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![Uros Bizjak](/assets/img/avatar_default.png)
Use try_cmpxchg instead of cmpxchg (*ptr, old, new) == old in list_add_tail_lockless. x86 CMPXCHG instruction returns success in ZF flag, so this change saves a compare after cmpxchg (and related move instruction in front of cmpxchg). No functional change intended. Link: https://lkml.kernel.org/r/20220714173255.12987-1-ubizjak@gmail.com Signed-off-by: Uros Bizjak <ubizjak@gmail.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2417 lines
65 KiB
C
2417 lines
65 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* fs/eventpoll.c (Efficient event retrieval implementation)
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* Copyright (C) 2001,...,2009 Davide Libenzi
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*
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* Davide Libenzi <davidel@xmailserver.org>
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*/
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/sched/signal.h>
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#include <linux/fs.h>
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#include <linux/file.h>
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#include <linux/signal.h>
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#include <linux/errno.h>
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#include <linux/mm.h>
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#include <linux/slab.h>
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#include <linux/poll.h>
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#include <linux/string.h>
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#include <linux/list.h>
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#include <linux/hash.h>
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#include <linux/spinlock.h>
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#include <linux/syscalls.h>
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#include <linux/rbtree.h>
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#include <linux/wait.h>
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#include <linux/eventpoll.h>
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#include <linux/mount.h>
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#include <linux/bitops.h>
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#include <linux/mutex.h>
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#include <linux/anon_inodes.h>
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#include <linux/device.h>
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#include <linux/uaccess.h>
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#include <asm/io.h>
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#include <asm/mman.h>
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#include <linux/atomic.h>
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#include <linux/proc_fs.h>
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#include <linux/seq_file.h>
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#include <linux/compat.h>
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#include <linux/rculist.h>
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#include <net/busy_poll.h>
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/*
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* LOCKING:
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* There are three level of locking required by epoll :
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*
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* 1) epmutex (mutex)
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* 2) ep->mtx (mutex)
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* 3) ep->lock (rwlock)
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*
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* The acquire order is the one listed above, from 1 to 3.
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* We need a rwlock (ep->lock) because we manipulate objects
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* from inside the poll callback, that might be triggered from
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* a wake_up() that in turn might be called from IRQ context.
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* So we can't sleep inside the poll callback and hence we need
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* a spinlock. During the event transfer loop (from kernel to
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* user space) we could end up sleeping due a copy_to_user(), so
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* we need a lock that will allow us to sleep. This lock is a
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* mutex (ep->mtx). It is acquired during the event transfer loop,
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* during epoll_ctl(EPOLL_CTL_DEL) and during eventpoll_release_file().
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* Then we also need a global mutex to serialize eventpoll_release_file()
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* and ep_free().
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* This mutex is acquired by ep_free() during the epoll file
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* cleanup path and it is also acquired by eventpoll_release_file()
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* if a file has been pushed inside an epoll set and it is then
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* close()d without a previous call to epoll_ctl(EPOLL_CTL_DEL).
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* It is also acquired when inserting an epoll fd onto another epoll
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* fd. We do this so that we walk the epoll tree and ensure that this
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* insertion does not create a cycle of epoll file descriptors, which
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* could lead to deadlock. We need a global mutex to prevent two
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* simultaneous inserts (A into B and B into A) from racing and
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* constructing a cycle without either insert observing that it is
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* going to.
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* It is necessary to acquire multiple "ep->mtx"es at once in the
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* case when one epoll fd is added to another. In this case, we
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* always acquire the locks in the order of nesting (i.e. after
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* epoll_ctl(e1, EPOLL_CTL_ADD, e2), e1->mtx will always be acquired
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* before e2->mtx). Since we disallow cycles of epoll file
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* descriptors, this ensures that the mutexes are well-ordered. In
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* order to communicate this nesting to lockdep, when walking a tree
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* of epoll file descriptors, we use the current recursion depth as
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* the lockdep subkey.
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* It is possible to drop the "ep->mtx" and to use the global
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* mutex "epmutex" (together with "ep->lock") to have it working,
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* but having "ep->mtx" will make the interface more scalable.
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* Events that require holding "epmutex" are very rare, while for
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* normal operations the epoll private "ep->mtx" will guarantee
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* a better scalability.
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*/
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/* Epoll private bits inside the event mask */
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#define EP_PRIVATE_BITS (EPOLLWAKEUP | EPOLLONESHOT | EPOLLET | EPOLLEXCLUSIVE)
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#define EPOLLINOUT_BITS (EPOLLIN | EPOLLOUT)
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#define EPOLLEXCLUSIVE_OK_BITS (EPOLLINOUT_BITS | EPOLLERR | EPOLLHUP | \
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EPOLLWAKEUP | EPOLLET | EPOLLEXCLUSIVE)
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/* Maximum number of nesting allowed inside epoll sets */
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#define EP_MAX_NESTS 4
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#define EP_MAX_EVENTS (INT_MAX / sizeof(struct epoll_event))
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#define EP_UNACTIVE_PTR ((void *) -1L)
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#define EP_ITEM_COST (sizeof(struct epitem) + sizeof(struct eppoll_entry))
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struct epoll_filefd {
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struct file *file;
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int fd;
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} __packed;
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/* Wait structure used by the poll hooks */
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struct eppoll_entry {
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/* List header used to link this structure to the "struct epitem" */
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struct eppoll_entry *next;
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/* The "base" pointer is set to the container "struct epitem" */
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struct epitem *base;
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/*
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* Wait queue item that will be linked to the target file wait
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* queue head.
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*/
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wait_queue_entry_t wait;
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/* The wait queue head that linked the "wait" wait queue item */
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wait_queue_head_t *whead;
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};
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/*
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* Each file descriptor added to the eventpoll interface will
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* have an entry of this type linked to the "rbr" RB tree.
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* Avoid increasing the size of this struct, there can be many thousands
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* of these on a server and we do not want this to take another cache line.
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*/
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struct epitem {
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union {
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/* RB tree node links this structure to the eventpoll RB tree */
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struct rb_node rbn;
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/* Used to free the struct epitem */
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struct rcu_head rcu;
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};
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/* List header used to link this structure to the eventpoll ready list */
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struct list_head rdllink;
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/*
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* Works together "struct eventpoll"->ovflist in keeping the
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* single linked chain of items.
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*/
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struct epitem *next;
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/* The file descriptor information this item refers to */
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struct epoll_filefd ffd;
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/* List containing poll wait queues */
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struct eppoll_entry *pwqlist;
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/* The "container" of this item */
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struct eventpoll *ep;
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/* List header used to link this item to the "struct file" items list */
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struct hlist_node fllink;
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/* wakeup_source used when EPOLLWAKEUP is set */
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struct wakeup_source __rcu *ws;
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/* The structure that describe the interested events and the source fd */
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struct epoll_event event;
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};
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/*
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* This structure is stored inside the "private_data" member of the file
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* structure and represents the main data structure for the eventpoll
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* interface.
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*/
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struct eventpoll {
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/*
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* This mutex is used to ensure that files are not removed
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* while epoll is using them. This is held during the event
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* collection loop, the file cleanup path, the epoll file exit
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* code and the ctl operations.
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*/
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struct mutex mtx;
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/* Wait queue used by sys_epoll_wait() */
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wait_queue_head_t wq;
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/* Wait queue used by file->poll() */
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wait_queue_head_t poll_wait;
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/* List of ready file descriptors */
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struct list_head rdllist;
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/* Lock which protects rdllist and ovflist */
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rwlock_t lock;
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/* RB tree root used to store monitored fd structs */
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struct rb_root_cached rbr;
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/*
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* This is a single linked list that chains all the "struct epitem" that
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* happened while transferring ready events to userspace w/out
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* holding ->lock.
