| /* |
| * fs/eventpoll.c ( Efficent event polling implementation ) |
| * Copyright (C) 2001,...,2002 Davide Libenzi |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License as published by |
| * the Free Software Foundation; either version 2 of the License, or |
| * (at your option) any later version. |
| * |
| * Davide Libenzi <davidel@xmailserver.org> |
| * |
| */ |
| |
| #include <linux/module.h> |
| #include <linux/init.h> |
| #include <linux/kernel.h> |
| #include <linux/sched.h> |
| #include <linux/fs.h> |
| #include <linux/file.h> |
| #include <linux/signal.h> |
| #include <linux/errno.h> |
| #include <linux/mm.h> |
| #include <linux/slab.h> |
| #include <linux/poll.h> |
| #include <linux/smp_lock.h> |
| #include <linux/string.h> |
| #include <linux/list.h> |
| #include <linux/hash.h> |
| #include <linux/spinlock.h> |
| #include <linux/rwsem.h> |
| #include <linux/wait.h> |
| #include <linux/eventpoll.h> |
| #include <linux/mount.h> |
| #include <asm/bitops.h> |
| #include <asm/uaccess.h> |
| #include <asm/system.h> |
| #include <asm/io.h> |
| #include <asm/mman.h> |
| #include <asm/atomic.h> |
| |
| |
| |
| #define EVENTPOLLFS_MAGIC 0x03111965 /* My birthday should work for this :) */ |
| |
| #define DEBUG_EPOLL 0 |
| |
| #if DEBUG_EPOLL > 0 |
| #define DPRINTK(x) printk x |
| #define DNPRINTK(n, x) do { if ((n) <= DEBUG_EPOLL) printk x; } while (0) |
| #else /* #if DEBUG_EPOLL > 0 */ |
| #define DPRINTK(x) (void) 0 |
| #define DNPRINTK(n, x) (void) 0 |
| #endif /* #if DEBUG_EPOLL > 0 */ |
| |
| #define DEBUG_EPI 0 |
| |
| #if DEBUG_EPI != 0 |
| #define EPI_SLAB_DEBUG (SLAB_DEBUG_FREE | SLAB_RED_ZONE /* | SLAB_POISON */) |
| #else /* #if DEBUG_EPI != 0 */ |
| #define EPI_SLAB_DEBUG 0 |
| #endif /* #if DEBUG_EPI != 0 */ |
| |
| |
| /* Maximum number of poll wake up nests we are allowing */ |
| #define EP_MAX_POLLWAKE_NESTS 4 |
| |
| /* Maximum size of the hash in bits ( 2^N ) */ |
| #define EP_MAX_HASH_BITS 17 |
| |
| /* Minimum size of the hash in bits ( 2^N ) */ |
| #define EP_MIN_HASH_BITS 9 |
| |
| /* Number of hash entries ( "struct list_head" ) inside a page */ |
| #define EP_HENTRY_X_PAGE (PAGE_SIZE / sizeof(struct list_head)) |
| |
| /* Maximum size of the hash in pages */ |
| #define EP_MAX_HPAGES ((1 << EP_MAX_HASH_BITS) / EP_HENTRY_X_PAGE + 1) |
| |
| /* Number of pages allocated for an "hbits" sized hash table */ |
| #define EP_HASH_PAGES(hbits) ((int) ((1 << (hbits)) / EP_HENTRY_X_PAGE + \ |
| ((1 << (hbits)) % EP_HENTRY_X_PAGE ? 1: 0))) |
| |
| /* Macro to allocate a "struct epitem" from the slab cache */ |
| #define EPI_MEM_ALLOC() (struct epitem *) kmem_cache_alloc(epi_cache, SLAB_KERNEL) |
| |
| /* Macro to free a "struct epitem" to the slab cache */ |
| #define EPI_MEM_FREE(p) kmem_cache_free(epi_cache, p) |
| |
| /* Macro to allocate a "struct eppoll_entry" from the slab cache */ |
| #define PWQ_MEM_ALLOC() (struct eppoll_entry *) kmem_cache_alloc(pwq_cache, SLAB_KERNEL) |
| |
| /* Macro to free a "struct eppoll_entry" to the slab cache */ |
| #define PWQ_MEM_FREE(p) kmem_cache_free(pwq_cache, p) |
| |
| /* Fast test to see if the file is an evenpoll file */ |
| #define IS_FILE_EPOLL(f) ((f)->f_op == &eventpoll_fops) |
| |
| /* |
| * Remove the item from the list and perform its initialization. |
| * This is usefull for us because we can test if the item is linked |
| * using "EP_IS_LINKED(p)". |
| */ |
| #define EP_LIST_DEL(p) do { list_del(p); INIT_LIST_HEAD(p); } while (0) |
| |
| /* Tells us if the item is currently linked */ |
| #define EP_IS_LINKED(p) (!list_empty(p)) |
| |
| /* Get the "struct epitem" from a wait queue pointer */ |
| #define EP_ITEM_FROM_WAIT(p) ((struct epitem *) container_of(p, struct eppoll_entry, wait)->base) |
| |
| /* Get the "struct epitem" from an epoll queue wrapper */ |
| #define EP_ITEM_FROM_EPQUEUE(p) (container_of(p, struct ep_pqueue, pt)->epi) |
| |
| /* |
| * This is used to optimize the event transfer to userspace. Since this |
| * is kept on stack, it should be pretty small. |
| */ |
| #define EP_MAX_BUF_EVENTS 32 |
| |
| /* |
| * Used to optimize ready items collection by reducing the irqlock/irqunlock |
| * switching rate. This is kept in stack too, so do not go wild with this number. |
| */ |
| #define EP_MAX_COLLECT_ITEMS 64 |
| |
| |
| /* |
| * Node that is linked into the "wake_task_list" member of the "struct poll_safewake". |
| * It is used to keep track on all tasks that are currently inside the wake_up() code |
| * to 1) short-circuit the one coming from the same task and same wait queue head |
| * ( loop ) 2) allow a maximum number of epoll descriptors inclusion nesting |
| * 3) let go the ones coming from other tasks. |
| */ |
| struct wake_task_node { |
| struct list_head llink; |
| task_t *task; |
| wait_queue_head_t *wq; |
| }; |
| |
| /* |
| * This is used to implement the safe poll wake up avoiding to reenter |
| * the poll callback from inside wake_up(). |
| */ |
| struct poll_safewake { |
| struct list_head wake_task_list; |
| spinlock_t lock; |
| }; |
| |
| /* |
| * This structure is stored inside the "private_data" member of the file |
| * structure and rapresent the main data sructure for the eventpoll |
| * interface. |
| */ |
| struct eventpoll { |
| /* Protect the this structure access */ |
| rwlock_t lock; |
| |
| /* Wait queue used by sys_epoll_wait() */ |
| wait_queue_head_t wq; |
| |
| /* Wait queue used by file->poll() */ |
| wait_queue_head_t poll_wait; |
| |
| /* List of ready file descriptors */ |
| struct list_head rdllist; |
| |
| /* Size of the hash */ |
| unsigned int hashbits; |
| |
| /* Pages for the "struct epitem" hash */ |
| char *hpages[EP_MAX_HPAGES]; |
| }; |
| |
| /* Wait structure used by the poll hooks */ |
| struct eppoll_entry { |
| /* List header used to link this structure to the "struct epitem" */ |
| struct list_head llink; |
| |
