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fs/eventpoll.c
49.4 KB
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/* |
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* fs/eventpoll.c (Efficient event retrieval implementation) * Copyright (C) 2001,...,2009 Davide Libenzi |
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* * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * Davide Libenzi <davidel@xmailserver.org> * */ |
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#include <linux/init.h> #include <linux/kernel.h> #include <linux/sched.h> #include <linux/fs.h> #include <linux/file.h> #include <linux/signal.h> #include <linux/errno.h> #include <linux/mm.h> #include <linux/slab.h> #include <linux/poll.h> |
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#include <linux/string.h> #include <linux/list.h> #include <linux/hash.h> #include <linux/spinlock.h> #include <linux/syscalls.h> |
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#include <linux/rbtree.h> #include <linux/wait.h> #include <linux/eventpoll.h> #include <linux/mount.h> #include <linux/bitops.h> |
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#include <linux/mutex.h> |
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#include <linux/anon_inodes.h> |
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#include <asm/uaccess.h> #include <asm/system.h> #include <asm/io.h> #include <asm/mman.h> |
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#include <linux/atomic.h> |
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/* * LOCKING: * There are three level of locking required by epoll : * |
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* 1) epmutex (mutex) |
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* 2) ep->mtx (mutex) * 3) ep->lock (spinlock) |
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* * The acquire order is the one listed above, from 1 to 3. * We need a spinlock (ep->lock) because we manipulate objects * from inside the poll callback, that might be triggered from * a wake_up() that in turn might be called from IRQ context. * So we can't sleep inside the poll callback and hence we need * 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 |
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* 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 |
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* 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 |
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* close()d without a previous call to epoll_ctl(EPOLL_CTL_DEL). |
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* 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. |
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* 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. |
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* 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. |
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* Events that require holding "epmutex" are very rare, while for |
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* normal operations the epoll private "ep->mtx" will guarantee * a better scalability. |
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*/ |
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/* Epoll private bits inside the event mask */ #define EP_PRIVATE_BITS (EPOLLONESHOT | EPOLLET) |
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/* Maximum number of nesting allowed inside epoll sets */ #define EP_MAX_NESTS 4 |
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#define EP_MAX_EVENTS (INT_MAX / sizeof(struct epoll_event)) |
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#define EP_UNACTIVE_PTR ((void *) -1L) |
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#define EP_ITEM_COST (sizeof(struct epitem) + sizeof(struct eppoll_entry)) |
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struct epoll_filefd { struct file *file; int fd; }; /* |
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* Structure used to track possible nested calls, for too deep recursions * and loop cycles. |
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*/ |
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struct nested_call_node { |
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struct list_head llink; |
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void *cookie; |
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void *ctx; |
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}; /* |
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* This structure is used as collector for nested calls, to check for * maximum recursion dept and loop cycles. |
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*/ |
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struct nested_calls { struct list_head tasks_call_list; |
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spinlock_t lock; }; /* |
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* Each file descriptor added to the eventpoll interface will * have an entry of this type linked to the "rbr" RB tree. */ struct epitem { |
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/* RB tree node used to link this structure to the eventpoll RB tree */ |
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struct rb_node rbn; /* List header used to link this structure to the eventpoll ready list */ struct list_head rdllink; |
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/* * Works together "struct eventpoll"->ovflist in keeping the * single linked chain of items. */ struct epitem *next; |
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/* 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; |
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/* List header used to link this item to the "struct file" items list */ struct list_head fllink; |
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/* The structure that describe the interested events and the source fd */ struct epoll_event event; |
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}; /* |
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* This structure is stored inside the "private_data" member of the file |
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* structure and represents the main data structure for the eventpoll |
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* interface. */ struct eventpoll { |
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/* Protect the access to this structure */ |
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spinlock_t lock; |
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/* |
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* 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. |
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*/ |
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struct mutex mtx; |
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/* Wait queue used by sys_epoll_wait() */ wait_queue_head_t wq; /* Wait queue used by file->poll() */ wait_queue_head_t poll_wait; /* List of ready file descriptors */ struct list_head rdllist; |
