[uml-devel] Re: And the BUG of skas-2.6 with SMP active?

[Jeff Dike <jdike@addtoit.com>]

On Sat, Feb 28, 2004 at 09:36:31PM +0100, BlaisorBlade wrote:
> Ok, good diagnosys. So *in this* case activate_mm must be called somewhere. 
> But not in sys_ptrace, because that runs in process context, and would 
> activate the mm for "current", which cannot be the child.

Yup, right.

> Also, if the temporary HIGHMEM mappings created by kmap are stored in 
> current->active_mm, then we cannot even change the kernel thread active_mm 
> (it would also be difficult anyway, since you need to suspend it).

No one is proposing that.

> So, since I guess that CONFIG_SMP=n means the cpu_tlbstate does not exist, I 
> would propose this change in include/asm-i386/mmu_context.h:switch_mm() (and 
> removing the BUG_ON line since that could not any more be triggered):
> 
>          int cpu = smp_processor_id();
> +#ifdef CONFIG_SMP
> +       prev = cpu_tlbstate[cpu].active_mm;
> +#endif
>          if (likely(prev != next)) {

That looks reasonable with a quick look at the code.  You're forcing it into
the address-space-changed case, which is right.

				Jeff


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