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xianfeng |
/*
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* fs/eventpoll.c (Efficent event polling implementation)
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* Copyright (C) 2001,...,2007 Davide Libenzi
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* Davide Libenzi <davidel@xmailserver.org>
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*
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*/
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/sched.h>
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#include <linux/fs.h>
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#include <linux/file.h>
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#include <linux/signal.h>
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#include <linux/errno.h>
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#include <linux/mm.h>
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#include <linux/slab.h>
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#include <linux/poll.h>
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#include <linux/string.h>
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#include <linux/list.h>
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#include <linux/hash.h>
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#include <linux/spinlock.h>
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#include <linux/syscalls.h>
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#include <linux/rbtree.h>
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#include <linux/wait.h>
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#include <linux/eventpoll.h>
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#include <linux/mount.h>
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#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>
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#include <asm/system.h>
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#include <asm/io.h>
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#include <asm/mman.h>
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#include <asm/atomic.h>
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/*
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* LOCKING:
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* There are three level of locking required by epoll :
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*
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* 1) epmutex (mutex)
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* 2) ep->mtx (mutex)
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* 3) ep->lock (spinlock)
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*
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* The acquire order is the one listed above, from 1 to 3.
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* We need a spinlock (ep->lock) because we manipulate objects
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* from inside the poll callback, that might be triggered from
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* a wake_up() that in turn might be called from IRQ context.
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* So we can't sleep inside the poll callback and hence we need
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* a spinlock. During the event transfer loop (from kernel to
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* user space) we could end up sleeping due a copy_to_user(), so
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* 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,
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* during epoll_ctl(EPOLL_CTL_DEL) and during eventpoll_release_file().
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* Then we also need a global mutex to serialize eventpoll_release_file()
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* and ep_free().
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* 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()
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* if a file has been pushed inside an epoll set and it is then
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* close()d without a previous call toepoll_ctl(EPOLL_CTL_DEL).
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* It is possible to drop the "ep->mtx" and to use the global
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* mutex "epmutex" (together with "ep->lock") to have it working,
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* 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
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* a better scalability.
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*/
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#define DEBUG_EPOLL 0
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#if DEBUG_EPOLL > 0
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#define DPRINTK(x) printk x
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#define DNPRINTK(n, x) do { if ((n) <= DEBUG_EPOLL) printk x; } while (0)
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#else /* #if DEBUG_EPOLL > 0 */
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#define DPRINTK(x) (void) 0
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#define DNPRINTK(n, x) (void) 0
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#endif /* #if DEBUG_EPOLL > 0 */
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#define DEBUG_EPI 0
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#if DEBUG_EPI != 0
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#define EPI_SLAB_DEBUG (SLAB_DEBUG_FREE | SLAB_RED_ZONE /* | SLAB_POISON */)
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#else /* #if DEBUG_EPI != 0 */
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#define EPI_SLAB_DEBUG 0
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#endif /* #if DEBUG_EPI != 0 */
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/* Epoll private bits inside the event mask */
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#define EP_PRIVATE_BITS (EPOLLONESHOT | EPOLLET)
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/* Maximum number of poll wake up nests we are allowing */
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#define EP_MAX_POLLWAKE_NESTS 4
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/* Maximum msec timeout value storeable in a long int */
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#define EP_MAX_MSTIMEO min(1000ULL * MAX_SCHEDULE_TIMEOUT / HZ, (LONG_MAX - 999ULL) / HZ)
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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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struct epoll_filefd {
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struct file *file;
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int fd;
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};
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/*
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* Node that is linked into the "wake_task_list" member of the "struct poll_safewake".
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* It is used to keep track on all tasks that are currently inside the wake_up() code
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* to 1) short-circuit the one coming from the same task and same wait queue head
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* (loop) 2) allow a maximum number of epoll descriptors inclusion nesting
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* 3) let go the ones coming from other tasks.
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*/
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struct wake_task_node {
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struct list_head llink;
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struct task_struct *task;
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wait_queue_head_t *wq;
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};
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/*
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* This is used to implement the safe poll wake up avoiding to reenter
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* the poll callback from inside wake_up().
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*/
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struct poll_safewake {
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struct list_head wake_task_list;
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spinlock_t lock;
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};
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/*
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* Each file descriptor added to the eventpoll interface will
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* have an entry of this type linked to the "rbr" RB tree.
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*/
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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;
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/* List header used to link this structure to the eventpoll ready list */
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struct list_head rdllink;
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/*
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* Works together "struct eventpoll"->ovflist in keeping the
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* single linked chain of items.
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*/
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struct epitem *next;
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/* The file descriptor information this item refers to */
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struct epoll_filefd ffd;
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/* Number of active wait queue attached to poll operations */
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int nwait;
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/* List containing poll wait queues */
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struct list_head pwqlist;
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/* The "container" of this item */
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struct eventpoll *ep;
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/* List header used to link this item to the "struct file" items list */
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struct list_head fllink;
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/* The structure that describe the interested events and the source fd */
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struct epoll_event event;
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};
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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 rapresent the main data sructure for the eventpoll
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* interface.
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*/
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struct eventpoll {
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/* Protect the this structure access */
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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
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* while epoll is using them. This is held during the event
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* collection loop, the file cleanup path, the epoll file exit
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* 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() */
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wait_queue_head_t wq;
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/* Wait queue used by file->poll() */
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wait_queue_head_t poll_wait;
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/* List of ready file descriptors */
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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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/*
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* This is a single linked list that chains all the "struct epitem" that
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* happened while transfering ready events to userspace w/out
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* holding ->lock.
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*/
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struct epitem *ovflist;
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};
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/* Wait structure used by the poll hooks */
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struct eppoll_entry {
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/* List header used to link this structure to the "struct epitem" */
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struct list_head llink;
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/* The "base" pointer is set to the container "struct epitem" */
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void *base;
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/*
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* Wait queue item that will be linked to the target file wait
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* queue head.
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*/
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wait_queue_t wait;
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/* The wait queue head that linked the "wait" wait queue item */
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wait_queue_head_t *whead;
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};
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/* Wrapper struct used by poll queueing */
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struct ep_pqueue {
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poll_table pt;
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struct epitem *epi;
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};
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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 struct mutex epmutex;
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/* Safe wake up implementation */
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static struct poll_safewake psw;
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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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/* 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,
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struct file *file, int fd)
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{
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ffd->file = file;
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ffd->fd = fd;
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}
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/* Compare RB tree keys */
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static inline int ep_cmp_ffd(struct epoll_filefd *p1,
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struct epoll_filefd *p2)
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{
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return (p1->file > p2->file ? +1:
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(p1->file < p2->file ? -1 : p1->fd - p2->fd));
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}
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/* Special initialization for the RB tree node to detect linkage */
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static inline void ep_rb_initnode(struct rb_node *n)
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{
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rb_set_parent(n, n);
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}
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/* Removes a node from the RB tree and marks it for a fast is-linked check */
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static inline void ep_rb_erase(struct rb_node *n, struct rb_root *r)
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{
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rb_erase(n, r);
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rb_set_parent(n, n);
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}
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/* Fast check to verify that the item is linked to the main RB tree */
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static inline int ep_rb_linked(struct rb_node *n)
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{
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return rb_parent(n) != n;
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}
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/* Tells us if the item is currently linked */
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static inline int ep_is_linked(struct list_head *p)
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{
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return !list_empty(p);
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}
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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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{
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return container_of(p, struct eppoll_entry, wait)->base;
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}
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/* 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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{
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return container_of(p, struct ep_pqueue, pt)->epi;
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}
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/* 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_poll_safewake_init(struct poll_safewake *psw)
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{
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INIT_LIST_HEAD(&psw->wake_task_list);
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spin_lock_init(&psw->lock);
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}
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/*
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* Perform a safe wake up of the poll wait list. The problem is that
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* with the new callback'd wake up system, it is possible that the
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* poll callback is reentered from inside the call to wake_up() done
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* on the poll wait queue head. The rule is that we cannot reenter the
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* wake up code from the same task more than EP_MAX_POLLWAKE_NESTS times,
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* and we cannot reenter the same wait queue head at all. This will
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* enable to have a hierarchy of epoll file descriptor of no more than
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* EP_MAX_POLLWAKE_NESTS deep. We need the irq version of the spin lock
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* because this one gets called by the poll callback, that in turn is called
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* from inside a wake_up(), that might be called from irq context.
