diff options
Diffstat (limited to 'fs/eventpoll.c')
| -rw-r--r-- | fs/eventpoll.c | 626 |
1 files changed, 346 insertions, 280 deletions
diff --git a/fs/eventpoll.c b/fs/eventpoll.c index 011b9b8c90c6..a89f370fadb5 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -1,6 +1,6 @@ /* - * fs/eventpoll.c (Efficent event polling implementation) - * Copyright (C) 2001,...,2007 Davide Libenzi + * fs/eventpoll.c (Efficient event retrieval implementation) + * Copyright (C) 2001,...,2009 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 @@ -71,29 +71,11 @@ * a better scalability. */ -#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 */ - /* Epoll private bits inside the event mask */ #define EP_PRIVATE_BITS (EPOLLONESHOT | EPOLLET) -/* Maximum number of poll wake up nests we are allowing */ -#define EP_MAX_POLLWAKE_NESTS 4 +/* Maximum number of nesting allowed inside epoll sets */ +#define EP_MAX_NESTS 4 /* Maximum msec timeout value storeable in a long int */ #define EP_MAX_MSTIMEO min(1000ULL * MAX_SCHEDULE_TIMEOUT / HZ, (LONG_MAX - 999ULL) / HZ) @@ -110,24 +92,21 @@ struct epoll_filefd { }; /* - * 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. + * Structure used to track possible nested calls, for too deep recursions + * and loop cycles. */ -struct wake_task_node { +struct nested_call_node { struct list_head llink; - struct task_struct *task; - wait_queue_head_t *wq; + void *cookie; + int cpu; }; /* - * This is used to implement the safe poll wake up avoiding to reenter - * the poll callback from inside wake_up(). + * This structure is used as collector for nested calls, to check for + * maximum recursion dept and loop cycles. */ -struct poll_safewake { - struct list_head wake_task_list; +struct nested_calls { + struct list_head tasks_call_list; spinlock_t lock; }; @@ -213,7 +192,7 @@ struct eppoll_entry { struct list_head llink; /* The "base" pointer is set to the container "struct epitem" */ - void *base; + struct epitem *base; /* * Wait queue item that will be linked to the target file wait @@ -231,6 +210,12 @@ struct ep_pqueue { struct epitem *epi; }; +/* Used by the ep_send_events() function as callback private data */ +struct ep_send_events_data { + int maxevents; + struct epoll_event __user *events; +}; + /* * Configuration options available inside /proc/sys/fs/epoll/ */ @@ -242,8 +227,11 @@ static int max_user_watches __read_mostly; */ static DEFINE_MUTEX(epmutex); -/* Safe wake up implementation */ -static struct poll_safewake psw; +/* Used for safe wake up implementation */ +static struct nested_calls poll_safewake_ncalls; + +/* Used to call file's f_op->poll() under the nested calls boundaries */ +static struct nested_calls poll_readywalk_ncalls; /* Slab cache used to allocate "struct epitem" */ static struct kmem_cache *epi_cache __read_mostly; @@ -312,89 +300,230 @@ static inline int ep_op_has_event(int op) } /* Initialize the poll safe wake up structure */ -static void ep_poll_safewake_init(struct poll_safewake *psw) +static void ep_nested_calls_init(struct nested_calls *ncalls) { - - INIT_LIST_HEAD(&psw->wake_task_list); - spin_lock_init(&psw->lock); + INIT_LIST_HEAD(&ncalls->tasks_call_list); + spin_lock_init(&ncalls->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. +/** + * ep_call_nested - Perform a bound (possibly) nested call, by checking + * that the recursion limit is not exceeded, and that + * the same nested call (by the meaning of same cookie) is + * no re-entered. + * + * @ncalls: Pointer to the nested_calls structure to be used for this call. + * @max_nests: Maximum number of allowed nesting calls. + * @nproc: Nested call core function pointer. + * @priv: Opaque data to be passed to the @nproc callback. + * @cookie: Cookie to be used to identify this nested call. + * + * Returns: Returns the code returned by the @nproc callback, or -1 if + * the maximum recursion limit has been exceeded. */ -static void ep_poll_safewake(struct poll_safewake *psw, wait_queue_head_t *wq) +static int ep_call_nested(struct nested_calls *ncalls, int max_nests, + int (*nproc)(void *, void *, int), void *priv, + void *cookie) { - int wake_nests = 0; + int error, call_nests = 0; unsigned long flags; - struct task_struct *this_task = current; - struct list_head *lsthead = &psw->wake_task_list; - struct wake_task_node *tncur; - struct wake_task_node tnode; + int this_cpu = get_cpu(); + struct list_head *lsthead = &ncalls->tasks_call_list; + struct nested_call_node *tncur; + struct nested_call_node tnode; - spin_lock_irqsave(&psw->lock, flags); + spin_lock_irqsave(&ncalls->lock, flags); - /* Try to see if the current task is already inside this wakeup call */ + /* + * Try to see if the current task is already inside this wakeup call. + * We use a list here, since the population inside this set is always + * very much limited. + */ list_for_each_entry(tncur, lsthead, llink) { - - if (tncur->wq == wq || - (tncur->task == this_task && ++wake_nests > EP_MAX_POLLWAKE_NESTS)) { + if (tncur->cpu == this_cpu && + (tncur->cookie == cookie || ++call_nests > max_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; + error = -1; + goto out_unlock; } } - /* Add the current task to the list */ - tnode.task = this_task; - tnode.wq = wq; + /* Add the current task and cookie to the list */ + tnode.cpu = this_cpu; + tnode.cookie = cookie; list_add(&tnode.llink, lsthead); - spin_unlock_irqrestore(&psw->lock, flags); + spin_unlock_irqrestore(&ncalls->lock, flags); - /* Do really wake up now */ - wake_up_nested(wq, 1 + wake_nests); + /* Call the nested function */ + error = (*nproc)(priv, cookie, call_nests); /* Remove the current task from the list */ - spin_lock_irqsave(&psw->lock, flags); + spin_lock_irqsave(&ncalls->lock, flags); list_del(&tnode.llink); - spin_unlock_irqrestore(&psw->lock, flags); + out_unlock: + spin_unlock_irqrestore(&ncalls->lock, flags); + + put_cpu(); + return error; +} + +#ifdef CONFIG_DEBUG_LOCK_ALLOC +static inline void ep_wake_up_nested(wait_queue_head_t *wqueue, + unsigned long events, int subclass) +{ + unsigned long flags; + + spin_lock_irqsave_nested(&wqueue->lock, flags, subclass); + wake_up_locked_poll(wqueue, events); + spin_unlock_irqrestore(&wqueue->lock, flags); +} +#else +static inline void ep_wake_up_nested(wait_queue_head_t *wqueue, + unsigned long events, int subclass) +{ + wake_up_poll(wqueue, events); +} +#endif + +static int ep_poll_wakeup_proc(void *priv, void *cookie, int call_nests) +{ + ep_wake_up_nested((wait_queue_head_t *) cookie, POLLIN, + 1 + call_nests); + return 0; +} + +/* + * 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_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_NESTS deep. + */ +static void ep_poll_safewake(wait_queue_head_t *wq) +{ + ep_call_nested(&poll_safewake_ncalls, EP_MAX_NESTS, + ep_poll_wakeup_proc, NULL, wq); } /* - * 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. + * This function unregisters poll callbacks from the associated file + * descriptor. Must be called with "mtx" held (or "epmutex" if called from + * ep_free). */ 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); + while (!list_empty(lsthead)) { + pwq = list_first_entry(lsthead, struct eppoll_entry, llink); - if (nwait) { - while (!list_empty(lsthead)) { - pwq = list_first_entry(lsthead, struct eppoll_entry, llink); + list_del(&pwq->llink); + remove_wait_queue(pwq->whead, &pwq->wait); + kmem_cache_free(pwq_cache, pwq); + } +} - list_del_init(&pwq->llink); - remove_wait_queue(pwq->whead, &pwq->wait); - kmem_cache_free(pwq_cache, pwq); - } +/** + * ep_scan_ready_list - Scans the ready list in a way that makes possible for + * the scan code, to call f_op->poll(). Also allows for + * O(NumReady) performance. + * + * @ep: Pointer to the epoll private data structure. + * @sproc: Pointer to the scan callback. + * @priv: Private opaque data passed to the @sproc callback. + * + * Returns: The same integer error