diff options
Diffstat (limited to 'fs/eventpoll.c')
| -rw-r--r-- | fs/eventpoll.c | 2623 |
1 files changed, 1545 insertions, 1078 deletions
diff --git a/fs/eventpoll.c b/fs/eventpoll.c index 4284cd31eba..b10b48c2a7a 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -1,6 +1,6 @@ /* - * fs/eventpoll.c ( Efficent event polling implementation ) - * Copyright (C) 2001,...,2003 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 @@ -11,7 +11,6 @@ * */ -#include <linux/module.h> #include <linux/init.h> #include <linux/kernel.h> #include <linux/sched.h> @@ -22,33 +21,35 @@ #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 <linux/device.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> - +#include <linux/atomic.h> +#include <linux/proc_fs.h> +#include <linux/seq_file.h> +#include <linux/compat.h> +#include <linux/rculist.h> /* * LOCKING: * There are three level of locking required by epoll : * - * 1) epsem (semaphore) - * 2) ep->sem (rw_semaphore) - * 3) ep->lock (rw_lock) + * 1) epmutex (mutex) + * 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 @@ -58,96 +59,135 @@ * 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 "epsem" (together with "ep->lock") to have it working, - * but having "ep->sem" will make the interface more scalable. - * Events that require holding "epsem" are very rare, while for - * normal operations the epoll private "ep->sem" will guarantee - * a greater scalability. + * close()d without a previous call to epoll_ctl(EPOLL_CTL_DEL). + * It is also acquired when inserting an epoll fd onto another epoll + * fd. We do this so that we walk the epoll tree and ensure that this + * insertion does not create a cycle of epoll file descriptors, which + * could lead to deadlock. We need a global mutex to prevent two + * simultaneous inserts (A into B and B into A) from racing and + * constructing a cycle without either insert observing that it is + * going to. + * It is necessary to acquire multiple "ep->mtx"es at once in the + * case when one epoll fd is added to another. In this case, we + * always acquire the locks in the order of nesting (i.e. after + * epoll_ctl(e1, EPOLL_CTL_ADD, e2), e1->mtx will always be acquired + * before e2->mtx). Since we disallow cycles of epoll file + * descriptors, this ensures that the mutexes are well-ordered. In + * order to communicate this nesting to lockdep, when walking a tree + * of epoll file descriptors, we use the current recursion depth as + * the lockdep subkey. + * 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->mtx" will guarantee + * a better scalability. */ - -#define EVENTPOLLFS_MAGIC 0x03111965 /* My birthday should work for this :) */ - -#define DEBUG_EPOLL 0 - -#if DEBUG_EPOLL > 0 -#define DPRINTK(x) printk x -#define DNPRINTK(n, x) do { if ((n) <= DEBUG_EPOLL) printk x; } while (0) -#else /* #if DEBUG_EPOLL > 0 */ -#define DPRINTK(x) (void) 0 -#define DNPRINTK(n, x) (void) 0 -#endif /* #if DEBUG_EPOLL > 0 */ - -#define DEBUG_EPI 0 - -#if DEBUG_EPI != 0 -#define EPI_SLAB_DEBUG (SLAB_DEBUG_FREE | SLAB_RED_ZONE /* | SLAB_POISON */) -#else /* #if DEBUG_EPI != 0 */ -#define EPI_SLAB_DEBUG 0 -#endif /* #if DEBUG_EPI != 0 */ - /* Epoll private bits inside the event mask */ -#define EP_PRIVATE_BITS (EPOLLONESHOT | EPOLLET) +#define EP_PRIVATE_BITS (EPOLLWAKEUP | EPOLLONESHOT | EPOLLET) + +/* Maximum number of nesting allowed inside epoll sets */ +#define EP_MAX_NESTS 4 -/* Maximum number of poll wake up nests we are allowing */ -#define EP_MAX_POLLWAKE_NESTS 4 +#define EP_MAX_EVENTS (INT_MAX / sizeof(struct epoll_event)) -/* 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_UNACTIVE_PTR ((void *) -1L) +#define EP_ITEM_COST (sizeof(struct epitem) + sizeof(struct eppoll_entry)) struct epoll_filefd { struct file *file; int fd; -}; +} __packed; /* - * 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; - task_t *task; - wait_queue_head_t *wq; + void *cookie; + void *ctx; }; /* - * 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; }; /* + * Each file descriptor added to the eventpoll interface will + * have an entry of this type linked to the "rbr" RB tree. + * Avoid increasing the size of this struct, there can be many thousands + * of these on a server and we do not want this to take another cache line. + */ +struct epitem { + union { + /* RB tree node links this structure to the eventpoll RB tree */ + struct rb_node rbn; + /* Used to free the struct epitem */ + struct rcu_head rcu; + }; + + /* 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; + + /* wakeup_source used when EPOLLWAKEUP is set */ + struct wakeup_source __rcu *ws; + + /* 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 + * structure and represents the main data structure for the eventpoll * interface. */ struct eventpoll { - /* Protect the this structure access */ - rwlock_t lock; + /* Protect the access to this structure */ + 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; @@ -158,8 +198,27 @@ struct eventpoll { /* 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 transferring ready events to userspace w/out + * holding ->lock. + */ + struct epitem *ovflist; + + /* wakeup_source used when ep_scan_ready_list is running */ + struct wakeup_source *ws; + + /* The user that created the eventpoll descriptor */ + struct user_struct *user; + + struct file *file; + + /* used to optimize loop detection check */ + int visited; + struct list_head visited_list_link; }; /* Wait structure used by the poll hooks */ @@ -168,7 +227,7 @@ 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 @@ -180,144 +239,82 @@ struct eppoll_entry { 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; }; +/* Used by the ep_send_events() function as callback private data */ +struct ep_send_events_data { + int maxevents; + struct epoll_event __user *events; +}; - -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 struct super_block *eventpollfs_get_sb(struct file_system_type *fs_type, - int flags, const char *dev_name, - void *data); +/* + * Configuration options available inside /proc/sys/fs/epoll/ + */ +/* Maximum number of epoll watched descriptors, per user */ +static long max_user_watches __read_mostly; /* - * 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 semaphore epsem; +static DEFINE_MUTEX(epmutex); + +/* Used to check for epoll file descriptor inclusion loops */ +static struct nested_calls poll_loop_ncalls; + +/* Used for safe wake up implementation */ +static struct nested_calls poll_safewake_ncalls; -/* Safe wake up implementation */ -static struct poll_safewake psw; +/* 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 kmem_cache_t *epi_cache; +static struct kmem_cache *epi_cache __read_mostly; /* Slab cache used to allocate "struct eppoll_entry" */ -static kmem_cache_t *pwq_cache; +static struct kmem_cache *pwq_cache __read_mostly; -/* Virtual fs used to allocate inodes for eventpoll files */ -static struct vfsmount *eventpoll_mnt; - -/* File callbacks that implement the eventpoll file behaviour */ -static struct file_operations eventpoll_fops = { - .release = ep_eventpoll_close, - .poll = ep_eventpoll_poll -}; +/* Visited nodes during ep_loop_check(), so we can unset them when we finish */ +static LIST_HEAD(visited_list); /* - * This is used to register the virtual file system from where - * eventpoll inodes are allocated. + * List of files with newly added links, where we may need to limit the number + * of emanating paths. Protected by the