Rpi2 at r333141, no usable event timer

[bob prohaska]

An RPi2 at r333141 fails to boot with a series of "cannot allocate 
resource...." messages, ending with 
panic: No usable event timer found!
and a short backtrace. The console output is at


http://www.zefox.net/~fbsd/rpi2/crashes/20180505/console

Is there a workaround, short of reinstallation? One oddity
is that old kernels, which formerly worked, now fail in the
same way. Since both buildworld and kernel-toolchain failed
to build with "out of swap" messages this kernel was made
using "make kernel".

Swap is 2GB, formerly sufficient but seemingly no longer so.

Thanks for reading,

bob prohaska