Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756129Ab2K1VHb (ORCPT ); Wed, 28 Nov 2012 16:07:31 -0500 Received: from mail-da0-f46.google.com ([209.85.210.46]:61274 "EHLO mail-da0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755681Ab2K1VH3 (ORCPT ); Wed, 28 Nov 2012 16:07:29 -0500 Date: Wed, 28 Nov 2012 13:07:19 -0800 From: Tejun Heo To: Greg Thelen Cc: Li Zefan , containers@lists.linux-foundation.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Aaron Durbin Subject: Re: [PATCH] cgroup: fix lockdep warning for event_control Message-ID: <20121128210719.GB24683@htj.dyndns.org> References: <1354133742-22175-1-git-send-email-gthelen@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1354133742-22175-1-git-send-email-gthelen@google.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1801 Lines: 53 Hello, Greg. On Wed, Nov 28, 2012 at 12:15:42PM -0800, Greg Thelen wrote: > @@ -4276,6 +4276,7 @@ static int cgroup_destroy_locked(struct cgroup *cgrp) > DEFINE_WAIT(wait); > struct cgroup_event *event, *tmp; > struct cgroup_subsys *ss; > + struct list_head tmp_list; LIST_HEAD(tmp_list); > > lockdep_assert_held(&d->d_inode->i_mutex); > lockdep_assert_held(&cgroup_mutex); > @@ -4330,16 +4331,20 @@ static int cgroup_destroy_locked(struct cgroup *cgrp) > /* > * Unregister events and notify userspace. > * Notify userspace about cgroup removing only after rmdir of cgroup > - * directory to avoid race between userspace and kernelspace > + * directory to avoid race between userspace and kernelspace. Use > + * a temporary list to avoid a deadlock with cgroup_event_wake(). Since > + * cgroup_event_wake() is called with the wait queue head locked, > + * remove_wait_queue() cannot be called while holding event_list_lock. > */ > spin_lock(&cgrp->event_list_lock); > - list_for_each_entry_safe(event, tmp, &cgrp->event_list, list) { > + list_replace_init(&cgrp->event_list, &tmp_list); list_splice_init(); would be more conventional, I think. > + spin_unlock(&cgrp->event_list_lock); > + list_for_each_entry_safe(event, tmp, &tmp_list, list) { > list_del(&event->list); Maybe convert this to list_del_init() while at it? > remove_wait_queue(event->wqh, &event->wait); > eventfd_signal(event->eventfd, 1); > schedule_work(&event->remove); > } > - spin_unlock(&cgrp->event_list_lock); Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/