Contents of /alx-src/tags/kernel26-2.6.12-alx-r9/fs/eventpoll.c
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Wed Mar 4 11:03:09 2009 UTC (15 years, 3 months ago) by niro
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Wed Mar 4 11:03:09 2009 UTC (15 years, 3 months ago) by niro
File MIME type: text/plain
File size: 45038 byte(s)
Tag kernel26-2.6.12-alx-r9
1 | /* |
2 | * fs/eventpoll.c ( Efficent event polling implementation ) |
3 | * Copyright (C) 2001,...,2003 Davide Libenzi |
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 | |
14 | #include <linux/module.h> |
15 | #include <linux/init.h> |
16 | #include <linux/kernel.h> |
17 | #include <linux/sched.h> |
18 | #include <linux/fs.h> |
19 | #include <linux/file.h> |
20 | #include <linux/signal.h> |
21 | #include <linux/errno.h> |
22 | #include <linux/mm.h> |
23 | #include <linux/slab.h> |
24 | #include <linux/poll.h> |
25 | #include <linux/smp_lock.h> |
26 | #include <linux/string.h> |
27 | #include <linux/list.h> |
28 | #include <linux/hash.h> |
29 | #include <linux/spinlock.h> |
30 | #include <linux/syscalls.h> |
31 | #include <linux/rwsem.h> |
32 | #include <linux/rbtree.h> |
33 | #include <linux/wait.h> |
34 | #include <linux/eventpoll.h> |
35 | #include <linux/mount.h> |
36 | #include <linux/bitops.h> |
37 | #include <asm/uaccess.h> |
38 | #include <asm/system.h> |
39 | #include <asm/io.h> |
40 | #include <asm/mman.h> |
41 | #include <asm/atomic.h> |
42 | #include <asm/semaphore.h> |
43 | |
44 | |
45 | /* |
46 | * LOCKING: |
47 | * There are three level of locking required by epoll : |
48 | * |
49 | * 1) epsem (semaphore) |
50 | * 2) ep->sem (rw_semaphore) |
51 | * 3) ep->lock (rw_lock) |
52 | * |
53 | * The acquire order is the one listed above, from 1 to 3. |
54 | * We need a spinlock (ep->lock) because we manipulate objects |
55 | * from inside the poll callback, that might be triggered from |
56 | * a wake_up() that in turn might be called from IRQ context. |
57 | * So we can't sleep inside the poll callback and hence we need |
58 | * a spinlock. During the event transfer loop (from kernel to |
59 | * user space) we could end up sleeping due a copy_to_user(), so |
60 | * we need a lock that will allow us to sleep. This lock is a |
61 | * read-write semaphore (ep->sem). It is acquired on read during |
62 | * the event transfer loop and in write during epoll_ctl(EPOLL_CTL_DEL) |
63 | * and during eventpoll_release_file(). Then we also need a global |
64 | * semaphore to serialize eventpoll_release_file() and ep_free(). |
65 | * This semaphore is acquired by ep_free() during the epoll file |
66 | * cleanup path and it is also acquired by eventpoll_release_file() |
67 | * if a file has been pushed inside an epoll set and it is then |
68 | * close()d without a previous call toepoll_ctl(EPOLL_CTL_DEL). |
69 | * It is possible to drop the "ep->sem" and to use the global |
70 | * semaphore "epsem" (together with "ep->lock") to have it working, |
71 | * but having "ep->sem" will make the interface more scalable. |
72 | * Events that require holding "epsem" are very rare, while for |
73 | * normal operations the epoll private "ep->sem" will guarantee |
74 | * a greater scalability. |
75 | */ |
76 | |
77 | |
78 | #define EVENTPOLLFS_MAGIC 0x03111965 /* My birthday should work for this :) */ |
79 | |
80 | #define DEBUG_EPOLL 0 |
81 | |
82 | #if DEBUG_EPOLL > 0 |
83 | #define DPRINTK(x) printk x |
84 | #define DNPRINTK(n, x) do { if ((n) <= DEBUG_EPOLL) printk x; } while (0) |
85 | #else /* #if DEBUG_EPOLL > 0 */ |
86 | #define DPRINTK(x) (void) 0 |
87 | #define DNPRINTK(n, x) (void) 0 |
88 | #endif /* #if DEBUG_EPOLL > 0 */ |
89 | |
90 | #define DEBUG_EPI 0 |
91 | |
92 | #if DEBUG_EPI != 0 |
93 | #define EPI_SLAB_DEBUG (SLAB_DEBUG_FREE | SLAB_RED_ZONE /* | SLAB_POISON */) |
94 | #else /* #if DEBUG_EPI != 0 */ |
95 | #define EPI_SLAB_DEBUG 0 |
96 | #endif /* #if DEBUG_EPI != 0 */ |
97 | |
98 | /* Epoll private bits inside the event mask */ |
99 | #define EP_PRIVATE_BITS (EPOLLONESHOT | EPOLLET) |
100 | |
101 | /* Maximum number of poll wake up nests we are allowing */ |
102 | #define EP_MAX_POLLWAKE_NESTS 4 |
103 | |
104 | /* Macro to allocate a "struct epitem" from the slab cache */ |
105 | #define EPI_MEM_ALLOC() (struct epitem *) kmem_cache_alloc(epi_cache, SLAB_KERNEL) |
106 | |
107 | /* Macro to free a "struct epitem" to the slab cache */ |
108 | #define EPI_MEM_FREE(p) kmem_cache_free(epi_cache, p) |
109 | |
110 | /* Macro to allocate a "struct eppoll_entry" from the slab cache */ |
111 | #define PWQ_MEM_ALLOC() (struct eppoll_entry *) kmem_cache_alloc(pwq_cache, SLAB_KERNEL) |
112 | |
113 | /* Macro to free a "struct eppoll_entry" to the slab cache */ |
114 | #define PWQ_MEM_FREE(p) kmem_cache_free(pwq_cache, p) |
115 | |
116 | /* Fast test to see if the file is an evenpoll file */ |
117 | #define IS_FILE_EPOLL(f) ((f)->f_op == &eventpoll_fops) |
118 | |
119 | /* Setup the structure that is used as key for the rb-tree */ |
120 | #define EP_SET_FFD(p, f, d) do { (p)->file = (f); (p)->fd = (d); } while (0) |
121 | |
122 | /* Compare rb-tree keys */ |
123 | #define EP_CMP_FFD(p1, p2) ((p1)->file > (p2)->file ? +1: \ |
124 | ((p1)->file < (p2)->file ? -1: (p1)->fd - (p2)->fd)) |
125 | |
126 | /* Special initialization for the rb-tree node to detect linkage */ |
127 | #define EP_RB_INITNODE(n) (n)->rb_parent = (n) |
128 | |
129 | /* Removes a node from the rb-tree and marks it for a fast is-linked check */ |
130 | #define EP_RB_ERASE(n, r) do { rb_erase(n, r); (n)->rb_parent = (n); } while (0) |
131 | |
132 | /* Fast check to verify that the item is linked to the main rb-tree */ |
133 | #define EP_RB_LINKED(n) ((n)->rb_parent != (n)) |
134 | |
135 | /* |
136 | * Remove the item from the list and perform its initialization. |
137 | * This is useful for us because we can test if the item is linked |
138 | * using "EP_IS_LINKED(p)". |
139 | */ |
140 | #define EP_LIST_DEL(p) do { list_del(p); INIT_LIST_HEAD(p); } while (0) |
141 | |
142 | /* Tells us if the item is currently linked */ |
143 | #define EP_IS_LINKED(p) (!list_empty(p)) |
144 | |
145 | /* Get the "struct epitem" from a wait queue pointer */ |
146 | #define EP_ITEM_FROM_WAIT(p) ((struct epitem *) container_of(p, struct eppoll_entry, wait)->base) |
147 | |
148 | /* Get the "struct epitem" from an epoll queue wrapper */ |
149 | #define EP_ITEM_FROM_EPQUEUE(p) (container_of(p, struct ep_pqueue, pt)->epi) |
150 | |
151 | /* Tells if the epoll_ctl(2) operation needs an event copy from userspace */ |
152 | #define EP_OP_HASH_EVENT(op) ((op) != EPOLL_CTL_DEL) |
153 | |
154 | |
155 | struct epoll_filefd { |
156 | struct file *file; |
157 | int fd; |
158 | }; |
159 | |
160 | /* |
161 | * Node that is linked into the "wake_task_list" member of the "struct poll_safewake". |
162 | * It is used to keep track on all tasks that are currently inside the wake_up() code |
163 | * to 1) short-circuit the one coming from the same task and same wait queue head |
164 | * ( loop ) 2) allow a maximum number of epoll descriptors inclusion nesting |