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*/
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static void ep_poll_safewake(struct poll_safewake *psw, wait_queue_head_t *wq)
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{
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int wake_nests = 0;
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unsigned long flags;
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struct task_struct *this_task = current;
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struct list_head *lsthead = &psw->wake_task_list;
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struct wake_task_node *tncur;
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struct wake_task_node tnode;
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spin_lock_irqsave(&psw->lock, flags);
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/* Try to see if the current task is already inside this wakeup call */
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list_for_each_entry(tncur, lsthead, llink) {
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if (tncur->wq == wq ||
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(tncur->task == this_task && ++wake_nests > EP_MAX_POLLWAKE_NESTS)) {
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/*
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* Ops ... loop detected or maximum nest level reached.
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* We abort this wake by breaking the cycle itself.
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*/
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spin_unlock_irqrestore(&psw->lock, flags);
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return;
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}
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}
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/* Add the current task to the list */
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tnode.task = this_task;
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tnode.wq = wq;
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list_add(&tnode.llink, lsthead);
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spin_unlock_irqrestore(&psw->lock, flags);
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354 |
|
|
|
355 |
|
|
/* Do really wake up now */
|
356 |
|
|
wake_up(wq);
|
357 |
|
|
|
358 |
|
|
/* Remove the current task from the list */
|
359 |
|
|
spin_lock_irqsave(&psw->lock, flags);
|
360 |
|
|
list_del(&tnode.llink);
|
361 |
|
|
spin_unlock_irqrestore(&psw->lock, flags);
|
362 |
|
|
}
|
363 |
|
|
|
364 |
|
|
/*
|
365 |
|
|
* This function unregister poll callbacks from the associated file descriptor.
|
366 |
|
|
* Since this must be called without holding "ep->lock" the atomic exchange trick
|
367 |
|
|
* will protect us from multiple unregister.
|
368 |
|
|
*/
|
369 |
|
|
static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi)
|
370 |
|
|
{
|
371 |
|
|
int nwait;
|
372 |
|
|
struct list_head *lsthead = &epi->pwqlist;
|
373 |
|
|
struct eppoll_entry *pwq;
|
374 |
|
|
|
375 |
|
|
/* This is called without locks, so we need the atomic exchange */
|
376 |
|
|
nwait = xchg(&epi->nwait, 0);
|
377 |
|
|
|
378 |
|
|
if (nwait) {
|
379 |
|
|
while (!list_empty(lsthead)) {
|
380 |
|
|
pwq = list_first_entry(lsthead, struct eppoll_entry, llink);
|
381 |
|
|
|
382 |
|
|
list_del_init(&pwq->llink);
|
383 |
|
|
remove_wait_queue(pwq->whead, &pwq->wait);
|
384 |
|
|
kmem_cache_free(pwq_cache, pwq);
|
385 |
|
|
}
|
386 |
|
|
}
|
387 |
|
|
}
|
388 |
|
|
|
389 |
|
|
/*
|
390 |
|
|
* Removes a "struct epitem" from the eventpoll RB tree and deallocates
|
391 |
|
|
* all the associated resources. Must be called with "mtx" held.
|
392 |
|
|
*/
|
393 |
|
|
static int ep_remove(struct eventpoll *ep, struct epitem *epi)
|
394 |
|
|
{
|
395 |
|
|
unsigned long flags;
|
396 |
|
|
struct file *file = epi->ffd.file;
|
397 |
|
|
|
398 |
|
|
/*
|
399 |
|
|
* Removes poll wait queue hooks. We _have_ to do this without holding
|
400 |
|
|
* the "ep->lock" otherwise a deadlock might occur. This because of the
|
401 |
|
|
* sequence of the lock acquisition. Here we do "ep->lock" then the wait
|
402 |
|
|
* queue head lock when unregistering the wait queue. The wakeup callback
|
403 |
|
|
* will run by holding the wait queue head lock and will call our callback
|
404 |
|
|
* that will try to get "ep->lock".
|
405 |
|
|
*/
|
406 |
|
|
ep_unregister_pollwait(ep, epi);
|
407 |
|
|
|
408 |
|
|
/* Remove the current item from the list of epoll hooks */
|
409 |
|
|
spin_lock(&file->f_ep_lock);
|
410 |
|
|
if (ep_is_linked(&epi->fllink))
|
411 |
|
|
list_del_init(&epi->fllink);
|
412 |
|
|
spin_unlock(&file->f_ep_lock);
|
413 |
|
|
|
414 |
|
|
if (ep_rb_linked(&epi->rbn))
|
415 |
|
|
ep_rb_erase(&epi->rbn, &ep->rbr);
|
416 |
|
|
|
417 |
|
|
spin_lock_irqsave(&ep->lock, flags);
|
418 |
|
|
if (ep_is_linked(&epi->rdllink))
|
419 |
|
|
list_del_init(&epi->rdllink);
|
420 |
|
|
spin_unlock_irqrestore(&ep->lock, flags);
|
421 |
|
|
|
422 |
|
|
/* At this point it is safe to free the eventpoll item */
|
423 |
|
|
kmem_cache_free(epi_cache, epi);
|
424 |
|
|
|
425 |
|
|
DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_remove(%p, %p)\n",
|
426 |
|
|
current, ep, file));
|
427 |
|
|
|
428 |
|
|
return 0;
|
429 |
|
|
}
|
430 |
|
|
|
431 |
|
|
static void ep_free(struct eventpoll *ep)
|
432 |
|
|
{
|
433 |
|
|
struct rb_node *rbp;
|
434 |
|
|
struct epitem *epi;
|
435 |
|
|
|
436 |
|
|
/* We need to release all tasks waiting for these file */
|
437 |
|
|
if (waitqueue_active(&ep->poll_wait))
|
438 |
|
|
ep_poll_safewake(&psw, &ep->poll_wait);
|
439 |
|
|
|
440 |
|
|
/*
|
441 |
|
|
* We need to lock this because we could be hit by
|
442 |
|
|
* eventpoll_release_file() while we're freeing the "struct eventpoll".
|
443 |
|
|
* We do not need to hold "ep->mtx" here because the epoll file
|
444 |
|
|
* is on the way to be removed and no one has references to it
|
445 |
|
|
* anymore. The only hit might come from eventpoll_release_file() but
|
446 |
|
|
* holding "epmutex" is sufficent here.
|
447 |
|
|
*/
|
448 |
|
|
mutex_lock(&epmutex);
|
449 |
|
|
|
450 |
|
|
/*
|
451 |
|
|
* Walks through the whole tree by unregistering poll callbacks.
|
452 |
|
|
*/
|
453 |
|
|
for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) {
|
454 |
|
|
epi = rb_entry(rbp, struct epitem, rbn);
|
455 |
|
|
|
456 |
|
|
ep_unregister_pollwait(ep, epi);
|
457 |
|
|
}
|
458 |
|
|
|
459 |
|
|
/*
|
460 |
|
|
* Walks through the whole tree by freeing each "struct epitem". At this
|
461 |
|
|
* point we are sure no poll callbacks will be lingering around, and also by
|
462 |
|
|
* holding "epmutex" we can be sure that no file cleanup code will hit
|
463 |
|
|
* us during this operation. So we can avoid the lock on "ep->lock".
