powerpc64 head -r344018 stuck sleeping problems: th->th_scale * tc_delta(th) overflows unsigned 64 bits sometimes [patched failed]

[Mark Millard]

On 2019-Apr-2, at 15:27, Michael Tuexen <tuexen at fh-muenster.de> wrote:

>> On 24. Mar 2019, at 12:01, Konstantin Belousov <kostikbel at gmail.com> wrote:
>> 
>> On Sat, Mar 09, 2019 at 06:00:14PM +1100, Bruce Evans wrote:
>>> I more strongly disclike (sic) the more complete merge.  The central APIs
>>> have even more parameters and reduced type safety to describe objects as
>>> (offset, size) pairs.
>> I changed the patch to be type-safe.  Now I like it even more.  It provides
>> 1. internal
>> 2. concise
>> 3. type-safe
>> API to fetch data from timehands.  The implementation needs to be read
>> only once.
> Hi,
> 
> I'm a bit lost... I think this started to fix a problem on G5 PowerMacs.
> Do you think this patch solves the problem. Should this be tested?
> Or is this still work in progress or a general improvement not necessary
> fixing the problem on G5 PowerMacs?
> 
> Best regards
> Michael
> . . .

A much earlier version of the patch made things much worse
on the PowerMc G5 (massively long hangups, inability to
effectively enter commands). I had to cut power, repair
the file system, and undo the separately (not booted from
that media). I've not tried again since then.

I suspect that while my report prompted the looking into
the code, the issues noticed are likely not fixes to the
behavior observed on the old PowerMac G5's.

I've my own hack/workaround that has my context
operational, avoiding the original issue. Definitely not
what FreeBSD should be doing. It even involves constants
figured out by observation of the failing conditions
in the specific context.

From what I've seen, my detailed hack-text will not apply
to the new code. I'll likely have to work out a variant
until the original problem and a solution is identified
and provided.

Note: The only PowerPC contexts that I've access to are
old PowerMacs. I've no clue if other contexts have the
original issue or not.

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