |
abff55ce TB |
422 | error = -1; |
423 | goto out_unlock; | |
1da177e4 LT |
424 | } |
425 | } | |
426 | ||
5071f97e | 427 | /* Add the current task and cookie to the list */ |
3fe4a975 | 428 | tnode.ctx = ctx; |
5071f97e | 429 | tnode.cookie = cookie; |
1da177e4 LT |
430 | list_add(&tnode.llink, lsthead); |
431 | ||
5071f97e | 432 | spin_unlock_irqrestore(&ncalls->lock, flags); |
1da177e4 | 433 | |
5071f97e DL |
434 | /* Call the nested function */ |
435 | error = (*nproc)(priv, cookie, call_nests); | |
1da177e4 LT |
436 | |
437 | /* Remove the current task from the list */ | |
5071f97e | 438 | spin_lock_irqsave(&ncalls->lock, flags); |
1da177e4 | 439 | list_del(&tnode.llink); |
3fe4a975 | 440 | out_unlock: |
5071f97e DL |
441 | spin_unlock_irqrestore(&ncalls->lock, flags); |
442 | ||
443 | return error; | |
444 | } | |
445 | ||
02edc6fc SR |
446 | /* |
447 | * As described in commit 0ccf831cb lockdep: annotate epoll | |
448 | * the use of wait queues used by epoll is done in a very controlled | |
449 | * manner. Wake ups can nest inside each other, but are never done | |
450 | * with the same locking. For example: | |
451 | * | |
452 | * dfd = socket(...); | |
453 | * efd1 = epoll_create(); | |
454 | * efd2 = epoll_create(); | |
455 | * epoll_ctl(efd1, EPOLL_CTL_ADD, dfd, ...); | |
456 | * epoll_ctl(efd2, EPOLL_CTL_ADD, efd1, ...); | |
457 | * | |
458 | * When a packet arrives to the device underneath "dfd", the net code will | |
459 | * issue a wake_up() on its poll wake list. Epoll (efd1) has installed a | |
460 | * callback wakeup entry on that queue, and the wake_up() performed by the | |
461 | * "dfd" net code will end up in ep_poll_callback(). At this point epoll | |
462 | * (efd1) notices that it may have some event ready, so it needs to wake up | |
463 | * the waiters on its poll wait list (efd2). So it calls ep_poll_safewake() | |
464 | * that ends up in another wake_up(), after having checked about the | |
465 | * recursion constraints. That are, no more than EP_MAX_POLLWAKE_NESTS, to | |
466 | * avoid stack blasting. | |
467 | * | |
468 | * When CONFIG_DEBUG_LOCK_ALLOC is enabled, make sure lockdep can handle | |
469 | * this special case of epoll. | |
470 | */ | |
2dfa4eea DL |
471 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
472 | static inline void ep_wake_up_nested(wait_queue_head_t *wqueue, | |
473 | unsigned long events, int subclass) | |
474 | { | |
475 | unsigned long flags; | |
476 | ||
477 | spin_lock_irqsave_nested(&wqueue->lock, flags, subclass); | |
478 | wake_up_locked_poll(wqueue, events); | |
479 | spin_unlock_irqrestore(&wqueue->lock, flags); | |
480 | } | |
481 | #else | |
482 | static inline void ep_wake_up_nested(wait_queue_head_t *wqueue, | |
483 | unsigned long events, int subclass) | |
484 | { | |
485 | wake_up_poll(wqueue, events); | |
486 | } | |
487 | #endif | |
488 | ||
5071f97e DL |
489 | static int ep_poll_wakeup_proc(void *priv, void *cookie, int call_nests) |
490 | { | |
2dfa4eea DL |
491 | ep_wake_up_nested((wait_queue_head_t *) cookie, POLLIN, |
492 | 1 + call_nests); | |
5071f97e DL |
493 | return 0; |
494 | } | |
495 | ||
496 | /* | |
497 | * Perform a safe wake up of the poll wait list. The problem is that | |
498 | * with the new callback'd wake up system, it is possible that the | |
499 | * poll callback is reentered from inside the call to wake_up() done | |
500 | * on the poll wait queue head. The rule is that we cannot reenter the | |
501 | * wake up code from the same task more than EP_MAX_NESTS times, | |
502 | * and we cannot reenter the same wait queue head at all. This will | |
503 | * enable to have a hierarchy of epoll file descriptor of no more than | |
504 | * EP_MAX_NESTS deep. | |
505 | */ | |
506 | static void ep_poll_safewake(wait_queue_head_t *wq) | |
507 | { | |
3fe4a975 DL |
508 | int this_cpu = get_cpu(); |
509 | ||
5071f97e | 510 | ep_call_nested(&poll_safewake_ncalls, EP_MAX_NESTS, |
3fe4a975 DL |
511 | ep_poll_wakeup_proc, NULL, wq, (void *) (long) this_cpu); |
512 | ||
513 | put_cpu(); | |
1da177e4 LT |
514 | } |
515 | ||
971316f0 ON |
516 | static void ep_remove_wait_queue(struct eppoll_entry *pwq) |
517 | { | |
518 | wait_queue_head_t *whead; | |
519 | ||
520 | rcu_read_lock(); | |
6bf93860 ON |
521 | /* |
522 | * If it is cleared by POLLFREE, it should be rcu-safe. | |
523 | * If we read NULL we need a barrier paired with | |
524 | * smp_store_release() in ep_poll_callback(), otherwise | |
525 | * we rely on whead->lock. | |
526 | */ | |
527 | whead = smp_load_acquire(&pwq->whead); | |
971316f0 ON |
528 | if (whead) |
529 | remove_wait_queue(whead, &pwq->wait); | |
530 | rcu_read_unlock(); | |
531 | } | |
532 | ||
1da177e4 | 533 | /* |
d1bc90dd TB |
534 | * This function unregisters poll callbacks from the associated file |
535 | * descriptor. Must be called with "mtx" held (or "epmutex" if called from | |
536 | * ep_free). | |
1da177e4 | 537 | */ |
7699acd1 | 538 | static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi) |
1da177e4 | 539 | { |
7699acd1 DL |
540 | struct list_head *lsthead = &epi->pwqlist; |
541 | struct eppoll_entry *pwq; | |
1da177e4 | 542 | |
d1bc90dd TB |
543 | while (!list_empty(lsthead)) { |
544 | pwq = list_first_entry(lsthead, struct eppoll_entry, llink); | |
1da177e4 | 545 | |
d1bc90dd | 546 | list_del(&pwq->llink); |
971316f0 | 547 | ep_remove_wait_queue(pwq); |
d1bc90dd | 548 | kmem_cache_free(pwq_cache, pwq); |
1da177e4 | 549 | } |
1da177e4 LT |
550 | } |
551 | ||
eea1d585 EW |
552 | /* call only when ep->mtx is held */ |
553 | static inline struct wakeup_source *ep_wakeup_source(struct epitem *epi) | |
554 | { | |
555 | return rcu_dereference_check(epi->ws, lockdep_is_held(&epi->ep->mtx)); | |
556 | } | |
557 | ||
558 | /* call only when ep->mtx is held */ | |
559 | static inline void ep_pm_stay_awake(struct epitem *epi) | |
560 | { | |
561 | struct wakeup_source *ws = ep_wakeup_source(epi); | |
562 | ||
563 | if (ws) | |
564 | __pm_stay_awake(ws); | |
565 | } | |
566 | ||
567 | static inline bool ep_has_wakeup_source(struct epitem *epi) | |
568 | { | |
569 | return rcu_access_pointer(epi->ws) ? true : false; | |
570 | } | |
571 | ||
572 | /* call when ep->mtx cannot be held (ep_poll_callback) */ | |
573 | static inline void ep_pm_stay_awake_rcu(struct epitem *epi) | |
574 | { | |
575 | struct wakeup_source *ws; | |
576 | ||
577 | rcu_read_lock(); | |
578 | ws = rcu_dereference(epi->ws); | |
579 | if (ws) | |
580 | __pm_stay_awake(ws); | |
581 | rcu_read_unlock(); | |
582 | } | |
583 | ||
5071f97e DL |
584 | /** |
585 | * ep_scan_ready_list - Scans the ready list in a way that makes possible for | |
586 | * the scan code, to call f_op->poll(). Also allows for | |
587 | * O(NumReady) performance. | |
588 | * | |
589 | * @ep: Pointer to the epoll private data structure. | |
590 | * @sproc: Pointer to the scan callback. | |
591 | * @priv: Private opaque data passed to the @sproc callback. | |
d8805e63 | 592 | * @depth: The current depth of recursive f_op->poll calls. |
67347fe4 | 593 | * @ep_locked: caller already holds ep->mtx |
5071f97e DL |
594 | * |
595 | * Returns: The same integer error code returned by the @sproc callback. | |
596 | */ | |
597 | static int ep_scan_ready_list(struct eventpoll *ep, | |
598 | int (*sproc)(struct eventpoll *, | |
599 | struct list_head *, void *), | |
67347fe4 | 600 | void *priv, int depth, bool ep_locked) |
5071f97e DL |
601 | { |
602 | int error, pwake = 0; | |
603 | unsigned long flags; | |
604 | struct epitem *epi, *nepi; | |
296e236e | 605 | LIST_HEAD(txlist); |
5071f97e DL |
606 | |
607 | /* | |
608 | * We need to lock this because we could be hit by | |
e057e15f | 609 | * eventpoll_release_file() and epoll_ctl(). |
5071f97e | 610 | */ |
67347fe4 JB |
611 | |
612 | if (!ep_locked) | |
613 | mutex_lock_nested(&ep->mtx, depth); | |
5071f97e DL |
614 | |
615 | /* | |
616 | * Steal the ready list, and re-init the original one to the | |
617 | * empty list. Also, set ep->ovflist to NULL so that events | |
618 | * happening while looping w/out locks, are not lost. We cannot | |
619 | * have the poll callback to queue directly on ep->rdllist, | |
620 | * because we want the "sproc" callback to be able to do it | |
621 | * in a lockless way. | |
622 | */ | |
623 | spin_lock_irqsave(&ep->lock, flags); | |
296e236e | 624 | list_splice_init(&ep->rdllist, &txlist); |
5071f97e DL |
625 | ep->ovflist = NULL; |
626 | spin_unlock_irqrestore(&ep->lock, flags); | |
627 | ||
628 | /* | |
629 | * Now call the callback function. | |
630 | */ | |
631 | error = (*sproc)(ep, &txlist, priv); | |
632 | ||
633 | spin_lock_irqsave(&ep->lock, flags); | |
634 | /* | |
635 | * During the time we spent inside the "sproc" callback, some | |