|
464 |
|
|
*/
|
465 |
|
|
while ((rbp = rb_first(&ep->rbr)) != NULL) {
|
466 |
|
|
epi = rb_entry(rbp, struct epitem, rbn);
|
467 |
|
|
ep_remove(ep, epi);
|
468 |
|
|
}
|
469 |
|
|
|
470 |
|
|
mutex_unlock(&epmutex);
|
471 |
|
|
mutex_destroy(&ep->mtx);
|
472 |
|
|
kfree(ep);
|
473 |
|
|
}
|
474 |
|
|
|
475 |
|
|
static int ep_eventpoll_release(struct inode *inode, struct file *file)
|
476 |
|
|
{
|
477 |
|
|
struct eventpoll *ep = file->private_data;
|
478 |
|
|
|
479 |
|
|
if (ep)
|
480 |
|
|
ep_free(ep);
|
481 |
|
|
|
482 |
|
|
DNPRINTK(3, (KERN_INFO "[%p] eventpoll: close() ep=%p\n", current, ep));
|
483 |
|
|
return 0;
|
484 |
|
|
}
|
485 |
|
|
|
486 |
|
|
static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait)
|
487 |
|
|
{
|
488 |
|
|
unsigned int pollflags = 0;
|
489 |
|
|
unsigned long flags;
|
490 |
|
|
struct eventpoll *ep = file->private_data;
|
491 |
|
|
|
492 |
|
|
/* Insert inside our poll wait queue */
|
493 |
|
|
poll_wait(file, &ep->poll_wait, wait);
|
494 |
|
|
|
495 |
|
|
/* Check our condition */
|
496 |
|
|
spin_lock_irqsave(&ep->lock, flags);
|
497 |
|
|
if (!list_empty(&ep->rdllist))
|
498 |
|
|
pollflags = POLLIN | POLLRDNORM;
|
499 |
|
|
spin_unlock_irqrestore(&ep->lock, flags);
|
500 |
|
|
|
501 |
|
|
return pollflags;
|
502 |
|
|
}
|
503 |
|
|
|
504 |
|
|
/* File callbacks that implement the eventpoll file behaviour */
|
505 |
|
|
static const struct file_operations eventpoll_fops = {
|
506 |
|
|
.release = ep_eventpoll_release,
|
507 |
|
|
.poll = ep_eventpoll_poll
|
508 |
|
|
};
|
509 |
|
|
|
510 |
|
|
/* Fast test to see if the file is an evenpoll file */
|
511 |
|
|
static inline int is_file_epoll(struct file *f)
|
512 |
|
|
{
|
513 |
|
|
return f->f_op == &eventpoll_fops;
|
514 |
|
|
}
|
515 |
|
|
|
516 |
|
|
/*
|
517 |
|
|
* This is called from eventpoll_release() to unlink files from the eventpoll
|
518 |
|
|
* interface. We need to have this facility to cleanup correctly files that are
|
519 |
|
|
* closed without being removed from the eventpoll interface.
|
520 |
|
|
*/
|
521 |
|
|
void eventpoll_release_file(struct file *file)
|
522 |
|
|
{
|
523 |
|
|
struct list_head *lsthead = &file->f_ep_links;
|
524 |
|
|
struct eventpoll *ep;
|
525 |
|
|
struct epitem *epi;
|
526 |
|
|
|
527 |
|
|
/*
|
528 |
|
|
* We don't want to get "file->f_ep_lock" because it is not
|
529 |
|
|
* necessary. It is not necessary because we're in the "struct file"
|
530 |
|
|
* cleanup path, and this means that noone is using this file anymore.
|
531 |
|
|
* So, for example, epoll_ctl() cannot hit here sicne if we reach this
|
532 |
|
|
* point, the file counter already went to zero and fget() would fail.
|
533 |
|
|
* The only hit might come from ep_free() but by holding the mutex
|
534 |
|
|
* will correctly serialize the operation. We do need to acquire
|
535 |
|
|
* "ep->mtx" after "epmutex" because ep_remove() requires it when called
|
536 |
|
|
* from anywhere but ep_free().
|
537 |
|
|
*/
|
538 |
|
|
mutex_lock(&epmutex);
|
539 |
|
|
|
540 |
|
|
while (!list_empty(lsthead)) {
|
541 |
|
|
epi = list_first_entry(lsthead, struct epitem, fllink);
|
542 |
|
|
|
543 |
|
|
ep = epi->ep;
|
544 |
|
|
list_del_init(&epi->fllink);
|
545 |
|
|
mutex_lock(&ep->mtx);
|
546 |
|
|
ep_remove(ep, epi);
|
547 |
|
|
mutex_unlock(&ep->mtx);
|
548 |
|
|
}
|
549 |
|
|
|
550 |
|
|
mutex_unlock(&epmutex);
|
551 |
|
|
}
|
552 |
|
|
|
553 |
|
|
static int ep_alloc(struct eventpoll **pep)
|
554 |
|
|
{
|
555 |
|
|
struct eventpoll *ep = kzalloc(sizeof(*ep), GFP_KERNEL);
|
556 |
|
|
|
557 |
|
|
if (!ep)
|
558 |
|
|
return -ENOMEM;
|
559 |
|
|
|
560 |
|
|
spin_lock_init(&ep->lock);
|
561 |
|
|
mutex_init(&ep->mtx);
|
562 |
|
|
init_waitqueue_head(&ep->wq);
|
563 |
|
|
init_waitqueue_head(&ep->poll_wait);
|
564 |
|
|
INIT_LIST_HEAD(&ep->rdllist);
|
565 |
|
|
ep->rbr = RB_ROOT;
|
566 |
|
|
ep->ovflist = EP_UNACTIVE_PTR;
|
567 |
|
|
|
568 |
|
|
*pep = ep;
|
569 |
|
|
|
570 |
|
|
DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_alloc() ep=%p\n",
|
571 |
|
|
current, ep));
|
572 |
|
|
return 0;
|
573 |
|
|
}
|
574 |
|
|
|
575 |
|
|
/*
|
576 |
|
|
* Search the file inside the eventpoll tree. The RB tree operations
|
577 |
|
|
* are protected by the "mtx" mutex, and ep_find() must be called with
|
578 |
|
|
* "mtx" held.
|
579 |
|
|
*/
|
580 |
|
|
static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd)
|
581 |
|
|
{
|
582 |
|
|
int kcmp;
|
583 |
|
|
struct rb_node *rbp;
|
584 |
|
|
struct epitem *epi, *epir = NULL;
|
585 |
|
|
struct epoll_filefd ffd;
|
586 |
|
|
|
587 |
|
|
ep_set_ffd(&ffd, file, fd);
|
588 |
|
|
for (rbp = ep->rbr.rb_node; rbp; ) {
|
589 |
|
|
epi = rb_entry(rbp, struct epitem, rbn);
|
590 |
|
|
kcmp = ep_cmp_ffd(&ffd, &epi->ffd);
|
591 |
|
|
if (kcmp > 0)
|
592 |
|
|
rbp = rbp->rb_right;
|
593 |
|
|
else if (kcmp < 0)
|
594 |
|
|
rbp = rbp->rb_left;
|
595 |
|
|
else {
|
596 |
|
|
epir = epi;
|
597 |
|
|
break;
|
598 |
|
|
}
|
599 |
|
|
}
|
600 |
|
|
|
601 |
|
|
DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_find(%p) -> %p\n",
|
602 |
|
|
current, file, epir));
|
603 |
|
|
|
604 |
|
|
return epir;
|
605 |
|
|
}
|
606 |
|
|
|
607 |
|
|
/*
|
608 |
|
|
* This is the callback that is passed to the wait queue wakeup
|
609 |
|
|
* machanism. It is called by the stored file descriptors when they
|
610 |
|
|
* have events to report.
