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@@ -1,6 +1,6 @@
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/*
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- * fs/eventpoll.c ( Efficent event polling implementation )
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- * Copyright (C) 2001,...,2006 Davide Libenzi
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+ * fs/eventpoll.c (Efficent event polling implementation)
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+ * Copyright (C) 2001,...,2007 Davide Libenzi
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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@@ -26,7 +26,6 @@
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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/rwsem.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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@@ -39,15 +38,14 @@
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#include <asm/io.h>
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#include <asm/mman.h>
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#include <asm/atomic.h>
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-#include <asm/semaphore.h>
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/*
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* LOCKING:
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* There are three level of locking required by epoll :
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*
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* 1) epmutex (mutex)
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- * 2) ep->sem (rw_semaphore)
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- * 3) ep->lock (rw_lock)
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+ * 2) ep->mtx (mutex)
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+ * 3) ep->lock (spinlock)
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*
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* The acquire order is the one listed above, from 1 to 3.
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* We need a spinlock (ep->lock) because we manipulate objects
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@@ -57,20 +55,20 @@
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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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- * read-write semaphore (ep->sem). It is acquired on read during
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- * the event transfer loop and in write during epoll_ctl(EPOLL_CTL_DEL)
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- * and during eventpoll_release_file(). Then we also need a global
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- * semaphore to serialize eventpoll_release_file() and ep_free().
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- * This semaphore is acquired by ep_free() during the epoll file
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+ * mutex (ep->mtx). It is acquired during the event transfer loop,
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+ * during epoll_ctl(EPOLL_CTL_DEL) and during eventpoll_release_file().
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+ * Then we also need a global mutex to serialize eventpoll_release_file()
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+ * and ep_free().
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+ * This mutex is acquired by ep_free() during the epoll file
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* cleanup path and it is also acquired by eventpoll_release_file()
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* if a file has been pushed inside an epoll set and it is then
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* close()d without a previous call toepoll_ctl(EPOLL_CTL_DEL).
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- * It is possible to drop the "ep->sem" and to use the global
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- * semaphore "epmutex" (together with "ep->lock") to have it working,
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- * but having "ep->sem" will make the interface more scalable.
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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->sem" will guarantee
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- * a greater scalability.
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+ * normal operations the epoll private "ep->mtx" will guarantee
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+ * a better scalability.
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*/
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#define DEBUG_EPOLL 0
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@@ -102,6 +100,8 @@
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#define EP_MAX_EVENTS (INT_MAX / sizeof(struct epoll_event))
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+#define EP_UNACTIVE_PTR ((void *) -1L)
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+
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struct epoll_filefd {
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struct file *file;
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int fd;
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@@ -111,7 +111,7 @@ struct epoll_filefd {
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* Node that is linked into the "wake_task_list" member of the "struct poll_safewake".
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* It is used to keep track on all tasks that are currently inside the wake_up() code
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* to 1) short-circuit the one coming from the same task and same wait queue head
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- * ( loop ) 2) allow a maximum number of epoll descriptors inclusion nesting
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+ * (loop) 2) allow a maximum number of epoll descriptors inclusion nesting
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* 3) let go the ones coming from other tasks.
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*/
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struct wake_task_node {
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@@ -129,6 +129,42 @@ struct poll_safewake {
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spinlock_t lock;
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};
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+/*
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+ * Each file descriptor added to the eventpoll interface will
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+ * have an entry of this type linked to the "rbr" RB tree.
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+ */
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+struct epitem {
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+ /* RB tree node used to link this structure to the eventpoll RB tree */
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+ struct rb_node rbn;
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+
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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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+ /* Number of active wait queue attached to poll operations */
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+ int nwait;
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+
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+ /* List containing poll wait queues */
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+ struct list_head 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 list_head fllink;
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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 rapresent the main data sructure for the eventpoll
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@@ -136,15 +172,15 @@ struct poll_safewake {
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*/
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struct eventpoll {
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/* Protect the this structure access */
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- rwlock_t lock;
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+ spinlock_t lock;
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/*
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- * This semaphore is used to ensure that files are not removed
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- * while epoll is using them. This is read-held during the event
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- * collection loop and it is write-held during the file cleanup
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- * path, the epoll file exit code and the ctl operations.
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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 rw_semaphore sem;
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+ struct mutex mtx;
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/* Wait queue used by sys_epoll_wait() */
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wait_queue_head_t wq;
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@@ -155,8 +191,15 @@ struct eventpoll {
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/* List of ready file descriptors */
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struct list_head rdllist;
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- /* RB-Tree root used to store monitored fd structs */
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+ /* RB tree root used to store monitored fd structs */
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struct rb_root rbr;
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+
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+ /*
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+ * This is a single linked list that chains all the "struct epitem" that
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+ * happened while transfering ready events to userspace w/out
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+ * holding ->lock.
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+ */
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+ struct epitem *ovflist;
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};
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/* Wait structure used by the poll hooks */
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@@ -177,42 +220,6 @@ struct eppoll_entry {
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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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- */
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-struct epitem {
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- /* RB-Tree node used to link this structure to the eventpoll rb-tree */
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- struct rb_node rbn;
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-
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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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- /* The file descriptor information this item refers to */
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- struct epoll_filefd ffd;
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-
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- /* Number of active wait queue attached to poll operations */
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- int nwait;
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-
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- /* List containing poll wait queues */
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- struct list_head 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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- /* 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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- * Used to keep track of the usage count of the structure. This avoids
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- * that the structure will desappear from underneath our processing.
