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fs/eventpoll.c
60.1 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 <linux/device.h> |
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#include <asm/uaccess.h> |
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#include <asm/io.h> #include <asm/mman.h> |
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#include <linux/atomic.h> |
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#include <linux/proc_fs.h> #include <linux/seq_file.h> |
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#include <linux/compat.h> |
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#include <linux/rculist.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 */ |
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#define EP_PRIVATE_BITS (EPOLLWAKEUP | EPOLLONESHOT | EPOLLET | EPOLLEXCLUSIVE) |
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#define EPOLLINOUT_BITS (POLLIN | POLLOUT) #define EPOLLEXCLUSIVE_OK_BITS (EPOLLINOUT_BITS | POLLERR | POLLHUP | \ EPOLLWAKEUP | EPOLLET | EPOLLEXCLUSIVE) |
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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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} __packed; |
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/* |
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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. |
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* 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. |
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*/ struct epitem { |
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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; }; |
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/* 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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/* wakeup_source used when EPOLLWAKEUP is set */ |
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struct wakeup_source __rcu *ws; |
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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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/* wakeup_source used when ep_scan_ready_list is running */ struct wakeup_source *ws; |
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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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struct ctl_table epoll_table[] = { |
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{ |
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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); } |
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static inline struct eppoll_entry *ep_pwq_from_wait(wait_queue_t *p) { return container_of(p, struct eppoll_entry, wait); } |
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/* 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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{ |
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return op != EPOLL_CTL_DEL; |
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} |
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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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/* * 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. */ |
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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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static void ep_remove_wait_queue(struct eppoll_entry *pwq) { wait_queue_head_t *whead; 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(); } |
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/* |
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|
502 503 504 |
* This function unregisters poll callbacks from the associated file * descriptor. Must be called with "mtx" held (or "epmutex" if called from * ep_free). |
1da177e4c
|
505 |
*/ |
7699acd13
|
506 |
static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi) |
1da177e4c
|
507 |
{ |
7699acd13
|
508 509 |
struct list_head *lsthead = &epi->pwqlist; struct eppoll_entry *pwq; |
1da177e4c
|
510 |
|
d1bc90dd5
|
511 512 |
while (!list_empty(lsthead)) { pwq = list_first_entry(lsthead, struct eppoll_entry, llink); |
1da177e4c
|
513 |
|
d1bc90dd5
|
514 |
list_del(&pwq->llink); |
971316f05
|
515 |
ep_remove_wait_queue(pwq); |
d1bc90dd5
|
516 |
kmem_cache_free(pwq_cache, pwq); |
1da177e4c
|
517 |
} |
1da177e4c
|
518 |
} |
eea1d5859
|
519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 |
/* 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)); } /* 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); if (ws) __pm_stay_awake(ws); } static inline bool ep_has_wakeup_source(struct epitem *epi) { return rcu_access_pointer(epi->ws) ? true : false; } /* 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; rcu_read_lock(); ws = rcu_dereference(epi->ws); if (ws) __pm_stay_awake(ws); rcu_read_unlock(); } |
5071f97ec
|
550 551 552 553 554 555 556 557 |
/** * 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. |
d8805e633
|
558 |
* @depth: The current depth of recursive f_op->poll calls. |
67347fe4e
|
559 |
* @ep_locked: caller already holds ep->mtx |
5071f97ec
|
560 561 562 563 564 565 |
* * 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 *), |
67347fe4e
|
566 |
void *priv, int depth, bool ep_locked) |
5071f97ec
|
567 568 569 570 |
{ int error, pwake = 0; unsigned long flags; struct epitem *epi, *nepi; |
296e236e9
|
571 |
LIST_HEAD(txlist); |
5071f97ec
|
572 573 574 |
/* * We need to lock this because we could be hit by |
e057e15ff
|
575 |
* eventpoll_release_file() and epoll_ctl(). |
5071f97ec
|
576 |
*/ |
67347fe4e
|
577 578 579 |
if (!ep_locked) mutex_lock_nested(&ep->mtx, depth); |
5071f97ec
|
580 581 582 583 584 585 586 587 588 589 |
/* * 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); |
296e236e9
|
590 |
list_splice_init(&ep->rdllist, &txlist); |