636 | * other events might have been queued by the poll callback. | |
637 | * We re-insert them inside the main ready-list here. | |
638 | */ | |
639 | for (nepi = ep->ovflist; (epi = nepi) != NULL; | |
640 | nepi = epi->next, epi->next = EP_UNACTIVE_PTR) { | |
641 | /* | |
642 | * We need to check if the item is already in the list. | |
643 | * During the "sproc" callback execution time, items are | |
644 | * queued into ->ovflist but the "txlist" might already | |
645 | * contain them, and the list_splice() below takes care of them. | |
646 | */ | |
4d7e30d9 | 647 | if (!ep_is_linked(&epi->rdllink)) { |
5071f97e | 648 | list_add_tail(&epi->rdllink, &ep->rdllist); |
eea1d585 | 649 | ep_pm_stay_awake(epi); |
4d7e30d9 | 650 | } |
5071f97e DL |
651 | } |
652 | /* | |
653 | * We need to set back ep->ovflist to EP_UNACTIVE_PTR, so that after | |
654 | * releasing the lock, events will be queued in the normal way inside | |
655 | * ep->rdllist. | |
656 | */ | |
657 | ep->ovflist = EP_UNACTIVE_PTR; | |
658 | ||
659 | /* | |
660 | * Quickly re-inject items left on "txlist". | |
661 | */ | |
662 | list_splice(&txlist, &ep->rdllist); | |
4d7e30d9 | 663 | __pm_relax(ep->ws); |
5071f97e DL |
664 | |
665 | if (!list_empty(&ep->rdllist)) { | |
666 | /* | |
296e236e DL |
667 | * Wake up (if active) both the eventpoll wait list and |
668 | * the ->poll() wait list (delayed after we release the lock). | |
5071f97e DL |
669 | */ |
670 | if (waitqueue_active(&ep->wq)) | |
671 | wake_up_locked(&ep->wq); | |
672 | if (waitqueue_active(&ep->poll_wait)) | |
673 | pwake++; | |
674 | } | |
675 | spin_unlock_irqrestore(&ep->lock, flags); | |
676 | ||
67347fe4 JB |
677 | if (!ep_locked) |
678 | mutex_unlock(&ep->mtx); | |
5071f97e DL |
679 | |
680 | /* We have to call this outside the lock */ | |
681 | if (pwake) | |
682 | ep_poll_safewake(&ep->poll_wait); | |
683 | ||
684 | return error; | |
685 | } | |
686 | ||
ae10b2b4 JB |
687 | static void epi_rcu_free(struct rcu_head *head) |
688 | { | |
689 | struct epitem *epi = container_of(head, struct epitem, rcu); | |
690 | kmem_cache_free(epi_cache, epi); | |
691 | } | |
692 | ||
7699acd1 DL |
693 | /* |
694 | * Removes a "struct epitem" from the eventpoll RB tree and deallocates | |
c7ea7630 | 695 | * all the associated resources. Must be called with "mtx" held. |
7699acd1 DL |
696 | */ |
697 | static int ep_remove(struct eventpoll *ep, struct epitem *epi) | |
698 | { | |
7699acd1 DL |
699 | unsigned long flags; |
700 | struct file *file = epi->ffd.file; | |
1da177e4 LT |
701 | |
702 | /* | |
7699acd1 DL |
703 | * Removes poll wait queue hooks. We _have_ to do this without holding |
704 | * the "ep->lock" otherwise a deadlock might occur. This because of the | |
705 | * sequence of the lock acquisition. Here we do "ep->lock" then the wait | |
706 | * queue head lock when unregistering the wait queue. The wakeup callback | |
707 | * will run by holding the wait queue head lock and will call our callback | |
708 | * that will try to get "ep->lock". | |
1da177e4 | 709 | */ |
7699acd1 | 710 | ep_unregister_pollwait(ep, epi); |
1da177e4 | 711 | |
7699acd1 | 712 | /* Remove the current item from the list of epoll hooks */ |
68499914 | 713 | spin_lock(&file->f_lock); |
ae10b2b4 | 714 | list_del_rcu(&epi->fllink); |
68499914 | 715 | spin_unlock(&file->f_lock); |
1da177e4 | 716 | |
cdac75e6 | 717 | rb_erase(&epi->rbn, &ep->rbr); |
1da177e4 | 718 | |
c7ea7630 DL |
719 | spin_lock_irqsave(&ep->lock, flags); |
720 | if (ep_is_linked(&epi->rdllink)) | |
721 | list_del_init(&epi->rdllink); | |
722 | spin_unlock_irqrestore(&ep->lock, flags); | |
1da177e4 | 723 | |
eea1d585 | 724 | wakeup_source_unregister(ep_wakeup_source(epi)); |
ae10b2b4 JB |
725 | /* |
726 | * At this point it is safe to free the eventpoll item. Use the union | |
727 | * field epi->rcu, since we are trying to minimize the size of | |
728 | * 'struct epitem'. The 'rbn' field is no longer in use. Protected by | |
729 | * ep->mtx. The rcu read side, reverse_path_check_proc(), does not make | |
730 | * use of the rbn field. | |
731 | */ | |
732 | call_rcu(&epi->rcu, epi_rcu_free); | |
1da177e4 | 733 | |
52bd19f7 | 734 | atomic_long_dec(&ep->user->epoll_watches); |
7ef9964e | 735 | |
c7ea7630 | 736 | return 0; |
1da177e4 LT |
737 | } |
738 | ||
7699acd1 | 739 | static void ep_free(struct eventpoll *ep) |
1da177e4 | 740 | { |
7699acd1 DL |
741 | struct rb_node *rbp; |
742 | struct epitem *epi; | |
1da177e4 | 743 | |
7699acd1 DL |
744 | /* We need to release all tasks waiting for these file */ |
745 | if (waitqueue_active(&ep->poll_wait)) | |
5071f97e | 746 | ep_poll_safewake(&ep->poll_wait); |
1da177e4 | 747 | |
7699acd1 DL |
748 | /* |
749 | * We need to lock this because we could be hit by | |
750 | * eventpoll_release_file() while we're freeing the "struct eventpoll". | |
d47de16c | 751 | * We do not need to hold "ep->mtx" here because the epoll file |
7699acd1 DL |
752 | * is on the way to be removed and no one has references to it |
753 | * anymore. The only hit might come from eventpoll_release_file() but | |
25985edc | 754 | * holding "epmutex" is sufficient here. |
7699acd1 DL |
755 | */ |
756 | mutex_lock(&epmutex); | |
1da177e4 LT |
757 | |
758 | /* | |
7699acd1 | 759 | * Walks through the whole tree by unregistering poll callbacks. |
1da177e4 | 760 | */ |
7699acd1 DL |
761 | for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { |
762 | epi = rb_entry(rbp, struct epitem, rbn); | |
763 | ||
764 | ep_unregister_pollwait(ep, epi); | |
91cf5ab6 | 765 | cond_resched(); |
7699acd1 | 766 | } |
1da177e4 LT |
767 | |
768 | /* | |
7699acd1 DL |
769 | * Walks through the whole tree by freeing each "struct epitem". At this |
770 | * point we are sure no poll callbacks will be lingering around, and also by | |
d47de16c | 771 | * holding "epmutex" we can be sure that no file cleanup code will hit |
7699acd1 | 772 | * us during this operation. So we can avoid the lock on "ep->lock". |
ddf676c3 EW |
773 | * We do not need to lock ep->mtx, either, we only do it to prevent |
774 | * a lockdep warning. | |
1da177e4 | 775 | */ |
ddf676c3 | 776 | mutex_lock(&ep->mtx); |
c80544dc | 777 | while ((rbp = rb_first(&ep->rbr)) != NULL) { |
7699acd1 DL |
778 | epi = rb_entry(rbp, struct epitem, rbn); |
779 | ep_remove(ep, epi); | |
91cf5ab6 | 780 | cond_resched(); |
7699acd1 | 781 | } |
ddf676c3 | 782 | mutex_unlock(&ep->mtx); |
1da177e4 | 783 | |
7699acd1 | 784 | mutex_unlock(&epmutex); |
d47de16c | 785 | mutex_destroy(&ep->mtx); |
7ef9964e | 786 | free_uid(ep->user); |
4d7e30d9 | 787 | wakeup_source_unregister(ep->ws); |
f0ee9aab | 788 | kfree(ep); |
7699acd1 | 789 | } |
1da177e4 | 790 | |
7699acd1 DL |
791 | static int ep_eventpoll_release(struct inode *inode, struct file *file) |
792 | { | |
793 | struct eventpoll *ep = file->private_data; | |
1da177e4 | 794 | |
f0ee9aab | 795 | if (ep) |
7699acd1 | 796 | ep_free(ep); |
7699acd1 | 797 | |
7699acd1 | 798 | return 0; |
1da177e4 LT |
799 | } |
800 | ||
450d89ec EW |
801 | static inline unsigned int ep_item_poll(struct epitem *epi, poll_table *pt) |
802 | { | |
803 | pt->_key = epi->event.events; | |
804 | ||
805 | return epi->ffd.file->f_op->poll(epi->ffd.file, pt) & epi->event.events; | |
806 | } | |
807 | ||
296e236e DL |
808 | static int ep_read_events_proc(struct eventpoll *ep, struct list_head *head, |
809 | void *priv) | |
5071f97e DL |
810 | { |
811 | struct epitem *epi, *tmp; | |
626cf236 | 812 | poll_table pt; |
5071f97e | 813 | |
626cf236 | 814 | init_poll_funcptr(&pt, NULL); |
450d89ec | 815 | |
5071f97e | 816 | list_for_each_entry_safe(epi, tmp, head, rdllink) { |
450d89ec | 817 | if (ep_item_poll(epi, &pt)) |
5071f97e | 818 | return POLLIN | POLLRDNORM; |
296e236e | 819 | else { |
5071f97e DL |
820 | /* |
821 | * Item has been dropped into the ready list by the poll | |
822 | * callback, but it's not actually ready, as far as | |
823 | * caller requested events goes. We can remove it here. | |
824 | */ | |
eea1d585 | 825 | __pm_relax(ep_wakeup_source(epi)); |
5071f97e | 826 | list_del_init(&epi->rdllink); |
296e236e | 827 | } |
5071f97e DL |
828 | } |
829 | ||
830 | return 0; | |
831 | } | |
832 | ||
67347fe4 JB |
833 | static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, |
834 | poll_table *pt); | |
835 | ||
836 | struct readyevents_arg { | |
837 | struct eventpoll *ep; | |
838 | bool locked; | |
839 | }; | |
840 | ||
5071f97e DL |
841 | static int ep_poll_readyevents_proc(void *priv, void *cookie, int call_nests) |
842 | { | |
67347fe4 JB |
843 | struct readyevents_arg *arg = priv; |
844 | ||
845 | return ep_scan_ready_list(arg->ep, ep_read_events_proc, NULL, | |
846 | call_nests + 1, arg->locked); | |
5071f97e DL |
847 | } |
848 | ||
7699acd1 DL |
