From patchwork Wed Feb 25 14:14:36 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Michael S. Tsirkin" X-Patchwork-Id: 5880381 Return-Path: X-Original-To: patchwork-kvm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id CF5979F269 for ; Wed, 25 Feb 2015 14:15:09 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 10AF120383 for ; Wed, 25 Feb 2015 14:15:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3A5A220382 for ; Wed, 25 Feb 2015 14:15:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753324AbbBYOOu (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 Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 5DF2920382; Wed, 25 Feb 2015 14:14:46 +0000 (UTC) Received: from redhat.com (bzq-109-64-63-74.red.bezeqint.net [109.64.63.74]) (using TLSv1.2 with cipher AES128-SHA (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9327820122; Wed, 25 Feb 2015 14:14:39 +0000 (UTC) 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-Disposition: inline X-Mailer: git-send-email 2.0.0.545.gd9cabeb X-Mutt-Fcc: =sent X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP 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