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 18:31:34 +0000 |
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On 18/01/18 14:25, Suzuki K Poulose wrote: > 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 ;-)
Dave,
I have picked this up in my new series for revamping cpu capabilities and will send it after a bit of testing. So, no need to respin it.
Cheers Suzuki
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