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*/
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struct epitem *ovflist;
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/* wakeup_source used when ep_scan_ready_list is running */
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struct wakeup_source *ws;
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/* The user that created the eventpoll descriptor */
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struct user_struct *user;
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struct file *file;
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/* used to optimize loop detection check */
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u64 gen;
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struct hlist_head refs;
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#ifdef CONFIG_NET_RX_BUSY_POLL
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/* used to track busy poll napi_id */
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unsigned int napi_id;
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#endif
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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/* tracks wakeup nests for lockdep validation */
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u8 nests;
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#endif
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};
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/* Wrapper struct used by poll queueing */
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struct ep_pqueue {
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poll_table pt;
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struct epitem *epi;
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};
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/*
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* Configuration options available inside /proc/sys/fs/epoll/
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*/
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/* Maximum number of epoll watched descriptors, per user */
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static long max_user_watches __read_mostly;
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/*
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* This mutex is used to serialize ep_free() and eventpoll_release_file().
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*/
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static DEFINE_MUTEX(epmutex);
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static u64 loop_check_gen = 0;
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/* Used to check for epoll file descriptor inclusion loops */
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static struct eventpoll *inserting_into;
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/* Slab cache used to allocate "struct epitem" */
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static struct kmem_cache *epi_cache __read_mostly;
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/* Slab cache used to allocate "struct eppoll_entry" */
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static struct kmem_cache *pwq_cache __read_mostly;
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/*
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* List of files with newly added links, where we may need to limit the number
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* of emanating paths. Protected by the epmutex.
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*/
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struct epitems_head {
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struct hlist_head epitems;
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struct epitems_head *next;
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};
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static struct epitems_head *tfile_check_list = EP_UNACTIVE_PTR;
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static struct kmem_cache *ephead_cache __read_mostly;
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static inline void free_ephead(struct epitems_head *head)
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{
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if (head)
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kmem_cache_free(ephead_cache, head);
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}
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static void list_file(struct file *file)
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{
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struct epitems_head *head;
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head = container_of(file->f_ep, struct epitems_head, epitems);
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if (!head->next) {
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head->next = tfile_check_list;
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tfile_check_list = head;
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}
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}
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static void unlist_file(struct epitems_head *head)
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{
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struct epitems_head *to_free = head;
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struct hlist_node *p = rcu_dereference(hlist_first_rcu(&head->epitems));
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if (p) {
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struct epitem *epi= container_of(p, struct epitem, fllink);
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spin_lock(&epi->ffd.file->f_lock);
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if (!hlist_empty(&head->epitems))
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to_free = NULL;
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head->next = NULL;
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spin_unlock(&epi->ffd.file->f_lock);
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}
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free_ephead(to_free);
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}
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#ifdef CONFIG_SYSCTL
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#include <linux/sysctl.h>
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static long long_zero;
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static long long_max = LONG_MAX;
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static struct ctl_table epoll_table[] = {
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{
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.procname = "max_user_watches",
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.data = &max_user_watches,
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.maxlen = sizeof(max_user_watches),
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.mode = 0644,
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.proc_handler = proc_doulongvec_minmax,
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.extra1 = &long_zero,
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.extra2 = &long_max,
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},
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{ }
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};
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static void __init epoll_sysctls_init(void)
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{
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register_sysctl("fs/epoll", epoll_table);
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}
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#else
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#define epoll_sysctls_init() do { } while (0)
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#endif /* CONFIG_SYSCTL */
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static const struct file_operations eventpoll_fops;
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static inline int is_file_epoll(struct file *f)
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{
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return f->f_op == &eventpoll_fops;
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}
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/* Setup the structure that is used as key for the RB tree */
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static inline void ep_set_ffd(struct epoll_filefd *ffd,
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struct file *file, int fd)
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{
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ffd->file = file;
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ffd->fd = fd;
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}
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/* Compare RB tree keys */
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static inline int ep_cmp_ffd(struct epoll_filefd *p1,
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struct epoll_filefd *p2)
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{
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return (p1->file > p2->file ? +1:
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(p1->file < p2->file ? -1 : p1->fd - p2->fd));
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}
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/* Tells us if the item is currently linked */
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static inline int ep_is_linked(struct epitem *epi)
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{
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return !list_empty(&epi->rdllink);
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}
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static inline struct eppoll_entry *ep_pwq_from_wait(wait_queue_entry_t *p)
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{
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return container_of(p, struct eppoll_entry, wait);
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}
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/* Get the "struct epitem" from a wait queue pointer */
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static inline struct epitem *ep_item_from_wait(wait_queue_entry_t *p)
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{
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return container_of(p, struct eppoll_entry, wait)->base;
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}
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/**
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* ep_events_available - Checks if ready events might be available.
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*
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* @ep: Pointer to the eventpoll context.
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*
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* Return: a value different than %zero if ready events are available,
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* or %zero otherwise.
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*/
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static inline int ep_events_available(struct eventpoll *ep)
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{
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return !list_empty_careful(&ep->rdllist) ||
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READ_ONCE(ep->ovflist) != EP_UNACTIVE_PTR;
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}
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#ifdef CONFIG_NET_RX_BUSY_POLL
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static bool ep_busy_loop_end(void *p, unsigned long start_time)
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{
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struct eventpoll *ep = p;
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return ep_events_available(ep) || busy_loop_timeout(start_time);
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}
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/*
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* Busy poll if globally on and supporting sockets found && no events,
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* busy loop will return if need_resched or ep_events_available.
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*
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* we must do our busy polling with irqs enabled
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*/
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static bool ep_busy_loop(struct eventpoll *ep, int nonblock)
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{
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unsigned int napi_id = READ_ONCE(ep->napi_id);
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if ((napi_id >= MIN_NAPI_ID) && net_busy_loop_on()) {
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napi_busy_loop(napi_id, nonblock ? NULL : ep_busy_loop_end, ep, false,
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BUSY_POLL_BUDGET);
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if (ep_events_available(ep))
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return true;
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/*
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* Busy poll timed out. Drop NAPI ID for now, we can add
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* it back in when we have moved a socket with a valid NAPI
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* ID onto the ready list.
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*/
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ep->napi_id = 0;
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return false;
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}
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return false;
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}
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/*
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* Set epoll busy poll NAPI ID from sk.
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*/
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static inline void ep_set_busy_poll_napi_id(struct epitem *epi)
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{
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struct eventpoll *ep;
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unsigned int napi_id;
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struct socket *sock;
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struct sock *sk;
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if (!net_busy_loop_on())
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return;
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sock = sock_from_file(epi->ffd.file);
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if (!sock)
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return;
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sk = sock->sk;
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if (!sk)
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return;
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napi_id = READ_ONCE(sk->sk_napi_id);
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ep = epi->ep;
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/* Non-NAPI IDs can be rejected
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* or
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* Nothing to do if we already have this ID
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*/
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if (napi_id < MIN_NAPI_ID || napi_id == ep->napi_id)
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return;
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/* record NAPI ID for use in next busy poll */
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ep->napi_id = napi_id;
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}
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#else
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static inline bool ep_busy_loop(struct eventpoll *ep, int nonblock)
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{
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return false;
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}
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static inline void ep_set_busy_poll_napi_id(struct epitem *epi)
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{
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}
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#endif /* CONFIG_NET_RX_BUSY_POLL */
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/*
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* As described in commit 0ccf831cb lockdep: annotate epoll
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* the use of wait queues used by epoll is done in a very controlled
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* manner. Wake ups can nest inside each other, but are never done
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* with the same locking. For example:
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*
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* dfd = socket(...);
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* efd1 = epoll_create();
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* efd2 = epoll_create();
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* epoll_ctl(efd1, EPOLL_CTL_ADD, dfd, ...);
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* epoll_ctl(efd2, EPOLL_CTL_ADD, efd1, ...);
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*
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* When a packet arrives to the device underneath "dfd", the net code will
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* issue a wake_up() on its poll wake list. Epoll (efd1) has installed a
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* callback wakeup entry on that queue, and the wake_up() performed by the
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* "dfd" net code will end up in ep_poll_callback(). At this point epoll
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* (efd1) notices that it may have some event ready, so it needs to wake up
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* the waiters on its poll wait list (efd2). So it calls ep_poll_safewake()
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* that ends up in another wake_up(), after having checked about the
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* recursion constraints. That are, no more than EP_MAX_POLLWAKE_NESTS, to
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* avoid stack blasting.
