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Diffstat (limited to 'fs/eventpoll.c')
-rw-r--r--fs/eventpoll.c128
1 files changed, 96 insertions, 32 deletions
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 495d15558f42..deecc7294a67 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -105,7 +105,7 @@
struct epoll_filefd {
struct file *file;
int fd;
-};
+} __packed;
/*
* Structure used to track possible nested calls, for too deep recursions
@@ -129,6 +129,8 @@ struct nested_calls {
/*
* Each file descriptor added to the eventpoll interface will
* have an entry of this type linked to the "rbr" RB tree.
+ * Avoid increasing the size of this struct, there can be many thousands
+ * of these on a server and we do not want this to take another cache line.
*/
struct epitem {
/* RB tree node used to link this structure to the eventpoll RB tree */
@@ -159,7 +161,7 @@ struct epitem {
struct list_head fllink;
/* wakeup_source used when EPOLLWAKEUP is set */
- struct wakeup_source *ws;
+ struct wakeup_source __rcu *ws;
/* The structure that describe the interested events and the source fd */
struct epoll_event event;
@@ -537,6 +539,38 @@ static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi)
}
}
+/* call only when ep->mtx is held */
+static inline struct wakeup_source *ep_wakeup_source(struct epitem *epi)
+{
+ return rcu_dereference_check(epi->ws, lockdep_is_held(&epi->ep->mtx));
+}
+
+/* call only when ep->mtx is held */
+static inline void ep_pm_stay_awake(struct epitem *epi)
+{
+ struct wakeup_source *ws = ep_wakeup_source(epi);
+
+ if (ws)
+ __pm_stay_awake(ws);
+}
+
+static inline bool ep_has_wakeup_source(struct epitem *epi)
+{
+ return rcu_access_pointer(epi->ws) ? true : false;
+}
+
+/* call when ep->mtx cannot be held (ep_poll_callback) */
+static inline void ep_pm_stay_awake_rcu(struct epitem *epi)
+{
+ struct wakeup_source *ws;
+
+ rcu_read_lock();
+ ws = rcu_dereference(epi->ws);
+ if (ws)
+ __pm_stay_awake(ws);
+ rcu_read_unlock();
+}
+
/**
* ep_scan_ready_list - Scans the ready list in a way that makes possible for
* the scan code, to call f_op->poll(). Also allows for
@@ -600,7 +634,7 @@ static int ep_scan_ready_list(struct eventpoll *ep,
*/
if (!ep_is_linked(&epi->rdllink)) {
list_add_tail(&epi->rdllink, &ep->rdllist);
- __pm_stay_awake(epi->ws);
+ ep_pm_stay_awake(epi);
}
}
/*
@@ -669,7 +703,7 @@ static int ep_remove(struct eventpoll *ep, struct epitem *epi)
list_del_init(&epi->rdllink);
spin_unlock_irqrestore(&ep->lock, flags);
- wakeup_source_unregister(epi->ws);
+ wakeup_source_unregister(ep_wakeup_source(epi));
/* At this point it is safe to free the eventpoll item */
kmem_cache_free(epi_cache, epi);
@@ -712,11 +746,15 @@ static void ep_free(struct eventpoll *ep)
* point we are sure no poll callbacks will be lingering around, and also by
* holding "epmutex" we can be sure that no file cleanup code will hit
* us during this operation. So we can avoid the lock on "ep->lock".
+ * We do not need to lock ep->mtx, either, we only do it to prevent
+ * a lockdep warning.
