/*
- * fs/eventpoll.c ( Efficent event polling implementation )
- * Copyright (C) 2001,...,2006 Davide Libenzi
+ * fs/eventpoll.c (Efficent event polling implementation)
+ * Copyright (C) 2001,...,2007 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
*
*/
-#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/sched.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/syscalls.h>
-#include <linux/rwsem.h>
#include <linux/rbtree.h>
#include <linux/wait.h>
#include <linux/eventpoll.h>
#include <linux/mount.h>
#include <linux/bitops.h>
#include <linux/mutex.h>
+#include <linux/anon_inodes.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#include <asm/io.h>
#include <asm/mman.h>
#include <asm/atomic.h>
-#include <asm/semaphore.h>
-
/*
* LOCKING:
* There are three level of locking required by epoll :
*
* 1) epmutex (mutex)
- * 2) ep->sem (rw_semaphore)
- * 3) ep->lock (rw_lock)
+ * 2) ep->mtx (mutex)
+ * 3) ep->lock (spinlock)
*
* The acquire order is the one listed above, from 1 to 3.
* We need a spinlock (ep->lock) because we manipulate objects
* a spinlock. During the event transfer loop (from kernel to
* user space) we could end up sleeping due a copy_to_user(), so
* we need a lock that will allow us to sleep. This lock is a
- * read-write semaphore (ep->sem). It is acquired on read during
- * the event transfer loop and in write during epoll_ctl(EPOLL_CTL_DEL)
- * and during eventpoll_release_file(). Then we also need a global
- * semaphore to serialize eventpoll_release_file() and ep_free().
- * This semaphore is acquired by ep_free() during the epoll file
+ * mutex (ep->mtx). It is acquired during the event transfer loop,
+ * during epoll_ctl(EPOLL_CTL_DEL) and during eventpoll_release_file().
+ * Then we also need a global mutex to serialize eventpoll_release_file()
+ * and ep_free().
+ * This mutex is acquired by ep_free() during the epoll file
* cleanup path and it is also acquired by eventpoll_release_file()
* if a file has been pushed inside an epoll set and it is then
* close()d without a previous call toepoll_ctl(EPOLL_CTL_DEL).
- * It is possible to drop the "ep->sem" and to use the global
- * semaphore "epmutex" (together with "ep->lock") to have it working,
- * but having "ep->sem" will make the interface more scalable.
+ * It is possible to drop the "ep->mtx" and to use the global
+ * mutex "epmutex" (together with "ep->lock") to have it working,
+ * but having "ep->mtx" will make the interface more scalable.
* Events that require holding "epmutex" are very rare, while for
- * normal operations the epoll private "ep->sem" will guarantee
- * a greater scalability.
+ * normal operations the epoll private "ep->mtx" will guarantee
+ * a better scalability.
*/
-
-#define EVENTPOLLFS_MAGIC 0x03111965 /* My birthday should work for this :) */
-
#define DEBUG_EPOLL 0
#if DEBUG_EPOLL > 0
/* Maximum msec timeout value storeable in a long int */
#define EP_MAX_MSTIMEO min(1000ULL * MAX_SCHEDULE_TIMEOUT / HZ, (LONG_MAX - 999ULL) / HZ)
+#define EP_MAX_EVENTS (INT_MAX / sizeof(struct epoll_event))
+
+#define EP_UNACTIVE_PTR ((void *) -1L)
struct epoll_filefd {
struct file *file;
* 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
+ * (loop) 2) allow a maximum number of epoll descriptors inclusion nesting
* 3) let go the ones coming from other tasks.
*/
struct wake_task_node {
spinlock_t lock;
};
+/*
+ * Each file descriptor added to the eventpoll interface will
+ * have an entry of this type linked to the "rbr" RB tree.
+ */
+struct epitem {
+ /* RB tree node used to link this structure to the eventpoll RB tree */
+ struct rb_node rbn;
+
+ /* List header used to link this structure to the eventpoll ready list */
+ struct list_head rdllink;
+
+ /*
+ * Works together "struct eventpoll"->ovflist in keeping the
+ * single linked chain of items.
+ */
+ struct epitem *next;
+
+ /* The file descriptor information this item refers to */
+ struct epoll_filefd ffd;
+
+ /* 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;
+
+ /* List header used to link this item to the "struct file" items list */
+ struct list_head fllink;
+
+ /* The structure that describe the interested events and the source fd */
+ struct epoll_event event;
+};
+
/*
* This structure is stored inside the "private_data" member of the file
* structure and rapresent the main data sructure for the eventpoll
*/
struct eventpoll {
/* Protect the this structure access */
- rwlock_t lock;
+ spinlock_t lock;
/*
- * This semaphore is used to ensure that files are not removed
- * while epoll is using them. This is read-held during the event
- * collection loop and it is write-held during the file cleanup
- * path, the epoll file exit code and the ctl operations.
+ * This mutex is used to ensure that files are not removed
+ * while epoll is using them. This is held during the event
+ * collection loop, the file cleanup path, the epoll file exit
+ * code and the ctl operations.
*/
- struct rw_semaphore sem;
+ struct mutex mtx;
/* Wait queue used by sys_epoll_wait() */
wait_queue_head_t wq;
/* List of ready file descriptors */
struct list_head rdllist;
- /* RB-Tree root used to store monitored fd structs */
+ /* RB tree root used to store monitored fd structs */
struct rb_root rbr;
+
+ /*
+ * This is a single linked list that chains all the "struct epitem" that
+ * happened while transfering ready events to userspace w/out
+ * holding ->lock.
+ */
+ struct epitem *ovflist;
};
/* Wait structure used by the poll hooks */
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 {
- /* RB-Tree node used to link this structure to the eventpoll rb-tree */
- struct rb_node rbn;
-
- /* List header used to link this structure to the eventpoll ready list */
- struct list_head rdllink;
-
- /* The file descriptor information this item refers to */
- struct epoll_filefd ffd;
-
- /* 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 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;
-
- /* List header used to link the item to the transfer list */
- struct list_head txlink;
-
- /*
- * This is used during the collection/transfer of events to userspace
- * to pin items empty events set.