epmutex. */ -static struct file_system_type eventpoll_fs_type = { - .name = "eventpollfs", - .get_sb = eventpollfs_get_sb, - .kill_sb = kill_anon_super, +static LIST_HEAD(tfile_check_list); + +#ifdef CONFIG_SYSCTL + +#include <linux/sysctl.h> + +static long zero; +static long long_max = LONG_MAX; + +struct ctl_table epoll_table[] = { + { + .procname = "max_user_watches", + .data = &max_user_watches, + .maxlen = sizeof(max_user_watches), + .mode = 0644, + .proc_handler = proc_doulongvec_minmax, + .extra1 = &zero, + .extra2 = &long_max, + }, + { } }; +#endif /* CONFIG_SYSCTL */ -/* Very basic directory entry operations for the eventpoll virtual file system */ -static struct dentry_operations eventpollfs_dentry_operations = { - .d_delete = eventpollfs_delete_dentry, -}; +static const struct file_operations eventpoll_fops; - - -/* 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) { @@ -325,7 +322,7 @@ static inline void ep_set_ffd(struct epoll_filefd *ffd, 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) { @@ -333,477 +330,407 @@ static inline int ep_cmp_ffd(struct epoll_filefd *p1, (p1->file < p2->file ? -1 : p1->fd - p2->fd)); } -/* Special initialization for the rb-tree node to detect linkage */ -static inline void ep_rb_initnode(struct rb_node *n) -{ - n->rb_parent = 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; -} - -/* 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); -} - /* Tells us if the item is currently linked */ static inline int ep_is_linked(struct list_head *p) { return !list_empty(p); } +static inline struct eppoll_entry *ep_pwq_from_wait(wait_queue_t *p) +{ + return container_of(p, struct eppoll_entry, wait); +} + /* Get the "struct epitem" from a wait queue pointer */ -static inline struct epitem * ep_item_from_wait(wait_queue_t *p) +static inline struct epitem *ep_item_from_wait(wait_queue_t *p) { return container_of(p, struct eppoll_entry, wait)->base; } /* Get the "struct epitem" from an epoll queue wrapper */ -static inline struct epitem * ep_item_from_epqueue(poll_table *p) +static inline struct epitem *ep_item_from_epqueue(poll_table *p) { return container_of(p, struct ep_pqueue, pt)->epi; } /* 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; } /* 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); } +/** + * ep_events_available - Checks if ready events might be available. + * + * @ep: Pointer to the eventpoll context. + * + * Returns: Returns a value different than zero if ready events are available, + * or zero otherwise. + */ +static inline int ep_events_available(struct eventpoll *ep) +{ + return !list_empty(&ep->rdllist) || ep->ovflist != EP_UNACTIVE_PTR; +} -/* - * 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. + * @ctx: This instance context. + * + * 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, void *ctx) { - int wake_nests = 0; + int error, call_nests = 0; unsigned long flags; - task_t *this_task = current; - struct list_head *lsthead = &psw->wake_task_list, *lnk; - struct wake_task_node *tncur; - struct wake_task_node tnode; + 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 */ - list_for_each(lnk, lsthead) { - tncur = list_entry(lnk, struct wake_task_node, llink); - - if (tncur->wq == wq || - (tncur->task == this_task && ++wake_nests > EP_MAX_POLLWAKE_NESTS)) { + /* + * 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->ctx == ctx && + (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.ctx = ctx; + 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(wq); + /* 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); + return error; +} -/* Used to initialize the epoll bits inside the "struct file" */ -void eventpoll_init_file(struct file *file) +/* + * As described in commit 0ccf831cb lockdep: annotate epoll + * the use of wait queues used by epoll is done in a very controlled + * manner. Wake ups can nest inside each other, but are never done + * with the same locking. For example: + * + * dfd = socket(...); + * efd1 = epoll_create(); + * efd2 = epoll_create(); + * epoll_ctl(efd1, EPOLL_CTL_ADD, dfd, ...); + * epoll_ctl(efd2, EPOLL_CTL_ADD, efd1, ...); + * + * When a packet arrives to the device underneath "dfd", the net code will + * issue a wake_up() on its poll wake list. Epoll (efd1) has installed a + * callback wakeup entry on that queue, and the wake_up() performed by the + * "dfd" net code will end up in ep_poll_callback(). At this point epoll + * (efd1) notices that it may have some event ready, so it needs to wake up + * the waiters on its poll wait list (efd2). So it calls ep_poll_safewake() + * that ends up in another wake_up(), after having checked about the + * recursion constraints. That are, no more than EP_MAX_POLLWAKE_NESTS, to + * avoid stack blasting. + * + * When CONFIG_DEBUG_LOCK_ALLOC is enabled, make sure lockdep can handle + * this special case of epoll. + */ +#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; - INIT_LIST_HEAD(&file->f_ep_links); - spin_lock_init(&file->f_ep_lock); + 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; +} /* - * 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. + * 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. */ -void eventpoll_release_file(struct file *file) +static void ep_poll_safewake(wait_queue_head_t *wq) { - struct list_head *lsthead = &file->f_ep_links; - struct eventpoll *ep; - struct epitem *epi; + int this_cpu = get_cpu(); - /* - * 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 "epsem" because ep_remove() requires it when called - * from anywhere but ep_free(). - */ - down(&epsem); + ep_call_nested(&poll_safewake_ncalls, EP_MAX_NESTS, + ep_poll_wakeup_proc, NULL, wq, (void *) (long) this_cpu); - while (!list_empty(lsthead)) { - epi = list_entry(lsthead->next, struct epitem, fllink); + put_cpu(); +} - ep = epi->ep; - ep_list_del(&epi->fllink); - down_write(&ep->sem); - ep_remove(ep, epi); - up_write(&ep->sem); - } +static void ep_remove_wait_queue(struct eppoll_entry *pwq) +{ + wait_queue_head_t *whead; - up(&epsem); + rcu_read_lock(); + /* If it is cleared by POLLFREE, it should be rcu-safe */ + whead = rcu_dereference(pwq->whead); + if (whead) + remove_wait_queue(whead, &pwq->wait); + rcu_read_unlock(); } - /* - * 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). + * This function unregisters poll callbacks from the associated file + * descriptor. Must be called with "mtx" held (or "epmutex" if called from + * ep_free). */ -asmlinkage long sys_epoll_create(int size) +static void ep_unregister_pollwait(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)); + struct list_head *lsthead = &epi->pwqlist; + struct eppoll_entry *pwq; - /* - * 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 eexit_1; + while (!list_empty(lsthead)) { + pwq = list_first_entry(lsthead, struct eppoll_entry, llink); - /* - * 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; + list_del(&pwq->llink); + ep_remove_wait_queue(pwq); + kmem_cache_free(pwq_cache, pwq); + } +} - DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n", - current, size, fd)); +/* call only when ep->mtx is held */ +static inline struct wakeup_source *ep_wakeup_source(struct epitem *epi) +{ + return rcu_dereference_check(epi->ws, lockdep_is_held(&epi->ep->mtx)); +} - return fd; +/* call only when ep->mtx is held */ +static inline void ep_pm_stay_awake(struct epitem *epi) +{ + struct wakeup_source *ws = ep_wakeup_source(epi); -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; + if (ws) + __pm_stay_awake(ws); } - -/* - * 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) +static inline bool ep_has_wakeup_source(struct epitem *epi) { - int error; - struct file *file, *tfile; - struct eventpoll *ep; - struct epitem *epi; - struct epoll_event epds; + return rcu_access_pointer(epi->ws) ? true : false; +} - DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %p)\n", - current, epfd, op, fd, event)); +/* call when ep->mtx cannot be held (ep_poll_callback) */ +static inline void ep_pm_stay_awake_rcu(struct epitem *epi) +{ + struct wakeup_source *ws; - error = -EFAULT; - if (ep_op_hash_event(op) && - copy_from_user(&epds, event, sizeof(struct epoll_event))) - goto eexit_1; + rcu_read_lock(); + ws = rcu_dereference(epi->ws); + if (ws) + __pm_stay_awake(ws); + rcu_read_unlock(); +} - /* Get the "struct file *" for the eventpoll file */ - error = -EBADF; - file = fget(epfd); - if (!file) - goto eexit_1; +/** + * 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. + * @depth: The current depth of recursive f_op->poll calls. + * @ep_locked: caller already holds ep->mtx + * + * 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 depth, bool ep_locked) +{ + int error, pwake = 0; + unsigned long flags; + struct epitem *epi, *nepi; + LIST_HEAD(txlist); - /* Get the "struct file *" for the target file */ - tfile = fget(fd); - if (!tfile) - goto eexit_2; + /* + * We need to lock this because we could be hit by + * eventpoll_release_file() and epoll_ctl(). + */ - /* The target file descriptor must support poll */ - error = -EPERM; - if (!tfile->f_op || !tfile->f_op->poll) - goto eexit_3; + if (!ep_locked) + mutex_lock_nested(&ep->mtx, depth); /* - * 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. + * 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. */ - error = -EINVAL; - if (file == tfile || !is_file_epoll(file)) - goto eexit_3; + spin_lock_irqsave(&ep->lock, flags); + list_splice_init(&ep->rdllist, &txlist); + ep->ovflist = NULL; + spin_unlock_irqrestore(&ep->lock, flags); /* - * At this point it is safe to assume that the "private_data" contains - * our own data structure. + * Now call the callback function. */ - ep = file->private_data; - - down_write(&ep->sem); - - /* Try to lookup the file inside our hash table */ - 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; - } + error = (*sproc)(ep, &txlist, priv); + spin_lock_irqsave(&ep->lock, flags); /* - * The function ep_find() increments the usage count of the structure - * so, if this is not NULL, we need to release it. + * 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. */ - 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; -} - -#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) -{ - 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; + 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); + ep_pm_stay_awake(epi); + } } - - /* Get the "struct file *" for the eventpoll file */ - error = -EBADF; - file = fget(epfd); - if (!file) - goto eexit_1; - /* - * We have to check that the file structure underneath the fd - * the user passed to us _is_ an eventpoll file. + * 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. */ - error = -EINVAL; - if (!is_file_epoll(file)) - goto eexit_2; + ep->ovflist = EP_UNACTIVE_PTR; /* - * At this point it is safe to assume that the "private_data" contains - * our own data structure. + * Quickly re-inject items left on "txlist". */ - ep = file->private_data; + list_splice(&txlist, &ep->rdllist); + __pm_relax(ep->ws); - /* Time to fish for events ... */ - error = ep_poll(ep, events, maxevents, timeout); + 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); + + if (!ep_locked) + mutex_unlock(&ep->mtx); -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)); + /* We have to call this outside the lock */ + if (pwake) + ep_poll_safewake(&ep->poll_wait); return error; } +static void epi_rcu_free(struct rcu_head *head) +{ + struct epitem *epi = container_of(head, struct epitem, rcu); + kmem_cache_free(epi_cache, epi); +} /* - * Creates the file descriptor to be used by the epoll interface. + * Removes a "struct epitem" from the eventpoll RB tree and deallocates + * all the associated resources. Must be called with "mtx" held. */ -static int ep_getfd(int *efd, struct inode **einode, struct file **efile, - struct eventpoll *ep) +static int ep_remove(struct eventpoll *ep, struct epitem *epi) { - 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; + unsigned long flags; + struct file *file = epi->ffd.file; /* - * Link the inode to a directory entry by creating a unique name - * using the inode number. + * 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 = -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; - -eexit_4: - put_unused_fd(fd); -eexit_3: - iput(inode); -eexit_2: - put_filp(file); -eexit_1: - return error; -} + ep_unregister_pollwait(ep, epi); + /* Remove the current item from the list of epoll hooks */ + spin_lock(&file->f_lock); + list_del_rcu(&epi->fllink); + spin_unlock(&file->f_lock); -static int ep_alloc(struct eventpoll **pep) -{ - struct eventpoll *ep = kzalloc(sizeof(*ep), GFP_KERNEL); + rb_erase(&epi->rbn, &ep->rbr); - if (!ep) - return -ENOMEM; + spin_lock_irqsave(&ep->lock, flags); + if (ep_is_linked(&epi->rdllink)) + list_del_init(&epi->rdllink); + spin_unlock_irqrestore(&ep->lock, flags); - rwlock_init(&ep->lock); - init_rwsem(&ep->sem); - init_waitqueue_head(&ep->wq); - init_waitqueue_head(&ep->poll_wait); - INIT_LIST_HEAD(&ep->rdllist); - ep->rbr = RB_ROOT; + wakeup_source_unregister(ep_wakeup_source(epi)); + /* + * At this point it is safe to free the eventpoll item. Use the union + * field epi->rcu, since we are trying to minimize the size of + * 'struct epitem'. The 'rbn' field is no longer in use. Protected by + * ep->mtx. The rcu read side, reverse_path_check_proc(), does not make + * use of the rbn field. + */ + call_rcu(&epi->rcu, epi_rcu_free); - *pep = ep; + atomic_long_dec(&ep->user->epoll_watches); - DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_alloc() ep=%p\n", - current, ep)); return 0; } - static void ep_free(struct eventpoll *ep) { struct rb_node *rbp; @@ -811,17 +738,17 @@ 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 * eventpoll_release_file() while we're freeing the "struct eventpoll". - * We do not need to hold "ep->sem" here because the epoll file + * 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 "epsem" is sufficent here. + * holding "epmutex" is sufficient here. */ - down(&epsem); + mutex_lock(&epmutex); /* * Walks through the whole tree by unregistering poll callbacks. @@ -830,38 +757,227 @@ static void ep_free(struct eventpoll *ep) epi = rb_entry(rbp, struct epitem, rbn); ep_unregister_pollwait(ep, epi); + cond_resched(); } /* - * 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 + * 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". + * We do not need to lock ep->mtx, either, we only do it to prevent + * a lockdep warning. */ - while ((rbp = rb_first(&ep->rbr)) != 0) { + mutex_lock(&ep->mtx); + while ((rbp = rb_first(&ep->rbr)) != NULL) { epi = rb_entry(rbp, struct epitem, rbn); ep_remove(ep, epi); + cond_resched(); + } + mutex_unlock(&ep->mtx); + + mutex_unlock(&epmutex); + mutex_destroy(&ep->mtx); + free_uid(ep->user); + wakeup_source_unregister(ep->ws); + kfree(ep); +} + +static int ep_eventpoll_release(struct inode *inode, struct file *file) +{ + struct