849 | static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait) |
850 | { | |
5071f97e | 851 | int pollflags; |
7699acd1 | 852 | struct eventpoll *ep = file->private_data; |
67347fe4 JB |
853 | struct readyevents_arg arg; |
854 | ||
855 | /* | |
856 | * During ep_insert() we already hold the ep->mtx for the tfile. | |
857 | * Prevent re-aquisition. | |
858 | */ | |
859 | arg.locked = wait && (wait->_qproc == ep_ptable_queue_proc); | |
860 | arg.ep = ep; | |
1da177e4 | 861 | |
7699acd1 DL |
862 | /* Insert inside our poll wait queue */ |
863 | poll_wait(file, &ep->poll_wait, wait); | |
864 | ||
5071f97e DL |
865 | /* |
866 | * Proceed to find out if wanted events are really available inside | |
867 | * the ready list. This need to be done under ep_call_nested() | |
868 | * supervision, since the call to f_op->poll() done on listed files | |
869 | * could re-enter here. | |
870 | */ | |
871 | pollflags = ep_call_nested(&poll_readywalk_ncalls, EP_MAX_NESTS, | |
67347fe4 | 872 | ep_poll_readyevents_proc, &arg, ep, current); |
7699acd1 | 873 | |
296e236e | 874 | return pollflags != -1 ? pollflags : 0; |
7699acd1 DL |
875 | } |
876 | ||
138d22b5 | 877 | #ifdef CONFIG_PROC_FS |
a3816ab0 | 878 | static void ep_show_fdinfo(struct seq_file *m, struct file *f) |
138d22b5 CG |
879 | { |
880 | struct eventpoll *ep = f->private_data; | |
881 | struct rb_node *rbp; | |
138d22b5 CG |
882 | |
883 | mutex_lock(&ep->mtx); | |
884 | for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { | |
885 | struct epitem *epi = rb_entry(rbp, struct epitem, rbn); | |
886 | ||
a3816ab0 JP |
887 | seq_printf(m, "tfd: %8d events: %8x data: %16llx\n", |
888 | epi->ffd.fd, epi->event.events, | |
889 | (long long)epi->event.data); | |
890 | if (seq_has_overflowed(m)) | |
138d22b5 CG |
891 | break; |
892 | } | |
893 | mutex_unlock(&ep->mtx); | |
138d22b5 CG |
894 | } |
895 | #endif | |
896 | ||
7699acd1 DL |
897 | /* File callbacks that implement the eventpoll file behaviour */ |
898 | static const struct file_operations eventpoll_fops = { | |
138d22b5 CG |
899 | #ifdef CONFIG_PROC_FS |
900 | .show_fdinfo = ep_show_fdinfo, | |
901 | #endif | |
7699acd1 | 902 | .release = ep_eventpoll_release, |
6038f373 AB |
903 | .poll = ep_eventpoll_poll, |
904 | .llseek = noop_llseek, | |
7699acd1 DL |
905 | }; |
906 | ||
b611967d | 907 | /* |
7699acd1 DL |
908 | * This is called from eventpoll_release() to unlink files from the eventpoll |
909 | * interface. We need to have this facility to cleanup correctly files that are | |
910 | * closed without being removed from the eventpoll interface. | |
b611967d | 911 | */ |
7699acd1 | 912 | void eventpoll_release_file(struct file *file) |
b611967d | 913 | { |
7699acd1 | 914 | struct eventpoll *ep; |
ebe06187 | 915 | struct epitem *epi, *next; |
b611967d DL |
916 | |
917 | /* | |
68499914 | 918 | * We don't want to get "file->f_lock" because it is not |
7699acd1 | 919 | * necessary. It is not necessary because we're in the "struct file" |
25985edc | 920 | * cleanup path, and this means that no one is using this file anymore. |
5071f97e | 921 | * So, for example, epoll_ctl() cannot hit here since if we reach this |
67647d0f | 922 | * point, the file counter already went to zero and fget() would fail. |
d47de16c | 923 | * The only hit might come from ep_free() but by holding the mutex |
7699acd1 | 924 | * will correctly serialize the operation. We do need to acquire |
d47de16c | 925 | * "ep->mtx" after "epmutex" because ep_remove() requires it when called |
7699acd1 | 926 | * from anywhere but ep_free(). |
68499914 JC |
927 | * |
928 | * Besides, ep_remove() acquires the lock, so we can't hold it here. | |
b611967d | 929 | */ |
7699acd1 | 930 | mutex_lock(&epmutex); |
ebe06187 | 931 | list_for_each_entry_safe(epi, next, &file->f_ep_links, fllink) { |
7699acd1 | 932 | ep = epi->ep; |
d8805e63 | 933 | mutex_lock_nested(&ep->mtx, 0); |
7699acd1 | 934 | ep_remove(ep, epi); |
d47de16c | 935 | mutex_unlock(&ep->mtx); |
b611967d | 936 | } |
7699acd1 | 937 | mutex_unlock(&epmutex); |
b611967d DL |
938 | } |
939 | ||
53d2be79 | 940 | static int ep_alloc(struct eventpoll **pep) |
1da177e4 | 941 | { |
7ef9964e DL |
942 | int error; |
943 | struct user_struct *user; | |
944 | struct eventpoll *ep; | |
1da177e4 | 945 | |
7ef9964e | 946 | user = get_current_user(); |
7ef9964e DL |
947 | error = -ENOMEM; |
948 | ep = kzalloc(sizeof(*ep), GFP_KERNEL); | |
949 | if (unlikely(!ep)) | |
950 | goto free_uid; | |
1da177e4 | 951 | |
c7ea7630 | 952 | spin_lock_init(&ep->lock); |
d47de16c | 953 | mutex_init(&ep->mtx); |
1da177e4 LT |
954 | init_waitqueue_head(&ep->wq); |
955 | init_waitqueue_head(&ep->poll_wait); | |
956 | INIT_LIST_HEAD(&ep->rdllist); | |
957 | ep->rbr = RB_ROOT; | |
d47de16c | 958 | ep->ovflist = EP_UNACTIVE_PTR; |
7ef9964e | 959 | ep->user = user; |
1da177e4 | 960 | |
53d2be79 | 961 | *pep = ep; |
1da177e4 | 962 | |
1da177e4 | 963 | return 0; |
7ef9964e DL |
964 | |
965 | free_uid: | |
966 | free_uid(user); | |
967 | return error; | |
1da177e4 LT |
968 | } |
969 | ||
1da177e4 | 970 | /* |
c7ea7630 DL |
971 | * Search the file inside the eventpoll tree. The RB tree operations |
972 | * are protected by the "mtx" mutex, and ep_find() must be called with | |
973 | * "mtx" held. | |
1da177e4 LT |
974 | */ |
975 | static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd) | |
976 | { | |
977 | int kcmp; | |
1da177e4 LT |
978 | struct rb_node *rbp; |
979 | struct epitem *epi, *epir = NULL; | |
980 | struct epoll_filefd ffd; | |
981 | ||
b030a4dd | 982 | ep_set_ffd(&ffd, file, fd); |
1da177e4 LT |
983 | for (rbp = ep->rbr.rb_node; rbp; ) { |
984 | epi = rb_entry(rbp, struct epitem, rbn); | |
b030a4dd | 985 | kcmp = ep_cmp_ffd(&ffd, &epi->ffd); |
1da177e4 LT |
986 | if (kcmp > 0) |
987 | rbp = rbp->rb_right; | |
988 | else if (kcmp < 0) | |
989 | rbp = rbp->rb_left; | |
990 | else { | |
1da177e4 LT |
991 | epir = epi; |
992 | break; | |
993 | } | |
994 | } | |
1da177e4 | 995 | |
1da177e4 LT |
996 | return epir; |
997 | } | |
998 | ||
1da177e4 | 999 | /* |
7699acd1 | 1000 | * This is the callback that is passed to the wait queue wakeup |
bf6a41db | 1001 | * mechanism. It is called by the stored file descriptors when they |
7699acd1 | 1002 | * have events to report. |
1da177e4 | 1003 | */ |
7699acd1 | 1004 | static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *key) |
1da177e4 | 1005 | { |
7699acd1 DL |
1006 | int pwake = 0; |
1007 | unsigned long flags; | |
1008 | struct epitem *epi = ep_item_from_wait(wait); | |
1009 | struct eventpoll *ep = epi->ep; | |
1da177e4 | 1010 | |
c7ea7630 | 1011 | spin_lock_irqsave(&ep->lock, flags); |
1da177e4 | 1012 | |
7699acd1 DL |
1013 | /* |
1014 | * If the event mask does not contain any poll(2) event, we consider the | |
1015 | * descriptor to be disabled. This condition is likely the effect of the | |
1016 | * EPOLLONESHOT bit that disables the descriptor when an event is received, | |
1017 | * until the next EPOLL_CTL_MOD will be issued. | |
1018 | */ | |
1019 | if (!(epi->event.events & ~EP_PRIVATE_BITS)) | |
d47de16c DL |
1020 | goto out_unlock; |
1021 | ||
2dfa4eea DL |
1022 | /* |
1023 | * Check the events coming with the callback. At this stage, not | |
1024 | * every device reports the events in the "key" parameter of the | |
1025 | * callback. We need to be able to handle both cases here, hence the | |
1026 | * test for "key" != NULL before the event match test. | |
1027 | */ | |
1028 | if (key && !((unsigned long) key & epi->event.events)) | |
1029 | goto out_unlock; | |
1030 | ||
d47de16c | 1031 | /* |
bf6a41db | 1032 | * If we are transferring events to userspace, we can hold no locks |
d47de16c | 1033 | * (because we're accessing user memory, and because of linux f_op->poll() |
bf6a41db | 1034 | * semantics). All the events that happen during that period of time are |
d47de16c DL |
1035 | * chained in ep->ovflist and requeued later on. |
1036 | */ | |
1037 | if (unlikely(ep->ovflist != EP_UNACTIVE_PTR)) { | |
1038 | if (epi->next == EP_UNACTIVE_PTR) { | |
1039 | epi->next = ep->ovflist; | |
1040 | ep->ovflist = epi; | |
4d7e30d9 AH |
1041 | if (epi->ws) { |
1042 | /* | |
1043 | * Activate ep->ws since epi->ws may get | |
1044 | * deactivated at any time. | |
1045 | */ | |
1046 | __pm_stay_awake(ep->ws); | |
1047 | } | |
1048 | ||
d47de16c DL |
1049 | } |
1050 | goto out_unlock; | |
1051 | } | |
1da177e4 | 1052 | |
7699acd1 | 1053 | /* If this file is already in the ready list we exit soon */ |
4d7e30d9 | 1054 | if (!ep_is_linked(&epi->rdllink)) { |
5071f97e | 1055 | list_add_tail(&epi->rdllink, &ep->rdllist); |
eea1d585 | 1056 | ep_pm_stay_awake_rcu(epi); |
4d7e30d9 | 1057 | } |
7699acd1 | 1058 | |
7699acd1 DL |
1059 | /* |