- */
- unsigned int revents;
-};
-
/* 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 int ep_getfd(int *efd, struct inode **einode, struct file **efile,
- struct eventpoll *ep);
-static int ep_alloc(struct eventpoll **pep);
-static void ep_free(struct eventpoll *ep);
-static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd);
-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 void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi);
-static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
- struct file *tfile, int fd);
-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, void *key);
-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 list_head *txlist, int maxevents);
-static int ep_send_events(struct eventpoll *ep, struct list_head *txlist,
- struct epoll_event __user *events);
-static void ep_reinject_items(struct eventpoll *ep, struct list_head *txlist);
-static int ep_events_transfer(struct eventpoll *ep,
- struct epoll_event __user *events,
- int maxevents);
-static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
- int maxevents, long timeout);
-static int eventpollfs_delete_dentry(struct dentry *dentry);
-static struct inode *ep_eventpoll_inode(void);
-static int eventpollfs_get_sb(struct file_system_type *fs_type,
- int flags, const char *dev_name,
- void *data, struct vfsmount *mnt);
-
/*
- * This semaphore is used to serialize ep_free() and eventpoll_release_file().
+ * This mutex is used to serialize ep_free() and eventpoll_release_file().
*/
static struct mutex epmutex;
static struct poll_safewake psw;
/* Slab cache used to allocate "struct epitem" */
-static kmem_cache_t *epi_cache __read_mostly;
+static struct kmem_cache *epi_cache __read_mostly;
/* Slab cache used to allocate "struct eppoll_entry" */
-static kmem_cache_t *pwq_cache __read_mostly;
-
-/* Virtual fs used to allocate inodes for eventpoll files */
-static struct vfsmount *eventpoll_mnt __read_mostly;
-
-/* File callbacks that implement the eventpoll file behaviour */
-static const 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,
-};
-
+static struct kmem_cache *pwq_cache __read_mostly;
-/* Fast test to see if the file is an evenpoll file */
-static inline int is_file_epoll(struct file *f)
-{
- return f->f_op == &eventpoll_fops;
-}
-
-/* Setup the structure that is used as key for the rb-tree */
+/* Setup the structure that is used as key for the RB tree */
static inline void ep_set_ffd(struct epoll_filefd *ffd,
struct file *file, int fd)
{
ffd->fd = fd;
}
-/* Compare rb-tree keys */
+/* Compare RB tree keys */
static inline int ep_cmp_ffd(struct epoll_filefd *p1,
struct epoll_filefd *p2)
{
(p1->file < p2->file ? -1 : p1->fd - p2->fd));
}
-/* Special initialization for the rb-tree node to detect linkage */
+/* Special initialization for the RB tree node to detect linkage */
static inline void ep_rb_initnode(struct rb_node *n)
{
rb_set_parent(n, n);
}
-/* Removes a node from the rb-tree and marks it for a fast is-linked check */
+/* Removes a node from the RB tree and marks it for a fast is-linked check */
static inline void ep_rb_erase(struct rb_node *n, struct rb_root *r)
{
rb_erase(n, r);
rb_set_parent(n, n);
}
-/* Fast check to verify that the item is linked to the main rb-tree */
+/* Fast check to verify that the item is linked to the main RB tree */
static inline int ep_rb_linked(struct rb_node *n)
{
return rb_parent(n) != n;
}
-/*
- * Remove the item from the list and perform its initialization.
- * This is useful for us because we can test if the item is linked
- * using "ep_is_linked(p)".
- */
-static inline void ep_list_del(struct list_head *p)
-{
- list_del(p);
- INIT_LIST_HEAD(p);
-}
-
/* Tells us if the item is currently linked */
static inline int ep_is_linked(struct list_head *p)
{
}
/* Tells if the epoll_ctl(2) operation needs an event copy from userspace */
-static inline int ep_op_hash_event(int op)
+static inline int ep_op_has_event(int op)
{
return op != EPOLL_CTL_DEL;
}
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
int wake_nests = 0;
unsigned long flags;
struct task_struct *this_task = current;
- struct list_head *lsthead = &psw->wake_task_list, *lnk;
+ struct list_head *lsthead = &psw->wake_task_list;
struct wake_task_node *tncur;
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) {
- tncur = list_entry(lnk, struct wake_task_node, llink);
+ list_for_each_entry(tncur, lsthead, llink) {
if (tncur->wq == wq ||
(tncur->task == this_task && ++wake_nests > EP_MAX_POLLWAKE_NESTS)) {
spin_unlock_irqrestore(&psw->lock, flags);
/* Do really wake up now */
- wake_up(wq);
+ wake_up_nested(wq, 1 + wake_nests);
/* Remove the current task from the list */
spin_lock_irqsave(&psw->lock, flags);
spin_unlock_irqrestore(&psw->lock, flags);
}
-
/*
- * This is called from eventpoll_release() 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.
+ * 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.
*/
-void eventpoll_release_file(struct file *file)
+static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi)
{
- struct list_head *lsthead = &file->f_ep_links;
- struct eventpoll *ep;
- struct epitem *epi;
+ int nwait;
+ struct list_head *lsthead = &epi->pwqlist;
+ struct eppoll_entry *pwq;
- /*
- * 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. We do need to acquire
- * "ep->sem" after "epmutex" because ep_remove() requires it when called
- * from anywhere but ep_free().
- */
- mutex_lock(&epmutex);
+ /* This is called without locks, so we need the atomic exchange */
+ nwait = xchg(&epi->nwait, 0);
- while (!list_empty(lsthead)) {
- epi = list_entry(lsthead->next, struct epitem, fllink);
+ if (nwait) {
+ while (!list_empty(lsthead)) {
+ pwq = list_first_entry(lsthead, struct eppoll_entry, llink);
- ep = epi->ep;
- ep_list_del(&epi->fllink);
- down_write(&ep->sem);
- ep_remove(ep, epi);
- up_write(&ep->sem);
+ list_del_init(&pwq->llink);
+ remove_wait_queue(pwq->whead, &pwq->wait);
+ kmem_cache_free(pwq_cache, pwq);
+ }
}
-
- mutex_unlock(&epmutex);
}
-
/*
- * 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).
+ * Removes a "struct epitem" from the eventpoll RB tree and deallocates
+ * all the associated resources. Must be called with "mtx" held.
*/
-asmlinkage long sys_epoll_create(int size)
+static int ep_remove(struct eventpoll *ep, struct epitem *epi)
{
- int error, fd;
- struct eventpoll *ep;
- struct inode *inode;
- struct file *file;
-
- DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d)\n",
- current, size));
+ unsigned long flags;
+ struct file *file = epi->ffd.file;
/*
- * Sanity check on the size parameter, and create the internal data
- * structure ( "struct eventpoll" ).
