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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
Davide Libenzic7ea7632007-05-15 01:40:47 -07002 * fs/eventpoll.c (Efficent event polling implementation)
3 * Copyright (C) 2001,...,2007 Davide Libenzi
Linus Torvalds1da177e2005-04-16 15:20:36 -07004 *
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
Linus Torvalds1da177e2005-04-16 15:20:36 -070014#include <linux/init.h>
15#include <linux/kernel.h>
16#include <linux/sched.h>
17#include <linux/fs.h>
18#include <linux/file.h>
19#include <linux/signal.h>
20#include <linux/errno.h>
21#include <linux/mm.h>
22#include <linux/slab.h>
23#include <linux/poll.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070024#include <linux/string.h>
25#include <linux/list.h>
26#include <linux/hash.h>
27#include <linux/spinlock.h>
28#include <linux/syscalls.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070029#include <linux/rbtree.h>
30#include <linux/wait.h>
31#include <linux/eventpoll.h>
32#include <linux/mount.h>
33#include <linux/bitops.h>
Arjan van de Ven144efe32006-03-23 03:00:32 -080034#include <linux/mutex.h>
Davide Libenzida66f7c2007-05-10 22:23:21 -070035#include <linux/anon_inodes.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070036#include <asm/uaccess.h>
37#include <asm/system.h>
38#include <asm/io.h>
39#include <asm/mman.h>
40#include <asm/atomic.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070041
Linus Torvalds1da177e2005-04-16 15:20:36 -070042/*
43 * LOCKING:
44 * There are three level of locking required by epoll :
45 *
Arjan van de Ven144efe32006-03-23 03:00:32 -080046 * 1) epmutex (mutex)
Davide Libenzic7ea7632007-05-15 01:40:47 -070047 * 2) ep->mtx (mutex)
48 * 3) ep->lock (spinlock)
Linus Torvalds1da177e2005-04-16 15:20:36 -070049 *
50 * The acquire order is the one listed above, from 1 to 3.
51 * We need a spinlock (ep->lock) because we manipulate objects
52 * from inside the poll callback, that might be triggered from
53 * a wake_up() that in turn might be called from IRQ context.
54 * So we can't sleep inside the poll callback and hence we need
55 * a spinlock. During the event transfer loop (from kernel to
56 * user space) we could end up sleeping due a copy_to_user(), so
57 * we need a lock that will allow us to sleep. This lock is a
Davide Libenzid47de162007-05-15 01:40:41 -070058 * mutex (ep->mtx). It is acquired during the event transfer loop,
59 * during epoll_ctl(EPOLL_CTL_DEL) and during eventpoll_release_file().
60 * Then we also need a global mutex to serialize eventpoll_release_file()
61 * and ep_free().
62 * This mutex is acquired by ep_free() during the epoll file
Linus Torvalds1da177e2005-04-16 15:20:36 -070063 * cleanup path and it is also acquired by eventpoll_release_file()
64 * if a file has been pushed inside an epoll set and it is then
65 * close()d without a previous call toepoll_ctl(EPOLL_CTL_DEL).
Davide Libenzid47de162007-05-15 01:40:41 -070066 * It is possible to drop the "ep->mtx" and to use the global
67 * mutex "epmutex" (together with "ep->lock") to have it working,
68 * but having "ep->mtx" will make the interface more scalable.
Arjan van de Ven144efe32006-03-23 03:00:32 -080069 * Events that require holding "epmutex" are very rare, while for
Davide Libenzid47de162007-05-15 01:40:41 -070070 * normal operations the epoll private "ep->mtx" will guarantee
71 * a better scalability.
Linus Torvalds1da177e2005-04-16 15:20:36 -070072 */
73
Linus Torvalds1da177e2005-04-16 15:20:36 -070074#define DEBUG_EPOLL 0
75
76#if DEBUG_EPOLL > 0
77#define DPRINTK(x) printk x
78#define DNPRINTK(n, x) do { if ((n) <= DEBUG_EPOLL) printk x; } while (0)
79#else /* #if DEBUG_EPOLL > 0 */
80#define DPRINTK(x) (void) 0
81#define DNPRINTK(n, x) (void) 0
82#endif /* #if DEBUG_EPOLL > 0 */
83
84#define DEBUG_EPI 0
85
86#if DEBUG_EPI != 0
87#define EPI_SLAB_DEBUG (SLAB_DEBUG_FREE | SLAB_RED_ZONE /* | SLAB_POISON */)
88#else /* #if DEBUG_EPI != 0 */
89#define EPI_SLAB_DEBUG 0
90#endif /* #if DEBUG_EPI != 0 */
91
92/* Epoll private bits inside the event mask */
93#define EP_PRIVATE_BITS (EPOLLONESHOT | EPOLLET)
94
95/* Maximum number of poll wake up nests we are allowing */
96#define EP_MAX_POLLWAKE_NESTS 4
97
Davide Libenzie3306dd2005-09-27 21:45:33 -070098/* Maximum msec timeout value storeable in a long int */
99#define EP_MAX_MSTIMEO min(1000ULL * MAX_SCHEDULE_TIMEOUT / HZ, (LONG_MAX - 999ULL) / HZ)
100
Davide Libenzib6119672006-10-11 01:21:44 -0700101#define EP_MAX_EVENTS (INT_MAX / sizeof(struct epoll_event))
102
Davide Libenzid47de162007-05-15 01:40:41 -0700103#define EP_UNACTIVE_PTR ((void *) -1L)
104
Linus Torvalds1da177e2005-04-16 15:20:36 -0700105struct epoll_filefd {
106 struct file *file;
107 int fd;
108};
109
110/*
111 * Node that is linked into the "wake_task_list" member of the "struct poll_safewake".
112 * It is used to keep track on all tasks that are currently inside the wake_up() code
113 * to 1) short-circuit the one coming from the same task and same wait queue head
Davide Libenzid47de162007-05-15 01:40:41 -0700114 * (loop) 2) allow a maximum number of epoll descriptors inclusion nesting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700115 * 3) let go the ones coming from other tasks.
116 */
117struct wake_task_node {
118 struct list_head llink;
Ingo Molnar36c8b582006-07-03 00:25:41 -0700119 struct task_struct *task;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700120 wait_queue_head_t *wq;
121};
122
123/*
124 * This is used to implement the safe poll wake up avoiding to reenter
125 * the poll callback from inside wake_up().
126 */
127struct poll_safewake {
128 struct list_head wake_task_list;
129 spinlock_t lock;
130};
131
132/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700133 * Each file descriptor added to the eventpoll interface will
Davide Libenzi6192bd52007-05-08 00:25:41 -0700134 * have an entry of this type linked to the "rbr" RB tree.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700135 */
136struct epitem {
137 /* RB-Tree node used to link this structure to the eventpoll rb-tree */
138 struct rb_node rbn;
139
140 /* List header used to link this structure to the eventpoll ready list */
141 struct list_head rdllink;
142
Davide Libenzic7ea7632007-05-15 01:40:47 -0700143 /*
144 * Works together "struct eventpoll"->ovflist in keeping the
145 * single linked chain of items.