1060 | * Wake up ( if active ) both the eventpoll wait list and the ->poll() | |
1061 | * wait list. | |
1062 | */ | |
1063 | if (waitqueue_active(&ep->wq)) | |
4a6e9e2c | 1064 | wake_up_locked(&ep->wq); |
7699acd1 DL |
1065 | if (waitqueue_active(&ep->poll_wait)) |
1066 | pwake++; | |
1067 | ||
d47de16c | 1068 | out_unlock: |
c7ea7630 | 1069 | spin_unlock_irqrestore(&ep->lock, flags); |
1da177e4 | 1070 | |
7699acd1 DL |
1071 | /* We have to call this outside the lock */ |
1072 | if (pwake) | |
5071f97e | 1073 | ep_poll_safewake(&ep->poll_wait); |
7699acd1 | 1074 | |
6bf93860 ON |
1075 | |
1076 | if ((unsigned long)key & POLLFREE) { | |
1077 | /* | |
1078 | * If we race with ep_remove_wait_queue() it can miss | |
1079 | * ->whead = NULL and do another remove_wait_queue() after | |
1080 | * us, so we can't use __remove_wait_queue(). | |
1081 | */ | |
1082 | list_del_init(&wait->task_list); | |
1083 | /* | |
1084 | * ->whead != NULL protects us from the race with ep_free() | |
1085 | * or ep_remove(), ep_remove_wait_queue() takes whead->lock | |
1086 | * held by the caller. Once we nullify it, nothing protects | |
1087 | * ep/epi or even wait. | |
1088 | */ | |
1089 | smp_store_release(&ep_pwq_from_wait(wait)->whead, NULL); | |
1090 | } | |
1091 | ||
7699acd1 DL |
1092 | return 1; |
1093 | } | |
1da177e4 LT |
1094 | |
1095 | /* | |
1096 | * This is the callback that is used to add our wait queue to the | |
1097 | * target file wakeup lists. | |
1098 | */ | |
1099 | static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, | |
1100 | poll_table *pt) | |
1101 | { | |
b030a4dd | 1102 | struct epitem *epi = ep_item_from_epqueue(pt); |
1da177e4 LT |
1103 | struct eppoll_entry *pwq; |
1104 | ||
e94b1766 | 1105 | if (epi->nwait >= 0 && (pwq = kmem_cache_alloc(pwq_cache, GFP_KERNEL))) { |
1da177e4 LT |
1106 | init_waitqueue_func_entry(&pwq->wait, ep_poll_callback); |
1107 | pwq->whead = whead; | |
1108 | pwq->base = epi; | |
1109 | add_wait_queue(whead, &pwq->wait); | |
1110 | list_add_tail(&pwq->llink, &epi->pwqlist); | |
1111 | epi->nwait++; | |
296e236e | 1112 | } else { |
1da177e4 LT |
1113 | /* We have to signal that an error occurred */ |
1114 | epi->nwait = -1; | |
296e236e | 1115 | } |
1da177e4 LT |
1116 | } |
1117 | ||
1da177e4 LT |
1118 | static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi) |
1119 | { | |
1120 | int kcmp; | |
1121 | struct rb_node **p = &ep->rbr.rb_node, *parent = NULL; | |
1122 | struct epitem *epic; | |
1123 | ||
1124 | while (*p) { | |
1125 | parent = *p; | |
1126 | epic = rb_entry(parent, struct epitem, rbn); | |
b030a4dd | 1127 | kcmp = ep_cmp_ffd(&epi->ffd, &epic->ffd); |
1da177e4 LT |
1128 | if (kcmp > 0) |
1129 | p = &parent->rb_right; | |
1130 | else | |
1131 | p = &parent->rb_left; | |
1132 | } | |
1133 | rb_link_node(&epi->rbn, parent, p); | |
1134 | rb_insert_color(&epi->rbn, &ep->rbr); | |
1135 | } | |
1136 | ||
a80a6b85 AM |
1137 | |
1138 | ||
28d82dc1 JB |
1139 | #define PATH_ARR_SIZE 5 |
1140 | /* | |
1141 | * These are the number paths of length 1 to 5, that we are allowing to emanate | |
1142 | * from a single file of interest. For example, we allow 1000 paths of length | |
1143 | * 1, to emanate from each file of interest. This essentially represents the | |
1144 | * potential wakeup paths, which need to be limited in order to avoid massive | |
1145 | * uncontrolled wakeup storms. The common use case should be a single ep which | |
1146 | * is connected to n file sources. In this case each file source has 1 path | |
1147 | * of length 1. Thus, the numbers below should be more than sufficient. These | |
1148 | * path limits are enforced during an EPOLL_CTL_ADD operation, since a modify | |
1149 | * and delete can't add additional paths. Protected by the epmutex. | |
1150 | */ | |
1151 | static const int path_limits[PATH_ARR_SIZE] = { 1000, 500, 100, 50, 10 }; | |
1152 | static int path_count[PATH_ARR_SIZE]; | |
1153 | ||
1154 | static int path_count_inc(int nests) | |
1155 | { | |
93dc6107 JB |
1156 | /* Allow an arbitrary number of depth 1 paths */ |
1157 | if (nests == 0) | |
1158 | return 0; | |
1159 | ||
28d82dc1 JB |
1160 | if (++path_count[nests] > path_limits[nests]) |
1161 | return -1; | |
1162 | return 0; | |
1163 | } | |
1164 | ||
1165 | static void path_count_init(void) | |
1166 | { | |
1167 | int i; | |
1168 | ||
1169 | for (i = 0; i < PATH_ARR_SIZE; i++) | |
1170 | path_count[i] = 0; | |
1171 | } | |
1172 | ||
1173 | static int reverse_path_check_proc(void *priv, void *cookie, int call_nests) | |
1174 | { | |
1175 | int error = 0; | |
1176 | struct file *file = priv; | |
1177 | struct file *child_file; | |
1178 | struct epitem *epi; | |
1179 | ||
ae10b2b4 JB |
1180 | /* CTL_DEL can remove links here, but that can't increase our count */ |
1181 | rcu_read_lock(); | |
1182 | list_for_each_entry_rcu(epi, &file->f_ep_links, fllink) { | |
28d82dc1 JB |
1183 | child_file = epi->ep->file; |
1184 | if (is_file_epoll(child_file)) { | |
1185 | if (list_empty(&child_file->f_ep_links)) { | |
1186 | if (path_count_inc(call_nests)) { | |
1187 | error = -1; | |
1188 | break; | |
1189 | } | |
1190 | } else { | |
1191 | error = ep_call_nested(&poll_loop_ncalls, | |
1192 | EP_MAX_NESTS, | |
1193 | reverse_path_check_proc, | |
1194 | child_file, child_file, | |
1195 | current); | |
1196 | } | |
1197 | if (error != 0) | |
1198 | break; | |
1199 | } else { | |
1200 | printk(KERN_ERR "reverse_path_check_proc: " | |
1201 | "file is not an ep!\n"); | |
1202 | } | |
1203 | } | |
ae10b2b4 | 1204 | rcu_read_unlock(); |
28d82dc1 JB |
1205 | return error; |
1206 | } | |
1207 | ||
1208 | /** | |
1209 | * reverse_path_check - The tfile_check_list is list of file *, which have | |
1210 | * links that are proposed to be newly added. We need to | |
1211 | * make sure that those added links don't add too many | |
1212 | * paths such that we will spend all our time waking up | |
1213 | * eventpoll objects. | |
1214 | * | |
1215 | * Returns: Returns zero if the proposed links don't create too many paths, | |
1216 | * -1 otherwise. | |
1217 | */ | |
1218 | static int reverse_path_check(void) | |
1219 | { | |
28d82dc1 JB |
1220 | int error = 0; |
1221 | struct file *current_file; | |
1222 | ||
1223 | /* let's call this for all tfiles */ | |
1224 | list_for_each_entry(current_file, &tfile_check_list, f_tfile_llink) { | |
28d82dc1 JB |
1225 | path_count_init(); |
1226 | error = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, | |
1227 | reverse_path_check_proc, current_file, | |
1228 | current_file, current); | |
1229 | if (error) | |
1230 | break; | |
1231 | } | |
1232 | return error; | |
1233 | } | |
1234 | ||
4d7e30d9 AH |
1235 | static int ep_create_wakeup_source(struct epitem *epi) |
1236 | { | |
1237 | const char *name; | |
eea1d585 | 1238 | struct wakeup_source *ws; |
4d7e30d9 AH |
1239 | |
1240 | if (!epi->ep->ws) { | |
1241 | epi->ep->ws = wakeup_source_register("eventpoll"); | |
1242 | if (!epi->ep->ws) | |
1243 | return -ENOMEM; | |
1244 | } | |
1245 | ||
1246 | name = epi->ffd.file->f_path.dentry->d_name.name; | |
eea1d585 EW |
1247 | ws = wakeup_source_register(name); |
1248 | ||
1249 | if (!ws) | |
4d7e30d9 | 1250 | return -ENOMEM; |
eea1d585 | 1251 | rcu_assign_pointer(epi->ws, ws); |
4d7e30d9 AH |
1252 | |
1253 | return 0; | |
1254 | } | |
1255 | ||
eea1d585 EW |
1256 | /* rare code path, only used when EPOLL_CTL_MOD removes a wakeup source */ |
1257 | static noinline void ep_destroy_wakeup_source(struct epitem *epi) | |
4d7e30d9 | 1258 | { |
eea1d585 EW |
1259 | struct wakeup_source *ws = ep_wakeup_source(epi); |
1260 | ||
d6d67e72 | 1261 | RCU_INIT_POINTER(epi->ws, NULL); |
eea1d585 EW |
1262 | |
1263 | /* | |
1264 | * wait for ep_pm_stay_awake_rcu to finish, synchronize_rcu is | |
1265 | * used internally by wakeup_source_remove, too (called by | |
1266 | * wakeup_source_unregister), so we cannot use call_rcu | |
1267 | */ | |
1268 | synchronize_rcu(); | |
1269 | wakeup_source_unregister(ws); | |
4d7e30d9 AH |
1270 | } |
1271 | ||
c7ea7630 DL |
1272 | /* |
1273 | * Must be called with "mtx" held. | |
1274 | */ | |
1da177e4 | 1275 | static int ep_insert(struct eventpoll *ep, struct epoll_event *event, |
67347fe4 | 1276 | struct file *tfile, int fd, int full_check) |
1da177e4 LT |
1277 | { |
1278 | int error, revents, pwake = 0; | |
1279 | unsigned long flags; | |
52bd19f7 | 1280 | long user_watches; |
1da177e4 LT |
1281 | struct epitem *epi; |
1282 | struct ep_pqueue epq; | |
1283 | ||
52bd19f7 RH |
1284 | user_watches = atomic_long_read(&ep->user->epoll_watches); |
1285 | if (unlikely(user_watches >= max_user_watches)) | |
7ef9964e | 1286 | return -ENOSPC; |
e94b1766 | 1287 | if (!(epi = kmem_cache_alloc(epi_cache, GFP_KERNEL))) |
7ef9964e | 1288 | return -ENOMEM; |