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*
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* When CONFIG_DEBUG_LOCK_ALLOC is enabled, make sure lockdep can handle
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* this special case of epoll.
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*/
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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static void ep_poll_safewake(struct eventpoll *ep, struct epitem *epi)
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{
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struct eventpoll *ep_src;
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unsigned long flags;
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|
u8 nests = 0;
|
|
|
|
/*
|
|
* To set the subclass or nesting level for spin_lock_irqsave_nested()
|
|
* it might be natural to create a per-cpu nest count. However, since
|
|
* we can recurse on ep->poll_wait.lock, and a non-raw spinlock can
|
|
* schedule() in the -rt kernel, the per-cpu variable are no longer
|
|
* protected. Thus, we are introducing a per eventpoll nest field.
|
|
* If we are not being call from ep_poll_callback(), epi is NULL and
|
|
* we are at the first level of nesting, 0. Otherwise, we are being
|
|
* called from ep_poll_callback() and if a previous wakeup source is
|
|
* not an epoll file itself, we are at depth 1 since the wakeup source
|
|
* is depth 0. If the wakeup source is a previous epoll file in the
|
|
* wakeup chain then we use its nests value and record ours as
|
|
* nests + 1. The previous epoll file nests value is stable since its
|
|
* already holding its own poll_wait.lock.
|
|
*/
|
|
if (epi) {
|
|
if ((is_file_epoll(epi->ffd.file))) {
|
|
ep_src = epi->ffd.file->private_data;
|
|
nests = ep_src->nests;
|
|
} else {
|
|
nests = 1;
|
|
}
|
|
}
|
|
spin_lock_irqsave_nested(&ep->poll_wait.lock, flags, nests);
|
|
ep->nests = nests + 1;
|
|
wake_up_locked_poll(&ep->poll_wait, EPOLLIN);
|
|
ep->nests = 0;
|
|
spin_unlock_irqrestore(&ep->poll_wait.lock, flags);
|
|
}
|
|
|
|
#else
|
|
|
|
static void ep_poll_safewake(struct eventpoll *ep, struct epitem *epi)
|
|
{
|
|
wake_up_poll(&ep->poll_wait, EPOLLIN);
|
|
}
|
|
|
|
#endif
|
|
|
|
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.
|
|
* If we read NULL we need a barrier paired with
|
|
* smp_store_release() in ep_poll_callback(), otherwise
|
|
* we rely on whead->lock.
|
|
*/
|
|
whead = smp_load_acquire(&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 eppoll_entry **p = &epi->pwqlist;
|
|
struct eppoll_entry *pwq;
|
|
|
|
while ((pwq = *p) != NULL) {
|
|
*p = pwq->next;
|
|
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->mutex needs to be held because we could be hit by
|
|
* eventpoll_release_file() and epoll_ctl().
|
|
*/
|
|
static void ep_start_scan(struct eventpoll *ep, struct list_head *txlist)
|
|
{
|
|
/*
|
|
* 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.
|
|
*/
|
|
lockdep_assert_irqs_enabled();
|
|
write_lock_irq(&ep->lock);
|
|
list_splice_init(&ep->rdllist, txlist);
|
|
WRITE_ONCE(ep->ovflist, NULL);
|
|
write_unlock_irq(&ep->lock);
|
|
}
|
|
|
|
static void ep_done_scan(struct eventpoll *ep,
|
|
struct list_head *txlist)
|
|
{
|
|
struct epitem *epi, *nepi;
|
|
|
|
write_lock_irq(&ep->lock);
|
|
/*
|
|
* 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 = READ_ONCE(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)) {
|
|
/*
|
|
* ->ovflist is LIFO, so we have to reverse it in order
|
|
* to keep in FIFO.
|
|
*/
|
|
list_add(&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.
|
|
*/
|
|
WRITE_ONCE(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)) {
|
|
if (waitqueue_active(&ep->wq))
|
|
wake_up(&ep->wq);
|
|
}
|
|
|
|
write_unlock_irq(&ep->lock);
|
|
}
|
|
|
|
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)
|
|
{
|
|
struct file *file = epi->ffd.file;
|
|
struct epitems_head *to_free;
|
|
struct hlist_head *head;
|
|
|
|
lockdep_assert_irqs_enabled();
|
|
|
|
/*
|
|
* Removes poll wait queue hooks.
|
|
*/
|
|
ep_unregister_pollwait(ep, epi);
|
|
|
|
/* Remove the current item from the list of epoll hooks */
|
|
spin_lock(&file->f_lock);
|
|
to_free = NULL;
|
|
head = file->f_ep;
|
|
if (head->first == &epi->fllink && !epi->fllink.next) {
|
|
file->f_ep = NULL;
|
|
if (!is_file_epoll(file)) {
|
|
struct epitems_head *v;
|
|
v = container_of(head, struct epitems_head, epitems);
|
|
if (!smp_load_acquire(&v->next))
|
|
to_free = v;
|
|
}
|
|
}
|
|
hlist_del_rcu(&epi->fllink);
|
|
spin_unlock(&file->f_lock);
|
|
free_ephead(to_free);
|
|
|
|
rb_erase_cached(&epi->rbn, &ep->rbr);
|
|
|
|
write_lock_irq(&ep->lock);
|
|
if (ep_is_linked(epi))
|
|
list_del_init(&epi->rdllink);
|
|
write_unlock_irq(&ep->lock);
|
|
|
|
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);
|
|
|
|
percpu_counter_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, NULL);
|
|
|
|
/*
|
|
* 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_cached(&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_cached(&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 __poll_t ep_item_poll(const struct epitem *epi, poll_table *pt, int depth);
|
|
|
|
static __poll_t __ep_eventpoll_poll(struct file *file, poll_table *wait, int depth)
|
|
{
|
|
struct eventpoll *ep = file->private_data;
|
|
LIST_HEAD(txlist);
|
|
struct epitem *epi, *tmp;
|
|
poll_table pt;
|
|
__poll_t res = 0;
|
|
|
|
init_poll_funcptr(&pt, NULL);
|
|
|
|
/* 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.
|
|
*/
|
|
mutex_lock_nested(&ep->mtx, depth);
|
|
ep_start_scan(ep, &txlist);
|
|
list_for_each_entry_safe(epi, tmp, &txlist, rdllink) {
|
|
if (ep_item_poll(epi, &pt, depth + 1)) {
|
|
res = EPOLLIN | EPOLLRDNORM;
|
|
break;
|
|
} 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);
|
|
}
|
|
}
|
|
ep_done_scan(ep, &txlist);
|
|
mutex_unlock(&ep->mtx);
|
|
return res;
|
|
}
|
|
|
|
/*
|
|
* Differs from ep_eventpoll_poll() in that internal callers already have
|
|
* the ep->mtx so we need to start from depth=1, such that mutex_lock_nested()
|
|
* is correctly annotated.
