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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> | |
174cd4b1 | 16 | #include <linux/sched/signal.h> |
1da177e4 LT |
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> |
7c0f6ba6 | 37 | #include <linux/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> |
bf3b9f63 | 45 | #include <net/busy_poll.h> |
1da177e4 | 46 | |
1da177e4 LT |
47 | /* |
48 | * LOCKING: | |
49 | * There are three level of locking required by epoll : | |
50 | * | |
144efe3e | 51 | * 1) epmutex (mutex) |
c7ea7630 | 52 | * 2) ep->mtx (mutex) |
ee8ef0a4 | 53 | * 3) ep->wq.lock (spinlock) |
1da177e4 LT |
54 | * |
55 | * The acquire order is the one listed above, from 1 to 3. | |
ee8ef0a4 | 56 | * We need a spinlock (ep->wq.lock) because we manipulate objects |
1da177e4 LT |
57 | * from inside the poll callback, that might be triggered from |
58 | * a wake_up() that in turn might be called from IRQ context. | |
59 | * So we can't sleep inside the poll callback and hence we need | |
60 | * a spinlock. During the event transfer loop (from kernel to | |
61 | * user space) we could end up sleeping due a copy_to_user(), so | |
62 | * we need a lock that will allow us to sleep. This lock is a | |
d47de16c DL |
63 | * mutex (ep->mtx). It is acquired during the event transfer loop, |
64 | * during epoll_ctl(EPOLL_CTL_DEL) and during eventpoll_release_file(). | |
65 | * Then we also need a global mutex to serialize eventpoll_release_file() | |
66 | * and ep_free(). | |
67 | * This mutex is acquired by ep_free() during the epoll file | |
1da177e4 LT |
68 | * cleanup path and it is also acquired by eventpoll_release_file() |
69 | * if a file has been pushed inside an epoll set and it is then | |
bf6a41db | 70 | * close()d without a previous call to epoll_ctl(EPOLL_CTL_DEL). |
22bacca4 DL |
71 | * It is also acquired when inserting an epoll fd onto another epoll |
72 | * fd. We do this so that we walk the epoll tree and ensure that this | |
73 | * insertion does not create a cycle of epoll file descriptors, which | |
74 | * could lead to deadlock. We need a global mutex to prevent two | |
75 | * simultaneous inserts (A into B and B into A) from racing and | |
76 | * constructing a cycle without either insert observing that it is | |
77 | * going to. | |
d8805e63 NE |
78 | * It is necessary to acquire multiple "ep->mtx"es at once in the |
79 | * case when one epoll fd is added to another. In this case, we | |
80 | * always acquire the locks in the order of nesting (i.e. after | |
81 | * epoll_ctl(e1, EPOLL_CTL_ADD, e2), e1->mtx will always be acquired | |
82 | * before e2->mtx). Since we disallow cycles of epoll file | |
83 | * descriptors, this ensures that the mutexes are well-ordered. In | |
84 | * order to communicate this nesting to lockdep, when walking a tree | |
85 | * of epoll file descriptors, we use the current recursion depth as | |
86 | * the lockdep subkey. | |
d47de16c | 87 | * It is possible to drop the "ep->mtx" and to use the global |
ee8ef0a4 | 88 | * mutex "epmutex" (together with "ep->wq.lock") to have it working, |
d47de16c | 89 | * but having "ep->mtx" will make the interface more scalable. |
144efe3e | 90 | * Events that require holding "epmutex" are very rare, while for |
d47de16c DL |
91 | * normal operations the epoll private "ep->mtx" will guarantee |
92 | * a better scalability. | |
1da177e4 LT |
93 | */ |
94 | ||
1da177e4 | 95 | /* Epoll private bits inside the event mask */ |
df0108c5 | 96 | #define EP_PRIVATE_BITS (EPOLLWAKEUP | EPOLLONESHOT | EPOLLET | EPOLLEXCLUSIVE) |
1da177e4 | 97 | |
a9a08845 | 98 | #define EPOLLINOUT_BITS (EPOLLIN | EPOLLOUT) |
b6a515c8 | 99 | |
a9a08845 | 100 | #define EPOLLEXCLUSIVE_OK_BITS (EPOLLINOUT_BITS | EPOLLERR | EPOLLHUP | \ |
b6a515c8 JB |
101 | EPOLLWAKEUP | EPOLLET | EPOLLEXCLUSIVE) |
102 | ||
5071f97e DL |
103 | /* Maximum number of nesting allowed inside epoll sets */ |
104 | #define EP_MAX_NESTS 4 | |
1da177e4 | 105 | |
b611967d DL |
106 | #define EP_MAX_EVENTS (INT_MAX / sizeof(struct epoll_event)) |
107 | ||
d47de16c DL |
108 | #define EP_UNACTIVE_PTR ((void *) -1L) |
109 | ||
7ef9964e DL |
110 | #define EP_ITEM_COST (sizeof(struct epitem) + sizeof(struct eppoll_entry)) |
111 | ||
1da177e4 LT |
112 | struct epoll_filefd { |
113 | struct file *file; | |
114 | int fd; | |
39732ca5 | 115 | } __packed; |
1da177e4 LT |
116 | |
117 | /* | |
5071f97e DL |
118 | * Structure used to track possible nested calls, for too deep recursions |
119 | * and loop cycles. | |
1da177e4 | 120 | */ |
5071f97e | 121 | struct nested_call_node { |
1da177e4 | 122 | struct list_head llink; |
5071f97e | 123 | void *cookie; |
3fe4a975 | 124 | void *ctx; |
1da177e4 LT |
125 | }; |
126 | ||
127 | /* | |
5071f97e DL |
128 | * This structure is used as collector for nested calls, to check for |
129 | * maximum recursion dept and loop cycles. | |
1da177e4 | 130 | */ |
5071f97e DL |
131 | struct nested_calls { |
132 | struct list_head tasks_call_list; | |
1da177e4 LT |
133 | spinlock_t lock; |
134 | }; | |
135 | ||
d47de16c DL |
136 | /* |
137 | * Each file descriptor added to the eventpoll interface will | |
138 | * have an entry of this type linked to the "rbr" RB tree. | |
39732ca5 EW |
139 | * Avoid increasing the size of this struct, there can be many thousands |
140 | * of these on a server and we do not want this to take another cache line. | |
d47de16c DL |
141 | */ |
142 | struct epitem { | |
ae10b2b4 JB |
143 | union { |
144 | /* RB tree node links this structure to the eventpoll RB tree */ | |
145 | struct rb_node rbn; | |
146 | /* Used to free the struct epitem */ | |
147 | struct rcu_head rcu; | |
148 | }; | |
d47de16c DL |
149 | |
150 | /* List header used to link this structure to the eventpoll ready list */ | |
151 | struct list_head rdllink; | |
152 | ||
c7ea7630 DL |
153 | /* |
154 | * Works together "struct eventpoll"->ovflist in keeping the | |
155 | * single linked chain of items. | |
156 | */ | |
157 | struct epitem *next; | |
158 | ||
d47de16c DL |
159 | /* The file descriptor information this item refers to */ |
160 | struct epoll_filefd ffd; | |
161 | ||
162 | /* Number of active wait queue attached to poll operations */ | |
163 | int nwait; | |
164 | ||
165 | /* List containing poll wait queues */ | |
166 | struct list_head pwqlist; | |
167 | ||
168 | /* The "container" of this item */ | |
169 | struct eventpoll *ep; | |
170 | ||
d47de16c DL |
171 | /* List header used to link this item to the "struct file" items list */ |
172 | struct list_head fllink; | |
173 | ||
4d7e30d9 | 174 | /* wakeup_source used when EPOLLWAKEUP is set */ |
eea1d585 | 175 | struct wakeup_source __rcu *ws; |
4d7e30d9 | 176 | |
c7ea7630 DL |
177 | /* The structure that describe the interested events and the source fd */ |
178 | struct epoll_event event; | |
d47de16c DL |
179 | }; |
180 | ||
1da177e4 LT |
181 | /* |
182 | * This structure is stored inside the "private_data" member of the file | |
bf6a41db | 183 | * structure and represents the main data structure for the eventpoll |
1da177e4 | 184 | * interface. |
ee8ef0a4 CH |
185 | * |
186 | * Access to it is protected by the lock inside wq. | |
1da177e4 LT |
187 | */ |
188 | struct eventpoll { | |
1da177e4 | 189 | /* |
d47de16c DL |
190 | * This mutex is used to ensure that files are not removed |
191 | * while epoll is using them. This is held during the event | |
192 | * collection loop, the file cleanup path, the epoll file exit | |
193 | * code and the ctl operations. | |
1da177e4 | 194 | */ |
d47de16c | 195 | struct mutex mtx; |
1da177e4 LT |
196 | |
197 | /* Wait queue used by sys_epoll_wait() */ | |
198 | wait_queue_head_t wq; | |
199 | ||
200 | /* Wait queue used by file->poll() */ | |
201 | wait_queue_head_t poll_wait; | |
202 | ||
203 | /* List of ready file descriptors */ | |
204 | struct list_head rdllist; | |
205 | ||
67647d0f | 206 | /* RB tree root used to store monitored fd structs */ |
b2ac2ea6 | 207 | struct rb_root_cached rbr; |
d47de16c DL |
208 | |
209 | /* | |
210 | * This is a single linked list that chains all the "struct epitem" that | |
25985edc | 211 | * happened while transferring ready events to userspace w/out |
ee8ef0a4 | 212 | * holding ->wq.lock. |
d47de16c DL |
213 | */ |
214 | struct epitem *ovflist; | |
7ef9964e | 215 | |
4d7e30d9 AH |
216 | /* wakeup_source used when ep_scan_ready_list is running */ |
217 | struct wakeup_source *ws; | |
218 | ||
7ef9964e DL |
219 | /* The user that created the eventpoll descriptor */ |
220 | struct user_struct *user; | |
28d82dc1 JB |
221 | |
222 | struct file *file; | |
223 | ||
224 | /* used to optimize loop detection check */ | |
225 | int visited; | |
226 | struct list_head visited_list_link; | |
bf3b9f63 SS |
227 | |
228 | #ifdef CONFIG_NET_RX_BUSY_POLL | |
229 | /* used to track busy poll napi_id */ | |
230 | unsigned int napi_id; | |
231 | #endif | |
1da177e4 LT |
232 | }; |
233 | ||
234 | /* Wait structure used by the poll hooks */ | |
235 | struct eppoll_entry { | |
236 | /* List header used to link this structure to the "struct epitem" */ | |
237 | struct list_head llink; | |
238 | ||
239 | /* The "base" pointer is set to the container "struct epitem" */ | |
4f0989db | 240 | struct epitem *base; |
1da177e4 LT |
241 | |
242 | /* | |
243 | * Wait queue item that will be linked to the target file wait | |
244 | * queue head. | |
245 | */ | |
ac6424b9 | 246 | wait_queue_entry_t wait; |
1da177e4 LT |
247 | |
248 | /* The wait queue head that linked the "wait" wait queue item */ | |
249 | wait_queue_head_t *whead; | |
250 | }; | |
251 | ||
1da177e4 LT |
252 | /* Wrapper struct used by poll queueing */ |
253 | struct ep_pqueue { | |
254 | poll_table pt; | |
255 | struct epitem *epi; | |
256 | }; | |
257 | ||
5071f97e DL |
258 | /* Used by the ep_send_events() function as callback private data */ |
259 | struct ep_send_events_data { | |
260 | int maxevents; | |
261 | struct epoll_event __user *events; | |
d7ebbe46 | 262 | int res; |
5071f97e DL |
263 | }; |
264 | ||
7ef9964e DL |
265 | /* |
266 | * Configuration options available inside /proc/sys/fs/epoll/ | |
267 | */ | |
7ef9964e | 268 | /* Maximum number of epoll watched descriptors, per user */ |
52bd19f7 | 269 | static long max_user_watches __read_mostly; |
7ef9964e | 270 | |
1da177e4 | 271 | /* |
d47de16c | 272 | * This mutex is used to serialize ep_free() and eventpoll_release_file(). |
1da177e4 | 273 | */ |
7ef9964e | 274 | static DEFINE_MUTEX(epmutex); |
1da177e4 | 275 | |
22bacca4 DL |
276 | /* Used to check for epoll file descriptor inclusion loops */ |
277 | static struct nested_calls poll_loop_ncalls; | |
278 | ||
1da177e4 | 279 | /* Slab cache used to allocate "struct epitem" */ |
e18b890b | 280 | static struct kmem_cache *epi_cache __read_mostly; |
1da177e4 LT |
281 | |
282 | /* Slab cache used to allocate "struct eppoll_entry" */ | |
e18b890b | 283 | static struct kmem_cache *pwq_cache __read_mostly; |
1da177e4 | 284 | |
28d82dc1 JB |
285 | /* Visited nodes during ep_loop_check(), so we can unset them when we finish */ |
286 | static LIST_HEAD(visited_list); | |
287 | ||
288 | /* | |
289 | * List of files with newly added links, where we may need to limit the number | |
290 | * of emanating paths. Protected by the epmutex. | |
291 | */ | |
292 | static LIST_HEAD(tfile_check_list); | |
293 | ||
7ef9964e DL |
294 | #ifdef CONFIG_SYSCTL |
295 | ||
296 | #include <linux/sysctl.h> | |
297 | ||
52bd19f7 RH |
298 | static long zero; |
