epoll: Add a flag, EPOLLWAKEUP, to prevent suspend while epoll events are ready
When an epoll_event, that has the EPOLLWAKEUP flag set, is ready, a wakeup_source will be active to prevent suspend. This can be used to handle wakeup events from a driver that support poll, e.g. input, if that driver wakes up the waitqueue passed to epoll before allowing suspend. Signed-off-by: Arve Hjønnevåg <arve@android.com> Reviewed-by: NeilBrown <neilb@suse.de> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
This commit is contained in:
Arve Hjønnevåg
Rafael J. Wysocki
parent
b86ff9820f
commit
4d7e30d989
3 changed files with 103 additions and 4 deletions
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@ -33,6 +33,7 @@
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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 <asm/uaccess.h>
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#include <asm/io.h>
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#include <asm/mman.h>
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@ -87,7 +88,7 @@
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*/
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/* Epoll private bits inside the event mask */
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#define EP_PRIVATE_BITS (EPOLLONESHOT | EPOLLET)
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#define EP_PRIVATE_BITS (EPOLLWAKEUP | EPOLLONESHOT | EPOLLET)
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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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@ -154,6 +155,9 @@ struct epitem {
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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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/* wakeup_source used when EPOLLWAKEUP is set */
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struct wakeup_source *ws;
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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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@ -194,6 +198,9 @@ struct eventpoll {
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*/
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struct epitem *ovflist;
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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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/* The user that created the eventpoll descriptor */
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struct user_struct *user;
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@ -588,8 +595,10 @@ static int ep_scan_ready_list(struct eventpoll *ep,
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* queued into ->ovflist but the "txlist" might already
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* contain them, and the list_splice() below takes care of them.
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*/
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if (!ep_is_linked(&epi->rdllink))
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if (!ep_is_linked(&epi->rdllink)) {
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list_add_tail(&epi->rdllink, &ep->rdllist);
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__pm_stay_awake(epi->ws);
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}
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}
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/*
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* We need to set back ep->ovflist to EP_UNACTIVE_PTR, so that after
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@ -602,6 +611,7 @@ static int ep_scan_ready_list(struct eventpoll *ep,
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* Quickly re-inject items left on "txlist".
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*/
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list_splice(&txlist, &ep->rdllist);
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__pm_relax(ep->ws);
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if (!list_empty(&ep->rdllist)) {
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/*
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@ -656,6 +666,8 @@ static int ep_remove(struct eventpoll *ep, struct epitem *epi)
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list_del_init(&epi->rdllink);
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spin_unlock_irqrestore(&ep->lock, flags);
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wakeup_source_unregister(epi->ws);
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/* At this point it is safe to free the eventpoll item */
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kmem_cache_free(epi_cache, epi);
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@ -706,6 +718,7 @@ static void ep_free(struct eventpoll *ep)
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mutex_unlock(&epmutex);
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mutex_destroy(&ep->mtx);
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free_uid(ep->user);
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wakeup_source_unregister(ep->ws);
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kfree(ep);
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}
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@ -737,6 +750,7 @@ static int ep_read_events_proc(struct eventpoll *ep, struct list_head *head,
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* callback, but it's not actually ready, as far as
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* caller requested events goes. We can remove it here.
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*/
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__pm_relax(epi->ws);
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list_del_init(&epi->rdllink);
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}
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}
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@ -927,13 +941,23 @@ static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *k
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if (epi->next == EP_UNACTIVE_PTR) {
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epi->next = ep->ovflist;
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ep->ovflist = epi;
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if (epi->ws) {
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/*
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* Activate ep->ws since epi->ws may get
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* deactivated at any time.
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*/
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__pm_stay_awake(ep->ws);
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}
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}
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goto out_unlock;
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}
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/* If this file is already in the ready list we exit soon */
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if (!ep_is_linked(&epi->rdllink))
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if (!ep_is_linked(&epi->rdllink)) {
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list_add_tail(&epi->rdllink, &ep->rdllist);
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__pm_stay_awake(epi->ws);
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}
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/*
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* Wake up ( if active ) both the eventpoll wait list and the ->poll()
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@ -1091,6 +1115,30 @@ static int reverse_path_check(void)
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return error;
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}
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static int ep_create_wakeup_source(struct epitem *epi)
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{
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const char *name;
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if (!epi->ep->ws) {
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epi->ep->ws = wakeup_source_register("eventpoll");
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if (!epi->ep->ws)
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return -ENOMEM;
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}
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name = epi->ffd.file->f_path.dentry->d_name.name;
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epi->ws = wakeup_source_register(name);
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if (!epi->ws)
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return -ENOMEM;
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return 0;
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}
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static void ep_destroy_wakeup_source(struct epitem *epi)
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{
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wakeup_source_unregister(epi->ws);
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epi->ws = NULL;
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}
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/*
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* Must be called with "mtx" held.
