Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* |
| 2 | * fs/eventpoll.c ( Efficent event polling implementation ) |
Davide Libenzi | 3419b23 | 2006-06-25 05:48:14 -0700 | [diff] [blame] | 3 | * Copyright (C) 2001,...,2006 Davide Libenzi |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 14 | #include <linux/init.h> |
| 15 | #include <linux/kernel.h> |
| 16 | #include <linux/sched.h> |
| 17 | #include <linux/fs.h> |
| 18 | #include <linux/file.h> |
| 19 | #include <linux/signal.h> |
| 20 | #include <linux/errno.h> |
| 21 | #include <linux/mm.h> |
| 22 | #include <linux/slab.h> |
| 23 | #include <linux/poll.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 24 | #include <linux/string.h> |
| 25 | #include <linux/list.h> |
| 26 | #include <linux/hash.h> |
| 27 | #include <linux/spinlock.h> |
| 28 | #include <linux/syscalls.h> |
| 29 | #include <linux/rwsem.h> |
| 30 | #include <linux/rbtree.h> |
| 31 | #include <linux/wait.h> |
| 32 | #include <linux/eventpoll.h> |
| 33 | #include <linux/mount.h> |
| 34 | #include <linux/bitops.h> |
Arjan van de Ven | 144efe3 | 2006-03-23 03:00:32 -0800 | [diff] [blame] | 35 | #include <linux/mutex.h> |
Davide Libenzi | da66f7c | 2007-05-10 22:23:21 -0700 | [diff] [blame] | 36 | #include <linux/anon_inodes.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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 | * |
Arjan van de Ven | 144efe3 | 2006-03-23 03:00:32 -0800 | [diff] [blame] | 49 | * 1) epmutex (mutex) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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 |
Arjan van de Ven | 144efe3 | 2006-03-23 03:00:32 -0800 | [diff] [blame] | 70 | * semaphore "epmutex" (together with "ep->lock") to have it working, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 71 | * but having "ep->sem" will make the interface more scalable. |
Arjan van de Ven | 144efe3 | 2006-03-23 03:00:32 -0800 | [diff] [blame] | 72 | * Events that require holding "epmutex" are very rare, while for |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 73 | * normal operations the epoll private "ep->sem" will guarantee |
| 74 | * a greater scalability. |
| 75 | */ |
| 76 | |
| 77 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 78 | #define DEBUG_EPOLL 0 |
| 79 | |
| 80 | #if DEBUG_EPOLL > 0 |
| 81 | #define DPRINTK(x) printk x |
| 82 | #define DNPRINTK(n, x) do { if ((n) <= DEBUG_EPOLL) printk x; } while (0) |
| 83 | #else /* #if DEBUG_EPOLL > 0 */ |
| 84 | #define DPRINTK(x) (void) 0 |
| 85 | #define DNPRINTK(n, x) (void) 0 |
| 86 | #endif /* #if DEBUG_EPOLL > 0 */ |
| 87 | |
| 88 | #define DEBUG_EPI 0 |
| 89 | |
| 90 | #if DEBUG_EPI != 0 |
| 91 | #define EPI_SLAB_DEBUG (SLAB_DEBUG_FREE | SLAB_RED_ZONE /* | SLAB_POISON */) |
| 92 | #else /* #if DEBUG_EPI != 0 */ |
| 93 | #define EPI_SLAB_DEBUG 0 |
| 94 | #endif /* #if DEBUG_EPI != 0 */ |
| 95 | |
| 96 | /* Epoll private bits inside the event mask */ |
| 97 | #define EP_PRIVATE_BITS (EPOLLONESHOT | EPOLLET) |
| 98 | |
| 99 | /* Maximum number of poll wake up nests we are allowing */ |
| 100 | #define EP_MAX_POLLWAKE_NESTS 4 |
| 101 | |
Davide Libenzi | e3306dd | 2005-09-27 21:45:33 -0700 | [diff] [blame] | 102 | /* Maximum msec timeout value storeable in a long int */ |
| 103 | #define EP_MAX_MSTIMEO min(1000ULL * MAX_SCHEDULE_TIMEOUT / HZ, (LONG_MAX - 999ULL) / HZ) |
| 104 | |
Davide Libenzi | b611967 | 2006-10-11 01:21:44 -0700 | [diff] [blame] | 105 | #define EP_MAX_EVENTS (INT_MAX / sizeof(struct epoll_event)) |
| 106 | |
Davide Libenzi | e3306dd | 2005-09-27 21:45:33 -0700 | [diff] [blame] | 107 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 108 | struct epoll_filefd { |
| 109 | struct file *file; |
| 110 | int fd; |
| 111 | }; |
| 112 | |
| 113 | /* |
| 114 | * Node that is linked into the "wake_task_list" member of the "struct poll_safewake". |
| 115 | * It is used to keep track on all tasks that are currently inside the wake_up() code |
| 116 | * to 1) short-circuit the one coming from the same task and same wait queue head |
| 117 | * ( loop ) 2) allow a maximum number of epoll descriptors inclusion nesting |
| 118 | * 3) let go the ones coming from other tasks. |
| 119 | */ |
| 120 | struct wake_task_node { |
| 121 | struct list_head llink; |
Ingo Molnar | 36c8b58 | 2006-07-03 00:25:41 -0700 | [diff] [blame] | 122 | struct task_struct *task; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 123 | wait_queue_head_t *wq; |
| 124 | }; |
| 125 | |
| 126 | /* |
| 127 | * This is used to implement the safe poll wake up avoiding to reenter |
| 128 | * the poll callback from inside wake_up(). |
| 129 | */ |
| 130 | struct poll_safewake { |
| 131 | struct list_head wake_task_list; |
| 132 | spinlock_t lock; |
| 133 | }; |
| 134 | |
| 135 | /* |
| 136 | * This structure is stored inside the "private_data" member of the file |
| 137 | * structure and rapresent the main data sructure for the eventpoll |
| 138 | * interface. |
| 139 | */ |
| 140 | struct eventpoll { |
| 141 | /* Protect the this structure access */ |
| 142 | rwlock_t lock; |
| 143 | |
| 144 | /* |
| 145 | * This semaphore is used to ensure that files are not removed |
| 146 | * while epoll is using them. This is read-held during the event |
| 147 | * collection loop and it is write-held during the file cleanup |
| 148 | * path, the epoll file exit code and the ctl operations. |
| 149 | */ |
| 150 | struct rw_semaphore sem; |
| 151 | |
| 152 | /* Wait queue used by sys_epoll_wait() */ |
| 153 | wait_queue_head_t wq; |
| 154 | |
| 155 | /* Wait queue used by file->poll() */ |
| 156 | wait_queue_head_t poll_wait; |
| 157 | |
| 158 | /* List of ready file descriptors */ |
| 159 | struct list_head rdllist; |
| 160 | |
| 161 | /* RB-Tree root used to store monitored fd structs */ |
| 162 | struct rb_root rbr; |
| 163 | }; |
| 164 | |
| 165 | /* Wait structure used by the poll hooks */ |
| 166 | struct eppoll_entry { |
| 167 | /* List header used to link this structure to the "struct epitem" */ |
| 168 | struct list_head llink; |
| 169 | |
| 170 | /* The "base" pointer is set to the container "struct epitem" */ |
| 171 | void *base; |
| 172 | |
| 173 | /* |
| 174 | * Wait queue item that will be linked to the target file wait |
| 175 | * queue head. |
| 176 | */ |
| 177 | wait_queue_t wait; |
| 178 | |
| 179 | /* The wait queue head that linked the "wait" wait queue item */ |
| 180 | wait_queue_head_t *whead; |
| 181 | }; |
| 182 | |
| 183 | /* |
| 184 | * Each file descriptor added to the eventpoll interface will |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 185 | * have an entry of this type linked to the "rbr" RB tree. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 186 | */ |
| 187 | struct epitem { |
| 188 | /* RB-Tree node used to link this structure to the eventpoll rb-tree */ |
| 189 | struct rb_node rbn; |
| 190 | |
| 191 | /* List header used to link this structure to the eventpoll ready list */ |
| 192 | struct list_head rdllink; |
| 193 | |
| 194 | /* The file descriptor information this item refers to */ |
| 195 | struct epoll_filefd ffd; |
| 196 | |
| 197 | /* Number of active wait queue attached to poll operations */ |
| 198 | int nwait; |
| 199 | |
| 200 | /* List containing poll wait queues */ |
| 201 | struct list_head pwqlist; |
| 202 | |
| 203 | /* The "container" of this item */ |
| 204 | struct eventpoll *ep; |
| 205 | |
| 206 | /* The structure that describe the interested events and the source fd */ |
| 207 | struct epoll_event event; |
| 208 | |
| 209 | /* |
| 210 | * Used to keep track of the usage count of the structure. This avoids |
| 211 | * that the structure will desappear from underneath our processing. |
| 212 | */ |
| 213 | atomic_t usecnt; |
| 214 | |
| 215 | /* List header used to link this item to the "struct file" items list */ |
| 216 | struct list_head fllink; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 217 | }; |
| 218 | |
| 219 | /* Wrapper struct used by poll queueing */ |
| 220 | struct ep_pqueue { |
| 221 | poll_table pt; |
| 222 | struct epitem *epi; |
| 223 | }; |
| 224 | |
| 225 | |
| 226 | |
| 227 | static void ep_poll_safewake_init(struct poll_safewake *psw); |