165 | * 3) let go the ones coming from other tasks. |
166 | */ |
167 | struct wake_task_node { |
168 | struct list_head llink; |
169 | task_t *task; |
170 | wait_queue_head_t *wq; |
171 | }; |
172 | |
173 | /* |
174 | * This is used to implement the safe poll wake up avoiding to reenter |
175 | * the poll callback from inside wake_up(). |
176 | */ |
177 | struct poll_safewake { |
178 | struct list_head wake_task_list; |
179 | spinlock_t lock; |
180 | }; |
181 | |
182 | /* |
183 | * This structure is stored inside the "private_data" member of the file |
184 | * structure and rapresent the main data sructure for the eventpoll |
185 | * interface. |
186 | */ |
187 | struct eventpoll { |
188 | /* Protect the this structure access */ |
189 | rwlock_t lock; |
190 | |
191 | /* |
192 | * This semaphore is used to ensure that files are not removed |
193 | * while epoll is using them. This is read-held during the event |
194 | * collection loop and it is write-held during the file cleanup |
195 | * path, the epoll file exit code and the ctl operations. |
196 | */ |
197 | struct rw_semaphore sem; |
198 | |
199 | /* Wait queue used by sys_epoll_wait() */ |
200 | wait_queue_head_t wq; |
201 | |
202 | /* Wait queue used by file->poll() */ |
203 | wait_queue_head_t poll_wait; |
204 | |
205 | /* List of ready file descriptors */ |
206 | struct list_head rdllist; |
207 | |
208 | /* RB-Tree root used to store monitored fd structs */ |
209 | struct rb_root rbr; |
210 | }; |
211 | |
212 | /* Wait structure used by the poll hooks */ |
213 | struct eppoll_entry { |
214 | /* List header used to link this structure to the "struct epitem" */ |
215 | struct list_head llink; |
216 | |
217 | /* The "base" pointer is set to the container "struct epitem" */ |
218 | void *base; |
219 | |
220 | /* |
221 | * Wait queue item that will be linked to the target file wait |
222 | * queue head. |
223 | */ |
224 | wait_queue_t wait; |
225 | |
226 | /* The wait queue head that linked the "wait" wait queue item */ |
227 | wait_queue_head_t *whead; |
228 | }; |
229 | |
230 | /* |
231 | * Each file descriptor added to the eventpoll interface will |
232 | * have an entry of this type linked to the hash. |
233 | */ |
234 | struct epitem { |
235 | /* RB-Tree node used to link this structure to the eventpoll rb-tree */ |
236 | struct rb_node rbn; |
237 | |
238 | /* List header used to link this structure to the eventpoll ready list */ |
239 | struct list_head rdllink; |
240 | |
241 | /* The file descriptor information this item refers to */ |
242 | struct epoll_filefd ffd; |
243 | |
244 | /* Number of active wait queue attached to poll operations */ |
245 | int nwait; |
246 | |
247 | /* List containing poll wait queues */ |
248 | struct list_head pwqlist; |
249 | |
250 | /* The "container" of this item */ |
251 | struct eventpoll *ep; |
252 | |
253 | /* The structure that describe the interested events and the source fd */ |
254 | struct epoll_event event; |
255 | |
256 | /* |
257 | * Used to keep track of the usage count of the structure. This avoids |
258 | * that the structure will desappear from underneath our processing. |
259 | */ |
260 | atomic_t usecnt; |
261 | |
262 | /* List header used to link this item to the "struct file" items list */ |
263 | struct list_head fllink; |
264 | |
265 | /* List header used to link the item to the transfer list */ |
266 | struct list_head txlink; |
267 | |
268 | /* |
269 | * This is used during the collection/transfer of events to userspace |
270 | * to pin items empty events set. |
271 | */ |
272 | unsigned int revents; |
273 | }; |
274 | |
275 | /* Wrapper struct used by poll queueing */ |
276 | struct ep_pqueue { |
277 | poll_table pt; |
278 | struct epitem *epi; |
279 | }; |
280 | |
281 | |
282 | |
283 | static void ep_poll_safewake_init(struct poll_safewake *psw); |
284 | static void ep_poll_safewake(struct poll_safewake *psw, wait_queue_head_t *wq); |
285 | static int ep_getfd(int *efd, struct inode **einode, struct file **efile); |
286 | static int ep_file_init(struct file *file); |
287 | static void ep_free(struct eventpoll *ep); |
288 | static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd); |
289 | static void ep_use_epitem(struct epitem *epi); |
290 | static void ep_release_epitem(struct epitem *epi); |
291 | static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, |
292 | poll_table *pt); |
293 | static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi); |
294 | static int ep_insert(struct eventpoll *ep, struct epoll_event *event, |
295 | struct file *tfile, int fd); |
296 | static int ep_modify(struct eventpoll *ep, struct epitem *epi, |
297 | struct epoll_event *event); |
298 | static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi); |
299 | static int ep_unlink(struct eventpoll *ep, struct epitem *epi); |
300 | static int ep_remove(struct eventpoll *ep, struct epitem *epi); |
301 | static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *key); |
302 | static int ep_eventpoll_close(struct inode *inode, struct file *file); |
303 | static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait); |
304 | static int ep_collect_ready_items(struct eventpoll *ep, |
305 | struct list_head *txlist, int maxevents); |
306 | static int ep_send_events(struct eventpoll *ep, struct list_head *txlist, |
307 | struct epoll_event __user *events); |
308 | static void ep_reinject_items(struct eventpoll *ep, struct list_head *txlist); |
309 | static int ep_events_transfer(struct eventpoll *ep, |
310 | struct epoll_event __user *events, |
311 | int maxevents); |
312 | static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, |
313 | int maxevents, long timeout); |
314 | static int eventpollfs_delete_dentry(struct dentry *dentry); |
315 | static struct inode *ep_eventpoll_inode(void); |
316 | static struct super_block *eventpollfs_get_sb(struct file_system_type *fs_type, |
317 | int flags, const char *dev_name, |
318 | void *data); |
319 | |
320 | /* |
321 | * This semaphore is used to serialize ep_free() and eventpoll_release_file(). |
322 | */ |
323 | static struct semaphore epsem; |
324 | |
325 | /* Safe wake up implementation */ |
326 | static struct poll_safewake psw; |
327 | |
328 | /* Slab cache used to allocate "struct epitem" */ |
329 | static kmem_cache_t *epi_cache; |
330 | |
331 | /* Slab cache used to allocate "struct eppoll_entry" */ |
332 | static kmem_cache_t *pwq_cache; |
333 | |
334 | /* Virtual fs used to allocate inodes for eventpoll files */ |
335 | static struct vfsmount *eventpoll_mnt; |
336 | |
337 | /* File callbacks that implement the eventpoll file behaviour */ |
338 | static struct file_operations eventpoll_fops = { |
339 | .release = ep_eventpoll_close, |
340 | .poll = ep_eventpoll_poll |
341 | }; |
342 | |
343 | /* |
344 | * This is used to register the virtual file system from where |
345 | * eventpoll inodes are allocated. |
346 | */ |
347 | static struct file_system_type eventpoll_fs_type = { |
348 | .name = "eventpollfs", |
349 | .get_sb = eventpollfs_get_sb, |
