Subject: Re: [PATCH][RFC] Implement arch primitives for busywait loops

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Mon, 19 Sep 2016 10:35:37 +0530

> diff --git a/include/linux/bit_spinlock.h b/include/linux/bit_spinlock.h
> index 3b5bafc..695743c 100644
> --- a/include/linux/bit_spinlock.h
> +++ b/include/linux/bit_spinlock.h
> @@ -25,9 +25,8 @@ static inline void bit_spin_lock(int bitnum, unsigned long *addr)
>  #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
>  	while (unlikely(test_and_set_bit_lock(bitnum, addr))) {
>  		preempt_enable();
> -		do {
> -			cpu_relax();
> -		} while (test_bit(bitnum, addr));
> +		spin_do {
> +		} spin_while (test_bit(bitnum, addr));
>  		preempt_disable();
>  	}
>  #endif

That usage is strange, with nothing in the do{ }while loop. May be add a
macro for usages like this ?

-aneesh