| 228 | static void ep_poll_safewake(struct poll_safewake *psw, wait_queue_head_t *wq); |
Davide Libenzi | 53d2be7 | 2005-09-16 19:28:06 -0700 | [diff] [blame] | 229 | static int ep_alloc(struct eventpoll **pep); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 230 | static void ep_free(struct eventpoll *ep); |
| 231 | static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd); |
| 232 | static void ep_use_epitem(struct epitem *epi); |
| 233 | static void ep_release_epitem(struct epitem *epi); |
| 234 | static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, |
| 235 | poll_table *pt); |
| 236 | static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi); |
| 237 | static int ep_insert(struct eventpoll *ep, struct epoll_event *event, |
| 238 | struct file *tfile, int fd); |
| 239 | static int ep_modify(struct eventpoll *ep, struct epitem *epi, |
| 240 | struct epoll_event *event); |
| 241 | static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi); |
| 242 | static int ep_unlink(struct eventpoll *ep, struct epitem *epi); |
| 243 | static int ep_remove(struct eventpoll *ep, struct epitem *epi); |
| 244 | static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *key); |
| 245 | static int ep_eventpoll_close(struct inode *inode, struct file *file); |
| 246 | static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 247 | static int ep_send_events(struct eventpoll *ep, struct list_head *txlist, |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 248 | struct epoll_event __user *events, int maxevents); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 249 | static int ep_events_transfer(struct eventpoll *ep, |
| 250 | struct epoll_event __user *events, |
| 251 | int maxevents); |
| 252 | static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, |
| 253 | int maxevents, long timeout); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 254 | |
| 255 | /* |
| 256 | * This semaphore is used to serialize ep_free() and eventpoll_release_file(). |
| 257 | */ |
Arjan van de Ven | 144efe3 | 2006-03-23 03:00:32 -0800 | [diff] [blame] | 258 | static struct mutex epmutex; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 259 | |
| 260 | /* Safe wake up implementation */ |
| 261 | static struct poll_safewake psw; |
| 262 | |
| 263 | /* Slab cache used to allocate "struct epitem" */ |
Christoph Lameter | e18b890 | 2006-12-06 20:33:20 -0800 | [diff] [blame] | 264 | static struct kmem_cache *epi_cache __read_mostly; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 265 | |
| 266 | /* Slab cache used to allocate "struct eppoll_entry" */ |
Christoph Lameter | e18b890 | 2006-12-06 20:33:20 -0800 | [diff] [blame] | 267 | static struct kmem_cache *pwq_cache __read_mostly; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 268 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 269 | /* File callbacks that implement the eventpoll file behaviour */ |
Arjan van de Ven | 4b6f5d2 | 2006-03-28 01:56:42 -0800 | [diff] [blame] | 270 | static const struct file_operations eventpoll_fops = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 271 | .release = ep_eventpoll_close, |
| 272 | .poll = ep_eventpoll_poll |
| 273 | }; |
| 274 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 275 | |
| 276 | |
Pekka Enberg | b030a4d | 2005-06-23 00:10:03 -0700 | [diff] [blame] | 277 | /* Fast test to see if the file is an evenpoll file */ |
| 278 | static inline int is_file_epoll(struct file *f) |
| 279 | { |
| 280 | return f->f_op == &eventpoll_fops; |
| 281 | } |
| 282 | |
| 283 | /* Setup the structure that is used as key for the rb-tree */ |
| 284 | static inline void ep_set_ffd(struct epoll_filefd *ffd, |
| 285 | struct file *file, int fd) |
| 286 | { |
| 287 | ffd->file = file; |
| 288 | ffd->fd = fd; |
| 289 | } |
| 290 | |
| 291 | /* Compare rb-tree keys */ |
| 292 | static inline int ep_cmp_ffd(struct epoll_filefd *p1, |
| 293 | struct epoll_filefd *p2) |
| 294 | { |
| 295 | return (p1->file > p2->file ? +1: |
| 296 | (p1->file < p2->file ? -1 : p1->fd - p2->fd)); |
| 297 | } |
| 298 | |
| 299 | /* Special initialization for the rb-tree node to detect linkage */ |
| 300 | static inline void ep_rb_initnode(struct rb_node *n) |
| 301 | { |
David Woodhouse | c569882 | 2006-04-21 13:17:24 +0100 | [diff] [blame] | 302 | rb_set_parent(n, n); |
Pekka Enberg | b030a4d | 2005-06-23 00:10:03 -0700 | [diff] [blame] | 303 | } |
| 304 | |
| 305 | /* Removes a node from the rb-tree and marks it for a fast is-linked check */ |
| 306 | static inline void ep_rb_erase(struct rb_node *n, struct rb_root *r) |
| 307 | { |
| 308 | rb_erase(n, r); |
David Woodhouse | c569882 | 2006-04-21 13:17:24 +0100 | [diff] [blame] | 309 | rb_set_parent(n, n); |
Pekka Enberg | b030a4d | 2005-06-23 00:10:03 -0700 | [diff] [blame] | 310 | } |
| 311 | |
| 312 | /* Fast check to verify that the item is linked to the main rb-tree */ |
| 313 | static inline int ep_rb_linked(struct rb_node *n) |
| 314 | { |
David Woodhouse | c569882 | 2006-04-21 13:17:24 +0100 | [diff] [blame] | 315 | return rb_parent(n) != n; |
Pekka Enberg | b030a4d | 2005-06-23 00:10:03 -0700 | [diff] [blame] | 316 | } |
| 317 | |
Pekka Enberg | b030a4d | 2005-06-23 00:10:03 -0700 | [diff] [blame] | 318 | /* Tells us if the item is currently linked */ |
| 319 | static inline int ep_is_linked(struct list_head *p) |
| 320 | { |
| 321 | return !list_empty(p); |
| 322 | } |
| 323 | |
| 324 | /* Get the "struct epitem" from a wait queue pointer */ |
| 325 | static inline struct epitem * ep_item_from_wait(wait_queue_t *p) |
| 326 | { |
| 327 | return container_of(p, struct eppoll_entry, wait)->base; |
| 328 | } |
| 329 | |
| 330 | /* Get the "struct epitem" from an epoll queue wrapper */ |
| 331 | static inline struct epitem * ep_item_from_epqueue(poll_table *p) |
| 332 | { |
| 333 | return container_of(p, struct ep_pqueue, pt)->epi; |
| 334 | } |
| 335 | |
| 336 | /* Tells if the epoll_ctl(2) operation needs an event copy from userspace */ |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 337 | static inline int ep_op_has_event(int op) |
Pekka Enberg | b030a4d | 2005-06-23 00:10:03 -0700 | [diff] [blame] | 338 | { |
| 339 | return op != EPOLL_CTL_DEL; |
| 340 | } |
| 341 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 342 | /* Initialize the poll safe wake up structure */ |
| 343 | static void ep_poll_safewake_init(struct poll_safewake *psw) |
| 344 | { |
| 345 | |
| 346 | INIT_LIST_HEAD(&psw->wake_task_list); |
| 347 | spin_lock_init(&psw->lock); |
| 348 | } |
| 349 | |
| 350 | |
| 351 | /* |
| 352 | * Perform a safe wake up of the poll wait list. The problem is that |
| 353 | * with the new callback'd wake up system, it is possible that the |
| 354 | * poll callback is reentered from inside the call to wake_up() done |
| 355 | * on the poll wait queue head. The rule is that we cannot reenter the |
| 356 | * wake up code from the same task more than EP_MAX_POLLWAKE_NESTS times, |
| 357 | * and we cannot reenter the same wait queue head at all. This will |
| 358 | * enable to have a hierarchy of epoll file descriptor of no more than |
| 359 | * EP_MAX_POLLWAKE_NESTS deep. We need the irq version of the spin lock |
| 360 | * because this one gets called by the poll callback, that in turn is called |
| 361 | * from inside a wake_up(), that might be called from irq context. |
| 362 | */ |
| 363 | static void ep_poll_safewake(struct poll_safewake *psw, wait_queue_head_t *wq) |
| 364 | { |
| 365 | int wake_nests = 0; |
| 366 | unsigned long flags; |
Ingo Molnar | 36c8b58 | 2006-07-03 00:25:41 -0700 | [diff] [blame] | 367 | struct task_struct *this_task = current; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 368 | struct list_head *lsthead = &psw->wake_task_list, *lnk; |
| 369 | struct wake_task_node *tncur; |
| 370 | struct wake_task_node tnode; |
| 371 | |
| 372 | spin_lock_irqsave(&psw->lock, flags); |
| 373 | |
| 374 | /* Try to see if the current task is already inside this wakeup call */ |
| 375 | list_for_each(lnk, lsthead) { |
| 376 | tncur = list_entry(lnk, struct wake_task_node, llink); |
| 377 | |
| 378 | if (tncur->wq == wq || |
