From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751346Ab0E0GRA (ORCPT ); Thu, 27 May 2010 02:17:00 -0400 Received: from mail-bw0-f46.google.com ([209.85.214.46]:54158 "EHLO mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750819Ab0E0GQ7 (ORCPT ); Thu, 27 May 2010 02:16:59 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:user-agent:mime-version:to:cc:subject :references:in-reply-to:x-enigmail-version:content-type :content-transfer-encoding; b=cgCkKisoL+FCK9hqSod42+wlHX8u4LrcaSlS1ZbFXvI9fB2YKA0QwnMBTDIhljOF1W b46/Wbn02JYpabmK9/5kjUgMwb8VW4v/OOjE7pY/ox+eCT7JXYUgKId+GQ5QuS6mgMAt Nq96vgJFDUj5lOVGGFvcJfc/mtvhzKlZ7+lhA= Message-ID: <4BFE0E57.7050306@gmail.com> Date: Thu, 27 May 2010 08:16:55 +0200 From: Jiri Slaby User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; cs-CZ; rv:1.9.2.4) Gecko/20100522 SUSE/3.1rc1-2.1 Thunderbird/3.1 MIME-Version: 1.0 To: Haiyang Zhang CC: Greg KH , "'devel@driverdev.osuosl.org'" , "'virtualization@lists.osdl.org'" , "'linux-kernel@vger.kernel.org'" Subject: Re: [PATCH 1/1] staging: hv: Fix race condition on IC channel initialization (modified) References: <1FB5E1D5CA062146B38059374562DF7266B8C4AC@TK5EX14MBXC128.redmond.corp.microsoft.com> <20100526205134.GC7343@suse.de> <1FB5E1D5CA062146B38059374562DF7266B8C72B@TK5EX14MBXC128.redmond.corp.microsoft.com> In-Reply-To: <1FB5E1D5CA062146B38059374562DF7266B8C72B@TK5EX14MBXC128.redmond.corp.microsoft.com> X-Enigmail-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/26/2010 11:25 PM, Haiyang Zhang wrote: >> From: Greg KH [mailto:gregkh@suse.de] >>> + VmbusChannelOpen(newChannel, 2 * PAGE_SIZE, >>> + 2 * PAGE_SIZE, NULL, 0, >>> + hv_cb_utils[cnt].callback, >>> + newChannel) == 0) { >>> + hv_cb_utils[cnt].channel = newChannel; >>> + mb(); >> >> What is the mb() call for? Why is it necessary? (hint, if you need it, >> something else is really wrong...) > > It ensures the channel assignment happens before the wakeup call: > osd_WaitEventSet(ic_channel_ready), if the compiler optimization re-arrange > the execution order. wake_up() is a barrier, you don't need the mb() there. BTW osd_WaitEventSet et al. can be easily converted to completion. -- js