[PATCH v3 1/5] asm-generic: barrier: Add smp_cond_load_relaxed_timewait()

[Arnd Bergmann]

On Wed, Aug 13, 2025, at 18:09, Catalin Marinas wrote:
> On Mon, Aug 11, 2025 at 02:15:56PM -0700, Ankur Arora wrote:
>
>> This also gives the WFET a clear end time (though it would still need
>> to be converted to timer cycles) but the WFE path could stay simple
>> by allowing an overshoot instead of falling back to polling.
>
> For arm64, both WFE and WFET would be woken up by the event stream
> (which is enabled on all production systems). The only reason to use
> WFET is if you need smaller granularity than the event stream period
> (100us). In this case, we should probably also add a fallback from WFE
> to a busy loop.

I think there is a reasonable chance that in the future we may want
to turn the event stream off on systems that support WFET, since that
is better for both low-power systems and virtual machines with CPU
overcommit.

    Arnd