| 379 | (tncur->task == this_task && ++wake_nests > EP_MAX_POLLWAKE_NESTS)) { |
| 380 | /* |
| 381 | * Ops ... loop detected or maximum nest level reached. |
| 382 | * We abort this wake by breaking the cycle itself. |
| 383 | */ |
| 384 | spin_unlock_irqrestore(&psw->lock, flags); |
| 385 | return; |
| 386 | } |
| 387 | } |
| 388 | |
| 389 | /* Add the current task to the list */ |
| 390 | tnode.task = this_task; |
| 391 | tnode.wq = wq; |
| 392 | list_add(&tnode.llink, lsthead); |
| 393 | |
| 394 | spin_unlock_irqrestore(&psw->lock, flags); |
| 395 | |
| 396 | /* Do really wake up now */ |
| 397 | wake_up(wq); |
| 398 | |
| 399 | /* Remove the current task from the list */ |
| 400 | spin_lock_irqsave(&psw->lock, flags); |
| 401 | list_del(&tnode.llink); |
| 402 | spin_unlock_irqrestore(&psw->lock, flags); |
| 403 | } |
| 404 | |
| 405 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 406 | /* |
| 407 | * This is called from eventpoll_release() to unlink files from the eventpoll |
| 408 | * interface. We need to have this facility to cleanup correctly files that are |
| 409 | * closed without being removed from the eventpoll interface. |
| 410 | */ |
| 411 | void eventpoll_release_file(struct file *file) |
| 412 | { |
| 413 | struct list_head *lsthead = &file->f_ep_links; |
| 414 | struct eventpoll *ep; |
| 415 | struct epitem *epi; |
| 416 | |
| 417 | /* |
| 418 | * We don't want to get "file->f_ep_lock" because it is not |
| 419 | * necessary. It is not necessary because we're in the "struct file" |
| 420 | * cleanup path, and this means that noone is using this file anymore. |
| 421 | * The only hit might come from ep_free() but by holding the semaphore |
| 422 | * will correctly serialize the operation. We do need to acquire |
Arjan van de Ven | 144efe3 | 2006-03-23 03:00:32 -0800 | [diff] [blame] | 423 | * "ep->sem" after "epmutex" because ep_remove() requires it when called |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 424 | * from anywhere but ep_free(). |
| 425 | */ |
Arjan van de Ven | 144efe3 | 2006-03-23 03:00:32 -0800 | [diff] [blame] | 426 | mutex_lock(&epmutex); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 427 | |
| 428 | while (!list_empty(lsthead)) { |
Pavel Emelianov | b5e6181 | 2007-05-08 00:30:19 -0700 | [diff] [blame] | 429 | epi = list_first_entry(lsthead, struct epitem, fllink); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 430 | |
| 431 | ep = epi->ep; |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 432 | list_del_init(&epi->fllink); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 433 | down_write(&ep->sem); |
| 434 | ep_remove(ep, epi); |
| 435 | up_write(&ep->sem); |
| 436 | } |
| 437 | |
Arjan van de Ven | 144efe3 | 2006-03-23 03:00:32 -0800 | [diff] [blame] | 438 | mutex_unlock(&epmutex); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 439 | } |
| 440 | |
| 441 | |
| 442 | /* |
| 443 | * It opens an eventpoll file descriptor by suggesting a storage of "size" |
| 444 | * file descriptors. The size parameter is just an hint about how to size |
| 445 | * data structures. It won't prevent the user to store more than "size" |
| 446 | * file descriptors inside the epoll interface. It is the kernel part of |
| 447 | * the userspace epoll_create(2). |
| 448 | */ |
| 449 | asmlinkage long sys_epoll_create(int size) |
| 450 | { |
Davide Libenzi | b611967 | 2006-10-11 01:21:44 -0700 | [diff] [blame] | 451 | int error, fd = -1; |
Davide Libenzi | 53d2be7 | 2005-09-16 19:28:06 -0700 | [diff] [blame] | 452 | struct eventpoll *ep; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 453 | struct inode *inode; |
| 454 | struct file *file; |
| 455 | |
| 456 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d)\n", |
| 457 | current, size)); |
| 458 | |
Davide Libenzi | 53d2be7 | 2005-09-16 19:28:06 -0700 | [diff] [blame] | 459 | /* |
| 460 | * Sanity check on the size parameter, and create the internal data |
| 461 | * structure ( "struct eventpoll" ). |
| 462 | */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 463 | error = -EINVAL; |
Davide Libenzi | 53d2be7 | 2005-09-16 19:28:06 -0700 | [diff] [blame] | 464 | if (size <= 0 || (error = ep_alloc(&ep)) != 0) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 465 | goto eexit_1; |
| 466 | |
| 467 | /* |
| 468 | * Creates all the items needed to setup an eventpoll file. That is, |
| 469 | * a file structure, and inode and a free file descriptor. |
| 470 | */ |
Davide Libenzi | da66f7c | 2007-05-10 22:23:21 -0700 | [diff] [blame] | 471 | error = anon_inode_getfd(&fd, &inode, &file, "[eventpoll]", |
| 472 | &eventpoll_fops, ep); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 473 | if (error) |
| 474 | goto eexit_2; |
| 475 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 476 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n", |
| 477 | current, size, fd)); |
| 478 | |
| 479 | return fd; |
| 480 | |
| 481 | eexit_2: |
Davide Libenzi | 53d2be7 | 2005-09-16 19:28:06 -0700 | [diff] [blame] | 482 | ep_free(ep); |
| 483 | kfree(ep); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 484 | eexit_1: |
| 485 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n", |
| 486 | current, size, error)); |
| 487 | return error; |
| 488 | } |
| 489 | |
| 490 | |
| 491 | /* |
| 492 | * The following function implements the controller interface for |
| 493 | * the eventpoll file that enables the insertion/removal/change of |
| 494 | * file descriptors inside the interest set. It represents |
| 495 | * the kernel part of the user space epoll_ctl(2). |
| 496 | */ |
| 497 | asmlinkage long |
| 498 | sys_epoll_ctl(int epfd, int op, int fd, struct epoll_event __user *event) |
| 499 | { |
| 500 | int error; |
| 501 | struct file *file, *tfile; |
| 502 | struct eventpoll *ep; |
| 503 | struct epitem *epi; |
| 504 | struct epoll_event epds; |
| 505 | |
| 506 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %p)\n", |
| 507 | current, epfd, op, fd, event)); |
| 508 | |
| 509 | error = -EFAULT; |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 510 | if (ep_op_has_event(op) && |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 511 | copy_from_user(&epds, event, sizeof(struct epoll_event))) |
| 512 | goto eexit_1; |
| 513 | |
| 514 | /* Get the "struct file *" for the eventpoll file */ |
| 515 | error = -EBADF; |
| 516 | file = fget(epfd); |
| 517 | if (!file) |
| 518 | goto eexit_1; |
| 519 | |
| 520 | /* Get the "struct file *" for the target file */ |
| 521 | tfile = fget(fd); |
| 522 | if (!tfile) |
| 523 | goto eexit_2; |
| 524 | |
| 525 | /* The target file descriptor must support poll */ |
| 526 | error = -EPERM; |
| 527 | if (!tfile->f_op || !tfile->f_op->poll) |
| 528 | goto eexit_3; |
| 529 | |
| 530 | /* |
| 531 | * We have to check that the file structure underneath the file descriptor |
| 532 | * the user passed to us _is_ an eventpoll file. And also we do not permit |
| 533 | * adding an epoll file descriptor inside itself. |
| 534 | */ |
| 535 | error = -EINVAL; |
Pekka Enberg | b030a4d | 2005-06-23 00:10:03 -0700 | [diff] [blame] | 536 | if (file == tfile || !is_file_epoll(file)) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 537 | goto eexit_3; |
| 538 | |
| 539 | /* |
| 540 | * At this point it is safe to assume that the "private_data" contains |
| 541 | * our own data structure. |
| 542 | */ |
| 543 | ep = file->private_data; |
| 544 | |
| 545 | down_write(&ep->sem); |
| 546 | |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 547 | /* Try to lookup the file inside our RB tree */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 548 | epi = ep_find(ep, tfile, fd); |
| 549 | |
| 550 | error = -EINVAL; |
| 551 | switch (op) { |
| 552 | case EPOLL_CTL_ADD: |
| 553 | if (!epi) { |
Davide Libenzi | 2395140 | 2006-04-10 22:54:12 -0700 | [diff] [blame] | 554 | epds.events |= POLLERR | POLLHUP; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 555 | |
| 556 | error = ep_insert(ep, &epds, tfile, fd); |
| 557 | } else |
| 558 | error = -EEXIST; |
| 559 | break; |
| 560 | case EPOLL_CTL_DEL: |
| 561 | if (epi) |
| 562 | error = ep_remove(ep, epi); |
| 563 | else |
