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1da177e4 1/*
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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)
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DL
52 * 2) ep->mtx (mutex)
53 * 3) ep->lock (spinlock)
1da177e4
LT
54 *
55 * The acquire order is the one listed above, from 1 to 3.
56 * We need a spinlock (ep->lock) because we manipulate objects
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
DL
87 * It is possible to drop the "ep->mtx" and to use the global
88 * mutex "epmutex" (together with "ep->lock") to have it working,
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
b6a515c8
JB
98#define EPOLLINOUT_BITS (POLLIN | POLLOUT)
99
100#define EPOLLEXCLUSIVE_OK_BITS (EPOLLINOUT_BITS | POLLERR | POLLHUP | \
101 EPOLLWAKEUP | EPOLLET | EPOLLEXCLUSIVE)
102
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DL
103/* Maximum number of nesting allowed inside epoll sets */
104#define EP_MAX_NESTS 4
1da177e4 105
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DL
106#define EP_MAX_EVENTS (INT_MAX / sizeof(struct epoll_event))
107
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108#define EP_UNACTIVE_PTR ((void *) -1L)
109
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DL
110#define EP_ITEM_COST (sizeof(struct epitem) + sizeof(struct eppoll_entry))
111
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LT
112struct epoll_filefd {
113 struct file *file;
114 int fd;
39732ca5 115} __packed;
1da177e4
LT
116
117/*
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118 * Structure used to track possible nested calls, for too deep recursions
119 * and loop cycles.
1da177e4 120 */
5071f97e 121struct nested_call_node {
1da177e4 122 struct list_head llink;
5071f97e 123 void *cookie;
3fe4a975 124 void *ctx;
1da177e4
LT
125};
126
127/*
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128 * This structure is used as collector for nested calls, to check for
129 * maximum recursion dept and loop cycles.
1da177e4 130 */
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131struct nested_calls {
132 struct list_head tasks_call_list;
1da177e4
LT
133 spinlock_t lock;
134};
135
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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 */
142struct 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 };
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DL
149
150 /* List header used to link this structure to the eventpoll ready list */
151 struct list_head rdllink;
152
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DL
153 /*
154 * Works together "struct eventpoll"->ovflist in keeping the
155 * single linked chain of items.
156 */
157 struct epitem *next;
158
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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
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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
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DL
177 /* The structure that describe the interested events and the source fd */
178 struct epoll_event event;
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DL
179};
180
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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
LT
184 * interface.
185 */
186struct eventpoll {
bf6a41db 187 /* Protect the access to this structure */
c7ea7630 188 spinlock_t lock;
1da177e4
LT
189
190 /*
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DL
191 * This mutex is used to ensure that files are not removed
192 * while epoll is using them. This is held during the event
193 * collection loop, the file cleanup path, the epoll file exit
194 * code and the ctl operations.
1da177e4 195 */
d47de16c 196 struct mutex mtx;
1da177e4
LT
197
198 /* Wait queue used by sys_epoll_wait() */
199 wait_queue_head_t wq;
200
201 /* Wait queue used by file->poll() */
202 wait_queue_head_t poll_wait;
203
204 /* List of ready file descriptors */
205 struct list_head rdllist;
206
67647d0f 207 /* RB tree root used to store monitored fd structs */
1da177e4 208 struct rb_root rbr;
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DL
209
210 /*
211 * This is a single linked list that chains all the "struct epitem" that
25985edc 212 * happened while transferring ready events to userspace w/out
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DL
213 * holding ->lock.
214 */
215 struct epitem *ovflist;
7ef9964e 216
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AH
217 /* wakeup_source used when ep_scan_ready_list is running */
218 struct wakeup_source *ws;
219
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DL
220 /* The user that created the eventpoll descriptor */
221 struct user_struct *user;
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JB
222
223 struct file *file;
224
225 /* used to optimize loop detection check */
226 int visited;
227 struct list_head visited_list_link;
bf3b9f63
SS
228
229#ifdef CONFIG_NET_RX_BUSY_POLL
230 /* used to track busy poll napi_id */
231 unsigned int napi_id;
232#endif
1da177e4
LT
233};
234
235/* Wait structure used by the poll hooks */
236struct eppoll_entry {
237 /* List header used to link this structure to the "struct epitem" */
238 struct list_head llink;
239
240 /* The "base" pointer is set to the container "struct epitem" */
4f0989db 241 struct epitem *base;
1da177e4
LT
242
243 /*
244 * Wait queue item that will be linked to the target file wait
245 * queue head.
246 */
ac6424b9 247 wait_queue_entry_t wait;
1da177e4
LT
248
249 /* The wait queue head that linked the "wait" wait queue item */
250 wait_queue_head_t *whead;
251};
252
1da177e4
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253/* Wrapper struct used by poll queueing */
254struct ep_pqueue {
255 poll_table pt;
256 struct epitem *epi;
257};
258
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DL
259/* Used by the ep_send_events() function as callback private data */
260struct ep_send_events_data {
261 int maxevents;
262 struct epoll_event __user *events;
263};
264
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DL
265/*
266 * Configuration options available inside /proc/sys/fs/epoll/
267 */
7ef9964e 268/* Maximum number of epoll watched descriptors, per user */
52bd19f7 269static 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 274static DEFINE_MUTEX(epmutex);
1da177e4 275
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DL
276/* Used to check for epoll file descriptor inclusion loops */
277static struct nested_calls poll_loop_ncalls;
278
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DL
279/* Used for safe wake up implementation */
280static struct nested_calls poll_safewake_ncalls;
281
282/* Used to call file's f_op->poll() under the nested calls boundaries */
283static struct nested_calls poll_readywalk_ncalls;
1da177e4
LT
284
285/* Slab cache used to allocate "struct epitem" */
e18b890b 286static struct kmem_cache *epi_cache __read_mostly;
1da177e4
LT
287
288/* Slab cache used to allocate "struct eppoll_entry" */
e18b890b 289static struct kmem_cache *pwq_cache __read_mostly;
1da177e4 290
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JB
291/* Visited nodes during ep_loop_check(), so we can unset them when we finish */
292static LIST_HEAD(visited_list);
293
294/*
295 * List of files with newly added links, where we may need to limit the number
296 * of emanating paths. Protected by the epmutex.
297 */
298static LIST_HEAD(tfile_check_list);
299
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DL
300#ifdef CONFIG_SYSCTL
301
302#include <linux/sysctl.h>
303
52bd19f7
RH
304static long zero;
305static long long_max = LONG_MAX;
7ef9964e 306
1f7e0616 307struct ctl_table epoll_table[] = {
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DL
308 {
309 .procname = "max_user_watches",
310 .data = &max_user_watches,
52bd19f7 311 .maxlen = sizeof(max_user_watches),
7ef9964e 312 .mode = 0644,
52bd19f7 313 .proc_handler = proc_doulongvec_minmax,
7ef9964e 314 .extra1 = &zero,
52bd19f7 315 .extra2 = &long_max,
7ef9964e 316 },
ab09203e 317 { }
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DL
318};
319#endif /* CONFIG_SYSCTL */
320
28d82dc1
JB
321static const struct file_operations eventpoll_fops;
322
323static inline int is_file_epoll(struct file *f)
324{
325 return f->f_op == &eventpoll_fops;
326}
b030a4dd 327
67647d0f 328/* Setup the structure that is used as key for the RB tree */
b030a4dd
PE
329static inline void ep_set_ffd(struct epoll_filefd *ffd,
330 struct file *file, int fd)
331{
332 ffd->file = file;
333 ffd->fd = fd;
334}
335
67647d0f 336/* Compare RB tree keys */
b030a4dd
PE
337static inline int ep_cmp_ffd(struct epoll_filefd *p1,
338 struct epoll_filefd *p2)
339{
340 return (p1->file > p2->file ? +1:
341 (p1->file < p2->file ? -1 : p1->fd - p2->fd));
342}
343
b030a4dd
PE
344/* Tells us if the item is currently linked */
345static inline int ep_is_linked(struct list_head *p)
346{
347 return !list_empty(p);
348}
349
ac6424b9 350static inline struct eppoll_entry *ep_pwq_from_wait(wait_queue_entry_t *p)
971316f0
ON
351{
352 return container_of(p, struct eppoll_entry, wait);
353}
354
b030a4dd 355/* Get the "struct epitem" from a wait queue pointer */
ac6424b9 356static inline struct epitem *ep_item_from_wait(wait_queue_entry_t *p)
b030a4dd
PE
357{
358 return container_of(p, struct eppoll_entry, wait)->base;
359}
360
361/* Get the "struct epitem" from an epoll queue wrapper */
cdac75e6 362static inline struct epitem *ep_item_from_epqueue(poll_table *p)
b030a4dd
PE
363{
364 return container_of(p, struct ep_pqueue, pt)->epi;
365}
366
367/* Tells if the epoll_ctl(2) operation needs an event copy from userspace */
6192bd53 368static inline int ep_op_has_event(int op)
b030a4dd 369{
a80a6b85 370 return op != EPOLL_CTL_DEL;
b030a4dd
PE
371}
372
1da177e4 373/* Initialize the poll safe wake up structure */
5071f97e 374static void ep_nested_calls_init(struct nested_calls *ncalls)
1da177e4 375{
5071f97e
DL
376 INIT_LIST_HEAD(&ncalls->tasks_call_list);
377 spin_lock_init(&ncalls->lock);
1da177e4
LT
378}
379
3fb0e584
DL
380/**
381 * ep_events_available - Checks if ready events might be available.
382 *
383 * @ep: Pointer to the eventpoll context.
384 *
385 * Returns: Returns a value different than zero if ready events are available,
386 * or zero otherwise.
387 */
388static inline int ep_events_available(struct eventpoll *ep)
389{
390 return !list_empty(&ep->rdllist) || ep->ovflist != EP_UNACTIVE_PTR;
391}
392
bf3b9f63
SS
393#ifdef CONFIG_NET_RX_BUSY_POLL
394static bool ep_busy_loop_end(void *p, unsigned long start_time)
395{
396 struct eventpoll *ep = p;
397
398 return ep_events_available(ep) || busy_loop_timeout(start_time);
399}
400#endif /* CONFIG_NET_RX_BUSY_POLL */
401
402/*
403 * Busy poll if globally on and supporting sockets found && no events,
404 * busy loop will return if need_resched or ep_events_available.
405 *
406 * we must do our busy polling with irqs enabled
407 */
408static void ep_busy_loop(struct eventpoll *ep, int nonblock)
409{
410#ifdef CONFIG_NET_RX_BUSY_POLL
411 unsigned int napi_id = READ_ONCE(ep->napi_id);
412
413 if ((napi_id >= MIN_NAPI_ID) && net_busy_loop_on())
414 napi_busy_loop(napi_id, nonblock ? NULL : ep_busy_loop_end, ep);
415#endif
416}
417
418static inline void ep_reset_busy_poll_napi_id(struct eventpoll *ep)
419{
420#ifdef CONFIG_NET_RX_BUSY_POLL
421 if (ep->napi_id)
422 ep->napi_id = 0;
423#endif
424}
425
426/*
427 * Set epoll busy poll NAPI ID from sk.