299 | static long long_max = LONG_MAX; | |
7ef9964e | 300 | |
1f7e0616 | 301 | struct ctl_table epoll_table[] = { |
7ef9964e DL |
302 | { |
303 | .procname = "max_user_watches", | |
304 | .data = &max_user_watches, | |
52bd19f7 | 305 | .maxlen = sizeof(max_user_watches), |
7ef9964e | 306 | .mode = 0644, |
52bd19f7 | 307 | .proc_handler = proc_doulongvec_minmax, |
7ef9964e | 308 | .extra1 = &zero, |
52bd19f7 | 309 | .extra2 = &long_max, |
7ef9964e | 310 | }, |
ab09203e | 311 | { } |
7ef9964e DL |
312 | }; |
313 | #endif /* CONFIG_SYSCTL */ | |
314 | ||
28d82dc1 JB |
315 | static const struct file_operations eventpoll_fops; |
316 | ||
317 | static inline int is_file_epoll(struct file *f) | |
318 | { | |
319 | return f->f_op == &eventpoll_fops; | |
320 | } | |
b030a4dd | 321 | |
67647d0f | 322 | /* Setup the structure that is used as key for the RB tree */ |
b030a4dd PE |
323 | static inline void ep_set_ffd(struct epoll_filefd *ffd, |
324 | struct file *file, int fd) | |
325 | { | |
326 | ffd->file = file; | |
327 | ffd->fd = fd; | |
328 | } | |
329 | ||
67647d0f | 330 | /* Compare RB tree keys */ |
b030a4dd PE |
331 | static inline int ep_cmp_ffd(struct epoll_filefd *p1, |
332 | struct epoll_filefd *p2) | |
333 | { | |
334 | return (p1->file > p2->file ? +1: | |
335 | (p1->file < p2->file ? -1 : p1->fd - p2->fd)); | |
336 | } | |
337 | ||
b030a4dd | 338 | /* Tells us if the item is currently linked */ |
992991c0 | 339 | static inline int ep_is_linked(struct epitem *epi) |
b030a4dd | 340 | { |
992991c0 | 341 | return !list_empty(&epi->rdllink); |
b030a4dd PE |
342 | } |
343 | ||
ac6424b9 | 344 | static inline struct eppoll_entry *ep_pwq_from_wait(wait_queue_entry_t *p) |
971316f0 ON |
345 | { |
346 | return container_of(p, struct eppoll_entry, wait); | |
347 | } | |
348 | ||
b030a4dd | 349 | /* Get the "struct epitem" from a wait queue pointer */ |
ac6424b9 | 350 | static inline struct epitem *ep_item_from_wait(wait_queue_entry_t *p) |
b030a4dd PE |
351 | { |
352 | return container_of(p, struct eppoll_entry, wait)->base; | |
353 | } | |
354 | ||
355 | /* Get the "struct epitem" from an epoll queue wrapper */ | |
cdac75e6 | 356 | static inline struct epitem *ep_item_from_epqueue(poll_table *p) |
b030a4dd PE |
357 | { |
358 | return container_of(p, struct ep_pqueue, pt)->epi; | |
359 | } | |
360 | ||
361 | /* Tells if the epoll_ctl(2) operation needs an event copy from userspace */ | |
6192bd53 | 362 | static inline int ep_op_has_event(int op) |
b030a4dd | 363 | { |
a80a6b85 | 364 | return op != EPOLL_CTL_DEL; |
b030a4dd PE |
365 | } |
366 | ||
1da177e4 | 367 | /* Initialize the poll safe wake up structure */ |
5071f97e | 368 | static void ep_nested_calls_init(struct nested_calls *ncalls) |
1da177e4 | 369 | { |
5071f97e DL |
370 | INIT_LIST_HEAD(&ncalls->tasks_call_list); |
371 | spin_lock_init(&ncalls->lock); | |
1da177e4 LT |
372 | } |
373 | ||
3fb0e584 DL |
374 | /** |
375 | * ep_events_available - Checks if ready events might be available. | |
376 | * | |
377 | * @ep: Pointer to the eventpoll context. | |
378 | * | |
379 | * Returns: Returns a value different than zero if ready events are available, | |
380 | * or zero otherwise. | |
381 | */ | |
382 | static inline int ep_events_available(struct eventpoll *ep) | |
383 | { | |
384 | return !list_empty(&ep->rdllist) || ep->ovflist != EP_UNACTIVE_PTR; | |
385 | } | |
386 | ||
bf3b9f63 SS |
387 | #ifdef CONFIG_NET_RX_BUSY_POLL |
388 | static bool ep_busy_loop_end(void *p, unsigned long start_time) | |
389 | { | |
390 | struct eventpoll *ep = p; | |
391 | ||
392 | return ep_events_available(ep) || busy_loop_timeout(start_time); | |
393 | } | |
bf3b9f63 SS |
394 | |
395 | /* | |
396 | * Busy poll if globally on and supporting sockets found && no events, | |
397 | * busy loop will return if need_resched or ep_events_available. | |
398 | * | |
399 | * we must do our busy polling with irqs enabled | |
400 | */ | |
401 | static void ep_busy_loop(struct eventpoll *ep, int nonblock) | |
402 | { | |
bf3b9f63 SS |
403 | unsigned int napi_id = READ_ONCE(ep->napi_id); |
404 | ||
405 | if ((napi_id >= MIN_NAPI_ID) && net_busy_loop_on()) | |
406 | napi_busy_loop(napi_id, nonblock ? NULL : ep_busy_loop_end, ep); | |
bf3b9f63 SS |
407 | } |
408 | ||
409 | static inline void ep_reset_busy_poll_napi_id(struct eventpoll *ep) | |
410 | { | |
bf3b9f63 SS |
411 | if (ep->napi_id) |
412 | ep->napi_id = 0; | |
bf3b9f63 SS |
413 | } |
414 | ||
415 | /* | |
416 | * Set epoll busy poll NAPI ID from sk. | |
417 | */ | |
418 | static inline void ep_set_busy_poll_napi_id(struct epitem *epi) | |
419 | { | |
bf3b9f63 SS |
420 | struct eventpoll *ep; |
421 | unsigned int napi_id; | |
422 | struct socket *sock; | |
423 | struct sock *sk; | |
424 | int err; | |
425 | ||
426 | if (!net_busy_loop_on()) | |
427 | return; | |
428 | ||
429 | sock = sock_from_file(epi->ffd.file, &err); | |
430 | if (!sock) | |
431 | return; | |
432 | ||
433 | sk = sock->sk; | |
434 | if (!sk) | |
435 | return; | |
436 | ||
437 | napi_id = READ_ONCE(sk->sk_napi_id); | |
438 | ep = epi->ep; | |
439 | ||
440 | /* Non-NAPI IDs can be rejected | |
441 | * or | |
442 | * Nothing to do if we already have this ID | |
443 | */ | |
444 | if (napi_id < MIN_NAPI_ID || napi_id == ep->napi_id) | |
445 | return; | |
446 | ||
447 | /* record NAPI ID for use in next busy poll */ | |
448 | ep->napi_id = napi_id; | |
bf3b9f63 SS |
449 | } |
450 | ||
514056d5 DB |
451 | #else |
452 | ||
453 | static inline void ep_busy_loop(struct eventpoll *ep, int nonblock) | |
454 | { | |
455 | } | |
456 | ||
457 | static inline void ep_reset_busy_poll_napi_id(struct eventpoll *ep) | |
458 | { | |
459 | } | |
460 | ||
461 | static inline void ep_set_busy_poll_napi_id(struct epitem *epi) | |
462 | { | |
463 | } | |
464 | ||
465 | #endif /* CONFIG_NET_RX_BUSY_POLL */ | |
466 | ||
5071f97e DL |
467 | /** |
468 | * ep_call_nested - Perform a bound (possibly) nested call, by checking | |
469 | * that the recursion limit is not exceeded, and that | |
470 | * the same nested call (by the meaning of same cookie) is | |
471 | * no re-entered. | |
472 | * | |
473 | * @ncalls: Pointer to the nested_calls structure to be used for this call. | |
5071f97e DL |
474 | * @nproc: Nested call core function pointer. |
475 | * @priv: Opaque data to be passed to the @nproc callback. | |
476 | * @cookie: Cookie to be used to identify this nested call. | |
3fe4a975 | 477 | * @ctx: This instance context. |
5071f97e DL |
478 | * |
479 | * Returns: Returns the code returned by the @nproc callback, or -1 if | |
480 | * the maximum recursion limit has been exceeded. | |
1da177e4 | 481 | */ |
74bdc129 | 482 | static int ep_call_nested(struct nested_calls *ncalls, |
5071f97e | 483 | int (*nproc)(void *, void *, int), void *priv, |
3fe4a975 | 484 | void *cookie, void *ctx) |
1da177e4 | 485 | { |
5071f97e | 486 | int error, call_nests = 0; |
1da177e4 | 487 | unsigned long flags; |
5071f97e DL |
488 | struct list_head *lsthead = &ncalls->tasks_call_list; |
489 | struct nested_call_node *tncur; | |
490 | struct nested_call_node tnode; | |
1da177e4 | 491 | |
5071f97e | 492 | spin_lock_irqsave(&ncalls->lock, flags); |
1da177e4 | 493 | |
5071f97e DL |
494 | /* |
495 | * Try to see if the current task is already inside this wakeup call. | |
496 | * We use a list here, since the population inside this set is always | |
497 | * very much limited. | |
498 | */ | |
b70c3940 | 499 | list_for_each_entry(tncur, lsthead, llink) { |
3fe4a975 | 500 | if (tncur->ctx == ctx && |
74bdc129 | 501 | (tncur->cookie == cookie || ++call_nests > EP_MAX_NESTS)) { |
1da177e4 LT |
502 | /* |
503 | * Ops ... loop detected or maximum nest level reached. | |
504 | * We abort this wake by breaking the cycle itself. | |
505 | */ | |
abff55ce TB |
506 | error = -1; |
507 | goto out_unlock; | |
1da177e4 LT |
508 | } |
509 | } | |
510 | ||
5071f97e | 511 | /* Add the current task and cookie to the list */ |
3fe4a975 | 512 | tnode.ctx = ctx; |
5071f97e | 513 | tnode.cookie = cookie; |
1da177e4 LT |
514 | list_add(&tnode.llink, lsthead); |
515 | ||
5071f97e | 516 | spin_unlock_irqrestore(&ncalls->lock, flags); |
1da177e4 | 517 | |
5071f97e DL |
518 | /* Call the nested function */ |
519 | error = (*nproc)(priv, cookie, call_nests); | |
1da177e4 LT |
520 | |
521 | /* Remove the current task from the list */ | |
5071f97e | 522 | spin_lock_irqsave(&ncalls->lock, flags); |
1da177e4 | 523 | list_del(&tnode.llink); |
3fe4a975 | 524 | out_unlock: |
5071f97e DL |
525 | spin_unlock_irqrestore(&ncalls->lock, flags); |
526 | ||
527 | return error; | |
528 | } | |
529 | ||
02edc6fc SR |
530 | /* |
531 | * As described in commit 0ccf831cb lockdep: annotate epoll | |
532 | * the use of wait queues used by epoll is done in a very controlled | |
533 | * manner. Wake ups can nest inside each other, but are never done | |
534 | * with the same locking. For example: | |
535 | * | |
536 | * dfd = socket(...); | |
537 | * efd1 = epoll_create(); | |
538 | * efd2 = epoll_create(); | |
539 | * epoll_ctl(efd1, EPOLL_CTL_ADD, dfd, ...); | |
540 | * epoll_ctl(efd2, EPOLL_CTL_ADD, efd1, ...); | |
541 | * | |
542 | * When a packet arrives to the device underneath "dfd", the net code will | |
543 | * issue a wake_up() on its poll wake list. Epoll (efd1) has installed a | |
544 | * callback wakeup entry on that queue, and the wake_up() performed by the | |
545 | * "dfd" net code will end up in ep_poll_callback(). At this point epoll | |
546 | * (efd1) notices that it may have some event ready, so it needs to wake up | |
547 | * the waiters on its poll wait list (efd2). So it calls ep_poll_safewake() | |
548 | * that ends up in another wake_up(), after having checked about the | |
549 | * recursion constraints. That are, no more than EP_MAX_POLLWAKE_NESTS, to | |
550 | * avoid stack blasting. | |
551 | * | |
552 | * When CONFIG_DEBUG_LOCK_ALLOC is enabled, make sure lockdep can handle | |
553 | * this special case of epoll. | |
554 | */ | |
2dfa4eea | 555 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
57a173bd JB |
556 | |
557 | static struct nested_calls poll_safewake_ncalls; | |
558 | ||
559 | static int ep_poll_wakeup_proc(void *priv, void *cookie, int call_nests) | |
2dfa4eea DL |
560 | { |
561 | unsigned long flags; | |
57a173bd | 562 | wait_queue_head_t *wqueue = (wait_queue_head_t *)cookie; |
2dfa4eea | 563 | |
57a173bd | 564 | spin_lock_irqsave_nested(&wqueue->lock, flags, call_nests + 1); |
a9a08845 | 565 | wake_up_locked_poll(wqueue, EPOLLIN); |
2dfa4eea | 566 | spin_unlock_irqrestore(&wqueue->lock, flags); |
2dfa4eea | 567 | |
5071f97e DL |
568 | return 0; |
569 | } | |
570 | ||
5071f97e DL |
571 | static void ep_poll_safewake(wait_queue_head_t *wq) |
572 | { | |
3fe4a975 DL |
573 | int this_cpu = get_cpu(); |
574 | ||
74bdc129 | 575 | ep_call_nested(&poll_safewake_ncalls, |
3fe4a975 DL |
576 | ep_poll_wakeup_proc, NULL, wq, (void *) (long) this_cpu); |
577 | ||
578 | put_cpu(); | |
1da177e4 LT |
579 | } |
580 | ||
57a173bd JB |
581 | #else |
582 | ||
583 | static void ep_poll_safewake(wait_queue_head_t *wq) | |
584 | { | |
a9a08845 | 585 | wake_up_poll(wq, EPOLLIN); |
57a173bd JB |
586 | } |
587 | ||
588 | #endif | |
589 | ||
971316f0 ON |
590 | static void ep_remove_wait_queue(struct eppoll_entry *pwq) |
591 | { | |
592 | wait_queue_head_t *whead; | |
593 | ||
594 | rcu_read_lock(); | |
138e4ad6 ON |
595 | /* |
596 | * If it is cleared by POLLFREE, it should be rcu-safe. | |