| 564 | error = -ENOENT; |
| 565 | break; |
| 566 | case EPOLL_CTL_MOD: |
| 567 | if (epi) { |
Davide Libenzi | 2395140 | 2006-04-10 22:54:12 -0700 | [diff] [blame] | 568 | epds.events |= POLLERR | POLLHUP; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 569 | error = ep_modify(ep, epi, &epds); |
| 570 | } else |
| 571 | error = -ENOENT; |
| 572 | break; |
| 573 | } |
| 574 | |
| 575 | /* |
| 576 | * The function ep_find() increments the usage count of the structure |
| 577 | * so, if this is not NULL, we need to release it. |
| 578 | */ |
| 579 | if (epi) |
| 580 | ep_release_epitem(epi); |
| 581 | |
| 582 | up_write(&ep->sem); |
| 583 | |
| 584 | eexit_3: |
| 585 | fput(tfile); |
| 586 | eexit_2: |
| 587 | fput(file); |
| 588 | eexit_1: |
| 589 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %p) = %d\n", |
| 590 | current, epfd, op, fd, event, error)); |
| 591 | |
| 592 | return error; |
| 593 | } |
| 594 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 595 | |
| 596 | /* |
| 597 | * Implement the event wait interface for the eventpoll file. It is the kernel |
| 598 | * part of the user space epoll_wait(2). |
| 599 | */ |
| 600 | asmlinkage long sys_epoll_wait(int epfd, struct epoll_event __user *events, |
| 601 | int maxevents, int timeout) |
| 602 | { |
| 603 | int error; |
| 604 | struct file *file; |
| 605 | struct eventpoll *ep; |
| 606 | |
| 607 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_wait(%d, %p, %d, %d)\n", |
| 608 | current, epfd, events, maxevents, timeout)); |
| 609 | |
| 610 | /* The maximum number of event must be greater than zero */ |
Davide Libenzi | b611967 | 2006-10-11 01:21:44 -0700 | [diff] [blame] | 611 | if (maxevents <= 0 || maxevents > EP_MAX_EVENTS) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 612 | return -EINVAL; |
| 613 | |
| 614 | /* Verify that the area passed by the user is writeable */ |
| 615 | if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event))) { |
| 616 | error = -EFAULT; |
| 617 | goto eexit_1; |
| 618 | } |
| 619 | |
| 620 | /* Get the "struct file *" for the eventpoll file */ |
| 621 | error = -EBADF; |
| 622 | file = fget(epfd); |
| 623 | if (!file) |
| 624 | goto eexit_1; |
| 625 | |
| 626 | /* |
| 627 | * We have to check that the file structure underneath the fd |
| 628 | * the user passed to us _is_ an eventpoll file. |
| 629 | */ |
| 630 | error = -EINVAL; |
Pekka Enberg | b030a4d | 2005-06-23 00:10:03 -0700 | [diff] [blame] | 631 | if (!is_file_epoll(file)) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 632 | goto eexit_2; |
| 633 | |
| 634 | /* |
| 635 | * At this point it is safe to assume that the "private_data" contains |
| 636 | * our own data structure. |
| 637 | */ |
| 638 | ep = file->private_data; |
| 639 | |
| 640 | /* Time to fish for events ... */ |
| 641 | error = ep_poll(ep, events, maxevents, timeout); |
| 642 | |
| 643 | eexit_2: |
| 644 | fput(file); |
| 645 | eexit_1: |
| 646 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_wait(%d, %p, %d, %d) = %d\n", |
| 647 | current, epfd, events, maxevents, timeout, error)); |
| 648 | |
| 649 | return error; |
| 650 | } |
| 651 | |
| 652 | |
Davide Libenzi | b611967 | 2006-10-11 01:21:44 -0700 | [diff] [blame] | 653 | #ifdef TIF_RESTORE_SIGMASK |
| 654 | |
| 655 | /* |
| 656 | * Implement the event wait interface for the eventpoll file. It is the kernel |
| 657 | * part of the user space epoll_pwait(2). |
| 658 | */ |
| 659 | asmlinkage long sys_epoll_pwait(int epfd, struct epoll_event __user *events, |
| 660 | int maxevents, int timeout, const sigset_t __user *sigmask, |
| 661 | size_t sigsetsize) |
| 662 | { |
| 663 | int error; |
| 664 | sigset_t ksigmask, sigsaved; |
| 665 | |
| 666 | /* |
| 667 | * If the caller wants a certain signal mask to be set during the wait, |
| 668 | * we apply it here. |
| 669 | */ |
| 670 | if (sigmask) { |
| 671 | if (sigsetsize != sizeof(sigset_t)) |
| 672 | return -EINVAL; |
| 673 | if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) |
| 674 | return -EFAULT; |
| 675 | sigdelsetmask(&ksigmask, sigmask(SIGKILL) | sigmask(SIGSTOP)); |
| 676 | sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); |
| 677 | } |
| 678 | |
| 679 | error = sys_epoll_wait(epfd, events, maxevents, timeout); |
| 680 | |
| 681 | /* |
| 682 | * If we changed the signal mask, we need to restore the original one. |
| 683 | * In case we've got a signal while waiting, we do not restore the |
| 684 | * signal mask yet, and we allow do_signal() to deliver the signal on |
| 685 | * the way back to userspace, before the signal mask is restored. |
| 686 | */ |
| 687 | if (sigmask) { |
| 688 | if (error == -EINTR) { |
| 689 | memcpy(¤t->saved_sigmask, &sigsaved, |
| 690 | sizeof(sigsaved)); |
| 691 | set_thread_flag(TIF_RESTORE_SIGMASK); |
| 692 | } else |
| 693 | sigprocmask(SIG_SETMASK, &sigsaved, NULL); |
| 694 | } |
| 695 | |
| 696 | return error; |
| 697 | } |
| 698 | |
| 699 | #endif /* #ifdef TIF_RESTORE_SIGMASK */ |
| 700 | |
| 701 | |
Davide Libenzi | 53d2be7 | 2005-09-16 19:28:06 -0700 | [diff] [blame] | 702 | static int ep_alloc(struct eventpoll **pep) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 703 | { |
Davide Libenzi | 53d2be7 | 2005-09-16 19:28:06 -0700 | [diff] [blame] | 704 | struct eventpoll *ep = kzalloc(sizeof(*ep), GFP_KERNEL); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 705 | |
Davide Libenzi | 53d2be7 | 2005-09-16 19:28:06 -0700 | [diff] [blame] | 706 | if (!ep) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 707 | return -ENOMEM; |
| 708 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 709 | rwlock_init(&ep->lock); |
| 710 | init_rwsem(&ep->sem); |
| 711 | init_waitqueue_head(&ep->wq); |
| 712 | init_waitqueue_head(&ep->poll_wait); |
| 713 | INIT_LIST_HEAD(&ep->rdllist); |
| 714 | ep->rbr = RB_ROOT; |
| 715 | |
Davide Libenzi | 53d2be7 | 2005-09-16 19:28:06 -0700 | [diff] [blame] | 716 | *pep = ep; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 717 | |
Davide Libenzi | 53d2be7 | 2005-09-16 19:28:06 -0700 | [diff] [blame] | 718 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_alloc() ep=%p\n", |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 719 | current, ep)); |
| 720 | return 0; |
| 721 | } |
| 722 | |
| 723 | |
| 724 | static void ep_free(struct eventpoll *ep) |
| 725 | { |
| 726 | struct rb_node *rbp; |
| 727 | struct epitem *epi; |
| 728 | |
| 729 | /* We need to release all tasks waiting for these file */ |
| 730 | if (waitqueue_active(&ep->poll_wait)) |
| 731 | ep_poll_safewake(&psw, &ep->poll_wait); |
| 732 | |
| 733 | /* |
| 734 | * We need to lock this because we could be hit by |
| 735 | * eventpoll_release_file() while we're freeing the "struct eventpoll". |
| 736 | * We do not need to hold "ep->sem" here because the epoll file |
| 737 | * is on the way to be removed and no one has references to it |
| 738 | * anymore. The only hit might come from eventpoll_release_file() but |
Arjan van de Ven | 144efe3 | 2006-03-23 03:00:32 -0800 | [diff] [blame] | 739 | * holding "epmutex" is sufficent here. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 740 | */ |
Arjan van de Ven | 144efe3 | 2006-03-23 03:00:32 -0800 | [diff] [blame] | 741 | mutex_lock(&epmutex); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 742 | |
| 743 | /* |
| 744 | * Walks through the whole tree by unregistering poll callbacks. |
| 745 | */ |
| 746 | for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { |
| 747 | epi = rb_entry(rbp, struct epitem, rbn); |
| 748 | |
| 749 | ep_unregister_pollwait(ep, epi); |
| 750 | } |
| 751 | |
| 752 | /* |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 753 | * Walks through the whole tree by freeing each "struct epitem". At this |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 754 | * point we are sure no poll callbacks will be lingering around, and also by |
| 755 | * write-holding "sem" we can be sure that no file cleanup code will hit |
| 756 | * us during this operation. So we can avoid the lock on "ep->lock". |
| 757 | */ |
| 758 | while ((rbp = rb_first(&ep->rbr)) != 0) { |
| 759 | epi = rb_entry(rbp, struct epitem, rbn); |
