[patch 00/13] preempt: Make preempt count unconditional

[Herbert Xu]

On Tue, Sep 15, 2020 at 09:20:59AM +0300, Ard Biesheuvel wrote:
>
> The documentation of kmap_atomic() states the following:
> 
>  * The use of kmap_atomic/kunmap_atomic is discouraged - kmap/kunmap
>  * gives a more generic (and caching) interface. But kmap_atomic can
>  * be used in IRQ contexts, so in some (very limited) cases we need
>  * it.
> 
> so if this is no longer accurate, perhaps we should fix it?

This hasn't been accurate for at least ten years :)

> But another reason I tried to avoid kmap_atomic() is that it disables
> preemption unconditionally, even on 64-bit architectures where HIGHMEM
> is irrelevant. So using kmap_atomic() here means that the bulk of
> WireGuard packet encryption runs with preemption disabled, essentially
> for legacy reasons.

Agreed.  We should definitely fix that.

Thanks,
-- 
Email: Herbert Xu <herbert at gondor.apana.org.au>
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