5071f97ec
|
591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 |
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. */ |
4d7e30d98
|
613 |
if (!ep_is_linked(&epi->rdllink)) { |
5071f97ec
|
614 |
list_add_tail(&epi->rdllink, &ep->rdllist); |
eea1d5859
|
615 |
ep_pm_stay_awake(epi); |
4d7e30d98
|
616 |
} |
5071f97ec
|
617 618 619 620 621 622 623 624 625 626 627 628 |
} /* * 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); |
4d7e30d98
|
629 |
__pm_relax(ep->ws); |
5071f97ec
|
630 631 632 |
if (!list_empty(&ep->rdllist)) { /* |
296e236e9
|
633 634 |
* Wake up (if active) both the eventpoll wait list and * the ->poll() wait list (delayed after we release the lock). |
5071f97ec
|
635 636 637 638 639 640 641 |
*/ if (waitqueue_active(&ep->wq)) wake_up_locked(&ep->wq); if (waitqueue_active(&ep->poll_wait)) pwake++; } spin_unlock_irqrestore(&ep->lock, flags); |
67347fe4e
|
642 643 |
if (!ep_locked) mutex_unlock(&ep->mtx); |
5071f97ec
|
644 645 646 647 648 649 650 |
/* We have to call this outside the lock */ if (pwake) ep_poll_safewake(&ep->poll_wait); return error; } |
ae10b2b4e
|
651 652 653 654 655 |
static void epi_rcu_free(struct rcu_head *head) { struct epitem *epi = container_of(head, struct epitem, rcu); kmem_cache_free(epi_cache, epi); } |
1da177e4c
|
656 |
/* |
7699acd13
|
657 |
* Removes a "struct epitem" from the eventpoll RB tree and deallocates |
c7ea76302
|
658 |
* all the associated resources. Must be called with "mtx" held. |
7699acd13
|
659 660 661 |
*/ static int ep_remove(struct eventpoll *ep, struct epitem *epi) { |
7699acd13
|
662 663 |
unsigned long flags; struct file *file = epi->ffd.file; |
1da177e4c
|
664 665 |
/* |
7699acd13
|
666 667 668 669 670 671 |
* 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
|
672 |
*/ |
7699acd13
|
673 |
ep_unregister_pollwait(ep, epi); |
1da177e4c
|
674 |
|
7699acd13
|
675 |
/* Remove the current item from the list of epoll hooks */ |
684999149
|
676 |
spin_lock(&file->f_lock); |
ae10b2b4e
|
677 |
list_del_rcu(&epi->fllink); |
684999149
|
678 |
spin_unlock(&file->f_lock); |
1da177e4c
|
679 |
|
cdac75e6f
|
680 |
rb_erase(&epi->rbn, &ep->rbr); |
1da177e4c
|
681 |
|
c7ea76302
|
682 683 684 685 |
spin_lock_irqsave(&ep->lock, flags); if (ep_is_linked(&epi->rdllink)) list_del_init(&epi->rdllink); spin_unlock_irqrestore(&ep->lock, flags); |
1da177e4c
|
686 |
|
eea1d5859
|
687 |
wakeup_source_unregister(ep_wakeup_source(epi)); |
ae10b2b4e
|
688 689 690 691 692 693 694 695 |
/* * 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); |
1da177e4c
|
696 |
|
52bd19f76
|
697 |
atomic_long_dec(&ep->user->epoll_watches); |
7ef9964e6
|
698 |
|
c7ea76302
|
699 |
return 0; |
1da177e4c
|
700 |
} |
7699acd13
|
701 |
static void ep_free(struct eventpoll *ep) |
1da177e4c
|
702 |
{ |
7699acd13
|
703 704 |
struct rb_node *rbp; struct epitem *epi; |
1da177e4c
|
705 |
|
7699acd13
|
706 707 |
/* We need to release all tasks waiting for these file */ if (waitqueue_active(&ep->poll_wait)) |
5071f97ec
|
708 |
ep_poll_safewake(&ep->poll_wait); |
1da177e4c
|
709 |
|
7699acd13
|
710 711 712 |
/* * We need to lock this because we could be hit by * eventpoll_release_file() while we're freeing the "struct eventpoll". |
d47de16c7
|
713 |
* We do not need to hold "ep->mtx" here because the epoll file |
7699acd13
|
714 715 |
* 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
|
716 |
* holding "epmutex" is sufficient here. |
7699acd13
|
717 718 |
*/ mutex_lock(&epmutex); |
1da177e4c
|
719 720 |
/* |
7699acd13
|
721 |
* Walks through the whole tree by unregistering poll callbacks. |
1da177e4c
|
722 |
*/ |
7699acd13
|
723 724 725 726 |
for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { epi = rb_entry(rbp, struct epitem, rbn); ep_unregister_pollwait(ep, epi); |
91cf5ab60
|
727 |
cond_resched(); |
7699acd13
|
728 |
} |
1da177e4c
|
729 730 |
/* |
7699acd13
|
731 732 |
* 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
|
733 |
* holding "epmutex" we can be sure that no file cleanup code will hit |
7699acd13
|
734 |
* us during this operation. So we can avoid the lock on "ep->lock". |
ddf676c38
|
735 736 |
* We do not need to lock ep->mtx, either, we only do it to prevent * a lockdep warning. |
1da177e4c
|
737 |
*/ |
ddf676c38
|
738 |
mutex_lock(&ep->mtx); |
c80544dc0
|
739 |
while ((rbp = rb_first(&ep->rbr)) != NULL) { |
7699acd13
|
740 741 |
epi = rb_entry(rbp, struct epitem, rbn); ep_remove(ep, epi); |
91cf5ab60
|
742 |
cond_resched(); |
7699acd13
|
743 |
} |
ddf676c38
|
744 |
mutex_unlock(&ep->mtx); |
1da177e4c
|
745 |
|
7699acd13
|
746 |
mutex_unlock(&epmutex); |
d47de16c7
|
747 |
mutex_destroy(&ep->mtx); |
7ef9964e6
|
748 |
free_uid(ep->user); |
4d7e30d98
|
749 |
wakeup_source_unregister(ep->ws); |
f0ee9aabb
|
750 |
kfree(ep); |
7699acd13
|
751 |
} |
1da177e4c
|
752 |
|
7699acd13
|
753 754 755 |
static int ep_eventpoll_release(struct inode *inode, struct file *file) { struct eventpoll *ep = file->private_data; |
1da177e4c
|
756 |
|
f0ee9aabb
|
757 |
if (ep) |
7699acd13
|
758 |
ep_free(ep); |
7699acd13
|
759 |
|
7699acd13
|
760 |
return 0; |
1da177e4c
|
761 |
} |
450d89ec0
|
762 763 764 765 766 767 |
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; } |
296e236e9
|
768 769 |
static int ep_read_events_proc(struct eventpoll *ep, struct list_head *head, void *priv) |
5071f97ec
|
770 771 |
{ struct epitem *epi, *tmp; |
626cf2366
|
772 |
poll_table pt; |
5071f97ec
|
773 |
|
626cf2366
|
774 |
init_poll_funcptr(&pt, NULL); |
450d89ec0
|
775 |
|
5071f97ec
|
776 |
list_for_each_entry_safe(epi, tmp, head, rdllink) { |
450d89ec0
|
777 |
if (ep_item_poll(epi, &pt)) |
5071f97ec
|
778 |
return POLLIN | POLLRDNORM; |
296e236e9
|
779 |
else { |
5071f97ec
|
780 781 782 783 784 |
/* * 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. */ |
eea1d5859
|
785 |
__pm_relax(ep_wakeup_source(epi)); |
5071f97ec
|
786 |
list_del_init(&epi->rdllink); |
296e236e9
|
787 |
} |
5071f97ec
|
788 789 790 791 |
} return 0; } |