+ * 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".
*/
- error = -EINVAL;
- if (size <= 0 || (error = ep_alloc(&ep)) != 0)
- goto eexit_1;
+ ep_unregister_pollwait(ep, epi);
- /*
- * 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, ep);
- if (error)
- goto eexit_2;
+ /* Remove the current item from the list of epoll hooks */
+ spin_lock(&file->f_ep_lock);
+ if (ep_is_linked(&epi->fllink))
+ list_del_init(&epi->fllink);
+ spin_unlock(&file->f_ep_lock);
- DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n",
- current, size, fd));
+ if (ep_rb_linked(&epi->rbn))
+ ep_rb_erase(&epi->rbn, &ep->rbr);
- return fd;
+ spin_lock_irqsave(&ep->lock, flags);
+ if (ep_is_linked(&epi->rdllink))
+ list_del_init(&epi->rdllink);
+ spin_unlock_irqrestore(&ep->lock, flags);
-eexit_2:
- ep_free(ep);
- kfree(ep);
-eexit_1:
- DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n",
- current, size, error));
- return error;
-}
+ /* At this point it is safe to free the eventpoll item */
+ kmem_cache_free(epi_cache, epi);
+ DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_remove(%p, %p)\n",
+ current, ep, file));
-/*
- * The following function implements the controller interface for
- * the eventpoll file that enables the insertion/removal/change of
- * file descriptors inside the interest set. It represents
- * the kernel part of the user space epoll_ctl(2).
- */
-asmlinkage long
-sys_epoll_ctl(int epfd, int op, int fd, struct epoll_event __user *event)
+ return 0;
+}
+
+static void ep_free(struct eventpoll *ep)
{
- int error;
- struct file *file, *tfile;
- struct eventpoll *ep;
+ struct rb_node *rbp;
struct epitem *epi;
- struct epoll_event epds;
-
- DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %p)\n",
- current, epfd, op, fd, event));
-
- error = -EFAULT;
- if (ep_op_hash_event(op) &&
- 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;
+ /* We need to release all tasks waiting for these file */
+ if (waitqueue_active(&ep->poll_wait))
+ ep_poll_safewake(&psw, &ep->poll_wait);
- /* The target file descriptor must support poll */
- error = -EPERM;
- if (!tfile->f_op || !tfile->f_op->poll)
- goto eexit_3;
+ /*
+ * We need to lock this because we could be hit by
+ * eventpoll_release_file() while we're freeing the "struct eventpoll".
+ * We do not need to hold "ep->mtx" here because the epoll file
+ * is on the way to be removed and no one has references to it
+ * anymore. The only hit might come from eventpoll_release_file() but
+ * holding "epmutex" is sufficent here.
+ */
+ mutex_lock(&epmutex);
/*
- * 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.
+ * Walks through the whole tree by unregistering poll callbacks.
*/
- error = -EINVAL;
- if (file == tfile || !is_file_epoll(file))
- goto eexit_3;
+ for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) {
+ epi = rb_entry(rbp, struct epitem, rbn);
+
+ ep_unregister_pollwait(ep, epi);
+ }
/*
- * At this point it is safe to assume that the "private_data" contains
- * our own data structure.
+ * Walks through the whole tree by freeing each "struct epitem". At this
+ * point we are sure no poll callbacks will be lingering around, and also by
+ * holding "epmutex" we can be sure that no file cleanup code will hit
+ * us during this operation. So we can avoid the lock on "ep->lock".
*/
- ep = file->private_data;
+ while ((rbp = rb_first(&ep->rbr)) != NULL) {
+ epi = rb_entry(rbp, struct epitem, rbn);
+ ep_remove(ep, epi);
+ }
- down_write(&ep->sem);
+ mutex_unlock(&epmutex);
+ mutex_destroy(&ep->mtx);
+ kfree(ep);
+}
- /* Try to lookup the file inside our hash table */
- epi = ep_find(ep, tfile, fd);
+static int ep_eventpoll_release(struct inode *inode, struct file *file)
+{
+ struct eventpoll *ep = file->private_data;
- error = -EINVAL;
- switch (op) {
- case EPOLL_CTL_ADD:
- if (!epi) {
- epds.events |= POLLERR | POLLHUP;
+ if (ep)
+ ep_free(ep);
- error = ep_insert(ep, &epds, tfile, fd);
- } 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);
-
- up_write(&ep->sem);
-
-eexit_3:
- fput(tfile);
-eexit_2:
- fput(file);
-eexit_1:
- DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %p) = %d\n",
- current, epfd, op, fd, event, error));
-
- return error;
+ DNPRINTK(3, (KERN_INFO "[%p] eventpoll: close() ep=%p\n", current, ep));
+ return 0;
}
-#define MAX_EVENTS (INT_MAX / sizeof(struct epoll_event))
-
-/*
- * Implement the event wait interface for the eventpoll file. It is the kernel
- * part of the user space epoll_wait(2).
- */
-asmlinkage long sys_epoll_wait(int epfd, struct epoll_event __user *events,
- int maxevents, int timeout)
+static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait)
{
- 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 || maxevents > MAX_EVENTS)
- return -EINVAL;
-
- /* Verify that the area passed by the user is writeable */
- if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event))) {
- error = -EFAULT;
- goto eexit_1;
- }
-
- /* Get the "struct file *" for the eventpoll file */
- error = -EBADF;
- file = fget(epfd);
- if (!file)
- goto eexit_1;
+ unsigned int pollflags = 0;
+ unsigned long flags;
+ struct eventpoll *ep = file->private_data;
- /*
- * We have to check that the file structure underneath the fd
- * the user passed to us _is_ an eventpoll file.
- */
- error = -EINVAL;
- if (!is_file_epoll(file))
- goto eexit_2;
+ /* Insert inside our poll wait queue */
+ poll_wait(file, &ep->poll_wait, wait);
- /*
- * At this point it is safe to assume that the "private_data" contains
- * our own data structure.
