From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756642AbbIUMRO (ORCPT ); Mon, 21 Sep 2015 08:17:14 -0400 Received: from mo4-p00-ob.smtp.rzone.de ([81.169.146.160]:45837 "EHLO mo4-p00-ob.smtp.rzone.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752966AbbIUMRM (ORCPT ); Mon, 21 Sep 2015 08:17:12 -0400 X-RZG-AUTH: :P2EQZWCpfu+qG7CngxMFH1J+yackYocTD1iAi8x+OWi/zfN1cLnDYU0tRQWJl4Hh2o4ySGRMBlDHYMqccew1oDb73L4= X-RZG-CLASS-ID: mo00 Date: Mon, 21 Sep 2015 14:17:06 +0200 From: Olaf Hering To: Vitaly Kuznetsov Cc: "K. Y. Srinivasan" , Greg KH , linux-kernel@vger.kernel.org, devel@linuxdriverproject.org, apw@canonical.com, jasowang@redhat.com Subject: Re: [PATCH 2/5] hv: add helpers to handle hv_util device state Message-ID: <20150921121706.GA9172@aepfle.de> References: <1442363823-22428-1-git-send-email-kys@microsoft.com> <1442363874-22508-1-git-send-email-kys@microsoft.com> <1442363874-22508-2-git-send-email-kys@microsoft.com> <20150921052532.GA24350@kroah.com> <20150921102626.GB4252@aepfle.de> <87y4g0hv4d.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <87y4g0hv4d.fsf@vitty.brq.redhat.com> User-Agent: Mutt/1.5.24 (6503) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 21, Vitaly Kuznetsov wrote: > I'd like to see a trace from the hang, it is not obvious to me how it > happened and what caused it. (or if you have such hang scenario in your > head, can you please reveal it?) There is no trace. I think fcopy_respond_to_host notifies the host, which in turn triggers an interrupt right away which is processed while fcopy_on_msg is executing somewhere between the return from fcopy_respond_to_host and the call into hv_fcopy_onchannelcallback. > AFAICS barriers you introduced don't give you guarantees in an SMP environment. Happens to work on x86, and for this purpose. I will see how to add locking around access to state and context. Olaf