67347fe4e
|
792 793 794 795 796 797 798 |
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; }; |
5071f97ec
|
799 800 |
static int ep_poll_readyevents_proc(void *priv, void *cookie, int call_nests) { |
67347fe4e
|
801 802 803 804 |
struct readyevents_arg *arg = priv; return ep_scan_ready_list(arg->ep, ep_read_events_proc, NULL, call_nests + 1, arg->locked); |
5071f97ec
|
805 |
} |
7699acd13
|
806 807 |
static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait) { |
5071f97ec
|
808 |
int pollflags; |
7699acd13
|
809 |
struct eventpoll *ep = file->private_data; |
67347fe4e
|
810 811 812 813 814 815 816 817 |
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; |
1da177e4c
|
818 |
|
7699acd13
|
819 820 |
/* Insert inside our poll wait queue */ poll_wait(file, &ep->poll_wait, wait); |
5071f97ec
|
821 822 823 824 825 826 827 |
/* * 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, |
67347fe4e
|
828 |
ep_poll_readyevents_proc, &arg, ep, current); |
7699acd13
|
829 |
|
296e236e9
|
830 |
return pollflags != -1 ? pollflags : 0; |
7699acd13
|
831 |
} |
138d22b58
|
832 |
#ifdef CONFIG_PROC_FS |
a3816ab0e
|
833 |
static void ep_show_fdinfo(struct seq_file *m, struct file *f) |
138d22b58
|
834 835 836 |
{ struct eventpoll *ep = f->private_data; struct rb_node *rbp; |
138d22b58
|
837 838 839 840 |
mutex_lock(&ep->mtx); for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { struct epitem *epi = rb_entry(rbp, struct epitem, rbn); |
a3816ab0e
|
841 842 843 844 845 |
seq_printf(m, "tfd: %8d events: %8x data: %16llx ", epi->ffd.fd, epi->event.events, (long long)epi->event.data); if (seq_has_overflowed(m)) |
138d22b58
|
846 847 848 |
break; } mutex_unlock(&ep->mtx); |
138d22b58
|
849 850 |
} #endif |
7699acd13
|
851 852 |
/* File callbacks that implement the eventpoll file behaviour */ static const struct file_operations eventpoll_fops = { |
138d22b58
|
853 854 855 |
#ifdef CONFIG_PROC_FS .show_fdinfo = ep_show_fdinfo, #endif |
7699acd13
|
856 |
.release = ep_eventpoll_release, |
6038f373a
|
857 858 |
.poll = ep_eventpoll_poll, .llseek = noop_llseek, |
7699acd13
|
859 |
}; |
b611967de
|
860 |
/* |
7699acd13
|
861 862 863 |
* 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
|
864 |
*/ |
7699acd13
|
865 |
void eventpoll_release_file(struct file *file) |
b611967de
|
866 |
{ |
7699acd13
|
867 |
struct eventpoll *ep; |
ebe06187b
|
868 |
struct epitem *epi, *next; |
b611967de
|
869 870 |
/* |
684999149
|
871 |
* We don't want to get "file->f_lock" because it is not |
7699acd13
|
872 |
* necessary. It is not necessary because we're in the "struct file" |
25985edce
|
873 |
* cleanup path, and this means that no one is using this file anymore. |
5071f97ec
|
874 |
* So, for example, epoll_ctl() cannot hit here since if we reach this |
67647d0fb
|
875 |
* point, the file counter already went to zero and fget() would fail. |
d47de16c7
|
876 |
* The only hit might come from ep_free() but by holding the mutex |
7699acd13
|
877 |
* will correctly serialize the operation. We do need to acquire |
d47de16c7
|
878 |
* "ep->mtx" after "epmutex" because ep_remove() requires it when called |
7699acd13
|
879 |
* from anywhere but ep_free(). |
684999149
|
880 881 |
* * Besides, ep_remove() acquires the lock, so we can't hold it here. |
b611967de
|
882 |
*/ |
7699acd13
|
883 |
mutex_lock(&epmutex); |
ebe06187b
|
884 |
list_for_each_entry_safe(epi, next, &file->f_ep_links, fllink) { |
7699acd13
|
885 |
ep = epi->ep; |
d8805e633
|
886 |
mutex_lock_nested(&ep->mtx, 0); |
7699acd13
|
887 |
ep_remove(ep, epi); |
d47de16c7
|
888 |
mutex_unlock(&ep->mtx); |
b611967de
|
889 |
} |
7699acd13
|
890 |
mutex_unlock(&epmutex); |
b611967de
|
891 |
} |
53d2be79d
|
892 |
static int ep_alloc(struct eventpoll **pep) |
1da177e4c
|
893 |
{ |
7ef9964e6
|
894 895 896 |
int error; struct user_struct *user; struct eventpoll *ep; |
1da177e4c
|
897 |
|
7ef9964e6
|
898 |
user = get_current_user(); |
7ef9964e6
|
899 900 901 902 |
error = -ENOMEM; ep = kzalloc(sizeof(*ep), GFP_KERNEL); if (unlikely(!ep)) goto free_uid; |
1da177e4c
|
903 |
|
c7ea76302
|
904 |
spin_lock_init(&ep->lock); |
d47de16c7
|
905 |
mutex_init(&ep->mtx); |
1da177e4c
|
906 907 908 909 |
init_waitqueue_head(&ep->wq); init_waitqueue_head(&ep->poll_wait); INIT_LIST_HEAD(&ep->rdllist); ep->rbr = RB_ROOT; |
d47de16c7
|
910 |
ep->ovflist = EP_UNACTIVE_PTR; |
7ef9964e6
|
911 |
ep->user = user; |
1da177e4c
|
912 |
|
53d2be79d
|
913 |
*pep = ep; |
1da177e4c
|
914 |
|
1da177e4c
|
915 |
return 0; |
7ef9964e6
|
916 917 918 919 |
free_uid: free_uid(user); return error; |
1da177e4c
|
920 |
} |
1da177e4c
|
921 |
/* |
c7ea76302
|
922 923 924 |
* 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
|
925 926 927 928 |
*/ static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd) { int kcmp; |
1da177e4c
|
929 930 931 |
struct rb_node *rbp; struct epitem *epi, *epir = NULL; struct epoll_filefd ffd; |
b030a4dd6
|
932 |
ep_set_ffd(&ffd, file, fd); |
1da177e4c
|
933 934 |
for (rbp = ep->rbr.rb_node; rbp; ) { epi = rb_entry(rbp, struct epitem, rbn); |
b030a4dd6
|
935 |
kcmp = ep_cmp_ffd(&ffd, &epi->ffd); |
1da177e4c
|
936 937 938 939 940 |
if (kcmp > 0) rbp = rbp->rb_right; else if (kcmp < 0) rbp = rbp->rb_left; else { |
1da177e4c
|
941 942 943 944 |
epir = epi; break; } } |
1da177e4c
|
945 |
|
1da177e4c
|
946 947 |
return epir; } |
1da177e4c
|
948 |
/* |
7699acd13
|
949 |
* This is the callback that is passed to the wait queue wakeup |
bf6a41db7
|
950 |
* mechanism. It is called by the stored file descriptors when they |
7699acd13
|
951 |
* have events to report. |
1da177e4c
|
952 |
*/ |
7699acd13
|
953 |
static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *key) |
1da177e4c
|
954 |
{ |
7699acd13
|
955 956 957 958 |
int pwake = 0; unsigned long flags; struct epitem *epi = ep_item_from_wait(wait); struct eventpoll *ep = epi->ep; |
df0108c5d
|
959 |
int ewake = 0; |
1da177e4c
|
960 |
|
971316f05
|
961 962 963 964 965 966 967 968 |