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/* RB tree root used to store monitored fd structs */ |
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struct rb_root rbr; |
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/* * This is a single linked list that chains all the "struct epitem" that |
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* happened while transferring ready events to userspace w/out |
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* holding ->lock. */ struct epitem *ovflist; |
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/* The user that created the eventpoll descriptor */ struct user_struct *user; |
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struct file *file; /* used to optimize loop detection check */ int visited; struct list_head visited_list_link; |
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}; /* Wait structure used by the poll hooks */ struct eppoll_entry { /* List header used to link this structure to the "struct epitem" */ struct list_head llink; /* The "base" pointer is set to the container "struct epitem" */ |
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struct epitem *base; |
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/* * Wait queue item that will be linked to the target file wait * queue head. */ wait_queue_t wait; /* The wait queue head that linked the "wait" wait queue item */ wait_queue_head_t *whead; }; |
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/* Wrapper struct used by poll queueing */ struct ep_pqueue { poll_table pt; struct epitem *epi; }; |
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/* Used by the ep_send_events() function as callback private data */ struct ep_send_events_data { int maxevents; struct epoll_event __user *events; }; |
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/* |
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* Configuration options available inside /proc/sys/fs/epoll/ */ |
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/* Maximum number of epoll watched descriptors, per user */ |
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static long max_user_watches __read_mostly; |
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/* |
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* This mutex is used to serialize ep_free() and eventpoll_release_file(). |
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*/ |
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static DEFINE_MUTEX(epmutex); |
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/* Used to check for epoll file descriptor inclusion loops */ static struct nested_calls poll_loop_ncalls; |
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/* Used for safe wake up implementation */ static struct nested_calls poll_safewake_ncalls; /* Used to call file's f_op->poll() under the nested calls boundaries */ static struct nested_calls poll_readywalk_ncalls; |
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/* Slab cache used to allocate "struct epitem" */ |
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static struct kmem_cache *epi_cache __read_mostly; |
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/* Slab cache used to allocate "struct eppoll_entry" */ |
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static struct kmem_cache *pwq_cache __read_mostly; |
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/* Visited nodes during ep_loop_check(), so we can unset them when we finish */ static LIST_HEAD(visited_list); /* * List of files with newly added links, where we may need to limit the number * of emanating paths. Protected by the epmutex. */ static LIST_HEAD(tfile_check_list); |
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#ifdef CONFIG_SYSCTL #include <linux/sysctl.h> |
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static long zero; static long long_max = LONG_MAX; |
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ctl_table epoll_table[] = { { |
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.procname = "max_user_watches", .data = &max_user_watches, |
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.maxlen = sizeof(max_user_watches), |
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.mode = 0644, |
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.proc_handler = proc_doulongvec_minmax, |
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.extra1 = &zero, |
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.extra2 = &long_max, |
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}, |
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{ } |
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}; #endif /* CONFIG_SYSCTL */ |
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static const struct file_operations eventpoll_fops; static inline int is_file_epoll(struct file *f) { return f->f_op == &eventpoll_fops; } |
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/* Setup the structure that is used as key for the RB tree */ |
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static inline void ep_set_ffd(struct epoll_filefd *ffd, struct file *file, int fd) { ffd->file = file; ffd->fd = fd; } |
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/* Compare RB tree keys */ |
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static inline int ep_cmp_ffd(struct epoll_filefd *p1, struct epoll_filefd *p2) { return (p1->file > p2->file ? +1: (p1->file < p2->file ? -1 : p1->fd - p2->fd)); } |
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/* Tells us if the item is currently linked */ static inline int ep_is_linked(struct list_head *p) { return !list_empty(p); } /* Get the "struct epitem" from a wait queue pointer */ |
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static inline struct epitem *ep_item_from_wait(wait_queue_t *p) |
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{ return container_of(p, struct eppoll_entry, wait)->base; } /* Get the "struct epitem" from an epoll queue wrapper */ |
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static inline struct epitem *ep_item_from_epqueue(poll_table *p) |
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{ return container_of(p, struct ep_pqueue, pt)->epi; } /* Tells if the epoll_ctl(2) operation needs an event copy from userspace */ |
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static inline int ep_op_has_event(int op) |
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{ return op != EPOLL_CTL_DEL; } |
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/* Initialize the poll safe wake up structure */ |
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static void ep_nested_calls_init(struct nested_calls *ncalls) |
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{ |
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INIT_LIST_HEAD(&ncalls->tasks_call_list); spin_lock_init(&ncalls->lock); |
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} |
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/** |
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* 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; } /** |
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* 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. |
