/*
* fs/eventpoll.c ( Efficent event polling implementation )
- * Copyright (C) 2001,...,2003 Davide Libenzi
+ * Copyright (C) 2001,...,2006 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
/* 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))
+
struct epoll_filefd {
struct file *file;
*/
struct wake_task_node {
struct list_head llink;
- task_t *task;
+ struct task_struct *task;
wait_queue_head_t *wq;
};
/*
* Each file descriptor added to the eventpoll interface will
- * have an entry of this type linked to the hash.
+ * 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 */
/* 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 */
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);
+ struct epoll_event __user *events, int maxevents);
static int ep_events_transfer(struct eventpoll *ep,
struct epoll_event __user *events,
int maxevents);
int maxevents, long 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, const char *dev_name,
- void *data);
+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().
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;
+static struct kmem_cache *pwq_cache __read_mostly;
/* Virtual fs used to allocate inodes for eventpoll files */
static struct vfsmount *eventpoll_mnt __read_mostly;
/* Special initialization for the rb-tree node to detect linkage */
static inline void ep_rb_initnode(struct rb_node *n)
{
- n->rb_parent = n;
+ rb_set_parent(n, n);
}
/* 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);
- n->rb_parent = n;
+ rb_set_parent(n, n);
}
/* 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 n->rb_parent != 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);
+ return rb_parent(n) != n;
}
/* Tells us if the item is currently linked */
}
/* 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;
}
{
int wake_nests = 0;
unsigned long flags;
- task_t *this_task = current;
+ struct task_struct *this_task = current;
struct list_head *lsthead = &psw->wake_task_list, *lnk;
struct wake_task_node *tncur;
struct wake_task_node tnode;
epi = list_entry(lsthead->next, struct epitem, fllink);
ep = epi->ep;
- ep_list_del(&epi->fllink);
+ list_del_init(&epi->fllink);
down_write(&ep->sem);
ep_remove(ep, epi);
up_write(&ep->sem);
*/
asmlinkage long sys_epoll_create(int size)
{
- int error, fd;
+ int error, fd = -1;
struct eventpoll *ep;
struct inode *inode;
struct file *file;
current, epfd, op, fd, event));
error = -EFAULT;
- if (ep_op_hash_event(op) &&
+ if (ep_op_has_event(op) &&
copy_from_user(&epds, event, sizeof(struct epoll_event)))
goto eexit_1;
down_write(&ep->sem);
- /* Try to lookup the file inside our hash table */
+ /* Try to lookup the file inside our RB tree */
epi = ep_find(ep, tfile, fd);
error = -EINVAL;
return error;
}
-#define MAX_EVENTS (INT_MAX / sizeof(struct epoll_event))
/*
* Implement the event wait interface for the eventpoll file. It is the kernel
current, epfd, events, maxevents, timeout));
/* The maximum number of event must be greater than zero */
- if (maxevents <= 0 || maxevents > MAX_EVENTS)
+ if (maxevents <= 0 || maxevents > EP_MAX_EVENTS)
return -EINVAL;
/* Verify that the area passed by the user is writeable */
}
+#ifdef TIF_RESTORE_SIGMASK
+
+/*
+ * 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)
+{
+ 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 */
+
+
/*
* Creates the file descriptor to be used by the epoll interface.
*/
/* Allocates an inode from the eventpoll file system */
inode = ep_eventpoll_inode();
- error = PTR_ERR(inode);
- if (IS_ERR(inode))
+ if (IS_ERR(inode)) {
+ error = PTR_ERR(inode);
goto eexit_2;
+ }
/* Allocates a free descriptor to plug the file onto */
error = get_unused_fd();
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_path.mnt = mntget(eventpoll_mnt);
+ file->f_path.dentry = dentry;
file->f_mapping = inode->i_mapping;
file->f_pos = 0;
}
/*
- * Walks through the whole hash by freeing each "struct epitem". At this
+ * 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
* 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".
/*
- * Search the file inside the eventpoll hash. It add usage count to
+ * Search the file inside the eventpoll tree. It add usage count to
* the returned item, so the caller must call ep_release_epitem()
* after finished using the "struct epitem".