350 | .kill_sb = kill_anon_super, |
351 | }; |
352 | |
353 | /* Very basic directory entry operations for the eventpoll virtual file system */ |
354 | static struct dentry_operations eventpollfs_dentry_operations = { |
355 | .d_delete = eventpollfs_delete_dentry, |
356 | }; |
357 | |
358 | |
359 | |
360 | /* Initialize the poll safe wake up structure */ |
361 | static void ep_poll_safewake_init(struct poll_safewake *psw) |
362 | { |
363 | |
364 | INIT_LIST_HEAD(&psw->wake_task_list); |
365 | spin_lock_init(&psw->lock); |
366 | } |
367 | |
368 | |
369 | /* |
370 | * Perform a safe wake up of the poll wait list. The problem is that |
371 | * with the new callback'd wake up system, it is possible that the |
372 | * poll callback is reentered from inside the call to wake_up() done |
373 | * on the poll wait queue head. The rule is that we cannot reenter the |
374 | * wake up code from the same task more than EP_MAX_POLLWAKE_NESTS times, |
375 | * and we cannot reenter the same wait queue head at all. This will |
376 | * enable to have a hierarchy of epoll file descriptor of no more than |
377 | * EP_MAX_POLLWAKE_NESTS deep. We need the irq version of the spin lock |
378 | * because this one gets called by the poll callback, that in turn is called |
379 | * from inside a wake_up(), that might be called from irq context. |
380 | */ |
381 | static void ep_poll_safewake(struct poll_safewake *psw, wait_queue_head_t *wq) |
382 | { |
383 | int wake_nests = 0; |
384 | unsigned long flags; |
385 | task_t *this_task = current; |
386 | struct list_head *lsthead = &psw->wake_task_list, *lnk; |
387 | struct wake_task_node *tncur; |
388 | struct wake_task_node tnode; |
389 | |
390 | spin_lock_irqsave(&psw->lock, flags); |
391 | |
392 | /* Try to see if the current task is already inside this wakeup call */ |
393 | list_for_each(lnk, lsthead) { |
394 | tncur = list_entry(lnk, struct wake_task_node, llink); |
395 | |
396 | if (tncur->wq == wq || |
397 | (tncur->task == this_task && ++wake_nests > EP_MAX_POLLWAKE_NESTS)) { |
398 | /* |
399 | * Ops ... loop detected or maximum nest level reached. |
400 | * We abort this wake by breaking the cycle itself. |
401 | */ |
402 | spin_unlock_irqrestore(&psw->lock, flags); |
403 | return; |
404 | } |
405 | } |
406 | |
407 | /* Add the current task to the list */ |
408 | tnode.task = this_task; |
409 | tnode.wq = wq; |
410 | list_add(&tnode.llink, lsthead); |
411 | |
412 | spin_unlock_irqrestore(&psw->lock, flags); |
413 | |
414 | /* Do really wake up now */ |
415 | wake_up(wq); |
416 | |
417 | /* Remove the current task from the list */ |
418 | spin_lock_irqsave(&psw->lock, flags); |
419 | list_del(&tnode.llink); |
420 | spin_unlock_irqrestore(&psw->lock, flags); |
421 | } |
422 | |
423 | |
424 | /* Used to initialize the epoll bits inside the "struct file" */ |
425 | void eventpoll_init_file(struct file *file) |
426 | { |
427 | |
428 | INIT_LIST_HEAD(&file->f_ep_links); |
429 | spin_lock_init(&file->f_ep_lock); |
430 | } |
431 | |
432 | |
433 | /* |
434 | * This is called from eventpoll_release() to unlink files from the eventpoll |
435 | * interface. We need to have this facility to cleanup correctly files that are |
436 | * closed without being removed from the eventpoll interface. |
437 | */ |
438 | void eventpoll_release_file(struct file *file) |
439 | { |
440 | struct list_head *lsthead = &file->f_ep_links; |
441 | struct eventpoll *ep; |
442 | struct epitem *epi; |
443 | |
444 | /* |
445 | * We don't want to get "file->f_ep_lock" because it is not |
446 | * necessary. It is not necessary because we're in the "struct file" |
447 | * cleanup path, and this means that noone is using this file anymore. |
448 | * The only hit might come from ep_free() but by holding the semaphore |
449 | * will correctly serialize the operation. We do need to acquire |
450 | * "ep->sem" after "epsem" because ep_remove() requires it when called |
451 | * from anywhere but ep_free(). |
452 | */ |
453 | down(&epsem); |
454 | |
455 | while (!list_empty(lsthead)) { |
456 | epi = list_entry(lsthead->next, struct epitem, fllink); |
457 | |
458 | ep = epi->ep; |
459 | EP_LIST_DEL(&epi->fllink); |
460 | down_write(&ep->sem); |
461 | ep_remove(ep, epi); |
462 | up_write(&ep->sem); |
463 | } |
464 | |
465 | up(&epsem); |
466 | } |
467 | |
468 | |
469 | /* |
470 | * It opens an eventpoll file descriptor by suggesting a storage of "size" |
471 | * file descriptors. The size parameter is just an hint about how to size |
472 | * data structures. It won't prevent the user to store more than "size" |
473 | * file descriptors inside the epoll interface. It is the kernel part of |
474 | * the userspace epoll_create(2). |
475 | */ |
476 | asmlinkage long sys_epoll_create(int size) |
477 | { |
478 | int error, fd; |
479 | struct inode *inode; |
480 | struct file *file; |
481 | |
482 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d)\n", |
483 | current, size)); |
484 | |
485 | /* Sanity check on the size parameter */ |
486 | error = -EINVAL; |
487 | if (size <= 0) |
488 | goto eexit_1; |
489 | |
490 | /* |
491 | * Creates all the items needed to setup an eventpoll file. That is, |
492 | * a file structure, and inode and a free file descriptor. |
493 | */ |
494 | error = ep_getfd(&fd, &inode, &file); |
495 | if (error) |
496 | goto eexit_1; |
497 | |
498 | /* Setup the file internal data structure ( "struct eventpoll" ) */ |
499 | error = ep_file_init(file); |
500 | if (error) |
501 | goto eexit_2; |
502 | |
503 | |
504 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n", |
505 | current, size, fd)); |
506 | |
507 | return fd; |
508 | |
509 | eexit_2: |
510 | sys_close(fd); |
511 | eexit_1: |
512 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n", |
513 | current, size, error)); |
514 | return error; |
515 | } |
516 | |
517 | |
518 | /* |
519 | * The following function implements the controller interface for |
520 | * the eventpoll file that enables the insertion/removal/change of |
521 | * file descriptors inside the interest set. It represents |
522 | * the kernel part of the user space epoll_ctl(2). |
523 | */ |
524 | asmlinkage long |
525 | sys_epoll_ctl(int epfd, int op, int fd, struct epoll_event __user *event) |
526 | { |
527 | int error; |
528 | struct file *file, *tfile; |
529 | struct eventpoll *ep; |
530 | struct epitem *epi; |
531 | struct epoll_event epds; |
532 | |
533 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %p)\n", |
534 | current, epfd, op, fd, event)); |
535 | |
536 | error = -EFAULT; |
537 | if (EP_OP_HASH_EVENT(op) && |
538 | copy_from_user(&epds, event, sizeof(struct epoll_event))) |
539 | goto eexit_1; |
540 | |
541 | /* Get the "struct file *" for the eventpoll file */ |
542 | error = -EBADF; |
543 | file = fget(epfd); |
544 | if (!file) |
545 | goto eexit_1; |
546 | |
547 | /* Get the "struct file *" for the target file */ |
548 | tfile = fget(fd); |
549 | if (!tfile) |
550 | goto eexit_2; |
551 | |
552 | /* The target file descriptor must support poll */ |
553 | error = -EPERM; |