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* @ctx: This instance context. |
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* * Returns: Returns the code returned by the @nproc callback, or -1 if * the maximum recursion limit has been exceeded. |
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*/ |
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static int ep_call_nested(struct nested_calls *ncalls, int max_nests, int (*nproc)(void *, void *, int), void *priv, |
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void *cookie, void *ctx) |
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{ |
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int error, call_nests = 0; |
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unsigned long flags; |
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struct list_head *lsthead = &ncalls->tasks_call_list; struct nested_call_node *tncur; struct nested_call_node tnode; |
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spin_lock_irqsave(&ncalls->lock, flags); |
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/* * 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. */ |
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list_for_each_entry(tncur, lsthead, llink) { |
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if (tncur->ctx == ctx && |
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(tncur->cookie == cookie || ++call_nests > max_nests)) { |
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/* * Ops ... loop detected or maximum nest level reached. * We abort this wake by breaking the cycle itself. */ |
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error = -1; goto out_unlock; |
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} } |
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/* Add the current task and cookie to the list */ |
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tnode.ctx = ctx; |
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tnode.cookie = cookie; |
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list_add(&tnode.llink, lsthead); |
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spin_unlock_irqrestore(&ncalls->lock, flags); |
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/* Call the nested function */ error = (*nproc)(priv, cookie, call_nests); |
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/* Remove the current task from the list */ |
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spin_lock_irqsave(&ncalls->lock, flags); |
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list_del(&tnode.llink); |
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out_unlock: |
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spin_unlock_irqrestore(&ncalls->lock, flags); return error; } |
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#ifdef CONFIG_DEBUG_LOCK_ALLOC static inline void ep_wake_up_nested(wait_queue_head_t *wqueue, unsigned long events, int subclass) { unsigned long flags; spin_lock_irqsave_nested(&wqueue->lock, flags, subclass); wake_up_locked_poll(wqueue, events); spin_unlock_irqrestore(&wqueue->lock, flags); } #else static inline void ep_wake_up_nested(wait_queue_head_t *wqueue, unsigned long events, int subclass) { wake_up_poll(wqueue, events); } #endif |
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static int ep_poll_wakeup_proc(void *priv, void *cookie, int call_nests) { |
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ep_wake_up_nested((wait_queue_head_t *) cookie, POLLIN, 1 + call_nests); |
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return 0; } /* * Perform a safe wake up of the poll wait list. The problem is that * with the new callback'd wake up system, it is possible that the * poll callback is reentered from inside the call to wake_up() done * on the poll wait queue head. The rule is that we cannot reenter the * wake up code from the same task more than EP_MAX_NESTS times, * and we cannot reenter the same wait queue head at all. This will * enable to have a hierarchy of epoll file descriptor of no more than * EP_MAX_NESTS deep. */ static void ep_poll_safewake(wait_queue_head_t *wq) { |
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int this_cpu = get_cpu(); |
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ep_call_nested(&poll_safewake_ncalls, EP_MAX_NESTS, |
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ep_poll_wakeup_proc, NULL, wq, (void *) (long) this_cpu); put_cpu(); |
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} |
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/* |
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* This function unregisters poll callbacks from the associated file * descriptor. Must be called with "mtx" held (or "epmutex" if called from * ep_free). |
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*/ |
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static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi) |
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{ |
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struct list_head *lsthead = &epi->pwqlist; struct eppoll_entry *pwq; |
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while (!list_empty(lsthead)) { pwq = list_first_entry(lsthead, struct eppoll_entry, llink); |
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list_del(&pwq->llink); remove_wait_queue(pwq->whead, &pwq->wait); kmem_cache_free(pwq_cache, pwq); |
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} |
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} |
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/** * 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. |
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* @depth: The current depth of recursive f_op->poll calls. |
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* * 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 *), |
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void *priv, int depth) |
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{ int error, pwake = 0; unsigned long flags; struct epitem *epi, *nepi; |
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LIST_HEAD(txlist); |
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/* * We need to lock this because we could be hit by |
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* eventpoll_release_file() and epoll_ctl(). |
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*/ |
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mutex_lock_nested(&ep->mtx, depth); |
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/* * Steal the ready list, and re-init the original one to the * empty list. Also, set ep->ovflist to NULL so that events * happening while looping w/out locks, are not lost. We cannot * have the poll callback to queue directly on ep->rdllist, * because we want the "sproc" callback to be able to do it * in a lockless way. */ spin_lock_irqsave(&ep->lock, flags); |
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list_splice_init(&ep->rdllist, &txlist); |
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|
