Re: [rfc] data race in page table setup/walking?

[Nick Piggin <npiggin-l3A5Bk7waGM@public.gmane.org>]

On Tue, Apr 29, 2008 at 11:05:43PM -0700, David Miller wrote:
> From: Nick Piggin <npiggin-l3A5Bk7waGM@public.gmane.org>
> Date: Wed, 30 Apr 2008 08:03:40 +0200
> 
> > Hardware walkers, I shouldn't worry too much about, except as a thought
> > exercise to realise that we have lockless readers. I think(?) alpha can
> > walk the linux ptes in hardware on TLB miss, but surely they will have
> > to do the requisite barriers in hardware too (otherwise things get
> > really messy)
> 
> My understanding is that all Alpha implementations walk the
> page tables in PAL code.

Ah OK. I guess that's effectively "hardware" as far as Linux is concerned.
I guess even x86 really walks the page tables in microcode as well. Basically
I just mean something that is invisible to, and obvlivious of, Linux's
locking.

 
> > Powerpc's find_linux_pte is one of the software walked lockless ones.
> > That's basically how I imagine hardware walkers essentially should operate.
> 
> Sparc64 walks the page tables lockless in it's TLB hash table miss
> handling.
> 
> MIPS does something similar.

Interesting, thanks.