|
611 |
|
|
*/
|
612 |
|
|
static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *key)
|
613 |
|
|
{
|
614 |
|
|
int pwake = 0;
|
615 |
|
|
unsigned long flags;
|
616 |
|
|
struct epitem *epi = ep_item_from_wait(wait);
|
617 |
|
|
struct eventpoll *ep = epi->ep;
|
618 |
|
|
|
619 |
|
|
DNPRINTK(3, (KERN_INFO "[%p] eventpoll: poll_callback(%p) epi=%p ep=%p\n",
|
620 |
|
|
current, epi->ffd.file, epi, ep));
|
621 |
|
|
|
622 |
|
|
spin_lock_irqsave(&ep->lock, flags);
|
623 |
|
|
|
624 |
|
|
/*
|
625 |
|
|
* If the event mask does not contain any poll(2) event, we consider the
|
626 |
|
|
* descriptor to be disabled. This condition is likely the effect of the
|
627 |
|
|
* EPOLLONESHOT bit that disables the descriptor when an event is received,
|
628 |
|
|
* until the next EPOLL_CTL_MOD will be issued.
|
629 |
|
|
*/
|
630 |
|
|
if (!(epi->event.events & ~EP_PRIVATE_BITS))
|
631 |
|
|
goto out_unlock;
|
632 |
|
|
|
633 |
|
|
/*
|
634 |
|
|
* If we are trasfering events to userspace, we can hold no locks
|
635 |
|
|
* (because we're accessing user memory, and because of linux f_op->poll()
|
636 |
|
|
* semantics). All the events that happens during that period of time are
|
637 |
|
|
* chained in ep->ovflist and requeued later on.
|
638 |
|
|
*/
|
639 |
|
|
if (unlikely(ep->ovflist != EP_UNACTIVE_PTR)) {
|
640 |
|
|
if (epi->next == EP_UNACTIVE_PTR) {
|
641 |
|
|
epi->next = ep->ovflist;
|
642 |
|
|
ep->ovflist = epi;
|
643 |
|
|
}
|
644 |
|
|
goto out_unlock;
|
645 |
|
|
}
|
646 |
|
|
|
647 |
|
|
/* If this file is already in the ready list we exit soon */
|
648 |
|
|
if (ep_is_linked(&epi->rdllink))
|
649 |
|
|
goto is_linked;
|
650 |
|
|
|
651 |
|
|
list_add_tail(&epi->rdllink, &ep->rdllist);
|
652 |
|
|
|
653 |
|
|
is_linked:
|
654 |
|
|
/*
|
655 |
|
|
* Wake up ( if active ) both the eventpoll wait list and the ->poll()
|
656 |
|
|
* wait list.
|
657 |
|
|
*/
|
658 |
|
|
if (waitqueue_active(&ep->wq))
|
659 |
|
|
__wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE |
|
660 |
|
|
TASK_INTERRUPTIBLE);
|
661 |
|
|
if (waitqueue_active(&ep->poll_wait))
|
662 |
|
|
pwake++;
|
663 |
|
|
|
664 |
|
|
out_unlock:
|
665 |
|
|
spin_unlock_irqrestore(&ep->lock, flags);
|
666 |
|
|
|
667 |
|
|
/* We have to call this outside the lock */
|
668 |
|
|
if (pwake)
|
669 |
|
|
ep_poll_safewake(&psw, &ep->poll_wait);
|
670 |
|
|
|
671 |
|
|
return 1;
|
672 |
|
|
}
|
673 |
|
|
|
674 |
|
|
/*
|
675 |
|
|
* This is the callback that is used to add our wait queue to the
|
676 |
|
|
* target file wakeup lists.
|
677 |
|
|
*/
|
678 |
|
|
static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead,
|
679 |
|
|
poll_table *pt)
|
680 |
|
|
{
|
681 |
|
|
struct epitem *epi = ep_item_from_epqueue(pt);
|
682 |
|
|
struct eppoll_entry *pwq;
|
683 |
|
|
|
684 |
|
|
if (epi->nwait >= 0 && (pwq = kmem_cache_alloc(pwq_cache, GFP_KERNEL))) {
|
685 |
|
|
init_waitqueue_func_entry(&pwq->wait, ep_poll_callback);
|
686 |
|
|
pwq->whead = whead;
|
687 |
|
|
pwq->base = epi;
|
688 |
|
|
add_wait_queue(whead, &pwq->wait);
|
689 |
|
|
list_add_tail(&pwq->llink, &epi->pwqlist);
|
690 |
|
|
epi->nwait++;
|
691 |
|
|
} else {
|
692 |
|
|
/* We have to signal that an error occurred */
|
693 |
|
|
epi->nwait = -1;
|
694 |
|
|
}
|
695 |
|
|
}
|
696 |
|
|
|
697 |
|
|
static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi)
|
698 |
|
|
{
|
699 |
|
|
int kcmp;
|
700 |
|
|
struct rb_node **p = &ep->rbr.rb_node, *parent = NULL;
|
701 |
|
|
struct epitem *epic;
|
702 |
|
|
|
703 |
|
|
while (*p) {
|
704 |
|
|
parent = *p;
|
705 |
|
|
epic = rb_entry(parent, struct epitem, rbn);
|
706 |
|
|
kcmp = ep_cmp_ffd(&epi->ffd, &epic->ffd);
|
707 |
|
|
if (kcmp > 0)
|
708 |
|
|
p = &parent->rb_right;
|
709 |
|
|
else
|
710 |
|
|
p = &parent->rb_left;
|
711 |
|
|
}
|
712 |
|
|
rb_link_node(&epi->rbn, parent, p);
|
713 |
|
|
rb_insert_color(&epi->rbn, &ep->rbr);
|
714 |
|
|
}
|
715 |
|
|
|
716 |
|
|
/*
|
717 |
|
|
* Must be called with "mtx" held.
|
718 |
|
|
*/
|
719 |
|
|
static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
|
720 |
|
|
struct file *tfile, int fd)
|
721 |
|
|
{
|
722 |
|
|
int error, revents, pwake = 0;
|
723 |
|
|
unsigned long flags;
|
724 |
|
|
struct epitem *epi;
|
725 |
|
|
struct ep_pqueue epq;
|
726 |
|
|
|
727 |
|
|
error = -ENOMEM;
|
728 |
|
|
if (!(epi = kmem_cache_alloc(epi_cache, GFP_KERNEL)))
|
729 |
|
|
goto error_return;
|
730 |
|
|
|
731 |
|
|
/* Item initialization follow here ... */
|
732 |
|
|
ep_rb_initnode(&epi->rbn);
|
733 |
|
|
INIT_LIST_HEAD(&epi->rdllink);
|
734 |
|
|
INIT_LIST_HEAD(&epi->fllink);
|
735 |
|
|
INIT_LIST_HEAD(&epi->pwqlist);
|
736 |
|
|
epi->ep = ep;
|
737 |
|
|
ep_set_ffd(&epi->ffd, tfile, fd);
|
738 |
|
|
epi->event = *event;
|
739 |
|
|
epi->nwait = 0;
|
740 |
|
|
epi->next = EP_UNACTIVE_PTR;
|
741 |
|
|
|
742 |
|
|
/* Initialize the poll table using the queue callback */
|
743 |
|
|
epq.epi = epi;
|
744 |
|
|
init_poll_funcptr(&epq.pt, ep_ptable_queue_proc);
|
745 |
|
|
|
746 |
|
|
/*
|
747 |
|
|
* Attach the item to the poll hooks and get current event bits.
|
748 |
|
|
* We can safely use the file* here because its usage count has
|
749 |
|
|
* been increased by the caller of this function. Note that after
|
750 |
|
|
* this operation completes, the poll callback can start hitting
|
751 |
|
|
* the new item.
|
752 |
|
|
*/
|
753 |
|
|
revents = tfile->f_op->poll(tfile, &epq.pt);
|
754 |
|
|
|
755 |
|
|
/*
|
756 |
|
|
* We have to check if something went wrong during the poll wait queue
|
757 |
|
|
* install process. Namely an allocation for a wait queue failed due
|
758 |
|
|
* high memory pressure.