597 | * If we read NULL we need a barrier paired with | |
598 | * smp_store_release() in ep_poll_callback(), otherwise | |
599 | * we rely on whead->lock. | |
600 | */ | |
601 | whead = smp_load_acquire(&pwq->whead); | |
971316f0 ON |
602 | if (whead) |
603 | remove_wait_queue(whead, &pwq->wait); | |
604 | rcu_read_unlock(); | |
605 | } | |
606 | ||
1da177e4 | 607 | /* |
d1bc90dd TB |
608 | * This function unregisters poll callbacks from the associated file |
609 | * descriptor. Must be called with "mtx" held (or "epmutex" if called from | |
610 | * ep_free). | |
1da177e4 | 611 | */ |
7699acd1 | 612 | static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi) |
1da177e4 | 613 | { |
7699acd1 DL |
614 | struct list_head *lsthead = &epi->pwqlist; |
615 | struct eppoll_entry *pwq; | |
1da177e4 | 616 | |
d1bc90dd TB |
617 | while (!list_empty(lsthead)) { |
618 | pwq = list_first_entry(lsthead, struct eppoll_entry, llink); | |
1da177e4 | 619 | |
d1bc90dd | 620 | list_del(&pwq->llink); |
971316f0 | 621 | ep_remove_wait_queue(pwq); |
d1bc90dd | 622 | kmem_cache_free(pwq_cache, pwq); |
1da177e4 | 623 | } |
1da177e4 LT |
624 | } |
625 | ||
eea1d585 EW |
626 | /* call only when ep->mtx is held */ |
627 | static inline struct wakeup_source *ep_wakeup_source(struct epitem *epi) | |
628 | { | |
629 | return rcu_dereference_check(epi->ws, lockdep_is_held(&epi->ep->mtx)); | |
630 | } | |
631 | ||
632 | /* call only when ep->mtx is held */ | |
633 | static inline void ep_pm_stay_awake(struct epitem *epi) | |
634 | { | |
635 | struct wakeup_source *ws = ep_wakeup_source(epi); | |
636 | ||
637 | if (ws) | |
638 | __pm_stay_awake(ws); | |
639 | } | |
640 | ||
641 | static inline bool ep_has_wakeup_source(struct epitem *epi) | |
642 | { | |
643 | return rcu_access_pointer(epi->ws) ? true : false; | |
644 | } | |
645 | ||
646 | /* call when ep->mtx cannot be held (ep_poll_callback) */ | |
647 | static inline void ep_pm_stay_awake_rcu(struct epitem *epi) | |
648 | { | |
649 | struct wakeup_source *ws; | |
650 | ||
651 | rcu_read_lock(); | |
652 | ws = rcu_dereference(epi->ws); | |
653 | if (ws) | |
654 | __pm_stay_awake(ws); | |
655 | rcu_read_unlock(); | |
656 | } | |
657 | ||
5071f97e DL |
658 | /** |
659 | * ep_scan_ready_list - Scans the ready list in a way that makes possible for | |
660 | * the scan code, to call f_op->poll(). Also allows for | |
661 | * O(NumReady) performance. | |
662 | * | |
663 | * @ep: Pointer to the epoll private data structure. | |
664 | * @sproc: Pointer to the scan callback. | |
665 | * @priv: Private opaque data passed to the @sproc callback. | |
d8805e63 | 666 | * @depth: The current depth of recursive f_op->poll calls. |
67347fe4 | 667 | * @ep_locked: caller already holds ep->mtx |
5071f97e DL |
668 | * |
669 | * Returns: The same integer error code returned by the @sproc callback. | |
670 | */ | |
d85e2aa2 AV |
671 | static __poll_t ep_scan_ready_list(struct eventpoll *ep, |
672 | __poll_t (*sproc)(struct eventpoll *, | |
5071f97e | 673 | struct list_head *, void *), |
67347fe4 | 674 | void *priv, int depth, bool ep_locked) |
5071f97e | 675 | { |
d85e2aa2 AV |
676 | __poll_t res; |
677 | int pwake = 0; | |
5071f97e | 678 | struct epitem *epi, *nepi; |
296e236e | 679 | LIST_HEAD(txlist); |
5071f97e | 680 | |
92e64178 DB |
681 | lockdep_assert_irqs_enabled(); |
682 | ||
5071f97e DL |
683 | /* |
684 | * We need to lock this because we could be hit by | |
e057e15f | 685 | * eventpoll_release_file() and epoll_ctl(). |
5071f97e | 686 | */ |
67347fe4 JB |
687 | |
688 | if (!ep_locked) | |
689 | mutex_lock_nested(&ep->mtx, depth); | |
5071f97e DL |
690 | |
691 | /* | |
692 | * Steal the ready list, and re-init the original one to the | |
693 | * empty list. Also, set ep->ovflist to NULL so that events | |
694 | * happening while looping w/out locks, are not lost. We cannot | |
695 | * have the poll callback to queue directly on ep->rdllist, | |
696 | * because we want the "sproc" callback to be able to do it | |
697 | * in a lockless way. | |
698 | */ | |
002b3436 | 699 | spin_lock_irq(&ep->wq.lock); |
296e236e | 700 | list_splice_init(&ep->rdllist, &txlist); |
5071f97e | 701 | ep->ovflist = NULL; |
002b3436 | 702 | spin_unlock_irq(&ep->wq.lock); |
5071f97e DL |
703 | |
704 | /* | |
705 | * Now call the callback function. | |
706 | */ | |
d85e2aa2 | 707 | res = (*sproc)(ep, &txlist, priv); |
5071f97e | 708 | |
002b3436 | 709 | spin_lock_irq(&ep->wq.lock); |
5071f97e DL |
710 | /* |
711 | * During the time we spent inside the "sproc" callback, some | |
712 | * other events might have been queued by the poll callback. | |
713 | * We re-insert them inside the main ready-list here. | |
714 | */ | |
715 | for (nepi = ep->ovflist; (epi = nepi) != NULL; | |
716 | nepi = epi->next, epi->next = EP_UNACTIVE_PTR) { | |
717 | /* | |
718 | * We need to check if the item is already in the list. | |
719 | * During the "sproc" callback execution time, items are | |
720 | * queued into ->ovflist but the "txlist" might already | |
721 | * contain them, and the list_splice() below takes care of them. | |
722 | */ | |
992991c0 | 723 | if (!ep_is_linked(epi)) { |
5071f97e | 724 | list_add_tail(&epi->rdllink, &ep->rdllist); |
eea1d585 | 725 | ep_pm_stay_awake(epi); |
4d7e30d9 | 726 | } |
5071f97e DL |
727 | } |
728 | /* | |
729 | * We need to set back ep->ovflist to EP_UNACTIVE_PTR, so that after | |
730 | * releasing the lock, events will be queued in the normal way inside | |
731 | * ep->rdllist. | |
732 | */ | |
733 | ep->ovflist = EP_UNACTIVE_PTR; | |
734 | ||
735 | /* | |
736 | * Quickly re-inject items left on "txlist". | |
737 | */ | |
738 | list_splice(&txlist, &ep->rdllist); | |
4d7e30d9 | 739 | __pm_relax(ep->ws); |
5071f97e DL |
740 | |
741 | if (!list_empty(&ep->rdllist)) { | |
742 | /* | |
296e236e DL |
743 | * Wake up (if active) both the eventpoll wait list and |
744 | * the ->poll() wait list (delayed after we release the lock). | |
5071f97e DL |
745 | */ |
746 | if (waitqueue_active(&ep->wq)) | |
747 | wake_up_locked(&ep->wq); | |
748 | if (waitqueue_active(&ep->poll_wait)) | |
749 | pwake++; | |
750 | } | |
002b3436 | 751 | spin_unlock_irq(&ep->wq.lock); |
5071f97e | 752 | |
67347fe4 JB |
753 | if (!ep_locked) |
754 | mutex_unlock(&ep->mtx); | |
5071f97e DL |
755 | |
756 | /* We have to call this outside the lock */ | |
757 | if (pwake) | |
758 | ep_poll_safewake(&ep->poll_wait); | |
759 | ||
d85e2aa2 | 760 | return res; |
5071f97e DL |
761 | } |
762 | ||
ae10b2b4 JB |
763 | static void epi_rcu_free(struct rcu_head *head) |
764 | { | |
765 | struct epitem *epi = container_of(head, struct epitem, rcu); | |
766 | kmem_cache_free(epi_cache, epi); | |
767 | } | |
768 | ||
7699acd1 DL |
769 | /* |
770 | * Removes a "struct epitem" from the eventpoll RB tree and deallocates | |
c7ea7630 | 771 | * all the associated resources. Must be called with "mtx" held. |
7699acd1 DL |
772 | */ |
773 | static int ep_remove(struct eventpoll *ep, struct epitem *epi) | |
774 | { | |
7699acd1 | 775 | struct file *file = epi->ffd.file; |
1da177e4 | 776 | |
92e64178 DB |
777 | lockdep_assert_irqs_enabled(); |
778 | ||
1da177e4 | 779 | /* |
ee8ef0a4 | 780 | * Removes poll wait queue hooks. |
1da177e4 | 781 | */ |
7699acd1 | 782 | ep_unregister_pollwait(ep, epi); |
1da177e4 | 783 | |
7699acd1 | 784 | /* Remove the current item from the list of epoll hooks */ |
68499914 | 785 | spin_lock(&file->f_lock); |
ae10b2b4 | 786 | list_del_rcu(&epi->fllink); |
68499914 | 787 | spin_unlock(&file->f_lock); |
1da177e4 | 788 | |
b2ac2ea6 | 789 | rb_erase_cached(&epi->rbn, &ep->rbr); |
1da177e4 | 790 | |
304b18b8 | 791 | spin_lock_irq(&ep->wq.lock); |
992991c0 | 792 | if (ep_is_linked(epi)) |
c7ea7630 | 793 | list_del_init(&epi->rdllink); |
304b18b8 | 794 | spin_unlock_irq(&ep->wq.lock); |
1da177e4 | 795 | |
eea1d585 | 796 | wakeup_source_unregister(ep_wakeup_source(epi)); |
ae10b2b4 JB |
797 | /* |
798 | * At this point it is safe to free the eventpoll item. Use the union | |
799 | * field epi->rcu, since we are trying to minimize the size of | |
800 | * 'struct epitem'. The 'rbn' field is no longer in use. Protected by | |
801 | * ep->mtx. The rcu read side, reverse_path_check_proc(), does not make | |
802 | * use of the rbn field. | |
803 | */ | |
804 | call_rcu(&epi->rcu, epi_rcu_free); | |
1da177e4 | 805 | |
52bd19f7 | 806 | atomic_long_dec(&ep->user->epoll_watches); |
7ef9964e | 807 | |
c7ea7630 | 808 | return 0; |
1da177e4 LT |
809 | } |
810 | ||
7699acd1 | 811 | static void ep_free(struct eventpoll *ep) |
1da177e4 | 812 | { |
7699acd1 DL |
813 | struct rb_node *rbp; |
814 | struct epitem *epi; | |
1da177e4 | 815 | |
7699acd1 DL |
816 | /* We need to release all tasks waiting for these file */ |
817 | if (waitqueue_active(&ep->poll_wait)) | |
5071f97e | 818 | ep_poll_safewake(&ep->poll_wait); |
1da177e4 | 819 | |
7699acd1 DL |
820 | /* |
821 | * We need to lock this because we could be hit by | |
822 | * eventpoll_release_file() while we're freeing the "struct eventpoll". | |
d47de16c | 823 | * We do not need to hold "ep->mtx" here because the epoll file |
7699acd1 DL |
824 | * is on the way to be removed and no one has references to it |
825 | * anymore. The only hit might come from eventpoll_release_file() but | |
25985edc | 826 | * holding "epmutex" is sufficient here. |
7699acd1 DL |
827 | */ |
828 | mutex_lock(&epmutex); | |
1da177e4 LT |
829 | |
830 | /* | |
7699acd1 | 831 | * Walks through the whole tree by unregistering poll callbacks. |
1da177e4 | 832 | */ |
b2ac2ea6 | 833 | for (rbp = rb_first_cached(&ep->rbr); rbp; rbp = rb_next(rbp)) { |
7699acd1 DL |
834 | epi = rb_entry(rbp, struct epitem, rbn); |
835 | ||
836 | ep_unregister_pollwait(ep, epi); | |
91cf5ab6 | 837 | cond_resched(); |
7699acd1 | 838 | } |
1da177e4 LT |
839 | |
840 | /* | |
7699acd1 DL |
841 | * Walks through the whole tree by freeing each "struct epitem". At this |
842 | * point we are sure no poll callbacks will be lingering around, and also by | |
d47de16c | 843 | * holding "epmutex" we can be sure that no file cleanup code will hit |
ee8ef0a4 | 844 | * us during this operation. So we can avoid the lock on "ep->wq.lock". |
ddf676c3 EW |
845 | * We do not need to lock ep->mtx, either, we only do it to prevent |
846 | * a lockdep warning. | |
1da177e4 | 847 | */ |
ddf676c3 | 848 | mutex_lock(&ep->mtx); |
b2ac2ea6 | 849 | while ((rbp = rb_first_cached(&ep->rbr)) != NULL) { |
7699acd1 DL |
850 | epi = rb_entry(rbp, struct epitem, rbn); |
851 | ep_remove(ep, epi); | |
91cf5ab6 | 852 | cond_resched(); |
7699acd1 | 853 | } |
ddf676c3 | 854 | mutex_unlock(&ep->mtx); |
1da177e4 | 855 | |
7699acd1 | 856 | mutex_unlock(&epmutex); |
d47de16c | 857 | mutex_destroy(&ep->mtx); |
7ef9964e | 858 | free_uid(ep->user); |
4d7e30d9 | 859 | wakeup_source_unregister(ep->ws); |
f0ee9aab | 860 | kfree(ep); |
7699acd1 | 861 | } |
1da177e4 | 862 | |
7699acd1 DL |
863 | static int ep_eventpoll_release(struct inode *inode, struct file *file) |
864 | { | |
865 | struct eventpoll *ep = file->private_data; | |
1da177e4 | 866 | |
f0ee9aab | 867 | if (ep) |
7699acd1 | 868 | ep_free(ep); |
7699acd1 | 869 | |
7699acd1 | 870 | return 0; |
1da177e4 LT |
871 | } |
872 | ||
d85e2aa2 | 873 | static __poll_t ep_read_events_proc(struct eventpoll *ep, struct list_head *head, |
37b5e521 JB |
874 | void *priv); |
875 | static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, | |
876 | poll_table *pt); | |
877 | ||
878 | /* | |
879 | * Differs from ep_eventpoll_poll() in that internal callers already have | |