499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 |
ep->ovflist = NULL; spin_unlock_irqrestore(&ep->lock, flags); /* * Now call the callback function. */ error = (*sproc)(ep, &txlist, priv); spin_lock_irqsave(&ep->lock, flags); /* * During the time we spent inside the "sproc" callback, some * other events might have been queued by the poll callback. * We re-insert them inside the main ready-list here. */ for (nepi = ep->ovflist; (epi = nepi) != NULL; nepi = epi->next, epi->next = EP_UNACTIVE_PTR) { /* * We need to check if the item is already in the list. * During the "sproc" callback execution time, items are * queued into ->ovflist but the "txlist" might already * contain them, and the list_splice() below takes care of them. */ if (!ep_is_linked(&epi->rdllink)) list_add_tail(&epi->rdllink, &ep->rdllist); } /* * We need to set back ep->ovflist to EP_UNACTIVE_PTR, so that after * releasing the lock, events will be queued in the normal way inside * ep->rdllist. */ ep->ovflist = EP_UNACTIVE_PTR; /* * Quickly re-inject items left on "txlist". */ list_splice(&txlist, &ep->rdllist); if (!list_empty(&ep->rdllist)) { /* |
296e236e9
|
538 539 |
* Wake up (if active) both the eventpoll wait list and * the ->poll() wait list (delayed after we release the lock). |
5071f97ec
|
540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 |
*/ if (waitqueue_active(&ep->wq)) wake_up_locked(&ep->wq); if (waitqueue_active(&ep->poll_wait)) pwake++; } spin_unlock_irqrestore(&ep->lock, flags); mutex_unlock(&ep->mtx); /* We have to call this outside the lock */ if (pwake) ep_poll_safewake(&ep->poll_wait); return error; } |
1da177e4c
|
556 |
/* |
7699acd13
|
557 |
* Removes a "struct epitem" from the eventpoll RB tree and deallocates |
c7ea76302
|
558 |
* all the associated resources. Must be called with "mtx" held. |
7699acd13
|
559 560 561 |
*/ static int ep_remove(struct eventpoll *ep, struct epitem *epi) { |
7699acd13
|
562 563 |
unsigned long flags; struct file *file = epi->ffd.file; |
1da177e4c
|
564 565 |
/* |
7699acd13
|
566 567 568 569 570 571 |
* 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". |
1da177e4c
|
572 |
*/ |
7699acd13
|
573 |
ep_unregister_pollwait(ep, epi); |
1da177e4c
|
574 |
|
7699acd13
|
575 |
/* Remove the current item from the list of epoll hooks */ |
684999149
|
576 |
spin_lock(&file->f_lock); |
7699acd13
|
577 578 |
if (ep_is_linked(&epi->fllink)) list_del_init(&epi->fllink); |
684999149
|
579 |
spin_unlock(&file->f_lock); |
1da177e4c
|
580 |
|
cdac75e6f
|
581 |
rb_erase(&epi->rbn, &ep->rbr); |
1da177e4c
|
582 |
|
c7ea76302
|
583 584 585 586 |
spin_lock_irqsave(&ep->lock, flags); if (ep_is_linked(&epi->rdllink)) list_del_init(&epi->rdllink); spin_unlock_irqrestore(&ep->lock, flags); |
1da177e4c
|
587 |
|
7699acd13
|
588 |
/* At this point it is safe to free the eventpoll item */ |
c7ea76302
|
589 |
kmem_cache_free(epi_cache, epi); |
1da177e4c
|
590 |
|
52bd19f76
|
591 |
atomic_long_dec(&ep->user->epoll_watches); |
7ef9964e6
|
592 |
|
c7ea76302
|
593 |
return 0; |
1da177e4c
|
594 |
} |
7699acd13
|
595 |
static void ep_free(struct eventpoll *ep) |
1da177e4c
|
596 |
{ |
7699acd13
|
597 598 |
struct rb_node *rbp; struct epitem *epi; |
1da177e4c
|
599 |
|
7699acd13
|
600 601 |
/* We need to release all tasks waiting for these file */ if (waitqueue_active(&ep->poll_wait)) |
5071f97ec
|
602 |
ep_poll_safewake(&ep->poll_wait); |
1da177e4c
|
603 |
|
7699acd13
|
604 605 606 |
/* * We need to lock this because we could be hit by * eventpoll_release_file() while we're freeing the "struct eventpoll". |
d47de16c7
|
607 |
* We do not need to hold "ep->mtx" here because the epoll file |
7699acd13
|
608 609 |
* 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 |
25985edce
|
610 |
* holding "epmutex" is sufficient here. |
7699acd13
|
611 612 |
*/ mutex_lock(&epmutex); |
1da177e4c
|
613 614 |
/* |
7699acd13
|
615 |
* Walks through the whole tree by unregistering poll callbacks. |
1da177e4c
|
616 |
*/ |
7699acd13
|
617 618 619 620 621 |
for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { epi = rb_entry(rbp, struct epitem, rbn); ep_unregister_pollwait(ep, epi); } |
1da177e4c
|
622 623 |
/* |
7699acd13
|
624 625 |
* 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 |
d47de16c7
|
626 |
* holding "epmutex" we can be sure that no file cleanup code will hit |
7699acd13
|
627 |
* us during this operation. So we can avoid the lock on "ep->lock". |
1da177e4c
|
628 |
*/ |
c80544dc0
|
629 |
while ((rbp = rb_first(&ep->rbr)) != NULL) { |
7699acd13
|
630 631 632 |
epi = rb_entry(rbp, struct epitem, rbn); ep_remove(ep, epi); } |
1da177e4c
|
633 |
|
7699acd13
|
634 |
mutex_unlock(&epmutex); |
d47de16c7
|
635 |
mutex_destroy(&ep->mtx); |
7ef9964e6
|
636 |
free_uid(ep->user); |
f0ee9aabb
|
637 |
kfree(ep); |
7699acd13
|
638 |
} |
1da177e4c
|
639 |
|
7699acd13
|
640 641 642 |
static int ep_eventpoll_release(struct inode *inode, struct file *file) { struct eventpoll *ep = file->private_data; |
1da177e4c
|
643 |
|
f0ee9aabb
|
644 |
if (ep) |
7699acd13
|
645 |
ep_free(ep); |
7699acd13
|
646 |
|
7699acd13
|
647 |
return 0; |
1da177e4c
|
648 |
} |
296e236e9
|
649 650 |
static int ep_read_events_proc(struct eventpoll *ep, struct list_head *head, void *priv) |
5071f97ec
|
651 652 653 654 655 656 657 |
{ struct epitem *epi, *tmp; list_for_each_entry_safe(epi, tmp, head, rdllink) { if (epi->ffd.file->f_op->poll(epi->ffd.file, NULL) & epi->event.events) return POLLIN | POLLRDNORM; |
296e236e9
|
658 |
else { |
5071f97ec
|
659 660 661 662 663 664 |
/* * Item has been dropped into the ready list by the poll * callback, but it's not actually ready, as far as * caller requested events goes. We can remove it here. */ list_del_init(&epi->rdllink); |
296e236e9
|
665 |
} |
5071f97ec
|
666 667 668 669 670 671 672 |
} return 0; } static int ep_poll_readyevents_proc(void *priv, void *cookie, int call_nests) { |
d8805e633
|
673 |
return ep_scan_ready_list(priv, ep_read_events_proc, NULL, call_nests + 1); |
5071f97ec
|
674 |
} |
7699acd13
|
675 676 |
static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait) { |
5071f97ec
|
677 |
int pollflags; |
7699acd13
|
678 |
struct eventpoll *ep = file->private_data; |
1da177e4c
|
679 |
|
7699acd13
|
680 681 |
/* Insert inside our poll wait queue */ poll_wait(file, &ep->poll_wait, wait); |
5071f97ec
|
682 683 684 685 686 687 688 |
/* * 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, |
3fe4a975d
|
689 |
ep_poll_readyevents_proc, ep, ep, current); |
7699acd13
|
690 |
|
296e236e9
|
691 |
return pollflags != -1 ? pollflags : 0; |
7699acd13
|
692 693 694 695 696 |
} /* File callbacks that implement the eventpoll file behaviour */ static const struct file_operations eventpoll_fops = { .release = ep_eventpoll_release, |
6038f373a
|
697 698 |
.poll = ep_eventpoll_poll, .llseek = noop_llseek, |
7699acd13
|
699 |
}; |
b611967de
|
700 |
/* |
7699acd13
|
701 702 703 |
* 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. |
b611967de
|
704 |
*/ |
7699acd13
|
705 |
void eventpoll_release_file(struct file *file) |
b611967de
|
706 |
{ |
7699acd13
|
707 708 709 |
struct list_head *lsthead = &file->f_ep_links; struct eventpoll *ep; struct epitem *epi; |
