The patch titled
Subject: fs/epoll: simplify ep_send_events_proc() ready-list loop
has been added to the -mm tree. Its filename is
fs-epoll-simplify-ep_send_events_proc-ready-list-loop.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/fs-epoll-simplify-ep_send_events_proc-ready-list-loop.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/fs-epoll-simplify-ep_send_events_proc-ready-list-loop.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Subject: 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@xxxxxxxxxxxx
Signed-off-by: Davidlohr Bueso <dbueso@xxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Jason Baron <jbaron@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/eventpoll.c | 73 +++++++++++++++++++++++------------------------
1 file changed, 37 insertions(+), 36 deletions(-)
--- a/fs/eventpoll.c~fs-epoll-simplify-ep_send_events_proc-ready-list-loop
+++ a/fs/eventpoll.c
@@ -1624,21 +1624,22 @@ static __poll_t ep_send_events_proc(stru
{
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(stru
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);
}
}
_
Patches currently in -mm which might be from dave@xxxxxxxxxxxx are
fs-epoll-remove-max_nests-argument-from-ep_call_nested.patch
fs-epoll-simplify-ep_send_events_proc-ready-list-loop.patch
fs-epoll-drop-ovflist-branch-prediction.patch
fs-epoll-robustify-ep-mtx-held-checks.patch
fs-epoll-reduce-the-scope-of-wq-lock-in-epoll_wait.patch
fs-epoll-reduce-the-scope-of-wq-lock-in-epoll_wait-fix.patch
fs-epoll-avoid-barrier-after-an-epoll_wait2-timeout.patch
fs-epoll-avoid-barrier-after-an-epoll_wait2-timeout-fix.patch
