Re: [PATCH] locking/rtmutex: remove unused cmpxchg_relaxed

[Alex Shi]

在 2020/2/1 上午4:23, Thomas Gleixner 写道:
> Davidlohr Bueso <dave@xxxxxxxxxxxx> writes:
>> On Tue, 21 Jan 2020, Alex Shi wrote:
> 
>   Subject: locking/rtmutex: remove unused cmpxchg_relaxed
> 
> should be
> 
>   Subject: locking/rtmutex: Remove unused rt_mutex_cmpxchg_relaxed()
> 
> You're not removing cmpxchg_relaxed, right?
> 
>>> No one use this macro after it was introduced. Better to remove it?
> 
> Please make that factual.
> 
>  The macro was never used at all. Remove it.
> 
>> You also need to remove it for the CONFIG_DEBUG_RT_MUTEXES=y case.
> 
> Yes.
> 
>> Hmm unrelated, but do we want CCAS for rtmutex fastpath? Ie:
>>
>>      (l->owner == c && cmpxchg_acquire(&l->owner, c, n) == c)
>>
>> That would optimize for the contended case and avoid the cmpxchg - it would
>> also help if we ever do the top-waiter spin thing.
> 
> Not sure if it buys much, but it kinda makes sense.
> 
> Thanks,
> 
>         tglx
> 
Thanks Thomas and David!
Is this following patch ok?

Thanks
Alex
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