Re: Kernel preemption

[Christoph Egger <Christoph_Egger%gmx.de@localhost>]

Andrew Doran wrote:
> Hi,
>
> The below patch implments in-kernel preemption for the i386 port. By default
> LWPs will only preempt in kernel if they are in a real-time priority band.
> The priority level is tunable via sysctl. Setting it to zero seems to shake
> out a lot of interesting bugs.

I believe that. curcpu() must be cached in a local variable, for
example.

> It needs a bit more work, for stuff like FPU state, and I also want to
> extend it to amd64. I think it should not be enabled by default until the
> bugs it exposes are shaken out. Any comments?
>
> http://www.netbsd.org/~ad/preempt.diff

In pmap.c, pmap_copy_page() shouldn't be this

+       id = cpu_number();
+       kpreempt_disable();

changed to

+       kpreempt_disable();
+       id = cpu_number();

as you do in pmap_zero_page() ?

Christoph