From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keith Chew Subject: Re: PCM multi A/V Sync bug on SMP system Date: Thu, 29 Apr 2010 08:12:33 +1200 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-yw0-f176.google.com (mail-yw0-f176.google.com [209.85.211.176]) by alsa0.perex.cz (Postfix) with ESMTP id 93E3224559 for ; Wed, 28 Apr 2010 22:12:35 +0200 (CEST) Received: by ywh6 with SMTP id 6so7746918ywh.16 for ; Wed, 28 Apr 2010 13:12:34 -0700 (PDT) In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: alsa-devel-bounces@alsa-project.org Errors-To: alsa-devel-bounces@alsa-project.org To: alsa-devel@alsa-project.org List-Id: alsa-devel@alsa-project.org > I would like to help out in fixing this, but need a little bit of > guidance from the experts here. Have I identified the problem > correctly? Ie interaction between "multi" and "dmix" on a 5.1 channel > card giving timing issues on an SMP system? If it is unlikely, I will > investigate other areas. Ok, I don't seem to be getting much help from this mailing list, so I have dug deeper into the code, and found the problem. In pcm_dmix_i386.c, we have: if (!strncmp(line, "processor", 9)) smp++; I have commented out the smp++, so that it thinks that I am on a uni processor. Voila, so AV sync issues! My question now is what are the implications of this change? Looking at pcm_dmix_i386.h, it uses locks on an SMP system, but exclude them if not SMP. Do we still need this lock, even if I am on a dual core, ie 1 processor 2 cores? I have CC'ed the author of the file, Jaroslav Kysela. Regards Keith