| /* The "base" pointer is set to the container "struct epitem" */ |
| void *base; |
| |
| /* |
| * Wait queue item that will be linked to the target file wait |
| * queue head. |
| */ |
| wait_queue_t wait; |
| |
| /* The wait queue head that linked the "wait" wait queue item */ |
| wait_queue_head_t *whead; |
| }; |
| |
| /* |
| * Each file descriptor added to the eventpoll interface will |
| * have an entry of this type linked to the hash. |
| */ |
| struct epitem { |
| /* List header used to link this structure to the eventpoll hash */ |
| struct list_head llink; |
| |
| /* List header used to link this structure to the eventpoll ready list */ |
| struct list_head rdllink; |
| |
| /* Number of active wait queue attached to poll operations */ |
| int nwait; |
| |
| /* List containing poll wait queues */ |
| struct list_head pwqlist; |
| |
| /* The "container" of this item */ |
| struct eventpoll *ep; |
| |
| /* The file this item refers to */ |
| struct file *file; |
| |
| /* The structure that describe the interested events and the source fd */ |
| struct epoll_event event; |
| |
| /* |
| * Used to keep track of the usage count of the structure. This avoids |
| * that the structure will desappear from underneath our processing. |
| */ |
| atomic_t usecnt; |
| |
| /* List header used to link this item to the "struct file" items list */ |
| struct list_head fllink; |
| }; |
| |
| /* Wrapper struct used by poll queueing */ |
| struct ep_pqueue { |
| poll_table pt; |
| struct epitem *epi; |
| }; |
| |
| |
| |
| static void ep_poll_safewake_init(struct poll_safewake *psw); |
| static void ep_poll_safewake(struct poll_safewake *psw, wait_queue_head_t *wq); |
| static unsigned int ep_get_hash_bits(unsigned int hintsize); |
| static int ep_getfd(int *efd, struct inode **einode, struct file **efile); |
| static int ep_alloc_pages(char **pages, int numpages); |
| static int ep_free_pages(char **pages, int numpages); |
| static int ep_file_init(struct file *file, unsigned int hashbits); |
| static unsigned int ep_hash_index(struct eventpoll *ep, struct file *file); |
| static struct list_head *ep_hash_entry(struct eventpoll *ep, unsigned int index); |
| static int ep_init(struct eventpoll *ep, unsigned int hashbits); |
| static void ep_free(struct eventpoll *ep); |
| static struct epitem *ep_find(struct eventpoll *ep, struct file *file); |
| static void ep_use_epitem(struct epitem *epi); |
| static void ep_release_epitem(struct epitem *epi); |
| static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, poll_table *pt); |
| static int ep_insert(struct eventpoll *ep, struct epoll_event *event, struct file *tfile); |
| static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_event *event); |
| static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi); |
| static int ep_unlink(struct eventpoll *ep, struct epitem *epi); |
| static int ep_remove(struct eventpoll *ep, struct epitem *epi); |
| static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync); |
| static int ep_eventpoll_close(struct inode *inode, struct file *file); |
| static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait); |
| static int ep_collect_ready_items(struct eventpoll *ep, struct epitem **aepi, int maxepi); |
| static int ep_send_events(struct eventpoll *ep, struct epitem **aepi, int nepi, |
| struct epoll_event *events); |
| static int ep_events_transfer(struct eventpoll *ep, struct epoll_event *events, int maxevents); |
| static int ep_poll(struct eventpoll *ep, struct epoll_event *events, int maxevents, |
| int timeout); |
| static int eventpollfs_delete_dentry(struct dentry *dentry); |
| static struct inode *ep_eventpoll_inode(void); |
| static struct super_block *eventpollfs_get_sb(struct file_system_type *fs_type, |
| int flags, char *dev_name, void *data); |
| |
| |
| /* Safe wake up implementation */ |
| static struct poll_safewake psw; |
| |
| /* |
| * This semaphore is used to ensure that files are not removed |
| * while epoll is using them. Namely the f_op->poll(), since |
| * it has to be called from outside the lock, must be protected. |
| * This is read-held during the event transfer loop to userspace |
| * and it is write-held during the file cleanup path and the epoll |
| * file exit code. |
| */ |
| static struct rw_semaphore epsem; |
| |
| /* Slab cache used to allocate "struct epitem" */ |
| static kmem_cache_t *epi_cache; |
| |
| /* Slab cache used to allocate "struct eppoll_entry" */ |
| static kmem_cache_t *pwq_cache; |
| |
| /* Virtual fs used to allocate inodes for eventpoll files */ |
| static struct vfsmount *eventpoll_mnt; |
| |
| /* File callbacks that implement the eventpoll file behaviour */ |
| static struct file_operations eventpoll_fops = { |
| .release = ep_eventpoll_close, |
| .poll = ep_eventpoll_poll |
| }; |
| |
| /* |
| * This is used to register the virtual file system from where |
| * eventpoll inodes are allocated. |
| */ |
| static struct file_system_type eventpoll_fs_type = { |
| .name = "eventpollfs", |
| .get_sb = eventpollfs_get_sb, |
| .kill_sb = kill_anon_super, |
| }; |
| |
| /* Very basic directory entry operations for the eventpoll virtual file system */ |
| static struct dentry_operations eventpollfs_dentry_operations = { |
| .d_delete = eventpollfs_delete_dentry, |
| }; |
| |
| |
| |
| /* Initialize the poll safe wake up structure */ |
| static void ep_poll_safewake_init(struct poll_safewake *psw) |
| { |
| |
| INIT_LIST_HEAD(&psw->wake_task_list); |
| spin_lock_init(&psw->lock); |
| } |
| |
| |
| /* |
| * Perform a safe wake up of the poll wait list. The problem is that |
| * with the new callback'd wake up system, it is possible that the |
| * poll callback is reentered from inside the call to wake_up() done |
| * on the poll wait queue head. The rule is that we cannot reenter the |
| * wake up code from the same task more than EP_MAX_POLLWAKE_NESTS times, |