146 */
147 struct epitem *next;
148
Linus Torvalds1da177e2005-04-16 15:20:36 -0700149 /* The file descriptor information this item refers to */
150 struct epoll_filefd ffd;
151
152 /* Number of active wait queue attached to poll operations */
153 int nwait;
154
155 /* List containing poll wait queues */
156 struct list_head pwqlist;
157
158 /* The "container" of this item */
159 struct eventpoll *ep;
160
Linus Torvalds1da177e2005-04-16 15:20:36 -0700161 /* List header used to link this item to the "struct file" items list */
162 struct list_head fllink;
Davide Libenzid47de162007-05-15 01:40:41 -0700163
Davide Libenzic7ea7632007-05-15 01:40:47 -0700164 /* The structure that describe the interested events and the source fd */
165 struct epoll_event event;
Davide Libenzid47de162007-05-15 01:40:41 -0700166};
167
168/*
169 * This structure is stored inside the "private_data" member of the file
170 * structure and rapresent the main data sructure for the eventpoll
171 * interface.
172 */
173struct eventpoll {
174 /* Protect the this structure access */
Davide Libenzic7ea7632007-05-15 01:40:47 -0700175 spinlock_t lock;
Davide Libenzid47de162007-05-15 01:40:41 -0700176
177 /*
178 * This mutex is used to ensure that files are not removed
179 * while epoll is using them. This is held during the event
180 * collection loop, the file cleanup path, the epoll file exit
181 * code and the ctl operations.
182 */
183 struct mutex mtx;
184
185 /* Wait queue used by sys_epoll_wait() */
186 wait_queue_head_t wq;
187
188 /* Wait queue used by file->poll() */
189 wait_queue_head_t poll_wait;
190
191 /* List of ready file descriptors */
192 struct list_head rdllist;
193
194 /* RB-Tree root used to store monitored fd structs */
195 struct rb_root rbr;
196
197 /*
198 * This is a single linked list that chains all the "struct epitem" that
199 * happened while transfering ready events to userspace w/out
200 * holding ->lock.
201 */
202 struct epitem *ovflist;
203};
204
205/* Wait structure used by the poll hooks */
206struct eppoll_entry {
207 /* List header used to link this structure to the "struct epitem" */
208 struct list_head llink;
209
210 /* The "base" pointer is set to the container "struct epitem" */
211 void *base;
212
213 /*
214 * Wait queue item that will be linked to the target file wait
215 * queue head.
216 */
217 wait_queue_t wait;
218
219 /* The wait queue head that linked the "wait" wait queue item */
220 wait_queue_head_t *whead;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700221};
222
223/* Wrapper struct used by poll queueing */
224struct ep_pqueue {
225 poll_table pt;
226 struct epitem *epi;
227};
228
Linus Torvalds1da177e2005-04-16 15:20:36 -0700229/*
Davide Libenzid47de162007-05-15 01:40:41 -0700230 * This mutex is used to serialize ep_free() and eventpoll_release_file().
Linus Torvalds1da177e2005-04-16 15:20:36 -0700231 */
Arjan van de Ven144efe32006-03-23 03:00:32 -0800232static struct mutex epmutex;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700233
234/* Safe wake up implementation */
235static struct poll_safewake psw;
236
237/* Slab cache used to allocate "struct epitem" */
Christoph Lametere18b8902006-12-06 20:33:20 -0800238static struct kmem_cache *epi_cache __read_mostly;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700239
240/* Slab cache used to allocate "struct eppoll_entry" */
Christoph Lametere18b8902006-12-06 20:33:20 -0800241static struct kmem_cache *pwq_cache __read_mostly;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700242
Pekka Enbergb030a4d2005-06-23 00:10:03 -0700243
244/* Setup the structure that is used as key for the rb-tree */
245static inline void ep_set_ffd(struct epoll_filefd *ffd,
246 struct file *file, int fd)
247{
248 ffd->file = file;
249 ffd->fd = fd;
250}
251
252/* Compare rb-tree keys */
253static inline int ep_cmp_ffd(struct epoll_filefd *p1,
254 struct epoll_filefd *p2)
255{
256 return (p1->file > p2->file ? +1:
257 (p1->file < p2->file ? -1 : p1->fd - p2->fd));
258}
259
260/* Special initialization for the rb-tree node to detect linkage */
261static inline void ep_rb_initnode(struct rb_node *n)
262{
David Woodhousec5698822006-04-21 13:17:24 +0100263 rb_set_parent(n, n);
Pekka Enbergb030a4d2005-06-23 00:10:03 -0700264}
265
266/* Removes a node from the rb-tree and marks it for a fast is-linked check */
267static inline void ep_rb_erase(struct rb_node *n, struct rb_root *r)
268{
269 rb_erase(n, r);
David Woodhousec5698822006-04-21 13:17:24 +0100270 rb_set_parent(n, n);
Pekka Enbergb030a4d2005-06-23 00:10:03 -0700271}
272
273/* Fast check to verify that the item is linked to the main rb-tree */
274static inline int ep_rb_linked(struct rb_node *n)
275{
David Woodhousec5698822006-04-21 13:17:24 +0100276 return rb_parent(n) != n;
Pekka Enbergb030a4d2005-06-23 00:10:03 -0700277}
278
Pekka Enbergb030a4d2005-06-23 00:10:03 -0700279/* Tells us if the item is currently linked */
280static inline int ep_is_linked(struct list_head *p)
281{
282 return !list_empty(p);
283}
284
285/* Get the "struct epitem" from a wait queue pointer */
286static inline struct epitem * ep_item_from_wait(wait_queue_t *p)
287{
288 return container_of(p, struct eppoll_entry, wait)->base;
289}
290
291/* Get the "struct epitem" from an epoll queue wrapper */
292static inline struct epitem * ep_item_from_epqueue(poll_table *p)
293{
294 return container_of(p, struct ep_pqueue, pt)->epi;
295}
296
297/* Tells if the epoll_ctl(2) operation needs an event copy from userspace */
Davide Libenzi6192bd52007-05-08 00:25:41 -0700298static inline int ep_op_has_event(int op)
Pekka Enbergb030a4d2005-06-23 00:10:03 -0700299{
300 return op != EPOLL_CTL_DEL;
301}
302
Linus Torvalds1da177e2005-04-16 15:20:36 -0700303/* Initialize the poll safe wake up structure */
304static void ep_poll_safewake_init(struct poll_safewake *psw)
305{
306
307 INIT_LIST_HEAD(&psw->wake_task_list);
308 spin_lock_init(&psw->lock);
309}
310
Linus Torvalds1da177e2005-04-16 15:20:36 -0700311/*
312 * Perform a safe wake up of the poll wait list. The problem is that
313 * with the new callback'd wake up system, it is possible that the
314 * poll callback is reentered from inside the call to wake_up() done
315 * on the poll wait queue head. The rule is that we cannot reenter the
316 * wake up code from the same task more than EP_MAX_POLLWAKE_NESTS times,
317 * and we cannot reenter the same wait queue head at all. This will
318 * enable to have a hierarchy of epoll file descriptor of no more than
319 * EP_MAX_POLLWAKE_NESTS deep. We need the irq version of the spin lock
320 * because this one gets called by the poll callback, that in turn is called
321 * from inside a wake_up(), that might be called from irq context.
