From patchwork Mon Mar 17 18:11:35 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Cornelia Huck X-Patchwork-Id: 3845731 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 1C0F4BF549 for ; Mon, 17 Mar 2014 18:12:01 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 4AB6520204 for ; Mon, 17 Mar 2014 18:12:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 58A6220212 for ; Mon, 17 Mar 2014 18:11:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755886AbaCQSLw (ORCPT ); Mon, 17 Mar 2014 14:11:52 -0400 Received: from e06smtp12.uk.ibm.com ([195.75.94.108]:38451 "EHLO e06smtp12.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755233AbaCQSLt (ORCPT ); Mon, 17 Mar 2014 14:11:49 -0400 Received: from /spool/local by e06smtp12.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 17 Mar 2014 18:11:48 -0000 Received: from d06dlp01.portsmouth.uk.ibm.com (9.149.20.13) by e06smtp12.uk.ibm.com (192.168.101.142) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; Mon, 17 Mar 2014 18:11:46 -0000 Received: from b06cxnps4075.portsmouth.uk.ibm.com (d06relay12.portsmouth.uk.ibm.com [9.149.109.197]) by d06dlp01.portsmouth.uk.ibm.com (Postfix) with ESMTP id 784AE17D8059; Mon, 17 Mar 2014 18:12:28 +0000 (GMT) Received: from d06av05.portsmouth.uk.ibm.com (d06av05.portsmouth.uk.ibm.com [9.149.37.229]) by b06cxnps4075.portsmouth.uk.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id s2HIBYLh63045764; Mon, 17 Mar 2014 18:11:34 GMT Received: from d06av05.portsmouth.uk.ibm.com (localhost [127.0.0.1]) by d06av05.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s2HIBjuW008234; Mon, 17 Mar 2014 12:11:46 -0600 Received: from gondolin.boeblingen.de.ibm.com (dyn-9-152-224-49.boeblingen.de.ibm.com [9.152.224.49]) by d06av05.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVin) with ESMTP id s2HIBgxt008188; Mon, 17 Mar 2014 12:11:45 -0600 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 v2 1/5] KVM: eventfd: Fix lock order inversion. Date: Mon, 17 Mar 2014 19:11:35 +0100 Message-Id: <1395079899-29239-2-git-send-email-cornelia.huck@de.ibm.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1395079899-29239-1-git-send-email-cornelia.huck@de.ibm.com> References: <1395079899-29239-1-git-send-email-cornelia.huck@de.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14031718-8372-0000-0000-0000090255B7 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, 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 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 Reviewed-by: Christian Borntraeger --- 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