554 | if (!tfile->f_op || !tfile->f_op->poll) |
555 | goto eexit_3; |
556 | |
557 | /* |
558 | * We have to check that the file structure underneath the file descriptor |
559 | * the user passed to us _is_ an eventpoll file. And also we do not permit |
560 | * adding an epoll file descriptor inside itself. |
561 | */ |
562 | error = -EINVAL; |
563 | if (file == tfile || !IS_FILE_EPOLL(file)) |
564 | goto eexit_3; |
565 | |
566 | /* |
567 | * At this point it is safe to assume that the "private_data" contains |
568 | * our own data structure. |
569 | */ |
570 | ep = file->private_data; |
571 | |
572 | down_write(&ep->sem); |
573 | |
574 | /* Try to lookup the file inside our hash table */ |
575 | epi = ep_find(ep, tfile, fd); |
576 | |
577 | error = -EINVAL; |
578 | switch (op) { |
579 | case EPOLL_CTL_ADD: |
580 | if (!epi) { |
581 | epds.events |= POLLERR | POLLHUP; |
582 | |
583 | error = ep_insert(ep, &epds, tfile, fd); |
584 | } else |
585 | error = -EEXIST; |
586 | break; |
587 | case EPOLL_CTL_DEL: |
588 | if (epi) |
589 | error = ep_remove(ep, epi); |
590 | else |
591 | error = -ENOENT; |
592 | break; |
593 | case EPOLL_CTL_MOD: |
594 | if (epi) { |
595 | epds.events |= POLLERR | POLLHUP; |
596 | error = ep_modify(ep, epi, &epds); |
597 | } else |
598 | error = -ENOENT; |
599 | break; |
600 | } |
601 | |
602 | /* |
603 | * The function ep_find() increments the usage count of the structure |
604 | * so, if this is not NULL, we need to release it. |
605 | */ |
606 | if (epi) |
607 | ep_release_epitem(epi); |
608 | |
609 | up_write(&ep->sem); |
610 | |
611 | eexit_3: |
612 | fput(tfile); |
613 | eexit_2: |
614 | fput(file); |
615 | eexit_1: |
616 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %p) = %d\n", |
617 | current, epfd, op, fd, event, error)); |
618 | |
619 | return error; |
620 | } |
621 | |
622 | #define MAX_EVENTS (INT_MAX / sizeof(struct epoll_event)) |
623 | |
624 | /* |
625 | * Implement the event wait interface for the eventpoll file. It is the kernel |
626 | * part of the user space epoll_wait(2). |
627 | */ |
628 | asmlinkage long sys_epoll_wait(int epfd, struct epoll_event __user *events, |
629 | int maxevents, int timeout) |
630 | { |
631 | int error; |
632 | struct file *file; |
633 | struct eventpoll *ep; |
634 | |
635 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_wait(%d, %p, %d, %d)\n", |
636 | current, epfd, events, maxevents, timeout)); |
637 | |
638 | /* The maximum number of event must be greater than zero */ |
639 | if (maxevents <= 0 || maxevents > MAX_EVENTS) |
640 | return -EINVAL; |
641 | |
642 | /* Verify that the area passed by the user is writeable */ |
643 | if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event))) { |
644 | error = -EFAULT; |
645 | goto eexit_1; |
646 | } |
647 | |
648 | /* Get the "struct file *" for the eventpoll file */ |
649 | error = -EBADF; |
650 | file = fget(epfd); |
651 | if (!file) |
652 | goto eexit_1; |
653 | |
654 | /* |
655 | * We have to check that the file structure underneath the fd |
656 | * the user passed to us _is_ an eventpoll file. |
657 | */ |
658 | error = -EINVAL; |
659 | if (!IS_FILE_EPOLL(file)) |
660 | goto eexit_2; |
661 | |
662 | /* |
663 | * At this point it is safe to assume that the "private_data" contains |
664 | * our own data structure. |
665 | */ |
666 | ep = file->private_data; |
667 | |
668 | /* Time to fish for events ... */ |
669 | error = ep_poll(ep, events, maxevents, timeout); |
670 | |
671 | eexit_2: |
672 | fput(file); |
673 | eexit_1: |
674 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_wait(%d, %p, %d, %d) = %d\n", |
675 | current, epfd, events, maxevents, timeout, error)); |
676 | |
677 | return error; |
678 | } |
679 | |
680 | |
681 | /* |
682 | * Creates the file descriptor to be used by the epoll interface. |
683 | */ |
684 | static int ep_getfd(int *efd, struct inode **einode, struct file **efile) |
685 | { |
686 | struct qstr this; |
687 | char name[32]; |
688 | struct dentry *dentry; |
689 | struct inode *inode; |
690 | struct file *file; |
691 | int error, fd; |
692 | |
693 | /* Get an ready to use file */ |
694 | error = -ENFILE; |
695 | file = get_empty_filp(); |
696 | if (!file) |
697 | goto eexit_1; |
698 | |
699 | /* Allocates an inode from the eventpoll file system */ |
700 | inode = ep_eventpoll_inode(); |
701 | error = PTR_ERR(inode); |
702 | if (IS_ERR(inode)) |
703 | goto eexit_2; |
704 | |
705 | /* Allocates a free descriptor to plug the file onto */ |
706 | error = get_unused_fd(); |
707 | if (error < 0) |
708 | goto eexit_3; |
709 | fd = error; |
710 | |
711 | /* |
712 | * Link the inode to a directory entry by creating a unique name |
713 | * using the inode number. |
714 | */ |
715 | error = -ENOMEM; |
716 | sprintf(name, "[%lu]", inode->i_ino); |
717 | this.name = name; |
718 | this.len = strlen(name); |
719 | this.hash = inode->i_ino; |
720 | dentry = d_alloc(eventpoll_mnt->mnt_sb->s_root, &this); |
721 | if (!dentry) |
722 | goto eexit_4; |
723 | dentry->d_op = &eventpollfs_dentry_operations; |
724 | d_add(dentry, inode); |
725 | file->f_vfsmnt = mntget(eventpoll_mnt); |
726 | file->f_dentry = dentry; |
727 | file->f_mapping = inode->i_mapping; |
728 | |
729 | file->f_pos = 0; |
730 | file->f_flags = O_RDONLY; |
731 | file->f_op = &eventpoll_fops; |
732 | file->f_mode = FMODE_READ; |
733 | file->f_version = 0; |
734 | file->private_data = NULL; |
735 | |
736 | /* Install the new setup file into the allocated fd. */ |
737 | fd_install(fd, file); |
738 | |
739 | *efd = fd; |
740 | *einode = inode; |
741 | *efile = file; |
742 | return 0; |
743 | |
744 | eexit_4: |
745 | put_unused_fd(fd); |
746 | eexit_3: |
747 | iput(inode); |
748 | eexit_2: |
749 | put_filp(file); |
750 | eexit_1: |
751 | return error; |
752 | } |
753 | |
754 | |
755 | static int ep_file_init(struct file *file) |
756 | { |
757 | struct eventpoll *ep; |
758 | |
759 | if (!(ep = kmalloc(sizeof(struct eventpoll), GFP_KERNEL))) |
760 | return -ENOMEM; |
761 | |
762 | memset(ep, 0, sizeof(*ep)); |
763 | rwlock_init(&ep->lock); |
764 | init_rwsem(&ep->sem); |
765 | init_waitqueue_head(&ep->wq); |
766 | init_waitqueue_head(&ep->poll_wait); |
767 | INIT_LIST_HEAD(&ep->rdllist); |
768 | ep->rbr = RB_ROOT; |
769 | |
770 | file->private_data = ep; |
771 | |
772 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_file_init() ep=%p\n", |
773 | current, ep)); |
774 | return 0; |
775 | } |
776 | |
777 | |
778 | static void ep_free(struct eventpoll *ep) |
779 | { |
780 | struct rb_node *rbp; |
781 | struct epitem *epi; |
782 | |
783 | /* We need to release all tasks waiting for these file */ |
784 | if (waitqueue_active(&ep->poll_wait)) |
785 | ep_poll_safewake(&psw, &ep->poll_wait); |
786 | |
787 | /* |
788 | * We need to lock this because we could be hit by |
789 | * eventpoll_release_file() while we're freeing the "struct eventpoll". |
790 | * We do not need to hold "ep->sem" here because the epoll file |
791 | * is on the way to be removed and no one has references to it |
