Messages in this thread | | | Subject | Re: [PATCH v2 0/2] arm64: Run enable method for errata work arounds on late CPUs | From | Suzuki K Poulose <> | Date | Thu, 18 Jan 2018 14:25:52 +0000 |
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On 18/01/18 14:21, Dave Martin wrote: > On Thu, Jan 18, 2018 at 12:08:43PM +0000, Robin Murphy wrote: >> On 18/01/18 12:00, Robin Murphy wrote: >> [...] >>>> +struct enable_arg { >>>> + int (*enable)(struct arm64_cpu_capabilities const *); >>>> + struct arm64_cpu_capabilities const *cap; >>>> +}; >>>> + >>>> +static int __enable_cpu_capability(void *arg) >>>> +{ >>>> + struct enable_arg const *e = arg; >>>> + >>>> + return e->enable(e->cap); >>>> +} >>> >>> AFAICS, you shouldn't even need the intermediate struct - if you were >>> instead to call stop_machine(&caps->enable, ...), the wrapper could be: >>> >>> <type> **fn = arg; >>> *fn(container_of(fn, struct arm64_cpu_capabilities, enable)); >>> >>> (cheaty pseudocode because there's no way I'm going to write a >>> pointer-to-function-pointer type correctly in an email client...) >>> >>> That's certainly a fair bit simpler in terms of diffstat; whether it's >>> really as intuitive as I think it is is perhaps another matter, though. >> >> Ah, right, but then you'd be back to casting away const, and at that point >> it makes no sense to do the container_of dance instead of just passing the >> struct pointer itself around... >> >> I shall now excuse myself from this discussion, as I'm clearly not helping >> :) >> >> Robin. > > That's what I was about to say... but neat trick. > > However, it does concentrate the type fudge in one place and keeps the > arm64_cpu_capabilities::enable() prototype correct, so it's still better > than the original. > > > Thinking about it, the following is probably clearer and no worse: > > static int __enable_cpu_capability(void *arg) > { > struct arm64_cpu_capabilities const *cap = arg; > > return cap->enable(cap); > } > > ... > > stop_machine(__enable_cpu_capability, (void *)caps, cpu_online_mask); > > > In your version, the argument would be (void *)&caps->enable, which is > really just a proxy for (void *)caps, unless I missed something. > > > What do you think Suzuki? I can respin my patch if you fancy picking it > up. Either way, it's not urgent.
Thanks for cooking that up Dave & Robin. I prefer your second version. Please feel free to respin it. As you rightly said, this is not urgent and could pick it up in my re-writing of the capability infrastructure ;-)
Meanwhile, I would really like some reviews on the original patch and push it for 4.16 (as a fix at least).
Cheers Suzuki
> > Cheers > ---Dave >
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