eventpoll *ep = file->private_data; + + if (ep) + ep_free(ep); + + return 0; +} + +static inline unsigned int ep_item_poll(struct epitem *epi, poll_table *pt) +{ + pt->_key = epi->event.events; + + return epi->ffd.file->f_op->poll(epi->ffd.file, pt) & epi->event.events; +} + +static int ep_read_events_proc(struct eventpoll *ep, struct list_head *head, + void *priv) +{ + struct epitem *epi, *tmp; + poll_table pt; + + init_poll_funcptr(&pt, NULL); + + list_for_each_entry_safe(epi, tmp, head, rdllink) { + if (ep_item_poll(epi, &pt)) + 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. + */ + __pm_relax(ep_wakeup_source(epi)); + list_del_init(&epi->rdllink); + } + } + + return 0; +} + +static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, + poll_table *pt); + +struct readyevents_arg { + struct eventpoll *ep; + bool locked; +}; + +static int ep_poll_readyevents_proc(void *priv, void *cookie, int call_nests) +{ + struct readyevents_arg *arg = priv; + + return ep_scan_ready_list(arg->ep, ep_read_events_proc, NULL, + call_nests + 1, arg->locked); +} + +static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait) +{ + int pollflags; + struct eventpoll *ep = file->private_data; + struct readyevents_arg arg; + + /* + * During ep_insert() we already hold the ep->mtx for the tfile. + * Prevent re-aquisition. + */ + arg.locked = wait && (wait->_qproc == ep_ptable_queue_proc); + arg.ep = ep; + + /* Insert inside our poll wait queue */ + poll_wait(file, &ep->poll_wait, wait); + + /* + * 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, &arg, ep, current); + + return pollflags != -1 ? pollflags : 0; +} + +#ifdef CONFIG_PROC_FS +static int ep_show_fdinfo(struct seq_file *m, struct file *f) +{ + struct eventpoll *ep = f->private_data; + struct rb_node *rbp; + int ret = 0; + + mutex_lock(&ep->mtx); + for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { + struct epitem *epi = rb_entry(rbp, struct epitem, rbn); + + ret = seq_printf(m, "tfd: %8d events: %8x data: %16llx\n", + epi->ffd.fd, epi->event.events, + (long long)epi->event.data); + if (ret) + break; } + mutex_unlock(&ep->mtx); + + return ret; +} +#endif + +/* File callbacks that implement the eventpoll file behaviour */ +static const struct file_operations eventpoll_fops = { +#ifdef CONFIG_PROC_FS + .show_fdinfo = ep_show_fdinfo, +#endif + .release = ep_eventpoll_release, + .poll = ep_eventpoll_poll, + .llseek = noop_llseek, +}; - up(&epsem); +/* + * 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. + */ +void eventpoll_release_file(struct file *file) +{ + struct eventpoll *ep; + struct epitem *epi, *next; + + /* + * 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 no one is using this file anymore. + * 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); + list_for_each_entry_safe(epi, next, &file->f_ep_links, fllink) { + ep = epi->ep; + mutex_lock_nested(&ep->mtx, 0); + ep_remove(ep, epi); + mutex_unlock(&ep->mtx); + } + mutex_unlock(&epmutex); } +static int ep_alloc(struct eventpoll **pep) +{ + int error; + struct user_struct *user; + struct eventpoll *ep; + + user = get_current_user(); + error = -ENOMEM; + ep = kzalloc(sizeof(*ep), GFP_KERNEL); + if (unlikely(!ep)) + goto free_uid; + + 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; + ep->user = user; + + *pep = ep; + + return 0; + +free_uid: + free_uid(user); + return error; +} /* - * 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); @@ -870,43 +986,103 @@ static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd) 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 + * mechanism. 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); -} + if ((unsigned long)key & POLLFREE) { + ep_pwq_from_wait(wait)->whead = NULL; + /* + * whead = NULL above can race with ep_remove_wait_queue() + * which can do another remove_wait_queue() after us, so we + * can't use __remove_wait_queue(). whead->lock is held by + * the caller. + */ + list_del_init(&wait->task_list); + } + 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); -} + /* + * 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 transferring 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 happen 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; + if (epi->ws) { + /* + * Activate ep->ws since epi->ws may get + * deactivated at any time. + */ + __pm_stay_awake(ep->ws); + } + + } + goto out_unlock; + } + + /* If this file is already in the ready list we exit soon */ + if (!ep_is_linked(&epi->rdllink)) { + list_add_tail(&epi->rdllink, &ep->rdllist); + ep_pm_stay_awake_rcu(epi); + } + + /* + * 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(&ep->poll_wait); + + return 1; +} /* * This is the callback that is used to add our wait queue to the @@ -918,7 +1094,7 @@ static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, 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; @@ -931,7 +1107,6 @@ static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, } } - static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi) { int kcmp; @@ -952,29 +1127,174 @@ static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi) } + +#define PATH_ARR_SIZE 5 +/* + * These are the number paths of length 1 to 5, that we are allowing to emanate + * from a single file of interest. For example, we allow 1000 paths of length + * 1, to emanate from each file of interest. This essentially represents the + * potential wakeup paths, which need to be limited in order to avoid massive + * uncontrolled wakeup storms. The common use case should be a single ep which + * is connected to n file sources. In this case each file source has 1 path + * of length 1. Thus, the numbers below should be more than sufficient. These + * path limits are enforced during an EPOLL_CTL_ADD operation, since a modify + * and delete can't add additional paths. Protected by the epmutex. + */ +static const int path_limits[PATH_ARR_SIZE] = { 1000, 500, 100, 50, 10 }; +static int path_count[PATH_ARR_SIZE]; + +static int path_count_inc(int nests) +{ + /* Allow an arbitrary number of depth 1 paths */ + if (nests == 0) + return 0; + + if (++path_count[nests] > path_limits[nests]) + return -1; + return 0; +} + +static void path_count_init(void) +{ + int i; + + for (i = 0; i < PATH_ARR_SIZE; i++) + path_count[i] = 0; +} + +static int reverse_path_check_proc(void *priv, void *cookie, int call_nests) +{ + int error = 0; + struct file *file = priv; + struct file *child_file; + struct epitem *epi; + + /* CTL_DEL can remove links here, but that can't increase our count */ + rcu_read_lock(); + list_for_each_entry_rcu(epi, &file->f_ep_links, fllink) { + child_file = epi->ep->file; + if (is_file_epoll(child_file)) { + if (list_empty(&child_file->f_ep_links)) { + if (path_count_inc(call_nests)) { + error = -1; + break; + } + } else { + error = ep_call_nested(&poll_loop_ncalls, + EP_MAX_NESTS, + reverse_path_check_proc, + child_file, child_file, + current); + } + if (error != 0) + break; + } else { + printk(KERN_ERR "reverse_path_check_proc: " + "file is not an ep!