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>
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index c0b3c70..2cf0f21 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -33,6 +33,7 @@
#include <linux/bitops.h>
#include <linux/mutex.h>
#include <linux/anon_inodes.h>
+#include <linux/device.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <asm/mman.h>
@@ -87,7 +88,7 @@
*/
/* Epoll private bits inside the event mask */
-#define EP_PRIVATE_BITS (EPOLLONESHOT | EPOLLET)
+#define EP_PRIVATE_BITS (EPOLLWAKEUP | EPOLLONESHOT | EPOLLET)
/* Maximum number of nesting allowed inside epoll sets */
#define EP_MAX_NESTS 4
@@ -154,6 +155,9 @@
/* List header used to link this item to the "struct file" items list */
struct list_head fllink;
+ /* wakeup_source used when EPOLLWAKEUP is set */
+ struct wakeup_source *ws;
+
/* The structure that describe the interested events and the source fd */
struct epoll_event event;
};
@@ -194,6 +198,9 @@
*/
struct epitem *ovflist;
+ /* wakeup_source used when ep_scan_ready_list is running */
+ struct wakeup_source *ws;
+
/* The user that created the eventpoll descriptor */
struct user_struct *user;
@@ -588,8 +595,10 @@
* queued into ->ovflist but the "txlist" might already
* contain them, and the list_splice() below takes care of them.
*/
- if (!ep_is_linked(&epi->rdllink))
+ if (!ep_is_linked(&epi->rdllink)) {
list_add_tail(&epi->rdllink, &ep->rdllist);
+ __pm_stay_awake(epi->ws);
+ }
}
/*
* We need to set back ep->ovflist to EP_UNACTIVE_PTR, so that after
@@ -602,6 +611,7 @@
* Quickly re-inject items left on "txlist".
*/
list_splice(&txlist, &ep->rdllist);
+ __pm_relax(ep->ws);
if (!list_empty(&ep->rdllist)) {
/*
@@ -656,6 +666,8 @@
list_del_init(&epi->rdllink);
spin_unlock_irqrestore(&ep->lock, flags);
+ wakeup_source_unregister(epi->ws);
+
/* At this point it is safe to free the eventpoll item */
kmem_cache_free(epi_cache, epi);
@@ -706,6 +718,7 @@
mutex_unlock(&epmutex);
mutex_destroy(&ep->mtx);
free_uid(ep->user);
+ wakeup_source_unregister(ep->ws);
kfree(ep);
}
@@ -737,6 +750,7 @@
* callback, but it's not actually ready, as far as
* caller requested events goes. We can remove it here.
*/
+ __pm_relax(epi->ws);
list_del_init(&epi->rdllink);
}
}
@@ -927,13 +941,23 @@
if (epi->next == EP_UNACTIVE_PTR) {
epi->next = ep->ovflist;
ep->ovflist = epi;
+ if (epi->ws) {
+ /*
+ * Activate ep->ws since epi->ws may get
+ * deactivated at any time.
+ */
+ __pm_stay_awake(ep->ws);
+ }
+
}
goto out_unlock;
}
/* If this file is already in the ready list we exit soon */
- if (!ep_is_linked(&epi->rdllink))
+ if (!ep_is_linked(&epi->rdllink)) {
list_add_tail(&epi->rdllink, &ep->rdllist);
+ __pm_stay_awake(epi->ws);
+ }
/*
* Wake up ( if active ) both the eventpoll wait list and the ->poll()
@@ -1091,6 +1115,30 @@
return error;
}
+static int ep_create_wakeup_source(struct epitem *epi)
+{
+ const char *name;
+
+ if (!epi->ep->ws) {
+ epi->ep->ws = wakeup_source_register("eventpoll");
+ if (!epi->ep->ws)
+ return -ENOMEM;
+ }
+
+ name = epi->ffd.file->f_path.dentry->d_name.name;
+ epi->ws = wakeup_source_register(name);
+ if (!epi->ws)
+ return -ENOMEM;
+
+ return 0;
+}
+
+static void ep_destroy_wakeup_source(struct epitem *epi)
+{
+ wakeup_source_unregister(epi->ws);
+ epi->ws = NULL;
+}
+
/*
* Must be called with "mtx" held.
*/
@@ -1118,6 +1166,13 @@
epi->event = *event;
epi->nwait = 0;
epi->next = EP_UNACTIVE_PTR;
+ if (epi->event.events & EPOLLWAKEUP) {
+ error = ep_create_wakeup_source(epi);
+ if (error)
+ goto error_create_wakeup_source;
+ } else {
+ epi->ws = NULL;
+ }
/* Initialize the poll table using the queue callback */
epq.epi = epi;
@@ -1164,6 +1219,7 @@
/* 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);
+ __pm_stay_awake(epi->ws);
/* Notify waiting tasks that events are available */
if (waitqueue_active(&ep->wq))
@@ -1204,6 +1260,9 @@
list_del_init(&epi->rdllink);
spin_unlock_irqrestore(&ep->lock, flags);
+ wakeup_source_unregister(epi->ws);
+
+error_create_wakeup_source:
kmem_cache_free(epi_cache, epi);
return error;
@@ -1229,6 +1288,12 @@
epi->event.events = event->events;
pt._key = event->events;
epi->event.data = event->data; /* protected by mtx */
+ if (epi->event.events & EPOLLWAKEUP) {
+ if (!epi->ws)
+ ep_create_wakeup_source(epi);
+ } else if (epi->ws) {
+ ep_destroy_wakeup_source(epi);
+ }
/*
* Get current event bits. We can safely use the file* here because
@@ -1244,6 +1309,7 @@
spin_lock_irq(&ep->lock);
if (!ep_is_linked(&epi->rdllink)) {
list_add_tail(&epi->rdllink, &ep->rdllist);
+ __pm_stay_awake(epi->ws);
/* Notify waiting tasks that events are available */
if (waitqueue_active(&ep->wq))
@@ -1282,6 +1348,18 @@
!list_empty(head) && eventcnt < esed->maxevents;) {
epi = list_first_entry(head, struct epitem, rdllink);
+ /*
+ * Activate ep->ws before deactivating epi->ws to prevent
+ * triggering auto-suspend here (in case we reactive epi->ws
+ * below).
+ *
+ * This could be rearranged to delay the deactivation of epi->ws
+ * instead, but then epi->ws would temporarily be out of sync
+ * with ep_is_linked().
+ */
+ if (epi->ws && epi->ws->active)
+ __pm_stay_awake(ep->ws);
+ __pm_relax(epi->ws);
list_del_init(&epi->rdllink);
pt._key = epi->event.events;
@@ -1298,6 +1376,7 @@
if (__put_user(revents, &uevent->events) ||
__put_user(epi->event.data, &uevent->data)) {
list_add(&epi->rdllink, head);
+ __pm_stay_awake(epi->ws);
return eventcnt ? eventcnt : -EFAULT;
}
eventcnt++;
@@ -1317,6 +1396,7 @@
* poll callback will queue them in ep->ovflist.
*/
list_add_tail(&epi->rdllink, &ep->rdllist);
+ __pm_stay_awake(epi->ws);
}
}
}
@@ -1629,6 +1709,10 @@
if (!tfile->f_op || !tfile->f_op->poll)
goto error_tgt_fput;
+ /* Check if EPOLLWAKEUP is allowed */
+ if ((epds.events & EPOLLWAKEUP) && !capable(CAP_EPOLLWAKEUP))
+ goto error_tgt_fput;
+
/*
* We have to check that the file structure underneath the file descriptor
* the user passed to us _is_ an eventpoll file. And also we do not permit