b611967de
|
710 711 |
/* |
684999149
|
712 |
* We don't want to get "file->f_lock" because it is not |
7699acd13
|
713 |
* necessary. It is not necessary because we're in the "struct file" |
25985edce
|
714 |
* cleanup path, and this means that no one is using this file anymore. |
5071f97ec
|
715 |
* So, for example, epoll_ctl() cannot hit here since if we reach this |
67647d0fb
|
716 |
* point, the file counter already went to zero and fget() would fail. |
d47de16c7
|
717 |
* The only hit might come from ep_free() but by holding the mutex |
7699acd13
|
718 |
* will correctly serialize the operation. We do need to acquire |
d47de16c7
|
719 |
* "ep->mtx" after "epmutex" because ep_remove() requires it when called |
7699acd13
|
720 |
* from anywhere but ep_free(). |
684999149
|
721 722 |
* * Besides, ep_remove() acquires the lock, so we can't hold it here. |
b611967de
|
723 |
*/ |
7699acd13
|
724 |
mutex_lock(&epmutex); |
b611967de
|
725 |
|
7699acd13
|
726 727 |
while (!list_empty(lsthead)) { epi = list_first_entry(lsthead, struct epitem, fllink); |
b611967de
|
728 |
|
7699acd13
|
729 730 |
ep = epi->ep; list_del_init(&epi->fllink); |
d8805e633
|
731 |
mutex_lock_nested(&ep->mtx, 0); |
7699acd13
|
732 |
ep_remove(ep, epi); |
d47de16c7
|
733 |
mutex_unlock(&ep->mtx); |
b611967de
|
734 |
} |
7699acd13
|
735 |
mutex_unlock(&epmutex); |
b611967de
|
736 |
} |
53d2be79d
|
737 |
static int ep_alloc(struct eventpoll **pep) |
1da177e4c
|
738 |
{ |
7ef9964e6
|
739 740 741 |
int error; struct user_struct *user; struct eventpoll *ep; |
1da177e4c
|
742 |
|
7ef9964e6
|
743 |
user = get_current_user(); |
7ef9964e6
|
744 745 746 747 |
error = -ENOMEM; ep = kzalloc(sizeof(*ep), GFP_KERNEL); if (unlikely(!ep)) goto free_uid; |
1da177e4c
|
748 |
|
c7ea76302
|
749 |
spin_lock_init(&ep->lock); |
d47de16c7
|
750 |
mutex_init(&ep->mtx); |
1da177e4c
|
751 752 753 754 |
init_waitqueue_head(&ep->wq); init_waitqueue_head(&ep->poll_wait); INIT_LIST_HEAD(&ep->rdllist); ep->rbr = RB_ROOT; |
d47de16c7
|
755 |
ep->ovflist = EP_UNACTIVE_PTR; |
7ef9964e6
|
756 |
ep->user = user; |
1da177e4c
|
757 |
|
53d2be79d
|
758 |
*pep = ep; |
1da177e4c
|
759 |
|
1da177e4c
|
760 |
return 0; |
7ef9964e6
|
761 762 763 764 |
free_uid: free_uid(user); return error; |
1da177e4c
|
765 |
} |
1da177e4c
|
766 |
/* |
c7ea76302
|
767 768 769 |
* 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. |
1da177e4c
|
770 771 772 773 |
*/ static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd) { int kcmp; |
1da177e4c
|
774 775 776 |
struct rb_node *rbp; struct epitem *epi, *epir = NULL; struct epoll_filefd ffd; |
b030a4dd6
|
777 |
ep_set_ffd(&ffd, file, fd); |
1da177e4c
|
778 779 |
for (rbp = ep->rbr.rb_node; rbp; ) { epi = rb_entry(rbp, struct epitem, rbn); |
b030a4dd6
|
780 |
kcmp = ep_cmp_ffd(&ffd, &epi->ffd); |
1da177e4c
|
781 782 783 784 785 |
if (kcmp > 0) rbp = rbp->rb_right; else if (kcmp < 0) rbp = rbp->rb_left; else { |
1da177e4c
|
786 787 788 789 |
epir = epi; break; } } |
1da177e4c
|
790 |
|
1da177e4c
|
791 792 |
return epir; } |
1da177e4c
|
793 |
/* |
7699acd13
|
794 |
* This is the callback that is passed to the wait queue wakeup |
bf6a41db7
|
795 |
* mechanism. It is called by the stored file descriptors when they |
7699acd13
|
796 |
* have events to report. |
1da177e4c
|
797 |
*/ |
7699acd13
|
798 |
static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *key) |
1da177e4c
|
799 |
{ |
7699acd13
|
800 801 802 803 |
int pwake = 0; unsigned long flags; struct epitem *epi = ep_item_from_wait(wait); struct eventpoll *ep = epi->ep; |
1da177e4c
|
804 |
|
c7ea76302
|
805 |
spin_lock_irqsave(&ep->lock, flags); |
1da177e4c
|
806 |
|
7699acd13
|
807 808 809 810 811 812 813 |
/* * 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)) |
d47de16c7
|
814 815 816 |
goto out_unlock; /* |
2dfa4eeab
|
817 818 819 820 821 822 823 824 825 |
* 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; /* |
bf6a41db7
|
826 |
* If we are transferring events to userspace, we can hold no locks |
d47de16c7
|
827 |
* (because we're accessing user memory, and because of linux f_op->poll() |
bf6a41db7
|
828 |
* semantics). All the events that happen during that period of time are |
d47de16c7
|
829 830 831 832 833 834 835 836 837 |
* chained in ep->ovflist and requeued later on. */ if (unlikely(ep->ovflist != EP_UNACTIVE_PTR)) { if (epi->next == EP_UNACTIVE_PTR) { epi->next = ep->ovflist; ep->ovflist = epi; } goto out_unlock; } |
1da177e4c
|
838 |
|
7699acd13
|
839 |
/* If this file is already in the ready list we exit soon */ |
5071f97ec
|
840 841 |
if (!ep_is_linked(&epi->rdllink)) list_add_tail(&epi->rdllink, &ep->rdllist); |
7699acd13
|
842 |
|
7699acd13
|
843 844 845 846 847 |
/* * Wake up ( if active ) both the eventpoll wait list and the ->poll() * wait list. */ if (waitqueue_active(&ep->wq)) |
4a6e9e2ce
|
848 |
wake_up_locked(&ep->wq); |
7699acd13
|
849 850 |
if (waitqueue_active(&ep->poll_wait)) pwake++; |
d47de16c7
|
851 |
out_unlock: |
c7ea76302
|
852 |
spin_unlock_irqrestore(&ep->lock, flags); |
1da177e4c
|
853 |
|
7699acd13
|
854 855 |
/* We have to call this outside the lock */ if (pwake) |
5071f97ec
|
856 |
ep_poll_safewake(&ep->poll_wait); |
7699acd13
|
857 858 859 |
return 1; } |
1da177e4c
|
860 861 862 863 864 865 866 867 |
/* * This is the callback that is used to add our wait queue to the * target file wakeup lists. */ static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, poll_table *pt) { |
b030a4dd6
|
868 |
struct epitem *epi = ep_item_from_epqueue(pt); |
1da177e4c
|
869 |
struct eppoll_entry *pwq; |
e94b17660
|
870 |
if (epi->nwait >= 0 && (pwq = kmem_cache_alloc(pwq_cache, GFP_KERNEL))) { |
1da177e4c
|
871 872 873 874 875 876 |
init_waitqueue_func_entry(&pwq->wait, ep_poll_callback); pwq->whead = whead; pwq->base = epi; add_wait_queue(whead, &pwq->wait); list_add_tail(&pwq->llink, &epi->pwqlist); epi->nwait++; |
296e236e9
|
877 |
} else { |
1da177e4c
|
878 879 |
/* We have to signal that an error occurred */ epi->nwait = -1; |
296e236e9
|
880 |
} |
1da177e4c
|
881 |
} |
1da177e4c
|
882 883 884 885 886 887 888 889 890 |
static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi) { int kcmp; struct rb_node **p = &ep->rbr.rb_node, *parent = NULL; struct epitem *epic; while (*p) { parent = *p; epic = rb_entry(parent, struct epitem, rbn); |
b030a4dd6
|
891 |
kcmp = ep_cmp_ffd(&epi->ffd, &epic->ffd); |
1da177e4c
|
892 893 894 895 896 897 898 899 |
if (kcmp > 0) p = &parent->rb_right; else p = &parent->rb_left; } rb_link_node(&epi->rbn, parent, p); rb_insert_color(&epi->rbn, &ep->rbr); } |
28d82dc1c
|
900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 |
#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) { 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; list_for_each_entry(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! "); } } 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 length = 0; 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) { length++; 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; } |
c7ea76302
|
993 994 995 |
/* * Must be called with "mtx" held. */ |
1da177e4c
|
996 997 998 999 1000 |
