From mboxrd@z Thu Jan  1 00:00:00 1970
From: Pekka Enberg <penberg@kernel.org>
Subject: Re: [PATCH 1/3] kvm tools: Make virtio-net kvm__irq_line thread safe
Date: Fri, 29 Apr 2011 13:42:35 +0300
Message-ID: <BANLkTimfMK2GyLhC0ghN9HQ66cJH2zZeZQ@mail.gmail.com>
References: <1304058985-13833-1-git-send-email-asias.hejun@gmail.com>
	<20110429073006.GB16371@elte.hu>
	<4DBA6CFE.5090400@gmail.com>
	<20110429103210.GB24217@elte.hu>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Cc: Asias He <asias.hejun@gmail.com>,
	Cyrill Gorcunov <gorcunov@gmail.com>,
	Sasha Levin <levinsasha928@gmail.com>,
	Prasad Joshi <prasadjoshi124@gmail.com>, kvm@vger.kernel.org
To: Ingo Molnar <mingo@elte.hu>
Return-path: <kvm-owner@vger.kernel.org>
Received: from mail-vw0-f46.google.com ([209.85.212.46]:38530 "EHLO
	mail-vw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1751029Ab1D2Kmf (ORCPT <rfc822;kvm@vger.kernel.org>);
	Fri, 29 Apr 2011 06:42:35 -0400
Received: by vws1 with SMTP id 1so2636901vws.19
        for <kvm@vger.kernel.org>; Fri, 29 Apr 2011 03:42:35 -0700 (PDT)
In-Reply-To: <20110429103210.GB24217@elte.hu>
Sender: kvm-owner@vger.kernel.org
List-ID: <kvm.vger.kernel.org>

On Fri, Apr 29, 2011 at 1:32 PM, Ingo Molnar <mingo@elte.hu> wrote:
>> Without the mutex around the kvm__irq_line, I am still seeing the
>> hangs(with the irq assertion movement patch).
>
> since the mutex has no effect on the other party that modifies the virtual
> queue (the guest OS), this at best only changes timings and hides the bug.

Yes, I don't think it has anything to do with the queues - it's simply
a bug in the RX path which requires other work to happen to raise the
IRQ.