On 2017-07-26, at 2:02 PM, Helge Deller wrote:
> Instead I'd then suggest the patch below.
> The if-clause in switch_mm_irqs_off() will then probably be optimized
> away by the compiler.
>
> diff --git a/arch/parisc/include/asm/mmu_context.h b/arch/parisc/include/asm/mmu_context.h
> index a812262..e4a6570 100644
> --- a/arch/parisc/include/asm/mmu_context.h
> +++ b/arch/parisc/include/asm/mmu_context.h
> @@ -63,6 +63,9 @@ static inline void switch_mm(struct mm_struct *prev,
> {
> unsigned long flags;
>
> + if (prev == next)
> + return;
> +
> local_irq_save(flags);
> switch_mm_irqs_off(prev, next, tsk);
> local_irq_restore(flags);
You are correct. I missed the fact that switch_mm_irqs_off() is used by kernel/sched/core.c.
Maybe we should replace the "switch_mm_irqs_off(prev, next, tsk);" with the mtctl and load_context
lines to ensure that the if-clause is optimized?
Dave
--
John David Anglin dave.anglin@xxxxxxxx
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