From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gregory Haskins Subject: [KVM PATCH v2 1/2] Allow waiters to be notified about the eventfd file* going away, and give Date: Thu, 04 Jun 2009 08:48:07 -0400 Message-ID: <20090604124807.10544.6071.stgit@dev.haskins.net> References: <20090604124047.10544.38861.stgit@dev.haskins.net> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: linux-kernel@vger.kernel.org, avi@redhat.com, davdel@xmailserver.org, mst@redhat.com, paulmck@linux.vnet.ibm.com, akpm@linux-foundation.org To: kvm@vger.kernel.org Return-path: Received: from victor.provo.novell.com ([137.65.250.26]:35386 "EHLO victor.provo.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754109AbZFDMsL (ORCPT ); Thu, 4 Jun 2009 08:48:11 -0400 In-Reply-To: <20090604124047.10544.38861.stgit@dev.haskins.net> Sender: kvm-owner@vger.kernel.org List-ID: From: Davide Libenzi them a change to unregister from the wait queue. This is turn allows eventfd users to use the eventfd file* w/out holding a live reference to it. After the eventfd user callbacks returns, any usage of the eventfd file* should be dropped. The eventfd user callback can acquire sleepy locks since it is invoked lockless. This is a feature, needed by KVM to avoid an awkward workaround when using eventdf. [gmh: pulled from -mmotm for inclusion in kvm.git] Signed-off-by: Davide Libenzi Tested-by: Gregory Haskins Signed-off-by: Andrew Morton Signed-off-by: Gregory Haskins --- fs/eventfd.c | 10 +++++++++- 1 files changed, 9 insertions(+), 1 deletions(-) diff --git a/fs/eventfd.c b/fs/eventfd.c index 3f0e197..72f5f8d 100644 --- a/fs/eventfd.c +++ b/fs/eventfd.c @@ -61,7 +61,15 @@ EXPORT_SYMBOL_GPL(eventfd_signal); static int eventfd_release(struct inode *inode, struct file *file) { - kfree(file->private_data); + struct eventfd_ctx *ctx = file->private_data; + + /* + * No need to hold the lock here, since we are on the file cleanup + * path and the ones still attached to the wait queue will be + * serialized by wake_up_locked_poll(). + */ + wake_up_locked_poll(&ctx->wqh, POLLHUP); + kfree(ctx); return 0; }