linux-kernel - Re: [PATCH v2] smp_call_function: use inline helpers instead of macros

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Message-ID: <cc227181-ef9f-dede-d478-ba0714e4bfbb@redhat.com>
Date:   Wed, 26 Jul 2017 16:42:07 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Arnd Bergmann <arnd@...db.de>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Ralf Baechle <ralf@...ux-mips.org>,
        James Hogan <james.hogan@...tec.com>,
        Paul Burton <paul.burton@...tec.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juergen Gross <jgross@...e.com>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-mips@...ux-mips.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] smp_call_function: use inline helpers instead of
 macros

On 26/07/2017 15:32, Arnd Bergmann wrote:
> A new caller of smp_call_function() passes a local variable as the 'wait'
> argument, and that variable is otherwise unused, so we get a warning
> in non-SMP configurations:
> 
> virt/kvm/kvm_main.c: In function 'kvm_make_all_cpus_request':
> virt/kvm/kvm_main.c:195:7: error: unused variable 'wait' [-Werror=unused-variable]
>   bool wait = req & KVM_REQUEST_WAIT;
> 
> This addresses the warning by changing the two macros into inline functions.
> As reported by the 0day build bot, a small change is required in the MIPS
> r4k code for this, which then gets a warning about a missing variable.
> 
> Fixes: 7a97cec26b94 ("KVM: mark requests that need synchronization")
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Link: https://patchwork.kernel.org/patch/9722063/
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

This is not needed anymore, I've fixed it in KVM:

    commit b49defe83659cefbb1763d541e779da32594ab10
    Author: Paolo Bonzini <pbonzini@...hat.com>
    Date:   Fri Jun 30 13:25:45 2017 +0200

    kvm: avoid unused variable warning for UP builds

    The uniprocessor version of smp_call_function_many does not evaluate
    all of its argument, and the compiler emits a warning about "wait"
    being unused.  This breaks the build on architectures for which
    "-Werror" is enabled by default.

    Work around it by moving the invocation of smp_call_function_many to
    its own inline function.

    Reported-by: Paul Mackerras <paulus@...abs.org>
    Cc: stable@...r.kernel.org
    Fixes: 7a97cec26b94c909f4cbad2dc3186af3e457a522
    Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>

Paolo