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. */ |
d80e731ec
|
969 |
list_del_init(&wait->task_list); |
971316f05
|
970 |
} |
d80e731ec
|
971 |
|
c7ea76302
|
972 |
spin_lock_irqsave(&ep->lock, flags); |
1da177e4c
|
973 |
|
7699acd13
|
974 975 976 977 978 979 980 |
/* * 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
|
981 982 983 |
goto out_unlock; /* |
2dfa4eeab
|
984 985 986 987 988 989 990 991 992 |
* 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
|
993 |
* If we are transferring events to userspace, we can hold no locks |
d47de16c7
|
994 |
* (because we're accessing user memory, and because of linux f_op->poll() |
bf6a41db7
|
995 |
* semantics). All the events that happen during that period of time are |
d47de16c7
|
996 997 998 999 1000 1001 |
* 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; |
4d7e30d98
|
1002 1003 1004 1005 1006 1007 1008 |
if (epi->ws) { /* * Activate ep->ws since epi->ws may get * deactivated at any time. */ __pm_stay_awake(ep->ws); } |
d47de16c7
|
1009 1010 1011 |
} goto out_unlock; } |
1da177e4c
|
1012 |
|
7699acd13
|
1013 |
/* If this file is already in the ready list we exit soon */ |
4d7e30d98
|
1014 |
if (!ep_is_linked(&epi->rdllink)) { |
5071f97ec
|
1015 |
list_add_tail(&epi->rdllink, &ep->rdllist); |
eea1d5859
|
1016 |
ep_pm_stay_awake_rcu(epi); |
4d7e30d98
|
1017 |
} |
7699acd13
|
1018 |
|
7699acd13
|
1019 1020 1021 1022 |
/* * Wake up ( if active ) both the eventpoll wait list and the ->poll() * wait list. */ |
df0108c5d
|
1023 |
if (waitqueue_active(&ep->wq)) { |
b6a515c8a
|
1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 |
if ((epi->event.events & EPOLLEXCLUSIVE) && !((unsigned long)key & POLLFREE)) { switch ((unsigned long)key & EPOLLINOUT_BITS) { case POLLIN: if (epi->event.events & POLLIN) ewake = 1; break; case POLLOUT: if (epi->event.events & POLLOUT) ewake = 1; break; case 0: ewake = 1; break; } } |
4a6e9e2ce
|
1040 |
wake_up_locked(&ep->wq); |
df0108c5d
|
1041 |
} |
7699acd13
|
1042 1043 |
if (waitqueue_active(&ep->poll_wait)) pwake++; |
d47de16c7
|
1044 |
out_unlock: |
c7ea76302
|
1045 |
spin_unlock_irqrestore(&ep->lock, flags); |
1da177e4c
|
1046 |
|
7699acd13
|
1047 1048 |
/* We have to call this outside the lock */ if (pwake) |
5071f97ec
|
1049 |
ep_poll_safewake(&ep->poll_wait); |
7699acd13
|
1050 |
|
df0108c5d
|
1051 1052 |
if (epi->event.events & EPOLLEXCLUSIVE) return ewake; |
7699acd13
|
1053 1054 |
return 1; } |
1da177e4c
|
1055 1056 1057 1058 1059 1060 1061 1062 |
/* * 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
|
1063 |
struct epitem *epi = ep_item_from_epqueue(pt); |
1da177e4c
|
1064 |
struct eppoll_entry *pwq; |
e94b17660
|
1065 |
if (epi->nwait >= 0 && (pwq = kmem_cache_alloc(pwq_cache, GFP_KERNEL))) { |
1da177e4c
|
1066 1067 1068 |
init_waitqueue_func_entry(&pwq->wait, ep_poll_callback); pwq->whead = whead; pwq->base = epi; |
df0108c5d
|
1069 1070 1071 1072 |
if (epi->event.events & EPOLLEXCLUSIVE) add_wait_queue_exclusive(whead, &pwq->wait); else add_wait_queue(whead, &pwq->wait); |
1da177e4c
|
1073 1074 |
list_add_tail(&pwq->llink, &epi->pwqlist); epi->nwait++; |
296e236e9
|
1075 |
} else { |
1da177e4c
|
1076 1077 |
/* We have to signal that an error occurred */ epi->nwait = -1; |
296e236e9
|
1078 |
} |
1da177e4c
|
1079 |
} |
1da177e4c
|
1080 1081 1082 1083 1084 1085 1086 1087 1088 |
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
|
1089 |
kcmp = ep_cmp_ffd(&epi->ffd, &epic->ffd); |
1da177e4c
|
1090 1091 1092 1093 1094 1095 1096 1097 |
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); } |
a80a6b85b
|
1098 |
|
28d82dc1c
|
1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 |
#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) { |
93dc6107a
|
1116 1117 1118 |
/* Allow an arbitrary number of depth 1 paths */ if (nests == 0) return 0; |
28d82dc1c
|
1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 |
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; |
ae10b2b4e
|
1138 1139 1140 |
/* 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) { |
28d82dc1c
|
1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 |
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! "); } } |
ae10b2b4e
|
1163 |
rcu_read_unlock(); |
28d82dc1c
|
1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 |
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) { |
28d82dc1c
|
1179 1180 1181 1182 1183 |
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) { |
28d82dc1c
|
1184 1185 1186 1187 1188 1189 1190 1191 1192 |
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; } |
4d7e30d98
|
1193 1194 1195 |
static int ep_create_wakeup_source(struct epitem *epi) { const char *name; |
eea1d5859
|
1196 |
struct wakeup_source *ws; |
4d7e30d98
|
1197 1198 1199 1200 1201 1202 1203 1204 |
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; |
eea1d5859
|
1205 1206 1207 |
ws = wakeup_source_register(name); if (!ws) |
4d7e30d98
|
1208 |
return -ENOMEM; |
eea1d5859
|
1209 |
rcu_assign_pointer(epi->ws, ws); |
4d7e30d98
|
1210 1211 1212 |
return 0; } |
eea1d5859
|
1213 1214 |
/* rare code path, only used when EPOLL_CTL_MOD removes a wakeup source */ static noinline void ep_destroy_wakeup_source(struct epitem *epi) |
4d7e30d98
|
1215 |
{ |
eea1d5859
|
1216 |
struct wakeup_source *ws = ep_wakeup_source(epi); |
d6d67e723
|
1217 |
RCU_INIT_POINTER(epi->ws, NULL); |
eea1d5859
|
1218 1219 1220 1221 1222 1223 1224 1225 |
/* * 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); |
4d7e30d98
|
1226 |
} |
c7ea76302
|
1227 1228 1229 |
/* * Must be called with "mtx" held. */ |
1da177e4c
|
1230 |
static int ep_insert(struct eventpoll *ep, struct epoll_event *event, |
67347fe4e
|
1231 |
struct file *tfile, int fd, int full_check) |
1da177e4c
|
1232 1233 1234 |
{ int error, revents, pwake = 0; unsigned long flags; |
52bd19f76
|
1235 |
long user_watches; |
1da177e4c
|
1236 1237 |
struct epitem *epi; struct ep_pqueue epq; |
52bd19f76
|
1238 1239 |
