From owner-p4-projects@FreeBSD.ORG Sat Feb 16 23:21:08 2008 Return-Path: Delivered-To: p4-projects@freebsd.org Received: by hub.freebsd.org (Postfix, from userid 32767) id 0309016A421; Sat, 16 Feb 2008 23:21:08 +0000 (UTC) Delivered-To: perforce@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id A382D16A419; Sat, 16 Feb 2008 23:21:07 +0000 (UTC) (envelope-from raj@semihalf.com) Received: from mail.semihalf.com (mail.semihalf.com [83.15.139.206]) by mx1.freebsd.org (Postfix) with ESMTP id 1273513C455; Sat, 16 Feb 2008 23:21:06 +0000 (UTC) (envelope-from raj@semihalf.com) Received: from localhost (unknown [127.0.0.1]) by mail.semihalf.com (Postfix) with ESMTP id 91F73143D2; Sun, 17 Feb 2008 00:29:18 +0100 (CET) Received: from mail.semihalf.com ([127.0.0.1]) by localhost (mail.semihalf.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 22152-07; Sun, 17 Feb 2008 00:29:12 +0100 (CET) Message-ID: <47B76FDA.7070008@semihalf.com> Date: Sun, 17 Feb 2008 00:20:58 +0100 From: Rafal Jaworowski MIME-Version: 1.0 To: Marcel Moolenaar References: <200802162141.m1GLfgkj048217@repoman.freebsd.org> <47B75EB3.2020001@semihalf.com> <504560A3-EABB-4896-8B3E-C7FC89F31EFB@mac.com> <47B76A8E.5060607@semihalf.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at semihalf.com Cc: Marcel Moolenaar , Perforce Change Reviews Subject: Re: PERFORCE change 135517 for review X-BeenThere: p4-projects@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: p4 projects tree changes List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 16 Feb 2008 23:21:08 -0000 Marcel Moolenaar wrote: >>>>> >>>>> Save U-Boot's registers at startup and restore them when >>>>> performing a syscall. This way we don't have to compile >>>>> code specially to avoid using those registers. Otherwise >>>>> we have to encode knowledge of those registers in at least >>>>> 4 makefiles and introduce a build knob to enable it all. >>>>> This does not allow us to build everything with a single >>>>> build world. >>>>> >>>> >>>> Hi Marcel, >>>> >>>> I'm not quite sure this is sufficient... I already had a similar >>>> save/restore >>>> in place, but there is some general problem with U-Boot that leads to >>>> hangs >>>> (experienced): >>> >>> Interesting, I didn't see any such problems with 1.3.2-rc1. >>> >> >> Chances are it might not surface, depending on the regs usage pattern, >> compiler etc., for example a -O0 build would usually hide this issue, >> but in >> principle those regs are not exception/interrupt safe. > > Agreed. I didn't see it at -O2, BTW. > When I was looking at this it also did not always pop up (with -O2 too), although typically when loader(8) was executed and left idle for some time it would hang sooner or later. > We can disable interrupts when not running in U-Boot, right? > The impact should be marginal... > Yes, this could be worked around like this, but with degraded functionality: all timer-related calls from the API would not make sense, and things like autoboot count down will not work. Even worse, the [polled] networking might not work at all if decrementer was shut, as we'd not be able to time out while waiting on the packet, status registers' change and so on. I think this issue needs some further investigation and proper resolution. Rafal