322 */
323static void ep_poll_safewake(struct poll_safewake *psw, wait_queue_head_t *wq)
324{
325 int wake_nests = 0;
326 unsigned long flags;
Ingo Molnar36c8b582006-07-03 00:25:41 -0700327 struct task_struct *this_task = current;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700328 struct list_head *lsthead = &psw->wake_task_list, *lnk;
329 struct wake_task_node *tncur;
330 struct wake_task_node tnode;
331
332 spin_lock_irqsave(&psw->lock, flags);
333
334 /* Try to see if the current task is already inside this wakeup call */
335 list_for_each(lnk, lsthead) {
336 tncur = list_entry(lnk, struct wake_task_node, llink);
337
338 if (tncur->wq == wq ||
339 (tncur->task == this_task && ++wake_nests > EP_MAX_POLLWAKE_NESTS)) {
340 /*
341 * Ops ... loop detected or maximum nest level reached.
342 * We abort this wake by breaking the cycle itself.
343 */
344 spin_unlock_irqrestore(&psw->lock, flags);
345 return;
346 }
347 }
348
349 /* Add the current task to the list */
350 tnode.task = this_task;
351 tnode.wq = wq;
352 list_add(&tnode.llink, lsthead);
353
354 spin_unlock_irqrestore(&psw->lock, flags);
355
356 /* Do really wake up now */
357 wake_up(wq);
358
359 /* Remove the current task from the list */
360 spin_lock_irqsave(&psw->lock, flags);
361 list_del(&tnode.llink);
362 spin_unlock_irqrestore(&psw->lock, flags);
363}
364
Davide Libenzi7699acd2007-05-10 22:23:23 -0700365/*
366 * This function unregister poll callbacks from the associated file descriptor.
367 * Since this must be called without holding "ep->lock" the atomic exchange trick
368 * will protect us from multiple unregister.
369 */
370static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi)
371{
372 int nwait;
373 struct list_head *lsthead = &epi->pwqlist;
374 struct eppoll_entry *pwq;
375
376 /* This is called without locks, so we need the atomic exchange */
377 nwait = xchg(&epi->nwait, 0);
378
379 if (nwait) {
380 while (!list_empty(lsthead)) {
381 pwq = list_first_entry(lsthead, struct eppoll_entry, llink);
382
383 list_del_init(&pwq->llink);
384 remove_wait_queue(pwq->whead, &pwq->wait);
385 kmem_cache_free(pwq_cache, pwq);
386 }
387 }
388}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700389
Linus Torvalds1da177e2005-04-16 15:20:36 -0700390/*
Davide Libenzi7699acd2007-05-10 22:23:23 -0700391 * Removes a "struct epitem" from the eventpoll RB tree and deallocates
Davide Libenzic7ea7632007-05-15 01:40:47 -0700392 * all the associated resources. Must be called with "mtx" held.
Davide Libenzi7699acd2007-05-10 22:23:23 -0700393 */
394static int ep_remove(struct eventpoll *ep, struct epitem *epi)
395{
Davide Libenzi7699acd2007-05-10 22:23:23 -0700396 unsigned long flags;
397 struct file *file = epi->ffd.file;
398
399 /*
400 * Removes poll wait queue hooks. We _have_ to do this without holding
401 * the "ep->lock" otherwise a deadlock might occur. This because of the
402 * sequence of the lock acquisition. Here we do "ep->lock" then the wait
403 * queue head lock when unregistering the wait queue. The wakeup callback
404 * will run by holding the wait queue head lock and will call our callback
405 * that will try to get "ep->lock".
406 */
407 ep_unregister_pollwait(ep, epi);
408
409 /* Remove the current item from the list of epoll hooks */
410 spin_lock(&file->f_ep_lock);
411 if (ep_is_linked(&epi->fllink))
Davide Libenzi6192bd52007-05-08 00:25:41 -0700412 list_del_init(&epi->fllink);
Davide Libenzi7699acd2007-05-10 22:23:23 -0700413 spin_unlock(&file->f_ep_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700414
Davide Libenzic7ea7632007-05-15 01:40:47 -0700415 if (ep_rb_linked(&epi->rbn))
416 ep_rb_erase(&epi->rbn, &ep->rbr);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700417
Davide Libenzic7ea7632007-05-15 01:40:47 -0700418 spin_lock_irqsave(&ep->lock, flags);
419 if (ep_is_linked(&epi->rdllink))
420 list_del_init(&epi->rdllink);
421 spin_unlock_irqrestore(&ep->lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700422
Davide Libenzi7699acd2007-05-10 22:23:23 -0700423 /* At this point it is safe to free the eventpoll item */
Davide Libenzic7ea7632007-05-15 01:40:47 -0700424 kmem_cache_free(epi_cache, epi);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700425
Davide Libenzic7ea7632007-05-15 01:40:47 -0700426 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_remove(%p, %p)\n",
427 current, ep, file));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700428
Davide Libenzic7ea7632007-05-15 01:40:47 -0700429 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700430}
431
Linus Torvalds1da177e2005-04-16 15:20:36 -0700432static void ep_free(struct eventpoll *ep)
433{
434 struct rb_node *rbp;
435 struct epitem *epi;
436
437 /* We need to release all tasks waiting for these file */
438 if (waitqueue_active(&ep->poll_wait))
439 ep_poll_safewake(&psw, &ep->poll_wait);
440
441 /*
442 * We need to lock this because we could be hit by
443 * eventpoll_release_file() while we're freeing the "struct eventpoll".
Davide Libenzid47de162007-05-15 01:40:41 -0700444 * We do not need to hold "ep->mtx" here because the epoll file
Linus Torvalds1da177e2005-04-16 15:20:36 -0700445 * is on the way to be removed and no one has references to it
446 * anymore. The only hit might come from eventpoll_release_file() but
Arjan van de Ven144efe32006-03-23 03:00:32 -0800447 * holding "epmutex" is sufficent here.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700448 */
Arjan van de Ven144efe32006-03-23 03:00:32 -0800449 mutex_lock(&epmutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700450
451 /*
452 * Walks through the whole tree by unregistering poll callbacks.
453 */
454 for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) {
455 epi = rb_entry(rbp, struct epitem, rbn);
456
457 ep_unregister_pollwait(ep, epi);
458 }
459
460 /*
Davide Libenzi6192bd52007-05-08 00:25:41 -0700461 * Walks through the whole tree by freeing each "struct epitem". At this
Linus Torvalds1da177e2005-04-16 15:20:36 -0700462 * point we are sure no poll callbacks will be lingering around, and also by
Davide Libenzid47de162007-05-15 01:40:41 -0700463 * holding "epmutex" we can be sure that no file cleanup code will hit
Linus Torvalds1da177e2005-04-16 15:20:36 -0700464 * us during this operation. So we can avoid the lock on "ep->lock".
