From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752441AbeAWP6O (ORCPT ); Tue, 23 Jan 2018 10:58:14 -0500 Received: from mx1.redhat.com ([209.132.183.28]:38770 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752016AbeAWP6B (ORCPT ); Tue, 23 Jan 2018 10:58:01 -0500 Date: Tue, 23 Jan 2018 17:57:58 +0200 From: "Michael S. Tsirkin" To: Jason Wang Cc: linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org Subject: Re: [PATCH net 1/2] vhost: use mutex_lock_nested() in vhost_dev_lock_vqs() Message-ID: <20180123175752-mutt-send-email-mst@kernel.org> References: <1516699646-7321-1-git-send-email-jasowang@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1516699646-7321-1-git-send-email-jasowang@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 23, 2018 at 05:27:25PM +0800, Jason Wang wrote: > We used to call mutex_lock() in vhost_dev_lock_vqs() which tries to > hold mutexes of all virtqueues. This may confuse lockdep to report a > possible deadlock because of trying to hold locks belong to same > class. Switch to use mutex_lock_nested() to avoid false positive. > > Fixes: 6b1e6cc7855b0 ("vhost: new device IOTLB API") > Reported-by: syzbot+dbb7c1161485e61b0241@syzkaller.appspotmail.com > Signed-off-by: Jason Wang Acked-by: Michael S. Tsirkin > --- > drivers/vhost/vhost.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > index 33ac2b1..549771a 100644 > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -904,7 +904,7 @@ static void vhost_dev_lock_vqs(struct vhost_dev *d) > { > int i = 0; > for (i = 0; i < d->nvqs; ++i) > - mutex_lock(&d->vqs[i]->mutex); > + mutex_lock_nested(&d->vqs[i]->mutex, i); > } > > static void vhost_dev_unlock_vqs(struct vhost_dev *d) > -- > 2.7.4