From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753349AbbBYOOu (ORCPT ); Wed, 25 Feb 2015 09:14:50 -0500 Received: from mail.kernel.org ([198.145.29.136]:43325 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753312AbbBYOOr (ORCPT ); Wed, 25 Feb 2015 09:14:47 -0500 Date: Wed, 25 Feb 2015 15:14:36 +0100 From: "Michael S. Tsirkin" To: linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org, Thomas Huth , Rusty Russell , virtualization@lists.linux-foundation.org, kvm@vger.kernel.org Subject: [PATCH] virtio-balloon: do not call blocking ops when !TASK_RUNNING Message-ID: <1424873603-16386-1-git-send-email-mst@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Mailer: git-send-email 2.0.0.545.gd9cabeb X-Mutt-Fcc: =sent Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org virtio balloon has this code: wait_event_interruptible(vb->config_change, (diff = towards_target(vb)) != 0 || vb->need_stats_update || kthread_should_stop() || freezing(current)); Which is a problem because towards_target() call might block after wait_event_interruptible sets task state to TAST_INTERRUPTIBLE, causing the task_struct::state collision typical of nesting of sleeping primitives See also http://lwn.net/Articles/628628/ or Thomas's bug report http://article.gmane.org/gmane.linux.kernel.virtualization/24846 for a fuller explanation. To fix, rewrite using wait_woken. Cc: stable@vger.kernel.org Reported-by: Thomas Huth Signed-off-by: Michael S. Tsirkin --- drivers/virtio/virtio_balloon.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index 0413157..2f19f65 100644 --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -29,6 +29,7 @@ #include #include #include +#include /* * Balloon device works in 4K page units. So each page is pointed to by @@ -334,12 +335,25 @@ static int virtballoon_oom_notify(struct notifier_block *self, static int balloon(void *_vballoon) { struct virtio_balloon *vb = _vballoon; + DEFINE_WAIT_FUNC(wait, woken_wake_function); set_freezable(); while (!kthread_should_stop()) { s64 diff; try_to_freeze(); + + add_wait_queue(&vb->config_change, &wait); + for (;;) { + if ((diff = towards_target(vb)) != 0 || + vb->need_stats_update || + kthread_should_stop() || + freezing(current)) + break; + wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT); + } + remove_wait_queue(&vb->config_change, &wait); + wait_event_interruptible(vb->config_change, (diff = towards_target(vb)) != 0 || vb->need_stats_update -- MST