|
759 |
|
|
*/
|
760 |
|
|
if (epi->nwait < 0)
|
761 |
|
|
goto error_unregister;
|
762 |
|
|
|
763 |
|
|
/* Add the current item to the list of active epoll hook for this file */
|
764 |
|
|
spin_lock(&tfile->f_ep_lock);
|
765 |
|
|
list_add_tail(&epi->fllink, &tfile->f_ep_links);
|
766 |
|
|
spin_unlock(&tfile->f_ep_lock);
|
767 |
|
|
|
768 |
|
|
/*
|
769 |
|
|
* Add the current item to the RB tree. All RB tree operations are
|
770 |
|
|
* protected by "mtx", and ep_insert() is called with "mtx" held.
|
771 |
|
|
*/
|
772 |
|
|
ep_rbtree_insert(ep, epi);
|
773 |
|
|
|
774 |
|
|
/* We have to drop the new item inside our item list to keep track of it */
|
775 |
|
|
spin_lock_irqsave(&ep->lock, flags);
|
776 |
|
|
|
777 |
|
|
/* If the file is already "ready" we drop it inside the ready list */
|
778 |
|
|
if ((revents & event->events) && !ep_is_linked(&epi->rdllink)) {
|
779 |
|
|
list_add_tail(&epi->rdllink, &ep->rdllist);
|
780 |
|
|
|
781 |
|
|
/* Notify waiting tasks that events are available */
|
782 |
|
|
if (waitqueue_active(&ep->wq))
|
783 |
|
|
__wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE);
|
784 |
|
|
if (waitqueue_active(&ep->poll_wait))
|
785 |
|
|
pwake++;
|
786 |
|
|
}
|
787 |
|
|
|
788 |
|
|
spin_unlock_irqrestore(&ep->lock, flags);
|
789 |
|
|
|
790 |
|
|
/* We have to call this outside the lock */
|
791 |
|
|
if (pwake)
|
792 |
|
|
ep_poll_safewake(&psw, &ep->poll_wait);
|
793 |
|
|
|
794 |
|
|
DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_insert(%p, %p, %d)\n",
|
795 |
|
|
current, ep, tfile, fd));
|
796 |
|
|
|
797 |
|
|
return 0;
|
798 |
|
|
|
799 |
|
|
error_unregister:
|
800 |
|
|
ep_unregister_pollwait(ep, epi);
|
801 |
|
|
|
802 |
|
|
/*
|
803 |
|
|
* We need to do this because an event could have been arrived on some
|
804 |
|
|
* allocated wait queue. Note that we don't care about the ep->ovflist
|
805 |
|
|
* list, since that is used/cleaned only inside a section bound by "mtx".
|
806 |
|
|
* And ep_insert() is called with "mtx" held.
|
807 |
|
|
*/
|
808 |
|
|
spin_lock_irqsave(&ep->lock, flags);
|
809 |
|
|
if (ep_is_linked(&epi->rdllink))
|
810 |
|
|
list_del_init(&epi->rdllink);
|
811 |
|
|
spin_unlock_irqrestore(&ep->lock, flags);
|
812 |
|
|
|
813 |
|
|
kmem_cache_free(epi_cache, epi);
|
814 |
|
|
error_return:
|
815 |
|
|
return error;
|
816 |
|
|
}
|
817 |
|
|
|
818 |
|
|
/*
|
819 |
|
|
* Modify the interest event mask by dropping an event if the new mask
|
820 |
|
|
* has a match in the current file status. Must be called with "mtx" held.
|
821 |
|
|
*/
|
822 |
|
|
static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_event *event)
|
823 |
|
|
{
|
824 |
|
|
int pwake = 0;
|
825 |
|
|
unsigned int revents;
|
826 |
|
|
unsigned long flags;
|
827 |
|
|
|
828 |
|
|
/*
|
829 |
|
|
* Set the new event interest mask before calling f_op->poll(), otherwise
|
830 |
|
|
* a potential race might occur. In fact if we do this operation inside
|
831 |
|
|
* the lock, an event might happen between the f_op->poll() call and the
|
832 |
|
|
* new event set registering.
|
833 |
|
|
*/
|
834 |
|
|
epi->event.events = event->events;
|
835 |
|
|
|
836 |
|
|
/*
|
837 |
|
|
* Get current event bits. We can safely use the file* here because
|
838 |
|
|
* its usage count has been increased by the caller of this function.
|
839 |
|
|
*/
|
840 |
|
|
revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL);
|
841 |
|
|
|
842 |
|
|
spin_lock_irqsave(&ep->lock, flags);
|
843 |
|
|
|
844 |
|
|
/* Copy the data member from inside the lock */
|
845 |
|
|
epi->event.data = event->data;
|
846 |
|
|
|
847 |
|
|
/*
|
848 |
|
|
* If the item is "hot" and it is not registered inside the ready
|
849 |
|
|
* list, push it inside.
|
850 |
|
|
*/
|
851 |
|
|
if (revents & event->events) {
|
852 |
|
|
if (!ep_is_linked(&epi->rdllink)) {
|
853 |
|
|
list_add_tail(&epi->rdllink, &ep->rdllist);
|
854 |
|
|
|
855 |
|
|
/* Notify waiting tasks that events are available */
|
856 |
|
|
if (waitqueue_active(&ep->wq))
|
857 |
|
|
__wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE |
|
858 |
|
|
TASK_INTERRUPTIBLE);
|
859 |
|
|
if (waitqueue_active(&ep->poll_wait))
|
860 |
|
|
pwake++;
|
861 |
|
|
}
|
862 |
|
|
}
|
863 |
|
|
spin_unlock_irqrestore(&ep->lock, flags);
|
864 |
|
|
|
865 |
|
|
/* We have to call this outside the lock */
|
866 |
|
|
if (pwake)
|
867 |
|
|
ep_poll_safewake(&psw, &ep->poll_wait);
|
868 |
|
|
|
869 |
|
|
return 0;
|
870 |
|
|
}
|
871 |
|
|
|
872 |
|
|
static int ep_send_events(struct eventpoll *ep, struct epoll_event __user *events,
|
873 |
|
|
int maxevents)
|
874 |
|
|
{
|
875 |
|
|
int eventcnt, error = -EFAULT, pwake = 0;
|
876 |
|
|
unsigned int revents;
|
877 |
|
|
unsigned long flags;
|
878 |
|
|
struct epitem *epi, *nepi;
|
879 |
|
|
struct list_head txlist;
|
880 |
|
|
|
881 |
|
|
INIT_LIST_HEAD(&txlist);
|
882 |
|
|
|
883 |
|
|
/*
|
884 |
|
|
* We need to lock this because we could be hit by
|
885 |
|
|
* eventpoll_release_file() and epoll_ctl(EPOLL_CTL_DEL).
|
886 |
|
|
*/
|
887 |
|
|
mutex_lock(&ep->mtx);
|
888 |
|
|
|
889 |
|
|
/*
|
890 |
|
|
* Steal the ready list, and re-init the original one to the
|
891 |
|
|
* empty list. Also, set ep->ovflist to NULL so that events
|
892 |
|
|
* happening while looping w/out locks, are not lost. We cannot
|
893 |
|
|
* have the poll callback to queue directly on ep->rdllist,
|
894 |
|
|
* because we are doing it in the loop below, in a lockless way.
|
895 |
|
|
*/
|
896 |
|
|
spin_lock_irqsave(&ep->lock, flags);
|
897 |
|
|
list_splice(&ep->rdllist, &txlist);
|
898 |
|
|
INIT_LIST_HEAD(&ep->rdllist);
|
899 |
|
|
ep->ovflist = NULL;
|
900 |
|
|
spin_unlock_irqrestore(&ep->lock, flags);
|
901 |
|
|
|
902 |
|
|
/*
|
903 |
|
|
* We can loop without lock because this is a task private list.
