RPi2 snapshot for armv7 won't boot.

[bob prohaska]

On Wed, Nov 01, 2017 at 05:27:52PM -0700, Mark Millard wrote:
> 
> [Sometime between -r324743 and -r325156 armv7
> has been broken such that /sbin/init fails,
> apparently no matter how the build is done.
> I'm ignoring that issue here.]
> 
I've never come close to getting far enough for init to
be an issue. Something has always stopped buildworld, or
at least interfered enough to stop installworld.

> 
> Crochet has one major configuration problem for
> reliability when swapping is to be involved on
> the target: Crochet creates a context using a
> swapfile instead of using a swap partition.
>
At least on 11-stable the swap file was enough for
buildworld/kernel, though I don't know how thin the 
margin is. That particular host doesn't get fiddled 
with much, so long as it works.
 
> See bugzilla 206048 about the swapfile issue.
> 
> An RPI2 self-hosted likely(?) swaps extensively at
> times. ("Only" 1 GiByte of RAM but clang is built,
> for example.) I expect that having swap space is a
> requirement to have self-hosting work. I'm not
> familiar with what a near-minimal size might be.
>
The box I'm trying to get from v6 to v7 uses a dedicated
swap partition on a usb-flash drive. Highest swap usage
I've noticed is a little under 1GB out of 2GB total.
  
> I'm not claiming this explains what you might be
> seeing. But the use of swapfiles is a known
> problem, apparently known long before that bugzilla
> submittal was made (2016-Jan-08).
> 
The first problem encounted was fixed per you, simply
hardcoding the result of uname -p (=armv7) in Makefile.inc1.
Off and on, there were pmap faults (pt2map abort) which
superficially resemble what you reported about a year ago.
At first, they went away spontaneously, then returned (always
late in buildworld). A single-user buildworld succeeded, 
but installworld reported a strip error in clang and clang
was never updated. Seemingly most else was updated. At this
point installworld is failing very quickly in /usr/src/rescue,
so I'm trying again to do a clean kernel, world, install cycle.


 
> My experience has lead me to always use swap
> partitions --and never swap files.
> 
Agreed entirely.

> 
> Another issue is significant swapping activity is
> likely not a good match to most sdcards. For this
> class of devices, I normally configure causing the
> root file system and swap space to be on a USB
> drive, such as a USB SSD. So mostly it is the
> kernel and earlier stages that come from the
> sdcard and the sdcard is otherwise little used
> in normal operation.
>
So far, I've gotten away with leaving / on the microSD card
and (most) everything else on a USB flash drive. I'm rather
curious to see if I can wear either one out. So far, no.
 

I'd be very encouraged to know if anyone at all is trying to self
host -current on RPI2, in any configuration. 

Thanks for reading!

bob prohaska