cregit-Linux how code gets into the kernel

Release 4.11 fs/eventpoll.c

Directory: fs
/*
 *  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/signal.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 <linux/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 | EPOLLEXCLUSIVE)


#define EPOLLINOUT_BITS (POLLIN | POLLOUT)


#define EPOLLEXCLUSIVE_OK_BITS (EPOLLINOUT_BITS | POLLERR | POLLHUP | \
                                EPOLLWAKEUP | EPOLLET | EPOLLEXCLUSIVE)

/* 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; }

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/* 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; }

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Davide Libenzi2990.62%375.00%
Andrew Morton39.38%125.00%
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/* 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)); }

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Davide Libenzi52100.00%2100.00%
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/* Tells us if the item is currently linked */
static inline int ep_is_linked(struct list_head *p) { return !list_empty(p); }

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Davide Libenzi19100.00%3100.00%
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static inline struct eppoll_entry *ep_pwq_from_wait(wait_queue_t *p) { return container_of(p, struct eppoll_entry, wait); }

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Oleg Nesterov24100.00%1100.00%
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/* 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; }

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Davide Libenzi26100.00%4100.00%
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/* 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; }

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Davide Libenzi26100.00%4100.00%
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/* 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; }

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Davide Libenzi1386.67%375.00%
Andrew Morton213.33%125.00%
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/* 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); }

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Davide Libenzi27100.00%3100.00%
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/** * ep_events_available - Checks if ready events might be available. * * @ep: Pointer to the eventpoll context. * * Returns: Returns a value different than zero if ready events are available, * or zero otherwise. */
static inline int ep_events_available(struct eventpoll *ep) { return !list_empty(&ep->rdllist) || ep->ovflist != EP_UNACTIVE_PTR; }

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Davide Libenzi28100.00%1100.00%
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/** * ep_call_nested - Perform a bound (possibly) nested call, by checking * that the recursion limit is not exceeded, and that * the same nested call (by the meaning of same cookie) is * no re-entered. * * @ncalls: Pointer to the nested_calls structure to be used for this call. * @max_nests: Maximum number of allowed nesting calls. * @nproc: Nested call core function pointer. * @priv: Opaque data to be passed to the @nproc callback. * @cookie: Cookie to be used to identify this nested call. * @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; }

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Davide Libenzi19393.69%975.00%
Tony Battersby83.88%18.33%
Matthias Kaehlcke41.94%18.33%
Peter Zijlstra10.49%18.33%
Total206100.00%12100.00%

/* * 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); }

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#else
static inline void ep_wake_up_nested(wait_queue_head_t *wqueue, unsigned long events, int subclass) { wake_up_poll(wqueue, events); }

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#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; }

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Davide Libenzi35100.00%2100.00%
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/* * 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(); }

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Davide Libenzi42100.00%3100.00%
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static void ep_remove_wait_queue(struct eppoll_entry *pwq) { wait_queue_head_t *whead; rcu_read_lock(); /* If it is cleared by POLLFREE, it should be rcu-safe */ whead = rcu_dereference(pwq->whead); if (whead) remove_wait_queue(whead, &pwq->wait); rcu_read_unlock(); }

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Oleg Nesterov45100.00%1100.00%
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/* * This function unregisters poll callbacks from the associated file * descriptor. Must be called with "mtx" held (or "epmutex" if called from * ep_free). */
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); } }

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Davide Libenzi6994.52%457.14%
Andrew Morton22.74%114.29%
Oleg Nesterov11.37%114.29%
Tony Battersby11.37%114.29%
Total73100.00%7100.00%

/* 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)); }

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/* 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); }

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static inline bool ep_has_wakeup_source(struct epitem *epi) { return rcu_access_pointer(epi->ws) ? true : false; }

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/* 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(); }

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Eric Wong41100.00%1100.00%
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/** * ep_scan_ready_list - Scans the ready list in a way that makes possible for * the scan code, to call f_op->poll(). Also allows for * O(NumReady) performance. * * @ep: Pointer to the epoll private data structure. * @sproc: Pointer to the scan callback. * @priv: Private opaque data passed to the @sproc callback. * @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; }

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Davide Libenzi28188.92%1368.42%
Jason Baron134.11%15.26%
Arve Hjönnevåg134.11%15.26%
Nelson Elhage61.90%15.26%
Tony Battersby10.32%15.26%
Andrew Morton10.32%15.26%
Eric Wong10.32%15.26%
Total316100.00%19100.00%


static void epi_rcu_free(struct rcu_head *head) { struct epitem *epi = container_of(head, struct epitem, rcu); kmem_cache_free(epi_cache, epi); }