792 | * anymore. The only hit might come from eventpoll_release_file() but |
793 | * holding "epsem" is sufficent here. |
794 | */ |
795 | down(&epsem); |
796 | |
797 | /* |
798 | * Walks through the whole tree by unregistering poll callbacks. |
799 | */ |
800 | for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { |
801 | epi = rb_entry(rbp, struct epitem, rbn); |
802 | |
803 | ep_unregister_pollwait(ep, epi); |
804 | } |
805 | |
806 | /* |
807 | * Walks through the whole hash by freeing each "struct epitem". At this |
808 | * point we are sure no poll callbacks will be lingering around, and also by |
809 | * write-holding "sem" we can be sure that no file cleanup code will hit |
810 | * us during this operation. So we can avoid the lock on "ep->lock". |
811 | */ |
812 | while ((rbp = rb_first(&ep->rbr)) != 0) { |
813 | epi = rb_entry(rbp, struct epitem, rbn); |
814 | ep_remove(ep, epi); |
815 | } |
816 | |
817 | up(&epsem); |
818 | } |
819 | |
820 | |
821 | /* |
822 | * Search the file inside the eventpoll hash. It add usage count to |
823 | * the returned item, so the caller must call ep_release_epitem() |
824 | * after finished using the "struct epitem". |
825 | */ |
826 | static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd) |
827 | { |
828 | int kcmp; |
829 | unsigned long flags; |
830 | struct rb_node *rbp; |
831 | struct epitem *epi, *epir = NULL; |
832 | struct epoll_filefd ffd; |
833 | |
834 | EP_SET_FFD(&ffd, file, fd); |
835 | read_lock_irqsave(&ep->lock, flags); |
836 | for (rbp = ep->rbr.rb_node; rbp; ) { |
837 | epi = rb_entry(rbp, struct epitem, rbn); |
838 | kcmp = EP_CMP_FFD(&ffd, &epi->ffd); |
839 | if (kcmp > 0) |
840 | rbp = rbp->rb_right; |
841 | else if (kcmp < 0) |
842 | rbp = rbp->rb_left; |
843 | else { |
844 | ep_use_epitem(epi); |
845 | epir = epi; |
846 | break; |
847 | } |
848 | } |
849 | read_unlock_irqrestore(&ep->lock, flags); |
850 | |
851 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_find(%p) -> %p\n", |
852 | current, file, epir)); |
853 | |
854 | return epir; |
855 | } |
856 | |
857 | |
858 | /* |
859 | * Increment the usage count of the "struct epitem" making it sure |
860 | * that the user will have a valid pointer to reference. |
861 | */ |
862 | static void ep_use_epitem(struct epitem *epi) |
863 | { |
864 | |
865 | atomic_inc(&epi->usecnt); |
866 | } |
867 | |
868 | |
869 | /* |
870 | * Decrement ( release ) the usage count by signaling that the user |
871 | * has finished using the structure. It might lead to freeing the |
872 | * structure itself if the count goes to zero. |
873 | */ |
874 | static void ep_release_epitem(struct epitem *epi) |
875 | { |
876 | |
877 | if (atomic_dec_and_test(&epi->usecnt)) |
878 | EPI_MEM_FREE(epi); |
879 | } |
880 | |
881 | |
882 | /* |
883 | * This is the callback that is used to add our wait queue to the |
884 | * target file wakeup lists. |
885 | */ |
886 | static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, |
887 | poll_table *pt) |
888 | { |
889 | struct epitem *epi = EP_ITEM_FROM_EPQUEUE(pt); |
890 | struct eppoll_entry *pwq; |
891 | |
892 | if (epi->nwait >= 0 && (pwq = PWQ_MEM_ALLOC())) { |
893 | init_waitqueue_func_entry(&pwq->wait, ep_poll_callback); |
894 | pwq->whead = whead; |
895 | pwq->base = epi; |
896 | add_wait_queue(whead, &pwq->wait); |
897 | list_add_tail(&pwq->llink, &epi->pwqlist); |
898 | epi->nwait++; |
899 | } else { |
900 | /* We have to signal that an error occurred */ |
901 | epi->nwait = -1; |
902 | } |
903 | } |
904 | |
905 | |
906 | static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi) |
907 | { |
908 | int kcmp; |
909 | struct rb_node **p = &ep->rbr.rb_node, *parent = NULL; |
910 | struct epitem *epic; |
911 | |
912 | while (*p) { |
913 | parent = *p; |
914 | epic = rb_entry(parent, struct epitem, rbn); |
915 | kcmp = EP_CMP_FFD(&epi->ffd, &epic->ffd); |
916 | if (kcmp > 0) |
917 | p = &parent->rb_right; |
918 | else |
919 | p = &parent->rb_left; |
920 | } |
921 | rb_link_node(&epi->rbn, parent, p); |
922 | rb_insert_color(&epi->rbn, &ep->rbr); |
923 | } |
924 | |
925 | |
926 | static int ep_insert(struct eventpoll *ep, struct epoll_event *event, |
927 | struct file *tfile, int fd) |
928 | { |
929 | int error, revents, pwake = 0; |
930 | unsigned long flags; |
931 | struct epitem *epi; |
932 | struct ep_pqueue epq; |
933 | |
934 | error = -ENOMEM; |
935 | if (!(epi = EPI_MEM_ALLOC())) |
936 | goto eexit_1; |
937 | |
938 | /* Item initialization follow here ... */ |
939 | EP_RB_INITNODE(&epi->rbn); |
940 | INIT_LIST_HEAD(&epi->rdllink); |
941 | INIT_LIST_HEAD(&epi->fllink); |
942 | INIT_LIST_HEAD(&epi->txlink); |
943 | INIT_LIST_HEAD(&epi->pwqlist); |
944 | epi->ep = ep; |
945 | EP_SET_FFD(&epi->ffd, tfile, fd); |
946 | epi->event = *event; |
947 | atomic_set(&epi->usecnt, 1); |
948 | epi->nwait = 0; |
949 | |
950 | /* Initialize the poll table using the queue callback */ |
951 | epq.epi = epi; |
952 | init_poll_funcptr(&epq.pt, ep_ptable_queue_proc); |
953 | |
954 | /* |
955 | * Attach the item to the poll hooks and get current event bits. |
956 | * We can safely use the file* here because its usage count has |
957 | * been increased by the caller of this function. |
958 | */ |
959 | revents = tfile->f_op->poll(tfile, &epq.pt); |
960 | |
961 | /* |
962 | * We have to check if something went wrong during the poll wait queue |
963 | * install process. Namely an allocation for a wait queue failed due |
964 | * high memory pressure. |
965 | */ |
966 | if (epi->nwait < 0) |
967 | goto eexit_2; |
968 | |
969 | /* Add the current item to the list of active epoll hook for this file */ |
970 | spin_lock(&tfile->f_ep_lock); |
971 | list_add_tail(&epi->fllink, &tfile->f_ep_links); |
972 | spin_unlock(&tfile->f_ep_lock); |
973 | |
974 | /* We have to drop the new item inside our item list to keep track of it */ |
975 | write_lock_irqsave(&ep->lock, flags); |
976 | |
977 | /* Add the current item to the rb-tree */ |
978 | ep_rbtree_insert(ep, epi); |
979 | |
980 | /* If the file is already "ready" we drop it inside the ready list */ |
981 | if ((revents & event->events) && !EP_IS_LINKED(&epi->rdllink)) { |
982 | list_add_tail(&epi->rdllink, &ep->rdllist); |
983 | |
984 | /* Notify waiting tasks that events are available */ |
985 | if (waitqueue_active(&ep->wq)) |
986 | wake_up(&ep->wq); |
987 | if (waitqueue_active(&ep->poll_wait)) |
988 | pwake++; |
989 | } |
990 | |
991 | write_unlock_irqrestore(&ep->lock, flags); |
992 | |
993 | /* We have to call this outside the lock */ |
994 | if (pwake) |
995 | ep_poll_safewake(&psw, &ep->poll_wait); |
996 | |
997 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_insert(%p, %p, %d)\n", |
998 | current, ep, tfile, fd)); |
999 | |
1000 | return 0; |
1001 | |
1002 | eexit_2: |
1003 | ep_unregister_pollwait(ep, epi); |
1004 | |
1005 | /* |
1006 | * We need to do this because an event could have been arrived on some |
1007 | * allocated wait queue. |
1008 | */ |
1009 | write_lock_irqsave(&ep->lock, flags); |
1010 | if (EP_IS_LINKED(&epi->rdllink)) |
1011 | EP_LIST_DEL(&epi->rdllink); |