1da177e4 LT |
1289 | |
1290 | /* Item initialization follow here ... */ | |
1da177e4 LT |
1291 | INIT_LIST_HEAD(&epi->rdllink); |
1292 | INIT_LIST_HEAD(&epi->fllink); | |
1da177e4 LT |
1293 | INIT_LIST_HEAD(&epi->pwqlist); |
1294 | epi->ep = ep; | |
b030a4dd | 1295 | ep_set_ffd(&epi->ffd, tfile, fd); |
1da177e4 | 1296 | epi->event = *event; |
1da177e4 | 1297 | epi->nwait = 0; |
d47de16c | 1298 | epi->next = EP_UNACTIVE_PTR; |
4d7e30d9 AH |
1299 | if (epi->event.events & EPOLLWAKEUP) { |
1300 | error = ep_create_wakeup_source(epi); | |
1301 | if (error) | |
1302 | goto error_create_wakeup_source; | |
1303 | } else { | |
eea1d585 | 1304 | RCU_INIT_POINTER(epi->ws, NULL); |
4d7e30d9 | 1305 | } |
1da177e4 LT |
1306 | |
1307 | /* Initialize the poll table using the queue callback */ | |
1308 | epq.epi = epi; | |
1309 | init_poll_funcptr(&epq.pt, ep_ptable_queue_proc); | |
1310 | ||
1311 | /* | |
1312 | * Attach the item to the poll hooks and get current event bits. | |
1313 | * We can safely use the file* here because its usage count has | |
c7ea7630 DL |
1314 | * been increased by the caller of this function. Note that after |
1315 | * this operation completes, the poll callback can start hitting | |
1316 | * the new item. | |
1da177e4 | 1317 | */ |
450d89ec | 1318 | revents = ep_item_poll(epi, &epq.pt); |
1da177e4 LT |
1319 | |
1320 | /* | |
1321 | * We have to check if something went wrong during the poll wait queue | |
1322 | * install process. Namely an allocation for a wait queue failed due | |
1323 | * high memory pressure. | |
1324 | */ | |
7ef9964e | 1325 | error = -ENOMEM; |
1da177e4 | 1326 | if (epi->nwait < 0) |
7699acd1 | 1327 | goto error_unregister; |
1da177e4 LT |
1328 | |
1329 | /* Add the current item to the list of active epoll hook for this file */ | |
68499914 | 1330 | spin_lock(&tfile->f_lock); |
ae10b2b4 | 1331 | list_add_tail_rcu(&epi->fllink, &tfile->f_ep_links); |
68499914 | 1332 | spin_unlock(&tfile->f_lock); |
1da177e4 | 1333 | |
c7ea7630 DL |
1334 | /* |
1335 | * Add the current item to the RB tree. All RB tree operations are | |
1336 | * protected by "mtx", and ep_insert() is called with "mtx" held. | |
1337 | */ | |
1da177e4 LT |
1338 | ep_rbtree_insert(ep, epi); |
1339 | ||
28d82dc1 JB |
1340 | /* now check if we've created too many backpaths */ |
1341 | error = -EINVAL; | |
67347fe4 | 1342 | if (full_check && reverse_path_check()) |
28d82dc1 JB |
1343 | goto error_remove_epi; |
1344 | ||
c7ea7630 DL |
1345 | /* We have to drop the new item inside our item list to keep track of it */ |
1346 | spin_lock_irqsave(&ep->lock, flags); | |
1347 | ||
1da177e4 | 1348 | /* If the file is already "ready" we drop it inside the ready list */ |
b030a4dd | 1349 | if ((revents & event->events) && !ep_is_linked(&epi->rdllink)) { |
1da177e4 | 1350 | list_add_tail(&epi->rdllink, &ep->rdllist); |
eea1d585 | 1351 | ep_pm_stay_awake(epi); |
1da177e4 LT |
1352 | |
1353 | /* Notify waiting tasks that events are available */ | |
1354 | if (waitqueue_active(&ep->wq)) | |
4a6e9e2c | 1355 | wake_up_locked(&ep->wq); |
1da177e4 LT |
1356 | if (waitqueue_active(&ep->poll_wait)) |
1357 | pwake++; | |
1358 | } | |
1359 | ||
c7ea7630 | 1360 | spin_unlock_irqrestore(&ep->lock, flags); |
1da177e4 | 1361 | |
52bd19f7 | 1362 | atomic_long_inc(&ep->user->epoll_watches); |
7ef9964e | 1363 | |
1da177e4 LT |
1364 | /* We have to call this outside the lock */ |
1365 | if (pwake) | |
5071f97e | 1366 | ep_poll_safewake(&ep->poll_wait); |
1da177e4 | 1367 | |
1da177e4 LT |
1368 | return 0; |
1369 | ||
28d82dc1 JB |
1370 | error_remove_epi: |
1371 | spin_lock(&tfile->f_lock); | |
ae10b2b4 | 1372 | list_del_rcu(&epi->fllink); |
28d82dc1 JB |
1373 | spin_unlock(&tfile->f_lock); |
1374 | ||
1375 | rb_erase(&epi->rbn, &ep->rbr); | |
1376 | ||
7699acd1 | 1377 | error_unregister: |
1da177e4 LT |
1378 | ep_unregister_pollwait(ep, epi); |
1379 | ||
1380 | /* | |
1381 | * We need to do this because an event could have been arrived on some | |
67647d0f DL |
1382 | * allocated wait queue. Note that we don't care about the ep->ovflist |
1383 | * list, since that is used/cleaned only inside a section bound by "mtx". | |
1384 | * And ep_insert() is called with "mtx" held. | |
1da177e4 | 1385 | */ |
c7ea7630 | 1386 | spin_lock_irqsave(&ep->lock, flags); |
b030a4dd | 1387 | if (ep_is_linked(&epi->rdllink)) |
6192bd53 | 1388 | list_del_init(&epi->rdllink); |
c7ea7630 | 1389 | spin_unlock_irqrestore(&ep->lock, flags); |
1da177e4 | 1390 | |
eea1d585 | 1391 | wakeup_source_unregister(ep_wakeup_source(epi)); |
4d7e30d9 AH |
1392 | |
1393 | error_create_wakeup_source: | |
b030a4dd | 1394 | kmem_cache_free(epi_cache, epi); |
7ef9964e | 1395 | |
1da177e4 LT |
1396 | return error; |
1397 | } | |
1398 | ||
1da177e4 LT |
1399 | /* |
1400 | * Modify the interest event mask by dropping an event if the new mask | |
c7ea7630 | 1401 | * has a match in the current file status. Must be called with "mtx" held. |
1da177e4 LT |
1402 | */ |
1403 | static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_event *event) | |
1404 | { | |
1405 | int pwake = 0; | |
1406 | unsigned int revents; | |
626cf236 HV |
1407 | poll_table pt; |
1408 | ||
1409 | init_poll_funcptr(&pt, NULL); | |
1da177e4 LT |
1410 | |
1411 | /* | |
e057e15f TB |
1412 | * Set the new event interest mask before calling f_op->poll(); |
1413 | * otherwise we might miss an event that happens between the | |
1414 | * f_op->poll() call and the new event set registering. | |
1da177e4 | 1415 | */ |
128dd175 | 1416 | epi->event.events = event->events; /* need barrier below */ |
e057e15f | 1417 | epi->event.data = event->data; /* protected by mtx */ |
4d7e30d9 | 1418 | if (epi->event.events & EPOLLWAKEUP) { |
eea1d585 | 1419 | if (!ep_has_wakeup_source(epi)) |
4d7e30d9 | 1420 | ep_create_wakeup_source(epi); |
eea1d585 | 1421 | } else if (ep_has_wakeup_source(epi)) { |
4d7e30d9 AH |
1422 | ep_destroy_wakeup_source(epi); |
1423 | } | |
1da177e4 | 1424 | |
128dd175 EW |
1425 | /* |
1426 | * The following barrier has two effects: | |
1427 | * | |
1428 | * 1) Flush epi changes above to other CPUs. This ensures | |
1429 | * we do not miss events from ep_poll_callback if an | |
1430 | * event occurs immediately after we call f_op->poll(). | |
1431 | * We need this because we did not take ep->lock while | |
1432 | * changing epi above (but ep_poll_callback does take | |
1433 | * ep->lock). | |
1434 | * | |
1435 | * 2) We also need to ensure we do not miss _past_ events | |
1436 | * when calling f_op->poll(). This barrier also | |
1437 | * pairs with the barrier in wq_has_sleeper (see | |
1438 | * comments for wq_has_sleeper). | |
1439 | * | |
1440 | * This barrier will now guarantee ep_poll_callback or f_op->poll | |
1441 | * (or both) will notice the readiness of an item. | |
1442 | */ | |
1443 | smp_mb(); | |
1444 | ||
1da177e4 LT |
1445 | /* |
1446 | * Get current event bits. We can safely use the file* here because | |
1447 | * its usage count has been increased by the caller of this function. | |
1448 | */ | |
450d89ec | 1449 | revents = ep_item_poll(epi, &pt); |
1da177e4 | 1450 | |
1da177e4 | 1451 | /* |
c7ea7630 | 1452 | * If the item is "hot" and it is not registered inside the ready |
67647d0f | 1453 | * list, push it inside. |
1da177e4 | 1454 | */ |
c7ea7630 | 1455 | if (revents & event->events) { |
e057e15f | 1456 | spin_lock_irq(&ep->lock); |
c7ea7630 DL |
1457 | if (!ep_is_linked(&epi->rdllink)) { |
1458 | list_add_tail(&epi->rdllink, &ep->rdllist); | |
eea1d585 | 1459 | ep_pm_stay_awake(epi); |
c7ea7630 DL |
1460 | |
1461 | /* Notify waiting tasks that events are available */ | |
1462 | if (waitqueue_active(&ep->wq)) | |
4a6e9e2c | 1463 | wake_up_locked(&ep->wq); |
c7ea7630 DL |
1464 | if (waitqueue_active(&ep->poll_wait)) |
1465 | pwake++; | |
7699acd1 | 1466 | } |
e057e15f | 1467 | spin_unlock_irq(&ep->lock); |
7699acd1 | 1468 | } |
1da177e4 | 1469 | |
7699acd1 DL |
1470 | /* We have to call this outside the lock */ |
1471 | if (pwake) | |
5071f97e | 1472 | ep_poll_safewake(&ep->poll_wait); |
1da177e4 | 1473 | |
7699acd1 | 1474 | return 0; |
1da177e4 LT |
1475 | } |
1476 | ||
296e236e DL |
1477 | static int ep_send_events_proc(struct eventpoll *ep, struct list_head *head, |
1478 | void *priv) | |
1da177e4 | 1479 | { |
5071f97e DL |
1480 | struct ep_send_events_data *esed = priv; |
1481 | int eventcnt; | |
296e236e | 1482 | unsigned int revents; |
5071f97e DL |
1483 | struct epitem *epi; |
1484 | struct epoll_event __user *uevent; | |
eea1d585 | 1485 | struct wakeup_source *ws; |
626cf236 HV |
1486 | poll_table pt; |
1487 | ||
1488 | init_poll_funcptr(&pt, NULL); | |
1da177e4 | 1489 | |
296e236e | 1490 | /* |
5071f97e DL |
1491 | * We can loop without lock because we are passed a task private list. |
