mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-27 11:19:37 +00:00
![Joe Perches](/assets/img/avatar_default.png)
This typedef is unnecessary and should just be removed. Signed-off-by: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2135 lines
59 KiB
C
2135 lines
59 KiB
C
/*
|
|
* fs/eventpoll.c (Efficient event retrieval implementation)
|
|
* Copyright (C) 2001,...,2009 Davide Libenzi
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License as published by
|
|
* the Free Software Foundation; either version 2 of the License, or
|
|
* (at your option) any later version.
|
|
*
|
|
* Davide Libenzi <davidel@xmailserver.org>
|
|
*
|
|
*/
|
|
|
|
#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>
|
|
#include <linux/string.h>
|
|
#include <linux/list.h>
|
|
#include <linux/hash.h>
|
|
#include <linux/spinlock.h>
|
|
#include <linux/syscalls.h>
|
|
#include <linux/rbtree.h>
|
|
#include <linux/wait.h>
|
|
#include <linux/eventpoll.h>
|
|
#include <linux/mount.h>
|
|
#include <linux/bitops.h>
|
|
#include <linux/mutex.h>
|
|
#include <linux/anon_inodes.h>
|
|
#include <linux/device.h>
|
|
#include <asm/uaccess.h>
|
|
#include <asm/io.h>
|
|
#include <asm/mman.h>
|
|
#include <linux/atomic.h>
|
|
#include <linux/proc_fs.h>
|
|
#include <linux/seq_file.h>
|
|
#include <linux/compat.h>
|
|
#include <linux/rculist.h>
|
|
|
|
/*
|
|
* LOCKING:
|
|
* There are three level of locking required by epoll :
|
|
*
|
|
* 1) epmutex (mutex)
|
|
* 2) ep->mtx (mutex)
|
|
* 3) ep->lock (spinlock)
|
|
*
|
|
* The acquire order is the one listed above, from 1 to 3.
|
|
* We need a spinlock (ep->lock) because we manipulate objects
|
|
* 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
|
|
* mutex (ep->mtx). It is acquired during the event transfer loop,
|
|
* during epoll_ctl(EPOLL_CTL_DEL) and during eventpoll_release_file().
|
|
* Then we also need a global mutex to serialize eventpoll_release_file()
|
|
* and ep_free().
|
|
* This mutex is acquired by ep_free() during the epoll file
|
|
* cleanup path and it is also acquired by eventpoll_release_file()
|
|
* if a file has been pushed inside an epoll set and it is then
|
|
* close()d without a previous call to epoll_ctl(EPOLL_CTL_DEL).
|
|
* It is also acquired when inserting an epoll fd onto another epoll
|
|
* fd. We do this so that we walk the epoll tree and ensure that this
|
|
* insertion does not create a cycle of epoll file descriptors, which
|
|
* could lead to deadlock. We need a global mutex to prevent two
|
|
* simultaneous inserts (A into B and B into A) from racing and
|
|
* constructing a cycle without either insert observing that it is
|
|
* going to.
|
|
* It is necessary to acquire multiple "ep->mtx"es at once in the
|
|
* case when one epoll fd is added to another. In this case, we
|
|
* always acquire the locks in the order of nesting (i.e. after
|
|
* epoll_ctl(e1, EPOLL_CTL_ADD, e2), e1->mtx will always be acquired
|
|
* before e2->mtx). Since we disallow cycles of epoll file
|
|
* descriptors, this ensures that the mutexes are well-ordered. In
|
|
* order to communicate this nesting to lockdep, when walking a tree
|
|
* of epoll file descriptors, we use the current recursion depth as
|
|
* the lockdep subkey.
|
|
* It is possible to drop the "ep->mtx" and to use the global
|
|
* mutex "epmutex" (together with "ep->lock") to have it working,
|
|
* but having "ep->mtx" will make the interface more scalable.
|
|
* Events that require holding "epmutex" are very rare, while for
|
|
* normal operations the epoll private "ep->mtx" will guarantee
|
|
* a better scalability.
|
|
*/
|
|
|
|
/* Epoll private bits inside the event mask */
|
|
#define EP_PRIVATE_BITS (EPOLLWAKEUP | EPOLLONESHOT | EPOLLET)
|
|
|
|
/* Maximum number of nesting allowed inside epoll sets */
|
|
#define EP_MAX_NESTS 4
|
|
|
|
#define EP_MAX_EVENTS (INT_MAX / sizeof(struct epoll_event))
|
|
|
|
#define EP_UNACTIVE_PTR ((void *) -1L)
|
|
|
|
#define EP_ITEM_COST (sizeof(struct epitem) + sizeof(struct eppoll_entry))
|
|
|
|
struct epoll_filefd {
|
|
struct file *file;
|
|
int fd;
|
|
} __packed;
|
|
|
|
/*
|
|
* Structure used to track possible nested calls, for too deep recursions
|
|
* and loop cycles.
|
|
*/
|
|
struct nested_call_node {
|
|
struct list_head llink;
|
|
void *cookie;
|
|
void *ctx;
|
|
};
|
|
|
|
/*
|
|
* This structure is used as collector for nested calls, to check for
|
|
* maximum recursion dept and loop cycles.
|
|
*/
|
|
struct nested_calls {
|
|
struct list_head tasks_call_list;
|
|
spinlock_t lock;
|
|
};
|
|
|
|
/*
|
|
* Each file descriptor added to the eventpoll interface will
|
|
* have an entry of this type linked to the "rbr" RB tree.
|
|
* Avoid increasing the size of this struct, there can be many thousands
|
|
* of these on a server and we do not want this to take another cache line.
|
|
*/
|
|
struct epitem {
|
|
union {
|
|
/* RB tree node links this structure to the eventpoll RB tree */
|
|
struct rb_node rbn;
|
|
/* Used to free the struct epitem */
|
|
struct rcu_head rcu;
|
|
};
|
|
|
|
/* List header used to link this structure to the eventpoll ready list */
|
|
struct list_head rdllink;
|
|
|
|
/*
|
|
* Works together "struct eventpoll"->ovflist in keeping the
|
|
* single linked chain of items.
|
|
*/
|
|
struct epitem *next;
|
|
|
|
/* The file descriptor information this item refers to */
|
|
struct epoll_filefd ffd;
|
|
|
|
/* Number of active wait queue attached to poll operations */
|
|
int nwait;
|
|
|
|
/* List containing poll wait queues */
|
|
struct list_head pwqlist;
|
|
|
|
/* The "container" of this item */
|
|
struct eventpoll *ep;
|
|
|
|
/* List header used to link this item to the "struct file" items list */
|
|
struct list_head fllink;
|
|
|
|
/* wakeup_source used when EPOLLWAKEUP is set */
|
|
struct wakeup_source __rcu *ws;
|
|
|
|
/* The structure that describe the interested events and the source fd */
|
|
struct epoll_event event;
|
|
};
|
|
|
|
/*
|
|
* This structure is stored inside the "private_data" member of the file
|
|
* structure and represents the main data structure for the eventpoll
|
|
* interface.
|
|
*/
|
|
struct eventpoll {
|
|
/* Protect the access to this structure */
|
|
spinlock_t lock;
|
|
|
|
/*
|
|
* This mutex is used to ensure that files are not removed
|
|
* while epoll is using them. This is held during the event
|
|
* collection loop, the file cleanup path, the epoll file exit
|
|
* code and the ctl operations.
|
|
*/
|
|
struct mutex mtx;
|
|
|
|
/* 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;
|
|
|
|
/* RB tree root used to store monitored fd structs */
|
|
struct rb_root rbr;
|
|
|
|
/*
|
|
* This is a single linked list that chains all the "struct epitem" that
|
|
* happened while transferring ready events to userspace w/out
|
|
* holding ->lock.
|
|
*/
|
|
struct epitem *ovflist;
|
|
|
|
/* wakeup_source used when ep_scan_ready_list is running */
|
|
struct wakeup_source *ws;
|
|
|
|
/* The user that created the eventpoll descriptor */
|
|
struct user_struct *user;
|
|
|
|
struct file *file;
|
|
|
|
/* used to optimize loop detection check */
|
|
int visited;
|
|
struct list_head visited_list_link;
|
|
};
|
|
|
|
/* Wait structure used by the poll hooks */
|
|
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" */
|
|
struct epitem *base;
|
|
|
|
/*
|
|
* 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;
|
|
};
|
|
|
|
/* Wrapper struct used by poll queueing */
|
|
struct ep_pqueue {
|
|
poll_table pt;
|
|
struct epitem *epi;
|
|
};
|
|
|
|
/* Used by the ep_send_events() function as callback private data */
|
|
struct ep_send_events_data {
|
|
int maxevents;
|
|
struct epoll_event __user *events;
|
|
};
|
|
|
|
/*
|
|
* Configuration options available inside /proc/sys/fs/epoll/
|
|
*/
|
|
/* Maximum number of epoll watched descriptors, per user */
|
|
static long max_user_watches __read_mostly;
|
|
|
|
/*
|
|
* This mutex is used to serialize ep_free() and eventpoll_release_file().
