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2387 lines
64 KiB
2387 lines
64 KiB
// 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 <[email protected]> |
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*/ |
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|
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#include <linux/init.h> |
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#include <linux/kernel.h> |
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#include <linux/sched/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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/* |
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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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|
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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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|
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#define EPOLLINOUT_BITS (EPOLLIN | EPOLLOUT) |
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|
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#define EPOLLEXCLUSIVE_OK_BITS (EPOLLINOUT_BITS | EPOLLERR | EPOLLHUP | \ |
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EPOLLWAKEUP | EPOLLET | EPOLLEXCLUSIVE) |
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|
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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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|
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#define EP_MAX_EVENTS (INT_MAX / sizeof(struct epoll_event)) |
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|
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#define EP_UNACTIVE_PTR ((void *) -1L) |
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|
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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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|
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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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|
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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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/* |
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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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|
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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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|
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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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/* |
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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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|
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/* The file descriptor information this item refers to */ |
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struct epoll_filefd ffd; |
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|
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/* List containing poll wait queues */ |
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struct eppoll_entry *pwqlist; |
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|
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/* The "container" of this item */ |
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struct eventpoll *ep; |
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|
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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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|
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/* wakeup_source used when EPOLLWAKEUP is set */ |
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struct wakeup_source __rcu *ws; |
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|
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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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/* |
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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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|
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/* Wait queue used by sys_epoll_wait() */ |
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wait_queue_head_t wq; |
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|
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/* Wait queue used by file->poll() */ |
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wait_queue_head_t poll_wait; |
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|
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/* List of ready file descriptors */ |
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struct list_head rdllist; |
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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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/* |
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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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/* |
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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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|
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static u64 loop_check_gen = 0; |
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|
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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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|
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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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|
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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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/* |
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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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|
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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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|
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static long long_zero; |
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static long long_max = LONG_MAX; |
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struct ctl_table epoll_table[] = { |
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{ |
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.procname = "max_user_watches", |
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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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#endif /* CONFIG_SYSCTL */ |
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static const struct file_operations eventpoll_fops; |
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|
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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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|
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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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|
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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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|
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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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|
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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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/** |
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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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|
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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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|
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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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/* |
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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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|
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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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/* |
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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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|
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if (!net_busy_loop_on()) |
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return; |
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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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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|
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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; |
|
|
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/* |
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* To set the subclass or nesting level for spin_lock_irqsave_nested() |
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* it might be natural to create a per-cpu nest count. However, since |
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* we can recurse on ep->poll_wait.lock, and a non-raw spinlock can |
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* schedule() in the -rt kernel, the per-cpu variable are no longer |
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* protected. Thus, we are introducing a per eventpoll nest field. |
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* If we are not being call from ep_poll_callback(), epi is NULL and |
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* we are at the first level of nesting, 0. Otherwise, we are being |
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* called from ep_poll_callback() and if a previous wakeup source is |
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* not an epoll file itself, we are at depth 1 since the wakeup source |
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* is depth 0. If the wakeup source is a previous epoll file in the |
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* wakeup chain then we use its nests value and record ours as |
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* nests + 1. The previous epoll file nests value is stable since its |
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* already holding its own poll_wait.lock. |
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*/ |
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if (epi) { |
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if ((is_file_epoll(epi->ffd.file))) { |
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ep_src = epi->ffd.file->private_data; |
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nests = ep_src->nests; |
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} else { |
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nests = 1; |
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} |
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} |
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spin_lock_irqsave_nested(&ep->poll_wait.lock, flags, nests); |
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ep->nests = nests + 1; |
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wake_up_locked_poll(&ep->poll_wait, EPOLLIN); |
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ep->nests = 0; |
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spin_unlock_irqrestore(&ep->poll_wait.lock, flags); |
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} |
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|
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#else |
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|
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static void ep_poll_safewake(struct eventpoll *ep, struct epitem *epi) |
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{ |
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wake_up_poll(&ep->poll_wait, EPOLLIN); |
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} |
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|
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#endif |
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|
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static void ep_remove_wait_queue(struct eppoll_entry *pwq) |
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{ |
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wait_queue_head_t *whead; |
|
|
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rcu_read_lock(); |
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/* |
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* If it is cleared by POLLFREE, it should be rcu-safe. |
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* If we read NULL we need a barrier paired with |
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* smp_store_release() in ep_poll_callback(), otherwise |
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* we rely on whead->lock. |
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*/ |
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whead = smp_load_acquire(&pwq->whead); |
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if (whead) |
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remove_wait_queue(whead, &pwq->wait); |
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rcu_read_unlock(); |
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} |
|
|
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/* |
|
* This function unregisters poll callbacks from the associated file |
|
* descriptor. Must be called with "mtx" held (or "epmutex" if called from |
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* ep_free). |
|
*/ |
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static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi) |
|
{ |
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struct eppoll_entry **p = &epi->pwqlist; |
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struct eppoll_entry *pwq; |
|
|
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while ((pwq = *p) != NULL) { |
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*p = pwq->next; |
|
ep_remove_wait_queue(pwq); |
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kmem_cache_free(pwq_cache, pwq); |
|
} |
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} |
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|
|
/* 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 (cmpxchg(&new->next, new, head) != new) |
|
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; |
|
} |
|
|
|
/** |
|
* 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. |
|
*/ |
|
init_wait(&wait); |
|
|
|
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); |
|
|
|
ephead_cache = kmem_cache_create("ep_head", |
|
sizeof(struct epitems_head), 0, SLAB_PANIC|SLAB_ACCOUNT, NULL); |
|
|
|
return 0; |
|
} |
|
fs_initcall(eventpoll_init);
|
|
|