- */
- ep = file->private_data;
+ /* Check our condition */
+ spin_lock_irqsave(&ep->lock, flags);
+ if (!list_empty(&ep->rdllist))
+ pollflags = POLLIN | POLLRDNORM;
+ spin_unlock_irqrestore(&ep->lock, flags);
- /* Time to fish for events ... */
- error = ep_poll(ep, events, maxevents, timeout);
+ return pollflags;
+}
-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));
+/* File callbacks that implement the eventpoll file behaviour */
+static const struct file_operations eventpoll_fops = {
+ .release = ep_eventpoll_release,
+ .poll = ep_eventpoll_poll
+};
- return error;
+/* Fast test to see if the file is an evenpoll file */
+static inline int is_file_epoll(struct file *f)
+{
+ return f->f_op == &eventpoll_fops;
}
-
/*
- * Creates the file descriptor to be used by the epoll interface.
+ * This is called from eventpoll_release() 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.
*/
-static int ep_getfd(int *efd, struct inode **einode, struct file **efile,
- struct eventpoll *ep)
+void eventpoll_release_file(struct file *file)
{
- 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;
+ struct list_head *lsthead = &file->f_ep_links;
+ struct eventpoll *ep;
+ struct epitem *epi;
/*
- * Link the inode to a directory entry by creating a unique name
- * using the inode number.
+ * 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.
+ * So, for example, epoll_ctl() cannot hit here sicne if we reach this
+ * point, the file counter already went to zero and fget() would fail.
+ * The only hit might come from ep_free() but by holding the mutex
+ * will correctly serialize the operation. We do need to acquire
+ * "ep->mtx" after "epmutex" because ep_remove() requires it when called
+ * from anywhere but ep_free().
*/
- 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 = dentry;
- file->f_mapping = inode->i_mapping;
-
- 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 = ep;
-
- /* Install the new setup file into the allocated fd. */
- fd_install(fd, file);
-
- *efd = fd;
- *einode = inode;
- *efile = file;
- return 0;
+ mutex_lock(&epmutex);
-eexit_4:
- put_unused_fd(fd);
-eexit_3:
- iput(inode);
-eexit_2:
- put_filp(file);
-eexit_1:
- return error;
-}
+ while (!list_empty(lsthead)) {
+ epi = list_first_entry(lsthead, struct epitem, fllink);
+
+ ep = epi->ep;
+ list_del_init(&epi->fllink);
+ mutex_lock(&ep->mtx);
+ ep_remove(ep, epi);
+ mutex_unlock(&ep->mtx);
+ }
+ mutex_unlock(&epmutex);
+}
static int ep_alloc(struct eventpoll **pep)
{
if (!ep)
return -ENOMEM;
- rwlock_init(&ep->lock);
- init_rwsem(&ep->sem);
+ spin_lock_init(&ep->lock);
+ mutex_init(&ep->mtx);
init_waitqueue_head(&ep->wq);
init_waitqueue_head(&ep->poll_wait);
INIT_LIST_HEAD(&ep->rdllist);
ep->rbr = RB_ROOT;
+ ep->ovflist = EP_UNACTIVE_PTR;
*pep = ep;
return 0;
}
-
-static void ep_free(struct eventpoll *ep)
-{
- struct rb_node *rbp;
- struct epitem *epi;
-
- /* We need to release all tasks waiting for these file */
- if (waitqueue_active(&ep->poll_wait))
- ep_poll_safewake(&psw, &ep->poll_wait);
-
- /*
- * We need to lock this because we could be hit by
- * eventpoll_release_file() while we're freeing the "struct eventpoll".
- * We do not need to hold "ep->sem" here because the epoll file
- * is on the way to be removed and no one has references to it
- * anymore. The only hit might come from eventpoll_release_file() but
- * holding "epmutex" is sufficent here.
- */
- mutex_lock(&epmutex);
-
- /*
- * Walks through the whole tree by unregistering poll callbacks.
- */
- for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) {
- epi = rb_entry(rbp, struct epitem, rbn);
-
- 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 "sem" we can be sure that no file cleanup code will hit
- * us during this operation. So we can avoid the lock on "ep->lock".
- */
- while ((rbp = rb_first(&ep->rbr)) != 0) {
- epi = rb_entry(rbp, struct epitem, rbn);
- ep_remove(ep, epi);
- }
-
- mutex_unlock(&epmutex);
-}
-
-
/*
- * 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".
+ * Search the file inside the eventpoll tree. The RB tree operations
+ * are protected by the "mtx" mutex, and ep_find() must be called with
+ * "mtx" held.
*/
static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd)
{
int kcmp;
- unsigned long flags;
struct rb_node *rbp;
struct epitem *epi, *epir = NULL;
struct epoll_filefd ffd;
ep_set_ffd(&ffd, file, fd);
- read_lock_irqsave(&ep->lock, flags);
for (rbp = ep->rbr.rb_node; rbp; ) {
epi = rb_entry(rbp, struct epitem, rbn);
kcmp = ep_cmp_ffd(&ffd, &epi->ffd);
else if (kcmp < 0)
rbp = rbp->rb_left;
else {
- ep_use_epitem(epi);
epir = epi;
break;
}
}
- read_unlock_irqrestore(&ep->lock, flags);
DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_find(%p) -> %p\n",
current, file, epir));
return epir;
}
-
/*
- * Increment the usage count of the "struct epitem" making it sure
- * that the user will have a valid pointer to reference.
+ * 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 void ep_use_epitem(struct epitem *epi)
+static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *key)
{
+ int pwake = 0;
+ unsigned long flags;
+ struct epitem *epi = ep_item_from_wait(wait);
+ struct eventpoll *ep = epi->ep;
- atomic_inc(&epi->usecnt);
-}
+ DNPRINTK(3, (KERN_INFO "[%p] eventpoll: poll_callback(%p) epi=%p ep=%p\n",
+ current, epi->ffd.file, epi, ep));
+ spin_lock_irqsave(&ep->lock, flags);
-/*
- * 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 the event mask does not contain any poll(2) event, we consider the
+ * descriptor to be disabled. This condition is likely the effect of the
+ * EPOLLONESHOT bit that disables the descriptor when an event is received,
+ * until the next EPOLL_CTL_MOD will be issued.
+ */
+ if (!(epi->event.events & ~EP_PRIVATE_BITS))
+ goto out_unlock;
- if (atomic_dec_and_test(&epi->usecnt))
- kmem_cache_free(epi_cache, epi);
-}
+ /*
+ * If we are trasfering events to userspace, we can hold no locks
+ * (because we're accessing user memory, and because of linux f_op->poll()
+ * semantics). All the events that happens during that period of time are
+ * chained in ep->ovflist and requeued later on.
