I have submitted bugzilla 237590 for old powerpc64 FreeBSD on G5 PowerMac's crashing for "ofwdump -ap" and the like: timeout trying to sleep the CPUs

[Mark Millard]

The biggest issue here may be the inability to sufficiently sleep
CPUs on powerpc64 in general, with ofwdump on old PowerMac G5's
just being a good way to test that.

But my test context is limited to old PowerMacs.

This was originally observed on head -r345758.

"bisecting" based on:

https://artifact.ci.freebsd.org/snapshot/head/r*

I found that for the likes of "ofwdump -ap > /dev/null" :

-r330572: does not crash the system (or program).
-r330614: crashes the system: timeout trying to sleep cpus.

There are no other  https://artifact.ci.freebsd.org/snapshot/head/r*
between -r330572 and -r330614 with powerpc64 present. So I stopped
at this range.

Turns out that between those two versions is:

Revision 330610 . . .
Modified Wed Mar 7 17:08:07 2018 UTC . . . by nwhitehorn 
. . .
Move the powerpc64 direct map base address from zero to high memory. This
accomplishes a few things:
- Makes NULL an invalid address in the kernel, which is useful for catching
 bugs.
. . .

(It may be that -r330610 exposed another problem that was
accidentally avoided before that.)




Side note:

For some reason when I submitted the bugzilla entry the following
folks were automatically sent Email:

piotr.pietruszewski at intel.com, krzysztof.galazka at intel.com

(despite the powerpc context).

===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)