| * and we cannot reenter the same wait queue head at all. This will |
| * enable to have a hierarchy of epoll file descriptor of no more than |
| * EP_MAX_POLLWAKE_NESTS deep. We need the irq version of the spin lock |
| * because this one gets called by the poll callback, that in turn is called |
| * from inside a wake_up(), that might be called from irq context. |
| */ |
| static void ep_poll_safewake(struct poll_safewake *psw, wait_queue_head_t *wq) |
| { |
| int wake_nests = 0; |
| unsigned long flags; |
| task_t *this_task = current; |
| struct list_head *lsthead = &psw->wake_task_list, *lnk; |
| struct wake_task_node tnode; |
| |
| spin_lock_irqsave(&psw->lock, flags); |
| |
| /* Try to see if the current task is already inside this wakeup call */ |
| list_for_each(lnk, lsthead) { |
| struct wake_task_node *tncur = list_entry(lnk, struct wake_task_node, llink); |
| |
| if (tncur->task == this_task) { |
| if (tncur->wq == wq || ++wake_nests > EP_MAX_POLLWAKE_NESTS) { |
| /* |
| * Ops ... loop detected or maximum nest level reached. |
| * We abort this wake by breaking the cycle itself. |
| */ |
| spin_unlock_irqrestore(&psw->lock, flags); |
| return; |
| } |
| } |
| } |
| |
| /* Add the current task to the list */ |
| tnode.task = this_task; |
| tnode.wq = wq; |
| list_add(&tnode.llink, lsthead); |
| |
| spin_unlock_irqrestore(&psw->lock, flags); |
| |
| /* Do really wake up now */ |
| wake_up(wq); |
| |
| /* Remove the current task from the list */ |
| spin_lock_irqsave(&psw->lock, flags); |
| list_del(&tnode.llink); |
| spin_unlock_irqrestore(&psw->lock, flags); |
| } |
| |
| |
| /* |
| * Calculate the size of the hash in bits. The returned size will be |
| * bounded between EP_MIN_HASH_BITS and EP_MAX_HASH_BITS. |
| */ |
| static unsigned int ep_get_hash_bits(unsigned int hintsize) |
| { |
| unsigned int i, val; |
| |
| for (i = 0, val = 1; val < hintsize && i < EP_MAX_HASH_BITS; i++, val <<= 1); |
| return i < EP_MIN_HASH_BITS ? EP_MIN_HASH_BITS: i; |
| } |
| |
| |
| /* Used to initialize the epoll bits inside the "struct file" */ |
| void eventpoll_init_file(struct file *file) |
| { |
| |
| INIT_LIST_HEAD(&file->f_ep_links); |
| spin_lock_init(&file->f_ep_lock); |
| } |
| |
| |
| /* |
| * This is called from inside fs/file_table.c:__fput() to unlink files |
| * from the eventpoll interface. We need to have this facility to cleanup |
| * correctly files that are closed without being removed from the eventpoll |
| * interface. |
| */ |
| void eventpoll_release(struct file *file) |
| { |
| struct list_head *lsthead = &file->f_ep_links; |
| struct epitem *epi; |
| |
| /* |
| * Fast check to avoid the get/release of the semaphore. Since |
| * we're doing this outside the semaphore lock, it might return |
| * false negatives, but we don't care. It'll help in 99.99% of cases |
| * to avoid the semaphore lock. False positives simply cannot happen |
| * because the file in on the way to be removed and nobody ( but |
| * eventpoll ) has still a reference to this file. |
| */ |
| if (list_empty(lsthead)) |
| return; |
| |
| /* |
| * We don't want to get "file->f_ep_lock" because it is not |
| * necessary. It is not necessary because we're in the "struct file" |
| * cleanup path, and this means that noone is using this file anymore. |
| * The only hit might come from ep_free() but by holding the semaphore |
| * will correctly serialize the operation. |
| */ |
| down_write(&epsem); |
| while (!list_empty(lsthead)) { |
| epi = list_entry(lsthead->next, struct epitem, fllink); |
| |
| EP_LIST_DEL(&epi->fllink); |
| ep_remove(epi->ep, epi); |
| } |
| up_write(&epsem); |
| } |
| |
| |
| /* |
| * It opens an eventpoll file descriptor by suggesting a storage of "size" |
| * file descriptors. The size parameter is just an hint about how to size |
| * data structures. It won't prevent the user to store more than "size" |
| * file descriptors inside the epoll interface. It is the kernel part of |
| * the userspace epoll_create(2). |
| */ |
| asmlinkage int sys_epoll_create(int size) |
| { |
| int error, fd; |
| unsigned int hashbits; |
| struct inode *inode; |
| struct file *file; |
| |
| DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d)\n", |
| current, size)); |
| |
| /* Correctly size the hash */ |
| hashbits = ep_get_hash_bits((unsigned int) size); |
| |
| /* |
| * Creates all the items needed to setup an eventpoll file. That is, |
| * a file structure, and inode and a free file descriptor. |
| */ |
| error = ep_getfd(&fd, &inode, &file); |
| if (error) |
| goto eexit_1; |
| |
| /* Setup the file internal data structure ( "struct eventpoll" ) */ |
| error = ep_file_init(file, hashbits); |
| if (error) |
| goto eexit_2; |
| |
| |
| DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n", |
| current, size, fd)); |
| |
| return fd; |
| |
| eexit_2: |
| sys_close(fd); |
| eexit_1: |
| DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n", |
| current, size, error)); |
| return error; |
| } |
| |
| |
| /* |
| * The following function implement the controller interface for the eventpoll |
| * file that enable the insertion/removal/change of file descriptors inside |
| * the interest set. It rapresents the kernel part of the user spcae epoll_ctl(2). |
| */ |
| asmlinkage int sys_epoll_ctl(int epfd, int op, int fd, struct epoll_event *event) |
| { |
| int error; |
| struct file *file, *tfile; |
| struct eventpoll *ep; |
| struct epitem *epi; |
| struct epoll_event epds; |
| |
| DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %u)\n", |
| current, epfd, op, fd, event->events)); |
| |
| error = -EFAULT; |
| if (copy_from_user(&epds, event, sizeof(struct epoll_event))) |
| goto eexit_1; |
| |
| /* Get the "struct file *" for the eventpoll file */ |
| error = -EBADF; |
| file = fget(epfd); |
| if (!file) |
| goto eexit_1; |
| |
| /* Get the "struct file *" for the target file */ |