| 760 | ep_remove(ep, epi); |
| 761 | } |
| 762 | |
Arjan van de Ven | 144efe3 | 2006-03-23 03:00:32 -0800 | [diff] [blame] | 763 | mutex_unlock(&epmutex); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 764 | } |
| 765 | |
| 766 | |
| 767 | /* |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 768 | * Search the file inside the eventpoll tree. It add usage count to |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 769 | * the returned item, so the caller must call ep_release_epitem() |
| 770 | * after finished using the "struct epitem". |
| 771 | */ |
| 772 | static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd) |
| 773 | { |
| 774 | int kcmp; |
| 775 | unsigned long flags; |
| 776 | struct rb_node *rbp; |
| 777 | struct epitem *epi, *epir = NULL; |
| 778 | struct epoll_filefd ffd; |
| 779 | |
Pekka Enberg | b030a4d | 2005-06-23 00:10:03 -0700 | [diff] [blame] | 780 | ep_set_ffd(&ffd, file, fd); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 781 | read_lock_irqsave(&ep->lock, flags); |
| 782 | for (rbp = ep->rbr.rb_node; rbp; ) { |
| 783 | epi = rb_entry(rbp, struct epitem, rbn); |
Pekka Enberg | b030a4d | 2005-06-23 00:10:03 -0700 | [diff] [blame] | 784 | kcmp = ep_cmp_ffd(&ffd, &epi->ffd); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 785 | if (kcmp > 0) |
| 786 | rbp = rbp->rb_right; |
| 787 | else if (kcmp < 0) |
| 788 | rbp = rbp->rb_left; |
| 789 | else { |
| 790 | ep_use_epitem(epi); |
| 791 | epir = epi; |
| 792 | break; |
| 793 | } |
| 794 | } |
| 795 | read_unlock_irqrestore(&ep->lock, flags); |
| 796 | |
| 797 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_find(%p) -> %p\n", |
| 798 | current, file, epir)); |
| 799 | |
| 800 | return epir; |
| 801 | } |
| 802 | |
| 803 | |
| 804 | /* |
| 805 | * Increment the usage count of the "struct epitem" making it sure |
| 806 | * that the user will have a valid pointer to reference. |
| 807 | */ |
| 808 | static void ep_use_epitem(struct epitem *epi) |
| 809 | { |
| 810 | |
| 811 | atomic_inc(&epi->usecnt); |
| 812 | } |
| 813 | |
| 814 | |
| 815 | /* |
| 816 | * Decrement ( release ) the usage count by signaling that the user |
| 817 | * has finished using the structure. It might lead to freeing the |
| 818 | * structure itself if the count goes to zero. |
| 819 | */ |
| 820 | static void ep_release_epitem(struct epitem *epi) |
| 821 | { |
| 822 | |
| 823 | if (atomic_dec_and_test(&epi->usecnt)) |
Pekka Enberg | b030a4d | 2005-06-23 00:10:03 -0700 | [diff] [blame] | 824 | kmem_cache_free(epi_cache, epi); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 825 | } |
| 826 | |
| 827 | |
| 828 | /* |
| 829 | * This is the callback that is used to add our wait queue to the |
| 830 | * target file wakeup lists. |
| 831 | */ |
| 832 | static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, |
| 833 | poll_table *pt) |
| 834 | { |
Pekka Enberg | b030a4d | 2005-06-23 00:10:03 -0700 | [diff] [blame] | 835 | struct epitem *epi = ep_item_from_epqueue(pt); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 836 | struct eppoll_entry *pwq; |
| 837 | |
Christoph Lameter | e94b176 | 2006-12-06 20:33:17 -0800 | [diff] [blame] | 838 | if (epi->nwait >= 0 && (pwq = kmem_cache_alloc(pwq_cache, GFP_KERNEL))) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 839 | init_waitqueue_func_entry(&pwq->wait, ep_poll_callback); |
| 840 | pwq->whead = whead; |
| 841 | pwq->base = epi; |
| 842 | add_wait_queue(whead, &pwq->wait); |
| 843 | list_add_tail(&pwq->llink, &epi->pwqlist); |
| 844 | epi->nwait++; |
| 845 | } else { |
| 846 | /* We have to signal that an error occurred */ |
| 847 | epi->nwait = -1; |
| 848 | } |
| 849 | } |
| 850 | |
| 851 | |
| 852 | static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi) |
| 853 | { |
| 854 | int kcmp; |
| 855 | struct rb_node **p = &ep->rbr.rb_node, *parent = NULL; |
| 856 | struct epitem *epic; |
| 857 | |
| 858 | while (*p) { |
| 859 | parent = *p; |
| 860 | epic = rb_entry(parent, struct epitem, rbn); |
Pekka Enberg | b030a4d | 2005-06-23 00:10:03 -0700 | [diff] [blame] | 861 | kcmp = ep_cmp_ffd(&epi->ffd, &epic->ffd); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 862 | if (kcmp > 0) |
| 863 | p = &parent->rb_right; |
| 864 | else |
| 865 | p = &parent->rb_left; |
| 866 | } |
| 867 | rb_link_node(&epi->rbn, parent, p); |
| 868 | rb_insert_color(&epi->rbn, &ep->rbr); |
| 869 | } |
| 870 | |
| 871 | |
| 872 | static int ep_insert(struct eventpoll *ep, struct epoll_event *event, |
| 873 | struct file *tfile, int fd) |
| 874 | { |
| 875 | int error, revents, pwake = 0; |
| 876 | unsigned long flags; |
| 877 | struct epitem *epi; |
| 878 | struct ep_pqueue epq; |
| 879 | |
| 880 | error = -ENOMEM; |
Christoph Lameter | e94b176 | 2006-12-06 20:33:17 -0800 | [diff] [blame] | 881 | if (!(epi = kmem_cache_alloc(epi_cache, GFP_KERNEL))) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 882 | goto eexit_1; |
| 883 | |
| 884 | /* Item initialization follow here ... */ |
Pekka Enberg | b030a4d | 2005-06-23 00:10:03 -0700 | [diff] [blame] | 885 | ep_rb_initnode(&epi->rbn); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 886 | INIT_LIST_HEAD(&epi->rdllink); |
| 887 | INIT_LIST_HEAD(&epi->fllink); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 888 | INIT_LIST_HEAD(&epi->pwqlist); |
| 889 | epi->ep = ep; |
Pekka Enberg | b030a4d | 2005-06-23 00:10:03 -0700 | [diff] [blame] | 890 | ep_set_ffd(&epi->ffd, tfile, fd); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 891 | epi->event = *event; |
| 892 | atomic_set(&epi->usecnt, 1); |
| 893 | epi->nwait = 0; |
| 894 | |
| 895 | /* Initialize the poll table using the queue callback */ |
| 896 | epq.epi = epi; |
| 897 | init_poll_funcptr(&epq.pt, ep_ptable_queue_proc); |
| 898 | |
| 899 | /* |
| 900 | * Attach the item to the poll hooks and get current event bits. |
| 901 | * We can safely use the file* here because its usage count has |
| 902 | * been increased by the caller of this function. |
| 903 | */ |
| 904 | revents = tfile->f_op->poll(tfile, &epq.pt); |
| 905 | |
| 906 | /* |
| 907 | * We have to check if something went wrong during the poll wait queue |
| 908 | * install process. Namely an allocation for a wait queue failed due |
| 909 | * high memory pressure. |
| 910 | */ |
| 911 | if (epi->nwait < 0) |
| 912 | goto eexit_2; |
| 913 | |
| 914 | /* Add the current item to the list of active epoll hook for this file */ |
| 915 | spin_lock(&tfile->f_ep_lock); |
| 916 | list_add_tail(&epi->fllink, &tfile->f_ep_links); |
| 917 | spin_unlock(&tfile->f_ep_lock); |
| 918 | |
| 919 | /* We have to drop the new item inside our item list to keep track of it */ |
| 920 | write_lock_irqsave(&ep->lock, flags); |
| 921 | |
| 922 | /* Add the current item to the rb-tree */ |
| 923 | ep_rbtree_insert(ep, epi); |
| 924 | |
| 925 | /* If the file is already "ready" we drop it inside the ready list */ |
Pekka Enberg | b030a4d | 2005-06-23 00:10:03 -0700 | [diff] [blame] | 926 | if ((revents & event->events) && !ep_is_linked(&epi->rdllink)) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 927 | list_add_tail(&epi->rdllink, &ep->rdllist); |
| 928 | |
| 929 | /* Notify waiting tasks that events are available */ |
| 930 | if (waitqueue_active(&ep->wq)) |
Davide Libenzi | 3419b23 | 2006-06-25 05:48:14 -0700 | [diff] [blame] | 931 | __wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 932 | if (waitqueue_active(&ep->poll_wait)) |
| 933 | pwake++; |
| 934 | } |
| 935 | |
| 936 | write_unlock_irqrestore(&ep->lock, flags); |
| 937 | |
| 938 | /* We have to call this outside the lock */ |
| 939 | if (pwake) |
| 940 | ep_poll_safewake(&psw, &ep->poll_wait); |
| 941 | |
| 942 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_insert(%p, %p, %d)\n", |
| 943 | current, ep, tfile, fd)); |
| 944 | |
| 945 | return 0; |
| 946 | |
| 947 | eexit_2: |
| 948 | ep_unregister_pollwait(ep, epi); |
| 949 | |
| 950 | /* |
| 951 | * We need to do this because an event could have been arrived on some |
| 952 | * allocated wait queue. |
| 953 | */ |
| 954 | write_lock_irqsave(&ep->lock, flags); |