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- */
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- atomic_t usecnt;
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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 list_head fllink;
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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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@@ -220,7 +227,7 @@ struct ep_pqueue {
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};
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/*
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- * This semaphore is used to serialize ep_free() and eventpoll_release_file().
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+ * This mutex is used to serialize ep_free() and eventpoll_release_file().
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*/
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static struct mutex epmutex;
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@@ -234,7 +241,7 @@ static struct kmem_cache *epi_cache __read_mostly;
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static struct kmem_cache *pwq_cache __read_mostly;
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-/* Setup the structure that is used as key for the rb-tree */
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+/* 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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@@ -242,7 +249,7 @@ static inline void ep_set_ffd(struct epoll_filefd *ffd,
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ffd->fd = fd;
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}
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-/* Compare rb-tree keys */
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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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@@ -250,20 +257,20 @@ static inline int ep_cmp_ffd(struct epoll_filefd *p1,
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(p1->file < p2->file ? -1 : p1->fd - p2->fd));
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}
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-/* Special initialization for the rb-tree node to detect linkage */
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+/* Special initialization for the RB tree node to detect linkage */
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static inline void ep_rb_initnode(struct rb_node *n)
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{
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rb_set_parent(n, n);
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}
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-/* Removes a node from the rb-tree and marks it for a fast is-linked check */
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+/* Removes a node from the RB tree and marks it for a fast is-linked check */
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static inline void ep_rb_erase(struct rb_node *n, struct rb_root *r)
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{
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rb_erase(n, r);
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rb_set_parent(n, n);
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}
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-/* Fast check to verify that the item is linked to the main rb-tree */
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+/* Fast check to verify that the item is linked to the main RB tree */
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static inline int ep_rb_linked(struct rb_node *n)
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{
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return rb_parent(n) != n;
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@@ -380,79 +387,12 @@ static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi)
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}
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}
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-/*
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- * Unlink the "struct epitem" from all places it might have been hooked up.
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- * This function must be called with write IRQ lock on "ep->lock".
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- */
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-static int ep_unlink(struct eventpoll *ep, struct epitem *epi)
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-{
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- int error;
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-
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- /*
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- * It can happen that this one is called for an item already unlinked.
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- * The check protect us from doing a double unlink ( crash ).
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- */
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- error = -ENOENT;
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- if (!ep_rb_linked(&epi->rbn))
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- goto error_return;
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-
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- /*
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- * Clear the event mask for the unlinked item. This will avoid item
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- * notifications to be sent after the unlink operation from inside
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- * the kernel->userspace event transfer loop.
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- */
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- epi->event.events = 0;
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-
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- /*
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- * At this point is safe to do the job, unlink the item from our rb-tree.
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- * This operation togheter with the above check closes the door to
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- * double unlinks.
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- */
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- ep_rb_erase(&epi->rbn, &ep->rbr);
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-
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- /*
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- * If the item we are going to remove is inside the ready file descriptors
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- * we want to remove it from this list to avoid stale events.
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- */
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- if (ep_is_linked(&epi->rdllink))
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- list_del_init(&epi->rdllink);
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-
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- error = 0;
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-error_return:
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-
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- DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_unlink(%p, %p) = %d\n",
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- current, ep, epi->ffd.file, error));
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-
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- return error;
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-}
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-
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-/*
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- * Increment the usage count of the "struct epitem" making it sure
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- * that the user will have a valid pointer to reference.
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- */
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-static void ep_use_epitem(struct epitem *epi)
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-{
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- atomic_inc(&epi->usecnt);
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-}
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-
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-/*
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- * Decrement ( release ) the usage count by signaling that the user
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- * has finished using the structure. It might lead to freeing the
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- * structure itself if the count goes to zero.
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- */
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-static void ep_release_epitem(struct epitem *epi)
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-{
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- if (atomic_dec_and_test(&epi->usecnt))
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- kmem_cache_free(epi_cache, epi);
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-}
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-
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/*
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* Removes a "struct epitem" from the eventpoll RB tree and deallocates
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- * all the associated resources.
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+ * all the associated resources. Must be called with "mtx" held.
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*/
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static int ep_remove(struct eventpoll *ep, struct epitem *epi)
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{
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- int error;
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unsigned long flags;
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struct file *file = epi->ffd.file;
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@@ -472,26 +412,21 @@ static int ep_remove(struct eventpoll *ep, struct epitem *epi)
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list_del_init(&epi->fllink);
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spin_unlock(&file->f_ep_lock);
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- /* We need to acquire the write IRQ lock before calling ep_unlink() */
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- write_lock_irqsave(&ep->lock, flags);
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-
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- /* Really unlink the item from the RB tree */
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- error = ep_unlink(ep, epi);
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-
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- write_unlock_irqrestore(&ep->lock, flags);
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+ if (ep_rb_linked(&epi->rbn))
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+ ep_rb_erase(&epi->rbn, &ep->rbr);
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- if (error)
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- goto error_return;
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+ spin_lock_irqsave(&ep->lock, flags);
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+ if (ep_is_linked(&epi->rdllink))
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+ list_del_init(&epi->rdllink);
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+ spin_unlock_irqrestore(&ep->lock, flags);
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/* At this point it is safe to free the eventpoll item */
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- ep_release_epitem(epi);
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+ kmem_cache_free(epi_cache, epi);
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- error = 0;
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-error_return:
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- DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_remove(%p, %p) = %d\n",
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- current, ep, file, error));
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+ DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_remove(%p, %p)\n",
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+ current, ep, file));
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- return error;
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+ return 0;
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}
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static void ep_free(struct eventpoll *ep)
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@@ -506,7 +441,7 @@ static void ep_free(struct eventpoll *ep)
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/*
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* We need to lock this because we could be hit by
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* eventpoll_release_file() while we're freeing the "struct eventpoll".