|
|
*/
|
|
static DEFINE_MUTEX(epmutex);
|
|
|
|
/* Used to check for epoll file descriptor inclusion loops */
|
|
static struct nested_calls poll_loop_ncalls;
|
|
|
|
/* Used for safe wake up implementation */
|
|
static struct nested_calls poll_safewake_ncalls;
|
|
|
|
/* Used to call file's f_op->poll() under the nested calls boundaries */
|
|
static struct nested_calls poll_readywalk_ncalls;
|
|
|
|
/* Slab cache used to allocate "struct epitem" */
|
|
static struct kmem_cache *epi_cache __read_mostly;
|
|
|
|
/* Slab cache used to allocate "struct eppoll_entry" */
|
|
static struct kmem_cache *pwq_cache __read_mostly;
|
|
|
|
/* 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);
|
|
|
|
#ifdef CONFIG_SYSCTL
|
|
|
|
#include <linux/sysctl.h>
|
|
|
|
static long zero;
|
|
static long long_max = LONG_MAX;
|
|
|
|
struct ctl_table epoll_table[] = {
|
|
{
|
|
.procname = "max_user_watches",
|
|
.data = &max_user_watches,
|
|
.maxlen = sizeof(max_user_watches),
|
|
.mode = 0644,
|
|
.proc_handler = proc_doulongvec_minmax,
|
|
.extra1 = &zero,
|
|
.extra2 = &long_max,
|
|
},
|
|
{ }
|
|
};
|
|
#endif /* CONFIG_SYSCTL */
|
|
|
|
static const struct file_operations eventpoll_fops;
|
|
|
|
static inline int is_file_epoll(struct file *f)
|
|
{
|
|
return f->f_op == &eventpoll_fops;
|
|
}
|
|
|
|
/* Setup the structure that is used as key for the RB tree */
|
|
static inline void ep_set_ffd(struct epoll_filefd *ffd,
|
|
struct file *file, int fd)
|
|
{
|
|
ffd->file = file;
|
|
ffd->fd = fd;
|
|
}
|
|
|
|
/* Compare RB tree keys */
|
|
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));
|
|
}
|
|
|
|
/* Tells us if the item is currently linked */
|
|
static inline int ep_is_linked(struct list_head *p)
|
|
{
|
|
return !list_empty(p);
|
|
}
|
|
|
|
static inline struct eppoll_entry *ep_pwq_from_wait(wait_queue_t *p)
|
|
{
|
|
return container_of(p, struct eppoll_entry, wait);
|
|
}
|
|
|
|
/* Get the "struct epitem" from a wait queue pointer */
|
|
static inline struct epitem *ep_item_from_wait(wait_queue_t *p)
|
|
{
|
|
return container_of(p, struct eppoll_entry, wait)->base;
|
|
}
|
|
|
|
/* Get the "struct epitem" from an epoll queue wrapper */
|
|
static inline struct epitem *ep_item_from_epqueue(poll_table *p)
|
|
{
|
|
return container_of(p, struct ep_pqueue, pt)->epi;
|
|
}
|
|
|
|
/* Tells if the epoll_ctl(2) operation needs an event copy from userspace */
|
|
static inline int ep_op_has_event(int op)
|
|
{
|
|
return op != EPOLL_CTL_DEL;
|
|
}
|
|
|
|
/* Initialize the poll safe wake up structure */
|
|
static void ep_nested_calls_init(struct nested_calls *ncalls)
|
|
{
|
|
INIT_LIST_HEAD(&ncalls->tasks_call_list);
|
|
spin_lock_init(&ncalls->lock);
|
|
}
|
|
|
|
/**
|
|
* ep_events_available - Checks if ready events might be available.
|
|
*
|
|
* @ep: Pointer to the eventpoll context.
|
|
*
|
|
* Returns: Returns a value different than zero if ready events are available,
|
|
* or zero otherwise.
|
|
*/
|
|
static inline int ep_events_available(struct eventpoll *ep)
|
|
{
|
|
return !list_empty(&ep->rdllist) || ep->ovflist != EP_UNACTIVE_PTR;
|
|
}
|
|
|
|
/**
|
|
* ep_call_nested - Perform a bound (possibly) nested call, by checking
|
|
* that the recursion limit is not exceeded, and that
|
|
* the same nested call (by the meaning of same cookie) is
|
|
* no re-entered.
|
|
*
|
|
* @ncalls: Pointer to the nested_calls structure to be used for this call.
|
|
* @max_nests: Maximum number of allowed nesting calls.
|
|
* @nproc: Nested call core function pointer.
|
|
* @priv: Opaque data to be passed to the @nproc callback.
|
|
* @cookie: Cookie to be used to identify this nested call.
|
|
* @ctx: This instance context.
|
|
*
|
|
* Returns: Returns the code returned by the @nproc callback, or -1 if
|
|
* the maximum recursion limit has been exceeded.
|
|
*/
|
|
static int ep_call_nested(struct nested_calls *ncalls, int max_nests,
|
|
int (*nproc)(void *, void *, int), void *priv,
|
|
void *cookie, void *ctx)
|
|
{
|
|
int error, call_nests = 0;
|
|
unsigned long flags;
|
|
struct list_head *lsthead = &ncalls->tasks_call_list;
|
|
struct nested_call_node *tncur;
|
|
struct nested_call_node tnode;
|
|
|
|
spin_lock_irqsave(&ncalls->lock, flags);
|
|
|
|
/*
|
|
* Try to see if the current task is already inside this wakeup call.
|
|
* We use a list here, since the population inside this set is always
|
|
* very much limited.
|
|
*/
|
|
list_for_each_entry(tncur, lsthead, llink) {
|
|
if (tncur->ctx == ctx &&
|
|
(tncur->cookie == cookie || ++call_nests > max_nests)) {
|
|
/*
|
|
* Ops ... loop detected or maximum nest level reached.
|
|
* We abort this wake by breaking the cycle itself.
|
|
*/
|
|
error = -1;
|
|
goto out_unlock;
|
|
}
|
|
}
|
|
|
|
/* Add the current task and cookie to the list */
|
|
tnode.ctx = ctx;
|
|
tnode.cookie = cookie;
|
|
list_add(&tnode.llink, lsthead);
|
|
|
|
spin_unlock_irqrestore(&ncalls->lock, flags);
|
|
|
|
/* Call the nested function */
|
|
error = (*nproc)(priv, cookie, call_nests);
|
|
|
|
/* Remove the current task from the list */
|
|
spin_lock_irqsave(&ncalls->lock, flags);
|
|
list_del(&tnode.llink);
|
|
out_unlock:
|
|
spin_unlock_irqrestore(&ncalls->lock, flags);
|
|
|
|
return error;
|
|
}
|
|
|
|
/*
|
|
* As described in commit 0ccf831cb lockdep: annotate epoll
|
|
* the use of wait queues used by epoll is done in a very controlled
|
|
* manner. Wake ups can nest inside each other, but are never done
|
|
* with the same locking. For example:
|
|
*
|
|
* dfd = socket(...);
|
|
* efd1 = epoll_create();
|
|
* efd2 = epoll_create();
|
|
* epoll_ctl(efd1, EPOLL_CTL_ADD, dfd, ...);
|
|
* epoll_ctl(efd2, EPOLL_CTL_ADD, efd1, ...);
|
|
*
|
|
* When a packet arrives to the device underneath "dfd", the net code will
|
|
* issue a wake_up() on its poll wake list. Epoll (efd1) has installed a
|
|
* callback wakeup entry on that queue, and the wake_up() performed by the
|
|
* "dfd" net code will end up in ep_poll_callback(). At this point epoll
|
|
* (efd1) notices that it may have some event ready, so it needs to wake up
|
|
* the waiters on its poll wait list (efd2). So it calls ep_poll_safewake()
|
|
* that ends up in another wake_up(), after having checked about the
|
|
* recursion constraints. That are, no more than EP_MAX_POLLWAKE_NESTS, to
|
|
* avoid stack blasting.
|
|
*
|
|
* When CONFIG_DEBUG_LOCK_ALLOC is enabled, make sure lockdep can handle
|
|
* this special case of epoll.
|
|
*/
|
|
#ifdef CONFIG_DEBUG_LOCK_ALLOC
|
|
static inline void ep_wake_up_nested(wait_queue_head_t *wqueue,
|
|
unsigned long events, int subclass)
|
|
{
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave_nested(&wqueue->lock, flags, subclass);
|
|
wake_up_locked_poll(wqueue, events);
|
|
spin_unlock_irqrestore(&wqueue->lock, flags);
|
|
}
|
|
#else
|
|
static inline void ep_wake_up_nested(wait_queue_head_t *wqueue,
|
|
unsigned long events, int subclass)
|
|
{
|
|
wake_up_poll(wqueue, events);
|
|
}
|
|
#endif
|
|
|
|
static int ep_poll_wakeup_proc(void *priv, void *cookie, int call_nests)
|
|
{
|
|
ep_wake_up_nested((wait_queue_head_t *) cookie, POLLIN,
|
|
1 + call_nests);
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Perform a safe wake up of the poll wait list. The problem is that
|
|
* with the new callback'd wake up system, it is possible that the
|
|
* poll callback is reentered from inside the call to wake_up() done
|
|
* on the poll wait queue head. The rule is that we cannot reenter the
|
|
* wake up code from the same task more than EP_MAX_NESTS times,
|
|
* and we cannot reenter the same wait queue head at all. This will
|
|
* enable to have a hierarchy of epoll file descriptor of no more than
|
|
* EP_MAX_NESTS deep.
