From owner-freebsd-arm@freebsd.org Thu Jan 7 21:29:18 2016 Return-Path: Delivered-To: freebsd-arm@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 0D23DA67820 for ; Thu, 7 Jan 2016 21:29:18 +0000 (UTC) (envelope-from hps@selasky.org) Received: from mail.turbocat.net (mail.turbocat.net [IPv6:2a01:4f8:d16:4514::2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id CACC61977; Thu, 7 Jan 2016 21:29:17 +0000 (UTC) (envelope-from hps@selasky.org) Received: from laptop015.home.selasky.org (unknown [62.141.129.119]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.turbocat.net (Postfix) with ESMTPSA id 19A8B1FE022; Thu, 7 Jan 2016 22:29:16 +0100 (CET) Subject: Re: FYI: various 11.0-CURRENT -r293227 (and older) hangs on arm (rpi2): a description of sorts To: Mark Millard References: <1452183170.1215.4.camel@freebsd.org> <1452196099.1215.12.camel@freebsd.org> <568EC4D8.7010106@selasky.org> <8B728C93-9C90-4821-A607-5D157F028812@dsl-only.net> <568ED810.8010309@selasky.org> Cc: freebsd-arm , Ian Lepore From: Hans Petter Selasky Message-ID: <568ED92C.9070602@selasky.org> Date: Thu, 7 Jan 2016 22:31:24 +0100 User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:38.0) Gecko/20100101 Thunderbird/38.4.0 MIME-Version: 1.0 In-Reply-To: <568ED810.8010309@selasky.org> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-arm@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: "Porting FreeBSD to ARM processors." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 07 Jan 2016 21:29:18 -0000 On 01/07/16 22:26, Hans Petter Selasky wrote: > On 01/07/16 21:20, Mark Millard wrote: >> >> On 2016-Jan-7, at 12:04 PM, Hans Petter Selasky >> wrote: >>> >>> On 01/07/16 20:48, Ian Lepore wrote: >>>> If the filesystems and swap space are on a usb drive, then maybe it's >>>> the usb subsystem that's hanging. The wait states you showed for those >>>> processes are consistant with what I've seen when all buffers get >>>> backed up in a queue on one non-responsive or slow device. It may be >>>> that there's a way to get the system deadlocked when it's low on >>>> buffers and there is memory pressure causing the swap to be used (I >>>> generally run arms systems without any swap configured). >>>> >>>> Running gstat in another window while this is going on may give you >>>> some insight into the situation. Beyond that I don't know what to look >>>> at, especially since you generally can't launch any new tools once the >>>> system gets into this kind of state. >>>> >>>> -- Ian >>> >>> Hi, >>> >>> All USB transfers towards disk devices have timeouts, so if something >>> is hanging at USB level, you'll get a printout eventually. >> >> What sort of timescale after deadlock/live-lock is observed to >> apparently have started does one have to wait in order to conclude >> that the timeouts would have happened and so they do not apply to the >> deadlock/live-lock? >> >>> The USB kernel processes needed for doing I/O transfers are not >>> pinned to RAM. Can it happen if a USB process is swapped to disk, >>> that the system cannot wakeup a swapped out process to get more swap? >>> >>> --HPS >> > > Hi, > >> Wow. Could I use ddb to somehow check on the "USB kernel processes" >> swap status when the overall context is deadlocked/live-locked? > > Are you able to run something like: > > ps auxwwH | grep usb > > > If yes, how? Otherwise something in top or some such display that I'd > left running over the serial console would have to present useful > information on the subject. Is there anything that would? > Are you able to SSH into the box or ping it? --HPS