1012 | write_unlock_irqrestore(&ep->lock, flags); |
1013 | |
1014 | EPI_MEM_FREE(epi); |
1015 | eexit_1: |
1016 | return error; |
1017 | } |
1018 | |
1019 | |
1020 | /* |
1021 | * Modify the interest event mask by dropping an event if the new mask |
1022 | * has a match in the current file status. |
1023 | */ |
1024 | static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_event *event) |
1025 | { |
1026 | int pwake = 0; |
1027 | unsigned int revents; |
1028 | unsigned long flags; |
1029 | |
1030 | /* |
1031 | * Set the new event interest mask before calling f_op->poll(), otherwise |
1032 | * a potential race might occur. In fact if we do this operation inside |
1033 | * the lock, an event might happen between the f_op->poll() call and the |
1034 | * new event set registering. |
1035 | */ |
1036 | epi->event.events = event->events; |
1037 | |
1038 | /* |
1039 | * Get current event bits. We can safely use the file* here because |
1040 | * its usage count has been increased by the caller of this function. |
1041 | */ |
1042 | revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL); |
1043 | |
1044 | write_lock_irqsave(&ep->lock, flags); |
1045 | |
1046 | /* Copy the data member from inside the lock */ |
1047 | epi->event.data = event->data; |
1048 | |
1049 | /* |
1050 | * If the item is not linked to the hash it means that it's on its |
1051 | * way toward the removal. Do nothing in this case. |
1052 | */ |
1053 | if (EP_RB_LINKED(&epi->rbn)) { |
1054 | /* |
1055 | * If the item is "hot" and it is not registered inside the ready |
1056 | * list, push it inside. If the item is not "hot" and it is currently |
1057 | * registered inside the ready list, unlink it. |
1058 | */ |
1059 | if (revents & event->events) { |
1060 | if (!EP_IS_LINKED(&epi->rdllink)) { |
1061 | list_add_tail(&epi->rdllink, &ep->rdllist); |
1062 | |
1063 | /* Notify waiting tasks that events are available */ |
1064 | if (waitqueue_active(&ep->wq)) |
1065 | wake_up(&ep->wq); |
1066 | if (waitqueue_active(&ep->poll_wait)) |
1067 | pwake++; |
1068 | } |
1069 | } |
1070 | } |
1071 | |
1072 | write_unlock_irqrestore(&ep->lock, flags); |
1073 | |
1074 | /* We have to call this outside the lock */ |
1075 | if (pwake) |
1076 | ep_poll_safewake(&psw, &ep->poll_wait); |
1077 | |
1078 | return 0; |
1079 | } |
1080 | |
1081 | |
1082 | /* |
1083 | * This function unregister poll callbacks from the associated file descriptor. |
1084 | * Since this must be called without holding "ep->lock" the atomic exchange trick |
1085 | * will protect us from multiple unregister. |
1086 | */ |
1087 | static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi) |
1088 | { |
1089 | int nwait; |
1090 | struct list_head *lsthead = &epi->pwqlist; |
1091 | struct eppoll_entry *pwq; |
1092 | |
1093 | /* This is called without locks, so we need the atomic exchange */ |
1094 | nwait = xchg(&epi->nwait, 0); |
1095 | |
1096 | if (nwait) { |
1097 | while (!list_empty(lsthead)) { |
1098 | pwq = list_entry(lsthead->next, struct eppoll_entry, llink); |
1099 | |
1100 | EP_LIST_DEL(&pwq->llink); |
1101 | remove_wait_queue(pwq->whead, &pwq->wait); |
1102 | PWQ_MEM_FREE(pwq); |
1103 | } |
1104 | } |
1105 | } |
1106 | |
1107 | |
1108 | /* |
1109 | * Unlink the "struct epitem" from all places it might have been hooked up. |
1110 | * This function must be called with write IRQ lock on "ep->lock". |
1111 | */ |
1112 | static int ep_unlink(struct eventpoll *ep, struct epitem *epi) |
1113 | { |
1114 | int error; |
1115 | |
1116 | /* |
1117 | * It can happen that this one is called for an item already unlinked. |
1118 | * The check protect us from doing a double unlink ( crash ). |
1119 | */ |
1120 | error = -ENOENT; |
1121 | if (!EP_RB_LINKED(&epi->rbn)) |
1122 | goto eexit_1; |
1123 | |
1124 | /* |
1125 | * Clear the event mask for the unlinked item. This will avoid item |
1126 | * notifications to be sent after the unlink operation from inside |
1127 | * the kernel->userspace event transfer loop. |
1128 | */ |
1129 | epi->event.events = 0; |
1130 | |
1131 | /* |
1132 | * At this point is safe to do the job, unlink the item from our rb-tree. |
1133 | * This operation togheter with the above check closes the door to |
1134 | * double unlinks. |
1135 | */ |
1136 | EP_RB_ERASE(&epi->rbn, &ep->rbr); |
1137 | |
1138 | /* |
1139 | * If the item we are going to remove is inside the ready file descriptors |
1140 | * we want to remove it from this list to avoid stale events. |
1141 | */ |
1142 | if (EP_IS_LINKED(&epi->rdllink)) |
1143 | EP_LIST_DEL(&epi->rdllink); |
1144 | |
1145 | error = 0; |
1146 | eexit_1: |
1147 | |
1148 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_unlink(%p, %p) = %d\n", |
1149 | current, ep, epi->file, error)); |
1150 | |
1151 | return error; |
1152 | } |
1153 | |
1154 | |
1155 | /* |
1156 | * Removes a "struct epitem" from the eventpoll hash and deallocates |
1157 | * all the associated resources. |
1158 | */ |
1159 | static int ep_remove(struct eventpoll *ep, struct epitem *epi) |
1160 | { |
1161 | int error; |
1162 | unsigned long flags; |
1163 | struct file *file = epi->ffd.file; |
1164 | |
1165 | /* |
1166 | * Removes poll wait queue hooks. We _have_ to do this without holding |
1167 | * the "ep->lock" otherwise a deadlock might occur. This because of the |
1168 | * sequence of the lock acquisition. Here we do "ep->lock" then the wait |
1169 | * queue head lock when unregistering the wait queue. The wakeup callback |
1170 | * will run by holding the wait queue head lock and will call our callback |
1171 | * that will try to get "ep->lock". |
1172 | */ |
1173 | ep_unregister_pollwait(ep, epi); |
1174 | |
1175 | /* Remove the current item from the list of epoll hooks */ |
1176 | spin_lock(&file->f_ep_lock); |
1177 | if (EP_IS_LINKED(&epi->fllink)) |
1178 | EP_LIST_DEL(&epi->fllink); |
1179 | spin_unlock(&file->f_ep_lock); |
1180 | |
1181 | /* We need to acquire the write IRQ lock before calling ep_unlink() */ |
1182 | write_lock_irqsave(&ep->lock, flags); |
1183 | |
1184 | /* Really unlink the item from the hash */ |
1185 | error = ep_unlink(ep, epi); |
1186 | |
1187 | write_unlock_irqrestore(&ep->lock, flags); |
1188 | |
1189 | if (error) |
1190 | goto eexit_1; |
1191 | |
1192 | /* At this point it is safe to free the eventpoll item */ |
1193 | ep_release_epitem(epi); |
1194 | |
1195 | error = 0; |
1196 | eexit_1: |
1197 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_remove(%p, %p) = %d\n", |
1198 | current, ep, file, error)); |
1199 | |
1200 | return error; |
1201 | } |
1202 | |
1203 | |
1204 | /* |
1205 | * This is the callback that is passed to the wait queue wakeup |
1206 | * machanism. It is called by the stored file descriptors when they |
1207 | * have events to report. |
1208 | */ |
1209 | static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *key) |
1210 | { |
1211 | int pwake = 0; |
1212 | unsigned long flags; |
1213 | struct epitem *epi = EP_ITEM_FROM_WAIT(wait); |
1214 | struct eventpoll *ep = epi->ep; |
1215 | |