1492 | * Items cannot vanish during the loop because ep_scan_ready_list() is | |
1493 | * holding "mtx" during this call. | |
296e236e | 1494 | */ |
5071f97e DL |
1495 | for (eventcnt = 0, uevent = esed->events; |
1496 | !list_empty(head) && eventcnt < esed->maxevents;) { | |
1497 | epi = list_first_entry(head, struct epitem, rdllink); | |
d47de16c | 1498 | |
4d7e30d9 AH |
1499 | /* |
1500 | * Activate ep->ws before deactivating epi->ws to prevent | |
1501 | * triggering auto-suspend here (in case we reactive epi->ws | |
1502 | * below). | |
1503 | * | |
1504 | * This could be rearranged to delay the deactivation of epi->ws | |
1505 | * instead, but then epi->ws would temporarily be out of sync | |
1506 | * with ep_is_linked(). | |
1507 | */ | |
eea1d585 EW |
1508 | ws = ep_wakeup_source(epi); |
1509 | if (ws) { | |
1510 | if (ws->active) | |
1511 | __pm_stay_awake(ep->ws); | |
1512 | __pm_relax(ws); | |
1513 | } | |
1514 | ||
d47de16c | 1515 | list_del_init(&epi->rdllink); |
1da177e4 | 1516 | |
450d89ec | 1517 | revents = ep_item_poll(epi, &pt); |
5071f97e | 1518 | |
296e236e | 1519 | /* |
5071f97e DL |
1520 | * If the event mask intersect the caller-requested one, |
1521 | * deliver the event to userspace. Again, ep_scan_ready_list() | |
1522 | * is holding "mtx", so no operations coming from userspace | |
1523 | * can change the item. | |
296e236e DL |
1524 | */ |
1525 | if (revents) { | |
5071f97e | 1526 | if (__put_user(revents, &uevent->events) || |
d0305882 TB |
1527 | __put_user(epi->event.data, &uevent->data)) { |
1528 | list_add(&epi->rdllink, head); | |
eea1d585 | 1529 | ep_pm_stay_awake(epi); |
296e236e | 1530 | return eventcnt ? eventcnt : -EFAULT; |
d0305882 | 1531 | } |
296e236e | 1532 | eventcnt++; |
5071f97e | 1533 | uevent++; |
296e236e DL |
1534 | if (epi->event.events & EPOLLONESHOT) |
1535 | epi->event.events &= EP_PRIVATE_BITS; | |
1536 | else if (!(epi->event.events & EPOLLET)) { | |
1537 | /* | |
1538 | * If this file has been added with Level | |
1539 | * Trigger mode, we need to insert back inside | |
1540 | * the ready list, so that the next call to | |
1541 | * epoll_wait() will check again the events | |
25985edc | 1542 | * availability. At this point, no one can insert |
296e236e DL |
1543 | * into ep->rdllist besides us. The epoll_ctl() |
1544 | * callers are locked out by | |
1545 | * ep_scan_ready_list() holding "mtx" and the | |
1546 | * poll callback will queue them in ep->ovflist. | |
1547 | */ | |
1548 | list_add_tail(&epi->rdllink, &ep->rdllist); | |
eea1d585 | 1549 | ep_pm_stay_awake(epi); |
296e236e DL |
1550 | } |
1551 | } | |
1552 | } | |
5071f97e DL |
1553 | |
1554 | return eventcnt; | |
1555 | } | |
d47de16c | 1556 | |
296e236e DL |
1557 | static int ep_send_events(struct eventpoll *ep, |
1558 | struct epoll_event __user *events, int maxevents) | |
5071f97e DL |
1559 | { |
1560 | struct ep_send_events_data esed; | |
1da177e4 | 1561 | |
5071f97e DL |
1562 | esed.maxevents = maxevents; |
1563 | esed.events = events; | |
6192bd53 | 1564 | |
67347fe4 | 1565 | return ep_scan_ready_list(ep, ep_send_events_proc, &esed, 0, false); |
1da177e4 LT |
1566 | } |
1567 | ||
0781b909 ED |
1568 | static inline struct timespec ep_set_mstimeout(long ms) |
1569 | { | |
1570 | struct timespec now, ts = { | |
1571 | .tv_sec = ms / MSEC_PER_SEC, | |
1572 | .tv_nsec = NSEC_PER_MSEC * (ms % MSEC_PER_SEC), | |
1573 | }; | |
1574 | ||
1575 | ktime_get_ts(&now); | |
1576 | return timespec_add_safe(now, ts); | |
1577 | } | |
1578 | ||
f4d93ad7 SB |
1579 | /** |
1580 | * ep_poll - Retrieves ready events, and delivers them to the caller supplied | |
1581 | * event buffer. | |
1582 | * | |
1583 | * @ep: Pointer to the eventpoll context. | |
1584 | * @events: Pointer to the userspace buffer where the ready events should be | |
1585 | * stored. | |
1586 | * @maxevents: Size (in terms of number of events) of the caller event buffer. | |
1587 | * @timeout: Maximum timeout for the ready events fetch operation, in | |
1588 | * milliseconds. If the @timeout is zero, the function will not block, | |
1589 | * while if the @timeout is less than zero, the function will block | |
1590 | * until at least one event has been retrieved (or an error | |
1591 | * occurred). | |
1592 | * | |
1593 | * Returns: Returns the number of ready events which have been fetched, or an | |
1594 | * error code, in case of error. | |
1595 | */ | |
1da177e4 LT |
1596 | static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, |
1597 | int maxevents, long timeout) | |
1598 | { | |
f4d93ad7 | 1599 | int res = 0, eavail, timed_out = 0; |
1da177e4 | 1600 | unsigned long flags; |
f4d93ad7 | 1601 | long slack = 0; |
1da177e4 | 1602 | wait_queue_t wait; |
95aac7b1 SB |
1603 | ktime_t expires, *to = NULL; |
1604 | ||
1605 | if (timeout > 0) { | |
0781b909 ED |
1606 | struct timespec end_time = ep_set_mstimeout(timeout); |
1607 | ||
95aac7b1 SB |
1608 | slack = select_estimate_accuracy(&end_time); |
1609 | to = &expires; | |
1610 | *to = timespec_to_ktime(end_time); | |
1611 | } else if (timeout == 0) { | |
f4d93ad7 SB |
1612 | /* |
1613 | * Avoid the unnecessary trip to the wait queue loop, if the | |
1614 | * caller specified a non blocking operation. | |
1615 | */ | |
95aac7b1 | 1616 | timed_out = 1; |
f4d93ad7 SB |
1617 | spin_lock_irqsave(&ep->lock, flags); |
1618 | goto check_events; | |
95aac7b1 | 1619 | } |
1da177e4 | 1620 | |
f4d93ad7 | 1621 | fetch_events: |
c7ea7630 | 1622 | spin_lock_irqsave(&ep->lock, flags); |
1da177e4 | 1623 | |
3fb0e584 | 1624 | if (!ep_events_available(ep)) { |
1da177e4 LT |
1625 | /* |
1626 | * We don't have any available event to return to the caller. | |
1627 | * We need to sleep here, and we will be wake up by | |
1628 | * ep_poll_callback() when events will become available. | |
1629 | */ | |
1630 | init_waitqueue_entry(&wait, current); | |
a93d2f17 | 1631 | __add_wait_queue_exclusive(&ep->wq, &wait); |
1da177e4 LT |
1632 | |
1633 | for (;;) { | |
1634 | /* | |
1635 | * We don't want to sleep if the ep_poll_callback() sends us | |
1636 | * a wakeup in between. That's why we set the task state | |
1637 | * to TASK_INTERRUPTIBLE before doing the checks. | |
1638 | */ | |
1639 | set_current_state(TASK_INTERRUPTIBLE); | |
3fb0e584 | 1640 | if (ep_events_available(ep) || timed_out) |
1da177e4 LT |
1641 | break; |
1642 | if (signal_pending(current)) { | |
1643 | res = -EINTR; | |
1644 | break; | |
1645 | } | |
1646 | ||
c7ea7630 | 1647 | spin_unlock_irqrestore(&ep->lock, flags); |
c511851d | 1648 | if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS)) |
95aac7b1 SB |
1649 | timed_out = 1; |
1650 | ||
c7ea7630 | 1651 | spin_lock_irqsave(&ep->lock, flags); |
1da177e4 | 1652 | } |
1da177e4 | 1653 | |
4d5755b1 DB |
1654 | __remove_wait_queue(&ep->wq, &wait); |
1655 | __set_current_state(TASK_RUNNING); | |
1da177e4 | 1656 | } |
f4d93ad7 | 1657 | check_events: |
1da177e4 | 1658 | /* Is it worth to try to dig for events ? */ |
3fb0e584 | 1659 | eavail = ep_events_available(ep); |
1da177e4 | 1660 | |
c7ea7630 | 1661 | spin_unlock_irqrestore(&ep->lock, flags); |
1da177e4 LT |
1662 | |
1663 | /* | |
1664 | * Try to transfer events to user space. In case we get 0 events and | |
1665 | * there's still timeout left over, we go trying again in search of | |
1666 | * more luck. | |
1667 | */ | |
1668 | if (!res && eavail && | |
95aac7b1 | 1669 | !(res = ep_send_events(ep, events, maxevents)) && !timed_out) |
f4d93ad7 | 1670 | goto fetch_events; |
1da177e4 LT |
1671 | |
1672 | return res; | |
1673 | } | |
1674 | ||
22bacca4 DL |
1675 | /** |
1676 | * ep_loop_check_proc - Callback function to be passed to the @ep_call_nested() | |
1677 | * API, to verify that adding an epoll file inside another | |
1678 | * epoll structure, does not violate the constraints, in | |
1679 | * terms of closed loops, or too deep chains (which can | |
1680 | * result in excessive stack usage). | |
1681 | * | |
1682 | * @priv: Pointer to the epoll file to be currently checked. | |
1683 | * @cookie: Original cookie for this call. This is the top-of-the-chain epoll | |
1684 | * data structure pointer. | |
1685 | * @call_nests: Current dept of the @ep_call_nested() call stack. | |
1686 | * | |
1687 | * Returns: Returns zero if adding the epoll @file inside current epoll | |
1688 | * structure @ep does not violate the constraints, or -1 otherwise. | |
1689 | */ | |
1690 | static int ep_loop_check_proc(void *priv, void *cookie, int call_nests) | |
1691 | { | |
1692 | int error = 0; | |
1693 | struct file *file = priv; | |
1694 | struct eventpoll *ep = file->private_data; | |
28d82dc1 | 1695 | struct eventpoll *ep_tovisit; |
22bacca4 DL |
1696 | struct rb_node *rbp; |
1697 | struct epitem *epi; | |