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- * We do not need to hold "ep->sem" here because the epoll file
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+ * We do not need to hold "ep->mtx" here because the epoll file
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* is on the way to be removed and no one has references to it
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* anymore. The only hit might come from eventpoll_release_file() but
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* holding "epmutex" is sufficent here.
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@@ -525,7 +460,7 @@ static void ep_free(struct eventpoll *ep)
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/*
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* Walks through the whole tree by freeing each "struct epitem". At this
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* point we are sure no poll callbacks will be lingering around, and also by
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- * write-holding "sem" we can be sure that no file cleanup code will hit
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+ * holding "epmutex" we can be sure that no file cleanup code will hit
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* us during this operation. So we can avoid the lock on "ep->lock".
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*/
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while ((rbp = rb_first(&ep->rbr)) != 0) {
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@@ -534,16 +469,16 @@ static void ep_free(struct eventpoll *ep)
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}
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mutex_unlock(&epmutex);
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|
+ mutex_destroy(&ep->mtx);
|
|
|
+ kfree(ep);
|
|
|
}
|
|
|
|
|
|
static int ep_eventpoll_release(struct inode *inode, struct file *file)
|
|
|
{
|
|
|
struct eventpoll *ep = file->private_data;
|
|
|
|
|
|
- if (ep) {
|
|
|
+ if (ep)
|
|
|
ep_free(ep);
|
|
|
- kfree(ep);
|
|
|
- }
|
|
|
|
|
|
DNPRINTK(3, (KERN_INFO "[%p] eventpoll: close() ep=%p\n", current, ep));
|
|
|
return 0;
|
|
|
@@ -559,10 +494,10 @@ static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait)
|
|
|
poll_wait(file, &ep->poll_wait, wait);
|
|
|
|
|
|
/* Check our condition */
|
|
|
- read_lock_irqsave(&ep->lock, flags);
|
|
|
+ spin_lock_irqsave(&ep->lock, flags);
|
|
|
if (!list_empty(&ep->rdllist))
|
|
|
pollflags = POLLIN | POLLRDNORM;
|
|
|
- read_unlock_irqrestore(&ep->lock, flags);
|
|
|
+ spin_unlock_irqrestore(&ep->lock, flags);
|
|
|
|
|
|
return pollflags;
|
|
|
}
|
|
|
@@ -594,9 +529,11 @@ void eventpoll_release_file(struct file *file)
|
|
|
* We don't want to get "file->f_ep_lock" because it is not
|
|
|
* necessary. It is not necessary because we're in the "struct file"
|
|
|
* cleanup path, and this means that noone is using this file anymore.
|
|
|
- * The only hit might come from ep_free() but by holding the semaphore
|
|
|
+ * So, for example, epoll_ctl() cannot hit here sicne 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->sem" after "epmutex" because ep_remove() requires it when called
|
|
|
+ * "ep->mtx" after "epmutex" because ep_remove() requires it when called
|
|
|
* from anywhere but ep_free().
|
|
|
*/
|
|
|
mutex_lock(&epmutex);
|
|
|
@@ -606,9 +543,9 @@ void eventpoll_release_file(struct file *file)
|
|
|
|
|
|
ep = epi->ep;
|
|
|
list_del_init(&epi->fllink);
|
|
|
- down_write(&ep->sem);
|
|
|
+ mutex_lock(&ep->mtx);
|
|
|
ep_remove(ep, epi);
|
|
|
- up_write(&ep->sem);
|
|
|
+ mutex_unlock(&ep->mtx);
|
|
|
}
|
|
|
|
|
|
mutex_unlock(&epmutex);
|
|
|
@@ -621,12 +558,13 @@ static int ep_alloc(struct eventpoll **pep)
|
|
|
if (!ep)
|
|
|
return -ENOMEM;
|
|
|
|
|
|
- rwlock_init(&ep->lock);
|
|
|
- init_rwsem(&ep->sem);
|
|
|
+ spin_lock_init(&ep->lock);
|
|
|
+ mutex_init(&ep->mtx);
|
|
|
init_waitqueue_head(&ep->wq);
|
|
|
init_waitqueue_head(&ep->poll_wait);
|
|
|
INIT_LIST_HEAD(&ep->rdllist);
|
|
|
ep->rbr = RB_ROOT;
|
|
|
+ ep->ovflist = EP_UNACTIVE_PTR;
|
|
|
|
|
|
*pep = ep;
|
|
|
|
|
|
@@ -636,20 +574,18 @@ static int ep_alloc(struct eventpoll **pep)
|
|
|
}
|
|
|
|
|
|
/*
|
|
|
- * Search the file inside the eventpoll tree. It add usage count to
|
|
|
- * the returned item, so the caller must call ep_release_epitem()
|
|
|
- * after finished using the "struct epitem".