user_watches = atomic_long_read(&ep->user->epoll_watches); if (unlikely(user_watches >= max_user_watches)) |
7ef9964e6
|
1240 |
return -ENOSPC; |
e94b17660
|
1241 |
if (!(epi = kmem_cache_alloc(epi_cache, GFP_KERNEL))) |
7ef9964e6
|
1242 |
return -ENOMEM; |
1da177e4c
|
1243 1244 |
/* Item initialization follow here ... */ |
1da177e4c
|
1245 1246 |
INIT_LIST_HEAD(&epi->rdllink); INIT_LIST_HEAD(&epi->fllink); |
1da177e4c
|
1247 1248 |
INIT_LIST_HEAD(&epi->pwqlist); epi->ep = ep; |
b030a4dd6
|
1249 |
ep_set_ffd(&epi->ffd, tfile, fd); |
1da177e4c
|
1250 |
epi->event = *event; |
1da177e4c
|
1251 |
epi->nwait = 0; |
d47de16c7
|
1252 |
epi->next = EP_UNACTIVE_PTR; |
4d7e30d98
|
1253 1254 1255 1256 1257 |
if (epi->event.events & EPOLLWAKEUP) { error = ep_create_wakeup_source(epi); if (error) goto error_create_wakeup_source; } else { |
eea1d5859
|
1258 |
RCU_INIT_POINTER(epi->ws, NULL); |
4d7e30d98
|
1259 |
} |
1da177e4c
|
1260 1261 1262 1263 1264 1265 1266 1267 |
/* 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
|
1268 1269 1270 |
* been increased by the caller of this function. Note that after * this operation completes, the poll callback can start hitting * the new item. |
1da177e4c
|
1271 |
*/ |
450d89ec0
|
1272 |
revents = ep_item_poll(epi, &epq.pt); |
1da177e4c
|
1273 1274 1275 1276 1277 1278 |
/* * 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
|
1279 |
error = -ENOMEM; |
1da177e4c
|
1280 |
if (epi->nwait < 0) |
7699acd13
|
1281 |
goto error_unregister; |
1da177e4c
|
1282 1283 |
/* Add the current item to the list of active epoll hook for this file */ |
684999149
|
1284 |
spin_lock(&tfile->f_lock); |
ae10b2b4e
|
1285 |
list_add_tail_rcu(&epi->fllink, &tfile->f_ep_links); |
684999149
|
1286 |
spin_unlock(&tfile->f_lock); |
1da177e4c
|
1287 |
|
c7ea76302
|
1288 1289 1290 1291 |
/* * 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
|
1292 |
ep_rbtree_insert(ep, epi); |
28d82dc1c
|
1293 1294 |
/* now check if we've created too many backpaths */ error = -EINVAL; |
67347fe4e
|
1295 |
if (full_check && reverse_path_check()) |
28d82dc1c
|
1296 |
goto error_remove_epi; |
c7ea76302
|
1297 1298 |
/* We have to drop the new item inside our item list to keep track of it */ spin_lock_irqsave(&ep->lock, flags); |
1da177e4c
|
1299 |
/* If the file is already "ready" we drop it inside the ready list */ |
b030a4dd6
|
1300 |
if ((revents & event->events) && !ep_is_linked(&epi->rdllink)) { |
1da177e4c
|
1301 |
list_add_tail(&epi->rdllink, &ep->rdllist); |
eea1d5859
|
1302 |
ep_pm_stay_awake(epi); |
1da177e4c
|
1303 1304 1305 |
/* Notify waiting tasks that events are available */ if (waitqueue_active(&ep->wq)) |
4a6e9e2ce
|
1306 |
wake_up_locked(&ep->wq); |
1da177e4c
|
1307 1308 1309 |
if (waitqueue_active(&ep->poll_wait)) pwake++; } |
c7ea76302
|
1310 |
spin_unlock_irqrestore(&ep->lock, flags); |
1da177e4c
|
1311 |
|
52bd19f76
|
1312 |
atomic_long_inc(&ep->user->epoll_watches); |
7ef9964e6
|
1313 |
|
1da177e4c
|
1314 1315 |
/* We have to call this outside the lock */ if (pwake) |
5071f97ec
|
1316 |
ep_poll_safewake(&ep->poll_wait); |
1da177e4c
|
1317 |
|
1da177e4c
|
1318 |
return 0; |
28d82dc1c
|
1319 1320 |
error_remove_epi: spin_lock(&tfile->f_lock); |
ae10b2b4e
|
1321 |
list_del_rcu(&epi->fllink); |
28d82dc1c
|
1322 1323 1324 |
spin_unlock(&tfile->f_lock); rb_erase(&epi->rbn, &ep->rbr); |
7699acd13
|
1325 |
error_unregister: |
1da177e4c
|
1326 1327 1328 1329 |
ep_unregister_pollwait(ep, epi); /* * We need to do this because an event could have been arrived on some |
67647d0fb
|
1330 1331 1332 |
* 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
|
1333 |
*/ |
c7ea76302
|
1334 |
spin_lock_irqsave(&ep->lock, flags); |
b030a4dd6
|
1335 |
if (ep_is_linked(&epi->rdllink)) |
6192bd536
|
1336 |
list_del_init(&epi->rdllink); |
c7ea76302
|
1337 |
spin_unlock_irqrestore(&ep->lock, flags); |
1da177e4c
|
1338 |
|
eea1d5859
|
1339 |
wakeup_source_unregister(ep_wakeup_source(epi)); |
4d7e30d98
|
1340 1341 |
error_create_wakeup_source: |
b030a4dd6
|
1342 |
kmem_cache_free(epi_cache, epi); |
7ef9964e6
|
1343 |
|
1da177e4c
|
1344 1345 |
return error; } |
1da177e4c
|
1346 1347 |
/* * Modify the interest event mask by dropping an event if the new mask |
c7ea76302
|
1348 |
* has a match in the current file status. Must be called with "mtx" held. |
1da177e4c
|
1349 1350 1351 1352 1353 |
*/ static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_event *event) { int pwake = 0; unsigned int revents; |
626cf2366
|
1354 1355 1356 |
poll_table pt; init_poll_funcptr(&pt, NULL); |
1da177e4c
|
1357 1358 |
/* |
e057e15ff
|
1359 1360 1361 |
* 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
|
1362 |
*/ |
128dd1759
|
1363 |
epi->event.events = event->events; /* need barrier below */ |
e057e15ff
|
1364 |
epi->event.data = event->data; /* protected by mtx */ |
4d7e30d98
|
1365 |
if (epi->event.events & EPOLLWAKEUP) { |
eea1d5859
|
1366 |
if (!ep_has_wakeup_source(epi)) |
4d7e30d98
|
1367 |
ep_create_wakeup_source(epi); |
eea1d5859
|
1368 |
} else if (ep_has_wakeup_source(epi)) { |
4d7e30d98
|
1369 1370 |
ep_destroy_wakeup_source(epi); } |
1da177e4c
|
1371 1372 |
/* |
128dd1759
|
1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 |
* 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. */ smp_mb(); /* |
1da177e4c
|
1393 1394 1395 |
* Get current event bits. We can safely use the file* here because * its usage count has been increased by the caller of this function. */ |
450d89ec0
|
1396 |
revents = ep_item_poll(epi, &pt); |
1da177e4c
|
1397 |
|
1da177e4c
|
1398 |
/* |
c7ea76302
|
1399 |
* If the item is "hot" and it is not registered inside the ready |
67647d0fb
|
1400 |
* list, push it inside. |
1da177e4c
|
1401 |
*/ |
c7ea76302
|
1402 |
if (revents & event->events) { |
e057e15ff
|
1403 |
spin_lock_irq(&ep->lock); |
c7ea76302
|
1404 1405 |
if (!ep_is_linked(&epi->rdllink)) { list_add_tail(&epi->rdllink, &ep->rdllist); |
eea1d5859
|
1406 |
ep_pm_stay_awake(epi); |
c7ea76302
|
1407 1408 1409 |