| tfile = fget(fd); |
| if (!tfile) |
| goto eexit_2; |
| |
| /* The target file descriptor must support poll */ |
| error = -EPERM; |
| if (!tfile->f_op || !tfile->f_op->poll) |
| goto eexit_3; |
| |
| /* |
| * We have to check that the file structure underneath the file descriptor |
| * the user passed to us _is_ an eventpoll file. And also we do not permit |
| * adding an epoll file descriptor inside itself. |
| */ |
| error = -EINVAL; |
| if (file == tfile || !IS_FILE_EPOLL(file)) |
| goto eexit_3; |
| |
| /* |
| * At this point it is safe to assume that the "private_data" contains |
| * our own data structure. |
| */ |
| ep = file->private_data; |
| |
| /* |
| * Try to lookup the file inside our hash table. When an item is found |
| * ep_find() increases the usage count of the item so that it won't |
| * desappear underneath us. The only thing that might happen, if someone |
| * tries very hard, is a double insertion of the same file descriptor. |
| * This does not rapresent a problem though and we don't really want |
| * to put an extra syncronization object to deal with this harmless condition. |
| */ |
| epi = ep_find(ep, tfile); |
| |
| error = -EINVAL; |
| switch (op) { |
| case EPOLL_CTL_ADD: |
| if (!epi) { |
| epds.events |= POLLERR | POLLHUP; |
| |
| error = ep_insert(ep, &epds, tfile); |
| } else |
| error = -EEXIST; |
| break; |
| case EPOLL_CTL_DEL: |
| if (epi) |
| error = ep_remove(ep, epi); |
| else |
| error = -ENOENT; |
| break; |
| case EPOLL_CTL_MOD: |
| if (epi) { |
| epds.events |= POLLERR | POLLHUP; |
| error = ep_modify(ep, epi, &epds); |
| } else |
| error = -ENOENT; |
| break; |
| } |
| |
| /* |
| * The function ep_find() increments the usage count of the structure |
| * so, if this is not NULL, we need to release it. |
| */ |
| if (epi) |
| ep_release_epitem(epi); |
| |
| eexit_3: |
| fput(tfile); |
| eexit_2: |
| fput(file); |
| eexit_1: |
| DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %u) = %d\n", |
| current, epfd, op, fd, event->events, error)); |
| |
| return error; |
| } |
| |
| |
| /* |
| * Implement the event wait interface for the eventpoll file. It is the kernel |
| * part of the user space epoll_wait(2). |
| */ |
| asmlinkage int sys_epoll_wait(int epfd, struct epoll_event *events, int maxevents, |
| int timeout) |
| { |
| int error; |
| struct file *file; |
| struct eventpoll *ep; |
| |
| DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_wait(%d, %p, %d, %d)\n", |
| current, epfd, events, maxevents, timeout)); |
| |
| /* The maximum number of event must be greater than zero */ |
| if (maxevents <= 0) |
| return -EINVAL; |
| |
| /* Verify that the area passed by the user is writeable */ |
| if ((error = verify_area(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event)))) |
| goto eexit_1; |
| |
| /* Get the "struct file *" for the eventpoll file */ |
| error = -EBADF; |
| file = fget(epfd); |
| if (!file) |
| goto eexit_1; |
| |
| /* |
| * We have to check that the file structure underneath the file descriptor |
| * the user passed to us _is_ an eventpoll file. |
| */ |
| error = -EINVAL; |
| if (!IS_FILE_EPOLL(file)) |
| goto eexit_2; |
| |
| /* |
| * At this point it is safe to assume that the "private_data" contains |
| * our own data structure. |
| */ |
| ep = file->private_data; |
| |
| /* Time to fish for events ... */ |
| error = ep_poll(ep, events, maxevents, timeout); |
| |
| eexit_2: |
| fput(file); |
| eexit_1: |
| DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_wait(%d, %p, %d, %d) = %d\n", |
| current, epfd, events, maxevents, timeout, error)); |
| |
| return error; |
| } |
| |
| |
| /* |
| * Creates the file descriptor to be used by the epoll interface. |
| */ |
| static int ep_getfd(int *efd, struct inode **einode, struct file **efile) |
| { |
| struct qstr this; |
| char name[32]; |
| struct dentry *dentry; |
| struct inode *inode; |
| struct file *file; |
| int error, fd; |
| |
| /* Get an ready to use file */ |
| error = -ENFILE; |
| file = get_empty_filp(); |
| if (!file) |
| goto eexit_1; |
| |
| /* Allocates an inode from the eventpoll file system */ |
| inode = ep_eventpoll_inode(); |
| error = PTR_ERR(inode); |
| if (IS_ERR(inode)) |
| goto eexit_2; |
| |
| /* Allocates a free descriptor to plug the file onto */ |
| error = get_unused_fd(); |
| if (error < 0) |
| goto eexit_3; |
| fd = error; |
| |
| /* |
| * Link the inode to a directory entry by creating a unique name |
| * using the inode number. |
| */ |
| error = -ENOMEM; |
| sprintf(name, "[%lu]", inode->i_ino); |
| this.name = name; |
| this.len = strlen(name); |
| this.hash = inode->i_ino; |
| dentry = d_alloc(eventpoll_mnt->mnt_sb->s_root, &this); |
| if (!dentry) |
| goto eexit_4; |
| dentry->d_op = &eventpollfs_dentry_operations; |
| d_add(dentry, inode); |
| file->f_vfsmnt = mntget(eventpoll_mnt); |
| file->f_dentry = dget(dentry); |
| |
| /* |
| * Initialize the file as read/write because it could be used |
| * with write() to add/remove/change interest sets. |
| */ |
| file->f_pos = 0; |
| file->f_flags = O_RDONLY; |
| file->f_op = &eventpoll_fops; |
| file->f_mode = FMODE_READ; |
| file->f_version = 0; |
| file->private_data = NULL; |
| |
| /* Install the new setup file into the allocated fd. */ |
| fd_install(fd, file); |
| |
| *efd = fd; |
| *einode = inode; |
| *efile = file; |
| return 0; |
| |
| eexit_4: |
| put_unused_fd(fd); |
| eexit_3: |
| iput(inode); |
| eexit_2: |
| put_filp(file); |
| eexit_1: |
| return error; |
| } |
| |
| |
| static int ep_alloc_pages(char **pages, int numpages) |
| { |
| int i; |
| |
| for (i = 0; i < numpages; i++) { |
| pages[i] = (char *) __get_free_pages(GFP_KERNEL, 0); |
| if (!pages[i]) { |
| for (--i; i >= 0; i--) { |
| ClearPageReserved(virt_to_page(pages[i])); |
| free_pages((unsigned long) pages[i], 0); |
| } |
| return -ENOMEM; |
| } |
