linux-kernel - Re: [PATCH] x86/cacheinfo: Remove set but unused variable 'trace'

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Date:   Fri, 02 Dec 2022 14:04:05 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>
Cc:     mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        x86@...nel.org, hpa@...or.com, linux-kernel@...r.kernel.org,
        Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>,
        Abaci Robot <abaci@...ux.alibaba.com>
Subject: Re: [PATCH] x86/cacheinfo: Remove set but unused variable 'trace'

On Wed, Nov 23 2022 at 14:01, Jiapeng Chong wrote:

> Variable 'trace' is not effectively used in the function, so delete it.
>
> arch/x86/kernel/cpu/cacheinfo.c:737:15: warning: variable 'trace' set but not used.
>
> Link: https://bugzilla.openanolis.cn/show_bug.cgi?id=3243

This link is really pointless.

> Reported-by: Abaci Robot <abaci@...ux.alibaba.com>
> Signed-off-by: Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>
> ---
>  arch/x86/kernel/cpu/cacheinfo.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/cacheinfo.c b/arch/x86/kernel/cpu/cacheinfo.c
> index f4e5aa27eec6..c6c0052def8e 100644
> --- a/arch/x86/kernel/cpu/cacheinfo.c
> +++ b/arch/x86/kernel/cpu/cacheinfo.c
> @@ -734,7 +734,7 @@ void init_hygon_cacheinfo(struct cpuinfo_x86 *c)
>  void init_intel_cacheinfo(struct cpuinfo_x86 *c)
>  {
>  	/* Cache sizes */
> -	unsigned int trace = 0, l1i = 0, l1d = 0, l2 = 0, l3 = 0;
> +	unsigned int l1i = 0, l1d = 0, l2 = 0, l3 = 0;
>  	unsigned int new_l1d = 0, new_l1i = 0; /* Cache sizes from cpuid(4) */
>  	unsigned int new_l2 = 0, new_l3 = 0, i; /* Cache sizes from cpuid(4) */
>  	unsigned int l2_id = 0, l3_id = 0, num_threads_sharing, index_msb;
> @@ -836,7 +836,6 @@ void init_intel_cacheinfo(struct cpuinfo_x86 *c)
>  							l3 += cache_table[k].size;
>  							break;
>  						case LVL_TRACE:
> -							trace += cache_table[k].size;
>  							break;

Sure, that makes the warning go away, but what's the purpose of
'case LVL_TRACE:' now?

Now if you remove that you really want look at the surrounding logic of
LVL_TRACE. Hint: There is way more completely useless code to remove.

Thanks,

        tglx