428 */
429static inline void ep_set_busy_poll_napi_id(struct epitem *epi)
430{
431#ifdef CONFIG_NET_RX_BUSY_POLL
432 struct eventpoll *ep;
433 unsigned int napi_id;
434 struct socket *sock;
435 struct sock *sk;
436 int err;
437
438 if (!net_busy_loop_on())
439 return;
440
441 sock = sock_from_file(epi->ffd.file, &err);
442 if (!sock)
443 return;
444
445 sk = sock->sk;
446 if (!sk)
447 return;
448
449 napi_id = READ_ONCE(sk->sk_napi_id);
450 ep = epi->ep;
451
452 /* Non-NAPI IDs can be rejected
453 * or
454 * Nothing to do if we already have this ID
455 */
456 if (napi_id < MIN_NAPI_ID || napi_id == ep->napi_id)
457 return;
458
459 /* record NAPI ID for use in next busy poll */
460 ep->napi_id = napi_id;
461#endif
462}
463
5071f97e
DL
464/**
465 * ep_call_nested - Perform a bound (possibly) nested call, by checking
466 * that the recursion limit is not exceeded, and that
467 * the same nested call (by the meaning of same cookie) is
468 * no re-entered.
469 *
470 * @ncalls: Pointer to the nested_calls structure to be used for this call.
471 * @max_nests: Maximum number of allowed nesting calls.
472 * @nproc: Nested call core function pointer.
473 * @priv: Opaque data to be passed to the @nproc callback.
474 * @cookie: Cookie to be used to identify this nested call.
3fe4a975 475 * @ctx: This instance context.
5071f97e
DL
476 *
477 * Returns: Returns the code returned by the @nproc callback, or -1 if
478 * the maximum recursion limit has been exceeded.
1da177e4 479 */
5071f97e
DL
480static int ep_call_nested(struct nested_calls *ncalls, int max_nests,
481 int (*nproc)(void *, void *, int), void *priv,
3fe4a975 482 void *cookie, void *ctx)
1da177e4 483{
5071f97e 484 int error, call_nests = 0;
1da177e4 485 unsigned long flags;
5071f97e
DL
486 struct list_head *lsthead = &ncalls->tasks_call_list;
487 struct nested_call_node *tncur;
488 struct nested_call_node tnode;
1da177e4 489
5071f97e 490 spin_lock_irqsave(&ncalls->lock, flags);
1da177e4 491
5071f97e
DL
492 /*
493 * Try to see if the current task is already inside this wakeup call.
494 * We use a list here, since the population inside this set is always
495 * very much limited.
496 */
b70c3940 497 list_for_each_entry(tncur, lsthead, llink) {
3fe4a975 498 if (tncur->ctx == ctx &&
5071f97e 499 (tncur->cookie == cookie || ++call_nests > max_nests)) {
1da177e4
LT
500 /*
501 * Ops ... loop detected or maximum nest level reached.
502 * We abort this wake by breaking the cycle itself.
503 */
abff55ce
TB
504 error = -1;
505 goto out_unlock;
1da177e4
LT
506 }
507 }
508
5071f97e 509 /* Add the current task and cookie to the list */
3fe4a975 510 tnode.ctx = ctx;
5071f97e 511 tnode.cookie = cookie;
1da177e4
LT
512 list_add(&tnode.llink, lsthead);
513
5071f97e 514 spin_unlock_irqrestore(&ncalls->lock, flags);
1da177e4 515
5071f97e
DL
516 /* Call the nested function */
517 error = (*nproc)(priv, cookie, call_nests);
1da177e4
LT
518
519 /* Remove the current task from the list */
5071f97e 520 spin_lock_irqsave(&ncalls->lock, flags);
1da177e4 521 list_del(&tnode.llink);
3fe4a975 522out_unlock:
5071f97e
DL
523 spin_unlock_irqrestore(&ncalls->lock, flags);
524
525 return error;
526}
527
02edc6fc
SR
528/*
529 * As described in commit 0ccf831cb lockdep: annotate epoll
530 * the use of wait queues used by epoll is done in a very controlled
531 * manner. Wake ups can nest inside each other, but are never done
532 * with the same locking. For example:
533 *
534 * dfd = socket(...);
535 * efd1 = epoll_create();
536 * efd2 = epoll_create();
537 * epoll_ctl(efd1, EPOLL_CTL_ADD, dfd, ...);
538 * epoll_ctl(efd2, EPOLL_CTL_ADD, efd1, ...);
539 *
540 * When a packet arrives to the device underneath "dfd", the net code will
541 * issue a wake_up() on its poll wake list. Epoll (efd1) has installed a
542 * callback wakeup entry on that queue, and the wake_up() performed by the
543 * "dfd" net code will end up in ep_poll_callback(). At this point epoll
544 * (efd1) notices that it may have some event ready, so it needs to wake up
545 * the waiters on its poll wait list (efd2). So it calls ep_poll_safewake()
546 * that ends up in another wake_up(), after having checked about the
547 * recursion constraints. That are, no more than EP_MAX_POLLWAKE_NESTS, to
548 * avoid stack blasting.
549 *
550 * When CONFIG_DEBUG_LOCK_ALLOC is enabled, make sure lockdep can handle
551 * this special case of epoll.
552 */
2dfa4eea
DL
553#ifdef CONFIG_DEBUG_LOCK_ALLOC
554static inline void ep_wake_up_nested(wait_queue_head_t *wqueue,
555 unsigned long events, int subclass)
556{
557 unsigned long flags;
558
559 spin_lock_irqsave_nested(&wqueue->lock, flags, subclass);
560 wake_up_locked_poll(wqueue, events);
561 spin_unlock_irqrestore(&wqueue->lock, flags);
562}
563#else
564static inline void ep_wake_up_nested(wait_queue_head_t *wqueue,
565 unsigned long events, int subclass)
566{
567 wake_up_poll(wqueue, events);
568}
569#endif
570
5071f97e
DL
571static int ep_poll_wakeup_proc(void *priv, void *cookie, int call_nests)
572{
2dfa4eea
DL
573 ep_wake_up_nested((wait_queue_head_t *) cookie, POLLIN,
574 1 + call_nests);
5071f97e
DL
575 return 0;
576}
577
578/*
579 * Perform a safe wake up of the poll wait list. The problem is that
580 * with the new callback'd wake up system, it is possible that the
581 * poll callback is reentered from inside the call to wake_up() done
582 * on the poll wait queue head. The rule is that we cannot reenter the
583 * wake up code from the same task more than EP_MAX_NESTS times,
584 * and we cannot reenter the same wait queue head at all. This will
585 * enable to have a hierarchy of epoll file descriptor of no more than
586 * EP_MAX_NESTS deep.
587 */
588static void ep_poll_safewake(wait_queue_head_t *wq)
589{
3fe4a975
DL
590 int this_cpu = get_cpu();
591
5071f97e 592 ep_call_nested(&poll_safewake_ncalls, EP_MAX_NESTS,
3fe4a975
DL
593 ep_poll_wakeup_proc, NULL, wq, (void *) (long) this_cpu);
594
595 put_cpu();
1da177e4
LT
596}
597
971316f0
ON
598static void ep_remove_wait_queue(struct eppoll_entry *pwq)
599{
600 wait_queue_head_t *whead;
601
602 rcu_read_lock();
138e4ad6
ON
603 /*
604 * If it is cleared by POLLFREE, it should be rcu-safe.
605 * If we read NULL we need a barrier paired with
606 * smp_store_release() in ep_poll_callback(), otherwise
607 * we rely on whead->lock.
608 */
609 whead = smp_load_acquire(&pwq->whead);
971316f0
ON
610 if (whead)
611 remove_wait_queue(whead, &pwq->wait);
612 rcu_read_unlock();
613}
614
1da177e4 615/*
d1bc90dd
TB
616 * This function unregisters poll callbacks from the associated file
617 * descriptor. Must be called with "mtx" held (or "epmutex" if called from
618 * ep_free).
1da177e4 619 */
7699acd1 620static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi)
1da177e4 621{
7699acd1
DL
622 struct list_head *lsthead = &epi->pwqlist;
623 struct eppoll_entry *pwq;
1da177e4 624
d1bc90dd
TB
625 while (!list_empty(lsthead)) {
626 pwq = list_first_entry(lsthead, struct eppoll_entry, llink);
1da177e4 627
d1bc90dd 628 list_del(&pwq->llink);
971316f0 629 ep_remove_wait_queue(pwq);
d1bc90dd 630 kmem_cache_free(pwq_cache, pwq);
1da177e4 631 }
1da177e4
LT
632}
633
eea1d585
EW
634/* call only when ep->mtx is held */
635static inline struct wakeup_source *ep_wakeup_source(struct epitem *epi)
636{
637 return rcu_dereference_check(epi->ws, lockdep_is_held(&epi->ep->mtx));
638}
639
640/* call only when ep->mtx is held */
641static inline void ep_pm_stay_awake(struct epitem *epi)
642{
643 struct wakeup_source *ws = ep_wakeup_source(epi);
644
645 if (ws)
646 __pm_stay_awake(ws);
647}
648
649static inline bool ep_has_wakeup_source(struct epitem *epi)
650{
651 return rcu_access_pointer(epi->ws) ? true : false;
652}
653
654/* call when ep->mtx cannot be held (ep_poll_callback) */
655static inline void ep_pm_stay_awake_rcu(struct epitem *epi)
656{
657 struct wakeup_source *ws;
658
659 rcu_read_lock();
660 ws = rcu_dereference(epi->ws);
661 if (ws)
662 __pm_stay_awake(ws);
663 rcu_read_unlock();
664}
665
5071f97e
DL
666/**
667 * ep_scan_ready_list - Scans the ready list in a way that makes possible for
668 * the scan code, to call f_op->poll(). Also allows for
669 * O(NumReady) performance.
670 *
671 * @ep: Pointer to the epoll private data structure.
672 * @sproc: Pointer to the scan callback.
673 * @priv: Private opaque data passed to the @sproc callback.
d8805e63 674 * @depth: The current depth of recursive f_op->poll calls.
67347fe4 675 * @ep_locked: caller already holds ep->mtx
5071f97e
DL
676 *
677 * Returns: The same integer error code returned by the @sproc callback.
678 */
679static int ep_scan_ready_list(struct eventpoll *ep,
680 int (*sproc)(struct eventpoll *,
681 struct list_head *, void *),
67347fe4 682 void *priv, int depth, bool ep_locked)
5071f97e
DL
683{
684 int error, pwake = 0;
685 unsigned long flags;
686 struct epitem *epi, *nepi;
296e236e 687 LIST_HEAD(txlist);
5071f97e
DL
688
689 /*
690 * We need to lock this because we could be hit by
e057e15f 691 * eventpoll_release_file() and epoll_ctl().
5071f97e 692 */
67347fe4
JB
693
694 if (!ep_locked)
695 mutex_lock_nested(&ep->mtx, depth);
5071f97e
DL
696
697 /*
698 * Steal the ready list, and re-init the original one to the
699 * empty list. Also, set ep->ovflist to NULL so that events
700 * happening while looping w/out locks, are not lost. We cannot
701 * have the poll callback to queue directly on ep->rdllist,
702 * because we want the "sproc" callback to be able to do it
703 * in a lockless way.
704 */
705 spin_lock_irqsave(&ep->lock, flags);
296e236e 706 list_splice_init(&ep->rdllist, &txlist);
5071f97e
DL
707 ep->ovflist = NULL;
708 spin_unlock_irqrestore(&ep->lock, flags);
709
710 /*
711 * Now call the callback function.
712 */
713 error = (*sproc)(ep, &txlist, priv);
714
715 spin_lock_irqsave(&ep->lock, flags);
716 /*
717 * During the time we spent inside the "sproc" callback, some
718 * other events might have been queued by the poll callback.
719 * We re-insert them inside the main ready-list here.