| SetPageReserved(virt_to_page(pages[i])); |
| } |
| return 0; |
| } |
| |
| |
| static int ep_free_pages(char **pages, int numpages) |
| { |
| int i; |
| |
| for (i = 0; i < numpages; i++) { |
| ClearPageReserved(virt_to_page(pages[i])); |
| free_pages((unsigned long) pages[i], 0); |
| } |
| return 0; |
| } |
| |
| |
| static int ep_file_init(struct file *file, unsigned int hashbits) |
| { |
| int error; |
| struct eventpoll *ep; |
| |
| if (!(ep = kmalloc(sizeof(struct eventpoll), GFP_KERNEL))) |
| return -ENOMEM; |
| |
| memset(ep, 0, sizeof(*ep)); |
| |
| error = ep_init(ep, hashbits); |
| if (error) { |
| kfree(ep); |
| return error; |
| } |
| |
| file->private_data = ep; |
| |
| DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_file_init() ep=%p\n", |
| current, ep)); |
| return 0; |
| } |
| |
| |
| /* |
| * Calculate the index of the hash relative to "file". |
| */ |
| static unsigned int ep_hash_index(struct eventpoll *ep, struct file *file) |
| { |
| |
| return (unsigned int) hash_ptr(file, ep->hashbits); |
| } |
| |
| |
| /* |
| * Returns the hash entry ( struct list_head * ) of the passed index. |
| */ |
| static struct list_head *ep_hash_entry(struct eventpoll *ep, unsigned int index) |
| { |
| |
| return (struct list_head *) (ep->hpages[index / EP_HENTRY_X_PAGE] + |
| (index % EP_HENTRY_X_PAGE) * sizeof(struct list_head)); |
| } |
| |
| |
| static int ep_init(struct eventpoll *ep, unsigned int hashbits) |
| { |
| int error; |
| unsigned int i, hsize; |
| |
| rwlock_init(&ep->lock); |
| init_waitqueue_head(&ep->wq); |
| init_waitqueue_head(&ep->poll_wait); |
| INIT_LIST_HEAD(&ep->rdllist); |
| |
| /* Hash allocation and setup */ |
| ep->hashbits = hashbits; |
| error = ep_alloc_pages(ep->hpages, EP_HASH_PAGES(ep->hashbits)); |
| if (error) |
| goto eexit_1; |
| |
| /* Initialize hash buckets */ |
| for (i = 0, hsize = 1 << hashbits; i < hsize; i++) |
| INIT_LIST_HEAD(ep_hash_entry(ep, i)); |
| |
| return 0; |
| eexit_1: |
| return error; |
| } |
| |
| |
| static void ep_free(struct eventpoll *ep) |
| { |
| unsigned int i, hsize; |
| struct list_head *lsthead, *lnk; |
| |
| /* |
| * We need to lock this because we could be hit by |
| * eventpoll_release() while we're freeing the "struct eventpoll". |
| */ |
| down_write(&epsem); |
| |
| /* |
| * Walks through the whole hash by unregistering poll callbacks. |
| */ |
| for (i = 0, hsize = 1 << ep->hashbits; i < hsize; i++) { |
| lsthead = ep_hash_entry(ep, i); |
| |
| list_for_each(lnk, lsthead) { |
| struct epitem *epi = list_entry(lnk, struct epitem, llink); |
| |
| ep_unregister_pollwait(ep, epi); |
| } |
| } |
| |
| /* |
| * Walks through the whole hash by freeing each "struct epitem". At this |
| * point we are sure no poll callbacks will be lingering around, and also by |
| * write-holding "epsem" we can be sure that no file cleanup code will hit |
| * us during this operation. So we can avoid the lock on "ep->lock". |
| */ |
| for (i = 0, hsize = 1 << ep->hashbits; i < hsize; i++) { |
| lsthead = ep_hash_entry(ep, i); |
| |
| while (!list_empty(lsthead)) { |
| struct epitem *epi = list_entry(lsthead->next, struct epitem, llink); |
| |
| ep_remove(ep, epi); |
| } |
| } |
| |
| up_write(&epsem); |
| |
| /* Free hash pages */ |
| ep_free_pages(ep->hpages, EP_HASH_PAGES(ep->hashbits)); |
| } |
| |
| |
| /* |
| * Search the file inside the eventpoll hash. It add usage count to |
| * the returned item, so the caller must call ep_release_epitem() |
| * after finished using the "struct epitem". |
| */ |
| static struct epitem *ep_find(struct eventpoll *ep, struct file *file) |
| { |
| unsigned long flags; |
| struct list_head *lsthead, *lnk; |
| struct epitem *epi = NULL; |
| |
| read_lock_irqsave(&ep->lock, flags); |
| |
| lsthead = ep_hash_entry(ep, ep_hash_index(ep, file)); |
| list_for_each(lnk, lsthead) { |
| epi = list_entry(lnk, struct epitem, llink); |
| |
| if (epi->file == file) { |
| ep_use_epitem(epi); |
| break; |
| } |
| epi = NULL; |
| } |
| |
| read_unlock_irqrestore(&ep->lock, flags); |
| |
| DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_find(%p) -> %p\n", |
| current, file, epi)); |
| |
| return epi; |
| } |
| |
| |
| /* |
| * Increment the usage count of the "struct epitem" making it sure |
| * that the user will have a valid pointer to reference. |
| */ |
| static void ep_use_epitem(struct epitem *epi) |
| { |
| |
| atomic_inc(&epi->usecnt); |
| } |
| |
| |
| /* |
| * Decrement ( release ) the usage count by signaling that the user |
| * has finished using the structure. It might lead to freeing the |
| * structure itself if the count goes to zero. |
| */ |
| static void ep_release_epitem(struct epitem *epi) |
| { |
| |
| if (atomic_dec_and_test(&epi->usecnt)) |
| EPI_MEM_FREE(epi); |
| } |
| |
| |
| /* |
| * This is the callback that is used to add our wait queue to the |
| * target file wakeup lists. |
| */ |
| static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, poll_table *pt) |
| { |
| struct epitem *epi = EP_ITEM_FROM_EPQUEUE(pt); |
| struct eppoll_entry *pwq; |
| |
| if (epi->nwait >= 0 && (pwq = PWQ_MEM_ALLOC())) |
| { |
| init_waitqueue_func_entry(&pwq->wait, ep_poll_callback); |
| pwq->whead = whead; |
| pwq->base = epi; |
| add_wait_queue(whead, &pwq->wait); |
| list_add_tail(&pwq->llink, &epi->pwqlist); |
| epi->nwait++; |
| } |
| else |
| { |
| /* We have to signal that an error occured */ |
| epi->nwait = -1; |
| } |
| } |
| |
| |
| static int ep_insert(struct eventpoll *ep, struct epoll_event *event, struct file *tfile) |
| { |
| int error, revents, pwake = 0; |
| unsigned long flags; |
| struct epitem *epi; |
| struct ep_pqueue epq; |
| |
| error = -ENOMEM; |
| if (!(epi = EPI_MEM_ALLOC())) |
| goto eexit_1; |
| |
| /* Item initialization follow here ... */ |
| INIT_LIST_HEAD(&epi->llink); |
| INIT_LIST_HEAD(&epi->rdllink); |
| INIT_LIST_HEAD(&epi->fllink); |