\n"); + } + } + rcu_read_unlock(); + return error; +} + +/** + * reverse_path_check - The tfile_check_list is list of file *, which have + * links that are proposed to be newly added. We need to + * make sure that those added links don't add too many + * paths such that we will spend all our time waking up + * eventpoll objects. + * + * Returns: Returns zero if the proposed links don't create too many paths, + * -1 otherwise. + */ +static int reverse_path_check(void) +{ + int error = 0; + struct file *current_file; + + /* let's call this for all tfiles */ + list_for_each_entry(current_file, &tfile_check_list, f_tfile_llink) { + path_count_init(); + error = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, + reverse_path_check_proc, current_file, + current_file, current); + if (error) + break; + } + return error; +} + +static int ep_create_wakeup_source(struct epitem *epi) +{ + const char *name; + struct wakeup_source *ws; + + if (!epi->ep->ws) { + epi->ep->ws = wakeup_source_register("eventpoll"); + if (!epi->ep->ws) + return -ENOMEM; + } + + name = epi->ffd.file->f_path.dentry->d_name.name; + ws = wakeup_source_register(name); + + if (!ws) + return -ENOMEM; + rcu_assign_pointer(epi->ws, ws); + + return 0; +} + +/* rare code path, only used when EPOLL_CTL_MOD removes a wakeup source */ +static noinline void ep_destroy_wakeup_source(struct epitem *epi) +{ + struct wakeup_source *ws = ep_wakeup_source(epi); + + RCU_INIT_POINTER(epi->ws, NULL); + + /* + * wait for ep_pm_stay_awake_rcu to finish, synchronize_rcu is + * used internally by wakeup_source_remove, too (called by + * wakeup_source_unregister), so we cannot use call_rcu + */ + synchronize_rcu(); + wakeup_source_unregister(ws); +} + +/* + * Must be called with "mtx" held. + */ static int ep_insert(struct eventpoll *ep, struct epoll_event *event, - struct file *tfile, int fd) + struct file *tfile, int fd, int full_check) { int error, revents, pwake = 0; unsigned long flags; + long user_watches; struct epitem *epi; struct ep_pqueue epq; - error = -ENOMEM; - if (!(epi = kmem_cache_alloc(epi_cache, SLAB_KERNEL))) - goto eexit_1; + user_watches = atomic_long_read(&ep->user->epoll_watches); + if (unlikely(user_watches >= max_user_watches)) + return -ENOSPC; + if (!(epi = kmem_cache_alloc(epi_cache, GFP_KERNEL))) + return -ENOMEM; /* 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; + if (epi->event.events & EPOLLWAKEUP) { + error = ep_create_wakeup_source(epi); + if (error) + goto error_create_wakeup_source; + } else { + RCU_INIT_POINTER(epi->ws, NULL); + } /* Initialize the poll table using the queue callback */ epq.epi = epi; @@ -983,686 +1303,833 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event, /* * 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); + revents = ep_item_poll(epi, &epq.pt); /* * We have to check if something went wrong during the poll wait queue * install process. Namely an allocation for a wait queue failed due * high memory pressure. */ + error = -ENOMEM; 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); + spin_lock(&tfile->f_lock); + list_add_tail_rcu(&epi->fllink, &tfile->f_ep_links); + spin_unlock(&tfile->f_lock); - /* 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); + /* now check if we've created too many backpaths */ + error = -EINVAL; + if (full_check && reverse_path_check()) + goto error_remove_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); + ep_pm_stay_awake(epi); /* Notify waiting tasks that events are available */ if (waitqueue_active(&ep->wq)) - wake_up(&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); + + atomic_long_inc(&ep->user->epoll_watches); /* 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; -eexit_2: +error_remove_epi: + spin_lock(&tfile->f_lock); + list_del_rcu(&epi->fllink); + spin_unlock(&tfile->f_lock); + + rb_erase(&epi->rbn, &ep->rbr); + +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); + + wakeup_source_unregister(ep_wakeup_source(epi)); +error_create_wakeup_source: kmem_cache_free(epi_cache, epi); -eexit_1: + return error; } - /* * Modify the interest event mask by dropping an event if the new mask - * has a match in the current file status. + * 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) { int pwake = 0; unsigned int revents; - unsigned long flags; + poll_table pt; + + init_poll_funcptr(&pt, NULL); + + /* + * 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; /* need barrier below */ + epi->event.data = event->data; /* protected by mtx */ + if (epi->event.events & EPOLLWAKEUP) { + if (!ep_has_wakeup_source(epi)) + ep_create_wakeup_source(epi); + } else if (ep_has_wakeup_source(epi)) { + ep_destroy_wakeup_source(epi); + } /* - * 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. + * The following barrier has two effects: + * + * 1) Flush epi changes above to other CPUs. This ensures + * we do not miss events from ep_poll_callback if an + * event occurs immediately after we call f_op->poll(). + * We need this because we did not take ep->lock while + * changing epi above (but ep_poll_callback does take + * ep->lock). + * + * 2) We also need to ensure we do not miss _past_ events + * when calling f_op->poll(). This barrier also + * pairs with the barrier in wq_has_sleeper (see + * comments for wq_has_sleeper). + * + * This barrier will now guarantee ep_poll_callback or f_op->poll + * (or both) will notice the readiness of an item. */ - epi->event.events = event->events; + smp_mb(); /* * Get current event bits. We can safely use the file* here because * its usage count has been increased by the caller of this function. */ - revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL); - - write_lock_irqsave(&ep->lock, flags); - - /* Copy the data member from inside the lock */ - epi->event.data = event->data; + revents = ep_item_poll(epi, &pt); /* - * 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); + if (revents & event->events) { + spin_lock_irq(&ep->lock); + if (!ep_is_linked(&epi->rdllink)) { + list_add_tail(&epi->rdllink, &ep->rdllist); + ep_pm_stay_awake(epi); - /* Notify waiting tasks that events are available */ - if (waitqueue_active(&ep->wq)) - wake_up(&ep->wq); - if (waitqueue_active(&ep->poll_wait)) - pwake++; - } + /* Notify waiting tasks that events are available */ + if (waitqueue_active(&ep->wq)) + wake_up_locked(&ep->wq); + if (waitqueue_active(&ep->poll_wait)) + pwake++; } + spin_unlock_irq(&ep->lock); } - write_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; } - -/* - * 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_proc(struct eventpoll *ep, struct list_head *head, + void *priv) { - int nwait; - struct list_head *lsthead = &epi->pwqlist; - struct eppoll_entry *pwq; + struct ep_send_events_data *esed = priv; + int eventcnt; + unsigned int revents; + struct epitem *epi; + struct epoll_event __user *uevent; + struct wakeup_source *ws; + poll_table pt; - /* This is called without locks, so we need the atomic exchange */ - nwait = xchg(&epi->nwait, 0); + init_poll_funcptr(&pt, NULL); - if (nwait) { - while (!list_empty(lsthead)) { - pwq = list_entry(lsthead->next, struct eppoll_entry, llink); + /* + * 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, uevent = esed->events; + !list_empty(head) && eventcnt < esed->maxevents;) { + epi = list_first_entry(head, struct epitem, rdllink); - ep_list_del(&pwq->llink); - remove_wait_queue(pwq->whead, &pwq->wait); - kmem_cache_free(pwq_cache, pwq); + /* + * Activate ep->ws before deactivating epi->ws to prevent + * triggering auto-suspend here (in case we reactive epi->ws + * below). + * + * This could be rearranged to delay the deactivation of epi->ws + * instead, but then epi->ws would temporarily be out of sync + * with ep_is_linked(). + */ + ws = ep_wakeup_source(epi); + if (ws) { + if (ws->active) + __pm_stay_awake(ep->ws); + __pm_relax(ws); } - } -} + list_del_init(&epi->rdllink); -/* - * 