/* Notify waiting tasks that events are available */ if (waitqueue_active(&ep->wq)) |
4a6e9e2ce
|
1410 |
wake_up_locked(&ep->wq); |
c7ea76302
|
1411 1412 |
if (waitqueue_active(&ep->poll_wait)) pwake++; |
7699acd13
|
1413 |
} |
e057e15ff
|
1414 |
spin_unlock_irq(&ep->lock); |
7699acd13
|
1415 |
} |
1da177e4c
|
1416 |
|
7699acd13
|
1417 1418 |
/* We have to call this outside the lock */ if (pwake) |
5071f97ec
|
1419 |
ep_poll_safewake(&ep->poll_wait); |
1da177e4c
|
1420 |
|
7699acd13
|
1421 |
return 0; |
1da177e4c
|
1422 |
} |
296e236e9
|
1423 1424 |
static int ep_send_events_proc(struct eventpoll *ep, struct list_head *head, void *priv) |
1da177e4c
|
1425 |
{ |
5071f97ec
|
1426 1427 |
struct ep_send_events_data *esed = priv; int eventcnt; |
296e236e9
|
1428 |
unsigned int revents; |
5071f97ec
|
1429 1430 |
struct epitem *epi; struct epoll_event __user *uevent; |
eea1d5859
|
1431 |
struct wakeup_source *ws; |
626cf2366
|
1432 1433 1434 |
poll_table pt; init_poll_funcptr(&pt, NULL); |
1da177e4c
|
1435 |
|
296e236e9
|
1436 |
/* |
5071f97ec
|
1437 1438 1439 |
* 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
|
1440 |
*/ |
5071f97ec
|
1441 1442 1443 |
for (eventcnt = 0, uevent = esed->events; !list_empty(head) && eventcnt < esed->maxevents;) { epi = list_first_entry(head, struct epitem, rdllink); |
d47de16c7
|
1444 |
|
4d7e30d98
|
1445 1446 1447 1448 1449 1450 1451 1452 1453 |
/* * 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(). */ |
eea1d5859
|
1454 1455 1456 1457 1458 1459 |
ws = ep_wakeup_source(epi); if (ws) { if (ws->active) __pm_stay_awake(ep->ws); __pm_relax(ws); } |
d47de16c7
|
1460 |
list_del_init(&epi->rdllink); |
1da177e4c
|
1461 |
|
450d89ec0
|
1462 |
revents = ep_item_poll(epi, &pt); |
5071f97ec
|
1463 |
|
296e236e9
|
1464 |
/* |
5071f97ec
|
1465 1466 1467 1468 |
* 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
|
1469 1470 |
*/ if (revents) { |
5071f97ec
|
1471 |
if (__put_user(revents, &uevent->events) || |
d03058828
|
1472 1473 |
__put_user(epi->event.data, &uevent->data)) { list_add(&epi->rdllink, head); |
eea1d5859
|
1474 |
ep_pm_stay_awake(epi); |
296e236e9
|
1475 |
return eventcnt ? eventcnt : -EFAULT; |
d03058828
|
1476 |
} |
296e236e9
|
1477 |
eventcnt++; |
5071f97ec
|
1478 |
uevent++; |
296e236e9
|
1479 1480 1481 1482 1483 1484 1485 1486 |
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
|
1487 |
* availability. At this point, no one can insert |
296e236e9
|
1488 1489 1490 1491 1492 1493 |
* 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); |
eea1d5859
|
1494 |
ep_pm_stay_awake(epi); |
296e236e9
|
1495 1496 1497 |
} } } |
5071f97ec
|
1498 1499 1500 |
return eventcnt; } |
d47de16c7
|
1501 |
|
296e236e9
|
1502 1503 |
static int ep_send_events(struct eventpoll *ep, struct epoll_event __user *events, int maxevents) |
5071f97ec
|
1504 1505 |
{ struct ep_send_events_data esed; |
1da177e4c
|
1506 |
|
5071f97ec
|
1507 1508 |
esed.maxevents = maxevents; esed.events = events; |
6192bd536
|
1509 |
|
67347fe4e
|
1510 |
return ep_scan_ready_list(ep, ep_send_events_proc, &esed, 0, false); |
1da177e4c
|
1511 |
} |
766b9f928
|
1512 |
static inline struct timespec64 ep_set_mstimeout(long ms) |
0781b909b
|
1513 |
{ |
766b9f928
|
1514 |
struct timespec64 now, ts = { |
0781b909b
|
1515 1516 1517 |
.tv_sec = ms / MSEC_PER_SEC, .tv_nsec = NSEC_PER_MSEC * (ms % MSEC_PER_SEC), }; |
766b9f928
|
1518 1519 |
ktime_get_ts64(&now); return timespec64_add_safe(now, ts); |
0781b909b
|
1520 |
} |
f4d93ad74
|
1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 |
/** * 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
|
1538 1539 1540 |
static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, int maxevents, long timeout) { |
f4d93ad74
|
1541 |
int res = 0, eavail, timed_out = 0; |
1da177e4c
|
1542 |
unsigned long flags; |
da8b44d5a
|
1543 |
u64 slack = 0; |
1da177e4c
|
1544 |
wait_queue_t wait; |
95aac7b1c
|
1545 1546 1547 |
ktime_t expires, *to = NULL; if (timeout > 0) { |
766b9f928
|
1548 |
struct timespec64 end_time = ep_set_mstimeout(timeout); |
0781b909b
|
1549 |
|
95aac7b1c
|
1550 1551 |
slack = select_estimate_accuracy(&end_time); to = &expires; |
766b9f928
|
1552 |
*to = timespec64_to_ktime(end_time); |
95aac7b1c
|
1553 |
} else if (timeout == 0) { |
f4d93ad74
|
1554 1555 1556 1557 |
/* * Avoid the unnecessary trip to the wait queue loop, if the * caller specified a non blocking operation. */ |
95aac7b1c
|
1558 |
timed_out = 1; |
f4d93ad74
|
1559 1560 |
spin_lock_irqsave(&ep->lock, flags); goto check_events; |
95aac7b1c
|
1561 |
} |
1da177e4c
|
1562 |
|
f4d93ad74
|
1563 |
fetch_events: |
c7ea76302
|
1564 |
spin_lock_irqsave(&ep->lock, flags); |
1da177e4c
|
1565 |
|
3fb0e584a
|
1566 |
if (!ep_events_available(ep)) { |
1da177e4c
|
1567 1568 1569 1570 1571 1572 |
/* * 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
|
1573 |
__add_wait_queue_exclusive(&ep->wq, &wait); |
1da177e4c
|
1574 1575 1576 1577 1578 1579 1580 1581 |
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
|
1582 |
if (ep_events_available(ep) || timed_out) |
1da177e4c
|
1583 1584 1585 1586 1587 |
break; if (signal_pending(current)) { res = -EINTR; break; } |
c7ea76302
|
1588 |
spin_unlock_irqrestore(&ep->lock, flags); |
c511851de
|
1589 |
if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS)) |
95aac7b1c
|
1590 |
timed_out = 1; |
c7ea76302
|
1591 |
spin_lock_irqsave(&ep->lock, flags); |
1da177e4c
|
1592 |
} |
1da177e4c
|
1593 |
|
4d5755b14
|
1594 1595 |
__remove_wait_queue(&ep->wq, &wait); __set_current_state(TASK_RUNNING); |
1da177e4c
|
1596 |
} |
f4d93ad74
|
1597 |
check_events: |
1da177e4c
|
1598 |
/* Is it worth to try to dig for events ? */ |
3fb0e584a
|
1599 |
eavail = ep_events_available(ep); |
1da177e4c
|
1600 |
|
c7ea76302
|
1601 |
spin_unlock_irqrestore(&ep->lock, flags); |
1da177e4c
|
1602 1603 1604 1605 1606 1607 1608 |
/* * 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
|
1609 |
!(res = ep_send_events(ep, events, maxevents)) && !timed_out) |