+ */
+ if (unlikely(ep->ovflist != EP_UNACTIVE_PTR)) {
+ if (epi->next == EP_UNACTIVE_PTR) {
+ epi->next = ep->ovflist;
+ ep->ovflist = epi;
+ }
+ goto out_unlock;
+ }
+ /* 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_locked(&ep->wq);
+ if (waitqueue_active(&ep->poll_wait))
+ pwake++;
+
+out_unlock:
+ spin_unlock_irqrestore(&ep->lock, flags);
+
+ /* We have to call this outside the lock */
+ if (pwake)
+ ep_poll_safewake(&psw, &ep->poll_wait);
+
+ return 1;
+}
/*
* This is the callback that is used to add our wait queue to the
struct epitem *epi = ep_item_from_epqueue(pt);
struct eppoll_entry *pwq;
- if (epi->nwait >= 0 && (pwq = kmem_cache_alloc(pwq_cache, SLAB_KERNEL))) {
+ if (epi->nwait >= 0 && (pwq = kmem_cache_alloc(pwq_cache, GFP_KERNEL))) {
init_waitqueue_func_entry(&pwq->wait, ep_poll_callback);
pwq->whead = whead;
pwq->base = epi;
}
}
-
static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi)
{
int kcmp;
rb_insert_color(&epi->rbn, &ep->rbr);
}
-
+/*
+ * Must be called with "mtx" held.
+ */
static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
struct file *tfile, int fd)
{
struct ep_pqueue epq;
error = -ENOMEM;
- if (!(epi = kmem_cache_alloc(epi_cache, SLAB_KERNEL)))
- goto eexit_1;
+ if (!(epi = kmem_cache_alloc(epi_cache, GFP_KERNEL)))
+ goto error_return;
/* Item initialization follow here ... */
ep_rb_initnode(&epi->rbn);
INIT_LIST_HEAD(&epi->rdllink);
INIT_LIST_HEAD(&epi->fllink);
- INIT_LIST_HEAD(&epi->txlink);
INIT_LIST_HEAD(&epi->pwqlist);
epi->ep = ep;
ep_set_ffd(&epi->ffd, tfile, fd);
epi->event = *event;
- atomic_set(&epi->usecnt, 1);
epi->nwait = 0;
+ epi->next = EP_UNACTIVE_PTR;
/* Initialize the poll table using the queue callback */
epq.epi = epi;
/*
* 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.
+ * been increased by the caller of this function. Note that after
+ * this operation completes, the poll callback can start hitting
+ * the new item.
*/
revents = tfile->f_op->poll(tfile, &epq.pt);
* high memory pressure.
*/
if (epi->nwait < 0)
- goto eexit_2;
+ goto error_unregister;
/* 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 rb-tree */
+ /*
+ * Add the current item to the RB tree. All RB tree operations are
+ * protected by "mtx", and ep_insert() is called with "mtx" held.
+ */
ep_rbtree_insert(ep, epi);
+ /* We have to drop the new item inside our item list to keep track of it */
+ spin_lock_irqsave(&ep->lock, flags);
+
/* 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_locked(&ep->wq, TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE);
+ wake_up_locked(&ep->wq);
if (waitqueue_active(&ep->poll_wait))
pwake++;
}
- write_unlock_irqrestore(&ep->lock, flags);
+ spin_unlock_irqrestore(&ep->lock, flags);
/* We have to call this outside the lock */
if (pwake)
return 0;
-eexit_2:
+error_unregister:
ep_unregister_pollwait(ep, epi);
/*
* We need to do this because an event could have been arrived on some
- * allocated wait queue.
+ * allocated wait queue. Note that we don't care about the ep->ovflist
+ * list, since that is used/cleaned only inside a section bound by "mtx".
+ * And ep_insert() is called with "mtx" held.
*/
- write_lock_irqsave(&ep->lock, flags);
+ spin_lock_irqsave(&ep->lock, flags);
if (ep_is_linked(&epi->rdllink))
- ep_list_del(&epi->rdllink);
- write_unlock_irqrestore(&ep->lock, flags);
+ list_del_init(&epi->rdllink);
+ spin_unlock_irqrestore(&ep->lock, flags);
kmem_cache_free(epi_cache, epi);
-eexit_1:
+error_return:
return error;
}
-
/*
* Modify the interest event mask by dropping an event if the new mask
- * has a match in the current file status.
+ * has a match in the current file status. Must be called with "mtx" held.
*/
static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_event *event)
{
*/
revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL);
- write_lock_irqsave(&ep->lock, flags);
+ spin_lock_irqsave(&ep->lock, flags);
/* Copy the data member from inside the lock */
epi->event.data = event->data;
/*
- * If the item is not linked to the hash it means that it's on its
- * way toward the removal. Do nothing in this case.
+ * If the item is "hot" and it is not registered inside the ready
+ * list, push it inside.
*/
- if (ep_rb_linked(&epi->rbn)) {
- /*
- * If the item is "hot" and it is not registered inside the ready
- * list, push it inside. If the item is not "hot" and it is currently
- * registered inside the ready list, unlink it.
- */
- if (revents & event->events) {
- if (!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_locked(&ep->wq, TASK_UNINTERRUPTIBLE |
- TASK_INTERRUPTIBLE);
- if (waitqueue_active(&ep->poll_wait))
- pwake++;
- }
+ if (revents & event->events) {
+ if (!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_locked(&ep->wq);
+ if (waitqueue_active(&ep->poll_wait))
+ pwake++;
}
}
-
- write_unlock_irqrestore(&ep->lock, flags);
+ spin_unlock_irqrestore(&ep->lock, flags);
/* We have to call this outside the lock */
if (pwake)
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)
+static int ep_send_events(struct eventpoll *ep, struct epoll_event __user *events,
+ int maxevents)
{
- int nwait;
- struct list_head *lsthead = &epi->pwqlist;
- struct eppoll_entry *pwq;
+ int eventcnt, error = -EFAULT, pwake = 0;
+ unsigned int revents;
+ unsigned long flags;
+ struct epitem *epi, *nepi;
+ struct list_head txlist;
- /* This is called without locks, so we need the atomic exchange */
- nwait = xchg(&epi->nwait, 0);
+ INIT_LIST_HEAD(&txlist);
- 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);
- kmem_cache_free(pwq_cache, 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_rb_linked(&epi->rbn))
- goto eexit_1;
-
- /*
- * Clear the event mask for the unlinked item. This will avoid item
- * notifications to be sent after the unlink operation from inside
- * the kernel->userspace event transfer loop.