465 */
466 while ((rbp = rb_first(&ep->rbr)) != 0) {
467 epi = rb_entry(rbp, struct epitem, rbn);
468 ep_remove(ep, epi);
469 }
470
Arjan van de Ven144efe32006-03-23 03:00:32 -0800471 mutex_unlock(&epmutex);
Davide Libenzid47de162007-05-15 01:40:41 -0700472
473 mutex_destroy(&ep->mtx);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700474}
475
Davide Libenzi7699acd2007-05-10 22:23:23 -0700476static int ep_eventpoll_release(struct inode *inode, struct file *file)
477{
478 struct eventpoll *ep = file->private_data;
479
480 if (ep) {
481 ep_free(ep);
482 kfree(ep);
483 }
484
485 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: close() ep=%p\n", current, ep));
486 return 0;
487}
488
489static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait)
490{
491 unsigned int pollflags = 0;
492 unsigned long flags;
493 struct eventpoll *ep = file->private_data;
494
495 /* Insert inside our poll wait queue */
496 poll_wait(file, &ep->poll_wait, wait);
497
498 /* Check our condition */
Davide Libenzic7ea7632007-05-15 01:40:47 -0700499 spin_lock_irqsave(&ep->lock, flags);
Davide Libenzi7699acd2007-05-10 22:23:23 -0700500 if (!list_empty(&ep->rdllist))
501 pollflags = POLLIN | POLLRDNORM;
Davide Libenzic7ea7632007-05-15 01:40:47 -0700502 spin_unlock_irqrestore(&ep->lock, flags);
Davide Libenzi7699acd2007-05-10 22:23:23 -0700503
504 return pollflags;
505}
506
507/* File callbacks that implement the eventpoll file behaviour */
508static const struct file_operations eventpoll_fops = {
509 .release = ep_eventpoll_release,
510 .poll = ep_eventpoll_poll
511};
512
513/* Fast test to see if the file is an evenpoll file */
514static inline int is_file_epoll(struct file *f)
515{
516 return f->f_op == &eventpoll_fops;
517}
518
519/*
520 * This is called from eventpoll_release() to unlink files from the eventpoll
521 * interface. We need to have this facility to cleanup correctly files that are
522 * closed without being removed from the eventpoll interface.
523 */
524void eventpoll_release_file(struct file *file)
525{
526 struct list_head *lsthead = &file->f_ep_links;
527 struct eventpoll *ep;
528 struct epitem *epi;
529
530 /*
531 * We don't want to get "file->f_ep_lock" because it is not
532 * necessary. It is not necessary because we're in the "struct file"
533 * cleanup path, and this means that noone is using this file anymore.
Davide Libenzid47de162007-05-15 01:40:41 -0700534 * The only hit might come from ep_free() but by holding the mutex
Davide Libenzi7699acd2007-05-10 22:23:23 -0700535 * will correctly serialize the operation. We do need to acquire
Davide Libenzid47de162007-05-15 01:40:41 -0700536 * "ep->mtx" after "epmutex" because ep_remove() requires it when called
Davide Libenzi7699acd2007-05-10 22:23:23 -0700537 * from anywhere but ep_free().
538 */
539 mutex_lock(&epmutex);
540
541 while (!list_empty(lsthead)) {
542 epi = list_first_entry(lsthead, struct epitem, fllink);
543
544 ep = epi->ep;
545 list_del_init(&epi->fllink);
Davide Libenzid47de162007-05-15 01:40:41 -0700546 mutex_lock(&ep->mtx);
Davide Libenzi7699acd2007-05-10 22:23:23 -0700547 ep_remove(ep, epi);
Davide Libenzid47de162007-05-15 01:40:41 -0700548 mutex_unlock(&ep->mtx);
Davide Libenzi7699acd2007-05-10 22:23:23 -0700549 }
550
551 mutex_unlock(&epmutex);
552}
553
554static int ep_alloc(struct eventpoll **pep)
555{
556 struct eventpoll *ep = kzalloc(sizeof(*ep), GFP_KERNEL);
557
558 if (!ep)
559 return -ENOMEM;
560
Davide Libenzic7ea7632007-05-15 01:40:47 -0700561 spin_lock_init(&ep->lock);
Davide Libenzid47de162007-05-15 01:40:41 -0700562 mutex_init(&ep->mtx);
Davide Libenzi7699acd2007-05-10 22:23:23 -0700563 init_waitqueue_head(&ep->wq);
564 init_waitqueue_head(&ep->poll_wait);
565 INIT_LIST_HEAD(&ep->rdllist);
566 ep->rbr = RB_ROOT;
Davide Libenzid47de162007-05-15 01:40:41 -0700567 ep->ovflist = EP_UNACTIVE_PTR;
Davide Libenzi7699acd2007-05-10 22:23:23 -0700568
569 *pep = ep;
570
571 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_alloc() ep=%p\n",
572 current, ep));
573 return 0;
574}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700575
576/*
Davide Libenzic7ea7632007-05-15 01:40:47 -0700577 * Search the file inside the eventpoll tree. The RB tree operations
578 * are protected by the "mtx" mutex, and ep_find() must be called with
579 * "mtx" held.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700580 */
581static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd)
582{
583 int kcmp;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700584 struct rb_node *rbp;
585 struct epitem *epi, *epir = NULL;
586 struct epoll_filefd ffd;
587
Pekka Enbergb030a4d2005-06-23 00:10:03 -0700588 ep_set_ffd(&ffd, file, fd);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700589 for (rbp = ep->rbr.rb_node; rbp; ) {
590 epi = rb_entry(rbp, struct epitem, rbn);
Pekka Enbergb030a4d2005-06-23 00:10:03 -0700591 kcmp = ep_cmp_ffd(&ffd, &epi->ffd);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700592 if (kcmp > 0)
593 rbp = rbp->rb_right;
594 else if (kcmp < 0)
595 rbp = rbp->rb_left;
596 else {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700597 epir = epi;
598 break;
599 }
600 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700601
602 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_find(%p) -> %p\n",
603 current, file, epir));
604
605 return epir;
606}
607
Linus Torvalds1da177e2005-04-16 15:20:36 -0700608/*
Davide Libenzi7699acd2007-05-10 22:23:23 -0700609 * This is the callback that is passed to the wait queue wakeup
610 * machanism. It is called by the stored file descriptors when they
611 * have events to report.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700612 */
Davide Libenzi7699acd2007-05-10 22:23:23 -0700613static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *key)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700614{
Davide Libenzi7699acd2007-05-10 22:23:23 -0700615 int pwake = 0;
616 unsigned long flags;
617 struct epitem *epi = ep_item_from_wait(wait);
618 struct eventpoll *ep = epi->ep;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700619
Davide Libenzi7699acd2007-05-10 22:23:23 -0700620 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: poll_callback(%p) epi=%p ep=%p\n",
621 current, epi->ffd.file, epi, ep));
622
Davide Libenzic7ea7632007-05-15 01:40:47 -0700623 spin_lock_irqsave(&ep->lock, flags);
Davide Libenzi7699acd2007-05-10 22:23:23 -0700624
625 /*
626 * If the event mask does not contain any poll(2) event, we consider the
627 * descriptor to be disabled. This condition is likely the effect of the
628 * EPOLLONESHOT bit that disables the descriptor when an event is received,
629 * until the next EPOLL_CTL_MOD will be issued.
630 */
631 if (!(epi->event.events & ~EP_PRIVATE_BITS))
Davide Libenzid47de162007-05-15 01:40:41 -0700632 goto out_unlock;
633
634 /*
635 * If we are trasfering events to userspace, we can hold no locks
636 * (because we're accessing user memory, and because of linux f_op->poll()
637 * semantics). All the events that happens during that period of time are
638 * chained in ep->ovflist and requeued later on.
639 */
640 if (unlikely(ep->ovflist != EP_UNACTIVE_PTR)) {
641 if (epi->next == EP_UNACTIVE_PTR) {
642 epi->next = ep->ovflist;
643 ep->ovflist = epi;
644 }
645 goto out_unlock;
646 }
Davide Libenzi7699acd2007-05-10 22:23:23 -0700647
648 /* If this file is already in the ready list we exit soon */
649 if (ep_is_linked(&epi->rdllink))
650 goto is_linked;
651
652 list_add_tail(&epi->rdllink, &ep->rdllist);
653
654is_linked:
655 /*
656 * Wake up ( if active ) both the eventpoll wait list and the ->poll()
657 * wait list.
