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Date:   Sat, 2 May 2020 15:08:00 +0200
From:   Rasmus Villemoes <linux@...musvillemoes.dk>
To:     Peter Zijlstra <peterz@...radead.org>, x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, rostedt@...dmis.org,
        mhiramat@...nel.org, bristot@...hat.com, jbaron@...mai.com,
        torvalds@...ux-foundation.org, tglx@...utronix.de,
        mingo@...nel.org, namit@...are.com, hpa@...or.com, luto@...nel.org,
        ard.biesheuvel@...aro.org, jpoimboe@...hat.com,
        pbonzini@...hat.com, mathieu.desnoyers@...icios.com
Subject: Re: [PATCH v4 14/18] static_call: Add static_cond_call()

On 01/05/2020 22.29, Peter Zijlstra wrote:
> Extend the static_call infrastructure to optimize the following common
> pattern:
> 
> 	if (func_ptr)
> 		func_ptr(args...)
> 
> +
>  #define static_call(name)	__static_call(name)
> +#define static_cond_call(name)	(void)__static_call(name)
>  
> +
>  #define static_call(name)	__static_call(name)
> +#define static_cond_call(name)	(void)__static_call(name)
>  

> +#define static_cond_call(name)						\
> +	if (STATIC_CALL_KEY(name).func)					\
> +		((typeof(STATIC_CALL_TRAMP(name))*)(STATIC_CALL_KEY(name).func))
> +

This addresses neither the READ_ONCE issue nor the fact that, AFAICT,
the semantics of

  static_cond_call(foo)(i++)

will depend on CONFIG_HAVE_STATIC_CALL. Also, I'd have appreciated being
cc'ed on new revisions instead of stumbling on it by chance.

Rasmus

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