|
904 |
|
|
* We just splice'd out the ep->rdllist in ep_collect_ready_items().
|
905 |
|
|
* Items cannot vanish during the loop because we are holding "mtx".
|
906 |
|
|
*/
|
907 |
|
|
for (eventcnt = 0; !list_empty(&txlist) && eventcnt < maxevents;) {
|
908 |
|
|
epi = list_first_entry(&txlist, struct epitem, rdllink);
|
909 |
|
|
|
910 |
|
|
list_del_init(&epi->rdllink);
|
911 |
|
|
|
912 |
|
|
/*
|
913 |
|
|
* Get the ready file event set. We can safely use the file
|
914 |
|
|
* because we are holding the "mtx" and this will guarantee
|
915 |
|
|
* that both the file and the item will not vanish.
|
916 |
|
|
*/
|
917 |
|
|
revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL);
|
918 |
|
|
revents &= epi->event.events;
|
919 |
|
|
|
920 |
|
|
/*
|
921 |
|
|
* Is the event mask intersect the caller-requested one,
|
922 |
|
|
* deliver the event to userspace. Again, we are holding
|
923 |
|
|
* "mtx", so no operations coming from userspace can change
|
924 |
|
|
* the item.
|
925 |
|
|
*/
|
926 |
|
|
if (revents) {
|
927 |
|
|
if (__put_user(revents,
|
928 |
|
|
&events[eventcnt].events) ||
|
929 |
|
|
__put_user(epi->event.data,
|
930 |
|
|
&events[eventcnt].data))
|
931 |
|
|
goto errxit;
|
932 |
|
|
if (epi->event.events & EPOLLONESHOT)
|
933 |
|
|
epi->event.events &= EP_PRIVATE_BITS;
|
934 |
|
|
eventcnt++;
|
935 |
|
|
}
|
936 |
|
|
/*
|
937 |
|
|
* At this point, noone can insert into ep->rdllist besides
|
938 |
|
|
* us. The epoll_ctl() callers are locked out by us holding
|
939 |
|
|
* "mtx" and the poll callback will queue them in ep->ovflist.
|
940 |
|
|
*/
|
941 |
|
|
if (!(epi->event.events & EPOLLET) &&
|
942 |
|
|
(revents & epi->event.events))
|
943 |
|
|
list_add_tail(&epi->rdllink, &ep->rdllist);
|
944 |
|
|
}
|
945 |
|
|
error = 0;
|
946 |
|
|
|
947 |
|
|
errxit:
|
948 |
|
|
|
949 |
|
|
spin_lock_irqsave(&ep->lock, flags);
|
950 |
|
|
/*
|
951 |
|
|
* During the time we spent in the loop above, some other events
|
952 |
|
|
* might have been queued by the poll callback. We re-insert them
|
953 |
|
|
* here (in case they are not already queued, or they're one-shot).
|
954 |
|
|
*/
|
955 |
|
|
for (nepi = ep->ovflist; (epi = nepi) != NULL;
|
956 |
|
|
nepi = epi->next, epi->next = EP_UNACTIVE_PTR) {
|
957 |
|
|
if (!ep_is_linked(&epi->rdllink) &&
|
958 |
|
|
(epi->event.events & ~EP_PRIVATE_BITS))
|
959 |
|
|
list_add_tail(&epi->rdllink, &ep->rdllist);
|
960 |
|
|
}
|
961 |
|
|
/*
|
962 |
|
|
* We need to set back ep->ovflist to EP_UNACTIVE_PTR, so that after
|
963 |
|
|
* releasing the lock, events will be queued in the normal way inside
|
964 |
|
|
* ep->rdllist.
|
965 |
|
|
*/
|
966 |
|
|
ep->ovflist = EP_UNACTIVE_PTR;
|
967 |
|
|
|
968 |
|
|
/*
|
969 |
|
|
* In case of error in the event-send loop, or in case the number of
|
970 |
|
|
* ready events exceeds the userspace limit, we need to splice the
|
971 |
|
|
* "txlist" back inside ep->rdllist.
|
972 |
|
|
*/
|
973 |
|
|
list_splice(&txlist, &ep->rdllist);
|
974 |
|
|
|
975 |
|
|
if (!list_empty(&ep->rdllist)) {
|
976 |
|
|
/*
|
977 |
|
|
* Wake up (if active) both the eventpoll wait list and the ->poll()
|
978 |
|
|
* wait list (delayed after we release the lock).
|
979 |
|
|
*/
|
980 |
|
|
if (waitqueue_active(&ep->wq))
|
981 |
|
|
__wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE |
|
982 |
|
|
TASK_INTERRUPTIBLE);
|
983 |
|
|
if (waitqueue_active(&ep->poll_wait))
|
984 |
|
|
pwake++;
|
985 |
|
|
}
|
986 |
|
|
spin_unlock_irqrestore(&ep->lock, flags);
|
987 |
|
|
|
988 |
|
|
mutex_unlock(&ep->mtx);
|
989 |
|
|
|
990 |
|
|
/* We have to call this outside the lock */
|
991 |
|
|
if (pwake)
|
992 |
|
|
ep_poll_safewake(&psw, &ep->poll_wait);
|
993 |
|
|
|
994 |
|
|
return eventcnt == 0 ? error: eventcnt;
|
995 |
|
|
}
|
996 |
|
|
|
997 |
|
|
static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
|
998 |
|
|
int maxevents, long timeout)
|
999 |
|
|
{
|
1000 |
|
|
int res, eavail;
|
1001 |
|
|
unsigned long flags;
|
1002 |
|
|
long jtimeout;
|
1003 |
|
|
wait_queue_t wait;
|
1004 |
|
|
|
1005 |
|
|
/*
|
1006 |
|
|
* Calculate the timeout by checking for the "infinite" value ( -1 )
|
1007 |
|
|
* and the overflow condition. The passed timeout is in milliseconds,
|
1008 |
|
|
* that why (t * HZ) / 1000.
|
1009 |
|
|
*/
|
1010 |
|
|
jtimeout = (timeout < 0 || timeout >= EP_MAX_MSTIMEO) ?
|
1011 |
|
|
MAX_SCHEDULE_TIMEOUT : (timeout * HZ + 999) / 1000;
|
1012 |
|
|
|
1013 |
|
|
retry:
|
1014 |
|
|
spin_lock_irqsave(&ep->lock, flags);
|
1015 |
|
|
|
1016 |
|
|
res = 0;
|
1017 |
|
|
if (list_empty(&ep->rdllist)) {
|
1018 |
|
|
/*
|
1019 |
|
|
* We don't have any available event to return to the caller.
|
1020 |
|
|
* We need to sleep here, and we will be wake up by
|
1021 |
|
|
* ep_poll_callback() when events will become available.
|
1022 |
|
|
*/
|
1023 |
|
|
init_waitqueue_entry(&wait, current);
|
1024 |
|
|
wait.flags |= WQ_FLAG_EXCLUSIVE;
|
1025 |
|
|
__add_wait_queue(&ep->wq, &wait);
|
1026 |
|
|
|
1027 |
|
|
for (;;) {
|
1028 |
|
|
/*
|
1029 |
|
|
* We don't want to sleep if the ep_poll_callback() sends us
|
1030 |
|
|
* a wakeup in between. That's why we set the task state
|
1031 |
|
|
* to TASK_INTERRUPTIBLE before doing the checks.