720 */
721 for (nepi = ep->ovflist; (epi = nepi) != NULL;
722 nepi = epi->next, epi->next = EP_UNACTIVE_PTR) {
723 /*
724 * We need to check if the item is already in the list.
725 * During the "sproc" callback execution time, items are
726 * queued into ->ovflist but the "txlist" might already
727 * contain them, and the list_splice() below takes care of them.
728 */
4d7e30d9 729 if (!ep_is_linked(&epi->rdllink)) {
5071f97e 730 list_add_tail(&epi->rdllink, &ep->rdllist);
eea1d585 731 ep_pm_stay_awake(epi);
4d7e30d9 732 }
5071f97e
DL
733 }
734 /*
735 * We need to set back ep->ovflist to EP_UNACTIVE_PTR, so that after
736 * releasing the lock, events will be queued in the normal way inside
737 * ep->rdllist.
738 */
739 ep->ovflist = EP_UNACTIVE_PTR;
740
741 /*
742 * Quickly re-inject items left on "txlist".
743 */
744 list_splice(&txlist, &ep->rdllist);
4d7e30d9 745 __pm_relax(ep->ws);
5071f97e
DL
746
747 if (!list_empty(&ep->rdllist)) {
748 /*
296e236e
DL
749 * Wake up (if active) both the eventpoll wait list and
750 * the ->poll() wait list (delayed after we release the lock).
5071f97e
DL
751 */
752 if (waitqueue_active(&ep->wq))
753 wake_up_locked(&ep->wq);
754 if (waitqueue_active(&ep->poll_wait))
755 pwake++;
756 }
757 spin_unlock_irqrestore(&ep->lock, flags);
758
67347fe4
JB
759 if (!ep_locked)
760 mutex_unlock(&ep->mtx);
5071f97e
DL
761
762 /* We have to call this outside the lock */
763 if (pwake)
764 ep_poll_safewake(&ep->poll_wait);
765
766 return error;
767}
768
ae10b2b4
JB
769static void epi_rcu_free(struct rcu_head *head)
770{
771 struct epitem *epi = container_of(head, struct epitem, rcu);
772 kmem_cache_free(epi_cache, epi);
773}
774
7699acd1
DL
775/*
776 * Removes a "struct epitem" from the eventpoll RB tree and deallocates
c7ea7630 777 * all the associated resources. Must be called with "mtx" held.
7699acd1
DL
778 */
779static int ep_remove(struct eventpoll *ep, struct epitem *epi)
780{
7699acd1
DL
781 unsigned long flags;
782 struct file *file = epi->ffd.file;
1da177e4
LT
783
784 /*
7699acd1
DL
785 * Removes poll wait queue hooks. We _have_ to do this without holding
786 * the "ep->lock" otherwise a deadlock might occur. This because of the
787 * sequence of the lock acquisition. Here we do "ep->lock" then the wait
788 * queue head lock when unregistering the wait queue. The wakeup callback
789 * will run by holding the wait queue head lock and will call our callback
790 * that will try to get "ep->lock".
1da177e4 791 */
7699acd1 792 ep_unregister_pollwait(ep, epi);
1da177e4 793
7699acd1 794 /* Remove the current item from the list of epoll hooks */
68499914 795 spin_lock(&file->f_lock);
ae10b2b4 796 list_del_rcu(&epi->fllink);
68499914 797 spin_unlock(&file->f_lock);
1da177e4 798
cdac75e6 799 rb_erase(&epi->rbn, &ep->rbr);
1da177e4 800
c7ea7630
DL
801 spin_lock_irqsave(&ep->lock, flags);
802 if (ep_is_linked(&epi->rdllink))
803 list_del_init(&epi->rdllink);
804 spin_unlock_irqrestore(&ep->lock, flags);
1da177e4 805
eea1d585 806 wakeup_source_unregister(ep_wakeup_source(epi));
ae10b2b4
JB
807 /*
808 * At this point it is safe to free the eventpoll item. Use the union
809 * field epi->rcu, since we are trying to minimize the size of
810 * 'struct epitem'. The 'rbn' field is no longer in use. Protected by
811 * ep->mtx. The rcu read side, reverse_path_check_proc(), does not make
812 * use of the rbn field.
813 */
814 call_rcu(&epi->rcu, epi_rcu_free);
1da177e4 815
52bd19f7 816 atomic_long_dec(&ep->user->epoll_watches);
7ef9964e 817
c7ea7630 818 return 0;
1da177e4
LT
819}
820
7699acd1 821static void ep_free(struct eventpoll *ep)
1da177e4 822{
7699acd1
DL
823 struct rb_node *rbp;
824 struct epitem *epi;
1da177e4 825
7699acd1
DL
826 /* We need to release all tasks waiting for these file */
827 if (waitqueue_active(&ep->poll_wait))
5071f97e 828 ep_poll_safewake(&ep->poll_wait);
1da177e4 829
7699acd1
DL
830 /*
831 * We need to lock this because we could be hit by
832 * eventpoll_release_file() while we're freeing the "struct eventpoll".
d47de16c 833 * We do not need to hold "ep->mtx" here because the epoll file
7699acd1
DL
834 * is on the way to be removed and no one has references to it
835 * anymore. The only hit might come from eventpoll_release_file() but
25985edc 836 * holding "epmutex" is sufficient here.
7699acd1
DL
837 */
838 mutex_lock(&epmutex);
1da177e4
LT
839
840 /*
7699acd1 841 * Walks through the whole tree by unregistering poll callbacks.
1da177e4 842 */
7699acd1
DL
843 for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) {
844 epi = rb_entry(rbp, struct epitem, rbn);
845
846 ep_unregister_pollwait(ep, epi);
91cf5ab6 847 cond_resched();
7699acd1 848 }
1da177e4
LT
849
850 /*
7699acd1
DL
851 * Walks through the whole tree by freeing each "struct epitem". At this
852 * point we are sure no poll callbacks will be lingering around, and also by
d47de16c 853 * holding "epmutex" we can be sure that no file cleanup code will hit
7699acd1 854 * us during this operation. So we can avoid the lock on "ep->lock".
ddf676c3
EW
855 * We do not need to lock ep->mtx, either, we only do it to prevent
856 * a lockdep warning.
1da177e4 857 */
ddf676c3 858 mutex_lock(&ep->mtx);
c80544dc 859 while ((rbp = rb_first(&ep->rbr)) != NULL) {
7699acd1
DL
860 epi = rb_entry(rbp, struct epitem, rbn);
861 ep_remove(ep, epi);
91cf5ab6 862 cond_resched();
7699acd1 863 }
ddf676c3 864 mutex_unlock(&ep->mtx);
1da177e4 865
7699acd1 866 mutex_unlock(&epmutex);
d47de16c 867 mutex_destroy(&ep->mtx);
7ef9964e 868 free_uid(ep->user);
4d7e30d9 869 wakeup_source_unregister(ep->ws);
f0ee9aab 870 kfree(ep);
7699acd1 871}
1da177e4 872
7699acd1
DL
873static int ep_eventpoll_release(struct inode *inode, struct file *file)
874{
875 struct eventpoll *ep = file->private_data;
1da177e4 876
f0ee9aab 877 if (ep)
7699acd1 878 ep_free(ep);
7699acd1 879
7699acd1 880 return 0;
1da177e4
LT
881}
882
450d89ec
EW
883static inline unsigned int ep_item_poll(struct epitem *epi, poll_table *pt)
884{
885 pt->_key = epi->event.events;
886
887 return epi->ffd.file->f_op->poll(epi->ffd.file, pt) & epi->event.events;
888}
889
296e236e
DL
890static int ep_read_events_proc(struct eventpoll *ep, struct list_head *head,
891 void *priv)
5071f97e
DL
892{
893 struct epitem *epi, *tmp;
626cf236 894 poll_table pt;
5071f97e 895
626cf236 896 init_poll_funcptr(&pt, NULL);
450d89ec 897
5071f97e 898 list_for_each_entry_safe(epi, tmp, head, rdllink) {
450d89ec 899 if (ep_item_poll(epi, &pt))
5071f97e 900 return POLLIN | POLLRDNORM;
296e236e 901 else {
5071f97e
DL
902 /*
903 * Item has been dropped into the ready list by the poll
904 * callback, but it's not actually ready, as far as
905 * caller requested events goes. We can remove it here.
906 */
eea1d585 907 __pm_relax(ep_wakeup_source(epi));
5071f97e 908 list_del_init(&epi->rdllink);
296e236e 909 }
5071f97e
DL
910 }
911
912 return 0;
913}
914
67347fe4
JB
915static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead,
916 poll_table *pt);
917
918struct readyevents_arg {
919 struct eventpoll *ep;
920 bool locked;
921};
922
5071f97e
DL
923static int ep_poll_readyevents_proc(void *priv, void *cookie, int call_nests)
924{
67347fe4
JB
925 struct readyevents_arg *arg = priv;
926
927 return ep_scan_ready_list(arg->ep, ep_read_events_proc, NULL,
928 call_nests + 1, arg->locked);
5071f97e
DL
929}
930
7699acd1
DL
931static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait)
932{
5071f97e 933 int pollflags;
7699acd1 934 struct eventpoll *ep = file->private_data;
67347fe4
JB
935 struct readyevents_arg arg;
936
937 /*
938 * During ep_insert() we already hold the ep->mtx for the tfile.
939 * Prevent re-aquisition.
940 */
941 arg.locked = wait && (wait->_qproc == ep_ptable_queue_proc);
942 arg.ep = ep;
1da177e4 943
7699acd1
DL
944 /* Insert inside our poll wait queue */
945 poll_wait(file, &ep->poll_wait, wait);
946
5071f97e
DL
947 /*
948 * Proceed to find out if wanted events are really available inside
949 * the ready list. This need to be done under ep_call_nested()
950 * supervision, since the call to f_op->poll() done on listed files
951 * could re-enter here.
952 */
953 pollflags = ep_call_nested(&poll_readywalk_ncalls, EP_MAX_NESTS,
67347fe4 954 ep_poll_readyevents_proc, &arg, ep, current);
7699acd1 955
296e236e 956 return pollflags != -1 ? pollflags : 0;
7699acd1
DL
957}
958
138d22b5 959#ifdef CONFIG_PROC_FS
a3816ab0 960static void ep_show_fdinfo(struct seq_file *m, struct file *f)
138d22b5
CG
961{
962 struct eventpoll *ep = f->private_data;
963 struct rb_node *rbp;
138d22b5
CG
964
965 mutex_lock(&ep->mtx);
966 for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) {
967 struct epitem *epi = rb_entry(rbp, struct epitem, rbn);
77493f04 968 struct inode *inode = file_inode(epi->ffd.file);
138d22b5 969
77493f04
CG
970 seq_printf(m, "tfd: %8d events: %8x data: %16llx "
971 " pos:%lli ino:%lx sdev:%x\n",
a3816ab0 972 epi->ffd.fd, epi->event.events,
77493f04
CG
973 (long long)epi->event.data,
974 (long long)epi->ffd.file->f_pos,
975 inode->i_ino, inode->i_sb->s_dev);
a3816ab0 976 if (seq_has_overflowed(m))
138d22b5
CG
977 break;
978 }
979 mutex_unlock(&ep->mtx);
138d22b5
CG
980}
981#endif
982
7699acd1
DL
983/* File callbacks that implement the eventpoll file behaviour */
984static const struct file_operations eventpoll_fops = {
138d22b5
CG
985#ifdef CONFIG_PROC_FS
986 .show_fdinfo = ep_show_fdinfo,
987#endif
7699acd1 988 .release = ep_eventpoll_release,
6038f373
AB
989 .poll = ep_eventpoll_poll,
990 .llseek = noop_llseek,
7699acd1
DL
991};
992
b611967d 993/*
7699acd1
DL
994 * This is called from eventpoll_release() to unlink files from the eventpoll
995 * interface. We need to have this facility to cleanup correctly files that are
996 * closed without being removed from the eventpoll interface.
b611967d 997 */
7699acd1 998void eventpoll_release_file(struct file *file)
b611967d 999{
7699acd1 1000 struct eventpoll *ep;
ebe06187 1001 struct epitem *epi, *next;
b611967d
DL
1002
1003 /*
68499914 1004 * We don't want to get "file->f_lock" because it is not
7699acd1 1005 * necessary. It is not necessary because we're in the "struct file"
25985edc 1006 * cleanup path, and this means that no one is using this file anymore.
