From owner-aic7xxx Mon Sep 21 12:28:34 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id MAA15753 for aic7xxx-outgoing; Mon, 21 Sep 1998 12:28:34 -0700 (PDT) (envelope-from owner-aic7xxx@FreeBSD.ORG) Received: from dledford.dialnet.net (dledford.dialnet.net [206.65.249.116]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id MAA15739 for ; Mon, 21 Sep 1998 12:28:26 -0700 (PDT) (envelope-from dledford@dialnet.net) Received: from dialnet.net (dledford@localhost [127.0.0.1]) by dledford.dialnet.net (8.8.7/8.8.7) with ESMTP id OAA22366; Mon, 21 Sep 1998 14:27:33 -0500 Message-ID: <3606A8A4.E4EC9BD8@dialnet.net> Date: Mon, 21 Sep 1998 14:27:32 -0500 From: Doug Ledford X-Mailer: Mozilla 4.06 [en] (X11; I; Linux 2.0.35 i686) MIME-Version: 1.0 To: "Robert G. Brown" CC: Heinz Mauelshagen , aic7xxx@FreeBSD.ORG, mge@u9ete.ez-darmstadt.telekom.de Subject: Re: IRQ deadlocks References: Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-aic7xxx@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org Robert G. Brown wrote: > > On Mon, 21 Sep 1998, Heinz Mauelshagen wrote: > > > Does the vm bug show up in kernel > 2.1.120 on SMP too? > > I'm also curious; I know that there is a vm bug, but why does it strike > one person and not another? I would have thought that if there was a > really significant problem with the aic7xxx driver and virtual memory or > memory mapping, the driver would fail for nearly everyone using the > driver in an SMP system. Because it isn't a driver issue at all. It's a race condition in the fork() code that was worsened by the swapping of COW shared pages because now the fork code has to call swap_duplicate() on any swapped out COW pages when it forks off a new program, and then does a tlb flush afterwards, and somewhere in there it is getting into a loop. When it didn't have to do the extra work, it didn't happen as often. Also, the faster your disks subsystem gets, the worse the problem is. Presumably this is because that with the faster disks, something that should be happening after the fork completes, is happening in the middle of the fork and causing problems. Anyway, that's what I've gathered from some testing and from what Stephen Tweedie has had to say about the problem. -- Doug Ledford Opinions expressed are my own, but they should be everybody's. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-aic7xxx" in the body of the message