FYI: various 11.0-CURRENT -r293227 (and older) hangs on arm (rpi2): a description of sorts

[Hans Petter Selasky]

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