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epoll: clean up ep_modify 

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@cybernetics.com>
Acked-by: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Tony Battersby 2009-03-31 15:24:15 -07:00 committed by Linus Torvalds
parent d1bc90dd5d
commit e057e15ff6
1 changed files with 7 additions and 12 deletions
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19
fs/eventpoll.c
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@ -435,7 +435,7 @@ static int ep_scan_ready_list(struct eventpoll *ep,
/*
* 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 *ep, struct epitem *epi, struct epoll_even
{
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 *ep, struct epitem *epi, struct epoll_even
*/
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 *ep, struct epitem *epi, struct epoll_even
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)