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Jason Baron33100.00%1100.00%
Total33100.00%1100.00%

/* * 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; }

Contributors

PersonTokensPropCommitsCommitProp
Davide Libenzi12484.35%550.00%
Jason Baron85.44%110.00%
Andrew Morton64.08%110.00%
Arve Hjönnevåg53.40%110.00%
Eric Wong32.04%110.00%
Robin Holt10.68%110.00%
Total147100.00%10100.00%


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); }

Contributors

PersonTokensPropCommitsCommitProp
Davide Libenzi14679.78%758.33%
Eric Wong179.29%18.33%
Arve Hjönnevåg73.83%18.33%
Eric Dumazet63.28%18.33%
Andrew Morton63.28%18.33%
Lucas De Marchi10.55%18.33%
Total183100.00%12100.00%


static int ep_eventpoll_release(struct inode *inode, struct file *file) { struct eventpoll *ep = file->private_data; if (ep) ep_free(ep); return 0; }

Contributors

PersonTokensPropCommitsCommitProp
Davide Libenzi3697.30%583.33%
Jesper Juhl12.70%116.67%
Total37100.00%6100.00%


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; }

Contributors

PersonTokensPropCommitsCommitProp
Eric Wong53100.00%1100.00%
Total53100.00%1100.00%


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; }

Contributors

PersonTokensPropCommitsCommitProp
Davide Libenzi6775.28%660.00%
Hans Verkuil1314.61%110.00%
Arve Hjönnevåg55.62%110.00%
Eric Wong44.49%220.00%
Total89100.00%10100.00%

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); }

Contributors

PersonTokensPropCommitsCommitProp
Davide Libenzi2659.09%466.67%
Jason Baron1431.82%116.67%
Nelson Elhage49.09%116.67%
Total44100.00%6100.00%


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; }

Contributors

PersonTokensPropCommitsCommitProp
Davide Libenzi6971.88%787.50%
Jason Baron2728.12%112.50%
Total96100.00%8100.00%

#ifdef CONFIG_PROC_FS
static void ep_show_fdinfo(struct seq_file *m, struct file *f) { struct eventpoll *ep = f->private_data; struct rb_node *rbp; mutex_lock(&ep->mtx); for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { struct epitem *epi = rb_entry(rbp, struct epitem, rbn); seq_printf(m, "tfd: %8d events: %8x data: %16llx\n", epi->ffd.fd, epi->event.events, (long long)epi->event.data); if (seq_has_overflowed(m)) break; } mutex_unlock(&ep->mtx); }

Contributors

PersonTokensPropCommitsCommitProp
Cyrill V. Gorcunov11695.87%150.00%
Joe Perches54.13%150.00%
Total121100.00%2100.00%

#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, *next; /* * We don't want to get "file->f_lock" because it is not * necessary. It is not necessary because we're in the "struct file" * cleanup path, and this means that no one is using this file anymore. * So, for example, epoll_ctl() cannot hit here since if we reach this * point, the file counter already went to zero and fget() would fail. * The only hit might come from ep_free() but by holding the mutex * will correctly serialize the operation. We do need to acquire * "ep->mtx" after "epmutex" because ep_remove() requires it when called * from anywhere but ep_free(). * * Besides, ep_remove() acquires the lock, so we can't hold it here. */ mutex_lock(&epmutex); list_for_each_entry_safe(epi, next, &file->f_ep_links, fllink) { ep = epi->ep; mutex_lock_nested(&ep->mtx, 0); ep_remove(ep, epi); mutex_unlock(&ep->mtx); } mutex_unlock(&epmutex); }

Contributors

PersonTokensPropCommitsCommitProp
Davide Libenzi6582.28%660.00%
Konstantin Khlebnikov67.59%110.00%
Jason Baron45.06%110.00%
Nelson Elhage33.80%110.00%
Lucas De Marchi11.27%110.00%
Total79100.00%10100.00%


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; }

Contributors

PersonTokensPropCommitsCommitProp
Davide Libenzi135100.00%8100.00%
Total135100.00%8100.00%

/* * 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; }

Contributors

PersonTokensPropCommitsCommitProp
Davide Libenzi12798.45%571.43%
Andrew Morton10.78%114.29%
Pekka J Enberg10.78%114.29%
Total129100.00%7100.00%