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; + revents = ep_item_poll(epi, &pt); - /* - * 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; + /* + * 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, &uevent->events) || + __put_user(epi->event.data, &uevent->data)) { + list_add(&epi->rdllink, head); + ep_pm_stay_awake(epi); + return eventcnt ? eventcnt : -EFAULT; + } + eventcnt++; + uevent++; + if (epi->event.events & EPOLLONESHOT) + epi->event.events &= EP_PRIVATE_BITS; + 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, no one 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); + ep_pm_stay_awake(epi); + } + } + } - /* - * 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; + return eventcnt; +} - /* - * 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); +static int ep_send_events(struct eventpoll *ep, + struct epoll_event __user *events, int maxevents) +{ + struct ep_send_events_data esed; - /* - * 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); + esed.maxevents = maxevents; + esed.events = events; - error = 0; -eexit_1: + return ep_scan_ready_list(ep, ep_send_events_proc, &esed, 0, false); +} - DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_unlink(%p, %p) = %d\n", - current, ep, epi->file, error)); +static inline struct timespec ep_set_mstimeout(long ms) +{ + struct timespec now, ts = { + .tv_sec = ms / MSEC_PER_SEC, + .tv_nsec = NSEC_PER_MSEC * (ms % MSEC_PER_SEC), + }; - return error; + ktime_get_ts(&now); + return timespec_add_safe(now, ts); } - -/* - * Removes a "struct epitem" from the eventpoll hash and deallocates - * all the associated resources. +/** + * ep_poll - Retrieves ready events, and delivers them to the caller supplied + * event buffer. + * + * @ep: Pointer to the eventpoll context. + * @events: Pointer to the userspace buffer where the ready events should be + * stored. + * @maxevents: Size (in terms of number of events) of the caller event buffer. + * @timeout: Maximum timeout for the ready events fetch operation, in + * milliseconds. If the @timeout is zero, the function will not block, + * while if the @timeout is less than zero, the function will block + * until at least one event has been retrieved (or an error + * occurred). + * + * Returns: Returns the number of ready events which have been fetched, or an + * error code, in case of error. */ -static int ep_remove(struct eventpoll *ep, struct epitem *epi) +static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, + int maxevents, long timeout) { - int error; + int res = 0, eavail, timed_out = 0; 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); + long slack = 0; + wait_queue_t wait; + ktime_t expires, *to = NULL; - error = 0; -eexit_1: - DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_remove(%p, %p) = %d\n", - current, ep, file, error)); + if (timeout > 0) { + struct timespec end_time = ep_set_mstimeout(timeout); - return error; -} + slack = select_estimate_accuracy(&end_time); + to = &expires; + *to = timespec_to_ktime(end_time); + } else if (timeout == 0) { + /* + * Avoid the unnecessary trip to the wait queue loop, if the + * caller specified a non blocking operation. + */ + timed_out = 1; + spin_lock_irqsave(&ep->lock, flags); + goto check_events; + } +fetch_events: + spin_lock_irqsave(&ep->lock, flags); -/* - * 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; + if (!ep_events_available(ep)) { + /* + * We don't have any available event to return to the caller. + * We need to sleep here, and we will be wake up by + * ep_poll_callback() when events will become available. + */ + init_waitqueue_entry(&wait, current); + __add_wait_queue_exclusive(&ep->wq, &wait); - DNPRINTK(3, (KERN_INFO "[%p] eventpoll: poll_callback(%p) epi=%p ep=%p\n", - current, epi->file, epi, ep)); + for (;;) { + /* + * We don't want to sleep if the ep_poll_callback() sends us + * a wakeup in between. That's why we set the task state + * to TASK_INTERRUPTIBLE before doing the checks. + */ + set_current_state(TASK_INTERRUPTIBLE); + if (ep_events_available(ep) || timed_out) + break; + if (signal_pending(current)) { + res = -EINTR; + break; + } - write_lock_irqsave(&ep->lock, flags); + spin_unlock_irqrestore(&ep->lock, flags); + if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS)) + timed_out = 1; - /* - * 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 is_disabled; + spin_lock_irqsave(&ep->lock, flags); + } + __remove_wait_queue(&ep->wq, &wait); - /* If this file is already in the ready list we exit soon */ - if (ep_is_linked(&epi->rdllink)) - goto is_linked; + set_current_state(TASK_RUNNING); + } +check_events: + /* Is it worth to try to dig for events ? */ + eavail = ep_events_available(ep); - list_add_tail(&epi->rdllink, &ep->rdllist); + spin_unlock_irqrestore(&ep->lock, flags); -is_linked: /* - * Wake up ( if active ) both the eventpoll wait list and the ->poll() - * wait list. + * Try to transfer events to user space. In case we get 0 events and + * there's still timeout left over, we go trying again in search of + * more luck. */ - if (waitqueue_active(&ep->wq)) - wake_up(&ep->wq); - 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); + if (!res && eavail && + !(res = ep_send_events(ep, events, maxevents)) && !timed_out) + goto fetch_events; - return 1; + return res; } - -static int ep_eventpoll_close(struct inode *inode, struct file *file) +/** + * ep_loop_check_proc - Callback function to be passed to the @ep_call_nested() + * API, to verify that adding an epoll file inside another + * epoll structure, does not violate the constraints, in + * terms of closed loops, or too deep chains (which can + * result in excessive stack usage). + * + * @priv: Pointer to the epoll file to be currently checked. + * @cookie: Original cookie for this call. This is the top-of-the-chain epoll + * data structure pointer. + * @call_nests: Current dept of the @ep_call_nested() call stack. + * + * Returns: Returns zero if adding the epoll @file inside current epoll + * structure @ep does not violate the constraints, or -1 otherwise. + */ +static int ep_loop_check_proc(void *priv, void *cookie, int call_nests) { + int error = 0; + struct file *file = priv; struct eventpoll *ep = file->private_data; + struct eventpoll *ep_tovisit; + struct rb_node *rbp; + struct epitem *epi; - if (ep) { - ep_free(ep); - kfree(ep); + mutex_lock_nested(&ep->mtx, call_nests + 1); + ep->visited = 1; + list_add(&ep->visited_list_link, &visited_list); + for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { + epi = rb_entry(rbp, struct epitem, rbn); + if (unlikely(is_file_epoll(epi->ffd.file))) { + ep_tovisit = epi->ffd.file->private_data; + if (ep_tovisit->visited) + continue; + error = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, + ep_loop_check_proc, epi->ffd.file, + ep_tovisit, current); + if (error != 0) + break; + } else { + /* + * If we've reached a file that is not associated with + * an ep, then we need to check if the newly added + * links are going to add too many wakeup paths. We do + * this by adding it to the tfile_check_list, if it's + * not already there, and calling reverse_path_check() + * during ep_insert(). + */ + if (list_empty(&epi->ffd.file->f_tfile_llink)) + list_add(&epi->ffd.file->f_tfile_llink, + &tfile_check_list); + } } + mutex_unlock(&ep->mtx); - DNPRINTK(3, (KERN_INFO "[%p] eventpoll: close() ep=%p\n", current, ep)); - return 0; + return