Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753947AbbBYPiI (ORCPT ); Wed, 25 Feb 2015 10:38:08 -0500 Received: from e06smtp14.uk.ibm.com ([195.75.94.110]:57664 "EHLO e06smtp14.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753844AbbBYPiG (ORCPT ); Wed, 25 Feb 2015 10:38:06 -0500 Date: Wed, 25 Feb 2015 16:37:56 +0100 From: Thomas Huth To: Cornelia Huck Cc: "Michael S. Tsirkin" , linux-kernel@vger.kernel.org, stable@vger.kernel.org, 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: <20150225163756.3eee5502@oc7435384737.ibm.com> In-Reply-To: <20150225161127.51f06c8c.cornelia.huck@de.ibm.com> References: <1424874878-17155-1-git-send-email-mst@redhat.com> <20150225161127.51f06c8c.cornelia.huck@de.ibm.com> Organization: IBM X-Mailer: Claws Mail 3.9.0 (GTK+ 2.24.23; x86_64-redhat-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: 15022515-0017-0000-0000-00000327F3D0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1941 Lines: 53 On Wed, 25 Feb 2015 16:11:27 +0100 Cornelia Huck wrote: > 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 Right, I just applied the patch on my system, too, and the problem is indeed gone! Thanks for the quick fix! Tested-by: Thomas Huth -- 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/