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authorDavidlohr Bueso <dave@stgolabs.net>2019-01-03 23:27:05 (GMT)
committerLinus Torvalds <torvalds@linux-foundation.org>2019-01-04 21:13:46 (GMT)
commit4e0982a00564c80cb849a892043450860ef91e14 (patch)
tree3463957586c8b7a5a5772366681b1ee27f097929 /fs
parent74bdc129850c32eaddc625ce557da560303fbf25 (diff)
fs/epoll: simplify ep_send_events_proc() ready-list loop
The current logic is a bit convoluted. Lets simplify this with a standard list_for_each_entry_safe() loop instead and just break out after maxevents is reached. While at it, remove an unnecessary indentation level in the loop when there are in fact ready events. Link: http://lkml.kernel.org/r/20181108051006.18751-3-dave@stgolabs.net Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Jason Baron <jbaron@akamai.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/eventpoll.c73
1 files changed, 37 insertions, 36 deletions
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index be50799..aaf614e 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1624,21 +1624,22 @@ static __poll_t ep_send_events_proc(struct eventpoll *ep, struct list_head *head
{
struct ep_send_events_data *esed = priv;
__poll_t revents;
- struct epitem *epi;
- struct epoll_event __user *uevent;
+ struct epitem *epi, *tmp;
+ struct epoll_event __user *uevent = esed->events;
struct wakeup_source *ws;
poll_table pt;
init_poll_funcptr(&pt, NULL);
+ esed->res = 0;
/*
* We can loop without lock because we are passed a task private list.
* Items cannot vanish during the loop because ep_scan_ready_list() is
* holding "mtx" during this call.
*/
- for (esed->res = 0, uevent = esed->events;
- !list_empty(head) && esed->res < esed->maxevents;) {
- epi = list_first_entry(head, struct epitem, rdllink);
+ list_for_each_entry_safe(epi, tmp, head, rdllink) {
+ if (esed->res >= esed->maxevents)
+ break;
/*
* Activate ep->ws before deactivating epi->ws to prevent
@@ -1658,42 +1659,42 @@ static __poll_t ep_send_events_proc(struct eventpoll *ep, struct list_head *head
list_del_init(&epi->rdllink);
- revents = ep_item_poll(epi, &pt, 1);
-
/*
* If the event mask intersect the caller-requested one,
* deliver the event to userspace. Again, ep_scan_ready_list()
- * is holding "mtx", so no operations coming from userspace
+ * is holding ep->mtx, so no operations coming from userspace
* can change the item.
*/
- if (revents) {
- if (__put_user(revents, &uevent->events) ||
- __put_user(epi->event.data, &uevent->data)) {
- list_add(&epi->rdllink, head);
- ep_pm_stay_awake(epi);
- if (!esed->res)
- esed->res = -EFAULT;
- return 0;
- }
- esed->res++;
- uevent++;
- if (epi->event.events & EPOLLONESHOT)
- epi->event.events &= EP_PRIVATE_BITS;
- else if (!(epi->event.events & EPOLLET)) {
- /*
- * If this file has been added with Level
- * Trigger mode, we need to insert back inside
- * the ready list, so that the next call to
- * epoll_wait() will check again the events
- * availability. At this point, no one can insert
- * into ep->rdllist besides us. The epoll_ctl()
- * callers are locked out by
- * ep_scan_ready_list() holding "mtx" and the
- * poll callback will queue them in ep->ovflist.
- */
- list_add_tail(&epi->rdllink, &ep->rdllist);
- ep_pm_stay_awake(epi);
- }
+ revents = ep_item_poll(epi, &pt, 1);
+ if (!revents)
+ continue;
+
+ if (__put_user(revents, &uevent->events) ||
+ __put_user(epi->event.data, &uevent->data)) {
+ list_add(&epi->rdllink, head);
+ ep_pm_stay_awake(epi);
+ if (!esed->res)
+ esed->res = -EFAULT;
+ return 0;
+ }
+ esed->res++;
+ uevent++;
+ if (epi->event.events & EPOLLONESHOT)
+ epi->event.events &= EP_PRIVATE_BITS;
+ else if (!(epi->event.events & EPOLLET)) {
+ /*
+ * If this file has been added with Level
+ * Trigger mode, we need to insert back inside
+ * the ready list, so that the next call to
+ * epoll_wait() will check again the events
+ * availability. At this point, no one can insert
+ * into ep->rdllist besides us. The epoll_ctl()
+ * callers are locked out by
+ * ep_scan_ready_list() holding "mtx" and the
+ * poll callback will queue them in ep->ovflist.
+ */
+ list_add_tail(&epi->rdllink, &ep->rdllist);
+ ep_pm_stay_awake(epi);
}
}

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