|
|
|
+ * 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;
|
|
|
- unsigned long flags;
|
|
|
struct rb_node *rbp;
|
|
|
struct epitem *epi, *epir = NULL;
|
|
|
struct epoll_filefd ffd;
|
|
|
|
|
|
ep_set_ffd(&ffd, file, fd);
|
|
|
- read_lock_irqsave(&ep->lock, flags);
|
|
|
for (rbp = ep->rbr.rb_node; rbp; ) {
|
|
|
epi = rb_entry(rbp, struct epitem, rbn);
|
|
|
kcmp = ep_cmp_ffd(&ffd, &epi->ffd);
|
|
|
@@ -658,12 +594,10 @@ static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd)
|
|
|
else if (kcmp < 0)
|
|
|
rbp = rbp->rb_left;
|
|
|
else {
|
|
|
- ep_use_epitem(epi);
|
|
|
epir = epi;
|
|
|
break;
|
|
|
}
|
|
|
}
|
|
|
- read_unlock_irqrestore(&ep->lock, flags);
|
|
|
|
|
|
DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_find(%p) -> %p\n",
|
|
|
current, file, epir));
|
|
|
@@ -686,7 +620,7 @@ static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *k
|
|
|
DNPRINTK(3, (KERN_INFO "[%p] eventpoll: poll_callback(%p) epi=%p ep=%p\n",
|
|
|
current, epi->ffd.file, epi, ep));
|
|
|
|
|
|
- write_lock_irqsave(&ep->lock, flags);
|
|
|
+ spin_lock_irqsave(&ep->lock, flags);
|
|
|
|
|
|
/*
|
|
|
* If the event mask does not contain any poll(2) event, we consider the
|
|
|
@@ -695,7 +629,21 @@ static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *k
|
|
|
* until the next EPOLL_CTL_MOD will be issued.
|
|
|
*/
|
|
|
if (!(epi->event.events & ~EP_PRIVATE_BITS))
|
|
|
- goto is_disabled;
|
|
|
+ goto out_unlock;
|
|
|
+
|
|
|
+ /*
|
|
|
+ * If we are trasfering 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 happens during that period of time are
|
|
|
+ * chained in ep->ovflist and requeued later on.
|
|
|
+ */
|
|
|
+ if (unlikely(ep->ovflist != EP_UNACTIVE_PTR)) {
|
|
|
+ if (epi->next == EP_UNACTIVE_PTR) {
|
|
|
+ epi->next = ep->ovflist;
|
|
|
+ ep->ovflist = epi;
|
|
|
+ }
|
|
|
+ goto out_unlock;
|
|
|
+ }
|
|
|
|
|
|
/* If this file is already in the ready list we exit soon */
|
|
|
if (ep_is_linked(&epi->rdllink))
|
|
|
@@ -714,8 +662,8 @@ is_linked:
|
|
|
if (waitqueue_active(&ep->poll_wait))
|
|
|
pwake++;
|
|
|
|
|
|
-is_disabled:
|
|
|
- write_unlock_irqrestore(&ep->lock, flags);
|
|
|
+out_unlock:
|
|
|
+ spin_unlock_irqrestore(&ep->lock, flags);
|
|
|
|
|
|
/* We have to call this outside the lock */
|
|
|
if (pwake)
|
|
|
@@ -766,6 +714,9 @@ static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi)
|
|
|
rb_insert_color(&epi->rbn, &ep->rbr);
|
|
|
}
|
|
|
|
|
|
+/*
|
|
|
+ * Must be called with "mtx" held.
|
|
|
+ */
|
|
|
static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
|
|
|
struct file *tfile, int fd)
|
|
|
{
|
|
|
@@ -786,8 +737,8 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
|
|
|
epi->ep = ep;
|
|
|
ep_set_ffd(&epi->ffd, tfile, fd);
|
|
|
epi->event = *event;
|
|
|
- atomic_set(&epi->usecnt, 1);
|
|
|
epi->nwait = 0;
|
|
|
+ epi->next = EP_UNACTIVE_PTR;
|
|
|
|
|
|
/* Initialize the poll table using the queue callback */
|
|
|
epq.epi = epi;
|
|
|
@@ -796,7 +747,9 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
|
|
|
/*
|
|
|
* 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.
|
|
|
+ * been increased by the caller of this function. Note that after
|
|
|
+ * this operation completes, the poll callback can start hitting
|
|
|
+ * the new item.
|
|
|
*/
|
|
|
revents = tfile->f_op->poll(tfile, &epq.pt);
|
|
|
|
|
|
@@ -813,12 +766,15 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
|
|
|
list_add_tail(&epi->fllink, &tfile->f_ep_links);
|
|
|
spin_unlock(&tfile->f_ep_lock);
|
|
|
|
|
|
- /* We have to drop the new item inside our item list to keep track of it */
|
|
|
- write_lock_irqsave(&ep->lock, flags);
|
|
|
-
|
|
|
- /* Add the current item to the rb-tree */
|
|
|
+ /*
|
|
|
+ * 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);
|
|
|
|
|
|
+ /* We have to drop the new item inside our item list to keep track of it */
|
|
|
+ spin_lock_irqsave(&ep->lock, flags);
|
|
|
+
|
|
|
/* If the file is already "ready" we drop it inside the ready list */
|
|
|
if ((revents & event->events) && !ep_is_linked(&epi->rdllink)) {
|
|
|
list_add_tail(&epi->rdllink, &ep->rdllist);
|
|
|
@@ -830,7 +786,7 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
|
|
|
pwake++;
|
|
|
}
|
|
|
|
|
|
- write_unlock_irqrestore(&ep->lock, flags);
|
|
|
+ spin_unlock_irqrestore(&ep->lock, flags);
|
|
|
|
|
|
/* We have to call this outside the lock */
|
|
|
if (pwake)
|
|
|
@@ -846,12 +802,14 @@ error_unregister:
|
|
|
|
|
|
/*
|
|
|
* We need to do this because an event could have been arrived on some
|
|
|
- * allocated wait queue.