static int ep_insert(struct eventpoll *ep, struct epoll_event *event, struct file *tfile, int fd) { int error, revents, pwake = 0; unsigned long flags; |
52bd19f76
|
1001 |
long user_watches; |
1da177e4c
|
1002 1003 |
struct epitem *epi; struct ep_pqueue epq; |
52bd19f76
|
1004 1005 |
user_watches = atomic_long_read(&ep->user->epoll_watches); if (unlikely(user_watches >= max_user_watches)) |
7ef9964e6
|
1006 |
return -ENOSPC; |
e94b17660
|
1007 |
if (!(epi = kmem_cache_alloc(epi_cache, GFP_KERNEL))) |
7ef9964e6
|
1008 |
return -ENOMEM; |
1da177e4c
|
1009 1010 |
/* Item initialization follow here ... */ |
1da177e4c
|
1011 1012 |
INIT_LIST_HEAD(&epi->rdllink); INIT_LIST_HEAD(&epi->fllink); |
1da177e4c
|
1013 1014 |
INIT_LIST_HEAD(&epi->pwqlist); epi->ep = ep; |
b030a4dd6
|
1015 |
ep_set_ffd(&epi->ffd, tfile, fd); |
1da177e4c
|
1016 |
epi->event = *event; |
1da177e4c
|
1017 |
epi->nwait = 0; |
d47de16c7
|
1018 |
epi->next = EP_UNACTIVE_PTR; |
1da177e4c
|
1019 1020 1021 1022 1023 1024 1025 1026 |
/* Initialize the poll table using the queue callback */ epq.epi = epi; init_poll_funcptr(&epq.pt, ep_ptable_queue_proc); /* * Attach the item to the poll hooks and get current event bits. * We can safely use the file* here because its usage count has |
c7ea76302
|
1027 1028 1029 |
* been increased by the caller of this function. Note that after * this operation completes, the poll callback can start hitting * the new item. |
1da177e4c
|
1030 1031 1032 1033 1034 1035 1036 1037 |
*/ revents = tfile->f_op->poll(tfile, &epq.pt); /* * We have to check if something went wrong during the poll wait queue * install process. Namely an allocation for a wait queue failed due * high memory pressure. */ |
7ef9964e6
|
1038 |
error = -ENOMEM; |
1da177e4c
|
1039 |
if (epi->nwait < 0) |
7699acd13
|
1040 |
goto error_unregister; |
1da177e4c
|
1041 1042 |
/* Add the current item to the list of active epoll hook for this file */ |
684999149
|
1043 |
spin_lock(&tfile->f_lock); |
1da177e4c
|
1044 |
list_add_tail(&epi->fllink, &tfile->f_ep_links); |
684999149
|
1045 |
spin_unlock(&tfile->f_lock); |
1da177e4c
|
1046 |
|
c7ea76302
|
1047 1048 1049 1050 |
/* * Add the current item to the RB tree. All RB tree operations are * protected by "mtx", and ep_insert() is called with "mtx" held. */ |
1da177e4c
|
1051 |
ep_rbtree_insert(ep, epi); |
28d82dc1c
|
1052 1053 1054 1055 |
/* now check if we've created too many backpaths */ error = -EINVAL; if (reverse_path_check()) goto error_remove_epi; |
c7ea76302
|
1056 1057 |
/* We have to drop the new item inside our item list to keep track of it */ spin_lock_irqsave(&ep->lock, flags); |
1da177e4c
|
1058 |
/* If the file is already "ready" we drop it inside the ready list */ |
b030a4dd6
|
1059 |
if ((revents & event->events) && !ep_is_linked(&epi->rdllink)) { |
1da177e4c
|
1060 1061 1062 1063 |
list_add_tail(&epi->rdllink, &ep->rdllist); /* Notify waiting tasks that events are available */ if (waitqueue_active(&ep->wq)) |
4a6e9e2ce
|
1064 |
wake_up_locked(&ep->wq); |
1da177e4c
|
1065 1066 1067 |
if (waitqueue_active(&ep->poll_wait)) pwake++; } |
c7ea76302
|
1068 |
spin_unlock_irqrestore(&ep->lock, flags); |
1da177e4c
|
1069 |
|
52bd19f76
|
1070 |
atomic_long_inc(&ep->user->epoll_watches); |
7ef9964e6
|
1071 |
|
1da177e4c
|
1072 1073 |
/* We have to call this outside the lock */ if (pwake) |
5071f97ec
|
1074 |
ep_poll_safewake(&ep->poll_wait); |
1da177e4c
|
1075 |
|
1da177e4c
|
1076 |
return 0; |
28d82dc1c
|
1077 1078 1079 1080 1081 1082 1083 |
error_remove_epi: spin_lock(&tfile->f_lock); if (ep_is_linked(&epi->fllink)) list_del_init(&epi->fllink); spin_unlock(&tfile->f_lock); rb_erase(&epi->rbn, &ep->rbr); |
7699acd13
|
1084 |
error_unregister: |
1da177e4c
|
1085 1086 1087 1088 |
ep_unregister_pollwait(ep, epi); /* * We need to do this because an event could have been arrived on some |
67647d0fb
|
1089 1090 1091 |
* 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. |
1da177e4c
|
1092 |
*/ |
c7ea76302
|
1093 |
spin_lock_irqsave(&ep->lock, flags); |
b030a4dd6
|
1094 |
if (ep_is_linked(&epi->rdllink)) |
6192bd536
|
1095 |
list_del_init(&epi->rdllink); |
c7ea76302
|
1096 |
spin_unlock_irqrestore(&ep->lock, flags); |
1da177e4c
|
1097 |
|
b030a4dd6
|
1098 |
kmem_cache_free(epi_cache, epi); |
7ef9964e6
|
1099 |
|
1da177e4c
|
1100 1101 |
return error; } |
1da177e4c
|
1102 1103 |
/* * Modify the interest event mask by dropping an event if the new mask |
c7ea76302
|
1104 |
* has a match in the current file status. Must be called with "mtx" held. |
1da177e4c
|
1105 1106 1107 1108 1109 |
*/ static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_event *event) { int pwake = 0; unsigned int revents; |
1da177e4c
|
1110 1111 |
/* |
e057e15ff
|
1112 1113 1114 |
* 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. |
1da177e4c
|
1115 1116 |
*/ epi->event.events = event->events; |
e057e15ff
|
1117 |
epi->event.data = event->data; /* protected by mtx */ |
1da177e4c
|
1118 1119 1120 1121 1122 1123 |
/* * 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); |
1da177e4c
|
1124 |
/* |
c7ea76302
|
1125 |
* If the item is "hot" and it is not registered inside the ready |
67647d0fb
|
1126 |
* list, push it inside. |
1da177e4c
|
1127 |
*/ |
c7ea76302
|
1128 |
if (revents & event->events) { |
e057e15ff
|
1129 |
spin_lock_irq(&ep->lock); |
c7ea76302
|
1130 1131 1132 1133 1134 |
if (!ep_is_linked(&epi->rdllink)) { list_add_tail(&epi->rdllink, &ep->rdllist); /* Notify waiting tasks that events are available */ if (waitqueue_active(&ep->wq)) |
4a6e9e2ce
|
1135 |
wake_up_locked(&ep->wq); |
c7ea76302
|
1136 1137 |
if (waitqueue_active(&ep->poll_wait)) pwake++; |
7699acd13
|
1138 |
} |
e057e15ff
|
1139 |
spin_unlock_irq(&ep->lock); |
7699acd13
|
1140 |
} |
1da177e4c
|
1141 |
|
7699acd13
|
1142 1143 |
/* We have to call this outside the lock */ if (pwake) |
5071f97ec
|
1144 |
ep_poll_safewake(&ep->poll_wait); |
1da177e4c
|
1145 |
|
7699acd13
|
1146 |
return 0; |
1da177e4c
|
1147 |
} |
296e236e9
|
1148 1149 |
static int ep_send_events_proc(struct eventpoll *ep, struct list_head *head, void *priv) |
1da177e4c
|
1150 |
{ |
5071f97ec
|
1151 1152 |
struct ep_send_events_data *esed = priv; int eventcnt; |
296e236e9
|
1153 |
unsigned int revents; |
5071f97ec
|
1154 1155 |
struct epitem *epi; struct epoll_event __user *uevent; |
1da177e4c
|
1156 |
|
296e236e9
|
1157 |
/* |
5071f97ec
|
1158 1159 1160 |
* 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. |
296e236e9
|
1161 |
*/ |
5071f97ec
|
1162 1163 1164 |
for (eventcnt = 0, uevent = esed->events; !list_empty(head) && eventcnt < esed->maxevents;) { epi = list_first_entry(head, struct epitem, rdllink); |
d47de16c7
|
1165 1166 |
list_del_init(&epi->rdllink); |
1da177e4c
|
1167 |
|
296e236e9
|
1168 1169 |
revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL) & epi->event.events; |
5071f97ec
|
1170 |
|
296e236e9
|
1171 |
/* |
5071f97ec
|
1172 1173 1174 1175 |
* 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. |
296e236e9
|
1176 1177 |
*/ if (revents) { |
5071f97ec
|
1178 |
if (__put_user(revents, &uevent->events) || |
d03058828
|
1179 1180 |
__put_user(epi->event.data, &uevent->data)) { list_add(&epi->rdllink, head); |
296e236e9
|
1181 |
return eventcnt ? eventcnt : -EFAULT; |
d03058828
