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epoll: switch epitem->pwqlist to single-linked list

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We only traverse it once to destroy all associated eppoll_entry at
epitem destruction time.  The order of traversal is irrelevant there.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2020-09-02 11:45:57 -04:00
parent 3650b228f8
commit 80285b75c6
1 changed files with 25 additions and 26 deletions
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51
fs/eventpoll.c
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@ -128,6 +128,24 @@ struct nested_calls {
spinlock_t lock;
};
/* Wait structure used by the poll hooks */
struct eppoll_entry {
/* List header used to link this structure to the "struct epitem" */
struct eppoll_entry *next;
/* The "base" pointer is set to the container "struct epitem" */
struct epitem *base;
/*
* Wait queue item that will be linked to the target file wait
* queue head.
*/
wait_queue_entry_t wait;
/* The wait queue head that linked the "wait" wait queue item */
wait_queue_head_t *whead;
};
/*
* Each file descriptor added to the eventpoll interface will
* have an entry of this type linked to the "rbr" RB tree.
@ -158,7 +176,7 @@ struct epitem {
int nwait;
/* List containing poll wait queues */
struct list_head pwqlist;
struct eppoll_entry *pwqlist;
/* The "container" of this item */
struct eventpoll *ep;
@ -231,24 +249,6 @@ struct eventpoll {
#endif
};
/* Wait structure used by the poll hooks */
struct eppoll_entry {
/* List header used to link this structure to the "struct epitem" */
struct list_head llink;
/* The "base" pointer is set to the container "struct epitem" */
struct epitem *base;
/*
* Wait queue item that will be linked to the target file wait
* queue head.
*/
wait_queue_entry_t wait;
/* The wait queue head that linked the "wait" wait queue item */
wait_queue_head_t *whead;
};
/* Wrapper struct used by poll queueing */
struct ep_pqueue {
poll_table pt;
@ -617,13 +617,11 @@ static void ep_remove_wait_queue(struct eppoll_entry *pwq)
*/
static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi)
{
struct list_head *lsthead = &epi->pwqlist;
struct eppoll_entry **p = &epi->pwqlist;
struct eppoll_entry *pwq;
while (!list_empty(lsthead)) {
pwq = list_first_entry(lsthead, struct eppoll_entry, llink);
list_del(&pwq->llink);
while ((pwq = *p) != NULL) {
*p = pwq->next;
ep_remove_wait_queue(pwq);
kmem_cache_free(pwq_cache, pwq);
}
@ -1320,7 +1318,8 @@ static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead,
add_wait_queue_exclusive(whead, &pwq->wait);
else
add_wait_queue(whead, &pwq->wait);
list_add_tail(&pwq->llink, &epi->pwqlist);
pwq->next = epi->pwqlist;
epi->pwqlist = pwq;
epi->nwait++;
} else {
/* We have to signal that an error occurred */
@ -1507,7 +1506,7 @@ static int ep_insert(struct eventpoll *ep, const struct epoll_event *event,
/* Item initialization follow here ... */
INIT_LIST_HEAD(&epi->rdllink);
INIT_LIST_HEAD(&epi->fllink);
INIT_LIST_HEAD(&epi->pwqlist);
epi->pwqlist = NULL;
epi->ep = ep;
ep_set_ffd(&epi->ffd, tfile, fd);
epi->event = *event;