Pekka Enberg | b030a4d | 2005-06-23 00:10:03 -0700 | [diff] [blame] | 955 | if (ep_is_linked(&epi->rdllink)) |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 956 | list_del_init(&epi->rdllink); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 957 | write_unlock_irqrestore(&ep->lock, flags); |
| 958 | |
Pekka Enberg | b030a4d | 2005-06-23 00:10:03 -0700 | [diff] [blame] | 959 | kmem_cache_free(epi_cache, epi); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 960 | eexit_1: |
| 961 | return error; |
| 962 | } |
| 963 | |
| 964 | |
| 965 | /* |
| 966 | * Modify the interest event mask by dropping an event if the new mask |
| 967 | * has a match in the current file status. |
| 968 | */ |
| 969 | static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_event *event) |
| 970 | { |
| 971 | int pwake = 0; |
| 972 | unsigned int revents; |
| 973 | unsigned long flags; |
| 974 | |
| 975 | /* |
| 976 | * Set the new event interest mask before calling f_op->poll(), otherwise |
| 977 | * a potential race might occur. In fact if we do this operation inside |
| 978 | * the lock, an event might happen between the f_op->poll() call and the |
| 979 | * new event set registering. |
| 980 | */ |
| 981 | epi->event.events = event->events; |
| 982 | |
| 983 | /* |
| 984 | * Get current event bits. We can safely use the file* here because |
| 985 | * its usage count has been increased by the caller of this function. |
| 986 | */ |
| 987 | revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL); |
| 988 | |
| 989 | write_lock_irqsave(&ep->lock, flags); |
| 990 | |
| 991 | /* Copy the data member from inside the lock */ |
| 992 | epi->event.data = event->data; |
| 993 | |
| 994 | /* |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 995 | * If the item is not linked to the RB tree it means that it's on its |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 996 | * way toward the removal. Do nothing in this case. |
| 997 | */ |
Pekka Enberg | b030a4d | 2005-06-23 00:10:03 -0700 | [diff] [blame] | 998 | if (ep_rb_linked(&epi->rbn)) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 999 | /* |
| 1000 | * If the item is "hot" and it is not registered inside the ready |
| 1001 | * list, push it inside. If the item is not "hot" and it is currently |
| 1002 | * registered inside the ready list, unlink it. |
| 1003 | */ |
| 1004 | if (revents & event->events) { |
Pekka Enberg | b030a4d | 2005-06-23 00:10:03 -0700 | [diff] [blame] | 1005 | if (!ep_is_linked(&epi->rdllink)) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1006 | list_add_tail(&epi->rdllink, &ep->rdllist); |
| 1007 | |
| 1008 | /* Notify waiting tasks that events are available */ |
| 1009 | if (waitqueue_active(&ep->wq)) |
Davide Libenzi | 3419b23 | 2006-06-25 05:48:14 -0700 | [diff] [blame] | 1010 | __wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE | |
| 1011 | TASK_INTERRUPTIBLE); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1012 | if (waitqueue_active(&ep->poll_wait)) |
| 1013 | pwake++; |
| 1014 | } |
| 1015 | } |
| 1016 | } |
| 1017 | |
| 1018 | write_unlock_irqrestore(&ep->lock, flags); |
| 1019 | |
| 1020 | /* We have to call this outside the lock */ |
| 1021 | if (pwake) |
| 1022 | ep_poll_safewake(&psw, &ep->poll_wait); |
| 1023 | |
| 1024 | return 0; |
| 1025 | } |
| 1026 | |
| 1027 | |
| 1028 | /* |
| 1029 | * This function unregister poll callbacks from the associated file descriptor. |
| 1030 | * Since this must be called without holding "ep->lock" the atomic exchange trick |
| 1031 | * will protect us from multiple unregister. |
| 1032 | */ |
| 1033 | static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi) |
| 1034 | { |
| 1035 | int nwait; |
| 1036 | struct list_head *lsthead = &epi->pwqlist; |
| 1037 | struct eppoll_entry *pwq; |
| 1038 | |
| 1039 | /* This is called without locks, so we need the atomic exchange */ |
| 1040 | nwait = xchg(&epi->nwait, 0); |
| 1041 | |
| 1042 | if (nwait) { |
| 1043 | while (!list_empty(lsthead)) { |
Pavel Emelianov | b5e6181 | 2007-05-08 00:30:19 -0700 | [diff] [blame] | 1044 | pwq = list_first_entry(lsthead, struct eppoll_entry, llink); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1045 | |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 1046 | list_del_init(&pwq->llink); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1047 | remove_wait_queue(pwq->whead, &pwq->wait); |
Pekka Enberg | b030a4d | 2005-06-23 00:10:03 -0700 | [diff] [blame] | 1048 | kmem_cache_free(pwq_cache, pwq); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1049 | } |
| 1050 | } |
| 1051 | } |
| 1052 | |
| 1053 | |
| 1054 | /* |
| 1055 | * Unlink the "struct epitem" from all places it might have been hooked up. |
| 1056 | * This function must be called with write IRQ lock on "ep->lock". |
| 1057 | */ |
| 1058 | static int ep_unlink(struct eventpoll *ep, struct epitem *epi) |
| 1059 | { |
| 1060 | int error; |
| 1061 | |
| 1062 | /* |
| 1063 | * It can happen that this one is called for an item already unlinked. |
| 1064 | * The check protect us from doing a double unlink ( crash ). |
| 1065 | */ |
| 1066 | error = -ENOENT; |
Pekka Enberg | b030a4d | 2005-06-23 00:10:03 -0700 | [diff] [blame] | 1067 | if (!ep_rb_linked(&epi->rbn)) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1068 | goto eexit_1; |
| 1069 | |
| 1070 | /* |
| 1071 | * Clear the event mask for the unlinked item. This will avoid item |
| 1072 | * notifications to be sent after the unlink operation from inside |
| 1073 | * the kernel->userspace event transfer loop. |
| 1074 | */ |
| 1075 | epi->event.events = 0; |
| 1076 | |
| 1077 | /* |
| 1078 | * At this point is safe to do the job, unlink the item from our rb-tree. |
| 1079 | * This operation togheter with the above check closes the door to |
| 1080 | * double unlinks. |
| 1081 | */ |
Pekka Enberg | b030a4d | 2005-06-23 00:10:03 -0700 | [diff] [blame] | 1082 | ep_rb_erase(&epi->rbn, &ep->rbr); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1083 | |
| 1084 | /* |
| 1085 | * If the item we are going to remove is inside the ready file descriptors |
| 1086 | * we want to remove it from this list to avoid stale events. |
| 1087 | */ |
Pekka Enberg | b030a4d | 2005-06-23 00:10:03 -0700 | [diff] [blame] | 1088 | if (ep_is_linked(&epi->rdllink)) |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 1089 | list_del_init(&epi->rdllink); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1090 | |
| 1091 | error = 0; |
| 1092 | eexit_1: |
| 1093 | |
| 1094 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_unlink(%p, %p) = %d\n", |
Masoud Asgharifard Sharbiani | 45f17e0 | 2006-08-27 01:23:48 -0700 | [diff] [blame] | 1095 | current, ep, epi->ffd.file, error)); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1096 | |
| 1097 | return error; |
| 1098 | } |
| 1099 | |
| 1100 | |
| 1101 | /* |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 1102 | * Removes a "struct epitem" from the eventpoll RB tree and deallocates |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1103 | * all the associated resources. |
| 1104 | */ |
| 1105 | static int ep_remove(struct eventpoll *ep, struct epitem *epi) |
| 1106 | { |
| 1107 | int error; |
| 1108 | unsigned long flags; |
| 1109 | struct file *file = epi->ffd.file; |
| 1110 | |
| 1111 | /* |
| 1112 | * Removes poll wait queue hooks. We _have_ to do this without holding |
| 1113 | * the "ep->lock" otherwise a deadlock might occur. This because of the |
| 1114 | * sequence of the lock acquisition. Here we do "ep->lock" then the wait |
| 1115 | * queue head lock when unregistering the wait queue. The wakeup callback |
| 1116 | * will run by holding the wait queue head lock and will call our callback |
| 1117 | * that will try to get "ep->lock". |
| 1118 | */ |
| 1119 | ep_unregister_pollwait(ep, epi); |
| 1120 | |
| 1121 | /* Remove the current item from the list of epoll hooks */ |
| 1122 | spin_lock(&file->f_ep_lock); |
Pekka Enberg | b030a4d | 2005-06-23 00:10:03 -0700 | [diff] [blame] | 1123 | if (ep_is_linked(&epi->fllink)) |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 1124 | list_del_init(&epi->fllink); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1125 | spin_unlock(&file->f_ep_lock); |