|
1182 |
} |
296e236e9
|
1183 |
eventcnt++; |
5071f97ec
|
1184 |
uevent++; |
296e236e9
|
1185 1186 1187 1188 1189 1190 1191 1192 |
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 |
25985edce
|
1193 |
* availability. At this point, no one can insert |
296e236e9
|
1194 1195 1196 1197 1198 1199 1200 1201 1202 |
* 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); } } } |
5071f97ec
|
1203 1204 1205 |
return eventcnt; } |
d47de16c7
|
1206 |
|
296e236e9
|
1207 1208 |
static int ep_send_events(struct eventpoll *ep, struct epoll_event __user *events, int maxevents) |
5071f97ec
|
1209 1210 |
{ struct ep_send_events_data esed; |
1da177e4c
|
1211 |
|
5071f97ec
|
1212 1213 |
esed.maxevents = maxevents; esed.events = events; |
6192bd536
|
1214 |
|
d8805e633
|
1215 |
return ep_scan_ready_list(ep, ep_send_events_proc, &esed, 0); |
1da177e4c
|
1216 |
} |
0781b909b
|
1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 |
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), }; ktime_get_ts(&now); return timespec_add_safe(now, ts); } |
f4d93ad74
|
1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 |
/** * 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. */ |
1da177e4c
|
1244 1245 1246 |
static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, int maxevents, long timeout) { |
f4d93ad74
|
1247 |
int res = 0, eavail, timed_out = 0; |
1da177e4c
|
1248 |
unsigned long flags; |
f4d93ad74
|
1249 |
long slack = 0; |
1da177e4c
|
1250 |
wait_queue_t wait; |
95aac7b1c
|
1251 1252 1253 |
ktime_t expires, *to = NULL; if (timeout > 0) { |
0781b909b
|
1254 |
struct timespec end_time = ep_set_mstimeout(timeout); |
95aac7b1c
|
1255 1256 1257 1258 |
slack = select_estimate_accuracy(&end_time); to = &expires; *to = timespec_to_ktime(end_time); } else if (timeout == 0) { |
f4d93ad74
|
1259 1260 1261 1262 |
/* * Avoid the unnecessary trip to the wait queue loop, if the * caller specified a non blocking operation. */ |
95aac7b1c
|
1263 |
timed_out = 1; |
f4d93ad74
|
1264 1265 |
spin_lock_irqsave(&ep->lock, flags); goto check_events; |
95aac7b1c
|
1266 |
} |
1da177e4c
|
1267 |
|
f4d93ad74
|
1268 |
fetch_events: |
c7ea76302
|
1269 |
spin_lock_irqsave(&ep->lock, flags); |
1da177e4c
|
1270 |
|
3fb0e584a
|
1271 |
if (!ep_events_available(ep)) { |
1da177e4c
|
1272 1273 1274 1275 1276 1277 |
/* * 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); |
a93d2f174
|
1278 |
__add_wait_queue_exclusive(&ep->wq, &wait); |
1da177e4c
|
1279 1280 1281 1282 1283 1284 1285 1286 |
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); |
3fb0e584a
|
1287 |
if (ep_events_available(ep) || timed_out) |
1da177e4c
|
1288 1289 1290 1291 1292 |
break; if (signal_pending(current)) { res = -EINTR; break; } |
c7ea76302
|
1293 |
spin_unlock_irqrestore(&ep->lock, flags); |
95aac7b1c
|
1294 1295 |
if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS)) timed_out = 1; |
c7ea76302
|
1296 |
spin_lock_irqsave(&ep->lock, flags); |
1da177e4c
|
1297 |
} |
3419b23a9
|
1298 |
__remove_wait_queue(&ep->wq, &wait); |
1da177e4c
|
1299 1300 1301 |
set_current_state(TASK_RUNNING); } |
f4d93ad74
|
1302 |
check_events: |
1da177e4c
|
1303 |
/* Is it worth to try to dig for events ? */ |
3fb0e584a
|
1304 |
eavail = ep_events_available(ep); |
1da177e4c
|
1305 |
|
c7ea76302
|
1306 |
spin_unlock_irqrestore(&ep->lock, flags); |
1da177e4c
|
1307 1308 1309 1310 1311 1312 1313 |
/* * Try to transfer events to user space. In case we get 0 events and * there's still timeout left over, we go trying again in search of * more luck. */ if (!res && eavail && |
95aac7b1c
|
1314 |
!(res = ep_send_events(ep, events, maxevents)) && !timed_out) |
f4d93ad74
|
1315 |
goto fetch_events; |
1da177e4c
|
1316 1317 1318 |
return res; } |
22bacca48
|
1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 |
/** * 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; |
28d82dc1c
|
1339 |
struct eventpoll *ep_tovisit; |
22bacca48
|
1340 1341 |
struct rb_node *rbp; struct epitem *epi; |
d8805e633
|
1342 |
mutex_lock_nested(&ep->mtx, call_nests + 1); |
28d82dc1c
|
1343 1344 |
ep->visited = 1; list_add(&ep->visited_list_link, &visited_list); |
22bacca48
|
1345 1346 1347 |
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))) { |
28d82dc1c
|
1348 1349 1350 |
ep_tovisit = epi->ffd.file->private_data; if (ep_tovisit->visited) continue; |
22bacca48
|
1351 |
error = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, |
28d82dc1c
|
1352 1353 |
ep_loop_check_proc, epi->ffd.file, ep_tovisit, current); |
22bacca48
|
1354 1355 |
if (error != 0) break; |
28d82dc1c
|
1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 |
} 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); |
22bacca48
|
1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 |
} } mutex_unlock(&ep->mtx); return error; } /** * 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) { |
28d82dc1c
|
1388 1389 1390 1391 |
int ret; struct eventpoll *ep_cur, *ep_next; ret = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, |
22bacca48
|
1392 |
ep_loop_check_proc, file, ep, current); |
28d82dc1c
|
1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 |
/* 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; } static void clear_tfile_check_list(void) { struct file *file; /* 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); |
22bacca48
|
1413 |
} |
7699acd13
|
1414 |
/* |
523723bb5
|
1415 |
* Open an eventpoll file descriptor. |
7699acd13
|
1416 |
*/ |
5a8a82b1d
|
1417 |
SYSCALL_DEFINE1(epoll_create1, int, flags) |
7699acd13
|
1418 |
{ |
28d82dc1c
|
1419 |
int error, fd; |
bb57c3edc
|
1420 |
struct eventpoll *ep = NULL; |
28d82dc1c
|
1421 |
struct file *file; |
7699acd13
|
1422 |
|
e38b36f32
|
1423 1424 |
/* Check the EPOLL_* constant for consistency. */ BUILD_BUG_ON(EPOLL_CLOEXEC != O_CLOEXEC); |
296e236e9
|
1425 1426 |
if (flags & ~EPOLL_CLOEXEC) return -EINVAL; |
7699acd13
|
1427 |
/* |
bb57c3edc
|
1428 |
* Create the internal data structure ("struct eventpoll"). |
7699acd13
|
1429 |
*/ |
9fe5ad9c8
|
1430 |
error = ep_alloc(&ep); |
bb57c3edc
|
1431 1432 |
if (error < 0) return error; |
7699acd13
|
1433 1434 |
/* * Creates all the items needed to setup an eventpoll file. That is, |
2030a42ce
|
1435 |
* a file structure and a free file descriptor. |
7699acd13
|
1436 |
*/ |
28d82dc1c
|
1437 1438 1439 1440 1441 1442 |
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, |
628ff7c1d
|
1443 |
O_RDWR | (flags & O_CLOEXEC)); |
28d82dc1c
|
1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 |
if (IS_ERR(file)) { error = PTR_ERR(file); goto out_free_fd; } fd_install(fd, file); ep->file = file; return fd; out_free_fd: put_unused_fd(fd); out_free_ep: ep_free(ep); |
bb57c3edc
|
1456 |
return error; |
7699acd13
|
1457 |
} |
5a8a82b1d
|
1458 |
SYSCALL_DEFINE1(epoll_create, int, size) |
a0998b50c
|
1459 |
{ |
bfe3891a5
|
1460 |
if (size <= 0) |
9fe5ad9c8
|
1461 1462 1463 |
return -EINVAL; return sys_epoll_create1(0); |
a0998b50c
|
1464 |
} |
7699acd13
|
1465 1466 1467 |
/* * The following function implements the controller interface for * the eventpoll file that enables the insertion/removal/change of |
67647d0fb
|
1468 |
* file descriptors inside the interest set. |
7699acd13
|
1469 |