|
|
*/
|
|
static void ep_poll_safewake(wait_queue_head_t *wq)
|
|
{
|
|
int this_cpu = get_cpu();
|
|
|
|
ep_call_nested(&poll_safewake_ncalls, EP_MAX_NESTS,
|
|
ep_poll_wakeup_proc, NULL, wq, (void *) (long) this_cpu);
|
|
|
|
put_cpu();
|
|
}
|
|
|
|
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();
|
|
}
|
|
|
|
/*
|
|
* This function unregisters poll callbacks from the associated file
|
|
* descriptor. Must be called with "mtx" held (or "epmutex" if called from
|
|
* ep_free).
|
|
*/
|
|
static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi)
|
|
{
|
|
struct list_head *lsthead = &epi->pwqlist;
|
|
struct eppoll_entry *pwq;
|
|
|
|
while (!list_empty(lsthead)) {
|
|
pwq = list_first_entry(lsthead, struct eppoll_entry, llink);
|
|
|
|
list_del(&pwq->llink);
|
|
ep_remove_wait_queue(pwq);
|
|
kmem_cache_free(pwq_cache, pwq);
|
|
}
|
|
}
|
|
|
|
/* 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();
|
|
}
|
|
|
|
/**
|
|
* ep_scan_ready_list - Scans the ready list in a way that makes possible for
|
|
* the scan code, to call f_op->poll(). Also allows for
|
|
* O(NumReady) performance.
|
|
*
|
|
* @ep: Pointer to the epoll private data structure.
|
|
* @sproc: Pointer to the scan callback.
|
|
* @priv: Private opaque data passed to the @sproc callback.
|
|
* @depth: The current depth of recursive f_op->poll calls.
|
|
* @ep_locked: caller already holds ep->mtx
|
|
*
|
|
* Returns: The same integer error code returned by the @sproc callback.
|
|
*/
|
|
static int ep_scan_ready_list(struct eventpoll *ep,
|
|
int (*sproc)(struct eventpoll *,
|
|
struct list_head *, void *),
|
|
void *priv, int depth, bool ep_locked)
|
|
{
|
|
int error, pwake = 0;
|
|
unsigned long flags;
|
|
struct epitem *epi, *nepi;
|
|
LIST_HEAD(txlist);
|
|
|
|
/*
|
|
* We need to lock this because we could be hit by
|
|
* eventpoll_release_file() and epoll_ctl().
|
|
*/
|
|
|
|
if (!ep_locked)
|
|
mutex_lock_nested(&ep->mtx, depth);
|
|
|
|
/*
|
|
* Steal the ready list, and re-init the original one to the
|
|
* empty list. Also, set ep->ovflist to NULL so that events
|
|
* happening while looping w/out locks, are not lost. We cannot
|
|
* have the poll callback to queue directly on ep->rdllist,
|
|
* because we want the "sproc" callback to be able to do it
|
|
* in a lockless way.
|
|
*/
|
|
spin_lock_irqsave(&ep->lock, flags);
|
|
list_splice_init(&ep->rdllist, &txlist);
|
|
ep->ovflist = NULL;
|
|
spin_unlock_irqrestore(&ep->lock, flags);
|
|
|
|
/*
|
|
* Now call the callback function.
|
|
*/
|
|
error = (*sproc)(ep, &txlist, priv);
|
|
|
|
spin_lock_irqsave(&ep->lock, flags);
|
|
/*
|
|
* During the time we spent inside the "sproc" callback, some
|
|
* other events might have been queued by the poll callback.
|
|
* We re-insert them inside the main ready-list here.
|
|
*/
|
|
for (nepi = ep->ovflist; (epi = nepi) != NULL;
|
|
nepi = epi->next, epi->next = EP_UNACTIVE_PTR) {
|
|
/*
|
|
* We need to check if the item is already in the list.
|
|
* During the "sproc" callback execution time, items are
|
|
* queued into ->ovflist but the "txlist" might already
|
|
* contain them, and the list_splice() below takes care of them.
|
|
*/
|
|
if (!ep_is_linked(&epi->rdllink)) {
|
|
list_add_tail(&epi->rdllink, &ep->rdllist);
|
|
ep_pm_stay_awake(epi);
|
|
}
|
|
}
|
|
/*
|
|
* 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);
|
|
__pm_relax(ep->ws);
|
|
|
|
if (!list_empty(&ep->rdllist)) {
|
|
/*
|
|
* Wake up (if active) both the eventpoll wait list and
|
|
* the ->poll() wait list (delayed after we release the lock).
|
|
*/
|
|
if (waitqueue_active(&ep->wq))
|
|
wake_up_locked(&ep->wq);
|
|
if (waitqueue_active(&ep->poll_wait))
|
|
pwake++;
|
|
}
|
|
spin_unlock_irqrestore(&ep->lock, flags);
|
|
|
|
if (!ep_locked)
|
|
mutex_unlock(&ep->mtx);
|
|
|
|
/* We have to call this outside the lock */
|
|
if (pwake)
|
|
ep_poll_safewake(&ep->poll_wait);
|
|
|
|
return error;
|
|
}
|
|
|
|
static void epi_rcu_free(struct rcu_head *head)
|
|
{
|
|
struct epitem *epi = container_of(head, struct epitem, rcu);
|
|
kmem_cache_free(epi_cache, epi);
|
|
}
|
|
|
|
/*
|
|
* Removes a "struct epitem" from the eventpoll RB tree and deallocates
|
|
* all the associated resources. Must be called with "mtx" held.
|
|
*/
|
|
static int ep_remove(struct eventpoll *ep, struct epitem *epi)
|
|
{
|
|
unsigned long flags;
|
|
struct file *file = epi->ffd.file;
|
|
|
|
/*
|
|
* Removes poll wait queue hooks. We _have_ to do this without holding
|
|
* the "ep->lock" otherwise a deadlock might occur. This because of the
|
|
* sequence of the lock acquisition. Here we do "ep->lock" then the wait
|
|
* queue head lock when unregistering the wait queue. The wakeup callback
|
|
* will run by holding the wait queue head lock and will call our callback
|
|
* that will try to get "ep->lock".
|
|
*/
|
|
ep_unregister_pollwait(ep, epi);
|
|
|
|
/* Remove the current item from the list of epoll hooks */
|
|
spin_lock(&file->f_lock);
|
|
list_del_rcu(&epi->fllink);
|
|
spin_unlock(&file->f_lock);
|
|
|
|
rb_erase(&epi->rbn, &ep->rbr);
|
|
|
|
spin_lock_irqsave(&ep->lock, flags);
|
|
if (ep_is_linked(&epi->rdllink))
|
|
list_del_init(&epi->rdllink);
|
|
spin_unlock_irqrestore(&ep->lock, flags);
|
|
|
|
wakeup_source_unregister(ep_wakeup_source(epi));
|
|
/*
|
|
* At this point it is safe to free the eventpoll item. Use the union
|
|
* field epi->rcu, since we are trying to minimize the size of
|
|
* 'struct epitem'. The 'rbn' field is no longer in use. Protected by
|
|
* ep->mtx. The rcu read side, reverse_path_check_proc(), does not make
|
|
* use of the rbn field.
|
|
*/
|
|
call_rcu(&epi->rcu, epi_rcu_free);
|
|
|
|
atomic_long_dec(&ep->user->epoll_watches);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void ep_free(struct eventpoll *ep)
|
|
{
|
|
struct rb_node *rbp;
|
|
struct epitem *epi;
|
|
|
|
/* We need to release all tasks waiting for these file */
|
|
if (waitqueue_active(&ep->poll_wait))
|
|
ep_poll_safewake(&ep->poll_wait);
|
|
|
|
/*
|
|
* We need to lock this because we could be hit by
|
|
* eventpoll_release_file() while we're freeing the "struct eventpoll".
|
|
* We do not need to hold "ep->mtx" here because the epoll file
|
|
* is on the way to be removed and no one has references to it
|
|
* anymore. The only hit might come from eventpoll_release_file() but
|
|
* holding "epmutex" is sufficient here.
|
|
*/
|
|
mutex_lock(&epmutex);
|
|
|
|
/*
|
|
* Walks through the whole tree by unregistering poll callbacks.
|
|
*/
|
|
for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) {
|
|
epi = rb_entry(rbp, struct epitem, rbn);
|
|
|
|
ep_unregister_pollwait(ep, epi);
|
|
cond_resched();
|
|
}
|
|
|
|
/*
|
|
* 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
|
|
* holding "epmutex" we can be sure that no file cleanup code will hit
|
|
* us during this operation. So we can avoid the lock on "ep->lock".
|
|
* We do not need to lock ep->mtx, either, we only do it to prevent
|
|
* a lockdep warning.