|
|
*/
|
|
static __poll_t ep_item_poll(const struct epitem *epi, poll_table *pt,
|
|
int depth)
|
|
{
|
|
struct file *file = epi->ffd.file;
|
|
__poll_t res;
|
|
|
|
pt->_key = epi->event.events;
|
|
if (!is_file_epoll(file))
|
|
res = vfs_poll(file, pt);
|
|
else
|
|
res = __ep_eventpoll_poll(file, pt, depth);
|
|
return res & epi->event.events;
|
|
}
|
|
|
|
static __poll_t ep_eventpoll_poll(struct file *file, poll_table *wait)
|
|
{
|
|
return __ep_eventpoll_poll(file, wait, 0);
|
|
}
|
|
|
|
#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_cached(&ep->rbr); rbp; rbp = rb_next(rbp)) {
|
|
struct epitem *epi = rb_entry(rbp, struct epitem, rbn);
|
|
struct inode *inode = file_inode(epi->ffd.file);
|
|
|
|
seq_printf(m, "tfd: %8d events: %8x data: %16llx "
|
|
" pos:%lli ino:%lx sdev:%x\n",
|
|
epi->ffd.fd, epi->event.events,
|
|
(long long)epi->event.data,
|
|
(long long)epi->ffd.file->f_pos,
|
|
inode->i_ino, inode->i_sb->s_dev);
|
|
if (seq_has_overflowed(m))
|
|
break;
|
|
}
|
|
mutex_unlock(&ep->mtx);
|
|
}
|
|
#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;
|
|
struct hlist_node *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);
|
|
if (unlikely(!file->f_ep)) {
|
|
mutex_unlock(&epmutex);
|
|
return;
|
|
}
|
|
hlist_for_each_entry_safe(epi, next, file->f_ep, 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;
|
|
|
|
mutex_init(&ep->mtx);
|
|
rwlock_init(&ep->lock);
|
|
init_waitqueue_head(&ep->wq);
|
|
init_waitqueue_head(&ep->poll_wait);
|
|
INIT_LIST_HEAD(&ep->rdllist);
|
|
ep->rbr = RB_ROOT_CACHED;
|
|
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_root.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;
|
|
}
|
|
|
|
#ifdef CONFIG_KCMP
|
|
static struct epitem *ep_find_tfd(struct eventpoll *ep, int tfd, unsigned long toff)
|
|
{
|
|
struct rb_node *rbp;
|
|
struct epitem *epi;
|
|
|
|
for (rbp = rb_first_cached(&ep->rbr); rbp; rbp = rb_next(rbp)) {
|
|
epi = rb_entry(rbp, struct epitem, rbn);
|
|
if (epi->ffd.fd == tfd) {
|
|
if (toff == 0)
|
|
return epi;
|
|
else
|
|
toff--;
|
|
}
|
|
cond_resched();
|
|
}
|
|
|
|
return NULL;
|
|
}
|
|
|
|
struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd,
|
|
unsigned long toff)
|
|
{
|
|
struct file *file_raw;
|
|
struct eventpoll *ep;
|
|
struct epitem *epi;
|
|
|
|
if (!is_file_epoll(file))
|
|
return ERR_PTR(-EINVAL);
|
|
|
|
ep = file->private_data;
|
|
|
|
mutex_lock(&ep->mtx);
|
|
epi = ep_find_tfd(ep, tfd, toff);
|
|
if (epi)
|
|
file_raw = epi->ffd.file;
|
|
else
|
|
file_raw = ERR_PTR(-ENOENT);
|
|
mutex_unlock(&ep->mtx);
|
|
|
|
return file_raw;
|
|
}
|
|
#endif /* CONFIG_KCMP */
|
|
|
|
/*
|
|
* Adds a new entry to the tail of the list in a lockless way, i.e.
|
|
* multiple CPUs are allowed to call this function concurrently.
|
|
*
|
|
* Beware: it is necessary to prevent any other modifications of the
|
|
* existing list until all changes are completed, in other words
|
|
* concurrent list_add_tail_lockless() calls should be protected
|
|
* with a read lock, where write lock acts as a barrier which
|
|
* makes sure all list_add_tail_lockless() calls are fully
|
|
* completed.
|
|
*
|
|
* Also an element can be locklessly added to the list only in one
|
|
* direction i.e. either to the tail or to the head, otherwise
|
|
* concurrent access will corrupt the list.
|
|
*
|
|
* Return: %false if element has been already added to the list, %true
|
|
* otherwise.
|
|
*/
|
|
static inline bool list_add_tail_lockless(struct list_head *new,
|
|
struct list_head *head)
|
|
{
|
|
struct list_head *prev;
|
|
|
|
/*
|
|
* This is simple 'new->next = head' operation, but cmpxchg()
|
|
* is used in order to detect that same element has been just
|
|
* added to the list from another CPU: the winner observes
|
|
* new->next == new.
|
|
*/
|
|
if (!try_cmpxchg(&new->next, &new, head))
|
|
return false;
|
|
|
|
/*
|
|
* Initially ->next of a new element must be updated with the head
|
|
* (we are inserting to the tail) and only then pointers are atomically
|
|
* exchanged. XCHG guarantees memory ordering, thus ->next should be
|
|
* updated before pointers are actually swapped and pointers are
|
|
* swapped before prev->next is updated.
|
|
*/
|
|
|
|
prev = xchg(&head->prev, new);
|
|
|
|
/*
|
|
* It is safe to modify prev->next and new->prev, because a new element
|
|
* is added only to the tail and new->next is updated before XCHG.
|
|
*/
|
|
|
|
prev->next = new;
|
|
new->prev = prev;
|
|
|
|
return true;
|
|
}
|
|
|
|
/*
|
|
* Chains a new epi entry to the tail of the ep->ovflist in a lockless way,
|
|
* i.e. multiple CPUs are allowed to call this function concurrently.
|
|
*
|
|
* Return: %false if epi element has been already chained, %true otherwise.
|
|
*/
|
|
static inline bool chain_epi_lockless(struct epitem *epi)
|
|
{
|
|
struct eventpoll *ep = epi->ep;
|
|
|
|
/* Fast preliminary check */
|
|
if (epi->next != EP_UNACTIVE_PTR)
|
|
return false;
|
|
|
|
/* Check that the same epi has not been just chained from another CPU */
|
|
if (cmpxchg(&epi->next, EP_UNACTIVE_PTR, NULL) != EP_UNACTIVE_PTR)
|
|
return false;
|
|
|
|
/* Atomically exchange tail */
|
|
epi->next = xchg(&ep->ovflist, epi);
|
|
|
|
return true;
|
|
}
|
|
|
|
/*
|
|
* 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.
|
|
*
|
|
* This callback takes a read lock in order not to contend with concurrent
|
|
* events from another file descriptor, thus all modifications to ->rdllist
|
|
* or ->ovflist are lockless. Read lock is paired with the write lock from
|
|
* ep_scan_ready_list(), which stops all list modifications and guarantees
|
|
* that lists state is seen correctly.
|
|
*
|
|
* Another thing worth to mention is that ep_poll_callback() can be called
|
|
* concurrently for the same @epi from different CPUs if poll table was inited
|
|
* with several wait queues entries. Plural wakeup from different CPUs of a
|
|
* single wait queue is serialized by wq.lock, but the case when multiple wait
|
|
* queues are used should be detected accordingly. This is detected using
|
|
* cmpxchg() operation.