- */
- epi->event.events = 0;
-
- /*
- * At this point is safe to do the job, unlink the item from our rb-tree.
- * This operation togheter with the above check closes the door to
- * double unlinks.
- */
- ep_rb_erase(&epi->rbn, &ep->rbr);
-
- /*
- * 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->ffd.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;
- struct file *file = epi->ffd.file;
-
- /*
- * 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(&file->f_ep_lock);
- if (ep_is_linked(&epi->fllink))
- ep_list_del(&epi->fllink);
- spin_unlock(&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, 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, void *key)
-{
- 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->ffd.file, epi, ep));
-
- write_lock_irqsave(&ep->lock, flags);
+ /*
+ * We need to lock this because we could be hit by
+ * eventpoll_release_file() and epoll_ctl(EPOLL_CTL_DEL).
+ */
+ mutex_lock(&ep->mtx);
/*
- * If the event mask does not contain any poll(2) event, we consider the
- * descriptor to be disabled. This condition is likely the effect of the
- * EPOLLONESHOT bit that disables the descriptor when an event is received,
- * until the next EPOLL_CTL_MOD will be issued.
+ * Steal the ready list, and re-init the original one to the
+ * empty list. Also, set ep->ovflist to NULL so that events
+ * happening while looping w/out locks, are not lost. We cannot
+ * have the poll callback to queue directly on ep->rdllist,
+ * because we are doing it in the loop below, in a lockless way.
*/
- if (!(epi->event.events & ~EP_PRIVATE_BITS))
- goto is_disabled;
-
- /* 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_locked(&ep->wq, TASK_UNINTERRUPTIBLE |
- TASK_INTERRUPTIBLE);
- if (waitqueue_active(&ep->poll_wait))
- pwake++;
-
-is_disabled:
- 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 list_head *txlist, int maxevents)
-{
- int nepi;
- unsigned long flags;
- struct list_head *lsthead = &ep->rdllist, *lnk;
- struct epitem *epi;
-
- write_lock_irqsave(&ep->lock, flags);
-
- for (nepi = 0, lnk = lsthead->next; lnk != lsthead && nepi < maxevents;) {
- epi = list_entry(lnk, struct epitem, rdllink);
-
- lnk = lnk->next;
-
- /* If this file is already in the ready list we exit soon */
- if (!ep_is_linked(&epi->txlink)) {
- /*
- * This is initialized in this way so that the default
- * behaviour of the reinjecting code will be to push back
- * the item inside the ready list.
- */
- epi->revents = epi->event.events;
-
- /* Link the ready item into the transfer list */
- list_add(&epi->txlink, txlist);
- nepi++;
-
- /*
- * Unlink the item from the ready list.
- */
- ep_list_del(&epi->rdllink);
- }
- }
-
- 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 list_head *txlist,
- struct epoll_event __user *events)
-{
- int eventcnt = 0;
- unsigned int revents;
- struct list_head *lnk;
- struct epitem *epi;
+ spin_lock_irqsave(&ep->lock, flags);
+ list_splice(&ep->rdllist, &txlist);
+ INIT_LIST_HEAD(&ep->rdllist);
+ ep->ovflist = NULL;
+ spin_unlock_irqrestore(&ep->lock, flags);
/*
* We can loop without lock because this is a task private list.
- * The test done during the collection loop will guarantee us that
- * another task will not try to collect this file. Also, items
- * cannot vanish during the loop because we are holding "sem".
+ * We just splice'd out the ep->rdllist in ep_collect_ready_items().
+ * Items cannot vanish during the loop because we are holding "mtx".
*/
- list_for_each(lnk, txlist) {
- epi = list_entry(lnk, struct epitem, txlink);
+ for (eventcnt = 0; !list_empty(&txlist) && eventcnt < maxevents;) {
+ epi = list_first_entry(&txlist, struct epitem, rdllink);
+
+ list_del_init(&epi->rdllink);
/*
* Get the ready file event set. We can safely use the file
- * because we are holding the "sem" in read and this will
- * guarantee that both the file and the item will not vanish.
+ * because we are holding the "mtx" and this will guarantee
+ * that both the file and the item will not vanish.
*/
revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL);
+ revents &= epi->event.events;
/*
- * Set the return event set for the current file descriptor.
- * Note that only the task task was successfully able to link
- * the item to its "txlist" will write this field.
+ * Is the event mask intersect the caller-requested one,
+ * deliver the event to userspace. Again, we are holding
+ * "mtx", so no operations coming from userspace can change
+ * the item.
*/
- epi->revents = revents & epi->event.events;
-
- if (epi->revents) {
- if (__put_user(epi->revents,
+ if (revents) {
+ if (__put_user(revents,
&events[eventcnt].events) ||
__put_user(epi->event.data,
&events[eventcnt].data))
- return -EFAULT;
+ goto errxit;
if (epi->event.events & EPOLLONESHOT)
epi->event.events &= EP_PRIVATE_BITS;
eventcnt++;
}
+ /*
+ * At this point, noone can insert into ep->rdllist besides
+ * us. The epoll_ctl() callers are locked out by us holding
+ * "mtx" and the poll callback will queue them in ep->ovflist.
+ */
+ if (!(epi->event.events & EPOLLET) &&
+ (revents & epi->event.events))
+ list_add_tail(&epi->rdllink, &ep->rdllist);
}
- return eventcnt;
-}
-
-
-/*
- * Walk through the transfer list we collected with ep_collect_ready_items()
- * and, if 1) the item is still "alive" 2) its event set is not empty 3) it's
- * not already linked, links it to the ready list. Same as above, we are holding
- * "sem" so items cannot vanish underneath our nose.
- */
-static void ep_reinject_items(struct eventpoll *ep, struct list_head *txlist)
-{
- int ricnt = 0, pwake = 0;
- unsigned long flags;
- struct epitem *epi;
-
- write_lock_irqsave(&ep->lock, flags);
-
- while (!list_empty(txlist)) {
- epi = list_entry(txlist->next, struct epitem, txlink);
+ error = 0;
- /* Unlink the current item from the transfer list */
- ep_list_del(&epi->txlink);
+errxit:
- /*
- * If the item is no more linked to the interest set, we don't
- * have to push it inside the ready list because the following
- * ep_release_epitem() is going to drop it. Also, if the current
- * item is set to have an Edge Triggered behaviour, we don't have
- * to push it back either.
