Re: pg_jobc going negative?

[Robert Elz <kre%munnari.OZ.AU@localhost>]

    Date:        Fri, 10 Jul 2020 16:47:28 +0200
    From:        Rhialto <rhialto%falu.nl@localhost>
    Message-ID:  <20200710144728.GY3362%falu.nl@localhost>

  | It also seems to be involved in deciding wether to send a SIGTTOU or
  | SIGTTIN to a process

Ah, right, thanks ... when I was reviewing uses in the kernel I
was concentrating on places where pg_jobc changes, and just sort of
dismissed the places where it was simply examined....   then I never
went back to them again.   I will make sure my plans keep this working
(I knew that orphaned pg processes no longer do any kind of auto-stop,
though they can stil be sent SIGSTOP I believe).


  | I found this above fixjobc() which goes into a bit more detail what is
  | being counted:

Yes, I've been looking at that - that's where things are going wrong I
think, when looking at the children each child can decrement pg_jobc
but it only seems to get incremented once.   Easy to see how it becomes 
negative.

mouse%Rodents-Montreal.ORG@localhost said:
  | But each of those steps involves some winnowing-down.

Yes, again speculating, but my guess would be (for libkvm)
"if someone uses it, we make it available, if no-one does,
we don't" and quite probably ps was using it via /dev/mem
already (though what use that was supposed to have I cannot guess,
perhaps just for debugging the kernel implementation)

After that it appears that everything was just copied to each new
interface, based upon the philosophy of phasing out uses of libkvm,
which would mean making sure that the alternate interface could do
everything libkvm could do, otherwise someone would find the missing
data a justification for sticking with libkvm.

mouse%Rodents-Montreal.ORG@localhost said:
  | Did your userland sweep include pkgsrc? 

No, I don't have the resources to do that.  I don't use many packages
(so don't have many distfiles) and have even fewer of those unpacked.
My test system for HEAD has none of it at all.

mouse%Rodents-Montreal.ORG@localhost said:
  | [...] I'd be astonished if there aren't at least a few
  | programs there that grub around in things like this.

No question, there are, but this particular field seems very unlikely
to have any users - really really unlikely.

kre