|
|
*/
|
|
static int ep_poll_callback(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
|
|
{
|
|
int pwake = 0;
|
|
struct epitem *epi = ep_item_from_wait(wait);
|
|
struct eventpoll *ep = epi->ep;
|
|
__poll_t pollflags = key_to_poll(key);
|
|
unsigned long flags;
|
|
int ewake = 0;
|
|
|
|
read_lock_irqsave(&ep->lock, flags);
|
|
|
|
ep_set_busy_poll_napi_id(epi);
|
|
|
|
/*
|
|
* 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 (pollflags && !(pollflags & 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 (READ_ONCE(ep->ovflist) != EP_UNACTIVE_PTR) {
|
|
if (chain_epi_lockless(epi))
|
|
ep_pm_stay_awake_rcu(epi);
|
|
} else if (!ep_is_linked(epi)) {
|
|
/* In the usual case, add event to ready list. */
|
|
if (list_add_tail_lockless(&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) &&
|
|
!(pollflags & POLLFREE)) {
|
|
switch (pollflags & EPOLLINOUT_BITS) {
|
|
case EPOLLIN:
|
|
if (epi->event.events & EPOLLIN)
|
|
ewake = 1;
|
|
break;
|
|
case EPOLLOUT:
|
|
if (epi->event.events & EPOLLOUT)
|
|
ewake = 1;
|
|
break;
|
|
case 0:
|
|
ewake = 1;
|
|
break;
|
|
}
|
|
}
|
|
wake_up(&ep->wq);
|
|
}
|
|
if (waitqueue_active(&ep->poll_wait))
|
|
pwake++;
|
|
|
|
out_unlock:
|
|
read_unlock_irqrestore(&ep->lock, flags);
|
|
|
|
/* We have to call this outside the lock */
|
|
if (pwake)
|
|
ep_poll_safewake(ep, epi);
|
|
|
|
if (!(epi->event.events & EPOLLEXCLUSIVE))
|
|
ewake = 1;
|
|
|
|
if (pollflags & POLLFREE) {
|
|
/*
|
|
* If we race with ep_remove_wait_queue() it can miss
|
|
* ->whead = NULL and do another remove_wait_queue() after
|
|
* us, so we can't use __remove_wait_queue().
|
|
*/
|
|
list_del_init(&wait->entry);
|
|
/*
|
|
* ->whead != NULL protects us from the race with ep_free()
|
|
* or ep_remove(), ep_remove_wait_queue() takes whead->lock
|
|
* held by the caller. Once we nullify it, nothing protects
|
|
* ep/epi or even wait.
|
|
*/
|
|
smp_store_release(&ep_pwq_from_wait(wait)->whead, NULL);
|
|
}
|
|
|
|
return ewake;
|
|
}
|
|
|
|
/*
|
|
* 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 ep_pqueue *epq = container_of(pt, struct ep_pqueue, pt);
|
|
struct epitem *epi = epq->epi;
|
|
struct eppoll_entry *pwq;
|
|
|
|
if (unlikely(!epi)) // an earlier allocation has failed
|
|
return;
|
|
|
|
pwq = kmem_cache_alloc(pwq_cache, GFP_KERNEL);
|
|
if (unlikely(!pwq)) {
|
|
epq->epi = NULL;
|
|
return;
|
|
}
|
|
|
|
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);
|
|
pwq->next = epi->pwqlist;
|
|
epi->pwqlist = pwq;
|
|
}
|
|
|
|
static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi)
|
|
{
|
|
int kcmp;
|
|
struct rb_node **p = &ep->rbr.rb_root.rb_node, *parent = NULL;
|
|
struct epitem *epic;
|
|
bool leftmost = true;
|
|
|
|
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;
|
|
leftmost = false;
|
|
} else
|
|
p = &parent->rb_left;
|
|
}
|
|
rb_link_node(&epi->rbn, parent, p);
|
|
rb_insert_color_cached(&epi->rbn, &ep->rbr, leftmost);
|
|
}
|
|
|
|
|
|
|
|
#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(struct hlist_head *refs, int depth)
|
|
{
|
|
int error = 0;
|
|
struct epitem *epi;
|
|
|
|
if (depth > EP_MAX_NESTS) /* too deep nesting */
|
|
return -1;
|
|
|
|
/* CTL_DEL can remove links here, but that can't increase our count */
|
|
hlist_for_each_entry_rcu(epi, refs, fllink) {
|
|
struct hlist_head *refs = &epi->ep->refs;
|
|
if (hlist_empty(refs))
|
|
error = path_count_inc(depth);
|
|
else
|
|
error = reverse_path_check_proc(refs, depth + 1);
|
|
if (error != 0)
|
|
break;
|
|
}
|
|
return error;
|
|
}
|
|
|
|
/**
|
|
* reverse_path_check - The tfile_check_list is list of epitem_head, 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.
|
|
*
|
|
* Return: %zero if the proposed links don't create too many paths,
|
|
* %-1 otherwise.
|
|
*/
|
|
static int reverse_path_check(void)
|
|
{
|
|
struct epitems_head *p;
|
|
|
|
for (p = tfile_check_list; p != EP_UNACTIVE_PTR; p = p->next) {
|
|
int error;
|
|
path_count_init();
|
|
rcu_read_lock();
|
|
error = reverse_path_check_proc(&p->epitems, 0);
|
|
rcu_read_unlock();
|
|
if (error)
|
|
return error;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static int ep_create_wakeup_source(struct epitem *epi)
|
|
{
|
|
struct name_snapshot n;
|
|
struct wakeup_source *ws;
|
|
|
|
if (!epi->ep->ws) {
|
|
epi->ep->ws = wakeup_source_register(NULL, "eventpoll");
|
|
if (!epi->ep->ws)
|
|
return -ENOMEM;
|
|
}
|
|
|
|
take_dentry_name_snapshot(&n, epi->ffd.file->f_path.dentry);
|
|
ws = wakeup_source_register(NULL, n.name.name);
|
|
release_dentry_name_snapshot(&n);
|
|
|
|
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);
|
|
}
|
|
|
|
static int attach_epitem(struct file *file, struct epitem *epi)
|
|
{
|
|
struct epitems_head *to_free = NULL;
|
|
struct hlist_head *head = NULL;
|
|
struct eventpoll *ep = NULL;
|
|
|
|
if (is_file_epoll(file))
|
|
ep = file->private_data;
|
|
|
|
if (ep) {
|
|
head = &ep->refs;
|
|
} else if (!READ_ONCE(file->f_ep)) {
|
|
allocate:
|
|
to_free = kmem_cache_zalloc(ephead_cache, GFP_KERNEL);
|
|
if (!to_free)
|
|
return -ENOMEM;
|
|
head = &to_free->epitems;
|
|
}
|
|
spin_lock(&file->f_lock);
|
|
if (!file->f_ep) {
|
|
if (unlikely(!head)) {
|
|
spin_unlock(&file->f_lock);
|
|
goto allocate;
|
|
}
|
|
file->f_ep = head;
|
|
to_free = NULL;
|
|
}
|
|
hlist_add_head_rcu(&epi->fllink, file->f_ep);
|
|
spin_unlock(&file->f_lock);
|
|
free_ephead(to_free);
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Must be called with "mtx" held.