- */
- if (ep_rb_linked(&epi->rbn) && !(epi->event.events & EPOLLET) &&
- (epi->revents & epi->event.events) && !ep_is_linked(&epi->rdllink)) {
+ spin_lock_irqsave(&ep->lock, flags);
+ /*
+ * During the time we spent in the loop above, some other events
+ * might have been queued by the poll callback. We re-insert them
+ * here (in case they are not already queued, or they're one-shot).
+ */
+ for (nepi = ep->ovflist; (epi = nepi) != NULL;
+ nepi = epi->next, epi->next = EP_UNACTIVE_PTR) {
+ if (!ep_is_linked(&epi->rdllink) &&
+ (epi->event.events & ~EP_PRIVATE_BITS))
list_add_tail(&epi->rdllink, &ep->rdllist);
- ricnt++;
- }
}
+ /*
+ * We need to set back ep->ovflist to EP_UNACTIVE_PTR, so that after
+ * releasing the lock, events will be queued in the normal way inside
+ * ep->rdllist.
+ */
+ ep->ovflist = EP_UNACTIVE_PTR;
+
+ /*
+ * In case of error in the event-send loop, or in case the number of
+ * ready events exceeds the userspace limit, we need to splice the
+ * "txlist" back inside ep->rdllist.
+ */
+ list_splice(&txlist, &ep->rdllist);
- if (ricnt) {
+ if (!list_empty(&ep->rdllist)) {
/*
- * Wake up ( if active ) both the eventpoll wait list and the ->poll()
- * wait list.
+ * Wake up (if active) both the eventpoll wait list and the ->poll()
+ * wait list (delayed after we release the lock).
*/
if (waitqueue_active(&ep->wq))
- __wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE |
- TASK_INTERRUPTIBLE);
+ wake_up_locked(&ep->wq);
if (waitqueue_active(&ep->poll_wait))
pwake++;
}
+ spin_unlock_irqrestore(&ep->lock, flags);
- write_unlock_irqrestore(&ep->lock, flags);
+ mutex_unlock(&ep->mtx);
/* We have to call this outside the lock */
if (pwake)
ep_poll_safewake(&psw, &ep->poll_wait);
-}
-
-/*
- * Perform the transfer of events to user space.
- */
-static int ep_events_transfer(struct eventpoll *ep,
- struct epoll_event __user *events, int maxevents)
-{
- int eventcnt = 0;
- struct list_head txlist;
-
- INIT_LIST_HEAD(&txlist);
-
- /*
- * We need to lock this because we could be hit by
- * eventpoll_release_file() and epoll_ctl(EPOLL_CTL_DEL).
- */
- down_read(&ep->sem);
-
- /* Collect/extract ready items */
- if (ep_collect_ready_items(ep, &txlist, maxevents) > 0) {
- /* Build result set in userspace */
- eventcnt = ep_send_events(ep, &txlist, events);
-
- /* Reinject ready items into the ready list */
- ep_reinject_items(ep, &txlist);
- }
-
- up_read(&ep->sem);
-
- return eventcnt;
+ return eventcnt == 0 ? error: eventcnt;
}
-
static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
int maxevents, long timeout)
{
MAX_SCHEDULE_TIMEOUT : (timeout * HZ + 999) / 1000;
retry:
- write_lock_irqsave(&ep->lock, flags);
+ spin_lock_irqsave(&ep->lock, flags);
res = 0;
if (list_empty(&ep->rdllist)) {
* ep_poll_callback() when events will become available.
*/
init_waitqueue_entry(&wait, current);
+ wait.flags |= WQ_FLAG_EXCLUSIVE;
__add_wait_queue(&ep->wq, &wait);
for (;;) {
break;
}
- write_unlock_irqrestore(&ep->lock, flags);
+ spin_unlock_irqrestore(&ep->lock, flags);
jtimeout = schedule_timeout(jtimeout);
- write_lock_irqsave(&ep->lock, flags);
+ spin_lock_irqsave(&ep->lock, flags);
}
__remove_wait_queue(&ep->wq, &wait);
/* Is it worth to try to dig for events ? */
eavail = !list_empty(&ep->rdllist);
- write_unlock_irqrestore(&ep->lock, flags);
+ spin_unlock_irqrestore(&ep->lock, flags);
/*
* Try to transfer events to user space. In case we get 0 events and
* more luck.
*/
if (!res && eavail &&
- !(res = ep_events_transfer(ep, events, maxevents)) && jtimeout)
+ !(res = ep_send_events(ep, events, maxevents)) && jtimeout)
goto retry;
return res;
}
-
-static int eventpollfs_delete_dentry(struct dentry *dentry)
+/*
+ * It opens an eventpoll file descriptor. The "size" parameter is there
+ * for historical reasons, when epoll was using an hash instead of an
+ * RB tree. With the current implementation, the "size" parameter is ignored
+ * (besides sanity checks).
+ */
+asmlinkage long sys_epoll_create(int size)
{
+ int error, fd = -1;
+ struct eventpoll *ep;
+ struct inode *inode;
+ struct file *file;
- return 1;
+ DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d)\n",
+ current, size));
+
+ /*
+ * Sanity check on the size parameter, and create the internal data
+ * structure ( "struct eventpoll" ).
+ */
+ error = -EINVAL;
+ if (size <= 0 || (error = ep_alloc(&ep)) != 0)
+ goto error_return;
+
+ /*
+ * Creates all the items needed to setup an eventpoll file. That is,
+ * a file structure, and inode and a free file descriptor.
+ */
+ error = anon_inode_getfd(&fd, &inode, &file, "[eventpoll]",
+ &eventpoll_fops, ep);
+ if (error)
+ goto error_free;
+
+ DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n",
+ current, size, fd));
+
+ return fd;
+
+error_free:
+ ep_free(ep);
+error_return:
+ DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n",
+ current, size, error));
+ return error;
}
+/*
+ * The following function implements the controller interface for
+ * the eventpoll file that enables the insertion/removal/change of
+ * file descriptors inside the interest set.