658 */
659 if (waitqueue_active(&ep->wq))
660 __wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE |
661 TASK_INTERRUPTIBLE);
662 if (waitqueue_active(&ep->poll_wait))
663 pwake++;
664
Davide Libenzid47de162007-05-15 01:40:41 -0700665out_unlock:
Davide Libenzic7ea7632007-05-15 01:40:47 -0700666 spin_unlock_irqrestore(&ep->lock, flags);
Davide Libenzi7699acd2007-05-10 22:23:23 -0700667
668 /* We have to call this outside the lock */
669 if (pwake)
670 ep_poll_safewake(&psw, &ep->poll_wait);
671
672 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700673}
674
Linus Torvalds1da177e2005-04-16 15:20:36 -0700675/*
676 * This is the callback that is used to add our wait queue to the
677 * target file wakeup lists.
678 */
679static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead,
680 poll_table *pt)
681{
Pekka Enbergb030a4d2005-06-23 00:10:03 -0700682 struct epitem *epi = ep_item_from_epqueue(pt);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700683 struct eppoll_entry *pwq;
684
Christoph Lametere94b1762006-12-06 20:33:17 -0800685 if (epi->nwait >= 0 && (pwq = kmem_cache_alloc(pwq_cache, GFP_KERNEL))) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700686 init_waitqueue_func_entry(&pwq->wait, ep_poll_callback);
687 pwq->whead = whead;
688 pwq->base = epi;
689 add_wait_queue(whead, &pwq->wait);
690 list_add_tail(&pwq->llink, &epi->pwqlist);
691 epi->nwait++;
692 } else {
693 /* We have to signal that an error occurred */
694 epi->nwait = -1;
695 }
696}
697
Linus Torvalds1da177e2005-04-16 15:20:36 -0700698static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi)
699{
700 int kcmp;
701 struct rb_node **p = &ep->rbr.rb_node, *parent = NULL;
702 struct epitem *epic;
703
704 while (*p) {
705 parent = *p;
706 epic = rb_entry(parent, struct epitem, rbn);
Pekka Enbergb030a4d2005-06-23 00:10:03 -0700707 kcmp = ep_cmp_ffd(&epi->ffd, &epic->ffd);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700708 if (kcmp > 0)
709 p = &parent->rb_right;
710 else
711 p = &parent->rb_left;
712 }
713 rb_link_node(&epi->rbn, parent, p);
714 rb_insert_color(&epi->rbn, &ep->rbr);
715}
716
Davide Libenzic7ea7632007-05-15 01:40:47 -0700717/*
718 * Must be called with "mtx" held.
719 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700720static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
721 struct file *tfile, int fd)
722{
723 int error, revents, pwake = 0;
724 unsigned long flags;
725 struct epitem *epi;
726 struct ep_pqueue epq;
727
728 error = -ENOMEM;
Christoph Lametere94b1762006-12-06 20:33:17 -0800729 if (!(epi = kmem_cache_alloc(epi_cache, GFP_KERNEL)))
Davide Libenzi7699acd2007-05-10 22:23:23 -0700730 goto error_return;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700731
732 /* Item initialization follow here ... */
Pekka Enbergb030a4d2005-06-23 00:10:03 -0700733 ep_rb_initnode(&epi->rbn);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700734 INIT_LIST_HEAD(&epi->rdllink);
735 INIT_LIST_HEAD(&epi->fllink);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700736 INIT_LIST_HEAD(&epi->pwqlist);
737 epi->ep = ep;
Pekka Enbergb030a4d2005-06-23 00:10:03 -0700738 ep_set_ffd(&epi->ffd, tfile, fd);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700739 epi->event = *event;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700740 epi->nwait = 0;
Davide Libenzid47de162007-05-15 01:40:41 -0700741 epi->next = EP_UNACTIVE_PTR;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700742
743 /* Initialize the poll table using the queue callback */
744 epq.epi = epi;
745 init_poll_funcptr(&epq.pt, ep_ptable_queue_proc);
746
747 /*
748 * Attach the item to the poll hooks and get current event bits.
749 * We can safely use the file* here because its usage count has
Davide Libenzic7ea7632007-05-15 01:40:47 -0700750 * been increased by the caller of this function. Note that after
751 * this operation completes, the poll callback can start hitting
752 * the new item.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700753 */
754 revents = tfile->f_op->poll(tfile, &epq.pt);
755
756 /*
757 * We have to check if something went wrong during the poll wait queue
758 * install process. Namely an allocation for a wait queue failed due
759 * high memory pressure.
760 */
761 if (epi->nwait < 0)
Davide Libenzi7699acd2007-05-10 22:23:23 -0700762 goto error_unregister;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700763
764 /* Add the current item to the list of active epoll hook for this file */
765 spin_lock(&tfile->f_ep_lock);
766 list_add_tail(&epi->fllink, &tfile->f_ep_links);
767 spin_unlock(&tfile->f_ep_lock);
768
Davide Libenzic7ea7632007-05-15 01:40:47 -0700769 /*
770 * Add the current item to the RB tree. All RB tree operations are
771 * protected by "mtx", and ep_insert() is called with "mtx" held.
772 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700773 ep_rbtree_insert(ep, epi);
774
Davide Libenzic7ea7632007-05-15 01:40:47 -0700775 /* We have to drop the new item inside our item list to keep track of it */
776 spin_lock_irqsave(&ep->lock, flags);
777
Linus Torvalds1da177e2005-04-16 15:20:36 -0700778 /* If the file is already "ready" we drop it inside the ready list */
Pekka Enbergb030a4d2005-06-23 00:10:03 -0700779 if ((revents & event->events) && !ep_is_linked(&epi->rdllink)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700780 list_add_tail(&epi->rdllink, &ep->rdllist);
781
782 /* Notify waiting tasks that events are available */
783 if (waitqueue_active(&ep->wq))
Davide Libenzi3419b232006-06-25 05:48:14 -0700784 __wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700785 if (waitqueue_active(&ep->poll_wait))
786 pwake++;
787 }
788
Davide Libenzic7ea7632007-05-15 01:40:47 -0700789 spin_unlock_irqrestore(&ep->lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700790
791 /* We have to call this outside the lock */
792 if (pwake)
793 ep_poll_safewake(&psw, &ep->poll_wait);
794
795 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_insert(%p, %p, %d)\n",
796 current, ep, tfile, fd));
797
798 return 0;
799
Davide Libenzi7699acd2007-05-10 22:23:23 -0700800error_unregister:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700801 ep_unregister_pollwait(ep, epi);
802
803 /*
804 * We need to do this because an event could have been arrived on some
805 * allocated wait queue.
