From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759558Ab3DBXC0 (ORCPT ); Tue, 2 Apr 2013 19:02:26 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:33948 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758144Ab3DBWuf (ORCPT ); Tue, 2 Apr 2013 18:50:35 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Al Viro Subject: [ 13/56] vt: synchronize_rcu() under spinlock is not nice... Date: Tue, 2 Apr 2013 15:49:40 -0700 Message-Id: <20130402224713.407794747@linuxfoundation.org> X-Mailer: git-send-email 1.8.1.rc1.5.g7e0651a In-Reply-To: <20130402224711.840825715@linuxfoundation.org> References: <20130402224711.840825715@linuxfoundation.org> User-Agent: quilt/0.60-5.1.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.0-stable review patch. If anyone has any objections, please let me know. ------------------ From: Al Viro commit e8cd81693bbbb15db57d3c9aa7dd90eda4842874 upstream. vcs_poll_data_free() calls unregister_vt_notifier(), which calls atomic_notifier_chain_unregister(), which calls synchronize_rcu(). Do it *after* we'd dropped ->f_lock. Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman --- drivers/tty/vt/vc_screen.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/drivers/tty/vt/vc_screen.c +++ b/drivers/tty/vt/vc_screen.c @@ -92,7 +92,7 @@ vcs_poll_data_free(struct vcs_poll_data static struct vcs_poll_data * vcs_poll_data_get(struct file *file) { - struct vcs_poll_data *poll = file->private_data; + struct vcs_poll_data *poll = file->private_data, *kill = NULL; if (poll) return poll; @@ -121,10 +121,12 @@ vcs_poll_data_get(struct file *file) file->private_data = poll; } else { /* someone else raced ahead of us */ - vcs_poll_data_free(poll); + kill = poll; poll = file->private_data; } spin_unlock(&file->f_lock); + if (kill) + vcs_poll_data_free(kill); return poll; }