Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752168AbdIMUJG (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 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: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1127 Lines: 40 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); } -- 2.12.0