linux-kernel - Re: [PATCH v2] sched/core: silence a warning in sched

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Date:   Mon, 08 Jul 2019 10:32:44 -0400
From:   Qian Cai <cai@....pw>
To:     mingo@...hat.com, peterz@...radead.org
Cc:     valentin.schneider@....com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] sched/core: silence a warning in sched_init()

Ping. Per discussion, sounds like this is the best thing to do in order to avoid
compilation warnings.

On Tue, 2019-06-25 at 08:44 -0400, Qian Cai wrote:
> Compiling a kernel with both FAIR_GROUP_SCHED=n and RT_GROUP_SCHED=n
> will generate a warning using W=1,
> 
> kernel/sched/core.c: In function 'sched_init':
> kernel/sched/core.c:5906:32: warning: variable 'ptr' set but not used
> [-Wunused-but-set-variable]
>   unsigned long alloc_size = 0, ptr;
>                                 ^~~
> 
> It apparently the maintainers don't like the previous fix [1] which
> contains ugly idefs, so silence it by appending the __maybe_unused
> attribute for it instead.
> 
> [1] https://lore.kernel.org/lkml/1559681162-5385-1-git-send-email-cai@lca.pw/
> 
> Reviewed-by: Valentin Schneider <valentin.schneider@....com>
> Signed-off-by: Qian Cai <cai@....pw>
> ---
> 
> v2: Incorporate the feedback from Valentin.
> 
>  kernel/sched/core.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 874c427742a9..12b9b69c8a66 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -5903,7 +5903,8 @@ int in_sched_functions(unsigned long addr)
>  void __init sched_init(void)
>  {
>  	int i, j;
> -	unsigned long alloc_size = 0, ptr;
> +	unsigned long alloc_size = 0;
> +	unsigned long __maybe_unused ptr;
>  
>  	wait_bit_init();
>