880 | * the ep->mtx so we need to start from depth=1, such that mutex_lock_nested() | |
881 | * is correctly annotated. | |
882 | */ | |
d85e2aa2 | 883 | static __poll_t ep_item_poll(const struct epitem *epi, poll_table *pt, |
bec1a502 | 884 | int depth) |
450d89ec | 885 | { |
37b5e521 JB |
886 | struct eventpoll *ep; |
887 | bool locked; | |
888 | ||
450d89ec | 889 | pt->_key = epi->event.events; |
37b5e521 | 890 | if (!is_file_epoll(epi->ffd.file)) |
9965ed17 | 891 | return vfs_poll(epi->ffd.file, pt) & epi->event.events; |
450d89ec | 892 | |
37b5e521 JB |
893 | ep = epi->ffd.file->private_data; |
894 | poll_wait(epi->ffd.file, &ep->poll_wait, pt); | |
895 | locked = pt && (pt->_qproc == ep_ptable_queue_proc); | |
450d89ec | 896 | |
37b5e521 JB |
897 | return ep_scan_ready_list(epi->ffd.file->private_data, |
898 | ep_read_events_proc, &depth, depth, | |
899 | locked) & epi->event.events; | |
450d89ec EW |
900 | } |
901 | ||
d85e2aa2 | 902 | static __poll_t ep_read_events_proc(struct eventpoll *ep, struct list_head *head, |
296e236e | 903 | void *priv) |
5071f97e DL |
904 | { |
905 | struct epitem *epi, *tmp; | |
626cf236 | 906 | poll_table pt; |
37b5e521 | 907 | int depth = *(int *)priv; |
5071f97e | 908 | |
626cf236 | 909 | init_poll_funcptr(&pt, NULL); |
37b5e521 | 910 | depth++; |
450d89ec | 911 | |
5071f97e | 912 | list_for_each_entry_safe(epi, tmp, head, rdllink) { |
37b5e521 | 913 | if (ep_item_poll(epi, &pt, depth)) { |
a9a08845 | 914 | return EPOLLIN | EPOLLRDNORM; |
37b5e521 | 915 | } else { |
5071f97e DL |
916 | /* |
917 | * Item has been dropped into the ready list by the poll | |
918 | * callback, but it's not actually ready, as far as | |
919 | * caller requested events goes. We can remove it here. | |
920 | */ | |
eea1d585 | 921 | __pm_relax(ep_wakeup_source(epi)); |
5071f97e | 922 | list_del_init(&epi->rdllink); |
296e236e | 923 | } |
5071f97e DL |
924 | } |
925 | ||
926 | return 0; | |
927 | } | |
928 | ||
a11e1d43 | 929 | static __poll_t ep_eventpoll_poll(struct file *file, poll_table *wait) |
11c5ad0e BN |
930 | { |
931 | struct eventpoll *ep = file->private_data; | |
932 | int depth = 0; | |
7699acd1 | 933 | |
a11e1d43 LT |
934 | /* Insert inside our poll wait queue */ |
935 | poll_wait(file, &ep->poll_wait, wait); | |
936 | ||
5071f97e DL |
937 | /* |
938 | * Proceed to find out if wanted events are really available inside | |
37b5e521 | 939 | * the ready list. |
5071f97e | 940 | */ |
37b5e521 JB |
941 | return ep_scan_ready_list(ep, ep_read_events_proc, |
942 | &depth, depth, false); | |
7699acd1 DL |
943 | } |
944 | ||
138d22b5 | 945 | #ifdef CONFIG_PROC_FS |
a3816ab0 | 946 | static void ep_show_fdinfo(struct seq_file *m, struct file *f) |
138d22b5 CG |
947 | { |
948 | struct eventpoll *ep = f->private_data; | |
949 | struct rb_node *rbp; | |
138d22b5 CG |
950 | |
951 | mutex_lock(&ep->mtx); | |
b2ac2ea6 | 952 | for (rbp = rb_first_cached(&ep->rbr); rbp; rbp = rb_next(rbp)) { |
138d22b5 | 953 | struct epitem *epi = rb_entry(rbp, struct epitem, rbn); |
77493f04 | 954 | struct inode *inode = file_inode(epi->ffd.file); |
138d22b5 | 955 | |
77493f04 CG |
956 | seq_printf(m, "tfd: %8d events: %8x data: %16llx " |
957 | " pos:%lli ino:%lx sdev:%x\n", | |
a3816ab0 | 958 | epi->ffd.fd, epi->event.events, |
77493f04 CG |
959 | (long long)epi->event.data, |
960 | (long long)epi->ffd.file->f_pos, | |
961 | inode->i_ino, inode->i_sb->s_dev); | |
a3816ab0 | 962 | if (seq_has_overflowed(m)) |
138d22b5 CG |
963 | break; |
964 | } | |
965 | mutex_unlock(&ep->mtx); | |
138d22b5 CG |
966 | } |
967 | #endif | |
968 | ||
7699acd1 DL |
969 | /* File callbacks that implement the eventpoll file behaviour */ |
970 | static const struct file_operations eventpoll_fops = { | |
138d22b5 CG |
971 | #ifdef CONFIG_PROC_FS |
972 | .show_fdinfo = ep_show_fdinfo, | |
973 | #endif | |
7699acd1 | 974 | .release = ep_eventpoll_release, |
a11e1d43 | 975 | .poll = ep_eventpoll_poll, |
6038f373 | 976 | .llseek = noop_llseek, |
7699acd1 DL |
977 | }; |
978 | ||
b611967d | 979 | /* |
7699acd1 DL |
980 | * This is called from eventpoll_release() to unlink files from the eventpoll |
981 | * interface. We need to have this facility to cleanup correctly files that are | |
982 | * closed without being removed from the eventpoll interface. | |
b611967d | 983 | */ |
7699acd1 | 984 | void eventpoll_release_file(struct file *file) |
b611967d | 985 | { |
7699acd1 | 986 | struct eventpoll *ep; |
ebe06187 | 987 | struct epitem *epi, *next; |
b611967d DL |
988 | |
989 | /* | |
68499914 | 990 | * We don't want to get "file->f_lock" because it is not |
7699acd1 | 991 | * necessary. It is not necessary because we're in the "struct file" |
25985edc | 992 | * cleanup path, and this means that no one is using this file anymore. |
5071f97e | 993 | * So, for example, epoll_ctl() cannot hit here since if we reach this |
67647d0f | 994 | * point, the file counter already went to zero and fget() would fail. |
d47de16c | 995 | * The only hit might come from ep_free() but by holding the mutex |
7699acd1 | 996 | * will correctly serialize the operation. We do need to acquire |
d47de16c | 997 | * "ep->mtx" after "epmutex" because ep_remove() requires it when called |
7699acd1 | 998 | * from anywhere but ep_free(). |
68499914 JC |
999 | * |
1000 | * Besides, ep_remove() acquires the lock, so we can't hold it here. | |
b611967d | 1001 | */ |
7699acd1 | 1002 | mutex_lock(&epmutex); |
ebe06187 | 1003 | list_for_each_entry_safe(epi, next, &file->f_ep_links, fllink) { |
7699acd1 | 1004 | ep = epi->ep; |
d8805e63 | 1005 | mutex_lock_nested(&ep->mtx, 0); |
7699acd1 | 1006 | ep_remove(ep, epi); |
d47de16c | 1007 | mutex_unlock(&ep->mtx); |
b611967d | 1008 | } |
7699acd1 | 1009 | mutex_unlock(&epmutex); |
b611967d DL |
1010 | } |
1011 | ||
53d2be79 | 1012 | static int ep_alloc(struct eventpoll **pep) |
1da177e4 | 1013 | { |
7ef9964e DL |
1014 | int error; |
1015 | struct user_struct *user; | |
1016 | struct eventpoll *ep; | |
1da177e4 | 1017 | |
7ef9964e | 1018 | user = get_current_user(); |
7ef9964e DL |
1019 | error = -ENOMEM; |
1020 | ep = kzalloc(sizeof(*ep), GFP_KERNEL); | |
1021 | if (unlikely(!ep)) | |
1022 | goto free_uid; | |
1da177e4 | 1023 | |
d47de16c | 1024 | mutex_init(&ep->mtx); |
1da177e4 LT |
1025 | init_waitqueue_head(&ep->wq); |
1026 | init_waitqueue_head(&ep->poll_wait); | |
1027 | INIT_LIST_HEAD(&ep->rdllist); | |
b2ac2ea6 | 1028 | ep->rbr = RB_ROOT_CACHED; |
d47de16c | 1029 | ep->ovflist = EP_UNACTIVE_PTR; |
7ef9964e | 1030 | ep->user = user; |
1da177e4 | 1031 | |
53d2be79 | 1032 | *pep = ep; |
1da177e4 | 1033 | |
1da177e4 | 1034 | return 0; |
7ef9964e DL |
1035 | |
1036 | free_uid: | |
1037 | free_uid(user); | |
1038 | return error; | |
1da177e4 LT |
1039 | } |
1040 | ||
1da177e4 | 1041 | /* |
c7ea7630 DL |
1042 | * Search the file inside the eventpoll tree. The RB tree operations |
1043 | * are protected by the "mtx" mutex, and ep_find() must be called with | |
1044 | * "mtx" held. | |
1da177e4 LT |
1045 | */ |
1046 | static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd) | |
1047 | { | |
1048 | int kcmp; | |
1da177e4 LT |
1049 | struct rb_node *rbp; |
1050 | struct epitem *epi, *epir = NULL; | |
1051 | struct epoll_filefd ffd; | |
1052 | ||
b030a4dd | 1053 | ep_set_ffd(&ffd, file, fd); |
b2ac2ea6 | 1054 | for (rbp = ep->rbr.rb_root.rb_node; rbp; ) { |
1da177e4 | 1055 | epi = rb_entry(rbp, struct epitem, rbn); |
b030a4dd | 1056 | kcmp = ep_cmp_ffd(&ffd, &epi->ffd); |
1da177e4 LT |
1057 | if (kcmp > 0) |
1058 | rbp = rbp->rb_right; | |
1059 | else if (kcmp < 0) | |
1060 | rbp = rbp->rb_left; | |
1061 | else { | |
1da177e4 LT |
1062 | epir = epi; |
1063 | break; | |
1064 | } | |
1065 | } | |
1da177e4 | 1066 | |
1da177e4 LT |
1067 | return epir; |
1068 | } | |
1069 | ||
92ef6da3 | 1070 | #ifdef CONFIG_CHECKPOINT_RESTORE |
0791e364 CG |
1071 | static struct epitem *ep_find_tfd(struct eventpoll *ep, int tfd, unsigned long toff) |
1072 | { | |
1073 | struct rb_node *rbp; | |
1074 | struct epitem *epi; | |
1075 | ||
b2ac2ea6 | 1076 | for (rbp = rb_first_cached(&ep->rbr); rbp; rbp = rb_next(rbp)) { |
0791e364 CG |
1077 | epi = rb_entry(rbp, struct epitem, rbn); |
1078 | if (epi->ffd.fd == tfd) { | |
1079 | if (toff == 0) | |
1080 | return epi; | |
1081 | else | |
1082 | toff--; | |
1083 | } | |
1084 | cond_resched(); | |
1085 | } | |
1086 | ||
1087 | return NULL; | |
1088 | } | |
1089 | ||
1090 | struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, | |
1091 | unsigned long toff) | |
1092 | { | |
1093 | struct file *file_raw; | |
1094 | struct eventpoll *ep; | |
1095 | struct epitem *epi; | |
1096 | ||
1097 | if (!is_file_epoll(file)) | |
1098 | return ERR_PTR(-EINVAL); | |
1099 | ||
1100 | ep = file->private_data; | |
1101 | ||
1102 | mutex_lock(&ep->mtx); | |
1103 | epi = ep_find_tfd(ep, tfd, toff); | |
1104 | if (epi) | |
1105 | file_raw = epi->ffd.file; | |
1106 | else | |
1107 | file_raw = ERR_PTR(-ENOENT); | |
1108 | mutex_unlock(&ep->mtx); | |
1109 | ||
1110 | return file_raw; | |
1111 | } | |
92ef6da3 | 1112 | #endif /* CONFIG_CHECKPOINT_RESTORE */ |
0791e364 | 1113 | |
1da177e4 | 1114 | /* |
7699acd1 | 1115 | * This is the callback that is passed to the wait queue wakeup |
bf6a41db | 1116 | * mechanism. It is called by the stored file descriptors when they |
7699acd1 | 1117 | * have events to report. |
1da177e4 | 1118 | */ |
ac6424b9 | 1119 | static int ep_poll_callback(wait_queue_entry_t *wait, unsigned mode, int sync, void *key) |
1da177e4 | 1120 | { |
7699acd1 DL |
1121 | int pwake = 0; |
1122 | unsigned long flags; | |
1123 | struct epitem *epi = ep_item_from_wait(wait); | |
1124 | struct eventpoll *ep = epi->ep; | |
3ad6f93e | 1125 | __poll_t pollflags = key_to_poll(key); |
df0108c5 | 1126 | int ewake = 0; |
1da177e4 | 1127 | |
ee8ef0a4 | 1128 | spin_lock_irqsave(&ep->wq.lock, flags); |
1da177e4 | 1129 | |
bf3b9f63 SS |
1130 | ep_set_busy_poll_napi_id(epi); |
1131 | ||
7699acd1 DL |
1132 | /* |
1133 | * If the event mask does not contain any poll(2) event, we consider the | |
1134 | * descriptor to be disabled. This condition is likely the effect of the | |
1135 | * EPOLLONESHOT bit that disables the descriptor when an event is received, | |
1136 | * until the next EPOLL_CTL_MOD will be issued. | |
1137 | */ | |
1138 | if (!(epi->event.events & ~EP_PRIVATE_BITS)) | |
d47de16c DL |
1139 | goto out_unlock; |
1140 | ||
2dfa4eea DL |
1141 | /* |
1142 | * Check the events coming with the callback. At this stage, not | |
1143 | * every device reports the events in the "key" parameter of the | |
1144 | * callback. We need to be able to handle both cases here, hence the | |
1145 | * test for "key" != NULL before the event match test. | |
1146 | */ | |
3ad6f93e | 1147 | if (pollflags && !(pollflags & epi->event.events)) |
2dfa4eea DL |
1148 | goto out_unlock; |
1149 | ||
d47de16c | 1150 | /* |
bf6a41db | 1151 | * If we are transferring events to userspace, we can hold no locks |
d47de16c | 1152 | * (because we're accessing user memory, and because of linux f_op->poll() |
bf6a41db | 1153 | * semantics). All the events that happen during that period of time are |
d47de16c DL |
1154 | * chained in ep->ovflist and requeued later on. |
1155 | */ | |
1156 | if (unlikely(ep->ovflist != EP_UNACTIVE_PTR)) { | |
1157 | if (epi->next == EP_UNACTIVE_PTR) { | |
1158 | epi->next = ep->ovflist; | |
1159 | ep->ovflist = epi; | |
4d7e30d9 AH |
1160 | if (epi->ws) { |