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*/
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@ -1118,6 +1166,13 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
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epi->event = *event;
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epi->nwait = 0;
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epi->next = EP_UNACTIVE_PTR;
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if (epi->event.events & EPOLLWAKEUP) {
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error = ep_create_wakeup_source(epi);
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if (error)
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goto error_create_wakeup_source;
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} else {
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epi->ws = NULL;
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}
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/* Initialize the poll table using the queue callback */
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epq.epi = epi;
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@ -1164,6 +1219,7 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
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/* If the file is already "ready" we drop it inside the ready list */
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if ((revents & event->events) && !ep_is_linked(&epi->rdllink)) {
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list_add_tail(&epi->rdllink, &ep->rdllist);
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__pm_stay_awake(epi->ws);
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/* Notify waiting tasks that events are available */
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if (waitqueue_active(&ep->wq))
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@ -1204,6 +1260,9 @@ error_unregister:
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list_del_init(&epi->rdllink);
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spin_unlock_irqrestore(&ep->lock, flags);
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wakeup_source_unregister(epi->ws);
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error_create_wakeup_source:
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kmem_cache_free(epi_cache, epi);
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return error;
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@ -1229,6 +1288,12 @@ static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_even
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epi->event.events = event->events;
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pt._key = event->events;
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epi->event.data = event->data; /* protected by mtx */
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if (epi->event.events & EPOLLWAKEUP) {
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if (!epi->ws)
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ep_create_wakeup_source(epi);
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} else if (epi->ws) {
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ep_destroy_wakeup_source(epi);
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}
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/*
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* Get current event bits. We can safely use the file* here because
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@ -1244,6 +1309,7 @@ static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_even
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spin_lock_irq(&ep->lock);
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if (!ep_is_linked(&epi->rdllink)) {
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list_add_tail(&epi->rdllink, &ep->rdllist);
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__pm_stay_awake(epi->ws);
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/* Notify waiting tasks that events are available */
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if (waitqueue_active(&ep->wq))
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@ -1282,6 +1348,18 @@ static int ep_send_events_proc(struct eventpoll *ep, struct list_head *head,
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!list_empty(head) && eventcnt < esed->maxevents;) {
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epi = list_first_entry(head, struct epitem, rdllink);
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/*
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* Activate ep->ws before deactivating epi->ws to prevent
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* triggering auto-suspend here (in case we reactive epi->ws
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* below).
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*
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* This could be rearranged to delay the deactivation of epi->ws
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* instead, but then epi->ws would temporarily be out of sync
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* with ep_is_linked().
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*/
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if (epi->ws && epi->ws->active)
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__pm_stay_awake(ep->ws);
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__pm_relax(epi->ws);
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list_del_init(&epi->rdllink);
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pt._key = epi->event.events;
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@ -1298,6 +1376,7 @@ static int ep_send_events_proc(struct eventpoll *ep, struct list_head *head,
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if (__put_user(revents, &uevent->events) ||
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__put_user(epi->event.data, &uevent->data)) {
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list_add(&epi->rdllink, head);
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__pm_stay_awake(epi->ws);
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return eventcnt ? eventcnt : -EFAULT;
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}
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eventcnt++;
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@ -1317,6 +1396,7 @@ static int ep_send_events_proc(struct eventpoll *ep, struct list_head *head,
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* poll callback will queue them in ep->ovflist.
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*/
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list_add_tail(&epi->rdllink, &ep->rdllist);
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__pm_stay_awake(epi->ws);
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}
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}
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}
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@ -1629,6 +1709,10 @@ SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd,
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if (!tfile->f_op || !tfile->f_op->poll)
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goto error_tgt_fput;
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/* Check if EPOLLWAKEUP is allowed */
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if ((epds.events & EPOLLWAKEUP) && !capable(CAP_EPOLLWAKEUP))
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goto error_tgt_fput;
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/*
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* We have to check that the file structure underneath the file descriptor
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* the user passed to us _is_ an eventpoll file. And also we do not permit
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@ -360,8 +360,11 @@ struct cpu_vfs_cap_data {
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#define CAP_WAKE_ALARM 35
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/* Allow preventing system suspends while epoll events are pending */
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#define CAP_LAST_CAP CAP_WAKE_ALARM
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#define CAP_EPOLLWAKEUP 36
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#define CAP_LAST_CAP CAP_EPOLLWAKEUP
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#define cap_valid(x) ((x) >= 0 && (x) <= CAP_LAST_CAP)
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@ -26,6 +26,18 @@
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#define EPOLL_CTL_DEL 2
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#define EPOLL_CTL_MOD 3
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/*
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* Request the handling of system wakeup events so as to prevent system suspends
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* from happening while those events are being processed.
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*
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* Assuming neither EPOLLET nor EPOLLONESHOT is set, system suspends will not be
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* re-allowed until epoll_wait is called again after consuming the wakeup
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* event(s).
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*
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* Requires CAP_EPOLLWAKEUP
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*/
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#define EPOLLWAKEUP (1 << 29)
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/* Set the One Shot behaviour for the target file descriptor */
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#define EPOLLONESHOT (1 << 30)
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