Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753079AbbBYPLi (ORCPT ); Wed, 25 Feb 2015 10:11:38 -0500 Received: from e06smtp11.uk.ibm.com ([195.75.94.107]:54699 "EHLO e06smtp11.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752492AbbBYPLg (ORCPT ); Wed, 25 Feb 2015 10:11:36 -0500 Date: Wed, 25 Feb 2015 16:11:27 +0100 From: Cornelia Huck To: "Michael S. Tsirkin" Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, Thomas Huth , Rusty Russell , virtualization@lists.linux-foundation.org, kvm@vger.kernel.org Subject: Re: [PATCH v2] virtio-balloon: do not call blocking ops when !TASK_RUNNING Message-ID: <20150225161127.51f06c8c.cornelia.huck@de.ibm.com> In-Reply-To: <1424874878-17155-1-git-send-email-mst@redhat.com> References: <1424874878-17155-1-git-send-email-mst@redhat.com> Organization: IBM Deutschland Research & Development GmbH Vorsitzende des Aufsichtsrats: Martina Koederitz =?UTF-8?B?R2VzY2jDpGZ0c2bDvGhydW5nOg==?= Dirk Wittkopp Sitz der Gesellschaft: =?UTF-8?B?QsO2Ymxpbmdlbg==?= Registergericht: Amtsgericht Stuttgart, HRB 243294 X-Mailer: Claws Mail 3.8.0 (GTK+ 2.24.10; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15022515-0041-0000-0000-000003800B83 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1618 Lines: 45 On Wed, 25 Feb 2015 15:36:02 +0100 "Michael S. Tsirkin" wrote: > 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 > --- > > changes from v1: > remove wait_event_interruptible > noticed by Cornelia Huck > > drivers/virtio/virtio_balloon.c | 19 ++++++++++++++----- > 1 file changed, 14 insertions(+), 5 deletions(-) > I was able to reproduce Thomas' original problem and can confirm that it is gone with this patch. Reviewed-by: Cornelia Huck -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/