*/
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;
struct ep_pqueue epq;
error = -ENOMEM;
- if (!(epi = kmem_cache_alloc(epi_cache, SLAB_KERNEL)))
+ if (!(epi = kmem_cache_alloc(epi_cache, GFP_KERNEL)))
goto eexit_1;
/* 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);
/* Notify waiting tasks that events are available */
if (waitqueue_active(&ep->wq))
- wake_up(&ep->wq);
+ __wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE);
if (waitqueue_active(&ep->poll_wait))
pwake++;
}
*/
write_lock_irqsave(&ep->lock, flags);
if (ep_is_linked(&epi->rdllink))
- ep_list_del(&epi->rdllink);
+ list_del_init(&epi->rdllink);
write_unlock_irqrestore(&ep->lock, flags);
kmem_cache_free(epi_cache, epi);
epi->event.data = event->data;
/*
- * If the item is not linked to the hash it means that it's on its
+ * If the item is not linked to the RB tree it means that it's on its
* way toward the removal. Do nothing in this case.
*/
if (ep_rb_linked(&epi->rbn)) {
/* Notify waiting tasks that events are available */
if (waitqueue_active(&ep->wq))
- wake_up(&ep->wq);
+ __wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE |
+ TASK_INTERRUPTIBLE);
if (waitqueue_active(&ep->poll_wait))
pwake++;
}
while (!list_empty(lsthead)) {
pwq = list_entry(lsthead->next, struct eppoll_entry, llink);
- ep_list_del(&pwq->llink);
+ list_del_init(&pwq->llink);
remove_wait_queue(pwq->whead, &pwq->wait);
kmem_cache_free(pwq_cache, pwq);
}
* we want to remove it from this list to avoid stale events.
*/
if (ep_is_linked(&epi->rdllink))
- ep_list_del(&epi->rdllink);
+ list_del_init(&epi->rdllink);
error = 0;
eexit_1:
DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_unlink(%p, %p) = %d\n",
- current, ep, epi->file, error));
+ current, ep, epi->ffd.file, error));
return error;
}
/*
- * Removes a "struct epitem" from the eventpoll hash and deallocates
+ * Removes a "struct epitem" from the eventpoll RB tree and deallocates
* all the associated resources.
*/
static int ep_remove(struct eventpoll *ep, struct epitem *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);
+ list_del_init(&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 */
+ /* Really unlink the item from the RB tree */
error = ep_unlink(ep, epi);
write_unlock_irqrestore(&ep->lock, flags);
struct eventpoll *ep = epi->ep;
DNPRINTK(3, (KERN_INFO "[%p] eventpoll: poll_callback(%p) epi=%p ep=%p\n",
- current, epi->file, epi, ep));
+ current, epi->ffd.file, epi, ep));
write_lock_irqsave(&ep->lock, flags);
* wait list.
*/
if (waitqueue_active(&ep->wq))
- wake_up(&ep->wq);
+ __wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE |
+ TASK_INTERRUPTIBLE);
if (waitqueue_active(&ep->poll_wait))
pwake++;
}
-/*
- * 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)
+ struct epoll_event __user *events, int maxevents)
{
- int eventcnt = 0;
+ int eventcnt, error = -EFAULT, pwake = 0;
unsigned int revents;
- struct list_head *lnk;
+ unsigned long flags;
struct epitem *epi;
+ struct list_head injlist;
+
+ INIT_LIST_HEAD(&injlist);
/*
* 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 "sem" in
+ * read.
*/
- list_for_each(lnk, txlist) {
- epi = list_entry(lnk, struct epitem, txlink);
+ for (eventcnt = 0; !list_empty(txlist) && eventcnt < maxevents;) {
+ epi = list_entry(txlist->next, struct epitem, rdllink);
+ prefetch(epi->rdllink.next);
/*
* Get the ready file event set. We can safely use the file
* 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
+ * "sem" in read, 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++;
}
- }
- 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);
-
- /* Unlink the current item from the transfer list */
- ep_list_del(&epi->txlink);
/*
- * 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.
+ * This is tricky. We are holding the "sem" in read, and this
+ * means that the operations that can change the "linked" status
+ * of the epoll item (epi->rbn and epi->rdllink), cannot touch
+ * them. Also, since we are "linked" from a epi->rdllink POV
+ * (the item is linked to our transmission list we just
+ * spliced), the ep_poll_callback() cannot touch us either,
+ * because of the check present in there. Another parallel
+ * epoll_wait() will not get the same result set, since we
+ * spliced the ready list before. Note that list_del() still
+ * shows the item as linked to the test in ep_poll_callback().