1698 | ||
d8805e63 | 1699 | mutex_lock_nested(&ep->mtx, call_nests + 1); |
28d82dc1 JB |
1700 | ep->visited = 1; |
1701 | list_add(&ep->visited_list_link, &visited_list); | |
22bacca4 DL |
1702 | for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { |
1703 | epi = rb_entry(rbp, struct epitem, rbn); | |
1704 | if (unlikely(is_file_epoll(epi->ffd.file))) { | |
28d82dc1 JB |
1705 | ep_tovisit = epi->ffd.file->private_data; |
1706 | if (ep_tovisit->visited) | |
1707 | continue; | |
22bacca4 | 1708 | error = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, |
28d82dc1 JB |
1709 | ep_loop_check_proc, epi->ffd.file, |
1710 | ep_tovisit, current); | |
22bacca4 DL |
1711 | if (error != 0) |
1712 | break; | |
28d82dc1 JB |
1713 | } else { |
1714 | /* | |
1715 | * If we've reached a file that is not associated with | |
1716 | * an ep, then we need to check if the newly added | |
1717 | * links are going to add too many wakeup paths. We do | |
1718 | * this by adding it to the tfile_check_list, if it's | |
1719 | * not already there, and calling reverse_path_check() | |
1720 | * during ep_insert(). | |
1721 | */ | |
1722 | if (list_empty(&epi->ffd.file->f_tfile_llink)) | |
1723 | list_add(&epi->ffd.file->f_tfile_llink, | |
1724 | &tfile_check_list); | |
22bacca4 DL |
1725 | } |
1726 | } | |
1727 | mutex_unlock(&ep->mtx); | |
1728 | ||
1729 | return error; | |
1730 | } | |
1731 | ||
1732 | /** | |
1733 | * ep_loop_check - Performs a check to verify that adding an epoll file (@file) | |
1734 | * another epoll file (represented by @ep) does not create | |
1735 | * closed loops or too deep chains. | |
1736 | * | |
1737 | * @ep: Pointer to the epoll private data structure. | |
1738 | * @file: Pointer to the epoll file to be checked. | |
1739 | * | |
1740 | * Returns: Returns zero if adding the epoll @file inside current epoll | |
1741 | * structure @ep does not violate the constraints, or -1 otherwise. | |
1742 | */ | |
1743 | static int ep_loop_check(struct eventpoll *ep, struct file *file) | |
1744 | { | |
28d82dc1 JB |
1745 | int ret; |
1746 | struct eventpoll *ep_cur, *ep_next; | |
1747 | ||
1748 | ret = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, | |
22bacca4 | 1749 | ep_loop_check_proc, file, ep, current); |
28d82dc1 JB |
1750 | /* clear visited list */ |
1751 | list_for_each_entry_safe(ep_cur, ep_next, &visited_list, | |
1752 | visited_list_link) { | |
1753 | ep_cur->visited = 0; | |
1754 | list_del(&ep_cur->visited_list_link); | |
1755 | } | |
1756 | return ret; | |
1757 | } | |
1758 | ||
1759 | static void clear_tfile_check_list(void) | |
1760 | { | |
1761 | struct file *file; | |
1762 | ||
1763 | /* first clear the tfile_check_list */ | |
1764 | while (!list_empty(&tfile_check_list)) { | |
1765 | file = list_first_entry(&tfile_check_list, struct file, | |
1766 | f_tfile_llink); | |
1767 | list_del_init(&file->f_tfile_llink); | |
1768 | } | |
1769 | INIT_LIST_HEAD(&tfile_check_list); | |
22bacca4 DL |
1770 | } |
1771 | ||
7699acd1 | 1772 | /* |
523723bb | 1773 | * Open an eventpoll file descriptor. |
7699acd1 | 1774 | */ |
5a8a82b1 | 1775 | SYSCALL_DEFINE1(epoll_create1, int, flags) |
7699acd1 | 1776 | { |
28d82dc1 | 1777 | int error, fd; |
bb57c3ed | 1778 | struct eventpoll *ep = NULL; |
28d82dc1 | 1779 | struct file *file; |
7699acd1 | 1780 | |
e38b36f3 UD |
1781 | /* Check the EPOLL_* constant for consistency. */ |
1782 | BUILD_BUG_ON(EPOLL_CLOEXEC != O_CLOEXEC); | |
1783 | ||
296e236e DL |
1784 | if (flags & ~EPOLL_CLOEXEC) |
1785 | return -EINVAL; | |
7699acd1 | 1786 | /* |
bb57c3ed | 1787 | * Create the internal data structure ("struct eventpoll"). |
7699acd1 | 1788 | */ |
9fe5ad9c | 1789 | error = ep_alloc(&ep); |
bb57c3ed DL |
1790 | if (error < 0) |
1791 | return error; | |
7699acd1 DL |
1792 | /* |
1793 | * Creates all the items needed to setup an eventpoll file. That is, | |
2030a42c | 1794 | * a file structure and a free file descriptor. |
7699acd1 | 1795 | */ |
28d82dc1 JB |
1796 | fd = get_unused_fd_flags(O_RDWR | (flags & O_CLOEXEC)); |
1797 | if (fd < 0) { | |
1798 | error = fd; | |
1799 | goto out_free_ep; | |
1800 | } | |
1801 | file = anon_inode_getfile("[eventpoll]", &eventpoll_fops, ep, | |
628ff7c1 | 1802 | O_RDWR | (flags & O_CLOEXEC)); |
28d82dc1 JB |
1803 | if (IS_ERR(file)) { |
1804 | error = PTR_ERR(file); | |
1805 | goto out_free_fd; | |
1806 | } | |
28d82dc1 | 1807 | ep->file = file; |
98022748 | 1808 | fd_install(fd, file); |
28d82dc1 JB |
1809 | return fd; |
1810 | ||
1811 | out_free_fd: | |
1812 | put_unused_fd(fd); | |
1813 | out_free_ep: | |
1814 | ep_free(ep); | |
bb57c3ed | 1815 | return error; |
7699acd1 DL |
1816 | } |
1817 | ||
5a8a82b1 | 1818 | SYSCALL_DEFINE1(epoll_create, int, size) |
a0998b50 | 1819 | { |
bfe3891a | 1820 | if (size <= 0) |
9fe5ad9c UD |
1821 | return -EINVAL; |
1822 | ||
1823 | return sys_epoll_create1(0); | |
a0998b50 UD |
1824 | } |
1825 | ||
7699acd1 DL |
1826 | /* |
1827 | * The following function implements the controller interface for | |
1828 | * the eventpoll file that enables the insertion/removal/change of | |
67647d0f | 1829 | * file descriptors inside the interest set. |
7699acd1 | 1830 | */ |
5a8a82b1 HC |
1831 | SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd, |
1832 | struct epoll_event __user *, event) | |
7699acd1 DL |
1833 | { |
1834 | int error; | |
67347fe4 | 1835 | int full_check = 0; |
7e3fb584 | 1836 | struct fd f, tf; |
7699acd1 DL |
1837 | struct eventpoll *ep; |
1838 | struct epitem *epi; | |
1839 | struct epoll_event epds; | |
67347fe4 | 1840 | struct eventpoll *tep = NULL; |
7699acd1 | 1841 | |
7699acd1 DL |
1842 | error = -EFAULT; |
1843 | if (ep_op_has_event(op) && | |
1844 | copy_from_user(&epds, event, sizeof(struct epoll_event))) | |
1845 | goto error_return; | |
1846 | ||
7699acd1 | 1847 | error = -EBADF; |
7e3fb584 AV |
1848 | f = fdget(epfd); |
1849 | if (!f.file) | |
7699acd1 DL |
1850 | goto error_return; |
1851 | ||
1852 | /* Get the "struct file *" for the target file */ | |
7e3fb584 AV |
1853 | tf = fdget(fd); |
1854 | if (!tf.file) | |
7699acd1 DL |
1855 | goto error_fput; |
1856 | ||
1857 | /* The target file descriptor must support poll */ | |
1858 | error = -EPERM; | |
72c2d531 | 1859 | if (!tf.file->f_op->poll) |
7699acd1 DL |
1860 | goto error_tgt_fput; |
1861 | ||
4d7e30d9 | 1862 | /* Check if EPOLLWAKEUP is allowed */ |
c680e41b NI |
1863 | if (ep_op_has_event(op)) |
1864 | ep_take_care_of_epollwakeup(&epds); | |
4d7e30d9 | 1865 | |
7699acd1 DL |
1866 | /* |
1867 | * We have to check that the file structure underneath the file descriptor | |
1868 | * the user passed to us _is_ an eventpoll file. And also we do not permit | |
1869 | * adding an epoll file descriptor inside itself. | |
1870 | */ | |
1871 | error = -EINVAL; | |
7e3fb584 | 1872 | if (f.file == tf.file || !is_file_epoll(f.file)) |
7699acd1 DL |
1873 | goto error_tgt_fput; |
1874 | ||
1875 | /* | |
1876 | * At this point it is safe to assume that the "private_data" contains | |
1877 | * our own data structure. | |
1878 | */ | |
7e3fb584 | 1879 | ep = f.file->private_data; |
7699acd1 | 1880 | |
22bacca4 DL |
1881 | /* |
1882 | * When we insert an epoll file descriptor, inside another epoll file | |
1883 | * descriptor, there is the change of creating closed loops, which are | |
28d82dc1 JB |
1884 | * better be handled here, than in more critical paths. While we are |
1885 | * checking for loops we also determine the list of files reachable | |
1886 | * and hang them on the tfile_check_list, so we can check that we | |
1887 | * haven't created too many possible wakeup paths. | |
22bacca4 | 1888 | * |
67347fe4 JB |
1889 | * We do not need to take the global 'epumutex' on EPOLL_CTL_ADD when |
1890 | * the epoll file descriptor is attaching directly to a wakeup source, | |
1891 | * unless the epoll file descriptor is nested. The purpose of taking the | |
1892 | * 'epmutex' on add is to prevent complex toplogies such as loops and | |
1893 | * deep wakeup paths from forming in parallel through multiple | |
1894 | * EPOLL_CTL_ADD operations. | |
22bacca4 | 1895 | */ |
67347fe4 | 1896 | mutex_lock_nested(&ep->mtx, 0); |
28d82dc1 | 1897 | if (op == EPOLL_CTL_ADD) { |
67347fe4 JB |
1898 | if (!list_empty(&f.file->f_ep_links) || |
1899 | is_file_epoll(tf.file)) { | |
1900 | full_check = 1; | |
1901 | mutex_unlock(&ep->mtx); | |
1902 | mutex_lock(&epmutex); | |
1903 | if (is_file_epoll(tf.file)) { | |
1904 | error = -ELOOP; | |
1905 | if (ep_loop_check(ep, tf.file) != 0) { | |
1906 | clear_tfile_check_list(); | |
1907 | goto error_tgt_fput; | |
1908 | } | |
1909 | } else | |
1910 | list_add(&tf.file->f_tfile_llink, | |
1911 | &tfile_check_list); | |
1912 | mutex_lock_nested(&ep->mtx, 0); | |
