netdev - Re: [PATCH bpf-next] bpf: fix compiler warning with CONFIG

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Message-ID: <2A287A9B-F7F8-4C71-BA49-0FD66399E292@fb.com>
Date:   Wed, 26 Jun 2019 01:16:04 +0000
From:   Song Liu <songliubraving@...com>
To:     Yonghong Song <yhs@...com>
CC:     Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Networking <netdev@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        Kernel Team <Kernel-team@...com>,
        "arnd@...db.de" <arnd@...db.de>
Subject: Re: [PATCH bpf-next] bpf: fix compiler warning with CONFIG_MODULES=n



> On Jun 25, 2019, at 5:35 PM, Yonghong Song <yhs@...com> wrote:
> 
> With CONFIG_MODULES=n, the following compiler warning occurs:
>  /data/users/yhs/work/net-next/kernel/trace/bpf_trace.c:605:13: warning:
>      ‘do_bpf_send_signal’ defined but not used [-Wunused-function]
>  static void do_bpf_send_signal(struct irq_work *entry)
> 
> The __init function send_signal_irq_work_init(), which calls
> do_bpf_send_signal(), is defined under CONFIG_MODULES. Hence,
> when CONFIG_MODULES=n, nobody calls static function do_bpf_send_signal(),
> hence the warning.
> 
> The init function send_signal_irq_work_init() should work without
> CONFIG_MODULES. Moving it out of CONFIG_MODULES
> code section fixed the compiler warning, and also make bpf_send_signal()
> helper work without CONFIG_MODULES.
> 
> Fixes: 8b401f9ed244 ("bpf: implement bpf_send_signal() helper")
> Reported-By: Arnd Bergmann <arnd@...db.de>
> Signed-off-by: Yonghong Song <yhs@...com>

Thanks for the fix!

Acked-by: Song Liu <songliubraving@...com>


> ---
> kernel/trace/bpf_trace.c | 27 ++++++++++++++-------------
> 1 file changed, 14 insertions(+), 13 deletions(-)
> 
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index c102c240bb0b..ca1255d14576 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -1431,6 +1431,20 @@ int bpf_get_perf_event_info(const struct perf_event *event, u32 *prog_id,
> 	return err;
> }
> 
> +static int __init send_signal_irq_work_init(void)
> +{
> +	int cpu;
> +	struct send_signal_irq_work *work;
> +
> +	for_each_possible_cpu(cpu) {
> +		work = per_cpu_ptr(&send_signal_work, cpu);
> +		init_irq_work(&work->irq_work, do_bpf_send_signal);
> +	}
> +	return 0;
> +}
> +
> +subsys_initcall(send_signal_irq_work_init);
> +
> #ifdef CONFIG_MODULES
> static int bpf_event_notify(struct notifier_block *nb, unsigned long op,
> 			    void *module)
> @@ -1478,18 +1492,5 @@ static int __init bpf_event_init(void)
> 	return 0;
> }
> 
> -static int __init send_signal_irq_work_init(void)
> -{
> -	int cpu;
> -	struct send_signal_irq_work *work;
> -
> -	for_each_possible_cpu(cpu) {
> -		work = per_cpu_ptr(&send_signal_work, cpu);
> -		init_irq_work(&work->irq_work, do_bpf_send_signal);
> -	}
> -	return 0;
> -}
> -
> fs_initcall(bpf_event_init);
> -subsys_initcall(send_signal_irq_work_init);
> #endif /* CONFIG_MODULES */
> -- 
> 2.17.1
>