|
1032 |
|
|
*/
|
1033 |
|
|
set_current_state(TASK_INTERRUPTIBLE);
|
1034 |
|
|
if (!list_empty(&ep->rdllist) || !jtimeout)
|
1035 |
|
|
break;
|
1036 |
|
|
if (signal_pending(current)) {
|
1037 |
|
|
res = -EINTR;
|
1038 |
|
|
break;
|
1039 |
|
|
}
|
1040 |
|
|
|
1041 |
|
|
spin_unlock_irqrestore(&ep->lock, flags);
|
1042 |
|
|
jtimeout = schedule_timeout(jtimeout);
|
1043 |
|
|
spin_lock_irqsave(&ep->lock, flags);
|
1044 |
|
|
}
|
1045 |
|
|
__remove_wait_queue(&ep->wq, &wait);
|
1046 |
|
|
|
1047 |
|
|
set_current_state(TASK_RUNNING);
|
1048 |
|
|
}
|
1049 |
|
|
|
1050 |
|
|
/* Is it worth to try to dig for events ? */
|
1051 |
|
|
eavail = !list_empty(&ep->rdllist);
|
1052 |
|
|
|
1053 |
|
|
spin_unlock_irqrestore(&ep->lock, flags);
|
1054 |
|
|
|
1055 |
|
|
/*
|
1056 |
|
|
* Try to transfer events to user space. In case we get 0 events and
|
1057 |
|
|
* there's still timeout left over, we go trying again in search of
|
1058 |
|
|
* more luck.
|
1059 |
|
|
*/
|
1060 |
|
|
if (!res && eavail &&
|
1061 |
|
|
!(res = ep_send_events(ep, events, maxevents)) && jtimeout)
|
1062 |
|
|
goto retry;
|
1063 |
|
|
|
1064 |
|
|
return res;
|
1065 |
|
|
}
|
1066 |
|
|
|
1067 |
|
|
/*
|
1068 |
|
|
* It opens an eventpoll file descriptor. The "size" parameter is there
|
1069 |
|
|
* for historical reasons, when epoll was using an hash instead of an
|
1070 |
|
|
* RB tree. With the current implementation, the "size" parameter is ignored
|
1071 |
|
|
* (besides sanity checks).
|
1072 |
|
|
*/
|
1073 |
|
|
asmlinkage long sys_epoll_create(int size)
|
1074 |
|
|
{
|
1075 |
|
|
int error, fd = -1;
|
1076 |
|
|
struct eventpoll *ep;
|
1077 |
|
|
struct inode *inode;
|
1078 |
|
|
struct file *file;
|
1079 |
|
|
|
1080 |
|
|
DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d)\n",
|
1081 |
|
|
current, size));
|
1082 |
|
|
|
1083 |
|
|
/*
|
1084 |
|
|
* Sanity check on the size parameter, and create the internal data
|
1085 |
|
|
* structure ( "struct eventpoll" ).
|
1086 |
|
|
*/
|
1087 |
|
|
error = -EINVAL;
|
1088 |
|
|
if (size <= 0 || (error = ep_alloc(&ep)) != 0)
|
1089 |
|
|
goto error_return;
|
1090 |
|
|
|
1091 |
|
|
/*
|
1092 |
|
|
* Creates all the items needed to setup an eventpoll file. That is,
|
1093 |
|
|
* a file structure, and inode and a free file descriptor.
|
1094 |
|
|
*/
|
1095 |
|
|
error = anon_inode_getfd(&fd, &inode, &file, "[eventpoll]",
|
1096 |
|
|
&eventpoll_fops, ep);
|
1097 |
|
|
if (error)
|
1098 |
|
|
goto error_free;
|
1099 |
|
|
|
1100 |
|
|
DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n",
|
1101 |
|
|
current, size, fd));
|
1102 |
|
|
|
1103 |
|
|
return fd;
|
1104 |
|
|
|
1105 |
|
|
error_free:
|
1106 |
|
|
ep_free(ep);
|
1107 |
|
|
error_return:
|
1108 |
|
|
DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n",
|
1109 |
|
|
current, size, error));
|
1110 |
|
|
return error;
|
1111 |
|
|
}
|
1112 |
|
|
|
1113 |
|
|
/*
|
1114 |
|
|
* The following function implements the controller interface for
|
1115 |
|
|
* the eventpoll file that enables the insertion/removal/change of
|
1116 |
|
|
* file descriptors inside the interest set.
|
1117 |
|
|
*/
|
1118 |
|
|
asmlinkage long sys_epoll_ctl(int epfd, int op, int fd,
|
1119 |
|
|
struct epoll_event __user *event)
|
1120 |
|
|
{
|
1121 |
|
|
int error;
|
1122 |
|
|
struct file *file, *tfile;
|
1123 |
|
|
struct eventpoll *ep;
|
1124 |
|
|
struct epitem *epi;
|
1125 |
|
|
struct epoll_event epds;
|
1126 |
|
|
|
1127 |
|
|
DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %p)\n",
|
1128 |
|
|
current, epfd, op, fd, event));
|
1129 |
|
|
|
1130 |
|
|
error = -EFAULT;
|
1131 |
|
|
if (ep_op_has_event(op) &&
|
1132 |
|
|
copy_from_user(&epds, event, sizeof(struct epoll_event)))
|
1133 |
|
|
goto error_return;
|
1134 |
|
|
|
1135 |
|
|
/* Get the "struct file *" for the eventpoll file */
|
1136 |
|
|
error = -EBADF;
|
1137 |
|
|
file = fget(epfd);
|
1138 |
|
|
if (!file)
|
1139 |
|
|
goto error_return;
|
1140 |
|
|
|
1141 |
|
|
/* Get the "struct file *" for the target file */
|
1142 |
|
|
tfile = fget(fd);
|
1143 |
|
|
if (!tfile)
|
1144 |
|
|
goto error_fput;
|
1145 |
|
|
|
1146 |
|
|
/* The target file descriptor must support poll */
|
1147 |
|
|
error = -EPERM;
|
1148 |
|
|
if (!tfile->f_op || !tfile->f_op->poll)
|
1149 |
|
|
goto error_tgt_fput;
|
1150 |
|
|
|
1151 |
|
|
/*
|
1152 |
|
|
* We have to check that the file structure underneath the file descriptor
|
1153 |
|
|
* the user passed to us _is_ an eventpoll file. And also we do not permit
|
1154 |
|
|
* adding an epoll file descriptor inside itself.
|
1155 |
|
|
*/
|
1156 |
|
|
error = -EINVAL;
|
1157 |
|
|
if (file == tfile || !is_file_epoll(file))
|
1158 |
|
|
goto error_tgt_fput;
|
1159 |
|
|
|
1160 |
|
|
/*
|
1161 |
|
|
* At this point it is safe to assume that the "private_data" contains
|
1162 |
|
|
* our own data structure.
|
1163 |
|
|
*/
|
1164 |
|
|
ep = file->private_data;
|
1165 |
|
|
|
1166 |
|
|
mutex_lock(&ep->mtx);
|
1167 |
|
|
|
1168 |
|
|
/*
|
1169 |
|
|
* Try to lookup the file inside our RB tree, Since we grabbed "mtx"
|
1170 |
|
|
* above, we can be sure to be able to use the item looked up by
|
1171 |
|
|
* ep_find() till we release the mutex.