806 */
Davide Libenzic7ea7632007-05-15 01:40:47 -0700807 spin_lock_irqsave(&ep->lock, flags);
Pekka Enbergb030a4d2005-06-23 00:10:03 -0700808 if (ep_is_linked(&epi->rdllink))
Davide Libenzi6192bd52007-05-08 00:25:41 -0700809 list_del_init(&epi->rdllink);
Davide Libenzic7ea7632007-05-15 01:40:47 -0700810 spin_unlock_irqrestore(&ep->lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700811
Pekka Enbergb030a4d2005-06-23 00:10:03 -0700812 kmem_cache_free(epi_cache, epi);
Davide Libenzi7699acd2007-05-10 22:23:23 -0700813error_return:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700814 return error;
815}
816
Linus Torvalds1da177e2005-04-16 15:20:36 -0700817/*
818 * Modify the interest event mask by dropping an event if the new mask
Davide Libenzic7ea7632007-05-15 01:40:47 -0700819 * has a match in the current file status. Must be called with "mtx" held.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700820 */
821static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_event *event)
822{
823 int pwake = 0;
824 unsigned int revents;
825 unsigned long flags;
826
827 /*
828 * Set the new event interest mask before calling f_op->poll(), otherwise
829 * a potential race might occur. In fact if we do this operation inside
830 * the lock, an event might happen between the f_op->poll() call and the
831 * new event set registering.
832 */
833 epi->event.events = event->events;
834
835 /*
836 * Get current event bits. We can safely use the file* here because
837 * its usage count has been increased by the caller of this function.
838 */
839 revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL);
840
Davide Libenzic7ea7632007-05-15 01:40:47 -0700841 spin_lock_irqsave(&ep->lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700842
843 /* Copy the data member from inside the lock */
844 epi->event.data = event->data;
845
846 /*
Davide Libenzic7ea7632007-05-15 01:40:47 -0700847 * If the item is "hot" and it is not registered inside the ready
848 * list, push it inside. If the item is not "hot" and it is currently
849 * registered inside the ready list, unlink it.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700850 */
Davide Libenzic7ea7632007-05-15 01:40:47 -0700851 if (revents & event->events) {
852 if (!ep_is_linked(&epi->rdllink)) {
853 list_add_tail(&epi->rdllink, &ep->rdllist);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700854
Davide Libenzic7ea7632007-05-15 01:40:47 -0700855 /* Notify waiting tasks that events are available */
856 if (waitqueue_active(&ep->wq))
857 __wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE |
858 TASK_INTERRUPTIBLE);
859 if (waitqueue_active(&ep->poll_wait))
860 pwake++;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700861 }
862 }
Davide Libenzic7ea7632007-05-15 01:40:47 -0700863 spin_unlock_irqrestore(&ep->lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700864
865 /* We have to call this outside the lock */
866 if (pwake)
867 ep_poll_safewake(&psw, &ep->poll_wait);
868
869 return 0;
870}
871
Davide Libenzid47de162007-05-15 01:40:41 -0700872static int ep_send_events(struct eventpoll *ep, struct epoll_event __user *events,
873 int maxevents)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700874{
Davide Libenzi6192bd52007-05-08 00:25:41 -0700875 int eventcnt, error = -EFAULT, pwake = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700876 unsigned int revents;
Davide Libenzi6192bd52007-05-08 00:25:41 -0700877 unsigned long flags;
Davide Libenzid47de162007-05-15 01:40:41 -0700878 struct epitem *epi, *nepi;
879 struct list_head txlist;
Davide Libenzi6192bd52007-05-08 00:25:41 -0700880
Davide Libenzid47de162007-05-15 01:40:41 -0700881 INIT_LIST_HEAD(&txlist);
882
883 /*
884 * We need to lock this because we could be hit by
885 * eventpoll_release_file() and epoll_ctl(EPOLL_CTL_DEL).
886 */
887 mutex_lock(&ep->mtx);
888
889 /*
890 * Steal the ready list, and re-init the original one to the
891 * empty list. Also, set ep->ovflist to NULL so that events
892 * happening while looping w/out locks, are not lost. We cannot
893 * have the poll callback to queue directly on ep->rdllist,
894 * because we are doing it in the loop below, in a lockless way.
895 */
Davide Libenzic7ea7632007-05-15 01:40:47 -0700896 spin_lock_irqsave(&ep->lock, flags);
Davide Libenzid47de162007-05-15 01:40:41 -0700897 list_splice(&ep->rdllist, &txlist);
898 INIT_LIST_HEAD(&ep->rdllist);
899 ep->ovflist = NULL;
Davide Libenzic7ea7632007-05-15 01:40:47 -0700900 spin_unlock_irqrestore(&ep->lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700901
902 /*
903 * We can loop without lock because this is a task private list.
Davide Libenzi6192bd52007-05-08 00:25:41 -0700904 * We just splice'd out the ep->rdllist in ep_collect_ready_items().
Davide Libenzid47de162007-05-15 01:40:41 -0700905 * Items cannot vanish during the loop because we are holding "mtx".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700906 */
Davide Libenzid47de162007-05-15 01:40:41 -0700907 for (eventcnt = 0; !list_empty(&txlist) && eventcnt < maxevents;) {
908 epi = list_first_entry(&txlist, struct epitem, rdllink);
909
910 list_del_init(&epi->rdllink);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700911
912 /*
913 * Get the ready file event set. We can safely use the file
Davide Libenzid47de162007-05-15 01:40:41 -0700914 * because we are holding the "mtx" and this will guarantee
915 * that both the file and the item will not vanish.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700916 */
917 revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL);
Davide Libenzi6192bd52007-05-08 00:25:41 -0700918 revents &= epi->event.events;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700919
920 /*
Davide Libenzi6192bd52007-05-08 00:25:41 -0700921 * Is the event mask intersect the caller-requested one,
922 * deliver the event to userspace. Again, we are holding
Davide Libenzid47de162007-05-15 01:40:41 -0700923 * "mtx", so no operations coming from userspace can change
924 * the item.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700925 */
Davide Libenzi6192bd52007-05-08 00:25:41 -0700926 if (revents) {
927 if (__put_user(revents,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700928 &events[eventcnt].events) ||
929 __put_user(epi->event.data,
930 &events[eventcnt].data))
Davide Libenzi6192bd52007-05-08 00:25:41 -0700931 goto errxit;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700932 if (epi->event.events & EPOLLONESHOT)
933 epi->event.events &= EP_PRIVATE_BITS;
934 eventcnt++;
935 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700936 /*
Davide Libenzid47de162007-05-15 01:40:41 -0700937 * At this point, noone can insert into ep->rdllist besides
938 * us. The epoll_ctl() callers are locked out by us holding
939 * "mtx" and the poll callback will queue them in ep->ovflist.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700940 */
Davide Libenzi6192bd52007-05-08 00:25:41 -0700941 if (!(epi->event.events & EPOLLET) &&
Davide Libenzid47de162007-05-15 01:40:41 -0700942 (revents & epi->event.events))
943 list_add_tail(&epi->rdllink, &ep->rdllist);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700944 }
Davide Libenzi6192bd52007-05-08 00:25:41 -0700945 error = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700946
Davide Libenzid47de162007-05-15 01:40:41 -0700947errxit:
948
Davide Libenzic7ea7632007-05-15 01:40:47 -0700949 spin_lock_irqsave(&ep->lock, flags);
Davide Libenzid47de162007-05-15 01:40:41 -0700950 /*
951 * During the time we spent in the loop above, some other events
952 * might have been queued by the poll callback. We re-insert them
953 * here (in case they are not already queued, or they're one-shot).
954 */
955 for (nepi = ep->ovflist; (epi = nepi) != NULL;
956 nepi = epi->next, epi->next = EP_UNACTIVE_PTR) {
957 if (!ep_is_linked(&epi->rdllink) &&
958 (epi->event.events & ~EP_PRIVATE_BITS))
959 list_add_tail(&epi->rdllink, &ep->rdllist);
960 }
961 /*
962 * We need to set back ep->ovflist to EP_UNACTIVE_PTR, so that after
963 * releasing the lock, events will be queued in the normal way inside
964 * ep->rdllist.