f4d93ad74
|
1610 |
goto fetch_events; |
1da177e4c
|
1611 1612 1613 |
return res; } |
22bacca48
|
1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 |
/** * 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
|
1634 |
struct eventpoll *ep_tovisit; |
22bacca48
|
1635 1636 |
struct rb_node *rbp; struct epitem *epi; |
d8805e633
|
1637 |
mutex_lock_nested(&ep->mtx, call_nests + 1); |
28d82dc1c
|
1638 1639 |
ep->visited = 1; list_add(&ep->visited_list_link, &visited_list); |
22bacca48
|
1640 1641 1642 |
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
|
1643 1644 1645 |
ep_tovisit = epi->ffd.file->private_data; if (ep_tovisit->visited) continue; |
22bacca48
|
1646 |
error = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, |
28d82dc1c
|
1647 1648 |
ep_loop_check_proc, epi->ffd.file, ep_tovisit, current); |
22bacca48
|
1649 1650 |
if (error != 0) break; |
28d82dc1c
|
1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 |
} 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
|
1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 |
} } 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
|
1683 1684 1685 1686 |
int ret; struct eventpoll *ep_cur, *ep_next; ret = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, |
22bacca48
|
1687 |
ep_loop_check_proc, file, ep, current); |
28d82dc1c
|
1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 |
/* 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
|
1708 |
} |
7699acd13
|
1709 |
/* |
523723bb5
|
1710 |
* Open an eventpoll file descriptor. |
7699acd13
|
1711 |
*/ |
5a8a82b1d
|
1712 |
SYSCALL_DEFINE1(epoll_create1, int, flags) |
7699acd13
|
1713 |
{ |
28d82dc1c
|
1714 |
int error, fd; |
bb57c3edc
|
1715 |
struct eventpoll *ep = NULL; |
28d82dc1c
|
1716 |
struct file *file; |
7699acd13
|
1717 |
|
e38b36f32
|
1718 1719 |
/* Check the EPOLL_* constant for consistency. */ BUILD_BUG_ON(EPOLL_CLOEXEC != O_CLOEXEC); |
296e236e9
|
1720 1721 |
if (flags & ~EPOLL_CLOEXEC) return -EINVAL; |
7699acd13
|
1722 |
/* |
bb57c3edc
|
1723 |
* Create the internal data structure ("struct eventpoll"). |
7699acd13
|
1724 |
*/ |
9fe5ad9c8
|
1725 |
error = ep_alloc(&ep); |
bb57c3edc
|
1726 1727 |
if (error < 0) return error; |
7699acd13
|
1728 1729 |
/* * Creates all the items needed to setup an eventpoll file. That is, |
2030a42ce
|
1730 |
* a file structure and a free file descriptor. |
7699acd13
|
1731 |
*/ |
28d82dc1c
|
1732 1733 1734 1735 1736 1737 |
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
|
1738 |
O_RDWR | (flags & O_CLOEXEC)); |
28d82dc1c
|
1739 1740 1741 1742 |
if (IS_ERR(file)) { error = PTR_ERR(file); goto out_free_fd; } |
28d82dc1c
|
1743 |
ep->file = file; |
98022748f
|
1744 |
fd_install(fd, file); |
28d82dc1c
|
1745 1746 1747 1748 1749 1750 |
return fd; out_free_fd: put_unused_fd(fd); out_free_ep: ep_free(ep); |
bb57c3edc
|
1751 |
return error; |
7699acd13
|
1752 |
} |
5a8a82b1d
|
1753 |
SYSCALL_DEFINE1(epoll_create, int, size) |
a0998b50c
|
1754 |
{ |
bfe3891a5
|
1755 |
if (size <= 0) |
9fe5ad9c8
|
1756 1757 1758 |
return -EINVAL; return sys_epoll_create1(0); |
a0998b50c
|
1759 |
} |
7699acd13
|
1760 1761 1762 |
/* * The following function implements the controller interface for * the eventpoll file that enables the insertion/removal/change of |
67647d0fb
|
1763 |
* file descriptors inside the interest set. |
7699acd13
|
1764 |
*/ |
5a8a82b1d
|
1765 1766 |
SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd, struct epoll_event __user *, event) |
7699acd13
|
1767 1768 |
{ int error; |
67347fe4e
|
1769 |
int full_check = 0; |
7e3fb5842
|
1770 |
struct fd f, tf; |
7699acd13
|
1771 1772 1773 |
struct eventpoll *ep; struct epitem *epi; struct epoll_event epds; |
67347fe4e
|
1774 |
struct eventpoll *tep = NULL; |
7699acd13
|
1775 |
|
7699acd13
|
1776 1777 1778 1779 |
error = -EFAULT; if (ep_op_has_event(op) && copy_from_user(&epds, event, sizeof(struct epoll_event))) goto error_return; |
7699acd13
|
1780 |
error = -EBADF; |
7e3fb5842
|
1781 1782 |
f = fdget(epfd); if (!f.file) |
7699acd13
|
1783 1784 1785 |
goto error_return; /* Get the "struct file *" for the target file */ |
7e3fb5842
|
1786 1787 |
tf = fdget(fd); if (!tf.file) |
7699acd13
|
1788 1789 1790 1791 |
goto error_fput; /* The target file descriptor must support poll */ error = -EPERM; |
72c2d5319
|
1792 |
if (!tf.file->f_op->poll) |
7699acd13
|
1793 |
goto error_tgt_fput; |
4d7e30d98
|
1794 |
/* Check if EPOLLWAKEUP is allowed */ |
c680e41b3
|
1795 1796 |
if (ep_op_has_event(op)) ep_take_care_of_epollwakeup(&epds); |
4d7e30d98
|
1797 |
|
7699acd13
|
1798 1799 1800 1801 1802 1803 |
/* * 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; |
7e3fb5842
|
1804 |
if (f.file == tf.file || !is_file_epoll(f.file)) |
7699acd13
|
1805 1806 1807 |
goto error_tgt_fput; /* |
df0108c5d
|
1808 1809 1810 1811 |
* epoll adds to the wakeup queue at EPOLL_CTL_ADD time only, * so EPOLLEXCLUSIVE is not allowed for a EPOLL_CTL_MOD operation. * Also, we do not currently supported nested exclusive wakeups. */ |
b6a515c8a
|
1812 1813 1814 1815 1816 1817 1818 |
if (epds.events & EPOLLEXCLUSIVE) { if (op == EPOLL_CTL_MOD) goto error_tgt_fput; if (op == EPOLL_CTL_ADD && (is_file_epoll(tf.file) || (epds.events & ~EPOLLEXCLUSIVE_OK_BITS))) goto error_tgt_fput; } |
df0108c5d
|
1819 1820 |
/* |
7699acd13
|
1821 1822 1823 |
* At this point it is safe to assume that the "private_data" contains * our own data structure. */ |
7e3fb5842
|
1824 |
ep = f.file->private_data; |
7699acd13
|
1825 |
|
22bacca48
|
1826 1827 1828 |
/* * When we insert an epoll file descriptor, inside another epoll file * descriptor, there is the change of creating closed loops, which are |
28d82dc1c
|
1829 1830 1831 1832 |
* 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
|
1833 |
* |
67347fe4e
|
1834 1835 1836 1837 1838 1839 |
* 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. |
22bacca48
|
1840 |
*/ |
67347fe4e
|
1841 |
mutex_lock_nested(&ep->mtx, 0); |
