From mboxrd@z Thu Jan  1 00:00:00 1970
From: Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>
Subject: Re: [PATCH v2 08/14] KVM: x86: remove notifiers from PIT discard
 policy
Date: Fri, 19 Feb 2016 16:09:34 +0100
Message-ID: <20160219150933.GB25910@potion.brq.redhat.com>
References: <1455736496-374-1-git-send-email-rkrcmar@redhat.com>
 <1455736496-374-9-git-send-email-rkrcmar@redhat.com>
 <56C6088A.5080207@redhat.com>
 <20160219150434.GA25910@potion.brq.redhat.com>
 <56C72F62.5060307@redhat.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: QUOTED-PRINTABLE
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	Yuki Shibuya <shibuya.yk@ncos.nec.co.jp>
To: Paolo Bonzini <pbonzini@redhat.com>
Return-path: <kvm-owner@vger.kernel.org>
Received: from mx1.redhat.com ([209.132.183.28]:35554 "EHLO mx1.redhat.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1949248AbcBSPJh (ORCPT <rfc822;kvm@vger.kernel.org>);
	Fri, 19 Feb 2016 10:09:37 -0500
Content-Disposition: inline
In-Reply-To: <56C72F62.5060307@redhat.com>
Sender: kvm-owner@vger.kernel.org
List-ID: <kvm.vger.kernel.org>

2016-02-19 16:06+0100, Paolo Bonzini:
> On 19/02/2016 16:04, Radim Kr=C4=8Dm=C3=A1=C5=99 wrote:
>>>> ... 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?
>> There was/is no harm in having reinject non-atomic.  This patch adde=
d
>> notifiers, which is the reason for re-introducing a mutex.
>>=20
>> Userspace can (and SHOULDN'T) call this function multiple times,
>> concurrently, so the mutex prevents a situations where, e.g. only on=
e
>> notifier is registered in the end.
>=20
> Yes, I understand why you added the mutex here; good catch indeed.  T=
he
> atomic_t is just to show that it's okay to read it outside the lock.
> It's just for a bit of extra documentation.

Hm, good point.  I will add it.  Thanks.