965 */
966 ep->ovflist = EP_UNACTIVE_PTR;
Davide Libenzi6192bd52007-05-08 00:25:41 -0700967
968 /*
Davide Libenzid47de162007-05-15 01:40:41 -0700969 * In case of error in the event-send loop, we might still have items
970 * inside the "txlist". We need to splice them back inside ep->rdllist.
Davide Libenzi6192bd52007-05-08 00:25:41 -0700971 */
Davide Libenzid47de162007-05-15 01:40:41 -0700972 list_splice(&txlist, &ep->rdllist);
Davide Libenzi6192bd52007-05-08 00:25:41 -0700973
Davide Libenzid47de162007-05-15 01:40:41 -0700974 if (!list_empty(&ep->rdllist)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700975 /*
Davide Libenzid47de162007-05-15 01:40:41 -0700976 * Wake up (if active) both the eventpoll wait list and the ->poll()
Linus Torvalds1da177e2005-04-16 15:20:36 -0700977 * wait list.
978 */
979 if (waitqueue_active(&ep->wq))
Davide Libenzi3419b232006-06-25 05:48:14 -0700980 __wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE |
981 TASK_INTERRUPTIBLE);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700982 if (waitqueue_active(&ep->poll_wait))
983 pwake++;
Davide Libenzi6192bd52007-05-08 00:25:41 -0700984 }
Davide Libenzic7ea7632007-05-15 01:40:47 -0700985 spin_unlock_irqrestore(&ep->lock, flags);
Davide Libenzid47de162007-05-15 01:40:41 -0700986
987 mutex_unlock(&ep->mtx);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700988
989 /* We have to call this outside the lock */
990 if (pwake)
991 ep_poll_safewake(&psw, &ep->poll_wait);
Davide Libenzi6192bd52007-05-08 00:25:41 -0700992
993 return eventcnt == 0 ? error: eventcnt;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700994}
995
Linus Torvalds1da177e2005-04-16 15:20:36 -0700996static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
997 int maxevents, long timeout)
998{
999 int res, eavail;
1000 unsigned long flags;
1001 long jtimeout;
1002 wait_queue_t wait;
1003
1004 /*
1005 * Calculate the timeout by checking for the "infinite" value ( -1 )
1006 * and the overflow condition. The passed timeout is in milliseconds,
1007 * that why (t * HZ) / 1000.
1008 */
Davide Libenzie3306dd2005-09-27 21:45:33 -07001009 jtimeout = (timeout < 0 || timeout >= EP_MAX_MSTIMEO) ?
1010 MAX_SCHEDULE_TIMEOUT : (timeout * HZ + 999) / 1000;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001011
1012retry:
Davide Libenzic7ea7632007-05-15 01:40:47 -07001013 spin_lock_irqsave(&ep->lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001014
1015 res = 0;
1016 if (list_empty(&ep->rdllist)) {
1017 /*
1018 * We don't have any available event to return to the caller.
1019 * We need to sleep here, and we will be wake up by
1020 * ep_poll_callback() when events will become available.
1021 */
1022 init_waitqueue_entry(&wait, current);
Davide Libenzid47de162007-05-15 01:40:41 -07001023 wait.flags |= WQ_FLAG_EXCLUSIVE;
Davide Libenzi3419b232006-06-25 05:48:14 -07001024 __add_wait_queue(&ep->wq, &wait);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001025
1026 for (;;) {
1027 /*
1028 * We don't want to sleep if the ep_poll_callback() sends us
1029 * a wakeup in between. That's why we set the task state
1030 * to TASK_INTERRUPTIBLE before doing the checks.
1031 */
1032 set_current_state(TASK_INTERRUPTIBLE);
1033 if (!list_empty(&ep->rdllist) || !jtimeout)
1034 break;
1035 if (signal_pending(current)) {
1036 res = -EINTR;
1037 break;
1038 }
1039
Davide Libenzic7ea7632007-05-15 01:40:47 -07001040 spin_unlock_irqrestore(&ep->lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001041 jtimeout = schedule_timeout(jtimeout);
Davide Libenzic7ea7632007-05-15 01:40:47 -07001042 spin_lock_irqsave(&ep->lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001043 }
Davide Libenzi3419b232006-06-25 05:48:14 -07001044 __remove_wait_queue(&ep->wq, &wait);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001045
1046 set_current_state(TASK_RUNNING);
1047 }
1048
1049 /* Is it worth to try to dig for events ? */
1050 eavail = !list_empty(&ep->rdllist);
1051
Davide Libenzic7ea7632007-05-15 01:40:47 -07001052 spin_unlock_irqrestore(&ep->lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001053
1054 /*
1055 * Try to transfer events to user space. In case we get 0 events and
1056 * there's still timeout left over, we go trying again in search of
1057 * more luck.
1058 */
1059 if (!res && eavail &&
Davide Libenzid47de162007-05-15 01:40:41 -07001060 !(res = ep_send_events(ep, events, maxevents)) && jtimeout)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001061 goto retry;
1062
1063 return res;
1064}
1065
Davide Libenzi7699acd2007-05-10 22:23:23 -07001066/*
1067 * It opens an eventpoll file descriptor by suggesting a storage of "size"
1068 * file descriptors. The size parameter is just an hint about how to size
1069 * data structures. It won't prevent the user to store more than "size"
1070 * file descriptors inside the epoll interface. It is the kernel part of
1071 * the userspace epoll_create(2).
1072 */
1073asmlinkage long sys_epoll_create(int size)
1074{
1075 int error, fd = -1;
1076 struct eventpoll *ep;
1077 struct inode *inode;
1078 struct file *file;
1079
1080 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d)\n",
1081 current, size));
1082
1083 /*
1084 * Sanity check on the size parameter, and create the internal data
1085 * structure ( "struct eventpoll" ).
1086 */
1087 error = -EINVAL;
1088 if (size <= 0 || (error = ep_alloc(&ep)) != 0)
1089 goto error_return;
1090
1091 /*
1092 * Creates all the items needed to setup an eventpoll file. That is,
1093 * a file structure, and inode and a free file descriptor.
1094 */
1095 error = anon_inode_getfd(&fd, &inode, &file, "[eventpoll]",
1096 &eventpoll_fops, ep);
1097 if (error)
1098 goto error_free;
1099
1100 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n",
1101 current, size, fd));
1102
1103 return fd;
1104
1105error_free:
1106 ep_free(ep);
1107 kfree(ep);
1108error_return:
1109 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n",
1110 current, size, error));
1111 return error;
1112}
1113
1114/*
1115 * The following function implements the controller interface for
1116 * the eventpoll file that enables the insertion/removal/change of
1117 * file descriptors inside the interest set. It represents
1118 * the kernel part of the user space epoll_ctl(2).