|
|
*/
|
|
static int ep_insert(struct eventpoll *ep, const struct epoll_event *event,
|
|
struct file *tfile, int fd, int full_check)
|
|
{
|
|
int error, pwake = 0;
|
|
__poll_t revents;
|
|
struct epitem *epi;
|
|
struct ep_pqueue epq;
|
|
struct eventpoll *tep = NULL;
|
|
|
|
if (is_file_epoll(tfile))
|
|
tep = tfile->private_data;
|
|
|
|
lockdep_assert_irqs_enabled();
|
|
|
|
if (unlikely(percpu_counter_compare(&ep->user->epoll_watches,
|
|
max_user_watches) >= 0))
|
|
return -ENOSPC;
|
|
percpu_counter_inc(&ep->user->epoll_watches);
|
|
|
|
if (!(epi = kmem_cache_zalloc(epi_cache, GFP_KERNEL))) {
|
|
percpu_counter_dec(&ep->user->epoll_watches);
|
|
return -ENOMEM;
|
|
}
|
|
|
|
/* Item initialization follow here ... */
|
|
INIT_LIST_HEAD(&epi->rdllink);
|
|
epi->ep = ep;
|
|
ep_set_ffd(&epi->ffd, tfile, fd);
|
|
epi->event = *event;
|
|
epi->next = EP_UNACTIVE_PTR;
|
|
|
|
if (tep)
|
|
mutex_lock_nested(&tep->mtx, 1);
|
|
/* Add the current item to the list of active epoll hook for this file */
|
|
if (unlikely(attach_epitem(tfile, epi) < 0)) {
|
|
if (tep)
|
|
mutex_unlock(&tep->mtx);
|
|
kmem_cache_free(epi_cache, epi);
|
|
percpu_counter_dec(&ep->user->epoll_watches);
|
|
return -ENOMEM;
|
|
}
|
|
|
|
if (full_check && !tep)
|
|
list_file(tfile);
|
|
|
|
/*
|
|
* 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);
|
|
if (tep)
|
|
mutex_unlock(&tep->mtx);
|
|
|
|
/* now check if we've created too many backpaths */
|
|
if (unlikely(full_check && reverse_path_check())) {
|
|
ep_remove(ep, epi);
|
|
return -EINVAL;
|
|
}
|
|
|
|
if (epi->event.events & EPOLLWAKEUP) {
|
|
error = ep_create_wakeup_source(epi);
|
|
if (error) {
|
|
ep_remove(ep, epi);
|
|
return error;
|
|
}
|
|
}
|
|
|
|
/* 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, 1);
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
if (unlikely(!epq.epi)) {
|
|
ep_remove(ep, epi);
|
|
return -ENOMEM;
|
|
}
|
|
|
|
/* We have to drop the new item inside our item list to keep track of it */
|
|
write_lock_irq(&ep->lock);
|
|
|
|
/* record NAPI ID of new item if present */
|
|
ep_set_busy_poll_napi_id(epi);
|
|
|
|
/* If the file is already "ready" we drop it inside the ready list */
|
|
if (revents && !ep_is_linked(epi)) {
|
|
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(&ep->wq);
|
|
if (waitqueue_active(&ep->poll_wait))
|
|
pwake++;
|
|
}
|
|
|
|
write_unlock_irq(&ep->lock);
|
|
|
|
/* We have to call this outside the lock */
|
|
if (pwake)
|
|
ep_poll_safewake(ep, NULL);
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* 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,
|
|
const struct epoll_event *event)
|
|
{
|
|
int pwake = 0;
|
|
poll_table pt;
|
|
|
|
lockdep_assert_irqs_enabled();
|
|
|
|
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.
|
|
* If the item is "hot" and it is not registered inside the ready
|
|
* list, push it inside.
|
|
*/
|
|
if (ep_item_poll(epi, &pt, 1)) {
|
|
write_lock_irq(&ep->lock);
|
|
if (!ep_is_linked(epi)) {
|
|
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(&ep->wq);
|
|
if (waitqueue_active(&ep->poll_wait))
|
|
pwake++;
|
|
}
|
|
write_unlock_irq(&ep->lock);
|
|
}
|
|
|
|
/* We have to call this outside the lock */
|
|
if (pwake)
|
|
ep_poll_safewake(ep, NULL);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int ep_send_events(struct eventpoll *ep,
|
|
struct epoll_event __user *events, int maxevents)
|
|
{
|
|
struct epitem *epi, *tmp;
|
|
LIST_HEAD(txlist);
|
|
poll_table pt;
|
|
int res = 0;
|
|
|
|
/*
|
|
* Always short-circuit for fatal signals to allow threads to make a
|
|
* timely exit without the chance of finding more events available and
|
|
* fetching repeatedly.
|
|
*/
|
|
if (fatal_signal_pending(current))
|
|
return -EINTR;
|
|
|
|
init_poll_funcptr(&pt, NULL);
|
|
|
|
mutex_lock(&ep->mtx);
|
|
ep_start_scan(ep, &txlist);
|
|
|
|
/*
|
|
* We can loop without lock because we are passed a task private list.
|
|
* Items cannot vanish during the loop we are holding ep->mtx.
|
|
*/
|
|
list_for_each_entry_safe(epi, tmp, &txlist, rdllink) {
|
|
struct wakeup_source *ws;
|
|
__poll_t revents;
|
|
|
|
if (res >= maxevents)
|
|
break;
|
|
|
|
/*
|
|
* 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);
|
|
|
|
/*
|
|
* If the event mask intersect the caller-requested one,
|
|
* deliver the event to userspace. Again, we are holding ep->mtx,
|
|
* so no operations coming from userspace can change the item.
|
|
*/
|
|
revents = ep_item_poll(epi, &pt, 1);
|
|
if (!revents)
|
|
continue;
|
|
|
|
events = epoll_put_uevent(revents, epi->event.data, events);
|
|
if (!events) {
|
|
list_add(&epi->rdllink, &txlist);
|
|
ep_pm_stay_awake(epi);
|
|
if (!res)
|
|
res = -EFAULT;
|
|
break;
|
|
}
|
|
res++;
|
|
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);
|
|
}
|
|
}
|
|
ep_done_scan(ep, &txlist);
|
|
mutex_unlock(&ep->mtx);
|
|
|
|
return res;
|
|
}
|
|
|
|
static struct timespec64 *ep_timeout_to_timespec(struct timespec64 *to, long ms)
|
|
{
|
|
struct timespec64 now;
|
|
|
|
if (ms < 0)
|
|
return NULL;
|
|
|
|
if (!ms) {
|
|
to->tv_sec = 0;
|
|
to->tv_nsec = 0;
|
|
return to;
|
|
}
|
|
|
|
to->tv_sec = ms / MSEC_PER_SEC;
|
|
to->tv_nsec = NSEC_PER_MSEC * (ms % MSEC_PER_SEC);
|
|
|
|
ktime_get_ts64(&now);
|
|
*to = timespec64_add_safe(now, *to);
|
|
return to;
|
|
}
|
|
|
|
/*
|
|
* autoremove_wake_function, but remove even on failure to wake up, because we
|
|
* know that default_wake_function/ttwu will only fail if the thread is already
|
|
* woken, and in that case the ep_poll loop will remove the entry anyways, not
|
|
* try to reuse it.
|
|
*/
|
|
static int ep_autoremove_wake_function(struct wait_queue_entry *wq_entry,
|
|
unsigned int mode, int sync, void *key)
|
|
{
|
|
int ret = default_wake_function(wq_entry, mode, sync, key);
|
|
|
|
list_del_init(&wq_entry->entry);
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* 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
|
|
* timespec. If the timeout is zero, the function will not block,
|
|
* while if the @timeout ptr is NULL, the function will block
|
|
* until at least one event has been retrieved (or an error
|
|
* occurred).
|
|
*
|
|
* Return: 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, struct timespec64 *timeout)
|
|
{
|
|
int res, eavail, timed_out = 0;
|
|
u64 slack = 0;
|
|
wait_queue_entry_t wait;
|
|
ktime_t expires, *to = NULL;
|
|
|
|
lockdep_assert_irqs_enabled();
|
|
|
|
if (timeout && (timeout->tv_sec | timeout->tv_nsec)) {
|
|
slack = select_estimate_accuracy(timeout);
|
|
to = &expires;
|
|
*to = timespec64_to_ktime(*timeout);
|
|
} else if (timeout) {
|
|
/*
|
|
* Avoid the unnecessary trip to the wait queue loop, if the
|
|
* caller specified a non blocking operation.
