From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965451AbbJIK0w (ORCPT ); Fri, 9 Oct 2015 06:26:52 -0400 Received: from mail-wi0-f181.google.com ([209.85.212.181]:36332 "EHLO mail-wi0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752256AbbJIK0u (ORCPT ); Fri, 9 Oct 2015 06:26:50 -0400 Subject: Re: [PATCH] kvm: fix waitqueue_active without memory barrier in virt/kvm/async_pf.c To: Kosuke Tatsukawa References: <56177EAC.2070601@redhat.com> <17EC94B0A072C34B8DCF0D30AD16044A02874CB2@BPXM09GP.gisp.nec.co.jp> Cc: Gleb Natapov , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" From: Paolo Bonzini Message-ID: <56179667.8010609@redhat.com> Date: Fri, 9 Oct 2015 12:26:47 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: <17EC94B0A072C34B8DCF0D30AD16044A02874CB2@BPXM09GP.gisp.nec.co.jp> Content-Type: text/plain; charset=iso-2022-jp Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/10/2015 11:04, Kosuke Tatsukawa wrote: > smp_store_mb() called from set_current_state(), which is called from > prepare_to_wait() should prevent reordering such as below from > happening. wait_event*() also calls set_current_state() inside. Ah, I missed that set_current_state has a memory barrier in it. The patch is okay, but please expand the comment to say that this memory barrier pairs with prepare_to_wait's set_current_state(). Paolo