Re: [PATCH] futex: Set USER_DS for the futex_detect_cmpxchg() test

Max Filippov
2018-09-28T21:36:33Z

On Fri, Sep 28, 2018 at 2:08 PM, Andy Lutomirski <luto@amacapital.net> wrote:
>
>
>> On Sep 28, 2018, at 1:26 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
>>
>>> On Fri, 28 Sep 2018, Max Filippov wrote:
>>>
>>>> On Fri, Sep 28, 2018 at 11:02 AM, Andy Lutomirski <luto@amacapital.net> wrote:
>>>> There may be a much nicer solution. Unless I missed something, only
>>>> mips and xtensa even have the possibility of cmpxchg being missing.
>>>> We could just make those arches supply a futex-detecting helper.
>>>
>>> In case of xtensa availability of cmpxchg is known at build time.
>>
>> That makes it even simpler. Could you provide a patch which selects
>> CONFIG_HAVE_FUTEX_CMPXCHG for the right set of CPUs please?
>>
>>
>
> I think that’s the wrong approach, since it won’t cover mips. How about adding this to mips and xtensa only:
>
> static inline void arch_have_futex_cmpxchg(void) {...};
> #define arch_have_futex_cmpxchg arch_have_futex_cmpxchg
>
> And getting rid of the config option.

I'd rather do that, given that defining Kconfig entries that describe
parts of xtensa configuration is somewhat awkward and redundant.

--
Thanks.
-- Max