|
|
|
+ * allocated wait queue. Note that we don't care about the ep->ovflist
|
|
|
+ * list, since that is used/cleaned only inside a section bound by "mtx".
|
|
|
+ * And ep_insert() is called with "mtx" held.
|
|
|
*/
|
|
|
- write_lock_irqsave(&ep->lock, flags);
|
|
|
+ spin_lock_irqsave(&ep->lock, flags);
|
|
|
if (ep_is_linked(&epi->rdllink))
|
|
|
list_del_init(&epi->rdllink);
|
|
|
- write_unlock_irqrestore(&ep->lock, flags);
|
|
|
+ spin_unlock_irqrestore(&ep->lock, flags);
|
|
|
|
|
|
kmem_cache_free(epi_cache, epi);
|
|
|
error_return:
|
|
|
@@ -860,7 +818,7 @@ error_return:
|
|
|
|
|
|
/*
|
|
|
* Modify the interest event mask by dropping an event if the new mask
|
|
|
- * has a match in the current file status.
|
|
|
+ * has a match in the current file status. Must be called with "mtx" held.
|
|
|
*/
|
|
|
static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_event *event)
|
|
|
{
|
|
|
@@ -882,36 +840,28 @@ static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_even
|
|
|
*/
|
|
|
revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL);
|
|
|
|
|
|
- write_lock_irqsave(&ep->lock, flags);
|
|
|
+ spin_lock_irqsave(&ep->lock, flags);
|
|
|
|
|
|
/* Copy the data member from inside the lock */
|
|
|
epi->event.data = event->data;
|
|
|
|
|
|
/*
|
|
|
- * If the item is not linked to the RB tree it means that it's on its
|
|
|
- * way toward the removal. Do nothing in this case.
|
|
|
+ * If the item is "hot" and it is not registered inside the ready
|
|
|
+ * list, push it inside.
|
|
|
*/
|
|
|
- if (ep_rb_linked(&epi->rbn)) {
|
|
|
- /*
|
|
|
- * If the item is "hot" and it is not registered inside the ready
|
|
|
- * list, push it inside. If the item is not "hot" and it is currently
|
|
|
- * registered inside the ready list, unlink it.
|
|
|
- */
|
|
|
- if (revents & event->events) {
|
|
|
- if (!ep_is_linked(&epi->rdllink)) {
|
|
|
- list_add_tail(&epi->rdllink, &ep->rdllist);
|
|
|
-
|
|
|
- /* Notify waiting tasks that events are available */
|
|
|
- if (waitqueue_active(&ep->wq))
|
|
|
- __wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE |
|
|
|
- TASK_INTERRUPTIBLE);
|
|
|
- if (waitqueue_active(&ep->poll_wait))
|
|
|
- pwake++;
|
|
|
- }
|
|
|
+ if (revents & event->events) {
|
|
|
+ if (!ep_is_linked(&epi->rdllink)) {
|
|
|
+ list_add_tail(&epi->rdllink, &ep->rdllist);
|
|
|
+
|
|
|
+ /* Notify waiting tasks that events are available */
|
|
|
+ if (waitqueue_active(&ep->wq))
|
|
|
+ __wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE |
|
|
|
+ TASK_INTERRUPTIBLE);
|
|
|
+ if (waitqueue_active(&ep->poll_wait))
|
|
|
+ pwake++;
|
|
|
}
|
|
|
}
|
|
|
-
|
|
|
- write_unlock_irqrestore(&ep->lock, flags);
|
|
|
+ spin_unlock_irqrestore(&ep->lock, flags);
|
|
|
|
|
|
/* We have to call this outside the lock */
|
|
|
if (pwake)
|
|
|
@@ -920,36 +870,50 @@ static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_even
|
|
|
return 0;
|
|
|
}
|
|
|
|
|
|
-/*
|
|
|
- * This function is called without holding the "ep->lock" since the call to
|
|
|
- * __copy_to_user() might sleep, and also f_op->poll() might reenable the IRQ
|
|
|
- * because of the way poll() is traditionally implemented in Linux.
|
|
|
- */
|
|
|
-static int ep_send_events(struct eventpoll *ep, struct list_head *txlist,
|
|
|
- struct epoll_event __user *events, int maxevents)
|
|
|
+static int ep_send_events(struct eventpoll *ep, struct epoll_event __user *events,
|
|
|
+ int maxevents)
|
|
|
{
|
|
|
int eventcnt, error = -EFAULT, pwake = 0;
|
|
|
unsigned int revents;
|
|
|
unsigned long flags;
|
|
|
- struct epitem *epi;
|
|
|
- struct list_head injlist;
|
|
|
+ struct epitem *epi, *nepi;
|
|
|
+ struct list_head txlist;
|
|
|
+
|
|
|
+ INIT_LIST_HEAD(&txlist);
|
|
|
+
|
|
|
+ /*
|
|
|
+ * We need to lock this because we could be hit by
|
|
|
+ * eventpoll_release_file() and epoll_ctl(EPOLL_CTL_DEL).