5071f97e 1007 * So, for example, epoll_ctl() cannot hit here since if we reach this
67647d0f 1008 * point, the file counter already went to zero and fget() would fail.
d47de16c 1009 * The only hit might come from ep_free() but by holding the mutex
7699acd1 1010 * will correctly serialize the operation. We do need to acquire
d47de16c 1011 * "ep->mtx" after "epmutex" because ep_remove() requires it when called
7699acd1 1012 * from anywhere but ep_free().
68499914
JC
1013 *
1014 * Besides, ep_remove() acquires the lock, so we can't hold it here.
b611967d 1015 */
7699acd1 1016 mutex_lock(&epmutex);
ebe06187 1017 list_for_each_entry_safe(epi, next, &file->f_ep_links, fllink) {
7699acd1 1018 ep = epi->ep;
d8805e63 1019 mutex_lock_nested(&ep->mtx, 0);
7699acd1 1020 ep_remove(ep, epi);
d47de16c 1021 mutex_unlock(&ep->mtx);
b611967d 1022 }
7699acd1 1023 mutex_unlock(&epmutex);
b611967d
DL
1024}
1025
53d2be79 1026static int ep_alloc(struct eventpoll **pep)
1da177e4 1027{
7ef9964e
DL
1028 int error;
1029 struct user_struct *user;
1030 struct eventpoll *ep;
1da177e4 1031
7ef9964e 1032 user = get_current_user();
7ef9964e
DL
1033 error = -ENOMEM;
1034 ep = kzalloc(sizeof(*ep), GFP_KERNEL);
1035 if (unlikely(!ep))
1036 goto free_uid;
1da177e4 1037
c7ea7630 1038 spin_lock_init(&ep->lock);
d47de16c 1039 mutex_init(&ep->mtx);
1da177e4
LT
1040 init_waitqueue_head(&ep->wq);
1041 init_waitqueue_head(&ep->poll_wait);
1042 INIT_LIST_HEAD(&ep->rdllist);
1043 ep->rbr = RB_ROOT;
d47de16c 1044 ep->ovflist = EP_UNACTIVE_PTR;
7ef9964e 1045 ep->user = user;
1da177e4 1046
53d2be79 1047 *pep = ep;
1da177e4 1048
1da177e4 1049 return 0;
7ef9964e
DL
1050
1051free_uid:
1052 free_uid(user);
1053 return error;
1da177e4
LT
1054}
1055
1da177e4 1056/*
c7ea7630
DL
1057 * Search the file inside the eventpoll tree. The RB tree operations
1058 * are protected by the "mtx" mutex, and ep_find() must be called with
1059 * "mtx" held.
1da177e4
LT
1060 */
1061static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd)
1062{
1063 int kcmp;
1da177e4
LT
1064 struct rb_node *rbp;
1065 struct epitem *epi, *epir = NULL;
1066 struct epoll_filefd ffd;
1067
b030a4dd 1068 ep_set_ffd(&ffd, file, fd);
1da177e4
LT
1069 for (rbp = ep->rbr.rb_node; rbp; ) {
1070 epi = rb_entry(rbp, struct epitem, rbn);
b030a4dd 1071 kcmp = ep_cmp_ffd(&ffd, &epi->ffd);
1da177e4
LT
1072 if (kcmp > 0)
1073 rbp = rbp->rb_right;
1074 else if (kcmp < 0)
1075 rbp = rbp->rb_left;
1076 else {
1da177e4
LT
1077 epir = epi;
1078 break;
1079 }
1080 }
1da177e4 1081
1da177e4
LT
1082 return epir;
1083}
1084
92ef6da3 1085#ifdef CONFIG_CHECKPOINT_RESTORE
0791e364
CG
1086static struct epitem *ep_find_tfd(struct eventpoll *ep, int tfd, unsigned long toff)
1087{
1088 struct rb_node *rbp;
1089 struct epitem *epi;
1090
1091 for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) {
1092 epi = rb_entry(rbp, struct epitem, rbn);
1093 if (epi->ffd.fd == tfd) {
1094 if (toff == 0)
1095 return epi;
1096 else
1097 toff--;
1098 }
1099 cond_resched();
1100 }
1101
1102 return NULL;
1103}
1104
1105struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd,
1106 unsigned long toff)
1107{
1108 struct file *file_raw;
1109 struct eventpoll *ep;
1110 struct epitem *epi;
1111
1112 if (!is_file_epoll(file))
1113 return ERR_PTR(-EINVAL);
1114
1115 ep = file->private_data;
1116
1117 mutex_lock(&ep->mtx);
1118 epi = ep_find_tfd(ep, tfd, toff);
1119 if (epi)
1120 file_raw = epi->ffd.file;
1121 else
1122 file_raw = ERR_PTR(-ENOENT);
1123 mutex_unlock(&ep->mtx);
1124
1125 return file_raw;
1126}
92ef6da3 1127#endif /* CONFIG_CHECKPOINT_RESTORE */
0791e364 1128
1da177e4 1129/*
7699acd1 1130 * This is the callback that is passed to the wait queue wakeup
bf6a41db 1131 * mechanism. It is called by the stored file descriptors when they
7699acd1 1132 * have events to report.
1da177e4 1133 */
ac6424b9 1134static int ep_poll_callback(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
1da177e4 1135{
7699acd1
DL
1136 int pwake = 0;
1137 unsigned long flags;
1138 struct epitem *epi = ep_item_from_wait(wait);
1139 struct eventpoll *ep = epi->ep;
df0108c5 1140 int ewake = 0;
1da177e4 1141
c7ea7630 1142 spin_lock_irqsave(&ep->lock, flags);
1da177e4 1143
bf3b9f63
SS
1144 ep_set_busy_poll_napi_id(epi);
1145
7699acd1
DL
1146 /*
1147 * If the event mask does not contain any poll(2) event, we consider the
1148 * descriptor to be disabled. This condition is likely the effect of the
1149 * EPOLLONESHOT bit that disables the descriptor when an event is received,
1150 * until the next EPOLL_CTL_MOD will be issued.
1151 */
1152 if (!(epi->event.events & ~EP_PRIVATE_BITS))
d47de16c
DL
1153 goto out_unlock;
1154
2dfa4eea
DL
1155 /*
1156 * Check the events coming with the callback. At this stage, not
1157 * every device reports the events in the "key" parameter of the
1158 * callback. We need to be able to handle both cases here, hence the
1159 * test for "key" != NULL before the event match test.
1160 */
1161 if (key && !((unsigned long) key & epi->event.events))
1162 goto out_unlock;
1163
d47de16c 1164 /*
bf6a41db 1165 * If we are transferring events to userspace, we can hold no locks
d47de16c 1166 * (because we're accessing user memory, and because of linux f_op->poll()
bf6a41db 1167 * semantics). All the events that happen during that period of time are
d47de16c
DL
1168 * chained in ep->ovflist and requeued later on.
1169 */
1170 if (unlikely(ep->ovflist != EP_UNACTIVE_PTR)) {
1171 if (epi->next == EP_UNACTIVE_PTR) {
1172 epi->next = ep->ovflist;
1173 ep->ovflist = epi;
4d7e30d9
AH
1174 if (epi->ws) {
1175 /*
1176 * Activate ep->ws since epi->ws may get
1177 * deactivated at any time.
1178 */
1179 __pm_stay_awake(ep->ws);
1180 }
1181
d47de16c
DL
1182 }
1183 goto out_unlock;
1184 }
1da177e4 1185
7699acd1 1186 /* If this file is already in the ready list we exit soon */
4d7e30d9 1187 if (!ep_is_linked(&epi->rdllink)) {
5071f97e 1188 list_add_tail(&epi->rdllink, &ep->rdllist);
eea1d585 1189 ep_pm_stay_awake_rcu(epi);
4d7e30d9 1190 }
7699acd1 1191
7699acd1
DL
1192 /*
1193 * Wake up ( if active ) both the eventpoll wait list and the ->poll()
1194 * wait list.
1195 */
df0108c5 1196 if (waitqueue_active(&ep->wq)) {
b6a515c8
JB
1197 if ((epi->event.events & EPOLLEXCLUSIVE) &&
1198 !((unsigned long)key & POLLFREE)) {
1199 switch ((unsigned long)key & EPOLLINOUT_BITS) {
1200 case POLLIN:
1201 if (epi->event.events & POLLIN)
1202 ewake = 1;
1203 break;
1204 case POLLOUT:
1205 if (epi->event.events & POLLOUT)
1206 ewake = 1;
1207 break;
1208 case 0:
1209 ewake = 1;
1210 break;
1211 }
1212 }
4a6e9e2c 1213 wake_up_locked(&ep->wq);
df0108c5 1214 }
7699acd1
DL
1215 if (waitqueue_active(&ep->poll_wait))
1216 pwake++;
1217
d47de16c 1218out_unlock:
c7ea7630 1219 spin_unlock_irqrestore(&ep->lock, flags);
1da177e4 1220
7699acd1
DL
1221 /* We have to call this outside the lock */
1222 if (pwake)
5071f97e 1223 ep_poll_safewake(&ep->poll_wait);
7699acd1 1224
138e4ad6
ON
1225 if (!(epi->event.events & EPOLLEXCLUSIVE))
1226 ewake = 1;
1227
1228 if ((unsigned long)key & POLLFREE) {
1229 /*
1230 * If we race with ep_remove_wait_queue() it can miss
1231 * ->whead = NULL and do another remove_wait_queue() after
1232 * us, so we can't use __remove_wait_queue().
1233 */
1234 list_del_init(&wait->entry);
1235 /*
1236 * ->whead != NULL protects us from the race with ep_free()
1237 * or ep_remove(), ep_remove_wait_queue() takes whead->lock
1238 * held by the caller. Once we nullify it, nothing protects
1239 * ep/epi or even wait.
1240 */
1241 smp_store_release(&ep_pwq_from_wait(wait)->whead, NULL);
1242 }
df0108c5 1243
138e4ad6 1244 return ewake;
7699acd1 1245}
1da177e4
LT
1246
1247/*
1248 * This is the callback that is used to add our wait queue to the
1249 * target file wakeup lists.