1216 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: poll_callback(%p) epi=%p ep=%p\n", |
1217 | current, epi->file, epi, ep)); |
1218 | |
1219 | write_lock_irqsave(&ep->lock, flags); |
1220 | |
1221 | /* |
1222 | * If the event mask does not contain any poll(2) event, we consider the |
1223 | * descriptor to be disabled. This condition is likely the effect of the |
1224 | * EPOLLONESHOT bit that disables the descriptor when an event is received, |
1225 | * until the next EPOLL_CTL_MOD will be issued. |
1226 | */ |
1227 | if (!(epi->event.events & ~EP_PRIVATE_BITS)) |
1228 | goto is_disabled; |
1229 | |
1230 | /* If this file is already in the ready list we exit soon */ |
1231 | if (EP_IS_LINKED(&epi->rdllink)) |
1232 | goto is_linked; |
1233 | |
1234 | list_add_tail(&epi->rdllink, &ep->rdllist); |
1235 | |
1236 | is_linked: |
1237 | /* |
1238 | * Wake up ( if active ) both the eventpoll wait list and the ->poll() |
1239 | * wait list. |
1240 | */ |
1241 | if (waitqueue_active(&ep->wq)) |
1242 | wake_up(&ep->wq); |
1243 | if (waitqueue_active(&ep->poll_wait)) |
1244 | pwake++; |
1245 | |
1246 | is_disabled: |
1247 | write_unlock_irqrestore(&ep->lock, flags); |
1248 | |
1249 | /* We have to call this outside the lock */ |
1250 | if (pwake) |
1251 | ep_poll_safewake(&psw, &ep->poll_wait); |
1252 | |
1253 | return 1; |
1254 | } |
1255 | |
1256 | |
1257 | static int ep_eventpoll_close(struct inode *inode, struct file *file) |
1258 | { |
1259 | struct eventpoll *ep = file->private_data; |
1260 | |
1261 | if (ep) { |
1262 | ep_free(ep); |
1263 | kfree(ep); |
1264 | } |
1265 | |
1266 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: close() ep=%p\n", current, ep)); |
1267 | return 0; |
1268 | } |
1269 | |
1270 | |
1271 | static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait) |
1272 | { |
1273 | unsigned int pollflags = 0; |
1274 | unsigned long flags; |
1275 | struct eventpoll *ep = file->private_data; |
1276 | |
1277 | /* Insert inside our poll wait queue */ |
1278 | poll_wait(file, &ep->poll_wait, wait); |
1279 | |
1280 | /* Check our condition */ |
1281 | read_lock_irqsave(&ep->lock, flags); |
1282 | if (!list_empty(&ep->rdllist)) |
1283 | pollflags = POLLIN | POLLRDNORM; |
1284 | read_unlock_irqrestore(&ep->lock, flags); |
1285 | |
1286 | return pollflags; |
1287 | } |
1288 | |
1289 | |
1290 | /* |
1291 | * Since we have to release the lock during the __copy_to_user() operation and |
1292 | * during the f_op->poll() call, we try to collect the maximum number of items |
1293 | * by reducing the irqlock/irqunlock switching rate. |
1294 | */ |
1295 | static int ep_collect_ready_items(struct eventpoll *ep, struct list_head *txlist, int maxevents) |
1296 | { |
1297 | int nepi; |
1298 | unsigned long flags; |
1299 | struct list_head *lsthead = &ep->rdllist, *lnk; |
1300 | struct epitem *epi; |
1301 | |
1302 | write_lock_irqsave(&ep->lock, flags); |
1303 | |
1304 | for (nepi = 0, lnk = lsthead->next; lnk != lsthead && nepi < maxevents;) { |
1305 | epi = list_entry(lnk, struct epitem, rdllink); |
1306 | |
1307 | lnk = lnk->next; |
1308 | |
1309 | /* If this file is already in the ready list we exit soon */ |
1310 | if (!EP_IS_LINKED(&epi->txlink)) { |
1311 | /* |
1312 | * This is initialized in this way so that the default |
1313 | * behaviour of the reinjecting code will be to push back |
1314 | * the item inside the ready list. |
1315 | */ |
1316 | epi->revents = epi->event.events; |
1317 | |
1318 | /* Link the ready item into the transfer list */ |
1319 | list_add(&epi->txlink, txlist); |
1320 | nepi++; |
1321 | |
1322 | /* |
1323 | * Unlink the item from the ready list. |
1324 | */ |
1325 | EP_LIST_DEL(&epi->rdllink); |
1326 | } |
1327 | } |
1328 | |
1329 | write_unlock_irqrestore(&ep->lock, flags); |
1330 | |
1331 | return nepi; |
1332 | } |
1333 | |
1334 | |
1335 | /* |
1336 | * This function is called without holding the "ep->lock" since the call to |
1337 | * __copy_to_user() might sleep, and also f_op->poll() might reenable the IRQ |
1338 | * because of the way poll() is traditionally implemented in Linux. |
1339 | */ |
1340 | static int ep_send_events(struct eventpoll *ep, struct list_head *txlist, |
1341 | struct epoll_event __user *events) |
1342 | { |
1343 | int eventcnt = 0; |
1344 | unsigned int revents; |
1345 | struct list_head *lnk; |
1346 | struct epitem *epi; |
1347 | |
1348 | /* |
1349 | * We can loop without lock because this is a task private list. |
1350 | * The test done during the collection loop will guarantee us that |
1351 | * another task will not try to collect this file. Also, items |
1352 | * cannot vanish during the loop because we are holding "sem". |
1353 | */ |
1354 | list_for_each(lnk, txlist) { |
1355 | epi = list_entry(lnk, struct epitem, txlink); |
1356 | |
1357 | /* |
1358 | * Get the ready file event set. We can safely use the file |
1359 | * because we are holding the "sem" in read and this will |
1360 | * guarantee that both the file and the item will not vanish. |
1361 | */ |
1362 | revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL); |
1363 | |
1364 | /* |
1365 | * Set the return event set for the current file descriptor. |
1366 | * Note that only the task task was successfully able to link |
1367 | * the item to its "txlist" will write this field. |
1368 | */ |
1369 | epi->revents = revents & epi->event.events; |
1370 | |
1371 | if (epi->revents) { |
1372 | if (__put_user(epi->revents, |
1373 | &events[eventcnt].events) || |
1374 | __put_user(epi->event.data, |
1375 | &events[eventcnt].data)) |
1376 | return -EFAULT; |
1377 | if (epi->event.events & EPOLLONESHOT) |
1378 | epi->event.events &= EP_PRIVATE_BITS; |
1379 | eventcnt++; |
1380 | } |
1381 | } |
1382 | return eventcnt; |
1383 | } |
1384 | |
1385 | |
1386 | /* |
1387 | * Walk through the transfer list we collected with ep_collect_ready_items() |
1388 | * and, if 1) the item is still "alive" 2) its event set is not empty 3) it's |
1389 | * not already linked, links it to the ready list. Same as above, we are holding |
1390 | * "sem" so items cannot vanish underneath our nose. |
1391 | */ |
1392 | static void ep_reinject_items(struct eventpoll *ep, struct list_head *txlist) |
1393 | { |
1394 | int ricnt = 0, pwake = 0; |
1395 | unsigned long flags; |
1396 | struct epitem *epi; |
1397 | |
1398 | write_lock_irqsave(&ep->lock, flags); |
1399 | |
1400 | while (!list_empty(txlist)) { |
1401 | epi = list_entry(txlist->next, struct epitem, txlink); |
1402 | |
1403 | /* Unlink the current item from the transfer list */ |
1404 | EP_LIST_DEL(&epi->txlink); |
1405 | |
1406 | /* |
1407 | * If the item is no more linked to the interest set, we don't |
1408 | * have to push it inside the ready list because the following |
1409 | * ep_release_epitem() is going to drop it. Also, if the current |
1410 | * item is set to have an Edge Triggered behaviour, we don't have |
1411 | * to push it back either. |
1412 | */ |
1413 | if (EP_RB_LINKED(&epi->rbn) && !(epi->event.events & EPOLLET) && |
1414 | (epi->revents & epi->event.events) && !EP_IS_LINKED(&epi->rdllink)) { |