|
|
|
+ */
|
|
|
+ mutex_lock(&ep->mtx);
|
|
|
|
|
|
- INIT_LIST_HEAD(&injlist);
|
|
|
+ /*
|
|
|
+ * 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 are doing it in the loop below, in a lockless way.
|
|
|
+ */
|
|
|
+ spin_lock_irqsave(&ep->lock, flags);
|
|
|
+ list_splice(&ep->rdllist, &txlist);
|
|
|
+ INIT_LIST_HEAD(&ep->rdllist);
|
|
|
+ ep->ovflist = NULL;
|
|
|
+ spin_unlock_irqrestore(&ep->lock, flags);
|
|
|
|
|
|
/*
|
|
|
* We can loop without lock because this is a task private list.
|
|
|
* We just splice'd out the ep->rdllist in ep_collect_ready_items().
|
|
|
- * Items cannot vanish during the loop because we are holding "sem" in
|
|
|
- * read.
|
|
|
+ * Items cannot vanish during the loop because we are holding "mtx".
|
|
|
*/
|
|
|
- for (eventcnt = 0; !list_empty(txlist) && eventcnt < maxevents;) {
|
|
|
- epi = list_first_entry(txlist, struct epitem, rdllink);
|
|
|
- prefetch(epi->rdllink.next);
|
|
|
+ for (eventcnt = 0; !list_empty(&txlist) && eventcnt < maxevents;) {
|
|
|
+ epi = list_first_entry(&txlist, struct epitem, rdllink);
|
|
|
+
|
|
|
+ list_del_init(&epi->rdllink);
|
|
|
|
|
|
/*
|
|
|
* Get the ready file event set. We can safely use the file
|
|
|
- * because we are holding the "sem" in read and this will
|
|
|
- * guarantee that both the file and the item will not vanish.
|
|
|
+ * because we are holding the "mtx" and this will guarantee
|
|
|
+ * that both the file and the item will not vanish.
|
|
|
*/
|
|
|
revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL);
|
|
|
revents &= epi->event.events;
|
|
|
@@ -957,8 +921,8 @@ static int ep_send_events(struct eventpoll *ep, struct list_head *txlist,
|
|
|
/*
|
|
|
* Is the event mask intersect the caller-requested one,
|
|
|
* deliver the event to userspace. Again, we are holding
|
|
|
- * "sem" in read, so no operations coming from userspace
|
|
|
- * can change the item.
|
|
|
+ * "mtx", so no operations coming from userspace can change
|
|
|
+ * the item.
|
|
|
*/
|
|
|
if (revents) {
|
|
|
if (__put_user(revents,
|
|
|
@@ -970,59 +934,59 @@ static int ep_send_events(struct eventpoll *ep, struct list_head *txlist,
|
|
|
epi->event.events &= EP_PRIVATE_BITS;
|
|
|
eventcnt++;
|
|
|
}
|
|
|
-
|
|
|
/*
|
|
|
- * This is tricky. We are holding the "sem" in read, and this
|
|
|
- * means that the operations that can change the "linked" status
|
|
|
- * of the epoll item (epi->rbn and epi->rdllink), cannot touch
|
|
|
- * them. Also, since we are "linked" from a epi->rdllink POV
|
|
|
- * (the item is linked to our transmission list we just
|
|
|
- * spliced), the ep_poll_callback() cannot touch us either,
|
|
|
- * because of the check present in there. Another parallel
|
|
|
- * epoll_wait() will not get the same result set, since we
|
|
|
- * spliced the ready list before. Note that list_del() still
|
|
|
- * shows the item as linked to the test in ep_poll_callback().
|
|
|
+ * At this point, noone can insert into ep->rdllist besides
|
|
|
+ * us. The epoll_ctl() callers are locked out by us holding
|
|
|
+ * "mtx" and the poll callback will queue them in ep->ovflist.
|
|
|
*/
|
|
|
- list_del(&epi->rdllink);
|
|
|
if (!(epi->event.events & EPOLLET) &&
|
|
|
- (revents & epi->event.events))
|
|
|
- list_add_tail(&epi->rdllink, &injlist);
|
|
|
- else {
|
|
|
- /*
|
|
|
- * Be sure the item is totally detached before re-init
|
|
|
- * the list_head. After INIT_LIST_HEAD() is committed,
|
|
|
- * the ep_poll_callback() can requeue the item again,
|
|
|
- * but we don't care since we are already past it.
|
|
|
- */
|
|
|
- smp_mb();
|
|
|
- INIT_LIST_HEAD(&epi->rdllink);
|
|
|
- }
|
|
|
+ (revents & epi->event.events))
|
|
|
+ list_add_tail(&epi->rdllink, &ep->rdllist);
|
|
|
}
|
|
|
error = 0;
|
|
|
|
|
|
- errxit:
|
|
|
+errxit:
|
|
|
|
|
|
+ spin_lock_irqsave(&ep->lock, flags);
|
|
|
/*
|
|
|
- * If the re-injection list or the txlist are not empty, re-splice
|
|
|
- * them to the ready list and do proper wakeups.