code returned by the @sproc callback. + */ +static int ep_scan_ready_list(struct eventpoll *ep, + int (*sproc)(struct eventpoll *, + struct list_head *, void *), + void *priv) +{ + int error, pwake = 0; + unsigned long flags; + struct epitem *epi, *nepi; + LIST_HEAD(txlist); + + /* + * We need to lock this because we could be hit by + * eventpoll_release_file() and epoll_ctl(). + */ + mutex_lock(&ep->mtx); + + /* + * 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 want the "sproc" callback to be able to do it + * in a lockless way. + */ + spin_lock_irqsave(&ep->lock, flags); + list_splice_init(&ep->rdllist, &txlist); + ep->ovflist = NULL; + spin_unlock_irqrestore(&ep->lock, flags); + + /* + * Now call the callback function. + */ + error = (*sproc)(ep, &txlist, priv); + + spin_lock_irqsave(&ep->lock, flags); + /* + * During the time we spent inside the "sproc" callback, some + * other events might have been queued by the poll callback. + * We re-insert them inside the main ready-list here. + */ + for (nepi = ep->ovflist; (epi = nepi) != NULL; + nepi = epi->next, epi->next = EP_UNACTIVE_PTR) { + /* + * We need to check if the item is already in the list. + * During the "sproc" callback execution time, items are + * queued into ->ovflist but the "txlist" might already + * contain them, and the list_splice() below takes care of them. + */ + if (!ep_is_linked(&epi->rdllink)) + list_add_tail(&epi->rdllink, &ep->rdllist); + } + /* + * 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; + + /* + * Quickly re-inject items left on "txlist". + */ + list_splice(&txlist, &ep->rdllist); + + if (!list_empty(&ep->rdllist)) { + /* + * 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); + if (waitqueue_active(&ep->poll_wait)) + pwake++; } + spin_unlock_irqrestore(&ep->lock, flags); + + mutex_unlock(&ep->mtx); + + /* We have to call this outside the lock */ + if (pwake) + ep_poll_safewake(&ep->poll_wait); + + return error; } /* @@ -417,10 +546,10 @@ static int ep_remove(struct eventpoll *ep, struct epitem *epi) ep_unregister_pollwait(ep, epi); /* Remove the current item from the list of epoll hooks */ - spin_lock(&file->f_ep_lock); + spin_lock(&file->f_lock); if (ep_is_linked(&epi->fllink)) list_del_init(&epi->fllink); - spin_unlock(&file->f_ep_lock); + spin_unlock(&file->f_lock); rb_erase(&epi->rbn, &ep->rbr); @@ -434,9 +563,6 @@ static int ep_remove(struct eventpoll *ep, struct epitem *epi) atomic_dec(&ep->user->epoll_watches); - DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_remove(%p, %p)\n", - current, ep, file)); - return 0; } @@ -447,7 +573,7 @@ static void ep_free(struct eventpoll *ep) /* We need to release all tasks waiting for these file */ if (waitqueue_active(&ep->poll_wait)) - ep_poll_safewake(&psw, &ep->poll_wait); + ep_poll_safewake(&ep->poll_wait); /* * We need to lock this because we could be hit by @@ -492,26 +618,54 @@ static int ep_eventpoll_release(struct inode *inode, struct file *file) if (ep) ep_free(ep); - DNPRINTK(3, (KERN_INFO "[%p] eventpoll: close() ep=%p\n", current, ep)); return 0; } +static int ep_read_events_proc(struct eventpoll *ep, struct list_head *head, + void *priv) +{ + struct epitem *epi, *tmp; + + list_for_each_entry_safe(epi, tmp, head, rdllink) { + if (epi->ffd.file->f_op->poll(epi->ffd.file, NULL) & + epi->event.events) + return POLLIN | POLLRDNORM; + else { + /* + * Item has been dropped into the ready list by the poll + * callback, but it's not actually ready, as far as + * caller requested events goes. We can remove it here. + */ + list_del_init(&epi->rdllink); + } + } + + return 0; +} + +static int ep_poll_readyevents_proc(void *priv, void *cookie, int call_nests) +{ + return ep_scan_ready_list(priv, ep_read_events_proc, NULL); +} + static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait) { - unsigned int pollflags = 0; - unsigned long flags; + int pollflags; struct eventpoll *ep = file->private_data; /* Insert inside our poll