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authorDavid S. Miller <davem@davemloft.net>2013-01-16 00:05:59 +0400
committerDavid S. Miller <davem@davemloft.net>2013-01-16 00:05:59 +0400
commit4b87f922598acf91eee18f71688a33f54f57bcde (patch)
tree9cdfe30c6b96c47093da5392ed82d147290cd64c /fs/eventpoll.c
parent55eb555d9674e2ebe9d4de0146602f96ff18e7d6 (diff)
parentdaf3ec688e057f6060fb9bb0819feac7a8bbf45c (diff)
downloadlinux-4b87f922598acf91eee18f71688a33f54f57bcde.tar.xz
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net
Conflicts: Documentation/networking/ip-sysctl.txt drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.c Both conflicts were simply overlapping context. A build fix for qlcnic is in here too, simply removing the added devinit annotations which no longer exist. Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'fs/eventpoll.c')
-rw-r--r--fs/eventpoll.c22
1 files changed, 21 insertions, 1 deletions
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index be56b21435f8..9fec1836057a 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1313,7 +1313,7 @@ static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_even
* otherwise we might miss an event that happens between the
* f_op->poll() call and the new event set registering.
*/
- epi->event.events = event->events;
+ 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) {
@@ -1324,6 +1324,26 @@ static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_even
}
/*
+ * The following barrier has two effects:
+ *
+ * 1) Flush epi changes above to other CPUs. This ensures
+ * we do not miss events from ep_poll_callback if an
+ * event occurs immediately after we call f_op->poll().
+ * We need this because we did not take ep->lock while
+ * changing epi above (but ep_poll_callback does take
+ * ep->lock).
+ *
+ * 2) We also need to ensure we do not miss _past_ events
+ * when calling f_op->poll(). This barrier also
+ * pairs with the barrier in wq_has_sleeper (see
+ * comments for wq_has_sleeper).
+ *
+ * This barrier will now guarantee ep_poll_callback or f_op->poll
+ * (or both) will notice the readiness of an item.
+ */
+ smp_mb();
+
+ /*
* Get current event bits. We can safely use the file* here because
* its usage count has been increased by the caller of this function.
*/