| INIT_LIST_HEAD(&epi->pwqlist); |
| epi->ep = ep; |
| epi->file = tfile; |
| epi->event = *event; |
| atomic_set(&epi->usecnt, 1); |
| epi->nwait = 0; |
| |
| /* Initialize the poll table using the queue callback */ |
| epq.epi = epi; |
| init_poll_funcptr(&epq.pt, ep_ptable_queue_proc); |
| |
| /* |
| * Attach the item to the poll hooks and get current event bits. |
| * We can safely use the file* here because its usage count has |
| * been increased by the caller of this function. |
| */ |
| revents = tfile->f_op->poll(tfile, &epq.pt); |
| |
| /* |
| * We have to check if something went wrong during the poll wait queue |
| * install process. Namely an allocation for a wait queue failed due |
| * high memory pressure. |
| */ |
| if (epi->nwait < 0) |
| goto eexit_2; |
| |
| /* Add the current item to the list of active epoll hook for this file */ |
| spin_lock(&tfile->f_ep_lock); |
| list_add_tail(&epi->fllink, &tfile->f_ep_links); |
| spin_unlock(&tfile->f_ep_lock); |
| |
| /* We have to drop the new item inside our item list to keep track of it */ |
| write_lock_irqsave(&ep->lock, flags); |
| |
| /* Add the current item to the hash table */ |
| list_add(&epi->llink, ep_hash_entry(ep, ep_hash_index(ep, tfile))); |
| |
| /* If the file is already "ready" we drop it inside the ready list */ |
| if ((revents & event->events) && !EP_IS_LINKED(&epi->rdllink)) { |
| list_add_tail(&epi->rdllink, &ep->rdllist); |
| |
| /* Notify waiting tasks that events are available */ |
| if (waitqueue_active(&ep->wq)) |
| wake_up(&ep->wq); |
| if (waitqueue_active(&ep->poll_wait)) |
| pwake++; |
| } |
| |
| write_unlock_irqrestore(&ep->lock, flags); |
| |
| /* We have to call this outside the lock */ |
| if (pwake) |
| ep_poll_safewake(&psw, &ep->poll_wait); |
| |
| DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_insert(%p, %p)\n", |
| current, ep, tfile)); |
| |
| return 0; |
| |
| eexit_2: |
| ep_unregister_pollwait(ep, epi); |
| |
| /* |
| * We need to do this because an event could have been arrived on some |
| * allocated wait queue. |
| */ |
| write_lock_irqsave(&ep->lock, flags); |
| if (EP_IS_LINKED(&epi->rdllink)) |
| EP_LIST_DEL(&epi->rdllink); |
| write_unlock_irqrestore(&ep->lock, flags); |
| |
| EPI_MEM_FREE(epi); |
| eexit_1: |
| return error; |
| } |
| |
| |
| /* |
| * Modify the interest event mask by dropping an event if the new mask |
| * has a match in the current file status. |
| */ |
| static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_event *event) |
| { |
| int pwake = 0; |
| unsigned int revents; |
| unsigned long flags; |
| |
| /* |
| * Set the new event interest mask before calling f_op->poll(), otherwise |
| * a potential race might occur. In fact if we do this operation inside |
| * the lock, an event might happen between the f_op->poll() call and the |
| * new event set registering. |
| */ |
| epi->event.events = event->events; |
| |
| /* |
| * Get current event bits. We can safely use the file* here because |
| * its usage count has been increased by the caller of this function. |
| */ |
| revents = epi->file->f_op->poll(epi->file, NULL); |
| |
| write_lock_irqsave(&ep->lock, flags); |
| |
| /* Copy the data member from inside the lock */ |
| epi->event.data = event->data; |
| |
| /* If the file is already "ready" we drop it inside the ready list */ |
| if ((revents & event->events) && EP_IS_LINKED(&epi->llink) && |
| !EP_IS_LINKED(&epi->rdllink)) { |
| list_add_tail(&epi->rdllink, &ep->rdllist); |
| |
| /* Notify waiting tasks that events are available */ |
| if (waitqueue_active(&ep->wq)) |
| wake_up(&ep->wq); |
| if (waitqueue_active(&ep->poll_wait)) |
| pwake++; |
| } |
| |
| write_unlock_irqrestore(&ep->lock, flags); |
| |
| /* We have to call this outside the lock */ |
| if (pwake) |
| ep_poll_safewake(&psw, &ep->poll_wait); |
| |
| return 0; |
| } |
| |
| |
| /* |
| * This function unregister poll callbacks from the associated file descriptor. |
| * Since this must be called without holding "ep->lock" the atomic exchange trick |
| * will protect us from multiple unregister. |
| */ |
| static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi) |
| { |
| int nwait; |
| struct list_head *lsthead = &epi->pwqlist; |
| struct eppoll_entry *pwq; |
| |
| /* This is called without locks, so we need the atomic exchange */ |
| nwait = xchg(&epi->nwait, 0); |
| |
| if (nwait) |
| { |
| while (!list_empty(lsthead)) { |
| pwq = list_entry(lsthead->next, struct eppoll_entry, llink); |
| |
| EP_LIST_DEL(&pwq->llink); |
| remove_wait_queue(pwq->whead, &pwq->wait); |
| PWQ_MEM_FREE(pwq); |
| } |
| } |
| } |
| |
| |
| /* |
| * Unlink the "struct epitem" from all places it might have been hooked up. |
| * This function must be called with write IRQ lock on "ep->lock". |
| */ |
| static int ep_unlink(struct eventpoll *ep, struct epitem *epi) |
| { |
| int error; |
| |
| /* |
| * It can happen that this one is called for an item already unlinked. |
| * The check protect us from doing a double unlink ( crash ). |
| */ |
| error = -ENOENT; |
| if (!EP_IS_LINKED(&epi->llink)) |
| goto eexit_1; |
| |
| /* |
| * At this point is safe to do the job, unlink the item from our list. |
| * This operation togheter with the above check closes the door to |
| * double unlinks. |
| */ |
| EP_LIST_DEL(&epi->llink); |
| |
| /* |
| * If the item we are going to remove is inside the ready file descriptors |
| * we want to remove it from this list to avoid stale events. |
| */ |
| if (EP_IS_LINKED(&epi->rdllink)) |
| EP_LIST_DEL(&epi->rdllink); |
| |
| error = 0; |
| eexit_1: |
| |
| DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_unlink(%p, %p) = %d\n", |
| current, ep, epi->file, error)); |
| |
| return error; |
| } |
| |
| |
| /* |
| * Removes a "struct epitem" from the eventpoll hash and deallocates |
| * all the associated resources. |
| */ |
| static int ep_remove(struct eventpoll *ep, struct epitem *epi) |