wait queue */ poll_wait(file, &ep->poll_wait, wait); - /* Check our condition */ - spin_lock_irqsave(&ep->lock, flags); - if (!list_empty(&ep->rdllist)) - pollflags = POLLIN | POLLRDNORM; - spin_unlock_irqrestore(&ep->lock, flags); + /* + * Proceed to find out if wanted events are really available inside + * the ready list. This need to be done under ep_call_nested() + * supervision, since the call to f_op->poll() done on listed files + * could re-enter here. + */ + pollflags = ep_call_nested(&poll_readywalk_ncalls, EP_MAX_NESTS, + ep_poll_readyevents_proc, ep, ep); - return pollflags; + return pollflags != -1 ? pollflags : 0; } /* File callbacks that implement the eventpoll file behaviour */ @@ -538,15 +692,17 @@ void eventpoll_release_file(struct file *file) struct epitem *epi; /* - * We don't want to get "file->f_ep_lock" because it is not + * We don't want to get "file->f_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 + * So, for example, epoll_ctl() cannot hit here since 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(). + * + * Besides, ep_remove() acquires the lock, so we can't hold it here. */ mutex_lock(&epmutex); @@ -586,8 +742,6 @@ static int ep_alloc(struct eventpoll **pep) *pep = ep; - DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_alloc() ep=%p\n", - current, ep)); return 0; free_uid: @@ -621,9 +775,6 @@ static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd) } } - DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_find(%p) -> %p\n", - current, file, epir)); - return epir; } @@ -639,9 +790,6 @@ static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *k 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)); - spin_lock_irqsave(&ep->lock, flags); /* @@ -654,6 +802,15 @@ static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *k goto out_unlock; /* + * Check the events coming with the callback. At this stage, not + * every device reports the events in the "key" parameter of the + * callback. We need to be able to handle both cases here, hence the + * test for "key" != NULL before the event match test. + */ + if (key && !((unsigned long) key & epi->event.events)) + goto out_unlock; + + /* * 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 @@ -668,12 +825,9 @@ static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *k } /* 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); + if (!ep_is_linked(&epi->rdllink)) + list_add_tail(&epi->rdllink, &ep->rdllist); -is_linked: /* * Wake up ( if active ) both the eventpoll wait list and the ->poll() * wait list. @@ -688,7 +842,7 @@ out_unlock: /* We have to call this outside the lock */ if (pwake) - ep_poll_safewake(&psw, &ep->poll_wait); + ep_poll_safewake(&ep->poll_wait); return 1; } @@ -785,9 +939,9 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event, goto error_unregister; /* Add the current item to the list of active epoll hook for this file */ - spin_lock(&tfile->f_ep_lock); + spin_lock(&tfile->f_lock); list_add_tail(&epi->fllink, &tfile->f_ep_links); - spin_unlock(&tfile->f_ep_lock); + spin_unlock(&tfile->f_lock); /* * Add the current item to the RB tree. All RB tree operations are @@ -815,10 +969,7 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event, /* 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, %d)\n", - current, ep, tfile, fd)); + ep_poll_safewake(&ep->poll_wait); return 0; @@ -849,15 +1000,14 @@ static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_even { 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. + * Set the new event interest mask before calling f_op->poll(); + * otherwise we might miss an event that happens between the + * f_op->poll() call and the new event set registering. */ epi->event.events = event->events; + epi->event.data = event->data; /* protected by mtx */ /* * Get current event bits. We can safely use the file* here because @@ -865,16 +1015,12 @@ static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_even */ revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL); - spin_lock_irqsave(&ep->lock, flags); - - /* Copy the data member from inside the lock */ - epi->event.data = event->data; - /* * If the item is "hot" and it is not registered inside the ready * list, push it inside. */ if (revents & event->events) { + spin_lock_irq(&ep->lock); if (!ep_is_linked(&epi->rdllink)) { list_add_tail(&epi->rdllink, &ep->rdllist); @@ -884,142 +1030,84 @@ static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_even if (waitqueue_active(&ep->poll_wait)) pwake++; } + spin_unlock_irq(&ep->lock); } - spin_unlock_irqrestore(&ep->lock, flags); /* We have to call this outside the lock */ if (pwake) - ep_poll_safewake(&psw, &ep->poll_wait); + ep_poll_safewake(&ep->poll_wait); return 0; } -static int ep_send_events(struct eventpoll *ep, struct epoll_event __user *events, - int maxevents) +static int ep_send_events_proc(struct eventpoll *ep, struct list_head *head, + void *priv) { - int eventcnt, error = -EFAULT, pwake = 0; + struct ep_send_events_data *esed = priv; + int eventcnt; unsigned int revents; - unsigned long flags; - struct epitem *epi, *nepi; - 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). - */ - mutex_lock(&ep->mtx); - - /* - * 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. - */ - 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); + struct epitem *epi; + struct epoll_event __user *uevent; /* - * We can loop without lock because this is a task private list. - * We just splice'd out the ep->rdllist in ep_collect_ready_items(). - * Items cannot vanish during the loop because we are holding "mtx". + * We can loop without lock because we are passed a task private list. + * Items cannot vanish during the loop because ep_scan_ready_list() is + * holding "mtx" during this call. */ - for (eventcnt = 0; !list_empty(&txlist) && eventcnt < maxevents;) { - epi = list_first_entry(&txlist, struct epitem, rdllink); + for (eventcnt = 0, uevent = esed->events; + !list_empty(head) && eventcnt < esed->maxevents;) { + epi = list_first_entry(head, 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 "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; + revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL) & + epi->event.events; /* - * 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. + * If the event mask intersect the caller-requested one, + * deliver the event to userspace. Again, ep_scan_ready_list() + * is holding "mtx", so no operations coming from userspace + * can change the item. */ if (revents) { - if (__put_user(revents, - &events[eventcnt].events) || - __put_user(epi->event.data, - &events[eventcnt].data)) - goto errxit; + if (__put_user(revents, &uevent->events) || + __put_user(epi->event.data, &uevent->data)) { + list_add(&epi->rdllink, head); + return eventcnt ? eventcnt : -EFAULT; + } + eventcnt++; + uevent++; if (epi->event.events & EPOLLONESHOT) epi->event.events &= EP_PRIVATE_BITS; - eventcnt++; + else if (!(epi->event.events & EPOLLET)) { + /* + * If this file has been added with Level + * Trigger mode, we need to insert back inside + * the ready list, so that the next call to + * epoll_wait() will check again the events + * availability. At this point, noone can insert + * into ep->rdllist besides us. The epoll_ctl() + * callers are locked out by + * ep_scan_ready_list() holding "mtx" and the + * poll callback will queue them in ep->ovflist. + */ + list_add_tail(&epi->rdllink, &ep->rdllist); + } } - /* - * 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); - } - error = 0; - -errxit: - - 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 - * inside the main ready-list here. - */ - for (nepi = ep->ovflist; (epi = nepi) != NULL; - nepi = epi->next, epi->next = EP_UNACTIVE_PTR) { - /* - * If the above loop quit with errors, the epoll item might still - * be linked to "txlist", and the list_splice() done below will - * take care of those cases. - */ - if (!ep_is_linked(&epi->rdllink)) - list_add_tail(&epi->rdllink, &ep->rdllist); } - /* - * 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 (!list_empty(&ep->rdllist)) { - /* - * 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); - if (waitqueue_active(&ep->poll_wait)) - pwake++; - } - spin_unlock_irqrestore(&ep->lock, flags); + return eventcnt; +} - mutex_unlock(&ep->mtx); +static int ep_send_events(struct eventpoll *ep, + struct epoll_event __user *events, int maxevents) +{ + struct ep_send_events_data esed; - /* We have to call this outside the lock */ - if (pwake) - ep_poll_safewake(&psw, &ep->poll_wait); + esed.maxevents = maxevents; + esed.events = events; - return eventcnt == 0 ? error: eventcnt; + return ep_scan_ready_list(ep, ep_send_events_proc, &esed); } static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, @@ -1031,7 +1119,7 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, wait_queue_t wait; /* - * Calculate the timeout by checking for the "infinite" value ( -1 ) + * Calculate the timeout by checking for the "infinite" value (-1) * and the overflow condition. The passed timeout is in milliseconds, * that why (t * HZ) / 1000. */ @@ -1074,9 +1162,8 @@ retry: set_current_state(TASK_RUNNING); } - /* Is it worth to try to dig for events ? */ - eavail = !list_empty(&ep->rdllist); + eavail = !list_empty(&ep->rdllist) || ep->ovflist != EP_UNACTIVE_PTR; spin_unlock_irqrestore(&ep->lock, flags); @@ -1097,41 +1184,30 @@ retry: */ SYSCALL_DEFINE1(epoll_create1, int, flags) { - int error, fd = -1; - struct eventpoll *ep; + int error; + struct eventpoll *ep = NULL; /* Check the EPOLL_* constant for consistency. */ BUILD_BUG_ON(EPOLL_CLOEXEC != O_CLOEXEC); if (flags & ~EPOLL_CLOEXEC) return -EINVAL; - - DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d)\n", - current, flags)); - /* - * Create the internal data structure ( "struct eventpoll" ). + * Create the internal data structure ("struct eventpoll"). */ error = ep_alloc(&ep); - if (error < 0) { - fd = error; - goto error_return; - } - + if (error < 0) + return error; /* * Creates all the items needed to setup an eventpoll file. That is, * a file structure and a free file descriptor. */ - fd = anon_inode_getfd("[eventpoll]", &eventpoll_fops, ep, - flags & O_CLOEXEC); - if (fd < 0) + error = anon_inode_getfd("[eventpoll]", &eventpoll_fops, ep, + flags & O_CLOEXEC); + if (error < 0) ep_free(ep); -error_return: - DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n", - current, flags, fd)); - - return fd; + return error; } SYSCALL_DEFINE1(epoll_create, int, size) @@ -1156,9 +1232,6 @@ SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd, 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))) @@ -1209,7 +1282,6 @@ SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd, case EPOLL_CTL_ADD: if (!epi) { epds.events |= POLLERR | POLLHUP; - error = ep_insert(ep, &epds, tfile, fd); } else error = -EEXIST; @@ -1235,8 +1307,6 @@ error_tgt_fput: 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; } @@ -1252,9 +1322,6 @@ SYSCALL_DEFINE4(epoll_wait, int, epfd, struct epoll_event __user *, events, 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 > EP_MAX_EVENTS) return -EINVAL; @@ -1291,8 +1358,6 @@ SYSCALL_DEFINE4(epoll_wait, int, epfd, struct epoll_event __user *, events, 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; } @@ -1357,17 +1422,18 @@ static int __init eventpoll_init(void) EP_ITEM_COST; /* Initialize the structure used to perform safe poll wait head wake ups */ - ep_poll_safewake_init(&psw); + ep_nested_calls_init(&poll_safewake_ncalls); + + /* Initialize the structure used to perform file's f_op->poll() calls */ + ep_nested_calls_init(&poll_readywalk_ncalls); /* 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); + 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, 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); + sizeof(struct eppoll_entry), 0, SLAB_PANIC, NULL); return 0; } |