1250 */
1251static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead,
1252 poll_table *pt)
1253{
b030a4dd 1254 struct epitem *epi = ep_item_from_epqueue(pt);
1da177e4
LT
1255 struct eppoll_entry *pwq;
1256
e94b1766 1257 if (epi->nwait >= 0 && (pwq = kmem_cache_alloc(pwq_cache, GFP_KERNEL))) {
1da177e4
LT
1258 init_waitqueue_func_entry(&pwq->wait, ep_poll_callback);
1259 pwq->whead = whead;
1260 pwq->base = epi;
df0108c5
JB
1261 if (epi->event.events & EPOLLEXCLUSIVE)
1262 add_wait_queue_exclusive(whead, &pwq->wait);
1263 else
1264 add_wait_queue(whead, &pwq->wait);
1da177e4
LT
1265 list_add_tail(&pwq->llink, &epi->pwqlist);
1266 epi->nwait++;
296e236e 1267 } else {
1da177e4
LT
1268 /* We have to signal that an error occurred */
1269 epi->nwait = -1;
296e236e 1270 }
1da177e4
LT
1271}
1272
1da177e4
LT
1273static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi)
1274{
1275 int kcmp;
1276 struct rb_node **p = &ep->rbr.rb_node, *parent = NULL;
1277 struct epitem *epic;
1278
1279 while (*p) {
1280 parent = *p;
1281 epic = rb_entry(parent, struct epitem, rbn);
b030a4dd 1282 kcmp = ep_cmp_ffd(&epi->ffd, &epic->ffd);
1da177e4
LT
1283 if (kcmp > 0)
1284 p = &parent->rb_right;
1285 else
1286 p = &parent->rb_left;
1287 }
1288 rb_link_node(&epi->rbn, parent, p);
1289 rb_insert_color(&epi->rbn, &ep->rbr);
1290}
1291
a80a6b85
AM
1292
1293
28d82dc1
JB
1294#define PATH_ARR_SIZE 5
1295/*
1296 * These are the number paths of length 1 to 5, that we are allowing to emanate
1297 * from a single file of interest. For example, we allow 1000 paths of length
1298 * 1, to emanate from each file of interest. This essentially represents the
1299 * potential wakeup paths, which need to be limited in order to avoid massive
1300 * uncontrolled wakeup storms. The common use case should be a single ep which
1301 * is connected to n file sources. In this case each file source has 1 path
1302 * of length 1. Thus, the numbers below should be more than sufficient. These
1303 * path limits are enforced during an EPOLL_CTL_ADD operation, since a modify
1304 * and delete can't add additional paths. Protected by the epmutex.
1305 */
1306static const int path_limits[PATH_ARR_SIZE] = { 1000, 500, 100, 50, 10 };
1307static int path_count[PATH_ARR_SIZE];
1308
1309static int path_count_inc(int nests)
1310{
93dc6107
JB
1311 /* Allow an arbitrary number of depth 1 paths */
1312 if (nests == 0)
1313 return 0;
1314
28d82dc1
JB
1315 if (++path_count[nests] > path_limits[nests])
1316 return -1;
1317 return 0;
1318}
1319
1320static void path_count_init(void)
1321{
1322 int i;
1323
1324 for (i = 0; i < PATH_ARR_SIZE; i++)
1325 path_count[i] = 0;
1326}
1327
1328static int reverse_path_check_proc(void *priv, void *cookie, int call_nests)
1329{
1330 int error = 0;
1331 struct file *file = priv;
1332 struct file *child_file;
1333 struct epitem *epi;
1334
ae10b2b4
JB
1335 /* CTL_DEL can remove links here, but that can't increase our count */
1336 rcu_read_lock();
1337 list_for_each_entry_rcu(epi, &file->f_ep_links, fllink) {
28d82dc1
JB
1338 child_file = epi->ep->file;
1339 if (is_file_epoll(child_file)) {
1340 if (list_empty(&child_file->f_ep_links)) {
1341 if (path_count_inc(call_nests)) {
1342 error = -1;
1343 break;
1344 }
1345 } else {
1346 error = ep_call_nested(&poll_loop_ncalls,
1347 EP_MAX_NESTS,
1348 reverse_path_check_proc,
1349 child_file, child_file,
1350 current);
1351 }
1352 if (error != 0)
1353 break;
1354 } else {
1355 printk(KERN_ERR "reverse_path_check_proc: "
1356 "file is not an ep!\n");
1357 }
1358 }
ae10b2b4 1359 rcu_read_unlock();
28d82dc1
JB
1360 return error;
1361}
1362
1363/**
1364 * reverse_path_check - The tfile_check_list is list of file *, which have
1365 * links that are proposed to be newly added. We need to
1366 * make sure that those added links don't add too many
1367 * paths such that we will spend all our time waking up
1368 * eventpoll objects.
1369 *
1370 * Returns: Returns zero if the proposed links don't create too many paths,
1371 * -1 otherwise.
1372 */
1373static int reverse_path_check(void)
1374{
28d82dc1
JB
1375 int error = 0;
1376 struct file *current_file;
1377
1378 /* let's call this for all tfiles */
1379 list_for_each_entry(current_file, &tfile_check_list, f_tfile_llink) {
28d82dc1
JB
1380 path_count_init();
1381 error = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS,
1382 reverse_path_check_proc, current_file,
1383 current_file, current);
1384 if (error)
1385 break;
1386 }
1387 return error;
1388}
1389
4d7e30d9
AH
1390static int ep_create_wakeup_source(struct epitem *epi)
1391{
1392 const char *name;
eea1d585 1393 struct wakeup_source *ws;
4d7e30d9
AH
1394
1395 if (!epi->ep->ws) {
1396 epi->ep->ws = wakeup_source_register("eventpoll");
1397 if (!epi->ep->ws)
1398 return -ENOMEM;
1399 }
1400
1401 name = epi->ffd.file->f_path.dentry->d_name.name;
eea1d585
EW
1402 ws = wakeup_source_register(name);
1403
1404 if (!ws)
4d7e30d9 1405 return -ENOMEM;
eea1d585 1406 rcu_assign_pointer(epi->ws, ws);
4d7e30d9
AH
1407
1408 return 0;
1409}
1410
eea1d585
EW
1411/* rare code path, only used when EPOLL_CTL_MOD removes a wakeup source */
1412static noinline void ep_destroy_wakeup_source(struct epitem *epi)
4d7e30d9 1413{
eea1d585
EW
1414 struct wakeup_source *ws = ep_wakeup_source(epi);
1415
d6d67e72 1416 RCU_INIT_POINTER(epi->ws, NULL);
eea1d585
EW
1417
1418 /*
1419 * wait for ep_pm_stay_awake_rcu to finish, synchronize_rcu is
1420 * used internally by wakeup_source_remove, too (called by
1421 * wakeup_source_unregister), so we cannot use call_rcu
1422 */
1423 synchronize_rcu();
1424 wakeup_source_unregister(ws);
4d7e30d9
AH
1425}
1426
c7ea7630
DL
1427/*
1428 * Must be called with "mtx" held.
1429 */
1da177e4 1430static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
67347fe4 1431 struct file *tfile, int fd, int full_check)
1da177e4
LT
1432{
1433 int error, revents, pwake = 0;
1434 unsigned long flags;
52bd19f7 1435 long user_watches;
1da177e4
LT
1436 struct epitem *epi;
1437 struct ep_pqueue epq;
1438
52bd19f7
RH
1439 user_watches = atomic_long_read(&ep->user->epoll_watches);
1440 if (unlikely(user_watches >= max_user_watches))
7ef9964e 1441 return -ENOSPC;
e94b1766 1442 if (!(epi = kmem_cache_alloc(epi_cache, GFP_KERNEL)))
7ef9964e 1443 return -ENOMEM;
1da177e4
LT
1444
1445 /* Item initialization follow here ... */
1da177e4
LT
1446 INIT_LIST_HEAD(&epi->rdllink);
1447 INIT_LIST_HEAD(&epi->fllink);
1da177e4
LT
1448 INIT_LIST_HEAD(&epi->pwqlist);
1449 epi->ep = ep;
b030a4dd 1450 ep_set_ffd(&epi->ffd, tfile, fd);
1da177e4 1451 epi->event = *event;
1da177e4 1452 epi->nwait = 0;
d47de16c 1453 epi->next = EP_UNACTIVE_PTR;
4d7e30d9
AH
1454 if (epi->event.events & EPOLLWAKEUP) {
1455 error = ep_create_wakeup_source(epi);
1456 if (error)
1457 goto error_create_wakeup_source;
1458 } else {
eea1d585 1459 RCU_INIT_POINTER(epi->ws, NULL);
4d7e30d9 1460 }
1da177e4
LT
1461
1462 /* Initialize the poll table using the queue callback */
1463 epq.epi = epi;
1464 init_poll_funcptr(&epq.pt, ep_ptable_queue_proc);
1465
1466 /*
1467 * Attach the item to the poll hooks and get current event bits.
1468 * We can safely use the file* here because its usage count has
c7ea7630
DL
1469 * been increased by the caller of this function. Note that after
1470 * this operation completes, the poll callback can start hitting
1471 * the new item.
1da177e4 1472 */
450d89ec 1473 revents = ep_item_poll(epi, &epq.pt);
1da177e4
LT
1474
1475 /*
1476 * We have to check if something went wrong during the poll wait queue
1477 * install process. Namely an allocation for a wait queue failed due
1478 * high memory pressure.
1479 */
7ef9964e 1480 error = -ENOMEM;
1da177e4 1481 if (epi->nwait < 0)
7699acd1 1482 goto error_unregister;
1da177e4
LT
1483
1484 /* Add the current item to the list of active epoll hook for this file */
68499914 1485 spin_lock(&tfile->f_lock);
ae10b2b4 1486 list_add_tail_rcu(&epi->fllink, &tfile->f_ep_links);
68499914 1487 spin_unlock(&tfile->f_lock);
1da177e4 1488
c7ea7630
DL
1489 /*
1490 * Add the current item to the RB tree. All RB tree operations are
1491 * protected by "mtx", and ep_insert() is called with "mtx" held.
1492 */
1da177e4
LT
1493 ep_rbtree_insert(ep, epi);
1494
28d82dc1
JB
1495 /* now check if we've created too many backpaths */
1496 error = -EINVAL;
67347fe4 1497 if (full_check && reverse_path_check())
28d82dc1
JB
1498 goto error_remove_epi;
1499
c7ea7630
DL
1500 /* We have to drop the new item inside our item list to keep track of it */
1501 spin_lock_irqsave(&ep->lock, flags);
1502
bf3b9f63
SS
1503 /* record NAPI ID of new item if present */
1504 ep_set_busy_poll_napi_id(epi);
1505
1da177e4 1506 /* If the file is already "ready" we drop it inside the ready list */
b030a4dd 1507 if ((revents & event->events) && !ep_is_linked(&epi->rdllink)) {
1da177e4 1508 list_add_tail(&epi->rdllink, &ep->rdllist);
eea1d585 1509 ep_pm_stay_awake(epi);
1da177e4
LT
1510
1511 /* Notify waiting tasks that events are available */
1512 if (waitqueue_active(&ep->wq))
4a6e9e2c 1513 wake_up_locked(&ep->wq);
1da177e4
LT
1514 if (waitqueue_active(&ep->poll_wait))
1515 pwake++;
1516 }
1517
c7ea7630 1518 spin_unlock_irqrestore(&ep->lock, flags);
1da177e4 1519
52bd19f7 1520 atomic_long_inc(&ep->user->epoll_watches);
7ef9964e 1521
1da177e4
LT
1522 /* We have to call this outside the lock */
1523 if (pwake)
5071f97e 1524 ep_poll_safewake(&ep->poll_wait);
1da177e4 1525
1da177e4
LT
1526 return 0;
1527
28d82dc1
JB
1528error_remove_epi:
1529 spin_lock(&tfile->f_lock);
ae10b2b4 1530 list_del_rcu(&epi->fllink);
28d82dc1
JB
1531 spin_unlock(&tfile->f_lock);
1532
1533 rb_erase(&epi->rbn, &ep->rbr);
1534
7699acd1 1535error_unregister:
1da177e4
LT
1536 ep_unregister_pollwait(ep, epi);
1537
1538 /*
1539 * We need to do this because an event could have been arrived on some
67647d0f
DL
1540 * allocated wait queue. Note that we don't care about the ep->ovflist
1541 * list, since that is used/cleaned only inside a section bound by "mtx".