1913 | if (is_file_epoll(tf.file)) { | |
1914 | tep = tf.file->private_data; | |
1915 | mutex_lock_nested(&tep->mtx, 1); | |
13d51807 | 1916 | } |
67347fe4 JB |
1917 | } |
1918 | } | |
7699acd1 | 1919 | |
67647d0f DL |
1920 | /* |
1921 | * Try to lookup the file inside our RB tree, Since we grabbed "mtx" | |
1922 | * above, we can be sure to be able to use the item looked up by | |
1923 | * ep_find() till we release the mutex. | |
1924 | */ | |
7e3fb584 | 1925 | epi = ep_find(ep, tf.file, fd); |
7699acd1 DL |
1926 | |
1927 | error = -EINVAL; | |
1928 | switch (op) { | |
1929 | case EPOLL_CTL_ADD: | |
1930 | if (!epi) { | |
1931 | epds.events |= POLLERR | POLLHUP; | |
67347fe4 | 1932 | error = ep_insert(ep, &epds, tf.file, fd, full_check); |
7699acd1 DL |
1933 | } else |
1934 | error = -EEXIST; | |
67347fe4 JB |
1935 | if (full_check) |
1936 | clear_tfile_check_list(); | |
7699acd1 DL |
1937 | break; |
1938 | case EPOLL_CTL_DEL: | |
1939 | if (epi) | |
1940 | error = ep_remove(ep, epi); | |
1941 | else | |
1942 | error = -ENOENT; | |
1943 | break; | |
1944 | case EPOLL_CTL_MOD: | |
1945 | if (epi) { | |
1946 | epds.events |= POLLERR | POLLHUP; | |
1947 | error = ep_modify(ep, epi, &epds); | |
1948 | } else | |
1949 | error = -ENOENT; | |
1950 | break; | |
1951 | } | |
67347fe4 JB |
1952 | if (tep != NULL) |
1953 | mutex_unlock(&tep->mtx); | |
d47de16c | 1954 | mutex_unlock(&ep->mtx); |
7699acd1 DL |
1955 | |
1956 | error_tgt_fput: | |
67347fe4 | 1957 | if (full_check) |
22bacca4 DL |
1958 | mutex_unlock(&epmutex); |
1959 | ||
7e3fb584 | 1960 | fdput(tf); |
7699acd1 | 1961 | error_fput: |
7e3fb584 | 1962 | fdput(f); |
7699acd1 | 1963 | error_return: |
7699acd1 DL |
1964 | |
1965 | return error; | |
1966 | } | |
1967 | ||
1968 | /* | |
1969 | * Implement the event wait interface for the eventpoll file. It is the kernel | |
1970 | * part of the user space epoll_wait(2). | |
1971 | */ | |
5a8a82b1 HC |
1972 | SYSCALL_DEFINE4(epoll_wait, int, epfd, struct epoll_event __user *, events, |
1973 | int, maxevents, int, timeout) | |
7699acd1 | 1974 | { |
2903ff01 AV |
1975 | int error; |
1976 | struct fd f; | |
7699acd1 DL |
1977 | struct eventpoll *ep; |
1978 | ||
7699acd1 DL |
1979 | /* The maximum number of event must be greater than zero */ |
1980 | if (maxevents <= 0 || maxevents > EP_MAX_EVENTS) | |
1981 | return -EINVAL; | |
1982 | ||
1983 | /* Verify that the area passed by the user is writeable */ | |
2903ff01 AV |
1984 | if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event))) |
1985 | return -EFAULT; | |
7699acd1 DL |
1986 | |
1987 | /* Get the "struct file *" for the eventpoll file */ | |
2903ff01 AV |
1988 | f = fdget(epfd); |
1989 | if (!f.file) | |
1990 | return -EBADF; | |
7699acd1 DL |
1991 | |
1992 | /* | |
1993 | * We have to check that the file structure underneath the fd | |
1994 | * the user passed to us _is_ an eventpoll file. | |
1995 | */ | |
1996 | error = -EINVAL; | |
2903ff01 | 1997 | if (!is_file_epoll(f.file)) |
7699acd1 DL |
1998 | goto error_fput; |
1999 | ||
2000 | /* | |
2001 | * At this point it is safe to assume that the "private_data" contains | |
2002 | * our own data structure. | |
2003 | */ | |
2903ff01 | 2004 | ep = f.file->private_data; |
7699acd1 DL |
2005 | |
2006 | /* Time to fish for events ... */ | |
2007 | error = ep_poll(ep, events, maxevents, timeout); | |
2008 | ||
2009 | error_fput: | |
2903ff01 | 2010 | fdput(f); |
7699acd1 DL |
2011 | return error; |
2012 | } | |
2013 | ||
7699acd1 DL |
2014 | /* |
2015 | * Implement the event wait interface for the eventpoll file. It is the kernel | |
2016 | * part of the user space epoll_pwait(2). | |
2017 | */ | |
5a8a82b1 HC |
2018 | SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events, |
2019 | int, maxevents, int, timeout, const sigset_t __user *, sigmask, | |
2020 | size_t, sigsetsize) | |
7699acd1 DL |
2021 | { |
2022 | int error; | |
2023 | sigset_t ksigmask, sigsaved; | |
2024 | ||
2025 | /* | |
2026 | * If the caller wants a certain signal mask to be set during the wait, | |
2027 | * we apply it here. | |
2028 | */ | |
2029 | if (sigmask) { | |
2030 | if (sigsetsize != sizeof(sigset_t)) | |
2031 | return -EINVAL; | |
2032 | if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) | |
2033 | return -EFAULT; | |
77d55918 ON |
2034 | sigsaved = current->blocked; |
2035 | set_current_blocked(&ksigmask); | |
7699acd1 DL |
2036 | } |
2037 | ||
2038 | error = sys_epoll_wait(epfd, events, maxevents, timeout); | |
2039 | ||
2040 | /* | |
2041 | * If we changed the signal mask, we need to restore the original one. | |
2042 | * In case we've got a signal while waiting, we do not restore the | |
2043 | * signal mask yet, and we allow do_signal() to deliver the signal on | |
2044 | * the way back to userspace, before the signal mask is restored. | |
2045 | */ | |
2046 | if (sigmask) { | |
2047 | if (error == -EINTR) { | |
2048 | memcpy(¤t->saved_sigmask, &sigsaved, | |
c7ea7630 | 2049 | sizeof(sigsaved)); |
4e4c22c7 | 2050 | set_restore_sigmask(); |
7699acd1 | 2051 | } else |
77d55918 | 2052 | set_current_blocked(&sigsaved); |
7699acd1 DL |
2053 | } |
2054 | ||
2055 | return error; | |
2056 | } | |
2057 | ||
35280bd4 AV |
2058 | #ifdef CONFIG_COMPAT |
2059 | COMPAT_SYSCALL_DEFINE6(epoll_pwait, int, epfd, | |
2060 | struct epoll_event __user *, events, | |
2061 | int, maxevents, int, timeout, | |
2062 | const compat_sigset_t __user *, sigmask, | |
2063 | compat_size_t, sigsetsize) | |
2064 | { | |
2065 | long err; | |
2066 | compat_sigset_t csigmask; | |
2067 | sigset_t ksigmask, sigsaved; | |
2068 | ||
2069 | /* | |
2070 | * If the caller wants a certain signal mask to be set during the wait, | |
2071 | * we apply it here. | |
2072 | */ | |
2073 | if (sigmask) { | |
2074 | if (sigsetsize != sizeof(compat_sigset_t)) | |
2075 | return -EINVAL; | |
2076 | if (copy_from_user(&csigmask, sigmask, sizeof(csigmask))) | |
2077 | return -EFAULT; | |
2078 | sigset_from_compat(&ksigmask, &csigmask); | |
77d55918 ON |
2079 | sigsaved = current->blocked; |
2080 | set_current_blocked(&ksigmask); | |
35280bd4 AV |
2081 | } |
2082 | ||
2083 | err = sys_epoll_wait(epfd, events, maxevents, timeout); | |
2084 | ||
2085 | /* | |
2086 | * If we changed the signal mask, we need to restore the original one. | |
2087 | * In case we've got a signal while waiting, we do not restore the | |
2088 | * signal mask yet, and we allow do_signal() to deliver the signal on | |
2089 | * the way back to userspace, before the signal mask is restored. | |
2090 | */ | |
2091 | if (sigmask) { | |
2092 | if (err == -EINTR) { | |
2093 | memcpy(¤t->saved_sigmask, &sigsaved, | |
2094 | sizeof(sigsaved)); | |
2095 | set_restore_sigmask(); | |
2096 | } else | |
77d55918 | 2097 | set_current_blocked(&sigsaved); |
35280bd4 AV |
2098 | } |
2099 | ||
2100 | return err; | |
2101 | } | |
2102 | #endif | |
2103 | ||
1da177e4 LT |
2104 | static int __init eventpoll_init(void) |
2105 | { | |
7ef9964e DL |
2106 | struct sysinfo si; |
2107 | ||
2108 | si_meminfo(&si); | |
9df04e1f DL |
2109 | /* |
2110 | * Allows top 4% of lomem to be allocated for epoll watches (per user). | |
2111 | */ | |
2112 | max_user_watches = (((si.totalram - si.totalhigh) / 25) << PAGE_SHIFT) / | |
7ef9964e | 2113 | EP_ITEM_COST; |
52bd19f7 | 2114 | BUG_ON(max_user_watches < 0); |
1da177e4 | 2115 | |
22bacca4 DL |
2116 | /* |
2117 | * Initialize the structure used to perform epoll file descriptor | |
2118 | * inclusion loops checks. | |
2119 | */ | |
2120 | ep_nested_calls_init(&poll_loop_ncalls); | |
2121 | ||
1da177e4 | 2122 | /* Initialize the structure used to perform safe poll wait head wake ups */ |
5071f97e DL |
2123 | ep_nested_calls_init(&poll_safewake_ncalls); |
2124 | ||
2125 | /* Initialize the structure used to perform file's f_op->poll() calls */ | |
2126 | ep_nested_calls_init(&poll_readywalk_ncalls); | |
1da177e4 | 2127 | |
39732ca5 EW |
2128 | /* |
2129 | * We can have many thousands of epitems, so prevent this from | |
2130 | * using an extra cache line on 64-bit (and smaller) CPUs | |
2131 | */ | |
2132 | BUILD_BUG_ON(sizeof(void *) <= 8 && sizeof(struct epitem) > 128); | |
2133 | ||
1da177e4 LT |
2134 | /* Allocates slab cache used to allocate "struct epitem" items */ |
2135 | epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem), | |
bb57c3ed | 2136 | 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); |
1da177e4 LT |
2137 | |
2138 | /* Allocates slab cache used to allocate "struct eppoll_entry" */ | |
2139 | pwq_cache = kmem_cache_create("eventpoll_pwq", | |
bb57c3ed | 2140 | sizeof(struct eppoll_entry), 0, SLAB_PANIC, NULL); |
1da177e4 | 2141 | |
1da177e4 | 2142 | return 0; |
1da177e4 | 2143 | } |
cea69241 | 2144 | fs_initcall(eventpoll_init); |