|
|
*/
|
|
mutex_lock(&ep->mtx);
|
|
while ((rbp = rb_first(&ep->rbr)) != NULL) {
|
|
epi = rb_entry(rbp, struct epitem, rbn);
|
|
ep_remove(ep, epi);
|
|
cond_resched();
|
|
}
|
|
mutex_unlock(&ep->mtx);
|
|
|
|
mutex_unlock(&epmutex);
|
|
mutex_destroy(&ep->mtx);
|
|
free_uid(ep->user);
|
|
wakeup_source_unregister(ep->ws);
|
|
kfree(ep);
|
|
}
|
|
|
|
static int ep_eventpoll_release(struct inode *inode, struct file *file)
|
|
{
|
|
struct eventpoll *ep = file->private_data;
|
|
|
|
if (ep)
|
|
ep_free(ep);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static inline unsigned int ep_item_poll(struct epitem *epi, poll_table *pt)
|
|
{
|
|
pt->_key = epi->event.events;
|
|
|
|
return epi->ffd.file->f_op->poll(epi->ffd.file, pt) & epi->event.events;
|
|
}
|
|
|
|
static int ep_read_events_proc(struct eventpoll *ep, struct list_head *head,
|
|
void *priv)
|
|
{
|
|
struct epitem *epi, *tmp;
|
|
poll_table pt;
|
|
|
|
init_poll_funcptr(&pt, NULL);
|
|
|
|
list_for_each_entry_safe(epi, tmp, head, rdllink) {
|
|
if (ep_item_poll(epi, &pt))
|
|
return POLLIN | POLLRDNORM;
|
|
else {
|
|
/*
|
|
* Item has been dropped into the ready list by the poll
|
|
* callback, but it's not actually ready, as far as
|
|
* caller requested events goes. We can remove it here.
|
|
*/
|
|
__pm_relax(ep_wakeup_source(epi));
|
|
list_del_init(&epi->rdllink);
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead,
|
|
poll_table *pt);
|
|
|
|
struct readyevents_arg {
|
|
struct eventpoll *ep;
|
|
bool locked;
|
|
};
|
|
|
|
static int ep_poll_readyevents_proc(void *priv, void *cookie, int call_nests)
|
|
{
|
|
struct readyevents_arg *arg = priv;
|
|
|
|
return ep_scan_ready_list(arg->ep, ep_read_events_proc, NULL,
|
|
call_nests + 1, arg->locked);
|
|
}
|
|
|
|
static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait)
|
|
{
|
|
int pollflags;
|
|
struct eventpoll *ep = file->private_data;
|
|
struct readyevents_arg arg;
|
|
|
|
/*
|
|
* During ep_insert() we already hold the ep->mtx for the tfile.
|
|
* Prevent re-aquisition.
|
|
*/
|
|
arg.locked = wait && (wait->_qproc == ep_ptable_queue_proc);
|
|
arg.ep = ep;
|
|
|
|
/* Insert inside our poll wait queue */
|
|
poll_wait(file, &ep->poll_wait, wait);
|
|
|
|
/*
|
|
* Proceed to find out if wanted events are really available inside
|
|
* the ready list. This need to be done under ep_call_nested()
|
|
* supervision, since the call to f_op->poll() done on listed files
|
|
* could re-enter here.
|
|
*/
|
|
pollflags = ep_call_nested(&poll_readywalk_ncalls, EP_MAX_NESTS,
|
|
ep_poll_readyevents_proc, &arg, ep, current);
|
|
|
|
return pollflags != -1 ? pollflags : 0;
|
|
}
|
|
|
|
#ifdef CONFIG_PROC_FS
|
|
static int ep_show_fdinfo(struct seq_file *m, struct file *f)
|
|
{
|
|
struct eventpoll *ep = f->private_data;
|
|
struct rb_node *rbp;
|
|
int ret = 0;
|
|
|
|
mutex_lock(&ep->mtx);
|
|
for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) {
|
|
struct epitem *epi = rb_entry(rbp, struct epitem, rbn);
|
|
|
|
ret = seq_printf(m, "tfd: %8d events: %8x data: %16llx\n",
|
|
epi->ffd.fd, epi->event.events,
|
|
(long long)epi->event.data);
|
|
if (ret)
|
|
break;
|
|
}
|
|
mutex_unlock(&ep->mtx);
|
|
|
|
return ret;
|
|
}
|
|
#endif
|
|
|
|
/* File callbacks that implement the eventpoll file behaviour */
|
|
static const struct file_operations eventpoll_fops = {
|
|
#ifdef CONFIG_PROC_FS
|
|
.show_fdinfo = ep_show_fdinfo,
|
|
#endif
|
|
.release = ep_eventpoll_release,
|
|
.poll = ep_eventpoll_poll,
|
|
.llseek = noop_llseek,
|
|
};
|
|
|
|
/*
|
|
* This is called from eventpoll_release() to unlink files from the eventpoll
|
|
* interface. We need to have this facility to cleanup correctly files that are
|
|
* closed without being removed from the eventpoll interface.
|
|
*/
|
|
void eventpoll_release_file(struct file *file)
|
|
{
|
|
struct eventpoll *ep;
|
|
struct epitem *epi;
|
|
|
|
/*
|
|
* We don't want to get "file->f_lock" because it is not
|
|
* necessary. It is not necessary because we're in the "struct file"
|
|
* cleanup path, and this means that no one is using this file anymore.
|
|
* So, for example, epoll_ctl() cannot hit here since if we reach this
|
|
* point, the file counter already went to zero and fget() would fail.
|
|
* The only hit might come from ep_free() but by holding the mutex
|
|
* will correctly serialize the operation. We do need to acquire
|
|
* "ep->mtx" after "epmutex" because ep_remove() requires it when called
|
|
* from anywhere but ep_free().
|
|
*
|
|
* Besides, ep_remove() acquires the lock, so we can't hold it here.
|
|
*/
|
|
mutex_lock(&epmutex);
|
|
list_for_each_entry_rcu(epi, &file->f_ep_links, fllink) {
|
|
ep = epi->ep;
|
|
mutex_lock_nested(&ep->mtx, 0);
|
|
ep_remove(ep, epi);
|
|
mutex_unlock(&ep->mtx);
|
|
}
|
|
mutex_unlock(&epmutex);
|
|
}
|
|
|
|
static int ep_alloc(struct eventpoll **pep)
|
|
{
|
|
int error;
|
|
struct user_struct *user;
|
|
struct eventpoll *ep;
|
|
|
|
user = get_current_user();
|
|
error = -ENOMEM;
|
|
ep = kzalloc(sizeof(*ep), GFP_KERNEL);
|
|
if (unlikely(!ep))
|
|
goto free_uid;
|
|
|
|
spin_lock_init(&ep->lock);
|
|
mutex_init(&ep->mtx);
|
|
init_waitqueue_head(&ep->wq);
|
|
init_waitqueue_head(&ep->poll_wait);
|
|
INIT_LIST_HEAD(&ep->rdllist);
|
|
ep->rbr = RB_ROOT;
|
|
ep->ovflist = EP_UNACTIVE_PTR;
|
|
ep->user = user;
|
|
|
|
*pep = ep;
|
|
|
|
return 0;
|
|
|
|
free_uid:
|
|
free_uid(user);
|
|
return error;
|
|
}
|
|
|
|
/*
|
|
* Search the file inside the eventpoll tree. The RB tree operations
|
|
* are protected by the "mtx" mutex, and ep_find() must be called with
|
|
* "mtx" held.
|
|
*/
|
|
static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd)
|
|
{
|
|
int kcmp;
|
|
struct rb_node *rbp;
|
|
struct epitem *epi, *epir = NULL;
|
|
struct epoll_filefd ffd;
|
|
|
|
ep_set_ffd(&ffd, file, fd);
|
|
for (rbp = ep->rbr.rb_node; rbp; ) {
|
|
epi = rb_entry(rbp, struct epitem, rbn);
|
|
kcmp = ep_cmp_ffd(&ffd, &epi->ffd);
|
|
if (kcmp > 0)
|
|
rbp = rbp->rb_right;
|
|
else if (kcmp < 0)
|
|
rbp = rbp->rb_left;
|
|
else {
|
|
epir = epi;
|
|
break;
|
|
}
|
|
}
|
|
|
|
return epir;
|
|
}
|
|
|
|
/*
|
|
* This is the callback that is passed to the wait queue wakeup
|
|
* mechanism. It is called by the stored file descriptors when they
|
|
* have events to report.
|
|
*/
|
|
static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *key)
|
|
{
|
|
int pwake = 0;
|
|
unsigned long flags;
|
|
struct epitem *epi = ep_item_from_wait(wait);
|
|
struct eventpoll *ep = epi->ep;
|
|
|
|
if ((unsigned long)key & POLLFREE) {
|
|
ep_pwq_from_wait(wait)->whead = NULL;
|
|
/*
|
|
* whead = NULL above can race with ep_remove_wait_queue()
|
|
* which can do another remove_wait_queue() after us, so we
|
|
* can't use __remove_wait_queue(). whead->lock is held by
|
|
* the caller.
|
|
*/
|
|
list_del_init(&wait->task_list);
|
|
}
|
|
|
|
spin_lock_irqsave(&ep->lock, flags);
|
|
|
|
/*
|
|
* If the event mask does not contain any poll(2) event, we consider the
|
|
* descriptor to be disabled. This condition is likely the effect of the
|
|
* EPOLLONESHOT bit that disables the descriptor when an event is received,
|
|
* until the next EPOLL_CTL_MOD will be issued.
