From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759682AbZBXRbD (ORCPT ); Tue, 24 Feb 2009 12:31:03 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759415AbZBXR27 (ORCPT ); Tue, 24 Feb 2009 12:28:59 -0500 Received: from host64.cybernetics.com ([98.174.209.230]:1945 "EHLO mail.cybernetics.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759956AbZBXR26 (ORCPT ); Tue, 24 Feb 2009 12:28:58 -0500 Message-ID: <49A42E58.50805@cybernetics.com> Date: Tue, 24 Feb 2009 12:28:56 -0500 From: Tony Battersby User-Agent: Thunderbird 2.0.0.19 (X11/20090105) MIME-Version: 1.0 To: Andrew Morton , Davide Libenzi Cc: Jonathan Corbet , linux-kernel@vger.kernel.org Subject: [PATCH 5/6] [-mm] epoll: clean up ep_modify Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- This patch is against the current -mm tree, and might not apply to 2.6.29. Since this patch probably won't go into 2.6.29, you may apply this version of the patch after the other patches in -mm. --- a/fs/eventpoll.c 2009-02-23 14:02:49.000000000 -0500 +++ b/fs/eventpoll.c 2009-02-23 14:02:55.000000000 -0500 @@ -454,7 +454,7 @@ 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); @@ -1037,15 +1037,14 @@ 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 @@ -1053,16 +1052,12 @@ 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); @@ -1072,8 +1067,8 @@ 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)