Re: [PATCH 1/6] freepgt: free_pgtables use vma list

[Hugh Dickins <hugh@veritas.com>]

On Wed, 30 Mar 2005, Andi Kleen wrote:
> 
> Ok. I will defer the bitvector patch now. 
> 
> I had it mostly working with hacks, but than I ran into
> a nasty include ordering problem that scared me off so far.

Hah, you too!  I knew Ben and Nick had designs in that kind
of direction, and meant to leave the field clear for them; but
once the vma idea struck me, it seemed silly not to pursue it.

> Ok. I will change it to a VMA.

Thanks.  (It's only the 32-bit emulation case I'm caring about,
that poses a problem for free_pgtables: I'm not sure whether you're
meaning to VMA-ize the 64-bit one too, that's entirely up to you.)

> Only bad thing is that this has to be done at program startup.
> At fault time we cannot upgrade the read lock on mmap sem to a write
> lock that is needed to insert the VMA :/ But I guess that is ok
> because with modern glibc basically all programs will use vsyscsall.

Sorry for bumping you into this, but I think it's the right approach.
ARM can justify its special FIRST_USER_ADDRESS treatment because (as
I understaned it) the low vectors just have to be set up earlier and
cleared later, but your case is at a higher level.

Hugh