From patchwork Tue Feb 25 17:24:41 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Cornelia Huck X-Patchwork-Id: 3718081 Return-Path: X-Original-To: patchwork-kvm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 45D05BF40C for ; Tue, 25 Feb 2014 17:26:28 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 7D657201ED for ; Tue, 25 Feb 2014 17:26:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 96589201E4 for ; Tue, 25 Feb 2014 17:26:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753065AbaBYRZ1 (ORCPT ); Tue, 25 Feb 2014 12:25:27 -0500 Received: from e06smtp13.uk.ibm.com ([195.75.94.109]:47317 "EHLO e06smtp13.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753058AbaBYRZE (ORCPT ); Tue, 25 Feb 2014 12:25:04 -0500 Received: from /spool/local by e06smtp13.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 25 Feb 2014 17:25:02 -0000 Received: from d06dlp02.portsmouth.uk.ibm.com (9.149.20.14) by e06smtp13.uk.ibm.com (192.168.101.143) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; Tue, 25 Feb 2014 17:25:00 -0000 Received: from b06cxnps3074.portsmouth.uk.ibm.com (d06relay09.portsmouth.uk.ibm.com [9.149.109.194]) by d06dlp02.portsmouth.uk.ibm.com (Postfix) with ESMTP id A98732190046; Tue, 25 Feb 2014 17:24:56 +0000 (GMT) Received: from d06av07.portsmouth.uk.ibm.com (d06av07.portsmouth.uk.ibm.com [9.149.37.248]) by b06cxnps3074.portsmouth.uk.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id s1PHOlwr53608480; Tue, 25 Feb 2014 17:24:47 GMT Received: from d06av07.portsmouth.uk.ibm.com (localhost [127.0.0.1]) by d06av07.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s1PHOwPF028451; Tue, 25 Feb 2014 12:24:59 -0500 Received: from gondolin.boeblingen.de.ibm.com (dyn-9-152-224-49.boeblingen.de.ibm.com [9.152.224.49]) by d06av07.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVin) with ESMTP id s1PHOrce028268; Tue, 25 Feb 2014 12:24:58 -0500 From: Cornelia Huck To: kvm@vger.kernel.org, linux-s390@vger.kernel.org, qemu-devel@nongnu.org Cc: borntraeger@de.ibm.com, agraf@suse.de, pbonzini@redhat.com, gleb@kernel.org, Cornelia Huck Subject: [PATCH 3/7] KVM: eventfd: Fix lock order inversion. Date: Tue, 25 Feb 2014 18:24:41 +0100 Message-Id: <1393349085-18122-4-git-send-email-cornelia.huck@de.ibm.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1393349085-18122-1-git-send-email-cornelia.huck@de.ibm.com> References: <1393349085-18122-1-git-send-email-cornelia.huck@de.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14022517-2966-0000-0000-00000A66FDFA Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, 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 When registering a new irqfd, we call its ->poll method to collect any event that might have previously been pending so that we can trigger it. This is done under the kvm->irqfds.lock, which means the eventfd's ctx lock is taken under it. However, if we get a POLLHUP in irqfd_wakeup, we will be called with the ctx lock held before getting the irqfds.lock to deactivate the irqfd, causing lockdep to complain. Calling the ->poll method does not really need the irqfds.lock, so let's just move it after we've given up the irqfds.lock in kvm_irqfd_assign(). Signed-off-by: Cornelia Huck --- virt/kvm/eventfd.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c index abe4d60..29c2a04 100644 --- a/virt/kvm/eventfd.c +++ b/virt/kvm/eventfd.c @@ -391,19 +391,19 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args) lockdep_is_held(&kvm->irqfds.lock)); irqfd_update(kvm, irqfd, irq_rt); - events = f.file->f_op->poll(f.file, &irqfd->pt); - list_add_tail(&irqfd->list, &kvm->irqfds.items); + spin_unlock_irq(&kvm->irqfds.lock); + /* * Check if there was an event already pending on the eventfd * before we registered, and trigger it as if we didn't miss it. */ + events = f.file->f_op->poll(f.file, &irqfd->pt); + if (events & POLLIN) schedule_work(&irqfd->inject); - spin_unlock_irq(&kvm->irqfds.lock); - /* * do not drop the file until the irqfd is fully initialized, otherwise * we might race against the POLLHUP