Re: Need help from a VAX abi expert (was: Reproducable kernel crash)

[Anders Magnusson <ragge%tethuvudet.se@localhost>]

    Den 2025-01-11 kl. 15:04, skrev Martin Husemann:
> > Followup question is: If this is not the correct way of working (which means
> > I misunderstood something sometime ? ), how should it work?
> >       
> What you describe is correct and all fine, this is probably something that
> didn't matter much some years ago but now is causing confusion (at least
> confusing me).
>
> I see pmap_activate(l) does basically two things:
>
>  - fiddle with the PCB of l (this is the part needed in the call that I
>    want to remove)
>
>  - if l == curlwp also switch the CPU to this pmap
>
> I think (but I am not sure) in modern semantics pmap_activate() should only
> do the l == curlwp part (and probably uncoditionally), and the first part
> should be moved elsewhere (that could be inline into the call I was trying
> to remove) and only be done once at lwp creation time.
>     
    I tried to understand how it should work, but it is not clear to me
    either :-)  
    The bugs section of the manpage says that it need to be clarified as
    well.
    It do state that it is always called with the current lwp though.
    
    Anyway; adding the settings of the page registers to cpu_lwp_fork()
    is 
    non-trivial (if the goal is just to remove the pmap_activate() call).



> Side note:
> what I don't undstand is why VAX needs a list of PCBs in its struct pmap.
> Doesn't this always map 1:1 to the list pcbs of all lwp's in the process?
> This list handling seems to be different to all other pmaps I have seen.
>     
    Do you mean the list in PCB; pcb_pmnext?  IIRC it had to do with the
    logic 
    for handling the page table resource map (since all lwp:s in a
    process share
    the same page table but have different PCBs).
    
    -- R