Re: [RFC & PATCH] fixing tlb flush race problem on smp

[Ralf Baechle <ralf@linux-mips.org>]

On Mon, Jan 27, 2003 at 05:03:46PM -0800, Jun Sun wrote:

> I also find a stupid typo and a subtle hole in my original patch.
> Here is an updated version, for 2.4/mips only.  If it looks ok, I 
> will extend to other sub-arches/trees.
> 
> This new one is pretty nice in that all mmu related operations
> are put into one file and it is much easier to ensure correctness
> later.

I like this one.

> +
> +	/*
> +	 * Mark current->active_mm as not "active" anymore.
> +	 * We don't want to mislead possible IPI tlb flush routines.
> +	 */
> +	clear_bit(cpu, &prev->cpu_vm_mask);
> +	set_bit(cpu, &next->cpu_vm_mask);
> +
> +	local_irq_restore(flags);

I don't think it's necessary to protect the clear_bit and set_bit operations
with local_irq_save ... local_irq_restore.

In addition because switch_mm is always called with interrupts enabled you
can simplify that to local_irq_disable ... local_irq_enable.

  Ralf