|
1172 |
|
|
*/
|
1173 |
|
|
epi = ep_find(ep, tfile, fd);
|
1174 |
|
|
|
1175 |
|
|
error = -EINVAL;
|
1176 |
|
|
switch (op) {
|
1177 |
|
|
case EPOLL_CTL_ADD:
|
1178 |
|
|
if (!epi) {
|
1179 |
|
|
epds.events |= POLLERR | POLLHUP;
|
1180 |
|
|
|
1181 |
|
|
error = ep_insert(ep, &epds, tfile, fd);
|
1182 |
|
|
} else
|
1183 |
|
|
error = -EEXIST;
|
1184 |
|
|
break;
|
1185 |
|
|
case EPOLL_CTL_DEL:
|
1186 |
|
|
if (epi)
|
1187 |
|
|
error = ep_remove(ep, epi);
|
1188 |
|
|
else
|
1189 |
|
|
error = -ENOENT;
|
1190 |
|
|
break;
|
1191 |
|
|
case EPOLL_CTL_MOD:
|
1192 |
|
|
if (epi) {
|
1193 |
|
|
epds.events |= POLLERR | POLLHUP;
|
1194 |
|
|
error = ep_modify(ep, epi, &epds);
|
1195 |
|
|
} else
|
1196 |
|
|
error = -ENOENT;
|
1197 |
|
|
break;
|
1198 |
|
|
}
|
1199 |
|
|
mutex_unlock(&ep->mtx);
|
1200 |
|
|
|
1201 |
|
|
error_tgt_fput:
|
1202 |
|
|
fput(tfile);
|
1203 |
|
|
error_fput:
|
1204 |
|
|
fput(file);
|
1205 |
|
|
error_return:
|
1206 |
|
|
DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %p) = %d\n",
|
1207 |
|
|
current, epfd, op, fd, event, error));
|
1208 |
|
|
|
1209 |
|
|
return error;
|
1210 |
|
|
}
|
1211 |
|
|
|
1212 |
|
|
/*
|
1213 |
|
|
* Implement the event wait interface for the eventpoll file. It is the kernel
|
1214 |
|
|
* part of the user space epoll_wait(2).
|
1215 |
|
|
*/
|
1216 |
|
|
asmlinkage long sys_epoll_wait(int epfd, struct epoll_event __user *events,
|
1217 |
|
|
int maxevents, int timeout)
|
1218 |
|
|
{
|
1219 |
|
|
int error;
|
1220 |
|
|
struct file *file;
|
1221 |
|
|
struct eventpoll *ep;
|
1222 |
|
|
|
1223 |
|
|
DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_wait(%d, %p, %d, %d)\n",
|
1224 |
|
|
current, epfd, events, maxevents, timeout));
|
1225 |
|
|
|
1226 |
|
|
/* The maximum number of event must be greater than zero */
|
1227 |
|
|
if (maxevents <= 0 || maxevents > EP_MAX_EVENTS)
|
1228 |
|
|
return -EINVAL;
|
1229 |
|
|
|
1230 |
|
|
/* Verify that the area passed by the user is writeable */
|
1231 |
|
|
if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event))) {
|
1232 |
|
|
error = -EFAULT;
|
1233 |
|
|
goto error_return;
|
1234 |
|
|
}
|
1235 |
|
|
|
1236 |
|
|
/* Get the "struct file *" for the eventpoll file */
|
1237 |
|
|
error = -EBADF;
|
1238 |
|
|
file = fget(epfd);
|
1239 |
|
|
if (!file)
|
1240 |
|
|
goto error_return;
|
1241 |
|
|
|
1242 |
|
|
/*
|
1243 |
|
|
* We have to check that the file structure underneath the fd
|
1244 |
|
|
* the user passed to us _is_ an eventpoll file.
|
1245 |
|
|
*/
|
1246 |
|
|
error = -EINVAL;
|
1247 |
|
|
if (!is_file_epoll(file))
|
1248 |
|
|
goto error_fput;
|
1249 |
|
|
|
1250 |
|
|
/*
|
1251 |
|
|
* At this point it is safe to assume that the "private_data" contains
|
1252 |
|
|
* our own data structure.
|
1253 |
|
|
*/
|
1254 |
|
|
ep = file->private_data;
|
1255 |
|
|
|
1256 |
|
|
/* Time to fish for events ... */
|
1257 |
|
|
error = ep_poll(ep, events, maxevents, timeout);
|
1258 |
|
|
|
1259 |
|
|
error_fput:
|
1260 |
|
|
fput(file);
|
1261 |
|
|
error_return:
|
1262 |
|
|
DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_wait(%d, %p, %d, %d) = %d\n",
|
1263 |
|
|
current, epfd, events, maxevents, timeout, error));
|
1264 |
|
|
|
1265 |
|
|
return error;
|
1266 |
|
|
}
|
1267 |
|
|
|
1268 |
|
|
#ifdef TIF_RESTORE_SIGMASK
|
1269 |
|
|
|
1270 |
|
|
/*
|
1271 |
|
|
* Implement the event wait interface for the eventpoll file. It is the kernel
|
1272 |
|
|
* part of the user space epoll_pwait(2).
|
1273 |
|
|
*/
|
1274 |
|
|
asmlinkage long sys_epoll_pwait(int epfd, struct epoll_event __user *events,
|
1275 |
|
|
int maxevents, int timeout, const sigset_t __user *sigmask,
|
1276 |
|
|
size_t sigsetsize)
|
1277 |
|
|
{
|
1278 |
|
|
int error;
|
1279 |
|
|
sigset_t ksigmask, sigsaved;
|
1280 |
|
|
|
1281 |
|
|
/*
|
1282 |
|
|
* If the caller wants a certain signal mask to be set during the wait,
|
1283 |
|
|
* we apply it here.
|
1284 |
|
|
*/
|
1285 |
|
|
if (sigmask) {
|
1286 |
|
|
if (sigsetsize != sizeof(sigset_t))
|
1287 |
|
|
return -EINVAL;
|
1288 |
|
|
if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
|
1289 |
|
|
return -EFAULT;
|
1290 |
|
|
sigdelsetmask(&ksigmask, sigmask(SIGKILL) | sigmask(SIGSTOP));
|
1291 |
|
|
sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
|
1292 |
|
|
}
|
1293 |
|
|
|
1294 |
|
|
error = sys_epoll_wait(epfd, events, maxevents, timeout);
|
1295 |
|
|
|
1296 |
|
|
/*
|
1297 |
|
|
* If we changed the signal mask, we need to restore the original one.
|
1298 |
|
|
* In case we've got a signal while waiting, we do not restore the
|
1299 |
|
|
* signal mask yet, and we allow do_signal() to deliver the signal on
|
1300 |
|
|
* the way back to userspace, before the signal mask is restored.
|
1301 |
|
|
*/
|
1302 |
|
|
if (sigmask) {
|
1303 |
|
|
if (error == -EINTR) {
|
1304 |
|
|
memcpy(¤t->saved_sigmask, &sigsaved,
|
1305 |
|
|
sizeof(sigsaved));
|
1306 |
|
|
set_thread_flag(TIF_RESTORE_SIGMASK);
|
1307 |
|
|
} else
|
1308 |
|
|
sigprocmask(SIG_SETMASK, &sigsaved, NULL);
|
1309 |
|
|
}
|
1310 |
|
|
|
1311 |
|
|
return error;
|
1312 |
|
|
}
|
1313 |
|
|
|
1314 |
|
|
#endif /* #ifdef TIF_RESTORE_SIGMASK */
|
1315 |
|
|
|
1316 |
|
|
static int __init eventpoll_init(void)
|
1317 |
|
|
{
|
1318 |
|
|
mutex_init(&epmutex);
|
1319 |
|
|
|
1320 |
|
|
/* Initialize the structure used to perform safe poll wait head wake ups */
|
1321 |
|
|
ep_poll_safewake_init(&psw);
|
1322 |
|
|
|
1323 |
|
|
/* Allocates slab cache used to allocate "struct epitem" items */
|
1324 |
|
|
epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem),
|
1325 |
|
|
0, SLAB_HWCACHE_ALIGN|EPI_SLAB_DEBUG|SLAB_PANIC,
|
1326 |
|
|
NULL);
|
1327 |
|
|
|
1328 |
|
|
/* Allocates slab cache used to allocate "struct eppoll_entry" */
|
1329 |
|
|
pwq_cache = kmem_cache_create("eventpoll_pwq",
|
1330 |
|
|
sizeof(struct eppoll_entry), 0,
|
1331 |
|
|
EPI_SLAB_DEBUG|SLAB_PANIC, NULL);
|
1332 |
|
|
|
1333 |
|
|
return 0;
|
1334 |
|
|
}
|
1335 |
|
|
fs_initcall(eventpoll_init);
|
1336 |
|
|
|