| 1126 | |
| 1127 | /* We need to acquire the write IRQ lock before calling ep_unlink() */ |
| 1128 | write_lock_irqsave(&ep->lock, flags); |
| 1129 | |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 1130 | /* Really unlink the item from the RB tree */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1131 | error = ep_unlink(ep, epi); |
| 1132 | |
| 1133 | write_unlock_irqrestore(&ep->lock, flags); |
| 1134 | |
| 1135 | if (error) |
| 1136 | goto eexit_1; |
| 1137 | |
| 1138 | /* At this point it is safe to free the eventpoll item */ |
| 1139 | ep_release_epitem(epi); |
| 1140 | |
| 1141 | error = 0; |
| 1142 | eexit_1: |
| 1143 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_remove(%p, %p) = %d\n", |
| 1144 | current, ep, file, error)); |
| 1145 | |
| 1146 | return error; |
| 1147 | } |
| 1148 | |
| 1149 | |
| 1150 | /* |
| 1151 | * This is the callback that is passed to the wait queue wakeup |
| 1152 | * machanism. It is called by the stored file descriptors when they |
| 1153 | * have events to report. |
| 1154 | */ |
| 1155 | static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *key) |
| 1156 | { |
| 1157 | int pwake = 0; |
| 1158 | unsigned long flags; |
Pekka Enberg | b030a4d | 2005-06-23 00:10:03 -0700 | [diff] [blame] | 1159 | struct epitem *epi = ep_item_from_wait(wait); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1160 | struct eventpoll *ep = epi->ep; |
| 1161 | |
| 1162 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: poll_callback(%p) epi=%p ep=%p\n", |
Masoud Asgharifard Sharbiani | 45f17e0 | 2006-08-27 01:23:48 -0700 | [diff] [blame] | 1163 | current, epi->ffd.file, epi, ep)); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1164 | |
| 1165 | write_lock_irqsave(&ep->lock, flags); |
| 1166 | |
| 1167 | /* |
| 1168 | * If the event mask does not contain any poll(2) event, we consider the |
| 1169 | * descriptor to be disabled. This condition is likely the effect of the |
| 1170 | * EPOLLONESHOT bit that disables the descriptor when an event is received, |
| 1171 | * until the next EPOLL_CTL_MOD will be issued. |
| 1172 | */ |
| 1173 | if (!(epi->event.events & ~EP_PRIVATE_BITS)) |
| 1174 | goto is_disabled; |
| 1175 | |
| 1176 | /* If this file is already in the ready list we exit soon */ |
Pekka Enberg | b030a4d | 2005-06-23 00:10:03 -0700 | [diff] [blame] | 1177 | if (ep_is_linked(&epi->rdllink)) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1178 | goto is_linked; |
| 1179 | |
| 1180 | list_add_tail(&epi->rdllink, &ep->rdllist); |
| 1181 | |
| 1182 | is_linked: |
| 1183 | /* |
| 1184 | * Wake up ( if active ) both the eventpoll wait list and the ->poll() |
| 1185 | * wait list. |
| 1186 | */ |
| 1187 | if (waitqueue_active(&ep->wq)) |
Davide Libenzi | 3419b23 | 2006-06-25 05:48:14 -0700 | [diff] [blame] | 1188 | __wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE | |
| 1189 | TASK_INTERRUPTIBLE); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1190 | if (waitqueue_active(&ep->poll_wait)) |
| 1191 | pwake++; |
| 1192 | |
| 1193 | is_disabled: |
| 1194 | write_unlock_irqrestore(&ep->lock, flags); |
| 1195 | |
| 1196 | /* We have to call this outside the lock */ |
| 1197 | if (pwake) |
| 1198 | ep_poll_safewake(&psw, &ep->poll_wait); |
| 1199 | |
| 1200 | return 1; |
| 1201 | } |
| 1202 | |
| 1203 | |
| 1204 | static int ep_eventpoll_close(struct inode *inode, struct file *file) |
| 1205 | { |
| 1206 | struct eventpoll *ep = file->private_data; |
| 1207 | |
| 1208 | if (ep) { |
| 1209 | ep_free(ep); |
| 1210 | kfree(ep); |
| 1211 | } |
| 1212 | |
| 1213 | DNPRINTK(3, (KERN_INFO "[%p] eventpoll: close() ep=%p\n", current, ep)); |
| 1214 | return 0; |
| 1215 | } |
| 1216 | |
| 1217 | |
| 1218 | static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait) |
| 1219 | { |
| 1220 | unsigned int pollflags = 0; |
| 1221 | unsigned long flags; |
| 1222 | struct eventpoll *ep = file->private_data; |
| 1223 | |
| 1224 | /* Insert inside our poll wait queue */ |
| 1225 | poll_wait(file, &ep->poll_wait, wait); |
| 1226 | |
| 1227 | /* Check our condition */ |
| 1228 | read_lock_irqsave(&ep->lock, flags); |
| 1229 | if (!list_empty(&ep->rdllist)) |
| 1230 | pollflags = POLLIN | POLLRDNORM; |
| 1231 | read_unlock_irqrestore(&ep->lock, flags); |
| 1232 | |
| 1233 | return pollflags; |
| 1234 | } |
| 1235 | |
| 1236 | |
| 1237 | /* |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1238 | * This function is called without holding the "ep->lock" since the call to |
| 1239 | * __copy_to_user() might sleep, and also f_op->poll() might reenable the IRQ |
| 1240 | * because of the way poll() is traditionally implemented in Linux. |
| 1241 | */ |
| 1242 | static int ep_send_events(struct eventpoll *ep, struct list_head *txlist, |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 1243 | struct epoll_event __user *events, int maxevents) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1244 | { |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 1245 | int eventcnt, error = -EFAULT, pwake = 0; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1246 | unsigned int revents; |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 1247 | unsigned long flags; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1248 | struct epitem *epi; |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 1249 | struct list_head injlist; |
| 1250 | |
| 1251 | INIT_LIST_HEAD(&injlist); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1252 | |
| 1253 | /* |
| 1254 | * We can loop without lock because this is a task private list. |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 1255 | * We just splice'd out the ep->rdllist in ep_collect_ready_items(). |
| 1256 | * Items cannot vanish during the loop because we are holding "sem" in |
| 1257 | * read. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1258 | */ |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 1259 | for (eventcnt = 0; !list_empty(txlist) && eventcnt < maxevents;) { |
Pavel Emelianov | b5e6181 | 2007-05-08 00:30:19 -0700 | [diff] [blame] | 1260 | epi = list_first_entry(txlist, struct epitem, rdllink); |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 1261 | prefetch(epi->rdllink.next); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1262 | |
| 1263 | /* |
| 1264 | * Get the ready file event set. We can safely use the file |
| 1265 | * because we are holding the "sem" in read and this will |
| 1266 | * guarantee that both the file and the item will not vanish. |
| 1267 | */ |
| 1268 | revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL); |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 1269 | revents &= epi->event.events; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1270 | |
| 1271 | /* |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 1272 | * Is the event mask intersect the caller-requested one, |
| 1273 | * deliver the event to userspace. Again, we are holding |
| 1274 | * "sem" in read, so no operations coming from userspace |
| 1275 | * can change the item. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1276 | */ |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 1277 | if (revents) { |
| 1278 | if (__put_user(revents, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1279 | &events[eventcnt].events) || |
| 1280 | __put_user(epi->event.data, |
| 1281 | &events[eventcnt].data)) |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 1282 | goto errxit; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1283 | if (epi->event.events & EPOLLONESHOT) |
| 1284 | epi->event.events &= EP_PRIVATE_BITS; |
| 1285 | eventcnt++; |
| 1286 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1287 | |
| 1288 | /* |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 1289 | * This is tricky. We are holding the "sem" in read, and this |
| 1290 | * means that the operations that can change the "linked" status |
| 1291 | * of the epoll item (epi->rbn and epi->rdllink), cannot touch |
| 1292 | * them. Also, since we are "linked" from a epi->rdllink POV |
| 1293 | * (the item is linked to our transmission list we just |