1161 | /* | |
1162 | * Activate ep->ws since epi->ws may get | |
1163 | * deactivated at any time. | |
1164 | */ | |
1165 | __pm_stay_awake(ep->ws); | |
1166 | } | |
1167 | ||
d47de16c DL |
1168 | } |
1169 | goto out_unlock; | |
1170 | } | |
1da177e4 | 1171 | |
7699acd1 | 1172 | /* If this file is already in the ready list we exit soon */ |
992991c0 | 1173 | if (!ep_is_linked(epi)) { |
5071f97e | 1174 | list_add_tail(&epi->rdllink, &ep->rdllist); |
eea1d585 | 1175 | ep_pm_stay_awake_rcu(epi); |
4d7e30d9 | 1176 | } |
7699acd1 | 1177 | |
7699acd1 DL |
1178 | /* |
1179 | * Wake up ( if active ) both the eventpoll wait list and the ->poll() | |
1180 | * wait list. | |
1181 | */ | |
df0108c5 | 1182 | if (waitqueue_active(&ep->wq)) { |
b6a515c8 | 1183 | if ((epi->event.events & EPOLLEXCLUSIVE) && |
3ad6f93e AV |
1184 | !(pollflags & POLLFREE)) { |
1185 | switch (pollflags & EPOLLINOUT_BITS) { | |
a9a08845 LT |
1186 | case EPOLLIN: |
1187 | if (epi->event.events & EPOLLIN) | |
b6a515c8 JB |
1188 | ewake = 1; |
1189 | break; | |
a9a08845 LT |
1190 | case EPOLLOUT: |
1191 | if (epi->event.events & EPOLLOUT) | |
b6a515c8 JB |
1192 | ewake = 1; |
1193 | break; | |
1194 | case 0: | |
1195 | ewake = 1; | |
1196 | break; | |
1197 | } | |
1198 | } | |
4a6e9e2c | 1199 | wake_up_locked(&ep->wq); |
df0108c5 | 1200 | } |
7699acd1 DL |
1201 | if (waitqueue_active(&ep->poll_wait)) |
1202 | pwake++; | |
1203 | ||
d47de16c | 1204 | out_unlock: |
ee8ef0a4 | 1205 | spin_unlock_irqrestore(&ep->wq.lock, flags); |
1da177e4 | 1206 | |
7699acd1 DL |
1207 | /* We have to call this outside the lock */ |
1208 | if (pwake) | |
5071f97e | 1209 | ep_poll_safewake(&ep->poll_wait); |
7699acd1 | 1210 | |
138e4ad6 ON |
1211 | if (!(epi->event.events & EPOLLEXCLUSIVE)) |
1212 | ewake = 1; | |
1213 | ||
3ad6f93e | 1214 | if (pollflags & POLLFREE) { |
138e4ad6 ON |
1215 | /* |
1216 | * If we race with ep_remove_wait_queue() it can miss | |
1217 | * ->whead = NULL and do another remove_wait_queue() after | |
1218 | * us, so we can't use __remove_wait_queue(). | |
1219 | */ | |
1220 | list_del_init(&wait->entry); | |
1221 | /* | |
1222 | * ->whead != NULL protects us from the race with ep_free() | |
1223 | * or ep_remove(), ep_remove_wait_queue() takes whead->lock | |
1224 | * held by the caller. Once we nullify it, nothing protects | |
1225 | * ep/epi or even wait. | |
1226 | */ | |
1227 | smp_store_release(&ep_pwq_from_wait(wait)->whead, NULL); | |
1228 | } | |
df0108c5 | 1229 | |
138e4ad6 | 1230 | return ewake; |
7699acd1 | 1231 | } |
1da177e4 LT |
1232 | |
1233 | /* | |
1234 | * This is the callback that is used to add our wait queue to the | |
1235 | * target file wakeup lists. | |
1236 | */ | |
1237 | static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, | |
1238 | poll_table *pt) | |
1239 | { | |
b030a4dd | 1240 | struct epitem *epi = ep_item_from_epqueue(pt); |
1da177e4 LT |
1241 | struct eppoll_entry *pwq; |
1242 | ||
e94b1766 | 1243 | if (epi->nwait >= 0 && (pwq = kmem_cache_alloc(pwq_cache, GFP_KERNEL))) { |
1da177e4 LT |
1244 | init_waitqueue_func_entry(&pwq->wait, ep_poll_callback); |
1245 | pwq->whead = whead; | |
1246 | pwq->base = epi; | |
df0108c5 JB |
1247 | if (epi->event.events & EPOLLEXCLUSIVE) |
1248 | add_wait_queue_exclusive(whead, &pwq->wait); | |
1249 | else | |
1250 | add_wait_queue(whead, &pwq->wait); | |
1da177e4 LT |
1251 | list_add_tail(&pwq->llink, &epi->pwqlist); |
1252 | epi->nwait++; | |
296e236e | 1253 | } else { |
1da177e4 LT |
1254 | /* We have to signal that an error occurred */ |
1255 | epi->nwait = -1; | |
296e236e | 1256 | } |
1da177e4 LT |
1257 | } |
1258 | ||
1da177e4 LT |
1259 | static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi) |
1260 | { | |
1261 | int kcmp; | |
b2ac2ea6 | 1262 | struct rb_node **p = &ep->rbr.rb_root.rb_node, *parent = NULL; |
1da177e4 | 1263 | struct epitem *epic; |
b2ac2ea6 | 1264 | bool leftmost = true; |
1da177e4 LT |
1265 | |
1266 | while (*p) { | |
1267 | parent = *p; | |
1268 | epic = rb_entry(parent, struct epitem, rbn); | |
b030a4dd | 1269 | kcmp = ep_cmp_ffd(&epi->ffd, &epic->ffd); |
b2ac2ea6 | 1270 | if (kcmp > 0) { |
1da177e4 | 1271 | p = &parent->rb_right; |
b2ac2ea6 DB |
1272 | leftmost = false; |
1273 | } else | |
1da177e4 LT |
1274 | p = &parent->rb_left; |
1275 | } | |
1276 | rb_link_node(&epi->rbn, parent, p); | |
b2ac2ea6 | 1277 | rb_insert_color_cached(&epi->rbn, &ep->rbr, leftmost); |
1da177e4 LT |
1278 | } |
1279 | ||
a80a6b85 AM |
1280 | |
1281 | ||
28d82dc1 JB |
1282 | #define PATH_ARR_SIZE 5 |
1283 | /* | |
1284 | * These are the number paths of length 1 to 5, that we are allowing to emanate | |
1285 | * from a single file of interest. For example, we allow 1000 paths of length | |
1286 | * 1, to emanate from each file of interest. This essentially represents the | |
1287 | * potential wakeup paths, which need to be limited in order to avoid massive | |
1288 | * uncontrolled wakeup storms. The common use case should be a single ep which | |
1289 | * is connected to n file sources. In this case each file source has 1 path | |
1290 | * of length 1. Thus, the numbers below should be more than sufficient. These | |
1291 | * path limits are enforced during an EPOLL_CTL_ADD operation, since a modify | |
1292 | * and delete can't add additional paths. Protected by the epmutex. | |
1293 | */ | |
1294 | static const int path_limits[PATH_ARR_SIZE] = { 1000, 500, 100, 50, 10 }; | |
1295 | static int path_count[PATH_ARR_SIZE]; | |
1296 | ||
1297 | static int path_count_inc(int nests) | |
1298 | { | |
93dc6107 JB |
1299 | /* Allow an arbitrary number of depth 1 paths */ |
1300 | if (nests == 0) | |
1301 | return 0; | |
1302 | ||
28d82dc1 JB |
1303 | if (++path_count[nests] > path_limits[nests]) |
1304 | return -1; | |
1305 | return 0; | |
1306 | } | |
1307 | ||
1308 | static void path_count_init(void) | |
1309 | { | |
1310 | int i; | |
1311 | ||
1312 | for (i = 0; i < PATH_ARR_SIZE; i++) | |
1313 | path_count[i] = 0; | |
1314 | } | |
1315 | ||
1316 | static int reverse_path_check_proc(void *priv, void *cookie, int call_nests) | |
1317 | { | |
1318 | int error = 0; | |
1319 | struct file *file = priv; | |
1320 | struct file *child_file; | |
1321 | struct epitem *epi; | |
1322 | ||
ae10b2b4 JB |
1323 | /* CTL_DEL can remove links here, but that can't increase our count */ |
1324 | rcu_read_lock(); | |
1325 | list_for_each_entry_rcu(epi, &file->f_ep_links, fllink) { | |
28d82dc1 JB |
1326 | child_file = epi->ep->file; |
1327 | if (is_file_epoll(child_file)) { | |
1328 | if (list_empty(&child_file->f_ep_links)) { | |
1329 | if (path_count_inc(call_nests)) { | |
1330 | error = -1; | |
1331 | break; | |
1332 | } | |
1333 | } else { | |
1334 | error = ep_call_nested(&poll_loop_ncalls, | |
28d82dc1 JB |
1335 | reverse_path_check_proc, |
1336 | child_file, child_file, | |
1337 | current); | |
1338 | } | |
1339 | if (error != 0) | |
1340 | break; | |
1341 | } else { | |
1342 | printk(KERN_ERR "reverse_path_check_proc: " | |
1343 | "file is not an ep!\n"); | |
1344 | } | |
1345 | } | |
ae10b2b4 | 1346 | rcu_read_unlock(); |
28d82dc1 JB |
1347 | return error; |
1348 | } | |
1349 | ||
1350 | /** | |
1351 | * reverse_path_check - The tfile_check_list is list of file *, which have | |
1352 | * links that are proposed to be newly added. We need to | |
1353 | * make sure that those added links don't add too many | |
1354 | * paths such that we will spend all our time waking up | |
1355 | * eventpoll objects. | |
1356 | * | |
1357 | * Returns: Returns zero if the proposed links don't create too many paths, | |
1358 | * -1 otherwise. | |
1359 | */ | |
1360 | static int reverse_path_check(void) | |
1361 | { | |
28d82dc1 JB |
1362 | int error = 0; |
1363 | struct file *current_file; | |
1364 | ||
1365 | /* let's call this for all tfiles */ | |
1366 | list_for_each_entry(current_file, &tfile_check_list, f_tfile_llink) { | |
28d82dc1 | 1367 | path_count_init(); |
74bdc129 | 1368 | error = ep_call_nested(&poll_loop_ncalls, |
28d82dc1 JB |
1369 | reverse_path_check_proc, current_file, |
1370 | current_file, current); | |
1371 | if (error) | |
1372 | break; | |
1373 | } | |
1374 | return error; | |
1375 | } | |
1376 | ||
4d7e30d9 AH |
1377 | static int ep_create_wakeup_source(struct epitem *epi) |
1378 | { | |
1379 | const char *name; | |
eea1d585 | 1380 | struct wakeup_source *ws; |
4d7e30d9 AH |
1381 | |
1382 | if (!epi->ep->ws) { | |
1383 | epi->ep->ws = wakeup_source_register("eventpoll"); | |
1384 | if (!epi->ep->ws) | |
1385 | return -ENOMEM; | |
1386 | } | |
1387 | ||
1388 | name = epi->ffd.file->f_path.dentry->d_name.name; | |
eea1d585 EW |
1389 | ws = wakeup_source_register(name); |
1390 | ||
1391 | if (!ws) | |
4d7e30d9 | 1392 | return -ENOMEM; |
eea1d585 | 1393 | rcu_assign_pointer(epi->ws, ws); |
4d7e30d9 AH |
1394 | |
1395 | return 0; | |
1396 | } | |
1397 | ||
eea1d585 EW |
1398 | /* rare code path, only used when EPOLL_CTL_MOD removes a wakeup source */ |
1399 | static noinline void ep_destroy_wakeup_source(struct epitem *epi) | |
4d7e30d9 | 1400 | { |
eea1d585 EW |
1401 | struct wakeup_source *ws = ep_wakeup_source(epi); |
1402 | ||
d6d67e72 | 1403 | RCU_INIT_POINTER(epi->ws, NULL); |
eea1d585 EW |
1404 | |
1405 | /* | |
1406 | * wait for ep_pm_stay_awake_rcu to finish, synchronize_rcu is | |
1407 | * used internally by wakeup_source_remove, too (called by | |
1408 | * wakeup_source_unregister), so we cannot use call_rcu | |
1409 | */ | |
1410 | synchronize_rcu(); | |
1411 | wakeup_source_unregister(ws); | |
4d7e30d9 AH |
1412 | } |
1413 | ||
c7ea7630 DL |
1414 | /* |
1415 | * Must be called with "mtx" held. | |
1416 | */ | |
bec1a502 | 1417 | static int ep_insert(struct eventpoll *ep, const struct epoll_event *event, |
67347fe4 | 1418 | struct file *tfile, int fd, int full_check) |
1da177e4 | 1419 | { |
d85e2aa2 AV |
1420 | int error, pwake = 0; |
1421 | __poll_t revents; | |
52bd19f7 | 1422 | long user_watches; |
1da177e4 LT |
1423 | struct epitem *epi; |
1424 | struct ep_pqueue epq; | |
1425 | ||
92e64178 DB |
1426 | lockdep_assert_irqs_enabled(); |
1427 | ||
52bd19f7 RH |
1428 | user_watches = atomic_long_read(&ep->user->epoll_watches); |
1429 | if (unlikely(user_watches >= max_user_watches)) | |
7ef9964e | 1430 | return -ENOSPC; |
e94b1766 | 1431 | if (!(epi = kmem_cache_alloc(epi_cache, GFP_KERNEL))) |
7ef9964e | 1432 | return -ENOMEM; |
1da177e4 LT |
1433 | |
1434 | /* Item initialization follow here ... */ | |
1da177e4 LT |
1435 | INIT_LIST_HEAD(&epi->rdllink); |
1436 | INIT_LIST_HEAD(&epi->fllink); | |
1da177e4 LT |
1437 | INIT_LIST_HEAD(&epi->pwqlist); |
1438 | epi->ep = ep; | |
b030a4dd | 1439 | ep_set_ffd(&epi->ffd, tfile, fd); |
1da177e4 | 1440 | epi->event = *event; |
1da177e4 | 1441 | epi->nwait = 0; |
d47de16c | 1442 | epi->next = EP_UNACTIVE_PTR; |
4d7e30d9 AH |
1443 | if (epi->event.events & EPOLLWAKEUP) { |
1444 | error = ep_create_wakeup_source(epi); | |
1445 | if (error) | |
1446 | goto error_create_wakeup_source; | |
1447 | } else { | |
eea1d585 | 1448 | RCU_INIT_POINTER(epi->ws, NULL); |
4d7e30d9 | 1449 | } |
1da177e4 LT |
1450 | |
1451 | /* Initialize the poll table using the queue callback */ | |
1452 | epq.epi = epi; | |
1453 | init_poll_funcptr(&epq.pt, ep_ptable_queue_proc); | |
1454 | ||
1455 | /* | |
1456 | * Attach the item to the poll hooks and get current event bits. | |
1457 | * We can safely use the file* here because its usage count has | |
c7ea7630 DL |
1458 | * been increased by the caller of this function. Note that after |