1542 * And ep_insert() is called with "mtx" held.
1da177e4 1543 */
c7ea7630 1544 spin_lock_irqsave(&ep->lock, flags);
b030a4dd 1545 if (ep_is_linked(&epi->rdllink))
6192bd53 1546 list_del_init(&epi->rdllink);
c7ea7630 1547 spin_unlock_irqrestore(&ep->lock, flags);
1da177e4 1548
eea1d585 1549 wakeup_source_unregister(ep_wakeup_source(epi));
4d7e30d9
AH
1550
1551error_create_wakeup_source:
b030a4dd 1552 kmem_cache_free(epi_cache, epi);
7ef9964e 1553
1da177e4
LT
1554 return error;
1555}
1556
1da177e4
LT
1557/*
1558 * Modify the interest event mask by dropping an event if the new mask
c7ea7630 1559 * has a match in the current file status. Must be called with "mtx" held.
1da177e4
LT
1560 */
1561static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_event *event)
1562{
1563 int pwake = 0;
1564 unsigned int revents;
626cf236
HV
1565 poll_table pt;
1566
1567 init_poll_funcptr(&pt, NULL);
1da177e4
LT
1568
1569 /*
e057e15f
TB
1570 * Set the new event interest mask before calling f_op->poll();
1571 * otherwise we might miss an event that happens between the
1572 * f_op->poll() call and the new event set registering.
1da177e4 1573 */
128dd175 1574 epi->event.events = event->events; /* need barrier below */
e057e15f 1575 epi->event.data = event->data; /* protected by mtx */
4d7e30d9 1576 if (epi->event.events & EPOLLWAKEUP) {
eea1d585 1577 if (!ep_has_wakeup_source(epi))
4d7e30d9 1578 ep_create_wakeup_source(epi);
eea1d585 1579 } else if (ep_has_wakeup_source(epi)) {
4d7e30d9
AH
1580 ep_destroy_wakeup_source(epi);
1581 }
1da177e4 1582
128dd175
EW
1583 /*
1584 * The following barrier has two effects:
1585 *
1586 * 1) Flush epi changes above to other CPUs. This ensures
1587 * we do not miss events from ep_poll_callback if an
1588 * event occurs immediately after we call f_op->poll().
1589 * We need this because we did not take ep->lock while
1590 * changing epi above (but ep_poll_callback does take
1591 * ep->lock).
1592 *
1593 * 2) We also need to ensure we do not miss _past_ events
1594 * when calling f_op->poll(). This barrier also
1595 * pairs with the barrier in wq_has_sleeper (see
1596 * comments for wq_has_sleeper).
1597 *
1598 * This barrier will now guarantee ep_poll_callback or f_op->poll
1599 * (or both) will notice the readiness of an item.
1600 */
1601 smp_mb();
1602
1da177e4
LT
1603 /*
1604 * Get current event bits. We can safely use the file* here because
1605 * its usage count has been increased by the caller of this function.
1606 */
450d89ec 1607 revents = ep_item_poll(epi, &pt);
1da177e4 1608
1da177e4 1609 /*
c7ea7630 1610 * If the item is "hot" and it is not registered inside the ready
67647d0f 1611 * list, push it inside.
1da177e4 1612 */
c7ea7630 1613 if (revents & event->events) {
e057e15f 1614 spin_lock_irq(&ep->lock);
c7ea7630
DL
1615 if (!ep_is_linked(&epi->rdllink)) {
1616 list_add_tail(&epi->rdllink, &ep->rdllist);
eea1d585 1617 ep_pm_stay_awake(epi);
c7ea7630
DL
1618
1619 /* Notify waiting tasks that events are available */
1620 if (waitqueue_active(&ep->wq))
4a6e9e2c 1621 wake_up_locked(&ep->wq);
c7ea7630
DL
1622 if (waitqueue_active(&ep->poll_wait))
1623 pwake++;
7699acd1 1624 }
e057e15f 1625 spin_unlock_irq(&ep->lock);
7699acd1 1626 }
1da177e4 1627
7699acd1
DL
1628 /* We have to call this outside the lock */
1629 if (pwake)
5071f97e 1630 ep_poll_safewake(&ep->poll_wait);
1da177e4 1631
7699acd1 1632 return 0;
1da177e4
LT
1633}
1634
296e236e
DL
1635static int ep_send_events_proc(struct eventpoll *ep, struct list_head *head,
1636 void *priv)
1da177e4 1637{
5071f97e
DL
1638 struct ep_send_events_data *esed = priv;
1639 int eventcnt;
296e236e 1640 unsigned int revents;
5071f97e
DL
1641 struct epitem *epi;
1642 struct epoll_event __user *uevent;
eea1d585 1643 struct wakeup_source *ws;
626cf236
HV
1644 poll_table pt;
1645
1646 init_poll_funcptr(&pt, NULL);
1da177e4 1647
296e236e 1648 /*
5071f97e
DL
1649 * We can loop without lock because we are passed a task private list.
1650 * Items cannot vanish during the loop because ep_scan_ready_list() is
1651 * holding "mtx" during this call.
296e236e 1652 */
5071f97e
DL
1653 for (eventcnt = 0, uevent = esed->events;
1654 !list_empty(head) && eventcnt < esed->maxevents;) {
1655 epi = list_first_entry(head, struct epitem, rdllink);
d47de16c 1656
4d7e30d9
AH
1657 /*
1658 * Activate ep->ws before deactivating epi->ws to prevent
1659 * triggering auto-suspend here (in case we reactive epi->ws
1660 * below).
1661 *
1662 * This could be rearranged to delay the deactivation of epi->ws
1663 * instead, but then epi->ws would temporarily be out of sync
1664 * with ep_is_linked().
1665 */
eea1d585
EW
1666 ws = ep_wakeup_source(epi);
1667 if (ws) {
1668 if (ws->active)
1669 __pm_stay_awake(ep->ws);
1670 __pm_relax(ws);
1671 }
1672
d47de16c 1673 list_del_init(&epi->rdllink);
1da177e4 1674
450d89ec 1675 revents = ep_item_poll(epi, &pt);
5071f97e 1676
296e236e 1677 /*
5071f97e
DL
1678 * If the event mask intersect the caller-requested one,
1679 * deliver the event to userspace. Again, ep_scan_ready_list()
1680 * is holding "mtx", so no operations coming from userspace
1681 * can change the item.
296e236e
DL
1682 */
1683 if (revents) {
5071f97e 1684 if (__put_user(revents, &uevent->events) ||
d0305882
TB
1685 __put_user(epi->event.data, &uevent->data)) {
1686 list_add(&epi->rdllink, head);
eea1d585 1687 ep_pm_stay_awake(epi);
296e236e 1688 return eventcnt ? eventcnt : -EFAULT;
d0305882 1689 }
296e236e 1690 eventcnt++;
5071f97e 1691 uevent++;
296e236e
DL
1692 if (epi->event.events & EPOLLONESHOT)
1693 epi->event.events &= EP_PRIVATE_BITS;
1694 else if (!(epi->event.events & EPOLLET)) {
1695 /*
1696 * If this file has been added with Level
1697 * Trigger mode, we need to insert back inside
1698 * the ready list, so that the next call to
1699 * epoll_wait() will check again the events
25985edc 1700 * availability. At this point, no one can insert
296e236e
DL
1701 * into ep->rdllist besides us. The epoll_ctl()
1702 * callers are locked out by
1703 * ep_scan_ready_list() holding "mtx" and the
1704 * poll callback will queue them in ep->ovflist.
1705 */
1706 list_add_tail(&epi->rdllink, &ep->rdllist);
eea1d585 1707 ep_pm_stay_awake(epi);
296e236e
DL
1708 }
1709 }
1710 }
5071f97e
DL
1711
1712 return eventcnt;
1713}
d47de16c 1714
296e236e
DL
1715static int ep_send_events(struct eventpoll *ep,
1716 struct epoll_event __user *events, int maxevents)
5071f97e
DL
1717{
1718 struct ep_send_events_data esed;
1da177e4 1719
5071f97e
DL
1720 esed.maxevents = maxevents;
1721 esed.events = events;
6192bd53 1722
67347fe4 1723 return ep_scan_ready_list(ep, ep_send_events_proc, &esed, 0, false);
1da177e4
LT
1724}
1725
766b9f92 1726static inline struct timespec64 ep_set_mstimeout(long ms)
0781b909 1727{
766b9f92 1728 struct timespec64 now, ts = {
0781b909
ED
1729 .tv_sec = ms / MSEC_PER_SEC,
1730 .tv_nsec = NSEC_PER_MSEC * (ms % MSEC_PER_SEC),
1731 };
1732
766b9f92
DD
1733 ktime_get_ts64(&now);
1734 return timespec64_add_safe(now, ts);
0781b909
ED
1735}
1736
f4d93ad7
SB
1737/**
1738 * ep_poll - Retrieves ready events, and delivers them to the caller supplied
1739 * event buffer.
1740 *
1741 * @ep: Pointer to the eventpoll context.
1742 * @events: Pointer to the userspace buffer where the ready events should be
1743 * stored.
1744 * @maxevents: Size (in terms of number of events) of the caller event buffer.
1745 * @timeout: Maximum timeout for the ready events fetch operation, in
1746 * milliseconds. If the @timeout is zero, the function will not block,
1747 * while if the @timeout is less than zero, the function will block
1748 * until at least one event has been retrieved (or an error
1749 * occurred).
1750 *
1751 * Returns: Returns the number of ready events which have been fetched, or an
1752 * error code, in case of error.
1753 */
1da177e4
LT
1754static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
1755 int maxevents, long timeout)
1756{
f4d93ad7 1757 int res = 0, eavail, timed_out = 0;
1da177e4 1758 unsigned long flags;
da8b44d5 1759 u64 slack = 0;
ac6424b9 1760 wait_queue_entry_t wait;
95aac7b1
SB
1761 ktime_t expires, *to = NULL;
1762
1763 if (timeout > 0) {
766b9f92 1764 struct timespec64 end_time = ep_set_mstimeout(timeout);
0781b909 1765
95aac7b1
SB
1766 slack = select_estimate_accuracy(&end_time);
1767 to = &expires;
766b9f92 1768 *to = timespec64_to_ktime(end_time);
95aac7b1 1769 } else if (timeout == 0) {
f4d93ad7
SB
1770 /*
1771 * Avoid the unnecessary trip to the wait queue loop, if the
1772 * caller specified a non blocking operation.
1773 */
95aac7b1 1774 timed_out = 1;
f4d93ad7
SB
1775 spin_lock_irqsave(&ep->lock, flags);
1776 goto check_events;
95aac7b1 1777 }
1da177e4 1778
f4d93ad7 1779fetch_events:
bf3b9f63
SS
1780
1781 if (!ep_events_available(ep))
1782 ep_busy_loop(ep, timed_out);
1783
c7ea7630 1784 spin_lock_irqsave(&ep->lock, flags);
1da177e4 1785
3fb0e584 1786 if (!ep_events_available(ep)) {
bf3b9f63
SS
1787 /*
1788 * Busy poll timed out. Drop NAPI ID for now, we can add
1789 * it back in when we have moved a socket with a valid NAPI
1790 * ID onto the ready list.