|
|
|
+ * During the time we spent in the loop above, some other events
|
|
|
+ * might have been queued by the poll callback. We re-insert them
|
|
|
+ * here (in case they are not already queued, or they're one-shot).
|
|
|
*/
|
|
|
- if (!list_empty(&injlist) || !list_empty(txlist)) {
|
|
|
- write_lock_irqsave(&ep->lock, flags);
|
|
|
+ for (nepi = ep->ovflist; (epi = nepi) != NULL;
|
|
|
+ nepi = epi->next, epi->next = EP_UNACTIVE_PTR) {
|
|
|
+ if (!ep_is_linked(&epi->rdllink) &&
|
|
|
+ (epi->event.events & ~EP_PRIVATE_BITS))
|
|
|
+ list_add_tail(&epi->rdllink, &ep->rdllist);
|
|
|
+ }
|
|
|
+ /*
|
|
|
+ * We need to set back ep->ovflist to EP_UNACTIVE_PTR, so that after
|
|
|
+ * releasing the lock, events will be queued in the normal way inside
|
|
|
+ * ep->rdllist.
|
|
|
+ */
|
|
|
+ ep->ovflist = EP_UNACTIVE_PTR;
|
|
|
+
|
|
|
+ /*
|
|
|
+ * In case of error in the event-send loop, or in case the number of
|
|
|
+ * ready events exceeds the userspace limit, we need to splice the
|
|
|
+ * "txlist" back inside ep->rdllist.
|
|
|
+ */
|
|
|
+ list_splice(&txlist, &ep->rdllist);
|
|
|
|
|
|
- list_splice(txlist, &ep->rdllist);
|
|
|
- list_splice(&injlist, &ep->rdllist);
|
|
|
+ if (!list_empty(&ep->rdllist)) {
|
|
|
/*
|
|
|
- * Wake up ( if active ) both the eventpoll wait list and the ->poll()
|
|
|
- * wait list.
|
|
|
+ * Wake up (if active) both the eventpoll wait list and the ->poll()
|
|
|
+ * wait list (delayed after we release the lock).
|
|
|
*/
|
|
|
if (waitqueue_active(&ep->wq))
|
|
|
__wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE |
|
|
|
TASK_INTERRUPTIBLE);
|
|
|
if (waitqueue_active(&ep->poll_wait))
|
|
|
pwake++;
|
|
|
-
|
|
|
- write_unlock_irqrestore(&ep->lock, flags);
|
|
|
}
|
|
|
+ spin_unlock_irqrestore(&ep->lock, flags);
|
|
|
+
|
|
|
+ mutex_unlock(&ep->mtx);
|
|
|
|
|
|
/* We have to call this outside the lock */
|
|
|
if (pwake)
|
|
|
@@ -1031,41 +995,6 @@ static int ep_send_events(struct eventpoll *ep, struct list_head *txlist,
|
|
|
return eventcnt == 0 ? error: eventcnt;
|
|
|
}
|
|
|
|
|
|
-/*
|
|
|
- * Perform the transfer of events to user space.
|
|
|
- */
|
|
|
-static int ep_events_transfer(struct eventpoll *ep,
|
|
|
- struct epoll_event __user *events, int maxevents)
|
|
|
-{
|
|
|
- int eventcnt;
|
|
|
- unsigned long flags;
|
|
|
- struct list_head txlist;
|
|
|
-
|
|
|
- INIT_LIST_HEAD(&txlist);
|
|
|
-
|
|
|
- /*
|
|
|
- * We need to lock this because we could be hit by
|
|
|
- * eventpoll_release_file() and epoll_ctl(EPOLL_CTL_DEL).
|
|
|
- */
|
|
|
- down_read(&ep->sem);
|
|
|
-
|
|
|
- /*
|
|
|
- * Steal the ready list, and re-init the original one to the
|
|
|
- * empty list.
|
|
|
- */
|
|
|
- write_lock_irqsave(&ep->lock, flags);
|
|
|
- list_splice(&ep->rdllist, &txlist);
|
|
|
- INIT_LIST_HEAD(&ep->rdllist);
|
|
|
- write_unlock_irqrestore(&ep->lock, flags);
|
|
|
-
|
|
|
- /* Build result set in userspace */
|
|
|
- eventcnt = ep_send_events(ep, &txlist, events, maxevents);
|
|
|
-
|
|
|
- up_read(&ep->sem);
|
|
|
-
|
|
|
- return eventcnt;
|
|
|
-}
|
|
|
-
|
|
|
static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
|
|
|
int maxevents, long timeout)
|
|
|
{
|
|
|
@@ -1083,7 +1012,7 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
|
|
|
MAX_SCHEDULE_TIMEOUT : (timeout * HZ + 999) / 1000;
|
|
|
|
|
|
retry:
|
|
|
- write_lock_irqsave(&ep->lock, flags);
|
|
|
+ spin_lock_irqsave(&ep->lock, flags);
|
|
|
|
|
|
res = 0;
|
|
|
if (list_empty(&ep->rdllist)) {
|
|
|
@@ -1093,6 +1022,7 @@ retry:
|
|
|
* ep_poll_callback() when events will become available.