|
|
*/
|
|
if (!(epi->event.events & ~EP_PRIVATE_BITS))
|
|
goto out_unlock;
|
|
|
|
/*
|
|
* Check the events coming with the callback. At this stage, not
|
|
* every device reports the events in the "key" parameter of the
|
|
* callback. We need to be able to handle both cases here, hence the
|
|
* test for "key" != NULL before the event match test.
|
|
*/
|
|
if (key && !((unsigned long) key & epi->event.events))
|
|
goto out_unlock;
|
|
|
|
/*
|
|
* If we are transferring events to userspace, we can hold no locks
|
|
* (because we're accessing user memory, and because of linux f_op->poll()
|
|
* semantics). All the events that happen during that period of time are
|
|
* chained in ep->ovflist and requeued later on.
|
|
*/
|
|
if (unlikely(ep->ovflist != EP_UNACTIVE_PTR)) {
|
|
if (epi->next == EP_UNACTIVE_PTR) {
|
|
epi->next = ep->ovflist;
|
|
ep->ovflist = epi;
|
|
if (epi->ws) {
|
|
/*
|
|
* Activate ep->ws since epi->ws may get
|
|
* deactivated at any time.
|
|
*/
|
|
__pm_stay_awake(ep->ws);
|
|
}
|
|
|
|
}
|
|
goto out_unlock;
|
|
}
|
|
|
|
/* If this file is already in the ready list we exit soon */
|
|
if (!ep_is_linked(&epi->rdllink)) {
|
|
list_add_tail(&epi->rdllink, &ep->rdllist);
|
|
ep_pm_stay_awake_rcu(epi);
|
|
}
|
|
|
|
/*
|
|
* Wake up ( if active ) both the eventpoll wait list and the ->poll()
|
|
* wait list.
|
|
*/
|
|
if (waitqueue_active(&ep->wq))
|
|
wake_up_locked(&ep->wq);
|
|
if (waitqueue_active(&ep->poll_wait))
|
|
pwake++;
|
|
|
|
out_unlock:
|
|
spin_unlock_irqrestore(&ep->lock, flags);
|
|
|
|
/* We have to call this outside the lock */
|
|
if (pwake)
|
|
ep_poll_safewake(&ep->poll_wait);
|
|
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* This is the callback that is used to add our wait queue to the
|
|
* target file wakeup lists.
|
|
*/
|
|
static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead,
|
|
poll_table *pt)
|
|
{
|
|
struct epitem *epi = ep_item_from_epqueue(pt);
|
|
struct eppoll_entry *pwq;
|
|
|
|
if (epi->nwait >= 0 && (pwq = kmem_cache_alloc(pwq_cache, GFP_KERNEL))) {
|
|
init_waitqueue_func_entry(&pwq->wait, ep_poll_callback);
|
|
pwq->whead = whead;
|
|
pwq->base = epi;
|
|
add_wait_queue(whead, &pwq->wait);
|
|
list_add_tail(&pwq->llink, &epi->pwqlist);
|
|
epi->nwait++;
|
|
} else {
|
|
/* We have to signal that an error occurred */
|
|
epi->nwait = -1;
|
|
}
|
|
}
|
|
|
|
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);
|
|
kcmp = ep_cmp_ffd(&epi->ffd, &epic->ffd);
|
|
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);
|
|
}
|
|
|
|
|
|
|
|
#define PATH_ARR_SIZE 5
|
|
/*
|
|
* These are the number paths of length 1 to 5, that we are allowing to emanate
|
|
* from a single file of interest. For example, we allow 1000 paths of length
|
|
* 1, to emanate from each file of interest. This essentially represents the
|
|
* potential wakeup paths, which need to be limited in order to avoid massive
|
|
* uncontrolled wakeup storms. The common use case should be a single ep which
|
|
* is connected to n file sources. In this case each file source has 1 path
|
|
* of length 1. Thus, the numbers below should be more than sufficient. These
|
|
* path limits are enforced during an EPOLL_CTL_ADD operation, since a modify
|
|
* and delete can't add additional paths. Protected by the epmutex.
|
|
*/
|
|
static const int path_limits[PATH_ARR_SIZE] = { 1000, 500, 100, 50, 10 };
|
|
static int path_count[PATH_ARR_SIZE];
|
|
|
|
static int path_count_inc(int nests)
|
|
{
|
|
/* Allow an arbitrary number of depth 1 paths */
|
|
if (nests == 0)
|
|
return 0;
|
|
|
|
if (++path_count[nests] > path_limits[nests])
|
|
return -1;
|
|
return 0;
|
|
}
|
|
|
|
static void path_count_init(void)
|
|
{
|
|
int i;
|
|
|
|
for (i = 0; i < PATH_ARR_SIZE; i++)
|
|
path_count[i] = 0;
|
|
}
|
|
|
|
static int reverse_path_check_proc(void *priv, void *cookie, int call_nests)
|
|
{
|
|
int error = 0;
|
|
struct file *file = priv;
|
|
struct file *child_file;
|
|
struct epitem *epi;
|
|
|
|
/* CTL_DEL can remove links here, but that can't increase our count */
|
|
rcu_read_lock();
|
|
list_for_each_entry_rcu(epi, &file->f_ep_links, fllink) {
|
|
child_file = epi->ep->file;
|
|
if (is_file_epoll(child_file)) {
|
|
if (list_empty(&child_file->f_ep_links)) {
|
|
if (path_count_inc(call_nests)) {
|
|
error = -1;
|
|
break;
|
|
}
|
|
} else {
|
|
error = ep_call_nested(&poll_loop_ncalls,
|
|
EP_MAX_NESTS,
|
|
reverse_path_check_proc,
|
|
child_file, child_file,
|
|
current);
|
|
}
|
|
if (error != 0)
|
|
break;
|
|
} else {
|
|
printk(KERN_ERR "reverse_path_check_proc: "
|
|
"file is not an ep!\n");
|
|
}
|
|
}
|
|
rcu_read_unlock();
|
|
return error;
|
|
}
|
|
|
|
/**
|
|
* reverse_path_check - The tfile_check_list is list of file *, which have
|
|
* links that are proposed to be newly added. We need to
|
|
* make sure that those added links don't add too many
|
|
* paths such that we will spend all our time waking up
|
|
* eventpoll objects.
|
|
*
|
|
* Returns: Returns zero if the proposed links don't create too many paths,
|
|
* -1 otherwise.
|
|
*/
|
|
static int reverse_path_check(void)
|
|
{
|
|
int error = 0;
|
|
struct file *current_file;
|
|
|
|
/* let's call this for all tfiles */
|
|
list_for_each_entry(current_file, &tfile_check_list, f_tfile_llink) {
|
|
path_count_init();
|
|
error = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS,
|
|
reverse_path_check_proc, current_file,
|
|
current_file, current);
|
|
if (error)
|
|
break;
|
|
}
|
|
return error;
|
|
}
|
|
|
|
static int ep_create_wakeup_source(struct epitem *epi)
|
|
{
|
|
const char *name;
|
|
struct wakeup_source *ws;
|
|
|
|
if (!epi->ep->ws) {
|
|
epi->ep->ws = wakeup_source_register("eventpoll");
|
|
if (!epi->ep->ws)
|
|
return -ENOMEM;
|
|
}
|
|
|
|
name = epi->ffd.file->f_path.dentry->d_name.name;
|
|
ws = wakeup_source_register(name);
|
|
|
|
if (!ws)
|
|
return -ENOMEM;
|
|
rcu_assign_pointer(epi->ws, ws);
|
|
|
|
return 0;
|
|
}
|
|
|
|
/* rare code path, only used when EPOLL_CTL_MOD removes a wakeup source */
|
|
static noinline void ep_destroy_wakeup_source(struct epitem *epi)
|
|
{
|
|
struct wakeup_source *ws = ep_wakeup_source(epi);
|
|
|
|
RCU_INIT_POINTER(epi->ws, NULL);
|
|
|
|
/*
|
|
* wait for ep_pm_stay_awake_rcu to finish, synchronize_rcu is
|
|
* used internally by wakeup_source_remove, too (called by
|
|
* wakeup_source_unregister), so we cannot use call_rcu
|
|
*/
|
|
synchronize_rcu();
|
|
wakeup_source_unregister(ws);
|
|
}
|
|
|
|
/*
|
|
* Must be called with "mtx" held.
|
|
*/
|
|
static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
|
|
struct file *tfile, int fd, int full_check)
|
|
{
|
|
int error, revents, pwake = 0;
|
|
unsigned long flags;
|
|
long user_watches;
|
|
struct epitem *epi;
|
|
struct ep_pqueue epq;
|
|
|
|
user_watches = atomic_long_read(&ep->user->epoll_watches);
|
|
if (unlikely(user_watches >= max_user_watches))
|
|
return -ENOSPC;
|
|
if (!(epi = kmem_cache_alloc(epi_cache, GFP_KERNEL)))
|
|
return -ENOMEM;
|
|
|
|
/* Item initialization follow here ... */
|
|
INIT_LIST_HEAD(&epi->rdllink);
|
|
INIT_LIST_HEAD(&epi->fllink);
|
|
INIT_LIST_HEAD(&epi->pwqlist);
|
|
epi->ep = ep;
|
|
ep_set_ffd(&epi->ffd, tfile, fd);
|
|
epi->event = *event;
|
|
epi->nwait = 0;
|
|
epi->next = EP_UNACTIVE_PTR;
|
|
if (epi->event.events & EPOLLWAKEUP) {
|
|
error = ep_create_wakeup_source(epi);
|
|
if (error)
|
|
goto error_create_wakeup_source;
|
|
} else {
|
|
RCU_INIT_POINTER(epi->ws, NULL);
|
|
}
|
|
|
|
/* Initialize the poll table using the queue callback */
|
|
epq.epi = epi;
|
|
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
|
|
* been increased by the caller of this function. Note that after
|
|
* this operation completes, the poll callback can start hitting
|
|
* the new item.