1459 | * this operation completes, the poll callback can start hitting | |
1460 | * the new item. | |
1da177e4 | 1461 | */ |
37b5e521 | 1462 | revents = ep_item_poll(epi, &epq.pt, 1); |
1da177e4 LT |
1463 | |
1464 | /* | |
1465 | * We have to check if something went wrong during the poll wait queue | |
1466 | * install process. Namely an allocation for a wait queue failed due | |
1467 | * high memory pressure. | |
1468 | */ | |
7ef9964e | 1469 | error = -ENOMEM; |
1da177e4 | 1470 | if (epi->nwait < 0) |
7699acd1 | 1471 | goto error_unregister; |
1da177e4 LT |
1472 | |
1473 | /* Add the current item to the list of active epoll hook for this file */ | |
68499914 | 1474 | spin_lock(&tfile->f_lock); |
ae10b2b4 | 1475 | list_add_tail_rcu(&epi->fllink, &tfile->f_ep_links); |
68499914 | 1476 | spin_unlock(&tfile->f_lock); |
1da177e4 | 1477 | |
c7ea7630 DL |
1478 | /* |
1479 | * Add the current item to the RB tree. All RB tree operations are | |
1480 | * protected by "mtx", and ep_insert() is called with "mtx" held. | |
1481 | */ | |
1da177e4 LT |
1482 | ep_rbtree_insert(ep, epi); |
1483 | ||
28d82dc1 JB |
1484 | /* now check if we've created too many backpaths */ |
1485 | error = -EINVAL; | |
67347fe4 | 1486 | if (full_check && reverse_path_check()) |
28d82dc1 JB |
1487 | goto error_remove_epi; |
1488 | ||
c7ea7630 | 1489 | /* We have to drop the new item inside our item list to keep track of it */ |
304b18b8 | 1490 | spin_lock_irq(&ep->wq.lock); |
c7ea7630 | 1491 | |
bf3b9f63 SS |
1492 | /* record NAPI ID of new item if present */ |
1493 | ep_set_busy_poll_napi_id(epi); | |
1494 | ||
1da177e4 | 1495 | /* If the file is already "ready" we drop it inside the ready list */ |
992991c0 | 1496 | if (revents && !ep_is_linked(epi)) { |
1da177e4 | 1497 | list_add_tail(&epi->rdllink, &ep->rdllist); |
eea1d585 | 1498 | ep_pm_stay_awake(epi); |
1da177e4 LT |
1499 | |
1500 | /* Notify waiting tasks that events are available */ | |
1501 | if (waitqueue_active(&ep->wq)) | |
4a6e9e2c | 1502 | wake_up_locked(&ep->wq); |
1da177e4 LT |
1503 | if (waitqueue_active(&ep->poll_wait)) |
1504 | pwake++; | |
1505 | } | |
1506 | ||
304b18b8 | 1507 | spin_unlock_irq(&ep->wq.lock); |
1da177e4 | 1508 | |
52bd19f7 | 1509 | atomic_long_inc(&ep->user->epoll_watches); |
7ef9964e | 1510 | |
1da177e4 LT |
1511 | /* We have to call this outside the lock */ |
1512 | if (pwake) | |
5071f97e | 1513 | ep_poll_safewake(&ep->poll_wait); |
1da177e4 | 1514 | |
1da177e4 LT |
1515 | return 0; |
1516 | ||
28d82dc1 JB |
1517 | error_remove_epi: |
1518 | spin_lock(&tfile->f_lock); | |
ae10b2b4 | 1519 | list_del_rcu(&epi->fllink); |
28d82dc1 JB |
1520 | spin_unlock(&tfile->f_lock); |
1521 | ||
b2ac2ea6 | 1522 | rb_erase_cached(&epi->rbn, &ep->rbr); |
28d82dc1 | 1523 | |
7699acd1 | 1524 | error_unregister: |
1da177e4 LT |
1525 | ep_unregister_pollwait(ep, epi); |
1526 | ||
1527 | /* | |
1528 | * We need to do this because an event could have been arrived on some | |
67647d0f DL |
1529 | * allocated wait queue. Note that we don't care about the ep->ovflist |
1530 | * list, since that is used/cleaned only inside a section bound by "mtx". | |
1531 | * And ep_insert() is called with "mtx" held. | |
1da177e4 | 1532 | */ |
304b18b8 | 1533 | spin_lock_irq(&ep->wq.lock); |
992991c0 | 1534 | if (ep_is_linked(epi)) |
6192bd53 | 1535 | list_del_init(&epi->rdllink); |
304b18b8 | 1536 | spin_unlock_irq(&ep->wq.lock); |
1da177e4 | 1537 | |
eea1d585 | 1538 | wakeup_source_unregister(ep_wakeup_source(epi)); |
4d7e30d9 AH |
1539 | |
1540 | error_create_wakeup_source: | |
b030a4dd | 1541 | kmem_cache_free(epi_cache, epi); |
7ef9964e | 1542 | |
1da177e4 LT |
1543 | return error; |
1544 | } | |
1545 | ||
1da177e4 LT |
1546 | /* |
1547 | * Modify the interest event mask by dropping an event if the new mask | |
c7ea7630 | 1548 | * has a match in the current file status. Must be called with "mtx" held. |
1da177e4 | 1549 | */ |
bec1a502 AV |
1550 | static int ep_modify(struct eventpoll *ep, struct epitem *epi, |
1551 | const struct epoll_event *event) | |
1da177e4 LT |
1552 | { |
1553 | int pwake = 0; | |
626cf236 HV |
1554 | poll_table pt; |
1555 | ||
92e64178 DB |
1556 | lockdep_assert_irqs_enabled(); |
1557 | ||
626cf236 | 1558 | init_poll_funcptr(&pt, NULL); |
1da177e4 LT |
1559 | |
1560 | /* | |
e057e15f TB |
1561 | * Set the new event interest mask before calling f_op->poll(); |
1562 | * otherwise we might miss an event that happens between the | |
1563 | * f_op->poll() call and the new event set registering. | |
1da177e4 | 1564 | */ |
128dd175 | 1565 | epi->event.events = event->events; /* need barrier below */ |
e057e15f | 1566 | epi->event.data = event->data; /* protected by mtx */ |
4d7e30d9 | 1567 | if (epi->event.events & EPOLLWAKEUP) { |
eea1d585 | 1568 | if (!ep_has_wakeup_source(epi)) |
4d7e30d9 | 1569 | ep_create_wakeup_source(epi); |
eea1d585 | 1570 | } else if (ep_has_wakeup_source(epi)) { |
4d7e30d9 AH |
1571 | ep_destroy_wakeup_source(epi); |
1572 | } | |
1da177e4 | 1573 | |
128dd175 EW |
1574 | /* |
1575 | * The following barrier has two effects: | |
1576 | * | |
1577 | * 1) Flush epi changes above to other CPUs. This ensures | |
1578 | * we do not miss events from ep_poll_callback if an | |
1579 | * event occurs immediately after we call f_op->poll(). | |
ee8ef0a4 | 1580 | * We need this because we did not take ep->wq.lock while |
128dd175 | 1581 | * changing epi above (but ep_poll_callback does take |
ee8ef0a4 | 1582 | * ep->wq.lock). |
128dd175 EW |
1583 | * |
1584 | * 2) We also need to ensure we do not miss _past_ events | |
1585 | * when calling f_op->poll(). This barrier also | |
1586 | * pairs with the barrier in wq_has_sleeper (see | |
1587 | * comments for wq_has_sleeper). | |
1588 | * | |
1589 | * This barrier will now guarantee ep_poll_callback or f_op->poll | |
1590 | * (or both) will notice the readiness of an item. | |
1591 | */ | |
1592 | smp_mb(); | |
1593 | ||
1da177e4 LT |
1594 | /* |
1595 | * Get current event bits. We can safely use the file* here because | |
1596 | * its usage count has been increased by the caller of this function. | |
c7ea7630 | 1597 | * If the item is "hot" and it is not registered inside the ready |
67647d0f | 1598 | * list, push it inside. |
1da177e4 | 1599 | */ |
69112736 | 1600 | if (ep_item_poll(epi, &pt, 1)) { |
ee8ef0a4 | 1601 | spin_lock_irq(&ep->wq.lock); |
992991c0 | 1602 | if (!ep_is_linked(epi)) { |
c7ea7630 | 1603 | list_add_tail(&epi->rdllink, &ep->rdllist); |
eea1d585 | 1604 | ep_pm_stay_awake(epi); |
c7ea7630 DL |
1605 | |
1606 | /* Notify waiting tasks that events are available */ | |
1607 | if (waitqueue_active(&ep->wq)) | |
4a6e9e2c | 1608 | wake_up_locked(&ep->wq); |
c7ea7630 DL |
1609 | if (waitqueue_active(&ep->poll_wait)) |
1610 | pwake++; | |
7699acd1 | 1611 | } |
ee8ef0a4 | 1612 | spin_unlock_irq(&ep->wq.lock); |
7699acd1 | 1613 | } |
1da177e4 | 1614 | |
7699acd1 DL |
1615 | /* We have to call this outside the lock */ |
1616 | if (pwake) | |
5071f97e | 1617 | ep_poll_safewake(&ep->poll_wait); |
1da177e4 | 1618 | |
7699acd1 | 1619 | return 0; |
1da177e4 LT |
1620 | } |
1621 | ||
d85e2aa2 | 1622 | static __poll_t ep_send_events_proc(struct eventpoll *ep, struct list_head *head, |
296e236e | 1623 | void *priv) |
1da177e4 | 1624 | { |
5071f97e | 1625 | struct ep_send_events_data *esed = priv; |
d85e2aa2 | 1626 | __poll_t revents; |
5071f97e DL |
1627 | struct epitem *epi; |
1628 | struct epoll_event __user *uevent; | |
eea1d585 | 1629 | struct wakeup_source *ws; |
626cf236 HV |
1630 | poll_table pt; |
1631 | ||
1632 | init_poll_funcptr(&pt, NULL); | |
1da177e4 | 1633 | |
296e236e | 1634 | /* |
5071f97e DL |
1635 | * We can loop without lock because we are passed a task private list. |
1636 | * Items cannot vanish during the loop because ep_scan_ready_list() is | |
1637 | * holding "mtx" during this call. | |
296e236e | 1638 | */ |
d7ebbe46 AV |
1639 | for (esed->res = 0, uevent = esed->events; |
1640 | !list_empty(head) && esed->res < esed->maxevents;) { | |
5071f97e | 1641 | epi = list_first_entry(head, struct epitem, rdllink); |
d47de16c | 1642 | |
4d7e30d9 AH |
1643 | /* |
1644 | * Activate ep->ws before deactivating epi->ws to prevent | |
1645 | * triggering auto-suspend here (in case we reactive epi->ws | |
1646 | * below). | |
1647 | * | |
1648 | * This could be rearranged to delay the deactivation of epi->ws | |
1649 | * instead, but then epi->ws would temporarily be out of sync | |
1650 | * with ep_is_linked(). | |
1651 | */ | |
eea1d585 EW |
1652 | ws = ep_wakeup_source(epi); |
1653 | if (ws) { | |
1654 | if (ws->active) | |
1655 | __pm_stay_awake(ep->ws); | |
1656 | __pm_relax(ws); | |
1657 | } | |
1658 | ||
d47de16c | 1659 | list_del_init(&epi->rdllink); |
1da177e4 | 1660 | |
37b5e521 | 1661 | revents = ep_item_poll(epi, &pt, 1); |
5071f97e | 1662 | |
296e236e | 1663 | /* |
5071f97e DL |
1664 | * If the event mask intersect the caller-requested one, |
1665 | * deliver the event to userspace. Again, ep_scan_ready_list() | |
1666 | * is holding "mtx", so no operations coming from userspace | |
1667 | * can change the item. | |
296e236e DL |
1668 | */ |
1669 | if (revents) { | |
5071f97e | 1670 | if (__put_user(revents, &uevent->events) || |
d0305882 TB |
1671 | __put_user(epi->event.data, &uevent->data)) { |
1672 | list_add(&epi->rdllink, head); | |
eea1d585 | 1673 | ep_pm_stay_awake(epi); |
d7ebbe46 AV |
1674 | if (!esed->res) |
1675 | esed->res = -EFAULT; | |
1676 | return 0; | |
d0305882 | 1677 | } |
d7ebbe46 | 1678 | esed->res++; |
5071f97e | 1679 | uevent++; |
296e236e DL |
1680 | if (epi->event.events & EPOLLONESHOT) |
1681 | epi->event.events &= EP_PRIVATE_BITS; | |
1682 | else if (!(epi->event.events & EPOLLET)) { | |
1683 | /* | |
1684 | * If this file has been added with Level | |
1685 | * Trigger mode, we need to insert back inside | |
1686 | * the ready list, so that the next call to | |
1687 | * epoll_wait() will check again the events | |
25985edc | 1688 | * availability. At this point, no one can insert |
296e236e DL |
1689 | * into ep->rdllist besides us. The epoll_ctl() |
1690 | * callers are locked out by | |
1691 | * ep_scan_ready_list() holding "mtx" and the | |
1692 | * poll callback will queue them in ep->ovflist. | |
1693 | */ | |
1694 | list_add_tail(&epi->rdllink, &ep->rdllist); | |
eea1d585 | 1695 | ep_pm_stay_awake(epi); |
296e236e DL |
1696 | } |
1697 | } | |
1698 | } | |
5071f97e | 1699 | |
d7ebbe46 | 1700 | return 0; |
5071f97e | 1701 | } |
d47de16c | 1702 | |
296e236e DL |
1703 | static int ep_send_events(struct eventpoll *ep, |
1704 | struct epoll_event __user *events, int maxevents) | |
5071f97e DL |
1705 | { |
1706 | struct ep_send_events_data esed; | |
1da177e4 | 1707 | |
5071f97e DL |
1708 | esed.maxevents = maxevents; |
1709 | esed.events = events; | |
6192bd53 | 1710 | |
d7ebbe46 AV |
1711 | ep_scan_ready_list(ep, ep_send_events_proc, &esed, 0, false); |
1712 | return esed.res; | |
1da177e4 LT |
1713 | } |
1714 | ||
766b9f92 | 1715 | static inline struct timespec64 ep_set_mstimeout(long ms) |
0781b909 | 1716 | { |
766b9f92 | 1717 | struct timespec64 now, ts = { |
0781b909 ED |
1718 | .tv_sec = ms / MSEC_PER_SEC, |
1719 | .tv_nsec = NSEC_PER_MSEC * (ms % MSEC_PER_SEC), | |
1720 | }; | |
1721 | ||
766b9f92 DD |
1722 | ktime_get_ts64(&now); |
1723 | return timespec64_add_safe(now, ts); | |
0781b909 ED |
1724 | } |
1725 | ||
f4d93ad7 SB |
1726 | /** |
1727 | * ep_poll - Retrieves ready events, and delivers them to the caller supplied | |