|
|
|
*/
|
|
|
init_waitqueue_entry(&wait, current);
|
|
|
+ wait.flags |= WQ_FLAG_EXCLUSIVE;
|
|
|
__add_wait_queue(&ep->wq, &wait);
|
|
|
|
|
|
for (;;) {
|
|
|
@@ -1109,9 +1039,9 @@ retry:
|
|
|
break;
|
|
|
}
|
|
|
|
|
|
- write_unlock_irqrestore(&ep->lock, flags);
|
|
|
+ spin_unlock_irqrestore(&ep->lock, flags);
|
|
|
jtimeout = schedule_timeout(jtimeout);
|
|
|
- write_lock_irqsave(&ep->lock, flags);
|
|
|
+ spin_lock_irqsave(&ep->lock, flags);
|
|
|
}
|
|
|
__remove_wait_queue(&ep->wq, &wait);
|
|
|
|
|
|
@@ -1121,7 +1051,7 @@ retry:
|
|
|
/* Is it worth to try to dig for events ? */
|
|
|
eavail = !list_empty(&ep->rdllist);
|
|
|
|
|
|
- write_unlock_irqrestore(&ep->lock, flags);
|
|
|
+ spin_unlock_irqrestore(&ep->lock, flags);
|
|
|
|
|
|
/*
|
|
|
* Try to transfer events to user space. In case we get 0 events and
|
|
|
@@ -1129,18 +1059,17 @@ retry:
|
|
|
* more luck.
|
|
|
*/
|
|
|
if (!res && eavail &&
|
|
|
- !(res = ep_events_transfer(ep, events, maxevents)) && jtimeout)
|
|
|
+ !(res = ep_send_events(ep, events, maxevents)) && jtimeout)
|
|
|
goto retry;
|
|
|
|
|
|
return res;
|
|
|
}
|
|
|
|
|
|
/*
|
|
|
- * It opens an eventpoll file descriptor by suggesting a storage of "size"
|
|
|
- * file descriptors. The size parameter is just an hint about how to size
|
|
|
- * data structures. It won't prevent the user to store more than "size"
|
|
|
- * file descriptors inside the epoll interface. It is the kernel part of
|
|
|
- * the userspace epoll_create(2).
|
|
|
+ * It opens an eventpoll file descriptor. The "size" parameter is there
|
|
|
+ * for historical reasons, when epoll was using an hash instead of an
|
|
|
+ * RB tree. With the current implementation, the "size" parameter is ignored
|
|
|
+ * (besides sanity checks).
|
|
|
*/
|
|
|
asmlinkage long sys_epoll_create(int size)
|
|
|
{
|
|
|
@@ -1176,7 +1105,6 @@ asmlinkage long sys_epoll_create(int size)
|
|
|
|
|
|
error_free:
|
|
|
ep_free(ep);
|
|
|
- kfree(ep);
|
|
|
error_return:
|
|
|
DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n",
|
|
|
current, size, error));
|
|
|
@@ -1186,8 +1114,7 @@ error_return:
|
|
|
/*
|
|
|
* The following function implements the controller interface for
|
|
|
* the eventpoll file that enables the insertion/removal/change of
|
|
|
- * file descriptors inside the interest set. It represents
|
|
|
- * the kernel part of the user space epoll_ctl(2).
|
|
|
+ * file descriptors inside the interest set.
|
|
|
*/
|
|
|
asmlinkage long sys_epoll_ctl(int epfd, int op, int fd,
|
|
|
struct epoll_event __user *event)
|
|
|
@@ -1237,9 +1164,13 @@ asmlinkage long sys_epoll_ctl(int epfd, int op, int fd,
|
|
|
*/
|
|
|
ep = file->private_data;
|
|
|
|
|
|
- down_write(&ep->sem);
|
|
|
+ mutex_lock(&ep->mtx);
|
|
|
|
|
|
- /* Try to lookup the file inside our RB tree */
|
|
|
+ /*
|
|
|
+ * 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, tfile, fd);
|
|
|
|
|
|
error = -EINVAL;
|
|
|
@@ -1266,13 +1197,7 @@ asmlinkage long sys_epoll_ctl(int epfd, int op, int fd,
|
|
|
error = -ENOENT;
|
|
|
break;
|
|
|
}
|
|
|
- /*
|
|
|
- * The function ep_find() increments the usage count of the structure
|
|
|
- * so, if this is not NULL, we need to release it.
|
|
|
- */
|
|
|
- if (epi)
|
|
|
- ep_release_epitem(epi);
|
|
|
- up_write(&ep->sem);
|
|
|
+ mutex_unlock(&ep->mtx);
|
|
|
|
|
|
error_tgt_fput:
|
|
|
fput(tfile);
|
|
|
@@ -1378,7 +1303,7 @@ asmlinkage long sys_epoll_pwait(int epfd, struct epoll_event __user *events,
|
|
|
if (sigmask) {
|
|
|
if (error == -EINTR) {
|
|
|
memcpy(¤t->saved_sigmask, &sigsaved,
|
|
|
- sizeof(sigsaved));
|
|
|
+ sizeof(sigsaved));
|
|
|
set_thread_flag(TIF_RESTORE_SIGMASK);
|
|
|
} else
|
|
|
sigprocmask(SIG_SETMASK, &sigsaved, NULL);
|
Trond Myklebust