1415 | list_add_tail(&epi->rdllink, &ep->rdllist); |
1416 | ricnt++; |
1417 | } |
1418 | } |
1419 | |
1420 | if (ricnt) { |
1421 | /* |
1422 | * Wake up ( if active ) both the eventpoll wait list and the ->poll() |
1423 | * wait list. |
1424 | */ |
1425 | if (waitqueue_active(&ep->wq)) |
1426 | wake_up(&ep->wq); |
1427 | if (waitqueue_active(&ep->poll_wait)) |
1428 | pwake++; |
1429 | } |
1430 | |
1431 | write_unlock_irqrestore(&ep->lock, flags); |
1432 | |
1433 | /* We have to call this outside the lock */ |
1434 | if (pwake) |
1435 | ep_poll_safewake(&psw, &ep->poll_wait); |
1436 | } |
1437 | |
1438 | |
1439 | /* |
1440 | * Perform the transfer of events to user space. |
1441 | */ |
1442 | static int ep_events_transfer(struct eventpoll *ep, |
1443 | struct epoll_event __user *events, int maxevents) |
1444 | { |
1445 | int eventcnt = 0; |
1446 | struct list_head txlist; |
1447 | |
1448 | INIT_LIST_HEAD(&txlist); |
1449 | |
1450 | /* |
1451 | * We need to lock this because we could be hit by |
1452 | * eventpoll_release_file() and epoll_ctl(EPOLL_CTL_DEL). |
1453 | */ |
1454 | down_read(&ep->sem); |
1455 | |
1456 | /* Collect/extract ready items */ |
1457 | if (ep_collect_ready_items(ep, &txlist, maxevents) > 0) { |
1458 | /* Build result set in userspace */ |
1459 | eventcnt = ep_send_events(ep, &txlist, events); |
1460 | |
1461 | /* Reinject ready items into the ready list */ |
1462 | ep_reinject_items(ep, &txlist); |
1463 | } |
1464 | |
1465 | up_read(&ep->sem); |
1466 | |
1467 | return eventcnt; |
1468 | } |
1469 | |
1470 | |
1471 | static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, |
1472 | int maxevents, long timeout) |
1473 | { |
1474 | int res, eavail; |
1475 | unsigned long flags; |
1476 | long jtimeout; |
1477 | wait_queue_t wait; |
1478 | |
1479 | /* |
1480 | * Calculate the timeout by checking for the "infinite" value ( -1 ) |
1481 | * and the overflow condition. The passed timeout is in milliseconds, |
1482 | * that why (t * HZ) / 1000. |
1483 | */ |
1484 | jtimeout = timeout == -1 || timeout > (MAX_SCHEDULE_TIMEOUT - 1000) / HZ ? |
1485 | MAX_SCHEDULE_TIMEOUT: (timeout * HZ + 999) / 1000; |
1486 | |
1487 | retry: |
1488 | write_lock_irqsave(&ep->lock, flags); |
1489 | |
1490 | res = 0; |
1491 | if (list_empty(&ep->rdllist)) { |
1492 | /* |
1493 | * We don't have any available event to return to the caller. |
1494 | * We need to sleep here, and we will be wake up by |
1495 | * ep_poll_callback() when events will become available. |
1496 | */ |
1497 | init_waitqueue_entry(&wait, current); |
1498 | add_wait_queue(&ep->wq, &wait); |
1499 | |
1500 | for (;;) { |
1501 | /* |
1502 | * We don't want to sleep if the ep_poll_callback() sends us |
1503 | * a wakeup in between. That's why we set the task state |
1504 | * to TASK_INTERRUPTIBLE before doing the checks. |
1505 | */ |
1506 | set_current_state(TASK_INTERRUPTIBLE); |
1507 | if (!list_empty(&ep->rdllist) || !jtimeout) |
1508 | break; |
1509 | if (signal_pending(current)) { |
1510 | res = -EINTR; |
1511 | break; |
1512 | } |
1513 | |
1514 | write_unlock_irqrestore(&ep->lock, flags); |
1515 | jtimeout = schedule_timeout(jtimeout); |
1516 | write_lock_irqsave(&ep->lock, flags); |
1517 | } |
1518 | remove_wait_queue(&ep->wq, &wait); |
1519 | |
1520 | set_current_state(TASK_RUNNING); |
1521 | } |
1522 | |
1523 | /* Is it worth to try to dig for events ? */ |
1524 | eavail = !list_empty(&ep->rdllist); |
1525 | |
1526 | write_unlock_irqrestore(&ep->lock, flags); |
1527 | |
1528 | /* |
1529 | * Try to transfer events to user space. In case we get 0 events and |
1530 | * there's still timeout left over, we go trying again in search of |
1531 | * more luck. |
1532 | */ |
1533 | if (!res && eavail && |
1534 | !(res = ep_events_transfer(ep, events, maxevents)) && jtimeout) |
1535 | goto retry; |
1536 | |
1537 | return res; |
1538 | } |
1539 | |
1540 | |
1541 | static int eventpollfs_delete_dentry(struct dentry *dentry) |
1542 | { |
1543 | |
1544 | return 1; |
1545 | } |
1546 | |
1547 | |
1548 | static struct inode *ep_eventpoll_inode(void) |
1549 | { |
1550 | int error = -ENOMEM; |
1551 | struct inode *inode = new_inode(eventpoll_mnt->mnt_sb); |
1552 | |
1553 | if (!inode) |
1554 | goto eexit_1; |
1555 | |
1556 | inode->i_fop = &eventpoll_fops; |
1557 | |
1558 | /* |
1559 | * Mark the inode dirty from the very beginning, |
1560 | * that way it will never be moved to the dirty |
1561 | * list because mark_inode_dirty() will think |
1562 | * that it already _is_ on the dirty list. |
1563 | */ |
1564 | inode->i_state = I_DIRTY; |
1565 | inode->i_mode = S_IRUSR | S_IWUSR; |
1566 | inode->i_uid = current->fsuid; |
1567 | inode->i_gid = current->fsgid; |
1568 | inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; |
1569 | inode->i_blksize = PAGE_SIZE; |
1570 | return inode; |
1571 | |
1572 | eexit_1: |
1573 | return ERR_PTR(error); |
1574 | } |
1575 | |
1576 | |
1577 | static struct super_block * |
1578 | eventpollfs_get_sb(struct file_system_type *fs_type, int flags, |
1579 | const char *dev_name, void *data) |
1580 | { |
1581 | return get_sb_pseudo(fs_type, "eventpoll:", NULL, EVENTPOLLFS_MAGIC); |
1582 | } |
1583 | |
1584 | |
1585 | static int __init eventpoll_init(void) |
1586 | { |
1587 | int error; |
1588 | |
1589 | init_MUTEX(&epsem); |
1590 | |
1591 | /* Initialize the structure used to perform safe poll wait head wake ups */ |
1592 | ep_poll_safewake_init(&psw); |
1593 | |
1594 | /* Allocates slab cache used to allocate "struct epitem" items */ |
1595 | epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem), |
1596 | 0, SLAB_HWCACHE_ALIGN|EPI_SLAB_DEBUG|SLAB_PANIC, |
1597 | NULL, NULL); |
1598 | |
1599 | /* Allocates slab cache used to allocate "struct eppoll_entry" */ |
1600 | pwq_cache = kmem_cache_create("eventpoll_pwq", |
1601 | sizeof(struct eppoll_entry), 0, |
1602 | EPI_SLAB_DEBUG|SLAB_PANIC, NULL, NULL); |
1603 | |
1604 | /* |
1605 | * Register the virtual file system that will be the source of inodes |
1606 | * for the eventpoll files |
1607 | */ |
1608 | error = register_filesystem(&eventpoll_fs_type); |
1609 | if (error) |
1610 | goto epanic; |
1611 | |
1612 | /* Mount the above commented virtual file system */ |
1613 | eventpoll_mnt = kern_mount(&eventpoll_fs_type); |
1614 | error = PTR_ERR(eventpoll_mnt); |
1615 | if (IS_ERR(eventpoll_mnt)) |
1616 | goto epanic; |
1617 | |
1618 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: successfully initialized.\n", |
1619 | current)); |
1620 | return 0; |
1621 | |
1622 | epanic: |
1623 | panic("eventpoll_init() failed\n"); |
1624 | } |
1625 | |
1626 | |
1627 | static void __exit eventpoll_exit(void) |
1628 | { |
1629 | /* Undo all operations done inside eventpoll_init() */ |
1630 | unregister_filesystem(&eventpoll_fs_type); |
1631 | mntput(eventpoll_mnt); |
1632 | kmem_cache_destroy(pwq_cache); |
1633 | kmem_cache_destroy(epi_cache); |
1634 | } |
1635 | |
1636 | module_init(eventpoll_init); |
1637 | module_exit(eventpoll_exit); |
1638 | |
1639 | MODULE_LICENSE("GPL"); |