|
|
*/
|
|
timed_out = 1;
|
|
}
|
|
|
|
/*
|
|
* This call is racy: We may or may not see events that are being added
|
|
* to the ready list under the lock (e.g., in IRQ callbacks). For cases
|
|
* with a non-zero timeout, this thread will check the ready list under
|
|
* lock and will add to the wait queue. For cases with a zero
|
|
* timeout, the user by definition should not care and will have to
|
|
* recheck again.
|
|
*/
|
|
eavail = ep_events_available(ep);
|
|
|
|
while (1) {
|
|
if (eavail) {
|
|
/*
|
|
* 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.
|
|
*/
|
|
res = ep_send_events(ep, events, maxevents);
|
|
if (res)
|
|
return res;
|
|
}
|
|
|
|
if (timed_out)
|
|
return 0;
|
|
|
|
eavail = ep_busy_loop(ep, timed_out);
|
|
if (eavail)
|
|
continue;
|
|
|
|
if (signal_pending(current))
|
|
return -EINTR;
|
|
|
|
/*
|
|
* Internally init_wait() uses autoremove_wake_function(),
|
|
* thus wait entry is removed from the wait queue on each
|
|
* wakeup. Why it is important? In case of several waiters
|
|
* each new wakeup will hit the next waiter, giving it the
|
|
* chance to harvest new event. Otherwise wakeup can be
|
|
* lost. This is also good performance-wise, because on
|
|
* normal wakeup path no need to call __remove_wait_queue()
|
|
* explicitly, thus ep->lock is not taken, which halts the
|
|
* event delivery.
|
|
*
|
|
* In fact, we now use an even more aggressive function that
|
|
* unconditionally removes, because we don't reuse the wait
|
|
* entry between loop iterations. This lets us also avoid the
|
|
* performance issue if a process is killed, causing all of its
|
|
* threads to wake up without being removed normally.
|
|
*/
|
|
init_wait(&wait);
|
|
wait.func = ep_autoremove_wake_function;
|
|
|
|
write_lock_irq(&ep->lock);
|
|
/*
|
|
* Barrierless variant, waitqueue_active() is called under
|
|
* the same lock on wakeup ep_poll_callback() side, so it
|
|
* is safe to avoid an explicit barrier.
|
|
*/
|
|
__set_current_state(TASK_INTERRUPTIBLE);
|
|
|
|
/*
|
|
* Do the final check under the lock. ep_scan_ready_list()
|
|
* plays with two lists (->rdllist and ->ovflist) and there
|
|
* is always a race when both lists are empty for short
|
|
* period of time although events are pending, so lock is
|
|
* important.
|
|
*/
|
|
eavail = ep_events_available(ep);
|
|
if (!eavail)
|
|
__add_wait_queue_exclusive(&ep->wq, &wait);
|
|
|
|
write_unlock_irq(&ep->lock);
|
|
|
|
if (!eavail)
|
|
timed_out = !schedule_hrtimeout_range(to, slack,
|
|
HRTIMER_MODE_ABS);
|
|
__set_current_state(TASK_RUNNING);
|
|
|
|
/*
|
|
* We were woken up, thus go and try to harvest some events.
|
|
* If timed out and still on the wait queue, recheck eavail
|
|
* carefully under lock, below.
|
|
*/
|
|
eavail = 1;
|
|
|
|
if (!list_empty_careful(&wait.entry)) {
|
|
write_lock_irq(&ep->lock);
|
|
/*
|
|
* If the thread timed out and is not on the wait queue,
|
|
* it means that the thread was woken up after its
|
|
* timeout expired before it could reacquire the lock.
|
|
* Thus, when wait.entry is empty, it needs to harvest
|
|
* events.
|
|
*/
|
|
if (timed_out)
|
|
eavail = list_empty(&wait.entry);
|
|
__remove_wait_queue(&ep->wq, &wait);
|
|
write_unlock_irq(&ep->lock);
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* ep_loop_check_proc - 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).
|
|
*
|
|
* @ep: the &struct eventpoll to be currently checked.
|
|
* @depth: Current depth of the path being checked.
|
|
*
|
|
* Return: %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(struct eventpoll *ep, int depth)
|
|
{
|
|
int error = 0;
|
|
struct rb_node *rbp;
|
|
struct epitem *epi;
|
|
|
|
mutex_lock_nested(&ep->mtx, depth + 1);
|
|
ep->gen = loop_check_gen;
|
|
for (rbp = rb_first_cached(&ep->rbr); rbp; rbp = rb_next(rbp)) {
|
|
epi = rb_entry(rbp, struct epitem, rbn);
|
|
if (unlikely(is_file_epoll(epi->ffd.file))) {
|
|
struct eventpoll *ep_tovisit;
|
|
ep_tovisit = epi->ffd.file->private_data;
|
|
if (ep_tovisit->gen == loop_check_gen)
|
|
continue;
|
|
if (ep_tovisit == inserting_into || depth > EP_MAX_NESTS)
|
|
error = -1;
|
|
else
|
|
error = ep_loop_check_proc(ep_tovisit, depth + 1);
|
|
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().
|
|
*/
|
|
list_file(epi->ffd.file);
|
|
}
|
|
}
|
|
mutex_unlock(&ep->mtx);
|
|
|
|
return error;
|
|
}
|
|
|
|
/**
|
|
* ep_loop_check - Performs a check to verify that adding an epoll file (@to)
|
|
* into another epoll file (represented by @ep) does not create
|
|
* closed loops or too deep chains.
|
|
*
|
|
* @ep: Pointer to the epoll we are inserting into.
|
|
* @to: Pointer to the epoll to be inserted.
|
|
*
|
|
* Return: %zero if adding the epoll @to inside the epoll @from
|
|
* does not violate the constraints, or %-1 otherwise.
|
|
*/
|
|
static int ep_loop_check(struct eventpoll *ep, struct eventpoll *to)
|
|
{
|
|
inserting_into = ep;
|
|
return ep_loop_check_proc(to, 0);
|
|
}
|
|
|
|
static void clear_tfile_check_list(void)
|
|
{
|
|
rcu_read_lock();
|
|
while (tfile_check_list != EP_UNACTIVE_PTR) {
|
|
struct epitems_head *head = tfile_check_list;
|
|
tfile_check_list = head->next;
|
|
unlist_file(head);
|
|
}
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
/*
|
|
* Open an eventpoll file descriptor.
|
|
*/
|
|
static int do_epoll_create(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_create1, int, flags)
|
|
{
|
|
return do_epoll_create(flags);
|
|
}
|
|
|
|
SYSCALL_DEFINE1(epoll_create, int, size)
|
|
{
|
|
if (size <= 0)
|
|
return -EINVAL;
|
|
|
|
return do_epoll_create(0);
|
|
}
|
|
|
|
static inline int epoll_mutex_lock(struct mutex *mutex, int depth,
|
|
bool nonblock)
|
|
{
|
|
if (!nonblock) {
|
|
mutex_lock_nested(mutex, depth);
|
|
return 0;
|
|
}
|
|
if (mutex_trylock(mutex))
|
|
return 0;
|
|
return -EAGAIN;
|
|
}
|
|
|
|
int do_epoll_ctl(int epfd, int op, int fd, struct epoll_event *epds,
|
|
bool nonblock)
|
|
{
|
|
int error;
|
|
int full_check = 0;
|
|
struct fd f, tf;
|
|
struct eventpoll *ep;
|
|
struct epitem *epi;
|
|
struct eventpoll *tep = NULL;
|
|
|
|
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 (!file_can_poll(tf.file))
|
|
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 chance 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.