1791 */
1792 ep_reset_busy_poll_napi_id(ep);
1793
1da177e4
LT
1794 /*
1795 * We don't have any available event to return to the caller.
1796 * We need to sleep here, and we will be wake up by
1797 * ep_poll_callback() when events will become available.
1798 */
1799 init_waitqueue_entry(&wait, current);
a93d2f17 1800 __add_wait_queue_exclusive(&ep->wq, &wait);
1da177e4
LT
1801
1802 for (;;) {
1803 /*
1804 * We don't want to sleep if the ep_poll_callback() sends us
1805 * a wakeup in between. That's why we set the task state
1806 * to TASK_INTERRUPTIBLE before doing the checks.
1807 */
1808 set_current_state(TASK_INTERRUPTIBLE);
c257a340
DR
1809 /*
1810 * Always short-circuit for fatal signals to allow
1811 * threads to make a timely exit without the chance of
1812 * finding more events available and fetching
1813 * repeatedly.
1814 */
1815 if (fatal_signal_pending(current)) {
1816 res = -EINTR;
1817 break;
1818 }
3fb0e584 1819 if (ep_events_available(ep) || timed_out)
1da177e4
LT
1820 break;
1821 if (signal_pending(current)) {
1822 res = -EINTR;
1823 break;
1824 }
1825
c7ea7630 1826 spin_unlock_irqrestore(&ep->lock, flags);
c511851d 1827 if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS))
95aac7b1
SB
1828 timed_out = 1;
1829
c7ea7630 1830 spin_lock_irqsave(&ep->lock, flags);
1da177e4 1831 }
1da177e4 1832
4d5755b1
DB
1833 __remove_wait_queue(&ep->wq, &wait);
1834 __set_current_state(TASK_RUNNING);
1da177e4 1835 }
f4d93ad7 1836check_events:
1da177e4 1837 /* Is it worth to try to dig for events ? */
3fb0e584 1838 eavail = ep_events_available(ep);
1da177e4 1839
c7ea7630 1840 spin_unlock_irqrestore(&ep->lock, flags);
1da177e4
LT
1841
1842 /*
1843 * Try to transfer events to user space. In case we get 0 events and
1844 * there's still timeout left over, we go trying again in search of
1845 * more luck.
1846 */
1847 if (!res && eavail &&
95aac7b1 1848 !(res = ep_send_events(ep, events, maxevents)) && !timed_out)
f4d93ad7 1849 goto fetch_events;
1da177e4
LT
1850
1851 return res;
1852}
1853
22bacca4
DL
1854/**
1855 * ep_loop_check_proc - Callback function to be passed to the @ep_call_nested()
1856 * API, to verify that adding an epoll file inside another
1857 * epoll structure, does not violate the constraints, in
1858 * terms of closed loops, or too deep chains (which can
1859 * result in excessive stack usage).
1860 *
1861 * @priv: Pointer to the epoll file to be currently checked.
1862 * @cookie: Original cookie for this call. This is the top-of-the-chain epoll
1863 * data structure pointer.
1864 * @call_nests: Current dept of the @ep_call_nested() call stack.
1865 *
1866 * Returns: Returns zero if adding the epoll @file inside current epoll
1867 * structure @ep does not violate the constraints, or -1 otherwise.
1868 */
1869static int ep_loop_check_proc(void *priv, void *cookie, int call_nests)
1870{
1871 int error = 0;
1872 struct file *file = priv;
1873 struct eventpoll *ep = file->private_data;
28d82dc1 1874 struct eventpoll *ep_tovisit;
22bacca4
DL
1875 struct rb_node *rbp;
1876 struct epitem *epi;
1877
d8805e63 1878 mutex_lock_nested(&ep->mtx, call_nests + 1);
28d82dc1
JB
1879 ep->visited = 1;
1880 list_add(&ep->visited_list_link, &visited_list);
22bacca4
DL
1881 for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) {
1882 epi = rb_entry(rbp, struct epitem, rbn);
1883 if (unlikely(is_file_epoll(epi->ffd.file))) {
28d82dc1
JB
1884 ep_tovisit = epi->ffd.file->private_data;
1885 if (ep_tovisit->visited)
1886 continue;
22bacca4 1887 error = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS,
28d82dc1
JB
1888 ep_loop_check_proc, epi->ffd.file,
1889 ep_tovisit, current);
22bacca4
DL
1890 if (error != 0)
1891 break;
28d82dc1
JB
1892 } else {
1893 /*
1894 * If we've reached a file that is not associated with
1895 * an ep, then we need to check if the newly added
1896 * links are going to add too many wakeup paths. We do
1897 * this by adding it to the tfile_check_list, if it's
1898 * not already there, and calling reverse_path_check()
1899 * during ep_insert().
1900 */
1901 if (list_empty(&epi->ffd.file->f_tfile_llink))
1902 list_add(&epi->ffd.file->f_tfile_llink,
1903 &tfile_check_list);
22bacca4
DL
1904 }
1905 }
1906 mutex_unlock(&ep->mtx);
1907
1908 return error;
1909}
1910
1911/**
1912 * ep_loop_check - Performs a check to verify that adding an epoll file (@file)
1913 * another epoll file (represented by @ep) does not create
1914 * closed loops or too deep chains.
1915 *
1916 * @ep: Pointer to the epoll private data structure.
1917 * @file: Pointer to the epoll file to be checked.
1918 *
1919 * Returns: Returns zero if adding the epoll @file inside current epoll
1920 * structure @ep does not violate the constraints, or -1 otherwise.
1921 */
1922static int ep_loop_check(struct eventpoll *ep, struct file *file)
1923{
28d82dc1
JB
1924 int ret;
1925 struct eventpoll *ep_cur, *ep_next;
1926
1927 ret = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS,
22bacca4 1928 ep_loop_check_proc, file, ep, current);
28d82dc1
JB
1929 /* clear visited list */
1930 list_for_each_entry_safe(ep_cur, ep_next, &visited_list,
1931 visited_list_link) {
1932 ep_cur->visited = 0;
1933 list_del(&ep_cur->visited_list_link);
1934 }
1935 return ret;
1936}
1937
1938static void clear_tfile_check_list(void)
1939{
1940 struct file *file;
1941
1942 /* first clear the tfile_check_list */
1943 while (!list_empty(&tfile_check_list)) {
1944 file = list_first_entry(&tfile_check_list, struct file,
1945 f_tfile_llink);
1946 list_del_init(&file->f_tfile_llink);
1947 }
1948 INIT_LIST_HEAD(&tfile_check_list);
22bacca4
DL
1949}
1950
7699acd1 1951/*
523723bb 1952 * Open an eventpoll file descriptor.
7699acd1 1953 */
5a8a82b1 1954SYSCALL_DEFINE1(epoll_create1, int, flags)
7699acd1 1955{
28d82dc1 1956 int error, fd;
bb57c3ed 1957 struct eventpoll *ep = NULL;
28d82dc1 1958 struct file *file;
7699acd1 1959
e38b36f3
UD
1960 /* Check the EPOLL_* constant for consistency. */
1961 BUILD_BUG_ON(EPOLL_CLOEXEC != O_CLOEXEC);
1962
296e236e
DL
1963 if (flags & ~EPOLL_CLOEXEC)
1964 return -EINVAL;
7699acd1 1965 /*
bb57c3ed 1966 * Create the internal data structure ("struct eventpoll").
7699acd1 1967 */
9fe5ad9c 1968 error = ep_alloc(&ep);
bb57c3ed
DL
1969 if (error < 0)
1970 return error;
7699acd1
DL
1971 /*
1972 * Creates all the items needed to setup an eventpoll file. That is,
2030a42c 1973 * a file structure and a free file descriptor.
7699acd1 1974 */
28d82dc1
JB
1975 fd = get_unused_fd_flags(O_RDWR | (flags & O_CLOEXEC));
1976 if (fd < 0) {
1977 error = fd;
1978 goto out_free_ep;
1979 }
1980 file = anon_inode_getfile("[eventpoll]", &eventpoll_fops, ep,
628ff7c1 1981 O_RDWR | (flags & O_CLOEXEC));
28d82dc1
JB
1982 if (IS_ERR(file)) {
1983 error = PTR_ERR(file);
1984 goto out_free_fd;
1985 }
28d82dc1 1986 ep->file = file;
98022748 1987 fd_install(fd, file);
28d82dc1
JB
1988 return fd;
1989
1990out_free_fd:
1991 put_unused_fd(fd);
1992out_free_ep:
1993 ep_free(ep);
bb57c3ed 1994 return error;
7699acd1
DL
1995}
1996
5a8a82b1 1997SYSCALL_DEFINE1(epoll_create, int, size)
a0998b50 1998{
bfe3891a 1999 if (size <= 0)
9fe5ad9c
UD
2000 return -EINVAL;
2001
2002 return sys_epoll_create1(0);
a0998b50
UD
2003}
2004
7699acd1
DL
2005/*
2006 * The following function implements the controller interface for
2007 * the eventpoll file that enables the insertion/removal/change of
67647d0f 2008 * file descriptors inside the interest set.
7699acd1 2009 */
5a8a82b1
HC
2010SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd,
2011 struct epoll_event __user *, event)
7699acd1
DL
2012{
2013 int error;
67347fe4 2014 int full_check = 0;
7e3fb584 2015 struct fd f, tf;
7699acd1
DL
2016 struct eventpoll *ep;
2017 struct epitem *epi;
2018 struct epoll_event epds;
67347fe4 2019 struct eventpoll *tep = NULL;
7699acd1 2020
7699acd1
DL
2021 error = -EFAULT;
2022 if (ep_op_has_event(op) &&
2023 copy_from_user(&epds, event, sizeof(struct epoll_event)))
2024 goto error_return;
2025
7699acd1 2026 error = -EBADF;
7e3fb584
AV
2027 f = fdget(epfd);
2028 if (!f.file)
7699acd1
DL
2029 goto error_return;
2030
2031 /* Get the "struct file *" for the target file */
7e3fb584
AV
2032 tf = fdget(fd);
2033 if (!tf.file)
7699acd1
DL
2034 goto error_fput;
2035
2036 /* The target file descriptor must support poll */
2037 error = -EPERM;
72c2d531 2038 if (!tf.file->f_op->poll)
7699acd1
DL
2039 goto error_tgt_fput;
2040
4d7e30d9 2041 /* Check if EPOLLWAKEUP is allowed */
c680e41b
NI
2042 if (ep_op_has_event(op))
2043 ep_take_care_of_epollwakeup(&epds);
4d7e30d9 2044
7699acd1
DL
2045 /*
2046 * We have to check that the file structure underneath the file descriptor
2047 * the user passed to us _is_ an eventpoll file. And also we do not permit
2048 * adding an epoll file descriptor inside itself.
2049 */
2050 error = -EINVAL;
7e3fb584 2051 if (f.file == tf.file || !is_file_epoll(f.file))
7699acd1
DL
2052 goto error_tgt_fput;
2053
df0108c5
JB
2054 /*
2055 * epoll adds to the wakeup queue at EPOLL_CTL_ADD time only,
2056 * so EPOLLEXCLUSIVE is not allowed for a EPOLL_CTL_MOD operation.
2057 * Also, we do not currently supported nested exclusive wakeups.