|
|
*/
|
|
revents = ep_item_poll(epi, &epq.pt);
|
|
|
|
/*
|
|
* We have to check if something went wrong during the poll wait queue
|
|
* install process. Namely an allocation for a wait queue failed due
|
|
* high memory pressure.
|
|
*/
|
|
error = -ENOMEM;
|
|
if (epi->nwait < 0)
|
|
goto error_unregister;
|
|
|
|
/* Add the current item to the list of active epoll hook for this file */
|
|
spin_lock(&tfile->f_lock);
|
|
list_add_tail_rcu(&epi->fllink, &tfile->f_ep_links);
|
|
spin_unlock(&tfile->f_lock);
|
|
|
|
/*
|
|
* Add the current item to the RB tree. All RB tree operations are
|
|
* protected by "mtx", and ep_insert() is called with "mtx" held.
|
|
*/
|
|
ep_rbtree_insert(ep, epi);
|
|
|
|
/* now check if we've created too many backpaths */
|
|
error = -EINVAL;
|
|
if (full_check && reverse_path_check())
|
|
goto error_remove_epi;
|
|
|
|
/* We have to drop the new item inside our item list to keep track of it */
|
|
spin_lock_irqsave(&ep->lock, flags);
|
|
|
|
/* If the file is already "ready" we drop it inside the ready list */
|
|
if ((revents & event->events) && !ep_is_linked(&epi->rdllink)) {
|
|
list_add_tail(&epi->rdllink, &ep->rdllist);
|
|
ep_pm_stay_awake(epi);
|
|
|
|
/* Notify waiting tasks that events are available */
|
|
if (waitqueue_active(&ep->wq))
|
|
wake_up_locked(&ep->wq);
|
|
if (waitqueue_active(&ep->poll_wait))
|
|
pwake++;
|
|
}
|
|
|
|
spin_unlock_irqrestore(&ep->lock, flags);
|
|
|
|
atomic_long_inc(&ep->user->epoll_watches);
|
|
|
|
/* We have to call this outside the lock */
|
|
if (pwake)
|
|
ep_poll_safewake(&ep->poll_wait);
|
|
|
|
return 0;
|
|
|
|
error_remove_epi:
|
|
spin_lock(&tfile->f_lock);
|
|
list_del_rcu(&epi->fllink);
|
|
spin_unlock(&tfile->f_lock);
|
|
|
|
rb_erase(&epi->rbn, &ep->rbr);
|
|
|
|
error_unregister:
|
|
ep_unregister_pollwait(ep, epi);
|
|
|
|
/*
|
|
* We need to do this because an event could have been arrived on some
|
|
* allocated wait queue. 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.
|
|
*/
|
|
spin_lock_irqsave(&ep->lock, flags);
|
|
if (ep_is_linked(&epi->rdllink))
|
|
list_del_init(&epi->rdllink);
|
|
spin_unlock_irqrestore(&ep->lock, flags);
|
|
|
|
wakeup_source_unregister(ep_wakeup_source(epi));
|
|
|
|
error_create_wakeup_source:
|
|
kmem_cache_free(epi_cache, epi);
|
|
|
|
return error;
|
|
}
|
|
|
|
/*
|
|
* Modify the interest event mask by dropping an event if the new mask
|
|
* has a match in the current file status. Must be called with "mtx" held.
|
|
*/
|
|
static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_event *event)
|
|
{
|
|
int pwake = 0;
|
|
unsigned int revents;
|
|
poll_table pt;
|
|
|
|
init_poll_funcptr(&pt, NULL);
|
|
|
|
/*
|
|
* Set the new event interest mask before calling f_op->poll();
|
|
* otherwise we might miss an event that happens between the
|
|
* f_op->poll() call and the new event set registering.
|
|
*/
|
|
epi->event.events = event->events; /* need barrier below */
|
|
epi->event.data = event->data; /* protected by mtx */
|
|
if (epi->event.events & EPOLLWAKEUP) {
|
|
if (!ep_has_wakeup_source(epi))
|
|
ep_create_wakeup_source(epi);
|
|
} else if (ep_has_wakeup_source(epi)) {
|
|
ep_destroy_wakeup_source(epi);
|
|
}
|
|
|
|
/*
|
|
* 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();
|
|
|
|
/*
|
|
* Get current event bits. We can safely use the file* here because
|
|
* its usage count has been increased by the caller of this function.
|
|
*/
|
|
revents = ep_item_poll(epi, &pt);
|
|
|
|
/*
|
|
* If the item is "hot" and it is not registered inside the ready
|
|
* list, push it inside.
|
|
*/
|
|
if (revents & event->events) {
|
|
spin_lock_irq(&ep->lock);
|
|
if (!ep_is_linked(&epi->rdllink)) {
|
|
list_add_tail(&epi->rdllink, &ep->rdllist);
|
|
ep_pm_stay_awake(epi);
|
|
|
|
/* Notify waiting tasks that events are available */
|
|
if (waitqueue_active(&ep->wq))
|
|
wake_up_locked(&ep->wq);
|
|
if (waitqueue_active(&ep->poll_wait))
|
|
pwake++;
|
|
}
|
|
spin_unlock_irq(&ep->lock);
|
|
}
|
|
|
|
/* We have to call this outside the lock */
|
|
if (pwake)
|
|
ep_poll_safewake(&ep->poll_wait);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int ep_send_events_proc(struct eventpoll *ep, struct list_head *head,
|
|
void *priv)
|
|
{
|
|
struct ep_send_events_data *esed = priv;
|
|
int eventcnt;
|
|
unsigned int revents;
|
|
struct epitem *epi;
|
|
struct epoll_event __user *uevent;
|
|
struct wakeup_source *ws;
|
|
poll_table pt;
|
|
|
|
init_poll_funcptr(&pt, NULL);
|
|
|
|
/*
|
|
* We can loop without lock because we are passed a task private list.
|
|
* Items cannot vanish during the loop because ep_scan_ready_list() is
|
|
* holding "mtx" during this call.
|
|
*/
|
|
for (eventcnt = 0, uevent = esed->events;
|
|
!list_empty(head) && eventcnt < esed->maxevents;) {
|
|
epi = list_first_entry(head, struct epitem, rdllink);
|
|
|
|
/*
|
|
* Activate ep->ws before deactivating epi->ws to prevent
|
|
* triggering auto-suspend here (in case we reactive epi->ws
|
|
* below).
|
|
*
|
|
* This could be rearranged to delay the deactivation of epi->ws
|
|
* instead, but then epi->ws would temporarily be out of sync
|
|
* with ep_is_linked().
|
|
*/
|
|
ws = ep_wakeup_source(epi);
|
|
if (ws) {
|
|
if (ws->active)
|
|
__pm_stay_awake(ep->ws);
|
|
__pm_relax(ws);
|
|
}
|
|
|
|
list_del_init(&epi->rdllink);
|
|
|
|
revents = ep_item_poll(epi, &pt);
|
|
|
|
/*
|
|
* If the event mask intersect the caller-requested one,
|
|
* deliver the event to userspace. Again, ep_scan_ready_list()
|
|
* is holding "mtx", so no operations coming from userspace
|
|
* can change the item.
|
|
*/
|
|
if (revents) {
|
|
if (__put_user(revents, &uevent->events) ||
|
|
__put_user(epi->event.data, &uevent->data)) {
|
|
list_add(&epi->rdllink, head);
|
|
ep_pm_stay_awake(epi);
|
|
return eventcnt ? eventcnt : -EFAULT;
|
|
}
|
|
eventcnt++;
|
|
uevent++;
|
|
if (epi->event.events & EPOLLONESHOT)
|
|
epi->event.events &= EP_PRIVATE_BITS;
|
|
else if (!(epi->event.events & EPOLLET)) {
|
|
/*
|
|
* If this file has been added with Level
|
|
* Trigger mode, we need to insert back inside
|
|
* the ready list, so that the next call to
|
|
* epoll_wait() will check again the events
|
|
* availability. At this point, no one can insert
|
|
* into ep->rdllist besides us. The epoll_ctl()
|
|
* callers are locked out by
|
|
* ep_scan_ready_list() holding "mtx" and the
|
|
* poll callback will queue them in ep->ovflist.
