The patch titled
epoll: clean up ep_modify
has been added to the -mm tree. Its filename is
epoll-clean-up-ep_modify.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/SubmitChecklist when testing your code ***
See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find
out what to do about this
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: epoll: clean up ep_modify
From: Tony Battersby <tonyb@xxxxxxxxxxxxxxx>
ep_modify() doesn't need to set event.data from within the ep->lock
spinlock as the comment suggests. The only place event.data is used is
ep_send_events_proc(), and this is protected by ep->mtx instead of
ep->lock. Also update the comment for mutex_lock() at the top of
ep_scan_ready_list(), which mentions epoll_ctl(EPOLL_CTL_DEL) but not
epoll_ctl(EPOLL_CTL_MOD).
ep_modify() can also use spin_lock_irq() instead of spin_lock_irqsave().
Signed-off-by: Tony Battersby <tonyb@xxxxxxxxxxxxxxx>
Acked-by: Davide Libenzi <davidel@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/eventpoll.c | 19 +++++++------------
1 file changed, 7 insertions(+), 12 deletions(-)
diff -puN fs/eventpoll.c~epoll-clean-up-ep_modify fs/eventpoll.c
--- a/fs/eventpoll.c~epoll-clean-up-ep_modify
+++ a/fs/eventpoll.c
@@ -435,7 +435,7 @@ static int ep_scan_ready_list(struct eve
/*
* We need to lock this because we could be hit by
- * eventpoll_release_file() and epoll_ctl(EPOLL_CTL_DEL).
+ * eventpoll_release_file() and epoll_ctl().
*/
mutex_lock(&ep->mtx);
@@ -972,15 +972,14 @@ static int ep_modify(struct eventpoll *e
{
int pwake = 0;
unsigned int revents;
- unsigned long flags;
/*
- * Set the new event interest mask before calling f_op->poll(), otherwise
- * a potential race might occur. In fact if we do this operation inside
- * the lock, an event might happen between the f_op->poll() call and the
- * new event set registering.
+ * Set the new event interest mask before calling f_op->poll();
+ * 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.data = event->data; /* protected by mtx */
/*
* Get current event bits. We can safely use the file* here because
@@ -988,16 +987,12 @@ static int ep_modify(struct eventpoll *e
*/
revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL);
- spin_lock_irqsave(&ep->lock, flags);
-
- /* Copy the data member from inside the lock */
- epi->event.data = event->data;
-
/*
* If the item is "hot" and it is not registered inside the ready
* list, push it inside.
*/
if (revents & event->events) {
+ spin_lock_irq(&ep->lock);
if (!ep_is_linked(&epi->rdllink)) {
list_add_tail(&epi->rdllink, &ep->rdllist);
@@ -1007,8 +1002,8 @@ static int ep_modify(struct eventpoll *e
if (waitqueue_active(&ep->poll_wait))
pwake++;
}
+ spin_unlock_irq(&ep->lock);
}
- spin_unlock_irqrestore(&ep->lock, flags);
/* We have to call this outside the lock */
if (pwake)
_
Patches currently in -mm which might be from tonyb@xxxxxxxxxxxxxxx are
origin.patch
linux-next.patch
vfs-improve-comment-describing-fget_light.patch
epoll-dont-use-current-in-irq-context.patch
epoll-remember-the-event-if-epoll_wait-returns-efault.patch
epoll-remove-unnecessary-xchg.patch
epoll-clean-up-ep_modify.patch
epoll-use-real-type-instead-of-void.patch
make-shm_get_stat-more-robust.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
