From owner-freebsd-current@FreeBSD.ORG Mon Jul 26 21:55:32 2004 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 9F2E316A4CE for ; Mon, 26 Jul 2004 21:55:32 +0000 (GMT) Received: from gw.catspoiler.org (217-ip-163.nccn.net [209.79.217.163]) by mx1.FreeBSD.org (Postfix) with ESMTP id 0B9DF43D1D for ; Mon, 26 Jul 2004 21:55:32 +0000 (GMT) (envelope-from truckman@FreeBSD.org) Received: from FreeBSD.org (mousie.catspoiler.org [192.168.101.2]) by gw.catspoiler.org (8.12.11/8.12.11) with ESMTP id i6QLtNuZ058373; Mon, 26 Jul 2004 14:55:27 -0700 (PDT) (envelope-from truckman@FreeBSD.org) Message-Id: <200407262155.i6QLtNuZ058373@gw.catspoiler.org> Date: Mon, 26 Jul 2004 14:55:23 -0700 (PDT) From: Don Lewis To: conrads@cox.net In-Reply-To: MIME-Version: 1.0 Content-Type: TEXT/plain; charset=us-ascii cc: freebsd-current@FreeBSD.org Subject: Re: Questionable code in sys/dev/sound/pcm/channel.c X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 26 Jul 2004 21:55:32 -0000 On 26 Jul, Conrad J. Sabatier wrote: > I'm a little perplexed at the following bit of logic in chn_write() > (which is where the "interrupt timeout, channel dead" messages are > being generated). > > Within an else branch within the main while loop, we have: > > else { > timeout = (hz * sndbuf_getblksz(bs)) / > (sndbuf_getspd(bs) * sndbuf_getbps(bs)); > if (timeout < 1) > timeout = 1; > timeout = 1; > > Why the formulaic calculation of timeout, if it's simply going to be > unconditionally set to 1 immediately afterwards anyway? What's going on > here? Hmn, looks bogus to me. I think the intention is to round timeout up to 1 if the result of the formula is zero. The final assignment statement looks bogus to me. Maybe a too short timeout is the source of this problem. It looks like this assignment appeared in rev 1.65. > Also, at the end of the function: > > if (count <= 0) { > c->flags |= CHN_F_DEAD; > printf("%s: play interrupt timeout, channel dead\n", c->name); > } > > return ret; > } > > Could it be that the conditional test is wrong here? Perhaps > we should be using (count < 0) instead? > > I don't know. I'm having no small difficulty understanding this code, > but these two items caught my attention. I ran into the same problem when I was looking at the code a few days ago. BTW, the trace output that was posted showed write() returning 0 immediately before the failure occurred.