Re: [PATCH, RFC] improved hacks to allow -rt to run kernbench on POWER

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Tue, 2007-11-13 at 10:10 +0100, Peter Zijlstra wrote:
> 
> Correct, -rt can't allocate -anything- when preemption if off. That is
> the cost for having the allocators itself preemptable.
> 
> Even radix_tree_preload() will not work as its functionality was based
> on preempt disable to limit access to a global (per cpu) object
> reserve.
> But maybe something similar could be done with a local reserve by
> using
> struct radix_tree_context to pass it along.
> 
> I'll see if I can come up with anything like that, that is, if that
> would suffice?

For that specific problem, as long as the radix tree can be made to work
while non-preemptible, I'm fine :-)

I'm still worried by other cases where things expect GFP_ATOMIC to work
at any time.

Ben.