*/
- if (ep_rb_linked(&epi->rbn) && !(epi->event.events & EPOLLET) &&
- (epi->revents & epi->event.events) && !ep_is_linked(&epi->rdllink)) {
- list_add_tail(&epi->rdllink, &ep->rdllist);
- ricnt++;
+ list_del(&epi->rdllink);
+ if (!(epi->event.events & EPOLLET) &&
+ (revents & epi->event.events))
+ list_add_tail(&epi->rdllink, &injlist);
+ else {
+ /*
+ * Be sure the item is totally detached before re-init
+ * the list_head. After INIT_LIST_HEAD() is committed,
+ * the ep_poll_callback() can requeue the item again,
+ * but we don't care since we are already past it.
+ */
+ smp_mb();
+ INIT_LIST_HEAD(&epi->rdllink);
}
}
+ error = 0;
- if (ricnt) {
+ errxit:
+
+ /*
+ * If the re-injection list or the txlist are not empty, re-splice
+ * them to the ready list and do proper wakeups.
+ */
+ if (!list_empty(&injlist) || !list_empty(txlist)) {
+ write_lock_irqsave(&ep->lock, flags);
+
+ list_splice(txlist, &ep->rdllist);
+ list_splice(&injlist, &ep->rdllist);
/*
* Wake up ( if active ) both the eventpoll wait list and the ->poll()
* wait list.
*/
if (waitqueue_active(&ep->wq))
- wake_up(&ep->wq);
+ __wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE |
+ TASK_INTERRUPTIBLE);
if (waitqueue_active(&ep->poll_wait))
pwake++;
- }
- write_unlock_irqrestore(&ep->lock, flags);
+ write_unlock_irqrestore(&ep->lock, flags);
+ }
/* We have to call this outside the lock */
if (pwake)
ep_poll_safewake(&psw, &ep->poll_wait);
+
+ return eventcnt == 0 ? error: eventcnt;
}
static int ep_events_transfer(struct eventpoll *ep,
struct epoll_event __user *events, int maxevents)
{
- int eventcnt = 0;
+ int eventcnt;
+ unsigned long flags;
struct list_head txlist;
INIT_LIST_HEAD(&txlist);
*/
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);
+ /*
+ * Steal the ready list, and re-init the original one to the
+ * empty list.
+ */
+ write_lock_irqsave(&ep->lock, flags);
+ list_splice(&ep->rdllist, &txlist);
+ INIT_LIST_HEAD(&ep->rdllist);
+ write_unlock_irqrestore(&ep->lock, flags);
- /* Reinject ready items into the ready list */
- ep_reinject_items(ep, &txlist);
- }
+ /* Build result set in userspace */
+ eventcnt = ep_send_events(ep, &txlist, events, maxevents);
up_read(&ep->sem);
* ep_poll_callback() when events will become available.
*/
init_waitqueue_entry(&wait, current);
- add_wait_queue(&ep->wq, &wait);
+ __add_wait_queue(&ep->wq, &wait);
for (;;) {
/*
jtimeout = schedule_timeout(jtimeout);
write_lock_irqsave(&ep->lock, flags);
}
- remove_wait_queue(&ep->wq, &wait);
+ __remove_wait_queue(&ep->wq, &wait);
set_current_state(TASK_RUNNING);
}
return res;
}
-
static int eventpollfs_delete_dentry(struct dentry *dentry)
{
return 1;
}
-
static struct inode *ep_eventpoll_inode(void)
{
int error = -ENOMEM;
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 *
+static int
eventpollfs_get_sb(struct file_system_type *fs_type, int flags,
- const char *dev_name, void *data)
+ const char *dev_name, void *data, struct vfsmount *mnt)
{
- return get_sb_pseudo(fs_type, "eventpoll:", NULL, EVENTPOLLFS_MAGIC);
+ return get_sb_pseudo(fs_type, "eventpoll:", NULL, EVENTPOLLFS_MAGIC,
+ mnt);
}
Code Review / linux-2.6.git / blobdiff