/* * 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; int ewake = 0; 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)) { if ((epi->event.events & EPOLLEXCLUSIVE) && !((unsigned long)key & POLLFREE)) { switch ((unsigned long)key & EPOLLINOUT_BITS) { case POLLIN: if (epi->event.events & POLLIN) ewake = 1; break; case POLLOUT: if (epi->event.events & POLLOUT) ewake = 1; break; case 0: ewake = 1; break; } } 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); if (epi->event.events & EPOLLEXCLUSIVE) return ewake; return 1; }

Contributors

PersonTokensPropCommitsCommitProp
Davide Libenzi22358.84%952.94%
Jason Baron10126.65%211.76%
Oleg Nesterov307.92%211.76%
Arve Hjönnevåg225.80%15.88%
Matthew Wilcox10.26%15.88%
Daniel Baluta10.26%15.88%
Eric Wong10.26%15.88%
Total379100.00%17100.00%

/* * 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; if (epi->event.events & EPOLLEXCLUSIVE) add_wait_queue_exclusive(whead, &pwq->wait); else 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; } }

Contributors

PersonTokensPropCommitsCommitProp
Davide Libenzi11684.67%583.33%
Jason Baron2115.33%116.67%
Total137100.00%6100.00%


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); }

Contributors

PersonTokensPropCommitsCommitProp
Davide Libenzi12497.64%777.78%
Pekka J Enberg21.57%111.11%
Andrew Morton10.79%111.11%
Total127100.00%9100.00%

#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; }

Contributors

PersonTokensPropCommitsCommitProp
Jason Baron3692.31%266.67%
Davide Libenzi37.69%133.33%
Total39100.00%3100.00%


static void path_count_init(void) { int i; for (i = 0; i < PATH_ARR_SIZE; i++) path_count[i] = 0; }

Contributors

PersonTokensPropCommitsCommitProp
Jason Baron31100.00%1100.00%
Total31100.00%1100.00%


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; }

Contributors

PersonTokensPropCommitsCommitProp
Jason Baron10574.47%233.33%
Davide Libenzi3121.99%350.00%
Robin Holt53.55%116.67%
Total141100.00%6100.00%

/** * 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; }

Contributors

PersonTokensPropCommitsCommitProp
Jason Baron58100.00%1100.00%
Total58100.00%1100.00%


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; }

Contributors

PersonTokensPropCommitsCommitProp
Arve Hjönnevåg8686.00%150.00%
Eric Wong1414.00%150.00%
Total100100.00%2100.00%

/* 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); }

Contributors

PersonTokensPropCommitsCommitProp
Eric Wong2152.50%266.67%
Arve Hjönnevåg1947.50%133.33%
Total40100.00%3100.00%

/* * 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; }

Contributors

PersonTokensPropCommitsCommitProp
Davide Libenzi29756.90%1155.00%
Jason Baron16731.99%315.00%
Arve Hjönnevåg458.62%15.00%
Eric Wong101.92%210.00%
Matthew Wilcox10.19%15.00%
Pekka J Enberg10.19%15.00%
Robin Holt10.19%15.00%
Total522100.00%20100.00%

/* * 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; }

Contributors

PersonTokensPropCommitsCommitProp
Davide Libenzi13961.78%1062.50%
Arve Hjönnevåg3816.89%16.25%
Tony Battersby229.78%16.25%
Hans Verkuil135.78%16.25%
Eric Wong135.78%318.75%
Total225100.00%16100.00%


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; }

Contributors

PersonTokensPropCommitsCommitProp
Davide Libenzi19772.69%1062.50%
Arve Hjönnevåg2810.33%16.25%
Eric Wong207.38%212.50%
Hans Verkuil134.80%16.25%
Tony Battersby124.43%16.25%
Lucas De Marchi10.37%16.25%
Total271100.00%16100.00%


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); }

Contributors

PersonTokensPropCommitsCommitProp
Davide Libenzi4792.16%250.00%
Jason Baron23.92%125.00%
Nelson Elhage23.92%125.00%
Total51100.00%4100.00%


static inline struct timespec64 ep_set_mstimeout(long ms) { struct timespec64 now, ts = { .tv_sec = ms / MSEC_PER_SEC, .tv_nsec = NSEC_PER_MSEC * (ms % MSEC_PER_SEC), }; ktime_get_ts64(&now); return timespec64_add_safe(now, ts); }

Contributors

PersonTokensPropCommitsCommitProp
Eric Dumazet4792.16%150.00%
Deepa Dinamani47.84%150.00%
Total51100.00%2100.00%