| { |
| int error; |
| unsigned long flags; |
| |
| /* |
| * Removes poll wait queue hooks. We _have_ to do this without holding |
| * the "ep->lock" otherwise a deadlock might occur. This because of the |
| * sequence of the lock acquisition. Here we do "ep->lock" then the wait |
| * queue head lock when unregistering the wait queue. The wakeup callback |
| * will run by holding the wait queue head lock and will call our callback |
| * that will try to get "ep->lock". |
| */ |
| ep_unregister_pollwait(ep, epi); |
| |
| /* Remove the current item from the list of epoll hooks */ |
| spin_lock(&epi->file->f_ep_lock); |
| if (EP_IS_LINKED(&epi->fllink)) |
| EP_LIST_DEL(&epi->fllink); |
| spin_unlock(&epi->file->f_ep_lock); |
| |
| /* We need to acquire the write IRQ lock before calling ep_unlink() */ |
| write_lock_irqsave(&ep->lock, flags); |
| |
| /* Really unlink the item from the hash */ |
| error = ep_unlink(ep, epi); |
| |
| write_unlock_irqrestore(&ep->lock, flags); |
| |
| if (error) |
| goto eexit_1; |
| |
| /* At this point it is safe to free the eventpoll item */ |
| ep_release_epitem(epi); |
| |
| error = 0; |
| eexit_1: |
| DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_remove(%p, %p) = %d\n", |
| current, ep, epi->file, error)); |
| |
| return error; |
| } |
| |
| |
| /* |
| * This is the callback that is passed to the wait queue wakeup |
| * machanism. It is called by the stored file descriptors when they |
| * have events to report. |
| */ |
| static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync) |
| { |
| int pwake = 0; |
| unsigned long flags; |
| struct epitem *epi = EP_ITEM_FROM_WAIT(wait); |
| struct eventpoll *ep = epi->ep; |
| |
| DNPRINTK(3, (KERN_INFO "[%p] eventpoll: poll_callback(%p) epi=%p ep=%p\n", |
| current, epi->file, epi, ep)); |
| |
| write_lock_irqsave(&ep->lock, flags); |
| |
| /* If this file is already in the ready list we exit soon */ |
| if (EP_IS_LINKED(&epi->rdllink)) |
| goto is_linked; |
| |
| list_add_tail(&epi->rdllink, &ep->rdllist); |
| |
| is_linked: |
| /* |
| * Wake up ( if active ) both the eventpoll wait list and the ->poll() |
| * wait list. |
| */ |
| if (waitqueue_active(&ep->wq)) |
| wake_up(&ep->wq); |
| if (waitqueue_active(&ep->poll_wait)) |
| pwake++; |
| |
| write_unlock_irqrestore(&ep->lock, flags); |
| |
| /* We have to call this outside the lock */ |
| if (pwake) |
| ep_poll_safewake(&psw, &ep->poll_wait); |
| |
| return 1; |
| } |
| |
| |
| static int ep_eventpoll_close(struct inode *inode, struct file *file) |
| { |
| struct eventpoll *ep = file->private_data; |
| |
| if (ep) { |
| ep_free(ep); |
| kfree(ep); |
| } |
| |
| DNPRINTK(3, (KERN_INFO "[%p] eventpoll: close() ep=%p\n", current, ep)); |
| return 0; |
| } |
| |
| |
| static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait) |
| { |
| unsigned int pollflags = 0; |
| unsigned long flags; |
| struct eventpoll *ep = file->private_data; |
| |
| /* Insert inside our poll wait queue */ |
| poll_wait(file, &ep->poll_wait, wait); |
| |
| /* Check our condition */ |
| read_lock_irqsave(&ep->lock, flags); |
| if (!list_empty(&ep->rdllist)) |
| pollflags = POLLIN | POLLRDNORM; |
| read_unlock_irqrestore(&ep->lock, flags); |
| |
| return pollflags; |
| } |
| |
| |
| /* |
| * Since we have to release the lock during the __copy_to_user() operation and |
| * during the f_op->poll() call, we try to collect the maximum number of items |
| * by reducing the irqlock/irqunlock switching rate. |
| */ |
| static int ep_collect_ready_items(struct eventpoll *ep, struct epitem **aepi, int maxepi) |
| { |
| int nepi; |
| unsigned long flags; |
| struct list_head *lsthead = &ep->rdllist; |
| |
| write_lock_irqsave(&ep->lock, flags); |
| |
| for (nepi = 0; nepi < maxepi && !list_empty(lsthead);) { |
| struct epitem *epi = list_entry(lsthead->next, struct epitem, rdllink); |
| |
| /* Remove the item from the ready list */ |
| EP_LIST_DEL(&epi->rdllink); |
| |
| /* |
| * We need to increase the usage count of the "struct epitem" because |
| * another thread might call EPOLL_CTL_DEL on this target and make the |
| * object to vanish underneath our nose. |
| */ |
| ep_use_epitem(epi); |
| |
| aepi[nepi++] = epi; |
| } |
| |
| write_unlock_irqrestore(&ep->lock, flags); |
| |
| return nepi; |
| } |
| |
| |
| /* |
| * This function is called without holding the "ep->lock" since the call to |
| * __copy_to_user() might sleep, and also f_op->poll() might reenable the IRQ |
| * because of the way poll() is traditionally implemented in Linux. |
| */ |
| static int ep_send_events(struct eventpoll *ep, struct epitem **aepi, int nepi, |
| struct epoll_event *events) |
| { |
| int i, eventcnt, eventbuf, revents; |
| struct epitem *epi; |
| struct epoll_event event[EP_MAX_BUF_EVENTS]; |
| |
| for (i = 0, eventcnt = 0, eventbuf = 0; i < nepi; i++, aepi++) { |
| epi = *aepi; |
| |
| /* Get the ready file event set */ |
| revents = epi->file->f_op->poll(epi->file, NULL); |
| |
| if (revents & epi->event.events) { |
| event[eventbuf] = epi->event; |
| event[eventbuf].events &= revents; |
| eventbuf++; |
| if (eventbuf == EP_MAX_BUF_EVENTS) { |
| if (__copy_to_user(&events[eventcnt], event, |
| eventbuf * sizeof(struct epoll_event))) { |
| for (; i < nepi; i++, aepi++) |
| ep_release_epitem(*aepi); |
| return -EFAULT; |
| } |
| eventcnt += eventbuf; |
| eventbuf = 0; |
| } |
| } |
| |
| ep_release_epitem(epi); |
| } |
| |
| if (eventbuf) { |
| if (__copy_to_user(&events[eventcnt], event, |
| eventbuf * sizeof(struct epoll_event))) |
| return -EFAULT; |
| eventcnt += eventbuf; |
| } |
| |
| return eventcnt; |
| } |
| |
| |
| /* |
| * Perform the transfer of events to user space. |
| */ |
| static int ep_events_transfer(struct eventpoll *ep, struct epoll_event *events, int maxevents) |
| { |
| int eventcnt, nepi, sepi, maxepi; |