+ */
+asmlinkage long sys_epoll_ctl(int epfd, int op, int fd,
+ struct epoll_event __user *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, %p)\n",
+ current, epfd, op, fd, event));
+
+ error = -EFAULT;
+ if (ep_op_has_event(op) &&
+ copy_from_user(&epds, event, sizeof(struct epoll_event)))
+ goto error_return;
+
+ /* Get the "struct file *" for the eventpoll file */
+ error = -EBADF;
+ file = fget(epfd);
+ if (!file)
+ goto error_return;
+
+ /* Get the "struct file *" for the target file */
+ tfile = fget(fd);
+ if (!tfile)
+ goto error_fput;
+
+ /* The target file descriptor must support poll */
+ error = -EPERM;
+ if (!tfile->f_op || !tfile->f_op->poll)
+ goto error_tgt_fput;
+
+ /*
+ * 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 error_tgt_fput;
+
+ /*
+ * At this point it is safe to assume that the "private_data" contains
+ * our own data structure.
+ */
+ ep = file->private_data;
+
+ mutex_lock(&ep->mtx);
+
+ /*
+ * Try to lookup the file inside our RB tree, Since we grabbed "mtx"
+ * above, we can be sure to be able to use the item looked up by
+ * ep_find() till we release the mutex.
+ */
+ epi = ep_find(ep, tfile, fd);
+
+ error = -EINVAL;
+ switch (op) {
+ case EPOLL_CTL_ADD:
+ if (!epi) {
+ epds.events |= POLLERR | POLLHUP;
+
+ error = ep_insert(ep, &epds, tfile, fd);
+ } 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;
+ }
+ mutex_unlock(&ep->mtx);
+
+error_tgt_fput:
+ fput(tfile);
+error_fput:
+ fput(file);
+error_return:
+ DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %p) = %d\n",
+ current, epfd, op, fd, event, error));
+
+ return error;
+}
-static struct inode *ep_eventpoll_inode(void)
+/*
+ * Implement the event wait interface for the eventpoll file. It is the kernel
+ * part of the user space epoll_wait(2).
+ */
+asmlinkage long sys_epoll_wait(int epfd, struct epoll_event __user *events,
+ int maxevents, int timeout)
{
- int error = -ENOMEM;
- struct inode *inode = new_inode(eventpoll_mnt->mnt_sb);
+ int error;
+ struct file *file;
+ struct eventpoll *ep;
- if (!inode)
- goto eexit_1;
+ 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 || maxevents > EP_MAX_EVENTS)
+ return -EINVAL;
- inode->i_fop = &eventpoll_fops;
+ /* Verify that the area passed by the user is writeable */
+ if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event))) {
+ error = -EFAULT;
+ goto error_return;
+ }
+
+ /* Get the "struct file *" for the eventpoll file */
+ error = -EBADF;
+ file = fget(epfd);
+ if (!file)
+ goto error_return;
/*
- * 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.
+ * We have to check that the file structure underneath the fd
+ * the user passed to us _is_ an eventpoll file.
*/
- 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;
- return inode;
-
-eexit_1:
- return ERR_PTR(error);
+ error = -EINVAL;
+ if (!is_file_epoll(file))
+ goto error_fput;
+
+ /*
+ * 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);
+
+error_fput:
+ fput(file);
+error_return:
+ DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_wait(%d, %p, %d, %d) = %d\n",
+ current, epfd, events, maxevents, timeout, error));
+
+ return error;
}
+#ifdef TIF_RESTORE_SIGMASK
-static int
-eventpollfs_get_sb(struct file_system_type *fs_type, int flags,
- const char *dev_name, void *data, struct vfsmount *mnt)
+/*
+ * Implement the event wait interface for the eventpoll file. It is the kernel
+ * part of the user space epoll_pwait(2).
+ */
+asmlinkage long sys_epoll_pwait(int epfd, struct epoll_event __user *events,
+ int maxevents, int timeout, const sigset_t __user *sigmask,
+ size_t sigsetsize)
{
- return get_sb_pseudo(fs_type, "eventpoll:", NULL, EVENTPOLLFS_MAGIC,
- mnt);
+ int error;
+ sigset_t ksigmask, sigsaved;
+
+ /*
+ * If the caller wants a certain signal mask to be set during the wait,
+ * we apply it here.
+ */
+ if (sigmask) {
+ if (sigsetsize != sizeof(sigset_t))
+ return -EINVAL;
+ if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
+ return -EFAULT;
+ sigdelsetmask(&ksigmask, sigmask(SIGKILL) | sigmask(SIGSTOP));
+ sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
+ }
+
+ error = sys_epoll_wait(epfd, events, maxevents, timeout);
+
+ /*
+ * If we changed the signal mask, we need to restore the original one.
+ * In case we've got a signal while waiting, we do not restore the
+ * signal mask yet, and we allow do_signal() to deliver the signal on
+ * the way back to userspace, before the signal mask is restored.
+ */
+ if (sigmask) {
+ if (error == -EINTR) {
+ memcpy(¤t->saved_sigmask, &sigsaved,
+ sizeof(sigsaved));
+ set_thread_flag(TIF_RESTORE_SIGMASK);
+ } else
+ sigprocmask(SIG_SETMASK, &sigsaved, NULL);
+ }
+
+ return error;
}
+#endif /* #ifdef TIF_RESTORE_SIGMASK */
static int __init eventpoll_init(void)
{
- int error;
-
mutex_init(&epmutex);
/* Initialize the structure used to perform safe poll wait head wake ups */
/* Allocates slab cache used to allocate "struct epitem" items */
epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem),
0, SLAB_HWCACHE_ALIGN|EPI_SLAB_DEBUG|SLAB_PANIC,
- NULL, NULL);
+ NULL);
/* Allocates slab cache used to allocate "struct eppoll_entry" */
pwq_cache = kmem_cache_create("eventpoll_pwq",
sizeof(struct eppoll_entry), 0,
- EPI_SLAB_DEBUG|SLAB_PANIC, NULL, NULL);
-
- /*
- * 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 epanic;
-
- /* 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 epanic;
+ EPI_SLAB_DEBUG|SLAB_PANIC, NULL);
- DNPRINTK(3, (KERN_INFO "[%p] eventpoll: successfully initialized.\n",
- current));
return 0;
-
-epanic:
- panic("eventpoll_init() failed\n");
-}
-
-
-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);
}
+fs_initcall(eventpoll_init);
-module_init(eventpoll_init);
-module_exit(eventpoll_exit);
-
-MODULE_LICENSE("GPL");
Code Review / linux-2.6.git / blobdiff