From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-Id: <20130411202602.168619128@goodmis.org> Date: Thu, 11 Apr 2013 16:26:41 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Al Viro Subject: [ 098/171 ] vt: synchronize_rcu() under spinlock is not nice... References: <20130411202503.783159048@goodmis.org> Content-Disposition: inline; filename=0098-vt-synchronize_rcu-under-spinlock-is-not-nice.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.6.11.2 stable review patch. If anyone has any objections, please let me know. ------------------ From: Al Viro [ Upstream commit e8cd81693bbbb15db57d3c9aa7dd90eda4842874 ] 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. Cc: stable@vger.kernel.org (all kernels since 2.6.37) Signed-off-by: Al Viro Signed-off-by: Steven Rostedt --- drivers/tty/vt/vc_screen.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/tty/vt/vc_screen.c b/drivers/tty/vt/vc_screen.c index fa7268a..6abb92c 100644 --- a/drivers/tty/vt/vc_screen.c +++ b/drivers/tty/vt/vc_screen.c @@ -93,7 +93,7 @@ vcs_poll_data_free(struct vcs_poll_data *poll) 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; @@ -122,10 +122,12 @@ 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; } -- 1.7.10.4