Date: Thu, 7 Jan 2016 21:04:40 +0100 From: Hans Petter Selasky <hps@selasky.org> To: Ian Lepore <ian@freebsd.org>, Mark Millard <markmi@dsl-only.net> Cc: freebsd-arm <freebsd-arm@freebsd.org> Subject: Re: FYI: various 11.0-CURRENT -r293227 (and older) hangs on arm (rpi2): a description of sorts Message-ID: <568EC4D8.7010106@selasky.org> In-Reply-To: <1452196099.1215.12.camel@freebsd.org> References: <E0379BE9-308A-4219-A8AE-A5FFE828BA93@dsl-only.net> <1452183170.1215.4.camel@freebsd.org> <FB0D5486-AD27-44A7-86CA-68989AE08EC7@dsl-only.net> <1452196099.1215.12.camel@freebsd.org>
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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
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