linux-kernel - Re: [PATCH] KVM: Eliminate unused variable warning on uniprocessor configs

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Message-ID: <20170512061009.rq3rrvbo2xbsy6ml@oak.ozlabs.ibm.com>
Date:   Fri, 12 May 2017 16:10:09 +1000
From:   Paul Mackerras <paulus@...abs.org>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, kvm-ppc@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] KVM: Eliminate unused variable warning on uniprocessor
 configs

On Thu, May 11, 2017 at 09:44:06AM +0200, Paolo Bonzini wrote:
> 
> 
> On 11/05/2017 05:40, Paul Mackerras wrote:
> > When the
> > kernel is compiled with CONFIG_SMP=n, smp_call_function_many() turns
> > into a macro which doesn't use the 'wait' argument, leading to a
> > warning about the variable 'wait' being unused:
> > 
> > /home/paulus/kernel/kvm/arch/powerpc/kvm/../../../virt/kvm/kvm_main.c: In function ‘kvm_make_all_cpus_request’:
> > /home/paulus/kernel/kvm/arch/powerpc/kvm/../../../virt/kvm/kvm_main.c:195:7: error: unused variable ‘wait’ [-Werror=unused-variable]
> >   bool wait = req & KVM_REQUEST_WAIT;
> 
> Maybe the macro should not be a macro:

Sounds fair, and with a couple of semicolons removed, it works and
fixes the problem.  Do you want to send it to the appropriate
maintainer(s) or will I?

> diff --git a/include/linux/smp.h b/include/linux/smp.h
> index 8e0cb7a0f836..899c72f0933f 100644
> --- a/include/linux/smp.h
> +++ b/include/linux/smp.h
> @@ -128,17 +128,18 @@ static inline void smp_send_stop(void) { }
>   *	These macros fold the SMP functionality into a single CPU system
>   */
>  #define raw_smp_processor_id()			0
> -static inline int up_smp_call_function(smp_call_func_t func, void *info)
> +static inline void smp_call_function_many(const struct cpumask *mask,
> +					  smp_call_func_t func, void *info,
> +					  bool wait);

No semicolon on the end of this line...

>  {
> -	return 0;
> +}
> +
> +static inline void smp_call_function(smp_call_func_t func, void *info, bool wait);

or this one.

Paul.