| 1294 | * spliced), the ep_poll_callback() cannot touch us either, |
| 1295 | * because of the check present in there. Another parallel |
| 1296 | * epoll_wait() will not get the same result set, since we |
| 1297 | * spliced the ready list before. Note that list_del() still |
| 1298 | * shows the item as linked to the test in ep_poll_callback(). |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1299 | */ |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 1300 | list_del(&epi->rdllink); |
| 1301 | if (!(epi->event.events & EPOLLET) && |
| 1302 | (revents & epi->event.events)) |
| 1303 | list_add_tail(&epi->rdllink, &injlist); |
| 1304 | else { |
| 1305 | /* |
| 1306 | * Be sure the item is totally detached before re-init |
| 1307 | * the list_head. After INIT_LIST_HEAD() is committed, |
| 1308 | * the ep_poll_callback() can requeue the item again, |
| 1309 | * but we don't care since we are already past it. |
| 1310 | */ |
| 1311 | smp_mb(); |
| 1312 | INIT_LIST_HEAD(&epi->rdllink); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1313 | } |
| 1314 | } |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 1315 | error = 0; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1316 | |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 1317 | errxit: |
| 1318 | |
| 1319 | /* |
| 1320 | * If the re-injection list or the txlist are not empty, re-splice |
| 1321 | * them to the ready list and do proper wakeups. |
| 1322 | */ |
| 1323 | if (!list_empty(&injlist) || !list_empty(txlist)) { |
| 1324 | write_lock_irqsave(&ep->lock, flags); |
| 1325 | |
| 1326 | list_splice(txlist, &ep->rdllist); |
| 1327 | list_splice(&injlist, &ep->rdllist); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1328 | /* |
| 1329 | * Wake up ( if active ) both the eventpoll wait list and the ->poll() |
| 1330 | * wait list. |
| 1331 | */ |
| 1332 | if (waitqueue_active(&ep->wq)) |
Davide Libenzi | 3419b23 | 2006-06-25 05:48:14 -0700 | [diff] [blame] | 1333 | __wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE | |
| 1334 | TASK_INTERRUPTIBLE); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1335 | if (waitqueue_active(&ep->poll_wait)) |
| 1336 | pwake++; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1337 | |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 1338 | write_unlock_irqrestore(&ep->lock, flags); |
| 1339 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1340 | |
| 1341 | /* We have to call this outside the lock */ |
| 1342 | if (pwake) |
| 1343 | ep_poll_safewake(&psw, &ep->poll_wait); |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 1344 | |
| 1345 | return eventcnt == 0 ? error: eventcnt; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1346 | } |
| 1347 | |
| 1348 | |
| 1349 | /* |
| 1350 | * Perform the transfer of events to user space. |
| 1351 | */ |
| 1352 | static int ep_events_transfer(struct eventpoll *ep, |
| 1353 | struct epoll_event __user *events, int maxevents) |
| 1354 | { |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 1355 | int eventcnt; |
| 1356 | unsigned long flags; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1357 | struct list_head txlist; |
| 1358 | |
| 1359 | INIT_LIST_HEAD(&txlist); |
| 1360 | |
| 1361 | /* |
| 1362 | * We need to lock this because we could be hit by |
| 1363 | * eventpoll_release_file() and epoll_ctl(EPOLL_CTL_DEL). |
| 1364 | */ |
| 1365 | down_read(&ep->sem); |
| 1366 | |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 1367 | /* |
| 1368 | * Steal the ready list, and re-init the original one to the |
| 1369 | * empty list. |
| 1370 | */ |
| 1371 | write_lock_irqsave(&ep->lock, flags); |
| 1372 | list_splice(&ep->rdllist, &txlist); |
| 1373 | INIT_LIST_HEAD(&ep->rdllist); |
| 1374 | write_unlock_irqrestore(&ep->lock, flags); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1375 | |
Davide Libenzi | 6192bd5 | 2007-05-08 00:25:41 -0700 | [diff] [blame] | 1376 | /* Build result set in userspace */ |
| 1377 | eventcnt = ep_send_events(ep, &txlist, events, maxevents); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1378 | |
| 1379 | up_read(&ep->sem); |
| 1380 | |
| 1381 | return eventcnt; |
| 1382 | } |
| 1383 | |
| 1384 | |
| 1385 | static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, |
| 1386 | int maxevents, long timeout) |
| 1387 | { |
| 1388 | int res, eavail; |
| 1389 | unsigned long flags; |
| 1390 | long jtimeout; |
| 1391 | wait_queue_t wait; |
| 1392 | |
| 1393 | /* |
| 1394 | * Calculate the timeout by checking for the "infinite" value ( -1 ) |
| 1395 | * and the overflow condition. The passed timeout is in milliseconds, |
| 1396 | * that why (t * HZ) / 1000. |
| 1397 | */ |
Davide Libenzi | e3306dd | 2005-09-27 21:45:33 -0700 | [diff] [blame] | 1398 | jtimeout = (timeout < 0 || timeout >= EP_MAX_MSTIMEO) ? |
| 1399 | MAX_SCHEDULE_TIMEOUT : (timeout * HZ + 999) / 1000; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1400 | |
| 1401 | retry: |
| 1402 | write_lock_irqsave(&ep->lock, flags); |
| 1403 | |
| 1404 | res = 0; |
| 1405 | if (list_empty(&ep->rdllist)) { |
| 1406 | /* |
| 1407 | * We don't have any available event to return to the caller. |
| 1408 | * We need to sleep here, and we will be wake up by |
| 1409 | * ep_poll_callback() when events will become available. |
| 1410 | */ |
| 1411 | init_waitqueue_entry(&wait, current); |
Davide Libenzi | 3419b23 | 2006-06-25 05:48:14 -0700 | [diff] [blame] | 1412 | __add_wait_queue(&ep->wq, &wait); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1413 | |
| 1414 | for (;;) { |
| 1415 | /* |
| 1416 | * We don't want to sleep if the ep_poll_callback() sends us |
| 1417 | * a wakeup in between. That's why we set the task state |
| 1418 | * to TASK_INTERRUPTIBLE before doing the checks. |
| 1419 | */ |
| 1420 | set_current_state(TASK_INTERRUPTIBLE); |
| 1421 | if (!list_empty(&ep->rdllist) || !jtimeout) |
| 1422 | break; |
| 1423 | if (signal_pending(current)) { |
| 1424 | res = -EINTR; |
| 1425 | break; |
| 1426 | } |
| 1427 | |
| 1428 | write_unlock_irqrestore(&ep->lock, flags); |
| 1429 | jtimeout = schedule_timeout(jtimeout); |
| 1430 | write_lock_irqsave(&ep->lock, flags); |
| 1431 | } |
Davide Libenzi | 3419b23 | 2006-06-25 05:48:14 -0700 | [diff] [blame] | 1432 | __remove_wait_queue(&ep->wq, &wait); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1433 | |
| 1434 | set_current_state(TASK_RUNNING); |
| 1435 | } |
| 1436 | |
| 1437 | /* Is it worth to try to dig for events ? */ |
| 1438 | eavail = !list_empty(&ep->rdllist); |
| 1439 | |
| 1440 | write_unlock_irqrestore(&ep->lock, flags); |
| 1441 | |
| 1442 | /* |
| 1443 | * Try to transfer events to user space. In case we get 0 events and |
| 1444 | * there's still timeout left over, we go trying again in search of |
| 1445 | * more luck. |
| 1446 | */ |
| 1447 | if (!res && eavail && |
| 1448 | !(res = ep_events_transfer(ep, events, maxevents)) && jtimeout) |
| 1449 | goto retry; |
| 1450 | |
| 1451 | return res; |
| 1452 | } |
| 1453 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1454 | static int __init eventpoll_init(void) |
| 1455 | { |
Arjan van de Ven | 144efe3 | 2006-03-23 03:00:32 -0800 | [diff] [blame] | 1456 | mutex_init(&epmutex); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1457 | |
| 1458 | /* Initialize the structure used to perform safe poll wait head wake ups */ |
| 1459 | ep_poll_safewake_init(&psw); |
| 1460 | |
| 1461 | /* Allocates slab cache used to allocate "struct epitem" items */ |
| 1462 | epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem), |
| 1463 | 0, SLAB_HWCACHE_ALIGN|EPI_SLAB_DEBUG|SLAB_PANIC, |
| 1464 | NULL, NULL); |
| 1465 | |
| 1466 | /* Allocates slab cache used to allocate "struct eppoll_entry" */ |
| 1467 | pwq_cache = kmem_cache_create("eventpoll_pwq", |
| 1468 | sizeof(struct eppoll_entry), 0, |
| 1469 | EPI_SLAB_DEBUG|SLAB_PANIC, NULL, NULL); |
| 1470 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1471 | return 0; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1472 | } |
Davide Libenzi | cea6924 | 2007-05-10 22:23:22 -0700 | [diff] [blame^] | 1473 | fs_initcall(eventpoll_init); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1474 | |