Builworld stalls on rpi2

[bob prohaska]

Trying to self-host a build of r327859 using a GENERIC kernel at  
r327664, make seems to stall, with top showing

last pid: 28822;  load averages:  3.12,  3.95,  5.09    up 0+08:39:01  16:39:49
50 processes:  1 running, 47 sleeping, 2 waiting
CPU:  0.0% user,  0.0% nice,  0.2% system,  0.9% interrupt, 98.9% idle
Mem: 527M Active, 16M Inact, 98M Laundry, 148M Wired, 86M Buf, 3272K Free
Swap: 2048M Total, 52M Used, 1996M Free, 2% Inuse

  PID USERNAME    THR PRI NICE   SIZE    RES STATE   C   TIME    WCPU COMMAND
  769 bob           1  20    0  6204K  1344K CPU0    0   3:02   0.68% top
  674 bob           1  20    0 11188K  1636K select  1   0:18   0.04% sshd
  719 root          1  20    0  4572K   552K select  0   0:03   0.01% make
28760 root          1  52    0   346M   302M pfault  2  13:59   0.00% c++
28812 root          1  52    0   208M   167M pfault  2   2:54   0.00% c++
28815 root          1  52    0   212M   171M pfault  1   2:20   0.00% c++
22172 root          1  20    0 13036K  4484K select  2   2:09   0.00% make
28820 root          1  52    0   145M   104M pfault  1   2:00   0.00% c++
21438 root          1  20    0  7092K   556K select  0   0:05   0.00% make
  695 root          1  20    0  4016K   552K select  1   0:04   0.00% make
  593 root          1  20    0  8156K  1596K vmwait  1   0:04   0.00% sendmail
20119 root          1  20    0  4516K   548K select  1   0:03   0.00% make
21427 root          1  20    0  4484K   556K select  2   0:02   0.00% make
  590 root          1  20    0 10148K  1552K vmwait  1   0:02   0.00% sshd
22168 root          1  20    0  3956K   560K select  0   0:02   0.00% make
  600 root          1  20    0  4960K     0K WAIT    2   0:01   0.00% <cron>
  461 root          1  20    0  4916K  1020K select  1   0:01   0.00% syslogd

The machine seems dead, none of the ssh sessions responds to keystrokes, 
nor the serial console. There are a smattering of 
smsc0: warning: Failed to write register 0x114
smsc0: warning: Failed to read register 0x114
smsc0: warning: MII is busy
smsc0: warning: Failed to write register 0x114

The machine still answers ping. Typing escape control-b does not
bring up a debugger, did the keysequence change? Power cycling seems
to be the only way out.

Thanks for reading, and any suggestions.

bob prohaska