*/
+ mutex_lock(&ep->mtx);
while ((rbp = rb_first(&ep->rbr)) != NULL) {
epi = rb_entry(rbp, struct epitem, rbn);
ep_remove(ep, epi);
}
+ mutex_unlock(&ep->mtx);
mutex_unlock(&epmutex);
mutex_destroy(&ep->mtx);
@@ -735,6 +773,13 @@ static int ep_eventpoll_release(struct inode *inode, struct file *file)
return 0;
}
+static inline unsigned int ep_item_poll(struct epitem *epi, poll_table *pt)
+{
+ pt->_key = epi->event.events;
+
+ return epi->ffd.file->f_op->poll(epi->ffd.file, pt) & epi->event.events;
+}
+
static int ep_read_events_proc(struct eventpoll *ep, struct list_head *head,
void *priv)
{
@@ -742,10 +787,9 @@ static int ep_read_events_proc(struct eventpoll *ep, struct list_head *head,
poll_table pt;
init_poll_funcptr(&pt, NULL);
+
list_for_each_entry_safe(epi, tmp, head, rdllink) {
- pt._key = epi->event.events;
- if (epi->ffd.file->f_op->poll(epi->ffd.file, &pt) &
- epi->event.events)
+ if (ep_item_poll(epi, &pt))
return POLLIN | POLLRDNORM;
else {
/*
@@ -753,7 +797,7 @@ static int ep_read_events_proc(struct eventpoll *ep, struct list_head *head,
* callback, but it's not actually ready, as far as
* caller requested events goes. We can remove it here.
*/
- __pm_relax(epi->ws);
+ __pm_relax(ep_wakeup_source(epi));
list_del_init(&epi->rdllink);
}
}
@@ -985,7 +1029,7 @@ static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *k
/* If this file is already in the ready list we exit soon */
if (!ep_is_linked(&epi->rdllink)) {
list_add_tail(&epi->rdllink, &ep->rdllist);
- __pm_stay_awake(epi->ws);
+ ep_pm_stay_awake_rcu(epi);
}
/*
@@ -1147,6 +1191,7 @@ static int reverse_path_check(void)
static int ep_create_wakeup_source(struct epitem *epi)
{
const char *name;
+ struct wakeup_source *ws;
if (!epi->ep->ws) {
epi->ep->ws = wakeup_source_register("eventpoll");
@@ -1155,17 +1200,29 @@ static int ep_create_wakeup_source(struct epitem *epi)
}
name = epi->ffd.file->f_path.dentry->d_name.name;
- epi->ws = wakeup_source_register(name);
- if (!epi->ws)
+ ws = wakeup_source_register(name);
+
+ if (!ws)
return -ENOMEM;
+ rcu_assign_pointer(epi->ws, ws);
return 0;
}
-static void ep_destroy_wakeup_source(struct epitem *epi)
+/* rare code path, only used when EPOLL_CTL_MOD removes a wakeup source */
+static noinline void ep_destroy_wakeup_source(struct epitem *epi)
{
- wakeup_source_unregister(epi->ws);
- epi->ws = NULL;
+ struct wakeup_source *ws = ep_wakeup_source(epi);
+
+ RCU_INIT_POINTER(epi->ws, NULL);
+
+ /*
+ * wait for ep_pm_stay_awake_rcu to finish, synchronize_rcu is
+ * used internally by wakeup_source_remove, too (called by
+ * wakeup_source_unregister), so we cannot use call_rcu
+ */
+ synchronize_rcu();
+ wakeup_source_unregister(ws);
}
/*
@@ -1200,13 +1257,12 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
if (error)
goto error_create_wakeup_source;
} else {
- epi->ws = NULL;
+ RCU_INIT_POINTER(epi->ws, NULL);
}
/* Initialize the poll table using the queue callback */
epq.epi = epi;
init_poll_funcptr(&epq.pt, ep_ptable_queue_proc);
- epq.pt._key = event->events;
/*
* Attach the item to the poll hooks and get current event bits.
@@ -1215,7 +1271,7 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
* this operation completes, the poll callback can start hitting
* the new item.
*/
- revents = tfile->f_op->poll(tfile, &epq.pt);
+ revents = ep_item_poll(epi, &epq.pt);
/*
* We have to check if something went wrong during the poll wait queue
@@ -1248,7 +1304,7 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
/* 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);
+ ep_pm_stay_awake(epi);
/* Notify waiting tasks that events are available */
if (waitqueue_active(&ep->wq))
@@ -1289,7 +1345,7 @@ error_unregister:
list_del_init(&epi->rdllink);
spin_unlock_irqrestore(&ep->lock, flags);
- wakeup_source_unregister(epi->ws);
+ wakeup_source_unregister(ep_wakeup_source(epi));
error_create_wakeup_source:
kmem_cache_free(epi_cache, epi);
@@ -1315,12 +1371,11 @@ static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_even
* f_op->poll() call and the new event set registering.