|
|
*/
|
|
list_add_tail(&epi->rdllink, &ep->rdllist);
|
|
ep_pm_stay_awake(epi);
|
|
}
|
|
}
|
|
}
|
|
|
|
return eventcnt;
|
|
}
|
|
|
|
static int ep_send_events(struct eventpoll *ep,
|
|
struct epoll_event __user *events, int maxevents)
|
|
{
|
|
struct ep_send_events_data esed;
|
|
|
|
esed.maxevents = maxevents;
|
|
esed.events = events;
|
|
|
|
return ep_scan_ready_list(ep, ep_send_events_proc, &esed, 0, false);
|
|
}
|
|
|
|
static inline struct timespec ep_set_mstimeout(long ms)
|
|
{
|
|
struct timespec now, ts = {
|
|
.tv_sec = ms / MSEC_PER_SEC,
|
|
.tv_nsec = NSEC_PER_MSEC * (ms % MSEC_PER_SEC),
|
|
};
|
|
|
|
ktime_get_ts(&now);
|
|
return timespec_add_safe(now, ts);
|
|
}
|
|
|
|
/**
|
|
* ep_poll - Retrieves ready events, and delivers them to the caller supplied
|
|
* event buffer.
|
|
*
|
|
* @ep: Pointer to the eventpoll context.
|
|
* @events: Pointer to the userspace buffer where the ready events should be
|
|
* stored.
|
|
* @maxevents: Size (in terms of number of events) of the caller event buffer.
|
|
* @timeout: Maximum timeout for the ready events fetch operation, in
|
|
* milliseconds. If the @timeout is zero, the function will not block,
|
|
* while if the @timeout is less than zero, the function will block
|
|
* until at least one event has been retrieved (or an error
|
|
* occurred).
|
|
*
|
|
* Returns: Returns the number of ready events which have been fetched, or an
|
|
* error code, in case of error.
|
|
*/
|
|
static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
|
|
int maxevents, long timeout)
|
|
{
|
|
int res = 0, eavail, timed_out = 0;
|
|
unsigned long flags;
|
|
long slack = 0;
|
|
wait_queue_t wait;
|
|
ktime_t expires, *to = NULL;
|
|
|
|
if (timeout > 0) {
|
|
struct timespec end_time = ep_set_mstimeout(timeout);
|
|
|
|
slack = select_estimate_accuracy(&end_time);
|
|
to = &expires;
|
|
*to = timespec_to_ktime(end_time);
|
|
} else if (timeout == 0) {
|
|
/*
|
|
* Avoid the unnecessary trip to the wait queue loop, if the
|
|
* caller specified a non blocking operation.
|
|
*/
|
|
timed_out = 1;
|
|
spin_lock_irqsave(&ep->lock, flags);
|
|
goto check_events;
|
|
}
|
|
|
|
fetch_events:
|
|
spin_lock_irqsave(&ep->lock, flags);
|
|
|
|
if (!ep_events_available(ep)) {
|
|
/*
|
|
* We don't have any available event to return to the caller.
|
|
* We need to sleep here, and we will be wake up by
|
|
* ep_poll_callback() when events will become available.
|
|
*/
|
|
init_waitqueue_entry(&wait, current);
|
|
__add_wait_queue_exclusive(&ep->wq, &wait);
|
|
|
|
for (;;) {
|
|
/*
|
|
* We don't want to sleep if the ep_poll_callback() sends us
|
|
* a wakeup in between. That's why we set the task state
|
|
* to TASK_INTERRUPTIBLE before doing the checks.
|
|
*/
|
|
set_current_state(TASK_INTERRUPTIBLE);
|
|
if (ep_events_available(ep) || timed_out)
|
|
break;
|
|
if (signal_pending(current)) {
|
|
res = -EINTR;
|
|
break;
|
|
}
|
|
|
|
spin_unlock_irqrestore(&ep->lock, flags);
|
|
if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS))
|
|
timed_out = 1;
|
|
|
|
spin_lock_irqsave(&ep->lock, flags);
|
|
}
|
|
__remove_wait_queue(&ep->wq, &wait);
|
|
|
|
set_current_state(TASK_RUNNING);
|
|
}
|
|
check_events:
|
|
/* Is it worth to try to dig for events ? */
|
|
eavail = ep_events_available(ep);
|
|
|
|
spin_unlock_irqrestore(&ep->lock, flags);
|
|
|
|
/*
|
|
* 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 &&
|
|
!(res = ep_send_events(ep, events, maxevents)) && !timed_out)
|
|
goto fetch_events;
|
|
|
|
return res;
|
|
}
|
|
|
|
/**
|
|
* ep_loop_check_proc - Callback function to be passed to the @ep_call_nested()
|
|
* API, to verify that adding an epoll file inside another
|
|
* epoll structure, does not violate the constraints, in
|
|
* terms of closed loops, or too deep chains (which can
|
|
* result in excessive stack usage).
|
|
*
|
|
* @priv: Pointer to the epoll file to be currently checked.
|
|
* @cookie: Original cookie for this call. This is the top-of-the-chain epoll
|
|
* data structure pointer.
|
|
* @call_nests: Current dept of the @ep_call_nested() call stack.
|
|
*
|
|
* Returns: Returns zero if adding the epoll @file inside current epoll
|
|
* structure @ep does not violate the constraints, or -1 otherwise.
|
|
*/
|
|
static int ep_loop_check_proc(void *priv, void *cookie, int call_nests)
|
|
{
|
|
int error = 0;
|
|
struct file *file = priv;
|
|
struct eventpoll *ep = file->private_data;
|
|
struct eventpoll *ep_tovisit;
|
|
struct rb_node *rbp;
|
|
struct epitem *epi;
|
|
|
|
mutex_lock_nested(&ep->mtx, call_nests + 1);
|
|
ep->visited = 1;
|
|
list_add(&ep->visited_list_link, &visited_list);
|
|
for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) {
|
|
epi = rb_entry(rbp, struct epitem, rbn);
|
|
if (unlikely(is_file_epoll(epi->ffd.file))) {
|
|
ep_tovisit = epi->ffd.file->private_data;
|
|
if (ep_tovisit->visited)
|
|
continue;
|
|
error = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS,
|
|
ep_loop_check_proc, epi->ffd.file,
|
|
ep_tovisit, current);
|
|
if (error != 0)
|
|
break;
|
|
} else {
|
|
/*
|
|
* If we've reached a file that is not associated with
|
|
* an ep, then we need to check if the newly added
|
|
* links are going to add too many wakeup paths. We do
|
|
* this by adding it to the tfile_check_list, if it's
|
|
* not already there, and calling reverse_path_check()
|
|
* during ep_insert().
|
|
*/
|
|
if (list_empty(&epi->ffd.file->f_tfile_llink))
|
|
list_add(&epi->ffd.file->f_tfile_llink,
|
|
&tfile_check_list);
|
|
}
|
|
}
|
|
mutex_unlock(&ep->mtx);
|
|
|
|
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)
|
|
{
|
|
int ret;
|
|
struct eventpoll *ep_cur, *ep_next;
|
|
|
|
ret = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS,
|
|
ep_loop_check_proc, file, ep, current);
|
|
/* clear visited list */
|
|
list_for_each_entry_safe(ep_cur, ep_next, &visited_list,
|
|
visited_list_link) {
|
|
ep_cur->visited = 0;
|
|
list_del(&ep_cur->visited_list_link);
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
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);
|
|
}
|
|
|
|
/*
|
|
* Open an eventpoll file descriptor.
|
|
*/
|
|
SYSCALL_DEFINE1(epoll_create1, int, flags)
|
|
{
|
|
int error, fd;
|
|
struct eventpoll *ep = NULL;
|
|
struct file *file;
|
|
|
|
/* Check the EPOLL_* constant for consistency. */
|
|
BUILD_BUG_ON(EPOLL_CLOEXEC != O_CLOEXEC);
|
|
|
|
if (flags & ~EPOLL_CLOEXEC)
|
|
return -EINVAL;
|
|
/*
|
|
* Create the internal data structure ("struct eventpoll").
|
|
*/
|
|
error = ep_alloc(&ep);
|
|
if (error < 0)
|
|
return error;
|
|
/*
|
|
* Creates all the items needed to setup an eventpoll file. That is,
|
|
* a file structure and a free file descriptor.
|
|
*/
|
|
fd = get_unused_fd_flags(O_RDWR | (flags & O_CLOEXEC));
|
|
if (fd < 0) {
|
|
error = fd;
|
|
goto out_free_ep;
|
|
}
|
|
file = anon_inode_getfile("[eventpoll]", &eventpoll_fops, ep,
|
|
O_RDWR | (flags & O_CLOEXEC));
|
|
if (IS_ERR(file)) {
|
|
error = PTR_ERR(file);
|
|
goto out_free_fd;
|
|
}
|
|
ep->file = file;
|
|
fd_install(fd, file);
|
|
return fd;
|
|
|
|
out_free_fd:
|
|
put_unused_fd(fd);
|
|
out_free_ep:
|
|
ep_free(ep);
|
|
return error;
|
|
}
|
|
|
|
SYSCALL_DEFINE1(epoll_create, int, size)
|
|
{
|
|
if (size <= 0)
|
|
return -EINVAL;
|
|
|
|
return sys_epoll_create1(0);
|
|
}
|
|
|
|
/*
|
|
* The following function implements the controller interface for
|
|
* the eventpoll file that enables the insertion/removal/change of
|
|
* file descriptors inside the interest set.