*/ |
5a8a82b1d
|
1470 1471 |
SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd, struct epoll_event __user *, event) |
7699acd13
|
1472 1473 |
{ int error; |
22bacca48
|
1474 |
int did_lock_epmutex = 0; |
7699acd13
|
1475 1476 1477 1478 |
struct file *file, *tfile; struct eventpoll *ep; struct epitem *epi; struct epoll_event epds; |
7699acd13
|
1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 |
error = -EFAULT; if (ep_op_has_event(op) && copy_from_user(&epds, event, sizeof(struct epoll_event))) goto error_return; /* Get the "struct file *" for the eventpoll file */ error = -EBADF; file = fget(epfd); if (!file) goto error_return; /* Get the "struct file *" for the target file */ tfile = fget(fd); if (!tfile) goto error_fput; /* The target file descriptor must support poll */ error = -EPERM; if (!tfile->f_op || !tfile->f_op->poll) goto error_tgt_fput; /* * We have to check that the file structure underneath the file descriptor * the user passed to us _is_ an eventpoll file. And also we do not permit * adding an epoll file descriptor inside itself. */ error = -EINVAL; if (file == tfile || !is_file_epoll(file)) goto error_tgt_fput; /* * At this point it is safe to assume that the "private_data" contains * our own data structure. */ ep = file->private_data; |
22bacca48
|
1514 1515 1516 |
/* * When we insert an epoll file descriptor, inside another epoll file * descriptor, there is the change of creating closed loops, which are |
28d82dc1c
|
1517 1518 1519 1520 |
* 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. |
22bacca48
|
1521 |
* |
28d82dc1c
|
1522 1523 1524 |
* We need to hold the epmutex across both ep_insert and ep_remove * b/c we want to make sure we are looking at a coherent view of * epoll network. |
22bacca48
|
1525 |
*/ |
28d82dc1c
|
1526 |
if (op == EPOLL_CTL_ADD || op == EPOLL_CTL_DEL) { |
22bacca48
|
1527 1528 |
mutex_lock(&epmutex); did_lock_epmutex = 1; |
22bacca48
|
1529 |
} |
28d82dc1c
|
1530 1531 1532 1533 1534 1535 1536 1537 |
if (op == EPOLL_CTL_ADD) { if (is_file_epoll(tfile)) { error = -ELOOP; if (ep_loop_check(ep, tfile) != 0) goto error_tgt_fput; } else list_add(&tfile->f_tfile_llink, &tfile_check_list); } |
22bacca48
|
1538 |
|
d8805e633
|
1539 |
mutex_lock_nested(&ep->mtx, 0); |
7699acd13
|
1540 |
|
67647d0fb
|
1541 1542 1543 1544 1545 |
/* * 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. */ |
7699acd13
|
1546 1547 1548 1549 1550 1551 1552 |
epi = ep_find(ep, tfile, fd); error = -EINVAL; switch (op) { case EPOLL_CTL_ADD: if (!epi) { epds.events |= POLLERR | POLLHUP; |
7699acd13
|
1553 1554 1555 |
error = ep_insert(ep, &epds, tfile, fd); } else error = -EEXIST; |
28d82dc1c
|
1556 |
clear_tfile_check_list(); |
7699acd13
|
1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 |
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; } |
d47de16c7
|
1572 |
mutex_unlock(&ep->mtx); |
7699acd13
|
1573 1574 |
error_tgt_fput: |
28d82dc1c
|
1575 |
if (did_lock_epmutex) |
22bacca48
|
1576 |
mutex_unlock(&epmutex); |
7699acd13
|
1577 1578 1579 1580 |
fput(tfile); error_fput: fput(file); error_return: |
7699acd13
|
1581 1582 1583 1584 1585 1586 1587 1588 |
return error; } /* * Implement the event wait interface for the eventpoll file. It is the kernel * part of the user space epoll_wait(2). */ |
5a8a82b1d
|
1589 1590 |
SYSCALL_DEFINE4(epoll_wait, int, epfd, struct epoll_event __user *, events, int, maxevents, int, timeout) |
7699acd13
|
1591 1592 1593 1594 |
{ int error; struct file *file; struct eventpoll *ep; |
7699acd13
|
1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 |
/* 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))) { error = -EFAULT; goto error_return; } /* Get the "struct file *" for the eventpoll file */ error = -EBADF; file = fget(epfd); if (!file) goto error_return; /* * We have to check that the file structure underneath the fd * the user passed to us _is_ an eventpoll file. */ error = -EINVAL; if (!is_file_epoll(file)) goto error_fput; /* * At this point it is safe to assume that the "private_data" contains * our own data structure. */ ep = file->private_data; /* Time to fish for events ... */ error = ep_poll(ep, events, maxevents, timeout); error_fput: fput(file); error_return: |
7699acd13
|
1631 1632 1633 |
return error; } |
f3de272b8
|
1634 |
#ifdef HAVE_SET_RESTORE_SIGMASK |
7699acd13
|
1635 1636 1637 1638 1639 |
/* * Implement the event wait interface for the eventpoll file. It is the kernel * part of the user space epoll_pwait(2). */ |
5a8a82b1d
|
1640 1641 1642 |
SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events, int, maxevents, int, timeout, const sigset_t __user *, sigmask, size_t, sigsetsize) |
7699acd13
|
1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 |
{ int error; sigset_t ksigmask, sigsaved; /* * If the caller wants a certain signal mask to be set during the wait, * we apply it here. */ if (sigmask) { if (sigsetsize != sizeof(sigset_t)) return -EINVAL; if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) return -EFAULT; sigdelsetmask(&ksigmask, sigmask(SIGKILL) | sigmask(SIGSTOP)); sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); } error = sys_epoll_wait(epfd, events, maxevents, timeout); /* * If we changed the signal mask, we need to restore the original one. * In case we've got a signal while waiting, we do not restore the * signal mask yet, and we allow do_signal() to deliver the signal on * the way back to userspace, before the signal mask is restored. */ if (sigmask) { if (error == -EINTR) { memcpy(¤t->saved_sigmask, &sigsaved, |
c7ea76302
|
1671 |
sizeof(sigsaved)); |
4e4c22c71
|
1672 |
set_restore_sigmask(); |
7699acd13
|
1673 1674 1675 1676 1677 1678 |
} else sigprocmask(SIG_SETMASK, &sigsaved, NULL); } return error; } |
f3de272b8
|
1679 |
#endif /* HAVE_SET_RESTORE_SIGMASK */ |
7699acd13
|
1680 |
|
1da177e4c
|
1681 1682 |
static int __init eventpoll_init(void) { |
7ef9964e6
|
1683 1684 1685 |
struct sysinfo si; si_meminfo(&si); |
9df04e1f2
|
1686 1687 1688 1689 |
/* * Allows top 4% of lomem to be allocated for epoll watches (per user). */ max_user_watches = (((si.totalram - si.totalhigh) / 25) << PAGE_SHIFT) / |
7ef9964e6
|
1690 |
EP_ITEM_COST; |
52bd19f76
|
1691 |
BUG_ON(max_user_watches < 0); |
1da177e4c
|
1692 |
|
22bacca48
|
1693 1694 1695 1696 1697 |
/* * Initialize the structure used to perform epoll file descriptor * inclusion loops checks. */ ep_nested_calls_init(&poll_loop_ncalls); |
1da177e4c
|
1698 |
/* Initialize the structure used to perform safe poll wait head wake ups */ |
5071f97ec
|
1699 1700 1701 1702 |
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); |
1da177e4c
|
1703 1704 1705 |
/* Allocates slab cache used to allocate "struct epitem" items */ epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem), |
bb57c3edc
|
1706 |
0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); |
1da177e4c
|
1707 1708 1709 |
/* Allocates slab cache used to allocate "struct eppoll_entry" */ pwq_cache = kmem_cache_create("eventpoll_pwq", |
bb57c3edc
|
1710 |
sizeof(struct eppoll_entry), 0, SLAB_PANIC, NULL); |
1da177e4c
|
1711 |
|
1da177e4c
|
1712 |
return 0; |
1da177e4c
|
1713 |
} |
cea692418
|
1714 |
fs_initcall(eventpoll_init); |