1728 | * event buffer. | |
1729 | * | |
1730 | * @ep: Pointer to the eventpoll context. | |
1731 | * @events: Pointer to the userspace buffer where the ready events should be | |
1732 | * stored. | |
1733 | * @maxevents: Size (in terms of number of events) of the caller event buffer. | |
1734 | * @timeout: Maximum timeout for the ready events fetch operation, in | |
1735 | * milliseconds. If the @timeout is zero, the function will not block, | |
1736 | * while if the @timeout is less than zero, the function will block | |
1737 | * until at least one event has been retrieved (or an error | |
1738 | * occurred). | |
1739 | * | |
1740 | * Returns: Returns the number of ready events which have been fetched, or an | |
1741 | * error code, in case of error. | |
1742 | */ | |
1da177e4 LT |
1743 | static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, |
1744 | int maxevents, long timeout) | |
1745 | { | |
f4d93ad7 | 1746 | int res = 0, eavail, timed_out = 0; |
da8b44d5 | 1747 | u64 slack = 0; |
ac6424b9 | 1748 | wait_queue_entry_t wait; |
95aac7b1 SB |
1749 | ktime_t expires, *to = NULL; |
1750 | ||
679abf38 DB |
1751 | lockdep_assert_irqs_enabled(); |
1752 | ||
95aac7b1 | 1753 | if (timeout > 0) { |
766b9f92 | 1754 | struct timespec64 end_time = ep_set_mstimeout(timeout); |
0781b909 | 1755 | |
95aac7b1 SB |
1756 | slack = select_estimate_accuracy(&end_time); |
1757 | to = &expires; | |
766b9f92 | 1758 | *to = timespec64_to_ktime(end_time); |
95aac7b1 | 1759 | } else if (timeout == 0) { |
f4d93ad7 SB |
1760 | /* |
1761 | * Avoid the unnecessary trip to the wait queue loop, if the | |
1762 | * caller specified a non blocking operation. | |
1763 | */ | |
95aac7b1 | 1764 | timed_out = 1; |
679abf38 | 1765 | spin_lock_irq(&ep->wq.lock); |
f4d93ad7 | 1766 | goto check_events; |
95aac7b1 | 1767 | } |
1da177e4 | 1768 | |
f4d93ad7 | 1769 | fetch_events: |
bf3b9f63 SS |
1770 | |
1771 | if (!ep_events_available(ep)) | |
1772 | ep_busy_loop(ep, timed_out); | |
1773 | ||
679abf38 | 1774 | spin_lock_irq(&ep->wq.lock); |
1da177e4 | 1775 | |
3fb0e584 | 1776 | if (!ep_events_available(ep)) { |
bf3b9f63 SS |
1777 | /* |
1778 | * Busy poll timed out. Drop NAPI ID for now, we can add | |
1779 | * it back in when we have moved a socket with a valid NAPI | |
1780 | * ID onto the ready list. | |
1781 | */ | |
1782 | ep_reset_busy_poll_napi_id(ep); | |
1783 | ||
1da177e4 LT |
1784 | /* |
1785 | * We don't have any available event to return to the caller. | |
1786 | * We need to sleep here, and we will be wake up by | |
1787 | * ep_poll_callback() when events will become available. | |
1788 | */ | |
1789 | init_waitqueue_entry(&wait, current); | |
a93d2f17 | 1790 | __add_wait_queue_exclusive(&ep->wq, &wait); |
1da177e4 LT |
1791 | |
1792 | for (;;) { | |
1793 | /* | |
1794 | * We don't want to sleep if the ep_poll_callback() sends us | |
1795 | * a wakeup in between. That's why we set the task state | |
1796 | * to TASK_INTERRUPTIBLE before doing the checks. | |
1797 | */ | |
1798 | set_current_state(TASK_INTERRUPTIBLE); | |
c257a340 DR |
1799 | /* |
1800 | * Always short-circuit for fatal signals to allow | |
1801 | * threads to make a timely exit without the chance of | |
1802 | * finding more events available and fetching | |
1803 | * repeatedly. | |
1804 | */ | |
1805 | if (fatal_signal_pending(current)) { | |
1806 | res = -EINTR; | |
1807 | break; | |
1808 | } | |
3fb0e584 | 1809 | if (ep_events_available(ep) || timed_out) |
1da177e4 LT |
1810 | break; |
1811 | if (signal_pending(current)) { | |
1812 | res = -EINTR; | |
1813 | break; | |
1814 | } | |
1815 | ||
679abf38 | 1816 | spin_unlock_irq(&ep->wq.lock); |
c511851d | 1817 | if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS)) |
95aac7b1 SB |
1818 | timed_out = 1; |
1819 | ||
679abf38 | 1820 | spin_lock_irq(&ep->wq.lock); |
1da177e4 | 1821 | } |
1da177e4 | 1822 | |
4d5755b1 DB |
1823 | __remove_wait_queue(&ep->wq, &wait); |
1824 | __set_current_state(TASK_RUNNING); | |
1da177e4 | 1825 | } |
f4d93ad7 | 1826 | check_events: |
1da177e4 | 1827 | /* Is it worth to try to dig for events ? */ |
3fb0e584 | 1828 | eavail = ep_events_available(ep); |
1da177e4 | 1829 | |
679abf38 | 1830 | spin_unlock_irq(&ep->wq.lock); |
1da177e4 LT |
1831 | |
1832 | /* | |
1833 | * Try to transfer events to user space. In case we get 0 events and | |
1834 | * there's still timeout left over, we go trying again in search of | |
1835 | * more luck. | |
1836 | */ | |
1837 | if (!res && eavail && | |
95aac7b1 | 1838 | !(res = ep_send_events(ep, events, maxevents)) && !timed_out) |
f4d93ad7 | 1839 | goto fetch_events; |
1da177e4 LT |
1840 | |
1841 | return res; | |
1842 | } | |
1843 | ||
22bacca4 DL |
1844 | /** |
1845 | * ep_loop_check_proc - Callback function to be passed to the @ep_call_nested() | |
1846 | * API, to verify that adding an epoll file inside another | |
1847 | * epoll structure, does not violate the constraints, in | |
1848 | * terms of closed loops, or too deep chains (which can | |
1849 | * result in excessive stack usage). | |
1850 | * | |
1851 | * @priv: Pointer to the epoll file to be currently checked. | |
1852 | * @cookie: Original cookie for this call. This is the top-of-the-chain epoll | |
1853 | * data structure pointer. | |
1854 | * @call_nests: Current dept of the @ep_call_nested() call stack. | |
1855 | * | |
1856 | * Returns: Returns zero if adding the epoll @file inside current epoll | |
1857 | * structure @ep does not violate the constraints, or -1 otherwise. | |
1858 | */ | |
1859 | static int ep_loop_check_proc(void *priv, void *cookie, int call_nests) | |
1860 | { | |
1861 | int error = 0; | |
1862 | struct file *file = priv; | |
1863 | struct eventpoll *ep = file->private_data; | |
28d82dc1 | 1864 | struct eventpoll *ep_tovisit; |
22bacca4 DL |
1865 | struct rb_node *rbp; |
1866 | struct epitem *epi; | |
1867 | ||
d8805e63 | 1868 | mutex_lock_nested(&ep->mtx, call_nests + 1); |
28d82dc1 JB |
1869 | ep->visited = 1; |
1870 | list_add(&ep->visited_list_link, &visited_list); | |
b2ac2ea6 | 1871 | for (rbp = rb_first_cached(&ep->rbr); rbp; rbp = rb_next(rbp)) { |
22bacca4 DL |
1872 | epi = rb_entry(rbp, struct epitem, rbn); |
1873 | if (unlikely(is_file_epoll(epi->ffd.file))) { | |
28d82dc1 JB |
1874 | ep_tovisit = epi->ffd.file->private_data; |
1875 | if (ep_tovisit->visited) | |
1876 | continue; | |
74bdc129 | 1877 | error = ep_call_nested(&poll_loop_ncalls, |
28d82dc1 JB |
1878 | ep_loop_check_proc, epi->ffd.file, |
1879 | ep_tovisit, current); | |
22bacca4 DL |
1880 | if (error != 0) |
1881 | break; | |
28d82dc1 JB |
1882 | } else { |
1883 | /* | |
1884 | * If we've reached a file that is not associated with | |
1885 | * an ep, then we need to check if the newly added | |
1886 | * links are going to add too many wakeup paths. We do | |
1887 | * this by adding it to the tfile_check_list, if it's | |
1888 | * not already there, and calling reverse_path_check() | |
1889 | * during ep_insert(). | |
1890 | */ | |
1891 | if (list_empty(&epi->ffd.file->f_tfile_llink)) | |
1892 | list_add(&epi->ffd.file->f_tfile_llink, | |
1893 | &tfile_check_list); | |
22bacca4 DL |
1894 | } |
1895 | } | |
1896 | mutex_unlock(&ep->mtx); | |
1897 | ||
1898 | return error; | |
1899 | } | |
1900 | ||
1901 | /** | |
1902 | * ep_loop_check - Performs a check to verify that adding an epoll file (@file) | |
1903 | * another epoll file (represented by @ep) does not create | |
1904 | * closed loops or too deep chains. | |
1905 | * | |
1906 | * @ep: Pointer to the epoll private data structure. | |
1907 | * @file: Pointer to the epoll file to be checked. | |
1908 | * | |
1909 | * Returns: Returns zero if adding the epoll @file inside current epoll | |
1910 | * structure @ep does not violate the constraints, or -1 otherwise. | |
1911 | */ | |
1912 | static int ep_loop_check(struct eventpoll *ep, struct file *file) | |
1913 | { | |
28d82dc1 JB |
1914 | int ret; |
1915 | struct eventpoll *ep_cur, *ep_next; | |
1916 | ||
74bdc129 | 1917 | ret = ep_call_nested(&poll_loop_ncalls, |
22bacca4 | 1918 | ep_loop_check_proc, file, ep, current); |
28d82dc1 JB |
1919 | /* clear visited list */ |
1920 | list_for_each_entry_safe(ep_cur, ep_next, &visited_list, | |
1921 | visited_list_link) { | |
1922 | ep_cur->visited = 0; | |
1923 | list_del(&ep_cur->visited_list_link); | |
1924 | } | |
1925 | return ret; | |
1926 | } | |
1927 | ||
1928 | static void clear_tfile_check_list(void) | |
1929 | { | |
1930 | struct file *file; | |
1931 | ||
1932 | /* first clear the tfile_check_list */ | |
1933 | while (!list_empty(&tfile_check_list)) { | |
1934 | file = list_first_entry(&tfile_check_list, struct file, | |
1935 | f_tfile_llink); | |
1936 | list_del_init(&file->f_tfile_llink); | |
1937 | } | |
1938 | INIT_LIST_HEAD(&tfile_check_list); | |
22bacca4 DL |
1939 | } |
1940 | ||
7699acd1 | 1941 | /* |
523723bb | 1942 | * Open an eventpoll file descriptor. |
7699acd1 | 1943 | */ |
791eb22e | 1944 | static int do_epoll_create(int flags) |
7699acd1 | 1945 | { |
28d82dc1 | 1946 | int error, fd; |
bb57c3ed | 1947 | struct eventpoll *ep = NULL; |
28d82dc1 | 1948 | struct file *file; |
7699acd1 | 1949 | |
e38b36f3 UD |
1950 | /* Check the EPOLL_* constant for consistency. */ |
1951 | BUILD_BUG_ON(EPOLL_CLOEXEC != O_CLOEXEC); | |
1952 | ||
296e236e DL |
1953 | if (flags & ~EPOLL_CLOEXEC) |
1954 | return -EINVAL; | |
7699acd1 | 1955 | /* |
bb57c3ed | 1956 | * Create the internal data structure ("struct eventpoll"). |
7699acd1 | 1957 | */ |
9fe5ad9c | 1958 | error = ep_alloc(&ep); |
bb57c3ed DL |
1959 | if (error < 0) |
1960 | return error; | |
7699acd1 DL |
1961 | /* |
1962 | * Creates all the items needed to setup an eventpoll file. That is, | |
2030a42c | 1963 | * a file structure and a free file descriptor. |
7699acd1 | 1964 | */ |
28d82dc1 JB |
1965 | fd = get_unused_fd_flags(O_RDWR | (flags & O_CLOEXEC)); |
1966 | if (fd < 0) { | |
1967 | error = fd; | |
1968 | goto out_free_ep; | |
1969 | } | |
1970 | file = anon_inode_getfile("[eventpoll]", &eventpoll_fops, ep, | |
628ff7c1 | 1971 | O_RDWR | (flags & O_CLOEXEC)); |
28d82dc1 JB |
1972 | if (IS_ERR(file)) { |
1973 | error = PTR_ERR(file); | |
1974 | goto out_free_fd; | |
1975 | } | |
28d82dc1 | 1976 | ep->file = file; |
98022748 | 1977 | fd_install(fd, file); |
28d82dc1 JB |
1978 | return fd; |
1979 | ||
1980 | out_free_fd: | |
1981 | put_unused_fd(fd); | |
1982 | out_free_ep: | |
1983 | ep_free(ep); | |
bb57c3ed | 1984 | return error; |
7699acd1 DL |
1985 | } |
1986 | ||
791eb22e DB |
1987 | SYSCALL_DEFINE1(epoll_create1, int, flags) |
1988 | { | |
1989 | return do_epoll_create(flags); | |
1990 | } | |
1991 | ||
5a8a82b1 | 1992 | SYSCALL_DEFINE1(epoll_create, int, size) |
a0998b50 | 1993 | { |
bfe3891a | 1994 | if (size <= 0) |
9fe5ad9c UD |
1995 | return -EINVAL; |
1996 | ||
791eb22e | 1997 | return do_epoll_create(0); |
a0998b50 UD |
1998 | } |
1999 | ||
7699acd1 DL |
2000 | /* |
2001 | * The following function implements the controller interface for | |
2002 | * the eventpoll file that enables the insertion/removal/change of | |
67647d0f | 2003 | * file descriptors inside the interest set. |
7699acd1 | 2004 | */ |
5a8a82b1 HC |
2005 | SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd, |
2006 | struct epoll_event __user *, event) | |
7699acd1 DL |
2007 | { |
2008 | int error; | |
67347fe4 | 2009 | int full_check = 0; |
7e3fb584 | 2010 | struct fd f, tf; |
7699acd1 DL |
2011 | struct eventpoll *ep; |