/** * 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; u64 slack = 0; wait_queue_t wait; ktime_t expires, *to = NULL; if (timeout > 0) { struct timespec64 end_time = ep_set_mstimeout(timeout); slack = select_estimate_accuracy(&end_time); to = &expires; *to = timespec64_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; }

Contributors

PersonTokensPropCommitsCommitProp
Davide Libenzi20066.23%847.06%
Shawn Bohrer9130.13%211.76%
Eric Dumazet41.32%15.88%
Deepa Dinamani20.66%15.88%
Davidlohr Bueso A10.33%15.88%
John Stultz10.33%15.88%
Andrew Morton10.33%15.88%
Changli Gao10.33%15.88%
Rafael J. Wysocki10.33%15.88%
Total302100.00%17100.00%

/** * 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; }

Contributors

PersonTokensPropCommitsCommitProp
Davide Libenzi14565.02%133.33%
Jason Baron7332.74%133.33%
Nelson Elhage52.24%133.33%
Total223100.00%3100.00%

/** * 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; }

Contributors

PersonTokensPropCommitsCommitProp
Jason Baron4357.33%150.00%
Davide Libenzi3242.67%150.00%
Total75100.00%2100.00%


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); }

Contributors

PersonTokensPropCommitsCommitProp
Jason Baron52100.00%1100.00%
Total52100.00%1100.00%

/* * 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 */ if (ep_op_has_event(op)) 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; /* * epoll adds to the wakeup queue at EPOLL_CTL_ADD time only, * so EPOLLEXCLUSIVE is not allowed for a EPOLL_CTL_MOD operation. * Also, we do not currently supported nested exclusive wakeups. */ if (ep_op_has_event(op) && (epds.events & EPOLLEXCLUSIVE)) { if (op == EPOLL_CTL_MOD) goto error_tgt_fput; if (op == EPOLL_CTL_ADD && (is_file_epoll(tf.file) || (epds.events & ~EPOLLEXCLUSIVE_OK_BITS))) goto error_tgt_fput; } /* * 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) { if (!(epi->event.events & EPOLLEXCLUSIVE)) { 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(&current->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(&current->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; }

Contributors

PersonTokensPropCommitsCommitProp
Davide Libenzi10074.07%861.54%
Eric Wong2014.81%17.69%
Andrew Morton85.93%323.08%
Robin Holt75.19%17.69%
Total135100.00%13100.00%

fs_initcall(eventpoll_init);

Overall Contributors

PersonTokensPropCommitsCommitProp
Davide Libenzi438060.99%3530.17%
Jason Baron118416.49%76.03%
Eric Wong3124.34%65.17%
Arve Hjönnevåg2853.97%10.86%
Al Viro2303.20%54.31%
Cyrill V. Gorcunov1442.01%21.72%
Oleg Nesterov1141.59%32.59%
Shawn Bohrer921.28%21.72%
Heiko Carstens841.17%10.86%
Eric Dumazet570.79%21.72%
Tony Battersby480.67%54.31%
Andrew Morton440.61%119.48%
Hans Verkuil390.54%10.86%
Ulrich Drepper330.46%43.45%
Robin Holt300.42%10.86%
Nelson Elhage240.33%10.86%
Nicolas Iooss70.10%10.86%
Konstantin Khlebnikov60.08%10.86%
Christoph Hellwig60.08%10.86%
Arnd Bergmann60.08%10.86%
Deepa Dinamani60.08%10.86%
Joe Perches60.08%21.72%
Lucas De Marchi40.06%10.86%
Pekka J Enberg40.06%10.86%
Matthias Kaehlcke40.06%10.86%
Roland Dreier40.06%10.86%
Daniel Baluta40.06%10.86%
Arjan van de Ven30.04%10.86%
Rafael J. Wysocki30.04%21.72%
Amit Pundir30.04%10.86%
Roland McGrath20.03%10.86%
Matthew Wilcox20.03%10.86%
Peter Zijlstra10.01%10.86%
Adrian Bunk10.01%10.86%
Jesper Juhl10.01%10.86%
Ingo Molnar10.01%10.86%
John Stultz10.01%10.86%
Steven Rostedt10.01%10.86%
Davidlohr Bueso A10.01%10.86%
Eric W. Biedermann10.01%10.86%
Arun Sharma10.01%10.86%
Linus Torvalds10.01%10.86%
Changli Gao10.01%10.86%
Total7181100.00%116100.00%
Directory: fs
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