|
|
*/
|
|
SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd,
|
|
struct epoll_event __user *, event)
|
|
{
|
|
int error;
|
|
int full_check = 0;
|
|
struct fd f, tf;
|
|
struct eventpoll *ep;
|
|
struct epitem *epi;
|
|
struct epoll_event epds;
|
|
struct eventpoll *tep = NULL;
|
|
|
|
error = -EFAULT;
|
|
if (ep_op_has_event(op) &&
|
|
copy_from_user(&epds, event, sizeof(struct epoll_event)))
|
|
goto error_return;
|
|
|
|
error = -EBADF;
|
|
f = fdget(epfd);
|
|
if (!f.file)
|
|
goto error_return;
|
|
|
|
/* Get the "struct file *" for the target file */
|
|
tf = fdget(fd);
|
|
if (!tf.file)
|
|
goto error_fput;
|
|
|
|
/* The target file descriptor must support poll */
|
|
error = -EPERM;
|
|
if (!tf.file->f_op->poll)
|
|
goto error_tgt_fput;
|
|
|
|
/* Check if EPOLLWAKEUP is allowed */
|
|
ep_take_care_of_epollwakeup(&epds);
|
|
|
|
/*
|
|
* We have to check that the file structure underneath the file descriptor
|
|
* the user passed to us _is_ an eventpoll file. And also we do not permit
|
|
* adding an epoll file descriptor inside itself.
|
|
*/
|
|
error = -EINVAL;
|
|
if (f.file == tf.file || !is_file_epoll(f.file))
|
|
goto error_tgt_fput;
|
|
|
|
/*
|
|
* At this point it is safe to assume that the "private_data" contains
|
|
* our own data structure.
|
|
*/
|
|
ep = f.file->private_data;
|
|
|
|
/*
|
|
* When we insert an epoll file descriptor, inside another epoll file
|
|
* descriptor, there is the change of creating closed loops, which are
|
|
* better be handled here, than in more critical paths. While we are
|
|
* checking for loops we also determine the list of files reachable
|
|
* and hang them on the tfile_check_list, so we can check that we
|
|
* haven't created too many possible wakeup paths.
|
|
*
|
|
* We do not need to take the global 'epumutex' on EPOLL_CTL_ADD when
|
|
* the epoll file descriptor is attaching directly to a wakeup source,
|
|
* unless the epoll file descriptor is nested. The purpose of taking the
|
|
* 'epmutex' on add is to prevent complex toplogies such as loops and
|
|
* deep wakeup paths from forming in parallel through multiple
|
|
* EPOLL_CTL_ADD operations.
|
|
*/
|
|
mutex_lock_nested(&ep->mtx, 0);
|
|
if (op == EPOLL_CTL_ADD) {
|
|
if (!list_empty(&f.file->f_ep_links) ||
|
|
is_file_epoll(tf.file)) {
|
|
full_check = 1;
|
|
mutex_unlock(&ep->mtx);
|
|
mutex_lock(&epmutex);
|
|
if (is_file_epoll(tf.file)) {
|
|
error = -ELOOP;
|
|
if (ep_loop_check(ep, tf.file) != 0) {
|
|
clear_tfile_check_list();
|
|
goto error_tgt_fput;
|
|
}
|
|
} else
|
|
list_add(&tf.file->f_tfile_llink,
|
|
&tfile_check_list);
|
|
mutex_lock_nested(&ep->mtx, 0);
|
|
if (is_file_epoll(tf.file)) {
|
|
tep = tf.file->private_data;
|
|
mutex_lock_nested(&tep->mtx, 1);
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Try to lookup the file inside our RB tree, Since we grabbed "mtx"
|
|
* above, we can be sure to be able to use the item looked up by
|
|
* ep_find() till we release the mutex.
|
|
*/
|
|
epi = ep_find(ep, tf.file, fd);
|
|
|
|
error = -EINVAL;
|
|
switch (op) {
|
|
case EPOLL_CTL_ADD:
|
|
if (!epi) {
|
|
epds.events |= POLLERR | POLLHUP;
|
|
error = ep_insert(ep, &epds, tf.file, fd, full_check);
|
|
} else
|
|
error = -EEXIST;
|
|
if (full_check)
|
|
clear_tfile_check_list();
|
|
break;
|
|
case EPOLL_CTL_DEL:
|
|
if (epi)
|
|
error = ep_remove(ep, epi);
|
|
else
|
|
error = -ENOENT;
|
|
break;
|
|
case EPOLL_CTL_MOD:
|
|
if (epi) {
|
|
epds.events |= POLLERR | POLLHUP;
|
|
error = ep_modify(ep, epi, &epds);
|
|
} else
|
|
error = -ENOENT;
|
|
break;
|
|
}
|
|
if (tep != NULL)
|
|
mutex_unlock(&tep->mtx);
|
|
mutex_unlock(&ep->mtx);
|
|
|
|
error_tgt_fput:
|
|
if (full_check)
|
|
mutex_unlock(&epmutex);
|
|
|
|
fdput(tf);
|
|
error_fput:
|
|
fdput(f);
|
|
error_return:
|
|
|
|
return error;
|
|
}
|
|
|
|
/*
|
|
* Implement the event wait interface for the eventpoll file. It is the kernel
|
|
* part of the user space epoll_wait(2).
|
|
*/
|
|
SYSCALL_DEFINE4(epoll_wait, int, epfd, struct epoll_event __user *, events,
|
|
int, maxevents, int, timeout)
|
|
{
|
|
int error;
|
|
struct fd f;
|
|
struct eventpoll *ep;
|
|
|
|
/* The maximum number of event must be greater than zero */
|
|
if (maxevents <= 0 || maxevents > EP_MAX_EVENTS)
|
|
return -EINVAL;
|
|
|
|
/* Verify that the area passed by the user is writeable */
|
|
if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event)))
|
|
return -EFAULT;
|
|
|
|
/* Get the "struct file *" for the eventpoll file */
|
|
f = fdget(epfd);
|
|
if (!f.file)
|
|
return -EBADF;
|
|
|
|
/*
|
|
* We have to check that the file structure underneath the fd
|
|
* the user passed to us _is_ an eventpoll file.
|
|
*/
|
|
error = -EINVAL;
|
|
if (!is_file_epoll(f.file))
|
|
goto error_fput;
|
|
|
|
/*
|
|
* At this point it is safe to assume that the "private_data" contains
|
|
* our own data structure.
|
|
*/
|
|
ep = f.file->private_data;
|
|
|
|
/* Time to fish for events ... */
|
|
error = ep_poll(ep, events, maxevents, timeout);
|
|
|
|
error_fput:
|
|
fdput(f);
|
|
return error;
|
|
}
|
|
|
|
/*
|
|
* Implement the event wait interface for the eventpoll file. It is the kernel
|
|
* part of the user space epoll_pwait(2).
|
|
*/
|
|
SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events,
|
|
int, maxevents, int, timeout, const sigset_t __user *, sigmask,
|
|
size_t, sigsetsize)
|
|
{
|
|
int 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;
|
|
sigsaved = current->blocked;
|
|
set_current_blocked(&ksigmask);
|
|
}
|
|
|
|
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,
|
|
sizeof(sigsaved));
|
|
set_restore_sigmask();
|
|
} else
|
|
set_current_blocked(&sigsaved);
|
|
}
|
|
|
|
return error;
|
|
}
|
|
|
|
#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);
|
|
sigsaved = current->blocked;
|
|
set_current_blocked(&ksigmask);
|
|
}
|
|
|
|
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
|
|
set_current_blocked(&sigsaved);
|
|
}
|
|
|
|
return err;
|
|
}
|
|
#endif
|
|
|
|
static int __init eventpoll_init(void)
|
|
{
|
|
struct sysinfo si;
|
|
|
|
si_meminfo(&si);
|
|
/*
|
|
* Allows top 4% of lomem to be allocated for epoll watches (per user).
|
|
*/
|
|
max_user_watches = (((si.totalram - si.totalhigh) / 25) << PAGE_SHIFT) /
|
|
EP_ITEM_COST;
|
|
BUG_ON(max_user_watches < 0);
|
|
|
|
/*
|
|
* Initialize the structure used to perform epoll file descriptor
|
|
* inclusion loops checks.
|
|
*/
|
|
ep_nested_calls_init(&poll_loop_ncalls);
|
|
|
|
/* Initialize the structure used to perform safe poll wait head wake ups */
|
|
ep_nested_calls_init(&poll_safewake_ncalls);
|
|
|
|
/* Initialize the structure used to perform file's f_op->poll() calls */
|
|
ep_nested_calls_init(&poll_readywalk_ncalls);
|
|
|
|
/*
|
|
* We can have many thousands of epitems, so prevent this from
|
|
* using an extra cache line on 64-bit (and smaller) CPUs
|
|
*/
|
|
BUILD_BUG_ON(sizeof(void *) <= 8 && sizeof(struct epitem) > 128);
|
|
|
|
/* Allocates slab cache used to allocate "struct epitem" items */
|
|
epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem),
|
|
0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
|
|
|
|
/* Allocates slab cache used to allocate "struct eppoll_entry" */
|
|
pwq_cache = kmem_cache_create("eventpoll_pwq",
|
|
sizeof(struct eppoll_entry), 0, SLAB_PANIC, NULL);
|
|
|
|
return 0;
|
|
}
|
|
fs_initcall(eventpoll_init);
|