*/
epi->event.events = event->events; /* need barrier below */
- pt._key = event->events;
epi->event.data = event->data; /* protected by mtx */
if (epi->event.events & EPOLLWAKEUP) {
- if (!epi->ws)
+ if (!ep_has_wakeup_source(epi))
ep_create_wakeup_source(epi);
- } else if (epi->ws) {
+ } else if (ep_has_wakeup_source(epi)) {
ep_destroy_wakeup_source(epi);
}
@@ -1348,7 +1403,7 @@ static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_even
* Get current event bits. We can safely use the file* here because
* its usage count has been increased by the caller of this function.
*/
- revents = epi->ffd.file->f_op->poll(epi->ffd.file, &pt);
+ revents = ep_item_poll(epi, &pt);
/*
* If the item is "hot" and it is not registered inside the ready
@@ -1358,7 +1413,7 @@ static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_even
spin_lock_irq(&ep->lock);
if (!ep_is_linked(&epi->rdllink)) {
list_add_tail(&epi->rdllink, &ep->rdllist);
- __pm_stay_awake(epi->ws);
+ ep_pm_stay_awake(epi);
/* Notify waiting tasks that events are available */
if (waitqueue_active(&ep->wq))
@@ -1384,6 +1439,7 @@ static int ep_send_events_proc(struct eventpoll *ep, struct list_head *head,
unsigned int revents;
struct epitem *epi;
struct epoll_event __user *uevent;
+ struct wakeup_source *ws;
poll_table pt;
init_poll_funcptr(&pt, NULL);
@@ -1406,14 +1462,16 @@ static int ep_send_events_proc(struct eventpoll *ep, struct list_head *head,
* 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);
+ ws = ep_wakeup_source(epi);
+ if (ws) {
+ if (ws->active)
+ __pm_stay_awake(ep->ws);
+ __pm_relax(ws);
+ }
+
list_del_init(&epi->rdllink);
- pt._key = epi->event.events;
- revents = epi->ffd.file->f_op->poll(epi->ffd.file, &pt) &
- epi->event.events;
+ revents = ep_item_poll(epi, &pt);
/*
* If the event mask intersect the caller-requested one,
@@ -1425,7 +1483,7 @@ static int ep_send_events_proc(struct eventpoll *ep, struct list_head *head,
if (__put_user(revents, &uevent->events) ||
__put_user(epi->event.data, &uevent->data)) {
list_add(&epi->rdllink, head);
- __pm_stay_awake(epi->ws);
+ ep_pm_stay_awake(epi);
return eventcnt ? eventcnt : -EFAULT;
}
eventcnt++;
@@ -1445,7 +1503,7 @@ static int ep_send_events_proc(struct eventpoll *ep, struct list_head *head,
* poll callback will queue them in ep->ovflist.
*/
list_add_tail(&epi->rdllink, &ep->rdllist);
- __pm_stay_awake(epi->ws);
+ ep_pm_stay_awake(epi);
}
}
}
@@ -2011,6 +2069,12 @@ static int __init eventpoll_init(void)
/* Initialize the structure used to perform file's f_op->poll() calls */
ep_nested_calls_init(&poll_readywalk_ncalls);
+ /*
+ * We can have many thousands of epitems, so prevent this from
+ * using an extra cache line on 64-bit (and smaller) CPUs
+ */
+ BUILD_BUG_ON(sizeof(void *) <= 8 && sizeof(struct epitem) > 128);
+
/* Allocates slab cache used to allocate "struct epitem" items */
epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem),
0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
generated by cgit v1.2.3 (git 2.39.0) at 2024-12-17 13:31:28 +0300