linux-kernel - Re: [PATCH -next v2] arm64/spinlock: fix a -Wunused-function warning

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Date:   Thu, 23 Jan 2020 15:24:43 -0500
From:   Waiman Long <longman@...hat.com>
To:     Qian Cai <cai@....pw>, peterz@...radead.org
Cc:     will@...nel.org, mingo@...hat.com, catalin.marinas@....com,
        clang-built-linux@...glegroups.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next v2] arm64/spinlock: fix a -Wunused-function warning

On 1/23/20 3:20 PM, Qian Cai wrote:
> The commit f5bfdc8e3947 ("locking/osq: Use optimized spinning loop for
> arm64") introduced a warning from Clang because vcpu_is_preempted() is
> compiled away,
>
> kernel/locking/osq_lock.c:25:19: warning: unused function 'node_cpu'
> [-Wunused-function]
> static inline int node_cpu(struct optimistic_spin_node *node)
>                   ^
> 1 warning generated.
>
> Fix it by converting vcpu_is_preempted() to a static inline function.
>
> Fixes: f5bfdc8e3947 ("locking/osq: Use optimized spinning loop for arm64")
> Signed-off-by: Qian Cai <cai@....pw>
> ---
>
> v2: convert vcpu_is_preempted() to a static inline function.
>
>  arch/arm64/include/asm/spinlock.h | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/include/asm/spinlock.h b/arch/arm64/include/asm/spinlock.h
> index 102404dc1e13..9083d6992603 100644
> --- a/arch/arm64/include/asm/spinlock.h
> +++ b/arch/arm64/include/asm/spinlock.h
> @@ -18,6 +18,10 @@
>   * See:
>   * https://lore.kernel.org/lkml/20200110100612.GC2827@hirez.programming.kicks-ass.net
>   */
> -#define vcpu_is_preempted(cpu)	false
> +#define vcpu_is_preempted vcpu_is_preempted
> +static inline bool vcpu_is_preempted(int cpu)
> +{
> +	return false;
> +}
>  
>  #endif /* __ASM_SPINLOCK_H */

Acked-by: Waiman Long <longman@...hat.com>