2012 | struct epitem *epi; | |
2013 | struct epoll_event epds; | |
67347fe4 | 2014 | struct eventpoll *tep = NULL; |
7699acd1 | 2015 | |
7699acd1 DL |
2016 | error = -EFAULT; |
2017 | if (ep_op_has_event(op) && | |
2018 | copy_from_user(&epds, event, sizeof(struct epoll_event))) | |
2019 | goto error_return; | |
2020 | ||
7699acd1 | 2021 | error = -EBADF; |
7e3fb584 AV |
2022 | f = fdget(epfd); |
2023 | if (!f.file) | |
7699acd1 DL |
2024 | goto error_return; |
2025 | ||
2026 | /* Get the "struct file *" for the target file */ | |
7e3fb584 AV |
2027 | tf = fdget(fd); |
2028 | if (!tf.file) | |
7699acd1 DL |
2029 | goto error_fput; |
2030 | ||
2031 | /* The target file descriptor must support poll */ | |
2032 | error = -EPERM; | |
9965ed17 | 2033 | if (!file_can_poll(tf.file)) |
7699acd1 DL |
2034 | goto error_tgt_fput; |
2035 | ||
4d7e30d9 | 2036 | /* Check if EPOLLWAKEUP is allowed */ |
c680e41b NI |
2037 | if (ep_op_has_event(op)) |
2038 | ep_take_care_of_epollwakeup(&epds); | |
4d7e30d9 | 2039 | |
7699acd1 DL |
2040 | /* |
2041 | * We have to check that the file structure underneath the file descriptor | |
2042 | * the user passed to us _is_ an eventpoll file. And also we do not permit | |
2043 | * adding an epoll file descriptor inside itself. | |
2044 | */ | |
2045 | error = -EINVAL; | |
7e3fb584 | 2046 | if (f.file == tf.file || !is_file_epoll(f.file)) |
7699acd1 DL |
2047 | goto error_tgt_fput; |
2048 | ||
df0108c5 JB |
2049 | /* |
2050 | * epoll adds to the wakeup queue at EPOLL_CTL_ADD time only, | |
2051 | * so EPOLLEXCLUSIVE is not allowed for a EPOLL_CTL_MOD operation. | |
2052 | * Also, we do not currently supported nested exclusive wakeups. | |
2053 | */ | |
c857ab64 | 2054 | if (ep_op_has_event(op) && (epds.events & EPOLLEXCLUSIVE)) { |
b6a515c8 JB |
2055 | if (op == EPOLL_CTL_MOD) |
2056 | goto error_tgt_fput; | |
2057 | if (op == EPOLL_CTL_ADD && (is_file_epoll(tf.file) || | |
2058 | (epds.events & ~EPOLLEXCLUSIVE_OK_BITS))) | |
2059 | goto error_tgt_fput; | |
2060 | } | |
df0108c5 | 2061 | |
7699acd1 DL |
2062 | /* |
2063 | * At this point it is safe to assume that the "private_data" contains | |
2064 | * our own data structure. | |
2065 | */ | |
7e3fb584 | 2066 | ep = f.file->private_data; |
7699acd1 | 2067 | |
22bacca4 DL |
2068 | /* |
2069 | * When we insert an epoll file descriptor, inside another epoll file | |
2070 | * descriptor, there is the change of creating closed loops, which are | |
28d82dc1 JB |
2071 | * better be handled here, than in more critical paths. While we are |
2072 | * checking for loops we also determine the list of files reachable | |
2073 | * and hang them on the tfile_check_list, so we can check that we | |
2074 | * haven't created too many possible wakeup paths. | |
22bacca4 | 2075 | * |
67347fe4 JB |
2076 | * We do not need to take the global 'epumutex' on EPOLL_CTL_ADD when |
2077 | * the epoll file descriptor is attaching directly to a wakeup source, | |
2078 | * unless the epoll file descriptor is nested. The purpose of taking the | |
2079 | * 'epmutex' on add is to prevent complex toplogies such as loops and | |
2080 | * deep wakeup paths from forming in parallel through multiple | |
2081 | * EPOLL_CTL_ADD operations. | |
22bacca4 | 2082 | */ |
67347fe4 | 2083 | mutex_lock_nested(&ep->mtx, 0); |
28d82dc1 | 2084 | if (op == EPOLL_CTL_ADD) { |
67347fe4 JB |
2085 | if (!list_empty(&f.file->f_ep_links) || |
2086 | is_file_epoll(tf.file)) { | |
2087 | full_check = 1; | |
2088 | mutex_unlock(&ep->mtx); | |
2089 | mutex_lock(&epmutex); | |
2090 | if (is_file_epoll(tf.file)) { | |
2091 | error = -ELOOP; | |
2092 | if (ep_loop_check(ep, tf.file) != 0) { | |
2093 | clear_tfile_check_list(); | |
2094 | goto error_tgt_fput; | |
2095 | } | |
2096 | } else | |
2097 | list_add(&tf.file->f_tfile_llink, | |
2098 | &tfile_check_list); | |
2099 | mutex_lock_nested(&ep->mtx, 0); | |
2100 | if (is_file_epoll(tf.file)) { | |
2101 | tep = tf.file->private_data; | |
2102 | mutex_lock_nested(&tep->mtx, 1); | |
13d51807 | 2103 | } |
67347fe4 JB |
2104 | } |
2105 | } | |
7699acd1 | 2106 | |
67647d0f DL |
2107 | /* |
2108 | * Try to lookup the file inside our RB tree, Since we grabbed "mtx" | |
2109 | * above, we can be sure to be able to use the item looked up by | |
2110 | * ep_find() till we release the mutex. | |
2111 | */ | |
7e3fb584 | 2112 | epi = ep_find(ep, tf.file, fd); |
7699acd1 DL |
2113 | |
2114 | error = -EINVAL; | |
2115 | switch (op) { | |
2116 | case EPOLL_CTL_ADD: | |
2117 | if (!epi) { | |
a9a08845 | 2118 | epds.events |= EPOLLERR | EPOLLHUP; |
67347fe4 | 2119 | error = ep_insert(ep, &epds, tf.file, fd, full_check); |
7699acd1 DL |
2120 | } else |
2121 | error = -EEXIST; | |
67347fe4 JB |
2122 | if (full_check) |
2123 | clear_tfile_check_list(); | |
7699acd1 DL |
2124 | break; |
2125 | case EPOLL_CTL_DEL: | |
2126 | if (epi) | |
2127 | error = ep_remove(ep, epi); | |
2128 | else | |
2129 | error = -ENOENT; | |
2130 | break; | |
2131 | case EPOLL_CTL_MOD: | |
2132 | if (epi) { | |
b6a515c8 | 2133 | if (!(epi->event.events & EPOLLEXCLUSIVE)) { |
a9a08845 | 2134 | epds.events |= EPOLLERR | EPOLLHUP; |
b6a515c8 JB |
2135 | error = ep_modify(ep, epi, &epds); |
2136 | } | |
7699acd1 DL |
2137 | } else |
2138 | error = -ENOENT; | |
2139 | break; | |
2140 | } | |
67347fe4 JB |
2141 | if (tep != NULL) |
2142 | mutex_unlock(&tep->mtx); | |
d47de16c | 2143 | mutex_unlock(&ep->mtx); |
7699acd1 DL |
2144 | |
2145 | error_tgt_fput: | |
67347fe4 | 2146 | if (full_check) |
22bacca4 DL |
2147 | mutex_unlock(&epmutex); |
2148 | ||
7e3fb584 | 2149 | fdput(tf); |
7699acd1 | 2150 | error_fput: |
7e3fb584 | 2151 | fdput(f); |
7699acd1 | 2152 | error_return: |
7699acd1 DL |
2153 | |
2154 | return error; | |
2155 | } | |
2156 | ||
2157 | /* | |
2158 | * Implement the event wait interface for the eventpoll file. It is the kernel | |
2159 | * part of the user space epoll_wait(2). | |
2160 | */ | |
791eb22e DB |
2161 | static int do_epoll_wait(int epfd, struct epoll_event __user *events, |
2162 | int maxevents, int timeout) | |
7699acd1 | 2163 | { |
2903ff01 AV |
2164 | int error; |
2165 | struct fd f; | |
7699acd1 DL |
2166 | struct eventpoll *ep; |
2167 | ||
7699acd1 DL |
2168 | /* The maximum number of event must be greater than zero */ |
2169 | if (maxevents <= 0 || maxevents > EP_MAX_EVENTS) | |
2170 | return -EINVAL; | |
2171 | ||
2172 | /* Verify that the area passed by the user is writeable */ | |
2903ff01 AV |
2173 | if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event))) |
2174 | return -EFAULT; | |
7699acd1 DL |
2175 | |
2176 | /* Get the "struct file *" for the eventpoll file */ | |
2903ff01 AV |
2177 | f = fdget(epfd); |
2178 | if (!f.file) | |
2179 | return -EBADF; | |
7699acd1 DL |
2180 | |
2181 | /* | |
2182 | * We have to check that the file structure underneath the fd | |
2183 | * the user passed to us _is_ an eventpoll file. | |
2184 | */ | |
2185 | error = -EINVAL; | |
2903ff01 | 2186 | if (!is_file_epoll(f.file)) |
7699acd1 DL |
2187 | goto error_fput; |
2188 | ||
2189 | /* | |
2190 | * At this point it is safe to assume that the "private_data" contains | |
2191 | * our own data structure. | |
2192 | */ | |
2903ff01 | 2193 | ep = f.file->private_data; |
7699acd1 DL |
2194 | |
2195 | /* Time to fish for events ... */ | |
2196 | error = ep_poll(ep, events, maxevents, timeout); | |
2197 | ||
2198 | error_fput: | |
2903ff01 | 2199 | fdput(f); |
7699acd1 DL |
2200 | return error; |
2201 | } | |
2202 | ||
791eb22e DB |
2203 | SYSCALL_DEFINE4(epoll_wait, int, epfd, struct epoll_event __user *, events, |
2204 | int, maxevents, int, timeout) | |
2205 | { | |
2206 | return do_epoll_wait(epfd, events, maxevents, timeout); | |
2207 | } | |
2208 | ||
7699acd1 DL |
2209 | /* |
2210 | * Implement the event wait interface for the eventpoll file. It is the kernel | |
2211 | * part of the user space epoll_pwait(2). | |
2212 | */ | |
5a8a82b1 HC |
2213 | SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events, |
2214 | int, maxevents, int, timeout, const sigset_t __user *, sigmask, | |
2215 | size_t, sigsetsize) | |
7699acd1 DL |
2216 | { |
2217 | int error; | |
2218 | sigset_t ksigmask, sigsaved; | |
2219 | ||
2220 | /* | |
2221 | * If the caller wants a certain signal mask to be set during the wait, | |
2222 | * we apply it here. | |
2223 | */ | |
ded653cc DD |
2224 | error = set_user_sigmask(sigmask, &ksigmask, &sigsaved, sigsetsize); |
2225 | if (error) | |
2226 | return error; | |
7699acd1 | 2227 | |
791eb22e | 2228 | error = do_epoll_wait(epfd, events, maxevents, timeout); |
7699acd1 | 2229 | |
854a6ed5 | 2230 | restore_user_sigmask(sigmask, &sigsaved); |
7699acd1 DL |
2231 | |
2232 | return error; | |
2233 | } | |
2234 | ||
35280bd4 AV |
2235 | #ifdef CONFIG_COMPAT |
2236 | COMPAT_SYSCALL_DEFINE6(epoll_pwait, int, epfd, | |
2237 | struct epoll_event __user *, events, | |
2238 | int, maxevents, int, timeout, | |
2239 | const compat_sigset_t __user *, sigmask, | |
2240 | compat_size_t, sigsetsize) | |
2241 | { | |
2242 | long err; | |
35280bd4 AV |
2243 | sigset_t ksigmask, sigsaved; |
2244 | ||
2245 | /* | |
2246 | * If the caller wants a certain signal mask to be set during the wait, | |
2247 | * we apply it here. | |
2248 | */ | |
ded653cc DD |
2249 | err = set_compat_user_sigmask(sigmask, &ksigmask, &sigsaved, sigsetsize); |
2250 | if (err) | |
2251 | return err; | |
35280bd4 | 2252 | |
791eb22e | 2253 | err = do_epoll_wait(epfd, events, maxevents, timeout); |
35280bd4 | 2254 | |
854a6ed5 | 2255 | restore_user_sigmask(sigmask, &sigsaved); |
35280bd4 AV |
2256 | |
2257 | return err; | |
2258 | } | |
2259 | #endif | |
2260 | ||
1da177e4 LT |
2261 | static int __init eventpoll_init(void) |
2262 | { | |
7ef9964e DL |
2263 | struct sysinfo si; |
2264 | ||
2265 | si_meminfo(&si); | |
9df04e1f DL |
2266 | /* |
2267 | * Allows top 4% of lomem to be allocated for epoll watches (per user). | |
2268 | */ | |
2269 | max_user_watches = (((si.totalram - si.totalhigh) / 25) << PAGE_SHIFT) / | |
7ef9964e | 2270 | EP_ITEM_COST; |
52bd19f7 | 2271 | BUG_ON(max_user_watches < 0); |
1da177e4 | 2272 | |
22bacca4 DL |
2273 | /* |
2274 | * Initialize the structure used to perform epoll file descriptor | |
2275 | * inclusion loops checks. | |
2276 | */ | |
2277 | ep_nested_calls_init(&poll_loop_ncalls); | |
2278 | ||
57a173bd | 2279 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
1da177e4 | 2280 | /* Initialize the structure used to perform safe poll wait head wake ups */ |
5071f97e | 2281 | ep_nested_calls_init(&poll_safewake_ncalls); |
57a173bd | 2282 | #endif |
1da177e4 | 2283 | |
39732ca5 EW |
2284 | /* |
2285 | * We can have many thousands of epitems, so prevent this from | |
2286 | * using an extra cache line on 64-bit (and smaller) CPUs | |
2287 | */ | |
2288 | BUILD_BUG_ON(sizeof(void *) <= 8 && sizeof(struct epitem) > 128); | |
2289 | ||
1da177e4 LT |
2290 | /* Allocates slab cache used to allocate "struct epitem" items */ |
2291 | epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem), | |
2ae928a9 | 2292 | 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL); |
1da177e4 LT |
2293 | |
2294 | /* Allocates slab cache used to allocate "struct eppoll_entry" */ | |
2295 | pwq_cache = kmem_cache_create("eventpoll_pwq", | |
2ae928a9 | 2296 | sizeof(struct eppoll_entry), 0, SLAB_PANIC|SLAB_ACCOUNT, NULL); |
1da177e4 | 2297 | |
1da177e4 | 2298 | return 0; |
1da177e4 | 2299 | } |
cea69241 | 2300 | fs_initcall(eventpoll_init); |