error; } - -static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait) +/** + * ep_loop_check - Performs a check to verify that adding an epoll file (@file) + * another epoll file (represented by @ep) does not create + * closed loops or too deep chains. + * + * @ep: Pointer to the epoll private data structure. + * @file: Pointer to the epoll file to be checked. + * + * Returns: Returns zero if adding the epoll @file inside current epoll + * structure @ep does not violate the constraints, or -1 otherwise. + */ +static int ep_loop_check(struct eventpoll *ep, struct file *file) { - 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); + int ret; + struct eventpoll *ep_cur, *ep_next; + + ret = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, + ep_loop_check_proc, file, ep, current); + /* clear visited list */ + list_for_each_entry_safe(ep_cur, ep_next, &visited_list, + visited_list_link) { + ep_cur->visited = 0; + list_del(&ep_cur->visited_list_link); + } + return ret; +} - /* Check our condition */ - read_lock_irqsave(&ep->lock, flags); - if (!list_empty(&ep->rdllist)) - pollflags = POLLIN | POLLRDNORM; - read_unlock_irqrestore(&ep->lock, flags); +static void clear_tfile_check_list(void) +{ + struct file *file; - return pollflags; + /* first clear the tfile_check_list */ + while (!list_empty(&tfile_check_list)) { + file = list_first_entry(&tfile_check_list, struct file, + f_tfile_llink); + list_del_init(&file->f_tfile_llink); + } + INIT_LIST_HEAD(&tfile_check_list); } - /* - * 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. + * Open an eventpoll file descriptor. */ -static int ep_collect_ready_items(struct eventpoll *ep, struct list_head *txlist, int maxevents) +SYSCALL_DEFINE1(epoll_create1, int, flags) { - 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; + int error, fd; + struct eventpoll *ep = NULL; + struct file *file; - /* Link the ready item into the transfer list */ - list_add(&epi->txlink, txlist); - nepi++; + /* Check the EPOLL_* constant for consistency. */ + BUILD_BUG_ON(EPOLL_CLOEXEC != O_CLOEXEC); - /* - * Unlink the item from the ready list. - */ - ep_list_del(&epi->rdllink); - } + if (flags & ~EPOLL_CLOEXEC) + return -EINVAL; + /* + * Create the internal data structure ("struct eventpoll"). + */ + error = ep_alloc(&ep); + 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 = get_unused_fd_flags(O_RDWR | (flags & O_CLOEXEC)); + if (fd < 0) { + error = fd; + goto out_free_ep; } + file = anon_inode_getfile("[eventpoll]", &eventpoll_fops, ep, + O_RDWR | (flags & O_CLOEXEC)); + if (IS_ERR(file)) { + error = PTR_ERR(file); + goto out_free_fd; + } + ep->file = file; + fd_install(fd, file); + return fd; - write_unlock_irqrestore(&ep->lock, flags); - - return nepi; +out_free_fd: + put_unused_fd(fd); +out_free_ep: + ep_free(ep); + return error; } +SYSCALL_DEFINE1(epoll_create, int, size) +{ + if (size <= 0) + return -EINVAL; + + return sys_epoll_create1(0); +} /* - * 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. + * The following function implements the controller interface for + * the eventpoll file that enables the insertion/removal/change of + * file descriptors inside the interest set. */ -static int ep_send_events(struct eventpoll *ep, struct list_head *txlist, - struct epoll_event __user *events) +SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd, + struct epoll_event __user *, event) { - int eventcnt = 0; - unsigned int revents; - struct list_head *lnk; + int error; + int full_check = 0; + struct fd f, tf; + struct eventpoll *ep; struct epitem *epi; + struct epoll_event epds; + struct eventpoll *tep = NULL; - /* - * 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". - */ - list_for_each(lnk, txlist) { - epi = list_entry(lnk, struct epitem, txlink); - - /* - * 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. - */ - revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL); + error = -EFAULT; + if (ep_op_has_event(op) && + copy_from_user(&epds, event, sizeof(struct epoll_event))) + goto error_return; - /* - * 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. - */ - epi->revents = revents & epi->event.events; - - if (epi->revents) { - if (__put_user(epi->revents, - &events[eventcnt].events) || - __put_user(epi->event.data, - &events[eventcnt].data)) - return -EFAULT; - if (epi->event.events & EPOLLONESHOT) - epi->event.events &= EP_PRIVATE_BITS; - eventcnt++; - } - } - return eventcnt; -} + error = -EBADF; + f = fdget(epfd); + if (!f.file) + goto error_return; + /* Get the "struct file *" for the target file */ + tf = fdget(fd); + if (!tf.file) + goto error_fput; -/* - * 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; + /* The target file descriptor must support poll */ + error = -EPERM; + if (!tf.file->f_op->poll) + goto error_tgt_fput; - write_lock_irqsave(&ep->lock, flags); + /* Check if EPOLLWAKEUP is allowed */ + ep_take_care_of_epollwakeup(&epds); - while (!list_empty(txlist)) { - epi = list_entry(txlist->next, struct epitem, txlink); + /* + * 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 (f.file == tf.file || !is_file_epoll(f.file)) + goto error_tgt_fput; - /* Unlink the current item from the transfer list */ - ep_list_del(&epi->txlink); + /* + * At this point it is safe to assume that the "private_data" contains + * our own data structure. + */ + ep = f.file->private_data; - /* - * 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)) { - list_add_tail(&epi->rdllink, &ep->rdllist); - ricnt++; + /* + * When we insert an epoll file descriptor, inside another epoll file + * descriptor, there is the change of creating closed loops, which are + * better be handled here, than in more critical paths. While we are + * checking for loops we also determine the list of files reachable + * and hang them on the tfile_check_list, so we can check that we + * haven't created too many possible wakeup paths. + * + * We do not need to take the global 'epumutex' on EPOLL_CTL_ADD when + * the epoll file descriptor is attaching directly to a wakeup source, + * unless the epoll file descriptor is nested. The purpose of taking the + * 'epmutex' on add is to prevent complex toplogies such as loops and + * deep wakeup paths from forming in parallel through multiple + * EPOLL_CTL_ADD operations. + */ + mutex_lock_nested(&ep->mtx, 0); + if (op == EPOLL_CTL_ADD) { + if (!list_empty(&f.file->f_ep_links) || + is_file_epoll(tf.file)) { + full_check = 1; + mutex_unlock(&ep->mtx); + mutex_lock(&epmutex); + if (is_file_epoll(tf.file)) { + error = -ELOOP; + if (ep_loop_check(ep, tf.file) != 0) { + clear_tfile_check_list(); + goto error_tgt_fput; + } + } else + list_add(&tf.file->f_tfile_llink, + &tfile_check_list); + mutex_lock_nested(&ep->mtx, 0); + if (is_file_epoll(tf.file)) { + tep = tf.file->private_data; + mutex_lock_nested(&tep->mtx, 1); + } } } - if (ricnt) { - /* - * Wake up ( if active ) both the eventpoll wait list and the ->poll() - * wait list. - */ - if (waitqueue_active(&ep->wq)) - wake_up(&ep->wq); - if (waitqueue_active(&ep->poll_wait)) - pwake++; + /* + * 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, tf.file, fd); + + error = -EINVAL; + switch (op) { + case EPOLL_CTL_ADD: + if (!epi) { + epds.events |= POLLERR | POLLHUP; + error = ep_insert(ep, &epds, tf.file, fd, full_check); + } else + error = -EEXIST; + if (full_check) + clear_tfile_check_list(); + 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; } + if (tep != NULL) + mutex_unlock(&tep->mtx); + mutex_unlock(&ep->mtx); - write_unlock_irqrestore(&ep->lock, flags); +error_tgt_fput: + if (full_check) + mutex_unlock(&epmutex); - /* We have to call this outside the lock */ - if (pwake) - ep_poll_safewake(&psw, &ep->poll_wait); -} + fdput(tf); +error_fput: + fdput(f); +error_return: + return error; +} /* - * Perform the transfer of events to user space. + * Implement the event wait interface for the eventpoll file. It is the kernel + * part of the user space epoll_wait(2). */ -static int ep_events_transfer(struct eventpoll *ep, - struct epoll_event __user *events, int maxevents) +SYSCALL_DEFINE4(epoll_wait, int, epfd, struct epoll_event __user *, events, + int, maxevents, int, timeout) { - int eventcnt = 0; - struct list_head txlist; + int error; + struct fd f; + struct eventpoll *ep; - INIT_LIST_HEAD(&txlist); + /* The maximum number of event must be greater than zero */ + if (maxevents <= 0 || maxevents > EP_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))) + return -EFAULT; + + /* Get the "struct file *" for the eventpoll file */ + f = fdget(epfd); + if (!f.file) + return -EBADF; /* - * We need to lock this because we could be hit by - * eventpoll_release_file() and epoll_ctl(EPOLL_CTL_DEL). + * We have to check that the file structure underneath the fd + * the user passed to us _is_ an eventpoll file. */ - 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); + error = -EINVAL; + if (!is_file_epoll(f.file)) + goto error_fput; - /* Reinject ready items into the ready list */ - ep_reinject_items(ep, &txlist); - } + /* + * At this point it is safe to assume that the "private_data" contains + * our own data structure. + */ + ep = f.file->private_data; - up_read(&ep->sem); + /* Time to fish for events ... */ + error = ep_poll(ep, events, maxevents, timeout); - return eventcnt; +error_fput: + fdput(f); + return error; } - -static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, - int maxevents, long timeout) +/* + * Implement the event wait interface for the eventpoll file. It is the kernel + * part of the user space epoll_pwait(2). + */ +SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events, + int, maxevents, int, timeout, const sigset_t __user *, sigmask, + size_t, sigsetsize) { - int res, eavail; - unsigned long flags; - long jtimeout; - wait_queue_t wait; + int error; + sigset_t ksigmask, sigsaved; /* - * 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. + * If the caller wants a certain signal mask to be set during the wait, + * we apply it here. */ - jtimeout = (timeout < 0 || timeout >= EP_MAX_MSTIMEO) ? - MAX_SCHEDULE_TIMEOUT : (timeout * HZ + 999) / 1000; - -retry: - write_lock_irqsave(&ep->lock, flags); - - res = 0; - if (list_empty(&ep->rdllist)) { - /* - * We don't have any available event to return to the caller. - * We need to sleep here, and we will be wake up by - * ep_poll_callback() when events will become available. - */ - init_waitqueue_entry(&wait, current); - add_wait_queue(&ep->wq, &wait); - - for (;;) { - /* - * We don't want to sleep if the ep_poll_callback() sends us - * a wakeup in between. That's why we set the task state - * to TASK_INTERRUPTIBLE before doing the checks. - */ - set_current_state(TASK_INTERRUPTIBLE); - if (!list_empty(&ep->rdllist) || !jtimeout) - break; - if (signal_pending(current)) { - res = -EINTR; - break; - } - - write_unlock_irqrestore(&ep->lock, flags); - jtimeout = schedule_timeout(jtimeout); - write_lock_irqsave(&ep->lock, flags); - } - remove_wait_queue(&ep->wq, &wait); - - set_current_state(TASK_RUNNING); + if (sigmask) { + if (sigsetsize != sizeof(sigset_t)) + return -EINVAL; + if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) + return -EFAULT; + sigsaved = current->blocked; + set_current_blocked(&ksigmask); } - /* Is it worth to try to dig for events ? */ - eavail = !list_empty(&ep->rdllist); - - write_unlock_irqrestore(&ep->lock, flags); + error = sys_epoll_wait(epfd, events, maxevents, timeout); /* - * Try to transfer events to user space. In case we get 0 events and - * there's still timeout left over, we go trying again in search of - * more luck. + * If 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 (!res && eavail && - !(res = ep_events_transfer(ep, events, maxevents)) && jtimeout) - goto retry; + if (sigmask) { + if (error == -EINTR) { + memcpy(¤t->saved_sigmask, &sigsaved, + sizeof(sigsaved)); + set_restore_sigmask(); + } else + set_current_blocked(&sigsaved); + } - return res; + return error; } - -static int eventpollfs_delete_dentry(struct dentry *dentry) +#ifdef CONFIG_COMPAT +COMPAT_SYSCALL_DEFINE6(epoll_pwait, int, epfd, + struct epoll_event __user *, events, + int, maxevents, int, timeout, + const compat_sigset_t __user *, sigmask, + compat_size_t, sigsetsize) { + long err; + compat_sigset_t csigmask; + sigset_t ksigmask, sigsaved; - return 1; -} - - -static struct inode *ep_eventpoll_inode(void) -{ - int error = -ENOMEM; - struct inode *inode = new_inode(eventpoll_mnt->mnt_sb); - - if (!inode) - goto eexit_1; + /* + * If the caller wants a certain signal mask to be set during the wait, + * we apply it here. + */ + if (sigmask) { + if (sigsetsize != sizeof(compat_sigset_t)) + return -EINVAL; + if (copy_from_user(&csigmask, sigmask, sizeof(csigmask))) + return -EFAULT; + sigset_from_compat(&ksigmask, &csigmask); + sigsaved = current->blocked; + set_current_blocked(&ksigmask); + } - inode->i_fop = &eventpoll_fops; + err = sys_epoll_wait(epfd, events, maxevents, timeout); /* - * 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. + * 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. */ - inode->i_state = I_DIRTY; - inode->i_mode = S_IRUSR | S_IWUSR; - inode->i_uid = current->fsuid; - inode->i_gid = current->fsgid; - inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; - inode->i_blksize = PAGE_SIZE; - return inode; - -eexit_1: - return ERR_PTR(error); -} - + if (sigmask) { + if (err == -EINTR) { + memcpy(¤t->saved_sigmask, &sigsaved, + sizeof(sigsaved)); + set_restore_sigmask(); + } else + set_current_blocked(&sigsaved); + } -static struct super_block * -eventpollfs_get_sb(struct file_system_type *fs_type, int flags, - const char *dev_name, void *data) -{ - return get_sb_pseudo(fs_type, "eventpoll:", NULL, EVENTPOLLFS_MAGIC); + return err; } - +#endif static int __init eventpoll_init(void) { - int error; + struct sysinfo si; - init_MUTEX(&epsem); + si_meminfo(&si); + /* + * Allows top 4% of lomem to be allocated for epoll watches (per user). + */ + max_user_watches = (((si.totalram - si.totalhigh) / 25) << PAGE_SHIFT) / + EP_ITEM_COST; + BUG_ON(max_user_watches < 0); + + /* + * Initialize the structure used to perform epoll file descriptor + * inclusion loops checks. + */ + ep_nested_calls_init(&poll_loop_ncalls); /* 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); + + /* + * We can have many thousands of epitems, so prevent this from + * using an extra cache line on 64-bit (and smaller) CPUs + */ + BUILD_BUG_ON(sizeof(void *) <= 8 && sizeof(struct epitem) > 128); /* 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); + 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, NULL); + sizeof(struct eppoll_entry), 0, SLAB_PANIC, 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; - - 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); -} - -module_init(eventpoll_init); -module_exit(eventpoll_exit); - -MODULE_LICENSE("GPL"); +fs_initcall(eventpoll_init); |