From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1426781AbcBRSIO (ORCPT ); Thu, 18 Feb 2016 13:08:14 -0500 Received: from mail-wm0-f66.google.com ([74.125.82.66]:35957 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1423478AbcBRSIN (ORCPT ); Thu, 18 Feb 2016 13:08:13 -0500 Subject: Re: [PATCH v2 08/14] KVM: x86: remove notifiers from PIT discard policy To: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , linux-kernel@vger.kernel.org References: <1455736496-374-1-git-send-email-rkrcmar@redhat.com> <1455736496-374-9-git-send-email-rkrcmar@redhat.com> Cc: kvm@vger.kernel.org, Yuki Shibuya From: Paolo Bonzini Message-ID: <56C6088A.5080207@redhat.com> Date: Thu, 18 Feb 2016 19:08:10 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.0 MIME-Version: 1.0 In-Reply-To: <1455736496-374-9-git-send-email-rkrcmar@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 17/02/2016 20:14, Radim Krčmář wrote: > + /* pit->pit_state.lock was overloaded to prevent userspace from getting > + * an inconsistent state after running multiple KVM_REINJECT_CONTROL > + * ioctls in parallel. Use a separate lock if that ioctl isn't rare. > + */ > + mutex_lock(&pit->pit_state.lock); > + kvm_pit_set_reinject(pit, control->pit_reinject); > + mutex_unlock(&pit->pit_state.lock); ... so in patch 7 concurrent _writes_ of reinject are protected by the lock, but reads are done outside it (in pit_timer_fn). WDYT about making reinject an atomic_t? Paolo