1119 */
1120asmlinkage long sys_epoll_ctl(int epfd, int op, int fd,
1121 struct epoll_event __user *event)
1122{
1123 int error;
1124 struct file *file, *tfile;
1125 struct eventpoll *ep;
1126 struct epitem *epi;
1127 struct epoll_event epds;
1128
1129 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %p)\n",
1130 current, epfd, op, fd, event));
1131
1132 error = -EFAULT;
1133 if (ep_op_has_event(op) &&
1134 copy_from_user(&epds, event, sizeof(struct epoll_event)))
1135 goto error_return;
1136
1137 /* Get the "struct file *" for the eventpoll file */
1138 error = -EBADF;
1139 file = fget(epfd);
1140 if (!file)
1141 goto error_return;
1142
1143 /* Get the "struct file *" for the target file */
1144 tfile = fget(fd);
1145 if (!tfile)
1146 goto error_fput;
1147
1148 /* The target file descriptor must support poll */
1149 error = -EPERM;
1150 if (!tfile->f_op || !tfile->f_op->poll)
1151 goto error_tgt_fput;
1152
1153 /*
1154 * We have to check that the file structure underneath the file descriptor
1155 * the user passed to us _is_ an eventpoll file. And also we do not permit
1156 * adding an epoll file descriptor inside itself.
1157 */
1158 error = -EINVAL;
1159 if (file == tfile || !is_file_epoll(file))
1160 goto error_tgt_fput;
1161
1162 /*
1163 * At this point it is safe to assume that the "private_data" contains
1164 * our own data structure.
1165 */
1166 ep = file->private_data;
1167
Davide Libenzid47de162007-05-15 01:40:41 -07001168 mutex_lock(&ep->mtx);
Davide Libenzi7699acd2007-05-10 22:23:23 -07001169
1170 /* Try to lookup the file inside our RB tree */
1171 epi = ep_find(ep, tfile, fd);
1172
1173 error = -EINVAL;
1174 switch (op) {
1175 case EPOLL_CTL_ADD:
1176 if (!epi) {
1177 epds.events |= POLLERR | POLLHUP;
1178
1179 error = ep_insert(ep, &epds, tfile, fd);
1180 } else
1181 error = -EEXIST;
1182 break;
1183 case EPOLL_CTL_DEL:
1184 if (epi)
1185 error = ep_remove(ep, epi);
1186 else
1187 error = -ENOENT;
1188 break;
1189 case EPOLL_CTL_MOD:
1190 if (epi) {
1191 epds.events |= POLLERR | POLLHUP;
1192 error = ep_modify(ep, epi, &epds);
1193 } else
1194 error = -ENOENT;
1195 break;
1196 }
Davide Libenzid47de162007-05-15 01:40:41 -07001197 mutex_unlock(&ep->mtx);
Davide Libenzi7699acd2007-05-10 22:23:23 -07001198
1199error_tgt_fput:
1200 fput(tfile);
1201error_fput:
1202 fput(file);
1203error_return:
1204 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %p) = %d\n",
1205 current, epfd, op, fd, event, error));
1206
1207 return error;
1208}
1209
1210/*
1211 * Implement the event wait interface for the eventpoll file. It is the kernel
1212 * part of the user space epoll_wait(2).
1213 */
1214asmlinkage long sys_epoll_wait(int epfd, struct epoll_event __user *events,
1215 int maxevents, int timeout)
1216{
1217 int error;
1218 struct file *file;
1219 struct eventpoll *ep;
1220
1221 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_wait(%d, %p, %d, %d)\n",
1222 current, epfd, events, maxevents, timeout));
1223
1224 /* The maximum number of event must be greater than zero */
1225 if (maxevents <= 0 || maxevents > EP_MAX_EVENTS)
1226 return -EINVAL;
1227
1228 /* Verify that the area passed by the user is writeable */
1229 if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event))) {
1230 error = -EFAULT;
1231 goto error_return;
1232 }
1233
1234 /* Get the "struct file *" for the eventpoll file */
1235 error = -EBADF;
1236 file = fget(epfd);
1237 if (!file)
1238 goto error_return;
1239
1240 /*
1241 * We have to check that the file structure underneath the fd
1242 * the user passed to us _is_ an eventpoll file.
1243 */
1244 error = -EINVAL;
1245 if (!is_file_epoll(file))
1246 goto error_fput;
1247
1248 /*
1249 * At this point it is safe to assume that the "private_data" contains
1250 * our own data structure.
1251 */
1252 ep = file->private_data;
1253
1254 /* Time to fish for events ... */
1255 error = ep_poll(ep, events, maxevents, timeout);
1256
1257error_fput:
1258 fput(file);
1259error_return:
1260 DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_wait(%d, %p, %d, %d) = %d\n",
1261 current, epfd, events, maxevents, timeout, error));
1262
1263 return error;
1264}
1265
1266#ifdef TIF_RESTORE_SIGMASK
1267
1268/*
1269 * Implement the event wait interface for the eventpoll file. It is the kernel
1270 * part of the user space epoll_pwait(2).
1271 */
1272asmlinkage long sys_epoll_pwait(int epfd, struct epoll_event __user *events,
1273 int maxevents, int timeout, const sigset_t __user *sigmask,
1274 size_t sigsetsize)
1275{
1276 int error;
1277 sigset_t ksigmask, sigsaved;
1278
1279 /*
1280 * If the caller wants a certain signal mask to be set during the wait,
1281 * we apply it here.
1282 */
1283 if (sigmask) {
1284 if (sigsetsize != sizeof(sigset_t))
1285 return -EINVAL;
1286 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
1287 return -EFAULT;
1288 sigdelsetmask(&ksigmask, sigmask(SIGKILL) | sigmask(SIGSTOP));
1289 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
1290 }
1291
1292 error = sys_epoll_wait(epfd, events, maxevents, timeout);
1293
1294 /*
1295 * If we changed the signal mask, we need to restore the original one.
1296 * In case we've got a signal while waiting, we do not restore the
1297 * signal mask yet, and we allow do_signal() to deliver the signal on
1298 * the way back to userspace, before the signal mask is restored.
1299 */
1300 if (sigmask) {
1301 if (error == -EINTR) {
1302 memcpy(&current->saved_sigmask, &sigsaved,
Davide Libenzic7ea7632007-05-15 01:40:47 -07001303 sizeof(sigsaved));
Davide Libenzi7699acd2007-05-10 22:23:23 -07001304 set_thread_flag(TIF_RESTORE_SIGMASK);
1305 } else
1306 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
1307 }
1308
1309 return error;
1310}
1311
1312#endif /* #ifdef TIF_RESTORE_SIGMASK */
1313
Linus Torvalds1da177e2005-04-16 15:20:36 -07001314static int __init eventpoll_init(void)
1315{
Arjan van de Ven144efe32006-03-23 03:00:32 -08001316 mutex_init(&epmutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001317
1318 /* Initialize the structure used to perform safe poll wait head wake ups */
1319 ep_poll_safewake_init(&psw);
1320
1321 /* Allocates slab cache used to allocate "struct epitem" items */
1322 epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem),
1323 0, SLAB_HWCACHE_ALIGN|EPI_SLAB_DEBUG|SLAB_PANIC,
1324 NULL, NULL);
1325
1326 /* Allocates slab cache used to allocate "struct eppoll_entry" */
1327 pwq_cache = kmem_cache_create("eventpoll_pwq",
1328 sizeof(struct eppoll_entry), 0,
1329 EPI_SLAB_DEBUG|SLAB_PANIC, NULL, NULL);
1330
Linus Torvalds1da177e2005-04-16 15:20:36 -07001331 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001332}
Davide Libenzicea69242007-05-10 22:23:22 -07001333fs_initcall(eventpoll_init);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001334