2058 */
c857ab64 2059 if (ep_op_has_event(op) && (epds.events & EPOLLEXCLUSIVE)) {
b6a515c8
JB
2060 if (op == EPOLL_CTL_MOD)
2061 goto error_tgt_fput;
2062 if (op == EPOLL_CTL_ADD && (is_file_epoll(tf.file) ||
2063 (epds.events & ~EPOLLEXCLUSIVE_OK_BITS)))
2064 goto error_tgt_fput;
2065 }
df0108c5 2066
7699acd1
DL
2067 /*
2068 * At this point it is safe to assume that the "private_data" contains
2069 * our own data structure.
2070 */
7e3fb584 2071 ep = f.file->private_data;
7699acd1 2072
22bacca4
DL
2073 /*
2074 * When we insert an epoll file descriptor, inside another epoll file
2075 * descriptor, there is the change of creating closed loops, which are
28d82dc1
JB
2076 * better be handled here, than in more critical paths. While we are
2077 * checking for loops we also determine the list of files reachable
2078 * and hang them on the tfile_check_list, so we can check that we
2079 * haven't created too many possible wakeup paths.
22bacca4 2080 *
67347fe4
JB
2081 * We do not need to take the global 'epumutex' on EPOLL_CTL_ADD when
2082 * the epoll file descriptor is attaching directly to a wakeup source,
2083 * unless the epoll file descriptor is nested. The purpose of taking the
2084 * 'epmutex' on add is to prevent complex toplogies such as loops and
2085 * deep wakeup paths from forming in parallel through multiple
2086 * EPOLL_CTL_ADD operations.
22bacca4 2087 */
67347fe4 2088 mutex_lock_nested(&ep->mtx, 0);
28d82dc1 2089 if (op == EPOLL_CTL_ADD) {
67347fe4
JB
2090 if (!list_empty(&f.file->f_ep_links) ||
2091 is_file_epoll(tf.file)) {
2092 full_check = 1;
2093 mutex_unlock(&ep->mtx);
2094 mutex_lock(&epmutex);
2095 if (is_file_epoll(tf.file)) {
2096 error = -ELOOP;
2097 if (ep_loop_check(ep, tf.file) != 0) {
2098 clear_tfile_check_list();
2099 goto error_tgt_fput;
2100 }
2101 } else
2102 list_add(&tf.file->f_tfile_llink,
2103 &tfile_check_list);
2104 mutex_lock_nested(&ep->mtx, 0);
2105 if (is_file_epoll(tf.file)) {
2106 tep = tf.file->private_data;
2107 mutex_lock_nested(&tep->mtx, 1);
13d51807 2108 }
67347fe4
JB
2109 }
2110 }
7699acd1 2111
67647d0f
DL
2112 /*
2113 * Try to lookup the file inside our RB tree, Since we grabbed "mtx"
2114 * above, we can be sure to be able to use the item looked up by
2115 * ep_find() till we release the mutex.
2116 */
7e3fb584 2117 epi = ep_find(ep, tf.file, fd);
7699acd1
DL
2118
2119 error = -EINVAL;
2120 switch (op) {
2121 case EPOLL_CTL_ADD:
2122 if (!epi) {
2123 epds.events |= POLLERR | POLLHUP;
67347fe4 2124 error = ep_insert(ep, &epds, tf.file, fd, full_check);
7699acd1
DL
2125 } else
2126 error = -EEXIST;
67347fe4
JB
2127 if (full_check)
2128 clear_tfile_check_list();
7699acd1
DL
2129 break;
2130 case EPOLL_CTL_DEL:
2131 if (epi)
2132 error = ep_remove(ep, epi);
2133 else
2134 error = -ENOENT;
2135 break;
2136 case EPOLL_CTL_MOD:
2137 if (epi) {
b6a515c8
JB
2138 if (!(epi->event.events & EPOLLEXCLUSIVE)) {
2139 epds.events |= POLLERR | POLLHUP;
2140 error = ep_modify(ep, epi, &epds);
2141 }
7699acd1
DL
2142 } else
2143 error = -ENOENT;
2144 break;
2145 }
67347fe4
JB
2146 if (tep != NULL)
2147 mutex_unlock(&tep->mtx);
d47de16c 2148 mutex_unlock(&ep->mtx);
7699acd1
DL
2149
2150error_tgt_fput:
67347fe4 2151 if (full_check)
22bacca4
DL
2152 mutex_unlock(&epmutex);
2153
7e3fb584 2154 fdput(tf);
7699acd1 2155error_fput:
7e3fb584 2156 fdput(f);
7699acd1 2157error_return:
7699acd1
DL
2158
2159 return error;
2160}
2161
2162/*
2163 * Implement the event wait interface for the eventpoll file. It is the kernel
2164 * part of the user space epoll_wait(2).
2165 */
5a8a82b1
HC
2166SYSCALL_DEFINE4(epoll_wait, int, epfd, struct epoll_event __user *, events,
2167 int, maxevents, int, timeout)
7699acd1 2168{
2903ff01
AV
2169 int error;
2170 struct fd f;
7699acd1
DL
2171 struct eventpoll *ep;
2172
7699acd1
DL
2173 /* The maximum number of event must be greater than zero */
2174 if (maxevents <= 0 || maxevents > EP_MAX_EVENTS)
2175 return -EINVAL;
2176
2177 /* Verify that the area passed by the user is writeable */
2903ff01
AV
2178 if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event)))
2179 return -EFAULT;
7699acd1
DL
2180
2181 /* Get the "struct file *" for the eventpoll file */
2903ff01
AV
2182 f = fdget(epfd);
2183 if (!f.file)
2184 return -EBADF;
7699acd1
DL
2185
2186 /*
2187 * We have to check that the file structure underneath the fd
2188 * the user passed to us _is_ an eventpoll file.
2189 */
2190 error = -EINVAL;
2903ff01 2191 if (!is_file_epoll(f.file))
7699acd1
DL
2192 goto error_fput;
2193
2194 /*
2195 * At this point it is safe to assume that the "private_data" contains
2196 * our own data structure.
2197 */
2903ff01 2198 ep = f.file->private_data;
7699acd1
DL
2199
2200 /* Time to fish for events ... */
2201 error = ep_poll(ep, events, maxevents, timeout);
2202
2203error_fput:
2903ff01 2204 fdput(f);
7699acd1
DL
2205 return error;
2206}
2207
7699acd1
DL
2208/*
2209 * Implement the event wait interface for the eventpoll file. It is the kernel
2210 * part of the user space epoll_pwait(2).
2211 */
5a8a82b1
HC
2212SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events,
2213 int, maxevents, int, timeout, const sigset_t __user *, sigmask,
2214 size_t, sigsetsize)
7699acd1
DL
2215{
2216 int error;
2217 sigset_t ksigmask, sigsaved;
2218
2219 /*
2220 * If the caller wants a certain signal mask to be set during the wait,
2221 * we apply it here.
2222 */
2223 if (sigmask) {
2224 if (sigsetsize != sizeof(sigset_t))
2225 return -EINVAL;
2226 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
2227 return -EFAULT;
77d55918
ON
2228 sigsaved = current->blocked;
2229 set_current_blocked(&ksigmask);
7699acd1
DL
2230 }
2231
2232 error = sys_epoll_wait(epfd, events, maxevents, timeout);
2233
2234 /*
2235 * If we changed the signal mask, we need to restore the original one.
2236 * In case we've got a signal while waiting, we do not restore the
2237 * signal mask yet, and we allow do_signal() to deliver the signal on
2238 * the way back to userspace, before the signal mask is restored.
2239 */
2240 if (sigmask) {
2241 if (error == -EINTR) {
2242 memcpy(&current->saved_sigmask, &sigsaved,
c7ea7630 2243 sizeof(sigsaved));
4e4c22c7 2244 set_restore_sigmask();
7699acd1 2245 } else
77d55918 2246 set_current_blocked(&sigsaved);
7699acd1
DL
2247 }
2248
2249 return error;
2250}
2251
35280bd4
AV
2252#ifdef CONFIG_COMPAT
2253COMPAT_SYSCALL_DEFINE6(epoll_pwait, int, epfd,
2254 struct epoll_event __user *, events,
2255 int, maxevents, int, timeout,
2256 const compat_sigset_t __user *, sigmask,
2257 compat_size_t, sigsetsize)
2258{
2259 long err;
2260 compat_sigset_t csigmask;
2261 sigset_t ksigmask, sigsaved;
2262
2263 /*
2264 * If the caller wants a certain signal mask to be set during the wait,
2265 * we apply it here.
2266 */
2267 if (sigmask) {
2268 if (sigsetsize != sizeof(compat_sigset_t))
2269 return -EINVAL;
2270 if (copy_from_user(&csigmask, sigmask, sizeof(csigmask)))
2271 return -EFAULT;
2272 sigset_from_compat(&ksigmask, &csigmask);
77d55918
ON
2273 sigsaved = current->blocked;
2274 set_current_blocked(&ksigmask);
35280bd4
AV
2275 }
2276
2277 err = sys_epoll_wait(epfd, events, maxevents, timeout);
2278
2279 /*
2280 * If we changed the signal mask, we need to restore the original one.
2281 * In case we've got a signal while waiting, we do not restore the
2282 * signal mask yet, and we allow do_signal() to deliver the signal on
2283 * the way back to userspace, before the signal mask is restored.
2284 */
2285 if (sigmask) {
2286 if (err == -EINTR) {
2287 memcpy(&current->saved_sigmask, &sigsaved,
2288 sizeof(sigsaved));
2289 set_restore_sigmask();
2290 } else
77d55918 2291 set_current_blocked(&sigsaved);
35280bd4
AV
2292 }
2293
2294 return err;
2295}
2296#endif
2297
1da177e4
LT
2298static int __init eventpoll_init(void)
2299{
7ef9964e
DL
2300 struct sysinfo si;
2301
2302 si_meminfo(&si);
9df04e1f
DL
2303 /*
2304 * Allows top 4% of lomem to be allocated for epoll watches (per user).
2305 */
2306 max_user_watches = (((si.totalram - si.totalhigh) / 25) << PAGE_SHIFT) /
7ef9964e 2307 EP_ITEM_COST;
52bd19f7 2308 BUG_ON(max_user_watches < 0);
1da177e4 2309
22bacca4
DL
2310 /*
2311 * Initialize the structure used to perform epoll file descriptor
2312 * inclusion loops checks.
2313 */
2314 ep_nested_calls_init(&poll_loop_ncalls);
2315
1da177e4 2316 /* Initialize the structure used to perform safe poll wait head wake ups */
5071f97e
DL
2317 ep_nested_calls_init(&poll_safewake_ncalls);
2318
2319 /* Initialize the structure used to perform file's f_op->poll() calls */
2320 ep_nested_calls_init(&poll_readywalk_ncalls);
1da177e4 2321
39732ca5
EW
2322 /*
2323 * We can have many thousands of epitems, so prevent this from
2324 * using an extra cache line on 64-bit (and smaller) CPUs
2325 */
2326 BUILD_BUG_ON(sizeof(void *) <= 8 && sizeof(struct epitem) > 128);
2327
1da177e4
LT
2328 /* Allocates slab cache used to allocate "struct epitem" items */
2329 epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem),
bb57c3ed 2330 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
1da177e4
LT
2331
2332 /* Allocates slab cache used to allocate "struct eppoll_entry" */
2333 pwq_cache = kmem_cache_create("eventpoll_pwq",
bb57c3ed 2334 sizeof(struct eppoll_entry), 0, SLAB_PANIC, NULL);
1da177e4 2335
1da177e4 2336 return 0;
1da177e4 2337}
cea69241 2338fs_initcall(eventpoll_init);