From patchwork Wed Sep 13 20:08:24 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Davidlohr Bueso X-Patchwork-Id: 9952003 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 0145860360 for ; Wed, 13 Sep 2017 20:09:35 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id E939D28CF1 for ; Wed, 13 Sep 2017 20:09:34 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id D7D3628479; Wed, 13 Sep 2017 20:09:34 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 7C60A28CDA for ; Wed, 13 Sep 2017 20:09:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752177AbdIMUJG (ORCPT ); Wed, 13 Sep 2017 16:09:06 -0400 Received: from smtp2.provo.novell.com ([137.65.250.81]:59387 "EHLO smtp2.provo.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752103AbdIMUIh (ORCPT ); Wed, 13 Sep 2017 16:08:37 -0400 Received: from linux-80c1.suse (prv-ext-foundry1int.gns.novell.com [137.65.251.240]) by smtp2.provo.novell.com with ESMTP (TLS encrypted); Wed, 13 Sep 2017 14:08:34 -0600 From: Davidlohr Bueso To: mingo@kernel.org, peterz@infradead.org, pbonzini@redhat.com Cc: npiggin@gmail.com, paulmck@linux.vnet.ibm.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, dave@stgolabs.net, Davidlohr Bueso Subject: [PATCH 7/7] kvm,mips: Fix potential swait_active() races Date: Wed, 13 Sep 2017 13:08:24 -0700 Message-Id: <20170913200824.28067-8-dave@stgolabs.net> X-Mailer: git-send-email 2.12.0 In-Reply-To: <20170913200824.28067-1-dave@stgolabs.net> References: <20170913200824.28067-1-dave@stgolabs.net> Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP For example, the following could occur, making us miss a wakeup: CPU0 CPU1 kvm_vcpu_block kvm_mips_comparecount_func [L] swait_active(&vcpu->wq) [S] prepare_to_swait(&vcpu->wq) [L] if (!kvm_vcpu_has_pending_timer(vcpu)) schedule() [S] queue_timer_int(vcpu) Ensure that the swait_active() check is not hoisted over the interrupt. Signed-off-by: Davidlohr Bueso --- arch/mips/kvm/mips.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c index bce2a6431430..d535edc01434 100644 --- a/arch/mips/kvm/mips.c +++ b/arch/mips/kvm/mips.c @@ -514,7 +514,7 @@ int kvm_vcpu_ioctl_interrupt(struct kvm_vcpu *vcpu, dvcpu->arch.wait = 0; - if (swait_active(&dvcpu->wq)) + if (swq_has_sleeper(&dvcpu->wq)) swake_up(&dvcpu->wq); return 0; @@ -1179,7 +1179,7 @@ static void kvm_mips_comparecount_func(unsigned long data) kvm_mips_callbacks->queue_timer_int(vcpu); vcpu->arch.wait = 0; - if (swait_active(&vcpu->wq)) + if (swq_has_sleeper(&vcpu->wq)) swake_up(&vcpu->wq); }