|
|
*/
|
|
error = epoll_mutex_lock(&ep->mtx, 0, nonblock);
|
|
if (error)
|
|
goto error_tgt_fput;
|
|
if (op == EPOLL_CTL_ADD) {
|
|
if (READ_ONCE(f.file->f_ep) || ep->gen == loop_check_gen ||
|
|
is_file_epoll(tf.file)) {
|
|
mutex_unlock(&ep->mtx);
|
|
error = epoll_mutex_lock(&epmutex, 0, nonblock);
|
|
if (error)
|
|
goto error_tgt_fput;
|
|
loop_check_gen++;
|
|
full_check = 1;
|
|
if (is_file_epoll(tf.file)) {
|
|
tep = tf.file->private_data;
|
|
error = -ELOOP;
|
|
if (ep_loop_check(ep, tep) != 0)
|
|
goto error_tgt_fput;
|
|
}
|
|
error = epoll_mutex_lock(&ep->mtx, 0, nonblock);
|
|
if (error)
|
|
goto error_tgt_fput;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* 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 |= EPOLLERR | EPOLLHUP;
|
|
error = ep_insert(ep, epds, tf.file, fd, full_check);
|
|
} else
|
|
error = -EEXIST;
|
|
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 |= EPOLLERR | EPOLLHUP;
|
|
error = ep_modify(ep, epi, epds);
|
|
}
|
|
} else
|
|
error = -ENOENT;
|
|
break;
|
|
}
|
|
mutex_unlock(&ep->mtx);
|
|
|
|
error_tgt_fput:
|
|
if (full_check) {
|
|
clear_tfile_check_list();
|
|
loop_check_gen++;
|
|
mutex_unlock(&epmutex);
|
|
}
|
|
|
|
fdput(tf);
|
|
error_fput:
|
|
fdput(f);
|
|
error_return:
|
|
|
|
return error;
|
|
}
|
|
|
|
/*
|
|
* 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)
|
|
{
|
|
struct epoll_event epds;
|
|
|
|
if (ep_op_has_event(op) &&
|
|
copy_from_user(&epds, event, sizeof(struct epoll_event)))
|
|
return -EFAULT;
|
|
|
|
return do_epoll_ctl(epfd, op, fd, &epds, false);
|
|
}
|
|
|
|
/*
|
|
* Implement the event wait interface for the eventpoll file. It is the kernel
|
|
* part of the user space epoll_wait(2).
|
|
*/
|
|
static int do_epoll_wait(int epfd, struct epoll_event __user *events,
|
|
int maxevents, struct timespec64 *to)
|
|
{
|
|
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(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, to);
|
|
|
|
error_fput:
|
|
fdput(f);
|
|
return error;
|
|
}
|
|
|
|
SYSCALL_DEFINE4(epoll_wait, int, epfd, struct epoll_event __user *, events,
|
|
int, maxevents, int, timeout)
|
|
{
|
|
struct timespec64 to;
|
|
|
|
return do_epoll_wait(epfd, events, maxevents,
|
|
ep_timeout_to_timespec(&to, timeout));
|
|
}
|
|
|
|
/*
|
|
* Implement the event wait interface for the eventpoll file. It is the kernel
|
|
* part of the user space epoll_pwait(2).
|
|
*/
|
|
static int do_epoll_pwait(int epfd, struct epoll_event __user *events,
|
|
int maxevents, struct timespec64 *to,
|
|
const sigset_t __user *sigmask, size_t sigsetsize)
|
|
{
|
|
int error;
|
|
|
|
/*
|
|
* If the caller wants a certain signal mask to be set during the wait,
|
|
* we apply it here.
|
|
*/
|
|
error = set_user_sigmask(sigmask, sigsetsize);
|
|
if (error)
|
|
return error;
|
|
|
|
error = do_epoll_wait(epfd, events, maxevents, to);
|
|
|
|
restore_saved_sigmask_unless(error == -EINTR);
|
|
|
|
return error;
|
|
}
|
|
|
|
SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events,
|
|
int, maxevents, int, timeout, const sigset_t __user *, sigmask,
|
|
size_t, sigsetsize)
|
|
{
|
|
struct timespec64 to;
|
|
|
|
return do_epoll_pwait(epfd, events, maxevents,
|
|
ep_timeout_to_timespec(&to, timeout),
|
|
sigmask, sigsetsize);
|
|
}
|
|
|
|
SYSCALL_DEFINE6(epoll_pwait2, int, epfd, struct epoll_event __user *, events,
|
|
int, maxevents, const struct __kernel_timespec __user *, timeout,
|
|
const sigset_t __user *, sigmask, size_t, sigsetsize)
|
|
{
|
|
struct timespec64 ts, *to = NULL;
|
|
|
|
if (timeout) {
|
|
if (get_timespec64(&ts, timeout))
|
|
return -EFAULT;
|
|
to = &ts;
|
|
if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
|
|
return -EINVAL;
|
|
}
|
|
|
|
return do_epoll_pwait(epfd, events, maxevents, to,
|
|
sigmask, sigsetsize);
|
|
}
|
|
|
|
#ifdef CONFIG_COMPAT
|
|
static int do_compat_epoll_pwait(int epfd, struct epoll_event __user *events,
|
|
int maxevents, struct timespec64 *timeout,
|
|
const compat_sigset_t __user *sigmask,
|
|
compat_size_t sigsetsize)
|
|
{
|
|
long err;
|
|
|
|
/*
|
|
* If the caller wants a certain signal mask to be set during the wait,
|
|
* we apply it here.
|
|
*/
|
|
err = set_compat_user_sigmask(sigmask, sigsetsize);
|
|
if (err)
|
|
return err;
|
|
|
|
err = do_epoll_wait(epfd, events, maxevents, timeout);
|
|
|
|
restore_saved_sigmask_unless(err == -EINTR);
|
|
|
|
return err;
|
|
}
|
|
|
|
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)
|
|
{
|
|
struct timespec64 to;
|
|
|
|
return do_compat_epoll_pwait(epfd, events, maxevents,
|
|
ep_timeout_to_timespec(&to, timeout),
|
|
sigmask, sigsetsize);
|
|
}
|
|
|
|
COMPAT_SYSCALL_DEFINE6(epoll_pwait2, int, epfd,
|
|
struct epoll_event __user *, events,
|
|
int, maxevents,
|
|
const struct __kernel_timespec __user *, timeout,
|
|
const compat_sigset_t __user *, sigmask,
|
|
compat_size_t, sigsetsize)
|
|
{
|
|
struct timespec64 ts, *to = NULL;
|
|
|
|
if (timeout) {
|
|
if (get_timespec64(&ts, timeout))
|
|
return -EFAULT;
|
|
to = &ts;
|
|
if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
|
|
return -EINVAL;
|
|
}
|
|
|
|
return do_compat_epoll_pwait(epfd, events, maxevents, to,
|
|
sigmask, sigsetsize);
|
|
}
|
|
|
|
#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);
|
|
|
|
/*
|
|
* 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|SLAB_ACCOUNT, NULL);
|
|
|
|
/* Allocates slab cache used to allocate "struct eppoll_entry" */
|
|
pwq_cache = kmem_cache_create("eventpoll_pwq",
|
|
sizeof(struct eppoll_entry), 0, SLAB_PANIC|SLAB_ACCOUNT, NULL);
|
|
epoll_sysctls_init();
|
|
|
|
ephead_cache = kmem_cache_create("ep_head",
|
|
sizeof(struct epitems_head), 0, SLAB_PANIC|SLAB_ACCOUNT, NULL);
|
|
|
|
return 0;
|
|
}
|
|
fs_initcall(eventpoll_init);
|