From owner-freebsd-arm@freebsd.org Thu Jan 7 20:02:43 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 73C5BA6763C for ; Thu, 7 Jan 2016 20:02:43 +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 3E3661A17; Thu, 7 Jan 2016 20:02:43 +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 8D70A1FE022; Thu, 7 Jan 2016 21:02:32 +0100 (CET) Subject: Re: FYI: various 11.0-CURRENT -r293227 (and older) hangs on arm (rpi2): a description of sorts To: Ian Lepore , Mark Millard References: <1452183170.1215.4.camel@freebsd.org> <1452196099.1215.12.camel@freebsd.org> Cc: freebsd-arm From: Hans Petter Selasky Message-ID: <568EC4D8.7010106@selasky.org> Date: Thu, 7 Jan 2016 21:04:40 +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: <1452196099.1215.12.camel@freebsd.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 20:02:43 -0000 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. 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