28d82dc1c
|
1842 |
if (op == EPOLL_CTL_ADD) { |
67347fe4e
|
1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 |
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); |
13d518074
|
1861 |
} |
67347fe4e
|
1862 1863 |
} } |
7699acd13
|
1864 |
|
67647d0fb
|
1865 1866 1867 1868 1869 |
/* * 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. */ |
7e3fb5842
|
1870 |
epi = ep_find(ep, tf.file, fd); |
7699acd13
|
1871 1872 1873 1874 1875 1876 |
error = -EINVAL; switch (op) { case EPOLL_CTL_ADD: if (!epi) { epds.events |= POLLERR | POLLHUP; |
67347fe4e
|
1877 |
error = ep_insert(ep, &epds, tf.file, fd, full_check); |
7699acd13
|
1878 1879 |
} else error = -EEXIST; |
67347fe4e
|
1880 1881 |
if (full_check) clear_tfile_check_list(); |
7699acd13
|
1882 1883 1884 1885 1886 1887 1888 1889 1890 |
break; case EPOLL_CTL_DEL: if (epi) error = ep_remove(ep, epi); else error = -ENOENT; break; case EPOLL_CTL_MOD: if (epi) { |
b6a515c8a
|
1891 1892 1893 1894 |
if (!(epi->event.events & EPOLLEXCLUSIVE)) { epds.events |= POLLERR | POLLHUP; error = ep_modify(ep, epi, &epds); } |
7699acd13
|
1895 1896 1897 1898 |
} else error = -ENOENT; break; } |
67347fe4e
|
1899 1900 |
if (tep != NULL) mutex_unlock(&tep->mtx); |
d47de16c7
|
1901 |
mutex_unlock(&ep->mtx); |
7699acd13
|
1902 1903 |
error_tgt_fput: |
67347fe4e
|
1904 |
if (full_check) |
22bacca48
|
1905 |
mutex_unlock(&epmutex); |
7e3fb5842
|
1906 |
fdput(tf); |
7699acd13
|
1907 |
error_fput: |
7e3fb5842
|
1908 |
fdput(f); |
7699acd13
|
1909 |
error_return: |
7699acd13
|
1910 1911 1912 1913 1914 1915 1916 1917 |
return error; } /* * Implement the event wait interface for the eventpoll file. It is the kernel * part of the user space epoll_wait(2). */ |
5a8a82b1d
|
1918 1919 |
SYSCALL_DEFINE4(epoll_wait, int, epfd, struct epoll_event __user *, events, int, maxevents, int, timeout) |
7699acd13
|
1920 |
{ |
2903ff019
|
1921 1922 |
int error; struct fd f; |
7699acd13
|
1923 |
struct eventpoll *ep; |
7699acd13
|
1924 1925 1926 1927 1928 |
/* 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 */ |
2903ff019
|
1929 1930 |
if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event))) return -EFAULT; |
7699acd13
|
1931 1932 |
/* Get the "struct file *" for the eventpoll file */ |
2903ff019
|
1933 1934 1935 |
f = fdget(epfd); if (!f.file) return -EBADF; |
7699acd13
|
1936 1937 1938 1939 1940 1941 |
/* * We have to check that the file structure underneath the fd * the user passed to us _is_ an eventpoll file. */ error = -EINVAL; |
2903ff019
|
1942 |
if (!is_file_epoll(f.file)) |
7699acd13
|
1943 1944 1945 1946 1947 1948 |
goto error_fput; /* * At this point it is safe to assume that the "private_data" contains * our own data structure. */ |
2903ff019
|
1949 |
ep = f.file->private_data; |
7699acd13
|
1950 1951 1952 1953 1954 |
/* Time to fish for events ... */ error = ep_poll(ep, events, maxevents, timeout); error_fput: |
2903ff019
|
1955 |
fdput(f); |
7699acd13
|
1956 1957 |
return error; } |
7699acd13
|
1958 1959 1960 1961 |
/* * Implement the event wait interface for the eventpoll file. It is the kernel * part of the user space epoll_pwait(2). */ |
5a8a82b1d
|
1962 1963 1964 |
SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events, int, maxevents, int, timeout, const sigset_t __user *, sigmask, size_t, sigsetsize) |
7699acd13
|
1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 |
{ 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; |
77d559180
|
1978 1979 |
sigsaved = current->blocked; set_current_blocked(&ksigmask); |
7699acd13
|
1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 |
} 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
|
1993 |
sizeof(sigsaved)); |
4e4c22c71
|
1994 |
set_restore_sigmask(); |
7699acd13
|
1995 |
} else |
77d559180
|
1996 |
set_current_blocked(&sigsaved); |
7699acd13
|
1997 1998 1999 2000 |
} return error; } |
35280bd4a
|
2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 |
#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; /* * 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); |
77d559180
|
2022 2023 |
sigsaved = current->blocked; set_current_blocked(&ksigmask); |
35280bd4a
|
2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 |
} err = 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 (err == -EINTR) { memcpy(¤t->saved_sigmask, &sigsaved, sizeof(sigsaved)); set_restore_sigmask(); } else |
77d559180
|
2040 |
set_current_blocked(&sigsaved); |
35280bd4a
|
2041 2042 2043 2044 2045 |
} return err; } #endif |
1da177e4c
|
2046 2047 |
static int __init eventpoll_init(void) { |
7ef9964e6
|
2048 2049 2050 |
struct sysinfo si; si_meminfo(&si); |
9df04e1f2
|
2051 2052 2053 2054 |
/* * Allows top 4% of lomem to be allocated for epoll watches (per user). */ max_user_watches = (((si.totalram - si.totalhigh) / 25) << PAGE_SHIFT) / |
7ef9964e6
|
2055 |
EP_ITEM_COST; |
52bd19f76
|
2056 |
BUG_ON(max_user_watches < 0); |
1da177e4c
|
2057 |
|
22bacca48
|
2058 2059 2060 2061 2062 |
/* * Initialize the structure used to perform epoll file descriptor * inclusion loops checks. */ ep_nested_calls_init(&poll_loop_ncalls); |
1da177e4c
|
2063 |
/* Initialize the structure used to perform safe poll wait head wake ups */ |
5071f97ec
|
2064 2065 2066 2067 |
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
|
2068 |
|
39732ca5a
|
2069 2070 2071 2072 2073 |
/* * 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); |
1da177e4c
|
2074 2075 |
/* Allocates slab cache used to allocate "struct epitem" items */ epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem), |
bb57c3edc
|
2076 |
0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); |
1da177e4c
|
2077 2078 2079 |
/* Allocates slab cache used to allocate "struct eppoll_entry" */ pwq_cache = kmem_cache_create("eventpoll_pwq", |
bb57c3edc
|
2080 |
sizeof(struct eppoll_entry), 0, SLAB_PANIC, NULL); |
1da177e4c
|
2081 |
|
1da177e4c
|
2082 |
return 0; |
1da177e4c
|
2083 |
} |
cea692418
|
2084 |
fs_initcall(eventpoll_init); |