| struct epitem *aepi[EP_MAX_COLLECT_ITEMS]; |
| |
| /* |
| * We need to lock this because we could be hit by |
| * eventpoll_release() while we're transfering |
| * events to userspace. Read-holding "epsem" will lock |
| * out eventpoll_release() during the whole |
| * transfer loop and this will garantie us that the |
| * file will not vanish underneath our nose when |
| * we will call f_op->poll() from ep_send_events(). |
| */ |
| down_read(&epsem); |
| |
| for (eventcnt = 0; eventcnt < maxevents;) { |
| /* Maximum items we can extract this time */ |
| maxepi = min(EP_MAX_COLLECT_ITEMS, maxevents - eventcnt); |
| |
| /* Collect/extract ready items */ |
| nepi = ep_collect_ready_items(ep, aepi, maxepi); |
| |
| if (nepi) { |
| /* Send events to userspace */ |
| sepi = ep_send_events(ep, aepi, nepi, &events[eventcnt]); |
| if (sepi < 0) { |
| up_read(&epsem); |
| return sepi; |
| } |
| eventcnt += sepi; |
| } |
| |
| if (nepi < maxepi) |
| break; |
| } |
| |
| up_read(&epsem); |
| |
| return eventcnt; |
| } |
| |
| |
| static int ep_poll(struct eventpoll *ep, struct epoll_event *events, int maxevents, |
| int timeout) |
| { |
| int res, eavail; |
| unsigned long flags; |
| long jtimeout; |
| wait_queue_t wait; |
| |
| /* |
| * Calculate the timeout by checking for the "infinite" value ( -1 ). |
| * The passed timeout is in milliseconds, that why (t * HZ) / 1000. |
| */ |
| jtimeout = timeout == -1 ? MAX_SCHEDULE_TIMEOUT: (timeout * HZ) / 1000; |
| |
| retry: |
| write_lock_irqsave(&ep->lock, flags); |
| |
| res = 0; |
| if (list_empty(&ep->rdllist)) { |
| /* |
| * We don't have any available event to return to the caller. |
| * We need to sleep here, and we will be wake up by |
| * ep_poll_callback() when events will become available. |
| */ |
| init_waitqueue_entry(&wait, current); |
| add_wait_queue(&ep->wq, &wait); |
| |
| for (;;) { |
| /* |
| * We don't want to sleep if the ep_poll_callback() sends us |
| * a wakeup in between. That's why we set the task state |
| * to TASK_INTERRUPTIBLE before doing the checks. |
| */ |
| set_current_state(TASK_INTERRUPTIBLE); |
| if (!list_empty(&ep->rdllist) || !jtimeout) |
| break; |
| if (signal_pending(current)) { |
| res = -EINTR; |
| break; |
| } |
| |
| write_unlock_irqrestore(&ep->lock, flags); |
| jtimeout = schedule_timeout(jtimeout); |
| write_lock_irqsave(&ep->lock, flags); |
| } |
| remove_wait_queue(&ep->wq, &wait); |
| |
| set_current_state(TASK_RUNNING); |
| } |
| |
| /* Is it worth to try to dig for events ? */ |
| eavail = !list_empty(&ep->rdllist); |
| |
| write_unlock_irqrestore(&ep->lock, flags); |
| |
| /* |
| * Try to transfer events to user space. In case we get 0 events and |
| * there's still timeout left over, we go trying again in search of |
| * more luck. |
| */ |
| if (!res && eavail && |
| !(res = ep_events_transfer(ep, events, maxevents)) && jtimeout) |
| goto retry; |
| |
| return res; |
| } |
| |
| |
| static int eventpollfs_delete_dentry(struct dentry *dentry) |
| { |
| |
| return 1; |
| } |
| |
| |
| static struct inode *ep_eventpoll_inode(void) |
| { |
| int error = -ENOMEM; |
| struct inode *inode = new_inode(eventpoll_mnt->mnt_sb); |
| |
| if (!inode) |
| goto eexit_1; |
| |
| inode->i_fop = &eventpoll_fops; |
| |
| /* |
| * Mark the inode dirty from the very beginning, |
| * that way it will never be moved to the dirty |
| * list because mark_inode_dirty() will think |
| * that it already _is_ on the dirty list. |
| */ |
| inode->i_state = I_DIRTY; |
| inode->i_mode = S_IRUSR | S_IWUSR; |
| inode->i_uid = current->fsuid; |
| inode->i_gid = current->fsgid; |
| inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; |
| inode->i_blksize = PAGE_SIZE; |
| return inode; |
| |
| eexit_1: |
| return ERR_PTR(error); |
| } |
| |
| |
| static struct super_block *eventpollfs_get_sb(struct file_system_type *fs_type, |
| int flags, char *dev_name, void *data) |
| { |
| |
| return get_sb_pseudo(fs_type, "eventpoll:", NULL, EVENTPOLLFS_MAGIC); |
| } |
| |
| |
| static int __init eventpoll_init(void) |
| { |
| int error; |
| |
| /* Initialize the semaphore used to syncronize the file cleanup code */ |
| init_rwsem(&epsem); |
| |
| /* Initialize the structure used to perform safe poll wait head wake ups */ |
| ep_poll_safewake_init(&psw); |
| |
| /* Allocates slab cache used to allocate "struct epitem" items */ |
| error = -ENOMEM; |
| epi_cache = kmem_cache_create("eventpoll epi", |
| sizeof(struct epitem), |
| 0, |
| SLAB_HWCACHE_ALIGN | EPI_SLAB_DEBUG, NULL, NULL); |
| if (!epi_cache) |
| goto eexit_1; |
| |
| /* Allocates slab cache used to allocate "struct eppoll_entry" */ |
| error = -ENOMEM; |
| pwq_cache = kmem_cache_create("eventpoll pwq", |
| sizeof(struct eppoll_entry), |
| 0, |
| EPI_SLAB_DEBUG, NULL, NULL); |
| if (!pwq_cache) |
| goto eexit_2; |
| |
| /* |
| * Register the virtual file system that will be the source of inodes |
| * for the eventpoll files |
| */ |
| error = register_filesystem(&eventpoll_fs_type); |
| if (error) |
| goto eexit_3; |
| |
| /* Mount the above commented virtual file system */ |
| eventpoll_mnt = kern_mount(&eventpoll_fs_type); |
| error = PTR_ERR(eventpoll_mnt); |
| if (IS_ERR(eventpoll_mnt)) |
| goto eexit_4; |
| |
| DNPRINTK(3, (KERN_INFO "[%p] eventpoll: successfully initialized.\n", current)); |
| |
| return 0; |
| |
| eexit_4: |
| unregister_filesystem(&eventpoll_fs_type); |
| eexit_3: |
| kmem_cache_destroy(pwq_cache); |
| eexit_2: |
| kmem_cache_destroy(epi_cache); |
| eexit_1: |
| |
| return error; |
| } |
| |
| |
| static void __exit eventpoll_exit(void) |
| { |
| /* Undo all operations done inside eventpoll_init() */ |
| unregister_filesystem(&eventpoll_fs_type); |
| mntput(eventpoll_mnt); |
| kmem_cache_destroy(pwq_cache); |
| kmem_cache_destroy(epi_cache); |
| } |
| |
| module_init(eventpoll_init); |
| module_exit(eventpoll_exit); |
| |
| MODULE_LICENSE("GPL"); |
| |